Hybrid structure for sensors, process for manufacturing a hybrid structure, and use of a hybrid structure

Abstract

The present invention relates to a hybrid structure for sensors comprising copper oxide nanoparticles, a conductive film layer made of stainless steel, and a flexible polymeric substrate. In addition, the invention also discloses a technological process for manufacturing said hybrid structure, which, owing to the specific properties of copper(II) oxide nanoparticles, may be used as the functional and / or sensing part of an electrochemical sensor for applications in a range of industries, including, but not limited to, the medical, food and agricultural sectors.

Description

HYBRID STRUCTURE FOR SENSORS, MANUFACTURING PROCESS OF A HYBRID STRUCTURE, AND USE OF A HYBRID STRUCTURE FIELD OF THE INVENTION

[0001] The present invention falls within the field of functional / principal materials for electrochemical sensors for application in various industries including, but not limited to, the medical, food and agricultural industries. More specifically, the present invention relates to a conductive stainless steel film layer structure decorated with metal oxide nanoparticles and its application in an electrochemical sensor. A manufacturing process for said structure is also disclosed. FUNDAMENTALS OF THE INVENTION

[0002] Chemical sensors are devices that allow for data collection and information retrieval with minimal manipulation of the system under study. In this way, the results obtained can be analyzed and correlated with other parameters in the environment in which they are used. These devices possess unique characteristics that distinguish them from large-scale instrumental methods, which, in turn, are increasingly precise, sensitive, stable, and selective, but often do not allow for the acquisition of in situ and real-time information. Data under these experimental conditions are easily obtained with sensors, and even if the measurements do not have precision and accuracy comparable to those of instrumental methods, on many occasions there is sufficient information for decision-making. Advantageous characteristics inherent to the use of chemical sensors also include portability, ease of automation, possibility of miniaturization, and low cost.

[0003] The sensitivity and selectivity of electrochemical methods are increased by the types of materials used as sensory units and the relationships between them. Nanostructured materials, such as, for example, Metallic nanoparticles or metal oxides and carbon-based nanomaterials are widely used for the detection of various substances. Although carbon-based nanomaterials possess many desirable properties, they are generally expensive and undergo several complex technological manufacturing steps, such as the activation step, which must be rigorously performed to achieve optimal use. On the other hand, nanoparticles, such as metallic nanoparticles or metal oxides, have distinct optical and electrical properties for electrochemical analyses and do not require complicated functionalization processes.

[0004] Furthermore, the use of polymers as substrates for nanoparticles has revolutionized various sectors, from medicine to electronics. This combination offers unique and synergistic properties, opening doors to innovative applications. Among the main advantages of using polymers, the following stand out: - Versatility: There is a wide range of polymers with distinct chemical and physical properties, allowing the substrate to be adapted to the specific needs of the application.

[0005] Ease of processing: Many polymers can be molded, coated, or processed into different shapes, facilitating the manufacture of complex devices.

[0006] - Compatibility: The compatibility between polymers and nanoparticles can be adjusted through chemical modifications, optimizing the dispersion and stability of the nanoparticles in the polymeric material.

[0007] - Biocompatibility: Many polymers are biocompatible, making them excellent candidates for biomedical applications such as controlled drug release and tissue engineering.

[0008] Thus, nanoparticles supported on polymers can be applied, for example, in the areas of: - Medicine: Nanoparticles encapsulated in polymers can release drugs gradually and in a targeted manner, increasing effectiveness and reducing side effects. - Electronics: the incorporation of nanoparticles into conductive polymers can lead to the development of flexible and lightweight electronic devices, with applications in displays, sensors, and solar cells; - Catalysis: Metal nanoparticles supported on polymers can act as efficient catalysts in various chemical reactions, with applications in chemical and energy production; - Agriculture: Nanoparticles incorporated into polymers can be used to develop sensors capable of detecting nutrients, pathogens, and other parameters important for plant and soil health.

