In situ FTIR study of oxygen adsorption on nanostructured RuO2 thin-film electrode

In situ Fourier transform spectroscopy (FTIR) was used to study interactions of nanostructured ruthenium oxide (RuO₂) thin-film sensing electrode with O₂ at room temperature. RuO₂ nanostructures were pretreated at 1,000 °C for 1 h in order to obtain good crystallinity of amorphous RuO₂ nanoparticles. Morphology and properties of nanostructured RuO₂ were characterized by X-ray diffraction, thermo-gravimetric/differential thermal analysis, scanning electron microscopy, and FTIR. It was shown that pretreated RuO₂ is quite active for O₂ ⁻, O₂ ²⁻, and O²⁻ adsorption with clear 722 cm⁻¹ band for superoxide ions (O₂ ⁻) adsorption for the different oxygen concentrations. The results of in situ FTIR measurements revealed that the active sites for oxygen adsorption are not limited to the triple boundaries, but extended to surfaces of RuO₂ electrodes. Fundamental vibration frequencies of ruthenium–oxygen bond at a temperature of 23 °C as well as region above fundamental frequencies for the nanostructured RuO₂ were identified.     

An ionic liquid-type multiwall carbon nanotubes paste electrode for electrochemical investigation and determination of morphine

The direct electrochemistry of morphine on modified multiwall carbon nanotubes using carbon ionic liquid (i.e., 1-butyl-3-methylimidazolium hexafluoro phosphate, ([C4mim]–[PF6])) was studied. It was found that the electrode showed sensitive voltammetric response to morphine. The experimental results suggested that the modified electrode promoted electron transfer reaction for the oxidation of morphine. The electron transfer coefficient and charge transfer resistant (R _ct) of morphine at the modified electrode were calculated. Under the optimized conditions at pH 8.0, the peak current was linear to morphine concentrations over the concentration range of 0.45–450 μmol L⁻¹, using differential pulse voltammetry. The detection limit was 0.14 μmol L⁻¹. The proposed method was successfully applied to the determination of morphine in both ampoules and urine samples.     

Nanosized IrO<Subscript>2</Subscript> electrocatalysts for oxygen evolution reaction in an SPE electrolyzer

Nanosized IrO₂ electrocatalysts (d ~ 7–9 nm) with specific surface area up to 100 m² g⁻¹ were synthesized and characterized for the oxygen evolution reaction in a solid polymer electrolyte (SPE) electrolyzer. The catalysts were prepared by a colloidal method in aqueous solution and a subsequent thermal treatment. An iridium hydroxide hydrate precursor was obtained at ~100 °C, which was, successively, calcined at different temperatures from 200 to 500 °C. The physico-chemical characterization was carried out by X-ray diffraction (XRD), thermogravimetry–differential scanning calorimetry (TG–DSC) and transmission electron microscopy (TEM). IrO₂ catalysts were sprayed onto a Nafion 115 membrane up to a loading of 3 mg cm⁻². A Pt catalyst was used at the cathode compartment with a loading of 0.6 mg cm⁻². The electrochemical activity for water electrolysis of the membrane-electrode assemblies (MEAs) was investigated in a single cell SPE electrolyzer by steady-state polarization curves, impedance spectroscopy and chrono-amperometric measurements. A maximum current density of 1.3 A cm⁻² was obtained at 1.8 V and 80 °C for the IrO₂ catalyst calcined at 400 °C for 1 h. A stable performance was recorded in single cell for this anode catalyst at 80 °C. The suitable catalytic activity and stability of the most performing catalyst were interpreted in terms of proper combination between nanostructure and suitable morphology.     

