A flexible SERS sensor for detecting sulfamethoxazole antibiotic and a preparation method thereof

Abstract

The application provides a SERS nanosensor for detecting sulfonamide oxazole antibiotic and a preparation method, and belongs to the technical field of high polymer materials. The application adopts two high polymer materials, polyurethane (PU) and polyarylether oxime (PEA), to configure solutions with different proportions, and uses electrospinning technology to prepare PU-PEA nanofiber membranes with a special 'bead-net' structure. Then, a silver layer is coated on the PUx membrane, and heat annealing treatment is performed, so that a novel SERS flexible substrate is obtained. The optimized SERS flexible substrate has good stability and repeatability, and can detect as low as 10 ‑10 M sulfonamide methoxazole (SMZ) antibiotic.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, and in particular relates to a flexible SERS sensor for detecting sulfamethoxazole antibiotic and its preparation method. Background Technology

[0002] Sulfonamide antibiotics are widely used in agriculture, medicine, and personal healthcare due to their broad spectrum, convenience, low cost, and significant efficacy. However, the overuse of sulfonamide antibiotics has led to a significant increase in antibiotic resistance among various microorganisms. Furthermore, the overuse of sulfonamide antibiotics can cause some chronic diseases in humans. For example, long-term exposure to sulfonamide antibiotics can deplete the beneficial bacteria in the human gut, thereby impairing the immune system and increasing susceptibility to disease. In addition, it causes serious environmental pollution, disrupts the balance of beneficial bacteria in the soil, and consequently affects soil fertility and the balance of the ecosystem. Although traditional instrumental analytical methods can achieve highly sensitive detection of these antibiotics, they are generally cumbersome to operate and costly. Therefore, developing analytical techniques and methods for rapid detection of antibiotics has significant practical value.

[0003] Surface-enhanced Raman scattering (SERS) is an emerging molecular spectroscopy technique that enables label-free, specific detection of trace organic compounds by effectively providing fingerprint structural information of organic molecules. For example, previous researchers have developed various SERS nanosensors based on plasmonic noble metal nanostructures, which can sensitively and non-destructively detect sulfonamide antibiotics. Although previously reported SERS nanosensors have shown good analytical performance in antibiotic detection, these SERS nanosensors are typically fabricated using rigid materials (glass, silicon, etc.) as substrates, which obviously hinders their application in complex sample environments with complex, curved, and irregular surfaces. Therefore, constructing flexible SERS sensing structures on various types of soft substrates is considered an effective means of developing conformal detection capabilities or wearable flexible sensors.

[0004] Among them, electrospun membrane substrates possess high surface roughness, providing high-quality surface signals and thus improving experimental accuracy. Simultaneously, the high mechanical properties and chemical stability of electrospun membranes allow for the fabrication of substrates of various shapes and sizes to meet experimental requirements. Furthermore, electrospun membranes have low preparation costs and are easy to mass-produce. Polyurethane (PU) is a polymer material with excellent spinnability, and its electrospun membranes have extremely important application value. PU electrospun membranes have stronger mechanical properties than other polymers, and their interference signals as Raman substrates are extremely weak. However, under normal circumstances, their long-term operating temperature generally does not exceed 80℃, and their short-term operating temperature should not exceed 120℃, and their acid and alkali resistance is poor. Therefore, their further application as substrates is limited. Polyarylene ether nitrile electrospun membranes, with their excellent thermodynamic properties, corrosion resistance, and high-temperature resistance, have been applied in many fields. However, they exhibit some interference signals as SERS substrates, so they are generally not used directly as Raman substrates. Summary of the Invention

[0005] The purpose of this invention is to address the problems existing in the background technology by proposing a method for preparing a flexible SERS nanosensor for the detection of sulfamethoxazole antibiotic. This invention involves preparing solutions of polyurethane (PU) and polyarylene oxime (PEA) in different proportions, and then using electrospinning technology to prepare a layered "beaded mesh" nanofiber membrane, named PUx membrane (where x represents the proportion of PU in the PU-PEA membrane). Then, a nanoscale thick silver layer is formed on the PUx membrane by vacuum physical vapor deposition, followed by thermal annealing, thereby obtaining a novel nanosilver-modified PUx composite membrane, named Ag-PUx. Benefiting from its unique surface roughness and the near-field optical effect of nanosilver, the Ag-PUx composite membrane exhibits excellent Raman sensitization performance, making it a good flexible SERS substrate. Furthermore, the flexible SERS substrate obtained after optimization of experimental conditions can significantly enhance the characteristic Raman signal of sulfamethoxazole (SMZ) antibiotic, achieving label-free detection of 0.1 nM concentration SMZ.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing a flexible SERS sensor for detecting sulfamethoxazole antibiotic includes the following steps:

