Stöber’s method and two-component systems (considering alkoxysilanes) were used to develop tech-niques for the synthesis of spherical silica particles with ≡Si(CH2)3NH2 groups in the surface layer. The in-fluence of synthesis conditions on the size of synthesized spherical particles and concentration of functional groups were studied. DRIFT, SEM and acid–base titration were used to identify the composition of the sur-face layers and morphology of the obtained silica particles. There was analyzed the influence of the order entry components, the stirring time, the drying mode, the ratio of reacting of alkoxysilanes, the tempera-ture, and the amount of water and solvent on the morphology, the size of synthesized spherical particles and the content of functional groups in the silica spheres.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3525

Melnyk, Yu.L.

Tomina, V.V.

Zub, Y.L.

Electronic Sumy State University Institutional Repository

PROCEEDINGS OF THE INTERNATIONAL CONFERENCE  NANOMATERIALS: APPLICATIONS AND PROPERTIES Vol. 2 No 2, 02PCN40(3pp) (2013)   2304-1862/2013/2(2)02PCN40(3) 02PCN40-1  2013 Institute of Surface Chemistry Synthesis Submicro- and Nanoscale Spherical Silica Particles with 3-aminopropyl Groups in the Surface Layer  І.V. Melnyk, V.V. Tomina, Yu.L. Zub  Chuiko Institute of Surface Chemistry of NAS of Ukraine, 17, General Naumov Str., 03164 Kyiv, Ukraine  (Received 16 June 2013; published online 03 September 2013)  Stöber’s method and two-component systems (considering alkoxysilanes) were used to develop tech-niques for the synthesis of spherical silica particles with ≡Si(CH2)3NH2 groups in the surface layer. The in-fluence of synthesis conditions on the size of synthesized spherical particles and concentration of functional groups were studied. DRIFT, SEM and acid–base titration were used to identify the composition of the sur-face layers and morphology of the obtained silica particles. There was analyzed the influence of the order entry components, the stirring time, the drying mode, the ratio of reacting of alkoxysilanes, the tempera-ture, and the amount of water and solvent on the morphology, the size of synthesized spherical particles and the content of functional groups in the silica spheres.   Keywords: Stöber’s method, silica submicro- and nanoparticles, amino groups.   PACS numbers: 81.20.Fw, 94.20.Qq   1. INTRODUCTION  There have recently been published papers describ-ing synthesis of non-porous silica nano- and submicro-spheres with functional groups in the surface layer [1,2]. The suggested technique was based on Stöber method [3]. These silica spheres due to their excellent properties, such as adjustable size and surface layer composition, along with their chemical stability and biocompatibility, are promising materials for applica-tion in wide range of areas (chromatography, controlled drug delivery, bioseparation, chemo- and biosensors, biocatalysis). There are two most commonly used tech-niques for the synthesis of functionalized silica nano- and submicrospheres. The first of them is based on the surface modification of silica spheres obtained by Stöber method with trifunctional silanes, (RO)3SiR'. The second technique applies one-step synthesis. In other words, the structural agent (usually tetraethox-ysilane, TEOS) and functionalizing agent are entered simultaneously or sequentially (in some order) in the reactive solution. However, the very first works showed that, despite their simplicity, both approaches are characterized by the existence of unknown factors af-fecting the shape and size of particles, the content of functional groups, hydrolytic stability of the surface layer, and even the final product yield. Thus, in the first studies examining the preparation of nanoparti-cles with 3-aminopropyl groups, it was shown that heating suspension in DMF at 100°C for 24 h does not increase the content of surface amino groups, but im-proves the stability of the surface layer [2].  It was determined [1] that the introduction of 3-aminopropyltriethoxysilane (APTES) to TEOS alkosol at a molar ratio of 1/1 yields nanoparticles with an average diameter about 66 nm, but their surface layer contains almost no amino groups. At 3/1 TEOS/APTES molar ratio, the surface layer contains amine groups (1.56 mmol/g), but the particle size decreases to about 9 nm. When the order of components was changed, the content of functional groups increased to 3.2 mmol/g; however, according to 29Si NMR spectroscopy, the number of Q4 structural units decreases. This may indicate the looseness of the particles polysiloxane network. Therefore, the current paper is aimed to establish a number of factors affecting the morphology of spherical silica, their particle size, the content of the functional groups. As functional groups, there was chosen com-plexing 3-aminopropyl group.  