Platinum Sheets Research Articles

Electro-microgellation of CS/PL spheres in situ self-embedded with AgNPs as a losartan delivery system

In situ electrosynthesis of new hybrid colloidal microgel particles of chitosan (CS)-pullulan (PL) self-embedded with AgNPs and introduced as a drug carrier for losartan (LOS) as a drug model. The impact of using Platinum (Pt) and Silver (Ag) sheets as anode and the electrosynthesis time on the formation mechanism, morphology, compositional and structural properties have been examined. The prepared samples characterized using uv–visible spectroscopy (UV–vis), transmission electron microscope (TEM), zeta potential, Fourier transform infrared spectroscopy (FTIR), Inductively coupled plasma optical emission spectroscopy (ICP-OES), x-ray diffraction analysis (XRD), and stability test. In addition to the Assessment of the antibacterial activity of the prepared samples. Also, incorporation of LOS in situ during the preparation of the microgel was investigated. The results demonstrated that uniform AgNPs with an average size 5.4 nm successfully in situ self-embedded within CS/PL microgel particles of a dual size distribution 151.4 and 43.5 nm with surface charge +25 mV. Besides, the incorporation of AgNPs during the electrosynthesis process played a crucial role in the morphology transition from pearl-necklace to microsphere. additionally, stability examination of the microgel particles introduced a valuable result that the single sphere containing Ag+ ions underwent a slow reduction rate in consistency with nucleation favored overgrowth. Incorporation of AgNPs within CS/PL microgel has considerably enhanced the antimicrobial potential of the realized CS/PL against both gram-positive and gram-negative bacteria Investigation of the ability of the losartan incorporation explored a stable core/shell like structure with average size 95 nm and zeta potential + 39 mV promoting the spheres stability.

Gas-phase microactuation using kinetically controlled surface states of ultrathin catalytic sheets

Biological systems convert chemical energy into mechanical work by using protein catalysts that assume kinetically controlled conformational states. Synthetic chemomechanical systems using chemical catalysis have been reported, but they are slow, require high temperatures to operate, or indirectly perform work by harnessing reaction products in liquids (e.g., heat or protons). Here, we introduce a bioinspired chemical strategy for gas-phase chemomechanical transduction that sequences the elementary steps of catalytic reactions on ultrathin (<10nm) platinum sheets to generate surface stresses that directly drive microactuation (bending radii of 700nm) at ambient conditions (T = 20°C; Ptotal = 1atm). When fueled by hydrogen gas and either oxygen or ozone gas, we show how kinetically controlled surface states of the catalyst can be exploited to achieve fast actuation (600ms/cycle) at 20°C. We also show that the approach can integrate photochemically controlled reactions and can be used to drive the reconfiguration of microhinges and complex origami- and kirigami-based microstructures.

Interface and Charge Induced Molecular Self-Assembly Strategy for the Synthesis of Reduced Graphene Oxide Coated with Mesoporous Platinum Sheets.

The design of porous noble metal catalysts holds great promise in various electrocatalytic applications. However, it is still a challenge to improve the durability performance through constructing stable framework. Here, an interface and charge induced strategy is developed to synthesize large-sized continuous reduced graphene oxide@mesoporous platinum (denoted as rGO@mPt) sheets under kinetic control by molecular self-assembly design. Graphene oxide (GO) is a promising large-sized growth interface for platinum. Cationic surfactant dioctadecyldimethylammonium chloride bridges the negatively charged GO and platinum precursors, while creating interconnected mesopores. The successful synthesis of rGO@mPt sheets relies on proper kinetic control, which is achieved by controlling pH, temperature, and the complexation of bromide ions. rGO@mPt sheets present strong crystallinity with a pure face-centered cubic Pt phase. Worm-like mesostructures with an average pore size of 2.2nm exist throughout the sheets. rGO@mPt sheets possess both stable framework and abundant active sites, which markedly improve the durability on methanol oxidation reaction while maintaining relatively good catalytic activity. Long-term stability test shows a slight loss of 1.2% activity after 250 cycles. Amperometric i-t curves reveal the mass current three times higher compared to commercial Pt/C at 3000s.

