was then subsequently quaternised with p-iodobenzyltriisopropoxy-
silane. The bridged silsesquioxane 5 was fully characterized by
1H, 31P, 29Si, 13C NMR spectroscopies, and elemental analysis.
Finally, isopropoxide/ethoxide exchange was achieved just before
reacting, yielding 1.
The multifunctional material was prepared by co-hydrolysis
and polycondensation of 1, tetraethylorthosilicate (TEOS) and
3-mercaptopropyltriethoxysilane (MPTE) in lyotropic liquid
crystal medium. Indeed, as the bridging organic groups are rather
large and flexible, i.e. do not present structural rigidity required to
order the material, high surfactant concentration of the non ionic
triblock copolymers P123 was preferred. Furthermore, such
conditions allow obtaining a monolith, which could be an
advantage for applications. The procedure was the following:
0.70 g of EO20PO70EO20 was dissolved in 1.7 mL of an aqueous
HCl solution (pH 1.5). 3.25 g (15.62 mmol) of TEOS was then
added. The mixture was stirred until a clear solution was obtained.
0.31 g (1.28 mmol) of MPTE was added and 30 min later, 0.17 g
(0.17 mmol) of 1 was put into the clear solution obtained. When
the mixture was clear, ethanol was removed under vacuum. The
monolith was kept 24 h at room temperature and then
hydrothermally treated at 95 uC for 20 h. The solid was recovered
by hot ethanol extraction in a Soxhlet apparatus for 24 h, dried
and washed as previously described to yield 1.40 g of an orange
Fig. 2 TEM image of material S1,SHAu. Scale bar 5 100 nm.
(7.63 nm) was estimated from the d100 spacing and the mean pore
size. It is worth noting that this value is large compared to the
mean thickness of the pore walls for silica containing functional
groups only in the channel pores and prepared in the presence of
P123 as a template.16–18 That is a good indication of the location of
the bridged azobenzene groups in the framework.
The solid state 31P NMR spectrum of S1,SH displays one signal
at 22.48 ppm proving that the phosphonium group was not
modified during the sol–gel process. 29Si CP-MAS NMR spectrum
exhibits a signal centered at 265.4 ppm, attributed to T3 resonance
in addition to an intense peak at 2100.7 ppm and another one at
2108.0 ppm, respectively, assigned to Q3 and Q4 substructures.
Gold(0) nanoparticles were prepared according to a procedure,
which we adjusted previously on SBA-15 type materials containing
mercapto groups in the channels pores:13 S1,SH was first treated
with chloro(tetrahydrothiophene)gold(I) AuCl(THT) as organo-
gold precursor with a [Au]/[SH] ratio of 0.05 then with an
ethanolic sodium borohydride (NaBH4) solution for 8 h to give an
orange–brown solid after filtration and drying (see ESI{). The
powder (89% yield), which was called S1,SH
.
The results of the elemental analysis of the final material led to
the experimental formula PS13Si130I, the calculated formula being
PS9Si101I. That indicates that the loading in mercaptopropyl
groups (17.8% w) is close to the expected value (16.0% w), while
that of the bridged azobenzene phosphonium salt was inferior
(8.0% w instead of 10.0). That is probably due to the large size of
the phosphonium group. The N2 adsorption–desorption isotherm
of the material (Fig. 1) was of type IV, characteristic of
mesoporous materials with a narrow pore size distribution. The
SBET was found to be 656 m2 g21 and the mean pore diameter
ranges from 3.5–5.5 nm.
Au
SAXS pattern of the resulting material S1,SH revealed the
absence of a diffraction peak, which is an indication of the pore
filling of the host material.13 A notable decrease in BET surface
area (Fig. 1) was also observed (SBET 5 207 m2 g21) confirming
the pore filling. Finally the TEM image (see Fig. 2) shows
uniformly sized spherical nanoparticles centred at 5.5 ¡ 1.5 nm in
agreement with the pore size range of the host material.
Small-angle X-ray scattering pattern of S1,SH exhibits a single
diffraction peak, characteristic of a wormhole framework with a
d100 spacing of 9.48 nm. The mean thickness of the pore walls
In conclusion, we described a one-step methodology (the direct
liquid crystal templating (LCT) approach) allowing a mesoporous
silica, containing a NLO chromophore12 in the framework
(bridged azobenzene phosphonium salts) and mercaptopropyl
groups able to stabilize gold(0) nanoparticles in the channel pores,
to be obtained.13 This is the first example of ordered mesoporous
materials containing a large functional group in the framework,
and another in the channel pores prepared in one step thanks to
the LCT approach. This methodology could be a general route for
such materials coupling two properties, which could interact.14
Eric Besson, Ahmad Mehdi, Victor Matsura, Yannick Guari,
Catherine Reye´ and Robert J. P. Corriu*
Laboratoire de Chimie Mole´culaire et Organisation du Solide, UMR
5637 CNRS, Universite´ de Montpellier II, Sciences et Techniques du
Languedoc, Place E. Bataillon, F-34095 Montpellier Cedex 5, France
Notes and references
1 S. Inagaki, S. Guan, Y. Fukushima, T. Oshuna and O. Terasaki, J. Am.
Chem. Soc., 1999, 121, 9611.
2 B. J. Melde, B. T. Holland, C. F. Blanford and A. Stein, Chem. Mater.,
1999, 11, 3302.
Fig. 1 N2 adsorption–desorption isotherms of S1,SH (a) and S1,SHAu (b).
The inset shows the BJH pore size distribution plot at desorption of S1,SH
.
1776 | Chem. Commun., 2005, 1775–1777
This journal is ß The Royal Society of Chemistry 2005
Besson, Eric
