Table of contents

This article is a thorough tutorial on the traditional approach to Bardeen's tunnelling theory in the context of scanning tunnelling microscopy. We follow Duke's interpretation of Bardeen's theory as the tunnelling analogue of Oppenheimer's perturbation theory for field ionization of atomic hydrogen. We explain Oppenheimer's ideas, Fermi's golden rule, and Bardeen's formulae; and we derive the celebrated Tersoff–Hamann formula using an argument due to Chen. Finally, we discuss the application of Bardeen's theory to scanning tunnelling microscopy beyond the Tersoff–Hamann approximation.

Molecular dynamics (MD) simulations of atomic-scale stick–slip have been performed for a diamond tip in contact with the (100) surface of fcc Ag, bcc Fe, Si and H-terminated Si, at a temperature of 300 K. Simulations were carried out at different support displacements between 5 and 15 Å. The simulations illustrate the important mechanisms that take place during stick–slip. In particular, for the case of the metals they show a direct link between tip slip events and the emission of dislocations from the point of contact of the tip with the substrate. This occurs both during indentation and scratching. For the case of silicon, no slip events were observed and no subsurface dislocations were generated underneath the scratch groove. At the deeper support displacement of 15 Å the silicon atoms undergo some local phase transformations and the atom coordination number varies between 5 and 8, with the majority being five-fold or six-fold coordinated. Both the dynamic and the static friction coefficients were found to be higher for Si compared to the corresponding values for H-terminated Si. Comparisons were made between the MD simulations and experimental measurements for indentation on the (100) surface of Si and Al. A good qualitative agreement was observed between the experimental and theoretical results. However, in both the cases of Si and metals the MD simulations give a contact pressure under load that is depth dependent and values that are higher than experimental nanohardness values.

Silica-coated anisotropic gold nanoparticles (Au@SiO₂), including rod- and 'dogbone'-like outlines with different aspect ratios, have been prepared using an improved Stöber method. The obtained Au@SiO₂ have a pure silica surface for straightforward and rapid self-assembly onto poly(4-vinylpyridine) (PVP) functionalized quartz substrates. The large-scale assemblies exhibit highly reversible optical changes that can be observed spectroscopically or with the naked eye when repeatedly cycled between a dry and wet process. The relationship among the optical properties of two-dimensional assemblies, the aspect ratio and shape of the gold nanoparticles and the environmental refractive index is also investigated.

The development of membrane protein reconstitution methods in polymersomes is regarded as a major challenge in replicating cellular functions in engineered cellular mimetic systems. We present a solvent-free membrane protein reconstitution method which can be used in polymersomes. To test our method, we reconstructed in vitro proton-powered ATP synthesis using engineered artificial organelles (BR/F₀F₁-ATP synthase reconstituted proteopolymersomes). We compared the functionality of BR and ATP synthase between two preparation methods. From the difference in the direction of proton pumping and the ATP production profile, it is evident that the relative orientation of BR can be determined by the condition of the proteins (BR monomer, purple membrane), together with the incorporation techniques. As the new procedure eliminates the problem of protein denaturation during incorporation, this research is expected to enhance the potential applications of synthetic membranes in the future fabrication of hybrid protein/polymer systems.

Low density InAs/InP(001) quantum dots, formed by the ripening of self-organized quantum sticks, are subjected to optical spectroscopy by photoluminescence and micro-photoluminescence. The presence of neutral multi-exciton states in single quantum dots is observed up to the 4X state. The large energy spacing between the s- and p-shells (90 meV) reveals the strong spatial confinement of carriers in such InAs/InP quantum dots. Micro-photoluminescence studies show that some dots are charged which allows us to measure the exchange energies in the InAs/InP quantum dots.

The possibility of a ferromagnetic semiconductor single-wall carbon nanotube (SWCNT), where ferromagnetism is due to coupling between a doped magnetic impurity on a zigzag SWCNT and electron spin, is investigated. We found in the weak impurity–spin couplings, at low impurity concentrations, the spin up electron density of states remains semiconducting while the spin down electron density of states shows a 2D semi-metallic graphene behaviour. By increasing impurity concentrations the semiconducting gap of spin up electrons in the density of states is closed, hence a semiconductor to semi-metallic disordered graphene phase transition takes place. In contrast, for the case of strong coupling, the spin up electron density of states remains semiconducting and that for spin down electrons has a semi-metallic 2D graphene behaviour. Also by increasing the magnitude of the spin impurity, the semiconducting gap of spin up electrons is increased.

