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Many carbon allotropes can act as host materials for reversible lithium uptake 1 , 2 , thereby laying the foundations for existing and future electrochemical energy storage. However, insight into how lithium is arranged within these hosts is difficult to obtain from a working system. For example, the use of in situ transmission electron microscopy 3 – 5 to probe light elements (especially lithium) 6 , 7 is severely hampered by their low scattering cross-section for impinging electrons and their susceptibility to knock-on damage 8 . Here we study the reversible intercalation of lithium into bilayer graphene by in situ low-voltage transmission electron microscopy, using both spherical and chromatic aberration correction 9 to enhance contrast and resolution to the required levels. The microscopy is supported by electron energy-loss spectroscopy and density functional theory calculations. On their remote insertion from an electrochemical cell covering one end of the long but narrow bilayer, we observe lithium atoms to assume multi-layered close-packed order between the two carbon sheets. The lithium storage capacity associated with this superdense phase far exceeds that expected from formation of LiC 6 , which is the densest configuration known under normal conditions for lithium intercalation within bulk graphitic carbon 10 . Our findings thus point to the possible existence of distinct storage arrangements of ions in two-dimensional layered materials as compared to their bulk parent compounds. Using a double-aberration-corrected transmission electron microscope, intercalation of lithium between two graphene sheets is found to produce a dense, multilayer lithium phase, rather than the expected single layer.

A novel hybrid material with excellent microwave absorption property has been designed by decorating reduced graphene oxide with Ba Tb0.2Eu0.2Fe11.6O19/PANI composite, and the effect of graphene content on microwave absorption property has been investigated. The microstructure of the composite is characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, field emission scanning electron microscope, transmission electron microscope and Raman spectroscopy. The mechanism of microwave absorption is discussed minutely. The result shows that the ternary nanocomposites demonstrate unexceptionable microwave absorption property due to its special nanostructures and synergistic effect among BaTb0.2Eu0.2Fe11.6O19, PANI and RGO. The minimum reflection loss can reach − 60.9 dB at 16.4 GHz with a thickness of only 1.95 mm, and the corresponding effective absorption bandwidth (below − 10 dB) is 4.2 GHz. BaTb0.2Eu0.2Fe11.6O19/PANI/RGO composite can be one of the most promising microwave absorption materials.

In this work, biocompatibility of bacterial cellulose (BC) was assessed as the scaffold for corneal stroma replacement. Biocompatibility was evaluated by examining rabbit corneal epithelial and stromal cells cultured on the BC scaffold. The growth of primary cells was assessed by optical microscope, scanning electron microscope (SEM), and transmission electron microscope (TEM). Live/dead viability/cytotoxicity assay and CCK-8 assay were used to evaluate cell survival. BC was surgically implanted in vivo into a stromal pocket. During a 3-month follow-up, the biocompatibility of BC was assessed. We found that epithelial and stromal cells grew well on BC and showed a survival rate of nearly 100%. The SEM examination for both kinds of cell showed abundant leafy protrusions, spherical projections, filopodia, cytoskeletons, and cellular interconnections. The stromal cells cultured on BC arranged regularly. TEM observation revealed normal cellular microstructure and a tight adhesion to the BC membrane. In vivo observation confirmed the optical transparency of BC during 3-month follow-up. The results demonstrated that BC had good biocompatibility for the tissue engineering of corneal stroma.

Cerium-based CeMO3 (M = Co, Ni, Cu) perovskites were efficiently synthesized by electrospinning process. The structures, morphologies, elemental compositions, and valence states of CeMO3 perovskites were manifested in detail using X-ray diffraction analysis, Raman spectroscopic analysis, UV–vis diffuse reflectance spectroscopy, scanning electron microscope, transmission electron microscope, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy, respectively. The tolerance factor (t) was accurately calculated to confirm the perovskite structure stability. The electrochemical properties of CeMO3 perovskites were investigated, and the specific capacitances of CeCoO3, CeNiO3, and CeCuO3 perovskites are 128, 189, and 117 F g−1 at the current density of 0.5 A g−1, respectively. This study could provide an efficient and potential applications of the cerium-based perovskites into the supercapacitor electrode materials.

Despite the use of electrons with wavelengths of just a few picometers, spatial resolution in a transmission electron microscope (TEM) has been limited by spherical aberration to typically around 0.15 nanometer. Individual atomic columns in a crystalline lattice can therefore only be imaged for a few low-order orientations, limiting the range of defects that can be imaged at atomic resolution. The recent development of spherical aberration correctors for transmission electron microscopy allows this limit to be overcome. We present direct images from an aberration-corrected scanning TEM that resolve a lattice in which the atomic columns are sepa-rated by less than 0.1 nanometer.

