Preparation and application of fluorescent optical fiber sensor with wide-range pH response

Abstract

The invention discloses a preparation method and application of a wide-range pH-responsive fluorescent optical fiber sensor, and mainly relates to the field of chemistry and sensing science. The invention aims to prepare the pH-sensitive silicon quantum dots, fix the silicon quantum dots on the surface of the optical fiber by using a hydrogel polymerization reaction, and realize sensitive detection of pH through the change of fluorescence intensity. According to the invention, the pH response characteristic of the fluorescent silicon quantum dot and the convenience of the optical fiber are combined, the advantages of small size, simplicity and convenience in operation and high sensitivity and specificity are realized, and the ultra-wide detection of wide-range pH (3-12) is realized. The invention provides a feasible method for on-line sensitive detection of the pH value of the biological fluid, and has important research significance on complex biological sample analysis, early diagnosis of diseases and emergency analysis.

Description

Technical Field

[0001] The present application relates to the fields of chemistry, nanomaterial science and biosensing, and more specifically, to a method for preparing a fluorescent optical fiber with wide-range pH response and its application. Background Art

[0002] Accurate measurement of pH is crucial to many fields such as chemistry and biology. The glass electrode method is a commonly used method, but it has some limitations, such as susceptibility to electromagnetic interference, poor stability in certain complex environments (such as highly corrosive solutions and microenvironments in vivo), and large size. Fluorescent fiber optic detection technology uses optical fiber as a conductive medium to transmit excitation light to the fluorescent material and transmit the generated fluorescent signal back for detection. Fluorescent fiber optic detection technology can achieve remote detection and reduce external interference, and the optical fiber is small in size and can be used for microenvironment detection. For example, in biomedical research, it is difficult to accurately measure the changes in pH values ​​in cells or tissues using traditional methods, and fluorescent fiber optic pH detection technology makes it possible to detect in this special environment.

[0003] In fluorescent fiber optic pH sensors, the selection of fluorescent materials plays a key role in the performance of the sensor. Existing fluorescent fiber optic pH sensors are mainly based on organic fluorescent dye molecules with pH-sensitive properties, such as fluorescein and 1-hydroxypyrene-3,6,8-trisulfonic acid, which have shortcomings such as poor photostability, narrow pH response range, easy leakage of small molecules, and susceptibility to ambient temperature interference. Compared with organic fluorescent dyes, fluorescent nanomaterials have the advantages of good photostability and thermal stability, chemical inertness, and easy modification. However, the application of such materials in fluorescent fiber optic pH sensors has rarely been reported. Summary of the invention

[0004] Based on this, in view of the shortcomings of existing fluorescent fiber optic pH sensors, this application proposes a preparation method and application of a fluorescent fiber optic sensor with a wide range of pH response to solve the technical bottlenecks of the prior art that the pH response range is narrow and easily interfered by environmental factors.

[0005] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is a method for preparing a wide-range pH-responsive fluorescent optical fiber sensor. The preparation method comprises: (1) preparing pH-sensitive silicon quantum dots: using N-[3-(trimethoxysilyl)propyl]ethylenediamine and neutral red as precursors, and preparing silicon quantum dots by hydrothermal treatment; (2) preparing an optical fiber sensor: after removing the organic cladding of the optical fiber, a tapered optical fiber is obtained after hydrofluoric acid corrosion; the optical fiber is placed in a sleeve containing a hydrogel precursor and a silicon quantum dot solution, and the silicon quantum dots are fixed on the surface of the optical fiber by a light-induced hydrogel polymerization reaction, so as to prepare a fluorescent optical fiber sensor suitable for wide-range pH response.

[0006] Furthermore, step (1) is specifically as follows:

[0007] (1.1) Neutral red and N-[3-(trimethoxysilyl)propyl]ethylenediamine are dissolved in deionized water, the mixed solution is transferred to a reaction kettle, and the reaction kettle is reacted at high temperature for a period of time.

[0008] (1.2) After the solution obtained in step 1.1 is cooled to room temperature, the solution is filtered, and then ethyl acetate is added and stirred evenly. After phase separation occurs, the lower layer solution is the silicon quantum dot solution.

