Department of Materials Science, University of Patras, 26504 Rio Patras, Greece, Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, 48 Vass. Constantinou Avenue, 116 35 Athens, Greece, Institut de Biologie Moleculaire et Cellulaire, UPR9021 CNRS, Immunologie et Chimie Therapeutiques, 67084 Strasbourg, France, and Dipartimento di Scienze Farmaceutiche, Universita di Trieste, Piazzale Europa 1, 34127 Trieste, Italy

Chemistry of Carbon Nanotubes

Since their discovery, carbon nanotubes have attracted the attention of many a scientist around the world. This extraordinary interest stems from their outstanding structural, mechanical, and electronic properties. In fact, apart from being the best and most easily available one-dimensional (1D) model system, carbon nanotubes show strong application potential in electronics, scanning probe microscopy, chemical and biological sensing, reinforced composite materials, and in many more areas. While some of the proposed applications remain still a far-off dream, others are close to technical realization. Recent advances in the development of reliable methods for the chemical functionalization of the nanotubes provide an additional impetus towards extending the scope of their application spectrum. In particular, covalent modification schemes allow persistent alteration of the electronic properties of the tubes, as well as to chemically tailor their surface properties, whereby new functions can be implemented that cannot otherwise be acquired by pristine nanotubes.

/pdf/chemically-functionalized-carbon-nanotubes-3t5j50n2w8.pdf

Chemically functionalized carbon nanotubes.

Polyoxometalates (POMs) are discrete anionic metaloxygen clusters which can be regarded as soluble oxide fragments. They exhibit a great diversity of sizes, nuclearities, and shapes. They are built from the connection of {MOx} polyhedra, M being a d-block element in high oxidation state, usually VIV,V, MoVI, or WVI.1 While these species have been known for almost two centuries, they still attract much interest partly based on their large domains of applications. They play a great role in various areas ranging from catalysis,2 medicine,3 electrochemistry,4 photochromism,5 to magnetism.6 This palette of applications is intrinsically due to the combination of their added value properties (redox properties, large sizes, high negative charges, nucleophilicity...). Parallel to this domain, the organic-inorganic hybrids area has followed a similar expansion during the last 10 years. The concept of organic-inorganic hybrid materials * To whom correspondence should be addressed. E-mail: dolbecq@ chimie.uvsq.fr. Chem. Rev. 2010, 110, 6009–6048 6009

Hybrid Organic−Inorganic Polyoxometalate Compounds: From Structural Diversity to Applications

Surface chemistry is the topic of this tutorial review. It describes the electrochemical reduction of aryl diazonium salts on carbon, silicon or metals which leads to the formation of an aromatic organic layer covalently bonded to the surface. The method which permits such a modification is set forth. The proof for the existence of the organic layer is brought forward. The grafting mechanism and the covalent bonding between the surface and the aryl group are discussed. The formation of mono or multilayers depending on the experimental conditions is rationalized. Finally some examples of the possible uses of this reaction are given.

Attachment of organic layers to conductive or semiconductive surfaces by reduction of diazonium salts

Electrografting refers to the electrochemical reaction that permits organic layers to be attached to solid conducting substrates. This definition can be extended to reactions involving an electron transfer between the substrate to be modified and the reagent, but also to examples where a reducing or oxidizing reagent is added to produce the reactive species. These methods are interesting as they provide a real bond between the surface and the organic layer. Electrografting applies to a variety of substrates including carbon, metals and their oxides, but also dielectrics such as polymers. Since the 1980s several methods have been developed, either by reduction or oxidation, and some of them have reached an industrial stage. This critical review describes the methods that are used for electrografting, their mechanism, the formation and growth of the layers as well as their applications (742 references).

