Silapillar[n]arenes: Their Enhanced Electronic Conjugation and Conformational Versatility.

During recent decades, methylene-bridged macrocyclic arenes have been widely used in supramolecular chemistry. However, their π-conjugations are very weak, as the methylene bridges disrupt the electronic communication between π orbitals of the aromatic units. Herein, we successfully synthesized a series of silapillar[n]arenes (n = 4, 6, and 8) using silylene bridging. These showed enhanced electronic conjugation compared with the parent pillar[n]arenes because of σ*-π* conjugation between σ* (Si-C) orbitals and π* orbitals of the benzenes. Owing to the longer Si-C bond compared with the C-C bond, silylene-bridging provides additional structural flexibility into the pillar[n]arene scaffolds; a strained silapillar[4]arene was formed, which is unavailable in the parent pillar[n]arenes because of the steric requirements. Furthermore, silapillar[n]arenes displayed interesting size-dependent structural and optical properties.

Effect of solid-electrolyte pellet density on failure of solid-state batteries.

Despite the potentially higher energy density and improved safety of solid-state batteries (SSBs) relative to Li-ion batteries, failure due to Li-filament penetration of the solid electrolyte and subsequent short circuit remains a critical issue. Herein, we show that Li-filament growth is suppressed in solid-electrolyte pellets with a relative density beyond ~95%. Below this threshold value, however, the battery shorts more easily as the density increases due to faster Li-filament growth within the percolating pores in the pellet. The microstructural properties (e.g., pore size, connectivity, porosity, and tortuosity) of [Formula: see text] with various relative densities are quantified using focused ion beam-scanning electron microscopy tomography and permeability tests. Furthermore, modeling results provide details on the Li-filament growth inside pores ranging from 0.2 to 2 µm in size. Our findings improve the understanding of the failure modes of SSBs and provide guidelines for the design of dendrite-free SSBs.

Ultrasensitive Photothermal Switching with Resonant Silicon Metasurfaces at Visible Bands.

Dynamic access to quasi-bound states in the continuum (q-BICs) offers a highly desired platform for silicon-based active nanophotonic applications, while the prevailing tuning approaches by free carrier injections via an all-optical stimulus are yet limited to THz and infrared ranges and are less effective in visible bands. In this work, we present the realization of active manipulations on q-BICs for nanoscale optical switching in the visible by introducing a local index perturbation through a photothermal mechanism. The sharp q-BIC resonance exhibits an ultrasensitive susceptibility to the complex index perturbation, which can be flexibly fulfilled by optical heating of silicon. Consequently, a mild pump intensity of 1 MW/cm2 can yield a modification of the imaginary part of the refractive index of less than 0.05, which effectively suppresses the sharp q-BIC resonances and renders an active modulation depth of reflectance exceeding 80%. Our research might open up an enabling platform for ultrasensitive dynamic nanophotonic devices.

Friedel-Crafts Acylation for Accessing Multi-Bridge-Functionalized Large Pillar[n]arenes.

Pillar[n]arenes can be constructed using a Friedel-Crafts alkylation process. However, due to the reversible nature of the alkylation, mixture of large pillar[n]arenes (n≥7) are obtained as minor products, and thus laborious purification are necessary to isolate the larger pillar[n]arenes. Moreover, inert methylene bridges are introduced during the alkylation process, and the multi-functionalization of the bridges has never been investigated. Herein, an irreversible Friedel-Crafts acylation is used to prepare pillar[n]arenes. Due to the irreversible nature of the acylation, the reaction of precursors bearing carboxylic acids and electron-rich arene rings results in a size-exclusive formation of pillar[n]arenes, in which the ring-size is determined by the precursor length. Because of this size-selective formation, laborious separation of undesired macrocycles is not necessary. Moreover, the bridges of pillar[n]arenes are selectively installed with reactive carbonyl groups using the acylation method, whose positions are determined by the precursor used. The carbonyl bridges can be easily converted into versatile functional groups, leading to various laterally modified pillar[n]arenes, which cannot be accessed by the alkylation strategy.

