Table of contents

We report the functionalization of individual ultra-short (20–80 nm lengths) single-walled carbon nanotubes (US-tubes) via in situ Bingel cyclopropanation. Upon chemical reduction (K°/THF) of bundled US-tubes, the bundling forces are electrostatically overcome to yield single, negatively charged US-tubes in solution. These single US-tubes can then be functionalized with malonic acid bis-(3-tert-butoxycarbonylaminopropyl) ester using Bingel chemistry (CBr₄/DBU) to yield 4–5 adducts nm⁻¹, as determined by x-ray photoelectron spectroscopy (XPS). The derivatized US-tubes remain as individuals after functionalization and charge quenching. Thermogravimetric analysis (TGA) and solid-state NMR spectroscopy confirmed covalent attachment of the adducts and indicated tight wrapping of the adduct arms about the US-tubes. The resulting debundled and derivatized US-tubes serve as a prototype single-molecule-like 'capsule' for the containment and delivery of medically-useful payloads.

We present a full process based on chemical vapour deposition that allows fabrication and integration at the wafer scale of carbon-nanotube-based field effect transistors. We make a statistical analysis of the integration yield that allows assessment of the parameter fluctuations of the titanium–nanotube contact obtained by self-assembly. This procedure is applied to raw devices without post-process. Statistics at the wafer scale reveal the respective role of semiconducting and metallic connected nanotubes and show that connection yields up to 86% can be reached. For large scale device integration, our process has to implement both wafer-scale self-assembly of the nanotubes and high transistor performances. In order to address this last issue, a gate engineering process has been investigated. We present the improvements obtained using low and high κ dielectrics for the gate oxide.

In this paper, we report a synthetic route to curved 3D microspheres assembled by TiO₂ nanorods, which were built from pure 1D TiO₂ nanocrystals through a solvothermal approach under controlled conditions. The method involves the reaction of titanium trichloride with urea in an n-butanol and water mixture at 150 °C assisted by a surfactant (span80). The decomposition of urea provided OH⁻ to form 1D TiO₂ nanostructures that further assembled giving rise to 3D microspheres.

This paper studies the transport phenomena of disordered systems in the thermal relaxation process by cluster impact on a solid surface. Constant-temperature molecular dynamics simulations were applied for nanoscale modelling. The surface wetting and epitaxial behaviours of deposited clusters with various flow and internal kinetic energy were investigated. This revealed that the internal temperature of clusters enhanced the lateral activity of atoms, while normal incident energy was related to atomic implantation. By exchanging momentum and energy from the system to a heat sink with constant temperature, the collision system reached thermal equilibrium after a long enough simulation time. The temperature decay profiles of the system were presented as an exponential-type function, which is dependent on the efficiency of the cooling model and the heat conductivity of the material. Finally, the nanostructure growth mechanism by cluster deposition was studied. It showed that both epitaxial film and voids were constructed by the cluster–island and island–island collision mechanism, which was dependent on the incident energy of the cluster and the surface temperature. As a dynamic behaviour of a nanostructure with a non-zero momentum of its mass centre, the rocking phenomenon was presented as an important characteristic of thin films by cluster deposition.

We have investigated the effects of the interfacial bond arrangement on the electronic transport features of metal–nanotube–metal systems. The transport properties of finite, defect-free armchair and zigzag single-walled carbon nanotubes attached to Au(111) metallic contacts have been calculated by means of the non-equilibrium Green functional formalism with the tight-binding and the extended Hückel Hamiltonians. Our calculations show that the electrode material is not the only factor which rules contact transparency. Indeed, for the same electrode, but changing nanotube helicities, we have observed an overall complex behaviour of the transmission spectra due to band mixing and interference. A comparison of the two models shows that the tight-binding approach fails to give a satisfactory representation of the transmission function when a more accurate description of the C–C and Au–C chemical bonds has to be considered. We have furthermore examined the effect of interface geometry variance on conduction and found that the contact–nanotube distance has a significant impact, while the contact–nanotube symmetry plays a marginal, yet evident role.

