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RH Sensing by Means of TiO2 Nanoparticles: A Comparison among Different Sensing Techniques Based on Modeling and Chemical/Physical Interpretation

Department of Information Engineering and Mathematical Sciences, University of Siena, 53100 Siena, Italy
Author to whom correspondence should be addressed.
Chemosensors 2020, 8(4), 89;
Received: 30 August 2020 / Revised: 18 September 2020 / Accepted: 22 September 2020 / Published: 25 September 2020
(This article belongs to the Section Analytical Method and Apparatus)
TiO2 nanoparticles coating has been proven to be an extremely performing sensing material for relative humidity (RH) measurements. The chemical activity of TiO2 toward water vapor adsorption and the very large surface to volume ratio typical of nanostructures are ideal characteristics for the development of RH fast and sensitive sensors. Different sensor technologies can be used in conjunction with this material to realize devices with satisfactory performance. In this paper, the authors aim to describe and discuss the main different possible choices and highlight the advantages and disadvantages, and linking them both to the underlying mechanism of water adsorption on the TiO2 sensing layer and to the modification of the electrical behavior due to the water adsorption. In particular, the authors start from results obtained by depositing TiO2 nanoparticles on a novel MEMS microbalance operating at low frequency, which allows to sense only the adsorbed water mass, and they exploit the sensor output to obtain a dynamic model of the water adsorption. They also link these results to those obtained with a Quartz Crystal Microbalance (QCM) functionalized with the same material operating at 10 MHz as a part of an oscillator. Finally, they establish a link with the results obtained by an RH impedance sensor, which exploits the same active material and the same deposition technique. With this sensor technology, the conductive and electrical behavior of the sensing and adsorbed films play a role. The whole work tries to unravel the different phenomena that contribute to the response of RH sensors not only based on TiO2 nanoparticles but also, more generally, based on nanostructured metal oxide materials. View Full-Text
Keywords: TiO2 humidity sensor; TiO2 nanoparticles; water adsorption TiO2 humidity sensor; TiO2 nanoparticles; water adsorption
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Cappelli, I.; Fort, A.; Lo Grasso, A.; Panzardi, E.; Mugnaini, M.; Vignoli, V. RH Sensing by Means of TiO2 Nanoparticles: A Comparison among Different Sensing Techniques Based on Modeling and Chemical/Physical Interpretation. Chemosensors 2020, 8, 89.

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