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Search Results: 1 - 10 of 401087 matches for " M. Willander "
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Non-Enzymatic Glucose Sensor Based on the Novel Flower Like Morphology of Nickel Oxide  [PDF]
Z. H. Ibupoto, K. Khun, V. Beni, M. Willander
Soft Nanoscience Letters (SNL) , 2013, DOI: 10.4236/snl.2013.34A013
Abstract: In this study, novel nickel oxide (NiO) flowers like nanostructures were fabricated onto gold coated glass substrate by hydrothermal method using high alkaline pH medium. The structural study of nickel oxide nanostructures was performed by scanning electron microscopy (SEM) and X-ray differaction (XRD) techniques. Nickel oxide nanostructures are highly dense, uniform and possess good crystalline quality. The so prepared structures were investigated for their electrochemical properties by cyclic voltammetry and amperometric techniques. The nickel oxide flower like morphology has shown good electrochemical performances for the oxidation of glucose. The presented sensing material was able to detected glucose in a wide range of concentration of 0.001 mM to 8 mM with a high sensitivity (123 μmA/mM) and regression coefficient of 0.99. Moreover, the NiO nanostructures based sensor is highly reproducible, stable, exhibiting a fast response time and selective in the response. All the obtained results indicate the potential use of this material in the development of enzyme free sensors for the detection of glucose.
QUANTUM MECHANICAL MODEL AND SIMULATION OF GaAs/AlGaAs QUANTUM WELL INFRARED PHOTO-DETECTOR-Ⅰ OPTICAL ASPECTS
QUANTUM MECHANICAL MODEL AND SIMULATION OF GaAs/AlGaAs QUANTUM WELL INFRARED PHOTO- DETECTOR-Ⅰ OPTICAL ASPECTS

Fu Y,Willander M,
Fu Y
,Willander M

红外与毫米波学报 , 2002,
Abstract: IntroductionInfrareddetectortechniquehasbeenakeyfactorinthedevelopmentoftheinfraredtechnologyformorethan 4 0 years .Since 1970 ,semiconductorslikeInSbandHgCdTehavebeentheprincipalmaterialsforvariousinfrareddetectorapplications .Theformatoftheinfrareddetectormotivatedbysmartthermalimagingsystemchangedfromsingleelementdevicetofocalplanarrays(FPAs)inthemiddleof 80’s 1].Today’stechnologyofinfrareddetectorconcentrateslargelyonfocalplanarrays ,expeciallyforsensitive ,homogeneousandlargeformatscaledevices .HgCdTe...
The Semantic Representation of Event Information Depends on the Cue Modality: An Instance of Meaning-Based Retrieval
Kristina Karlsson, Sverker Sikstr?m, Johan Willander
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0073378
Abstract: The semantic content, or the meaning, is the essence of autobiographical memories. In comparison to previous research, which has mainly focused on the phenomenological experience and the age distribution of retrieved events, the present study provides a novel view on the retrieval of event information by quantifying the information as semantic representations. We investigated the semantic representation of sensory cued autobiographical events and studied the modality hierarchy within the multimodal retrieval cues. The experiment comprised a cued recall task, where the participants were presented with visual, auditory, olfactory or multimodal retrieval cues and asked to recall autobiographical events. The results indicated that the three different unimodal retrieval cues generate significantly different semantic representations. Further, the auditory and the visual modalities contributed the most to the semantic representation of the multimodally retrieved events. Finally, the semantic representation of the multimodal condition could be described as a combination of the three unimodal conditions. In conclusion, these results suggest that the meaning of the retrieved event information depends on the modality of the retrieval cues.
