Nor Azah Yusof

Putra University, Malaysia, Putrajaya, Putrajaya, Malaysia

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Publications (73)83.71 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Precious metal oxides exhibit impressive characteristics that caught worldwide attention due to their promising capacitive performance, excellent electrochemical stability and low resistance, and these metal oxides have been extensively employed in supercapacitor application. This type of supercapacitors is known as redox supercapacitors or pseudocapacitors which applied faradaic process in storing energy in their systems. Thus, new materials with impressive electrochemical performance are highly demanded. In this aspect, cobaltite system with spinel structure has been the subject of intense research due to its established applications in electrochemistry. Besides, carbonaceous materials like activated carbons, carbon nanotubes, graphites, graphenes and fullerenes utilize electric double-layer capacitance whereby energy is stored by charge separation at an electrode/electrolyte interface. With greater development conducted on metal oxides and carbonaceous materials for supercapacitor application, introduction of hybrid and composite electrodes comprise of these two types of materials have been well received.
    Ceramics International. 01/2015; 41(1).
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    ABSTRACT: This work describes the incorporation of SiNWs/AuNPs composite as a sensing material for DNA detection on indium tin-oxide (ITO) coated glass slide. The morphology of SiNWs/AuNPs composite as the modifier layer on ITO was studied by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The morphological studies clearly showed that SiNWs were successfully decorated with 20 nm-AuNPs using self-assembly monolayer (SAM) technique. The effective surface area for SiNWs/AuNPs-modified ITO enhanced about 10 times compared with bare ITO electrode. SiNWs/AuNPs nanocomposite was further explored as a matrix for DNA probe immobilization in detection of dengue virus as a bio-sensing model to evaluate its performance in electrochemical sensors. The hybridization of complementary DNA was monitored by differential pulse voltammetry (DPV) using methylene blue (MB) as the redox indicator. The fabricated biosensor was able to discriminate significantly complementary, non-complementary and single-base mismatch oligonucleotides. The electrochemical biosensor was sensitive to target DNA related to dengue virus in the range of 9.0–178.0 ng/ml with detection limit of 3.5 ng/ml. In addition, SiNWs/AuNPs-modified ITO, regenerated up to 8 times and its stability was up to 10 weeks at 4 °C in silica gel.
    Materials Science and Engineering: C. 12/2014; 45:270–276.
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    ABSTRACT: The genus Trichoderma is a soil-borne fungi which in numerous reports has been successfully used as a biological control agent against various plant pathogens. The identification of Trichoderma species worldwide is currently deduced from micro-morphological descriptions which are tedious and prone to error. Electrochemical approaches are currently being developed for the detection and analysis of DNA. In the present study, an electrochemical DNA biosensor was successfully developed based on ionic liquid (e.g., 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([EMIM][Otf])), ZnO nanoparticles and a chitosan (CHIT) nanocomposite membrane on a modified gold electrode (AuE). A single-stranded DNA probe was immobilized on this electrode. Methylene blue (MB) was used as the hybridization indicator to monitor the hybridization reaction of the target DNA. Under optimal conditions using differential pulse voltammetry (DPV), the target DNA sequences were detectable at concentration ranges of 1.0 × 10−18–1.82 × 10−4 mol L−1, and the detectable limit was 1.0 × 10−19 mol L−1. The developed DNA biosensor enables the study of hybridization with crude DNA fragments and the results of this study confirm that this DNA biosensor provides a fast, sensitive and convenient way for the species level identification of Trichoderma harzianum.
    Sensing and Bio-Sensing Research. 10/2014;
  • Faruq Mohammad, Nor Azah Yusof
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    ABSTRACT: There have been a number of studies which deal with either toxic or non-toxic nature of superparamagnetic iron oxide nanoparticles (SPIONs); however, there is no clear cut information about their exact behavior and the reasons for its dual action. The objective of the present study was to investigate the SPIONs having similar oxidation states, but varying surface ligands and their role in terms of protecting the iron-mediated toxic responses. The four different SPIONs includes: (i) SPIONs containing oleic acid (SPIONs-1), (ii) SPIONs without any surface ligand (SPIONs-2), (iii) SPIONs containing cysteamine ligand (SPIONs-3), and (iv) SPIONs having both of oleic acid and cysteamine ligand. The particle size, surface functionality, and electronic oxidation states were confirmed by the HRTEM, FT-IR, and XPS analysis, respectively. On in vitro testing of all four SPIONs with H9c2 cardiomyocyte cell line, the SPIONs-2 without any surface ligand found to exhibit significant decrease in the viability of cells at a concentration of 200 μg mL−1 for 16-h exposure period. Further investigation of toxicity mechanism resulted in the fact that the SPIONs-2 involved in the formation of ROS due to the role played by the more electron deficient Fe3+ form of iron, there by decreased the glutathione release, increased DNA cleavage, and disrupted the mitochondrial transmembrane potential. However, the presence of unsaturation and/or thiol group (–SH) containing ligands on other SPIONs protected the cardiac cells from undergoing ROS-induced oxidative stress. Further, the results of the study confirming the importance of having unsaturated double bonds and/or –SH group possessing ligands onto the surface of SPIONs by means of protecting the cells from the influence of electron deficient Fe3+ state of iron.
