Since the 1991 discovery of hollow cylindrical carbon-based unidimensional structures, the nanotubular form of matter has been thoroughly investigated leading to a wealth of literature. Their particular features are not limited to graphite but are common in many inorganic highly anisotropic two-dimensional layered compounds. The first non-mineral inorganic nanotubes, constituted of lamellar molybdenum and tungsten disulfides, were synthesized in 1992. Afterwards, a large number of inorganic nanotubes have been synthesized, opening the path to the development of nanoelectronics, due to their dielectric properties. The unique mineral phase that crystallizes with a tubular morphology is chrysotile, which has been tentatively used to prepare ultra-thin wires by filling its hollow nanodimensional core with a conductive material. To overcome its natural heterogeneity in composition, morphology, and structure, synthetic chrysotile-inspired nanotubes have been recently synthesized. These geoinspired nanotubes can be prepared with specific properties, finalized to focused achievements such as preparation of new quantum wires. The existing knowledge on the structural and physicochemical properties of mineral and synthetic chrysotile nanotubes is reviewed, with the aim of emphasizing their potential applications as nonlinear optical and conducting technological devices. Bibliography encompasses over one hundred references.

We have proposed in 1992 that nanoparticles of layered compounds will be unstable against folding and close into fullerene-like structures and nanotubes (IF). Nanotubes and fullerene-like structures were prepared from numerous compounds with layered and recently also non-layered structure by various groups. Much progress has been achieved in the synthesis of inorganic nanotubes and fullerene-like nanoparticles of WS2 and MoS2 and many other metal dichalcogenides over the last few years. Substantial progress has been accomplished in the use of such nanoparticles for tribological applications and lately for impact resilient nanocomposites. These tests indicated that IF-MoS2 and IF-WS2 are heading for large scale applications in the automotive, machining, aerospace, electronics, defense, medical and numerous other kinds of industries. A few products based on these nanoparticles have been recently commercialized by “ApNano Materials, Inc”. Novel applications of inorganic nanotubes and fullerene-like nanoparticles in the fields of catalysis; microelectronics; Li rechargeable batteries; medical and opto-electronics will be discussed.

The search for cleaner and more efficient energy storage and conversion technologies has become an urgent task due to increasing environmental issues and limited energy resources. The aim of energy storage and conversion is to obtain energy with environmental benefit, high efficiency, and low cost (namely, maximum atomic and recycling economy). Progress has been made in the fields of hydrogen storage and rechargeable batteries. The emerging nanotechnology offers great opportunities to improve the performance of existing energy storage systems. Applying nanoscale materials to energy storage offers a higher capacity compared to the bulk counterparts due to the unique properties of nanomaterials such as high surface areas, large surface-to-volume atom ratio, and size-confinement effect. In particular, one- dimensional (1D) inorganic nanostructures like tubes and wires exhibit superior electrochemical characteristics because of the combined advantages of small size and 1D morphology. Hydrogen and lithium can be stored in different 1D nanostructures in various ways, including physical and/or chemical sorption, intercalation, and electrochemical reactions. This review highlights some of the latest progress with the studies of hydrogen and lithium storage in inorganic nanotubes and nanowires such as MoS2, WS2, TiS2, BN, TiO2, MnO2, V2O5, Fe2O3, Co3O4, NiO, and SnO2.

Carbon nanotubes have been shown to be effective broadband optical limiters for nanosecond laser pulses. In this paper, we review the recent developments of carbon nanotube-based optical limiters, in particular the effects of modifying carbon nanotubes for device applications. The techniques used to modify carbon nanotubes mainly include thin film coating, doping, and blending with optical absorbing dye. These modifications can greatly enhance the optical limiting performance of carbon nanotubes, with the goal of fabricating an optimal optical limiter system.

Polymerized nitrogen-containing carbon nanobell structures were fabricated by microwave plasma-assisted chemical vapor deposition using the mixture of source gases: methane, nitrogen, and hydrogen. The nanobells with one end sealed and another open contained a nitrogen concentration of about 1–10 at.%. A first-principles calculation was performed to understand the nitrogen effect on the formation of a bell structure. Based on the growth mechanism, a continual nanojunction formed between nanobell and nanotube. The unique structures with a weak connection between two adjacent nanobells were useful for producing short nanotubes several tens of nanometers in length and diameter. In addition, the short length and open edges at the outside surfaces of nanobells also benefited the electron field emission, energy storage, and chemical reactivity.

We introduce the concept of meta-nanotubes, among which are hybrid carbon nanotubes (X@CNTs), which are CNTs whose hollow core is filled—fully or partially—with foreign atoms, molecules, or compounds. The article focuses on the latter, describing their potential interest and the various ways currently available to synthesize them, while providing examples of the resulting materials mainly taken from the author’s works but also from literature, as characterized by means of high-resolution microscopy and related techniques. We discuss advantages and drawbacks of the various synthesis routes to help willing scientists and engineers to define a strategy for X@CNT synthesis with respect to their specific goals and expectations. Some examples of peculiar properties and behaviors of X@CNTs will be provided as well, although such related investigations are still scarcely reported because we are dealing with quite new nanomaterials.

