Carbon dots (C-Dots) from mangosteen peel has been synthesized by pyrolysis method. Synthesis of C-Dots is done using precursor solution which is prepared from extract of mangosteen peel as carbon source and urea as passivation agent. C-Dots is successfully formed with absorbance spectra at wavelength 350-550 nm. Urea affects to the formed C-Dots, while the absorbance and the luminescent spectra are independent toward urea. C-Dots from extract of mangosteen peel has size in range *2-15 nm. The absorbance peaks of C-Dots shows significant wavelength shift at visible region as the increasing of synthesized temperature. Shift of wavelength absorbance indicates the change of electronic transition of C-Dots. Meanwhile, the luminescent of C-Dots can be controlled by synthesized temperature as well. C-Dots luminescent were increasing as higher synthesized temperature. It was shown by the shift of wavelength emission into shorter wavelength, 465 nm at 200°C, 450 nm at 250°C, and 423 nm at 300°C. Synthesized temperature also affects size of C-Dots. It has size *10-15 nm at 200°C, *7-11 nm at 250°C and *2-4 nm at 300°C. In addition, temperature corresponds to the structure of carbon chains and C-N configuration of formed C-Dots from mangosteen peel extract.

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Abstract:Carbon nanodots (C-Dots) of frying oil could be a photocatalyst for the degradation of methylene blue solution with assisted solar light irradiation. C-Dots of frying oil were resulted from the heating process at T = 300°C for 2 h. C-Dots of frying oil were used as a catalyst in methylene blue solution with variations the number of C-Dots and the time of solar light irradiation. The results of photocatalytic process show the degradation of concentration from methylene blue solution. It was observed from the color change of the solution and the absorbance intensity decreases with increasing time of photocatalytic process. FTIR spectra showed that the hydroxyl functional group -OH changes and more widened at wavenumber 3468 cm −1 because the result of photocatytic process of methylene blue solution is water (H 2 O) and carbon dioxide (CO 2 ). Meanwhile, the intensity of the alkene functional group C = N at wavenumber 1650 cm −1 decreased during the photocatalytic process. These results indicate that C-Dots of frying oil have an excellent potential to be developed as a photocatalyst materials.