    Journal of Materials Science 09/2014; 49(18). · 2.31 Impact Factor
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    ABSTRACT: Abstract Modification with suitable chemical substance highly increases the adsorption capacity of activated carbon towards the desired contaminants/pollutants. In this study, activated carbon was modified with dimercapto ligand for mercury removal from wastewaters. However, before modification, the AC was characterized by FT-IR, XRD, TGA, and BET and then subjected to batch adsorption studies for mercury removal from wastewaters at an initial mercury concentration of 100mgL-1. Atomic Absorption Spectrometer was used to determine mercury concentrations. The experimental equilibrium adsorption results were fitted to both the Langmuir and Freundlich models but, Freundlich model (R2 = 0.99) represented better sorption process than the Langmuir (R2 = 0.92). The kinetic data correlated well with pseudo-second order complemented by intra-particle diffusion. Keywords: Activated carbon; mercury; adsorption; kinetic; equilibrium
    FUNDAMENTAL SCIENCE CONFERENCE, UNIVERSITY PUTRA MALAYSIA; 08/2014
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    ABSTRACT: A novel optical detection system consisting of combination of uricase/HRP-CdS quantum dots (QDs) for the determination of uric acid in urine sample is described. The QDs was used as an indicator to reveal fluorescence property of the system resulting from enzymatic reaction of uricase and HRP (horseradish peroxidase), which is involved in oxidizing uric acid to allaintoin and hydrogen peroxide. The hydrogen peroxide produced was able to quench the QDs fluorescence, which was proportional to uric acid concentration. The system demonstrated sufficient activity of uricase and HRP at a ratio of 5U:5U and pH 7.0. The linearity of the system toward uric acid was in the concentration range of 125-1000µM with detection limit of 125µM.
    Biosensors & bioelectronics. 07/2014;
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    ABSTRACT: In this study, novel active nanolayers in combination with surface plasmon resonance (SPR) system for zinc ion (Zn(2+)) detection has been developed. The gold surface used for the SPR system was modified with the novel developed active nanolayers, i.e. chitosan and chitosan-tetrabutyl thiuram disulfide (chitosan-TBTDS). Both chitosan and chitosan-TBTDS active layers were fabricated on the gold surface by spin coating technique. The system was used to monitor SPR signal for Zn(2+) in aqueous media with and without sensitivity enhancement by TBTDS. For both active nanolayers, the shift of resonance angle is directly proportional to the concentration of Zn(2+) in aqueous media. The higher shift of resonance angle was obtained for chitosan-TBTDS active nanolayer due to a specific binding of TBTDS with Zn(2+). The chitosan-TBTDS active nanolayer enhanced the sensitivity of detection down to 0.1mg/l and also induced a selective detection towards Zn(2+).
    Spectrochimica Acta Part A Molecular and Biomolecular Spectroscopy 06/2014; 134C:48-52. · 1.98 Impact Factor
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    ABSTRACT: A sensitive approach for the determination of Ganoderma boninense DNA is reported based on an electrochemical affinity system using a modified gold sensor. Covalent attachment of probe DNA was achieved by attachment of the amine group to a carboxylic acid group of a 3,3’-dithiodipropionic acid monolayer on a nanocomposite film of gold nanoparticles bound to poly(3,4-ethylenedioxythiophen)–poly(styrenesulfonate) on a gold working electrode. The electrochemical detection of sequence-specific DNA of probe and target DNA hybridization was monitored using a new ruthenium complex [Ru(dppz) 2 (qtpy)Cl 2 ; dppz = dipyrido [3,2–a:2’,3’-c] phenazine; qtpy = 2,2’,-4,4”.4’4”’-quarterpyridyl redox marker. The potential was selected through the study of the electrochemical behavior of trisaminomethane-hydrochloride containing a ethylenediaminetetraacetic acid supporting electrolyte on the bare and modified gold electrode. The effect of the hybridization temperature and time were measured. The sensor demonstrated specific detection for the target over a concentration range of 1.0 × 10− 15 M to 1.0 × 10− 9 M with a detection limit of 1.59 × 10− 17 M. Control experiments verified the specificity of the biosensor in the presence of a single mismatched DNA sequence. This detection technology was shown to be effective in terms of sensitivity and selectivity of hybridization events and is a promising device for early detection of Ganoderma boninense and other pathogenic threat agents.
