Organic distributed feedback (DFB) lasers have been attractive for optical chemosensors since the amplified light-matter interaction leads to high sensitivity and detectability of the sensor. However, quenching quantum efficiency of the probe dye under multiple optical pumping marks the limit on the life time of the organic DFB laser based chemosensor. Here, we report the usefulness of the short lived organic DFB laser fabricated by spin-coated natural silk protein and sodium fluorescein dye solution on the permanently useable quartz grating as a physically transient, cost-effective and eco-friendly laser chemosensor. The physically transient and eco-friendly DFB laser showed high sensitivity to hydrochloric acid (HCl) acid vapor. The HCl vapor exposure to the fabricated physically transient DFB laser attenuates the lasing by degrading the optical response of the dye-doped silk film. The response of the physically transient DFB laser chemosensor to HCl is 30 times faster than that in fluorescence. We show the elapsed time to cease lasing depends on the concentration of HCl vapor and the thickness of the active silk/dye layer. Moreover, a new laser sample can be simply fabricated by washing-out and recoating silk/dye solution on the quartz grating. Additionally, the use of silk protein promises eco- and bio-friendly chemosensing due to favorable material traits like no creation of pollution and biocompatibility. Our approach would expand to detection of other important analytes by choosing proper probe dyes.
Transparent, flexible, and conducting films are of great interest for wearable electronics. For better biotic/abiotic interface, the films to integrate the electronics components requires the patterned surface conductors with optical transparency, smoothness, good electrical conductivity, along with the biofriendly traits of films. We focus on silk fibroin, a natural biopolymer extracted from the Bombyx mori cocoons, for this bioelectronics applications. Here we report an optically transparent, flexible, and patterned surface conductor on a silk film by burying a silver nanowires (AgNW) network below the surface of the silk film. The conducting silk film reveals high optical transparency of ~80% and the excellent electronic conductivity of ~15 Ω/sq, along with smooth surface. The integration of light emitting diode (LED) chip on the patterned electrodes confirms that the current can flow through the transparent and patterned electrodes on the silk film, and this result shows an application for integration of functional electronic/opto-electronic devices. Additionally, we fabricate a transparent and flexible radio frequency (RF) antenna and resistor on a silk film and apply these as a food sensor by monitoring the increasing resistance by the flow of gases from the spoiled food.