Table of contents

New modern technologies require new materials. During the past decade, the movement towards nanodimensions in many areas of technology aroused a huge interest in nanostructurized materials. The present article reviews recent works dealing with electrochemistry-related aspects of nanostructurized conducting polymers. Electrochemical synthesis and some properties of nanostructurized conducting polymers, and nanocomposites derived from conducting polymers and metals, carbon, and inorganic and organic materials are considered. Some potential areas for electrochemistry-related applications of nanocomposites are highlighted, including batteries, supercapacitors, energy conversion systems, corrosion protection, and sensors.

This article details a simple four-step procedure to create a one-dimensional nanogap on a buried oxide substrate that relies on conventional photolithography performed on a stack of silicon/silicon oxide/silicon, metal evaporation, and hydrofluoric acid oxide removal. Once the nanogap was fabricated it was bridged with an assembly of 1,8-octanedithiol and 5 nm Au nanoparticles capped with a sacrificial dodecylamine coating. Before assembly, characterization of the nanogaps was performed through electrical measurements and SEM imaging. Post assembly, the resistance of the nanogaps was evaluated. The current increased from 70 fA to 200 µA at +1 V bias, clearly indicating a modification due to nanoparticle molecule assembly. Control experiments without nanoparticles or octanedithiol did not show an increase in current.

Nanocolumn pseudo-regular arrays of silicon with controlled aspect ratio and porosity are fabricated by electron-beam evaporation using the glancing angle deposition (GLAD) method with vapour impinging at oblique incidence onto rapidly rotating substrates. The width W at positions y along the height of one individual column scales with y following a power law dependence W∼y^p. We demonstrate that the scaling exponent value, p, can be modified from 0.6 to 0.3 by varying the vapour incidence angle from 75° to a glancing 89° from the substrate normal. This exponent is an important morphological factor for thin films, as it determines the morphological correlation length, nanocolumn profile, size, and spacing. The nanocolumn mean diameter can be varied between 12 and 40 nm, while the intercolumnar spacing can be adjusted between 37 and 85 nm via changing the incidence angle. The growth mechanism and film morphology are explored in detail.

We discuss a method for analysing the number of GFP–LacI fusion transcription factors bound to a construct of 256 contiguous LacI binding sites using photon bleaching statics. We show by using a combination of imaging of the construct in nanochannels, photon statistics and addition of IGFP that the binding coefficient of the LacI decreases with increasing occupation of the construct, with a binding coefficient of 10⁻⁶ M when only 15 of the 256 possible sites are occupied. We model this effect by assuming that the GFP–LacI dimer introduces elastic strain into the helix by generalized deformations, and that this strain propagates over distances at least as large as the persistence length.

Fluorescent semiconductor nanoparticles, or quantum dots, have potential uses as an optical material, in which the optoelectronic properties can be tuned precisely by particle size. Advances in chemical synthesis have led to improvements in size and shape control, cost, and safety. A limiting step in large-scale production is identified to be the raw materials cost, in which a common synthesis solvent, octadecene, accounts for most of the materials cost for a batch of CdSe quantum dots. Thus, less expensive solvents are needed. In this paper, we identify heat transfer fluids, a class of organic liquids commonly used in chemical process industries to transport heat between unit operations, as alternative solvents for quantum dot synthesis. We specifically show that two heat transfer fluids can be used successfully in the synthesis of CdSe quantum dots with uniform particle sizes. We show that the synthesis chemistry for CdSe/CdS core/shell quantum dots and CdSe quantum rods can also be performed in heat transfer fluids. With the aid of a population balance model, we interpret the effect of different HT fluids on QD growth kinetics in terms of solvent effects, i.e., solvent viscosity, CdSe bulk solubility in the solvent, and surface free energy.

ε-Fe₃N–GaN core–shell nanowires are synthesized by the wet chemical route and by nitridation of the Fe–Ga-oxide nanowires in flowing NH₃ (g). The encapsulation by the GaN shell protects the ε-Fe₃N core and spin-glass-like cooperative ordering is observed at low temperatures. Magnetic disorder occurs at the ε-Fe₃N–GaN interface, giving rise to the spin-glass-like state below 50 K because of the presence of anti-ferromagnetic (AF) mixed oxynitrides and ferromagnetic (FM) ε-Fe₃N nitride and the random distribution of ε-Fe₃N in the interface region. The spin-glass-like ordering is probed by relaxation and ac susceptibility experiments.

Nanoclay-reinforced agarose nanocomposite films with varying weight concentration ranging from 0 to 80% of nanoclay were prepared, and structurally and mechanically characterized. Structural characterization was carried out by transmission electron microscopy (TEM), scanning electron microscopy (SEM) and atomic force microscopy (AFM). It was found that pre-exfoliated clay platelets were re-aggregated into particles (stacked platelets) during the composite preparation process. Each particle consists of approximately 11 clay platelets stacked together. The nanoclay particles were homogeneously dispersed within an agarose matrix. The clay particles were oriented with a slight preference of the stacked platelets being parallel to the composite film's surface within the low loading composite films. Mechanical properties of the nanocomposite films were measured by tensile, three-point bending and nanoindentation tests. Mechanical testing results show that nanoclays provide a significant enhancement to the tensile modulus and strength. For the 60% clay nanocomposite, its elastic modulus increases up to 21.4 GPa, which is five times higher than that of the agarose matrix. Based upon the structural characterization, a theoretical model has been developed to simulate the mechanical behaviour of the nanoclay-reinforced polymer composites.

Nanowires composed of pure copper were synthesized using (KI)_1.5(CuI)_8.5 thin film under a direct current electric field (DCEF). The (KI)_1.5(CuI)_8.5 film was used as the medium for transmitting cuprous ions. Investigation shows the copper nanowires with diameters in the range of 20–150 nm were single crystals with a face-centred cubic (fcc) structure. The electric field strength (EFS) was also found to play an important role in determining the diameter of the nanowires.

A study of sonochemically synthesized ZnS:Mn nanoparticles is presented. The particles prepared at low rf power (about 20 W) and room temperature coalesce to form morphologically amorphous large species (30–100 nm in diameter). As the power is increased in the range from 20 to 70 W, and the solution temperature is raised to 60 to 80 °C, finer particles are produced with the size ranging from 2 to 20 nm and improved crystallinity. The results indicate the dispersion of the Mn²⁺ ions at near-surface sites in the particles. It is shown that the sonochemically fabricated particles approach the quality of the ones obtained by a standard chemical route and show a reasonable luminescence performance.

Large-scale well-aligned ZnO nanotubes with outer diameters of 100–300 nm and lengths of tens of micrometres have been prepared by a template-based chemical vapour deposition method. The photoluminescence spectrum of the ZnO nanotube arrays consists of a strong violet band at 414 nm, a blue band at 462 nm and a weak shoulder peak at around 480 nm. The field emission of the ZnO nanotube arrays shows a turn-on field of about 7.3 V µm⁻¹ at a current density of 0.1 µA cm⁻² and emission current density up to 1.3 mA cm⁻² at a bias field of 11.8 V µm⁻¹.

