Inner filter effect of gold nanoparticles on the fluorescence of rare-earth phosphate nanocrystals and its application for determination of biological aminothiols

A simple, sensitive fluorescent method for detecting biological aminothiols has been developed based on the inner filter effect principle that utilizes CePO4:Tb3+ luminescent nanoparticles as the donor and gold nanoparticles (AuNPs) as the energy receptor. Stable, water-soluble and well-dispersible CePO4:Tb3+ nanoparticles with low photobleaching features were synthesized conveniently by a facile solvothermal method. At the same time, AuNPs with a high extinction coefficient are expected to be capable of functioning as powerful receptor. Based on the complementary overlap between the emission spectrum of CePO4:Tb3+ nanoparticles and the absorption spectrum of Au NPs, an inner filter effect system was constructed. In the presence of aminothiols (such as cysteine), AuNPs interacted with the aminothiols, thereby inducing the aggregation of AuNPs, which induced the fluorescence recovery. In the present work, we developed a turn-on fluorescent assay for the determination of biological aminothiols. Under the optimum conditions, the linear concentration ranges were 1.0×10−7–2.0×10−6 M for cysteine, 5.0×10−8–5.0×10−7 M for glutathione and 8.0×10−8–1.0×10−6 M for homocysteine, respectively. The method is successfully applied to the quantification of biological aminothiols in synthetic samples.