Exploring Surface State and Exciplex Dominated Aggregation Induced Electrochemiluminescence of Graphene Quantum Dots Prepared via Electrochemical Exfoliation.

Graphene quantum dots (GQDs) have emerged as promising materials for electrochemiluminescence (ECL) applications due to their unique optical and electronic properties. In this study, GQDs were synthesized via electrochemical exfoliation of graphite in a constant current density mode, enabling scalable production with controlled size and surface functionalization. GQDs-4 and GQDs-20, synthesized at applied current densities of 4 mA/cm and 20 mA/cm to the graphite electrode, respectively, were investigated on roles of surface states and exciplex dominated aggregation-induced emission (AIE) in their ECL performance. GQDs-4 obtained an absolute ECL quantum efficiency of 0.0012 %±0.0002 %. GQDs-20, with a smaller particle size, achieved an absolute ECL quantum efficiency of 0.028±0.002 %, demonstrating high efficiency in converting electrons into photons. While GQDs-4 exhibited minor intensity in PL and ECL, they displayed a similar emission spectrum to GQDs-20 in the ECL process. This finding highlights the significant role of surface states and AIE in influencing the emission properties of GQDs, independent from core-state transitions. These results provide critical insights into the mechanisms governing GQD-based ECL and offer pathways for optimizing these materials for use in biosensing, optoelectronics, and imaging applications. Keywords: Electrochemiluminescence, Graphene Quantum Dots, Exciplex, Surface States, Multi-color Emission.