GB2368908A - Exposure sensor for oxygen or water - Google Patents
Exposure sensor for oxygen or water Download PDFInfo
- Publication number
- GB2368908A GB2368908A GB0027366A GB0027366A GB2368908A GB 2368908 A GB2368908 A GB 2368908A GB 0027366 A GB0027366 A GB 0027366A GB 0027366 A GB0027366 A GB 0027366A GB 2368908 A GB2368908 A GB 2368908A
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- Prior art keywords
- sensing means
- oxygen
- sensing
- water
- complex
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N31/00—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods
- G01N31/22—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods using chemical indicators
- G01N31/223—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods using chemical indicators for investigating presence of specific gases or aerosols
- G01N31/225—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods using chemical indicators for investigating presence of specific gases or aerosols for oxygen, e.g. including dissolved oxygen
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/75—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated
- G01N21/77—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated by observing the effect on a chemical indicator
- G01N21/78—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated by observing the effect on a chemical indicator producing a change of colour
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N31/00—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods
- G01N31/22—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods using chemical indicators
- G01N31/222—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods using chemical indicators for investigating moisture content
Abstract
Sensing means for sensing the presence of one or both of oxygen and water comprises a material whose interactions with electromagnetic radiation change on exposure to one or both of oxygen and water. The sensing means may be incorporated into food packaging so as to give an indication as to the amount of time that a food package has been opened. The material may be a transition metal compound or a polymer and preferably the sensing is via a visual colour change. Also claimed is a sensing means for oxygen comprising a metal-air battery and a display means.
Description
Exposure sensor
This invention relates to the field of sensing of gases and liquids, particularly to the field of sensing the presence of one or both of oxygen and water.
Sensors are available which measure either or both of the oxygen and water content of a gaseous atmosphere. However, such sensors are usually expensive and can be difficult to use.
The invention in suit provides cheap, easily-used sensors which indicate the time for which a sensor has been exposed to one or both of oxygen and water. Such detectors are useful in many fields, such as a timer for use with degradable chemicals (e. g. photographic materials), and in swimming pools and aquaria where water treatments need to be performed at regular intervals. The present invention is of particular relevance to the field of food safety. Virtually all packaged fresh foods are marked with a period after opening in which the food should be consumed. This period is typically between a few days and several weeks. If the consumer does not label the food packaging with either the opening date or consequential use-by date, then it is difficult to determine whether this use-by date has been passed. As a consequence, many valid foodstuffs are thrown away and, more importantly, many poor ones eaten. It is an aim of the present invention to provide a sensor which can be used to minimise this problem.
In accordance with the present invention a sensing means for sensing the presence of one or both of oxygen and water, wherein the sensing means comprises a material whose interactions with electromagnetic radiation change on exposure to one or both of oxygen and water.
It is preferred that the change is visible to the naked human eye. This gives a cheap and ready indication that the material has been exposed to at least one of oxygen and water.
The material may comprise at least one species which reacts with one or both of oxygen or water.
In one embodiment, the species comprises a metal species, preferably a transition metal species. The metal species is preferably selected from the list consisting of Cu+, Cu, Co,
3+. 3+ V3+ C 2+ N'2+ M 2+ F 2+ d F 3+ S I f..
Co, Ti, V, Cr, Ni, Mn, Fe and Fe. Some salts of transition metals are known to
change colour on reaction with one or both of water and oxygen.
The Cr2'species is preferably in the form of any one of the group consisting of 1 ! 71 Cr (OCOCFhh. 2H O and fCr (H. 0) 6 complex. The Cr (II) acetate complex is red and is oxidised to a Cr (lll) complex of a different colour.
The Mn"'species may be in the form of Mn (OH b. This pink material is oxidised rapidly in air to generate brown Mn2O,.
The \li--may be in the form of any one of the group consisting of an anhydrous nickel (11) halide or a Ni (OH) . In an alkali solution, nickel (II) hydroxide is oxidised by oxygen to give a Ni (HI) material.
