Ph sensor, method of manufacturing such a sensor, and method of measuring ph using such a sensor

Abstract

The invention relates to a pH sensor comprising: - a substrate (1); - a semiconducting layer (2); - a layer sensitive to hydrogen ions (2a) covering the semiconducting layer; - a source (3) and a drain (4) in ohmic contact with the semiconducting layer (2); characterized in that the layer sensitive to hydrogen ions (2a) consists of molecules comprising groups capable of generating and / or capturing hydrogen ions, said molecules being bonded to the semiconducting layer (2) by non-covalent interactions, thereby forming a molecular assembly.

Description

Technical Field

[0001] This invention relates to improvements in ion-sensitive field-effect transistors (ISFETs) used as pH sensors and methods for manufacturing such sensors. The invention also relates to methods for measuring the pH of solutions using such sensors. Background Technology

[0002] There are many applications that require measuring the pH of aqueous solutions.

[0003] Various sensors have been developed to perform such measurements.

[0004] Electrochemical probes consist of a reference electrode with a known potential and a measuring electrode with a potential dependent on pH, designed to contact the solution to be analyzed. pH measurement is based on the measurement of the potential difference between the two electrodes. However, these probes require complex electronics and are relatively fragile.

[0005] There are also ISFET-type pH sensors. An ISFET sensor is a field-effect transistor used to measure the concentration of ions in a liquid or solution. An ISFET sensor typically includes: an ion-sensitive layer having a surface in contact with the solution and an opposing surface in contact with a channel located between the drain and source electrodes; and a reference electrode (or gate) in contact with the solution. When the H+ in the solution... + or OH - When the concentration of ions changes, the current flowing through the channel changes accordingly. Summary of the Invention

[0006] The purpose of this invention is to improve the performance of ISFET-type pH sensors by means of a method that is easy to implement and improves the sensor’s sensitivity and stability while making it behave as linearly as possible over a wide pH range.

[0007] Therefore, the present invention proposes a pH sensor comprising:

[0008] - Substrate;

[0009] - Semiconductor layer;

[0010] - A hydrogen ion-sensitive layer covering the semiconductor layer;

[0011] - The source and drain electrodes that are in ohmic contact with the semiconductor layer;

[0012] The hydrogen ion sensitive layer is characterized in that it comprises molecules containing groups capable of generating and / or capturing hydrogen ions, the molecules being bonded to the semiconductor layer via non-covalent interactions to form a molecular assembly. The molecules containing groups capable of generating and / or capturing hydrogen ions comprise at least two distinct groups capable of generating and / or capturing hydrogen ions, the pKa of which are separated from each other by at least one pH unit, preferably by two to six pH units.

[0013] Specifically, the hydrogen ion sensitive layer is through - Stacked self-assembly layers. This enables the obtaining of stable assemblies with semiconductor layers without structural modifications to those layers, and allows the preservation of the inherent properties of the semiconductor layers.

[0014] Furthermore, the properties of the hydrogen ion-sensitive layer can be easily adjusted to change the linear region according to the pH range required by the sensor.

[0015] Based on other advantageous but optional features of the sensor:

[0016] - Different groups capable of generating and / or capturing hydrogen ions may be carried by the same molecule or by separate molecules;

[0017] - The sensor further includes a gate that is electrically isolated from the sensitive layer and has a free surface suitable for contacting the solution to be analyzed;

[0018] - The gate is arranged on the substrate at a certain distance from the sensitive layer, such that the semiconductor layer, source, drain and gate together form a liquid gate field-effect transistor, and the semiconductor layer forms the channel of the transistor;

[0019] - The gate is covered with a hydrogen ion sensitive layer, which is composed of molecules containing groups capable of generating and / or capturing hydrogen ions, and the molecules are bonded to the gate through non-covalent interactions to form a molecular assembly;

[0020] - The semiconductor layer comprises a single layer of graphene or several stacked single layers of graphene;

[0021] - The semiconductor layer comprises one or more molybdenum disulfide monolayers;

[0022] - Molecules containing groups capable of generating and / or capturing hydrogen ions are monocyclic aromatic molecules, polycyclic aromatic molecules, monocyclic heteroaromatic molecules, polycyclic heteroaromatic molecules, or mixtures thereof;

[0023] - The group capable of generating and / or capturing hydrogen ions is selected from carboxylic acids, boric acids, sulfonic acids, pyridines, amines and mixtures thereof;

[0024] - Molecules containing groups capable of generating and / or capturing hydrogen ions are selected from aniline, porphyrin, porphyrin, pyrene-1-boronic acid, 1-pyrenebutyric acid, 1-aminopyrene, phthalocyanine and mixtures thereof;

[0025] - The sensor also includes a dialysis membrane arranged opposite to the hydrogen concentration-sensitive layer to protect the layer from contamination by microorganisms or protein membranes;

[0026] - The sensor also includes an absorbent pad disposed on the side of the semiconductor layer opposite to the hydrogen ion sensitive layer and an aperture formed in the semiconductor layer to circulate the solution to be analyzed in the absorbent pad via capillary action.

[0027] Another aspect of the invention relates to a method for manufacturing the sensor. The method includes:

[0028] - A molecular assembly is formed between a semiconductor layer and a molecule containing a group capable of generating and / or capturing hydrogen ions, the molecule being connected to the semiconductor layer via non-covalent interactions, thereby forming a hydrogen ion sensitive layer on the semiconductor layer;

[0029] - Two conductive tracks are formed that are far apart from each other and make ohmic contact with the semiconductor layer in order to form the source and drain.

[0030] The method may further include forming a gate electrically isolated from the semiconductor layer, the gate having a free surface suitable for contacting the solution to be analyzed.

[0031] Another aspect of the present invention relates to a method for measuring the pH of a solution using the sensor described above. The method includes:

[0032] - Make the solution come into contact with the free surface of the sensor's sensitive layer.

[0033] - Apply a potential difference between the source and the drain to allow current to flow through the semiconductor layer.

[0034] - Measure the changes in the electrical properties of the semiconductor layer.

[0035] - The pH of the solution is determined by the change in the electrical properties.

