Self-assembled monolayers presenting imidazolium ions at the tail ends (SAMIMs) having different counteranions have been prepared on Au, and the measurement of water contact angles of the surfaces proved to be an extremely valuable simple technique for quantifying the effects of counteranions on hydrophilicity and hydrophobicity of SAMIMs, which will be extrapolated to the water miscibility of the related ionic liquids.
Multiwalled carbon nanotubes (MWCNTs) were covalently modified with imidazolium salt-based ionic
liquids (ILs). Coupling of acid chloride-functionalized MWCNTs with commercially available (3-aminopropyl)imidazole, followed by the reaction with n-butyl bromide, afforded 1-butylimidazolium
bromide salt-functionalized MWCNTs (
f
-3a). The bromide anion of
f-
3a could be exchanged with BF4
-,
PF6
-, and NTf2
- (N,N-bis((trifluoromethyl)sulfonyl)amide) by metathesis and afforded functionalized
MWCNTs,
f
-3b (BF4
-),
f
-3c (PF6
-), and
f
-3d (NTf2
-), bearing different counteranions. Raman, IR, NMR,
TGA, and XPS analyses clearly confirmed covalent functionalization and imidazolium salt formation as
well as anion exchange of the IL-functionalized MWCNTs. UV−vis data imply that counteranions have
an effect on the relative solubility of the IL-functionalized MWCNTs in water: the solubility of
f
-3 in
water is of the order
f
-3a (Br-) >
f
-3b (BF4
-) >
f
-3c (PF6
-) >
f
-3d (NTf2
-), and the water-soluble
f
-3a
was phase-transferred from the aqueous phase to the chloroform phase via simple anion exchange with
NTf2
-. All of the IL-functionalized MWCNTs, including the water-soluble
f
-3a, exhibited a preferential
solubility in an ionic liquid, [bmim][NTf2].
1,3-Dialkylimidazolium salts, known as one of the ionic liquids, are very attractive molecules because their physicochemical properties can easily be tuned by the variation of the alkyl appendages of the imidazolium cations and counteranions. In this paper we report that the self-assembled monolayers (SAMs) terminating in 1,3-dialkylimidazolium salts with various counteranions [except Fe(CN)6(3-)] on a gold substrate exhibited a selective electron-transfer toward redox-probe molecules: the electron transfer occurred in the presence of Fe(CN)6(3-) (anionic redox-probe molecule) but did not occur in the presence of Ru(NH3)6(3+) (cationic redox-probe molecule). The SAM having Fe(CN)6(3-) as an anion showed the electron-transfer toward Ru(NH3)6(3+), and the Ru3+/2+ redox-switchable SAM was generated by reversible anion exchange between Fe(CN)6(3-) and SCN (or OCN-).
Twenty four thiol-functionalized ionic liquids based on imidazolium cation, 1-(12-mercaptododecyl)-3-alkylimidazolium salts, have been synthesized, and utilized to investigate the effects of alkyl-chain length and anion on the wettability of Au surfaces on the basis of self-assembled monolayers presenting [(CnSAMIM)X], where n = 1-6, X = Br, BF 4 , PF 4 and NTf 2 . Water wettabilities of the surfaces were measured as a water contact angle by contact angle goniometry. It was found that water wettability of the Au surfaces coated with imidazolium ions was largely dependent not only on counter anions but also on the length of alkyl chains. In the case of SAMs of N-alkylimidazolium ions having short length of N-alkyl chain (C 1 -C 4 ), anions played great role in determining water wettability of the surfaces.
Asymmetric electrostatic interactions dependent on pH between the redox molecules and the terminal group on the top of the self-assembled monolayer (SAM) afford control of the electron transfer property of the SAM having the imidazole terminal group.
CO 2 capture from the exhaust flue gases of fossil-fuel power plants has become one of the hot issues for a sustainable society because of the strong impact of CO 2 on global warming. Industrially, CO 2 is being removed from flue gases by a
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