| Abstract [eng] |
Graphene oxide quantum dots (GOKT) are receiving a lot of attention from scientists due to their low toxicity, large surface area, ability to functionalize, and stable luminescence. However, GOKT has low stability in suspensions, a narrow range of emitted color, and a high concentration of defects in the structure. Considering the existing problems, the aim of this work was to synthesize quantum points of graphite oxide from different graphite oxides (GO) by hydrothermal method and perform their structural and optical properties. The products of graphite oxidation have been synthesized using traditional Hummers methods and its different modification. GO was used to obtain graphene oxide quantum dots by performing two different syntheses by the hydrothermal method. In the first synthesis - oxidizer H2O2 and where the time of synthesis was changed from 80 min to 160 min, by doing 40 min step. In the second synthesis - oxidizer KMnO4 and where the temperature of synthesis was changed from 90 ° C to 150 ° C, by doing 20 °C step. GO and GOKT products were examined by different methods. XPS spectra were used to identify and confirm oxygen-containing functional groups. Raman spectra were used to evaluate the structural changes of graphene sheet during synthesis of graphene oxide quantum dots. UV light absorption and luminescent analysis was exercised to investigate optical properties. GO and GOKT products were analyzed by DLS to determine the particle size distribution. SEM analysis was used to examine morphology of GOKT and GO From the obtained results, it was determind that the lowest concentration of defects was found in GOKT, which are obtained using H2O2 oxidizer and GO_CrO3. The XPS study showed that in all GOKTs the number of epoxy-functional groups is significantly reduced and the π conjugated bond system is restored. Based on the results obtained in the study of optical properties, it was found that the synthesis of GOKT and the use of KMnO4 oxidizer achieve the highest value of moderate fluorescence quenching. KT_GO_CrO3_KMnO4_110 was also found to emit from blue to orange when excited at 300 nm to 500 nm light wave. Meanwhile, DLS study has shown that the smallest particles are obtained when KMnO4 is used as an oxidant. |
