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Search Results: 1 - 10 of 1141 matches for " Magnus Willander "
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The Deterministic Circuit Model for Noise Influence on the Averaged Transient Responses of Large-scale Nonlinear ICs Analyzed with It?'s Stochastic Differential Equations
Magnus Willander,Yevgeny Mamontov,Jonathan Vincent
VLSI Design , 2001, DOI: 10.1155/2001/92043
Abstract: The second-order nonrandom ordinary differential equation (ODE) system derived as the noise-source-aware model for expectations of solutions of Itô's stochastic differential equation (ISDE) system is discussed in connection with large-scale integrated circuits (ICs). The work explains the reason why the new model consistently allows for the noise-induced phenomena in the expectations, namely, stochastic resonance, stochastic linearization, stochastic self-oscillations and stochastic chaos. The case of stochastic resonance is considered as an example. In spite of the fact that the above second-order model is more complex than the nonrandom first-order IC ODE system for the expectations commonly used in engineering, an efficient practical technique for its implementation is proposed. The corresponding predicted computing time is only in 2.5 times greater than in the case of the first-order model which does not include any noise-source influence upon the expectations of the modelled IC responses.
The pH Response and Sensing Mechanism of n-Type ZnO/Electrolyte Interfaces
Safaa Al-Hilli,Magnus Willander
Sensors , 2009, DOI: 10.3390/s90907445
Abstract: Ever since the discovery of the pH-sensing properties of ZnO crystals, researchers have been exploring their potential in electrochemical applications. The recent expansion and availability of chemical modification methods has made it possible to generate a new class of electrochemically active ZnO nanorods. This reduction in size of ZnO (to a nanocrystalline form) using new growth techniques is essentially an example of the nanotechnology fabrication principle. The availability of these ZnO nanorods opens up an entire new and exciting research direction in the field of electrochemical sensing. This review covers the latest advances and mechanism of pH-sensing using ZnO nanorods, with an emphasis on the nano-interface mechanism. We discuss methods for calculating the effect of surface states on pH-sensing at a ZnO/electrolyte interface. All of these current research topics aim to explain the mechanism of pH-sensing using a ZnO bulk- or nano-scale single crystal. An important goal of these investigations is the translation of these nanotechnology-modified nanorods into potential novel applications.
A Selective Iodide Ion Sensor Electrode Based on Functionalized ZnO Nanotubes
Zafar Hussain Ibupoto,Kimleang Khun,Magnus Willander
Sensors , 2013, DOI: 10.3390/s130201984
Abstract: In this research work, ZnO nanotubes were fabricated on a gold coated glass substrate through chemical etching by the aqueous chemical growth method. For the first time a nanostructure-based iodide ion selective electrode was developed. The ZnO nanotubes were functionalized with miconazole ion exchanger and the electromotive force (EMF) was measured by the potentiometric method. The iodide ion sensor exhibited a linear response over a wide range of concentrations (1 × 10 ?6 to 1 × 10 ?1 M) and excellent sensitivity of –62 ± 1 mV/decade. The detection limit of the proposed sensor was found to be 5 × 10 ?7 M. The effects of pH, temperature, additive, plasticizer and stabilizer on the potential response of iodide ion selective electrode were also studied. The proposed iodide ion sensor demonstrated a fast response time of less than 5 s and high selectivity against common organic and the inorganic anions. All the obtained results revealed that the iodide ion sensor based on functionalized ZnO nanotubes may be used for the detection of iodide ion in environmental water samples, pharmaceutical products and other real samples.
The correlation between radiative surface defect states and high color rendering index from ZnO nanotubes
Sadaf Jamil,Israr Muhammad,Nur Omer,Willander Magnus
Nanoscale Research Letters , 2011,
Abstract: Combined surface, structural and opto-electrical investigations are drawn from the chemically fashioned ZnO nanotubes and its heterostructure with p-GaN film. A strong correlation has been found between the formation of radiative surface defect states in the nanotubes and the pure cool white light possessing averaged eight color rendering index value of 96 with appropriate color temperature. Highly important deep-red color index value has been realized > 95 which has the capability to render and reproduce natural and vivid colors accurately. Diverse types of deep defect states and their relative contribution to the corresponding wavelengths in the broad emission band is suggested.