2. EXPERIMENTAL PART  2.1 Reagents  The following substances were used as precursors for synthesis of the samples: tetraethoxysilane, Si(OC2H5)4 (Aldrich, 98%); 3-aminopropyl-triethoxysilane, (C2H5O)3Si(CH2)3NH2 (Fluka, 98%); ethanol (96%); ammonium hydroxide (25% aq.) (reagent grade, “Makrohim”, Ukraine). Reagents for acid-base titration: 0.1 N solutions of HCl and NaOH prepared from fixanal; indicator was methylene orange.  2.2 Syntheses   Sample 1. 4.5 сm3 of TEOS were added at constant stirring to ethanol-ammonium solution (see Table 1).  Opalescence was appeared after 5 min. and it was in-creased with time. 1.5 cm3 of  APTES were added to the suspension after stirring for 1 h. The suspension was stirred 23 h and the precipitate was centrifuged (for 10 min at 5000 rpm), and washed triply with ethanol. The sample was dried in air and after that in the drying oven at 100°С for 1 day.  Samples 2-7. 21 сm3 of  25% aq. NH4OH and 14 сm3 of distilled water (besides sample 7) were added at con-stant stirring to 100 сm3 of ethanol. In several minutes, 2 cm3  APTES (6 cm3 in the case of sample 2, 1 cm3 in the case of sample 3) were added to the mixture. The solution immediately turned cloudy; however, in few minutes it got transparent again. Then 6 сm3 of ТЕОS were added to it. In two minutes, the solution was cloudy again, and the amount of precipitate started increasing. The suspension was stirred for some hours  І.V. MELNYK, V.V.TOMINA, YU.L. ZUB PROC. NAP 2, 02PCN40 (2013)   02PCN40-2 (see Table 1), and was centrifuged, washed and dried like sample 1 (except for sample 6 - it was dried in air, and 6* - it was dried under vacuum at 100ºC for 3 h). Sample 8. 1 cm3 of TEOS and 1 cm3 of APTES were added at constant stirring to 6 сm3 of ethanol in an ice bath.  In 15 min. obtained sol was left at room tempera-ture. In 30 min. it turned cloudy, and after 24 h sedi-ment was observed throughout the all volume. It was crushed and dried like sample 1. Sample 9. TEOS and APTES were mixed in ethanol in an ice bath. After the appearance of opalescence (45 min.) the solution of ammonia was added. The suspen-sion was stirred for 2h 15min. more and carried out similar to the sample 1.  Sample 10. Synthesis of the sample was carried out similarly to the sample 9, but at room temperature (20 ºC). The solution of ammonia was added after the ap-pearance of opalescence (30 min.). Sample 11. Synthesis of the sample was carried out similarly to the sample 9, but with heating to 45 ºC. The solution of ammonia was added after the appearance of opalescence (15 min.). The composition of the reaction solution and other parameters of syntheses are presented in Table 1.  2.3 Characterization  For SEM studies by JSM-6060LA Analytical Scan-ning Electron Microscope (Jeol, Tokyo, Japan) using secondary electrons at accelerating voltage of 30 kV, the samples were fixed on the surface of objective table. To prevent the accumulation of the positive charges and to receive contrasting images, the surface of the samples was covered with thin continues layer of gold or platinum by cathodic sputtering in vacuum. The content of amino groups was determined by aid–base titration [4]. Batches of  the samples (0.1 g) were treated with a 0.1 N HCl solution (20 cm3) for 24 h. The resulting precipitates were filtered and the fil-trate was titrated with 0.1 M NaOH in the presence of the indicator. The amine concentration was estimated using the difference between the content of protons in solution before and after sorption.   3. RESULTS AND DISCUSSION  The search for the methods of synthesis of spherical silica particles with 3-aminopropyl groups in their surface layer dates back to the 1990s. Some authors have suggested single [2] and two-stage [1,2] tech-niques, at room temperature [5] and with boiling solu-tion [1], and using different solvents [2]. Firstly, we synthesized sample 1 using the technique of [6]. In-deed, there was observed the formation of silica parti-cles under these conditions (Fig. 1), but IR spectroscopy and acid-base titration analyses showed no amine groups on their surfaces. Therefore, in the following synthesis (sample 2) there was used a method of suc-cessive addition of APTES and, later, TEOS, to the ethanol-ammonia medium [1]. However, sample 2 con-tained both spherical particles and non-spherical (Fig. 1). It was found, that the increasing molar ratio of TEOS/APTES improves the morphological characteris-tics of the samples (Fig. 1, samples 3 and 4). However, with the increase in the molar ratio to 6/1, the number of functional groups is significantly reduced (Table 1, sample 3). Therefore, in the following syntheses, we adhered to the optimal ratio of TEOS/APTES equal to 3/1 (Table 1, sample 4). It should be noted, that the increasing stirring time caused the reduction of func-tional groups content (see samples 4 and 5, Table 1) and the product yield. Therefore, the stirring was less than 1 h, which was marked in other papers [7]. Changing the drying mode (Table 1, samples 4, 6 and 6*) does not affect the morphology of samples (Fig. 1). However, the content of amine groups slightly increas-es for sample 4 due to more complete removal of water. For this reason, all the next samples were dried in the oven at 100ºC for 24 h.  