Chemochromic Materials for Hydrogen Sensors

Ag-WOj (Pd) Fiber-optic sensors/surface plasmon resonance Benson et al. (1998) 

Polyoxo compounds of W and Mo Smart paint sensors Mohajeri et al. (2009) 

H4[SiW12O40]—silico-tungstic acid (STA) H3[P(W3O10)4]—phospho-tungstic add (PTA) H3[P(Mo3O10)4]— phospho-molybdic acid (PMA) 

Benson et al. (1998) also observed a strong influence of air humidity on the parameters of WO3-based sensors. Water adsorbed onto the nanoporous structure of the WO3 increases its refractive index. Conversely, exposure of the sensor to dry air causes rapid loss of adsorbed water from the film and a shift in the SPR that mimics exposure to hydrogen. The use of a protective layer detreases this effect. However, the sensor SPR was still susceptible to severe drift under conditions of changing humidity. 

It was found that, for sensor design, both thin-fihn (Benson et al. 1998) and thick-film (Whitten et al. 2006 Mohajeri et al. 2009) technologies can be nsed. In the latter case, various light-colored metal oxides in the form of fine powders (0.01-100 pm) can be used as a support for the POC of W and Mo, 

---