[0009] Furthermore, step (1) is specifically as follows:

[0010] Neutral red and N-[3-(trimethoxysilyl)propyl]ethylenediamine are mixed in a mass ratio of (1-10):(500-2000), and the mixture solution is reacted at a hydrothermal temperature of 140-200° C. for 4-12 hours.

[0011] The hydrothermal product is filtered using a 0.22 μm water filter head, and ethyl acetate is added for phase separation, wherein the volume ratio of the silicon quantum dot solution to ethyl acetate is 1:(0.5-5). The phase separation is performed by standing or centrifuging, and the lower layer solution is taken out to obtain a silicon quantum dot solution.

[0012] Furthermore, step (2) is specifically as follows:

[0013] The coating layer on the surface of the multimode optical fiber is removed with a wire stripper, the optical fiber end face is cut flat with a cutting knife, washed and dried with ethanol, then immersed in a 40% hydrofluoric acid solution, etched at room temperature for 30 to 90 minutes, and washed to obtain a tapered optical fiber.

[0014] Polyethylene glycol diacrylate, 2-hydroxy-2-methylpropiophenone and silicon quantum dots are mixed in a mass ratio of (1-8): (0.05-0.15): (0.005-0.01) to prepare a hydrogel precursor solution containing silicon quantum dots; wherein the molecular weight of the polyethylene glycol diacrylate is 700 Da.

[0015] A hydrogel precursor solution containing 0.5 to 10 microliters of silicon quantum dots is injected into a silicone sleeve with a syringe, and a tapered optical fiber is placed vertically into the sleeve. The hydrogel polymerization reaction is carried out under ultraviolet light irradiation; the wavelength of the ultraviolet light is 365nm, and the irradiation time is 5 to 30 seconds, so as to obtain a fluorescent optical fiber sensor suitable for wide-range pH response.

[0016] Furthermore, within the pH range of 3 to 12, the fluorescence intensity of the prepared fluorescent optical fiber sensor shows a linear relationship with the pH value change.

[0017] Furthermore, the fluorescent optical fiber sensor is used for wide-range pH detection in the pH range of 3-12.

[0018] Beneficial technical effects of the present invention:

[0019] 1. In the preparation method provided by the present invention, the silicon quantum dots prepared by the hydrothermal method have the advantages of simple synthesis, good photostability, good chemical stability, and a wide pH response range;

[0020] 2. The preparation method provided by the present invention fixes silicon quantum dots on the surface of optical fiber through light-induced hydrogel polymerization reaction, effectively preventing the leakage of fluorescent materials, reducing interference from environmental factors, and extending the service life of the sensor.

[0021] 3. The fluorescent optical fiber sensor prepared by the preparation method provided by the present invention has the advantages of small size, simple operation, good light stability, good accuracy, strong anti-interference ability, wide pH response range and good reversibility;

[0022] 4. The fluorescent fiber sensor provided by the present invention has a wide range of fluorescence response to pH value, and is linearly related to the fluorescence intensity in the pH range of 3-12; and is basically not affected by environmental factors such as temperature, salinity, etc. Therefore, the fluorescent fiber sensor has potential application prospects in real-time monitoring of pH in biological samples. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Except as otherwise specified, the equipment and reagents used in the embodiments and experimental examples are all commercially available. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] 1. According to a typical embodiment of the present invention, a method for preparing a fluorescent optical fiber sensor with wide-range pH response is provided.

[0025] The present invention is specifically described below in conjunction with embodiments.

[0026] Example 1

[0027] A method for preparing a wide-range pH-responsive fluorescent optical fiber sensor. The method comprises: (1) preparing pH-sensitive silicon quantum dots: using N-[3-(trimethoxysilyl)propyl]ethylenediamine and neutral red as precursors, and preparing silicon quantum dots by hydrothermal treatment; (2) preparing an optical fiber probe: removing the organic cladding of the optical fiber, and then etching it with hydrofluoric acid to obtain a tapered optical fiber; placing the optical fiber in a sleeve containing a hydrogel precursor and a silicon quantum dot solution, and fixing the silicon quantum dots on the surface of the optical fiber by a light-induced hydrogel polymerization reaction, thereby preparing a fluorescent optical fiber sensor suitable for wide-range pH response.

