The sol-gel synthesis of β-cyclodextrin-containing silica materials is reported. Organosilicas were pre-pared in tetraethylorthosilicate–3-(chloropropyl)triethoxysilane–β-cyclodextrin–ethanol–water system. These materials were characterized by IR spectroscopy and thermogravimetric analysis. Porosity of orga-nosilicas was characterized on nitrogen adsorption/desorption isotherms. The porosity analysis demon-strates that cyclodextrin-silica based materials are an isotherm Type I substance. The surface areas of the organosilicas with incorporated β-cyclodextrin are in the range 430–580 m2 g1; materials containing up to 0.005 mmol g1of β-cyclodextrin moieties have been successfully prepared. Synthesized organosilicas are stable in aqueous medium and could be used in processes of pollutants removal. The present study demon-strates a simple time-saving method of cyclodextrin-containing silicas obtaining via one-pot synthesis in mild condition without using toxic solvents, costly templates or cyclodextrin derivatives.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3523

Belyakova, L.A.

Trofymchuk, I.M.

SocioEconomic Challenges Journal (Sumy State University)

PROCEEDINGS OF THE INTERNATIONAL CONFERENCE  
NANOMATERIALS: APPLICATIONS AND PROPERTIES 
Vol. 2 No 3, 03NCNN10 (4pp) (2013) 
 
 
2304-1862/2013/2(3)03NCNN10(4) 03NCNN10-1  2013 Sumy State University 
Sol-gel Synthesis of β-Cyclodextrin-containing Silicas with  
3-(chloropropyl)triethoxysilane as Precursor 
 
I.M. Trofymchuk*, L.A. Belyakova 
 
Chuiko Institute of Surface Chemistry of NAS of Ukraine, 17 General Naumov Str., 03164 Kyiv, Ukraine  
 
(Received 16 May 2013; published online 30 August 2013) 
 
The sol-gel synthesis of β-cyclodextrin-containing silica materials is reported. Organosilicas were pre-
pared in tetraethylorthosilicate–3-(chloropropyl)triethoxysilane–β-cyclodextrin–ethanol–water system. 
These materials were characterized by IR spectroscopy and thermogravimetric analysis. Porosity of orga-
nosilicas was characterized on nitrogen adsorption/desorption isotherms. The porosity analysis demon-
strates that cyclodextrin-silica based materials are an isotherm Type I substance. The surface areas of the 
organosilicas with incorporated β-cyclodextrin are in the range 430–580 m2 g1; materials containing up to 
0.005 mmol g1of β-cyclodextrin moieties have been successfully prepared. Synthesized organosilicas are 
stable in aqueous medium and could be used in processes of pollutants removal. The present study demon-
strates a simple time-saving method of cyclodextrin-containing silicas obtaining via one-pot synthesis in 
mild condition without using toxic solvents, costly templates or cyclodextrin derivatives. 
 
Keywords: Sol-gel synthesis, Silica, Incorporation, β-Cyclodextrine, Tetraethylorthosilicate,  
3-(chloropropyl)triethoxysilane. 
 
 PACS number(s): 81.20.Fw, 82.80.Gk, 81.70.Gk 
 
 
                                                        
* trofymchuk_iryna@ukr.net 
1. INTRODUCTION 
 
Amongst the numerous organic materials, metal 
surfaces or inorganic oxide supports, silica has a high 
potential for creation functional nanomaterials owing 
to its physical and chemical properties. The aim of 
study cyclodextrin(CD)/silica materials preparation is 
twofold. The first is the possibility of CDs utilization as 
template (porogen) in the synthesis of porous substanc-
es with regular structure (so-called, nanocasting) [1-4]. 
Here, “worm-type” pore system is formed [1-2, 5]. Am-
phiphilic nature of CDs and their high water solubility 
[4] are defining properties for using CDs as porogens. 
The second is the application of CD/silica compositions 
as carriers in liquid chromatography or adsorbents for 
water purification [6]. Here, CDs water solubility is 
unacceptable. Therefore, formation of strong binding 
between CD moiety and silica surface is one of the 
main requirements in the application fields of CD-
containing materials. There are three pathways for 
CDs embedding in silica structure. The first two (coat-
ing and grafting methods) are based on the use of 
ready-made support [7-14]. They are studied and de-
scribed in detail. The third approach supposes the in-
troduction of CD moiety into the siliceous framework 
directly during the synthesis of silica material. A few 
investigations devoted to this approach have been de-
scribed in the literature. This procedure, as a rule, is 
realized by sol-gel synthesis with costly templates and 
CDs derivatives using [5, 8, 15]. Such materials were 
tested in processes of pollutants removal from aqueous 
media [5, 8-10, 16-18]. 
In this research, we report attempts at preparing 
CD-containing silicas from pristine β-cyclodextrin and a 
mixture of alkoxy silane compounds by sol-gel method. 
These materials were characterized by IR spectroscopy 
and N2 sorption experiments. The probably effective-
ness of CD-containing silicas from these approaches for 
adsorption of aromatic molecules is discussed. 
 
