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UV-enhanced hydrogen sensor based on nanocone-assembled 3D SnO2 at low temperature
Author’s Accepted Manuscript UV-enhanced Hydrogen Sensor Based on Nanocone-assembled 3D SnO2 at Low Temperature Tianming Li, Wen Zeng, Dongfeng Shi, Shahid Hussain www.elsevier.com
PII: DOI: Reference:
S0167-577X(15)30588-7 http://dx.doi.org/10.1016/j.matlet.2015.09.077 MLBLUE19593
To appear in: Materials Letters Received date: 6 August 2015 Revised date: 14 September 2015 Accepted date: 15 September 2015 Cite this article as: Tianming Li, Wen Zeng, Dongfeng Shi and Shahid Hussain, UV-enhanced Hydrogen Sensor Based on Nanocone-assembled 3D SnO 2 at Low Temperature, Materials Letters, http://dx.doi.org/10.1016/j.matlet.2015.09.077 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
UV-enhanced Hydrogen Sensor Based on Nanocone-assembled 3D SnO2 at Low Temperature Tianming Li, Wen Zeng*, Dongfeng Shi, Shahid Hussain College of Materials Science and Engineering, Chongqing University, Chongqing, China 400030 Abstract: In this paper, nanocone-assembled hedgehog-like SnO2 was synthesized via a facile hydrothermal process. Once under UV irradiation, the response of the as-prepared 3D SnO2 towards 100 ppm H2 at low temperature (50oC) was improved almost 3.5 times (S= 9.5) over that in dark. The enhancement may be attributed to the co-effect from three aspects: (1) the heavy electron depletion induced by oxygen chemisorption due to the Debye length scale dimensions of nanocones; (2) vast reaction sites and sufficient diffusion spaces provided by the 1D-3D configuration; (3) the possibility that the refreshed photoinduced oxygen ions on the surface of SnO2 are more energetic than chemisorbed oxygen ions and promote the photo-catalytic reaction of H2 even at low temperature. Keywords: Sensors; UV irradiation; hedgehog-like SnO2; low temperature; Semiconductors 1. Introduction Resistive gas sensors based on nanoscale metal oxides such as SnO2 are extensively investigated due to the far reaching application potential[1, 2]. However, one of the obstacles placed in the road is the high temperature that needed to activate the gas-sensing reaction and accelerate desorption of the molecules, which restricts the application of gas sensor in many areas, such as inflammable and explosive environments[3, 4]. Recently, much effort has been devoted to reducing the operating temperature, mainly including the doping of noble metals[5] and UV irradiation[6]. Research has demonstrated that modifying the surface condition of the oxides *
Corresponding author E-mail: [email protected] (W. Zeng) Tel: +86-23-65102466 1
induced by UV irradiation is a promising strategy. Peng et al. investigated the room temperature HCHO sensor using ZnO nanorods, the response of which was about 120 times higher under UV illumination than that in dark [7]. Deng et al. attributed the enhancement in gas-sensing performance of mesoporous WO3 towards HCHO to the higher surface interaction rate among photoelectron, photoinduced oxygen ion and target gas [8]. However, the sensitivity of metal oxide based gas sensor under UV illumination is usually not as good as that at high temperature[9, 10]. Much can be done to further enhance the gas-sensing properties under UV irradiation. Apart from being functionalized with a secondary component[11, 12], the sensing material can be designed into 1D building blocks assembled 3D hierarchical architecture (denoted as 1D-3D)[13], which not only prevents the 1D units from serious stacking but also inherits the merits of 1D nanomaterials. It is believed that, with large surface-to-volume ratios and a Debye length comparable to their dimensions, 1D nanostructures have great potential to improve the sensing materials’ properties due to the fact that a significant fraction of the atoms in such systems are surface atoms that can participate in surface reactions[3]. In this 1D-3D framework under UV irradiation, a huge number of photoinduced electrons and holes exist as well as vast reaction sites[12, 14]. Herein, nanocone-assembled SnO2 was successfully synthesized under hydrothermal condition. The maximum diameter of an individual nanocone was comparable to twice Debye length of bulk SnO2, which was believed to be beneficial for gas sensing. It turned out that response of the as-prepared 3D SnO2 towards 100 ppm H2 at low temperature (50oC) increased from 2.7 to 9.5 once under UV irradiation, the reasons behind which may be attributed to unique 1D-3D structural characteristics and the rearrangement of surface Sn-O bonding induced by the 2
UV irradiation through transforming chemisorbed . It is proposed that
into highly active photoinduced
ions are responsible for the low-temperature gas sensing
phenomena and promise enhanced sensor performance through further optimization. 2. Experimental Nanocone-assembled 3D SnO2 was synthesized by a facile hydrothermal process. Typically, 2 mmol SnCl2•2H2O was added into 30 mL of an ethanol/water (1:1) solution under vigorous stirring for 5 min. After the adding of 0.04 g Na(CH3COO)2•H2O with stirring, the resultant solution was loaded into a 50 mL Teflon-lined stainless steel autoclave and heated to 180 oC for 24h. After cooling to room temperature naturally, the precipitates were collected, and washed with DI water and ethanol sequentially, and dried in air at 60 oC overnight. The surface morphology of the as-prepared sample was inspected by scanning electron microscopy (SEM, JEOL, JSM-7500F) and transmission electron microscope (TEM, ZEISS, LIBRA200). X-ray diffraction (XRD) patterns of the samples were conducted on a Rigaku D/max 2550 X-ray diffractometer (λ = 1.5045 Å). Gas-sensing properties were investigated by the flat-plat device printed with SnO2 film (as shown in Fig.1a), which was held in a chamber with two vents. The device cell was connected with a computer-controlled translation system (Fig.1b) by the data acquisition device (PCI-6225, National Instrument Co. Ltd.). The testing photocurrent range of the platform was 10−9 A to 10−3 A in gas-phase condition. Most importantly, various parameters were all well-controlled by the computer, including the bias voltage (5 V), the testing time, the concentration of the target gas, and the light intensity (LED array light source 313 nm, 40 W/m2, Shenzhen Ti-Times Co.). The schematic diagram was given in Fig. 1. Gas response in this paper is defined as S=Ig/Ip, where Ig 3
and Ip are the maximum and minimum photocurrent amplitude within a cycle. 3. Results and discussion Fig.2 shows the XRD pattern of the obtained SnO2 powder. The identified peaks for the sample can be indexed to tetragonal rutile SnO2 (JCPDS card No. 41-1445) without observable impurity peaks, which suggests that the as-synthesized SnO2 have high phase purity. The strong diffraction peaks of (110), (101) and (211) planes reveal a layered crystal structure, or a highly anisotropic growth of the oxides[15]. The highly anisotropic growth of the SnO2 is confirmed by SEM and STM investigations, as shown in Fig.3. A general view in Fig.3a demonstrates that the product is composed of monodispersed hedgehog-like 3D hierarchical architectures with 1D nanostructures as building blocks. The magnified image displayed in Fig.3b shows that the self-assembled unit is in the form of nanocone, which is further verified by the TEM image of Fig.3c. Comprehensive analysis of Fig.3b and c reveals that the nanocones tend to stack radially, leaving a hedgehog-like 3D structure. From Fig.3d, it is can be deduced that the nanocone is in the manner of single crystal with orientation growth along [110], as confirmed by the SAED pattern. What’s more, a representative diameter of the nanocone is measured to be 38 nm, which is close to twice Debye length (LD) of bulk SnO2 (~36 nm). Theoretically, the nanocone will get majority carriers heavily depleted due to the ionization of adsorbed oxygen by thoroughly drawing electrons from the conduction band of the LD-scale SnO2 nanomaterials, which is beneficial to enhance the low temperature gas sensing performance under UV irradiation[4]. Nanoparticles typically exhibit large surface areas desired for gas sensor application, however, the grain boundaries do act as electron captures, thus hindering efficient electron transport under UV exposure. In contrast, hierarchical structures assembled from single-crystalline 1D building blocks, such as nanocones make it possible to improve the electrical signal transmission speed. 4
