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Denis GAROLI

Professore Associato
Dipartimento di Scienze e Metodi dell'Ingegneria

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Pubblicazioni

2024 - Dry synthesis of bi-layer nanoporous metal films as plasmonic metamaterial [Articolo su rivista]
Caligiuri, Vincenzo; Kwon, Hyunah; Griesi, Andrea; Ivanov, Yurii P.; Schirato, Andrea; Alabastri, Alessandro; Cuscunà, Massimo; Balestra, Gianluca; De Luca, Antonio; Tapani, Tlek; Lin, Haifeng; Maccaferri, Nicolò; Krahne, Roman; Divitini, Giorgio; Fischer, Peer; Garoli, Denis
abstract

2024 - Gate-All-Around Nanopore Osmotic Power Generators [Articolo su rivista]
Tsutsui, Makusu; Hsu, Wei-Lun; Garoli, Denis; Leong, Iat Wai; Yokota, Kazumichi; Daiguji, Hirofumi; Kawai, Tomoji
abstract

: Nanofluidic channels in a membrane represent a promising avenue for harnessing blue energy from salinity gradients, relying on permselectivity as a pivotal characteristic crucial for inducing electricity through diffusive ion transport. Surface charge emerges as a central player in the osmotic energy conversion process, emphasizing the critical significance of a judicious selection of membrane materials to achieve optimal ion permeability and selectivity within specific channel dimensions. Alternatively, here we report a field-effect approach for in situ manipulation of the ion selectivity in a nanopore. Application of voltage to a surround-gate electrode allows precise adjustment of the surface charge density at the pore wall. Leveraging the gating control, we demonstrate permselectivity turnover to enhanced cation selective transport in multipore membranes, resulting in a 6-fold increase in the energy conversion efficiency with a power density of 15 W/m2 under a salinity gradient. These findings not only advance our fundamental understanding of ion transport in nanochannels but also provide a scalable and efficient strategy for nanoporous membrane osmotic power generation.

2024 - Peltier cooling for thermal management in nanofluidic devices [Articolo su rivista]
Tsutsui, Makusu; Yokota, Kazumichi; Hsu, Wei Lun; Garoli, Denis; Daiguji, Hirofumi; Kawai, Tomoji
abstract

2024 - Probing Temperature Changes Using Nonradiative Processes in Hyperbolic Meta-Antennas [Articolo su rivista]
Henriksson, Nils; Gabbani, Alessio; Petrucci, Gaia; Garoli, Denis; Pineider, Francesco; Maccaferri, Nicolò
abstract

2024 - Universal Click-Chemistry Approach for the DNA Functionalization of Nanoparticles [Articolo su rivista]
Siegel, Nicole; Hasebe, Hiroaki; Chiarelli, Germán; Garoli, Denis; Sugimoto, Hiroshi; Fujii, Minoru; Acuna, Guillermo P; Kołątaj, Karol
abstract

: Nanotechnology has revolutionized the fabrication of hybrid species with tailored functionalities. A milestone in this field is the deoxyribonucleic acid (DNA) conjugation of nanoparticles, introduced almost 30 years ago, which typically exploits the affinity between thiol groups and metallic surfaces. Over the last decades, developments in colloidal research have enabled the synthesis of an assortment of nonmetallic structures, such as high-index dielectric nanoparticles, with unique properties not previously accessible with traditional metallic nanoparticles. However, to stabilize, integrate, and provide further functionality to nonmetallic nanoparticles, reliable techniques for their functionalization with DNA will be crucial. Here, we combine well-established dibenzylcyclooctyne-azide click-chemistry with a simple freeze-thaw method to achieve the functionalization of silica and silicon nanoparticles, which form exceptionally stable colloids with a high DNA surface density of ∼0.2 molecules/nm2. Furthermore, we demonstrate that these functionalized colloids can be self-assembled into high-index dielectric dimers with a yield of over 50% via the use of DNA origami. Finally, we extend this method to functionalize other important nanomaterials, including oxides, polymers, core-shell, and metal nanostructures. Our results indicate that the method presented herein serves as a crucial complement to conventional thiol functionalization chemistry and thus greatly expands the toolbox of DNA-functionalized nanoparticles currently available.

2023 - Advances in ultrafast plasmonics [Articolo su rivista]
Koya, An; Romanelli, M; Kuttruff, J; Henriksson, N; Stefancu, A; Grinblat, G; De Andres, A; Schnur, F; Vanzan, M; Marsili, M; Rahaman, M; Rodriguez, Av; Tapani, T; Lin, Hf; Dana, Bd; Lin, Jq; Barbillon, G; Zaccaria, Rp; Brida, D; Jariwala, D; Veisz, L; Cortes, E; Corni, S; Garoli, D; Maccaferri, N
abstract

In the past twenty years, we have reached a broad understanding of many light-driven phenomena in nanoscale systems. The temporal dynamics of the excited states are instead quite challenging to explore, and, at the same time, crucial to study for understanding the origin of fundamental physical and chemical processes. In this review we examine the current state and prospects of ultrafast phenomena driven by plasmons both from a fundamental and applied point of view. This research area is referred to as ultrafast plasmonics and represents an outstanding playground to tailor and control fast optical and electronic processes at the nanoscale, such as ultrafast optical switching, single photon emission and strong coupling interactions to tailor photochemical reactions. Here, we provide an overview of the field, and describe the methodologies to monitor and control nanoscale phenomena with plasmons at ultrafast timescales in terms of both modeling and experimental characterization. Various directions are showcased, among others recent advances in ultrafast plasmon-driven chemistry and multi-functional plasmonics, in which charge, spin, and lattice degrees of freedom are exploited to provide active control of the optical and electronic properties of nanoscale materials. As the focus shifts to the development of practical devices, such as all-optical transistors, we also emphasize new materials and applications in ultrafast plasmonics and highlight recent development in the relativistic realm. The latter is a promising research field with potential applications in fusion research or particle and light sources providing properties such as attosecond duration.

2023 - Aptamer Conformational Dynamics Modulate Neurotransmitter Sensing in Nanopores [Articolo su rivista]
Stuber, Annina; Douaki, Ali; Hengsteler, Julian; Buckingham, Denis; Momotenko, Dmitry; Garoli, Denis; Nakatsuka, Nako
abstract

: Aptamers that undergo conformational changes upon small-molecule recognition have been shown to gate the ionic flux through nanopores by rearranging the charge density within the aptamer-occluded orifice. However, mechanistic insight into such systems where biomolecular interactions are confined in nanoscale spaces is limited. To understand the fundamental mechanisms that facilitate the detection of small-molecule analytes inside structure-switching aptamer-modified nanopores, we correlated experimental observations to theoretical models. We developed a dopamine aptamer-functionalized nanopore sensor with femtomolar detection limits and compared the sensing behavior with that of a serotonin sensor fabricated with the same methodology. When these two neurotransmitters with comparable mass and equal charge were detected, the sensors showed an opposite electronic behavior. This distinctive phenomenon was extensively studied using complementary experimental techniques such as quartz crystal microbalance with dissipation monitoring, in combination with theoretical assessment by the finite element method and molecular dynamic simulations. Taken together, our studies demonstrate that the sensing behavior of aptamer-modified nanopores in detecting specific small-molecule analytes correlates with the structure-switching mechanisms of individual aptamers. We believe that such investigations not only improve our understanding of the complex interactions occurring in confined nanoscale environments but will also drive further innovations in biomimetic nanopore technologies.

2023 - Plasmon-driven Photochemistry for Metallic Nanopore Arrays Fabrication [Relazione in Atti di Convegno]
Lanzavecchia, G.; Kuttruff, J.; Doricchi, A.; Rodríguez, A. V.; Krahne, R.; Maccaferri, N.; Garoli, D.
abstract

2023 - Plasmonic Photochemistry as a Tool to Prepare Metallic Nanopores with Controlled Diameter for Optimized Detection of Single Entities [Articolo su rivista]
Lanzavecchia, German; Kuttruff, Joel; Doricchi, Andrea; Douaki, Ali; Kumaranchira Ramankutty, Krishnadas; Garc??a, Isabel; Lin, Lyuye; Viejo Rodr??guez, Alba; W??gberg, Thomas; Krahne, Roman; Maccaferri, Nicol??; Garoli, Denis
abstract

Plasmonic solid-state nanopores with tunable hole diameters can be prepared via a photocatalytic effect resulting from the enhanced electromagnetic (EM) field inside a metallic ring on top of a dielectric nanotube. Under white light illumination, the plasmon-enhanced EM-field induces a site-selective metal nucleation and growth within the ring. This approach is used to prepare Au and bimetallic Au-Ag nano-rings and demonstrate the reduction of the initial inner diameter of the nanopore down to 4 nm. The tunability of the nanopore diameter can be used to enable optimized detection of single entities with different sizes. As a proof-of-concept, single object detection of double stranded DNA (dsDNA) and Au nanoparticles (AuNPs) with a diameter down to 15 nm is performed. Numerical simulations provide insights into the EM-field distribution and confinement, showing that a field intensity enhancement of up to 10(4) can be achieved inside the nanopores. This localized EM-field can be used to perform enhanced optical measurements and generate local heating, thereby modifying the properties of the nanopore. Such a flexible approach also represents a valuable tool to investigate plasmon-driven photochemical reactions, and it can represent an important step toward the realization of new plasmonic devices.

2023 - Swarm of lightsail nanosatellites for Solar System exploration [Articolo su rivista]
Santi, Giovanni; Corso, Alain J.; Garoli, Denis; Lio, Giuseppe Emanuele; Manente, Marco; Favaro, Giulio; Bazzan, Marco; Piotto, Giampaolo; Andriolli, Nicola; Strambini, Lucanos; Pavarin, Daniele; Badia, Leonardo; Proietti Zaccaria, Remo; Lubin, Philip; Ragazzoni, Roberto; Pelizzo, Maria G.
abstract

2023 - Theoretical Analysis of Divalent Cation Effects on Aptamer Recognition of Neurotransmitter Targets [Articolo su rivista]
Douaki, Ali; Stuber, Annina; Hengsteler, Julian; Momotenko, Dmitry; Rogers, David M.; Rocchia, Walter; Hirst, Jonathan; Nakatsuka, Nako; Garoli, Denis
abstract

2023 - Transformable Plasmonic Helix with Swinging Gold Nanoparticles [Articolo su rivista]
Peil, Andreas; Zhan, Pengfei; Duan, Xiaoyang; Krahne, Roman; Garoli, Denis; M Liz-Marzán, Luis; Liu, Na
abstract

Control over multiple optical elements that can be dynamically rearranged to yield substantial three-dimensional structural transformations is of great importance to realize reconfigurable plasmonic nanoarchitectures with sensitive and distinct optical feedback. In this work, we demonstrate a transformable plasmonic helix system, in which multiple gold nanoparticles (AuNPs) can be directly transported by DNA swingarms to target positions without undergoing consecutive stepwise movements. The swingarms allow for programmable AuNP translocations in large leaps within plasmonic nanoarchitectures, giving rise to tailored circular dichroism spectra. Our work provides an instructive bottom-up solution to building complex dynamic plasmonic systems, which can exhibit prominent optical responses through cooperative rearrangements of the constituent optical elements with high fidelity and programmability.

