High Internal Phase Emulsion As A Reaction Medium For Fabrication Of Brushite Crystal

This present work was aimed at fabrication of porous brushite crystals using oil-in-water high internal phase emulsion stabilized by synthesized palm-based nonionic surfactant as a reaction medium. This research work was divided into four categories. The first part of the work involved synthesizing palm-based nonionic surfactants. Palm oil derivatives, lauryl, palmityl and stearyl alcohols as renewable resources, were ethoxylated with an average of three, six (or eight or nine) and 100 moles of ethylene oxide. The critical micelle concentration of the synthesized surfactants was found to decrease with increasing ethylene oxide head groups due to intertwist amongst the head groups. This phenomenon enhances surfactant-surfactant interaction rather than surfactant-solvent interaction which increases the rate of micellization as proven by the Gibbs energy. The increase in the surfactant tail length had minimal effect on micellization. The second part of the work was to stabilize the high internal phase emulsion using the synthesized surfactants. The oil phase was vegetable oil, namely olive and olein oils. These UPLOAD emulsions, with dispersed phase of more than 75 wt%, were easily prepared by one-pot homogenization. Due to the high oil volume fraction, the oil droplets were no longer spherical but were squeezed to take the shape of polyhedral. Light scattering results showed that the droplet size increased with increasing ethylene oxide chain length. The rheology of the emulsions was governed by droplet size and oil volume fraction. The emulsions exhibited high stability as indicated by the rheological measurements even after storage at 40oC for three months. The third part of the work was on the fabrication of brushite crystals with high degree of porosity using the high internal phase emulsion as a reaction medium. The porosity of the crystals was manifested by precursor concentration, surfactant concentration, oil volume fraction, mixing method, mixing time, aging temperature, precursor type, mode of recovery and surfactant head group. Pore size of the brushite crystals was less than 5 μm. The mechanism for the formation of porous brushite crystals was postulated schematically based on the small angle x-ray scattering analysis. The fourth and final part of this work was related to the application of the porous brushite crystals as drug delivery devices. Prior to the controlled release study, the crystals were subjected to cytotoxicity test to ensure their compatibility with synoviocytes, which are cells that line the knee joints of rabbits. The crystals were found to enable cell growth for up to five days. Sodium ampicillin, a wide spectrum antibiotic, was successfully loaded into the pores of the crystals and subsequently released in vitro for 14 days. This work underlines the simplicity of using highly stable high internal phase emulsion as a reaction medium for the fabrication of porous brushite crystals, in which when loaded with drug, exhibited potential as localized bone treatment demonstrated by the promising controlled release rate

Enhanced photovoltaic performance of silver@titania plasmonic photoanode in dye-sensitized solar cells

In the present investigation, silver@titania (Ag@TiO2) plasmonic nanocomposite materials with different Ag content were prepared using a simple one-step chemical reduction method and used as a photoanode in high-performance dye-sensitized solar cells. Transmission electron microscopic images revealed the uniform distribution of ultra-small Ag nanoparticles with a particle size range of 2–4 nm on the TiO2 surface. The incorporation of Ag on the TiO2 surface significantly influenced the optical properties in the region of 400–500 nm because of the surface plasmon resonance effect. The dye-sensitized solar cells (DSSCs) assembled with the Ag@TiO2-modified photoanode demonstrated an enhanced solar-to-electrical energy conversion efficiency (4.86%) compared to that of bare TiO2 (2.57%), due to the plasmonic effect of Ag. In addition, the Ag nanoparticles acted as an electron sink, which retarded the charge recombination. The influence of the Ag content on the overall efficiency was also investigated, and the optimum Ag content with TiO2 was found to be 2.5 wt%. The enhanced solar energy conversion efficiency of the Ag@TiO2 nanocomposite makes it a promising alternative to conventional photoanode-based DSSCs

Aerosol assisted chemical vapour deposited (AACVD) of TiO2 thin film as compact layer for dye-sensitised solar cell

