A highly sensitive upconversion nanoparticles@zeolitic imidazolate frameworks fluorescent nanoprobe for gallic acid analysis

In this work, a core-shell structured upconversion [email protected] imidazolate frameworks (ZIF-8) fluorescent nanoprobe (NaErF4:[email protected]2@ZIF-8) has been designed for the detection of gallic acid (GA). The mechanism is according to the 3, 3′, 5, 5′-tetramethylbenzidine (TMB) can be oxidized to oxidized TMB (oxTMB) by Ag+. Under 980 nm laser excitation, NaErF4:[email protected]2@ZIF-8 can emit red light at 652 nm, which have a good overlap with the absorption spectra of oxTMB, resulting in the fluorescence quenching at 652 nm. Continually adding GA into the above solution, oxTMB will restore to TMB, and the fluorescence intensity at 652 nm gradually recovers, which can realize the detection towards GA. The linear detection range of GA is from 0 to 30 μM, and the limit of detection (LOD) of GA is 0.35 μM. The ZIF-8 can largely enhance the sensitivity of the nanoprobe, due to the physical absorption and the electrostatic attraction between ZIF-8 and the oxTMB. More importantly, this is the first time to realize the detection of GA with high sensitivity by using upconversion fluorescence. Besides, we have realized the analysis of GA in real samples, which certify the feasible of the nanoprobe in potential applications.