Table 1 – The composition of the reaction solution and some properties of the synthesized samples  Sample EtOH, cm3 H2O, cm3 NH4OH, cm3 TEOS, cm3 APTES, cm3 Time, h Size, nm CNH2, mmol/g 1 40 - 21 4.5 1.5 24 450 not determ 2 100 14 21 6 6 2 200 2.1 3 100 14 21 6 1 1.5 700 0.3 4 100 14 21 6 2 1 400 1.3 5 100 14 21 6 2 6 400 0.7 6 100 14 21 6 2 1 300 1.1 6* 100 14 21 6 2 1 300 0.9 7 100 - 21 6 2 1 300 1.1 8 6 - - 1 1 24 100 2.1 9 100 - 1.8 4 1.4 3 100 1.3 10 100 - 1.8 4 1.4 2 300 1.4 11 100 - 1.8 4 1.4 1.5 700 1.7  Some authors believe, that the amount of water in the syntheses should be increased [1,2], but others consider that water from ammonia solution is enough for the reaction of hydrolytic polycondensation [8]. Comparing samples 6 and 7 (Table 1 and Figure 1), it is easy to conclude, that the additional amount of water does not affect the particle size and number of func-tional groups. Finally, there was analysed the effect of the synthe-sis temperature on the particle size and the content of functional groups, in terms of samples 9, 10, and 11. It should be mentioned, that in addition to the tempera-ture variation, the stirring time for these samples was also varied (Table 1). The fact is that after 1 h stirring time (sample 9), there was observed the formation of particles, too small to be centrifuged in our conditions. However, in our opinion, this factor (stirring time) would not significantly affect the particle size, and the temperature of hydrolytic polycondensation reaction of alkoxysilanes has a more significant effect. Comparing the size of these samples (Table 1), it is easy to con-clude, that the increase in temperature from the ice bath (≈ 2ºC) to 45ºC leads to 7 times increase in diame-ter of the particles. It is also accompanied by the in-crease in the content of functional groups (Table 1). It is interesting to note, that during the synthesis of xerogels with 3-aminopropyl groups [9] these groups created alkaline medium in water for hydrolytic poly-condensation reaction. Indeed, the synthesis of sample 8 at TEOS/APTES ratio of 1/1, without using ammonia  SYNTHESIS SUBMICRO- AND NANOSCALE SPHERICAL… PROC. NAP 2, 02PCN40 (2013)   02PCN40-3 solution (water source was 96% ethanol), the formation of spherical silica particles was also observed (Fig. 1). In the synthesis under similar conditions, but without TE-OS, the appearance of precipitate was not observed even when the solution was heated. Compared with the sam-ple 2, where the same ratio of alkoxysilanes was used, we found that the diameter of the particles for sample 8 is twice less, but both samples are characterized by the same content of amino groups (Table 1). Thus, nanoscale spherical silica particles with amino groups can be ob-tained without introducing ammonia. However, the synthesis of the sample 8 requires further research for improving the morphology of the particles.      Fig. 1 – Photomicrographs of synthesized samples obtained by SEM  4. CONCLUSIONS  The influence of factors, such as the order entry components, the stirring time, the drying mode, the ratio of reacting of alkoxysilanes, the temperature, and the amounts of water and solvent on the morphology and the content of functional groups in the silica spheres was analysed. It was shown, that the shape and size of the particles are majorly affected by the synthesis temperature, and the ratio of reacting alkoxysilanes determines the content of 3-aminopropyl groups.  AKNOWLEDGEMENTS  This work was carried out within the framework to the State Target Scientific and Technical Program of NASU “Nanotechnologies and Nanomaterials” (project #6.22.5.42) and the Target Complex Program of Fun-damental Research of NASU "Fundamental Problems of Nanostructures, Nanomaterials, Nanotechnologies" (project #57/13-Н).  REFERENCES  1. The Colloid Chemistry of Silica (Ed.: H. Bergna) Adv.in Chem.Series 234, Amer.Chem.Sci., (Washington, DC 1994) 2. R.D. Badley, W.T. Ford, F.J. McEnroe, R.A. Assinks, Langmuir 6, 792 (1990) 3. W. Stober, A.Fink, E. Bohn, J. Of Coll. And Interf. Sci, 26, 62 (1968) 4. I. Khatib, R. Parish, J. Organomet. Chem., 369, 9 (1989). 5. Z. Wu, H. Xiang, T. Kim, M.-S. Chun, K. Lee, J. Of Coll. And Interf. Sci. 304, 119 (2006). 6. G. Berriozabal, Y. R. de Miguel, Phys. Status Solidi C 7, N. 11–12, 2692 (2010) 7. G. Deng, M. A. Markowitz, P. R. Kust , B. P. Gaber, Mater. Sci. and Eng. C 11, 165 (2000)  8. A. van Blaaderen, A.Vrij, J. of Coll. And Interface Science, 156, 1 (1993) 9. Yu.L.Zub, O.O.Chuiko, O.V.Stechenko, Reports of NAS of Ukraine, 4, 150 (2002).  

