Application of TEM and XPS in the interpretation of the kinetics of deuterium evolution from ultrathin TiD<Subscript><Emphasis Type="BoldItalic">y</Emphasis></Subscript>/Pd films evaporated on quartz

The kinetics of thermal evolution of deuterium from ultrathin TiD _y /Pd bilayer films has been studied by means of thermal desorption mass spectrometry (TDMS). Using a combination of transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy, we made a study of the complex structural and chemical transformations of the TiD _y /Pd film as a result of TDMS-induced evolution of deuterium and simultaneous annealing of this film. Both preparation and TDMS processing of the TiD _y /Pd bilayer films were performed in situ under UHV conditions. It was found that the high-temperature TDMS processing of an ultrathin TiD _y /Pd film, which was carried out in a relatively short time, leads to a significant film structure transformation. Energy-filtered TEM mapping of cross-section images and EDX analysis revealed extensive interdiffusion of Ti and Pd within the Ti–Pd bi-layer film. This process leads to a progressive change in chemical composition within the surface and subsurface area of the film during the TDMS processing. As the temperature of TDMS heating increases, segregation of Ti at the Pd top layer surface becomes significant. As a result, the kinetics of deuterium desorption is progressively changed during TDMS; at lower temperatures, the kinetics is limited by recombinative processes at the Pd surface, at temperatures beyond 500 K, it becomes dominated by interdiffusion of Ti into the Pd surface.     

Vacuum annealing phenomena in ultrathin TiD y /Pd bi-layer films evaporated on Si(100) as studied by TEM and XPS

Using a combination of TEM and XPS, we made an analysis of the complex high-temperature annealing effect on ultrathin titanium deuteride (TiD _y ) films evaporated on a Si(100) substrate and covered by an ultrathin palladium layer. Both the preparation and annealing of the TiD _y /Pd bi-layer films were performed in situ under UHV conditions. It was found that the surface and bulk morphology of the bi-layer film as well as that of the Si substrate material undergo a microstructural and chemical conversion after annealing and annealing-induced deuterium evolution from the TiD _y phase. Energy-filtered TEM (EFTEM) mapping of cross-section images and argon ion sputter depth profiling XPS analysis revealed both a broad intermixing between the Ti and Pd layers and an extensive inter-diffusion of Si from the substrate into the film bulk area. Segregation of Ti at the Pd top layer surface was found to occur by means of angle-resolved XPS (ARXPS) and the EFTEM analyses. Selected area diffraction (SAD) and XPS provided evidence for the formation of a new PdTi₂ bimetallic phase within the top region of the annealed film. Moreover, these techniques allowed to detect the initial stages of TiSi phase formation within the film–substrate interlayer.     

Structural and chemical characterisation of titanium deuteride films covered by nanoscale evaporated palladium layers

Thin titanium deuteride (TiD_y) films, covered by an ultra-thin palladium layer, have been compared with the corresponding titanium and palladium films using a combination of scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The TiD_y layers were prepared under ultra-high vacuum (UHV) conditions by precisely controlled deuterium sorption at 298 K on a Ti film evaporated onto a Si(100) substrate. Both Ti and TiD_y films were then covered in situ by a nanoscale Pd layer. It was found that a 10- to 12-nm-thick Pd layer protects the TiD_y films efficiently against extensive air interaction. The morphology of both the surface and bulk Pd/TiD_y (Ti) films have been observed using SEM and cross-sectional TEM analysis, respectively. A polycrystalline bulk morphology in both Ti and TiD_y films accompanied by a fine-grained Pd surface was observed. High-magnification cross-sectional TEM images reveal the TiD_y film to be plastically deformed leading to an increase in the roughness of the top Pd layer. Complex structures, including Moiré patterns, have been identified within the Pd/TiD_y interface. The chemical nature of this interface has been analysed after partial sputtering of the Pd top layer using XPS. Besides TiD_y and Pd, TiO and PdO were found to be the main chemical species in the interface region of the Pd/TiH_y film. The XPS valence-band spectra of the Pd/TiD_y interface reveal electronic features characteristic of a Pd–Ti bimetallic structure.     

