Papers by Author: Tengku Ishak Tengku Kudin

Abstract: Graphene is a material that has been heavily investigated in many researches due to its beneficial characteristics such as large surface area, low manufacturing cost, high electro conductivity and incredible mechanical strength. Applying the graphene in water-based solvents however can cause agglomeration due to its hydrophobic properties. Researchers have composited the graphene with other materials in overcoming its hydrophobicity. In this research, graphene was nanocomposited with thionine to make it disperse well in water-based solvents while preserving its intrinsic properties. The nanocomposition process involves mixing of both graphene oxide with thionine and were reduced by hydrazine hydrate while reflux heating. The produced mixture was then filtered to obtain the Thionine-Graphene nanocomposite. The obtained sample was then characterized to confirm the composition of both graphene and thionine. Fourier transfer infrared spectroscopy was operated to investigate the chemical bonds and hence concluding the presence of both graphene and thionine in the sample. The preservation of the intrinsic properties of graphene was also investigated through observing the absence of functionalized graphene bonds. Post-investigation reports that the chemical bonds from both of the materials, graphene and thionine were detected confirming the successfulness of the nanocomposition.

Abstract: A new carbon material viz. graphene has been attracted an increasing research interest owing to its unique electrical and mechanical properties that is useful for the various device applications. The synthesis of graphene from graphene oxide usually involves harmful chemical reducing agents that are toxic and undesirable to human and the environment. By avoiding the use of toxic and environmentally harmful reductants, we report a green approach to effectively reduce graphene oxide to graphene in glucose solution at room temperature. Graphite oxide was synthesized from graphite powder using modified Hummers’ method. Graphite oxide then further exfoliated to graphene oxide by using ultrasonic irradiation. The mild reduction of graphene oxide is carried out by mixing graphene oxide solution with glucose. The reduction time is varied with 15, 30, 45 and 60 minutes. TEM images provide clear evidence for the formation of few layer graphene. Characterization of theresulting glucose reduced graphene oxide by FTIR indicates the partial removal of oxygen-containing functional groups from the surface of graphene oxide and formation of graphene with defects.

Abstract: In this study, gel polymer electrolytes (GPEs) system is prepared by the solution cast technique. The system consists of cellulose acetate (CA) as a host polymer, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) as a dopant salt and diethylene glycol dibutylether (BDG) from glyme based family as a plasticizer. GPEs (65 wt. % CA–25 wt. % LiTFSI–10 wt. % BDG) sample is the highest conductivity of 2.88×10^-3 S.cm⁻¹ at room temperature. The lithium-electrolyte interfaced stability is established and the highest ionic conducting electrolyte is able to withstand up to 3.8V vs Li/Li⁺.

Abstract: Polymer electrolytes consist of poly(vinylidene fluoride –hexafluoropropylene) (PVDF-HFP) and lithium trifluoromethanesulfonate, LiTf (LiCF3SO3) were prepared by dissolving in dimethylformamide (DMF) using solution casting method and further dried in vacuum oven. The conductivity of each sample was investigated using electrochemical impedance spectroscopy (EIS) method. The samples were measured in two different environments viz. in humidity chamber (40% RH; 27°C) and at ambient condition (~60% RH; 27°C). The maximum conductivity obtained for the samples in humidity chamber was 8.05 × 10-5 S/cm with addition of 35 wt% of LiTf. Meanwhile, the highest conducting samples (with addition of 45 wt% of LiTf) exhibited the ambient condition temperature of 1.11 ×10-4 S/cm. Further increased salt concentration from the optimize concentration values has reduced the conductivity of the polymer electrolyte. Dielectric permittivity studies revealed that samples showed the non-Debye behaviors