A method for manufacturing an integrated photoelectric sensing probe with synchronous response to pH and DO
By combining silver nanowires with pH fluorescent optical fibers, the problem of low detection accuracy of pH and DO in microreactors has been solved, realizing real-time detection and fully automated environmental control in confined spaces.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- NANJING TECH UNIV
- Filing Date
- 2023-07-17
- Publication Date
- 2026-06-02
AI Technical Summary
Existing pH and DO detection methods have low accuracy and cannot be used in real time in microreactors. Traditional sensing probes cannot be applied to confined spaces, making it difficult to match with industrial environments.
A photoelectric sensing probe combining silver nanowires and pH fluorescent optical fibers was developed. The silver nanowires were prepared by hydrothermal method, and the electrodes were prepared by screen printing. By combining photochemical and electrochemical technologies, the simultaneous response detection of pH and DO was achieved.
It enables high-precision real-time detection of pH and DO in a microreactor, solving the detection bottleneck of traditional methods in confined spaces and providing fully automated environmental control and online real-time data acquisition capabilities.
Smart Images
Figure CN116879365B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the fields of electrochemistry and fluorescence technology, and relates to a method for fabricating an integrated photoelectric sensing probe with simultaneous pH and DO response. Background Technology
[0002] Oxygen consumption rate is one of the most important parameters indicating the metabolic state of microorganisms. Aerobic bacteria typically use oxygen as the final electron acceptor, obtaining energy through aerobic respiration. Therefore, fluctuations in dissolved oxygen (DO) concentration can be used to determine bacterial growth rates and optimize reaction operations. Furthermore, the pH value in the fermentation tank affects the activity of microbial enzymes during fermentation. Different pH values often lead to different metabolic processes in the cells, altering the quality and proportion of metabolites.
[0003] Currently, pH and DO detection methods include chromatography, spectrophotometry, qualitative chemistry, refractive index, and polarimetry. These methods either require expensive and bulky equipment, are time-consuming, and complex to operate. Furthermore, when the sample size is small or the detection system volume is too small, these methods can result in significant errors in accuracy. Therefore, a key scientific problem in this field is how to accurately control pH and DO within the confined space of a reactor with an extremely miniaturized volume, thereby matching the industrial growth environment and eliminating the confinement effect. Secondly, from a technical perspective, the large size of traditional industrial pH and DO sensors makes them unsuitable for use in microreactors, hindering real-time monitoring of microbial metabolic growth parameters within the confined space. This makes it difficult to assess dynamic cultivation patterns under different environments and provide crucial guidance data for matching industrial environments. The lack of online sensing tools is a key technical challenge of this research. Summary of the Invention
[0004] This invention addresses the problems existing in traditional pH and DO detection systems by proposing a method for fabricating an integrated photoelectric sensor probe with simultaneous pH and DO responses. The purpose of this invention is to prepare a detection device combining a DO sensing electrode and a pH fluorescence fiber for real-time detection of pH and DO parameters. This solves the problems of low accuracy and inability to perform online real-time detection of metabolic growth parameters in existing microbial strains.
[0005] To achieve the above objectives, the present invention is implemented using the following technical solution:
[0006] A method for fabricating an integrated photoelectric sensor probe with simultaneous pH and DO responses, the specific steps of which are as follows:
[0007] (1) Preparation of silver nanowires
[0008] Using silver nitrate as the silver source, polyvinylpyrrolidone as the surfactant, and ethylene glycol as the reducing agent, the specific steps are as follows: Solution A is prepared by dissolving silver nitrate in ethylene glycol solution; Solution B is prepared by dissolving polyvinylpyrrolidone in ethylene glycol solution; NaCl-EG solution is prepared by dissolving NaCl in ethylene glycol solution; Solutions A and B are mixed, and then NaCl-EG solution is added and stirred until clear and transparent. The mixture is then transferred to a hydrothermal reactor for hydrothermal synthesis to obtain a silver nanowire solution. The silver nanowires are then centrifuged and washed to obtain a silver nanowire precipitate.
