Sari, Iran
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Khordad R.,Yasouj University
Optical and Quantum Electronics | Year: 2014

In this work, we have studied the optical properties of a GaAs/Al x}xGa1-x As T-shaped quantum wire. In this regard, we have obtained the refractive index change and absorption coefficient. We have also studied the temperature effect on absorption coefficient. The results show that the refractive index change and absorption coefficient decrease and shift towards higher energies when temperature increases. Finally, to check our results, we have compared the absorption coefficient obtained from this work with experimental data at 5 K. Our theoretical prediction has some deviations with experimental data. © 2013 Springer Science+Business Media New York.


The present study seeks to scrutinize the optical properties of an ellipsoidal quantum dot (EQD) containing an electron in the presence of an external electric field and a donor (acceptor) impurity. In this regard, the perturbation theory is used and for different values of the confinement strength and the electric field, the linear, nonlinear and total absorption coefficients are calculated as functions of the incident photon energy. The oscillator strength between the ground and first excited states in the EQD is also calculated in terms of the confinement strength. The results show that the optical properties of an EQD decrease with increases in the ellipticity constant and electric field. © 2011 Elsevier Ltd. All rights reserved.


Khordad R.,Yasouj University
Solid State Sciences | Year: 2013

In the present work, we have considered a GaAs/Ga1-xAl xAs V-shaped quantum wire with a hydrogenic donor impurity at the center. First, the Schrödinger equation is analytically solved without the impurity. Second, we have used variational approximation to obtain the ground state binding energy. Third, the spin-orbit interaction (SOI) is studied by the perturbation theory. We also have investigated the effect of pressure on the binding energy and SOI in this quantum wire. According to the obtained results, it is found that i) the binding energy increases with increasing pressure, ii) the level splitting increases by increasing pressure, iii) the splitting decreases with increasing wire size. © 2013 Elsevier Ltd. All rights reserved.


Khordad R.,Yasouj University
Journal of Luminescence | Year: 2013

In the present paper, the optical properties of a InAs quasi-one- dimensional (1D) quantum wire are studied under an external magnetic field parallel to the z-direction and the Rashba spin-orbit interaction (SOI). For this purpose, we have used analytical expressions for optical properties obtained by the compact-density matrix formalism. In this work, we have investigated the intersubband optical absorption coefficients and refractive index changes as a function of applied magnetic field (B) and strength of the SOI. According to the obtained results, it is found that (i) The total refractive index changes decrease and shift towards lower energies when the magnetic field and strength of the SOI increases. (ii) The total absorption coefficient decreases and shift towards lower energies as the magnetic field and strength of the SOI decreases. © 2012 Elsevier B.V. All rights reserved.


We study in this paper the direct interband transitions in quantum pseudodot system under the influence of an external magnetic field. We obtain the analytical expressions for the light interband absorption coefficient and threshold frequency of absorption as the functions of applied magnetic field and geometrical size of quantum pseudodot system. We study the absorption threshold frequency (ATF) at small and high applied magnetic field and also as a function of size of quantum pseudodot. According to the results obtained from the present work, we find that (i) the ATF is linear at large magnetic field. (ii) It is nonlinear at small magnetic field. (iii) The ATF depends on the geometrical size of quantum pseudodot and decreases when the size of quantum pseudodot increases. Therefore, the magnetic field and quantum pseudodot size play important roles in the ATF. © 2010 Elsevier Masson SAS. All rights reserved.


Khordad R.,Yasouj University
Physica B: Condensed Matter | Year: 2012

In the present work, we intend to study the pressure effect on optical properties of spherical quantum dots by using the modified Gaussian potential. In this regard, the linear, nonlinear and total intersubband absorption coefficients and refractive index changes are investigated for different hydrostatic pressures. According to the results obtained from the present work, it is deduced that: (i) the linear, nonlinear and total refractive index changes decrease and shift towards higher energies when the pressure increases and (ii) the linear, nonlinear and total absorption coefficients increase and shift towards higher energies by increasing the pressure. © 2012 Elsevier B.V. All rights reserved.