[0008] Step 1: Synthesize polyurethane; Place a measured amount of polyol into a three-necked flask, heat to 100°C, and evacuate under vacuum for 2 hours. After evacuation, lower the temperature to 80°C, add a measured amount of diisocyanate, and maintain the temperature for 2-3 hours of reaction. After the reaction is complete, add a small-molecule chain extender (after removing moisture) to the prepolymer, and continue the reaction at 80°C for 3 hours to obtain the polyurethane (PU) used in the experiment.

[0009] Furthermore, the polyols mentioned above are one or more of polyethylene glycol (PEG), polypropylene glycol (PPG), and polytetrahydrofuran glycol (PTMG) with a molecular weight of 600-2000; the diisocyanates are isophorone diisocyanate (IPDI), toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), dicyclohexylmethane diisocyanate (HMDI), etc.; and the small molecule chain extenders are various small molecule diols and diamines, such as ethylene glycol and 1,4-butanediol.

[0010] Step 2: Synthesis of polyarylene ether oxime (PEA); 10 parts (by mass) of polyarylene ether nitrile, 7.5 parts (by mass) of hydroxylamine hydrochloride, 50 parts (by volume) of methanol, and 50 parts (by volume) of deionized water were weighed and mixed. The pH of the system was adjusted to 7-8 using potassium hydroxide. The reaction was carried out at 80℃ for 12-48 hours. After the reaction was completed, the mixture was repeatedly washed with deionized water until the filtrate was neutral. The filtered product was then dried at 80℃ to obtain polyarylene ether oxime (PEA).

[0011] The chemical structural formula of the obtained PEA is:

[0012]

[0013] Ar can be any one of biphenyl hydroquinone, bisphenol A, phenolphthalein, fluorinated bisphenol A, or phenolphthalein.

[0014] Step 3: Prepare PU-PEA-DMF (N,N-dimethylformamide) solutions by mixing PU and PEA at different mass ratios (PU mass ratio increases proportionally from 0% to 100%, while PEA mass ratio decreases proportionally from 100% to 0%), maintaining a consistent viscosity. After complete dissolution, allow to stand overnight to remove air bubbles. Then, introduce the degassed PU-PEA-DMF solution into a 10mL syringe with a 23-gauge needle at a feed rate of 0.6mL / h. During electrospinning, the spinning voltage is 20kV, and the operating distance between the needle tip and the rotating drum is 25cm. The prepared electrospun membrane is named PUx (x represents the mass percentage of PU).

[0015] Step 4: Cut the PUx nanofiber membrane from Step 3 into 20mm diameter circles using a cutter and fix them onto a vacuum evaporation plate. Next, deposit an ultrathin silver layer onto the PUx membrane using physical vapor deposition. During the deposition process, the following methods are employed: The thickness of the surface silver layer is controlled within the range of 5-25 nm by a constant evaporation rate. The hybrid silver-modified PUx film (Ag-PUx) obtained under these conditions is then subjected to heat treatment at different times (1-5 h) and different temperatures (80-120 °C) to obtain the SERS nanosensor.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] 1. This invention provides a method for preparing a flexible SERS nanosensor for the detection of sulfamethoxazole antibiotic. By changing the relative ratio of PU to PEA, a series of nanofiber membranes with different structures and properties are prepared. On the one hand, PU has higher molecular chain segment mobility and optical transparency. During the heat treatment of the nanofiber membrane, PU tends to migrate to the surface of the composite fiber, thus laying the foundation for shielding the background signal of polyarylene oxime that may exist in the flexible SERS sensor later. On the other hand, aromatic PEA has higher mechanical strength, which also makes the PU-PEA nanocomposite fiber membrane have better mechanical properties.

