Publications

Heavy rare earth chromites of the formula LnCrO3 with Ln = Ho, Er, Yb, Lu and Y are shown to be multiferroic, exhibiting canted antiferromagnetism at low temperatures (TN = 113–140 K) and a ferroelectric transition in the 472–516 K range.

Temperature effects on the various features in the Raman spectra of several graphene samples and graphene nanoribbons have been investigated over the temperature range 77-573 K. The temperature coefficient of the G and 2D band frequencies are found to depend on the number of layers, the former decreasing with the increase in the number of layers. The number of layers also affects the temperature coefficients of the FWHMs of these bands. Doping of graphene affects these Raman features significantly. The defect-related bands D and D(') bands are not sensitive to the number of layers or doping. We can understand the observed temperature effects on the basis of electron-phonon coupling, thermal expansion and anharmonic phonon-phonon interactions.

Nanocomposites formed by poly(diallyldimethylammonium chloride) (PDDA, shown as P)-functionalized reduced graphene oxide (RGO) and borocarbonitride (BC6N, shown as BCN for simplicity) sheets with layers of negatively charged MoS2 and MoSe2 have been synthesized by a solution process. The nanocomposites exhibit superior photocatalytic hydrogen evolution reaction (HER) activity compared to the individual components, with the value increasing with the MoS2/MoSe2 content. The highest photocatalytic HER activity obtained is 11230 μmol h–1 g–1 in the nanocomposite P.RGO-MoS2, with a P.RGO-MoS2 ratio of 1:5. The P.RGO-MoSe2 (1:5) and P.BCN-MoS2 (1:5) nanocomposites exhibit somewhat lower activities of 9540 and 8593 μmol h–1 g–1, respectively. Prompted by literature reports that carbon-rich BCNs are efficient HER electrocatalysts, we have examined the electrocatalytic HER activity of P.BCN-MoS2 (1:1, 1:5, and 1:7) nanocomposites. The electrocatalytic HER activity of P.BCN-MoS2 (1:5) is found to be extraordinary, with an onset potential of −50 mV (vs RHE), comparable to that of platinum.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

In the Communication by S. J. George, C. N. R. Rao et al., the wrong journal was cited in reference 2a, the correct reference is included below. We apologize for this oversight.

Effect of ruthenium and nickel on the reduction behavior of Fe 3+ Al 2 O 3 to give the Fe1bAl2O3 metal-ceramic composite has been studied by employing x-ray diffraction. 57Fe Mössbauer spectroscopy and electron microscopy. Both ruthenium and nickel promote the hydrogen reduction of Fe3+, giving nearly total reduction to the metallic phase at 1220K. Besides metallic iron in the ferromagnetic α-form, paramagnetic alloys of Fe with Ru and Ni are formed during the reduction.

Thin films of bilayered manganates of the formula LnSr2Mn2O7 (Ln=rare-earth), deposited on LaAlO3(100) substrates by nebulized spray pyrolysis, show charge-ordering transitions in the resistivity data. The transition temperatures decrease from 205 K to 185 K as the rare-earth ionic radii decrease from Ln=La to Gd. While magnetic-fields up to 6 tesla have little effect on the charge-ordering transition, small electric currents prevent the onset of the charge-ordered state. Furthermore, the resistance decreases markedly with increasing current, with nonlinear behavior, in polycrystalline films deposited on Si(100) substrates.

Density measurements on large single-crystal specimens of La2NiO4+δ and Pr2NiO4+δ show that oxygen nonstoichiometry arises from the presence of excess lattice oxygen. X-ray photoelectron spectra as well as X-ray absorption edge studies provide no evidence for the existence of Ni3+ in these oxygen-excess nickelates under the conditions of the measurements. Transmission electron microscopy has revealed a novel type of exsolution process of the stoichiometric phase out of nonstoichiometric La2NiO4 during heating in CO2 at 870 K for 3 h. An interpretation of the results in terms of the existence of peroxide species within the conducting layers is proposed.