One of the most important effects of water on earth is that surfaces in air adsorb small amounts of water, usually in the form of a thin film. Real surfaces, especially the rather soft biomolecular surfaces, are covered by highly curved micro- and nanostructures, which induce more complex wetting geometries, such as films, droplets, and filaments. This effect, though ubiquitous, has not yet been investigated on the nanoscale. We have approached the situation by combining a soft proteinous surface, made up from very resilient tubular plant viruses, with ionic liquids. Their low vapor pressure allowed us to observe nanoscale wetting patterns at very high spatial resolution with AFM (atomic force microscopy), SEM (scanning electron microscopy) and STEM (scanning transmission electron microscopy). We found droplets, filaments and layers, with meniscus diameters down to below 10 nm. All geometries are comparable with results obtained on the microscale, and with standard macroscale wetting models. (C) 2018 Elsevier B.V. All rights reserved.

Tobacco mosaic virus (TMV) is the best-characterized virus. Compared to most other viruses, its structure and physical and chemical properties are well known. TMV exclusively infects plants and is completely harmless for mammals. This virus is resilient against environmental changes, and it can easily be modified with functional materials. Our review gives a summary about the known physical properties of TMV (structure, thermodynamics, and electromagnetism). We believe that the current progress in nanobiotechnology makes the fabrication of functional TMV-based biotechnology devices simpler than ever.

Nanoscale science refers to the study and manipulation of matter at the atomic and molecular scales, including nanometer-sized single objects, while nanotechnology is used for the synthesis, characterization, and for technical applications of structures up to 100 nm size (and more). The broad nature of the fields encompasses disciplines such as solid-state physics, microfabrication, molecular biology, surface science, organic chemistry and also virology. Indeed, viruses and viral particles constitute nanometer-sized ordered architectures, with some of them even able to self-assemble outside cells. They possess remarkable physical, chemical and biological properties, their structure can be tailored by genetic engineering and by chemical means, and their production is commercially viable. As a consequence, viruses are becoming the basis of a new approach to the manufacture of nanoscale materials, made possible only by the development of imaging and manipulation techniques. Such techniques reach the scale of single molecules and nanoparticles. The most important ones are electron microscopy and scanning probe microscopy (both awarded with the Nobel Prize in Physics 1986 for the engineers and scientists who developed the respective instruments). With nanotechnology being based more on experimental than on theoretical investigations, it emerges that physical virology can be seen as an intrinsic part of it.

We report the binding of nanoparticles (NPs) to wild type (unmodified) tobacco mosaic virus (TMV). The viruses are simply mixed with citrate-coated, negatively charged gold and iron oxide nanoparticles (IONPs) in acidic solution. This results in TMV decorated along its whole length by the respective particles. Such a decoration usually requires chemical modification or mutation of TMV (e.g., cysteine residues), but here we simply reduce TMV's natural negative charge by protonation. The particles are protonated to a much smaller extent. This charge-based mechanism does not operate for neutral particles.

The rod-shaped plant virus tobacco mosaic virus (TMV) is widely used as a nano-fabrication template, and chimeric peptide expression on its major coat protein has extended its potential applications. Here we describe a simple bacterial expression system for production and rapid purification of recombinant chimeric TMV coat protein carrying C-terminal peptide tags. These proteins do not bind TMV RNA or form disks at pH 7. However, they retain the ability to self-assemble into virus-like arrays at acidic pH. C-terminal peptide tags in such arrays are exposed on the protein surface, allowing interaction with target species. We have utilized a C-terminal His-tag to create virus coat protein-templated nano-rods able to bind gold nanoparticles uniformly. These can be transformed into gold nano-wires by deposition of additional gold atoms from solution, followed by thermal annealing. The resistivity of a typical annealed wire created by this approach is significantly less than values reported for other nano-wires made using different bio-templates. This expression construct is therefore a useful additional tool for the creation of chimeric TMV-like nano-rods for bio-templating.

The use of plasma-polymerised fluoropolymer (CFxOy) thin films in the manufacture of microelectromechanical systems (MEMS) devices is well-established, being employed in the passivation step of the deep reactive ion etching (DRIE) process, for example. This paper presents an investigation of the effect of exposure to organic and aqueous liquid media on plasma-polymerised CFxOy thin films. Atomic force microscopy (AFM), scanning electron microscopy (SEM), ellipsometry, X-ray photoelectron spectroscopy (XPS) and dynamic wetting measurements were all employed as characterisation techniques. Highly basic aqueous solutions, including known silicon etchants, were found to cause delamination via degradation of the countersurface below the CFxOy thin film. Films were found to be stable in organic solvents, acidic aqueous solutions and slightly basic aqueous solutions.