Fe''may be in the form of any one of the group consisting of Fe (OH) . a hydrated Fe (M) complex. FeO, an Fe (ll) cysteine complex. an Fe (II) hystidine comp) ex. Fe (H) phthaiocyanine tetrasuiphonate. an Fe (ll)-dimethylglyoxime-base complex, The green iron (II) hydroxide turns brown on oxidation in alkaline solution. Green FeO is oxidised in the solid state to brown FeCh. lron (11) compounds in acid perch ! orate solution oxidise slovs lv to differentcoloured iron ( ! ! !) materials, \vhereas iron (Il) cysteine comple\es oxidise \ery quickly. This gives se) ect) ity as to the rate at which the sensor changes colour.
C'u 2 tmay be in the form of anhydrous CuSO4. This white compound is hydrated to form the stunning blue hydrated salt.
The Ti'* species may be in the form of any one of the group consisting of [I i (HO) h]'". TIF. TiCh. TiBr and Tih. The coloured titanium (fil) halides are oxidised in moist air to form hydrated Tir.
V may be in the form of any one of the group consisting of VF VCh, VBr, and VI. The halides are strongly-coloured materials which undergo hydrolysis in moist air.
The Co species may be in the form of any one of the group consisting ofCo (OH) 2, anhydrous [CoCI4]2-salts, a Co (lui) myoglobin complex, a Co (II) L-hystidine complex, a
Co (vil) salen complex, Co (phthalocyanine), a Co (lI) cysteine complex and bis (histidinoato) Co (II). Cobalt (II) hydroxide in alkaline solution is blue and is oxidised by oxygen to give a brown product. The blue cobalt tetrachloro complexes are hydrated to form pink complexes. The bis (histidinoato) complex, on exposure to oxygen, undergoes the reversible formation of a deep brown Co (II) dioxygen complex, which in turn is slowly and irreversibly oxidised to a dark pink Co (ill) material. This slow reaction may be useful for detection prolonged exposure to oxygen. Brown Co (II) salen undergoes a reversible transition to a black compound on exposure to oxygen. The reversibility of such colour change will be advantageous for some sensor applications.
The Fe species may be in the form of any one of the group consisting of Fe (Cl04) 3. 10H20, Fe (N03) 3. 6H20 and Fe2 (SO4) 3. 9H20. These pale coloured materials undergo hydrolysis on exposure to water to form brown products.
In an alternative embodiment, the material comprises a polymer, such as poly-3alkylthiophene. This material changes colour on exposure to oxygen. A polymer may be simpler and easier to work than some metal species.
The sensing means preferably further comprises containment means, the containment means being arranged so as to prevent egress of the material from the sensing means. The containment means preferably permits contact of water or oxygen with the material. This means that the containment means does not have to be punctured or removed to enable the sensor to function.
The containment means may comprise a polymeric matrix in which the material is entrapped.
Alternatively, the containment means comprises a gel. This would allow quick and easy manufacture of a sensing means that is easy to handle compared with one that uses solution chemistry.
The sensing means may comprise a plurality of sensing areas, each of the said sensing areas comprising a material, which may be the same or different in each area, wherein the interactions of each of the materials with electromagnetic radiation change on exposure to one or both of oxygen and water, and wherein the changes in the interactions of at least two
materials with electromagnetic radiation are mutually different when the corresponding at least two areas are exposed to substantially the same amount of oxygen and water vapour.
. zu This provides the user with a series of areas which change colour differently when exposed to at least one of water and oxygen, thus allowing the progress of prolonged exposure to be monitored.
In order to achieve the effect of different colour changes, the at least two materials may comprise mutually different reactive moities Alternatively, or in addition to this, the at least two materials may be of mutually different concentrations. This would alter the relative rates of reactions in the sensing areas, and thus the change m colour. The at least two materials may further have mutually different permeabilities to one or both of water and oxygen. Such a
sensing means may have each sensing area further comprising a containment means which is L--Z7 permeable to at least one of water and oxygen, whereby the at least two materials are each contained by containment means having mutually different permeabilities to at least one of water and oxygen. This latter embodiment may be achieved by using at least two mutually
different polymers as containment means for different areas.
A metal-air battery may also be used to sense the presence oxygen. A sensing means for sensing the presence of oxygen comprises a metal-air battery and a display means, wherein the said metal-air battery comprises a first electrode that is permeable to gases, a second electrode and an electrolyte, said electrodes comprising mutually different metals and being in contact with said electrolyte and there being a potential difference between the two electrodes. wherein the display means indicates the potential difference between the two electrodes, whereby oxygen permeates the first electrode and causes the oxidation of the surface of one of the electrodes, thus altering the potential difference between the two electrodes.
