WO2002056001A2 - Metal ion sensor - Google Patents
Metal ion sensor Download PDFInfo
- Publication number
- WO2002056001A2 WO2002056001A2 PCT/EP2002/000300 EP0200300W WO02056001A2 WO 2002056001 A2 WO2002056001 A2 WO 2002056001A2 EP 0200300 W EP0200300 W EP 0200300W WO 02056001 A2 WO02056001 A2 WO 02056001A2
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- solution
- semiconductor
- resistance
- metal ions
- semiconductor surface
- Prior art date
Links
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
- G01N27/041—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body
-
- 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
- G01N27/002—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating the work function voltage
Definitions
- the invention relates to a method for determining the concentration of metal ions in a solution and a sensor for determining the concentration of metal ions in a solution.
- the electrical potential (electrode potential) of a corresponding metal electrode in this solution can be used compared to a reference electrode.
- the voltage established between the metal electrode and the reference electrode is tapped.
- the voltage is proportional to the metal ion concentration in the solution.
- the object of the invention is to provide a method for the determination of metal ions, which provides good measurement results, especially at low concentrations, and can also be used in the case of dynamic concentration changes. It is also an object of the invention to provide a sensor for determining the concentration of metal ions in solution which can be produced in a simple manner and which is both sensitive to low metal ion concentrations and can also be used for dynamic processes.
- the method according to the invention is based on the principle that a semiconductor surface in contact with an electrolyte forms an electronic barrier layer, the electrical resistance or the electronic barrier of which is a function of the ion concentration in the presence of metal ions in the electrolyte.
- the Fermi level of the electrons of the semiconductor and the electrochemical potential of the redox system will generally degrade energetically.
- This compensation process forms a so-called space charge zone in the edge layer of the semiconductor, which is compensated for by excess ions on the electrolyte-side semiconductor surface.
- a dipole layer is created, which is referred to as Helmhotz's double layer.
- the electrolyte contains metal ions, these are deposited on the semiconductor surface in accordance with their concentration in the solution.
- the semiconductor is electrically contacted, there is usually a one-time current flow which results, for example, from the transfer of electrons from the semiconductor layer to the deposited metal ions and reduces them.
- the surface potential changes due to the metal ions attached to the semiconductor surface in such a way that the semiconductor / electrolyte dipole loses its blocking action and a current flow between the semiconductor and the electrolyte is possible.
- the semiconductor is suitably electrically biased compared to the solution, there is a permanent current flow through the semiconductor / electrolyte interface. In watery Solution, this can result in a hydrogen potential when a negative potential is applied, and in an oxygen development when a positive potential is applied.
- the near-surface space charge zone is formed by positively charged, stationary donors of the semiconductor, which are opposed by negatively charged metal ions on the electrolyte-side semiconductor surface.
- the advantage of this determination method is that the "permanent" current can be chosen to be large compared to the "one-time” current caused, for example, by the metal ion reduction. Furthermore, this "permanent" current with constant ion concentration is not zero, like that of pure metal deposition with equilibrium occupancy, but is different from zero and constant with a constant potential difference between semiconductor and electrolyte.
- the ion concentration of the solution can thus be determined by measuring the interface resistance of the semiconductor / electrolyte interface, which is sensitive to surface conditions, and comparing it with reference data.
- the semiconductor surface thus represents a sensor surface which allows the determination of a metal ion concentration via its influence on the surface states of the semiconductor surface.
- a resistance measurement can take place, for example, at a predetermined potential difference between the semiconductor surface and the solution via a measurement of the electrical interface current between the semiconductor and the solution.
- at least one preferably metallic counter electrode is provided in contact with the solution.
- the total resistance measured in this way between the counterelectrode and the electrically contacted semiconductor surface serving as the detection electrode in this case includes, in addition to the actual interface resistance, also the electrical resistance of the solution which surrounds the counterelectrode and the semiconductor surface.
- a three-electrode or multi-electrode structure is particularly advantageous, in which at least one additional reference electrode is provided in addition to the metallic counter electrode and the semiconductor.
- This reference electrode can preferably be constructed similarly to the semiconducting detection electrode. However, it preferably has an interface coating such that its interface resistance does not change with the ion concentration, but otherwise has the same resistance characteristic, in particular the same current and temperature dependency as the detection electrode.
