Preparation method of dissolved oxygen sensitive film

Abstract

The invention discloses a preparation method of a dissolved oxygen sensitive film, and belongs to the technical field of gas sensing and optical detection. The problems that in an existing optical dissolved oxygen sensitive film, dye is prone to photobleaching and gathering self-quenching, and the oxygen diffusion rate and dye protection are difficult to consider at the same time are solved. The method comprises the following steps: 1, preparing polystyrene nano / micron particle powder; and 2, preparing the oxygen sensitive film. The method is used for preparing the dissolved oxygen sensitive film.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of gas sensing and optical detection. BACKGROUND

[0002] Dissolved oxygen is one of the most critical chemical quantities in water environment monitoring. The dissolved oxygen data can directly reflect the intensity of biological and biochemical activities in the aquatic ecosystem. Therefore, the dissolved oxygen concentration is often used as a core indicator to measure the health status of the aquatic ecosystem, and it is of great significance to realize high-sensitivity and high-stability detection of dissolved oxygen. At present, the measurement of dissolved oxygen widely uses Clark-type sensors based on electrochemical principle, but the sensitivity of the sensor is low and the long-term stability is poor, which greatly limits its application in water environment monitoring. Optical dissolved oxygen sensors are attracting much attention in the field of dissolved oxygen monitoring due to their high precision, high accuracy and no need to replace electrolyte. The working principle of the optical dissolved oxygen sensor does not consume oxygen and does not involve electrochemical reaction. In addition, the optical dissolved oxygen sensor can be manufactured at different scales from macro to micro, and can be miniaturized to realize less invasive measurement. However, the research on optical dissolved oxygen sensor is still in its infancy, and there are still some technical bottlenecks and challenges in practical application. The oxygen-sensitive film of the optical dissolved oxygen sensor is its weak link, and its performance decay will directly lead to measurement deviation. The fluorescent dye in the sensitive film will undergo photobleaching effect under long-term light, especially blue light excitation, which will cause the destruction of the molecular structure of the fluorescent substance and the decrease of the fluorescence efficiency. In addition, when the dye molecules are unevenly distributed and aggregated in the matrix, self-quenching effect will occur, which will significantly reduce the fluorescence intensity and oxygen sensing sensitivity. At the same time, the traditional solid polymer matrix may hinder the diffusion of oxygen, affecting the response speed. SUMMARY

[0003] The present application solves the problems of easy photobleaching and easy aggregation of the dye in the existing optical dissolved oxygen sensitive film, and the difficulty in balancing the oxygen diffusion rate and dye protection, and provides a preparation method of a dissolved oxygen sensitive film.

[0004] A preparation method of a dissolved oxygen sensitive film, which is carried out according to the following steps:

[0005] I. Preparation of polystyrene nano / microparticle powder:

[0006] ① Dissolve the foamed polystyrene waste in ethyl acetate to obtain an EPS solution;

[0007] ② Under stirring, add the EPS solution dropwise into a mixed anti-solvent of ethanol and water, and continue stirring until complete precipitation to obtain a suspension;

[0008] ③ Centrifuge the suspension to collect the precipitate, then wash and dry to obtain polystyrene nano / microparticle powder;

[0009] II. Preparation of oxygen-sensitive film:

[0010] ① PtOEP dye was dissolved in toluene to obtain a dye solution;

[0011] ② Polystyrene nano / micro particle powder was added to ethyl acetate to obtain an EPS particle solution;

[0012] ③ The dye solution was mixed with the EPS particle solution to obtain a mixed solution;

[0013] ④ The mixed solution was added dropwise to a mixed anti-solvent of ethanol and water under stirring, and after the dropwise addition was completed, the precipitate was separated by centrifugation and washed to obtain a washed precipitate;

[0014] ⑤ The washed precipitate was uniformly coated on a substrate and dried to obtain a sensitive intermediate layer, and a layer of PDMS prepolymer was coated on the sensitive intermediate layer and cured to form an encapsulation layer, thereby completing the preparation method of the dissolved oxygen-sensitive film.

[0015] The beneficial effects of the present application are:

[0016] The present application proposes an oxygen-sensitive film preparation method using polystyrene (EPS) as a raw material to synthesize nano / micro particle powder as a dye carrier, combined with polydimethylsiloxane (PDMS) encapsulation technology, to improve the sensitivity of the sensor:

[0017] The polystyrene nano / micro particle powder synthesized by the anti-solvent method effectively prevents the aggregation and self-quenching of PtOEP dye. The loose structure provides a rapid diffusion channel for oxygen, making the film have high oxygen sensitivity. The PDMS encapsulation layer effectively blocks water molecules, enhancing the chemical stability and anti-photobleaching ability of the dye.

