Chemistry Reference
In-Depth Information
solar energy conversion or electronic device manufacture; one of the earliest
reports of linking QDs to a polymer with a pendant linking functionality,
[(norbornenylmethoxy-carbonyl) biphenyl-yl-
tert
-butylphenyl oxadiazole]
150
[norbornene-2-yl-CH
2
O(CH
2
)
5
P(oct)
2
]
10
, was carried out to allow fabrication
of a light-emitting device.
211
We will also concentrate on polymers that have
been added a
er nanoparticle synthesis, to replace the ligands described
above, although we appreciate that some polymers are included during
synthesis and are an inherent part of the resulting materials, such as the
addition of block copolymers during the synthesis of Co particles
212
or
conjugated polymers such as poly(3-hexylthiophene) which have been used
instead of TOPO in the synthesis of CdSe QDs, potentially allowing charge
transfer between the polymer and the nanoparticle without hindrance
from a native capping agent.
213
Closely related to this is the inclusion of
[(4-bromophenyl)methyl]dioctylphosphine oxide as a capping agent during
the synthesis of CdSe, which then facilitated the gra
d
n
1
y
4
n
g
|
6
ing of a conjugated
polymer onto the capping agent by a palladium-catalysed Heck coupling.
214
The resulting composites have since found use in photovoltaic devices.
215
Other reports that are worthy of note include the use of poly(
N
-isopropyl-
co
-
t
-
butylacrylamide) as an
in situ
reaction capping agent for cobalt and Fe
2
O
3
.
216
The polymer has a sharp coil-to-globule phase transition at a low critical
solution temperature below which the polymer is water-soluble but above
which it is organically soluble. Nanoparticles can therefore be prepared by
the thermolysis of metal carbonyl complexes at relatively high temperatures
in organic solvents, yet yields particles that are water-soluble on cooling and
hence require no further phase-transfer procedures. Related to this is the use
of (poly-4-vinylpyridine-
co
-acrylamidoethylamine-
co
-polyethylene-glycol-
co
-
polyethyeleneglycolic acid) which has three pendant groups
.
—
amine, PEGy-
lated hydroxy and a PEGylated carboxylic acid
as an
in situ
stabiliser for the
synthesis of amphiphilic Fe
3
O
4
nanoparticles.
217
The chemistry does not necessarily need to be complicated; simple poly-
mers, such as PVP and poly(ethylenimine) (PEI) have been used to replace
oleic acid and OAm on magnetic nanoparticles such as FePt at room
temperature changing the solubility in di
—
ering solvents which allowed
controllable self-assembly on a substrate.
218
This use of simple polymers
such as PEI has been extended to induce phase transfer in organically soluble
QDs, using the pendant amine groups both as attachment points to the
particles, and potentially as linking points to biological entities. The phase
transfer appeared to induce photo-oxidation, but the particles in water
appeared stable if stored in the dark.
219
PEI has also been used as a transfer
agent when linked to PEG, which provided a branched capping agent with
the amine linking functionalities supplied by PEI, and the bene
ts of the
pendant long-chain PEG. This work was also extended to link PEG to
diethylenetriamine (DETA) giving a linear capping agent again with amine
binding units and a pendant PEG group.
220
PEG
was used to phase-transfer QDs, chain-like aggregates were observed leading
to an increased hydrodynamic radius. A triblock polymer based on PEI,
Interestingly, when DETA
-
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