Ionic Liquid Aggregation Mechanism for Nanoparticle Synthesis

Abstract

Nanoparticle synthesis with silylamine reversible ionic liquids (RevILs) has been previously demonstrated to offer unique alternatives to traditional nanoparticle syntheses, allowing for size control and facile deposition onto support surfaces via the switchable nature of the IL. However, the mechanism of nanoparticle synthesis remains uncharacterized. The use of RevILs facilitates the synthesis of size-controlled nanoparticles without the use of additional stabilizing agents (i.e., surfactants, ligands, and polymers) that passivate the nanoparticle surface, which are traditionally required to control the nanoparticle size. Traditional techniques often require harsh activation steps that ultimately impact nanoparticle size and morphology. While RevIL syntheses offer an excellent alternative, as they do not require additional activation steps, the mechanism through which nanoparticles are synthesized in these systems has not been studied previously. Preceding work hypothesized nanoparticles prepared with RevILs are formed via a reverse micelle mechanism, in which nanoparticles are stabilized and templated within the aqueous core of the organized micelle structures. In this work, DOSY-NMR is used to demonstrate that nanoparticles synthesized with 3-aminopropyltriethylsilane RevIL are not formed through a reverse micelle mechanism but rather a switchable aggregation mechanism that affords control over the nanoparticle size via manipulation of the RevIL structure and concentration. Furthermore, it is shown that the addition of water to RevIL systems has detrimental effects on the aggregation behavior of the ionic liquid molecules in solution, causing disassembly of the ion pairs. However, because nanoparticle reduction likely occurs faster than the disassembly of the ion pairs, nanoparticle size is unaffected by the addition of water during nanoparticle reduction.

Ionic Liquid Electrolyte-Based Switchable Mirror with Fast Response and Improved Durability

“…The calculated adsorption energy of different organic cations is in the following order: [DBIz] + < [DBPd] + < [TBA] + < [DBMp] + < [DBPl] + < [DBPz] + , which was consistent with the result of Raman and SERS. According to the previous literature, it is easier for cations to adhere to metal surfaces, and the higher adsorption energy indicates stronger adhesion between the cations and Ag(111) surfaces. , This strong adsorption prevented the aggregation and agglomeration phenomenon during the nucleation of metal nanoparticles, which would lead to a faster switching speed and the formation of a denser and more compact electrodeposited metal film. , Consequently, increasing the adsorption energy between the cations and surfaces of AgNPs might be an effective strategy to optimize the performance of silver mirrors that are made using IL-based electrolytes.…”

“…To better study the role that cations played in reversible metal Ag electrodeposition, we have analyzed the adsorption behavior (Figure b,c) of different cations on the surface of the silver electrode. ,,, The adsorption of ions on the Ag surfaces could be accurately monitored via Raman and SERS techniques. − Here, the adsorption of cations to the metal Ag nanoparticle film was monitored through the combination of FT-IR, Raman, and SERS spectra, as illustrated in Figure d,e. In the FT-IR spectra of DBPz-Br (Figure e), the band at 1281 cm –1 was attributed to the stretching vibration of the N-N.…”

“…53,54 This strong adsorption prevented the aggregation and agglomeration phenomenon during the nucleation of metal nanoparticles, which would lead to a faster switching speed and the formation of a denser and more compact electrodeposited metal film. 47,48 Consequently, increasing the adsorption energy between the cations and surfaces of AgNPs might be an effective strategy to optimize the performance of silver mirrors that are made using IL-based electrolytes.…”

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

“…ILs have been shown to possess a supramolecular structure with contact ion pairs or aggregates of IL ions. [35][36][37][38] Indeed, Bryant et al recently proposed that ion aggregates act as templating regions for NP synthesis within ILs. [38] Herein, LiBH 4 NCs as well as Pt and Au NPs were prepared in a tetraalkylphosphonium IL, trihexyltetradecylphosphonium bis(trifluorosulfonyl)imide (P 66614 NTf 2 ).…”

“…[35][36][37][38] Indeed, Bryant et al recently proposed that ion aggregates act as templating regions for NP synthesis within ILs. [38] Herein, LiBH 4 NCs as well as Pt and Au NPs were prepared in a tetraalkylphosphonium IL, trihexyltetradecylphosphonium bis(trifluorosulfonyl)imide (P 66614 NTf 2 ). NC and NP impacts were recorded at a CF-UME.…”