Research ArticleSynthesis of Hollow ZnSnO3 Nanospheres with High EthanolSensing Properties
Qiong Wang Na Yao Chen Liu Dongmin An Yan Li Yunling Zou and Xiaoqiang Tong
College of Science Civil Aviation University of China Tianjin 300300 China
Correspondence should be addressed to Qiong Wang q wangcauceducn
Received 19 May 2016 Revised 5 September 2016 Accepted 25 September 2016
Academic Editor Nguyen V Hieu
Copyright copy 2016 Qiong Wang et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited
Hollow ZnSnO3nanospheres were synthesized by a hydrothermal method using ZnO nanospheres as the hard template and raw
material simultaneously The combined characterizations of X-ray diffraction (XRD) scanning electron microscope (SEM) andhigh-resolution transmission electronmicroscopy (HRTEM) confirmed the successful preparation of hollowZnSnO
3nanospheres
The gas-sensing results indicated that the sensormade fromhollowZnSnO3nanospheres exhibited high sensitivity good selectivity
and stability to ethanol at a low operating temperature of 200∘C The sensitivity was about 32 and the response and recovery timewere about 4 s and 30 s for 100 ppm ethanol respectively The enhancement in gas-sensing properties was attributed to the hollownanostructures and high specific surface areas of ZnSnO
3
1 Introduction
As an important ternary semiconducting oxide zinc stannate(ZnSnO
3) has been attracting considerable attention for its
potential application in various fields such as gas sensor[1 2] photo-catalyst [3] and lithium-ion batteries [4] Vari-ous ZnSnO
3nanostructures including nanotubes nanorods
nanocages hollow structures and so on have been synthe-sized by a variety of methods [5ndash8] Among these typeshollow structures have aroused a great deal of interests dueto their low density large reaction surface area high poros-ity and surface permeability which are considered greatlybeneficial to the enhancement of gas-sensing performanceTemplating method has been considered as a representativeand straightforward method toward hollow structures [9]However the removal of template usually suffers from dis-advantages of high cost and long time
In this work we presented a simple and effective templat-ing method for the synthesis of hollow ZnSnO
3nanospheres
by using hollow ZnO nanospheres not only as hard templatebut also as raw material The as-synthesized products areilluminated in terms of their crystallinity morphologyand structure Gas sensor based on these hollow ZnSnO
3
nanospheres showed a high sensitivity good selectivity andstability to ethanol gas at the optimal temperature of 200∘C
2 Experimental
All chemicals used were analytic reagents without furtherpurification Hollow ZnSnO
3nanospheres were synthesized
by a simple hydrothermalmethodUnder a typical procedure05 g urea 01 g K
2SnO3sdot3H2O 10mL distilled water and
20mL ethanol were mixed and stirred for about 10min tobecome dissolved and form a transparent solution Then004 g hollow ZnO nanospheres [10] were added into theabove-mentioned solution The mixed solution was sealedinto a Teflon-lined stainless autoclave of 50mL capacity andheated at 180∘C for 4 h After the autoclave cooled downnaturally the white product was collected by centrifugationthen washed with distilled water and absolute ethanol forseveral times and dried in air at 80∘C for 4 h
The morphology and structure of the obtained prod-ucts were characterized by X-ray diffraction (XRD DMax2500) field-emission scanning electronmicroscope (FESEMJEOL-6701F) and transmission electron microscopy (TEM
Hindawi Publishing CorporationJournal of NanomaterialsVolume 2016 Article ID 2381823 5 pageshttpdxdoiorg10115520162381823
2 Journal of Nanomaterials
20 30 40 50 60 70 80
Inte
nsity
(au
)
hollow nanospheres
(c) ZnO precursor
(JCPDS number 11-0274)
2120579 (degree)
(b) ZnSnO3
(a) ZnSnO3
Figure 1 The XRD patterns of (a) the standard of ZnSnO3 (b) the as-prepared hollow ZnSnO
3nanospheres and (c) the ZnO precursor
JEOL2010) In this work the fabrication procedure of side-heated gas sensor was briefly described as that in our previousstudy [11 12] The as-prepared ZnSnO
