At different temperatures, the interactions between imidacloprid (IMI) and bovine serum albumin (BSA) were investigated with a fluorescence quenching spectrum, a synchronous fluorescence spectrum, a three-dimensional fluorescence spectrum and an ultraviolet-visible spectrum. The average values of bonding constants (KLB: 3.424 ×104 L·mol-1), thermodynamic parameters (△H: 5.188 kJ·mol-1, △G(e): -26.36 kJ·mol-1, △S: 103.9 J·K-1·mol-1) and the numbers of bonding sites (n: 1.156) could be obtained through Stern-Volmer, Lineweaver-Burk and thermodynamic equations. It was shown that the fluorescence of BSA could be quenched for its reactions with IMI to form a certain kind of new compound. The quenching belonged to a static fluorescence quenching, with a non-radiation energy transfer happening within a single molecule. The thermodynamic parameters agree with △H＞0, △S＞0 and △G(e)＜0, suggesting that the binding power between IMI and BSA should be mainly a hydrophobic interaction.
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