Structure and phase stability of nanocrystalline Ce1−x Ln x O2−x/2−δ (Ln = Yb, Lu) in oxidizing and reducing atmosphere

The structure and phase evolution of nanocrystalline Ce_{1− x} Ln _x O_{2− x/2−δ} (Ln = Yb, Lu, x = 0 − 1) oxides upon heating in H₂ was studied for the first time. Up to 950 °C the samples were single-phase, with structure changing smoothly with x from fluorite type (F) to bixbyite type (C). For the Lu-doped samples heated at 1100 °C in the air and H₂, phase separation into coexisting F- and C-type structures was observed for ~0.40 < x < ~0.70 and ~0.25 < x < ~0.70, respectively. It was found also that addition of Lu³⁺ and Yb³⁺ strongly hinders the crystallite growth of ceria during heat treatment at 800 and 950 °C in both atmospheres. Valency of Ce and Yb in Ce_0.1Lu_0.9O_1.55−δ and Ce_0.95Yb_0.05O_1.975−δ samples heated at 1100 °C was studied by XANES and magnetic measurements. In the former Ce was dominated by Ce⁴⁺, with small contribution of Ce³⁺ after heating in H₂. In the latter, Yb existed exclusively as 3+ in both O₂ and H₂.     

Orientation dependence of electrical properties of 0.96Na<Subscript>0.5</Subscript>Bi<Subscript>0.5</Subscript>TiO<Subscript>3</Subscript>-0.04BaTiO<Subscript>3</Subscript> lead-free piezoelectric single crystal

In this paper, a single crystal of 0.96Na_0.5Bi_0.5TiO₃-0.04BaTiO₃ with dimensions of Φ 30×10 mm was grown by the top-seeded-solution growth method. X-ray powder diffraction results show that the as-grown crystal possesses the rhombohedral perovskite-type structure. The dielectric, piezoelectric and electrical conductivity properties were systematically investigated with 〈001〉, 〈110〉 and 〈111〉 oriented crystal samples. The room-temperature dielectric constants for the 〈001〉, 〈110〉 and 〈111〉 oriented crystal samples are found to be 650, 740 and 400 at 1 kHz. The (T _m, ε _m) values of the dielectric temperature spectra are almost independent of the crystal orientations; they are (306°C, 3718), (305°C, 3613) and (307°C, 3600) at 1 kHz for the 〈001〉, 〈110〉 and 〈111〉 oriented crystal. The optimum poling conditions were obtained by investigating the piezoelectric constants d ₃₃ as a function of poling temperature and poling electric field. For the 〈001〉 and 〈110〉 crystal samples, the maximum d ₃₃ values of 146 and 117 pC/N are obtained when a poling electric field of 3.5 kV/mm and a poling temperature of 80°C were applied during the poling process. The as-grown 0.96Na_0.5Bi_0.5TiO₃-0.04BaTiO₃ crystal possesses a relatively large dc electrical conductivity, especially at higher temperature, having a value of 1.98×10⁻¹¹ Ω⁻¹⋅m⁻¹ and 3.95×10⁻⁹ Ω⁻¹⋅m⁻¹ at 25°C and 150°C for the 〈001〉 oriented crystal sample.     

Effect of mixed glass formers on the crystallization kinetics in AgI–Ag<Subscript>2</Subscript>O–V<Subscript>2</Subscript>O<Subscript>5</Subscript>–MoO<Subscript>3</Subscript> glassy superionic system

The crystallization and glass transition kinetics using differential scanning calorimetry (DSC) in 50AgI–33.33Ag₂O–16.67[(V₂O₅)_1−x –(MoO₃) _x ] superionic glassy system is discussed. Thermal stability of glass, studied using various criteria, does not vary significantly with glass former variation. However, the activation energies for structural relaxation (E _s) at glass transition temperature and crystallization (E _c) obtained using Moynihan and Kissinger, Matusita-Sakka formulations found to exhibit interesting trends with MoO₃ substitution in the glass matrix. It is noticed that the electrical conductivity (σ)–temperature (T) cycles obtained at a typical heating rate of 1 °C/min do exhibit significant thermal events. The conductivity after first heating cycle at room temperature is found to be increasing with MoO₃ content and maximum for x = 0.3 (~10⁻³ Ω⁻¹ cm⁻¹ at 30 °C) which is comparable to that of the host 50AgI–33.33Ag₂O–16.67V₂O₅ glassy system. The parameters obtained from σ–T plots and DSC scans do complement each other in a particular range of composition.     

