Synthesis and characterization of Ag/PVA nanorods by chemical reduction method

Silver (Ag) nanorods with the average length of 280 nm and diameters of around 25 nm were synthesized by a simple reduction process of silver nitrate in the presence of polyvinyl alcohol (PVA) and investigated by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission-electron microscopy (TEM) and UV–vis spectrum. It was found out that both temperature and reaction time are the important factors in determining the morphology and aspect ratios of nanorods. TEM images showed the prepared Ag nanorods have a face centered shape (fcc) with fivefold symmetry consisting of multiply twinned face centered cubes as revealed in the cross-section observations. The fivefold axis, i.e. the growth direction, normally goes along the (1 1 1) zone axis direction of the basic fcc Ag-structure. Preferred crystallographic orientation along the (1 1 1), (2 0 0) or (2 2 0) crystallographic planes and the crystallite size of the Ag nanorods are briefly analyzed.     

A competition between (0 0 1) and (0 1 1) alignments in yttria stabilized zirconia thin films fabricated by ion beam assisted deposition

Biaxially textured yttria stabilized zirconia (YSZ) thin films, were deposited on glass substrates by ion beam assisted deposition method with different deposition time. As contrasts, films were also fabricated without assisting ion beam. The orientation properties of the films were characterized by X-ray diffraction. A comparative study shows that there is a competition between (0 0 1) and (0 1 1) alignments during the growth process. Assisting ions make the films (0 0 1)-advantaged and biaxially textured. The competitive growth and the orientation development are explained by selective resputtering and anisotropic damage on growing films induced by assisting ions.     

Alterations of the optic pathway between unilateral and bilateral optic nerve damage in multiple sclerosis as revealed by the combined use of advanced diffusion kurtosis imaging and visual evoked potentials

ObjectivesWe investigated changes in the optic tract and optic radiation in patients with multiple sclerosis (MS) by comparing unilateral and bilateral optic nerve damage assessed based on visual evoked potentials (VEPs) using advanced diffusion MR metrics.MethodsIn 21 MS patients, diffusion MRI was performed. Maps of fractional anisotropy, apparent diffusion coefficient (ADC), and mean kurtosis (MK) were computed. On the basis of the P100 latency in VEPs, the MS patients were divided into three groups: bilateral (n = 7), unilateral (n = 7), and no abnormality (n = 7). Their optic tracts and optic radiations were analyzed with diffusion MRI-based fiber tracking. We also investigated the correlations between diffusion parameters and VEPs (n = 21).ResultsIn the optic tract, the diffusion changes in each of the three groups showed step-like changes. The diffusion changes in the optic radiations of the unilateral group were similar to those in the normal VEP group. Only the bilateral group showed significantly higher ADC and lower MK relative to the other two groups (P < 0.05, Steel–Dwass multiple-comparison test). A significant positive correlation between VEP latency and ADC and a significant negative correlation between VEP latency and MK were observed (P < 0.01, Spearman's correction).ConclusionsWe first evaluated the relationship between VEPs and DKI and concluded that the lateral geniculate nucleus may compensate for unilateral damage in the pre-geniculate optic pathway via neural plasticity.     

Crystallographic orientation-dependent optical properties of GaInSb mid-infrared quantum well laser

The optical properties of compressively strained GaInSb/GaInAlSb quantum well (QW) laser are numerically studied in different crystal orientations solving envelope function equation using finite difference method. The simulation results demonstrate that there is a strong correlation between the optical gain and its emission wavelength with crystal orientation of the QW. The maximum and minimum optical gains are evaluated in the (1 1 3) and (1 1 1) crystal orientations, respectively, due to band mixing effects. The peak emission wavelength can be tuned from 2.4 μm to 2.25 μm by changing the crystal orientation from (1 1 0) to (1 1 1). Typical optical gains are evaluated 3115, 3080, 2790, 3415, and 2940 cm^?1 in (0 0 1), (1 1 0), (1 1 1), (1 1 3), and (1 3 1) crystal orientations, respectively, when the injection carrier density is 3.5 × 10¹⁸ cm^?3. The highest optical power and lower threshold current are obtained in (1 1 3) orientation for the number of quantum wells three.     

