GB2180348A - Semiconducting oxide sensor - Google Patents
Semiconducting oxide sensor Download PDFInfo
- Publication number
- GB2180348A GB2180348A GB8620798A GB8620798A GB2180348A GB 2180348 A GB2180348 A GB 2180348A GB 8620798 A GB8620798 A GB 8620798A GB 8620798 A GB8620798 A GB 8620798A GB 2180348 A GB2180348 A GB 2180348A
- Authority
- GB
- United Kingdom
- Prior art keywords
- semi
- sensor
- conducting oxide
- layer
- charge distribution
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
- G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
- G01N27/12—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body in dependence upon absorption of a fluid; of a solid body in dependence upon reaction with a fluid, for detecting components in the fluid
- G01N27/128—Microapparatus
Abstract
A sensor for use in selective sensing of a chemical species in a liquid. The sensor has a semi-conducting oxide 2 in communication with a material 5 which is capable of affecting charge distribution in the semi-conducting oxide when the material is exposed to a selected chemical species. Means 3,4 are also provided for detecting a change in charge distribution in the semi- conducting oxide, by measuring changes in resistance or capacitance of the device. By way of example, potassium ions may be detected in solution by a sensor having a tin dioxide layer provided with a layer or coating of trichlorooctadecyl silane in which Valinomycin is incorporated. The sensor comprises a supporting substrate 1 and the charge distribution change is sensed by gold electrodes 3,4, <IMAGE>
Description
SPECIFICATION
Sensor
The present invention relates to sensors and in particular to sensors for use in selective sensing of chemical species in a liquid.
In accordance with one aspect of the present invention is provided a sensor, comprising a semi-conducting oxide in communication with a material which is capable of affecting charge distribution in the semi-conducting oxide when the material is exposed to a selected chemical species.
Preferably the semi-conducting oxide is in the form of a layer. The layer, optionally, may be supported on a substrate (eg. a silica substrate or an alumina substrate).
By way of example, a thin layer may be used i.e. a layer having a thickness of about 100 to 200 nm.
Examples of semi-conducting oxides which may be used in accordance with the present invention are SnO2, ZnO and W03. It will be appreciated that other semi-conducting oxides may be used in accordance with the present invention.
It is preferred that the material capable of affecting charge distribution in the semi-conducting oxide is a coating or layer on the semi-conducting oxide.
Electrodes may be provided in communication with the semi-conducting oxide for connection to a means for detecting a change of charge distribution in the semi-conducting oxide. The sensor may be used to detect the presence or absence in a liquid of a selected chemical species. Also the sensor may be used to detect the concentration, or variation of concentration, of a chemical species in a liquid.
The change in charge distribution may be monitored in any suitable way.
For example, electrical capacitance or electrical conductance or electrical resistance may be measured in order to monitor the change in charge distribution. Also, for example, an
AC or a DC signal may be used as is appropriate.
A sensor in accordance with the present invention may be so constructed as to be a low impedance sensor.
The material capable of affecting charge distribution in the semi-conducting oxide layer may consist of one component or more than one component.
By way of example the material may comprise a first component which acts as a carrier for a second component, which second component is capable of reacting selectively with a selected chemical species thereby to affect charge distribution in the second component which then affects the charge distribution in the semi-conducting oxide.
The first component may be chemically bonded to the semi-conducting oxide layer.
For example, the first component may be a silane chemically bonded to a semi-conducting oxide.
The first component may act as a carrier for the second component by acting as a solid or semi-solid solvent therefor. (E.g. a first component comprising trichlorooctadecyl silane may be applied to a semi-conducting oxide to form a layer or coating chemically bonded to the semi-conducting oxide layer and a second component (e.g. Valinomycin) capable of reacting selectively with a selected chemical species may be incorporated).
The sensitivity of a sensor in accordance with the present invention to different chemical species in a liquid (e.g. in solution) may be obtained by appropriate choice of the material capable of affecting charge distribution in the semi-conducting oxide.
