Electrochemical sensor for vascular endothelial growth factor based on self-assembling DNA aptamer structure.

Developing vascular endothelial growth factor (VEGF) protein is essential for early cancer diagnosis and cancer treatment monitoring. This study presents the design and characterisation of an electrochemical sensor utilising a self-assembling DNA aptamer structure for the sensitive and selective detection of VEGF. The aptamer structure comprises three different parts of single-stranded DNA that are assembled prior to integration into the sensor.

In situ optical sub-wavelength thickness control of porous anodic aluminum oxide.

Porous anodic aluminum oxide (PAAO), sometimes referred to as nanoporous anodic alumina, serves as a cost-effective template for nanofabrication in many fields of science and engineering. However, production of ultrathin PAAO membranes with precise thickness in the optical sub-wavelength range remains challenging because of difficulties regarding process control at the initial stage of anodic oxidation. In this study, we demonstrate a technique for consistently manufacturing PAAO with the targeted thickness.

Characterization of Mechanical Oscillations in Bismuth Selenide Nanowires at Low Temperatures.

A single transistor preamplifier circuit was designed to facilitate electrical detection of mechanical oscillations in nanoelectromechanical systems (NEMSs) at low temperatures. The amplifier was integrated in the close vicinity of the nanowire inside the cryostat to minimize cabling load and interference. The function of the circuit was impedance conversion for current flow measurements in NEMSs with a high internal resistance.

Low-Vacuum Catalyst-Free Physical Vapor Deposition and Magnetotransport Properties of Ultrathin BiSe Nanoribbons.

In this work, a simple catalyst-free physical vapor deposition method is optimized by adjusting source material pressure and evaporation time for the reliable obtaining of freestanding nanoribbons with thicknesses below 15 nm. The optimum synthesis temperature, time and pressure were determined for an increased yield of ultrathin BiSe nanoribbons with thicknesses of 8-15 nm. Physical and electrical characterization of the synthesized BiSe nanoribbons with thicknesses below 15 nm revealed no degradation of properties of the nanoribbons, as well as the absence of the contribution of trivial bulk charge carriers to the total conductance of the nanoribbons.

Humidity-dependent electrical performance of CuO nanowire networks studied by electrochemical impedance spectroscopy.

Electrochemical impedance spectroscopy was applied for studying copper oxide (CuO) nanowire networks assembled between metallic microelectrodes by dielectrophoresis. The influence of relative humidity (RH) on electrical characteristics of the CuO nanowire-based system was assessed by measurements of the impedance . A slight increase of with increasing RH at low humidity was followed by a three orders of magnitude decrease of at RH above 50-60%.

Positive and Negative Changes in the Electrical Conductance Related to Hybrid Filler Distribution Gradient in Composite Flexible Thermoelectric Films Subjected to Bending.

P-type multiwalled carbon nanotubes (MWCNTs), as well as heterostructures fabricated by direct deposition of inorganic thermoelectric materials as antimony and bismuth chalcogenides on MWCNT networks are known as perspective materials for application in flexible thermoelectric polymer-based composites. In this work, the electrical response of three types of SbTe-MWCNT heterostructures-based flexible films-free standing on a flexible substrate, encapsulated in polydimethylsiloxane (PDMS), and mixed in polyvinyl alcohol (PVA) is studied in comparison with the flexible films prepared by the same methods using bare MWCNTs. The electrical conductance of these films when each side of it was subsequently subjected to compressive and tensile stress during the film bending down to a 3 mm radius is investigated in relation to the distribution gradient of SbTe-MWCNT heterostructures or bare MWCNTs within the film.

Electrochemical Immunosensor for the Determination of Antibodies against Prostate-Specific Antigen Based on ZnO Nanostructures.

In this study, ZnO nanostructures with different types of morphologies and particle sizes were evaluated and applied for the development of an immunosensor. The first material was composed of spherical, polydisperse nanostructures with a particle size in the range of 10-160 nm. The second was made up of more compact rod-like spherical nanostructures with the diameter of these rods in the range of 50-400 nm, and approximately 98% of the particles were in the range of 20-70 nm.

p-Type PVA/MWCNT-SbTe Composites for Application in Different Types of Flexible Thermoelectric Generators in Combination with n-Type PVA/MWCNT-BiSe Composites.

This work is devoted to the fabrication of p-type polyvinyl alcohol (PVA)-based flexible thermoelectric composites using multiwall carbon nanotubes-antimony telluride (MWCNT-SbTe) hybrid filler, the study of the thermoelectrical and mechanical properties of these composites, and the application of these composites in two types (planar and radial) of thermoelectric generators (TEG) in combination with the previously reported PVA/MWCNT-BiSe flexible thermoelectric composites. While the power factors of PVA/MWCNT-SbTe and PVA/MWCNT-BiSe composites with 15 wt.% filler were found to be similar, the PVA/MWCNT-SbTe composite with 25 wt.