Synthesis Submicro- and Nanoscale Spherical Silica Particles with 3-aminopropyl Groups in the Surface Layer

SocioEconomic Challenges Journal (Sumy State University)

PROCEEDINGS OF THE INTERNATIONAL CONFERENCE  
NANOMATERIALS: APPLICATIONS AND PROPERTIES 
Vol. 2 No 2, 02PCN40(3pp) (2013) 
 
 
2304-1862/2013/2(2)02PCN40(3) 02PCN40-1  2013 Institute of Surface Chemistry 
Synthesis Submicro- and Nanoscale Spherical Silica Particles with 
3-aminopropyl Groups in the Surface Layer 
 
І.V. Melnyk, V.V. Tomina, Yu.L. Zub 
 
Chuiko Institute of Surface Chemistry of NAS of Ukraine, 17, General Naumov Str., 03164 Kyiv, Ukraine 
 
(Received 16 June 2013; published online 03 September 2013) 
 
Stöber’s method and two-component systems (considering alkoxysilanes) were used to develop tech-
niques for the synthesis of spherical silica particles with ≡Si(CH2)3NH2 groups in the surface layer. The in-
fluence of synthesis conditions on the size of synthesized spherical particles and concentration of functional 
groups were studied. DRIFT, SEM and acid–base titration were used to identify the composition of the sur-
face layers and morphology of the obtained silica particles. There was analyzed the influence of the order 
entry components, the stirring time, the drying mode, the ratio of reacting of alkoxysilanes, the tempera-
ture, and the amount of water and solvent on the morphology, the size of synthesized spherical particles 
and the content of functional groups in the silica spheres.  
 
Keywords: Stöber’s method, silica submicro- and nanoparticles, amino groups. 
 
