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Zervos M.,Materials Science Group | Papageorgiou P.,University of Cyprus | Othonos A.,University of Cyprus
Journal of Crystal Growth | Year: 2010

Indium sulphide nanowires (NWs) have been grown on Si via the reaction of In and InCl3 with H2S using chemical vapor deposition at temperatures as low as 250 °C. We find that the growth of InxSy NWs via the direct reaction of In with H2S is hindered by the formation of InxSy around the source of In which limits its vapor pressure. Thus a low yield of InxSy NWs with diameters of ≈100 nm, lengths up to ≈5 μm and hexagonal crystals measuring ≈500 nm across, were obtained between 500 and 600 °C, but their growth was not uniform or reproducible. These exhibited weak, but nevertheless clear peaks, in the X-ray diffraction (XRD) spectrum corresponding to tetragonal β-In2S3 and orthorhombic InS. No NWs were obtained for TG≤500 °C while for TG>600 °C we obtained a polycrystalline layer with oriented grains of triangular shape. In contrast, a high yield of InS NWs with diameters ≤200 nm and lengths up to ≈2 μm were obtained at temperatures as low as 250 °C via the reaction of In and InCl3 with H2S. The sublimation of InCl3 enhances the vapor pressure of In and the growth of InS NWs, which organize themselves in urchin like structures at 300 °C, exhibiting very intense peaks in the XRD spectrum, corresponding mainly to orthorhombic InS. Optical transmission measurements through the InS NWs gave a band-gap of 2.4 eV. © 2009 Elsevier B.V. All rights reserved. Source

Othonos A.,University of Cyprus | Zervos M.,Materials Science Group
Nanoscale Research Letters | Year: 2011

Ultrafast hole carrier relaxation dynamics in CuO nanowires have been investigated using transient absorption spectroscopy. Following femtosecond pulse excitation in a non-collinear pump-probe configuration, a combination of non-degenerate transmission and reflection measurements reveal initial ultrafast state filling dynamics independent of the probing photon energy. This behavior is attributed to the occupation of states by photo-generated carriers in the intrinsic hole region of the p-type CuO nanowires located near the top of the valence band. Intensity measurements indicate an upper fluence threshold of 40 μJ/cm 2 where carrier relaxation is mainly governed by the hole dynamics. The fast relaxation of the photo-generated carriers was determined to follow a double exponential decay with time constants of 0.4 ps and 2.1 ps. Furthermore, time-correlated single photon counting measurements provide evidence of three exponential relaxation channels on the nanosecond timescale. © 2011 Othonos and Zervos; licensee Springer. Source

Gorcea M.,University of London | Gorcea M.,Materials Science Group | Hadgraft J.,University of London | Lane M.E.,University of London | Moore D.J.,Center for Skin Science and Applied Dermatology
International Journal of Cosmetic Science | Year: 2013

Recently, we developed a biophysical approach to characterize in vivo facial cheek skin as a function of stratum corneum (SC) depth, barrier function and during a 24-h recovery period. The current study extends this work and characterizes the human facial cheek after barrier challenge and, for the first time, facial SC barrier recovery over a 4-week period. Changes in the corneocyte size over the 4-week recovery period, and correlations with changes in Trans-Epidermal Water Loss (TEWL) were monitored. This approach allows complete characterization of SC barrier function after a full biological regeneration of the SC barrier following tape stripping. The structural and compositional changes in facial cheek were investigated using Attenuated Total Reflectance-Fourier Transform Infra Red (ATR-FTIR) spectroscopy, tape stripping, TEWL measurements and image analysis combined with optical microscopy to characterize the SC depth profile during the tape stripping stress and over 4-week recovery period. TEWL increased significantly from baseline after sequential tape stripping. Corneocyte size decreased with successive tape stripping. An inverse direct correlation was determined between TEWL and corneocyte surface area. After 4 weeks, the corneocyte size and TEWL for the facial cheek recovered 100% from the tape stripping procedure. The in vivo ATR-FTIR data demonstrated that lipid and sebum components on the surface of the facial cheek SC recovered within 24 h post tape stripping, whereas protein (Amide II) and water components recovered after 1 week. © 2012 Society of Cosmetic Scientists and the Société Française de Cosmétologie. Source

Bhowmik R.N.,Pondicherry University | Bharathi A.,Materials Science Group
AIP Conference Proceedings | Year: 2013

We have developed ferromagnetic Co1.5Fe1.5O 4 ferrite by chemical route. Size of the magnetic grains is below 10 nm and assumed to be in single domain range. At room temperature (RT), the samples have shown soft ferromagnetic properties. Below RT, ferromagnetic parameters have increased and high magnetic squareness (∼ 0.8-0.9) is seen at 4 K. Ferromagnetic parameters has been tuned by varying pH value during chemical reaction of the metal salts solution. © 2013 American Institute of Physics. Source

Sornadurai D.,Materials Science Group | Ravindran T.R.,Materials Science Group | Paul V.T.,Metallurgy and Materials Group | Sastry V.S.,Indira Gandhi Center for Atomic Research
AIP Conference Proceedings | Year: 2012

Synthesis parameters are optimized in order to grow single crystals of multiferroic BiFeO3. 2 to 3 mm size pyramid (tetrahedron) shaped single crystals were successfully obtained by solvothermal method. Scanning electron microscopy with EDAX confirmed the phase formation. Raman scattering spectra of bulk BiFeO3 single crystals have been measured which match well with reported spectra. © 2012 American Institute of Physics. Source

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