This provides a sensitive and simple means for sensing the presence of oxygen.
The first electrode is preferably the cathode and the second electrode is the anode. The anode preferably comprises at least one of aluminium, zinc. magnesium or lithium, whereas the cathode typically comprises carbon impregnated with a metal catalyst such as silver, cobalt,
platinum or manganese. For the anode, other metals may be used.
The electrolyte may comprise at least one of NaCl and a hydroxide, typically NaOH or KOH.
These preferred electrolytes are readily-available and cheap.
The display means preferably comprises a voltmeter, such as a digital voltmeter or a Duracel) @ voltmeter strip. The former provides an accurate measure of change in potential difference, whereas the latter means is cheap and disposable.
Any of the sensing means above may further comprise sealing means, said sealing means preventing unwanted exposure of the material to oxygen and water. This permits long-term storage of the sensing means without a substantial degradation in performance, even if the sensing means is kept in an environment containing at least one of oxygen and water.
The sensing means may further comprise attachment means to enable attachment and positioning of the sensing means.
The invention is now described by way of example only with reference to the following figures of which :
Figure 1 is a schematic representation of a cross-section through a sensing means in accordance with the present invention;
Figure 2 is a schematic representation of a cross-section through a sensing means in accordance with the present invention having many sensing areas;
Figure 3 is a schematic representation of food packaging comprising a sensing means in accordance with the present invention having many sensing areas arranged in the form of an informative slogan;
Figure 4 is a schematic representation of a sensing means in accordance with the present invention having many sensing areas arranged in a clock-face formation ; and
Figure 5 is a schematic representation of an alternative arrangement of a sensing means in
accordance with the present invention, said sensor being based upon a metal-air battery.
Example 1
Figure 1 shows a cross-section or a sensing means in accordance with the present invention.
The sensing means comprises a material I and a containment means 2'having a substrate portion 2 and a cover portion 3. On exposure to one or both of water and oxygen, the interactions of the material I with incident electromagnetic radiation change. The material 1
comprises FeO. the substrate portion :. : comprises a plastics material which is permeable to neither oxygen nor water and the cover portion 3 comprises a permeable membrane, such as those used to make certain types ofophthalmic contact lens. Altematively, the membrane may be similar to that found in a commercially-available device for the separation of enriched oxygen from air. The substrate portion 2 and cover portion 3 are joined such that neither oxygen nor water can pass through their mutual interface. In this case, the join is achieved using an adhesive. Hot-pressing could be used. wherein the interface regions of both the substrate portion 2 and cover portion 3 are heated as pressure is applied to those regions to cause mutual bonding. The cover portion 3 prevents egress of the material 1, while permitting
ingress of atmospheric oxygen to the contained material I. The oxygen reacts with the FeO to form Fen thus givmg a colour change from green to brown. This shows that the sensing means has been exposed to atmospheric oxy (yen. Note that the change in the material's interaction with electromagnetic radiation does not have to be a visible change : however. such a change is easier and simplex ta use. The substrate portion :. : may be part of food packaging, for mstance.
Note that the sensing means may be free-standmg (i. e. not attached to a substrate). The containment means 2'may surround the material. A portion of the containment means 2' It ni I may, as above, be impermeable to one or both of oxygen and water. Alternatively, the whole of the containment means 2'may be permeable to at least one of water and oxygen.
T) 6)//7 < :'. / ?. < ./ yy'. s The design of the sensing means (e. g. identity of oxygen-sensitive material I, properties of the containment means 2') is dependent on many factors, some of which are set-out below. It is preferred that there are clearly visible differences between the unoxidised and oxidised material. The change in colour should occur over the desired timescale and at the desired temperature and partial pressure of oxygen. The colour of each of the oxidised and unoxidised material will depend on the response spectrum of the eye and the absorption
characteristics of the material. The eye is relatively sensitive to green light and insensitive to blue light, and so one may be able to use a sensing means where both the oxidised and unoxidised materials are green, but not if both appear to be blue.
The appearance of the sensor at a given wavelength of light depends on the amount of light adsorbed at that wavelength as shown in equation 1.
1 =/, (-' (I) wherein Io (k) is the incident intensity of radiation at a given wavelength, k, 8 (k) is the absorption co-efficient per unit concentration of a particular species and I is the thickness of the sample. Hence, the appearance of the sensing means depends strongly on sample thickness and on both the absorption co-efficient and concentration of the light-absorbent material.
