Tetrazolium Blue-Based Colorimetric Sensor for Hydrogen Gas

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* = C 5 Me 5 –, 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%).