Experimental and numerical investigation of gas–liquid flow in water electrolysis under magnetic field

The effect of a uniform magnetic field on the water electrolysis reaction in 4.46mol/L KOH solution was investigated. A set of magnets is used to set up the uniform field which is parallel to the electrode surfaces. Two parallel platinum sheets (4×4mm) embedded into glass surfaces are used as cathode and anode. Experiment results show that when the direction of Lorentz force is opposite to gravity, the force plays positive effect on the decrease of cell voltage all the time within experiment current range. If the orientation of Lorentz force is inversed, i.e. same to gravity, the force is no longer useful to decrease the cell voltage with the current density of 1.5A/cm2 below. Furthermore, Euler-Euler model is used to simulate the gas generation, electrolyte flow and gas distribution. The simulation results show that if Lorentz force is in the opposite direction of gravity, it helps gaseous product outflow directly. On the contrary, if the force is in the direction of gravity, it induces a vortex around anode and cathode which is against of expelling gas off the electrodes especially in the case of lower current density.

5V-class bulk-type all-solid-state rechargeable lithium batteries with electrode-solid electrolyte composite electrodes prepared by aerosol deposition

Composite electrodes (∼9 μm in thickness) composed of 5V-class electrode of LiNi0.5Mn1.5O4 (LNM) and high Li+ conductive crystalline-glass solid electrolyte (LATP, Ohara Inc.) were prepared at room temperature by aerosol deposition (AD) on platinum sheets. The resultant LNM-LATP composite electrodes were combined with LiPON and Li, and 5V-class bulk-type all-solid-state rechargeable lithium batteries (SSBs) were prepared. The crystallnity of the LNM in the LNM-LATP composite electrode was improved by annealing. Both thermogravimetry-mass spectroscopy analysis and XRD analysis clarified that the side reactions between the LNM and the LATP occurred over 500 °C with oxygen release. From these results, annealing temperature of the LNM-LATP composite electrode system was optimized at 500 °C due to the improved crystallinity of the LNM with avoiding the side-reactions. The SSBs with the composite electrodes (9 μm in thickness, 40 vol% of the LNM) annealed at 500 °C delivered 100 mAh g−1 at 10 μA cm−2 at 100 °C. Degradation of the discharge capacity with the repetition of the charge-discharge reactions was observed, which will originate from large volume change of the LNM (∼6.5%) during the reactions.

Preparation and Performance of Polypyrrole Film with Micro-Antennal Morphology for Medical Biology

PPy film with micro-antennal morphology was prepared by potentio-static method without any templates directly onto the surfaces of iron, platinum and gold-plated plastic sheets, respectively. Morphology of PPy film was observed with scanning electron microscopy, and its electrochemical properties were determined by means of cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Attention was paid to the influence of reaction time, potential value, types of substrates, types and conconcentrations of electrolyte on the morphology and electrochemical properties of PPy film. Stable PPy film with thriftily long antennae was obtained on different substrates with good electrochemical properties. The film was applied for a prototype of biosensor, in which bioactive substance of glucose oxidase was immobilized.

PtTe 2: Potential new material for the growth of defect-free TeO 2 single crystals

The dissociation of Te–O bonds is the main drawback, which hampers the yield of large-sized paratellurite single crystals of high optical quality when using platinum crucibles. In this work, it is assumed that a catalytic dissociation process involves the intermediate formation of platinum tellurides, these ones being then responsible for entrapment of gas bubbles and black precipitates when growth proceeds. To alleviate this difficulty, we suggest that platinum ditelluride could be a chemically more appropriate compound instead of pure platinum. First experiments on direct transformation of platinum sheets into PtTe 2 under tellurium gas atmosphere are described, as well as the procedure used to elaborate a PtTe 2 crucible. First seeded Bridgman growth performed in such container yielded a TeO 2 single crystal free of defects, thus confirming the validity of our hypothesis about the dissociation process of Te–O bonds.

