Wang Bingchen, Li Lei
Department of Chemical & Petroleum Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, United States.
Langmuir. 2021 Dec 21;37(50):14753-14759. doi: 10.1021/acs.langmuir.1c02722. Epub 2021 Dec 8.
Fundamental understandings of the interfacial molecular structure of solid-confined ionic liquids (ILs) have significant impacts on the development of many cutting-edge applications. Among the extensive studies on the molecular structure at the IL/solid interface, direct observation of a double-layering quantized growth of [Cmim][FAP] on mica was recently reported. In the current work, the atomic force microscopy (AFM) results directly show that the growths of [Bmim][FAP] nanofilms on silica and amorphous carbon are different from the double-layering growth on mica. The growth of [Bmim][FAP] nanofilms on silica is dominated by the aggregation of the IL molecules, which can be attributed to the inadequate negative charging of the silica surface resulting in a weak electrostatic interaction between silica and the IL cation. [Bmim][FAP] on amorphous carbon shows a fairly smooth film for the thinner nanofilms, which can be attributed to the π-π parallel stacking between the cation imidazolium ring and the randomly distributed sp carbon on the amorphous carbon surface. Our findings highlight the effect of different IL/solid interactions, among the several competing interactions at the interface, on the resulting molecular arrangements of various IL.
对固体受限离子液体（ILs）界面分子结构的基本理解对许多前沿应用的发展具有重大影响。在对IL/固体界面分子结构的广泛研究中，最近有报道直接观察到[Cmim][FAP]在云母上的双层量子化生长。在当前工作中，原子力显微镜（AFM）结果直接表明，[Bmim][FAP]纳米膜在二氧化硅和无定形碳上的生长不同于在云母上的双层生长。[Bmim][FAP]纳米膜在二氧化硅上的生长主要由IL分子的聚集主导，这可归因于二氧化硅表面负电荷不足，导致二氧化硅与IL阳离子之间的静电相互作用较弱。对于较薄的纳米膜，[Bmim][FAP]在无定形碳上呈现出相当光滑的薄膜，这可归因于阳离子咪唑环与无定形碳表面随机分布的sp碳之间的π-π平行堆积。我们的研究结果突出了在界面处几种相互竞争的相互作用中，不同的IL/固体相互作用对各种IL最终分子排列的影响。
