Mohd. Shahid Khan

Electronic absorption spectra of amino substituted anthraquinones and their interpretation using the ZINDO/S and AM1 methods.

Electronic absorption spectra of 1,2-diamino-9,10-anthraquinone (12DAAQ), 1,4-diamino-9,10-anthraquinone (14DAAQ), 1,5-diamino-9,10-anthraquinone (15DAAQ), and 2,6-diamino-9,10-anthraquinone (26DAAQ) are investigated. Molecular geometries of the amino anthraquinones in the ground state are optimized using the semiempirical ZINDO/1 and AM1 methods without imposing any symmetry constraints. The ground state geometries of all the molecular systems are found to be planar. For interpretation of the spectra, ZINDO/S-CI and AM1-CI calculations employing singly excited configuration using the completely optimized geometry are carried out. Such calculations on the electronic spectra of amino anthraquinones are carried out for the first time. On the basis of these calculations, the assignment of the spectra are successfully made.

Experimental and theoretical investigations of nonlinear optical properties of 1,4-Diamino-9,10-Anthraquionone.

Nonlinear optical properties of 1,4-Diamino-9,10-Anthraquinone dye in solution at different concentrations are investigated by utilizing single beam Z-scan technique using a low power continuous wave laser (λ=532 nm). The anthraquinone dye is found to exhibit self-defocusing and reverse saturable absorption behavior. Effect of concentration on nonlinear refractive index and nonlinear absorption coefficient are also studied. The nonlinear absorption coefficient (β) and nonlinear refractive index (n2) have been evaluated from the open aperture and closed aperture Z-scan data and are found to increase with increase in concentration. The order of magnitude obtained for nonlinear refractive index and nonlinear absorption coefficient are found to be 10(-6) esu and 10(-4) m/W, respectively. The optical limiting behavior and induced self-diffraction patterns are also observed. To have a theoretical insight of nonlinear optical properties of 1,4-Diamino-9,10-Anthraquinone, first hyperpolarizability (β) is also evaluated by using quantum chemical calculations employing DFT method using 6-311 G basis set. The results obtained confirm the nonlinear optical behavior of 1,4-Diamino-9,10-Anthraquinone dye.

Retracted: Computational study of hydrogen adsorption on potassium-decorated boron nitride nanotubes

RetractionThis article was mistakenly published twice. For this reason this duplicate article has now been retracted. For citation purposes please cite the original:http://www.inljournal.com/?_action=articleInfo&article=19AbstractWe have investigated the potassium-decorated boron nitride nanotubes for hydrogen storage using semi-empirical AM1 method. The ultra narrow (3,3) and (5,0) boron nitride nanotubes of same diameter but of different chirality have been used. Both of them show hydrogen storage greater than 8 % by weight. Density of states have been calculated, and it is found that the presence of alpha density of state of potassium results in smaller energy gap; as a result of which, the conductivity of the potassium-decorated boron nitride nanotubes is enhanced as compared to pristine boron nitride nanotubes. Charge decomposition analysis showed that there is significant transfer of charge from adsorbate potassium to boron nitride nanotubes; the same is also confirmed by Mulliken population analysis. For same diameter, due to different electronic configuration, zigzag tube is found to be slightly more favorable for hydrogen adsorption. The results of the present simulation study suggest that the potassium-decorated boron nitride nanotubes are good candidate for hydrogen adsorption.

Förster's resonance energy transfer between Fullerene C60 and Coumarin C440

The interaction between Coumarin C440 with Fullerene C60 has been studied by fluorescence and time resolved spectroscopic techniques. The Coumarin C440-Fullerene C60 pair shows Forsters resonance energy transfer (FRET) from Coumarin C440 (donor) to Fullerenes C60 (acceptor). The FRET efficiency of this pair increases with the increase of the acceptor concentration. The critical energy transfer distance (R0) at which transfer efficiency is 50% is found to be 34Ǻ. Stern-Volmer plot indicates static as well as dynamic quenching. However, the FRET studies show highest efficiency at the critical stage of dimer formation.

Study of self-defocusing, reverse saturable absorption and photoluminescence in anthraquinone PMMA nanocomposite film.

The nanocomposite film of 1,5-diamino-9,10-anthraquinone in poly methyl methacrylate has been fabricated by following guest-host method. Intense reverse saturable absorption and self-defocusing effect have been investigated by employing Z-scan technique with low power CW laser at 532 nm with different intensities for the dye-polymer composite film. The estimated values of nonlinear absorption coefficient β, nonlinear refractive index n2 and third order susceptibility χ((3)) of the composite film are of the order of 10(-3) (m/W), 10(-11) (m(2)/W) and 10(-4) (esu), respectively. The dye molecules have been encapsulated uniformly between molecules of polymer as a nanocomposite with average roughness ∼7.96 nm as characterized by AFM technique. The nanocomposite film also exhibited strong photoluminescence emission when excited with 532 nm. The second order hyperpolarizability of composite film has also been estimated. The evaluated figure of merit W having a value greater than 1, and the results obtained suggest that the composite film of 1,5-diamino-9,10-anthraquinone-PMMA has potential applications in nonlinear optical devices.