Atomically smooth gold nanowires with high aspect ratios are grown using the seeded growth process. This allows control of the diameter of the nanowires to a high degree of precision. Two and four-probe nanoscale transport measurements reveal that the nanowires have low resistivity. Only a small increase in resistivity is observed between diameters of 29 nm and 185 nm suggesting that surface scattering is only a small contribution.

A novel method for the synthesis of high-active-surface-area, platinum tobacco mosaic virus (Pt-TMV) nanotubes is presented. A platinum salt is reduced to its metallic form on the external surface of a rod-shaped TMV by methanol, which serves as a solvent and reductant simultaneously. it was found that for the same Pt loading the Pt-TMV nanotubes had an electrochemically active surface area between 4 to 8 times larger than similarly sized Pt nanoparticles. A Pt-TMV catalyst displays greater stability in acidic conditions than those based on nanoparticles. When used as a catalyst for methanol oxidation, these Pt nanotubes display a 65% increase in catalytic mass activity compared to that based on Pt nanoparticles.

Semiconducting copper(I) oxide nanowires were fabricated by electrochemical deposition into porous polycarbonate membranes from a copper lactate electrolyte. Nanowire composition and structure were varied by controlling the deposition potential and deposition rate, respectively. Nanowires formed at more negative potentials had increased metallic Cu content leading to Cu2O/Cu composites. The nanowires were highly resistive but displayed enhanced conductivity under UV/visible light illumination. Optical spectra show both a plasmon resonance due to metallic copper and an interband absorption due to the bandgap of copper(I) oxide, calculated at 2.28 +/- 0.02 eV. (C) 2009 The Electrochemical Society. [DOI:10.1149/1.3208038] All rights reserved.

Self-assembled monolayer (SAM) formation of silanes on SiO2 surfaces has been extensively studied. However, SAMs formed on silicon nitride (Si3N4) substrates have not been explored to the same level as SiO2, even though they are of technological interest with a view to the chemical modification of microelectromechanical systems (MEMS). Therefore, this article presents the formation and characterisation of 3-aminopropyltrimethoxysilane (APTMS) SAMs on Si3N4 substrates from solution phase and vapour phase, compared to the well characterised APTMS SAMs formed on SiO2 surfaces. Contact angle, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and ellipsometric data indicate the formation of APTMS SAMs (0.55nm ellipsometric thickness) after 60min immersion of either SiO2 or Si3N4 substrates in APTMS solution (0.5mM in EtOH). By comparison Si3N4 substrates exposed to APTMS vapour, at 168 mbar for 60min, result in the formation of the equivalent of a bi or trilayer of APTMS.

The electrical transport and structural properties of tobacco mosaic virus ( TMV)-based nanostructures have been studied. Electroless deposition was used to coat the TMV outer surface with a 13 nm thick homogeneous Pt layer. SEM, TEM and electrical characterization of the obtained nanostructures has been performed. Using four independently controlled scanning tunnelling microscope tips we were able to perform four-point probe resistance measurements on linear virus assemblies and demonstrate the continuous nature of the metallic coating. The measured resistivity values of the virial nanowires exceeded the bulk value by 10-100 times; notwithstanding this the coated structure allowed high current densities, of the order of 10(5)-10(8) A cm(-2). The four-probe technique proved to be useful for analysing the electrical properties of bio-inorganic nanowires.

We present an improved method for fabricating tungsten STM tips for measuring nanoscale objects using a multiprobe STM. The tips were prepared by a ‘drop-off’ technique combined with a magnetic field. For magnetic field strengths above 150 Oe the electrolyte was seen to rotate about the tungsten anode. This rotation reduced the adhesion of bubbles and led to a reduction in the cone angle of the tips produced. This property is advantageous for multiprobe measurements as it allows one to bring multiple tips into close proximity.

This work presents nanoscale four-probe measurements on metallic nanowires using independently controlled scanning tunnelling microscope tips. This technique has allowed us to follow the change in resistance with probe separation. Gold, zinc and nickel nanowires were grown by electrodeposition within porous polycarbonate membranes. Their structure and composition were studied by transmission electron microscopy. Four-probe electrical transport measurements were taken using four independently controlled scanning tunnelling microscope tips positioned using a high resolution scanning electron microscope. Multiple I-V measurements were taken at varying tip separations, on each nanowire, and the change in resistance with separation was observed to be in good agreement with predictions based on the nanowire geometry. The resistivity values of the nanowires were found to be close to bulk values.