Electrolyte/insulator/semiconductor

The concept of light addressable potentiometric sensors (LAPS) was introduced in 1988 [67], LAPS is a semiconductor-based sensor with either electrolyte-insulator-semiconductor (EIS) or metal-insulator-semiconductor (MIS) structure, respectively. Figure 4.13 illustrates a schematic representation of a typical LAPS with EIS structure. A semiconductor substrate (silicone) is covered with an insulator (Si02). A sensing ion-selective layer, for instance, pH-sensitive S3N4, is deposited on top of the insulator. The whole assembly is placed in contact with the sample solution. 

Another example of an Si-based pH sensing device is an electrolyte-insulator-semiconductor (EIS) structure. In a typical EIS sensor, a voltage applied to the semiconductor back gate (Vgate) attracts ions in the electrolyte to the oxide surface. The... 

One possible solution is to obtain new experimental data, which is independent of co/pH curves. The zeta potential is of course a possibility, but it suffers from the intrinsic indeterminacy of the exact location in the double layer where it occurs. Another possibility is the surface potential, Vo, which will be defined below. Variations of Vo can be measured by using electrolyte/insulator/semiconductor structures. It has been shown by Bousse et al. (14) that the Vo/pH characteristics are determined mainly by the number of charged but uncomplexed surface sites, and are insensitive to complex-ation. This means that combined consideration of tro/pH and Vo/pH characteristics should lead to a more complete and reliable determination of model parameters. 

The ideal situation would be a combined and simultaneous experiment in which an electrolyte/insulator/semiconductor device is used to monitor if>o while a colloid dispersion of the same oxide is titrated to measure parameter determination that could result from such an experiment would be the set as, Kno+ an[Pg.96]

SAW, surface acoustic wave (impedance) FET, field-effect transistor EIS, electrolyte-insulator-semiconductor GOx, glucose oxidase LDH, lactate dehydrogenase LOx, lactate oxidase. 

Design and fabrication of ISFET was described in Ref. [88] The interest in ISFET arises chiefly from their application as pH and ion sensors. A graphical procedure to find PZC from capacitance-voltage characteristics of electrolyte-insulator-semiconductor and metal-insulator-semiconductor structures was discussed [89]. Due to the choice of electrolyte (2 mol dm Na2S04) the PZC values reported in this study (2.5 for Si02, 2.8 for Ta20s and 3-3.4 for Si3N4) are not likely to be the pristine values due to specific adsorption of anions. 

A one-dimensional model for electrol3Ae-insulator-metal-oxide-semiconductor and electrolyte-insulator-semiconductor structures modified with a chained membrane has been presented [34], It was shown that the largest sensitivity occurs at low electroljfte concentrations, and that the signal from hybridization is expected to be smaller than that from probe immobilization. 

Another impedance-based imaging technique for laterally resolved characterization of thin films or electrochemical systems is Scanning Photo-induced Impedance Microscopy (SPIM) [44]. It is based on photocurrent measurements at field-effect structures. In their simplest arrangement, field-effect structures consist of a semiconductor substrate with a thin insulator, and a gate electrode. This gate electrode can be a metal film resulting in the structure Metal Insulator Semiconductor (MIS) or, alternatively. Electrolyte Insulator Semiconductor structures are used, in which the electrolyte is in direct contact with the insulator, and a reference electrode is required to fulfill the function of the gate electrode. 

Abouzar, M. H., Siqueira, Jr., J. R., Poghossian, A., Oliveira, Jr., O. N., Moritz, W., Schoning, M.J. Capacitive electrolyte-insulator-semiconductor structures functionalised with a polyelectrolyte-enzyme multilayer new strategy for enhanced field-effect biosensing. Phys. Stat. Sol. A 207, 884-890 (2010)... 

Branquinho, R., Veigas, B., Pinto, J.V., Martins, R., Fortunato, E., and Baptista, P.V. (2011) Real-time monitoring of PCR amplification of proto-oncogene c-MYC using a Ta205 electrolyte-insulator-semiconductor sensor. Biosens. Bioelectron., 28, 44-49. 

Recently, LAPS has been developed for detection of analytes. LAPS is a semiconductor-based potential-sensitive device that usually consists of the metal—insulator-semiconductor or electrolyte—insulator—semiconductor stmcture. LAPS measures an... 

Electrolyte-insulator-semiconductors are the basis for silicon field-effect chemical sensors and include ISFETs/ChemFETs, light-addressable potentiometric sensors (LAPSs) and capacitive sensors. The first ISFET was invented in 1970. ... 

Vlasov YG, Tarantov YA, Bobrov PV (2003) Analytical characteristics and sensitivity mechanisms of electrolyte-insulator-semiconductor system-based chemical sensors - a critical review. Anal Bioanal Chem 376 788-796... 

Shinwari MW, Deen MJ, Landheer D (2007) Study of the electrolyte-insulator-semiconductor field-effect transistor (EISFET) with applications in biosensor design. Microelectron Reliab 47 2025-2057... 

Also the polysiloxane gel functionalized by sensitive macromolecules a-CD and p CD have been synthesized and used as a receptor for Ion-Sensitive Field Transistors (ISFET) and Electrolyte Insulator Semiconductor (EIS) ions sensors [25]. The samples were characterized by electrochemical measurements in several ionic concentrations in aqueous solution. The role of interfering ions and sensor stability was investigated. The sensor performance sensitivity increases by incorporating of CD receptor in the gel structure. The responses of a-CD-PS/EIS and a-CD-PS/ISFET to Cd ion are similar. These results indicate that sensitivity... 

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