Showing papers on "Transmission electron microscopy published in 2010"
TL;DR: Annular dark-field imaging in an aberration-corrected scanning transmission electron microscope optimized for low voltage operation can resolve and identify the chemical type of every atom in monolayer hexagonal boron nitride that contains substitutional defects.
Abstract: An imaging technique able to resolve and identify all individual atoms in non-periodic solids would be a very useful tool for materials analysis. Annular dark-field (ADF) imaging in an aberration-corrected scanning transmission electron microscope optimized for low voltage operation allows such an analysis, as shown by Ondrej Krivanek and co-workers. The technique was used to examine a monolayer of boron nitride, in which it revealed individual atomic substitutions involving carbon and oxygen impurity atoms. Careful analysis of the data enables the construction of a detailed map of the atomic structure, with all the atoms of the four species resolved and identified. An imaging technique that could identify all the individual atoms, including defects, in a material would be a useful tool. Here an electron-microscopy approach to the problem, based on annular dark-field imaging, is described. A monolayer of boron nitride was studied, and three types of atomic substitution were identified. Careful analysis of the data enabled the construction of a detailed map of the atomic structure. Direct imaging and chemical identification of all the atoms in a material with unknown three-dimensional structure would constitute a very powerful general analysis tool. Transmission electron microscopy should in principle be able to fulfil this role, as many scientists including Feynman realized early on1. It images matter with electrons that scatter strongly from individual atoms and whose wavelengths are about 50 times smaller than an atom. Recently the technique has advanced greatly owing to the introduction of aberration-corrected optics2,3,4,5,6,7,8. However, neither electron microscopy nor any other experimental technique has yet been able to resolve and identify all the atoms in a non-periodic material consisting of several atomic species. Here we show that annular dark-field imaging in an aberration-corrected scanning transmission electron microscope optimized for low voltage operation can resolve and identify the chemical type of every atom in monolayer hexagonal boron nitride that contains substitutional defects. Three types of atomic substitutions were found and identified: carbon substituting for boron, carbon substituting for nitrogen, and oxygen substituting for nitrogen. The substitutions caused in-plane distortions in the boron nitride monolayer of about 0.1 A magnitude, which were directly resolved, and verified by density functional theory calculations. The results demonstrate that atom-by-atom structural and chemical analysis of all radiation-damage-resistant atoms present in, and on top of, ultra-thin sheets has now become possible.
1,152 citations
TL;DR: A new SnO(2) nanoarchitecture is synthesized: extremely thin sheets, with minimum thicknesses of 1.5-3.0 nm, that exhibit a high lithium storage capacity and excellent cyclability due to its nanometer-sized frame and breathable characteristic.
Abstract: In this communication, we successfully synthesized a new SnO(2) nanoarchitecture: extremely thin sheets, with minimum thicknesses of 1.5-3.0 nm. The products were prepared through a facile hydrothermal treatment using tin dichloride as the precursor. Planar or scrolled SnO(2) sheets were carefully examined by transmission electron microscopy. The assemblies of these sheets have a high BET surface area of 180.3 m(2)/g and extraordinarily large pore volume of 1.028 cm(3)/g. They also exhibit a high lithium storage capacity and excellent cyclability due to its nanometer-sized frame and breathable characteristic.
624 citations
TL;DR: In this paper, the preparation of ultrathin, transparent graphene films for use in supercapacitor applications is described, revealing a very homogeneous surface with intimate contact between graphene sheets.
Abstract: This study reports the preparation of ultrathin, transparent graphene films for use in supercapacitor applications. The surface morphology of the films was investigated by scanning electron microscopy and transmission electron microscopy, revealing a very homogeneous surface with intimate contact between graphene sheets. Electrochemical characterization demonstrated nearly ideal electrical double layer capacitive behavior. The capacitance obtained from charge-discharge analysis is 135 F/g for a film of approximately 25 nm which has a transmittance of 70% at 550 nm and a high power density of 7200 W/kg in 2 M KCl electrolyte.
371 citations
TL;DR: The photocatalytic performance indicated that Ag deposit acted as not only electron sinks to enhance the separation of photoexcited electrons from holes, but also charge carrier recombination centers, so the optimized amount of Ag deposit was investigated.
365 citations
TL;DR: This work uses HRTEM imaging combined with image simulations to show that BN bilayers can have AB stacking and are not limited to just AA stacking.
