3 research outputs found
Effect of Ionic Liquid Impurities on the Synthesis of Silver Nanoparticles
Imidazolium-based ionic liquids have been widely utilized
as versatile
solvents for metal nanoparticle synthesis; however, reactions to synthesize
silver nanoparticles that are performed identically in different commercially
obtained lots of 1-butyl-3-methylimidazolium tetrafluoroborate (BMIM-BF<sub>4</sub>) give divergent results. This suggests that impurities in
these nominally identical solvents play an important role in the resulting
silver nanoparticle quality. To test the effect that impurities have
on the quality of silver nanoparticles synthesized in BMIM-BF<sub>4</sub>, silver nanoparticles were synthesized in carefully prepared
and purified BMIM-BF<sub>4</sub> and compared against silver nanoparticles
that were synthesized in the purified BMIM-BF<sub>4</sub> that had
been spiked with trace amounts of water, chloride, and 1-methylimidazole.
It was clearly demonstrated that trace amounts of these common ionic
liquid impurities cause significant deviation in size and shape (creating
polydisperse and irregularly shaped ensembles of both large and small
particles), and also negatively impact the stabilization of the resulting
silver nanoparticles
Two-Phase Microfluidic Droplet Flows of Ionic Liquids for the Synthesis of Gold and Silver Nanoparticles
Droplet-based microfluidic platforms have the potential
to provide
superior control over mixing as compared to traditional batch reactions.
Ionic liquids have advantageous properties for metal nanoparticle
synthesis as a result of their low interfacial tension and complexing
ability; however, droplet formation of ionic liquids within microfluidic
channels in a two-phase system has not yet been attained because of
their complex interfacial properties and high viscosities. Here, breakup
of an imidazolium-based ionic liquid into droplets in a simple two-phase
system has for the first time been achieved and characterized by using
a microchannel modified with a thin film fluoropolymer. This microfluidic/ionic
liquid droplet system was used to produce small, spherical gold (4.28
± 0.84 nm) and silver (3.73 ± 0.77 nm) nanoparticles
Chalcogenol Ligand Toolbox for CdSe Nanocrystals and Their Influence on Exciton Relaxation Pathways
We have employed a simple modular approach to install small chalcogenol ligands on the surface of CdSe nanocrystals. This versatile modification strategy provides access to thiol, selenol, and tellurol ligand sets <i>via</i> the <i>in situ</i> reduction of R<sub>2</sub>E<sub>2</sub> (R = <sup><i>t</i></sup>Bu, Bn, Ph; E = S, Se, Te) by diphenylphosphine (Ph<sub>2</sub>PH). The ligand exchange chemistry was analyzed by solution NMR spectroscopy, which reveals that reduction of the R<sub>2</sub>E<sub>2</sub> precursors by Ph<sub>2</sub>PH directly yields active chalcogenol ligands that subsequently bind to the surface of the CdSe nanocrystals. Thermogravimetric analysis, FT-IR spectroscopy, and energy dispersive X-ray spectroscopy provide further evidence for chalcogenol addition to the CdSe surface with a concomitant reduction in overall organic content from the displacement of native ligands. Time-resolved and low temperature photoluminescence measurements showed that all of the phenylchalcogenol ligands rapidly quench the photoluminescence by hole localization onto the ligand. Selenol and tellurol ligands exhibit a larger driving force for hole transfer than thiol ligands and therefore quench the photoluminescence more efficiently. The hole transfer process could lead to engineering long-lived, partially separated excited states