3products were mixed
with deionized water at a weight ratio of 2 1 to form ahomogeneous paste Then the paste was coated on an alu-mina ceramic tube (size and dimension of about 25ndash40mm)to form a thin 20 120583m sensing film The ceramic tube waspreviously positioned with a pair of Au electrodes and twoPt wires on each end A NindashCr alloy coil was inserted intothe tube as a heater which provided the working temperatureof the gas sensor by tuning the heating voltage Finally thealumina tube was welded onto a pedestal with six probes
The electrical properties of the gas sensor were measuredby using a CGS-8 gas-sensing testing system (Beijing EliteTech Co Ltd China) The measurement followed a station-ary state gas distribution process a given amount of tested gaswas injected into a glass chamber and fullymixedwith airThesensorwas put into the test chamber at the controllable testingtemperature (25plusmn2∘C) and the relative humidity (sim30 plusmn 5RH) The sensor sensitivity (S) was defined as 119877a119877g where119877a and 119877g were the resistance of the sensor in air and intested gas respectivelyThe response timewas defined as timereaching 90 of the steady resistance and the recovery timewas defined as time attaining to 10 of the initial resistance
3 Results and Discussion
As shown in Figure 1 all of the diffraction peaks of theas-prepared hollow ZnSnO
3nanospheres could be indexed
to the standard diffraction pattern of a perovskite ZnSnO3
structure (JCPDS card number 11-0274) No diffraction peaksfrom any other impurities such as SnO
2and ZnO were
observed indicating the pure crystallinity of the obtainedZnSnO
3products
The SEM images in Figures 2(a) and 2(b) show anoverview of the ZnO precursor and the as-prepared ZnSnO
3
products respectively It is apparent that hollow ZnSnO3
nanosphere structures with an average of 120ndash150 nm wereobtained The inset of Figure 2(b) gives an enlarged imageof a broken ldquonanosphererdquo disclosing the nature of its hollowstructure A typical TEM image of the products in Figures2(c) and 2(d) also confirms that the ZnSnO
3product con-
sisted of spherical hollow particles with a size in the rangeof 120ndash150 nm and a shell thickness of about 20 nm Fromthe HRTEM image in Figure 2(e) it can be clearly seen thatthe interplanar lattice spacing of 0262 nm corresponded tothe (110) plane indicating that the ZnSnO
3nanoparticle was
single-crystalline in natureIn general in the hydrothermal condition the hydrolysis
of urea released a large amount of OHminus ions then the excessOHminus ions reacted withH
2SnO3and formed the [Sn(OH)
6]2minus
Interestingly in this reaction system ZnO nanospheres notonly were used as hard template but also played a role ofprecursor If no ZnO nanospheres were added only SnO
2
products were obtained Chemical reaction processes ofZnSnO
3can be formulated as
[Sn (OH)6]2minus+ ZnO 997888rarr ZnSnO
3+ 2H2O + 2OHminus (1)
As shown in Figure 3(a) the gas response of the sensormade from the hollow ZnSnO
3nanospheres was measured
by exposing it to different tested gases including acetoneethanol benzene andmethanol at the operating temperaturefrom 160∘C to 300∘C It reveals that the sensor showed highsensitivity to 100 ppm ethanol with the response of 32 atthe optimal temperature of 200∘C which was at least twotimes higher than that to other gases implying the preferableselectivity of the sensor to ethanol The response of the gassensor to different ethanol gas concentrations in the rangeof 5ndash100 ppm is shown in Figure 3(b) The sensor responsevalues to 5 10 30 50 and 100 ppm ethanol were 39 76106 183 and 280 respectively As illustrated in Figure 3(c)response-recovery curves of the sensor to 100 ppm ethanolat 200∘C demonstrate that the gas response could be wellretained which suggested that the sensor device had a good
Journal of Nanomaterials 3
(a) (b)
(c)
20nm
(d)
0262nm
(e)
Figure 2 SEM images of (a) ZnO precursor and (b) hollow ZnSnO3nanospheres TEM (c) and HRTEM (d) (e) images of hollow ZnSnO
3
