Graphene oxide (GO) based on coconut shell waste was successfully synthesized using a modified Hummers method, and the obtained GO was confirmed using XRD, FTIR, Raman spectroscopy, UV-Vis spectroscopy, and SEM-EDX. The XRD spectroscopy obtained the fractional content of the 2H graphite phase of 71.53%, 14.47% phosphorus, 10.02% calcium, and 3.97% potassium in coconut shell charcoal, where the GO sample tend to forms a phase of reduced graphene oxide (rGO). FTIR spectra shows compound functional groups of hydroxyl (- OH) at peak 1 (3449.92 cm −1 ), carboxyl (-COOH) at peak 2 (1719.42 cm −1 ) and peak 3 (1702.62 cm −1 ), and alcohol (C–OH) at peak 4 (1628.12 cm −1 ) and epoxy (CO) at peak 5 (1158.51 cm −1 ), which is similar to the GO synthesis from pure graphite. Raman spectroscopy analysis shows that the value of the I D /I G intensity ratio of the GO sample was 0.89 with a 2D single layer, and SEM results showed that surface morphology with an abundance of granular particles were found with different size distribution. The UV-visible results showed sufficient optical properties characterized by the spectrum, which formed because of the light absorption of the energy passed on the sample. The bandgap energy value of the sample obtained by the Tauc plot method was 4.38 eV, which indicates semiconductor properties.

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Neodymium Ferrite Oxide (Nd1.2FeO3) has been successfully synthesized using solid state reaction by varying annealing time. Structural crystallographic characteristics were obtained by X-ray diffraction. The results of X-ray diffraction analysis showed the samples had been identified composed of NdFeO3 and Nd2-O3 phase, with peak dominant correspond to hkl (121), FWHM value of 0.22° and estimated crystal size of 393 nm. Analysis using Rietveld methods obtained Nd1.2FeO3 oxide material has a crystal structure is orthorhombic with space-group of PNMA. The results are comparable as was reported elsewhere that the oxide material is useful for gas sensor application.