Influence of annealing temperature on material properties of red emitting ZnGa<Subscript>2</Subscript>O<Subscript>4</Subscript>: Cr<Superscript>3+</Superscript> nanostructures

Zinc gallate (ZnGa₂O₄) nanopowders doped with Cr³⁺ (1?mo%) were synthesized by the citric acid assisted sol–gel method. The influence of annealing temperature, structural, morphological, and optical properties of ZnGa₂O₄: Cr³⁺ (1?mol%) nanosized particles were investigated. The X-ray diffraction (XRD) spectra indicated that the nanoparticles are cubic in structure and the annealing temperature did not influence any c in structure. The average crystallite size of ZnGa₂O₄: Cr³⁺ nanoparticles were observed to increase from 11.85 to 30.88?nm as the annealing temperature increased from 600 to 1000?°C. The scanning electron microscopy (SEM) showed nearly spherical nanostructures that change in size with annealing temperature. The high resolution transmission electron microscope (HR-TEM) images show well resolved lattice fringes which is an indications of highly crystalline samples. Ultraviolet–visible (UV–Vis) measurement show decrease in reflectance in visible region and energy band gap was found to decrease with annealing temperature. The photoluminescence (PL) intensity was found to be maximum for sample annealed at high temperature (1000?°C) and least with sample annealed at low temperature (600?°C). An increase in annealing temperature leads significantly increment in PL intensity. The degree of crystallinity also increased with annealing temperature from XRD, SEM, and HR-TEM analysis. The photoluminescence lifetimes, particle size, and emission spectra are comparable with reports on bioimaging applications.

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Rapid response behavior,at room temperature,of a nanofiber-structured TiO<Subscript>2</Subscript> sensor to selected simulant chemical-warfare agents

A chemical prototype sensor was constructed based on nanofiber-structured TiO₂ and highly sensitive quartz resonators. The gas-sensing behavior of this new sensor to selected simulant warfare agents was investigated at room temperature. Results showed rapid response and good reversibility of this sensor when used with high-purity nitrogen. This provides a simple approach to preparation of materials needed as chemical sensors for selected organic volatiles or warfare agents. Figure Sensing behavior of TiO₂ nanofiber sensor to chemical vapors     

Ammonium tungstate modified Li-rich Li<Subscript>1+x</Subscript>Ni<Subscript>0.35</Subscript>Co<Subscript>0.35</Subscript>Mn<Subscript>0.30</Subscript>O<Subscript>2</Subscript> to improve rate capability and productivity of lithium-ion batteries

LiNi_1-x-yCo_xMn_yO₂ (NCM) with excessive lithium is known to exhibit high rate capability and charge–discharge cycling durability. However, the practical usage of NCM is difficult, because the positive electrode slurry is unstable and battery cells swell due to the alkaline residual lithium compound generated on the surface of NCM particles. To reduce the residual lithium compound, ammonium metatungstate (AMT) added to NCM is studied, and the effect is investigated by scanning electron microscopy, aberration-corrected scanning transmission electron microscopy, X-ray diffractometry, synchrotron X-ray diffractometry, and several electrochemical measurements. It is found that the AMT modification reduces the amount of alkaline residual lithium compound and improves the rate capability due to the ~1-nm-thick W-rich layer generated on the NCM surface.

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Graphical abstract ?

     

Preparation and characterization of the Ti/IrO<Subscript>2</Subscript>/WO<Subscript>3</Subscript> as supercapacitor electrode materials

WO₃ films have been prepared onto IrO₂-coated Ti substrate by electro-deposition, and as-deposited and annealed films have been characterized by using Raman spectroscopy. It was found that the asdeposited film consists of orthorhombic WO₃ · H₂O phase, which transforms to amorphous WO₃ by annealing at 250°C and to monoclinic phase by annealing at and above 350°C. All electrochemical experiments were carried on Ti/IrO₂/WO₃ annealed at 450°C. The open-circuit potential could change significantly due to the hydration of the coating film. However this process is fairly slow. Reproducible voltammograms could be obtained quickly, further revealing high electrochemical stability of the Ti/IrO₂/WO₃ electrode. And the shapes of CV show the approximate rectangular mirror image, showing the typical characteristic of capacitive behavior. The specific capacitance obtained at a scan rate of 50 mV s⁻¹ is 46 F g⁻¹.     

Preparation of Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>-C18 nano-magnetic composite materials and their cleanup properties for organophosphorous pesticides

Magnetic Fe₃O₄-C18 composite nanoparticles of approximately 5–10 nm in size were synthesized and characterized by IR spectroscopy, atomic absorption spectroscopy, X-ray diffraction, and transmission electron microscopy. The magnetic Fe₃O₄-C18 composite nanoparticles were applied for cleanup and enrichment of organophosphorous pesticides. Comparative studies were carried out between magnetic Fe₃O₄-C18 composite nanoparticles and common C18 materials. Residues of organophosphorous pesticides were determined by gas chromatography in combination with a nitrogen/phosphorus detector. The cleanup and enrichment properties of magnetic Fe₃O₄-C18 composite nanoparticles are comparable with those of common C18 materials for enrichment of organophosphorous pesticides, but the cleanup and enrichment are faster and easier to perform. Figure Presumed mechanism for the adhesion of the OPs to the Fe₃O₄-C18 magnetic nanoparticles     