For a preliminary study, the gas sensing performance of the 1D-3D SnO2 based sensor was investigated towards 100 ppm H2 at 50oC, as shown in Fig.4a. It is obvious that, as the H2 introduced without illumination, the response increased to 2.7 slowly. Once under UV irradiation (313 nm), the response was improved almost 3.5 times (S= 9.5) in few seconds. In addition, as obviously deduced from the size of the slopes as well as the amount of coloured circles in Fig. 4a, the response/recovery kinetics is fast than that in the dark condition, which may be attributed to the efficient diffusion of photon-generated carrier. All of the results toward a conclusion that the irradiation of UV light significantly improves the H2 sensing properties of the 1D-3D SnO2 at low temperature. It is well known that the sensing mechanism of metal oxides mainly depends on the change in surface conductivity[3]. Before light off, the process is divided into 3 stages: A-C, as shown in Fig.4b. At stage A (in dark), the resistance of the sensor is relatively high due to the chemisorption of oxygen at low temperature, which trapping electrons from the conduction band of SnO2
, even resulting in electron-depleted region once the diameter of
the exposed nanocone falling into 2LD[8, 14]. Upon exposure to H2 (in stage B), the current begins to rise because of the release of the trapped electrons
[16].
However, the proceeding of the reaction is impeded due to large adhesive energy of
at
low temperature. Once under UV illumination (in stage C), photogenerated electron-hole pairs are produced
and
holes
release
the
chemisorbed
by
. Simultaneously, the ambient oxygen molecules react with the photogenerated electrons
[17]. The highly active photoinduced
ions are bound to the SnO2 surface much weakly than crucial reactant participating in
ions, which are the even at low temperature,
leading to serious shrinking of the depletion region[7, 12]. 4. Conclusions In this paper, nanocone-assembled hedgehog-like 3D SnO2 was synthesized by a facile hydrothermal process. The maximum diameter of an individual nanocone was comparable to twice 5
Debye length of bulk SnO2, leading to heavy electron depletion induced by oxygen chemisorption, which was believed to be beneficial for gas sensing. Once under UV irradiation at low temperature (50oC), the response of the as-prepared 3D SnO2 towards 100 ppm H2 increased from 2.7 to 9.5, the reasons behind which may be attributed to not only the novel 1D-3D configuration, providing vast reaction sites and sufficient diffusion spaces, but also the rearrangement of surface Sn-O bonding from Sn-
to Sn-
, which makes it possible to detect H2 at low temperature
effectively. Acknowledgements This work was supported in part by National Natural Science of China (51202302), Chongqing Graduate Student Research Innovation Project (No. CYS14011) and Fundamental Research Funds for Central Universities (grant no. 106112015CDJXY130013). References [1] Zeng W, Li T, Li T, Hao J, Li Y. J Mater Sci-Materi El 2014;26:1192-7. [2] Zeng W, Zhang H, Li Y, Chen W, Wang Z. Mater Res Bull 2014;57:91-6. [3] Das S, Jayaraman V. Prog Mater Sci 2014;66:112-255. [4] Hübert T, Boon-Brett L, Black G, Banach U. Sens Actuators B 2011;157:329-52. [5] Wang Z, Li Z, Jiang T, Xu X, Wang C. Acs Appl Mater interfaces. 2013;5:2013-21. [6] Peng L, Zhao Q, Wang D, Zhai J, Wang P, Pang S, et al. Sens Actuators B 2009;136:80-5. [7] Peng L, Zhai J, Wang D, Zhang Y, Wang P, Zhao Q, et al. Sens Actuators B 2010;148:66-73. [8] Deng L, Ding X, Zeng D, Tian S, Li H, Xie C. Sens Actuators B 2012;163:260-6. [9] Ao D, Ichimura M. Solid State Electron 2012;69:1-3. [10] Mishra S, Ghanshyam C, Ram N, Bajpai RP, Bedi RK. Sens Actuators B 2004;97:387-90. 6
[11] Shukla S, Agrawal R, Cho HJ, Seal S, Ludwig L. J Appl Phys 2005; 97: 054307 - -13. [12] Shukla S, Zhang P, Cho HJ, Rahman Z, Drake C. J Appl Phys 2005; 98: 104306 - -15. [13] Yan A, Xie C, Zeng D, Cai S, Li H. J Alloy Compod 2010;495:88-92. [14] Fan S-W, Srivastava AK, Dravid VP. Appl Phys Lett 2009;95:142106. [15] Wang S, Zhang Y, Ma X, Wang W, Li X. Solid State Commun 2005;136:283-7. [16] Karaduman I, Yıldız DE, Sincar MM, Mat Sci Semicon Proc 2014;28:43-7. [17] Liu L, Li X, Dutta PK, Wang J. Sens Actuators B 2013;185:1-9.