Pulsed laser deposition of Zr–N codoped <Emphasis Type="Italic">p</Emphasis>-type ZnO thin films

Present p-type ZnO films tend to exhibit high resistivity and low carrier concentration, and they revert to their natural n-type state within days after deposition. One approach to grow higher quality p-type ZnO is by codoping the ZnO during growth. This article describes recent results from the growth and characterization of Zr–N codoped p-type ZnO thin films by pulsed laser deposition (PLD) on (0001) sapphire substrates. For this work, both N-doped and Zr–N codoped p-type ZnO films were grown for comparison purposes at substrate temperatures ranging between 400 to 700 °C and N₂O background pressures between 10⁻⁵ to 10⁻² Torr. The carrier type and conduction were found to be very sensitive to substrate temperature and N₂O deposition pressure. P-type conduction was observed for films grown at pressures between 10⁻³ to 10⁻² Torr. The Zr–N codoped ZnO films grown at 550 °C in 1×10⁻³ Torr of N₂O show p-type conduction behavior with a very low resistivity of 0.89 Ω-cm, a carrier concentration of 5.0×10¹⁸ cm⁻³, and a Hall mobility of 1.4 cm² V⁻¹ s⁻¹. The structure, morphology and optical properties were also evaluated for both N-doped and Zr–N codoped ZnO films.     

Influence of pH on the preparation of dispersed Ag–TiO<Subscript>2</Subscript> nanocomposite

In this paper, data concerning the effect of pH on the morphology of Ag–TiO₂ nanocomposite during photodeposition of Ag on TiO₂ nanoparticles is reported. TiO₂ nanoparticles prepared by sol–gel method were coated with Ag by photodeposition from an aqueous solution of AgNO₃ at various pH levels ranging from 1 to 10 in a titania sol, under UV light. The as-prepared nanocomposite particles were characterized by UV–vis absorption spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), and N₂ adsorption/desorption method at liquid nitrogen temperature (−196 °C) from Brunauer–Emmett–Teller (BET) measurements. It is shown that at a Ag loading of 1.25 wt.% on TiO₂, a high-surface area nanocomposite morphology corresponding to an average of one Ag nanoparticle per titania nanoparticle was achieved. The diameter of the titania crystallites/particles were in the range of 10–20 nm while the size of Ag particles attached to the larger titania particles were 3 ± 1 nm as deduced from crystallite size by XRD and particle size by TEM. Ag recovery by photo harvesting from the solution was nearly 100%. TEM micrographs revealed that Ag-coated TiO₂ nanoparticles showed a sharp increase in the degree of agglomeration for nanocomposites prepared at basic pH values, with a corresponding sharp decrease in BET surface area especially at pH > 9. The BET surface area of the Ag–TiO₂ nanoparticles was nearly constant at around a value of 140 m² g⁻¹ at all pH from 1–8 with an anomalous maximum of 164 m² g⁻¹ when prepared from a sol at pH of 4, and a sharp decrease to 78 m² g⁻¹ at pH of 10.     

Microstructure and electrode properties of La0.6Sr0.4Co0.2Fe0.8O3-δ spin-coated on Ce0.8Sm0.2O2?δ electrolyte

Fine and uniform La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ powder was synthesized by a glycine–nitrate combustion process. La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ electrodes were prepared on dense Ce_0.8Sm_0.2O_2−δ electrolyte substrates using a spin-coating technique by sintering at 900–1,000 °C. The electrode properties of La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ were investigated by electrochemical impedance spectroscopy and chronopotentiometry techniques with respect to preparation conditions and the resulting microstructures. The results indicate a significant effect of the microstructure on the electrode processes and polarization characteristics. The oxygen adsorption and dissociation process acted as a larger contribution to the overall electrode polarization R _p in magnitude compared with the charge transfer process due to relatively low porosity levels of the electrodes. It was detected that the grain size of the electrodes exhibited a crucial role on the electrocatalytic reactivity. At 800 °C, the electrode sintered at 950 °C attained a polarization resistance of 0.18 Ω cm², an overpotential of 27 mV at a current density of 200 mA cm⁻², and an exchange current density of 308 mA cm⁻².     