Thus, for example, selected ion-exchange reagents in the material could give sensitivity to a chosen ionic species. By way of further example, enzyme reagents could be incorporated in the material to give sensitivity to various molecular species, according to the choice of enzyme. Immunoreagents, for example appropriate antibodies, could be incorporated into the material to give sensitivity to species according to the choice of immunoreagents.
It will be appreciated that a sensor in accordance with the present invention is sensitive to electrical charge changes in the material which give rise to changes in the charge distribution in the semi-conducting oxide.
In one embodiment a sensor in accordance with the present invention comprises a substrate, a layer of a semi-conducting oxide on the substrate, means for making electrical contact with the semi-conducting oxide layer, and on the semi-conducting oxide layer a coating of a material which is capable of affecting charge distribution in the semi-conducting oxide layer when the material is exposed to a selected chemical species.
The means for making electrical contact with the semi-conducting oxide layer, for example, may be conducting electrical contacts (e.g. of gold) in contact with the semiconducting oxide layer. Alternatively, by way of further example, the substrate may be provided with conductive tracks, to act as means for making electrical contact with the semiconducting oxide layer by doping appropriately (e.g. silicon may be doped appropriately to provide it with conductive tracks).
In a further embodiment a sensor in accordance with the present invention comprises a substrate, a layer of a dielectric material on the substrate, means for making electrical contact with the dielectric layer, a layer of semiconducting oxide on the dielectric layer and on the semi-conducting oxide layer a coating of a material capable of affecting charge distribution in the semi-conducting oxide layer when the material is exposed to a selected chemical species.
The means for making electrical contact with the dielectric layer may be, for example, conductive electrical contacts (e.g-. of gold) in contact with the dielectric- layer. Alternatively, by way of example, the substrate may be provided with conductive tracks, to act as means for making electrical contact with the dielectric layer, by doping appropriately (e.g. silicon may be doped to give conductive tracks). Where the substrate is silicon, the dielectric layer could be silicon dioxide or silicon nitride which could be prepared, for example, by chemical vapour deposition.
It is to be understood that where a dielectric layer is used, it can be arranged, if desired, to give good isolation of the means for making electrical contact from the environment. The electrical capacitance of a device having a dielectric layer may be used to monitor response to chemical species.
By way of example electrical contacts (e.g.
of gold) may be screen printed onto a substrate (e.g. an alumina tile or a silica disc) and, for example, a semi-conducting oxide (e.g. SnO2) may be sputtered onto the electrical contacts and substrate.
Interdigitated electrical contacts, may be used, in accordance with the present invention to give means for making electrical contact.
In accordance with another aspect of the present invention, there is provided a process for the preparation of a sensor which comprises bringing into communication a semiconducting oxide and a material which is capable of affecting the charge distribution in the semi-conducting oxide when the material is exposed to a selected chemical species.
Preferably, the semi-conducting oxide is prepared in the form of a layer. The layer, optionally, may be supported on a substrate (e.g. a substrate of alumina or silica).
In one embodiment of the immediately foregoing aspect of the present invention there is provided a process for the preparation of a sensor which comprises applying a layer of semi-conducting oxide to a substrate, providing means for making electrical contact with the semi-conducting oxide, and providing on the semi-conducting oxide layer a coating of a material which is capable of affecting the charge distribution in the semi-conducting oxide layer when the material is exposed to a selective chemical species.
In another embodiment of the immediately foregoing aspect of the present invention there is provided a process for the preparation of a sensor in accordance with the present invention which comprises applying a layer of a dielectric material to a substrate, providing means for making electrical contact with the dielectric layer, providing a layer of semi-conducting oxide on the dielectric layer and providing on the semi-conducting oxide layer a coating of a material capable of affecting the charge distribution in the semi-conducting oxide when the material is exposed to a selected chemical species.
