Table of contents

In 1959, Richard Feynman pointed out that nanometre-scale machines could be built and operated, and that the precision inherent in molecular construction would make it easy to build multiple identical copies. This raised the possibility of exponential manufacturing, in which production systems could rapidly and cheaply increase their productive capacity, which in turn suggested the possibility of destructive runaway self-replication. Early proposals for artificial nanomachinery focused on small self-replicating machines, discussing their potential productivity and their potential destructiveness if abused. In the light of controversy regarding scenarios based on runaway replication (so-called 'grey goo'), a review of current thinking regarding nanotechnology-based manufacturing is in order. Nanotechnology-based fabrication can be thoroughly non-biological and inherently safe: such systems need have no ability to move about, use natural resources, or undergo incremental mutation. Moreover, self-replication is unnecessary: the development and use of highly productive systems of nanomachinery (nanofactories) need not involve the construction of autonomous self-replicating nanomachines.

Accordingly, the construction of anything resembling a dangerous self-replicating nanomachine can and should be prohibited. Although advanced nanotechnologies could (with great difficulty and little incentive) be used to build such devices, other concerns present greater problems. Since weapon systems will be both easier to build and more likely to draw investment, the potential for dangerous systems is best considered in the context of military competition and arms control.

The controlled deposition of functional layers is the key to converting nanomechanical cantilevers into chemical or biochemical sensors. Here, we introduce inkjet printing as a rapid and general method to coat cantilever arrays efficiently with various sensor layers. Self-assembled monolayers of alkanethiols were deposited on selected Au-coated cantilevers and rendered them sensitive to ion concentrations or pH in liquids. The detection of gene fragments was achieved with cantilever sensors coated with thiol-linked single-stranded DNA oligomers on Au. A selective etch protocol proved the uniformity of the monolayer coatings at a microscopic level. A chemical gas sensor was fabricated by printing thin layers of different polymers from dilute solutions onto cantilevers. The inkjet method is easy to use, faster and more versatile than coating via microcapillaries or the use of pipettes. In addition, it is scalable to large arrays and can coat arbitrary structures in non-contact.

We present an approach to building defect-tolerant, nanoscale compute fabrics out of assemblies of defective crossbars of configurable FETs and switches. The simplest structure, the complementary/symmetry array, can implement AND-OR-INVERT functions, which are powerful enough to implement general computation. These arrays can be combined to create logic blocks capable of implementing sum-of-product functions, and still larger computations, such as state machines, can be obtained by adding additional routing blocks. We demonstrate the defect tolerance of such structures through experimental studies of the compilation of a small microprocessor onto a crossbar fabric with varying defect rates and compiler mapping parameters.

Carbon nanofibres have been proposed as a possible new orthopaedic/dental implant material due to their unique mechanical, electrical, and cytocompatibility properties. Specifically, these fibres have dimensions (diameters ranging between 60 and 200 nm and aspect ratios of about 500) similar to hydroxyapatite crystals and collagen fibres found in bone. More importantly, previous in vitro studies have provided evidence that nanophase ( nm diameter) carbon fibres enhance osteoblast (the bone-producing cell) function over conventional (>100 nm diameter) carbon fibres and current orthopaedic implant materials such as titanium, Ti6Al4V, and CoCrMo. However, articulating components of orthopaedic implant materials may generate harmful wear debris. To determine, for the first time, the influence of carbon nanofibre wear debris on osteoblast viability, direct contact toxicity studies were performed in the present in vitro study. Not surprisingly, the results from direct-contact toxicity studies over a 24 h time period provided evidence of time- and concentration-dependent cell viability decreases when exposed to carbon nanofibres. Most importantly, the results from this study provided the first evidence that nanophase carbon fibres were less detrimental to osteoblast viability compared to larger diameter conventional carbon fibres. For this reason, this in vitro study provided continuing evidence of the promise of nanophase materials (particularly, carbon nanofibres) in improving orthopaedic implant efficiency.

With an increasing demand for ultra-high-density information storage, patterned media have received much attention as a solution to overcome the limits of conventional continuous magnetic media. One of the current methods to fabricate the patterned media is to use direct patterning and etching. However, those procedures are very costly and are not suitable for mass production. In this study, we investigate the possibility of mass production of patterned media by nano-moulding technology with a metallic nano-stamper. The physically and chemically resistant metallic nano-stamper was fabricated using an electroforming process, and then the nano-patterned substrate was replicated using a nano-moulding process without additional etching. For evaluation of the replication quality, a magnetic layer was deposited on the substrate. We finally confirmed that the magnetic islands were successfully formed as a single magnetic domain on the nano-patterned substrate.

