Biomedical Engineering Reference
In-Depth Information
A
B
+5V
C
-5V
2
1
0
-1
-2
2
1
0
-1
-2
9
6
3
79 nm
79 nm
79 nm
50
150 250
X(nm)
0
100 200
0
100 200
X(nm)
X(nm)
FIGURE 1.8
(See.color.insert.).(A).Topographic.AFM.image.of.6His-SP1-GNP.chain.formation.on.mica.(insets.shows.a.cross-
section. on. the. chain).. (B. and. C). EFM. at. positive. and. negative. bias. voltage. of. 6His-SP1-GNP. chain. on. mica,.
showing.clear.polarization.of.the.embedded.GNPs.(no.signal.is.observed.at.0.V)..The.insets.show.the.signal.
strength..From.Medalsy.et.al..2008.
existence.of.the.GNP.in.the.6His-SP1-GNP.chain.was.conirmed.by.EFM.measurements.in.
both.positive.and.negative.bias.voltages,.as.shown.in.Figure 1.8B.and.C,.respectively..From.
the.dark.signal.obtained.for.both.positive.and.negative.bias.voltage.we.can.conclude.that.
polarizable.objects,.i.e.,.the.GNPs,.are.positioned.within.the.tube.
Measurements. of. the. physical. strength. of. the. 6His-SP1-GNP. chain. were. performed.
on. a. highly. oriented. polarized. graphite. (HOPG). surface. using. the. AFM. tip. in. contact.
mode.. After. deposition. of. 6His-SP1-GNP. solution. on. HOPG. short. tubes. were. observed.
(Figure 1.9A).
As.can.be.seen.in.Figure 1.9,.the.formation.of.tubes.on.HOPG.is.evident..The.height.and.
structure.of.the.tubes.are.9.nm,.as.expected.(Figure 1.9B)..By.using.contact.mode.AFM.on.
a.single.line,.we.were.able.to.exert.gentle.lateral.sheer.forces.in.the.direction.of.movement.
of.the.cantilever.on.the.side.of.the.tube.by.the.AFM.tip.(arrow.in.Figure 1.9B)..Because.of.
the.scratch,.the.tube.was.moved.but.not.broken,.as.seen.in.Figure 1.9C..The.resistivity.of.
the.tube.to.sheer.forces.shows.that.strong.attachment.exists.between.the.chain.elements.
A
B
C
8
6
4
2
8
6
4
2
0 0.5
1
X(nm)
1.5 2
0 100
200
X(nm)
300 400
80 nm
80 nm
400 nm
FIGURE 1.9
(See.color.insert.).6His-SP1-GNP.tube.structures.on.HOPG..(A).Large-area.topographic.imaging.shows.multiple.
tubes..(B).A.single.tube.with.a.height. of.~9.nm.(dashed. line)..(C). With.contact.mode. AFM,. a.single.line.was.
scratched,.thus.applying.lateral.sheer.force.on.the.tube.(the.arrow.in.B)..The.tube.was.moved.and.bent.but.not.
torn,.indicating.the.physical.strength.of.the.structure.
