Grafinin fonksiyonelleştirilmesi ve stokiyometrik grafin türevleri

Recent developments in experimental techniques have made the design and production of materials atnanoscale possible. In particular, graphene has been the focus of research in diverse fields owingto high mobility carrier transport and other exceptional properties. Over the past four yearsexperimental studies have demonstrated that chemical conversion of graphene to its stoichiometricderivatives is possible by hydrogenation, fluorination and chlorination. The aim of this thesis isto predict stable stoichiometric graphene derivatives and explore their mechanical, electronic andmagnetic properties. Moreover, the functionalization of graphene and its derivatives are achieved,whereby their physical properties are modified to derive novel materials. Our predictions revealingstable 2D single layer conformers, which can be used as novel nanocoeting materials, are obtainedfrom state-of-the art first-principles Density Functional calculations of total energy, phonons,transition state analysis and ab-initio molecular dynamics.An extensive theoretical study on the stability of hydrogenated graphene (C$_{n}$H),fully hydrogenated graphane i.e graphane (CH), and their quasi one-dimensional nanoribbons is performed. The formation ofmeshes of dehydrogenated domains on graphane resulted in geometry specific magnetic structuresshowing interesting magnetic interactions. Creation of H and CH vacancies, as well as adsorption of transition metal atomsgive rise to significant spin-polarization in graphane nanoribbons. It is shown that as a result of one-sided or two-sidedfluorination of graphene one can obtain nanostructures with diverse electronic and magnetic properties. Fully fluorinatedgraphene or fluorographene CF is a stable, stiff and non-magnetic semiconductor. Additionally, this conformer of buckledgraphene is functionalized by alkali, non-metal, metalloid and transition metal atoms, and each group leads to diverseadsorption properties.Adsorption of chlorine to graphene is dramatically different from those of hydrogen and fluorine.While the binding energy of chlorine is significant, its migration on the surface of perfect graphenetakes place almost without barrier. This is crucial for energy harvesting on graphene surface.Energy optimization and phonon calculations indicate that the chair configuration of fully chlorinatedgraphene (chlorographene) is energetically most favorable and stable. It is a nonmagnetic semiconductorwith 1.2 eV direct band gap, which can be tuned by applied uniform strain.Graphene by itself can be functionalized by creating meshes of vacancies or adatoms conserving specific symmetries.Under these circumstances linearly crossing bands and hence the massless Dirac Fermion behavior can be maintained.Finally, it is demonstrated that multilayer, even single layer graphene constitute an excellentnanoscale coating, which can prevent a reactive metal surface from oxidation without changing thesize and other physical properties. Graphene can stick to flat metal surfaces and hinders freeoxygen atom and molecule from penetrating to the metal surface. Single layer fluorographene canbe used also for the same purposes.Design of novel nanomaterials, in particular biological molecules and complexes using first-principlesmethods derived from quantum theory indicates a new direction in theory, which promises a productivehybridization with experimental studies.