Abstract: Here, we present a simple method for preparing thin few-layer sheets of hexagonal BN with micrometer-sized dimensions using chemical exfoliation in the solvent 1,2-dichloroethane. The atomic structure of both few-layer and monolayer BN sheets is directly imaged using aberration-corrected high-resolution transmission electron microscopy. Electron beam induced sputtering effects are examined in real time. The removal of layers of BN by electron beam irradiation leads to the exposure of a step edge between a monolayer and bilayer region. We use HRTEM imaging combined with image simulations to show that BN bilayers can have AB stacking and are not limited to just AA stacking.
354 citations
TL;DR: In this paper, the microstructural changes of the membrane electrode assembly (MEA) cathode and the compositional changes along the MEA cathode thickness and within individual Pt x Co nanoparticles before and after voltage cycling were investigated.
Abstract: Electrochemical measurements showed an ≈75% Pt surface area loss and an ≈40% specific activity loss for a membrane electrode assembly (MEA) cathode with acid-treated "Pt 3 Co" catalyst particles in a H 2 /N 2 proton exchange membrane fuel cell after 24 h voltage cycling between 0.65 and 1.05 V vs reversible hydrogen electrode. Transmission electron microscopy, scanning transmission electron microscopy, associated X-ray energy dispersive spectroscopy, and high angle annular dark-field techniques were used to probe the microstructural changes of the MEA cathode and the compositional changes along the MEA cathode thickness and within individual Pt x Co nanoparticles before and after voltage cycling. Further Co dissolution from acid-treated Pt x Co particles that leads to an increased thickness of a Pt-enriched surface layer and the development of core/shell Pt x Co particles was largely responsible for the reduction in the specific activity of Pt x Co nanoparticle after potential cycling. The Pt weight loss associated with the formation of Pt crystallites near the cathode/membrane interface largely contributed to the measured electro- chemical surface area loss, while particle growth of the Pt x Co particles via Ostwald ripening played a lesser role.
325 citations
TL;DR: In this article, the plastic deformation behavior and the effects of the impact time on the LY2 aluminum (Al) alloy during multiple laser shock processing (LSP) impacts were investigated.
316 citations
TL;DR: In this paper, the authors demonstrate resistive switches and memories that use SiO(x) as the sole active material and can be implemented in entirely metal-free embodiments through cross-sectional transmission electron microscopy.
Abstract: Because of its excellent dielectric properties, silicon oxide (SiO(x)) has long been used and considered as a passive, insulating component in the construction of electronic devices. In contrast, here we demonstrate resistive switches and memories that use SiO(x) as the sole active material and can be implemented in entirely metal-free embodiments. Through cross-sectional transmission electron microscopy, we determine that the switching takes place through the voltage-driven formation and modification of silicon (Si) nanocrystals (NCs) embedded in the SiO(x) matrix, with SiO(x) itself also serving as the source of the formation of this Si pathway. The small sizes of the Si NCs (d ∼ 5 nm) suggest that scaling to ultrasmall domains could be feasible. Meanwhile, the switch also shows robust nonvolatile properties, high ON/OFF ratios (>10(5)), fast switching (sub-100-ns), and good endurance (10(4) write-erase cycles). These properties in a SiO(x)-based material composition showcase its potentials in constructing memory or logic devices that are fully CMOS compatible.
315 citations
TL;DR: In this paper, the shape evolution of Cu2O crystals from cubes, truncated octahedra, octahedral, and finally to nanospheres was first realized in high yield by reducing the copper−citrate complex solution with glucose.
Abstract: An interesting shape evolution of Cu2O crystals, that is, from cubes, truncated octahedra, octahedra, and finally to nanospheres was first realized in high yield by reducing the copper−citrate complex solution with glucose. X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FESEM), and high-resolution transmission electron microscopy (HRTEM) techniques were employed to characterize the samples. We elucidate the important parameters (including poly (vinyl pyrrolidone) (PVP) concentration, reaction time, and reaction temperature) responsible for the shape-controlled synthesis of Cu2O crystals. The possible formation mechanism for the products with various architectures is presented, which is mainly based on the variation of the ratio (R) of the growth rates along the ⟨100⟩ and ⟨111⟩ direction. In addition, the effect of the low supersaturation on the formation of star-shaped samples with six symmetric branches is also taken into account. This polymer-mediated method should be readi...
282 citations
TL;DR: In this paper, a sequential evolution process involving surface deposition, mutual diffusion, interior dissolution, and interfacial reaction is proposed to account for the formation of CuS/ZnS hollow spheres.
