Table of contents

A method is described for designing nanoparticle agglomerate films with desired film porosity and film thickness. Nanoparticle agglomerates generated in aerosol reactors can be directly deposited on substrates to form uniform porous films in one step, a significant advance over existing technologies. The effect of agglomerate morphology and deposition mechanism on film porosity and thickness are discussed. Film porosity was calculated for a given number and size of primary particles that compose the agglomerates, and fractal dimension. Agglomerate transport was described by the Langevin equation of motion. Deposition enhancing forces such as thermophoresis are incorporated in the model. The method was validated for single spherical particles using previous theoretical studies. An S-shape film porosity dependence on the particle Peclet number typical for spherical particles was also observed for agglomerates, but films formed from agglomerates had much higher porosities than films from spherical particles. Predicted film porosities compared well with measurements reported in the literature. Film porosities increased with the number of primary particles that compose an agglomerate and higher fractal dimension agglomerates resulted in denser films. Film thickness as a function of agglomerate deposition time was calculated from the agglomerate deposition flux in the presence of thermophoresis. The calculated film thickness was in good agreement with measured literature values. Thermophoresis can be used to reduce deposition time without affecting the film porosity.

A novel synthetic route for nearly monodispersed poly(methyl methacrylate)/SiO₂ composite particles (PMSCP) is reported. Silica nanoparticles modified with oleic acid were used as 'seeds'. Methyl methacrylate (MMA) monomer was copolymerized with oleic acid via in situ emulsion polymerization, in the presence of an initiator; it resulted finally in the formation of composites with core–shell morphology. The composite particles were examined by transmission electron microscopy (TEM), scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA). The number of silica particles inside the composite particles increases with an increase in the silica concentration. The effect of grafted silica concentration on the morphology of PMSCP is also reported in detail. It was found by thermogravimetric analysis that PMSCP show a potential application for fire retardance.

Formation of nano-fibres ranging from 30 to 300 nm in diameter and exceeding the length of one millimetre was observed during explosive ablation of As₂S₃ glass by femtosecond pulses at high fluence (>5 J cm⁻²) irradiation of the 800 nm wavelength, 160 fs duration pulses in air. Spheres of up to several microns in diameter were also found to form, competing with nano-fibre formation and significantly deteriorating their morphology. Theoretical analysis of thermo-capillary and heat exchange mechanisms of the fibre formation predicts conditions under which the good nano-fibre morphology can be preserved.

We demonstrate a new method for preparing metal sulfide nanocrystals using alkyl thiols as a sulfur precursor. Alkyl thiols have many advantages for practical synthesis because they are miscible with most organic solvents and very stable under an air atmosphere. CdS nanocrystals were made with CdO and thiols with different alkyl chains such as n-octanethiol and octadecanethiol. They exhibited uniform size, highly crystalline structure and a sharp photoluminescence spectrum. Also, CdSe/CdS core/shell nanocrystals can be prepared by single injection of a mixture consisting of alkyl thiol and Se in trioctylphosphine to a Cd precursor. A reaction scheme is proposed as alkyl thiols react with the metal precursor to form stable metal thiolate intermediates during the initial period of reaction, and the thiolate decomposes slowly to form homogeneous nuclei.

The controllable growth of vertically aligned ZnO nanowires using a simple vapour deposition method system is reported. The growth properties are studied as a function of the thickness of the Au catalyst layer, total pressure, deposition temperature and oxygen partial pressure. The experiments indicate the existence of five main zones of growth. The zone in which the aligned wires grow varies according to the pressure, temperature and oxygen partial pressure. A specific level of low supersaturation of Zn and oxygen vapour are both necessary to ensure the correct rate of growth, which then leads to having thin and densely aligned wires. The growth kinetics are discussed in terms of the interdependent variables. It was found that the diameter and density of the nanowires is controlled mostly by the growth temperature and pressure. The zone with the most aligned nanowires with the highest aspect ratio was found to be at 5 mbar in a temperature range of 860–800 °C with a flow of 27 sccm of a N₂/O₂ mixture.

