Lateral size selection of liquid exfoliated hexagonal boron nitride nanosheets

Abstract

Hexagonal boron nitride (h-BN) is of great importance in imaging, thermal and quantum applications in the mid-infrared regions (most of which are size related) for its natural hyperbolic properties.

Co-Solvent Exfoliation of Hexagonal Boron Nitride: Effect of Raw Bulk Boron Nitride Size and Co-Solvent Composition

“…Along with the drop of BNNS concentration, the size of BNNSs decreases with the increased centrifugation speed ( Figure 3 b), as high speed centrifugation works as an effective separation of BNNS with different sizes in suspension [ 45 , 46 ]. For BNNS 2 , the average size decreases from 442 nm at 1000 rpm to 171 nm at 10,000 rpm.…”

“…The extraction of BNNSs from h-BN by ultrasound contains two successive steps of ultrasonic treatment and centrifugation. Processing parameters, such as ultrasonic time, and centrifugation speed have strong influence on the resultant BNNS concentration and size [42,45]. Figure 3 presents the variation of BNNS concentration and average size with centrifugation speed and ultrasonic time under constant IPA fraction of 19 mol%.…”

“…It is most likely that the liquid exfoliation process is a dynamic process in which the large BNNSs are continuously exfoliated off, and the large BNNSs are continuously fragmented into smaller and thinner pieces, due to the presence of ultrasonic waves [48]. Along with the drop of BNNS concentration, the size of BNNSs decreases with the increased centrifugation speed (Figure 3b), as high speed centrifugation works as an effective separation of BNNS with different sizes in suspension [45,46]. For BNNS 2 , the average size decreases from 442 nm at 1000 rpm to 171 nm at 10,000 rpm.…”

Atomically Thin Hexagonal Boron Nitride and Its Heterostructures

“…To realize above applications, the most important thing is controllable preparation of high‐quality h‐BN samples. Up to now, two types of strategies have been developed to prepare h‐BN: one is top‐down exfoliation of bulk h‐BN crystals via mechanical and solvothermal forces; [ 19,20 ] the other is bottom‐up growth methods via chemical vapor deposition (CVD), [ 21,22 ] metal–organic chemical vapor deposition (MOCVD) [ 23 ] and molecular beam epitaxy (MBE). [ 24 ] The mechanical exfoliation can achieve high‐quality of h‐BN flakes, but with limitation of lateral sizes and yields, thereby its usage is only in proof‐of‐concept of devices.…”

Boron Nitride Nanosheets Supported Cu2O Nanoparticles: Synthesis and Catalytic Reduction for 4-nitrophenol

“…BNNSs 具有与石墨烯不同的电子结构, 虽然存在大 π 键, 但电子离域性低。 在硼氢化钠还原对硝基苯酚 反应中, 氢吸附后的 BNNSs 物性发生变化, 原本定 域在 N 原子周围的电子流动起来 [16] , 可以避免 Cu 2 O NPs 被氧化成 CuO。 上述特性使氮化硼纳米片 可以作为 Cu 2 O NPs 的理想载体材料。 本工作在传统冻融法 [17] 的基础上, 利用聚乙烯 吡咯烷酮(PVP) [18] 与水相变提供的"推-拉"协同作用 [19] , 水分子巨大的比 表面能及强烈的搅拌作用大大提高插层效率。当温 度降至 0 ℃以下时, 水分子逐渐聚集成蜂窝状结构, 水结冰产生的"体积膨胀力"(250 kPa) [20] [23] 。Raman 图谱表明, 由于 BNNSs [25] , O1s 图谱中 530.1 eV 信号对应 Cu 2 O 中晶格氧 O1s 的电子结合能 [26] , Cu2p 轨道能 谱图中位于 932.3 (FWHM=1.8 eV)和 952.1 eV 的强 峰分别对应 Cu2p 3/2 和 Cu2p 1/2 的电子结合能, 均属 于 Cu 2 O 中 Cu(I)的特征峰, 且 Cu2p 3/2 出峰位置与块 状 Cu 2 O(932.6 eV) [27] 相比向低电子结合能方向移动, 说明 Cu 2 O 以纳米晶体形式负载在 BNNSs-OH 表面 上 [28] [31] , Cu 2 O NPs 作为电子 和氢原子的中转位点, 传递表面氢原子和电子至对 硝基苯酚阴离子, 最终使-NO 2 加入质子移除氧转 化为-NH 2 (式(2)) [31] 。而 Cu 单质及 CuO 颗粒尺寸较 大且电子迁移能力相对较弱, Cu 2 O-Cu 基催化剂因…”