Nanocrystalline SnO2 powder was successfully prepared by using simple sol-gel technique. The sol-gel
obtained was washed and calcinated at 400 C to obtain the SnO2 nano-powder. The structural property of
(SnO2) nanocrystalline powder was investigated by using X-ray diffraction (XRD) technique. The optical
properties were studied using Uv-Vis Spectroscopy, by recording the absorbance and transmittance spectra.
The XRD pattern of the as-prepared sample demonstrated the formation of a rutile structure of SnO2
nanocrystallites. The Scanning Electron Microscopic (SEM) analysis showed a homogeneous distribution of
quite small grains over scanned area. The Uv-Vis absorbance spectra also showed a characteristic peak of
absorbance at   312 nm corresponding to SnO2. The energy band gap measurement for nanocrystalline
SnO2 thin film was done from the graph of variation of (hν)2 versus hν. The measured value of optical
bandgap energies for SnO2 thin film is 3.78 eV. The results show that the transmittance of the synthesized
SnO2 film is 78 % in the spectral range 350 nm to 800 nm

Ankamwar, B.G.

Bhagwat, A.D.

Mahajan, C.M.

Sawant, S.S.

English

SocioEconomic Challenges Journal (Sumy State University)

JOURNAL OF NANO- AND ELECTRONIC PHYSICS ЖУРНАЛ НАНО- ТА ЕЛЕКТРОННОЇ ФІЗИКИ 
Vol. 7 No 4, 04037(4pp) (2015) Том 7 № 4, 04037(4cc) (2015) 
 
2077-6772/2015/7(4)04037(4) 04037-1  2015 Sumy State University 
Synthesis of Nanostructured Tin Oxide (SnO2) Powders and Thin Films  
Prepared by Sol-Gel Method 
 
Ashok D. Bhagwat1,2, Sachin S. Sawant1, Balaprasad G. Ankamwar3, Chandrashekhar M. Mahajan1,* 
 
1 Department of Engineering Sciences and Humanities, Vishwakarma Institute of Technology,  
Pune – 411037, Maharashtra, India 
2 Dnyanshree Institute of Engineering and Technology, Satara – 415013, Maharashtra, India 
3 Department of Chemistry, Savitribai Phule Pune University, Ganeshkhind, Pune, 411007, India 
 
(Received 09 July 2015; revised manuscript received 08 December 2015; published online 10 December, 2015) 
 
Nanocrystalline SnO2 powder was successfully prepared by using simple sol-gel technique. The sol-gel 
obtained was washed and calcinated at 400 C to obtain the SnO2 nano-powder. The structural property of 
(SnO2) nanocrystalline powder was investigated by using X-ray diffraction (XRD) technique. The optical 
properties were studied using Uv-Vis Spectroscopy, by recording the absorbance and transmittance spec-
tra. The XRD pattern of the as-prepared sample demonstrated the formation of a rutile structure of SnO2 
nanocrystallites. The Scanning Electron Microscopic (SEM) analysis showed a homogeneous distribution of 
quite small grains over scanned area. The Uv-Vis absorbance spectra also showed a characteristic peak of 
absorbance at   312 nm corresponding to SnO2. The energy band gap measurement for nanocrystalline 
SnO2 thin film was done from the graph of variation of (hν)2 versus hν. The measured value of optical 
bandgap energies for SnO2 thin film is 3.78 eV. The results show that the transmittance of the synthesized 
SnO2 film is 78 % in the spectral range 350 nm to 800 nm. 
 
Keywords:  Bandgap, Metal oxide, Tin oxide, nanocrystallites, Sol-gel. 
 
