Synthesis of Small‐Sized,Porous, and Low‐Toxic Magnetite Nanoparticles by Thin POSS Silica Coating

In this communication, we report the synthesis of small‐sized (<10 nm), water‐soluble, magnetic nanoparticles (MNPs) coated with polyhedral oligomeric silsesquioxanes (POSS), which contain either polyethylene glycol (PEG) or octa(tetramethylammonium) (OctaTMA) as functional groups. The POSS‐coated MNPs exhibit superparamagnetic behavior with saturation magnetic moments (51–53 emu g^?1) comparable to silica‐coated MNPs. They also provide good colloidal stability at different pH and salt concentrations, and low cytotoxicity to MCF‐7 human breast epithelial cells. The relaxivity data and magnetic resonance (MR) phantom images demonstrate the potential application of these MNPs in bioimaging.     

Metabolic profile of glyburide in human liver microsomes using LC‐DAD‐Q‐TRAP‐MS/MS

The sulfonylurea urea drug glyburide (glibenclamide) is widely used for the treatment of diabetes milletus and gestational diabetes. In previous studies monohydroxylated metabolites were identified and characterized for glyburide in different species, but the metabolite owing to the loss of cyclohexyl ring was identified only in mouse. Glyburide upon incubation with hepatic microsomes resulted in 10 metabolites for human. The current study identifies new metabolites of glyburide along with the hydroxylated metabolites that were reported earlier. The newly identified drug metabolites are dihydroxylated metabolites, a metabolite owing to the loss of cyclohexyl ring and one owing to hydroxylation with dehydrogenation. Among the 10 identified metabolites, there were six monohydroxylated metabolites, one dihydroxylated metabolite, two metabolites owing to hydroxylation and dehydrogenation, and one metabolite owing to the loss of cyclohexyl ring. New metabolites of glyburide were identified and characterized using liquid chromatography–diode array detector–quadruple‐ion trap–mass spectrometry/mass spectrometry (LC‐DAD‐Q‐TRAP‐MS/MS). An enhanced mass scan–enhanced product ion scan with information‐dependent acquisition mode in a Q‐TRAP‐MS/MS system was used to characterize the metabolites. Liquid chromatography with diode array detection was used as a complimentary technique to confirm and identify the metabolites. Metabolites formed in higher amounts were detected in both diode array detection and mass spectrometry detection. Copyright © 2012 John Wiley & Sons, Ltd.     

Persistence of nematic liquid crystalline phase in a polyfluorene‐based organic semiconductor: A high pressure study

The role of high pressure on a low molecular weight nematic liquid crystalline organic semiconductor, ethyl‐hexyl substituted polyfluorene (PF2/6) is investigated using photoluminescence (PL), Raman scattering, and X‐ray scattering studies at pressures from 1 to 8 GPa. The PL and the Raman data under pressure are consistent with each other with no abrupt changes in the pressure coefficients of PL or Raman peaks. The PL energies redshift and broaden, consistent with both enhanced intra‐ and interchain interactions. The Raman peak positions yield pressure coefficients similar to other phenyl based π‐conjugated polymers. The broadening of a doublet peak in the 1135 cm^?1 region indicates a more planar backbone conformation with increasing pressure. X‐ray scattering indicates that the torsion angle between adjacent repeats reduces with increasing pressure and reverts back with decompression. The intermolecular structure is weakly ordered (frozen nematic) and essentially maintained with increasing pressure, in contrast to a high molecular weight PF2/6. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 1014–1023     

M4C9+(M = Ti, V): New gas phase clusters

New metal-carbon clusters, M₄C₉ ⁺ (M = Ti, V), generated using a combined thermal arc discharge evaporation set-up, have been studied with quadrupole mass spectrometry. Reactivities of these clusters have been investigated by means of association reactions with H₂O. Metal-carbon clusters of other compositions have also been studied. We speculate on the mechanism of formation of larger metal-carbon clusters.     

Synthesis,electrolyte properties and solar cell performance of hyperbranched poly(aryl-ether-urea)s

Hyperbranched poly(aryl-ether-urea)s with phenyl, N,N-dimethylamino ethyl and polyethylene oxide end-groups linked through urethane group – HBPEU-1, HBPEU-2 and HBPEU-3 respectively – were synthesized from an AB₂-type blocked isocyanate monomer and characterized by FT-IR, ¹H-NMR, SEC-MALLS, TGA and DSC techniques. The molecular weight of the polymers were found to be ranged from 4.9 × 10³ ? 1.96 × 10⁴ g/mol. The TGA results showed that the polymers decompose between 175°C – 220°C. In the DSC curves, HBPEU-1 and HBPEU-3 showed T_g at 160°C and 53°C respectively, whereas HBPEU-2 did not showed clear T_g. All the three polymers were converted into polymer electrolytes by doping with LiI/I₂. The doped polymers showed remarkably high ionic conductivity, up to 222 – 277 times compared to the un-doped polymers and the highest conductivity was observed with doped HBPEU-2. The TiO₂ based dye-sensitized solar cells (DSSCs) were fabricated using the doped polymer electrolytes and their performance was tested; HBPEU-2 showed good performance by yielding energy conversion efficiency (η) of 4.5%.     

