Dalton Transactions
Paper
factor of ten, the intermolecular distances between the chro-
mophores on the surface should clearly be in the range of
nanometres rather than the 4.4 Å observed for, e.g., self-
assembled monolayers of alkyl silanes.39 Nevertheless, aggre-
gation of the dye molecules via e.g. π-bonding interactions
cannot be ruled out completely. The fluorescence emissions of
the coated particles, which have qualitatively been observed to
be weaker than those of the neat chromophores in solution,19
may therefore be influenced not only by the surface polarity
and the chromophore structure but also by concentration-
dependent effects inside the organic thin film. It will be of
future interest to evaluate the correlation between different
grafting conditions, the amount of heterogenised organic
material, and the luminescence intensities of the hybrid
compounds.
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M. K. Müller, B. Erb, Y. Sun, L. J. Gooßen, M. Gerhards and
W. R. Thiel, Eur. J. Org. Chem., 2012, 2142.
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Solvents: Physical Properties and Methods of Purification,
Wiley, 4th edn, 1986.
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We have presented an easy and largely applicable route
towards fluorescent phosphonates for surface modification of
transition and main group metal oxides. Due to their binding
properties, these phosphonates are especially suitable for graft-
ing on ZrO2 under very mild conditions. It has been demon-
strated how the photoluminescence of the organic species
could be used to evaluate the interaction with the ceramic sub-
strate using solid state emission spectroscopy. The xylene
derived phosphonate 2e and, to a certain extent, the triphenyl-
amino bridged phosphonate 3e have proven to be useful in the
fluorescence labelling of bulk zirconia and alumina surfaces.
We may point out that, in order to select a photoluminescent
marker for a given ceramic surface, one has to take into
account the polarity and partial charge of the surface as much
as the structure of the fluorophore, which all may strongly
affect the performance in analytical and sensing applications.
The reproducibly high yields in the synthesis of the new phos-
phonates and their facile heterogenisation will enable us to
use them for a variety of applications, including tracing of
enzyme separation using core–shell nanoparticles. With
respect to our UV/Vis studies on thiophene substituted ary-
lenes, we are currently making efforts to make similar phos-
phonates available, which may carry a variety of functional
groups suitable for analytic purposes. Moreover, it will be our
goal to increase the loading of the ceramic particles by using
more strongly binding free phosphonic acids. Once we achieve
a reproducible grafting of the acids as well, we will further
investigate concentration-dependent emission properties and
surface-related quenching effects in order to tailor our coatings
and thus improve their performance in defined applications.
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24 A. F. Mironov, V. D. Rumyantseva and O. N. Ponamoreva,
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25 B. H. Lipshutz, S. K. Kim, P. Mollard, P. A. Blomgren and
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Notes and references
1 R. Hofer, M. Textor and N. D. Spencer, Langmuir, 2001, 17, 26 P. J. Daughenbaugh and J. B. Allison, J. Am. Chem. Soc.,
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1929, 51, 3665.
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Dalton Trans., 2013, 42, 6344–6352 | 6351