Gel polymer electrolytes (GPEs) are developed using poly(1-vinylpyrrolidone-co-vinyl acetate) [P(VP-co-VAc)] as the host polymer, lithium bis(trifluoromethane) sulfonimide [LiTFSI] as the lithium salt and ionic liquid, and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide [EMImTFSI] by using solution casting technique. The effect of ionic liquid on ionic conductivity is studied and the optimum ionic conductivity at room temperature is found to be 2.14 × 10(-6) S cm(-1) for sample containing 25 wt% of EMImTFSI. The temperature dependence of ionic conductivity from 303 K to 353 K exhibits Arrhenius plot behaviour. The thermal stability of the polymer electrolyte system is studied by using thermogravimetric analysis (TGA) while the structural and morphological properties of the polymer electrolyte is studied by using Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction analysis (XRD), respectively.
This paper presents a compact sized inset-fed rectangular microstrip patch antenna embedded with double-P slots. The proposed antenna has been designed and fabricated on ceramic-PTFE composite material substrate of high dielectric constant value. The measurement results from the fabricated prototype of the antenna show -10 dB reflection coefficient bandwidths of 200 MHz and 300 MHz with center resonant frequency of 1.5 GHz and 4 GHz, respectively. The fabricated antenna has attained gains of 3.52 dBi with 81% radiation efficiency and 5.72 dBi with 87% radiation efficiency for lower band and upper band, respectively. The measured E- and H-plane radiation patterns are also presented for better understanding. Good agreement between the simulation and measurement results and consistent radiation patterns make the proposed antenna suitable for GPS and C-band applications.
This paper presents a new type diode connected MOS transistor to improve CMOS conventional rectifier's performance in RF energy harvester systems for wireless sensor networks in which the circuits are designed in 0.18 μm TSMC CMOS technology. The proposed diode connected MOS transistor uses a new bulk connection which leads to reduction in the threshold voltage and leakage current; therefore, it contributes to increment of the rectifier's output voltage, output current, and efficiency when it is well important in the conventional CMOS rectifiers. The design technique for the rectifiers is explained and a matching network has been proposed to increase the sensitivity of the proposed rectifier. Five-stage rectifier with a matching network is proposed based on the optimization. The simulation results shows 18.2% improvement in the efficiency of the rectifier circuit and increase in sensitivity of RF energy harvester circuit. All circuits are designed in 0.18 μm TSMC CMOS technology.
Bestari Jaya, former tin mining catchment covers an area of 2656.31 hectares comprised of four hundred and forty-two different-size lakes and ponds. The present study area comprise of 92 hectares of the catchment that include four large size lakes. Arc GIS version 9.2 used to develop bathymetric map, Global Positioning System (GPS) for hydrographical survey and flow meter was utilized for water discharge analysis (flow routing) of the catchment. The water quality parameters (pH, temperature, electric conductivity, dissolved oxygen DO, total dissolved solids TDS, chlorides, ammonium, nitrates) were analyzed by using Hydrolab. Quality assurance (QA) and quality control (QC) procedures were strictly followed throughout the field work and data analysis. Different procedures were employed to evaluate the analytical data and to check for possible transcription or dilution errors, changes during analysis, or unusual or unlikely values. The results obtained are compared with interim national water quality standards for Malaysia indicates that water quality of area is highly degraded. It is concluded that Bestri Jaya ex-mining catchment has a high pollution potential due to mining activities and River Ayer Hitam, recipient of catchment water, is a highly polluted river.
