Harraz F.A.,Najran University |
Harraz F.A.,Central Metallurgical Research and Development Institute
Sensors and Actuators, B: Chemical | Year: 2014
The use of porous silicon (PSi) as a sensor for detection of various analytes is reviewed. The optical or electrical properties of PSi are key sensing parameters that have been used in many chemical and biological sensing applications. PSi is a promising candidate due to ease of fabrication, large surface area, various accessible pore sizes and morphologies, controllable surface modification and its compatibility with conventional silicon processing technology. The adsorption of chemical or biological molecules into the pores modifies the electrical and/or optical properties, allowing convenient and sensitive measurement approach. In this review, we provide a critical assessment of the development of PSi as a promising material for chemical and biosensing applications. Formation procedures of PSi with various pore sizes and morphologies are firstly given. Surface properties and structural characteristics of the material are briefly described. The recent progress on utilization of such porous structures in chemical and biosensing applications is then addressed in the context of surface chemistry effects and nanostructures, measuring approaches, operating concepts and device sensitivity and stability. Finally, concluding remarks with existing challenges that hinder the material for commercial use are highlighted. © 2014 Elsevier B.V.
Bouarissa N.,Najran University
Journal of Computational and Theoretical Nanoscience | Year: 2013
We calculated size-dependent quantum well lattice-vibration properties for a semiconductor nanostructured InP, within the framework of the pseudopotential approach. Computed results on energy band gap, dielectric constant, and phonon frequencies from our investigations showed that noticeable differences relative to the bulk values are seen only when the quantum well size is smaller than about 9 nm. A parametrization of the energy gap and phonon frequencies versus quantum well size is provided. The information gathered by the present study may be useful for obtaining derived lattice vibration properties that were not possible in bulk InP. Copyright © 2013 American Scientific Publishers All rights reserved.
Ismail A.A.,Central Metallurgical Research and Development Institute |
Ismail A.A.,Najran University |
Ismail A.A.,Leibniz University of Hanover |
Bahnemann D.W.,Leibniz University of Hanover
Solar Energy Materials and Solar Cells | Year: 2014
Hydrogen production from water using a catalyst and solar energy is an ideal future fuel source. The search for suitable semiconductors as photocatalysts for water splitting into molecular hydrogen and oxygen has been considered to be an urgent subject for our daily life. In this review, we aim to focus on the research efforts that have been made so far for H2 generation from water splitting by UV and visible light-driven photocatalysis. A number of synthetic modification methods for adapting the electronic structure to enhance the charge separation in the photocatalyst materials are discussed. Sacrificial reagents and electron mediators for the overall water splitting are also reviewed. The quantum efficiency of photocatalyst materials upon visible and UV illumination will be reviewed, summarized and discussed. © 2014 Elsevier B.V.
Eid K.M.,Ain Shams University |
Ammar H.Y.,Najran University
Applied Surface Science | Year: 2011
The adsorption of sulfur dioxide molecule (SO2) on Li atom deposited on the surfaces of metal oxide MgO (1 0 0) on both anionic and defect (Fs-center) sites located on various geometrical defects (terrace, edge and corner) has been studied using density functional theory (DFT) in combination with embedded cluster model. The adsorption energy (Eads) of SO2 molecule (S-atom down as well as O-atom down) in different positions on both of O-2 and Fs sites is considered. The spin density (SD) distribution due to the presence of Li atom is discussed. The geometrical optimizations have been done for the additive materials and MgO substrate surfaces (terrace, edge and corner). The oxygen vacancy formation energies have been evaluated for MgO substrate surfaces. The ionization potential (IP) for defect free and defect containing of the MgO surfaces has been calculated. The adsorption properties of SO2 are analyzed in terms of the Eads, the electron donation (basicity), the elongation of S-O bond length and the atomic charges on adsorbed materials. The presence of the Li atom increases the catalytic effect of the anionic O-2 site of MgO substrate surfaces (converted from physisorption to chemisorption). On the other hand, the presence of the Li atom decreases the catalytic effect of the Fs-site of MgO substrate surfaces. Generally, the SO2 molecule is strongly adsorbed (chemisorption) on the MgO substrate surfaces containing Fs-center. © 2011 Elsevier B.V. All rights reserved.
Al-Mattarneh H.,Najran University
Construction and Building Materials | Year: 2014
Introducing steel fiber to concrete materials enhances the performance of concrete structures in terms of their flexural strength, impact load resistance and limited crack propagation. The fiber concrete performance depends on the fiber content, dispersion and orientation. No standard method is currently available to evaluate these three parameters, especially in situ. This paper describes the feasibility of using a surface electromagnetic sensor as nondestructive radio wave test system to determine the concentration, dispersion and orientation of steel fibers in the concrete. The system needs to contact the concrete material and requires only one face of the concrete material for testing. The surface electromagnetic sensor can slide on the fiber concrete surface and measure the dielectric properties at various locations to assess the fiber distribution. In addition, the sensor can rotate to polarize the electric field to various angles and evaluate the fiber orientation. The mean and standard deviation of the measured dielectric properties increase with increasing fiber content and fiber dispersion. The results indicate that the dielectric properties are maximal when the fiber is oriented in the direction of the electric field and minimal when perpendicular. A simple linear model was established to determine the fiber content and flexural strength from the measured electromagnetic properties. © 2014 Elsevier Ltd. All rights reserved.