Preparation method of cobalt modified polyheptazinyl imide and application of cobalt modified polyheptazinyl imide in rhodamine B photosensitization detection of paracetamol

Abstract

The invention discloses a preparation method of cobalt-modified polyheptazinyl imide and application of cobalt-modified polyheptazinyl imide in rhodamine B photosensitization detection of paracetamol, and relates to the technical field of visual ultra-sensitive detection of colorless paracetamol. The method comprises the following steps: detecting paracetamol by adopting cobalt modified polyheptazinyl imide according to any one of the following modes: mode I, uniformly mixing rhodamine B-cobalt modified polyheptazinyl imide with a paracetamol solution to obtain turbid liquid to be detected; the preparation method comprises the following steps: putting the raw materials into a Pomfiley multi-channel photocatalytic reactor, stirring and adsorbing under the condition of no illumination, starting 532nm visible light illumination, filtering by adopting a filter membrane, and detecting by adopting an ultraviolet and visible spectrophotometer; in the second mode, the turbid liquid to be detected is injected into the liquid core optical fiber probe and packaged, then a 532 nm single-wavelength light source is turned on, and illumination is conducted for 3-5 min. The invention can obtain the preparation method of the cobalt modified polyheptazinyl imide and the application of the cobalt modified polyheptazinyl imide in rhodamine B photosensitization detection of paracetamol.

Description

Technical Field

[0001] The present invention relates to the technical field of visualized ultrasensitive detection of colorless paracetamol, and particularly to a preparation method of cobalt-modified polyheptazine imide and application thereof in rhodamine B photosensitized detection of paracetamol. Background Art

[0002] Paracetamol, a widely used nonsteroidal anti-inflammatory drug and analgesic, can enter aquatic environments through various channels, including pharmaceutical industrial wastewater and human and animal metabolism. Due to its widespread use and high bioaccumulation, paracetamol is one of the most frequently detected pharmaceutical contaminants in water. Although paracetamol concentrations in aquatic ecosystems are lower than those used for therapeutic purposes, its poor biodegradability and long-term exposure can negatively impact organisms. Excessive use or accumulation of paracetamol can cause hepatotoxicity, renal failure, and even nephrotoxicity. Due to its high and increasing use and persistent degradation, paracetamol has become one of the most frequently detected emerging contaminants in pharmaceuticals and personal care products (PPCPs) in aquatic ecosystems worldwide. Studies have shown that global average concentrations are generally in the microgram and nanogram range, posing a serious threat to aquatic ecosystems through long-term accumulation. Therefore, rapid and ultrasensitive detection of paracetamol is of great significance for environmental monitoring and protecting ecological and human health.

[0003] Currently, common methods for detecting paracetamol include chromatography, mass spectrometry, and Raman spectroscopy. Chromatography exploits the differences in the physicochemical properties of paracetamol in a mixture between the stationary phase and the mobile phase (mostly methanol or acetonitrile), resulting in different residence times due to interactions between the two phases, enabling separation and detection. Mass spectrometry utilizes the ionization of paracetamol in an ion source, generating charged ions with varying mass-to-charge ratios. These ions are accelerated by an electric field to form an ion beam, which enters a mass analyzer, where the paracetamol is analyzed based on the different mass-to-nuclear ratios obtained. Raman spectroscopy uses a beam of infrared light directed at paracetamol, recording its light scattering absorption spectrum. This method is limited to qualitative analysis and is difficult to quantitatively analyze. Consequently, these methods require specialized, large-scale testing equipment, complex pretreatment processes, and the use of toxic organic solvents such as methanol and acetonitrile. These methods also place high demands on the operator, hindering rapid on-site detection and resulting in lengthy testing cycles. Therefore, a sensitive, in-situ, and remote visual detection method is needed. Summary of the Invention

[0004] The purpose of the present invention is to solve the above technical problems and to provide a method for preparing cobalt-modified polyheptazinimide and its application in the photosensitization detection of paracetamol by rhodamine B.

[0005] The preparation method of cobalt-modified polyheptazine imide is carried out according to the following steps: Step S1: Melamine and cyanuric acid are added to deionized water, respectively, and stirred at 50-100°C until completely dissolved, to obtain solutions A and B, respectively. Solution B is added to solution A at 50-100°C and stirred evenly to obtain mixture C. After heating and stirring for 20-40 minutes, potassium thiocyanate is added, and heating and stirring are continued for 20-40 minutes, followed by cobalt nitrate, and heating and stirring are continued for 1.5-3 hours. After heating and stirring, the mixture is cooled, centrifuged, and the supernatant is discarded. The white particles are collected, washed, dried, and ground to obtain powder D. Step S2: Under nitrogen protection, the powder D obtained in step S1 is placed in a tube furnace, heated to 500-550°C, and calcined at 500-550°C for 3-5 hours; after calcination, it is naturally cooled to room temperature to obtain a sample after primary calcination; the sample after primary calcination is placed in a tube furnace again, heated to 450-510°C under air conditions, and calcined at 450-510°C for 1.5-3 hours; after calcination, it is naturally cooled to room temperature to obtain a sample after secondary calcination; the sample after secondary calcination is mixed with chlorine The potassium hydroxide and lithium chloride are mixed and ground, and then placed in a tube furnace, heated to 530-570°C under nitrogen protection, and calcined at 530-570°C for 3.5-4.5 hours. After the calcination, the mixture is naturally cooled to room temperature to obtain a molten salt calcined sample. The molten salt calcined sample is added to a nitric acid solution, stirred in a water bath at 60-80°C for 1-2 hours, cooled and centrifuged, the supernatant is discarded, the remaining solid is collected, washed, dried, and then dispersed in deionized water to prepare a solution with a concentration of 1.0-3.0 g·L -1 Cobalt-modified polyheptazinimide (PHI).