[0018] 2. This invention provides a method for preparing a SERS nanosensor for the detection of sulfamethoxazole antibiotic. Due to the different surface segregation behaviors of PU and PEA, and their potential interfacial reactions, the prepared Ag-PUx membrane exhibits an interesting "bead-network" hierarchical morphology. The Ag-PUx nanofiber membrane possesses a unique hierarchical surface roughness, which significantly improves its Raman enhancement effect, enabling the detection of concentrations as low as 10. -12 The signal of the Raman dye 1,2-bis(4-pyridyl)ethylene (BPE) molecule in solution M and 10 -10 Sulfamethoxazole (SMZ) antibiotic at concentration M.

[0019] 3. This invention provides a method for preparing a SERS nanosensor for the detection of sulfamethoxazole antibiotic. By optimizing different PU / PEA ratios, silver film thicknesses, and heat treatment temperatures, a SERS nanosensor with superior performance is obtained. The preparation method is simple, safe, and environmentally friendly. Attached Figure Description

[0020] Figure 1 The TGA images are of the PUx nanofiber membranes prepared in steps 1-3 of Examples 1-5.

[0021] Figure 2Infrared spectra of PU0, PU100 and PU50 nanofiber membranes prepared in steps 1-3 of Examples 1, 3 and 5.

[0022] Figure 3 The changes in the contact angle of the PUx nanofiber membranes prepared in steps 1-3 of Examples 1-15 are shown.

[0023] Figure 4 Examples 1-5 show the SERS curves of the Ag-PUx nanofiber membrane prepared in step 4 under a 10nm thick Ag membrane.

[0024] Figure 5 Examples 1-15 show the SERS curves of the Ag-PUx nanofiber membrane prepared in step 4 under a 10 nm thick Ag membrane for BPE testing.

[0025] Figure 6 The SERS test curves of BPE were obtained for the Ag-PU50 nanofiber membranes prepared in step 4 of Examples 3, 10, 11, 16-21.

[0026] Figure 7 The time stability diagram of the Ag-PU50 nanofiber membrane prepared in step 4 of Example 20 is shown.

[0027] Figure 8 The figures show the fitting curve and linear fitting graph of the Raman signal intensity generated by the Ag-PU50 nanofiber membrane prepared in step 4 of Example 20 against BPE and the BPE concentration.

[0028] Figure 9 The graph shows the repeatability of the Ag-PU50 nanofiber membrane prepared in step 4 of Example 20 against BPE.

[0029] Figure 10 The image shows the SERS test result of the Ag-PU50 nanofiber membrane prepared in step 4 of Example 20 on SMZ.

[0030] Figure 11 The figures show the fitting curve and linear fitting graph of the Raman signal intensity (609nm band) generated by SMZ and the SMZ concentration of the Ag-PU50 nanofiber membrane prepared in step 4 of Example 20.

[0031] Figure 12 The figures show the fitting curve and linear fitting graph of the Raman signal intensity (772nm band) generated by the Ag-PU50 nanofiber membrane prepared in step 4 of Example 20 against the SMZ concentration.

[0032] Figure 13 This is a schematic diagram of the composition of the sensor of the present invention. Detailed Implementation

[0033] The present invention will be further described below through specific embodiments, but this is not a limitation of the present invention. Those skilled in the art can make various modifications or variations based on the basic idea of ​​the present invention, as long as they do not depart from the basic idea of ​​the present invention, they are all within the scope of the present invention.

[0034] Example 1

[0035] Step 1: Synthesize polyurethane. Place 10g of PTMG650 (polytetrahydrofuran glycol 650) in a three-necked flask, heat to 110℃, and evacuate under vacuum for 2 hours. After evacuation, lower the temperature to 80℃, add 10.039g of IPDI, and maintain the temperature for 2-3 hours of reaction. Step 2: Add 2.182g of ethylene glycol (after removing moisture) as a chain extender to the above prepolymer, and continue the reaction at 80℃ for 3 hours to obtain the polyurethane (PU) used in the experiment.

[0036] Step 2: Weigh out 10g of polyarylene ether nitrile, 7.5g of hydroxylamine hydrochloride, 50mL of methanol, and 50mL of deionized water and mix them together. Adjust the pH of the system to 7.8 using potassium hydroxide. React at 80℃ for 24 hours. After conversion, wash repeatedly with deionized water until the filtrate is neutral. Then dry the filter residue at 80℃ to obtain PEA.

[0037] Step 3: Prepare a PU-PEA-DMF solution with a PU / PEA mass ratio of 0 / 10, maintaining a consistent concentration. After complete dissolution, let it stand overnight to remove air bubbles, and then use electrospinning technology to prepare a PU0 film.

[0038] Step 4: Cut the POO nanofiber membrane from Step 3 into 20mm diameter circles using a cutter and fix them onto a vacuum evaporation plate. Next, deposit an ultrathin silver layer onto the POO membrane using physical vapor deposition. During the deposition process, the following methods are employed: The thickness of the surface silver layer was controlled to be 10 nm by a constant evaporation rate. The deposited hybrid silver-modified electrospun polyurethane film (Ag-PU0) was then heat-treated at 80 °C for 1 h and used as a SERS nanosensor for further experiments.

[0039] Example 2

[0040] The difference between this embodiment and embodiment 1 is that the PU / PEA mass ratio is adjusted to 3 / 7 in step 3; the remaining steps are exactly the same as in embodiment 1.

[0041] Example 3

[0042] The difference between this embodiment and embodiment 1 is that the PU / PEA mass ratio in step 3 is adjusted to 5 / 5; the remaining steps are exactly the same as in embodiment 1.

[0043] Example 4

[0044] The difference between this embodiment and embodiment 1 is that the PU / PEA mass ratio in step 3 is adjusted to 7 / 3; the remaining steps are exactly the same as in embodiment 1.

[0045] Example 5

[0046] The difference between this embodiment and embodiment 1 is that the PU / PEA mass ratio is adjusted to 10 / 0 in step 3; the remaining steps are exactly the same as in embodiment 1.

[0047] Example 6

[0048] The difference between this embodiment and embodiment 1 is that the heat treatment temperature in step 4 is adjusted to 100℃; the remaining steps are exactly the same as in embodiment 1.

[0049] Example 7

[0050] The difference between this embodiment and embodiment 1 is that the heat treatment temperature in step 4 is adjusted to 120°C; the remaining steps are exactly the same as in embodiment 1.

[0051] Example 8

[0052] The difference between this embodiment and embodiment 2 is that the heat treatment temperature in step 4 is adjusted to 100℃; the remaining steps are exactly the same as in embodiment 2.

[0053] Example 9

[0054] The difference between this embodiment and embodiment 2 is that the heat treatment temperature in step 4 is adjusted to 120°C; the remaining steps are exactly the same as in embodiment 2.

[0055] Example 10

[0056] The difference between this embodiment and embodiment 3 is that the heat treatment temperature in step 4 is adjusted to 100℃; the remaining steps are exactly the same as in embodiment 3.

[0057] Example 11

[0058] The difference between this embodiment and embodiment 3 is that the heat treatment temperature in step 4 is adjusted to 120°C; the remaining steps are exactly the same as in embodiment 3.

[0059] Example 12

[0060] The difference between this embodiment and embodiment 4 is that the heat treatment temperature in step 4 is adjusted to 100℃; the remaining steps are exactly the same as in embodiment 4.

[0061] Example 13

[0062] The difference between this embodiment and embodiment 4 is that the heat treatment temperature in step 4 is adjusted to 120°C; the remaining steps are exactly the same as in embodiment 4.

[0063] Example 14

[0064] The difference between this embodiment and embodiment 5 is that the heat treatment temperature in step 4 is adjusted to 100℃; the remaining steps are exactly the same as in embodiment 5.

[0065] Example 15

[0066] The difference between this embodiment and embodiment 5 is that the heat treatment temperature in step 4 is adjusted to 120°C; the remaining steps are exactly the same as in embodiment 5.

[0067] Example 16

[0068] The difference between this embodiment and embodiment 3 is that the Ag thickness in step 4 is adjusted to 15nm; the remaining steps are exactly the same as in embodiment 3.

[0069] Example 17

[0070] The difference between this embodiment and embodiment 3 is that the Ag thickness in step 4 is adjusted to 20nm; the remaining steps are exactly the same as in embodiment 3.

[0071] Example 18

[0072] The difference between this embodiment and embodiment 10 is that the Ag thickness in step 4 is adjusted to 15nm; the remaining steps are exactly the same as in embodiment 10.

[0073] Example 19

[0074] The difference between this embodiment and embodiment 10 is that the Ag thickness in step 4 is adjusted to 20nm; the remaining steps are exactly the same as in embodiment 10.

[0075] Example 20

[0076] The difference between this embodiment and embodiment 11 is that the Ag thickness in step 4 is adjusted to 15nm; the remaining steps are exactly the same as in embodiment 11.

[0077] Example 21

[0078] The difference between this embodiment and embodiment 11 is that the Ag thickness in step 4 is adjusted to 20nm; the remaining steps are exactly the same as in embodiment 11.

[0079] Figure 1The TGA images show the PUx nanofiber membranes prepared in steps 1-3 of Examples 1-5. It can be seen that the thermal stability of PUx increases with the increase of the relative PEA content. It should be noted that the TGA curve of the PU0 sample decreases slightly near 160°C, which should be attributed to the decomposition of its suspended aminooxime groups. The initial decomposition temperatures of PU30, PU50, and PU70 samples are slightly higher than those of PU0, which may be due to a potential chemical reaction between the isocyanate groups of PU and the aminooxime groups of PEA.

[0080] Figure 2 The images show the infrared spectra of PU0, PU100, and the heat-treated PU50 nanofiber membranes prepared in steps 1-3 of Examples 1, 3, and 5. The PU50 sample exhibits a tensile vibration peak of -NH and a characteristic absorption peak of -CN. More importantly, the PU0 sample also shows a characteristic absorption peak of -C=N, and the PU100 sample shows a characteristic absorption peak of -C=O. Compared to the PU50 sample, these two peaks show a significant shift. Based on these results, it is demonstrated that a chemical reaction occurs between PU and PEA, forming a chemical crosslink, rather than simply PU physically covering the PEA surface. This indicates that the thermal stability of the PUx membrane is further improved. Therefore, the PU-PEA nanofiber membrane not only exhibits the unique advantages of the combination of PU and PEA, but also enables us to create the following plasmonic nanostructures over a wider temperature range and chemical environment.

[0081] Figure 3 The figures show the changes in the contact angle (WCA) of the PUx nanofiber membranes prepared in steps 1-3 of Examples 1-15. The WCA of the PU0 sample remained unchanged after heat annealing at different temperatures, indicating good stability of the morphology and surface composition of the PEA matrix. However, the WCA of the PU100 sample gradually decreased after heating at higher temperatures. Furthermore, the WCA trend of all Ag-PUx samples was similar to that of PU100. Given that PU is more hydrophilic than PEA, the molecular thermal motion of PU accelerates with increasing heat treatment temperature, leading to the migration of more PU phase to the outer surface of the composite nanofibers. Therefore, the decrease in WCA value of the PUx nanofiber membrane during higher-temperature annealing also signifies that the rigid PEA core is encapsulated by an optically transparent PU shell.

[0082] Figure 4 Examples 1, 3, and 5 show the SERS curves of the Ag-PUx nanofiber membrane prepared in step 4 under a 10nm thick Ag film. It can be seen that PU0 itself has a very strong background signal, while the substrate test baseline of PU100 is stable and no interference signal appears. Meanwhile, the composite film PU50 also shows no background signal.

[0083] Figure 5Examples 1-15 show the SERS curves of the Ag-PUx nanofiber membrane prepared in step 4 under a 10nm thick Ag membrane for BPE testing; it can be seen that the sample in Example 11 has the best detection effect.

[0084] Figure 6 The SERS test curves of BPE were obtained for the Ag-PU50 nanofiber membranes prepared in step 4 of Examples 3, 10, 11, 16-21; it can be seen that Example 20 has the best detection effect.

[0085] Figure 7 The image shows the time stability of the Ag-PU50 nanofiber membrane prepared in step 4 of Example 20, indicating that the SERS flexible substrate remains stable after being placed at room temperature for 30 days.

[0086] Figure 8 The figures show the fitting curve and linear fitting graph of the Raman signal intensity generated by the Ag-PU50 nanofiber membrane prepared in step 4 of Example 20 against BPE concentration; illustrating that the SERS flexible substrate can detect 10 -12 The ultra-low content of M. Furthermore, using 1637cm -1 The peak intensity of the band was plotted as a dependency curve on BPE concentration. It can be seen that there is a good power function relationship between the two and a good linear relationship between the peak intensity and the logarithmic concentration of BPE.

[0087] Figure 9 The image shows the repeatability test of the Ag-PU50 nanofiber membrane prepared in step 4 of Example 20 against BPE. The test was repeated 20 times and still maintained high repeatability, with a relative standard deviation (RSD) of only 8.196% (the requirement of RSD in the prior art is less than 20%).

