Instrumental Measurements with Carbon Paste Electrodes, Sensors, and Detectors - Electroanalysis with Carbon Paste Electrodes - page 148

the.effect.of.surfactant.incorporation.into.carbon.paste.upon.the.coverage.degree.of.graphite.particles.
[243,1639,1661],.or.the.generation.of.mercury.ilms.onto.HgO-modiied.CPEs.[617].
SEM.observations.were.irst.devoted.to.the.analysis.of.the.surface.state.of.unmodiied.electrodes.
to.characterize.the.relations.between.the.quality.and.mutual.ratio.of.both.main.carbon.paste.con-
stituents.and.the.resulting.electrochemical.behavior.of.CPEs..In.spite.of.the.heterogeneous.nature.
of.the.matrix,.some.“models”.have.been.proposed.(see.[175].and.references.therein),.which.were.
mainly.based.on.the.inluence.of.the.carbon-to-binder.ratio,.considering.two.limiting.situations.and.
one.intermediary.case:.(L1).at.higher.contents.of.binder,.essentially.all.graphite.particles.are.coated.
with.a.thin.ilm.of.liquid;.(Im).as.the.content.of.binder.decreases,.some.“empty.spaces”.appear.that.
are.attributed.to.expansive.air/oxygen.gaps.inside.the.paste;.(L2).an.extreme.situation.when.carbon.
paste.contains.only.a.minimal.amount.of.pasting.liquid.yet.suficient.to.stick.the.carbon.particles.
together.(the.so-called.“dry”.limit;.see.also.discussions.in.Chapters.2.and.3,.as.well.as.Figure.2.4).
The.usefulness.of.SEM.imaging.is.documented.in.Figure.6.13.and.in.its.legend,.which.speciies.
the.individual.changes.in.the.overall.pattern.of.all.the.bismuth.ilm.microstructures..Here,.it.could.be.

5 μm

5 μm

(A) (B)

5 μm 5 μm

(C) (D)

FIGURE 6.13 Three. phases. of. the. bismuth. ilm. microstructure. and. the. respective. changes. in. the. overall.
morphology. in. dependence. of. the. deposition. intensity.. SEM. images.. (A). CP. substrate:. the. surface-micro-
structure. pattern. of. carbon. paste. (CP). made. of. silicone. oil. and. used. for. electrolytic. deposition. of. bismuth.
ilms;.(B).BiF,.phase.I:.unconsolidated.assembly.of.tiny.crystallites.forming.a.bismuth.ilm.(BiF,.noticeable.as.
small.whitish.objects);.(C).BiF,.phase.II:.initial.crystalline.structure.growing.from.small.agreggates;.(D) BiF,.
phase. III:. the. fully. developed. crystals. with. distinct. cross-chaining. growth. and. the. spruce-branch. structure..
Experimental parameters :. Deposition. conditions:. 0.05.M. HCl. +. 0.15.M. KCl. (pH. 2.5),. E DEP . =. −1.0.V. vs.. Ag/
AgCl.(I-III),. t DEP .=.30.s.(I),. 60.s. (II),. and. 180.s. (III);. scanning. electron. microscope. (model. “JSM-5500LV”;.
JEOL,.Japan),.magniication.used:.1:3000..(Unpublished.images.from.authors'.archives;.for.further.details,.see.
Švancara,.I..et.al.,.Microscopic.studies.with.bismuth-modiied.carbon.paste.electrodes:.Morphological.trans-
formations.of.bismuth.microstructures.and.related.observations,.in. Sensing in Electroanalysis ,.Vol..2,.Eds..
K..Vytras.and.K..Kalcher,.University.of.Pardubice,.Pardubice,.Czech.Republic,.2007,.pp..35-58;.Švancara,.I..
et al.,. Electroanalysis ,.17,.120,.2005.)