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. 2023 Oct 17;13(20):2780.
doi: 10.3390/nano13202780.

Convergence Gas Sensors with One-Dimensional Nanotubes and Pt Nanoparticles Based on Ultraviolet Photonic Energy for Room-Temperature NO2 Gas Sensing

Sohyeon Kim  1 , Ju-Eun Yang  1 , Yoon-Seo Park  1 , Minwoo Park  1 , Sang-Jo Kim  2 , Kyoung-Kook Kim  1
Affiliations

Convergence Gas Sensors with One-Dimensional Nanotubes and Pt Nanoparticles Based on Ultraviolet Photonic Energy for Room-Temperature NO2 Gas Sensing

Sohyeon Kim et al. Nanomaterials (Basel). .

Abstract

Zinc oxide (ZnO) is a promising material for nitrogen dioxide (NO2) gas sensors because of its nontoxicity, low cost, and small size. We fabricated one-dimensional (1D) and zero-dimensional (0D) convergence gas sensors activated via ultraviolet (UV) photonic energy to sense NO2 gas at room temperature. One-dimensional ZnO nanorod (ZNR)-based and ZnO nanotube (ZNT)-based gas sensors were synthesized using a simple hydrothermal method. All the sensors were tested under UV irradiation (365 nm) so that they could be operated at room temperature rather than a high temperature. In addition, we decorated 0D Pt nanoparticles (NPs) on the gas sensors to further improve their sensing responsivity. The NO2-sensing response of the ZNT/Pt NP convergence gas sensor was 2.93 times higher than that of the ZNR gas sensor. We demonstrated the complex effects of UV radiation on 1D ZnO nanostructures and 0D metal nanostructures in NO2 gas sensing.

Keywords: NO2 gas sensor; ZnO; metal nanoparticles; nanorod; nanotube.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Fabrication procedure for ZNR-based and ZNT-based gas sensors. Schematics of (a) ZnO seed layer grown on sapphire substrate, (b) ZNR-based gas sensor, (c) ZNR/Pt NP-based gas sensor, (d) ZNT-based gas sensor, and (e) ZNT/Pt NP-based convergence gas sensor.
Figure 2
Figure 2
FE-SEM images of (a) ZNRs, (b) ZNRs covered with Pt NPs (ZNRs/Pt NPs), (c) ZNTs, and (d) ZNTs covered with Pt NPs (ZNTs/Pt NPs). (a′–d′) High-magnification FE-SEM images of ZNRs, ZNRs/Pt NPs, ZNTs, and ZNTs/Pt NPs, respectively.
Figure 3
Figure 3
FE-TEM images of (a) ZNR, (b) ZNT, (c) ZNRs/Pt NPs, and (d) ZNTs/Pt NPs. High-magnification FE-TEM images show the average lattice spacings of (a′) ZNR, (b′) ZNT, and (c′,d′) Pt NPs formed on ZNRs and ZNTs. SAED patterns of (a″) ZNR and (b″) ZNT.
Figure 4
Figure 4
(a) Schematic of the FDTD simulation model. (b) Electric field intensities in Y-plane monitor. (c) Electric field intensities in Z-plane monitor.
Figure 5
Figure 5
(a) Resistance of gas sensors at different NO2 gas concentrations in the dark and (b) under UV irradiation. (c) Gas-sensing response of sensors under UV irradiation. (d) Gas-sensing response according to the sensor nanostructures.
Figure 6
Figure 6
RT-operated NO2-gas-sensing mechanism under UV irradiation. (a) Oxygen species are chemisorbed on the surface in air. (b) Electron–hole pairs are photogenerated under UV light. (c) In the case of Pt NP modification, the Pt NPs on the ZnO surface enhance surface reactions in air due to the spillover effect. (d) Hot electrons are generated in Pt NPs and injected into ZnO. (e) NO2 gas reacts with oxygen species chemisorbed on the ZnO surface.
Figure 7
Figure 7
(a,a′,b,b′) Schematic and FE-SEM images of ZNRs and ZNTs that are vertically aligned in random directions. (c) Effective surface area for gas sensing and surface-to-volume ratio depending on the sensor structures. (d) Schematics for comparing sizes and Debye length of fabricated ZnO nanostructures.
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