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Nanocomposites of SmFeO3/YFeO3 (1:0, 0.8:0.2, 0.6:0.4, 0.4:0.6, 0.2:0.8, and 0:1) with different molar proportions were prepared by the sol–gel method. The material's properties were characterized by various test methods, such as scanning-electron microscopy (SEM) and X-ray photoelectron-diffraction spectrometry (XPS). The gas-sensing characteristics of the sensor were tested in darkness and under illumination using monochromatic light with various selected wavelengths. The test results show that the SmFeO3/YFeO3 sensor with the molar ratio of 0.4:0.6 had the highest gas response to volatile organic compound (VOC) gases and that the optimum operating temperature was lower (120 °C). The light illumination improved the sensor's sensitivity to gas. Under the 370-nanometer light illumination, the sensor's responses to 30 ppm of ethanol, acetone, and methanol gases were 163.59, 134.02, and 111.637, respectively, which were 1.35, 1.28, and 1.59 times higher, respectively, than those without light. The high gas sensitivity of the sensor was mainly due to the adsorption of oxygen on the material's surface and the formation of a p–p heterojunction. The SmFeO3/YFeO3 sensor, which can respond to different VOC gases, can be used to detect the safety of unknown environments and provide a timely warning of the presence of dangerous gases in working environments. [ABSTRACT FROM AUTHOR]

• The LaFeO 3 sensor has a low optimum operating temperature of 110 °C. • Multi-wavelength light illumination improved the sensor's response. • The sensor's response to 30 ppm ethanol was 154.5 under 370 nm light illumination. • The sensor's response to 30 ppm methanol was 109.3 under 370 nm light illumination. The LaFeO 3 (500–900 °C) powders were prepared using the sol–gel method. Multi-wavelength light illumination improved the LaFeO 3 (700 °C) sensor's response. Under the 370 nm light illumination, the LaFeO 3 (700 °C) sensor's responses to 30 ppm ethanol and methanol were 154.5 and 109.3 at 110 °C, and the response/recovery times were 70/127 s and 82/136 s. The LaFeO 3 planar electrode sensor had a high response value to ethanol and methanol. Its high response value and low working temperature have great potential for gas detection in an unknown environment. [ABSTRACT FROM AUTHOR]

• Gas sensor was prepared using 1.5 × 1 mm plane electrodes. • Light illumination improved the sensor's response to gases. • The response of the SmFeO 3 sensor under light to 30 ppm acetone was 29.228. • The SmFeO 3 sensor has a low working temperature of 120 °C. In this study, we prepared SmFeO 3 nanopowders by the sol–gel method. The planar electrode sensor (1.5 × 1 mm) based on SmFeO 3 nanopowder is responsive to methanol, ethanol, acetone, and other gases. Different wavelengths (470 nm, 420 nm, and 370 nm) of light illumination affect the sensor's response to gas. The response under light illumination (370 nm, 98 mW) at 120 °C to 30 ppm methanol, ethanol, and acetone were 26.41, 23.804, and 29.228, which were 2.0, 1.4, and 1.4 times higher than those in the dark, respectively. The planar electrode sensor can reduce optimum working temperature and reduce energy consumption, so it has great potential for application in real life. [ABSTRACT FROM AUTHOR]

The challenge encountered by the sensor in practical application is that the optimal working temperature is high, which will cause certain dangers in the work. Herein, we fabricated a p-p heterojunction composite LaFeO 3 /YFeO 3 planar electrode sensor for gas detection. The planar electrode sensor adopts the method of direct heating, which reduces the optimal working temperature of the sensor compared with the traditional side-heated alumina ceramic tube sensor. The optimal operating temperature of the LaFeO 3 /YFeO 3 (0.8:0.2) planar electrode sensor is 110 °C. In addition, we also performed multi-wavelength (470, 420, and 370 nm) light illumination experiments on the LaFeO 3 /YFeO 3 sensor to improve gas response. Under 370 nm light illumination, the response values of the LaFeO 3 /YFeO 3 (0.8:0.2) sensor to 30 ppm methanol, acetone, and ethanol were 166.82, 199.58, and 292.67, which were 1.19, 1.33, and 1.36 times than those in the dark. The lowest detection limits of the LaFeO 3 /YFeO 3 (0.8:0.2) sensor under 370 nm light illumination for methanol, acetone, and ethanol were 0.3, 0.8, and 0.2 ppm, respectively. Therefore, the LaFeO 3 /YFeO 3 (0.8:0.2) planar electrode sensor has the advantages of small size, low optimal operating temperature, low power consumption, high response value to volatile organic compounds gases, and high-cost performance for use in different gas environments. • The LaFeO 3 /YFeO 3 (a:b) materials were fabricated by the sol-gel method. • Gas sensor was prepared using 1.5 × 1 mm plane electrodes. • The sensors were tested under multi-wavelength light illumination. • The optimal operating temperature of LaFeO 3 /YFeO 3 (0.8:0.2) sensor was 110 °C. • Light illumination improved the sensor's response to VOCs gases. [ABSTRACT FROM AUTHOR]

The planar electrode sensors of the La 1−x Y x FeO 3 (x = 0, 0.2, 0.4, 0.6, 0.8, and 1) perovskite material were prepared for volatile organic compounds (VOCs) gas detection. The La 1−x Y x FeO 3 (x = 0.8) sensor has a higher gas response than La 1−x Y x FeO 3 (x = 0, 0.2, 0.4, 0.6, and 1) due to a higher surface adsorbed-oxygen content of the material. Light illumination improves the gas response of the La 0.2 Y 0.8 FeO 3 sensor to VOCs gases. A higher gas response of the La 0.2 Y 0.8 FeO 3 sensor was attained as the light-source wavelength was shortened. The gas responses of the La 0.2 Y 0.8 FeO 3 sensor under 370 nm light illumination at 100 °C to 5 ppm ethanol, methanol, acetone, and formaldehyde were 36.369, 32.352, 36.357, and 12.545, respectively. Additionally, at 110 °C, the response to 5 ppm acetylacetone was 35.94. In conclusion, the La 0.2 Y 0.8 FeO 3 planar electrode sensor has greater gas responses and lower operating temperature to VOCs gases. Therefore, the planar electrode sensor can reduce power consumption and be used in various locations with known gases. • The La 1−x Y x FeO 3 gas sensors were prepared using 1.5 × 1 mm plane electrodes. • The La 0.2 Y 0.8 FeO 3 sensor has high responses to VOCs under light illumination. • The plane electrode sensor has a low optimum working temperature of 100 °C. • Multi-wavelength light illumination can improve the gas response of sensor. [ABSTRACT FROM AUTHOR]