Structural, magnetic and electronic structure studies of NdFe_1−<i>x</i>Ni_<i>x</i>O₃ (0 ≤ <i>x</i> ≤ 0.3)

Bashir, Abida,Ikram, M,Kumar, Ravi,Thakur, P,Chae, K H,Choi, W K,Reddy, V R IOP Pub 2009 Journal of Physics, Condensed Matter Vol.21 No.32

<P>We present here the structural, electronic structure, magnetic and Mossbauer studies of NdFe1-xNixO3 (0 <= x <= 0.3) samples. All the samples exhibit a single-phase orthorhombic structure with space group Pbnm. The near-edge x-ray absorption fine structure (NEXAFS) studies reveal that, with the Ni substitution at Fe sites, a new spectral feature about 1.5 eV lower than the pre-edge structure of NdFeO3 in the O K edge is observed due to the 3d contraction effect and is growing monotonically with the increase of Ni concentration. The Fe L-3,L-2, Ni L-3,L-2 and Nd M-5,M-4 edges confirm the trivalent state of Fe, Ni and Nd ions. The Mossbauer spectra fitted with two Zeeman sextets confirm the different surroundings of Ni around Fe ions. With the increase in Ni concentration, the sextets are broadened. The increase of quadrupole splitting and the decrease of the hyperfine field suggest the change in the ordered regime of the system. The magnetic behaviour at low temperatures is explained in the context of competition among moments of rare earth (Nd) and transition metal ions (Fe/Ni). The strong paramagnetic contribution of the Nd magnetic sublattice and spin flip phenomenon is observed from the temperature dependence of zero-field-cooled and field-cooled magnetization where spin crossover is observed. The isothermal hysteresis loops show a decrease of magnetization and increase of coercivity with the increase in temperature and complements magnetization versus temperature. The results are explained on the basis of the spin reorientation phenomenon.</P>

Structural, electronic structure and magnetic studies of SmFe_1-xNi_xO₃ (x@?0.5)

Bashir, A.,Ikram, M.,Kumar, R.,Lisboa-Filho, P.N.,Thakur, P. Elsevier 2010 Materials science and engineering B. Advanced Func Vol.172 No.3

We present the structural, electronic structure and magnetic studies of Ni doped SmFeO<SUB>3</SUB>. The X-ray diffraction (XRD) studies confirm the single phase nature of the samples having orthorhombic Pbnm structure and the unit-cell volume is decreasing with the increase of Ni concentration. X-ray absorption spectroscopy (XAS) studies on O K, Fe L<SUB>3,2</SUB>, Ni L<SUB>3,2</SUB> and Sm M<SUB>5,4</SUB> edges of SmFe<SUB>1-x</SUB>Ni<SUB>x</SUB>O<SUB>3</SUB> (x@?0.5) samples along with the reference compounds revealed the homo-valence state of Fe and Ni in these materials. From magnetization studies it has been observed the materials exhibit ferromagnetic and antiferromagnetic sub-lattices, which are strongly dependent on the thermo-magnetic state of the system.

Influence of fullerene derivative replacement with TiO2 nanoparticles in organic bulk heterojunction solar cells

M. Ikram,S. Ali,R. Murray,A. Hussain,Islah-u-din,S. Ismat Shah 한국물리학회 2015 Current Applied Physics Vol.15 No.1

In an effort to develop hybrid organic solar cells with improved power conversion efficiency (PCE), devices based on poly (3-hexylthiophene) (P3HT):phenyl C61-butyric acid methyl ester (PCBM) active layer and poly (3,4-ethylenedioxythiophene) (PEDOT):poly (styrenesulfonate) (PSS) buffer layers were prepared. A systematic replacement of PCBM was achieved by introducing nanostructured TiO2 (~15 nm particle size), dissolved separately in chlorobenzene (CB) and 1,2 edichlorobenzene (DCB), to the (P3HT:PCBM) active layer while keeping a fixed amount for P3HT. To understand the effect of fullerene replacement with the inorganic metal oxide nanoparticles on different properties of resulting devices, a variety of techniques such as CurrenteVoltage (JeV) characteristics, Field Emission Scanning Electron Microscopy (FESEM), Atomic Force Microscopy (AFM), Ultravoilet-Visible (UVeVis) Spectrophotometry and External Quantum Efficiency (EQE) were employed. The addition of TiO2 nanoparticles in the active layer improved the power conversion efficiency (PCE) of P3HT:PCBM devices. The addition of TiO2 nanoparticles using CB as solvent enhanced the absorption in visible region and also introduced a red shift in the absorption spectra. A significant increase in EQE was observed for devices with TiO2 nanoparticles in the active layer. Mixing TiO2 also increased the surface roughness of the active layer where TiO2 nanoparticles were found to agglomerate as their concentration increased relative to fullerene derivative. A complete agglomeration of TiO2 was observed in the absence of PCBM.

