Oxidation etching induced dual-signal response of carbon dots/silver nanoparticles system for ratiometric optical sensing of H2O2 and H2O2-related bioanalysis

Highlights: • A ratiometric sensor of H₂O₂ was fabricated by Ag nanoparticles (AgNPs) and carbon dots (CDs). • The sensor was developed by combining fluorescence and second-order Rayleigh scattering. • The CDs/AgNPs system was endowed with weak fluorescence and strong scattering. • Fluorescence increased and scattering declined after AgNPs were etched by H₂O₂. • The sensor was extended to ratiometric assay of glucose and glucose oxidase activity. -- Abstract: Ratiometric sensing suffers from less interference and can obtain more accurate results than single-signal assay. Here, a new ratiometric optical sensing strategy for H₂O₂ detection is developed by etching silver nanoparticles (AgNPs) to deactivate fluorescence resonance energy transfer (FRET) and reduce Rayleigh scattering based on a hyphenated technique of fluorescence and second-order Rayleigh scattering (SRS). The ratiometric detection of H₂O₂ is achieved through exploiting a hybrid system fabricated by fluorescent carbon dots and silver nanoparticles (CDs/AgNPs). In the CDs/AgNPs system, the fluorescence of CDs is quenched because of FRET, and the scattering is strong due to the intrinsic high light-scattering power of AgNPs. With the introduction of H₂O₂, the AgNPs are etched and the CDs are released from the AgNP surface, resulting in the fluorescence enhancement and scattering decline. As a result, ratiometric sensing of H₂O₂ can be achieved based on the CDs/AgNPs system by simultaneous collection of fluorescence and SRS signals. The sensing system is further used for H₂O₂-generation bioanalysis, and as a proof-of-concept, ratiometric assay of glucose and evaluation of glucose oxidase activity are performed successfully. This work provides a new perspective for sensing applications of plasmonic nanoparticles.