Polymer optical fiber microprobe for modifying molecularly imprinted polymer and CdTe quantum dots and application of polymer optical fiber microprobe

Abstract

The invention belongs to the technical field of polymer optical fiber microprobes, and particularly discloses a polymer optical fiber microprobe modified with molecularly imprinted polymer and CdTe quantum dots and application of the polymer optical fiber microprobe modified with molecularly imprinted polymer and CdTe quantum dots. Then, a core-shell structure polymer optical fiber microprobe with the surface modified with MIP-QDs is prepared at the tail end of a standard single-mode optical fiber through a free radical photopolymerization method, and the response is faster and detection balance can be achieved only in 10 minutes; the microprobe has a good linear response relationship to amoxicillin in a concentration range of 0.5-50 [mu] g / L, and the detection limit can be as low as 0.31 [mu] g / L, which is superior to the detection requirements of European Union food and drug residue standards. The fluorescence intensity is monotonically decreased along with the change of the target concentration, so that quantitative analysis can be realized; besides, the microprobe has excellent reuse performance and good sensing stability, and the relative standard deviation in multiple rounds of measurement is lower than 1.5%, so that the feasibility and stability of long-term application of the microprobe are shown.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer optical fiber microprobes, in particular to a polymer optical fiber microprobe modified with molecular imprinting polymer and CdTe quantum dots and applications thereof. Background Art

[0002] Amoxicillin (AMX) is an antibiotic used to treat human and animal infectious diseases. Its excessive residues in the food chain and the environment pose a serious threat to public health. Therefore, it is crucial to develop an efficient detection technology to accurately monitor AMX residues in body fluids, food, and the environment.

[0003] Currently, various analytical methods are available for detecting AMX, including chromatography, electrochemistry, surface plasmon resonance, and spectrophotometry. Fluorescence spectroscopy has attracted considerable attention due to its advantages, including rapid analysis, ease of operation, low equipment cost, and minimal solvent consumption. Traditional organic dyes, when used as photoluminescent probes, suffer from drawbacks such as broad emission bands and spectral asymmetry. To address these issues, researchers have employed QDs (quantum dots) (QDs), which possess narrow, symmetrical emission peaks, long fluorescence lifetimes, excellent optical stability, and good water dispersibility, as photoluminescent probes for the detection of ions, molecules, proteins, and cells. However, antibiotics within the same class share similar chemical structures. For example, amoxicillin and ampicillin, both β-lactam antibiotics, exhibit similar chemical structures when reacting with QDs, making them difficult to distinguish. Furthermore, most QDs that are sensitive to analytes (such as CdTe and CdSe QDs) exhibit biotoxicity, raising safety concerns when used in biological samples or biological environments. In summary, traditional fluorescent probes based on organic dyes or quantum dots (QDs) have limitations such as difficult separation, easy contamination, lack of specificity and in situ detection.

[0004] To achieve specific detection, the surface of QDs must be modified with target-specific materials. Molecularly imprinted polymers (MIPs) are an effective strategy for modifying the surface of quantum dots. They can be synthesized specifically for a specific target molecule. After polymerization, the target molecule is removed to obtain a specific recognition cavity. They have the advantages of good biocompatibility, simple preparation, low cost, and good stability. Currently, the combination of MIPs and QDs has been developed as a photoluminescent probe for the selective detection of compounds such as histamine, malachite green, chlorpyrifos, and alpha-fetoprotein. The excellent biocompatibility of MIPs coated with quantum dots can address the biotoxicity of some quantum dots when they come into direct contact with the analyte. However, to date, the use of MIPs-coated QDs for the detection of antibiotics has mostly involved directly mixing the fluorescent probe with the test solution before detection. This not only results in waste of the fluorescent probe and the test solution (the fluorescent probe and the test solution cannot be recovered), but also prevents accurate in situ detection.

[0005] Therefore, since the current conventional detection methods cannot simultaneously take into account the characteristics of high sensitivity, selectivity, good structural stability, biosafety, biocompatibility, in situ detection and easy preparation, it is necessary to develop a polymer optical fiber microprobe modified with molecularly imprinted polymers and CdTe quantum dots and its application. Summary of the Invention

[0006] In order to solve the above technical problems, the present invention provides a polymer optical fiber microprobe modified with molecularly imprinted polymer and CdTe quantum dots and its application.