A novel anode-supported stable BaCe0.7Ta0.1Y0.2O3− δ membrane prepared by all-solid-state process for solid oxide fuel cells

BaCe_0.7Ta_0.1Y_0.2O_{3− δ} (BCTY) and BaCe_0.8Y_0.2O_{3− δ} (BCY) were synthesized by solid-state reaction method at 1,300 °C for 20 h. After being exposed in 3% CO₂ + 3% H₂O + 94% N₂ at 700 °C for 20 h, the BCTY exhibited adequate chemical stability against carbonations while BCY decomposed into BaCO₃ and CeO₂. The BCTY showed the similar thermal expansion behavior to BCY from room temperature to 1,000 °C in air. The BCTY displayed a conductivity of 0.007 S/cm at 700 °C in humid hydrogen, lower than that of BCY (0.009 S/cm). A fuel cell with 10-μm thick BCTY membrane prepared through an all-solid-state process exhibited 1.004 V for OCV, 330 mW/cm² for maximum output at 700 °C, respectively. Short-term test shows that the fuel cell performance does not degrade after 20 h.     

Preparation and electrochemical properties of nano Al<Subscript>0.2</Subscript>V<Subscript>2</Subscript>O<Subscript>5.3−<Emphasis Type="BoldItalic">δ</Emphasis></Subscript> cathode materials for rechargeable lithium batteries

Nano-sized Al³⁺-doped V₂O₅ cathode materials, Al_0.2V₂O_5.3−δ , were prepared by an oxalic acid assisted sol–gel method at 350 °C (sample A) and 400 °C (sample B). X-ray diffraction confirmed that samples A and B were pure phase Al_0.2V₂O_5.3−δ with an orthorhombic structure close to that of V₂O₅. Scanning electron microscopy showed that sample A was in nanoscale with a mean particle size about 50 nm. Cyclic voltammetry showed the good electrochemical and structural reversibility of the Al_0.2V₂O_5.3−δ nanoparticles during the Li⁺ insertion/extraction process. The Al_0.2V₂O_5.3−δ nanoparticles exhibited excellent charge–discharge cycling performance and rate capability compared to that of bulky V₂O₅ electrodes. For instance, the materials delivered a reversible specific capacity about 180 mAh g⁻¹ (sample A) and 150 mAh g⁻¹ (sample B), in the potential window of 4.0–2.0 V at the current density of 150 mA g⁻¹. The Al_0.2V₂O_5.3−δ nanoparticles in particular showed almost no capacity fading for at least 50 cycles.     

Structure and electrical properties of HfO<Subscript>2</Subscript> high-<Emphasis Type="Italic">k</Emphasis> films prepared by pulsed laser deposition on Si (100)

High-k gate dielectric hafnium dioxide films were grown on Si (100) substrate by pulsed laser deposition at room temperature. The as-deposited films were amorphous and that were monoclinic and orthorhombic after annealed at 500°C in air and N₂ atmosphere, respectively. After annealed, the accumulation capacitance values increase rapidly and the flat-band voltage shifts from −1.34 V to 0.449 V due to the generation of negative charges via post-annealing. The dielectric constant is in the range of 8–40 depending on the microstructure. The I–V curve indicates that the films possess of a promising low leakage current density of 4.2×10⁻⁸ A/cm² at the applied voltage of −1.5 V.     

Synthesis and characterization of ZnxHg1?xSeyS1?y quantum dots

This article describes the synthesis of highly water-soluble Zn _x Hg_1−x Se _y S_1−y quantum dots (QDs) in aqueous solution through a simple photo-assisted reaction between ZnSe QDs and mercury(I) nitrate dihydrate [Hg₂(NO₃)₂·2H₂O]. In order to deduce the optimal synthesis conditions, we varied several parameters, including the concentrations of mercaptosuccinic acid (MSA) and Hg₂(NO₃)₂·2H₂O, the illumination time, and the reaction temperature. When irradiated at temperatures below 80 °C, the ZnSe QDs reacted with the S²⁻ ions formed rapidly from MSA and the Hg²⁺ ions formed from Hg₂ ²⁺ ions to form Zn _x Hg_1−x Se _y S_1−y QDs through a process of photo-etching and surface combination. Under different conditions, we prepared a series of Zn _x Hg_1−x Se _y S_1−y QDs that emit fluorescence at the maximum wavelengths ranging from 405 to 760 nm. Inductively coupled plasma-mass spectrometry and transmission electron microscopy/energy dispersive spectrometry revealed that the content of Hg in the Zn _x Hg_1−x Se _y S_1−y QDs was greater when the synthesis was conducted at higher temperature. The Zn_0.88Hg_0.12Se_0.44S_0.56 QDs exhibit improved photostability than crude ZnSe QDs and possess long lifetimes (τ₁ ~ 38 ns and τ₂ ~ 158 ns).     

