Study on the interaction between an ionic liquid and L-tryptophan by fluorescence spectroscopic technique

In this work, the interaction of an ionic liquid (IL) 1-octyl-3-methylimidazolium chloride ([Omim]Cl) and L -tryptophan was investigated with fluorescence spectroscopic method. The quenching mechanism and binding characteristics of [Omim]Cl with L -tryptophan at different temperatures were studied from fluorescence measurement. The thermodynamic parameters such as free energy change (Δ G ), enthalpy change (Δ H ) and entropy change (Δ S ), were calculated by thermodynamic equations. The experimental results indicated that [Omim]Cl and L -tryptophan had weak interaction and the mechanism of quenching belonged to static quenching. Hydrogen bonds and van der Waals interactions played important roles in the binding of [Omim]Cl with L -tryptophan.