Zn2SnO4/ZnO heterojunction conditioned by mineralizer sodium hydroxide promotes highly sensitive detection of NH3 at room temperature

Ammonia (NH 3 ) is a common but potentially hazardous gas that may cause inflammation of the lungs or other respiratory illnesses when exposed to high levels of NH 3 for extended periods. Therefore, preparing a gas sensor for real-time monitoring of NH 3 gas at room temperature is of great practical significance. In this paper, a Zn 2 SnO 4 /ZnO (ZZ) metal-oxide-semiconductor gas sensor with high response to NH 3 gas, low cost, easy fabrication, and high selectivity was successfully prepared by using a one-pot hydrothermal method. It was discovered that the content of the mineralizer NaOH serves to regulate the morphology of the samples. The results indicated that this method facilitated a more favorable formation of the n-n type heterojunction between Zn 2 SnO 4 and ZnO, leading to a substantial improvement in the sensor's sensitivity to NH 3 gas. Upon the addition of 3.75 mol/L NaOH, the Zn 2 SnO 4 and ZnO contents in the Zn 2 SnO 4 /ZnO (ZZ-3) samples were approximately equivalent. As a result, under the n-n heterojunction and synergistic interaction, the sensor demonstrated a significantly higher response (1756.1) to 500 ppm of NH 3 at RT, compared to the response values of the pure Zn 2 SnO 4 sample (24.3) and pure ZnO (23.6). Moreover, compared with the response values to other common harmful gases (500 ppm) in daily life, the response to NH 3 was approximately 10.7–1393.7 times higher. Meanwhile, the ZZ-3 samples also exhibit excellent long-term stability. This work provides an idea of using NaOH to modulate the material morphology for the preparation of gas-sensitive sensors.