Tetrazolium Blue-Based Colorimetric Sensor for Hydrogen Gas

Abstract

Hydrogen gas (H_2(g)) is a viable alternative to current fossil fuels due to its clean combustion, yielding water and energy. Although H_2(g) offers significant advantages as a renewable energy source, several factors impede its large-scale adoption: It is highly flammable and explosive and lacks odor. Therefore, if it is to be used as an alternative fuel source, then reliable and selective detection methods must be studied. The development of H_2(g) sensors is an ever-growing field, though current technologies are not without practical use and sensitivity limitations. In this work, we study a combination of the commercially available dye, nitrotetrazolium blue chloride (NTB), and a hydrogen-activating compound [{Ir(Cp*)(Cl)}₂(thbpym)](Cl)₂] (Cp* = C₅Me₅^–, thbpym = 4,4′,6,6′-tetrahydroxy-2,2′-bipyrimidine, IrCp*) as components of a H_2(g) detection gasochromic tape. When exposed to H_2(g), this mixture changes from pale yellow to deep blue/purple in either solution (enclosed in polydimethylsiloxane (PDMS)) or solid state (on paper), showing response times on the order of seconds. On exposure to varying H_2(g) concentrations, the sensor was additionally found to detect as little as 100 ppm of H_2(g), a value 400-fold lower than the lower flammability limit of H_2(g) (4%).