The absorption co-efficient is constant for a particular species at a particular concentration.
The concentration of a particular species will depend on several factors. If we assume that a typical oxidation reaction involves the oxidation of one molar equivalent of species A to form one molar equivalent of species B and that this reaction obeys first order kinetics, then A, = A'') (2) and Bt=Ao (l-eHd) (3) wherein At is the concentration of A at time t, Bt is the concentration of B at time t, Ao is the initial concentration of A and k is the rate constant. Hence, the concentration of A decreases exponentially over time and the concentration of B increases in a related manner. Note that the trends in changes in concentration will be similar for all orders of reaction kinetics i. e. concentration of the unoxidised form (in this case A) decreases and the concentration of the oxidised form (in this case B) increases as the reaction progresses.
equations 2 and 3 show that the concentration of a given species at a given time depends strongly on the rate constant. The rate constant typically depends on temperature as shown in pi equation 4. k (4) wherein k is the rate constant C is a constant, E is the activation energy for the reaction and T is the temperature. Thus, k shows a strong dependence on temperature. This may prove to be a problem for some uses of a sensing means in accordance with the present invention, since a small change in temperature may lead to a large change in the rate of oxidation and thus the rate at which the sensing means appears to change colour. For many uses of the sensing means this may not be a problem, since an increase in temperature of the substances that are being monitored by the sensing means may lead to a large increase in the rate of degradation of those substances. The rate constant, k, will depend on the state of the reactive material (i.e. solid, liquid, gaseous or in solution) and other factors such as surface area of reagents. For
oxidation caused by exposure to at least one of oxygen and water, the rate of ingress or these o xi I species to the material in the sensing means will be important. This will be determined by, itzict- (ili (i, the permeability of the containment means, the air flow, the partial pressure of oxygen-relative humidity and temperature. The permeability of the containment means depends on its chemical composition and the physical structure of the containment means.
Hence, the relationships between the observed colour of the sensing means, the sensing of at least one of oxygen and water and the reagents and products of the reaction are explained.
This teaching could be readily used by those skilled in the art to make sensing means in accordance with the present invention.
Note that the references above to oxidised and unoxidised species do not exclude the use of this teaching in conjunction with materials that do not undergo oxidation. For example, anhydrous copper sulphate could be used; on hydration, this material changes from white to blue.
Selection of material Many materials change colour on exposure to one or both of oxygen and water. The reader is directed to Advanced Inorganic Chemistry, Cotton and Wilkinson ; Advanced Chemical Series No. 100, 1971, p. III-134, by Wilkins and references therein;"Reversible oxidation",
Struct. Bond., 28, p. 1-50, 1976, Erskine and Field; Chemistry of the Elements,
N. N. Greenwood and A. Eamshaw. One of the other primary determining factors as to the selection of material is the speed with which the user wishes the material to change colour.
For example, iron (II) cysteine complexes change colour very quickly (in a matter of milliseconds to seconds), but iron (II) materials in acid perchlorate change colour much more slowly. Another determining factor is the chemistry of the material itself ; some materials will only react with oxygen in the presence of water, whereas others will react with oxygen in the absence of water. Another important factor is the difference in colour between the starting material and the product.
Selection of containment means
The containment means prevents the egress of the material, while preferably permitting ingress of at least one of water and oxygen. Examples of polymers which may be used in the construction of containment means are given in Table 1.
Polymer oxygen Pwater Polyvinylidene chloride. 0053 1 Barex. 0054 660 Polydimethyl siloxane 605 40,000 . 992 density polyethylene 6. 9 90 Teflon 4. 9 33 Cellulose acetate. 08 6,800 Table !-Permeability co-efficients of water and oxygen for various polymers
Poxygen and P water are the permeability co-efficients of oxygen and water respectively for the named polymers, unit is cm (STP) cm/ (cm2 sec cm Hg) x 1010. Source: S. Pauly,"Permeability and diffusion data"in Polymer Handbook, 3rd Edition, Brandrup and Immergut (Eds. ), John Wiley and Sons, New York, 1989, p. VI.
Table 1 illustrates that it is possible to select the substance from which preferab) y at least part of the containment means is produced to allow selective permeation of one or both of water and oxygen through the containment means to the material. The containment means, or at least some portion of it, should be accessible to electro-magnetic radiation to allow the user to
determine whether the sensing means has been exposed to one or both of water and oxygen.
L7 L The containment means may comprise a gel or polymer matrix in which the material is entrapped. This would allow quick and easy manufacture of a sensing means that is easy to handle compared with one that uses solution chemistry.
Example2
Figure 2 shows a cross-section through another sensing means in accordance with the present
I'I'he sensiii (y means cor'ses invention. The sensing means comprises a substrate portion 2. several sensor areas. 4."'. 6. 7. each sensor area comprising a cover portion 3a. 3b. 3c. 3d and a respective material. la. ! b.
I I I g the iiiiter'al ot'tlic co%, er I c. I d. The areas 4. 5. 6. 7 arc made mutually discrete by adhering the material of the cover portions 3a-d to the substrate portion 2. The interactions of each of the materials la-ld with electromagnetic radiation change on exposure to one or both of oxygen and water. The changes in the interactions are mutually different when areas 4-7 are exposed to substantially the same amount of one or more of both water vapour and oxygen. Hence, in this example. material la darkens after a rclati\eiy short exposure to oxvgen or water. Material Ib darkens after slightly greater exposure, material I c with greater exposure still, with ld darkening after means can the longest exposure. Hence, this sensing means can be used to indicate how long the sensing means has been exposed to the atmosphere.
In order to achieve a mutually different response from each of the sensor areas, it is possible to use mutually different materials) a-d. Alternatively, mutually different cover portions 3a-d may be used to control the rate at which the materials I a-d are exposed to oxygen and water vapour. It may be desired to use mutually different materials I a-d and mutually different cover portions 3a-d. The materials I a-d may be made mutually different by using different reactive chemical species in each sensor area or by using mutually different concentrations of reactive species in the areas 4-7. The cover portions 3a-d may be made mutually different by, for example, varying the thickness of the cover portions or by varying the material from which each cover portion 3a-d is made.
Example 3 Figure 3 shows an example of food packaging comprising a sensing means in accordance with the present invention. The food packaging comprises, inter alia, a substrate portion 10, several sensor areas 11-17, each sensor area comprising a cover portion (not shown) and a material (not shown) whose interactions with electromagnetic radiation change when exposed to one or both of oxygen and water. Each material is enclosed by the substrate portion 10 and the relevant cover portion. The food (not shown) that is placed in the packaging will typically be fresh food that perishes on exposure to one or both of water and oxygen. The food is packed in an inert atmosphere, hence neither the food nor the sensing means are exposed to significant amounts of water or oxygen until the packaging is opened. Hence, there will be no change in colour of any of the sensor areas 11-17 until the packaging is opened. On opening of the packaging, both the sensing means and the food are exposed to water and oxygen. The sensing means is designed such that the sensor areas 11-17 darken on exposure to the atmosphere. The sensor areas 11-17 are designed to darken at different rates such that when all seven areas are darkened the food has been exposed to the atmosphere for a given period after which the food is thus probably not fit to eat. The sensor areas are relatively easy to design to darken in the desired period because virtually all fresh food is kept in refrigeration units in which the temperature, air flow, relative humidity and partial pressure of oxygen are approximately constant. Furthermore, inadvertent or deliberate rupturing of the packaging prior to the actual opening of the packaging will be apparent from the change in colour of the
sensing means.
Example 4 The conformation and layout of the sensor areas may be readily altered. Figure 4 shows a sensing means in accordance with the present invention comprising a substrate portion 29, sensor areas 21-28, each of which comprises a cover portion (not shown) and a material (not shown) whose interactions with electromagnetic radiation change on exposure to at least one of oxygen and water. The sensor areas are arranged in a clock-face configuration. The sensing means operates in a similar manner to those of figures 2 and 3. As duration of exposure is increased, more of the sensor areas 21-28 darken. When all areas are darkened, the relevant time period has elapsed.
