Avaliação da incorporação de nanopartículas de ouro em filmes automontados de polieletrólitos fracos

Abstract

Nanotechnology has brought some new challenges such as the development of quality and synthesis processes on nanostructures based on inorganic and organic substances. The development of new materials with organic and inorganic compounds on the nanometer scale, has been featured at the forefront of materials science due to the large potential for applications such as composites, catalysis, nonlinear optics, sensors and microelectronic systems [1, 2, 3]. The development of nanostructured materials has attracted great interest for the new technological reality, due to the wide range of applications including catalytic properties, magnetic and photonic [4, 5, 6]. However the objective of this dissertation was to obtain self-assembled polyelectrolyte films fabricated by sequential adsorption of aqueous solutions of weak polyelectrolytes based on electrostatic interaction of polymers with opposite charges and analyze the distribution of gold nanoparticles (Au NPs) stabilized by sodium citrate and poly (vinylpyrrolidone) (PVP). In this work we used the following polymers, PEI (poly (ethylene imine)) and PAH hydrochloride poly (allylamine) as polycations and PAA (poly (acrylic acid) as polyanion. The presence of gold nanoparticles was confirmed by UV VIS NIR spectroscopy and X-ray Diffraction (XRD). The morphology and distribution of films with self-assembled gold nanoparticles was analyzed by Atomic Force Microscopy (AFM) and transmission electron microscopy (TEM). Quantification and thickness of the samples were analyzed by Rutherford backscattering spectrometry (RBS), and then evaluated in conjunction with the techniques of UV VIS NIR spectroscopy and TEM. The experimental approaches used in this work showed the great importance of pH for the fabrication of LbL self-assembled films due to its influence on the functional groups of polyelectrolytes, affecting the electrostatic interaction between them and between the nanoparticles subsequently disseminated. Smaller the charge density of the polyelectrolyte molecule, greater the required number of them to compensate a given surface charge of the substrate and/or lower layer. With the increase of that number, the greater the amount of sites present subject of electrostatic interactions. Among the systems studied, the most efficient was (PAH7/PAA4)20, which showed a greater incorporation of Au NPs, and consequently the greatest amount of Au NPs in the system.