An improved method for fabrication of patterned composites made of silver or gold nanoparticles embedded in PDMS structures and their colorimetric characterization

Abstract

In this work, nanoparticles loaded polydimethylsiloxane (PDMS) nanocomposites were obtained by the direct reduction of Ag+ or Au3+ in ethanolic solution. Taking advantage of the colorful appearance of PDMS/Ag (yellow) and PDMS/Au (red), a colorimetric characterization was used to analyze the samples during their fabrication. For both types of samples, their colors become darker depending on the reaction time due to the increasing amount of nanosilver or nanogold formed on PDMS structures. Consequently, the collected colorimetric data expressed as ΔEab values presented a correlation with the reaction time. For both systems, it was detected a color saturation after 24 h, indicating that this time is a critical point and the color of the samples reaches a uniformity. Simultaneously, the spectrophotometer also measured the visible spectra, and with this analysis it was possible to detect the surface plasmon resonance bands of nanosilver and nanogold at 410 and 530 nm, respectively. The nanometric nature and distributions of silver and gold nanostructures on the PDMS matrix were confirmed by transmission electron microscopy. This analysis showed that silver and gold nanostructures are small than 100 nm and exhibited different shapes.