Boron nitride nanotube (BNNT)/polystyrene (PS) composite films were fabricated for the first time using high-quality BNNTs synthesized via a chemical-vapor-deposition method. The composite films exhibited good transparency. Tensile tests indicated that the elastic modulus of the films was increased by ∼21% when a ∼1 wt% soluble BNNT fraction was in use. Dispersion of BNNTs in PS and interfacial interactions between them were investigated using transmission electron microscopy. The film thermal properties, such as stability to oxidation and glass transition temperatures were measured. The experimental results and simple theoretical estimates indicate that BNNTs is a promising additive material for polymeric composites.

GaP–GaAsP segmented nanowires (NWs), with diameters ranging between 20 and 500 nm and lengths between 0.5 and 2 μm, were catalytically grown from Au particles on a GaAs (111)B substrate in a gas source molecular beam epitaxy system. The morphology of the NWs was either pencil-shaped with a tapered tip or rod-shaped with a constant diameter along the entire length. Stacking faults were observed for most NWs with diameters greater than 30 nm, but thinner ones tended to exhibit fewer defects. Moreover, stacking faults were more likely found in GaAsP than in GaP. The composition of the pencil NWs exhibited a core–shell structure at the interface region, and rod-shaped NWs resulted in planar and atomically abrupt heterointerfaces. A detailed growth mechanism is presented based on a layer-by-layer growth mode for the rod-shaped NWs and a step-flow growth mode for the tapered region of the pencil NWs.

A uniaxial tensile loading process was simulated on rectangular [001] oriented single-crystal Au, Ag, and Cu nanowires using the modified embedded atom method. The calculated theoretical tensile strength as well as elastic modulus and “yield strength” increases with decreasing wire width almost logarithmically, which is qualitatively consistent with relevant experimental results. According to the present observed linear relationship among these three parameters, we think, the size dependent mechanical behaviors in nanowires may be due to the enhanced attraction between atoms, which is caused by the accumulation of electron charges along wire axial direction.

We recently observed that surfactant sodium dodecyl sulfate (SDS)-encased HiPco single-walled carbon nanotubes (SWNTs) respond optically to hydrogen peroxide (H2O2) in the near-infrared region. In this report, we demonstrate that SDS-encased SWNTs immobilized with glucose oxidase (GOx) can be used to optically detect an enzymatic reaction of glucose based on their H2O2 sensitivity as well as pH sensitivity. Only the enzymatic product H2O2 induces the SWNT near-infrared spectral changes in buffer solutions (pH = 6.0), but both H2O2 and gluconic acid products do this in unbuffered solutions. The SWNT optical response to glucose possesses sensitivity and selectivity similar to an electrochemical method using carbon nanotube nanoelectrode arrays. Our results suggest possible carbon nanotube-based optical tools for molecular recognition applications.

The present work reports nitrogen doping of self-organized TiO2 nanotubular layers. Different thicknesses of the nanotubular layer architecture were formed by electrochemical anodization of Ti in different fluoride-containing electrolytes; tube lengths were 500 nm, 2.5 μm, and 6.1 μm. As-formed nanotube layers were annealed to an anatase structure and treated in ammonia environment at 550 °C to achieve nitrogen doping. The crystal structure, morphology, composition and photoresponse of the N-doped were characterized by scanning electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy, and photoelectrochemical measurements. Results clearly show that successful N-doping of the TiO2 nanotubular layers can be achieved upon ammonia treatment. The magnitude of the photoresponse in ultraviolet and visible light is strongly dependent on the thicknesses of the layers. This effect is ascribed to recombination effects along the tube length.

Systems with typical dimensions in the range of 1–100 nm are in an intermediate state between solid and molecular. Such systems are characterized by the fact that the ratio of the number of surface to volume atoms is not small. This is known to lead to size and shape effects on their cohesive properties. In this work, the phase diagram of nanowires was studied in the framework of classical thermodynamics. The roles of the size, shape, and surface tensions were emphasized. The melting temperatures of nanowires of 21 elements were evaluated theoretically. In the case of binary systems, it was shown that the experimental or theoretical knowledge of the size-dependent phase diagrams of a given binary system allows the evaluation of the one of nanowires. The procedure is described in this paper.

Single-walled carbon nanotubes (SWNTs) were successfully synthesized by pyrolysis of pyridine over MgO supported Fe–Mo or Co–Mo catalysts in the presence of pure H2 or a mixture of H2 and NH3 atmospheres. The average diameters of SWNTs are ∼1.5 and ∼3 nm for pure H2 and the H2 and HN3 mixture, respectively. Scanning tunneling spectroscopy (STS) studies show that the SWNTs grown in both atmospheres are doped with nitrogen substituted into the lattice in a pyridine-type structure. This results in a donor feature in the local density of states with an energy that depends on the nitrogen doping concentration.