The size control of vertically aligned ZnO nanorod arrays (NRAs) grown by catalyst-free metalorganic chemical vapour deposition is accomplished by changing the O/Zn precursor ratio. At a higher O/Zn precursor ratio, fat ZnO NRAs with excellent alignment are produced. In contrast, slim ZnO NRAs that are considerably less well aligned grow at a lower O/Zn precursor ratio. Irrespective of their different sizes and alignments, the individual ZnO nanorods are of a defect-free single-crystalline nature and of high optical quality, indicating that changing the precursor ratio is a promising way of fabricating size-controlled ZnO NRAs.

Silver flowerlike and dendritic nanostructures were synthesized in an aqueous solution of a hydrolysable amphiphilic block copolymer polyvinylacetone (PVKA) via in situ reduction of Ag⁺ and hydrolysis of PVKA at room temperature. Compared with a previous result, the complete hydrolysis time of PVKA is greatly shortened in this process.

The ability to directly deposit materials in ultraminiaturized domains with nanoscale accuracy could play a central role in the realization of some forms of nanotechnology. In this report we demonstrate the direct deposition of quantum dots in patterns with ultramicroscale (1–15 µm) and nanoscale (<1 µm) features. Unlike bottom up approaches that require preconfigured patterning steps, this top down 'direct write' method should be amenable to the construction of a large variety of patterns and features essentially 'on the fly'. To accomplish the direct writing/deposition of quantum dots we used a system that integrates high resolution motion control with microfabricated fluid delivery cartridges. This process is termed FEMTO (fluidics enhanced molecular transfer operation). The methodology demonstrated here may be extended to surface patterning and deposition of a broad spectrum of other nanoscale materials and thereby create opportunities in a variety of fields ranging from microelectronics to bio/nanotechnology.

We report a simple method for fabricating a lotus-like micro–nanoscale binary structured surface of copper phosphate dihydrate. The copper phosphate dihydrate nanosheets were generated by galvanic cell corrosion of a copper foil with aqueous phosphorus acid solution drops and dried in an oxygen gas atmosphere, and they self-organized into a film with a lotus-like micro–nanoscale binary structured surface. The wettability of this surface can be changed from superhydrophilic to highly hydrophobic or superhydrophobic by heating or modifying it with an n-dodecanethiol monolayer.

Single, square voltage pulses in the microsecond timescale result in selective 5'-end covalent bonding (immobilization) of thiolated single-stranded (ss) DNA probes to a modified silicon dioxide flat surface and in specific hybridization of ssDNA targets to the immobilized probe. Immobilization and hybridization rates using microsecond voltage pulses at or below 1 V are at least 10⁸ times faster than in the passive control reactions performed without electric field (E), and can be achieved with at least three differently functionalized thin-film surfaces on plastic or glass substrates. The systematic study of the effect of DNA probe and target concentrations, of DNA probe and target length, and the application of asymmetric pulses on E-assisted DNA immobilization and hybridization showed that: (1) the rapidly rising edge of the pulse is most critical to the E-assisted processes, but the duration of the pulse is also important; (2) E-assisted immobilization and hybridization can be performed with micrometre-sized pixels, proving the potential for use on microelectronic length scales, and the applied voltage can be scaled down together with the electrode spacing to as low as 25 mV; and (3) longer DNA chains reduce the yield in the E-assisted immobilization and hybridization because the density of physisorbed single-stranded DNA is reduced. The results show that the E-induced reactions can be used as a general method in DNA microarrays to produce high-density DNA chips (E-immobilization) and speed the microarray-based analysis (E-hybridization).

High-quality large-area β-MnO₂ nanowires can be easily synthesized using KNO₃ as the mineralizing agent in a process of mineralization from Mn(NO₃)₂ aqueous solution. The morphological evolution of the β-MnO₂ nanowires and the influences of mineralizing agents and their concentrations on the morphology of the final products were investigated in detail. KNO₃ was the best mineralizing agent among KNO₃, NaNO₃, KCl, and NaCl. More interestingly, when the concentration of the mineralizing agent KNO₃ was not saturated, only irregular short faceted nanorods, instead of nanowires, can be observed. Finally, the formation mechanism is discussed.

We report on a new simple route to realize a high resolution nanograting. By adopting an InAlGaAs matrix and strain-compensated technique, we have proved that a uniform self-assembled InAs nanowire array can be fabricated by molecular beam epitaxy (MBE). A nanograting woven by self-assembled semiconductor nanowires shows a conspicuous diffraction feature. The good agreement between the theoretical and experimental values of diffraction peak positions indicates that a uniform nanowire array is a promising nanograting. This simple one-step MBE growth method will open exciting opportunities for the field of clever optics design.

An applied bias voltage between the atomic force microscope tip and the substrate is one of the important factors related to the growth of oxide patterns. A pulse modulator was used to apply a pulsed bias voltage that synchronizes with the resonance frequency of the cantilever between the tip and the substrate in tapping mode. The height of the protruded oxide structure was increased for short duration times of the pulsed bias due to the reduction of built-up space charge in oxide. The aspect ratio of patterns using pulsed bias voltage was about two times higher than that using continuous bias voltage. This study revealed that the pulsed bias has an advantage for obtaining a higher aspect ratio pattern than the continuous bias by reducing the effect of space charge in oxide.

A stacked plate model for the vibration of multi-layered graphene sheets (MLGSs), in which the van der Waals (vdW) interaction between layers is described by an explicit formula, is presented. Explicit formulae are derived for predicting the natural frequencies of double- and triple-layered graphene sheets, and they clearly indicate the effect of vdW interaction on the natural frequencies. The natural frequencies are calculated for various numbers of layered graphene sheets, and the results show that the vdW interaction has no influence on the lowest natural frequency (classical frequency) of an MLGS but plays a significant role in all higher natural frequencies (resonant frequencies) for a given combination of m and n. The vibration modes that are associated with the classical frequencies for each sheet of an MLGS are identical. In contrast, the vibration modes that are associated with the resonant frequencies are non-identical and give various vibration patterns, which indicates that MLGSs are highly suited to use as high frequency resonators.

By sputtering synthesis of cubic Cu₃N, which decomposes at moderate temperatures, film growth proceeds with simultaneous nitrogen reemission from inside, leading to the formation of some unusual structures or morphology. We report a relief morphology comprising densely packed rosette-like features. The rosettes, typically 20 µm in size, show a radial furcation followed by successive bifurcation at ∼74°, resulting in a fivefold symmetric structure sometimes. The area expansion of the features can be as large as ten per cent with regard to the underlying bottom. Scanning electron micrographs reveal that it is the gliding of Cu₃N nanocrystals along the Cu-rich {111}-planes that is responsible for the unusually large area expansion. The gliding and packing along the {111}-planes also explain the bifurcation angle of the ramified rosettes. Such a relief morphology can serve as a template for large-area fabrication of concave structures by inverse duplication, adding to the already abundant innovative applications of this material.