The mechanical and dynamical properties of a model Au(111)/thiol surface system were investigated by using localized atomic-type orbital density functional theory in the local density approximation. Relaxing the system gives a configuration where the sulfur atom forms covalent bonds to two adjacent gold atoms as the lowest energy structure. Investigations based on ab initio molecular dynamics simulations at 300, 350 and 370 K show that this tethering system is stable. The rupture behaviour between the thiol and the surface was studied by displacing the free end of the thiol. Calculated energy profiles show a process of multiple successive ruptures that account for experimental observations. The process features successive ruptures of the two Au–S bonds followed by the extraction of one S-bonded Au atom from the surface. The force required to rupture the thiol from the surface was found to be dependent on the direction in which the thiol was displaced, with values comparable with AFM measurements. These results aid the understanding of failure dynamics of Au(111)-thiol-tethered biosurfaces in microfluidic devices where fluidic shear and normal forces are of concern.

Ethylenediamine-modified multi-walled carbon nanotubes (MWNTs-NH₂) were prepared and characterized with a Fourier transform infra-red (FT-IR) spectrometer and a transmission electron microscope (TEM). Meanwhile, the electrochemical behaviour of Cu²⁺ ions (aq) on the electrodes coated with MWNTs-NH₂ was investigated by using cyclic voltammetry. The results show that the electrodes coated with MWNTs-NH₂ exhibit high sensitivity to Cu²⁺ ions (aq) with a detectable concentration of 1 × 10⁻¹⁰ mol dm⁻³. As compared with the bare indium-doped tin oxide (ITO) electrodes, the sensitivity to Cu²⁺ ions of the electrode coated with MWNTs-NH₂ is enhanced by four orders, implying that the carbon nanotubes modified with functional groups may be used in the fabrication of highly sensitive sensors to detect trace Cu²⁺ ions (aq).

We report the synthesis of tungsten oxide W₁₈O₄₉ nanowires by thermal evaporation at low temperature without using catalysts. By placing tungsten powder in the high temperature zone at 650 °C and tungsten substrate in the low temperature zone at 400 °C of a tube furnace, W₁₈O₄₉ nanowires with diameters of 10–50 nm are produced with high yield. The nanowires extend to 500–1500 nm length, and the cross-sectional shapes are circular or polygonal. The roles of the source material, the pre-oxide layer on the substrate and the temperature of the reactor are also investigated. It is shown that the presence of oxygen on the W surface is essential for tungsten oxide nanowire growth.

A solution phase method has been used to synthesize triangular and hexagonal Ni nanosheets with different edge lengths by controlling the reaction kinetics. This procedure is realized by introducing Fe(CO)₅ into the reaction system to slow the formation rate of Ni(0). The introduced Fe(CO)₅ exists as Fe(III) ions in the solution, which could oxidize Ni(0) back to Ni(II). By controlling the nucleation density, the sheet edge lengths could be changed from 19 nm to several hundreds of nanometres. The Ni nanosheets exhibit the transition from superparamagnetism to ferromagnetism with increasing sheet edge lengths. Their blocking temperature decreases with applied field and increasing sheet edge lengths. The Ni nanosheets also exhibit a surface plasmon resonance (SPR) feature, which is quite different from that of the Ni nanoparticles.

We report on the field emission properties of tungsten oxide nanowires grown on a tungsten tip and its emission performance in various vacuum conditions. Tungsten oxide (W₁₈O₄₉) nanowires were grown by thermal chemical vapour deposition in a mixture of CH₄ and H₂ on an electrochemically sharpened tungsten tip. The field emission measurements showed a low threshold field of ∼0.95 V µm⁻¹, high emission current of 170 µA and a large field enhancement factor of ∼19 800. High emission current of a few µA was also observed in relatively poor vacuum at 3 × 10⁻³ Torr, and the emission properties were recoverable at 1 × 10⁻⁶ Torr.

