"Chemically modified field effect transistors with nitrite or fluoride selectivity". "Durability of phosphate-selective CHEMFETs". ^ Wróblewski, Wojciech Wojciechowski, Kamil Dybko, Artur Brzózka, Zbigniew Egberink, Richard J.M Snellink-Ruël, Bianca H.M Reinhoudt, David N (2001)."Potentiometric Anion Selective Sensors".
"Thirty Years of CHEMFETs – A Personal View". ^ a b c Janata, Jiri (1 November 2004).Journal of the Chemical Society, Perkin Transactions 2 (9): 1937. "Polysiloxane based CHEMFETs for the detection of heavy metal ions". "Application of supramolecular chemistry in the development of ion-selective CHEMFETs". Whereas an ISFET only detects ions, a ChemFET detects any chemical (including ions). There is some confusion as to the relationship between ChemFETs and ISFETs. ĬhemFETs are based on a modified ISFET, a concept developed by Bergveld in the 1970s. In the ISFET structure, the metal gate of a standard MOSFET is replaced by an ion-sensitive membrane, electrolyte solution and reference electrode. He described the ISFET as "a special type of MOSFET with a gate at a certain distance". In 1970, Bergveld invented the ion-sensitive field-effect transistor (ISFET). However, the unavoidable requirement for a separate reference electrode makes the system more bulky overall and potentially more fragile.ĭutch engineer Piet Bergveld studied the MOSFET and realized it could be adapted into a sensor for chemical and biological applications. The body of a ChemFET is generally found to be robust. Anion-sensing is more complicated than cation-sensing in ChemFETs due to many factors, including the size, shape, geometry, polarity, and pH of the species of interest. More work has been done with cation-sensing ChemFETs than anion-sensing ChemFETs. There is a wide range of applications of ChemFETs, including most notably anion or cation selective sensing. Applications ĬhemFETs can be utilized in either liquid or gas phase to detect target analyte, requiring reversible binding of analyte with a receptor located in the gate electrode membrane. For example, when targeting anions, quaternary ammonium salts (such as tetraoctylammonium bromide) are used to provide cationic nature to the membrane, facilitating anion mobility through the substrate to the receptor moieties. Often, ionophores are used to facilitate analyte ion mobility through the substrate to the receptor. A ChemFET's threshold voltage depends on the concentration gradient between the analyte in solution and the analyte in contact with its receptor-embedded semi-permeable barrier. The gate electrode's interface with the solution is a semi-permeable membrane containing the receptors, and a gap to allow the substance under test to come in contact with the sensitive receptor moieties. The gate potential controls the current between the source and drain electrodes.Ī ChemFET's source and drain are constructed as for an ISFET, with the gate electrode separated from the source electrode by a solution. The electron flow takes place in a channel between the drain and source. Source, drain, and gate are the three electrodes used in a FET system.
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