Electroless Deposition of Base Metals at the Liquid/Liquid Interface of Ionic Liquids
Authors: Nishi Naoya , Yoshida Naohiro , Zhou Yishan , Yokoyama Yuko , Sakka Tetsuo 
Published: February 2024

Metal nanostructures can be formed at the electrochemical liquid/liquid interface, so-called ITIES. Our group has presented a method to form metal nanostructures at the liquid/liquid interface between ionic liquid (IL) and water (W) [1-10]. This IL/W method utilizes the spatial selectivity of the reaction site only at the liquid/liquid interface, which is achieved by the separation of metal precursor ions dissolved in the W phase and reducing agent in the IL phase. The metal reduction reaction is regarded as the electron transfer across the IL/W interface, which enables us to analyze the reaction process with liquid-liquid electrochemistry at the IL/W interface [11]. Moreover, the usage of ILs (not molecular oils) leads to the formation of 1-dimensional (1D) nanostructures despite the inherent 2D geometry of the liquid/liquid interface, as a result of the structure-forming ability of ILs at the air [12-14], liquid [14-16], and solid [17-19] interfaces. By using this IL/W method, we have successfully prepared 1D nanostructures of noble metals such as Au [1,6], Ag [7], Pt [3], and Pd [5,6], and also their composites with polymer [2] and nanocarbons [8-10].
In this presentation, we would like to introduce our very recent efforts to develop a sister method that uses another liquid/liquid interface between IL and oil (O). Wet chemical techniques for the metal nanostructure formation in general, including our IL/W method described above, involve water and therefore cannot escape from the limitation of metal elements to noble ones. In contrast, the IL/O method [20-22] is water-free and therefore can be used even for base metals, expanding the applicability and versatility of wet chemistry for metal nanostructure formation. In the presentation, we introduce our water-free liquid/liquid interface method, the electrochemical measurements of the electron and ion transfers across the interface, and the obtained nanostructures of base metals such as zinc, aluminum, and magnesium.

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