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Fabrication and characterization of tungsten disulphide/silicon heterojunction photodetector for near infrared illumination
No full textTungsten disulphide (WS 2 ), a member of the transition metal dichalcogenide (TMD) family that is known for its superior optoelectronic properties is used in this work to fabricate a low cost and highly efficient photodetector for operation in the near infrared (NIR) region. The WS 2 /Si heterojunction photodetector is fabricated using the drop cast method. Sample analysis shows Raman shifts at the E 1 2g and A 1g phonon modes located at 349.84 cm −1 and 419.62 cm −1 , validating the growth of monolayer 2H-WS 2 with a direct bandgap of 2.06 eV. Field emission scanning electron microscope (FESEM) analysis reveals an inhomogeneous surface on the film, while energy-dispersive X-ray (EDX) spectroscopy shows non-stoichiometric WS 2 layer growth on the Si wafer. Current-voltage (IV) measurements are performed in the NIR region with a 785 nm red laser source under dark and illuminated conditions. From the IV measurements, the threshold voltage is determined to be 2.2 V, and the photocurrent is found to be highly dependent on the laser power. The fabricated photodetector has a high responsivity of 10.46 mA/W and detectivity of 1.17 × 10 9 Jones for an incident light intensity of 11.696 mW.cm -2 . These results are promising as an alternative low-cost fabrication method with potential for the development of photovoltaic and optoelectronic applications. © 2019 Elsevier Gmb
Depressed cladding erbium-doped fiber laser passively mode-locked with carbon nanotube saturable absorber
No full textA depressed cladding erbium doped fiber (DC-EDF) laser with a carbon nanotube saturable absorber is proposed and demonstrated. The laser is able to generate a mode-locked output with a narrow pulse width of 0.77 ps at a lasing wavelength of 1496 nm. A 200 m long single-mode fiber together with the DC-EDF, with a negative and positive dispersion respectively is used to balance the effect of dispersion and the non-linearity of the system. The output is highly stable, with a signal to noise ratio in the radio frequency domain of 51.2 dB as well as a pulse energy, average output power and repetition rate of 58.9 pJ, -12.75 dBm and 900.9 KHz at the maximum pump power. The proposed laser would have significant applications for S-band communications systems. © 2019 Astro Ltd
New magnetic silica-based hybrid organic-inorganic nanocomposite for the removal of lead(II) and nickel(II) ions from aqueous solutions
No full textA novel magnetic sol-gel silica-based hybrid organic-inorganic adsorbent (MNPs@SiO 2 -TSD-TEOS) was synthesized by immobilizing silica (SiO 2 ) shell on Fe 3 O 4 magnetic nanoparticles (MNPs) prior to binding with hybrid organic-inorganic tetraethylorthosilicate (TEOS) and N-[3-(trimethoxysilyl)propyl]ethylenediamine (TSD)). The proposed material was characterized using Fourier transform infrared spectrometer (FTIR), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscope (EDS) and X-ray diffraction (XRD). MNPs@SiO 2 -TSD-TEOS was applied as an adsorbent for the simultaneous adsorption of Pb(II) and Ni(II) ions from aqueous solutions. The adsorption process, reusability test and field application of MNPs@SiO 2 -TSD-TEOS were performed using batch adsorption of metal ions at pH 5. The adsorption process was well-matched to type III isotherm model (multilayer sorption) set by IUPAC. The experimental adsorption data were well-fitted to the Freundlich adsorption isotherm since its coefficient of determination (R 2 = 0.997) is higher than that of the Langmuir isotherm (R 2 = 0.871). The adsorption kinetics were fitted well to pseudo-2 nd -order model as compared to pseudo-1 st -order. Furthermore, the results showed maximum adsorption capacities of 417 and 357 mg g −1 for Pb(II) and Ni(II), respectively. Isotherm model (type III), Freundlich isotherm and pseudo-2 nd -order model confirm a multilayer chemical/physical adsorption process. © 2019 Elsevier B.V
Quantitative duplex real-time polymerase chain reaction assay with TaqMan probe detects and quantifies Crocodylus porosus in food chain and traditional medicines