Short, histidine-containing peptides can be conjugated to lysine-containing protein scaffolds to controllably attach quantum dots (QDs) to the scaffold, allowing for generic attachment of quantum dots to any protein without the use of specially engineered domains. This technique was used to bind quantum dots from aqueous solution to both chicken IgG and cowpea mosaic virus (CPMV), a 30 nm viral particle. These quantum dot–protein assemblies were studied in detail. The IgG–QD complexes were shown to retain binding specificity to their antigen after modification. The CPMV–QD complexes have a local concentration of quantum dots greater than 3000 nmol ml⁻¹, and show a 15% increase in fluorescence quantum yield over free quantum dots in solution.

Block copolymer micellar templates were used for the controlled synthesis of large arrays of mono-metallic (Fe, Co, Ni, Mo) and bi-metallic (Fe–Mo) nanoparticles with average diameters ranging from 1 to 4 nm and the distance between the nanoparticles ranging from 40 to 45 nm. XPS data reveal the presence of mono-metallic nanoparticles in their oxidized states. These uniform arrays of nanoparticles serve as an excellent tool to investigate the catalytic effect of different metal/metal oxide nanoparticles for the growth of carbon nanotubes, and in this work, they were used to investigate the growth of single-walled carbon nanotubes with the chemical vapour deposition (CVD) process, using both ethanol and hydrocarbon (methane + ethylene) gases as carbon sources. The periodicity and the arrangement of nanoparticles were unaffected even at high growth temperatures, indicating that nanoparticle agglomeration on the Si substrate does not take place during growth. AFM and SEM results reveal uniform growth of nanotubes with diameters smaller than the initial size of the catalyst nanoparticles. The Fe, Co and Ni nanoparticles all serve as effective catalysts for nanotube growth with both types of carbon feed stock, and Co and Ni give rise to a relatively higher yield than Fe. The catalytic activity of Fe and bi-metallic Fe–Mo nanoparticles of similar size and identical densities using ethanol CVD are also compared.

Zinc oxide–soluble starch nanocomposites (nano-ZnO) synthesized using water as a solvent and soluble starch as a stabilizer is impregnated onto cotton fabrics to impart antibacterial and UV-protection functions. Nano-ZnO synthesized by reacting zinc nitrate with sodium hydroxide in the presence of soluble starch absorbed strongly at 361 nm due to the quantum confinement effect. The average size of ZnO nanoparticles is estimated to be 38 ± 3 nm using a transmission electron microscope (TEM); this was confirmed by x-ray diffraction analysis and the effective mass approximation method. The starch content in synthesized nano-ZnO was estimated to be 37.57% using thermo-gravimetric analysis. The nano-ZnO impregnated cotton fabrics showed excellent antibacterial activity against two representative bacteria, Staphylococcus aureus (Gram positive) and Klebsiella pneumoniae (Gram negative). Also, nano-ZnO impregnation enhanced the protection of cotton fabrics against UV radiation in comparison with the untreated cotton fabrics.

ZnO tetrapods doped with Mg (Mg-ZnOTs) were produced by thermally oxidizing Zn and Mg powders. TEM and XRD patterns indicated that Mg-ZnOTs were crystalline with wurtzite structure. The transport measurements of Mg-ZnOT powder demonstrated that Mg-doped ZnO tetrapods are characteristic of a semiconductor with lower threshold voltage. Two peaks were clearly observed in the electroluminescence spectra. The blue light emission is related to the inter-band transition. The green or yellow light emission was induced by impurity centre recombination. Mg-doped ZnO exhibited better field emission properties with higher emission current density and lower turn-on field than pure ZnO nanowires. And ZnO with higher Mg content exhibited better field-emission properties with higher emission current density than ZnO with lower Mg content.

Stable high-field anodization (1500–4000 A m⁻²) for the fabrication of highly ordered porous anodic alumina films has been realized in a H₃PO₄–H₂O–C₂H₅OH system. By maintaining the self-ordering voltage and adjusting the anodizing current density, high-quality self-ordered alumina films with a controllable inter-pore distance over a large range are achieved. The high anodizing current densities lead to high-speed film growth (4–10 µm min⁻¹). The inter-pore distance is not solely dependent on the anodizing voltage, but is also influenced by the anodizing current density. This approach is simple and cost-effective, and is of great value for applications in diverse areas of nanotechnology.

