Showing papers on "Transmission electron microscopy published in 2009"
TL;DR: A freestanding single layer of hexagonal boron nitride (h-BN) has been successfully fabricated by controlled energetic electron irradiation through a layer-by-layer sputtering process and the dominating zigzag-type edges are proved to be nitrogen terminated.
Abstract: A freestanding single layer of hexagonal boron nitride (h-BN) has been successfully fabricated by controlled energetic electron irradiation through a layer-by-layer sputtering process. We have successfully resolved atomic defects in h-BN with triangle shapes by means of an aberration corrected high-resolution transmission electron microscopy with exit-wave reconstruction. Boron monovacancies are found to be preferably formed and the dominating zigzag-type edges are proved to be nitrogen terminated.
1,009 citations
TL;DR: Electron diffraction shows that on average the underlying carbon lattice maintains the order and lattice-spacings of graphene; a structure that is clearly resolved in 80 kV aberration-corrected atomic resolution TEM images.
Abstract: We report on the structural analysis of graphene oxide (GO) by transmission electron microscopy (TEM). Electron diffraction shows that on average the underlying carbon lattice maintains the order and lattice-spacings of graphene; a structure that is clearly resolved in 80 kV aberration-corrected atomic resolution TEM images. These results also reveal that single GO sheets are highly electron transparent and stable in the electron beam, and hence ideal support films for the study of nanoparticles and macromolecules by TEM. We demonstrate this through the structural analysis of physiological ferritin, an iron-storage protein.
629 citations
TL;DR: In this article, a method to prepare monolayer and multilayer suspended sheets of hexagonal boron nitride (h-BN) using a combination of mechanical exfoliation and reactive ion etching is presented.
Abstract: We present a method to prepare monolayer and multilayer suspended sheets of hexagonal boron nitride (h-BN), using a combination of mechanical exfoliation and reactive ion etching. Ultrahigh-resolution transmission electron microscope imaging is employed to resolve the atoms, and intensity profiles for reconstructed phase images are used to identify the chemical nature (boron or nitrogen) of every atom throughout the sample. Reconstructed phase images are distinctly different for h-BN multilayers of even or odd number. Unusual triangular defects and zigzag and armchair edge reconstructions are uniquely identified and characterized.
488 citations
TL;DR: The alpha-Fe(2)O(3) with various morphologies has been successfully synthesized via an ionic liquid-assisted hydrothermal synthetic method and is expected to be a useful technique for controlling the diverse shapes of crystalline inorganic materials for a variety of applications, including sensors, gas and heavy metal ion adsorbents, catalytic fields, hydrogen and Li ion storage, and controlled drug delivery.
Abstract: The α-Fe2O3 with various morphologies has been successfully synthesized via an ionic liquid-assisted hydrothermal synthetic method. The samples are characterized by X-ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscope (FE-SEM), transmission electron microscopy, and high-resolution transmission electron microscopy. The results indicate that the as-prepared samples are α-Fe2O3 nanoparticles, mesoporous hollow microspheres, microcubes, and porous nanorods. The effects of the ionic liquid 1-n-butyl-3-methylimidazolium chloride ([bmim][Cl]) on the formation of the α-Fe2O3 with various morphologies have been investigated systematically. The proposed formation mechanisms have also been investigated on the basis of a series of FE-SEM studies of the products obtained at different durations. Because of the unique porous structure, the potential application in water treatment of the α-Fe2O3 porous nanorods was investigated. The UV−vis measurements suggest that the a...
471 citations
TL;DR: Liquid STEM is a unique approach for imaging single molecules in whole cells with significantly improved resolution and imaging speed over existing methods.
Abstract: Single gold-tagged epidermal growth factor (EGF) molecules bound to cellular EGF receptors of fixed fibroblast cells were imaged in liquid with a scanning transmission electron microscope (STEM). The cells were placed in buffer solution in a microfluidic device with electron transparent windows inside the vacuum of the electron microscope. A spatial resolution of 4 nm and a pixel dwell time of 20 μs were obtained. The liquid layer was sufficiently thick to contain the cells with a thickness of 7 ± 1 μm. The experimental findings are consistent with a theoretical calculation. Liquid STEM is a unique approach for imaging single molecules in whole cells with significantly improved resolution and imaging speed over existing methods.