Measurements of the temperature and water vapor concentration in a hot zone by tunable diode laser absorption spectrometry

A tunable diode laser absorption spectroscopy (TDLAS) technique and appropriate instrumentation was developed for the measurement of temperature and water vapor concentrations in heated gases. The technique is based on the detection of the spectra of H₂O absorption lines with different energies of low levels. The following absorption lines of H₂O were used: 7189.344 cm⁻¹ (E″=142 cm⁻¹), 7189.541 cm⁻¹ (E″=1255 cm⁻¹), 7189.715 cm⁻¹ (E″=2005 cm⁻¹). Spectra were recorded using fast frequency scanning of a single distributed feedback (DFB) laser. A unique differential scheme for the recording of the absorption spectra was developed. An optimal technique for fitting the experimental spectra was developed.     

On the enzymatic formation of platinum nanoparticles

A dimeric hydrogenase enzyme (44.5 and 39.4 kDa sub units) was isolated in a 39.5% yield from the fungus Fusarium oxysporum and purified 4.64-fold by ion exchange chromatography on Sephacryl S-200. Characterisation of the enzyme afforded pH and temperature optima of 7.5 and 38 °C, respectively, a half-life stability of 36 min and a V _max and K _m of 3.57 nmol min⁻¹ mL⁻¹ and 2.25 mM, respectively. This enzyme was inhibited (non-competitively) by hydrogen hexachloroplatinic acid (H₂PtCl₆) at 1 or 2 mM with a K _i value of 118 μM. Incubation of the platinum salt with the pure enzyme under an atmosphere of hydrogen and optimum enzyme conditions (pH 7.5, 38 °C) afforded <10% bioreduction after 8 h while at conditions suitable for platinum nanoparticle formation (pH 9, 65 °C) over 90% reduction took place after the same length of time. Cell-free extract from the fungal isolates produced nearly 90% bioreduction of the platinum salt under both pH and temperature conditions. The bioreduction of the platinum salt by a hydrogenase enzyme takes place by a passive process and not an active one as previously understood.     

Study on the Binding Behavior of Lysozyme with Cephalosporin Analogues by Fluorescence Spectroscopy

It was first found that the intrinsic fluorescence of lysozyme at 340 nm can be quenched by cephalosporin analogues through the static quenching and non-radiative energy transferring procedure. In the acetate buffer solution with pH 7.0 and 298 K, the quenching fluorescence intensity was in a good linearity over the concentration of drugs in the range of 1–100 μmol L⁻¹, 0.1–100 μmol L⁻¹, 0.5–100 μmol L⁻¹ and 0.05–100 μmol L⁻¹ for cefradine, cefuroxime, cefotaxime and ceftriaxone, respectively. The quenching ability or the binding ability of the studied drugs followed the pattern: ceftriaxone > cefotaxime > cefuroxime > cefradine, which was close to the order of their antibacterial ability. The binding parameters including the association constant and the number of binding potential point were calculated at different temperatures (288, 298 and 308 K), and thermodynamic parameters ΔH°, ΔS° and ΔG° were given. The binding mode of lysozyme with cephalosporins showed that the hydrophobic effect might play a major role. The binding distance between cephalosporin and tryptophan residue in lysozyme was obtained. The results provided the quantitative information for the binding of cephalosporin to lysozyme, and it was suggested that the drugs probably bound to the active site near Trp62 in lysozyme.     