Single-walled carbon nanotubes (SWNTs) have been used as electrocatalyst support for fuel cells. A toluene solution of a platinum salt, bis(dibenzylideneacetone) platinum, has been used for the first time to decorate the outer surface of SWNT bundles with Pt nanoparticles. The obtained Pt/SWNT materials were then used as catalytic layer in electrodes for fuel cell electrocatalysis. The used platinum salt concentration in the initial SWNT dispersion determined the Pt nanoparticle size and, consequently, the activity of the Pt/SWNT electrodes toward the oxygen reduction reaction. The achieved results were compared with those corresponding to a commercial Pt/carbon black catalyst with similar Pt loading and surface area.

One-dimensional α-MnO2 nanowires with a controlled width of 10–20 nm have been developed by means of ultrasonic waves from mesoporous carbon using KMnO4 as the precursor. The formation mechanism has been proposed based on the results. A peak around 100 K was detected in the temperature-dependence of magnetization curve, indicating the ferromagnetic state in nanocomposite mesoporous carbon-MnO2, which is in agreement with the transition temperature found from the magnetization versus applied magnetic field curve. The magnetization versus temperature curve of the obtained MnO2 nanowires showed a magnetic transition at about 50 K, illustrating that a parasitic ferromagnetic component is composed on the antiferromagnetic structure of MnO2. The advantage of the method reported here is that phase-controlled synthesis of α-MnO2 nanowires was implemented regardless of pH, temperature, and types of ions in the reaction system. A major advantage of this approach is the efficient, fast, and reproducible control of width and the facile strategy to synthesize nanowires MnO2, in addition to the high purity of the resultant material.

Using concepts of hierarchical multiscale modeling, we report development of a mesoscopic model for single-wall carbon nanotubes with parameters completely derived from full atomistic simulations. The parameters in the mesoscopic model are fit to reproduce elastic, fracture, and adhesion properties of carbon nanotubes, in this article demonstrated for (5,5) carbon nanotubes. The mesoscale model enables modeling of the dynamics of systems with hundreds of ultralong carbon nanotubes over time scales approaching microseconds. We apply our mesoscopic model to study self-assembly processes, including self-folding, bundle formation, as well as the response of bundles of carbon nanotubes to severe mechanical stimulation under compression, bending, and tension. Our results with mesoscale modeling corroborate earlier results, suggesting a novel self-folding mechanism, leading to creation of racket-shaped carbon nanotube structures, provided that the aspect ratio of the carbon nanotube is sufficiently large. We find that the persistence length of the (5,5) carbon nanotube is on the order of a few micrometers in the temperature regime from 300 to 1000 K.

Multilayered Co/Cu nanowires were fabricated using anodic alumina templates, containing 40-nm-diameter nanopores, and electrochemical deposition. The Cu layer thickness was varied to study the resulting differences in coercivity and magnetization reversal. Magnetization versus field loops both parallel and perpendicular to an applied field were measured to investigate the mechanisms of magnetization reversal. It was found that the coercivity decreased with increasing Cu thickness. In addition, the magnetization reversal appeared to be a combination of rotation and spin flipping, which was dependent on the Cu thickness and on the angle of the nanowires with the applied field.

The effect of growth conditions on the composition and structure of Si1−xGex nanowires grown by the vapor–liquid–solid method using gaseous precursors (SiH4 and GeH4) was investigated. Transmission electron microscopy was used to characterize the structural properties and elemental composition of the nanowires. At higher growth temperatures (>425 °C), Ge thin film deposition on the nanowire surface resulted in Au loss during growth and the formation of tapered structures. By simultaneously reducing the growth temperature from 425 to 325 °C to suppress the rate of Ge film deposition and increasing the GeH4/(GeH4 + SiH4) gas ratio, Si1−xGex nanowires were produced with Ge fractions spanning the entire composition range. The Ge fraction follows that predicted from the elemental nanowire growth rates in the Ge-rich (x > 0.5) regime, but deviates to higher Ge fractions in Si-rich (x < 0.5) nanowires. A mechanism was proposed whereby surface diffusion provides an additional pathway to Ge incorporation in Si-rich Si1−xGex nanowires.

The deformation behavior of single-crystal GaN nanowires was studied by directly performing three-point bending tests on each individual nanowire in an atomic force microscope. The elastic modulus calculated from the load–displacement response of the nanowires was 43.9 ± 2.2 GPa. Single-crystal GaN nanowires investigated in this study were synthesized by chemical vapor deposition techniques based on the vapor–liquid–solid growth mechanism and had a diameter range from 60 to 110 nm. Crystalline GaN nanowires did not show obvious plastic deformation in bending and usually failed in a brittle manner.