- the geometrical arrangement of the detection, counter and reference electrodes relative to one another is advantageously known, so that solution resistances between the electrodes would be calculable if the specific solution conductivity was known.
- the geometric arrangement of the detection, counter and reference electrodes is particularly preferably chosen such that the solution resistance between the counter and the detection electrodes corresponds to that between the counter and the reference electrode. In this case, the interfacial resistance dependent on ion concentration can be determined in a simple manner from the difference in the total resistances between counter and detection electrode and counter and reference electrode.
- a resistance bridge measurement can also be used to determine the interface resistance, in which a preferably currentless determination of the interface resistance is possible by comparing a resistance bridge, the unknown resistance of which is the semiconductor / electrolyte interface resistance.
- a sensor for determining a concentration of Metal ions in a solution which is particularly suitable for carrying out the method according to the invention
- At least one detection electrode with a semiconductor which is designed such that its electrically conductively contacted semiconductor surface can at least partially come into contact with the solution;
- At least one counter electrode for contacting the solution
- a resistance determination device which is electrically connected to the detection and the counterelectrode, in order to determine the interface resistance between the semiconductor surface and the solution; and an evaluation device which is connected to the resistance determination device in order to determine the concentration of the metal ions by comparing the interface resistance with reference data.
- All semiconductor materials which have a diode effect in contact with an electrolyte are suitable for the sensor according to the invention, such as III-V semiconductors, in particular GaAs. Both p and n semiconductors can be used.
- the doping should be selected such that a space charge zone can form in the boundary layer of the semiconductor, i.e. the boundary layer should not be degenerate (metallic) doped.
- Organic semiconductors such as phthalocyanines or polymers such as oligophenes or polythiophenes are also suitable.
Abstract
Description
Claims
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AU2002225004A AU2002225004A1 (en) | 2001-01-13 | 2002-01-14 | Metal ion sensor |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE10101376.0 | 2001-01-13 | ||
DE2001101376 DE10101376A1 (en) | 2001-01-13 | 2001-01-13 | Metal ion sensor |
Publications (2)
Publication Number | Publication Date |
---|---|
WO2002056001A2 true WO2002056001A2 (en) | 2002-07-18 |
WO2002056001A3 WO2002056001A3 (en) | 2003-03-13 |
Family
ID=7670476
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/EP2002/000300 WO2002056001A2 (en) | 2001-01-13 | 2002-01-14 | Metal ion sensor |
Country Status (3)
Country | Link |
---|---|
AU (1) | AU2002225004A1 (en) |
DE (1) | DE10101376A1 (en) |
WO (1) | WO2002056001A2 (en) |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4057823A (en) * | 1976-07-02 | 1977-11-08 | International Business Machines Corporation | Porous silicon dioxide moisture sensor and method for manufacture of a moisture sensor |
US4334880A (en) * | 1980-10-20 | 1982-06-15 | Malmros Mark K | Analytical device having semiconductive polyacetylene element associated with analyte-binding substance |
US4587543A (en) * | 1981-05-29 | 1986-05-06 | Tokyo Shibaura Denki Kabushiki Kaisha | Method and device for detecting metal ions |
-
2001
- 2001-01-13 DE DE2001101376 patent/DE10101376A1/en not_active Withdrawn
-
2002
- 2002-01-14 AU AU2002225004A patent/AU2002225004A1/en not_active Abandoned
- 2002-01-14 WO PCT/EP2002/000300 patent/WO2002056001A2/en not_active Application Discontinuation
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4057823A (en) * | 1976-07-02 | 1977-11-08 | International Business Machines Corporation | Porous silicon dioxide moisture sensor and method for manufacture of a moisture sensor |
US4334880A (en) * | 1980-10-20 | 1982-06-15 | Malmros Mark K | Analytical device having semiconductive polyacetylene element associated with analyte-binding substance |
US4587543A (en) * | 1981-05-29 | 1986-05-06 | Tokyo Shibaura Denki Kabushiki Kaisha | Method and device for detecting metal ions |
Also Published As
Publication number | Publication date |
---|---|
WO2002056001A3 (en) | 2003-03-13 |
AU2002225004A1 (en) | 2002-07-24 |
DE10101376A1 (en) | 2002-07-18 |
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