[0007] To achieve the above object, the present invention is implemented according to the following technical solutions:

[0008] The first technical solution provided by the present invention is a method for preparing a polymer optical fiber microprobe modified with a molecularly imprinted polymer and CdTe quantum dots, comprising the following steps:

[0009] S1. Amoxicillin was used as a template molecule to synthesize MIPs-coated CdTe quantum dots composite fluorescent material MIP-QDs by sol-gel method;

[0010] S2. A core-shell polymer optical fiber microprobe with surface modified MIP-QDs was prepared at one end of a standard single-mode optical fiber by free radical photopolymerization.

[0011] Furthermore, the step S1 specifically includes:

[0012] S11. Dissolve 1 mg of amoxicillin as a template molecule in 250 μL of deionized water, mix with 5 μL of γ-aminopropyltriethoxysilane (APTES) in a brown bottle, and stir at 25°C for 1 h to obtain a mixed solution.

[0013] S12, adding 100 μL of 10 mg / mL mercaptopropionic acid (MPA)-capped and surface-carboxylated CdTe quantum dots, 30 μL of a cross-linking agent, and 50 μL of a catalyst to the above mixture, and continuing stirring for 6 h;

[0014] S13. After the reaction is completed, the product is collected by centrifugation at 3500RCF for 10 minutes, washed with ethanol solution, and centrifuged again, and repeated three times; the composite structure fluorescent material MIP-QDs of MIPs-coated CdTe quantum dots with the template molecules fully removed is obtained; finally, the obtained MIP-QDs are dried in an oven at 40°C for 1 hour for use.

[0015] Preferably, in step S12, the crosslinking agent is tetraethoxysilane TEOS.

[0016] Preferably, in step S12, the catalyst is an aqueous ammonia solution with a volume concentration of 3%.

[0017] Furthermore, the step S2 specifically includes:

[0018] S21, taking a multifunctional acrylate monomer and a cleavage-type photoinitiator in a mass ratio of 95:5, adding MIP-QDs in an amount half the total mass of the multifunctional acrylate monomer and the cleavage-type photoinitiator, and magnetically stirring at room temperature for 10 minutes to mix uniformly to prepare a solution;

[0019] S22. Place the standard single-mode optical fiber vertically on a three-dimensional micro-adjustment stand, then adjust the micro-adjustment stand up and down to immerse one end of the standard single-mode optical fiber vertically in the prepared solution and then slowly lift it up to allow the solution to adhere to the surface of the micro-fiber probe; at this time, turn on the laser, and emit a 1μW power laser that is transmitted through the optical fiber to the surface of the standard single-mode optical fiber and irradiates the droplets adhered to its surface, and the droplets are solidified based on the aforementioned cleavage-type free radical photopolymerization reaction, thereby forming a layer of MIP-QDs coating film on the surface of one end of the standard single-mode optical fiber, and finally turn off the laser and rinse the uncured residual solution with ethanol multiple times to obtain a core-shell structure polymer optical fiber microprobe with surface modified MIP-QDs.

[0020] Preferably, in step S21, the multifunctional acrylate monomer is polyethylene glycol diacrylate.

[0021] Preferably, in step S21, the cleavage-type photoinitiator is 2-hydroxy-2-methylpropiophenone.

[0022] The second technical solution provided by the present invention is a polymer optical fiber microprobe modified with molecularly imprinted polymer and CdTe quantum dots prepared by the above method. The polymer optical fiber microprobe is a core-shell structure polymer optical fiber microprobe with surface modified MIP-QDs prepared at one end of a standard single-mode optical fiber.

[0023] The third technical solution provided by the present invention is the use of a polymer optical fiber microprobe modified with a molecularly imprinted polymer and CdTe quantum dots in the detection of amoxicillin concentration. Specifically, the polymer optical fiber microprobe modified with a molecularly imprinted polymer and CdTe quantum dots is used as an amoxicillin concentration sensor.

[0024] Compared with the existing technology, the present invention uses amoxicillin as a template molecule to synthesize a composite structure of MIPs coated with CdTe quantum dots (MIP-QDs) fluorescent materials through a sol-gel method, and then prepares a core-shell structure polymer optical fiber microprobe with surface modified MIP-QDs at the end of a standard single-mode optical fiber through free radical photopolymerization. The core-shell structure polymer microprobe responds more quickly and can reach detection equilibrium in just 10 minutes. The microprobe has a good linear response relationship (R) to amoxicillin in the concentration range of 0.5-50 μg / L. 2 =0.99695), with a detection limit as low as 0.31μg / L, which exceeds the detection requirements of EU food and drug residue standards. Its fluorescence intensity shows a monotonic downward trend with changes in target concentration, enabling quantitative analysis. In addition, the microprobe has excellent reusability and good sensing stability. The relative standard deviation in multiple rounds of measurement is less than 1.5%, indicating its feasibility and stability for long-term application. In addition, the microprobe sensor has good biocompatibility and environmental friendliness. It does not require organic solvents during operation, is easy to operate, safe and environmentally friendly, and is suitable for detection needs in complex samples. Its in situ detection characteristics enable real-time detection of amoxicillin in liquid or biological environments without extracting and processing samples, greatly improving work efficiency and application flexibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Flow chart of the preparation of MIP-QDs.