Use of film thickness and Cu additive to improve (0 0 1) texture in MgO/FePtCu(C) bilayers

A multilayer structure has been proposed that demonstrates improved (0 0 1) texture for FePt-based L1₀ perpendicular media. Achieving a strong perpendicular magnetic anisotropy requires aligning the L1₀ crystallographic c-axis along the film normal. The ordered L1₀ FePt structure is tetragonal with a c/a ratio close to 0.965. This makes discriminating between the three crystallographic variants ([1 0 0], [0 1 0], and the desired [0 0 1]) difficult. Alloying FePt with Cu to reduce the c/a ratio and using a multilayer approach to keep the magnetic layers thin results in a structure with an adjustable M_rt and a strong (0 0 1) texture (rocking curve widths around 2°). This is a remarkable improvement in texture from pure FePt multilayered films or monolithic FePt(X) films. The proposed [MgO(2 nm)/Fe_50−xPt₅₀Cu_x(5 nm)]_×n structure limits grain size in the vertical (perpendicular) direction albeit not in the plane of the film. Carbon can be added to the FePtCu layer to reduce the grain size with minimal degradation of the (0 0 1) orientation.     

In situ magneto-optical Kerr effect study of uncovered Fe films on ZnSe(0 0 1)

The magnetic properties of uncovered Fe/ZnSe/GaAs(1 0 0) ultrathin films have been determined in situ by magneto-optical Kerr effect (MOKE). Fe films up to 10 monolayers (ML) thick were deposited on c(2×2) Zn-rich ZnSe/GaAs(0 0 1) surfaces at 180 °C. We have studied the thickness dependence of the in-plane lattice parameter of the Fe films and of the MOKE hysteresis loops in the longitudinal geometry, at 150 K, under magnetic fields up to 0.1 T applied along the [1 1 0] and [1-1 0] directions of the ZnSe(0 0 1). Reflection high energy electron diffraction show that in the low thickness regime the Fe films present an in-plane structural anisotropy characterized by an expansion along the [1 1 0] direction. Hysteretic loops were obtained only starting from ∼5 ML Fe. We found the onset of an uniaxial magnetic anisotropy with [1 1 0] magnetic easy axis at 7 ML Fe.     

Dependence of microstructure and magnetic properties of FePt films on Cr90Ru10 underlayers

The effect of the thickness of Cr₉₀Ru₁₀ underlayers on the microstructure and magnetic properties of FePt films has been studied. Experimental results showed that the FePt films grown on the Cr₉₀Ru₁₀ underlayers exhibited a (0 0 1) preferred orientation with out-of-plane magnetic anisotropy. The degree of the FePt(0 0 1) preferred orientation was closely related to that of the Cr(0 0 2) preferred orientation. The degree of ordering of the FePt films increased with the thickness of the Cr₉₀Ru₁₀ underlayers. The angular dependence of the coercivity curves suggested that an incoherent curling rotational mode be a dominant magnetic reversal mechanism in the FePt films at various Cr₉₀Ru₁₀ underlayer thicknesses.     

Growth and characterization of CoSi2 films on Si (1 0 0) substrates

In the present work, a special solid phase epitaxy method has been adapted for the preparation of CoSi₂ film. This method includes an epitaxial growth of Co films on Si (1 0 0) substrate, and in situ annealing of the Co/Si films in vacuum. It has been found that at the substrate temperature of 360°C, fcc cobalt film grows epitaxially on the Si (1 0 0) surface. The crystallographic orientation relations between fcc Co film and Si substrate determined from the electron diffraction result are: (0 0 1) Co//(0 0 1) Si, [1 0 0] Co//[1 1 0]Si. Upon annealing at temperatures range from 500 to 600°C, Co film reacts with Si substrate and transforms into CoSi₂. The CoSi₂ films prepared by this way are characterized by XTEM, XPS and AFM.     

