Analysis of the MNPs Dispersed in Ionic Liquids

In this model we assume the presence of two phases a crystalline phase (nanocrystal or NPs) and a semi-ordered phase (IL) [8, 28, 107, 108]. This model can be used since ILs are not considered as statistical aggregates of anions and cations but instead as a three-dimensional network of anions and cations i.e. polymeric supramolecular structures constituted from aggregates of the type [(BMI) (X),t )] [(BMI), (X)J] . In this context, the two-phase model was adopted to represent the nanocrystals dispersed in the IL [109]. Applying the interface distribution function to the experimental data, the extended molecular lengths of pure 

ILs (semi-ordered phase) were estimated to be 2.8, 4.0, and 4.0nm for BMI.BF4, BMI.PFs and BMI.OTF, respectively. Note that the extended molecular length of 2.8nm obtained for BMI.BF4 is around twice that of the calculated value for a monomeric BMI.BF4 unit [110, 111]. Moreover, the calculated molecular lengths (AMI) for [(BM1)2(BF4)3] and [(BMl)4(PFs)5] supramolecular clusters are 2.4nm and 4.1nm, respectively. 

Inasmuch as most of the 1,3-dialkylimidazolium ILs have extremely low vapor pressure and relatively high viscosity at room temperature, in situ TEM observations in dispersed ILs can be carried out. Indeed, this method was applied for size and shape in situ analysis of various transition-metal NPs dispersed in the ILs (see Table 6.1). The size and shape determined by this in situ technique are the same as those obtained with NPs mixed with an epoxy resin distributed between two silicon wafer pieces and dried at 50 °C. In these cases the samples were pre-thinned mechanically to a thickness of about 20 nm and then ion milled to an electron transparency using 3kV Ar ion beams. 

It was also possible, by HRTEM measurements, to observe defects in the crystalline lattice of the Pt(0) NPs prepared in BMI.BF4 (Fig. 6.7). Note that twin defects are typical for small particles. 

Using D2 and NMR spectroscopy in the formation of lr(0) NPs from the reduction of [Ir(cod)(MeCN)2] in BM I.NTf2/acetone and proton sponge, Finke and coworkers have detected surface-ligand-coordinated N-heterocyclic carbenes. 

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