Chia J.S.Y.,University of Nottingham Malaysia Campus |
Tan M.T.T.,University of Nottingham Malaysia Campus |
Khiew P.S.,University of Nottingham Malaysia Campus |
Chin J.K.,University of Nottingham Malaysia Campus |
Siong C.W.,Low Dimensional Materials Research Center
Sensors and Actuators, B: Chemical | Year: 2015
In this work, pristine graphene was produced through a novel single step exfoliation of graphite in mild sonochemical alcohol-water treatment. The developed green synthesis approach successfully eradicates issues associated with conventional methods which use organic solvents, acids and oxidizers, leaving undesirable functional groups attached to the graphene surface. Results from cyclic voltammetry and amperometric analysis showed a wide linear range up to 5 mM and sensitivity improvements of more than 22 times in comparison to the control sample. Subsequently, an electrochemical glucose biosensor was fabricated by the immobilization of glucose oxidase (GOx) via bi-functional linkers. This reliable surface modification method provides irreversible non-covalent bonding between graphene and the enzymatic amide groups, while preserving the sp2 graphene structure, whilst promoting better electron transfer kinetics between the FAD/FADH2 redox sites of GOx at the modified electrode surface. The fabricated biosensor exhibited satisfactory long-term stability, reproducibility and high selectivity for glucose detection and showed significant improvements when compared to unmodified electrodes. © 2015 Elsevier B.V. All rights reserved.
Al-Ta'Ii H.M.J.,Low Dimensional Materials Research Center |
Al-Ta'Ii H.M.J.,University of Al Muthana |
Periasamy V.,Low Dimensional Materials Research Center |
Amin Y.M.,University of Malaya
Journal of Applied Physics | Year: 2015
Deoxyribonucleic acid or DNA can be utilized in an organic-metallic rectifying structure to detect radiation, especially alpha particles. This has become much more important in recent years due to crucial environmental detection needs in both peace and war. In this work, we fabricated an aluminum (Al)/DNA/Al structure and generated current-voltage characteristics upon exposure to alpha radiation. Two models were utilized to investigate these current profiles; the standard conventional thermionic emission model and Cheung and Cheung's method. Using these models, the barrier height, Richardson constant, ideality factor and series resistance of the metal-DNA-metal structure were analyzed in real time. The barrier height, Φ value calculated using the conventional method for non-radiated structure was 0.7149 eV, increasing to 0.7367 eV after 4 min of radiation. Barrier height values were observed to increase after 20, 30 and 40 min of radiation, except for 6, 8, and 10 min, which registered a decrease of about 0.67 eV. This was in comparison using Cheung and Cheung's method, which registered 0.6983 eV and 0.7528 eV for the non-radiated and 2 min of radiation, respectively. The barrier height values, meanwhile, were observed to decrease after 4 (0.61 eV) to 40 min (0.6945 eV). The study shows that conventional thermionic emission model could be practically utilized for estimating the diode parameters including the effect of series resistance. These changes in the electronic properties of the Al/DNA/Al junctions could therefore be utilized in the manufacture of sensitive alpha particle sensors. © 2015 AIP Publishing LLC.
Ahmad Z.,Low Dimensional Materials Research Center |
Abdullah S.M.,Low Dimensional Materials Research Center |
Taguchi D.,Tokyo Institute of Technology |
Sulaiman K.,Low Dimensional Materials Research Center |
And 2 more authors.
Laser Physics | Year: 2014
We analyze the carrier transit behavior in poly[N-9′-heptadecanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)] (PCDTBT), which has been reported as a donor material for efficient bulk heterojunction photovoltaic devices. The transfer and transient carrier mobilities in the PCDTBT thin films have been measured and analyzed. The transfer mobility has been measured by the transfer curve of the OFET, whereas the transient mobility is recorded using a time-resolved electric field-induced optical second harmonic generation (TRM-SHG) technique. Using the TRM-SHG technique, the dynamic motion of the charge carriers in the PCDTBT thin films has been directly visualized. We anticipate that the analysis of the carrier motion by TRM-SHG will be effective for the understanding of carrier behavior in PCDTBT thin film and will help to make further improvements in the efficiency of the PCDTBT-based photovoltaic devices. © 2014 Astro Ltd.
Goh B.T.,Low Dimensional Materials Research Center |
Wah C.K.,Low Dimensional Materials Research Center |
Aspanut Z.,Low Dimensional Materials Research Center |
Rahman S.A.,Low Dimensional Materials Research Center
Journal of Materials Science: Materials in Electronics | Year: 2014
Hydrogenated nanocrystalline silicon (nc-Si:H) thin films deposited on c-Si and quartz substrates by layer-by-layer (LBL) technique using radio-frequency plasma enhanced chemical vapour deposition system. The effects of rf power on the interlayer elemental profiling, structural and optical properties of the films were investigated by Auger electron spectroscopy, Fourier transform infrared spectroscopy, Raman scattering spectroscopy, X-ray diffraction and optical transmission and reflection spectros-copy. The results revealed that the LBL deposition leads to a formation of different ranges of crystallite sizes of nc-Si corresponds 3-6 and 8-26 nm respectively. LBL deposition also demonstrated a capability to increase the crystalline volume fraction of nc-Si up to 65.3 % with the crystallite size in between 5 and 6 nm, at the rf power in between 80 and 100 W. However, the crystalline volume fraction decreased for the rf power above 100 W due to the growth of nc-Si was suppressed by the formation of SiO2. In addition, the onset of crystallization of the films deposited on c-Si and quartz substrates are different with increase in the rf power. The effects of rf power on the growth of nc-Si, and the hydrogen content, structural disorder, crystallite size of nc-Si and oxygen diffusion into the LBL layer with the change of optical energy gap under the variation of rf power are also discussed. © Springer Science+Business Media New York 2013.