Facile route to functionalized mesoporous silica nanoparticles by click chemistry

Article abstract of DOI:10.1039/c1jm12066b

Mesoporous silica nanoparticles containing clickable functions (azide or alkyne, 1 or 10 mol%) were synthesized by the sol-gel method directly from molecular precursors using CTAB as structure directing agent. Their structures were discussed on the basis of TEM, DLS, SAXS, N₂-sorption analyses, FTIR, Raman and elemental analysis. The success of their functionalization by pyrene derivatives using CuAAC reactions opens new perspectives in the synthesis of functional MSNs for applications as nanomachines.

Full text of DOI:10.1039/c1jm12066b

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PAPER
Facile route to functionalized mesoporous silica nanoparticles by click
chemistry†
Nirmalya Moitra, Philippe Trens, Laurence Raehm, Jean-Olivier Durand,* Xavier Catto €e n*
and Michel Wong Chi Man
Received 10th May 2011, Accepted 4th July 2011
DOI: 10.1039/c1jm12066b
Mesoporous silica nanoparticles containing clickable functions (azide or alkyne, 1 or 10 mol%) were
synthesized by the sol–gel method directly from molecular precursors using CTAB as structure
2
directing agent. Their structures were discussed on the basis of TEM, DLS, SAXS, N -sorption
analyses, FTIR, Raman and elemental analysis. The success of their functionalization by pyrene
derivatives using CuAAC reactions opens new perspectives in the synthesis of functional MSNs for
applications as nanomachines.
Introduction
MSN, we present here the synthesis of hybrid organic–inorganic
MSN functionalized with azide or alkyne groups by the sol–gel
co-condensation method to obtain a noticeable amount of
clickable functions located both inside the pores and on the
surface of the MSN, and their successful dedicated post-func-
tionalization using click chemistry.
Mesoporous silica nanoparticles have attracted considerable
1–6
interest in life and materials science. Their unique properties,
such as tunable monodisperse diameter (50–200 nm), tunable
2
pore size (2 to 4 nm) and high specific surface area (800–1000 m
ꢀ
1
7–11
g ), offer a large range of applications such as drug delivery,
12–15
16–18
19,20
MRI,
therapy
devoted to the functionalization of MSN and many different
cancer cells targeting,
1–23
catalysis,
24
photodynamic
2
Experimental section
or antireflective coatings. Tremendous efforts are
Materials
21
25
26
functions such as amine, epoxide or thiol are routinely used
with MSN depending on the application aimed. The function-
alization with azide or alkyne groups emerges as an important
contribution for the modification of the MSN surface by click
chemistry due to the mild conditions of the click reaction,
compatible with sophisticated systems. Recently, a major goal
has been achieved using click chemistry with MSN to design
a stimuli–responsive nanovehicle for drug delivery on demand.
Cetyltrimethylammonium bromide (CTAB) (98%, Alfa Aesar,
A15235), tetraethoxysilane (TEOS) (99%, Sigma-Aldrich),
3
-(mercaptopropyl)triethoxysilane (MPTES) (94%, Alfa Aesar),
sodium hydride (95%, Sigma-Aldrich), propargyl bromide (80 wt
in toluene, 97%, Alfa Aesar), copper sulfate (Prolabo), sodium
ascorbate (99%, Alfa Aesar) and N,N-diethyldithiocarbamate
%
(
98%, Alfa Aesar) were used as received. 3-(Azidopropyl)trie-
34
32,33
27,28
thoxysilane (AzPTES),
1-(propargyloxymethyl)pyrene 3
Zink, Stoddart and co-workers
have closed the mesopores of
35
and 1-(azidomethyl)pyrene 4 were synthesized according to
previously described procedures. Ion-exchanged water was used;
THF and pentane were dried using a solvent purification system.
MSN with a rotaxane based-cyclodextrin or cucurbit[6]uril
valve. Click chemistry was used to attach a stoppering group on
the system. Kim et al. used a cyclodextrin stopper linked by click
29,30
chemistry to cap the pores of the MSN.
