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We have prepared borocarbonitride (B x C y N z ) nanotubes of various compositions by a simple, template‐ and catalyst‐free procedure. The procedure involves heating borocarbonitride nanosheets at a high temperature (≈ 900 °C), having prepared the nanosheets by heating a mixture of boric acid and glycine at 475 °C. The nanotubes have been characterized by electron microscopy, X‐ray photoelectron spectroscopy and other techniques. Supercapacitor performance of the nanotube with high carbon content, BC 3 N, is noteworthy, with a specific capacitance of 164 F/g at a current density of 1.0 A/g.
Two different strategies for the synthesis of t-selenium nanorods and nanowires are described, wherein the solution based method involves a reaction of selenium powder with NaBH4 while the other employs the thermal decomposition of [(CH3)4N]4Ge4Se10.
The short‐range order in noncrystalline and crystalline silicates can be investigated with 29 Si magic‐angle‐spinning (MAS) NMR spectroscopy. Different 29 Si chemical shifts are observed depending on the degree of cross‐linkage of the silicate, the SiOSi bond angles, and the interatomic distances. In this way, the distribution of SiOSi angles in glasses, the crystallinity of which lies between 0 and 100%, can be obtained.
Superconducting oxides of the Bi1.5Pb0.5(Ca, Sr) n+1Cu n O2n+4+δ series with n = 1, 2, 3 and 4 have been characterized. The superconducting transition temperature increases markedly with n up to n = 3, but the T c of the n = 4 member is not much higher than that of the n = 3 member. The T c does not change significantly in Bi2−x Pb x CaSr2Cu2O8+δ with x (0.1 < x ≤ 0.5).
Ordered mesoscale hollow spheres (1000 nm diameter) of binary oxides such as TiO2 and ZrO2 as well as of ternary oxides such as ferroelectric PbTiO3 and Pb(ZrTi)O3 have been prepared by templating against colloidal crystals of polystyrene, by adopting different procedures.
Simulated catalysts wherein controlled amounts of Ni are deposited on Al2O3 layers grown in situ on an Al surface have been investigated; dissociative adsorption of CO is favoured on these catalyst surfaces.
Interatomic ${L}_{3}(M){M}_{23}(M)V(O)$ and ${L}_{3}(M)V(O)V(O)$ Auger transitions of some transition-metal oxides are reported for the first time. The interatomic mode of decay becomes progressively more dominant (relative to the intra-atomic mode) as the metal $d$ level gets depleted or as the oxidation state of the metal increases. The usefulness of interatomic Auger transitions in studying oxidation of metals has been examined.
Both superoxo and peroxo species are formed when oxygen is adsorbed on a polycrystalline Ag surface as evidenced by the characteristic O-O stretching frequencies in the EEL spectra. Based on temperature-variation studies of the vibration bands in the EELS and of the O(1s) core level peaks in the XPS, characteristic O(1s) binding energies are assigned to the two molecular species; the superoxo species is associated with a significantly higher binding energy as expected. The superoxo species appears to be relatively less thermally stable than the peroxo species, being associated with a ∼1300 cm−1 stretching vibration, the highest O-O stretching frequency observed so far due to a chemisorbed species.
Recent work related to gold catalysis has been discussed addressing the important issue ofhow the nobleness of gold breaks down at nanometric sizes when in contact with oxidic supports. The high reactivity of gold catalysts in comparison to other metal catalysts is illustrated by reactions such as oxidation of CO and reduction ofNO under ambient conditions, as weil as epoxidation and hydrochlorination of unsaturated hydrocarbons. Investigations carried out on gold catalysts using a variety of spectroscopy and microscopy techniques are discussed along with the general mechanism of the catalytic process. The observation ofmaximum reactivity at a cluster size of2-3 nm, coincident with the size-induced metal to non-metal transition in gold forms the central theme of the article.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe Metal-Nonmetal Transition: A Global PerspectiveP. P. Edwards, T. V. Ramakrishnan, and C. N. R. RaoCite this: J. Phys. Chem. 1995, 99, 15, 5228–5239Publication Date (Print):April 1, 1995Publication History Published online1 May 2002Published inissue 1 April 1995https://pubs.acs.org/doi/10.1021/j100015a002https://doi.org/10.1021/j100015a002research-articleACS PublicationsRequest reuse permissionsArticle Views696Altmetric-Citations92LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access options Get e-Alerts
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Compounds possessing the Kagome network are truly interesting because of their unusual low-energy properties. They exhibit magnetic frustration because of the triangular lattice inherent to the hexagonal bronze structure they possess, as indeed demonstrated by some of the Fe(3+) jarosites, but this is not the general case. Kagome compounds formed by transition metal ions with varying spins exhibit novel magnetic properties, some even showing evidence for magnetic order and absence of frustration. We describe the structure and magnetic properties of this interesting class of materials and attempt to provide an explanation for the variety of properties on the basis of theoretical considerations.
A correlation of the infrared spectra of thiocarbonyl derivatives based on the literature data has been carried out. Assignments have also been made in some new systems. Since simple alkyl thioketones are unstable, we have prepared thiofenchone in order to obtain a reference C=S stretching frequency. The C=S stretching frequency in thiofenchone has been found around 1180 cm−1 which is in fair agreement with the value calculated for thioformaldehyde. In the case of the thiocarbonyl derivatives where the C=S group is linked to elements other than nitrogen, the stretching frequency is generally found in the region 1025–1225 cm−1. Strong vibrational coupling is operative in the case of the nitrogen containing thiocarbonyl derivatives and three bands seem to consistently appear in the regions 1395–1570 cm−1, 1260–1420 cm−1, 940–1140 cm−1 due to the mixed vibrations. These bands, which may be tentatively designated as the “-N-C=S I, II and III bands”, could be useful in qualitative analysis.
Ultra-thin films of ZnS have been prepared by the reaction of zinc cupferronate or zinc stearate in a toluene solution with an aqueous solution of Na2S. The films have been examined by electron microscopy and other techniques. The reaction at the interface yields excellent films which are generally single-crystalline. The effects of reaction parameters such as temperature and reactant concentration have been examined. Ultra-thin crystalline films of PbS have been obtained by the reaction of a toluene solution of lead cupferronate with the aqueous solution of Na2S. The organic–aqueous interface provides a simple and elegant method of producing good crystalline films of important semiconducting materials.