2. EXPERIMENTAL 
 
2.1 Synthesis 
 
Sol-gel materials were prepared by the acidic hy-
drolysis (0.1M HCl) of tetraethylorthosilicate (TEOS) 
or TEOS/3-(chloropropyl)triethoxysilane(CPTEOS) 
blend in ethanol. The molar ratio 5 : 1 and 8 : 1 of 
alkoxysilanes were used. CD-functionalized materials 
were obtain by agitation a β-CD and alkoxysilanes 
compounds together with a solvent (C2H5OH) to give a 
mixture. The reaction mixture was blended on mag-
netic stirrer about 20 min. Then the appropriate 
amount of water was added to cause hydrolysis of the 
alkoxysilane compounds and gelation of the hydroly-
zate to give a uniform gelled mass. Gelling of sols was 
carried out via ageing at 70 C up the viscosity of the 
solution was gradually increased and was finally 
gelled and solidified into a jelly-like uniform mass. 
Also the gelling of sols was realized via hydrothermal 
treatment (HTT) in autoclave at 150 C during 3 h. 
Obtained xerogels were washed by water and dried at 
ambient temperature. 
 
2.2 Analysis  
 
Infrared spectra were registered in the range from 
4000 to 400 cm–1 using Thermo Nicolet NEXUS 
FTIR spectrophotometer equipped with an environ-
mental chamber for selector DRIFT. The spectra were 
performed in KBr pellets with 1 : 20 ratio of sample 
and KBr, respectively.  
Porosity measurements were obtained with a No-
va 1200 apparatus from Quantachrome Corporation. 
Specific surface areas were determined using the BET 
 I.M. TROFYMCHUK, L.A. BELYAKOVA PROC. NAP 2, 03NCNN10 (2013) 
 
 
03NCNN10-2 
method. The pore volumes and the pore size distribu-
tions were obtained using BJI isotherm. 
Thermogravimetric analysis was carried out on a 
Derivatograph-Q (MOM, Budapest) in the temperature 
range 30–600 C with a heating rate of 10 min–1.  
The content of β-CD in organosilicas was deter-
mined with acid hydrolysis of cyclodextrin up to glu-
cose. The concentration of glucose after the reaction 
with potassium ferrocyanide was defined by spectro-
photometry using Specord M-40 equipment (Germany, 
Carl Zeiss Jena) at λ = 420 nm [19]. 
 
3. RESULTS AND DISCUSSIONS  
 
The possibility of preparing CD-silica by using sol-
gel approach has been recently proposed. CD-silica 
composite was prepared by the hydrolysis and silanol 
condensation of TEOS in the presence of CD to give a 
gelled siliceous mass, into which molecules of CD are 
incorporated presumably or mostly by forming Si–O–C 
linkages [20]. 
Our aim was to obtain stable in aqueous media CD-
containing silicas with using functional silanes and 
unmodified β-CD. It was shown that CD-containing 
silicas prepared from TEOS in water-ethanol solution 
with acid catalyst are hydrolytically unstable and could 
not be used as adsorbents for the removal of toxic con-
taminants from water.  
In the DRIFT spectra of washed silica obtained 
from β-CD/TEOS mixture in the range 3800–3150 cm–
1 there is no clear maximum as in the spectra of β-CD 
and  
β-CD-containing xerogel, which is likely to cause the 
valence vibrations of the O–H bonds in the hydroxyl 
groups of β-CD connected by hydrogen bonds. Also, 
the band with absorption maximum at 2932 cm−1 (va-
lence vibrations of the C–H bonds in the CH and CH2 
groups of β-CD molecules) disappears in washed xero-
gel. The band assignments in the DRIFT spectra of β-
CD and  
β-CD-containing xerogel in the interval 1400500 cm–1 
showed, that only in unwashed xerogel absorption 
bands of β-CD groups are present. Thus, in the region 
14001200 cm1 the absorption bands of the 
deformation vibrations δC–H in the primary and 
secondary hydroxyl groups of β-СD are registered. In 
the interval 12001030 сm1 the absorption bands of 
the valence vibrations of the СО bonds in the ether 
and hydroxyl groups of β-СD (1078 and 1030 cm1) are 
observed. The absorption bands in the range 
950700 cm1 belong to deformation vibration δC–H 
and the pulsation vibrations in the glucopyranose 
cycle. 
The drastic decrease of β-CD moieties on the surface 
of prepared materials was also confirmed by chemical 
analysis. Hence, it is obvious that hydrolytically unsta-
ble Si–O–C linkages are formed as a result of sol-gel 
synthesis of CD-containing silicas from TEOS and CD. 
 