[0009] (2) Fabrication of bare carbon chips by screen printing
[0010] The conductive carbon ink is heated while the silver / silver chloride paste is cooled to achieve the required viscosity for printing. The conductive carbon ink serves as the paste for the working electrode and the counter electrode, while the silver / silver chloride paste serves as the paste for the reference electrode. The two are printed according to a pre-set pattern using a screen printing machine and then dried in an oven to obtain a screen-printed bare carbon chip.
[0011] (3) Fabrication of DO sensing electrode
[0012] The bare carbon chip printed in step (2) was cleaned with ultrapure water to clean the working electrode. The prepared silver nanowires were added to a suspension of water and Nafion to prepare a silver nanowire mixed solution. The silver nanowire mixed solution was drop-coated onto the working electrode surface of the electrochemical three-electrode and dried at room temperature. The working electrode surface was rinsed with ultrapure water to wash away the silver nanowires that were not fixed on the working electrode surface, and the silver nanowire modified DO electrode was obtained.
[0013] (4) Fabrication of an integrated photoelectric sensor probe with simultaneous pH and DO response
[0014] The silver nanowire-modified DO electrode obtained in step (3) was cleaned with ethanol. Then, fluorescent optical fiber was wrapped around the prepared DO electrode, and the conductive carbon ink from step (2) was used to fix it onto the membrane. Finally, the membrane was dried to obtain an integrated photoelectric membrane with simultaneous pH and DO response. Next, the photoelectric membrane was connected to the contact point of the light signal receiver and the electrochemical three electrodes (reference electrode, counter electrode, and working electrode) at the end of the probe rod, and the membrane was installed into the pre-reserved clip at the end of the probe rod to obtain an integrated photoelectric sensing probe with simultaneous pH and DO response.
[0015] As a further improvement of the present invention, in step (1), the ion concentration range of solution A and solution B is 0.1-0.4 mM, the ion concentration of both is the same, the concentration range of NaCl-EG solution is 0.1-0.3 mM, the volume ratio of solution A: solution B: NaCl-EG solution is 3:17:0.2, the hydrothermal synthesis temperature is 90-180℃, the hydrothermal synthesis time is 0.5h-2h, the centrifugation rate is 6000-12000 r / min, and the centrifugation time is 5-20 min.
[0016] As a further improvement of the present invention, in step (2), the heating temperature of the conductive carbon paste is 30-90℃ and the heating time is 5-15min; the cooling temperature of the silver / silver chloride paste is -5-0℃ and the cooling time is 5-15min; the printing viscosity of the conductive carbon ink and the silver / silver chloride paste is 50-150dpa·S; the drying temperature of the bare carbon chip is 30-60℃ and the drying time is 2-6h.
[0017] As a further improvement of the present invention, in step (3), the mass concentration of Nafion solution is 1-5%, the mass concentration of silver nanowires in the silver nanowire mixed solution is 8-15 mg / L, the amount added at the working electrode is 5-10 μL, and the chip drying time is 30-50 min.
[0018] As a further improvement of the present invention, the drying temperature of the photoelectric film in step (4) is 30-60℃ and the drying time is 2-6h.
[0019] This invention provides an integrated photoelectric sensing probe with simultaneous pH and DO response. Its features include a DO electrode and a fluorescent optical fiber. The DO electrode comprises a working electrode, a reference electrode, and a counter electrode. The working electrode is circular, the counter electrode is arc-shaped, and the reference electrode is rectangular. The counter electrode and reference electrode surround the working electrode but do not contact each other. The surface of the circular working electrode is covered with silver nanowires. The fluorescent optical fiber is annular and surrounds the DO electrode without contact. The working electrode is circular with a radius of 0.15 cm, the arc-shaped counter electrode has a radius of 0.7 cm, and the rectangular reference electrode has an area of 0.07 cm². 2 .
[0020] In the synthesis of silver nanowires in this invention, the concentrations of silver nitrate and polyvinylpyrrolidone (PVP) are controlled. PVP acts as a surfactant and crystal plane guiding agent, directing the directional growth of silver nanowires during hydrothermal processes, resulting in a more regular morphology and exposing more active sites. This lowers the detection potential of the chip and simultaneously improves the linear range of dissolved oxygen detection. Furthermore, screen-printed chips have attracted widespread attention due to their excellent electrochemical performance while maintaining design flexibility, low cost, simple structure, good repeatability, and ease of integration and miniaturization. The core of the screen-printed chip is the paste. Since nano-electrocatalytic materials possess extremely high sensing performance, this invention uses silver nanowires with high oxygen molecular four-electron reduction catalytic performance as the electrode material and pH-sensitive fluorescent optical fiber as the pH detection electrode, thus solving the need for simultaneous detection of pH and dissolved oxygen (DO) in different detection environments.