Optimization of Colloidal Gold Nanoparticles on Porous Anodic Aluminum Oxide Substrates for Refractometric Sensing.

A new composite metal-insulator-metal (MIM) system consisting of exceptionally dense non-close-packed (NCP) arrays of gold or silver nanoparticles, porous anodic aluminum oxide (PAAO), and bulk aluminum substrate interacts strongly with visible light and may become a very useful component for optical applications. The proposed MIM structure can be synthesized using accessible lithography-free chemical and physical processes (anodization and capillary force assisted colloidal particle deposition) that are suitable for the low-cost production of specialized devices. Here, we present a systematic study to determine the essential MIM structure parameters (nanoparticle size and PAAO layer thickness) for localized surface plasmon resonance (LSPR) refractometric sensing.

Distribution of Iron Nanoparticles in Arrays of Vertically Aligned Carbon Nanotubes Grown by Chemical Vapor Deposition.

Arrays of aligned carbon nanotubes (CNTs) are anisotropic nanomaterials possessing a high length-to-diameter aspect ratio, channels passing through the array, and mechanical strength along with flexibility. The arrays are produced in one step using aerosol-assisted catalytic chemical vapor deposition (CCVD), where a mixture of carbon and metal sources is fed into the hot zone of the reactor. Metal nanoparticles catalyze the growth of CNTs and, during synthesis, are partially captured into the internal cavity of CNTs.

Nanometric Moiré Stripes on the Surface of BiSe Topological Insulator.

Mismatch between adjacent atomic layers in low-dimensional materials, generating moiré patterns, has recently emerged as a suitable method to tune electronic properties by inducing strong electron correlations and generating novel phenomena. Beyond graphene, van der Waals structures such as three-dimensional (3D) topological insulators (TIs) appear as ideal candidates for the study of these phenomena due to the weak coupling between layers. Here we discover and investigate the origin of 1D moiré stripes on the surface of BiSe TI thin films and nanobelts.

Magnetotransport Studies of Encapsulated Topological Insulator BiSe Nanoribbons.

The majority of proposed exotic applications employing 3D topological insulators require high-quality materials with reduced dimensions. Catalyst-free, PVD-grown BiSe nanoribbons are particularly promising for these applications due to the extraordinarily high mobility of their surface Dirac states, and low bulk carrier densities. However, these materials are prone to the formation of surface accumulation layers; therefore, the implementation of surface encapsulation layers and the choice of appropriate dielectrics for building gate-tunable devices are important.

Flexible N-Type Thermoelectric Composites Based on Non-Conductive Polymer with Innovative BiSe-CNT Hybrid Nanostructured Filler.

This research is devoted to the fabrication of polyvinyl alcohol (PVOH) based n-type thermoelectric composites with innovative hybrid bismuth selenide-multiwalled carbon nanotube (BiSe-MWCNT) fillers for application in flexible thermoelectric devices. Hybrid fillers were synthesized by direct deposition of BiSe on multiwalled carbon nanotubes using a physical vapor deposition method, thus ensuring direct electrical contact between the carbon nanotubes and BiSe. The Seebeck coefficient of prepared PVOH/BiSe-MWCNT composites was found to be comparable with that for the BiSe thin films, reaching -100 µV·K for the composite with 30 wt.

High-Yield Growth and Tunable Morphology of BiSe Nanoribbons Synthesized on Thermally Dewetted Au.

The yield and morphology (length, width, thickness) of stoichiometric BiSe nanoribbons grown by physical vapor deposition is studied as a function of the diameters and areal number density of the Au catalyst nanoparticles of mean diameters 8-150 nm formed by dewetting Au layers of thicknesses 1.5-16 nm. The highest yield of the BiSe nanoribbons is reached when synthesized on dewetted 3 nm thick Au layer (mean diameter of Au nanoparticles ~10 nm) and exceeds the nanoribbon yield obtained in catalyst-free synthesis by almost 50 times.

Fabrication of an Extremely Cheap Poly(3,4-ethylenedioxythiophene) Modified Pencil Lead Electrode for Effective Hydroquinone Sensing.

Hydroquinone (HQ) is one of the major deleterious metabolites of benzene in the human body, which has been implicated to cause various human diseases. In order to fabricate a feasible sensor for the accurate detection of HQ, we attempted to electrochemically modify a piece of common 2B pencil lead (PL) with the conductive poly(3,4-ethylenedioxythiophene) or PEDOT film to construct a PEDOT/PL electrode. We then examined the performance of PEDOT/PL in the detection of hydroquinone with different voltammetry methods.

Fabrication and Characterization of Double- and Single-Clamped CuO Nanowire Based Nanoelectromechanical Switches.

Electrostatically actuated nanoelectromechanical (NEM) switches hold promise for operation with sharply defined ON/OFF states, high ON/OFF current ratio, low OFF state power consumption, and a compact design. The present challenge for the development of nanoelectromechanical system (NEMS) technology is fabrication of single nanowire based NEM switches. In this work, we demonstrate the first application of CuO nanowires as NEM switch active elements.

