Exceptionally Fast Separation of Xylene Isomers with Zeolitic Nanotube Array Membranes.

The separation of xylene isomers is of vital importance in chemical industry but remains challenging due to their similar structure and overlapping physiochemical properties. Membrane-based separations using the zeolite MFI, graphene oxide, and metal-organic frameworks have been intensively studied for this application, but the performance is limited by the well-known rule that the filtrate permeance scales inversely with the membrane thickness. We propose a novel membrane design that is capable of breaking this rule, based on an array of recently discovered zeolite nanotubes. Each zeolite nanotube possesses a 3.6-nm-wide central channel, connecting to dense, uniform 0.8-nm-wide holes on its wall that act as selective pores. Comprehensive molecular dynamics simulations show that this membrane exhibits permeance exceeding current state-of-the-art membranes by at least an order of magnitude while simultaneously maintaining an acceptable selectivity. In particular, a thicker membrane featuring longer zeolite nanotubes exhibits a higher permeance due to the presence of more selective pores. The proposed membrane design is expected to be broadly applied to other gas separations and even desalination as long as zeolitic nanotubes with customized pores are available.

Strain Engineering of Twisted Bilayer Graphene: The Rise of Strain-Twistronics.

The layer-by-layer stacked van der Waals structures (termed vdW hetero/homostructures) offer a new paradigm for materials design-their physical properties can be tuned by the vertical stacking sequence as well as by adding a mechanical twist, stretch, and hydrostatic pressure to the atomic structure. In particular, simple twisting and stacking of two layers of graphene can form a uniform and ordered Moiré superlattice, which can effectively modulate the electrons of graphene layers and lead to the discovery of unconventional superconductivity and strong correlations. However, the twist angle of twisted bilayer graphene (tBLG) is almost unchangeable once the interlayer stacking is determined, while applying mechanical elastic strain provides an alternative way to deeply regulate the electronic structure by controlling the lattice spacing and symmetry. In this review, diverse experimental advances are introduced in straining tBLG by in-plane and out-of-plane modes, followed by the characterizations and calculations toward quantitatively tuning the strain-engineered electronic structures. It is further discussed that the structural relaxation in strained Moiré superlattice and its influence on electronic structures. Finally, the conclusion entails prospects for opportunities of strained twisted 2D materials, discussions on existing challenges, and an outlook on the intriguing emerging field, namely "strain-twistronics".

Cascaded plastic optical fiber based SPR sensor for simultaneous measurement of refractive index and temperature.

A cascaded side-polish plastic optical fiber (POF) and FONTEX optical fiber based surface plasmon resonance (SPR) sensor is proposed for simultaneous measurement of refractive index (RI) and temperature. The side-polish POF and FONTEX optical fiber are connected by using the UV glue in a Teflon plastic tube. The SPR phenomenon can be excited at both of the side-polish region and the FONTEX fiber cladding. The polydimethylsiloxane (PDMS) is coated on the side-polish POF to get a temperature sensing channel. Due to the low RI sensitivity of the FONTEX optical fiber, the cascaded fiber sensor can obtain a broader RI measurement range with a low crosstalk. An RI sensitivity of 700 nm/RIU in the RI measurement range of 1.335-1.39 and a temperature sensitivity of -1.02 nm/°C measured in deionized water with a range of 20-60 °C are obtained. In addition, the cascaded POF based SPR sensor has potential application prospects in the field of biochemical sensing.

Graphene binding on black phosphorus enables high on/off ratios and mobility.

Graphene is one of the most promising candidates for integrated circuits due to its robustness against short-channel effects, inherent high carrier mobility and desired gapless nature for Ohmic contact, but it is difficult to achieve satisfactory on/off ratios even at the expense of its carrier mobility, limiting its device applications. Here, we present a strategy to realize high back-gate switching ratios in a graphene monolayer with well-maintained high mobility by forming a vertical heterostructure with a black phosphorus multi-layer. By local current annealing, strain is introduced within an established area of the graphene, which forms a reflective interface with the rest of the strain-free area and thus generates a robust off-state via local current depletion. Applying a positive back-gate voltage to the heterostructure can keep the black phosphorus insulating, while a negative back-gate voltage changes the black phosphorus to be conductive because of hole accumulation. Then, a parallel channel is activated within the strain-free graphene area by edge-contacted electrodes, thereby largely inheriting the intrinsic carrier mobility of graphene in the on-state. As a result, the device can provide an on/off voltage ratio of >103 as well as a mobility of ∼8000 cm2 V-1 s-1 at room temperature, meeting the low-power criterion suggested by the International Roadmap for Devices and Systems.

