Electromechanical actuators based on sheets of single-walled carbon nanotubes were shown to generate higher stresses than natural muscle and higher strains than high-modulus ferroelectrics. Like natural muscles, the macroscopic actuators are assemblies of billions of individual nanoscale actuators. The actuation mechanism (quantum chemical–based expansion due to electrochemical double-layer charging) does not require ion intercalation, which limits the life and rate of faradaic conducting polymer actuators. Unlike conventional ferroelectric actuators, low operating voltages of a few volts generate large actuator strains. Predictions based on measurements suggest that actuators using optimized nanotube sheets may eventually provide substantially higher work densities per cycle than any previously known technology

Porous carbons that are three-dimensionally periodic on the scale of optical wavelengths were made by a synthesis route resembling the geological formation of natural opal. Porous silica opal crystals were sintered to form an intersphere interface through which the silica was removed after infiltration with carbon or a carbon precursor. The resulting porous carbons had different structures depending on synthesis conditions. Both diamond and glassy carbon inverse opals resulted from volume filling. Graphite inverse opals, comprising 40-angstrom-thick layers of graphite sheets tiled on spherical surfaces, were produced by surface templating. The carbon inverse opals provide examples of both dielectric and metallic optical photonic crystals. They strongly diffract light and may provide a route toward photonic band-gap materials.

Microwave-assisted functionalization of single-wall carbon nanotubes (SWNTs) in a mixture of nitric and sulfuric acids was carried out to synthesize highly water-dispersible nanotubes. Stable concentrations as high as 10 mg/mL were obtained in deionized water that are nearly 2 orders of magnitude higher than those previously reported. This was after only 3 min of functionalization reaction. Fourier transform infrared spectra showed the presence of carboxylated (-COOH) and acid sulfonated (-SO(2).OH or -SO(3)(-) H(+)) groups on the SWNTs. On the basis of elemental analysis, it was estimated that one out of three carbon atoms was carboxylated, while one out of 10 carbon atoms was sulfonated. The Raman spectra taken both in aqueous dispersion and in the solid phase indicated charge transfer from the SWNT backbone to the functional groups. Scanning electron microscope images of thin films deposited from an aqueous suspension showed that the SWNTs were aligned parallel to one another on the substrate. The images also indicated some reduction in average length of the nanotubes. Transmission electron microscope images of thin films from a dilute methanol dispersion showed that the SWNTs were extensively debundled. Laser light scattering particle size measurements did not show evidence for the existence of particles in the 3-800 nm size range, indicating that the functionalized SWNTs might have dispersed to have formed a true solution. Moreover, the microwave-processed SWNTs were found to contain significantly smaller amounts of the original iron catalyst relative to that present in the starting nanotubes. The electrical conductivity of a thermally annealed thin membrane obtained from the microwave-functionalized SWNTs was found to be the same as that of a similar membrane obtained from a suspension of the starting nanotubes.

