Hydrangea-Like In2O3@In2S3 n–n Heterostructures for High-Efficiency TMA Measurement

Metal sulfides have emerged as appealing materials for high-performance gas sensors. However, little attention has been paid to the effect of its heterojunction on gas-sensing properties. In this work, hydrangea-like In2O3@In
$_{2}\text{S}_{3}~n$
–
$n$
heterostructures were designed and synthesized by a hydrothermal method followed by a subsequent in situ oxidization treatment. The well-designed In2O3@In2S3 heterostructures exhibit superior trimethylamine (TMA)-sensing performance, which could be ascribed to the synergistic effect of unique
$n$
–
$n$
heterojunction at the interface of In2S3 and In2O3, high surface area, the catalytic effect of In2O3, and peculiar hydrangea-like morphology. Specifically, the 0.5-In2O3@In2S3 sensor shows the highest response value (5.5 at
$100~^{\circ }\text{C}$
) to 10-ppm TMA, which is
$\approx 4.2$
times higher than the In2S3 sensor (1.3 at 150 °C). Besides, the 0.5-In2O3@In2S3 sensor exhibits outstanding reproducibility, low detection limits (1.3–0.1 ppm), excellent long-term stability, and high selectivity, showing its potential applications in detecting TMA gas.