[0036] In some implementations, the property is the conductivity of the semiconductor layer.

[0037] In other embodiments, the electrical property is the offset on the conductivity variation curve of the sensitive semiconductor layer as a function of the gate voltage, where conductivity is at its minimum.

[0038] The application of this invention relates to a flexible patch incorporating a sensor as described above. The patch comprises a polymer membrane having an inner surface suitable for contact with food, skin, or cellular tissue. A pH sensor is disposed on the inner surface such that a free surface of a hydrogen ion concentration-sensitive layer contacts the food, skin, or cellular tissue to measure the pH of the food, skin, or cellular tissue.

[0039] Another application of the invention relates to a device for monitoring pH in a water tank or circuit, the device incorporating the sensor described above. Attached Figure Description

[0040] Other features and advantages of the invention will become apparent from the following detailed description with reference to the accompanying drawings, in which:

[0041] - Figure 1 This is a schematic cross-section of the pH sensor according to the first embodiment;

[0042] - Figure 2 This is a schematic cross-section of the pH sensor according to the second embodiment;

[0043] - Figure 3 This is a schematic cross-section of the pH sensor according to the third embodiment;

[0044] - Figure 4 It shows Figure 3 A cross-sectional view of the sensor at the hydrogen ion-sensitive layer protected by the dialysis membrane;

[0045] - Figure 5 This is a graph illustrating the change in conductivity of the sensitive semiconductor layer of a sensor based on the first principle of pH measurement.

[0046] - Figure 6 An example is shown where the change in resistance of a semiconductor layer as a function of time is measured.

[0047] - Figure 7 It is a graph showing the shift of the charge neutral point (i.e., the gate voltage with minimum conductivity) on the field-effect curve (the curve showing the change in conductivity of the sensitive semiconductor layer as a function of the gate voltage).

[0048] - Figure 8 This is a cross-sectional view of a sensor with an absorption pad.

[0049] - Figure 9 This is a graph illustrating the shift of the charge neutral point of a PBA1-functionalized graphene layer with pH (not based on the present invention).

[0050] - Figure 10This is a graph illustrating the shift of the charge neutral point of a PBA2-functionalized graphene layer with pH (not based on the present invention).

[0051] - Figure 11 This is a graph illustrating the shift of the charge neutral point of the graphene layer functionalized according to the present invention as a function of pH.

[0052] - Figure 12A , 12B 12C and 12D are graphs showing the shift of the charge neutral point with pH in the presence and absence of bovine serum albumin (BSA) in the solution to be analyzed, with and without a dialysis membrane.

[0053] For readability reasons, the accompanying figures are not necessarily drawn to scale. Detailed Implementation

[0054] Sensor Structure

[0055] The sensor comprises: a semiconductor material layer supported by a substrate; a pH detection layer, which is sensitive to hydrogen ions, self-assembled on the semiconductor material, and designed to be exposed to the solution to be analyzed; and electrical contacts located at opposite ends of the semiconductor material layer to allow current to flow through the semiconductor layer. Therefore, the sensor has the form of an ISFET.

[0056] substrate

[0057] The substrate acts as a mechanical support for the ISFET.

[0058] In a preferred embodiment, the substrate is in the form of a thin, flexible film that can deform to conform to the geometry of the medium whose pH is to be measured. Herein, “flexible” means that the substrate can be bent in at least two orthogonal directions without breaking or being damaged. The flexibility of the substrate is advantageously selected based on the properties of the transistor’s electrical contacts so as not to subject these contacts to bending or torsional stresses that would easily damage them.

[0059] In a particularly advantageous manner, the substrate can therefore be formed from one of the following materials: parylene (poly(p-xylene)), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyimide, polyamide-imide (PAI), poly-2,2'-(m-phenylene)-5,5'-bibenzimidazole, or an elastomer such as thermoplastic polyurethane (TPU).

[0060] The substrate can typically have a thickness of about 1 to 125 micrometers, which makes it particularly well-suited for roll-to-roll methods of manufacturing sensors by lamination, as described below.

[0061] In other embodiments, particularly when sensor flexibility is not required, the substrate can take the form of a rigid layer, which can be relatively thick. In this case, the substrate can be made of one of the following materials: alumina, sapphire, silicon nitride, silicon carbide, silicon, quartz, or glass.

[0062] An intermediate layer can be disposed between the substrate and the semiconductor layer. Particularly advantageously, the intermediate layer is a flexible conformal coating, such as poly(p-xylene) or copolymers thereof containing chlorinated substituted units on the benzene rings or CF2 linking units between each benzene ring, polyimide, polyamide, polyamide-imide, silicone polymer, acrylic, epoxy, polyurethane, or styrene rubber copolymer.

[0063] semiconductor layer

[0064] According to a preferred embodiment, the semiconductor layer comprises or is composed of graphene. The semiconductor layer may comprise a single graphene monolayer or a plurality of stacked graphene monolayers; in other words, a multilayer consisting of a stack of a plurality of graphene monolayers is typically a stack comprising 2 to 7 graphene layers.

[0065] Graphene is an advantageous material due to its electronic properties, particularly the high mobility of its charge carriers, its stable crystal structure (without native oxides on its surface), and the thickness of its ultrathin layers. Furthermore, its biocompatibility and transparency make it particularly beneficial for applications in the health, cosmetics, and food industries.

[0066] In another embodiment, the semiconductor layer comprises or is composed of molybdenum disulfide (MoS2). Like graphene, molybdenum disulfide has a two-dimensional structure. The semiconductor layer may comprise one or more molybdenum disulfide monolayers.

[0067] The semiconductor layer can be encapsulated as a single layer of hexagonal boron nitride (h-BN) or as a stack of multiple layers of hexagonal boron nitride. Hexagonal boron nitride is actually a material with a structure close to that of graphene, possessing a smooth, charge-free surface. Furthermore, this material is biocompatible. Therefore, it allows for the protection and preservation of the sensor's properties, resulting in improved performance.

[0068] In another embodiment, the semiconductor layer comprises silicon coated with a hexagonal boron layer or is composed of silicon coated with a hexagonal boron layer.

