Non-metallic plasmon-assisted upconversion fluorescence for ultrasensitive hydrogen peroxide detection from nM to μM

Precise monitoring and quantification of H₂O₂ is highly urgent and of great significance for biomedicine, food safety, environmental monitoring, etc. Herein, we proposed a facile near-infrared (NIR) excited fluorescent probe composed of upconversion nanoparticles (UCNPs) and non-metallic plasmonic WO_3-x for ultrasensitive quantitative H₂O₂ detection. Plasmonic WO_3-x with oxygen vacancy-induced LSPR achieved over 680-fold enhancement of upconversion fluorescence at 520 nm, and also acts as the sensitive recognition site for H₂O₂. H₂O₂ quenched the LSPR band of plasmonic WO_3-x, further significantly influencing adjacent fluorescence signals depending on its concentration. The probe exhibits a good linear response to H₂O₂ with a low detection limit (10^-9 M) and a wide concentration range (0-50 μM), and shows satisfactory application in the determination of H₂O₂ in blood and milk. This work may provide new ideas for the development of non-invasive fluorescent nanoprobes and plasmon-assisted biochemical detection methods.