|
AVINASH VIKATAKAVI
|
Home |
Curriculum(pdf) |
Pubblicazioni
2022
- Interaction of Hydrogen with Cu-Modified Cerium Oxide Surfaces
[Articolo su rivista]
Vikatakavi, Avinash; Benedetti, Stefania; Righi, Giulia; Magri, Rita; D'Addato, Sergio; Luches, Paola; Selloni, Annabella
abstract
2021
- Ultrafast Dynamics of Plasmon-Mediated Charge Transfer in Ag@CeO2 Studied by Free Electron Laser Time-Resolved X-ray Absorption Spectroscopy
[Articolo su rivista]
Pelli Cresi, Jacopo Stefano; Principi, Emiliano; Spurio, Eleonora; Catone, Daniele; O'Keeffe, Patrick; Turchini, Stefano; Benedetti, Stefania; Vikatakavi, Avinash; D'Addato, Sergio; Mincigrucci, Riccardo; Foglia, Laura; Kurdi, Gabor; Nikolov, Ivaylo P; De Ninno, Giovanni; Masciovecchio, Claudio; Nannarone, Stefano; Kopula Kesavan, Jagadesh; Boscherini, Federico; Luches, Paola
abstract
Expanding the activity of wide bandgap semiconductors from the UV into the visible range has become a central goal for their application in green solar photocatalysis. The hybrid plasmonic/semiconductor system, based on silver nanoparticles (Ag NPs) embedded in a film of CeO2, is an example of a functional material developed with this aim. In this work, we take advantage of the chemical sensitivity of free electron laser (FEL) time-resolved soft X-ray absorption spectroscopy (TRXAS) to investigate the electron transfer process from the Ag NPs to the CeO2 film generated by the NPs plasmonic resonance photoexcitation. Ultrafast changes (<200 fs) of the Ce N4,5 absorption edge allowed us to conclude that the excited Ag NPs transfer electrons to the Ce atoms of the CeO2 film through a highly efficient electron-based mechanism. These results demonstrate the potential of FEL-based TRXAS measurements for the characterization of energy transfer in novel hybrid plasmonic/semiconductor materials.
2019
- Physical Synthesis and Study of Ag@CaF 2 Core@Shell Nanoparticles: Morphology and Tuning of Optical Properties
[Articolo su rivista]
D'Addato, Sergio; Vikatakavi, Avinash; Spadaro, Maria Chiara; Valeri, Sergio; Pasquali, Luca
abstract
Pre-formed Ag nanoparticles (NPs) and Ag@CaF 2 core–shell NPs are physically synthesized using DC magnetron-based NP source and deposited on Si-SiO x wafers. The samples are prepared by co-depositing Ag nanoparticles and CaF 2 produced by an evaporation source, or by sequential deposition method, i.e., by depositing in a sequence a CaF 2 buffer layer, the Ag NPs generated by the NP source and a capping CaF 2 layer. The supported films are characterized by Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS), and Surface Differential Reflectivity (SDR). SEM shows that Ag NPs deposited directly on Si-SiO x tend to diffuse and to agglomerate, affecting the size distribution of the nanostructures. The presence of a CaF 2 buffer layer between Ag and Si-SiO x limits this effect, while XPS reveals electrical charging, caused by the insulating nature of the CaF 2 continuous film. The surface plasmon resonance behavior for different samples is analyzed using SDR with p-polarized light. There is a clear evidence of a blue shift in the plasmon excitation due to the presence of CaF 2 on Si, which can represent a potential advantage for the technological applications in photovoltaics and optoelectronics.