Influence of Boron Substitution on Conductance of Pyridine- and Pentane-Based Molecular Single Electron Transistors: First-Principles Analysis

We have investigated the modeling of boron-substituted molecular single-electron transistor (SET), under the influence of a weak coupling regime of Coulomb blockade between source and drain metal electrodes. The SET consists of a single organic molecule (pyridine/pentane/1,2-azaborine/butylborane) placed over the dielectric, with boron (B) as a substituent. The impact of B-substitution on pyridine and pentane molecules in isolated, as well as SET, environments has been analyzed by using density functional theory-based ab initio packages Atomistix toolkit-Virtual NanoLab and Gaussian03. The performance of proposed SETs was analyzed through charging energies, total energy as a function of gate potential and charge stability diagrams. The analysis confirms that the B-substituted pentane (butylborane) and the boron-substituted pyridine (1,2-azaborine) show remarkably improved conductance in SET environment in comparison to simple pyridine and pentane molecules.

Growth of Zn1−x Cd x O nanocrystalline thin films by sol-gel method and their characterization for optoelectronic applications

This paper describes the growth of Cd doped ZnO thin films on a glass substrate via sol-gel spin coating technique. The effect of Cd doping on ZnO thin films was investigated using X-ray diffraction (XRD), UV-Vis spectroscopy, photoluminescence spectroscopy, I–V characteristics and field emission scanning electron microscopy (FESEM). X-ray diffraction patterns showed that the films have preferred orientation along (002) plane with hexagonal wurtzite structure. The average crystallite sizes decreased from 24 nm to 9 nm, upon increasing of Cd doping. The films transmittance was found to be very high (92 to 95 %) in the visible region of solar spectrum. The optical band gap of ZnO and Cd doped ZnO thin films was calculated using the transmittance spectra and was found to be in the range of 3.30 to 2.77 eV. On increasing Cd concentration in ZnO binary system, the absorption edge of the films showed the red shifting. Photoluminescence spectra of the films showed the characteristic band edge emission centred over 377 to 448 nm. Electrical characterization revealed that the films had semiconducting and light sensitive behaviour.

Azole-based compounds as antiamoebic agents: a perspective using theoretical calculations

Diseases caused by protozoal organisms are responsible for significant mortality and morbidity worldwide. Amoebiasis caused by Entamoeba histolytica is an example of such diseases. In the quest for safe and effective antiamoebic agents, several heterocyclic moieties have been reported, out of which members of the azole family (dioxazole, pyrazoline, tetrazole, triazole and thiazolidinone derivatives) have attracted wide attention. This class of heterocyclic compounds have emerged as potential chemotherapeutic agents exhibiting promising antiamoebic activity with a non-cytotoxic nature. In the present article, some important breakthroughs in this area have been discussed. To get an insight at the supra-molecular level, computational studies like Lipinskis and DFT studies were carried out. Potent activity, chemical potential and hardness of the active compounds based on theoretical calculations were explained. The DFT study indicated that the LUMO energy level should lie between −1.34 and −0.54 eV to show high activity. We also observed that the LUMO level was mainly distributed over the 2-methyl 5-nitro imidazole ring in most of the active compounds.

Synthesis and Characterization of Screen Printed Zn0.97Cu0.03O Thick Film for Semiconductor Device Applications

The studies on doped ZnO thick films deposited over large surface area are still a very promising area of research and development. We report characteristic properties of thick film of Zn0.97Cu0.03O prepared by the economic screen printing technique. The film was characterized by XRD, SEM, diffused reflectance, FTIR, and dark resistivity measurement techniques. The XRD and SEM studies revealed polycrystalline, single phase, porous, and granular surface morphology of this Cu doped ZnO thick films. The direct band gap energy of this film determined by diffuse reflectance technique is 3.18 eV. IR transmission spectrum measured in 4000–600 cm−1 region at ambient temperature confirmed the incorporation of Cu2

Effect of polarization on spectral anomalies of diffracted stochastic electromagnetic beams

Theoretical and experimental studies are reported on the effect of polarization on spectral anomalies of diffracted stochastic electromagnetic beams (SEB). To the best of our knowledge we are the first to report experimental results that show the effect of the degree of polarization on spectral anomalies in diffracted SEB. The study might be useful in understanding the spectral behavior of SEB near phase singularities. Moreover, it might provide a sophisticated control mechanism for spectral switching.