[0021] Compared with the prior art, the advantages and positive effects of the present invention are as follows:
[0022] 1. The nanoprinted sensing paste synthesized in this invention has unique advantages for DO detection. Among them, the silver wires have high conductivity and unique advantages for oxygen reduction. At the same time, the silver wire material is nanoscale. Nanomaterials not only have a wide range of analyte detection, but also can effectively overcome the problems of species interference, low signal output, and hysteresis signal response. Furthermore, the presence of silver nanowires can not only control the working potential at a low potential of -0.2V, but also have good anti-interference performance, and can achieve an extremely wide linear range for DO detection, thus greatly improving the linear range of DO detection and meeting the needs of DO detection in the fermentation market.
[0023] 2. This invention proposes a method for fabricating an integrated photoelectric sensor probe with simultaneous pH and DO response. The prepared sensor probe addresses the bottleneck of traditional micro parallel reactors in reproducing industrial environments during bacterial culture. By combining photochemistry and electrochemistry to develop an integrated photoelectric sensor membrane and its detection probe, the invention enables dynamic monitoring of DO and pH values in the well plate. This provides fully automated environmental control and multi-dimensional online real-time data acquisition for bacterial well plate culture and screening. Attached Figure Description
[0024] Figure 1 This is a scanning electron microscope image of the silver nanowires synthesized by hydrothermal method in Example 1.
[0025] Figure 2 This is a schematic diagram of the integrated photoelectric sensing membrane structure with simultaneous pH and DO response in Example 1.
[0026] Figure 3 This is an external view of the integrated photoelectric sensor probe with simultaneous pH and DO response in Example 1.
[0027] Figure 4 The images show the cyclic voltammetry and linear fitting plot of the integrated photoelectric sensor probe with synchronized pH and DO response in Example 1.
[0028] Figure 5 This is a multi-potential step method diagram for pH detection using an integrated photoelectric sensor probe with synchronized pH and DO responses in Example 1.
[0029] The figures are labeled as follows: 1 working electrode, 2 counter electrode, 3 reference electrode, 4 silver nanowire, 5 fluorescent optical fiber. Detailed Implementation
[0030] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described below with reference to specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.
[0031] Numerous specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways than those described herein, and therefore the invention is not limited to the specific embodiments disclosed in the following specification.
[0032] Unless otherwise specified, the preparation process of the DO electrode in the following embodiments is as follows: First, silver nanowire structured silver material is synthesized by hydrothermal method using silver nitrate as the silver source, polyvinylpyrrolidone (PVP) as the surfactant, and ethylene glycol as the reducing agent. A certain amount of silver material is dispersed in a mixed solution of ultrapure water and Nafion to obtain a silver nanowire mixed solution; conductive carbon ink is used as the ink for printing the counter electrode and working electrode, and silver / silver chloride is used as the ink for printing the reference electrode. A three-electrode bare carbon chip is printed according to a pre-set pattern using screen printing technology. A certain amount of silver nanowire mixed solution is drop-coated onto the working electrode of the bare carbon chip.
[0033] The fabrication process of the integrated photoelectric sensor probe with simultaneous pH and DO response is as follows: A pH-sensitive fluorescent optical fiber (Protonex Green 500 pH fluorescent probe, Ex (nm): 445-Em (nm): 503, Shanghai Qiyuan Biotechnology Co., Ltd.) is wrapped around the periphery of the prepared DO electrode (without contact), and fixed to the membrane using conductive carbon paste. Finally, the membrane is dried to obtain an integrated photoelectric membrane with simultaneous pH and DO response. Next, the photoelectric membrane is connected to the contact point of the optical signal receiver (Lifuan, model: AFBR-2418MZ) and the electrochemical three electrodes (reference electrode, working electrode, and counter electrode) at the end of the probe rod. The fluorescent optical fiber is connected to the optical signal receiver, and the DO sensing electrode is connected to the contact point of the three electrodes. Finally, the membrane is installed into the pre-reserved clip at the end of the probe rod (the probe rod can be customized), resulting in the integrated photoelectric sensor probe with simultaneous pH and DO response.
