Sphere-To-Tube Transition toward Nanotube Formation: A Universal Route by Inverse Plateau-Rayleigh Instability

Phosphorus Nitride Imide Nanotubes for Uranium Capture from Seawater

Nuclear power plays a pivotal role in the global energy supply. The adsorption-based extraction of uranium from seawater is crucial for the rapid advancement of nuclear power. The phosphorus nitride imide (PN) nanotubes were synthesized in this study using a solvothermal method, resulting in chemically stable cross-linked tubular hollow structures that draw inspiration from the intricate snowflake fractal pattern. Detailed characterization showed that these nanotubes possess a uniformly distributed five-coordinated nanopocket, which exhibited great selectivity and efficiency in binding uranium. PN nanotubes captured 97.34% uranium from the low U-spiked natural seawater (∼355 μg L-1) and showed a high adsorption capacity (435.58 mg g-1), along with a distribution coefficient, KdU > 8.71 × 107 mL g-1. In addition, PN nanotubes showed a high adsorption capacity of 7.01 mg g-1 in natural seawater. The facile and scalable production of PN nanotubes presented in this study holds implications for advancing their large-scale implementation in the selective extraction of uranium from seawater.

Post-bifurcation behaviour of elasto-capillary necking and bulging in soft tubes

Previous linear bifurcation analyses have evidenced that an axially stretched soft cylindrical tube may develop an infinite-wavelength (localized) instability when one or both of its lateral surfaces are under sufficient surface tension. Phase transition interpretations have also highlighted that the tube admits a final evolved ‘two-phase’ state. How the localized instability initiates and evolves into the final ‘two-phase’ state is still a matter of contention, and this is the focus of the current study. Through a weakly nonlinear analysis conducted for a general material model, the initial sub-critical bifurcation solution is found to be localized bulging or necking depending on whether the axial stretch is greater or less than a certain threshold value. At this threshold value, an exceptionally super-critical kink-wave solution arises in place of localization. A thorough interpretation of the anticipated post-bifurcation behaviour based on our theoretical results is also given, and this is supported by finite-element method simulations.

Nodal Flexible-surface Semimetals: Case of Carbon Nanotube Networks

Nodal surface-based topological semimetals (TSMs) are drawing attention due to their unique excitation and plasmon behaviors. However, only nodal flat-surface and nodal sphere TSMs are theoretically proposed due to strict symmetry requirements. Here, we propose that a series of surface-based topological phases can be realized in a tight-binding (TB) model with sublattice symmetry. These topological phases, named as nodal flexible-surface semimetals, include not only nodal surface and nodal sphere TSMs but also novel phases, like nodal tube, nodal crossbar, and nodal hourglass-like surface TSMs. According to the TB model, a family of carbon nanotube networks are then identified as nodal flexible-surface TSMs by first-principles calculations, and the topological phase transitions between these TSMs can be induced by strains. Moreover, the nodal flexible-surface TSMs with intrinsic high density of states at the Fermi level and special drumhead surface states are promising for studying high-temperature superconductors and strong correlation effects.

Soft Three-Dimensional Microscale Vibratory Platforms for Characterization of Nano-Thin Polymer Films

Vibrational resonances of microelectromechanical systems (MEMS) can serve as means for assessing physical properties of ultrathin coatings in sensors and analytical platforms. Most such technologies exist in largely two-dimensional configurations with a limited total number of accessible vibration modes and modal displacements, thereby placing constraints on design options and operational capabilities. This study presents a set of concepts in three-dimensional (3D) microscale platforms with vibrational resonances excited by Lorentz-force actuation for purposes of measuring properties of thin-film coatings. Nanoscale films including photodefinable epoxy, cresol novolak resin, and polymer brush with thicknesses as small as 270 nm serve as the test vehicles for demonstrating the advantages of these 3D MEMS for detection of multiple physical properties, such as modulus and density, within a single polymer sample. The stability and reusability of the structure are demonstrated through multiple measurements of polymer samples using a single platform, and via integration with thermal actuators, the temperature-dependent physical properties of polymer films are assessed. Numerical modeling also suggests the potential for characterization of anisotropic mechanical properties in single or multilayer films. The findings establish unusual opportunities for interrogation of the physical properties of polymers through advanced MEMS design.

