Abstract

Mesoporous silica based composites are widely used for humidity sensors. But a physical mixing is needed to load humidity sensitive materials in the mesoporous silica materials, so the uniform dispersion of humidity active materials could not be guaranteed. A chemically modification method has been used to ensure the uniform dispersion and stable structure of the humidity active units in this work. Novel organic-inorganic hybrid materials have been prepared via modifying the sulfhydryl functionalized mesoporous silica SBA-15 (SBA-15-propyl-SH) with hydrophilic unit methacrylatoethyl trimethyl ammonium chloride (DMC) via a thiol-ene click reaction. Mesoporous silica skeletons could ensure the stability at high humidities and hydrophilic groups modified on the skeletons behave as humidity sensitive parts. The content of DMC on the silica could be tuned by the feed ratios. The obtained hybrid materials keep the mesoporous characteristics of silica, which is beneficial for the transport of water molecules in adsorption and desorption processes. The humidity sensing properties of the sensors based on SBA-15-propyl-SH and SBA-15-propyl-S-DMCx were investigated in details. The impedance modulus of the optimized sensor changes by more than three orders of magnitude over the relative humidity (RH) range of 11% to 95%, with prompt response to RH change (11 s and 60 s for adsorption and desorption processes, respectively).

Graphical abstract