Selective Improvement of NO₂ Gas Sensing Behavior in SnO₂ Nanowires by Ion-Beam Irradiation

Abstract

We irradiated SnO2 nanowires with He ions (45 MeV) with different ion fluences. Structure and morphology of the SnO2 nanowires did not undergo noticeable changes upon ion-beam irradiation. Chemical equilibrium in SnO2/gas systems was calculated from thermodynamic principles, which were used to study the sensing selectivity of the tested gases, demonstrating the selective sensitivity of the SnO2 surface to NO2 gas. Being different from other gases, including H2, ethanol, acetone, SO2, and NH3, the sensor response to NO2 gas significantly increases as the ion fluence increases, showing a maximum under an ion fluence of 1 × 10(16) ions/cm(2). Photoluminescence analysis shows that the relative intensity of the peak at 2.1 eV to the peak at 2.5 eV increases upon ion-beam irradiation, suggesting that structural defects and/or tin interstitials have been generated. X-ray photoelectron spectroscopy indicated that the ionic ratio of Sn(2+/)Sn(4+) increases by the ion-beam irradiation, supporting the formation of surface Sn interstitials. Using thermodynamic calculations, we explained the observed selective sensing behavior. A molecular level model was also established for the adsorption of NO2 on ion-irradiated SnO2 (110) surfaces. We propose that the adsorption of NO2-related species is considerably enhanced by the generation of surface defects that are comprised of Sn interstitials.

Silver Nanowire Templating Synthesis of Mesoporous SnO2 Nanotubes: An Effective Gas Sensor for Methanol with a Rapid Response and Recovery

“…To further determine the valent state of Sn and O elements of mesoporous SnO 2 nanotubes, the X‐ray photoelectron (XPS) measurement spectra was performed in Figure S2a, which shows the XPS of Sn 3d of mesoporous SnO 2 nanotubes. The XPS of Sn 3d peaks exhibit a doublet with respective binding energies of 487.2 (3d 5/2 ) and 495.6 eV (3d 3/2 ), which demonstrate that the mesoporous SnO 2 nanotubes contain Sn 4+ ions . The deconvoluted XPS peaks of O 1s (Figure S2b) display a doublet with binding energies of 530.4 eV and 531.9 eV, which may be ascribed to the lattice oxygen and adsorbed oxygen .…”

Recent advances in energy-saving chemiresistive gas sensors: A review

“…The sensing mechanism was explained based on modifications of the potential barriers at the SnO 2 NW-NW junctions and establishment of depletion layers at the SnO 2 NWs [ 75 ]. When the sensors were exposed to NO 2 gas, NO 2 molecules were adsorbed on the surface of the SnO 2 NW sensor, and electrons were extracted from the conduction band of SnO 2 NWs to form NO 2 − ionic species [ 76 ], which resulted in an increased number of depletion layers and potential barriers with increased heights.

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“…Thus, Joule heating can be increased by increasing the applied voltage. The responses of a Pd-SnO 2 -ZnO core-shell NW sensor toward benzene at different concentrations were measured under different applied voltages from 1 to 20 V. With increasing concentration and applied voltages, the response also increased, and the highest response of 2.62 was obtained for 50-ppm benzene at 20 V. The high selectivity of the Pd-SnO 2 -ZnO core-shell NW sensor toward benzene can be attributed to the interaction between the π electrons of benzene and the d-band electrons of Pd NPs [ 76 ]. A response of 43.13 was obtained for 50-ppm benzene at a temperature of 200 °C.…”

State-of-the-Art Research on Chemiresistive Gas Sensors in Korea: Emphasis on the Achievements of the Research Labs of Professors Hyoun Woo Kim and Sang Sub Kim

“…At high energies, electron excitation/ionization occurs (electronic energy loss) due to inelastic collisions [ 131 , 132 , 133 ]. Kwon et al [ 134 ] irradiated SnO 2 NWs with He ions (45 MeV) through different ionic fluences, where the NO 2 response of the sensor increased considerably with an increase in the ion fluence. The highest response was achieved under an ion fluence of 1 × 10 16 ions/cm 2 .…”