on these results, nanocomposite particles consisting of an oxide core bound to an mPMMA may be described as one huge molecule, RÀ À(CÀ À
À ÀO)À ÀOÀ À(oxide particle).
The structural formula of methyl methacrylate (MMA) and a model of the connection of the polymer to the particle are shown in Figure 9.23, together with the
position where the CH 3 group is cut off.
Figure 9.22 Photoluminescence intensity of oxide/PMMA nanocomposites as a function of
absorbance at 325 nm, the excitation wavelength. Note the increase in photoluminescence
intensity with increasing absorbance at the excitation wavelength.
Figure 9.23 Model of the attachment and
polymerization of MMA molecules at the
surface of oxide particles, according to Weng
et al. [15] and Meyer et al. [16]. The PMMA
molecules touching the oxide surface are bound
with an ester-like linkage to the surface; as
shown in the insert, the methyl group (CH 3 )
adjacent to an oxygen ion is cut off. An oxide
particle coated with PMMA may be described as
one huge molecule, RÀ À(CÀ À
À ÀO)À ÀOÀ À(oxide
particle). The carbonyl groups (CÀ À
À ÀO) directly at
the surface are essential for luminescence
phenomena.
9.4 Quantum Dots and Other Lumophores j227