The preparation of carbon nitride nanotubes has proved extremely difficult—to date only small quantities of nitrogen (≤5%) have been incorporated into carbon nanotubes or filaments and the synthesis of crystalline C3N4 and CN nanotubes with their interesting predicted properties remains a challenge for the future. Now the generation of aligned C13Nx (x ≤ 1) nanofibers in high yield by pyrolyzing melamine over laser‐patterned thin films of Fe and Ni catalyst deposited on a silica substrate is reported. The resulting aligned, hollow, thin‐walled fibers exhibit unusual graphitic corrugated morphologies. The authors suggest that pyrolysis of organic precursors containing N (e.g., melamine) may provide an additional route to CN nanostructures.

The addition of iron to high-area TiO2 (Degussa P25, a mixture of anatase and rutile) increases the number of oxygen defect sites that react with O2 to form peroxide and superoxide species. In the presence of gold nanoclusters on the TiO2 surface, the superoxide species become highly reactive, and the activity of the supported gold catalyst for CO oxidation is approximately twice that of the most active comparable catalysts described in the literature. Images of the catalyst obtained by scanning transmission electron microscopy combined with spectra of the catalyst measured in the working state (Raman, extended X-ray absorption fine structure, and X-ray absorption near-edge structure) indicate strong interactions of gold with the support and the presence of iron near the interfaces between the gold clusters and the TiO2 support. The high activity of the catalysts is attributed to the presence of defects in these sites that activate oxygen.

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A systematic study of the effect of different synthesis parameters on N incorporation into C nanotubes is presented. CNx nanotubes prepared by catalyzed pyrolysis of melamine exhibit a highly compartmentalized morphology with a remarkable periodicity structure along the nanotube axis. Spatially resolved electron energy loss spectroscopy (spectrum-imaging mode) indicates that the nanotubes are made of carbon and nitrogen, inhomogeneously distributed with an enrichment of carbon on the external surfaces. The evolution of the C-K-edge shape across the nanotube reveals a transition from a graphitic stacking on the outside to a disorganized-mixed type in the core of the nanotube. For the N-K edge, the situation is more complex. The fine structure of the N-K edge differs depending on the used catalyst, which indicates differences in the bonding configuration. When Ni is used as a catalyst, N replaces C in the graphitic structure whereas C–N pyridinic-like bonds are formed when the catalyst is Fe. The compartmentalized periodic morphology is the result of a systematic catalytic particle movement from the root of the nanotube to the tip. This displacement is defined by the nature of the catalytic particle, diffusion, and supersaturation (C/N) in the liquid particle and precipitation process.

Transmission Electron Microscopy (TEM), X-ray Absorption Near Edge Spectroscopy (XANES), Electron Energy-Loss Spectroscopy (EELS), Small-Angle X-ray Scattering (SAXS), and SQUID magnetic studies were performed in a batch of horse spleen ferritins from which iron had been gradually removed, yielding samples containing 2200, 1200, 500, and 200 iron atoms. Taken together, findings obtained demonstrate that the ferritin iron core consists of a polyphasic structure (ferrihydrite, magnetite, hematite) and that the proportion of phases is modified by iron removal. Thus, the relative amount of magnetite in ferritin containing 2200 to 200 iron atoms rose steadily from approximately 20% to approximately 70% whereas the percentage of ferrihydrite fell from approximately 60% to approximately 20%. These results indicate a ferrihydrite-magnetite core-shell structure. It was also found that the magnetite in the ferritin iron core is not a source of free toxic ferrous iron, as previously believed. Therefore, the presence of magnetite in the ferritin cores of patients with Alzheimer's disease is not a cause of their increased brain iron(II) concentration.

This work reports on the hydrogen interaction with a 3 wt % Au/Ce 0.62 Zr 0.38 O 2 (Au/CZ) catalyst prepared by deposition-precipitation. As deduced from X-ray powder diffraction, electron microscopy (scanning transmission electron microscopy-high-angle angular dark field and high-resolution electron microscopy), and CO volumetric/Fourier transform IR (FTIR) adsorption studies, the investigated catalyst shows a good metal dispersion. By combining FTIR spectroscopy and volumetric chemisorption studies, it is shown that upon treating the Au/CZ catalyst with 40 Torr of H 2 at room temperature a fast and very intense spillover effect occurs. As determined from the recorded isotherm, very high values of the apparent H/Au ratio (>8.0) and of the atomic hydrogen surface density (>11.0 H/nm 2 ) are reached. In parallel with this observation, the onset of a characteristic IR band at 2133 cm -1 shows the occurrence of significant support reduction with inherent appearance of Ce 3+ species. Moreover, the simultaneous growth of the IR band at 1630 cm -1 due to molecular water strongly suggests that even at room temperature oxygen vacancies are also formed. Additional FTIR spectroscopy studies have shown that the hydrogen spillover is strongly inhibited by either co-adsorption of CO or a reducing pretreatment with flowing 5% H 2 /Ar at 673 K. These deactivation effects, however, may be reverted by very mild regeneration treatments at room temperature.

Photochemical reduction of tetrachloroaurate (AuCl4-) ions in the highly constrained aqueous domains of a nanostructured ionogel template, formed via self-assembly of the ionic liquid 1-decyl-3-methylimidazolium chloride (C10mim+Cl-) in water, results in the formation of anisotropic gold nanoparticles with a variety of sizes and morphologies, which include previously unattainable trigonal prismatic nanorods. Unexpectedly, small-angle X-ray scattering studies of the Au-ionogel composite reveal that the in situ formation of the nanoparticles increases the mesoscopic order of the ionogel, which results in its conversion to a near-monodomain structure. The findings demonstrate that nanostructured, ionic liquid-based gels can be used to template the formation of new nanoparticle morphologies with technologically important optical, electronic, and catalytic properties. It may also be possible to design soft templates that permit the fabrication of highly ordered nanoparticle array-hydrogel composites, thereby enabling control and tuning of the collective properties of the encapsulated nanoparticles.

We demonstrate a counterintuitive approach for improving exchange-spring magnets. Contrary to the general belief that the exchange-spring interface must be ideal and atomically coherent, we thermally process, by annealing or high-temperature deposition, epitaxial Sm-Co/ Fe thin-film bilayers to induce interfacial mixing. Synchrotron x-ray scattering and electron microscopy elemental mapping confirm the formation of a graded interface. The thermal processing enhances the nucleation field and the energy product. The hysteresis loop becomes more single-phase-like yet the magnetization remains fully reversible. Model simulations produce demagnetization behaviors similar to experimental observations.