6 results on '"Gul Rahman"'
Search Results
2. Synthesis of graphene nanoplatelets/polythiophene as a high performance supercapacitor electrode material
- Author
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Javed Iqbal, Ata Ur Rahman, Zeeshan Nawaz, Muhammad Yaseen, Hamsa Noreen, and Gul Rahman
- Subjects
Supercapacitor ,chemistry.chemical_compound ,Electrode material ,Exfoliated graphite nano-platelets ,chemistry ,Materials Chemistry ,Polythiophene ,Nanotechnology ,General Chemistry ,Catalysis - Abstract
The preparation of a stable, efficient, inexpensive and high capacitance electrode material for supercapacitors is posing great challenges for researchers.
- Published
- 2021
3. Investigating the adsorption mechanism of glycine in comparison with catechol on cristobalite surface using density functional theory for bio-adhesive materials
- Author
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Mohammad Adil Khan, Gul Rahman, Shabeer Ahmad Mian, Uzair Ahmad, Younas Khan, and Shahid Ali
- Subjects
Catechol ,Hydrogen bond ,General Chemical Engineering ,Binding energy ,Inorganic chemistry ,02 engineering and technology ,General Chemistry ,Adhesion ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Cristobalite ,0104 chemical sciences ,chemistry.chemical_compound ,Adsorption ,chemistry ,Glycine ,Molecule ,0210 nano-technology - Abstract
Using periodic Density Functional Theory (DFT) calculations and DFT-based molecular dynamics simulations, we studied the adhesion mechanism of glycine amino acid and the catechol part of L-dopa on the cristobalite surface. The optimized glycine and catechol molecules are initially placed vertically 3 A above the cristobalite surface with a vacuum thickness of approximately 40 A. The catechol adhesion on the cristobalite surface previously studied showed strong binding energy both in dry and wet adsorption. Glycine is the second most abundant amino acid in the mussel adhesive protein, which would have a significant contribution in mussel adhesion. This study of glycine will further enlighten the understanding of marine mussel adhesion. We believe that all the proteins exist in the Mytilus edulis foot protein (mefp) are contributing in this unique and versatile adhesion of marine mussel. We observed that glycine molecules formed four hydrogen bonds with the surface silanols and acted as donors and acceptors. Four hydrogen bond formation is also observed during catechol adhesion on the cristobalite surface. The average binding energy of both molecules on the cristobalite surface lies in the range of hydrogen binding energy. Surface binding energy values of 20.23 and 14.45 kcal mol−1 were obtained for glycine and catechol adsorption, respectively. Including the dispersion energy term further raised the binding energy to 31.29 kcal mol−1 for glycine and 28.58 kcal mol−1 for catechol. The binding energy values suggest that glycine adsorption on the dry cristobalite surface is much stronger as compared to that of catechol.
- Published
- 2016
4. Nitrogen-induced ferromagnetism in BaO
- Author
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Gul Rahman
- Subjects
Condensed Matter - Materials Science ,Materials science ,Condensed matter physics ,Magnetic moment ,Magnetism ,General Chemical Engineering ,Fermi level ,Materials Science (cond-mat.mtrl-sci) ,FOS: Physical sciences ,Astrophysics::Cosmology and Extragalactic Astrophysics ,General Chemistry ,Condensed Matter::Materials Science ,symbols.namesake ,Ferromagnetism ,Condensed Matter::Superconductivity ,Density of states ,symbols ,Antiferromagnetism ,Condensed Matter::Strongly Correlated Electrons ,Density functional theory ,Ground state - Abstract