 PACS numbers: 61.05.C, 61.82.Rx, 68.37.Hk, 81.20.Fw 
 
 
                                                                
* c_mahajan9@yahoo.com 
1. INTRODUCTION 
 
Nano-crystals of semiconductor metal oxides have at-
tracted a great interest due to their intriguing properties, 
which are different from those of their corresponding bulk 
state. Tin Oxide (SnO2) is one of the important metal 
oxides due to its many useful properties such as its wide 
band gap (Eg  3.64 eV, 330 K), n-type conductivity, high 
transparency in the visible range ( 80 %). It crystallizes 
in rutile structure and can be synthesized in variety of 
shapes and sizes using different low cost synthesis tech-
niques relevant for a wide range of applications such as in 
solid-state gas sensors, flat panel displays, solar energy 
cells [1, 2]. The thin films of SnO2 shows high free carrier 
density in the range of 1019-1020 cm – 3 which is mainly due 
to oxygen vacancies, incorporation of excess interstitial tin 
and unintentional chlorine doping (mainly from glass 
substrates at higher deposition or calcination tempera-
tures due to softening of soda lime glass). 
Various impressive and effective methods have been 
used to prepare SnO2 nanostructures with better control 
over particle size and physical properties. These in-
cludes hydrothermal method [3, 4], polymeric [5], or-
gano-metallic precursor synthesis [6], sonication [7, 8], 
microwave [9, 10] and surfactant-mediated method [11]. 
However, they are either complicated, costly and energy 
or time-consuming. It takes at least 24hrs. for the hy-
drothermal method to synthesize SnO2 nanoparticles. 
Besides, the polymeric and sonication techniques are 
complicated and give fewer throughputs, hence are not 
favorable for mass production. Conversely, sol-gel is a 
simple technique to synthesize homogeneous nanoparti-
cles of high purity and crystallinity at a low tempera-
ture. In a sol-gel process, the precursor solution is trans-
formed into an inorganic solid by (a) dispersion of colloi-
dal particles in a liquid (sol) and (b) conversion of sol 
into rigid phase (gel) by hydrolysis and condensation 
reactions [12]. Generally it leads to synthesis of amor-
phous precipitates and heat treatment is necessary to 
induce particle growth by re-crystallization and to alter 
the particle morphology. However, amongst different 
synthesis methods for preparation of tin oxide, sol gel 
method offers several advantages over other methods in 
terms of lower processing temperature, better homoge-
neity and controlled stoichiometry, flexibility of forming 
dense monoliths, thin films, and nanoparticles. In the 
present work we have investigated the structural, mor-
phological and optical properties of SnO2 nano-powder 
and thin film synthesized by simple and facile sol-gel 
technique. The properties of these SnO2 nanocrystallites 
have been studied using different characterization tech-
niques such as X-ray diffraction (XRD), Scanning Elec-
tron Microscopy (SEM), UV-VIS spectroscopy. 
 
2. EXPERIMENTAL 
 
2.1 Materials 
 
Analytical Reagent (A.R.) grade chemicals such as 
tin tetrachloride penta-hydrate (SnCl4.5H2O), ethylene 
glycol and ammonia (Make: Loba Chemie Pvt. Ltd. 
Mumbai, India), were used for synthesis of SnO2 nano-
particles without any further purification. The double 
distilled water was used during the synthesis as a sol-
vent for precursors such as SnCl4.5H2O, ethylene glycol 
and liquid ammonia. 
 
 A.D. BHAGWAT, S.S. SAWANT, C.M. MAHAJAN J. NANO- ELECTRON. PHYS. 7, 04037 (2015) 
 
 
04037-2 
2.2 Method 
 
The sol-gel technique was used for the synthesis of 
tin oxide nano-powder. The 0.1 molar of tin-tetrachloride 
penta-hydrate (3.51 g of SnCl4.5H2O) was dissolved in 
50 ml of double distilled water in a beaker to which 
50 ml of ethylene glycol was added to make a 100 ml 
precursor mixture. The resulted precursor mixture was 
kept for stirring on a magnetic stirrer (Make: Remi) at 
300 RPM and while stirring into this mixture, 0.1M of 
an aqueous ammonia solution was added in drop wise 
manner (with a rate of 10 drops/minute). On addition of 
roughly 50 drops of aqueous ammonia the sol-gel was 
formed approximately within the 5 minutes. The result-
ing gel was filtered by using Whatman filter paper 
(grade-42) and then washed 3-4 times by double distilled 
water to remove excess ammonia. The content on the 
filter paper was then transferred carefully in a crucible 
as well as on a glass substrate with 1 μm commercial 
applicator to form a thin film. The precipitate in the 
crucible and a thin film was dried at 150 ºC for 2 hrs. in 
order to remove water molecules. Finally, black brown 
colored tin oxide nano-powder was obtained for a crucible 
sample and a film on glass substrate after drying, were 
further calcinated at 400 ºC for 2 hrs. [13]. Fig. 1 shows 
the Photographic illustration of different steps involved in 
synthesis process of SnO2 nanocrystallites by sol-gel 
method. 
 