 PACS numbers: 81.20.Fw, 94.20.Qq 
 
 
1. INTRODUCTION 
 
There have recently been published papers describ-
ing synthesis of non-porous silica nano- and submicro-
spheres with functional groups in the surface layer 
[1,2]. The suggested technique was based on Stöber 
method [3]. These silica spheres due to their excellent 
properties, such as adjustable size and surface layer 
composition, along with their chemical stability and 
biocompatibility, are promising materials for applica-
tion in wide range of areas (chromatography, controlled 
drug delivery, bioseparation, chemo- and biosensors, 
biocatalysis). There are two most commonly used tech-
niques for the synthesis of functionalized silica nano- 
and submicrospheres. The first of them is based on the 
surface modification of silica spheres obtained by 
Stöber method with trifunctional silanes, (RO)3SiR'. 
The second technique applies one-step synthesis. In 
other words, the structural agent (usually tetraethox-
ysilane, TEOS) and functionalizing agent are entered 
simultaneously or sequentially (in some order) in the 
reactive solution. However, the very first works showed 
that, despite their simplicity, both approaches are 
characterized by the existence of unknown factors af-
fecting the shape and size of particles, the content of 
functional groups, hydrolytic stability of the surface 
layer, and even the final product yield. Thus, in the 
first studies examining the preparation of nanoparti-
cles with 3-aminopropyl groups, it was shown that 
heating suspension in DMF at 100°C for 24 h does not 
increase the content of surface amino groups, but im-
proves the stability of the surface layer [2].  It was 
determined [1] that the introduction of 3-
aminopropyltriethoxysilane (APTES) to TEOS alkosol 
at a molar ratio of 1/1 yields nanoparticles with an 
average diameter about 66 nm, but their surface layer 
contains almost no amino groups. At 3/1 TEOS/APTES 
molar ratio, the surface layer contains amine groups 
(1.56 mmol/g), but the particle size decreases to about 9 
nm. When the order of components was changed, the 
content of functional groups increased to 3.2 mmol/g; 
however, according to 29Si NMR spectroscopy, the 
number of Q4 structural units decreases. This may 
indicate the looseness of the particles polysiloxane 
network. 
Therefore, the current paper is aimed to establish a 
number of factors affecting the morphology of spherical 
silica, their particle size, the content of the functional 
groups. As functional groups, there was chosen com-
plexing 3-aminopropyl group. 
 
2. EXPERIMENTAL PART 
 
2.1 Reagents 
 
The following substances were used as precursors 
for synthesis of the samples: tetraethoxysilane, 
Si(OC2H5)4 (Aldrich, 98%); 3-aminopropyl-
triethoxysilane, (C2H5O)3Si(CH2)3NH2 (Fluka, 98%); 
ethanol (96%); ammonium hydroxide (25% aq.) (reagent 
grade, “Makrohim”, Ukraine). Reagents for acid-base 
titration: 0.1 N solutions of HCl and NaOH prepared 
from fixanal; indicator was methylene orange. 
 
2.2 Syntheses  
 
Sample 1. 4.5 сm3 of TEOS were added at constant 
stirring to ethanol-ammonium solution (see Table 1).  
Opalescence was appeared after 5 min. and it was in-
creased with time. 1.5 cm3 of  APTES were added to the 
suspension after stirring for 1 h. The suspension was 
stirred 23 h and the precipitate was centrifuged (for 10 
min at 5000 rpm), and washed triply with ethanol. The 
sample was dried in air and after that in the drying 
oven at 100°С for 1 day.  
Samples 2-7. 21 сm3 of  25% aq. NH4OH and 14 сm3 
of distilled water (besides sample 7) were added at con-
stant stirring to 100 сm3 of ethanol. In several minutes, 
2 cm3  APTES (6 cm3 in the case of sample 2, 1 cm3 in 
the case of sample 3) were added to the mixture. The 
solution immediately turned cloudy; however, in few 
minutes it got transparent again. Then 6 сm3 of ТЕОS 
were added to it. In two minutes, the solution was 
cloudy again, and the amount of precipitate started 
increasing. The suspension was stirred for some hours 
 І.V. MELNYK, V.V.TOMINA, YU.L. ZUB PROC. NAP 2, 02PCN40 (2013) 
 
 
02PCN40-2 
(see Table 1), and was centrifuged, washed and dried 
like sample 1 (except for sample 6 - it was dried in air, 
and 6* - it was dried under vacuum at 100ºC for 3 h). 
Sample 8. 1 cm3 of TEOS and 1 cm3 of APTES were 
added at constant stirring to 6 сm3 of ethanol in an ice 
bath.  In 15 min. obtained sol was left at room tempera-
ture. In 30 min. it turned cloudy, and after 24 h sedi-
ment was observed throughout the all volume. It was 
crushed and dried like sample 1. 
Sample 9. TEOS and APTES were mixed in ethanol 
in an ice bath. After the appearance of opalescence (45 
min.) the solution of ammonia was added. The suspen-
sion was stirred for 2h 15min. more and carried out 
similar to the sample 1.  
Sample 10. Synthesis of the sample was carried out 
similarly to the sample 9, but at room temperature (20 
ºC). The solution of ammonia was added after the ap-
pearance of opalescence (30 min.). 
Sample 11. Synthesis of the sample was carried out 
similarly to the sample 9, but with heating to 45 ºC. The 
solution of ammonia was added after the appearance of 
opalescence (15 min.). 
The composition of the reaction solution and other 
parameters of syntheses are presented in Table 1. 
 