[0034] Figure 4 DO's CV and Figure 5 The pH characterization method was as follows: First, a phosphate-buffered saline (PBS) solution with a pH of 6.8 was prepared. The probe was then immersed in an electrolytic cell filled with the PBS. The working electrode, reference electrode, and counter electrode of the probe were connected to the interfaces on the electrochemical workstation, and the fluorescent fiber was connected to the optical signal receiver. The dissolved oxygen concentration in the electrolytic cell was controlled by bubbling nitrogen and oxygen in different proportions. Finally, the potential window was set to -0.6 to 0.6 V, and CV scans were performed at different concentrations of dissolved oxygen (DO). The electrochemical workstation received the current signal from the DO and the potential signal transmitted by the optical signal receiver.
[0035] Example 1
[0036] This embodiment provides a method for fabricating an integrated photoelectric sensor probe with simultaneous pH and DO responses, and the steps are as follows.
[0037] (1) Weigh 0.34 g of silver nitrate and dissolve it in 6 ml of ethylene glycol. Stir the solution until it is clear and transparent to obtain solution A (0.2 mmol). Weigh 0.333 g of polyvinylpyrrolidone and dissolve it in 34 ml of ethylene glycol. Stir the solution until it is clear and transparent to obtain solution B (0.2 mmol). Mix solutions A and B and stir for 30 min to ensure that the silver nitrate and polyvinylpyrrolidone are mixed evenly. Weigh 1.1688 g of NaCl and dissolve it in 100 ml of ethylene glycol. Stir the solution until it is clear and transparent to obtain NaCl-EG solution (0.2 mM). Add 400 μL of NaCl-EG solution to the mixture of solutions A and B and stir until it is clear and transparent. Then transfer the mixture to a hydrothermal reactor for hydrothermal synthesis reaction. The temperature of the hydrothermal reactor is controlled at 160 °C and the hydrothermal synthesis time is 1.5 h. After the hydrothermal synthesis reaction was completed, the product was allowed to cool naturally to room temperature. The product was then transferred to a 50 ml centrifuge tube, centrifuged three times with ethanol, and then washed three times with ultrapure water. The centrifuge speed was 8000 rpm, and each centrifugation time was 10 min. After centrifugation, the waste liquid was discarded, and the solid was collected to obtain silver nanowires. The microstructure of the silver nanowires is shown in the attached figure. Figure 1 As shown. From the appendix Figure 1 It can be seen that the silver nanowires prepared in this embodiment have a regular and uniform morphology.
[0038] (2) The conductive carbon ink is placed in an oven and heated at 60°C for 10 minutes. The silver / silver chloride paste is placed in a refrigerator and cooled at -2°C for 10 minutes. The processing time is adjusted appropriately to make the two pastes reach the viscosity required for printing (100 dpa·S). The conductive carbon ink is used as the paste for the working electrode and the counter electrode, and the silver / silver chloride paste is used as the paste for the reference electrode. After printing the pattern according to the pre-set pattern through a screen printing machine, the paste is placed in an oven and dried at 60°C for 3 hours to obtain a screen-printed bare carbon chip.
[0039] (3) Clean the working electrode of the bare carbon chip printed in step (2) with ultrapure water, wipe the chip dry with lint-free paper, add the prepared silver nanowires to a suspension of 1% Nafion to prepare a silver nanowire mixture with a concentration of 10 mg / ml; take 5 μL of the silver nanowire mixture and drop it onto the working electrode surface of the electrochemical three-electrode, and dry it at room temperature for 30 min; rinse the working electrode surface with ultrapure water to wash away the silver nanowires that are not fixed on the working electrode surface, and obtain the silver nanowire modified DO electrode.