Frequency dependent electrical transport in the conducting networks of single walled carbon nanotubes embedded in polymers was studied by scanning impedance microscopy (SIM). SIM allows current flow in the nanotubes inside the polymer matrix at up to 100 nm below the surface to be imaged directly, providing a non-invasive approach for studying transport in these materials. The conductance of the composite is shown to be limited by a small number of bundle–bundle and bundle–contact junctions. For high frequencies, the SIM phase distribution along the networks is governed by the capacitive interaction between the nanotubes and the substrate and is in agreement with a transmission line model. For low driving frequencies the capacitive coupling to the back gate can be minimized and an approach for determining the potential distribution along the network by accounting for tip–surface capacitance variations is demonstrated. Thus, SIM provides a direct method for characterizing electrical transport through percolation networks formed by nanotube bundles in polymers or, more generally, nanorods in various matrices.

We report a new approach for fabricating layer-by-layer (LBL) structured ultrathin hybrid films on electrospun nanofibres. Oppositely charged anatase TiO₂ nanoparticles and poly(acrylic acid) (PAA) were alternately deposited on the surface of negatively charged cellulose acetate (CA) nanofibres using the electrostatic LBL self-assembly technique. The fibrous mats were characterized by wide-angle x-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy and Brunauer–Emmett–Teller (BET) surface area techniques. The crystalline phase of anatase TiO₂ remained unchanged in the resultant TiO₂/PAA films coated on CA fibrous mats. Moreover, the TiO₂/PAA film coated fibres showed rough surfaces with grains due to the deposition of aggregated TiO₂ particles. The average diameter of the fibres increased from 344 to 584 nm and the BET surface area of the fibrous mats increased from 2.5 to 6.0 m² g⁻¹ after coating with five bilayers of TiO₂/PAA films.

InP and GaP nanowires have been synthesized from an Ullmann-like reaction of elemental indium and gallium with triphenyl phosphine at about 350–400 °C for 8 h. The as-prepared samples have been structurally characterized by powder x-ray diffractometer (XRD), x-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), high-resolution TEM, energy dispersive x-ray spectroscopy (EDS), GCT-MS, FTIR and ¹H-NMR. XRD, electron diffraction patterns and HRTEM images show that the nanowires have the zinc blende structure based on a vapour–liquid–solid growth mechanism.

The recently introduced torsional resonance mode (TR mode) technique has been applied for friction force measurements at the micro/nanoscale. In this technique, an atomic force microscope (AFM) with a vibrating cantilever tip in torsional mode is used, and the contact torsional vibration amplitude of the tip motion (TR amplitude) is monitored at a contact resonance frequency under constant normal load. In this paper, the TR mode friction force images are compared to the friction force images acquired by conventional contact mode friction force microscopy on three samples: a self-assembled monolayer (SAM) with two phase structure, a silicon ruler, and a metal evaporated (ME) tape. The results from those samples show that the TR mode friction force images are much less affected by the surface topography and are almost independent of the scanning direction of the tip, whereas this is not the case for the contact mode friction force measurements. Mechanisms responsible for these observations are also discussed in the paper. In order to predict coefficient of friction as a function of the change in the TR amplitude, an energy balance model is proposed.

The thermal conductivities of three types of single-wall carbon nanotubes are studied using the homogeneous non-equilibrium Green–Kubo method based on the Brenner potential. The thermal conductivity of a carbon nanotube is found to have dependence on its chirality. The thermal conductivities of three types of nanotube seem to have similar temperature dependence. The thermal conductivity of the chiral nanotube is lower than that of the other two types of nanotube.

A new synthesis of Bi(0) nanoparticles is reported. A low temperature solution phase reduction of BiCl₃ with t-BuONa activated sodium hydride at 65 °C has been successfully used to prepare large quantities of colloidal Bi(0) nanoparticles with a diameter in the range 1.8–3.0 nm. The resulting Bi nanoparticles were characterized using transmission electron microscopy, XPS analysis and x-ray powder diffraction.

