Materials Literature
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We analyze the electronic structure of group III-V semiconductors obtained within full potential linearized augmented plane wave (FP-LAPW) method and arrive at a realistic and minimal tight-binding model, parametrized to provide an accurate description of both valence and conduction bands. It is shown that the cation…
Magnetization measurements of Mn12 molecular nanomagnets with spin ground states of S=10 and S=19/2 show resonance tunneling at avoided energy level crossings. The observed oscillations of the tunnel probability as a function of the magnetic field applied along the hard anisotropy axis are due to topological quantum p…
We report the results of first-principles calculations showing that boron can form a wide variety of metastable planar and tubular forms with unusual electronic and mechanical properties. The preferred planar structure is a buckled triangular lattice that breaks the threefold ground state degeneracy of the flat triang…
Difference of degeneracy of the low-spin (LS) and high-spin (HS) states causes interesting entropy effects on spin-crossover phase transitions and charge transfer phase transitions in materials composed of the spin-crossover atoms. Mechanisms of the spin-crossover (SC) phase transitions have been studied by using Wajn…
Frequency shifts, radiative decay rates, the Ohmic loss contribution to the nonradiative decay rates, fluorescence yields, and photobleaching of a two-level atom radiating anywhere inside or outside a complex spherical nanoshell, i.e. a stratified sphere consisting of alternating silica and gold concentric spherical s…
We present a theory of tunneling and resonant transitions in one-dimensional molecular systems which is based on Green's function theory of electron sub-barrier scattering off the structural units (or functional groups) of a molecular chain. We show that the many-electron effects are of paramount importance in electro…
We have studied the effective response of composites of spherical particles with a dielectric profile which varies along the radius of the particles. We developed a differential effective dipole theory to compute the dipole moment of individual spherical particle and hence the effective dielectric response of a dilute…
By employing a novel low-temperature synthetic pathway, highly ordered cubic mesoporous materials with hitherto the largest pores (up to 27 nm) and unit cells (up to 44 nm) have been successfully obtained.
Iron(III)-doped TiO(2) nanopowders, with controlled iron to titanium atomic ratios (R(Fe/Ti)) ranging from nominal 0 to 20%, were synthesized using oxidative pyrolysis of liquid-feed metallorganic precursors in a radiation-frequency (RF) thermal plasma. The valence of iron doped in the TiO(2), phase formation, defect…
Watch your step! Decoupling the individual contributions of edge-plane steps (A) and basal-plane terraces (B) to the voltammetry of graphite electrodes can provide information of fundamental importance. This was done by selectively blocking the basal-plane terraces with insulating material to form nanotrench arrays of…
Hydrogen-bonded disk-shaped aggregates (rosettes) composed of azobenzene-appended melamine and barbiturate or cyanurate are investigated in view of their hierarchical organization and photoresponsive behavior by (1)H NMR and UV/vis spectroscopies, dynamic light scattering, and gelation behavior in aliphatic solvents a…
Vorsicht Stufe! Durch das Entkoppeln der Einzelbeiträge von Kantenebenen-Stufen (A) und Basisebenen-Terrassen (B) zur Voltammetrie von Graphitelektroden lassen sich wichtige Informationen gewinnen. Dies gelang durch selektives Blockieren der Basisebenen-Terrassen mit Isolatormaterial, das zu Nanograben-Anordnungen von…
In order to answer the question of whether there is another source of magnetism that plays an important role in tuning ferromagnetism in diluted magnetic oxide thin films, investigations on magnetic and structural properties of some types of transition-metal-doped semiconductors had been done. Results on Cr-doped ZnO…
We formulate a U(1) gauge theory of the Hubbard model in the slave-rotor representation. From this formalism it is argued that spin liquid phases may exist near the Mott transition in the Hubbard model on triangular and honeycomb lattices at half filling. The organic compound $\ensuremath{\kappa}\mathrm{\text{\ensurem…
Wet and dry: Titanium dioxide nanorod films with micro- and nanoscale hierarchical surface structures have been successfully prepared (left). The nanorod films, which show superhydrophobicity (middle), reversibly become superhydrophilic (right) when exposed to UV light. The mechanism involves the cooperation of the sp…
Complex perovskite oxides exhibit a rich spectrum of properties, including magnetism, ferroelectricity, strongly correlated electron behaviour, superconductivity and magnetoresistance, which have been research areas of great interest among the scientific and technological community for decades. There exist very few ma…
The changes in the electronic absorption spectra (UV-Vis) of some metallocene-doped poly(methyl methacrylate) (PMMA) thin films containing chloroform molecules as impurities were studied after photoexcitation in the nitrogen atmosphere. Photoexcitations were made by monochromatic radiation (using a Xe-lamp source and…
The role of ``impurities'' or doping on the living polymerization of sulfur has been put under focus by means of a temperature dependent Raman study of the ${\mathrm{As}}_{x}{\mathrm{S}}_{100\ensuremath{-}x}$ and ${\mathrm{Se}}_{y}{\mathrm{S}}_{100\ensuremath{-}y}$ ($x=0.5,2,5$ and $y=2,5$) systems. Reduced isotropic…
Abstract The product distribution of the acid‐mediated condensation of dipyrromethanes and aldehydes was studied and a novel type of macrocycle phlorin‐dipyrrin conjugate was isolated and identified by X‐ray analysis. The generality of its formation from sterically hindered dipyrromethanes and pentafluorophenyldipyrro…
The lightly doped ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{MnO}}_{3}$ system was investigated using x-ray diffraction and far-infrared spectroscopy in the insulating range for $x\ensuremath{\leqslant}0.125$ on single crystalline samples. Special emphasis was set on the evolution of the Jahn-Teller (J…