Materials Literature
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The sonochemical reaction of an aqueous solution of GaCl 3 led to the formation of gallium oxide hydroxide rolled up in a scroll-like layered structure to give cylinders 80−120 nm in diameter and 500−600 nm in length. Small amounts of metallic Ga were incorporated with these tubes. A mechanism for this reaction has be…
Recent experiments (R. A. Baragiola and C. A. Dukes, Phys. Rev. Lett. {\bf 76}, 2547 (1996)) with slow ions incident at grazing angle on metal surfaces have shown that bulk plasmons are excited under conditions where the ions do not penetrate the surface, contrary to the usual statement that probes exterior to an elec…
In the last ten years significant advances have been made in our understanding and ability to compute and predict properties of ferroelectrics and piezoelectrics using fundamental physics. Phase diagrams, electromechanical and elastic properties, and effects of defects and surfaces are now amenable to computation. Mos…
The structural and electrochemical properties of nanoparticles were found to be different from those of the corresponding bulk semiconductors. Due to the specific binding of modifiers to “corner defects”, the optical properties of small titania particles were red shifted 1.6 eV compared to unmodified nanocrystallites.…
Ein erstaunlich breites Anwendungspotential in der Biotechnologie, Biomimetik und Nanotechnologie ergaben Untersuchungen von Struktur, Chemie, Biosynthese, Genetik, Morphogenese und Funktion supramolekularer S-Schicht-Gitter („S”︁ für surface). Bei diesen handelt es sich um monomolekulare, kristalline Anordnungen aus…
Optical spectroscopy and topography techniques were used to study the local photoinduced insulator-metal transition (IMT) in a Pr0.7Ca0.3MnO3 crystal. Although the change of reflectivity due to the transition exhibits features which are characteristic for the IMT, the spectrum reveals strong modifications as compared…
Thermal conductivity of low-temperature-grown GaAs(LT GaAs) was measured at room temperature using a self-heated photolithographically patterned platinum wire on the surface of the sample. Finite element calculations were performed to extract the thermal conductivity from the nonlinear I–V characteristic of the wires.…
A new metathetical route to diazoalkane complexes is described which allows the introduction of such ligands into previously inaccessible environments. The method, which involves the exchange of oxo and [N2 CR2 ] ligands, is illustrated by the preparation of the first diazoalkane-polyoxometalate complex 1.
A tetranuclear iron cluster is the principal component of the purple coatings produced by treating a mild steel surface with a salicylaldoxime corrosion inhibitor. This was shown by comparison of the spectroscopic data with those of the cluster [{Fe(salH)(HsalH)}4 ], which was obtained from FeCl3 and salicylaldoxime (…
Gold nanocrystals, stabilized by thiols covalently bound to a dibenzo[24]crown-8 moiety, have been programmed to recognize and selectively bind dibenzylammonium cations in solution. This results in a self-organization process at the surface of a nanocrystal with the assembly of a pseudorotaxane (see picture).
Nach den Prinzipien der Geometrie der Körper können Kryptanden, Carceranden, Polyoxometallate und molekulare Kapseln strukturell klassifiziert werden. Diese käfigartigen Wirtverbindungen komplexieren die Gäste durch Einkapseln. Nach der Entdeckung eines supramolekularen, käfigartigen Sphäroids im Nanometermaßstab wurd…
We study the melting behavior of a finite number ( $N\ensuremath{\le}45$) of paramagnetic colloidal spheres in a two-dimensional circular hard wall cavity. The interaction strength between the particles is varied by applying a magnetic field $B$. At high $B$, i.e., strong interaction, the particles are arranged in a h…
A rare example of a molecular species prepared by solvothermal synthesis is the macrocyclic cobalt phosphonate/carboxylate 1, whose structure is shown schematically. At low temperatures this compound displays spontaneous magnetization due to canted antiferromagnetic ordering, which is very unusual for a discrete molec…
We study the static screening in a Hubbard-like model using fixed-node diffusion Monte Carlo. We find that the random phase approximation is surprisingly accurate even for metallic systems close to the Mott transition. As a specific application we discuss the implications of the efficient screening for the superconduc…
A precision radio-frequency (RF) transverse modulation technique based on a resonant tunnel diode oscillator (TDO) has been used to study the dynamic susceptibility in novel ring-shaped single domain Fe nanoparticles synthesized using reverse-micelle chemistry. Hysteresis loops measured using a SQUID magnetometer indi…
Energetics, electronic structure, charging, and capacitive properties of bare and thiol-passivated ${\mathrm{Au}}_{38}$ gold nanocrystals were investigated via density-functional calculations. In the energy-optimized passivated nanocrystal, comprised of a truncated-octahedral face-centered-cubic ${\mathrm{Au}}_{38}$ c…
Cryptands, carcerands, polyoxometalates, and molecular capsules are cagelike hosts that complex guests through encapsulation. Following the discovery of a nanometer scale supramolecular shell-like spheroid, these and other shell-like hosts were structurally classified. Their frameworks may be catalogued according to p…
A systematic classification of the tourmaline-group minerals, general formula X Y3Z6 (T6O18) (BO3)3 V3W, is proposed, based on chemical composition and ordering at the different crystallographic sites of the tourmaline structure. There are currently thirteen accepted tourmaline species. However, based on the actual ch…
Hydrogen adsorption on crystalline ropes of carbon single-walled nanotubes (SWNT) was found to exceed 8 wt. %, which is the highest capacity of any carbon material. Hydrogen is first adsorbed on the outer surfaces of the crystalline ropes. At pressures higher than about 40 bar at 80 K, however, a phase transition occu…
Poly(ethylene glycol)-poly(L-lactide) diblock and triblock copolymers were prepared by ring-opening polymerization of L-lactide with poly(ethylene glycol) methyl ether or with poly(ethylene glycol) in the presence of stannous octoate. Molecular weight, thermal properties, and crystalline structure of block copolymers…