This paper describes a simple solution route to ZnS nanotubes assisted by CNTs and to ZnS hollow nanospheres by templating with in situ generated bubbles at low temperature. Two types of nanotube exist. One has two open ends with a very thin wall; the other has a sealed end with a thicker wall. The hollow nanospheres have uniform thickness of  nm and they formed dynamically controlled by the quantity of water. HREM results reveal that the nanotubes and hollow nanospheres are both composed of ZnS nanoparticles. The UV–vis absorption spectra exhibit large blue shifts because of quantum size effects. These hollow structures may have potential applications in some areas.

We report on the controlled growth of novel self-assembled nanostructures (nanoaeroplanes, nanocombs, and tetrapod-like networks of zinc oxide) by a simple thermal evaporation technique in a single-stage furnace. Scanning electron microscopy and transmission electron microscopy are used to investigate their morphologies and structures. Shapes are regular and unit sizes vary from 80 nm to 5 µm. The relationship between the preparation conditions and the nanomorphologies in the experiments is helpful for controlling the physical properties of the nanosystems and, hence, is described in some detail. A possible growth mechanism is discussed.

We employed nanoimprint lithography and soft moulding techniques to print one-dimensional nanostructures with submicron periodicity onto organic films made of different light-emitting materials. We studied and compared the emission and absorption of the chromophores before and after the lithography processes, demonstrating that the lithography techniques actually preserve the optical properties of light-emitting molecules. In particular, we investigated the photoluminescence efficiency, finding that all our patterned light-emitting materials show enhanced luminescence emission (up to a factor larger than two) with respect to the untextured film, as a consequence of the printed nanostructure. This is ascribed to the decrease of the self-absorption path induced by the grating-enhanced forward scattering.

We report the self-assembly and characterization of amorphous SiO_x nanospheres with diameters 210–240 nm. The preparation method was based on hydrolysation-induced self-assembly with Na₂SiO₃ as the silica precursor and polyacrylamide gels as the template. Ultraviolet and blue–green photoluminescence were observed at room temperature from amorphous SiO_x nanospheres. The photoluminescence spectrum has peaks at 400 and 530 nm. From the x-ray photoelectron spectroscopy and energy disperse x-ray spectroscopy we found that the atomic ratio of Si to O is about 1:2.1. From the infrared spectrum and x-ray photoelectron spectroscopy, we suggest that the origin of the stable emission is Si–OH complexes located on the surface of the nanospheres. The silica nanospheres may have potential applications in future integrated optical devices.

Silver nanoshells on styrene–acrylic acid copolymer latex spheres (PSA) were deposited by an in situ chemical reduction method, ageing a colloid solution at 85 °C containing PSA latex, AgNO₃, urotropine, and poly-(vinylpyrrolidone). SEM and TEM observations showed that the silver nanoshells were made of closely packed silver nanoparticles of different sizes and morphologies. UV–visible absorption spectra were recorded to investigate their optical properties.

We present a theoretical investigation of the interaction of intrinsic localized modes with plasmons. The anharmonic localized modes for a 1D diatomic lattice are determined using a two-body potential which describes the interactions among particles in a zinc-blende structure material. The localized mode frequency is inside the gap between acoustic and optical phonons. Calculations have been performed for GaN because it has a large phonon gap, can be highly n-doped, and the plasma frequency of free carriers is in the range of phonon and intrinsic localized mode frequencies. To study the coupling we add to the equations of motion an electric field to simulate the plasmon. Solving the system we obtain the dynamical displacements pattern from which we evaluate the total polarization. From the polarization we determine the frequency of the combined mode for which the dielectric function is zero. In this investigation we have analysed both the case of small localized mode amplitudes and the case of larger amplitudes, obtaining different behaviour. In the first case the mixed mode has a frequency above the top of the optical branch, which can be explained in terms of the theory of the harmonic dielectric response of polar lattice vibrations. In the second case the coupled mode exists only for a finite slab, and its frequency is inside the phonon gap.

In this paper, we report a novel method of fabricating patterned magnetic metal alloy CoCrPt nanodots via selective ion etching using a self-organized array of spherical domains of an ordered block copolymer (PS-b-PMMA) film as a template. Reactive ion etching and Ar⁺ ion milling were controlled accurately to avoid excess etching and pattern loss in the etching processes. The nanodot arrays had a dot density as high as approximately 10¹¹ dots cm⁻², and the magnetic hysteresis loops showed that the coercivity of the isolated CoCrPt dots made using the self-assembled block copolymer was considerably higher than that of the continuous magnetic film. The present method is applicable to other magnetic metals.