nanospheres Scale bar 100 nm in (a) (b) (c) and (d) 5 nm in (e)
gas-sensing stability and reproducibility Figure 3(d) showsthat the response and recovery time of the sensor were about4 s and 30 s respectively
The excellent performance of the sensor based on thehollow ZnSnO
3nanospheres is attributed to the large reac-
tion surface area for electrons oxygen species and target gasmolecules and hollow structure for gas diffusion and masstransport The gas-sensing results reveal that hollow ZnSnO
3
can achieve the high sensitivity and faster respond rate thehigh specific surface area of which provides a significantfraction of active sites from both inner and outer surfaceregions to adsorb oxygen species and target molecules Atthe same time the gas diffusion and transportation are alsosignificantly improved by the hollow nature Meanwhilethe crystallite size (119863) of the hollow ZnSnO
3spheres was
calculated by using the (200) diffraction peak (2120579 = 222∘)according to the Debye-Scherrer formula 119863 = 09120582120573 cos 120579where 120582 is the X-ray wavelength 120573 is the FWHM (full widthat half maximum intensity) and 120579 is the Bragg angle Thecrystallite size of the ZnSnO
3hollow spheres was only about
7 nm which is not only helpful to improve the reaction rateof chemisorbed oxygen ions with ethanol molecules but alsocan reduce the activation energy barrier of the reoxidationprocess
4 Conclusions
In summary we demonstrated a new synthetic route forpreparing hollowZnSnO
3nanospheres by using ZnOprecur-
sor which acted not only as template but also as rawmaterialThe as-prepared hollow ZnSnO
3nanospheres have an aver-
age diameter of 120ndash150 nm and the shell thickness is about20 nm It was found that the sensor based on hollow ZnSnO
3
nanospheres showed high response good selectivity andstability as well as fast response and recovery time towardethanol gas at a low temperature suggesting the potentialapplications as advanced gas-sensing materials
Competing Interests
The authors declare that they have no competing interests
Acknowledgments
The project was mainly supported by the FundamentalResearch Funds for the Central Universities (3122013k007)the National College Studentsrsquo Innovation EntrepreneurialTraining Project (IECAUC201510059045) and the NationalNatural Science Foundation of China (21501196)
4 Journal of Nanomaterials
160 200 240 2800
5
10
15
20
25
30
35Re
spon
se
AcetoneEthanol
BenzeneMethanol
Temperature (∘C)
(a)
0 250 500 750 1000 1250 1500
0
5
10
15
20
25
30
35
Time (s)
Resp
onse
5ppm10ppm
30ppm
50ppm
100ppm
(b)
0 100 200 300 400 500 600 700
0
20
40
60
Time (s)
Resis
tanc
e (M
Ω)
(c)
300 350 400
0
20
40
60
Time (s)
Resis
tanc
e (M
Ω)
(d)
Figure 3 (a) Gas response versus operating temperature of hollow ZnSnO3nanospheres sensors to different target gases with a concentration
of 100 ppm (b) dynamic response-recovery curves of the sensor to different concentrations of ethanol at 200∘C and (c) and (d) response-recovery curves of the sensor to 100 ppm ethanol at 200∘C
References
[1] Y Bing Y Zeng C Liu et al ldquoAssembly of hierarchical ZnSnO3
hollow microspheres from ultra-thin nanorods and the en-hanced ethanol-sensing performancesrdquo Sensors and ActuatorsB Chemical vol 190 pp 370ndash377 2014
[2] HWang X-X Liu J XieMDuan and J-L Tang ldquoCO sensingproperties of a cubic ZnSn(OH)6 synthesized by hydrothermalmethodrdquo Chinese Chemical Letters vol 27 no 3 pp 464ndash4662016
[3] M-K Lo S-Y Lee and K-S Chang ldquoStudy of ZnSnO3-
nanowire piezophotocatalyst using two-step hydrothermal syn-thesisrdquo The Journal of Physical Chemistry C vol 119 no 9 pp5218ndash5224 2015
[4] Y Wang D Li Y Liu and J Zhang ldquoSelf-assembled 3DZnSnO
3hollow cubesreduced graphene oxide aerogels as
high capacity anode materials for lithium-ion batteriesrdquo Elec-trochimica Acta vol 203 pp 84ndash90 2016
[5] W Guo T Liu W Yu L Huang Y Chen and Z Wang ldquoRapidselective detection of formaldehyde by hollow ZnSnO
3nanoc-
agesrdquo Physica E Low-Dimensional Systems and Nanostructuresvol 48 pp 46ndash52 2013
