Porous hydroxyapatite (HAp) as a bone graft substitute was produced via gas technique with three different concentrations of hydrogen peroxide (H2O2) namely 20, 30 and 50%. Hydroxyapatite(HA) slurries with different concentration were produced by mixing between H2O2 solutions and HA powder (L/P) with different ratio i.e. 0.9 to 2.20 ml.g-1. Different L/P ratio and H2O2 concentration affected the porosity, interconnectivity and compressive strength of HAp sample. Changes in L/P ratio between 0.9 to 2.20 ml.g-1, increases the porosity around 50 - 65% at 20% H2O2 concentration. Porosity increases with the L/P values and H2O2 concentration which 76% of porosity was obtained at 50% H2O2 and 2.20 mlg-1 of L/P. The compressive strength of HAp is in the range of 0.5 to 2.15 MPa and is found decreasing with the increasing of L/P values.
Magnetite (Fe3O4) nanoparticles have been synthesized using the chemical coprecipitation method. The Fe3O4 nanoparticles were likely formed via dissolution-recrystallization process. During the precipitation process, ferrihydrite and Fe(OH)2 particles formed aggregates and followed by the formation of spherical Fe3O4 particles. The synthesized Fe3O4 nanoparticles exhibited superparamagnetic behavior and in single crystal form. The synthesis temperature and the degree of agitation during the precipitation were found to be decisive in controlling the crystallite and particle size of the produced Fe3O4 nanoparticles. Lower temperature and higher degree of agitation were the favorable conditions for producing smaller particle. The magnetic properties (saturation magnetization and coercivity) of the Fe3O4 nanoparticles increased with the particle size.
Biofiber is used in the polymer based composite as a renewable resource due to its positive environmental benefits, biodegradable properties, low cost and high toughness. Biocomposite was fabricated using oil palm empty fruit bunch (EFB) as filler in phenolated EFB (PEFB) matrix. Phenolated EFB (PEFB) obtained from liquefaction of EFB in phenol was used as a biopolymer to replace novolak phenolic resin which is commonly used in composite materials. Sulfuric acid was used as a catalyst in the liquefaction reaction. The effect of thermal aging and blending ratio of PEFB matrix and EFB fibers on the mechanical properties of composites has been studied. The flexural data before and after thermal aging revealed the optimum amount of EFB filler is 50% . The result showed better compatibility between EFB and PEFB when compared with EFB and commercial novolak resin.
Jatropha curcas oil was extracted using n-hexane as solvent in the Soxhlet extraction method. The physicochemical properties of Malaysian Jatropha curcas oil were evaluated. The result showed that the Jatropha seeds consist of 60% (dry w/w) crude oil. The physicochemical properties showed that the seed oil contained low moisture level of 0.02±0.01%, acid value (1.50±0.07%), iodine value (91.70 ± 1.44 mg/g), peroxide value (0.66±0.04 miliequivalence/kg) and saponification value of 208.5±0.47 mg/g respectively. Gas chromatography analysis showed that oleic acid (46.00±0.19%) appears as dominant fatty acid in seed oil followed by linoleic acid (31.96±0.19%) and palmitic acid (13.89±0.06%). High performance liquid chromatography (HPLC) results showed that the dominant triacylglycerols present were PLL (22.00%), POP(16.48%), 000(16.48%), 00L(16.23%) and OLL(13.00%).
Molecularly imprinted polymer (MIP) based on acrylate monomer was prepared at 80°C for 5 hours using p-xylene and ethylene glycol dimethacrylate (EGDMA) as a template and crosslinking agent respectively. The polymer obtained was washed with a mixture of acetic acid and methanol (1:4) and dried in the vacuum oven at 80°C. FTIR spectrum showed that all the templates were leached out from polymer during excessive washing and drying stage. The rebinding test result showed that the MIP was bonded with the analyte in the presence of organic solvents as shown by FTIR spectroscopy. The SEM micrograph showed that non-imprinted polymer (NIP) had no cavity as compared to MIP.
In the attempt to isolate indigenous marine sulphate-reducing bacteria (SRB) from coastal samples, we obtained some swarm forming bacteria. The isolates were screening using Starkey’s medium and detection of main groups of SRB were carried out using commercially kits (SRB BART kits, Droycon Bioconcepts Inc., Canada). From the growth characteristic, only two isolates were strongly suggested as marine SRB. Based on the 16S rRNA gene sequence analysis these SRB were closely related and could be designated as Desulfovibrio sp. and Citrobacter freundii, with the highest sequence similarity of 98% and 93%, respectively.
Surface sediments collected from two transects (30 sampling points) in the Kerteh mangrove forest had been analyzed for Co, Cu, Pb, Zn and Cr concentrations with the Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). The average concentration of Co was 8.91±1.89 µg/g dry weight, Cu was 29.0±12.8 µg/g dry weight, Pb was 11.7±6.85 µg/g dry weight, Zn was 22.3±13.7 µg/g dry weight and Cr was 13.2±9.07 µg/g dry weight. Their concentrations are significantly higher near the front mangrove and decline as the sampling points of each transect near the back mangrove area. The calculated enrichment factors (EF) obtained for Zn and Cr can be considered to have the terigeneous in sources while Co, Cu and Pb, which had slightly higher value, were probably influenced by anthropogenic input.