A sol–gel method followed by a hydrogen reduction procedure was proposed in this work for the preparation of metal nanotubes. The tube length, diameter, wall thickness and, most importantly, the chemical components can be adjusted conveniently. Several examples of metal nanotubes (Fe, Ni, Pb and CoFe) were prepared by using anodic aluminium oxide (AAO) templates. The fabricated nanotubes are uniform in diameter and wall thickness through the entire tubes. The length of the nanotubes is about 100 µm, with an aspect ratio of about 1000.

The electrical properties of self-assembled Ge quantum dots were investigated by using conductive atomic force microscopy (CAFM). It was found that the conductive properties of quantum dots were strongly affected by the native oxide layer formed on the quantum dots. With the existing oxide layer, the current–voltage curves of the quantum dots obviously depended on the applied normal forces, and all the curves could be well fitted by the Fowler–Nordheim tunnelling model by changing the oxide layer thicknesses. After the oxide layer was removed by HF etching, the current–voltage characteristics could be well explained by the Schottky emission model. But when the etched sample was exposed to air for more than 150 min, its current–voltage behaviour returned back to that before the etching. Despite the significant effects of the oxide layer on the current–voltage characteristics, the current distributions of individual quantum dots remained almost the same for different thicknesses of the oxide layer or different normal forces applied. Therefore, the effects of the oxide layer on the current distribution can be ignored, though the absolute current values were strongly affected. Our results thus provide important evidence for the reliability of CAFM measurements in ambient conditions.

This paper presents a study on the synthesis and characterization of ZnO nanoparticles by a two-step synthesis procedure. The first step is the solution-free mechanochemical synthesis of ZnC₂O₄·2H₂O nanoparticles by grinding a powder mixture of Zn(CH₃COO)₂ and H₂C₂O₄·2H₂O at room temperature for a certain time. The second step is the thermal decomposition of ZnC₂O₄·2H₂O nanoparticles at 450 °C to form ZnO nanoparticles. The obtained ZnO nanoparticles have been structurally characterized by x-ray diffraction, indicating a wurtzite structure (hexagonal phase, space group P6₃mc) with high crystallinity. The average grain size of the ZnO nanoparticles is in the range of 24–40 nm, depending on the mechanical grinding time. The UV–vis diffuse reflectance spectrum of the ZnO nanoparticles indicates a band gap of about 3.3 eV with an onset of absorption at about 3.1 eV, showing a weak red shift compared to 3.37 eV for the bulk ZnO. X-ray photoelectron spectroscopy and Raman spectra showed a nonadsorption on the surface and a very low concentration of oxygen vacancies, respectively, indicating a high quality of the prepared ZnO nanoparticles. The formation process of the ZnC₂O₄·2H₂O nanoparticles by the solution-free mechanochemical reaction is discussed.

Gold wires 90 nm wide were fabricated on a 100 nm thin silicon nitride membrane using electron beam lithography. Application of a bias voltage across the wires caused them to break, due to resistive heating and electromigration, and produced a nanoscale gap in their structure. Placing the gold wires on a thin silicon nitride membrane allowed us to image the wires with transmission electron microscopy as they proceeded through the breaking process with a very high resolution. The images revealed extensive rearrangement of the metal grains and the exact shape of the final gap. A voltage-ramp algorithm using the effective conductance of the wires as the feedback parameter was developed to reproducibly generate 2 nm gaps in the wire structure. We observed that the measured relative current noise increased more than two orders of magnitude more than the resistance in the first stage of the disassembly process. The large change of the current noise makes it an attractive candidate as a parameter to be used in the control feedback loop to break the wires. Initial results for using noise to control the disassembly process are presented.

A means for synthesizing paramagnetic nanoparticles composed of an Au–Fe alloy is described using pulsed laser deposition (PLD) of the alloy into a mesoporous alumina membrane template. Nanoparticles 46 ± 13 nm in diameter and composed of a 17% Fe alloy have been created by depositing a 35% Fe alloy into a template with 65 nm diameter pores. These paramagnetic nanoparticles had a saturation magnetization of 11.5 emu g⁻¹ at 2000 G, and their UV–visible extinction spectrum was dominated by strong absorption similar to that of Fe₃O₄ nanoparticles. The surfaces of these nanoparticles were readily functionalized with a dense monolayer of DNA oligonucleotides that had a 5' thiol group. The Au–Fe nanoparticles appear to be well suited for biotechnological applications and single molecule measurements as they can be synthesized in a specific size range, are strongly paramagnetic, and may be easily functionalized with biological macromolecules.

