2018 New's Items

Electron delocalization and charge mobility as a function of reduction in a metal–organic framework

M. L. Aubrey
B. M. Wiers
S. C. Andrews
J. B. Neaton
P. Yang
J. R. Long
2018

Conductive metal–organic frameworks are an emerging class of three-dimensional architectures with degrees of modularity, synthetic flexibility and structural predictability that are unprecedented in other porous materials. However, engendering long-range charge delocalization and establishing synthetic strategies that are broadly applicable to the diverse range of structures encountered for this class of materials remain challenging. Here, we report the synthesis of K x Fe2(BDP)3 (0 ≤ x ≤ 2;...

Concentration Dependence of Dopant Electronic Structure in Bottom-up Graphene Nanoribbons

Z. Pedramrazi
C. Chen
F. Zhao
T. Cao
G. Nguyen
A. Omrani
H-Z. Tsai
R. Cloke
T. Marangoni
D. Rizzo
T. Joshi
C. Bronner
W-W. Choi
F. R. Fischer
S. G. Louie
M. Crommie
2018

Bottom-up fabrication techniques enable atomically precise integration of dopant atoms into the structure of graphene nanoribbons (GNRs). Such dopants exhibit perfect alignment within GNRs and behave differently from bulk semiconductor dopants. The effect of dopant concentration on the electronic structure of GNRs, however, remains unclear despite its importance in future electronics applications. Here we use scanning tunneling microscopy and first-principles calculations to investigate the electronic structure of bottom-up synthesized N = 7 armchair GNRs featuring...

Intrinsic Two-Dimensional Ferroelectricity with Dipole Locking

J. Xiao
H. Zhu
Y. Wang
W. Feng
Y. Hu
A. Dasgupta
Y. Han
Y. Wang
D. Muller
L. Martin
P. Hu
X. Zhang
2018

Out-of-plane ferroelectricity with a high transition temperature in ultrathin films is important for the exploration of new domain physics and scaling down of memory devices. However, depolarizing electrostatic fields and interfacial chemical bonds can destroy this long-range polar order at two-dimensional (2D) limit. Here we report the experimental discovery of the locking between out-of-plane dipoles and in-plane lattice asymmetry in atomically thin In2...

Molecular Orientations Change Reaction Kinetics and Mechanism: A review on Catalytic Alcohol Oxidation in Gas Phase and Liquid Phase on Size-Controlled Pt Nanoparticles

Fudong Liu
Haliang Wang
Andras Sapi
Hironori Tatsumi
Danylo Zherebetskyy
Hui-Ling Han
Lindsay M. Carl
Gabor A. Somorjai
2018

Catalytic oxidation of alcohols is an essential process for energy conversion, production of fine chemicals and pharmaceutical intermediates. Although it has been broadly utilized in industry, the basic understanding for catalytic alcohol oxidations at a molecular level, especially under both gas and liquid phases, is still lacking. In this paper, we systematically summarized our work on catalytic alcohol oxidation over size-controlled Pt nanoparticles. The studied alcohols included methanol, ethanol, 1-propanol, 2-propanol, and 2-butanol. The turnover rates of different alcohols on...

Universal Imaging of Material Functionality Through Nanoscale Tracking of Energy Flow

M. D. Delor
H. L. Weaver
Q. Yu
N. S. Ginsberg
2018

The ability of energy carriers to move within and between atoms and molecules underlies virtually all biochemical and material function. Understanding and controlling energy flow, however, requires observing it on ultrasmall and ultrafast spatiotemporal scales, where energetic and structural roadblocks dictate the fate of energy carriers. We therefore developed a universal, non-invasive optical scheme that leverages interferometric scattering to track energy transport in four dimensions of spacetime with few-nanometer precision and directly correlate it to material morphology. We...

Imaging of Pure Spin-valley Diffusion Current in WS2-WSe2 Heterostructures

C. Jin
J. Kim
M. I. B. Tuama
E. C. Regan
H. Kleemann
H. Cai
Y. Sen
M. J. Shinne
A. Sengupta
K. Watanabe
T. Taniguchi
S. Tongay
A. Zettl
F. Wan
2018

Transition metal dichalcogenide (TMDC) materials are promising for spintronic and valleytronic applications because valley-polarized excitations can be generated and manipulated with circularly polarized photons and the valley and spin degrees of freedom are locked by strong spin-orbital interactions. In this study we demonstrate efficient generation of a pure and locked spin-valley diffusion current in tungsten disulfide (WS2)–tungsten diselenide (WSe2) heterostructures without any driving electric field. We imaged the propagation...

High- Pressure Chemistry of Hydrocarbons Relevant to Planetary Interiors and Inertial Confinement Fusion

Kraus
Hartley
Frydrych
2018

Diamond formation in polystyrene (C8H8)n, which is laser-compressed and heated to conditions around 150 GPa and 5000 K, has recently been demonstrated in the laboratory [Kraus et al., Nat. Astron. 1, 606–611 (2017)]. Here, we show an extended analysis and comparison to first-principles simulations of the acquired data and their implications for planetary physics and inertial confinement fusion. Moreover, we discuss the advanced diagnostic capabilities of adding high-quality small...

Enhancement of CO2 binding and mechanical properties upon diamine functionalization of M2(dobpdc) metal-organic frameworks

Jung-Hoon Lee
Rebecca L. Siegelman
L. Maserati
T. Rangel
B. Helms
J. Long
J. B. Neaton
2018

The family of diamine-appended metal–organic frameworks exemplified by compounds of the type mmen–M2(dobpdc) (mmen = N,N′-dimethylethylenediamine; M = Mg, Mn, Fe, Co, Zn; dobpdc4− = 4,4′-dioxidobiphenyl-3,3′-dicarboxylate) are adsorbents with significant potential for carbon capture, due to their high working capacities and strong selectivity for CO2 that stem from a cooperative adsorption mechanism. Herein, we use...

Using Graphene Liquid Cell Transmission Electron Microscopy to Study in Situ Nanocrystal Etching

Matthew R. Hauwiller
Justin C. Ondry
A. Paul Alivisatos
2018

Graphene liquid cell electron microscopy provides the ability to observe nanoscale chemical transformations and dynamics as the reactions are occurring in liquid environments. This manuscript describes the process for making graphene liquid cells through the example of graphene liquid cell transmission electron microscopy (TEM) experiments of gold nanocrystal etching. The protocol for making graphene liquid cells involves coating gold, holey-carbon TEM grids with chemical vapor deposition graphene and then using those graphene-coated grids to encapsulate liquid between two graphene...

Excitation Intensity Dependence of Photoluminescence Blinking in CsPbBr3 Perovskite Nanocrystals

Natalie A. Gibson
Brent A. Koscher
A. Paul Alivisatos
Stephen R. Leone
2018

Perovskite semiconductors have emerged as a promising class of materials for optoelectronic applications. Their favorable device performances can be partly justified by the defect tolerance that originates from their electronic structure. The effect of this inherent defect tolerance, namely the absence of deep trap states, on the photoluminescence (PL) of perovskite nanocrystals (NCs) is currently not well understood. The PL emission of NCs fluctuates in time according to power law kinetics (PL intermittency, or blinking), a phenomenon that has been explored over the past two decades...