Fourier transform infrared (FT-IR), X-ray diffraction (XRD), and transference number measurement (TNM) techniques were applied to investigate the complexation, structural, and ionic transport properties of and the dominant charge-carrier species in a solid biopolymer electrolyte (SBE) system based on carboxymethyl cellulose (CMC) doped with ammonium fluoride (NH4F), which was prepared via a solution casting technique. The SBEs were partially opaque in appearance, with no phase separation. The presence of interactions between the host polymer (CMC) and the ionic dopant (NH4F) was proven by FT-IR analysis at the C-O band. XRD spectra analyzed using Origin 8 software disclose that the degree of crystallinity (χc%) of the SBEs decreased with the addition of NH4F, indicating an increase in the amorphous nature of the SBEs. Analysis of the ionic transport properties reveals that the ionic conductivity of the SBEs is dependent on the ionic mobility (μ) and diffusion of ions (D). TNM analysis confirms that the SBEs are proton conductors.
Fire is one of the major issues facing Southeast Asian peatlands causing socio-economic, human health and climate crises. Many of these fires in the region are associated with land clearing or management practices for oil palm plantations. Here we study the direct post-fire impacts of slash-and-burn oil palm agriculture on greenhouse gas emissions, peat physico-chemical properties and nutrient concentrations. Greenhouse gas (GHG) emissions were measured using Los Gatos ultraportable greenhouse gas analyser one month after a fire in dry season and five months after the fire event, in wet season. Surface soil samples were collected from each individual GHG measurement points, along with 50 cm cores from both burnt and non-burnt control areas for lab analyses. As an immediate post-fire impact, carbon dioxide (CO2) and methane (CH4) emissions, pH, electrical conductivity, and all macronutrient concentrations except nitrogen (N) were increased multi-fold, while the redox potential, carbon (C) and N content were greatly reduced in the burnt region. While some of the properties such as CO2 emissions, and electrical conductivity reverted to normal after five months, other properties such as CH4 emissions, pH and nutrient concentrations remained high in the burnt region. This study also found very high loss of surface peat C content in the burnt region post fire, which is irreversible. The results also show that surface peat layers up to 20 cm depth were affected the most by slash-and-burn activity in oil palm agriculture, however the intensity of fire can vary widely between different oil palm management and needs further research to fully understand the long term and regional impacts of such slash-and-burn activity in tropical peatlands.
The aim of this work was to study radiation and the effects of temperature on conductivity properties of polyvinyl alcohol (PVA)-based potassium hydroxide (KOH) and propylene carbonate (PC), where the ionic conduction preferentially occurs in the amorphous phase by free radicals ions through gamma-irradiation. Alkaline composite polymer electrolyte (ACPE) consisting of PVA, KOH and PC of different concentration ratios were prepared by solvent-casting technique. The ACPE were irradiated with different doses from 5 kGy up to 200 kGy. The conductivity properties of the electrolyte films were measured at different frequencies in the range 20 Hz to 1 MHz using LCR meter. The results showed that the conductivity properties were dependent on the radiation dose, temperature and the concentration of the polymer blends.
A reversed-phase high-performance liquid chromatographic method with capacitively coupled contactless conductivity detector (C(4)D) has been developed for the separation and the simultaneous determination of five underivatized long chain fatty acids (FAs), namely myristic, palmitic, stearic, oleic, and linoleic acids. An isocratic elution mode using methanol/1mM sodium acetate (78:22, v/v) as mobile phase with a flow rate of 0.6 mL min(-1) was used. The separation was effected by using a Hypersil ODS C(18) analytical column (250 mm x 4.6 mm x 5 microm) and was operated at 45 degrees C. Calibration curves of the five FAs were well correlated (r(2)>0.999) within the range of 5- 200 microg mL(-1) for stearic acid, and 2-200 microg mL(-1) for the other FAs. The proposed method was tested on four vegetable oils, i.e., pumpkin, soybean, rice bran and palm olein oils; good agreement was found with the standard gas chromatographic (GC) method. The proposed method offers distinct advantages over the official GC method, especially in terms of simplicity, faster separation times and sensitivity.
Polymer electrolytes based on poly(ethylene oxide)-lithium triflate (PEO-LiCF3SO3) and poly(ethylene oxide)-lithium sulphate (PEO-Li2S4) were prepared by using solution casting method. Measurements of conductivity and dielectric were carried out on these films as a function of frequency at various temperatures. It was observed that PEO-LiCF3SO3 polymer electrolytes have higher conductivity. The interaction between PEO and Li salts were studied by Fourier transform infrared (FTIR).
