Boron nitride (BN) structures are featured by their excellent thermal and chemical stability and unique electronic and optical properties. However, the lack of controlled synthesis of quality samples and the electrically insulating property largely prevent realizing the full potential of BN nanostructures. A comprehensive overview of the current status of the synthesis of two-dimensional hexagonal BN sheets, three dimensional porous hexagonal BN materials and BN-involved heterostructures is provided, highlighting the advantages of different synthetic methods. In addition, structural characterization, functionalizations and prospective applications of hexagonal BN sheets are intensively discussed. One-dimensional BN nanoribbons and nanotubes are then discussed in terms of structure, fabrication and functionality. In particular, the existing routes in pursuit of tunable electronic and magnetic properties in various BN structures are surveyed, calling upon synergetic experimental and theoretical efforts to address the challenges for pioneering the applications of BN into functional devices. Finally, the progress in BN superstructures and novel B/N nanostructures is also briefly introduced.

(1 of 22)allotropes of boron have been discovered up to now. Four of them are thermodynamically stable, including α-rhombohedral, [6] β-rhombohedral, [7] γ-orthorhombic, [1f,2d,8] and β-tetragonal boron crystals. [1d,9] These materials are often called boron-icosahedral cluster solids (B-ICSs), [5b,10] consisting of icosahedral closo-cluster B 12 to link with each other or with other clusters to form boron allotropes and B-rich compounds, such as various types of BN, [11] B 12 As 2 , [12] B 12 P 2 , [13] B 12 O 2 , [14] YB 66 , [15] AlB 12 , [16] and boron carbide. [17] Apart from three-dimensional (3D) boron icosahedral solids, 2D boron also exhibits many unique structures owning to its electron deficiency, different from other well-known 2D materials. Generally, 2D boron crystals can be classified into three categories: 1) graphene-like atomically monolayered boron sheets, [18] 2) 2D boron structures with thickness of a single or a few unit cells, [19] and 3) new kinds of 2D boron structures reported recently. [20] For the first category, "borophene" was coined to refer to a general class of atomically thin boron sheets, [21] unlike other structures with the suffix ene, where each name always corresponds to a certain structure. For example, graphene, as the most attractive 2D crystals, is a single monolayer of carbon atoms, while phosphorene (monolayered black phosphorus) exists with puckered layer structures in nature. Both graphene and phosphorene have corresponding bulk counterparts, allowing for facile access to 2D-layered van der Waals structures through mechanical exfoliations. Other elemental 2D materials, such as silicene, [22] germanene, [23] stanene, [24] arsenene, [25] and antimonene, [26] actually do not have layered bulk counterparts. Similarly, 2D single-layered boron could not be produced by exfoliating from its bulk materials because there is no layered bulk boron. As a result, it is suggested that 2D boron sheets can be synthesized via chemical vapor deposition, thermal evaporation deposition, or molecular beam epitaxy. In the past decade, extensive theoretical efforts have been paid to investigate possible boron sheets, many of which have been predicted to have potential applications in electronic devices, [18c,d] photoelectric devices, [27] superconductivity, [20a,28] field-emission (FE) materials, [29] hydrogen storage media, [30] and lithium-ion batteries. [31] However, the fabrication of 2D boron crystals is a great challenge. Until very recently, three types of monolayered Boron, as a unique element nearest to carbon in the periodic table, has been predicted to form many distinctive two-dimensional (2D) structures that significantly differ from other well-studied 2D materials, owning to its exceptional ability to form strong covalent two-center-two-electron bonds as well as stable electron-deficient multi-center-two-electron bonds. Until recently, the successful syntheses of atomically thin crystalline 2D boron sheets (i.e., borophenes) provoked growing passion in 2D boron crysta...

Mixed hemimicelles solid-phase extraction (SPE) based on cetyltrimethylammonium bromide (CTAB)-coated nano-magnets Fe 3 O 4 was investigated for the preconcentration of four chlorophenols (CPs) in environmental water samples prior to HPLC-spectrophotometry determination in this paper. By the rapid isolating (about 5 min) of Fe 3 O 4 nanoparticles (NPs) through placing a Nd-Fe-B strong magnet on the bottom of beaker, the time-consuming preconcentration process of loading large volume sample in conversional SPE method with a column can be avoided. The unique properties of Fe 3 O 4 NPs such as high surface area and strong magnetism were utilized adequately in the SPE process. This novel separation method produced a high preconcentration rate and factor. A comprehensive study of the adsorption conditions such as the Fe 3 O 4 NPs zeta-potential, CTAB added amounts, pH value, standing time and maximal extraction volume was also presented. Under optimized conditions, four analytes of 2-chlorophenol (2-CP), 2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (TCP) and pentachlorophenol (PCP) were quantitatively extracted. The method was then used to determine four CPs in five real environmental water samples. High concentration factors (700) were achieved for each of the analytes, with observed detection limits ranging between 0.11 and 0.15 g L −1 . The accuracy of method was evaluated by recovery measurements on spiked samples. Good recovery results (83-98%) with satisfactory relative standard deviation (RSD) were achieved. It is important to note that satisfactory preconcentration factors and extraction recoveries for the four CPs were obtained with only a little amount of Fe 3 O 4 NPs (0.1 g) and CTAB (60 mg). To the best of our knowledge, this was the first time a mixed hemimicelles SPE method based on Fe 3 O 4 NPs magnetic separation had been used for the pretreatment of environmental water samples.

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Purpose This study aimed to describe the epidemiologic characteristics of fracture in the elderly during the COVID-19. Methods This was a retrospective multi-centre study, which included patients who sustained fractures between 20 January and 19 February 2020. The collected data included patients' demographics (age and gender), injury-related (injury type, fracture location, injury mechanism, places where fracture occurred), and treatment modality. SPSS 23.0 was used to describe the data and perform some analysis. Results A total of 436 patients with 453 fractures were included; there were 153 males and 283 females, with an average age of 76.2 years (standard deviation, SD, 7.7 years; 65 to 105). For either males or females, 70-74 years was the most commonly involved age group. A total of 317 (72.7%) patients had their fractures occurring at home. Among 453 fractures, there were 264 (58.3%) hip fractures, accounting for 58.3%. Fall from standing height was the most common cause of fracture, making a proportion of 89.4% (405/453). Most fractures (95.8%, 434/453) were treated surgically, and 4.2% (19/453) were treated by plaster fixation or traction. Open reduction and internal fixation (ORIF) was the most used surgical method, taking a proportion of 49.2% (223/453).

To improve the mechanical properties of bone tissue and achieve the desired bone tissue regeneration for orthopedic surgery, newly designed hydroxyapatite/polyurethane (HA/PU) porous scaffolds were developed via in situ polymerization. The results showed that the molecular modification of PU soft segments by glyceride of castor oil (GCO) can increase the scaffold compressive strength by 48% and the elastic modulus by 96%. When nano-HA (n-HA) particles were incorporated into the GCO-PU matrix, the compressive strength and elastic modulus further increased by 49 and 74%, from 2.91 to 4.34 MPa and from 95 to 165.36 MPa, respectively. The n-HA particles with fine dispersity not only improved the interface bonding with the GCO-PU matrix but also provided effective bioactivity for bonding with bone tissue. The hierarchical structure and mechanical quality of the n-HA/GCO-PU composite scaffold were determined to be appropriate for the growth of cells and the regeneration of bony tissues, demonstrating promising prospects for bone repair and regeneration.

Hexagonal boron nitride monolayers with domain sizes up to 700 μm2 and geometry from triangle to hexagon are fabricated through a refined control over the precursor and morphology of the copper substrate. Hydrogen etching is shown to tailor the h‐BN monolayers precisely along the grain boundaries, providing their morphology over micro­meter scale and a new avenue toward fabricating nanoribbons.

Ionic liquid mixed hemimicelles-based solid-phase extraction for the preconcentration of five phthalates in environmental water sample was investigated in this paper. A comparative study on the use of room temperature ionic liquids (RTILs) 1-hexyl-3-methylimidazolium bromide ([C 6 mim]Br) and 1-dodecyl-3-methylimidazolium bromide ([C 12 mim]Br)-coated silica as sorbents was presented. Owing to having bigger adsorption amounts for analytes [C 12 mim], Br-coated silica was selected as SPE material and the five analytes di-ethyl-phthalate (DEP), di-n-propyl-phthalate (DnPP), di-n-butyl-phthalate (DnBP), di-cyclohexyl-phthalate (DcHP) and di-(2-ethylhexyl)-phthalate (DEHP) can be quantitatively extracted under optimal conditions. The analytes retained on the cartridge were desorbed completely with 3 mL methanol (pH 2). Predominant factors influencing the extraction efficiency, such as RTILs concentration, pH value, ionic strength and breakthrough volume were discussed. The proposed method had been applied to determining the five phthalates in four environmental water samples and concentration factor of 600 was achieved easily. Detection limits obtained ranged between 0.12 and 0.17 g/L. The accuracy of this method was evaluated by recovery measurement on spiked samples, and good recovery results (85-107%) with relative standard deviation (R.S.D.) of below 6% were achieved.