Absorption and Fluorescence Properties of Oxidized and N-doped Graphene Quantum Dots: A Time-dependent DFT Study

摘要

Absorption and emission properties of oxidized graphene quantum dots(GQDs) and amino functionalized GQDs(NG) were explored by B3 LYP method combined with 6-31G(d) basis set.The oxygen- and nitrogen-containing groups can tune the intensity as well as the wavelength of absorption and emission.The groups such as hydroxyl,carboxyl,amino,amide,and pyridine-like N can appropriately lengthen the absorption and emission wavelength of GQDs.However,the carbonyl group,graphitic-like N,and pyrrolic-like N obviously decrease the oscillator strength and lengthen the emission wavelength of GQDs out of the visible region.The lowest excited state S_1 of NG has the strongest emission in investigated complexes,which indicates that it is an excellent luminous material.The theoretical investigations verify that the oxygen- and nitrogen-related groups can tune the luminescence of GQDs.The fluorescence quenching of GQDs reduced by ammonia mainly depends on the graphitic-like and pyrrolic-like N.