Figure 2.1. The process of forming a self-assembled monolayer. A
substrate is immersed into a dilute solution of a surface-active
material that adsorbs onto the surface and organizes via a selfassembly process. The result is a highly ordered and well-packed
molecular monolayer. (Adapted from Ref. 9 by permission of
American Chemical Society.)
Figure 2.2. Schematic representations of an alkanethiolate monolayer on gold.
The alkyl chains tilt at a 30 angle from the surface normal, maximizing the
inter-chain van der Waals interactions. The sulfur atoms are arranged in a
hexagonally close packed formation on the Au(111) surface. The X groups
terminating the alkyl chains provide chemical versatility at the monolayer
interface. (From Ref. 12 by permission of WILEY-VCH Verlag GmbH & Co.)
Figure 2.3. A schematic representation of Reed and Tour’s molecular
junction containing a benzene-1,4-dithiolate SAM that bridges two
proximal gold electrodes. (From Ref. 10 by permission of American
Association for the Advancement of Science.)
Figure 2.4. (a) Structures of the long and short linked cobalt
coordinated terpyridine thiols used as gate molecules. (b) A
topographic AFM image of the gold electrodes with a gap. (c) A
schematic representation of the assembled single atom transistor.
(From Ref. 11 by permission of Macmillan Magazines Ltd.)
Figure 2.5. (a) A schematic representation of the STM patterning of SAMs. (i) Normal STM
imaging of the SAM with tip bias Vb; (ii) Removal of SAM by applying a pulse Vp to the gold
substrate; (iii) The same as (ii) in solution of conjugated oligomers; (iv) insertion of conjugated
oligomers in the patterened sites. (b) STM image of dodecanthiol and conjugated oligomeric
patterned SAMs. (i) The STM image after consecutive pulsing at three different locations
indicating insertion of molecules (two peaks) and one pit without insertion. (ii) The same region
imaged a few minutes later showing adsorption into the remaining pit. (iii) A programmed pattern
consisting of circles tracing out a rectangle. (iv) The resulting image of the patterned dodecanthiol
SAM after chemisorption of the conjugated oligomers showing the produced rectangular frame.
(From Ref. 13 by permission of American Institute of Physics.)
Figure 2.6. Formation of molecular assemblies and corresponding STM images. (a)
STM image of diacyl 2,6-diaminopyridine (DAP) decanethiol binder inserted into a
surrounding decanthiol monolayer. (b) Image after binding the complementary
electroactive Fc-uracil showing an increase in the current-dependent apparent height
contrast. (c) “Erased” pattern after replacing the electroactive guest with a more
insulating dodecyl functionalized uracil. (From Ref. 14 by permission of American
Chemical Society.)
Figure 2.7. (a) Schematic
illustration of the CP procedure for
patterning an alkanethiol
(hexadecanethiol-HDT) on a flat
gold substrate. (b) Lateral force
microscope (LFM) images (at two
different magnifications) of a
patterned gold substrate with SAMs
terminated in chemically different
head groups (HDT-CH3 and16mercaptohexadecanoic acidCOOH). The image contrast results
from differences in frictional forces
between the surface and the probe
tip. Carboxylic acid terminated
SAM show high measured frictional
forces (light regions) and methyl
terminated SAM show low
measured frictional forces (dark
regions). (From Ref. 12 by
permission of WILEY-VCH Verlag
GmbH & Co.)
Figure 2.8. (a) Schematic representation of dippen nanolithography (DPN). A water meniscus
formed between AFM tip and the gold substrate
directs the thiol molecules onto the substrate. The
size of the water meniscus is controlled by the
relative humidity that in turn affects the overall
resolution of DPN. (b) LFM image of an array of
octadecanethiol dots on a gold surface generated
by holding an ODT-coated AFM tip in contact
with the surface for ca. 20 s. (c) LFM image of a
molecule-based grid consisting of eight lines 100
nm in width and 2 m in length. (From Ref. 17 by
permission of American Association for the
Advancement of Science.)
Figure 2.9. (a) Schematic representation of
the nanotransfer printing (nTP) procedure
to create gold patterns on Si substrates.
Optical micrographs of a gold pattern
formed by nTP on (b) a silica wafer, and
(c) a plastic sheet [organosilsesquioxane
modified poly(ethylene terephthalate)],
demonstrating the wide applicability of the
technique. (From Ref. 18 by permission of
American Chemical Society.)
Figure 2.10. (a) The solution-based procedure developed by Brust and
Schiffrin for synthesizing alkanethiolate stabilized gold nanoparticles.
(b) Schematic illustration showing the curved surface and different
regions of a nanopartice SAM.
Figure 2.11. Film growth by the
LBL technique: (a) Repeated
dipping of a charged-surface
slide into polyanion and
polycation solutions (steps 1 and
3, respectively) with
intermediate washing steps (2
and 4) results in alternate
deposition of the corresponding
polyions (b). (c) Chemical
structures of two typical
polyions: sulfonated polystyrene
(SPS) and poly(allylamine
hydrochloride) (PAH). ( From
Ref. 25 by permission of
American Association for the
Advancement of Science.)
Figure 2.12. LBL engineering of a light-emitting device: (a)
Multilayer of PPV/PMA performs similarly to PPV alone. (b)
Combined architecture of PPV/PMA multilayer on top of PPV/SPS
multilayer allows better hole-transport between the PPV/PMA and the
ITO anode, and results in enhanced electroluminescence. (From Ref.
32 by permission of American Institute of Physics.)
Figure 2.13. Electrostatic
assembly method for creation
of functionalized sensing
electrodes: alternating
deposition steps of (a)
negatively charged gold
nanoparticles, and (b)
positively charged host
molecules. Electrodes
modified in this fashion with
the host shown proved highly
sensitive for detection of
adrenaline (as the guest
molecule). (From Ref. 33 by
permission of WILEY-VCH
Verlag GmbH & Co.)
Figure 2.14. Polymer capsules: Consecutive adsorption of positively (grey) and
negatively (black) charged polyelectrolytes onto negatively charged particles (a,b) and
subsequent decomposition of the colloidal core (c,d) yields a suspension of hollow
polyelectrolyte capsules (e, TEM image). Addition of crystalline molecules bearing
charged groups (f) and changing the ionic or solvent composition drives the molecules
into the capsules, where nucleation centers form and crystals are grown. (h) TEM image
of a volume-confined crystal of 6-carboxyfluorescein grown inside a capsule that was
based on discocyte biocolloid. (From Refs. 35 and 37 by permission of WILEY-VCH
Verlag GmbH & Co.)
Figure 2.15. (a) DNA-directed assembly strategy
for preparation of network materials from two
different-sized oligonucleotide-functionalized
nanoparticles. TEM images of: (b) Aggregate
formed by linking 8-nm and 31-nm gold
nanoparticles, (c) “Satellite” structure obtained in
120-fold excess of the 8-nm colloids. (From
Inorg. Chem. 39(11), 2258-2272 (2000) by
permission of American Chemical Society and
Ref. 41 by permission of American Chemical
Society.)
Figure 2.16. (a) Multiple
recognition events are
translated into nanoparticle
aggregate formation. (b)
TEM images of spherical
aggregates formed at
ambient temperature and (c)
at –20 °C, showing thermal
control over aggregate size.
(From Ref. 43 by
permission of Macmillan
Magazines Ltd.)
Figure 2.17. Schematic illustration of the synthetic routes to
homopolymers, random copolymers, and block copolymers.
Figure 2.18. (a) Fundamental differences in phase behavior of different
polymers: A blend of two incompatible homopolymer separates into distinct
phases on a large scale (left), whereas block copolymers microphase separate
into periodic domains on the scale of a single polymer strand (right). (b) Basic
morphologies obtained by different block copolymer compositions.
Figure 2.19. Metal nanowire formation using a block copolymer template:
Shown are TEM images of: (a) Gold metal vapor-deposited onto a preformed
PS-b-PMMA template. (b) After annealing at 180 °C for 1 min., gold
nanoparticles segregate selectively to the PS domains and form chains. (c)
Repeated deposition and short-time annealing increases the metal loading,
forming continuous conductive nanowires. (From Ref. 54 by permission of
Macmillan Magazines Ltd.)
Figure 2.20. (a) Schematic of the unit cell of the double gyroid morphology
(space group Ia3d) found in certain triblock copolymers of specific block
compositions, where the minority component forms three-dimensionally
continuous networks of cylinder-like connectors. Selective removal of the PI
component of PI-b-P(PMDSS)-b-PI yields: (b) A porous ceramic matrix (for a
24/100/26 kg mole-1 polymer composition, where the PI forms networks), or
(c) Silicon oxicarbide strut networks (for a 44/168/112 kg mole-1 composition,
where the PI forms the matrix). AFM height images (maximum height 10 nm,
high regions appear bright); insets: computer simulations of corresponding
volume-rendered surfaces in the double gyroid unit cell. (From Ref. 55 by
permission of American Association for the Advancement of Science. )
Figure 2.21. Lithographic mask
fabrication from PS-b-PB templates
with spherical PB domains. Spherical
voids are created by ozonolysis
(which degrades the PB into water
dispersible fragments), while OsO4
staining increases the PB domain
resistance toward etching, and thus
negative or positive etching masks are
produced. Shown are corresponding
TEM images: top: Negative/positive
masks that were used to create
holes/lines (respectively), where light
spots in the left image are voids and
dark lines in the right image are
stained PB domains; bottom:
Transferred patterns on the silicon
nitride substrates, where light regions
in the left image are ~15-nm-deep
etched-out holes in the substrate, and
dark regions in the right image are
~15-nm-thick ridges in the substrate,
which were protected from etching.
(From Ref. 56 by permission of
American Association for the
Advancement of Science.)
Figure 2.22. High-density nanowire fabrication in a polymer matrix. (a) Array of hexagonally-packed cylinders aligned
normal to the substrate is obtained by annealing an asymmetric diblock copolymer above its glass transition under an
applied electric field. (b) Cross-sectional TEM image of an 800-nm thick film of PS-b-PMMA on gold after annealing in an
electric field of 25 V/m reveals that the PMMA cylinders penetrate all the way through the film. (c) The minor
component is degraded and removed, leaving a porous film. (d) Field emission scanning electron microgram (FE-SEM)
of PS-b-PMMA thin film after removal of the PMMA cylindrical domains (cross-sectional view). (e) Metal nanowires are
grown inside the pores by electrodeposition. (f) SEM image of a fracture surface showing cobalt nanowires partially
filling the pores in the block copolymer template. (From Ref. 58 by permission of WILEY-VCH Verlag GmbH & Co and
Ref. 59 by permission of American Association for the Advancement of Science.)