3.1 FTIR spectrophotometry 
 
Hydrolytically stable CD-containing silacas could be 
prepared by hydrolysis and polycondensation of TEOS 
and CPTEOS. In the presence of CPTEOS stronger 
COC linkages are possible to form. 
Infrared spectra of pristine silica, functionalized 
organosilica and CD-containing silica are shown in 
Figure 1. The silanol groups disposed on the silica 
surface and the presence of remaining water mole-
cules produce the broad stretching band around 
3046 cm1, followed by a band around 1640 cm1, at-
tributed to deformation vibration δO–H. A strong ab-
sorption band near 1100 cm1, attributed to asymmet-
ric stretching of Si–O–Si bonds, is observed in all sili-
ca samples. When analyzing organosilica materials, 
the presence of absorption band of deformation vibra-
tions of the СН bonds at 1443 cm1 is observed. After 
the hydrolysis and polycondensation of TE-
OS/CPTEOS mixture both in the absence and pres-
ence of β-СD, the characteristic bands in the region 
14001200 cm1 and 1200900 сm1are appeared in 
the spectra of silica materials. These bands related to 
the valence vibrations of the СО, СОH, and СОC 
bonds as well as deformation vibrations of the СH 
bonds. Indication of the presence of CDs on silica is 
the appearance of specific vibration band ascribed to 
β-CD at 2943 cm1. 
 
4000 3500 3000 2500 2000 1500 1000 500
2943 cm
-1
 (CH)
2960 cm
-1
 (CH)
d
c
b
a
R
e
fle
ct
io
n
 [
%
]
Wavenumber [cm
-1
]
 
Fig. 1 – DRIFT spectra of β-cyclodextrin (a) and silicas pre-
pared from TEOS (b), TEOS/CPTEOS=5 : 1 (c), and cyclodex-
trin-silica based material (d) 
 
The band assignments in DRIFT spectra confirm 
the presence of β-CD on the surface of synthesized ma-
terials. Since the primary hydroxyl groups of the β-CD 
are more nucleophilic, more basic and less sterically 
hindered than the secondary hydroxyls, the primary 
hydroxyl groups exhibit also greater reactivity. Conse-
quently, CDs are predominantly attached via this 
group and an appropriate spacer to the surface [21]. 
However, the formation of C–O–C bound with partici-
pation of the secondary hydroxyl groups of β-CD is not 
excluded. 
 
3.2 Structural characterization of sol-gel CD-
silica composites 
 
Texture is one of the main characteristics, which 
could explain later the behaviour of materials in decon-
tamination applications. Figure 2 shows the nitrogen 
adsorption and desorption isotherms of the pristine 
silica and functionalized silicas. The textural character-
istics derived from N2 adsorption/desorption experi-
ments of studied materials are summarized in Table 1. 
 
