Gold nanoparticles reinforced poly (vinyl alcohol) of self-standing optical films

A simple one-step process is developed to synthesize self-standing optical films of Au-doped polymer of poly(vinyl alcohol) (PVA). The visible color could be tuned precisely over a wide range from the violet to a yellowish with selective Au-contents from 0.1 to 5.0 wt%. The synthetic procedure involves a caloric Au3+ --> Au reaction in aqueous PVA at 60-90 degrees C temperatures followed by casting the sample (Au-nanocrystals (NCs) embedding in the PVA polymer molecules) as films or other shapes. Stable color persists of nanocolloids as well as films. The NCs are thin platelets of triangular, square, rectangular, or hexagonal shapes. There are very few pentagonal platelets and nanorods. As analyzed with microstructure, the NCs formation results in a structural anisotropy by the preferential adsorption of PVA on selective facets. An Au-content dependent emission occurs in the 400-650 nm regions, useful for possible optical data storage, nonlinear optical devices, and color pigments.