Nb₂O₅ Microcolumns for Ethanol Sensing

Pseudohexagonal Nb₂O₅ microcolumns spanning a size range of 50 to 610 nm were synthesized utilizing a cost-effective hydrothermal process (maintained at 180 °C for 30 min), followed by a subsequent calcination step at 500 °C for 3 h. Raman spectroscopy analysis unveiled three distinct reflection peaks at 220.04 cm^-1, 602.01 cm^-1, and 735.3 cm^-1, indicative of the pseudohexagonal crystal lattice of Nb₂O₅. The HRTEM characterization confirmed the inter-lattice distance of 1.8 Å for the 110 plain and 3.17 Å for the 100 plain. The conductometry sensors were fabricated by drop-casting a dispersion of Nb₂O₅ microcolumns, in ethanol, on Pt electrodes. The fabricated sensors exhibited excellent selectivity in detecting C₂H₅OH (ΔG/G = 2.51 for 10 ppm C₂H₅OH) when compared to a variety of tested gases, including CO, CO₂, NO₂, H₂, H₂S, and C₃H₆O. The optimal operating temperature for this selective detection was determined to be 500 °C in a dry air environment. Moreover, the sensors demonstrated exceptional repeatability over the course of three testing cycles and displayed strong humidity resistance, even when exposed to 90% relative humidity. This excellent humidity resistance gas sensing property can be attributed to their nanoporous nature and elevated operating temperature.