Comparison of the synthesis routes for the ZnO/porous silica nanocomposite
ZnO/porous silica nanocomposites were successfully fabricated by three different types of synthesis techniques. In all cases, the molecular sieve SBA-16 was used as a porous matrix. The in situ growth the nanoparticles of zinc oxide within the matrix pores was done using either gaseous or liquid pre...
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Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України
2016
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| Zitieren: | Comparison of the synthesis routes for the ZnO/porous silica nanocomposite / G.Yu. Rudko, S.A. Kovalenko, E.G. Gule, V.V. Bobyk, V.M. Solomakha, A.B. Bogoslovskaya // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2016. — Т. 19, № 4. — С. 352-357. — Бібліогр.: 31 назв. — англ. |
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nasplib_isofts_kiev_ua-123456789-1216552025-02-23T17:49:43Z Comparison of the synthesis routes for the ZnO/porous silica nanocomposite Rudko, G.Yu. Kovalenko, S.A. Gule, E.G. Bobyk, V.V. Solomakha, V.M. Bogoslovskaya, A.B. ZnO/porous silica nanocomposites were successfully fabricated by three different types of synthesis techniques. In all cases, the molecular sieve SBA-16 was used as a porous matrix. The in situ growth the nanoparticles of zinc oxide within the matrix pores was done using either gaseous or liquid precursors. The ex-situ method implied growing of nanoparticles in a colloidal solution with further penetration of the ripened ZnO nanoparticles into the pores of the matrix. Physico-chemical studies of the synthesized ZnO/porous silica nanocomposites showed that the introduction of zinc oxide by any of the methods did not lead to destruction of the structure of the molecular matrix SBA-16. The structure of ZnO nanoparticles, on the contrary, was strongly dependent on the growing method. The best defectless ZnO nanoparticles were obtained by in situ growing using gaseous precursors. This work is supported by National Academy of Science of Ukraine (Project No. 6116-H). 2016 Article Comparison of the synthesis routes for the ZnO/porous silica nanocomposite / G.Yu. Rudko, S.A. Kovalenko, E.G. Gule, V.V. Bobyk, V.M. Solomakha, A.B. Bogoslovskaya // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2016. — Т. 19, № 4. — С. 352-357. — Бібліогр.: 31 назв. — англ. 1560-8034 DOI: 10.15407/spqeo19.04.352 PACS 81.05.Dz, 81.05.Rm, 81.07.St, 81.16.Be https://nasplib.isofts.kiev.ua/handle/123456789/121655 en Semiconductor Physics Quantum Electronics & Optoelectronics application/pdf Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України |
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ZnO/porous silica nanocomposites were successfully fabricated by three different types of synthesis techniques. In all cases, the molecular sieve SBA-16 was used as a porous matrix. The in situ growth the nanoparticles of zinc oxide within the matrix pores was done using either gaseous or liquid precursors. The ex-situ method implied growing of nanoparticles in a colloidal solution with further penetration of the ripened ZnO nanoparticles into the pores of the matrix. Physico-chemical studies of the synthesized ZnO/porous silica nanocomposites showed that the introduction of zinc oxide by any of the methods did not lead to destruction of the structure of the molecular matrix SBA-16. The structure of ZnO nanoparticles, on the contrary, was strongly dependent on the growing method. The best defectless ZnO nanoparticles were obtained by in situ growing using gaseous precursors. |
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| author |
Rudko, G.Yu. Kovalenko, S.A. Gule, E.G. Bobyk, V.V. Solomakha, V.M. Bogoslovskaya, A.B. |
| spellingShingle |
Rudko, G.Yu. Kovalenko, S.A. Gule, E.G. Bobyk, V.V. Solomakha, V.M. Bogoslovskaya, A.B. Comparison of the synthesis routes for the ZnO/porous silica nanocomposite Semiconductor Physics Quantum Electronics & Optoelectronics |
| author_facet |
Rudko, G.Yu. Kovalenko, S.A. Gule, E.G. Bobyk, V.V. Solomakha, V.M. Bogoslovskaya, A.B. |
| author_sort |
Rudko, G.Yu. |
| title |
Comparison of the synthesis routes for the ZnO/porous silica nanocomposite |
| title_short |
