Study of structural properties and defects of Ni-doped SnO₂nanorods as ethanol gas sensors

Abstract

An ethanol gas sensor with enhanced sensor response was fabricated using Ni-doped SnO nanorods, synthesized via a simple hydrothermal method. It was found that the response (R = R /R) of a 5.0 mol% Ni-doped SnO (5.0Ni:SnO) nanorod sensor was 1.4 × 10 for 1000 ppm CHOH gas, which is about 13 times higher than that of pure SnO nanorods, (1.1 × 10) at the operating temperature of 450 °C. Moreover, for 50 ppm CHOH gas, the 5.0Ni:SnO nanorod sensor still recorded a significant response reading, namely 2.0 × 10 with a response time of 30 s and recovery time of 10 min. To investigate the effect of Ni dopant (0.5-5.0 mol%) on SnO nanorods, structural characterizations were demonstrated using field emission scanning electron microscopy, high-resolution transmission electron microscopy, Fourier transform infrared spectroscopy, x-ray diffraction (XRD) analysis, x-ray photoelectron spectroscopy and an ultraviolet-visible spectrometer. XRD results confirmed that all the samples consisted of tetragonal-shaped rutile SnO nanorods. It was found that the average diameter and length of the nanorods formed in 5.0Ni:SnO were four times smaller (∼6 and ∼35 nm, respectively) than those of the nanorods formed in pure SnO (∼25 and 150 nm). Interestingly, both samples had the same aspect ratio, ∼6. It is proposed that the high response of the 5.0Ni:SnO nanorod sensor can be attributed to the particle size, which causes an increase in the thickness of the charge depletion layer, and the presence of oxygen vacancies within the matrix of SnO nanorods.

A reliable chemiresistive sensor of nickel-doped tin oxide (Ni-SnO2) for sensing carbon dioxide gas and humidity

“…These results suggest that nickel ions can be doped into the tin lattice without structural deviation. 34,35 Fig. 5a-c display the FTIR transmittance spectra of Ni-SnO 2 NPs containing different concentrations of nickel.…”

The role of oxygen vacancies in the sensing properties of Ni substituted SnO2 microspheres

“…The sensing responses were observed to increase upon an increase in the operating temperature from 130 to 180 C. This result is due to an increase in the presence of surface adsorbed oxygen in the form of O 2 À , O 2À and O À at higher temperatures and because more ethanol molecules react with the surface of the sensing material, decreasing the resistance of the sample. 2,32 Subsequently, the response of the sensor based on S1 reached a maximum value of 51.3 for 100 ppm of ethanol, which was 3.62 times higher than the sensor based on S0 at the same operating temperature of 180 C. Aer the maximum value, the response decreased upon a further increase in the operating temperature, which might be caused by the adsorption of ethanol molecules being lower than the desorption at such a high temperature. 33,34 All other sensing tests were performed at the optimum operating temperature.…”

A Comparative Study of Structural and Ethanol Gas Sensing Properties of Pure, Nickel and Palladium Doped SnO2 Nanorods Synthesised by the Hydrothermal Method

“…The hydrothermal method for synthesis, pure and Ni-doped SnO 2 (Ni:SnO 2 ) nanorods had been reported in previous works. 16,17 In brief, the precursor, including repeatedly washed with distilled water and ethanol, and later oven-dried at 55°C overnight. The pure SnO 2 sample was prepared as per the previously-mentioned process, except that heat treatment was carried out for 24 h without dopant.…”

“…Details of the sensor preparation and the configuration of custom-built gas sensing measurement instrumentation can be found in our previous work. 16 In brief, a proper amount of as-synthesised SnO 2 samples were mixed in sensor ink separately to form a slurry. 18 Subsequently, the slurry was coated onto an Au-interdigitated alumina substrate covering a dimension of 5 mm × 5 mm (Case: Western Reserve University, Cleveland, United States).…”

“…In our previous study, we found that the ethanol sensor response was greatly enhanced (by approximately 13 times) after SnO 2 was doped with 5 mol% Ni. 16 It was proposed that the thickness of charge depletion layer and the presence of oxygen vacancies mainly contributed to the high sensor response.…”