Abstract:
In this study, the synthesis of carbon dots from cup lumps via a hydrothermal process at 200 °C was studied. Various factors were investigated including reaction time, precursor amount, solvent volume and chemical types doped for synthesizing carbon dots in order to optimize the optical properties. The functional groups of carbon dots were studied using fourier transform infrared spectroscopy. The binding energy of carbon dots was measured using the X-ray photoelectron spectroscopy technique. The morphology of CDs was analyzed by transmission electron microscope. Optical properties were characterized using UVvis and fluorescence spectrophotometers. The wettability was determined by contact angle technique. The results showed that the use of reaction time at 18 h, amount of 0.4 g and DI water of 20 ml were the suitable factors for most likely to be synthesis carbon dot, considering based on their physical properties, concentration and optical properties. Moreover, the ammonium persulfate as a doped chemical resulted in the presence of -NH and S=O functional groups on the surface, leading to the increased polarity of carbon dots. The particle size of carbon dots was approximately 6.31 nm. The quantum yield was also increased from 4.3 to 12.0% compared to no chemical doping. In addition, the band gap energy of carbon dots was significantly decreased from 6.24 to 5.18 eV (ammonium persulfate doping). Accordingly, the carbon dots obtained from this research was suitable properties for applying as an environmentally friendly fluorescent ink in anti-counterfeiting application.