Observation of Solvatochromic Fluorescent in Environmental Friendly Carbon Dots Prepared by Hydrothermal Treatment

Carbon dots (CDs) are novel class of fluorescent carbon nanoparticles with the size of less than 10 nm [1]. CDs have attracted significant interest due to their unique chemical and physical properties; and they have found various applications such as bioimaging probes, biosensors, gene delivery vehicle, drug delivery vehicle, light absorbent in solar cell and catalyst. Although the physicochemical properties of CDs were systematically explored, there is very little knowledge in the fluorescence behavior of CDs in different solvent environment. Therefore, the aim of this study is to synthesize and to study solvatochromic fluorescence of CDs in different solvents.In the present study, CDs were prepared from tomato extract by following the hydrothermal synthesis reaction. The as-prepared CDs were, then, dissolved in organic solvents, and their fluorescent spectra were registered in the solvents by using a fluorescence spectrophotometer. Results indicated that the as-prepared CDs exhibit high solubility in both apolar such as acetic acid and polar media for example dimethyl sulfoxide, methanol, ethanol, acetone, phenol and water. The strongest solvation effect on CDs can be clearly attributed to the donation of HB from Protic solvents such as methanol (93542) and ethanol (85735) to the CDs. On the other hand, the surface of CDs may also donate a proton to the solvent, although this interaction barel influences emission. Results show that in aromatic solvents, such as phenol: 15414, the fluorescence peak was weak in comparison to hydrogen bonded and aprotic solvents (DMSO:77622, acetone:35819). Thus, the fluorescence intensity of CDs directly correlates with polarity of solvent. We observed that the structure, dielectric constant and the polarity of solvent strongly influenced the fluoresce intensity of CDs. It is found that the fluorescence intensity of the CDs varies with the change in the solvent polarity indicating the dependency of fluorescence properties on the solvent nature. This study showed aromatic solvents as well as apolar solvents have minimum effects on the fluorescence intensity of CDs. In conclusion, the results indicate strong effects of solvents on the behavior of CDs. These results can be used to tune the solvation of CDs in order to maximize the fluorescence intensity of these nanomaterials.