2.3 Characterization 
 
For SEM studies by JSM-6060LA Analytical Scan-
ning Electron Microscope (Jeol, Tokyo, Japan) using 
secondary electrons at accelerating voltage of 30 kV, 
the samples were fixed on the surface of objective table. 
To prevent the accumulation of the positive charges 
and to receive contrasting images, the surface of the 
samples was covered with thin continues layer of gold 
or platinum by cathodic sputtering in vacuum. 
The content of amino groups was determined by 
aid–base titration [4]. Batches of  the samples (0.1 g) 
were treated with a 0.1 N HCl solution (20 cm3) for 24 
h. The resulting precipitates were filtered and the fil-
trate was titrated with 0.1 M NaOH in the presence of 
the indicator. The amine concentration was estimated 
using the difference between the content of protons in 
solution before and after sorption.  
 
3. RESULTS AND DISCUSSION 
 
The search for the methods of synthesis of spherical 
silica particles with 3-aminopropyl groups in their 
surface layer dates back to the 1990s. Some authors 
have suggested single [2] and two-stage [1,2] tech-
niques, at room temperature [5] and with boiling solu-
tion [1], and using different solvents [2]. Firstly, we 
synthesized sample 1 using the technique of [6]. In-
deed, there was observed the formation of silica parti-
cles under these conditions (Fig. 1), but IR spectroscopy 
and acid-base titration analyses showed no amine 
groups on their surfaces. Therefore, in the following 
synthesis (sample 2) there was used a method of suc-
cessive addition of APTES and, later, TEOS, to the 
ethanol-ammonia medium [1]. However, sample 2 con-
tained both spherical particles and non-spherical (Fig. 
1). It was found, that the increasing molar ratio of 
TEOS/APTES improves the morphological characteris-
tics of the samples (Fig. 1, samples 3 and 4). However, 
with the increase in the molar ratio to 6/1, the number 
of functional groups is significantly reduced (Table 1, 
sample 3). Therefore, in the following syntheses, we 
adhered to the optimal ratio of TEOS/APTES equal to 
3/1 (Table 1, sample 4). It should be noted, that the 
increasing stirring time caused the reduction of func-
tional groups content (see samples 4 and 5, Table 1) 
and the product yield. Therefore, the stirring was less 
than 1 h, which was marked in other papers [7]. 
Changing the drying mode (Table 1, samples 4, 6 and 
6*) does not affect the morphology of samples (Fig. 1). 
However, the content of amine groups slightly increas-
es for sample 4 due to more complete removal of water. 
For this reason, all the next samples were dried in the 
oven at 100ºC for 24 h. 
 
Table 1 – The composition of the reaction solution and some 
properties of the synthesized samples 
 
S
a
m
p
le
 
EtOH, 
cm3 
H2O, 
cm3 
NH4OH, 
cm3 
TEOS, 
cm3 
APTES, 
cm3 
Time, 
h 
Size, 
nm 
CNH2, 
mmol/g 
1 40 - 21 4.5 1.5 24 450 not 
determ 
2 100 14 21 6 6 2 200 2.1 
3 100 14 21 6 1 1.5 700 0.3 
4 100 14 21 6 2 1 400 1.3 
5 100 14 21 6 2 6 400 0.7 
6 100 14 21 6 2 1 300 1.1 
6* 100 14 21 6 2 1 300 0.9 
7 100 - 21 6 2 1 300 1.1 
8 6 - - 1 1 24 100 2.1 
9 100 - 1.8 4 1.4 3 100 1.3 
10 100 - 1.8 4 1.4 2 300 1.4 
11 100 - 1.8 4 1.4 1.5 700 1.7 
 