An Sb (40 nm diameter)–Bi (30 nm diameter) segment nanowire nanojunction array was fabricated by pulsed electrodeposition. Electric transport properties of the junction array were studied down to 4.2 K and in magnetic fields up to 5 T. Temperature versus resistance measurements exhibited a resistive switching behaviour at zero magnetic field, but this feature disappeared with increasing magnetic field. These features might find application in sub-100 nm metal–semiconductor field effect transistors.

Composite nanopeas with ZnSe nanodots/rods embedded in an SiO₂ nanowire/tube configuration have been fabricated via a simple thermochemistry method. The nanopeas are uniform with an average outer diameter of ∼80 nm. The SiO₂ nanowires/tubes are amorphous, whereas the encapsulated ZnSe nanodots/rods are single crystalline. Two key experimental factors are identified for the composite nanopea formation, which enables such methodology to be generally applied to a variety of other material systems.

Aligned ZnO nanorods on film, tetrapod nanowires and nanotubes have been selectively fabricated by a simple one-step route and characterized by x-ray diffractometry (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM) and photoluminescence (PL). PL spectra exhibit different intensity of the green emission relative to the UV emission for different nanostructures. The effects of the process parameters on different nanostructures have been discussed. The wettability of well aligned nanorods on film was investigated, which reveals a super-hydrophobicity.

We have demonstrated that multicomponent carbon nanotube micropatterns, in which different nanotubes are interposed in an intimate fashion, can be prepared by pyrolytic growth of carbon nanotubes on interposed micropatterns of different metal nanoparticles generated by template-free pulsed electrodeposition of metal-containing salts onto a photolithographically prepatterned conductive surface at different peak potentials. The resultant multicomponent interposed carbon nanotube micropatterns should have important implications for the construction of multicomponent and multifunctional nanomaterials and nanodevices based on carbon nanotubes for a wide range of potential applications.

Density functional theory (DFT) is a powerful approach to electronic structure calculations in extended systems, but suffers currently from inadequate incorporation of long-range dispersion, or Van der Waals (VdW) interactions. VdW-corrected DFT is tested for interactions involving molecular hydrogen, graphite, single-walled carbon nanotubes (SWCNTs), and SWCNT bundles. The energy correction, based on an empirical London dispersion term with a damping function at short range, allows a reasonable physisorption energy and equilibrium distance to be obtained for H₂ on a model graphite surface. The VdW-corrected DFT calculation for an (8, 8) nanotube bundle reproduces accurately the experimental lattice constant. For H₂ inside or outside an (8, 8) SWCNT, we find the binding energies are respectively higher and lower than that on a graphite surface, correctly predicting the well known curvature effect. We conclude that the VdW correction is a very effective method for implementing DFT calculations, allowing a reliable description of both short-range chemical bonding and long-range dispersive interactions. The method will find powerful applications in areas of SWCNT research where empirical potential functions either have not been developed, or do not capture the necessary range of both dispersion and bonding interactions.

A simple two-step hydrogen reduction method was used to synthesize FePt/Fe composite nanotubes. As the first step, L1₀ FePt nanotubes were prepared by heating a porous alumina template loaded with an alcohol solution of a Fe chloride and Pt chloride mixture in flowing hydrogen at 670 °C. Then, FePt/Fe composite nanotubes were obtained by reducing the alcohol solution of the Fe chloride within the formed FePt nanotubes at a lower temperature, namely 470 °C. Through changing the concentrations of initial alcohol solutions, the FePt:Fe atomic ratios of the composite nanotubes were easily adjusted and the magnetic properties were tuned accordingly. For (FePt)_100−x/Fe_x composite nanotubes with x ranging between 0 and 26 at.%, the hard and soft phases were well coupled and the coercivity was tunable over a large range (1.27–2.73 T). Furthermore, the marked interdiffusion between Fe and FePt, which usually exists in FePt-based composites fabricated by using conventional methods, was not observed in the formed composite nanotubes. This indicates the two-step hydrogen reduction method to be a promising route for synthesizing nanocomposites which are difficult to fabricate by using conventional methods due to the interdiffusion between different phases.

Aluminium orthophosphate (AlPO₄) nanocrystals were synthesized by a microemulsion-based solvothermal approach. The reaction temperature and concentration of reactants as well as the molar ratio of the two reactants have significant effects on the shape and size of the AlPO₄ nanocrystals obtained. A possible formation mechanism for the AlPO₄ nanocrystals with different shapes is discussed.

We prepared multiwall carbon nanotubes (MWCNTs) from the pyrolysis of ferrocene, and CN_x nanotubes from a mixture of ferrocene and melamine. Under well chosen synthesis conditions, massive multiwall CN_x/carbon nanotube intramolecular junctions were successfully fabricated. The individual nanotubes were used as conductance channels to obtain their transport characteristic information. Measurement results showed that the current–voltage (I–V) curve of the CN_x/CNT junction is highly asymmetric, behaving like a diode. Moreover, the devices are very stable in ambient environment. We attribute this nonlinear property of the CN_x/CNT junctions to their two different atomic and electronic sections.

Electrospun polymer nanofibres were originally developed for their durability and resistance to all forms of degradation and biodegradation. Some polymer nanofibres are biocompatible and biodegradable and therefore suitable for replacement of structurally or physiologically deficient tissues and organs in humans. Here, biocompatible polycaprolactone (PCL) nanofibre scaffolds modified with collagen types I and III were used for vascular tissue engineering. Coronary artery smooth muscle cells (SMCs) were grown on PCL nanofibres, modified PCL/collagen biocomposite nanofibres and collagen nanofibres. The results show that the modified PCL/collagen biocomposite nanofibre scaffolds provide required mechanical properties for regulation of normal cell function in vascular tissue engineering.

We present electronic transport measurements through thiolated C₆₀ molecules in a liquid environment. The molecules were placed within a mechanically controllable break junction using a single anchoring group per molecule. On varying the electrode separation of the C₆₀-modified junctions, we observed a peak in the conductance traces. The shape of the curves is strongly influenced by the environment of the junction as shown by measurements in two distinct solvents. In the framework of a simple resonant tunnelling model, we can extract the electronic tunnelling rates governing the transport properties of the junctions.

We demonstrate the use of gas phase electrophoresis to size classify CNTs grown in a continuous aerosol process. The separation process occurs at atmospheric pressure and involves electrostatic mobility separation which classifies fibres on the basis of equivalent projected surface area. This implies that one can, for diameter-controlled CNTs, obtain an on-the-fly determination of the CNT length distribution during CNT synthesis, or alternatively have a method for producing size separated CNTs. The method should be generic to any fibre based material.

A detailed parametric study of single-walled carbon nanotubes (SWNTs) synthesized in powder form and on substrates using the alcohol catalytic chemical vapour deposition (ACCVD) method is reported. As-grown SWNTs were analysed using transmission electron microscopy (TEM), field-emission scanning electron microscopy (FE-SEM), Raman spectroscopy and UV–vis–NIR spectroscopy to obtain structural and electronic information. We found that nucleation and growth of SWNTs occurs within seconds after introduction of the alcohol vapour and that high quality SWNTs with a narrow diameter distribution without amorphous carbon can be grown using Co acetate catalyst doped with Fe acetate above 750 °C. Defective multiwalled nanotubes were observed at lower temperatures, with the optimum temperature being 850 °C. These and other results reported in this paper allow the basis for optimizing the ACCVD process for the synthesis of large numbers of SWNTs.