[0040] (4) The silver nanowire-modified DO electrode obtained in step (3) was cleaned with ethanol. Then, fluorescent optical fiber was wrapped around the prepared DO electrode and fixed onto the membrane using conductive carbon paste. Finally, the membrane was placed in an oven at 40°C for 4 hours to obtain an integrated photoelectric membrane with simultaneous pH and DO response. The photoelectric membrane was then connected to the contact points of the optical signal receiver and the electrochemical three electrodes (reference electrode, counter electrode, and working electrode) at the end of the probe rod. The membrane was then installed into the pre-drilled clip 6 at the end of the probe rod to obtain an integrated photoelectric sensing probe with simultaneous pH and DO response. Its structure is shown in the attached figure. Figure 2 As shown, the electrode includes a DO sensing electrode, which includes a working electrode 1, and the working electrode 1 is covered with silver nanowires 4.
[0041] The sensing probe also includes a reference electrode 3 and a counter electrode 2. In this embodiment, the working electrode 1 is a circular disc with a radius of 0.15 cm, and the counter electrode 2 and the reference electrode 3 are respectively an arc shape (radius of 0.7 cm) and a rectangle (area of 0.07 cm²). 2 The arc-shaped counter electrode 2 and reference electrode 3 surround the working electrode 3 without contacting each other. In this embodiment, the working electrode 1 is covered with silver nanowires 4 in a circular sheet. The silver nanowires undergo a reversible chemical reaction with oxygen. The sensitive material responds differently to dissolved oxygen at different dissolved oxygen concentrations, making the measurement of trace dissolved oxygen more accurate. The sensing probe also includes a fluorescent optical fiber 5, which is a ring with a radius of 1 cm, and surrounds the DO electrode without contacting each other.
[0042] (5) Testing using cyclic voltammetry electrodes: such as Figure 4 As shown, the sensing probe obtained in this embodiment is sensitive to DO at a potential of -0.2V and exhibits good linearity within a concentration range of 3.88-19.38 mg / L. The pH signal received and converted by the photodetector has a high-step potential response and does not interfere with the DO signal response. After testing, the sensing probe was placed in a PBS buffer solution with pH 7.0 at 0°C for one week, and its response signal remained essentially unchanged. After one month, its response signal was 98% of the initial signal; after three months, its response signal was still 94% of the initial signal, indicating that the sensing probe with synchronous pH and DO response has excellent stability. Therefore, the sensing probe prepared in this embodiment has good detection performance with a very small size.
[0043] Depend on Figure 1 SEM characterization showed that the silver nanowires synthesized using step (1) had a stable structure and uniform distribution, indicating that the quality of the synthesized material was stable and controllable, which facilitated the preparation of industrial-scale sensing pastes.
[0044] Depend on Figure 4 The CV electrochemical characterization and linear fitting plots show that the probe has the highest sensitivity to DO at a potential of -0.2V, and exhibits good linearity in the concentration range of DO from 3.88 to 19.38 mg / L. This material is very advantageous for increasing the linear range of DO detection.
[0045] Depend on Figure 5 pH characterization shows that by changing the pH value in the buffer solution, the fluorescence intensity of the fluorescent fiber is changed, and the pH signal received and converted by the optical signal receiver has a high potential step. Furthermore, the detected potential signal does not interfere with the current signal of the DO, proving that the probe responds accurately to pH.
[0046] Example 2
[0047] This embodiment provides a method for fabricating an integrated photoelectric sensor probe with simultaneous pH and DO responses. Unless otherwise specified, this embodiment is consistent with Embodiment 1. The steps are as follows.
[0048] (1) Weigh 0.17g of silver nitrate and dissolve it in 6ml of ethylene glycol. Stir the solution until it is clear and transparent to obtain solution A (0.1mmol). Weigh 0.1665g of polyvinylpyrrolidone and dissolve it in 34ml of ethylene glycol. Stir the solution until it is clear and transparent to obtain solution B (0.1mmol). Mix solutions A and B and stir for 30min to ensure that the silver nitrate and polyvinylpyrrolidone are mixed evenly. Weigh 0.5844g of NaCl and dissolve it in 100ml of ethylene glycol. Stir the solution until it is clear and transparent to obtain NaCl-EG solution (0.1mM). Add 400μL of NaCl-EG solution to the mixture of solutions A and B and stir until it is clear and transparent. Then transfer the mixture to a hydrothermal reactor for hydrothermal synthesis reaction. The temperature of the hydrothermal reactor is controlled at 180℃ and the hydrothermal synthesis time is 2h. After the hydrothermal synthesis reaction was completed, the product was allowed to cool naturally to room temperature. The product was then transferred to a 50 ml centrifuge tube, centrifuged three times with ethanol, and then washed three times with ultrapure water. The centrifuge speed was 10000 r / min, and each centrifugation time was 15 min. After centrifugation, the waste liquid was discarded, and the solid obtained after centrifugation was collected to obtain silver nanowires. The microstructure and adhesion of the silver nanowires are described. Figure 1 No significant difference.
