We report the fabrication and characterisation of the first graphene ring micro electrodes with the addition of a miniature concentric Ag/AgCl reference electrode. The graphene ring electrode is formed by dip coating fibre optics with graphene produced by a modified Hummers method. The reference electrode is formed using an established photocatalytically initiated electroless deposition (PIED) plating method. The performance of the so-formed graphene ring micro electrodes (GRiMEs) and associated reference electrode is studied using the probe redox system ferricyanide and electrode thicknesses assessed using established electrochemical methods. Using 220 μm diameter fibre optics, a ∼15 nm thick graphene ring electrode is obtained corresponding to an inner to outer radius ratio of >0.999, so allowing for use of extant analytical descriptions of very thin ring microelectrodes in data analysis. GRiMEs are highly reliable (current response invariant over >3,000 scans), with the concentric reference electrode showing comparable stability (current response invariant over >300 scans). Furthermore the micro-ring design allows for efficient use of electrochemically active graphene edge sites and the associated nA scale currents obtained neatly obviate issues relating to the high resistivity of undoped graphene. Thus, the use of graphene in ring microelectrodes improves the reliability of existing micro-electrode designs and expands the range of use of graphene-based electrochemical devices.
We report the novel use of semiconductor photocatalysis for the deposition of metal onto insulating surfaces and the in-process formation of nano-structured porosity within this metal. In the process of Photocatalytically Initiated Electroless Deposition (PIED) we have developed a controllable, spatially selective and versatile metallisation technique with several advantages over traditional, non-photocatalytic techniques such as enhanced controllability and purity of the deposit as well as reduced operational costs and environmental impact. With the addition of a self-assembled, hexagonally close-packed microparticle template to the substrate prior to metal deposition, PIED can be used to fabricate thin metal films with highly ordered porosity on the nano-scale. Nanoporous metallisation in this way is able to produce substrates with potentially wide applications such as membrane and separation technology, energy storage and sensors – especially surface enhanced resonance Raman spectroscopy (SERRS).
Abstract. For the study of the coupled interfacial-mass transfer kinetics of, inter alia, TBP, TODGA, CyMe 4 -BTBP and CyMe 4 -BTPhen based solvent extraction processes, a new rotating diffusion cell (RDC) apparatus has been established at Lancaster University. RDC studies of Ce(IV)/TBP and Ce(III)/TODGA extraction systems have been undertaken in order to improve the understanding of the chemical and kinetic processes involved. In each case, an interesting dependency on local hydrodynamics at the solution phase boundary with results suggesting that the organic extractant molecules migrate into the aqueous phase in order to capture Ce.
We present the novel use of Photocatalytically Initiated Electroless Deposition (PIED) for the deposition of metal films with highly ordered arrays of sub-µm (hemi)spherical pores directly onto the surface of insulating organic membrane-based substrates. This is achieved by sensitisation of the target substrate with a TiO2 photocatalyst followed by the self-assembly of a hexagonally close packed polystyrene microsphere template at the substrate surface. Metallisation then occurs through PIED into the template interstices and directly onto the TiO2 sensitised membrane surface. The dimensions of the resultant pores in the deposited metal are determined by the size of the template microspheres while metal film thickness may be controlled by the deposition period. The fabrication of nanoporous metal by this novel method adds a conductive and permeable metallic structure of high surface area to an otherwise electrically insulating polymer membrane surface. Such metallised insulating membranes have potentially wide applications in membrane and separation technology, desalination and electrode / solid electrolyte composites for fuel cells.
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