Biofunctional europium (Ⅲ)-doped ZnS (ZnS:Eu) nanocrystals are prepared by a sol-gel method.The characteristic luminescence of ZnS∶Eu is used as a probe signal to realize sensitive immunoassay.The luminescence intensity of the Eu3+ in the ZnS matrix shows strong concentration dependence,and the optimal doping concentration is 4％.However,the emission wavelengths of the ZnS:Eu nanocrystals are not dependent on doping concentration nor the temperature (from 100 K to 300 K).Our results show that these features allow for reliable immunoassay.Human immunoglobulin,used as a target analyte,is captured by antibody modified ZnS∶Eu probe and is finally enriched on gold substrate for detection.High specificity of the assay is demonstrated by control experiments.The linear detection range is 10 nM-800 nM,and the detection limit is about 9.6 nM.