posted on 2024-02-29, 17:04authored byYuxiang Qin, Haoxuan Wang, Chuan Zhou, Yinan Bai
As
a typical phase-transition material, VO2 could show
great potential in the process of precise modulation of gas-sensing
selectivity. However, the effect and mechanism of the phase transition
on its gas sensitivity have not yet been clearly elucidated. In this
paper, a temperature-controlled VO2 gas sensor capable
of phase change has been created using a one-step solvothermal method.
With controllable transition of VO2 from the monoclinic
phase to the rutile phase by adjusting the operating temperature,
the corresponding VO2 sensor shows obvious changes in gas-sensing
selectivity from acetone to ammonia. At room temperature (∼25
°C), the monoclinic VO2 sensor produces response values
of 93 and 29% to 10 ppm of acetone vapor and ammonia gas, respectively.
Comparatively, the response values for the sensor based on rutile-phase
VO2 that operates at 100 °C are 41 and 95% for 10
ppm of acetone vapor and ammonia gas. Based on the first-principles
mortise–tenon-style construction as well as Lewis acid–base
theory, the mechanism of dual selectivity generated with the phase
transition of VO2 is demonstrated in terms of crystal structure,
electronic orbitals, and adsorption energy calculations. The unique
characteristic of adjustable dual-phase detectability of VO2 contributes to the selective capability of gas sensing. It thus
presents an effective strategy for developing gas sensors with regulated
selectivity by phase transition of certain special semiconductor oxides.