 
 
Fig. 1 – Stepwise photographic illustration of synthesis process 
of SnO2 nanocrystallites (a) precursor, SnCl4.5H2O, (b) solutions 
in beakers contain from left to right SnCl4.5H2O, ethylene gly-
col, (c) simultaneous addition, (d) gel formed by drop-wise addi-
tion aqueous ammonia under constant magnetic stirring, (e) 
filtration and washing, (f) gel of SnO2 nanocrystallites, (g) dried 
SnO2 nanocrystallites at 150 ºC for 2 hrs. and (h) calcinated at 
400 C to obtain SnO2 nanocrystallites in powder form 
 
2.3 Characterization 
 
The structural properties of SnO2 nano-powder were 
studied by X-ray diffraction measurements (Bruker D-8 
advance diffractometer, Billerica, MA) using the Cu Kα 
(  1.5406 Å) as a radiation source, operated at 40kV 
and 30 mA with a scan rate of 0.02°/s over the range of 
10°-80°. The average crystallite size d(hkl) of all crystal 
planes for SnO2 powder was estimated from the classical 
Scherrer formula [14]: 
 
 

cos
K
D   (1) 
 
where K is the shape factor usually has a value 0.9,  is 
the X‐ray wavelength and  the Bragg angle and  gives 
the full width of the half  maxima (FWHM). 
The surface morphology of the SnO2 powder was 
studied by scanning electron microscope (SEM). The 
spectral transmittance and absorbance measurements 
were obtained using UV-VIS spectrometer (Shimatzu 
1650PC) in the spectral range of 250 nm to 800 nm. The 
X-intercept obtained by extrapolating the linear portion 
of the exponential curve from of the graph of (hν2) ver-
sus photon energy (hν) is the bandgap energy of the 
material. 
 
3. RESULTS AND DISCUSSIONS 
 
3.1 Structural and Morphological Properties 
 
The powder X-ray diffraction analysis of the SnO2 
sample was performed in order to identify the phase, 
crystal structure and to estimate average grain size. The 
as recorded X-ray diffraction pattern of SnO2 powder 
sample by sol-gel technique is as presented in Fig. 2. The 
XRD pattern reveals the formation of SnO2 nanoparti-
cles with polycrystalline phase demonstrating rutile 
structure [JCPDS Card No: 41-1445, a  4.743 Å. 
c  3.1859 Å]. The crystal planes (110), (101), (211), 
(002), (310), (301) were prominently seen in XRD indicat-
ing the polycrystalline nature of powder. The average 
value of lattice constant from different (hkl) planes was 
determined by using the formula, 2 2 2a d h k l    
where d is inter-planer distance and (hkl) are Miller 
indices. The calculated average values of lattice constant 
were a  4.7470 Å, c  3.1854 Å. No impurity phase was 
observed. The average crystallite size (D) as determined 
from the XRD spectra using Scherer’s formula was 
52 nm. The respective angles of peak positions (2θ), hkl 
planes and inter-planar distance (d) are represented in 
Table 1. 
 
