Surface facet engineering of ZnIn2S4 via supercritical hydrothermal synthesis for enhanced NO gas sensing performance

In this study, we investigate the novel application of ZnIn₂S₄ as an NO gas detection device by precisely modulating its surface facets through crystal growth control in a supercritical water environment. The supercritical hydrothermal synthesis successfully transforms ZnIn₂S₄ from a flower-like structure into a hexagonal plate morphology, driven by the preferential growth of the basal plane (003) surface facet. This morphological control, which is unattainable in a subcritical environment, is evidenced by a substantial increase in the (003)/(011) facet ratio from 0.52 to 1.98 with rising temperature. NO detection results indicate that this surface morphology modification significantly accelerates sensor response, attributed to enhanced interaction between the ZnIn₂S₄ surface and NO gas, as well as reduced diffusion limitations compared to the flower-like morphology. The hexagonal plates exhibit a remarkably fast response time of approximately 25 s, in contrast to 181 s for the flower-like counterpart. These findings underscore the crucial role of surface facet engineering in optimizing the gas-sensing properties of ZnIn₂S₄, highlighting its potential for advanced gas sensor applications.