Dense arrays of aligned carbon nanotubes are designed into strips, nanowicks, as a miniature wicking element for liquid delivery and potential microfluidic chemical analysis devices. Liquid wicks away along the nanowicks spontaneously. This delivery function of nanowicks enables novel fluid transport devices to run without any power input, moving parts or external pump. Flow around the opaque nanotubes can be detected either directly or indirectly. Direct signals of the flow come out of dyed liquid or from the liquid–air interface; indirect signals are detected through observing surface-tension-induced deformation and dislocation of the nanotubes. Here we show that flow progression around and inside nanowicks is sensitive to liquid properties. Different flow progression leaves different traces of liquid. These traces not only allow liquid diagnosis any time after sampling, but also enable analysis of flow at a nanoscale resolution with scanning electron microscopy.

In this study, distinct regions of trapped charges on glass substrates created by electron beam bombardment were utilized to attract and to immobilize DNA molecules. The negatively charged DNA molecules were attracted by the positive charge layer beneath the substrate surface resulting from escape of secondary electrons. With this mechanism, we demonstrated high-precision patterning of unmodified DNA molecules, independent of the length, sequence, and number of DNA strands, and with an attachment to the glass surface strong enough to withstand vigorous washing with water. DNA patterns with the line width of 50 nm were achieved.

ZnO nanorod-based single quantum well heterostructures were fabricated in a two-step process. Nanorods were first grown using vapour transport. Subsequently, high-quality ZnO/Zn_0.85Mg_0.15O heterostructures were grown on the nanorods using molecular beam epitaxy. The nanorods are well aligned along the c-axis of ZnO, as indicated by a very narrow rocking curve full width at half maximum. Quantum confinement was clearly observed within the ZnO well for different well widths. The quantum wells show photoluminescence peaks with a full width at half maximum as small as 15 meV.

Layered La₂Ti₂O₇ nanosheets were prepared through a one-step hydrothermal method at low temperature. The concentration of NaOH mineralizer plays an important role in the synthesis. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images show that the thickness of every nanosheet is about 5–10 nm, while the planar dimension is more than 1 µm. The photo-catalytic activities of the nanosheets were characterized by the decolourization of methyl orange solution and the evolution rate of H₂. The results demonstrated that the La₂Ti₂O₇ nanosheets possess significantly improved photocatalytic properties in water purification and evolution rate of H₂ from water–ethanol solution compared with those of samples prepared by conventional solid-state reaction.

The n-ZnO single nanowire/p⁺-Si heterojunctions are fabricated using two types (A and B) of ZnO nanowires. Both types of nanowires are synthesized using the vapour phase transport method. Nanowires A, with growth direction along the high index, are grown on Si substrates. Nanowires B, with growth direction along [0001], are grown on In_0.2Ga_0.8N substrates. The electrical transport properties of nanowires A and B are investigated by fabricating single nanowire field effect transistors. The measured resistivities are 0.06 and 0.001 Ω cm, respectively. Sharp UV emission resulting from free exciton recombination in ZnO nanowire is observed in the electroluminescence spectra from both types of n-ZnO single nanowire/p⁺-Si heterojunctions.

A simple technique for fabricating single nanowires with well-defined position is presented. The process implies the use of a silicon nitride mask for selective electrochemical growth of the nanowires in a porous alumina template. We show that this method allows the realization of complex nanowire patterns as well as arrays of single nanowires with a precise position and spacing.

The results on the synthesis, microstructure, structure and DC magnetization studies of nanocomposite Zn,Ni ferrite/NiO powder obtained by thermal decomposition of acetylacetonato complexes are reported in this paper. According to the results obtained by inductively coupled plasma optical emission spectroscopy (ICP-OES) element analysis and multiphase Rietveld refinement, the three samples made are composed of spinel-ferrite (86.7%–96.7%) and NiO (3.3%–13.3%) phases. The compositions of the spinel-ferrite (SP) phase in the investigated samples, S1–S3, are Zn_0.72Ni_0.24Fe_1.98O₄, Zn_0.56Ni_0.29Fe_2.07O₄ and Zn_0.40Ni_0.40Fe_2.10O₄, respectively. Due to the cation deficiency in spinels, created vacancies induce a partial change in the cation valence, . The vacancy distribution is found to be random at 8a and 16d cation sites, except in sample S3, where all vacancies are over octahedral sites. The x-ray line broadening due to crystallite size effect is found to be isotropic for all spinels, while the x-ray line broadening due to the strain effect is anisotropic. A correlation between the Zn²⁺ occupancy of the tetrahedral site and the 650 cm⁻¹ Raman peak intensities is shown. The observed coercivity decrease and shift in hysteresis loop in the samples are caused by the interaction between spinel and NiO phase. The results of M(H) measurements point to the properties of an ensemble of interacting nanoparticles. High saturation magnetization values and superparamagnetic behaviour at room temperature point to the technological significance of the title compounds.

