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ChemistryOpen 6 (2017) 137

Synthesis of metal nanoparticles and metal fluoride nanoparticles from metal amidinate precursors in 1-butyl-3-methylimidazolium ionic liquids and propylene carbonate

by K. Schütte, J. Barthel, M. Endres, M. Siebels, B. M. Smarsly, J. Yue, and C. Janiak

Decomposition of transition-metal amidinates [M{MeC(NiPr)2}n] [M(AMD)n; M=MnII, FeII, CoII, NiII, n=2; CuI, n=1) induced by microwave heating in the ionic liquids (ILs) 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIm][BF4]), 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIm][PF6]), 1-butyl-3-methylimidazolium trifluoromethanesulfonate (triflate) ([BMIm][TfO]), and 1-butyl-3-methylimidazolium tosylate ([BMIm][Tos]) or in propylene carbonate (PC) gives transition-metal nanoparticles (M-NPs) in non-fluorous media (e.g. [BMIm][Tos] and PC) or metal fluoride nanoparticles (MF2-NPs) for M=Mn, Fe, and Co in [BMIm][BF4]. FeF2-NPs can be prepared upon Fe(AMD)2 decomposition in [BMIm][BF4], [BMIm][PF6], and [BMIm][TfO].

The nanoparticles are stable in the absence of capping ligands (surfactants) for more than 6 weeks. The crystalline phases of the metal or metal fluoride synthesized in [BMIm][BF4] were identified by powder X-ray diffraction (PXRD) to exclusively Ni- and Cu-NPs or to solely MF2-NPs for M=Mn, Fe, and Co. The size and size dispersion of the nanoparticles were determined by transmission electron microscopy (TEM) to an average diameter of 2(±2) to 14(±4) nm for the M-NPs, except for the Cu-NPs in PC, which were 51(±8) nm. The MF2-NPs from [BMIm][BF4] were 15(±4) to 65(±18) nm. The average diameter from TEM is in fair agreement with the size evaluated from PXRD with the Scherrer equation. The characterization was complemented by energy-dispersive X-ray spectroscopy (EDX). Electrochemical investigations of the CoF2-NPs as cathode materials for lithium-ion batteries were simply evaluated by galvanostatic charge/discharge profiles, and the results indicated that the reversible capacity of the CoF2-NPs was much lower than the theoretical value, which may have originated from the complex conversion reaction mechanism and residue on the surface of the nanoparticles.

Further reading:

K. Schütte, J. Barthel, M. Endres, M. Siebels, B. M. Smarsly, J. Yue, and C. Janiak: Synthesis of metal nanoparticles and metal fluoride nanoparticles from metal amidinate precursors in 1-butyl-3-methylimidazolium ionic liquids and propylene carbonate
, ChemistryOpen 6 (2017) 137
   
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