Graphene is a carbon-based material that has attracted tremendous attention due to its eccentric chemical and physical properties. Additionally, graphene can be converted into graphene oxide (GO) or reduced graphene oxide (rGO), depending on its application. In this paper, a simple step-by-step synthetisation of GO using Modified Hummers' method is report. The synthetisation enables the production of large scale by increasing the KMnO4 ratio. The prepared GO was then characterised by FTIR spectra in order to confirm the functional groups of the prepared sample. UV-Vis characterisation was done and the results supported the FTIR results, confirming the existence of oxygen functional groups. In addition, the prepared GO was characterised using XRD, FESEM, and RAMAN to investigate its interlayer distance, surface morphology, and structural information respectively.

Uric acid detection based on ZnO coated polymer optical fiber (POF) by using intensity modulation technique is proposed. Zinc oxide was prepared using sol-gel method and characterized using UV-Vis spectrometer in order to determine its optical properties such as transmittance, absorbance and refractive index. The POF cladding is removed by using acetone and the unclad length of 2 cm was coated with ZnO by using dip coating method. The unclad fiber without coating is tested under uric acid solutions for comparison purpose. As the uric acid concentration increases until 500 ppm, the power output increases for ZnO coated fiber and produces a sensitivity of 4x10(-6) mW/ppm with a slope linearity of more than 88.56 %. The refractive index of ZnO is changing due to the interaction with uric acid and allows more light to propagate inside the fiber. The sensitivity for 2 cm and 4 cm of uncoated fiber is 2x10(-6) mW/ppm and 7x10(-6) mW/ppm. The longer the length of unclad fiber, the higher the evanescent wave absorbanceas well as the number of reflections inside the fiber.