Effect of SnO2 coating on the magnetic properties of nanocrystalline CuFe2O4

Nanocrystalline CuFe₂O₄ and CuFe₂O₄/xSnO₂ nanocomposites (x=0, 1, 5 wt%) have been successfully synthesized by one-pot reaction of urea-nitrate combustion method. The transmission electron microscope study reveals that the particle size of the as synthesized CuFe₂O₄ and CuFe₂O₄/5 wt%SnO₂ are 10 and 20 nm, respectively. The SnO₂ coating on the nanocrystalline CuFe₂O₄ was confirmed from HRTEM studies. The resultant products were sintered at 1100 °C and characterized by XRD and SQUID for compound formation and magnetic studies, respectively. The X-ray diffraction pattern shows the well-defined sharp peak that confirms the phase pure compound formation of tetragonal CuFe₂O₄. The zero field cooled (ZFC) and field cooled (FC) magnetization was performed using SQUID magnetometer from 2 to 350 K and the magnetic hysteresis measurement was carried out to study the magnetic properties of nanocomposites.     

Electrical and electrochemical properties of molten salt-synthesized Li4Ti5−xSnxO12 (x=0.0, 0.05 and 0.1) as anodes for Li-ion batteries

Submicron-sized polyhedral Li₄Ti_5−xSn_xO₁₂ (x=0.0, 0.05, and 0.1) materials were successfully prepared by a single-step molten salt method. The structural, morphological, transport and electrochemical properties of the Li₄Ti_5−xSn_xO₁₂ were studied. X-ray diffraction patterns showed the formation of a cubic structure with a lattice constant of 8.31 Å, and the addition of dopants follows Vegard's law. Furthermore, FT-IR spectra revealed symmetric stretching vibrations of octahedral groups of MO₆ lattice in Li₄Ti₅O₁₂. The formation of polyhedral submicron Li₄Ti_5−xSn_xO₁₂ particles was inferred from FE-SEM images, and a particle size reduction was observed for Sn-doped Li₄Ti₅O₁₂. The chemical composition of Ti, O and Sn was verified by EDAX. The DC electrical conductivity was found to increase with increasing temperature, and a maximum conductivity of 8.96×10⁻⁶ S cm⁻¹ was observed at 200 °C for Li₄Ti₅O₁₂. The galvanostatic charge–discharge behavior indicates that the Sn-doped Li₄Ti₅O₁₂ could be used as an anode for Li-ion batteries due to its enhanced electrochemical properties.     

Influence of metal organic and inorganic precursors on spray pyrolyzed ceramic MgO (2 0 0) thin films for epitaxial over layers

The MgO (2 0 0) surface is widely used as a substrate for epitaxial growth of superconducting and ferro-electric films. Highly oriented, single crystalline, extremely flat and transparent MgO films have been successfully deposited on quartz substrates by the chemical spray pyrolysis technique using economically viable metal organic and inorganic precursors under optimized conditions at the substrate temperature of 600 °C. Thermal analysis (TGA/DTA) in the temperature range 30-600 °C with the heating rate of 10 °C/min revealed the decomposition behavior of the precursors and confirmed the suitable substrate temperature range for film processing. The heat of reaction, ΔH due to decomposition of metal organic precursor contributed additional heat energy to the substrate for better crystallization. The intensity of the (2 0 0) peak in X-ray diffraction (XRD) measurements and the smooth surface profiles revealed the dependency of precursor on film formation. The compositional purity and the metal-oxide bond formation were tested for all the films. UV-Vis-NIR optical absorption in the 200-1500 nm range revealed an optical transmittance above 80% and the absorption edge at about 238 nm corresponding to an optical band gap E_g = 5.25 eV. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) micrographs of MgO films confirmed better crystallinity with larger grain size (0.85 μm) and reduced surface roughness (26 nm), respectively.     

Magnesium indium oxide (MgIn2O4) spinel thin films: chemical spray pyrolysis (CSP) growth and materials characterizations

MgIn(2)O(4), which has an inverse spinel structure, has been adopted as the transparent material in optoelectronic device fabrication due to its high optical transparency and electrical conductivity. Such a technologically important material was prepared by the spray pyrolysis technique. Precursors prepared for the cationic ratio Mg/In=0.5 were thermally sprayed onto glass substrates at 400 and 450 degrees C. We report herein the preparation and characterization of the films by X-ray diffraction (XRD), energy-dispersive absorption X-ray spectroscopy (EDAX), and atomic force microscopy (AFM). The XRD results showed the single phase formation of the material that revealed the presence of Mg(2+) and In(3+) in the inverse spinel-related structure. The FTIR and EDAX results further confirmed that the nanocrystalline films were mainly composed of magnesium, indium, and oxygen, in agreement with XRD analysis. We surmised from the AFM micrographs that the atoms have enough diffusion activation energy to occupy the correct site in the crystal lattice. For the 423-nm-thick magnesium indium oxide films grown at 400 degrees C, the electrical conductivity was 5.63x10(-6) Scm(-1) and the average optical transmittance was 63% in the visible range (400-700 nm). Similar MgIn(2)O(4) films deposited at 450 degrees C have a conductivity value of 1.5x10(-5) Scm(-1) and an average transmittance of 75%. Hall coefficient observations showed n-type electrical conductivity and high electron carrier concentration of 2.7x10(19) cm(-3).