A near-infrared luminescent Mn2+-doped NaYF4:Yb,Tm/Fe3+ upconversion nanoparticles redox reaction system for the detection of GSH/Cys/AA

An upconversion luminescence method was developed for the determination of glutathione (GSH), L-cysteine (Cys) or L-ascorbic acid (AA) based on redox reaction. We synthesized poly(acrylic acid) (PAA)-modified Mn2+-doped NaYF4:Yb,Tm upconversion nanoparticles (UCNPs), and the luminescence of these UCNPs was effectively quenched due to their carboxyl groups coordinating with Fe3+ to form a UCNPs/Fe3+ system. GSH, Cys or AA reduced Fe3+ to Fe2+, which induced the luminescence recovery of the UCNPs. Under the optimized conditions, wide linear concentration ranges from 0.25-300 mu M for GSH, 0.5-875 mu M for Cys and 0.5-350 mu M for AA were found, and the detection limits (3 S/K) were 0.2 mu M, 0.5 mu M and 0.2 mu M, respectively. Thus, the UCNPs/Fe3+ system was successfully applied for sensing GSH, Cys or AA.