Structure,thermal properties,conductivity and electrochemical stability of di-urethanesil hybrids doped with LiCF<Subscript>3</Subscript>SO<Subscript>3</Subscript>

Variable chain length di-urethane cross-linked poly(oxyethylene) (POE)/siloxane hybrid networks were prepared by application of a sol-gel strategy. These materials, designated as di-urethanesils (represented as d-Ut(Y′), where Y′ indicates the average molecular weight of the polymer segment), were doped with lithium triflate (LiCF₃SO₃). The two host hybrid matrices used, d-Ut(300) and d-Ut(600), incorporate POE chains with approximately 6 and 13 (OCH₂CH₂) repeat units, respectively. All the samples studied, with compositions ∞ > n ≥ 1 (where n is the molar ratio of (OCH₂CH₂) repeat units per Li⁺), are entirely amorphous. The di-urethanesils are thermally stable up to at least 200 °C. At room temperature the conductivity maxima of the d-Ut(300)- and d-Ut(600)-based di-urethanesil families are located at n = 1 (approximately 2.0 × 10⁻⁶ and 7.4 × 10⁻⁵ Scm⁻¹, respectively). At about 100 °C, both these samples also exhibit the highest conductivity of the two electrolyte systems (approximately 1.6 × 10⁻⁴ and 1.0 × 10⁻³ Scm⁻¹, respectively). The d-Ut(600)-based xerogel with n = 1 displays excellent redox stability.     

Evidence for formation of Se molecular clusters during precipitation of CdSe<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>S<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> nanoparticles in glass

While studying the effect of thermal treatment at 625–700°C on the formation of borosilicate glass-embedded CdSe or CdSe_1−x S _x nanocrystals, pronounced bands at 323 and 646 cm⁻¹ were observed in the Raman spectra. They are assigned to Se₂ clusters on the base of their frequency positions, widths, intensities, and resonance behavior. The precipitation of Se₂ molecular clusters in borosilicate glass is shown to occur when the heat treatment temperature and/or duration are beyond the range, most suitable for the formation of CdSe or CdSe-rich CdSe_1−x S _x nanocrystals.     

Electrochemical study of P(VDF-HFP)/PMMA blended polymer electrolyte with high-temperature stability for polymer lithium secondary batteries

In the present study, a kind of solid polymer electrolyte (SPE) based on poly(vinylidene difluoride-co-hexafluoropropylene)/poly(methyl methacrylate) blends was prepared by a casting method to solve the safety problem of lithium secondary batteries. Owing to being plasticized with a room temperature ionic liquid, N-butyl-N′-methyl-imidiazolium hexafluorophosphate, the obtained SPE shows a thermal decomposition temperature over 300°C and an ionic conductivity close to 10⁻³ S cm⁻¹. The SPE-3 sample, in which the weight of two polymers is equivalent, possesses an ionic conductivity of 0.45 × 10⁻³ S cm⁻¹ at 25°C and presents an electrochemical window of 4.43 V. The ionic conductivity of the SPE-3 is as high as 1.73 × 10⁻³ S cm⁻¹ at 75°C approaching to that of liquid electrolyte. The electrochemical performances of the Li/LiFePO₄ cells confirmed its feasibility in lithium secondary batteries.     

Electrical conductivity and chemical stability of perovskite-type BaCe0.8-xTixY0.2O3-δ

Here we report the synthesis, chemical stability, and electrical conductivity of Ti-doped perovskite-type BaCe_0.8-x Ti _x Y_0.2O_3-δ (x = 0.05, 0.1, 0.2, and 0.3; BCTY). Samples were synthesized by conventional solid state (ceramic) reaction from corresponding metal salts and oxides at elevated temperature of 1,300–1,500 °C in air. The powder X-ray diffraction confirmed the formation of a simple cubic perovskite-type structure with a lattice constant of a = 4.374(1), 4.377(1), and 4.332(1) ? for x = 0.05, 0.1, and 0.2 members of BCTY, respectively. Like BaCe_0.8Y_0.2O_3-δ (BCY), Ti substituted BCTY was found to be chemically not stable in 100% CO₂ and form BaCO₃ at elevated temperature. The bulk electrical conductivity of BCTY decreased with increasing Ti content and the x = 0.05 member exhibited the highest conductivity of 2.3 × 10⁻³ S cm⁻¹ at 650 °C in air, while a slight increase in the conductivity, especially at low temperatures (below 600 °C), was observed in humidified atmospheres.