Materials Literature
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The colossal magnetoresistance (CMR) effect in perovskite manganites is a magnetic-field-induced transition from a paramagnetic insulating (PI) to a ferromagnetic metallic state. The large electrical resistivity of the PI state lies at the heart of the CMR effect. This enhanced resistivity stems, in part, from strong…
An assumed B 2 CN crystal system containing seven possible diamond-structured configurations in boron-carbonitride B–C–N compounds has been studied by using an ab initio pseudopotential density functional method. After structural relaxation, the lattice constant, bulk modulus and shear modulus, and electronic band str…
Nickel formate serves as an ideal catalyst precursor for surface-bound thermal and plasma-enhanced CVD growth of carbon nanotubes. As the method of deposition of the Ni catalyst is solution-based, it benefits from a low-cost, large-area growth, ease of operation and suitability for coating substrates with complex shap…
Using NMR inversion recovery experiments and XPLOR distance restraint calculations, we recently deduced the structure of ferriprotoporphyrin IX (FPIX) heme mu oxo dimer-antimalarial drug complexes for chloroquine (CQ), quinine (QN), and quinidine (QD) at atomic resolution [A. Leed et al., Biochemistry 2002, 41, 10245-…
We report on the effect of Mn site substitution of Al on the structural, magnetic and transport properties of charge ordered Pr 0.5 Ca 0.5 MnO 3 . This substitution introduces non-magnetic impurities in the Mn–O–Mn network, causes the Mn 3+ /Mn 4+ ratio to deviate away from unity and is seen to predominantly replace M…
Li+ motion in quartz and β-eucryptite (LiAlSiO4) is investigated by dielectric spectroscopy and classical simulations. Simulations are performed using a combination of traditional energy-minimization (using the GULP code) and a mechanical approach derived from Rigid Unit modelling, implemented in the GASP code. Compar…
Lines of formation and decomposition of the hcp (ε) molybdenum deuteride in the T–P phase diagram of the Mo–D system are constructed via the measurement of isotherms of the electrical resistance of molybdenum in a deuterium atmosphere at temperatures up to 550 °C and pressures up to 6 GPa. The diagram is compared to t…
An in situ Raman spectroscopic study was conducted to explore the pressure-induced phase transformation of Sr2CaWO6 to pressures of 50.8 GPa and room temperature. Group theory yields 24 Raman active modes for Sr2CaWO6, of which 17 are observed at ambient conditions. Upon elevation of pressure to 3.2 GPa, the results s…
The series of the SrTi(1-x)Co(x)O(3-delta) polycrystalline samples has been prepared via solid-state reaction in air. The structural study shows that a solid solution exists for all compositions, such as 0 < or = x < or = 0.9, which discards the presence of ferromagnetic and metallic cobalt clusters for the low level…
At temperatures below the metal–insulator transition of La 1− x Sr x MnO 3 with 0.1 < x < 0.15, a peculiar ferromagnetic and insulating phase is observed which has been intensively discussed over the last few years. We present a detailed investigation of this phase by means of resonant and high energy x-ray scattering…
We investigated the temperature-dependent optical absorption spectra of LaMnO 3 and NdMnO 3 epitaxial thin films. We found that both spectra have strong absorption features around 2 eV, and that the 2 eV peak of LaMnO 3 has a weak temperature dependence. As the La ions are replaced with Nd ions, the spectral weight of…
Colossal magneto-resistance manganites are characterized by a complex interplay of charge, spin, orbital and lattice degrees of freedom. Formulating microscopic models for these compounds aims at meeting two conflicting objectives: sufficient simplification without excessive restrictions on the phase space. We give a…
We present high-temperature powder x-ray diffraction data of the orbital-order-induced structural distortion of RMnO 3 , with R a rare earth element. The associated phase transition takes place in a temperature interval of ≈200 K in which the orbitally ordered phase and the orbitally disordered phase coexist. We analy…
The synthetic approach to the new class of mesomorphous nanocomposite polymer systems was developed. It is based on the in situ reduction of silver ions in the liquid crystalline (LC) polymer matrix leading to the formation of nanoparticles with typical sizes in the range of 5-30 nm. The influence of silver nanopartic…
Highly ordered hexagonal arrays of latex spheres on highly ordered pyrolytic graphite (HOPG) have been prepared from a Langmuir-Blodgett-like (LB-like) technique using both polymers and surfactants as spreading agents. The role of spreading agent concentration in forming a well-ordered, stable monolayer at the air-liq…
A family of new meso-arylsulfanyl- and alkylsulfanyl-substituted porphyrins were efficiently synthesized from direct reactions of meso-brominated porphyrins with thiols via palladium-mediated C-S bond formation. The catalytic method can be performed under mild conditions with both mono- and bis-substituted meso-bromop…
This paper reports the first detailed study on meso-unsubstituted azuliporphyrins, an important family of porphyrin-like molecules where one of the usual pyrrole rings has been replaced by an azulene subunit. Although the azulene moiety introduces an element of cross-conjugation, zwitterionic resonance contributors wi…
Previous studies on conjugated polymer nanotubules, prepared by the template method, established that improvements in the molecular and supermolecular structure are responsible for the increase in the room temperature conductivity when the diameter decreases. Our study clearly indicates that a more complex situation c…
Sapphyrins are an important group of expanded porphyrins that show valuable anion binding characteristics. In this study, a "4 + 1" route to sapphyrin systems has been developed. Reaction of dialdehydes with a known tetrapyrrole intermediate 11b incorporating a bipyrrolic subunit afforded a wide range of sapphyrin-typ…
We report the observation of photoluminescence from single-walled carbon nanotubes (SWNTs) dispersed in a tetrahydrofuran(THF)/octylamine solution, providing the first clear evidence for individual SWNTs in nonaqueous solution. We also report the effective amine-assisted dispersion of C 60 and La@C 82 peapods. This so…