Fourier transform infrared (FT-IR) spectroscopic studies have been undertaken to investigate the interactions among components in a system of hexanoyl chitosan-lithium trifluoromethanesulfonate (LiCF(3)SO(3))-diethyl carbonate (DEC)/ethylene carbonate (EC). LiCF(3)SO(3) interacts with the hexanoyl chitosan to form a hexanoyl chitosan-salt complex that results in the shifting of the N(COR)(2), CONHR and OCOR bands to lower wavenumbers. Interactions between EC and DEC with LiCF(3)SO(3) has been noted and discussed. Evidence of interaction between EC and DEC has been obtained experimentally. Studies on polymer-plasticizer spectra suggested that there is no interaction between the polymer host and plasticizers. Competition between plasticizer and polymer on associating with Li(+) ions was observed from the spectral data for gel polymer electrolytes. The obtained spectroscopic data has been correlated with the conductivity performance of hexanoyl chitosan-based polymer electrolytes.
In this study, the ability of the Capillary-attached conductive gas sensor (CGS) in real-time gas identification was investigated. The structure of the prototype fabricated CGS is presented. Portions were selected from the beginning of the CGS transient response including the first 11 samples to the first 100 samples. Different feature extraction and classification methods were applied on the selected portions. Validation of methods was evaluated to study the ability of an early portion of the CGS transient response in target gas (TG) identification. Experimental results proved that applying extracted features from an early part of the CGS transient response along with a classifier can distinguish short-chain alcohols from each other perfectly. Decreasing time of exposition in the interaction between target gas and sensing element improved the reliability of the sensor. Classification rate was also improved and time of identification was decreased. Moreover, the results indicated the optimum interval of the early transient response of the CGS for selecting portions to achieve the best classification rates.
Zinc oxide (ZnO) nanorods (NRs) have been synthesized via the hydrothermal process. The NRs were grown over a conductive glass substrate. A non-enzymatic electrochemical sensor for hydrogen peroxide (H₂O₂), based on the prepared ZnO NRs, was examined through the use of current-voltage measurements. The measured currents, as a function of H₂O₂ concentrations ranging from 10 μM to 700 μM, revealed two distinct behaviours and good performance, with a lower detection limit (LOD) of 42 μM for the low range of H₂O₂ concentrations (first region), and a LOD of 143.5 μM for the higher range of H₂O₂ concentrations (second region). The prepared ZnO NRs show excellent electrocatalytic activity. This enables a measurable and stable output current. The results were correlated with the oxidation process of the H₂O₂ and revealed a good performance for the ZnO NR non-enzymatic H₂O₂ sensor.
A corrosive environment leaves in-service conductive structures prone to subsurface corrosion which poses a severe threat to the structural integrity. It is indispensable to detect and quantitatively evaluate subsurface corrosion via non-destructive evaluation techniques. Although the gradient-field pulsed eddy current technique (GPEC) has been found to be superior in the evaluation of corrosion in conductors, it suffers from a technical drawback resulting from the non-uniform field excited by the conventional pancake coil. In light of this, a new GPEC probe with uniform field excitation for the imaging of subsurface corrosion is proposed in this paper. The excited uniform field makes the GPEC signal correspond only to the field perturbation due to the presence of subsurface corrosion, which benefits the corrosion profiling and sizing. A 3D analytical model of GPEC is established to analyze the characteristics of the uniform field induced within a conductor. Following this, experiments regarding the imaging of subsurface corrosion via GPEC have been carried out. It has been found from the results that the proposed GPEC probe with uniform field excitation not only applies to the imaging of subsurface corrosion in conductive structures, but provides high-sensitivity imaging results regarding the corrosion profile and opening size.
