FRANCESCO TASSINARI - personale UniMoRe

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FRANCESCO TASSINARI

Ricercatore t.d. art. 24 c. 3 lett. B
Dipartimento di Scienze Chimiche e Geologiche - Sede Dipartimento di Scienze Chimiche e Geologiche

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Pubblicazioni

2023 - A Trifunctional ATRP Initiator Bearing Adaptable Bonds [Poster]
Scurani, Giulia; Braidi, Niccolo'; Porcelli, Nicola; Tassinari, Francesco; Parenti, Francesca
abstract

Atom Transfer Radical Polymerization (ATRP) allows for the production of polymers with precise control over molecular weight, dispersity, topology, composition, and functionality. Functional groups can be introduced into the polymer through post-functionalization of chain ends, or on the alkyl residue of the initiator, or by introducing functionalized (co)monomers, greatly greatly enhancing the targetable applications. In addition, the desired functional group can also be carried by the ATRP initiator. Some researchers have explored initiators with hydrolysis- or heat-sensitive functionalities to impart self-healing properties to the final polymer. However, the commonly used aliphatic halide ester initiators have shown poor thermal stability. To address this issue, we recently developed a novel bifunctional benzamide-containing initiator employed in ARGET ATRP of styrene, demonstrating enhanced thermal stability. Covalent Adaptable Networks (CANs) have emerged as a solution for improving the recyclability of thermoset materials. CANs can reorganize connectivity between chains upon thermal treatment, enabling reprocessing. Our goal is to modify the structure of the benzamide-containing initiator to develop a trifunctional initiator bearing adaptable bonds.

2023 - Challenges in the Direct Detection of Chirality-induced Spin Selectivity: Investigation of Foldamer-based Donor-Acceptor Dyads [Articolo su rivista]
Privitera, Alberto; Faccio, Davide; Giuri, Demetra; Latawiec, Elisabeth I.; Genovese, Damiano; Tassinari, Francesco; Mummolo, Liviana; Chiesa, Mario; Fontanesi, Claudio; Salvadori, Enrico; Cornia, Andrea; Wasielewski, Michael R.; Tomasini, Claudia; Sessoli, Roberta
abstract

Over the past two decades, the chirality-induced spin selectivity (CISS) effect was reported in several experiments disclosing a unique connection between chirality and electron spin. Recent theoretical works highlighted time-resolved Electron Paramagnetic Resonance (trEPR) as a powerful tool to directly detect the spin polarization resulting from CISS. Here, we report a first attempt to detect CISS at the molecular level by linking the pyrene electron donor to the fullerene acceptor with chiral peptide bridges of different lengths and electric dipole moment. The dyads are investigated by an array of techniques, including cyclic voltammetry, steady-state and transient optical spectroscopies, and trEPR. Despite the promising energy alignment of the electronic levels, our multi-technique analysis reveals no evidence of electron transfer (ET), highlighting the challenges of spectroscopic detection of CISS. However, the analysis allows the formulation of guidelines for the design of chiral organic model systems suitable to directly probe CISS-polarized ET.

2023 - Electron Spin Polarization and Rectification Driven by Chiral Perylene Diimide-Based Nanodonuts [Articolo su rivista]
Ko, C. -H.; Zhu, Q.; Bullard, G.; Tassinari, F.; Morisue, M.; Naaman, R.; Therien, M. J.
abstract

The chirality-induced spin selectivity (CISS) effect allows thin-film layers of chiral conjugated molecules to function as spin filters at ambient temperature. Through solvent-modulated dropcasting of chiral l- and d-perylene diimide (PDI) monomeric building blocks, two types of aggregate morphologies, nanofibers and nanodonuts, may be realized. Spin-diode behavior is evidenced in the nanodonut structures. Stacked PDI units, which form the conjugated core of these nanostructures, dominate the nanodonut-Au electrode contact; in contrast, the AFM tip contacts largely the high-resistance solubilizing alkyl chains of the chiral monomers that form these nanodonuts. Current-voltage responses of the nanodonuts, measured by magnetic conductive AFM (mC-AFM), demonstrate substantial spin polarizations as well as spin current rectification ratios (>10) that exceed the magnitudes of those determined to date for other chiral nanoscale systems. These results underscore the potential for chiral nanostructures, featuring asymmetric molecular junctions, to enable CISS-based nanoscale spin current rectifiers.

2023 - Influences of nitrogen base excess on ARGET ATRP of styrene with ascorbic acid acetonide and traces of oxygen and water [Articolo su rivista]
Braidi, N; Parenti, F; Scurani, G; Tassinari, F; Buffagni, M; Bonifaci, L; Cavalca, G; Pettenuzzo, N; Ghelfi, F
abstract

Ascorbic acid is a promising regenerating agent for Activators ReGenerated by Electron Transfer Atom Transfer Radical Polymerization (ARGET ATRP) thanks to its sustainability and environmental friendlyness. The ascorbate anion has even more potential because it has a higher kinetic rate constant of reduction toward the copper catalyst than its protonated counterpart. Although ascorbic acid can be easily neutralized with inorganic bases, the resulting heterogeneous system in the polymerization of hydrophobic monomers (such as styrene) is not well-suited for industrial applications. To overcome this problem, in this study we investigate the use of ascorbic acid acetonide, a more lipophilic derivative, together with soluble nitrogen bases of different basicity. The results show how the pK(a) of the protonated form of the nitrogen base affects the process, especially in the presence of traces of water and/or oxygen. Additionally, we report that milder bases yield better results in terms of dispersity and chain-end fidelity, while high pK(a) bases lead to a complete loss of control.

2023 - Spin-dependent electrochemistry and electrochemical enantioselective recognition with chiral methylated bis(ethylenedithio)-tetrathiafulvalenes [Articolo su rivista]
Stefani, A.; Bogdan, A.; Pop, F.; Tassinari, F.; Pasquali, L.; Fontanesi, C.; Avarvari, N.
abstract

: Enantio-discrimination and spin-dependent electrochemistry (SDE), as a manifestation of the chirality-induced spin selectivity (CISS) effect, are important phenomena that can be probed by "chiral" electrochemistry. Here, we prepared chiralized surfaces of gold and nickel, to serve as working electrodes, through effective chemisorption of enantiopure dimethyl-bis(ethylenedithio)-tetrathiafulvalene (DM-BEDT-TTF) 1, tetramethyl-bis(ethylenedithio)-tetrathiafulvalene (TM-BEDT-TTF) 2, and their capped silver nanoparticle (AgNPs) aggregate by simple incubation of the metallic substrates. The effective chemisorption was checked by means of ultrahigh vacuum x-ray photoelectron spectroscopy (XPS) and by electro-desorption experiments, i.e., cyclic voltammetry (CV) scans showing a first electro-desorption peak at about -1.0 V. The Au|1 and Au|2 chiral electrodes were successfully used in CV experiments exploiting chiral redox probes. Finally, the hybrid interfaces Ni|enantiopure 1 or 2|AgNPs served as working electrodes in SDE experiments. In particular, the hybrid chiral interfaces Ni|(R)-2|AgNPs and Ni|(S)-2|AgNPs exhibited a significant spin-filtering ability, as a manifestation of the CISS effect, with average spin polarization values of 15%.

2022 - Chirality enhances oxygen reduction [Articolo su rivista]
Sang, Y.; Tassinari, F.; Santra, K.; Zhang, W.; Fontanesi, C.; Bloom, B. P.; Waldeck, D. H.; Fransson, J.; Naaman, R.
abstract

Controlled reduction of oxygen is important for developing clean energy technologies, such as fuel cells, and is vital to the existence of aerobic organisms. The process starts with oxygen in a triplet ground state and ends with products that are all in singlet states. Hence, spin constraints in the oxygen reduction must be considered. Here, we show that the electron transfer efficiency from chiral electrodes to oxygen (oxygen reduction reaction) is enhanced over that from achiral electrodes. We demonstrate lower overpotentials and higher current densities for chiral catalysts versus achiral ones. This finding holds even for electrodes composed of heavy metals with large spin-orbit coupling. The effect results from the spin selectivity conferred on the electron current by the chiral assemblies, the chiral-induced spin selectivity effect.

2022 - Foreword [Articolo su rivista]
Tassinari, Francesco; Naaman, Ron
abstract

2022 - Novel Bifunctional Amide-Based Initiator for the Atom Transfer Radical Polymerization of Styrene with Ascorbic Acid Acetonide as Reducing Agent [Poster]
Scurani, Giulia; Braidi, Niccolo'; Tassinari, Francesco; Parenti, Francesca
abstract

This study focuses on the synthesis and characterization of a new bifunctional benzamide initiator, CMB2HexDA, for the production of thermostable α,ω-dichloropolystyrene via ARGET ATRP. The motivation behind this research is the need to obtain functionalized polystyrene that can withstand the high temperatures used in industrial extrusion processes, as well as the previous development of a method to obtain α,ω-dialkenepolystyrene by solventless thermal dehydrohalogenation. The commonly used initiators in ATRP undergo thermal fragmentation, leading to chain length reduction and loss of telechelicity. The synthesized initiator was purified and characterized, and the resulting α,ω-dichloropolystyrenes were analyzed through GPC and NMR. The telechelic polystyrene produced with the new initiator exhibited enhanced thermal stability compared to aliphatic-halide ester initiators. Although the specific diamine used does not confer specific functionality, the developed synthetic pathway allows for the introduction of other functionalities into thermostable polystyrenes. Furthermore, the benzamidic function could be exploited to achieve controlled chemical degradation of polystyrene, resulting in more readly degradable oligomeric fragments.

2022 - Spin-induced asymmetry reaction - The formation of asymmetric carbon by electropolymerization [Articolo su rivista]
Bhowmick, D. K.; Das, T. K.; Santra, K.; Mondal, A. K.; Tassinari, F.; Schwarz, R.; Diesendruck, C. E.; Naaman, R.
abstract

We describe the spin polarization–induced chirogenic electropolymerization of achiral 2-vinylpyridine, which forms a layer of enantioenhanced isotactic polymer on the electrode. The product formed is enantioenriched in asymmetric carbon polymer. To confirm the chirality of the polymer film formed on the electrode, we also measured its electron spin polarization properties as a function of its thickness. Two methods were used: First, spin polarization was measured by applying magnetic contact atomic force microscopy, and second, magnetoresistance was assessed in a sandwich-like four-point contact structure. We observed high spin-selective electron transmission, even for a layer thickness of 120 nm. A correlation exists between the change in the circular dichroism signal and the change in the spin polarization, as a function of thickness. The spin-filtering efficiency increases with temperature.

2022 - Temperature-Dependent Chiral-Induced Spin Selectivity Effect: Experiments and Theory [Articolo su rivista]
Das, T. K.; Tassinari, F.; Naaman, R.; Fransson, J.
abstract

The theoretical explanation for the chiral-induced spin selectivity effect, in which electrons’ passage through a chiral system depends on their spin and the handedness of the system, remains incomplete. Although most experimental work was performed at room temperature, most of the proposed theories did not include vibrations. Here, we present temperature-dependent experiments and a theoretical model that captures all observations and provides spin polarization values that are consistent with the experimental results. The model includes the vibrational contribution to the spin orbit coupling. It highlights the importance of dissipation and the relation between the effect and the optical activity. The model explains the main features related to the chiral-induced spin selectivity effect and provides a new framework for future calculations and experiments.

