Human hair is a huge untapped waste resource whose useful compounds require toxic and environmentally harmful chemicals to extract. Herein, the optical properties of human hair without using such chemicals, turning waste into a site-selective multicolored display, and a chemical sensor with a visual indicator through tunable fluorescence are transformed. The tunable fluorescence color, which includes both visible light and infrared components, is achieved using a scanning laser beam (microscopic) and hotplate heating at a low temperature of 360 °C for 3 min (macroscopic and large-scale production). These fluorescing hairs readily detect methylene blue molecules within a concentration range of 10-12 - 10-21 M due to the formation of tryptophan byproducts and electron contributing pyrrolic nitrogen. This work's simple yet impactful consequence lays the foundation on which the industrial applicability of the functionalized human hair waste can be achieved, realizing a possible cyclical economy through sustainable resources.
Source: Image: Alex Dykes/iStockphoto_172188388