Towards Selective Photo-induced Reactivity of Individual single walled Carbon NanoTubes – SPRINT

Making carbon nanotubes with control diameter is done in our project by using a special growth chamber, and metallic particles playing the role of catalysts. We chemically modify the carbon nanotubes through organic syntheses assisted by microwave or visible light irradiation in the presence of especially chosen molecules to furnish specific properties to the nanotubes.
To analyze the nanotubes before and after their chemical modification, we employ a set of complementary techniques such as transmission electron microscopy, spectroscopies and thermal analyses. The challenge in these analyses is to obtain information specific to an individual carbon nanotube. To do so, we are working on individualization methods as well as on setting up analytical tools adapted to the nanometric spatial scale.
Finally, we are doing theoretical modelling of carbon nanotubes before and after chemical modification.

Individual carbon nanotubes have been successfully synthesized. Their diameter range is quite narrow, which facilitates the comprehensive study of their chemical reactivity towards specifically chosen molecules. We have grafted electron shuttle groups that interact with enzymes. These functionalized carbon nanotubes have been incorporated into electrochemical devices to measure the level of glucose in a sample. We have characterized the physico-chemical properties of carbon nanotubes before and after functionalization. We have also managed to individualize carbon nanotube through a non covalent interaction with cellulose nanocystals. Strong progress has been made in developping theoretical understanding.

We expect to use our functionalized carbon nanotubes in developping new bioreactors and biosensors.

Over the past 18 months, we have produced: 12 full articles accepted in refereed journals, 6 articles submitted, 21 presentations in international meetings, 7 presentations in French meetings. Here are four representative references :
1. Tuning the Raman resonance behaviour of single-walled carbon nanotubes via covalent functionalization, J.Y. Mevellec, C. Bergeret, J. Cousseau, J. P. Buisson, C. Ewels, S. Lefrant, J. Am. Chem. Soc. 133 (42), 16938 (2011).
2. Gold Nanoparticles as Probes for Nano-Raman Spectroscopy: Preliminary Experimental Results and Modeling, V. Le Nader, J.-Y. Mevellec, T. Minea, and G. Louarn, Int. J. Optics, 591083-91, 2012.
3. Al(OTf)3 as a New Efficient Catalyst for the Direct Nucleophilic Substitution of Ferrocenyl Alcohol Substrates. Convenient Preparation of Ferrocenyl-PEG Compounds, N. Allali, V. Mamane, Tetrahedron Lett. 53, 2604 (2012).
4. Effects on Raman spectra of functionalisation of single wall carbon nanotubes by nitric acid, M. Mases, M. Noël, G. Mercier, M. Dossot, B. Vigolo, V. Mamane, Y. Fort, A. V. Soldatov, E..McRae, Phys. stat. sol. (b) 248, 2552 (2011).

Single wall carbon nanotubes (CNTs) are promising materials because of their electronic and mechanical properties and their 1D character. Incorporation of these materials into a matrix or into a nanostructured device requires chemical functionalisation of the tube walls in order i) to render them chemically compatible with the host and ii) to provide them with new physicochemical properties for some specific application (e.g., light emission, sensors, actuators). The major challenge in covalent functionalisation concerns its yield and its selectivity according to the metallic or semiconducting nature of the tubes, i.e., the diameter and chirality. All of this is true for tubes whether in the form of bundles or individualised. The ambition of the SPRINT project is to understand the origin of the reactivity and the possible selectivity of different processes of covalent functionalisation. To do so, the project involves: i) the synthesis of metallic catalysts, of growth substrates and of some of the CNTs to be used; ii) original protocols for the functionalisation of bundled or individual CNTs: iii) the use of different tools for the characterisation of the functionalisation; iv) quantum modelling. The originality of the project lies first in the different strategies of CNT individualisation: i) a low-temperature chemical vapour deposition of isolated CNTs; ii) use of oriented mesoporous silica films in the aim of obtaining individualised CNTs the diameter of which will be fixed by that of the pores and iii) development of a process for individualisation by interaction with a polysaccharides in the liquid phase. The second orientation, which constitutes the heart of the SPRINT project, concerns covalent functionalisation of the CNTs by a radical attack of the CNT walls either via a microwave-assisted thermal means or via a photochemical process in the aim of controlling the yield and selectivity of the functionalisation. The aromatic cycle of the aryl radicals will be modified by various electron donor or acceptor groups, certain of which will be specifically used as markers or tags for certain analytical techniques (spectroscopy, microscopy, thermal analysis). These analyses will permit ascertaining the covalent nature of the functionalisation. Furthermore, individualised CNTs obtained using the new substrates will be pre-functionalised in a pressure-controlled chamber under defined levels of water vapour under visible and near-IR monochromatic irradiation. The innovative objective is to excite the CNTs in their van Hove singularities so as to promote the covalent grafting on the CNT walls as a function of tube diameter. One of the major challenges in the SPRINT project will be to carry out the analysis of the CNTs before and after (pre-)functionalisation on individual tubes and individual bundles. For this, we will combine techniques of electron and atomic force microscopy with spectroscopic methods (Raman scattering, UV-Vis- and near- and mid-IR absorption, EPR) and thermodynamic investigation techniques (thermogravimetric analysis coupled with mass spectrometry, gas adsorption volumetric). The ensemble of the obtained experimental data will be compared with the results of quantum calculations carried out on both phononic properties (radial breathing modes, “RBM”) and on the CNT electronic density of photo-excited states. This comparison should allow overall understanding; perhaps even allow predicting, of the thermal or photo-induced reactivity of CNTs, the ultimate aim of the SPRINT project.