The optical absorption coefficient of an inhomogeneous quantum dot system is calculated analytically and numerically. The quantum dots are approximated as spheres whose surfaces constitute infinite potential barriers, with a size distribution described by a Gaussian function. The effects of size nonuniformity on the optical absorption spectrum of quantum dot systems are analysed. The effects of shape are also discussed through the comparison of these results to those relating to cubic quantum dots. It is shown that the optical absorption spectrum of spherical quantum dots depends strongly on the dot size distribution and that, although the curves obtained for cubic and spherical quantum dots with comparable volumes are similar, there are differences in the relative energy positions and relative intensities of the optical absorption peaks.

Ni nanoplatelets were prepared through the reduction reaction with hydrazine by the sonochemistry method. The obtained Ni nanoplatelets are single-phased Ni and have a face-centred cubic crystal structure. The lattice constant is slightly larger than the corresponding bulk value. The Ni nanoplatelets are plate-like in shape and have an average diameter of 100 nm and an average thickness of 10 nm. An oxidation layer is found on the nanoplatelet surface and this serves to prevent further oxidation. The surface oxidation layer leads to the reduction of the saturation magnetization of the Ni nanoplatelets compared with the bulk value. Magnetic hysteresis loops along different directions deviating from the nanoplatelet plane are obviously different, indicating that the easy-axis is in the in-plane direction and the magnetization reversal is incoherent mode. The micromagnetic simulation results for an array composed of 36 Ni nanoplatelets are in agreement with the measured data.

Nanoscale Au/Fe₂O₃ catalysts for CO oxidation were prepared by a deposition–precipitation technique using the thermal decomposition of urea. Freshly precipitated amorphous Fe(OH)₃ was used as a support. The resulting products were characterized by transmission electron microscopy and x-ray powder diffraction. The catalysts in the 'as prepared' state demonstrated exceptionally high activity toward CO oxidation. Compared to conventional coprecipitation with the same amount of gold precursor, the deposition–precipitation method was shown to produce more active catalysts because it allows complete precipitation of gold from solution.

A novel class of moire fringe patterns in scanning tunnelling microscope (STM) imaging is presented and analysed in this paper. The moire fringe is generated from the interference of the atomic lattice of the specimen and STM scanning lines. Both parallel and rotational STM moire fringes of the surface of highly oriented pyrolytic graphite (HOPG) are investigated. The formation principle and experimental techniques of STM moire fringes are discussed. Nanometre scale resolution and sensitivity are found in the moire fringe patterns. They precisely magnify the STM image of lattice irregularities. A potential application—measuring surface deformation and defects in the nanometre range—is proposed.

Several techniques have already been developed for synthesizing silicon carbide (SiC) material in the form of nanospheres and nanowires/rods. Here, we report the synthesis of a distinctly different kind of SiC nanostructure in the form of three-dimensional crystalline nanowire-based flower-like structures. Interest in such structures centres around the combination of a simple growth process based on SiC nanowire formation, with a resultant structure having potentially complex mechanical and optical properties, the latter a consequence of the wide band gap of bulk SiC. The synthesis of these SiC nanowire flowers is via a vapour–liquid–solid (VLS) process, on which a detailed study of both the chemical and structural composition has been carried out.

Using first-principles calculations, we investigate the comparative stability of sub-0.4 nm carbon nanotubes. Compared to the fullerenes C₂₀ and C₆₀, it is found that the most likely carbon nanotubes with a small diameter 0.3 nm are (2,2),(3,1) and (4,0) nanotubes. The spontaneous symmetry breaking of an isolated (2,2) nanotube produces an energy gap at the Fermi level converting it into a semiconductor. The curvature effects lowered the π^* band to cross the Fermi energy, leading to the (4,0) nanotube being metallic.

Non-filled MgO nanotube bundles have been fabricated via a thermal evaporation method using Mg strips as the source material. The samples were characterized using x-ray diffraction, scanning electron microscopy and transmission electron microscopy. The as-synthesized nanotubes self-assembled into bundles, and the nanotubes in a bundle had the same growth direction. The nanotubes are about 100 nm in diameter and several micrometres in length. The possible growth process for the MgO nanotube bundles has been discussed.