Comparison of the synthesis routes for the ZnO/porous silica nanocomposite |
| title_full |
Comparison of the synthesis routes for the ZnO/porous silica nanocomposite |
| title_fullStr |
Comparison of the synthesis routes for the ZnO/porous silica nanocomposite |
| title_full_unstemmed |
Comparison of the synthesis routes for the ZnO/porous silica nanocomposite |
| title_sort |
comparison of the synthesis routes for the zno/porous silica nanocomposite |
| publisher |
Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України |
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2016 |
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https://nasplib.isofts.kiev.ua/handle/123456789/121655 |
| citation_txt |
Comparison of the synthesis routes for the ZnO/porous silica nanocomposite / G.Yu. Rudko, S.A. Kovalenko, E.G. Gule, V.V. Bobyk, V.M. Solomakha, A.B. Bogoslovskaya // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2016. — Т. 19, № 4. — С. 352-357. — Бібліогр.: 31 назв. — англ. |
| series |
Semiconductor Physics Quantum Electronics & Optoelectronics |
| work_keys_str_mv |
AT rudkogyu comparisonofthesynthesisroutesfortheznoporoussilicananocomposite AT kovalenkosa comparisonofthesynthesisroutesfortheznoporoussilicananocomposite AT guleeg comparisonofthesynthesisroutesfortheznoporoussilicananocomposite AT bobykvv comparisonofthesynthesisroutesfortheznoporoussilicananocomposite AT solomakhavm comparisonofthesynthesisroutesfortheznoporoussilicananocomposite AT bogoslovskayaab comparisonofthesynthesisroutesfortheznoporoussilicananocomposite |
| first_indexed |
2025-11-24T04:22:05Z |
| last_indexed |
2025-11-24T04:22:05Z |
| _version_ |
1849644155047772160 |
| fulltext |
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2016. V. 19, N 4. P. 352-357.
doi: https://doi.org/10.15407/spqeo19.04.352
© 2016, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
352
PACS 81.05.Dz, 81.05.Rm, 81.07.St, 81.16.Be
Comparison of the synthesis routes
for the ZnO/porous silica nanocomposite
G.Yu. Rudko1, S.A. Kovalenko1, E.G. Gule1, V.V. Bobyk2, V.M. Solomakha2, A.B. Bogoslovskaya1
1V. Lashkaryov Institute of Semiconductors Physics, NAS of Ukraine
45, prospect Nauky, 03028 Kyiv, Ukraine; e-mail: g.yu.rudko@gmail.com
2L. Pisarzhevskii Institute of Physical Chemistry, NAS of Ukraine
31, prospect Nauky, 03028 Kyiv, Ukraine
Abstract. ZnO/porous silica nanocomposites were successfully fabricated by three
different types of synthesis techniques. In all cases, the molecular sieve SBA-16 was
used as a porous matrix. The in situ growth the nanoparticles of zinc oxide within the
matrix pores was done using either gaseous or liquid precursors. The ex-situ method
implied growing of nanoparticles in a colloidal solution with further penetration of the
ripened ZnO nanoparticles into the pores of the matrix. Physico-chemical studies of the
synthesized ZnO/porous silica nanocomposites showed that the introduction of zinc
oxide by any of the methods did not lead to destruction of the structure of the molecular
matrix SBA-16. The structure of ZnO nanoparticles, on the contrary, was strongly
dependent on the growing method. The best defectless ZnO nanoparticles were obtained
by in situ growing using gaseous precursors.
Keywords: ZnO nanoparticles, synthesis, nanoporous silica, luminescence.
Manuscript received 14.06.16; revised version received 22.08.16; accepted for
publication 16.11.16; published online 05.12.16.
1. Introduction
Nanomaterials are a rapidly developing area of materials
science. They are represented by one-dimensional
nanowires or rods, quazi-zero-dimensional nanoparticles
(NPs), which are also called quantum dots, and
numerous composite materials based on the above
species. Due to their small particle size and high surface-
to-volume ratio NPs demonstrate various specific
properties that are promising for creating new
semiconductors devices. An important issue for
successful applications of NPs is the stability of their
characteristics. Low thermal and chemical stability can
limit the practical use of NPs. One way to solve this
problem is the insertion of NPs into the confining host,
which would eliminate the agglomeration and prevent
chemical reactions on the surface. Porous materials are
an advantageous candidate for a hosting environment.