Qu, Ren and co-
workers prepared MSN capped with a DNA duplex. Click
chemistry also allowed attaching the DNA strand to the MSN
Synthesis of 3-(propargylthiopropyl)triethoxysilane 2
To a solution of sodium hydride (445 mg, 20 mmol) in dry THF
ꢁ
31
surface. In these examples, the outer sphere of the MSN was
functionalized. In connection with our work on the synthesis of
(
100 mL) at ꢀ40 C was added dry ethanol (920 mg, 20 mmol).
After 20 minutes, MPTES (7.76 mg, 20 mmol) was added. The
reaction mixture was brought to room temperature and stirred
for 2 hours, after which time it was added dropwise over 1 hour
Institut
Charles
Gerhardt
Montpellier,
UMR
5253
ꢁ
to a cold solution (ꢀ40 C) of propargyl bromide (80 wt% in
CNRS-UM2-ENSCM-UM1, CC1701 Place Eug eꢀ ne Bataillon, 34095
Montpellier Cedex 05, France. E-mail: durand@univ-montp2.fr; xavier.
cattoen@enscm.fr
toluene, 2.95 mg, 20 mmol) in dry THF (50 mL). After one hour
ꢁ
ꢁ
at ꢀ40 C, the temperature was raised to 20 C then the solvent
was distilled off, and the residue extracted with dry n-pentane
†
histograms, SAXS, -sorption isotherms, a-plot, pore size
Electronic supplementary information (ESI) available: DLS
N
2
(
3 ꢂ 15 mL). Concentration of the n-pentane fraction yielded
distribution, TGA, UV absorption and fluorescence spectra of the
MSN. See DOI: 10.1039/c1jm12066b
pure compound 2 as a yellowish oil (4.42 g, 16 mmol). Yield:
1
3476 | J. Mater. Chem., 2011, 21, 13476–13482
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1
0%. H NMR (CDCl , 400 MHz): d (ppm) 0.74 (m, 2H); 1.22 (t,
8
with a mono internal reflexion ATR module. Raman spectra
were recorded with a LabRAM ARAMIS (Horiba) spectrometer
using a HeNe laser (633 nm). Particle size measurements were
performed by DLS using a DL 135 Particle size analyzer (Cor-
douan Technologies). TEM micrographs were obtained using
a JEOL 1200 EX2 apparatus equipped with a SIS Olympus
Quemesa 11 Mpixel camera. X-Ray diffraction measurements on
dried powders were carried out at the Laboratoire Charles
Coulomb in Montpellier, in 1.5 mm diameter glass capillaries in
a transmission configuration. A copper rotating anode X-ray
source (functioning at 4 kW) with a multilayer focusing Osmic
monochromator giving a high flux and a punctual collimation
was employed. An image plate 2D detector was used. X-Ray
diffractograms were obtained, giving the scattering intensity as
3
J 7.0 Hz, 9H); 1.73 (m, 2H); 2.21 (t, J 2.6 Hz, 1H); 2.70 (t, J
13
7
.5 Hz, 2H); 3.23 (d, J 2.6 Hz, 2H); 3.80 (q, J 7.0 Hz, 6H). C
3
NMR (CDCl , 100 MHz): d (ppm) 9.8; 18.3; 18.9; 22.5; 34.6;
+
5
8.4; 70.8; 80.2. HRMS (ESI ): calc. for C12
99.1113; found: 299.1095.
