Optical properties investigation of two synthesis methods and highlighting the optimal method for cellular assessments

Carbon dots (CDs) can be extensively applied in diverse sciences, such as biology. To improve photophysical properties of these materials, nitrogenous groups are used. These materials can transfer electrons into CDs and surface modification is occurred. Also, it can improve the optical performance of particles and the efficiency of cell imaging. In this study, two methods for CDs synthesis were investigated for optical properties improvement. First, CDs were synthesized from a green source via hydrothermal method. Then, the arginine amino acid was used to functionalize the particles with nitrogenous groups. In the first method, ۳۰ mL of the plant extraction and ۰.۵ g amino acid were mixed, while in the second method, a dry powder of plant extraction was prepared using a freeze-dryer. Then, ۲ g of the resultant powder and ۰.۴ g arginine were dissolved in water. The resulting solutions from both methods were used for CDs synthesis by Teflon-lined autoclave at ۱۲۰ °C for ۵ hours. After physical properties confirmation of CDs, the fluorescence evaluation of both samples under the UV-light were done. These results indicate blue and green emissions of our particles. However, the sample obtained from the first method illustrated higher fluorescence intensity. The fluorescence spectroscopy analysis and UV-Vis spectroscopy were used for measurement of fluorescence intensity and the quantum yield calculation, respectively. Comparison of two syntheses showed that both methods could create the main properties of CDs; however, the quantum yield of the first method was significantly higher than the second one. The fluorometry results of particles at ۳۹۳ and ۳۹۸ nm wavelengths showed the higher fluorescence intensity of CDs in first method. Therefore, the first method has more efficient role in cell imaging.

Keywords:

Carbon dots , Nitrogen , Luminescence , Cellular imaging