Preparation and characterization of highly conducting and transparent Al doped CdO thin films by pulsed laser deposition

Highly conducting and transparent aluminum doped CdO thin films were deposited using pulsed laser deposition technique. The effect of growth temperature on structural, electrical, and optical properties was studied. It is observed that the film orientation changes from preferred (1 1 1) plane to (2 0 0) plane with increase in growth temperature. The electrical resistivity of the films was found to increase with increase in growth temperature. The low resistivity of 4.3 × 10⁻⁵ Ω cm and high transparency (∼85%) was obtained for the film grown at 150 °C. The band gap of the films varies from 2.74 eV to 2.84 eV.     

Chemical solution processing and properties of Sr2FeMoO6 thin films

Crack-free and oriented Sr₂FeMoO₆ (SFMO) thin film with double perovskite structure has been fabricated by the chemical solution deposition (CSD) method. A homogeneous and stable SFMO precursor solution was successfully prepared by controlling the reaction of starting metal-organic compounds in a mixture solvent of 1-propanol and 2-methoxyethanol. SFMO thin films with c-axis preferred orientation could successfully be synthesized on MgO (0 0 1) and SrTiO₃ (0 0 1) substrates by optimizing the several processing conditions. SFMO thin film prepared on SrTiO₃ (0 0 1) showed a magnetoresistance effect at a low magnetic field.     

Stress and morphological development of CdS and ZnS thin films during the SILAR growth on (1 0 0)GaAs

Cadmium sulfide and zinc sulfide films were grown on (1 0 0)GaAs substrate by successive ionic layer adsorption and reaction (SILAR) technique from aqueous precursor solutions at room temperature and normal pressure. The stress development of the thin films was characterized by laser interferometry as a function of the thickness of the films. The morphology and roughness of the films were monitored by atomic force microscopy. Additionally the crystallinity and crystallite size were analyzed by X-ray diffraction and composition by electron spectroscopy for chemical analysis. The CdS thin films had significantly higher stress level and also better crystallinity compared with ZnS thin films. Both films were polycrystalline and cubic, but the CdS thin films followed the substrate (1 0 0) orientation, whereas the ZnS films were (1 1 1) orientated. The roughness vs. film thickness curves of both films followed each other in shape, but the CdS films consisted of smaller particles.     

Investigation of hillocks formation on (1 0 0) HgCdTe layers grown by MOCVD on GaAs epi-ready substrates

In this paper we present the recent progress in the growth of (1 0 0) HgCdTe epilayers using metal organic chemical vapour deposition on GaAs epi-ready substrates. Particular progress has been achieved in the reduction of macro-defects known as “hillocks”, revealed on the surface of HgCdTe epilayers with (1 0 0) crystallographic orientation. The large-scale defects can arise from such sources as poor substrate processing, dust and remnants from previous deposition, and non optimal parameters of nucleation and growth process. In our experiment, hillocks density was decreased to <10² cm⁻² by proper choice of the growth parameters.Obtained epilayers are suitable for device fabrication. So far, significant improvements has been obtained in photoconductors operated at near-room temperatures. Devices fabricated from (1 0 0) HgCdTe have about one order of magnitude higher voltage responsivity than their (1 1 1) B counterparts.     

Mapping of left ventricle wall thickness in mice using 11.7-T magnetic resonance imaging

BackgroundThe left ventricle (LV) wall thickness is an important and routinely measured cardiologic parameter. Here we introduce three-dimensional (3D) mapping of LV wall thickness and function using a self-gated magnetic resonance (MR) sequence for ultra-high-field 11.7-T MR cine imaging of mouse hearts.Methods and resultsSix male C57BL/6-j mice were subjected to 11.7-T MR imaging (MRI). Three standard views—short axis, long axis four-chamber, and long axis two-chamber—and eight consecutive short axis scans from the apex to base were performed for each mouse. The resulting 11 self-gated cine images were used for fast low-angle shot analysis with a navigator echo over an observation period of approximately 35 min. The right ventricle (RV) and LV were identified in the short axis and four-chamber views. On 3D color-coded maps, the interventricular septum wall (diastole: 0.94 ± 0.05 mm, systole: 1.20 ± 0.09 mm) and LV free wall (diastole: 1.07 ± 0.15 mm, systole: 1.79 ± 0.11 mm) thicknesses were measured.ConclusionThis 3D wall thickness mapping technique can be used to observe regional wall thickness at the end-diastole and end-systole. Self-gated cine imaging based on ultra-high-field MRI can be used to accurately and easily measure cardiac function and wall thickness in normal mouse hearts. As in the preclinical study, this versatile and simple method will be clinically useful for the high-field-MRI evaluation of cardiac function and wall thickness.     

