Carol Lynam

Carbon nanotube network modified carbon fibre paper for Li-ion batteries

Here we report on the direct deposition of large quantities of highly porous carbon nanotube networks onto a carbon fibre paper support; subsequently utilised as the anode in a Li-ion battery application showing improved long-term performance and chemical stability with a significant fully reversible capacity of 546 mAh g−1.

Photocatalytic oxidation of methanol using titanium dioxide/single-walled carbon nanotube composite

Titanium dioxide/single-walled carbon nanotube (TiO 2 /SWNT) composites were prepared for photocatalytic applications. The composites were characterized using UV-visible and Raman spectroscopy, zeta-potential measurements, cyclic voltammetry coupled with a photoreactor, scanning electron microscopy, and transmission electron microscopy coupled with energy dispersive X-ray spectroscopy. The photocatalytic activity of TiO 2 and the TiO 2 /SWNT composite was investigated using the photo-oxidation of methanol in sulfuric acid as supporting electrolyte. The results indicate that the TiO 2 /SWNT composite enhances the photocatalytic activity compared to TiO 2 alone. Electrochemical studies of the TiO 2 /SWNT composite were also carried out in various supporting electrolytes and the presence of SWNTs was shown to increase the current achieved in voltammetric measurements.

Carbon-Nanotube Biofiber Microelectrodes

All-biocompatible carbon-nanotube fibers were formed using wet spinning. In this process the spinning solutions used are carbon nanotubes dispersed using biomolecules such as hyaluronic acid and chitosan. We compare the effect of a coagulation bath containing either a polymer binder, e.g., polyethyleneimine, or simply a precipitating solvent system, e.g., acetone. The electrical, mechanical, and morphological properties of the resulting fibers were studied. Biocompatible electrode structures were generated suitable for a variety of biomedical applications, e.g., in biosensors or in systems where the application of an electrical field is advantageous (e.g., stimulation of electrically excitable cells such as nerve and muscle cells).

Direct ascorbic acid detection with ferritin immobilized on single-walled carbon nanotubes

Ferritin protein was noncovalently immobilized onto single-walled carbon nanotubes (SWNTs). This SWNT/ferritin composite was characterized using cyclic voltammetry, UV-visible spectroscopy, Raman spectroscopy, and high-resolution transmission electron microscopy. The use of the SWNT/ferritin film as an amperometric biosensor was demonstrated by sensing 1.0 mM ascorbic acid in phosphate-buffered saline solution with a sensitivity of 767 μA/mg. It demonstrated that ferritin protein bound to SWNTs enhances the oxidation reaction of ascorbic acid over 11-fold.

Varying solvent polarity to tune the enantioselective quenching of a calixarene host

Calixarene L1 has been designed to behave as a fluorescent molecular sensor capable of distinguishing between chiral amines on the basis of their size and chirality. Fluorescence quenching studies of calixarene L1 in methanol demonstrated no enantiomeric selectivity for a short chain amino alcohol, phenylglycinol, while excellent selectivity was observed for a longer chain amino alcohol, phenylalaninol (PA). The effect of solvent on the fluorescent properties of this calixarene in the presence of PA has been studied, and demonstrates that varying solvent polarity allows the wavelength of enantiomer selectivity to be tuned from 227 nm to 440 nm. While enantiomeric selectivity is observed in methanol at 227 nm, no discrimination is achieved in acetonitrile. Chiral discrimination is statistically possible with L1 and PA in chloroform at 227 nm, but it is not comparable with the extent of discrimination achieved in methanol. In chloroform a new emission band at a longer wavelength (440 nm) is formed with R-PA in solution with L1, an effect that is not observed with the S-enantiomer. This new band in chloroform at 440 nm allows very effective chiral discrimination and has been attributed to the presence of two different conformations of calixarene L1, which is reinforced by 1H-NMR studies and molecular modelling studies.

The optimum functionalization of carbon nanotube/ferritin composites

We fabricated a covalently linked composite composed of functionalized single-walled carbon nanotubes (f-SWNT) and ferritin protein as nanoparticles. The various f-SWNTs were prepared using an acid treatment of purified SWNT for different functionalization times (30, 60, 120 and 180 min), and ferritin was immobilized on each of the f-SWNT by covalent immobilization. The specific capacitance of the f-SWNT and the electrochemical activity of the f-SWNT/ferritin composites showed a Gaussian distribution. From the electrochemical analysis, the ferritin composite with functionalized SWNT for 60 min showed the highest capacitance and electrochemical activity than other f-SWNT/ferritin composites. This result suggests the optimum value for the best performance of the electrochemical properties of f-SWNT/ferritin composites was found for a potential bioapplication.

Functionalising carbon nanotubes

The realisation of efficient functionalisation strategies is critical to the further development of CNT science and technology. The area has attracted a great deal of attention and a host of innovative approaches developed. However, as the examples highlighted here illustrate, many challenges remain.

Characterisation of titanium dioxide-single walled carbon nanotubes composite fibres prepared by the wet spinning technique

Carbon nanotubes (CNTs) have been extensively interested due to their unique mechanical and electrical properties. Owning to their outstanding electronic, thermal, structural properties, chemical stability, low density, high mechanical strength, large surface area, high modulus and high conductivity, CNTs are desired for a broad range of applications in many fields such as energy storage, molecular electronics, nanoprobes, sensors, composite materials and templates. To enhance the performance of titanium dioxide (TiO2) nanotubes for future applications, single-walled carbon nanotubes (SWNTs) were chosen for making the composite material with TiO2. In this work, a simple, rapid and effective wet spinning methodology has been conducted and successfully applied to fabricate the (TiO2) composites fibres. The (TiO2) nanorods were dispersed with SWNTs using biopolymer as a dispersant. By employing the wet spinning technique and choosing an appropriate coagulant, the stable suspension of TiO2. and (TiO2) composite were directly injected into the coagulation bath to produce fibres. These fibres were characterized using atomic force microscopy (AFM), scanning electron microscopy (SEM), conductivity measurement, and Raman spectroscopy. Moreover, the AFM results indicated the samples characteristics according to SWNTs at various concentrations in (TiO2) suspension. This study also suggested that different concentration of SWNTs affected the RMS roughness value. The Raman spectra showed peaks which corresponded to their characteristic peaks of (TiO2) and SWNTs. The SEM results revealed that the bundles of SWNTs connecting with 2 points of the TiO2 surface was clearly seen whereas some aggregations obtaining from either TiO2 or a dispersant were found. The compounds were identified mainly by comparing their Raman spectra with those of bare TiO2. and SWNTs. In addition, the combination between CNTs and (TiO2) has been studied to improve the properties of these composite fibres. The mechanical and electrical properties along with surface morphology and electrochemistry of the resulting fibres were also investigated. The presence of SWNTs clearly improved the electrical properties of the composite fibres compared to bare (TiO2) The application of the TiO2/SWNTs composites will be further investigated.

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.