430 citations
TL;DR: Tensile tests performed in situ in a focused-ion beam scanning electron microscope on Cu nanowhiskers reveal strengths close to the theoretical upper limit and confirm that the properties of nanomaterials can be engineered by controlling defect and flaw densities.
Abstract: The strength of metal crystals is reduced below the theoretical value by the presence of dislocations or by flaws that allow easy nucleation of dislocations. A straightforward method to minimize the number of defects and flaws and to presumably increase its strength is to increase the crystal quality or to reduce the crystal size. Here, we describe the successful fabrication of high aspect ratio nanowhiskers from a variety of face-centered cubic metals using a high temperature molecular beam epitaxy method. The presence of atomically smooth, faceted surfaces and absence of dislocations is confirmed using transmission electron microscopy investigations. Tensile tests performed in situ in a focused-ion beam scanning electron microscope on Cu nanowhiskers reveal strengths close to the theoretical upper limit and confirm that the properties of nanomaterials can be engineered by controlling defect and flaw densities.
417 citations
TL;DR: In this paper, the length scale of ligaments/channels in these nanoporous metals is associated with surface diffusion of more noble atoms, and increases with increasing diffusion coefficients in sequence: Pt/Pd < Au < Ag < Cu.
Abstract: Nanoporous metal ribbons including Au, Pd, Pt, Ag, and Cu can be fabricated through chemical dealloying of rapidly solidified Al-based alloys under free corrosion conditions. The formation and microstructure of these nanoporous metals have been investigated using X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis, transmission electron microscopy, and high-resolution transmission electron microscopy. All metal ribbons exhibit an open, three-dimensional bicontinuous interpenetrating ligament-channel structure with nanometer length scales. For a given dealloying solution, the length scale of ligaments/channels in these nanoporous metals is associated with surface diffusion of more noble atoms, and increases with increasing diffusion coefficients in sequence: Pt/Pd < Au < Ag < Cu. In addition, the length scale of ligaments/channels of these nanoporous metals can be modulated by simply changing the dealloying solution. Nanoindentation tests show that Young’s modulus and hardness...
406 citations
TL;DR: In this paper, a magnetic separable, hollow spherical Fe3O4/TiO2 hybrid photocatalysts were successfully prepared through a poly(styrene−acrylic acid) (PSA) template method.
Abstract: Well-defined magnetic separable, hollow spherical Fe3O4/TiO2 hybrid photocatalysts were successfully prepared through a poly(styrene−acrylic acid) (PSA) template method. This bifunctional product was characterized in terms of the particle size, surface morphology, chemical composition, and magnetic properties using transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), and X-ray powder diffraction (XRD) patterns. The M−H hysteresis loop for Fe3O4/TiO2 hollow spheres indicates that the composite spheres show superparamagnetic characteristics at room temperature. These magnetic TiO2 composites with hollow nature exhibit good photocatalytic activity under UV light irradiation and can be recycled six times by magnetic separation without major loss of activity. This method can be further applied to synthesize other bifunctional hollow spheres, such as Fe3O4/SnO2 and Fe3O4/CdS.
291 citations
TL;DR: In this article, a two-step template and surfactant-free, environmentally friendly method was used to prepare NiO with novel flower-like morphology, which was composed of many irregular nanosheets assembled together by weak interactions.
Abstract: NiO with novel flower-like morphology was prepared by using a two-step, template- and surfactant-free, environmentally friendly method. Flower-like NiO was composed of many irregular nanosheets that were assembled together by weak interactions. The as-prepared materials were characterized by X-ray diffraction, thermogravimetric analysis, differential scanning calorimetry, scanning electron microscopy, transmission electron microscopy with selected area electron diffraction patterns, N2 sorption, temperature-programmed reduction with CO, X-ray photoelectron spectroscopy (XPS), and in situ Fourier transform infrared (FT-IR) for CO adsorption. The catalytic behaviors for CO oxidation were studied by using a fixed bed microreactor. Compared to NiO nanoparticles, we found the flower-like NiO possessed a larger surface area, bimodal pore size distribution, higher reducibility, and superior catalytic activity for CO oxidation. The XPS and CO in situ FT-IR results showed that its catalytic property was morphology...