Abstract: Monodisperse CuS/ZnS nanocomposite hollow spheres with diameters of about 255 nm and shells composed of nanoparticles have been successfully synthesized in high yield by an ion-exchange method using monodisperse ZnS solid spheres as a precursor. The prepared samples were characterized by X-ray diffraction, scanning and transmission electron microscopy, X-ray photoelectron spectroscopy, N2 adsorption−desorption isotherms, and UV−visible absorption spectroscopy. The photocatalytic activity was evaluated by the photocatalytic decolorization of Rhodamine B (RhB) aqueous solution under visible-light irradiation. The results indicate that the difference of solubility products (Ksp) of ZnS and CuS is the main driving force for the formation of CuS/ZnS hollow spheres. A sequential evolution process involving surface deposition, mutual diffusion, interior dissolution, and interfacial reaction is proposed to account for the formation of CuS/ZnS nanocomposite hollow spheres. The reaction time greatly influences the ...
282 citations
TL;DR: In this paper, high-ordered TiO2 nanotube array (TNs) thin films were prepared by electrochemical anodization of titanium foil in a mixed electrolyte solution containing Na2SO4, H3PO4, NaF, and sodium citrate and then treated by calcination, vapor-thermal, and hydrothermal methods, respectively.
Abstract: Highly ordered TiO2 nanotube array (TNs) thin films were prepared by electrochemical anodization of titanium foil in a mixed electrolyte solution containing Na2SO4, H3PO4, NaF, and sodium citrate and then treated by calcination, vapor-thermal, and hydrothermal methods, respectively. The as-prepared samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The photocatalytic activity of the film samples was evaluated by photocatalytic degradation of methyl orange (MO) aqueous solution under UV light irradiation. The production of hydroxyl radicals (•OH) on the surface of UV-irradiated samples was detected by a photoluminescence technique using terephthalic acid as a probe molecule. The transient photocurrent response was measured by several on−off cycles of intermittent irradiation. It was found that post-treatment exhibited a great influence on the morphology, crystallization, and photocatalytic activity of TNs th...
TL;DR: In this article, a unique morphology of SrTiO 3 nanocubes precipitated on TiO 2 nanowires is successfully synthesized in the form of a thin-film heterojunctioned TiO2 / Sr TiO 3 photocatalyst using facile hydrothermal techniques, and the formation mechanisms of the synthesized photocatalysts are meticulously studied and described.
Abstract: A unique morphology of SrTiO 3 nanocubes precipitated on TiO 2 nanowires is successfully synthesized in the form of a thin-film heterojunctioned TiO 2 / SrTiO 3 photocatalyst using facile hydrothermal techniques. The formation mechanisms of the synthesized photocatalysts are meticulously studied and described. Growth of SrTiO 3 single crystal nanocubes (≈50 nm in width) on anatase polycrystalline nanowires follows an in situ dissolution-precipitation pathway. This is consonant with the classic LaMer model. By analyzing the results of field emission scanning electron microscopy (FESEM), field emission transmission electron microscopy (FETEM), X-ray diffraction (XRD), energy dispersive X-ray (EDX) spectroscopy, X-ray photoelectron spectroscopy (XPS), and UV-vis spectrophotometry, a comprehensive structural and morphological characterization of the photocatalysts is established. FESEM images reveal that the anatase film comprises mainly of nanowires bristles while the tausonite film is primarily made up of nanocube aggregations. In comparison to the respective pristine semiconductor photocatalysts, the heterostructured photocatalyst demonstrates the highest efficiency in photocatalytic splitting of water to produce H 2 , 4.9 times that of TiO 2 and 2.1 times that of SrTiO 3 . The enhanced photocatalytic efficiency is largely attributed to the efficient separation of photogenerated charges at heterojunctions of the two dissimilar semiconductors, as well as a negative redox potential shift in the Fermi level.
TL;DR: In this article, gold nanoparticles were deposited on the surface of a g-C 3 N 4 semiconductor by deposition-precipitation, photodeposition, and impregnation methods to make metal-semiconductor junctions for photocatalytic hydrogen evolution from aqueous solution containing an electron donor with visible light illumination.
Abstract: Gold nanoparticles were deposited on the surface of a g-C 3 N 4 semiconductor by deposition-precipitation, photodeposition, and impregnation methods to make metal-semiconductor junctions for photocatalytic hydrogen evolution from aqueous solution containing an electron donor with visible light illumination. The samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV/Vis, and transmission electron microscopy (TEM). Results show that the Au/g-C 3 N 4 prepared by the deposition-precipitation method possessed the best photocatalytic activity, due to the formation of tight Au-serniconductor heterojunctions effectively promoting the transfer of charge from light-excited g-C 3 N 4 . Surface modification of the Au/g-C 3 N 4 with a second metal further improved the activity of the photocatalytic system, which was explained by simultaneous optimization of electron transfer by the gold and chemical reactivity by the secondary metal.