Harvesting Energy from Atmospheric Water: Grand Challenges in Continuous Electricity Generation.

Atmospheric water is ubiquitous on earth and extensively participates in the natural water cycle through evaporation and condensation. This process involves tremendous energy exchange with the environment, but very little of the energy has so far been harnessed. The recently emerged hydrovoltaic technology, especially moisture-induced electricity, shows great potential in harvesting energy from atmospheric water and gives birth to moisture energy harvesting devices. The device performance, especially the long-term operational capacity, has been significantly enhanced over the past few years. Further development; however, requires in-depth understanding of mechanisms, innovative materials, and ingenious system designs. In this review, beginning with describing the basic properties of water, the key aspects of the water-hygroscopic material interactions and mechanisms of power generation are discussed. The current material systems and advances in promising material development are then summarized. Aiming at the chief bottlenecks of limited operational time, advanced system designs that are helpful to improve device performance are listed. Especially, the synergistic effect of moisture adsorption and water evaporation on material and system levels to accomplish sustained electricity generation is discussed. Last, the remaining challenges are analyzed and future directions for developing this promising technology are suggested.

Non-epitaxial growth of highly oriented transition metal dichalcogenides with density-controlled twin boundaries.

Twin boundaries (TBs) in transition metal dichalcogenides (TMDs) constitute distinctive one-dimensional electronic systems, exhibiting intriguing physical and chemical properties that have garnered significant attention in the fields of quantum physics and electrocatalysis. However, the controlled manipulation of TBs in terms of density and specific atomic configurations remains a formidable challenge. In this study, we present a non-epitaxial growth approach that enables the controlled and large-scale fabrication of homogeneous catalytically active TBs in monolayer TMDs on arbitrary substrates. Notably, the density achieved using this strategy is six times higher than that observed in convention chemical vapor deposition (CVD)-grown samples. Through rigorous experimental analysis and multigrain Wulff construction simulations, we elucidate the role of regulating the metal source diffusion process, which serves as the key factor for inducing the self-oriented growth of TMD grains and the formation of unified TBs. Furthermore, we demonstrate that this novel growth mode can be readily incorporated into the conventional CVD growth method by making a simple modification of the growth temperature profile, thereby offering a universal approach for engineering of grain boundaries in two-dimensional materials.

Growth Instability of 2D Materials on Non-Euclidean Surfaces.

Chemical growth of two-dimensional (2D) materials with controlled morphology is critical to bring their tantalizing properties to fruition. However, the growth must be on a substrate, which involves either intrinsic or intentionally introduced undulation, at a scale significantly larger than the materials thickness. Recent theory and experiments showed that 2D materials grown on a curved feature on substrates can incur a variety of topological defects and grain boundaries. Using a Monte Carlo method, we herein show that 2D materials growing on periodically undulated substrates with nonzero Gaussian curvature of practical relevance follow three distinct modes: defect-free conformal, defect-free suspension and defective conformal modes. The growth on the non-Euclidean surface can accumulate tensile stress that gradually lifts the materials from substrates and progressively turns the conformal mode into a suspension mode with increasing the undulation amplitude. Further enhancing the undulation can trigger Asaro-Tiller-Grinfield growth instability in the materials, manifested as discretely distributed topological defects due to strong stress concentration. We rationalize these results by model analyses and establish a "phase" diagram for guiding the control of growth morphology via substrate patterning. The undulation-induced suspension of 2D materials can help understand the formation of overlapping grain boundaries, spotted quite often in experiments, and guide how to avoid them.

Mechanism Regulating Self-Intercalation in Layered Materials.

