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. 2020 May 4:6:30.
doi: 10.1038/s41378-020-0142-6. eCollection 2020.

Hierarchical highly ordered SnO2 nanobowl branched ZnO nanowires for ultrasensitive and selective hydrogen sulfide gas sensing

Li-Yuan Zhu  1 , Kai-Ping Yuan  1 , Jia-He Yang  1 , Cheng-Zhou Hang  1 , Hong-Ping Ma  1 , Xin-Ming Ji  1 , Anjana Devi  2 , Hong-Liang Lu  1 , David Wei Zhang  1
Affiliations

Hierarchical highly ordered SnO2 nanobowl branched ZnO nanowires for ultrasensitive and selective hydrogen sulfide gas sensing

Li-Yuan Zhu et al. Microsyst Nanoeng. .

Abstract

Highly sensitive and selective hydrogen sulfide (H2S) sensors based on hierarchical highly ordered SnO2 nanobowl branched ZnO nanowires (NWs) were synthesized via a sequential process combining hard template processing, atomic-layer deposition, and hydrothermal processing. The hierarchical sensing materials were prepared in situ on microelectromechanical systems, which are expected to achieve high-performance gas sensors with superior sensitivity, long-term stability and repeatability, as well as low power consumption. Specifically, the hierarchical nanobowl SnO2@ZnO NW sensor displayed a high sensitivity of 6.24, a fast response and recovery speed (i.e., 14 s and 39 s, respectively), and an excellent selectivity when detecting 1 ppm H2S at 250 °C, whose rate of resistance change (i.e., 5.24) is 2.6 times higher than that of the pristine SnO2 nanobowl sensor. The improved sensing performance could be attributed to the increased specific surface area, the formation of heterojunctions and homojunctions, as well as the additional reaction between ZnO and H2S, which were confirmed by electrochemical characterization and band alignment analysis. Moreover, the well-structured hierarchical sensors maintained stable performance after a month, suggesting excellent stability and repeatability. In summary, such well-designed hierarchical highly ordered nanobowl SnO2@ZnO NW gas sensors demonstrate favorable potential for enhanced sensitive and selective H2S detection with long-term stability and repeatability.

Keywords: Nanowires; Sensors.

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Conflict of interest statement

Conflict of interestThe authors declare that they have no conflict of interest.

Figures

Fig. 1
Fig. 1. Synthesis of the hierarchical highly ordered nanobowl SnO2@ZnO NWs in situ on MEMS.
a The synthetic protocol for the hierarchical highly ordered nanobowl SnO2@ZnO NWs in situ on MEMS, combining a modified facile hard template method, an ALD process and a hydrothermal method; b the optical microscopy image of the MEMS heating appliance with gas sensing materials; c an enlarged image of heating electrodes and interdigital sensing electrodes
Fig. 2
Fig. 2. SEM characterization of all the samples.
a Pristine highly ordered SnO2 nanobowls (i.e., S@Z0); b highly ordered SnO2 nanobowls coated with 20nm ZnO film (i.e., S@Z20); c highly ordered SnO2 nanobowls branched ZnO NWs (i.e., S@Z20-Z5); d S@Z20-Z1; e S@Z20-Z3; f S@Z20-Z8; g S@Z0-Z5; h S@Z10-Z5; i S@Z30-Z5
Fig. 3
Fig. 3. TEM characterization of the highly ordered SnO2 nanobowl branched ZnO NW sample S@Z20-Z5.
a Low-magnification image of two nanowire-branched nanobowls; b the highly magnified image of a randomly selected single ZnO NW on S@Z20-Z5; c the HRTEM image and d the SAED pattern obtained on a single ZnO NW
Fig. 4
Fig. 4. Chemical components of S@Z0, S@Z20, and S@Z20-Z5.
a XRD patterns of S@Z0, S@Z20, and S@Z20-Z5; b high-resolution core level Sn 3d spectrum of the highly ordered SnO2 nanobowl sample S@Z0; c high-resolution core level Sn 3d and Zn Auger spectrum and d high-resolution core level Zn 2p spectrum of the highly ordered SnO2 nanobowl branched ZnO NWs sample S@Z20-Z5
Fig. 5
Fig. 5. Gas sensing properties of the three samples (i.e., S@Z0, S@Z20, and S@Z20-Z5).
a Response of all three samples at different operating temperatures (i.e., 150, 200, 250, and 300°C); b dynamic response curves of all three samples with different hierarchical structures facing the reducing gas of H2S with various concentrations ranging from 3 to 1 ppm at 250°C; c response of all three samples facing other various reducing gases (1 ppm), namely, NH3, CH3COCH3, C7H8, and HCHO, compared with 1 ppm H2S at 250°C; d the characterization of long-term stability for sample S@Z20-Z5 in air for a month; e enlarged responses of samples S@Z0, S@Z20, and S@Z20-Z5 facing 1 ppm H2S at 250°C with fast response and recovery
Fig. 6
Fig. 6. Schematics of the reducing gas sensing mechanism in the hierarchical highly ordered nanobowl SnO2@ZnO NWs.
a The three-dimensional schematic of the hierarchical highly ordered nanobowl SnO2@ZnO NWs exposed in H2S gas; b, c the schematic energy band diagrams for the hierarchical SnO2@ZnO NWs: b in separate state and c in air. The band structure data in figure (b) were determined from the literature
See this image and copyright information in PMC

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