Compact TiO2 has been introduced onto the surface of an indium tin oxide glass slide (ITO), using an aerosol-assisted chemical vapour deposition method. This serves as a blocking layer for a dye-sensitised solar cell (DSSC). The thickness of the compact TiO2 could be controlled by deposition time. X-ray diffraction and Raman spectroscopy analyses reveal that the compact TiO2 is made up of mixed anatase and rutile phases. The field emission scanning electron microscopy image displays a pyramidal morphology of the compact TiO2. A layer of P25 paste was then smeared onto the compact TiO2-modified ITO, using the doctor's blade method. A post-treatment procedure was applied to remove the contaminants from the prepared hybrid film, by immersing in a hydrochloric acid solution. The photoelectrochemical measurements and J–V characterisation of the hybrid film show an approximately fourfold increase in photocurrent density generation (114.22 µA/cm2), and approximately 25% enhancement of DSSC conversion efficiency (4.63%), compared to the acid-treated P25 paste alone (3.68%)

Silver/titania nanocomposite-modified photoelectrodes for photoelectrocatalytic methanol oxidation

Silver deposited titania (Ag/TiO2) nanocomposite thin films were fabricated by the simple sonochemical deposition of Ag on preformed aerosol-assisted chemical vapor deposited TiO2 thin films. The photelectrocatalytic performance of a newly fabricated Ag/TiO2-modified photoelectrode was studied for methanol oxidation under simulated solar AM 1.5G irradiation (100 mW/cm2). The Ag/TiO2-modified photoelectrode showed a photocurrent density of 1 mA/cm2, which is four times that of an unmodified TiO2 photoelectrode. The modification of Ag on the TiO2 surface significantly enhanced the photoelectrocatalytic performance by improving the interfacial charge transfer processes, which minimized the charge recombination. Density functional theory (DFT) calculation studies revealed that methanol could be easily adsorbed onto the Ag surfaces of Ag/TiO2 via a partial electron transfer from Ag to methanol. The newly fabricated Ag/TiO2-modified photoelectrode could be a promising candidate for photoelectrochemical applications

Effect of electropolymerization potential on the preparation of PEDOT/graphene oxide hybrid material for supercapacitor application

Conducting polymer poly(3,4-ethylenedioxythipohene) (PEDOT) hybrid with carbon-based material, graphene oxide (GO), was prepared for supercapacitor application. Different applied potentials were employed in order to study the effect of electropolymerization potential on PEDOT/GO thin film. Field emission scanning electron microscopy (FESEM) images showed that PEDOT/GO possessed more pronounced wrinkle paper-like sheet surface morphology as the potential increased from 1.0 to 2.0 V. Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy revealed that GO was successfully incorporated into PEDOT during electropolymerization. The cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) measurements revealed that the PEDOT/GO composite electropolymerized at the applied potential of 1.2 V exhibited a maximum specific capacitance of 115.15 F/g with energy density and power density of 13.60 Wh/kg and 139.09 W/kg, respectively at current density 0.3 A/g. The EIS result showed that the Rct decreased as the electropolymerization potential rose from 1 V to 1.2 V and increased when the electropolymerization further increased to 2 V due to a large electron transfer resistance that makes the rate of charge transfer becomes slower

Adapting An Existing Example-Based Machine Translation (EBMT) System For New Language Pairs Based On An Optimized Bilingual Knowledge Bank (BKB).

Sourcing for large amount of text and translating them are some of the challenges in building an Example-Based Machine Translation (EBMT) system. These big amounts of translated texts are annotated into the S-SSTC format to cover an extensive vocabulary and sentence structures. However, the Bilingual Knowledge Bank (BKB), which is a collection of the S-SSTCs, will normally contain redundancy. Hence, the idea of an optimized BKB is born. An optimized BKB (redundancy reduced; is smaller in size but is as equally extensive in term of its sentence structure coverage compared to an un-optimized BKB. Therefore, an optimized BKB enhances the performance of the EBMT. In this paper, we introduce the idea of an optimized BKB and propose it to be re-used to effectively construct new BKBs in order to adapt an existing EBMT for new language pairs

Spherical Tin Oxide, SnO2 Particles Fabricated via Facile Hydrothermal Method for Detection of Mercury (II) Ions.