In this paper a unified quantum correction charge model for nanoscale single- and double-gate MOS structures is presented. Based on the numerical solution of Schrödinger–Poisson equations, the developed quantum correction charge model is mainly optimized with respect to (i) the left and right positions of the charge concentration peak, (ii) the maximum of the charge concentration, (iii) the total inversion charge sheet density, and (iv) the average inversion charge depth, respectively. For nanoscale single- and double-gate MOS structures, this model predicts inversion layer electron density for various oxide thicknesses, silicon film thicknesses, and applied voltages. Compared to the Schrödinger–Poisson results, our model prediction is within 2.5% of accuracy for both the single- and double gate MOS structures on average. This quantum correction model has continuous derivatives and is therefore amenable to a device simulator.

The true residual area measured from atomic force microscopy (AFM) images can subsequently be used to recalculate the hardness of the material measured by nanoindentation more accurately. In this study, nanoindentation with non-contact AFM has been used to investigate the mechanical properties of thin CN films deposited by RF magnetron sputtering on silicon (100) substrates. Micro Raman spectroscopy was used to measure the structural properties of the CN film. The hardness was determined at different loads and depths from nanoindentation using conventional analysis by the well known Oliver and Pharr method. The indents were imaged using AFM, and true residual contact areas as well as hardness values were determined. The hardness values obtained by AFM agreed with the hardness measured by the Oliver and Pharr method.

We study submicron organic field effect transistors with a pentacene channel, and observe either p-type or n-type behaviour under different gate and drain voltage conditions. Transistor structures of 0.8 µm channel lengths were fabricated by evaporating Au on a tilted substrate, featuring an oxide step. When evaporating pentacene on the step structure, the edge of the oxide step is used as a shadow mask to ensure the gap between source and drain. Current–voltage characteristics reveal that positive gate voltages increase the drain current, when the lower Au contact is operated as drain electrode, indicating electron transport through the channel. When the upper Au contact is used as a drain, the devices display p-type behaviour. These ambipolar device characteristics are explained in the light of electron injection enhanced by the submicron geometry, and by electron transport in the presence of electron traps.

The minimally invasive elimination of tumours using heating as a therapeutic agent is an emerging technology in medical applications. Particularly, the intratumoural application of magnetic nanoparticles as potential heating sources when exposed to an alternating magnetic field has been demonstrated. The present work deals with the estimation of the basic relationships when the magnetic material has access and binds to structures on cell membranes of target cells at the tumour region, particularly as a consequence of administration through tumour supplying vessels. Therefore, using mouse endothelial cells in culture, the binding of dextran coated magnetic nanoparticles (mean hydrodynamic particle diameter 65 nm) was modelled using the periodate method. The efficacy of cell labelling was demonstrated by magnetorelaxometry (MRX)—a selective method for the detection of only those magnetic nanoparticles that were immobilized—as well as by electron microscopy and iron staining. The amount of iron immobilized on cells was found to be 153 ± 56 µg Fe per 1 × 10⁷ cells as determined by atomic absorption spectrometry. Moreover, after exposure of those 1 × 10⁷ labelled cells to an alternating magnetic field (frequency 410 kHz, amplitude 11 kA m⁻¹) for 5 min, temperature increases of 2 °C were achieved. The consequences of particle immobilization are reflected by the results of the measurements related to the specific heating power (SHP) of the magnetic material. Basically, the heating potential is explained by the superposition of Brown and Neél relaxation while for immobilized nanoparticles the Brown contribution is absent. In the long term the data could open the door to targeted magnetic heating after further optimization of the heating potential of magnetic material as well as after functionalization with biomolecules which recognize specific structures on the surface of cells at the target region.

Cyanoacrylate–carbon nanotube arrays are prepared by embedding carbon nanotube (CNT) arrays grown on silicon substrate in cyanoacrylate adhesive. Upon laser treatment, enhanced field emission properties are obtained. Moreover, the binding force between the carbon nanotubes and the substrate is strengthened by the cyanoacrylate adhesive. When the field emission current is large enough at high electric field, the carbon nanotubes cannot be pulled out of the substrate by electric field force. A large field emission current can be obtained from cyanoacrylate–carbon nanotube arrays at relatively low voltage just by decreasing the distance between the anode and the cathode.