    Analytical Letters 03/2014; 47(5). · 0.97 Impact Factor
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    ABSTRACT: Although nanoparticle-enhanced biosensors have been extensively researched, few studies have systematically characterized the roles of nanoparticles in enhancing biosensor functionality. This paper describes a successful new method in which DNA binds directly to iron oxide nanoparticles for use in an optical biosensor. A wide variety of nanoparticles with different properties have found broad application in biosensors because their small physical size presents unique chemical, physical, and electronic properties that are different from those of bulk materials. Of all nanoparticles, magnetic nanoparticles are proving to be a versatile tool, an excellent case in point being in DNA bioassays, where magnetic nanoparticles are often used for optimization of the hybridization and separation of target DNA. A critical step in the successful construction of a DNA biosensor is the efficient attachment of biomolecules to the surface of magnetic nanoparticles. To date, most methods of synthesizing these nanoparticles have led to the formation of hydrophobic particles that require additional surface modifications. As a result, the surface to volume ratio decreases and nonspecific bindings may occur so that the sensitivity and efficiency of the device deteriorates. A new method of large-scale synthesis of iron oxide (Fe3O4) nanoparticles which results in the magnetite particles being in aqueous phase, was employed in this study. Small modifications were applied to design an optical DNA nanosensor based on sandwich hybridization. Characterization of the synthesized particles was carried out using a variety of techniques and CdSe/ZnS core-shell quantum dots were used as the reporter markers in a spectrofluorophotometer. We showed conclusively that DNA binds to the surface of ironoxide nanoparticles without further surface modifications and that these magnetic nanoparticles can be efficiently utilized as biomolecule carriers in biosensing devices.
    Molecules 01/2014; 19(4):4355-68. · 2.43 Impact Factor
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    ABSTRACT: In this paper, the electrochemical behavior of myricetin on a gold nanoparticle/ethylenediamine/multi-walled carbon-nanotube modified glassy carbon electrode (AuNPs/en/MWCNTs/GCE) has been investigated. Myricetin effectively accumulated on the AuNPs/en/MWCNTs/GCE and caused a pair of irreversible redox peaks at around 0.408 V and 0.191 V (vs. Ag/AgCl) in 0.1 mol L-1 phosphate buffer solution (pH 3.5) for oxidation and reduction reactions respectively. The heights of the redox peaks were significantly higher on AuNPs/en/MWNTs/GCE compare with MWCNTs/GC and there was no peak on bare GC. The electron-transfer reaction for myricetin on the surface of electrochemical sensor was controlled by adsorption. Some parameters including pH, accumulation potential, accumulation time and scan rate have been optimized. Under the optimum conditions, anodic peak current was proportional to myricetin concentration in the dynamic range of 5.0×10-8 to 4.0×10-5 mol L-1 with the detection limit of 1.2×10-8 mol L-1. The proposed method was successfully used for the determination of myricetin content in tea and fruit juices.
    PLoS ONE 01/2014; 9(5):e96686. · 3.53 Impact Factor
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    ABSTRACT: This paper presents the design and development of a planar Aligned-Gap and Centered-Gap Rectangular Multiple Split Ring Resonator (SRR) for microwave sensors that operates at a resonance frequency around 5 GHz. The sensor consists of a microstrip transmission line loaded with two elements of rectangular SRR on both sides. The proposed metamaterial sensors were designed and fabricated on Rogers RT5880 substrate having dielectric constant of 2.2 and thickness of 0.787 mm. The final dimension of the proposed sensor was measured at 35 × 14 mm2. Measured results show good agreement with simulated ones as well as exhibiting high Q-factor for use in sensing application. A remarkably shift of resonance frequency is observed upon introduction of several sample with different dielectric value.
    Sensors (Basel, Switzerland). 01/2014; 14(7):13134-13148.
