Rational design and synthesis of aldehyde-functionalized mesoporous SBA-15 for high-performance ammonia sensor

Abstract

Herein, we report novel ammonia gas sensor materials having aldehyde functional groups grafted onto the pore surface of highly ordered mesoporous materials SBA-15. The functional SBA-15 was synthesized via co-condensation of tetraethyl orthosilicate and formylsilanetriol using an amphiphilic block copolymer P123 as a structure-directing agent, in which formylsilanetriol was first synthesized through the reduction of 2-cyanoethyltriethoxysilane in the presence of diisobutylaluminium hydride. Structural and textural characterizations by x-ray diffraction, transmission electron microscopy and N2 adsorption–desorption porosimetry were conducted and the results show the materials having well-defined mesoporous long-range ordering with pore size of 6.2nm. Furthermore, FT-IR and solid-state magic angle spinning nuclear magnetic resonance spectroscopy studies proved covalent anchoring of the aldehyde functional group onto the pore walls of SBA-15. The results indicated that the materials successfully kept their mesoporous nature after grafting of the aldehyde groups. Gas-sensing tests were investigated by coating the aldehyde-functionalized SBA-15 onto quartz crystal microbalance transducers. The results reveal that the sensors can be as promising candidates as ammonia detectors with desirable sensing behaviors, including high sensitivity (the frequency shift was 22Hz at 1ppm and the QCM sensors were exposed to nitrogen stream until a stable baseline (±2Hzmin−1)), fast response (response time within 11s, recovery time within 13s) and good reversibility.