Precise Optical Fiber-Based Ammonia Sensor Using CdS Quantum Dots Decorated with ZnO at Heterointerface

Ammonia (NH3) sensing is crucial for environmental safety, necessitating the development of efficient NH3 sensors. In this study, an efficient NH3 sensor based on CdS quantum dots (QDs) decorated with ZnO (CdS/ZnO) covering optical fiber was successfully fabricated. The CdS/ZnO was first synthesized by a hydrothermal method, featuring an n-n heterojunction in the composite material. The optimal sensor with 10 wt% CdS QDs exhibits efficient performance, with a response sensitivity of 0.9 × 10−3 dB/ppm and R2 = 0.9858. Additionally, it demonstrates excellent selectivity and repeatability. Mechanistic insights for the NH3 sensor were elucidated through X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy, scanning electron microscopy, and transmission electron microscopy. These results confirm that the enhancement in NH3 sensing performance is attributed to the formation of well-defined n-n heterojunctions. This study contributes to the advancement of gas-sensing technology, particularly in the detection of harmful gases, such as NH3.