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 lessthan 10 nm [1]. CDs have attracted significant interest due to their unique chemical and physicalproperties; and they have found various applications such as bioimaging probes, biosensors, genedelivery vehicle, drug delivery vehicle, light absorbent in solar cell and catalyst. Although thephysicochemical properties of CDs were systematically explored, there is very little knowledgein the fluorescence behavior of CDs in different solvent environment. Therefore, the aim of thisstudy 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 hydrothermalsynthesis reaction. The as-prepared CDs were, then, dissolved in organic solvents, and theirfluorescent 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 aceticacid and polar media for example dimethyl sulfoxide, methanol, ethanol, acetone, phenol andwater. The strongest solvation effect on CDs can be clearly attributed to the donation of HB fromProtic solvents such as methanol (93542) and ethanol (85735) to the CDs. On the other hand, thesurface of CDs may also donate a proton to the solvent, although this interaction barelyinfluences emission. Results show that in aromatic solvents, such as phenol: 15414, thefluorescence peak was weak in comparison to hydrogen bonded and aprotic solvents(DMSO:77622, acetone:35819). Thus, the fluorescence intensity of CDs directly correlates withpolarity of solvent. We observed that the structure, dielectric constant and the polarity of solventstrongly influenced the fluoresce intensity of CDs. It is found that the fluorescence intensity ofthe CDs varies with the change in the solvent polarity indicating the dependency of fluorescenceproperties on the solvent nature. This study showed aromatic solvents as well as apolar solventshave minimum effects on the fluorescence intensity of CDs. In conclusion, the results indicatestrong effects of solvents on the behavior of CDs. These results can be used to tune the solvationof CDs in order to maximize the fluorescence intensity of these nanomaterials.

Keywords:

Solvatochromic , Carbon Dots , Fluorescent