[0009] Over the last few decades, there has been a search for electrode modifications and the use of new materials to be employed as electrochemical sensors and biosensors. Carbonaceous materials, as well as nanomaterials, and metals / metal oxides have been explored for applications in electroanalysis and sensing. In this sense, copper electrodes have been used for various electrochemical applications due to their physicochemical properties and their cost compared to noble metals. However, the stability of metallic copper for electroanalysis applications is one of the limiting factors. In the search for an alternative, several studies reporting the use of various forms of copper oxide have been reported, mainly for the detection of amino acids and sugars.

[0010] It is important to highlight that there is a significant difference in properties between solid copper and copper nanoparticles, especially due to the size of the particles.

[0011] Solid copper exhibits electrical and thermal conductivity. They have excellent ductility and malleability and can be used in electrical cables, piping and electronic components.

[0012] Copper nanoparticles, on the other hand, exhibit a drastic increase in the ratio of the number of atoms on the surface to the number of atoms in the volume (compared to solid material), which significantly increases electrochemical activities, in addition to causing significant changes in their physicochemical properties: luminescence and elevated catalytic activities in various chemical reactions, for example.

[0013] In summary, copper nanoparticles offer a wider range of properties and potential applications compared to solid copper.

[0014] Another important factor in the description / classification of sensors is the approach used for analyte detection: enzymatic and non-enzymatic sensing.

[0015] Enzyme sensing uses enzymes as molecular recognition elements. Enzymes catalyze specific reactions, generating detectable signals. Although enzymes are capable of detecting very low concentrations of analytes, they exhibit instability because they can be sensitive to changes in pH, temperature, and the presence of inhibitors, and have a limited shelf life. Furthermore, they are more difficult to handle and store.

[0016] Non-enzymatic sensing uses inorganic materials or polymers as molecular recognition elements. The interaction between the analyte and the material generates a detectable signal. Advantageously, it offers greater stability, lower cost, longer lifespan, and a wide range of available materials, allowing for the creation of customized sensors.

[0017] In summary, non-enzymatic sensors offer significant advantages in terms of stability, cost, reusability, and versatility. making them an attractive option for many applications.

[0018] Currently, metal oxides in the form of nanoparticles are being widely used as sensitive material in non-enzymatic sensors.

[0019] Some examples of prior art documents that reinforce this technical challenge are presented below.

[0020] The article in the journal Sensors and Actuators, published in 2015, discloses an integrated sensor based on CuO nanoparticles manufactured by direct thermal oxidation of the spray film by magnetron onto the planar substrate of the commercial sensor without the conventional coating procedure. The results of the sensing measurements show that the integrated CuO nanoparticle sensor exhibits the highest and fastest response towards 20-500 ppm ethanol vapor at 200 °C than the other two well-coated nanostructured CuO sensors. The deposited CuO nanoparticle sensor also shows good selectivity, reproducibility, and reversibility with respect to ethanol at 200 °C (YAN, 2015).

[0021] The article in the Journal of Electroanalytical Chemistry (2019) presents high-quality monolayer and full-coverage bilayer graphene on a substrate synthesized using the chemical vapor deposition method. It is then used directly as an electrode material, thus avoiding transfer processes, with the added benefit of avoiding manufacturing defects. Subsequently, the copper nanoparticle-graphene composite electrode can be used for amperometric glucose sensing with high sensitivity and excellent selectivity. Furthermore, the sensor was used for glucose detection in human blood serum samples, demonstrating potential for practical clinical application in glucose detection (WANG, 2019).

[0022] Patent application CN116875949, filed in 2023 by the Xian Thermal Power Research Institute, describes a method for preparing a functional film with a two-dimensional hybrid structure of CuO nanowires and nanoparticles, and a product thereof. It also describes the preparation method, which comprises the following steps: preparation of a titanium-copper double-layer film using magnetron spraying technology. Following this, the titanium-copper double-layer film is oxidized in an air atmosphere with controlled temperature and time to prepare the functional film with a two-dimensional hybrid structure. This allowed for the creation of hybrid structures of CuO nanowires and nanoparticles.

