Impedance spectroscopy of novel hybrid composite films of polyvinylbutyral (PVB)/functionalized mesoporous silica

Polyvinyl butyral/functionalized mesoporous silica hybrid composite films have been fabricated by solution casting technique with various weight percentages of functionalized silica. A polyol (tripentaerythritol-electron rich component), which acts as an electron donor to the polymer backbone, was added to enhance the conductivity. The prepared composites were characterized by Fourier transformed infrared spectroscopy and the morphology was evaluated by scanning electron microscopy. Dielectric properties of these freestanding composites were studied using the two-probe method. The dielectric constant and impedance value decreased with the increase in applied frequency as well as with the increase in functionalized silica content in the polyvinyl butyral matrix. An increase in conductivity of the PVB/functionalized silica composites was also observed. (C) 2013 Elsevier Ltd. All rights reserved.

Cloning and sequence of a cDNA encoding a novel hybrid prolme-rich protein associated with cytokinin-induced haustoria formation in Cuscuta reflexa

A complete cDNA encoding a novel hybrid Pro-rich protein (HyPRP) was identified by differentially screening 3x10(4) recombinant plaques of a Cuscuta reflexa cytokinin-induced haustorial cDNA library constructed in lambda gt10. The nucleotide (nt) sequence consists of: (i) a 424-bp 5'-non coding region having five start codons (ATGs) and three upstream open reading frames (uORFs); (ii) an ORF of 987 bp with coding potential for a 329-amino-acid (aa) protein of M(r), 35203 with a hydrophobic N-terminal region including a stretch of nine consecutive Phe followed by a Pro-rich sequence and a Cys-rich hydrophobic C terminus; and (iii) a 178-bp 3'-UTR (untranslated region). Comparison of the predicted aa sequence with the NBRF and SWISSPROT databases and with a recent report of an embryo-specific protein of maize [Jose-Estanyol et al., Plant Cell 4 (1992) 413-423] showed it to be similar to the class of HyPRPs encoded by genes preferentially expressed in young tomato fruits, maize embryos and in vitro-cultured carrot embryos. Northern analysis revealed an approx. 1.8-kb mRNA of this gene expressed in the subapical region of the C. reflexa vine which exhibited maximum sensitivity to cytokinin in haustorial induction.

Low-density three-dimensional foam using self-reinforced hybrid two-dimensional atomic layers

Low-density nanostructured foams are often limited in applications due to their low mechanical and thermal stabilities. Here we report an approach of building the structural units of three-dimensional (3D) foams using hybrid two-dimensional (2D) atomic layers made of stacked graphene oxide layers reinforced with conformal hexagonal boron nitride (h-BN) platelets. The ultra-low density (1/400 times density of graphite) 3D porous structures are scalably synthesized using solution processing method. A layered 3D foam structure forms due to presence of h-BN and significant improvements in the mechanical properties are observed for the hybrid foam structures, over a range of temperatures, compared with pristine graphene oxide or reduced graphene oxide foams. It is found that domains of h-BN layers on the graphene oxide framework help to reinforce the 2D structural units, providing the observed improvement in mechanical integrity of the 3D foam structure.

Novel thiophene derivative hybrid composite solar cells

In this work composites of poly(3-hexylethiophene) (P3HT) and a thiophene derivative (7, 9-di (thiophen-2-yl)-8H-cyclopenta[a]acenaphthylen-8-one) (DTCPA) having donor acceptor architecture (DAD) were prepared. Photovoltaic properties of these hybrid composites were evaluated. DTCPA, which is a highly crystalline organic molecule with wide absorption range, was observed to improve the open circuit voltage of the solar cell. Furthermore, DTCPA crystals acts as a nucleating center and increases the molecular ordering of P3HT in the composite. Improved charge separation efficiency was observed by photoluminescence spectroscopy. Because of high built in potential in these devices, large open circuit voltage was observed. (C) 2011 Elsevier B.V. All rights reserved.

Formation of crystalline diamond from amorphous diamond-like carbon films by pulsed laser irradiation

The formation of crystalline diamond films from amorphous diamond-like carbon films by pulsed laser irradiation with a 300 μs non-Q-switched Nd:YAG laser has been established by a combined study of transmission electron microscopy, x-ray photoelectron spectroscopy, and electrical resistivity. The films have been prepared by glow discharge decomposition of a mixture of propane, n-butane, and hydrogen in a rf plasma operating at a frequency of 13.56 MHz. Prior to laser irradiation, the films have been found to be amorphous by transmission electron microscope studies. After irradiation, the electron diffraction patterns clearly point out the formation of cubic diamond structure with a lattice spacing of 3.555 Å. However, the close similarity between diamond and graphite electron diffraction patterns could sometimes be misleading regarding the formation of a diamond structure, and hence, x-ray photoelectron spectroscopic studies have been carried out to confirm the results. A chemical shift in the C 1s core level binding energies towards higher values, viz., from 286.5 to 287.8 eV after laser irradiation, and a high electrical resistivity >1013 Ω cm are consistent with the growth of diamond structure. This novel "low-temperature, low-pressure" synthesis of diamond films offers enormous potential in terms of device compatibility with other solid-state devices.