The origin of the red emission in n-ZnO nanotubes/p-GaN white light emitting diodes
Alvi N,ul Hasan Kamran,Nur Omer,Willander Magnus
Nanoscale Research Letters , 2011,
Abstract: In this article, the electroluminescence (EL) spectra of zinc oxide (ZnO) nanotubes/p-GaN light emitting diodes (LEDs) annealed in different ambients (argon, air, oxygen, and nitrogen) have been investigated. The ZnO nanotubes by aqueous chemical growth (ACG) technique on p-GaN substrates were obtained. The as-grown ZnO nanotubes were annealed in different ambients at 600°C for 30 min. The EL investigations showed that air, oxygen, and nitrogen annealing ambients have strongly affected the deep level emission bands in ZnO. It was concluded from the EL investigation that more than one deep level defect is involved in the red emission appearing between 620 and 750 nm and that the red emission in ZnO can be attributed to oxygen interstitials (Oi) appearing in the range from 620 nm (1.99 eV) to 690 nm (1.79 eV), and to oxygen vacancies (Vo) appearing in the range from 690 nm (1.79 eV) to 750 nm (1.65 eV). The annealing ambients, especially the nitrogen ambient, were also found to greatly influence the color-rendering properties and increase the CRI of the as - grown LEDs from 87 to 96.
Hydrothermal Synthesis of Nanoclusters of ZnS Comprised on Nanowires
Zafar Hussain Ibupoto,Kimleang Khun,Xianjie Liu,Magnus Willander
Nanomaterials , 2013, DOI: 10.3390/nano3030564
Abstract: Cetyltrimethyl ammonium bromide cationic (CTAB) surfactant was used as template for the synthesis of nanoclusters of ZnS composed of nanowires, by hydrothermal method. The structural and morphological studies were performed by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM) techniques. The synthesized ZnS nanoclusters are composed of nanowires and high yield on the substrate was observed. The ZnS nanocrystalline consists of hexagonal phase and polycrystalline in nature. The chemical composition of ZnS nanoclusters composed of nanowires was studied by X-ray photo electron microscopy (XPS). This investigation has shown that the ZnS nanoclusters are composed of Zn and S atoms.
Incorporating β-Cyclodextrin with ZnO Nanorods: A Potentiometric Strategy for Selectivity and Detection of Dopamine
Sami Elhag,Zafar Hussain Ibupoto,Omer Nur,Magnus Willander
Sensors , 2014, DOI: 10.3390/s140101654
Abstract: We describe a chemical sensor based on a simple synthesis of zinc oxide nanorods (ZNRs) for the detection of dopamine molecules by a potentiometric approach. The polar nature of dopamine leads to a change of surface charges on the ZNR surface via metal ligand bond formation which results in a measurable electrical signal. ZNRs were grown on a gold-coated glass substrate by a low temperature aqueous chemical growth (ACG) method. Polymeric membranes incorporating β-cyclodextrin (β-CD) and potassium tetrakis (4-chlorophenyl) borate was immobilized on the ZNR surface. The fabricated electrodes were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The grown ZNRs were well aligned and exhibited good crystal quality. The present sensor system displays a stable potential response for the detection of dopamine in 10 ?2 mol·L ?1 acetic acid/sodium acetate buffer solution at pH 5.45 within a wide concentration range of 1 × 10 ?6 M –1 × 10 ?1 M, with sensitivity of 49 mV/decade. The electrode shows a good response time (less than 10 s) and excellent repeatability. This finding can contribute to routine analysis in laboratories studying the neuropharmacology of catecholamines. Moreover, the metal-ligand bonds can be further exploited to detect DA receptors, and for bio-imaging applications.
