Photoluminescent carbon dots derived from sugarcane molasses: synthesis, properties, and applications

Abstract

Carbon dots (C-dots) were prepared through a simple, environmentally friendly hydrothermal method, with the use of sugarcane molasses derived from industrial waste as the carbon source. The C-dots were characterized via X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR) spectroscopy, nuclear magnetic resonance (NMR), high-resolution transmission electron microscopy (HRTEM), thermogravimetric analysis (TGA), and UV-vis absorption spectroscopy, as well as fluorescence spectroscopy. The C-dots exhibited a spherical shape with a diameter of around 1.9 nm, and emitted blue photoluminescence with a quantum yield of approximately 5.8%. The effects of pH, sodium chloride (NaCl), amino acids and metal ions on the photoluminescence were further investigated. Not only was the biocompatibility of the C-dots assessed in vitro and in vivo, but also their bioimaging ability was observed in MCF-7 cells. The effect of C-dots on secondary structure of bovine serum albumin (BSA) was investigated. Additionally, it was found that the fluorescence intensity of the C-dots decreased after addition of Fe³⁺ or sunset yellow. Furthermore, the underlying mechanism of fluorescence quenching was proposed in the C-dots/sunset yellow system.