Synthesis and characterization of polyaniline/zinc oxide (PANI/ZnO) composite for potential gas sensing application

• Main Author: Foronda, Juanito Raphael F.
• Format: text
• Language: English
• Published: Animo Repository 2022
• Subjects: Gas detectors
• Online Access: https://animorepository.dlsu.edu.ph/etd_masteral/6189; https://animorepository.dlsu.edu.ph/context/etd_masteral/article/13275/viewcontent/FORONDA__JR_Edited.pdf
• Institution: De La Salle University

Emerging concerns about pollutants or harmful gasses lead to the development of gas sensors in the field of environmental monitoring, medical diagnosis, and industrial manufacturing. Individual detection of methanol, ethanol, ammonia, acetone, and formaldehyde were studied. A conducting polymer, polyaniline (PANI), was used as the main sensing element of the sensor due to its unique properties and simple synthesis. The addition of zinc oxide particles were employed to form polyaniline/ zinc oxide (PANI/ZnO) composites to see its effect as a gas sensor. Polyaniline and polyaniline/ zin oxide (PANI/ ZnO) composites were synthesized using chemical oxidative process. Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscope and Energy Dispersive X-ray Analysis (SEM/EDX) were done to verify PANI and PANI/ZnO successful synthesis. A simple sensor fabrication of 10 μL PANI was drop casted onto a Teflon substrate. Two gold wires with a separation distance of 0.5 mm act as electrodes on the Teflon substrate. It was connected to a non-inverting amplifier and Sparkvue for output data logging. The incorporation of zinc oxide increases the resistance of 100% PANI sensors. A simple gas sensing measurements of a static headspace analysis in gas chamber with six 20-minute cycles of analyte exposure and blank were done. All sensors exhibit selectivity on ammonia over all the gasses with an average sensor response of 3496.667 mV; however, the reaction is irreversible and no repeatability was observed. On the other hand, all sensor towards ammonia produces the same results, thus, it is reproducible. Response time varies but after exposure more than ~1400s the sensor reacts with ammonia. As for the methanol, ethanol, acetone, and formaldehyde, selectivity refers to the sensors – 100% PANI, 90:10 PANI/ZnO, 80:20 PANI/ZnO, 70:30 PANI/ZnO, 60:40 PANI/ZnO,and 50:50 PANI/ZnO;, pattern recognition using radar plots. Example of this is 100% PANI sensor was selective only to methanol and ethanol while 90:10 PANI/ZnO sensor was selective to formaldehyde. A predictive model was plotted using radar plot of a 6-array sensor using different ratios of PANI/ZnO sensors.