Hybrid Sol-Gel Combustion Synthesis of Nanoporous Anatase

Nanoporous anatase with a thin interconnected filmlike morphology has been synthesized in a single step by coupling a nonhydrolytic condensation reaction of a Ti precursor with a hybrid sol-gel combustion reaction. The method combines the advantages of a conventional sol-gel method for the formation of porous structures with the high crystallinity of the products obtained by combustion methods to yield highly crystalline, phase-pure nanoporous anatase. The generation of pores is initiated by the formation of reverse micelles in a polymeric polycondensation product, which expand during heating, leading to larger pores. A reaction scheme involving a complex formation and nonhydrolytic polycondensation reaction with ester elimination leads to the formation of ail extended Ti-O-Ti network. The effect of process parameters, such as temperature and relative ratio of cosurfactants, on phase formation has been studied. The possibility of band gap engineering by controlled doping during synthesis and the possibility of attachment of molecular/nanoparticle sensitizers provide opportunities for easy preparation of photoanodes for solar cell applications.

Transport and magnetic properties of conducting polyaniline doped with BX3 (X=F, Cl, and Br)

We report transport and magnetic properties of a different class of highly conducting polyaniline, doped with boron trihalides BX3 (X=F, Cl, and Br). In order to understand the transport mechanism we analyze the temperature dependence of resistivity of a large number of samples, made by pelletizing doped polyaniline powder and by doping films of polyaniline. We find that the charge transport in this class of conducting polyaniline is driven by the charging-energy limited transport of charge carriers, in contrast to the quasi-one-dimensional variable range hopping conduction prevalent in conventional proton-doped polyaniline samples. Magnetic susceptibility provides further insight into the unusually high intrinsic conductivity behavior.

Controlled photoluminescence from self-assembled semiconductor-metal quantum dot hybrid array films

Thin films of hybrid arrays of cadmium selenide quantum dots and polymer grafted gold nanoparticles have been prepared using a BCP template. Controlling the dispersion and location of the respective nanoparticles allows us to tune the exciton-plasmon interaction in such hybrid arrays and hence control their optical properties. The observed photoluminescence of the hybrid array films is interpreted in terms of the dispersion and location of the gold nanoparticles and quantum dots in the block copolymer matrix.

Cobalt oxide thin films prepared by metalorganic chemical vapor deposition from cobalt acetylacetonate

Thin films of cobalt oxide have been deposited on various substrates, such as glass, Si(100), SrTiO3(100), and LaAlO3(100), by low pressure metalorganic chemical vapor deposition (MOCVD) using cobalt(IL), acetylacetonate as the precursor. Films obtained in the temperature range 400-600 degreesC were uniform and highly crystalline having Co3O4 phase as revealed by x-ray diffraction. Under similar conditions of growth, highly oriented thin films of cobalt oxide grow on SrTiO3(100) and LaAlO3(100). The microstructure and the surface morphology of cobalt oxide films on glass, Si(100) and single crystalline substrates, SrTiO3(100) and LaAlO3(100) were studied by scanning electron microscopy. Optical properties of the films were studied by uv-visible-near IR spectrophotometry.

Energy-efficient synthesis of ferrite powders and films

In recent years, there has been significant effort in the synthesis of nanocrystalline spinel ferrites due to their unique properties. Among them, zinc ferrite has been widely investigated for countless applications. As traditional ferrite synthesis methods are energy- and time-intensive, there is need for a resource-effective process that can prepare ferrites quickly and efficiently without compromising material quality. We report on a novel microwave-assisted soft-chemical synthesis technique in the liquid medium for synthesis of ZnFe2O4 powder below 100 °C, within 5 min. The use of β-diketonate precursors, featuring direct metal-to-oxygen bonds in their molecular structure, not only reduces process temperature and duration sharply, but also leads to water-soluble and non-toxic by-products. As synthesized powder is annealed at 300 °C for 2 hrs in a conventional anneal (CA) schedule. An alternative procedure, a 2-min rapid anneal at 300 °C (RA) is shown to be sufficient to crystallize the ferrite particles, which show a saturation magnetization (MS) of 38 emu/g, compared with 39 emu/g for a 2-hr CA. This signifies that our process is efficient enough to reduce energy consumption by ∼85% just by altering the anneal scheme. Recognizing the criticality of anneal process to the energy budget, a more energy-efficient variation of the reaction process was developed, which obviates the need for post-synthesis annealing altogether. It is shown that the process also can be employed to deposit crystalline thin films of ferrites.

