Effect of NaOH concentration and reaction time on optical properties and particle size of CDs synthesized at room temperature

Carbon Dots (CDs) have been synthesized at room temperature from glucose. The optical properties of the CDs have been studied using UV–Vis spectroscopy and fluorescence spectroscopy. The CDs showed the presence of both optical as well as fundamental energy gaps. The presence of two emission sources (core and surface) has also been observed. The average particle size and the average fluorescence lifetime of the CDs have been calculated using field emission transmission electron microscopy (FETEM) images and time-resolved photoluminescence (TRPL) spectroscopy, respectively. It has been found that the average particle size has a strong dependency on the reaction time of glucose isomerization, whereas the average fluorescence lifetime is independent of the reaction time. Moreover, the gap energy of the CDs has also been changing with sodium hydroxide (NaOH) concentration. At lower alkaline (NaOH) concentrations, the change in gap energy with time is more prominent compared to the higher alkaline concentrations.