The adsorption characteristics of self-oriented multi-walled carbon nanotube (MWCNT) arrays are examined from N₂ (−196 °C) adsorption measurements. The arrays were synthesized in a laboratory by in situ chemical vapour deposition of iron or cobalt phthalocyanines at 880 and 950 °C, under otherwise constant conditions, in an attempt to obtain different morphological structures. For both precursors, increasing the temperature leads to MWCNT arrays with lower Brunauer–Emmett–Teller (BET) surface area and total pore volume, though the effect is more pronounced for those arising from the iron-based compound. Despite this, precursor yields of individual nanotubes of larger diameter, higher BET area and total pore volume characterize the resulting arrays compared to those arising from cobalt phthalocyanine for the same temperatures. As evidenced by SEM and TEM images, the arrays synthesized from iron phthalocyanine at 880 °C show better vertical alignment and denser structures than those obtained from this compound at 950 °C, and also from cobalt phthalocyanine at both temperatures. Further ultrasonication of the arrays produced from the iron compound brings about a significant reduction in their adsorption capacity, attributable to the pronounced disarrangement of the resulting structures. The present results demonstrate that the alignment of MWCNT arrays plays a crucial role in their N₂ adsorption characteristics.

Longitudinal resistivity measurements on single Mo₆S_9−xI_x (x = 4.5, 6 and 7) molecular nanowire bundles ranging in diameter from d = 7 nm to 1 µm are performed to investigate the longitudinal transport properties of individual bundles. Different contacting methods are used to study diverse nanocircuit manufacturing technologies that can be used for interconnects based on Mo₆S_9−xI_x. The measurements show ubiquitously linear I–V characteristics with Pd, Au, Ag and Ti contact metals. The highest room-temperature conductivity achieved is σ₀∼10 S m⁻¹ using Ag contacts. The critical current densities typically achieved are J_c∼10⁴ A cm⁻². The observed metallic behaviour at room temperature is consistent with the band structure calculated using density functional theory (DFT). At low temperatures, the conductivity is found to decrease, following variable range hopping (VRH) behaviour of the form σ = σ₀exp−(T₀/T)^β reasonably well, but the exponent β changes upon annealing. From fits to the temperature dependence of the conductivity, a change from β∼1/4 to β∼1/2 is observed, which may be explained by a change in dimensionality from 3D-like VRH to 1D-like VRH following the removal of intra-bundle interstitial iodine.

A simple approach for the large-scale synthesis of cotton-like nanogold by a liquid-based process at room temperature is described. The gold fibres have diameters in the range of 15–40 nm and lengths longer than 50 µm, entwined into a complex mass. The first step of the preparation procedure involves the formation of gold seeds by reducing HAuCl₄ with NaBH₄ in a solution containing the desired quantity of cetyltrimetylammonium bromide (CTAB). In the subsequent step, the gold seeds continuously grow to form cotton-like nanogold in a solution containing HAuCl₄, CTAB and L-ascorbic acid (AA) under an ultrasonic radiation field. The cotton-like nanogold has observable fluorescence, which might have great significance in biological and medical applications. HRTEM images showed that many defects and twin crystals exist in the turning junctions of as-prepared cotton fibres, which might be the reason the turning junctions in the fibres became stable.

Inspired by the self-cleaning silver ragwort leaf, we have recently fabricated a biomimetic super-hydrophobic fibrous mat surface comprising micro/nanoporous polystyrene (PS) microfibres via electrospinning. The rough surface of the silver ragwort leaf fibres, with nanometre-sized grooves along the fibre axis, was imitated by forming micro- and nanostructured pores on the electrospun fibre surface. The solvent composition ratios of tetrahydrofuran (THF) to N,N-dimethylformamide (DMF) in PS solutions were proved to be the key parameter to affect the fibre surface structures due to the various phase separation speeds of the solvents from PS fibres during electrospinning. The combination of the hierarchical surface roughness inherent in electrospun microfibrous PS mats and the low surface free energy of PS yielded a stable super-hydrophobicity with water contact angles as high as 159.5° for a 12 mg water droplet, exceeding that (147°) of the silver ragwort leaf. Moreover, the hydrophobicity of the porous PS mat surface was found to increase on increasing the surface roughness of the microfibres.

Using MgO nanowires as a reactive template, we fabricated for the first time single-crystal MgAl₂O₄ spinel nanotubes through an interfacial solid-state reaction of MgO–Al₂O₃ core–shell nanowires. Single-crystal MgO nanowires are coated with a conformal thin layer of amorphous Al₂O₃ via atomic layer deposition. Subsequent annealing at 700 °C activates the interfacial reaction between MgO and Al₂O₃, transforming the alumina shell into a spinel shell. Finally, after etching away the remaining MgO core in ammonia sulfuric solution, MgAl₂O₄ spinel nanotubes are obtained. As a transition from conventional planar spinel layers via thin-film interface reactions, our result might open a window for the fabrication of a wide variety of MgO-based spinel one-dimensional nanostructures.

Multiple shapes of nano- and micro-structured cystine aggregates, including spheres, rods, spindles, dendrites, and multipods, were easily synthesized just by adjusting the concentrations and pH values of L-Cysteine solutions under ultrasonic irritation. Importantly, highly monodispersed nanospheres of cystine aggregates 225 nm in diameter without any other shapes were easily obtained for the system of 0.1 M L-Cysteine with pH 8. This will provide a very simple and effective approach to produce monodispersed cystine microspheres, which could promote new possibilities for future applications in biosensor, drug delivery, medicine, and the production of nanomaterials.

Recently, several groups (Anderson, Halas, Zharov, and their co-workers, 2003; El-Sayed and co-workers, 2006) demonstrated, through pioneering results, the great potential of photothermal (PT) therapy for the selective treatment of cancer cells, bacteria, viruses, and DNA targeted with gold nanospheres, nanoshells, nanorods, and nanosphere clusters. However, the current understanding of the relationship between the nanoparticle/cluster parameters (size, shape, particle/cluster structure, etc) and the efficiency of PT therapy is limited. Here, we report theoretical simulations aimed at finding the optimal single-particle and cluster structures to achieve its maximal absorption, which is crucial for PT therapeutic effects. To characterize the optical amplification in laser-induced thermal effects, we introduce relevant parameters such as the ratio of the absorption cross section to the gold mass of a single-particle structure and absorption amplification, defined as the ratio of cluster absorption to the total absorption of non-interacting particles. We consider the absorption efficiency of single nanoparticles (gold spheres, rods, and silica/gold nanoshells), linear chains, 2D lattice arrays, 3D random volume clusters, and the random aggregated N-particle ensembles on the outer surface of a larger dielectric sphere, which mimic aggregation of nanosphere bioconjugates on or within cancer cells. The cluster particles are bare or biopolymer-coated gold nanospheres. The light absorption of cluster structures is studied by using the generalized multiparticle Mie solution and the T-matrix method. The gold nanoshells with (silica core diameter)/(gold shell thickness) parameters of (50–100)/(3–8) nm and nanorods with minor/major sizes of (15–20)/(50–70) nm are shown to be more efficient PT labels and sensitizers than the equivolume solid single gold spheres. In the case of nanosphere clusters, the interparticle separations and the short linear-chain fragments are the main structural parameters determining the absorption efficiency and its spectral shifting to the red. Although we have not found a noticeable dependence of absorption amplification on the cluster sphere size, 20–40 nm particles are found to be most effective, in accordance with our experimental observations. The long-wavelength absorption efficiency of random clusters increases with the cluster particle number N at small N and reveals a saturation behaviour at N>20.

