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    2020-08-18


    Fig. 2. SEM images of the produced GO (A,B) and graphene nanosheets (C,D).
    2.6. Characterization
    The morphology of the products was investigated using a Cam Scan MV2300 scanning electron microscope (SEM).FT-IR spectrometer (Magna-IR, 550 Nicolet) in the range of 400–4000 cm 1was used to perform the Fourier transform infrared spectra using KBr pellets. A
    Philips Company diffractometer with X'Pert Promonochromatized CuKα radiation (l = 1.54 Å) was employed in collecting Powder X-ray diffraction (XRD) patterns. Renishaw (New Mills, UK) in Via micro-Raman spectroscopy system with a 514.5-nm Ar + laser was used to record the Raman spectra.
    3. Results and discussion
    In addition, the determination of crystallinity, average crystallite size of materials, and their respective interlayer distance was facilitated by the powder XRD as represented in Fig. 1. An intense diffraction peak corresponding to 2θ = 10.69 (001) was observed with an interlayer distance of 0.83 nm which denoted the significant oxidation of graphite powder [28]. Previous literature suggested that a larger interlayer spacing was present in GO when compared to graphite powder which corresponds to the oxygen bearing functional groups insertion [29]. The incidence of a very minute peak at 2θ~26 indicated the presence of graphitic peak which got oxidized to GO with the occurrence of evident peak at 2θ = 10.69. PXRD pattern of SRGO was displayed in Fig. 1 inset. These results indicated that SRGO demonstrated a broad peak centred at 2θ is 25 in Marizomib to GO, which might denote the restacking of graphene layers. However, the absence of peak at 2θ = 9.75 denoted the efficient removal of oxygen containing groups of GO [30].
    SEM images of the synthesized graphene oxide (SRGO) nanosheets were displayed in Fig. 2 which presented completely exfoliated gra-phene oxide sheets. These sheets differ from the pristine graphene na-nosheets in their minimal electrical conductivity which is attributed to the presence of oxygen containing groups on the graphite oxide surface. It was generally observed that the graphene oxide sheets are usually thicker than that of graphene because of the presence of carboxyl, 
    carbonyl, epoxy, and hydroxyl groups on either sides of the primary graphene plane. SEM images of the synthesized graphene oxide sheets treated with reducing agent to form graphene as shown in Fig. 2 pre-sented transparent and smooth graphene sheets. Fig. 3 represents the typical Raman spectrum of the GS which pre-sented two strong peaks at 2693 and 1576 cm 1 attributing to 2D and G bands and few-layer GS are observed. It is well known that the GS in-tensity is stronger than that of the commercial graphitic flakes. This is in accordance with the earlier reports that as the number of layers decreases, the 2D peak location for GS shifts towards lower range than that of bulk graphite. Additionally, the ID/IG value of GS was de-termined to be 0.4, which was lower than 0.76 of GS that were formed by self-assembling. The ID/IG value is known to be the measure of the disorder, which could be charge puddles, edges, ripples, or any other defects.
    FTIR spectral date of GO and ORGO were displayed in Fig. 4. GO
    Fig. 3. Raman spectrum of graphene sheets.
    Fig. 4. FTIR spectrum of SRGO and GO.
    FTIR spectra has showna broad peak in the range of 3000 and 3700 cm -1and an intense peak at 1624.73 cm-1 which corresponds to the -OH group of water molecules adsorbed on to the GO surface. However, in the SRGO spectra, intense bands are identified in the region of 1614 cm-
    1 and 1644 cm-1 due to the C]O stretching while intense peaks at 1386 cm-1 and 1384.64 cm-1 indicated the distinctive CeOeC stretching due to epoxy groups and also C-O stretching recorded at 1034 cm-1 due to the removal of oxygen functionalities from the GO surface. However, the decline in the O-H and C-H intensity represented the effective GO reduction due to plant extract. Additionally, a peak 1600 cm-1 representing carbonyl groups and N-H stretching, confirmed the Sorafenib adsorption onto the surface of graphene. Since, the pre-sent approach is a green method, FTIR results of SRGO do not show the reduction of peak intensities other vibrational bands in case of SRGO after reduction, which is because of biconstituents of plant extracts that are present on the surface of SRGO formed after reduction.
    MTT assay was used to determine the percentage viability of cancer cell lines upon contact with blank NP, free SRF, and SRGO. The blank NPs have presented no obvious cancer cell proliferation even at a maximum concentration of 100 μg/ml as shown in Fig. 5a. The cell
    remained above 90% viable at the maximum concentration which re-presented its nontoxic nature. As shown in Fig. 5b represented a typical dose dependent cytotoxic effect of NP, free SRF, and SRGO against gastric cancer cells. At equivalent concentrations, SRGO stimulated potently higher anticancer effect compared to free SRF in SGC7901 cancer cell lines. SRGO treated cell lines have reported maximum cancer cell destruction, while the untreated groups remained viable.