Title: ion-selective field effect transistor
Long Title: IUPAC Gold Book - ion-selective field effect transistor
DOI: 10.1351/goldbook.09118
Status: current

Definition
Electrochemical sensor based on the principle of the field effect transistor (FET) in which the surface of the gate is modified in a way that makes the response ion-selective.

Notes
1) A field effect transistor is a semi-conductor device in which the electric current between two semiconductor electrodes (termed the source and the drain) is controlled by the third electrode, termed the gate. Changes in the concentration of the species in the solution in contact with the gate surface thus control the current between the source and drain.
2) The output signal of the ISFET is usually a potential difference, the magnitude of which varies with the change in the logarithm of sensed ion activity or concentration in the same way (but not necessarily in sign) as the corresponding ion-selective electrode. The graphical representation of results should be in accordance with previous recommendations for ISEs, that is, the output potential difference should be plotted versus the logarithm of ion activity or concentration so that the slope of the plot is positive for cation responsive devices and negative for anion-responsive ones.
3) Not all chemical-sensitive semiconductor devices are based on the field effect transistor (FET), metal oxide semiconductor field effect transistor (MOSFET), or insulated gate field effect transistor (IGFET). Also, not all chemically-sensitive field effect transistors (ChemFETs) are ion-sensitive (ISFETs), but considerations are restricted here solely to ISFETs. Generally, ChemFETs are sensitive to gases and to enzyme substrates as well as to ions. Structurally, the ISFET is very similar to the IGFET.
4) Symbols and techniques related to the performance of ISFETs with regard to the determination of ions in solution should be in accordance with the recommendations for ISEs.

Related Terms
- Electrochemical sensor: https://goldbook.iupac.org//terms/view/09072
- chemically-sensitive field effect transistors: https://goldbook.iupac.org//terms/view/09105

Source
- PAC, 2020, 92, 641. 'Terminology of Electrochemical Methods of Analysis (IUPAC Recommendations 2019)' on page 663 (https://doi.org/10.1515/pac-2018-0109)

Other Outputs
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- json: https://goldbook.iupac.org/terms/view/09118/json
- xml: https://goldbook.iupac.org/terms/view/09118/xml

Citation: Citation: 'ion-selective field effect transistor' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351/goldbook.09118
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Accessed: 2026-05-12T03:12:27+00:00