This study reports the synthesis and characterization of the red nanophosphors Zn 2 SiO 4 :Eu 3+ (ZSO:Eu 3+ ) and Mg 2 TiO 4 :Mn 4+ (MTO:Mn 4+ ). The use of phosphors as a fluorescence label for lateral flow immunochromatographic assay (LFIA) has also been described. The optimal photoluminescence (PL) for ZSO:Eu 3+ was obtained when it was synthesized with 7 mol% of Eu 3+ and annealed at 1100 °C for 1 h. Long fluorescence lifetime (1.01 ms), high activation energy E a (0.28 eV), and low PL degeneration (10% at 110 °C) are the characteristics of ZSO:Eu 3+ . MTO:Mn 4+ also exhibited high PL intensity along with a high E a of 0.32 eV. The emission wavelengths of phosphors are biocompatible with the optical bio-window of tissues. When human immunoglobulin G (human IgG) at a constant concentration of 100 μg/mL was used for detection, the PL ratios of the test line to the control line were 2.15 and 2.28 for the ZSO:Eu 3+ -and MTO:Mn 4+ -labeled LFIA, respectively. Thus, the ZSO:Eu 3+ and MTO:Mn 4+ nanophosphors are capable of human IgG recognition and are the promising candidates as fluorescent labels for on-site rapid optical biodetection.

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