In this paper we report for the first time, the photoconductivity of large area sheets of single wall carbon nanotube upon laser illumination. The photoconductivity exhibited an increase, decrease or even 'negative' values when the laser spot was on different positions between contact electrodes, showing a 'position' dependent effect of photoconductivity. Photon induced charge carrier generation in single wall carbon nanotubes and subsequent charge separation across the metal–carbon nanotube contacts is believed to cause the photoconductivity changes. A net photovoltage of ∼10 mV and a photocurrent of ∼1.6 mA were produced under the laser intensity of ∼160 mW with a quantum efficiency of ∼1.5% in vacuum. The effect of the contact area between the electrodes and nanotubes, ambient pressure, laser intensity and light pulse frequency on the photoconductivity is discussed.

CdS nanobelts and nanowires were successfully synthesized by simple thermal evaporation of CdS powder at a temperature as low as 650 °C, using pure H₂ as a carrier gas. The morphology of the products could be conveniently controlled by adjusting the deposition parameters. Electron microscopy studies of the materials showed that the single-crystalline CdS nanowires have a diameter of 200 nm and a length of tens of micrometres, and the nanobelts are 100–200 nm in width, 30 nm in thickness and tens of micrometres in length. High-resolution transmission electron microscopy demonstrated that the nanobelts, which are different from the nanowires growing along the direction, have three types of growth direction: , and . It is demonstrated that a reductive carrier gas, such as hydrogen, plays an important role in the whole growth process of CdS nanowires and nanobelts.

We report visible electroluminescence at room temperature in nanoporous TiO₂ films using solid-state heterojunction contacts. Electrons are injected from an n-type polymer layer, while hole injection occurs from a conductive SnO₂ substrate. As the polymer material penetrates into the TiO₂ nanopore structure a highly non-planar interface with a greatly enlarged area is created. This type of interface establishes very short current paths to the recombination region of the device and allows high carrier fluxes from the electron-injecting contact. The electroluminescence onset occurs at 7 V applied bias, and involves a broad emission band covering most of the visible region with a peak centred at 600 nm.

Carbon nanofibres (CNF) have been formed by polyethylene pyrolysis, using a Ni catalyst and a hydrogen–argon gaseous mixture. The temperature interval of 500–700 °C was chosen, because small sized Ni catalyst particles are formed in this case. TEM and high resolution TEM studies revealed catalyst particles of spherical, oval, conical and faceted shapes, some of which have been twinned. The variety of shapes and sizes can be explained by the different values of the surface tension forces in the catalyst and in graphite in the various cases. Unusual 'burst' CNFs, distinguished by the alternation of dense and sparse regions, have been found in the deposit. A model of a periodic process, based on the decay of Ni carbide, is assumed for the explanation of the 'burst' CNF formation.

We report on the growth of InAs quantum dots (QDs) on GaInAsP and InP buffers by metal–organic chemical vapour deposition on InP(100) substrates. Indium segregation and the As–P exchange reaction affect the QD nucleation and composition. The As–P exchange reaction has a more pronounced effect on the QDs grown on the InP buffer than on those grown on the GaInAsP buffer. A very thin (0.6 nm) GaAs interlayer grown between the buffer layer and the InAs QD layer consumes segregated indium and minimizes the As/P exchange reaction. Wavelength tuning from 1450 to 1750 nm covering the technologically important 1550 nm wavelength is also achieved for the InAs QDs grown with the thin GaAs interlayer.

Using photoinduced second-order non-linear optical methods, we have determined that monodisperse In₂O₃ nanocrystals of size ∼11–24 nm incorporated into poly(methyl methacrylate) (PMMA) matrices possess significant second-order optical susceptibilities up to 17 pm V⁻¹ at λ = 1.76 µm; this is almost one order higher than that of traditional nanolayers of In₂O₃. A substantial increase in the corresponding susceptibilities is dependent on a relatively high monodispersion of the nanocrystals. Calculations such as quantum chemical, molecular dynamics and band structure simulations of interfaces indicate that the principal role in the observed non-linear optical effects is played by interfaces on the borders separating the nanocrystals and the surrounding host polymer matrix. In order to clarify a role of the monodispersion and that of the surfaces, additional experiments were carried out using samples with a larger size-distribution of nanocrystals and highly polarized photopolymers of oligoethercrylates as the host matrix. A drastic decrease in the effective optical nonlinearity in these two cases further supports the crucial role of the nanointerfaces.