[0049] (2) The conductive carbon ink is placed in an oven and heated to 90°C for 5 minutes. The silver / silver chloride paste is placed in a refrigerator and cooled to -5°C for 5 minutes to achieve the required viscosity (100 dpa·S) for printing. The conductive carbon ink is used as the paste for the working electrode and the counter electrode, and the silver / silver chloride paste is used as the paste for the reference electrode. The paste is printed by a screen printing machine according to the pre-set pattern and then placed in an oven to dry. The oven temperature is set to 90°C and the drying is continued for 2 hours to obtain a screen-printed bare carbon chip.
[0050] (3) Clean the working electrode of the bare carbon chip printed in step (2) with ultrapure water, wipe the chip dry with lint-free paper, add the prepared silver nanowires to a suspension of 1% Nafion to prepare a silver nanowire mixture with a concentration of 15 mg / ml; take 10 μL of the silver nanowire mixture and drop it onto the working electrode surface of the electrochemical three-electrode, and dry it at room temperature for 50 min; rinse the working electrode surface with ultrapure water to wash away the silver nanowires that are not fixed on the working electrode surface, and obtain the silver nanowire modified DO electrode.
[0051] (4) The silver nanowire-modified DO electrode obtained in step (3) was cleaned with ethanol. Then, fluorescent optical fiber was wrapped around the prepared DO electrode and fixed onto the membrane using conductive carbon paste. Finally, the membrane was placed in an oven at 30°C for 6 hours to obtain an integrated photoelectric membrane with simultaneous pH and DO response. The photoelectric membrane was then connected to the contact points of the optical signal receiver and the electrochemical three electrodes (reference electrode, counter electrode, and working electrode) at the end of the probe rod. The membrane was then installed into the pre-drilled clip 6 at the end of the probe rod to obtain an integrated photoelectric sensing probe with simultaneous pH and DO response. Its structure is shown in the attached figure. Figure 2 As shown, the electrode includes a DO sensing electrode, which includes a working electrode 1, and the working electrode 1 is covered with silver nanowires 4.
[0052] (5) Testing using cyclic voltammetry electrodes: such as Figure 4 As shown, the sensing probe obtained in this embodiment is sensitive to DO at a potential of -0.25V and has a good linear range in the concentration range of 1.45-18.55 mg / L. The pH signal received and converted by the optical signal receiver has a high-step potential response and does not interfere with the DO signal response. After testing, the sensing probe was placed in PBS buffer at pH 7.0 at 0℃ for one week, and its response signal remained basically unchanged; after one month, its response signal was 96% of the initial signal; after three months, its response signal was still 94% of the initial signal, indicating that the sensing probe with synchronous pH and DO response has good stability.
[0053] Example 3
[0054] This embodiment provides a method for fabricating an integrated photoelectric sensor probe with simultaneous pH and DO responses. Unless otherwise specified, this embodiment is consistent with Embodiment 1. The steps are as follows.
[0055] (1) Weigh 0.68 g of silver nitrate and dissolve it in 6 ml of ethylene glycol. Stir the solution until it is clear and transparent to obtain solution A (0.4 mmol). Weigh 0.666 g of polyvinylpyrrolidone and dissolve it in 34 ml of ethylene glycol. Stir the solution until it is clear and transparent to obtain solution B (0.4 mmol). Mix solutions A and B and stir for 30 min to ensure that the silver nitrate and polyvinylpyrrolidone are mixed evenly. Weigh 1.7532 g of NaCl and dissolve it in 100 ml of ethylene glycol. Stir the solution until it is clear and transparent to obtain NaCl-EG solution (0.3 mM). Add 400 μL of NaCl-EG solution to the mixture of solutions A and B and stir until it is clear and transparent. Then transfer the mixture to a hydrothermal reactor for hydrothermal synthesis reaction. The temperature of the hydrothermal reactor is controlled at 100 °C and the hydrothermal synthesis time is 0.5 h. After the hydrothermal synthesis reaction was completed, the product was allowed to cool naturally to room temperature. The product was then transferred to a 50 ml centrifuge tube, centrifuged three times with ethanol, and then washed three times with ultrapure water. The centrifuge speed was 6000 rpm, and each centrifugation time was 5 min. After centrifugation, the waste liquid was discarded, and the solid residue was collected to obtain silver nanowires. The microstructure and adhesion of the silver nanowires were... Figure 1 No significant difference.