High demand of semiconductor gas sensor works at low operating temperature to as low as 100 °C has led to the fabrication of gas sensor based on TiO₂ nanoparticles. A sensing film of gas sensor was prepared by mixing the sensing material, TiO₂ (P25) and glass powder, and B₂O₃ with organic binder. The sensing film was annealed at temperature of 500 °C in 30 min. The morphological and structural properties of the sensing film were characterized by field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). The gas sensor was exposed to hydrogen with concentration of 100⁻1000 ppm and was tested at different operating temperatures which are 100 °C, 200 °C, and 300 °C to find the optimum operating temperature for producing the highest sensitivity. The gas sensor exhibited p-type conductivity based on decreased current when exposed to hydrogen. The gas sensor showed capability in sensing low concentration of hydrogen to as low as 100 ppm at 100 °C.
Recent advances in nanotechnology have revealed the superiority of nanocarbon species such as carbon nanotubes over other conventional materials for gas sensing applications. In this work, analytical modeling of the semiconducting zigzag carbon nanotube field-effect transistor (ZCNT-FET) based sensor for the detection of gas molecules is demonstrated. We propose new analytical models to strongly simulate and investigate the physical and electrical behavior of the ZCNT sensor in the presence of various gas molecules (CO2, H2O, and CH4). Therefore, we start with the modeling of the energy band structure by acquiring the new energy dispersion relation for the ZCNT and introducing the gas adsorption effects to the band structure model. Then, the electrical conductance of the ZCNT is modeled and formulated while the gas adsorption effect is considered in the conductance model. The band structure analysis indicates that, the semiconducting ZCNT experiences band gap variation after the adsorption of the gases. Furthermore, the bandgap variation influences the conductance of the ZCNT and the results exhibit increments of the ZCNT conductance in the presence of target gases while the minimum conductance shifted upward around the neutrality point. Besides, the I-V characteristics of the sensor are extracted from the conductance model and its variations after adsorption of different gas molecules are monitored and investigated. To verify the accuracy of the proposed models, the conductance model is compared with previous experimental and modeling data and a good consensus is observed. It can be concluded that the proposed analytical models can successfully be applied to predict sensor behavior against different gas molecules.
In this study, dye-sensitized solar cells (DSSCs) has been assembled with poly(1-vinylpyrrolidone-co-vinyl acetate) (P(VP-co-VAc)) gel polymer electrolytes (GPEs) which have been incorporated with binary salt and an ionic liquid. The potential of this combination was studied and reported. The binary salt system GPEs was having ionic conductivity and power conversion efficiency (PCE) that could reach up to 1.90 × 10(-3) S cm(-1) and 5.53%, respectively. Interestingly, upon the addition of the ionic liquid, MPII into the binary salt system the ionic conductivity and PCE had risen steadily up to 4.09 × 10(-3) S cm(-1) and 5.94%, respectively. In order to know more about this phenomenon, the electrochemical impedance studies (EIS) of the GPE samples have been done and reported. Fourier transform infrared studies (FTIR) and thermogravimetric analysis (TGA) have also been studied to understand more on the structural and thermal properties of the GPEs. The Nyquist plot and Bodes plot studies have been done in order to understand the electrochemical properties of the GPE based DSSCs and Tafel polarization studies were done to determine the electrocatalytic activity of the GPE samples.
