The Nanoporous Metallisation of Insulating Substrates through Photocatalytically Initiated Electroless Deposition (PIED)

Abstract

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).

The Nanoporous Metallization of Polymer Membranes through Photocatalytically Initiated Electroless Deposition

“…As previously described in our studies of the metallisation of glass substrates with nanoporous metal films (4, 7), hexagonally close packed arrays of 1 µm microspheres provide the template material around which PIED generated nanoporous metal film may be formed. We have found that such microsphere array templates may also be deposited onto the PVDF membrane substrates in the same manner as on glass, although the spheres exhibit less regular packing on membranes than on similarly prepared glass substrates (4,11). This may be attributable to two factors; firstly, the rough surface morphology of the PVDF membrane, Figure 3, disrupting the self-assembly process of the microspheres, leading to an increased number of dislocations within the array; and secondly, the potentially reduced efficiency of the non-annealed photocatalyst resulting in the super-hydrophilicity of the irradiated TiO 2 surface (9, 12) being less readily generated and the microsphere suspension spreading less freely over the substrate surface.…”

“…These activities are important in a wide range of industries including pharmaceuticals, mining, foodstuffs, wastewater processing, power generation and nuclear. Using our recently reported insulator metallisation process of Photocatalytically Initiated Electroless Deposition (PIED) (1)(2)(3)(4), we aim to develop novel, highly ion selective membrane-based separation technologies through a combination of supported ligand membranes and supplemental electrochemical control by overlying nano-engineered metal layers. Layers of porous metal with controllable pore size, distribution and metal thickness deposited on ion selective membranes (ISMs) may act as in-situ electrodes offering electrochemical control over the environment at the ISM-solution interface.…”

“…The principles of PIED have been described in detail elsewhere (1)(2)(3)(4) but may be summarised as follows. Metal deposition is initiated through a semiconductor photocatalysis based process whereby, initially, electron-hole pairs are generated in TiO 2 particles upon the absorption of ultra-band gap light energy (λ = 312 nm).…”