[0018] The sensitive film prepared by the present application follows the Stern-Volmer quenching equation and shows good linear response in the oxygen concentration range of 0%~100%, with a sensitivity (I0 / I 90 ) of 16.7±0.5. The entire preparation process does not require complex equipment, is simple to operate, and is easy to realize large-scale production. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 FIG. 1 is a schematic diagram of the three-layer structure of the dissolved oxygen-sensitive film prepared by the present application;

[0020] Figure 2 FIG. 2 is a scanning electron microscope (SEM) image of the polystyrene nano / micro particle powder prepared in step one of the embodiment, a is an SEM image with a scale of 5 μm, and b is an SEM image with a scale of 1 μm;

[0021] Figure 3Fluorescence emission spectrum (peak at 640 nm) of the dissolved oxygen sensitive film prepared in Example 1;

[0022] Figure 4 Schematic diagram of the experimental device for optical characterization of the sensor using the dissolved oxygen sensitive film prepared in Example 1;

[0023] Figure 5 Comparison diagram of the Stern-Volmer response curve of the dissolved oxygen sensitive film prepared in Example 1;

[0024] Figure 6 Comparison diagram of the sensitivity of the dissolved oxygen sensitive film prepared in Example 1 and the dissolved oxygen sensitive film prepared in Comparative Experiment 1 without EPS carrier;

[0025] Figure 7 Diagram of the change of the normalized intensity with time of the dissolved oxygen sensitive film prepared in Example 1 and the dissolved oxygen sensitive films prepared in Comparative Experiments 1 to 3. DETAILED DESCRIPTION

[0026] The technical solution of the present application is not limited to the following specific embodiments, but also includes any combination of the specific embodiments.

[0027] Specific embodiment one: a preparation method of a dissolved oxygen sensitive film according to the following steps:

[0028] I. Preparation of polystyrene nano / microparticle powder:

[0029] ①Dissolve the foamed polystyrene waste in ethyl acetate to obtain an EPS solution;

[0030] ②Under stirring, add the EPS solution dropwise into the mixed anti-solvent of ethanol and water, and continue stirring until complete precipitation to obtain a suspension;

[0031] ③Centrifuge the suspension, collect the precipitate, then wash and dry to obtain polystyrene nano / microparticle powder;

[0032] II. Preparation of oxygen sensitive film:

[0033] ①Dissolve the PtOEP dye in toluene to obtain a dye solution;

[0034] ②Add the polystyrene nano / microparticle powder into ethyl acetate to obtain an EPS particle solution;

[0035] ③Mix the dye solution and the EPS particle solution to obtain a mixed solution;

[0036] ④Under stirring, the mixed solution is added dropwise into the mixed anti-solvent of ethanol and water, and after the dropwise addition is completed, centrifugal separation and washing are performed to obtain a washed precipitate;

[0037] ⑤The washed precipitate is uniformly coated on a substrate and dried to obtain a sensitive intermediate layer, and a layer of PDMS prepolymer is covered on the sensitive intermediate layer and solidified to form an encapsulation layer, thereby completing the preparation method of the dissolved oxygen sensitive film.

[0038] Figure 1 A schematic diagram of the three-layer structure of the dissolved oxygen sensitive film prepared by the present application; as can be seen from the figure, the dissolved oxygen sensitive film prepared by the present application is a sandwich layered structure, which comprises:

[0039] The base layer: a thin glass substrate for transmitting excitation light and fluorescent emission signals.

[0040] The intermediate layer (sensitive layer): an oxygen sensitive active layer composed of PtOEP dye dispersed in polystyrene nano / microparticle powder. The polystyrene nano / microparticle powder is synthesized from expanded polystyrene (EPS) waste by an anti-solvent precipitation method.

[0041] The outer layer (encapsulation layer): a hydrophobic film composed of polydimethylsiloxane (PDMS) for protecting the sensitive layer from moisture and physical erosion while allowing free diffusion of oxygen.

