Abstract: Interest in research of supercapacitor has been in increasing trend because of high demand of supercapacitor application as energy storage device in both systems that require low and high power-energy usage. For supercapacitor using porous carbon electrodes, the energy storage mechanism involves the electrolyte ions in electrodes pores and electronic charges in electrodes to form electric double layers at the electrode-electrolyte interface without undergoes any chemical reaction. The specific surface area of porous electrodes, which affect the performance of supercapacitor, have been widely investigated by many researchers using the nitrogen adsorption-desorption measurement. However, despite its simplicity the X-ray diffraction method is rarely found being used to determine the specific surface area of porous electrodes. Therefore, in the present paper, we propose a new equation which expressed the specific surface area of electrodes as a function the electrode structural parameters obtained from the X-ray diffraction data, and duration of activation time employed during the electrode preparation. This equation is found to produce a satisfactory result and is expected to be beneficial for studying supercapacitor electrode materials.
Abstract: In this work, room temperature polarized infrared attenuated total reflection (ATR) spectroscopy was employed to characterize a nanoporous GaN thin film with honeycomb structure. Prominent ATR dips due to the surface phonon polariton (SPP) and guided waves of nanoporous GaN thin film were observed. Both SPP resonance and guided waves were detected in the p-polarized ATR spectrum while only guided waves were detected in the s-polarized ATR spectrum. The ATR results were compared with the theoretical spectra generated by means of effective medium model. Good agreement was achieved between the measured and theoretical spectra. Finally, the thickness and porosity of porous layer were determined unambiguously.
Abstract: The UV and IR block properties of superparamagnetic magnetite nanoparticles (SPMN) and SPMN/gold composite nanoparticles are investigated. The composite nanoparticles were prepared via sonochemical assisted reduction of gold precursor and deposition of gold nanoparticles (GNP) on amine functionalized SPMN. Protective properties of the SPMN and the composite nanoparticles were demonstrated via spectrophotometer measurements. Unlike in the visible and infrared region, there was 0% transmission of radiation through bare SPMN in the UV region. The presence GNP in the composites nanoparticles affects the protecting properties of the SPMN with almost 40% transmission in the UV region. The SPMN/GNP composite nanoparticles were able to block some radiation in the visible region. On the other hand, there was nearly uniform 90% and continuous transmission of infrared rays in naked SPMN and SPMN/GNP composite nanoparticles, respectively.
Abstract: The topology of electron density is a sketch that gives a clear picture about electronic distribution and details information of natural molecular bonding. In quantum mechanics or particularly in quantum chemistry, the electron density is a measure of the probability of an electron occupying at any infinitesimal element of space surrounding at any given point.Studies about the topology of electron density in Cd0.5Zn0.5S at plane (101) were conducted by the application of density functional theory (DFT) within linear augmented plane wave (LAPW) by using the WIEN2k software. In this calculation, generalized gradient approximation (GGA) methods were used to calculate the exchange-correlation potential of the electrons. Based on this calculation, the topology of electron density were presented in a contour plot (2D) and also inarelief map plot (3D) in order to see the way electron density, ρ of Cd0.5Zn0.5S defines the gradient field and hence the bonding type. From these plots, we identified the bond paths that coincide with the contours of electron to suggest that Cd0.5Zn0.5S exhibited characteristics of covalent and a slightly ionic bond character.
Abstract: This study deals with the ionic conduction mechanism of carboxymethyl cellulose (CMC) – NH4Br biopolymer electrolytes (BPEs) plasticized with ethylene carbonate (EC) prepared via solution-casting technique. The ionic conductivity of BPEs system was characterized by using impedance spectroscopy and shows the highest conductivity at ambient temperature for CMC–NH4Br BPEs is 1.12 x 10-4 S/cm and enhanced to 3.31 x 10-3 S/cm with the addition of 8 wt. % EC. The conductivity–temperature plot of the BPEs system obeys Arrhenius law where R2~1. The dielectric values were found to increase with increasing temperature thus divulged that the BPEs system to be non-Debye type. The temperature dependence of the power law exponent shows the CMC–NH4Br–EC BPEs system follows the quantum mechanical tunneling (QMT) model of conduction mechanism, where the enhanced protonation of NH4Br with addition of EC makes the charge transfer (polarons) able to tunnel through the potential barrier that exists between the lone pair electrons in carboxyl group of CMC and NH4Br.
Abstract: Free-standing carbon nanotubes (CNTs) film known as buckypaper is a method used to address dispersion problems of CNTs. Unique properties of CNTs made the CNTs buckypaper to be considered as promising reinforcement materials in development of high-performance of nanocomposites. Buckypaper was fabricated by dispersing multi-walled carbon nanotubes (MWCNTs) in two different types of solution namely Triton X-100 and ethanol then followed by filtration process. In this study, MWCNTs loading and pressure used during filtration process were manipulated. The morphology, thermal and electrical conductivity of the buckypaper produced was studied.
