Optical Detection of Hydrogen Gas using Organic Dyes and Metal-Based Activators: A Review

Abstract

The adoption of hydrogen gas (H2(g)) as a carbon-free energy source requires reliable, sensitive, and accessible detection technologies for use across various environments. Optical H2(g) sensors based on organic dyes offer an attractive alternative to traditional sensors by providing selective and sensitive visual readouts, with low power consumption, and compatibility with simple and miniature devices. However, the relative inertness of H2(g) under ambient conditions necessitates indirect detection strategies relying on H2(g) activation strategies coupled with optical response. This review provides a comprehensive and mechanistic overview of fluorescence- and colorimetric-based H2(g) sensors that employ organic dyes in combination with metal-based activating agents. We discuss how H2(g) activation is dominated through two strategies: (1) surface mediated activation at noble metal surfaces with supported catalysts and nanoparticles; and (2) organometallic mediated activation. Emphasis is placed on sensor performance and usability with respect to activation pathway, dye selection, and sensor architecture. By critically comparing reported sensing performances, we identify key design principles that directly influence H2(g) sensing ability across different dye-based sensors including dye, activator, and architecture selection. We also highlight the need for benchmarked parameters which currently limits cross-study comparison and rational design. Finally, we outline future opportunities for sustainable optical dye-based H2(g) detection related to improving currently available systems. Altogether, this review aims to provide a guide for the development of next-generation optical H2(g) sensors that support the safe and sustainable integration of H2(g)-based technologies into society.