I have synthesized carbon nanodots using ascorbic acid and EDTA, heating it to 200 degree centigrade for 24 hrs. The UV peak was obtained in a range between 200-300 and broad emissions spectra was observed between 370-550.
There are variety of approaches, including silica-gel column chromatography, dialysis, and centrifuge to conduct a purification experiment. But, amongst them, using chromatography under UV irradiation is the most promising one, because you can interestingly observe that your sample, which exhibited for example green emission before utilizing UV-exposed chromatography, is separated into several different colors. Therefore, I suggest silica column chromatography under UV exposure.
Carbon dots – Separative techniques: Tools-objective towards green analytical nanometrology focused on bioanalysis : doi.org/10.1016/j.microc.2020.105773