Effect of local chemical order on the irradiation-induced defect evolution in CrCoNi medium-entropy alloy.

High- (and medium-) entropy alloys have emerged as potentially suitable structural materials for nuclear applications, particularly as they appear to show promising irradiation resistance. Recent studies have provided evidence of the presence of local chemical order (LCO) as a salient feature of these complex concentrated solid-solution alloys. However, the influence of such LCO on their irradiation response has remained uncertain thus far. In this work, we combine ion irradiation experiments with large-scale atomistic simulations to reveal that the presence of chemical short-range order, developed as an early stage of LCO, slows down the formation and evolution of point defects in the equiatomic medium-entropy alloy CrCoNi during irradiation. In particular, the irradiation-induced vacancies and interstitials exhibit a smaller difference in their mobility, arising from a stronger effect of LCO in localizing interstitial diffusion. This effect promotes their recombination as the LCO serves to tune the migration energy barriers of these point defects, thereby delaying the initiation of damage. These findings imply that local chemical ordering may provide a variable in the design space to enhance the resistance of multi-principal element alloys to irradiation damage.

[Percutaneous hollow screw internal fixation combined with cementoplasty in treatment of periacetabular metastasis].

Objective: To explore the percutaneous hollow screw internal fixation combined with cementoplasty in the treatment of periacetabular metastasis. Methods: A retrospective study was performed on 16 patients with periacetabular metastasis who were treated with percutaneous hollow screw internal fixation combined with cementoplasty between May 2020 and May 2021. There were 9 males and 7 females. The age ranged from 40 to 73 years, with an average of 53.6 years. The tumor involved around the acetabulum, and 6 cases were located on the left and 10 cases on the right. Operation time, frequency of fluoroscopy, bed rest time, and complications were recorded. Before operation, and at 1 weeks, 3 months after operation, the visual analogue scale (VAS) score was used to evaluate the pain degree, the short-form 36 health survey scale (SF-36) score was used to evaluate the quality of life. At 3 months after operation, the Musculoskeletal Tumor Society (MSTS) scoring system was used to evaluate the functional recovery of patients. During follow-up, the loosening of internal fixator and bone cement leakage were observed by X-ray film. Results: All patients were performed operation successfully. The operation time ranged from 57 to 82 minutes, with an average of 70.4 minutes. The frequency of intraoperative fluoroscopy was 16-34 times, with an average of 23.1 times. After operation, 1 case of incision hematoma and 1 case of scrotal edema occurred. All patients felt the pain relieved after operation. The patients started walking at 1-3 days after operation, with an average of 1.4 days. All patients were followed up 6-12 months (mean 9.7 months). The VAS and SF-36 scores significantly improved after operation when compared with the preoperative scores, and the scores at 3 months after operation were significant better than those at 1 week after operation ( P<0.05). At 3 months after operation, the MSTS score ranged from 9 to 27, with an average of 19.8. Among them, 3 cases were excellent (18.75%), 8 cases were good (50%), 3 cases were fair (18.75%), and 2 cases were poor (12.5%). The excellent and good rate was 68.75%. And 11 patients returned to normal walking, 3 had mild claudication, and 2 had obvious claudication. Radiological examination showed that there were 2 cases of bone cement leakage after operation, and there was no internal fixator loosening or displacement. Conclusion: Percutaneous hollow screw internal fixation combined with cementoplasty can effectively relieve pain and improve the quality of life of patients with periacetabular metastasis.

Highly Strained Oxygen-Doped Chiral Molecular Belts of the Zigzag-Type with Strong Circularly Polarized Luminescence.

