Growth selectIvity and Applications of single wall carbon NanoTubes – GIANT

Industry is currently taking the lead to develop applications based on the genuine properties of Single Walled Carbon Nanotubes (SWNTs), that are their outstanding strength and aspect ratio, and ability to display metallic or semi-conducting characteristics, depending on their chiral structure. From a fundamental point of view, and also to make these applications commercially viable, finding a way to grow, on demand, metallic (m-) or semi-conducting (sc-) SWNTs with a reasonable yield and good selectivity, remains the biggest issue. The Catalytic Chemical Vapor Deposition (CVD) synthesis of SWNTs, that takes place at high temperature (600-1200 C), and in a complex chemical environment, is still not completely understood, though recent experiments, reporting a chiral selective growth, ignited a burst of questions, and new efforts to tackle this issue. In this context, the goal of the GIANT project is to build upon recent breakthrough results obtained in the understanding of the growth mechanisms, to gain an effective control of SWNT structure during their synthesis. In a previous project, involving the same partners, the importance of controlling the growth mode characterizing the geometry of the tube / catalyst nanoparticle (NP) interface during the growth, has been emphasized. A thermodynamic modeling relating interfacial energies to the resulting tube chirality has been developed. We also showed that using bi-metallic NPs, and fine tuning the growth conditions, led to a better SC/M selectivity.
The underlying idea is now to focus on the chemistry and structure of the tube / NP interfaces using dedicated new experiments. Guided by the understanding brought about by our modeling, we will develop new catalysts, by different methods, including our original route based on the grafting and calcination of Prussian Blue Analogs, that enables to form dispersed, stable bimetallic and carbide NPs with controlled stoichiometry. Real time, in situ investigations will shed new light on observations that were previously done after growth. A strong asset of this project will be the use of the NanoMAX HR-TEM facility, that combines state of the art environmental Transmission Electron Microscopy (TEM), with original developments of the gas injection system, that make it perform under the same conditions as the UHV-CVD setup used in the laboratory. The chemical and structural evolution of the catalysts will be also investigated in situ and real time in a dedicated facility (FENIX) at LPICM. Systematic cross-checking between TEM (imaging and diffraction) and Raman assignments of the chiral distributions of produced tubes, and a comparison of in situ data with advanced post growth characterizations will be performed. Theory and modeling will be in constant interaction with experiments, either to guide the choice and modifications of the catalysts or to help the interpretation of the results. The thermodynamic modeling of the interface will be extended to include growth kinetics, and detailed atomistic Monte Carlo computer simulations of two kind of systems with different affinities for C (from NiPt to W or Mo carbide NPs) will be performed, to check their influence on the growth modes and resulting chiralities. Each catalytic system family (NiPt, CoMo and CoW, WC or Mo2C, carbon precursors and growth conditions) will be iteratively analyzed, tested for its selective growth ability, and, if successful, eventually used for producing m- or sc-SWNTs incorporated in different types of devices (sensors, transistors, field emission tips …). A successful outcome of the project will be the identification of selective catalytic systems offering either sc- or m-selectivity, with a reasonable yield, and the understanding of the underlying mechanisms.