13 Creation of Organic-Metal Hybridized Nanocrystals …
265
thin film. There are essentially the two main reasons for reduction of (T + T )/T.
One is the absorption of incident pump beam by deposited Au NPs (Fig. 13.9b),
and the other scattering effect in the hybridized PDA NCFs. In other words, the
deposition amount (or coverage ratio) of Au NPs was still excessive even in the case
of hybridized PDA NCFs having lower coverage ratio. This fact would provide an
important suggestion and guideline for material design of hybridized PDA NCFs.
Probably, an extremely small amount of deposited Au NPs is enough to enhance
χ
(3) (ω) value, though no LSPR peak of Au NPs apparently appears in the extinction
spectrum. In a word, one should control the deposition number and size of Au NPs,
and avoid the aggregation by suitably selecting water-soluble polymers, improving
surface modification, and by developing the fabrication processes.
13.4 Conclusions
Aiming at optoelectronic and/or photonic device applications, π-conjugated organic
molecules and polymers are the promising NLO materials having high χ
(3) (ω) value
and rapid optical response. Especially, one-dimensional π-conjugated polymer, PDA,
is of much interest, which is produced by solid-state polymerization in a crystal state.
Morphologically-controlled PDA, that is, PDA NCFs are of great possible to fabricate
the corresponding solid thin films, which are an assembled PDA NCFs and regarded
as a kind of pseudo-bulk crystal of PDA. However, hybridization of PDA NCFs with
noble metal NPs should be needed so as to further enhance χ
(3) (ω) value. So, the basic
fabrication processes, technical issues, and characterization have been investigated
in details in this chapter.
The resulting core–shell-type hybridized PDA NCFs with Au NPs have silica
layer as a dielectric layer between PDA NCFs as a core and Au NPs as s shell, which
layer is important and effective for the purpose of controlling and tuning LSPR effect
from Au NPs. Namely, the silica-coating conditions of PDA NCFs were optimized
experimentally. Furthermore, the surface of silica layer was chemically modified by
introducing amino-function moiety, and then the deposition efficiency of Au NPs
was improved considerably.
The transient transmission spectra for PDA NCFs and hybridized PDA NCFs were
measured successfully with the pump-probe method. These results and complex
refractive index obtained by spectroscopic ellipsometry are fundamental data to
preciously evaluate the wavelength dispersion of χ
(3) (ω). It has become apparent
that the deposition amounts of Au NPs were still excessive in the case of hybridized
PDA NCFs. One should properly reduce the deposition amounts in the near future. To
do so, “polydopamine” will be preferably used at the next objective stage [40], instead
of amino-terminate silica layer. In addition, it should be necessary to produce welldefined solid thin films of hybridized PDA NCFs with too much low scattering loss
by suitably selecting water-soluble polymers, in addition to PVA, and by optimizing
the preparation processes.
265
thin film. There are essentially the two main reasons for reduction of (T + T )/T.
One is the absorption of incident pump beam by deposited Au NPs (Fig. 13.9b),
and the other scattering effect in the hybridized PDA NCFs. In other words, the
deposition amount (or coverage ratio) of Au NPs was still excessive even in the case
of hybridized PDA NCFs having lower coverage ratio. This fact would provide an
important suggestion and guideline for material design of hybridized PDA NCFs.
Probably, an extremely small amount of deposited Au NPs is enough to enhance
χ
(3) (ω) value, though no LSPR peak of Au NPs apparently appears in the extinction
spectrum. In a word, one should control the deposition number and size of Au NPs,
and avoid the aggregation by suitably selecting water-soluble polymers, improving
surface modification, and by developing the fabrication processes.
13.4 Conclusions
Aiming at optoelectronic and/or photonic device applications, π-conjugated organic
molecules and polymers are the promising NLO materials having high χ
(3) (ω) value
and rapid optical response. Especially, one-dimensional π-conjugated polymer, PDA,
is of much interest, which is produced by solid-state polymerization in a crystal state.
Morphologically-controlled PDA, that is, PDA NCFs are of great possible to fabricate
the corresponding solid thin films, which are an assembled PDA NCFs and regarded
as a kind of pseudo-bulk crystal of PDA. However, hybridization of PDA NCFs with
noble metal NPs should be needed so as to further enhance χ
(3) (ω) value. So, the basic
fabrication processes, technical issues, and characterization have been investigated
in details in this chapter.
The resulting core–shell-type hybridized PDA NCFs with Au NPs have silica
layer as a dielectric layer between PDA NCFs as a core and Au NPs as s shell, which
layer is important and effective for the purpose of controlling and tuning LSPR effect
from Au NPs. Namely, the silica-coating conditions of PDA NCFs were optimized
experimentally. Furthermore, the surface of silica layer was chemically modified by
introducing amino-function moiety, and then the deposition efficiency of Au NPs
was improved considerably.
The transient transmission spectra for PDA NCFs and hybridized PDA NCFs were
measured successfully with the pump-probe method. These results and complex
refractive index obtained by spectroscopic ellipsometry are fundamental data to
preciously evaluate the wavelength dispersion of χ
(3) (ω). It has become apparent
that the deposition amounts of Au NPs were still excessive in the case of hybridized
PDA NCFs. One should properly reduce the deposition amounts in the near future. To
do so, “polydopamine” will be preferably used at the next objective stage [40], instead
of amino-terminate silica layer. In addition, it should be necessary to produce welldefined solid thin films of hybridized PDA NCFs with too much low scattering loss
by suitably selecting water-soluble polymers, in addition to PVA, and by optimizing
the preparation processes.