Thirty two compounds of fatty acids were found in a 50 cm sediment core taken from Conwy Estuary, United Kingdom. Their distribution pattern changed with depth from short chain fatty acids (C12 - C20) predominance to long chain compounds (C21 – C25). The decrease of short chain fatty acids along the core suggested that early diagenesis occurred due to microbial and chemical degradation. The increase of longer chain compounds was probably caused by greater preservation or greater contribution from terrestrial organic matter. The percentage of branched fatty acids, odd/even and 18:1ω7/18:0 ratios showed similar distribution, linking them with bacterial activity in the sediment. Principal Component Analysis (PCA) separated the terrestrial derived fatty acids (long chain compounds) from the marine (short chain saturated compounds, mono and polyunsaturated fatty acids) and bacterial (odd chain length with their branched derivatives and 18:1ω7 acid) derived compounds.
Bottom-contact pentacene OTFTs are fabricated using cross-linked poly(vinyl alcohol) (PVA) insulator and its reliability characteristics are analyzed. The hysteresis of the OTFTs is mainly caused by the electrons that are injected from the gate electrode to the cross-linked PVA insulator. To block the injection of electrons, plasma-enhanced chemical vapor deposition (PECVD) SiO2 layer is inserted between the gate electrode and the cross-linked PVA layer, so that the minimum hysteresis can be obtained. In addition, the effects of the gate bias stress as a function of time is investigated to examine the long-term reliability of the device during the operation.
Carbon nanopipes catalyzed by high purity nickel oxide (NiO) nanoparticles were reported. The nanocrystals catalysts were first prepared using precipitation technique and characterized using x-ray diffraction (XRD), energy dispersive x-ray (EDX) and scanning electron microscopy (SEM) and subsequently used as catalyst for the formation of nanotubes. Pure phase, rhombohedral nickel oxide formation was identified from the XRD data, with the major peak located at 43.29o of the 2θ degree corresponding to a (202) plane. A pulsed laser ablation deposition technique (PLAD) was used to produce the CNTs. From the SEM micrograph, deposited CNTs shows a web-like structure, while the HR-TEM reveals carbon nanopipes with a length of 10 micron and diameter of 430 nm, suggesting that the nanocrystals aggregate and forms bigger cluster consequence of the ablation process.
ZnO nanostructures were synthesized on Si and Si/SiO2 substrate by well established thermal-evaporation-deposition method which involves vapor-solid growth process for non–catalysts activated growth. Scanning electron micrograph shows difference type of ZnO nanostructures have been synthesized. Electrical I-V characterization was measured by using Al as electrode at room temperature. Schottky contacts were obtained for both contact of ZnO nanowires and Al. A symmetric metal-semiconductor-metal junction was obtained. A two-opposit-diode equivalent circuit was applied to explain this I-V characteristic.
ZnO nanowires have been synthesized using a catalyst-free carbothermal reduction approach on SiO2-coated Si substrates in a flowing nitrogen atmosphere with a mixture of ZnO and graphite as reactants. The collected ZnO nanowires have been characterized by X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy and photoluminescence spectroscopy. Controlled growth of the ZnO nanowires was achieved by manipulating the reactants heating temperature from 700 to 1000 oC. It was found that the optimum temperature to synthesize high density and long ZnO nanowires was about 800 0C. The possible growth mechanism of ZnO nanowires is also proposed.
Titanium dioxide (TiO2), porphyrin and TiO2 coated with dye porphyrin thin films were prepared on Quartz Crystal Microbalance (QCM) using sol-gel dip coating method and were tested for sensing of volatile organic compounds (VOCs). The porphyrin used was 5,10,15,20-tetraphenyl-21H,23H-porphine manganese (III) chloride (MnTPPCl). The sensing sensitivity was based on the change in the fundamental frequency of the QCM upon exposure towards six vapor samples, namely ethanol, acetone, cyclohexane, toluene, o-xylene and 2-propanol. It was found that all the thin films were sensitive towards all the vapors. However, the TiO2 coated MnTPPCl thin film exhibit the most sensitive and has good selectivity property.
A series of hydrogenated amorphous carbon (a-C:H) thin films were deposited using home-built direct-current (DC) plasma enhanced chemical vapour deposition (PECVD) system. In this present study, the a-C:H thin films were deposited using pure methane (CH4) gas diluted either with hydrogen (H) or helium (He). The effects of hydrogen and helium dilution on the photoluminescence (PL) properties and optical band gap (E04) were studied. The dependence of PL properties and optical energy gap on the film thickness has also been investigated. The characterization techniques used were optical transmission and photoluminescence spectroscopies. The sp2 cluster sizes were determined from Raman spectra are in the range of 5 to 7 nm. Hydrogen and helium dilution of methane strongly influences the PL efficiency of the a-C:H films. The PL efficiency are enhanced with increase in film thickness for a-C:H films prepared both from H and He diluted CH4. The optical energy gap of these films decreases with increase in H or He dilution and film thickness.