2022 - Detection of small-sized DNA fragments in a glassy nanopore by utilization of CRISPR-Cas12a as a converter system [Articolo su rivista]
Zhang, Sm; Liu, My; Cui, Hf; Ziaee, Ma; Sun, Rw; Chen, Lt; Chen, Dq; Garoli, D; Wang, Jh
abstract

The fabrication of nanopores with a matched pore size, and the existence of multiple interferents make the reproducible detection of small-sized molecules by means of solid-state nanopores still challenging. A useful method to solve these problems is based on the detection of large DNA nanostructures related to the existence of small-sized targets. In particular, a DNA tetrahedron with a well-defined 3D nanostructure is the ideal candidate for use as a signal transducer. Here, we demonstrate the detection of an L1-encoding gene of HPV18 as a test DNA target sequence in a reaction buffer solution, where long single-stranded DNA linking DNA tetrahedra onto the surface of the magnetic beads is cleaved by a target DNA-Activated CRISPR-cas12 system. The DNA tetrahedra are subsequently released and can be detected by the current pulse in a glassy nanopore. This approach has several advantages: (1) one signal transducer can be used to detect different targets; (2) a glassy nanopore with a pore size much larger than the target DNA fragment can boost the tolerance of the contaminants and interferents which often degrade the performance of a nanopore sensor. This journal is

2022 - Emerging Approaches to DNA Data Storage: Challenges and Prospects [Articolo su rivista]
Doricchi, A.; Platnich, C. M.; Gimpel, A.; Horn, F.; Earle, M.; Lanzavecchia, G.; Cortajarena, A. L.; Liz-Marzan, L. M.; Liu, N.; Heckel, R.; Grass, R. N.; Krahne, R.; Keyser, U. F.; Garoli, D.
abstract

With the total amount of worldwide data skyrocketing, the global data storage demand is predicted to grow to 1.75 × 1014GB by 2025. Traditional storage methods have difficulties keeping pace given that current storage media have a maximum density of 103GB/mm3. As such, data production will far exceed the capacity of currently available storage methods. The costs of maintaining and transferring data, as well as the limited lifespans and significant data losses associated with current technologies also demand advanced solutions for information storage. Nature offers a powerful alternative through the storage of information that defines living organisms in unique orders of four bases (A, T, C, G) located in molecules called deoxyribonucleic acid (DNA). DNA molecules as information carriers have many advantages over traditional storage media. Their high storage density, potentially low maintenance cost, ease of synthesis, and chemical modification make them an ideal alternative for information storage. To this end, rapid progress has been made over the past decade by exploiting user-defined DNA materials to encode information. In this review, we discuss the most recent advances of DNA-based data storage with a major focus on the challenges that remain in this promising field, including the current intrinsic low speed in data writing and reading and the high cost per byte stored. Alternatively, data storage relying on DNA nanostructures (as opposed to DNA sequence) as well as on other combinations of nanomaterials and biomolecules are proposed with promising technological and economic advantages. In summarizing the advances that have been made and underlining the challenges that remain, we provide a roadmap for the ongoing research in this rapidly growing field, which will enable the development of technological solutions to the global demand for superior storage methodologies.

2022 - Enhanced Optical Spectroscopy for Multiplexed DNA and Protein-Sequencing with Plasmonic Nanopores: Challenges and Prospects [Articolo su rivista]
Li, W; Zhou, J; Maccaferri, N; Krahne, R; Wang, K; Garoli, D
abstract

2022 - High-Frequency Light Rectification by Nanoscale Plasmonic Conical Antenna in Point-Contact-Insulator-Metal Architecture [Articolo su rivista]
Mupparapu, R; Cunha, J; Tantussi, F; Jacassi, A; Summerer, L; Patrini, M; Giugni, A; Maserati, L; Alabastri, A; Garoli, D; Zaccaria, Rp
abstract

Numerous efforts have been undertaken to develop rectifying antennas operating at high frequencies, especially dedicated to light harvesting and photodetection applications. However, the development of efficient high frequency rectifying antennas has been a major technological challenge both due to a lack of comprehension of the underlying physics and limitations in the fabrication techniques. Various rectification strategies have been implemented, including metal-insulator-metal traveling-wave diodes, plasmonic nanogap optical antennas, and whisker diodes, although all show limited high-frequency operation and modest conversion efficiencies. Here a new type of rectifying antenna based on plasmonic carrier generation is demonstrated. The proposed structure consists of a resonant metallic conical nano-antenna tip in contact with the oxide surface of an oxide/metal bilayer. The conical shape allows for an improved current generation based on plasmon-mediated electromagnetic-to-electron conversion, an effect exploiting the nanoscale-tip contact of the rectifying antenna, and proportional to the antenna resonance and to the surface-electron scattering. Importantly, this solution provides rectification operation at 280 THz (1064 nm) with a 100-fold increase in efficiency compared to previously reported results. Finally, the conical rectifying antenna is also demonstrated to operate at 384 THz (780 nm), hence paving a way toward efficient rectennas toward the visible range.

2022 - Multilayers for directed energy accelerated lightsails [Articolo su rivista]
Santi, Giovanni; Favaro, Giulio; Corso, Alain J.; Lubin, Philip; Bazzan, Marco; Ragazzoni, Roberto; Garoli, Denis; Pelizzo, Maria G.
abstract

A lightsail accelerated via directed energy is a candidate technology to send a probe into the deep space in a time period compatible with human life. The light emitted by a ground-based large-aperture phased laser array is directed onto the lightsail to produce a thrust by transferring the momentum of the incident photons. Here we demonstrate that optimized multilayer structures allow ultralight spacecraft being accelerated by laser radiation pressure up to 20% of the light velocity, and eventually even above, as long as a compromise between efficiency and weight is achieved. Layer materials are selected to provide high reflectance in the Doppler-shifted laser wavelength range as well as high emissivity in the infrared, this last characteristic being required to survive to the temperature increase during the acceleration phase.Lightsails accelerated by ground-based laser arrays are a candidate technology to send probes into deep space in a timeframe compatible with human life. Here, an optimization study identifies the most promising multilayer structures that maximize propulsion efficiency, thermal stability, and mechanical stiffness.

2022 - Smart Approach for the Design of Highly Selective Aptamer-Based Biosensors [Articolo su rivista]
Douaki, Ali; Garoli, Denis; Inam, A K M Sarwar; Angeli, Martina Aurora Costa; Cantarella, Giuseppe; Rocchia, Walter; Wang, Jiahai; Petti, Luisa; Lugli, Paolo
abstract

Aptamers are chemically synthesized single-stranded DNA or RNA oligonucleotides widely used nowadays in sensors and nanoscale devices as highly sensitive biorecognition elements. With proper design, aptamers are able to bind to a specific target molecule with high selectivity. To date, the systematic evolution of ligands by exponential enrichment (SELEX) process is employed to isolate aptamers. Nevertheless, this method requires complex and time-consuming procedures. In silico methods comprising machine learning models have been recently proposed to reduce the time and cost of aptamer design. In this work, we present a new in silico approach allowing the generation of highly sensitive and selective RNA aptamers towards a specific target, here represented by ammonium dissolved in water. By using machine learning and bioinformatics tools, a rational design of aptamers is demonstrated. This "smart" SELEX method is experimentally proved by choosing the best five aptamer candidates obtained from the design process and applying them as functional elements in an electrochemical sensor to detect, as the target molecule, ammonium at different concentrations. We observed that the use of five different aptamers leads to a significant difference in the sensor's response. This can be explained by considering the aptamers' conformational change due to their interaction with the target molecule. We studied these conformational changes using a molecular dynamics simulation and suggested a possible explanation of the experimental observations. Finally, electrochemical measurements exposing the same sensors to different molecules were used to confirm the high selectivity of the designed aptamers. The proposed in silico SELEX approach can potentially reduce the cost and the time needed to identify the aptamers and potentially be applied to any target molecule.

2021 - Adaptive nanopores: A bioinspired label-free approach for protein sequencing and identification [Articolo su rivista]
Spitaleri, A; Garoli, D; Schutte, M; Lehrach, H; Rocchia, W; De Angelis, F
abstract

Single molecule protein sequencing would tremendously impact in proteomics and human biology and it would promote the development of novel diagnostic and therapeutic approaches. However, its technological realization can only be envisioned, and huge challenges need to be overcome. Major difficulties are inherent to the structure of proteins, which are composed by several different amino-acids. Despite long standing efforts, only few complex techniques, such as Edman degradation, liquid chromatography and mass spectroscopy, make protein sequencing possible. Unfortunately, these techniques present significant limitations in terms of amount of sample required and dynamic range of measurement. It is known that proteins can distinguish closely similar molecules. Moreover, several proteins can work as biological nanopores in order to perform single molecule detection and sequencing. Unfortunately, while DNA sequencing by means of nanopores is demonstrated, very few examples of nanopores able to perform reliable protein-sequencing have been reported so far. Here, we investigate, by means of molecular dynamics simulations, how a re-engineered protein, acting as biological nanopore, can be used to recognize the sequence of a translocating peptide by sensing the “shape” of individual amino-acids. In our simulations we demonstrate that it is possible to discriminate with high fidelity, 9 different amino-acids in a short peptide translocating through the engineered construct. The method, here shown for fluorescence-based sequencing, does not require any labelling of the peptidic analyte. These results can pave the way for a new and highly sensitive method of sequencing.[Figure not available: see fulltext.].

2021 - Dependence of the damage in optical metal/dielectric coatings on the energy of ions in irradiation experiments for space qualification [Articolo su rivista]
Pelizzo, M. G.; Corso, A. J.; Santi, G.; Hubner, R.; Garoli, D.; Doyle, D.; Lubin, P.; Cohen, A. N.; Erlikhman, J.; Favaro, G.; Bazzan, M.; Drobny, J.; Curreli, D.; Umansky, M.
abstract

Terrestrial accelerator facilities can generate ion beams which enable the testing of the resistance of materials and thin film coatings to be used in the space environment. In this work, a TiO 2/Al bi-layer coating has been irradiated with a He + beam at three different energies. The same flux and dose have been used in order to investigate the damage dependence on the energy. The energies were selected to be in the range 4–100 keV, in order to consider those associated to the quiet solar wind and to the particles present in the near-Earth space environment. The optical, morphological and structural modifications have been investigated by using various techniques. Surprisingly, the most damaged sample is the one irradiated at the intermediate energy, which, on the other hand, corresponds to the case in which the interface between the two layers is more stressed. Results demonstrate that ion energies for irradiation tests must be carefully selected to properly qualify space components.

2021 - Detecting COVID-19 from Breath: A Game Changer for a Big Challenge [Articolo su rivista]
Giovannini, G; Haick, H; Garoli, D
abstract

Coronavirus disease 2019 (COVID-19) is probably the most commonly heard word of the last 12 months. The outbreak of this virus (SARS-CoV-2) is strongly compromising worldwide healthcare systems, social behavior, and everyone's lives. The early diagnosis of COVID-19 and isolation of positive cases has proven to be fundamental in containing the spread of the infection. Even though the polymerase chain reaction (PCR) based methods remain the gold standard for SARS-CoV-2 detection, the urgent demand for rapid and wide-scale diagnosis precipitated the development of alternative diagnostic approaches. The millions of tests performed every day worldwide are still insufficient to achieve the desired goal, that of screening the population during daily life. Probably the most appealing approach to consistently monitor COVID-19 spread is the direct detection of SARS-CoV-2 from exhaled breath. For instance, the challenging incorporation of reliable, highly sensitive, and cost-efficient detection methods in masks could represent a breakthrough in the development of portable and noninvasive point-of-care diagnosis for COVID-19. In this perspective paper, we discuss the critical technical aspects related to the application of breath analysis in the diagnosis of viral infection. We believe that, if achieved, it could represent a game-changer in containing the pandemic spread.

2021 - Directional Plasmonic Excitation by Helical Nanotips [Articolo su rivista]
Singh, L; Maccaferri, N; Garoli, D; Gorodetski, Y
abstract

2021 - Electrolyte-gated carbon nanotube field-effect transistor-based biosensors: Principles and applications [Articolo su rivista]
Shkodra, B; Petrelli, M; Angeli, Mac; Garoli, D; Nakatsuka, N; Lugli, P; Petti, L
abstract

2021 - Magnetic control of particle trapping in a hybrid plasmonic nanopore [Articolo su rivista]
Maccaferri, N; Vavassori, P; Garoli, D
abstract

2021 - Nanoporous Metals: From Plasmonic Properties to Applications in Enhanced Spectroscopy and Photocatalysis [Articolo su rivista]
Koya, Alemayehu Nana; Zhu, Xiangchao; Ohannesian, Nareg; Yanik, A Ali; Alabastri, Alessandro; Proietti Zaccaria, Remo; Krahne, Roman; Shih, Wei-Chuan; Garoli, Denis
abstract

The field of plasmonics is capable of enabling interesting applications in different wavelength ranges, spanning from the ultraviolet up to the infrared. The choice of plasmonic material and how the material is nanostructured has significant implications for ultimate performance of any plasmonic device. Artificially designed nanoporous metals (NPMs) have interesting material properties including large specific surface area, distinctive optical properties, high electrical conductivity, and reduced stiffness, implying their potentials for many applications. This paper reviews the wide range of available nanoporous metals (such as Au, Ag, Cu, Al, Mg, and Pt), mainly focusing on their properties as plasmonic materials. While extensive reports on the use and characterization of NPMs exist, a detailed discussion on their connection with surface plasmons and enhanced spectroscopies as well as photocatalysis is missing. Here, we report on different metals investigated, from the most used nanoporous gold to mixed metal compounds, and discuss each of these plasmonic materials' suitability for a range of structural design and applications. Finally, we discuss the potentials and limitations of the traditional and alternative plasmonic materials for applications in enhanced spectroscopy and photocatalysis.