[0056] (2) The conductive carbon ink was heated in an oven at 30°C for 15 minutes; the silver / silver chloride paste was cooled in a refrigerator at 0°C for 15 minutes to achieve the required viscosity (100 dpa·S) for printing. The conductive carbon ink was used as the paste for the working electrode and the counter electrode, and the silver / silver chloride paste was used as the paste for the reference electrode. The two pastes were printed by a screen printing machine according to the pre-set pattern and then placed in an oven to dry at 30°C for 6 hours to obtain a screen-printed bare carbon chip.
[0057] (3) Clean the working electrode of the bare carbon chip printed in step (2) with ultrapure water, wipe the chip dry with lint-free paper, add the prepared silver nanowires to a suspension of 1% Nafion to obtain a silver nanowire mixture with a concentration of 8 mg / ml; take 5 μL of the silver nanowire mixture and drop it onto the working electrode surface of the electrochemical three-electrode, and dry it at room temperature for 30 min; rinse the working electrode surface with ultrapure water to wash away the silver nanowires that are not fixed on the working electrode surface, and obtain the silver nanowire modified DO electrode.
[0058] (4) The silver nanowire-modified DO electrode obtained in step (3) was cleaned with ethanol. Then, fluorescent optical fiber was wrapped around the prepared DO electrode and fixed onto the membrane using conductive carbon paste. Finally, the membrane was placed in an oven at 60°C for 2 hours to obtain an integrated photoelectric membrane with simultaneous pH and DO response. The photoelectric membrane was then connected to the contact points of the optical signal receiver and the electrochemical three electrodes (reference electrode, counter electrode, and working electrode) at the end of the probe rod. The membrane was then installed into the pre-drilled clip 6 at the end of the probe rod to obtain an integrated photoelectric sensing probe with simultaneous pH and DO response. Its structure is shown in the attached figure. Figure 2 As shown, the electrode includes a DO sensing electrode, which includes a working electrode 1, and the working electrode 1 is covered with silver nanowires 4.
[0059] (5) Testing using cyclic voltammetry electrodes: such as Figure 4 As shown, the sensing probe obtained in this embodiment is sensitive to DO at a potential of -0.22V and has a good linear range in the concentration range of 4.45-18.38 mg / L. The pH signal received and converted by the optical signal receiver has a high-step potential response and does not interfere with the DO signal response. After testing, the sensing probe was placed in PBS buffer at pH 7.0 at 0℃ for one week, and its response signal remained basically unchanged; after one month, its response signal was 97% of the initial signal; after three months, its response signal was still 96% of the initial signal, indicating that the pH and DO synchronous response sensing probe has good stability.
[0060] Comparative Example 1
[0061] In this comparative example, no NaCl-EG solution was added, and the remaining steps were the same as in Example 1. It was found that without the addition of NaCl-EG solution, the synthesis speed was too fast, causing the nanomaterials to agglomerate, resulting in irregular morphology and thus reducing the specific surface area of exposed silver nanoparticles.
[0062] Comparative Example 2
[0063] In this comparative example, the concentrations of solutions A and B, as well as the NaCl-EG solution, were all 0.08 mM. The hydrothermal temperature was 130°C, and the hydrothermal time was 1 h. All other conditions and steps were consistent with those in Example 1.
[0064] The results showed that reducing the solution concentration would cause the synthesis of silver nanoparticles to be too rapid, resulting in smaller particle sizes that did not exhibit a linear trend. Furthermore, the prematurely synthesized silver nanoparticles would be oxidized under high-temperature conditions, making the composition of the material more complex.