 
 
Fig. 2 – XRD pattern of SnO2 nanocrystallites 
 SOL-GEL SYNTHESIS OF SNO2 NANOSTRUCTURED … J. NANO- ELECTRON. PHYS. 7, 04037 (2015) 
 
 
04037-3 
Table 1 – XRD analysis of SnO2 nanocrystallites 
 
2 (hkl) planes Inter-planar distances (d) 
in nm 
26.60 (110) 58.9 
33.90 (101) 55.3 
38.00 (200) 43.6 
51.80 (211) 59.3 
57.90 (002) 57.7 
62.00 (310) 49.3 
66.00 (301) 51.7 
71.30 (202) 47.5 
78.70 (321) 44.4 
 
SEM analysis was performed to reveal morphological 
features of the sample. SEM micrograph of nanocrystal-
line SnO2 thin film is shown in Fig. 3. Fig. 3 shows a 
homogeneous, uniform distribution of SnO2 nanocrystal-
lines over a scanned area. 
 
 
 
Fig. 3 – SEM micrograph of SnO2 nanocrystallites 
 
3.2 Optical Properties 
 
The UV-VIS absorbance spectra of SnO2 nanocrystal-
lites are as represented in the Fig. 5. The characteristic 
absorption peak was found around 312 nm in the region 
(275 nm ≤  ≤ 350 nm). The substantial decrease in 
transmittance for SnO2 nanocrystallites near the band 
edge indicates the better crystallinity and lower defect 
density for synthesized thin film. 
The analysis of the transmission Fig. 4 (thin film) 
and absorbance spectra (absorbance for SnO2 nanocrys-
tallites sample) in the vicinity of the fundamental ab-
sorption edge shows that the variation of the absorption 
coefficient is in accordance with following relation which 
implies the direct transitions [15]. 
 
 ( )  gh h  
    (2) 
 
Here,  is an absorption coefficient, h is Planck con-
stant, ν is the frequency and hν is the incident photon 
energy. Fig. 6 represents the plot of (hν)2 vs hν for 
SnO2 nanocrystallites. 
 
 
 
 
 
Fig. 4 – Transmittance spectrum of SnO2 thin film 
 
 
 
Fig. 5 – UV-VIS  absorption spectrum of SnO2  
nanocrystallites 
 
 
 
Fig. 6 – The plot of (hν)2 vs hν for SnO2 nanocrystallites 
 A.D. BHAGWAT, S.S. SAWANT, C.M. MAHAJAN J. NANO- ELECTRON. PHYS. 7, 04037 (2015) 
 
 
04037-4 
The direct band gap (Eg) of our sample was measured 
from the absorption coefficient data as a function of 
wavelength using Tauc relation thereby extrapolating 
the straight line of the (hν)2 vs. hν plot to intercept on 
the horizontal photon energy axis and was found to 
3.78 eV as shown in Fig. 6. It is clear that the obtained 
tin oxide has the optical band gap larger than the value 
of 3.64 eV for bulk SnO2 [16] which can be attributed to 
quantum confinement effect. 
 
4. CONCLUSIONS 
 
Tin oxide (SnO2) nanocrystallites and thin film were 
synthesized successfully by Sol-Gel method. Here, we 
conclude from XRD analysis that particles are polycrys-
tallized with tetragonal rutile structure. Morphological 
characteristics of SnO2 nanocrystallines thin film are 
obtained from SEM image, shows uniform distribution 
of quite a small grains with average crystallite size of 
52 nm. The absorbance and transmittance spectra 
shows that synthesized tin oxide nanoparticles were 
smaller in size and homogenous. Uv-Vis analysis 
showed the characteristic absorbance peak at 
  312 nm for SnO2. The bandgap of SnO2 nanoparti-
cles was measured from the plot of variation of (hν)2 
versus hν was 3.78 eV. The transmittance analysis 
showed the transmittance of 78 % for as synthesized 
SnO2 thin film in the spectral range 350 nm to 800 nm. 
 
ACKNOWLEDGEMENTS 
 
The authors wish to thank for the support extended 
by the Management, Director, Vishwakarma Institute of 
Technology and Head, Department of Engineering Sci-
ences and Humanities (DESH), VIT Pune.  
 
 
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Synthesis of Nanostructured Tin Oxide (SnO2) Powders and Thin Films Prepared by Sol-Gel Method

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Synthesis of Nanostructured Tin Oxide (SnO2) Powders and Thin Films Prepared by Sol-Gel Method

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SocioEconomic Challenges Journal (Sumy State University)