Effects of Vanadium Substitution on the Structure and Humidity Sensing Behavior of Microporous Titanosilicate ETS-10

Humidity sensors hold an imperative role due to increased demand to control the indoor ambient environment, food and medicine storage, agriculture, health, industry, textile, and even space environments. There has been a rapid increase in developing humidity sensors with enhanced sensitivity at low and high relative humidity (<i>RH</i>) ranges for monitoring moisture, temperature, and chemical gases in various application fields.<br/>Zeo-type Titanosilicate ETS-10 is microporous material that shows competitive sensitivity to TiO₂. However similar to TiO₂ at low humidity range it needs some modifications. To achieve this, vanadium (V)-incorporated titanosilicate microporous thin films were successfully fabricated to investigate their performances as humidity sensors. A structure with both vanadium and titanium atoms of differing coordinations in the quantum wire of ETS-10 was used to better understand the sensing mechanism. The results indicated that vanadium incorporation led to structural changes in ETS-10, resulting in the formation of Ti³⁺ centers along with Ti⁴⁺ states with a more significant amount of V⁵⁺ as the incorporated vanadium level increased. Vanadium incorporation also resulted in the decreased bandgap, suggesting the introduction of disorders created along the -Ti-O-Ti- chains. The developed sensors showed full range sensitivity at an optimized amount of vanadium into the -Ti-O-Ti- quantum wires in ETS-10. It was observed that V-incorporated samples with an optimized amount of V/Ti+V ratio of 0.2 showed enhanced sensitivity at particularly low relative humidity (<i>RH</i>) levels for the first time. These results demonstrated that titanosilicate ETS-10 has potential application in fabricating humidity sensors, and the sensing performance is enhanced, particularly at an optimized vanadium amount.<br/><br/><br/>Keywords: Humidity Sensor, Titanosilicates, V-incorporated ETS-10, Impedance Spectroscopy