Alkali metal ion—oxygen donor solvent cages as well as coordination compounds, alkali metal oxide glasses and oxyanion salts of alkali metals exhibit low-frequency bands in the infrared spectrum characteristic of the cation—oxygen polyhedra. Similar bands are seen with nitrogen donors. Alkaline earth ions also show such absorption bands due to quantised vibration of cations. These bands not only provide a means of establishing the nature of cation coordination in diverse systems, but also serve as probes to examine ion-solvent interactions.
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No abstract is provided for this article.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTDependence of the Strength of Interaction of Carbon Monoxide with Transition Metal Clusters on the Cluster SizeA. K. Santra, Samrat Ghosh, and C. N. R. RaoCite this: Langmuir 1994, 10, 11, 3937–3939Publication Date (Print):November 1, 1994Publication History Published online1 May 2002Published inissue 1 November 1994https://doi.org/10.1021/la00023a006RIGHTS & PERMISSIONSArticle Views84Altmetric-Citations14LEARN 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 InReddit PDF (331 KB) Get e-Alerts Get e-Alerts
Based on a Bi – L 3 edge X-ray absorption spectroscopic study of superconducting bismuth cuprates and model Bi compounds, it is shown that Bi is essentially in the 3 + state in the cuprates. Tl – L 3 absorption edge studies a number of thallium cuprate superconductors along with those of model compounds show some evidence for the occupancy of the Tl -6s band, but Tl 3+ is the prepondarant species. Cu K-edge studies of the thallium cuprates show that Cu is essentially in the 2+ state.
Since the discovery of graphene, there has been intensive research on other two‐dimensional (2D) analogues. Some of them are elemental 2D materials such as phosphorene and bismuthene. Others are binary compounds fascinating in terms of energy applications are transition metal dichalcogenides (TMDCs: MoS 2 , MoSe 2 ) and MXenes (Ti 3 C 2 , Nb 2 C 3 ). 1T‐forms of MoS 2 and MoSe 2 are probably the best materials reported for dye‐sensitized photocatalytic hydrogen evolution reaction (HER). Here, we first highlight the phase engineering in 2D‐TMDCs to enhance hydrogen evolution activity. Generation of hetero‐superlattices of TMDCs with other HER active materials such as graphene, carbon nitride and borocarbonitrides, by utilizing coupling and electrostatic restacking strategies, appears to be advantageous for photocatalytic application. These hetero‐superlattices provide a counterpoint to the van der Waals heterostructures by means of covalent bonds. Ladder‐like networks of heterolayers generated due to cross‐linking enhance the interfacial area and charge‐transfer interactions, thereby improving HER activity. The use of 2D phosphorene as a photocatalytic material is limited by its ambient instability. Covalent functionalization of phosphorene surface with tris(pentafluorophenyl) borane and benzyl group increases ambient stability and dispersibility. The functionalized surface can be further utilized to cross‐link with amine or acid‐modified TMDCs. The HER activity obtained with phosphorene‐MoS 2 superlattices is the highest reported among the phosphorene‐based systems, thus setting a new example for metal‐free catalysis. The ambient instability of MXenes and other related 2d materials under photocatalytic conditions can be resolved either by functionalization or by forming hetero‐superlattices.
In order to understand the structure of aluminum phosphates, prepared by the sol-gel method, 27Al and 31P MAS NMR spectroscopy has been employed. The evolution of structure during the gel-glass-crystal transformation has been followed as a function of both temperature and compostion. Aluminum is octahedrally coordinated in the xerogel and on heating it is partially converted into tetrahedrally coordinated Al in the gel glass. Phosphorous is present in metaphosphate units. The structure of crystalline AlPO4 is shown to consist of an ordered covalent network involving [PO 4 2 ]+ and [AlO 4 2 ]− units.
The ultraviolet absorption spectra of 5-(substituted)amino-1,2,3,4-thiatriazoles and the corresponding isomeric 1-substituted-tetrazoline-5-thiones have been studied. The spectra and the dipole moments of the 5-(substituted)amino-1,2,3,4-thiatriazoles eliminate the possibility of meso-ionic structures for these compounds. The dipole moments of 5-amino-, 5-methylamino-, and 5-dimethylamino-1,2,3,4-thiatriazole were all high but approximately of the same value (5.77 to 5.84 D). This suggests that the amino thiatriazoles are best represented by conventional covalent structures with significant ionic resonance contributions. The thiatriazole ring system exhibits a characteristic absorption maximum at 250–255 mμ and an electron-withdrawing effect approximately equal to the tetrazolyl ring system. The tetrazolinethionolyl ring system is similarly electron-withdrawing. The relative acidities of the 1-substituted-tetrazoline-5-thiones and the 5-alkylmercaptotetrazoles have also been studied and the results support the observations made on the basis of their ultraviolet absorption spectra.
As-prepared single-walled carbon nanotubes (SWNTs) are generally mixtur es of semiconducting and metallic species, the proportion of the former being around 67%. Since most applications of SWNTs are best served by semiconducting or metallic nanotubes, rather than by mixtures of the two, methods which would directly yield semiconducting and metallic SWNTs in pure form are desirable. In this article, we present the available methods for the direct synthesis of such SWNTs along with the methods available to separate semiconducting and metallic SWNTs from mixtures. We also discuss the synthesis of Y-junction carbon nanotubes.
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