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Multi-user equipment approved in grant 2022/11983-4: darkfield microscope

Abstract

The excitation of plasmon-polariton modes on the surface of metallic nanoparticles (NPs) enables a variety of applications for these materials, such as photocatalysts and photovoltaic and sensing devices. Plasmon excitation in NPs implies an increase in the intensity of spectroscopic signals from adsorbed molecules, in particular, the enhancement of Raman spectra (surface-enhanced Raman scattering, SERS). In a resonance condition between the excitation radiation and an electronic transition of the molecule, the signal intensification also results from the resonant Raman effect (RR). The combination of NO and rare earth ions makes it possible to enhance luminescence by unconventional processes such as upconversion and persistent luminescence. Recent advances in the preparation of NPs include the use of new solvents such as ionic liquids (ILs) and deep eutectic solvents (DES) due to their performance in colloidal stabilization. These neoteric liquids, in turn, also have various applications as media for chemical reactions, catalysis, gas absorption etc.. The detailed understanding of the relationship between molecular structure, liquid structure and its physicochemical properties is still a challenge. In this sense, this Thematic Project brings together expertise in nanoparticle synthesis, spectroscopy, theory and computer simulation of researchers from different universities: USP-São Paulo, USP-São Carlos, UNIFESP and UNICAMP. It is intended to relate the morphology of NPs and plasmonic catalysis, in particular the nanostructures with the dual function of promoting the photocatalytic reaction and giving rise to the intensification of the Raman spectrum. The ILs and DES will be solvents for the preparation of NPs, but also as liquids for the absorption of polluting gases (CO2 and SO2), whether physical or chemical sorption. In SERS theory, classical electrodynamics calculations will be performed to obtain the spatial distribution of the electric field around the NPs, and in RR theory, quantum chemistry calculations of the dynamics of excited electronic states will be performed using multiconfiguration perturbative methods. Vibrational spectroscopy in a wide range of temperature and pressure will be used in the study of phase transitions of ILs or DES, and molecular dynamics (MD) simulation in the study of the structure and dynamics of liquids. MD simulations of these liquids will be performed for nanoparticle dispersion in order to understand the structure of the liquid-nanoparticle interface, and dispersion of porous carbon materials in order to assess the absorption of gases. (AU)

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