Among the porous materials, the mesoporous
molecular sieves are especially attractive due to very
small sizes of pores and very narrow distribution of pore
sizes. Typically, the molecular sieves are synthesized
from SiO2 or Al2O3. The most well-known types of
mesoporous silica, so to say, “classical” molecular
sieves are the ones from MCM group [1, 2]. These
materials are characterized by very large surface areas,
ordered pore systems, and well-defined pore radius
distributions. In general, any of the silica sieves has a
hard framework formed by Si and O atoms that are
organized into a three-dimensional network of pores and
interconnecting channels with the thickness of the
separating wall equal to the thickness of one SiO2
monolayer. The shapes and size of pores and channels in
different sieves vary within the range of several
nanometers that makes these materials attractive as an
enclosure for NPs. Recently, the SBA-type mesoporous
silica attracted a great attention due to large pore sizes,
thick pore walls, and better thermal and mechanical
stablility than those of MCM family [3-5]. Moreover, the
surfactant that is used for synthesis of these materials is
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2016. V. 19, N 4. P. 352-357.
doi: https://doi.org/10.15407/spqeo19.04.352
© 2016, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
353
nontoxic, biodegradable, and inexpensive [6]. Among
the cubic mesoporous silicas, the SBA-16 is considered
to be the most attractive. SBA-16 is formed by an
arrangement of spherical empty cages. Each cage is
connected to eight neighbouring cages by narrow
openings forming a 3D mesopores network having a
body-centered cubic symmetry Im3m. Due to well-
defined three-dimensional framework of mesopores,
high specific surface area, and good thermal stability
because of the thick walls inherent to SBA-16 this seave
seems to be an ideal candidate for enclosing NPs.
While incorporation of NPs into molecular sieves
can solve the stability and agglomeration problems, the
insertion process is a challenge by itself. Various
fabrication techniques to produce NPs inside the
molecular sieves have been proposed, namely: wet
impregnation, sol-gel method, radio-frequency
sputtering, one-pot surfactant-assisted procedure, direct
incorporation, grafting with organometallic compounds
and others [7-15].
The variety of materials for insertion into silica-
based sieves is very wide. In the present study, we
focused on the semiconductor zinc oxide NPs.
Nanocrystalline ZnO is one of the potential candidates
for applications in optoelectronic devices [16], chemical
gas sensors [17], solar cells [18], optical switches [19],
as a catalyst [15], etc. Moreover, ZnO has been paid
considerable attention as a promising electronic
luminescent device material that enables producing
light-emitting devices in the ultra-violet region. Thus, it
is considered as a material of the next generation in LED
development [20, 21].
The goal of this study is to investigate different
methods of incorporation of ZnO NPs into the molecular
sieve SBA-16 and to analyze the obtained ZnO/porous
silica nanocomposites. The structural and luminescent
properties of resulting ZnO/PS nanocomposites were
studied using XRD, adsorption of n-hexane, and
photoluminescent methods.
2. Materials and methods
2.1. Materials
For all synthesis methods the starting material for
fabrication ZnO/porous silica nanocomposites was the
ordered mesoporous molecular sieve SBA-16. The
source materials for in situ growing NPs in the porous
matrix were the solution of zinc nitrate Zn(NO3)2 for the
wet chemical process and sublimated gaseous zinc
acetylacetonate Zn(acac)2 in the case of NPs growing
from the gaseous phase. For the ex-situ method the
alcoholic sol of ZnO NPs with the average size about
5.2 nm was used.
2.1.1. Synthesis of the molecular sieve SBA-16
The mesoporous silica matrix SBA-16 was synthesized
using the chemical route described in [22] with
application of Pluronic F127 surfactant (three-block
copolymer EO106PO70EO106) as a template. For the
synthesis, the amount 0.57 g of Pluronic F-127 was
dissolved in 26 ml of water and 4.87 g of concentrated
HCl (37%). Then, 2.6 ml of TEOS were gradually added
to the solution under continuous mixing. The
components ratio (in moles) in the mixture of reactants
was as follows: 1 TEOS:0.004 F-127:4.2 HCl:119 H2O.
This solution was permanently stirred by the magnetic
mixer for 24 hours. The procedure was carried out at
60 °С. After this hydrothermal treatment, the resulting
mixture was kept at 100 °C for 24 hours, and the
surfactant was removed. Detemplatation was made using
calcination at 550 °C in air and continued for 4-5 hours
(temperature rise rate was 2 °C/min).