[0069] Other semiconductor materials can be used, as long as they can pass through... - Simply stack and bond them to a layer that is sensitive to hydrogen ion concentration.

[0070] Hydrogen ion sensitive layer

[0071] The hydrogen ion sensitive layer is composed of molecules containing groups capable of generating and / or capturing hydrogen ions. Therefore, the hydrogen ion sensitive layer is sensitive to the concentration of hydrogen ions in the medium in which the sensor is intended to operate.

[0072] Molecules containing groups capable of generating and / or capturing hydrogen ions are bonded to a semiconductor layer via non-covalent interactions, thereby forming a molecular assembly. Therefore, a hydrogen ion-sensitive layer formed by molecules containing groups capable of generating and / or capturing hydrogen ions is disposed on the surface of the semiconductor layer and bonded to it in a non-covalent manner. In other words, it can be said that the semiconductor layer is non-covalently functionalized by molecules containing groups capable of generating and / or capturing hydrogen ions.

[0073] Non-covalent interactions are typically - Stacked, usually referred to as Stacking. Therefore, layers sensitive to hydrogen ion concentration are typically formed by layers deposited on the surface of semiconductor layers via... - The accumulation of molecular assemblies forms.

[0074] Since semiconductor materials are inherently insensitive to hydrogen ion concentration, molecular assemblies can provide sensitivity to pH, or more precisely, sensitivity to pH changes, thereby altering the charge on the surface of the semiconductor layer.

[0075] Molecules containing groups capable of generating and / or capturing hydrogen ions are typically monocyclic aromatic molecules, polycyclic aromatic molecules, monocyclic heteroaromatic molecules, polycyclic heteroaromatic molecules, or mixtures thereof. It should be understood that these molecules can be natural molecules carrying groups capable of generating and / or capturing hydrogen ions, or they can be functionalized with groups capable of generating and / or capturing hydrogen ions.

[0076] Polycyclic molecules can contain two, three, four, five, six, or even more aromatic rings, such as 2 to 10 aromatic rings, which may be fused together. Polycyclic molecules may further contain non-aromatic rings.

[0077] Polycyclic aromatic molecules typically contain 10 to 40 carbon atoms, or even 14 to 32 carbon atoms.

[0078] The aromatic molecules preferably contain 1, 2, 3, 4, 5, 6 or 10 aromatic rings.

[0079] A heteroaromatic molecule contains one or more aromatic rings, which in addition to carbon atoms contain at least one heteroatom, preferably one to four heteroatoms, such as one or more sulfur, oxygen or nitrogen atoms or a mixture thereof.

[0080] Aromatic molecules are typically selected from benzene, naphthalene, anthracene, phenanthrene, etc. , pyrene, benzo[a]tetraphenyl, benzo[a]phenanthrene, benzo[a]pentaphenyl, benzo[a]pyrene, cyclohexene, cyclohexene, cyclohexene and mixtures thereof.

[0081] Polycyclic aromatic molecules can be selected from porphyrins, porphyrins and mixtures thereof.

[0082] The groups capable of generating or capturing hydrogen ions can be selected from carboxylic acids, boric acids, sulfonic acids, pyridines, amines, and mixtures thereof.

[0083] Molecules containing groups capable of generating and / or capturing hydrogen ions are typically selected from aniline, porphyrin, porphyrin, pyrene-1-boronic acid, 1-pyrenebutyric acid, 1-aminopyrene, phthalocyanine and mixtures thereof.

[0084] A molecule containing a group capable of generating and / or capturing hydrogen ions typically comprises at least two distinct groups capable of generating and / or capturing hydrogen ions, wherein the pKa of these groups is separated from each other by at least one pH unit, preferably by two to six pH units. The distinct groups capable of generating and / or capturing hydrogen ions can be carried by the same molecule or by separate molecules.

[0085] Therefore, in some embodiments, the molecular assembly comprises (or the molecule comprising a group capable of generating and / or capturing hydrogen ions comprises) at least one first molecule comprising a group capable of generating or capturing hydrogen ions and at least one second molecule comprising a group capable of generating or capturing hydrogen ions, wherein the pKa of the groups of the first and second molecules are separated from each other by at least 1 pH unit, preferably by 2 to 6 pH units.

[0086] In some embodiments, when the groups capable of generating and / or capturing hydrogen ions are carried by the same molecule, the molecular assembly comprises (or the molecule containing the groups capable of generating and / or capturing hydrogen ions comprises) at least one (first) molecule containing at least two groups capable of generating or capturing hydrogen ions, the pKa of the groups of the (first) molecule being separated from each other by at least 1 pH unit, preferably by 2 to 6 pH units. In these embodiments, the molecular assembly may further comprise a second molecule containing at least one group capable of generating or capturing hydrogen ions, or even further comprise two or three different molecules containing at least one group capable of generating or capturing hydrogen ions. In these embodiments, the pKa of the different groups capable of generating or capturing hydrogen ions are separated from each other by at least 1 pH unit, preferably by 2 to 6 pH units.

[0087] electrode

[0088] The sensor further includes two conductive tracks that are in ohmic contact with the semiconductor layer. The two tracks are arranged at two opposite ends of the semiconductor layer and form the source and drain.

[0089] The source and drain electrodes can be formed from solidified conductive ink, which typically contains one or more forms of carbon (e.g., carbon black or graphene), silver, gold, copper, platinum, palladium, or alloys of these metals contained in an organic binder. The advantage of such ink is that it adheres well to the substrate and can withstand a certain degree of bending and / or torsional deformation, allowing the use of flexible substrates.

[0090] The electrodes are connected to a power source, such as a cell or battery (not shown), such that current can flow in the semiconductor layer when a sufficient potential difference is applied between the source and drain.

[0091] The electrode can be isolated from the sensor's external environment, and especially from the solution to be analyzed, by an insulating varnish (such as epoxy varnish, polyurethane varnish, or silicone varnish).