[0026] Figure 2 Flowchart for the preparation of polymer optical fiber microprobes modified with MIP-QDs fluorescent materials: (a) non-core-shell polymer optical fiber microprobes modified with MIP-QDs; (b) core-shell polymer optical fiber microprobes modified with MIP-QDs.

[0027] Figure 3 SEM image of the polymer optical fiber microprobe modified with MIP-QDs.

[0028] Figure 4 Excitation spectra (a) and emission spectra (b) of MIP-QDs.

[0029] Figure 5 Schematic diagram of the experimental setup of the microspectrophotometer (20 / 20PV, CRAIC, Germany).

[0030] Figure 6 :(a) Photoluminescence spectra of MIP-QDs before (i) and after (ii) template molecule removal, and NIP-QDs (iii) in an amoxicillin-free solution environment; (b) Photoluminescence spectra of MIP-QDs before (i) and after (ii) template molecule removal, and NIP-QDs (iii) in an amoxicillin solution environment with a concentration of 8.5 μg / L.

[0031] Figure 7 : (a) Response time of the non-core-shell polymer optical fiber microprobe modified with MIP-QDs to the detection of amoxicillin concentration; (b) Response time of the core-shell polymer optical fiber microprobe modified with MIP-QDs to the detection of amoxicillin concentration.

[0032] Figure 8 Application of core-shell polymer fiber microprobe modified with MIP-QDs in amoxicillin concentration detection: (a) Optical microscopy image I of the microprobe and dark-field optical microscopy images of the microprobe in amoxicillin solutions with concentrations of 0.5 μg / L (II), 8.5 μg / L (III), and 50 μg / L (IV); (b) Fluorescence spectra of the microprobe in amoxicillin solutions with different concentrations (ranging from 0.5 μg / L to 50 μg / L); (c) Relationship curve between the peak fluorescence intensity ratio of the microprobe in amoxicillin solutions with different concentrations (ranging from 0.5 μg / L to 50 μg / L) and the concentration of the amoxicillin solution.

[0033] Figure 9 The repeatability and reversibility of the core-shell polymer optical fiber microprobe modified with MIP-QDs as an amoxicillin concentration sensor were tested.

[0034] Figure 10 Stability test of the core-shell polymer optical fiber microprobe modified with MIP-QDs as an amoxicillin concentration sensor: (a) 5 minutes; (b) 30 minutes.

[0035] Figure 11 Fluorescence spectra of the core-shell polymer optical fiber microprobe modified with MIP-QDs as an amoxicillin concentration sensor in solutions of amoxicillin and other similarly structured antibiotics at the same concentration (50 μg / L). DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. The specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0037] Example 1

[0038] The preparation of polymer optical fiber microprobes modified with molecularly imprinted polymers and CdTe quantum dots is as follows:

[0039] 1) Using amoxicillin as a template molecule, a composite fluorescent material MIP-QDs coated with MIPs and CdTe quantum dots was synthesized by sol-gel method. The reaction process Figure 1 shown; specifically:

[0040] First, 1 mg of amoxicillin was dissolved as a template molecule in 250 μL of deionized water, and mixed with 5 μL of γ-aminopropyltriethoxysilane APTES in a brown bottle, and stirred at 25°C for 1 hour to obtain a mixed solution; 100 μL of 10 mg / mL mercaptopropionic acid MPA-capped and surface-carboxylated CdTe quantum dots, 30 μL of tetraethoxysilane TEOS and 50 μL of 3% ammonia solution were added to the above mixed solution, and stirring was continued for 6 hours; after the reaction was completed, the product was collected by centrifugation at 3500RCF for 10 minutes, and washed with ethanol solution and centrifuged again, and repeated 3 times; a composite structure fluorescent material MIP-QDs of CdTe quantum dots coated with MIPs with the template molecules fully removed was obtained; finally, the obtained MIP-QDs were dried in a 40°C oven for 1 hour for use.

