Gold Nanostars based Microfluidic Optical Fiber Sensor for Enhanced Ethanol Detection

In this work, we present an ethanol sensor based on a D-shaped optical fiber functionalized with a nanostructured layer of gold nanostars (AuNSs). The functionalization was achieved via a seed-mediated growth method, enabling uniform and controlled nanoparticle deposition on the fiber surface. The sensor was integrated into a custom-designed microfluidic chip, allowing precise control of analyte delivery and ensuring highly reproducible measurements. The sensing mechanism relies on the interaction between the evanescent field of the D-shaped fiber and the AuNSs, which enhances light–matter interaction and increases sensitivity to refractive index variations induced by ethanol concentration changes. The device exhibited a highly linear response (R² = 99.960) over a concentration range of 0–40%, with a detection limit of 0.07% and a response time of approximately 10 s. The combination of nanostructured plasmonic materials and microfluidic integration results in improved sensitivity, repeatability, and response speed. These results demonstrate the potential of D-shaped fiber platforms functionalized with gold nanostructures for the development of compact and efficient chemical sensing systems.