2022 - The role of electrons? spin in DNA oxidative damage recognition [Articolo su rivista]
Zhu, Qr; Kapon, Y; Burrows, A; Mishra, S; Santra, K; Tassinari, F; Cohen, Sr; Das, Tk; Sang, Yt; Bhowmick, Dk; Burrows, Cj; Paltiel, Y; Naaman, R
abstract

Formation of 8-oxo-7,8-dihydro-20-deoxyguanosine (OG) is one of the most common forms of DNA oxidative damage found in human cells. Although this damage is prevalent in many disease states, it only marginally influences the structure and stability of double -stranded DNA (dsDNA). Therefore, it is a challenge to establish the mechanism by which this damage is detected by repair enzymes. We investigated the position-dependent effect of the damage on the interactions between dsDNA and oligopeptides using atomic force microscopy. The results were confirmed by monitoring the spin and location-dependent polarizability of the damaged DNA, applying a Hall device. The observations suggest that the interac-tion of peptide with DNA depends on oxidative damage in the DNA and on its location relative to the point of contact between the peptide and the DNA. Hence, a remote search mechanism for damage in DNA is possible.

2022 - Twisted molecular wires polarize spin currents at room temperature [Articolo su rivista]
Ko, C. -H.; Zhu, Q.; Tassinari, F.; Bullard, G.; Zhang, P.; Beratan, D. N.; Naaman, R.; Therien, M. J.
abstract

A critical spintronics challenge is to develop molecular wires that render efficiently spin-polarized currents. Interplanar torsional twisting, driven by chiral binucleating ligands in highly conjugated molecular wires, gives rise to large near-infrared rotational strengths. The large scalar product of the electric and magnetic dipole transition moments ([Formula: see text]), which are evident in the low-energy absorptive manifolds of these wires, makes possible enhanced chirality-induced spin selectivity-derived spin polarization. Magnetic-conductive atomic force microscopy experiments and spin-Hall devices demonstrate that these designs point the way to achieve high spin selectivity and large-magnitude spin currents in chiral materials.

2021 - ENANTIO-SPECIFIC CRYSTALLIZATION SYSTEM AND METHOD THEREOF [Brevetto]
Naaman, Ron; Tassinari, Francesco; Sang, Yutao; Santra, Kakali; Bhowmick, Debkumar
abstract

The present invention relates to a technique for flow crystallization. The system comprises a container having a bottom surface defining a first plane, the container including at least two planar magnetic surfaces being arranged in a spaced-apart manner along a first plane and being substantially parallel to a second plane; a magnetization vector of each of the magnetic surfaces being perpendicularly to the surface, wherein the container is configured such that the first plane is substantially perpendicularly to the second plane; wherein a cavity formed in between the planar magnetic surfaces is configured to accommodate a racemic mixture including different enantiomers such that each magnetic surface interacts differently with each of the different enantiomers to thereby enable enantio-selective crystallization. Therefore, the system of the present invention is based on enantio-separation of the crystals using magnetic surfaces.

2021 - Multistate Switching of Spin Selectivity in Electron Transport through Light-Driven Molecular Motors [Articolo su rivista]
Zhu, Q.; Danowski, W.; Mondal, A. K.; Tassinari, F.; van Beek, C. L. F.; Heideman, G. H.; Santra, K.; Cohen, S. R.; Feringa, B. L.; Naaman, R.
abstract

It is established that electron transmission through chiral molecules depends on the electron's spin. This phenomenon, termed the chiral-induced spin selectivity (CISS), effect has been observed in chiral molecules, supramolecular structures, polymers, and metal-organic films. Which spin is preferred in the transmission depends on the handedness of the system and the tunneling direction of the electrons. Molecular motors based on overcrowded alkenes show multiple inversions of helical chirality under light irradiation and thermal relaxation. The authors found here multistate switching of spin selectivity in electron transfer through first generation molecular motors based on the four accessible distinct helical configurations, measured by magnetic-conductive atomic force microscopy. It is shown that the helical state dictates the molecular organization on the surface. The efficient spin polarization observed in the photostationary state of the right-handed motor coupled with the modulation of spin selectivity through the controlled sequence of helical states, opens opportunities to tune spin selectivity on-demand with high spatio-temporal precision. An energetic analysis correlates the spin injection barrier with the extent of spin polarization.

2021 - Simultaneous High-Purity Enantiomeric Resolution of Conglomerates Using Magnetic Substrates [Articolo su rivista]
Bhowmick, D.; Sang, Y.; Santra, K.; Halbauer, M.; Capua, E.; Paltiel, Y.; Naaman, R.; Tassinari, F.
abstract

Applying magnetic substrates, magnetized perpendicular to the surface, we were able to crystallize from racemic solution pure conglomerates of several molecules. The resolution is based on the spin-dependent charge reorganization (SDCR) effect. By having two surfaces with opposite magnetization, it was possible to simultaneously crystallize on each surface a different enantiomer. The method does not require any seeding or chemical modification and is generally employable to any conglomerate. A system is presented for performing the separation, while the racemic mixture flows between the two magnetic surfaces.

2021 - Spin-selective electron transmission through self-assembled monolayers of double-stranded peptide nucleic acid [Articolo su rivista]
Mollers, P. V.; Ulku, S.; Jayarathna, D.; Tassinari, F.; Nurenberg, D.; Naaman, R.; Achim, C.; Zacharias, H.
abstract

Monolayers of chiral molecules can preferentially transmit electrons with a specific spin orientation, introducing chiral molecules as efficient spin filters. This phenomenon is established as chirality-induced spin selectivity (CISS) and was demonstrated directly for the first time in self-assembled monolayers (SAMs) of double-stranded DNA (dsDNA)1. Here, we discuss SAMs of double-stranded peptide nucleic acid (dsPNA) as a system which allows for systematic investigations of the influence of various molecular properties on CISS. In photoemission studies, SAMs of chiral, γ-modified PNA show significant spin filtering of up to P = (24.4 ± 4.3)% spin polarization. The polarization values found in PNA lacking chiral monomers are considerably lower at about P = 12%. The results confirm that the preferred spin orientation is directly linked to the molecular handedness and indicate that the spin filtering capacity of the dsPNA helices might be enhanced by introduction of chiral centers in the constituting peptide monomers.

2021 - Temperature Dependence of Charge and Spin Transfer in Azurin [Articolo su rivista]
Sang, Y.; Mishra, S.; Tassinari, F.; Karuppannan, S. K.; Carmieli, R.; Teo, R. D.; Migliore, A.; Beratan, D. N.; Gray, H. B.; Pecht, I.; Fransson, J.; Waldeck, D. H.; Naaman, R.
abstract

The steady-state charge and spin transfer yields were measured for three different Ru-modified azurin derivatives in protein films on silver electrodes. While the charge-transfer yields exhibit weak temperature dependences, consistent with operation of a near activation-less mechanism, the spin selectivity of the electron transfer improves as temperature increases. This enhancement of spin selectivity with temperature is explained by a vibrationally induced spin exchange interaction between the Cu(II) and its chiral ligands. These results indicate that distinct mechanisms control charge and spin transfer within proteins. As with electron charge transfer, proteins deliver polarized electron spins with a yield that depends on the protein's structure. This finding suggests a new role for protein structure in biochemical redox processes.

2020 - Asymmetric reactions induced by electron spin polarization [Articolo su rivista]
Bloom, B. P.; Lu, Y.; Metzger, T.; Yochelis, S.; Paltiel, Y.; Fontanesi, C.; Mishra, S.; Tassinari, F.; Naaman, R.; Waldeck, D. H.
abstract

Essential aspects of the chiral induced spin selectivity (CISS) effect and their implications for spin-controlled chemistry and asymmetric electrochemical reactions are described. The generation of oxygen through electrolysis is discussed as an example in which chirality-based spin-filtering and spin selection rules can be used to improve the reaction's efficiency and selectivity. Next the discussion shifts to illustrate how the spin selectivity of chiral molecules (CISS properties) allows one to use the electron spin as a chiral bias for inducing asymmetric reactions and promoting enantiospecific processes. Two enantioselective electrochemical reactions that have used polarized electron spins as a chiral reagent are described; enantioselective electroreduction to resolve an enantiomer from a racemic mixture and an oxidative electropolymerization to generate a chiral polymer from achiral monomers. A complementary approach that has used spin-polarized, but otherwise achiral, molecular films to enantiospecifically associate with one enantiomer from a racemic mixture is also discussed. Each of these reaction types use magnetized films to generate the spin polarized electrons and the enantiospecificity can be selected by choice of the magnetization direction, North pole versus South pole. Possible paths for future research in this area and its compatibility with existing methods based on chiral electrodes are discussed.

2020 - Correlation between Ferromagnetic Layer Easy Axis and the Tilt Angle of Self Assembled Chiral Molecules [Articolo su rivista]
Sukenik, N.; Tassinari, F.; Yochelis, S.; Millo, O.; Baczewski, L. T.; Paltiel, Y.
abstract

The spin-spin interactions between chiral molecules and ferromagnetic metals were found to be strongly affected by the chiral induced spin selectivity effect. Previous works unraveled two complementary phenomena: magnetization reorientation of ferromagnetic thin film upon adsorption of chiral molecules and different interaction rate of opposite enantiomers with a magnetic substrate. These phenomena were all observed when the easy axis of the ferromagnet was out of plane. In this work, the effects of the ferromagnetic easy axis direction, on both the chiral molecular monolayer tilt angle and the magnetization reorientation of the magnetic substrate, are studied using magnetic force microscopy. We have also studied the effect of an applied external magnetic field during the adsorption process. Our results show a clear correlation between the ferromagnetic layer easy axis direction and the tilt angle of the bonded molecules. This tilt angle was found to be larger for an in plane easy axis as compared to an out of plane easy axis. Adsorption under external magnetic field shows that magnetization reorientation occurs also after the adsorption event. These findings show that the interaction between chiral molecules and ferromagnetic layers stabilizes the magnetic reorientation, even after the adsorption, and strongly depends on the anisotropy of the magnetic substrate. This unique behavior is important for developing enantiomer separation techniques using magnetic substrates.

2020 - Electron transfer via helical oligopeptide to laccase including chiral schiff base copper mediators [Articolo su rivista]
Kashiwagi, K.; Tassinari, F.; Haraguchi, T.; Banerjee-Gosh, K.; Akitsu, T.; Naaman, R.
abstract

The oxygen reduction efficiency of a laccase-modified electrode was found to depend on the chirality of the oligopeptide linker used to bind the enzyme to the surface. At the same time, the electron transfer between the cathode electrode and the enzyme is improved by using a copper(II) complex with amino-acid derivative Schiff base ligand with/without azobenzene moiety as a mediator. The increased electrochemical current under both O2 and N2 proves that both the mediators are active towards the enzyme.