275 citations
TL;DR: In this article, X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FESEM), TEM, HRTEM, photoluminescence (PL) spectra, kinetic decay, and electron paramagnetic resonance (EPR) were used to characterize the obtained Ca5(PO4)3OH samples.
Abstract: Hydroxyapatite (Ca5(PO4)3OH) nano- and microcrystals with multiform morphologies (separated nanowires, nanorods, microspheres, microflowers, and microsheets) have been successfully synthesized by a facile hydrothermal process. X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), photoluminescence (PL) spectra, kinetic decay, and electron paramagnetic resonance (EPR) were used to characterize the samples. The experimental results indicate that the obtained Ca5(PO4)3OH samples show an intense and bright blue emission under long-wavelength UV light excitation. This blue emission might result from the CO2•− radical impurities in the crystal lattice. Furthermore, the organic additive (trisodium citrate) and pH values have an obvious impact on the morphologies and luminescence properties of the products to some degree. The possible formation ...
271 citations
TL;DR: Tracking real-time diffusion of both spherical and rod-shaped gold nanocrystals in a thin film of water-15% glycerol reveals complex movements, such as rolling motions coupled to large-step movements and macroscopic violations of the Stokes-Einstein relation for diffusion.
Abstract: We have directly observed motion of inorganic nanoparticles during fluid evaporation using a transmission electron microscope. Tracking real-time diffusion of both spherical (5−15 nm) and rod-shaped (5 × 10 nm) gold nanocrystals in a thin film of water−15% glycerol reveals complex movements, such as rolling motions coupled to large-step movements and macroscopic violations of the Stokes−Einstein relation for diffusion. As drying patches form during the final stages of evaporation, particle motion is dominated by the nearby retracting liquid front.
TL;DR: In this article, rotating disk electrode measurements of acid-treated nanoparticles showed specific oxygen reduction reaction (ORR) activity (∼0.7 mA/cmPt2 at 0.9 V vs RHE in 0.1 M HClO4 at room temperature), twice that of Pt nanoparticles.
Abstract: Rotating disk electrode measurements of acid-treated “Pt3Co” nanoparticles showed specific oxygen reduction reaction (ORR) activity (∼0.7 mA/cmPt2 at 0.9 V vs RHE in 0.1 M HClO4 at room temperature), twice that of Pt nanoparticles. Upon annealing at 1000 K in vacuum, the ORR activity at 0.9 V was increased to ∼1.4 mA/cmPt2 (four times that of Pt nanoparticles). High-resolution transmission electron microscopy and aberration-corrected high-angle annular dark-field in the scanning transmission electron microscope was used to reveal surface atomic structure and chemical composition variations of “Pt3Co” nanoparticles on the atomic scale. Such information was then correlated to averaged Pt−Pt distance obtained from synchrotron X-ray powder diffraction data, surface coverage of oxygenated species from cyclic voltammograms, and synchrotron X-ray absorption spectroscopy. It is proposed that ORR activity enhancement of acid-leached “Pt3Co” relative to Pt nanoparticles is attributed to the formation of a percolate...
TL;DR: The composite systems of the core particles and the platinum single nanocrystals exhibit an excellent colloidal stability, as well as high catalytic activity in hydrogenation reactions in the aqueous phase.
