Cactus-Like NiO Nanostructure-Based ppb Level Trimethylamine Gas Sensor for Monitoring Saltwater Fish Freshness

This paper presents a cactus-like NiO nanostructure-based chemiresistive gas sensor for monitoring saltwater fish freshness. The sensing material was synthesized via a low-temperature, facile hydrothermal method. The cubic crystal system and cactus-like morphology of the synthesized material were revealed using X-ray diffraction and a field emission scanning electron microscope. The sensing material was integrated with gold interdigitated electrodes for gas sensing measurements. The operating temperature of the sensor was optimized to be 250 °C. The fabricated sensor was more sensitive toward trimethylamine (TMA). A response of 56% was obtained in the presence of 10 ppm trimethylamine with the response and recovery times being 30 and 205 s, respectively. The experimental limit of detection of the sensor was 100 ppb. The sensor was exposed to vapors emitted from saltwater or marine fish. Fish samples were categorized according to the storage conditions of room temperature and deep fridge. The sensing measurements were performed with fish samples at a time interval of 24 h. Initially, the response of the sensor to a fresh sample was around 10%. After that, the response of the sensor increased with time. This study suggests a simple method for detecting marine fish freshness using chemiresistive sensing technology in a sensitive and efficacious manner.