Syed Ismat Shah
University of Delaware
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Featured researches published by Syed Ismat Shah.
Applied Physics Letters | 2009
Abdul K. Rumaiz; J. C. Woicik; Eric Cockayne; H. Lin; G. Hassnain Jaffari; Syed Ismat Shah
We have determined the electronic and atomic structure of N doped TiO2 using a combination of hard x-ray photoelectron spectroscopy and first-principles density functional theory calculations. Our results reveal that N doping of TiO2 leads to the formation of oxygen vacancies and the combination of both N impurity and oxygen vacancies accounts for the observed visible light catalytic behavior of N doped TiO2.
Journal of Colloid and Interface Science | 2010
Abdul Faheem Khan; Mazhar Mehmood; Muhammad Aslam; Syed Ismat Shah
Multilayer TiO(2)-Ge thin films have been deposited using electron beam evaporation and resistive heating. The thickness of the TiO(2) layers is 20 nm, while the thickness of the Ge layers varies from 2 to 20 nm with a step of 2 nm away from the substrate. These films were characterized by studying their optical, electrical, and structural properties. The films were annealed at various temperatures up to 500 degrees C for 2 h. The films are amorphous up to an annealing temperature of 400 degrees C, although Raman spectra suggest short-range ordering (and adjustments). The films annealed at 450 and 500 degrees C exhibit X-ray reflections of Ge and anatase TiO(2). Illumination in sunlight increases the conductivity of the as-deposited and annealed films. The band gap of the amorphous films changes from 1.27 to 1.41 eV up to 400 degrees C; the major contribution is possibly through direct transition. Two band gap regimes are clearly seen after 450 and 500 degrees C, which have been assigned to an indirect band gap at about 1.2 eV and a direct band gap at about 1.8 eV. Conductivity of the multilayer films has been higher than that of pure Ge film. The conductivity increases with annealing temperature with abrupt increase at about 380 degrees C. The results imply that the TiO(2)-Ge multilayer films may be employed as heterojunctions with tunable band gap energy as related to quantum confinement effects.
Journal of Applied Physics | 2010
Mustafa Coşkun; Mustafa Korkmaz; Tezer Fırat; G. H. Jaffari; Syed Ismat Shah
In this work, the results of synthesis of core-shell NiFe2O4 nanoparticles and influence of silica coating on the magnetic properties of nanoparticles are presented. Spherical NiFe2O4 nanoparticles were prepared via a normal micelles process. NiFe2O4 nanoparticles homogeneously coated with SiO2 of various shell thickness were synthesized by reverse microemulsion. The interparticle spacing was varied by changing the amount of added tetraethylorthosilicate. The microstructures and morphologies of these nanoparticles were studied by x-ray diffraction and transmission electron microscopy techniques. The magnetic parameters such as saturation magnetizations, blocking temperatures, and magnetic anisotropies have been calculated from dc magnetization and ac susceptibility measurements.
Journal of Physical Chemistry B | 2010
Saima Shabbir; Sonia Zulfiqar; Syed Ismat Shah; Zahoor Ahmad; Muhammad Ilyas Sarwar
Aramid (Ar), produced from the reaction of aromatic diamines and diacid chloride, was reactively compatibilized with amino-functionalized polystyrene (APS) to explore blend morphology and interfacial cohesion. Two blend systems, Ar/PS and Ar/APS, were investigated over a range of pristine polystyrene (PS) or modified APS ratios. Morphology and thermal and mechanical properties were probed to evaluate the effect of amine units of APS on the compatibility with Ar. π-π stacking interactions in tandem with the random distribution of graft attachment locations and polydispersity of graft length in Ar-g-APS copolymer, aided merger of unreacted chains to drive molecular self-assembly process thus fortifying the nanostructured blends. Considerable augmentation of the blend morphology and thermal stability was achieved by incorporation of reactivity into Ar/APS system. A 20 wt % APS-containing blend was found to demonstrate optimum mechanical reinforcement, complemented by the optimal, thermal, and morphological profiles of the same blend. Future prospects are envisaged.