[6] P Wadkar D Bauskar and P Patil ldquoHigh performance H2
sensor based on ZnSnO3cubic crystallites synthesized by a
hydrothermal methodrdquo Talanta vol 105 pp 327ndash332 2013[7] X Jia M Tian Z Zhang R Dai X Wu and H Song ldquoHighly
sensitive formaldehyde chemical sensor based on in situ precip-itation synthesis of ZnSnO
3microspheresrdquo Journal of Materials
Science Materials in Electronics vol 26 no 8 pp 6224ndash62312015
[8] HWang X Liu J Xie M Duan and J Tang ldquoEffect of humid-ity on the CO gas sensing of ZnSn(OH)
6film via quartz crystal
microbalance techniquerdquo Journal of Alloys and Compounds vol657 pp 691ndash696 2016
[9] P Song Q Wang and Z Yang ldquoBiomorphic synthesis ofZnSnO
3hollow fibers for gas sensing applicationrdquo Sensors and
Actuators B Chemical vol 156 no 2 pp 983ndash989 2011
Journal of Nanomaterials 5
[10] J Zhang SWang YWang et al ldquoZnOhollow spheres prepara-tion characterization and gas sensing propertiesrdquo Sensors andActuators B Chemical vol 139 no 2 pp 411ndash417 2009
[11] D An Q Wang X Tong et al ldquoSynthesis of Zn2SnO4via a
co-precipitation method and its gas-sensing property towardethanolrdquo Sensors and Actuators B Chemical vol 213 pp 155ndash163 2015
[12] QWang N Yao D An et al ldquoEnhanced gas sensing propertiesof hierarchical SnO
2nanoflower assembled from nanorods
via a one-pot template-free hydrothermal methodrdquo CeramicsInternational vol 42 no 14 pp 15889ndash15896 2016
Figure 1 The XRD patterns of (a) the standard of ZnSnO3 (b) the as-prepared hollow ZnSnO
3nanospheres and (c) the ZnO precursor
JEOL2010) In this work the fabrication procedure of side-heated gas sensor was briefly described as that in our previousstudy [11 12] The as-prepared ZnSnO
3products were mixed
with deionized water at a weight ratio of 2 1 to form ahomogeneous paste Then the paste was coated on an alu-mina ceramic tube (size and dimension of about 25ndash40mm)to form a thin 20 120583m sensing film The ceramic tube waspreviously positioned with a pair of Au electrodes and twoPt wires on each end A NindashCr alloy coil was inserted intothe tube as a heater which provided the working temperatureof the gas sensor by tuning the heating voltage Finally thealumina tube was welded onto a pedestal with six probes
The electrical properties of the gas sensor were measuredby using a CGS-8 gas-sensing testing system (Beijing EliteTech Co Ltd China) The measurement followed a station-ary state gas distribution process a given amount of tested gaswas injected into a glass chamber and fullymixedwith airThesensorwas put into the test chamber at the controllable testingtemperature (25plusmn2∘C) and the relative humidity (sim30 plusmn 5RH) The sensor sensitivity (S) was defined as 119877a119877g where119877a and 119877g were the resistance of the sensor in air and intested gas respectivelyThe response timewas defined as timereaching 90 of the steady resistance and the recovery timewas defined as time attaining to 10 of the initial resistance
3 Results and Discussion
As shown in Figure 1 all of the diffraction peaks of theas-prepared hollow ZnSnO
3nanospheres could be indexed
to the standard diffraction pattern of a perovskite ZnSnO3
structure (JCPDS card number 11-0274) No diffraction peaksfrom any other impurities such as SnO
2and ZnO were
observed indicating the pure crystallinity of the obtainedZnSnO
3products
The SEM images in Figures 2(a) and 2(b) show anoverview of the ZnO precursor and the as-prepared ZnSnO
3
products respectively It is apparent that hollow ZnSnO3
nanosphere structures with an average of 120ndash150 nm wereobtained The inset of Figure 2(b) gives an enlarged imageof a broken ldquonanosphererdquo disclosing the nature of its hollowstructure A typical TEM image of the products in Figures2(c) and 2(d) also confirms that the ZnSnO
3product con-
sisted of spherical hollow particles with a size in the rangeof 120ndash150 nm and a shell thickness of about 20 nm Fromthe HRTEM image in Figure 2(e) it can be clearly seen thatthe interplanar lattice spacing of 0262 nm corresponded tothe (110) plane indicating that the ZnSnO
