• ABDULLAH G AL-SEHEMI

      Articles written in Bulletin of Materials Science

    • Exploring the electronic, optical and charge transfer properties of acene-based organic semiconductor materials

      AHMAD IRFAN ABDULLAH G AL-SEHEMI MOHAMMED A ASSIRI MUHAMMAD WASEEM MUMTAZ

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      In order to tune the optoelectronic and charge transfer properties of 4,6-di(thiophen-2-yl)pyrimidine (1), some new compounds were designed, i.e., 4,6-bis(benzo[$b$]thiophen-2-yl)pyrimidine (2), 4,6-bis(naphtho[2,3-b]thiophen-2-yl)pyrimidine (3), 4,6-bis(anthra[2,3-b]thiophen-2-yl)pyrimidine (4), 4,6-bis(tetraceno[2,3-$b$]thiophen-2-yl)pyrimidine (5) and 4,6-bis(pentaceno[2,3-$b$]thiophen-2-yl)pyrimidine (6). Compounds 2–6 were designed by assimilation of benzene, naphthalene, anthracene, tetracene and pentacene, respectively at both ends of compound 1. Integration of oligocene end cores reduces the energy gap resulting in a red shift in the absorption and fluorescence emission spectra. The legible intra-molecularcharge transfer is significant from electron-rich moieties to the electron-deficient core (pyrimidine). The elongation of $\pi$-conjugation led to escalate the electron affinity, lower the ionization potential and hole reorganization energy. The hole reorganization energies of compounds 3–6 exposed that these materials would be effective hole transport contenders to be used in diverse semiconductor devices.

    • Electrical, mechanical and dynamic properties of ternary composites from acrylonitrile butadiene rubber and conductive fillers

      ABDULLAH G AL-SEHEMI AHMED A AL-GHAMDI NIKOLAY T DISHOVSKY PETRUNKA A MALINOVA NIKOLAY T ATANASOV GABRIELA L ATANASOVA

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      This paper presents comparative investigations on dual and ternary composites based on nitrile butadiene rubber. These composites were filled with carbon black and nickel powder at various ratios with each filler or with a combination of both. The focus of this study is on the electrical, mechanical and dynamic properties of the materials as influenced by the loading rate, applied pressure and bending degree have on the specific volume electrical resistivity. The investigations of the dynamic properties view the effect that the amount and chemical nature of the fillers have on the storage modulus and the tangent of the mechanical loss angle. It has been established that the specific characteristics of each of the fillers (particle size, specific surface, tendency to aggregate and agglomerate, interaction with the elastomeric matrix) have the greatest impact on composite properties. Scanning electron microscopy studies of the fillers and composites also confirm the results obtained.

    • Synthesis, characterization and quantum chemical study of optoelectronic nature of ferrocene derivatives

      AHMAD IRFAN FIRAS KHALIL AL-ZEIDANEEN ISHTIAQ AHMED ABDULLAH G AL-SEHEMI MOHAMMED A ASSIRI SAMI ULLAH GHULAM ABBAS

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      Two new ferrocene derivatives N-(2-hydroxy-5-methylphenyl) ferrocylideneamine (Fe1) and N-(2-hydroxy-5-chlorophenyl) ferrocylideneamine (Fe2) have been synthesized to study the effect on electronic, optical and charge transfer properties while changing the electron donating group with electron withdrawing group. The synthesized compounds were characterized by different spectroscopic (FTIR, UV–Vis, ${}^1$H NMR, ${}^{13}$C NMR) and spectrometric (EI) techniques. Thegeometries for ground and excited states were optimized by density functional theory (DFT/B3lyp/6-31G$^{**}$, LANL2DZ) and time-dependent DFT (TD-B3lyp/6-31G$^{**}$, LANL2DZ) levels, respectively. The absorption, fluorescence and phosphorescence spectra were estimated using TD-B3LYP and TD-wB97XD functionals and 6-31G$^{**}$ basis set for C, H, N, O and LANL2DZ for Fe atoms in dichloromethane.

    • Design and synthesis of organic dyes with various donor groups: promising dyes for dye-sensitized solar cells

      ABDULLAH G AL-SEHEMI SHUHRAH ALI S ALLAMI ABUL KALAM

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      The present work is involved in the computational and experimental studies of organic dyes and their applications as dye-sensitized solar cells (DSSCs). This comprised the study of three hydrazone-based sensitizers ($E$)-2-cyano-$N'$-((2-hydroxynaphthalen-1-yl)methylene)acetohydrazide (CHMA), ($E$)-2-cyano-$N'$-(4-(dimethylamino)benzylidene)acetohydrazide (CDBA), ($E$)-$N'$-(anthracen-9-ylmethylene)-2-cyanoacetohydrazide (AMCH) that have been prepared and confirmed by means of several analytical procedures like Fourier transform infrared, UV–visible and nuclear magnetic resonance techniques to investigate the best possible selection for DSSCs by computational and experimental techniques. The computational methods are applied to optimize the structures of prepared organic dyes via density functional theory (DFT) method at B3LYP/6-311G(p,d) level of theory. The time-dependent DFT (TD-B3LYP/6-311G**) was used with and without solvent to find out the absorption spectra and matched with the experimental data and the electro-optical and reorganization energies of prepared dyes were further investigated. The results revealed that the prepared dyes would be better sensitizers for DSSCs because of small highest-occupied molecular orbital–lowest unoccupied molecular orbital energy gap. Moreover, on the basis of the above results, we fabricated the devices via the doctor blade method to study the photovoltaic performance with the prepared dyes (CHMA, CDBA and AMCH). The dye AMCH exhibited the maximum efficiency with commercial TiO$_2$.

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      Posted on October 12, 2020

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