Recent experimental breakthrough demonstrated a powerful synthesis approach for intercalating the van der Waals gap of layered materials to achieve property modulation, thereby opening an avenue for exploring new physics and devising novel applications, but the mechanism governing intercalant assembly patterns and properties remains unclear. Based on extensive structural search and energetics analysis by ab initio calculations, we reveal a Sabatier-like principle that dictates spatial arrangement of self-intercalated atoms in transition metal dichalcogenides. We further construct a robust descriptor quantifying that strong intercalant-host interactions favor a monodispersing phase of intercalated atoms that may exhibit ferromagnetism, while weak interactions lead to a trimer phase with attenuated or quenched magnetism, which further evolves into tetramer and hexagonal phases at increasing intercalant density. These findings elucidate the mechanism underpinning experimental observations and paves the way for rational design and precise control of self-intercalation in layered materials.

Deep-Learning-Enhanced Diffusion Imaging Assay for Resolving Local-Density Effects on Membrane Receptors.

G-protein-coupled receptor (GPCR) density at the cell surface is thought to regulate receptor function. Spatially resolved measurements of local-density effects on GPCRs are needed but technically limited by density heterogeneity and mobility of membrane receptors. We now develop a deep-learning (DL)-enhanced diffusion imaging assay that can measure local-density effects on ligand-receptor interactions in the plasma membrane of live cells. In this method, the DL algorithm allows the transformation of 100 ms exposure images to density maps that report receptor numbers over any specified region with ∼95% accuracy by 1 s exposure images as ground truth. With the density maps, a diffusion assay is further established for spatially resolved measurements of receptor diffusion coefficient as well as to express relationships between receptor diffusivity and local density. By this assay, we scrutinize local-density effects on chemokine receptor CXCR4 interactions with various ligands, which reveals that an agonist prefers to act with CXCR4 at low density while an inverse agonist dominates at high density. This work suggests a new insight into density-dependent receptor regulation as well as provides an unprecedented assay that can be applicable to a wide variety of receptors in live cells.

Near-Infrared Blinking Carbon Dots Designed for Quantitative Nanoscopy.

Blinking carbon dots (CDs) have attracted attention as a probe for single molecule localization microscopy (SMLM), yet quantitative analysis is limited because of inept blinking and low signal-to-noise ratio (SNR). Here we report the design and synthesis of near-infrared (NIR) blinking CDs with a maximum emission of around 750 nm by weaving a nitrogen-doped aromatic backbone with surplus carboxyl groups on the surface. The NIR-CDs allow conjugation to monovalent antibody fragments for labeling and imaging of cellular receptors as well as afford increases of 52% in SNR and 33% in localization precision over visible CDs. Analysis of fluorescent bursts allows for accurate counting of cellular receptors at the nanoscale resolution. Using NIR-CDs-based SMLM, we demonstrate oligomerization and internalization of programmed cell death-ligand 1 by a small molecule inhibitor for checkpoint blockade. Our NIR-CDs can become a generally applicable probe for quantitative nanoscopy in chemistry and biology.

Computational Advances of Protein/Neurotransmitter-membrane Interactions Involved in Vesicle Fusion and Neurotransmitter Release.

Vesicle fusion is of crucial importance to neuronal communication at neuron terminals. The exquisite but complex fusion machinery for neurotransmitter release is tightly controlled and regulated by protein/neurotransmitter-membrane interactions. Computational 'microscopies', in particular molecular dynamics simulations and related techniques, have provided notable insight into the physiological process over the past decades, and have made enormous contributions to fields such as neurology, pharmacology and pathophysiology. Here we review the computational advances of protein/neurotransmitter-membrane interactions related to presynaptic vesicle-membrane fusion and neurotransmitter release, and outline the in silico challenges ahead for understanding this important physiological process.

Simultaneous Measurement of Magnetic Field and Temperature Utilizing Magnetofluid-Coated SMF-UHCF-SMF Fiber Structure.

We have proposed and experimentally demonstrated a dual-parameter optical fiber sensor for simultaneous measurement of magnetic field and temperature. The sensor is a magnetofluid-coated single-mode fiber (SMF)-U-shaped hollow-core fiber (UHCF)-single-mode fiber (SMF) (SMF-UHCF-SMF) fiber structure. Combined with the intermodal interference and the macro-bending loss of the U-shaped fiber structure, the U-shaped fiber sensor with different bend diameters was investigated. In our experiments, the transmission spectra of the sensor varied with magnetic field strength and temperature around the sensing structure, respectively. The dip wavelengths of the interference spectra of the proposed sensor exhibit red shifts with magnetic field strength and temperature, and the maximum sensitivity of magnetic field strength and temperature were 1.0898 nm/mT and 0.324 nm/°C, respectively.

