Study of ion transmission in an electrolyte of graphene quantum dots under ultraviolet light

Abstract

Graphene quantum dots (GQDs) can be used in electrolytes to improve ion transmission and conductivity, but this practice needs further investigation to improve its efficiency. This work focuses on the study of ion transmission in GQD electrolytes under ultraviolet light. A hydrothermal method was used to synthesise GQDs by using three-dimensional graphenes (3DGs) as a carbon precursor. Microstructural characterization showed that the GQDs were distributed at a distance of 10–20 nm, and that the surface of each GQD consisted solely of functional hydroxy groups. In addition, the GQDs exhibited excitation-dependent photoluminescent behaviour under excitation wavelengths, with maximum excitation and emission wavelengths at 360 nm and 452 nm, respectively. The electron transfer of GQDs was studied using electrochemical impedance spectroscopy (EIS) under ultraviolet irradiation (the GQDs were used as an electrolyte). Our results reveal that GQDs have good absorbance under ultraviolet light, and facilitate the decomposition of electron-hole pairs and improve electron transfer rates in solution. These results are attributed to the fact that the surfaces of GQDs only contain hydroxy functional groups. The number of H+ ions increases when GQDs are ionized under acidic conditions, resulting in the acceleration of ion transmission. Our findings have important implications for subjects such as water purification, electrolyte additives, and the simulation of ion transmission.