School of Materials Science and Engineering , Shandong University of Science and Technology , 579 Qianwangang Road, Economic & Technological Development Zones , Qingdao , Shandong 26650 , China.
Nano Lett. 2018 Mar 14;18(3):1875-1881. doi: 10.1021/acs.nanolett.7b05173. Epub 2018 Feb 9.
Au nanoplates (quasi-two-dimensional single crystals) are most commonly synthesized using a mixture of Au precursors via approaches involving multiple processing steps and the use of seed crystals. Here, we report the synthesis of truncated-hexagonal {111}-oriented micrometer-scale Au nanoplates on graphene multilayers using only potassium tetrabromoaurate (KAuBr) as the precursor. We demonstrate that the nanoplate sizes can be controllably varied from tens of nanometers up to a few micrometers by introducing desired concentrations of chloroauric acid (HAuCl) to KAuBr and their thicknesses from ∼13 to ∼46 nm with the synthesis time. Through a series of experiments carried out as a function of synthesis time and precursor composition [mixtures of HAuCl and KAuBr, KBr, or ionic liquid 1-butyl-3-methylimidazolium bromide ([Bmim]Br)], we identify the optimal HAuCl and KAuBr concentrations and synthesis times that yield the largest and the thinnest size nanoplates. We show that the nanoplates are kinetically limited morphologies resulting from preferential growth of {111} facets facilitated by bromide ions in KAuBr solutions; we suggest that the presence of chloride ions enhances the rate of Au deposition and the relative concentration of chloride and bromide ions determines the shape anisotropy of resulting crystals. Our results provide new insights into the kinetics of nanoplate formation and show that a single precursor containing both Au and Br is sufficient to crystallize nanoplates on graphitic layers, which serve as reducing agent while enabling the nucleation and growth of Au nanoplates. We suggest that a similar approach may be used for the synthesis of nanoplates of other metals on weakly interacting van der Waals layers for, potentially, a variety of new applications.
金纳米板（准二维单晶）通常使用金前体制备混合物，通过涉及多个处理步骤和使用晶种的方法合成。在这里，我们仅使用四溴金酸（KAuBr）作为前体制备了石墨烯多层上的截角六边形{111}取向的微米级金纳米板。我们证明，通过引入所需浓度的氯金酸（HAuCl）到 KAuBr 中，可以将纳米板的尺寸从几十纳米到几微米进行可控变化，并且通过合成时间可以将其厚度从约 13nm 到约 46nm 变化。通过一系列随合成时间和前体组成（HAuCl 和 KAuBr、KBr 或离子液体 1-丁基-3-甲基咪唑溴化物([Bmim]Br）的混合物）进行的实验，我们确定了生成最大和最薄尺寸纳米板的最佳 HAuCl 和 KAuBr 浓度和合成时间。我们表明，纳米板是由动力学限制的形态，是由 KAuBr 溶液中溴离子促进的{111}面优先生长形成的；我们认为，氯离子的存在会提高金沉积的速度，而氯离子和溴离子的相对浓度决定了所得晶体的形状各向异性。我们的结果提供了对纳米板形成动力学的新见解，并表明含有 Au 和 Br 的单一前体足以在石墨层上结晶纳米板，同时作为还原剂，还可以促进 Au 纳米板的成核和生长。我们建议，类似的方法可用于在弱相互作用的范德华层上合成其他金属的纳米板，这可能为各种新应用开辟道路。
