Self-Assembly of Electrically Conducting Biopolymer Thin Films by Cellulose Regeneration in Gold Nanoparticle Aqueous Dispersions

Electrically conducting cellulose films comprising interconnected networks of gold nanoparticles were prepared by a facile self-assembly procedure. The hybrid films were produced by immersing spin-coated viscous N-methylmorpholine-N-oxide/dimethyl sulfoxide solutions of cellulose into aqueous dispersions of gold nanoparticles of variable concentration Regeneration of an intact cellulose fiber matrix with integrated gold nanoparticles occurred spontaneously to produce self-supporting, defect-free metallized films, 2.5-12 mu m in thickness and with nanoparticle loadings of up to 44 wt %. The hybrid films displayed surface plasmon resonance bands consistent with discrete or uniaxially coupled nanoparticles depending on the extent of gold loading. Stress/strain measurements indicated that the cellulose films were not mechanically compromised by the incorporation of the gold nanoparticles, which were stabilized within the biopolymer matrix by interactions with the ether oxygen and hydroxyl groups of D-glucopyranose (FTIR spectrosopy results) Room temperature Van der Pauw measurements indicated that the hybrid films were electrically conducting above a gold nanoparticle loading of 20 wt % In addition, measurements of resistivity from 4 2 to 300 K showed a transformation from metallic band-like conduction (44 wt %) to Mott-type carrier hopping behavior at lower gold nanoparticle loadings (33 wt %) and low temperatures (T <100 K). Given the widespread nature of the existing cellulose industry, self-supporting gold nanoparticle/cellulose hybrid films could have diverse applications in smart papers and textiles, as well as in numerous devices involving microelectronic components, catalysts and chemical sensors