The interaction between gelatin and CdS in aqueous solution was studied using fluorescence, IR and UV-Vis spectra at pH 12.0 and different temperatures. It was shown that this compound had a quite strong ability to quench the fluorescence launched from gelatin. After analyzing the fluorescence quenching data according to Lineweave-Burk double-reciprocal equation, it was found that the gelatin had reacted with CdS to form a complex. The quenching belongs to static fluorescence quenching, with non-radiation energy transfer happening within single molecule. The binding locality was an area 4.09 nm away from tryptophan residue in gelatin based on Förster’s non-radiation energy transfer mechanism. According to Lineweave-Burk equation, K (285 K: 1.07×104 L•mol－1; 292 K: 9.69×103 L•mol－1; 299 K: 8.06×103 L•mol－1), the formation constants of the compound at different temperatures and the thermodynamic parameters (ΔrHm＝－14.18 kJ•mol－1; ΔrGm＝－21.98/－22.28/－22.36 kJ•mol－1; ΔrSm＝27.36/27.74/27.36 J•K－1•mol－1) at correspondence temperatures were obtained. The latter show that the binding power between them is mainly the static forces. The results are useful for understanding the chemical mechanism of interaction between nanoparticle and this kind of biological macromolecule.The interaction between gelatin and CdS in aqueous solution was studied using fluorescence, IR and UV-Vis spectra at pH 12.0 and different temperatures. It was shown that this compound had a quite strong ability to quench the fluorescence launched from gelatin. After analyzing the fluorescence quenching data according to Lineweave-Burk double-reciprocal equation, it was found that the gelatin had reacted with CdS to form a complex. The quenching belongs to static fluorescence quenching, with non-radiation energy transfer happening within single molecule. The binding locality was an area 4.09 nm away from tryptophan residue in gelatin based on Förster’s non-radiation energy transfer mechanism. According to Lineweave-Burk equation, K (285 K: 1.07×104 L•mol－1; 292 K: 9.69×103 L•mol－1; 299 K: 8.06×103 L•mol－1), the formation constants of the compound at different temperatures and the thermodynamic parameters (ΔrHm＝－14.18 kJ•mol－1; ΔrGm＝－21.98/－22.28/－22.36 kJ•mol－1; ΔrSm＝27.36/27.74/27.36 J•K－1•mol－1) at correspondence temperatures were obtained. The latter show that the binding power between them is mainly the static forces. The results are useful for understanding the chemical mechanism of interaction between nanoparticle and this kind of biological macromolecule.

Key words: nano-CdS, gelatin, fluoresence quenching, binding equilibrium constant, thermodynamic parameter