[0006] Application of cobalt-modified polyheptazinimide in the photosensitization detection of paracetamol by rhodamine B. Paracetamol can be detected by using cobalt-modified polyheptazinimide in any of the following ways: Method 1: The concentration is 1.0~3.0g·L -1 Cobalt-modified polyheptazinimide and concentrations of 1~8 mg·L -1 After the rhodamine B solution is evenly mixed, rhodamine B-cobalt-modified polyheptazine imide is obtained; the volume ratio of the cobalt-modified polyheptazine imide to the rhodamine B solution is (0.5-1.0): (0.5-1.0); Rhodamine B-cobalt-modified polyheptazinimide and paracetamol solution are uniformly mixed to obtain a suspension to be tested; the suspension to be tested is placed in a Perfil multi-channel photocatalytic reactor, and is first stirred and adsorbed for 4 to 7 minutes in the absence of light. 532 nm visible light is then applied for 3 to 5 minutes, and then filtered through a 22 μm aqueous filter membrane. The filtered filtrate is detected using a UV-visible spectrophotometer, thereby completing the detection of paracetamol using rhodamine B-cobalt-modified polyheptazinimide; Method 2: The concentration is 1.0~3.0g·L -1 Cobalt-modified polyheptazinimide and concentrations of 1~8 mg·L -1 After the rhodamine B solution is evenly mixed, rhodamine B-cobalt-modified polyheptazine imide is obtained; the volume ratio of the cobalt-modified polyheptazine imide to the rhodamine B solution is (0.5-1.0): (0.5-1.0); Rhodamine B-cobalt-modified polyheptazinimide and a paracetamol solution are uniformly mixed to obtain a suspension to be tested. The volume ratio of the rhodamine B solution, cobalt-modified polyheptazinimide, and paracetamol solution in the rhodamine B-cobalt-modified polyheptazinimide is (0.5-1.0):(0.5-1.0):0.2. The suspension to be tested is injected into a liquid-core optical fiber probe using a syringe and sealed. The liquid-core optical fiber probe is then connected to a HOURS-532 light source, and then a 532 nm single-wavelength light source is turned on for 3-5 minutes to complete the detection of paracetamol using the rhodamine B-cobalt-modified polyheptazinimide.

[0007] The preparation method of the liquid core optical fiber probe is carried out according to the following steps: Step 1: Polyethylene glycol acrylate and 2-hydroxy-2-methyl-1-phenyl-1-propanone were added to deionized water and ultrasonically mixed to obtain a hydrogel solution; Step 2: A silicone tube with an inner diameter of 3 mm was placed over a silicone tube with an inner diameter of 1 mm. The hydrogel solution obtained in step 1 was then injected into the sandwich formed by the two silicone tubes. After curing with a 365 nm UV lamp, the inner and outer silicone tubes were removed to obtain a tubular hydrogel layer. Step 3: The quartz optical fiber is inserted into the tubular hydrogel layer obtained in step 2, and after solidification, it is alternately soaked in sodium alginate solution and calcium chloride solution to obtain a liquid core optical fiber probe.

[0008] Principle of the present invention: Rhodamine B, a brightly colored xanthene dye, has unique spirocyclization properties and can rapidly transform between open-ring and closed-ring structures under certain conditions. Figure 1As shown, the spirocyclization of RhB, which triggers a color change, is demonstrated, making it an ideal probe for developing rapid visual detection systems. More interestingly, RhB can photosensitize the semiconductor under visible light, causing the dye's excited-state electrons to rapidly transfer to the lower-energy conduction band (CB) of the semiconductor. Upon electron loss, RhB can transform from a colored open-ring structure to a colorless closed-ring structure, triggering rapid photosensitized decolorization of RhB. Based on this property, if the semiconductor can competitively adsorb paracetamol, paracetamol can block electron transfer between the dye RhB and the semiconductor, thereby inhibiting the photosensitized decolorization process and achieving a color change. Therefore, leveraging the degree to which paracetamol inhibits RhB photosensitization decolorization in a RhB-semiconductor photosensitization system holds promise for developing novel methods for the visual detection of paracetamol.

[0009] Another key component of the photosensitized detection system is a semiconductor that matches the energy level of RhB. The lowest unoccupied molecular orbital (LUMO) of the RhB dye should be more negative than the semiconductor's CB, thermodynamically facilitating electron injection into the semiconductor. The emerging two-dimensional carbon nitride-based nanomaterial, polyheptazinimide (PHI), possesses a suitable semiconductor band edge position, making it easy to accept photoexcited electrons from the RhB dye. Its high crystallinity and two-dimensional lamellar structure facilitate surface charge transport, thus promoting photosensitized decolorization. Furthermore, PHI possesses abundant surface active sites and a readily tunable electronic structure, facilitating precise and selective adsorption of paracetamol through structural manipulation or modification, making it an ideal semiconductor material for photosensitized paracetamol detection. Therefore, exploring and establishing a novel RhB-PHI photosensitized detection method holds promise for rapid, visual, highly sensitive, and highly selective detection of paracetamol.