We report a method to modify Si nanostructures on Si(100) by Ar⁺ ion sputtering, which we call post ion milling, or PIM. The effect of PIM on the nanodot modification was found to strongly depend on the value of ion flux utilized. For the ion flux of 80 µA cm⁻² both the lateral and vertical dot sizes do not change significantly with the milling time, while for the ion flux of 15 µA cm⁻² these sizes are dramatically reduced. The effect of PIM is attributed to a surface morphology transition process from a starting steady surface state to a target one. However, the final steady state surface morphology is not necessarily identical to the target one, but influenced by both the starting and target surface morphologies. Our results indicate that, given sufficiently low ion flux and low ion energy, very small nanostructures can be readily achieved via PIM.

This paper describes a technique for the fabrication of ordered three-dimensional hierarchical nanostructures in polymer films via nanoimprint lithography. The hierarchical structure is obtained by a series of sequential imprinting steps, where smaller structures are imprinted on top of larger imprinted structures. Higher order hierarchy is achieved by sequentially adding imprinting steps. An important feature of this fabrication technique is that the subsequent imprinting is carried out at a temperature below the glass transition temperature of the polymer film and below the imprinting temperature of the preceding imprint without the assistance of any solvents or plasticizers. Various formats of hierarchical structures can be obtained by varying the mould geometries and mould orientations in the sequential imprinting. It is found that the secondary or higher-order imprints are enabled by a reduction in the modulus of the polymer after the primary imprinting.

The stable configurations of small fullerenes (C₂₀ and C₂₈) encapsulated inside single wall carbon nanotubes (SWNTs) of different diameters were investigated by molecular dynamics simulations. The interactions between carbon atoms were described by a combination of the many-body Brenner potential with the Lennard-Jones (LJ) potential. We observed that the filling of small fullerenes into nanotubes with diameters larger than 10.85 Å ((8, 8) SWNT) is an exothermic process. During the annealing process the fullerenes arrange themselves into complex phases, which may be one-(chain), two-(zigzag) or three-dimensional, depending on the tube diameter. This tube size dependence is very similar to that of C₆₀, which has been experimentally observed. A comparison with the prediction of the hard-sphere model also finds a satisfactory level of consistency, indicating the dense packing nature of fullerene configurations in SWNTs.

CdTe nanoparticles (CdTe-NPs) capped by 3-mercaptopropionic acid were synthesized and used to self-assemble (SA) with poly(allylamine hydrochloride) (PAH) layer-by-layer via electrostatic interaction to form luminescent multilayer films. Composite particles were prepared with polymer or SiO₂ beads as the core and PAH/CdTe-NP SA films as the shell. The composite particles were dissolved out of the core with tetrahydrofuran (THF) or HF to prepare hollow spheres, then treated with 1-ethyl-3-(3-dimethyl-aminopropyl)-carbodiimide hydrochloride (EDC) in aqueous solution to form stable hollow spheres with a crosslinked PAH/CdTe-NP shell. Both the crosslinked films and the hollow spheres with a high luminescence are very stable in aqueous solutions at a wide range of pH.

A laser-stimulated synthesis of large silver nanoaggregates consisting of hundreds or thousands of nanoparticles is investigated. It is shown that the morphology of the synthesized nanostructures can be controlled with light and monitored via the evolution of the colloid absorption spectra. A method is demonstrated that enables production of a significant number of metal nanoaggregates, which are of paramount importance for the subwavelength concentration of electromagnetic fields and the dramatic enhancement of nanoscale electromagnetically driven processes.

We report on the realization of a novel interdigitated cantilever array with electrostatic control of the shape of the interdigitated array. It consists of an array of SiO₂/metal double-finger cantilevers in a grating configuration together with an electrical connection part. The complete grating structure is fabricated with nanoimprint lithography, UV lithography and reactive ion etching. The patterns of the cantilever arrays are defined by nanoimprint lithography. The electrical contact pads are defined and aligned with the imprinted grating pattern by UV lithography. The two steps of reactive ion etching are optimized to get vertical sidewalls of the SiO₂ cantilevers and finally to release them from the Si substrate. By applying a bias, the shape of the cantilever array can be altered due to the electrostatic force. The dimensions of the cantilevers and the spacing between them are optimized to achieve the desired functional operating characteristics of the structures. Since the fabrication scheme is based on nanoimprint lithography, such electrostatically controlled periodic structures may be relatively easily and non-expensively realized in various configurations, allowing them to function as optical switching elements, electrical filters, mass sensors, etc.