Enhancing the electrocatalytic activity of 2H-WS2 for hydrogen evolution via defect engineering

Introduction of defects into 2H-WS₂ electrocatalysts by post-synthetic desulfurization leads to significantly improved H₂ evolution activity.

A Self-Growing Strategy for Large-Scale Crystal Assembly Tubes

Assembled tubular materials have attracted widespread attention due to their potential applications in catalysis, bionics, and optic-electronics. Many versatile methods, including template assistance and self-assembly, have been developed for fabrication of tubular materials. Here we demonstrate a self-growing strategy to prepare large-scale crystal assembly tubes. Addition of the template and the need for the sophisticated equipment are avoided with this method. The sidewall of the tubes is composed of a layer of polyhedral crystals that are connected together through grain coalescence. We demonstrate that the assembled tubular structure is obtained by the synergetic effect of the passivation layer and the dissolution-recrystallization process. This facile one-step strategy and the formation mechanism will offer guidance for fabrication of new superstructures.

Vibration of Mechanically-Assembled 3D Microstructures Formed by Compressive Buckling

Micro-electromechanical systems (MEMS) that rely on structural vibrations have many important applications, ranging from oscillators and actuators, to energy harvesters and vehicles for measurement of mechanical properties. Conventional MEMS, however, mostly utilize two-dimensional (2D) vibrational modes, thereby imposing certain limitations that are not present in 3D designs (e.g., multi-directional energy harvesting). 3D vibrational microplatforms assembled through the techniques of controlled compressive buckling are promising because of their complex 3D architectures and the ability to tune their vibrational behaviour (e.g., natural frequencies and modes) by reversibly changing their dimensions by deforming their soft, elastomeric substrates. A clear understanding of such strain-dependent vibration behaviour is essential for their practical applications. Here, we present a study on the linear and nonlinear vibration of such 3D mesostructures through analytical modeling, finite element analysis (FEA) and experiment. An analytical solution is obtained for the vibration mode and linear natural frequency of a buckled ribbon, indicating a mode change as the static deflection amplitude increases. The model also yields a scaling law for linear natural frequency that can be extended to general, complex 3D geometries, as validated by FEA and experiment. In the regime of nonlinear vibration, FEA suggests that an increase of amplitude of external loading represents an effective means to enhance the bandwidth. The results also uncover a reduced nonlinearity of vibration as the static deflection amplitude of the 3D structures increases. The developed analytical model can be used in the development of new 3D vibrational microplatforms, for example, to enable simultaneous measurement of diverse mechanical properties (density, modulus, viscosity etc.) of thin films and biomaterials.

Superstructures with diverse morphologies and highly ordered fullerene C60 arrays from 1 : 1 and 2 : 1 adamantane-C60 hybrid molecules

Superstructures from fullerene C₆₀-containing compounds, especially those tethered to rigid functional groups with defined shapes, remain largely unexplored. Being the smallest diamondoid, adamantane (Ad) can be viewed as a promising building block for the construction of well-defined superstructures. Here, we report the syntheses of 1 : 1 (4a) and 2 : 1 (4b) Ad-C₆₀ hybrid molecules, which were then used to construct superstructures in binary solvent mixtures via a modified liquid/liquid interfacial precipitation (LLIP) method using CHCl₃ as a good solvent. Typically in the combination of DMSO/CHCl₃ with a final concentration (c_f) of 1.0 mmol L^-1, 4a successively forms spheres, plates, nanoflowers and plicated particles with increasing content of DMSO while 4b forms cuboid blocks and microparticles with hierarchically organized surfaces. Changing from DMSO to other poor solvents including acetone, MeOH and EtOAc leads to variations of the morphology of the superstructures for both 4a and 4b. At the nanometer length scale, 4a and 4b adopt different organizations within the superstructures. While 4a tends to self-organize into lamellae with highly ordered C₆₀ layers, the hexagonal phase is dominant in the superstructures formed by 4b. Wettability tests indicate that films formed by the superstructures of 4a and 4b show anti-wetting properties. Besides the solvent effect, the morphology of the superstructures can be also tuned by concentration. For example, when c_f is lowered to 0.5 mmol L^-1, a new form of superstructure, i.e., fibers, was detected for 4a. Our results also indicate that besides the solvent-induced aggregate transition, gravity-induced sedimentation and subsequent structure ripening can have a significant influence on the final morphology of the superstructures and the aggregate transition pathways.