Many-body effects in transport through open systems: pinning of resonant levels
S. Ihnatsenka,I. V. Zozoulenko,M. Willander
Physics , 2007,
Abstract: The role of electron-electron interaction in transport properties of open quantum dots is studied. The self-consistent full quantum mechanical magnetotransport calculations within the Hartree, Density Functional Theory and Thomas-Fermi approximations were performed where a whole device, including the semi-infinitive leads, is treated on the same footing (i.e. the electron-electron interaction is accounted for both in the leads as well as in the dot region). The main finding of the present paper is the effect of pinning of the resonant levels to the Fermi energy due to the enhanced screening. Our results represent a significant departure from a conventional picture where a variation of external parameters (such as a gate voltage, magnetic field, etc.) causes the successive dot states to sweep past the Fermi level in a linear fashion. We instead demonstrate highly nonlinear behavior of the resonant levels in the vicinity of the Fermi energy. The pinning of the resonant levels in open quantum dots leads to the broadening of the conduction oscillations in comparison to the one electron picture. The effect of pinning becomes much more pronounced in the presence of the perpendicular magnetic field. This can be attributed to the enhanced screening efficiency because of the increased localization of the wave function. The strong pinning of the resonant energy levels in the presence of magnetic field can have a profound effect on transport properties of various devices operating in the edge state transport regime. We also critically examine an approximation often used in transport calculations where an inherently open system is replaced by a corresponding closed one.
Semiconductor ZnO Nano-Rods Thin Film Grown on Silver Wire for Hemoglobin Biosensor Fabrication  [PDF]
I. K. Battisha, H. A. Wahab, A. A. Salama, A. A. El Saeid, M. Willander, O. Nur
New Journal of Glass and Ceramics (NJGC) , 2015, DOI: 10.4236/njgc.2015.52002
Abstract: Wurtzite hexagonal ZnO semiconductor nano-rods (NRs) thin films were grown on silicon substrates and silver wire with diameter equal 68 nm. Sol gel (SG) and aqueous chemical growth (ACG) methods by two steps of preparation (seed layers and nano-rod growth) are used for samples preparation. The structural and morphological properties are evaluated using X-ray diffraction (XRD) and scanning electron microscope (SEM). The proposed iron ion sensor has shown good linearity for a wide concentration range from 0.078 M/L to 0.26 M/L of iron ions. The results show that the electrode is highly sensitive to iron ions with a slope around 47.8 mV/decade with a regression coefficient R2 = 0.96.
Study of Radiative Defects Using Current-Voltage Characteristics in ZnO Rods Catalytically Grown on 4H-p-SiC
N. Bano,I. Hussain,O. Nur,M. Willander,P. Klason
Journal of Nanomaterials , 2010, DOI: 10.1155/2010/817201
Abstract: High-quality ZnO rods were grown by the vapour-liquid-solid (VLS) technique on 4H-p-SiC substrate. The current transport mechanisms of the diodes at room temperature (RT) have been explained in term of the space-charge-limited current model based on the energy band diagram of ZnO rods/4H-p-SiC heterostructure. The tunneling mechanism via deep-level states was found to be the main conduction process at low-applied voltage but at trap-filled limit voltage all traps are filled and the space-charge-limited current conduction dominated the current transport. From the RT current voltage measurements, the energy of the deep level trap and the trap concentration were obtained as ?eV and , respectively. The deep level states observed correspond to zinc interstitial ( ), responsible for the violet emission. 