Up-converting nanoparticle is a novel rare earth fluorescence material in recent years. The optical mechanism which converts it into visible light at near infrared light excitation makes it possess the advantages as strong anti photo-bleaching, wide anti-stokes shift, lower toxicity and lack of auto fluorescence. These advantages can enhance sensitivity and signal-to-noise ratio in immunoassay detection. The water solution and dispersity of up-converting nanoparticles are weak. Therefore we produce good water solution and monodispersity of up-converting rare earth particles by chemical modification so as to conjugate to biomolecules. This paper reviews the chemical modification of up-converting particles, mechanism of fluorescence resonance energy transfer, application in immunoassay based on magnetic isolation, fluorescent biolabeling with solid-phase micro well, biosensor and lateral-flow assay. Application in up-converting technology solves low sensitivity for traditional nanomaterials and has potential in medical detection.
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