[0041] 2) A core-shell polymer optical fiber microprobe with surface modified MIP-QDs was prepared at one end of a standard single-mode optical fiber by free radical photopolymerization. The preparation process is as follows: Figure 2 As shown in (b); specifically:

[0042] First, take polyethylene glycol diacrylate and 2-hydroxy-2-methylpropiophenone with a mass ratio of 95:5, and add MIP-QDs half of the total mass of polyethylene glycol diacrylate and 2-hydroxy-2-methylpropiophenone at the same time, and mix them evenly under magnetic stirring at room temperature for 10 minutes to prepare a solution; then place a standard single-mode optical fiber vertically on a three-dimensional fine-adjustment frame, then adjust the fine-adjustment frame up and down to vertically immerse one end of the standard single-mode optical fiber in the prepared solution and slowly lift it up to allow the solution to adhere to the surface of the micro-fiber probe; at this time, turn on the laser, emit 1μW power laser, transmit it through the optical fiber to the surface of the standard single-mode optical fiber and irradiate the droplets adhered to its surface, and based on the aforementioned cleavage-type free radical photopolymerization reaction, initiate the solidification of the droplets, thereby forming a layer of MIP-QDs coating film on the surface of one end of the standard single-mode optical fiber; finally, turn off the laser and rinse the uncured residual solution with ethanol multiple times to obtain a core-shell structure polymer optical fiber microprobe with surface modified MIP-QDs.

[0043] Comparative Example 1

[0044] Preparation of non-core-shell polymer optical fiber microprobes modified with MIP-QDs

[0045] like Figure 2 As shown in (a), polyethylene glycol diacrylate is used as a multifunctional acrylate monomer and 2-hydroxy-2-methylpropiophenone is used as a cleavage-type photoinitiator (the excitation wavelength is still 375 nm), with the mass proportions of the two being 95% and 5%, respectively. At the same time, MIP-QDs, half of the total mass of polyethylene glycol diacrylate and 2-hydroxy-2-methylpropiophenone, are added and magnetically stirred at room temperature for 10 minutes to mix evenly as a preparation solution; the bare optical fiber end is then cut into a flat end face and placed vertically on a three-dimensional fine-tuning frame. The fine-tuning frame is then manipulated to vertically immerse the bare optical fiber end in the preparation solution and then slowly lifted, so that the solution remains on the flat end face and forms a hemispherical droplet. At this time, the laser is turned on, and a laser with a power of 1 μW and a wavelength of 375 nm is transmitted through the optical fiber to the bare optical fiber end face and irradiates the droplet. During the photopolymerization process, since the refractive index of the cured part is higher than that of the uncured part, an effective waveguide is formed, thus growing into a microprobe. Finally, the laser was turned off and the uncured residual solution was rinsed with ethanol several times; finally, a non-core-shell structured polymer optical fiber microprobe modified with MIP-QDs was prepared.

[0046] Comparative Example 2

[0047] Preparation of non-imprinted polymer-coated QDs (NIP-QDs) composite structures

[0048] The difference from Example 1 is that MIPs are not added during the preparation, and no amoxicillin template molecule is added during the reaction. The other synthesis processes are the same as in Example 1. NIP-QDs are used to replace MIP-QDs to prepare a polymer optical fiber microprobe modified with NIP-QDs.

[0049] In this example, the fluorescence properties of the prepared MIP-QDs were investigated: the prepared MIP-QDs sample was placed in the sample chamber, and a scanning electron microscope (SEM) was used to observe that a polymer optical fiber microprobe modified with MIP-QDs was formed on the end face of a standard single-mode optical fiber. Figure 3 As shown in the SEM image in the figure. We measured the excitation spectrum and emission spectrum of MIP-QDs. Figure 4 As shown in (b), the excitation efficiency is highest in the ultraviolet wavelength range. Therefore, based on the existing laboratory equipment, we choose to use a laser with a wavelength of 375nm to excite MIP-QDs. At the same time, under the excitation light of 375nm, the emission spectrum of MIP-QDs is as follows: Figure 4 As shown in (b), there is a symmetrical emission peak at a wavelength of 570nm.

