Single‐Entity Electrochemical Detection of As‐Prepared Metallic and Dielectric Nanoparticle Stochastic Impacts in a Phosphonium Ionic Liquid

Abstract

Nanoparticles (NPs) are of considerable interest, owing to their enhanced catalytic activity and optical properties. Ionic liquids (ILs) are employed as a medium to prepare small (<20 nm in diameter) and relatively low dispersity (typically, ±1–2 nm) NPs. While ensemble techniques (e. g., UV/Vis) can provide a great deal of information, increasingly, single‐entity electrochemistry (SEE) has been used to provide physical insight into individual NP catalysis and dynamics. Herein, Pt NP impact current spikes for particles prepared in the IL phase and based on electrocatalytic amplification (ECA) of the borohydride oxidation reaction (BOR) were recorded during i‐t measurements. Additionally, direct oxidative LiBH4 nanocrystal (NC) impact signals were observed herein for the first time. By quantifying the charge transferred during the stochastic collision events, the radius of the NCs (rNC) was calculated (∼5.5 nm) and compares favorably with TEM images. Critically, small additions (1 % v/v) of a molecular, polar organic solvent (tetrahydrofuran, THF) disrupt the ILs supramolecular fluidic nature, which enhances NC impact frequency and the aggregation of Pt NPs.

On-Chip Electrokinetic Micropumping for Nanoparticle Impact Electrochemistry

“…Our results highlight that negative ME potentials impair the chloride flux to a point such that the initial detection rate might be significantly reduced compared to moderate potentials. In fact, other recent work highlights the crucial role of the co-reactants in impact experiments, as the reaction dynamics are very sensitive to the presence/absence of the co-species at the electrode. , …”

Electrodeless Synthesis of Low Dispersity Au Nanoparticles and Nanoclusters at an Immiscible Micro Water/Ionic Liquid Interface

“…The double bar indicates the po able potential interface maintained at the pipette tip which, unless otherwise specified, had a eter of 25 µm. Cells 1b-3b were measured at ~60 °C using a water circulator (Polystat, Cole-Pa Micropipettes (25 µm diameter) as well as inlaid disc Pt and carbon fiber ultram electrodes (UME), 25 and 7 µm in diameter, respectively, were prepared as has bee scribed elsewhere [14,27]. UMEs were employed in a two-electrode mode in conjun with an Ag wire, which served as the counter/quasi-reference electrode.…”

“…Micropipettes (25 µm diameter) as well as inlaid disc Pt and carbon fiber ultramicroelectrodes (UME), 25 and 7 µm in diameter, respectively, were prepared as has been described elsewhere [14,27]. UMEs were employed in a two-electrode mode in conjunction with an Ag wire, which served as the counter/quasi-reference electrode.…”

“…Transmission electron microscopy (TEM) imaging was performed using a Tecnai Spirit TEM with samples deposited on 200 mesh Au ultrathin/lacey carbon grids. Micropipettes (25 µm diameter) as well as inlaid disc Pt and carbon fiber ultramic electrodes (UME), 25 and 7 µm in diameter, respectively, were prepared as has been d scribed elsewhere [14,27]. UMEs were employed in a two-electrode mode in conjunct with an Ag wire, which served as the counter/quasi-reference electrode.…”

“…They are desirable for several reasons including excellent thermal and electronic stability as well as enhanced catalytic properties and as a medium for NP preparation [26]. Indeed, NPs prepared in an IL phase are typically small (<10-20 nm) and have low dispersity; this is hypothesized to be owing to the supramolecular fluidic nature of ILs, which contain nanoscale pockets sandwiched between ion aggregates/contact ion pairs within which NPs can grow [26][27][28][29][30]. Nishi et al [31] first investigated electrochemically controlled Au NP synthesis at a micro w|IL interface using tri-p-tolylamine as the reducing agent dissolved in the IL, trioctylmethylammonium bis(nonafluorobutanesulfonyl)amide ([TOMA + ][C 4 C 4 N − ]), and were able to generate nanodendrites.…”