 SOL-GEL SYNTHESIS OF Β-CYCLODEXTRIN-CONTAINING SILICAS…. PROC. NAP 2, 03NCNN10 (2013) 
 
 
03NCNN10-3 
Table 1 – Physical and surface properties of cyclodextrin silica-based materials 
 
Sample TEOS/ 
CPTEOS  
ratio 
Synthesis 
condition 
Surface 
area 
(m2 g-1) 
Total spesific mi-
cropore volume 
Vmicro (cm3 g-1) 
Total spesific 
mesopore volume 
Vmeso (cm3 g-1) 
CD con-
tent 
(µmol g1) 
 Silica – 70 C 863 0,033 0,291 – 
 Silica – 150 C, 3h 720 0,044 0,206 – 
 Silica – CPTEOS 8 : 1 70 C 530 0,129 0,198 – 
 Silica – CPTEOS  8 : 1 150 C, 3h 489 0,124 0,188 – 
 Silica – CPTEOS  5 : 1 70 C 396 0,084 0,171 – 
 Silica – CPTEOS  5 : 1 150 C, 3h 470 0,081 0,155 – 
 Silica – β-CD 8 : 1 70 C 533 0,129 0,202 3,54 
 Silica – β-CD 8 : 1 150 C, 3h 577 0,131 0,131 2,76 
 Silica – β-CD 5 : 1 70 C 429 0,107 0,177 4,83 
 Silica – β-CD 5 : 1 150 C, 3h 485 0,083 0,134 2,66 
 
0,0 0,2 0,4 0,6 0,8 1,0
100
120
140
160
180
200
220
240
V
o
lu
m
e
 a
d
s
o
rb
e
d
 [
c
m
3
/g
]
P/P
0  
 
    a 
20 40 60 80 100 120
0,00
0,01
0,02
0,03
0,04
0,05
0,06
In
c
re
m
e
n
t 
P
o
re
 V
o
lu
m
e
 [
c
m
3
/g
]
Pore Diametr [A]   
 
    b 
 
Fig. 2 – N2 adsorption-desorption isotherms (a) and pore size 
distribution (b) for pristine SiO2 (square symbol), silica pre-
pared from TEOS/CPTEOS as precursors (circle symbol), and 
CD-silica composite (triangle symbol) 
 
According to the common classification of adsorp-
tion isotherms, the isotherms for all synthesized silicas 
are considered Type I. It could be concluded that there 
are no drastic changes in the morphology of materials. 
However, isotherms of silica prepared from TE-
OS/CPTEOS mixture and CD-silica composite exhibited 
narrow hysteresis loops in the wide range of P/P0. This 
hysteresis is not seen in the isotherm of pristine silica 
prepared from TEOS. The appearance of hysteresis 
loops could be explain by the present both micro and 
mesopores. The pore size distribution (Figure 2(b)) es-
timated from the desorption branch of the isotherm is 
narrower for pristine silica and CD-silica composite 
with the average pore diameter 2,5 nm. As expected, 
the specific surface area decreases for materials with 
higher TEOS/CPTEOS molar ratio. The total volume of 
micropores obtained from BJI model increases in the 
issue of silica functionalization. 
It was stated above that the characteristic FTIR 
bands qualitatively denoting the successful incorpora-
tion of CD groups into the silica frameworks. The pres-
ence of β-CD on the surface of prepared materials was 
confirmed by chemical analysis. The content of β-CD in 
organosilicas is shown in the Table 1. Compared to CD-
silica materials with TEOS/CPTEOS = 8 : 1 molar ratio 
of initial solution, the higher CD group loadings can be 
achieved using the molar ratio 5 : 1. 
 
3.3 Thermal analysis of CD-containing materials 
 
The three series samples (silicas from TEOS, silicas 
from TEOS/CPTEOS mixture, and CD-silicas from 
TEOS/CPTEOS mixture) in our study have different 
thermo destruction. Generally, it could be distinguish 
two main regions in thermogravimetric curves of all 
silicas. The region up to 150 C corresponds to desorp-
tion of physically adsorbed water or perhaps residual 
solvent. The principal weight loss is observed in the 
region after 150 C, and is related to the removal of 
organics accompained by polimerization, structural 
relaxation, and bond shrinkage.  
For the silicas, prepared from the hydrolytic con-
densation of TEOS, desorption of physically adsorbed 
water is observed at 100 C. Then the slow structure 
reorganization is occurred. Organosilicas have more 
drastic weight loss in the region 235–480 C. According 
to the thermogravimetric results obtained on CD-silica 
materials, the temperature, for which the rate of 
weight loss was the most significant, was about 295 C. 
This weight loss correlates with the thermal degrada-
tion of CD moieties on silica surfaces [12]. 
 