[0092] In a particularly advantageous manner, the electrodes can be isolated from the external environment by an encapsulation film, which can be formed from one of the following materials: polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyimide, polyamide-imide (PAI), poly-2,2'-(m-phenylene)-5,5'-bibenzimidazole, or an elastomer such as thermoplastic polyurethane (TPU). The encapsulation film can typically have a thickness of approximately 25 to 125 micrometers, making it particularly well-suited for methods of manufacturing sensors by lamination, as described below.

[0093] The encapsulation film is advantageously coated with a hot melt adhesive on its substrate-facing surface. The hot melt adhesive may be ethylene vinyl acetate (EVA), silicone elastomer, or reactive polyurethane (RPU).

[0094] Advantageously, but optionally, the sensor further includes a reference electrode having a free surface suitable for contact with the solution to be analyzed and disposed at a distance from the semiconductor channel. The reference electrode is configured to apply a reference voltage to the solution to be analyzed.

[0095] The reference electrode can be arranged on the same substrate as the semiconductor layer and thus extend in the same plane.

[0096] Alternatively, the reference electrode can extend in a plane parallel to the plane of the semiconductor layer. For example, the reference electrode can be arranged facing the semiconductor layer and spaced apart from the layer by the thickness of the solution to be analyzed. Thus, the reference electrode and the semiconductor layer can be integrated into a fluidic channel in which a sample of the solution to be analyzed is circulated.

[0097] In other configurations, the reference electrode can be separate from the sensor and placed in the solution to be analyzed near the hydrogen ion-sensitive layer. This electrode thus forms a liquid gate on the transistor channel.

[0098] The reference electrode can be formed from a metal layer, conductive ink, one or more graphene monolayers, or a combination of these materials.

[0099] In some implementations, the free surface of the reference electrode may have the same functionalization as the semiconductor layer.

[0100] Optionally, the sensor further includes a rear gate electrode (not shown) disposed between the substrate and the semiconductor layer and electrically isolated from the semiconductor layer by an electrical insulating layer. The primary purpose of the rear gate in the transistor is to modulate the conductivity of the semiconductor layer and to position the transistor at an optimal operating point (where conductivity changes most maximally with respect to the gate potential without interfering with the potential of the liquid gate).

[0101] Then, the sensor is constructed as a field-effect transistor, which can be used to measure H in the solution. + or OH - The concentration of ions. When the H+ in the solution... + or OH - When the concentration of ions changes, the current flowing through the channel changes accordingly.

[0102] Figures 1 to 3 Various non-limiting configurations of the pH sensor are shown.

[0103] Figure 1 This is a schematic cross-section of the pH sensor according to the first embodiment.

[0104] The sensor includes a substrate 1 on which a semiconductor layer 2 is disposed, the semiconductor layer 2 being covered by a layer 2a sensitive to hydrogen ion concentration. As described above, an intermediate layer (not shown) may be disposed between the semiconductor layer and the substrate.

[0105] Two conductive tracks 3 and 4, which are in ohmic contact with the semiconductor layer 2, form the source and drain, respectively.

[0106] The electrodes are isolated from the external environment of the sensor by an encapsulation film 5. The film has at least one opening 5a that exposes at least a portion of the free surface 2a of the sensitive layer, allowing the free surface 2a to come into contact with the solution S to be analyzed, while the solution does not come into contact with the source and drain electrodes.

[0107] Figure 2 This is a cross-sectional schematic diagram of the pH sensor according to the second embodiment. Due to... Figure 1 The same reference numerals in the figures indicate the same elements or perform the same function.

[0108] and Figure 1 Compared to sensors, Figure 2 The sensor further includes a gate 6 disposed on a substrate at a distance from the sensitive semiconductor layer 2. The gate is partially encapsulated in an encapsulation layer, however, the encapsulation layer includes an opening 5b, which differs from the opening 5a formed facing the sensitive layer 2, and exposes the free surface 6a of the gate. Therefore, both the hydrogen ion sensitive layer and the gate (which also forms a reference electrode) are in contact with the solution S to be analyzed.

[0109] Figure 3 This is a cross-sectional schematic diagram of the pH sensor according to the third embodiment. Due to... Figure 1 and 2 The same reference numerals in the figures indicate the same elements or perform the same function.

[0110] and Figure 2 Compared to sensors, Figure 3 The sensor further includes a hydrogen ion-sensitive layer 6a covering the gate 6. This functionalization of the gate allows for amplification of the sensor's response signal.

[0111] In addition, the hydrogen ion sensitive layer 2a is covered with a dialysis membrane 7, the advantages of which will be detailed below.

[0112] Methods for producing sensors

[0113] The pH sensor according to the present invention can be obtained by a manufacturing method comprising the following steps:

[0114] - A hydrogen ion-sensitive layer is formed on one surface of a semiconductor layer by contacting the surface with molecules containing groups capable of generating and / or capturing hydrogen ions;

[0115] - A semiconductor layer covered by the sensitive layer is placed on a substrate, such that the sensitive layer is opposite to the substrate.

[0116] - Two far-away conductive tracks are formed that are in ohmic contact with the sensitive layer, thus forming the source and drain.

[0117] - Optionally, a third conductive track is formed on the substrate to form a gate.

[0118] - Optionally, before placing the semiconductor layer on the substrate, a fourth conductive track is formed on the substrate to form a post-gate electrode, and an electrically insulating layer is inserted between the fourth conductive track and the sensitive semiconductor layer.

[0119] - Optionally, a protective layer, such as a dialysis membrane, is deposited on the hydrogen ion-sensitive layer.

[0120] - The encapsulation layer is placed on the substrate to completely surround the source and drain; as described above, the encapsulation layer has at least one opening facing the semiconductor layer to expose the free surface of the sensitive layer, and, if necessary, an opening facing the gate to expose its free surface.

[0121] The protective layer isolates the hydrogen ion-sensitive layer from any macromolecules or enzymes that might react with it. Dialysis membranes can be made of cellulose acetate, polysulfone, polyethersulfone, polyacrylonitrile, etc. Or it can be made from porous poly(p-xylene).

