Materials Literature
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A new mechanism for regulating the stability of colloidal suspensions has been discovered, known as nanoparticle haloing. 1 Colloidal microspheres suspended under conditions near their isoelectric point were stabilized by the addition of highly charged nanoparticles. Such species segregated to regions near negligibly…
Point-ion models have been extensively used to determine "hole numbers" at copper and oxygen sites in high-temperature superconducting cuprate compounds from measured nuclear quadrupole frequencies. The present study assesses the reliability of point-ion models to predict electric field gradients accurately and also t…
The degree of ionisation of a two-dimensional electron-hole plasma is calculated in the low-density (Boltzmann) limit. The electron-hole interaction is considered for all states: optically active and inactive, bound and unbound. The theory is applied to exciton/free-carrier plasma in GaN-based quantum wells at room te…
A numerical method based on the transfer matrix technique is developed to calculate the luminescence spectra of complex layered structures with photon recycling. Using this method we show a strong dependence of the emission spectra on the optical eigenmode structure of the device. The enhancement of the photon recycli…
A Comment on the Letter by J. B. Pendry, Phys. Rev. Lett. 85, 3966 (2000). The authors of the Letter offer a Reply.Issues similar to those made in the following two Comments were also raised in a paper by N. Garcia and M. Nieto-Vesperinas, Madrid, Spain.
The lowest conductance step for a Ni nanocontact is anomalously small in comparison with the large expected number of conducting channels. We present electronic structure calculations for an extremely idealized Ni nanobridge consisting of just a monatomic nanowire. Our calculations show that no less than eight single…
High-purity and homogeneous YBa2Cu3Oy single crystals with carrier doping level near the AFM-SC boundary have been obtained in the oxygen content range between y = 6.340 and 6.370. The crystals are ortho-II phase at room temperature and undergo the orthorhombic to tetragonal transition at about 140_Degree_C. They show…
We provide exact analytical expressions for the magnetic susceptibility function in the high-temperature expansion for finite Heisenberg spin systems with an arbitrary coupling matrix, arbitrary single-spin quantum number, and arbitrary number of spins. The results can be used to determine unknown exchange parameters…
This paper presents the stability analysis of a system sliding at low velocities ($< 100 μ$m.s$^{-1}$) under a periodically modulated normal load, preserving interfacial contact. Experiments clearly evidence that normal vibrations generally stabilize the system against stick-slip oscillations, at least for a modulatio…
Solid-state energy conversion technologies such as thermoelectric and thermionic refrigeration and power generation require materials with low thermal conductivity but good electrical conductivity and Seebeck coefficient, which are difficult to realize in bulk semiconductors. Nanostructures such as superlattices, quan…
Some unusual properties of layered graphite, including a linear energy dependence of the quasiparticle damping and weak ferromagnetism at low doping, are explained as a result of the proximity of a single graphene sheet to the excitonic insulator phase which can be further stabilized in a doped system of many layers s…
A model based on hexagonal mesopores connected by micropores allows evaluation of the porosity of SBA-15 silicas and elucidation of the literature problems on the subject. The presence of micropores in the walls between the mesopores renders unreliable the surface area determination by the Brunauer−Emmett−Teller equat…
Molecular-dynamics computer simulations of a model Ni nanocrystalline sample with a mean grain size of 12 nm under uniaxial tension is reported. The microscopic view of grain-boundary sliding is addressed. Two atomic processes are distinguished in the interfaces during sliding: atomic shuffling and stress-assisted fre…
Sapphyrin was the first expanded porphyrin to be reported in the literature and remains among the most extensively studied. Much of the interest in this macrocycle reflects its ability to bind anions, a phenomenon that has been examined in solution and in the solid state by a wide range of experimental techniques. In…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSupramolecular Structures from Rod−Coil Block CopolymersMyongsoo Lee, Byoung-Ki Cho, and Wang-Cheol ZinView Author Information Department of Chemistry, Yonsei University, Shinchon 134, Seoul 120-749, Korea, and Department of Materials Science and Engineering and Polymer Rese…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTConvergent Dendrons and Dendrimers: from Synthesis to ApplicationsScott M. Grayson and Jean M. J. FréchetView Author Information Department of Chemistry, University of California, Berkeley, California 94720-1460 Cite this: Chem. Rev. 2001, 101, 12, 3819–3868Publication Date…
The [(M+)x([18]crown-6)] supramolecular cations (SC+), in which M+ and [18]crown-6 are alkali metal ions (M+=Li+, Na+, and Cs+) and 1,4,7,10,13,16-hexaoxacyclooctadecane, respectively, form ionic channel structures through the regular stacks of [18]crown-6 in [Ni(dmit)2]-based molecular conductors (dmit2−=2-thioxo-1,3…
A binary Lennard-Jones alloy exhibits an entropically stabilized quasicrystal state in two dimensions at elevated temperatures. We consider the ground states of this model by calculating the convex hull of cohesive energy as a function of alloy composition. Only crystalline structures with rational values of the compo…
Abstract A series of thermotropic polyesters, derived from 4,4′‐biphenol (BP), 3‐phenyl‐4,4′‐biphenol (MPBP), and 3,3′‐bis(phenyl)‐4,4′‐biphenol (DPBP), 4,4′‐oxybisbenzoic acid (4,4′‐OBBA), and other aromatic dicarboxylic acids as comonomers, were prepared by melt polycondensation and were characterized for their ther…
Results are reported on the electron field emission properties of sulfur-incorporated nanocrystalline carbon (n-C:S) thin films grown by hot-filament chemical vapor deposition technique. The lowest turn-on field values observed were around 4.0–4.5 V/μm, which are about half of those measured for films grown without su…