Materials Literature
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Density-functional theory is used to investigate the phase behavior of colloidal binary hard-platelet and hard-rod fluids near a single hard wall or confined in a slit pore. The Zwanzig model, in which the orientations of the particles of rectangular shape are restricted to three orthogonal orientations, is analyzed b…
A kinetic model for the evolution of the cluster size distribution during crystal nucleation and growth is presented. The model allows one to establish precise links between model parameters and experimental measures of nucleation kinetics. This approach demonstrates the significance of several processes not accounted…
Two hydrogen and two silicon-related defect centers were detected and characterized by electron-spin resonance (ESR) in diamond films grown by chemical vapor deposition. Observation of hyperfine structure, combined with illumination and polishing treatments, suggests that the observed KUL2 and KUL9 ESR centers origina…
3D nanomanipulations of nano-order objects are realized with a 10-DOF nanorobotic manipulator, which is actuated with PZTs and Picomotors and operated inside a SEM. The coarse linear resolutions of the manipulator are better than 30 nm (X, Y, Z stages actuated by Picomotors) and the rotary one 2 mrad, while the resolu…
We study, with exact diagonalization, the zero temperature properties of the quarter-filled extended Hubbard model on a square lattice. We find that increasing the ratio of the intersite Coulomb repulsion, V, to the bandwidth drives the system from a metal to a charge ordered insulator. The evolution of the optical co…
Lead-based single crystal relaxor ferroelectrics have been developed with fundamental properties that in theory should dramatically enhance the bandwidth and sensitivity-bandwidth product for ultrasound transducers. High sensitivity array elements with fractional bandwidths of over 120% have been modeled using the pro…
We use a nondestructive technique of fluorescence confocal polarizing microscopy to visualize three-dimensional director patterns of defects in Grandjean-Cano wedges filled with a cholesteric liquid crystal of pitch p=5 microm. Strong surface anchoring of the director causes a stable lattice of dislocations in the bul…
We present an ultra-low temperature study (down to T = 20 mK) of the nuclear spin-lattice relaxation (SLR) in the 55Mn nuclei of the molecular magnet Mn12-ac. The nuclear spins act as local probes for the electronic spin fluctuations, due to thermal excitations and to tunnelling events. In the quantum regime (below T…
This work presents new experimental results on low-temperature (LT) characterization of local rf properties of passive superconducting (SC) microwave devices using a novel Laser Scanning Microscope (LSM). In this technique, a modulated laser beam is focused onto and scanned over the surface of a resonant SC device to…
We report a systematic study of xenon gas diffusion NMR in simple model porous media: random packs of mono-sized glass beads, and focus on three specific areas peculiar to gas-phase diffusion. These topics are: (i) diffusion of spins on the order of the pore dimensions during the application of the diffusion encoding…
We have extended the utility of NMR as a technique to probe porous media structure over length scales of ~ 100 - 2000 micron by using the spin 1/2 noble gas 129Xe imbibed into the system's pore space. Such length scales are much greater than can be probed with NMR diffusion studies of water-saturated porous media. We…
The segmental relaxations of poly(4-vinylphenol)/poly(vinyl ethyl ether) [PVPh/PVEE] blends, with PVPh content from 10 to 50 wt % and having a very large T g difference between the components, have been investigated using broadband dielectric spectroscopy. Although a single T g was observed for all compositions in DSC…
Terpyridine capped gold nanoparticles (ca. 2.0 nm diameter) form large aggregates in the presence of metal ions [Fe(II), Zn(II), Cu(I), Ag(I)]. The assembly process is a result of metal coordination between two terpyridines that are attached to separate nanoparticles. The stability of the aggregates in various solvent…
We have designed and synthesized new, novel photochromic copolymers composed of photochromic 2-indolyl fulgides or fulgimides and methyl methacrylate. The spectroscopic and photochromic properties of these copolymers have been determined and compared to their liquid solution analogues. The utilization and advantages o…
The effect of chemical surface treatment on the sensitivity, specificity, and stability of mesoporous Si thin film vapor sensors is studied. The vapor sensors operate by measurement of Fabry−Pérot interference from the porous Si layer, probed using a diode laser operating at a wavelength of 687 nm. Four chemically dis…
Exfoliated PS/Na−MMT nanocomposites were obtained up to 3 wt % of clay without modifying clay organically and DBS−Na affected the degree of exfoliation of silicate layers. The feed rate of monomers also had an effect on polymerization, and it was a key to controlling the total monomer concentration and maintaining a c…
Polyamidoamine (PAMAM) dendrimers are used as carriers to deliver complexed Fe(III) ions uniformly onto silicon oxide substrates for the formation of iron oxide nanoparticles with a narrow diameter in the range of 1−2 nm. Chemical vapor deposition (CVD) synthesis with these nanoparticles affords single-walled carbon n…
Recent studies on the Portevin - Le Chatelier effect report an intriguing crossover phenomenon from a low dimensional chaotic to an infinite dimensional scale invariant power law regime in experiments on CuAl single crystals and AlMg polycrystals, as a function of strain rate. We devise a fully dynamical model which r…
Polyelectrolyte brushes were formed at the interface between hydrophobized mica and water by adsorbing amphiphilic diblock copolymers consisting of a hydrophobic and a charged block. We measured force−distance profiles with the surface force apparatus (SFA) for several polyelectrolyte brushes of different lengths as a…
We report initial NMR studies of i) xenon gas diffusion in model heterogeneous porous media, and ii) continuous flow laser-polarized xenon gas. Both areas utilize the Pulsed Gradient Spin Echo techniques in the gas-phase, with the aim of obtaining more sophisticated information than just translational self-diffusion c…