[0010] Fiber optic probes are target detection tools based on the sensing and quantification of optical signals. They offer advantages such as compact design, integrated signal transmission and detection, and strong remote detection capabilities. They can also be easily combined with conventional physical and chemical processing methods to detect substances difficult to detect with other methods. They have been widely used in chemistry, biology, and medicine. However, the modification and etching of traditional solid-state optical fibers are complex and time-consuming. Light is primarily concentrated at the fiber end, resulting in uneven light distribution caused by scattering and refraction, and effective contact between the sensing material and contaminants is lost within the solid-state fiber. Hydrogel liquid-core optical fibers, with their high-refractive-index core and low-refractive-index cladding, allow light to be localized and transmitted within the hydrogel fiber. By embedding sensing materials within the hydrogel liquid-core optical fiber probe, the sample to be detected is automatically introduced into the fiber core and mixed with the sensing material. The RhB-Co / PHI photosensitized detection system reacts to induce changes in the optical signal, enabling rapid, on-site, in-situ detection of paracetamol.

[0011] Based on this, the present invention differs from traditional detection methods in its principles and procedures by proposing a novel dye-semiconductor photosensitization detection method. This method utilizes a novel cobalt-modified PHI nanomaterial (Co / PHI) and RhB to construct a visual detection method for paracetamol. This sensing material system is encapsulated in a liquid-core fiber optic probe, enabling rapid, on-site, remote reading of paracetamol concentration data simply by inserting the probe into a test water sample. The specific detection principle is that RhB photosensitizes Co / PHI under 532nm visible light. The excited electrons of RhB rapidly transfer to the lower-energy conduction band (CB) of Co / PHI. At this point, RhB loses electrons, transforming from a colored open-ring structure to a colorless closed-ring structure, triggering rapid photosensitization and decolorization of the RhB. However, when paracetamol coordinates with Co on PHI, enhancing the competitive selective adsorption of paracetamol by Co / PHI, it can block electron transfer between the dye RhB and Co / PHI, thereby inhibiting the photosensitized decolorization process of RhB and causing a color change in RhB. Therefore, a new method for visual paracetamol detection was developed by leveraging the degree of paracetamol's inhibition of RhB photosensitized decolorization in the RhB-Co / PHI photosensitizer system—that is, the change in RhB's visible light absorption intensity or color. Furthermore, the RhB-Co / PHI sensing system was encapsulated in a hydrogel liquid-core fiber probe equipped with a 532nm fiber light source. This allows the sample to enter the fiber core and mix thoroughly and evenly with the sensing material. The probe color change caused by the photosensitization reaction in the liquid-core fiber enables on-site, in-situ, rapid, and remote detection of paracetamol.

[0012] Beneficial effects of the present invention: This invention successfully establishes a RhB-Co / PHI photosensitizer system for portable, visual, and rapid paracetamol detection. This system requires only a single-wavelength, 532nm light source to illuminate the detection system, enabling visual detection of paracetamol through color changes. In this detection system, a novel synthesis method was employed to synthesize Co / PHI nanomaterials. The interaction between Co introduced onto PHI and paracetamol enhances its selective adsorption and enrichment capacity, thereby improving the selectivity and sensitivity of paracetamol detection.

[0013] In addition, compared to traditional solid-state fiber optic probes, their modification and corrosion are complex and time-consuming, and light is mainly concentrated at the end of the fiber. There are problems such as scattering and refraction that lead to uneven light distribution, and the sensing material and contaminants cannot effectively contact each other in the solid-state fiber. This patent prepares a hydrogel liquid-core fiber structure with a high-refractive index core and a low-refractive index cladding. Light can be positioned and transmitted within the hydrogel fiber, greatly improving the utilization rate of light. The RhB-Co / PHI sensing material is encapsulated into the hydrogel liquid-core fiber optic probe, which allows the sample to enter the fiber core and be fully and evenly mixed with the sensing material. By utilizing the color change of the probe caused by the photosensitization reaction in the liquid-core fiber optic probe, and with the help of a colorimetric card or a smartphone, on-site, in-situ, rapid and remote paracetamol detection can be achieved.

[0014] The invention provides a preparation method of cobalt-modified polyheptazinimide and application of the cobalt-modified polyheptazinimide in photosensitization detection of paracetamol using rhodamine B. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Indicates the spirocyclization transformation characteristics of RhB; Figure 2 Scanning electron microscopy (SEM) image of Co / PHI; Figure 3 EDS element distribution diagram of Co / PHI; Figure 4 represents the X-ray diffraction pattern (XRD) of Co / PHI; Figure 5 represents the Fourier transform infrared spectrum (FT-IR) of Co / PHI; Figure 6 It shows the trend of the concentration change of photosensitized decolorization of RhB with the extension of illumination time; Figure 7 It shows the UV-visible absorption spectra of RhB when different concentrations of paracetamol are added into the RhB-Co / PHI detection system; Figure 8 The logarithm of the RhB blocking rate lg( I ) and the linear fitting relationship between the logarithm of paracetamol concentration lg[c]; Figure 9 A diagram showing the effect of several potential interfering substances on the detection of paracetamol after being added to the RhB-Co / PHI system; Figure 10 The figure shows the change of blocking effect on sensitized decolorization as the concentration of paracetamol added to the system increases; Figure 11 It represents a standard color comparison card made according to different concentrations of paracetamol and the corresponding fiber optic probe colors; Figure 12A diagram showing an optical fiber paracetamol detection device according to the present invention; Figure 13 A physical diagram showing the cladding of the liquid core optical fiber of the present invention; Figure 14 Schematic diagram of the liquid core optical fiber of the present invention; Figure 15 A diagram showing the liquid core optical fiber and its testing process in the present invention; Figure 16 The present invention represents 1g (C 扑热息痛 ) and brightness. DETAILED DESCRIPTION

