Soft, Wet-Chemical Synthesis of Metastable Superparamagnetic Hexagonal Close-Packed Nickel Nanoparticles in Different Ionic Liquids.
Chemistry
; 23(26): 6330-6340, 2017 May 05.
Article
em En
| MEDLINE
| ID: mdl-28196305
ABSTRACT
The microwave-induced decomposition of bis{N,N'-diisopropylacetamidinate}nickel(II) [Ni{MeC(NiPr)2 }2 ] or bis(1,5-cyclooctadiene)nickel(0) [Ni(COD)2 ] in imidazolium-, pyridinium-, or thiophenium-based ionic liquids (ILs) with different anions (tetrafluoroborate, [BF4 ]- , hexafluorophosphate, [PF6 ]- , and bis(trifluoromethylsulfonyl)imide, [NTf2 ]- ) yields small, uniform nickel nanoparticles (Ni NPs), which are stable in the absence of capping ligands (surfactants) for more than eight weeks. The soft, wet-chemical synthesis yields the metastable Ni hexagonal close-packed (hcp) and not the stable Ni face-centered cubic (fcc) phase. The size of the nickel nanoparticles increases with the molecular volume of the used anions from about 5â
nm for [BF4 ]- to ≈10â
nm for [NTf2 ]- (with 1-alkyl-3-methyl-imidazolium cations). The n-butyl-pyridinium, [BPy]+ , cation ILs reproducibly yield very small nickel nanoparticles of 2(±1)â
nm average diameter. The Ni NPs were characterized by high-resolution transmission electron microscopy (HR-TEM) and powder X-ray diffraction. An X-ray photoelectron spectroscopic (XPS) analysis shows an increase of the binding energy (EB ) of the electron from the Ni 2p3/2 orbital of the very small 2(±1)â
nm diameter Ni particles by about 0.3â
eV to EB =853.2â
eV compared with bulk Ni0 , which is traced to the small cluster size. The Ni nanoparticles show superparamagnetic behavior from 150â
K up to room temperature. The saturation magnetization of a Ni (2±1â
nm) sample from [BPy][NTf2 ] is 2.08â
A m2 kg-1 and of a Ni (10±4â
nm) sample from [LMIm][NTf2 ] it is 0.99â
A m2 kg-1 , ([LMIm]=1-lauryl-3-methyl- imidazolium). The Ni NPs were active catalysts in IL dispersions for 1-hexene or benzene hydrogenation. Over 90 % conversion was reached under 5â
bar H2 in 1â
h at 100 °C for 1-hexene and a turnover frequency (TOF) up to 1330â
molhexane (molNi )-1 h-1 or in 60â
h at 100 °C for benzene hydrogenation and TOF=23â
molcyclohexane (molNi )-1 h-1 .
Texto completo:
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Coleções:
01-internacional
Base de dados:
MEDLINE
Idioma:
En
Revista:
Chemistry
Assunto da revista:
QUIMICA
Ano de publicação:
2017
Tipo de documento:
Article
País de afiliação:
Alemanha
País de publicação:
ALEMANHA
/
ALEMANIA
/
DE
/
DEUSTCHLAND
/
GERMANY