In this paper, we describe an easy procedure for the preparation of differently shaped and sized Au–Ag nanocomposites from gold nanorod (AuNR) seeds in various amino acid solutions—arginine (Arg), cysteine (Cys), glycine (Gly), glutamate (Glu), glutamine (Gln), histidine (His), lysine (Lys), and methionine (Met), respectively—at values of pH ranging from 8.0 to 11.5. Our results suggest that the pH, the nature of the amino acid, and its concentration all have significant impact on the preparation of Au–Ag nanocomposites; these factors exhibit their effects mainly through control over the reducing ability of ascorbate and/or its recognition capability, as well as through control over the surface charges of the amino acids on the AuNRs. Depending on the value of pH, we were able to prepare I-shaped, dumbbell-shaped, and/or sphere-shaped Au–Ag nanocomposites in 0.1 M solutions of Arg, Gly, Glu, Gln, Lys, and Met. In His solutions at pH 8.0 and 9.0, we obtained peanut-shaped Au–Ag nanocomposites. Corn-shaped Au–Ag nanocomposites were prepared in 0.1 M Met solutions (pH 9.0 and 10.0). By controlling the Lys concentration at pH 10.0, we synthesized pearl-necklace-shaped Au–Ag nanoparticles and Au–Ag wires. Based on the TEM images, we conclude that this simple and reproducible synthetic approach allows preparation of high-quality (>87%, beside>77% in His solutions) Au–Ag nanocomposites with various shapes and sizes under different conditions.

Nanocomposites are a promising new class of structural materials for the mechanical components of microelectromechanical systems (MEMS). This paper presents a detailed theoretical investigation of the utility of carbon nanotube-reinforced composites for designing actuators with low stiffness and high natural frequencies of vibration. The actuators are modelled as beams of solid rectangular cross-section consisting of an isotropic matrix reinforced with transversely isotropic carbon nanotubes. Three different types of nanotube reinforcements are considered: single-walled carbon nanotubes (SWNTs), multi-walled carbon nanotubes (MWNTs) and arrays of SWNTs. The effects of nanotube aspect ratio, dispersion, alignment and volume fraction on the elastic modulus and longitudinal wave velocity are analysed by recourse to the Eshelby–Mori–Tanaka theory. The calculated bounds on Young's modulus and wave velocity capture the trend of the experimental results reported in the literature. Polymer–matrix nanocomposites reinforced with aligned, dispersed SWNTs are identified as excellent candidates for microactuators and microresonators, with properties rivalling those of monolithic metallic and ceramic structures used in the current generation of MEMS. A qualitative comparison between the state-of-the-art in nanocomposite manufacturing technology and the predicted upper bound on Young's modulus and longitudinal wave velocity highlights the enormous improvements needed in materials processing and micromachining to harness the full potential of carbon nanotube-reinforced composites for microactuator applications. These results have immediate and significant implications for the use of nanotube composites in MEMS.

In this work, we used co-sputtering of noble metals together with polytetrafluorethylene (PTFE) as a method for producing antibacterial metal/polymer nanocomposite coatings, where the precious metals are only incorporated in a thin surface layer. Moreover, they are finely dispersed as nanoparticles, thus saving additional material and providing a very large effective surface for metal ion release. Nanocomposite films with thickness between 100 and 300 nm were prepared with a wide range of metal filling between 10 and 40%. The antimicrobial effect of the nanocomposite coatings was evaluated by means of two different assays. The bactericidal activity due to silver release from the surface was determined by a modification of conventional disc diffusion methods. Inhibition of bacterial growth on the coated surface was investigated through a modified proliferation assay. Staphylococcus aureus and S. epidermidis were used as test bacteria, as these species commonly cause infections associated with medical polymer devices. The antibacterial efficiency of the coatings against different bacteria was demonstrated at extremely small noble metal consumption: Au: ∼1 mg m⁻² and Ag: ∼0.1 g m⁻². The maximum ability for having an antibacterial effect was shown by the Ag–Au/PTFE nanocomposite, followed by the Ag/PTFE nanocomposite.