[0042] The beneficial effects of the present embodiment are:

[0043] The present embodiment proposes an oxygen sensitive film preparation method using polystyrene (EPS) as a raw material to synthesize nano / microparticle powder as a dye carrier, combined with polydimethylsiloxane (PDMS) encapsulation technology, to improve the sensitivity of the sensor:

[0044] The polystyrene nano / microparticle powder synthesized by the anti-solvent method in the present embodiment effectively prevents the aggregation and self-quenching of PtOEP dye. The loose structure provides a fast diffusion channel for oxygen, making the film have high oxygen sensitivity. The PDMS encapsulation layer effectively blocks water molecules, enhancing the chemical stability and anti-photobleaching ability of the dye.

[0045] The sensitive film prepared by the present embodiment follows the Stern-Volmer quenching equation and shows good linear response in the oxygen concentration range of 0% to 100%, with a sensitivity (I0 / I 90 ) of 16.7±0.5. The entire preparation process does not require complex equipment, is simple to operate, and is easy to realize large-scale production.

[0046] Embodiment two: different from embodiment one, the mass percentage of the EPS solution in step 1) is 1%~5%. The others are the same as embodiment one.

[0047] Embodiment three: different from either embodiment one or two, in step 1) ii), the EPS solution is added dropwise into the mixed anti-solvent of ethanol and water at a stirring speed of 1000 rpm~2000 rpm and a dropwise adding speed of 10 drops / min~20 drops / min, and after the dropwise adding is completed, the stirring is continued for 5 min~15 min at a stirring speed of 1000 rpm~2000 rpm until the precipitation is completed; the volume ratio of the EPS solution to the mixed anti-solvent of ethanol and water in step 1) ii) is 1:(10~25); the volume percentage of water in the mixed anti-solvent of ethanol and water in step 1) ii) is 40%~60%. The others are the same as either embodiment one or two.

[0048] Embodiment four: different from any one of embodiments one to three, in step 1) iii), the suspension is centrifuged at a centrifugal speed of 8000 rpm~12000 rpm, the precipitate is collected, then washed with deionized water for multiple times, and finally dried at a temperature of 50℃~70℃ for 10 h~15 h. The others are the same as embodiments one to three.

[0049] Embodiment five: different from any one of embodiments one to four, the concentration of the PtOEP dye in the dye solution in step 2) i) is 0.1 mg / mL~0.2 mg / mL. The others are the same as embodiments one to four.

[0050] Embodiment six: different from any one of embodiments one to five, the concentration of the polystyrene nano / micro-particle powder in the EPS particle solution in step 2) ii) is 1 mol / L~5 mol / L. The others are the same as embodiments one to five.

[0051] Embodiment seven: different from any one of embodiments one to six, the volume ratio of the dye solution to the EPS particle solution in step 2) iii) is 1:(10~30). The others are the same as embodiments one to six.

[0052] Specific embodiment eight: different from any one of specific embodiments one to seven, in step two (IV), the mixed solution is added dropwise to the mixed anti-solvent of ethanol and water under the conditions of a stirring speed of 2000 rpm to 3000 rpm and a dropwise adding speed of 20 drops / min to 30 drops / min, after the dropwise adding is completed, the precipitate is centrifugally separated and washed with deionized water to obtain the washed precipitate; in step two (IV), the volume ratio of the mixed solution to the mixed anti-solvent of ethanol and water is 1: (25 to 50); in step two (IV), the volume percentage of water in the mixed anti-solvent of ethanol and water is 60% to 100%. The others are the same as specific embodiments one to seven.

[0053] Specific embodiment nine: different from any one of specific embodiments one to eight, in step two (V), the substrate is a circular soda-lime glass substrate with a diameter of 15 mm to 30 mm and a thickness of 100 μm to 250 μm; in step two (V), the thickness of the sensitive intermediate layer is 1 μm to 50 μm; in step two (V), the thickness of the packaging layer is 1 μm to 50 μm. The others are the same as specific embodiments one to eight.

[0054] Specific embodiment ten: different from any one of specific embodiments one to nine, in step two (V), the drying is specifically drying for 15 h to 24 h under the condition of a temperature of 70 ℃ to 90 ℃. The others are the same as specific embodiments one to nine.

