Highly fluorescent dual-emission red carbon dots and their applications in optoelectronic devices and water detection

Heteroatom-doped carbon dots (CDs), due to their excellent fluorescence performance and multifunctional characteristics, have always been a focus of scientists. Herein, we reported a facile one-step solvothermal method for the synthesis of dual-emission nitrogen and sulfur co-doped (N,S)-CDs with a photoluminescence quantum yield (PLQY) of 29.7%. The synthesized CDs retain highly excitation-independent properties at a wide range of excitation wavelengths. To further investigate the optical properties and surface chemistry of the (N,S)-CDs, several characterization methods were used in this study, including fluorescence spectrophotometry, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and Raman spectroscopy. The as-prepared (N,S)-CDs exhibited two obvious maximum emission wavelengths of 600 and 650 nm with the best excitation wavelength of 560 nm, and emitted bright red fluorescence under UV light (365 nm). The (N,S)-CDs were developed into WLEDs with a comparable CRI and as a sensitive sensor for water in ethanol, suggesting the outstanding application prospects of the as-synthesized (N,S)-CDs.