Síntese de nanopartículas mistas de prata e platina ancoradas em substrato de sílica visando posterior aplicação em sensores ópticos

Abstract

The characteristic optical properties of metallic nanoparticles (NPs) originate from the plasmonic resonance phenomenon, in which the oscillation frequencies of the surface electrons and the frequency of oscillation of the incident radiation come into resonance. Silver NPs exhibit plasmon absorption in the visible region of the electromagnetic spectrum, varying the absorption maximum value according to their size, morphology and the environment in which they are found. This characteristic confers a potential application on optical sensors, which can confer greater selectivity and sensitivity to such devices. Systems containing NPs of different compositions tend to exhibit distinct properties from those found in isolated NPs. In this, way, the synthesis of mixed NPs of Ag and Pt can give rise to a material with new properties. Thus, this work aimed at the synthesis and characterization of Ag and Pt NPs anchored in silica substrate for the production of materials with potential application in optical sensor devices. The routes used followed the steps of functionalization of the silica surface by the silanizing agent APTES, followed by the anchoring and reduction of the metal cations. For the chemical route, NaBH4 was used as a reducing agent, while for the thermal route APTES itself was used as reducing agent by heat treatment. The reductions occurred using one and two-steps methods (concomitant and successive reductions). The obtained samples were characterized by the techniques of UV-Vis spectroscopy, Xray diffraction (XPS) and transmission electron microscopy (TEM). At some samples, the UV-Vis spectra obtained showed the occurrence of two maximum absorption bands near of the absorption regions of pure NPs. The X-ray diffractograms did not showed any NPs-related results, making it necessary to use a acessorie for thin film fittings for future analysis. By the analysis of the images obteined by TEM technique, it was possible to confirm the presence of NPs with a great variability of sizes and shapes for which proposed synthetic route.