Biomedical Engineering Reference
In-Depth Information
b
a
300 nm
300 nm
100 nm
1 µm
c
d
e
1 µm
(a) Various nonpatterned morphologies fabricated by GLAD
FIGURE 5.4
Various. morphologies. fabricated. by. GLAD.. (a). Various. nonpatterned. morphologies:. Ag. spheres. (a). and. tilt.
nanowires.(b).(unpublished.data);.Si.chevrons.(b).and.helical.posts.(c).(©.2007.Springer..Used.with.permission.);.
nanotubes. (d).(©.2007.American. Chemical. Society..Used.with.permission.)..(b).Various.patterned.nanostruc-
tures. fabricated. by. combining. GLAD. with. e-beam. lithography. (a,. b). (©. 2005. IEEE.. Used. with. permission.),.
nanosphere.lithography.(c),.and.photolithography.((d),.©.2007.American.Physical.Society..Used.with.permis-
sion..(e),.Unpublished.data.).
5.4 SurfaceBiofunctionalizationofPlasmonicNanomaterials
The.signiicant.advancement.in.the.controlled.nanofabrication.offers.researchers.the.capa-
bility.to.tune.plasmonic.properties.of.nanomaterials..However,.the.surface.of.plasmonic.
nanomaterials.(normally.gold.and.silver.NPs).cannot.interact.with.the.biological.analyte.
selectively..To.overcome.this.limit,.surface.functionalization.techniques.of.nanomaterials.
by. biological. recognition. elements. (bioreceptors. or. bioprobes). have. recently. been. devel-
oped.to.form.hybrid.nanomaterials.that.incorporate.the.highly.selective.catalytic.and.rec-
ognition.properties.of.biomaterials.such.as.enzymes.and.DNA,.with.the.highly.sensitive.
and.easily.tunable.electronic.and.photonic.features.of.plasmonic.nanomaterials.
7a,7c,84
Often,. NPs. synthesized. in. organic. medium. tend. to. aggregate. to. form. clusters. in. an.
aqueous.solution.that.is.generally.required.by.biomedical.applications..Therefore,.before.
they.can.be.modiied.by.any.bioreceptors,.an.additional.step,.called.water.solubilization,.
is.included,.during.which.colloidally.unstable.NPs.are.stabilized.in.an.aqueous.solution.
by. conjugating. with. hydrophilic. ligands.. The. ligands. could. be. ionic,. resulting. in. ionic.
stabilization.of.NPs.by.coulombic.repulsion..Another.way.to.stabilize.NPs.is.steric.stabili-
zation,.during.which.NP.aggregation.is.prevented.by.coating.with.a.physical.barrier..The.