Thin films of barium strontium titanate (Ba0.6Sr0.4TiO3) perovskite system are promising candidates for microelectronic devices that can be integrated with semiconductor technology. Ba0.6Sr0.4TiO3 thin films have been prepared onto BST/TiO2/RuO2/SiO2/Si substrate using the spin coating and sol-gel process. Then the samples were subsequently annealed at 600oC, 650oC and 700oC for 60 minutes in air. The microstructure and dielectric properties show that the crystallization improved as the annealing temperature was increased. All of the films have nanometer grain size. The average grain size of the films increased as the temperature was increased. The dielectric constant and ac conductivity of the films also increased as the average grain size increased. These results showed that the microstructure and dielectric properties depend on the annealing temperature.
A complete nanoscale study on GaN thin films doped with Mg. This study was carried out using TEM and associated techniques such as HREM, CBED, EDX and EELS. It was found that the presence of triangular defects (of few nanometers in size) within GaN:Mg films were at the origin of unexpected electrical and optical behaviors, such as a decrease in the free hole density at high Mg doping. It is shown that these defects are inversion domains limited with inversion-domains boundaries.
MeSH terms: Animals; Eels; Electricity; Mass Media
This research explores the possibility of using fluorescence technique to detect the presence of volatile organic compounds based on a single sensing material. The material used was TiO2 nanoparticles coated with porphyrin dye. The TiO2 nanoparticles colloid is in a sol-gel form synthesized from titanium (IV) ethoxide in ethanol with addition of kalium chloride (KCl) as stabilizer. TiO2 nanoparticles were then coated with porphyrin dye, Manganase (III) 5,10,15,20 tetra (4-pyridyl)-21H, 23H porphine chloride tetrakis (metachloride). The coated nanoparticles were deposited on quartz substrate using self-assembly through dip coating technique. The sensing properties of the thin film toward volatile organic compounds; ethanol, acetone, cyclohexane and 2-propanol were studied using luminescence spectrometer. It was found that the thin film produced different emission spectra peaks for different volatile organic compounds (VOCs). Hence, it eases chemical identification process and potentially be use as fluorescence gas sensor.
Inclusive analysis on the optical characteristics of InGaAs/GaAs QW structure for 980 nm semiconductor laser operation is presented from experimental and theoretical point of view. The InGaAs/GaAs quantum well structure is grown by molecular beam epitaxy at different indium composition and quantum well thickness for optical characteristic comparison. Photoluminescence spectra from the measurement show that the spectrum is in good agreement with the simulation results. Detail simulation on the material gain for the InGaAs/GaAs quantum well as a function of carrier densities and operating temperature is also performed in order to optimize the semiconductor laser design for device fabrication.
Conventional lateral and vertical n-channel MOS transistors with channel length in the range of 100nm to 50nm have been systematically investigated by means of device simulation. The comparison analysis includes critical parameters that govern device performance. Threshold voltage VT roll-off, leakage current Ioff, drain saturation current IDsat and sub-threshold swing S were analyze and compared between the device. Due to double gate (DG) structure over the side of silicon pillar a better electrostatics potential control of channel is obtained in vertical device shown by an analysis on VT roll-off. A two decade higher of Ioff in planar device is observed with Lg=50nm. A factor of three times larger IDsat is observed for vertical MOSFETs compared to planar device. The sub-threshold swing S remains almost the same when the Lg larger than 80 nm. It increased rapidly when the Lg is scaled down to 50 nm due to the short channel effect SCE. However, the vertical device has a steady increase whereas the planar device has suffered immediate enhance of SCE. The analysis results confirmed that vertical MOSFET with double-gate structure is a potential solution to overcome SCE when scaled the channel length to 50nm and beyond.
A set of hydrogenated nanocrystalline silicon (nc-Si:H) films prepared in a home-built plasma enhanced chemical vapour deposition (PECVD) system using the layer-by-layer (LBL) deposition technique have been studied. The 13.56 MHz rf power was varied from 20 W to 100 W to study the influence of rf power on the structural properties of the nc-Si:H films. The structure of the films was studied by X-ray diffraction (XRD) and Fourier Transform Infrared (FTIR) spectroscopy. Appearance of XRD peaks at 2q angles of 28o and 56o which correspond to silicon orientation of (111) and (311) respectively were observed in all films deposited on c-Si substrate indicating evidence of crystallinity in the films. The crystallite sizes were in the range of 8 to 100 nm as determined using the Scherrer technique. The integrated intensities of absorption bands at 630 cm-1, 780 - 880 cm-1 and 2000 – 2090 cm-1 from FTIR spectrum which corresponds to various Si-H bonding configurations in the films were studied and were related to the presence of small clusters of nanocrystallites embedded in an amorphous matrix. Based on the dependence of amplitudes of Si-H vibrational modes on crystallite size and rf power, the properties and the role of hydrogen in nc-Si:H films prepared using the LBL technique were discussed.