Optical Properties of Nanocomposite Films: Size-tuned vs. Shape-tuned Silver Nanoparticles

Color change is a desirable response when designing user-friendly chemical sensors. However, when preparing colored nanocomposites sensors, it can be challenging to transfer the color from solution into films. This work demonstrates that films of various colors can be prepared by blending premade nanoparticles with poly(vinyl alcohol) (PVA); however, the color in solution differed from the color in film. While, this color discrepancy and the appearance of the films depended on how the optical properties of nanoparticles were tuned, UV-visible spectroscopy and Transmission Electron Microscopy (TEM) showed that changes in nanoparticle’s morphology was not the cause of the color discrepancy. Reflecting the polydispersity of nanoparticles in solution, more homogeneous colored films were obtained by controlling the size of nanoparticles rather than their shape. This work shows how to readily prepare silver-PVA nanocomposite films of various colors, which may facilitate the design of nanocomposites intended for chemical sensing based on the optical properties of silver nanoparticles.