Herein we report a two-directional cyclization strategy for the synthesis of highly strained depth-expanded oxygen-doped chiral molecular belts of the zigzag-type. From the easily accessible resorcin[4]arenes, an unprecedented cyclization cascade generating fused 2,3-dihydro-1H-phenalenes has been developed to access expanded molecular belts. Stitching up the fjords through intramolecular nucleophilic aromatic substitution and ring-closing olefin metathesis reactions furnished a highly strained O-doped C2 -symmetric belt. The enantiomers of the acquired compounds exhibited excellent chiroptical properties. The calculated parallelly aligned electric (µ) and magnetic (m) transition dipole moments are translated to the high dissymmetry factor (|glum | up to 0.022). This study provides not only an appealing and useful strategy for the synthesis of strained molecular belts but also a new paradigm for the fabrication of belt-derived chiroptical materials with high CPL activities.

A Twisted Chiral Cavitand with 5-Fold Symmetry and Its Length-Selective Binding Properties.

Controlling bottom-up syntheses from chiral seeds to construct architectures with specific chiralities is currently challenging. Herein, a twisted chiral cavitand with 5-fold symmetry was constructed by bottom-up synthesis using corannulene as the chiral seed and pillar[5]arene as the chiral wall. After docking between the seed and the wall, their dynamic chiralities (M and P) are fixed. Moreover, the formed hedges also exhibit M and P chirality. Through dynamic covalent bonding, the thermodynamically stable product is obtained selectively as a pair of enantiomers (MMM and PPP), where all three subcomponents, i.e., the corannulene, hedges, and pillar[5]arene, are tilted in the same direction. Furthermore, the twisted cavitand exhibits length-selective binding to alkylene dibromides, with three maximum binding constants being unexpectedly observed.

A novel approach on designing ultrahigh burnup metallic TWR fuels: Upsetting the current technological limits.

Abstract: The grand challenge of "net-zero carbon" emission calls for technological breakthroughs in energy production. The traveling wave reactor (TWR) is designed to provide economical and safe nuclear power and solve imminent problems, including limited uranium resources and radiotoxicity burdens from back-end fuel reprocessing/disposal. However, qualification of fuels and materials for TWR remains challenging and it sets an "end of the road" mark on the route of R&D of this technology. In this article, a novel approach is proposed to maneuver reactor operations and utilize high-temperature transients to mitigate the challenges raised by envisioned TWR service environment. Annular U-50Zr fuel and oxidation dispersion strengthened (ODS) steels are proposed to be used instead of the current U-10Zr and HT-9 ferritic/martensitic steels. In addition, irradiation-accelerated transport of Mn and Cr to the cladding surface to form a protective oxide layer as a self-repairing mechanism was discovered and is believed capable of mitigating long-term corrosion. This work represents an attempt to disruptively overcome current technological limits in the TWR fuels. Impact statement: After the Fukushima accident in 2011, the entire nuclear industry calls for a major technological breakthrough that addresses the following three fundamental issues: (1) Reducing spent nuclear fuel reprocessing demands, (2) reducing the probability of a severe accident, and (3) reducing the energy production cost per kilowatt-hour. An inherently safe and ultralong life fast neutron reactor fuel form can be such one stone that kills the three birds. In light of the recent development findings on U-50Zr fuels, we hereby propose a disruptive, conceptual metallic fuel design that can serve the following purposes at the same time: (1) Reaching ultrahigh burnup of above 40% FIMA, (2) possessing strong inherent safety features, and (3) extending current limits on fast neutron irradiation dose to be far beyond 200 dpa. We believe that this technology will be able to bring about revolutionary changes to the nuclear industry by significantly lowering the operational costs as well as improving the reactor system safety to a large extent. Supplementary information: The online version contains supplementary material available at 10.1557/s43577-022-00420-4.

Real-time chirality transfer monitoring from statistically random to discrete homochiral nanotubes.