24 3
H O NaSiS:
2
Preparation of the nanoparticles
CTAB (686 mg, 1.88 mmol) was dissolved in a 0.2 M NaOH
ꢁ
solution in water (39 mL) under stirring (500 rpm) at 25 C until
the solution became homogeneous (ca. 15 min). A mixture of
TEOS [(15.7 ꢀ x) mmol] and organosilane (x mmol) was then
ꢁ
added. After 40 s, water (260 mL, at 25 C) was added. A white
precipitate formed. After 5 min, the reaction mixture was
quenched by adding 0.2 M HCl (approximately 35 mL) until the
pH dropped to 6–7. The mixture was then centrifuged
a function of the wave vector q. N
isotherms were obtained using
2
-adsorption–desorption
a
Micromeritics ASAP
ꢁ
2
020 apparatus after outgassing the samples for 24 h at 60 C.
(
20 000 rpm, 15 min), and the solid obtained was washed with
The BET specific surface areas were determined from the linear
part of the BET transform of the adsorption isotherms. The
water then ethanol. The removal of the template was carried out
by heating the dispersed solid in a 1 : 1 EtOH/HCl (37 wt%)
ꢁ
corresponding relative pressure range is 0.05 < p/p < 0.2 in the
ꢁ
mixture at 60 C for 2 h. After centrifugation (20 000 rpm,
case of NP-N
3
-py-1, NP-N
3
-py-10 and NP-Alk-py-1. This
ꢁ
1
5 min), the solid was washed several times with water (until the
ꢁ
domain was reduced to 0.05 < p/p < 0.1 in the case of NP-Alk-
washings were neutral), then with ethanol, and dried at 25 C for
2
py-10. The cross-section area of nitrogen was taken as 0.162 nm .
1
6 h.
NP-N
%): C: 3.94; H: 2.18; N: 0.79.
NP-N
Pore size distributions were determined using the classical model
3
-1: synthesized using 1 (x ¼ 0.16). Elemental analysis
built by Barrett, Joyner and Halenda (BJH) on the desorption
36
branches of the sorption isotherms. The occurrence of micro-
(
3
-10: synthesized using 1 (x ¼ 1.57). Elemental analysis
s
porosity was evaluated by deriving the a plots of the sorption
(
%): C: 9.69; H: 2.57; N: 4.45.
isotherms. The non-porous silica Aerosil200 was taken as the
reference and a standard adsorbed amount taken at a relative
NP-Alk-1: synthesized using 2 (x ¼ 0.16). Elemental analysis
%): C: 2.74; H: 1.76; S: 0.70.
(
ꢁ
pressure of 0.1 (instead of the more usual p/p ¼ 0.4 recom-
NP-Alk-10: synthesized using 2 (x ¼ 1.57). Elemental analysis
%): C: 7.57; H: 2.15; S: 1.34.
37
mended by K. S. W. Sing). Fluorescence spectra were obtained
(
using a Perkin-Elmer LS 55 fluorimeter. Emission spectra were
recorded with an excitation wavelength of 330 nm. Absorption
spectra were obtained from dispersions of 2.5 mg of nano-
particles in 5 mL of ethanol using an Agilent 8453 UV-visible
Spectroscopy System. Elemental analyses were performed at the
Universit eꢁ Montpellier 2 using a FLASH EA 1112 analyzer
32
General procedure for the CuAAC reaction
The clickable nanoparticle (0.1 mmol of clickable function) was
incubated with the corresponding organic partner (0.3 mmol) in
a 1 : 1 water/t-butanol mixture (2.5 mL) containing CuSO
16 mg, 0.1 mmol) and sodium ascorbate (80 mg, 0.4 mmol).
After 2 days, the nanoparticles were isolated by centrifugation
20 000 rpm, 15 min) then successively washed with water,
4
(
Thermo Scientific). TGA analyses were performed under air at
ꢀ1
(
ꢁ
1
0 C min on a TGA Q50 V6.7 Build 203 instrument.
(
sodium N,N-diethyldithiocarbamate (0.1 M in ethanol, 15 mL),
ethanol (15 mL) and acetone (15 mL). The last three washings
were repeated 5 times. The resulting material was dried under
reduced pressure.