Figures captions Fig.1 The schematic diagram of the self-devised high-throughput platform for gas sensing response testing Fig.2 XRD pattern of the obatined SnO2 powder. Fig.3 SEM (a ,b) and TEM (c,d) images of the obataind 1D-3D SnO2. The inset of Fig.3d is the corresponding SAED pattern recorded along [001] zone axis. Fig.4 (a) The response curve of the obataind 1D-3D SnO2 towards 100 ppm H2 at 50oC under UV irradiation.(b) The corresponding diagram illustration of the visible-light-activated gas sensing mechanism at low temperature Figure 1
Figure 2
7
Figure 3
Figure 4
8
Graphical abstract In this letter, nanocone-assembled 3D SnO2 as low temperature H2 sensing materials under UV irradiation was prepared via a hydrothermal method.
Highlights
Novel nanocone-assembled 3D SnO2 architectures have been successfully prepared.
UV-activated sensor based on the 1D-3D SnO2 exhibit superior gas-sensing performances.
Proposal the mechanism of the UV-enhanced H2 Sensor at low temperature.
9
PII: DOI: Reference:
S0167-577X(15)30588-7 http://dx.doi.org/10.1016/j.matlet.2015.09.077 MLBLUE19593
To appear in: Materials Letters Received date: 6 August 2015 Revised date: 14 September 2015 Accepted date: 15 September 2015 Cite this article as: Tianming Li, Wen Zeng, Dongfeng Shi and Shahid Hussain, UV-enhanced Hydrogen Sensor Based on Nanocone-assembled 3D SnO 2 at Low Temperature, Materials Letters, http://dx.doi.org/10.1016/j.matlet.2015.09.077 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
UV-enhanced Hydrogen Sensor Based on Nanocone-assembled 3D SnO2 at Low Temperature Tianming Li, Wen Zeng*, Dongfeng Shi, Shahid Hussain College of Materials Science and Engineering, Chongqing University, Chongqing, China 400030 Abstract: In this paper, nanocone-assembled hedgehog-like SnO2 was synthesized via a facile hydrothermal process. Once under UV irradiation, the response of the as-prepared 3D SnO2 towards 100 ppm H2 at low temperature (50oC) was improved almost 3.5 times (S= 9.5) over that in dark. The enhancement may be attributed to the co-effect from three aspects: (1) the heavy electron depletion induced by oxygen chemisorption due to the Debye length scale dimensions of nanocones; (2) vast reaction sites and sufficient diffusion spaces provided by the 1D-3D configuration; (3) the possibility that the refreshed photoinduced oxygen ions on the surface of SnO2 are more energetic than chemisorbed oxygen ions and promote the photo-catalytic reaction of H2 even at low temperature. Keywords: Sensors; UV irradiation; hedgehog-like SnO2; low temperature; Semiconductors 1. Introduction Resistive gas sensors based on nanoscale metal oxides such as SnO2 are extensively investigated due to the far reaching application potential[1, 2]. However, one of the obstacles placed in the road is the high temperature that needed to activate the gas-sensing reaction and accelerate desorption of the molecules, which restricts the application of gas sensor in many areas, such as inflammable and explosive environments[3, 4]. Recently, much effort has been devoted to reducing the operating temperature, mainly including the doping of noble metals[5] and UV irradiation[6]. Research has demonstrated that modifying the surface condition of the oxides *
Corresponding author E-mail: [email protected] (W. Zeng) Tel: +86-23-65102466 1