2.1.2. Methods of NPs synthesis
within the pores of SBA-16
Introduction of zinc oxide NPs into the molecular sieve
was carried out using three different methods. The main
difference between synthesis methods was the route used
for the ZnO NPs growth – inside or outside the
molecular sieve. Correspondingly, these methods can be
named in situ or ex-situ synthesis. During the in situ
growth, the precursors are supplied into the pores either
in liquid or gaseous phase, while the ex-situ growth
implies impregnation of the sieve with ZnO NPs that
have been preliminarily grown outside the matrix.
In-situ growing the NPs from gaseous precursors
The precursor of ZnO NPs for growing nanostructures
from the gaseous phase is zinc acetylacetonate
Zn(acac)2. The physical sorption of gaseous zinc
acetylacetonate in the pores of the molecular sieve is a
rather slow process. Thus, one can expect formation of
well-organized ensembles of ZnO NPs, provided that the
pores of the sieve are well-ordered. The synthesis
procedure started with calcination of molecular sieve
SBA-16 in a pumped-out vessel at 350 °C for 2 hours.
Afterwards, the molecular sieve in the vessel was slowly
cooled down to room temperature, and the calcinated
molecular sieve SBA-16 was mixed with zinc
acetylacetonate (also in vacuum). Then, the temperature
was increased once more up to 95 °C to achieve
sublimation of zinc acetylacetonate. The gaseous zinc
acetylacetonate penetrated into the pores via the
diffusion process. The next step was the hydrolysis of
zinc acetylacetonate inside the pores of molecular sieve
to obtain ZnO. For this purpose the samples were placed
into the atmosphere of water vapors and were calcinated
at 550 °C for three hours.
In-situ growing the NPs from liquid precursors
Solution of zinc nitrate Zn(NO3)2 was used as a liquid
precursor for impregnation of the molecular sieve by
using the wet synthesis route. To make a rough
estimation of the targeted content of ZnO in the
molecular sieve beforehand, we started with the
estimation of the moisture uptake by the matrix. The
uptake was measured using the distilled water. The
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2016. V. 19, N 4. P. 352-357.
doi: https://doi.org/10.15407/spqeo19.04.352
© 2016, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
354
corresponding value for SBA-16 is 2.5 mg. Using this
value, the concentration of zinc nitrate in the solution
was calculated.
The synthesis started with the dehydration of the
molecular sieve SBA-16 before ZnO NPs growing. The
procedure was performed at 120 °C and lasted for
2 hours. The synthesis procedure with zinc nitrate as a
precursor was carried out in one step: the preliminarily
dehydrated matrix was soaked in the solution of zinc
nitrate for more than 2 h and then was calcinated at
550 °C for 3 h using a muffle furnace at a ramping rate
of 2 °C/min.
Ex-situ method of nanocomposite synthesis
by sorption of pre-grown NPs
The formation of nanocomposite started with the
synthesis of NP-containing sol. The synthesis occurred
in ethanol by alkali hydrolysis of the zinc acetate
Zn(CH3COO)2 in the presence of NaOH. Thoroughly
triturated dry Zn(CH3COO)2 and NaOH were dissolved
in 45 and 5 ml of dry ethanol, correspondingly. The
solutions of acetate and alkali were cooled down to 0 °C.
NaOH solution was slowly drop-by-drop added to the
solution of Zn(CH3COO)2 under intense mixing. The
resulting product was the colorless transparent colloidal
solution. The latter was kept for 2 hours at 55-60 °C for
ripening. No additional stabilizers were used. The
ripened ZnO colloids were stored in the darkness at 0-
5 °C. The average size of ZnO NPs in the colloid was
~3.8 nm according to UV-spectroscopy data. As the size
of the pores in molecular sieve SBA-16 is about 5 nm,
they can accommodate the NPs of the latter size. The
concentration of NPs in the as-synthesized colloid was
close to 2·10–2 mol·l–1. The dehydrated molecular sieve
was added to this colloidal solution and mixed during 30
minutes. The samples obtained were washed with
ethanol, filtered and dried in air.
In what follows, we will label the samples in
accordance with the growing method: G – for the gas
phase growth, L – for the liquid phase growth, and C –
for the samples obtained by introduction of NPs that
were already formed in the colloidal solution into the
molecular sieve.