Pesticide Determination by Enzymatic Inhibition and Amperometric Detection in a Low-Temperature Cofired Ceramics Microsystem

Among the several fabrication techniques used to construct microflow systems, the low-temperature cofired ceramics (LTCC) technology, taking advantage of its multilayer approach, is one of the most versatile ones. It permits the integration of several unitary operations of an analytical process in a modular or monolithic way. Moreover, due to its perfect compatibility with screen-printing techniques, it also permits the integration of electronic components used to control the whole system setup. In this work the design, construction, and evaluation of a miniaturized analyzer for pesticide determination that integrates a pretreatment stage, based on two mixers or reactors, and an amperometric detection system to measure the product of an enzymatic inhibition reaction are presented. The detection system was monolithically integrated in the microfluidic platform, and it consisted of a screen-printed reference electrode and two platinum sheets, acting as auxiliary and working electrodes, which were embedded within the ceramic structure. The miniaturized system was characterized and successfully evaluated by determining carbofuran at the nanomolar level.

Foamlike Nanostructures Created from Dendritic Platinum Sheets on Liposomes

The synthesis of novel dendritic platinum sheets of 2-nm thickness by the reduction of an aqueous metal complex with ascorbic acid in the presence of liposomes is reported. Variation of the reaction conditions, including incorporation of a tin porphyrin photocatalyst within the liposomal bilayer to initiate seed-particle growth, allows access to a diverse range of platinum nanostructures, including dendritic nanosheets of uniform diameters and convoluted foamlike structures composed of interwoven dendritic nanosheets. The mechanism of formation of these nanomaterials is investigated with regard to the photocatalytic generation of platinum nanoparticle seeds, the autocatalytic dendritic growth, and the templating on liposomes. The discrete nanospheres of foamlike platinum are of particular interest, as they may have advantages over conventional platinum black in some applications. For example, they will likely exhibit improved electrical connectivity and mass-transport properties in electrocatalytic applications. Electrochemical CO-stripping measurements and N2 adsorption experiments show that the nanospheres of foamlike platinum possess high surface areas. In addition, these platinum foam nanospheres are as active as commercial platinum black in catalyzing the four-electron oxygen reduction reaction.

Free-standing nanofibrous platinum sheets and their conductivity

Nanofibrous platinum sheets with a thickness of one to a few tens of nanometres were prepared over the submicron pores of polymer substrates by using long and rigid cadmium hydroxide nanostrands as templates, and these free-standing sheets gave metallic conductivity that varied greatly with the thickness.

Controlled synthesis of 2-D and 3-D dendritic platinum nanostructures.

Seeding and autocatalytic reduction of platinum salts in aqueous surfactant solution using ascorbic acid as the reductant leads to remarkable dendritic metal nanostructures. In micellar surfactant solutions, spherical dendritic metal nanostructures are obtained, and the smallest of these nanodendrites resemble assemblies of joined nanoparticles and the nanodendrites are single crystals. With liposomes as the template, dendritic platinum sheets in the form of thin circular disks or solid foamlike nanomaterials can be made. Synthetic control over the morphology of these nanodendrites, nanosheets, and nanostructured foams is realized by using a tin-porphyrin photocatalyst to conveniently and effectively produce a large initial population of catalytic growth centers. The concentration of seed particles determines the ultimate average size and uniformity of these novel two- and three-dimensional platinum nanostructures.

The Preparation and Structure of Platinum Metal Nanosheets between Graphite Layers

Platinum chloride−graphite intercalated compounds (PtCl4−GICs) with a stage three structure were produced by mixing platinum tetrachloride and graphite at 723 K under 0.3 MPa of chlorine atmosphere. Two-dimensional platinum nanosheets with a thickness of 2−3 nm and a width of 5−300 nm were formed between graphite layers by hydrogen reduction of PtCl4−GICs at 573 K. The sheets had a number of hexagonal holes and edge angles of 120°, owing to the limited aggregation of the intercalated platinum chloride molecules to platinum sheets along regular hexagonal nets of carbon atoms between graphite layers.