MgF<Subscript>2</Subscript> films prepared from solvothermally treated precursor solutions

MgF₂ coating solutions were solvothermally treated at 160?°C for different time periods, this procedure induced crystallization and particle growth. Antireflection coatings prepared on glass from these solutions were compared to films derived from untreated precursor material. Ellipsometric porosimetry (EP) was employed to characterize structural features of coatings on glass as function of annealing temperature. Based on precursor solutions that had undergone solvothermal treatment antireflective coatings with a peak transparency exceeding 99% were prepared on PMMA substrates.

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Solvothermal treatment of MgF₂ precursor solutions results in crystallization of particles that can directly be applied to PMMA substrates for λ/4 antireflective films.

     

Synthesis,characterization, and application of sol gel derived Mg<Subscript>2</Subscript>SiO<Subscript>4</Subscript> powder

This paper reports a successful preparation of a pure forsterite Mg₂SiO₄ using the sol–gel approach and its application for the removal of impurities from a Tunisian frying oil. Magnesium nitrate hexahydrate and tetraethylortho-silicate were used as magnesium and silicon precursors, respectively. The synthesis was held at different calcination temperatures for 30?min. The annealed samples were characterized by X-ray diffraction, Fourier transform infrared, scanning electron microscopy, and laser diffraction. The results revealed that the sample calcined at 500?°C was forsterite with unimodal particle size distribution (PSD) centered at 122.8?±?0.3?μm. The dispersion index I (indicator of particle size uniformity) was 1.84. With the temperature increase, well crystallized compounds were obtained. Their PSDs remain unimodal and shift towards smaller particles. A decrease of the dispersion index was also noted, indicating the formation of Mg₂SiO₄ with more uniform particle size. This study showed that 900?°C could be selected as energy saving temperature suitable for the preparation of a pure and well crystallized Mg₂SiO₄ within just 30?min of annealing time. The obtained silicate exhibited promoting results for the purification of waste frying oils.

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Pure and fine Mg₂SiO₄ powder with unimodal particle size distribution was prepared by sol gel route under energy saving conditions. The obtained magnesium orthosilicate showed excellent results for waste frying oil purification

     

Amperometric CO<Subscript>2</Subscript> gas sensor based on interconnected web-like nanoparticles of La<Subscript>2</Subscript>O<Subscript>3</Subscript> synthesized by ultrasonic spray pyrolysis

Thin films of La₂O₃ were deposited onto glass substrates by ultrasonic spray pyrolysis. Their structural and morphological properties were characterized by X-ray diffraction, Fourier transform Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray photo-electron spectroscopy, Brunauer-Emmett-Teller and optical absorption techniques. The sensor displays superior CO₂ gas sensing performance at a low operating temperature of 498 K. The signal change on exposure to 300 ppm of CO₂ is about 75%, and the signal only drops to 91% after 30 days of operation.

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Graphical abstract Schematic diagram of the CO₂ gas sensing mechanism of an interconnected web-like La₂O₃ nanostructure in presence of 300 ppm of CO₂ gas and at an operating temperature of 498 K.

     

Preparation of epitaxial CaMn<Subscript>7</Subscript>O<Subscript>12</Subscript> film via sol-gel method and its ferromagnetic properties

CaMn₇O₁₂ precursor sol was prepared by using Ca(NO₃)₂·4H₂O and Mn(CH₃COO)₄·4H₂O as the raw materials, acetylacetone (AcAcH) as the chelating agent, and methyl alcohol (MeOH) as the solvent. The CaMn₇O₁₂ crystalline film was obtained via dip-coating and annealing treatment on the LaAlO₃ (001) single-crystal substrate. XRD θ-2θ scan indicated that the as-prepared CaMn₇O₁₂ film had strong preferred orientation along the c-axis. In addition, the results of the ω and ? scans demonstrated that the film exhibited outstanding out-of-plane and in-plane texture characteristics. The SEM characterization showed that the CaMn₇O₁₂ film was dense and free of cracks. The grain size was uniform with an average size of ~180?nm. Vibrating sample magnetometer (VSM) test results indicated the CaMn₇O₁₂ film was antiferromagnetic and had a saturation magnetization of 114.2?emu/cm³ at 50?K.

