Chemistry of nanomaterials inside outMechanically interlocked, endohedral and covalent derivatives of SWNTs and 2D materials

Resumen

Understanding the processes that take place at the nanoscale is essential in order to develop methodologies able to provide nanomaterials that fulfil the requirements of the latest technologies. We, chemists, are able to tune the properties of these materials on demand through chemical functionalization, as well as enhancing their processability. During this doctoral thesis, several tools for the functionalization of one and two-dimensional materials have been developed. The thesis is framed after the publication of the novel work described by our group in 2014 for the synthesis of mechanically interlocked carbon nanotubes (MINTs). The protocol allows the encapsulation of single walled carbon nanotubes (SWNTs) within organic macrocycles. In MINTs, there are no clearly defined energy minima for the movement of the macrocycle(s) along/around the SWNTs, which makes MINTs specially interesting models to study friction at the nanoscale. The initial objective of this doctoral thesis was to control the movement of MINTs systems in a certain direction, what required the nanotubes to be desymmetrized. One of the approaches chosen for this purpose was the encapsulation of charged materials in the nanotube’s inner cavity. This very first primitive idea led to the development of materials that were very interesting by themselves. The research carried out is cross disciplinary; besides organic synthesis, several different characterization techniques have been employed and various collaborations throughout the international community have been stablished. The thesis is divided in five chapters, Chapter 1 is an introduction in which a historical overview of the encapsulation of organic materials inside single wall carbon nanotubes (SWNTs) is presented. Each of the remaining chapters are accompanied by a brief introduction directly related to their content. A supplementary information section is added as well in each chapter following a classical paper structure. Chapter 3A is an adaptation of an already-published work. Chapters 2 to 4 have been dedicated to the science of carbon nanotubes. In Chapter 2, the nanoscale movement within nanotubes threaded through organic macrocycles has been explored by means of molecular dynamics and DFTB calculations. The question whether the interaction energy between macrocycle and SWNT conditions the final movement has been answered. Chapters 3 and 4 are focused on the encapsulation of different organic and organometallic materials in SWNTs. In the first section of Chapter 3 (3A), the encapsulation of organic salts inside SWNTs has been performed and the electrical properties of the final hybrids have been measured in field effect transistor like devices. In the second part of this chapter (3B), the encapsulation of the same molecules employing smoother conditions is studied. In Chapter 4, the encapsulation of Fe (II) spin cross-over complexes by means of gas-phase methods has been described. The spin cross over process has been observed by the study of the temperature-dependent current-voltage characteristics of the hybrids. Finally, moving to the two-dimensional materials, in Chapter 5, a protocol for the covalent functionalization of franckeite, a naturally occurring van der Waals heterostructure has been developed employing thiol-ene-like “click” chemistry. This new methodology has been used to decorate franckeite with maleimide reagents.