2020 - Helicity Control in the Aggregation of Achiral Squaraine Dyes in Solution and Thin Films [Articolo su rivista]
Rosch, A. T.; Zhu, Q.; Robben, J.; Tassinari, F.; Meskers, S. C. J.; Naaman, R.; Palmans, A. R. A.; Meijer, E. W.
abstract

Squaraine dyes are well known for their strong absorption in the visible regime. Reports on chiral squaraine dyes are, however, scarce. To address this gap, we here report two novel chiral squaraine dyes and their achiral counterparts. The presented dyes are aggregated in solution and in thin films. A detailed chiroptical study shows that thin films formed by co-assembling the chiral dye with its achiral counterpart exhibit exceptional photophysical properties. The circular dichroism (CD) of the co-assembled structures reaches a maximum when just 25 % of the chiral dye are present in the mixture. The solid structures with the highest relative CD effect are achieved when the chiral dye is used solely as a director, rather than the structural component. The chiroptical data are further supported by selected spin-filtering measurements using mc-AFM. These findings provide a promising platform for investigating the relationship between the dissymmetry of a supramolecular structure and emerging material properties rather than a comparison between a chiral molecular structure and an achiral counterpart.

2020 - Highly Efficient and Tunable Filtering of Electrons' Spin by Supramolecular Chirality of Nanofiber-Based Materials [Articolo su rivista]
Kulkarni, C.; Mondal, A. K.; Das, T. K.; Grinbom, G.; Tassinari, F.; Mabesoone, M. F. J.; Meijer, E. W.; Naaman, R.
abstract

Organic semiconductors and organic–inorganic hybrids are promising materials for spintronic-based memory devices. Recently, an alternative route to organic spintronic based on chiral-induced spin selectivity (CISS) is suggested. In the CISS effect, the chirality of the molecular system itself acts as a spin filter, thus avoiding the use of magnets for spin injection. Here, spin filtering in excess of 85% in helical π-conjugated materials based on supramolecular nanofibers at room temperature is reported. The high spin-filtering efficiency can even be observed in nanofibers assembled from mixtures of chiral and achiral molecules through chiral amplification effect. Furthermore and most excitingly, it is shown that both “up” and “down” orientations of filtered spins can be obtained in a single enantiopure system via the temperature-dependent helicity (P and M) inversion of supramolecular nanofibers. The findings showcase that materials based on helical noncovalently assembled systems are modular platforms with an emerging structure–property relationship for spintronic applications.

2020 - Magnetoelectrochemistry and asymmetric electrochemical reactions [Articolo su rivista]
Mishra, S.; Di Marzio, M.; Giovanardi, R.; Tassinari, F.
abstract

Magnetoelectrochemistry is a branch of electrochemistry where magnetic fields play a vital role in the oxidation and reduction process of the molecules. When it comes to spin-dependent electrochemistry (SDE), becomes a new paradigm. This work presents electrochemical response during the “chiral imprinting” on working electrodes and the effects of potentiostatic and galvanostatic methods. We explore the use of the SDE concept, which is implemented for chiral-ferromagnetic (CFM) hybrid working electrodes, and we compare various electrochemical parameters affecting the quality of deposition. We electrochemically co-deposited nickel (Ni) with a chiral compound (tartaric acid) in its enantiopure forms (L and D), which allows us to obtain a chiral co-deposited nickel-tartaric acid (Ni-LTA or Ni-DTA) working electrode.

2020 - Relation between Morphology and Chiroptical Properties in Chiral Conducting Polymer Films: A Case Study in Chiral PEDOT [Articolo su rivista]
Amsallem, D.; Bedi, A.; Tassinari, F.; Gidron, O.
abstract

The electronic properties of conducting polymers are influenced by their micro- and macrostructural orders, which can be tailored by substituent modification. However, while the effect of substituents on conducting polymers is extensively investigated, chiral substituents are far less studied. Furthermore, many chiral conducting polymers have regioirregular structures, which result in polymer films with inferior properties. In this work, we apply electronic circular dichroism (ECD) spectroscopy to study the morphological changes to the chiral polymers under different polymerization conditions. For this purpose, we investigated 3,4-ethylenedioxythiophene (EDOT) derivatives having two stereogenic centers on each monomer and bearing methyl or phenyl side groups (dimethyl-EDOT and diphenyl-EDOT, respectively). Polymerizing the enantiomerically pure monomers produces regioregular and stereoregular dimethyl-PEDOT and diphenyl-PEDOT, respectively. The effect of the electrolyte and solvent on polymer film morphology was studied using scanning electron microscopy (SEM) and ECD, showing a correlation between the polymer's morphology and the chiroptical properties of its films. We found that, for diphenyl-PEDOT, the combination of perchlorate anion electrolyte and acetonitrile solvent resulted in a unique morphology characterized by significant intermolecular interactions. These interactions were clearly observable in the ECD spectra in the form of exciton couplings, whose presence was supported by TD-DFT calculations. A small enantiomeric excess was sufficient to induce very intense ECD signals, demonstrating chiral amplification in electropolymerized films.

2020 - Spin-Dependent Enantioselective Electropolymerization [Articolo su rivista]
Tassinari, F.; Amsallem, D.; Bloom, B. P.; Lu, Y.; Bedi, A.; Waldeck, D. H.; Gidron, O.; Naaman, R.
abstract

The electro-oxidative polymerization of an enantiopure chiral 3,4-ethylenedioxythiophene monomer, performed using spin-polarized currents, is shown to depend on the electron spin orientation. The spin-polarized current is shown to influence the initial nucleation rate of the polymerization reaction. This observation is rationalized in the framework of the chiral-induced spin selectivity effect.

2020 - Spin-dependent charge transfer at chiral electrodes probed by magnetic resonance [Articolo su rivista]
Blumenschein, F.; Tamski, M.; Roussel, C.; Smolinsky, E. Z. B.; Tassinari, F.; Naaman, R.; Ansermet, J. -P.
abstract

Chirality-induced spin selectivity is evidenced by exciting the spin resonance of radicals in an electrochemical cell where the working electrode is covered with a chiral self-assembled monolayer. Because the electron transfer to and from the paramagnetic radical is spin dependent, the electrochemical current changes at resonance. This electrically-detected magnetic resonance (EDMR) is monitored by a lock-in detection based on electrode voltage modulation, at a frequency that optimizes the sensitivity of the differential conductance to the electrode charge transfer process. The method is validated using p-doped GaAs electrodes in which the conduction band electrons are hyperpolarized by a well-known method of optical spin pumping with circularly polarized light. Gold electrodes covered with peptides consisting of 5 alanine groups (Al5) present a relative current change of up to 5 × 10-5 when the resonance condition is met, corresponding to a spin filtering efficiency between 6 and 19%.

2020 - The electron spin as a chiral reagent [Articolo su rivista]
Naaman, Ron; Metzger, Tzuriel S; Mishra, Suryakant; Bloom, Brian P; Goren, Naama; Neubauer, Avner; Shmul, Guy; Wei, Jimeng; Yochelis, Shira; Tassinari, Francesco; Fontanesi, Claudio; Waldeck, David H; Paltiel, Yossi
abstract

In contrast to the notion that enantiospecific chemical reactions require a chiral reagent molecule or catalyst, this work shows that enantioselective chemical transformations can be induced by the electron spin itself. As electrons are injected from a magnetized electrode into an adsorbed molecule, they have a distinct spin orientation relative to their velocity; i.e., they have a well-defined helicity. Thus, it is possible to replace a conventional enantiopure chemical reagent by spin-polarized electrons that provide the chiral bias for enantioselective reactions. Three examples of enantioselective chemistry, resulting from electron spin polarization, are presented. The first example demonstrates enantioselective association of a chiral molecule with an achiral self-assembled monolayer film that is spin-polarized. The other two studies show that the chiral bias provided by the electron helicity can drive both reduction and oxidation enantiospecific electrochemical reactions. In each case, the enantioselectivity does not result from enantiospecific interaction of the molecule with the ferromagnetic electrode, but rather it arises from the polarized spin that crosses the interface between the substrate and the molecule. In all three cases, the direction of the electron spin polarization defines the sense (left-handed versus right-handed) of the enantioselectivity. This work demonstrates a new mechanism for realizing enantioselective chemistry.

2019 - A SYSTEM AND METHOD FOR PROMOTING CHEMICAL REACTIONS [Brevetto]
Naaman, Ron; Fontanesi, Claudio; Tassinari, Francesco; Mishra, Suryakant; Capua, Eyal; Paltiel, Yossef; Yochelis, Shira; Metzger, Tzuriel
abstract

A system and method for use in synthesis and promoting interactions of chiral molecules. The system comprising: a container configured for containing fluid mixture comprising one or more reactant molecules, and at least one surface comprising ferromagnetic or paramagnetic material, located to be in at least partial contact with reactants in said container. The ferromagnetic of paramagnetic material is magnetized with magnetization direction perpendicular to said at least one surface, thereby providing chiral selective synthesis from said one or more reactant molecules. The technique enables selective interactions of enantiomers of selected handedness of chiral molecules or formation of selected enantiomers from achiral molecule reactants.

2019 - Chiral, low-resistance organic and nanoscale frameworks that uniquely propagate spin polarized currents [Abstract in Atti di Convegno]
Bullard, G.; Tassinari, F.; Ko, C. H.; Mishra, S.; Mondal, A.; Wang, R.; Naaman, R.; Therien, M.
abstract

Spin based properties, applications and devices are typically related to ferromagnetic effects and therefore magnetic inorganic materials. The development of organic materials for spintronic applications was long encumbered by its reliance on ferromagnetic electrodes for polarized spin injection. The discovery of the chirality induced spin selectivity (CISS) effect defines a marked departure from this paradigm, as it exploits soft materials, operates at ambient temperature, and eliminates the need for a magnetic electrode. To date, the CISS effect has been explored almost exclusively in molecular insulators. This presentation describes the utility of highly conjugated molecular and nanoscale materials that drive large magnitude CISS effects, generate substantial spin-polarized currents, and define new compositions of matter important for spintronic devices that exploit the CISS effect. A combination of spin polarization Hall device measurements, along with magneto-conductive atomic force microscopy (mC-AFM) and conducting spin-dependent electrochemistry (SDE) data, underscore that these molecular and nanoscale materials display exceptional utility to propagate spin-polarized currents due to their low resistances and long spin lattice relaxation times

2019 - Controlling Chemical Selectivity in Electrocatalysis with Chiral CuO-Coated Electrodes [Articolo su rivista]
Ghosh, K. B.; Zhang, W.; Tassinari, F.; Mastai, Y.; Lidor-Shalev, O.; Naaman, R.; Mollers, P.; Nurenberg, D.; Zacharias, H.; Wei, J.; Wierzbinski, E.; Waldeck, D. H.
abstract

This work demonstrates the chiral-induced spin selectivity effect for inorganic copper oxide films and exploits it to enhance the chemical selectivity in electrocatalytic water splitting. Chiral CuO films are electrodeposited on a polycrystalline Au substrate, and their spin filtering effect on electrons is demonstrated using Mott polarimetry analysis of photoelectrons. CuO is known to act as an electrocatalyst for the oxygen evolution reaction; however, it also generates side products such as H 2 O 2 . We show that chiral CuO is selective for O 2 ; H 2 O 2 generation is strongly suppressed on chiral CuO but is present with achiral CuO. The selectivity is rationalized in terms of the electron spin-filtering properties of the chiral CuO and the spin constraints for the generation of triplet oxygen. These findings represent an important step toward the development of all-inorganic chiral materials for electron spin filtering and the creation of efficient, spin-selective (photo)electrocatalysts for water splitting.

