Multifunctional CNT-polymer composites for ultra-tough structural supercapacitors and desalination devices.

Pulsed electrodeposition of polyaniline (PANI) allows the fabrication of flexible, electrically conductive, nonwoven PANI-carbon nanotube (PANI-CNT) composite fabrics. They possess specific tensile strength and a modulus of toughness higher than that of aluminum matrix composites, titanium and aluminum alloys, steels, and many other structural materials. Electrochemical tests show that these nanocomposites additionally offer excellent cycle stability and ion electro-sorption and storage properties.

Ultra strong silicon-coated carbon nanotube nonwoven fabric as a multifunctional lithium-ion battery anode.

Materials that can perform simultaneous functions allow for reductions in the total system mass and volume. Developing technologies to produce flexible batteries with good performance in combination with high specific strength is strongly desired for weight- and power-sensitive applications such as unmanned or aerospace vehicles, high-performance ground vehicles, robotics, and smart textiles. State of the art battery electrode fabrication techniques are not conducive to the development of multifunctional materials due to their inherently low strength and conductivities. Here, we present a scalable method utilizing carbon nanotube (CNT) nonwoven fabric-based technology to develop flexible, electrochemically stable (∼494 mAh·g(-1) for 150 cycles) battery anodes that can be produced on an industrial scale and demonstrate specific strength higher than that of titanium, copper, and even a structural steel. Similar methods can be utilized for the formation of various cathode and anode composites with tunable strength and energy and power densities.

Intense pulsed light induced platinum-gold alloy formation on carbon nanotubes for non-enzymatic glucose detection.

We demonstrated a novel method for the formation of alloy nano-islands on carbon nanotube (CNT). The two metal layers (Pt, Au) were sputtered on CNTs and the intense pulsed light (IPL) was irradiated on the metal layers. The absorbed light provides enough energy for the diffusion mixing between Pt and Au, forming Pt-Au alloy phase. While the alloy is being formed by the IPL irradiation, the metal layers are broken into nano-islands on CNT due to the surface energy minimization between the metal layers and CNT. The surface characterizations of the Pt-Au/CNT were performed with X-ray diffraction, scanning electron microscope, and energy-dispersive X-ray spectroscopy. Different compositions of alloy nanoparticles were obtained by adjusting the deposition thicknesses of Pt and Au on CNT. Pt50Au50/CNT electrode showed the highest glucose oxidation current peak among Pt, Pt70Au30, Pt50Au50, Pt30Au70, and Au/CNT electrodes while the electroactive surface areas of them are kept to be similar (average surface area=7.00 cm2, coefficient of variation=0.06). The amperometric response of Pt50Au50/CNT electrode to the glucose concentrations showed a wide linear range up to 24.44 mM with a high detection sensitivity of 10.71 µA mM(-1) cm(-2). Reproducibility and long-term stability of the Pt-Au/CNT electrode were also proven in the experiments.

Carbon nanotube mat as mediator-less glucose sensor electrode.

In this paper, the direct electron transfer of glucose oxidase (GOx) on carbon nanotube (CNT) mat electrode is demonstrated. Because of the electrical conductivity and mechanical strength of CNT mat, it can be used as an electrode as well as a catalyst support. Therefore, the preparation process for the CNT mat based sensor electrode is simpler than that of the conventional CNT dispersed sensor electrodes. GOx was covalently immobilized on the oxidized CNT mat, which is connected to a wire by using silver paste and epoxy glue. Attenuated Total Reflectance Fourier Transform-Infrared (ATR-FTIR) result shows transmittance peaks at 1637 cm(-1) and 1525 cm(-1) which are corresponding to the band I and II of amide. Cyclic voltammetric shows a pair of well-defined redox peaks with the average formal potential of -0.425 V (vs. Ag/AgCl reference electrode) in the phosphate buffered saline solution (1 x PBS, pH 7.4). Calculated electron transfer rate constant and the surface density of GOx were 1.71 s(-1) and (3.27 +/- 0.20) x 10(-13) mol/cm2, respectively. Cyclic voltammograms of GOx-CNT mat in glucose solution show that the immobilized GOx retains its catalytic activity to glucose. The amperometric sensor response showed a linear dependence on the glucose concentration in the range of 0.2 mM to 2.18 mM with a detection sensitivity of 4.05 microA mM(-1) cm(-2). The Michaelis-Menten constant of the immobilized GOx was calculated to be 2.18 mM.

Carbon nanotubes with platinum nano-islands as glucose biofuel cell electrodes.

A novel method using intense pulsed light (IPL) for the metal nano-island formation on carbon nanotube (CNT) was introduced. The IPL-induced photothermal dewetting process improved platinum (Pt) catalyst utilization by transforming nano-islands from Pt film on CNT and increasing the surface area for the subsequent sputtering. The irradiation of high intensity of light on the Pt film causes surface-energy-driven diffusion of Pt atoms and forms the array of nano-islands on CNT. The thickness of Pt film can change the size of nano-islands. Cyclic voltammetry showed a dramatically improved glucose oxidation at the IPL morphology modified Pt-CNT electrode compared to the Pt sputtered CNT electrode without IPL irradiation. The power densities of glucose/air biofuel cell based on the morphology modified Pt-CNT electrode and the as-sputtered Pt-CNT electrode were 0.768 microW/cm(2) and 0.178 microW/cm(2), respectively. The biofuel cell based on morphology modified Pt-CNT electrode showed highly stable output in long-term performance. The power density dropped 14.1% in 30 days. Efforts are underway to improve the interface transfer to achieve higher potential and current output.