Preparation of Zn2GeO4:Mn,In persistent luminescence nanoparticle composites for the detection of copper ions

Abstract

Copper in vegetables can enter the human body, and excessive copper may cause uncomfortable symptoms; thus, it is urgent to test copper ions for safety concerns. Herein, we prepared Zn₂GeO₄:Mn²⁺,In³⁺ (ZGO:Mn,In) persistent luminescent nanoparticles (PLNPs) and then grafted glutathione for the determination of copper ions. ZGO:Mn,In was prepared by doping In³⁺ in ZGO:Mn to improve the emission at 532 nm under excitation at 258 nm. The doping amount, temperature, time, and pH were carefully optimized for a stronger emission intensity than ZGO:Mn. The fractional densities and energy band gaps were calculated by density functional theory, revealing the excitation enhancement mechanism of ZGO:Mn,In. The surface of ZGO:Mn,In was modified with carboxyl groups for linking glutathione to specially identify Cu²⁺ ions. The identification resulted in the aggregation-induced quenching of PLNPs’ emission. Thus, the sensor exhibited good selectivity for copper ions, and the composite was successfully applied to the detection of copper ions in serum and vegetable samples.