Molecular and structural insights into skin collagen reveals several factors that influence its architecture.

Although the biomechanical properties of skin and its molecular components have been extensively studied, little research has been devoted to understanding the links between them. Here, a comprehensive analysis of the molecular components of deer and cow skins was undertaken in order to understand the basis of their physical properties. These skins were chosen because they are known to be strong yet supple, exhibiting properties that have been exploited by man for centuries. Firstly, the tensile strength, tear strength and denaturation temperature of deer and cow skins were measured. Secondly, the organisation of the collagen fibrils and presence of glycosaminoglycans in each skin was investigated using polarising microscopy (PM), laser scanning confocal microscopy (LSCM), transmission electron microscopy (TEM), nuclear magnetic resonance (NMR) and small angle X-ray scattering (SAXS). Finally, amino acid, crosslink and glycosaminoglycan analyses were carried out on both skins in the study. The results of the study showed that individual physical properties such as tensile strength of the skin are derived from different combinations of biomolecular components which are reflected in collagen architecture. The "wavy" organisation of collagen fibres in deer skin was associated with a small fibril diameter, uniform glycosaminoglycan distribution and higher proportion of trivalent crosslinks. In contrast, the collagen fibrils in cow skin were large, contained a diverse glycosaminoglycan distribution and a higher proportion of tetravalent crosslinks, resulting in straight fibres. This study showed for the first time that the relationship between the structure of collagen in skin and its biomechanical functions is complex, arising from different architectural and molecular features including organisation of collagen fibres, diameters of collagen fibrils, distribution and amount of glycosaminoglycans and types and concentrations of crosslinks.

Elemental fingerprinting of mineral species in iron-fortified milk: anomalous small-angle X-ray scattering and resonant soft X-ray scattering studies.

Anomalous small-angle X-ray scattering (ASAXS) and resonant soft X-ray scattering (RSoXS) are two related techniques that can enable element-specific structural information to be obtained. The development of iron-fortified milk products can greatly benefit from such techniques, allowing the structure of iron and other minerals (such as native calcium) within the casein micelle to be determined. Each method has advantages and disadvantages: for ASAXS, the sample preparation is straightforward, but the signal is relatively low and information about the structure of Ca is difficult to access. RSoXS can be used to study both Ca and Fe, and the element-specific signals observed are proportionally much higher; however, the measurements are challenging due to the difficulty of precise control of the solution thickness using currently available vacuum-compatible liquid cells. Nevertheless, complementary results from both techniques indicate Fe is co-located with Ca, i.e. within the colloidal calcium phosphate nanoclusters that are present within native casein micelles in milk.

First stages of siderite crystallisation during CO2 corrosion of steel evaluated using in situ synchrotron small- and wide-angle X-ray scattering.

We use in situ synchrotron small- and wide-angle X-ray scattering (SAXS/WAXS) to demonstrate that the formation of crystalline siderite (FeCO(3)) during the corrosion of steel in CO(2)-saturated brine - a problem of practical interest relating to the growth of protective scales on the interior surface of oil and gas production pipelines - is preceded by the formation of a colloidal precipitate in the solution and an amorphous surface layer, both assumed to be amorphous ferrous carbonate. Grazing incidence SAXS shows instantaneous film formation upon the application of an anodic potential, followed by development of a separate population of particles at later times, then by the formation of crystalline species, observed by WAXS. These observations can be interpreted in terms of crystal nucleation within the amorphous surface layer. Traces of Cr(3+) in the solution significantly accelerate the precipitation rate of the colloidal precursor and accelerate the appearance of the crystalline scale. We speculate on the significance of these observations for the nucleation, growth and morphology of the corrosion scale and hence its protectiveness.

Understanding the selective etching of electrodeposited ZnO nanorods.

ZnO nanotubes were prepared by selective dissolution of electrodeposited nanorods. The effect of solution pH, rod morphology, and chloride ion concentration on the dissolution mechanism was studied. The selective etching was rationalized in terms of the surface energy of the different ZnO crystal faces and reactant diffusion. The nanorod diameter and chloride concentration are the most influential parameters on the dissolution mechanism because they control homogeneous dissolution or selective etching of the (110) and (002) surfaces. Bulk solution pH only has an effect on the rate of dissolution. By accurate control of the dissolution process, the nanomorphology can be tailored, and the formation of rods with a thin diameter (10-20 nm), cavity, or ultra-thin-walled tubes (2-5 nm) can be achieved.

Contamination of PDMS microchannels by lithographic molds.

By use of synchrotron X-ray fluorescence and Rutherford backscattering spectrometry, we show the SU-8 soft lithographic process contaminates PDMS. Residues of the antimony containing photoinitiator are transferred from the master mold to the surface of PDMS, uncontrollably intensifying the surface potential, leading to electroosmotic flow variability in PDMS microfluidic devices.

Can polymorphism be used to form branched metal nanostructures?

Branched metal nanostructures are of great technological importance because of their unique size- and shape-dependent properties. A kinetically controlled synthesis that uses polymorphism to produce branched nickel nanoparticles is presented. These nanoparticles consist of a face-centred cubic (fcc) core and extended arms of alternating fcc and hexagonal close-packed (hcp) nickel phases.

Synthesis, alignment, and magnetic properties of monodisperse nickel nanocubes.