[0028] In this embodiment, the preparation method of pH-sensitive silicon quantum dots is specifically as follows:

[0029] 1) Weigh 1 mL of N-[3-(trimethoxysilyl)propyl]ethylenediamine and 3 mg of neutral red and dissolve them in 20 mL of deionized water and mix well;

[0030] 2) The mixture was transferred into a 50 mL polytetrafluoroethylene-lined stainless steel autoclave and heated at 180° C. for 6 hours;

[0031] 3) The autoclave is cooled to room temperature, and the hydrothermal product is filtered using a 0.22 μm water filter membrane. The resulting solution is mixed evenly with an equal volume of ethyl acetate, and after standing for phase separation, the lower layer of the solution is taken out to obtain a pH-sensitive silicon quantum dot solution.

[0032] like Figure 1 As shown, the prepared silicon quantum dots have dual emission characteristics. When the excitation wavelength changes between 330 and 420 nm, the fluorescence emission peak of SiQDs at 430 nm gradually decreases with the increase of the excitation wavelength, and the fluorescence emission peak at 590 nm gradually increases. When the excitation wavelength is 360 nm, the emission wavelength of SiQDs at ~430 nm is more significant.

[0033] In this embodiment, step (2) is specifically as follows:

[0034] 1) Select a multimode optical fiber with a diameter of 105 / 125um (core / cladding), remove the coating on its surface with a wire stripper, cut the end face of the optical fiber flat with a cutting knife, and wash and dry it with ethanol;

[0035] 2) Immerse the optical fiber in 1) in a hydrofluoric acid solution with a concentration of 40%, etch for 60 minutes at room temperature, and wash to obtain a tapered optical fiber.

[0036] 3) 2 g of polyethylene glycol diacrylate (700 Da) and 0.09 g of 2-hydroxy-2-methylpropiophenone were mixed as a hydrogel precursor solution, and 20 μL of 5-fold diluted sensitive material SiQDs were added and mixed evenly, and allowed to stand for 3 h.

[0037] 4) Pipette 0.7 μL of the hydrogel precursor solution in 3) with a syringe and slowly inject it into a silicone tube (inner diameter 1000 μm); coaxially insert the prepared tapered optical fiber into the hydrogel precursor solution in the silicone tube and irradiate with an ultraviolet lamp (365 nm) for about 15 seconds.

[0038] 5) The photocured hydrogel optical fiber was removed from the silicone tube and then vertically immersed in a sodium alginate solution (0.2% w / v) and a CaCl2 solution (0.1 M) to form a calcium alginate hydrogel cladding, thereby preparing a fluorescent optical fiber sensor suitable for wide-range pH response.

[0039] Figure 2 1 is a microscope image of the tapered optical fiber and the sensor in Example 1 of the present invention.

[0040] Fluorescence analysis was performed on the fluorescent optical fiber sensor prepared in Example 1: the optical fiber sensing measurement platform (such as Figure 3 As shown), the light (360nm) emitted by the light source enters the fluorescent fiber optic sensor through the Y-type optical fiber, excites the silicon quantum dots to emit fluorescence, and the fluorescent signal enters the micro-ocean spectrometer through the Y-type optical fiber to be collected. The computer is connected to the output end of the spectrometer through a USB cable to output data.

[0041] Figure 4 The fluorescence emission spectrum of the SiQDs solution prepared in Example 1 of the present invention on the fluorescent fiber optic sensing platform. The results show that the fluorescence emission peak of the SiQDs solution at 590nm is more significant when detected on the fiber optic sensing platform. This shows that the luminescence performance of SiQDs varies with different light sources. After SiQDs are combined with optical fibers through hydrogel to prepare a sensor, the emission peak of SiQDs at 590nm is obviously blue-shifted, and there is only one emission peak (~540nm).