2021 - Photonic Cavity Effects for Enhanced Efficiency in Layered Perovskite-Based Light-Emitting Diodes [Articolo su rivista]
Lin, Lyy; Zaccaria, Rp; Garoli, D; Krahne, R
abstract

2021 - Plasmomechanical Systems: Principles and Applications [Articolo su rivista]
Koya, An; Cunha, J; Guerrero-Becerra, Ka; Garoli, D; Wang, T; Juodkazis, S; Zaccaria, Rp
abstract

Extreme confinement of electromagnetic waves and mechanical displacement fields to nanometer dimensions through plasmonic nanostructures offers unprecedented opportunities for greatly enhanced interaction strength, increased bandwidth, lower power consumption, chip-scale fabrication, and efficient actuation of mechanical systems at the nanoscale. Conversely, coupling mechanical oscillators to plasmonic nanostructures introduces mechanical degrees of freedom to otherwise static plasmonic structures thus giving rise to the generation of extremely large resonance shifts even for minor position changes. This nanoscale marriage of plasmonics and mechanics has led to the emergence of a new field of study called plasmomechanics that explores the fundamental principles underneath the coupling between light and plasmomechanical nanoresonators. In this review, both the fundamental concepts and applications of plasmomechanics as an emerging field of study are discussed. After an overview of the basic principles of plasmomechanics, the active tuning mechanisms of plasmonic nano-mechanical systems are extensively analyzed. Moreover, the recent developments on the practical implications of plasmomechanic systems for such applications as biosensing and infrared detection are highlighted. Finally, an outlook on the implications of the plasmomechanical nanosystems for development of point-of-care diagnostic devices that can help early and rapid detection of fatal diseases are forwarded.

2021 - Recent advances in plasmonic nanocavities for single-molecule spectroscopy [Articolo su rivista]
Maccaferri, N; Barbillon, G; Koya, An; Lu, Gw; Acuna, Gp; Garoli, D
abstract

2020 - Bio-Assisted Tailored Synthesis of Plasmonic Silver Nanorings and Site-Selective Deposition on Graphene Arrays [Articolo su rivista]
Giovannini, G; Ardini, M; Maccaferri, N; ZAMBRANA-PUYALTO, X; Panella, G; Angelucci, F; Ippoliti, R; Garoli, D; Deangelis, F
abstract

The spontaneous interaction between noble metals and biological scaffolds enables simple and cost-effective synthesis of nanomaterials with unique features. Here, plasmonic silver nanorings are synthesized on a ring-like protein, i.e., a peroxiredoxin (PRX), and used to assemble large arrays of functional nanostructures. The PRX drives the seeding growth of metal silver under wet reducing conditions, yielding nanorings with outer and inner diameters down to 28 and 3 nm, respectively. The obtained hybrid nanostructures are selectively deposited onto a solid-state 2D membrane made of graphene in order to prepare plasmonic nanopores. In particular, the interaction between the graphene and the PRX allows for the simple preparation of ordered arrays of plasmonic nanorings on a 2D-material membrane. This fabrication process can be finalized by drilling a nanometer scale pore in the middle of the ring. Fluorescence spectroscopic measurements in combination with numerical simulations demonstrate the plasmonic effects induced in the metallic nanoring cavity. The prepared nanopores represent one of the first examples of hybrid plasmonic nanopore structures integrated on a 2D-material membrane. The diameter of the nanopore and the atomically thick substrate make this proof-of-concept approach particularly interesting for nanopore-based technologies and applications such as next-generation sequencing and single-molecule detection.

2020 - Forster-Resonance Energy Transfer between Diffusing Molecules and a Functionalized Plasmonic Nanopore [Articolo su rivista]
Zambrana-Puyalto, X; Ponzellini, P; Maccaferri, N; Garoli, D
abstract

2020 - Galvanic Replacement Reaction as a Route to Prepare Nanoporous Aluminum for UV Plasmonics [Articolo su rivista]
Garoli, D; Schirato, A.; Giovannini, G.; Cattarin, S.; Ponzellini, P.; Calandrini, E.; Proietti Zaccaria, R.; Damico, F.; Pachetti, M.; Yang, W.; Jin, H-J.; Krahne, R.; Alabastri, A.
abstract

2020 - Mirrors for Space Telescopes: Degradation Issues [Articolo su rivista]
Garoli, Denis; Rodriguez De Marcos, Luis V.; Larruquert, Juan I.; Corso, Alain J.; Proietti Zaccaria, Remo; Pelizzo, Maria G.
abstract

Mirrors are a subset of optical components essential for the success of current and future space missions. Most of the telescopes for space programs ranging from earth observation to astrophysics and covering the whole electromagnetic spectrum from x-rays to far-infrared are based on reflective optics. Mirrors operate in diverse and harsh environments that range from low-earth orbit to interplanetary orbits and deep space. The operational life of space observatories spans from minutes (sounding rockets) to decades (large observatories), and the performance of the mirrors within the mission lifetime is susceptible to degrading, resulting in a drop in the instrument throughput, which in turn affects the scientific return. Therefore, the knowledge of potential degradation mechanisms, how they affect mirror performance, and how to prevent them is of paramount importance to ensure the long-term success of space telescopes. In this review, we report an overview of current mirror technology for space missions with a focus on the importance of the degradation and radiation resistance of coating materials. Special attention is given to degradation effects on mirrors for far and extreme UV, as in these ranges the degradation is enhanced by the strong absorption of most contaminants.

2020 - Multiplex discrimination of single amino acid residues in polypeptides by single SERS hot spot [Articolo su rivista]
Huang, J.; Mousavi, M.; Giovannini, G.; Zhao, Y.; Hubarevich, A.; Soler, M.; Rocchia, W.; Garoli, D; De Angelis, F.
abstract

2020 - Novel Plasmonic Nanocavities for Optical Trapping-Assisted Biosensing Applications [Articolo su rivista]
Koya, An; Cunha, J; Guo, Tl; Toma, A; Garoli, D; Wang, T; Juodkazis, S; Cojoc, D; Zaccaria, Rp
abstract

Plasmonic nanocavities have proved to confine electromagnetic fields into deep subwavelength volumes, implying their potentials for enhanced optical trapping and sensing of nanoparticles. In this review, the fundamentals and performances of various plasmonic nanocavity geometries are explored with specific emphasis on trapping and detection of small molecules and single nanoparticles. These applications capitalize on the local field intensity, which in turn depends on the size of plasmonic nanocavities. Indeed, properly designed structures provide significant local field intensity and deep trapping potential, leading to manipulation of nano-objects with low laser power. The relationship between optical trapping-induced resonance shift and potential energy of plasmonic nanocavity can be analytically expressed in terms of the intercavity field intensity. Within this framework, recent experimental works on trapping and sensing of single nanoparticles and small molecules with plasmonic nanotweezers are discussed. Furthermore, significant consideration is given to conjugation of optical tweezers with Raman spectroscopy, with the aim of developing innovative biosensors. These devices, which take the advantages of plasmonic nanocavities, will be capable of trapping and detecting nanoparticles at the single molecule level.

2020 - Particle trapping and beaming using a 3D nanotip excited with a plasmonic vortex [Articolo su rivista]
Liu, K; Maccaferri, N; Shen, Yf; Li, Xy; Zaccaria, Rp; Zhang, Xj; Gorodetski, Y; Garoli, D
abstract

Recent advances in nanotechnology have prompted the need for tools to accurately and noninvasively manipulate individual nano-objects. Among the possible strategies, optical forces have been widely used to enable nano-optical tweezers capable of trapping or moving a specimen with unprecedented accuracy. Here, we propose an architecture consisting of a nanotip excited with a plasmonic vortex enabling effective dynamic control of nanoparticles in three dimensions. The structure illuminated by a beam with angular momentum can generate an optical field that can be used to manipulate single dielectric nanoparticles. We demonstrate that it is possible to stably trap or push the particle from specific points, thus enabling a new, to the best of our knowledge, platform for nanoparticle manipulation. (C) 2020 Optical Society of America

2020 - Two-state switchable plasmonic tweezers for dynamic manipulation of nano-objects [Articolo su rivista]
Messina, Gc; Zambrana-Puyalto, X; Maccaferri, N; Garoli, D; De Angelis, F
abstract

In this work, we present a plasmonic platform capable of trapping nano-objects in two different spatial configurations. The switch between the two trapping states, localized on the tip and on the outer wall of a vertical gold nanochannel, can be activated by varying the focusing position of the excitation laser along the main axis of the nanotube. We show that the switching of the trapping site is induced by changes in the distribution of the electromagnetic field and of the trapping force. The "inner" and "outer" trapping states are characterized by a static and a dynamic behavior respectively, and their stiffness is measured by analyzing the positions of the trapped specimens as a function of time. In addition, we demonstrate that the stiffness of the static state is high enough to trap particles with diameter as small as 40 nm. These results show a simple, controllable way to generate a switchable two-state trapping regime, which could be used as a model for the study of dynamic trapping or as a mechanism for the development of nanofluidic devices.

2020 - Ultrafast all-optical switching enabled by epsilon-near-zero-tailored absorption in metal-insulator nanocavities [Articolo su rivista]
Kuttruff, J; Garoli, D; Allerbeck, J; Krahne, R; De Luca, A; Brida, D; Caligiuri, V; Maccaferri, N
abstract

Ultrafast control of light-matter interactions is fundamental in view of new technological frontiers of information processing. However, conventional optical elements are either static or feature switching speeds that are extremely low with respect to the time scales at which it is possible to control light. Here, we exploit the artificial epsilon-near-zero (ENZ) modes of a metal-insulator-metal nanocavity to tailor the linear photon absorption of our system and realize a nondegenerate all-optical ultrafast modulation of the reflectance at a specific wavelength. Optical pumping of the system at its high energy ENZ mode leads to a strong redshift of the low energy mode because of the transient increase of the local dielectric function, which leads to a sub-3-ps control of the reflectance at a specific wavelength with a relative modulation depth approaching 120%.

2019 - 3D nanoporous antennas as a platform for high sensitivity IR plasmonic sensing [Articolo su rivista]
Calandrini, E; Giovannini, G; Garoli, D
abstract

Nanoporous gold can be exploited as plasmonic material for enhanced spectroscopy both in the visible and in the near-infrared spectral regions. In particular, the peculiar morphology of such a substrate leads to a higher field confinement with respect to conventional plasmonic materials. This property can be exploited to achieve extremely high sensitivity to the changes in environmental conditions, making it an interesting tool for the development of sensors and biosensors. Here, we compared the sensitivity of a plasmonic resonator made of nanoporous gold with a similar structure made of homogeneous gold. To assess the enhanced sensitivity the same stoichiometric quantity of dielectric material was deposited via Atomic Layer Deposition onto the two considered structures. Experimental results proved the higher sensitivity was achievable using nanoporous gold. In particular. such 3D nanoporous structures can be proposed as a promising sensing platform in the near-infrared with a sensitivity over 4.000 nm/RIU. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

2019 - A hybrid metal–dielectric zero mode waveguide for enhanced single molecule detection [Articolo su rivista]
Zambrana-Puyalto, Xavier; Ponzellini, Paolo; Maccaferri, Nicolò; Tessarolo, Enrico; Pelizzo, Maria G.; Zhang, Weidong; Barbillon, Grégory; Lu, Guowei; Garoli, Denis
abstract

We fabricated hybrid metal-dielectric nanoslots and measured their optical response at three different wavelengths. The nanostructure is fabricated on a bilayer film formed by the sequential deposition of silicon and gold on a transparent substrate. The optical characterization is done via fluorescence spectroscopy measurements. We characterized the fluorescence enhancement, as well as the lifetime and the detection volume reduction for each wavelength. We observe that the hybrid metal-dielectric nanoslots behave as enhanced zero mode waveguides in the near-infrared spectral region. Their detection volume is such that they can perform enhanced single-molecule detection at tens of mu M. We compared their behavior with that of a golden ZMW, and we demonstrated that the dielectric silicon layer improves both the optical performance and the stability of the device.

