Journal of the American Chemical Society
Communication
ASSOCIATED CONTENT
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* Supporting Information
The Supporting Information is available free of charge at
Experimental details; supporting Schemes S1 and S2,
Figures S1−S63, and Tables S1−S3; and calculations of
the model compounds and cGNR (PDF)
X-ray crystallographic data for 1 (CIF)
X-ray crystallographic data for 2 (CIF)
Figure 3. (a) Time-resolved terahertz photoconductivity (propor-
tional to the relative changes in the transmitted field, −ΔE/E) of
cGNR following photoexcitation. The samples are photoexcited by a
short ∼50 fs laser pulse with the photon energy of 2.4 eV and an
absorbed photon density of 1.8 × 1015 cm−2. (b) The frequency-
resolved THz complex conductivity measured at 1.5 ps after
photoexcitation. The solid lines represent the Drude−Smith fitting
following the discussion in the main text and SI.
AUTHOR INFORMATION
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Corresponding Authors
Junzhi Liu − Center for Advancing Electronics Dresden (cfaed),
Faculty of Chemistry and Food Chemistry, Technische
̈
Universitat Dresden, D-01062 Dresden, Germany; Department
of Chemistry and State Key Laboratory of Synthetic Chemistry,
The University of Hong Kong, Hong Kong 999077, China;
Yiyong Mai − School of Chemistry and Chemical Engineering,
Frontiers Science Center for Transformative Molecules, Shanghai
Key Laboratory of Electrical Insulation and Thermal Ageing,
Shanghai Jiao Tong University, Shanghai 200240, China;
photon energy of 2.4 eV). The subsequent rapid decay is
consistent with the formation of the bound electron−hole pairs
(excitons).31,32 The frequency-resolved THz photoconductive
response at ∼1.5 ps after photoexcitation is shown in Figure
3b. The data can be well accounted for by the Drude−Smith
model (see SI), which describes the transport of free charges
subject to backscattering due to, e.g., structural deforma-
tions.24,33−35 In the model, a parameter c characterizes the
backscattering probability, ranging between 0 (random back-
scattering) to −1 (preferential backscattering). The best fit to
the data yields c = −1 0.02. The preferential backscattering
presumably occurs at the ends of the cGNR. Remarkably, the
charge scattering time τ is found to be 57 3 fs, substantially
larger than those of previously studied GNRs with the
Authors
Wenhui Niu − School of Chemistry and Chemical Engineering,
Frontiers Science Center for Transformative Molecules, Shanghai
Key Laboratory of Electrical Insulation and Thermal Ageing,
Shanghai Jiao Tong University, Shanghai 200240, China;
Center for Advancing Electronics Dresden (cfaed), Faculty of
̈
Chemistry and Food Chemistry, Technische Universitat Dresden,
D-01062 Dresden, Germany
armchair edge (20−30 fs).34,36 Using μ = eτ / m , with m*
*
Ji Ma − Center for Advancing Electronics Dresden (cfaed),
Faculty of Chemistry and Food Chemistry, Technische
the effective mass (obtained by DFT calculations, see SI), we
infer a record intrinsic carrier mobility μ of 617 32 cm2 V−1
s−1. Finally, we compare the transport properties of GNRs in
dispersion to that in the thin film (by drop cast). As shown in
Figure S25, we obtain the same charge scattering τ of 58 3 fs,
and a c parameter of ∼ −0.96. Therefore, our THz study not
only reveals a high intrinsic mobility of charge carriers in
cGNR, but also demonstrates that the deposition of the cGNR
into a solid film does not introduce additional charge scattering
events. On the other hand, the inferred c parameters indicate a
full confinement of the charge carriers for the ribbon dispersed
in solution (with 1 + c = 0), and some degree of charge
delocalization between ribbons on the substrates thanks to the
inter-ribbon coupling (with 1 + c > 0, see SI for details).
In summary, we demonstrated the bottom-up solution
synthesis of a novel cGNR with combined edge structures of
cove, zigzag, and armchair. Model compounds 1 and 2 were
also synthesized to manifest the double [4]helicene structures,
resulting in a curved geometry of the corresponding cGNR.
The cGNR exhibited excellent liquid-phase dispersibility and
unprecedented absorption in the NIR region, with a maximum
peak at ∼850 nm and a particularly narrow optical energy gap
of ∼1.22 eV. THz studies revealed equally high charge
scattering time (∼60 fs) and a record high intrinsic charge
carrier mobility of ∼600 cm2 V−1 s−1 for GNRs. The GNRs
with multi-edge structure hold great promise in many
applications, including photothermal conversion, photovol-
taics, and nanoelectronic devices.
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Universitat Dresden, D-01062 Dresden, Germany;
¶Paniz Soltani − Max Planck Institute for Polymer Research, D-
55128 Mainz, Germany
Wenhao Zheng − Max Planck Institute for Polymer Research,
D-55128 Mainz, Germany
Fupin Liu − Leibniz Institute for Solid State and Materials
Alexey A. Popov − Leibniz Institute for Solid State and
Materials Research, D-01069 Dresden, Germany; orcid.org/
Jan J. Weigand − Department of Inorganic Molecular Chemistry,
Technische Universitat Dresden, D-01062 Dresden, Germany;
̈
Hartmut Komber − Leibniz-Institut fur Polymerforschung
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Emanuele Poliani − Department of Chemistry, Manchester
University, Manchester M13 9PL, United Kingdom;
Cinzia Casiraghi − Department of Chemistry, Manchester
University, Manchester M13 9PL, United Kingdom;
̈
Jorn Droste − Institute of Physical Chemistry, Westfalische
Wilhelms-Universitat (WWU) Munster, D-48149 Munster,
Germany
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J. Am. Chem. Soc. XXXX, XXX, XXX−XXX