4. CONCLUSION 
 
Hydrolytically unstable Si–O–C linkages are formed 
as a result of sol-gel synthesis of CD-containing silicas 
from TEOS and CD. Hydrolytically stable CD-
containing silicas were prepared by hydrolysis and pol-
ycondensation of TEOS and CPTEOS, where the 
stronger C–O–C linkages are formed. The band as-
 I.M. TROFYMCHUK, L.A. BELYAKOVA PROC. NAP 2, 03NCNN10 (2013) 
 
 
03NCNN10-4 
signments of DRIFT spectra confirm the presence of β-
CD moieties in organosilicas. The porosity analysis 
demonstrates that CD-silica based materials are an 
isotherm Type I substance and pore size distribution 
with a small maximum at 2.5 nm. The surface areas of 
the organosilicas with incorporated β-CD are in the 
range 430–580 m2 g1; materials containing up to 
0.005 mmol g1of β-CD moieties have been successfully 
prepared. Thermogravimetric analysis of CD-
containing materials reveals an important weight loss 
in the temperature range 235–480 C, corresponding to 
the progressive decomposition of the organic moieties.  
Although synthesized organosilicas show smallest 
CD group loadings in comparison with known CD-
containing materials, they were obtained via a simple 
sol-gel technique in one-pot synthesis, which does not 
require high temperatures, toxic organic solvents and a 
huge investment of time. 
Direct sol-gel synthesis of hydrolytically stable CD-
containing silicas can therefore be considered for the 
preparation of sorbents for effective separation and 
removal of aromatic compounds from aqueous media. 
 
 
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Sol-gel Synthesis of β-Cyclodextrin-containing Silicas with 3-(chloropropyl)triethoxysilane as Precursor

