Nor Azura Malini Ahmad Hambali

Microwave and Electrical Properties of Zr-Doped SrTiO3 for Dielectric Resonator Antenna Application

Present investigation provides experimental studies on cylindrical dielectric resonator antennas (CDRAs) fabricated from SrTi1-xZrxO3 ceramic with different substitution of Zr in place of Ti for (0 ≤ x ≤1). Ceramic powder were prepared using conventional solid state reaction method. X-ray Diffraction exposes physical properties Zr-doped SrTiO3 which exhibit phase transition from cubic, tetragonal to orthorhombic phase. The electrical properties such as dielectric constant (εr) and dielectric loss (tan δ) were studied in variation of temperatures and frequencies. At room temperature the dielectric constant decreased from 240 to 21 with increase of Zr content however the amazing result was obtained for multiband antenna by Zr content. The dielectric loss obtain shows very low loss value roughly below 0.07 for all samples. The variations of return loss, resonance frequency and bandwidth of CDRAs at their respective resonant frequencies are studied experimentally.

Comparison of Structural and Electrical Behaviour of Phospho-Olivine LiNiPO4 and LiNi0.8Mn0.1Co0.1PO4 for High Voltage Rechargeable Li-Ion Batteries

Phase pure olivine LiNiPO4 and doped LiNi0.8Mn0.1Co0.1PO4 powders have been prepared by conventional solid state route. X-ray diffraction (XRD) combined with Rietveld refinements analysis reveals the formation of LiNiPO4 and doped LiNi0.8Mn0.1Co0.1PO4 with high crystalline nature at high temperature of 950 °C and 1000 °C. The lattice parameters of doped LiNi0.8Mn0.1Co0.1PO4 are significantly larger than LiNiPO4. It has been found out that the estimated crystallite size is in the order of nanometres for both samples. SEM analysis confirms that the particles have connected with each other in random shape and sub-microns size. The particle size has increased as small amount of Mn and Co are doped into LiNiPO4. The AC impedance spectroscopy measurements have revealed that the conductivity of LiNiPO4 is enhanced by around one order of magnitude by doping Mn and Co.

Impact of natural photosensitizer extraction solvent upon light absorbance in dye-sensitized solar cells

Natural pigmentations of Ardisia, Bawang Sabrang, Harum Manis mango, Oxalis Triangularis and Rosella were used to study the general trend in performance of dyes as a photosensitizer in the application of dye-sensitized solar cells (DSSCs) based on optical light absorbance and photoelectrochemical characteristics. From the Ultraviolet-Visible Spectrophotometer with the recorded absorption measurements in the range between 400 nm to 800 nm, the dyes extracted from Rosella and Oxalis Triangularis in water solvent exhibited the conversion efficiency up to 0.68% and 0.67%, respectively. The light absorbance peak for dye extracted from Ardisia, Bawang Sabrang, Oxalis Triangularis and Rosella in water and ethanol solvent resulted in the range between 500 nm to 650 nm, while the Harum Manis mango resulted in the broader spectra in both water and ethanol solvent. The light absorbance spectra of each the dyes shows shifted wavelength spectrum when the extracted dye is adsorbed onto TiO2 film surface that might influenced the absorption of light by TiO2 particle in the visible region. The capabilities of the dyes to absorb light when bonded onto the TiO2 photoanode was found to be significant with the current-voltage conversion of the cell. The results demonstrates just the tip of the vastness of natural dyes’ (native to tropical region) feasibility and applicability as a photosensitizer.

Temperature effect of natural organic extraction upon light absorbance in dye-sensitized solar cells

Natural organic dyes contain pigments which when safely extracted from plants have the potential to be used as a sensitizer while promising a low-cost fabrication, environmental friendly dye-sensitized solar cells (DSSCs). Ardisia, Bawang Sabrang, Harum Manis mango, Oxalis Triangularis and Rosella showed different absorption peaks when the extraction process were carried out at different temperatures. Hence, these were used as the basis to determine the conversion efficiency against the dyes extracting temperature. In this study, all dyes extracted in water have shown the best performance at a temperature of 100°C except for Harum Manis mango, while in ethanol, the optimum temperature was obtained between the room temperature, 25°C and 50°C. The absorption spectrum in water showed a broader absorption wavelength vis-à-vis ethanol solvent that resulted in the absorption peak for Ardisia, Harum Manis mango and Rosella between 450 nm and 550 nm. The highest conversion efficiency is observed to be achieved by Oxalis Triangularis extracted in water solution at 100°C, which was approximately 0.96% which corresponds to the broader absorbance trends in the literature. Thus, the optimum condition for extracting temperature for dyes in water and ethanol is room temperature and boiling points of water. Hence, Ardisia, Bawang Sabrang, Harum Manis mango, Oxalis Triangularis and Rosella can be an as alternative source for photosensitizer, and the impacts of temperature upon the light absorbance can be further investigated to produce the ultimate natural dye based solar cells.

