Investigation of interactions between organophosphorus compounds and TiO2 modified microcantilevers for molecule detection in air

Abstract

In order to develop a detector working in the gas phase for organophosphorus molecules, resonant microcantilever surfaces were chemically modified with pristine and functionalized TiO₂ nanorods. By using a solvothermal synthesis method a homogeneous film, composed of nanorods with square facets, covering completely the surface of the levers was obtained. The synthesized rods mainly exhibit [110] oriented crystals and this facet has especially demonstrated a high loading ability for grafted sensing molecules. Experimental results showed that the sensing response is three times higher when the TiO₂ sensor is functionalized with amine terminated molecules while no significant response is observed for bare cantilevers exposed to a DMMP simulant. The in situ IR analysis highlighted the formation of hydrogen bonds between the characteristic groups of DMMP and the TiO₂ surface at room temperature. The strength of this bond depends on the chemical groups present at the oxide surface. Molecules containing hydroxyl or amino functions form stronger hydrogen interactions with the OP simulant compared to the fluorine group. The kinetics of adsorption are characterized by a fast initial reaction followed by gradual slowing to a steady-state for all the samples.