Hu et al. designed a new yellow phosphor with high quantum yield by immobilizing a preslected chromophore into the rigid framework of a metal–organic framework (MOF); the structure was determined at Beamline 11.3.1. Coating a blue light-emitting diode (LED) with this compound readily generates white light with high luminous efficacy. The new yellow phosphor demonstrates great potential use in phosphor-converted white LEDs. Read more »
Journal Covers
Advances in Lithography
Work featured on Applied Optics cover from ALS Beamline 11.3.2. Field-dependent wavefront aberration distribution of an extreme ultraviolet single-lens zone-plate microscope, recovered by the gradient descent algorithm customized for partially coherent imaging and targeted for fast and accurate retrieval. Read more »
Mono- and Diboron Corroles: Factors Controlling Stoichiometry and Hydrolytic Reactivity
The synthesis and structural characterization of a diboryl triaryloctabromocorrole complex fills in a missing link in the family of diboron porphyrinoids. DFT calculations suggest that a strongly electron-withdrawing corrole ligand is required to stabilize the diboryl complex relative to the partially hydrolyzed diboron corrole complexes previously observed. New monoboryl corrole complexes are described, which do not have counterparts in porphyrin chemistry and are stabilized by internal F···H hydrogen bonding. Read more »
Platinum Corroles
Platinum has been inserted into corroles for the first time and three oxidized PtIV(corrole˙2−)ArAr′ complexes have been structurally characterized. The Soret maxima of these complexes exhibit an unusually strong dependence on the meso-aryl substituents on the corrole, indicating aryl → corrole˙2− charge transfer character in these transitions. Read more »
The influence of molecular orientation on organic bulk heterojunction solar cells
Work done on ALS Beamlines 11.0.1.2, 7.3.3, and 5.3.2.2. reveals that preferential orientation of polymer chains with respect to the fullerene domain leads to a high photovoltaic performance. Read more »
Crystal Nucleation and Near-Epitaxial Growth in Nacre
Nacre–the iridescent inner lining of many mollusk shells– has a unique strcuture that is remarkably resistant to fracture. The nacre featured on this cover is from Haliotis laevigata with average layer thickness 470-nm. The colors represent crystal orientationthe crystal lattice tilts across tablets.left stack all tablets are yellow, hence all aragonite crystals are co-oriented. Read more »
Ring Cycle for Dilating and Constricting the Nuclear Pore
Pictured is an illustration of several nuclear pore complexes (NPCs) embedded in a cell nucleus. NPCs act as gatekeepers between a cell’s cytoplasm and its nucleus. Based on crystallographic analyses, Sozanne R. Solmaz et al. uncover the molecular mechanism that underlies the large changes in diameter of NPCs and suggest a “ring cycle” mechanism for dilating and constricting the central NPC channel. The model could explain the ability of NPCs to accommodate transport substrates of a large size range and rapidly adjust to cellular transport needs. Read more »
Jamming Behavior of Domains in a Spiral Antiferromagnetic System
This schematic of x-ray scattering is from a spiral antiferromagnet with a spin structure that gives rise to domains with jamming behavior. Using resonant magnetic x-ray photon correlation spectroscopy, this research shows that the domains of a spiral antiferromagnet enter a jammed state at the onset of long-range order. Researchers found that slow thermal fluctuations of the domain walls exhibit a compressed exponential relaxation with an exponent of 1.5 found in a wide variety of solid-like jammed systems and can be qualitatively explained in terms of stress release in a stressed network. As the temperature decreases, the energy barrier for fluctuations becomes large enough to arrest further domain wall fluctuations, and the domains freeze into a spatial configuration within 10 K of the Néel temperature. The relaxation times can be fitted with the Vogel-Fulcher law as observed in polymers, glasses, and colloids, thereby indicating that the dynamics of domain walls in an ordered antiferromagnet exhibit some of the universal features associated with jamming behavior. Read more »
Solar Cells: Spin-Cast Bulk Heterojunction Solar Cells: A Dynamical Investigation
Spin-coating is extensively used in the lab-based manufacturing of organic solar cells, including most of the record-setting cells. Aram Amassian and co-workers report in this study the first direct observation of photoactive layer formation as it occurs during spin-coating. The study provides new insight into mechanisms and kinetics of bulk heterojunction formation, which may be crucial for successful transfer to printing processes and scaling up production. Read more »
Real-Time Quantitative Imaging of Failure Events in Materials Under Load at Temperatures Above 1,600 °C
Gathering information on the evolution of small cracks in ceramic matrix composites used in hostile environments such as in gas turbines and hypersonic flights has been a challenge. It is now shown that sequences of microcrack damage in ceramic composites under load at temperatures up to 1,750 °C can be fully resolved with the use of in situ synchrotron x-ray computed microtomography. Read more »
