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Late News: Effects of Water and Different Solutes on Carbon-Nanotube Low-Voltage Field-Effect Transistors
Raphael Pfattner1,2,Amir M. Foudeh1,Shiheng Lu1,3,Nicola S. Kubzdela1,Theodore Gao1,Ting Lei1,4,Zhenan Bao1
Stanford University1,Materials Science Institute of Barcelona (ICMAB-CSIC)2,Duke University3,Peking University4
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.[1,2] Functionalized and pristine individual CNTs have shown high sensitivity and selectivity down to the single molecule level.[3,4] However, single CNT devices are challenging to make and characterize compared to CNT networks which add further complexity due to inter-CNT contacts. Such systems may not be as sensitive or selective compared to single CNT devices, but may be a cost-effective alternative for particular environments.
Here, we report on the characteristics of single-walled carbon nanotube (swCNT) networks exposed directly to aqueous solutions containing different solutes. This was made possible by employing a solid-state dielectric poly(vinylidene fluoride-co-hexafluoropropylene) (ePVDF-HFP), which has been demonstrated to be compatible with swCNTs and also enables low-voltage field-effect transistor (FET) operation.[5,6]
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.
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