3 Methodology3.1 Chemicals Chemicals will be obtained from Sigma-Aldrich. Graphite powder will be used as raw material. Concentrated hydrochloric acid, sulfuric acid, potassium permanganate and hydrogen peroxide will be used for the oxidation process to oxidize the graphite powder into graphite oxide. The next process will be to obtain reduced graphene oxide. Hydrazine monohydrate will be used as reducing agents. To make graphene as a glucose sensor, glucose, chitosan, phosphate buffer saline, potassium chloride, acetic acid, chloroplatinic acid, sulfuric acid, hydrogen peroxide, ascorbic acid and uric acid will be used. All solutions used in the glucose sensor experiment will be prepared with ultrapure water.3.2 Sample Preparation3.2.1 Preparation of Graphite Oxide Graphite oxide will be synthesized from graphite powder through a pre-oxidation and oxidation process based on Hummers and Hummers Improved method (Marcano et al., 2010). 20 g of graphite powder will be stirred in a heated solution of 30 ml H2SO4, 10 g K2S2O8 and 10 g P2O5 at 80°C for 30 minutes until a dark blue mixture is formed. The mixture will be cooled to 25°C for 6 hours. Deionized water will then be added and the ingredient will be filtered and washed until the filtrate becomes pH neutral. Subsequently, the filtrate will be dried overnight in a vacuum desiccator at 25°C. 460 ml of concentrated H2SO4 will be used to oxidize the graphite in the ice bath after the drying process. KMnO4 will be added slowly under stirring and the temperature of the suspension will be maintained at 20°C. Then, the ice bath will be removed and the suspension will be heated in an oil bath at 35°C for 2 hours until the suspension has thickened and the brownish gray effervescent paste will be...... in the center of the paper ......at 3400 cm-1 by FTIR spectrum.3.4.3 Cyclic Voltammetry (CV)Cyclic voltammetric and amperometic measurements will be performed to measure and detect the current at the working electrode and plot it against the applied voltage . The electrochemical window of the working electrode and electrolyte solution can examine the oxidation/reduction peak of redox species. In the absence of the redox analyte, the cyclic voltammogram will form a rectangular shape as the voltage varies constantly, the current will reach steady state. GO (0.5 g/ml) will be added to the 0.05 M sodium perborate (PBS) solution. 30 continuous cyclic voltammograms will be performed in the potential range from 0 to -1.5 V with a scan rate at 30 mV/s. During the first cathode potential scan a cathode peak will emerge at -1.0 V with an onset potential of -0.75 V. The cathode peak will disappear completely after several cycles.