Electronic Sumy State University Institutional Repository

PROCEEDINGS OF THE INTERNATIONAL CONFERENCE  NANOMATERIALS: APPLICATIONS AND PROPERTIES Vol. 2 No 3, 03NCNN10 (4pp) (2013)   2304-1862/2013/2(3)03NCNN10(4) 03NCNN10-1  2013 Sumy State University Sol-gel Synthesis of β-Cyclodextrin-containing Silicas with  3-(chloropropyl)triethoxysilane as Precursor  I.M. Trofymchuk*, L.A. Belyakova  Chuiko Institute of Surface Chemistry of NAS of Ukraine, 17 General Naumov Str., 03164 Kyiv, Ukraine   (Received 16 May 2013; published online 30 August 2013)  The sol-gel synthesis of β-cyclodextrin-containing silica materials is reported. Organosilicas were pre-pared in tetraethylorthosilicate–3-(chloropropyl)triethoxysilane–β-cyclodextrin–ethanol–water system. These materials were characterized by IR spectroscopy and thermogravimetric analysis. Porosity of orga-nosilicas was characterized on nitrogen adsorption/desorption isotherms. The porosity analysis demon-strates that cyclodextrin-silica based materials are an isotherm Type I substance. The surface areas of the organosilicas with incorporated β-cyclodextrin are in the range 430–580 m2 g1; materials containing up to 0.005 mmol g1of β-cyclodextrin moieties have been successfully prepared. Synthesized organosilicas are stable in aqueous medium and could be used in processes of pollutants removal. The present study demon-strates a simple time-saving method of cyclodextrin-containing silicas obtaining via one-pot synthesis in mild condition without using toxic solvents, costly templates or cyclodextrin derivatives.  Keywords: Sol-gel synthesis, Silica, Incorporation, β-Cyclodextrine, Tetraethylorthosilicate,  3-(chloropropyl)triethoxysilane.   PACS number(s): 81.20.Fw, 82.80.Gk, 81.70.Gk                                                           * trofymchuk_iryna@ukr.net 1. INTRODUCTION  Amongst the numerous organic materials, metal surfaces or inorganic oxide supports, silica has a high potential for creation functional nanomaterials owing to its physical and chemical properties. The aim of study cyclodextrin(CD)/silica materials preparation is twofold. The first is the possibility of CDs utilization as template (porogen) in the synthesis of porous substanc-es with regular structure (so-called, nanocasting) [1-4]. Here, “worm-type” pore system is formed [1-2, 5]. Am-phiphilic nature of CDs and their high water solubility [4] are defining properties for using CDs as porogens. The second is the application of CD/silica compositions as carriers in liquid chromatography or adsorbents for water purification [6]. Here, CDs water solubility is unacceptable. Therefore, formation of strong binding between CD moiety and silica surface is one of the main requirements in the application fields of CD-containing materials. There are three pathways for CDs embedding in silica structure. The first two (coat-ing and grafting methods) are based on the use of ready-made support [7-14]. They are studied and de-scribed in detail. The third approach supposes the in-troduction of CD moiety into the siliceous framework directly during the synthesis of silica material. A few investigations devoted to this approach have been de-scribed in the literature. This procedure, as a rule, is realized by sol-gel synthesis with costly templates and CDs derivatives using [5, 8, 15]. Such materials were tested in processes of pollutants removal from aqueous media [5, 8-10, 16-18]. In this research, we report attempts at preparing CD-containing silicas from pristine β-cyclodextrin and a mixture of alkoxy silane compounds by sol-gel method. These materials were characterized by IR spectroscopy and N2 sorption experiments. The probably effective-ness of CD-containing silicas from these approaches for adsorption of aromatic molecules is discussed.  2. EXPERIMENTAL  2.1 Synthesis  Sol-gel materials were prepared by the acidic hy-drolysis (0.1M HCl) of tetraethylorthosilicate (TEOS) or TEOS/3-(chloropropyl)triethoxysilane(CPTEOS) blend in ethanol. The molar ratio 5 : 1 and 8 : 1 of alkoxysilanes were used. CD-functionalized materials were obtain by agitation a β-CD and alkoxysilanes compounds together with a solvent (C2H5OH) to give a mixture. The reaction mixture was blended on mag-netic stirrer about 20 min. Then the appropriate amount of water was added to cause hydrolysis of the alkoxysilane compounds and gelation of the hydroly-zate to give a uniform gelled mass. Gelling of sols was carried out via ageing at 70 C up the viscosity of the solution was gradually increased and was finally gelled and solidified into a jelly-like uniform mass. Also the gelling of sols was realized via hydrothermal treatment (HTT) in autoclave at 150 C during 3 h. Obtained xerogels were washed by water and dried at ambient temperature.  2.2 Analysis   Infrared spectra were registered in the range from 4000 to 400 cm–1 using Thermo Nicolet NEXUS FTIR spectrophotometer equipped with an environ-mental chamber for selector DRIFT. The spectra were performed in KBr pellets with 1 : 20 ratio of sample and KBr, respectively.  