Results and discussion
The syntheses of the azide and alkyne precursors 1 and 2 are
represented in Scheme 1. AzPTES 1 was synthesized according to
32
a published procedure, whereas the new alkyne precursor 2 was
obtained in 80% yield by deprotonation of 3-mercaptopropyl-
triethoxysilane with sodium ethoxide and subsequent reaction
with propargyl bromide.
NP-N -py-1: synthesized from NP-N -1 using 3; elemental
3
3
analysis (%): C: 6.77; H: 1.74; N: 0.54.
NP-N
3
-py-10: synthesized from NP-N
3
-10 using 3; elemental
analysis (%): C: 19.42; H: 2.53; N: 1.84.
The mesoporous silica nanoparticles were obtained using
a direct microemulsion synthesis method in alkaline medium
NP-Alk-py-1: synthesized from NP-Alk-1 using 4; elemental
analysis (%): C: 9.12; H: 2.62; N: 0.34; S: 0.50.
38
(
Scheme 1), with 1 or 10 mol% of 1 or 2 in TEOS, and were
NP-Alk-py-10: synthesized from NP-Alk-10 using 4; elemental
analysis (%): C: 10.21; H: 2.34; N: 1.49; S: 1.16.
characterized after surfactant removal under acidic conditions
and isolation as dry powders.
The formation of nanoparticles was checked by dynamic light
scattering (DLS). The hydrodynamic diameters were found to be
around 160 nm for the azide-containing nanoparticles, but
higher values of 280 and 338 nm were obtained for the ones
synthesized from 2 (Table 1 and Fig. S1†). The TEM images
(Fig. 1) reveal the formation of spherical mesoporous
Characterization
NMR spectra were recorded using a Bruker Avance II 400
3
spectrometer, in freshly dried CDCl . Chemical shifts are given
using the solvent residual signal as the internal reference. FTIR
spectra were recorded using a Perkin100 spectrometer equipped
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3 3
Fig. 1 TEM images of the nanoparticles: (a) NP-N -1; (b) NP-N -10; (c)
NP-Alk-1; (d) NP-Alk-10. The inset in (c) depicts the FFT of the portion
of the image delimited by the red square.
Scheme 1
nanoparticles for NP-N
3
3
-1, NP-N -10 and NP-Alk-1, with
diameters around 70, 60 and 75 nm, respectively. Interestingly,
39
a rodlike morphology (dimensions: 60 ꢂ 180 nm) was observed
when the synthesis was carried out with 10% of 2. It is note-
worthy that the mesostructure is more regular for the nano-
particles obtained from 2, as observed in the Fourier transform
of the image of NP-Alk-1 (Fig. 1c); in the case of the nanorods,
longitudinal mesopores are observed (Fig. 1d). Such a change in
morphology from nanospheres to nanorods upon increasing the
content of organosilane during the synthesis of mesoporous
40,41
organosilica nanoparticles has been recently addressed.
The powder X-ray diffraction study of the clickable nano-
particles at small angle (Fig. 2 and S2†) gave further insight into
the mesostructure of the samples. For all the samples, a sharp
Bragg peak is detected at low angle, evidencing the regularity of
the structure. In particular, the diffractograms of NP-Alk-1 and
NP-Alk-10 are characteristic of 2D-hexagonal structure (two
harmonics of the Bragg peak are discerned), whereas for NP-N3-
Fig. 2 SAXS of the alkyne-functionalized nanoparticles.
2
The N -adsorption–desorption isotherms performed on the
1
and NP-N
3
-10, only the Bragg peak is observed, which is in
different types of nanoparticles before the click reaction are
shown in Fig. 3 and S3†. The specific surface areas, calculated
using the BET transform of the adsorption isotherms range
agreement with the worm-like organization of the mesopores in
these materials as observed by TEM. The characteristic repeating
distances associated with the Bragg peaks are much smaller in the
case of the alkyne-containing nanoparticles (Table 1). This can
be explained by the high lipophilicity of the propargylthiopropyl
groups, that tend to strongly interact with the micelles’ core,
resulting in their contraction during the synthesis and thus in
smaller repeating distances.
2
ꢀ1
between 800 and 1000 m g . The shape of the different
adsorption isotherms gives evidence of the occurrence of meso-
porous materials characterized by type IV sorption isotherms.
Indeed, all the curves exhibit clear positive inflexion of the
adsorbed amounts after the monolayer–multilayer sorption
process typical of mesopores filling. These are followed by rather
Table 1 Geometrical parameters of the nanoparticles
2
DLS particle size/nm TEM particle size/nm XRD repeating distance/nm BET surface area/m g
ꢀ1
Material
BJH mesopore diameter/nm
NP-N
NP-N
NP-Alk-1
NP-Alk-10
3
-1
-10
165
159
280
338
206
60–80
50–70
4.5
4.3
3.5
3.3
—
—
—
—
1055
800
848
925
502
63
2.9
2.4
2.3
1.7
2.8
—
3
70–80
60 ꢂ 180
NP-N
NP-N
NP-Alk-py-1
3
-py-1
60–80
50–70
3
-py-10 237
216
NP-Alk-py-10 357
70–90
60 ꢂ 180
770
207
2.1
—
1
3478 | J. Mater. Chem., 2011, 21, 13476–13482
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Fig. 3
N
2
-adsorption–desorption isotherms of nanoparticles in the case of NP-Alk-1 (left) and NP-Alk-10 (right) before (circles) and after (squares) the
click reaction with 4 (adsorption branches (filled symbols), desorption branches (empty symbols)).
flat saturation plateaus indicative of the saturation of the mes-
oporosity and the adsorption on the external surface of the
samples. Furthermore, the location in relative pressure of these
Table 2 Textural properties of the materials
Beginning of
capillary
Uptake at saturation/ Part of the pore filling condensation, p/
ꢁ
ꢁ
inflexions varies between p/p ¼ 0.05 and p/p ¼ 0.22 which can
3
ꢁ
be interpreted by capillary condensation occurring in pores of
Sample cm (STP) per g
process (%)
p
different sizes. This can be precisely determined from the a plots
s
NP-
-1
NP-
-10
476
320
358
263
40
33
35
32
0.22
0.20
0.20
0.09
of the adsorption isotherms since mesopores filling commences
N
3
s s
as the a plot diverges from linearity. Furthermore, the a plots
also show that there is no evidence of any significant micropo-
rosity which discards the possibility of a hydrolysis of isolated
species of reagents in the silica framework which could have been
removed during the washing stage of the synthesis. This can be
N
3
NP-
Alk-1
NP-
Alk-10
s
seen by the intercept of the linear part of the a -plot curve with
the Y-axis of the graphs which has been found to be close to zero.
An example of such a curve is shown in Fig. S4† in the case of
NP-Alk-1. If we now go into more details, it can be noted that the
relative pressures corresponding to the pore fillings are rather
low, lower for instance than that usually found for MCM-41
is different when considering the four materials. Table 2
summarizes the differences observed in the case of these four
porous materials before the click reaction.
42
materials, when the same surfactant (CTAB) is employed. As
seen in Fig. 4 and S5†, where examples of pore size determination
are shown, this is especially true in the case of NP-Alk-10 which
could be seen as a super-microporous-type material. This is likely
due to the density of pending organic functions in the pores of
this material which results in a decrease of its average pore size.
However, it must be emphasized that the pores of this material
are still accessible to nitrogen species. As a consequence, the
contribution of the pores filling to the overall adsorption process
The infrared spectra of all the materials show a broad band
ꢀ1
(1000–1300 cm ) evidencing the formation of the SiOSi
network. In the case of the nanoparticles obtained from 1
ꢀ1
3
(Fig. 5), the signature of the N group at 2105 cm could be
clearly observed, with a relative intensity which increases with
the amount of 1 in the starting sol, evidencing the preservation of
the azido function under these synthetic conditions. The presence
of the C–C triple bond in the materials obtained from 2 was
ascertained by Raman spectroscopy (Fig. 6) for both materials
Fig. 4 Pore size distribution of the nanoparticles in the case of NP-Alk-1 (left) and NP-Alk-10 (right) before (circles) and after (squares) the click
reaction with 4.
