Materials Literature
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Porous poly(divinylbenzene) (DVB) resins have been prepared using suspension polymerization with toluene and an oligomer as coporogens. The oligomers investigated were poly(propylene glycol) 1000 (PPG 1000), poly(propylene glycol) 4000 (PPG 4000), and poly(dimethylsiloxane) (PDMS). The porogen was used in a 1/1 vol/vo…
A general and well-controlled process used to fabricate uniform metal nanotube arrays via a multi-step template replication and electrodeposition approach is reported. Each nanotube is highly ordered, uniform in wall thickness and diameter along the entire tube (see Figure).
A novel, innocuous method which utilizes carbon dioxide to fabricate optically transparent nanocellular polymeric materials using a fluorinated block copolymer as the template is reported. The CO2-soluble fluorinated blocks effectively localize CO2 in the nanoscopic domains. At 0 °C, with slow depressurization, the bl…
The manganese(II) ion has many favorable properties that lead to its potential use as an MRI contrast agent: high spin number, long electronic relaxation time, labile water exchange. The present work describes the design, synthesis, and evaluation of a novel Mn(II) complex (MnL1) based on EDTA and also contains a moie…
We present a method to compute the electrooptic tensor from first principles, explicitly taking into account the electronic, ionic and piezoelectric contributions. It allows us to study the non-linear optic behavior of three ferroelectric ABO_3 compounds : LiNbO_3, BaTiO_3 and PbTiO_3. Our calculations reveal the domi…
We report a novel atom extraction mechanism from the native substrate by means of a scanning tunneling microscope tip-crash on a Ag(111) surface at 5 K. Individual atoms are scattered on the surface when a silver coated tip is dipped into the substrate at low tunneling biases. Quantitative analyses reveal that the mec…
A tough non-woven material of single-walled carbon nanotubes (SWNTs) with an area of up to several tens of square centimeters (see Figure) has been prepared by a direct-floating chemical vapor deposition method followed by purification. The SWNT non-woven material exhibits an extremely high Young's modulus of ca. 0.4–…
We have demonstrated surface-plasmon induced change in spontaneous emission rate in the ultraviolet regime at ~ 375-380 nm, using AlN/GaN quantum dots (QD). Using time-resolved and continuous-wave photoluminescence measurements, the recombination rate in AlN/GaN QD is shown to be enhanced when spontaneous emission is…
Under pressure many rare earths and actinide metals transform to a-U structure or its lower symmetry distorted forms. We have reinterpreted the diffraction data of Dabos et al for Pu (reference 4) and find that a Am IV type distorted a-U structure in Pnma space group can explain this for its high pressure phase. The s…
We report a detailed investigation into the metamagnetism of Sr3Ru2O7 at low temperatures for the magnetic field parallel to the ruthenium oxygen planes. The metamagnetism is studied as a function of temperature, magnetic field and sample quality using magnetisation, magnetotransport and specific heat as probes. From…
Thin films of the molecular magnet Mn12-acetate, [Mn12 O12(CH3COO)16 (H2O)4] 2CH3COOH 4H2O, have been prepared using a laser ablation technique with a nitrogen laser at low laser energies of 0.8 and 2 mJ. Chemical and magnetic characterizations show that the Mn12-acetate cores remain intact and the films show similar…
The electrical properties of DNA molecules are investigated by charge injection and electric force microscopy experiments. Prior to injection, DNA molecules exhibit a weak positively charged state. We probe the electrical behaviour of DNA by measuring the localized or delocalized character of the DNA charge states upo…
We study in this article the mathematical properties of a class of orbital-free kinetic energy functionals. We prove that these models are linearly stable but nonlinearly unstable, in the sense that the corresponding kinetic energy functionals are not bounded from below. As a matter of illustration, we provide an exam…
Control of intramolecular spin alignment is studied theoretically in a model of polyene-based molecular magnets in which delocalized $π$ electrons are coupled with localized radical spins. In a previous paper [Phys. Rev. Lett. 90 (2003) 207203], we have demonstrated that charge doping is an effective way to realize co…
We summarize our recent findings on how current-driven magnetization switching and magnetoresistance in nanofabricated magnetic multilayers are affected by varying the spin-scattering properties of the non-magnetic spacers, the relative orientations of the magnetic layers, and spin-dependent scattering properties of t…
A simple method combining photolithography and shadow (or angle) evaporation is developed to fabricate single-walled carbon nanotube (SWCNT) devices with tube lengths of approximately 10-50 nm between metal contacts. Large numbers of such short devices are obtained without the need of complex tools such as electron be…
From a macroscopic viewpoint phase transitions as surface melting or growth mode can be described in term of Gibbs excess quantity duly amended by size effect. The aim of this study is to consider such amended quantities to describe surface melting and Stranski Krastanov transition of epitaxial layers. The size effect…
The non-linear response of infinite periodic solids to homogenous electric fields and collective atomic displacements is discussed in the framework of density functional perturbation theory. The approach is based on the 2n + 1 theorem applied to an electric-field-dependent energy functional. We report the expressions…
Raman microspectroscopy has been used for the first time to determine quantitatively the orientation of the beta-sheets in silk monofilaments from Bombyx mori and Samia cynthia ricini silkworms, and from the spider Nephila edulis. It is shown that, for systems with uniaxial symmetry such as silk, it is possible to det…
Abstract Since the first report on the synthesis of inorganic WS 2 nanotubes in 1992, the number of articles on the successful growth of different inorganic nanotubes has increased rapidly, emphasizing the importance of this field for nanotechnology. Although there are some geometrical similarities to carbon nanotubes…