Abstract: CdTe semiconductor nano-particles were synthesized with mercaptoethylic acid as the stabilizer as well as surface-modification reagent. The average size of CdTe nano-particles estimated from TEM graph was ca. 3 nm. The CdTe nano-particles exhibited a strong ultraviolet absorption at 320 nm and fluorescence emission at 524.8 nm, respectively. When surface-modification of CdTe nano-particles were replaced with pepsin, ultraviolet absorption peak kept the same, absorption intensity at 320 nm increased. It can be observed that the fluorescence emission intensity decreased as well as the fluorescence peak shifted to 467.2 nm. Temperature, ion strength and pH value influenced the surface-modification of CdTe nano-particles. Under the optimal conditions, a mass concentration of pepsin in the range of 4—40 mg/L shows a linear relationship with the fluorescence intensity decreasing value of CdTe nano-particles, with a detection limit 3σ of 0.28 mg/L(n=10). The proposed method was applied to detection of the concentration of pepsin in human gastric juice.

Key words: CdTe nano-particles, Pepsin, Surface-modification, Fluorescence determination