Numerical design and characterization of a novel parallel beam combined lens based on X-ray capillary optics.

A novel parallel beam combined lens (PBCL) was designed based on a parabolic monocapillary x-ray lens (PMXRL). The proposed PBCL converted a divergent X-ray beam into a near-solid parallel one, which retains the low divergence characteristics of PMXRL and significantly improves the intensity gain by about one order of magnitude. Compared with the traditional polycapillary parallel x-ray lens (PPXRL), the divergence performance of this lens is improved by an order of magnitude, and the light intensity gain is improved by 3-4 times. In addition, we developed a MATLAB-based visualization tool to simulate X-ray transmission within the PBCL through ray tracing. This tool facilitated the assessment of the PBCL's transmission efficiency and its comparison with conventional PMXRL and the PPXRL. The transport process of the PBCL is systematically investigated under the comprehensive consideration of multiple parameters. This study provided a new idea and theoretical basis for the further development of X-ray modulation technology.

Magnified x ray ghost imaging with tapered polycapillary optics free of the penumbra effect.

X ray ghost imaging (XGI) offers both radiation dose-reduction potential and cost-effective benefits owing to the utilization of a single-pixel detector. Most XGI schemes with laboratory x ray sources require a mechanically moving mask for either structured illumination or structured detection. In either configuration, however, its resolution remains limited by the source size and the unit size of the mask. Upon propagation, the details of the object can actually be magnified by the divergence of x rays, but at the same time, the penumbra effect produced by the finite source size is dramatically intensified, which ultimately leads to a degradation of image quality in XGI. To address these limitations, this work proposes a magnified XGI scheme using structured detection equipped with tapered polycapillary optics, which can efficiently suppress the object's penumbra as well as resolve the magnified details of the object. In general, the resolution of this scheme is no longer affected by the source size but by the microcapillary size of polycapillary. Our work fundamentally achieves cancellation of penumbra effect-induced aberration, thus paving the way for high-resolution magnified XGI.

Influence of the Degree of Swelling on the Stiffness and Toughness of Microgel-Reinforced Hydrogels.

The stiffness and toughness of conventional hydrogels decrease with increasing degree of swelling. This behavior makes the stiffness-toughness compromise inherent to hydrogels even more limiting for fully swollen ones, especially for load-bearing applications. The stiffness-toughness compromise of hydrogels can be addressed by reinforcing them with hydrogel microparticles, microgels, which introduce the double network (DN) toughening effect into hydrogels. However, to what extent this toughening effect is maintained in fully swollen microgel-reinforced hydrogels (MRHs) is unknown. Herein, it is demonstrated that the initial volume fraction of microgels contained in MRHs determines their connectivity, which is closely yet nonlinearly related to the stiffness of fully swollen MRHs. Remarkably, if MRHs are reinforced with a high volume fraction of microgels, they stiffen upon swelling. By contrast, the fracture toughness linearly increases with the effective volume fraction of microgels present in the MRHs regardless of their degree of swelling. These findings provide a universal design rule for the fabrication of tough granular hydrogels that stiffen upon swelling and hence, open up new fields of use of these hydrogels.

Topological Design of Highly Anisotropic Aligned Hole Transporting Molecular Bottlebrushes for Solution-Processed OLEDs.

Polyvinyl polymers bearing pendant hole transport functionalities have been extensively explored for solution-processed hole transport layer (HTL) technologies, yet there are only rare examples of high anisotropic packing of the HT moieties of these polymers into substrate-parallel orientations within HTL films. For small molecules, substrate-parallel alignment of HT moieties is a well-established approach to improve overall device performance. To address the longstanding challenge of extension from vapor-deposited small molecules to solution-processable polymer systems, a fundamental chemistry tactic is reported here, involving the positioning of HT side chains within macromolecular frameworks by the construction of HT polymers having bottlebrush topologies. Applying state-of-the-art polymer synthetic techniques, various functional subunits, including triphenylamine (TPA) for hole transport and adhesion to the substrate, and perfluoro alkyl-substituted benzyloxy styrene for migration to the air interface, were organized with exquisite control over the composition and placement throughout the bottlebrush topology. Upon assembling the HT bottlebrush (HTB) polymers into monolayered HTL films on various substrates through spin-casting and thermal annealing, the backbones of HTBs were vertically aligned while the grafts with pendant TPAs were extended parallel to the substrate. The overall design realized high TPA π-stacking along the out-of-plane direction of the substrate in the HTLs, which doubled the efficiency of organic light-emitting diodes compared with linear poly(vinyl triphenylamine)s.

High quality quasi-parallel x-ray microbeams based on a parabolic capillary.