TL;DR: In this article, an arc-discharge method using a buffer gas containing carbon dioxide has been developed for the efficient and large-scale synthesis of few-layered graphene, well-dispersed in organic solvents such as N,N-dimethylformamide (DMF) and 1,2-dichlorobenzene (o-DCB).
Abstract: An arc-discharge method using a buffer gas containing carbon dioxide has been developed for the efficient and large-scale synthesis of few-layered graphene. The resulting samples of few-layered graphene, well-dispersed in organic solvents such as N,N-dimethylformamide (DMF) and 1,2-dichlorobenzene (o-DCB), were examined by transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, atomic force microscopy (AFM), and thermal gravimetric analysis (TGA). The electrical conductivity and transparency of flexible films prepared using a direct solution process have also been studied.
TL;DR: In this article, a simple approach is proposed to synthesize nanostructured Li4Ti5O12 spinel materials with different morphologies (nanorods, hollow spheres and nanoparticles), in which the TiO2 precursor is first coated with a conductive carbon layer by the chemical vapour decomposition (CVD) method, followed by a solid-state reaction with lithium salt.
Abstract: A simple approach is proposed to synthesize nanostructured Li4Ti5O12 spinel materials with different morphologies (nanorods, hollow spheres and nanoparticles), in which the TiO2 precursor is first coated with a conductive carbon layer by the chemical vapour decomposition (CVD) method, followed by a solid-state reaction with lithium salt. The Li4Ti5O12 obtained was characterised by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), as well as galvanostatic measurements. The results indicate that, by employing the carbon pre-coating process, the carbon-coated nanostructured Li4Ti5O12 can maintain the initial morphologies of the TiO2 precursors and also show significant improvement in the rate capability for lithium-ion intercalation due to both good electronic conductivity and the short lithium-ion diffusion path.
TL;DR: In this article, MoO 3 was thermally evaporated onto gold interdigital fingers on quartz substrates and characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and TEM techniques.
Abstract: In this work, MoO 3 was thermally evaporated onto gold interdigital fingers on quartz substrates and characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques The deposited MoO 3 consist of stratified long rectangles (average length of 50 μm width of 5 μm and thickness of 500 nm) which are predominantly orthorhombic (α-MoO 3 ) Each of these plates was composed of many nano-thick layers (average ∼30 nm) placed by Van der Waals forces on top of each other forming lamellar patterns The devices were used as sensors and exhibited considerable change in surface conductivity when exposed to NO 2 and H 2 gases at elevated temperature of 225 °C The structural and gas sensing properties of thermally evaporated MoO 3 thin films were investigated
TL;DR: Pd−Ag bimetallic dendrites have been synthesized via a galvanic replacement reaction of Ag dendrite in a Na2PdCl4 solution as discussed by the authors, which showed up to four times higher catalytic activity toward the reduction of 4-nitrophenol (4-NP) by sodium borohydride (NaBH4) than the best recently reported catalysts.
Abstract: Pd−Ag bimetallic dendrites have been synthesized via a galvanic replacement reaction of Ag dendrites in a Na2PdCl4 solution. Scanning and transmission electron microscopy (SEM and TEM), energy dispersive X-ray spectrometry (EDX), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analysis reveal that the resulting product is composed of partially depleted Ag dendrites covered with a rough surface with many Pd granules protruding by up to about 20 nm. High-solution TEM combined with EDX and selected area electron diffraction (SAED) confirms the formation of bimetallic interfaces between Pd and Ag. These Pd−Ag dendrites show up to four times higher catalytic activity toward the reduction of 4-nitrophenol (4-NP) by sodium borohydride (NaBH4) than the best recently reported catalysts. This further enhancement over the already strong performance of similarly synthesized Au−Ag dendrites is explained by the presence of Pd, adding a hydrogen relay mechanism on top of the very effective electron r...
TL;DR: It is demonstrated that the formation of heterojunctions between Fe(2)O(3) and TiO( 2) for Fe(3)/TiO(2%) composites was pivotal for improving the separation and thus restraining the recombination of photogenerated electrons and holes, which accounts for the enhancement of photocatalytic activity.