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Table 3 Loading of clickable functions in the nanoparticles
Loading of
azide/mmol g
Loading of
alkyne/mmol g
N/S
ratio (expected)
ꢀ
1
ꢀ1
Material
NP-N
NP-N
NP-Alk-1
NP-Alk-10
NP-Alk-py-1
NP-Alk-py-10
3
-1
-10
0.19
1.06
—
—
—
—
—
0.16
0.42
—
—
—
—
—
3
1.6 ꢃ 1.6 (3)
—
—
2.9 ꢃ 0.9 (3)
Fig. 5 FTIR spectra of the N
after the click reaction with 3: (a) NP-N
0; (d) NP-N -py-10. The arrows indicate the positions of the N
and c) and of the pyrene groups (b and d).
3
-functionalized nanoparticles before and
-1; (b) NP-N -py-1; (c) NP-N
band (a
3
3
3
-
1
3
3
ꢀ1
with a characteristic peak at 2130 cm ; the band located around
ꢀ1
2
900 cm being ascribed to the CH groups.
2
The elemental analysis performed on the dried powders gave
loadings of anchored clickable functions between 0.16 and
Scheme 2
ꢀ
1
1
.1 mmol g depending on the starting mixture (Table 3, see
Fig. S6† for TGA). Following the synthesis conditions, the azido
groups should be located both at the external surface and within
the framework of the material.
functionalized nanoparticles, Raman spectra were acquired after
the reaction of NP-Alk-1 and NP-Alk-10 with hexyl azide as the
fluorescence of the nanoparticles clicked with pyrene derivative 4
was too high which is a disruptive factor for Raman measure-
ments (Fig. 6b). Besides the disappearance of the alkyne func-
The reactivity of these functional groups was probed using the
Cu-catalyzed Alkyne–Azide Cycloaddition (CuAAC) reaction
between the azide- or alkyne-functionalized nanoparticles and 1-
ꢀ1
(
propargyloxymethyl)pyrene
3
or 1-(azidomethyl)pyrene 4,
tion, the appearance of a sharp peak at 1458 cm attributed to
the N]N vibration within the triazole fragment is observed.
Furthermore, the nitrogen content in NP-Alk-py-1 and NP-Alk-
py-10 determined by microanalysis (Table 3) increases from 0 to
0.34 and 1.5 wt% for NP-Alk-py-1 and NP-Alk-py-10, respec-
tively. In the latter case, the calculated N/S molar ratio after the
click reaction is 2.9 (3.0 expected), whereas it is only 1.6 in the
case of the former material. However, the latter value is somehow
respectively in the presence of copper sulfate and sodium
ascorbate (Scheme 2).
In the case of NP-N -1 and NP-N -10, the total conversion of
3
3
the N3 groups was ascertained by FTIR (Fig. 5), with the
ꢀ1
3
disappearance of the N vibration band at 2105 cm , and the
ꢀ1
appearance of two bands located at 1324 and 1633 cm , char-
acteristic of the aromatic pyrene fragment. For the alkyne-
Fig. 6 Raman spectra of the alkyne functionalized nanoparticles (a) before and (b) after the click reaction with hexyl azide.
3480 | J. Mater. Chem., 2011, 21, 13476–13482 This journal is ª The Royal Society of Chemistry 2011
1

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nitrogen, (ii) the specific surface areas take into account the mass
of the pyrene species added to the material.
In the case of the 1% loaded materials, the pores of the
materials are still accessible (the pore fillings are still visible),
however, the pore volumes are decreased while the pore fillings
occur at slightly lower relative pressures. This suggests that there
is no pore blocking, but rather reaction on the organic function
on the original materials.
