Detection of Water Contaminants by Organic Transistors as Gas Sensors in a Bottom-Gate/Bottom-Contact Cross-Linked Structure

• Published in: Sensors (Basel, Switzerland) Vol. 23; no. 18; p. 7981
• Main Authors: Izquierdo, José Enrique Eirez, Cavallari, Marco Roberto, García, Dennis Cabrera, Oliveira, José Diogo da Silva, Nogueira, Vinicius Augusto Machado, Braga, Guilherme de Souza, Ando Junior, Oswaldo Hideo, Quivy, Alain A., Kymissis, Ioannis, Fonseca, Fernando Josepetti
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.09.2023; MDPI
• Subjects: Alcohol; Atomic force microscopy; Capacitors; Cyanobacteria; Drinking water; Electric properties; Electrodes; electronic nose; gas sensors; organic electronics; organic semiconductors; organic thin-film transistors; PBTTT-C14; Polymers; Semiconductors; Sensors; Silicon; Temperature; Thin films; Thiophene; Transistors; Volatile organic compounds; Water quality; Brazil; Japan; Germany; United States > US; China
• ISSN: 1424-8220; 1424-8220
• DOI: 10.3390/s23187981

Detecting volatile organic compounds is a fundamental step in water quality analysis. Methylisoborneol (MIB) provides a lousy odor to water, whereas geosmin (GEO) is responsible for its sour taste. A widely-used technique for their detection is gas-phase chromatography. On the other hand, an electronic nose from organic thin-film transistors is a cheaper and faster alternative. Poly(2,5-bis(3-tetradecyl-thiophen-2-yl)thieno[3,2-b]thiophene) (PBTTT-C14) features semiconducting properties suitable for organic electronics. However, in order to expose the active layer in a bottom-gate transistor structure with photolithographically patterned electrodes, a cross-linked dielectric such as poly(4-vinyl phenol) (PVP) is necessary. In this work, the cross-linking was demonstrated using FTIR and Raman spectroscopies, as well as high-k capacitors with a dielectric constant of 5.3. The presence of enhanced crystallinity with terrace formation in the semiconducting film was confirmed with UV-visible spectrophotometry, atomic force microscopy, and X-ray diffraction. Finally, for the first time, a PBTTT-C14 transistor on cross-linked PVP was shown to respond to isoborneol with a sensitivity of up to 6% change in mobility per ppm. Due to its similarity to MIB, a system comprising these sensors must be investigated in the future as a tool for sanitation companies in real-time water quality monitoring.