Ultrasensitive fluorescence "off-on" detection of H2O2 in processed meat products using carbon dots and Au@Ag nanorods as nanoprobes.

Herein, a novel fluorescence "off-on" sensing system was developed for ultrasensitive detection of H2O2 by integrating carbon dots (CDs) with Au@Ag core-shell nanorods (Au@Ag NRs). The detection mechanism lies in the H2O2-triggered etching of the silver shell on Au@Ag NRs, which enables reversible modulation of the fluorescence resonance energy transfer (FRET) between CDs (donor) and Au@Ag NRs (acceptor). Initially, the fluorescence of CDs is efficiently quenched (turn-off) by Au@Ag NRs via FRET. Upon addition of H2O2, the Ag0 shell is gradually oxidized into Ag+, including a red shift in the UV-vis absorption spectrum of Au@Ag NRs and thus weakening the FRET effect, leading to fluorescence recovery (turn on). The fluorescence recovery value (ΔF) is linearly correlated with H2O2 concentration in the range of 0.1-50 μM (R2 = 0.996), with a detection limit as low as 0.01 μM. The CDs-Au@Ag NRs nanoprobe exhibits excellent selectivity toward H2O2 over other potential interferents. The proposed system was successfully applied to detect H2O2 in real food samples, including sausages and pickled chicken feet, demonstrating its practical utility for routine monitoring of H2O2 residues in complex processed meat products.