[0065] Comparative Example 3
[0066] In this comparative example, NaS was dissolved in ethylene glycol to prepare a 0.2 mM NaS-EG solution to replace the NaCl-EG solution, and the remaining conditions were the same as in Example 1.
[0067] The results showed that the addition of NaS-EG solution caused the synthesized silver nanomaterials to vary in size and length, and have a complex and irregular morphology. As a result, the active sites exposed by the silver nanomaterials were irregular, and the performance was lower than that of regular silver nanomaterials.
[0068] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments for application in other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.
Claims
1. A method for fabricating an integrated photoelectric sensor probe with simultaneous pH and DO response, characterized in that, The steps are as follows: (1) Preparation of silver nanowires Solution A was prepared by dissolving silver nitrate in ethylene glycol solution; solution B was prepared by dissolving polyvinylpyrrolidone in ethylene glycol solution; NaCl-EG solution was prepared by dissolving NaCl in ethylene glycol solution; solutions A and B were mixed, and then NaCl-EG solution was added and stirred until clear and transparent, and then transferred to a hydrothermal reactor. After hydrothermal synthesis reaction, silver nanowire solution was obtained. The silver nanowire solution was centrifuged and washed to obtain silver nanowire precipitate. (2) Fabrication of bare carbon chips by screen printing Conductive carbon ink paste is printed using a screen printing machine to serve as the working electrode and counter electrode, while silver / silver chloride paste is printed using a screen printing machine to serve as the reference electrode. After printing, the chip is dried to obtain a screen-printed bare carbon chip. (3) Fabrication of DO sensing electrode Silver nanowire precipitate was added to a suspension of water and Nafion to prepare a silver nanowire mixed solution; the working electrode of the bare carbon chip was cleaned with ultrapure water, and the silver nanowire mixed solution was drop-coated onto the surface of the working electrode and dried at room temperature; then the surface of the working electrode was rinsed with ultrapure water to obtain a silver nanowire modified DO sensing electrode. (4) Fabrication of an integrated photoelectric sensor probe with simultaneous pH and DO response The surface of the DO sensing electrode is cleaned with ethanol, and then the fluorescent optical fiber is connected and wrapped around the periphery of the DO sensing electrode. The conductive carbon ink from step (2) is used to fix it onto the membrane. Finally, the membrane is dried to obtain an integrated photoelectric membrane with synchronous pH and DO response. The photoelectric membrane is connected to the contact points of the optical signal receiver, reference electrode, counter electrode, and working electrode. The photoelectric membrane is installed into the pre-reserved buckle at the end of the probe rod to obtain an integrated photoelectric sensing probe with synchronous pH and DO response. In step (1), the ion concentrations of solution A and solution B are the same, ranging from 0.1 to 0.4 mM. The concentration range of NaCl-EG solution is 0.1 to 0.3 mM. The volume ratio of solution A: solution B: NaCl-EG solution is 3:17:0.
2. The hydrothermal synthesis temperature is 90-180℃, and the hydrothermal synthesis time is 0.5 h to 2 h. The centrifugation rate is 6000-12000 r / min, and the centrifugation time is 5-20 min.
2. The method for preparing the integrated photoelectric sensor probe with simultaneous pH and DO response according to claim 1, characterized in that, In step (2), the printing viscosity of both the conductive carbon ink paste and the silver / silver chloride paste is 50-150 dpa·S; the drying temperature is 30-60℃ and the drying time is 2-6h.
3. The method for preparing the integrated photoelectric sensor probe with simultaneous pH and DO response according to claim 1, characterized in that, In step (3), the mass concentration of Nafion in the suspension is 1-5%, the mass concentration of silver nanowires in the silver nanowire mixed solution is 8-15 mg / L, the amount of working electrode drop is 5-10 μL, and the drying time at room temperature is 30-50 min.
4. An integrated photoelectric sensing probe with simultaneous pH and DO response, characterized in that, The device includes a DO electrode and a fluorescent optical fiber. The DO electrode comprises a working electrode, a reference electrode, and a counter electrode. The working electrode is disc-shaped, the counter electrode is arc-shaped, and the reference electrode is rectangular. The counter electrode and the reference electrode surround the working electrode but do not contact each other. The surface of the disc-shaped working electrode is covered with silver nanowires. The fluorescent optical fiber is annular and surrounds the DO electrode but does not contact each other.