Abstract
The development of even more compact, inexpensive, and highly sensitive gas sensors is widespread, even though their performances are still limited and technological improvements are in continuous evolution. Zeolite is a class of material which has received particular attention in different applications due to its interesting adsorption/desorption capabilities. The behavior of a zeolite 4A modified capacitor has been investigated for the adsorption of nitrogen (N2), nitric oxide (NO) and 1,1-Difluoroethane (C2H4F2), which are of interest in the field of chemical, biological, radiological, and nuclear threats. Sample measurements were carried out in different environmental conditions, and the variation of the sensor electric capacitance was investigated. The dielectric properties were influenced by the type and concentration of gas species in the environment. Higher changes in capacitance were shown during the adsorption of dry air (+4.2%) and fluorinated gas (+7.3%), while lower dielectric variations were found upon exposure to N2 (−0.4%) and NO (−0.5%). The proposed approach pointed-out that a simple fabrication process may provide a convenient and affordable fabrication of reusable capacitive gas sensor.
Highlights
The adsorption/desorption of a gas molecule onto a surface, and its detection, have deserved extensive research in the last decades since the increasing interest in the monitoring of hazardous species (chemical, biological, radiological, nuclear (CBRN) threats; environmental; and health-related) [1,2,3,4,5].Even more sophisticated laboratory equipment, such as gas chromatography and mass spectrometry, are widespread at laboratory level, achieving the desired detection performances with a very limited portability [6]
The adsorption capability of zeolites depends on several factors, including and and electrostatic attraction forces often come come into play
The behavior of a zeolite-based capacitive sensor was investigated for the adsorption of dry air, N2, nitric oxide (NO), and C2 H4 F2
Summary
The adsorption/desorption of a gas molecule onto a surface, and its detection, have deserved extensive research in the last decades since the increasing interest in the monitoring of hazardous species (chemical, biological, radiological, nuclear (CBRN) threats; environmental; and health-related) [1,2,3,4,5].Even more sophisticated laboratory equipment, such as gas chromatography and mass spectrometry, are widespread at laboratory level, achieving the desired detection performances with a very limited portability [6]. Continuous efforts are devoted to the development of compact and low-impact sensors for volatile chemical species with improved sensitivity, specificity, accuracy, response, and recovery times [7]. To this end, a plethora of transduction phenomena (chemiresistive, capacitive, mass-sensitive, calorimetric, and optical) were investigated to propose various technological solutions for the analysis of complex matrices [8,9,10,11,12,13]. From the analytical point of view, different models were developed to propose a relationship among the number of adsorbed/desorbed molecules, their interactions, and the sensor response, such as the Langmuir and Wolkenstein’s models [14,15,16]. The development of an ideal gas sensor is extremely difficult, and the lack of selectivity remains the major limitation
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