We have investigated the in situ isothermal nanocrystallization kinetics of binary Al₉₂Sm₈ glassy alloy using time-resolved x-ray diffraction. From diffraction spectra parameters we have calculated the mean grain size and crystalline phase volume fraction. The results show that the average grain size does not change by more than 15% of its initial value in the course of the nanocrystallization process. The first nanocrystals contributing to the crystalline phase signal are characterized by a mean crystal size of 11 nm which increases up to 13 nm at the end of the primary crystallization stage. These results are in agreement with a TEM analysis. Our observations indicate the very significant difference in growth rate of small and large clusters. Further, they show that the transformation kinetics is governed by the nucleation rate. We conclude that diffusion controlled growth plays a minor role in the overall transformation kinetics. Possible origins of the observed crystallization behaviour are given.

In this contribution we analyse the structural and optical properties of ZnO as well as ZnMgO nanopillars grown catalyst-free by metalorganic vapour-phase epitaxy.

The nanostructures were grown directly onto different substrate materials with various orientations. The nanopillars deposited on a-plane sapphire show the best vertical c-axis alignment and have a typical diameter of about 50 nm and a height of several micrometres, depending on growth time. We achieved well ordered, almost completely c-axis oriented pillars, as confirmed by scanning electron microscopy and high resolution x-ray diffraction. Photoluminescence measurements revealed very narrow donor-bound exciton emission lines with half widths as small as 0.5 meV. In order to investigate the possibility of a combination of band gap engineering and nanopillar growth, ZnMgO nanopillars were also grown. The Mg incorporation was confirmed by photoluminescence measurements and a blue shift of the band gap of up to 170 meV could be achieved for the nanopillars with the highest Mg concentration.

Highly conductive nanoscale deposits with solid gold cores can be made by electron beam deposition in an environmental scanning electron microscope (ESEM), suggesting the method to be used for constructing, connecting and soldering nanostructures. This paper presents a feasibility study for such applications. We identify several issues related to contamination and unwanted deposition, relevant for deposition in both vacuum (EBD) and environmental conditions (EEBD). We study relations between scan rate, deposition rate, angle and line width for three-dimensional structures. Furthermore, we measure the conductivity of deposits containing gold cores, and find these structures to be highly conductive, approaching the conductivity of solid gold and capable of carrying high current densities. Finally, we study the use of the technique for soldering nanostructures such as carbon nanotubes. Based on the presented results we are able to estimate limits for the applicability of the method for the various applications, but also demonstrate that it is a versatile and powerful tool for nanotechnology within these limits.

Magnetic Ni–Cu alloy nanocrystallites with a diameter of about 12 nm have been prepared by a hydrothermal approach with polymer–surfactant complex association at 80 °C. XRD, TEM and ICP-AES were employed to characterize alloy nanocrystallites. The magnetic properties of alloy nanocrystallites were measured using a vibrating sample magnetometer (VSM). The influences of polymer–micelle association, temperature and concentration of micelles on the formation of alloy are discussed. Polymer–micelle association provides a way for Ni and Cu to be reduced simultaneously and then occupy the Cu lattice to form Ni–Cu alloy nanocrystallites.

Palladium nanoparticles with low polydispersity were fabricated by thermally-induced reduction of Pd(fod)₂ in o-xylene in the presence of tetraalkylammonium salts as the surfactants. The particle size, ranging from 6.2 to 18.5 nm, can be controlled by variation of the surfactant, and the concentrations of precursor and surfactant. Self-assembly of the Pd nanoparticles in closest packing was observed in this study.

After discussing experimental works on the measurement of the conductance of a metal–molecule–metal tunnel junction with many down to a few molecules and down to only one molecule in the junction, we propose a comprehensive way of understanding the electron transport phenomenon through such a junction. The dependence of the junction conductance on the length of the molecule(s) is explained starting from the quantum super-exchange electron transfer phenomenon up to the effective mass of the tunnelling electrons in the coherent limit. This super-exchange mechanism results from the electronic coupling between the two electrodes introduced by the molecule(s). The molecular wire guides this interaction better than the electronic coupling through vacuum between the two electrodes of the junction. Dephasing and thermal effects during the electron transfer events along the molecular wire are described using a density matrix formalism. The implication of our understanding of this through junction electronic transport is described starting from hybrid molecular electronics towards mono-molecular electronics.

