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41.
H. Mallik 《Journal of Non》2006,352(8):795-800
Gum Arabica is a naturally occurring conducting biomaterial biopolymer, its various aspects of electrical and structural characteristics have been investigated in our earlier works. In the present work the ionic gel formation of Gum Arabica and its electro-chemical application were experimentally investigated. Hot concentrated aqueous solution of Gum Arabica with phosphoric acid, minimum 16% of solute, was found to form ionic hydrogel on slow cooling. It consists of polyelectrolyte molecules cross-linked by phosphate ions by chemical bonds into an integrated spatial network in water solvent. The increase in surface to volume ratio shows a gel collapse to provide transparent solid material. Gel formation of Gum Arabica was also studied with chromium and molybdenum oxide as cross-linking agent. The various studies carried out on the mentioned materials to investigate its structural and electrical characteristics are XRD, DSC, SEM and impedance spectroscopy. The said gel was found to provide a good electro-chemical cell with suitable redox pair. 相似文献
42.
Multilayer polyelectrolyte films as nanofiltration membranes for separating monovalent and divalent cations 总被引:1,自引:0,他引:1
Alternating adsorption of polyanions and polycations on porous supports provides a convenient way to prepare ion-selective nanofiltration membranes. This work examines optimization of ultrathin, multilayer polyelectrolyte films for monovalent/divalent cation separations relevant to water softening. Membranes composed of five bilayers of poly(styrene sulfonate)/poly(allylamine hydrochloride) (PSS/PAH) on porous alumina supports allow a solution flux of 0.85 m3/(m2 day) at 4.8 bar, and exhibit 95% rejection of MgCl2 along with a Na+/Mg2+ selectivity of 22. Similar results were obtained in Na+/Ca2+ separations. PSS/poly(diallyl-dimethylammonium chloride) (PDADMAC) films permit higher fluxes than PSS/PAH systems due to the higher swelling of films containing PDADMAC, but the Mg2+ rejection by PSS/PDADMAC membranes is less than 45%. However, capping PSS/PDADMAC films with a bilayer of PSS/PAH yields Mg2+ rejections and Na+/Mg2+ selectivities that are typical of pure PSS/PAH membranes. Separation performance can be optimized through control over deposition conditions (pH and supporting electrolyte concentration) and the charge of the outer layer since Donnan exclusion is a major factor in monovalent/divalent cation selectivity. Streaming potential measurements demonstrate that the magnitude of positive surface charge increases with increasing concentrations of Mg2+ in solution or when the outer polycation layer is deposited from a solution of high ionic strength. 相似文献
43.
Transparent conducting zinc oxide thin films were prepared by spray pyrolytic decomposition of zinc acetate onto glass substrates with different thickness. The crystallographic structure of the films was studied by X-ray diffraction (XRD). XRD measurement showed that the films were crystallized in the wurtzite phase type. The grain size, lattice constants and strain in films were calculated. The grain size increases with thickness. The studies on the optical properties show that the direct band gap value increases from 3.15 to 3.24 eV when the thickness varies from 600 to 2350 nm. The temperature dependence of the electrical conductivity during the heat treatment was studied. It was observed that heat treatment improve the electrical conductivity of the ZnO thin films. The conductivity was found to increase with film thickness. 相似文献
44.
The photocatalytic activity of TiO2 films deposited on different substrates by the spray-drying method using suspensions of commercially available TiO2 (Degussa P25 or Tronox) as starting material was studied. The influence of the type of the initial TiO2, preparation conditions (temperature of the substrate during the film deposition, temperature of the post-deposition annealing), substrate material (glass, fused silica, stainless steel and graphite), the presence of additives in the spraying suspension (polyethylene glycol, ethylene glycol and acetylacetone) and its sonication before spraying on the morphology, size of crystallites and phase composition (rutile/anatase ratio) was studied. Optimal conditions for spray deposition of the films are suggested. 相似文献
45.