Real time monitoring of chirality transfer processes is necessary to better understand their kinetic properties. Herein, we monitor an ideal chirality transfer process from a statistically random distribution to a diastereomerically pure assembly in real time. The chirality transfer is based on discrete trimeric tubular assemblies of planar chiral pillar[5]arenes, achieving the construction of diastereomerically pure trimers of pillar[5]arenes through synergistic effect of ion pairing between a racemic rim-differentiated pillar[5]arene pentaacid bearing five benzoic acids on one rim and five alkyl chains on the other, and an optically resolved pillar[5]arene decaamine bearing ten amines. When the decaamine is mixed with the pentaacid, the decaamine is sandwiched by two pentaacids through ten ion pairs, initially producing a statistically random mixture of a homochiral trimer and two heterochiral trimers. The heterochiral trimers gradually dissociate and reassemble into the homochiral trimers after unit flipping of the pentaacid, leading to chirality transfer from the decaamine and producing diastereomerically pure trimers.

Planar chiral metasurfaces with maximal and tunable chiroptical response driven by bound states in the continuum.

Optical metasurfaces with high quality factors (Q-factors) of chiral resonances can boost substantially light-matter interaction for various applications of chiral response in ultrathin, active, and nonlinear metadevices. However, current approaches lack the flexibility to enhance and tune the chirality and Q-factor simultaneously. Here, we suggest a design of chiral metasurface supporting bound state in the continuum (BIC) and demonstrate experimentally chiroptical responses with ultra-high Q-factors and near-perfect circular dichroism (CD = 0.93) at optical frequencies. We employ the symmetry-reduced meta-atoms with high birefringence supporting winding elliptical eigenstate polarizations with opposite helicity. It provides a convenient way for achieving the maximal planar chirality tuned by either breaking in-plane structure symmetry or changing illumination angle. Beyond linear CD, we also achieved strong near-field enhancement CD and near-unitary nonlinear CD in the same planar chiral metasurface design with circular eigen-polarization. Sharply resonant chirality realized in planar metasurfaces promises various practical applications including chiral lasers and chiral nonlinear filters.

Noncovalently bound and mechanically interlocked systems using pillar[n]arenes.

Pillar[n]arenes are pillar-shaped macrocyclic compounds owing to the methylene bridges linking the para-positions of the units. Owing to their unique pillar-shaped structures, these compounds exhibit various excellent properties compared with other cyclic host molecules, such as versatile functionality using various organic synthesis techniques, substituent-dependent solubility, cavity-size-dependent host-guest properties in organic media, and unit rotation along with planar chiral inversion. These advantages have enabled the high-yield synthesis and rational design of pillar[n]arene-based mechanically interlocked molecules (MIMs). In particular, new types of pillar[n]arene-based MIMs that can dynamically convert between interlocked and unlocked states through unit rotation have been produced. The highly symmetrical pillar-shaped structures of pillar[n]arenes result in simple NMR spectra, which are useful for studying the motion of pillar[n]arene wheels in MIMs and creating sophisticated MIMs with higher-order structures. The creation and application of polymeric MIMs based on pillar[n]arenes is also discussed.

Observation of localized magnetic plasmon skyrmions.

Optical skyrmions have recently been constructed by tailoring vectorial near-field distributions through the interference of multiple surface plasmon polaritons, offering promising features for advanced information processing, transport and storage. Here, we provide experimental demonstration of electromagnetic skyrmions based on magnetic localized spoof plasmons (LSP) showing large topological robustness against continuous deformations, without stringent external interference conditions. By directly measuring the spatial profile of all three vectorial magnetic fields, we reveal multiple π-twist target skyrmion configurations mapped to multi-resonant near-equidistant LSP eigenmodes. The real-space skyrmion topology is robust against deformations of the meta-structure, demonstrating flexible skyrmionic textures for arbitrary shapes. The observed magnetic LSP skyrmions pave the way to ultra-compact and robust plasmonic devices, such as flexible sensors, wearable electronics and ultra-compact antennas.

Vectorial Compound Metapixels for Arbitrary Nonorthogonal Polarization Steganography.