Khordad R.,Yasouj University
European Physical Journal B | Year: 2010

In this work, the diamagnetic susceptibility and the binding energy of a hydrogenic donor impurity both in the parabolic and non-parabolic conduction band models have been calculated within the effective mass approximation for a V-groove GaAs/Ga 1- x Al x As quantum wire. According to the results obtained from the present work reveals that (i) the value of diamagnetic susceptibility due to the non-parabolicity effect is higher than that of parabolicity effect; (ii) the values of diamagnetic susceptibility and binding energy due to the non-parabolicity effect is not appreciable at low Al mole fractions; (iii) the diamagnetic susceptibility approaches to the bulk value both in L → 0 or L → ∞; (iv) the effect of non-parabolocity is not appreciable in the binding energy and energy dependent effective mass, for energies lower than 50 MeV. © 2010 EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg.


The catalytic application of a novel manganese-containing periodic mesoporous organosilica with ionic-liquid framework (Mn@PMO-IL) in the Biginelli reaction was investigated. First, the Mn@PMO-IL nanocatalyst was prepared and characterized by TEM, SEM, X-ray photoelectron spectroscopy, and nitrogen-sorption analysis. The catalyst was then used in the one-pot Biginelli condensation of various aldehydes with urea and alkyl acetoacetates under solvent-free conditions. The corresponding dihydropyrimidone products were obtained in high to excellent yields and selectivities at short reaction times. Moreover, the catalyst was recovered and successfully reused many times with no notable decrease in activity and selectivity. Heterogeneous Biginelli catalyst: A manganese-containing periodic mesoporous organosilica with ionic-liquid framework (Mn@PMO-IL) was prepared, characterized, and used as a nanocatalyst in the Biginelli reaction. This catalyst showed excellent reactivity and selectivity in the Biginelli condensation of various aldehydes with urea and alkyl acetoacetates. Moreover, the catalyst could be recovered and reused at least 14 times with no decrease in activity and selectivity (see scheme). © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Adsorption of Sunset yellow (SY) onto cadmium hydroxide nanowires loaded on activated carbon (Cd(OH) 2-NW-AC) and silver nanoparticles loaded on activated carbon (Ag-NP-AC) was investigated. The effects of pH, contact time, amount of adsorbents, initial dye concentration, agitation speed and temperature on Sunset yellow removal on both adsorbents were studied. Following the optimization of variables, the experimental data were fitted to different conventional isotherm models like Langmuir, Freundlich, Tempkin and Dubinin-Radushkevich (D-R) based on linear regression coefficient R 2 the Langmuir isotherm was found to be the best fitting isotherm model and the maximum monolayer adsorption capacities calculated based on this model for Cd(OH) 2-NW-AC and Ag-NP-AC were found to be 76.9 and 37.03 mg g -1 at room temperatures, respectively. The experimental fitting of time dependency of adsorption of SY onto both adsorbent shows the applicability of second order kinetic model for interpretation of kinetic data. The pseudo-second order model best fits the adsorption kinetics. Thermodynamic parameters such as enthalpy, entropy, activation energy, sticking probability, and Gibb's free energy changes were also calculated. It was found that the sorption of SY over (Cd(OH) 2-NW-AC) and (Ag-NP-AC) was spontaneous and endothermic in nature. Efficiency of the adsorbent was also investigated using real effluents and more than 95% SY removal for both adsorbents was observed. © 2012 Elsevier B.V. All rights reserved.


Khordad R.,Yasouj University
Superlattices and Microstructures | Year: 2013

In the present work, we have considered an exciton confined in a spherical quantum dot with the modified Gaussian potential (A. Gharaati, R. Khordad, Superlatt. Microstruct. 48 (2010) 276). We have tried to study the electronic and optical properties of the system by using the numerical diagonalization of the Hamiltonian matrix. For this purpose, we have calculated the binding energy of the ground and first excited states as a function of the quantum dot radius. We have also computed the linear, nonlinear and total absorption coefficient between the ground and the first excited states. It is found that the quantum dot radius has an important role on the binding energy and absorption coefficient. © 2012 Elsevier Ltd. All rights reserved.

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