In accordance with a further aspect of the present invention there is provided a process for the selective sensing of a chemical species, which comprises contacting the chemical species with a sensor comprising a semi-conducting oxide in communication with a material which is capable of affecting charge distribution in the semi-conducting oxide when the material is exposed to the chemical species, and monitoring the change in charge distribution in the semi-conducting oxide.
The present invention will now be described, by way of example only with reference to Examples 1, 2 and 3 and with reference to Figures 1 and 2 of the accompanying drawings in which:
Figure 1 is a diagrammatic representation of one form of sensor in accordance with the present invention and
Figure 2 is a diagrammatic representation of another form of sensor in accordance with the present invention.
Example 1
A sensor was prepared as beiow.
Onto a silica disc of 2.5 cm diameter a 120 nm thick layer of SnO2 was formed by radio frequency sputtering in the presence of oxygen.
The SnO2 layer was reduced slightly, in order to increase its conductivity, by heating at 600 C for one hour in an atmosphere of CO2.
(A similar result could have been obtained by sputtering initially at a lower oxygen partial pressure, or, as an alternative, by sputtering in an argon atmosphere and oxidising the resulting coating by heating in C02 as above).
Two gold strips were sputtered onto the surface of the SnO2 layer about 1 cm apart to provide electrical contacts.
A solution of trichlorooctadecyl silane in chloroform (about 2mg/ml) was poured onto the surface of the tin oxide layer and allowed to evaporate.
The resulting coating of trichlorooctadecyl silane was warmed to about 100"C in a stream of hot air in order to cause a reaction between silane and the tin dioxide layer.
The silane layer was washed with chloroform and the procedure repeated (i.e. further solution of silane in chloroform was poured onto the tin dioxide layer, allowed to evaporate and warmed at 100 C).
The layer of trichlorooctadecyl silane was exposed to a dilute aqueous solution of Valinomycin such that Valinomycin was incorporated into the layer of trichlorooctadecyl silane.
(The Valinomycin could, alternatively , have been incorporated into the layer of trichlorooctadecyl silage by adding it to the chloroform solution of the silane prior to pouring onto the surface of the tin dioxide layer).
The gold contacts were covered with an epoxy material to protect them.
Example 2
The sensor prepared as in accordance with
Example 1 was contacted with H20 and the electrical resistance between the gold contacts was measured with an AC signal.
The resistance was observed to be 106 ohms.
Example 3
The sensor prepared in accordance with
Example 1 was contacted with a 1M aqueous solution of KC 1 and the electrical resistance between the gold contacts was measured with an AC signal.
The resistence was observed to be 103 ohms.
On comparing the measurements made in
Examples 2 and 3, it will be seen that the resistance of the sensor in a medium containing potassium was less than that in water.
The sensor was thus demonstrated to be sensitive to the presence of potassium ions.
Referring to Figure 1 of the accompanying drawings, there is shown a sensor having a supporting substrate 1, a layer of semi-conducting oxide 2 with electrodes 3 and 4 (e.g.
gold contacts) and a layer or coating of a material 5 which is capable of affecting the charge distribution in the semi-conducting oxide 2 when the layer or coating of material 5 is exposed to a selected chemical species in a liquid.
In operation the layer or coating 5 is exposed to a liquid and the electrodes 3 and 4 are connected to a suitable electrical measuring device (not shown) which can detect a change in charge distribution of the semi-conducting oxide 2.
By measuring the change in charge distribution (e.g. by monitoring resistance) the absence or presence in a liquid of a selected chemical species may be detected, or the concentration or change in concentration of a species may be measured.
Referring to Figure 2 of the accompanying drawings, there is shown a sensor having a supporting substrate 1, a layer of dielectric material 2, electrodes 3 and 4 (e.g. gold contacts) a layer of semi-conducting oxide 5 and a layer or coating of a material 6 which is capable of affecting the charge distribution in the semi-conducting oxide 5 when the layer or coating of materials is exposed to a selective chemical species in a liquid.
