Carbon Pastes and Carbon Paste Electrodes - Electroanalysis with Carbon Paste Electrodes - page 33

substrate current and ohmic resistance .for.studying.the.capacitive.characteristics.of.some.imidazo-
lium-based.ILs).and.its.direct.continuation.[126],.in.which.an.ionic.liquid.replaced.the.conventional.
binder,.the.(RT)IL-based.CPEs.have.been.the.central.subject.of.interest.in.ca..80.scientiic.papers.
appearing.up.until.now.[127,128,204,333,334,394,407,411,413-416,418,419,427,449,453-515].
The.individual.contributions.have.shown.clearly.that.electrochemical.measurements.with.CPEs.
may.beneit.from.a.number.of.speciic.properties.of.(RT)ILs.[451,452],.namely,.(i).their.excellent.
solvating. properties,. (ii). high. conductivity,. (iii). nonvolatility,. (iv). electrochemical. stability. with.
(v) wide.polarizability,.(vi).speciic.chemical.activity.(mainly.ion-exchanging.properties.and.elec-
trocatalytic.effect),.as.well.as.(vii).typically.low.toxicity..And.to.complete.this.characterization,.there.
is.also.(viii).favorable.surface.microstructure.of.IL-containing.carbon.pastes.with.their.markedly.
smooth.pattern.(see.Figure.3.1),.with.mutual.comparison.of.various.carbon.paste.mixtures.
Most.of.these.features.are.also.highlighted.by.Maleki.et.al..(other.pioneers.and.propagators.of.
ILs.in.the.carbon.paste.mixtures.[453,456,457]),.having.concluded.in.their.special.study.[459].that.
the.addition.of.an.ionic.liquid.into.a.CPE.gives.rise.to.(a).the.increased.conductivity.of.the.binder.
with.the.subsequent.(b).decrease.of.the.electrode.resistance,.(c).increase.of.ion-exchange.capabili-
ties,.and.(d).inherent.catalytic.activity.of.the.resultant.electrode.material.containing.such.an.(RT)IL.
In.their.concluding.remarks,.however,.the.authors.could.have.also.pointed.out.the.characteristic.
enhancement. of. the. overall. signal-to-noise-ratio. at. CILEs. and. related. conigurations,. when. the.
resultant.effect.in.faradic.experiments.is.very.similar.to.that.shown.earlier.for.the.CNT-based.CPEs..
Then,.also.an.experiment.with.the.model.redox.pair.yields.nearly.the.same.result—see.Figure.2.7.
and.compare.it.with.the.previous.one,.Figure.2.6.
Regarding.the.individual.types.of.ionic.liquids.used,.their.choice.was.often.routine.and.relatively.
conservative.[452],.preferring.largely.the.ion.associates.of.the.(i).[ n -R−py] + A − ,.(ii).[R,R′−pyr] + A − ,.
and. (iii). [R,R′−Im] + A − . type.. Speciically,. they. are. formed. by. the. quaternary. cations. with. alkyl/
heterocyclic.structure,.namely,.[ n -alkyl-pyridium] + ,.[ N -butyl- N -methyl-pyrrolidinium] + ,.and.[R,R′-
imidazolium] + ),.the.latter.representing.the.most.frequent.case..The.anionic.moieties.are.then.some.
voluminous. anions,. especially. hexaluorophosphate,. PF 6 − . (see,. e.g.,. [394,453,454,464,475,505]),.
tetraluoroborate,. BF 4 − . [410,415,486,494,510],. less. often. bis(triluoromethylsulfonyl)imide,. NTf 2 .
[127,454],. ethylsulfate,. Et-O-SO 3 − . [508],. or. bromide,. Br − . [468].. In. such. conigurations,. the. (RT)
ILs. of. choice. are. usually. declared. under. the. speciic. abbreviations,. when—in. the. order. of. the.

CILE

10 μA

CPE

(A)

(B)

[Fe(CN) 6 ] 3/4-

-0.50 -0.25 0 +0.25 +0.50 +0.75

E [ V ] vs. Ag/AgCl

FIGURE 2.7 Cyclic.voltammetry.of.the.[Fe(CN) 6 ] 3/4− .redox.pair.at.carbon.ionic.liquid.electrode.(CILE).and.
common.carbon.paste.electrode.(CPE)..(A).CILE:.0.3.g.graphite.powder.(“CR-5,”.Maziva.Tyn,.Czech.Rep.).+.
0.2.mL.BMIMPF6.(Sigma/Aldrich);.(B).CPE:.0.3.g.graphite.powder.+.0.2.mL.Nujol.oil.(Merck).. Experimental
conditions :.CV,.polarization.potential.from.−0.4.to.+0.8.V.vs..Ag/AgCl.and.back,.scan.rate:.25.mV.·.s −1 ;.0.25.M.
KCl;.c[K 4 Fe(CN) 6 ].=.0.005.mol.·.L −1 ..(Voltammograms.from.authors'.archives.)