Electron beams with a twist It has been possible to produce photon vortex beams — optical beams with spiralling wavefronts — for some time, and they have found widespread application as optical tweezers, in interferometry and in information transfer, for example. The production of vortex beams of electrons was demonstrated earlier this year ( http://go.nature.com/4H2xWR ) in a procedure involving the passage of electrons through a spiral stack of graphite thin films. The ability to generate such beams reproducibly in a conventional electron microscope would enable many new applications. Now Jo Verbeeck and colleagues have taken a step towards that goal. They describe a versatile holographic technique for generating these twisted electron beams, and demonstrate their potential use as probes of a material's magnetic properties. It was demonstrated recently that passing electrons through a spiral stack of graphite thin films generates an electron beam with orbital angular momentum — analogous to the spiralling wavefronts that can be introduced in photon beams and which have found widespread application. Here, a versatile holographic technique for generating these twisted electron beams is described. Moreover, a demonstration is provided of their potential use in probing a material's magnetic properties. Vortex beams (also known as beams with a phase singularity) consist of spiralling wavefronts that give rise to angular momentum around the propagation direction. Vortex photon beams are widely used in applications such as optical tweezers to manipulate micrometre-sized particles and in micro-motors to provide angular momentum 1 , 2 , improving channel capacity in optical 3 and radio-wave 4 information transfer, astrophysics 5 and so on 6 . Very recently, an experimental realization of vortex beams formed of electrons was demonstrated 7 . Here we describe the creation of vortex electron beams, making use of a versatile holographic reconstruction technique in a transmission electron microscope. This technique is a reproducible method of creating vortex electron beams in a conventional electron microscope. We demonstrate how they may be used in electron energy-loss spectroscopy to detect the magnetic state of materials and describe their properties. Our results show that electron vortex beams hold promise for new applications, in particular for analysing and manipulating nanomaterials, and can be easily produced.

Photocatalytic hybrid carbon nanotubes (CNTs)–mediated Ag-CuBi 2 O 4 /Bi 2 WO 6 photocatalyst was fabricated using a hydrothermal technique to effectively eliminate organic pollutants from wastewater. The as-prepared samples were characterized via Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction patterns (XRD), high-resolution transmission electron microscope (HR-TEM), UV–vis Diffuse Reflectance spectrum (UV–Vis DRS), and photoluminescence (PL) studies. The photocatalytic performance of fabricated pristine and hybrid composites was examined by photo-degradation of toxic dye viz. Rhodamine B (RhB) under visible light. Photo-degradation results revealed that the fabricated Ag-CuBi 2 O 4 /CNTs/Bi 2 WO 6 semiconductor photocatalyst followed pseudo-first-order kinetics and displayed a higher photocatalytic rate, which was found to be approximately 3.33 and 2.35 times higher than the pristine CuBi 2 O 4 and Bi 2 WO 6 semiconductor photocatalyst, respectively. Re-cyclic results demonstrated that the formed composite owns excellent stability, even after five consecutive cycles. As per the matched Fermi level of CNTs in between Ag-CuBi 2 O 4 and Bi 2 WO 6 , carbon nanotubes severed as electron transfer-bridge, Ag doping on CuBi 2 O 4 surface successfully increased photon absorption all across CuBi 2 O 4 surface. Also, it hindered the assimilation of photoinduced electron–hole pairs. The increased photocatalytic efficiency is contributed to the uniform dispersion of photo-generated electron–hole pairs via the construction of an S-scheme system. ROS trapping and ESR experiments suggested that (∙OH) and (O 2 − ∙) were the main radical species for enhanced photo-degradation of RhB dye. The current investigation, from our perspective, highlights the new insights for the fabrication of practical CNTs-mediated S-scheme–based semiconductor photocatalyst for the resolution of environmental issues based on practical considerations.

Electron-excited X-ray microanalysis performed in the scanning electron microscope with energy-dispersive X-ray spectrometry (EDS) is a core technique for characterization of the microstructure of materials. The recent advances in EDS performance with the silicon drift detector (SDD) enable accuracy and precision equivalent to that of the high spectral resolution wavelength-dispersive spectrometer employed on the electron probe microanalyzer platform. SDD-EDS throughput, resolution, and stability provide practical operating conditions for measurement of high-count spectra that form the basis for peak fitting procedures that recover the characteristic peak intensities even for elemental combination where severe peak overlaps occur, such PbS, MoS 2 , BaTiO 3 , SrWO 4 , and WSi 2 . Accurate analyses are also demonstrated for interferences involving large concentration ratios: a major constituent on a minor constituent (Ba at 0.4299 mass fraction on Ti at 0.0180) and a major constituent on a trace constituent (Ba at 0.2194 on Ce at 0.00407; Si at 0.1145 on Ta at 0.0041). Accurate analyses of low atomic number elements, C, N, O, and F, are demonstrated. Measurement of trace constituents with limits of detection below 0.001 mass fraction (1000 ppm) is possible within a practical measurement time of 500 s.