The limitation aspects of nanofocusing recording probes are discussed in this paper. The definitions of nanophotonics and nanofocusing are underlined. In this nano-age optical nanophenomena are described for nanometric architectures and nanostructural photonic devices. The nanofocusing probe limitations are connected with the wave-optics diffraction limit, geometrical beam tiny focusing, electromagnetic wave design, fabrication errors, nanoprobe energetic efficiency, near-field air gap and optical disk surface conditions. The micro-structure of the designed near-field optical head is discussed. The obtained nanofocused spot size is about 20 nm for the near-field space. The computed finite differential time domain (FDTD) power density spot is under 200 nm without any optical optimization. The far-field functions have a diffraction limit of 150 nm. The energy intensity can be elevated by more than 70 times in the FDTD calculated focal point using a convex microlens (ML) surface for focusing of a 8 µm vertical-cavity surface-emitting laser (VCSEL) beam. The optical power density is compressed up to 1024 times to the exact nanofocused spot in comparison with the entrance VCSEL micro-beam. The experimentally fabricated ML arrays and single lenses are presented. The optical quality and ML radius control with an AFM method is fulfilled. The optical integration technology for the proposed nanofocusing probe fabrication is announced. The nanofocusing probe spots are 10–13 nm for the central zone of the ML surface. The merit spot sizes are 10–18 nm for the entire ML nanofocusing diameter. For a single ML nanofocusing near-field head the energy spots have sizes from 9 to 15 nm, limited by technological aberrations.

Block copolymer-based membrane technology enables the development of a versatile class of nanoscale materials in which biomolecules, such as membrane proteins, can be reconstituted. These active materials possess a broad applicability in areas such as the enhancement of existing technologies or production of current-generating films for power sources. For example, these active materials can be integrated with fuel cell ion transport membranes such as Nafion^® in order to improve the ability of Nafion^® to retain leaking protons. Also, the demonstration of protein-driven current production across these membranes represents a possible alternative power source that is both highly efficient and light in weight. Our work has demonstrated the fabrication of large-area copolymer biomembranes that are functionalized by bacteriorhodopsin (BR) and cytochrome c oxidase (COX) ion transport proteins. Among their many advantages over conventional lipid-based membrane systems, block copolymers can mimic natural cell biomembrane environments in a single chain, enabling large-area membrane fabrication using methods such as Langmuir–Blodgett (LB) deposition. Following the large-scale insertion of proteins into block copolymer LB films, we have demonstrated significant pH changes based upon light-actuated proton pumping. Protein activity across the BR and COX-functionalized membrane has also been observed using impedance spectroscopy as well as direct current measurement.

Single-walled carbon nanotubes are candidates for a number of electronics and sensing applications, provided nanotubes with semiconducting and metallic band structure can be separated. Dielectrophoresis has recently been demonstrated as a route towards the separation of metallic nanotubes from semiconducting nanotubes, and is moreover a method for controlled assembly of the nanotubes on microstructures that has the possibility to be scaled to wafer-level manufacturing. In this paper we will present numerical calculations of carbon nanotubes subjected to dielectrophoresis, drag force and Brownian motion induced by application of an ac voltage to a set of microelectrodes in a microliquid channel. We calculate the probability of capturing various types of carbon nanotubes, the time frame for the assembly and the efficiency of separation, for different experimental parameters. Our results suggest that relatively low frequencies, where both semiconducting and metallic nanotubes are subject to positive dielectrophoresis, may be optimal for separation, due to large differences in the magnitude of the dielectrophoretic force.

A method of transferring a bilayer of polymer capped with metal to a substrate is developed with a mould that is coated with a metal followed by a polymer. A self-assembled monolayer chemisorbed on the mould surface plays a key role in the bilayer transfer. This bilayer reversal imprint lithography offers a distinct advantage over other imprint techniques in allowing for a high aspect ratio of the pattern transferred onto a substrate, which has been difficult to obtain for small feature sizes. The method requires only one etching step as opposed to the two etching steps typically needed in the imprint lithography, which can degrade the pattern fidelity.

The photoluminescence properties of mercaptocarboxylic acid-stabilized CdSe nanoparticles were modified by coating with polyelectrolyte. With a concentration of the positively charged polyelectrolyte poly(diallydimethyl-ammonium chloride) (PDDA) of 0.45 and 1.14 g l⁻¹, the intrinsic emission of CdSe nanoparticles was enhanced up to 31 times, with a simultaneous enhancement of the trap emission, and the stability of the CdSe nanoparticles was also enhanced dramatically. The negatively charged polyelectrolyte PSS had no effect on the intrinsic and trap emission of CdSe nanoparticles.

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