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Fabrication and Surface Properties of
Composite Films of SAM/Pt/
ZnO/SiO2
Ke Xin Yao and Hua Chun Zeng*
Department of Chemical and Biomolecular Engineering, Faculty of
Engineering, National UniVersity of
Singapore, 10 Kent Ridge Crescent, Singapore 119260
ReceiVed August 5, 2008. ReVised Manuscript ReceiVed September
22, 2008
Advisor：Dr.S.C.Wang
Student：Shih-Kai Shu
Outline
Introduction
 Experimental Section
 Results and Discussion
 Conclusion
 Future work

Introduction


Through synthetic architecture and
functionalization with self-assembled
monolayers (SAMs), complex nanocomposite
films of SAM/Pt/ZnO/SiO2 have been facilely
prepared in this work.
The nanostructured films are highly uniform
and porous, showing a wide range of tunable
wettabilities from superhydrophilicity to
superhydrophobicity (water contact angles: 0°
to 170°).


Our approach offers synthetic flexibility in
controlling film architecture, surface
topography, coating texture, crystallite size,
and chemical composition of modifiers (e.g.,
SAMs derived from alkanethiols).
For example, wettability properties of the
nanocomposite films can be finely tuned with
both inorganic phase and organic phase.


Due to the presence of catalytic components
Pt/ZnO within the nanocomposites, surface
reactions of the organic modifiers can further
take place at room temperature and elevated
temperatures, which provides a means for
SAM formation and elimination.
Because the Pt/ZnO forms an excellent pair of
metal-semiconductors for photocatalysis, the
anchored SAMs can also be modified or
depleted by UV irradiation (i.e., the films
possess self-cleaning ability).

Potential applications of these
nanocomposite films have been
addressed. Our durability tests also
confirm that the films are thermally
stable and structurally robust in
modification-regeneration cycles.
Experimental Section
(Synthesis of Zinc Carbonate Hydroxide)
Zn(OH)2
Na2CO3
水熱法
滴入
Zn4CO3(OH)6 ·H2O
Zn(NO3)2
攪拌
Zn4CO3(OH)6 ·H2O
產生白色沉澱
在烘箱中乾燥 60OC 12Hr
(Synthesis of Zinc Hydroxide Netlike Film on Glass Slides)
(Preparation of Nanostructured ZnO/SiO2 Films)
(Coating of Pt Nanoparticles onto the ZnO/SiO2 Films)
H2SO4/H2O2 混合比例1：3
加熱 90OC 4Hr
取定量 0.15-0.25g 的 Zn4CO3(OH)6 ·H2O 置
於40ml去離子水中
水熱法 180ml 180OC 2-24Hr
Zn(OH)2/SiO2 composite films
加熱 400OC 1Hr
Nanostructured ZnO/SiO2 Films
自動塗佈Pt
coating current of 10-30 mA and a coating time
of 30-180 s
(Modification withDTand MPA)
上述製程所做的玻璃基板
浸泡在20ml的酒精中
1-dodecanethiol [DT; CH3(CH2)11SH, 98+%, Aldrich] or 3-mercaptopropionic
acid [MPA; HS(CH2)2COOH, 99%]
浸泡10-30min
使用酒精清洗多次
DT/Pt/ZnO/SiO2, MPA/Pt/ZnO/SiO2, and MPA-DT/Pt/ZnO/SiO2, respectively, in
our discussion
In the replacement experiment (by MPA), the as-prepared DT/Pt/ZnO/SiO2 films
were immersed in 20 mL of ethanolic solution of MPA (0.46 M) for 5 h.
(Removal of DT and MPA)
上述玻璃基板
在高溫爐中 300OC 2Hr
the thiol functional groups on the nanocomposite films can be
removed
由疏水性轉變為親
水性
也可以利用紫外光照射薄膜來達到以上效果
Results and Discussion




Growth process of
nanostructured Zn(OH)2
flakes on the surface of
SiO2 substrate (i.e.,
formation of
Zn(OH)2/SiO2; FESEM
images)
(a) 4 h
(b) 6 h
(c,d) 10 h (see Experimental
Section for details).


(a) Formation of ZnO/SiO2
films through thermal
conversion of Zn(OH)2/SiO2.
(b-d) Pt nanoparticles
deposited on ZnO/SiO2 films
(i.e., formation of
Pt/ZnO/SiO2 composite films;
the Pt nanoparticles in b and c
were deposited with a coating
current of 20 mA while those
in d were with a coating
current of 30 mA; sputtering
time ) 180 s, see Experimental
Section).



TEMimages of PtNPs
on the
detachedZnOflakes
(a) sputtering time 30 s.
(b) sputtering time 180 s
(current ) 20 mA, see
Experimental Section).





Contact angle
measurements for
DT/Pt/ZnO/SiO2
composite films
prepared with various
DT concentrations
(a) 0.3 mM, 100.5°
(b) 0.6 mM, 136.7°
(c) 1.3 mM, 168.2°
(d) 2.6 mM, 170.3°


(a)Contact angles of water
on different films of
SAM/Pt/ZnO/SiO2
prepared with DT and
MPA mixed solutions
(total thiol concentration )
1.3 mM; see Experimental
Section, also denoted as
MPA-DT/ZnO/SiO2)
(b) contact angles of
different water-ethanol
mixed solutions on the
film of DT/Pt/ZnO/SiO2.

Surface wettability
switching between
superhydrophobicity and
superhydrophilicity with
addition of SAM (i.e.,
DT/Pt/ZnO/SiO2) and
thermal removal of SAM
(i.e., regenerated
Pt/ZnO/SiO2).

Water droplet on a
DT/Pt/ZnO/SiO2
composite film with
various sliding
angles in a series of
turnover events
(photographs of a to
e).
Conclusion

In summary, using Zn4CO3(OH)6 ·H2O as a
starting precursor, nanostructured Zn(OH)2 can
be deposited on SiO2 substrates (i.e.,
Zn(OH)2/SiO2) under hydrothermal conditions,
which can be later thermally converted to ZnO
phase, producing metaloxide films of
ZnO/SiO2. The surface topographies of the
prepared Zn(OH)2/SiO2 and ZnO/SiO2 films
are highly uniform and porous.


Our water contact angle measurements show
that the as-prepared films of ZnO/SiO2 and
Pt/ZnO/SiO2 are superhydrophilic and
hydrophilic, respectively.
On the other hand, they can also be readmitted
to the Pt/ZnO/ SiO2 films in order to regenerate
desired surface functionalities. Our
nanocomposite films have been proved to be
thermally stable and structurally robust to
withstand all process/treatment cycleswithout
any deterioration in performance.
謝謝聆聽
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