Example 5 Figure 5 shows a schematic representation of a sensing means in accordance with the present invention based on a metal-air battery. The sensing means comprises a first electrode 50, a second electrode 51, a display means 52 and an electrolyte 53. The electrolyte 53 is in contact with both the first and second electrodes 50, 51, and thus a potential difference exists between them. This is measured and displayed by the display means 52. In this example, the first electrode 50 is a zinc cathode which is permeable to atmospheric oxygen incident on its
external face. Oxygen permeates the cathode and causes oxidation of the second electrode 51, an aluminium anode. This changes the potential difference between the electrodes 50 and 51, a change which is reflected by the display means 52. Hence, the change in potential difference is indicative of the presence of oxygen in the region of the anode. The magnitude of the change will be indicative of the degree of oxidation that has occurred. The electrolyte may be a solution of at least one ofNaCI and NaOH. The display means may be an analogue or digital voltmeter or a Duracell@ voltmeter strip. Such a sensing means could be readily deployed in food packaging.
If desired, any of the sensing means in accordance with the present invention may have a sealing means deployed thereon to prevent unwanted ingress of atmospheric oxygen and water vapour to the air-sensitive or water-sensitive material within the sensing means by inserting a barrier which is substantially impermeable to one or both of water and oxygen between the atmosphere and the containment means. Such a sealing means may be in the form of a strip which would be fixed either to the sensing means or the substrate on which the sensing means is deployed. Such a strip would be removed when the user wishes to deploy the sensing means. The strip may be replaced on the sensing means to prevent subsequent exposure of material within the sensing means.
Those skilled in the art will realise that the sensing means of the present invention could be deployed in fields other than food packaging, such as the monitoring of degradable chemicals.
Claims (37)
1. Sensing means for sensing the presence of one or both of oxygen and water, wherein the sensing means comprises a material whose interactions with electromagnetic radiation change on exposure to one or both of oxygen and water.
2. Sensing means as claimed in claim I wherein exposure to one or both of oxygen and water causes a visible change in the interaction of electromagnetic radiation with the material.
3. Sensing means as claimed in either of claims I to 2 wherein the material comprises at least one species which reacts with one or both of oxygen or water.
4. Sensing means as claimed in claim 3 wherein the at least one species comprises a metal.
5. Sensing means as claimed in claim 4 wherein the metal is a transition metal.
6. Sensing means as claimed in any one of claims 3 to 5 wherein the at least one species is any one of the group consisting ofCu+, Cu+, Co+, Co3+, Ti3+, V3+, Cr2+, Ni2+, Mn2+, Fe2+ and Fe3+.
7. Sensing means as claimed in claim 6 wherein Cr2+ is in the form of any one of the group consisting of Cr (OCOCH3) 2. 2H2O and [Cr (H20) 6] complex.
8. Sensing means as claimed in claim 6 wherein Mn2+ is in the form of Mn (OH) 2.
9. Sensing means as claimed in claim 6 wherein Ni2+ is in the form of any one of the group consisting of an anhydrous nickel (II) halide or a Ni (OH) 2.
10. Sensing means as claimed in claim 6 wherein Fe is in the form of any one of the group consisting ofFe (OH) 2, a hydrated Fe (II) complex, FeO, an Fe (II) cysteine complex, an
Fe (II) hystidine complex, Fe (II) phthalocyanine tetrasulphonate, an Fe (II)- dimethylglyoxime-base complex.
11. Sensing means as claimed in claim 6 wherein CU2+ is in the form of anhydrous CUSO4.
12. Sensing means as claimed in claim 6 wherein Ti3+ is in the form of any one of the group
consisting of [TiCl2 (NH3) 4] [TiCT, TiF3, TiCh, TiBr3 and Til3.
13. Sensing means as claimed in claim 6 wherein V3+ is in the form of any one of the group consisting ofVF3, VCib, VBr3 and VI3.
14. Sensing means as claimed in claim 6 wherein Co2+ is in the form of any one of the group consisting ofCo (OH) 2, Co (phthalocyanine), anhydrous [CoCl4]2- salts, a Co (II) myoglobin complex, a Co (II) L-hystidine complex, a Co (II) salen complex, a Co (II) cysteine complex and bis (histidinoato) Co (II).
15. Sensing means as claimed in claim 6 wherein Fe is in the form of any one of the group consisting ofFe (CI04) 3. IOH20, Fe (NO3) 3. 6H2O and Fe2 (SO4) 3. 9H20.
16. Sensing means according to any one of claims I to 3 wherein the material comprises a polymer.
17. Sensing means according to claim 16 wherein the polymer comprises poly-3 alkylthiophenes.
18. Sensing means as claimed in any preceding claim wherein the sensing means further comprises containment means, the containment means being arranged so as to prevent egress of the material from the sensing means.