[0016] Specific embodiment 1: The preparation method of cobalt-modified polyheptazinimide in this embodiment is carried out according to the following steps: Step S1: Melamine and cyanuric acid are added to deionized water, respectively, and stirred at 50-100°C until completely dissolved, to obtain solutions A and B, respectively. Solution B is added to solution A at 50-100°C and stirred evenly to obtain mixture C. After heating and stirring for 20-40 minutes, potassium thiocyanate is added, and heating and stirring are continued for 20-40 minutes, followed by cobalt nitrate, and heating and stirring are continued for 1.5-3 hours. After heating and stirring, the mixture is cooled, centrifuged, and the supernatant is discarded. The white particles are collected, washed, dried, and ground to obtain powder D. Step S2: Under nitrogen protection, the powder D obtained in step S1 is placed in a tube furnace, heated to 500-550°C, and calcined at 500-550°C for 3-5 hours; after calcination, it is naturally cooled to room temperature to obtain a sample after primary calcination; the sample after primary calcination is placed in a tube furnace again, heated to 450-510°C under air conditions, and calcined at 450-510°C for 1.5-3 hours; after calcination, it is naturally cooled to room temperature to obtain a sample after secondary calcination; the sample after secondary calcination is mixed with chlorine The potassium hydroxide and lithium chloride are mixed and ground, and then placed in a tube furnace, heated to 530-570°C under nitrogen protection, and calcined at 530-570°C for 3.5-4.5 hours. After the calcination, the mixture is naturally cooled to room temperature to obtain a molten salt calcined sample. The molten salt calcined sample is added to a nitric acid solution, stirred in a water bath at 60-80°C for 1-2 hours, cooled and centrifuged, the supernatant is discarded, the remaining solid is collected, washed, dried, and then dispersed in deionized water to prepare a solution with a concentration of 1.0-3.0 g·L -1 Cobalt-modified polyheptazinimide.

[0017] Specific embodiment 2: This embodiment differs from specific embodiment 1 in that: the ratio of the mass of melamine, the mass of cyanuric acid and the volume of deionized water described in step S1 is (8-13) g: (3-5) g: (300-550) mL; the mass ratio of melamine, cyanuric acid, potassium thiocyanate and cobalt nitrate described in step S1 is (8-11): (3-5): (0.2-0.3): (0.2-0.3).

[0018] The other steps are the same as those in the first embodiment.

[0019] Specific embodiment three: The difference between this embodiment and specific embodiment one or two is that: the centrifugal speed in step S1 is 3000~5000r / min, and the centrifugation time is 3~7min; the cleaning is carried out by using deionized water and anhydrous ethanol for 3~5 times respectively; the drying temperature is 50~80℃.

[0020] The other steps are the same as those in the first or second embodiment.

[0021] Specific embodiment four: The difference between this embodiment and specific embodiments one to three is that: in step S2, nitrogen protection means that the nitrogen introduction rate is 120~180mL / min; in step S2, heating is performed to 500~550℃ at a heating rate of 1~3℃ / min; in step S2, heating is performed to 450~510℃ at a heating rate of 4~6℃ / min under air conditions; in step S2, heating is performed to 530~570℃ at a heating rate of 4~6℃ / min under nitrogen protection.

[0022] The other steps are the same as those in Specific Embodiments 1 to 3.

[0023] Specific embodiment 5: This embodiment differs from specific embodiments 1 to 4 in that the mass ratio of the sample after secondary calcination, potassium chloride, and lithium chloride in step S2 is (0.3-0.6): (0.4-0.45): (0.3-0.35); the ratio of the mass of the sample after molten salt calcination in step S2 to the volume of the nitric acid solution is (0.5-0.8) g: (50-80) mL, and the concentration of the nitric acid solution is 3-6 mol·L -1 .

[0024] The other steps are the same as those in Specific Embodiments 1 to 4.

[0025] Specific embodiment six: The difference between this embodiment and specific embodiments one to five is that: after cooling in step S2, centrifugation is performed at a speed of 3000~5000r / min for 4~6min; cleaning in step S2 is performed sequentially using deionized water and anhydrous ethanol for 3~5 times each; and the drying temperature is 40~70℃.

[0026] The other steps are the same as those in Specific Embodiments 1 to 5.

[0027] Specific embodiment seven: In this embodiment, cobalt-modified polyheptazinimide is used in the photosensitization detection of paracetamol by rhodamine B. Paracetamol is detected by using cobalt-modified polyheptazinimide in any of the following ways: Method 1: The concentration is 1.0~3.0g·L -1 Cobalt-modified polyheptazinimide and concentrations of 1~8 mg·L -1 After the rhodamine B solution is evenly mixed, rhodamine B-cobalt-modified polyheptazine imide is obtained; the volume ratio of the cobalt-modified polyheptazine imide to the rhodamine B solution is (0.5-1.0): (0.5-1.0); Rhodamine B-cobalt-modified polyheptazinimide and paracetamol solution are uniformly mixed to obtain a suspension to be tested; the suspension to be tested is placed in a Perfil multi-channel photocatalytic reactor, and is first stirred and adsorbed for 4 to 7 minutes in the absence of light. 532 nm visible light is then applied for 3 to 5 minutes, and then filtered through a 22 μm aqueous filter membrane. The filtered filtrate is detected using a UV-visible spectrophotometer, thereby completing the detection of paracetamol using rhodamine B-cobalt-modified polyheptazinimide; Method 2: The concentration is 1.0~3.0g·L -1 Cobalt-modified polyheptazinimide and concentrations of 1~8 mg·L -1 After the rhodamine B solution is evenly mixed, rhodamine B-cobalt-modified polyheptazine imide is obtained; the volume ratio of the cobalt-modified polyheptazine imide to the rhodamine B solution is (0.5-1.0): (0.5-1.0); Rhodamine B-cobalt-modified polyheptazinimide and a paracetamol solution are uniformly mixed to obtain a suspension to be tested. The volume ratio of the rhodamine B solution, cobalt-modified polyheptazinimide, and paracetamol solution in the rhodamine B-cobalt-modified polyheptazinimide is (0.5-1.0):(0.5-1.0):0.2. The suspension to be tested is injected into a liquid-core optical fiber probe using a syringe and sealed. The liquid-core optical fiber probe is then connected to a HOURS-532 light source, and then a 532 nm single-wavelength light source is turned on for 3-5 minutes to complete the detection of paracetamol using the rhodamine B-cobalt-modified polyheptazinimide.

[0028] Specific embodiment eight: This embodiment differs from specific embodiment seven in that the volume of the Rhodamine B aqueous solution is 5-8 mL, and the concentration is 1-3 mg·L -1 The volume of the cobalt-modified polyheptazinimide suspension is 2~4mL, and the concentration is 1~2.5g·L -1 ; The volume of the paracetamol aqueous solution is 0.5~2mL.

[0029] The other steps are the same as those in the seventh embodiment.

[0030] Specific embodiment 9: The preparation method of the liquid core optical fiber probe of this embodiment is carried out according to the following steps: Step 1: Polyethylene glycol acrylate and 2-hydroxy-2-methyl-1-phenyl-1-propanone were added to deionized water and ultrasonically mixed to obtain a hydrogel solution; Step 2: A silicone tube with an inner diameter of 3 mm was placed over a silicone tube with an inner diameter of 1 mm. The hydrogel solution obtained in step 1 was then injected into the sandwich formed by the two silicone tubes. After curing with a 365 nm UV lamp, the inner and outer silicone tubes were removed to obtain a tubular hydrogel layer. Step 3: The quartz optical fiber is inserted into the tubular hydrogel layer obtained in step 2, and after solidification, it is alternately soaked in sodium alginate solution and calcium chloride solution to obtain a liquid core optical fiber probe.

[0031] Specific embodiment ten: This embodiment differs from specific embodiment nine in that the volume ratio of polyethylene glycol acrylate, 2-hydroxy-2-methyl-1-phenyl-1-propanone and deionized water in step one is (2-4): (0.3-0.5): (4-6); the ultrasonic time in step one is 20-50 min; the mass fraction of sodium alginate in the sodium alginate solution in step three is 1-5%, and the concentration of the calcium chloride solution is 0.05-2 mol·L -1 .

[0032] The other steps are the same as those in the ninth embodiment.

[0033] The following examples are used to verify the beneficial effects of the present invention: Example 1: 1. The preparation method of cobalt-modified polyheptazinimide is carried out according to the following steps: Step S1: 10 g of melamine and 4 g of cyanuric acid were respectively added to 500 mL of deionized water and stirred at 80° C. until completely dissolved to obtain solution A and solution B, respectively; solution B was added to solution A at 80° C. and stirred evenly to obtain water-insoluble white particles; heating and stirring were continued for 30 minutes, and then 0.2526 g of potassium thiocyanate was added, and heating and stirring were continued for 30 minutes, and then 0.2278 g of cobalt nitrate was added, and heating and stirring were continued for 2 hours; after heating and stirring, the mixture was cooled, centrifuged at 4000 r / min for 5 minutes, the supernatant was discarded, and the white particles were collected, washed with deionized water and anhydrous ethanol three times each, dried in an oven at 60° C., and ground to obtain powder D; Step S2: Under nitrogen protection (introduction rate of 150 mL / min), the powder D obtained in step S1 was placed in a covered porcelain boat and compacted, then wrapped with aluminum foil and placed in a tube furnace, heated to 520°C at a heating rate of 1°C / min, and calcined at 520°C for 4 h; after calcination, it was naturally cooled to room temperature to obtain a once-calcined sample; the once-calcined sample was loosened, uncovered, wrapped with aluminum foil with holes, and placed in a tube furnace again, heated to 500°C at a heating rate of 5°C / min in air, and calcined at 500°C. The mixture was calcined under the conditions of 400 ° C for 2 h; after calcination, it was naturally cooled to room temperature to obtain a sample after secondary calcination; 0.5 g of the sample after secondary calcination was mixed with 0.4125 g of potassium chloride and 0.3375 g of lithium chloride and ground, and then placed in a covered porcelain boat wrapped with aluminum foil, and then placed in a tube furnace, and heated to 550 ° C at a heating rate of 5 ° C / min under nitrogen protection, and calcined at 550 ° C for 4 h; after calcination, it was naturally cooled to room temperature to obtain a sample after molten salt calcination; 0.7 g of the sample after molten salt calcination was added to 70 mL of 5 mol·L -1 The mixture was stirred in a nitric acid solution at 70°C in a water bath for 1.5 h. After cooling, it was centrifuged at 4000 r / min for 5 min. The supernatant was discarded and the remaining solid was collected and washed with deionized water and anhydrous ethanol 5 times each. The solid was dried in an oven at 60°C and then prepared to obtain a concentration of 1.0 g·L -1 Cobalt-modified polyheptazinimide solution.