No full textConsumption and exploitation of crocodiles have been rampant for their exotic, nutritive and medicinal attributes. These depredations are alarming and although they have continued to be monitored by wildlife and conservation agencies, unlawful trading of crocodiles shows an increasing trend worldwide. Recently, conventional polymerase chain reaction (PCR) and PCR-restriction fragment length polymorphism (RFLP) assays for crocodile have been documented but they are only suitable for identification and cannot quantify adulterations. We described here a quantitative duplex real-time PCR assay with probes to quantify contributions from Crocodylus porosus materials simultaneously. A very short amplicon size of 127bp was used because longer targets could have been broken down in samples, bringing considerable uncertainty in molecular analysis. We have validated a TaqMan probe-based duplex real-time PCR (qPCR) assay for the detection of 0.004 ng DNA in pure state and 0.1% target meat in model chicken meatball. False negative detection was eliminated through an endogenous control (141-bp site of eukaryotic 18S rRNA). Analysis of 12 model chicken meatballs adulterated with C. porosus reflected 96.3−120.2% target recovery at 0.1−10% adulterations. A validation test of 21 commercial food and traditional medicine (TM) crocodile-based products showed 100% effectiveness. Short amplicon sizes, alternative complementary target, exceptional stability and superior sensitivity suggested the assay could be used for the identification and quantitative determination of C. porosus in any food or TM samples even under degraded conditions. © 2019, © 2019 Taylor & Francis Group, LLC
Investigation of the Brillouin effect in highly nonlinear hafnium bismuth erbium doped fiber
No full textThis paper demonstrates the generation of the Brillouin fiber laser (BFL) with 0.5 m long hafnium bismuth erbium doped fiber (HBEDF) as a hybrid gain medium. As the gain medium is pumped by a 980 nm laser diode at the power of 170 mW, a stable Stokes is observed at the output power of −2.96 dBm with Brillouin pump (BP) power of 3 dBm. The laser operates at wavelength shifted by 0.09 nm from the BP. To the best of the authors' knowledge, this is the first report of a compact BFL without employing any lengthy SMF, which features a simple cavity configuration
From nanoengineering to nanomedicine: A facile route to enhance biocompatibility of graphene as a potential nano-carrier for targeted drug delivery using natural deep eutectic solvents
No full textGraphene has attracted massive interest in numerous biomedical applications such as anti-cancer therapy, drug delivery, bio-imaging and gene delivery. Therefore, it is important to ensure that graphene is nontoxic, and that its cellular biological behavior is safe and biocompatible. Herein, a new route was used to enhance the biocompatibility of graphene, using several natural deep eutectic solvents (DESs) as functionalizing agents, owing to their capability to introduce various functional groups and surface modifications. Characterization of the physicochemical changes in DES-functionalized graphene were conducted by FE-SEM, FTIR, XRD, and Raman spectroscopy. There were considerable improvements in the cytotoxicity profile of DES-functionalized graphene compared to pristine graphene and oxidized graphene, as demonstrated by cell viability, cell cycle progression, and reactive oxygen species evaluation assays. We also studied the association between cellular toxicity of DES-functionalized graphene and their physicochemical properties. To the best of our knowledge, this is the first study on the cytotoxicity profile improvement of graphene using DESs as functionalizing agents, and its cellular biological behavior. The application of DESs as functionalizing agents, especially for DES choline chloride (ChCl):malonic acid (1:1), significantly reduced the cytotoxicity level of graphenes. DES ChCl:malonic acid (1:1) also demonstrated higher tamoxifen entrapment efficiency and loading capacity in comparison to the functionalization with DES ChCl:glucose (2:1), ChCl:fructose (2:1) and ChCl:sucrose (2:1). Therefore, DES ChCl:malonic acid (1:1) is considered the most promising nano-carrier for drug delivery applications, owing to its lower cytotoxicity and higher drug loading capacity
Application of interface material and effects of oxygen gradient on the performance of single-chamber sediment microbial fuel cells (SSMFCs)
