The nanophotonic machinal cavity and its hydrogen sensing application

Abstract

Hydrogen, a clean energy carrier, possesses great potential to be an alternative fuel in the future. However, it also has a reputation for being explosive and dangerous. Thus, in the realization of hydrogen energy utilization, hydrogen safe storage and transport are the main issues which currently need to be solved at present. For safety, hydrogen leaks or concentration variations should be monitored accurately and timely during storage or transport. Among the many sensors, the optical hydrogen sensor can satisfy demands of safety, online detection, undisturbed surrounding, and lack of spark. Hence, a fiber-based nanophotonic machinal cavity (NPMC) is proposed and proved that it can be used for hydrogen sensing. This cavity is composed of two mirrors: One is fiber-air interface, another is gold (Au)/palladium (Pd) hybrid nanofilm, herein, Au film with low elastic modulus is employed as a reflective mirror and support substrate of Pd component. Since Pd-hydrogen reactions can induce deformation on this hybrid nanofilm, which will change the resonant characteristics of the cavity, Pd functions as hydrogen-sensitive nanomaterial. Experimentally, Au/Pd hybrid nanofilm-based NPMCs are prepared and used to demonstrates the feasibility of hydrogen sensing. The experimental results reveal that this proposed NPMC maintains advantages of reusable, durable, fast response/recovery (12/1s), low limit of detection (0.1%) and widely linear detection range (1–3.5%) in hydrogen sensing application. This intrinsically safe, miniaturized fiber optic device can be used in space constrained and hazardous environments.