[0023] Patent application IN202011019119, filed in 2020 by Jawaharlal Nehru University, discloses a capacitive nanobiosensor for the non-enzymatic detection of glucose and its method. Copper oxide nanoparticles with polyvinyl alcohol (PVA-CuO) are used for glucose detection. PVA-CuO nanoparticles are synthesized using the co-precipitation method. The parallel plate capacitor is fabricated by dripping PVA-CuO onto two glass electrodes coated with inverted indium tin oxide (ITO), where the conductive side of each ITO-coated glass faces the other, and the parallel plate capacitor connections are made using a copper wire contact point and conductive silver paint.

[0024] Thus, it is possible to verify that the industry always seeks to replace materials / structures for sensing, which advantageously have low cost, are simpler in production (require fewer manufacturing steps and / or steps with lower energy consumption), while maintaining high sensitivity, selectivity and stability. SUMMARY OF THE INVENTION

[0025] The objective of the present invention is to describe a hybrid structure on top of a flexible polymeric substrate comprising a A conductive film layer made of stainless steel decorated with copper oxide nanoparticles is described. A method for manufacturing it is also revealed. Furthermore, the application of the hybrid structure as a functional / sensitive part in an electrochemical sensor for various industries, including but not limited to the medical, food, and agricultural industries, is taught. BRIEF DESCRIPTION OF THE FIGURES

[0026] Figure 1 shows images of (a) the granulated stainless steel film and (b) copper oxide nanoparticles (light spots) on top of the stainless steel grains.

[0027] Figure 2 presents the technological process for obtaining a hybrid structure of copper oxide nanoparticles and a stainless steel film on a polymeric substrate. DETAILED DESCRIPTION OF THE INVENTION

[0028] The present invention seeks to solve a prior art technical problem concerning the fabrication of hybrid structures composed of metal layers and nanoparticles using a three-chamber DC sputtering machine in combination with thermal oxidation. The use of metal in nanoparticle form allows for a reduction in the high temperature, as well as the long time period generally required in the fabrication of metal oxide. Furthermore, it eliminates an additional step, such as the transfer of nanoparticles to another substrate, which is normally necessary for other applications.

[0029] The implemented technical solution involves using a combination of direct current sputtering and thermal oxidation to obtain a hybrid structure of a conductive layer made of stainless steel decorated with copper oxide nanoparticles for sensing applications. The use of these two combined processes reduces the complexity of the process in terms of temperature and time, as well as cost. in equipment because they are relatively simple to perform.

[0030] In one embodiment, the hybrid structure is arranged in the form of a film composed of copper oxide nanoparticles on a conductive layer of stainless steel applied to a flexible polymeric substrate.

[0031] Preferably, the flexible polymeric substrate is made from polymers that are biocompatible, have good adhesion to stainless steel layers, and are stable at temperatures up to 350°C. More preferably, the flexible polymeric substrate is made of polyimide.

[0032] The process for preparing the hybrid structure employs a combination of direct current sputtering (DC sputtering, or simply "sputtering" hereafter) assisted by a constant magnetic field magnetron and thermal oxidation.

[0033] In one embodiment according to the present invention, the flexible polymeric substrate is fixed in a machine composed of three vacuum chambers. In the first chamber, the substrate is heated to a temperature ranging from about 50°C to about 65°C. Subsequently, an argon RF plasma application is performed to clean and remove contaminants resulting from handling or atmospheric exposure. The RF plasma is generated by applying radiofrequency (RF) energy. The RF plasma works by using alternating current at high frequencies to maintain a plasma at much lower pressures than in other methods. This is achieved through the kinetic energy generated by the acceleration and inversion of electrons in the plasma, which is facilitated by the mass difference between the ionized gas particles and the electrons.

[0034] After this step, the substrate is cooled to room temperature and automatically moved to the second and third chambers for spraying / deposition of a conductive film layer made of stainless steel in the second chamber, and copper nanoparticles in the third chamber.

