Roll-to-Roll Manufacturing of Robust Superhydrophobic Coating on Metallic Engineering Materials

Creating a robust superhydrophobic surface on the conventional engineering materials at mass production is of great importance for a self-cleaning, anti-icing, nonwetting surface and low flow resistance in industrial applications. Herein, we report a roll-to-roll strategy to create durable and robust superhydrophobic surfaces with designed micro-/nanoscale hierarchical structures on many conventional engineering materials by combining electrical discharge machining and coating of carbon nanoparticles, followed by oil penetration and drying. The treated surface shows good superhydrophobic properties with a static water contact angle of 170 ± 2° and slide angle of 3 ± 1°. The treated surface also exhibits good resilience and maintains the performance after being tested in various harsh conditions, including water flushing for several days, sand abrasion, scratching with sandpapers, and corrosive solution. Significantly, the superhydrophobic surfaces also show a high efficiency of self-cleaning properties even after oil contamination during applications

A Robust Hybrid Zn-Battery with Ultralong Cycle Life

Advanced batteries with long cycle life and capable of harnessing more energies from multiple electrochemical reactions are both fundamentally interesting and practically attractive. Herein, we report a robust hybrid zinc-battery that makes use of transition-metal-based redox reaction (M–O–OH → M–O, M = Ni and Co) and oxygen reduction reaction (ORR) to deliver more electrochemical energies of comparably higher voltage with much longer cycle life. The hybrid battery was constructed using an integrated electrode of NiCo₂O₄ nanowire arrays grown on carbon-coated nickel foam, coupled with a zinc plate anode in alkaline electrolyte. Benefitted from the M–O/M–O–OH redox reactions and rich ORR active sites in NiCo₂O₄, the battery has concurrently exhibited high working voltage (by M–O–OH → M–O) and high energy density (by ORR). The good oxygen evolution reaction (OER) activity of the electrode and the reversible M–O ↔ M–O–OH reactions also enabled smooth recharging of the batteries, leading to excellent cycling stabilities. Impressively, the hybrid batteries maintained highly stable charge–discharge voltage profile under various testing conditions, for example, almost no change was observed over 5000 cycles at a current density of 5 mA cm^–2 after some initial stabilization. With merits of higher working voltage, high energy density, and ultralong cycle life, such hybrid batteries promise high potential for practical applications

AuAg Nanosheets Assembled from Ultrathin AuAg Nanowires

Assembly of noble metal nanocrystals into free-standing two-dimensional (2D) nanostructures with a regular shape is still a challenge. Here we report the preparation of a novel 2D AuAg nanosheet with length of 1.50 ± 0.30 μm, width of 510 ± 160 nm, and thickness of ∼100 nm via the assembly of ultrathin AuAg nanowires in the presence of the triblock copolymer Pluronic P123. The self-assembly of P123 and the fusion behavior of the nanowires during the assembly process are the key reasons for the formation of AuAg nanosheets in P123. Furthermore, the obtained AuAg nanosheet@​P123 is used as the active material in a memory device that exhibits the write-once-read-many-times memory behavior

Synthesis of Two-Dimensional CoS_1.097/Nitrogen-Doped Carbon Nanocomposites Using Metal–Organic Framework Nanosheets as Precursors for Supercapacitor Application

Two-dimensional (2D) metal–organic framework (MOF) nanosheets are attracting increasing research interest. Here, for the first time, we report the facile synthesis of 2D porphyrin paddlewheel framework-3 (PPF-3) MOF nanosheets with thickness of ca. 12–43 nm. Through the simultaneous sulfidation and carbonization of PPF-3 MOF nanosheets, we have prepared the 2D nanocomposite of CoS_1.097 nanoparticles (NPs) and nitrogen-doped carbon, referred to as CoSNC, in which the CoS_1.097 NPs with size of ca. 10 nm are embedded in the nitrogen-doped carbon matrix. As a proof-of-concept application, the obtained 2D CoSNC nanocomposite is used as an electrode material for a supercapacitor, which exhibits a specific capacitance of 360.1 F g^–1 at a current density of 1.5 A g^–1. Moreover, the composite electrode also shows high rate capability. Its specific capacitance delivered at a current density of 30.0 A g^–1 retains 56.8% of the value at 1.5 A g^–1

Uncovering the Role of Crystal Phase in Determining Nonvolatile Flash Memory Device Performance Fabricated from MoTe₂‑Based 2D van der Waals Heterostructures

Although the crystal phase of two-dimensional (2D) transition metal dichalcogenides (TMDs) has been proven to play an essential role in fabricating high-performance electronic devices in the past decade, its effect on the performance of 2D material-based flash memory devices still remains unclear. Here, we report the exploration of the effect of MoTe2 in different phases as the charge-trapping layer on the performance of 2D van der Waals (vdW) heterostructure-based flash memory devices, where a metallic 1T′-MoTe2 or semiconducting 2H-MoTe2 nanoflake is used as the floating gate. By conducting comprehensive measurements on the two kinds of vdW heterostructure-based devices, the memory device based on MoS2/h-BN/1T′-MoTe2 presents much better performance, including a larger memory window, faster switching speed (100 ns), and higher extinction ratio (107), than that of the device based on the MoS2/h-BN/2H-MoTe2 heterostructure. Moreover, the device based on the MoS2/h-BN/1T′-MoTe2 heterostructure also shows a long cycle (>1200 cycles) and retention (>3000 s) stability. Our study clearly demonstrates that the crystal phase of 2D TMDs has a significant impact on the performance of nonvolatile flash memory devices based on 2D vdW heterostructures, which paves the way for the fabrication of future high-performance memory devices based on 2D materials

High-Yield Exfoliation of Ultrathin Two-Dimensional Ternary Chalcogenide Nanosheets for Highly Sensitive and Selective Fluorescence DNA Sensors

High-yield preparation of ultrathin two-dimensional (2D) nanosheets is of great importance for the further exploration of their unique properties and promising applications. Herein, for the first time, the high-yield and scalable production of ultrathin 2D ternary chalcogenide nanosheets, including Ta₂NiS₅ and Ta₂NiSe₅, in solution is achieved by exfoliating their layered microflakes. The size of resulting Ta₂NiS₅ and Ta₂NiS₅ nanosheets ranges from tens of nanometers to few micrometers. Importantly, the production yield of single-layer Ta₂NiS₅ nanosheets is very high, ca. 86%. As a proof-of-concept application, the single-layer Ta₂NiS₅ is used as a novel fluorescence sensing platform for the detection of DNA with excellent selectivity and high sensitivity (with detection limit of 50 pM). These solution-processable, high-yield, large-amount ternary chalcogenide nanosheets may also have potential applications in electrocatalysis, supercapacitors, and electronic devices

Self-Assembled Chiral Nanofibers from Ultrathin Low-Dimensional Nanomaterials

Despite many developed methods, it still remains a challenge to provide a simple and general strategy for the controlled preparation of chiral nanostructures. Here we report a facile and universal approach for the high-yield and scalable preparation of chiral nanofibers based on the self-assembly of various ultrathin one-dimensional and two-dimensional nanomaterials in vigorously stirred polymeric solutions. The obtained chiral nanofibers can be further transformed to same-handed chiral nanorings. As a proof-of-concept application, chiral MoS₂ and multiwalled carbon nanotube nanofibers were used as promising active layers for flexible nonvolatile data storage devices. Impressively, the chiral MoS₂ nanofiber-based memory device presents a typical nonvolatile flash memory effect with excellent reproducibility and good stability. Our method offers a general route for the preparation of various functional chiral nanostructures that might have wide applications

Ultrathin Two-Dimensional Covalent Organic Framework Nanosheets: Preparation and Application in Highly Sensitive and Selective DNA Detection

The ability to prepare ultrathin two-dimensional (2D) covalent organic framework (COF) nanosheets (NSs) in high yield is of great importance for the further exploration of their unique properties and potential applications. Herein, by elaborately designing and choosing two flexible molecules with <i>C</i>_3<i>v</i> molecular symmetry as building units, a novel imine-linked COF, namely, TPA-COF, with a hexagonal layered structure and sheet-like morphology, is synthesized. Since the flexible building units are integrated into the COF skeletons, the interlayer stacking becomes weak, resulting in the easy exfoliation of TPA-COF into ultrathin 2D NSs. Impressively, for the first time, the detailed structural information, i.e., the pore channels and individual building units in the NSs, is clearly visualized by using the recently developed low-dose imaging technique of transmission electron microscopy (TEM). As a proof-of-concept application, the obtained ultrathin COF NSs are used as a novel fluorescence sensing platform for the highly sensitive and selective detection of DNA

Ultrathin Two-Dimensional Covalent Organic Framework Nanosheets: Preparation and Application in Highly Sensitive and Selective DNA Detection

The ability to prepare ultrathin two-dimensional (2D) covalent organic framework (COF) nanosheets (NSs) in high yield is of great importance for the further exploration of their unique properties and potential applications. Herein, by elaborately designing and choosing two flexible molecules with <i>C</i>_3<i>v</i> molecular symmetry as building units, a novel imine-linked COF, namely, TPA-COF, with a hexagonal layered structure and sheet-like morphology, is synthesized. Since the flexible building units are integrated into the COF skeletons, the interlayer stacking becomes weak, resulting in the easy exfoliation of TPA-COF into ultrathin 2D NSs. Impressively, for the first time, the detailed structural information, i.e., the pore channels and individual building units in the NSs, is clearly visualized by using the recently developed low-dose imaging technique of transmission electron microscopy (TEM). As a proof-of-concept application, the obtained ultrathin COF NSs are used as a novel fluorescence sensing platform for the highly sensitive and selective detection of DNA

Ordered Porous Pd Octahedra Covered with Monolayer Ru Atoms

Monolayer Ru atoms covered highly ordered porous Pd octahedra have been synthesized via the underpotential deposition and thermodynamic control. Shape evolution from concave nanocube to octahedron with six hollow cavities was observed. Using aberration-corrected high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy, we provide quantitative evidence to prove that only a monolayer of Ru atoms was deposited on the surface of porous Pd octahedra. The as-prepared monolayer Ru atoms covered Pd nanostructures exhibited excellent catalytic property in terms of semihydrogenation of alkynes