Synthesis of platinum-decorated iron vanadate nanorods with excellent sensing performance toward n-butylamine

The detection and monitoring of organic amines commonly found in food and medical industries (e.g. n-butylamine) has attracted increasing interests as they can induce adverse health effects to humans even at low concentrations. In this study, we have demonstrated the facile synthesis of platinum (Pt)-decorated iron vanadate (FeVO₄) nanorods through a combined hydrothermal-polyol method, for highly sensitive and selective detection of toxic n-butylamine vapor with fast response/recovery time. The pure and Pt-decorated FeVO₄ nanorods were successfully characterized using X-ray diffraction (XRD), scanning (SEM) and transmission electron microscopes (TEM), X-ray photoelectron spectroscopy (XPS), and nitrogen (N₂) adsorption-desorption isotherms. The as-synthesized FeVO₄ nanorods were highly porous, exhibiting pore diameters in the range of 2-20 nm, with a specific surface area of 21.4 m²/g. Following surface modification, small platinum (Pt) nanoparticles with varying sizes of 2-5 nm were uniformly loaded on the surface of these nanorods. The gas-sensing results reveal that the Pt-decorated FeVO₄ nanorods exhibited three times higher response as well as three times faster response/recovery time, along with 5 times higher selectivity toward n-butylamine compared to the pure FeVO₄ nanorods, under a relatively low optimum operating temperature of 240 °C. The enhanced sensing performance of the Pt-decorated FeVO₄ nanorods is attributed to a few factors, including: (i) the larger surface area exhibited by the Pt-decorated FeVO₄ nanorods compared to the pure FeVO₄ nanorods (∼1.5 times larger), which may provide more sites for the adsorption of both oxygen and gas molecules, (ii) the increase in surface oxygen content of the FeVO₄ nanorods after the Pt modification (based on XPS analysis), which may lead to the formation of more oxygen ions to react with the n-butylamine gas during the sensing process to produce more electrons, thus leading to improved conductivity, and (iii) the electronic and chemical sensitization induced by the deposited Pt nanoparticles. These findings will develop the potential of metal vanadate nanocomposites as highly sensitive and selective gas-sensing materials for detecting organic amines.