It was observed that each of the sensors differentiated the ethanol concentrations, presenting different electrical resistance values which are directly proportional to the ethanol concentration. Considering the five sensors, the overall mean value of electrical resistance for each alcoholic concentration is The value of the calculated F test ratio between the variance between sample groups and the variance within the sample groups is significant because it has a value greater than the table.
Therefore, it is concluded that the variability between the groups is large, that is, there are large differences between the sample means of the groups that are not due solely to sample fluctuations.
Then, the sensors are not suitable for reliable measurements of electrical resistance. As the electrically conductive PAni films were not homogeneous in morphology since they were obtained by chemical synthesis, the smallest gap possible between the interdigitated electrodes of the substrate was used to ensure a larger contact area of the polyaniline film with the electrodes.
The spacing of the interdigitated electrodes covered by electrically conductive PAni films act as variables resistors connected in series. The thickness of the conductive PAni film, obtained by in situ polymerization, is compatible with the thickness of PAni films reported in the literature. FTIR analysis showed a band near cm -1 which is characteristic of the conductive polymer due to relocation caused by protonation.
The data showed that the PAni films can be used in chemical sensors for measuring ethanol concentration. The presence of this band, both for HCl doped PAni and for HCl doped PAni mixed with anhydrous ethanol for 40 minutes, proves the fact reported in the literature that ethanol does not change the chemical structure of PAni.
The conductivity of the sensors was consistent with the work of other authors. When exposed to ethanol, a decrease in resistance of the sensors was found. The five tested sensors presented a response in terms of electric resistance which is directly proportional to the ethanol concentration. But the statistical evaluation of data one-way ANOVA identified a lack of selectivity of the sensor for different concentrations of ethanol in all measurements, i. The sensor data show a similar function, indicating that there is potential for the application as ethanol sensors.
Many issues remain open and thus studies about the effect of different concentrations and types of oxidants and dopants of PAni on the sensor characteristics must be performed as well as the electrochemical deposition of PAni film and the analysis of the thickness influence of the PAni film on the selectivity of the sensor exposed to different gases. Authors are grateful to the Lutheran University of Brazil for financial support.
We thank Profa. Abrir menu Brasil. Abrir menu. Keywords gas sensor; ethanol; polyaniline; electrical conductivity. Figure 1 Layout of the designed PCB used as substrate of the gas sensors. Figure 2 Sensors placed inside of the sealed lid of the desiccator.
Figure 3 Glass fiber reinforced epoxy resin substrate with interdigitated electrodes of copper covered with nickel and gold ENIG. Figure 5 situ deposition of PAni on sensor surface. Figure 7 SEM photomicrographs of PAni films: a thickness of PAni film on the sensor and b surface morphology for a an b deposition time 30 minutes in acid medium.
Figure 9 Electrical response of a PAni film sensor exposed to ethanol. Sci , v. PYO, M. Met , v. BAI, H. KIM, J. WU, H. AYAD, M. WANG, P. Publication Dates Publication in this collection History Received 02 Oct Accepted 09 Apr This is an Open Access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Jump to main content. Jump to site search.
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