The mechanism of the fluorescence quenching of L-tryptophan by graphene oxide

Graphene oxide (GO) was prepared by the modified Hummers method and used as a fluorescence quenching reagent of L-tryptophan (L-Trp). The structure of GO was characterized by FT-IR and Raman spectroscopy. The binding mechanism of L-Trp on GO and their reaction were investigated by UV spectroscopy and the fluorescence method. Results show that GO has a strong fluorescence quenching ability for L-Trp. The quenching efficiency is 95.6% for L-Trp with a concentration of 2x10(-5) mol. L-1 when the GO concentration is 16x10(-5) g.mL(-1). The binding constants of L-Trp on GO were 2.03 x 10(5), 1.83 x 10(5) and 1.63 x 10(5) mL.g(-1) at 25, 30 and 35, respectively, as revealed by the Lineweawer-Burk equation, indicating a strong interaction between GO and L-Trp. GO quenches the intrinsic fluorescence of L-Trp by the formation of a complex, and is a static quenching mechanism. The quenching rate constant was 6.65x10(12) mL.(g.s)(-1) at 25 degrees C as determined by the Stern-Volmer equation.