In-plane anisotropic nanostructures have been fabricated using deep ultraviolet (UV) lithography. Dimensions from over 100 nm down to 50 nm with periods of 300 nm for a diamond shape and 159 nm for a triangular shape can be obtained using one mask by the over-exposure technique. Patterns transferred to a substrate to create magnetic films containing dots and antidots have been demonstrated. Hysteresis loop measurements proved higher coercivity for patterned films compared with continuous film.

Selective epitaxial growth was used to fabricate narrow Si/Ge/Si pillar nanostructures in small holes in ultrathin oxide (UTO) on Si(100). The self-assembled holes with diameters of 5–30 nm were obtained by in situ partial removal of the UTO at high temperature. The UTO formation and the annealing process were optimized for a high density of holes. The SiGe nanopillars were grown with sizes determined by the initial hole diameter in the UTO. Crystalline Ge dots embedded in oxide were formed by oxidation of the pillar nanostructures. High-resolution transmission electron microscopy (HRTEM) was used to study the pillar nanostructures and the dot shapes before and after oxidation. Capacitors obtained with the oxidized samples showed a hysteresis in their C–V curves attributed to charge retention in the Ge dots embedded in the oxide.

The ubiquitous static friction (stiction) and adhesion forces comprise a major obstacle in the manipulation of matter at the nanoscale (Falvo et al 1999 Nature397 236; Urbakh M et al 2004 Nature430 525). In this work it is shown that a surface coated with vertically aligned carbon nanotubes—a nanotube forest—acts as an effective non-stick workbench for the manipulation of micro-objects and fibres/wires with one or more dimensions in the nano-range. These include organic nanofibres (Balzer and Rubahn 2001 Appl. Phys. Lett.79 3860) and microsized latex beads, which adhere strongly even to a conventional low surface-energy material like Teflon. Although organic nanofibres are attractive as device components due to their chemical adaptability, adhesion forces nearly always rule out manipulation as a route to assembly of prototype devices based on such materials, because organic materials are soft and fragile, and tend to stick to any surface. We demonstrate here that the nanotube forest due to its roughness not only exhibits very low stiction and dynamic friction; it also acts as a springy and mechanically compliant surface, making it possible to lift up and manipulate delicate nanostructures such as organic nanofibres in ways not possible on planar, rigid surfaces.

High yield hausmannite (Mn₃O₄) nanorods with diameters of about 100 nm and lengths up to 15–20 µm have been prepared by vacuum calcining of the precursor (Mn₃O₄+MnOOH), which was hydrothermally prepared by the reaction of PEG-20000 and KMnO₄ at 180 °C for 20 h. Transmission electron microscopy and the selected-area electron diffraction pattern reveal that these Mn₃O₄ nanorods show single-crystal growth along the [100] direction. The PEG-20000 and the calcination conditions have key effects on the morphology and phase purity of the product. Magnetism measurements show that the blocking temperature for these Mn₃O₄ nanorods is 41 K, which agrees with the bulk material value, whereas the remnant magnetization and coercivity are 0.89 μ_B and 6177 Oe respectively.

This work reports a newly developed synthesis method, i.e., a self-seeding coreduction method, for shape control of silver nanoparticles such as triangular nanoplates and circular nanodiscs. By this method, high surface-to-volume silver nanoplates (∼2.3 nm in thickness) were successfully generated. The distinct advantages of this method include no need to add external seeds, no need to use organic solvents that are environmentally unfriendly, being able to perform at room temperature, and synergetic use of a few reducing agents for better growth control of two-dimensional nanostructures. In particular, molecular dynamics simulation is used to quantify the interaction energies between surfactant molecules and different facets of silver crystal. Such molecular information, together with measurements using x-ray diffraction (XRD), transmission electron microscopy (TEM), atomic force microscopy (AFM) and ultraviolet–visible (UV–vis) spectroscopy, has proven to be useful in understanding the growth mechanisms of silver nanoplates.