  • Faruq Mohammad, Nor Azah Yusof
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    ABSTRACT: In the present work, nanohybrid of an anticancer drug, doxorubicin (Dox) loaded gold-coated superparamagnetic iron oxide nanoparticles (SPIONs@Au) were prepared for a combination therapy of cancer by means of both hyperthermia and drug delivery. The Dox molecules were conjugated to SPIONs@Au nanoparticles with the help of cysteamine (Cyst) as a non-covalent space linker and the Dox loading efficiency was investigated to be as high as 0.32mg/mg. Thus synthesized particles were characterized by HRTEM, UV-Vis, FT-IR, SQUID magnetic studies and further tested for heat and drug release at low frequency oscillatory magnetic fields. The hyperthermia studies investigated to be strongly influenced by the applied frequency and the solvents used. The Dox delivery studies indicated that the drug release efficacy is strongly improved by maintaining the acidic pH conditions and the oscillatory magnetic fields, i.e. an enhancement in the Dox release was observed from the oscillation of particles due to the applied frequency, and is not effected by heating of the solution. Finally, the in vitro cell viability and proliferation studies were conducted using two different immortalized cell lines containing a cancerous (MCF-7 breast cancer) and non-cancerous H9c2 cardiac cell type.
    Journal of Colloid and Interface Science 01/2014; 434:89–97. · 3.55 Impact Factor
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    ABSTRACT: The application of Silicon nanowire (SiNW) as sensing nanomaterial for detection of biological and chemical species has gained attention due to its unique properties. In this review, a short description is also demonstrated on the synthesis techniques of SiNWs and recent progress on sensor development based on electrochemical methods, fluorescence field-effect transistors (FET) and Surface-enhanced Raman scattering (SERS) spectroscopy. We also discussed on the challenges of SiNWs based sensors in the future.
    Journal of Nanomaterials 11/2013; · 1.55 Impact Factor
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    ABSTRACT: Poly(ethyl hydrazide)-grafted oil palm empty fruit bunch fibre (peh-g-opefb) was successfully prepared by heating poly(methyl acrylate)-grafted opefb (pma-g-opefb) at 60 °C for 4 h with a solution of hydrazine hydrate (15% v/v) in ethanol. The Fourier transform infrared spectrum of the product shows a secondary amine peak at 3267 cm-1, with amide carbonyl peaks at 1729 cm-1 and 1643 cm-1. The chelating ability of peh-g-opefb was tested with copper ion in aqueous solution. A batch adsorption study revealed that maximum adsorption of copper ion was achieved at pH 5. An isotherm study showed the adsorption follows a Langmuir model, with a maximum adsorption capacity of 43.48 mg g-1 at 25 °C. A kinetic study showed that the adsorption of copper ion rapidly reaches equilibrium and follows a pseudo-second-order kinetic model, with a constant rate of 7.02 × 10-4 g mg-1 min-1 at 25 °C. The Gibbs free energy, ∆G⁰, value is negative, indicating a spontaneous sorption process. Entropy, ∆S⁰, gives a positive value, indicating that the system is becoming increasingly disordered after the adsorption of copper ion. A positive enthalpy value, ∆H⁰, shows that the endothermic process takes place during the adsorption and is more favourable at high temperatures.
    Molecules 09/2013; 18(7):8461-72. · 2.43 Impact Factor
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    ABSTRACT: Amongst its various applications, activated carbon is widely used for pollutants removal from wastewaters. In this study, activated carbon (KI 30/40) was characterized by FT-IR, XRD, TGA, and BET then subjected to batch adsorption studies for mercury removal from wastewater at an initial mercury concentration of 100mgL-1. Atomic Absorption Spectrometer was used to determine mercury concentrations. The effect of contact time, adsorbent dose, solution pH, initial adsorbate concentration, and adsorption temperature were determined. Keywords: Activated carbon; optimum; mercury; adsorption.
    FUNDAMENTAL SCIENCE CONFERENCE, UNIVERSITY PUTRA MALAYSIA; 08/2013
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    ABSTRACT: The oil palm, an economically important tree, has been one of the world's major sources of edible oil and a significant precursor of biodiesel fuel. Unfortunately, it now faces the threat of a devastating disease. Many researchers have identified Ganoderma boninense as the major pathogen that affects the oil palm tree and eventually kills it. But identification of the pathogen is just the first step. No single method has yet been able to halt the continuing spread of the disease. This paper discusses the modes of infection and transmission of Ganoderma boninense and suggests techniques for its early detection. Additionally, the paper proposes some possible ways of controlling the disease. Such measures, if implemented, could contribute significantly to the sustainability of the palm oil industry in South East Asia.