2019 - Electric-Field-Enhanced Adsorption of Chiral Molecules on Ferromagnetic Substrates [Articolo su rivista]
Santra, K.; Zhang, Q.; Tassinari, F.; Naaman, R.
abstract

The effect of an electric field on the adsorption of oligopeptides and DNA on a ferromagnetic substrate magnetized perpendicular to the surface was investigated. The direction of the magnetic moment of the substrate defines different adsorption rates for different enantiomers, and the direction of the electric field, perpendicular to the surface, defines different adsorption rates depending on the direction of the dipole moment of the adsorbed molecules.

2019 - Enantioselective Reduction of Camphorsulphonic Acid Using a Spin-polarized Electrode. [Abstract in Atti di Convegno]
Tassinari, F.; Mishra, S.; Naaman, R.
abstract

2019 - Enantioseparation by crystallization using magnetic substrates [Articolo su rivista]
Tassinari, F.; Steidel, J.; Paltiel, S.; Fontanesi, C.; Lahav, M.; Paltiel, Y.; Naaman, R.
abstract

Enantiospecific crystallization of the three amino acids asparagine (Asn), glutamic acid hydrochloride (Glu·HCl) and threonine (Thr), induced by ferromagnetic (FM) substrates, is reported. The FM substrates were prepared by evaporating nickel capped with a thin gold layer on standard silicon wafers. Magnets were positioned underneath the substrate with either their North (N) or South (S) poles pointing up. Asymmetric induction, controlled by the magnetic substrates, was demonstrated for the crystallization of the pure enantiomers and was then extended for the racemic mixtures of Asn and Glu·HCl. In the case of the solution of the pure enantiomers, the l enantiomer was crystallized preferentially at one pole of the magnet and the d enantiomer at the other. Consequently, the racemates of Asn and Glu·HCl undergo separation under the influence of the magnetic substrate. With Thr, however, despite the enantiospecific interactions of the pure enantiomers with the FM, no separation of the emerging crystals could be achieved with the racemates, although they crystallize as conglomerates, implying differences taking place in the crystallization step. The results reported here are not directly related to the magnetic field, but rather to the aligned spins within the ferromagnets. The findings provide a novel method for resolving enantiomers by crystallization and offer a new perspective for a possible role played by magnetic substrates regarding the origin of chirality in nature.

2019 - Enantiospecific interactions between chiral molecules and magnetic surfaces [Abstract in Atti di Convegno]
Tassinari, Francesco; BANERJEE-GOSH, Koyel; Naaman, Ron; Paltiel, Yossi
abstract

The Chiral-Induced Spin Selectivity (CISS) effect was reported for the first time in 1999, and later it was found that photo-electrons moving through a self-assembled monolayer of DNA showed a 60% spin-polarization. This effect shows that when electrons move through chiral molecules, their transport is spin-dependent, with the preferred spin-orientation determined by the handedness of the molecule and the direction of motion. More recent studies demonstrated that upon adsorption of a chiral self-assembled monolayer (SAM), a soft ferromagnetic layer could be permanently magnetized in one direction, depending on the handedness of the adsorbed molecule. This effect originates from the well-known phenomenon in which the formation of a SAM with a large dipole moment involves charge transfer that equalizes the electrochemical potential of the adsorbed layer and the sample surface: as a result of the CISS effect, this charge transfer is spin-polarized and thus can magnetize the ferromagnetic layer. Based on these studies, we investigated the complimentary phenomenon, the possible use of a magnetized ferromagnetic layer to induce enantioselective adsorption of chiral molecules. The results indicate that the interaction of chiral molecules with a perpendicularly magnetized substrate is enantiospecific. Thus, one enantiomer adsorbs preferentially when the magnetic dipole is pointing up, whereas the other adsorbs faster for the opposite alignment of the magnetization. The interaction is not controlled by the magnetic field per se, but rather by the electron spin orientations, and opens prospects for a distinct approach to enantiomeric separations. These results suggest that the same approach can be used to achieve chiral resolution in the crystallization processes of conglomerates. The spin-polarized surface promotes crystallization of enantiomorphous crystals depending on the direction of the magnetic moment.

2019 - Low-Resistance Molecular Wires Propagate Spin-Polarized Currents [Articolo su rivista]
Bullard, G.; Tassinari, F.; Ko, C. -H.; Mondal, A. K.; Wang, R.; Mishra, S.; Naaman, R.; Therien, M. J.
abstract

Spin based properties, applications, and devices are typically related to inorganic ferromagnetic materials. The development of organic materials for spintronic applications has long been encumbered by its reliance on ferromagnetic electrodes for polarized spin injection. The discovery of the chirality-induced spin selectivity (CISS) effect, in which chiral organic molecules serve as spin filters, defines a marked departure from this paradigm because it exploits soft materials, operates at ambient temperature, and eliminates the need for a magnetic electrode. To date, the CISS effect has been explored exclusively in molecular insulators. Here we combine chiral molecules, which serve as spin filters, with molecular wires that despite not being chiral, function to preserve spin polarization. Self-Assembled monolayers (SAMs) of right-handed helical (l-proline)8 (Pro8) and corresponding peptides, N-Terminal conjugated to (porphinato)zinc or meso-To-meso ethyne-bridged (porphinato)zinc structures (Pro8PZnn), were interrogated via magnetic conducting atomic force microscopy (mC-AFM), spin-dependent electrochemistry, and spin Hall devices that measure the spin polarizability that accompanies the charge polarization. These data show that chiral molecules are not required to transmit spin-polarized currents made possible by the CISS mechanism. Measured Hall voltages for Pro8PZn1-3 substantially exceed that determined for the Pro8 control and increase dramatically as the conjugation length of the achiral PZnn component increases; mC-AFM data underscore that measured spin selectivities increase with an increasing Pro8PZn1-3 N-Terminal conjugation. Because of these effects, spin-dependent electrochemical data demonstrate that spin-polarized currents, which trace their genesis to the chiral Pro8 moiety, propagate with no apparent dephasing over the augmented Pro8PZnn length scales, showing that spin currents may be transmitted over molecular distances that greatly exceed the length of the chiral moiety that makes possible the CISS effect.

2018 - Chirality Dependent Charge Transfer Rate in Oligopeptides [Articolo su rivista]
Tassinari, F.; Jayarathna, D. R.; Kantor-Uriel, N.; Davis, K. L.; Varade, V.; Achim, C.; Naaman, R.
abstract

It is shown that “spontaneous magnetization” occurs when chiral oligopeptides are attached to ferrocene and are self-assembled on a gold substrate. As a result, the electron transfer, measured by electrochemistry, shows asymmetry in the reduction and oxidation rate constants; this asymmetry is reversed between the two enantiomers. The results can be explained by the chiral induced spin selectivity of the electron transfer. The measured magnetization shows high anisotropy and the “easy axis” of magnetization is along the molecular axis.

2018 - Enhanced Electrochemical Water Splitting with Chiral Molecule-Coated Fe3O4 Nanoparticles [Articolo su rivista]
Zhang, W.; Banerjee-Ghosh, K.; Tassinari, F.; Naaman, R.
abstract

Photoelectrochemical (PEC) water splitting is a promising approach for generating hydrogen from water. In order to enhance PEC water splitting efficiency, it is essential to inhibit the production of the hydrogen peroxide byproduct and to reduce the overpotential required by an inexpensive catalyst and with high current density. In the past, it was shown that coating TiO2 electrodes by chiral molecules or chiral films enhances the hydrogen production and reduces the production of H2O2 byproduct. This was explained to be a result of the chiral-induced spin selectivity (CISS) effect that induces spin correlation between the electrons transferred to the anode. However, typically the current observed in those studies was in the range of 1-100 μA/cm2. Here we report currents in the range of 10 mA/cm2 obtained by adsorbing chiral molecules on a well-established Fe3O4 nanoparticle (NP) catalyst deposited on the anode. The results indicate a new strategy for designing low-cost earth-abundant catalysts where the advantages of the CISS effect are combined with the large effective area provided by the NPs to promote PEC water splitting with high current density.

2018 - SYSTEM AND METHOD FOR SEPARATION OF CHIRAL COMPOUNDS USING MAGNETIC INTERACTIONS [Brevetto]
Naaman, Ron; Capua, Eyal; Lahav, Meir; Tassinari, Francesco; Paltiel, Yossef; Yochelis, Shira
abstract

Systems and methods are disclosed for use in the separation of chiral compounds, and enantiomers in particular. The system comprises a cavity (110) for containing a fluid mixture that comprises one or more types of chiral molecules, which may also include enantiomers, and at least one ferromagnetic or paramagnetic substrate (120) providing at least one interface (130) with said fluid mixture. The substrate (120) is magnetized providing a magnetic field Bz perpendicular to said ferromagnetic or paramagnetic interface (130), thereby providing a variation in the interaction energy of chiral molecules of different handedness, aka. enantiomers, with said substrate (120).

2018 - Separation of chiral molecules by enantio-specific interactions using magnetic surfaces. [Poster]
Capua, E.; Banerjee-Ghosh, K.; Tassinari, F.; Ben Dor, O.; Yochelis, S.; Paltiel, Y.; Naaman, R.
abstract

It is commonly assumed that recognition of chirality and enantio-selectivity, both in nature and in artificial systems, are solely related to a spatial geometrical effect, with the recognition process typically described by a “lock and key” model. In recent years, it has been suggested that as electrons move through or as charge is redistributed in chiral molecules, an enantio-specific electron spin orientation is preferred via the effect we address as the chiral induced spin selectivity (CISS) effect. These results led to the proposal that the spin polarization may affect enantio-recognition. Here, we show experimentally that the interaction of chiral molecules with a perpendicularly magnetized magnetic substrate is enantio-specific. Thus, one enantiomer adsorbs preferentially when the magnetic dipole is pointing up, whereas the other is adsorbed faster for the opposite alignment of the magnetic field. The interaction is not controlled by the magnetic field, but rather by the electron spin. This approach allows the development of a generic method for enantiomeric separations.