induced by UV irradiation is a promising strategy. Peng et al. investigated the room temperature HCHO sensor using ZnO nanorods, the response of which was about 120 times higher under UV illumination than that in dark [7]. Deng et al. attributed the enhancement in gas-sensing performance of mesoporous WO3 towards HCHO to the higher surface interaction rate among photoelectron, photoinduced oxygen ion and target gas [8]. However, the sensitivity of metal oxide based gas sensor under UV illumination is usually not as good as that at high temperature[9, 10]. Much can be done to further enhance the gas-sensing properties under UV irradiation. Apart from being functionalized with a secondary component[11, 12], the sensing material can be designed into 1D building blocks assembled 3D hierarchical architecture (denoted as 1D-3D)[13], which not only prevents the 1D units from serious stacking but also inherits the merits of 1D nanomaterials. It is believed that, with large surface-to-volume ratios and a Debye length comparable to their dimensions, 1D nanostructures have great potential to improve the sensing materials’ properties due to the fact that a significant fraction of the atoms in such systems are surface atoms that can participate in surface reactions[3]. In this 1D-3D framework under UV irradiation, a huge number of photoinduced electrons and holes exist as well as vast reaction sites[12, 14]. Herein, nanocone-assembled SnO2 was successfully synthesized under hydrothermal condition. The maximum diameter of an individual nanocone was comparable to twice Debye length of bulk SnO2, which was believed to be beneficial for gas sensing. It turned out that response of the as-prepared 3D SnO2 towards 100 ppm H2 at low temperature (50oC) increased from 2.7 to 9.5 once under UV irradiation, the reasons behind which may be attributed to unique 1D-3D structural characteristics and the rearrangement of surface Sn-O bonding induced by the 2
UV irradiation through transforming chemisorbed . It is proposed that
into highly active photoinduced
ions are responsible for the low-temperature gas sensing
phenomena and promise enhanced sensor performance through further optimization. 2. Experimental Nanocone-assembled 3D SnO2 was synthesized by a facile hydrothermal process. Typically, 2 mmol SnCl2•2H2O was added into 30 mL of an ethanol/water (1:1) solution under vigorous stirring for 5 min. After the adding of 0.04 g Na(CH3COO)2•H2O with stirring, the resultant solution was loaded into a 50 mL Teflon-lined stainless steel autoclave and heated to 180 oC for 24h. After cooling to room temperature naturally, the precipitates were collected, and washed with DI water and ethanol sequentially, and dried in air at 60 oC overnight. The surface morphology of the as-prepared sample was inspected by scanning electron microscopy (SEM, JEOL, JSM-7500F) and transmission electron microscope (TEM, ZEISS, LIBRA200). X-ray diffraction (XRD) patterns of the samples were conducted on a Rigaku D/max 2550 X-ray diffractometer (λ = 1.5045 Å). Gas-sensing properties were investigated by the flat-plat device printed with SnO2 film (as shown in Fig.1a), which was held in a chamber with two vents. The device cell was connected with a computer-controlled translation system (Fig.1b) by the data acquisition device (PCI-6225, National Instrument Co. Ltd.). The testing photocurrent range of the platform was 10−9 A to 10−3 A in gas-phase condition. Most importantly, various parameters were all well-controlled by the computer, including the bias voltage (5 V), the testing time, the concentration of the target gas, and the light intensity (LED array light source 313 nm, 40 W/m2, Shenzhen Ti-Times Co.). The schematic diagram was given in Fig. 1. Gas response in this paper is defined as S=Ig/Ip, where Ig 3