2019 - Effect of Ni Doping on the MoS2 Structure and Its Hydrogen Evolution Activity in Acid and Alkaline Electrolytes [Articolo su rivista]
Mosconi, Dario; Till, Paul; Calvillo, Laura; Kosmala, Tomasz; Garoli, Denis; Debellis, Doriana; Martucci, Alessandro; Agnoli, Stefano; Granozzi, Gaetano
abstract

2019 - Electrophoretic Deposition of WS2 Flakes on Nanoholes Arrays—Role of Used Suspension Medium [Articolo su rivista]
Mosconi, D; Giovannini, G; Maccaferri, N; Serri, M; Agnoli, S; Garoli, D
abstract

2019 - Metallic Nanoporous Aluminum-Magnesium Alloy for UV-Enhanced Spectroscopy [Articolo su rivista]
Ponzellini, P; Giovannini, G; Cattarin, S; Zaccaria, Rp; Marras, S; Prato, M; Schirato, A; D'Amico, F; Calandrini, E; De Angelis, F; Yang, W; Jin, Hj; Alabastri, A; Garoli, D
abstract

We report the first preparation of nanoporous Al-Mg alloy films by selective dissolution of Mg from a Mg-rich alloy AlxMg1-x We show how to tune the stoichiometry, the porosity, and the oxide contents in the final film by modulating the starting ratio between Al and Mg and the dealloying procedure. The obtained porous metal can be exploited for enhanced UV spectroscopy. In this respect, we experimentally demonstrate its efficacy in enhancing fluorescence and surface Raman scattering for excitation wavelengths of 360 and 257 nm, respectively. Finally, we numerically show the superior performance of the nanoporous Al-Mg alloy in the UV range when compared to equivalent porous gold structures. The large area to surface ratio provided by this material makes it a promising platform for a wide range of applications in UV/deep-UV plasmonics.

2019 - Nanoporous gold metamaterials for high sensitivity plasmonic sensing [Articolo su rivista]
Garoli, D; Calandrini, E; Giovannini, G; Hubarevich, A; Caligiuri, V; Angelis, F
abstract

Surface plasmon resonance sensors are a well-established class of sensors that includes a very large variety of materials and detection schemes. However, the development of portable devices is still challenging due to the intrinsic complexity of the optical excitation/detection schemes. This work shows that nanoporous gold (NPG) films can overcome the said limitations by providing an excellent sensitivity without the need for sophisticated fabrication approaches and/or optical setups. The sensing mechanism is related to the co-localization of optical energy and analytes in the pores fostering an enhanced light-matter coupling. As a result, when molecules are adsorbed in the pores, the NPG film shows a significant spectral shift of the effective plasma frequency and an abrupt change of the reflectivity. By monitoring the reflectivity in the spectral region close to the plasma frequency (namely the plasma edge), it is possible to detect the analyte. Through a series of experiments, the authors demonstrated a sensitivity exceeding 15 000 nm per RIU in the near infrared range comparable with the state of the art of plasmonic metamaterials.

2019 - Nanoscale thermal gradients activated by antenna-enhanced molecular absorption in the mid-infrared [Articolo su rivista]
Mancini, A; Giliberti, V; Alabastri, A; Calandrini, E; De Angelis, F; Garoli, D; Ortolani, M
abstract

We investigate local heat generation by molecules at the apex of polymer-embedded vertical antennas excited at resonant midinfrared wavelengths, exploiting the surface enhanced infrared absorption effect. The embedding of vertical nanoantennas in a non-absorbing polymer creates thermal isolation between the apical hotspot and the heat sink represented by the substrate. Vibrational mid-infrared absorption by strongly absorbing molecules located at the antenna apex then generates nanoscale temperature gradients at the surface. We imaged the thermal gradients by using a nano-photothermal expansion microscope, and we found values up to 10K/mu m in conditions where the radiation wavelength resonates with both the molecule vibrations and the plasmonic mode of the antennas. Values up to 1000 K/mu m can be foreseen at maximum quantum cascade laser power. The presented system provides a promising thermoplasmonic platform for antenna-assisted thermophoresis and resonant mid-infrared photocatalysis.

2019 - Plasmonic Nanopores for Single-Molecule Detection and Manipulation: Toward Sequencing Applications [Articolo su rivista]
Garoli, D; Yamazaki, H; Maccaferri, N; Wanunu, M
abstract

Solid-state nanopore-based sensors are promising platforms for next-generation sequencing technologies, featuring label-free single-molecule sensitivity, rapid detection, and low-cost manufacturing. In recent years, solid-state nanopores have been explored due to their miscellaneous fabrication methods and their use in a wide range of sensing applications. Here, we highlight a novel family of solid-state nanopores which have recently appeared, namely plasmonic nanopores. The use of plasmonic nanopores to engineer electromagnetic fields around a nanopore sensor allows for enhanced optical spectroscopies, local control over temperature, thermophoresis of molecules and ions to/from the sensor, and trapping of entities. This Mini Review offers a comprehensive understanding of the current state-of-the-art plasmonic nano pores for single-molecule detection and biomolecular sequencing applications and discusses the latest advances and future perspectives on plasmonic nano-porebased technologies.

2019 - Plasmonic nanopore prepared on MoS2 membrane - hybrid nanostructures based on site selective deposition [Relazione in Atti di Convegno]
Mosconi, D; Miele, E; Giovannini, G; Jacassi, A; Maccaferri, N; Garoli, D
abstract

2019 - Pump-probe spectroscopy study of ultrafast temperature dynamics in nanoporous gold [Articolo su rivista]
Ortolani, M; Mancini, A; Budweg, A; Garoli, D; Brida, D; de Angelis, F
abstract

We explore the influence of the nanoporous structure on the thermal relaxation of electrons and holes excited by ultrashort laser pulses (similar to 7 fs) in thin gold films. Plasmon decay into hot electron-hole pairs results in the generation of a Fermi-Dirac distribution thermalized at a temperature T-e higher than the lattice temperature T-1. The relaxation times of the energy exchange between electrons and lattice, here measured by pump-probe spectroscopy, is slowed down by the nanoporous structure, resulting in much higher peak T-e than for bulk gold films. The electron-phonon coupling constant and the Debye temperature are found to scale with the metal filling factor f and a two-temperature model reproduces the data. The results open the way for electron temperature control in metals by engineering of the nanoporous geometry.

2019 - SERS discrimination of single DNA bases in single oligonucleotides by electro-plasmonic trapping [Articolo su rivista]
Huang, Jian-An; Mousavi, Mansoureh Z; Zhao, Yingqi; Hubarevich, Aliaksandr; Omeis, Fatima; Giovannini, Giorgia; Schütte, Moritz; Garoli, Denis; De Angelis, Francesco
abstract

Surface-enhanced Raman spectroscopy (SERS) sensing of DNA bases by plasmonic nanopores could pave a way to novel methods for DNA analyses and new generation single-molecule sequencing platforms. The SERS discrimination of single DNA bases depends critically on the time that a DNA strand resides within the plasmonic hot spot. In fact, DNA molecules flow through the nanopores so rapidly that the SERS signals collected are not sufficient for single-molecule analysis. Here, we report an approach to control the residence time of molecules in the hot spot by an electro-plasmonic trapping effect. By directly adsorbing molecules onto a gold nanoparticle and then trapping the single nanoparticle in a plasmonic nanohole up to several minutes, we demonstrate single-molecule SERS detection of all four DNA bases as well as discrimination of single nucleobases in a single oligonucleotide. Our method can be extended easily to label-free sensing of single-molecule amino acids and proteins.

2019 - Site-Selective Integration of MoS2 Flakes on Nanopores by Means of Electrophoretic Deposition [Articolo su rivista]
Mosconi, D.; Giovannini, Gabriele; Jacassi, A.; Ponzellini, P.; Maccaferri, N.; Vavassori, P.; Serri, M.; Dipalo, M.; Darvill, D.; DE ANGELIS, Francesco; Agnoli, S.; Garoli, D.
abstract

Here, we propose an easy method for site-selective deposition of two-dimensional (2D) material flakes onto nanoholes by means of electrophoretic deposition. This method can be applied to both simple flat nanostructures and complex three-dimensional structures incorporating nanoholes. The deposition method is here used for the decoration of large ordered arrays of plasmonic structures with either a single or few layers of MoS2. In principle, the plasmonic field generated by the nanohole can significantly interact with the 2D layer leading to enhanced light–material interaction. This makes our platform an ideal system for hybrid 2D material/plasmonic investigations. The engineered deposition of 2D materials on plasmonic nanostructures is useful for several important applications such as enhanced light emission, strong coupling, hot-electron generation, and 2D material sensors.

2019 - Site-selective functionalization of plasmonic nanopores for enhanced fluorescence emission rate and Forster resonance energy transfer [Articolo su rivista]
Zambrana-Puyalto, X; Maccaferri, N; Ponzellini, P; Giovannini, G; De Angelis, F; Garoli, D
abstract

In this work, we use a site-selective functionalization strategy to decorate plasmonic nanopores with fluorescent dyes. Using an easy and robust fabrication method, we manage to build plasmonic rings on top of dielectric nanotubes with different inner diameters. The modulation of the dimension of the nanopores allows us to tailor their field confinement and their Purcell factor in the visible spectral range. In order to investigate how the changes in geometry influence the fluorescence emission rate efficiency, thiol-conjugated dyes are anchored on the plasmonic ring, thus forming a functional nanopore. We study the lifetime of ATTO 520 and ATTO 590 attached in two different configurations: single dye and FRET pair. For the single dye configuration, we observe that the lifetime of both single dyes decreases as the size of the nanopore is reduced. The smallest nanopores yield an experimental Purcell factor of 6. For the FRET pair configuration, we measure two regimes. For large nanopore sizes, the FRET efficiency remains constant. Whereas for smaller sizes, the FRET efficiency increases from 30 up to 45% with a decrease of the nanopore size. These findings, which have been supported by numerical simulations, may open new perspectives towards energy transfer engineering in plasmonic nanopores with potential applications in photonics and biosensing, in particular in single-molecule detection and sequencing.

2018 - Coreactant electrochemiluminescence at nanoporous gold electrodes [Articolo su rivista]
Villani, E; Valenti, G; Marcaccio, M; Mattarozzi, L; Barison, S; Villani, E; Valenti, G; Marcaccio, M; Mattarozzi, L; Barison, S; Garoli, D; Cattarin, S; Paolucci, F; Garoli, D; Cattarin, S; Paolucci, F
abstract

The electrochemiluminescence (ECL) performances were comparatively investigated at flat and nanoporous gold (NPG) electrodes of different thicknesses (120 and 200 nm) and roughness factors (fr). The phenomena were studied using either tripropylamine (TPrA) or peroxydisulfate (S2O82-) as sacrificial coreactant and Ruthenium (II)- tris(2,2'-bipyridine) as emitting species. The experiments performed using TPrA showed, at first glance, a linear dependence of the ECL emission with respect to the effective surface area of the NPG electrodes. However, ECL signals were not stable in the measuring conditions, presumably due to amine absorption on the metal surface, leading to electrode corrosion and modification of the surface morphology. The experiments made using peroxydisulfate as coreactant provided conversely a stable ECL response, about proportional to the effective electrode surface area, in the considered range of thicknesses. (C) 2018 Elsevier Ltd. All rights reserved.

2018 - Fractal plasmonic metamaterial with tunable properties in the near-infrared [Relazione in Atti di Convegno]
Calandrini, E; Ortolani, M; Cattarin, S; Ponzellini, P; Perotto, S; Toma, A; Garoli, D
abstract

2018 - Fractal-Like Plasmonic Metamaterial with a Tailorable Plasma Frequency in the near-Infrared [Articolo su rivista]
Garoli, D; Calandrini, E; Bozzola, A; Toma, A; Cattarin, S; Ortolani, M; De Angelis, F
abstract

In this work, we show that modulating the fractal dimension of nanoporous gold allows its effective dielectric response to be tailored over a wide spectral range of infrared wavelengths. In particular, the plasma edge and effective plasma frequency depend linearly on the fractal dimension, which can be controlled by varying the pore and ligament sizes. Importantly, the fractal porous metal exhibits superior plasmonic properties compared to its bulk counterpart. These properties, combined with a longer skin depth on the order of 100-200 nm, enables the penetration of optical energy deep into the nanopores where molecules can be loaded, thus, achieving more effective light-matter coupling. These findings may open new pathways to engineering the optical response of fractal-like or self-similar metamaterials without the need for sophisticated lithographic patterning.

2018 - Helical light emission from plasmonic vortices via magnetic tapered tip [Articolo su rivista]
Maccaferri, N; Gorodetski, Y; Garoli, D
abstract

We investigate an architecture where a plasmonic vortex excited in a gold surface propagates on an adiabatically tapered magnetic tip and detaches to the far-field while carrying a well-defined optical angular momentum. We analyze the out-coming light and show that, despite generally high losses of flat magnetic surface, our 3D structure exhibits high energy throughput. Moreover, we show that once a magneto-optical activity is activated inside the magnetic tip a modulation of the total power transmittance is possible.