Structural and magnetic properties of BCC Fe/Co (0 0 1) superlattices

In thin layered Fe/Co (0 0 1), grown on MgO (0 0 1), both Fe and Co crystallize in the body-centered cubic (BCC) structure, as seen in a series of superlattices where the layer thickness of the components is varied from two to twelve atomic monolayers. These superlattices have novel magnetic properties as observed by magnetization and polarized neutron reflectivity measurements. There is a significant enhancement of the magnetic moments of both Fe and Co at the interfaces. Furthermore, the easy axis of the system changes from [1 0 0] for films of low cobalt content to [1 1 0] for a Co content exceeding 33%. No indication of a uniaxial anisotropy component is found in any of the samples. The first anisotropy constant (K₁) of BCC Co is found to be negative with an estimated magnitude of 110 kJ/m³ at 10 K. In all cases, the magnetic moments of Fe and Co have parallel alignment.     

Substrate bias effects during diamond like carbon film deposition by microwave ECR plasma CVD

Diamond like carbon (DLC) coatings were deposited on silicon(1 1 1) substrates by microwave electron cyclotron resonance (ECR) plasma CVD process using a plasma of Ar and CH₄ gases under the influence of DC self bias generated on the substrates by application of RF (13.56 MHz) power. DLC coatings were deposited under the varying influence of DC bias (−60 V to −150 V) on the Si substrates. Deposited films were analyzed by different techniques like: X-ray photoelectron spectroscopy (XPS), spectroscopic ellipsometry (SE), atomic force microscopy (AFM), Hardness and elastic modulus determination technique, Raman spectroscopy, scanning electron microscopy (SEM) and contact angle measurement. The results indicate that the film grown at −100 V bias has optimised properties like high sp³/sp² ratio of carbon bonding, high refractive index (2.26–2.17) over wide spectral range 400–1200 nm, low roughness of 0.8 nm, high contact angle (80°) compared to the films deposited at other bias voltages (−60 V and −150 V). The results are consistent with each other and find august explanation under the subplantation model for DLC growth.     

Instant controlled pressure drop technology and ultrasound assisted extraction for sequential extraction of essential oil and antioxidants

The instant controlled pressure drop (DIC) technology enabled both the extraction of essential oil and the expansion of the matrix itself which improved solvent extraction. The sequential use of DIC and Ultrasound Assisted Extraction (UAE) triggered complementary actions materialized by supplementary effects. We visualized these combination impacts by comparing them to standard techniques: Hydrodistillation (HD) and Solvent Extraction (SE). First, the extraction of orange peel Essential Oils (EO) was achieved by HD during 4 h and DIC process (after optimization) during 2 min; EO yields was 1.97 mg/g dry material (dm) with HD compared to 16.57 mg/g dm with DIC. Second, the solid residue was recovered to extract antioxidant compounds (naringin and hesperidin) by SE and UAE. Scanning electron microscope showed that after HD the recovered solid shriveled as opposite to DIC treatment which expanded the product structure. HPLC analyses showed that the best kinetics and yields of naringin and hesperidin extraction was when DIC and UAE are combined. Indeed, after 1 h of extraction, DIC treated orange peels with UAE were 0.825 ± 1.6 × 10^?2 g/g of dry material (dm) for hesperidin and 6.45 × 10^?2 ± 2.3 × 10^?4 g/g dm for naringin compared to 0.64 ± 2.7 × 10^?2 g/g of dry material (dm) and 5.7 × 10^?2 ± 1.6 × 10^?3 g/g dm, respectively with SE. By combining DIC to UAE, it was possible to enhance kinetics and yields of antioxidant extraction.     