Selective Thallium (I) Ion Sensor Based on Functionalised ZnO Nanorods
Z. H. Ibupoto,Syed M. Usman Ali,K. Khun,Magnus Willander
Journal of Nanotechnology , 2012, DOI: 10.1155/2012/619062
Abstract: Well controlled in length and highly aligned ZnO nanorods were grown on the gold-coated glass substrate by hydrothermal growth method. ZnO nanorods were functionalised with selective thallium (I) ion ionophore dibenzyldiaza-18-crown-6 (DBzDA18C6). The thallium ion sensor showed wide linear potentiometric response to thallium (I) ion concentrations ( ?M to ?M) with high sensitivity of 36.87 ± 1.49?mV/decade. Moreover, thallium (I) ion demonstrated fast response time of less than 5?s, high selectivity, reproducibility, storage stability, and negligible response to common interferents. The proposed thallium (I) ion-sensor electrode was also used as an indicator electrode in the potentiometric titration, and it has shown good stoichiometric response for the determination of thallium (I) ion. 1. Introduction When zinc, cadmium, and lead metals are produced by the burning of coal, during this thallium (Tl+1) a poisonous metal ion penetrates into the atmosphere as a major waste product [1]. Thallium are dangerous to all people when they come in contact for very short time with the environment where amount of thallium ions is too much, and due to this they can suffer from the gastrointestinal aggravation as well as nerve problems [2]. The compounds of thallium in which two atoms of thallium (I) are present are very toxic such as thallium sulphate (Tl2SO4), even the compounds containing single atom of thallium as thallium acetate (CH3COOTl) and thallium carbonate (Tl2CO3). Furthermore, thallium (I) ion has the ability to replace K+1 in energizing the few vital enzymes such as ATPase and pyruvate kinase [3]. Thallium (I) is atoxic, when its concentration is very low as about 0.5?mg/100?g of tissue [4]. If thallium (I) ion concentration in the human body is present in excess for long time, this in result brings a change in the blood composition, harms liver, kidney, intestinal, testicular tissue, and causes hair loss [5]. Because of the poisonous effects of thallium (I) ion and its different chemical compounds, it is highly needed to measure the concentration of thallium (I) ion in real biological and environmental samples. There are many methods which have been used for the determination of thallium (I) ion such as spectrophotometric measurement, graphite-furnace atomic absorption spectrometric, flame atomic absorption spectrometric (FAAS) afterwards the extraction [6, 7], respectively, inductive-coupled plasma mass spectrometric (ICP-MS), voltammetry, and potentiometric methods. There are many advantageous of potentiometric technique such as cheap, simple,
ZnO Nanorods Based Enzymatic Biosensor for Selective Determination of Penicillin
Zafar Hussain Ibupoto,Syed Muhammad Usman Ali,Kimleang Khun,Chan Oeurn Chey,Omer Nur,Magnus Willander
Biosensors , 2011, DOI: 10.3390/bios1040153
Abstract: In this study, we have successfully demonstrated the fabrication of a biosensor based on well aligned single-crystal zinc oxide (ZnO) nanorods which were grown on gold coated glass substrate using a low temperature aqueous chemical growth (ACG) method. The ZnO nanorods were immobilized with penicillinase enzyme using the physical adsorption approach in combination with N-5-azido-2-nitrobenzoyloxysuccinimide (ANB-NOS) as cross linking molecules. The potentiometric response of the sensor configuration revealed good linearity over a large logarithmic concentration range from 100 μM to 100 mM. During the investigations, the proposed sensor showed a good stability with high sensitivity of ~121 mV/decade for sensing of penicillin. A quick electrochemical response of less than 5 s with a good selectivity, repeatability, reproducibility and a negligible response to common interferents such as Na 1+, K 1+, d-glucose, l-glucose, ascorbic acid, uric acid, urea, sucrose, lactose, glycine, penicilloic acid and cephalosporins, was observed.
Study of the Distribution of Radiative Defects and Reabsorption of the UV in ZnO Nanorods-Organic Hybrid White Light Emitting Diodes (LEDs)
Ijaz Hussain,Nargis Bano,Sajjad Hussain,Yousuf Soomro,Omer Nur,Magnus Willander
Materials , 2011, DOI: 10.3390/ma4071260
Abstract: In this study, the low temperature aqueous chemical growth (ACG) method was employed to synthesized ZnO nanorods to process-organic hybrid white light emitting diodes (LEDs) on glass substrate. Electroluminescence spectra of the hybrid white LEDs demonstrate the combination of emission bands arising from radiative recombination of the organic and ZnO nanorods (NRs). Depth resolved luminescence was used for probing the nature and spatial distribution of radiative defects, especially to study the re-absorption of ultraviolet (UV) in this hybrid white LEDs structure. At room temperature the cathodoluminescence (CL) spectra intensity of the deep band emission (DBE) is increased with the increase of the electron beam penetration depth due to the increase of defect concentration at the ZnO NRs/Polyfluorene (PFO) interface and probably due to internal absorption of the UV. A strong dependency between the intensity ratio of the UV to the DBE bands and the spatial distribution of the radiative defects in ZnO NRs has been found. The comparison of the CL spectra from the PFO and the ZnO NRs demonstrate that PFO has a very weak violet-blue emission band, which confirms that most of the white emission components originate from the ZnO NRs.
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