Abstract
Abstract Metal oxides are ideal for the fabrication of gas sensors: they are sensitive to many gases while allowing the device to be simple, tiny, and inexpensive. Nonetheless, their lack of selectivity remains a limitation. In order to achieve good selectivity in applications with many possible interfering gases, the sensors are inserted into an electronic nose that combines the signals from nonselective sensors and analyzes them with multivariate statistical algorithms in order to obtain selectivity. This review analyzes the scientific articles published in the last decade regarding electronic noses based on metal oxide nanowires. After a general introduction, Section 2 discusses the issues related to poor intrinsic selectivity. Section 3 briefly reviews the main algorithms that have hitherto been used and the results they can provide. Section 4 classifies the recent literature into fundamental research, agrifood, health, security. In Section 5, the literature is analyzed regarding the metal oxides, the surface decoration nanoparticles, the features that differentiate the sensors in a given array, the application for which the device was developed, the algorithm used, and the type of information obtained. Section 6 concludes by discussing the present state and points out the requirements for their use in real-world applications.
Highlights
Gas sensors are increasingly needed in many areas of human life, from monitoring indoor and outdoor air quality, industrial processes, food quality, and even to carry out noninvasive diagnostic screening
This review focuses on electronic noses based on metal oxide nanowires since metal oxide semiconductors are the most used materials for solid-state gas sensors and nanowires, with their very high surface/volume ratio reaching unthinkable performance for previous generations
The review focuses on the “brains” used so far for electronic noses based on metal oxide nanowires, and on the type of information obtained from them
Summary
Gas sensors are increasingly needed in many areas of human life, from monitoring indoor and outdoor air quality, industrial processes, food quality, and even to carry out noninvasive diagnostic screening. Despite the strong interest in both nanowire-based gas sensors and electronic noses, scientific papers studying nanowire-based electronic noses are still very few This can be explained by the fact that nanowires have better performance than previous generations (thin films) and lower stability and reliability over time, and are less mature for practical applications. The analysis of the published articles shows that the development obtained by nanosciences in controlling the structural, morphological, and compositional properties of nanomaterials is not matched by the computer processing counterpart For this reason, the review focuses on the “brains” used so far for electronic noses based on metal oxide nanowires, and on the type of information obtained from them. We think that such an analysis can support groups working on chemosensors on their way for the realization of successful electronic noses by indicating possible strategies and achievable results
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