Influence of Iron Doping on Structural, Optical and Magnetic Properties of TiO2 Nanoparticles

R. Zahid,M. Manzoor,A. Rafi q,M. Ikram,M. Nafees,A. R. Butt,S. G. Hussain,S. Ali 대한금속·재료학회 2018 ELECTRONIC MATERIALS LETTERS Vol.14 No.5

In this study, various concentrations of Fe doped TiO2nanoparticles have been successfully synthesized using the sol–gelmethod. A variety of characterization techniques as ultra-violet visible (UV–Vis) spectroscopy, X-ray diffractometer (XRD),vibrating sample magnetometry (VSM) and field emission scanning electron microscopy (FESEM) were employed to analyzethe prepared nanopowders. XRD measurement confirmed the substitution of Fe ion without disturbing the tetragonal crystalsystem of TiO2. The crystallite size was found to decrease and lattice strain increases upon doping estimated by WilliamsonHall plot. Furthermore, the average grain size calculated by FESEM found was between 10 and 30 nm for pure and dopedTiO2. UV–Vis spectroscopy showed an increase in absorption accompanied red shift and increase in band gap energies from3.36 to 3.62 eV with the addition of Fe. The FTIR spectroscopy was employed to confirm the presence of functional groupsin the fabricated nanopowders. Upon mixing the saturation magnetization (Ms) varying from (2.12 to 1.51)10−2 emu/g wasobserved.

Zwitterionic mesoporous nanoparticles with a bioresponsive gatekeeper for cancer therapy

Khatoon, S.,Han, H.S.,Lee, M.,Lee, H.,Jung, D.W.,Thambi, T.,Ikram, M.,Kang, Y.M.,Yi, G.R.,Park, J.H. Elsevier BV 2016 ACTA BIOMATERIALIA Vol.40 No.-

To enhance cellular uptake and site-specific drug release in the tumor microenvironment, zwitterionic mesoporous silica nanoparticles (Z-MSN) were prepared by introducing a bioresponsive gatekeeper composed of negatively charged carboxylic groups and positively charged quaternary amine groups. When these Z-MSN encountered a mildly acidic environment, their surface charge readily switched from negative to positive by cleavage of an acid-labile maleic amide linkage, thus allowing for effective cellular uptake into tumor tissue. Doxorubicin (DOX) encapsulated in Z-MSN was not significantly released in physiological conditions (pH 7.4), whereas the release rate of DOX remarkably increased in mildly acidic conditions through disintegration of the gatekeeper. The antitumor efficacy of DOX-loaded Z-MSN (DOX-Z-MSN) was evaluated after their systemic administration to tumor-bearing mice. Compared to free DOX and DOX-loaded MSN without the gatekeeper, DOX-Z-MSN exhibited much higher antitumor efficacy in vivo. Overall, these results demonstrated that the hydrophilic negative surface of Z-MSN, with their closed gate, allowed for their effective accumulation in tumor tissue after systemic administration, and that their charge-swapping and gate-opening in the tumor environment enhanced their cellular uptake and drug release rate simultaneously, implying a highly promising potential for development of Z-MSN as a drug carrier for cancer therapy. Statement of Significance: In an attempt to address the issues of enhanced cellular uptake and site-specific drug release of nanoparticles, we herein report on zwitterionic MSN (Z-MSN) with a pH-responsive gatekeeper which can be internalized into cancer cells via switching their surface charge from negative, in physiological conditions, to positive, in the tumor microenvironment. We hypothesized that the hydrophilic negative surface of Z-MSN with a closed gate allows for their accumulation into tumor tissue after systemic administration, whereas their charge-swapping and gate-opening in the tumor environment enhance cellular uptake and drug release rate simultaneously. Overall, Z-MSN constitute a promising drug delivery carrier for cancer therapy.

Effects of Pasternak foundation on the bending behavior of FG porous plates in hygrothermal environment

Ikram Kheira Bot,Abdelmoumen Anis Bousahla,Amine Zemri,Mohamed Sekkal,Abdelhakim Kaci,Fouad Bourada,Abdelouahed Tounsi,M.H. Ghazwani,S. R. Mahmoud 국제구조공학회 2022 Steel and Composite Structures, An International J Vol.43 No.6

This research is devoted to study the effects of humidity and temperature on the bending behavior of functionally graded (FG) ceramic-metal porous plates resting on Pasternak elastic foundation using a quasi-3D hyperbolic shear deformation theory developed recently. The present plate theory with only four unknowns, takes into account both transverse shear and normal deformations and satisfies the zero traction boundary conditions on the surfaces of the functionally graded plate without using shear correction factors. Material properties of porous FG plate are defined by rule of the mixture with an additional term of porosity in the through-thickness direction. The governing differential equations are obtained using the "principle of virtual work". Analytically, the Navier method is used to solve the equations that govern a simply supported FG porous plate. The obtained results are checked by comparing the results determined for the perfect and imperfect FG plates with those available in the scientific literature. Effects due to material index, porosity factors, moisture and thermal loads, foundation rigidities, geometric ratios on the FG porous plate are all examined. Finally, this research will help us to design advanced functionally graded materials to ensure better durability and efficiency for hygro-thermal environments.