Simultaneous Measurement of Refractive Index and Temperature Based on SMF-HCF-FCF-HCF-SMF Fiber Structure.

In this research, we proposed and experimentally verified a compact all-fiber sensor that can measure refractive index (RI) and temperature simultaneously. Two segments of hollow-core fiber (HCF) are connected to the two ends of the four-core fiber (FCF) as a beam splitter and a coupler, and then spliced with two sections of single-mode fibers (lead-in and lead-out SMF), respectively. The two hollow-core fibers can excite the higher-order modes of the four-core fiber and recouple the core modes and higher-order modes into the outgoing single-mode fiber, thereby forming inter-mode interference. The different response sensitivities of two interference dips to RI and temperature manifest that the proposed structure can achieve simultaneous measurement. From the experimental results, it can be seen that the maximum sensitivity of the sensor to RI and temperature is 275.30 nm/RIU and 94.4 pm/°C, respectively. When the wavelength resolution is 0.02 nm, the RI and temperature resolutions of the sensor are 7.74 × 10-5 RIU and 0.335 °C. The proposed dual-parameter optical sensor has the advantages of high sensitivities, good repeatability, simple fabrication, and structure. In addition, it has potential application value in multi-parameter simultaneous measurement.

An analog of Friedel oscillations in nanoconfined water.

Water confined in nanometer-scale crevices and cavities underpins a wide range of fundamental processes, such as capillary flow, ion transport and protein folding. However, how water responds within these confined spaces, with prevalent inhomogeneity built in or caused by impurities, is not well understood. Here, we show theoretically that water confined in one-dimensional nanochannels with localized perturbation exhibits pronounced density oscillations. The oscillations occur vividly like the Friedel oscillations in electron density resulting from defects in metals. A model analysis reveals that the density oscillations result from the perturbation-induced molecular scattering that is augmented by the confinement-enhanced correlation of water dipoles. This renders the oscillations a general behavior independent of the channel geometries and specific forms of the perturbation. Under confinements comparable to biological ion channels, such oscillations can strikingly extend over 10 nm, resulting in non-trivial effects at large distances that, for example, repel all ions from the channels with their long-range force. These results deepen the understanding of biological functions and inspire new applications in a variety of domains, such as ionic sensing and seawater desalination.

Side-Polish Plastic Optical Fiber Based SPR Sensor for Refractive Index and Liquid-Level Sensing.

In this work, a simple side-polish plastic optical fiber (POF)-based surface plasmon resonance (SPR) sensor is proposed and demonstrated for simultaneous measurement of refractive index (RI) and liquid level. The effects of side-polish depths on the sensing performance were studied. The experimental results show that the SPR peak wavelength will be changed as the RI changes, and the SPR peak intensity will be changed with the liquid level variation. By monitoring the changes in peak wavelength and intensity, the RI and liquid level can be detected simultaneously. Experimental results show that an RI sensitivity of 2008.58 nm/RIU can be reached at an RI of 1.39. This sensor has the advantages of simple structure and low cost, which has a good prospect in the field of biochemical sensing.

Symmetry Breaking and Anomalous Conductivity in a Double-Moiré Superlattice.

In a two-dimensional moiré superlattice, the atomic reconstruction of constituent layers could introduce significant modifications to the lattice symmetry and electronic structure at small twist angles. Here, we employ conductive atomic force microscopy to investigate a twisted trilayer graphene double-moiré superlattice. Two sets of moiré superlattices are observed. At neighboring domains of the large moiré, the current exhibits either 2- or 6-fold rotational symmetry, indicating delicate symmetry breaking beyond the rigid model. Moreover, an anomalous current appears at the "A-A" stacking site of the larger moiré, contradictory to previous observations on twisted bilayer graphene. Both behaviors can be understood by atomic reconstruction, and we also show that the measured current is dominated by the tip-graphene contact resistance that maps the local work function qualitatively. Our results reveal new insights of atomic reconstruction in novel moiré superlattices and opportunities for manipulating exotic quantum states on the basis of twisted van der Waals heterostructures.

