Optimization of Tb 3+ /Gd 3+ Molar Ratio for Rapid Detection of Naja Atra Cobra Venom by Immunoglobulin G-Conjugated GdPO 4 ·nH 2 O : Tb 3+ Nanorods

In this report, GdPO 4 ·nH 2 O and Tb 3+ -doped GdPO 4 ·nH 2 O nanorods@silica-NH 2 conjugated with IgG antibody were synthesized by applying hydrothermal, sol-gel, and coprecipitation methods successively. The effects of Tb 3+ /Gd 3+ molar ratios of reactants on the size, morphology, and luminescence of the synthesized samples were also investigated. For the optimized GdPO 4 ·nH 2 O : Tb 3+ 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-NH 2 and conjugated with IgG antibody, all luminescence characteristic peaks of GdPO 4 ·nH 2 O : Tb 3+ corresponding to the process of energy transfer from Gd 3+ to Tb 3+ and then the emission from 5 D 4 → 7 F J ( J = 6,5,4,3 ) of Tb 3+ were still clearly observed. The initial results of using the optimized Tb 3+ -doped GdPO 4 ·nH 2 O nanorods@silica-NH 2 conjugated with IgG antibody for rapid selective detection of Naja atra cobra venom were also reported.