Electrografting: a powerful method for surface modification

Anderson-type polyoxomolybdates [MMo6O18{(OCH2)3CNH2}2]3− (M = MnIII, FeIII) were prepared and structurally characterized. The tris(alkoxo) ligands are bound to the central heteroatom via their oxygen atoms. The corresponding compounds with M = NiII or ZnII are not accessible since these cations have a preference for the amino functionality. The pendant amino groups of the manganese-containing derivative react with pyridinecarbaldehydes to give the corresponding imines. This provides new mono- and bidentate binding sites for metal cations. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

/pdf/developing-remote-metal-binding-sites-in-1h21ruxjkx.pdf

Developing Remote Metal Binding Sites in Heteropolymolybdates

Hydroxylated C60 molecules, also called fullerols, are a class of water-soluble fullerenes. Here we report the synthesis in acidic conditions of a highly derivatized fullerol (up to 36 carbons per C60 are oxidized). Spectroscopic investigations (X-ray photoelectron spectroscopy and infrared absorption) highlight the coexistence of both acidic and basic forms for the hydroxyl addends of derivatized C60. pH titrimetry reveals that, at millimolar concentrations, only ten protons per fullerol molecule are labile. Such a low value, as compared to 36 hydroxyl groups, is explained by the formation of clusters. A UV-vis absorption study performed over a large range of concentrations also points to the aggregation phenomenon. Moreover, this study shows that the clusters of fullerols appear at relatively low (micromolar) concentrations. An electron spin resonance (ESR) study, based on the attack of singlet oxygen (1Δg) on 2,2,6,6-tetramethyl-4-piperidinol (TMP-OH), has proved the potential of hydroxylated C60 for performing efficient generation of singlet oxygen in aqueous solution. ESR measurements, which allow detection and quantification of 1Δg, have also revealed the generation of reactive oxygen species (ROS). The yield of generation of 1Δg and ROS is strongly correlated to the concentration of fullerol, thus also pointing to the aggregation of fullerol molecules. Exposing glioblastoma cells to oxidative stress in the presence of hydroxylated C60 and visible light has also been performed. Atomic force microscopy is used to monitor the relevant diminishment of the Young's modulus values for cells exposed to the oxidative stress. These results point to a possible application field of fullerols for performing bio-oxidations.

Spectroscopic and Photophysical Properties of a Highly Derivatized C60 Fullerol

Covalent exohedral derivatizations of HiPco nanotubes, through electrochemical reduction of aryldiazonium salts, is described. Four different aryldiazonium salts have been used under the same experimental conditions: 4-bromophenyl, 4-chloromethylphenyl, 4-sulfophenyl and 4-carboxyphenyl. Derivatized samples were characterized through X-ray photoelectron spectroscopy and micro-Raman diffusion. The evolution of the spectra (area of the D-band), as a function of the number of grafted groups, led us to the conclusion that the electrochemical reduction of aryldiazonium salts into radicals gives rise to the growth of aryl chains on the sidewalls of the nanotubes.

/pdf/electrochemical-functionalization-of-nanotube-films-growth-55v1lpl34g.pdf

Electrochemical functionalization of nanotube films: growth of aryl chains on single-walled carbon nanotubes

The manipulation of isolated single-wall carbon nanotubes (SWNTs), rather than bundles, has led to active research in the field of the functionalisation of such carbon compounds. Different ways exist today to obtain some new soluble macromolecules from SWNTs. Here we focus on the fluorination functionalisation. As the solubility properties depend essentially on the degree of functionalisation, it is important to develop reliable and simple methods to quantify this. The CnF stoichiometry of three different fluorinated SWNTs samples are determined with X-ray photoelectron spectroscopy (XPS). Then the evolution of the Raman spectra with the degree of fluorination of these samples is discussed. An atomic force microscopy (AFM) study highlights the good solvation properties of the most fluorinated sample with a majority of isolated nanotubes being observed. Then we take advantage of these good solvation properties, combined with the
possibility of recovering the pristine non-fluorinated nanotubes, to carry out surface enhanced Raman spectroscopy (SERS) studies of well-dispersed SWNTs. These studies put in evidence the bundle effect, which is due to the agglomeration of SWNTs into bundles. This effect can be readily observed by Raman spectroscopy.

/pdf/a-spectroscopic-study-of-the-fluorination-and-defluorination-18kjuskqrt.pdf

Pierre Marcoux

Papers

Developing Remote Metal Binding Sites in Heteropolymolybdates

Spectroscopic and Photophysical Properties of a Highly Derivatized C60 Fullerol

Electrochemical functionalization of nanotube films: growth of aryl chains on single-walled carbon nanotubes

A spectroscopic study of the fluorination and defluorination reactions on single-walled carbon nanotubes

Evidence of lipid peroxidation and protein phosphorylation in cells upon oxidative stress photo-generated by fullerols.