Highly Sensitive\nSurface-Enhanced Raman Scattering\nDetection of Hydroxyl Radicals in Water Microdroplets Using Phthalhydrazide/Ag\nNanoparticles Nanosensor

The spontaneous generation of hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>) within atmospheric microdroplets, such as raindrops\nand\naerosols, plays a crucial role in various environmental processes\nincluding pollutant degradation and oxidative stress. However, quantifying\nhydroxyl radicals (•OH), essential for H<sub>2</sub>O<sub>2</sub> formation, remains challenging due to their short lifespan and low\nconcentration. This study addresses this gap by presenting a highly\nsensitive and selective surface-enhanced Raman scattering (SERS) nanosensor\nspecifically designed for quantifying •OH within water microdroplets.\nUtilizing a phthalhydrazide (Phth) probe, the SERS technique enables\nrapid, interference-free detection of •OH at nanomolar concentrations.\nIt achieves a linear detection range from 2 nM to 2 μM and a\nlimit of detection as low as 0.34 nM. Importantly, the SERS sensor\ndemonstrates robustness and accuracy within water microdroplets, paving\nthe way for comprehensive mechanistic studies of H<sub>2</sub>O<sub>2</sub> generation in the atmosphere. This innovative approach not\nonly offers a powerful tool for environmental research but also holds\npotential for advancing our understanding of atmospheric H<sub>2</sub>O<sub>2</sub> formation and its impact on air quality and pollutant\ndegradation.