457 Cerâmica 61 (2015) 457-461 http://dx.doi.org/10.1590/0366-69132015613601932
INTRODUCTION
Semiconductor nanoparticles have attracted much
attention in the industrial and energy production applications
[1-3]. ZnO nanoparticles exhibit excellent electrical,
opticaland chemical properties, widely applied to produce
semiconductors, optical devices, piezoelectric devices,
surface acoustic wave devices, sensors, transparent electrodes
and solar cells [4-6]. Besides, ZnO nanoparticles also
exhibiting antimicrobial activities against Escherichiacoli
and Staphylococcus aureus [7-11]. Several researchers
reported doping of ZnO with metals such as Mn, Co, Cr,
Cu, In and Laby various methods such as hydrothermal,
sol-gel and coprecipitation method but only few reports are
available ZnO doped with Al and Y [12-16].
In view of the above, pure and Y-doped ZnO nanoparticles
synthesized by cost effective co-precipitation method and
characterized by XRD, TEM, UV-Vis and bacterial activities
were investigated. Results are presented in this paper.
EXPERIMENTAL
Samples with compositional formula Zn
1-x
Y
x
O, with x =
0.00, 0.05, 0.10 and 0.15 were prepared by co-precipitation
route in an alcoholic medium. In this procedure, zinc acetate
dehydrate dissolved in methanol (100 mL) and NaOH in
methanol (100 mL) were prepared and added by stirring with
heating at 52
o
C for 2 h. The precipitate separated from the
solution by ltration, washed several times with distilled
water and ethanol then dried in air at 127
o
C to obtain ZnO
nanoparticles. The samples obtained were annealed at 450
o
C
for 8 h. For the synthesis of Y-doped ZnO nanoparticles, zinc
acetate dehydrate and yttrium acetate tetrahydrate were
dissolved in methanol (100 mL) and NaOH in methanol
(100 mL) were prepared and added by stirring with heating
at 52
o
C for 2 h. The precipitate separated from the solution
by ltration, washed several times with distilled water and
ethanol then dried in air at 127
o
C to obtain Y-doped ZnO
nanoparticles. The samples were annealed at 450
o
C for 8 h.
Structural, optical and antibacterial properties of yttrium
doped ZnO nanoparticles
(Propriedades estruturais, ópticas e antibacterianas de
nanopartículas de ZnO dopadas com ítrio)
V. D. Mote
1*
, Y. Purushotham
2
, R. S. Shinde
3
, S. D. Salunke
3
, B. N. Dole
4
1
Department of Physics, Dayanand Science College, Latur - 413 512, India
2
Centre for Materials for Electronics Technology, Cherlapally, Hyderabad - 500 051, India
3
Department of Chemistry, RajarshiShahuMahavidyalay, Latur - 413 512, India
4
Advanced Materials Research Laboratory, Department of Physics, Dr. B. A. M. University,
Aurangabad - 431 004, India
*corresponding author: motevd15@gmail.com
Abstract
Yttrium-doped ZnO nanoparticles were synthesized by co-precipitation method to investigate structural, optical and antibacterial
properties. X-ray diffraction analysis conrms hexagonal (wurtzite) structure with average crystallite size between 16 and 30
nm. Optical energy band gap decreaseswith increasing Y-doping concentration. ZnO nanoparticles were found to be highly
effective against S. aureus and Y-doped ZnO nanoparticles against E. coli, B. subtilis and S. typhi. Undoped and Y-doped ZnO
nanoparticles are good inorganic antimicrobial agents and can be synthesized by cost effective co-precipitation method.
Keywords: nanoparticles, ZnO, coprecipitation, antibacterial properties.
Resumo
Nanopartículas de ZnO dopado com ítrio foram sintetizadas pelo método de coprecipitação para investigar as propriedades
estruturais, ópticas e antibacterianas. A análise de difração de raios X conrma a estrutura hexagonal (wurtzita) com tamanho
médio de cristalito entre 16 e 30 nm. O gap de energia óptica diminui com o aumento da concentração do dopante Y. Foi
vericado qu nanopartículas de ZnO sãoaltamente ecazes para S. aureus e nanopartículas de ZnO dopado com Y para E. coli,
B. subtilis e S. typhi. Nanopartículas de ZnO não dopadas e dopadas com Y são bons agentes antimicrobianos inorgânicos e
podem ser sintetizadas pelo método de baixo custo de coprecipitação.
Palavras-chave: nanopartículas, ZnO, coprecipitação, propriedades antibacterianas.
458
The crystalline structure, phase purity and size of the
nanoparticles were determined by XRD (Philips PW-3710).
Optical properties of the samples were recorded using UV-
Vis spectrophotometer (Jasco) in the range 200-800 nm.
Anti-bacterial studies: nutrient broth (1.3 g) dissolved in
100 mL distilled water, pH adjusted to 6.8 then sterilized in
autoclave at 121
o
C for 20 min (15 lb). Nutrient agar (2.5 g)
added tothe distilled water by adjusting pH then autoclaved
at 121
o
C for 20 min (15 lb). Pure cultures of bacteria E. coli,
B. subtilis, S. typhi and S. aureus were used.
Preparation of Inolculum:100 mL nutrient broth
distributed 25 mL each in 4 conical asks labeled as E. coli,
B. subtilis, S. typhi and S. aureus and autoclaved at 121
o
C
for 20 min. Pure culture of all these clinically isolated strain
bacteria were added to each conical ask, kept on rotary
shaker for 24 h at 37
o
C.
Preparation and Inoculation of test plates: Nutrient broth
(1.3 g) and Agar (2.5 g) mixed in 100 mL distilled water and
sterilized in autoclave at 121
o
C for 20 min then poured into
sterile petriplates (15-20 mL) to solidify. Plates were labeled
for each test organism then pure cultures of test organisms
spreaded entire surface of the plates by swabbing in three
directions. Plates were allowed to dry for 5 min. Then wells
were cut on each plate with sterile cup borer and labeled as
S1, S2, S3, S4. Each sample was then loaded with sterile
pipettes in respective plates. Plates were incubated at 37
o
C
for 24 h.
RESULTS AND DISCUSSION
Structural properties
XRD patterns of undoped and Y-doped ZnO nanoparticles
are shown in Fig. 1, all samples showing hexagonal ZnO
phase and indexed peaks correspond to (100), (002), (101)
and (110) are matching well with the JCPDS data. Further,
there are no extra impurities or formations of any phase of Y
were detected in the prepared samples. Yttrium doping shows
a pronounced effect on the lattice parameters of ‘a’ and ‘c’ as
compared to undoped ZnO. The lattice parameters increased
with increasing Y concentration as shown in Fig. 2. Similar
trend for was reported for Y-doped ZnS nanoparticles [17].
The unit cell volume is also following similar trend. This is
attributed to ionic radius difference between Zn (0.74 Å) and
Y (1.04 Å) ions. The variation of unit cell volume and X-ray
density with Y content is shown in Fig 3. X-ray density
decreases with increasing Y concentration, indicating the
substitution of Y ions in ZnO nanoparticles. All values are
in Table I.
Bond lengthof doped and undoped ZnO are shown
in Table II. It is found that the bond length values of
perpendicular (C^) as well as parallel (C
) to c-axis
increasing with increasing Y concentration. It could be due
to the induced growth of the particle at higher temperature.
Figure 1: XRD patterns of pure and Y-doped ZnO nanoparticles.
[Figura 1: Difratogramas de raios X de nanopartículas de ZnO
puro e dopado com Y.]
20
2q (degree)
Intensity
40 60 7030 50
Figure 2: Variation of lattice parameter (a and c)with Y content of
Zn
1-x
Y
x
O nanoparticles.
[Figura 2: Variação do parâmetro de rede (a e c) com teor de Y de
nanopartículas de Zn
1-x
Y
x
O.]
3.275 5.24
3.265 5.22
3.255 5.20
0.00
Y contente
Lattice parameter (a) (Å)
Lattice parameter (c) (Å)
0.100.05 0.15
3.270 5.23
3.260 5.21
Figure 3: Unit cell volume and X-ray density vs Y concentration.
[Figura 3: Volume da célula unitária e densidade por difração de
raios X em função da concentração de Y.]
5.6848.8
5.60
5.62
48.2
5.52
5.54
0.00
Y contente
V (Å)
3
X-ray-density (g/cm
3
)
0.100.05 0.15
5.64
48.0
47.8
47.6
48.4
5.66
48.6
5.56
5.58
V. D. Mote et al. / Cerâmica 61 (2015) 457-461
459
The lattice distortion (ε
v
) was calculated using following
equation:
e
v
=
a
2
c - a
0
2
c
0
a
0
2
c
0
(A)
where a
0
and c
0
are the lattice parameters of pure ZnO
single crystal. The ε
v
values are shown in Table II and are
enhancing with increasing Y. It indicates that Y ions go into
Zn crystallographic 2b site in ZnO crystal structure. Further,
the atomic packing fraction (APF) was also calculated using
XRD data and found that APF in the range of 75-76%. The
crystalline size correspond to the most pronounce diffraction
peak (101) has been calculated using Debye-Scherrer’s
formula
D=
Kl
b
hkl
Cosq
(B)
where K is the shape factor, λ is wavelength, β
hkl
is the
full width at half maximum, θ is glancing angle. Table II
summaries the results of crystallite sizes. The average
crystalline size is in the range of 16-30 nm.
Optical properties
The UV-Vis absorption spectra of pure and Y doped
nanoparticles are shown in Fig. 4 and vary linearly with
increasing Y concentration. This may be due to the change
Table I - Lattice parameters, unit cell volume and X-ray density of Y-doped ZnO nanoparticles.
[Tabela I - Parâmetros de rede, volume da célula unitária e densidade obtida por difração de raios X
de nanopartículas de ZnO dopado com Y.]
Sample
code
Y
concentration
(x)
a (Å) c (Å) V (Å
3
)
X - r a y d e n s i t y
(g/cm
3
)
S1 0.00 3.2552 5.1988 47.7078 5.6624
S2 0.05 3.2557 5.2187 47.9051 5.6437
S3 0.10 3.2658 5.2338 48.3423 5.5789
S4 0.15 3.2752 5.2389 48.6683 5.5324
in the average crystallite size of nanoparticles. Using optical
absorption data, band gap energies were calculated.
As per theory of inter band optical absorption, at the
absorption edge, the optical absorption coefcient (αhv)
varies with the photon energy (hv) according to the following
expression
(ahn)
n
= A(hn - E
g
) (C)
Figure 4: UV-Vis spectra of Y-doped ZnO nanoparticles.
[Figura 4: Espectros UV-Vis de nanopartículas de ZnO dopado
com Y.]
2.5
1.5
0.5
2.0
1.0
0
200
Wavelength (nm)
400 700300 600500 800
Absorption (a.u.)
Samples
C^ C
ε
v
D (nm) APF
S1 1.9933 1.9746 0.001751 26.1157 0.75675
S2 1.9937 1.9779 0.005905 16.9898 0.75398
S3 1.9998 1.9839 0.015058 19.4205 0.75414
S4 2.0056 1.9880 0.021605 29.5443 0.75557
Table II - Bond length, lattice distortion parameter, crystallite size and APF of ZnO nanoparticles.
[Tabela II - Comprimento de ligação, parâmetro distorção da rede, tamanho de cristalito e APF de
nanopartículas de ZnO.]
V. D. Mote et al. / Cerâmica 61 (2015) 457-461
460
where A is constant, E
g
band gap energy and n is a number
which characterizes the transition process.
The absorption coefcient (α) is calculated using the
equation
a = 2.303
A
t
(D)
where A is the absorption and t is the thickness of cuvate,
i.e., 1 cm. The E
g
values for direct and indirect transition
obtained by the plots of (αhv)
2
Vs photon energy (hv) and
are shown in Fig 5. The optical band gap energies are found
to be 3.16, 2.99, 2.68, 2.66 eV and are decreasing with
increasing Y concentration. The values are relatively smaller
than that of bulk ZnO (3.34 eV). This maybe due to average
crystallite size and quantum connement effect on Y doped
ZnO nanoparticles.
Antibacterial activity
Well diffusion method is used for the assessment of
antibacterial activity and the results are shown in Figs.
6-9. S
2
and S
3
samples are not showing any antibacterial
activity against any of the test microorganisms, whereas,
S
1
showingmaximum antibacterial activity against S.aureus
and S
4
sample showing maximum antibacterial activity
against B.subtilis (18 mm), followed by E. coli and S. typhi
(16 mm both) and no antibacterial activity against S.aureus.
Undoped ZnO nanoparticles (S
1
) showing maximum
antibacterial activity against S. aureus, i.e., 18 nm as
compared to 15% Y doped (S
4
) ZnO nanoparticles (16 mm).
Other microorganisms E. coli, S. typhi and B. subtils was
not detected the antibacterial activity. Several researchers
reported the antibacterial activity of undoped ZnO for E.coli
[18, 19]. Zone of inhibition observed against pathogenic
bacteria suggests that ZnO nanoparticles exhibit excellent
Figure 5: Photon energy (αhv)
2
against (hv) of the Y-doped ZnO
nanoparticles.
[Figura 5: Energia dos fótons (αhv)
2
em função de (hv) das
nanopartículas de ZnO dopado com Y.]
30
20
10
5
25
15
0
hn (eV)
2.1 2.4 2.7 3.0 3.3
(ahn)
2
(cm
-1
eV)
2
Figure 6: S
1
sample activity against S. aureus.
[Figura 6: Atividade da amostra S
1
para S. aureus.]
Figure 7: S
4
sample activity against S. typhi.
[Figura 7: Atividade da amostra S
4
para S. typhi.]
Figure 8: Activity of S
4
sample against B. subtilis.
[Figura 8: Atividade da amostra S
4
para B. subtilis.]
V. D. Mote et al. / Cerâmica 61 (2015) 457-461
461
antibacterial activity for S. aureus.The antibacterial activity
of ZnO nanoparticles depends on its size, surface area
and concentration. The inhibitory effect increases with
increasing Y concentration. The antibacterial activity results
of pure ZnO and Y doped ZnO nanoparticles are in good
agreement with reported literature [20-22].
CONCLUSIONS
Pure and yttrium-doped ZnO nanoparticles were
synthesized by the co-precipitation method. Lattice
parameters and unit cell volume increases with increasing
Y concentration, indicating successful doping of Y ions into
ZnO lattice. The average crystalline size is in the range 16-
30 nm. The energy band gap decreases with increasing Y
content. Antibacterial activity was observed using the disc
diffusion method. Undoped ZnO (S
1
) nanoparticles have
antibacterial activity against S. aureus. The doping of Y in
ZnO (S
4
) increases its potential against E. coli, B. subtilis, S.
typhi and no effect against S. aureus.
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