The synthesis of carbon dots and investigation of their photoluminescence properties

In this thesis, carbon quantum dot samples were prepared by using the red onion. XRD and FTIR spectra were taken to determine the structure of the obtained carbon dot samples. It was also analyzed the size and surface load of the carbon dots sample. The photophysical properties of these samples were investigated. For this purpose, absorption and fluorescence measurements of the samples were taken at room temperature in aqueous media. The optimum excitation wavelength for the carbon dot sample was determined with the fluorescence spectra taken at different excitation wavelengths. Then, the effect of concentration, pH and temperature on the photophysical properties of the carbon dots sample was investigated. The concentration studies indicated that the appropriate solution was a mixture of 250 μl / 4950 μl pure water. With the pH study performed at this concentration, it was observed that the carbon dot had a very good fluorescence property at values close to physiological pH and high temperatures and it maintained its stability over a long period of time (3 months). These results showed that carbon dot obtained from a natural plant can be used in many field, such as bio-imaging, chemical-sensors, nanomedical and light emitting diodes.