2.2. Characterization methods
The structure and sorption properties of the obtained
nanocomposites were studied using X-ray diffraction
(XRD) and surface area measurements. The powder
small-angle XRD patterns were recorded using the
DRON-3M diffractometer equipped with the Cu Kα
radiation source, λ = 1.542 Å.
The area of the inner surface in the molecular sieve
was measured by hexane adsorption–desorption method
using Sorptomatic 1990. The adsorption-desorption
isotherms were obtained at 77 K under continuous
adsorption conditions. The adsorption data were used to
calculate Brunauer–Emmett–Teller (BET) specific
surface area of the samples. The Barrett–Joyner–
Halenda (BJH) algorithm was used to obtain the pore
size distribution curves from the analysis of the
adsorption branch of the isotherm.
Photoluminescence was studied at room
temperature using the MDR-23 spectrometer with PMP-
100 photomultiplier as a detector. The excitation sources
were the N2-laser (λ = 337 nm) and LED operating at λ =
375 nm.
3. Results and discussion
Small-angle X-ray diffraction patterns for the unloaded
molecular sieve SBA-16 and ZnO-loaded
nanocomposites obtained using different types of
fabrication methods (curves L, G, C) are shown in
Fig. 1. The pure molecular sieve SBA-16 exhibits the
peak corresponding to (110) reflection 0.81° (2θ), which
is typical for the cubic cage-like (Im3m) structure
[23, 24].
After ZnO incorporation into molecular sieve, all
the ZnO/porous silica nanocomposites exhibit very
similar patterns with well-resolved diffraction peaks at
2θ about 0.80°. This is the evidence of the periodically
organized mesoporous structure of the synthesized
nanocomposites. The presence of the (110) reflection
and insignificant change of the lattice parameter a0 of the
parent SBA-16 molecular sieve demonstrate
preservation of the regular porous structure of
mesoporous silica matrix. A minor variation in the
position and intensity of diffraction peaks of synthesized
ZnO/porous silica nanocomposites could be an
indication of a violation of the regularity in the pore
structure of molecular sieve. The reason for this can be
somewhat uneven distribution of ZnO in the silica
matrix pores as in the case of CuO inside MCM-41 [25],
FeCo inside SBA-16 [7] and Pt inside SBA-15 [26].
Fig. 1. The small-angle X-ray diffraction patterns for the
unloaded SBA-16 (curve SBA-16) and ZnO-loaded
nanocomposites obtained by growing the NPs with gaseous
and liquid phase precursors (curves G and L) and by loading
with NPs from the ready colloidal solution (curve C).
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2016. V. 19, N 4. P. 352-357.
doi: https://doi.org/10.15407/spqeo19.04.352
© 2016, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
355
Table. Textural properties of pure SBA-16 and ZnO-
containing nanocomposites.
Method of ZnO
loading into
matrix
ZnO
content,
wt.%
Vtotal,
cm3/g
SBET,
m2/g
Pure SBA-16 0 0.52 619
Liquid phase
growth 4.95 0.30 300
Colloidal
solution 2.3 0.38 328
Gas phase
growth 5.3 0.33 369
Based on the analysis of small-angle X-ray
diffraction pattern results, ZnO may be located in the
pores of the mesoporous silica matrix or on their
external surface as individual particles. The results of
XRD studies of ZnO-containing nanocomposite
materials within the range of angles 10…70° show the
absence of the reflections related to the wurtzite ZnO
structure. This fact indicates the absence of a bulk-like
phase of ZnO. Thus, the size of NPs is too small for
identifying them by XRD. To determine the location of
the zinc oxide NPs and to compare the methods of zinc
oxide introduction into silica matrix, the investigations
of adsorption of n-hexane have been carried out for the
synthesized ZnO/porous silica nanocomposites.
Fig. 2 shows the hexane absorption-desorption
isotherms for the molecular sieve SBA-16 and
ZnO/porous silica nanocomposites that were synthesized
from the gaseous phase, liquid phase and from colloidal
solution. It is seen that all isotherms demonstrate the
type IV behavior, which is characteristic of adsorption
by mesoporous materials [27]. The analysis of these
adsorption-desorption isotherms gives us pore
characteristics of pure SBA-16 and mesoporous silica
nanocomposites after ZnO incorporation. The textural
properties of pure SBA-16 and ZnO-containing
nanocomposites calculated from experimental data are
listed in Table. The calculated parameters of pure SBA-
16, such as the surface area (SBET) and the pore volume
(Vtotal), are in good agreement with the data of [7, 28].
