High-sensitivity reflectometric interference spectroscopy for label-free glucose detection using facile one-step anodic alumina

Glucose monitoring is crucial for maintaining overall health. The primary method for glucose monitoring, electrochemical detection, requires complex solutions and operational procedures. Therefore, optical sensing is a promising alternative for glucose detection due to its operational simplicity. Reflectometric interference spectroscopy (RIfS) has garnered significant attention due to its simplicity, ease of use, and compatibility with various materials. However, the current RIfS fabrication process is time-consuming and typically requires functionalization to achieve improved sensitivity and detection limits, restricting its practical application. Here, a facile one-step anodic aluminum oxide (AAO) substrate for RIfS-based glucose detection is proposed. AAO fabricated by short-duration anodization possesses a lower optical interference order. Compared to AAO produced by conventional long-duration anodization, it offers enhanced sensitivity and a lower detection limit. The facile one-step fabricated AAO demonstrates a strong linear relationship (R² of 0.9957) between the red-shift (Δλ) and glucose concentration. The linear range for glucose detection is 400–800 ppm, addressing a previously unfilled gap in reported techniques. With a limit of detection (LOD) of 277 ppm, the one-step AAO fabrication method developed in this study outperforms reported non-functionalized substrates, demonstrating high sensitivity and strong potential for glucose sensing applications.