Malus' law regulating the intensity of light when passed through a polarizer, forms the solid basis for image steganography based on orthogonal polarizations of light to convey hidden information without adverse perceptions, which underpins important practices in information encryptions, anti-counterfeitings, and security labels. Unfortunately, the restriction to orthogonal states being taken for granted in the common perceptions fails to advance cryptoinformation to upgraded levels of security. By introducing a vectorial compound metapixel design, arbitrary nonorthogonal polarization multiplexing of independent grayscale images with high fidelity and strong concealment is demonstrated. The Jones matrix treatment of compound metapixels consisting of double atoms with tailored in-plane orientation sum and difference allows point-by-point configuring of both the amplitude and polarization rotations of the output beam in an analytical and linear form. With this, both multiplexing two continuous grayscale images in arbitrary nonorthogonal polarization angles and concealing grayscale image on another in an arbitrary disclosure angle window are experimentally demonstrated in the visible TiO2 metasurface platform. The methods shed new light on multifarious metaoptics by harnessing the new degree of freedom and unlock the full potential of metasurface polarization optics.

Comparative study of two contrast agents for intraoperative identification of sentinel lymph nodes in patients with early breast cancer.

BACKGROUND: The use of contrast-enhanced ultrasound (CEUS) to locate sentinel lymph nodes (SLNs) in breast cancer has been studied more and more in recent years. This prospective study aimed to compare periareolar injection of two different contrast agents, SonoVue® (SNV) and Sonazoid® (SNZ), followed by CEUS to identify SLNs in breast cancer patients with clinically negative nodes. METHODS: A total of 205 patients with T1-2N0M0 breast cancer were divided into the SNV group and SNZ group. All were administered a periareolar injection of SNV or SNZ and underwent US to identify contrast-enhanced SLNs. Each contrast-enhanced SLN underwent a biopsy with blue dye and examined again by CEUS in vitro. RESULTS: In all cases, contrast-enhanced lymphatic vessels were clearly visualized using US soon after the periareolar injection of SNZ, and the SLNs were easily identified. The SLN identification rates were 75.27% (210/279) for SNV and 93.58% (102/109) for SNZ. Although the accuracy of detecting SLN metastasis was slightly different between the two groups, there was no statistically significant difference between those groups (P=0.615). Moreover, it was possible to identify SLNs in vitro in the SNZ group, and these could be compared with the lymph nodes (LNs) located using SNZ during the preoperative stage and with blue dye during the procedure. This helped in determining the resection requirements. CONCLUSIONS: When comparing the subdermal use of SNV and SNZ, no significant differences in the number of detected SLNs and the diagnosis of metastatic LNs were observed. Because SLNs can be detected for a longer time in living tissues with SNZ, this contrast agent may provide more intraoperative information for complete resection of all preoperative localization of SLN.

π-phase modulated monolayer supercritical lens.

The emerging monolayer transition metal dichalcogenides have provided an unprecedented material platform for miniaturized opto-electronic devices with integrated functionalities. Although excitonic light-matter interactions associated with their direct bandgaps have received tremendous research efforts, wavefront engineering is less appreciated due to the suppressed phase accumulation effects resulting from the vanishingly small thicknesses. By introducing loss-assisted singular phase behaviour near the critical coupling point, we demonstrate that integration of monolayer MoS2 on a planar ZnO/Si substrate, approaching the physical thickness limit of the material, enables a π phase jump. Moreover, highly dispersive extinctions of MoS2 further empowers broadband phase regulation and enables binary phase-modulated supercritical lenses manifesting constant sub-diffraction-limited focal spots of 0.7 Airy units (AU) from the blue to yellow wavelength range. Our demonstrations downscaling optical elements to atomic thicknesses open new routes for ultra-compact opto-electronic systems harnessing two-dimensional semiconductor platforms with integrated functionalities.

Promises and Challenges of Next-Generation "Beyond Li-ion" Batteries for Electric Vehicles and Grid Decarbonization.