Recent advances in electron microscopy are shown to allow vibrational spectroscopy at high spatial resolution in a scanning transmission electron microscope, and also to enable the direct detection of hydrogen. Vibrational spectroscopy in the electron microscope Spectroscopies sensitive to the vibrational behaviour of materials and chemical compounds — infrared and Raman spectroscopy for instance — are widely used to give insights into chemical and physical properties. These vibrational excitations can in principle also be detected by electron energy loss spectroscopy (EELS); but the effect is relatively weak and the energy resolution needed to extract such signals has not hitherto been available in electron microscopy. Here Ondrej Krivanek and colleagues demonstrate that recent advances in electron microscopy now mean that vibrational spectroscopy can be undertaken at high spatial resolution in the scanning transmission electron microscope. The authors present examples of applications in inorganic and organic materials, including the direct detection of hydrogen, a capability that could be of great use in the analysis of systems as diverse as hydrogen storage materials and biological tissues. Vibrational spectroscopies using infrared radiation 1 , 2 , Raman scattering 3 , neutrons 4 , low-energy electrons 5 and inelastic electron tunnelling 6 are powerful techniques that can analyse bonding arrangements, identify chemical compounds and probe many other important properties of materials. The spatial resolution of these spectroscopies is typically one micrometre or more, although it can reach a few tens of nanometres or even a few ångströms when enhanced by the presence of a sharp metallic tip 6 , 7 . If vibrational spectroscopy could be combined with the spatial resolution and flexibility of the transmission electron microscope, it would open up the study of vibrational modes in many different types of nanostructures. Unfortunately, the energy resolution of electron energy loss spectroscopy performed in the electron microscope has until now been too poor to allow such a combination. Recent developments that have improved the attainable energy resolution of electron energy loss spectroscopy in a scanning transmission electron microscope to around ten millielectronvolts now allow vibrational spectroscopy to be carried out in the electron microscope. Here we describe the innovations responsible for the progress, and present examples of applications in inorganic and organic materials, including the detection of hydrogen. We also demonstrate that the vibrational signal has both high- and low-spatial-resolution components, that the first component can be used to map vibrational features at nanometre-level resolution, and that the second component can be used for analysis carried out with the beam positioned just outside the sample—that is, for ‘aloof’ spectroscopy that largely avoids radiation damage.

Imaging atoms: 'Invisible' graphene brings electron microscopy to single carbons and hydrogens Scanning tunnelling microscopes made it possible to image atomic-scale features on a solid-state surface. But they have limitations in terms of sample conductivity, cleanliness and data acquisition rate. An older technology, the transmission electron microscope (TEM), meanwhile evolved to be able to image individual heavy atoms. But lighter atoms remained beyond its range because of their low contrast. Enter graphene, the one-atom-thick sheet of carbon atoms packed in a dense two-dimensional honeycomb lattice. Meyer et al . show that atoms as small as carbon and even hydrogen adsorbed onto graphene can be imaged using standard TEM technology. Ultrathin graphene is an ideal support, either invisible or, if the lattice is resolved at high resolution, its contribution to the imaging signal is easily removed. This approach brings atomic resolution to biomolecules as well as to graphene itself. The cover shows hydrogen atoms (purple) on a graphene sheet (red), with a carbon atom (yellow tipped) near left centre. Yellow peaks are amorphous carbon. Detecting individual low-atomic-number atoms is extremely challenging using conventional transmission electron microscopy. This paper reports the direct imaging in a transmission electron microscope (TEM) of atomic carbon and hydrogen using graphene as a substrate which provides a near-invisible background. The approach could be used for the direct study at the atomic level of organic species such as biomolecules. Observing the individual building blocks of matter is one of the primary goals of microscopy. The invention of the scanning tunnelling microscope 1 revolutionized experimental surface science in that atomic-scale features on a solid-state surface could finally be readily imaged. However, scanning tunnelling microscopy has limited applicability due to restrictions in, for example, sample conductivity, cleanliness, and data acquisition rate. An older microscopy technique, that of transmission electron microscopy (TEM) 2 , 3 , has benefited tremendously in recent years from subtle instrumentation advances, and individual heavy (high-atomic-number) atoms can now be detected by TEM 4 , 5 , 6 , 7 even when embedded within a semiconductor material 8 , 9 . But detecting an individual low-atomic-number atom, for example carbon or even hydrogen, is still extremely challenging, if not impossible, via conventional TEM owing to the very low contrast of light elements 2 , 3 , 10 , 11 , 12 . Here we demonstrate a means to observe, by conventional TEM, even the smallest atoms and molecules: on a clean single-layer graphene membrane, adsorbates such as atomic hydrogen and carbon can be seen as if they were suspended in free space. We directly image such individual adatoms, along with carbon chains and vacancies, and investigate their dynamics in real time. These techniques open a way to reveal dynamics of more complex chemical reactions or identify the atomic-scale structure of unknown adsorbates. In addition, the study of atomic-scale defects in graphene may provide insights for nanoelectronic applications of this interesting material.