Tailoring titanosilicate molecular sieves by vanadium substitution for humidity sensing applications

There is a great interest in developing humidity sensors with enhanced sensitivity at all relative humidity (RH) ranges. To explore this, vanadium (V)-incorporated titanosilicate microporous thin films were successfully fabricated to investigate their performances as humidity sensors. The V-precursor was directly added to obtain V/V+Ti atomic of 0.1 (V0.1ETS-10) to 0.2 (V0.2ETS-10) and 0.3 (V0.3ETS-10), and characterized by FE-SEM, XRD, Raman, UV-Vis, and XPS analyses. The ETS-10 sensor displayed high sensitivity (1.11 x 10(4)) and linearity (R-2=0.9818) at room temperature across medium (32-67 %) and high (>67 %) relative humidity (RH), with rapid response (similar to 8 s) and recovery times (similar to 35 s). The sensor with an optimized amount of vanadium doping (V0.2ETS-10), showed a significant improvement in the performance in the low RH region (8-32 %) with enhanced sensitivity (1.75 x 10(4)) and linearity (R-2=0.9914). The results of our study indicate that the formation of Ti3+ with the emergence of V4+ and V5+ states resulted in enhanced sensitivity at low RH levels. Based on the obtained results, a plausible shift in the humidity sensing mechanism evolves from chemisorbed intracrystalline water to physisorbed intercrytalline and surface water with increasing RH. However, higher vanadium content led to structural alteration and impurities resulting in a notable reduction in sensitivity (1.17 x 10(3)) and linearity (R-2=0.8927).