Rapid and Sensitive Ethanol Detection Using Ag-Functionalized ZnO Nanorods-Clad Optic Fiber Sensor for Dual-Spectral Region Operation

Nowadays, ethanol detection has garnered significant interest from researchers as a valuable tool for monitoring breath tests in drunken driving, checking the safety of food packaging, controlling fermentation processes, and detecting leaks from chemical plants. As a result, it is highly important to build a sensor that detects ethanol quickly and has improved sensor properties. Thus, herein, a fiber optic ethanol sensor utilizing Ag-functionalized ZnO nanorods was fabricated and characterized to enhance ethanol sensing performance. ZnO nanorods were prepared by the hydrothermal route and a functionalized ZnO surface with metal Ag nanoparticles via the chemical reduction method. Numerous characterizations were performed to investigate the material properties of the synthesized nanorods. The XRD plot confirmed the hexagonal wurzite crystallite structure of ZnO and three additional peaks of metal Ag appeared at 38.50°, 44.70°, and 64.89° might be matched to the (1 1 1), (2 0 0), and (2 2 0) planes, respectively. The fiber optic sensor (FOS) head was fabricated by modification of the original cladding through chemical etching and dip-coated using Ag-functionalized ZnO nanorods. Subsequently, the sensor head was exposed to test volatile organic compounds (VOCs), including ethanol, isopropyl alcohol (IPA), acetone, and methanol (0–500 ppm) to investigate the gas sensor response behavior of pristine and Ag-functionalized ZnO nanorods at room temperature. Noticeably, the Ag-functionalized ZnO-based gas sensor possesses higher selectivity toward ethanol along with enhanced sensor response (S.R.) ~33.6% at 693 nm and ~34.7% at 772 nm. The sensor showed better linearity ( ${R}^{{2}}={0.97}$ ) toward ethanol over a 0–500-ppm dynamic concentration range, faster response/recovery time of 12/20 s, limit of detection (LOD) of 53 ppm, better repeatability, and stability. The proposed enhanced ethanol sensing mechanism is thoroughly detailed. The exemplary sensor results demonstrated the possibility of Ag-functionalized ZnO as a potential nanomaterial for ethanol sensor fabrication, capable of operating effectively in both the visible and NIR regions.