Nanopartículas recobertas com óxidos aplicadas em espectroscopias intensificadas por superfícies e células solares

Abstract

The present work shows the synthesis, characterization and application of silver nanoparticles (AgNP), silver nanoparticles encapsulated in a layer of silicon dioxide (Ag@SiO2) and in a layer of niobium pentoxide (Ag@Nb2O5). Although Ag nanoparticles exhibit high intensity plasmonic modes, these particles tend to aggregate in solution, so encapsulation was performed in an oxide layer thick enough to allow stabilization against aggregation without complete surface plasmon dumping inside the oxide layer. The nanoparticles were characterized by UV-VIS spectroscopy, transmission electron microscopy (TEM) and dynamic light scattering (DLS). The spectra of the oxide-coated samples show a redshift of the extinction mode, which suggests the formation of an oxide layer on the nanoparticles, resulting in an increase in the mean refractive index of the medium. The nanoparticles were used as substrate for surface intensified Raman scattering (SERS) and for surface intensified fluorescence (SEF). The tests were performed with the IR-820 molecules adsorbed on the nanoparticles. SERS measurements were performed with incident radiation at 633 nm and SEF measurements with incident radiation at 785 nm. To evaluate the effect of nanoparticles in stimulating the generation of charge carriers in solar cells, AgNP and Ag@SiO2 nanoparticles were incorporated within the mesoporous TiO2 film used to assemble dye-sensitized solar cells (DSSC) and incorporated in the hole transporting layer in organic solar cell .The results show that the Ag@SiO2 and Ag@Nb2O5 nanoparticles are promising for application in SERS and SEF and the AgNP and Ag@SiO2 nanoparticles have resulted in increased photocurrent generation in the DSSCs. In the organic solar cell, the lower concentration of Ag@SiO2 resulted in increased photocurrent generation.