A biodegradable and flexible temperature sensor supported on avocado peel and its enhancement of detection by sensitizing with the La0.5Sr0.5CoO3 perovskite

Abstract

We report the performance of flexible and biodegradable temperature sensors fabricated with avocado peel (biodegradable waste used as support), graphene (G), carbon nanotubes (CNTs) and La0.5Sr0.5CoO3 (LSCO) perovskite. The LSCO powder is formed by agglomerates of microparticles with average size of 1.63 μm and they are decorated by smaller nanoplates with sizes of 50–150 nm. According to the X-ray diffraction (XRD) analysis, the LSCO presents a rhombohedral crystalline phase. The performance of the temperature sensor made without LSCO (it contained only G + CNTs as active materials) was firstly evaluated to detect a temperature of 60 °C and response/recovery times of 35.3/155.5 s were obtained. Later, the sensor was sensitized with LSCO microparticles deposited on its surface and the response/recovery times were lowered to 8.5/27.6 s for the same detection temperature of 60 °C, thus, the response time was decreased by ≈ 76%. The sensor made with LSCO was also subjected to 300 bending cycles. Interestingly, it produced a low response/recovery times of 9.7/7.1 s for the detection temperature of 90 °C. Moreover, the temperature sensor made with LSCO microparticles could detect temperatures in the range of 60–140 °C and the response/recovery times increased from 8.5/27.6 s to 15.3/122.3 s after increasing the detection temperature from 60 °C to 140 °C. Furthermore, the XPS, Raman and FTIR analysis revealed the formation of amorphous carbon and structural defects on the sensor's surface after its use for the temperature detection, which contributed to the enhancement of the sensor's sensitivity by ≈ 139%. Overall, the new class of temperature sensor presented in this work can pave the way for the development of eco-friendly sensors, which can find applications in wearable/industrial devices.