Abstract: Small metal nanoparticles that are also highly crystalline have the potential for showing enhanced catalytic activity. We describe the preparation of single nanocrystals of platinum that are 2 to 3 nanometers in diameter. These particles were generated and immobilized on spherical polyelectrolyte brushes consisting of a polystyrene core (diameter of ∼100 nanometers) onto which long chains of a cationic polyelectrolyte were affixed. In a first step, a nanoalloy of gold and platinum (a solid solution) was generated within the layer of cationic polyelectrolyte chains. In a second step, the gold was slowly and selectively dissolved by cyanide ions in the presence of oxygen. Cryogenic transmission electron microscopy, wide-angle x-ray scattering, and high-resolution transmission electron microscopy showed that the resulting platinum nanoparticles are faceted single crystals that remain embedded in the polyelectrolyte-chain layer. The composite systems of the core particles and the platinum single nanocrystals exhibit an excellent colloidal stability, as well as high catalytic activity in hydrogenation reactions in the aqueous phase.
TL;DR: In this paper, a novel synthesis of nanoparticles Ni and NiO using thermal decomposition and their physicochemical characterization was presented, where the nanoparticles were prepared using [bis(2-hydroxyacetophenato)nickel(II)] as precursor.
TL;DR: In this article, the mechanism of the increase in coercivity caused by post-sinter annealing of Nd-Fe-B-based magnets was investigated by high-resolution scanning electron microscopy, transmission electron microscope and atom probe tomography.
TL;DR: In this paper, a simple self-templated approach was developed to convert solid SiO2 microspheres into hollow structures by initial partial dissolution of silica cores in a NaBH4 solution and subsequent shell formation due to redeposition of the silicate species back onto the colloid surfaces.
Abstract: A simple, mild, and effective self-templated approach has been developed to directly convert solid SiO2 microspheres into hollow structures. The reaction involves initial partial dissolution of silica cores in a NaBH4 solution and subsequent shell formation due to the redeposition of the silicate species back onto the colloid surfaces. The increasing concentration of NaBO2 as the result of the slow decomposition of NaBH4 in water is found to be responsible for the regrowth of the silica shell. This method allows the production of hollow silica spheres with sizes ranging from ∼70 nanometers to several micrometers, largely determined by the size of the starting silica colloids. The solid-to-hollow transformation mechanism is investigated in detail by transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier Transform Infrared (FTIR) spectrometry, X-ray absorption spectroscopy (XAS), N2 adsorption−desorption, and X-ray diffraction (XRD). We also study the reaction conditions that al...
TL;DR: It has been indicated that the nanostructured core-shell Au@TiO2 photocatalyst represents high photocatalytic activity when exposed to UV or visible light irradiation and is largely attributed to the preferentially grown TiO2 shell structures and metal (Au)-TiO 2 heterointerfaces.
Abstract: Core−shell Au@TiO2 nanoparticles with truncated wedge-shaped TiO2 morphology have been synthesized successfully by a simple and flexible hydrothermal route. Morphological evolution of TiO2 shells was investigated by transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and X-ray diffraction technique. It has been revealed that the truncated wedge-shaped TiO2 shells experience an epitaxially segmented orientation growth. Also, the (101) crystal planes of TiO2 crystals grow preferentially on the surface of gold nanocrystals stabilizing the heterointerfaces, then faster [001] growth results in the “budding” process occurs, producing growth sites on the initial deposition TiO2 layers, where the TiO2 crystals grow up into truncated wedge-shaped morphologies. It is also found that morphological evolution of TiO2 shells is dependent on the produced F− ion concentration from hydrolyzed TiF4 precursors. The produced F− ions not only facilitate the formation of well-defin...
TL;DR: In this paper, a novel electrochemical method of preparing long-lived silver nanoparticles suspended in aqueous solution as well as silver powders was proposed, which does not involve the use of any chemical stabilizing agents.
Abstract: The article deals with a novel electrochemical method of preparing long-lived silver nanoparticles suspended in aqueous solution as well as silver powders. The method does not involve the use of any chemical stabilising agents. The morphology of the silver nanoparticles obtained was studied using transmission electron microscopy, scanning electron microscopy, atomic force microscopy and dynamic light scattering measurements. Silver nanoparticles suspended in water solution that were produced by the present technique are nearly spherical and their size distribution lies in the range of 2 to 20 nm, the average size being about 7 nm. Silver nanoparticles synthesised by the proposed method were sufficiently stable for more than 7 years even under ambient conditions. Silver crystal growth on the surface of the cathode in the electrochemical process used was shown to result in micron-sized structures consisting of agglomerated silver nanoparticles with the sizes below 40 nm.
TL;DR: In this article, a facile hydrothermal method was used to synthesize α-Fe2O3 nanorods with diameters in the range of 60-80nm and lengths extending from 300 to 500nm.
TL;DR: In this article, a polypyrrole-coated SnO2 hollow spheres hybrid materials have been synthesized through an in situ polymerization of pyrrole monomers in the presence of preprepared hollow spheres.
Abstract: Polypyrrole-coated SnO2 hollow spheres hybrid materials have been synthesized through an in situ polymerization of pyrrole monomers in the presence of preprepared SnO2 hollow spheres. The hybrids were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectrometer (FTIR), and thermogravimetric analysis (TG). Experimental data showed certain synergetic interaction existed in the hybrids, probably resulting in the enhanced thermal stability of polypyrrole coatings. Gas sensing tests showed that the hybrids possessed very fast response and high sensitivity to ammonia gas at room temperature, implying its potential application for gas sensors.
TL;DR: In this paper, a general method has been developed for the synthesis of homogeneous hollow core−shell microspheres of spinel ferrites (MFe2O4, M = Zn, Co, Ni, Cd) by using carbonaceous saccharide microsheres as template.
Abstract: A general method has been developed for the synthesis of homogeneous hollow core−shell microspheres of spinel ferrites (MFe2O4, M = Zn, Co, Ni, Cd) by using carbonaceous saccharide microspheres as template. The products were characterized by X-ray powder diffraction, inductively coupled plasma-atomic emission spectroscopy, scanning electronic microscopy, transmission electron microscopy, and nitrogen sorption measurement. The effects of the concentration of metal salts have been studied using ZnFe2O4 as an example. Increasing the concentration of metal salts could avoid the generation of impurity phase. The core size and shell thickness of hollow spheres obtained can be manipulated by changing the concentration of metal salts. Gas-sensor investigations revealed the ZnFe2O4 hollow spheres used as gas-sensor materials possess high sensitivity and quick responses to organic gases such as ethanol.
TL;DR: In this paper, a gas-bubble-assisted Ostwald ripening process was proposed to explain the formation of hollow structures, and hollow Fe(3)O(4) and MnFe(2)O (4) ferrite microspheres with controlled particle size were obtained using urea and ammonia as structure-directing agents.
Abstract: Monodisperse Fe(3)O(4) hollow spheres with average diameter of 400 nm and shell thickness of 60 nm were prepared through a one-pot solvothermal process with the presence of NH(4)Ac as the structure-directing agent, and a novel gas-bubble-assisted Ostwald ripening process was proposed to explain the formation of hollow structures. According to this mechanism, hollow Fe(3)O(4) and MnFe(2)O(4) ferrite microspheres with controlled particle size were obtained using urea and ammonia as the structure-directing agents, and porous Fe(3)O(4) spheres with particle size of 100 nm and pore size of 10 nm were obtained by the assistance of bicarbonate of ammonia. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and high-resolution transmission electron microscopy were used to characterize the structure of synthesized products, and the magnetic property investigation shows that the hollow microspheres exhibit a ferromagnetic behavior and possess a higher saturation magnetization (M(s)) than that of the solid microspheres.
TL;DR: In this paper, a new photocatalyst (WO x -TiO 2 ) powder was successfully prepared by a sol-gel method with an attempt to extend light absorption of the TiO 2 -based photocATalyst towards the visible light range and eliminate the rapid recombination of excited electrons/holes during photoreaction.