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Interlaced polyaniline/carbon nanotube nanocomposite co-electrodeposited on TiO<Subscript>2</Subscript> nanotubes/Ti for high-performance supercapacitors

A series of PANI-CNTs/TiO₂ nanotubes/Ti electrodes were fabricated via pulse current co-electrodeposition of polyaniline and functionalized carbon nanotubes onto TiO₂ nanotubes/Ti electrodes. FT-IR spectrometry, X-ray photoelectron spectroscopy, and scanning electron microscopy were applied in order to characterize the modified TiO₂ nanotubes/Ti electrodes. The morphology studies showed that the PANI-CNTs/TiO₂ nanotubes/Ti nanocomposite electrode has many interlaced PANI-CNTs nanorods on the surface of TiO₂ nanotubes. The electrochemical measurements of the modified electrodes confirmed that the CNTs in the composite can significantly improve the capacitive behavior as well which have been compared with that of PANI/TiO₂ nanotubes/Ti electrodes. The modified electrode exhibited much higher specific capacitance (190 mF cm^?2 with 90% retention after 1000 cycles) compared to the PANI/TiO₂ nanotubes/Ti (70 mF cm^?2 with 77% retention after 1000 cycles) at a current density of 0.85 mA cm^?2, indicating its great potential for supercapacitor applications.

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Graphical abstract Interlaced polyaniline/carbon nanotube nanocomposite electrodeposited on TiO₂ nanotubes/Ti

     

Sol-gel synthesis of ZnO/Zn<Subscript>2-x</Subscript>Fe<Subscript>x</Subscript>TiO<Subscript>4</Subscript> powders: structural properties,electrical conductivity and dielectric behavior

The aim of this work was an investigation of structural and electrical properties of ZnO/Zn_2-xFe_xTiO₄ (x?=?0.7, 1, 1.4) powders. The compounds obtained by sol-gel method are characterized by several techniques: X-ray diffraction (XRD), N₂ adsorption–desorption isotherms, scanning and transmission electron microscopy (SEM and TEM), X-ray photoelectron spectroscopy (XPS), electrical and dielectrical measurements. The XRD, SEM and XPS analysis confirmed the formation of ZnFeTiO₄ inverse spinel structure. The electrical and dielectrical properties of ZnO/Zn_2-xFe_xTiO₄ (x?=?0.7, 1, 1.4) were measured by impedance spectroscopy, revealing a decrease in the electrical conductivity and the dielectric constant with Fe content.

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Mesoporous TiO<Subscript>2</Subscript> thin films prepared from hydrothermally treated precursor powder sols

Two series of TiO₂ thin films were prepared based on soluble precursor powders: The first run originated directly from an alcohol-based coating solution whereas for the second batch the aqueous precursor powder sol had previously undergone a hydrothermal treatment. The respective microstructures were characterized by electron microscopy, the phase evolution was monitored by X-ray diffraction. Ellipsometric porosimetry (EP) was employed to reveal changes of porosity and pore size induced by thermal treatment of the films.

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Soluble TiO₂ precursor powders were hydrothermally treated to yield coating solutions. Films from these sols were compared with those directly obtained by dissolving the precursor powders. Results indicate that crystallization to anatase is induced under hydrothermal conditions and the resulting films mostly maintain their porosity throughout thermal treatment. In contrast to that coatings processed from as-dissolved precursor powders undergo more extensive densification

     

Hydrothermal synthesis of brookite TiO<Subscript>2</Subscript> nanoparticles for dye-sensitized solar cell

We obtained Tannin-4-azobenzoic acid (azo dye) by the conventional method of diazotization and coupling of aromatic amines. The properties of the azo dye were characterized via ultraviolet-visible (UV–vis), infrared (IR), and nuclear magnetic resonance (NMR) spectroscopy. Nanocrystalline titanium dioxide (TiO₂) thin films were deposited by hydrothermal method onto fluorine-doped tin (IV) oxide (FTO)-coated glass substrate at 353 K for 4 h. The as-deposited and annealed films were characterized for structural, morphological, optical, thickness, and wettability properties. The synthesized metal free azo dye was used to sensitize the prepared TiO₂ thin film with thickness of 26 μm. The photoelectrochemical (PEC) performance of TiO₂ sensitized with the azo dye was evaluated in polyiodide (0.1 M KI + 0.01 M I₂ + 0.1 M KCl) electrolyte at 40 mW cm^?2 illumination intensity. The cell yielded a short circuit current of 2.82 mA, open circuit voltage of 314.3 mV, a fill factor of 0.30, and a photovoltaic conversion efficiency value of 0.64%.

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Graphical abstract ?