Neural stem cells isolated from an adult rat's spinal cord were loaded with superparamagnetic gold-coated monocrystalline iron oxide nanoparticles (Au-MION) intended for use as contrast enhancers in magnetic resonance imaging (MRI). A dose-dependent attenuation of MRI signals was observed for Au-MION down to 0.001 µg Fe/µl and for nanoparticle-loaded clusters of only 20 cells. The labelled cells were infused into the spinal cord of anaesthetized rats and tracked by MRI at 1 h, 48 h and 1 month post-injection. Histological analysis revealed that MRI signals correlated well with gold-positive staining of transplanted cells. The present results show that Au-MION exerts powerful contrast-enhancing properties and may represent novel MRI labels for labelling and tracking the transplanted cells in vivo.

One-dimensional nanostructure growth behaves very differently on the ± (0001) polar surfaces of wurtzite ZnO, resulting in asymmetric growth in these two directions. In this report we show that by tuning the degree of supersaturation, the growth asymmetry can either be rationally utilized or broken to obtain single- or double-sided ZnO nanocombs, respectively. The nanowires grown on the two polar surfaces of the double-sided nanocombs are of comparable length, suggesting some kind of symmetric growth, but they are distributed on the two sides in an asymmetric manner. More interestingly, the two sides of the double-sided nanocomb exhibit distinct optical properties. Possible mechanisms are proposed to explain the growth and optical properties of the double-sided nanocombs.

We report the electrochemical growth of gold nanowires with controlled dimensions and crystallinity. By systematically varying the deposition conditions, both polycrystalline and single-crystalline wires with diameters between 20 and 100 nm are successfully synthesized in etched ion-track membranes. The nanowires are characterized using scanning electron microscopy, high resolution transmission electron microscopy, scanning tunnelling microscopy and x-ray diffraction. The influence of the deposition parameters, especially those of the electrolyte, on the nanowire structure is investigated. Gold sulfite electrolytes lead to polycrystalline structure at the temperatures and voltages employed. In contrast, gold cyanide solution favours the growth of single crystals at temperatures between 50 and 65 °C under both direct current and reverse pulse current deposition conditions. The single-crystalline wires possess a [110] preferred orientation.

In order to achieve better photocatalytic performance, rutile nanorods dispersed in anatase and brookite phases were synthesized from titanium isopropoxide (TIP) in a concentrated HNO₃ solution at room temperature (23 °C). X-ray diffraction results indicated that the percentage of rutile increased with increasing peptization time. Scanning electron microscopy and and high-resolution transmission electron microscopy measurements revealed that the nanosized titania particles mainly consisted of granular anatase and brookite, and rod-like rutile. It was interesting that the stability of the colloid increased with increasing nanoparticle concentration, and the tricrystalline titania showed a photocatalytic activity higher than that of pure anatase. These nanocrystals were applied onto cotton fabrics, and achieved a promising bactericidal photocatalytic activity and excellent protection against UV radiation.

Efficient field electron emission from ZnO nanoparticles synthesized by a chemical route has been observed. Nanostructures were synthesized in three different morphologies, namely needles, rods, and spheres. The field emission studies carried out in diode configuration show that the onset fields required to draw a current density of ∼0.1 µA cm⁻² from the needles, rods, and spherical particles were 2.3, 2.5, and 3.5 V µm⁻¹, respectively. The field emission current and applied field follow the Fowler–Nordheim (F–N) relationship. The observed results indicate that the field emission characteristics of chemically grown ZnO nanostructures are at par with those reported for solid–vapour phase grown ZnO nanostructures.

Quantum-dot cellular automata (QCAs) are increasingly becoming one of the most promising candidates for the alternative processing platform of the future. Since their advent in the early 1990s the required technological processes, as well as the QCA structures that implement the basic and functionally complete set of binary logic functions, have been developed. This paper, however, presents an extension of the (standard) binary quantum-dot cell that is focused on the enrichment of the cell's processing capabilities. It is shown that the newly introduced ternary quantum-dot cell can be used to represent three logic values and that only minor modifications of the corresponding binary QCA structures are required to implement the functionally complete set of Łukasiewicz ternary logic functions.

