Ionic Liquids of Bis(alkylethylenediamine)silver(I) Salts and the Formation of Silver(0) Nanoparticles from the Ionic Liquid System

Abstract

We have prepared novel ionic liquids of bis(N-2-ethylhexylethylenediamine)silver(I) nitrate ([Ag(eth-hex-en)(2)]NO(3) and bis(N-hexylethylenediamine)silver(I) hexafluorophosphate ([Ag(hex-en)(2)]PF(6)), which have transition points at -54 and -6 degrees C, respectively. Below these transition temperatures, both the silver complexes assume amorphous states, in which the extent of the vitrification is larger for the eth-hex-en complex than for the hex-en complex. The diffusion coefficients of both the complex cations, measured between 30 (or 35) and 70 degrees C, are largely dependent on temperature; the dependence is particularly large in the case of the eth-hex-en complex cation below 40 degrees C. Small-angle X-ray scattering studies showed that the bilayer structure of the metal complex is formed in the liquid state for both the silver complexes. A direct observation of the yellowish [Ag(eth-hex-en)(2)]NO(3) liquid by transmission electron microscopy (TEM) indicates the presence of nanostructures, as a microemulsion, of less than 5 nm. Such structures were not clearly observed in the [Ag(hex-en)(2)]PF(6) liquid. Although the [Ag(eth-hex-en)(2)]NO(3) liquid is sparingly soluble in bulk water, it readily incorporates a small amount of water up to [water]/[metal complex] = 7:1. Homogeneous and uniformly sized silver(0) nanoparticles in water were created by the reduction of the [Ag(eth-hex-en)(2)]NO(3) liquid with aqueous NaBH(4), whereas silver(0) nanoparticles were not formed from the [Ag(hex-en)(2)]PF(6) liquid in the same way.

Preparation of Inorganic Materials Using Ionic Liquids

“…[72,73] 6 ]} by NaBH 4 . [99] The examples highlighted above demonstrate the potential of using ionic liquids in the preparation and stabilization of metal nanoparticles. The key advantage of using ionic liquids in this regard is that the metal nanoparticles reported in these studies are often very small and uniform, owing to the stabilization effect and low interface tensions of ionic liquids.…”

Liquid Nickel Salts: Synthesis, Crystal Structure Determination, and Electrochemical Synthesis of Nickel Nanoparticles

“…[8][9][10][11][12][13] Several examples of electrodepositiono fm etals from liquid metal salts can be found in the literature. [14][15][16][17][18][19][20][21][22] Our research group has obtainedv ery promising resultsf or the electrodeposition of copper, [23][24][25] silver, [26][27][28][29][30] palladium [31] and lithium. [32] Metal coatings of ag ood quality were achieved at very high current densities,e ven withoutt he use of additives.…”

Ionic Liquids as Designer Solvents for the Synthesis of Metal Nanoparticles

“…metal ion-containing ILs, which can be directly reduced, leading to metal nanoparticles synthesis in ILs without requiring any additional metal salts. (Iida et al, 2008). Another category of functionalized ILs includes those which contain certain functional groups that may bond onto metal surfaces, and thus stabilize the formed metal nanoparticles more effectively.…”

“…This indicates that more research is warranted to correlate the influence of type of ILs with metal nanoparticles stabilization and their size profile. Particularly interesting is the observation that ILs can themselves be functionalized to either incorporate metal ions (Iida et al, 2008) or reducing agent (Dinda et al, 2008) within the IL structure. This provides a great deal of flexibility towards facile synthesis and stabilization of metal nanoparticles towards narrow and small size range with a potential ability to control their shape anisotropy (Davis, 2004;Fei el al., 2006;Lee, 2006;Li et al, 2006;Davis & Wassercheid, 2008).…”