March 10, 2011 / Vol. 9, No. 3 / CHINESE OPTICS LETTERS 032401-1
Optical property of nanocomposite of mesoporous silica
thin films incorporated with gold nanoparticles
Jingyue Fang (方方方靖靖靖岳岳岳)
1∗
, Xueao Zhang (张张张学学学骜骜骜)
2
, Shiqiao Qin (秦秦秦石石石乔乔乔)
2
, and Shengli Chang (常常常胜胜胜利利利)
2
1
College of Opto electric Science and Technology, National University of Defense Technology,
Changsha 410073, China
2
College of Science, National University of Defense Technology, Changsha 410073, China
∗
Corresp onding author: fjy nudt@yahoo.com.cn
Received August 24, 2010; accepted Novemb er 15, 2010; posted online February 21, 2011
Amino-functionalized mesoporous silica thin films (MTFs) are produced using surface active agent F127,
and then gold nanoparticles are introduced into the pore channels to prepare the Au/SiO
2
nano compos-
ite. After assembling the gold, the amino-functionalized MTF undergoes some shrinkage but remains a
p eriodic structure as demonstrated by X-ray diffraction (XRD) patterns. The nanocomposite shows an
acute characteristic diffraction peak assigned to (111) plane of the face-centered-cubic structure of gold,
indicating that gold nanoparticles crystallize well and grow in a preferred orientation in the p ore channels.
The surface plasma resonance (SPR) absorption peak near 570 nm undergoes a red-shift accompanied by
a strengthening of intensity when HAuCl
4
is used to react with the amino groups on the internal pore
surfaces for 4, 6, and 8 h. The simulative results are consistent with the experimental ones shows that the
absorption property of the Au/SiO
2
nano composite is influenced by the dipping time, which affects the
size and volume fraction of emb edded gold nanoparticles.
OCIS co des: 240.0310, 310.6860, 240.6680.
doi: 10.3788/COL201109.032401.
Nanofabrication includes two approaches: the top-down
approach with ultrahigh resolution, developed from op-
tical lithography, and the bottom-up approach using
biochemical effects to recombine or assemble molecules
or atoms. Both electron beam lithography (EBL) and ion
beam lithography (IBL) transfer patterns to substrates
via high energy beams
[1−4]
, while scanning probe optical
lithography (SPOL) draws support from the effects of
tunneling current, mechanical force, or near-field optical
wave existing between the probe and sample to carve
patterns
[5−8]
. EBL, IBL, and SPOL are top-down tech-
nologies. Using materials with a periodic array of islands
or holes as templates, and using ordered physical pro-
cesses or chemical reactions to structure nanomaterials
are called bottom-up methods
[9−11]
. Solid porous ma-
trices such as mesoporous silica thin films (MTFs) have
large surface areas (up to ca. 1500 m
2
/g), high pore
volumes (up to ca. 1.5 cm
3
/g), uniform nanopores of
tunable sizes (2 – 50 nm), different shapes (cylindrical
and cage-like), and mesostructures, thereby providing
considerable opportunities in the synthesis of nanostruc-
tural materials. Because the pore size of MTF can be
controlled using different surfactants, they can be used
as templates for the synthesis of metallic nanoparticles
with controlled size and morphology. To date, the fab-
rication of MTFs incorporated with gold nanoparticles
have been reported by some groups
[12−14]
. However, few
studies have been conducted to analyze the nanocompos-
ite’s optical properties influenced by the size and volume
fraction of the embedded gold nanoparticles.
Recently, optical properties based mainly on the
surface plasma resonance (SPR) of noble metal par-
ticles have attracted considerable interest because of
their potential uses in a wide range of technological
applications
[10,15,16]
. Here, we present the preparation
of a Au/SiO
2
nanocomposite by the down-up route, and
analyze how dipping time influences the SPR absorption
properties of the Au/SiO
2
nanocomposite.
The functionalized silica films were deposited on a
glass substrate by co-condensation of tetraethoxysilane
(TEOS) and 3-aminopropyltriethoxysilane (APTES) in
the presence of Pluronic EO
106
PO
70
EO
106
(F127) un-
der acidic conditions. In the synthesis, TEOS (98%,
Aldrich), ethanol, deionized water, and dilute HCl
(0.1 mol) were refluxed at 60
◦
C for 1 h. The solu-
tion was cooled to room temperature and diluted with
ethanol followed by further addition of deionized water
and concentrated HCl (37%). To this solution, APTES
(99%, Acros) was added slowly with vigorous stirring at
0
◦
C. Finally, F127 was dissolved in ethanol and added to
the prehydrolyzed solution. The final reactant molar ra-
tios were: 0.9 TEOS: 0.1 APTES: 0.15 HCl: 20 C
2
H
5
OH:
5 H
2
O: 0.006 F127. The final solution was stirred for 1 h
prior to dip-coating on glass substrates at the withdraw-
ing rate of 16 cm/min. After the as-deposited thin films
were dried in air at ambient temp erature for 24 h, they
were heat-treated in air at 120
◦
C for 24 h and complete
siloxane condensation. The F127 surfactant was removed
from the thin films by extraction with hot ethanol under
reflux for 24 h, and the amino-functionalized MTFs with
open pore structures were obtained
[17,18]
.
A standard HAuCl
4
solution with a concentration of
0.05 mol was prepared by dissolving HAuCl
4
·4H
2
O pow-
der with deionized water. The three pieces of glass that
deposited functionalized mesoporous silica films were
placed in the HAuCl
4
solution for 4, 6, and 8 h, respec-
tively, followed by rinsing with water for 5 min. The
samples were rinsed with deionized water and dried in
1671-7694/2011/032401(4)
c
° 2011 Chinese Optics Letters