Gang Lian

Controlled fabrication of ultrathin-shell BN hollow spheres with excellent performance in hydrogen storage and wastewater treatment

We developed a facile template-free solid state synthesis route, by which BN hollow spheres (BNHSs) with ultrathin shells (1–3 nm) were successfully prepared. Furthermore, the shell thickness of the BNHSs could be effectively adjusted by varying the reaction temperature. The as-prepared BNHSs with ultrathin shells possess high specific surface area, large pore volume and high density structural defects. These characteristics result in the excellent performance of BNHSs in hydrogen storage and adsorption of organic pollutants from wastewater. The hydrogen uptake capacity is up to 4.07 wt.% at 298 K and 10 MPa. The maximum adsorption capacities for basic yellow 1 and methylene blue are 191.7 and 116.5 mg g−1, respectively. Besides, the BNHSs preferentially adsorb organic aromatic compounds from mixed solutions of aromatic dyes and heavy metal ions, so they can be used to separate and recover some valuable organic compounds from wastewater.

Boron nitride nanocarpets: controllable synthesis and their adsorption performance to organic pollutants

Boron nitride (BN) nanocarpets were synthesized at 260 °C and 150 MPa by a hot-press benzene-thermal method, using NaN3 and NH4BF4 as the reactants. The as-prepared BN nanocarpets are constructed of thin BN nano-sheets and a large amount of twisted nanorods rooted onto these nano-sheets. Besides the high density structural defects, BN nanocarpets also have a rather large specific surface area of 117.2 m2 g−1. Due to these characteristics, BN nanocarpets exhibit a very quick adsorption rate for methylene blue (MB) and the capacity is as high as ∼272.4 mg g−1. Furthermore, these BN nanocarpets can also selectively adsorb methylene blue from a mixed solution of MB and CuSO4. It is reasonable to believe that BN nanocarpets may find wide applications in wastewater treatment and the recovery of valuable organic compounds from wastewater.

Facile synthesis of 3D boron nitride nanoflowers composed of vertically aligned nanoflakes and fabrication of graphene-like BN by exfoliation

Here, we present a facile solid phase method for preparing unique, 3D hexagonal boron nitride (hBN) nanoflowers, which are composed of vertically aligned BN nanoflakes. The growth process of BN nanoflowers is well-controlled by appropriately changing the reaction times and can be explained by a delayed-release mechanism. These BN nanoflowers present good thermal stability and high specific surface area. In addition, the nanoflakes composing the nanoflowers can be easily exfoliated into few-layered graphene-like BN, which is readily dispersible in strong polar organic solvents. By FTIR spectra and theoretical calculation, it is believed that the interaction of BN nanosheet and solvent predominately induces the exfoliation of graphene-like BN. Furthermore, the graphene-like BN film displays superhydrophobicity with a contact angle of 140°.

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.

Ultrathin BN nanosheets with zigzag edge: one-step chemical synthesis, applications in wastewater treatment and preparation of highly thermal-conductive BN–polymer composites

Ultrathin BN nanosheets (BNNSs) were prepared at 300 °C by a new variable-pressure one-step chemical synthesis route. It was found that the thickness of BNNSs decreased from 8 nm to 3 nm with the pressure increasing from 10 MPa to 90 MPa, and all the BNNSs are triangular in shape with a zigzag edge. These BNNSs have high specific surface area, and thus exhibit high adsorption capacities for the organic dye methylene blue (MB). The maximum specific surface area and adsorption capacity of BNNSs are 182 m2 g−1 and 436 mg g−1, respectively. Besides, the BNNSs can also be used as excellent thermal-conducting additives in BN–polymer (Nylon66 and polyvinyl alcohol (PVA)) composites. Especially, the thermal conductivity of BN–PVA film can be improved up to 3.44 times with only 3 wt% of BNNSs.

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 × 10(3) A W(1-) and high external quantum efficiency of ∼4.75 × 10(5) % at 532 nm, which are much higher than most of the photodetector devices.

A facile solid state reaction route towards nearly monodisperse hexagonal boron nitride nanoparticles

Nearly monodisperse hexagonal boron nitride (hBN) nanoparticles with low agglomeration degree were successfully synthesized via a modified solid state metathesis reaction route. It was found that sulfur was essential for preparing monodisperse hBN nanoparticles at 250 °C. However, when the temperature exceeded 300 °C, hBN nanoparticles with uniform size could also be quickly synthesized even without sulfur, and the yield was up to ∼65%. Furthermore, the experimental results were properly explained by a fast reaction and explosive dispersion mechanism, which was proposed according to the exothermal reaction between sulfur and NaN3 and the explosive decomposition of the latter. Besides, the good thermal stability and high specific surface area made the as-prepared hBN nanoparticles applicable in many areas.

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 p-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.

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 (e.g., 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.