John Watt

Au-Pd core-shell nanoparticles as alcohol oxidation catalysts: effect of shape and composition.

The right combination: Shape and composition are two important factors governing the catalytic properties of bimetallic nanocatalysts. Combining gold and palladium in a Au-core–Pd-shell structure coupled with an icosahedral morphology is shown to maximize catalytic performance for the selective oxidation of the biorenewable sources glycerol and 1,2-propanediol to glyceric and lactic acids, respectively.

Formation of Metal Nanoparticles Directly from Bulk Sources Using Ultrasound and Application to E‐Waste Upcycling

A method for creating nanoparticles directly from bulk metal by applying ultrasound to the surface in the presence of a two-part surfactant system is presented. Implosive collapse of cavitation bubbles near the bulk metal surface generates powerful microjets, leading to material ejection. This liberated material is captured and stabilized by a surfactant bilayer in the form of nanoparticles. The method is characterized in detail using gold, but is also demonstrated on other metals and alloys, and is generally applicable. It is shown that nanoparticles can be produced regardless of the bulk metal form factor, and the method is extended to an environmentally important problem, the reclamation of gold from an electronic waste stream.

Efficient conversion of lignin into a water-soluble polymer by a chelator-mediated Fenton reaction: optimization of H2O2 use and performance as a dispersant

Room temperature Fenton (FEN) and chelator-mediated Fenton (CMF) reactions were examined for transforming lignin into a water-soluble polymer. Compared to depolymerization of lignin, this has the advantage of potentially yielding a product directly without requiring further upgrading. With the goal of optimizing the use of the expensive reagent H2O2, initial studies were performed with lignin from an organsolv process (OS) in thin films with a multi-well format that allows simultaneous assay of 76 reaction conditions. The results showed that H2O2 is more efficiently used in CMF compared with FEN, and that the greatest amount of lignin solubilized per mass of H2O2 consumed occurs at low initial concentrations of H2O2 (<1%). Further optimization of reaction conditions was performed with OS lignin in powder form. Results obtained upon optimizing reactant concentrations, pH and Fe-chelator, and with O2 bubbling indicate that a yield of 1 g lignin solubilized per g of H2O2 consumed is achievable. Chemical and molecular weight analyses showed that the reaction results in extensive opening of the aromatic rings and generation of acid groups, yielding a water-soluble polymer with molecular weight distribution that is comparable to that of the starting material but with a small amount of low MW species. Similar yields and extents of ring opening resulted for three other distinctly different lignins. The effectiveness of the OS lignin-derived polymeric material in dispersing alumina particles was studied by zeta potential, light scattering, and Turbiscan stability measurements. These measurements showed that the lignin-derived material performs comparably to poly(acrylic acid) PAA of similar molecular weight. Considering that the selling price for bulk PAA is greater than twice that of H2O2 on a per mass basis, this approach holds promise for generating value from lignin.

Magnetic Nanocomposites and Their Incorporation into Higher Order Biosynthetic Functional Architectures

A magnetically active Fe3O4/poly(ethylene oxide)-block-poly(butadiene) (PEO-b-PBD) nanocomposite is formed by the encapsulation of magnetite nanoparticles with a short-chain amphiphilic block copolymer. This material is then incorporated into the self-assembly of higher order polymer architectures, along with an organic pigment, to yield biosynthetic, bifunctional optical and magnetically active Fe3O4/bacteriochlorophyll c/PEO-b-PBD polymeric chlorosomes.