[0034] 2. The preparation method of liquid core optical fiber probe is carried out according to the following steps: Step 1: 3 g of polyethylene glycol acrylate and 0.36 g of 2-hydroxy-2-methyl-1-phenyl-1-propanone were added to 5 mL of deionized water and ultrasonicated for 30 min to mix to obtain a hydrogel solution; Step 2: A silicone tube with an inner diameter of 3 mm was placed over a silicone tube with an inner diameter of 1 mm. The hydrogel solution obtained in step 1 was then injected into the sandwich formed by the two silicone tubes. After curing with a 365 nm UV lamp, the inner and outer silicone tubes were removed to obtain a tubular hydrogel layer. Step 3: Insert the quartz optical fiber into the tubular hydrogel layer obtained in step 2. After solidification, use sodium alginate solution (the mass fraction of sodium alginate is 5%) and calcium chloride solution (the concentration is 0.1 mol·L -1 ) are alternately immersed to form a cladding, and a liquid core optical fiber probe (such as Figure 13 shown).

[0035] 3. Characterization of Co / PHI materials: like Figure 2 As shown in Figure 2, Co / PHI exhibits an ultra-thin silk-like sheet structure, but no aggregated or separate Co appears in the TEM image, indicating that Co has not aggregated. Figure 3 As shown, further EDS element distribution map shows that Co, O, C and N elements are evenly distributed in the entire scanning area, indicating that the dispersion of Co on PHI is high.

[0036] like Figure 4 As shown in the X-ray diffraction (XRD) pattern of the material, the peaks at 8.2° and 28.0° correspond to the (100) and (002) characteristic diffraction peaks of PHI, respectively, indicating that PHI was successfully synthesized. In addition, after the introduction of Co, the peak intensity and position of XRD did not change significantly, indicating that the main structure and crystal structure of PHI were not affected.

[0037] like Figure 5 As shown, 2180cm -1 This is attributed to the characteristic peak of -C≡N in PHI, indicating that polyheptazine imide was successfully synthesized and the introduction of Co did not significantly change the main group structure of PHI.

[0038] 4. Application of cobalt-modified polyheptazinimide in the photosensitization detection of paracetamol by rhodamine B. Paracetamol can be detected by using cobalt-modified polyheptazinimide in any of the following ways: Method 1: 1) Solution preparation: Take 0.002g of RhB red powder and dilute it to 1000mL of deionized water to make 2mg·L -1 RhB aqueous solution (pink); 0.15 g of Co / PHI powder was placed in a 100 mL volumetric flask and diluted to volume with deionized water. The solution was thoroughly sonicated and stirred to form 1.5 g·L -1White suspension; take a certain amount of paracetamol powder and add it to a 100mL volumetric flask. First add 0.5mL of methanol and then make up to volume with deionized water. Thoroughly sonicate and stir to fully dissolve the paracetamol, and then dilute to form paracetamol aqueous solutions of different concentrations; 2) Cobalt-modified polyheptazinimide and rhodamine B solution were uniformly mixed to obtain rhodamine B-cobalt-modified polyheptazinimide; rhodamine B-cobalt-modified polyheptazinimide was then uniformly mixed with 1 mL of paracetamol solution of varying concentrations to obtain test solutions; all test solutions were placed in a Perfil multichannel photocatalytic reactor and first stirred and adsorbed in the absence of light for 5 minutes. Then, 532 nm visible light was applied for 5 minutes, and the solution was filtered through a 22 μm aqueous filter membrane. The filtrate was detected using a UV-visible spectrophotometer, completing the detection of paracetamol using rhodamine B-cobalt-modified polyheptazinimide.

[0039] The introduction of dispersed cobalt on PHI is expected to enhance the detection capability of paracetamol by improving the selective adsorption capacity of paracetamol and promoting the sensitization efficiency of RhB.

[0040] Use Co / PHI with a Co loading of 3% as the optimal detection material to configure the detection system according to the above steps and perform light irradiation. Figure 6 The changes in the photosensitized degradation concentration of RhB with the extension of illumination time are demonstrated, and the dark adsorption experiment of Co / PHI on RhB under no-light conditions is used as a control.

[0041] When paracetamol is added to the system, the paracetamol system can selectively adsorb on Co / PHI, which will block the photosensitization and decolorization of RhB, causing the absorption spectrum intensity of RhB to increase, such as Figure 7 As shown in the figure, the degree of photosensitization decolorization of RhB by paracetamol is measured by blocking rate. To express, Calculate using formula (1): ; Where, It represents the blocking rate of photosensitized decolorization of RhB after adding paracetamol; C I Indicates the RhB concentration in the test system after adding paracetamol, unit: mg·L -1 ; C Indicates the concentration of RhB after sensitization and decolorization in the absence of paracetamol, in mg·L -1 ; C 0 * Indicates the concentration of the solution after RhB is darkly adsorbed and filtered by Co / PHI, in mg·L-1 .

[0042] The results showed that when the paracetamol concentration was 10 ng·L -1 ~1mg·L -1 When the logarithm of the RhB blocking rate is within the range It has a linear fitting relationship with the logarithm of paracetamol concentration lg[c], see Figure 8 , the fitting linear equation is =0.306lg[C 扑热息痛 ]-0.7833, linear correlation coefficient R 2 The value was 0.99056, and the minimum quantification limit was 10 ng·L -1 .

[0043] Other PPCPs organic pollutants often coexist in actual environmental systems. In order to explore the selectivity of the Co / PHI photosensitized detection system for paracetamol detection, Figure 9 The effects of several potential interfering substances added to Co / PHI on the detection of paracetamol are shown. The results show that in the absence of paracetamol, the blocking rate of RhB by other coexisting interfering substances is low, and the system appears discolored white, indicating that the photosensitized system has no significant response to other interfering substances. However, in the presence of paracetamol, RhB turns pink, demonstrating a clear selective response to paracetamol. This indicates that environmental interference has little impact on the detection results of paracetamol, and therefore, this method achieves excellent selective detection of paracetamol.