The current–voltage (I–V) characteristics of carbon nanotubes (CNTs) during field emission were investigated by in situ imaging and field-emission (FE) measurement inside a field-emission scanning electron microscope (FE-SEM). A primary electron of the FE-SEM could induce and enhance a large stimulated electron emission from a CNT which might be due to the strong local field on the tip of the CNT in the presence of an applied voltage. FE of bent nanotubes (BNTs) can initially occur after they are fully straightened or it can start in the bent state (during geometrical straightening) as the applied field increases. The FE from a single CNT follows FN (Fowler–Nordheim) behaviour with a single linear slope in the FN plot. The FE from two nanotubes with a geometrical change during FE showed transition of the FN slope from the low voltage to the high voltage region, which could be due to interactions between two dynamic neighbouring BNTs.

Nanowires have significant potential in future technologies such as nanomechanical devices and electronics. Recent experiments suggest that nanowires with sub-100 nm diameters may be fabricated by filling cracks with various materials. The geometry of cracks becomes important on such a length scale, and the practical application of the approach requires an understanding of crack evolution in heterogeneous films. This paper proposes a level-set approach to model directed nanocracks on pre-patterned substrates. The approach does not require the explicit tracking of crack fronts and thus allows the simulation of complex crack patterns. Results indicate that pre-patterning a substrate can lead to various well controlled nanocrack patterns, suggesting a possibility to make designed and complex nanowires difficult to obtain with other methods.

Suspended highly oriented pyrolytic graphite (HOPG) nanosheets (10–300 nm thick) were created by direct mechanical cleavage of a bulk HOPG crystal onto silicon micropillars and microtracks. We show that suspended HOPG nanosheets can be used to engineer HOPG nanoresonators such as membranes, bridges, and cantilevers as thin as 28 carbon atom layers. We measured by Doppler laser heterodyne interferometry that the discrete vibration modes of an HOPG nanosheet membrane and the resonance frequency of a FIB-created HOPG microcantilever lie in the MHz frequency regime. Moreover, a new carbon nanostructure, named 'nanolace', was synthesized by focused ion beam (FIB) sputtering of suspended HOPG nanosheets. Graphite nanosheets suspended on micropillars were eroded by a FIB to create self-oriented pseudo-periodical ripples. Additional sputtering and subsequent milling of these ripples led to the formation of honeycomb-like shaped nanolaces suspended and linked by ribbons.

A layer-by-layer deposited polyelectrolyte spacer is used to attach CdSe nanocrystals (NCs), dye molecules and fluorescein-labelled bovine serum albumin (BSA-FITC) to flat glass and rough silver island surfaces in order to study the effect of spacer thickness on homogeneity and surface concentration of fluorophore coverage. Three different methods of fluorophore deposition atop the polyelectrolyte spacer are examined using steady-state spectroscopy, fluorescent microscopy and statistical analysis. The best homogeneous covering with nanocrystals at a controllable concentration was found for deposition from a solution of NCs which are electrostatically bound to polyelectrolyte macromolecules. This fluorophore deposition method allows one to avoid artefacts and to evaluate the fluorescence enhancement factor of BSA-FITC adsorbed on silver island films.

Si(100) substrates were used to fabricate various nanosized {111} facets between the (100) planes using photolithography and anisotropic wet chemical etching. Following simultaneous Ge chemical vapour deposition on the neighbouring (100) and {111} facets, the Ge nano-island formation and distribution was observed on both the (100) terraces and the {111} side walls using a dynamical atomic force microscope. The nano-island formation on the nanosized {111} strip facets was found to be strongly suppressed upon reducing the strip width due primarily to the interaction of adatoms on the neighbouring facets. Specifically, the difference in the effective chemical potential of Ge adatoms on the two neighbouring facets leads to the depletion of nano-islands on the {111} strip with width <500 nm under the growth condition used in this study.

Single walled carbon nanotubes (SWNT) were solubilized in ∼30 mM sodium dodecylsulfate (SDS) and sodium dodecylbenzene sulfonate (SDBS) aqueous solutions by severe sonication. Raman scattering experiments using three different excitation energies revealed that the distribution of the radial breathing modes (RBM) for SDBS–SWNT samples is shifted to lower frequencies compared to the SDS–SWNT samples. This effect is proposed here to be due to preferential solubilization of large diameter SWNTs by SDBS compared to SDS solutions, which may be accounted for by the increased effective dielectric constant and consequently increased transition energy as the tube solubilizes in an aqueous environment.

