2020 New's Items

A molecular shift register made using tunable charge patterns in one-dimensional molecular arrays on graphene

Tsai HZ
Lischner J
Omrani AA
Liou F
Aikawa AS
Karrasch C
Wickenburg S
Riss A
Natividad KC
Chen J
Choi WW
Watanabe K
Taniguchi T
Su C
Louie SG
Zettl A
Lu J
Crommie MF
2020

The ability to tune the electronic properties of molecular arrays is an important step in the development of molecule-scale electronic devices. However, control over internal device charge distributions by tuning interactions between molecules has proved challenging. Here, we show that gate-tunable charge patterning can occur in one-dimensional molecular arrays on graphene field-effect transistors. One-dimensional molecular arrays are fabricated using an edge-templated self-assembly process that allows organic molecules (F4TCNQ) to be precisely positioned on...

Graphene-Sealed Flow Cells for In Situ Transmission Electron Microscopy of Liquid Samples

Gabriel Dunn
Vivekananda P. Adiga
Thang Pham
Christopher Bryant
Donez J. Horton-Bailey
Jason N. Belling
Ben LaFrance
Jonathan A. Jackson
Hamid Reza Barzegar
Jong Min Yuk
Shaul Aloni
Michael F. Crommie
Alex Zettl
2020

We introduce a graphene-based nanofluidic cell that facilitates in situ imaging of liquid samples via transmission electron microscopy. The cell combines the benefits of graphene liquid cells—namely, high resolution, reduced charging effects, and excellent sample stability—with the ability to introduce reactants and control fluid concentrations as provided by conventional silicon-nitride-windowed flow cells. The graphene flow cell offers significantly less window bowing compared to existing commercial holders. We demonstrate the performance of the flow cell by imaging...

Single-chain heteropolymers transport protons selectively and rapidly

Jiang T
Hall A
Eres M
Hemmatian Z
Qiao B
Zhou Y
Ruan Z
Couse AD
Heller WT
Huang H
de la Cruz MO
Rolandi M
Xu T
2020

Precise protein sequencing and folding are believed to generate the structure and chemical diversity of natural channels1,...

Two-dimensional forms of robust CO2 reduction photocatalysts

Torrisi SB
Singh AK
Montoya JH
Biswas T
Persson KA
2020

Photoelectrocatalysts that use sunlight to power the CO2 reduction reaction will be crucial for carbon-neutral power and energy-efficient industrial processes. Scalable photoelectrocatalysts must satisfy a stringent set of criteria, such as stability under operating conditions, product selectivity, and efficient light absorption. Two-dimensional materials can offer high specific surface area, tunability, and potential for heterostructuring, providing a fresh landscape of candidate catalysts. From a set of promising bulk CO2...

Ion Pairing and Redissociaton in Low-Permittivity Electrolytes for Multivalent Battery Applications

Self J
Hahn NT
Fong KD
McClary SA
Zavadil KR
Persson KA
2020

Detailed speciation of electrolytes as a function of chemical system and concentration provides the foundation for understanding bulk transport as well as possible decomposition mechanisms. In particular, multivalent electrolytes have shown a strong coupling between anodic stability and solvation structure. Furthermore, solvents that are found to exhibit reasonable stability against alkaline-earth metals generally exhibit low permittivity, which typically increases the complexity of the electrolyte species. To improve our understanding of ionic population and associated transport in...

Incorporating Electronic Information into Machine Learning Potential Energy Surfaces via Approaching the Ground-State Electronic Energy as a Function of Atom-Based Electronic Populations

Xie X
Persson KA
Small DW
2020

Machine learning (ML) approximations to density functional theory (DFT) potential energy surfaces (PESs) are showing great promise for reducing the computational cost of accurate molecular simulations, but at present, they are not applicable to varying electronic states, and in particular, they are not well suited for molecular systems in which the local electronic structure is sensitive to the medium to long-range electronic environment. With this issue as the focal point, we present a new machine learning approach called “BpopNN” for obtaining efficient approximations to DFT PESs....

From Waste-Heat Recovery to Refrigeration: Compositional Tuning of Magnetocaloric Mn1+xSb

Cooley JA
Horton MK
Levin EE
Lapidus SH
Persson KA
Seshadri R
2020

Magnetic refrigeration, as well as waste-heat recovery, can be accomplished through the magnetocaloric effect, where temperature changes the magnetic state of a material or vice versa. Promising magnetocaloric materials display large changes in magnetic entropy (ΔSM) upon application of a moderate magnetic field and are often associated with magnetic materials possessing some degree of magnetostructural coupling. In such compounds, the magnetic transition is coupled to some structural transition at the ordering temperature, and indicators for these are...

Butyltin Keggin Ion with a Rare Four-Coordinate Ca Center

Hutchison DC
Stern RD
Zakharov LN
Persson KA
Nyman M
2020

Alkyltin clusters are exploited in nanolithography for the fabrication of microelectronics. The alkyltin Keggin family is unique among Keggin clusters across the periodic table; its members appear to favor the lower-symmetry β and γ isomers rather than the highly symmetrical α and ε isomers. Therefore, the alkyltin Keggin family may provide important fundamental information about the formation and isomerization of Keggin clusters. We have synthesized and structurally characterized a new butyltin Keggin cluster with a tetrahedral Ca2+ center, fully formulated...

Large-area epitaxial growth of curvature-stabilized ABC trilayer graphene

Gao Z
Wang S
Berry J
Zhang Q
Gebhardt J
Parkin WM
Avila J
Yi H
Chen C
Hurtado-Parra S
Drndić M
Rappe AM
Srolovitz DJ
Kikkawa JM
Luo Z
Asensio MC
Wang F
Johnson ATC
2020

The properties of van der Waals (vdW) materials often vary dramatically with the atomic stacking order between layers, but this order can be difficult to control. Trilayer graphene (TLG) stacks in either a semimetallic ABA or a semiconducting ABC configuration with a gate-tunable band gap, but the latter has only been produced by exfoliation. Here we present a chemical vapor deposition approach to TLG growth that yields greatly enhanced fraction and size of ABC domains. The key insight is that substrate curvature can stabilize ABC domains. Controllable ABC yields ~59% were achieved...

Surface and grain boundary carbon heterogeneity in CH3NH3PbI3 perovskites and its impact on optoelectronic properties

Li Y
Wang P
Chopdekar R
Scholl A
Zhao Z
Zou Y
Utama MIB
Wang F
Barnes M
Zhang Y
Russell TP
Liu F
2020

Rivaling state-of-the-art crystalline silicon, organic-inorganic hybrid perovskites have been intensely studied in recent years. Surface and interfacial engineering have been a focus for performance improvement. Even though significant progress has been made during the last decade in terms of the diversity and capability of perovskite-based devices, the structure-property relationship, particularly at the surface, which governs the real-world performance of these applications, is still unresolved. In the article, this issue was addressed by employing synchrotron-related experimental...