[0122] Figure 4 It shows Figure 3 The sensor is shown in a cross-sectional view at opening 5a. The semiconductor layer 2 extends over an intermediate layer 2b, for example, made of parylene, which provides a connection between the semiconductor layer and the substrate.

[0123] A dialysis membrane 7 is disposed on a hydrogen ion-sensitive layer 2a, which is separated from the ion by a thin layer of liquid or hydrogel. For this purpose, the membrane is wetted in deionized water.

[0124] As shown in Example 5, the dialysis membrane prevents the hydrogen ion sensitive layer from being contaminated by microorganisms or protein membranes by allowing the ion balance of the liquid in immediate vicinity of the sensor to be maintained while protecting it from adsorption by microorganisms or proteins.

[0125] Lamination methods are particularly well-suited for assembling sensors. For this purpose, the encapsulation layer is advantageously coated with a hot-melt adhesive that flows during lamination and ensures a fluid seal between the free surfaces of the semiconductor layers and the source and drain electrodes. However, any other assembly process can be implemented.

[0126] Typically, forming a hydrogen ion-sensitive layer on a surface of a semiconductor layer via molecular assembly can be performed according to the following steps:

[0127] - Contact one surface of the semiconductor layer with a solution containing molecules that include groups capable of generating and / or capturing hydrogen ions;

[0128] - Rinse with the solvent of the solution;

[0129] Rinse with deionized water.

[0130] The molecule containing groups capable of generating and / or capturing hydrogen ions is as described above.

[0131] The solvent used to prepare the contact solution can be any polar solvent capable of dissolving molecules containing groups capable of generating and / or capturing hydrogen ions. For example, the solvent can be dimethylformamide, dimethyl sulfoxide, or mixtures thereof.

[0132] Methods for measuring pH

[0133] The general principle of pH measurement using sensors is to measure the change in the electrical properties of a semiconductor layer affected by pH. A potential difference is applied between the source and drain to allow current to flow between them.

[0134] The electrical properties under consideration can vary depending on the sensor's structure and its control mode.

[0135] When the sensor does not have a gate (e.g.) Figure 1 As shown), the electrical property is the conductivity of the semiconductor layer, which corresponds to the intensity of the current flowing between the source and drain (usually expressed as I). ds The ratio between the source and drain, and the potential difference applied between the source and drain.

[0136] Therefore, the sensor can be used as a chemiresistor.

[0137] Figure 5 The principle of measuring the conductivity of a semiconductor layer as a function of time (chronoamperometry) is shown, demonstrating the change in conductivity when the solution to be analyzed comes into contact with the layer.

[0138] Figure 6 An example is shown where the change in resistance R (in %) of a semiconductor layer as a function of time t (in seconds) is measured. The corresponding pH values ​​are plotted at different points on the curve. The sensor was first rinsed with deionized water, then with a pH 6 buffer.

[0139] Add 500 μL of the pH 6 buffer to each opening, remove 400 μL, and leave 100 μL for electrical measurement.

[0140] After 300 seconds (5 minutes, pH 6a measurement), 400 μL of pH 7 buffer was added, the mixture was homogenized, and 400 μL was removed, leaving 100 μL for electrical measurement.

[0141] After 300 seconds (pH 7a measurement), 400 μL of pH 8 buffer was added and the mixture was homogenized. Then, 400 μL was removed, leaving 100 μL for electrical measurement.

[0142] After 300 seconds (pH 8 measurement), 400 μL of pH 7 buffer was added and the mixture was homogenized. Then, 400 μL was removed, leaving 100 μL for electrical measurement.

[0143] After 300 seconds (pH 7b measurement), 400 μL of pH 6 buffer was added and the mixture was homogenized. Then, 400 μL was removed, leaving 100 μL for electrical measurement (pH 6b).

[0144] The resistance changes are the same for pH 6a and pH 6b. The same applies to those for pH 7a and pH 7b.

[0145] The measurement principle can also be used when the sensor includes a rear gate electrode, which is subjected to a constant voltage.

[0146] When a gate is present, the field effect can be used to measure the pH of the solution being analyzed.

[0147] In fact, even if the gate is far from the semiconductor layer, the current flow in the semiconductor layer can be affected by applying a voltage to the gate.

[0148] As described above, the free surfaces of the semiconductor layer and the gate are exposed to the solution to be analyzed through openings formed in the encapsulation layer.

[0149] A double electrolytic layer is formed, that is, charged particles accumulate at the interface between the gate and the solution being analyzed (which is an electrolytic solution). Ions in the solution are attracted to the free surface of the gate, forming a positively charged layer and a negatively charged layer.

[0150] When a positive voltage is applied to the gate, the positive charge in the double electrolytic layer is attracted to the gate, causing depletion of charge carriers in the channel. This reduces conductivity and turns off the transistor, thus preventing current flow.

[0151] Conversely, applying a negative voltage to the gate attracts negative charges, thereby creating an accumulation of charge carriers in the channel. This increases conductivity and activates the transistor, allowing current to flow.

[0152] Therefore, the double electrolytic layer acts as a switch to control the conductivity of the channel: by changing the charge distribution within the electrolytic double layer through applying a voltage to the gate, the transistor can be turned on or off, thus allowing the current to be regulated.

[0153] As the voltage applied to the gate (denoted as V) gThe curve of the current between the source and drain as a function of the voltage (denoted as V) is shown. D The voltage has a minimum value, also known as the charge neutral point or Dirac offset point. Voltages below the charge neutral point favor hole conduction in the channel, while voltages above the charge neutral point favor electron conduction in the channel.

[0154] It has been demonstrated that the charge neutral point depends on the pH of the solution being analyzed. Therefore, the pH of the solution can be determined by measuring the shift of the charge neutral point under the influence of contact with the solution being analyzed.

[0155] The principle is shown in Figure 7 In the figure, it shows the voltage V applied to the gate for two different pH solutions. g The drain-source current curve of the function I ds (Also known as the field-effect curve). A shift of D was observed. S =V D2 -V D1 V D1 and V D2 It is the minimum value of each corresponding curve. This offset D S It changes linearly with pH.

[0156] Therefore, the sensor can be considered as an ISFET, with its channel functionalized by an assembly that ensures measurement stability and linearity over a wide pH range.

