Tuning Optical Properties of Carbon Dots by Co-Doping Strategy for Versatile Applications

Carbon dots (CDs) with tunable photoluminescence was successfully prepared via selective co-doping of three elements, including nitrogen, phosphorus and sulfur element by a simple and green one-step hydrothermal method. The as-synthesized nitrogen-sulfur-doped CDs emitting red fluorescence (red NS-CDs) under ultraviolet-light excitation were used for the detection of iron ions with a linear range of 1-50 μM and a limit of detection as low as 94 nM. The nitrogen-phosphorus-doped CDs (blue NP-CDs) emitting blue fluorescence with a quantum yield as high as 34.5% display excellent in vitro anticaner efficacy at a concentration of 800 μg/mL. The nitrogen-sulfur-phosphorus-doped CDs (green NPS-CDs) emitting green fluorescence exhibit a low cytotoxicity at a high concentration of 800 μg/mL and were used for intracelluar imaging of NCl-H292 cells. This work showed the photoluminescence properties of CDs whose peak fluorescence emission wavelengths are tunable by free combination of the given reagents under the similar hydrothermal conditions, but also implied the effective strategies for preparation of CDs for versatile application scenarios.