Abstract: An ion sensor includes an electrically conductive substrate, a redox layer coating the surface of the electrically conductive substrate, a barrier layer coating the surface of the redox layer, and an ion-selective layer coating the surface of the barrier layer. The barrier layer functions to prevent migration between the ion-selective layer and redox layer of substances constituting these layers, and to transmit a potential difference produced in the ion-selective layer by contact with an ion from the ion-selective layer to the redox layer.

Abstract: A gas sensor includes a multi-layered solid-state pH electrode and a reference electrode coated with a gas-sensitive layer (solid-state or gel-state) sensitive to an ion of interest, the surface of the combination being coated with a gas-permable layer. Also provided in a gas sensor having a pH electrode and a reference electrode immersed in a gas-sensitive solution within a gas-permeable layer. Preferably, a fixed distance is maintained between a sensitive portion of the pH electrode, a sensitive portion of the reference electrode and the gas-permeable layer isolated by means of a porous layer. In another emodiment, the gas sensor incorporates a common electrode and a thermister for temperature calibration.

Abstract: An ion-sensitive FET sensor has a MOSFET gate isolating membrane whose surface is covered by an ion-sensitive layer. A redox layer having a redox function is provided between the isolating membrane and the ion-sensitive layer to improve operating stability and speed of response. An electrically conductive layer or a combination of a thin metal film and an electrically conductive layer is provided between the isolating membrane and the redox layer to further improve operating stability, the adhesion of the layers and the durability of the sensor. Also disclosed are optimum materials for use as an ion carrier employed in the ion-sensitive layer.

Abstract: Disclosed is a solid-type ion sensor which does not have an internal liquid chamber. The ion sensor has a laminated structure basically includes an electrically conductive substrate, a redox layer having a redox function covering the surface of the electrically conductive substrate, and an ion-selective layer covering the surface of the redox layer. Also provided is an ion sensor of this type having an insulated thermister imbedded so as to contact the redox layer.

Abstract: Disclosed is an ion sensor having an ion-sensitive substrate provided within a tube at a position recessed from an open end of the tube and having an ion carrier membrane, which is selectively permeable to an ion of interest, filling the space between the opening of the tube and the surface of the ion-sensitive substrate on the open-end side of the tube. A method of manufacturing the ion sensor includes steps of inserting and retaining the ion-sensitive substrate in the tube, filling the space between the ion-sensitive substrate and the tube with a sol-like ion carrier membrane composition, and gelling the sol-like ion carrier membrane composition.

Abstract: A pH measurement device includes working and reference electrodes. The working electrode has a linear electrically conductive substrate, at least a distal end surface of which consists of platinum, and a selective hydrogen ion permeable layer formed on the distal end face of the substrate. The reference electrode includes an electric conductor formed to be insulated from the working electrode and surrounding the working electrode, a polymer-silver (I) complex layer formed on the outer circumferential surface of the conductor, and an ion-conductive layer containing an anionic compound and formed on the complex layer. The pH of a solution is measured in accordance with a difference between a potential of the working electrode and that of the reference electrode.

Abstract: A reference electrode is prepared by coating the surface of a conductive substrate with a silver complex polymer compound, which is either a compound prepared by the complex formation between a polymer compound containing a coordination nitrogen atom and a silver ion or an aforementioned complex compound containing a silver halide. This reference electrode can be used by a combination with ion sensor, a pH sensor and so on.