Optimization of Tb3+/Gd3+ molar ratio for rapid detection of Naja atra cobra venom by immunoglobulin G-conjugated GdPO4·NH2O:Tb3+ nanorods

Abstract

In this report, GdPO4·nH2O and Tb3+-doped GdPO4·nH2O nanorods@silica-NH2 conjugated with IgG antibody were synthesized by applying hydrothermal, sol-gel, and coprecipitation methods successively. The effects of Tb3+/Gd3+ molar ratios of reactants on the size, morphology, and luminescence of the synthesized samples were also investigated. For the optimized GdPO4·nH2O: Tb3+ sample, uniform nanorods sizing from 10 to 30 nm in diameter and from 200 to 300 nm in length were obtained with the strongest luminescence in green color with narrow bands under the UV excitation (325 nm). The results revealed that, after being coated with silica-NH2 and conjugated with IgG antibody, all luminescence characteristic peaks of GdPO4·nH2O: Tb3+ corresponding to the process of energy transfer from Gd3+ to Tb3+ and then the emission from 5D4 → 7FJ (J = 6,5,4,3) of Tb3+ were still clearly observed. The initial results of using the optimized Tb3+-doped GdPO4·nH2O nanorods@silica-NH2 conjugated with IgG antibody for rapid selective detection of Naja atra cobra venom were also reported.