In this study, it is found that as-prepared gold nanorods can be linked to each other in an end-to-end way by using cysteine as a molecular bridge. Both transmission electron microscopy and UV–visible optical spectroscopy demonstrated the uniaxial assembly of the gold nanorods. The controlled addition of cysteine into the gold nanorod solution resulted in their preferential binding to the two ends of the gold nanorods. As a result, end-to-end assembly was achieved through cooperative hydrogen bonding of bound cysteine molecules. The as-synthesized end-to-end linked assembly of gold nanorods is well ordered and on a large scale. For comparison, three other neutral amino acids, glycine, alanine and valine, were also investigated but the orderliness of their assembly is not as good as that in the case of cysteine.

Silica substrates were functionalized with a covalent 4-ClCH₂C₆H₄SiCl₃ monolayer. Additional covalent bonding of appropriate functional molecules to the silylated substrates was further achieved. The surface chemical characterization was carried out by angle resolved x-ray photoelectron measurements. Moreover, surface morphological characterizations were performed by atomic force microscopy measurements. Present results provide step by step information on the covalently linked monolayer during the synthetic procedure.

A method which is able to produce different types of nano-structured materials, namely nano-particles, nano-structured surfaces and nano-porous membranes, from two-phase metallic alloys is reviewed. The new process first establishes nano-structures in the bulk alloy and then separates them by selective phase dissolution. Variation in processing makes it possible to produce different types of nano-structure even from the same alloy. The process can be applied to many different alloy systems. An overview is presented emphasizing the versatility of the process with examples of different nano-structure types that can be produced. Further, the new method is discussed in relation to similar processes (specifically, electrochemical processes) which have been used for nano-structure synthesis.

The growth of large-area, patterned and oriented ZnO nanowires on silicon using a low temperature silicon–CMOS compatible process is demonstrated. Nanowire synthesis takes place using a thin nucleation layer of ZnO deposited by radiofrequency magnetron sputtering, followed by a hydrothermal growth step. No metal catalysts are used in the growth process. The ZnO nanowires have a wurtzite structure, grow along the c-axis direction and are distributed on the silicon substrate according to the pre-patterned nucleation layer. Room temperature PL measurements of the as-grown nanowires exhibit strong yellow–red emission under 325 nm excitation that is replaced by ultraviolet emission after annealing. This method can be used to integrate patterned 1D nanostructures in optoelectronic and sensing applications on standard silicon CMOS wafers.

Application of modest magnetic fields can be used to control the direction in which laser light incident on aqueous suspensions of magnetic Ni nanowires (∼200 nm in diameter and ∼10 µm in length) is preferentially scattered. Similar effects were observed for suspensions of these nanowires prepared in ethanol, ethylene glycol, and glycerol. In glycerol, the nanowires settle sufficiently slowly that the effects can be quantified. In particular, fields of the order of 100 Oe cause the intensity of light scattered in the forward direction to vary by as much as a factor of thirty-five simply by changing the direction of the field.

The chances of attaching organic molecules to silicon surfaces can be considerably enhanced if a robust nanogap structure with silicon electrodes can be used to connect the molecules. We describe the electrical properties of such an electrode structure, with a separation of the silicon surfaces in the 3–7 nm range. These silicon nanogaps are manufactured by partly removing the silicon dioxide insulator from a silicon–oxide–silicon material stack, by using a selective oxide etchant. After the activation of the gap (the etching), current instabilities appear, which are comparable to the properties of thin oxides after soft breakdown. Applying a constant voltage can reduce these current instabilities. We also address the issue of surface leakage currents for these nanogap structures.

We report experimental observations of shell buckling instabilities in free-standing, vertically aligned GaN nanotubes subjected to uniaxial compression. Highly uniform arrays of the GaN nanotubes standing on a GaN template were fabricated and subjected to uniaxial compression using a nanoindenter. The buckling load was found to be of the order of 150 µN for the GaN nanotubes with an outer radius of 40 nm, an inner radius of 20 nm, and heights of 500 and 300 nm. Good agreement was found between the experimental observations, the stress–strain relation equation study findings and the predictions from the cylindrical shell buckling theory.

We derive analytically the effective dipole polarizability tensor of a dimer of spheres located near a plane substrate. This is used to determine the extinction cross sections and other optical properties of the particles, and we use the results to study the experimentally observed red and blue shifts of the plasmon resonance of the dimer as a function of the distance between the particles or between the particles and the substrate. The results show that bringing the dimer towards the surface always leads to red shifted plasmon excitation. The plasmon resonance of the dimer may be red shifted or blue shifted as the particles are brought toward each other (at fixed distance from the surface) depending on the polarization. The size of the blue shift is smaller when the particles are close to the surface than when they are far away, but the red shifts are essentially unchanged.

Thin, uniform, single-walled carbon nanotube films, made by a simple filtration process, subsequently coated with palladium, are shown to be promising detectors of hydrogen. The films detected hydrogen with relative responses of 20% at 100 ppm and 40% at 500 ppm concentrations. Most of the initial film conductance was recovered within 30 s by exposing the samples to air. This quick and easy recoverability make the Pd-coated nanotubes suitable for practical applications in room temperature hydrogen sensing while consuming only ∼0.25 mW power. The film fabrication process provides highly reproducible control over the film thickness; an important ingredient for commercial production. In the course of this research strong evidence was obtained indicating that sputter deposition of metal onto the nanotubes, even under very low power, short exposure time conditions, does damage to the nanotubes.

A uniquely structured SiO_x-capped (x = 0.5–0.8) Si nanowire array with strong blue emission, like a nanobeacon array, was fabricated using electroless metal (silver) deposition on a water plasma-treated Si wafer. Formation of the nanoscale light source array can be understood on the basis of a self-assembled localized microscopic electrochemical cell model and a diffusion-limited aggregation process. Photoluminescence spectral analysis reveals that the intensity of the broad blue-emitting luminescent band centred at around 435 nm strongly depends upon the irradiation of H₂O⁺, HO⁺, and O⁺ ions, which are present in the water plasma. We attribute the blue PL band to the optical transition of the self-trapped excitons at the surfaces of SiO_x nanocaps.

Atomic force microscopes (AFM) have been used to measure the strength of adhesion of photoresist patterns which generally collapse during rinsing with water in the development process. We suggest how to measure the collapsing force of the photoresist patterns using an AFM in which a lateral force microscope (LFM) is engaged to determine the tip load at the moment of pattern collapse. The AFM tip was precisely positioned in the space between the patterns in non-contact mode and then scanned in contact mode to the collapse patterns. Loads F for collapse on a scale of nanonewtons (nN) were calculated from the signal of the position-sensitive photodiode. To investigate the variation of the collapsing load for different lengths of patterns, an AFM tip was also used to fabricate patterns with an appropriate length. Our method for measuring the strength of adhesion of photoresist patterns would enable an AFM to be applied to test this property for photoresists.