and Ip are the maximum and minimum photocurrent amplitude within a cycle. 3. Results and discussion Fig.2 shows the XRD pattern of the obtained SnO2 powder. The identified peaks for the sample can be indexed to tetragonal rutile SnO2 (JCPDS card No. 41-1445) without observable impurity peaks, which suggests that the as-synthesized SnO2 have high phase purity. The strong diffraction peaks of (110), (101) and (211) planes reveal a layered crystal structure, or a highly anisotropic growth of the oxides[15]. The highly anisotropic growth of the SnO2 is confirmed by SEM and STM investigations, as shown in Fig.3. A general view in Fig.3a demonstrates that the product is composed of monodispersed hedgehog-like 3D hierarchical architectures with 1D nanostructures as building blocks. The magnified image displayed in Fig.3b shows that the self-assembled unit is in the form of nanocone, which is further verified by the TEM image of Fig.3c. Comprehensive analysis of Fig.3b and c reveals that the nanocones tend to stack radially, leaving a hedgehog-like 3D structure. From Fig.3d, it is can be deduced that the nanocone is in the manner of single crystal with orientation growth along [110], as confirmed by the SAED pattern. What’s more, a representative diameter of the nanocone is measured to be 38 nm, which is close to twice Debye length (LD) of bulk SnO2 (~36 nm). Theoretically, the nanocone will get majority carriers heavily depleted due to the ionization of adsorbed oxygen by thoroughly drawing electrons from the conduction band of the LD-scale SnO2 nanomaterials, which is beneficial to enhance the low temperature gas sensing performance under UV irradiation[4]. Nanoparticles typically exhibit large surface areas desired for gas sensor application, however, the grain boundaries do act as electron captures, thus hindering efficient electron transport under UV exposure. In contrast, hierarchical structures assembled from single-crystalline 1D building blocks, such as nanocones make it possible to improve the electrical signal transmission speed. 4
For a preliminary study, the gas sensing performance of the 1D-3D SnO2 based sensor was investigated towards 100 ppm H2 at 50oC, as shown in Fig.4a. It is obvious that, as the H2 introduced without illumination, the response increased to 2.7 slowly. Once under UV irradiation (313 nm), the response was improved almost 3.5 times (S= 9.5) in few seconds. In addition, as obviously deduced from the size of the slopes as well as the amount of coloured circles in Fig. 4a, the response/recovery kinetics is fast than that in the dark condition, which may be attributed to the efficient diffusion of photon-generated carrier. All of the results toward a conclusion that the irradiation of UV light significantly improves the H2 sensing properties of the 1D-3D SnO2 at low temperature. It is well known that the sensing mechanism of metal oxides mainly depends on the change in surface conductivity[3]. Before light off, the process is divided into 3 stages: A-C, as shown in Fig.4b. At stage A (in dark), the resistance of the sensor is relatively high due to the chemisorption of oxygen at low temperature, which trapping electrons from the conduction band of SnO2
, even resulting in electron-depleted region once the diameter of
the exposed nanocone falling into 2LD[8, 14]. Upon exposure to H2 (in stage B), the current begins to rise because of the release of the trapped electrons
[16].
