A gas sensor includes an element body having an oxygen ion conductive solid electrolyte layer and internally provided with a measurement-object gas flow section that introduces a measurement-object gas and allows the gas to flow; a measurement-object gas-side electrode disposed in a portion of the element body, the portion being exposed to the measurement-object gas; and a reference electrode disposed inside of the element body. Let A [μA] be a limiting current when oxygen is pumped from the surroundings of the measurement-object gas-side electrode to the surroundings of the reference electrode with the measurement-object gas introduction section, and B [μA] be a limiting current when oxygen is pumped from the surroundings of the reference electrode to the surroundings of the measurement-object gas-side electrode with the reference gas introduction section, then a ratio A/B is greater than or equal to 0.005.

A breath sensor includes a base body, a first electrode provided on a part of a surface of the base body, a second electrode provided on a part of the surface of the base body, and a covering layer made of a material that does not pass moisture therethrough, the covering layer covering the second electrode with the base body. The base body is preferably made of a material whose surface potential changes due to attachment of moisture to one of a surface of the first electrode and the surface of the base body. A surface potential on a side of the first electrode of the base body changes when a breath containing moisture touches the surface of the first electrode.

A NO.sub.2 gas sensing element includes an electrolyte, a reference electrode in contact with the electrolyte, and a sensing electrode selective to NO.sub.2 in contact with the electrolyte spaced apart from the reference electrode. The NO.sub.2 selective sensing electrode includes an oxide material comprising: (1) a mixed oxide according to the formula (Mn.sub.2-u-v-wCo.sub.vMg.sub.wSiO.sub.4-u)+ξ(Mn.sub.3Al.sub.2Si.sub.3O.sub.12)+δ(SiO.sub.2), wherein 0≦(u+v+w)≦2.0, 0≦ξ≦0.5, and 0≦δ≦0.1; (2) a mixed oxide according to the formula (Mn.sub.2-x-y-zCo.sub.yMg.sub.zSiO.sub.4-x)+ξ(ZnO)+δ(SiO.sub.2), wherein 0≦(u+v+w)≦2.0, 0≦ξ≦0.5, and 0≦δ≦0.1; or combinations of mixed oxides (1) and (2).

A solid electrolyte CO.sub.2 sensor may include a solid electrolyte bonded to a substrate to join and seal the substrate, a sensing electrode formed at a first side of the solid electrolyte, and a reference electrode formed between a second side of the solid electrolyte and one surface of the substrate, and sealed by the solid electrolyte and the substrate.

A gas sensor includes a sensor element and a control unit for controlling the sensor element. The sensor element includes a main pump cell, an auxiliary pump cell, a measurement pump cell, and a reference electrode, wherein, in the main pump cell, a repeatedly on-off controlled main pump current is applied so that an auxiliary pump current flowing through the auxiliary pump cell is at a predetermined target current value, and, in the auxiliary pump cell, the auxiliary pump current is applied so that an electromotive force between an inner auxiliary pump electrode and the reference electrode is at a predetermined target voltage value. The control unit includes: a control power supply for applying the repeatedly on-off controlled main pump current; and a setting part for setting the target voltage value based on an electric potential difference generated between the inner main pump electrode and the reference electrode.

A gas sensor includes a sensor element and a controller. The sensor element includes an element body provided with a measurement-object gas flow section therein, a measurement electrode disposed in the measurement-object gas flow section, an outer pump electrode provided in the element body so that the outer pump electrode comes into contact with a measurement-object gas, a reference electrode, a reference-gas introduction section that causes a reference gas to flow to the reference electrode, and a reference-gas adjustment pump cell constituted by including the outer pump electrode and the reference electrode. The controller performs a moisture-absorption-state diagnosis process of diagnosing a moisture absorption state around the reference electrode based on a pump current flowing through the reference-gas adjustment pump cell when the reference-gas adjustment pump cell is controlled to pump out oxygen from a periphery of the reference electrode to a periphery of the outer pump electrode.

A gas sensor that detects a specific gas concentration in a measurement-object gas, the gas sensor includes: a sensor element having an element body provided with a measurement-object gas flow section therein, the measurement-object gas flow section introducing the measurement-object gas, a measurement electrode disposed in the measurement-object gas flow section, a measurement-object-gas side electrode provided on the element body, a reference electrode, a reference-gas introduction section that causes a reference gas to flow to the reference electrode, and a reference-gas adjustment pump cell constituted by including the measurement-object-gas side electrode and the reference electrode; and a controller that performs a moisture-concentration decrease process of controlling the reference-gas adjustment pump cell so that oxygen is pumped out from a periphery of the reference electrode to a periphery of the measurement-object-gas side electrode to decrease a moisture concentration around the reference electrode.

The present invention relates to a device, comprising at least one layer of an active material having a first optical thickness, the active material being selected so as to experience a change (i) of at least one size dimension, (ii) of the resistance, (iii) of the refractive index or (iv) combinations of two or more of the foregoing, when the active material is subjected to a change in environment, wherein at least one and preferably all of the layers of the at least one layer of the active material is composed of at least two nanosheets of the active material, with the at least two nanosheets randomly overlapping one another. The invention further relates to a nanosheet of active material and to a use of the nanosheet of the material.

A sensor element for detecting a parameter of a gas mixture in a gas chamber, having a first electrode and a first diffusion barrier layer arranged to be coupled to said first electrode in a predetermined first region, and arranged such that the gas mixture of the gas chamber only impinges on the first electrode in the first region via the first diffusion barrier layer. In addition, the sensor element has a second electrode arranged such that the gas mixture of the gas chamber impinges on the second electrode in a further first region. The sensor element includes a solid electrolyte designed to be coupled to the first and the second electrodes.

Disclosed herein is a sensor for measuring perfluoroalkyl acids and/or polyfluoroalkyl acids. The sensor includes a working electrode, a counter electrode and optionally a reference electrode. The working electrode includes a film disposed on the surface of the working electrode and the film includes a perfluorinated anion exchange ionomer. A method of using the sensor to detect perfluoroalkyl acids and/or polyfluoroalkyl acids is also described.