Improvement of humidity dependence in gas sensor based on SnO2

Sensors: From biosensors to the electronic nose

“…The p-type semiconductor (oxides of nickel or cobalt) responds to reducing compounds and its excitation promotes reactions with reducing compounds due to an electron deficiency in its valence band. These metal oxides (mostly SnO2, Ga2O3 and TiO2) can also be doped with metals such as Cu (Zhang and Liu 2000), Pt plus Nb (Comini et al 2000) and Sb, Bi, Fe, Au, Cd (Morimitsu et al 2000), or metal oxides of Co, Cr, La, Ce (Fukui and Katsuki 2000), Mg, Al , Ru, Rh and Ir (Lang et al 2000) among others. These doping metals help to diminish the humidity and temperature dependence (Fukui and Katsuki 2000;Morimitsu et al 2000), and to improve the sensitivity and the selectivity (Comini et al 2000;Mielle 1996).…”

Hydrogen Sensing Performance of ZnO Schottky Diodes in Humid Ambient Conditions with PMMA Membrane Layer

“…As water vapor chemisorbed on the Pt catalytic surface, it resulted in the decrease of surface adsorption sites available for hydrogen. The cross-sensitivity toward water vapor has been well reported in SnO2-based MOX gas sensors [18][19][20]. Water vapor has been shown not only to decrease the resistance of SnO2-based materials, but also to significantly interfere with most target gases, resulting in the selectivity issues of gas sensors in humid air.…”

“…One of the most challenging issues for highly precise gas sensors is the selectivity, which detects the specific gas molecules under other reducing gas mixtures as well as in humid ambient conditions. In the presence of water vapor, SnO 2 -based gas sensors have shown the increased sensitivity as well as degraded sensor signals over a certain period of time [16][17][18]. The increase in operation temperature and the addition of select dopants were proposed to mitigate the effects of water on the sensitivity [19,20].…”

Metal Oxide Nanoparticles

“…A wide range of different metal oxides [223,[228][229][230][231][232][233] and mixed oxides [38,228,229,232,234,235] have been investigated; however, tin oxide is probably the most common system due to the numerous gases it shows a response to. For example, tin oxide has been shown to respond to a wide range of flammable gases, including carbon monoxide, [236][237][238] hydrocarbons, [238][239][240] hydrogen [241,242] and other pollutant gases such as hydrogen sulfide [239,243] and nitrous oxides. [237,244] The use of metal oxide semiconductors as sensor materials is based on the change in resistance that is observed when they are exposed to oxidising or reducing gases.…”