However, the proceeding of the reaction is impeded due to large adhesive energy of
at
low temperature. Once under UV illumination (in stage C), photogenerated electron-hole pairs are produced
and
holes
release
the
chemisorbed
by
. Simultaneously, the ambient oxygen molecules react with the photogenerated electrons
[17]. The highly active photoinduced
ions are bound to the SnO2 surface much weakly than crucial reactant participating in
ions, which are the even at low temperature,
leading to serious shrinking of the depletion region[7, 12]. 4. Conclusions In this paper, nanocone-assembled hedgehog-like 3D SnO2 was synthesized by a facile hydrothermal process. The maximum diameter of an individual nanocone was comparable to twice 5
Debye length of bulk SnO2, leading to heavy electron depletion induced by oxygen chemisorption, which was believed to be beneficial for gas sensing. Once under UV irradiation at low temperature (50oC), the response of the as-prepared 3D SnO2 towards 100 ppm H2 increased from 2.7 to 9.5, the reasons behind which may be attributed to not only the novel 1D-3D configuration, providing vast reaction sites and sufficient diffusion spaces, but also the rearrangement of surface Sn-O bonding from Sn-
to Sn-
, which makes it possible to detect H2 at low temperature
effectively. Acknowledgements This work was supported in part by National Natural Science of China (51202302), Chongqing Graduate Student Research Innovation Project (No. CYS14011) and Fundamental Research Funds for Central Universities (grant no. 106112015CDJXY130013). References [1] Zeng W, Li T, Li T, Hao J, Li Y. J Mater Sci-Materi El 2014;26:1192-7. [2] Zeng W, Zhang H, Li Y, Chen W, Wang Z. Mater Res Bull 2014;57:91-6. [3] Das S, Jayaraman V. Prog Mater Sci 2014;66:112-255. [4] Hübert T, Boon-Brett L, Black G, Banach U. Sens Actuators B 2011;157:329-52. [5] Wang Z, Li Z, Jiang T, Xu X, Wang C. Acs Appl Mater interfaces. 2013;5:2013-21. [6] Peng L, Zhao Q, Wang D, Zhai J, Wang P, Pang S, et al. Sens Actuators B 2009;136:80-5. [7] Peng L, Zhai J, Wang D, Zhang Y, Wang P, Zhao Q, et al. Sens Actuators B 2010;148:66-73. [8] Deng L, Ding X, Zeng D, Tian S, Li H, Xie C. Sens Actuators B 2012;163:260-6. [9] Ao D, Ichimura M. Solid State Electron 2012;69:1-3. [10] Mishra S, Ghanshyam C, Ram N, Bajpai RP, Bedi RK. Sens Actuators B 2004;97:387-90. 6
[11] Shukla S, Agrawal R, Cho HJ, Seal S, Ludwig L. J Appl Phys 2005; 97: 054307 - -13. [12] Shukla S, Zhang P, Cho HJ, Rahman Z, Drake C. J Appl Phys 2005; 98: 104306 - -15. [13] Yan A, Xie C, Zeng D, Cai S, Li H. J Alloy Compod 2010;495:88-92. [14] Fan S-W, Srivastava AK, Dravid VP. Appl Phys Lett 2009;95:142106. [15] Wang S, Zhang Y, Ma X, Wang W, Li X. Solid State Commun 2005;136:283-7. [16] Karaduman I, Yıldız DE, Sincar MM, Mat Sci Semicon Proc 2014;28:43-7. [17] Liu L, Li X, Dutta PK, Wang J. Sens Actuators B 2013;185:1-9.
Figures captions Fig.1 The schematic diagram of the self-devised high-throughput platform for gas sensing response testing Fig.2 XRD pattern of the obatined SnO2 powder. Fig.3 SEM (a ,b) and TEM (c,d) images of the obataind 1D-3D SnO2. The inset of Fig.3d is the corresponding SAED pattern recorded along [001] zone axis. Fig.4 (a) The response curve of the obataind 1D-3D SnO2 towards 100 ppm H2 at 50oC under UV irradiation.(b) The corresponding diagram illustration of the visible-light-activated gas sensing mechanism at low temperature Figure 1
Figure 2
7
Figure 3
Figure 4
8
Graphical abstract In this letter, nanocone-assembled 3D SnO2 as low temperature H2 sensing materials under UV irradiation was prepared via a hydrothermal method.
Highlights
Novel nanocone-assembled 3D SnO2 architectures have been successfully prepared.
UV-activated sensor based on the 1D-3D SnO2 exhibit superior gas-sensing performances.
Proposal the mechanism of the UV-enhanced H2 Sensor at low temperature.
9