We observe the assembly of CdS nanorod superlattices by the combination of a DC electric field and solvent evaporation. In each electric field (1 V/um) assisted assembly, CdS nanorods (5 X 30 nm) suspended initially in toluene were observed to align perpendicularly to the substrate. Azimuthal alignment along the nanorod crystal faces and the presence of stacking faults indicate that both 2D and 3D assemblies were formed by a process of controlled super crystal growth.KEYWORDS Nanorod, Superlattice, assembly 2 Self assembly or directed assembly of discrete nanostructures into organized patterns provides a new route to the formation of functional materials. Colloidal nanocrystals are suitable building blocks as they can be synthesized with size and shape control. 1 The assembly of symmetrical nanospheres and nanocubes into superlattices is known; and in the case of silver nanocrystals, 3 nm in diameter, an insulator to metal transition is observed to occur as a function of sphere size and interparticle separation. [2][3][4] In effect, the superlattice functions as a novel nanocrystal solid where it is possible to control the electronic coupling by manipulating the size and position of the quantum confined structural units. The coupling can further be modified through exchange of the insulating organic ligands on the nanocrystal surface with low barrier organics e.g. hydrazine. Talapin and Murray used this approach to convert poorly conducting PbSe nanocrystal solids into n-and p-channel field effect transistors. 5 The ability to direct anisotropic structures such as cylindrical nanorods into superlattices is less well developed but also interesting. In organized nanorod superlattices, it may be possible to simultaneously and independently optimize quantities which depend on the diameter (such as band gap) from quantities which depend on length (total absorption, cross section or conductivity).Superlattice formation with spherical nanocrystals is strongly correlated to size monodispersity and their entropy driven packing under slow evaporation conditions. While dimensional control and monodispersity in nanorods has been achieved, their organization into superlattices is restricted as both positional and orientational ordering is required during assembly. Some progress has been made in preferred nanorod alignment in single layers with nematic and semectic ordering achieved from gentle evaporation of low boiling point solvents. [6][7][8][9] The rods align parallel to substrate in small domain sizes.There is further evidence for the preferred orientation of anisotropic nanostructured-rods, tubes and wires along electric field lines. The strength of the interaction is greatest in metallic nanostructures followed by nanostructures with permanent dipole moments e.g. CdSe, CdS nanorods. 10,11 Anisotropic structures with low polarizability such as silicon nanowires and carbon nanotubes can also be induced to align when the electric field induced torque is greater than the thermal excitation energy (kT). 12,13 The ...

We report the data on concurrent multiple point adsorption of two oppositely charged species of “target molecules” (aluminum ions and 1,3,6,8-pyrenetetrasulfonic sodium salt (Py-4)) by a polyampholyte gel of N-isopropylacrylamide (NIPA, 6 M) with methacrylic acid (MAA, 80 mM) and methacrylamidopropyl trimethylammonium chloride (MAPTAC, 80 mM). The goal of this study is to test the mutual frustrations created by adsorption of one species on the adsorption of the other. Understanding these frustrations is an important step toward elucidating the memory of conformations in heteropolymer systems. We found that in the absence of aluminum, the adsorption of Py-4 was suppressed by gel collapse, presumably because of an increase in MAA/MAPTAC ionic pairs that prevents the formation of potential adsorbing centers. Adding a moderate amount of aluminum significantly enhances adsorption of Py-4 by the collapsed gel, indicating that aluminum ions compete for bonds with MAA and help release vacant MAPTAC centers. Finally, with further increase of aluminum, the Py-4 multiple point adsorption is again suppressed, pointing out the frustrations created by aluminum-mediated effective cross-links. We analyze also the cooperativity of the adsorption process.

Previous studies have shown that beetroot juice (BJ) decreases systolic blood pressure (SBP) and oxygen demand. This study tests the hypothesis that a beetroot juice (BJ) treatment increases heart rate variability (HRV) measured by the average standard deviation of normal-normal electrocardiogram RR intervals (SDNN) and the low frequency (LF), mainly sympathetic, fast Fourier transform spectral index of HRV. The subjects were 13 healthy young adult African-American females. Placebo control orange juice (OJ) and BJ treatments were given on separate days. Blood nitric oxide [NO], SBP and RR intervals were measured at rest and at constant workloads set to 40% and 80% of the predetermined VO2peak. Two hours after ingestion the BJ treatment increased [NO] and decreased SBP. BJ also increased SDNN at rest and at the 40% VO2peak workload, without significant effects on LF. SDNN was significantly greater after the BJ than after the OJ treatment, across the two physical activity conditions and SDNN was (negatively) correlated with SBP. These results suggest that BJ decreases SBP and increases HRV at rest and during aerobic exercise. Similar results in subjects with prehypertension or hypertension could translate to a dietary nitrate treatment for hypertension.

We examine a method to mimic active sites in proteins by chemical imprinting of p-valent templates in heteropolymer gels. Previous studies have confirmed successful formation of sites by adsorption of targets with p >/= 2 contacts. We investigate the recovery of sites with p = 2 imprinted by lead methacrylate Pb(MAAc)(2) (placing two carboxyl groups in close proximity). The improved binding ability of gels with more cross-links, and the relative insensitivity to changes in gel volume contradict simple theory. We conclude that adsorber pairs are predominantly located on the same polymer chain, posing a challenge to mimicking protein-like function.