Desenvolvimento de nanopartículas metálicas e bimetálicas sobre filmes de polímeros condutores como substrato SERS reutilizáveis

Abstract

Polyaniline (PANI) with nanofiber and bulk morphologies were prepared and blended with cellulose acetate (CA) to form a plastic, flexible, and free-standing film. The PANI/CA was treated with hydrochloric or mandelic or tannic acid for PANI doping. These films were then used as reducing agents for Ag+ and Au3+ ions to synthesize silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs). Additionally, bimetallic Ag-Au NPs were prepared. These materials were characterized using X-ray diffraction, scanning electron microscopy (SEM), and Raman and UV-VIS absorption spectroscopies. SEM images showed that different acids used in the treatment of the PANI/CA blend led to different morphologies and sizes of NPs due to the different surface properties of PANI. X-ray diffraction confirmed the formation of metallic NPs, which exhibited crystalline structures on the amorphous polymer blend. Raman and visible reflectance spectroscopies allowed the observation of the persistent doped state of PANI during the synthesis process of these nanocomposites. This result is associated with the redox properties of PANI and the hydrolysis process of CA. SERS activity of films was tested using Nile blue dye (NB) at a concentration of 1.0×10-4 mol L-1 as a probe molecule. Different enhancements of the SERS signal of NB dye were obtained on these substrates due to the morphological characteristics of the metallic NPs, ranging from 103 to 105 . Furthermore, the reusability of these substrates was tested by washing the systems with solvent and also using UV radiation. Films containing AuNPs showed greater stability compared to AgNPs, which had their efficiency reduced more sharply during the reusability process. The degradation of the dye via UV radiation proved to be a more interesting methodology for removing the probe molecule and subsequent reuse of the SERS substrate.