19. Sensing means as claimed in claim 18 wherein the containment means permits contact of water or oxygen with the material.
20. Sensing means as claimed in either of claims 18 or 19 wherein the containment means comprises a polymeric matrix in which the material is entrapped.
21. Sensing means as claimed in either of claims 18 or 19 wherein the containment means comprises a gel.
22. Sensing means as claimed in any preceding claim comprising a plurality of sensing areas, each of the said sensing areas comprising a material, which may be the same or different in each area, wherein the interactions of each of the materials with electromagnetic radiation change on exposure to one or both of oxygen and water, and wherein the changes in the interactions of at least two materials with electromagnetic radiation are mutually different when the corresponding at least two areas are exposed to substantially the same amount of oxygen and water vapour.
23. Sensing means as claimed in claim 22 wherein the at least two materials comprise mutually different reactive moieties.
24. Sensing means as claimed in either of claims 22 and 23 wherein the at least two materials are of mutually different concentrations.
25. Sensing means as claimed in any one of claims 22 to 24 wherein the at least two materials have mutually different permeabilities to one or both of water and oxygen.
26. Sensing means according to any one of claims 22 to 25, wherein each sensing area further comprises a containment means which is permeable to at least one of water and oxygen, whereby the at least two materials are each contained by containment means having mutually different permeabilities to at least one of water and oxygen.
27. Sensing means for sensing the presence of oxygen, wherein the sensing means comprises a metal-air battery and a display means, wherein the said metal-air battery comprises a first electrode that is permeable to gases, a second electrode and an electrolyte, said electrodes comprising mutually different metals and being in contact with said electrolyte and there being a potential difference between the two electrodes, wherein the display means indicates the potential difference between the two electrodes, whereby oxygen permeates the first electrode and causes the oxidation of the surface of one of the electrodes, thus
altering the potential difference between the two electrodes.
28. Sensing means as claimed in claim 27 wherein the first electrode is the cathode and the second electrode is the anode.
29. Sensing means as claimed in either of claims 27 or 28 wherein the anode comprises at least one of aluminium, magnesium, lithium and zinc.
30. Sensing means as claimed in any one of claims 27 to 29 wherein the cathode comprises carbon impregnated with a metal selected from the group of silver, cobalt, platinum and manganese.
31. Sensing means as claimed in any one of claims 27 to 30 wherein the electrolyte comprises at least one ofNaCI and a hydroxide.
32. Sensing means as claimed in any one of claims 27 to 31 wherein the display means comprises a voltmeter.
33. Sensing means as claimed in any preceding claim further comprising sealing means, said sealing means preventing unwanted exposure of the material to oxygen and water.
34. Sensing means as claimed in any preceding claim further comprising attachment means to enable attachment and positioning of the sensing means.
35. Sensing means as hereinbefore described with reference to figures I to 5.
36. Food packaging comprising at least one sensing means as claimed in any one preceding claim.
37. Food packaging as hereinbefore described with reference to figure 3.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB0027366A GB2368908A (en) | 2000-11-09 | 2000-11-09 | Exposure sensor for oxygen or water |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB0027366A GB2368908A (en) | 2000-11-09 | 2000-11-09 | Exposure sensor for oxygen or water |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB0027366D0 GB0027366D0 (en) | 2000-12-27 |
| GB2368908A true GB2368908A (en) | 2002-05-15 |
Family
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB0027366A Withdrawn GB2368908A (en) | 2000-11-09 | 2000-11-09 | Exposure sensor for oxygen or water |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2368908A (en) |
