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Single crystals of LaMnO3, La1−x MnO3 (x=0, 0.04, 0.1) and LaMn1−x O3 (x=0.1) have been grown by the floating-zone melting technique. Electrical and magnetic properties of these crystals have been examined. Only La0.9MnO3 crystals exhibit ferromagnetism, (T c∼250 K), an insulator–metal transition around 250 K and CMR (58% at T c).
A tripodal cholamide-based hydrogel has been employed as a template to synthesize inorganic nanotubes. Besides nanotubes of oxides such as SiO2, TiO2, ZrO2, WO3 and ZnO, nanotubes of sulfates such as the water-soluble ZnSO4 as well as of BaSO4 have been obtained using this method. An advantage of the use of the hydrogel is that metal alkoxides are not required for the synthesis of the oxide nanotubes. The nanotubes have been characterized by X-ray diffraction and transmission electron microscopy.
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The 1122 (n=2) member of the Tl(Ca,Ba) n+1Cu n O2n+3 series containing a single Tl-O layer is shown to be associated with a T c of 90 K. This value of T c is significantly lower than that of the 2122 phase (T c∼110 K) with two Tl-O layers.
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Quantum mechanical calculations show that alkali metal ionic clusters of the type M3+ 4 have the tetrahedral structure, the stability varying as Na3+ 4 > K3+ 4 > Rb3+ 4. Raman spectroscopy has been employed to establish the tetrahedral structure of Na3+ 4.
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Electrical conductivities, electron spin resonance spectra, electronic spectra, and Seebeck coefficients of solid charge-transfer complexes of benzidine–iodine, p-phenylenediamine–iodine, and phenothiazine–iodine as well as two antimony chloride complexes of phenothiazine have been studied. The phenothiazine–I 2 system shows change in sign of the majority charge carriers with the donor–acceptor ratio. The effect of ambient gases on the conductivities of a few donors, acceptors, and their complexes in the solid state have been examined. Seebeck coefficient measurements show that the conduction in TCNQ salts takes place by a hopping mechanism.
Mössbauer studies of 2% 57Fe-doped Nd0.5Ca0.5MnO3 and Nd0.5Sr0.5MnO3 have been carried out over the 4.2–300K range after ensuring that such doping does not change their basic properties. The charge-ordering transition in these manganates is marked by abrupt changes in the quadrupole splitting. In the case of Nd0.5Ca0.5MnO3, two phases manifest themselves on cooling below the charge-ordering transition temperature. The evolution of the spectra as a function of temperature shows that long-range magnetic order does not occur sharply. The observed evolution with temperature is different in the two materials studied. In Nd0.5Ca0.5Mn0.98 57Fe0.02O3, it resembles that of a disordered magnetic material, whereas the temperature dependence of line shape of Nd0.5Sr0.5Mn0.98 57Fe0.02O3 is typical of a superparamagnetically relaxed magnetic system. Although both the manganates show well-resolved magnetic hyperfine spectra at 4.2K, the lines are slightly broad indicating possible coexistence of phases at low temperatures. A weak paramagnetic signal is also seen in the spectra of both the manganates at 4.2K.
Preface.Nanomaterials: An Introduction.Strategies for the Scalable Synthesis of Quantum Dots and Related Nanodimensional Materials.Moving Nanoparticles Around: Phase-Transfer Processes in Nanomaterials Synthesis.Mesoscopic Assembly and Other Properties of Metal and Semiconductor Nanocrystals.Oxide Nanoparticles.Sonochemistry and Other Novel Methods Developed for the Synthesis of Nanoparticles.Solvothermal Synthesis of Non-Oxide Nanomaterials.Nanotubes and Nanowires.Synthesis, Assembly and Reactivity of Metallic Nanorods.Oxide-Assisted Growth of Silicon and Related Nanowires: Growth Mechanism, Structure and Properties.Electronic Structure and Spectroscopy of Semiconductor Nanocrystals.Core-shell Semiconductor Nanocrystals for Biological Labeling.Large Semiconductor Molecules.Oxomolybdates: From Structures to Functions in a New Era of Nanochemistry.Nanostructural Polymers.Recent Developments in the Chemistry and Chemical Applications of Porous Silicon.Nanocatalysis.Nanoporous Materials.Photochemistry and Electrochemistry of Nanoassemblies.Electrochemistry with Nanoparticles.Nanolithography and Nanomanipulation.