Bimetallic nanoparticles are becoming increasingly interesting in nanoscience and nanotechnology. They have applications in, for example, catalysis and sensors, high density magnetic storage, and optical filters. However, experimentally it is relatively difficult to obtain homogeneous distributions of bimetallic nanoparticles: not only is their size distribution broad but, of greater concern, their chemical composition is generally non-uniform. For many applications, it is also important that the nanoparticles order in a regular array. Here, we present a new method that allows the generation of a regular two-dimensional array of bimetallic Au–Pd nanoparticles with tunable size and composition. The method provides a unique model for studying size and composition effects in the physical and chemical properties of bimetallic nanoparticles.

Novel dendritic nanostructures, which are actually self-assemblies of nanoparticles of poly(vinyl alcohol) (PVA) coated Ag and/or Cu₂O, were controllably synthesized in an aqueous solution of amphiphilic polyvinylacetone (PVKA) (D_H = 0.549), via a one-step in situ reduction of Ag⁺ and Cu²⁺ under γ-ray irradiation, using the low hydrolysis rate of the PVKA in the dilute acidic solution. Subsequently, the hydrolysis of PVKA yields PVA chains.

Oxygen plasma treated multi-walled carbon nanotubes (MWCNTs) have been decorated with gold nanoclusters by thermal evaporation. Transmission electron microscopy (TEM) shows that the nature and extent of gold coverage can be varied by simultaneously changing the parameters used for the plasma treatment and the gold evaporation time. The evaporated gold clusters on oxygen plasma treated MWCNTs have a more dense distribution than the clusters evaporated on as-synthesized MWCNTs. Analyses of the valence band and the core levels by x-ray photoelectron spectroscopy (XPS) suggest poor charge transfer between the gold clusters and the MWCNTs.

Magnetic nanodiscs are fabricated by depositing cobalt onto 10–30 nm diameter silicon nanopillars, which were prepatterned using gold colloids as etch masks. The magnetic anisotropy energy of individual nanodiscs is studied by measuring the angular dependence of switching fields using the micro-SQUID technique. The Stoner–Wohlfarth model, describing the magnetization reversal by unifom rotation, is used to analyse the data. The switching astroids of pure Co exhibit a cubic magnetocrystalline anisotropy indicating that the Co crystallites are fcc. After controlled oxidation of the nanoparticles, the anisotropy is dominated by a defect-induced uniaxial anisotropy, which means that the anisotropy can be used as a quality gauge.

The growth and formation of Ge nanocrystals embedded into a silicon oxide (SiO₂) system synthesized by furnace annealing have been studied based on the Ge content of co-sputtered Ge–SiO₂ films. The influence of a silicon oxide diffusion barrier inserted between the co-sputtered film and the substrate on the formation of the Ge nanocrystals is also examined. We found that the effect of Si reduction on the Ge oxides plays an important role in the synthesis of Ge nanocrystals in co-sputtered Ge plus SiO₂ samples with high Ge oxide concentration (80%) relative to the elemental Ge concentration (20%). The oxide diffusion barrier influenced the distribution of the nanocrystals by preventing Ge from diffusing into the substrate such that nanocrystals were formed throughout the film. When the Ge concentration was much higher (75%) than the Ge oxide concentration, the contribution from the effect of Si reduction on the Ge oxides in the formation of the nanocrystals is not significant. Again, the oxide diffusion barrier was very effective in preventing Ge atoms from diffusing into the Si substrate, and significant coarsening of the nanoclusters was observed in these samples.

Ion-beam synthesized (IBS) samples, prepared with a low dose of iron ions and subjected to rapid thermal annealing (RTA) were studied. The samples were characterized with cross-sectional transmission electron microscopy (XTEM), including high-resolution electron microscopy (HREM) and far infrared transmittance (FIRT) spectroscopy. The formation of β-FeSi₂ nanocrystallites, with various shapes and sizes, in the Si matrix was revealed. The optical constants dispersions of the samples were obtained from the reflectance (R) and transmittance (T) spectra, taken between 0.38 and 1.2 eV. From these dispersions, the energy band diagram of the interface β-FeSi₂/Si was determined, and compared to those reported by other authors.