2018 - Hybrid plasmonic nanostructures based on controlled integration of MoS2 flakes on metallic nanoholes [Articolo su rivista]
Garoli, D; Mosconi, D; Miele, E; Maccaferri, N; Ardini, M; Giovannini, G; Dipalo, M; Agnoli, S; De Angelis, F
abstract

Here, we propose an easy and robust strategy for the versatile preparation of hybrid plasmonic nanopores by means of controlled deposition of single flakes of MoS2 directly on top of metallic holes. The device is realized on silicon nitride membranes and can be further refined by TEM or FIB milling to achieve the passing of molecules or nanometric particles through a pore. Importantly, we show that the plasmonic enhancement provided by the nanohole is strongly accumulated in the 2D nanopore, thus representing an ideal system for single-molecule sensing and sequencing in a flow-through configuration. Here, we also demonstrate that the prepared 2D material can be decorated with metallic nanoparticles that can couple their resonance with the nanopore resonance to further enhance the electromagnetic field confinement at the nanoscale level. This method can be applied to any gold nanopore with a high level of reproducibility and parallelization; hence, it can pave the way to the next generation of solid-state nanopores with plasmonic functionalities. Moreover, the controlled/ordered integration of 2D materials on plasmonic nanostructures opens a pathway towards new investigation of the following: enhanced light emission; strong coupling from plasmonic hybrid structures; hot electron generation; and sensors in general based on 2D materials.

2018 - Live Intracellular Biorthogonal Imaging by Surface Enhanced Raman Spectroscopy using Alkyne-Silver Nanoparticles Clusters [Articolo su rivista]
Ardini, M; Huang, Ja; Sanchez, Cs; Mousavi, Mz; Caprettini, V; Maccaferri, N; Melle, G; Bruno, G; Pasquale, L; Garoli, D; De Angelis, F
abstract

Live intracellular imaging is a valuable tool in modern diagnostics and pharmacology. Surface Enhanced Raman Spectroscopy (SERS) stands out as a non-destructive and multiplexed technique, but intracellular SERS imaging still suffers from interfering background from endogenous components. Here we show the assembly of small colloidal SERS probes with Raman signal in the cell-silent window of 1800-2900 cm(-1) for biorthogonal intracellular SERS imaging of dopamine that was undistinguishable from the endogenous cell background. By linking colloidal silver nanoparticles with alkyne-dopamine adducts, clusters are formed by 2-6 nanoparticles spaced by tight interparticle gaps that exhibited high electric field enhancement and strong SERS signals of alkyne and dopamines. Due to the cell-silent signals of the alkyne, intracellular in-vitro Raman imaging shows that the dopamines on the internalized clusters remain distinguishable across the cytoplasm with good spatial resolution. Our method can be a general-purpose method for real-time imaging of biomolecules, such as proteins, peptides, DNA and drugs.

2018 - Optimizing FRET on Aluminum Surfaces via Controlled Attachment of Fluorescent Dyes [Articolo su rivista]
Petreto, A; Dos Santos, Mc; Lefebvre, O; Dos Santos, Gr; Ponzellini, P; Garoli, D; De Angelis, F; Ammar, M; Hildebrandt, N
abstract

Forster resonance energy transfer (FRET) between fluorescent dyes is a frequently applied technique for analyzing concentrations and conformations of biomolecules. Optimizing FRET by controlled dye-surface functionalization is an important requirement to develop sensors based on surface-biomolecule interactions. Here, we investigate the silanization of silica with aminosilanes ((3-aminopropyl)-triethoxysilane, APTES) and their subsequent functionalization with commercial organic fluorophores (ATTO-550 and ATTO-647N) for controlling the fluorescence intensity and FRET interaction between the dyes. Owing to the growing application of aluminum in plasmonics and the possibility to enhance FRET with aluminum nanostructures, we used plasma-enhanced atomic layer deposition (PEALD) to cover aluminum layers with thin silica coatings (similar to 4 nm) as a prototypical system to apply and characterize our controlled APTES-dye functionalization procedure. Detailed spectroscopic and fluorescence imaging analyses were used to optimize the silanization, control the dye functionalization, and rule out aluminum-related fluorescence quenching. The optimized protocol was then used to attach both dyes on the same surface, which enabled efficient FRET. As PEALD is in principle applicable to different substrates, we believe that our controlled FRET-functionalization approach may be adaptable to many other surfaces and nanostructures and may become a useful tool to advance the development of fluorescence biosensors.

2018 - Plasmonic meta-electrodes allow intracellular recordings at network level on high-density CMOS-multi-electrode arrays [Articolo su rivista]
Dipalo, M; Melle, G; Lovato, L; Jacassi, A; Santoro, F; Caprettini, V; Schirato, A; Alabastri, A; Garoli, D; Bruno, G; Tantussi, F; De Angelis, F
abstract

The ability to monitor electrogenic cells accurately plays a pivotal role in neuroscience, cardiology and cell biology. Despite pioneering research and long-lasting efforts, the existing methods for intracellular recording of action potentials on the large network scale suffer limitations that prevent their widespread use. Here, we introduce the concept of a meta-electrode, a planar porous electrode that mimics the optical and biological behaviour of three-dimensional plasmonic antennas but also preserves the ability to work as an electrode. Its synergistic combination with plasmonic optoacoustic poration allows commercial complementary metal-oxide semiconductor multi-electrode arrays to record intracellular action potentials in large cellular networks. We apply this approach to measure signals from human-induced pluripotent stem cell-derived cardiac cells, rodent primary cardiomyocytes and immortalized cell types and demonstrate the possibility of non-invasively testing a variety of relevant drugs. Due to its robustness and easiness of use, we expect the method will be rapidly adopted by the scientific community and by pharmaceutical companies.

2018 - Plasmonic zero mode waveguide for highly confined and enhanced fluorescence emission [Articolo su rivista]
Ponzellini, P; Zambrana-Puyalto, X; Maccaferri, N; Lanzano, L; De Angelis, F; Garoli, D
abstract

We fabricate a plasmonic nanoslot that is capable of performing enhanced single molecule detection at 10 mu M concentrations. The nanoslot combines the tiny detection volume of a zero-mode waveguide and the field enhancement of a plasmonic nanohole. The nanoslot is fabricated on a bi-metallic film formed by the sequential deposition of gold and aluminum on a transparent substrate. Simulations of the structure yield an average near-field intensity enhancement of two orders of magnitude at its resonant frequency. Experimentally, we measure the fluorescence stemming from the nanoslot and compare it with that of a standard aluminum zero-mode waveguide. We also compare the detection volume for both structures. We observe that while both structures have a similar detection volume, the nanoslot yields a 25-fold fluorescence enhancement.

2018 - Thermoplasmonic Effect of Surface-Enhanced Infrared Absorption in Vertical Nanoantenna Arrays [Articolo su rivista]
Mancini, A; Giliberti, V; Alabastri, A; Calandrini, E; De Angelis, F; Garoli, D; Ortolani, M
abstract

Thermoplasmonics is a method for increasing temperature remotely using focused visible or infrared laser beams interacting with plasmonic nanopartides. Here, local heating induced by mid-infrared quantum cascade laser illumination of vertical gold-coated nanoanterma arrays embedded into polymer layers is investigated by infrared nanospectroscopy and electromagnetic/thermal simulations. Nanoscale thermal hotspot images are obtained by a phototherrnal scanning probe microscopy technique with laser illumination wavelength tuned at the different plasmonic resonances of the arrays. Spectral analysis indicates that both Joule heating by the metal antennas and surface-enhanced-infrared absorption (SEIRA) by the polymer molecules located in the apical hotspots of the antennas are responsible for thermoplasmonic resonances, that is, for strong local temperature increase. At odds with more conventional planar nanoantennas, the vertical antenna structure enables thermal decoupling of the hotspot at the antenna apex from the heat sink constituted by the solid substrate. The temperature increase was evaluated by quantitative comparision of data obtained with the photothermal expansion technique to the results of electromagnetic/thermal simulations. In the case of strong SEIRA by the C=O bond of poly-methylmethacrylate at 1730 cm(-1), for focused mid-infrared laser power of about 20 mW, the evaluated order of magnitude of the nanoscale temperature increase is of 10 K. This result indicates that temperature increases of order of hundreds of K may he attainable with full mid-infrared laser power tuned at specific molecule vibrational fingerprints,

2017 - Boosting infrared energy transfer in 3D nanoporous gold antennas [Articolo su rivista]
Garoli, D; Calandrini, E; Bozzola, A; Ortolani, M; Cattarin, S; Barison, S; Toma, A; De Angelis, F
abstract

The applications of plasmonics to energy transfer from free-space radiation to molecules are currently limited to the visible region of the electromagnetic spectrum due to the intrinsic optical properties of bulk noble metals that support strong electromagnetic field confinement only close to their plasma frequency in the visible/ultraviolet range. In this work, we show that nanoporous gold can be exploited as a plasmonic material for the mid-infrared region to obtain strong electromagnetic field confinement, co-localized with target molecules into the nanopores and resonant with their vibrational frequency. The effective optical response of the nanoporous metal enables the penetration of optical fields deep into the nanopores, where molecules can be loaded thus achieving a more efficient light-matter coupling if compared to bulk gold. In order to realize plasmonic resonators made of nanoporous gold, we develop a nanofabrication method based on polymeric templates for metal deposition and we obtain antenna arrays resonating at mid-infrared wavelengths selected by design. We then coat the antennas with a thin (3 nm) silica layer acting as the target dielectric layer for optical energy transfer. We study the strength of the light-matter coupling at the vibrational absorption frequency of silica at 1240 cm(-1) through the analysis of the experimental Fano lineshape that is benchmarked against identical structures made of bulk gold. The boost in the optical energy transfer from free-space mid-infrared radiation to molecular vibrations in nanoporous 3D nanoantenna arrays can open new application routes for plasmon-enhanced physical-chemical reactions.

2017 - Efficient OAM generation at the nanoscale level by means of plasmonic vortex lens [Relazione in Atti di Convegno]
Gorodetsky, Y; Zilio, P; Ponzellini, P; Ardini, M; ZAMBRANA-PUYALYO, X; Jacassi, A; Calandrini, E; Garoli, D
abstract

2017 - Helicity locking of chiral light emitted from a plasmonic nanotaper [Articolo su rivista]
Garoli, D; Zilio, P; De Angelis, F; Gorodetski, Y
abstract

Surface plasmon waves carry an intrinsic transverse spin, which is locked to its propagation direction. Apparently, when a singular plasmonic mode is guided on a conic surface this spin-locking may lead to a strong circular polarization of the far-field emission. Specifically, a plasmonic vortex excited on a flat metal surface propagates on an adiabatically tapered gold nanocone where the mode accelerates and finally beams out from the tip apex. The helicity of this beam is shown to be single-handed and stems solely from the transverse spin-locking of the helical plasmonic wave-front. We present a simple geometric model that fully predicts the emerging light spin in our system. Finally, we experimentally demonstrate the helicity-locking phenomenon by using accurately fabricated nanostructures and confirm the results with the model and numerical data.

2017 - In situ real-time investigation of hydrogen-induced structural and optical changes in palladium thin films [Articolo su rivista]
Corso, ALAIN JODY; Martucci, Alessandro; Bazzan, Marco; Zuppella, Paola; Garoli, Denis; Pelizzo, Maria G.
abstract

2017 - Magnetoplasmonic control of plasmonic vortices [Articolo su rivista]
Maccaferri, N; Gorodetski, Y; Toma, A; Zilio, P; De Angelis, F; Garoli, D
abstract

We theoretically investigate the generation of far-field propagating optical beams with a desired orbital angular momentum by using an archetypical magnetoplasmonic tip surrounded by a gold spiral slit. The use of a magnetic material can lead to important implications once magneto-optical activity is activated through the application of an external magnetic field. The physical model and the numerical study presented here introduce the concept of magnetically tunable plasmonic vortex lens, namely a magnetoplasmonic vortex lens, which ensures a tunable selectivity in the polarization state of the generated nanostructured beam. The presented system provides a promising platform for a localized excitation of plasmonic vortices followed by their beaming in the far-field with an active modulation of both light's transmission and helicity. Published by AIP Publishing.

