Selective ion-sensing with membrane-functionalized electrolyte-gated carbon nanotube field-effect transistors

Abstract

In this work the ion-selective response of an electrolyte-gated carbon-nanotube field-effect transistor (CNT-FET) towards K(+), Ca(2+) and Cl(-) in the biologically relevant concentration range from 10(-1) M to 10(-6) M is demonstrated. The ion-selective response is achieved by modifying the gate-electrode of an electrolyte-gated CNT-FET with ion-selective membranes, which are selective towards the respective target analyte ions. The selectivity, assured by the ion-selective poly(vinyl chloride) based membrane, allows the successful application of the herein proposed K(+)-selective CNT-FET to detect changes in the K(+) activity in the μM range even in solutions containing different ionic backgrounds. The sensing mechanism relies on a superposition of both an ion-sensitive response of the CNT-network as well as a change of the effective gate potential present at the semiconducting channel due to a selective and ion activity-dependent response of the membrane towards different types of ions. Moreover, the combination of a CNT-FET as a transducing element gated with an ion-selective coated-wire electrode offers the possibility to miniaturize the already well-established conventional ion-selective electrode setup. This approach represents a valuable strategy for the realization of portable, multi-purpose and low-cost biosensing devices.

A membrane-free cation selective water-gated transistor

“…On the example of calcium, we here demonstrate a simplified OTFT architecture for selective detection of waterborne cations that requires no PVC membrane, and no electrochemical reference electrode as in previous reports 23,24 . We deliberately add a small amount (1% wt./wt.…”

“…Firstly, our sensor, as well as devices incorporating PVC membranes (e.g. 15,23,24 ), display near-Nernstian response only down to a limiting concentration, which sets a limit of detection (LoD) which is approximated as c st by the Nikolsky-Eisenman equation. As Nikolsky theory relates c st to the sensitiser rather than the transducer, we propose to dope rrP3HT with ionophores that are known to lead to very low LoD in potentiometric transducers, e.g.…”

“…Established sensors split these processes over two separate functional components: Typically, a sensitised PVC membrane for cation/ionophore complexation, and an electrochemical transducer [e.g. 15 ], or a TFT 23,24 , to detect potential shift. We here unite both functions in a single layer that is deposited in a single step.…”

Acidic Ionic Liquids as Sustainable Approach of Cellulose and Lignocellulosic Biomass Conversion without Additional Catalysts

“…Both single‐ and multi‐walled carbon nanotubes reached significant scientific attention as highly promising material for various applications, including electronics, optoelectronics, catalysis. Also different types of electrochemical sensors 1–5, benefit from applications of CNTs, including among others field effect transistors 1–4, 6, 7, 8, amperometric type devices/sensors [e.g. 9, 10] or solid contact ion‐selective electrodes 11–22.…”

Sub-nanomolar detection of cesium with water-gated transistor

“…An important sub-genre of WGTFTs are the ion-selective WGTFTs, first introduced by List-Kratochvil [5]. So far, the sensitiser in such devices always was an organic 'ionophore', for example a crown ether [6], calixarene [7,8], or valinomycin [9]. Typical 'target' ions are K + , Na + , Li + , Ca 2+ , Mg 2+ [10].…”