    SpringerPlus 01/2013; 2:555.
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    ABSTRACT: Application of surface plasmon resonance (SPR) in sensing heavy metal ions has been emerged since more than a decade ago. A wide range of active layers or recognition elements (e.g. polymer, protein, nanoparticles) have been developed to combine with SPR. The detection limit, sensitivity and selectivity of SPR sensing in heavy metal ions have been improved from time to time, until today. Different advancements on active layers or recognition elements have been discussed in detail and arranged in the order of their chronological evolution. The present study may provide researchers valuable information regarding novel optical sensor for heavy metal ion detection and hence for further research and development.
    Photonics (ICP), 2013 IEEE 4th International Conference on; 01/2013
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    ABSTRACT: Molecularly imprinted polymers (MIPs) were prepared by bulk polymerization in acetonitrile using 2,4-dinitrophenol, acrylamide, ethylene glycol dimethacrylate, and benzoyl peroxide, as the template, functional monomer, cross-linker, and initiator, respectively. The MIP membrane was prepared by hybridization of MIP particles with cellulose acetate (CA) and polystyrene (PS) after being ground and sieved. The prepared MIP membrane was characterized using Fourier transform infrared spectroscopy and scanning electron microscopy. The parameters studied for the removal of 2,4-dinitrophenol included the effect of pH, sorption kinetics, and the selectivity of the MIP membrane. Maximum sorption of 2,4-nitrophenol by the fabricated CA membrane with MIP (CA-MIP) and the PS membrane with MIP (PS-MIP) was observed at pH 7.0 and pH 5.0, respectively. The sorption of 2,4-dinitrophenol by CA-MIP and PS-MIP followed a pseudo-second-order kinetic model. For a selectivity study, 2,4-dichlorophenol, 3-chlorophenol, and phenol were selected as potential interferences. The sorption capability of CA-MIP and PS-MIP towards 2,4-dinitrophenol was observed to be higher than that of 2,4-dichlorophenol, 3-chlorophenol, or phenol.
    International Journal of Molecular Sciences 01/2013; 14(2):3993-4004. · 2.46 Impact Factor
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    ABSTRACT: In general, a classical Split Ring Resonator (SRR) structure exhibits high Q-factor based on deeper and sharper transmission dips at resonance as well as produce high electric field density at the gaps. It is believed, by introducing more gaps, a strong and localized E-field will be obtained in the area between the split gaps. Based on these features, three types of rectangular multiple Split Ring Resonators (SRRs) were proposed to resonate in the frequency range of 3–7 GHz and simulated using Computer Simulation Technology (CST) Microwave Studio to determine the transmission characteristics and the resonance frequency. A Nicolson-Ross-Weir (NRW) technique is used to retrieve the effective parameters from the resultant S-parameter. It is shown that the resonance frequency of investigated structures falls in a frequency region in which the real part of permeability is negative. Later, the simulated results were investigated and the performances as well as the size of each unit cell itself were compared. Simulation for three different type of dielectric samples were also presented to demonstrate that the proposed structure may be well suited for bio-sensing.
    Micro and Nanoelectronics (RSM), 2013 IEEE Regional Symposium on; 01/2013
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    ABSTRACT: Purpose – The purpose of this paper is to describe a capacitive biosensor device consisting of an enzyme electrode and a simple detector which has been developed for histamine measurement. Design/methodology/approach – In this analysis, degradation of histamine through enzymatic reaction produces signal that is monitored using a simple detector equipped with “astable” multivibrator operation circuit (in capacitor-resistor circuit). Findings – Different frequency (f) readings have been obtained for glucose, alcohol and histamine in different concentration levels, showing the ability of this simple device system to measure their dielectric constant (k) as formulated by the equation f=(1.44d)/ [kA (R1+2R2)]. The analysis using smaller electrode gap (d) produces higher value of f, indicating that d, is directly proportional to f. For histamine, by using immobilized enzyme electrode, the results show that the change of dielectric properties during the 300-second reaction period could also be monitored. A linear relationship is obtained between concentration and frequency from 50 to 200?ppm. Practical implications – Based on this result, an enzyme electrode and “astable” operation circuits have the potential to be used in the development of a simple capacitive biosensor device. Originality/value – The paper is an outcome of experimental work carried out to observe capacitive sensing behavior using an immobilized enzyme, to measure biological samples, especially histamine.
    Sensor Review 06/2012; 32(3):245-250. · 0.66 Impact Factor