[0050] Application Example 1

[0051] The polymer optical fiber microprobe of this embodiment is mainly operated by the test system based on the microspectrophotometer (20 / 20PV, CRAIC, Germany) built by us. Figure 5 As shown in Figure 1, the test system consists of a 375nm laser, a three-dimensional fine-tuning mount, a clamp mounted on the mount to secure the optical fiber, a stage for holding the amoxicillin solution, a microspectrophotometer mounted above the stage, a CCD camera, a spectrometer, and a personal computer. A standard single-mode optical fiber, containing a polymer fiber microprobe modified with MIP-QDs (MIP-QDs) on one end, is fixed to the stage of the microspectrophotometer via the three-dimensional fine-tuning mount. The probe end is immersed in amoxicillin solutions of varying concentrations. The other end of the fiber is connected to a 375nm laser via a fiber connector. When the laser is turned on, the laser light is coupled into the fiber and transmitted to the polymer fiber microprobe end, thereby exciting the MIP-QDs. Fluorescence emitted by the MIP-QDs is collected by the microscope objective and split into two paths by a beam splitter: one path is fed into the CCD camera for real-time observation and image acquisition; the other path is fed into a spectrometer to obtain the photoluminescence (PL) spectrum, which is then transmitted to the personal computer for display.

[0052] In order to verify that the prepared MIP-QDs can be used for amoxicillin concentration detection, this example studies the response properties of MIP-QDs and NIP-QDs to amoxicillin molecules before and after template removal. First, a laser with a wavelength of 375 nm (same power) is used to excite the MIP-QDs and NIP-QDs before and after template removal. The fluorescence spectra of the three are shown in Figure 2. Figure 6 As shown in (b) in the figure, it can be found that the fluorescence intensity of MIP-QDs before removing the template is very weak (see Figure 6 (b) (i)), this is because the specific amoxicillin molecular imprinting sites in the MIP-QDs are now filled with amoxicillin molecules, and amoxicillin molecules, as effective electron acceptors, can prevent the free electrons in the conduction band of CdTe quantum dots from recombining with the valence band holes, thereby leading to fluorescence quenching. In contrast, the fluorescence intensity of the MIP-QDs after removing the template molecules is significantly increased (see Figure 6 (ii) in (b) of Figure 1) and is close to the fluorescence intensity of NIP-QDs. This is because a very small amount of amoxicillin template molecules are not removed and remain in MIP-QDs, resulting in fluorescence quenching. However, NIP-QDs do not contain amoxicillin template during preparation, so the fluorescence intensity is the highest (see Figure 6 (iii) in (b)). However, the two spectral peaks are very close, which also shows that the amoxicillin template molecules are almost completely removed from the molecular imprinting sites of MIP-QDs.

[0053] Then, the MIP-QDs and NIP-QDs before and after template removal were placed in the same concentration (8.5 μg / L) amoxicillin solution and excited with the same power laser. The emitted fluorescence spectra are shown in Figure 2. Figure 5 Compared with the environment without amoxicillin solution, the fluorescence intensity of MIP-QDs before template removal increased by 5.119% (see Figure 6 (b) (i)), this is because there is an amoxicillin concentration gradient between the MIP-QDs before template removal and the ambient amoxicillin solution, which causes a small portion of the amoxicillin template molecules in the MIP-QDs before template removal to dissolve into the solution, reducing the number of molecular imprinting sites that bind to the amoxicillin molecules. Compared with the environment without amoxicillin solution, the fluorescence intensity of the MIP-QDs after template removal decreased by 41.605% (see Figure 6 (ii) in (b) of the figure) is due to the binding of amoxicillin molecules in the solution to the amoxicillin molecular imprinting sites in the MIP-QDs after template removal, resulting in quenching of quantum dot fluorescence. The fluorescence intensity of NIP-QDs also decreased by 1.342% (see Figure 6(iii) in (b) of Figure 1 is because amoxicillin molecules in the solution will contact a small portion of the quantum dots. Therefore, even if there are no amoxicillin molecular imprinting sites in the NIP-QDs, the fluorescence intensity will be reduced by the influence of amoxicillin molecules in the solution. In summary, the above experiments verify the recognition ability of the prepared MIP-QDs for amoxicillin molecules and further predict the feasibility and specificity of modifying them into polymer optical fiber microprobes for amoxicillin detection.