1. Introduction Zinc oxide (ZnO) with wurtzite structure has a large direct bandgap around 3.4?eV, and a large exciton binding energy (60?meV), has recently attracted global interest, especially in its nanostructure form [1]. This material is famous for its photonic and electronic applications such as UV light emitters/detectors and as high-power and high-temperature devices [2, 3]. ZnO has a number of other advantages compared to other wide band gap semiconductors including high-thermal/chemical stabilities; the possibility of wet chemical etching and existence of large area wafers have all led to the demonstration of ZnO as an alternative material to nitride semiconductors [2, 4]. Moreover, ZnO in its nanostructure form possesses self-organization growth property which facilitates the growth of ZnO nanostructures on any substrates such as glass, plastic, Si, GaN, AlGaN, and SiC. Among these materials 4H-SiC is a good candidate for the growth of n-ZnO rods because it has a similar energy bandgap. ZnO possesses a rich family of nanostructures such as nanorods (NRs), nanoparticles, nanotips, and nanoneedles, as some examples [2, 5–7]. All such nanostructures have been successfully synthesized and have attracted interest because they can be used as building blocks for different future optoelectronic devices. These nanostructures have many advantages among which are large surface area to volume ratio, good crystal quality and unique photonic properties [8, 9]. So far, among these structures, rods of ZnO is grown with relatively better crystalline quality with lower defect density compared to bulk and thin films due to their small foot print and the release of strain and stress due to the large surface area to volume ratio. At the same time, both ends of ZnO rods
Development of Galactose Biosensor Based on Functionalized ZnO Nanorods with Galactose Oxidase
K. Khun,Z. H. Ibupoto,O. Nur,M. Willander
Journal of Sensors , 2012, DOI: 10.1155/2012/696247
Abstract: The fabrication of galactose biosensor based on functionalised ZnO nanorods is described. The galactose biosensor was developed by immobilizing galactose oxidase on ZnO nanorods in conjunction with glutaraldehyde as a cross-linker molecule. The IRAS study provided evidence for the interaction of galactose oxidase with the surface of ZnO nanorods. The electromotive force (EMF) response of the galactose biosensor was measured by potentiometric method. We observed that the proposed biosensor has a linear detection range over a concentration range from 10 mM to 200 mM with good sensitivity of 89.10±1.23 mV/decade. In addition, the proposed biosensor has shown fast time response of less than 10 s and a good selectivity towards galactose in the presence of common interferents such as ascorbic acid, uric acid, glucose, and magnesium ions. The galactose biosensor based on galactose oxidase immobilized ZnO nanorods has a shelf life more than four weeks.
Intracellular ZnO Nanorods Conjugated with Protoporphyrin for Local Mediated Photochemistry and Efficient Treatment of Single Cancer Cell
Kishwar S,Asif MH,Nur O,Willander M
Nanoscale Research Letters , 2010,
Abstract: ZnO nanorods (NRs) with high surface area to volume ratio and biocompatibility is used as an efficient photosensitizer carrier system and at the same time providing intrinsic white light needed to achieve cancer cell necrosis. In this letter, ZnO nanorods used for the treatment of breast cancer cell (T47D) are presented. To adjust the sample for intracellular experiments, we have grown the ZnO nanorods on the tip of borosilicate glass capillaries (0.5 μm diameter) by aqueous chemical growth technique. The grown ZnO nanorods were conjugated using protoporphyrin dimethyl ester (PPDME), which absorbs the light emitted by the ZnO nanorods. Mechanism of cytotoxicity appears to involve the generation of singlet oxygen inside the cell. The novel findings of cell-localized toxicity indicate a potential application of PPDME-conjugated ZnO NRs in the necrosis of breast cancer cell within few minutes.
Superfluidity of two- dimensional excitons in flat and harmonic traps
Yu. E. Lozovik,I. L. Kurbakov,M. Willander
Physics , 2007, DOI: 10.1016/j.physleta.2007.01.080
Abstract: Superfluid exciton density and superfluid transition (crossover) temperature are calculated for 2D excitons in large-size flat and harmonic traps. A generalized local density approximation for the Kosterlitz-Thouless theory is developed.
Spin relaxation in asymmetrical heterostructures
N. S. Averkiev,L. E. Golub,M. Willander
Physics , 2000,
Abstract: Electron spin relaxation caused by the D'yakonov-Perel' mechanism is investigated theoretically in asymmetrical A$_3$B$_5$ heterostructures. The total spin relaxation anisotropy is demonstrated for a wide range of structure parameters and temperatures. The spin relaxation rates dependences are derived for GaAs-based heterojunction and triangular quantum well. The calculations show a few orders of magnitude difference in spin relaxation times.
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