Multifunctional hybrid nanocomposites based on carbon nanotubes and chemically modified graphene

La Tesis trata del desarrollo de materiales híbridos multifuncionales basados en nanotubos de carbono y grafeno con interés en magnetismo molecular y electrónica molecularThis Thesis deals with the chemistry and development of new hybrid multifunctional systems based on carbon nanotubes (CNTs) and graphene (G). To introduce both types of carbon nanoforms a brief historical overview of these systems has been briefly given at the Preface. Next and prior to the presentation of the results, two introductory chapters in which the principal aspects of the synthesis, properties and applications of carbon nanotubes (chapter 1) and graphene (chapter 2) are given. The results have been divided in three chapters: Chapter 3 is related with the development of hybrid materials based on CNTs, and it has been divided in two independent parts. The first part deals with the modification of the walls of the carbon nanotubes (CNTs) to drive their interaction with Mn4 single molecule magnets (SMMs). The deposition of SMMs along the CNT surface may have implications in molecular magnetism, field in which the organization of magnetic moieties along a conducting wire turns out to be essential. Our approach implies the use of weak electrostatic interactions which contribute to preserve the SMM structure. We will show how the magnetic properties of the attached molecules are significantly affected by the grafting process. In the second part, a hybrid between a photoactive polyoxometalate (POM) and single walled carbon nanotubes (SWNTs) has been developed. In contrast to the first system, in this case the POM has been conveniently modified with pyrene moieties capable to bind to the unmodified walls of the SWNTs. The deposition of photoactive molecules (POM) over CNTs may have important implications in photovoltaics and other electronic devices. Moreover, we will describe the system at the atomic level by the employment of microscopic techniques. Chapter 4 focuses on the chemical synthesis of graphene (G). This chapter has been divided in two parts. In a first part, G will be obtained from graphite oxide (GO) by a hydrothermal (HT) method. In particular, our work deals with the important role that the pH plays in the reduction of GO under HT conditions. An indepth description about the morphologies and characteristic of the prepared material will be given. In a second part, a bottom up approach to synthesize graphite will be described. With this aim, anthracene molecules have been used as starting material. Afterwards, some ideas toward the synthesis of graphitic nanoforms following the previous bottom up approach will be introduced. Finally, chapter 5 is devoted to the chemical functionalization of graphene via covalent bonds. In a first part, a general procedure to synthesize chemically modified graphene (CMG) by simple functionalization/reduction of GO under thermal treatment with DMF is described. The as-made CMG will be further decorated with gold nanoparticles (Au NPs). Our approach introduces a degree of control over the coverage of the CMG with Au NPs. We believe that the attained system could be useful for a wide range of applications such as sensing, energy storage, or catalysis. In a second part, a controlled doping of the layers with paramagnetic radicals will be directly synthesized by chemical functionalization of graphite through the Bingel-Hirsch cyclopropanation reaction. Those paramagnetic moieties have shown to influence the magnetoresistance response of the hybrid by the appearance of a low field magnetoresistance effect at low temperatures. This kind of arrangement can have important in sensing applications