212 9 Optical Properties
Figure 9.36 Luminescence intensity of ZrO 2 /PMMA nanocomposites as a function of the
inverse particle size following Eq. (9.10). The proportionality with
1
d
indicates a proportionality
of the intensity to the surface of the particles [6].
0
0.1
0.2
0.3
0.4
0.5
(particle diameter)
–1 [nm
–1
]
0
2
4
6
8
10
luminescence
intensity
[a.u.]
For a given quantity of material, the number of particles is proportional to d
−3 ,
the surface of one particle is proportional to d
2 ; therefore, at the surface this quantity of particulate matter is proportional d
−1 . Therefore, Eq. (9.10) says that the
luminescence intensity is directly proportional to the surface area of the particles.
This direct proportionality between luminescence intensity and the particle surface
is an additional proof of the idea that the ceramic/polymer interface is the source
of the luminescence. Figure 9.36 shows diminishing small luminescence intensities for particle sizes larger than ca. 10 nm. Certainly, this is why this phenomenon
was discovered with nanocomposites and not earlier.
The next question relates to the particle-size dependency of the emitted wavelength λ at the maximum. The experimental results are depicted in Figure 9.37.
Mathematical fitting leads to the relation
1 1
0
3
λ λ
=
+ bd .
(9.11)
This relation allows rectification on the coordinate system with the
1
λ
as abscissa
and d
3 as ordinate. The quantities λ 0 and b are fitting parameters; d is the diameter
of the ceramic core of the nanocomposite.
Analyzing the dependencies depicted in Figure 9.37 and based on Eq. (9.11),
one sees that the wavelength of the emitted light increases with increasing particle
diameter. The sign of the exponent of particle diameter is different from that of
any other described mechanisms. This means that there is a blueshift with increasing particle diameter.
Similarly to the blueshift with decreasing particle size, a reduction of the
line width at half-maximum intensity with decreasing particle size was observed
[6, 15].
Figure 9.36 Luminescence intensity of ZrO 2 /PMMA nanocomposites as a function of the
inverse particle size following Eq. (9.10). The proportionality with
1
d
indicates a proportionality
of the intensity to the surface of the particles [6].
0
0.1
0.2
0.3
0.4
0.5
(particle diameter)
–1 [nm
–1
]
0
2
4
6
8
10
luminescence
intensity
[a.u.]
For a given quantity of material, the number of particles is proportional to d
−3 ,
the surface of one particle is proportional to d
2 ; therefore, at the surface this quantity of particulate matter is proportional d
−1 . Therefore, Eq. (9.10) says that the
luminescence intensity is directly proportional to the surface area of the particles.
This direct proportionality between luminescence intensity and the particle surface
is an additional proof of the idea that the ceramic/polymer interface is the source
of the luminescence. Figure 9.36 shows diminishing small luminescence intensities for particle sizes larger than ca. 10 nm. Certainly, this is why this phenomenon
was discovered with nanocomposites and not earlier.
The next question relates to the particle-size dependency of the emitted wavelength λ at the maximum. The experimental results are depicted in Figure 9.37.
Mathematical fitting leads to the relation
1 1
0
3
λ λ
=
+ bd .
(9.11)
This relation allows rectification on the coordinate system with the
1
λ
as abscissa
and d
3 as ordinate. The quantities λ 0 and b are fitting parameters; d is the diameter
of the ceramic core of the nanocomposite.
Analyzing the dependencies depicted in Figure 9.37 and based on Eq. (9.11),
one sees that the wavelength of the emitted light increases with increasing particle
diameter. The sign of the exponent of particle diameter is different from that of
any other described mechanisms. This means that there is a blueshift with increasing particle diameter.
Similarly to the blueshift with decreasing particle size, a reduction of the
line width at half-maximum intensity with decreasing particle size was observed
[6, 15].