Polyvinylpyrrolidone (PVP)/Ag₂S composite fibres were successfully prepared by a facile method called the electrospinning technique. Scanning electron microscopy analysis revealed the fibre morphology of the composite. Transmission electron microscopy showed spherical nanoparticles of the Ag₂S component with an average particle size of about 15 nm and a good dispersion. X-ray diffraction results showed that a pure β-Ag₂S phase was obtained in the PVP fibres. X-ray photoelectron spectra (XPS) proved that the Ag and S elements exist in PVP/Ag₂S composite fibres and quantitative analysis of the XPS showed that the atomic ratio of silver and sulfur was about 2. Fourier transform infrared and ultraviolet–visible spectroscopy were used to characterize the structure of the PVP/Ag₂S composite fibres.

We have developed a straightforward approach for constructing single-walled carbon nanotube (SWNT) assemblies by using aligned surface DNA as a positioning template. A cationic surfactant, dodecyltrimethylammonium bromide, is utilized to suspend SWNTs in aqueous media and localize them on DNA through electrostatic interactions. SWNT positioning is controlled by the surface DNA arrangement, and the extent of deposition is influenced by the SWNT concentration. With lower-concentration SWNT suspensions, multiple surface treatments can increase the DNA coverage. Under optimized conditions, 83% of the length of surface DNAs was covered with SWNTs, and 76% of all surface-deposited SWNTs were on the DNA. In some regions, nearly continuous SWNT assemblies were formed. This approach should provide a useful tool for the fabrication of nanotube nanowires in nanoelectronic circuits.

Aligned Nafion^®-115 nanowire arrays have been synthesized by an extrusion method with anodic aluminium oxide (AAO) membranes templates in this work. A surface modification was carried out to improve the hydrophobicity of the AAO pore surface. The as-synthesized nanowires are about 85 nm in diameter and several to over ten micrometres in length. Near-IR Raman and IR spectrum studies show that the polymer nanowires are composed of pure Nafion^®-115 only.

To fabricate an atomic force microscope tip with an attached carbon nanotube (CNT), we simulated dielectrophoresis, produced by a nonuniform electric field. We calculated the dielectrophoretic force and torque of CNTs dispersed in a fluid. We then investigated the effect of various parameters such as the initial conditions of the CNT, the distance between the tip and the electrode, and the shape of the tip's apex. Using the results of the simulation, we examined the assembly conditions for achieving a high success rate. In particular, we found that the optimal distance between the tip and the electrode was 10 µm.

Nanoelectronic molecular and magnetic tunnel junction (MTJ) MRAM crossbar memory systems have the potential to present significant area advantages (4 to 6F²) compared to CMOS-based systems. The scalability of these conductivity-switched RAM arrays is examined by establishing criteria for correct functionality based on the readout margin. Using a combined circuit theoretical modelling and simulation approach, the impact of both the device and interconnect architecture on the scalability of a conductivity-state memory system is quantified. This establishes criteria showing the conditions and on/off ratios for the large-scale integration of molecular devices, guiding molecular device design. With 10% readout margin on the resistive load, a memory device needs to have an on/off ratio of at least 7 to be integrated into a 64 × 64 array, while an on/off ratio of 43 is necessary to scale the memory to 512 × 512.

The present work reports a feasibility study of the direct mechano-chemical synthesis by controlled reactive mechanical alloying (CRMA) in a magneto-ball mill of the nanostructured magnesium tetrahydroaluminate (magnesium alanate) Mg(AlH₄)₂ complex hydride. Three stoichiometric Mg–2Al mixtures, (a) elemental Mg and Al powders, (b) elemental Al powder and commercial AZ91 alloy (Mg–Al–Zn alloy) and (c) powder of as-cast Mg–2Al alloy, have been used. No successful synthesis of Mg(AlH₄)₂ has been achieved. The only nanocrystalline hydride formed up to 270 h of CRMA is β-MgH₂, and it does not react with Al and H₂ to form Mg(AlH₄)₂. It has been found that there is strong competition between formation of Al(Mg) solid solution and the β-MgH₂ hydride occurring to a various extent up to ∼10 h of CRMA in all three Mg–2Al mixtures. It is hypothesized that the presence of Al(Mg) solid solution inhibits the reaction of β-MgH₂, Al and H₂ to form Mg(AlH₄)₂. Furthermore, despite the fact that after prolonged milling the Al(Mg) solution eventually decomposes into secondary Al(s) (derived from solid solution), the latter retains its physico-chemical characteristics of the former solid solution which still inhibits the reaction to form Mg(AlH₄)₂. Experimental evidence from DSC measurements shows increasing ranges of the melting enthalpy with increasing amounts of Al(Mg) solid solution and consequently the secondary Al(s) for all the three Mg–2Al mixtures. This strongly supports the hypothesis about the different nature of Al(Mg) and the secondary Al(s) as compared to the primary elemental Al powder.

A simple procedure for fabrication of gold films with nanorod arrays is described. The method is based on thermal evaporation of gold onto a porous alumina (PA) membrane used as a template. The gold films were obtained after removing the template and characterized using scanning electron microscopy, atomic force microscopy and ultraviolet–visible spectrophotometry. The prepared gold films are composed of arrays of sharp (<20 nm at apex) rod-shaped gold nanostructures. These structures closely follow the organization and distribution of pores of the PA template. The length of the gold nanostructures is estimated to range from 300 nm to more than 1000 nm. It was found that their length is influenced by the size of the pores in the PA and the temperature of the PA during gold evaporation. Spectrophotometric characterization shows that the prepared gold films exhibit a surface plasmon resonance absorption peak located between 525 and 540 nm.

A simple chemical method for the production of single-crystalline α-Si₃N₄ nanobelts has been developed, consisting of nitridation of a high-Si-content Fe–Si 'catalyst' by ammonia at 1300 °C. The as-synthesized product was characterized by means of x-ray diffraction, electron microscopy and energy-dispersive x-ray spectroscopy. The α-Si₃N₄ nanobelts have widths of 60–120 nm, thicknesses of 10–30 nm and lengths up to microns. Four intense green–blue luminescence bands at 398 nm (3.12 eV), 434 nm (2.86 eV), 492 nm (2.52 eV) and 540 nm (2.30 eV) were observed and analysed for the product, which indicates the potential applications in optoelectronics. The growth mechanism has also been speculated upon. The potential technological importance of the product, the simplicity of the preparation procedure, as well as the cheap commercial precursor of Fe–Si alloy particles makes this study both scientifically and technologically interesting.

Monodisperse cobalt monoxide (CoO) nanocrystals ranging in size from 4.5 to 23 nm were prepared via the thermal decomposition of cobalt acetylacetonate (Co(acac)₂) in oleylamine under vigorous stirring. The size control of the nanocrystals was achieved by tailoring the reaction temperature or by seed-mediated growth. The nanocrystals have been characterized by x-ray diffraction, transmission electron microscopy, and Fourier transform infrared and x-ray photoelectron spectroscopy. The as-prepared nanocrystals are stable because of the organic coating (oleylamine) that occurred in situ. Magnetic measurement reveals that all of the nanocrystals are superparamagnetic at high temperatures and show ferromagnetic interactions at low temperatures due to the existence of uncompensated moments on the surface of the nanoparticles. The weak ferromagnetic interactions increase with decreasing particle size.

