Urea-functionalized SBA-15 hybrids: Post-grafting synthesis, high-performance organophosphorus sensing and their response mechanism

There is an urgent need for effective and portable gas sensors toward organophosphorus (OP) vapors in the areas of anti-terrorism and pesticides residue monitoring. Herein, we report a series of urea-functionalized SBA-15 (UXs/SBA-15: U1/SBA-15, U2/SBA-15 and U3/SBA-15) prepared by post-grafting methods and their applications in trace-level dimethyl methylphosphonate (DMMP, lab simulate of toxic OP agents) sensing by means of quartz crystal microbalance (QCM) transducers. U3/SBA-15 based QCM sensors exhibited excellent responses and remarkable selectivity toward DMMP vapors. A frequency shift (Δ F ) of −50 Hz was achieved when the DMMP vapors reached 30 ppb. And the limit of detection (LOD) of QCM sensor modified with U3/SBA-15 was found at 12.25 ppb. Moreover, the simulated adsorption enthalpies (Δ H ) of UXs and DMMP molecules were calculated with Gaussian 09 to investigate the sensing mechanism. The results indicated the existence of chemisorption between UXs and DMMP molecules caused by hydrogen-bonding interactions, among which a minimum Δ H (−71.96 kJ mol −1 ) between U3 and DMMP molecule was found, resulting a maximum response to DMMP compared with U1-DMMP (−52.53 kJ mol −1 ) and U2-DMMP (−57.01 kJ mol −1 ). Therefore, the well-defined UXs/SBA-15 lead to a great potential on the detection of OP vapors.