This Communication describes the synthesis of highly monodispersed 12 nm nickel nanocubes. The cubic shape was achieved by using trioctylphosphine and hexadecylamine surfactants under a reducing hydrogen atmosphere to favor thermodynamic growth and the stabilization of {100} facets. Varying the metal precursor to trioctylphosphine ratio was found to alter the nanoparticle size and shape from 5 nm spherical nanoparticles to 12 nm nanocubes. High-resolution transmission electron microscopy showed that the nanocubes are protected from further oxidation by a 1 nm NiO shell. Synchrotron-based X-ray diffraction techniques showed the nickel nanocubes order into [100] aligned arrays. Magnetic studies showed the nickel nanocubes have over 4 times enhancement in magnetic saturation compared to spherical superparamagnetic nickel nanoparticles.

Nonequilibrium 2-hydroxyoctadecanoic acid monolayers: effect of electrolytes.

2-Hydroxyacids display complex monolayer phase behavior due to the additional hydrogen bonding afforded by the presence of the second hydroxy group. The placement of this group at the position α to the carboxylic acid functionality also introduces the possibility of chelation, a utility important in crystallization including biomineralization. Biomineralization, like many biological processes, is inherently a nonequilibrium process. The nonequilibrium monolayer phase behavior of 2-hydroxyoctadecanoic acid was investigated on each of pure water, calcium chloride, sodium bicarbonate and calcium carbonate crystallizing subphases as a precursor study to a model calcium carbonate biomineralizing system, each at a pH of ∼6. The role of the bicarbonate co-ion in manipulating the monolayer structure was determined by comparison with monolayer phase behavior on a sodium chloride subphase. Monolayer phase behavior was probed using surface pressure/area isotherms, surface potential, Brewster angle microscopy, and synchrotron-based grazing incidence X-ray diffraction and X-ray reflectivity. Complex phase behavior was observed for all but the sodium chloride subphase with hydrogen bonding, electrostatic and steric effects defining the symmetry of the monolayer. On a pure water subphase hydrogen bonding dominates with three phases coexisting at low pressures. Introduction of calcium ions into the aqueous subphase ensures strong cation binding to the surfactant head groups through chelation. The monolayer becomes very unstable in the presence of bicarbonate ions within the subphase due to short-range hydrogen bonding interactions between the monolayer and bicarbonate ions facilitated by the sodium cation enhancing surfactant solubility. The combined effects of electrostatics and hydrogen bonding are observed on the calcium carbonate crystallizing subphase.

Ultrafast growth of highly branched palladium nanostructures for catalysis.

Palladium is widely used as a catalyst in pharmaceutical and chemical syntheses as well as in the reduction of harmful exhaust emissions. Therefore, the development of high performance palladium catalysts is an area of major concern. In this paper, we present the synthesis of highly branched palladium nanostructures in a simple solution phase reaction at room temperature. By varying the nature of the organic stabilizer system we demonstrate control over the reaction kinetics and hence the shape of the nanostructures. Investigations into the structural evolution of the nanostructures show that they form from multiply twinned face centered cubic (fcc) nanoparticle nuclei. Reaction kinetics then determine the resulting shape where ultrafast growth is shown to lead to the highly branched nanostructures. These results will contribute greatly to the understanding of complex nanoparticle growth from all fcc metals. The nanostructures then show excellent catalytic activity for the hydrogenation of nitrobenzene to aniline.

In situ and ex situ studies of platinum nanocrystals: growth and evolution in solution.

In situ studies on the growth and evolution of platinum nanocrystals in solution were carried out using synchrotron-based X-ray diffraction (XRD) techniques. Ex situ low- and high-resolution transmission electron microscopy (TEM) were used to investigate the nanocrystal morphologies through the different growth stages. In a reaction with low precursor concentration, both XRD and TEM results show that growth occurs at a relatively slow rate and yields faceted morphologies, which are characteristic of a thermodynamically controlled regime. In contrast, the platinum nanocrystals in the high-concentration reaction form branched structures and grow at much greater rates under a kinetically controlled regime. Additionally the growth mechanism of the high-concentration reaction involves a morphology transformation from octapod-like shapes to porous nanostructures, which is brought about by a novel mechanism involving selective growth and etching processes that occur simultaneously and at comparable rates.

In situ USAXS measurements of titania colloidal paint films during the drying process.

Real-time ultra-small-angle X-ray scattering (USAXS) was used to follow the flocculation of titania particles in two paint systems as the paint films were drying. The inter-particle scattering was extracted by comparing the time series with diluted titania dispersion (having negligible inter-particle interaction). The paint system with pigment affinic groups showed considerably less flocculation than a pure acrylic emulsion. The results were confirmed by scanning electron microscopy (SEM) images of the dried film. The likely cause of this difference and utility of USAXS for such measurements are discussed.

Layered tungsten oxide-based organic-inorganic hybrid materials: an infrared and Raman study.

Tungsten oxide-organic layered hybrid materials have been studied by infrared and Raman spectroscopy and demonstrate a difference in bonding nature as the length of the interlayer organic "spacer" molecule is increased. Ethylenediamine-tungsten oxide clearly displays a lack of terminal -NH3(+) ammonium groups which appear in hybrids with longer organic molecules, thus indicating that the longer chains are bound by electrostatic interactions as well as or in place of the hydrogen bonding that must be present in the shorter chain ethylenediamine hybrids. The presence of organic molecules between the tungsten oxide layers, compared with the layered tungstic acid H2WO4, shows a decrease in the apical W=O bond strength, as might be expected from the aforementioned electrostatic interaction.