2018 New's Items

For the Occasion of Japan Society of Coordination Chemistry International Award: Metal Coordination as a Template Strategy to Make Resilient Woven Materials

Y. Liu
O. M. Yaghi
2018

Transition metal ions as a template method has been widely used in the field of supramolecular chemistry. The metal complexation is advantageous in making complex supramocluar architectures because it pre-organizes the ligands into a desirable orientation which faciliatates the following ring-closing reaction, with shorter synthetic steps and generally higher yield. In a similar fashion, this synthetic strategy has recently been adopted to make extended materials by linking the metal-coordinated building blocks with design principles of reticular synthesis. Individual building units...

Fluoroethylene Carbonate Induces Ordered Electrolyte Interface on Silicon and Sapphire Surfaces as Revealed by Sum Frequency Generation Vibrational Spectroscopy and X-ray Reflectivity

Yonatan Horowitz
Hans-Georg Steinrück
Hui-Ling Han
Chuntian Cao
Iwnetim Iwnetu Abate
Yuchi Tsao
Michael F. Toney
Gabor A. Somorjai
2018

The cyclability of silicon anodes in lithium ion batteries (LIBs) is affected by the reduction of the electrolyte on the anode surface to produce a coating layer termed the solid electrolyte interphase (SEI). One of the key steps for a major improvement of LIBs is unraveling the SEI’s structure-related diffusion properties as charge and discharge rates of LIBs are diffusion-limited. To this end, we have combined two surface sensitive techniques, sum frequency generation (SFG) vibrational spectroscopy, and X-ray reflectivity (XRR), to explore the first monolayer and to probe the first...

Nanopatterning Hexagonal Boron Nitride with Helium Ion Milling: Towards Atomically-Thin, Nanostructured Insulators

S. M. Gilbert
S. Liu
G. Schumm
A. Zettl
2018

In this report, we demonstrate the use of helium ion milling for the controllable fabrication of nanostructures in few-layer hexagonal boron nitride (h-BN). Using the direct-write lithographic capabilities of a scanning helium ion microscope (HIM), nanopores with diameters as small as 4 nm and nanoribbons with widths of 3 – 10 nm are etched from suspended h-BN sheets. This ability to pattern h-BN sheets with high-throughput and sub-10 nm precision paves the way for future studies that make use of atomically-thin, nanostructured insulators such as those needed for nanopore sequencing...

Single-photon absorption by single photosynthetic light-harvesting complexes

H. C. H. Chan
O. E. Gamel
G. R. Fleming
K. B. Whaley
2018

We provide a unified theoretical approach to the quantum dynamics of absorption of single photons and subsequent excitonic energy transfer in photosynthetic light-harvesting complexes. Our analysis combines a continuous mode $ \langle n \rangle $ -photon quantum optical master equation for the chromophoric system with the hierarchy of equations of motion describing excitonic dynamics in presence of non-Markovian coupling to vibrations of the chromophores and...

Observation of Chiral Phonons

H. Zhu
J. Yi
M-Y. Li
J. Xiao
L. Zhang
C-W. Yang
R. A. Kaindl
L-J. Li
Y. Wang
X. Zhang
2018

Chirality reveals symmetry breaking of the fundamental interaction of elementary particles. In condensed matter, for example, the chirality of electrons governs many unconventional transport phenomena such as the quantum Hall effect. Here we show that phonons can exhibit intrinsic chirality in monolayer tungsten diselenide. The broken inversion symmetry of the lattice lifts the degeneracy of clockwise and counterclockwise phonon modes at the corners of the Brillouin zone. We identified the phonons by the intervalley transfer of holes through hole-phonon interactions during the...

Long-Lived Correlated Triplet Pairs in a π-Stacked Crystalline Pentacene Derivative

B. D. Folie
J. B. Haber
S. Refaely-Abramson
J. B. Neaton
N. S. Ginsberg
2018

Singlet fission is the spin-conserving process by which a singlet exciton splits into two triplet excitons. Singlet fission occurs via a correlated triplet pair intermediate, but direct evidence of this state has been scant, and in films of TIPS-pentacene, a small molecule organic semiconductor, even the rate of fission has been unclear. We use polarization-resolved transient absorption microscopy on individual crystalline domains of TIPS-pentacene to establish the fission rate and demonstrate that the initially created triplets remain bound for a surprisingly long time, hundreds of...

Hierarchical On-Surface Synthesis of Graphene Nanoribbon Heterojunctions

C. Bronner
R. A. Durr
D. J. Rizzo
Y-L. Lee
T. Marangoni
A. M. Kalayjian
H. Rodriguez
W. Zhao
S. G. Louie
F. R. Fischer
M. F. Crommie
2018

Bottom-up graphene nanoribbon (GNR) heterojunctions are nanoscale strips of graphene whose electronic structure abruptly changes across a covalently bonded interface. Their rational design offers opportunities for profound technological advancements enabled by their extraordinary structural and electronic properties. Thus far, the most critical aspect of their synthesis, the control over sequence and position of heterojunctions along the length of a ribbon, has been plagued by randomness in monomer sequences emerging from step-growth copolymerization of distinct monomers. All bottom-...

Probing Charge Transport through Peptide Bonds

J. M. Brisendine
S. Refaely-Abramson
Z-F. Liu
J. Cui
F. Ng
J. B. Neaton
R. L. Koder
L. Venkataraman
2018

We measure the conductance of unmodified peptides at the single-molecule level using the scanning tunneling microscope-based break-junction method, utilizing the N-terminal amine group and the C-terminal carboxyl group as gold metal-binding linkers. Our conductance measurements of oligoglycine and oligoalanine backbones do not rely on peptide side-chain linkers. We compare our results with alkanes terminated asymmetrically with an amine group on one end and a carboxyl group on the other to show that peptide bonds decrease the conductance of an otherwise saturated carbon chain. Using...

Self-Assembled PCBM Nanosheets; A Facile Route to Electronic Layer-on-Layer Heterostructures

H. R. Barzegar
C. Larsen
N. Boulanger
A. Zettl
L. Edman
T. Wagberg
2018

We report on the self-assembly of semicrystalline [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) nanosheets at the interface between a hydrophobic solvent and water, and utilize this opportunity for the realization of electronically active organic/organic molecular heterostructures. The self-assembled PCBM nanosheets can feature a lateral size of >1 cm2 and be transferred from the water surface to both hydrophobic and hydrophilic surfaces using facile transfer techniques. We employ a transferred single PCBM nanosheet as the...

Nonreciprocal Localization of Photons

H. Ramezani
P. K. Jha
Y. Wang
X. Zhang
2018

We demonstrate that it is possible to localize photons nonreciprocally in a moving photonic lattice made by spatiotemporally modulating the atomic response, where the dispersion acquires a spectral Doppler shift with respect to the probe direction. A static defect placed in such a moving lattice produces a spatial localization of light in the band gap with a shifting frequency that depends on the direction of incident field with respect to the moving lattice. This phenomenon has an impact not only in photonics but also in broader areas such as condensed matter and acoustics, opening...