We present a new approach for fabricating isolated, sealed, high-density nanofluidic channel arrays using combinatorial-mould nanoimprint lithography. This method provides a directed stamping technique for fabricating micro- to nanoscale channel arrays from the simple combination of two grating moulds of the proper geometry. In this method, a thin polymer film is cast on a silicon grating mould and subsequently embossed with a second grating mould. The film, after it is patterned on both sides, is then stamped onto a substrate and etched with oxygen plasma to remove the suspended residue layer and isolate the nanochannels. We have successfully fabricated arrays of high-density nanochannels on silicon and indium tin oxide glass (ITO glass) with well-controlled dimensions (i.e. 250 nm square, in cross-section). Placing a nanochannel array in contact with an aqueous fluorescein solution fills the channels by capillary action, and the integrity of the seal formed by the nanochannel enclosures was verified by observing a significant contrast in the photobleaching rate under fluorescence microscopy.

This paper reports the hydrothermal preparation of a new lanthanide compound, nanorod GdOOH, its crystal structure and related photoluminescent properties. Pure phase Gd(OH)₃ nanorods were prepared through a hydrothermal method which later served as the precursor for GdOOH nanorods. HRTEM investigation showed a preferred growth along the c axis for the precursor. GdOOH nanorods were obtained simply by calcinating the precursor at 600 K. Rietveld refinement revealed that the newly found phase belongs to the monoclinic system, with space group P 2₁/m (No. 11); cell parameter a = 6.086(1) Å, b = 3.7289(8) Å, c = 4.3465(8) Å, and β = 108.79(1)°. HRTEM also showed the single crystalline nature of the GdOOH nanorods, with a preferred growth also along the c axis direction. When Eu³⁺ ions were introduced to GdOOH lattice sites which replace the original Gd³⁺ ions, a strong red emission centred at 615 nm was observed upon UV illumination, due to the intrinsic Eu³⁺ transition between⁵D₀ and⁷F configurations.

In this paper we report on the development of TiO₂ surface-residing electrospun nanofibres with controllable density of TiO₂ on the support fibre surface by means of an electrospinning technique and a sol–gel process. The TiO₂ precursor/PAN composite nanofibres were synthesized by electrospinning a polyacrylonitrile (PAN) solution containing TiO₂ precursors. Subsequently, an immersion of the electrospun composite nanofibres in deionized water led to the hydrolysis of the TiO₂ precursors. SEM, TEM and XRD pattern analyses demonstrated that TiO₂ was formed and resided on the nanofibre surface. On further calcining the hydrolysed nanofibres in air at 300 °C, TiO₂ could be conveniently converted into anatase without essentially changing the morphology of the hydrolysed nanofibres. Furthermore, surface photovoltage spectroscopy (SPS) confirmed that the TiO₂ surface-residing nanofibre nonwovens had a strong SPS response. It can be attributed that the surface residence of TiO₂ permits the transfer of the photogenerated electron originating from TiO₂ to ITO electrodes. Potential applications of the TiO₂ surface-residing nanofibres include filters, catalysis films and environmental pollution remediation films.

Carbon nanotubes (CNTs) are frequently torn away by the electric field during field emission, which usually results in device failure due to short circuit or discharge. An AFM cantilever is employed to measure the tensile force experienced by individual field-emitting CNTs, from which the Maxwell stress and the local E-field at the CNT tip can be derived. We found that CNTs always initiate field emission at the same tensile stress. The turn-on field strength, however, increased from 2 to 60 V µm⁻¹ as the anode–cathode distances decreased from 0.3 mm to several microns. Depositing a thin film of titanium on the CNT tip was shown to effectively decrease the turn-on voltage and stress, a result crucial to the fabrication of CNT-based field emission flat panel displays (FE-FPDs).

Single-crystalline nanostructured Zn_1−xMn_xS, a diluted magnetic semiconductor, was achieved via a simple vapour phase deposition on silicon substrates. Morphology, structure, and composition of the nanostructured Zn_1−xMn_xS were studied by using x-ray diffraction, transmission electron microscopy, and energy-dispersive spectroscopy. The nanostructured Zn_1−xMn_xS is composed of nanowires and nanobelts, which are quite flexible and free of defects. Both of them have smooth and straight surfaces with lengths over 10 µm. They possess cubic structure with a principal axis along their axes. The nanostructured Zn_1−xMn_xS exhibits paramagnetic behaviour. Photoluminescence study shows a blue band and a yellow band, which are due to the surface states and the transitions of Mn²⁺ (⁴T₁(G)–⁶A₁(S)), respectively. The growth of the nanostructured Zn_1−xMn_xS could be explained by a self-catalyst growth mechanism.

