A physically transient and eco-friendly distributed feedback laser chemosensor for detecting acid vapor

Organic DFB lasers are ideal for fluorescence chemosensing, due to the amplified light-matter interaction at resonances, related to high sensitivity and detectability. However, an inherent limitation of organic lasers for the chemosensing application is their short lifetime, since the multiple optical pumping quenches the quantum yield of the probe dye. Natural silk protein containing sodium fluorescein (probe dye) spin-coated on a quartz grating enables a physically transient, cost-effective, and eco-friendly DFB laser for chemosensing. The attenuated lasing in optically pumped silk/dye DFB laser displays a sensitivity to hydrochloric acid (HCl) vapor that is more than 30 times higher than that obtained from fluorescence. We show that the elapsed time to cease lasing depends on the concentration of HCl and the thickness of the silk/dye layer. After washing out and recoating, the quenched silk/dye layer can be easily replaced by a new one. Additionally, the use of silk protein promises eco- and bio-friendly chemosensing due to favorable material traits, such as not creating pollution, and biocompatibility. Our approach would expand to the detection of other important analytes by choosing proper probe dyes.