High dose behind inhomogeneities during medium-energy x-ray irradiation

Medium-energy x-rays from orthovoltage treatment units are used for a variety of radiotherapy treatments ranging from cutaneous malignancies in the head and neck region to bone metastases. It was the aim of the present study to investigate the dose distribution due to secondary electrons close behind inhomogeneities in these radiation qualities. The dose was assessed in a solid water phantom using three plane-parallel ionization chambers (NE 2532/2, `Markus' and `Attix' chamber) and sheets of aluminium, copper, zinc, platinum, lead and bone equivalent material. The depth dose distribution directly behind the inhomogeneity was assessed using sheets of thick polyethylene foil. A dose increase was found directly behind inhomogeneities of high atomic number with a rapid dose fall-off over the first . The dose downstream of the inhomogeneity was found to increase with increasing beam quality from 120 kVp (HVL 2.8 mm Al) to 250 kVp (HVL 2 mm Cu). In the latter the dose was increased directly behind lead and platinum sheets by up to a factor of eight compared with a solid water depth of similar attenuation. The results of the study demonstrate the importance of using appropriate materials if shielding is in contact with the patient.

A Modified Z-Type Flow-through Cell for Optical, Electrochemical, and Optoelectrochemical Flow Injection Analysis Measurements

The design and construction of a modified Z-type flow-through cell that can be used for optical, electrochemical, and optoelectrochemical measurements are reported. In optical analysis, the proposed flow cell is placed in the light path of a spectrophotometer and worked as a commercial Z-type optical flow cell. In electrochemical analysis, the working and auxiliary electrodes are two platinum sheets placed at both ends of the cell cavity; the cell cavity is enclosed by two glass windows. The reference electrode is a saturated calomel electrode placed downstream in an overflow tube. The performance of the proposed electrochemical flow cell was studied by analysis of hexacyanoferrate solution as an electroactive species. In optoelectrochemical analysis, the proposed flow cell is operated optically and electrochemically, simultaneously. The flow cell is placed in the light path of a spectrophotometer, constant potential is applied to the electrodes, and the optical and electrochemical signals are recorded simultaneously by the use of two recorders.

The reactions of Bi(PbSrCaCuOAg supercnducting microcomposites placed in contact with silver, gold, palladium, nickel, copper and platinum substrates

Abstract Bi(Pb)SrCaCuOAg (BSCCO-Ag) superconducting microcomposites were produced by oxidation, annealing and deformation of metallic precursor alloys. Silver, gold, palladium, nickel, copper and platinum sheets have been used to produce two-dimensional superconducting composites via deformation-annealing processes. The reactions between BSCCO-Ag and these metallic elements and the effects of these reactions on the superconducting properties of the BSCCO-Ag microcomposites were studied by a combination of microstructural observation and microanalysis. Silver, gold and palladium do not oxidize at elevated temperatures, and they have very little or no reaction with BSCCO-Ag microcomposites. Microcomposite specimens in contact with silver, gold and palladium sheets possess a high T c (T R=0 = 102−108 K ) and reasonably good J c (J c(77 K ) = 400−1000 A cm −2 ) . The microstructure of these samples showed a well-developed textured 2:2:2:3 phase embedded in the silver matrix. Nickel and copper partially or fully oxidized under the annealing conditions. These elements reacted with BSCCO, prevented the formation of the 2:2:2:3 phase and resulted in a 2:2:1:2 phase dominant microstructure with lower T c (T R=0 ≈75 K ) . Platinum entered the silver phase in the BSCCO-Ag microcomposites, forming AgPt solid solutions, and reacted with the BSCCO compounds to form several complicated oxide phases. Thin silver sheets have been successfully used to separate BSCCO-Ag and stainless steel and thereby to prevent reactions between stainless steel and the microcomposite.

