Highly Sensitive, Temperature-Independent Oxygen Gas Sensor Based on Anatase TiO Nanoparticle Grafted, 2D Mixed Valent VO Nanoflakelets.

Herein, we report a facile approach for the synthesis of TiO nanoparticles tethered on 2D mixed valent vanadium oxide (VO /TiO) nanoflakelets using a thermal decomposition assisted hydrothermal method and investigation of its temperature-independent performance enhancement in oxygen-sensing properties. The material was structurally characterized using XRD, TEM, Raman, DSC, and XPS analysis. The presence of mixed valent states, such as VO and VO in VO , and the metastable properties of VO have been found to play crucial roles in the temperature-independent electrical conductivity of VO /TiO nanoflakelets. Though pristine VO exhibited characteristic semiconductor-to-metal transition of monoclinic VO, pure VO nanoflakelets exhibited poor sensitivity toward sensing oxygen. VO /TiO nanoflakelets showed a very low temperature coefficient of resistance above 150 °C with improved sensitivity (35 times higher than VO for 100 ppm) toward oxygen gas. VO /TiO nanoflakelets exhibited much higher response, faster adsorption and desorption toward oxygen as compared to pristine VO beyond 100 °C, which endowed the sensor with excellent temperature-independent sensor properties within 150-500 °C. The faster adsorption and desorption after 100 °C led to shorter response time (3-5 s) and recovery time (7-9 s). The results suggest that 2D VO /TiO can be a promising candidate for temperature-independent oxygen sensor applications.