An innovative single development process for integrated optical Mach-Zehnder interferometer pattern transfer

Integrated optical Mach-Zehnder interferometer (IO-MZI) has been widely researched for various usage including for biosensor application. However, the success rate of IO-MZI pattern transfer has been low using the conventional multidevelopment process. One of the main factors is the particle contamination due to the practice of reused developer bath. In this work, an innovative single development process had been proposed with the utilization of the same conventional set-up but with a different protocol. The concept of this method is the estimation of total development time based on the calculated development rate. By doing so, the development process can be completed with only one immersion of the substrate in the developer bath. Besides, the manipulation of development rate by varying exposure time in this work also had revealed the possibility of manipulation of line-width based on the exposure time. In short, the proposed single development process has increased the success rate of IO-MZI pattern transfer from 30% (multi-development method) to 90%.

The production of Malaysia bamboo charcoal (Gigantochloa albociliata) as the potential absorbent

Bamboo charcoal was successfully carbonized at 500 °C and 800 °C using Malaysia buluh madu (Gigantochloa albociliata). Structural analysis was done using Atomic Force Microscopy (AFM) in two different solvents; ethanol and DI water. The functional groups of bamboo charcoal were confirmed using Fourier Transform Infrared Spectroscopy (FTIR). The adsorption property of bamboo charcoal solution was investigated at different concentrations of 0.2, 0.4 and 0.7 mg/mL, using methylene blue test and characterized using UV-Vis Spectroscopy. Based on the adsorption investigation, it shows that the adsorption was increased as the concentration increased. It was also shown that at higher temperature and longer duration time, the adsorption process is improved.

Optimization of optical fiber splicer for optical communications applications

Optical splicing is regarded as the optical “welding” to combine two or more optical fiber to perform specific functions in modern optical telecommunication systems. In this paper, two crucial parameters in evaluating optical splicing; arc power and arc duration, are optimized for optical fiber splicing. Arc power of 32757 and arc duration of 12000 ms both yielded 0.01 dB splice loss while splicing 9/125 um FC optical fibers. Higher arc power and longer arc duration are found to yield lower splice loss. This paper has laid out optical fiber splicing optimizations and splicing strategies to be used for the development of improved and advanced optical communications applications.

Critical analysis on degradation mechanism of dye-sensitized solar cells

This paper reports on a précis of degradation mechanism for dye-sensitized solar cell (DSSCs). The review indicates progress in the understanding of degradation mechanism, in particular, the large improvement in the analysis of the materials used in DSSCs. The paper discussed on the stability issues of the dye, advancement of the photoelectrode film lifetime, changes in the electrolyte components and degradation analysis of the counter electrode. The photoelectrochemical parameters were evaluated in view of the possible degradation routes via open circuit voltage (Voc), short circuit current (Isc), fill factor (FF) and overall conversion efficiency (η) from the current-voltage curve. This analysis covers several types of materials that have paved the way for better-performing solar cells and directly influenced the stability and reliability of DSSCs. The new research trend together with the previous research has been highlighted to examine the key challenges faced in developing the ultimate DSSCs.

Motion behavior of mammalian AT-SC under evanescent field illumination

The motion behavior of mammalian adipose tissue derived stem cells (AT-SCs) on an integrated channel waveguide under the evanescent field illumination is demonstrated and analyzed. The AT-SCs, suspended to a concentration of 1 x 105 cells per ml, are deposited in a reservoir over a copper ion-exchanged channel waveguide. Light from a HeNe laser operating at 632.8nm was coupled into the waveguide, causing the cells under the illumination of evanescent field and moved in a skewed stochastic motion in accordance to the laser power. The trajectory angle of the motion of the cells towards the illuminated channel waveguide was investigated and analyzed to distinguish the factors that affect such behavior. The cells reach a position relative to the illuminated channel, which is dictated by the compounded effect of the convectional current and evanescent field. The observations deduced that motion due to the optical field exists and were more pronounced when considering the trajectory angle towards the output facet. However, the optical forces are not significantly large enough to counter the motion due to the convection current. The results are discussed in light of the potential application of optical channel waveguides for bioanalytical applications, namely in the identification, sorting and analysis of differently sized mammalian cells without recourse to fluorescence or antibody staining.

Annealing Effect on Titanium Dioxide Layer in paired Hybrid Carbon Nanotubes - Graphene as Dye Sensitized Solar Cell Working Electrode

Titanium Dioxide (TiO2) layer was deposited on conductive transparent glass substrate (ITO glass) at room temperature using doctor blade method. The TiO2 layer was annealed at 450 °C, 550 °C and 650 °C in a vacuum chamber for 1 hour. The morphology and porosity of TiO2 after annealed at different temperatures were characterized using Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and Spectrum Parameter Analyzer (SPA). Photocatalytic activity at different annealing temperatures was measured for dye sensitized solar cell that was fabricated using the new in-house carbon nanotubes-graphene hybrid as the dye material. The results showed that, the optimum annealing temperature was 450 °C. At that temperature, the active photocatalytic activity, which was initiated by the anatase TiO2 formation in paired with hybrid system as the working electrode, has contributed to the highest conversion efficiency of 0.0016% of the device performance.