During the past few years, nanotechnology has been recognized as a key field in a number of different applications. Among new molecular structures proposed in such a field, remarkable interest has been gained by those based on carbon nanotubes. In particular, recent investigations focus on functionalization of carbon nanotubes, i. e. on the design of nanotube-based nanostructured systems in which chemical and physical properties can be tuned through the interaction with other molecules. A possible functionalization route can be set out by extending the concept of metal-ligand bond to the case of carbon nanotubes. In fact, the wide range of possibilities offered by transition metal chemistry allow a fine-tuning of properties concerning the overall system, such as electrical and conductive properties. On the other hand, the modification of properties of carbon nanotubes upon interaction with external agents can be exploited for the construction of devices with technological interest, such as nanostructured sensors (Fig. 1). Accurate theoretical methods, based on quantum mechanics, allow to understand the processes on which the interaction between carbon nanotubes and external molecules are founded, with a high degree of detail, in order to design and synthetize more and more efficient devices. In particular, our recent studies concern investigations on the role of imperfections on the nanotube structure, such as structural defects, on chemical and physical properties, as they are able to induce large modifications.
Another field of interest is that of molecular machines and devices. In general, such systems are able to perform mechanical movements at a molecular level or to change some of their properties upon external inputs. Hence, investigations on such a field can be of primary interest, from the point of views of both fundamental research and applications, as in the case of electronic miniaturizing. Theoretical investigations can play a crucial role in the understanding of the working mechanism in molecular devices and machines as well as in their design stage, in order to optimize overall performances. Molecules as catenanes and rotaxanes have been recognized among the most interesting ones and theoretical investigations are mainly devoted to this field. In particular, simulations concern the study of the switching mechanism taking place between different conformations of the system upon the application of an external input (Fig. 2). Remarkable computational difficulties in reproducing accurately these kind of processes ask for the use of theoretical methods based on recently developed techniques for the dynamical study of rare events. Simulations allow to define the energetics involved in the switching process as well as microscopical details of the mechanism, thus providing information that can be used in further studies on this class of systems and in a molecular design stage.
Vedi anche:
Immagini:
