Effect of precursor and surfactant nature on geometrical characteristics of mesoporous silicas
Bimodal mesoporous silicas and materials MCM-41 type were synthesized with the use as a template cationic surfactants distinguished by a length of the alkyl chain. Fumed silica, tetraethyl orthosilicate as well as of mixture these compounds were applied as a silicate precursor. Obtained samples have...
Saved in:
| Date: | 2002 |
|---|---|
| Main Authors: | , , , , , |
| Format: | Article |
| Language: | English |
| Published: |
Chuiko Institute of Surface Chemistry National Academy of Sciences of Ukraine
2002
|
| Online Access: | https://surfacezbir.com.ua/index.php/surface/article/view/79 |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| Journal Title: | Surface |
| Download file: |  |
Institution
Surface| _version_ | 1869291167416320000 |
|---|---|
| author | Pavlenko, A. N. Yanishpolskii, V. V. Tertykh, V. A. Il'in, V. G. Leboda, R. Skubiszewska-Zieba, J. |
| author_facet | Pavlenko, A. N. Yanishpolskii, V. V. Tertykh, V. A. Il'in, V. G. Leboda, R. Skubiszewska-Zieba, J. |
| author_institution_txt_mv | [
{
"author": "A. N. Pavlenko",
"institution": "Інститут хімії поверхні НАН України"
},
{
"author": "V. V. Yanishpolskii",
"institution": "Інститут хімії поверхні НАН України"
},
{
"author": "V. A. Tertykh",
"institution": "Інститут хімії поверхні НАН України"
},
{
"author": "V. G. Il'in",
"institution": "L.V.Pisarzhevsky Institute of Physical Chemistry of National Academy of Sciences"
},
{
"author": "R. Leboda",
"institution": "Maria Curie-Sklodowska University"
},
{
"author": "J. Skubiszewska-Zieba",
"institution": "Maria Curie-Sklodowska University"
}
] |
| author_sort | Pavlenko, A. N. |
| baseUrl_str | |
| collection | OJS |
| datestamp_date | 2018-11-27T09:42:19Z |
| description | Bimodal mesoporous silicas and materials MCM-41 type were synthesized with the use as a template cationic surfactants distinguished by a length of the alkyl chain. Fumed silica, tetraethyl orthosilicate as well as of mixture these compounds were applied as a silicate precursor. Obtained samples have been characterized by the powder X-ray diffraction technique and adsorption measurements. Specific surface area, pore diameter, pore size distribution was determined from nitrogen ad(de)sorption isotherms at 77 K for the silicas prepared. The products with bimodal pore distribution have not ordered structure and contain macropores and mesopores, whose sizes are typical for MCM-41 materials. Effect of surfactant and precursor nature on the geometrical features of the ordered structure of MCM‑41 type and bimodal porous materials was studied. |
| first_indexed | 2025-07-22T19:30:06Z |
| format | Article |
| fulltext |
19
EFFECT OF PRECURSOR AND SURFACTANT NATURE
ON GEOMETRICAL CHARACTERISTICS OF
MESOPOROUS SILICAS
A.N. Pavlenko1, V.V. Yanishpolskii1, V.A. Tertykh1, V.G. Il'in2, R. Leboda3,
and J. Skubiszewska-Zieba3
1Institute of Surface Chemistry, National Academy of Sciences,
03680 Kyiv-164, Gen. Naumov Str. 17, UKRAINE
2L.V.Pisarzhevsky Institute of Physical Chemistry, National Academy of Sciences,
03039 Kyiv, Prospect Nauki 31, UKRAINE
3Faculty of Chemistry, Maria Curie-Sklodowska University, 20031 Lublin, POLAND
Abstract
Bimodal mesoporous silicas and materials MCM-41 type were synthesized with the use
as a template cationic surfactants distinguished by a length of the alkyl chain. Fumed silica,
tetraethyl orthosilicate as well as of mixture these compounds were applied as a silicate
precursor. Obtained samples have been characterized by the powder X-ray diffraction
technique and adsorption measurements. Specific surface area, pore diameter, pore size
distribution was determined from nitrogen ad(de)sorption isotherms at 77 K for the silicas
prepared. The products with bimodal pore distribution have not ordered structure and contain
macropores and mesopores, whose sizes are typical for MCM-41 materials. Effect of
surfactant and precursor nature on the geometrical features of the ordered structure of
MCM-41 type and bimodal porous materials was studied.