Size Distribution, Mechanical and Electrical Properties of CuO Nanowires Grown by Modified Thermal Oxidation Methods.

Size distribution, Young's moduli and electrical resistivity are investigated for CuO nanowires synthesized by different thermal oxidation methods. Oxidation in dry and wet air were applied for synthesis both with and without an external electrical field. An increased yield of high aspect ratio nanowires with diameters below 100 nm is achieved by combining applied electric field and growth conditions with additional water vapour at the first stage of synthesis.

Surface structure promoted high-yield growth and magnetotransport properties of BiSe nanoribbons.

In the present work, a catalyst-free physical vapour deposition method is used to synthesize high yield of BiSe nanoribbons. By replacing standard glass or quartz substrates with aluminium covered with ultrathin porous anodized aluminium oxide (AAO), the number of synthesized nanoribbons per unit area can be increased by 20-100 times. The mechanisms of formation and yield of the nanoribbons synthesized on AAO substrates having different arrangement and size of pores are analysed and discussed.

Surface Lattice Resonances in Self-Assembled Arrays of Monodisperse Ag Cuboctahedra.

Plasmonic metal nanoparticles arranged in periodic arrays can generate surface lattice plasmon resonances (SLRs) with high -factors. These collective resonances are interesting because the associated electromagnetic field is delocalized throughout the plane of the array, enabling applications such as biosensing and nanolasing. In most cases such periodic nanostructures are created top-down nanofabrication processes.

Investigating the mechanical properties of GeSn nanowires.

Germanium tin (GeSn) has been proposed as a promising material for electronic and optical applications due to the formation of a direct band-gap at a Sn content >7 at%. Furthermore, the ability to manipulate the properties of GeSn at the nanoscale will further permit the realisation of advanced mechanical devices. Here we report for the first time the mechanical properties of GeSn nanowires (7.

Zinc oxide nanorod based immunosensing platform for the determination of human leukemic cells.

Zinc oxide (ZnO) based nanostructures owing unique physical properties - high photoluminescence, biocompatibility and other characteristics, therefore, they attract attention as building blocks suitable for biosensor development. In this research as a target we have used human leukemic cell line IM9 (IM9). IM9 was derived from the patient with a multiple myeloma and expressed cluster of differentiation proteins СD19 on the surface of 85-95% here investigated cancer cells.

High-Density Plasmonic Nanoparticle Arrays Deposited on Nanoporous Anodic Alumina Templates for Optical Sensor Applications.

This study demonstrates a new, robust, and accessible deposition technique of metal nanoparticle arrays (NPAs), which uses nanoporous anodic alumina (NAA) as a template for capillary force-assisted convective colloid (40, 60, and 80 nm diameter Au) assembly. The NPA density and nanoparticle size can be independently tuned by the anodization conditions and colloid synthesis protocols. This enables production of non-touching variable-density NPAs with controllable gaps in the 20-60 nm range.

Effect of graphene substrate type on formation of BiSe nanoplates.

Knowledge of nucleation and further growth of BiSe nanoplates on different substrates is crucial for obtaining ultrathin nanostructures and films of this material by physical vapour deposition technique. In this work, BiSe nanoplates were deposited under the same experimental conditions on different types of graphene substrates (as-transferred and post-annealed chemical vapour deposition grown monolayer graphene, monolayer graphene grown on silicon carbide substrate). Dimensions of the nanoplates deposited on graphene substrates were compared with the dimensions of the nanoplates deposited on mechanically exfoliated mica and highly ordered pyrolytic graphite flakes used as reference substrates.

Bulk-free topological insulator BiSe nanoribbons with magnetotransport signatures of Dirac surface states.

Many applications of topological insulators (TIs) as well as new phenomena require devices with reduced dimensions. While much progress has been made to realize thin films of TIs with low bulk carrier densities, nanostructures have not yet been reported with similar properties, despite the fact that reduced dimensions should help diminish the contributions from bulk carriers. Here we demonstrate that BiSe nanoribbons, grown by a simple catalyst-free physical-vapour deposition, have inherently low bulk carrier densities, and can be further made bulk-free by thickness reduction, thus revealing the high mobility topological surface states.

Variable Thickness Porous Anodic Alumina/Metal Film Bilayers for Optimization of Plasmonic Scattering by Nanoholes on Mirror.

Continuously variable thickness porous anodic aluminum oxide (PAAO) films were obtained using electrochemical oxidation of bulk aluminum sheet while both electrodes were simultaneously withdrawn from the electrolyte solution. The thickness gradient was controlled by the withdrawal rate (1-10 mm/min range) and thickness variation demonstrated from below 50 nm to above 1 micrometer. The thickness increased linearly with the sample lateral coordinate, whereas the nanopore structure (diameter and interpore distance) remained unchanged.