Liquid exfoliation of five-coordinate layered titanate K2Ti2O5 single crystals in water
Liquid exfoliation of five-coordinate layered titanate K2Ti2O5 single crystals in water
复制标题
五配位层状钛酸K2Ti2O5单晶在水中的液体剥离
DOI：
10.1039/d2ce00512c
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发表时间：
2022
期刊：
影响因子：
3.1
通讯作者：
Teshima Katsuya
中科院分区：
文献类型：
--
作者：
Hayashi Fumitaka;Furui Kenta;Tatewaki Nanako;Sudare Tomohito;Kashiwazaki Maru;Shiiba Hiromasa;Tanaka Hideki;Koyama Michihisa;Terashima Chiaki;Teshima Katsuya
液体剥离是制备二维材料的一种可扩展和有效的技术，但存在几个问题，包括产率低和缺乏对纳米片横向尺寸的控制。在这里，我们报道了助熔剂蒸发辅助生长毫米级K2Ti2O5(KTO)单晶及其在水中液相水热剥离形成纳米片状胶体。在900℃的空气中，用KCl-KOH熔剂生长出毫米长的KTO单晶，并对几种剥离KTO的溶剂进行了研究。结果表明，H2O是最好的剥离溶剂。场发射扫描电子显微镜分析表明，典型的二维KTO纳米片的横向尺寸为5-15μm，与动态光散射结果一致。扫描探针显微镜分析表明，纳米片的剥离程度存在一定程度的分散，约60%的纳米片的厚度小于10 nm。此外，KTO纳米片状胶体的X射线吸收近边结构(XANES)测量表明，KTO晶体在水中发生部分水解，在表面产生羟基，从而削弱了阴离子骨架与层间阳离子之间的相互作用，加速了剥离。对剥离能的密度泛函理论计算表明，与裸KTO相比，该反应降低了剥离能。
Liquid exfoliation is a scalable and effective technique for preparing two-dimensional materials but suffers from several issues, including low yields and lack of control over the lateral size of the nanosheets. Herein, we report the flux-evaporation-assisted growth of millimeter-sized K2Ti2O5 (KTO) single crystals and their liquid-phase hydrothermal exfoliation to form nanosheet colloids in water. The parent millimeter-long KTO single crystals were grown from a KCl–KOH flux at 900 °C in air flow, and several solvents for the exfoliation of KTO were investigated. As a result, H2O was found to be the best solvent for exfoliation. Field-emission scanning electron microscopy analysis of a typical 2D KTO nanosheet revealed that its lateral size was 5–15 μm, consistent with dynamic light scattering results. Scanning probe microscopic analysis showed that there was some dispersion in the degree of exfoliation of the nanosheets and that approximately 60% of the nanosheets had thicknesses of less than 10 nm. In addition, X-ray absorption near edge structure (XANES) measurements of the KTO nanosheet colloid provide evidence that the KTO crystals undergo partial hydrolysis in water to generate hydroxyl groups on the surface, which weaken the interactions between the anionic frameworks and interlayer cations and accelerate exfoliation. Density functional theory calculations of the exfoliation energy reveal that this hydrolysis reaction decreased the exfoliation energy compared to that of bare KTO.