Dr. Nikos Tagmatarchis Nikos Tagmatarchis is Director of Research at the Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, in Athens, Greece. He has studied chemistry and received his PhD from the Chemistry Department, University of Crete, Greece (1997). His research interests focus on the chemistry of carbon-based nanostructured materials such as fullerenes, nanotubes and graphene, targeting applications in the fields of solar and photoelectrochemical cells, water splitting and hydrogen production, catalysis as well as purification of wastewater from toxic pollutants and organic dyes. His accomplishments in the area are reflected in over 170 scientific peer-reviewed research articles that he has published in prestigious scientific journals such as Angewandte Chemie an International Edition in English, The Journal of American Chemical Society, Physical Review Letters, Advanced Materials, Advanced Functional Materials, Chemistry-A European Journal and Chemical Communications, while his work has been cited more than 7000 times associated with an h-index = 36. He has also given numerous invited oral presentations at significant international scientific conferences. He has been recipient of the European Young Investigator Award (2004), Visiting Professor at the Chinese Academy of Sciences (2011) and Invited Fellow by the Japan Society for the Promotion of Science (2013).
Carbon-based nanostructured materials such as fullerenes, nanotubes and graphene attract the focus of considerable research and scientific interest. This is because each of them can be used as a probe to address the role of dimensionality and confinement in materials at the nanometer scale.
An interesting class of fullerene materials concerns azafullerenes and endohedral metallofullerenes. Azafullerenes derive upon substitution of a carbon atom with nitrogen in fullerene spheres. We developed a synthetic route that gives access to C59N-based carboxylic acid derivative as key material toward the preparation of diverse C59N-based dyads with organic electron donors. On the other hand, encapsulation of metals or metal nitrides within the empty space of fullerenes results on the formation of endohedral metallofullerenes. Electron transfer occurs from the encapsulated metal to the carbon cage while the energy band gap of endohedral metallofullerenes can be varied depending on the fullerene cage, the kind and the number of the encapsulated metal atoms.
Single-walled carbon nanotubes (SWCNTs) as 1D molecular wires possessing delocalized -electrons, exhibit unusual electronic, mechanical and adsorptive properties, while showing high electron mobility. Advantageously, SWCNTs possess fascinating hollow space to accommodate doping materials. A typical example is the so-called peapods, materials in which fullerenes are entrapped inside the empty pseudo-1D nanoscopic space of SWCNTs. Functionalization and solubilization of peapods is a major issue that would allow to study properties in solution – especially when considering the rich electrochemistry of fullerenes – while enable better manipulation and handling, and therefore, practical applications. Moreover, functionalized peapods become more useful than the original ones as the covalently grafted moieties on the outer skeleton of the nanotubes can be tailored for specific applications. On the other hand, carbon nanohorns (CNHs) present features similar to the ones of fullerenes (at sites near the conical-shaped tip) and nanotubes (at sites located away from the conical tip). However, nanohorns are morphologically different from nanotubes as they i) possess a conical-shaped tip, ii) are much shorter in length, and iii) aggregate in spherical superstructures. CNHs can be functionalized by i) covalent attachment of organic units onto their skeleton, and ii) non-covalent supramolecular, van der Waals, stacking interactions and/or coulombic electrostatic interactions with aromatic planar and/or charged organic moieties. Moreover, CNHs accept electrons and more importantly, can readily diffuse them along the cone main axis, with almost negligible loss of energy. Therefore, CNHs can be utilized as electron acceptors towards the formation of hybrid materials with organic electron donors, for application in photovoltaics.
Graphene is an outstanding material, consisting of a two-dimensional single layer of sp2-hybridized carbon atoms bonded together in a hexagonal “honeycomb” lattice and presents exceptional properties that allow its use in in energy conversion and storage systems. In this context, the covalent functionalization of graphene sheets with photoactive molecules such as porphyrin and phthalocyanine was carried out and most importantly, prototype devices were constructed by fabricating the graphene-based hybrid materials as photoanodes in photoelectrochemical cells, while their efficiency and response were examined.