We report an alternative technique for the immobilization of biological species in the sub-100 nm range. The feasibility of attaching DNA to electron-beam-deposited diamond-like carbon nanodots has been demonstrated. The key point of this approach is that direct patterning of a glass substrate is combined with a resist-free technique. Compared with conventional writing approaches, the high-resolution method presented here is simple, flexible, and compatible with the manipulation of a wide range of biological species.

During the first steps of vacuum deposition of thin films, grains appear randomly on the substrate as isolated islands. To characterize the formation of grains in thin films, the melting temperature of grains is studied theoretically as a function of their size and shape. Assuming a liquid grain that is a portion of a sphere, during the liquid–solid transformation the nano-grains could solidify adopting a sphere, portion of sphere, tetrahedron, or parallelepiped shape. These cases are investigated here. The effect of stress on the melting temperature is also considered.

Holographic gratings have been fabricated in networked polyurethane acrylates with various cross-linking densities. It was found that low (f = 2) and high (f = 6) functionality monomers gave narrow and clean polymer–liquid crystal (LC) phase separation due presumably to the insufficient migration of LC molecules out of the polymer domains. However, the mechanisms leading to poor phase separation seem different, i.e., reaction at a slow rate for f = 2, and entrapment of LC molecules within highly networked polymer for f = 6. With intermediate monomer functionality (f = 3), relatively large channels with large LC droplets gave the greatest diffraction due to a large difference in refractive index between polymer and LC phases.

By means of in situ high-temperature scanning tunnelling microscopy (STM), the thermal stability of highly ordered artificial Al nanocluster arrays, so-called two-dimensional nanocluster crystals, on vicinal Si (111)-7 × 7 surfaces has been investigated. It was found that Al nanocluster crystals are stable below 500 °C. Above 500 °C, the Al nanocluster crystal transforms into a surface phase with singular triangle shapes on down-terraces (the down-step side of a terrace). However, on up-terraces (the up-step side of a terrace), Al nanoclusters can move on Si (111)-7 × 7 surfaces over a large distance and the Al nanocluster crystal retracts toward the phase until the bare Si (111)-7 × 7 surface is completely recovered on up-terraces. The thermally activated motion of Al nanoclusters was not observed apparently below 400 °C, though Al nanocluster crystals can be formed even at 200 °C. This indicates that it is atom diffusion, not cluster diffusion, which is responsible for the formation process of metal cluster crystals on Si (111)-7 × 7 surfaces.

A facile method is first reported to fabricate uniform octahedral nanoporous inorganic silica membranes with a highly ordered and rigid array structure. The size of these uniform membranes ranged from 23.2 to 154.7 nm. In order to improve the mechanical strength of membranes, calcination was necessary and could adjust the size of these membranes in a limited range. Pore size distributions were tested by the mercury intrusion method.

Molecular dynamics simulations have been employed to investigate the dynamic behaviour of an unsupported Co particle of about 5 nm in size. Surface effects induce a martensitic hcp-to-fcc phase transition at temperatures significantly lower than the one observed in the case of bulk systems. The transformation nucleates at the surface and is mediated by atoms with defective coordination. Under proper conditions, the crystalline arrangement undergoes an oscillating behaviour governed by fluctuations in the potential energy of atoms in the interior of the particle.

Because of their unique physical and chemical properties, vertically aligned carbon nanofibres (VACNFs) show promise in improving current analytical measurement techniques. Chemical functionalization schemes will be necessary to fully realize this promise. Functionalization of the VACNFs with biomolecules or other species can impart specific chemical or physical properties. We report on two methods for immobilizing biomolecules on the surface of VACNFs. One attachment scheme makes use of a class of heterocyclic aromatic dye compounds to specifically adsorb onto VACNFs. The second scheme involves covalently coupling biomolecules through cross-linking to carboxylic acid sites on the sidewalls of the carbon nanofibres. The observed adsorption and covalent coupling properties are consistent with the physical structure and chemical characteristics of the VACNFs.

