High-sensitivity and fast-response fiber-tip Fabry-Pérot hydrogen sensor with suspended palladium-decorated graphene.

The safe utilization of hydrogen as a clean fuel and industry material requires the reliable detection of a gas leakage; thus, hydrogen sensors with high sensitivity and fast response are in urgent demand. Among various hydrogen detection techniques, optical hydrogen sensors are especially attractive because of their intrinsic safety. Herein, by integrating an optical fiber with a suspended palladium (Pd)-decorated graphene, we demonstrate a fiber-optic hydrogen sensor with fast-response that is sensitive, compact and capable of remote detection. The suspended Pd-decorated graphene, attached to the optical fiber tip with an air cavity, forms a flexible Fabry-Pérot interferometer. Upon hydrogen absorption, the ultrathin Pd film facilitates a fast hydrogen dissociation and the ultrathin graphene enables an effective conversion of the Pd lattice expansion to Pd/graphene film displacement, which can be readily measured by fiber-optic interferometery. With a hybrid film of ∼5.6 nm-thick Pd and ∼3 nm-thick suspended graphene, a low detection limit of ∼20 parts per million (ppm) and a short response time of ∼18 s have been achieved. In addition to providing a compact and all-optical solution to sensitive and fast-response hydrogen detection, the rationally-designed sensor can be used for diverse chemical/gas sensing applications by replacing Pd with other functional materials.