Gel polymer electrolytes using imidazolium based ionic liquids have attracted much attention in dye-sensitized solar cell applications. Hydroxypropyl cellulose (HPC), sodium iodide (NaI), 1-methyl-3-propylimidazolium iodide (MPII) as ionic liquid (IL), ethylene carbonate (EC) and propylene carbonate (PC) are used for preparation of non-volatile gel polymer electrolyte (GPE) system (HPC:EC:PC:NaI:MPII) for dye-sensitized solar cell (DSSC) applications. The highest ionic conductivity of 7.37 × 10(-3) S cm(-1) is achieved after introducing 100% of MPII with respect to the weight of HPC. Temperature-dependent ionic conductivity of gel polymer electrolytes is studied in this work. XRD patterns of gel polymer electrolytes are studied to confirm complexation between HPC polymer, NaI and MPII. Thermal behavior of the GPEs is studied using simultaneous thermal analyzer (STA) and differential scanning calorimetry (DSC). DSSCs are fabricated using gel polymer electrolytes and J-V centeracteristics of fabricated dye sensitized solar cells were analyzed. The gel polymer electrolyte with 100 wt.% of MPII ionic liquid shows the best performance and energy conversion efficiency of 5.79%, with short-circuit current density, open-circuit voltage and fill factor of 13.73 mA cm(-2), 610 mV and 69.1%, respectively.
Increased absorption of transverse-magnetic (TM)-polarised light by a graphene-oxide (GO) coated polymer waveguide has been observed in the presence of transverse-electric (TE)-polarised light. The GO-coated waveguide exhibits very strong photo-absorption of TE-polarised light--and acts as a TM-pass waveguide polariser. The absorbed TE-polarised light causes a significant temperature increase in the GO film and induces thermal reduction of the GO, resulting in an increase in optical-frequency conductivity and consequently increased optical propagation loss. This behaviour in a GO-coated waveguide gives the action of an inverted optical switch/modulator. By varying the incident TE-polarised light power, a maximum modulation efficiency of 72% was measured, with application of an incident optical power level of 57 mW. The GO-coated waveguide was able to respond clearly to modulated TE-polarised light with a pulse duration of as little as 100 μs. In addition, no wavelength dependence was observed in the response of either the modulation (TE-polarised light) or the signal (TM-polarised light).
In this work, Ni nanoparticles were directly decorated on graphene (G) nanosheets via mechanical ball milling. Based on transmission electron microscopy observations, the Ni nanoparticles were well dispersed and attached to the G nanosheet without any agglomerations. Electrochemical results showed that the capacitance of a G/Ni nanocomposite was 275 F g(-1) at a current density of 2 A g(-1), which is higher than the capacitance of bare G (145 F g(-1)) and bare Ni (3 F g(-1)). The G/Ni electrode also showed superior performance at a high current density, exhibiting a capacitance of 190 F g(-1) at a current density of 5 A g(-1) and a capacitance of 144 F g(-1) at a current density of 10 A g(-1). The equivalent series resistance for G/Ni nanocomposites also decreased. The enhanced performance of this hybrid supercapacitor is best described by the synergistic effect, i.e. dual charge-storage mechanism, which is demonstrated by electrical double layer and pseudocapacitance materials. Moreover, a high specific surface area and electrical conductivity of the materials enhanced the capacitance. These results indicate that the G/Ni nanocomposite is a potential supercapacitor.
Three-dimensional (3D) printing technology provides a novel approach to material fabrication for various applications because of its ability to create low-cost 3D printed platforms. In this study, a printable graphene-based conductive filament was employed to create a range of 3D printed electrodes (3DEs) using a commercial 3D printer. This printing technology provides a simplistic and low-cost approach, which eliminates the need for the ex-situ modification and post-treatment of the product. The conductive nature of the 3DEs provides numerous deposition platforms for electrochemical active nanomaterials such as graphene, polypyrrole, and cadmium sulfide, either through electrochemical or physical approaches. To provide proof-of-concept, these 3DEs were physiochemically and electrochemically evaluated and proficiently fabricated into a supercapacitor and photoelectrochemical sensor. The as-fabricated supercapacitor provided a good capacitance performance, with a specific capacitance of 98.37 Fg-1. In addition, these 3DEs were fabricated into a photoelectrochemical sensing platform. They had a photocurrent response that exceeded expectations (~724.1 μA) and a lower detection limit (0.05 μM) than an ITO/FTO glass electrode. By subsequently modifying the printing material and electrode architecture, this 3D printing approach could provide a facile and rapid manufacturing process for energy devices based on the conceptual design.