[0157] application

[0158] This sensor can be used in a variety of applications that require measuring the pH of a solution.

[0159] These applications include cosmetics, healthcare, environmental monitoring, precision agriculture, the food industry, and scientific research.

[0160] patch

[0161] Due to its flexibility and biocompatibility, a particularly advantageous application of the sensor is in the form of a patch designed to be applied to an individual's skin, cellular tissue, or food to monitor its pH.

[0162] The patch comprises at least one polymer film having an inner surface and an outer surface.

[0163] The inner surface is designed to be applied against a medium from which its pH needs to be measured. Optionally, a portion of the inner surface has an adhesive area, allowing the patch to adhere to the medium from which its pH needs to be measured.

[0164] The outer surface of the polymer film can be fluid-sealed and can have an area containing a pressure-sensitive adhesive layer for attaching the patch to the skin.

[0165] A pH sensor is positioned on the inner surface of the polymer membrane, allowing the free surface of the hydrogen ion-sensitive layer to come into contact with the food, skin, or cellular tissue.

[0166] Therefore, patches allow for continuous monitoring of the pH of chronic wounds. Chronic wounds are often prone to complications and delayed healing due to local pH imbalances. Wound pH is a particularly relevant indicator of wound condition. For example, infected wounds have an increased pH.

[0167] Therefore, using pH sensors integrated into the patch to monitor the pH of chronic wounds offers significant benefits to healthcare professionals and patients, as real-time monitoring of the pH of these wounds allows for accurate assessment of wound condition and rapid adjustment of treatment plans.

[0168] Advantageously, the sensor can be integrated with an absorbent pad for circulating the solution in contact with the sensor via capillary action.

[0169] Figure 8 An embodiment of a sensor with such a buffer solution incorporated at a window is shown, through which the hydrogen ion sensitive layer is exposed to the solution to be analyzed.

[0170] For example, an absorbent pad 8 made of cellulose, cotton, or any other hydrophilic material is disposed between the substrate 1 and the semiconductor layer 2. In the example shown, the semiconductor layer 2 is disposed on an intermediate layer 2b, which, if the semiconductor layer is made of graphene, is, for example, parylene. The absorbent pad is then inserted between the substrate 1 and the intermediate layer 2b. Purely for illustration, the absorbent pad in the agarose gel can have a thickness of approximately 0.3 mm to 1 mm.

[0171] An aperture 9 extends through the semiconductor layer 2 and the intermediate layer 2b to create a fluid connection between the sensor's free surface (i.e., the hydrogen ion sensitive layer 2a) and the absorber pad 8. The aperture 9 typically has a diameter between 50 μm and 500 μm.

[0172] The solution to be analyzed can then be circulated through the capillary action in the orifice 9 and the absorbent pad 8.

[0173] In the case of wound monitoring, this cycle allows the pH of the exudate to be measured as it leaves the wound, thus enabling faster detection of changes in the wound.

[0174] In cosmetics, patches can be applied to healthy skin to measure its acidity.

[0175] In the food industry, patches can be applied to food to monitor its storage status.

[0176] Device for monitoring pH in tanks or water circuits

[0177] pH sensors can be arranged such that the sensitive layer is in contact with the liquid medium, for example by placing the sensor on a side opening of a tank or water pipe.

[0178] Example

[0179] The following examples illustrate the subject matter of the invention in a non-limiting manner.

[0180] Comparative Example 1

[0181] In this example, the graphene semiconductor layer of the pH sensor is functionalized on its free surface by a molecular assembly consisting only of 1-pyrenebutyric acid (PBA1) with a pKa of 4.7.

[0182] The sensitive layer is prepared according to the following scheme:

[0183] 1) Prepare a 10 mM (mmol / L) solution of PBA1 in dimethylformamide (DMF);

[0184] 2) Clean the free surface of the graphene layer with deionized (DI) water to remove any impurities;

[0185] 3) Deposit a PBA1 solution (10 mM) on a graphene surface (4.5 μL);

[0186] 4) Rinse with DMF, then rinse with a buffer solution, and then dry with pressurized air.

[0187] 5) Rinse twice in DI water to remove free PBA1.

[0188] The electrical properties of the thus prepared sensitive layer were calibrated by sequential immersion in buffer solutions at different pH values ​​(6, 7, 8, then back to 7 to assess possible hysteresis). The sensitive layer was rinsed with deionized water between each measurement. The buffers used were 1X PBS reconstituted from monohydrogen phosphate and dihydrogen phosphate solutions at pH 6.0, 7.0, and 0.0, with a conductivity of 15 mS / cm. The measuring instrument was a GrapLab1: a DC current and gate voltage were applied, and the channel voltage or resistance as a function of the gate voltage was measured.

[0189] Figure 9 The Dirac shift of the charge neutral point as a function of pH is shown. S (in mV). A significant asymmetry was observed between acidic and alkaline pH values. The sensor exhibits high sensitivity of approximately 80 mV / pH at acidic pH, allowing for accurate and reactive detection within this pH range. However, for alkaline pH, the sensitivity is very low, approximately 25 mV / pH, which limits the sensor's ability to accurately detect pH changes within this range.

[0190] Therefore, functionalizing the surface of the semiconductor layer with PBA1 alone does not allow for a wide range of sensitivity to pH changes.

[0191] Comparative Example 2

[0192] In this example, the graphene semiconductor layer of the pH sensor is functionalized on its free surface by a molecular assembly consisting of pyrene-1-boronic acid (PBA2) with a pKa of 8.8.

[0193] The preparation of the sensitive layer and the testing of its electrical properties were carried out in the same manner as in Example 1.

[0194] Figure 10 The Dirac shift of the charge neutral point as a function of pH is shown. S (in mV). A significant asymmetry was observed between acidic and alkaline pH values. The sensor exhibits high sensitivity of approximately 65 mV / pH at alkaline pH, allowing for accurate and reactive detection within this pH range. However, for acidic pH, the sensitivity is very low, approximately 35 mV / pH, which limits the sensor's ability to accurately detect pH changes within this range.