2018 - Separation of enantiomers by their enantiospecific interaction with achiral magnetic substrates [Articolo su rivista]
Banerjee-Ghosh, K.; Dor, O. B.; Tassinari, F.; Capua, E.; Yochelis, S.; Capua, A.; Yang, S. -H.; Parkin, S. S. P.; Sarkar, S.; Kronik, L.; Baczewski, L. T.; Naaman, R.; Paltiel, Y.
abstract

It is commonly assumed that recognition and discrimination of chirality, both in nature and in artificial systems, depend solely on spatial effects. However, recent studies have suggested that charge redistribution in chiral molecules manifests an enantiospecific preference in electron spin orientation. We therefore reasoned that the induced spin polarization may affect enantiorecognition through exchange interactions. Here we show experimentally that the interaction of chiral molecules with a perpendicularly magnetized substrate is enantiospecific. Thus, one enantiomer adsorbs preferentially when the magnetic dipole is pointing up, whereas the other adsorbs faster for the opposite alignment of the magnetization. The interaction is not controlled by the magnetic field per se, but rather by the electron spin orientations, and opens prospects for a distinct approach to enantiomeric separations.

2018 - Spin-controlled electrochemistry using chiral electrodes: Effects on water electrolysis [Poster]
Tassinari, F.; Mtangi, W.; Banerjee-Ghosh, K.; Adelizzi, B.; Parenti, F.; Vankayala, K.; Palmans, A.; Jentzsch, A. V.; Fontanesi, C.; Mucci, A.; Meijer, E. W.; Naaman, R
abstract

Hydrogen is the ecologically ideal energy vector. Efficient photo-electrochemical production of hydrogen from water could be the optimal solution to the energy storage problems related to renewable sources. However, in the water splitting reaction the electric potential required to initiate the process significantly exceeds the thermodynamic limit. By controlling the spins of the electrons that are transferred from the solution to the anode, and ensuring that they are coaligned, the threshold voltage for the process can in theory be decreased to that of the thermodynamic voltage. In the present study, by using TiO2 anodes coated with chiral materials, we explore what are the effects of having a spin-polarized current on water electrolysis. The spin-polarization arises from exploiting what is known as Chiral Induced Spin Selectivity effect by using chiral molecules as spin filters. When using chiral molecules instead of a non-chiral analogue, the hydrogen production from water is enhanced, the threshold voltage is reduced and the by-product formation of hydrogen peroxide is suppressed. Figure: control of hydrogen peroxide production. UV-vis spectra from the titration of the used electrolyte (Na2SO4) with o-tolidine of bare TiO2 and TiO2 electrodes coated with (A) self-assembled Zn-porphyrins of either achiral (A-Zn) or chiral (S-Zn) and (B) TPyA molecules. (C) When the electrons transfer to the anodes is non spin specific the spins of the unpaired electrons on the two radicals are aligned antiparallel, hence the interaction is on a singlet surface that correlates with the production of hydrogen peroxide (H2O2). (D) When the electron transfer to the anode is spin specific, the spins of the two electrons are aligned parallel to each other, hence the two radicals interact on a triplet surface that forbids the formation of H2O2 and facilitates the production of oxygen in its ground state.

2018 - Spin-controlled electrochemistry using chiral electrodes: Effects on water electrolysis [Abstract in Atti di Convegno]
Tassinari, F; Mtangi, W; Banerjee-Ghosh, K; Adelizzi, B; Parenti, F; Vankayala, K; Palmans, A; Jentzsch, Av; Fontanesi, C; Mucci, A; Meijer, E; Naaman, R
abstract

2017 - Chiral Polythiophenes [Capitolo/Saggio]
Parenti, Francesca; Schenetti, Luisa; Tassinari, Francesco
abstract

This review reports the synthesis and the properties of chiral polythiophenes (PTs) and in particular it is focused on PTs bearing a sulfur atom directly bonded to the thiophene ring. These polymers show remarkable properties, related to their chirality and electrical conductivity and to the ability to interact with chiral molecules opening the possibility for using them in new potential applications, like chiral sensors, chiral resolution and electrodes.

2017 - Control of Electrons' Spin Eliminates Hydrogen Peroxide Formation during Water Splitting [Articolo su rivista]
Mtangi, Wilbert; Tassinari, Francesco; Vankayala, Kiran; Vargas Jentzsch, Andreas; Adelizzi, Beatrice; Palmans, Anja R. A.; Fontanesi, Claudio; Meijer, E. W; Naaman, Ron
abstract

The production of hydrogen through water splitting in a photoelectrochemical cell suffers from an overpotential that limits the efficiencies. In addition, hydrogen-peroxide formation is identified as a competing process affecting the oxidative stability of photoelectrodes. We impose spin-selectivity by coating the anode with chiral organic semiconductors from helically aggregated dyes as sensitizers; Zn-porphyrins and triarylamines. Hydrogen peroxide formation is dramatically suppressed, while the overall current through the cell, correlating with the water splitting process, is enhanced. Evidence for a strong spin-selection in the chiral semiconductors is presented by magnetic conducting (mc-)AFM measurements, in which chiral and achiral Zn-porphyrins are compared. These findings contribute to our understanding of the underlying mechanism of spin selectivity in multiple electron-transfer reactions and pave the way toward better chiral dye-sensitized photoelectrochemical cells.

2017 - Enhanced Hydrogen Production with Chiral Conductive Polymer-Based Electrodes [Articolo su rivista]
Tassinari, Francesco; Banerjee Ghosh, Koyel; Parenti, Francesca; Kiran, Vankayala; Mucci, Adele; Naaman, Ron
abstract

Efficient photo-electrochemical production of hydrogen from water is the aim of many studies in recent decades. Typically, one observes that the electric potential required to initiate the process significantly exceeds the thermodynamic limit. It was suggested that by controlling the spins of the electrons that are transferred from the solution to the anode, and ensuring that they are coaligned, the threshold voltage for the process can be decreased to that of the thermodynamic voltage. In the present study, by using anodes coated with chiral conductive polymer, the hydrogen production from water is enhanced, and the threshold voltage is reduced, as compared with anodes coated with achiral polymer. When CdSe quantum dots were embedded within the polymer, the current density was doubled. These new results point to a possible new direction for producing inexpensive, environmentally friendly, efficient water-splitting photo-electrochemical cells. (Graph Presented).

2017 - High Circular Polarization of Electroluminescence Achieved via Self-Assembly of a Light-Emitting Chiral Conjugated Polymer into Multidomain Cholesteric Films [Articolo su rivista]
Di Nuzzo, D.; Kulkarni, C.; Zhao, B.; Smolinsky, E.; Tassinari, F.; Meskers, S. C. J.; Naaman, R.; Meijer, E. W.; Friend, R. H.
abstract

We demonstrate a facile route to obtain high and broad-band circular polarization of electroluminescence in single-layer polymer OLEDs. As a light-emitting material we use a donor-acceptor polyfluorene with enantiomerically pure chiral side-chains. We show that upon thermal annealing the polymer self-assembles into a multidomain cholesteric film. By varying the thickness of the polymer emitting layer, we achieve high levels of circular polarization of electroluminescence (up to 40% excess of right-handed polarization), which are the highest reported for polymer OLEDs not using chiral dopants or alignment layers. Mueller matrix ellipsometry shows strong optical anisotropies in the film, indicating that the circular polarization of luminescence arises mainly after the photon has been generated, through selective scattering and birefringence correlated in the direction of the initial linear polarization of the photon. Our work demonstrates that chirally substituted conjugated polymers can combine photonic and semiconducting properties in advanced optoelectronic devices.

2017 - Polymers with Alkylsulfanyl Side Chains for Bulk Heterojunction Solar Cells: Toward a Greener Strategy [Articolo su rivista]
Tassinari, Francesco; Libertini, Emanuela; Parenti, Francesca; Mucci, Adele
abstract

The synthesis and properties of three co-polymers obtained through a Knoevenagel poly-condensation are reported. They are soluble in organic solvents, filmable and solvatochromic. They are characterized through GPC, NMR and UV-visible spectroscopies, CV, and AFM. They display some proneness to form π-stacks, broad absorptions up to about 700 nm, HOMO and LUMO energies that fit those of [60]PCBM. The polymers are incorporated in blends with PCBM within BHJ devices. The best results are found for PSCs obtained from P1 (2.7 % PCE). The insertion of alkylsulfanyl chains improves the photovoltaic performances, with respect to those of alkyl-substituted analogous polymers. The Jsc of the devices are greatly enhanced, supporting the employment of (alkylsulfanyl)thienyl units as base units in photoactive materials.

2017 - Π‑Stacking Signature in NMR Solution Spectra of Thiophene-Based Conjugated Polymers [Articolo su rivista]
Parenti, Francesca; Tassinari, Francesco; Libertini, Emanuela; Lanzi, Massimiliano; Mucci, Adele
abstract

Studies on conjugated polymers seldom report on their NMR characterization in solution. This paper shows how NMR experiments, both 1H NMR and routine 2D NMR spectra, can help in gaining a further insight into the aggregation behavior of conjugated polymers and could be used to flank the more employed solid-state NMR and other spectroscopy and microscopy techniques in the understanding of the aggregation processes. NMR spectroscopy allows distinguishing, within the class of poorly solvatochromic conjugated polymers, those highly prone to form π-stacked aggregates from the ones that have a low tendency toward π-stacking.

2016 - CONJUGATED POLYMERS FOR PHOTOVOLTAICS: FROM SOLUTION TO SOLID-STATE NMR [Abstract in Atti di Convegno]
Mucci, Adele; Parenti, Francesca; Libertini, Emanuela; Tassinari, Francesco; Schenetti, Luisa
abstract

Conjugated polymers are widely studied for applications in organic electronics.[1] The structural scenery is varied and the properties of polymers and copolymers can change heavily with the structure. The characterization of organic polymers used in organic electronics, and in particular in polymer solar cells (PSCs), is strongly multidisciplinary. It requires expertise within different branches of chemistry and at the border among chemistry, physics and engineering. Here, the contribution of solution NMR to the study of self-aggregation properties of thiophene based conjugated polymers will be presented. NMR findings on polymers in solution appear to be correlated to morphological properties and solvatochromism. Since one of the most actively investigated application of conjugated polymers is as donors in bulk hetero junction PSCs, also some results obtained with solid-state NMR on polymer/fullerene blends will be reported.

