A Facile Microwave Avenue to Electrochemiluminescent Two‐Color Graphene Quantum Dots

TLDR

Graphene quantum dots exhibit excitation‑dependent photoluminescence attributed to LUMO‑to‑HOMO transitions involving a carbene‑like triplet ground state. The authors investigate the electrochemiluminescence mechanism of graphene quantum dots and develop a Cd²⁺ sensor based on ECL quenching with cysteine masking. Microwave irradiation simultaneously cleaves and reduces graphene oxide to produce greenish‑yellow GQDs, while further NaBH₄ reduction yields bright blue GQDs, and the study details the ECL mechanism and sensor design. The microwave‑assisted synthesis delivers greenish‑yellow GQDs with up to 11.7 % quantum yield and blue GQDs with 22.9 % quantum yield, and for the first time observes electrochemiluminescence from these dots, indicating promise for biosensing and imaging.

Abstract

Abstract With the assistance of microwave irradiation, greenish‐yellow luminescent graphene quantum dots (gGQDs) with a quantum yield (QY) up to 11.7% are successfully prepared via cleaving graphene oxide (GO) under acid conditions. The cleaving and reduction processes are accomplished simultaneously using microwave treatment without additional reducing agent. When the gGQDs are further reduced with NaBH 4 , bright blue luminescent graphene quantum dots (bGQDs) are obtained with a QY as high as 22.9%. Both GQDs show well‐known excitation‐dependent PL behavior, which could be ascribed to the transition from the lowest unoccupied molecular orbital (LUMO) to the highest occupied molecular orbital (HOMO) with a carbene‐like triplet ground state. Electrochemiluminescence (ECL) is observed from the graphene quantum dots for the first time, suggesting promising applications in ECL biosensing and imaging. The ECL mechanism is investigated in detail. Furthermore, a novel sensor for Cd 2+ is proposed based on Cd 2+ induced ECL quenching with cysteine (Cys) as the masking agent.