[0195] Therefore, functionalizing the surface of a semiconductor layer with PBA2 alone does not allow for a wide range of sensitivity to pH changes.

[0196] According to Embodiment 3 of the present invention

[0197] In this example, the graphene semiconductor layer of the pH sensor according to the invention is functionalized on its free surface by a molecular assembly combining 1-pyrenebutyric acid (PBA1) and pyrene-1-boronic acid (PBA2).

[0198] The preparation of the sensitive layer and the testing of its electrical properties were carried out in the same manner as in Example 1, except that the 10 mM solution in DMF was an equimolar mixture of PBA1 and PBA2.

[0199] Figure 11 The Dirac shift of the charge neutral point as a function of pH is shown. S (in mV). Perfect symmetry between acidic and alkaline pH values ​​was observed in the results. Furthermore, a hysteresis of only 2 mV was observed at pH 7.0, demonstrating the high stability and accuracy of the pH sensor according to the invention.

[0200] The sensor also has good sensitivity, characterized by a value of about 75 mV / pH, which corresponds to the linear and sensitive response of the pH sensor according to the invention within this specific range.

[0201] Therefore, the bifunctionalization of PBA1 and PBA2 according to the present invention makes it possible to obtain approximately 75% for both acidic and alkaline pH values. Sensitivity of 5 mV / pH. This functionalization pathway has been shown to be effective in terms of sensitivity and allows for linear and accurate responses across the entire pH range.

[0202] Example 4: Study on pH sensor preservation

[0203] Five pH sensors were produced from the same batch of graphene and functionalized according to the method described in Example 3.

[0204] The five sensors were then placed in a plastic box and stored at room temperature (i.e., between 20 and 25°C). Measurements were performed biweekly. It appeared that the sensor characteristics (sensitivity, linearity, and hysteresis) did not change significantly after six weeks of storage.

[0205] Therefore, the pH sensor according to the present invention exhibits good stability at room temperature.

[0206] Example 5: Study on the resistance of the sensor according to the present invention

[0207] Importantly, the sensor's performance is not impeded by the presence of proteins or microorganisms from exudates (biocontamination). However, sensitivity to these factors can vary depending on the type of sensor. Some sensor technologies may be more sensitive to interference from proteins or microorganisms.

[0208] Therefore, it is important to take this into account when selecting and evaluating sensors for a specific application to ensure that sensor performance is not adversely affected by the presence of unwanted proteins or microorganisms, especially with the help of pretreatment or specific coatings.

[0209] Example 5a: The role of fetal bovine serum (FBS)

[0210] Fetal calf serum (FCS), also known as fetal bovine serum (FBS), is a component of the blood of a fetal cow. Like any blood serum, it is the supernatant fluid obtained after blood clotting and centrifugation. It lacks clotting cells and proteins, but in return, it contains many factors (proteins, hormones, ions) that contribute to cell growth. The diverse range of proteins in FCS makes it a good candidate for studying biocontamination.

[0211] The sensor was prepared according to the method described in Example 3, except that an additional layer was added by applying BSA (2% by mass) for one hour before using the sensor.

[0212] This additional layer advantageously protects the sensor from the potential inhibitory effects of the FBS protein.

[0213] The electrical properties of the sensor were measured in buffer solutions at pH 6.0, 7.0, and 8.0 at different concentrations of FBS (1%, 3%, 5%, and 10% by mass). It should be noted that the presence of serum and its contents did not significantly alter the pH of the solution.

[0214] Within the concentration range of 1% to 3% FBS, sensitivity increased slightly. From 3% to 5%, a decrease in sensitivity was observed, which did not affect the initial sensitivity of the sensor. Finally, from 5% to 10%, sensitivity decreased by 8%.

[0215] Therefore, using 10% FBS to reach the upper limit of saturation only resulted in an 8% decrease in sensor sensitivity. Thus, FBS has a minor inhibitory effect on sensor sensitivity and does not significantly impair the sensor's ability to accurately detect and measure pH changes.

[0216] Therefore, the sensor according to the invention exhibits good performance in terms of robustness and stability when the FBS is present at a reasonable saturation level.

[0217] Example 5b: The role of bovine serum albumin (BSA)

[0218] Albumin is the main protein in blood plasma. Bovine serum albumin (BSA) is commonly used in cell culture protocols, especially when supplemental protein needs to be added and when other serum components are not required. The concentration of BSA in exudate is estimated to be 2% by mass.

[0219] Figures 12A to 12D The D-value of the charge neutral point as a function of pH is shown for different sensor configurations. S (in mV).

[0220] exist Figure 12A In the absence of BSA (curve a) and in the presence of 2% BSA, the hydrogen ion sensing layer was directly exposed to the solution to be analyzed. Due to BSA contamination of the sensing layer (biocontamination), a significant decrease in sensor sensitivity was observed.

[0221] exist Figure 12B In this case, the hydrogen ion sensitive layer is made of a dialysis membrane (with dialysis membrane RC Spectra / Por TM SpectrumTM The tube, with a molecular retention threshold of 12,000 to 14,000 Da, provides protection, such as... Figure 4 As shown, the curves almost overlapped regardless of whether BSA was present in the solution (curve a) or at a concentration of 2% BSA (curve b). This demonstrates the protective effect of the dialysis membrane against biofouling.

[0222] Figure 12C The responses of the sensor to a solution containing 2% BSA were compared when the sensor did not have a dialysis membrane (curve a) and when it was protected by a dialysis membrane (curve b). It was inferred that the sensor sensitivity was improved by the protection against biocontamination provided by the dialysis membrane.

[0223] at last, Figure 12D The responses of the sensor to BSA-free buffer solutions were compared when the sensor was without a dialysis membrane (curve a) and when it was protected by a dialysis membrane (curve b). Since curves a and b almost overlap, it was inferred that the sensor's sensitivity is not altered by the presence of a dialysis membrane.