Abstract: New photocatalyst (WO x –TiO 2 ) powder was successfully prepared by a sol–gel method with an attempt to extend light absorption of the TiO 2 -based photocatalyst towards the visible light range and eliminate the rapid recombination of excited electrons/holes during photoreaction. The photo composite was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), BET, Raman spectra, UV–vis diffuse reflectance spectra (DRS), photoluminescence spectra (PLS) and X-ray photoelectron spectroscopy (XPS). XRD, Raman, HRTEM and XPS analysis indicated that WO x is uniformly dispersed on the surface of TiO 2 probably with monolayer thickness and the mean particle size of the composite was 12 nm. XPS analysis also indicated that the vacuum activated composites contained more W in reduced form while the calcined composites showed more W in hexavalent form. The beneficial effect of W can be explained by considering the formation of W +5 species by means of a transfer of photo-generated electrons from TiO 2 to W +6 .Subsequently W +5 could be oxidized to W +6 by transferring electrons to adsorbed O 2 .DRS showed an extension of light absorption into the visible region for this WO x composite and PL analysis indicated that the electron-hole recombination rate has been effectively inhibited when WO x is deposited on the surface of TiO 2 .The samples activated in vacuum showed higher photocatalytic activity than calcined samples in case of MO and superior activity in case of phenol. The optimal WO 3 dosage of 4.0% in WO x –TiO 2 achieved the highest rate of photodegradation in this experimental condition.
TL;DR: In this article, single crystal ZnO nanowires were synthesized by the thermal decomposition of zinc acetate dihydrate at 300°C in air for 3h without a catalyst.
TL;DR: In this article, a new magnetic Fe3O4/cellulose microspheres (MRCS) were fabricated by in situ synthesis of Fe 3O4nanoparticles into the cellulose pores of RCS, which were used as the solid template microreactor.
Abstract: Regenerated cellulose microspheres (RCS) were successfully prepared by using the sol-gel transition (SGT) method from cellulose drops in 7 wt% NaOH/12 wt% urea aqueous solution precooled to −12 °C. Subsequently, novel magnetic Fe3O4/cellulose microspheres (MRCS) were fabricated by in situ synthesis of Fe3O4nanoparticles into the cellulose pores of RCS, which were used as the solid template microreactor. Their structure and morphology were analysed using optical photomicrographs, scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The results indicated that the spherical magnetic Fe3O4nanoparticles were dispersed uniformly and immobilized in the cellulose matrix, and the structure and nature of Fe3O4 were conserved perfectly. The magnetometric measurements revealed that the MRCS exhibited sensitive magnetic-induced delivery, and had extremely small hysteresis loop and low coercivity. Moreover, MRCS displayed excellent adsorption and controlled release capabilities on bovine serum albumin (BSA). The Fe3O4nanoparticles in the cellulose microspheres play an important role in both the creation of the magnetic-induced transference and the improvement of the targeting protein delivery and release. It will be important for applications in the biomaterials field.
TL;DR: In this article, a core−shell Cu@Cu2O microsphere formation mechanism, which involved the in situ transformation of Cu to Cu2O, was proposed on the basis of the characterization results.
Abstract: In this study, core−shell Cu@Cu2O microspheres were synthesized with an interfacial hydrothermal method. The resulting products were systematically characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. A core−shell Cu@Cu2O microsphere formation mechanism, which involved the in situ transformation of Cu to Cu2O, was proposed on the basis of the characterization results. That is, pure Cu microspheres were first formed through the reduction of copper(II) acetylacetonate. Then surface Cu was oxidatively transformed to a Cu2O shell, resulting in the Cu@Cu2O core−shell structure. The content of Cu2O shell in the composite microspheres increased with prolonged reaction time. The as-prepared Cu@Cu2O core−shell microspheres exhibited enhanced photocatalytic activity as compared to Cu2O on the degradation of gaseous nitrogen monoxide under visible light irradiation. The reasons for v...
TL;DR: In this article, carbon-doped TiO2 hollow microspheres with mesoporous structure were prepared by a simple two-step template method, and the characterizations for the physicochemical properties of prepared samples under different calcination temperature were carried out by X-ray diffraction analysis, Brunauer−Emmett−Teller measurements, transmission electron microscopy, scanning electron microscope, Xray photoelectron spectroscopy, and UV−vis diffuse reflectance spectra.