3nanoparticle was
single-crystalline in natureIn general in the hydrothermal condition the hydrolysis
of urea released a large amount of OHminus ions then the excessOHminus ions reacted withH
2SnO3and formed the [Sn(OH)
6]2minus
Interestingly in this reaction system ZnO nanospheres notonly were used as hard template but also played a role ofprecursor If no ZnO nanospheres were added only SnO
2
products were obtained Chemical reaction processes ofZnSnO
3can be formulated as
[Sn (OH)6]2minus+ ZnO 997888rarr ZnSnO
3+ 2H2O + 2OHminus (1)
As shown in Figure 3(a) the gas response of the sensormade from the hollow ZnSnO
3nanospheres was measured
by exposing it to different tested gases including acetoneethanol benzene andmethanol at the operating temperaturefrom 160∘C to 300∘C It reveals that the sensor showed highsensitivity to 100 ppm ethanol with the response of 32 atthe optimal temperature of 200∘C which was at least twotimes higher than that to other gases implying the preferableselectivity of the sensor to ethanol The response of the gassensor to different ethanol gas concentrations in the rangeof 5ndash100 ppm is shown in Figure 3(b) The sensor responsevalues to 5 10 30 50 and 100 ppm ethanol were 39 76106 183 and 280 respectively As illustrated in Figure 3(c)response-recovery curves of the sensor to 100 ppm ethanolat 200∘C demonstrate that the gas response could be wellretained which suggested that the sensor device had a good
Journal of Nanomaterials 3
(a) (b)
(c)
20nm
(d)
0262nm
(e)
Figure 2 SEM images of (a) ZnO precursor and (b) hollow ZnSnO3nanospheres TEM (c) and HRTEM (d) (e) images of hollow ZnSnO
3
nanospheres Scale bar 100 nm in (a) (b) (c) and (d) 5 nm in (e)
gas-sensing stability and reproducibility Figure 3(d) showsthat the response and recovery time of the sensor were about4 s and 30 s respectively
The excellent performance of the sensor based on thehollow ZnSnO
3nanospheres is attributed to the large reac-
tion surface area for electrons oxygen species and target gasmolecules and hollow structure for gas diffusion and masstransport The gas-sensing results reveal that hollow ZnSnO
3
can achieve the high sensitivity and faster respond rate thehigh specific surface area of which provides a significantfraction of active sites from both inner and outer surfaceregions to adsorb oxygen species and target molecules Atthe same time the gas diffusion and transportation are alsosignificantly improved by the hollow nature Meanwhilethe crystallite size (119863) of the hollow ZnSnO
3spheres was
calculated by using the (200) diffraction peak (2120579 = 222∘)according to the Debye-Scherrer formula 119863 = 09120582120573 cos 120579where 120582 is the X-ray wavelength 120573 is the FWHM (full widthat half maximum intensity) and 120579 is the Bragg angle Thecrystallite size of the ZnSnO
3hollow spheres was only about
7 nm which is not only helpful to improve the reaction rateof chemisorbed oxygen ions with ethanol molecules but alsocan reduce the activation energy barrier of the reoxidationprocess
4 Conclusions
In summary we demonstrated a new synthetic route forpreparing hollowZnSnO
3nanospheres by using ZnOprecur-
sor which acted not only as template but also as rawmaterialThe as-prepared hollow ZnSnO
3nanospheres have an aver-
age diameter of 120ndash150 nm and the shell thickness is about20 nm It was found that the sensor based on hollow ZnSnO
3
nanospheres showed high response good selectivity andstability as well as fast response and recovery time towardethanol gas at a low temperature suggesting the potentialapplications as advanced gas-sensing materials
Competing Interests
The authors declare that they have no competing interests
Acknowledgments
The project was mainly supported by the FundamentalResearch Funds for the Central Universities (3122013k007)the National College Studentsrsquo Innovation EntrepreneurialTraining Project (IECAUC201510059045) and the NationalNatural Science Foundation of China (21501196)
4 Journal of Nanomaterials
160 200 240 2800
