title: Raman spectroscopy as a tool to investigate the structure and electronic properties of carbon-atom wires.
abstract: Graphene, nanotubes and other carbon nanostructures have shown potential as candidates for advanced technological applications due to the different coordination of carbon atoms and to the possibility of π-conjugation. In this context, atomic-scale wires comprised of sp-hybridized carbon atoms represent ideal 1D systems to potentially downscale devices to the atomic level. Carbon-atom wires (CAWs) can be arranged in two possible structures: a sequence of double bonds (cumulenes), resulting in a 1D metal, or an alternating sequence of single-triple bonds (polyynes), expected to show semiconducting properties. The electronic and optical properties of CAWs can be finely tuned by controlling the wire length (i.e., the number of carbon atoms) and the type of termination (e.g., atom, molecular group or nanostructure). Although linear, sp-hybridized carbon systems are still considered elusive and unstable materials, a number of nanostructures consisting of sp-carbon wires have been produced and characterized to date. In this short review, we present the main CAW synthesis techniques and stabilization strategies and we discuss the current status of the understanding of their structural, electronic and vibrational properties with particular attention to how these properties are related to one another. We focus on the use of vibrational spectroscopy to provide information on the structural and electronic properties of the system (e.g., determination of wire length). Moreover, by employing Raman spectroscopy and surface enhanced Raman scattering in combination with the support of first principles calculations, we show that a detailed understanding of the charge transfer between CAWs and metal nanoparticles may open the possibility to tune the electronic structure from alternating to equalized bonds.
authors.affiliation: Department of Chemistry, Materials and Chemical Engineering "G. Natta", Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano, Italy ; NEMAS - Center for NanoEngineered Materials and Surfaces, Politecnico di Milano, via Ponzio 34/3, 20133 Milano, Italy.
authors.forename: Alberto
authors.initials: A
authors.lastname: Milani
authors.affiliation: Department of Chemistry, Materials and Chemical Engineering "G. Natta", Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano, Italy ; NEMAS - Center for NanoEngineered Materials and Surfaces, Politecnico di Milano, via Ponzio 34/3, 20133 Milano, Italy.
authors.forename: Matteo
authors.initials: M
authors.lastname: Tommasini
authors.affiliation: NEMAS - Center for NanoEngineered Materials and Surfaces, Politecnico di Milano, via Ponzio 34/3, 20133 Milano, Italy ; Department of Energy, Politecnico di Milano, via Ponzio 34/3, 20133 Milano, Italy.
authors.forename: Valeria
authors.initials: V
authors.lastname: Russo
authors.affiliation: NEMAS - Center for NanoEngineered Materials and Surfaces, Politecnico di Milano, via Ponzio 34/3, 20133 Milano, Italy ; Department of Energy, Politecnico di Milano, via Ponzio 34/3, 20133 Milano, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Li Bassi
authors.affiliation: Department of Chemistry, Materials and Chemical Engineering "G. Natta", Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano, Italy ; NEMAS - Center for NanoEngineered Materials and Surfaces, Politecnico di Milano, via Ponzio 34/3, 20133 Milano, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Lucotti
authors.affiliation: Dipartimento di Scienze Ecologiche e Biologiche, Università della Tuscia, Via Camillo de Lellis, Viterbo, Italy ; Actinium Chemical Research srl, Via Casilina 1626A, 00133 Roma, Italy.
authors.forename: Franco
authors.initials: F
authors.lastname: Cataldo
authors.affiliation: NEMAS - Center for NanoEngineered Materials and Surfaces, Politecnico di Milano, via Ponzio 34/3, 20133 Milano, Italy ; Department of Energy, Politecnico di Milano, via Ponzio 34/3, 20133 Milano, Italy.
authors.forename: Carlo S
authors.initials: CS
authors.lastname: Casari
keywords: Raman spectroscopy; carbon nanostructures; cumulenes; polyynes; sp-hybridized carbon systems
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