Density functional theory with local spin density approximation has been used to propose possible room temperature ferromagnetism in N-doped NaCl-type BaO. Pristine BaO is a wide bandgap semiconductor, however, N induces a large density of states at the Fermi level in the nonmagnetic state, which suggests magnetic instability within the Stoner mean field model. The spin-polarized calculations show that N-doped BaO is a true half- metal, where N has a large magnetic moment, which is mainly localized around the N atoms and a small polarization at the O sites is also observed. The origin of magnetism is linked to the electronic structure. The ferromagnetic(FM) and antiferromagnetic (AFM) coupling between the N atoms in BaO reveal that doping N atoms have a FM ground state, and the calculated transition temperature ($T_{C}$), within the Heisenberg mean field theory, theorizes possible room temperature FM in N-doped BaO. Nitrogen also induces ferromagnetism when doping occurs at surface O site and has a smaller defect formation energy than the bulk N-doped BaO. The magnetism of N-doped BaO is also compared with Co-doped BaO, and we believe that N has a greater potential for tuning magnetism in BaO than Co., RSC Adv., 2015, 5, 33674
- Published
- 2015
5. Spin-polarized surface state in Li-doped SnO2(001)
- Author
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Gul Rahman and Naseem Ud Din
- Subjects
Condensed Matter - Materials Science ,Materials science ,Magnetic moment ,Orbital hybridisation ,General Chemical Engineering ,Doping ,Materials Science (cond-mat.mtrl-sci) ,FOS: Physical sciences ,General Chemistry ,Metal ,Condensed Matter::Materials Science ,Crystallography ,Ferromagnetism ,Rutile ,visual_art ,visual_art.visual_art_medium ,Condensed Matter::Strongly Correlated Electrons ,Ground state ,Spin (physics) - Abstract
Using LDA+$U$, we investigate Li-doped rutile SnO$_2$(001) surface. The surface defect formation energy shows that it is easier for Li to be doped at surface Sn site than bulk Sn site in SnO$_2$. Li at surface and sub-surface Sn sites has a magnetic ground state, and the induced magnetic moments are not localized at Li site, but spread over Sn and O sites. The surface electronic structures show that Li at surface Sn site shows $100%$ spin-polarization (half metallic), whereas Li at sub-surface Sn site does not have half metallic state due to Li-Sn hybridized orbitals. The spin-polarized surface has a ferromagnetic ground state, therefore, ferromagnetism is expected in Li-doped SnO$_2$(001) surface., LaTeX files
- Published
- 2014
6. Facile preparation of nanostructured α-Fe2O3 thin films with enhanced photoelectrochemical water splitting activity
- Author
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Oh-Shim Joo and Gul Rahman
- Subjects
Photocurrent ,Materials science ,Nanostructure ,Renewable Energy, Sustainability and the Environment ,Nanotechnology ,General Chemistry ,Substrate (electronics) ,symbols.namesake ,X-ray photoelectron spectroscopy ,Chemical engineering ,symbols ,Water splitting ,General Materials Science ,Particle size ,Thin film ,Raman spectroscopy - Abstract
We report on the use of a facile electrospray technique for the synthesis of α-Fe2O3 thin films on a FTO substrate for photoelectrochemical (PEC) water splitting. The effect of synthesis parameters such as substrate temperature, discharge potential and post-heat treatment on morphology, particle size and PEC performance of α-Fe2O3 films were investigated. With an increase in substrate temperature, the surface morphology of the α-Fe2O3 film was altered from a packed worm-like surface to highly porous nanostructures. XRD analysis revealed that the (110) grain orientation of the film was transformed to the (104) grain orientation at 300 °C, due to the oxidation of the precursor at the surface of the substrate. Raman spectroscopy and XPS analysis indicated the presence of highly pure α-Fe2O3 in the film. By changing the discharge potential, the size of particles in the film was reduced to a minimum of 23 nm. Under optimized conditions the nanostructured α-Fe2O3 films showed a water splitting photocurrent of ∼0.6 mA cm−2 at 1.23 V versus RHE under standard illumination conditions (AM 1.5 G 100 mW cm−2), and an incident photon to current efficiency (IPCE) of 13% at 350 nm (at 1.4 V versus RHE) which are among the best results obtained for undoped α-Fe2O3 photoanodes. This enhanced PEC performance can be attributed to the efficient charge separation at the α-Fe2O3-electrolyte interface due to the larger interfacial area of small-sized particles in the film. This study thus provides a simple route for the synthesis of highly active α-Fe2O3 thin films that can be extended to metal doped films such as Ti-doped α-Fe2O3.
- Published
- 2013
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