[0035] This spraying stage occurs under a pressure of around 10' 4 mbar, at room temperature, that is, between 18°C ​​and 24°C. Under these conditions, a direct current with a power of approximately 2 kW is applied to obtain a stainless steel film and approximately 3 kW to obtain copper nanoparticles.

[0036] Finally, the hybrid structure obtained in the pulverization stage undergoes a thermal oxidation process at a temperature between approximately 250°C and approximately 320°C for about 1 to 2 hours, in order to obtain copper(II) oxide from copper.

[0037] For the thermal oxidation stage, a conventional oven with free air access or a hot plate can be used.

[0038] Figure 2 presents a simplified flowchart of the steps of the method of the present invention.

[0039] The application area is in electrochemical sensors for the medical, food, and agricultural industries.

[0040] Specifically, the hybrid structure prepared by the process described here can be applied to an electrochemical sensor in a wearable and / or flexible format, such as sensors for the detection of monosaccharides and disaccharides in an individual or patient.

[0041] In a preferred embodiment, the sensor comprising the hybrid structure of the present invention can be used to detect at least one of glucose, fructose, and sucrose. Even more preferably, the hybrid structure can be used to detect glucose.

[0042] In a preferred embodiment, the object of the present invention comprises thin films of about 0.5 µm to about 3 µm thickness of conductive stainless steel layer covered by copper(II) oxide nanoparticles with a diameter of about 15 nm to about 25 nm. The copper(II) oxide is present in a concentration ranging from about 25% to about 100%.

[0043] In a further preferred embodiment, the object of the present invention comprises thin films of about 1 gm to about 2 gm thickness of stainless steel coated with copper(II) oxide nanoparticles of about 20 nm diameter. The copper(II) oxide is present in a concentration ranging from about 27% to about 47%. Example

[0044] The following test was prepared to exemplify the method for preparing the hybrid structure. However, it should not be considered exhaustive.

[0045] Initially, the substrate was prepared and assembled in the machine, which consists of three chambers under vacuum. In the first chamber, the substrate was heated to 55 °C and cleaned using argon RF plasma under pressure for approximately 10 minutes. 2 mbar, and then cooled to room temperature.

[0046] Next, the substrate was automatically moved to the second and third chambers to perform the deposition of stainless steel and copper, respectively.

[0047] The spraying step involving stainless steel and copper nanoparticles was carried out under pressure of approximately 10'. 4 mbar, at room temperature, applying direct current with power of 2 kW and 3 kW to stainless steel and copper targets, respectively. In this way, the deposition was carried out to obtain the hybrid structure, starting with the deposition of a stainless steel film in the second chamber, and the deposition of copper nanoparticles in the third chamber.

[0048] Finally, the resulting hybrid structure underwent thermal oxidation at 320 °C for 2 h to obtain copper(II) oxide (CuO) from copper (Cu), using a conventional furnace with free air access. The simplified scheme of the above steps is illustrated in Figure 2.

[0049] Figure 1 shows scanning electron microscopy images of a hybrid structure of stainless steel film decorated with copper oxide nanoparticles: (a) granulated stainless steel film and (b) Copper oxide nanoparticles (light spots) on top of the stainless steel grains.

[0050] From the structure prepared by the method described above, deconvolution tests of the XPS (X-ray photoelectron spectroscopy) peak of Cu2p3 / 2 obtained in the hybrid structures before and after heat treatment were performed, as can be seen in Table 1. Table 1 - Deconvolution results of the Cu2p / 2 XPS peak obtained in the hybrid structures before and after heat treatment.

[0051] Advantageously, the hybrid structure presents an ideal combination for the manufacture of sensors, namely: - the hybrid structure composed of nanostructured copper in the form of oxide (II), also known as copper(II) oxide nanoparticles, which are sensitive elements allowing their use in electrochemical sensors of mono- and disaccharides.

[0052] - the conductive stainless steel layer, which is a relatively low-cost, biocompatible, mechanically stable option that is resistant to chemically aggressive environments.