Highly oriented ZnO nanoneedle arrays were electrochemically prepared by anodization of zinc foil in a freshly prepared zincate saturated aqueous solution at room temperature. Typically, the needles have a length of 550–650 nm with a tip diameter of 10–15 nm and a root diameter of 50–60 nm, and grow along their [001] direction. The crystal structure of the ZnO nanoneedles was confirmed by scanning and transmission electron micrographs, x-ray diffraction patterns and photoluminescence spectra.

Based on the integral theorems for mean curvature and Gauss curvature, geometric conservation laws for perfect Y-branched carbon nanotubes are presented. From the conservation laws, simple geometric regulations observed by spontaneous Y-branched carbon nanotubes are revealed, i.e. the angle between two neighbouring branches should be 120° and the radii of the three branches should be equal. These results coincide well with all experimental facts without exceptions. Possible applications of the geometric regulations to the design of super carbon nanostructures with self-similarities are predicted.

Fabrication of silver nanowires on a domain-patterned lithium niobate template by inducing a photochemical reaction in an aqueous solution is reported. Silver deposition occurs preferentially along the domain boundaries which separate antiparallel domains. The nanowires can reach lengths of hundreds of micrometres, and their location can be controlled by generating domain patterns of a desired configuration while their width depends on deposition conditions, such as temperature, solution concentration and ultraviolet (UV) light exposure time. The selective deposition process is explained by a combination of the inhomogeneous distribution of the electric field in the vicinity of the domain wall and the polarization screening mechanism of the template material. Controllable and selective deposition of metal species onto nanoscale domain-patterned ferroelectric templates may provide an alternative bottom-up route to lithographic fabrication methods.

We report the growth and structural properties of hollow-opened ZnO/Zn and solid Zn/ZnO single crystal microspheres on a silicon (111) substrate. The microspheres were synthesized from ZnO mixed with Zn by chemical vapour deposition. The ZnO/Zn microspheres exhibit a hollow interior and a spherical shell with a partly opened mouth along the c-axis of the hexagonal wurtzite ZnO structure oriented vertically to the substrate. The Zn/ZnO microspheres are solid. The microsphere growth process includes the deposition of Zn and ZnO particles followed by the evaporation of Zn from the breaking shell of the ZnO microparticles. The break in the shell is caused by the evaporation of Zn. The morphologies, chemical composition and crystal structure of the microspheres were characterized using x-ray diffraction, energy dispersive x-ray spectroscopy, field-emission scanning electron microscopy, transmission electron microscopy and high-resolution transmission electron microscopy. The room-temperature photoluminescence spectra were investigated using a 325 nm He–Cd laser as the excitation source.

We report the fabrication of 30 nm pitch nanowire array imprint moulds by spatial frequency doubling a 60 nm pitch array generated by electron beam lithography. We have successfully fabricated nanowire arrays at a 30 nm pitch, which is targeted for the year 2020 by the International Technology Roadmap for Semiconductors, with an average line-width of 17 nm and a 3σ line width roughness (LWR) of 4.0 nm. In contrast to previously reported procedures, our spatial frequency doubling technique produces electrically isolated nanowires that are appropriate for crossbar circuits.

We report the preparation and characterization of Si nanoislands grown on a c-Si substrate by thermal annealing of silicon-rich oxide (SRO) films deposited using a conventional low pressure chemical vapour deposition (LPCVD) technique. Transmission electron microscopy revealed that a high density of Si nanoislands was formed on the surface of the c-Si substrate during thermal annealing. The nanoislands are nanocrystallites with the same crystal orientation as the substrate. The strain at the c-Si/SRO interface is probably the main reason for the nucleation of the self-assembled Si nanoislands that epitaxially grow on the c-Si substrate. The proposed method is very simple and compatible with Si integrated circuit technology.

