Utilização de filmes de polianilina na preparação de nanopartículas metálicas e bimetálicas

Abstract

In this work, Ag nanoparticles and bimetallic nanoparticles of Ag-Au and Au-Ag on polyaniline (PANI) nanofibre films were prepared. Each stage of the work was characterized using UV-VIS-NIR absorption and Raman spectroscopies, and scanning and transmission electron microscopies. The analysis of the composition of the bimetallic nanoparticles was performed by energy dispersion using the X-ray spectroscopy. PANI nanofibers doped with HCl were synthesised via a fast mixture of ammonium persulfate and aniline precursors. These nanofibers of esmeraldine salt (ES), which have an average thickness of 27 nm, were immersed in a basic solution for the deprotonation and formation of the base of esmeraldine base (EB). Bare glass substrates and modified glass substrates prepared by immersion in H2SO4/H2O2 and H2O/H2O2/NH4OH solutions, were used for the deposition of nanofibers, through immersion in the suspension of the ES, forming thin films of PANI. Thick films were also prepared by dripping the suspension of the PANI on the glass slide. In addition to the film doped with HCl, films doped with citric acid, phosphoric acid, mandelic acid, and toluene sulfonic acid were also prepared. The films of ES doped with the different acids and the EB film were immersed in AgNO3 solution for the reduction of Ag+ ions and formation of silver nanoparticles. It was noticed that the size and shape of the silver nanoparticles strong depend on the dopant and the thickness of the ES film. It was observed the formation of nano and microstructures in the range of 2 to 370 nm with shapes of needles, spheres, plates, and wires. The thin and thick films doped with HCl containing silver nanoparticles were subsequently immersed in HAuCl4 solution for the formation of bimetallic nanoparticles Ag-Au. It was also prepared bimetallic nanoparticles Au-Ag onto the films doped with HCl (thin and thick films) first by immersion in a gold salt solution and then immersion in a silver salt solution. The structures formed presented cubical, spherical, medium-sized wires in the range of 5 to 700 nm influenced by film thickness and synthesis mechanism. In addition, modifications in the polymeric structure were observed indicating the presence of phenazine, phenoxazine and safranin groups.