We report here the design, fabrication and testing of a novel nanofluidic device which we term a 'nano-nib' due to its resemblance to a nano-fountain pen. The nanofluidic device is an emitter tip which incorporates a nanofluidic capillary slot coupled to a microfluidic capillary slot. The microfluidic capillary slot is fabricated using reactive ion etching (RIE) whilst the nanofluidic capillary slot is fabricated using focused ion beam (FIB) etching. The microfluidic capillary slot has a length of 2 mm and capillary slot dimensions (w × h) of 1 µm × 4 µm, i.e. a volume of a few picolitres (pl). The smallest nanofluidic capillary slot has a length of 3 µm and capillary slot dimensions as small as 21 nm × 300 nm, i.e. a volume of a few attolitres (al). Current–voltage characterization in electrospray mode revealed a current of 1 nA at an applied voltage as low as 40 V. The applications for this nanofluidic device lie in high sensitivity electrospray mass spectrometry, direct nanowriting, ultralow volume sample extraction/spotting and printing.

One-dimensional semiconductor ZnO nanostructures with different morphologies can provide different practical and potential applications in a broad field. In this paper, a one-dimensional zigzag chain coordination polymer [Zn(4,4^'-bipy)Cl₂]_n and a two-dimensional coordination polymer are successfully promoted to obtain ZnO nanorods and radial nanoneedles on a large scale respectively, when they are directly employed as reactants. The different frameworks of coordination polymers can build various intermediates in the formation process, and the intermediates then mature to different morphologies in the final products. The possible formation mechanism and the PL spectra of both products are also investigated.

The velocity dependence of nanoscale friction is studied for the first time over a wide range of velocities between 1 µm s⁻¹ and 10 mm s⁻¹ on large scan lengths of 2 and 25 µm. High sliding velocities are achieved by modifying an existing commercial atomic force microscope (AFM) setup with a custom calibrated nanopositioning piezo stage. The friction and adhesive force dependences on velocity are studied on four different sample surfaces, namely dry (unlubricated), hydrophilic Si(100); dry, partially hydrophobic diamond-like carbon (DLC); a partially hydrophobic self-assembled monolayer (SAM) of hexadecanethiol (HDT); and liquid perfluoropolyether lubricant, Z-15. The friction force values are seen to reverse beyond a certain critical velocity for all the sample surfaces studied. A comprehensive friction model is developed to explain the velocity dependence of nanoscale friction, taking into consideration the contributions of adhesion at the tip–sample interface, high impact velocity-related deformation at the contacting asperities and atomic scale stick–slip. A molecular spring model is used for explaining the velocity dependence of friction force for HDT.

Recent studies have indicated that the force–extension properties of single molecules of double stranded (ds) DNA are sensitive to the presence of small molecule DNA binding agents, and also to their mode of binding. These observations raise the possibility of using this approach as a highly sensitive tool for the screening of such agents. However, particularly for studies employing the atomic force microscope (AFM), several non-trivial barriers hinder the progress of this approach to the non-specialist arena and hence also the full realization of this possibility. In this paper, we therefore address a series of key reproducibility and metrological issues associated with this type of measurement. Specifically, we present an improved immobilization method that covalently anchors one end (5' end) of a dual labelled (5'-thiol, 3'-biotin) p53 DNA molecule onto a gold substrate via gold–thiol chemistry, whilst the biotinylated 3' end is available for 'pick-up' using a streptavidin modified AFM tip. We also show that co-surface immobilization of DNA with 6-mercapto–1-hexanol (MCH) can also lead to a further increase the measured contour length. We demonstrate the impact of these improved protocols through the observation of the cooperative transition plateau in a DNA fragment of approximately 118 bp, a significantly smaller fragment than previously investigated. The results of a comparative study of the effects of a model minor groove binder (Hoechst 33258) and an intercalating drug (proflavine), alone, as a mixture and under different buffer conditions, are also presented.

Novel thermoplastic starch (TPS)–clay nanocomposite foams were prepared by melt-processing. The use of urea as plasticizer avoids the cracking of TPS during storage and enhances the dispersion of ammonium-treated clay in TPS. X-ray diffraction shows an increase in the basal plane spacings of both natural and treated clays, suggesting formation of nanocomposites. Scanning electron microscopy shows spontaneously formed regular foam structures with 84% porosity in TPS–ammonium-treated clay. This does not form in TPS or TPS–natural clay nanocomposites. This result implies that the regular foam formation is due to the ammonium surfactant of clay, which produces ammonia gas acting as an internal blowing agent. Thermogravimetric analysis confirms this deduction.

Nanosheet cupric oxide (CuO) was synthesized by a hydrothermal synthesis method and its electrochemical performance was tested with Li metal as the reference anode. This CuO electrode showed a good capacity retention with a reversible capacity of 400 mA h g⁻¹ during up to 100 cycles. Copper (Cu) nanoparticles were produced and separated from the lithiated CuO electrode. Structural analyses by means of electron microscopy (field emission scanning electron microscopy and transmission electron microscopy) indicated that rather uniform spherical copper particles of 30–40 nm were obtained. These copper nanoparticles were collected as the lithiation product and this electrochemical reduction method was put forward as a new approach for synthesizing metal nanoparticles.

Catalytic growth of GaN nanowires by hydride vapour phase epitaxy is demonstrated. Nickel–gold was used as a catalyst. Nanowire growth was limited to areas patterned with catalyst. Characterization of the nanowires with transmission electron microscopy, x-ray diffraction, and low temperature photoluminescence shows that the nanowires are stoichiometric 2H-GaN single crystals growing in the [0001] orientation when grown on sapphire, with occasional stacking faults along the c-axis as the only defect type observed in most of the wires. A red shift observed in the photoluminescence was too large to be explained by the minor strain observed alone, and was only marginally affected by temperature, suggesting a superposition of several factors.

Nanotechnology is expected to open new avenues to fight and prevent disease using atomic scale tailoring of materials. Among the most promising nanomaterials with antibacterial properties are metallic nanoparticles, which exhibit increased chemical activity due to their large surface to volume ratios and crystallographic surface structure. The study of bactericidal nanomaterials is particularly timely considering the recent increase of new resistant strains of bacteria to the most potent antibiotics. This has promoted research in the well known activity of silver ions and silver-based compounds, including silver nanoparticles. The present work studies the effect of silver nanoparticles in the range of 1–100 nm on Gram-negative bacteria using high angle annular dark field (HAADF) scanning transmission electron microscopy (STEM). Our results indicate that the bactericidal properties of the nanoparticles are size dependent, since the only nanoparticles that present a direct interaction with the bacteria preferentially have a diameter of ∼1–10 nm.

