Multiselective visual gas sensor using nickel oxide nanowires as chemiresistor

Nowadays the detection of unwanted volatile compounds in air is increasingly important in a wide range of fields. Metal oxide nanosensors are extremely small and cheap devices that could be integrated in any application, but their single resistance response make them non-selective. For this reason, sensor arrays are used where pollutant recognition is needed. Unfortunately, these electronic noses, consisting of different active materials, are complex and expensive. Here, we present a simple visual nanosensor that can detect and recognize selectively several volatile compounds at a relatively low temperature (200-300 °C). The dynamic resistance of a conductometric NiO nanosensor is simply transformed in a visual output that allows to recognize different gases and their concentration with a quick look. This way, one single nanostructured metal oxide can act as a sensitive and selective electronic nose, using the powerful post-processing given by the human eyes and brain. The sensor has proven to discriminate 8 different gases diluted in air (1 oxidizing and 7 reducing) and their respective concentration.