[0054] To ensure sufficient binding between amoxicillin molecules and the molecular imprinting sites of MIP-QDs, this example studies the response time of two polymer optical fiber microprobes modified with MIP-QDs to detect amoxicillin. First, the non-core-shell polymer optical fiber microprobe modified with MIP-QDs was placed in an amoxicillin solution with a concentration of 8.5μg / L, and a 375nm wavelength laser was used to excite the quantum dots. The changes in the emitted fluorescence intensity were observed to study the response to the amoxicillin molecules. The results are shown in Figure 2. Figure 7 As shown in (a) in the figure. The fluorescence intensity of MIP-QDs continued to decrease within 30 minutes and remained stable after 30 minutes. Therefore, the response time of the non-core-shell polymer optical fiber microprobe sensor modified with MIP-QDs was detected to be 30 minutes. With this structure, the amoxicillin molecules need sufficient time to diffuse into the entire polymer microprobe, so the response time is longer. In order to shorten the response time, we borrowed the practice of preparing a molecular imprinting polymer layer on the surface of an electrochemical sensor and designed and prepared a core-shell polymer optical fiber microprobe modified with MIP-QDs. In order to study its response time for detecting amoxicillin, we placed it in an amoxicillin solution with a concentration of 2.0 μg / L and used the same laser to excite the quantum dots to observe the changes in the fluorescence intensity of its emission. Under the core-shell structure, since the diffusion distance required for the amoxicillin molecules is greatly reduced, the response time of the sensor is also greatly reduced, as shown in the figure. Figure 7 As shown in (b). Amoxicillin can be detected after only 2 minutes, and about 80% of the total signal response occurs within 4 minutes, and equilibrium is reached in about 10 minutes (total signal response>98%). Therefore, by modifying MIP-QDs to the surface of the polymer optical fiber microprobe, the response time is successfully reduced from 30 minutes to 10 minutes. Subsequently, we replaced the amoxicillin solution with alcohol to remove the bound amoxicillin molecules. It can be observed that it only takes about 10 minutes to complete the removal of the bound amoxicillin molecules. It was then placed in an amoxicillin solution with a concentration of 8.5μg / L for verification, and the same results were obtained. Compared with the non-core-shell structure, the fluorescence intensity decreased by the same amount (about 55%), but the response time was greatly reduced. At the same time, by continuously measuring amoxicillin solutions of different concentrations (see Figure 7(b)) in the figure also demonstrates the reversibility of the sensor response and further confirms that the polymer microfiber probe we prepared can achieve near real-time detection of amoxicillin concentration.

[0055] As mentioned above, the core-shell structure polymer optical fiber microprobe modified with MIP-QDs showed a faster response time to amoxicillin, so this example proposed using this structured microprobe as an amoxicillin concentration sensor. In order to further verify its feasibility, the prepared core-shell structure polymer optical fiber microprobe modified with MIP-QDs (see Figure 8 The optical microscopic image in (a) (I) was immersed in standard test solutions with different amoxicillin concentrations at room temperature (25°C) to observe the changes in its fluorescence intensity. Figure 8 Panels II-IV in (a) show representative dark-field microscopy images of amoxicillin solutions at concentrations of 0.5 μg / L, 8.5 μg / L, and 50 μg / L, respectively. The fluorescence intensity decreases with increasing amoxicillin concentration. To further quantify the relationship between these two concentrations, we prepared nine amoxicillin test solutions ranging from 0.5 μg / L to 50 μg / L. Figure 8 (b) shows the fluorescence spectra of the core-shell polymer fiber microprobe modified with MIP-QDs in different concentrations of amoxicillin solution. The results show that when excited by a laser with a wavelength of 375nm, an emission spectrum with a peak wavelength of 570nm was obtained. In addition, the core-shell polymer fiber microprobe modified with MIP-QDs is highly sensitive to the concentration of amoxicillin. As the concentration of amoxicillin increases, the output fluorescence intensity decreases monotonically. This phenomenon is due to the fact that amoxicillin molecules, as effective electron acceptors, can prevent the free electrons in the conduction band of CdTe quantum dots from recombinating with the holes in the valence band, thereby leading to the quenching of quantum dot fluorescence. By observing the change of fluorescence intensity with amoxicillin concentration, we found that the ratio (F0 / F) of the peak fluorescence intensity (F) in the absence of amoxicillin and the peak fluorescence intensity (F) in various concentrations of amoxicillin solution is linearly related to the amoxicillin concentration. Figure 8 (c) shows the quantitative relationship curve between the peak fluorescence intensity ratio (F0 / F) and the concentration of various amoxicillin solutions. There is a good linear correlation between them. The fitting equation is y=0.07936x+1.13708, and the regression coefficient R 2 = 0.99695. Furthermore, based on the IUPAC standard, the limit of detection (LOD) is 3σ / k (where σ is the standard deviation of the blank measurement value, measured to be 0.00823 in this experiment, and k is the slope of the fitting curve). This theoretical limit of detection (LOD) for the amoxicillin concentration sensor can be calculated to be approximately 0.31 μg / L.

[0056] To evaluate the reusability, reversibility, stability, and specificity of the amoxicillin concentration sensor, the following experiment was conducted: the prepared MIP-QDs-modified core-shell polymer fiber microprobe was placed in a 0.5 μg / L amoxicillin solution, and its peak fluorescence intensity was measured after the fluorescence intensity stabilized. It was then washed with ethanol and placed in a 50 μg / L amoxicillin solution. The peak fluorescence intensity was also measured after 10 minutes. This cycle was repeated 20 times, and the changes in peak fluorescence intensity were recorded. Figure 9 It can be observed that there is no obvious fluctuation in the peak fluorescence intensity after each cycle, and the relative standard deviations (RSDs) of the peak fluorescence intensity at amoxicillin solution concentrations of 0.5 μg / L and 50 μg / L are calculated to be 1.37% and 1.12%, respectively, indicating that the proposed amoxicillin concentration sensor is highly reversible and reusable.

[0057] In addition, in order to verify the stability of the proposed amoxicillin sensor, we placed the core-shell structure polymer fiber microprobe with MIP-QDs in an amoxicillin solution with a concentration of 8.5 μg / L. After its fluorescence intensity stabilized, its peak fluorescence intensity was measured every 1 minute and repeated 6 times. The change of its peak fluorescence intensity is shown in the figure. Figure 10 As shown in (b) in the figure. At this time, the RSD of the peak fluorescence intensity was calculated to be 0.513%. Subsequently, the peak fluorescence intensity was measured every 5 minutes and repeated 5 times. The change of the peak fluorescence intensity at this time was shown as Figure 10 As shown in (b), the RSD is calculated to be 0.441%. The above experimental results show that the amoxicillin concentration sensor designed and prepared in this embodiment has good stability.

[0058] In order to verify the specificity of the designed and prepared MIP-QDs modified core-shell polymer optical fiber microprobe for amoxicillin detection, this example experimentally placed it in a potential interfering antibiotic solution and amoxicillin solution of the same concentration (50 μg / L) to observe the changes in its fluorescence intensity. The potential interfering antibiotics used in this example are ampicillin (AMP), cephalexin (CEP), cefaclor (CCL), cefradine (CDE) and cefadroxil (CDX). These antibiotics and amoxicillin all belong to the β-lactam antibiotic class and have the same or similar side chain structure as amoxicillin, so they may have similar interactions with CdTe quantum dots. The experimental results are shown in Figure 2. Figure 11As shown, the fluorescence intensity of the MIP-QD-modified core-shell polymer fiber microprobe in an amoxicillin solution (yellow curve) is much weaker than that in solutions of other potentially interfering antibiotics (other colored curves), with its peak fluorescence intensity being approximately 80% of that in solutions of other potentially interfering antibiotics. The peak fluorescence intensities in solutions of other potentially interfering antibiotics are very similar, with no significant difference between them. This indicates that the MIP-QD-modified core-shell polymer fiber microprobe sensor has strong specific recognition for amoxicillin. This specificity is attributed to the formation of a large number of molecularly imprinted binding sites with specific recognition capabilities for amoxicillin during the synthesis of the MIP-QDs, allowing amoxicillin to bind to them and trigger a fluorescence quenching effect. This also suggests that by using specific template molecules and reactive functional materials during the preparation of MIP-QDs, specific recognition of specific template molecules can be achieved, expanding the range of detectable targets (such as drugs, hormones, toxins, proteins, etc.) and promoting the development of biomedicine and environmental monitoring.

[0059] In summary, the core-shell polymer optical fiber microprobe with surface modified MIP-QDs of the present invention can be used as an amoxicillin concentration sensor, and it takes only 10 minutes to reach detection equilibrium. The amoxicillin concentration sensor has a good linear response relationship (R 2 =0.99695), with a detection limit as low as 0.31 μg / L, exceeding the requirements of EU food and drug residue standards. Its fluorescence intensity shows a monotonic downward trend with target concentration, enabling quantitative analysis. Furthermore, the amoxicillin concentration sensor exhibits excellent reusability and sensing stability, with a relative standard deviation of less than 1.5% across multiple measurement cycles, demonstrating its feasibility and stability for long-term application.

[0060] The technical solution of the present invention is not limited to the above-mentioned specific embodiments. Any technical variations made according to the technical solution of the present invention fall within the protection scope of the present invention.