Abstract: Fe2O3/TiO2 heterogeneous photocatalysts with different mass ratios of Fe2O3vs. TiO2 were synthesized by impregnation of Fe3+ on the surface of TiO2 microrods and calcination at 300 °C. Scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), photoluminescence spectra and X-ray diffraction (XRD) have been used to characterize the samples. The photocatalytic activities of Fe2O3/TiO2 heterocomposites, pure Fe2O3 and pure TiO2 were evaluated by the photodegrading efficiency of Orange II under visible light (λ > 420 nm). The experiments demonstrated that Orange II in aqueous solution was more efficiently photodegraded using Fe2O3/TiO2 heterogeneous photocatalysts than either pure Fe2O3 or TiO2 under visible light irradiation. With an optimal mass ratio of 7:3 in Fe2O3/TiO2 the highest rate of Orange II photodegradation was achieved under the experimental conditions. We have also compared the photoelectric properties of Fe2O3/TiO2 heterogeneous photocatalysts with that of pure Fe2O3 by surface photovoltage (SPV) and transient photovoltage (TPV) techniques. Based on the photovoltage responses, we discussed the influence of the hetero-interface between Fe2O3 and TiO2 on transfer characteristics of photogenerated charge carriers. We demonstrated that the formation of heterojunctions between Fe2O3 and TiO2 for Fe2O3/TiO2 composites was pivotal for improving the separation and thus restraining the recombination of photogenerated electrons and holes, which accounts for the enhancement of photocatalytic activity.
TL;DR: In this paper, a facile and green synthetic approach for preparing superparamagnetic Fe3O4 nanoparticles using α- d -glucose as reducing agent and gluconic acid (the oxidative product of glucose) as stabilizer and dispersant was demonstrated.
TL;DR: In this paper, the photocatalytic activity of ZnO-CuO nanocomposite was evaluated by the photodegradation of rhodamine B under simulated sunlight irradiation, and compared with those of the monocomponent oxides synthesized by the identical synthetic route.
TL;DR: A series of 0−3 metal oxide−polyolefin nanocomposites are synthesized via in situ olefin polymerization, using the following single-site metallocene catalysts: C2-symmetric dichloro[rac-ethylenebisindenyl]zirconium(IV), Me2Si(tBuN), and (η5-C5Me4)TiCl2, and
Abstract: A series of 0−3 metal oxide−polyolefin nanocomposites are synthesized via in situ olefin polymerization, using the following single-site metallocene catalysts: C2-symmetric dichloro[rac-ethylenebisindenyl]zirconium(IV), Me2Si(tBuN)(η5-C5Me4)TiCl2, and (η5-C5Me5)TiCl3 immobilized on methylaluminoxane (MAO)-treated BaTiO3, ZrO2, 3-mol %-yttria-stabilized zirconia, 8-mol %-yttria-stabilized zirconia, sphere-shaped TiO2 nanoparticles, and rod-shaped TiO2 nanoparticles. The resulting composite materials are structurally characterized via X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), 13C nuclear magnetic resonance (NMR) spectroscopy, and differential scanning calorimetry (DSC). TEM analysis shows that the nanoparticles are well-dispersed in the polymer matrix, with each individual nanoparticle surrounded by polymer. Electrical measurements reveal that most of these nanocomposites have leakage current densities of ∼10−6−10−8 A/cm2; relative permittivities in...
TL;DR: X-ray diffraction pattern reveals the regular stacking of graphene CN(x) monolayers along the (002) direction with the presence of turbostratic ordering of C and N atoms in the a-b basal planes, indicating a high nitrogen content.
Abstract: Bulk quantities of nitrogen-rich graphitic carbon nitride are synthesized via a facile reactive pyrolysis process with a mixture of melamine and cyanuric chloride as the molecular precursors. Scanning electron microscopy and transmission electron microscopy studies show that micrometer-sized hollow vessels with high aspect ratios have been successfully elaborated without the designed addition of any catalyst or template. The composition of the prepared carbon nitride determined by combustion method is C3N4.91H1.00O0.22, with the N/C ratio to be 1.64, indicating a high nitrogen content. X-ray diffraction pattern reveals the regular stacking of graphene CNx monolayers along the (002) direction with the presence of turbostratic ordering of C and N atoms in the a−b basal planes. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy investigations provide further evidence for graphite-like sp2-bonded building blocks based on both triazine and heptazine ring units bridged by 3-fold coordi...
