Recent advances and trends in optical devices and sensors for hydrogen peroxide detection

Hydrogen peroxide (H2O2) is a critically important, vital biomarker and hence a highly relevant analyte in a broad range of bioanalytical applications. The most recent trends furthering the ability of its reliable, reproducible, and sensitive quantification include the development of non-biological enzyme mimics, the investigation of smartphone cameras as transducers and detectors, and the continued development of semi-reversible and reversible detection strategies. While the non-biological catalysts offer stability-related advantages over enzymes while providing equally good limits of detection, critical questions regarding toxicity, persistence, (bio)accumulation, and overall environmental footprint need to be answered. In the case of heavy metal-based strategies a replacement by non-toxic, renewable alternatives should be an obvious research need. Signal recording has seen a dramatic change toward smartphones, with their ever-improving computing and image-acquisition abilities. Yet, with the sheer number of different camera and phone models progress can be difficult to assess, as reproducibility and comparability of results and experimental set-ups are too often elusive. In the area of semi- reversible sensors flow injection analysis (FIA) coupled with chemiluminescence (CL) remains the most advanced system. In the case of fully reversible sensors, research points toward oxygen-based sensing to be the most reliable. Analyzing publications from 2018 to 2024, it is not surprising that the important analytical figures of merit of low limits of detection (LODs), broad quantitation ranges, faster response and regeneration times combined with novel (reversible) probes continue to be and should remain central focus of future developments.