Effect of Surfactant Concentration and Aggregation on the Growth Kinetics of Nickel Nanoparticles

The effect of trioctylphosphine (TOP) concentration on the growth of nickel nanoparticles is studied using <i>in situ</i> synchrotron small-angle X-ray scattering. The growth kinetics are fitted using a two-step nucleation and autocatalytic growth model. TOP acts as a nucleating agent and then acts as an inhibitor against rapid particle growth. Increasing the TOP concentration results in smaller nanoparticles. Once there is a critical concentration of nickel particles above a certain size, they start to aggregate. This results in a broadening of the particle size distribution at later times due to particles on the outside of the aggregates continuing to grow, while those on the inside cease to grow as the nickel precursor is locally depleted

Controlling chain flexibility in collagen networks to produce hydrogels with distinct properties

<p>The structure, mechanical properties, and optical density of gels prepared from collagen in a manner that induces the dynamical arrest of the constituent polymers before substantial fibrillogenesis can take place have been investigated. Small angle X-ray scattering and confocal laser scanning fluorescence microscopy reveal that these gels exhibit substantially different network structures, over length scales ranging from a few nanometers to many microns, when compared with traditional collagen networks in which fibrillogenesis is intentionally induced. The highly associated arrangements of the more flexible structural components found in the arrested network yield a considerably lower optical density and higher viscoelastic storage modulus when compared to a “conventional” collagen gel; while the small amount of fibrils that do manage to form still yield strain stiffening and account for the fact that at high strains, moduli from both systems fall onto the same master curve.</p

Real-Time Synchrotron Small-Angle X‑ray Scattering Studies of Collagen Structure during Leather Processing

The collagen structure in skins is significantly influenced by the cross-linking chemistry adopted during leather processing. We have developed an in situ technique to measure real-time collagen structure changes using synchrotron-based small-angle X-ray scattering (SAXS). Three common mineral tanning systems, basic chromium sulfate (BCS), zirconium sulfate (ZIR) and an aluminosilicate-based reagent (ALS) were used to stabilize collagen in ovine skin. Studying the molecular changes by in situ SAXS revealed a range of tanning mechanisms: a complex combination of covalent cross-linking, electrostatic interactions and hydrogen bonding by BCS, hydrogen bonding interactions by ZIR, and the formation of colloidal aggregates by ALS. These results unravel the mechanisms of producing leathers with different properties, explaining why ZIR produces denser leathers while ALS produces softer leathers compared to conventional BCS leathers. ZIR and ALS are environment-friendly alternatives to BCS, and understanding their mechanisms is important for a more sustainable future for the leather industry

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