Here we identify a novel class of biological membrane ion channel blockers called single-walled carbon nanotubes (SWNTs). SWNTs with diameter distributions peaked at ϳ0.9 and 1.3 nm, C 60 fullerenes, multi wall nanotubes (MWNTs), and hyperfullerenes (nano-"onions") were synthesized by several techniques and applied to diverse channel types heterologously expressed in mammalian cells. External as-fabricated and purified SWNTs blocked K ؉ channel subunits in a dose-dependent manner. Blockage was dependent on the shape and dimensions of the nanoparticles used and did not require any electrochemical interaction. SWNTs were more effective than the spherical fullerenes and, for both, diameter was the determining factor. These findings postulate new uses for SWNTs in biological applications and provide unexpected insights into the current view of mechanisms governing the interaction of ion channels with blocking molecules.Because of the physiological role they play, ion channels exhibit unique structures, including the pore that provides the physical pathway for ion movements across the plasma membrane and several charged domains that attract and/or repel ions (1). These characteristics make ion channels easy targets for external agents such as natural toxins and synthetic drugs that react with them by establishing electrochemical interactions. Thus, blocking agents have been used not only as the basic components for commercial pesticides and potential therapeutic drugs but also to infer functional information (1).The identification of new classes of molecules to target ionchannels is of significant interest in biological research, and, therefore, we sought to explore the possibility of using novel materials such as selected single-walled carbon nanotubes (SWNTs), 1 as ion channel blockers. In recent years there have been several attempts to use nanotubes for biological purposes because of their unique mechanical, chemical, and electrical properties (2). For example, nanotubes have been successfully used for the helical crystallization of proteins (3) and the growth of embryonic rat brain neurons (4) and as potential biosensors and bioreactors (5, 6). Here we show that SWNTs of certain diameters can efficiently block K ϩ channels. MATERIALS AND METHODSNanotubes and Fullerene Synthesis-SWNTs, with a diameter distribution peaked in the 0.8 -0.9 nm range, were grown by chemical vapor deposition (CVD) in a horizontal tube reactor using a three-stage process. In the first stage, the catalyst/support system was obtained via wet mixing followed by combustive calcination. Magnesium nitrate hexahydrate, cobalt nitrate hexahydrate, ammonium heptamolybdate tetrahydrate, and citric acid (the latter to induce combustion) were mixed with enough distilled water to give a clear solution, which was heated to 550°C for 5-10 min in air. The resulting powder of general composition MgO (1-x-y) Co x Mo y (where nanoscale Co-Mo is the catalyst in a typical molybdenum/cobalt atomic ratio of 1:4, and MgO is the catalyst support) was taken out,...

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Raman scattering measurements on hydrogenated microcrystalline silicon prepared in a hydrogen plasma at deposition temperatures between approximately=65 and 400 degrees C are presented and discussed. The shifts of the crystalline (c) and 'amorphous-like' (a) components of the spectra to lower frequencies with decreasing crystallite size have been correlated with the lattice expansion and the finite dimensions of the crystallites in these films. The roles of hydrogen and of the compressive stress in the samples have been investigated by annealing experiments and a deposition of the samples under negative bias of the substrate, respectively. These results point to a probable mechanism of the crystalline-amorphous transition in silicon. The data presented allow an assignment of the amorphous-like feature in the Raman spectra to surface-like modes at grain boundaries of the crystallites. Strong arguments are given that suggest that the 480 cm-1 peak in the Raman spectra of X-ray amorphous silicon is of the same origin and is hence associated with some shearing modes of Si clusters rather than a broadened density of states. Results on the depolarisation ratio of Raman scattering in the microcrystalline and X-ray amorphous films are also presented and discussed.

Metal matrix nanocomposites (MMNCs) are those metal matrix composites where the reinforcement is of nanometer dimensions, typically less than 100 nm in size. Also, it is possible to have both the matrix and reinforcement phases of nanometer dimensions. The improvement in mechanical properties of MMNCs is attributed to the size and strength of the reinforcement as well as to the fine grain size of the matrix. Spark plasma sintering has been used extensively over the past years to consolidate wide range of materials including nanocomposites and was shown to be effective noneconventional sintering method for obtaining fully dense materials with preserved nanostructure features. The objective of this work is to briefly present the spark plasma sintering process and review published work on spark-plasma-sintered metals and metal matrix nanocomposites.

A novel immobilized fullerene-single wall carbon nanotube (C 60 -SWCNT) complex was synthesized via a microwave induced functionalization approach. It has been used as a component of the photoactive layer in a bulk heterojunction photovoltaic cell. As compared to a control device with only C 60 , the addition of SWCNTs resulted in an improvement of both the short circuit current density J SC and the fill factor (FF). This device takes advantage of the electron accepting feature of C 60 and the high electron transport capability of SWCNTs. The results indicate that C 60 decorated SWCNTs are promising additives for performance enhancement of polymer photovoltaic cells.