We present a molecular dynamics simulation of molecules translocating through carbon nanotubes in vacuo and in aqueous environment for applications in engineered nanofluidic channels. The molecules studied include both rigid and semi-flexible molecules. We show that in the absence of water solvation, the van der Waals interaction between the molecule and the nanotube wall can induce a rapid spontaneous encapsulation of the molecule inside the nanotube channel. The encapsulation process is strongly impeded for nanotubes dissolved in water due to the competition between the van der Waals, hydrophobic and hydrogen bonding interactions in the nanotube/water/molecule complex. Water adsorption inside the nanotube channel plays an important role in determining the dynamics of the spontaneous insertion process.

We propose a novel method for the simple visual (colorimetric) and spectroscopic monitoring of the conformational state of a biopolymer. We present an experimental example of the detection of the change in the conformation of a giant DNA molecule. This methodology is based on the difference in the manner of metallization with noble metals on a polymer scaffold depending on its conformation. Spectroscopic analysis of the metallization of DNA by metallic silver or gold provides information on the critical concentration of DNA binder, at which the folding transition from the elongated into the compact state occurs, together with the dimension and morphology of a compact DNA condensate. This method may be suitable for use in a rapid screening procedure for the high-throughput analysis of large chemical libraries to evaluate their ability to induce DNA compaction, protein folding and similar important processes.

We demonstrate arrays of cantilevers with different lengths, fabricated by focused ion beam milling. The arrays of oscillators generate a spectrum of different resonant frequencies, where each frequency correlates to the corresponding individual cantilever. The frequency response from all the cantilevers is collected from a single measurement under the same environment and conditions for the entire array. The mass response of the system generated the same Δf/f₀ for the cantilevers, within 0.1% accuracy. We denote the method MFSAC: multi-frequency signal analysis from an array of cantilevers. The simultaneous detection of several frequencies in one spectrum has great benefits in mass sensor applications, offering the possibility for true label-free detection.

The growth direction and morphology of one-dimensional ZnO nanostructures grown by metal–organic chemical vapour deposition (MOCVD) were modulated by changing the growth temperature of previously deposited ZnO buffer layers that were used as a template. The ZnO nanorods grown on the low-temperature deposited buffer layer were regularly inclined with respect to the substrate surface and show in-plane alignment with azimuthally six-fold symmetry. In contrast, deposition of the buffer layer at higher growth temperature led to the formation of vertically well-aligned ZnO nanorods. In addition, the ZnO nanorods grown on the buffer layer deposited at low growth temperature show a growth direction of , unlike the conventional ZnO nanorods showing a growth direction of [0001]. The microstructural analysis and atomic modelling of the formation of regularly inclined nanorods using transmission electron microscopy are presented.

Nanostructured carbon thin films have been actively investigated recently for their electroresistance (ER) properties. Furthermore, carbon films with nonlinear current–voltage (I–V) characteristics have potential application in field-emission devices. This has motivated us to study the effect of various growth parameters on the physical and morphological properties of carbon films grown by pulsed laser deposition (PLD). Carbon films have been deposited using a graphite target at different partial pressures of argon. The morphology of film surfaces deposited at various growth conditions was monitored using an atomic force microscope (AFM). AFM studies showed nanostructured grain growth with average grain size of about 80–90 nm. As the deposition time was decreased down to 1 min, the grain size was also found to decrease correspondingly. From Raman spectroscopic measurements an increase in the I(D)/I(G) ratio and a decrease in FWHM (G) clearly revealed the promotion of sp² hybridization as the substrate temperature increased. All the films show semiconducting behaviour with the dominant conduction process being the three-dimensional (3D) variable range hopping (VRH) mechanism. Nonlinear I–V curves were obtained for carbon films deposited on p-type Si indicating diode-like behaviour. The most significant result of this study was the observation of a large electroresistance value.

We investigate the effects of room-temperature irradiation of Au and Ge nanoislands grown on Si. Our studies show the formation of Au–Ge alloy phase within the islands and wetting of the substrate. High-resolution transmission electron microscopy along with synchrotron radiation-based x-ray reflectivity and grazing incidence x-ray diffraction measurements were performed to characterize the irradiation-induced changes brought into the sequentially deposited Au and Ge island thin films. The results are attributed to the recoil implantation and the transient melting of the nanoislands followed by the formation of crystalline alloy phase.