[0042] Phosphoric acid and sodium hydroxide were used to prepare PB solutions with a pH of 3 to 12. The fluorescence optical fiber sensor was immersed in a PB solution with a certain pH value, and the fluorescence emission spectrum of the solution was measured, and its fluorescence intensity at 540 nm was recorded; then the fluorescence optical sensor was taken out and washed three times with deionized water, and the pH value of the next solution was measured. The results showed that the fluorescence intensity of the fluorescence optical fiber sensor weakened with the increase of pH. Figure 5 The figure shows the change of fluorescence intensity of the prepared fluorescence optical fiber sensor at pH 3 to 12. Figure 6 The linear fitting curve of the fluorescence quenching efficiency at 540 nm and pH value is y = 0.069x-0.25 (R 2 =0.991. Therefore, the fluorescent optical fiber sensor provided by the present invention can detect a wide range of pH.

[0043] Example 2

[0044] This embodiment provides a performance test of a wide-range pH-responsive optical fiber sensor, which measures the reproducibility of the response of the hydrogel fluorescent optical fiber sensor based on silicon quantum dots to solutions with different pH values. The specific implementation steps are as follows:

[0045] 1) The fluorescent optical fiber sensor described in Example 1 was immersed in the solution of pH = 9.0 described in Example 1, and the fluorescence spectrum of the sensor and its fluorescence intensity at 540 nm were tested on the constructed optical fiber sensing platform. Then, the fluorescent optical fiber sensor was taken out and immersed in the solution of pH = 4.0 described in Example 1, and the fluorescence spectrum of the sensor and its fluorescence intensity at 540 nm were tested. The above operations were repeated in sequence for a total of 10 cycles to test the repeatable response characteristics of the sensor. Figure 7 The quenching rate of the fluorescent optical fiber sensor changes in response to the pH value in the 10-cycle test. The results show that the wide-range pH sensor provided by the present invention has the characteristic of continuous cyclic use and good practicality.

[0046] 2) 100 μL, 100 μM common interfering substances in serum, including metal ions (Zn 2+ 、Na + , Ca 2+ Mg 2+ , K + , Fe 3 + ) and biomolecules (Glu, Ser, Lys, Cys, GSH, Urea) were added to the PB solution with pH = 7.4 to prepare the interference solution.

[0047] 3) The fluorescent optical fiber sensor described in Example 1 was immersed in the interfering solution described in Example 2, and the fluorescence spectrum of the sensor and its fluorescence intensity at 540 nm were tested on the constructed optical fiber sensing platform.

[0048] Depend on Figure 8 It can be seen that in the pH selective response experiment, only the pH change can cause a significant response for the wide-range pH-responsive fluorescent optical fiber sensor prepared in Example 1 of the present invention, while other metal ions and biological molecules can only produce negligible signal responses. This phenomenon shows that the sensor has good pH response specificity and is suitable for detecting pH values ​​in biological samples or environmental matrices.

[0049] Example 3

[0050] This embodiment provides a wide-range pH response optical fiber sensor for biological applications in the field of bioanalysis. The hydrogel fluorescent optical fiber sensor based on silicon quantum dots is used to detect the actual human serum pH. The specific implementation steps are as follows:

[0051] The fluorescent fiber optic sensor described in the embodiment is immersed in an actual human serum sample, and the fluorescence spectrum of the sensor and its fluorescence intensity at 540nm are tested on the constructed optical fiber sensing platform. Then, the fluorescent fiber optic sensor is taken out and washed three times with deionized water, and the pH value of the next sample solution is measured. At the same time, in order to verify the accuracy of the sensor, the results of the actual human serum test are compared with the results of the pH meter test. The results show that the pH values ​​of the three actual human sera tested by the fluorescent sensor are 8.18, 8.22 and 8.11, respectively, which are basically consistent with the pH meter test results (8.20, 8.34 and 8.27). Therefore, the sensor of the present invention has good accuracy and practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0053] in:

[0054] Figure 1 This is an emission spectrum diagram of silicon quantum dots in Example 1 of the present invention;

[0055] Figure 2 This is a microscope image of the tapered optical fiber and its fluorescent optical fiber sensor in Example 1 of the present invention;

[0056] Figure 3 The fluorescent optical fiber sensing platform constructed in Example 1 of the present invention;

[0057] Figure 4 Fluorescence emission spectra of SiQDs solution and the sensor described in Example 1 of the present invention on the fluorescent optical fiber sensing platform built in Example 1;

