Peptides interact with the nanotube surface and each other to form wrapped nanotubes. Amphiphilic properties of the peptides make wrapped nanotubes soluble in water.

Self-assembly and specificity in biological systems derives from control of surfaces.  Proteins, DNA, and other biological materials have evolved diverse complementary surfaces that enable interactions that lead to self-assembly and specificity.  To endow inanimate materials with biological surfaces that exploit these assets, biological materials must interact with non-biological materials.  The theme of this idea is to develop systems where biological and non-biological materials interact and to use the systems in novel applications. Due to their extraordinary properties and sensitivity of these properties to local environment, carbon nanotubes and other synthetic nanostructures will be useful in biological applications ranging from biosensors that interface with living systems to artificial contractile organelles.  However, a critical problem in biological applications of carbon nanotubes is to make the nanotubes biocompatible.  The research is part of an ongoing  collaboration with several members of the Chemistry department at the University of Texas at Dallas using peptides that bind nanotubes both covalently and non-covalently. 

2.Properties and Applications of Multifunctional Carbon Nanotube Assemblies

All known bulk synthesis methods produce carbon single walled nanotubes (SWNTs) as impure soot. An important challenge is to develop practical technologies for transforming this soot into continuous fibres and assemblies having properties that are both fundamentally interesting and useful for important applications. In collaboration with the NanoTech Institute at UTD, by using novel spinning apparatus, spinning solutions, and spinning coagulants, we have spun nanotube fibres having record lengths, tensile strengths, and energy-to-break (toughness). This process can routinely make hundred-meter long reels of continuous nanotube-polymer composite fibre at 100X the prior-art rate, achieve fibre strength over 2 GPa and are tougher than any known material. The carbon nanotube fibres, combine mechanical integrity with a range of electrochemical based functionality enabling  the fabrication of  artificial muscles,  and supercapacitor/battery fibres that can be woven into electronic textiles,

Structure of polymer; (ii) STM image of two polymer wrapped SWNT lying on HOPG); (iii) TEM of  an open tube coated in polymer.  (iv)  polymer (4 repeat units) wrapped onto a (12,7) carbon nanotubes in toluene solution. (a) top view and (b) side view. Carbon, hydrogen and oxygen atoms are shown in gray, white and black, respectively.

3. Interfacial Engineering in Nanocomposites (Conjugated Polymer Nanocomposite-Photovoltaic Devices)

Research into polymeric photovoltaics is at a very early stage, but the results are encouraging.  Currently, conducting polymer-based photovoltaic devices perform less efficiently compared to their inorganic semiconductor counterparts. The power efficiency  achievable for today’s fully organic solid-state photocells is below 5%, and is about 3 % for the best polymeric cells. It is expected that these numbers can be markedly improved by controlling electronic processes at the nanoscale. In collaboration with colleagues at Trinity College Dublin, Hull University, and others,  we have  developed an efficient methodology to “tightly wrap” specifically engineered conjugated polymers onto the surface of carbon nanotubes. By careful control of back bone isomerism,  backbone flexibility  and engineering the aggregation state of the polymer in solution via sonochemical treatment and temperature control allows high wetability with the lattice of the nanotubes and excellent homogeneity in nanotube dispersion within the resulting matrix. We are now applying this technology to other nanocomposites based on optically active materials.