Morphology-dependent gas-sensing sensitivity of γ-Al2O3 for methacrolein

Abstract

Methacrolein (MACR) is a key precursor in the formation of secondary organic aerosols and a significant occupational chemical hazard, posing risks to both the environment and health. In this work, three types of γ-Al2O3 were synthesized via hydrothermal methods, including nanorods, nanosheets, and a mixed morphology. Characterization results revealed that rod-like γ-Al2O3 has the largest specific surface area and the highest oxygen vacancy content. The possible formation mechanism of γ-Al2O3 samples with different morphologies was discussed. Further study indicated that the morphology of γ-Al2O3 significantly affects its sensitivity in the cataluminescence (CTL) sensing of MACR, with rod-like γ-Al2O3 exhibiting the highest sensitivity, whereas sheet-like γ-Al2O3 showed the lowest sensitivity. Thus, a CTL sensor based on rod-like γ-Al2O3 for MACR detection was developed, demonstrating outstanding performance in terms of sensitivity, selectivity, reproducibility, and stability. This sensor was applied to the analysis of real samples, and the results were compared with those obtained by gas chromatography. The results obtained by the two methods were consistent, with relative error ranged from -4.0% to -4.9%. The sensing mechanism was further elucidated via density functional theory calculations, in situ Fourier transform infrared spectroscopy and gas chromatography-mass spectrometry. This work broadens the horizons for applying material science principles to enhance the performance of gas sensors, thereby contributing to design high-performance CTL sensors for air quality and occupational safety monitoring.