Asian Journal of Andrology | 2015
Michelle A Smith; Rowan Michael; Rolands G. Aravindan; Soma Dash; Syed Ismat Shah; Deni S. Galileo; Patricia A. Martin-DeLeon
Titanium dioxide (TiO 2 ) nanoparticles (TNPs) are widely used commercially and exist in a variety of products. To determine if anatase TNPs (ATNPs) in doses smaller than previously used reach the scrotum after entry in the body at a distant location and induce sperm defects, 100% ATNP (2.5 or 5 mg kg−1 body weight) was administered intraperitoneally to adult males for three consecutive days, followed by sacrifice 1, 2, 3, or 5 weeks later (long-) or 24, 48 or 120 h (short-term exposure). Transmission electron microscopy revealed the presence of ANTP in scrotal adipose tissues collected 120 h postinjection when cytokine evaluation showed an inflammatory response in epididymal tissues and fluid. At 120 h and up to 3 weeks postinjection, testicular histology revealed enlarged interstitial spaces. Significantly increased numbers of terminal deoxyribonucleotidyl transferase-mediated dUTP nick-end labeling-positive (apoptotic) germ (P = 0.002) and interstitial space cells (P = 0.04) were detected in treated males. Caudal epididymal sperm from the short-term, but not a long-term, arm showed significantly (P < 0.001) increased frequencies of flagellar abnormalities, excess residual cytoplasm (ERC), and unreacted acrosomes in treated versus controls (dose-response relationship). A novel correlation between ERC and unreacted acrosomes was uncovered. At 120 h, there were significant decreases in hyperactivated motility (P < 0.001) and mitochondrial membrane potential (P < 0.05), and increased reactive oxygen species levels (P < 0.00001) in treated versus control sperm. These results indicate that at 4-8 days postinjection, ANTP induce structural and functional sperm defects associated with infertility, and DNA damage via oxidative stress. Sperm defects were transient as they were not detected 10 days to 5 weeks postinjection.
Journal of Photonics for Energy | 2013
Roy Murray; Nopporn Rujisamphan; Salamat Ali; Steven G. Hegedus; Syed Ismat Shah
Abstract. The field of organic photovoltaics (OPV) has progressed rapidly. With new materials and methods being briskly developed, the characterization of OPV also needs to be updated. Current-voltage (JV) analysis of poly(3-hexlythiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM) OPV devices yield valuable insight into the internal physics of devices. A simple lumped circuit model, previously used to analyze various inorganic thin-film PV and more recently applied to OPV, has been used to study annealing parameters. To investigate the change in the lumped circuit model parameters, we carried out an annealing study of P3HT:PCBM blend OPV devices. We annealed devices at various temperatures and before and after evaporating the contact. We characterized and quantified the effect of thermal annealing by studying how the model parameters changed. We found that all parameters studied reacted favorably to annealing, including device resistances and parameters measuring recombination. While studying the resistances in unannealed and annealed devices, a barrier was found around the flat band voltage. This barrier disappeared upon annealing, indicating that it was due to material characteristics related to the crystallinity or the phase separation. The data were used to better characterize annealing effects.
Journal of Composite Materials | 2018
Iftikhar Ahmad; Mohammad Islam; Nabeel H. Alharthi; Hussain Alawadhi; Tayyab Subhani; Khurram S. Munir; Syed Ismat Shah; Fawad Inam; Yanqiu Zhu
Graphene nanosheets (GNS) reinforced Al2O3 nanocomposites were prepared by a rapid sintering route. The microhardness and fracture toughness values of the resulting nanocomposites simultaneously increased due to efficient graphene nanosheet incorporation and chemical interaction with the Al2O3 matrix grains. The properties enhancement is attributed to uniformly dispersed graphene nanosheet in the consolidated structure promoted by high surface roughness and ability of graphene nanosheet to decorate Al2O3 nanoparticles, strong GNS/Al2O3 chemical interaction during colloidal mixing and pullout/crack bridging toughening mechanisms during mechanical testing. The GNS/Al2O3 interaction during different processing stages was thoroughly examined by thermal and structural investigation of the interfacial area. We report formation of an intermediate aluminum oxycarbide phase via a confined carbothermal reduction reaction at the GNS/Al2O3 interface. The graphene nanosheet surface roughness improves GNS/Al2O3 mechanical attachment and chemical compatibility. The Al2O3/GNS interface phase facilitates efficient load transfer, thus delaying failure through impediment of crack propagation. The resulting nanocomposites, therefore, offer superior toughness.
MRS Proceedings | 2004
Abdul Rumaiz; Syed Ismat Shah; H. Lin; I. Baldytchev; J.G. Chen
WC nanoparticles where synthesized using various Physical Vapor Deposition (PVD) methods such as reactive sputtering and Pulsed Laser Deposition (PLD). In both the methods the metal flux obtained is condensed in the presence of He gas. The structural properties of the samples where investigated using X-ray Diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS). The feasibility of using nano-WC as an alternative catalyst for Pt is determined. A comparative study on two sample of WC, as-prepared and carburized W, was done. The samples were used to check for the reduction of NO x in a simple reactor. The carburized W shows activity at temperatures around 400°C whereas the as-prepared WC shows activity towards NO x reduction at a slightly higher temperature. The stability of both the sample was studied by performing the same experiment at a fixed temperature for an extended period of time. XPS and XRD confirm the formation of oxide phase after de-NO x experiments.
Powder Technology | 2010
Emre Yassitepe; Zaki Khalifa; G. Hassnain Jaffari; Chuen-Shii Chou; Sonia Zulfiqar; Muhammad Ilyas Sarwar; Syed Ismat Shah
Separation and Purification Technology | 2007
D.M. Wang; C.P. Huang; Jingguang G. Chen; H. Lin; Syed Ismat Shah