Abstract: Carbon-doped TiO2 hollow microspheres with mesoporous structure were prepared by a simple two-step template method. The characterizations for the physicochemical properties of prepared samples under different calcination temperature were carried out by X-ray diffraction analysis, Brunauer−Emmett−Teller measurements, transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, and UV−vis diffuse reflectance spectra. The carbon doping of TiO2 hollow spheres was easily achieved during the procedure for removal of carbon cores. With the doping of carbon, the absorption wavelength edge was expanded to the visible light region and the additional diffusive electronic states were observed on the valence band spectra of samples. C-doped TiO2 hollow spheres with rapid combustion at 500 °C exhibited the superior visible light photocatalytic activity for the degradation of toluene, 4.6 times greater than that of Degussa P25, due to its good crystallization, mesoporous structure co...
TL;DR: In this article, the electron diffraction data were consistent with that of CeO2 and not Ce2O3, as predicted by some researchers for very small particles sizes, and they interpreted this effect as due to the formation of substantial amounts of Ce3+ with corresponding oxygen vacancies.
Abstract: Nanoceria was produced by an aqueous precipitation technique in the presence of an organic stabilizer. The stable suspensions were diafiltered to remove reaction byproducts. Particles were characterized by transmission electron microscopy with images used to size the particles, and selected-area electron diffraction was used to determine the lattice structure and the lattice constant. For all particles studied, the electron diffraction data were consistent with that of CeO2 and not Ce2O3, as predicted by some researchers for very small particles sizes. At particle diameters of ∼1 nm, the lattice expansion approached 7%. In agreement with earlier researchers, we interpret this effect as due to the formation of substantial amounts of Ce3+ with corresponding oxygen vacancies, but within the fluorite lattice structure of CeO2. Even at a particle size of 1 nm, there was a measurable oxygen storage capacity, consistent with a still-reducible CeO2 structure, rather than the fully oxidized Ce2O3.
TL;DR: In this article, ZnO hollow nanofibers with diameters of 120−150 nm were successfully fabricated by electrospinning the precursor solution consisting of polyacrylonitrile (PAN), polyvinylpyrrolidone (PVP), and zinc acetate composite through a facile single capillary, followed by thermal decomposition for removal of the above polymers from the precursor fibers.
Abstract: In this work, ZnO hollow nanofibers with diameters of 120−150 nm were successfully fabricated by electrospinning the precursor solution consisting of polyacrylonitrile (PAN), polyvinylpyrrolidone (PVP), and zinc acetate composite through a facile single capillary, followed by thermal decomposition for removal of the above polymers from the precursor fibers. The as-prepared nanofibers were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), resonant Raman spectra, thermal gravimetric and differential thermal analysis (TG-DTA), and Fourier transform infrared spectroscopy (FT-IR) spectra, respectively. The results indicated that, during the electrospinning process, there occurred phase separation between the electrospun composite materials, while the obtained precursor nanofibers of PAN, PVP, and zinc acetate composite might possess a core−shell structure (PAN as the core and PVP/zinc acetate composite as the shell). Furthermore, the composite...
TL;DR: In this article, a suite of transmission electron microscopy (TEM) and associated electron spectroscopy methods were used to examine the local structure and changes in the electronic structure of LiNi 0.8 Co 0.15 Al 0.05 O 2 positive electrode material.
Abstract: We used a suite of transmission electron microscopy (TEM) and associated electron spectroscopy methods to examine the local structure and changes in the electronic structure of LiNi 0.8 Co 0.15 Al 0.05 O 2 positive electrode material. We found a scattered rock-salt phase near grain surfaces and grain boundaries, where Ni 3+ turned to Ni 2+ , deduced from relative intensity ratios and fine structures of the L 2,3 white-line peaks of the transition metals. The spatial distribution of the degraded phase throughout the secondary particle was found using a scanning TEM-electron energy loss spectroscopy spectral imaging technique and multivariate analysis. The degradation process and its relationship to the surface reactions with electrolytes is discussed based on the spatial-distribution map of the degraded phases.