We report on high resolution photoelectron core level spectroscopy (HRCLS) and scanning tunnelling microscopy (STM) measurements of the decomposition of lysine adsorbed on InP(001) substrates. We find that components from the lysine can be present on the InP surface even after annealing to 600 °C and desorption of the native surface oxide. We further observe that while a crystalline surface phase can be observed on the epi-ready surface after annealing, the lysine treated surface still appears rough. We conclude that lysine residues inhibit the formation of a flat crystalline structure on the InP(001) surface. These results are discussed in terms of the lysine promotion of [001] nanowire growth.

Colloidal gold nanoparticles were synthesized in a quaternary ammonium-based room-temperature ionic liquid (QAIL) by γ-radiation for the first time. Transmission electron microscopy, x-ray diffraction and optical techniques were used to characterize the colloidal nanoparticles. By changing the experimental conditions, the size of the gold nanoparticles can be varied between 10 and 50 nm. It was found that gold nanoparticles coated by QAIL are very stable in dispersion.

A method for obtaining detailed two-dimensional strain maps in nanowires and related nanoscale structures has been developed. The approach relies on a combination of lattice imaging by high-resolution transmission electron microscopy and geometric phase analysis of the resulting micrographs using Fourier transform routines. We demonstrate the method for a germanium nanowire grown epitaxially on Si(111) by obtaining the strain components ε_xx, ε_yy, ε_xy, the mean dilatation, and the rotation of the lattice planes. The resulting strain maps are demonstrated to allow detailed evaluation of the strains and loading on nanowires.

We report a technique for controlled synthesis of zero-, one-, and two-dimensional compound semiconductor nanostructures by using cubic, hexagonal, and lamellar lyotropic liquid crystals as templates, respectively. The liquid crystals were formed by self-assembly in a ternary system consisting of a poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) amphiphilic block copolymer as the surfactant, heptane as the non-polar dispersed phase, and formamide as the polar continuous phase. ZnSe quantum dots and nanowires with diameters smaller than 10 nm, as well as free-standing, disc-like quantum wells, were grown inside the spherical, cylindrical, and planar nanodomains, respectively, by reacting diethylzinc that was dissolved in the heptane domains with hydrogen selenide gas that was brought into contact with the liquid crystal in a sealed chamber at room temperature and atmospheric pressure. The shape and size of the resulting nanostructures can be manipulated by selecting the templating phase of the liquid crystal, the size of the dispersed nanodomains that is controlled by the composition of the template, and the concentration of diethylzinc in them.

PbS nanocrystals were synthesized directly in the conducting polymer, poly(3-hexylthiophene-2,5-diyl). Transmission electron microscopy shows that the PbS nanocrystals are faceted and relatively uniform in size with a mean size of 10 nm. FFT analysis of the atomic lattice planes observed in TEM and selected area electron diffraction confirm that the nanocrystals have the PbS rock salt structure. The synthesis conditions are explored to show control over the aggregation of PbS nanocrystals in the thiophene conducting polymer.

Multi-walled carbon nanotubes (MWNTs) irradiated with γ-rays were subjected to chemical modification with thionyl chloride and decylamine. Products from chemical treatment were characterized by both FTIR and Raman spectra. Element analysis (EA) and thermogravimetric analysis (TGA) for the modified soluble MWNTs (s-MWNTs) indicated that γ-radiation increased the concentration of functional groups bound to MWNTs, which arose due to the increasing number of defect sites created on the MWNTs by γ-photons. Compared with untreated MWNTs, γ-irradiation significantly enhanced the solubility of MWNTs in acetone and tetrahydrofuran (THF). We therefore conclude that γ-irradiation provides a novel approach to prepare various functionalized modifications of carbon nanotubes (CNTs).

A simple and facile method is described to directly synthesize TiO₂ nanostructures on titanium substrates by oxidizing Ti foil using small organic molecules as the oxygen source. The effect of reaction temperature and oxygen source on the formation of the TiO₂ nanostructures has been studied using scanning electron microscopy, x-ray diffraction, transmission electron microscopy, Raman spectroscopy and water contact angle measurement. Polycrystalline grains are formed when pure oxygen and formic acid are used as the oxygen source; elongated micro-crystals are produced when water vapour is used as the oxygen source; oriented and aligned TiO₂ nanorod arrays are synthesized when ethanol, acetaldehyde or acetone are used as the oxygen source. The growth mechanism of the TiO₂ nanostructures is discussed. The diffusion of Ti atoms to the oxide/gas interface via the network of the grain boundaries of the thin oxide layer is the determining factor for the formation of well-aligned TiO₂ nanorod arrays. The wetting properties of the TiO₂ nanostructured surfaces formed are dictated by their structure, varying from a hydrophilic surface to a strongly hydrophobic surface as the surface structure changes from polycrystalline grains to well-aligned nanorod arrays. This tunable growth of TiO₂ nanostructures is desirable for promising applications of TiO₂ nanostructures in the development of optical devices, sensors, photo-catalysts and self-cleaning coatings.

Nanofibres from para-hexaphenylene and functionalized quaterphenylene molecules are grown on mica surfaces and are thereafter transferred into solution, where they either freely rotate in water or are space-fixed in sucrose. From freely rotating aggregates highly anisotropic angular intensity distributions of emitted light for individual aggregates are determined. Luminescence is enhanced at the nanofibre tip as compared to the broad side by about an order of magnitude probably due to waveguiding along the long axis of the aggregates. For dense arrays of nanofibres on mica the increase of emitted intensity towards the substrate plane in the direction of the long axes of the nanofibres is smaller and it depends on the effective thickness of the nanofibre films. The difference between individual aggregates and aggregate arrays is interpreted in terms of light scattering at surface roughness inside the nanofibre film and on the border of the underlying mica substrate. Aggregates fixed in solution, with the help of femtosecond laser scanning microscopy, allow us to obtain two-photon absorption spectra of functionalized nanofibres between 720 and 900 nm as well as morphological features from three-dimensional optical images. The lateral resolution is about 400 nm.

We synthesized CdS nanorods through a conventional solvothermal method and studied their photoluminescence and electric transport properties before and after annealing. High-resolution transmission electron microscopy indicated that the surface layer of the annealed CdS nanorods was well crystallized, while that of the unannealed nanorods was amorphous. Energy-dispersive x-ray spectrography, x-ray photoelectron spectrography and thermogravimetric analysis were used to demonstrate that the amorphous layer at the surface of the as-prepared nanorods was pure CdS. The photoluminescence spectra showed that after annealing the intensity of the band-edge emission increased several times and the surface state emission at 548 nm disappeared. The unannealed CdS nanorods had approximately linear I–V characteristics and the conductance suddenly increased about 100 times upon visible light illumination by a halogen lamp. The annealed CdS nanorods exhibited nonlinear conductance with a turn-on voltage at about 2.2 V. These properties show that CdS nanorods have potential applications in nanophotoelectric or sensing devices.

Single-crystal MnWO₄ nanofibres with diameters as small as 3–4 nm and length up to 800–1000 nm have been successfully synthesized by a novel surfactant-assisted complexation–precipitation method. X-ray powder diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and electron diffraction (ED) were employed to study the crystal structure and morphologies of the products. Experiments show that the complexation and the surfactant are the crucial factors affecting the morphology of the products. The possible formation process and growth mechanism have been proposed.

