Crescimento de nanopartículas metálicas mistas de ouro e cobre em substrato de sílica visando a obtenção de materiais com uso potencial em sensores ópticos

Abstract

Metallic nanoparticles (Nps) are very interesting materials for application in optical devices due to the characteristic of plasma absorption, which can be understood as the resonant oscillation of conduction electrons in Nps stimulated by incident light. It is because of this plasmon resonance that noble metals in colloidal form show different coloration. Sensors and optical devices can have their sensitivity and selectivity modified and improved by the controlled deposition of nanoparticles on the surface of the device. Therefore, the objective of this work was focused on the synthesis and characterization of mixed copper and gold nanoparticles deposited on silica substrate, and, with control of the synthesis variables, to compare properties of the obtained samples aiming a future application in optical sensing with this system. For this, the silica coverslips were functionalized with 3-aminopropyltriethoxysilane (APTES), the gold and copper nanoparticles were deposited on the silica coverslip simultaneously with the functionalization and the reduction of the metallic cations was provided through the thermal route, was carried out a study about the precursors for the synthesis of copper nanoparticles, and the samples were extensively characterized with the aid of physical-chemical analysis techniques, such as X-ray diffraction (XRD), absorption electron spectroscopy in the ultraviolet- visible light (UV-Vis), atomic force microscopy (AFM), transmission electron microscopy (TEM) and Raman microscopy (Raman) techniques. So far, it has been possible to successfully obtain a film of simple metallic and bimetallic nanoparticles through the proposed synthetic route. With the results measured só far, we can observe that the films obtained from copper/gold bimetallic nanoparticles have different characteristics from those derived only from copper or gold. This allows recognizing that the optical properties are different, as seen in UV-Vis spectroscopy analyses, which indicates a wider range of applications in optical sensing with the use of these films to expand the measurement window. The proposed route for obtaining films of bimetallic nanoparticles proved to be efficient, resulting in homogeneous films depending on the precursor salt and the concentration of the precursor solutions used. With the completion of the characterizations proposed in the course of this work, we will reach an important range of characteristics and we will be able, thus, to try to correlate the synthetic variables with the quality of the samples obtained.