2018 New's Items

Quantum Coherence–Driven Self-Organized Criticality and Nonequilibrium Light Localization

K. L. Tsakmakidis
P. K. Jha
Y. Wang
X. Zhang
2018

Self-organized criticality emerges in dynamical complex systems driven out of equilibrium and characterizes a wide range of classical phenomena in physics, geology, and biology. We report on a quantum coherence–controlled self-organized critical transition observed in the light localization behavior of a coherence-driven nanophotonic configuration. Our system is composed of a gain-enhanced plasmonic heterostructure controlled by a coherent drive, in which photons close to the stopped-light regime interact in the presence of the active nonlinearities, eventually synchronizing their...

Fundamental Efficiency Limit of Lead Iodide Perovskite Solar Cells

L.M. Pazos-Outon
T.P. Xiao
E. Yablonovitch
2018

Lead halide materials have seen a recent surge of interest from the photovoltaics community following the observation of surprisingly high photovoltaic performance, with optoelectronic properties similar to GaAs. This begs the question: What is the limit for the efficiency of these materials? It has been known that under 1-sun illumination the efficiency limit of crystalline silicon is ∼29%, despite the Shockley–Queisser (SQ) limit for its bandgap being ∼33%: the discrepancy is due to strong Auger recombination. In this article, we show that methyl ammonium lead iodide (MAPbI...

Mid-IR broadband Supercontinuum Generation from a Suspended Silicon Waveguide

R. Kou
T. Hatakeyama
J. Kang
Y. Wang
X. Zhang
F. Wang
J. Horng
2018

Mid-infrared light provides numerous unexpected opportunities in scientific discoveries because this wavelength region covers the fingerprints of various molecular vibrational resonances. However, the light generation efficiency and bandwidth have been a long-standing bottleneck which has limited the development so far. Moreover, the light source that can be integrated with other components such as wavelength filters, detectors, and electronics, will be the key factor toward the future practical applications. Here, we propose an all-air-cladding silicon-rib waveguide to...

Supported Iron Catalysts for Michael Addition Reaction

Rong Ye
Franco F. Faucher
Gabor A. Somorjai
2018

In this paper, ZnS@CdS–Te composites with visible light response were successfully prepared by microwave-assisted hydrothermal method. X-ray diffraction(XRD), UV–vis diffuse reflectance spectroscopy (UV–vis/DRS), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy–energy dispersive spectrometer (SEM–EDS), high-resolution transmission electron microscopy (HR-TEM), and N2 adsorption–desorption measurements were utilized to test the structure, composition, morphology, surface physical and chemical properties, and optical absorption properties...

Carbon Dioxide Dimer Radical Anion as Surface Intermediate of Photoinduced CO2 Reduction at Aqueous Cu and CdSe Nanoparticle Catalysts by Rapid-Scan FT-IR Spectroscopy

H. Sheng
M. Hwan
W. T. Osowiecki
W. Kim
A. P. Alivisatos
H. Frei
2018

Monitoring of visible light sensitized reduction of CO2 at Cu nanoparticles in aqueous solution by rapid-scan ATR FT-IR spectroscopy on the time scale of seconds allowed structural identification of a one-electron intermediate and demonstrated its kinetic relevancy for the first time. Isotopic labeling (12C: 1632, 1358, 1346 cm–1; 13C: 1588, 1326, 1316 cm–1) revealed a species of carbon dioxide dimer radical anion structure, most likely bound to the...

The Methanol Economy: Methane and Carbon Dioxide Conversion

Wen-Chi Liu
Jayeon Baek
Gabor A. Somorjai
2018

Need for clean energy is imminent and methanol is considered as a promising alternative energy source. Conventional process for the production of methanol has been achieved via syngas which is derived by the steam reforming of methane or naphtha and the gasification of coal. Methanol can also be prepared by direct oxidation of methane (natural gas) or reduction of carbon dioxide (CO2) with hydrogen. In this way, carbon-neutral cycling can be achieved and world’s dependence on fossil fuels will be alleviated. In this minireview, we will address case by case...

Strongly Quantum Confined Colloidal Cesium Tin Iodide Perovskite Nanoplates: Lessons for Reducing Defect Density and Improving Stability

A. Wong
Y. Bekenstein
J. Kang
C. Kley
D. Kim
N. Gibson
D. Zhang
Y. Yu
S. Leone
L-W. Wang
A. P. Alivisatos
P. Yang
2018

Within the last several years, metal halide perovskites such as methylammonium lead iodide, CH3NH3PbI3, have come to the forefront of scientific investigation as defect-tolerant, solution-processable semiconductors that exhibit excellent optoelectronic properties. The vast majority of study has focused on Pb-based perovskites, which have limited applications because of their inherent toxicity. To enable the broad application of these materials, the properties of lead-free halide perovskites must be explored...

Mechanochemical Coupling and Bi-phasic Force-velocity Dependence in the Ultra-fast Ring ATPase SpoIIIE

N. Liu
G. Chistol
Y. Cui
C. Bustamante
2018

Multi-subunit ring-shaped ATPases are molecular motors that harness chemical free energy to perform vital mechanical tasks such as polypeptide translocation, DNA unwinding, and chromosome segregation. Previously we reported the intersubunit coordination and stepping behavior of the hexameric ring-shaped ATPase SpoIIIE (Liu et al., 2015). Here we use optical tweezers to characterize the motor's mechanochemistry. Analysis of the motor response to external force at various nucleotide concentrations identifies phosphate release as the likely force-generating step. Analysis of SpoIIIE...

The Role of Recticular Chemistry in the Design of CO2 Reduction Catalysts

C.S. Diercks
Y. Liu
K. E. Cordova
O. M. Yaghi
2018

The problem with current state-of-the-art catalysts for CO2 photo- or electroreduction is rooted in the notion that no single system can independently control, and thus optimize, the interplay between activity, selectivity and efficiency. At its core, reticular chemistry is recognized for its ability to control, with atomic precision, the chemical and structural features (activity and selectivity) as well as the output optoelectronic properties (efficiency) of porous, crystalline materials. The molecular building blocks that are in a reticular chemist’s...

Dynamics and Removal Pathway of Edge Dislocations in Imperfectly Attached PbTe Nanocrystal Pairs: Toward Design Rules for Oriented Attachment

Justin Ondry
Matthew Hauwiller
A. Paul Alivisatos
2018

Using in situ high-resolution TEM, we study the structure and dynamics of well-defined edge dislocations in imperfectly attached PbTe nanocrystals. We identify that attachment of PbTe nanocrystals on both {100} and {110} facets gives rise to b = a/2⟨110⟩ edge dislocations. Based on the Burgers vector of individual dislocations, we can identify the glide plane of the dislocations. We observe that defects in particles attached on {100} facets have glide planes that quickly intersect the surface, and HRTEM movies show that the defects follow the...