jp7b02246_si_001.pdf (417.54 kB)
Semiconductor-to-Metal Transition in Carbon-Atom Wires Driven by sp2 Conjugated End Groups
journal contribution
posted on 2017-04-24, 00:00 authored by Alberto Milani, Matteo Tommasini, Valentino Barbieri, Andrea Lucotti, Valeria Russo, Franco Cataldo, Carlo S. CasariBis(biphenyl)-capped
polyynes are investigated to unveil the modulation
of the electronic and optical properties of sp-hybridized carbon-atom
wires (CAWs) capped with π-conjugated sp2 end groups.
Raman and surface enhanced Raman spectroscopy experiments and density
functional theory (DFT) calculations reveal structural changes from
polyyne-like with alternating single–triple bonds toward cumulene-like
with more equalized bonds as a consequence of the charge transfer
occurring when wires interact with metallic nanoparticles. While polyynes
have semiconducting electronic properties, a more equalized system
tends to a cumulene-like structure characterized by a nearly metallic
behavior. The effect of different sp2 end groups in driving
a semiconductor-to-metal transition is investigated by DFT calculations
on a series of CAWs capped with different terminations. We discuss
how the modulation of the structural, electronic, and vibrational
properties of the sp-carbon chain toward the metallic wire is not
trivial and requires a suitable chemical design of the end group and
control of charge transfer. These results provide a guideline for
the design of novel sp–sp2 hybrid carbon nanosystems
with tunable properties, where graphene-like and polyyne-like domains
are closely interconnected. The capability to tune the final electronic
or optical response of the material makes these hybrid sp–sp2 systems appealing for a future all-carbon-based science and
technology.