Development of uniformly grown ZnO NPs films using single precursor solution by pulsed spray pyrolysis technique

In this article, we have reported the controlled synthesis of uniformly grown zinc oxide nanoparticles (ZnO NPs) films by a simple, low-cost, and scalable pulsed spray pyrolysis technique. From the surface analysis it is noticed that the as-deposited films have uniformly dispersed NPs-like morphology. The structural studies reveal that these NPs films have highly crystalline hexagonal crystal structure, which are preferentially orientated along the (001) planes. The size of the NPs varied between 5 and 100 nm, and exhibited good stoichiometric chemical composition. Raman spectroscopic analysis reveals that these ZnO NPs films have pure single phase and hexagonal crystal structure. These unique nanostructured films exhibited a low electrical resistivity (5 Omega cm) and high light transmittance (90 %) in visible region.

Synthesis and characterization of single-crystalline alpha-MoO3 nanofibers for enhanced Li-ion intercalation applications

High quality, single-crystalline alpha-MoO3 nanofibers are synthesized by rapid hydrothermal method using a polymeric nitrosyl-complex of molybdenum(II) as molybdenum source without employing catalysts, surfactants, or templates. The possible reaction pathway is decomposition and oxidation of the complex to the polymolybdate and then surface condensation on the energetically favorable 001] direction in the initially formed nuclei of solid alpha-MoO3 under hydrothermal conditions. Highly crystalline alpha-MoO3 nanofibers have grown along 001] with lengths up to several micrometres and widths ranging between 280 and 320 nm. The alpha-MoO3 nanofibers exhibit desirable electrochemical properties such as high capacity reversibility as a cathode material of a Li-ion battery.

MOCVD of aluminium oxide films using aluminiurn beta-diketonates as precursors

Deposition of Al2O3 coatings by CVD is of importance because they are often used as abrading material in cemented carbide cutting tools. The conventionally used CVD process for Al2O3 involves the corrosive reactant AlCl3. In this paper, we report on the thermal characterisation of the metalorganic precursors namely aluminium tristetramethyl-heptanedionate [Al(thd)(3)] and aluminium tris-acetylacetonate [Al(acac)(3)] and their application to the CVD of Al2O3 films. Crystalline Al2O3 films were deposited by MOCVD at low temperatures by the pyrolysis of Al(thd)(3) and Al(acac)(3). The films were deposited on a TiN-coated tungsten carbide (TiN/WC) and Si(100) substrates in the temperature range 500-1100degreesC. The as-deposited films were characterised by x-ray diffraction, optical microscopy, scanning and transmission electron microscopy, Auger electron spectroscopy. The observed crystallinity of films grown at low temperatures, their microstructure, and composition may be interpreted in terms of a growth process that involves the melting of the metalorganic precursor on the hot growth surface.

Dielectric relaxations above room temperature in DMPU derived polyaniline film

Dielectric measurements carried out on drop casted from solution of emeraldine base form of polyaniline films in the temperature range 30-300 degrees C revealed occurrence of two maxima in the loss tangent as a function of temperature. The activation energies corresponding to these two relaxation processes were found to be similar to 0.5 eV and similar to 1.5 eV. The occurrence of one relaxation peak in the dispersion curve of the imaginary part of the electric modulus suggests the absence of microphase separation in the film. Thermogravimetric analysis and infrared spectroscopic measurements showed that the films retained its integrity up to 300 degrees C. The dielectric relaxation at higher temperatures with large activation energy of 1.5 eV is attributed to increase in the barrier potential due to decrease in the polymer conjugation as a result of wide amplitude motion of the chain segments well above the glass transition temperature. (c) 2012 Elsevier B.V. All rights reserved.

Flexible Phynox Alloy with Integrated Piezoelectric Thin Film for Micro Actuation Application

In this paper, we report on the application aspect of piezoelectric ZnO thin film deposited on flexible phynox alloy substrate. Highly crystalline piezoelectric ZnO thin films were deposited by RF reactive magnetron sputtering and were characterized by XRD, SEM, AFM analysis. Also, the effective d(33) coefficient value measurement was performed. The actuator element is a circular diaphragm of phynox alloy on to which piezoelectric ZnO thin film was deposited. ZnO film deposited actuator element was firmly fixed inside a suitable concave perspex mounting designed specifically for micro actuation purpose. The actuator element was excited at different frequencies for the supply voltages of 2V, 5V and 8V. Maximum deflection of the ZnO film deposited diaphragm was measured to be 1.25 mu m at 100 Hz for the supply voltage of 8V. The developed micro actuator has the potential to be used as a micro pump for pumping nano liters to micro liters of fluids per minute for numerous biomedical and aerospace applications.