2016 - Conjugated Polymers for Solar Cells Incorporating the Dithienosilole Unit [Abstract in Atti di Convegno]
Parenti, Francesca; Tassinari, Francesco; Cugini, Alice; Schenetti, Luisa; Morvillo, P.; Ricciardi, R.; Mucci, Adele
abstract

Polymer Solar Cells (PSC) are widely studied as low cost, light weight and flexible alternative to silicon-based solar cells. The polymers suitable for this purpose should possess good solubility and filming properties and extended π-conjugated systems with high absorption coefficients, UV–Vis-NIR spectra ideally matching the solar spectrum, high hole mobility, and HOMO–LUMO energy levels suitable to be coupled with the acceptor species, such as fullerene derivatives. One of the newest monomeric units that can be used to build conjugated polymers for PSC is functionalized dithienosilole. This contribution will deal with the synthesis and properties of two different low band gap copolymers containing dithienosilole alternated to thienothiophene or to substituted bithiophene

2016 - Poly(Cyanovinylene Phenylene-Co-Thiophene)s For Polymer Solar Cells [Abstract in Atti di Convegno]
Tassinari, Francesco; Parenti, Francesca; Di Nicola, F. P.; Ballarin, B.; Lanzi, M.; Libertini, Emanuela; Mucci, Adele
abstract

We synthetized, using a Knoevenagel polycondensation reaction, three different poly(phenylenecyanovinylene-co-thiophenes) , slightly changing the structure of the thiophene comonomer, to study the effect that these changes can have on the efficiency of photovoltaic devices built using these polymers

2016 - Polymers for application in organic solar cells: Bithiophene can work better than thienothiophene when coupled to benzodithiophene [Articolo su rivista]
Parenti, Francesca; Ricciardi, Rosa; Diana, Rosita; Morvillo, Pasquale; Fontanesi, Claudio; Tassinari, Francesco; Schenetti, Luisa; Minarini, Carla; Mucci, Adele
abstract

The synthesis and characterization of two low band gap copolymers (P1 and P2) incorporating benzo[1,2-b:4,5- b’]dithiophene unit substituted with octylsulfanylthienyl groups (OSBT) are here reported. These materials, designed to be employed in polymer solar cells (PSCs), were obtained from alternating OSBT and bithiophene (P1) or thienothiophene (P2) units. Their structural electrochemical and photophysical properties were investigated. They are thermally stable and soluble in organic solvents from which they easily form films. They also form p-stacks in solution, in film and display a moderate solvatochromism. These polymers were tested with [70]PCBM in bulk-heterojunction (BHJ) PSCs where they act as donor materials and [70]PCBM is the electron acceptor. The best device, obtained using a 1:3 weight ratio for the P1:[70]PCBM blend, shows a PCE around 1.5%. A broad response from 350 to 700 nm is also observed in the external quantum efficiency (EQE) curves, wider for P1 with respect to P2.

2015 - Characterization of Conducting Polymers for Organic Solar Cells [Abstract in Atti di Convegno]
Parenti, Francesca; Tassinari, Francesco; Fontanesi, Claudio; Schenetti, Luisa; Morvillo, P.; Ricciardi, R.; Diana, R.; Minarini, C.; Lanzi, M.; Mucci, Adele
abstract

Thiophene based copolymers are widely studied as the donor active layer in bulk hetero junction polymer solar cells (PSCs). These copolymers, in some cases formed by an alternating structure of donor/acceptor units, can be fine tuned in their electronic energy levels in order to achieve better power conversion efficiencies values.1 The characterization of organic polymers for application in PSCs, or organic electronics in general, is multidisciplinary in nature, for it requires expertise within different branches of chemistry and at the border among chemistry, physics and engineering.2 As organic chemists, we have to check the structure and properties of these polymers and this is not always trivial. This contribution will be mainly focussed on the NMR characterization of polymers in solution and to the problems arising when aggregation occurs. This is particularly observed when benzodithiophene and thienothiophene (that are among the most popular units) are present in the backbone. NMR findings appear to be strongly correlated to solvatochromism or morphological properties

2015 - Chiral Conductive Polymers as Spin Filters [Articolo su rivista]
Mondal, Prakash Chandra; Kantor Uriel, Nirit; Mathew, Shinto P.; Tassinari, Francesco; Fontanesi, Claudio; Naaman, Ron
abstract

Conductive organic polymers are used in organic electronic devices and specifically in organic-based light-emitting diodes (OLEDs). It is expected that by controlling the spin of the electrons that are injected from and into these devices, their energy efficiency will increase significantly. However, it is commonly thought that this would require introducing ferromagnets into the device, which represents a technological challenge. We present data indicating that electron transport through a chiral conductive polymer is highly spin dependent; hence, the polymers themselves can serve as a spin filter and in principle, this may allow the operation of spin-OLED without any magnetic component.

2015 - Chiral Polythiophenes [Abstract in Atti di Convegno]
Schenetti, Luisa; Libertini, Emanuela; Mucci, Adele; Parenti, Francesca; Tassinari, Francesco
abstract

Polythiophenes (PT) belong to the class of Conducting organic polymers and Conducting organic polymers that possess chirality present some unique opportunities when used as chiral substrates or as chiral electrode materials. The properties of chiral conducting PT can be tunable modifying the functional groups to the polymer backbone) and since these polymers can be formed as particles, membranes or micro- and nanodimensional fibers ,it is possible to design and to develop specific molecular systems for molecular recognition. The chiroptical properties of CCP films were studied under different evaporation conditions. The chiral recognition abilities of CCP are reported and also a new application in the field of spin filter.

2015 - Chiral conductive polymers as spin filters [Abstract in Atti di Convegno]
Tassinari, Francesco; Parenti, Francesca; Mondal, P. C.; Kantor ‐Uriel, N.; Mathew, S. P.; Naaman, R.; Fontanesi, Claudio; Schenetti, Luisa; Mucci, Adele
abstract

We investigated spin-selective electron transport through poly{[methyl N -(tert-butoxycarbonyl)-S-3- thienyl- L -cysteinate]-cothiophene} (PCT-L)5. Measurements were performed in two configurations: in an electrochemical cell at room temperature or in a solid state device at various temperatures.

2015 - New one-step thiol functionalization procedure for Ni by self-assembled monolayers [Articolo su rivista]
Fontanesi, Claudio; Tassinari, Francesco; Parenti, Francesca; Cohen, Hagai; Mondal, Prakash Chandra; Kiran, Vankayala; Giglia, Angelo; Pasquali, Luca; Naaman, Ron
abstract

This article reports on a facile and fast strategy for the self-assembled monolayer (SAM) functionalization of nickel surfaces, employing cyclic voltammetry (CV) cycling of a suitable tailored solution containing the species to be adsorbed. Results are presented for ultrathin films formed on Ni by 1-hexadecanethiol (C16), L-cysteine (L-cys), and the polymethyl (2R)-3-(2,2'-bithiophen-4-ylsulfanyl)-2-[(tert-butoxycarbonyl)amino]propanoate (PCT-L) thiophene-based chiral polymer. The effective formation of high-quality ultrathin organic films on the nickel was verified both electrochemically and by exploiting typical surface characterization techniques such as contact angle, ellipsometry, atomic force microscopy (AFM), polarization modulation-infrared reflection-absorption spectroscopy (PM-IRRAS), and X-ray photoelectron spectroscopy (XPS).

2015 - Performance of polymer solar cells with (alkylsulfanyl)bithiophene copolymers [Relazione in Atti di Convegno]
Ricciardi, R.; Morvillo, P.; Diana, R.; Minarini, C.; Mucci, Adele; Parenti, Francesca; Tassinari, Francesco; Schenetti, Luisa
abstract

In this work we report the performances of PSCs realized with the following materials as electron donor: a polymer containing (alkylsulfanyl)bithiophene unit, the poly[4,4’- bis(butylsulfanyl)-2,2’-bithiophene] (PolyM), a copolymer having bis(octylsulfanyl)bithienyl (OSBT) unit alternated with a BDT unit substituted with ethylhexyloxyl groups, the poly[4,8-bis(2-ethylhexyloxy)benzo[1,2-b:4,5-b′]dithiophenealt- 4,4’-bis(octylsulfanyl)-2,2’-bithiophene] (PolyS) and a copolymer having OSBT unit alternated with BDT unit substituted with (octylsulfanyl)thienyl groups, the poly{4,8- bis[(5-octylsulfanyl)-2-thienyl]benzo[1,2-b:4,5- b′]dithiophene-alt-4,4’-bis(octylsulfanyl)-2,2’-bithiophene} (PolyA)

2015 - Synthesis Of Low Band-Gap Conjugated Polymers For Application In Solar Cells [Abstract in Atti di Convegno]
Libertini, Emanuela; Morvillo, P.; Mucci, Adele; Tassinari, Francesco; Schenetti, Luisa; Parenti, Francesca
abstract

Polymer solar cells are a fascinating low cost alternative to silicon-based solar cells1 thanks to light weight, mechanical flexibility and processability. The polymers suitable for this purpose should possess good filming and absorption properties (absorption coefficients >105 cm-1 and UV–Vis spectrum ideally matching the solar spectrum)2, high hole mobility, and HOMO–LUMO energy levels suitable to be coupled with the acceptor species3. In this presentation the synthesis of three different low band gap copolymers is reported and discussed. The properties of these materials are compared in order to gain an insight on the molecular structure-performance relationship of the final device

2014 - Effect of the Electric Field on the Structure of a Chiral Conductive Polymer Thin Film [Abstract in Atti di Convegno]
Tassinari, Francesco; Mathew, S. P.; Fontanesi, Claudio; Schenetti, Luisa; Mucci, Adele; Naaman, R.
abstract

The chemical-physical properties of conductive polymer thin films are strictly related to the structure and conformations of the chains in the polymer lattice. Crystallinity, chain length, substituents, doping level are just some of the many variables that play a role in the final properties of the polymer films. Another key factor is the orientation of the chains inside the thin film. A polymer chain is anisotropic, and so are its properties. However, a lattice where the chains are randomly arranged will have the same properties no matter which direction we measure them, whereas an oriented lattice will show different properties related to the preferential order of the macromolecular structure. We used different electric fields to align the macromolecules of a chiral conductive polymer (CCP), capable of self-organizing in chiral helixes in the solid state, and we studied its effect on the anisotropy of the obtained thin films, on the structure of the aggregates and on the conductive properties of the polymer by means of different instrumental techniques. All the measurements showed a preferential alignment of the polymer chains after the process under applied electric field. Circular dichroism was used to probe the chirality of the polymer aggregates, and it was found that the field strongly influences the helical superstructures of the CCP. The use of the electric field to fine tune the helical structures of this chiral polymer stands out as an interesting possibility which we are currently investigating.

2014 - Electric Field-Driven Alignment of Chiral Conductive Polymer Thin Films [Articolo su rivista]
Tassinari, Francesco; Mathew, Shinto P.; Fontanesi, Claudio; Schenetti, Luisa; Naaman, Ron
abstract

We investigated the effect of an electric field on the alignment and structural properties of thin films of a chiral polybithiophene-based conductive polymer, functionalized with a protected l-cysteine amino acid. Thin films were obtained by exploiting both drop-casting and spin-coating procedures. The electric properties, the polarized Raman spectrum, the UV–vis spectrum, and the CD spectra were measured as a function of the electric field intensity applied during film formation. It was found that beyond the enhancement of the conductivity observed when the electric field aligns the polymer, the electric field significantly affects the chiral properties and the effect depends on the method of deposition.

