Effects of Water and Different Solutes on Carbon‐Nanotube Low‐Voltage Field‐Effect Transistors

• Published in: Small (Weinheim an der Bergstrasse, Germany) Vol. 16; no. 34; pp. e2002875 - n/a
• Main Authors: Foudeh, Amir M., Pfattner, Raphael, Lu, Shiheng, Kubzdela, Nicola S., Gao, Theodore Z., Lei, Ting, Bao, Zhenan
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01.08.2020
• Subjects: Ammonia; Aqueous solutions; Biosensors; Carbon; Electric potential; Field effect transistors; low‐voltage field‐effect transistors; Mercury (metal); Nanotechnology; response mechanisms; Selectivity; Semiconductor devices; Single wall carbon nanotubes; single‐walled carbon nanotubes; Transistors; Vinylidene; Vinylidene fluoride; Voltage; water and electrolyte solutions; Water chemistry; biosensors; low-voltage field-effect transistors; response mechanisms; water and electrolyte solutions; single-walled carbon nanotubes
• ISSN: 1613-6810; 1613-6829; 1613-6829
• DOI: 10.1002/smll.202002875

Semiconducting single‐walled carbon nanotubes (swCNTs) are a promising class of materials for emerging applications. In particular, they are demonstrated to possess excellent biosensing capabilities, and are poised to address existing challenges in sensor reliability, sensitivity, and selectivity. This work focuses on swCNT field‐effect transistors (FETs) employing rubbery double‐layer capacitive dielectric poly(vinylidene fluoride‐co‐hexafluoropropylene). These devices exhibit small device‐to‐device variation as well as high current output at low voltages (<0.5 V), making them compatible with most physiological liquids. Using this platform, the swCNT devices are directly exposed to aqueous solutions containing different solutes to characterize their effects on FET current–voltage (FET I–V) characteristics. Clear deviation from ideal characteristics is observed when swCNTs are directly contacted by water. Such changes are attributed to strong interactions between water molecules and sp2‐hybridized carbon structures. Selective response to Hg2+ is discussed along with reversible pH effect using two distinct device geometries. Additionally, the influence of aqueous ammonium/ammonia in direct contact with the swCNTs is investigated. Understanding the FET I–V characteristics of low‐voltage swCNT FETs may provide insights for future development of stable, reliable, and selective biosensor systems. Low voltage carbon nanotube field‐effect transistors employing a rubbery double‐layer dielectric allow exposing devices to aqueous solutions and study effects on current–voltage characteristics. Selective response to Hg2+ is discussed along with reversible pH effect and compared with ammonium/ammonia in direct contact with the carbon nanotube network. Unraveling the sensing mechanisms is important and may provide insight for the development of stable, reliable and selective biosensor systems.