In operation the layer or coating of material 6 is exposed to a liquid and electrodes 3 and 4 are connected to a suitable electrical measuring device (not shown) which can detect a change in charge distribution of the semi-conducting oxide 5.
The change in charge distribution may be monitored in this type of sensor by measuring the change in electrical capacitance and thus by monitoring electrical capacitance the absence or presence of a selected chemical species in a liquid may be detected, or the concentration or change in concentration of a species may be measured.
Claims (32)
1. A sensor comprising a semi-conducting oxide in communication with a material which is capable of affecting charge distribution in the semi-conducting oxide when the material is exposed to a selected chemical species.
2. A sensor as claimed in Claim 1 wherein the semi-conducting oxide is in the form of a layer.
3. A sensor as claimed in Claim 2 wherein the layer is supported on a substrate.
4. A sensor as claimed in Claim 3 wherein the substrate is a silica substrate or an alumina substrate.
5. A sensor as claimed in Claim 2 or Claim 3 wherein the layer has a thickness of about 100 to 200 nm.
6. A sensor as claimed in any one of the preceding Claims wherein the semi-conducting oxide is SnO2, ZnO or WO2.
7. A sensor as claimed in any one of the preceding Claims wherein the material capable of affecting charge distribution in the semiconducting oxide is a coating or layer on the semi-conducting oxide.
8. A sensor as claimed in any one of the preceding Claims wherein electrodes are provided in communication with the semi-conducting oxide for connection to a means for detecting a change of charge distribution in the semi-conducting oxide.
9. A sensor as claimed in any one of the preceding Claims wherein the material capable of affecting charge distribution in the semiconducting oxide layer consists of one component.
10. A sensor as claimed in any of Claims 1 to 8 wherein the material capable of affecting charge distribution in the semi-conducting oxide layer consists of more than one component.
11. A sensor as claimed in Claim 1 wherein the material comprises a first component which acts as a carrier for a second component, which second component is capable of reacting selectively with a selected chemical species thereby to affect charge distribution in the second component which then affects the charge distribution in the semi-conducting oxide.
12. A sensor as claimed in Claim 11 wherein the first component is chemically bonded to a semi-conducting oxide layer.
13. A sensor as claimed in Claim 12 wherein the first component is a silane.
14. A sensor as claimed in Claim 13 wherein the silane is trichlorooctadecyl silane.
15. A sensor as claimed in any one of
Claims 11 to 14 wherein the second component is valinomycin.
16. A sensor as claimed in any one of
Claims 11 to 15 wherein the material contains a selected ion exchange reagent, an enzyme reagent or an immunoreagent.
17. A sensor as claimed in Claim 1 comprising a substrate, a layer of a semi-conducting oxide on the substrate, means for making electrical contact with the semi-conducting oxide layer, and on the semi-conducting oxide layer a coating of a material which is capable of affecting charge distribution in the semiconducting oxide layer when the material is exposed to a selected chemical species.
18. A sensor as claimed in Claim 17 wherein the means for making electrical contact with the semi-conducting oxide layer comprises conducting electrical contacts in contact with the semi-conducting oxide layer.
19. A sensor as claimed in Claim 17 wherein the substrate is provided with conductive tracks to act as means for making electrical contact with the semi-conducting oxide layer.
20. A sensor as claimed in Claim 1 comprising a substrate, a layer of a dielectric material on the suhstrate, means for making electrical contact with the dielectric layer, a layer of semi-conducting oxide on the dielectric layer and on the semi-conducting oxide layer a coating of a material capable of affecting charge distribution in the semi-conducting oxide layer when the material is exposed to a selected chemical species.
21. A sensor as claimed in Claim 20 wherein the means for making electrical contact with the dielectric layer comprises conducting electrical contacts in contact with the dielectric layer.
22. A sensor as claimed in Claim 20 wherein the substrate is provided with conductive tracks to act as means for making electrical contact with the Viielectric layer.
23. A process for the preparation of a sensor which comprises bringing into communication a semi-conducting oxide and a material which is capable of affecting the charge distribution in the semi-conducting oxide when the material is exposed to a selected chemical species.