5
10
15
20
25
30
35Re
spon
se
AcetoneEthanol
BenzeneMethanol
Temperature (∘C)
(a)
0 250 500 750 1000 1250 1500
0
5
10
15
20
25
30
35
Time (s)
Resp
onse
5ppm10ppm
30ppm
50ppm
100ppm
(b)
0 100 200 300 400 500 600 700
0
20
40
60
Time (s)
Resis
tanc
e (M
Ω)
(c)
300 350 400
0
20
40
60
Time (s)
Resis
tanc
e (M
Ω)
(d)
Figure 3 (a) Gas response versus operating temperature of hollow ZnSnO3nanospheres sensors to different target gases with a concentration
of 100 ppm (b) dynamic response-recovery curves of the sensor to different concentrations of ethanol at 200∘C and (c) and (d) response-recovery curves of the sensor to 100 ppm ethanol at 200∘C
References
[1] Y Bing Y Zeng C Liu et al ldquoAssembly of hierarchical ZnSnO3
hollow microspheres from ultra-thin nanorods and the en-hanced ethanol-sensing performancesrdquo Sensors and ActuatorsB Chemical vol 190 pp 370ndash377 2014
[2] HWang X-X Liu J XieMDuan and J-L Tang ldquoCO sensingproperties of a cubic ZnSn(OH)6 synthesized by hydrothermalmethodrdquo Chinese Chemical Letters vol 27 no 3 pp 464ndash4662016
[3] M-K Lo S-Y Lee and K-S Chang ldquoStudy of ZnSnO3-
nanowire piezophotocatalyst using two-step hydrothermal syn-thesisrdquo The Journal of Physical Chemistry C vol 119 no 9 pp5218ndash5224 2015
[4] Y Wang D Li Y Liu and J Zhang ldquoSelf-assembled 3DZnSnO
3hollow cubesreduced graphene oxide aerogels as
high capacity anode materials for lithium-ion batteriesrdquo Elec-trochimica Acta vol 203 pp 84ndash90 2016
[5] W Guo T Liu W Yu L Huang Y Chen and Z Wang ldquoRapidselective detection of formaldehyde by hollow ZnSnO
3nanoc-
agesrdquo Physica E Low-Dimensional Systems and Nanostructuresvol 48 pp 46ndash52 2013
[6] P Wadkar D Bauskar and P Patil ldquoHigh performance H2
sensor based on ZnSnO3cubic crystallites synthesized by a
hydrothermal methodrdquo Talanta vol 105 pp 327ndash332 2013[7] X Jia M Tian Z Zhang R Dai X Wu and H Song ldquoHighly
sensitive formaldehyde chemical sensor based on in situ precip-itation synthesis of ZnSnO
3microspheresrdquo Journal of Materials
Science Materials in Electronics vol 26 no 8 pp 6224ndash62312015
[8] HWang X Liu J Xie M Duan and J Tang ldquoEffect of humid-ity on the CO gas sensing of ZnSn(OH)
6film via quartz crystal
microbalance techniquerdquo Journal of Alloys and Compounds vol657 pp 691ndash696 2016
[9] P Song Q Wang and Z Yang ldquoBiomorphic synthesis ofZnSnO
3hollow fibers for gas sensing applicationrdquo Sensors and
Actuators B Chemical vol 156 no 2 pp 983ndash989 2011
Journal of Nanomaterials 5
[10] J Zhang SWang YWang et al ldquoZnOhollow spheres prepara-tion characterization and gas sensing propertiesrdquo Sensors andActuators B Chemical vol 139 no 2 pp 411ndash417 2009
[11] D An Q Wang X Tong et al ldquoSynthesis of Zn2SnO4via a
co-precipitation method and its gas-sensing property towardethanolrdquo Sensors and Actuators B Chemical vol 213 pp 155ndash163 2015
[12] QWang N Yao D An et al ldquoEnhanced gas sensing propertiesof hierarchical SnO
2nanoflower assembled from nanorods
via a one-pot template-free hydrothermal methodrdquo CeramicsInternational vol 42 no 14 pp 15889ndash15896 2016
Figure 2 SEM images of (a) ZnO precursor and (b) hollow ZnSnO3nanospheres TEM (c) and HRTEM (d) (e) images of hollow ZnSnO
3
nanospheres Scale bar 100 nm in (a) (b) (c) and (d) 5 nm in (e)
gas-sensing stability and reproducibility Figure 3(d) showsthat the response and recovery time of the sensor were about4 s and 30 s respectively
The excellent performance of the sensor based on thehollow ZnSnO
3nanospheres is attributed to the large reac-
tion surface area for electrons oxygen species and target gasmolecules and hollow structure for gas diffusion and masstransport The gas-sensing results reveal that hollow ZnSnO
3
can achieve the high sensitivity and faster respond rate thehigh specific surface area of which provides a significantfraction of active sites from both inner and outer surfaceregions to adsorb oxygen species and target molecules Atthe same time the gas diffusion and transportation are alsosignificantly improved by the hollow nature Meanwhilethe crystallite size (119863) of the hollow ZnSnO
3spheres was
calculated by using the (200) diffraction peak (2120579 = 222∘)according to the Debye-Scherrer formula 119863 = 09120582120573 cos 120579where 120582 is the X-ray wavelength 120573 is the FWHM (full widthat half maximum intensity) and 120579 is the Bragg angle Thecrystallite size of the ZnSnO
3hollow spheres was only about
7 nm which is not only helpful to improve the reaction rateof chemisorbed oxygen ions with ethanol molecules but alsocan reduce the activation energy barrier of the reoxidationprocess
4 Conclusions
In summary we demonstrated a new synthetic route forpreparing hollowZnSnO
3nanospheres by using ZnOprecur-
sor which acted not only as template but also as rawmaterialThe as-prepared hollow ZnSnO
3nanospheres have an aver-
age diameter of 120ndash150 nm and the shell thickness is about20 nm It was found that the sensor based on hollow ZnSnO
3
nanospheres showed high response good selectivity andstability as well as fast response and recovery time towardethanol gas at a low temperature suggesting the potentialapplications as advanced gas-sensing materials
Competing Interests
The authors declare that they have no competing interests
Acknowledgments
The project was mainly supported by the FundamentalResearch Funds for the Central Universities (3122013k007)the National College Studentsrsquo Innovation EntrepreneurialTraining Project (IECAUC201510059045) and the NationalNatural Science Foundation of China (21501196)
4 Journal of Nanomaterials
160 200 240 2800
5
10
15
20
25
30
35Re
spon
se
AcetoneEthanol
BenzeneMethanol
Temperature (∘C)
(a)
0 250 500 750 1000 1250 1500
0
5
10
15
20
25
30
35
Time (s)
Resp
onse
5ppm10ppm
30ppm
50ppm
100ppm
(b)
0 100 200 300 400 500 600 700
0
20
40
60
Time (s)
Resis
tanc
e (M
Ω)
(c)
300 350 400
0
20
40
60
Time (s)
Resis
tanc
e (M
Ω)
(d)
Figure 3 (a) Gas response versus operating temperature of hollow ZnSnO3nanospheres sensors to different target gases with a concentration
of 100 ppm (b) dynamic response-recovery curves of the sensor to different concentrations of ethanol at 200∘C and (c) and (d) response-recovery curves of the sensor to 100 ppm ethanol at 200∘C
References
[1] Y Bing Y Zeng C Liu et al ldquoAssembly of hierarchical ZnSnO3
hollow microspheres from ultra-thin nanorods and the en-hanced ethanol-sensing performancesrdquo Sensors and ActuatorsB Chemical vol 190 pp 370ndash377 2014
[2] HWang X-X Liu J XieMDuan and J-L Tang ldquoCO sensingproperties of a cubic ZnSn(OH)6 synthesized by hydrothermalmethodrdquo Chinese Chemical Letters vol 27 no 3 pp 464ndash4662016
[3] M-K Lo S-Y Lee and K-S Chang ldquoStudy of ZnSnO3-
nanowire piezophotocatalyst using two-step hydrothermal syn-thesisrdquo The Journal of Physical Chemistry C vol 119 no 9 pp5218ndash5224 2015
[4] Y Wang D Li Y Liu and J Zhang ldquoSelf-assembled 3DZnSnO
3hollow cubesreduced graphene oxide aerogels as
high capacity anode materials for lithium-ion batteriesrdquo Elec-trochimica Acta vol 203 pp 84ndash90 2016
[5] W Guo T Liu W Yu L Huang Y Chen and Z Wang ldquoRapidselective detection of formaldehyde by hollow ZnSnO
3nanoc-
agesrdquo Physica E Low-Dimensional Systems and Nanostructuresvol 48 pp 46ndash52 2013
[6] P Wadkar D Bauskar and P Patil ldquoHigh performance H2
sensor based on ZnSnO3cubic crystallites synthesized by a
hydrothermal methodrdquo Talanta vol 105 pp 327ndash332 2013[7] X Jia M Tian Z Zhang R Dai X Wu and H Song ldquoHighly
sensitive formaldehyde chemical sensor based on in situ precip-itation synthesis of ZnSnO
3microspheresrdquo Journal of Materials
Science Materials in Electronics vol 26 no 8 pp 6224ndash62312015
[8] HWang X Liu J Xie M Duan and J Tang ldquoEffect of humid-ity on the CO gas sensing of ZnSn(OH)
6film via quartz crystal
microbalance techniquerdquo Journal of Alloys and Compounds vol657 pp 691ndash696 2016
[9] P Song Q Wang and Z Yang ldquoBiomorphic synthesis ofZnSnO
3hollow fibers for gas sensing applicationrdquo Sensors and
Actuators B Chemical vol 156 no 2 pp 983ndash989 2011
Journal of Nanomaterials 5
[10] J Zhang SWang YWang et al ldquoZnOhollow spheres prepara-tion characterization and gas sensing propertiesrdquo Sensors andActuators B Chemical vol 139 no 2 pp 411ndash417 2009
[11] D An Q Wang X Tong et al ldquoSynthesis of Zn2SnO4via a
co-precipitation method and its gas-sensing property towardethanolrdquo Sensors and Actuators B Chemical vol 213 pp 155ndash163 2015
[12] QWang N Yao D An et al ldquoEnhanced gas sensing propertiesof hierarchical SnO
2nanoflower assembled from nanorods
via a one-pot template-free hydrothermal methodrdquo CeramicsInternational vol 42 no 14 pp 15889ndash15896 2016
Figure 3 (a) Gas response versus operating temperature of hollow ZnSnO3nanospheres sensors to different target gases with a concentration
of 100 ppm (b) dynamic response-recovery curves of the sensor to different concentrations of ethanol at 200∘C and (c) and (d) response-recovery curves of the sensor to 100 ppm ethanol at 200∘C
References
[1] Y Bing Y Zeng C Liu et al ldquoAssembly of hierarchical ZnSnO3
hollow microspheres from ultra-thin nanorods and the en-hanced ethanol-sensing performancesrdquo Sensors and ActuatorsB Chemical vol 190 pp 370ndash377 2014
[2] HWang X-X Liu J XieMDuan and J-L Tang ldquoCO sensingproperties of a cubic ZnSn(OH)6 synthesized by hydrothermalmethodrdquo Chinese Chemical Letters vol 27 no 3 pp 464ndash4662016
[3] M-K Lo S-Y Lee and K-S Chang ldquoStudy of ZnSnO3-
nanowire piezophotocatalyst using two-step hydrothermal syn-thesisrdquo The Journal of Physical Chemistry C vol 119 no 9 pp5218ndash5224 2015
[4] Y Wang D Li Y Liu and J Zhang ldquoSelf-assembled 3DZnSnO
3hollow cubesreduced graphene oxide aerogels as
high capacity anode materials for lithium-ion batteriesrdquo Elec-trochimica Acta vol 203 pp 84ndash90 2016
[5] W Guo T Liu W Yu L Huang Y Chen and Z Wang ldquoRapidselective detection of formaldehyde by hollow ZnSnO
3nanoc-
agesrdquo Physica E Low-Dimensional Systems and Nanostructuresvol 48 pp 46ndash52 2013
[6] P Wadkar D Bauskar and P Patil ldquoHigh performance H2
sensor based on ZnSnO3cubic crystallites synthesized by a
hydrothermal methodrdquo Talanta vol 105 pp 327ndash332 2013[7] X Jia M Tian Z Zhang R Dai X Wu and H Song ldquoHighly
sensitive formaldehyde chemical sensor based on in situ precip-itation synthesis of ZnSnO
3microspheresrdquo Journal of Materials
Science Materials in Electronics vol 26 no 8 pp 6224ndash62312015
[8] HWang X Liu J Xie M Duan and J Tang ldquoEffect of humid-ity on the CO gas sensing of ZnSn(OH)
6film via quartz crystal
microbalance techniquerdquo Journal of Alloys and Compounds vol657 pp 691ndash696 2016
[9] P Song Q Wang and Z Yang ldquoBiomorphic synthesis ofZnSnO
3hollow fibers for gas sensing applicationrdquo Sensors and
Actuators B Chemical vol 156 no 2 pp 983ndash989 2011
Journal of Nanomaterials 5
[10] J Zhang SWang YWang et al ldquoZnOhollow spheres prepara-tion characterization and gas sensing propertiesrdquo Sensors andActuators B Chemical vol 139 no 2 pp 411ndash417 2009
[11] D An Q Wang X Tong et al ldquoSynthesis of Zn2SnO4via a
co-precipitation method and its gas-sensing property towardethanolrdquo Sensors and Actuators B Chemical vol 213 pp 155ndash163 2015
[12] QWang N Yao D An et al ldquoEnhanced gas sensing propertiesof hierarchical SnO
2nanoflower assembled from nanorods
via a one-pot template-free hydrothermal methodrdquo CeramicsInternational vol 42 no 14 pp 15889ndash15896 2016
[10] J Zhang SWang YWang et al ldquoZnOhollow spheres prepara-tion characterization and gas sensing propertiesrdquo Sensors andActuators B Chemical vol 139 no 2 pp 411ndash417 2009
[11] D An Q Wang X Tong et al ldquoSynthesis of Zn2SnO4via a
co-precipitation method and its gas-sensing property towardethanolrdquo Sensors and Actuators B Chemical vol 213 pp 155ndash163 2015
[12] QWang N Yao D An et al ldquoEnhanced gas sensing propertiesof hierarchical SnO
2nanoflower assembled from nanorods
via a one-pot template-free hydrothermal methodrdquo CeramicsInternational vol 42 no 14 pp 15889ndash15896 2016