[0058] Figure 5 is a curve showing the change of the fluorescence intensity of the fluorescent optical fiber sensor as a function of the pH value in Example 1 of the present invention;

[0059] Figure 6 This is a graph showing the change in fluorescence quenching rate of the fluorescence optical fiber sensor described in Example 1 of the present invention as a function of pH value;

[0060] Figure 7 This is a test diagram of the reusability performance of the fluorescent optical fiber sensor described in Example 2 of the present invention;

[0061] Figure 8This is the selectivity of the fluorescent optical fiber sensor in sensing pH value described in Example 2 of the present invention.

Claims

1. A method for preparing a wide-range pH-responsive fluorescent optical fiber sensor, characterized in that: The method comprises: the preparation method comprises: (1) preparing pH-sensitive silicon quantum dots: using N-[3-(trimethoxysilyl)propyl]ethylenediamine and neutral red as precursors, and adopting hydrothermal treatment to prepare silicon quantum dots; (2) preparing an optical fiber sensor: removing the organic cladding of the optical fiber, and obtaining a tapered optical fiber after hydrofluoric acid corrosion; placing the optical fiber in a sleeve containing a hydrogel precursor and a silicon quantum dot solution, and fixing the silicon quantum dots on the surface of the optical fiber through a light-induced hydrogel polymerization reaction, so as to prepare a fluorescent optical fiber sensor suitable for wide-range pH response.

2. The method for preparing a wide-range pH-responsive fluorescent optical fiber sensor according to claim 1, characterized in that: In step (1), the preparation method of silicon quantum dots is: using N-[3-(trimethoxysilyl)propyl]ethylenediamine and neutral red as precursors, and preparing pH-sensitive silicon quantum dots after hydrothermal treatment.

3. The method for preparing a wide-range pH-responsive fluorescent optical fiber sensor according to claim 2, characterized in that: Step (1) is specifically: (1.1) Neutral red and N-[3-(trimethoxysilyl)propyl]ethylenediamine are mixed in a mass ratio of (1-10):(500-2000), and the mixture solution is reacted at a hydrothermal temperature of 140-200° C. for 4-12 hours. (1.2) The hydrothermal product is filtered through a 0.22 μm water filter head, and ethyl acetate is added for phase separation, wherein the volume ratio of the silicon quantum dot solution to ethyl acetate is 1:(0.5-5). The phase separation is performed by standing or centrifugation, and the lower layer solution is taken out to obtain a silicon quantum dot solution.

4. The method for preparing a wide-range pH-responsive fluorescent optical fiber sensor according to claim 1, characterized in that: Step (2) is specifically as follows: The coating layer on the surface of the multimode optical fiber is removed by a wire stripper, the end face of the optical fiber is cut flat by a cutting knife, and then it is washed and dried with ethanol, and then immersed in a 40% hydrofluoric acid solution, etched at room temperature for 30 to 90 minutes, and washed to obtain a tapered optical fiber; Mixing polyethylene glycol diacrylate, 2-hydroxy-2-methylpropiophenone and silicon quantum dots in a mass ratio of (1-8): (0.05-0.15): (0.005-0.01) to prepare a hydrogel precursor solution containing silicon quantum dots; A hydrogel precursor solution containing 5 to 50 microliters of silicon quantum dots is injected into a silicone sleeve with a syringe, and a tapered optical fiber is placed vertically into the sleeve. A hydrogel polymerization reaction is carried out under ultraviolet light irradiation; the wavelength of the ultraviolet light is 365nm, and the irradiation time is 5 to 30 seconds, thereby obtaining a fluorescent optical fiber sensor suitable for wide-range pH response.

5. The method for preparing a wide-range pH-responsive fluorescent optical fiber sensor according to claim 1, characterized in that: In the pH range of 3 to 12, the fluorescence response of the prepared fluorescent optical fiber sensor shows a linear relationship with the pH change.

6. Application of a fluorescent optical fiber sensor suitable for wide-range pH response obtained by the preparation method according to claims 1 to 5, characterized in that: The fluorescent optical fiber sensor is used for wide-range pH detection from pH 3 to 12.

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