The nearly simultaneous Mott (electronic) and Peierls (structural) transitions in vanadium dioxide are of significant scientific interest and have tremendous technological promise in computing, memory, optics, and micromechanics. The cover features nanoscale-resolution maps of the Mott and Peierls transitions imaged simultaneously by Kumar et al. using state-of-the-art in situ STXM at the ALS. Read more »
Journal Covers
Weaving of organic threads into a crystalline covalent organic framework
Threads made from organic molecules linked by strong covalent bonds were used to weave a 3D covalent organic framework with unusual dynamical and mechanical properties. This molecular weaving method will enable the production of materials with increased precision and functionality. Read more »
Misfolded opsin mutants display elevated β-sheet structure
Mutations in rhodopsin can cause misfolding and aggregation of the receptor, which leads to retinitis pigmentosa, a progressive retinal degenerative disease. Förster resonance energy transfer (FRET) and Fourier transform infrared (FTIR) microspectroscopy were utilized to probe within cells the structures formed by G188R and P23H opsins. Read more »
Narrowly Distributed Crystal Orientation in Biomineral Vaterite
The cover shows a scanning electron micrograph of vaterite crystals formed by the sea squirt Herdmania momus. These are the largest single crystals of vaterite ever observed, including biogenic, geologic or synthetic vaterite. Flat crystal faces are uncommon in biogenic crystals, but these crystals are clearly hexagonal pyramids. Pokroy et al. show that these crystals have smooth fracture surfaces; thus, they most likely formed ion-by-ion, rather than by attachment of particles. Narrowly distributed orientations and lack of organics at crystal interfaces suggest a new mechanism of biomineral crystal growth, perhaps spherulitic growth from solution. Read more »
The Crystallization of PEDOT:PSS Polymeric Electrodes Probed In Situ during Printing
Organic electronics have emerged into a highly interesting field of research with a great variety of applications. P. Müller-Buschbaum and co-workers demonstrate the importance of in situ investigations during the printing process of organic electronics. In situ grazing-incidence wide-angle x-ray scattering is used to follow the crystallization process of highly conductive PEDOT:PSS polymer mixtures. These findings are important for tuning transparent polymeric electrodes for organic electronics. Cover Image by Christoph Hohmann, Nanosystems Initiative Munich (NIM). Read more »
Ligand Noninnocence in Coinage Metal Corroles: A Silver Knife-Edge
In contrast to noninnocent copper corroles and essentially innocent gold corroles, silver corroles appear to be poised on a knife-edge between the two electronic-structural descriptions. The summit trail of Mount Sir Alexander, a peak of the Canadian Rockies described by mountaineer Chris Goulet as a knife-edge that only a mouse can walk on, provides anRead More Read more »
Electronic Structure Changes in Supercapacitor Electrodes Observed In Operando
Profound bias- and time-dependent changes in the electronic structure of graphene-based supercapacitor electrodes are demonstrated under operating conditions via a combination of in operando x-ray spectroscopy and ab initio modeling by J.R.I. Lee and co-workers. The evolution in electronic structure reflects changes in the surface chemistry and morphology induced by polarization of the electrode-electrolyte interface and points to distinct pseudocapacitive and electric-double-layer capacitive channels for charge storage. Read more »
MOF Coating a Promising Path to White LEDs
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 »
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 »
