Ultra-bright green carbon dots with excitation-independent fluorescence for bioimaging

Abstract

Current and future diagnostics urgently need imaging agents that are non-toxic and superior to clinically used small molecule dyes. Herein, we have developed luminescent green light-emitting carbon dots (GCDs) via a single-step hydrothermal reaction using a low-cost chemical precursor, p-toluenesulfonic acid. The GCDs exhibit excitation-independent fluorescence (FL) emission with the photoluminescence quantum yield of 70% and no FL quenching up to 1.25 mg/mL. The GCDs exhibit negligible cytotoxicity up to 250 µg/mL concentration in RAW 264.7 cells. Interestingly, GCDs exhibit an excitation-independent and concentration-dependent fluorescence emission behaviour. In vitro, the peak emission was obtained at 520 nm using the excitation at 430 nm.