2014 - Low band gap polymers for application in solar cells: synthesis and characterization of thienothiophene-thiophene copolymers [Articolo su rivista]
P., Morvillo; R., Diana; Fontanesi, Claudio; R., Ricciardi; M., Lanzi; Mucci, Adele; Tassinari, Francesco; Schenetti, Luisa; C., Minarini; Parenti, Francesca
abstract

In this paper we present the synthesis and characterization of two novel copolymers obtained from a bithiophene unit carrying octylsulfanyl side chains and thienothiophene units substituted with keto (PK) or ester (PE) groups. Their structural, electrochemical and photophysical properties were investigated by gel permeation chromatography (GPC), thermogravimetric analysis (TGA), NMR, UV-visible-NIR spectroscopy, cyclic voltammetry (CV) and atomic force microscopy (AFM). They possess good solubility in common organic solvents, filmability, proneness to form π-stacks, moderate solvatochromism, good thermal stability and low band gap energy. They were tested as donor materials in combination with [70]PCBM (electron acceptor) in bulk-heterojunction polymer solar cells. The geometry of the devices are: glass/ITO/PEDOT:PSS/ copolymer:[70]PCBM/Ca/Al. The external quantum efficiency curve of the best device, realized using a blend of PK:[70]PCBM, 1:2 weight ratio, shows a broad response from 350 to 1000 nm. The power conversion efficiency under 100 mW/cm2 AM 1.5G illumination is greater than 1%.

2014 - Polymer Solar Cells based on Benzodithiophene copolymers [Abstract in Atti di Convegno]
Parenti, Francesca; Diana, R.; Fontanesi, Claudio; Minarini, C.; Morvillo, P.; Ricciardi, R.; Schenetti, Luisa; Tassinari, Francesco; Mucci, Adele
abstract

Polymer solar cells are widely seen as the promise to a cheap alternative to the silicon-based ones. In addition to their low costs, they also have other advantages such as light weight, easy processability and compatibility with large scale flexible substrates, which make them suitable for a wide range of applications. However, the efficiency of photovoltaic energy conversion for these plastic devices is still low and this is limiting their commercial use. The efficiency of these polymeric photovoltaic cells got a significative increase when the bulk heterojunction (BHJ) configuration was introduced: it consists in an interpenetrating network of electron donor and acceptor materials that largely increases the active area and diminishes the distance that charge carriers have to travel. Recently, benzodithiophene (BDT) based polymers (Fig.1) have been used as electron donors in polymer solar cells showing very promising properties such as an increased charge transport and a red shift on the absorption spectra. In this work, the synthesis of different regioregular copolymers having substituted BDT as one of the monomers are described. The obtained polymers are characterized by spectroscopic and electrochemical techniques. Energy conversion measurements of BHJ solar cells produced with these polymers were conducted, and the electrical performances were compared in order to study the influence of the different comonomers on the overall efficiency of the devices.

2014 - Synthesis and characterization of an organic co-polymer for photovoltaic application [Abstract in Atti di Convegno]
Andrea, Copelli; Tassinari, Francesco; Mucci, Adele; Parenti, Francesca
abstract

Harvesting energy directly from sunlight using photovoltaic technology is considered as being one of the most important ways to address growing global energy needs using a renewable resource. Polymeric solar cells (PSCs) are a promising alternative to silicon-based solar cell for producing clean and renewable energy thanks to light weight, mechanical flexibility, processability and low costs [1]. The most studied polymers are the 3-alkyl substituted polythiophenes, but they show limited efficiency and, to improve power conversion, the synthesis of new systems is required [2]. Co-polymers formed by ThienoThiophene Carboxylate (TTC) and DiThienoSilole (DTS) units are widely studied as Donor systems in Bulk Heterojunction (BHJ) solar cells. In this presentation we report the synthesis of PSiTT (see the chemical structure) and it's characterization via UV-Vis-NIR, NMR Spectroscopy, IR, AFM and GPC.

2014 - Synthesis of low bandgap Thiophene-Based Copolymers: new donor material candidates in organic solar cells [Abstract in Atti di Convegno]
Parenti, Francesca; P., Morvillo; R., Diana; R., Ricciardi; C., Minarini; Fontanesi, Claudio; Mucci, Adele; A., Copelli; Schenetti, Luisa; Tassinari, Francesco
abstract

Polymer solar cells (PSCs) are emerging as promising alternatives to silicon-based solar cells [1] thanks to light weight, mechanical flexibility, processability and low costs. One of the common polymers used in PSCs are 3-alkyl substituted polythiophenes, but a low band gap alternative is needed in order to reach better cell performances [2]. Copolymers bearing thienothiophene (TT) and benzodithiophene (BDT) alternating units are widely studied as donor material in Bulk Heterojunction Cells [3]. In this poster communication we report on the synthesis and spectroscopic electrochemical, photovoltaic characterization of two thiophene based copolymers bearing thienyl substituted-BDT units alternating with bithiophene and TT-units respectively.

2013 - On the co-adsorption process of sodium dodecyl sulfate and sodium dodecylbenzenesulfonate on a 1-decanethiol-functionalized Au electrode, as a corrosion inhibiting mimic process [Articolo su rivista]
Fontanesi, Claudio; Camurri, Giulio; Tassinari, Francesco
abstract

The co-adsorption of sodium dodecyl sulfate (SDS) and sodium dodecylbenzenesulfonate (SDBS), on the 1-decanethiol self-assembled monolayer (SAM)-functionalized polycrystalline gold surface, is investigated by electrochemical techniques. The peak current (cyclic voltammetry) and charge transfer resistance (impedance spectra) variations are measured, concerning the [Fe(CN)6]3−/[Fe(CN)6]4− couple redox process. SDBS is found to yield a more efficient inhibiting barrier (towards the charge transfer process), when compared to the SDS one. Thus, it is suggesting that a higher tendency of SDBS to be co-adsorbed within the 1-decanethiol SAM with respect to SDS.

2013 - Regiochemistry in the electrochemical assisted grafting of glassy carbon. With focus on sterical hindrance of lateral chains in the electroreduction process of multi-functionalized bithiophene [Articolo su rivista]
Tassinari, Francesco; Vanossi, Davide; Mucci, Adele; Parenti, Francesca; Fontanesi, Claudio
abstract

The electrochemically assisted grafting process of glassy carbon (GC) surfaces is pursued by using the 7-[(5,50-diiodo-2,20-bithiophen-4-yl)sulfanyl]heptanenitrile (DIBHN). Which is an ad hoc synthesized bithiophene derivative: the DIBHN features two non-equivalent iodine substituents in the 5 (which is under the sterical hindrance of the sulfanylheptanenitrile group) and 50 positions. CV measurements show the occurrence of two reduction processes, the second, more cathodic one, induces the grafting. This result is in qualitative agreement with theoretical calculations (B3LYP/6-311G level of the theory) concerning the comparison of the optimized structures of the DIBHN neutral and radical anion species (first electroreduction process): the C–I bond length of the iodine in the 5 position varies from 2.098 (neutral) to 2.835 Å (radical anion), while the C–I bond length of the iodine in the 50 position remains virtually unchanged when comparing the geometries of the neutral and radical anion structures. Raman spectra are recorded for various polymer film thicknesses; the comparison with theoretical calculated Raman spectra further support the effective grafting of the glassy carbon surface.

2013 - Synthesis and properties of new bio-functionalized polythiophenes [Altro]
Tassinari, Francesco; Fontanesi, Claudio; Mucci, Adele; Schenetti, Luisa
abstract

Polythiophenes are part of the family of conductive polymers. They are extremely popular nowadays for their promising applications in the organic solar cells. Their reactivity is very well established, and a large number of reaction for their modification is available in the literature. The possibility of tailoring these polythiophenes with a large library of different functional groups opens the door to a great number of possible applications. We synthesized two bio-functionalized polythiophenes, one bearing a cysteine aminoacid[1], the other an aniline ring acting as a linker for a laccase enzyme. The presence of the cysteine aminoacid in the side-chain of the polymer backbone gives to the polythiophene a very large circular dichroism activity, and the sign of the effect is related to the chirality of the attached aminoacid. The wavelenght of the CD effect is in the absorption zone of the thiophene rings, which is a strong proof to the presence of helicoidal arrangement of the polymer backbone in the polymer aggregates. The helicoidal structure is promoted by the side-chain aminoacid, and the chirality of the substituent influence the direction of the helix. This chiral conductive polymer and the helical structures that are present in its solid state are a perfect material to study the spin-conduction inside organic molecules (such as the Chiral Induced Spin Selectivity effect). The aniline substituted polymer has been designed to be used for bio-sensing applications. The thiophene substituted monomer is electropolymerized directly on the electrode surface, and the presence of the aniline allows the direct linking of the laccase enzyme to the electrode surface. The laccase enzyme catalyses the oxidation of phenols and polyphenols, and the product of the oxidation can be reduced at the electrode surface to give a signal proportional to the analyte concentration[2]. The same approach can be used for a large range of enzymes, giving this kind of polythiophene-based sensor engineering a wide applicability.

2012 - A novel copolymer from benzodithiophene and alkylsulfanyl-bithiophene: Synthesis, characterization and application in polymer solar cells [Articolo su rivista]
P., Morvillo; Parenti, Francesca; R., Diana; Fontanesi, Claudio; Mucci, Adele; Tassinari, Francesco; Schenetti, Luisa
abstract

In this paper we present the synthesis and characterization of a novel copolymer from thienothiophene and bithiophene units carrying nonanoyl and octylsulfanyl side chains, poly[1-(thieno[3,4-b]thien-2-yl)nonan-1-one-alt-4,4’-bis(octylsulfanyl)-2,2’-bithiophene] (PolyH). The structural, electrochemical and photophysical properties of PolyH were investigated by gel permeation chromatography (GPC), thermogravimetric analysis (TGA), NMR, UV-VIS-NIR spectroscopy and cyclic voltammetry (CV). PolyH possesses good solubility in common organic solvents, filmability, a proneness to form π-stacks and a moderate solvatochromism. PolyH was tested as donor material in combination with [70]PCBM (electron acceptor) in bulk-heterojunction polymer solar cells. The geometry of the device is: glass/ITO/PEDOT:PSS/ PolyH:[70]PCBM/Ca/Al. The external quantum efficiency curve of the best device (realized using a blend of PolyH:[70]PCBM, 1:2 weight ratio) shows a broad response from 350 to 1000 nm. The power conversion efficiency under 100 mW/cm2 AM 1.5G illumination is greater than 1%.

2012 - Functionalization of glassy carbon surface by means of aliphatic and aromatic amino acids. An experimental and theoretical integrated approach [Articolo su rivista]
Vanossi, Davide; Benassi, Rois; Parenti, Francesca; Tassinari, Francesco; Giovanardi, Roberto; Florini, Nicola; DE RENZI, Valentina; Arnaud, Gaelle Francoise; Fontanesi, Claudio
abstract

Glassy Carbon (GC) electrode surfaces are functionalized through electrochemical assisted grafting, in oxidation regime, of six amino acids (AA): -Alanine (-Ala), L-Aspartic acid (Asp), 11-aminoundecanoic acid (UA), 4-Aminobenzoic acid (PABA), 4-(4-Amino-phenyl)-butyric acid (PFB), 3-(4-Amino-phenyl)-propionic acid (PFP). Thus, a GC/AA interface is produced featuring carboxylic groups facing the solution. Electrochemical (cyclic voltammetry and electrochemical impedance spectroscopy) and XPS techniques are used to experimentally characterize the grafting process and the surface state. The theoretical results are compared with the experimental evidence to determine, at a molecular level, the overall grafting mechanism. Ionization Potentials, Standard Oxidation Potentials, HOMO and electron spin distributions are calculated at the CCD/6-31G* level of the theory. The comparison of experimental and theoretical data suggests that the main electroactive species is the “zwitterionic” form for the three aliphatic amino acids, while the amino acids featuring the amino group bound to the phenyl aromatic moiety show a different behaviour. The comparison between experimental and theoretical results suggests that both the neutral and zwitterionic forms are present in the acetonitrile solution in the case of 4-(4-Amino-phenyl)-butyric acid (PFB) and 3-(4-Amino-phenyl)-propionic acid.