A novel polyaniline nanofibre supported platinum (Pt) nanoelectrocatalyst is developed for direct methanol fuel cells (DMFCs). Polyaniline nanofibres (PaniNFs) with a 60 nm diameter are synthesized by a scalable interfacial polymerization without the use of a template or functional dopant. PaniNF supported Pt electrocatalyst (Pt/PaniNFs) and carbon black supported Pt electrocatalyst (Pt/C) are prepared by an ethylene glycol (EG) reduction method. The Pt nanoparticles deposited onto PaniNFs have a smaller diameter (1.8 versus 2.3 nm by XRD) and narrower particle size distribution (1.5–3 nm versus 1–5 nm by TEM) than the Pt nanoparticles deposited onto carbon black. The Pt/PaniNFs catalyst shows a higher electrochemical active surface area (ECSA) and higher methanol oxidation reaction (MOR) catalytic activity than the Pt/C.

We present a non-linear operation of a nanomechanical beam resonator by photothermal excitation at 4 K. The resonators dimensions are 10 µm in length, 200 nm in width, and 200 nm in height. The actuation mechanism is based on a pulsed diode laser focused onto the centre of the beam resonator. Thermally induced stress caused by the different thermal expansion coefficients of the bi-layer system periodically deflects the resonator. Magnetomotively detected amplitudes up to 150 nm are reached at the fundamental resonance mode at a frequency of 8.9 MHz. Furthermore, the third eigenmode of the resonator at a frequency 36 MHz is also excited. We conclude that the photothermal excitation at 4 K should be applicable up to the GHz regime, the operation in the non-linear regime can be used for performance enhancement of nanomechanical systems, and the combination of photothermal excitation and magneto-motive detection avoids undesired cross talk.

In this paper, the application of an in situ stress measurement technique to a silicon nitride thin film deposited onto a thick silicon substrate is presented. The method is based on the measurement of the displacement field originated when a slot is milled into the material under study. Displacements are obtained by digital correlation analysis of scanning electron microscope (SEM) images, whereas milling is performed by ion milling in focused ion-beam equipment. Due to the mechanical constraint introduced by the substrate and the small thickness of the tested layer, the displacements generated by the milling process are in the range 0–5 nm, which is one of the smallest displacement ranges measured up to now in a relaxation-based measurement technique. The local stress value determined with this new method is in good agreement with values obtained by a classical method like the wafer bending test.

CdS nanorods along with nanostrips and plates have been prepared on a large scale by the solvothermal route using the precursor cadmium oxalate under mild conditions with ethylene glycol as the solvent and (NH₄)₂S as the sulfiding agent, without using catalysts, surfactants or template. The aspect ratio of the rods varied from 3 to 30. Characterization has been done by TEM, HR-TEM, EDX, HR-SEM, XRD, BET surface area, UV–vis absorption, photoluminescence and fluorescence studies. Photo-catalytic H₂ production activity was tested with as-synthesized CdS, calcined CdS, noble metal loaded CdS and for bulk CdS. The nanorods being formed are used as such for H₂ production. The as-synthesized CdS is found to have very good H₂ production capacity compared to that of the bulk CdS. Upon Pt loading much enhanced activity was observed in the rate of hydrogen production.

Molecular beam epitaxy of InAs on micro- and nano-scale patterned GaAs(001) substrates was studied. An InAs epilayer grown on the micro-scale patterned substrate exhibits islands with {1 1 3}-type facets, and is similar to that grown on the flat (unpatterned) substrate. In contrast, the preferred growth of InAs on the nano-scale patterned substrate is in the direction and exhibits islands with {1 1 0}-type facets. The thickness of the dense dislocation networks at the interface due to strain relaxation is reduced by the micro-scale pattern in comparison with the flat substrate, while for growth on the nano-scale patterned substrate, the strain relaxes via the formation of stacking faults more than dislocations. X-ray diffraction reveals that the strains in the 300 nm InAs epilayers are nearly fully relaxed, and the patterns tend to decrease the lattice constants of the epilayer, implying mass transport of Ga atoms into the epilayer from the GaAs substrates.