Kinetic modeling and experimental analysis of gold-coated carbon nanotube (gCNT) synthesis through gold(3+) reduction

Over 560,000 cancer-related deaths occur annually in the United States. While traditional cancer treatments save thousands of lives, alternative methods using nanotechnology are being developed to further reduce the number of cancer-related deaths and associated medical costs.;Gold-coated carbon nanotubes (gCNTs) are being developed at the Bio/Nano Technology Laboratory of the University of Arkansas in response to the urgent needs for PT applications. The gCNTs are new nanomaterials that uniquely combine the NIR responsiveness of carbon nanotubes (CNTs) with the biocompatibility and bioconjugation potential of gold. The gCNTs are synthesized by the interfacing of gold and carbon nanotubes through an electroless deposition process. Since the surface of gCNTs is coated with gold, gCNTs provide excellent biocompatibility and the same simple and robust bioconjugation as other gold nanoparticles. Furthermore, gCNTs are NIR responsive and the surface plasmon resonance in gCNTs shows strong responses in the NIR. However, challenges to the development of gCNTs are the very limited amounts of available information about the reaction mechanism, the characteristics of the starting materials, i.e., CNTs, and the system complexity.;The focus of this research was to achieve the process control of the gCNT synthesis through mathematical modeling and experimental validation. The goal was achieved by developing a mathematical model that quantitatively describes the reaction kinetics of the electroless deposition process for gCNT synthesis in terms of AuCl4- reduction and gold film thickness as functions of time and initial AuCl4 - concentrations. The model was verified through experimental testing. The model has provided insight into not only the reaction profile by identifying changes in the reaction behavior and quantifying the reduction rates but also the nature of the reaction mechanism of gold deposition onto carbon nanotubes, which has not been fully understood. Therefore, the results of this study would enable us to optimize the reaction conditions for the gold deposition onto CNTs, leading to the 'controlled' and 'reliable' production of gCNTs, which has an excellent potential for PT nanotherapy and nanodiagnostics.;Photothermal (PT) nanodiagnostics and PT nanotherapy are a very promising laser-based technology that utilizes light-absorbing nanoparticles as PT contrast agents (sensitizers) for biomedical purposes, ranging from diagnosing diseases to providing novel therapies. The PT techniques can cause localized heating of tissue surrounding the nanoparticles by laser-induced thermal and accompanying effects to treat as well as diagnose diseases, including cancer. Potential advantages of PT techniques include being less invasive and more selective than other cancer treatments. However, to realize the advantages of PT techniques, in particular the noninvasiveness, nanomaterials are needed which are both biocompatible and near-infrared (NIR) responsive. The NIR-responsiveness enables noninvasive PT applications because biological tissues are largely transparent to NIR.