TL;DR: In this paper, two transmission electron microscopy (TEM) techniques for characterizing polyamide nanostructure have been proposed, one of which produces cross-sectional images of isolated polyamide thin films by removing the polysulfone support from regular TEM cross-sections.
TL;DR: In this article, the specific grain interior and grain boundary conductivities, obtained from impedance spectroscopy and the brick layer model, are reported for BaZr 0.9 Y 0.1 O 3 − δ as a function of p O 2 and temperature.
TL;DR: In this paper, the photocatalytic degradation of rhodamine B (RhB) in the presence of H2O2 by one-dimensional (1D) nanorods of goethite (α-FeOOH) and hematite (β-Fe2O3) was investigated, and results were compared to those of micrometer-sized rods.
Abstract: Visible light (λ > 420 nm) induced photocatalytic degradation of rhodamine B (RhB) in the presence of H2O2 by one-dimensional (1D) nanorods of goethite (α-FeOOH) and hematite (α-Fe2O3) has been investigated, and results were compared to those of micrometer-sized rods. α-FeOOH nanorods were self-assembled by oriented attachment of α-FeOOH primary nanoparticles, while porous α-Fe2O3 rods were prepared by thermal dehydration of respective α-FeOOH precursors via a topotactic transformation. The as-prepared samples were characterized by powder X-ray diffraction, micro-Raman spectroscopy, diffuse reflectance UV−visible spectroscopy, X-ray photoelectron spectroscopy, nitrogen adsorption−desorption, high-angle annular dark-field scanning transmission electron microscopy, transmission electron microscopy, and high-resolution transmission electron microscopy. Nanosized α-FeOOH and α-Fe2O3 particles appeared to be more active than microsized ones in terms of surface area normalized reaction rate, suggesting intrinsi...
TL;DR: In this article, the photocatalytic activity of the prepared ZnO nanoparticles has been investigated for the degradation of ciprofloxacin drug under UV light irradiation in aqueous solutions of different pH values.
TL;DR: In this paper, three polymorphic forms, namely, pseudo-hexagonal, orthorhombic, and monoclinic, were developed by electrospinning a polymeric solution and by subsequent annealing.
Abstract: Nanowires of Nb2O5 were developed in three polymorphic forms, namely, pseudo-hexagonal, orthorhombic, and monoclinic, by electrospinning a polymeric solution and by subsequent annealing. The materials were characterized by X-ray and electron diffraction, scanning and transmission electron microscopy, BET surface area measurements, absorption spectrometry, and cyclic voltammometry. These characterizations indicate that the monoclinic phase has a higher conduction band edge compared with the other two and is likely to display higher open circuit voltage in solar cells. Dye-sensitized solar cells were fabricated using the above polymorphs, and the device performances were studied. The pseudo-hexagonal phase showed higher device performance owing to its higher specific surface area compared with the others. However, when normalized, the device performances with respect to the dye-loading, the monoclinic phase gave superior performance. Studies on the charge transport properties using electrochemical impedance...
TL;DR: In this article, the authors reported the coercivity enhancement of hydrogenation-disproportionation-desorption-recombination processed Nd-Fe-B nanocrystalline powders from 1321 to 1552 kA/m−1 (19.5 kOe) by the grain boundary diffusion.
TL;DR: It is concluded that the kinetics of hydrogen adsorption limits the observed response rate seen for the nanowire, and that hydrogen desorption from thenanowire limits the observation recovery rate; proton diffusion within PdHx does not limit the rates of either of these processes.
Abstract: Palladium nanowires prepared using the lithographically patterned nanowire electrodeposition (LPNE) method are used to detect hydrogen gas (H2) These palladium nanowires are prepared by electrodepositing palladium from EDTA-containing solutions under conditions favoring the formation of β-phase PdHx The Pd nanowires produced by this procedure are characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy These nanowires have a mean grain diameter of 15 nm and are composed of pure Pd with no XPS-detectable bulk carbon The four-point resistance of 50−100 μm segments of individual nanowires is used to detect H2 in N2 and air at concentrations ranging from 2 ppm to 10% For low [H2] < 1%, the response amplitude increases by a factor of 2−3 with a reduction in the lateral dimensions of the nanowire Smaller nanowires show accelerated response and recovery rates at all H2 concentrations from, 5 ppm to 10%
TL;DR: In this paper, a new and simple method to directly synthesize stable and crystalline pure phase CeO 2 nanoparticles has been developed using cationic surfactant (cetyltrimethylammonium bromide, CTAB) and cerium chloride (CeCl 3 ) at room temperature.