Síntese de Nanopartículas de Prata por Método Fotoquímico: Efeito da Concentração de Citrato de Sódio e Adição de PVP nas Propriedades Termo-Ópticas

Abstract

The study of metallic nanoparticles (NPs) is of significant scientific and technological interest due to their unique properties associated with Localized Surface Plasmon Resonance (LSPR). Therefore, special attention is given to synthesis as it is necessary to have control over the shape and size of the NPs. In this work, the synthesis of silver nanoparticles (AgNPs) through the photochemical method was investigated. This method involves the absorption of photons in a photochemically active compound that induces the reduction of metal ions. To obtain AgNPs, a solution of 1mMol of AgNO3 was used as a precursor, sodium citrate as a reducing agent, Polyvinylpyrrolidone (PVP) as a surfactant, and exposed to the light of an LED. Several parameters were altered for different syntheses, including the incident LED wavelength, the quantity and concentration of sodium citrate and PVP, and the LED light exposure time. After synthesis, UV-Vis spectroscopy measurements were conducted to verify NP formation, Dynamic Light Scattering (DLS) and Transmission Electron Microscopy (TEM) were employed to assess NP size, and Zeta Potential measurements were performed to examine NP stability. It was observed that with an increase in the quantity of sodium citrate, the absorption peak corresponding to the Plasmon resonance in the UV-Vis region increased, and the average NP size decreased. Conversely, the addition of PVP resulted in a decrease in the Plasmon resonance absorption peak. When altering the incident LED wavelengths, samples prepared with Ultraviolet (UV) LED exhibited a significantly higher absorption peak than samples prepared with other wavelengths. Additionally, Spatial Self-Phase Modulation (SSPM) measurements were carried out for the different syntheses to study the nonlinear properties of the NPs. Syntheses with higher amounts of citrate and PVP exhibited reduced nonlinear optical behavior.