Fabry–Pérot cavities based on chemical etching for high temperature and strain measurement

In this paper, two hybrid multimode/single mode fiber Fabry–Pérot (FP) cavities were compared. The cavities fabricated by chemical etching are presented as high temperature and strain sensors. In order to produce this FP cavity a single mode fiber was spliced to a graded index multimode fiber with 62.5 μm core diameter. The Fabry–Pérot cavities were tested as a high temperature sensor in the range between room temperature and 700 °C and as strain sensors. A reversible shift of the interferometric peaks with temperature allowed to estimate a sensitivity of 0.75 ± 0.03 pm/°C and 0.98 ± 0.04 pm/°C for the sensor A and B respectively. For strain measurement sensor A demonstrated a sensitivity of 1.85 ± 0.07 pm/μ? and sensor B showed a sensitivity of 3.14 ± 0.05 pm/μ?. The sensors demonstrated the feasibility of low cost fiber optic sensors for high temperature and strain.     

Structural and magnetic properties of thin epitaxial Fe films on (1 1 0) GaAs prepared by metalorganic chemical vapor deposition

Iron films have been grown on (1 1 0) GaAs substrates by atmospheric pressure metalorganic chemical vapor deposition at substrate temperatures (T_s) between 135°C and 400°C. X-ray diffraction (XRD) analysis showed that the Fe films grown at T_s between 200°C and 330°C were single crystals. Amorphous films were observed at T_s below 200°C and it was not possible to deposit films at T_s above 330°C. The full-width at half-maximum of the rocking curves showed that crystalline qualities were improved at T_s above 270°C. Single crystalline Fe films grown at different substrate temperature showed different structural behaviors in XRD measurements. Iron films grown at T_s between 200°C and 300°C showed bulk α-Fe like behavior regardless of film thickness (100–6400 Å). Meanwhile, Fe films grown at 330°C (144 and 300 Å) showed a biaxially compressed strain between substrate and epilayer, resulting in an expanded inter-planar spacing along the growth direction. Magnetization measurements showed that Fe films (>200 Å) grown at 280°C and 330°C were ferromagnetic with the in-plane easy axis along the [1 1 0] direction. For the thinner Fe films (⩽200 Å) regardless of growth temperature, square loops along the [1 0 0] easy axis were very weak and broad.     

Synthesis of Mg-Al and Zn-Al-layered double hydroxide nanocrystals using laser ablation in water

In this paper, we report our results on the synthesis of Mg-Al and Zn-Al-layered double hydroxides using the laser ablation in the liquid technique. To prepare these layered double hydroxides (LDH) we first began with the laser generation of a Mg (or zinc) target submerged in deionized water and then ablated an aluminum target submerged in the previously prepared Mg-deionized water suspensions (Mg-dw) to produce Mg-Al LDH and in Zn-dw to prepare Zn-Al LDH. In these ablation tests, the Mg ablation duration was selected to vary from 5 to 60 min, while the Al ablation duration was kept constant at 30 min for all samples. The generated Mg-Al LDH was a gel-like and well crystallized nanoparticles of a rod-like shape and were arranged in a well-organized pattern. When the Mg ablation duration between 25 and 35 min, the synthesized nanocrystals were stoichiometric with a formula of Mg₆Al₂(OH)₁₈4.5(H₂O), the interlayer distance (d_(0 0 3)-spacing) was 7.8 Å and the average grain size was 8.0 nm. The synthesized Zn-Al LDH revealed various lamellar thin plate-like nanostructures of hexagonal morphologies. The average diameters of these structures was about 500 nm and the thickness of a single layer was approximately about 6.0 nm. The XRD diffraction peaks were indexed in hexagonal lattice with a_o=3.07 Å and c_o=15.12 Å. These indexes were (0 0 2), (0 0 4), and (0 0 8) and the corresponding interlayer distances, d-spacing (Å), were 7.56 (0 0 2), 3.782 (0 0 4), and 1.891 (0 0 8), respectively.