Porosity measurements were obtained with a No-va 1200 apparatus from Quantachrome Corporation. Specific surface areas were determined using the BET  I.M. TROFYMCHUK, L.A. BELYAKOVA PROC. NAP 2, 03NCNN10 (2013)   03NCNN10-2 method. The pore volumes and the pore size distribu-tions were obtained using BJI isotherm. Thermogravimetric analysis was carried out on a Derivatograph-Q (MOM, Budapest) in the temperature range 30–600 C with a heating rate of 10 min–1.  The content of β-CD in organosilicas was deter-mined with acid hydrolysis of cyclodextrin up to glu-cose. The concentration of glucose after the reaction with potassium ferrocyanide was defined by spectro-photometry using Specord M-40 equipment (Germany, Carl Zeiss Jena) at λ = 420 nm [19].  3. RESULTS AND DISCUSSIONS   The possibility of preparing CD-silica by using sol-gel approach has been recently proposed. CD-silica composite was prepared by the hydrolysis and silanol condensation of TEOS in the presence of CD to give a gelled siliceous mass, into which molecules of CD are incorporated presumably or mostly by forming Si–O–C linkages [20]. Our aim was to obtain stable in aqueous media CD-containing silicas with using functional silanes and unmodified β-CD. It was shown that CD-containing silicas prepared from TEOS in water-ethanol solution with acid catalyst are hydrolytically unstable and could not be used as adsorbents for the removal of toxic con-taminants from water.  In the DRIFT spectra of washed silica obtained from β-CD/TEOS mixture in the range 3800–3150 cm–1 there is no clear maximum as in the spectra of β-CD and  β-CD-containing xerogel, which is likely to cause the valence vibrations of the O–H bonds in the hydroxyl groups of β-CD connected by hydrogen bonds. Also, the band with absorption maximum at 2932 cm−1 (va-lence vibrations of the C–H bonds in the CH and CH2 groups of β-CD molecules) disappears in washed xero-gel. The band assignments in the DRIFT spectra of β-CD and  β-CD-containing xerogel in the interval 1400500 cm–1 showed, that only in unwashed xerogel absorption bands of β-CD groups are present. Thus, in the region 14001200 cm1 the absorption bands of the deformation vibrations δC–H in the primary and secondary hydroxyl groups of β-СD are registered. In the interval 12001030 сm1 the absorption bands of the valence vibrations of the СО bonds in the ether and hydroxyl groups of β-СD (1078 and 1030 cm1) are observed. The absorption bands in the range 950700 cm1 belong to deformation vibration δC–H and the pulsation vibrations in the glucopyranose cycle. The drastic decrease of β-CD moieties on the surface of prepared materials was also confirmed by chemical analysis. Hence, it is obvious that hydrolytically unsta-ble Si–O–C linkages are formed as a result of sol-gel synthesis of CD-containing silicas from TEOS and CD.  3.1 FTIR spectrophotometry  Hydrolytically stable CD-containing silacas could be prepared by hydrolysis and polycondensation of TEOS and CPTEOS. In the presence of CPTEOS stronger COC linkages are possible to form. Infrared spectra of pristine silica, functionalized organosilica and CD-containing silica are shown in Figure 1. The silanol groups disposed on the silica surface and the presence of remaining water mole-cules produce the broad stretching band around 3046 cm1, followed by a band around 1640 cm1, at-tributed to deformation vibration δO–H. A strong ab-sorption band near 1100 cm1, attributed to asymmet-ric stretching of Si–O–Si bonds, is observed in all sili-ca samples. When analyzing organosilica materials, the presence of absorption band of deformation vibra-tions of the СН bonds at 1443 cm1 is observed. After the hydrolysis and polycondensation of TE-OS/CPTEOS mixture both in the absence and pres-ence of β-СD, the characteristic bands in the region 14001200 cm1 and 1200900 сm1are appeared in the spectra of silica materials. These bands related to the valence vibrations of the СО, СОH, and СОC bonds as well as deformation vibrations of the СH bonds. Indication of the presence of CDs on silica is the appearance of specific vibration band ascribed to β-CD at 2943 cm1.  4000 3500 3000 2500 2000 1500 1000 5002943 cm-1 (CH)2960 cm-1 (CH)dcbaReflection [%]Wavenumber [cm-1] Fig. 1 – DRIFT spectra of β-cyclodextrin (a) and silicas pre-pared from TEOS (b), TEOS/CPTEOS=5 : 1 (c), and cyclodex-trin-silica based material (d)  The band assignments in DRIFT spectra confirm the presence of β-CD on the surface of synthesized ma-terials. Since the primary hydroxyl groups of the β-CD are more nucleophilic, more basic and less sterically hindered than the secondary hydroxyls, the primary hydroxyl groups exhibit also greater reactivity. Conse-quently, CDs are predominantly attached via this group and an appropriate spacer to the surface [21]. However, the formation of C–O–C bound with partici-pation of the secondary hydroxyl groups of β-CD is not excluded.  3.2 Structural characterization of sol-gel CD-silica composites  Texture is one of the main characteristics, which could explain later the behaviour of materials in decon-tamination applications. Figure 2 shows the nitrogen adsorption and desorption isotherms of the pristine silica and functionalized silicas. The textural character-istics derived from N2 adsorption/desorption experi-ments of studied materials are summarized in Table 1.   