Functionalised polyanaline nanofibers

Polyaniline (PAni) is a conducting polymer which switches between distinct states exhibiting dramatically different properties. The colour, conductivity and redox state of PAni all depend on the local chemical environment of the material. Consequently PAni has great potential for sensing applications. The nanostructured form of PAni is particularly interesting as it provides a very large surface-to-volume ratio that can lead to dramatic enhancement of sensor sensitivity and response time. In this work, we focus on derivatising polyaniline nanofibres. Using the technique described, carboxylate terminated side-chains can be covalently bound to solution based fibres

Towards the development of adaptive nanostructured platforms

Since their discovery in 1977, intrinsically conducting polymers have been studies for applications such as electronic devices, sensors and actuators[1-3]. Polyaniline (PAni) is an example of a stable conducting polymer and can be classified as an ‘adaptive material’ in that it can be switched between two or more forms (each with their own distinct characteristics) using an external stimulus. In contrast to a classical metallic conductor or a polymeric insulator, PAni can be switched reversibly between an insulating emeraldine base form and a conducting emeraldine salt. More recently, interest has developed in the area of nanostructured polyaniline[4-6]. These one-dimensional objects combine the advantages of an organic conductor and a high surface area material, thus making them suitable for a diverse range of applications such as chemical sensors, flash memory and electro-optic devices[7-9]. Here we present how polyaniline nanofibres can be successfully functionalised with both amine and carboxylate groups. The modified nanofibres maintain their ability to switch between diffferent forms displaying distinctly different optical properties (as shown by Raman and UV-vis spectroscopy), thus making them suitable for adaptive sensing applications. The attachment of functional groups to polyaniline nanofibres provides a route for manipulating the surface chemistry of nanofibres. While interesting materials in themselves, these functionalised nanofibres are also attractive as molecular scaffolds for building yet more innovative derivatives that nonetheless retain the basic underlying nanostructure and intrinsic characteristics of PAni. That we have demonstrated the ability to regulate the extent of side-chain attachment to one-dimensional objects, in a safe and simple manner, represents a step forward in the area of adaptive nano-structured materials. Functionalisation can be controlled using a simple, scalable and inexpensive technique[10-11]. [1] C. O. Baker, B. Shedd, P. C. Innis, P. G. Whitten, G. M. Spinks, G. G. Wallace, R. B. Kaner, Adv Mater 20 (2008) 155-+. [2] W. R. Small, F. Masdarolomoor, G. G. Wallace, M. Panhuis, J Mater Chem 17 (2007) 4359-4361. [3] J. G. Roh, H. R. Hwang, J. B. Yu, J. O. Lim, J. S. Huh, Journal of Macromolecular Science-Pure and Applied Chemistry A39 (2002) 1095-1105. [4] J. X. Huang, R. B. Kaner, Chemical Communications (2006) 367-376. [5] N. R. Chiou, C. M. Lui, J. J. Guan, L. J. Lee, A. J. Epstein, Nat. Nanotechnol. 2 (2007) 354-357. [6] F. Masdarolomoor, P. C. Innis, S. Ashraf, R. B. Kaner, G. G. Wallace, Macromol. Rapid Commun. 27 (2006) 1995-2000. [7] S. Virji, J. X. Huang, R. B. Kaner, B. H. Weiller, Nano Lett. 4 (2004) 491-496. [8] S. Virji, R. B. Kaner, B. H. Weiller, J. Phys. Chem. B 110 (2006) 22266-22270. [9] S. Virji, R. B. Kaner, B. H. Weiller, Chemistry of Materials 17 (2005) 1256-1260. [10] E. Lahiff, T. Woods, W. Blau, G.G. Wallace, D. Diamond, Synth. Metals, accepted. [11] E. Lahiff, S. Bell, D. Diamond, Mat. Res. Soc. Symp. Proc., Vol. 1054, FF-05-05, 200

From science fiction to reality: the dawn of the biofabricator

[extract] Science is catching up to science fiction. Last year a paralysed man walked again after cell treatment bridged a gap in his spinal cord. Dozens of people have had bionic eyes implanted, and it may also be possible to augment them to see into the infra-red or ultra-violet. Amputees can control bionic limb implant with thoughts alone