No full textSingle-chamber sediment microbial fuel cells (SSMFCs) have received considerable attention nowadays because of their unique dual-functionality of power generation and enhancement of wastewater treatment performance. Thus, scaling up or upgrading SSMFCs for enhanced and efficient performance is a highly crucial task. Therefore, in order to achieve this goal, an innovative physical technique of using interface layers with four different pore sizes embedded in the middle of SSMFCs was utilized in this study. Experimental results showed that the performance of SSMFCs employing an interface layer was improved regardless of the pore size of the interface material, compared to those without such layers. The use of an interface layer resulted in a positive and significant effect on the performance of SSMFCs because of the effective prevention of oxygen diffusion from the cathode to the anode. Nevertheless, when a smaller pore size interface was utilized, better power performance and COD degradation were observed. A maximum power density of 0.032 mW/m2 and COD degradation of 47.3% were obtained in the case of an interface pore size of 0.28 μm. The findings in this study are of significance to promote the future practical application of SSMFCs in wastewater treatment plants
Performance Comparison of Fault-Tolerant Three-Phase Induction Motor Drives Considering Current and Voltage Limits
No full textWith the increasing demand for electric vehicles, reliability in motor drives is an issue of growing importance. Over the years, various fault-tolerant three-phase motor drive topologies have been introduced and their performances have been investigated. Evaluation of the postfault power of a fault-tolerant drive should take into account both the postfault torque and speed, which depend on both the postfault current and voltage limits. Nevertheless, the postfault motor voltage limits are usually omitted from discussion. Furthermore, current limit in induction motor drive is not as direct as that in permanent magnet motor drive, due to the presence of the flux current. In this paper, the performances of available fault-tolerant three-phase induction motor drives have been reinvestigated, taking into account the impact of not just currents, but also voltage limits for both the inverter and machine. By deriving the postfault machine voltage equations, the effects of machine parameters and operating point on the voltage limit and hence the speed limit are explained. Depending on the topology, the motor may be able to run above the rated speed to gain extra power. The analysis is verified through experiment results on a 1 kW induction machine for four different fault-tolerant drive topologies
Occurrence of zoonotic Cryptosporidium and Giardia duodenalis species/genotypes in urban rodents
No full textThis report describes the detection of zoonotic Cryptosporidium muris, C. parvum subgenotype IIa and Giardia duodenalis genotype B in urban rodents in Malaysia. A rare occurrence of C. meleagridis was also reported suggesting a role of rodents in mechanical transmission of this pathogen. Utilization of DNA sequencing and subtyping analysis confirmed the presence of zoonotic C. parvum subtypes IIaA17G2R1 and IIaA16G3R1 for the first time in rodents
Optimization of poly(vinyl alcohol-co-ethylene)-based gel polymer electrolyte containing nickel phosphate nanoparticles for dye-sensitized solar cell application
No full textFor the first time, metal phosphate, particularly nickel phosphate, Ni3(PO4)2 nanoparticle has been incorporated into gel polymer electrolyte (GPE) for the application in dye-sensitized solar cells (DSSCs). Poly(vinyl alcohol-co-ethylene), PVA-co-PE copolymer and sodium iodide, NaI have been employed as the host polymer and dopant salt, respectively. X-ray diffraction (XRD) studies revealed that the degree of crystallinity of the overall GPE reaches the minimum at 4 wt.% of Ni3(PO4)2 nanoparticles. The amorphous domains have boosted the mobility of the charge carriers and successfully increased the ionic conductivity from 2.27 mS cm−1 to 3.75 mS cm−1. Temperature dependence studies affirmed that the GPEs obey Arrhenius behavior in which ion hopping mechanism is dominant. This explanation was further corroborated by the results obtained from electrical modulus studies. The addition of Ni3(PO4)2 also increases both the dielectric constant and dielectric loss dramatically. Fourier transform infrared studies proved the complexation of different components found in the polymer electrolyte. Besides, the Ni3(PO4)2 nanoparticles also smoothen the morphologies of the GPE which was originally porous and rough. The efficiency of the fabricated DSSCs also nearly doubled from 3.3% to 5.8% with the incorporation of Ni3(PO4)2 nanoparticles