Claims

1. A method for preparing a polymer optical fiber microprobe modified with molecularly imprinted polymer and CdTe quantum dots, characterized in that: The following steps are involved: S1. Amoxicillin was used as a template molecule to synthesize MIPs-coated CdTe quantum dots composite fluorescent material MIP-QDs by sol-gel method; S2. A core-shell polymer optical fiber microprobe with surface modified MIP-QDs was prepared at one end of a standard single-mode optical fiber by free radical photopolymerization.

2. The method for preparing a polymer optical fiber microprobe modified with molecularly imprinted polymer and CdTe quantum dots according to claim 1, characterized in that: The step S1 specifically includes: S11. Dissolve 1 mg of amoxicillin as a template molecule in 250 μL of deionized water, mix with 5 μL of γ-aminopropyltriethoxysilane (APTES) in a brown bottle, and stir at 25°C for 1 h to obtain a mixed solution. S12, adding 100 μL of 10 mg / mL mercaptopropionic acid (MPA)-capped and surface-carboxylated CdTe quantum dots, 30 μL of a cross-linking agent, and 50 μL of a catalyst to the above mixture, and continuing stirring for 6 h; S13. After the reaction is completed, the product is collected by centrifugation at 3500RCF for 10 minutes, washed with ethanol solution, and centrifuged again, and repeated three times; the composite structure fluorescent material MIP-QDs of MIPs-coated CdTe quantum dots with the template molecules fully removed is obtained; finally, the obtained MIP-QDs are dried in an oven at 40°C for 1 hour for use.

3. The method for preparing a polymer optical fiber microprobe modified with molecularly imprinted polymer and CdTe quantum dots according to claim 2, characterized in that: In the step S12, the crosslinking agent is tetraethoxysilane TEOS.

4. The method for preparing a polymer optical fiber microprobe modified with molecularly imprinted polymer and CdTe quantum dots according to claim 2, characterized in that: In step S12, the catalyst is an ammonia solution with a volume concentration of 3%.

5. The method for preparing a polymer optical fiber microprobe modified with molecularly imprinted polymer and CdTe quantum dots according to claim 2, characterized in that: The step S2 specifically includes: S21, taking a multifunctional acrylate monomer and a cleavage-type photoinitiator in a mass ratio of 95:5, adding MIP-QDs in an amount half the total mass of the multifunctional acrylate monomer and the cleavage-type photoinitiator, and magnetically stirring at room temperature for 10 minutes to mix uniformly to prepare a solution; S22. Place the standard single-mode optical fiber vertically on a three-dimensional micro-adjustment stand, then adjust the micro-adjustment stand up and down to immerse one end of the standard single-mode optical fiber vertically in the prepared solution and then slowly lift it up to allow the solution to adhere to the surface of the micro-fiber probe; at this time, turn on the laser, and emit a 1μW power laser that is transmitted through the optical fiber to the surface of the standard single-mode optical fiber and irradiates the droplets adhered to its surface, and the droplets are solidified based on the aforementioned cleavage-type free radical photopolymerization reaction, thereby forming a layer of MIP-QDs coating film on the surface of one end of the standard single-mode optical fiber, and finally turn off the laser and rinse the uncured residual solution with ethanol multiple times to obtain a core-shell structure polymer optical fiber microprobe with surface modified MIP-QDs.

6. The method for preparing a polymer optical fiber microprobe modified with molecularly imprinted polymer and CdTe quantum dots according to claim 5, characterized in that: In step S21, the multifunctional acrylate monomer is polyethylene glycol diacrylate.

7. The method for preparing a polymer optical fiber microprobe modified with molecularly imprinted polymer and CdTe quantum dots according to claim 5, characterized in that: In step S21, the cleavage-type photoinitiator is 2-hydroxy-2-methylpropiophenone.

8. A polymer optical fiber microprobe modified with a molecularly imprinted polymer and CdTe quantum dots prepared by the method according to any one of claims 1 to 7, characterized in that: The polymer optical fiber microprobe is a core-shell structure polymer optical fiber microprobe with surface modified MIP-QDs prepared at one end of a standard single-mode optical fiber.

9. Use of the polymer optical fiber microprobe modified with molecularly imprinted polymer and CdTe quantum dots as claimed in claim 8 in the detection of amoxicillin concentration.

10. The use according to claim 9, characterized in that: The polymer optical fiber microprobe modified with molecularly imprinted polymer and CdTe quantum dots is used as an amoxicillin concentration sensor.

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