The decrease of pore volume with loading ZnO indicates
that ZnO is indeed confined within the pores of the
matrix and, thus, diminishes the free space within the
pores available for hexane sorption.
Fig. 3 shows the PL spectra of ZnO/mesoporous
silica nanocomposites obtained using different synthesis
techniques. It should be noted that the spectrum of the
ZnO/porous silica nanocomposite obtained from gaseous
phase (sample G) is measured with the excitation by the
337.1 nm line of the nitrogen gas laser, while the spectra
of nanocomposites obtained from liquid phase (sample
L) and from colloidal solution (sample C) were
measured using the 375 nm beam of the solid state laser
diode. The latter spectra were also recorded under
337.1 nm excitation (not shown here), however, the
signal-to-noise ratio was worse in the latter case. On the
other hand, the spectrum of the sample G cannot be
obtained at 375 nm excitation because the energy of
quanta is not sufficient to excite PL of this sample.
Fig. 2. Hexane adsorption–desorption isotherms for pure SBA-
16 and ZnO-containing nanocomposites L, G and C.
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2016. V. 19, N 4. P. 352-357.
doi: https://doi.org/10.15407/spqeo19.04.352
© 2016, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
356
Fig. 3. Room temperature photoluminescence spectra of SBA-
16 (curve SBA-16) and ZnO-containing nanocomposites G, L
and C (curves G, L and C). The PL excitation source for C
sample was N2-laser (λ = 337 nm), all other samples were
measured under excitation at 375 nm.
Analysis of the PL spectra (Fig. 3) shows that the
pure mesoporous silica matrix SBA-16 does not emit
light in the visible range, hence, the matrix does not
contribute to the PL spectra of the synthesized
ZnO/mesoporous silica nanocomposites. Introduction of
zinc oxide into a matrix leads to a significant change of
the PL spectra. Moreover, it is seen that the
luminescence characteristics of nanocomposites strongly
depend on the preparation method.
The nanocomposite obtained using impregnation
from gaseous phase (sample G) exhibits a strong narrow
luminescence line in the UV range. We attribute this
luminescence line at 375 nm to the recombination of
excitons in the ZnO NPs [29] that have been formed
inside the pores of the silica sieve SBA-16. It should be
noted that the spectrum of the sample G does not show
any other features, thus, one can conclude that the quality
of ZnO NPs in the nanocomposite, obtained from gaseous
phase, is very high, and they do not contain any defects
that may be detected using the PL technique.
PL spectra of nanocomposites, obtained from the
liquid phase as well as from colloidal solution, exhibit a
sufficiently broad luminescence band that is shifted to
longer wavelengths. The emission maximum for the
sample C is observed at 450 nm, whereas for the sample
L at about 480 nm. The absence of exciton lines and the
presence of very broad bands in the spectra of L and C
samples indicate a worse quality of ZnO NPs. In
accordance with [30, 31], we ascribe the broad PL band
to the defect-related emission, the defects being
presumably the vacancies of Zn.
4. Conclusions
In summary, porous silica matrix SBA-16 was
successfully loaded with ZnO NPs. Three different types
of synthesis techniques were used for fabrication. The in
situ growth of NPs within the matrix pores was
performed using either gaseous or liquid precursors. The
ex-situ method implied growing the NPs in a colloidal
solution with further penetration of the ripened ZnO NPs
into the pores of the matrix.
The resulting nanocomposites were characterized
by XRD, adsorption of n-hexane, and
photoluminescence methods. Physico-chemical studies
of the synthesized ZnO/porous silica nanocomposites
showed that introduction of zinc oxide by any of the
methods does not lead to destruction of the structure of
the molecular matrix SBA-16 – the unit cell parameters
are not changed, and no reflections related to the
wurtzite ZnO structure are observed, indicating the
absence of a bulk-like phase of ZnO. Adsorption
methods showed the decrease of sorption volume by 30-
40%. The structure of ZnO NPs, on the contrary, is
strongly dependent on the growing method. The best
defectless ZnO NPs were obtained using in situ growing
with gaseous precursors; two other methods produced
NPs with a lot of defects (presumably, Zn vacancies).
Acknowledgements
This work is supported by National Academy of Science
of Ukraine (Project No. 6116-H).
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