Andrea E. Russell

Lost at sea: where is all the plastic?

Millions of metric tons of plastic are produced annually. Countless large items of plastic debris are accumulating in marine habitats worldwide and may persist for centuries ([ 1 ][1]–[ 4 ][2]). Here we show that microscopic plastic fragments and fibers ([Fig. 1A][3]) are also widespread in the

Sculpted substrates for SERS.

Sculpted SERS-active substrates are prepared by assembling a closed packed monolayer of uniform polystyrene colloidal particles (diameter 350 to 800 nm) onto an evaporated gold surface and then electrodepositing gold through this template to produce films with controlled thicknesses, measured as fractions of the sphere diameter, d. The resulting surfaces consist of a regular hexagonal array of interconnected spherical cross-section dishes. The role of localised plasmons in determining the SERS enhancement factor obtained for benzene thiol adsorbed onto the surfaces is then investigated by correlation of the UV-visible reflectance spectra, 400 to 900 nm, measured at the same positions on the substrate surfaces, with the SERS spectra. The results are interpreted in terms of the relative contributions of plasmons that are free to propagate across the top surface and those trapped within the dishes of the sculpted surface.

Spectroelectrochemical Study of the Role Played by Carbon Functionality in Fuel Cell Electrodes

X-ray absorption spectroscopy was used to identify specific types of nitrogen and sulfur-based carbon functionality present in the carbon black supports of fuel cell anodes and cathodes. The effects of these functional groups on the electrocatalytic performance of small platinum particles, dispersed on the carbon, during methanol oxidation and oxygen reduction were assessed. Electrodes functionalized with nitrogen had enhanced catalytic activities toward oxygen reduction and methanol oxidation relative to untreated electrodes. Although electrodes with sulfur functionality had higher oxygen reduction activities than untreated carbons, the activity of these electrodes toward methanol oxidation was found to be lower than electrodes manufactured from untreated carbon. It was found that carbon supports functionalized with both nitrogen and sulfur initiated the formation of Pt particles smaller in size than those observed on untreated carbon supports.

The Development of a Stable Citrate Electrolyte for the Electrodeposition of Copper‐Nickel Alloys

The stability of citrate electrolytes for the electrodeposition of copper-nickel alloys and multilayers has been investigated. It was found that electrolytes operating at pH 4 are unstable due to the formation of an insoluble citrate complex. This complex had previously been thought to be copper citrate dihydrate, Cu 2 C 6 H 4 O 7 .2H 2 O, but elemental analysis of the precipitate revealed it to be a heteronuclear copper-nickel citrate complex. Calculations of the distribution of citrate species in a typical plating solution was undertaken to identify experimental conditions under which the insoluble citrate complex is not formed. These studies indicate that increasing the pH of the citrate solution from 4 to 6 should produce a stable electrolyte. Experimental studies show that the electrolytes at pH 6 are stable for periods of several weeks, in agreement with the predictions of the speciation calculations. The stable citrate electrolytes were used to deposit Cu-Ni alloys. It was found that alloys could be deposited from these electrolytes with almost 100% current efficiency and with a morphology and composition comparable to those obtained from the unstable citrate electrolytes.

In situ X-ray absorption spectroscopy and X-ray diffraction of fuel cell electrocatalysts

The utility of in situ X-ray absorption spectroscopy (XAS) in determining structural parameters, through analysis of the extended X-ray absorption fine structure (EXAFS), and electronic perturbations, through a white line analysis of the X-ray absorption near edge structure (XANES), is demonstrated for Pt/C, PtRu/C and PtMo/C fuel cell electrodes. The results provide verification that the enhancement of CO tolerance of the alloy catalysts occurs via an intrinsic mechanism for the PtRu alloy, whilst a promotion mechanism is in operation for the PtMo alloy. Preliminary results of an in situ powder X-ray diffraction (XRD) method which utilises synchrotron radiation (SR) and a curved image plate detector are also presented, using Pd/C as an example. The lattice expansion upon formation of the β-hydride is clearly observed.

Dressing plasmons in particle-in-cavity architectures

Metallic nanoparticles inside metal cavities show extremely strong plasmonic field enhancement both theoretically and experimentally. Plasmonic coupling gives a universal power-law dependence on particle-surface gap, both for field enhancement and resonant wavelength shift.

Quantitative electrochemical SERS of flavin at a structured silver surface.

In situ electrochemical surface enhanced Raman spectra (SERS) for an immobilized monolayer of a flavin analogue (isoalloxazine) at nanostructured silver surfaces are reported. Unique in the present study, the flavin is not directly adsorbed at the Ag surface but is attached through a chemical reaction between cysteamine adsorbed on the Ag surface and methylformylisoalloxazine. Even though the flavin is held away from direct contact with the metal, strong surface enhancements are observed. The nanostructured silver surfaces are produced by electrodeposition through colloidal templates to produce thin (<1 microm) films containing close-packed hexagonal arrays of uniform 900 nm sphere segment voids. The sphere segment void (SSV) structured silver surfaces are shown to be ideally suited to in situ electrochemical SERS studies at 633 nm, giving stable, reproducible surface enhancements at a range of electrode potentials, and we show that the SER spectra are sensitive to subfemtomole quantities of immobilized flavin. Studies of the SER spectra as a function of the electrode potential show clear evidence for the formation of the flavin semiquinone at the electrode surface at cathodic potentials.

Re-evaluation of the outcome of a multiple component reaction—2- and 3-amino-imidazo[1,2-a]pyrimidines?

Multi-component reactions between aldehydes, isonitriles and 2-aminoazines do not always give the expected products.

Water-splitting electrocatalysis in acid conditions using ruthenate-iridate pyrochlores

The pyrochlore solid solution (Na0.33Ce0.67)2(Ir1−xRux)2O7 (0≤x≤1), containing B-site RuIV and IrIV is prepared by hydrothermal synthesis and used as a catalyst layer for electrochemical oxygen evolution from water at pH<7. The materials have atomically mixed Ru and Ir and their nanocrystalline form allows effective fabrication of electrode coatings with improved charge densities over a typical (Ru,Ir)O2 catalyst. An in situ study of the catalyst layers using XANES spectroscopy at the Ir LIII and Ru K edges shows that both Ru and Ir participate in redox chemistry at oxygen evolution conditions and that Ru is more active than Ir, being oxidized by almost one oxidation state at maximum applied potential, with no evidence for ruthenate or iridate in +6 or higher oxidation states.

In situ far-infrared evidence for a potential dependence of silver–water interactions

The influence of the adsorption of fluoride on the bonding of water to a silver electrode surface has been studied by observing the ν(Ag–O) stretching vibration in the far-IR. The experiments were conducted using potential-difference external-reflectance spectroscopy with synchrotron radiation as the far-IR source. It was found that the adsorption of fluoride ions at potentials positive of the potential of zero charge (p.z.c.) decreased the coverage of water adsorbed onto the silver electrode surface. At potentials negative of the p.z.c., water molecules were found to be bound to the silver surface through the oxygen atom.