     

Novel La-doped Bi<Subscript>2</Subscript>WO<Subscript>6</Subscript> photocatalysts with enhanced visible-light photocatalytic activity

Novel La-doped Bi₂WO₆ composites were successfully prepared via a facile solvothermal method and well characterized by X-ray diffraction, Brunner?Emmet?Teller measurements, scanning electron microscopy, transmission electron microscopy/high-resolution, energy dispersive spectrometry, X-ray photoelectron spectroscopy, ultraviolet–visible spectroscopy, and Fourier transform infrared spectroscopy. The photocatalytic activity of modified catalysts was evaluated by degrading tetracycline hydrochloride under visible light (450?W Xe lamp irradiation). It was found 5%La-Bi₂WO₆ had the highest light-absorption ability, great morphology, and microstructures. The La dopant enlarged surface area and increased crystal defects, which may enhance the optical absorption activity and inhibit the recombination of the photo-generated charge carrier, respectively. After 150?min illumination, the photocatalysts that 5%La-Bi₂WO₆ and pure Bi₂WO₆ exhibited the best and worst photocatalytic performance, respectively (96.25% vs. 88.92%).

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Assembly of layer-by-layer films of heme proteins and single-walled carbon nanotubes: electrochemistry and electrocatalysis

After being treated by mixed acids, single-walled carbon nanotubes (SWNTs) were shortened and had negatively charged groups on the surface. Positively charged hemoglobin or myoglobin at pH 5.0 was successfully assembled with SWNTs into layer-by-layer films on solid surfaces, designated as {SWNT/protein} _n . While only those proteins in the first few bilayers closest to the electrode surface exhibited electroactivity, the {SWNT/protein} _n films demonstrated a much higher fraction of electroactive proteins and better controllability in film construction compared with cast films of the proteins and carbon nanotubes. The proteins in the {SWNT/protein} _n films retained their near-native structure at medium pH. The stable protein film electrode showed good electrocatalytic properties toward reduction of oxygen and hydrogen peroxide, demonstrating the potential application of the {SWNT/protein} _n films as a new type of biosensor based on the direct electrochemistry of proteins without using mediators. Figure Cyclic voltammograms at 0.2 V s⁻¹ in pH 7.0 buffers with different number of bilayers (n) for layer-by-layer {single-walled carbon nanotube/hemoglobin} _n films.     

Cis-dioxo-Mo(VI) salophen complex supported on Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>@SiO<Subscript>2</Subscript> nanoparticles as an efficient magnetically separable and reusable nanocatalyst for selective epoxidation of olefins

In this work, paramagnetic Fe₃O₄/SiO₂ nanoparticles were synthesized, characterized and functionalized with dioxo-Mo(VI) tetradentate Schiff base complex and characterized using IR spectroscopy, X-ray powder diffraction spectroscopy, scanning electron microscopy, transmission electron microscopy, vibrating sample magnetometry, diffuse reflectance spectroscopy and atomic absorption spectroscopy. Catalyst was used for the selective epoxidation of cyclooctene, cyclohexene, styrene, indene, α-pinene, 1-hepten, 1-octene, 1-dodecen and trans-stilbene using tert-butyl hydroperoxide as oxidant in 1,2-dichloroethane. This catalyst is efficient for oxidation of cyclooctene with a 100% selectivity for epoxidation with 100% conversion in 1 h. After the reaction, the magnetic nanocatalyst was easily separated by simply applying an external magnetic field and was used at least five successive times without significant decrease in conversion.

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Characteristics of Ag/Bi<Subscript>3.25</Subscript>La<Subscript>0.75</Subscript>Ti<Subscript>3</Subscript>O<Subscript>12</Subscript>/p-Si heterostructure prepared by sol-gel processing

The metal-ferroelectric-semiconductor (MFS) heterostructure has been fabricated using Bi_3.25La_0.75Ti₃O₁₂ (BLT) as a ferroelectric layer by sol-gel processing. The effect of annealing temperature on phase formation and electrical characteristics of Ag/BLT/p-Si heterostructure were investigated. The BLT thin films annealed at from 500°C to 650°C are polycrystalline, with no pyrochlore or other second phases. The C-V curves of Ag/BLT/p-Si heterostructure annealed at 600°C show a clockwise C-V ferroelectric hysteresis loops and obtain good electrical properties with low current density of below 2×10⁻⁸ A/cm² within ±4 V, a memory window of over 0.7 V for a thickness of 400 nm BLT films. The memory window enlarges and the current density reduces with the increase of annealing temperature, but a annealing temperature over 600°C is disadvantageous for good electrical properties.