Some authors believe, that the amount of water in 
the syntheses should be increased [1,2], but others 
consider that water from ammonia solution is enough 
for the reaction of hydrolytic polycondensation [8]. 
Comparing samples 6 and 7 (Table 1 and Figure 1), it 
is easy to conclude, that the additional amount of water 
does not affect the particle size and number of func-
tional groups. 
Finally, there was analysed the effect of the synthe-
sis temperature on the particle size and the content of 
functional groups, in terms of samples 9, 10, and 11. It 
should be mentioned, that in addition to the tempera-
ture variation, the stirring time for these samples was 
also varied (Table 1). The fact is that after 1 h stirring 
time (sample 9), there was observed the formation of 
particles, too small to be centrifuged in our conditions. 
However, in our opinion, this factor (stirring time) 
would not significantly affect the particle size, and the 
temperature of hydrolytic polycondensation reaction of 
alkoxysilanes has a more significant effect. Comparing 
the size of these samples (Table 1), it is easy to con-
clude, that the increase in temperature from the ice 
bath (≈ 2ºC) to 45ºC leads to 7 times increase in diame-
ter of the particles. It is also accompanied by the in-
crease in the content of functional groups (Table 1). 
It is interesting to note, that during the synthesis of 
xerogels with 3-aminopropyl groups [9] these groups 
created alkaline medium in water for hydrolytic poly-
condensation reaction. Indeed, the synthesis of sample 8 
at TEOS/APTES ratio of 1/1, without using ammonia 
 SYNTHESIS SUBMICRO- AND NANOSCALE SPHERICAL… PROC. NAP 2, 02PCN40 (2013) 
 
 
02PCN40-3 
solution (water source was 96% ethanol), the formation 
of spherical silica particles was also observed (Fig. 1). In 
the synthesis under similar conditions, but without TE-
OS, the appearance of precipitate was not observed even 
when the solution was heated. Compared with the sam-
ple 2, where the same ratio of alkoxysilanes was used, 
we found that the diameter of the particles for sample 8 
is twice less, but both samples are characterized by the 
same content of amino groups (Table 1). Thus, nanoscale 
spherical silica particles with amino groups can be ob-
tained without introducing ammonia. However, the 
synthesis of the sample 8 requires further research for 
improving the morphology of the particles. 
 
 
 
 
 
Fig. 1 – Photomicrographs of synthesized samples obtained by SEM 
 
4. CONCLUSIONS 
 
The influence of factors, such as the order entry components, 
the stirring time, the drying mode, the ratio of reacting of 
alkoxysilanes, the temperature, and the amounts of water and 
solvent on the morphology and the content of functional groups 
in the silica spheres was analysed. It was shown, that the shape 
and size of the particles are majorly affected by the synthesis 
temperature, and the ratio of reacting alkoxysilanes determines 
the content of 3-aminopropyl groups. 
 
AKNOWLEDGEMENTS 
 
This work was carried out within the framework to 
the State Target Scientific and Technical Program of 
NASU “Nanotechnologies and Nanomaterials” (project 
#6.22.5.42) and the Target Complex Program of Fun-
damental Research of NASU "Fundamental Problems 
of Nanostructures, Nanomaterials, Nanotechnologies" 
(project #57/13-Н). 
 
REFERENCES 
 
1. The Colloid Chemistry of Silica (Ed.: H. Bergna) Adv.in 
Chem.Series 234, Amer.Chem.Sci., (Washington, DC 1994) 
2. R.D. Badley, W.T. Ford, F.J. McEnroe, R.A. Assinks, 
Langmuir 6, 792 (1990) 
3. W. Stober, A.Fink, E. Bohn, J. Of Coll. And Interf. Sci, 26, 
62 (1968) 
4. I. Khatib, R. Parish, J. Organomet. Chem., 369, 9 (1989). 
5. Z. Wu, H. Xiang, T. Kim, M.-S. Chun, K. Lee, J. Of Coll. 
And Interf. Sci. 304, 119 (2006). 
6. G. Berriozabal, Y. R. de Miguel, Phys. Status Solidi C 7, 
N. 11–12, 2692 (2010) 
7. G. Deng, M. A. Markowitz, P. R. Kust , B. P. Gaber, Mater. 
Sci. and Eng. C 11, 165 (2000)  
8. A. van Blaaderen, A.Vrij, J. of Coll. And Interface Science, 
156, 1 (1993) 
9. Yu.L.Zub, O.O.Chuiko, O.V.Stechenko, Reports of NAS of 
Ukraine, 4, 150 (2002). 
 


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Synthesis Submicro- and Nanoscale Spherical Silica Particles with 3-aminopropyl Groups in the Surface Layer

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