Chemistry: electrical and wave energy – Apparatus – Electrolytic
Patent
1990-10-24
1993-03-02
Niebling, John
Chemistry: electrical and wave energy
Apparatus
Electrolytic
204419, G01N 2726
Patent
active
051906368
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an ion sensor, and particularly to a solid film type ion sensor comprising a conductive substrate which is provided with a layer containing a redox responsive substance and a polymeric substance containing and carrying an ion carrier substance.
BACKGROUND ART
It has been proposed to measure an ion concentration by measuring potential response or current response of a carbon material or the like used as a conductive material on which a redox functional layer is coated. However, in this case, the potential or current response of the electrode is generated on the boundary between the different substances. The adhesion between the different substances is therefore a problem. In addition, since an ion concentration is measured in an aqueous solution, differences between the degrees of swelling of the materials used cause the separation of the materials or the occurrence of pin-holes. It is thus difficult to form an ion sensor having stability for a long time.
DISCLOSURE OF THE INVENTION
It is an object of the present invention to solve the problems of prior art and provide an ion sensor having excellent durability, preservative stability and sensor characteristics.
In a conventional method of physically coating a redox manifesting substance and then an ion selective layer (in which an ion selective substance and polyvinyl chloride coexist together) on a conductive material, sensor characteristics with reproducibility cannot be expected because both layers are separated on the boundary therebetween. In the present invention, therefore, in order to solve the problem, an attempt is made to dissolve both substances in a common solvent, e.g., tetrahydrofuran (THF), so that both substances is apparently brought into a compatible system owing to electrolytic reaction.
The ion sensitive film of the present invention comprises a mixed layer containing a redox manifesting substance manifesting the redox function and a polymeric compound containing an ion carrier substance.
The ion sensitive film of the present invention is produced by electrolytic polymerization reaction using a three-pole cell in an electrolyte containing a redox-manifesting substance manifesting the redox function a polymeric compound containing an ion carrier substance to form a mixed layer containing both substances.
An ion sensor of the present invention comprises a conductive substance coated with an ion sensitive layer, wherein the ion sensitive layer comprises a mixed layer containing a redox manifesting substance manifesting the redox function and a polymeric compound containing an ion carrier substance.
The present invention can provide an ion sensor having excellent durability, preservative stability and sensor characteristics.
Specifically, a layer is formed on a conductive substrate by cross matrix polymerization of a redox responsive substance and a polyvinyl chloride layer containing an ion carrier substance by using an electrolytic polymerization process. This layer, the same layer coated on a conductive substance/redox functional layer or the same layer with an ion carrier layer coated thereon exhibits sensor characteristics (the gradient of the Nernst's equation, the response speed and so on) which are the same as those of the layer formed by the conventional method. The layer resistance can be reduced to about half of that of the layer formed by physically bonding layers in the conventional method.
It was also found that, since peeling hardly occurs in the composite layer of the present invention, the sensor exhibits stable electrode potential and good durability.
Further, other objects and effects will be clarified by reading the detailed description below of examples with reference to the the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic drawing of the structure of an ion sensor in accordance with an example of the present invention;
FIG. 2A is a drawing showing a cyclic voltamograph of simultaneous electrolytic polymerization of 4,4'-biphenol (THF system)
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Shimomura Takeshi
Uchida Naoto
Ushizawa Norihiko
Yamaguchi Shuichiro
Bell Bruce F.
Niebling John
Terumo Kabushiki Kaisha
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