[0053] - the flexible polymeric substrate, preferably polyimide, as a durable and biocompatible option, allowing the use of the structures for sensing in the human body or in other applications that require flexibility of the sensitive structures.

[0054] It should be understood that the implementation of other variations and modifications of the aspects and modalities described in the present invention is intended to be part of this disclosure and coverage. intended. The scope of the invention, in its various aspects, may be readily apparent to those skilled in the art, and the invention is not limited to the specific aspects or embodiments described herein, but is intended to cover any and all modifications, variations or equivalents that may become apparent from this disclosure.

Claims

CLAIMS 1. Hybrid structure for sensors, characterized by comprising: - copper oxide nanoparticles; - a conductive layer film made of stainless steel; and - a flexible polymeric substrate.

2. Hybrid structure according to claim 1, characterized in that the copper oxide is in the form of copper(II) oxide in a concentration ranging from 25% to about 100%.

3. Hybrid structure according to claim 2, characterized in that the copper(II) oxide is in a concentration ranging from about 27% to about 47%.

4. Hybrid structure according to any of the preceding claims, characterized in that it comprises films of about 0.5 pm to about 3 pm thickness of conductive stainless steel layer covered by copper(II) oxide nanoparticles of about 15 nm to about 25 nm diameter.

5. Hybrid structure according to claim 4, characterized in that it comprises films of about 1 pm to about 2 pm thick of stainless steel covered by copper(II) oxide nanoparticles of about 20 nm in diameter.

6. Hybrid structure according to any of the preceding claims, characterized in that the flexible polymeric substrate is made from polymers that are biocompatible, have good adhesion to stainless steel layers, and are stable at temperatures up to 350°C.

7. Hybrid structure according to any of the preceding claims, characterized in that the flexible polymeric substrate is made of polyimide.

8. A manufacturing process for a hybrid structure comprising copper oxide nanoparticles, a conductive layer film made of stainless steel, and a flexible polymeric substrate for sensing applications, characterized by comprising the combination of direct current sputtering and thermal oxidation.

9. Process according to claim 8, characterized in that the spraying step takes place in a machine containing three chambers under vacuum.

10. Process according to claim 8 or 9, characterized in that the pulverization step comprises the following steps: - fix the flexible polymeric substrate in the first chamber and heat it to a temperature ranging from about 50°C to about 65°C under vacuum; - Apply argon RF plasma for cleaning and removing contaminants; - Cool the clean polymer to room temperature; and - move the substrate to the second and third chambers, where the conductive layer film made of stainless steel is sprayed in the second chamber and the copper nanoparticles are sprayed in the third chamber.

11. Process according to any one of claims 8 to 10, characterized in that the spraying step occurs under a pressure of about 10' 4 mbar, at room temperature.

12. Process according to any one of claims 8 all, characterized in that direct current is applied with a power of about 2 kW and about 3 kW for stainless steel and copper targets, respectively.

13. Process according to any one of claims 8 to 12, characterized in that, after completing the pulverization step, the hybrid structure undergoes a thermal oxidation process at a temperature between about 250°C and about 350°C for about 1 hour to about 2 hours.

14. Process according to any one of claims 8 to 13, characterized in that thermal oxidation occurs in a conventional furnace with free access to air or a hot plate.

15. Use of a hybrid structure comprising copper oxide nanoparticles, a conductive layer film made of stainless steel, and a flexible polymeric substrate, characterized by its suitability for use in electrochemical sensors.

16. Use according to claim 15, characterized by being used for electrochemical sensors for the medical, food, and agricultural industries.

17. Use according to claim 15 or 16, characterized in that it is used for the detection of monosaccharides and disaccharides.

18. Use in accordance with any of claims 15 to 17, characterized by the fact that it is for the detection of at least one of glucose, fructose, and sucrose.

19. Use in accordance with any of claims 15 to 18, characterized by the fact that it is for glucose detection.

Images