Atlantic forcing of Pacific decadal variability

Kucharski, F.,Ikram, F.,Molteni, F.,Farneti, R.,Kang, I. S.,No, H. H.,King, M. P.,Giuliani, G.,Mogensen, K. Springer Science + Business Media 2016 Climate dynamics Vol.46 No.7

<P>This paper investigates the Atlantic Ocean influence on equatorial Pacific decadal variability. Using an ensemble of simulations, where the ICTPAGCM ('SPEEDY') is coupled to the NEMO/OPA ocean model in the Indo-Pacific region and forced by observed sea surface temperatures in the Atlantic region, it is shown that the Atlantic Multidecadal Oscillation (AMO) has had a substantial influence on the equatorial Pacific decadal variability. According to AMO phases we have identified three periods with strong Atlantic forcing of equatorial Pacific changes, namely (1) 1931-1950 minus 1910-1929, (2) 1970-1989 minus 1931-1950 and (3) 1994-2013 minus 1970-1989. Both observations and the model show easterly surface wind anomalies in the central Pacific, cooling in the central-eastern Pacific and warming in the western Pacific/Indian Ocean region in events (1) and (3) and the opposite signals in event (2). The physical mechanism for these responses is related to a modification of the Walker circulation because a positive (negative) AMO leads to an overall warmer (cooler) tropical Atlantic. The warmer (cooler) tropical Atlantic modifies the Walker circulation, leading to rising (sinking) and upper-level divergence (convergence) motion in the Atlantic region and sinking (rising) motion and upper-level convergence (divergence) in the central Pacific region.</P>

Analysis of a Non-Evaporable Getter of Ti-Al-Zr Thin Film with Enhanced Performance Used for Ultra-High Vacuum Generation

Muhammad Khalid Alamgir,M. Ikram,Ghalib Hussain Mughal,Ghulam Asghar,Sha q ur Rehman,S. Qaseem,M. Kamran,Amir Ullah,Sartaj Khan 한국물리학회 2019 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.75 No.5

Non-evaporable getter (NEG) thin films of Ti-Al-Zr and Ti-Zr were prepared on stainless-steel substrate by using the cathodic arc deposition technique. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and in-situ X-ray photoelectron spectroscopy (XPS) were used to analyze the getter behavior of the non-evaporable getter thin films. The SEM images displayed the porous and rough surfaces of the thin films, which is an indication of high adsorption and sticking probabilities for the residual gases present in the chamber. The volume elemental composition of the thin films was measured by using EDX. The XRD patterns of the synthesized thin films indicated that the films had an amorphous nature and high structural stability. The in-situ X-ray photoelectron spectroscopy (XPS) studies revealed that the superficial layers disappeared when the non-evaporable getter of Ti-Al-Zr thin films was heated at a temperature below 250~$^\circ$C for 30 minutes, there by activating the surface. However, for Ti-Zr thin films, no reasonable activation was observed at 250~$^\circ$C. This outcome reveals that thin films of Ti-Al-Zr are good for reducing the outgassing and producing an ultra-high vacuum.

Alkaloids from The Roots of Tabernaemontana Macrocarpa Jack

Husain, Khairana,Said, Ikram M.,Din, Laily B.,Takayama, Hiromitsu,Kitajima, Mariko,Aimi, Norio The Korean Society of Pharmacognosy 1997 Natural Product Sciences Vol.3 No.1

The roots of Tabernaemontana macrocarpa Jack (Apocynaceae) yielded nine indole alkaloids which were identified as coronaridine (2), voacangine hydroxy-indolenine (3), 3-oxo-coronaridine (4), 19-R-heyneanine (7), coronaridine pseudoindoxyl (8) and voacangine pseudoindoxyl (9) while 3-(2-oxopropyl)-coronaridine (1), 3-(2-oxopropyl)-coronaridine-pseudoindoxyl (5) and 3-(2-oxopropyl)-voacangine-pseudoindoxyl (6) were isolated as artefacts formed during the isolation process. All of the alkaloids were identified by spectroscopic methods $(UV,\;MS,\;^1H-NMR\;&\;^{13}C-NMR)$ and in comparison with the literature data.

Investigation of half metallicity in Fe doped CdSe and Co doped CdSe materials

Suneela Arif,B. Amin,Iftikhar Ahmad,M. Maqbool,R. Ahmad,M. Haneef,N. Ikram 한국물리학회 2012 Current Applied Physics Vol.12 No.1

The objective of the present work is to evaluate half metallicity and spin dependent transport properties of iron doped CdSe and cobalt doped CdSe compounds. The spin-polarized band structures (semiconductor in one spin state and conductor in the other spin state) predict that Cd0.875Fe0.125Se and Cd0.875Co0.125Se are half metals. The calculated crystal filed splitting energy show larger energy gap between eg and t2g for Fe than Co doped CdSe compound. Furthermore, magnetization, exchange coupling and band-gap increase with decrease in the lattice constant. Overall, Cd0.875Fe0.125Se and Cd0.875Co0.125Se in the zinc-blend phase show half-metallic ferromagnetic nature and are expected to be potential materials for spintronic devices.