[0044] Method 2 (fiber optic detection process): Solution preparation: Take a 25mL weighing bottle and add 0.2mL of paracetamol solution of different concentrations, 2mg·L -1 RhB solution 0.9 mL, 1.5 g L -1 0.9 mL of the Co / PHI solution was mixed evenly and used as the test solution. 40 μL of the test solution was injected into the liquid core using a syringe. The liquid core probe to be tested was connected to the HOURS-532 light source, and then the 532 nm single wavelength light source was turned on for 6 minutes. As the concentration of paracetamol added to the system continued to increase (40 μg L -1 →1mgL -1 ), its blocking effect on sensitized decolorization is significantly enhanced, and the color contrast is Figure 10 As shown in Figure 2, a standard color comparison card was made according to the different concentrations of paracetamol and the corresponding fiber optic probe colors. Figure 11 shown.

[0045] like Figure 14-15As shown, cobalt-modified polyheptazinimide and rhodamine B solution are mixed evenly to obtain rhodamine B-cobalt-modified polyheptazinimide; rhodamine B-cobalt-modified polyheptazinimide is mixed evenly with 0.2 mL of paracetamol solution to obtain a suspension to be tested; the solution to be tested is injected into the liquid core optical fiber probe using a syringe and encapsulated; the optical fiber liquid core probe is connected to a HOURS-532 light source, and then a 532 nm single wavelength light source is turned on for 3 minutes; Therefore, the color of the fiber optic probe obtained from the unknown sample can be compared with the standard colorimetric card to achieve visual semi-quantitative detection of paracetamol. The lowest detectable concentration that can be visually distinguished is 40 μg·L -1 , realizing the rapid visual detection of colorless paracetamol.

[0046] On the other hand, the RGB color recognition software on the mobile phone is used to identify the RGB value of the liquid core probe color. The specific detection device is shown in the figure below. Figure 12 As shown in the figure, the brightness value is calculated based on the RGB value obtained on the mobile phone = [0.299×R+ 0.587×G+ 0.114×B]. When paracetamol is at 40μgL -1 ~1mgL -1 Within the concentration range, the calculated brightness is related to the logarithm of the paracetamol concentration lg [C 扑热息痛 ] can be fitted into a linear equation, as Figure 16 As shown, the linear equation is brightness = -33.579lg[C 扑热息痛 ]+220.51, linear correlation coefficient R 2 The value is 0.9931, and accurate concentration quantitative detection can be achieved through this method.

[0047] 5. Innovations of the present invention: This invention successfully establishes a RhB-Co / PHI photosensitization system for portable, visual, and rapid detection of paracetamol. This system leverages the color change of RhB and the interaction between Co introduced onto PHI and paracetamol to enhance the selective adsorption and enrichment of paracetamol, thereby improving the selectivity and sensitivity of paracetamol detection. The use of a liquid-core fiber optic probe integrates detection and signal transmission, making detection more convenient and rapid.

Claims

1. A method for preparing cobalt-modified polyheptazine imide, characterized in that The preparation method is carried out according to the following steps: Step S1: Melamine and cyanuric acid are added to deionized water, respectively, and stirred at 50-100°C until completely dissolved, to obtain solutions A and B, respectively. Solution B is added to solution A at 50-100°C and stirred evenly to obtain mixture C. After heating and stirring for 20-40 minutes, potassium thiocyanate is added, and heating and stirring are continued for 20-40 minutes, followed by cobalt nitrate, and heating and stirring are continued for 1.5-3 hours. After heating and stirring, the mixture is cooled, centrifuged, and the supernatant is discarded. The white particles are collected, washed, dried, and ground to obtain powder D. Step S2: Under nitrogen protection, the powder D obtained in step S1 is placed in a tube furnace, heated to 500-550°C, and calcined at 500-550°C for 3-5 hours; after calcination, it is naturally cooled to room temperature to obtain a sample after primary calcination; the sample after primary calcination is placed in a tube furnace again, heated to 450-510°C under air conditions, and calcined at 450-510°C for 1.5-3 hours; after calcination, it is naturally cooled to room temperature to obtain a sample after secondary calcination; the sample after secondary calcination is mixed with chlorine The potassium hydroxide and lithium chloride are mixed and ground, and then placed in a tube furnace, heated to 530-570°C under nitrogen protection, and calcined at 530-570°C for 3.5-4.5 hours. After the calcination, the mixture is naturally cooled to room temperature to obtain a molten salt calcined sample. The molten salt calcined sample is added to a nitric acid solution, stirred in a water bath at 60-80°C for 1-2 hours, cooled and centrifuged, the supernatant is discarded, the remaining solid is collected, washed, dried, and then dispersed in deionized water to prepare a solution with a concentration of 1.0-3.0 g·L -1 Cobalt-modified polyheptazinimide.

2. The method for preparing cobalt-modified polyheptazinimide according to claim 1, wherein The mass ratio of melamine, cyanuric acid and deionized water in step S1 is (8-13) g: (3-5) g: (300-550) mL; the mass ratio of melamine, cyanuric acid, potassium thiocyanate and cobalt nitrate in step S1 is (8-11): (3-5): (0.2-0.3): (0.2-0.3).

