The Synthesis Of Fluorescent Carbon Dots Using Watermelon Peel As A Carbon Source And Its Bio-Analytical Applications

Recently fluorescent Carbon dots (C-dots) have attracted significant scientific attentions due to their excellent luminescence properties, good water-solubility and biocompatibility Although there have been some of development about synthetic methods such as arc discharge, laser ablation, electrochemical oxidation, combustion/thermal, supported synthetic, microwave methods and so on, the difficulty of collecting or the high cost of carbon source hender the development of fluorescence C-dots of extensive application. We report a facile method for the synthesis of fluorescent (C-dots) from watermelon peel, a waste and reproducible raw resource, disscuss the detailed formation mechanism of fluorescence C-dots and they have been successfully applied in bio-analysis. The main concents and results are listed as below:1. A facile method for the synthesis of fluorescent (C-dots) from watermelon peel, a waste and reproducible raw resource, through low-temperature carbonization and filtration. The The particle-size of C-dots was characterized by transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM). structure, morphology and.The optical properties of C-dots were investigated by ultra-violet visible (UV-Vis) and fluorescence spectrophotometer (FL). The structure and chemical composition of C-dots was acquired with fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and raman spectra. The results displayed that the obtained C-dots have amorphous structure, small particle size (～2.0 nn), exhibit high luminescent efficiency and show excitation dependent feature.good The fluorescent carbon dots with a large number of carboxyl groups on the surface are good water-solubility and stability. Furthermore, the formation mechanism of the fluorescent C-dots may be due to the carbonation reaction.2.The interactions between fluorescent C-dots and BSA have been studied by spectroscopic techniques. The results showed that the fluorescence of BSA could be strongly quenched by fluorescent C-dots, which was proved to be a static quenching procedure according to the stern-volmer equation. The results of thermodynamic parameters and effect of ion strength suggested that the possible mechanism of the interaction was in iterms of a synergetic effect of hydrophobic and electrostatic interactions.3. The cytotoxicity and cell imaging function of C-dots were detected by MTT assay and bio-imaging system, respectively. The results were suggested that fluorescent C-dots appeared to have low toxicity within a certain range of concentrations and good biocompatibility. In the application of bio-imaging, it is noteworthy the fluorescent C-dots showed high fluorescent property. It was found that large numbers of the fluorescent C-dots entered into the HeLa cells after 3 h co-incubation and then the cells could be visualized by laser scanning confocal microcopy. The result revealed that fluorescent C-dots could enter into cell across the plasma membrane by endocytosis, which also indicated that fluorescent C-dots can be served as a new effective bio-imaging materials.