The successful incorporation of the pyrene fragment within the
materials was checked by UV absorption (Fig. S7†). Indeed, the
pattern of the spectrum, with bands at around 330 and 350 nm is
characteristic of these pyrene derivatives. It should be noted that
the fluorescence of the pyrene moiety gives valuable information
on the proximity between the fluorescent fragments, as isolated
pyrene groups fluoresce in the long UV-blue (365–425 nm),
whereas excimers are formed when these molecules are in close
proximity (with a broad band of emission centered at 480 nm).
Fig. 7 TEM images of the nanoparticles after the CuAAC reaction: (a)
NP-N -py-1; (b) NP-N -py-10; (c) NP-Alk-py-1; (d) NP-Alk-py-10.
3
3
3
Indeed, with the lowest concentration of N in the starting
nanoparticles, the excimer band is hardly detectable, most of the
fluorescence arising from the monomer; with the highest
concentration, the proportion of the excimer drastically increases
32,33
(
Fig. 8 and S8†).
Conclusion
In summary, two routes to clickable MSNs featuring either azido
or propargyl functional groups are described using a direct
microemulsion method in alkaline medium using CTAB as the
surfactant. Spherical nanoparticles (ca. 50–80 nm) were obtained
in all cases except when a loading of 10% of organosilane 2 was
used, resulting in the formation of nanorods (60 ꢂ 180 nm). The
2
ꢀ1
texture of these highly porous nanoparticles (800–1000 m g )
revealed the presence of small mesopores (ca. 2.5 nm) in the case
of the nanospheres, and of ‘super micropores’ (ca. 1.7 nm) in the
case of the nanorods. The presence of the clickable functional
groups was clearly ascertained by FTIR and Raman, and
quantified by elemental analyses. The nanoparticles were almost
quantitatively functionalized using the ‘click’ CuAAC reaction
without significant morphological alteration. These studies
should lead to significant progress in the domain of functional
mesoporous nanoparticles for applications as drug nanocarriers
or nanomachines. Work is ongoing in this direction.
3
Fig. 8 Fluorescence spectra of the N -functionalized nanoparticles after
the click reaction with 3 (lexc ¼ 330 nm; spectra normalized at 415 nm).
uncertain, given the important experimental error in the micro-
analysis and the low values obtained (0.34 ꢃ 0.2 wt% and 0.50 ꢃ
0
.2 wt% for N and S, respectively).
Interestingly, no significant modifications of the morphology
of the nanoparticles could be detected: the TEM pictures of the
particles before and after the click reaction are very similar
Acknowledgements
(
Fig. 1 and 7), whereas the DLS experiments evidence moderate
increases of the mean hydrodynamic ratio of the nanoobjects,
The authors are grateful to the Agence Nationale de la Recher-
che (CP2D MESORCAT and P2N MECHANANO), the
Partner University Fund, a program of FACE, CNRS, ENSCM
mainly in the case of the N
and Fig. S1†).
3
-containing nanoparticles (Table 1
and Universite Montpellier 2 for financial supports. D. Bour-
ꢁ
After the click reaction, some textural changes can be seen
which is a confirmation that the click reaction took place (Fig. 3
and 4). Since this type of reaction results in a lengthening of the
pending organic chains in the pores, the pore volumes are
expected to decrease. This can be seen for both precursors and
this phenomenon is even more visible with the 10% loaded
materials for which the density of organic functions in the pores
is really important. In both cases, the click reaction results in
a complete vanishing of the mesoporosity and a strong decrease
of the specific surface area (Fig. 3). This likely originates from
two different reasons: (i) the pores are no longer accessible to
gogne (ICGM), F. Godiard (UM2) and P. Dieudonne (Labo-
ꢁ
ratoire Charles Coulomb Montpellier) are gratefully
acknowledged for performing the Raman, TEM and XRD
measurements.
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