Novel Nanogold Syntheses and Control of the Interaction between Nanogold and Wool Fibres

Abstract

The coloured characteristic of gold nanoparticles make them an appealing and useful material. Arising from localised surface plasmon resonance, this colour is strong and stable and can be manipulated by controlling the size and shape of the particles. Professor Jim Johnston and Dr Kerstin Lucas of Victoria University of Wellington have utilised these characteristics through the dyeing of New Zealand wool with nanoparticle gold, creating a valuable technology that is currently being commercialised by Noble Bond Ltd under the registered trade mark Aulana®. This research programme has been concerned with developing new gold nanoparticle syntheses to extend the colour range available without the use of toxic structure directing agents, and also with improving the strength of binding between nanogold and wool fibres. Novel gold nanoparticle syntheses have been developed by the application of two reducing agents simultaneously. The mechanism of particle growth differs from that obtained when either reductant is used alone and results in different shaped and sized nanoparticles and so different coloured colloids. The resulting colloids have been applied to yarn samples to produce nanogold-wool composites. Thorough characterisation and analysis of the colloids and the resulting composites has been completed. Efforts were made to improve the wash-fastness of the composites by replacing the electrostatic attraction between the nanogold and the fibres with a stronger chemical bond. A mordant traditionally used with organic dyes was employed as a linking agent between stabilised nanoparticles and the amino acids in wool. Additionally the sulfur-sulfur bond of the cystine amino acid in wool was reduced to facilitate the formation of a gold-sulfur bond. The wash-fastness of the composites produced by these methods were tested and the nature of the nanogold-wool bond analysed via comprehensive characterisation. This research builds upon work completed by Professor Johnston’s research group. It adds novel nanogold syntheses to the group’s body of knowledge and further improves understanding of the interaction between nanogold and wool fibres.