2012 - Low Bandgap Copolymers with (Alkylsulfanyl) Bithiophene Unit for Efficient Polymer Solar Cells [Relazione in Atti di Convegno]
P., Morvillo; Parenti, Francesca; R., Diana; E., Bobeico; Mucci, Adele; Tassinari, Francesco; Schenetti, Luisa; C., Minarini
abstract

Polymer solar cells have evolved as a promising cost-effective alternative to silicon-based ones. However, low efficiency of these plastic devices limits their feasibility for commercial use. The efficiencies of polymer photovoltaic cells got a major boost with the introduction of the bulk heterojunction (BHJ) configuration consisting of an interpenetrating network of electron donor and acceptor materials. Recently, benzodithiophene based polymers has been used as electron donors in polymer solar cells showing very promising properties such as an increasing charge transport and a red shift of the absorption spectra. In this work the synthesis, the spectroscopic and photovoltaic characterization of a copolymer based on (octylsulfanyl)bithiophene and benzo[1,2-b:4,5-b’]dithiophene units and a polymer based on (butylsulfanyl)bithiophene unit are reported. BHJ solar cells using these polymers as donor materials blended with [70]PCBM as acceptor were prepared and investigated. The geometry of the device is: glass/ITO/PEDOT:PSS/blend/Ca/Al. The electrical performances of the cells were compared in order to study the influence of the benzodithiophene unit on the polymer backbone. The power conversion efficiency of the best realized polymer solar cell is 2.3% under 100 mW/cm2 AM 1.5G illumination

2012 - Low band gap thienothiophene-thiophene copolymer: synthesis, characterization and application in polymer solar cells [Abstract in Atti di Convegno]
P., Morvillo; Parenti, Francesca; R., Diana; Fontanesi, Claudio; M., Lanzi; Mucci, Adele; Tassinari, Francesco; Schenetti, Luisa
abstract

Polymer solar cells (PSCs) have recently attracted considerable attention due to their advantages of low cost, light weight, processability and compatibility with large scale flexible substrates. The most efficient device architecture of polymer solar cells is based on the bulk heterojunction concept in which the active layer, sandwiched between two electrodes with different work functions, consists of a blend of electron donating material, e.g. a p-type conjugated polymer, and an electron accepting material (n-type), such as fullerene derivatives.Polythiophenes are quite interesting materials for this purpose, combining the above described advantages with an enhanced photochemical stability, compared with poly(p-phenylene vinylene) and poly p-phenylene. In this work the synthesis, the spectroscopic and photovoltaic characterization of a thienothiophene-thiophene copolymer are reported. Poly[2-nonanoylthieno[3,4-b]thiophene-4,6-diyl-alt-4,4’-bis(octylsulfanyl)-2,2’-bithiophene]) was obtained by Stille coupling between the dibromo derivative of 2-nonanoylthienothiophene and a distannyl derivative of bis(octylsulfanyl)bithiophene.Bulk heterojunction solar cells using these polymers as donor materials blended with PCBM as acceptor were prepared and investigated. The geometry of the device is: glass/ITO/PEDOT:PSS/Polymer:PCBM/Ca/Al. An efficient charge transfer between the donor and PCBM takes place and the best device obtained has and efficiency of 1% under simulated light (AM1.5G). Further improvement of the efficiency using different acceptors, optimizing layer thickness and lowering polymer impurities can be envisaged.

2012 - On the Hybrid Glassy Carbon Electrode/OligoThiophene/Ag(NP) Interface [Articolo su rivista]
Tassinari, Francesco; Tancini, Erik; Massimo, Innocenti; Schenetti, Luisa; Fontanesi, Claudio
abstract

GC/OligoThiophene/Ag(NP) hybrid interfaces are synthesized and characterized: GC is the glassy carbon surface; OligoThiophene stands for both an ultrathin bithiophene grafted film and a 4-Br-Bithiophene grafted polymer; Ag(NP) stands for silver nanoparticles. The hybrid interface preparation involves different steps: first, the electrode surface is functionalized through a combination of electrochemically assisted grafting (under reduction regime) and polymerization (under oxidation regime); then, silver nanoparticles are chemisorbed by dipping. In particular, an ultrathin film of grafted bithiophene can be obtained by applying one cyclic voltammetry reduction cycle (GC/BT surface), while subsequent cyclic voltammetry cycling under oxidation regime yields an immobilized 4Br-Bithiophene polymer (GC/4BrBT surface). AFM and TEM images were recorded to investigate the morphology and chemical composition of the Ag(NP). FeII/ FeIII cyclic voltammetry, Zn underpotential deposition (UPD), XPS, LA-ICP-MS, and Raman techniques were exploited to characterize both the GC/OligoThiophene and GC/OligoThiophene/Ag(NP) interfaces. Theoretical calculation, at the B3LYP/ 6-311G** level of the theory, enabled rationalization of the electroreduction mechanism and the Raman results.

2011 - (Alkylsulfanyl)bithiophene-alt-Fluorene: π-Conjugated Polymers for Organic Solar Cells [Articolo su rivista]
Parenti, Francesca; Pasquale, Morvillo; Eugenia, Bobeico; Rosita, Diana; Massimiliano, Lanzi; Fontanesi, Claudio; Tassinari, Francesco; Schenetti, Luisa; Mucci, Adele
abstract

We describe the synthesis of alternating bithiophene–fluorenecopolymers (P1–P3) with different regiochemistry of thebithienyl unit and different alkylsulfanyl chain lengths. Thestructural, electrochemical and photophysical properties ofthese polymers were investigated by gel permeationchromatography (GPC), differential scanning calorimetry(DSC), NMR, UV/Vis and photoluminescence (PL) spectroscopyand cyclic voltammetry (CV), and the polymerswere used to assemble organic solar cells (OSCs), in combi-IntroductionOrganic conjugated materials are attracting increased attentiondue to their potential in the fields of chemical sensors,[1] electroluminescent devices,[1c,2] field-effect transistors[3] and OSCs.[4] The last is one of the most appealingapplications of conjugated polymers because they have thepotential to be a low cost alternative to conventional inorganicsemiconductors.[5] The major desirable features ofOSCs are mechanical flexibility, very high speed of processingand low cost for large area fabrication.[6] The mostefficient device architecture of polymeric solar cells is basedon the bulk heterojunction concept (BHJ),[7] in which theactive layer, sandwiched between two electrodes with differentwork functions, consists of a blend of electron donatingmaterial, e.g. a p-type conjugated polymer, and an electronaccepting material (n-type), such as fullerene derivatives.For application in OSCs, conjugated polymers should[a] Dipartimento di Chimica, Università di Modena e ReggioEmilia,Via G. Campi 183, 41125 Modena, ItalyFax: +39-059373543E-mail: adele.mucci@unimore.it[b] ENEA, C.R. Portici,Piazzale E. Fermi 1, 80055 Portici (NA), ItalyE-mail: pasquale.morvillo@enea.it[c] Dipartimento di Chimica Industriale e dei Materiali, Universitàdi Bologna,V.le del Risorgimento 4, 40136 Bologna, ItalySupporting information for this article is available on theWWW under http://dx.doi.org/10.1002/ejoc.201100738.Eur. J. Org. Chem. 0000, 0–0 © 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 1nation with the fullerene derivative methyl [6,6]-phenyl-C61-butyrate (PCBM). P3, with a head-to-head bithienyl unit,shows a broader absorption and a lower band gap with respectto P1 and P2, which have tail-to-tail bithienyl units.The PL intensity of P1–P3 is dramatically quenched in thepresence of PCBM, demonstrating that an efficient chargetransfer between donor and acceptor occurs. The best OSCdevice was obtained with P3.

2011 - Organic Materials for Phovoltaics: Synthesis and Electrochemical Behaviour of a Thiophene Based Copolymer [Abstract in Atti di Convegno]
Parenti, Francesca; R., Diana; Fontanesi, Claudio; P., Morvillo; Mucci, Adele; Schenetti, Luisa; Tassinari, Francesco
abstract

Polymer solar cells (PSCs) have recently attracted considerable attention due to their advantages of low cost, light weight, processability and compatibility with large scale flexible substrates [1]. Polythiophenes are quite interesting materials for this purpose, combining the above described advantages with an enhanced photochemical stability, compared with poly(p-phenylene vinylene) and poly p-phenylene.In this communication the synthesis, the spectroscopic, the electrochemical and photovoltaic characterization of a thiophene based copolymerare reported. The synthesis was performed in analogy to ref. [2] via Stille coupling of a brominated and a stannilated comonomer as illustrated in Fig.1. The copolymer was characterised through 1H and 13C NMR, Uv-Vis spectroscopy, Cyclic Voltammetry.References[1] S. Gunes, H. Neugebauer, N. S. Sariciftci, “Conjugated Polymer-Based Organic Solar Cells” Chem. Rev. 107, 1324 (2007) ; M. Helgesen, R. Søndergaard, F. C. Krebs, “Advanced materials and processes for polymer solar cell devices”, J. Mater. Chem. 20, 36 (2010) ; J. Peet, J. Y. Kim, N. E. Coates, W. L. Ma, D. Moses, A. J. Heeger, G. C. Bazan, “Efficiency enhancement in low-bandgap polymer solar cells by processing with alkane dithiols”, Nat. Mater. 6, 497 (2007) ; S. A. Gevorgyan and F. C. Krebs in Handbook of thiophene-Based materials, I. F. Perepichka and D. F. Perepichka ed. (John Wiley and Sons Ltd., 2009). [2]Yongye Liang, Danqin Feng, Yue Wu, Szu-Ting Tsai, Gang Li, Claire Ray and Luping Yu, “Highly Efficient Solar Cell Polymers Developed via Fine-Tuning of Structural and Electronic Properties”, JACS 131, 7792-7799 (2009)

2011 - Preparation and characterization of bithiophene modified Si(1,1,1) electrodes [Abstract in Atti di Convegno]
Tassinari, Francesco; Fontanesi, Claudio; Mucci, Adele; Parenti, Francesca; Schenetti, Luisa
abstract

The purpose of this work is to prepare a substituted oligothiophene (OT) modified electrode, in which the oligomer is capable of acting as a conductive wire between the electrode surface and the solution bulk.A simple model system is represented by a bithiophene chemically grafted to the surface of a hydrogen terminated n-doped Si(111) electrode. The possibility to functionalize with different moieties the lateral chain and the thiophene rings makes these systems very versatile and easily customizable.

Università degli studi di Modena e Reggio Emilia

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