Facile Synthesis of Green and Red Emitting Carbon Dots and Multifunctional Applications: Ph Sensing, Anti-Counterfeiting and Latent Fingerprints Imaging

Green and red emission carbon dots (G-CDs and R-CDs) with different luminescence properties were prepared using neutral red and oxalic acid through solvothermal reactions and a simple layering procedure. The obtained R-CDs possess more hydrophilic functional groups than G-CDs, exhibiting better hydrophilicity and more sensitive pH responsiveness. Furthermore, based on their different colors and responsiveness to acidity and alkalinity they can be used for drawing fluorescent anti-counterfeiting patterns. In addition, solid-state fluorescent CDs composite materials were obtained by doping starch matrix with G-CDs and R-CDs. More importantly, S-R-CDs still maintain a significant pH response, which can be further applied in LFPs detection and anti-counterfeiting, expanding the application fields of CDs.