Advanced Materials Research Vols. 93-94

Abstract: The layer formation of bovine serum albumin (BSA) on a poly(styrene-co-maleic acid) (PSMA) surface was investigated by using quartz crystal microbalance (QCM) technique at various pH values. The formation of a BSA surface was examined by atomic force microscopy (AFM). To study the effect on the layer formation, the pH of solution was varied from 2 to 7.4 while the concentration of BSA was in the range of 0.01 to 5 mg/ml during the layer absorption. It was found that the BSA adsorption strongly depends on the pH of solution, and the concentration of BSA. The absorption layer occurred maximum at the pH value of 3.5 which resulted from the charge of PSMA and BSA molecules. The layer formation reached the saturate value at the concentration higher than 3 mg/ml. The molecular packing of the BSA layer at different pH values was determined by AFM and total mass change of QCM.

Abstract: In dye sensitized solar cell structure, the transparent electrodes of tin oxide doped fluorine (SnO2:F) was coated by titanium dioxide (TiO2) and platinum (Pt) for cathode and anode electrodes, respectively. In order to achieve high efficiency solar cell, both electrodes are required to have proper crystal structure size and morphology. These can be modified during the annealing process therefore the effects of electrode annealing on their crystal structure and surface modification were investigated in this study. Thick films of TiO2 and Pt were deposited by screen printing method on 3mm thick glass substrate (Nippon Sheet Glass) coated with 500nm thick SnO2:F. The glass substrate has sheet resistance of 20 ohm/square with the optical transmission of about 70%. The mixed TiO2 powder has the diameter of about 20 nm. The screen print structure was heated for drying in the oven at 150oC for 1 hour. Then the TiO2 thick films were annealed at various temperatures from 400 to 550oC for 2 hours, while the Pt films were annealed at lower temperature from 300 to 500oC. The obtained thickness of TiO2 and Pt film after annealing become about 10 and 3 µm, respectively. The crystallinity of the films was examined by x-ray diffraction while the surface morphology of both films was determined by atom force microscopy. To investigate the relation between material structure and the performance of the solar cell, the annealed electrodes at different temperature were used to fabricate the dye sensitized solar cell structure with standard rutherium(II) (N719) dye and then the current voltage characteristic was measured under light with air mass of 1.5. It found that the structure with higher anneal temperature electrode exhibited higher power conversion efficiency originating from the higher short circuit current density of better crystallinity and higher surface area.

Abstract: A solid-state (free of internal electrolyte solution) reference electrode based on metallic silver is simply fabricated via a simple electrodeposition from AgNO3. Potentiometry is carried out to study the performance of the solid-state reference electrode in comparison with the commercial Ag/AgCl reference electrode. In addition, the proposed solid-state reference electrode has been integrated with the PPy-modified pH electrode to form an all-solid-state pH sensor, showing the capability of pH measurement. Absence of the internal solution leads to the pH sensor that is convenient to use and maintenance. In addition, the proposed pH sensor is possibly applied to biochemical and medical processes as well as flow infection analysis.

Abstract: Gelatin, a hydrophilic protein derived from collagen, has been widely used in drug delivery system because of its biocompatibility and biodegradability. However, its high water solubility limited its interaction with hydrophilic drugs. The current works propose a method to improve surface activity of gelatin by modifying it into an amphiphilic molecule via conjugating with cholesterol. High contents of cholesterol were conjugated to amino groups (-NH2) of gelatin using N,N’-Disuccinimidyl carbonate. Cholesterol contents were varied from 100% by mole of free -NH2 group in gelatin. The reduction of free -NH2 groups on gelatin determined by 2,4,6-trinitrobenzenesulfonic acid (TNBS) decreased with the increases of cholesterol used in the conjugation. The percentage of reduction of -NH2 content was 74.63 by mole respectively. Hydrophilicity/hydrophobicity changes were evaluated from water and ethylene glycol contact angles. The conjugated-gelatin were aggregated to form micelles at a critical micelle concentration (CMC) of 8 mg/ml in DI water (pH 5), determined by surface tension testing. Average size of the micelles were in range of 459.05±54.59 nm. The micelles were tested for curcumin entrapment for a cancer research.

Abstract: In this work, we deal with galactomannan from seeds of Cassia fistula. Galactomannan widely use to improve and develop the products in various industries. It is linear polysaccharide having a backbone of -14 linked D-mannose residues. To this chain, single alfa-D-galactose residues are linked by C-1 through a glycosidic bond to C-6 of mannose. The physicochemical and viscoelastic properties of galactomannan were here investigated. The results showed that the mannose to galactose ratios were 3.35 and 3.54 for crude and purified galactomannans, respectively, while their intrinsic viscosities at 20oC were 11.55 and 12.03 dl/g for crude and purified galactomannans, respectively. Then, the rheological properties of galactomannan solutions at different concentrations from 0.6 to 3.4 %wt were analyzed using a Haake Rheometer RS75, equipped with C35Ti sensor at 20oC. The frequency sweeps for galactomannan solutions show the typical shape for macromolecular solutions. The cross-over frequency decreased as galactomannan concentration increased.