3. The method for preparing cobalt-modified polyheptazinimide according to claim 1, wherein In step S1, the centrifugal speed is 3000-5000 r / min, and the centrifugal time is 3-7 min. The washing is performed by sequentially using deionized water and anhydrous ethanol for 3-5 times each. The drying temperature is 50-80°C.

4. The method for preparing cobalt-modified polyheptazine imide according to claim 1, characterized in that In step S2, nitrogen protection means that the nitrogen introduction rate is 120~180mL / min; in step S2, heating is performed to 500~550°C at a heating rate of 1~3°C / min; in step S2, heating is performed to 450~510°C at a heating rate of 4~6°C / min under air conditions; in step S2, heating is performed to 530~570°C at a heating rate of 4~6°C / min under nitrogen protection.

5. The method for preparing cobalt-modified polyheptazinimide according to claim 1, characterized in that The mass ratio of the sample after secondary calcination in step S2, potassium chloride, and lithium chloride is (0.3-0.6): (0.4-0.45): (0.3-0.35); the ratio of the mass of the sample after molten salt calcination in step S2 to the volume of the nitric acid solution is (0.5-0.8) g: (50-80) mL, and the concentration of the nitric acid solution is 3-6 mol·L -1 .

6. The method for preparing cobalt-modified polyheptazine imide according to claim 1, characterized in that After cooling in step S2, centrifugation is performed at a speed of 3000-5000 r / min for 4-6 minutes; cleaning in step S2 is performed by sequentially using deionized water and anhydrous ethanol for 3-5 times each; and the drying temperature is 40-70°C.

7. Use of the cobalt-modified polyheptazinimide prepared by the method according to any one of claims 1 to 6 in the photosensitization detection of paracetamol by rhodamine B, characterized in that Paracetamol was detected using cobalt-modified polyheptazinimide in either of the following ways: Method 1: The concentration is 1.0~3.0g·L -1 Cobalt-modified polyheptazinimide and concentrations of 1~8 mg·L -1 After the rhodamine B solution is evenly mixed, rhodamine B-cobalt-modified polyheptazine imide is obtained; the volume ratio of the cobalt-modified polyheptazine imide to the rhodamine B solution is (0.5-1.0): (0.5-1.0); Rhodamine B-cobalt-modified polyheptazinimide and paracetamol solution are uniformly mixed to obtain a suspension to be tested; the suspension to be tested is placed in a Perfil multi-channel photocatalytic reactor, and is first stirred and adsorbed for 4 to 7 minutes in the absence of light. 532 nm visible light is then applied for 3 to 5 minutes, and then filtered through a 22 μm aqueous filter membrane. The filtered filtrate is detected using a UV-visible spectrophotometer, thereby completing the detection of paracetamol using rhodamine B-cobalt-modified polyheptazinimide; Method 2: The concentration is 1.0~3.0g·L -1 Cobalt-modified polyheptazinimide and concentrations of 1~8 mg·L -1 After the rhodamine B solution is evenly mixed, rhodamine B-cobalt-modified polyheptazine imide is obtained; the volume ratio of the cobalt-modified polyheptazine imide to the rhodamine B solution is (0.5-1.0): (0.5-1.0); Rhodamine B-cobalt-modified polyheptazinimide and a paracetamol solution are uniformly mixed to obtain a suspension to be tested. The volume ratio of the rhodamine B solution, cobalt-modified polyheptazinimide, and paracetamol solution in the rhodamine B-cobalt-modified polyheptazinimide is (0.5-1.0):(0.5-1.0):0.

2. The suspension to be tested is injected into a liquid-core optical fiber probe using a syringe and sealed. The liquid-core optical fiber probe is then connected to a HOURS-532 light source, and then a 532 nm single-wavelength light source is turned on for 3-5 minutes to complete the detection of paracetamol using the rhodamine B-cobalt-modified polyheptazinimide.

8. Use of the cobalt-modified polyheptazinimide according to claim 7 in the photosensitization detection of paracetamol by rhodamine B, characterized in that The volume of the Rhodamine B aqueous solution is 5-8 mL, and the concentration is 1-3 mg·L -1 The volume of the cobalt-modified polyheptazinimide suspension is 2~4mL, and the concentration is 1~2.5g·L -1 ; The volume of the paracetamol aqueous solution is 0.5~2mL.

9. The method for preparing a liquid core optical fiber probe according to claim 7, wherein The preparation method is carried out according to the following steps: Step 1: Polyethylene glycol acrylate and 2-hydroxy-2-methyl-1-phenyl-1-propanone were added to deionized water and ultrasonically mixed to obtain a hydrogel solution; Step 2: A silicone tube with an inner diameter of 3 mm was placed over a silicone tube with an inner diameter of 1 mm. The hydrogel solution obtained in step 1 was then injected into the sandwich formed by the two silicone tubes. After curing with a 365 nm UV lamp, the inner and outer silicone tubes were removed to obtain a tubular hydrogel layer. Step 3: The quartz optical fiber is inserted into the tubular hydrogel layer obtained in step 2, and after solidification, it is alternately soaked in sodium alginate solution and calcium chloride solution to obtain a liquid core optical fiber probe.

10. The method for preparing a liquid core optical fiber probe according to claim 9, characterized in that The volume ratio of polyethylene glycol acrylate, 2-hydroxy-2-methyl-1-phenyl-1-propanone, and deionized water in step 1 is (2-4): (0.3-0.5): (4-6); the ultrasonication time in step 1 is 20-50 min; the mass fraction of sodium alginate in the sodium alginate solution in step 3 is 1-5%, and the concentration of the calcium chloride solution is 0.05-2 mol·L -1 .

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