Xanthates as a tool for carbon nanotube and graphene functionalization : application in supported catalysis

The aim of this PhD thesis was the use of xanthate compounds to functionalize nanocarbonaceous materials in order to use them as support in homogeneous supported catalysis. The first part of this work was devoted to the study of the xanthate reactivity towards various types of nanocarbons: carbon nanotubes, reduced graphene oxide and magnetic carbon nanotubes. X-ray photoelectron spectroscopy, bulk elemental analysis, thermogravimetric analysis and Raman spectroscopy results have shown that a reaction between xanthate fragments and the sp2-skeleton of nanocarbons, when initiated by thermally decomposed peroxides, actually took place. The combination of results given by all these characterization techniques also revealed that fragments arising from the radical initiator were grafted at the nanocarbon surface along with xanthate fragments. The developed methodology was therefore redefined as a one-step double functionalization reaction. The second main part of this PhD thesis was dedicated to the study of post-functionalization reactions, performed using heterogeneized xanthate fragments as reactant. Various post-functionalization reactions such as amidation reaction, double Zard addition and anchoring of gold and platinum nanoparticles have successfully been performed at the functionalized nanocarbon surface, showing that the heterogeneization of these functions does not change their chemical nature or reactivity. As a consequence, we took benefit from the possible post-functionalization reactions to anchor different ligands at carbon nanotube surface. The last part of this manuscript was dedicated to the description of the preparation of supported catalysts and their use in the Suzuki-Miyaura cross-coupling reaction.(SC - Sciences) -- UCL, 201

One-step double covalent functionalization of reduced graphene oxide with xanthates and peroxides

Radical functionalization of reduced graphene oxide has been achieved by reaction with a xanthate in the presence of peroxide as a radical initiator. X-ray photoelectron spectroscopy, bulk elemental analyses, and thermogravimetric analyses showed that the xanthate grafting is covalent and efficient. The synthesis and use of seven xanthates and three peroxides showed that the highest grafting yield is obtained when xanthate and peroxide are introduced in stoichiometric amounts. It also revealed that the peroxide used as radical initiator is grafted at the graphenic surface during the functionalization. The method presented in this contribution therefore allows bifunctionalized reduced graphene oxide samples to be easily obtained in one single step. This method leads to undamaged graphene sheets with higher dispersibility than the pristine sample

Covalent functionalization of carbon nanotubes with xanthates and peroxides

The covalent grafting of xanthates onto carbon nanotubes (CNTs) by using peroxides as radical initiators was studied. Carbon nanotubes were functionalized with seven different xanthates by employing dilauroyl peroxide as a radical initiator. This allowed for the concomitant double functionalization by both xanthate and peroxide moieties. This one-step double functionalization was demonstrated by the use of a heteroatom-containing peroxide, and optimization reactions were performed to determine the maximum grafting yields of each component. The maximum grafting yield of the xanthate occurred when the xanthate and peroxide were introduced in stoichiometric amounts, whereas the grafting yield of the peroxide was simply a function of the quantity of peroxide introduced to the reaction. On the basis of these results, a mechanism for this double functionalization is proposed. Finally, some postfunctionalization reactions of the grafted moieties were performed as proof that their chemical integrity was retained after being anchored to the CNT surface. © 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim