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 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 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 (−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.