T. Mills L. G. Kaake X.-Y. Zhu 《Applied Physics A: Materials Science & Processing》2009,95(1):291-296
Electrolytes are finding applications as dielectric materials in low-voltage organic thin-film transistors (OTFT). The presence
of mobile ions in these materials (polymer electrolytes or ion gels) gives rise to very high capacitance (>10 μF/cm2) and thus low transistor turn-on voltage. In order to establish fundamental limits in switching speeds of electrolyte gated
OFETs, we carry out in situ optical spectroscopy measurement of a poly(3-hexylthiophene) (P3HT) OTFT gated with a LiClO4:poly(ethyleneoxide) (PEO) dielectric. Based on spectroscopic signatures of molecular vibrations and polaron transitions,
we quantitatively determine charge carrier concentration and diffusion constants. We find two distinctively different regions:
at V
G≥−1.5 V, drift-diffusion (parallel to the semiconductor/dielectric interface) of hole-polarons in P3HT controls charging of
the device; at V
G<−1.5 V, electrochemical doping of the entire P3HT film occurs and charging is controlled by drift/diffusion (perpendicular
to the interface) of ClO4
− counter ions into the polymer semiconductor. 相似文献
46.
The rate of change of magnetizing field (field-slope), applied for the nondestructive method of magnetic adaptive testing, influences both signal-to-noise ratio and sensitivity of the chosen magnetic parameters with respect to the investigated degradation of the ferromagnetic material (degradation functions). Dependence of the degradation functions sensitivity on the field-slope is analyzed in this paper. It is shown that whereas sensitivity of the top-responsive degradation functions from around the top permeability of the nondegraded (reference) material drops down with increasing field-slope, sensitivity of the mild-responsive degradation functions from regions with lower permeability of the reference material is frequently field-slope-independent. The most favorable choice of the best degradation functions and of the proper magnetizing field-slope remains to be a question of optimum adaptation of the tests both to the investigated material and to the applied measuring technique. 相似文献
47.
Ahmad Umar 《Talanta》2009,77(4):1376-677
High-aspect-ratio ZnO nanowires based ultra-sensitive hydrazine amperometric sensor has been fabricated which showed a high and reproducible sensitivity of 12.76 μA cm−2 nM−1, detection limit, based on S/N ratio, 84.7 nM, response time less than 5 s, linear range from 500 to 1200 nM and correlation coefficient of R = 0.9989. This is the first report in which such a very high-sensitivity and low detection limit has been achieved for the hydrazine sensors by using ZnO nanostructures modified electrodes. Therefore, this work opens a way to utilize simply grown ZnO nanostructures as an efficient electron mediator to fabricate efficient hydrazine sensors. 相似文献
48.
Polymer-like micelles are analogs to polymer solutions and provide an exciting class of materials for both applications and fundamental understanding of polyelectrolyte systems. Small angle neutron and X-ray scattering have been key to the characterization of these materials from the first observations of linear micelle growth. As new materials are developed, these techniques continue to be utilized and combined with other analytical tools to characterize the length and time scales of polymer-like micelle behavior. Recent reports on the use of small-angle scattering to characterize polymer-like and wormlike micelles are reviewed, with focus on new materials, improvements in analytical approaches and anisotropic structures. 相似文献
49.
Subba Reddy ChV Jin AP Zhu QY Mai LQ Chen W 《The European physical journal. E, Soft matter》2006,19(4):471-476
A sodium ion-conducting polymer electrolyte based on polyvinyl pyrrolidone (PVP) complexed with NaClO4 was prepared using the solution-cast technique. The cathode film of V2O5 xerogel modified with polyvinyl pyrrolidone was prepared using the sol-gel method. Investigations were conducted using X-ray
diffractometry (XRD), Fourier transformation infrared (FT-IR) spectroscopy. The ionic conductivity and transference number
measurements were performed to characterize the polymer electrolyte for battery applications. The transference number data
indicated that the conducting species in these electrolytes are the anions. Using the electrolyte, electrochemical cells with
a configuration Na/(PVP + NaClO4)/V2O5 modified by (PVP) were fabricated and their discharge profiles studied. 相似文献
50.
以(R)-叔丁基亚磺酰胺为手性助剂,与1,3-苯二甲醛经缩合反应制得关键中间体——(Rs,Rs)-双叔丁基亚磺酰亚胺(7);锂化的羧酸酯与7经不对称加成反应合成了两个新型的Rh_2(esp)_2配体类似物——(Rs,Rs',R,R')-β-胺基羧酸酯和(Rs,Rs',R,R',R,R')-α,β-氮杂环丙烷羧酸酯,产率分别为96%和65%,非对映选择性均大于20∶1。化合物的结构经1H NMR和13C NMR表征。 相似文献