Materials Literature
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Supramolecular hydrogels (see Figure for structure) are spontaneously formed by mixing aqueous dispersions of short-“legged” ammonium amphiphiles and fluorescent anions. Energy transfer between donor (naphthalene) and acceptor (anthracene) anions is shown to be more efficient in the hydrogels compared to that in dilut…
A new photochromic amorphous molecular material based on an azobenzene, BFlAB, has been designed and synthesized. BFlAB readily forms an amorphous glass with a glass-transition temperature of 97 °C and exhibits photochromism in the amorphous solid film as well as in solution. The BFlAB amorphous film forms a surface r…
Calcium carbonate single crystal structures (see Figure) have been precipitated in polymer membranes with bicontinuous structures whereby the morphologies are dictated by the polymer membrane. The single crystals exhibit intricate, sponge-like morphologies, demonstrating that synthesis of single crystals with complex…
This article summarizes the history associated with the research targeting the design and synthesis of new classes of magnets, namely, those prepared via conventional synthetic organic chemistry methodologies and where the building blocks of the magnetic materials are comprised of molecules as opposed to atoms and as…
Density-functional electronic structure calculations have been used to investigate the ambient pressure and low-temperature structural and elastic properties of uranium metal. The equilibrium volume and bulk modulus have been calculated within the generalized gradient approximation (GGA). Also, the effect of the relat…
The intermetallic compounds AAl2-xSix, where A = Ca, Sr or Ba, crystallize in the C32 structure, same as the recently discovered MgB2 with a high superconducting transition temperature of 39 K. For x = 1, superconductivity has been observed in AAlSi with A = Ca and Sr, but not with A = Ba. The transition temperatures…
Low-energy deposition of neutral Pd_N clusters (N=2-7 and 13) on a MgO(001) surface F-center (FC) was studied by spin-density-functional molecular dynamics simulations. The incident clusters are steered by an attractive "funnel" created by the FC, resulting in adsorption of the cluster, with one of its atoms bonded at…
We survey recent comprehensive studies of exciton relaxation in the crystals of lead halides. The luminescence and electron-spin-resonance studies have revealed that excitons in lead bromide spontaneously dissociate and both electrons and holes get self-trapped individually. Similar relaxation has been also clarified…
We show that the delivery of fracture work to the tip of an advancing planar crack is strongly reduced by surface phonon emission, leading to forbidden ranges of crack speed. The emission can be interpreted through dispersion of the group velocity, and Rayleigh and Love branches contribute as well as other high freque…
The interaction of vacancy with dislocations in Al is studied using the semidiscrete variational Peierls-Nabarro model with ab initio determined gamma surface. For the first time, we confirm theoretically the so-called vacancy lubrication effect on dislocation motion in Al, a discovery that can settle a long-standing…
Redispersible near-infrared emitting lanthanide-doped nanoparticles are reported. The emission and excitation spectra have been examined and the luminescence lifetimes of these materials have been determined. High quantum yields and lifetimes in the millisecond region were found. It is furthermore demonstrated that th…
The limited thermal stability of alkylammonium cations intercalated into smectite minerals (e.g., montmorillonite, MMT) and the processing instability of some polymers [polyamide-6 (PA-6) and polystyrene (PS)] in the presence of nanodispersed MMT have motivated the development of improved organophillic treatments for…
We report on the electrochemical study of three carbon nanotube ensemble electrodes: single-walled nanotube paper, as-produced multiwalled nanotube towers, and heat-treated multiwalled nanotube towers. Cyclic voltammetry was used in 0.10 M KCl containing 5.0 mM K 4 Fe(CN) 6 to obtain information on both the capacitive…
Thermoresponsive polymer brushes have been grown via surface-initiated atom-transfer radical polymerization from micropatterned substrates (see Figure). Atomic force microscopy both in topography and adhesion force mode shows that the brush domains undergo reversible phase changes in water around the polymer’s lower c…
Micelle-templated mesoporous silica materials are rapidly becoming important in many fields of chemistry for hosting reactants or catalysts in confined space. Fine control of the pore size, wall structure, surface functionalization, defects, and morphology is needed for fine-tuning the pores as nanoreactors. We review…
Large-area silicon nanowire arrays have been prepared on a silicon wafer without the use of a template. The simple method, which can be carried out near room temperature, involves the nanoelectrochemistry of silver nanowires in an aqueous HF solution containing silver nitrate. This technique may be generally applicabl…
Experimental evidence is provided that colossal dielectric constants ${\ensuremath{\varepsilon}}^{\ensuremath{'}}>~1000,$ sometimes reported to exist in a broad temperature range, can often be explained by Maxwell-Wagner-type contributions of depletion layers at the interface between sample and contacts or at grain…
Ambient optical detection of labeled molecules is limited for fluorescent dyes by photobleaching and for semiconducting nanoparticles by "blinking" effects. Because nanometer-sized metal particles do not optically bleach, they may be useful optical labels if suitable detection signals can be found. We demonstrate far-…
Crystalline silicon microcavities resonant at 1.1 μm were fabricated by using submicron thick Si membranes from a silicon on insulator substrate. These membranes were composed of a single crystalline Si film layered above and below two thin silicon dioxide layers. The low temperature photoluminescence (PL) of the memb…
Geometry optimization and harmonic vibrational frequency calculations have been carried out on various structures and low-lying, high- and low-spin electronic states of Al 2 N 4 and AlN n clusters, where n = 4 to 7, at the B3LYP, MP2, and QCISD levels. The aim of these calculations was to search for states/structures…