Humidity sensor based on solution processible microporous silica nanoparticles

Composites fabricated by mesoporous silica loading hydrophilic elements have been widely investigated as humidity sensitive materials. The physical mixing process for loading hydrophilic elements is difficult to guarantee the uniformity and structural stability of the composites. Furthermore, the poor dispersibility of the silica skeleton restricts its solution processability. Herein, solution processible organic-inorganic hybrid materials were synthesized via a thiol-ene click reaction between sulfhydryl functionalized microporous silica nanoparticles (MSNs) and hydrophilic alkenyl monomer. The optimal hybrid material could disperse in water stably with a concentration of 50 mg/mL owing to the small particle size (about 105 nm) and the hydrophilic characteristic. Humidity sensors were fabricated by solution process and the humidity sensing properties were investigated. The sensor exhibits high sensitivity (about three orders impedance modulus change), small hysteresis (∼2% RH) and rapid response (the response and recovery time are 5 and 40 s, respectively) in the humidity range of 11%-95% RH.