A Turn-On Fluorescent Probe for Determination of Ascorbic Acid Based on CaF2:Yb3+, Er3+ Upconversion Nanoparticles

A turn-on fluorometric probe is designed for the determination of ascorbic acid (AA) based on the inner filter effect (IFE) between CaF 2 : Yb 3 + , Er 3 + upconversion nanoparticles (CaF 2 : Yb 3 + , Er 3 + NPs) and the oxidized 3, 3 ′ , 5, 5 ′ -tetramethylbenzidine (oxTMB). The colorless TMB can be oxidized by H 2 O 2 / Cu 2 + to blue oxTMB. Under 980 nm photoexcitation, CaF 2 : Yb 3 + , Er 3 + NPs can emit red light, which can be absorbed by the blue oxTMB, leading to the fluorescence quenching at 657 nm. As AA can reduce the blue oxTMB to colorless TMB, the fluorescence at 657 nm can be recovered with the addition of AA, which can accomplish the detection towards AA. The linear detection range of AA is from 1 to 30 μ M, and the limit of detection (LOD) of AA is 0.1 μ M.