Hybrid organic/inorganic white light-emitting diodes (LEDs) were fabricated of semiconductor polymer poly(N-vinylcarbazole) (PVK) doped with CdSe/CdS core–shell semiconductor quantum dots (QDs). The device, with a structure of indium–tin-oxide (ITO)|3,4-polyethylene–dioxythiophene–polystyrene sulfonate (PEDOT:PSS)|PVK:CdSe/CdS|Al, emitted a pure white light spanning the whole visible region from 400 to 800 nm. The Commission Internationale del'Eclairage coordinates (CIE) remained at x = 0.33,y = 0.34 at wide applied voltages. The maximum brightness and electroluminescence (EL) efficiency reached 180 cd m⁻² at 19 V and 0.21 cd A⁻¹ at current density of 2 mA cm⁻², respectively. The realization of the pure white light emission is attributed to the incomplete energy and charge transfer from PVK to CdSe/CdS core–shell QDs.

Superhydrophobic surfaces have considerable technological potential for various applications due to their extreme water-repellent properties. A number of studies have been carried out to produce artificial biomimetic roughness-induced hydrophobic surfaces. It is not clear whether microstructures or nanostructures or their certain combination on the surface, are required for superhydrophobicity. A variety of micro- and nanopatterned surfaces of two different polymers, poly(methyl methacrylate) (PMMA) and polystyrene (PS), were fabricated. We show how static contact angles vary with micro- and nanopatterns on the polymer surfaces. Based on the experimental data and a numerical model, the trends are explained. Tribological properties play an important role in many applications requiring water-repellent properties. Therefore, it is important to study the adhesion and friction properties of these surfaces that mimic nature. An atomic/friction force microscope (AFM/FFM) was used for surface characterization and adhesion and friction measurements. To further examine the effect of meniscus force and real area of contact, scale dependence is considered with the use of AFM tips of various radii. The effect of relative humidity is also investigated to study the environmental effects on adhesion and friction.

Magnetism of a very thin antiferromagnetic (AFM) surface CuO has been investigated with partially oxidized nanocomposites of Cu–CuCl, ∼200 nm. The samples are characterized by x-ray diffraction, x-ray photoelectron spectroscopy, x-ray-excited Auger electron spectroscopy, transmission electron microscopy and magnetic measurements. The characterizations indicate that the composites have a core–shell structure. Before oxidation, it is (Cu)_core/(CuCl)_shell, and after oxidation it is (Cu)_core/(Cu₂O+CuCl+minute CuO)_shell. The magnetic measurements have revealed that a ferromagnetic (FM)-like open hysteresis exists at temperatures below the freezing point, T_F. In the high field region, a paramagnetic (PM) response appears without showing any sign of saturation. Also, the field dependent magnetization (M–H) measurement is PM-like at T>T_F. These interesting magnetic properties are shown to arise from the AFM CuO on the outer surface. They are attributed to the uncompensated surface spins of Cu²⁺ and the effect of random surface potential. More interestingly, the magnetic susceptibility is greatly enhanced in the presence of Cl⁻ anions at T<T_F, according to the field-cooled/zero-field-cooled (FC/ZFC) measurements. This further supports the point that the disorder or frustration effect of the impurity would reduce the AFM ordering of CuO and increase the level of uncompensated spins.

Silicon nanowire interconnects are dielectrophoretically assembled, reconfigured, and disassembled between gold electrodes in benzyl alcohol. Assembly of up to 55 µm long nanowires is demonstrated. Conductance enhancement is observed in the presence of single nanowires trapped between submerged electrodes. Phase inversion of electrode potentials allows the reversible reconfiguration of nanowires, either serially or in parallel. For disassembly, high-voltage bursts are observed to detonate trapped nanowires. The reconfiguration of colloidal electronic nanostructures opens up the possibility of nanostructured connection architectures for computation.

A nanolithographic process is introduced based on the self-organization of gold salt loaded inverse micelles formed by poly(styrene)-block-poly(2-vinylpyridine) di-block-copolymers in toluene. The developed procedure allows the fabrication of hexagonally arranged cylindrical nanoholes (diameters ≥20 nm, aspect ratios ∼7) in crystalline as well as in amorphous Si. In the latter case, applying the concept to amorphous Si layers evaporated onto any substrate results in nanomasks allowing the transfer of the hole pattern into the substrate.

