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Electrochemical Sensing via Porous Materials
Published in Antonio Doménech-Carbó, Electrochemistry of Porous Materials, 2021
Ionophore-based ion-selective electrodes (IES) have been extensively studied over the last decades for selectively determining the concentration of selected ions in solution. Their practical use, however, has been limited to a relatively narrow range of fields because of the limited concentration interval able to be determined with such devices. In general, Nernstian responses, characterized by a linear variation of the OCP on the pH with a slope of 59/n mV decade–1, are desired. Much metal/metal oxide electrodes display non-Nernstian responses, but applications in food control and medicine have been proposed. Lowering detection limits can be obtained, among other strategies, through solid-contact ISEs, prepared by direct contact of an ionophore-doped polymeric membrane with a metallic conductor. To avoid problems associated with poorly defined metal/membrane interfaces and unstable phase boundary potentials, intermediate layers with conducting polymers or localized redox-active units separating the sensing membrane and the metallic conductor can be used. More recently, ordered macroporous carbon contacts and other carbons have been tested. The used carbons consist of a skeleton of glassy carbon surrounding a periodic array of uniform spherical pores that are interconnected in three dimensions. Pore sizes are of a few hundred nanometers while skeletal walls are tens of nanometers thick. As a result of the mutually interconnected pore-wall structure of such materials, filling pores with an electrolyte solution results in a nanostructured material with both ionic and electronic conductivity [4].
pH Measurement
Published in John G. Webster, Halit Eren, Measurement, Instrumentation, and Sensors Handbook, 2017
Norman F. Sheppard, Anthony Guiseppi-Elie
Another type of electrochemical pH electrode is based on polymeric “liquid membranes,” most commonly used to construct ion-selective electrodes for ions such as potassium [8]. The membranes consist of a plasticized polymer film into which an ionophore has been incorporated. The ionophore is a molecule that selectively binds and transports a given ion across the membrane, making the membrane selectively permeable to the ion of interest. The ionophore N-tridodecylamine binds hydrogen ions and has been used in the construction of a pH sensor incorporated into a disposable cartridge device for measuring blood electrolytes [9].
Polymeric Indicator Substrates for Fiber Optic Chemical Sensors
Published in Richard P. Buck, William E. Hatfield, Mirtha UmañA, Edmond F. Bowden, Biosensor Technology Fundamentals and Applications, 2017
W. Rudolf Seitz, Yunke Zhang, Zhang Zhujun, Amy Sommers, Chen Jian, Richard Russell, Donald C. Sundberg
PVC is most familiar to analytical chemists as a membrane material widely used in ion selective electrodes. Neutral ionophores are incorporated into the membrane so that it selectively transports the ion to be sensed. Membranes are typically prepared by solvent casting using compounds such as dioctyl phthalate (DOP) as plasticizers.
Novel polymeric sensor for ultra-trace determination of cerium (III) based on CoNiFe2O4 nanocomposite
Published in Inorganic and Nano-Metal Chemistry, 2023
Fatemeh Sabeti Ghahfarokhi, Arezoo Ghaemi, Roya Mohammadzadeh Kakhki
To date, some methods have been used to determine cerium ions including potentiometry, voltammetry, atomic absorption spectrometry, and also some coupled techniques such as ICP coupled to atomic emission spectrometry.[2–5] Among these methods, potentiometry is an available, rapid, cheap, fast response, sensitive, and selective method.[2,6–16] The application of ion-selective electrodes in potentiometry is well established due to their selectivity, sensitivity, and high linear range. The selectivity of these electrodes returns to the use of the appropriate ionophore in the fabrication of the membrane. The characteristics of the ligand, such as its diameter of cavity and structural atoms, affect the host–guest complex stability and the electrode selectivity.[17,18]