Introduction
The synthesis of periodic mesoporous materials of the M41S type had become available
with the use of different surfactants as micellar templates. They play a role of the
structure-directing agents [1] in an assembly process of the periodic mesoporous materials
because surfactants have ability to self-organize into mesophases with the different dimensional
structure: hexagonal, cubic or lamellar.
For preparation of the MCM-41 type silica materials a series of the surfactants
CnH2n+1(CH3)3N+A-, where A- - counterion, n=14, 16 or 18, were mostly used as a micellar
template and sodium silicate, tetraethyl orthosilicate (TEOS), fumed silica were applied as a
silica source. Synthesis of the material with a hexagonal array of pores is usually carried out for
a few hours as well as some days [2]. It is conceivable that the formation of the silica
framework can come from both as a result of monomeric silicate ions adsorption on the micelle
surface and at the expense of using of the more bulky oligomeric silicate species. In the most
cases the synthesis of mesoporous silicas was performed under the conditions of hydrothermal
treatment, while the use of the condensed silicate species allows one to avoid this stage. The
some differences in the structure of surfactant, nature of counterion A-, value of the
surfactant/silica molar ratio, contents of water lead to obtain of the porous materials with the
bimodal pore size distribution, where the product obtained contains of mesopores, their sizes
being typical for the MCM-41 material and the larger ones [3].
20
In this work we have continued a systematic research in the field of synthesis of the
bimodal mesoporous materials with the purpose of study of an effect of the cationic surfactant
chain length on geometrical parameters of the mesoporous silicas.
Experimental
For preparation of the mesoporous silica matrices the fumed silica (Aerosil, 300 m2/g)
and tetraethoxysilane were used as a silicate precursor. Quaternary ammonium salts
hexadecyltrimethylammonium bromide (CTMABr), octadecyltrimethylammonium chloride
(ODTMACl) and tetramethylammonium bromide (TMABr) were applied as micellar templates.
These short- and long-chain surfactants were transformed into hydroxyl form with the use of
the ion-exchange column filled by the AB-17-8 anionite in hydroxyl form.
Synthesis of aerosilogel – Sample 1. Fumed silica (280 g; 4.67 mol) was suspended in
water (1250 ml; 69.44 mol) at the intensive stirring. Obtained suspension is allowed to stand
for 24-28 hrs at room temperature, then it was dried up at 150ºC and calcined at 540ºC for 6 h
on air.
Synthesis of mesoporous silicas with the use of the short- and long-chain surfactants:
with TMABr/OH – Sample 2; with ODTMACl/OH – Sample 3; with CTMABr/OH – Sample 4.
Weighed portion of the fumed silica (6.4 g, 0.11 mol – for Sample 2; 14.6g, 0.24 mol – for
Samples 3 and 4) was dissolved in an aqueous solution of the appropriate quaternary amine
hydroxide (15.4 wt % solution TMABr/OH; 8.7% solution ODTMACl/OH; and 9.1% solution
CTMABrOH) at stirring. Surfactant/silica molar ratios are indicated in the Table. Obtained
homogeneous milk-white mixtures were dried on air at room temperature up to formation of
the gel-like products. Finally the samples were calcined at 540ºC for 6 h on air.
Synthesis of mesoporous silica with the use of mixture of the fumed silica and TEOS as
a silicate precursor – Sample 5. 8.7 wt % aqueous solution ODTMACl/OH was added to the
mixture of the fumed silica (7.4 g, 0.123 mol) and TEOS (24 ml, 0.107 mol) at stirring. The
obtained caseous suspension is allowed to age on air up to formation of the solid product. The
sample prepared was calcined at 540ºC for 6 h on air.
Synthesis of mesoporous silica with the use of TEOS as a silica source – Sample 6.
TEOS (22.4 ml, 0.1 mol) was added at stirring to 3.48 wt % aqueous solution ODTMACl/OH.
Obtained homogeneous milk-white mixture was subjected to aging on air up to the gel-like
product formation and then was calcined at 540ºC for 6 h on air.
Synthesis of the MCM-41 materials with the use of CTMABr (Sample 7) and
ODTMACl (Sample 8) as a micellar template. Samples were synthesized according to the
following procedure. Weighed portion of the surfactant CTMABr (8.3 g, 0.023 mol) or
ODTMACl (7.9 g, 0.023 mol) was dissolved in 43 ml of concentrated ammonia solution and
intermixed to homogeneous milk-white mixture. After addition TEOS (9.67 ml, 0.043 mol) the
mixture obtained was stirred up to gelation. The resulting products were dried up at air with
following calcination at 540ºC for 6 h on air.
Characterization of the synthesized samples was performed by the powder X-ray
diffraction (XRD) data (automated diffractometer DRON-3M, CuKa radiation) and nitrogen
adsorption isotherm measurements at 77K on ASAP-2000 Micromeritics equipment. Average
pore diameter was estimated by Gurvich method (d=4V/S). The specific surface area, SBET,
was determined from the linear part of the BET equation (at p/ps=0.05-0.35). Pore volume
distribution was calculated from desorption branch of an isotherm of nitrogen adsorption using
the Barrett-Joyner-Halenda (BJH) formula [4-6].
21
Results and discussion
It has been known that XRD technique allows one to reveal a presence of a
dimensional self-organization in the mesoporous materials. The X-ray diffraction patterns of
the Samples 7 and 8 exhibit distinct small-angle peaks in the range 2q=2-6º, which can be
attributed to different hkl reflections and are characteristic of the well-ordered hexagonal
structure. The XRD patterns for MCM-41 samples are shown in Fig.1. The XRD
diffractograms for the rest synthesized mesoporous silicas are depicted in Fig.2.
The most complete and reliable information about mesoporous structure comes from
the low-temperature N2 ad(de)sorption isotherms [7]. Adsorption data for the synthesized
samples are represented in Table.
Table. Geometrical characteristics of the synthesized mesoporous silicas.
Sample
Micellar
template
Silicate
precursor, mol
Medium, mol
Surfac-
tant/
silica
molar
ratio
Pore
diameter
Å
BET
surface
area,
m2/g
Fumed
silica
TEOS
1 - 1.0 H2O, 14.9 - 208 253
2 TMABr/OH 1.0 H2O, 12.0 0.22 209 205
3 ODTMACl/OH 1.0 H2O, 23.2 0.10 98 388
4 CTMABr/OH 1.0 H2O, 22.9 0.10 136 416
5 ODTMACl/OH 1.0 1.2 H2O, 48.3 0.10 93 463
6 ODTMACl/OH 1.0 H2O, 55.6 0.10 63 784
7 CTMABr 1.0 NH4OH, 27.7 0.52 36 1171
8 ODTMACl 1.0 NH4OH, 27.7 0.52 49 977
0
20
40
60
80
100
120
0 2 4 6 8 10
2Q (degrees)
in
te
ns
ity
(a
rb
.u
ni
ts
)
(b)
(a)
Fig. 1. X-ray diffraction patterns of the MCM-41 type silicas:
(a) – Sample 7; (b) – Sample 8.
22
0
20
40
60
80
100
120
140
0 5 10 15 20 25 30 35 40
2Q (degrees)
in
te
ns
ity
(a
rb
.u
ni
ts
)
1
2
3
4
5
6
Fig. 2. X-ray diffraction patterns of the porous silicas (Samples 1-6).
0
20
40
60
80
100
120
140
160
10 100 1000 10000
Pore diameter (Angstrom)
D
S/
D
D
, m
2 /g
/A
0
0,1
0,2
0,3
0,4
0,5
D
V /
D
D
, m
l/g
/A
0
50
100
150
200
250
10 100 1000
Pore diameter (Angstrom)
DS
/ D
D
, m
2 /g
/A
0
0,1
0,2
0,3
0,4
DV
/ D
D
, m
l/g
/A
Fig. 3. Pore volume and pore surface area
distributions for the Sample 3.
Fig. 4. Pore volume and pore surface area
distributions for the Sample 6.
From the adsorption measurements and XRD data it follows that the carrying out of
syntheses with the use of the fumed silica, TEOS, mixture of the fumed silica and TEOS as a
silicate precursor and the cationic long-chain surfactants as a micellar template permits one to
obtain mesoporous materials. These samples have specific surface areas, which exceed in
different extent of SBET for the aerosilogel.
At the use of the short-chain surfactant (TMABr) the amorphous macroporous silicas
with low specific surface area are formed (Sample 2). In fact, in line with the data [8, 9]
surfactant molecules with a number of carbon atoms in alkyl chain less 7 do not form micelles
23
in aqueous solutions, and consequently, supramolecular templates are absent under these
synthetic conditions.
Bimodal pore distribution and an increase of specific surface area approximately up to
400 m2/g were observed for the Sample 3 (Fig. 3) and Sample 4 (see previous our work [6]),
prepared with the use of the long-chain surfactants ODTMACl/OH, CTMABr/OH and the
fumed silica as a silicate precursor. For the Sample 3 there are two maxima on a curve of pore
distribution at 33 and 434Å. The pore diameter 33Å in this sample corresponds to the pore
size of the MCM-41 type materials, however in XRD pattern of this sample we do not find a
presence of the reflections at small angles, which are characteristics of the well-ordered
hexagonal structure. At the same time the most considerable increase of surface is attributed to
these pores. The curve of pore distribution for Sample 4 reveals two maxima at 30 and 300Å
and hexagonal dimensional packing is also absent. In view of the fact that mesopore sizes for
the Sample 4 are smaller compared with those for the Sample 3, consequently the increment of
surface attributed to these mesopores for the former sample is larger as compared with the
Sample 3. The difference in mesopore sizes can be related to an effect of the alkyl chain length
in the molecules of applied cationic surfactants. Other authors [9, 10, 11] have also detected a
similar influence of a chain length in the template molecule on the pore size.
Application of a mixture of the fumed silica and TEOS as an inorganic precursor at the
molar ratio of surfactant/silica=0.1 does not improve of structural features of the Sample 5,
though a small increase of specific surface area is observed. The Sample 6, synthesized from
TEOS and ODTMACl/OH at the same molar ratio of surfactant/silica, reveals the bimodal
pore distribution (Fig. 4) as well as high specific surface area (784 m2/g). XRD pattern of this
mesoporous silica exhibits only the small-angle peak because of the poorly ordered pore
system [11]. It may well be that at the realization of the bimodal mesoporous materials
synthesis at the lower molar ratio of surfactant/silica the primary particles are small and
spherical in the shape due to insufficient silicate polymerization. Thereafter these particles
coalesce to form a secondary porous structure.
0
200
400
600
800
1000
1200
10 100 1000
Pore diameter (Angstrom)
DS
/ D
D
, m
2 /g
/A
0
0,2
0,4
0,6
0,8
1
DV
/ D
D
, m
l/g
/A
0
200
400
600
800
10 100 1000
Pore diameter (Angstrom)
D
S/
D
D
, m
2 /g
/A
0
0,2
0,4
0,6
0,8
1
D
V/
D
D
, m
l/g
/A
Fig. 5. Pore volume and pore surface area
distributions for the Sample 7.
Fig. 6. Pore volume and pore surface area
distributions for the Sample 8.
24
At an increase of a molar ratio of surfactant/silica to 0.52 the organic template
molecules self-organize into micellar structures, which are optimum for preparation of the
ordered mesopores materials in the basic media. From adsorption data and XRD results it
appears that in this case the highly ordered MCM-41 materials, possessing by the uniform pore
size structure (35-50Å) and extraordinary high specific surface area (980-1170 m2/g), can be
obtained. The curves of pore distributions for the Samples 7 and 8 are represented in Figs. 5
and 6 respectively. It is characteristically that an effect of the alkyl chain length of surfactant on
pore size of the synthesized mesoporous materials is also observed.
Hence, it can be stated that in the systems ODTMACl-TEOS and CTMABr-TEOS in
the NH4OH media the optimum geometrical and energy accordance is realized for preparation
MCM-41 products owing to the rigid silicate framework is formed around supramolecular
structures of the cationic surfactant.
Conclusion
The obtained results testify about essential effect of the surfactant and silicate precursor
nature on the geometrical parameters of mesoporous silicas. An use of tetraethyl orthosilicate
and fumed silica as a silica precursor, hexadecyltrimethylammonium bromide and
octadecyltrimethylammonium chloride as a micellar template at the molar ratio surfactant/silica
is equal 0.10 results in the bimodal mesoporous materials involved macropores as well as
mesopores and having non-ordered hexagonal structure. Synthesis of products exhibiting the
typical highly-ordered MCM-41 materials structure with the exclusively narrow mesopore
distribution, hexagonal symmetry of the porous framework and high specific surface was
executed at an increase of the molar ratio surfactant/silica to 0.52.
Acknowledgement
This work was supported by Foundation of Fundamental Research of the Ministry for
Education and Science of Ukraine (Project N03.07/00099) and in part by NATO grant
No.EST.CLG.976890.
References
1. Zhao X.S., (Max) Lu G.Q., and Millar G.J. Advances in mesoporous molecular sieve
MCM-41 // Ind. Eng. Chem. Res. - 1996. - V.35. - P.2075-2090.
2. Koyano K.A. and Tatsumi T. Synthesis of titanium-containing MCM-41 // Microporous
Materials. - 1997. - V.10. - P.259-271.
3. Schulz-Ekloff G., Rathousky J., and Zukal A. Controlling of morphology and
characterization of pore structure of ordered mesoporous silicas // Microporous and
Mesoporous Materials. - 1999. - V.27. - P.273-285.
4. Gregg S.J. and Sing K.S.W. Adsorption, Surface Area and Porosity. - London: Academic
Press, 1982.
5. Barrett E.P., Joyner L.J., and Halenda P.P. The determination of pore volume and area
distributions in porous substances. I. Computations from nitrogen isotherms // J. Am. Chem.
Soc. - 1951. – V.73. - P.373-380.
6. Tertykh V.A., Yanishpolskii V.V., Pavlenko A.N., Leboda R., and Skubiszewska-Zieba J.
Template-based approach in the preparation of nanoporous silicas and titania-silicas // In:
Chemistry, Physics and Technology of Surfaces, Issues 4-6. – Chuiko A.A. (Ed.) – Kyiv:
KM Academia. - 2001. - P.59-68.
25
7. Romero A.A., Alba M.D., Zhou W., and Klinowski J. Synthesis and characterization of the
mesoporous silicate molecular sieve MCM-48 // J. Phys. Chem. B – 1997.- V.101. -
P.5294-5300.
8. Voyutskii S.S. Course of Colloid Chemistry. – Moscow: Khimiya, 1975 (in Russian).
9. Raman N.K., Anderson M.T., and Brinker C.J. Template-based approaches to the
preparation of amorphous, nanoporous silicas // Chem. Mater. - 1998. - V.8. - P.1682-1701.
10. Beck J.S., Vartuli J.C., Roth W.J., Leonowicz M.E., Kresge C.T., Schmitt K.D.,
Chu C.T.W., Olson D.H., Sheppard E.W., McCullen S.B., Higgins J.B., and Schlenker J.L.
A new family of mesoporous molecular sieves prepared with liquid crystal templates // J. Am.
Chem. Soc. -1992. - V.114. - P. 10834-10843.
11. Sayari A. and Liu P. Non-silica periodic mesostructural materials: recent progress //
Microporous Materials. - 1997. - V.12. - P. 149-177.
Abstract
Abstract
Abstract
Abstract
Abstract
Introduction
Experimental
Conclusion
References
|
| id | oai:ojs.pkp.sfu.ca:article-79 |
| institution | Surface |
| keywords_txt_mv | keywords |
| language | English |
| last_indexed | 2025-07-22T19:30:06Z |
| publishDate | 2002 |
| publisher | Chuiko Institute of Surface Chemistry National Academy of Sciences of Ukraine |
| record_format | ojs |
| resource_txt_mv | surfacezbircomua/8b/bc3c7ec2a47421f61b31db70e378e08b.pdf |
| spelling | oai:ojs.pkp.sfu.ca:article-792018-11-27T09:42:19Z Effect of precursor and surfactant nature on geometrical characteristics of mesoporous silicas Effect of precursor and surfactant nature on geometrical characteristics of mesoporous silicas Effect of precursor and surfactant nature on geometrical characteristics of mesoporous silicas Pavlenko, A. N. Yanishpolskii, V. V. Tertykh, V. A. Il'in, V. G. Leboda, R. Skubiszewska-Zieba, J. Bimodal mesoporous silicas and materials MCM-41 type were synthesized with the use as a template cationic surfactants distinguished by a length of the alkyl chain. Fumed silica, tetraethyl orthosilicate as well as of mixture these compounds were applied as a silicate precursor. Obtained samples have been characterized by the powder X-ray diffraction technique and adsorption measurements. Specific surface area, pore diameter, pore size distribution was determined from nitrogen ad(de)sorption isotherms at 77 K for the silicas prepared. The products with bimodal pore distribution have not ordered structure and contain macropores and mesopores, whose sizes are typical for MCM-41 materials. Effect of surfactant and precursor nature on the geometrical features of the ordered structure of MCM‑41 type and bimodal porous materials was studied. Bimodal mesoporous silicas and materials MCM-41 type were synthesized with the use as a template cationic surfactants distinguished by a length of the alkyl chain. Fumed silica, tetraethyl orthosilicate as well as of mixture these compounds were applied as a silicate precursor. Obtained samples have been characterized by the powder X-ray diffraction technique and adsorption measurements. Specific surface area, pore diameter, pore size distribution was determined from nitrogen ad(de)sorption isotherms at 77 K for the silicas prepared. The products with bimodal pore distribution have not ordered structure and contain macropores and mesopores, whose sizes are typical for MCM-41 materials. Effect of surfactant and precursor nature on the geometrical features of the ordered structure of MCM‑41 type and bimodal porous materials was studied. Bimodal mesoporous silicas and materials MCM-41 type were synthesized with the use as a template cationic surfactants distinguished by a length of the alkyl chain. Fumed silica, tetraethyl orthosilicate as well as of mixture these compounds were applied as a silicate precursor. Obtained samples have been characterized by the powder X-ray diffraction technique and adsorption measurements. Specific surface area, pore diameter, pore size distribution was determined from nitrogen ad(de)sorption isotherms at 77 K for the silicas prepared. The products with bimodal pore distribution have not ordered structure and contain macropores and mesopores, whose sizes are typical for MCM-41 materials. Effect of surfactant and precursor nature on the geometrical features of the ordered structure of MCM‑41 type and bimodal porous materials was studied. Chuiko Institute of Surface Chemistry National Academy of Sciences of Ukraine 2002-06-12 Article Article application/pdf https://surfacezbir.com.ua/index.php/surface/article/view/79 Surface; No. 7-8 (2002): Chemistry, Physics and Technology of Surface; 19-25 Поверхность; № 7-8 (2002): Химия, физика и технология поверхности; 19-25 Поверхня; № 7-8 (2002): Хімія, фізика та технологія поверхні; 19-25 3154-8091 3154-8083 en https://surfacezbir.com.ua/index.php/surface/article/view/79/77 Авторське право (c) 2002 A.N. Pavlenko, V.V. Yanishpolskii, V.A. Tertykh, V.G. Il'in, R. Leboda, J. Skubiszewska-Zieba |
| spellingShingle | Pavlenko, A. N. Yanishpolskii, V. V. Tertykh, V. A. Il'in, V. G. Leboda, R. Skubiszewska-Zieba, J. Effect of precursor and surfactant nature on geometrical characteristics of mesoporous silicas |
| title | Effect of precursor and surfactant nature on geometrical characteristics of mesoporous silicas |
| title_alt | Effect of precursor and surfactant nature on geometrical characteristics of mesoporous silicas Effect of precursor and surfactant nature on geometrical characteristics of mesoporous silicas |
| title_full | Effect of precursor and surfactant nature on geometrical characteristics of mesoporous silicas |
| title_fullStr | Effect of precursor and surfactant nature on geometrical characteristics of mesoporous silicas |
| title_full_unstemmed | Effect of precursor and surfactant nature on geometrical characteristics of mesoporous silicas |
| title_short | Effect of precursor and surfactant nature on geometrical characteristics of mesoporous silicas |
| title_sort | effect of precursor and surfactant nature on geometrical characteristics of mesoporous silicas |
| url | https://surfacezbir.com.ua/index.php/surface/article/view/79 |
| work_keys_str_mv | AT pavlenkoan effectofprecursorandsurfactantnatureongeometricalcharacteristicsofmesoporoussilicas AT yanishpolskiivv effectofprecursorandsurfactantnatureongeometricalcharacteristicsofmesoporoussilicas AT tertykhva effectofprecursorandsurfactantnatureongeometricalcharacteristicsofmesoporoussilicas AT ilinvg effectofprecursorandsurfactantnatureongeometricalcharacteristicsofmesoporoussilicas AT lebodar effectofprecursorandsurfactantnatureongeometricalcharacteristicsofmesoporoussilicas AT skubiszewskaziebaj effectofprecursorandsurfactantnatureongeometricalcharacteristicsofmesoporoussilicas |