Apple fruit quality monitoring at room temperature using sol–gel spin coated Ni–SnO2 thin film sensor

Abstract

The application of metal oxides based gas sensors in the field of food and fruits quality measurement can significantly reduce the spoilage of food by monitoring the quality. In the present work, rotten apple has been monitored by detecting the ethylene (C2H4) gas efflux using a thin film Ni–SnO2 sensor. The sensor is prepared by simple and cost-effective sol–gel spin coating technique. Structural characteristics, surface morphology and elemental analysis of the deposited Ni–SnO2 layer have been studied through X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX), respectively. The response of the sensor is found appreciably high with ~ 82% sensitivity, high selectivity along with appreciable response and recovery time towards the rotten apple at room temperature (RT) in 50% relative humidity (RH) condition. High sensitivity and selectivity of the fabricated sensor towards the rotten apple is verified by observing the response towards the fresh apple, decayed banana, decayed kiwi and decayed non-climacteric fruits like oranges and grapes under similar conditions. The sensing behavior of the sensor is also analyzed for room temperature (25 °C) as well on higher temperatures (up to 50 °C) and humidity (50% RH–90% RH) to cover the higher ambient conditions. The obtained results are indicating that the fabricated Ni–SnO2 sensor has a great potential and may be used as a promising apple fruit quality monitoring device at room temperature with appreciable sensitivity and selectivity.