C-axis vertically aligned ZnO nanorod arrays were synthesized on a ZnO thin film through a simple hydrothermal route. The nanorods have a diameter of 30–100 nm and a length of about several hundred nanometres. The gas sensor fabricated from ZnO nanorod arrays showed a high sensitivity to H₂ from room temperature to a maximum sensitivity at 250 °C and a detection limit of 20 ppm. In addition, the ZnO gas sensor also exhibited excellent responses to NH₃ and CO exposure. Our results demonstrate that the hydrothermally grown vertically aligned ZnO nanorod arrays are very promising for the fabrication of cost effective and high performance gas sensors.

Novel spherical three-dimensional (3D) dendritic Bi₂S₃ /cross-linked poly(vinyl alcohol) (PVA) nanocomposites were successfully synthesized in aqueous solution of amphiphilic polyvinylacetone (PVKA) (ketalization degree D_H = 0.549), via one-step in situ decomposition of the complex [Bi(Tu)_x]³⁺ under γ-ray irradiation, utilizing the controllable hydrolysis property of PVKA in acidic solution. Herein, PVA chains are obtained from the hydrolysed PVKA. These uniform 3D spherical nanocomposites have a structure similar to that found in the natural lotus leaf, where every microscale papilla on the leaf surface is covered by nanoscale papillae.

In this paper, we demonstrate the potential of chemical vapour transport and condensation in tuning the architecture of a series of MgO nanostructures through adjusting experimental parameters. Different oxygen partial pressures lead to corresponding well-faceted nanostructures, such as nanowires, cubes, orthogonally branched structures and 'nanotrees', while nanotubes and 'nanoflowers' were formed through multi-step processes under modified experimental details. The synthesis roadmap may promote the in-depth understanding of the growth kinetics of nanostructures in vapour routes, and these intriguing nano-architectures may find various applications in nanotechnology.

Nickel phosphide (Ni₁₂P₅) hollow nanospheres with a mean diameter of 100 nm and a shell thickness of 15–20 nm have been successfully prepared by a hydrothermal-microemulsion route, using NaH₂PO₂ as a phosphorus source. XRD, EDS, (HR)TEM, SEM and the SAED pattern were used to characterize the final product. Experiments showed that the as-prepared nickel phosphide hollow nanospheres could selectively catalytically degrade some organic dyes such as methyl red and Safranine T under 254 nm UV light irradiation. At the same time, the nickel phosphide hollow nanospheres showed a stronger ability to promote electron transfer between the glass–carbon electrode and adrenalin than nickel phosphide honeycomb-like particles prepared by a simple hydrothermal route. A possible formation process for nickel phosphide hollow nanospheres was suggested based on the experimental results.

Composites of polyaniline with nanocrystalline maghemite capped with oleic acid were synthesized at various maghemite loadings and their electrical and magnetic properties were studied from 5 to 300 K. Chemisorption of oleic acid by the surface iron atoms provided excellent dispersion of maghemite in organic solvents and thus enabled their homogenous dispersion in the polymer matrix. The resulting nanocomposite materials exhibit properties of both the conductive matrix and the magnetic iron oxide component. Magnetoresistance studies indicated an increase in the resistance in the presence of an external magnetic field, while the absolute conductivity values decrease due to the addition of iron oxide nanoparticles.

A procedure for the fabrication of nano-structured micropatterns by direct UV photo-patterning of a monolayer of a self-assembled block copolymer/transition metal hybrid structure is described. The method exploits the selective photochemical modification of a self-assembled monolayer of hexagonally ordered block copolymer micelles loaded with a metal precursor salt. Solvent development of the monolayer after irradiation results in the desired pattern of micelles on the surface. Subsequent plasma treatment of the pattern leaves ordered metal nanodots. The presented technique is a simple and low-cost combination of 'top-down' and 'bottom-up' approaches that allows decoration of large areas with periodic and aperiodic patterns of nano-objects, with good control over two different length scales: nano- and micrometres.