2017 - Multilayer coatings for multiband spectral observations [Relazione in Atti di Convegno]
Zuccon, S.; Garoli, D.; Pelizzo, M. G.; Nicolosi, P.; Fineschi, S.; Windt, D.
abstract

2017 - Nanoporous Gold decorated with silver nanoparticle as large area efficient SERS substrate [Relazione in Atti di Convegno]
Ardini, M; Huang, J; Sanchez, C; Ponzellini, P; Maccaferri, N; Jacassi, A; Cattarin, S; Calandrini, E; Garoli, D
abstract

2016 - Beaming of Helical Light from Plasmonic Vortices via Adiabatically Tapered Nanotip [Articolo su rivista]
Garoli, D; Zilio, P; Gorodetski, Y; Tantussi, F; De Angelis, F
abstract

We demonstrate the generation of far-field propagating optical beams with a desired. Orbital angular momentum by using a smooth optical-mode transformation between a plasmonic vortex and free-space Laguerre Gaussian modes. This is obtained by means of an adiabatically tapered gold tip surrounded by a spiral slit. The proposed physical model, backed up by the numerical study, brings about an optimized structure: that is fabricated by using a highly reproducible secondary electron lithography technique. Optical measurements of the structure excellently agree with the theoretically predicted far-field distributions. This architecture provides a unique platform for a localized excitation of plasmonic vortices followed by its beaming.

2016 - Directly nanopatternable nanoporous titania - Application to cell growth engineering [Articolo su rivista]
Garoli, Denis; Lovato, L.; DELLA GIUSTINA, Gioia; Oliverio, M.; Francardi, M.; Zanchetta, Erika; Brusatin, Giovanna; De Angelis, F.
abstract

Titanium dioxide (TiO2) is a well-known biocompatible material with important applications in many fields of biomedicine. Here we show our results on the development of a new TiO2 based sol-gel system that can act as negative tone resist for both ultraviolet (UV) and electron beam (EB) lithographies. The system allows the direct patterning of high resolution structures (down to 40 nm). Moreover, it allows the preparation of nanopatterned nanoporous TiO2 simply by changing the conditions of resist development. The presented system can be used as functional tool for the systernatic investigation of cell behavior with respect to a complex topographic texture of the substrate (cell guidance). TiO2 structures of different dimensions, geometries and nanoporosity, whose size ranges from a few hundred to a few tens nanometer, are obtained after UV and/or EB lithography. The adhesion of different cell lines, i.e., human osteosarcoma (HOS) and neuroblastoma (N2A), on the patterns is assessed and our results show that cells have a preference for TiO2 patterns with respect to glass.

2016 - In situ study of structural and optical properties of Pd thin film during hydrogen exposure [Relazione in Atti di Convegno]
Pelizzo, MARIA-GUGLIELMINA; Corso, ALAIN JODY; Bazzan, Marco; Zuppella, Paola; Garoli, Denis; Martucci, Alessandro
abstract

2016 - Modified three-dimensional nanoantennas for infrared hydrogen detection [Articolo su rivista]
Cerea, Andrea; Garoli, Denis; Zilio, Pierfrancesco; Dipalo, Michele; Calandrini, Eugenio; Jacassi, Andrea; Caprettini, Valeria; Carrara, Angelica; Pelizzo, Maria G.; De Angelis, Francesco
abstract

Localized surface plasmon resonances (LSPRs), which are associated with collective oscillations of free electrons at a metal-dielectric interface, can generate large field confinement in an extremely small volume. This optical phenomenon is ideal for plasmonic sensing. Bearing this in mind, we combine the 3D nanoantennas design, developed recently by our group, with galvanic gold deposition to exploit LSPRs in the infrared spectral region. Here we report our theoretical and experimental results on this particular design. Moreover, our design comprises the use of a thin layer of Palladium, a well-known metal used for hydrogen sensing. The nanoantenna arrays are then applied to hydrogen detection using a mixture of 2% hydrogen in nitrogen atmosphere. The proposed device can fulfill all the requirements of conventional devices, combining easy and reproducible fabrication techniques with high sensitivity.

2016 - Optical vortex beam generator at nanoscale level [Articolo su rivista]
Garoli, D; Zilio, P; Gorodetski, Y; Tantussi, F; De Angelis, F
abstract

Optical beams carrying orbital angular momentum (OAM) can find tremendous applications in several fields. In order to apply these particular beams in photonic integrated devices innovative optical elements have been proposed. Here we are interested in the generation of OAM-carrying beams at the nanoscale level. We design and experimentally demonstrate a plasmonic optical vortex emitter, based on a metal-insulator-metal holey plasmonic vortex lens. Our plasmonic element is shown to convert impinging circularly polarized light to an orbital angular momentum state capable of propagating to the far-field. Moreover, the emerging OAM can be externally adjusted by switching the handedness of the incident light polarization. The device has a radius of few micrometers and the OAM beam is generated from subwavelength aperture. The fabrication of integrated arrays of PVLs and the possible simultaneous emission of multiple optical vortices provide an easy way to the large-scale integration of optical vortex emitters for wide-ranging applications.

2015 - Directly patternable high refractive index ferroelectric sol-gel resist [Articolo su rivista]
Garoli, Denis; DELLA GIUSTINA, Gioia
abstract

The development of a ferroelectric negative tone solegel resist for Ultraviolet (UV) and Electron Beam (EB) lithography is presented. A new system based on Lead Zirconate Titanate (PZT, with formula PbZr0.52Ti0.48O3) was synthesized by solegel method. The lithographic performances were investigated and several structures spanning from the micron range down to less than 50 nm have been achieved by UV and EB lithography. The system interaction with UV light and Electron beam was thoroughly characterized by FT-IT spectroscopy. The exposed PZT was annealed at high temperatures in order to study the crystalline phase evolution, the optical constants values and stability of patterned structures. After exposure and annealing, the refractive index of the material can vary from 1.68 up to 2.33 (@400 nm), while the ferroelectric behaviour seems to be maintained after high temperature annealing. These results suggest a possible application of PZT resist not only as ferroelectric but also as nanopatternable high refractive index material. Moreover, direct nanopatterning by means of Focused Ion Beam (FIB) lithography was verified and the potentiality for the preparation of high aspect ratio hollow nanostructures will be presented.

2015 - Nanoporous gold leaves: Preparation, optical characterization and plasmonic behavior in the visible and mid-infrared spectral regions [Articolo su rivista]
Garoli, Denis; Ruffato, Gianluca; Zilio, Pierfrancesco; Calandrini, Eugenio; De Angelis, Francesco; Romanato, Filippo; Cattarin, Sandro
abstract

2015 - Nanoporous gold leaves: preparation, optical characterization, and biosensing capabilities [Relazione in Atti di Convegno]
Ruffato, Gianluca; Garoli, Denis; Calandrini, Eugenio; Zilio, Pierfrancesco; De Angelis, Francesco; Romanato, Filippo; Cattarin, Sandro
abstract

2015 - Sub-wavelength confinement of the orbital angular momentum of light probed by plasmonic nanoantennae resonances [Relazione in Atti di Convegno]
Carli, Marta; Zilio, Pierfrancesco; Garoli, Denis; Giorgis, Valentina; Ruffato, Gianluca; Romanato, Filippo
abstract

We study how the Orbital Angular Momentum (OAM) of a plasmonic vortex (a surface plasmon-polariton with nonzero topological charge) can be probed by the Localized Surface Plasmon Resonance (LSPR) of rod-shaped nanoantennae. The nanorods are appropriately arranged and integrated within a Plasmonic Vortex Lens (PVL), a plasmonic nanofocusing device that converts a circularly polarized plane wave into a plasmonic vortex. We show that the LSPR of the nanorods is either excited or not, according to the OAM of the plasmonic vortex. In particular, we consider a specific type of PVL (single-arm Archimedean spiral) and we investigate the two cases that can be obtained by illuminating it with circularly polarized light with different handedness, corresponding to different values of the OAM of the generated plasmonic vortex. Four nanorods are placed in the center of the PVL and their response is studied by means of numerical simulations. We then present the fabrication of the simulated device and we discuss its characterization by Scanning Near-field Optical Microscopy (SNOM).

2014 - Bilayer holey plasmonic vortex lenses for the far field transmission of pure orbital angular momentum light states [Articolo su rivista]
Zilio, Pierfrancesco; G., Parisi; Garoli, Denis; Carli, Marta; Romanato, Filippo
abstract

We report the design of a holey plasmonic vortex lens (PVL) structure able to couple circularly polarized impinging light to a plasmonic vortex in the form of the fundamental TM mode of a metal–insulator–metal plasmonic waveguide. The field transmitted through the hole milled at the center of the second metal layer of the structure is characterized by a well-defined spiral harmonic, entirely determined by the spin of impinging light and by the chirality of the PVL structure. Scattering finite elements simulations are presented for single layer standard PVLs and for bilayer ones, comparing the spiral spectra of the transmitted field and the efficiencies of the architectures.

2014 - Development of a complete plasmonic grating-based sensor and its application for self-assembled monolayer detection [Articolo su rivista]
Perino, M; Pasqualotto, E; De Toni, A; Garoli, D; Scaramuzza, M; Zilio, P; Ongarello, T; Paccagnella, A; Romanato, F
abstract

This work presents an integrated plasmonic biosensing device consisting of a one-dimensional metallic lamellar grating designed to exploit extraordinary transmission of light toward an underlying silicon photodetector. By means of finite element simulations, the grating parameters have been optimized to maximize the light transmission variation induced by the functionalization of the gold nanostructures. An optimized grating was fabricated using an electron beam process and an optoelectronic test bench suitable for sample tests was developed. A clear difference in the grating transmitted light due to surface functionalization was observed in presence of TM polarized illumination. (C) 2014 Optical Society of America

2014 - Sub-wavelength confinement of the orbital angular momentum of light probed by plasmonic nanorods resonances [Articolo su rivista]
Carli, Marta; Zilio, Pierfrancesco; Garoli, Denis; V., Giorgis; Romanato, Filippo
abstract

We discuss how the topological charge of an OAM-carrying plasmon (Plasmonic Vortex) can be probed by monitoring the near-field response of plasmonic nanostructures suitably arranged inside a Plasmonic Vortex Lens. The turning "on" or "off" of four gold nanorods, detected by a Scanning Near field Optical Microscope (SNOM), acts as a fingerprint of the OAM state of the PV at the nanoscale. Different configurations are studied numerically, the integrated structure is fabricated and near field characterization is performed for a particularly meaningful case.

2013 - Microscopic view on a chemical vapor deposition route to boron-doped graphene nanostructures [Articolo su rivista]
M., Cattelan; S., Agnoli; M., Favaro; Garoli, D; F., Romanato; M., Meneghetti; A., Barinov; P. Dudin and G., Granozzi
abstract

2013 - Zirconia based functional sol-gel resist for UV and high resolution lithography [Articolo su rivista]
Della Giustina, G; Garoli, D; Romanato, F; Brusatin, G
abstract

The development of a functional negative tone sol-gel resist for Ultraviolet (UV) and Electron Beam (EB) lithography is presented. A new highly inorganic system based on ZrO2 is synthesized by sol-gel method. The lithographic performances have been optimized and several structures spanning from the micron range down to less than 50 nm have been achieved by UV and EB lithography. Moreover, in order to test the bio-affinity of the developed system, a genomic DNA probe has been attached onto the ZrO2 film surface. Different thermal treatments have been applied to the samples and preliminary results show different degrees of anchoring, depending on the final ZrO2 film structure (hybrid -> inorganic or amorphous -> crystalline). FT-IR characterization confirms the successful DNA functionalization of the patternable ZrO2 system, especially in the crystalline phase, opening the way to the design of new biosensor architectures. (C) 2013 Elsevier B.V. All rights reserved.

2012 - Design and Parametrical Analysis of Metamaterial Stacks in the Visible Spectral Range [Articolo su rivista]
Parisi, Giuseppe; Garoli, Denis; M., Natali; Romanato, Filippo
abstract

Recently, the fabrication and optimization of nano-hole arrays in noble metal layers have attracted much attention both because of the interesting new physics associated with them and for their potential applications in nano-optics and biosensing. In particular nano-hole arrays in metal-dielectric-metal stacks, also known as "fish-net" type structures, are nowadays the best candidates to accomplish some suggestive physical phenomena like negative refractive index. Here we report a design and a parametrical analysis of a fishnet in the optical spectral range. In particular the dependence of both the magnetic and the electric resonance on the geometric features of the fishnet is investigated.

