Structural and optical properties of nc-Si:H thin films deposited by layer-by-layer technique

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 spectroscopy. 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.     

Homology modeling of rho-crystallin from bullfrog (Rana catesbeiana) lens

rho-Crystallins are major protein component found in the eye lenses of frogs of the genus Rana. Structural analysis has indicated that frog rho-crystallins belong to aldo-keto reductase superfamily (AKRs) which include aldehyde and aldose reductases, prostaglandin F synthase and several detoxification enzymes. Members of AKRs catalyze the oxidation-reduction reaction over a range of substrates using NAD(P)(H) as a cofactor. In spite of higher structural similarity with AKRs and cofactor binding affinity, the rho-crystallins were found to be catalytically inactive. This study presents comparative or homology modeling of rho-crystallin from bullfrog (Rana catesbeiana) in presence and absence of cofactor NADP and a competitive inhibitor, testosterone. The predicted models are explored to examine the catalytic cleft, cofactor binding affinity characteristics and substrate binding pocket.     

Sustainable multi-period electricity planning for Iskandar Malaysia

This paper presents the current situation and projected planning of the electricity generation sector for Iskandar Malaysia by implementing a model to optimise the cost, utilise the usage of available renewable energy sources, and achieve carbon dioxide reduction targets. This Mixed Integer Linear Programming model was developed with the main objective of minimising the total cost of electricity generation, taking into consideration energy demand, reserve margin, electricity generation, peak and base generation, resource availability, and CO₂ emission. Data for the year 2013 were forecasted until 2025 to illustrate the analysis for this study, and are represented via four scenarios. This optimal model is capable of balancing types of fuel and switching coal plants to natural gas power plants. It also enhances the use of renewable energy (RE) to meet CO₂ emission targets. The model is further integrated with several other considerations related to energy systems, such as suitability of power plants as peak or base plants, RE resource availability, intermittency of solar power, losses during transmission, fuel selection for biomass, decision to retrofit existing coal power plant to NG power plant, and construction lead time of power plants. The results for this study determined that the optimal scenario is Scenario 3 (CS3). This research proves that Iskandar Malaysia can reduce CO₂ emission by 2025 via utilisation of RE. This model is generic and can be applied to any case study, which would be useful for assisting government policy-making.     

Xylitol: A Review on Bioproduction,Application, Health Benefits,and Related Safety Issues

Xylitol is a pentahydroxy sugar-alcohol which exists in a very low quantity in fruits and vegetables (plums, strawberries, cauliflower, and pumpkin). On commercial scale, xylitol can be produced by chemical and biotechnological processes. Chemical production is costly and extensive in purification steps. However, biotechnological method utilizes agricultural and forestry wastes which offer the possibilities of economic production of xylitol by reducing required energy. The precursor xylose is produced from agricultural biomass by chemical and enzymatic hydrolysis and can be converted to xylitol primarily by yeast strain. Hydrolysis under acidic condition is the more commonly used practice influenced by various process parameters. Various fermentation process inhibitors are produced during chemical hydrolysis that reduce xylitol production, a detoxification step is, therefore, necessary. Biotechnological xylitol production is an integral process of microbial species belonging to Candida genus which is influenced by various process parameters such as pH, temperature, time, nitrogen source, and yeast extract level. Xylitol has application and potential for food and pharmaceutical industries. It is a functional sweetener as it has prebiotic effects which can reduce blood glucose, triglyceride, and cholesterol level. This review describes recent research developments related to bioproduction of xylitol from agricultural wastes, application, health, and safety issues.     

Formation of gold nanoparticles in silicon suboxide films prepared by plasma enhanced chemical vapour deposition

Nanostructured materials fabricated by dispersing metal particles on the dielectric surface have potential application in the field of nanotechnology. Interfacial metal particles/dielectric matrix interaction is important in manipulating the structural and optical properties of metal/dielectric films. In this work, a thin layer of gold (Au) was sputtered onto the surface of silicon oxide, SiO_x (0.38 < x < 0.68) films which was deposited at different N₂O/SiH₄ flow rate ratios of 5 to 40 using plasma enhanced chemical vapor deposition (PECVD) technique prior to the annealing process at 800 °C. FTIR spectra demonstrate the intensity and full-width at half-maximum (FWHM) of Si-O-Si stretching peaks are significantly dependent on the N₂O/SiH₄ flow-rate ratio, η. The films deposited at low and high N₂O/SiH₄ flow rate ratios are dominated by the oxygen and silicon contents respectively. The size and concentration of Au particles distributed on the surface of SiO_x films are dependent on the N₂O/SiH₄ flow-rate ratio. High concentrations of Au nanoparticles are distributed evenly on the surface of the film deposited at N₂O/SiH₄ flow-rate ratio of 30. Crystallinity and crystallite sizes of Au are enhanced after the thermal annealing process. Appearance of surface plasma resonance (SPR) absorption peaks at 524 nm for all samples are observed as a result of the formation of Au particles. The annealing process has improved SPR peaks for all the as-deposited films. The energy gap of the as-deposited Au/SiO_x films are in the range of 3.58 to 4.38 eV. This energy gap increases after the thermal annealing process except for the film deposited at η = 5.     

Improvements and limitation of soy protein-based adhesive: A review

Soy protein is known for its eco-friendly, sustainable, and biodegradable qualities that are likely used as raw material in producing bioadhesive. However, soy protein-based adhesive are lacking in terms of adhesive strength and water-resistance compared to commercial formaldehyde-based adhesives such as phenol and urea-formaldehyde resin. Therefore, continuous research has been done to improve adhesive performance. This can be done via physical or modification methods, including the usage of cross-linking agents, structural modification, enzymatic modification, and the addition of additives. This review will cover these modification methods that give significant enhancement to the water-resistance and adhesive strength of soy protein-based adhesives.