J.H. Johnston, K.A. Lucas, M. Parry, J. Pflaum
Victoria University of Wellington,
Keywords: nanocomposite, nanogold, nanosilver, polymer, wool, textiles, luxury, dichroic
Summary:The nanofunctionalisation of natural fibres and polymers with particular noble metal nanoparticles to form new nanocomposite materials opens up exciting new applications and business opportunities. Noble metal nanoparticles, notably gold and silver, exhibit localised surface plasmon resonance (LSPR) absorption effects wherein the resonant interaction of visible electromagnetic radiation with the oscillation of surface electrons gives rise to specific LSPR visible absorptions. The wavelength and hence the colour exhibited, depends on the size and shape of the nanoparticle and the dielectric constant of the surrounding medium. We have innovatively captured this LSPR effect in Aulana®, a luxury nanogold-wool textile product suite, which uniquely combines the nanoscience of gold with wool fibre protein chemistry to produce a boutique colour range of nanogold-wool textiles for high value international luxury markets. Spherical gold nanoparticles of about 10-20 nm are pink-red and with increasing size the colour changes through shades of purple, blue-grey to grey. The Aulana® “Midas Rug” which is being commercialised by Noble Bond Ltd, www.noblebond.co.uk is a world first product for luxury rug markets. Nanogold and nanosilver polymer composites with the thermoplastic polyurethane and nylon polymers, and with polyurethane latex suspensions used in coating formulations have been developed. The nanogold polymer composites are pink to dark purple in colour, and the nanosilver polymer composites are yellow to brown, due to the LSPR interaction of light by the gold and silver nanoparticles respectively. The nanoparticles are bound to the polymer host and latex suspensions and do not leach out or rub off, as often is the case for silver nanoparticles in composites formed by the simple mixing of the polymer and nanoparticle components. This desirably results in very low metal ion leaching into the environment. The composites can be processed by conventional thermoplastic extrusion and moulding methods. The nanosilver-polymer and nanogold-polymer composites exhibit effective marine antifouling properties. The nanogold-polymer composite materials possess interesting dichroic properties wherein they exhibit one specific colour when viewed in transmitted light and another specific colour in reflected light. These dichroic polymer composites can be 3D printed to provide a range of devices and designer products inspired by such novel dichroic features for various new industry and consumer applications.