2012 - FIB lithography of nanoporous gold slits for extraordinary transmission [Articolo su rivista]
Ruffato, Gianluca; Garoli, Denis; S., Cattarin; Barison, Sonia; Romanato, Filippo
abstract

here is a growing interest in discovering new materials for sensing purposes that provide better sensitivity and efficiency. Thanks to a greatly enhanced surface-to-volume ratio, nanoporous gold reveals benefits for better reaction efficiency and detection sensitivity purposes. Moreover plasmonic properties in the near-IR range assure employment in plasmonic devices. Here we present our work of design, fabrication and characterization of nanoporous gold slit arrays that support the phenomenon of extraordinary transmission of the incident light. The gold surface of fabricated samples has been coated with dodecanethiol and the optical response to functionalization has been analyzed in zero-order transmission.

2012 - Focusing dynamics on circular distributed tapered metallic waveguides by means of plasmonic vortex lenses [Articolo su rivista]
Ongarello, Tommaso; Parisi, Giuseppe; Garoli, Denis; Mari, Elettra; Zilio, Pierfrancesco; Romanato, Filippo
abstract

We investigate the focusing effect on circularly distributed planar tapered plasmonic waveguides by means of three-dimensional (3D) finite elements simulations. The proposed configuration allows nanofocusing on four faced planar nanotips, showing efficient condensation of surface plasmons polaritons (SPPs) at the silver/air interface toward the endpoint of the tips. By means of a plasmonic vortex lens it is possible to illuminate the tips with SPP waves carrying orbital angular momentum (OAM), namely plasmonic vortices. Our 3D simulations show that by acting on the topological charge of the plasmonic vortex the electric field charge distribution at the tips apex can be controlled accordingly to the input electric field phase distribution. The results for three particular OAM values are shown, along with a generalization for arbitrary plasmonic vortex angular momentum values.

2012 - Growth and optical properties of silver nanostructures obtained on connected anodic aluminum oxide templates [Articolo su rivista]
Giallongo, Giuseppe; Durante, Christian; Pilot, Robertino; Garoli, Denis; Bozio, Renato; Romanato, Filippo; Gennaro, Armando; Rizzi, GIAN-ANDREA; Granozzi, Gaetano
abstract

Ag nanostructures are grown by AC electrodeposition on anodic alumina oxide (AAO) connected membranes acting as templates. Depending on the thickness of the template and on the voltage applied during the growth process, different Ag nanostructures with different optical properties are obtained. When AAO membranes about 1 m thick are used, the Ag nanostructures consist in Ag nanorods, at the bottom of the pores, and Ag nanotubes departing from the nanorods and filling the pores almost for the whole length. When AAO membranes about 3 m thick are used, the nanostructures are Ag spheroids, at the bottom of the pores, and Ag nanowires that do not reach the upper part of the alumina pores. The samples are characterized by angle resolved x-ray photoelectron spectroscopy, scanning electron microscopy and UV–vis and Raman spectroscopies. A simple NaOH etching procedure, followed by sonication in ethanol, allows one to obtain an exposed ordered array of Ag nanorods, suitable for surface-enhanced Raman spectroscopy, while in the other case (3 m thick AAO membranes) the sample can be used in sensing.

2012 - In vitro evaluation of sunscreens: an update for the clinicians [Articolo su rivista]
Pelizzo, Maria; Zattra, Edoardo; Nicolosi, Piergiorgio; PESERICO STECCHINI NEGRI DE SALVI, Andrea; Garoli, Denis; Alaibac, MAURO SALVATORE ALESSANDRO
abstract

Topical sunscreens contain molecules or molecular complexes that can absorb, reflect, or scatter UV photons. Evaluation of the efficacy of sunscreen products has been made through the Sun Protection Factor (SPF), a mean of quantitatively assessing in vivo the degree of protection offered by sunscreen products against solar radiation. In vivo evaluation of SPF has several drawbacks. First of all, this evaluation method is expensive in terms of money and time. Moreover, it raises several ethical issues concerning the potential damage to skin volunteers. Several in vitro techniques have been developed, but at present there is no broadly accepted method. In this paper, we will discuss some of the recent advances concerning the in vitro evaluation of sunscreens which would be acceptable for replacing in vivo assays.

2012 - Optical and structural properties of low thickness lead zirconate titanate films on sapphire substrates prepared via sol-gel method [Articolo su rivista]
Garoli, Denis; M., Natali; V., Rigato; Romanato, Filippo
abstract

Lead zirconate titanate (PZT) thin films in the range of 35-90 nm were deposited on a sapphire (1000) substrate using the sol-gel preparation method by diluting a PZT solution at different levels and using dichloromethane as the solvent. The microstructure, surface morphology, and stoichiometry of the films were studied by x-ray diffraction, atomic force microscopy, and Rutherford backscattering. Very smooth films characterized by single perovskite and mixed pyrochlore/perovskite polycrystalline phases were obtained and their optical properties were studied by spectroscopic ellipsometry in the ultraviolet-visible-near-infrared region. The refractive index was evaluated by analyzing the spectroscopic ellipsometry spectra. The ellipsometric data were also used to evaluate the bandgap energy of the films. The results show that the optical parameters of the films depend on the crystalline structure and demonstrate that higher bandgaps are obtained for perovskite films as compared to pyrochlore or mixed pyrochlore/perovskite structures. Data also confirm the higher bandgap of the amorphous structure compared to the polycrystalline PZT phases.

2012 - Patterned nanoporous-gold thin layers: structure control and tailoring of plasmonic properties [Articolo su rivista]
Ruffato, Gianluca; Garoli, Denis; S., Cattarin; S., Barison; M., Natali; P., Canton; A., Benedetti; DE SALVADOR, Davide; Romanato, Filippo
abstract

Nanoporous gold (NPG) layers have been fabricated by silver leaching of Ag–Au alloys with different dealloying processes and working temperatures. Structural, compositional and optical properties of the different samples have been analyzed with several experimental techniques: scanning and transmission electron microscopy (SEM/TEM), electrochemical impedance spectroscopy (EIS), Rutherford back scattering (RBS), spectroscopic ellipsometry. A periodic pattern has been realized on samples surface with focused ion beam (FIB) lithography in order to exploit NPG metallic behavior for surface plasmon polaritons (SPPs) excitation. The plasmonic response of the several NPG gratings has been analyzed and related to structural properties and fabrication conditions.

2012 - Plasmonic nanofocusing by means of metal coated dielectric nanowedges [Relazione in Atti di Convegno]
Garoli, Denis; Zilio, Pierfrancesco; M., Natali; Carli, Marta; Ongarello, Tommaso; Romanato, Filippo
abstract

We report our results on arrays of transparent metal coated wedges for plasmonic nanofocusing. FIB milling and chemical etching were used for the fabrication. FEM simulations were used to design the system. The design, fabrication and characterization of wedge structures are presented. The structure shows plasmonic properties in the optical spectral range, with excitation and propagation of surface plasmon polaritons at the wedge tip. The particular designs proposed allow the condensation of plasmonic waves at the wedge tips leading to the nanofocusing effects.

2012 - Wedge nanostructures for plasmonic nanofocusing [Articolo su rivista]
Garoli, D; Zilio, P; Natali, M; Carli, M; Enrichi, F; Romanato, F
abstract

We report numerical and experimental results on the optical response of transparent metal coated wedges arrays for plasmonic nanofocusing. Light normally impinging from the dielectric side is coupled to Surface Plasmon Polaritons (SPPs) at the oblique metal-air interfaces. A dielectric phase shifter has been implemented in the structure in order to allow constructive interference of SPPs at the wedge apex. Finite Elements simulations were used to design the system. Focused Ion Beam (FIB) milling, chemical etching and replica molding were used for the fabrication. NSOM and Raman measurements demonstrate that plasmonic nanofocusing actually takes place in the structure.

2011 - Design, fabrication and characterization of plasmonic gratings for SERS [Articolo su rivista]
Romanato, F; Pilot, R; Massari, M; Ongarello, T; Pirruccio, G; Zilio, P; Ruffato, G; Carli, M; Sammito, D; Giorgis, V; Garoli, D; Signorini, R; Schiavuta, P; Bozio, R
abstract

In order to fabricate SERS-active substrates suitable for sensing applications, reproducibility and efficiency issues must be tackled. Innovative nanofabrication techniques allow the preparation of substrates reproducible and easy to model. Theoretical modelling provides a very powerful method for optimizing the design of such substrates, i.e. tailoring their geometrical parameters for optimizing the optical response. In particular in this work a 1D digital metallic grating has been theoretically investigated to identify the configuration corresponding to the localization of the near-field radiation inside the slits. This chip has been fabricated by electron beam lithography (EBL) and electrolytic growth. The Raman enhancement factor of the chip has been measured and compared with the theoretical estimation. (C) 2011 Elsevier B.V. All rights reserved.

2011 - Extraordinary optical transmission in one-dimensional gold gratings: near- and far-field analysis [Articolo su rivista]
Romanato, F; Ongarello, T; Zacco, G; Garoli, D; Zilio, P; Massari, M
abstract

One-dimensional arrays of nanoslits fabricated on silicon nitride membranes show extraordinary optical transmission. Optical characterization techniques have been used to characterize the transmission spectra and the near-field optical configuration. Experimental results have been compared with numerical simulations in order to elucidate the different modes of light propagation. Near- and far-field optical distribution is studied as a function of the polarization of light. (c) 2011 Optical Society of America

2011 - Fabrication of metamaterials in the optical spectral range [Articolo su rivista]
Garoli, Denis; M., Natali; Parisi, Giuseppe; Ongarello, Tommaso; E., Sovernigo; M., Massari; V., Giorgis; Ruffato, Gianluca; S., De Zuani; Romanato, Filippo
abstract

Recently, the fabrication and optimization of nano-hole arrays in multi-layers has attracted much attention for their interesting applications in nano-optics and biosensing. In particular nano-hole arrays in metal-dielectric-metal stacks, also known as "fish-net" type structures, actually are the best candidates to accomplish some suggestive physical phenomena like negative refractive index, super-lensing and invisibility cloaks in the optical spectral range. Here, we report our preliminary results on the nanofabrication of "fish-net" type Au/dielectric/Au metamaterial stacks. Nano-hole arrays have been realized on Au (30 nm)-dielectric (50 nm)-Au (30 nm)/ITO stacks by means of direct ion milling with FIB using a FEI Nova 600i instrument. Finite element method (FEM) simulations were used to design the structures and to foresee their optical behavior. (C) 2010 Elsevier B.V. All rights reserved.

2011 - Nanoporous gold plasmonic structures for sensing applications [Articolo su rivista]
Ruffato, Gianluca; Romanato, Filippo; Garoli, Denis; S., Cattarin
abstract

The fabrication, characterization and functionalization of periodically patterned nanoporous gold layers is presented. The material shows plasmonic properties in the near infrared range, with excitation and propagation of surface plasmon polaritons. Functionalization shows a marked enhancement in the optical response in comparison with evaporated gold gratings, due to a great increase of the active surface. Due to its superior response, nanoporous gold patterns appear promising for the realization of compact plasmonic platforms for sensing purposes.

2011 - Spectroscopic study of β-SiC prepared via PLD at 1064 nm [Articolo su rivista]
Monaco, Gianni; Garoli, Denis; M., Natali; Romanato, Filippo; Nicolosi, Piergiorgio
abstract

The physical properties of the wide band-gap beta-SiC make it a promising material for future applications in high-power, high-temperature and high-frequency devices. Up to now, SiC has been successfully employed in field effect transistors, bipolar storage capacitors and ultraviolet detectors. In this work, we present new attempts to prepare crystalline beta-SiC at 650 degrees C by means of Pulsed Laser Deposition (PLD). X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM) have been used to determine the crystalline and morphological properties of the deposited beta-SiC thin films grown on different substrates: sapphire and silicon. The optical constants in the visible range and the band gap energy have been determined by Spectroscopic Ellipsometry (SE) which is a powerful non-destructive technique for high accuracy measurements. SiC thin films deposited on sapphire give rise to hetero-epitaxial growth resulting in an organized structure while the sample deposited on silicon grows polycrystalline. The correlation between the band-gap energy and the crystalline phases and growth conditions will be discussed. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

2011 - Structural characterization of lead zirconate titanate thin films prepared on different electrodes and on silicon substrates [Articolo su rivista]
M., Natali; Garoli, Denis; V., Rigato; Romanato, Filippo
abstract

Lead zirconate titanate (PZT) thin films were deposited by rf magnetron sputtering on Pt/Ti/SiO(2)//Si, Au/Ti/SiO2//Si, ITO//glass electrodes and on Si (100) substrates. As deposited films show large excesses of Pb and O and contain different Pb oxides. Annealing treatments in air at 650 and 750 degrees C carried out in a preheated muffle furnace lead to a decrease of Pb and O content and to formation of the perovskite phase via an intermediate nanocrystalline pyrochlore phase. Phase pure perovskite films are obtained on Pt and ITO electrodes by annealing at 750 degrees C for similar to 10 min, while for the same treatment significant amounts of pyrochlore remained on Au electrodes and on Si substrates.

