培氟沙星与金纳米粒子（AuNPs）之间发生荧光共振能量转移，导致培氟沙星荧光发生猝灭，由于硫脲和纳米金之间可以形成很强的Au-S键，可使培氟沙星从AuNPs表面释放，进而使体系的荧光恢复，基于此建立了测定硫脲的荧光光谱法。在优化试验条件下，培氟沙星-AuNPs体系的荧光强度与硫脲浓度在4.0×10^-7~5.0×10^-6mol·L^-1内呈线性关系，检出限（3s）为1.4×10^-7mol·L^-1。方法用于测定面粉和面条中硫脲的含量，测定值与催化动力学光度法的测定结果一致，相对标准偏差小于4.0%，加标回收率在92.5%~105%之间。

Fluorescence resonance energy transfer between pefloxacin and gold nanoparticles (AuNPs) resulted in fluorescence quenching of pefloxacin. Because of forming strong Au-S bond between thiourea and AuNPs, pefloxacin was released from the surface of AuNPs, then the fluorescence of the system recovered. A method for the determination of thiourea by fluorescence spectrometry was established based on the above facts. Under optimized experimental conditions, linear relationship was found between fluorescence intensity of pefloxacin-AuNPs system and the concentration of thiourea in the range of 4.0×10^-7-5.0×10^-6mol·L^-1, with detection limit (3s) of 1.4×10^-7mol·L^-1. The proposed method was applied to determination of thiourea in flour and noodles, giving results in contency with those obtained by catalytic kinetic spectrophotometry, with relative standard deviation less than 4.0%, and values of recovery obtained by standard addition method were in the range of 92.5%-105%.