An efficient fluorescence analysis for plant gallic acid based on dual-ligand Ag/Au nanoclusters

Gallic acid (GA) is a secondary metabolite derived from plant phenolics. It is essential to maintain normal physiological activities in plants facing adversity. This, in turn, helps maintain crop integrity. Consequently, the surveillance of GA levels in plants is of significant importance. This study developed a near-infrared (NIR) red fluorescent Ag/Au nanocluster sensor, utilizing glutathione and bovine serum albumin as dual ligands. This modification shifts the emission wavelength to the red spectrum, mitigating the interference from the plant's inherent fluorescence. The fluorescence resonance energy transfer (FRET) mechanism is exploited. When the presence of Ag⁺ induces the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) to oxTMB, which in turn quenches the fluorescence at 650 nm. GA's abundant phenolic hydroxyl group will reduce oxTMB to TMB, so the material's fluorescence will be turned on to detect GA. The established platform can quantify a wide range of GA thanks to the above reasons. In particular, this platform has a recovery of 96.09%-104.7 % for detecting GA in tomato samples with an error of no more than 3 % and a detection limit as low as 38.29 nM. On the other hand, a combination of probes and the fluorescence platform was used to visualize GA levels in tomato leaves under drought and salt stress. This can assist in elucidating the physiological adaptations of plants to environmental changes. The groundbreaking GSH/BSA-Au/Ag nanosensor shows great potential for trace detection of GA in plants and will contribute to a deeper understanding of plant physiology.