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. 2016 Nov 9;16(11):1881.
doi: 10.3390/s16111881.

The Impact of Sepiolite on Sensor Parameters during the Detection of Low Concentrations of Alcohols

Patrycja Suchorska-Woźniak  1 , Olga Rac  2 , Marta Fiedot  3 , Helena Teterycz  4
Affiliations

The Impact of Sepiolite on Sensor Parameters during the Detection of Low Concentrations of Alcohols

Patrycja Suchorska-Woźniak et al. Sensors (Basel). .

Abstract

The article presents the results of the detection of low-concentration C1-C4 alcohols using a planar sensor, in which a sepiolite filter was applied next to the gas-sensitive layer based on tin dioxide. The sepiolite layer is composed of tubes that have a length of several microns, and the diameter of the single tube ranges from several to tens of nanometers. The sepiolite layer itself demonstrated no chemical activity in the presence of volatile organic compounds (VOC), and the passive filter made of this material did not modify the chemical composition of the gaseous atmosphere diffusing to the gas-sensitive layer. The test results revealed that the structural remodelling of the sepiolite that occurs under the influence of temperature, as well as the effect of the filter (a compound with ionic bonds) with molecules of water, has a significant impact on the improvement of the sensitivity of the sensor in relation to volatile organic compounds when compared to the sensor without a filter.

Keywords: alcohols; gas detection; nanomaterial; resistive gas sensors; sepiolite filter.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
The cross-section of the structure of the thick-layered gas sensor based on tin dioxide (IV) with a sepiolite filter.
Figure 2
Figure 2
Schematic diagram of the construction of the measuring station used during the characterization of the sensors by the temperature-stimulated conductivity and voltammetric techniques.
Figure 3
Figure 3
The microstructure of: (a) the sepiolite; (b) the SnO2 layer.
Figure 4
Figure 4
Changes in the structure of the sepiolite under the influence of temperature [16].
Figure 5
Figure 5
The effect of the composition of the atmosphere on the temperature changes of the conductance in the sepiolite layer. According to the catalogue data, the lower range of the Solartron SI 1287 m used was 0.4 nA.
Figure 6
Figure 6
Thermal changes in the conductance of the sensors with the SnO2 layer or only the sepiolite layer in synthetic air.
Figure 7
Figure 7
The cross-section of the structure of a thick-layered gas sensor based on tin dioxide (IV) with a sepiolite filter with indicated phase borders.
Figure 8
Figure 8
Current-voltage characteristics of the resistive gas sensor; (a) SnO2 in air (30% RH); (b) SnO2 in 2 ppm ethanol+air (30% RH); (c) SnO2/sepiolite in air (30% RH); (d) SnO2/sepiolite in 2 ppm ethanol + air (30% RH). ΔU = 150 mV/s.
Figure 9
Figure 9
An equivalent electric circuit of the structure of the resistive gas sensor with a passive sepiolite filter.
Figure 10
Figure 10
Temperature changes in the conductance of the SnO2 sensor with and without the sepiolite filter in 2 ppm of ethanol or butanol.
Figure 11
Figure 11
Temperature changes of the SnO2 sensor sensitivity: (a) without a filter; (b) with a filter in the atmosphere with a different composition (air with 30% RH + alcohol).
Figure 12
Figure 12
A comparison of the sensitivity of the two sensors on 2 ppm alcohol (air 30% RH).
Figure 13
Figure 13
Diffusion of reactants and products to/from the SnO2 sensor with the sepiolite filter.
Figure 14
Figure 14
(a) Changes in the conductance of SnO2 sensor with and without a sepiolite filter as a function of temperature depending on the humidity; (b) the relationship of the conductance of the SnO2 sensor with the sepiolite filter to the conductance of the sensor without a filter in air, with a relative humidity of 11% and 75%.
Figure 15
Figure 15
Diagram of the chemical structure of the sepiolite with the adsorbed forms of water (a) prepared on the basis of [28]; and (b) the channels formed by the combination of unit cells.
Figure 16
Figure 16
Changes in the conductance of the sensor without a filter and the sensor with a filter as a function of humidity at a temperature of 550 °C.
See this image and copyright information in PMC

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