High quality quasi-parallel x-ray microbeams have an appreciable application value in the x-ray diffraction analysis technique, which is currently one of the most significant non-destructive analysis techniques. A simulation of a parabolic single capillary is carried out based on the Monte Carlo simulation toolkit Geant4. The simulation results show that it is feasible to obtain high quality quasi-parallel x-ray microbeams based on a parabolic capillary and a traditional laboratorial x-ray source. We manufacture a parabolic capillary based on the simulation results. The physical parameters of the obtained x-ray beams are characterized by building an x-ray imaging system. The experimental results show that the x-ray beam with submicrometer size and almost zero divergence can be obtained from the traditional laboratorial x-ray source by utilizing a parabolic single capillary as a collimator.

Coordination of Actinide Single Ions to Deformed Graphdiyne: Strategy on Essential Separation Processes in Nuclear Fuel Cycle.

The coordination of actinides and lanthanides, as well as strontium and cesium with graphdiyne (GDY) was studied experimentally and theoretically. On the basis of experimental results and/or theoretical calculations, it was suggested that Th4+ , Pu4+ , Am3+ , Cm3+ , and Cs+ exist in single-ion states on the special triangular structure of GDY with various coordination patterns, wherein GDY itself is deformed in different ways. Both experiment and theoretical calculations strongly indicate that UO2 2+ , La3+ , Eu3+ , Tm3+ and Sr2+ are not adsorbed by GDY at all. The distinguished adsorption behaviors of GDY afford an important strategy for highly selective separation of actinides and lanthanides, Th4+ and UO2 2+ , and Cs+ and Sr2+ , in the nuclear fuel cycle. Also, the present work sheds light on an approach to explore the unique functions and physicochemical properties of actinides in single-ion states.

Bis-Bipyridinium Gemini Surfactant-Based Supramolecular Helical Fibers and Solid State Thermochromism.

The processability and functional performance of stimuli-responsive supramolecular materials are key factors in determining their utility and potential for mass adoption, usage, and profitability. However, it is difficult to predict how structural changes to the molecular components of these systems will impact their operation. Here, a series of π-electron-deficient bis-bipyridinium gemini surfactants were synthesized and evaluated to elucidate the structure-property relationships that govern their ability to form helical-fiber-based donor-acceptor hydrogels, impact hydrogel strength, and influence their solid-state thermochromism. When combined with the π-electron-rich donor melatonin, the helical-fiber- and hydrogel-forming ability of the gemini surfactants was largely influenced by the dimensions of the rigid bridging group that connects the two bis-bipyridinium units. Dynamic viscoelastic rheology and linear sweep voltammetric analysis revealed a positive correlation between the length of the gemini-surfactant bridging group and both the hydrogel strength and the magnitude of the charge-transfer interaction between the donor-acceptor pair. Solid-state thermochromic transition temperatures of processed aerogels, xerogel films, and inkjet-printed patterns were positively correlated with the strength of the charge transfer interaction between the donor-acceptor pair and, thus, also with the length of the gemini surfactant bridging group. The results provide impactful insights that will enable the development of new donor-acceptor-based thermochromes with versatile processability and tunable functionality.

Assembly and Chiral Memory Effects of Dynamic Macroscopic Supramolecular Helices.

Macroscopic enantiomerically pure helical supramolecular fibers are bottom-up assembled in aqueous media from a chiral π-electron donor template and an achiral π-electron acceptor. The helices can be assembled to the sub-millimeter scale with controlled handedness. These dynamic supramolecular architectures allow for a quantitative exchange of the chiral donor template with achiral analogues. During this process, a chiral memory effect was observed, affording enantiomerically pure helices composed entirely of achiral components.

Robustness of coupled oscillator networks with heterogeneous natural frequencies.

Robustness of coupled oscillator networks against local degradation of oscillators has been intensively studied in this decade. The oscillation behavior on the whole network is typically reduced with an increase in the fraction of degraded (inactive) oscillators. The critical fraction of inactive oscillators, at which a transition from an oscillatory to a quiescent state occurs, has been used as a measure for the network robustness. The larger (smaller) this measure is, the more robust (fragile) the oscillatory behavior on the network is. Most previous studies have used oscillators with identical natural frequencies, for which the oscillators are necessarily synchronized and thereby the analysis is simple. In contrast, we focus on the effect of heterogeneity in the natural frequencies on the network robustness. First, we analytically derive the robustness measure for the coupled oscillator models with heterogeneous natural frequencies under some conditions. Then, we show that increasing the heterogeneity in natural frequencies makes the network fragile. Moreover, we discuss the optimal parameter condition to maximize the network robustness.

Extended Ladder-Type Benzo[k]tetraphene-Derived Oligomers.

Well-defined, fused-ring aromatic oligomers represent promising candidates for the fundamental understanding and application of advanced carbon-rich materials, though bottom-up synthesis and structure-property correlation of these compounds remain challenging. In this work, an efficient synthetic route was employed to construct extended benzo[k]tetraphene-derived oligomers with up to 13 fused rings. The molecular and electronic structures of these compounds were clearly elucidated. Precise correlation of molecular sizes and crystallization dynamics was established, thus demonstrating the pivotal balance between intermolecular interaction and molecular mobility for optimized processing of highly ordered solids of these extended conjugated molecules.