The development of nanoporous metal membranes for analytical separations

• Main Author: Bromley, Michael
• Other Authors: Boxall, Colin
• Published: Lancaster University 2013
• Subjects: 620.1
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.602577

This thesis reports the novel use of semiconductor photocatalysis for the deposition of metal on to insulating surfaces through Photocatalytically Initiated Electroless Deposition (PIED). In PIED, a controllable and spatially selective process has been developed for the photogeneration of robust, conducting metal layers on semiconductor-sensitised insulator surfaces with several advantages over traditional, non-photocatalytic techniques including enhanced controllability and deposit purity, reduced operational costs and environmental impact. Layers of various metals including Ag, Pd and Ni have been generated by PIED onto TiO2 sensitised quartz glass slides and organic membrane-based substrates. With the addition of a microparticle template material, nanoporous metal films with both single and multi-layer, highly ordered arrays of sub-µm (hemi) spherical pores have also been depsited directly onto the surface of insulating substrates. This has been achieved by the self-assembly, assisted by the photogenerated hydrophilicity of the TiO2 sensitiser, of a hexagonally close packed polystyrene microsphere template onto the target substrate prior to metallisation. Metal is then deposited through PIED into the interstitial spaces of the, subsequently removed, microsphere template and directly onto the TiO2 sensitised substrate surface. The dimensions of the resultant pores in the deposited metal are determined by the size of the microspheres used to for the template 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 substrates have potentially wide applications in membrane and separation technology, energy storage and sensors – especially surface enhanced resonance Raman spectroscopy (SERRS), desalination and electrode / solid electrolyte composites for fuel cells.