Abstract: Application of nano-structures of titanium dioxide (TiO2) films on photocatalytic activities of organic dyes was investigated. Methylene blue (MB) and cation yellow X-Gl 200% were used as organic dyes to observe decolorization. The TiO2 films were prepared on glass substrate by reactive DC magnetron sputtering. The films had thickness, grain size and root mean square surface roughness of 300 nm,  40 nm and  4 nm, respectively. Coated-TiO2 on glass and uncoated TiO2 (glass) were immerged in MB and cation yellow dyes solution. A weak ultraviolet (UV) A at peak wavelength  365 nm and intensity of 0.19 mW/cm2 was irradiated. Absorbance spectra of dyes at different UV irradiation time were observed. The efficiency of decolorization increased as UV irradiation time increased. At UV irradiation time 120 hours, coated-TiO2 showed higher percentage decolorization of MB than uncoated-TiO2 about 64%. While, at UV irradiation time 48 hours, coated-TiO2 showed higher percentage decolorization of cation yellow than uncoated-TiO2 about 84%. Under photocatalysis process of TiO2 films, at the end, MB (about 120 hours) and cation yellow dyes (about 48 hours) change to be colorless.

Abstract: Oil palm empty fruit bunch (OPEFB) cellulose fibre has been widely used as a reinforcing filler in polymer composites. Surface modification of OPEFB fibre was aimed enhancing inter-phase adhesion with a poly(lactic acid) matrix. In this study, the OPEFB fibres were pre-treated in a sodium hydroxide solution. Surface compositions and thermal stability of the fibres were studied using ATR-FTIR and TGA techniques, respectively. The pre-treatment resulted in the removal of non-cellulosic components leaving purer fibres. In addition, an acetylation of OPEFB cellulose fibres by acetic anhydride was conducted under solvent free condition at room temperature (30 °C). The acetylation reaction was catalyzed by iodine. The degree of substitution monitored by solid state 13C NMR depended upon reaction time and molar ratio of OPEFB cellulose and acetic anhydride. Crystalline structure and morphology of the partial acetylated fibres were investigated using WAXD and SEM, respectively.

Abstract: Effect of co-monomer content in Acrylonitrile-Butadiene-Styrene copolymer (ABS) on the rheological property of sawdust reinforced ABS composites was investigated using capillary die rheometer. Three grades of commercial ABS resin were used. Sawdust from Para rubber tree treated with N-2(aminoethyl) 3-aminopropyl trimethoxy silane was blended with ABS by melt blending process using twin-screw extruder. From the results, shear thinning behavior was found for all of composites in the same shear rate ranges for testing that were investigated. At the low shear rate, the composites which contain higher acrylonitrile content, showed higher viscosity. At high shear rate, the viscosity of each co-monomer dependent composites tends to come close to each other on the curves. In this study, Carreau’s model was used for curve fitting and those parameters were also determined. Die swell ratio of the composites tended to increase at the initial ranges of shear rate of 10-500 s-1, and then the swelling ratio value decreased dramatically once the shear rate were further applied. The molecular weight has more effects than comonomer content on the die swell behavior i.e., at the same molecular weight, composites with higher butadiene content show higher swelling ratio.

Abstract: Micro pumps are essential components of micro-fluidic systems and bio-sensing systems. In particular, the micro pump used for -TAS transports fluids at a micro flow rate with high precision. This micro pump is also used to transport high-viscosity fluids because there are various types of drugs to be transported. We developed a micro pump driven by a conducting polymer soft actuator that opens and closes. Although the developed micro pump contains no valve, the micro pump can transport fluids in one direction without backflow. A newly developed micro pump driven by a conducting polymer soft actuator can transport fluids in one direction without backflow by the opening and closing of two soft actuators.

Abstract: The electrospun natural rubber (NR) with two different components namely: acrylonitrile butadiene styrene (ABS) and carbon black (CB) have been extensively studied. The main objective was to investigate the mechanical properties and permeability dependency of NR/ABS and NR/CB as well as its contents. NR/CB was compounded by torque rheometer (Brabender) while ABS was dissolved with NR using tetrahydrofuran (THF) as its solvent. Sulfur was used as the vulcanizing agent in both systems. Mechanical properties were evaluated by universal testing machine and permeability was observed by water vapour permeability. The optimum conditions for electrospun NR/ABS and NR/CB non-woven mats were as follows: flow rate 30 ml/h, voltage 15 kV, collector distance 20 cm and collected on rotating circular plate at 1000 rpm. The results of mechanical properties showed that for electrospun NR/CB fiber membranes, the higher the CB loading it had, the lower its tensile strength and elongation it would be. Whilst electrospun NR/ABS fiber mats, the elongation behavior was affected by the ABS loading but not the tensile strength. For permeability, NR/CB was shown to possess relatively higher permeability than the NR/ABS non-woven mats.