Additive patterning processes of magnetic films grown using an ion-beam sputter (IBS) system designed to produce non-conformal films are described. The effects of the ion-gun beam current and Ar pressure on the sputtering rates and roughness of Ni₈₀Fe₂₀ and Co₇₀Fe₃₀ magnetic thin films are investigated using atomic-force microscopy (AFM) and the films' magnetic properties are measured using spatially resolved magneto-optical magnetometry. By tailoring the plasma solid angle, non-conformal film growth allows for simple additive patterning down to lateral dimensions ranging from a few microns to the deep-submicron regime, using templates defined by photolithography or electron-beam lithography, and shadow masks created using templated self-assembly. The magnetization reversal exhibited by patterned sub-200 nm nanodisc arrays with different lateral edge-roughness will be discussed.

A new procedure for the preparation of polymer/magnetic nanoparticle composites is described. Magnetite nanoparticles capped with methacrylate units were dispersed in a toluene solution of the monomer, and polymerization occurred after the addition of the initiator a^'-a-azo-iso-butyronitrile at reflux temperature. The structural properties were determined by infrared spectroscopy, x-ray diffractometry and transmission electron microscopy. The thermal properties of the resulting nanocomposite were studied extensively with modulated differential scanning calorimetry. An increase in the glass transition temperature was observed after the incorporation of the nanoparticles.

The industrially used flame synthesis of silica polymer fillers was extended to amorphous tricalcium phosphate (a-TCP) nanoparticles and resulted in a similar morphology as the traditionally used polymer fillers. Doping of poly(lactide-co-glycolide) (PLGA) with such highly agglomerated a-TCP was investigated for mechanical properties, increased in vitro biodegradation and the formation of a hydroxyapatite layer on the surface of the nanocomposite. PLGA films with particle loadings ranging from 0 to 30 wt% were prepared by solvent casting. Degradation in simulated body fluid (SBF) at 37 °C under sterile conditions for up to 42 days was followed by Raman spectroscopy, scanning electron microscopy (SEM), thermal analysis and tensile tests. The presence of nanoparticles in the PLGA matrix slightly increased the Young's modulus up to 30% compared to pure polymer reference materials. The nanoparticle doped films showed a significantly increased loss of polymer mass during degradation. Scanning electron microscopy images of doped films showed that the SBF degraded the PLGA by corrosion as facilitated by the incorporation of nanoparticulate calcium phosphate. Raman spectroscopy revealed that the deposition of about 10 nm sized hydroxyapatite crystallites on the surface of doped PLGA films was strongly increased by the addition of tricalcium phosphate fillers. The combination of increased hydroxyapatite formation and enhanced polymer degradation may suggest the use of such amorphous, aerosol derived a-TCP fillers for applications in non-load-bearing implant sites.

We have modelled NC-AFM imaging of organic molecules adsorbed on the MgO(100) and TiO₂(110) surfaces, to study whether molecules adsorbed at well determined surface sites could serve as markers for chemical resolution of surface species and possible mechanisms of adsorption and manipulation of such molecules with NC-AFM tips. We calculated images of perfect MgO and TiO₂ surfaces and considered the adsorption of the formate ion and 3-{4-[Tris-(3,5-di-tert-butyl-phenyl)-methyl]-phenoxy}-propionic acid (C₅₂H₇₂O₃) at the MgO(100) and TiO₂(110) surfaces, respectively, using several types of oxide tip models. The results demonstrate that using adsorption of even small molecules, such as formate, for identifying surface chemical species in NC-AFM images may not be practical. The interaction of hydrocarbon molecules with perfect oxide surfaces is weak and their adsorption should be aided by attaching special anchoring groups. Flat molecules can be identified by their shape, but simultaneous atomic resolution inside the molecule and on the substrate under the same imaging conditions is not feasible.

Silicon nanocrystals with well-controlled sizes below 5.0 nm at a number density up to 10¹² cm⁻² were directly grown in hydrogenated silicon oxide films by plasma-enhanced chemical vapour deposition using SiH₄, O₂ and H₂ as the precursor. For the immediate formation of silicon nanocrystals in deposits on a cold substrate, high-density hydrogen ions have to be maintained in the plasma. These innate silicon nanocrystals are found to be well isolated from each other and dispersed uniformly throughout the deposits. Intense visible photoluminescence was measured at room temperature from such samples, with the photon energy at about 1.67 eV being indifferent to the variation in particle size. The photoluminescence features can find a qualitative explanation in the nearly stabilized electronic states of silicon nanocrystals by Si = O surface-passivation.