SOL-GEL SYNTHESIS OF Β-CYCLODEXTRIN-CONTAINING SILICAS…. PROC. NAP 2, 03NCNN10 (2013)   03NCNN10-3 Table 1 – Physical and surface properties of cyclodextrin silica-based materials  Sample TEOS/ CPTEOS  ratio Synthesis condition Surface area (m2 g-1) Total spesific mi-cropore volume Vmicro (cm3 g-1) Total spesific mesopore volume Vmeso (cm3 g-1) CD con-tent (µmol g1)  Silica – 70 C 863 0,033 0,291 –  Silica – 150 C, 3h 720 0,044 0,206 –  Silica – CPTEOS 8 : 1 70 C 530 0,129 0,198 –  Silica – CPTEOS  8 : 1 150 C, 3h 489 0,124 0,188 –  Silica – CPTEOS  5 : 1 70 C 396 0,084 0,171 –  Silica – CPTEOS  5 : 1 150 C, 3h 470 0,081 0,155 –  Silica – β-CD 8 : 1 70 C 533 0,129 0,202 3,54  Silica – β-CD 8 : 1 150 C, 3h 577 0,131 0,131 2,76  Silica – β-CD 5 : 1 70 C 429 0,107 0,177 4,83  Silica – β-CD 5 : 1 150 C, 3h 485 0,083 0,134 2,66  0,0 0,2 0,4 0,6 0,8 1,0100120140160180200220240Volume adsorbed [cm3/g]P/P0       a 20 40 60 80 100 1200,000,010,020,030,040,050,06Increment Pore Volume [cm3/g]Pore Diametr [A]        b  Fig. 2 – N2 adsorption-desorption isotherms (a) and pore size distribution (b) for pristine SiO2 (square symbol), silica pre-pared from TEOS/CPTEOS as precursors (circle symbol), and CD-silica composite (triangle symbol)  According to the common classification of adsorp-tion isotherms, the isotherms for all synthesized silicas are considered Type I. It could be concluded that there are no drastic changes in the morphology of materials. However, isotherms of silica prepared from TE-OS/CPTEOS mixture and CD-silica composite exhibited narrow hysteresis loops in the wide range of P/P0. This hysteresis is not seen in the isotherm of pristine silica prepared from TEOS. The appearance of hysteresis loops could be explain by the present both micro and mesopores. The pore size distribution (Figure 2(b)) es-timated from the desorption branch of the isotherm is narrower for pristine silica and CD-silica composite with the average pore diameter 2,5 nm. As expected, the specific surface area decreases for materials with higher TEOS/CPTEOS molar ratio. The total volume of micropores obtained from BJI model increases in the issue of silica functionalization. It was stated above that the characteristic FTIR bands qualitatively denoting the successful incorpora-tion of CD groups into the silica frameworks. The pres-ence of β-CD on the surface of prepared materials was confirmed by chemical analysis. The content of β-CD in organosilicas is shown in the Table 1. Compared to CD-silica materials with TEOS/CPTEOS = 8 : 1 molar ratio of initial solution, the higher CD group loadings can be achieved using the molar ratio 5 : 1.  3.3 Thermal analysis of CD-containing materials  The three series samples (silicas from TEOS, silicas from TEOS/CPTEOS mixture, and CD-silicas from TEOS/CPTEOS mixture) in our study have different thermo destruction. Generally, it could be distinguish two main regions in thermogravimetric curves of all silicas. The region up to 150 C corresponds to desorp-tion of physically adsorbed water or perhaps residual solvent. The principal weight loss is observed in the region after 150 C, and is related to the removal of organics accompained by polimerization, structural relaxation, and bond shrinkage.  For the silicas, prepared from the hydrolytic con-densation of TEOS, desorption of physically adsorbed water is observed at 100 C. Then the slow structure reorganization is occurred. Organosilicas have more drastic weight loss in the region 235–480 C. According to the thermogravimetric results obtained on CD-silica materials, the temperature, for which the rate of weight loss was the most significant, was about 295 C. This weight loss correlates with the thermal degrada-tion of CD moieties on silica surfaces [12].  4. CONCLUSION  Hydrolytically unstable Si–O–C linkages are formed as a result of sol-gel synthesis of CD-containing silicas from TEOS and CD. Hydrolytically stable CD-containing silicas were prepared by hydrolysis and pol-ycondensation of TEOS and CPTEOS, where the stronger C–O–C linkages are formed. The band as- I.M. TROFYMCHUK, L.A. BELYAKOVA PROC. NAP 2, 03NCNN10 (2013)   03NCNN10-4 signments of DRIFT spectra confirm the presence of β-CD moieties in organosilicas. The porosity analysis demonstrates that CD-silica based materials are an isotherm Type I substance and pore size distribution with a small maximum at 2.5 nm. The surface areas of the organosilicas with incorporated β-CD are in the range 430–580 m2 g1; materials containing up to 0.005 mmol g1of β-CD moieties have been successfully prepared. Thermogravimetric analysis of CD-containing materials reveals an important weight loss in the temperature range 235–480 C, corresponding to the progressive decomposition of the organic moieties.  Although synthesized organosilicas show smallest CD group loadings in comparison with known CD-containing materials, they were obtained via a simple sol-gel technique in one-pot synthesis, which does not require high temperatures, toxic organic solvents and a huge investment of time. 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Sol-gel Synthesis of β-Cyclodextrin-containing Silicas with 3-(chloropropyl)triethoxysilane as Precursor

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