Cited By (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2006120237A1 (en) * | 2005-05-12 | 2006-11-16 | The Technical University Of Denmark | Portable and disposable solar dosimeter and oxygen sensor |
| WO2012101407A1 (en) * | 2011-01-25 | 2012-08-02 | Medical Research Council | Oxygen sensors and their uses |
| WO2012154314A1 (en) * | 2011-03-31 | 2012-11-15 | 3M Innovative Properties Company | Method and device for indicating moisture based on bis (glyoxime) -transition metal complexes |
| NL1038939C2 (en) * | 2011-07-12 | 2013-01-15 | Innovation Desk | DEVICE FOR INDICATING AN EXPIRED TIME PERIOD AND ITS USE. |
| CN101900683B (en) * | 2009-10-16 | 2013-09-04 | 北京智云达科技有限公司 | Test paper for detecting water injected meat and preparation method thereof |
| WO2013147934A1 (en) * | 2012-03-27 | 2013-10-03 | 3M Innovative Properties Company | Bis(glyoxime)-transition metal colorimetric moisture indicators |
| WO2015140797A3 (en) * | 2014-03-20 | 2015-12-03 | D.I.R. Technologies (Detection Ir) Ltd. | Method and system for determining package integrity |
| US9235194B2 (en) | 2010-01-26 | 2016-01-12 | Uwi Technology Ltd | Elapsed time indicator |
| JP2016503501A (en) * | 2012-11-14 | 2016-02-04 | スリーエム イノベイティブ プロパティズ カンパニー | Adjustable colorimetric moisture indicator |
| JP2016517527A (en) * | 2013-03-15 | 2016-06-16 | エイチズィーオー・インコーポレーテッド | Progressive moisture detector |
| JP2016173345A (en) * | 2015-03-18 | 2016-09-29 | 凸版印刷株式会社 | Oxygen indicator |
| CN113745711A (en) * | 2021-07-16 | 2021-12-03 | 北京印刷学院 | Flexible metal-air battery and application thereof |
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| WO1999030148A1 (en) * | 1997-12-05 | 1999-06-17 | Crown Cork & Seal Technologies Corporation | Shelf life indicator |
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Cited By (17)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2006120237A1 (en) * | 2005-05-12 | 2006-11-16 | The Technical University Of Denmark | Portable and disposable solar dosimeter and oxygen sensor |
| CN101900683B (en) * | 2009-10-16 | 2013-09-04 | 北京智云达科技有限公司 | Test paper for detecting water injected meat and preparation method thereof |
| US9235194B2 (en) | 2010-01-26 | 2016-01-12 | Uwi Technology Ltd | Elapsed time indicator |
| US9222925B2 (en) | 2011-01-25 | 2015-12-29 | Medical Research Council | Oxygen sensors and their uses |
| WO2012101407A1 (en) * | 2011-01-25 | 2012-08-02 | Medical Research Council | Oxygen sensors and their uses |
| US9921199B2 (en) | 2011-03-31 | 2018-03-20 | 3M Innovative Properties Company | Method for indicating moisture based on bis(glyoxime)-transition metal complexes |
| WO2012154314A1 (en) * | 2011-03-31 | 2012-11-15 | 3M Innovative Properties Company | Method and device for indicating moisture based on bis (glyoxime) -transition metal complexes |
| NL1038939C2 (en) * | 2011-07-12 | 2013-01-15 | Innovation Desk | DEVICE FOR INDICATING AN EXPIRED TIME PERIOD AND ITS USE. |
| WO2013147934A1 (en) * | 2012-03-27 | 2013-10-03 | 3M Innovative Properties Company | Bis(glyoxime)-transition metal colorimetric moisture indicators |
| CN104335040A (en) * | 2012-03-27 | 2015-02-04 | 3M创新有限公司 | Bis(glyoxime)-transition metal colorimetric moisture indicators |
| JP2016503501A (en) * | 2012-11-14 | 2016-02-04 | スリーエム イノベイティブ プロパティズ カンパニー | Adjustable colorimetric moisture indicator |
| EP2973474A4 (en) * | 2013-03-15 | 2016-11-09 | Hzo Inc | Progressive moisture detection |
| JP2016517527A (en) * | 2013-03-15 | 2016-06-16 | エイチズィーオー・インコーポレーテッド | Progressive moisture detector |
| WO2015140797A3 (en) * | 2014-03-20 | 2015-12-03 | D.I.R. Technologies (Detection Ir) Ltd. | Method and system for determining package integrity |
| JP2016173345A (en) * | 2015-03-18 | 2016-09-29 | 凸版印刷株式会社 | Oxygen indicator |
| CN113745711A (en) * | 2021-07-16 | 2021-12-03 | 北京印刷学院 | Flexible metal-air battery and application thereof |
| CN113745711B (en) * | 2021-07-16 | 2024-03-29 | 北京印刷学院 | Flexible metal-air battery and application thereof |
Also Published As
| Publication number | Publication date |
|---|---|
| GB0027366D0 (en) | 2000-12-27 |
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| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |