Innovative textile design using the optical properties of metal nanoparticles

Abstract

Metal nanoparticles have received a great deal of attention in recent years because of their unique optical properties. Instead of the appearances in bulk size, metal particles exhibit unique optical properties at nanoscale. The colors of metal nanoparticle solutions are based on the morphology of the nanoparticles, including the shape and size. If the morphology of the nanoparticles is precisely controlled, solutions with desired colors can be obtained. Approaches for applying metal nanoparticles as colorants for textile fabrics have been reported in recent years. Both gold and silver nanoparticles have been used to generate various colors on textile substrates. However, most of the published works employed gold nanospheres with different particle sizes for textile colorations. It has been reported that the optical properties of the nanoparticles depend more on the shape of the nanoparticles than on their sizes. Thus, the colors provided by gold nanospheres are limited. Motivated by the extraordinary optical properties of non-spherically shaped gold nanoparticles, this study develops an innovative approach for using gold nanorods as colorants for cotton and silk fabrics. The gold nanorods were synthesized following a seed-mediated method. Through a controlled oxidation shortening process, the aspect ratios (length-to-width) of the gold nanorods were tuned and the color of the gold nanorod solutions systematically changed from brownish red (in the NIR region) to green to purplish red. UV/visible/NIR extinction spectra and TEM images of the gold nanorods were assessed. The modification process of textile fabrics with a common gold nanorod solution (gold nanorods of the same lengths and widths) was first studied. A variety of shades can be achieved by immersing the fabrics in the solution at different temperatures. The optimal condition for the modification process was then suggested. The existence of the gold nanorods on the modified fabrics was confirmed by XPS and SEM images. The mechanism of assembling gold nanorods on the textile fibers was discussed. After that, gold nanorods of different aspect ratios were used as colorants for the fabrics, providing them a broad range of visible colors. The reflectance spectra, colorimetric values, and SEM images of the fabrics modified with gold nanorods of different morphologies were studied. Finally, the functional properties, including the fastness, anti-bacterial, and UV-blocking properties of the modified fabrics were evaluated. The overall results suggest that gold nanorods of different aspect ratios can be used as colorants for both cotton and silk fabrics effectively. Similar colors can be transferred from gold nanorod solutions to textile fabrics. Detailed characterizations confirm that the colors of the fabrics originate from the unique localized surface plasmon resonances of the gold nanorods, which are adsorbed on fabrics with their shapes and sizes remaining nearly unchanged. The adsorption process can be conceived to be driven by the electrostatic interaction between the negatively charged fiber surfaces and positively charged gold nanorods. The modified fabrics also exhibit improved and effective anti-bacterial and UV-blocking properties. The study provides an optimal approach for innovative textile design by applying the optical properties of plasmonic metal nanoparticles.