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Graphene oxide (GO) and reduced graphene oxide (RGO) presents great potential applications in various fields due to their extraordinary properties. However, to synthesize GO and RGO environmental friendly and inexpensive still is a big challenge for large scale production. Although chemical synthesis method is the easiest, low cost, and large amount production compares to the other methods but there are some disadvantages using chemical such as toxicity, hazardous and corrosive which are harmful to the environment and human health. Therefore, it is recommended to using green reduction agent to replace the chemical agent. This paper presents a summary and discussion of the green reduction of GO to RGO using Oolong Tea extract. It also reviews the characterization of GO and RGO using of X-ray diffiaction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and ultraviolet- visible spectroscopy (UV-Vis). [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) is known has some unique properties for various applications. GO is the oxidation form of graphene. It is synthesized from graphite through chemical oxidation. The structure of GO is different with graphite and graphene where the plane of the GO is attached with oxygen functional groups. In this research, GO was prepared by using improved Hummers' method from natural graphite powder. In addition, the effects of different reaction time of 24 hours, 48 hours, 72 hours and 96 hours on the yields of GO were studied. Results indicated that different samples of GO possessed different morphologies, attachment of functionalized groups, crystallinity and absorption peaks in Ultraviolet Visible (UV-Vis) spectroscopy. GO was characterized by using a Scanning Electron Microscope (SEM), Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD) and UV-Vis. SEM result showed platelet-like surface that appeared on the surface of GO (48 hours) as compared with GO (72 hours) where wavy wrinkled and layered-flakes, and crumpled structures were seen on GO (96 hours) surface respectively. In FTIR results, the existence of higher amount of abundant oxygen-containing functional groups was confirmed in GO (96 hours) as compared with GO (24 hours) due to the longer oxidation time. Furthermore, the absorption peak of GO was noticed at around 230 nm and the intensity of peak was increased with reaction time. By comparing these results, the oxidation of graphite to form GO can be determined accurately. Therefore, this study is a great beneficial to provide more understanding for many researchers about how to control the quality and amount of GO by varying reaction times for various applications. [ABSTRACT FROM AUTHOR]

Researchers studied graphene oxide (GO) and reduced graphene oxide (rGO), to explore its usefulness in different fields and applications. To produce rGO using conventional method at low-cost and environmental-friendly is a huge challenge because it involves harmful and hazardous chemicals such as hydrazine hydrate. Therefore, scientists proposed several green reducing agents as an alternative method to produce a same product. This research presents an outline and discussion of green synthesis of rGO using green tea extract as the reducing agents by manipulating their reaction time. Besides, it also gives an overview on the characterization of GO and rGO by analysing them using X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) with Energy-dispersive X-ray spectroscopy (EDX), Fourier Transmission Infrared (FTIR) and Ultraviolet-visible Spectroscopy (UV-Vis). XRD spectra has proven the GO and rGO were successfully synthesised by exhibiting the peak at 9.75 nm and 25.42 nm respectively. In SEM images, wrinkled and flaky structures were observed in both GO and rGO while the EDX showed the composition of them. Moreover, the FTIR analysis suggested that the amount of oxygen functional groups in GO were decreased when it was reduced to rGO whereas the UV-Vis spectra proved the presence of absorption peak of GO (230 nm) and rGO (280 nm) accurately at different locations. Thus, the objectives of this research were achieved, and this green method can be a substitution to lower down the rely on chemical substances. [ABSTRACT FROM AUTHOR]