Interaction of organophosphorous compounds with TiO2 and WO3 surfaces probed by vibrational spectroscopy

Flower-like tungsten oxide particles: Synthesis, characterization and dimethyl methylphosphonate sensing properties

“…As observed in the low-frequency spectral region, the frequency of P O stretching mode, which occurs at 1276 cm −1 in gaseous phase, shifted to 1231 and 1253 cm −1 upon adsorption within the first minute, 45 and 23 cm −1 lower than those of gaseous DMMP. According to previous reports [17][18][19], the two positions are the evidence of the formation of two types of bonding between P O and WO 3 surface sites: adsorption via hydrogen bonding (1231 cm −1 ) and with surface Brønsted sites (1253 cm −1 ). Although a third adsorption mode (Lewis acid site adsorption) existed, as reported before [18,19], no evidence was observed in the current experiment.…”

“…According to previous reports [17][18][19], the two positions are the evidence of the formation of two types of bonding between P O and WO 3 surface sites: adsorption via hydrogen bonding (1231 cm −1 ) and with surface Brønsted sites (1253 cm −1 ). Although a third adsorption mode (Lewis acid site adsorption) existed, as reported before [18,19], no evidence was observed in the current experiment. It can be easily understood if we consider that the adsorption herein occurred at room temperature rather than at higher temperature as in the previous reports.…”

Effects of Additives on the DMMP Sensing Behavior of SnO2Nanoparticles Synthesized by Hydrothermal Method

“…In particular, the Ni-doped SnO 2 nanoparticle sensor showed complete recovery. According to previous reports [19,26], the decomposition of the DMMP molecules occurs at active sites which exist on the surface of the catalyst materials. However, the irreversible interaction between the surface of the metal oxides and DMMP molecules causes the loss of these active sites, resulting in deactivation of the catalyst materials.…”

“…Also, only very small portions of Effects of Additives on the DMMP Sensing Behavior of SnO 2 Nanoparticles Synthesized by Hydrothermal Method the decreased resistance were recovered after switching to pure air gas at all operating temperatures. This incomplete resistance recovery behavior, or so called poisoning effect, is attributed to the irreversible interaction between the metal oxide and P=O bonding of the DMMP molecules [19].…”

“…However, semiconductor metal oxide sensors for DMMP exhibit a poisoning effect due to the irreversible reaction between surface atoms of the metal oxides and phosphorus atom of the DMMP molecules [18,19]. To solve this problem, various metal oxides have been added to the SnO 2 particles [20,21].…”