Smooth-surface spherical tin oxide particles were fabricated via hydrothermal processing route. X-ray diffraction (XRD) revealed that the particles consisted of the rutile phase of SnO2 with tetragonal structure. The spherical morphology was realized with the aid of ammonia. The aggregation of SnO2 particles could be avoided by adjusting the concentration of tin (II) chloride. Bare glassy carbon electrode (GCE) was modified with the hydrothermally prepared SnO2 particles to detect the presence of mercury (II) ions (Hg2+), in the presence of potassium chloride (KCl) as a supporting electrolyte. GCE modified with the spherical SnO2 particles that possessed small crystallite size and smooth surface exhibited significantly enhanced oxidative and reductive current of Hg2+ during cyclic voltammetry compared with its bare counterpart. The reductive current was observed to increase by two fold and the detection limit of 75 nM for Hg 2+ was achieved. This suggests that SnO2 particles are a promising chemical sensor for the detection of Hg2+ in natural waters

Palm-based nonionic surfactants as emulsifiers for high internal phase emulsions

In the present study, a series of as-synthesized palm-based nonionic surfactants with various hydrophile–lipophile balance values were successfully synthesized. The critical micelle concentration and the Gibbs energy of the surfactants were determined and discussed. For the first time, the surfactants were used to stabilize three-component olein oil-in-water high internal phase emulsions, with an oil volume fraction of 0.85, and which were easily prepared by one-pot homogenization. Proof of high stability was confirmed by the satisfactory rheological profiles and further enhanced by a three-month storage exercise at an elevated temperature which showed no significant physical and rheological changes. These results suggest that low concentration of the surfactants efficiently stabilized the emulsions with high content of oil. Based on the optical micrograph observation, an average droplet size of less than 10 μm increased with increasing ethylene oxide chain length and temperature. The varying degree of viscosity resulted from the various ethylene oxide chain lengths of the surfactants. The hydration efficacy of the emulsions was examined in vivo using a corneometer. The impressive hydration efficacy of olein oil suggests that it could well be a potential moisturizing lipid which might interest dermatologists

Microstructure of brushite crystals prepared via high internal phase emulsion

For the first time, various microstructures of calcium phosphates were successfully synthesized using a high internal phase emulsion process. The crystals were possessed in the brushite crystalline phase. The morphology of the crystals was influenced by the variables related to the emulsion process route, which consisted of flakes, dendrites and particulates structures

Effect of electrolytes on the electrochemical performance of nickel cobaltite–titania nanotubes composites as supercapacitive materials

The effects of electrolytes on the electrochemical performance of nickel cobaltite–titania nanotubes composites as electrochemical capacitors were evaluated. Four types of electrolytes were selected to assess their effects on the prepared composites, namely aqueous electrolytes of 1.0 M KCl, 1.0 M HCl, 1.0 M KOH; and an organic electrolyte, 0.27 M tetra-n-butylammonium tetrafluoroborate (TBATFB) ionic liquid salt in acetonitrile. The composites performed better in 1.0 M HCl and 1.0 M KOH, than in 1.0 M KCl and 0.27 M TBATFB, which suggested that aqueous electrolytes with non-neutral pH would improve the specific areal capacitance values of the composites. Results have shown optimal performance in 1.0 KOH, which endowed the composite with excellent rate capability up to 200 mV s−1. Cyclic voltammogram of the composite analysed in 1.0 M KOH produced a leaf-shaped like profile, with higher current densities towards more positive potentials. Charge–discharge analyses in 1.0 M KOH has shown that the composite possessed specific areal capacitance of up to 214.76 µF cm−2 when it was evaluated at the current density of 350 µA cm−2. The composite also retained up to 97.79% of its specific areal capacitance when current density was increased to 400 µA cm−2. This material has demonstrated potential application for electrochemical capacitors through its facile fabrication technique