[0088] Figure 10 This is a SERS test image of the Ag-PU50 nanofiber membrane prepared in step 4 of Example 20 on SMZ; this SERS substrate can detect up to 10 -10 The SMZ solution of M is used, and the Raman signal intensity increases with the increase of SMZ concentration.

[0089] Figure 11 The figures show the fitting curves and linear fitting diagrams of the Raman signal intensity (609 nm band) generated by the Ag-PU50 nanofiber membrane prepared in step 4 of Example 20 and the SMZ concentration. It can be seen that there is a good power function relationship between the two and a good linear relationship between the peak intensity and the logarithmic concentration of SMZ.

[0090] Figure 12The figures show the fitting curve and linear fitting graph of the Raman signal intensity (772nm band) generated by the Ag-PU50 nanofiber membrane prepared in step 4 of Example 20 to SMZ concentration; it can be seen that there is a good power function relationship between the two and a good linear relationship between the peak intensity and the logarithmic concentration of SMZ.

Claims

1. A method for preparing a flexible SERS sensor for detecting sulfamethoxazole antibiotic, characterized in that, Specifically, the following steps are included: Step 1: Synthesize polyurethane (PU); Place a measured amount of polyol into a three-necked flask and heat to 100°C. o C, vacuum for 2 hours; after vacuuming, the temperature drops to 80°C. o C, add a measured amount of diisocyanate and maintain the temperature for 2-3 hours of reaction; after the reaction is complete, add a small molecule chain extender (after removing moisture) and react at 80°C. o The reaction was continued at C for 3 hours to obtain the polyurethane used in the experiment. Step 2: Synthesis of polyarylene ether oxime (PEA); 10 parts by weight of polyarylene ether nitrile, 7.5 parts by weight of hydroxylamine hydrochloride, 50 parts by volume of methanol, and 50 parts by volume of deionized water were weighed and mixed. The pH of the system was adjusted to 7-8 using potassium hydroxide. o The reaction was carried out at a constant temperature of C for 12-48 hours. After the reaction was completed, the product was repeatedly washed with deionized water until the filtrate was neutral. Then, 80% of the filtered product was discharged. o C is dried to obtain polyarylene oxime; Step 3: Prepare PU-PEA-DMF solutions by mixing polyurethane / polyarylene oxime at different mass ratios, ensuring that the viscosity of the PU-PEA-DMF solutions remains consistent at different mass ratios; after complete dissolution, let stand overnight to remove air bubbles, and then use electrospinning technology to prepare a film from the degassed PU-PEA-DMF solution to obtain a PUx nanofiber membrane, where x represents the proportion of PU in the PU-PEA membrane; Step 4: Cut the PUx nanofiber membrane from Step 3 into 20 mm diameter circles using a cutter and fix them on a vacuum evaporation plate. Deposit an ultrathin silver layer onto the PUx membrane using physical vapor deposition. During deposition, a constant evaporation rate of 1 Å / s is used to control the thickness of the surface silver layer within the range of 5-25 nm. The resulting hybrid silver-modified PUx membrane is then cooled to 80-120 °C. o After heat treatment at a temperature of C for 1-5 hours, a flexible SERS sensor is obtained.

2. The preparation method according to claim 1, characterized in that, The polyol is one or more of polyethylene glycol, polypropylene glycol, and polytetrahydrofuran glycol with a molecular weight of 600-2000.

3. The preparation method according to claim 2, characterized in that, The diisocyanate is one or more of isophorone diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, and dicyclohexylmethane diisocyanate.

4. The preparation method according to claim 3, characterized in that, The small molecule chain extender is one or more of a small molecule diol and a diamine.

5. The preparation method according to claim 4, characterized in that, The chemical structural formula of the obtained PEA is: Ar can be any one of biphenyl hydroquinone, bisphenol A, phenolphthalein, fluorinated bisphenol A, or phenolphthalein.

6. The preparation method according to claim 5, characterized in that, During the electrospinning process, the degassed PU-PEA-DMF solution was introduced into a 10 mL syringe with a No. 23 needle at a feed rate of 0.6 mL / h, and the spinning voltage was 20 kV, with an operating distance of 25 cm between the needle tip and the rotating drum.

7. A flexible SERS sensor for detecting sulfamethoxazole antibiotic, characterized in that, The flexible SERS sensor is obtained by the method described in any one of claims 1-6, and the flexible SERS sensor consists of a PUx nanofiber membrane and an ultrathin silver layer deposited on the PUx nanofiber membrane.

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