24. A process as claimed in Claim 23 for the preparation of a sensor which comprises applying a layer of semiconducting oxide to a substrate, providing means for making electrical contact with the semi-conducting oxide, and providing on the semi-conducting oxide layer a coating of a material which is capable of affecting the charge distribution in the semi-conducting oxide layer when the material is exposed to a selective chemical species.
25. A process as claimed in Claim 23 for the preparation of a sensor in accordance with the present invention which comprises applying a layer of a dielectric material to a substrate, providing means for making electrical contact with the dielectric layer, providing a layer of semi-conducting oxide on the dielectric layer and providing on the semi-conducting oxide layer a coating of a material capable of affecting the charge distribution in the semi-conducting oxide when the material is exposed to a selected chemical species.
26. A process as claimed in Claim 24 or 25 wherein the substrate is alumina or silica.
27. A process for the selective sensing of a chemical species, which comprises contacting the chemical species with a sensor comprising a semi-conducting oxide in communication with a material which is capable of affecting charge distribution in the semi-conducting oxide when the material is exposed to the chemical species, and monitoring the change in charge distribution in the semi-conducting oxide.
28. A process as claimed in Claim 27 wherein potassium ions are detected in solution.
29. A sensor substantially as hereinbefore described with reference to Figure 1 or Figure 2 of the accompanying drawings.
30. A sensor substantially as hereinbefore described with reference to Example 1.
31. A process for the preparation of a sensor substantially as herein before described with reference to Example 1.
32. A process for the selective sensing of a chemical species substantially as hereinbefore described with reference to Example 3.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8521628A GB8521628D0 (en) | 1985-08-30 | 1985-08-30 | Sensor |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB8620798D0 GB8620798D0 (en) | 1986-10-08 |
| GB2180348A true GB2180348A (en) | 1987-03-25 |
Family
ID=10584495
Family Applications (2)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8521628A Pending GB8521628D0 (en) | 1985-08-30 | 1985-08-30 | Sensor |
| GB8620798A Withdrawn GB2180348A (en) | 1985-08-30 | 1986-08-28 | Semiconducting oxide sensor |
Family Applications Before (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8521628A Pending GB8521628D0 (en) | 1985-08-30 | 1985-08-30 | Sensor |
Country Status (1)
| Country | Link |
|---|---|
| GB (2) | GB8521628D0 (en) |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3831432A (en) * | 1972-09-05 | 1974-08-27 | Texas Instruments Inc | Environment monitoring device and system |
| EP0115183A2 (en) * | 1982-12-28 | 1984-08-08 | New Cosmos Electric Co., Ltd. | Hydrogen-selective sensor |
| US4481499A (en) * | 1982-05-07 | 1984-11-06 | Hitachi, Ltd. | Gas detector |
| GB2141544A (en) * | 1983-05-25 | 1984-12-19 | Nat Res Dev | Diagnostic device incorporating a biochemical ligand |
-
1985
- 1985-08-30 GB GB8521628A patent/GB8521628D0/en active Pending
-
1986
- 1986-08-28 GB GB8620798A patent/GB2180348A/en not_active Withdrawn
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3831432A (en) * | 1972-09-05 | 1974-08-27 | Texas Instruments Inc | Environment monitoring device and system |
| US4481499A (en) * | 1982-05-07 | 1984-11-06 | Hitachi, Ltd. | Gas detector |
| EP0115183A2 (en) * | 1982-12-28 | 1984-08-08 | New Cosmos Electric Co., Ltd. | Hydrogen-selective sensor |
| GB2141544A (en) * | 1983-05-25 | 1984-12-19 | Nat Res Dev | Diagnostic device incorporating a biochemical ligand |
Also Published As
| Publication number | Publication date |
|---|---|
| GB8521628D0 (en) | 1985-10-02 |
| GB8620798D0 (en) | 1986-10-08 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |