Boron Nitride Ultrathin Fibrous Nanonets: One-Step Synthesis and Applications for Ultrafast Adsorption for Water Treatment and Selective Filtration of Nanoparticles

Novel boron nitride (BN) ultrathin fibrous networks are firstly synthesized via an one-step solvothermal process. The average diameter of BN nanofibers is only ∼8 nm. This nanonets exhibit excellent performance for water treatment. The maximum adsorption capacity for methyl blue is 327.8 mg g^–1. Especially, they present the property of ultrafast adsorption for dye removal. Only ∼1 min is enough to almost achieve the adsorption equilibrium. In addition, the BN fibrous nanonets could be applied for the size-selective separation of nanoparticles via a filtration process

Pressure-Induced Oriented Attachment Growth of Large-Size Crystals for Constructing 3D Ordered Superstructures

Oriented attachment (OA), a nonclassical crystal growth mechanism, provides a powerful bottom-up approach to obtain ordered superstructures, which also demonstrate exciting charge transmission characteristic. However, there is little work observably pronouncing the achievement of 3D OA growth of crystallites with large size (<i>e.g.</i>, submicrometer crystals). Here, we report that SnO₂ 3D ordered superstructures can be synthesized by means of a self-limited assembly assisted by OA in a designed high-pressure solvothermal system. The size of primary building blocks is 200–250 nm, which is significantly larger than that in previous results (normally <10 nm). High pressure plays the key role in the formation of 3D configuration and fusion of adjacent crystals. Furthermore, this high-pressure strategy can be readily expanded to additional materials. We anticipate that the welded structures will constitute an ideal system with relevance to applications in optical responses, lithium ion battery, solar cells, and chemical sensing

Synthesis of Few-Atomic-Layer BN Hollow Nanospheres and Their Applications as Nanocontainers and Catalyst Support Materials

In this work, few-atomic-layer boron nitride (BN) hollow nanospheres were directly synthesized via a modified CVD method followed by subsequent high-temperature degassing treatment. The encapsulated impurities in the hollow nanospheres were effectively removed during the reaction process. The BN shells of most nanospheres consisted of 2–6 atomic layers. Because of the low thickness, the obtained BN hollow nanospheres presented excellent performance in many aspects. For instance, they were demonstrated as useful nanocontainers for controllable multistep release of iodine, which could diffuse and be encapsulated into the few-layer BN hollow nanospheres when heating. They were also promising support materials that could markedly increase the photocatalytic activity of TiO₂ nanocrystals

Pressure-Induced Synthesis and Evolution of Ceria Mesoporous Nanostructures with Enhanced Catalytic Performance

Evaluating the effect of pressure for the formation of nanomaterials is significant in solvothermal methods. In this study, a pressure-dependent template-free solvothermal method is developed to controllably synthesize four kinds of uniform CeO₂ mesoporous nanostructures in a single reaction system, i.e., mesoporous nanospheres, nanoporous mesocrystals, hollow nanospheres, and nanowires. They all comprise small nanoclusters (3–5 nm). Properly adjusting the reaction pressure allows for achieving the transition between them. Furthermore, the corresponding pressure-induced self-assembly (Ostwald ripening, reconstruction) mechanisms are proposed to illustrate the morphological evolution process. In addition, they also display large specific surface area and excellent catalytic activity for CO oxidation

Sn-Doped Rutile TiO₂ Hollow Nanocrystals with Enhanced Lithium-Ion Batteries Performance

Hollow structures and doping of rutile TiO₂ are generally believed to be effective ways to enhance the performance of lithium-ion batteries. Herein, uniformly distributed Sn-doped rutile TiO₂ hollow nanocrystals have been synthesized by a simple template-free hydrothermal method. A topotactic transformation mechanism of solid TiOF₂ precursor is proposed to illustrate the formation of rutile TiO₂ hollow nanocrystals. Then, the Sn-doped rutile TiO₂ hollow nanocrystals are calcined and tested as anode in the lithium-ion battery. They deliver a highly reversible specific capacity of 251.3 mA h g^–1 at 0.1 A g^–1 and retain ∼110 mA h g^–1 after 500 cycles at a high current rate 5 A g^–1 (30 C), which is much higher than most of the reported work

Large-Scale Synthesis of Few-Layer F‑BN Nanocages with Zigzag-Edge Triangular Antidot Defects and Investigation of the Advanced Ferromagnetism

Investigation of light-element magnetism system is essential in fundamental and practical fields. Here, few-layer (∼3 nm) fluorinated hexagonal boron nitride (F-BN) nanocages with zigzag-edge triangular antidot defects were synthesized via a facile one-step solid-state reaction. They are free of metallic impurities confirmed by X-ray photoelectron spectroscopy, electron energy loss spectroscopy, and inductively coupled plasma atomic emission spectroscopy. Ferromagnetism is obviously observed in the BN nanocages. Saturation magnetization values of them differed by less than 7% between 5 and 300 K, indicating that the Curie temperature (<i>T</i>_c) was much higher than 300 K. By adjusting the concentration of triangular antidot defects and fluorine dopants, the ferromagnetic performance of BN nanocages could be effectively varied, indicating that the observed magnetism originates from triangular antidot defects and fluorination. The corresponding theoretical calculation shows that antidot defects and fluorine doping in BN lattice both favor spontaneous spin polarization and the formation of local magnetic moment, which should be responsible for long-range magnetic ordering in the sp material

High-Quality CH₃NH₃PbI₃ Films Obtained via a Pressure-Assisted Space-Confined Solvent-Engineering Strategy for Ultrasensitive Photodetectors

High-quality organic–inorganic hybrid perovskite films are crucial for excellent performance of photoelectric devices. Herein, we demonstrate a pressure-assisted space-confined solvent-engineering strategy to grow highly oriented, pinhole-free thin films of CH₃NH₃PbI₃ with large-scale crystalline grains, high smoothness, and crystalline fusion on grain boundaries. These single-crystalline grains vertically span the entire film thickness. Such a film feature dramatically reduces recombination loss and then improves the transport property of charge carriers in the films. Consequently, the photodetector devices, based on the high-quality CH₃NH₃PbI₃ films, exhibit high photocurrent (105 μA under 671 nm laser with a power density of 20.6 mW/cm² at 10 V), good stability, and, especially, an ultrahigh on/off ratio (<i>I</i>_light<i>/I</i>_dark <i>></i> 2.2 × 10⁴ under an incident light of 20.6 mW/cm²). These excellent performances indicate that the high-quality films will be potential candidates in other CH₃NH₃PbI₃-based photoelectric devices

Vertically Aligned and Interconnected Graphene Networks for High Thermal Conductivity of Epoxy Composites with Ultralow Loading

Efficient removal of heat via thermal interface materials has become one of the most critical challenges in the development of modern microelectronic devices. However, traditional polymer composites present limited thermal conductivity even when highly loaded with highly thermally conductive fillers due to the lack of efficient heat transfer channels. In this work, vertically aligned and interconnected graphene networks are first used as the filler, which is prepared by a controlled three-step procedure: formation of graphene oxide liquid crystals, oriented freeze casting, and high-temperature annealing reduction under Ar. The obtained composite, at an ultralow graphene loading of 0.92 vol %, exhibits a high thermal conductivity (2.13 W m^–1 K^–1) that is equivalent to a dramatic enhancement of 1231% compared to the pure matrix. Furthermore, the composite also presents a much reduced coefficient of thermal expansion (∼37.4 ppm K^–1) and increased glass transition temperature (135.4 °C). This strategy provides an insight for the design of high-performance composites with potential to be used in advanced electronic packaging

Ultrafast Molecular Stitching of Graphene Films at the Ethanol/Water Interface for High Volumetric Capacitance

Compact graphene film electrodes with a high ion-accessible surface area have the promising potential to realize high-density electrochemical energy storage (or high volumetric capacitance), which is vital for the development of flexible, portable, and wearable energy storage devices. Here, a novel, ultrafast strategy for stitching graphene sheets into films, in which <i>p</i>-phenylenediamine (PPD) molecules are uniformly intercalated between the graphene sheets, is simply constructed at the ethanol/water interface. Due to uniformly interlayer spacing (∼1.1 nm), good wettability, and an interconnected ion transport channel, the binder-free PPD–graphene film with a high packing density (1.55 g cm^–3) delivers an ultrahigh volumetric capacitance (711 F cm^–3 at a current density of 0.5 A g^–1), high rate performance, high power and energy densities, and excellent cycling stability in aqueous electrolytes. This interfacial stitching strategy holds new promise for the future design of enhanced electrochemical energy-storage devices

Growth of Large-Size SnS Thin Crystals Driven by Oriented Attachment and Applications to Gas Sensors and Photodetectors

Freestanding large-size SnS thin crystals are synthesized via two-dimensional oriented attachment (OA) growth of colloidal quantum dots (CQDs) in a novel high-pressure solvothermal reaction. The SnS thin crystals present a uniform rectangular shape with a lateral size of 20–30 um and thickness of <10 nm. The evolution process demonstrates that a synergetic effect of pressure, aging time and organic ligands results in polycrystal-to-monocrystal formation and defect annihilation. Furthermore, gas sensor and photodetector devices, based on SnS thin single crystals, are also prepared. The sensing devices present high sensitivity, superior selectivity, low detection limit (≪100 ppb) and reversibility to NO₂ at room temperature. The fabricated photodetector devices exhibit a high responsivity of 2.04 × 10³ A W^1– and high external quantum efficiency of ∼4.75 × 10⁵ % at 532 nm, which are much higher than most of the photodetector devices