2011 - Synthesis of heteroepytaxial 3C-SiC by means of PLD [Articolo su rivista]
Monaco, G; Garoli, D; Natali, M; Pelizzo, Mg; Nicolosi, P
abstract

Thin films of silicon carbide (SiC) have been prepared by means of pulsed laser deposition (PLD) on sapphire (Al(2)O(3)) and Si(100) substrates with a Nd-YAG laser 1064 nm. We achieved the growth of cubic silicon carbide (3C-SiC) films at the temperatures of 650A degrees C from a SiC target in vacuum. The as-deposited films are morphologically and structurally characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray diffraction (XRD). The use of off-axis PLD method placing the sample at 90A degrees with respect to the target leads to a good quality smooth film.

2011 - X-ray absorption study of silicon carbide thin film deposited by pulsed laser deposition [Articolo su rivista]
Monaco, G; Suman, M; Garoli, D; Pelizzo, Mg; Nicolosi, P
abstract

Silicon carbide (SiC) is an important material for several applications ranging from electronics to Extreme UltraViolet (EUV) space optics. Crystalline cubic SiC (3C-SiC) has a wide band gap (near 2.4 eV) and it is a promising material to be used in high frequency and high energetic electronic devices. We have deposited, by means of pulsed laser deposition (PLD), different SiC films on sapphire and silicon substrates both at mild (650 degrees C) and at room temperature. The resulted films have different structures such as: highly oriented polycrystalline, polycrystalline and amorphous which have been studied by means of X-ray absorption spectroscopy (XAS) near the Si L(2,3) edge and the C K edge using PES (photoemission spectroscopy) for the analysis of the valence bands structure and film composition. The samples obtained by PLD have shown different spectra among the grown films, some of them showing typical 3C-SiC absorption structure, but also the presence of some Si-Si and graphitic bonds. (C) 2011 Elsevier B.V. All rights reserved.

2010 - Design, Fabrication and Characterization of Plasmonic Gratings for SERS [Abstract in Atti di Convegno]
Massari, M; Ongarello, T; Pirruccio, G; Zilio, P; Ruffato, G; Carli, Marta; Sammito, D; Giorgis, V; Garoli, Denis; Bozio, Renato; Pilot, R; Signorini, R; Schiavuta, P; Marinello, Francesco; Romanato, Filippo
abstract

2009 - Effectiveness of different substrate materials for in vitro sunscreen tests [Articolo su rivista]
Garoli, Denis; Pelizzo, Mg; Nicolosi, Piergiorgio; PESERICO STECCHINI NEGRI DE SALVI, Andrea; Tonin, E; Alaibac, MAURO SALVATORE ALESSANDRO
abstract

Background: In vitro measurements of sunscreen products are used to assess their reliability in terms of photoprotection and photo-stability. Objective: In this study, several substrates have been fully characterized for in vitro sunscreen testing. Methods: The following different substrates have been utilised in the study: roughened PMMA plates, Transpore, Vitro-Skin, roughened quartz plate and a laboratory prepared roughened PTFE plate. The suitability of these substrates for SPF evaluation has been investigated by performing total absorbance measurements of seven sunscreen products with different SPF values produced by the same manufacturer. Results and conclusions: Application of sunscreen products on Transpore, roughened quartz plate, PMMA, PTFE and Vitro-Skin was performed efficiently. With regard to photo-stability of the substrate materials, only PMMA plate, PTFE and roughened quartz plate showed to be photo-stable after UV irradiation. With regard to SPF tests, our results indicate that Transpore, roughened quartz plate and Vitro-Skin are preferable to assess SPF values because of a better correlation between in vitro and in vivomeasurements. Our study also confirms that an initial calibration must be performed for sunscreen products labelled with different SPF values. Finally, the results of our measurements demonstrate that, although a correlation between in vitro and in vivo SPF results can be established, it is never exactly 1:1.

2008 - Sunscreen tests: Correspondence between in vitro data and values reported by the manufacturers [Articolo su rivista]
Garoli, D.; Pelizzo, M. G.; Pelizzo, M; Bernardini, B.; Nicolosi, P.; Alaibac, M.
abstract

Background: In vitro sunscreen tests are diffusively used to test both the sun protection factor (SPF) and the photo-stability of filters. Spectrophotometric measurements of the absorbance of ultraviolet radiations through a sunscreen applied on a suitable substrate allow a rapid evaluation of its protection factor both at short and long wavelength ultraviolet radiation (UVB and UVA). Objectives: The objective of this study has been to demonstrate if Teflon can be adopted as substrate both for SPF evaluation and photo-stability tests. Moreover, we have investigated if there is a correspondence between in vitro SPF measurements and values reported by manufacturers on sunscreens. Material and methods: Teflon has been used to perform several photo-stability tests by irradiating the filters with different wavebands and analyzing the combined effect of UVand infrared (IR) light. Similar analyses have been carried out using PMMA Plates, which is the standard substrate for UVA in vitro test. Results: We have demonstrated that it is possible to establish a good correspondence between in vitro SPF and values reported by manufacturers on sunscreens. We have also verified that the in vitro/label SPF correlation curve depends on the quantity of product applied while this does not seem to be true for other parameters like Critical Wavelength and UVA ratio. With regard to photo-stability studies, our results indicate for the first time that IR irradiation may have a role on photo-degradation. Conclusions: The results show that there is a good correlation between the in vitro SPF determined by the present method and the SPF reported by the manufacturer.

2008 - Transmittance and optical constants of Pr films in the 4-1600 eV spectral range [Articolo su rivista]
Fernandez-Perea, M; Vidal-Dasilva, M; Aznarez, Ja; Larruquert, Ji; Mendez, Ja; Poletto, L; Garoli, D; Malvezzi, Am; Giglia, A; Nannarone, S
abstract

The optical constants of Pr films were obtained in the 4-1600 eV range from transmittance measurements performed at room temperature. Thin films of polycrystalline Pr were deposited by evaporation in ultrahigh vacuum conditions and their transmittance was measured in situ. Pr films were deposited onto grids coated with a thin, C support film. Transmittance measurements were used to obtain the optical extinction coefficient k of Pr films in the 4-1600 investigated photon energy range. The refractive index n of Pr was calculated using the Kramers-Kronig analysis. Data were extrapolated both on the high and low-energy sides by using experimental and calculated extinction coefficient data available from the literature. Pr, similar to other lanthanides, has a low-absorption band right below the O-2,O-3 edge onset; the lowest absorption was measured at about 17 eV. Therefore, Pr is a promising material for filters and multilayer coatings in the energy range below O-2,O-3 edge in which most materials have a strong absorption. A good consistency of the data were obtained through f and inertial sum rules. (C) 2008 American Institute of Physics.

2007 - Realization of a radiometric head for measurements of ultraviolet total erythemal effective irradiance [Articolo su rivista]
M. G., Pelizzo; Garoli, Denis; Nicolosi, Piergiorgio
abstract

An innovative sensor with a spectral response equivalent to the erythemal action curve for ultraviolet total effective irradiance measurements is presented. Optical and sensor components have been selected after the characterization of different samples. The design is based on an innovative interferential filter, which has been realized and tested. A first prototype has been assembled and characterized. Our measurements demonstrate the feasibility and potential of this instrument.

2006 - Optical constants in the EUV soft x-ray (5÷152 nm) spectral range of BProceedings of SPIE [Relazione in Atti di Convegno]
G., Monaco; D., Garoli; R., Frison; V., Mattarello; P., Nicolosi; M. G., Pelizzo; V., Rigato; L., Armelao; A., Giglia; Nannarone, Stefano
abstract

B4C optical coating represents, together with Ir, Pt, SiC, one of best choice for high reflectance in the extreme ultraviolet region (EUV 160-30 nm). This material is also used in multilayer for soft X-ray applications, such as Si/B4C or W/B4C, or as interlayer in Mo/Si multilayer to avoid interdiffusion also because of its high thermal stability. Our work concerns on B4C thin films deposited on Si [100] substrates by means of three different deposition techniques: RF plasma magnetron sputtering, e-beam evaporation, pulsed laser ablation (PLD). We performed reflectance vs incidence angle measurements from 5 nm to 152 nm on different samples deriving the optical constants with a least-square fitting method. Complete films characterization have been carried out with compositional (XPS), structural (XRD) and morphological (AFM, SEM) analyses.

2006 - Thin film and multilayer coating development for the extreme ultraviolet spectral region [Articolo su rivista]
Garoli, D; Monaco, G; Frassetto, F; Pelizzo, Mg; Nicolosi, P; Armelao, L; Mattarello, V; Rigato, V
abstract

B4C optical coating represents, together with Ir, Pt, SiC, one of best choice for high reflectance in the extreme ultraviolet region. This material is also used combined with others materials in multilayer such as Si/B4C or as interlayer in Mo/Si multilayer to avoid interdiffusion. In this study we have performed optical, compositional and structural analyses for thin film of B4C deposited by means of magnetron sputtering and on preliminary samples deposited by e-beam evaporation. Here we report reflectivity measurements and the derived optical constants of B4C in the 400-1500 angstrom region. (c) 2006 Elsevier Ltd. All rights reserved.

2005 - Space applications of Si/BProceedings of SPIE [Relazione in Atti di Convegno]
Frassetto, F.; Garoli, D.; Monaco, G.; Nicolosi, P.; Pascolini, M.; Pelizzo, M. G.; Mattarello, V.; Patelli, A.; Rigato, V.; Giglia, A.; Nannarone, S.; Antonucci, E.; Fineschi, S.; Romoli, M.
abstract

In the extreme ultra-violet region, multilayer coatings are the only technique to obtain high reflectivity in normal incidence optical configurations. The interference process which regulates periodic multilayers behavior offers narrow-band spectral filtering without the use of additional filters, fact that makes these coatings particularly suitable for lines emission observations. Despite the large amount of possible materials combinations, Mo/Si multilayers are the standard choice for space research on plasma physics in the 13 - 30 nm spectral region. In this work Si/B4C is presented as an alternative material couple for the 30.4 nm selection. Attractive features are the better spectral purity and the second order reflectivity reduction. A possible application to the Sounding CORonagraph Experiment is described as an example. B4C thin films have been used to characterize this material in terms of optical constants in the 40 nm - 150 nm spectral region where, currently, only few data are available.

2005 - VUV Reflectance measurements and optical constants of SiC thin films [Articolo su rivista]
Nicolosi, Piergiorgio; Pelizzo, M. G.; Garoli, Denis; V., Rigato; Patelli, Alessandro; F., Rigato
abstract

Optical constants of SiC thin films deposited with RF magnetron sputtering have been derived in the VUV. The films have been deposited with different parameters resulting in various C/Si ratios. Reflectance measurements have been made with a dedicated facility in the range 300–1300 ´°A . Index of refraction and absorption coefficient have been derived by fitting the reflectance data with the calculated ones.

2004 - Absolute spectral response measurements of different photodiodes useful for applications in the UV spectral region [Relazione in Atti di Convegno]
Pelizzo, Mg; Ceccherini, P; Garoli, D; Masut, P; Nicolosi, P
abstract

Long UV radiation exposure can result in damages of biological tissues, as burns, skin aging, erythema and even melanoma cancer. In the past years an increase of melanoma cancer has been observed and associated to the atmospheric ozone deployment. Attendance of sun tanning unit centers has become a huge social phenomena, and the maximum UV radiation dose that a human being can receive is regulated by law. On the other side, UV radiation is largely used for therapeutic and germicidal purposes. In all these areas, spectroradiometer and radiomenter are needed for monitoring UVA (lambda = 315-400 nm), UVB (lambda = 280-315 nm) and UVC (lambda=100-280 nm) irradiance. We have selected some commercial photodiodes which can be used as solid state detectors in these instruments. We have characterized them by measuring their absolute spectral response in the 200 - 400 nm spectral range.