At room temperature, without any template and in the solid phase, shape-controlled silver nanostructures are synthesized using solid electrolyte RbAg₄I₅ thin film under direct current electric field (DCEF) treatment. With different DCEF strengths, we have synthesized silver single-crystalline nanowires, nanotubes, nanoparticles and nanoframes. The growth mechanism and the relationship between the DCEF strength and the synthesized nanostructures are discussed briefly.

The growth of Bi₂S₃ nanotubes through a simple soft chemical route using the surfactant Triton-X 100 as the template at the relatively very low temperature of 115 °C/12 h has been reported for the first time. These nanotubes are nearly uniform in dimensions, with diameter around 120 nm and length up to 8 µm, their nature being single crystalline. The reaction conditions are optimized. Development of nanotubes and nanoparticles from the same precursor is discussed. The optical properties of the nanotubes are studied by means of UV–visible and photoluminescence spectra. The band gap calculated from the absorption spectra is found to be 1.76 eV, indicating a considerable blue shift relative to the bulk.

A simple method was developed to fabricate polyethylene glycol (PEG) nanostructures using capillary lithography mediated by ultraviolet (UV) exposure. Acrylate-containing PEG monomers, such as PEG dimethacrylate (PEG-DMA, MW = 330), were photo-cross-linked under UV exposure to generate patterned structures. In comparison to unpatterned PEG films, hydrophobicity of PEG nanostructure modified surfaces was significantly enhanced. This could be attributed to trapped air in the nanostructures as supported by water contact angle measurements. Proteins (fibronectin, immunoglobulin, and albumin) and cells (fibroblasts and P19 EC cells) were examined on the modified surfaces to test for the level of protein adsorption and cell adhesion. It was found that proteins and cells preferred to adhere on nanostructured PEG surfaces in comparison to unpatterned PEG films; however, this level of adhesion was significantly lower than that of glass controls. These results suggest that capillary lithography can be used to fabricate PEG nanostructures capable of modifying protein and cell adhesive properties of surfaces.

The equilibrium geometry, electronic structure and energetic stability of Bi nanolines on clean and hydrogenated Si(001) surfaces have been examined by means of ab initio total energy calculations and scanning tunnelling microscopy. For the Bi nanolines on a clean Si surface the two most plausible structural models, the Miki or M model (Miki et al 1999 Phys. Rev. B 59 14868) and the Haiku or H model (Owen et al 2002 Phys. Rev. Lett.88 226104), have been examined in detail. The results of the total energy calculations support the stability of the H model over the M model, in agreement with previous theoretical results. For Bi nanolines on the hydrogenated Si(001) surface, we find that an atomic configuration derived from the H model is also more stable than an atomic configuration derived from the M model. However, the energetically less stable (M) model exhibits better agreement with experimental measurements for equilibrium geometry. The electronic structures of the H and M models are very similar. Both models exhibit a semiconducting character, with the highest occupied Bi-derived bands lying at ∼0.5 eV below the valence band maximum. Simulated and experimental STM images confirm that at a low negative bias the Bi lines exhibit an 'antiwire' property for both structural models.

A water-based conducting ink, composed of well dispersed nano-silver particles, has been successfully inkjet printed using an ordinary commercial printer. The silver colloids with diameter around 50 nm were dispersed in a water and diethylene glycol cosolvent system. The 25 wt% silver ink had a viscosity of about 7.4 cP and surface tension of 33.5 dyn cm⁻¹ at 20 °C, which is appropriate for printing jobs. Continuous and smooth lines of 130 µm width could be printed on ordinary glass substrates using an Epson R210 printer. After baking at 260 °C for 3 min, these lines exhibited a resistivity of 1.6 × 10⁻⁵ Ω cm, which could serve as conducting lines for electronic applications.

In this paper, we report on the self-assembly growth of micro-pillars consisting of well-aligned carbon nanotubes on the uneven surfaces of silicon chips by chemical vapour deposition, which could be useful for the fabrication of electron field emitters, micro-electromechanical devices, interconnection for microelectronics, etc. The mechanism for the growth of isolated pillars within large-area aligned carbon nanotube arrays is also discussed.

We demonstrate the use of etched registration markers for the alignment of four-terminal ex situ macroscopic contacts created by conventional optical lithography to buried nanoscale Si:P devices, patterned by hydrogen-based scanning tunnelling microscope (STM) lithography. Using SiO₂ as a mask we are able to protect the silicon surface from contamination during marker fabrication and can achieve atomically flat surfaces with atomic-resolution imaging. The registration markers are shown to withstand substrate heating to ∼1200 °C and epitaxial overgrowth of ∼25 nm Si. Using a scanning electron microscope to position the STM tip with respect to the markers, we can achieve alignment accuracies of ∼100 nm, which allows us to contact buried Si:P structures. We have applied this technique to fabricate P-doped wires of different widths and measured their I–V characteristics at 4 K, finding ohmic behaviour down to a width of ∼27 nm.

Anatase single-crystal nanotubes were obtained using an in situ templated method. First, highly ordered titania arrays were formed through an anodization process in H₃PO₄ electrolytes containing 0.5 wt% HF. Under optimized conditions titania nanotubes with a diameter of up to 100 nm and a length of up to 1.1 µm were prepared. Second, the crystallization and stability of the titania nanotubes were studied in air at elevated temperatures. Anatase single-crystal nanotubes were fabricated after annealing the sample in air at 450 °C. The anatase single-crystal structure was verified by selected area diffraction pattern and HRTEM images.

Well-aligned ZnO nanowires were successfully synthesized on a silicon substrate at the low temperature of 550 °C by catalyst-free vapour phase deposition. The ZnO nanowires had diameters in the range of 70–100 nm and lengths over several tens of micrometres. The synthesized ZnO nanowires, which had a single-crystalline wurtzite structure, showed a uniform morphology and faceted planes at the tips of the nanowires. The photoluminescence of the ZnO nanowires showed a strong UV band at 3.28 eV and a broad green band at 2.29 and at 2.53 eV at room temperature. A detailed discussion regarding the growth behaviour and the growth mechanism of the ZnO nanowires on the silicon substrate is presented in this work.

Flower-shaped ZnO nanostructures were grown on Si(100) and Si(111) substrates by cyclic feeding chemical vapour deposition without the use of a metal catalyst. The structures obtained on the Si(100) substrate exhibited triangle-shaped leaves with lengths and diameters in the ranges 300–400 and 90–130 nm, respectively. Uniformly shaped leaves with hexagonal facets originating from one centre were observed on the flower-shaped structures grown on the Si(111) substrate. Transmission electron microscopy and selected area electron diffraction patterns showed that these structures are highly crystalline, with the wurtzite hexagonal phase, and preferentially oriented in the c-axis direction. Unlike star-shaped ZnO nanostructures grown on Au-coated silicon substrates, the flower-shaped nanostructures showed sharp and strong UV emission at 378 nm and broad and weak green emission at 520 nm, indicating a good crystal quality and few structural defects.