Abstract: Green composites of Glucose-reduced graphene oxide (GrGO) and manganese (IV) oxide (MnO2) were prepared in a typical chemical synthesis route assisted with ultrasonic irradiation. Conductivity studies conducted via 2-point probe method shows GrGO/MnO2 (4:1) possessed electrical conductivity of 30.29 S cm-1 with energy band gap of 8.47×10-1 eV. The increase of D/G intensity ratio of GrGO with increase MnO2 loading indicates more disorder carbon or defects are introduced from the reaction of carbon with MnO4-.
Abstract: This presentation provides a panoramic overview of the recent progress in nanoglass plasmonics, challenges, excitement, applied interests and the future promises. A glimpse of our gamut research activities with some significant results is highlighted and facilely analyzed. The term 'nanoglass' refers to the science and technology dealing with the manipulation of the physical properties of rare earth doped inorganic glasses by embedding metallic nanoparticles (NPs) or nanoclusters. On the other hand, the word 'plasmonics' refer to the coherent coupling of photons to free electron oscillations (called plasmon) at the interface between a conductor and a dielectric. Nanoglass plasmonis being an emerging concept in advanced optical material of nanophotonics has given photonics the ability to exploit the optical response at nanoscale and opened up a new avenue in metal-based glass optics. There is a vast array of nanoglass plasmonic concepts yet to be explored, with applications spanning solar cells, (bio) sensing, communications, lasers, solid-state lighting, waveguides, imaging, optical data transfer, display and even bio-medicine. Localized surface plasmon resonance (LSPR) can enhance the optical response of nanoglass by orders of magnitude as observed. The luminescence enhancement and surface enhanced Raman scattering (SERS) are new paradigm of research. A thumbnail sketch of the fundamental aspects of SPR, LSPR, SERS and photonic applications of various rare earth doped/co-doped binary glasses containing metallic NPs are presented. The recent development in nanoglass in the context of Malaysia at the outset of international scenario is projected.
Abstract: This paper reports on the fabrication and optical characteristics of erbium-doped silica/PVA nanofibers via sol gel and electrospinning techniques. Silica glass, PVA (polyvinyl alcohol) and SiO2/PVA composites displayed 85% to 90% transparent across 300 2000 nm wavelength range. The transmission spectra were measured using Cary 5000 UV-Vis-NIR spectrophotometer. Silica was synthesized using TEOS (tetraethylorthosilicate) as the precursor, while PVA solution comprised of 7.0 wt% in H2O. The compositional ratios of SiO2:PVA were from 6:4 to 1:9 and were doped with 0.2% to 0.6% of erbium. Suitable viscosities of Er3+-doped SiO2:PVA solutions were electrospun into mesh of long strands nanofibers. Morphological and material compositions in the nanofibers were analysed using FESEM (field-emission scanning electron microscopy) and EDX (energy-dispersive X-ray spectroscopy). Er3+-doped SiO2:PVA thin films were coated on fused-silica glass substrates via spin coating and were characterized for their refractive indices, optical transmission, and fluorescence using M-line technique, UV-Vis-NIR spectrometer and photoluminescence spectrophotometer, respectively. Lower ratios of silica to PVA solutions results in higher viscosities and produced more uniform nanofiber structures of diameters around 100 nm with lesser beads. The refractive index of 1.61 for Er-doped SiO2:PVA (1:9) thin film was measured with TE polarized 632.8 nm wavelength laser and the index shows to be higher for more content of PVA in the glass/polymer composites. The 0.4% of Er3+ in SiO2:PVA composite produced the highest luminescence intensity at 605 nm when excited with 514 nm source. Higher doping content caused ion clustering effect and leads to concentration quenching, hence decreased in the emission intensity.
Abstract: Ceramics powder of BaCe0.54Zr0.36Y0.1O2.95 (BCZY) was synthesized using three different methods namely sol-gel (SG), supercritical fluid (SC) and sol-gel assisted supercritical fluids (SGSF).The respective prepared samples were denoted as S1, S2 and S3. The calcined powder (T= 1100 °C) was analyzed using particle size analyzer (PSA), Pcynometer and scanning electron microscope (SEM). PSA showed a single particle size distribution (PSD) for all samples except for S3 which exhibits bimodial particle distribution. PSD of the samples were in the range of 295-396 nm for the primary powder and 712-820 nm for secondary powder. High relative powder density for S1, S2, S3 were recorded at 95 %, 93 % and 99 %, respectively. Morphology of the calcined powders by SEM micrograph revealed that S1 is in spherical shape, S2 is in cubic structure and S3 showed a mixture of spherical and rod-like structure. It was found that SG and SC produce a single shape of powder with lower density compared with SGSF.