The tremendous improvement in performance and cost of lithium-ion batteries (LIBs) have made them the technology of choice for electrical energy storage. While established battery chemistries and cell architectures for Li-ion batteries achieve good power and energy density, LIBs are unlikely to meet all the performance, cost, and scaling targets required for energy storage, in particular, in large-scale applications such as electrified transportation and grids. The demand to further reduce cost and/or increase energy density, as well as the growing concern related to natural resource needs for Li-ion have accelerated the investigation of so-called "beyond Li-ion" technologies. In this review, we will discuss the recent achievements, challenges, and opportunities of four important "beyond Li-ion" technologies: Na-ion batteries, K-ion batteries, all-solid-state batteries, and multivalent batteries. The fundamental science behind the challenges, and potential solutions toward the goals of a low-cost and/or high-energy-density future, are discussed in detail for each technology. While it is unlikely that any given new technology will fully replace Li-ion in the near future, "beyond Li-ion" technologies should be thought of as opportunities for energy storage to grow into mid/large-scale applications.

Oxygen- and Nitrogen-Embedded Zigzag Hydrocarbon Belts.

Despite the aesthetically appealing structures and tantalizing physical and chemical properties, zigzag hydrocarbon belts and their heteroatom-embedded analogues remain challenging synthetic targets. We report herein the synthesis of diverse O/N-doped zigzag hydrocarbon belts based on selective bridging of the fjords of resorcin[4]arene derivatives through intramolecular SN Ar and palladium-catalyzed intermolecular C-N bond formation reactions. Preorganized conformations of mono-macrocyclic, half-belt and quasi-belt compounds were revealed to facilitate cyclization reactions to construct heteroatom-linked octahydrobelt[8]arenes. The acquired products had strained square-prism-shaped belt structures in which all six-membered heterocyclic rings adopted an unusual boat conformation with equatorially configured alkyl groups. The unprecedented heteroatom-bearing belts also exhibited different photophysical and redox properties to those of octahydrobelt[8]arene analogues.

Full-visible transmissive metagratings with large angle/wavelength/polarization tolerance.

Metagratings have been shown to form an agile and efficient platform for extreme wavefront manipulation, going beyond the limitations of gradient metasurfaces. Here, we present all-dielectric transmissive metagratings with high diffraction efficiencies using simple rectangular inclusions with neither high index nor high aspect ratio requirement. We further experimentally demonstrate continuous phase encoding of a hologram based on such transmissive metagratings through displacement modulation of CMOS-compatible silicon nitride nanobars in the full visible range, manifesting broadband and wide-angle high diffraction efficiencies for both polarizations. Featured with extreme angle/wavelength/polarization tolerance and alleviated structural complexity for both design and fabrication, our demonstration unlocks the full potential of metagrating-based wavefront manipulation for a variety of practical applications.

The interplay between thermodynamics and kinetics in the solid-state synthesis of layered oxides.

In the synthesis of inorganic materials, reactions often yield non-equilibrium kinetic byproducts instead of the thermodynamic equilibrium phase. Understanding the competition between thermodynamics and kinetics is a fundamental step towards the rational synthesis of target materials. Here, we use in situ synchrotron X-ray diffraction to investigate the multistage crystallization pathways of the important two-layer (P2) sodium oxides Na0.67MO2 (M = Co, Mn). We observe a series of fast non-equilibrium phase transformations through metastable three-layer O3, O3' and P3 phases before formation of the equilibrium two-layer P2 polymorph. We present a theoretical framework to rationalize the observed phase progression, demonstrating that even though P2 is the equilibrium phase, compositionally unconstrained reactions between powder precursors favour the formation of non-equilibrium three-layered intermediates. These insights can guide the choice of precursors and parameters employed in the solid-state synthesis of ceramic materials, and constitutes a step forward in unravelling the complex interplay between thermodynamics and kinetics during materials synthesis.