Ion Hydration under Nanoscale Confinement: Dimensionality and Scale Effects.

How ions are hydrated in nanoconfined spaces is crucial for understanding many natural phenomena and practical applications, such as biological functionalities and energy conversion devices. In real systems, nanoconfinement shows structural diversity, but the influence of dimensionality and scale on ion hydration remains considerably unrevealed. Here, we study ion hydration under various confinements by systematic molecular dynamics simulations. In a given dimension, the structure and dynamics of water molecules in the first hydration shell are altered to a degree inversely correlated with the confinement scale, as long as there is no central bulk-like region. Further comparison of ion hydration among different dimensional systems shows that this scale effect becomes more pronounced in systems with lower dimensionality, due to a more significant water layering effect and lower probability for ions to stay away from confining surfaces. These findings provide a qualitatively new understanding of ion transport in biological channels and are instrumental for the design of functional nanofluidic devices.

Borophane Polymorphs.

Hydrogenated borophenes─borophanes─have recently been synthesized as a new platform for studying low-dimensional borides, but most of their lattice structures remain unknown. Here, we determine the structures of borophane polymorphs on Ag(111) by performing extensive structural search using the cluster expansion method augmented with first-principles calculations. Our results reveal rich borophane polymorphs whose stability depends on hydrogen pressure. At relatively low hydrogen pressures, borophane structures with rhombic patterns of two-center-two-electron B-H bonds are energetically preferred, in excellent agreement with two experimentally observed phases. In a wider range of hydrogen pressures, the structure with a combination of two-center-two-electron B-H and three-center-two-electron B-H-B bonds is a deep global minimum, rationalizing its experimental prevalence. For all these borophane polymorphs, their hydrogen "skin" raises the energy barriers for oxidation above 1.1 eV, while their work functions can be reduced by more than 0.5 eV through varying the hydrogen coverage.

Toripalimab-Induced Dermatomyositis in a Patient with Metastatic Melanoma.

Toripalimab is a monoclonal antibody targeting programmed cell death protein 1 (PD-1). It has recently been approved as an immune checkpoint inhibitor in second-line therapies in patients with unresectable or metastatic melanoma; however, it may be associated with various immune-related adverse events (irAEs). Here we report a case of toripalimab-induced dermatomyositis in a patient receiving treatment for metastatic melanoma. The symptoms were relieved by discontinuing toripalimab and administering once-daily intravenous methylprednisolone 1 mg/kg. We suggest that this case serves a warning to clinicians of the need to be aware of the possiblilty of toripalimab-induced dermatomyositis. Early recognition and treatment may prevent progression and improve prognosis of this irAE.

Diagnostic Evaluation of 18F-FDG PET/CT Imaging in Recurrent or Residual Urinary Bladder Cancer: A Meta-Analysis.

PURPOSE: To assess the diagnostic accuracy of fluorine-18 fluorodeoxyglucose positron emission tomography combined with the computed tomography (18F-FDG PET/CT) in the detection of recurrent or residual urinary bladder cancer with meta-analysis. METHODS: We searched PubMed/MEDLINE, Embase, Web of Science, CBM, CNKI, VIP, and Wanfang databases through October 2019. Two reviewers independently screened the full articles. The imaging findings were confirmed by either histopathology or clinical follow-up. Sensitivity, specificity likelihood ratio and diagnostic odds ratio were pooled with 95 % confidence intervals (CI). Overall test performance was summarized by a summary receiver operating characteristic (ROC) curve. The Meta-DiSc software (version 1.4) was used to perform the meta-analysis. RESULTS: The meta-analysis included 7 studies. The pooled sensitivity and specificity of PET/CT for the detection of recurrent or residual urinary bladder cancer was 94.0% (95% CI: 91.0%-96.0%) and 92.0% (95% CI: 88.0%- 95.0%), respectively. Positive likelihood ratio, negative likelihood ratio and diagnostic odds ratio were 9.77 (95% CI: 4.91-19.41), 0.99(95% CI: 0.06-0.13) and 95.09 (95% CI: 47.96-188.53), respectively. When residual urinary bladder cancer was excluded, sensitivity changed slightly. CONCLUSION: This meta-analysis suggested that the diagnostic accuracy of PET/CT was good in detecting recurrent or residual urinary bladder cancer.