A Study Of Diffusion Zones With Electron Microprobe Compositional Mapping

Digital compositional mapping with the electron microprobe has been used to study diffusion zones at metal-metal and metal-glass interfaces. Image enhancement techniques and concentration-histogram images (CHI’s) have been used with these digital maps to improve visual display and interpretation of the movement of elements in these zones.Metal-Metal Interface. In figure la is a WDS concentration map of gold taken from a specimen of a gold sheet about 40 μm wide sandwiched between two platinum sheets. This specimen was observed as part of a metallurgical study of some ancient Ecuadorian artifacts to better understand the original reaction/diffusion zone between these two metals. The specimen was annealed at 1350°C for 3 min. and then rapidly cooled. This temperature was sufficient to melt the gold (M.P. 1064°C) but not the platinum (M.P. 1769°C). The map in figure la shows that some platinum has diffused into the gold region, but the extent of diffusion is difficult to see in this original grey-level image.

Electrochemical studies of self-doped conducting polymers: Verification of the ‘cation-popping’ doping mechanism

Cyclic voltammetry in conjunction with X-ray microprobe analysis has been used to investigate the doping mechanism in covalently-bonded-anion (self-doped) conducting polymers. The polymers investigated are the acid and sodium salt forms of poly 3-(4-butanesulfonate) thiophene (P3-BTSH and P3-BTSNa, respectively) and poly 3-(2-ethane sulphonate) thiophene (P3-ETSNa). These water-soluble polymers, whose synthesis is described in detail, were used (in the form of films cast from solution onto ITO glass or platinum sheets) as working electrodes in cyclic voltammetry experiments in which the proton or Na + concentration of the electrolyte was monitored. The results directly verify the proposed doping mechanism: charge injection into the π-electron system of the conjugated polymer accompanied by proton or sodium ion ejection, without incorporation of electrolyte anion, leaving behind the oppositely charge counterion.

Faradaic electrochemistry at microcylinder, band, and tubular band electrodes

Current-time relationships of faradaic processes at microcylinder, band, and tubular band electrodes have been evaluated. Microcylinder electrodes were fabricated from platinum wires (5 μm radius) sealed in glass capillaries. Band and tubular electrodes were constructed with platinum sheets (∼ 20 μm width) or thin pieces of graphite (∼ 5 μm width) sealed between insulating mateials. The temporal response of the current at a microcylinder electrode for the reduction of ferricyanide in aqueous potassium chloride solutions is in excellent agreement with that predicted by equations derived for heat flux to a cylinder. An estimation of the magnitude and temporal properties of the measured current at a band electrode can be obtained when a hemicylinder geometry is assumed. The current respone is identical at band and tubular band electrodes even for the smallest tubular radius investigated, 0.54 mm. Cyclic voltammograms at electrodes of all three geometries show significant contributions from radial diffusion at slow scan rates (< 20 mV s −1). The current at a graphite tubular band electrode was found to be independent of flow of solution through the electrode at flow rates up to 3 ml min −1.

Untersuchungen über anionenadsorption an metalloberflächen in Abhängigkeit vom Potential

Following previous studies on the dependence of the absorption of SO42−, I− and Cl− from aqueous solutions upon the potential of the platinum sheets at which the adsorption of radioactively-tagged ions had been measured [cf Electrochim. Acta 6, 223 (1962)], equipment has now been set up which permits to measure the adsorption of 131I− on thin sheets and foils (Pt and Au were studied so far) in such a way that the concentration of I− by transference in a solution layer at the electrode cannot distort the results. The apparatus is modelled on the procedure described by Kafalos and Gatos [Rev. Sci. Instrum. 29, 47 (1958)] and gives well reproducible results. These results indicate that electrodes covered with oxygen by anodic pre-polarization in solutions not containing I− do not adsorp I−; adsorption occurs only after cathodic reduction of the oxygen and goes through a maximum with increasing anodic polarization. The decrease of the adsorption upon further increase of the anode potential is due to discharge of I− and desorption of I2. The maximum coverage with adsorbed I− corresponds to about a monolayer; complete desorption of I− can be brought about by cathodic polarization.