[0224] Example 5b: The effect of oxygen

[0225] One of the parameters that changes during wound healing is oxygen level. Oxygen plays a crucial role at every stage of healing: tissue oxygen pressure controls fibroblast proliferation, regulates the hydroxylation of proline and lysine (essential steps in collagen synthesis), and allows fibroblasts to release collagen and bind it into the scar matrix. In addition to pH, the sensor will also address local hypoxia at the wound site. Therefore, it is necessary to verify the impact of changes in oxygen level on sensor sensitivity.

[0226] The buffer solution is deoxygenated using a degassing technique consisting of an ultrasonic bath and a vacuum pump. The pH remains unchanged after deoxygenation.

[0227] For both standard and deoxygenated buffer solutions, the sensor sensitivity was observed to remain constant, regardless of whether it was in the standard or deoxygenated buffer solution.

[0228] Therefore, changes in the oxygen level in the buffer solution have no significant effect on the sensor's sensitivity. Thus, the pH sensor according to the invention is robust and can provide reliable and accurate measurements regardless of the buffer solution composition and environmental conditions.

Claims

1. pH sensor, comprising: - Substrate (1); - Semiconductor layer (2); - A hydrogen ion sensitive layer (2a) covering the semiconductor layer; - The source (3) and drain (4) are in ohmic contact with the semiconductor layer (2); The hydrogen ion sensitive layer (2a) is composed of molecules containing groups capable of generating and / or capturing hydrogen ions, which are bonded to the semiconductor layer (2) through non-covalent interactions to form a molecular assembly. Its features are, A molecule containing a group capable of generating and / or capturing hydrogen ions comprises at least two distinct groups capable of generating and / or capturing hydrogen ions, wherein the pKa of the groups is separated from each other by at least 1 pH unit.

2. The pH sensor of claim 1, wherein the molecule comprising a group capable of generating and / or capturing hydrogen ions comprises at least two different groups capable of generating and / or capturing hydrogen ions, the pKa of the groups being at least 2 to 6 pH units apart from each other.

3. The pH sensor of claim 2, wherein the different groups capable of generating and / or capturing hydrogen ions are carried by individual molecules.

4. The pH sensor according to any one of claims 1-3, further comprising a gate (6) electrically isolated from the sensitive layer (2a) and having a free surface (6a) suitable for contacting the solution to be analyzed.

5. The pH sensor according to claim 4, wherein the gate is arranged on the substrate (1) at a certain distance from the sensitive layer (2a), such that the semiconductor layer (2), the source (3), the drain (4) and the gate (6) together form a liquid gate field-effect transistor, and the semiconductor layer (2) forms the channel of the transistor.

6. The pH sensor according to claim 4 or 5, wherein the gate (6) is covered with a hydrogen ion sensitive layer (6b) comprising molecules containing groups capable of generating and / or capturing hydrogen ions, the molecules being bonded to the gate (6) via non-covalent interactions to form a molecular assembly.

7. The pH sensor according to any one of claims 1-6, wherein the semiconductor layer (2) comprises a single layer of graphene or a plurality of stacked single layers of graphene.

8. The pH sensor according to any one of claims 1-6, wherein the semiconductor layer (2) comprises one or more molybdenum disulfide monolayers.

9. The pH sensor according to any one of claims 1-8, wherein the molecule comprising a group capable of generating and / or capturing hydrogen ions is a monocyclic aromatic molecule, a polycyclic aromatic molecule, a monocyclic heteroaromatic molecule, a polycyclic heteroaromatic molecule, or a mixture thereof.

10. The pH sensor according to any one of claims 1-9, wherein the group capable of generating and / or capturing hydrogen ions is selected from carboxylic acids, boric acids, sulfonic acids, pyridines, amines, and mixtures thereof.

11. The pH sensor according to any one of claims 1-10, wherein the molecule containing a group capable of generating and / or capturing hydrogen ions is selected from aniline, porphyrin, porphyrin, pyrene-1-boronic acid, 1-pyrenebutyric acid, 1-aminopyrene, phthalocyanine and mixtures thereof.

12. The pH sensor according to any one of claims 1-11, further comprising a dialysis membrane (7) arranged opposite to the hydrogen concentration-sensitive layer (2a) to protect the layer (2a) from contamination by microorganisms or protein membranes.

13. The pH sensor according to any one of claims 1-12, further comprising an absorbent pad (8) disposed on the side of the semiconductor layer (2) opposite to the hydrogen ion sensitive layer (2a) and an aperture (9) formed in the semiconductor layer to circulate the solution to be analyzed in the absorbent pad (8) via capillary action.

14. A patch comprising a polymer membrane having an inner surface suitable for contact with food, skin, or cellular tissue, the patch comprising a pH sensor according to any one of claims 1-13, the pH sensor being disposed on the inner surface such that the free surface of the hydrogen ion concentration sensitive layer is in contact with the food, skin, or cellular tissue for measuring the pH of the food, skin, or cellular tissue.

15. A method for producing a pH sensor according to any one of claims 1-13, comprising: - A molecular assembly is formed between a semiconductor layer (2) and a molecule containing a group capable of generating and / or capturing hydrogen ions, the molecule being connected to the semiconductor layer (2) via non-covalent interactions, so as to form a hydrogen ion sensitive layer (2a) on the semiconductor layer; - Two conductive tracks are formed that are far apart from each other and are in ohmic contact with the semiconductor layer in order to form the source and drain.

16. The method of claim 15, further comprising forming a gate electrically isolated from the semiconductor layer (2), the gate having a free surface adapted to contact the solution to be analyzed.

17. Methods for measuring the pH of a solution, including: - To bring the solution into contact with the free surface of the sensitive layer of the sensor according to any one of claims 1-13. - Apply a potential difference between the source and the drain to allow current to flow through the semiconductor layer. - Measure the changes in the electrical properties of the semiconductor layer. - The pH of the solution is determined by the change in the electrical properties.

18. The method of claim 17, wherein the property is the conductivity of the semiconductor layer.

19. The method of claim 17, in conjunction with any one of claims 4-6, wherein the electrical property is the gate voltage (Vg) at which the conductivity of the sensitive semiconductor layer is minimized as a function of the gate voltage (Vg). D1 V D2 The offset (DS) of ).

Images