Formation Mechanisms of Hexagonal Boron Nitride Nanosheets in Solvothermal Exfoliation,Langmuir

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Formation Mechanisms of Hexagonal Boron Nitride Nanosheets in Solvothermal Exfoliation
Langmuir ( IF 3.7 ) Pub Date : 2023-01-19 , DOI: 10.1021/acs.langmuir.2c03049
Songfeng E ₁ , Jiayi Liu ₁ , Ruixia Zhao ₁ , Doudou Ning ₁ , Zhaoqing Lu ₁

Affiliation

Solvothermal techniques are widely used to exfoliate many two-dimensional materials, but the formation mechanisms of these nanomaterials have not been clearly revealed. Herein, we discovered the dissociation of hexagonal boron nitride (h-BN) in solvothermal exfoliation evidenced by the formation of B(OH)₃, NH₄B₅O₈·4H₂O, and (NH₄)₂B₁₀O₁₆·8H₂O. In the selected solvents, the lateral sizes of the formed boron nitride nanosheets (BNNSs) are increased in the order of N-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide (DMF), acetonitrile (MeCN), and isopropanol (IPA), suggesting the decreased dissolving abilities of these solvents to h-BN in turn. The dissociation behaviors are the properties of solvents themselves, but the inclusion of lithium chloride (LiCl) and cetyltrimethylammonium bromide (CTAB) can elevate the dissociation degree and yield BNNSs with smaller lateral sizes due to the intercalating effects. The cation−π interactions make CTAB more effective in obtaining uniform BNNSs than using the neutral halogenated hydrocarbons as assistant reagents. The dissociation abilities of the solvents have strong relationships with the surface tension, Hansen solubility parameters distances (R_a), and polarities, whereas there is little relevance with the pressures. Meanwhile, we also observed the cracking of CTAB and the polymerization of MeCN in these reactions. Our findings indicate that the impurities are prone to be attached to the BNNSs exfoliated by the solvothermal route.

中文翻译：

六方氮化硼纳米片在溶剂热剥离中的形成机制

溶剂热技术广泛用于剥离许多二维材料，但这些纳米材料的形成机制尚未明确揭示。在此，我们发现了六方氮化硼 ( h -BN) 在溶剂热剥离中的解离，其证据是 B(OH) ₃、NH ₄ B ₅ O ₈ ·4H ₂ O 和 (NH ₄ ) ₂ B ₁₀ O ₁₆的形成·8H ₂ O。在选定的溶剂中，形成的氮化硼纳米片（BNNSs）的横向尺寸按N-甲基-2-吡咯烷酮（NMP）、 N、 N、N-二甲基甲酰胺 (DMF)、乙腈 (MeCN) 和异丙醇 (IPA)，表明这些溶剂对h -BN 的溶解能力依次降低。解离行为是溶剂本身的特性，但加入氯化锂 (LiCl) 和十六烷基三甲基溴化铵 (CTAB) 可以提高解离度，并由于嵌入效应而产生横向尺寸较小的 BNNS。阳离子-π 相互作用使 CTAB 比使用中性卤代烃作为辅助试剂更有效地获得均匀的 BNNS。溶剂的解离能力与表面张力、汉森溶解度参数距离（R _a), 和极性, 而与压力几乎没有关系。同时，我们还观察了这些反应中CTAB的裂解和MeCN的聚合。我们的研究结果表明，杂质很容易附着在通过溶剂热途径剥离的 BNNS 上。

更新日期：2023-01-19

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