Moshrefi Reza, Stockmann Talia Jane
Core Science Facility, Chemistry Department, Memorial University of Newfoundland, 45 Artic Ave., St. John's, NL A1C 5S7, Canada.
Nanomaterials (Basel). 2022 Aug 11;12(16):2748. doi: 10.3390/nano12162748.
Owing to their biocompatibility, optical, and catalytic properties, Au nanoparticles (NPs) have been the subject of much research. Since smaller NPs have enhanced catalytic properties and NP morphology greatly impacts their effectiveness, controlled and reproducible methods of generating Au NPs are still being sought. Herein, Au NPs were electrochemically generated at a water|ionic liquid (w|IL) immiscible micro-interface, 25 µm in diameter, using a redox active IL and compared to results at a water|oil (w|o) one. The liquid|liquid interface is advantageous as it is pristine and highly reproducible, as well as an excellent means of species and charge separation. In this system, KAuCl4 dissolved in the aqueous phase reacts under external potential control at the water|P8888TB (tetraoctylphosphonium tetrakis(pentafluorophenyl)borate) with trioctyl(ferrocenylhexanoyl)phosphonium tetrakis(pentafluorophenyl)borate (FcIL), an electron donor and redox active IL. FcIL was prepared with a common anion to P8888TB, which greatly enhances its solubility in the bulk IL. Simple ion transfer of AuCl4− and AuCl(4−γ)(OH)γ− at the w|P8888TB micro-interface were characterized voltammetrically as well as their heterogeneous electron transfer reaction with FcIL. This interfacial reaction generates Au NPs whose size can be thermodynamically controlled by modifying the pH of the aqueous phase. Critically, at low pH, nanoclusters, <1.7 nm in diameter, were generated owing to inhibited thermodynamics in combination with the supramolecular fluidic nature of the IL microenvironment that was observed surrounding the as-prepared NPs.
由于金纳米颗粒（Au NPs）具有生物相容性、光学和催化特性，它们一直是众多研究的主题。由于较小的纳米颗粒具有增强的催化性能，且纳米颗粒的形态对其有效性有很大影响，因此仍在寻找可控且可重复的金纳米颗粒生成方法。在此，使用氧化还原活性离子液体，在直径为25 µm的水|离子液体（w|IL）不混溶微界面上通过电化学方法生成金纳米颗粒，并与在水|油（w|o）微界面上的结果进行比较。液|液界面具有优势，因为它是纯净的且具有高度可重复性，也是物种和电荷分离的极佳方式。在该体系中，溶解在水相中的KAuCl4在外部电位控制下，于水|P8888TB（四辛基鏻四（五氟苯基）硼酸盐）与三辛基（二茂铁基己酰基）鏻四（五氟苯基）硼酸盐（FcIL，一种电子供体和氧化还原活性离子液体）的界面处发生反应。FcIL与P8888TB具有共同的阴离子，这极大地提高了其在本体离子液体中的溶解度。通过伏安法对w|P8888TB微界面处AuCl4−和AuCl(4−γ)(OH)γ−的简单离子转移以及它们与FcIL的异相电子转移反应进行了表征。这种界面反应生成了金纳米颗粒，其尺寸可通过改变水相的pH值进行热力学控制。至关重要的是，在低pH值下，由于热力学抑制以及在制备的纳米颗粒周围观察到的离子液体微环境的超分子流体性质，生成了直径小于1.7 nm的纳米团簇。
