Emer Lahiff

Covalent attachment of functional side-groups to polyaniline nanofibres

Polyaniline (PAni) is an example of a conducting polymer that can be switched between an insulating and a conductive state. This switching is accompanied by a colour change. Recently, interest has developed in the nanofibre form of PAni as these low dimensional structures have a very high surface area, thus enabling a faster response time. We investigate how the surface chemistry of these nanofibres can be modified by covalently attaching functional side-groups. In particular, we demonstrate the attachment of both amide and carboxylic acid groups. This can be achieved using a simple reflux technique. The modified material retains its nanomorphology and the intrinsic electrochemical, spectroscopic and redox properties of PAni are also preserved. Both acid and amine side-groups are interesting in that they provide a template, which could be further altered to enhance the selectivity of PAni. Acid terminated chains can also be used to introduce self-doping behaviour to PAni.

Functionalised Nanostructured Polyaniline – A New Substrate for Building Adaptive Sensing Surfaces

A new method for covalently binding side-chains to the surface of solution based conducting polymer nanostructures is introduced in this paper. Modification of the structures is achieved by convenient reflux in the presence of a nucleophile, and post-functionalization purification is subsequently carried out by centrifugation. The entire process is easily scalable and hence suitable for bulk production of functionalized nanomaterials. In particular we focus on the modification of polyaniline nanofibres which can be synthesized by interfacial polymerization. Mercaptoundecanoic acid side-chains are attached to the polymer nanostructures, with the intrinsic nano-morphology of the material being maintained during the process. The modified PAni nanofibres provide a template for the attachment of other specific functional groups which could be used to target a particular species.

Controlling The Position And Morphology of Nanotubes For Device Fabrication

In producing nanotube based devices as diverse as composite materials and sensing platforms, the in‐situ growth of carbon nanotubes is most advantageous. Obtaining growth from organo‐metallic catalysts pre‐patterned on silicon wafers, precise structured nanotube patterns have then easily been incorporated into flexible stand‐alone composites. In an alternative approach, aligned and sometimes ultra‐long (>40μm) nanotubes have been obtained from catalytic growth in porous alumina membranes. Three‐way (T) and now four‐way (X) interconnects have been observed during the growth process, which can be incorporated into nanoscale electronic devices. Current approaches are for use as on‐chip interconnects and single tube devices that can be used as the transducer in small scale bio‐ and chemical‐sensors. In both these approaches, the density, morphology and position of the nanotubes can be controlled. This provides more precise placement of conduction channels in composites or devices, resulting in more efficient ...

Controllable Chemical Modification of Polyaniline Nanofibres

A method for simply and controllably modifying the surface of polyaniline nanofibres is described. The technique can be used to attach substituents bearing both acid and amine functional groups, making the materials suitable for further modification. Acid/amine functionalisation is achieved by a simple reflux reaction and therefore is a quick and easily scalable process. The modified nanofibres maintain their ability to switch between different states displaying distinctly different properties, thus making them suitable for adaptive sensing applications. As an example, we demonstrate how biomolecules can be attached to these functionalised nanofibres, to produce conducting polymer-based biosensors.

Controlled growth of arrays of straight and branched carbon nanotubes

Arrays of interconnect-type carbon nanotubes (CNTs) have been grown over etched silicon substrates. These tubes are grown over trenches ranging from 200-1000 nm in width. Through control of initial parameters such as trench size, catalyst concentration and the initial parameters for the chemical vapour deposition (CVD) of the tubes (gas flow rates, gas flow times and reaction temperature) dense arrays of CNTs spanning the trenches have been formed, with densities in the region of 1.6 interconnects per micron of trench length. High proportions of branch-structure CNTs have been noted within these arrays. The cleaved sections of silicon substrate are simply treated by drop-casting and drying catalyst-containing solution prior to CVD treatment. The density of the resultant arrays can be controlled through the density of the catalyst solution.