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Multiferroics were considered to be rare because magnetism and ferroelectricity require entirely different criteria for the materials. Several multiferroic oxides have, however, been discovered in the past few years by virtue of novel operating mechanisms, the most effective one being ferroelectricity driven by magnetism itself. Many such oxides where the magnetic and electric order parameters interact also exhibit magnetoelectric or magnetodielectric properties. In this Perspective, properties of manganites, ferrites, and other monophasic multiferroic oxides with spin-induced electric polarization are described. Multiferroic properties arising from charge ordering are examined. The present status of BiMnO3, which is an unusual example of a ferromagnetic-ferroelectric, is presented. Recent findings suggest that it is likely that many more multiferroic and magnetoelectric oxide materials exhibiting magnetically induced ferroelectricity will be found in the future.
UPS and XPS studies indicate that carbon monoxide preferentially adsorbs dissociatively on the surfaces of the metallic glasses, Ni76B12Si12 and Fe40Ni38Mo4B18, suggesting that such metglasses could be potential catalysts for some of the reactions involving CO.
Covalent linking of 2D structures such as graphene, MoS<sub>2</sub>and C<sub>3</sub>N<sub>4</sub>by employing coupling reactions provides a strategy to generate a variety of materials with new or improved properties.
Dip-pen lithography has been successfully demonstrated on mica substrates employing hydrosols of polyvinylpyrrolidone-capped Pd nanocrystals as well as Au nanocrystals stabilized by tetrakishydroxymethyl phosphonium chloride. Lines of widths as small as 30 nm and various aspect ratios have been successfully drawn by this method.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAn investigation of solid adamantane by a modified isothermal-isobaric ensemble Monte Carlo simulationS. Yashonath and C. N. R. RaoCite this: J. Phys. Chem. 1986, 90, 12, 2552–2554Publication Date (Print):June 1, 1986Publication History Published online1 May 2002Published inissue 1 June 1986https://pubs.acs.org/doi/10.1021/j100403a002https://doi.org/10.1021/j100403a002research-articleACS PublicationsRequest reuse permissionsArticle Views125Altmetric-Citations7LEARN 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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Electronic properties of graphene have been studied more extensively than its photonic applications, in spite of its exciting optical properties. Recent results on solar cells, light emitting diodes and photodetectors show its true potential in photonics and optoelectronics. Here, we have explored the use of reduced graphene oxide as a candidate for solution processed ultraviolet photodetectors. UV detection is demonstrated by reduced graphene oxide in terms of time resolved photocurrent as well as photoresponse. The responsivity of the detectors is found to be 0.12 A/W with an external quantum efficiency of 40%.
There is increasing interest in recent years in the structural chemistry and properties of layered metal oxides possessing the K2NiF4 or related structures. Many new oxides of this structure exhibiting novel properties are being reported from time to time in the literature. The crystal chemistry of the oxides of the general formula A 2 BO4 with particular reference to the stability of the K2NiF4 structure and the relations between the different structures exhibited by this family of oxides is discussed. Non-stoichiometry in these oxides is another aspect of interest discussed in the article. While K2NiF4 itself is a well-known two-dimensional antiferromagnet, oxides of this structure with a variety of magnetic properties are examined in some detail. Besides the ternary A 2 BO4 oxides, the structure and magnetic properties of complex oxides, where the A or/and the B ions are partly substituted by other cations, is discussed. Some of the problems related to this family of oxides that are worth investigating are indicated. Much of the discussion in this article would have relevance in understanding the structure and properties of layered materials.
Graphenes with varying number of layers can be synthesized by using different strategies. Thus, single-layer graphene is prepared by micromechanical cleavage, reduction of single-layer graphene oxide, chemical vapor deposition and other methods. Few-layer graphenes are synthesized by conversion of nanodiamond, arc discharge of graphite and other methods. In this article, we briefly overview the various synthetic methods and the surface, magnetic and electrical properties of the produced graphenes. Few-layer graphenes exhibit ferromagnetic features along with antiferromagnetic properties, independent of the method of preparation. Aside from the data on electrical conductivity of graphenes and graphene-polymer composites, we also present the field-effect transistor characteristics of graphenes. Only single-layer reduced graphene oxide exhibits ambipolar properties. The interaction of electron donor and acceptor molecules with few-layer graphene samples is examined in detail.
HeI photoelectron spectra of 1:1 electron donor-acceptor complexes are discussed in the light of molecular orbital calculations. The complexes discussed include those formed by BH3, BF3 and SO2. Some systematics have been found in the ionization energy shifts of the complexes compared to the free components and these are related to the strength of the donor-acceptor bond. Hel spectra of hydrogen bonded complexes are discussed in comparison with results from MO calculations. Limitations of such studies as well as scope for further investigations are indicated.
Rare earth manganates of the general formula, Ln1−x A x MnO3 (Ln=rare earth, A=alkaline earth) exhibit phase separation due to the occurrence of tiny clusters or small nanometric regions of one type of magnetic phase in the matrix of another (e.g., ferromagnetic metallic clusters in an insulating antiferromagnetic matrix) or phase segregation due to the coexistence of large domains of two phases. The phenomenon is nearly universal in the manganates and crucially depends on the composition, temperature, external magnetic field, dopant substitution in the Mn site and related factors. Percolative transport has been considered to result from the coexistence of the ferromagnetic metallic and insulating phases, but it is necessary to ensure whether these phases form large domains or remain as clusters (<100 nm) in the relevant composition.
Properties of hydrogen bonds formed by 1:1 interaction of H2O with oxygen, nitrogen, sulphur and other electron donors have been evaluated by extended Hückel and CNDO methods and the results are discussed in relation to the experimental data. A detailed analysis of the variation of the dissociation energies and charge densities with bond distances is presented for the amine-water system. 1:2 complexes of water with donors are found to contain weaker hydrogen bonds than 1:1 complexes. Results of molecular orbital calculations on the hydrogen bonding of H2S and CH3SH with some donors are presented. The theoretical value of hydrogen bond dissociation energy varies linearly with the overlap population, and stretching force constant of the hydrogen bond as well as with the experimental O—H frequency shift.
Although a few open‐framework metal sulfates and selenites have been synthesized and characterized recently, it has not been possible to prepare the corresponding selenates, probably because of the instability of the +6 oxidation state of Se in alkaline media. We have been able to synthesize, for the first time, organically templated open‐framework rare earth selenates with the general formula 0.5[C 2 N 2 H 10 ][Ln(H 2 O) 2 (SeO 4 ) 2 ] ( I ) (Ln = La, Nd or Pr) and 0.5[C 4 N 2 H 14 ][La(SeO 4 ) 2 ]·0.5H 2 O ( II ), under hydrothermal conditions in an acidic medium. Crystal data: I (Ln = La): triclinic, space group = P $\bar 1$ , M r = 491.91, a = 7.0105(8) Å, b = 7.3772(9) Å, c = 9.526(1) Å, α = 82.014(2), β = 84.514(2), γ = 84.247(2)°, V = 483.76(1) Å 3 , Z = 2; II : triclinic, space group = P $\bar 1$ , M r = 478.91, a = 5.94(2), b = 7.408(3), c = 11.048(2) Å, α = 86.899(2), β = 75.971(1), γ = 79.456(2)°, V = 463.7(2) Å 3 , Z = 4. Being the first report of complex layered selenates, it is likely to stimulate efforts to synthesize other novel open‐framework structures making use of the selenate ion as the building unit. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