[0055] The beneficial effects of the present application are verified by the following examples:

[0056] Example one:

[0057] A preparation method of a dissolved oxygen sensitive film, which is carried out according to the following steps:

[0058] I. Preparation of polystyrene nano / microparticle powder:

[0059] ①Dissolve the foamed polystyrene waste in ethyl acetate to obtain an EPS solution;

[0060] The mass percentage of the EPS solution is 1%;

[0061] ②Under the conditions of a stirring speed of 2000 rpm and a dropwise adding speed of 15 drops / min, the EPS solution is added dropwise to the mixed anti-solvent of ethanol and water, after the dropwise adding is completed, under the condition of a stirring speed of 2000 rpm, the stirring is continuously carried out for 15 min to fully precipitate, to obtain a suspension;

[0062] The volume ratio of the EPS solution to the mixed anti-solvent of ethanol and water is 1:20; the volume percentage of water in the mixed anti-solvent of ethanol and water is 40%;

[0063] ③ centrifuging the suspension at a centrifugal speed of 10000 rpm, collecting the precipitate, then washing the precipitate with deionized water for several times, and finally drying at a temperature of 60℃ for 12h to obtain polystyrene nano / microparticle powder;

[0064] II. Preparation of the oxygen-sensitive film:

[0065] ① dissolving PtOEP dye in toluene to obtain a dye solution;

[0066] The concentration of PtOEP dye in the dye solution is 0.1 mg / mL;

[0067] ② adding polystyrene nano / microparticle powder into ethyl acetate to obtain an EPS particle solution;

[0068] The concentration of polystyrene nano / microparticle powder in the EPS particle solution is 1 mol / L;

[0069] ③ mixing the dye solution with the EPS particle solution to obtain a mixed solution;

[0070] The volume ratio of the dye solution to the EPS particle solution is 1:10;

[0071] ④ adding the mixed solution into a mixed anti-solvent of ethanol and water at a stirring speed of 2000 rpm and a dropping speed of 20 drops / min, centrifuging the precipitate after the addition is completed, and washing the precipitate with deionized water to obtain a washed precipitate;

[0072] The volume ratio of the mixed solution to the mixed anti-solvent of ethanol and water is 1:25; the volume percentage of water in the mixed anti-solvent of ethanol and water in step two ④ is 60%;

[0073] ⑤ uniformly coating the washed precipitate on a substrate, and drying at a temperature of 60℃ for 12h to obtain a sensitive intermediate layer, covering a layer of PDMS prepolymer on the sensitive intermediate layer and solidifying to form an encapsulating layer, thereby completing the preparation method of the dissolved oxygen-sensitive film;

[0074] The substrate is a circular soda-lime glass substrate with a diameter of 18mm and a thickness of 160μm;

[0075] The thickness of the sensitive intermediate layer is 10μm; and the thickness of the encapsulating layer is 50μm.

[0076] Comparative Experiment One: The difference between this comparative experiment and Example One is that the use of EPS particle solution in step two ② is cancelled; and step two ⑤ obtains a dissolved oxygen-sensitive film prepared by PDMS encapsulation without EPS carrier. The others are the same as Example One.

[0077] Comparative Experiment 2: This comparative experiment differs from Example 1 in that step 2.5, which involves covering the sensitive intermediate layer with a layer of PDMS prepolymer and curing it to form an encapsulation layer, is omitted; step 2.5 yields a dissolved oxygen sensitive film prepared with an EPS carrier encapsulated without PDMS. Everything else is the same as in Example 1.

[0078] Comparative Experiment 3: This comparative experiment differs from Example 1 in that: the use of EPS particle solution in step 2② is omitted; the process of covering the sensitive intermediate layer with a layer of PDMS prepolymer and curing it to form an encapsulation layer in step 2⑤ is omitted; step 2⑤ yields a dissolved oxygen sensitive film prepared without PDMS encapsulation and without an EPS carrier. Everything else is the same as in Example 1.

[0079] Figure 2 The images show scanning electron microscope (SEM) images of the polystyrene nano / micron particle powder prepared in step one of Example 1. Image a is an SEM image with a scale bar of 5 μm, and image b is an SEM image with a scale bar of 1 μm. As can be seen from the images, the obtained particle diameter is approximately between 100 nm and 500 nm, and the distribution is relatively uniform.

[0080] Figure 3 The fluorescence emission spectrum (peak at 640 nm) of the dissolved oxygen sensitive film prepared in Example 1 is shown. The front sensitive layer is the substrate side, and the back encapsulation layer is the encapsulation layer side. The typical emission spectrum response of the dissolved oxygen sensitive film at room temperature was obtained using a visible spectrometer. It can be seen that the absorption band has the largest peak at a wavelength of 367 nm, which is 10. 9 Therefore, a 367nm LED light source driven by a square wave pulse and coupled to a fiber bundle splitter was chosen to excite the sample. Furthermore, the figure shows that the thin film exhibits strong absorption and emission in the visible light region, making it suitable for optical sensing systems.

[0081] Figure 4 This is a schematic diagram of the experimental setup for optical characterization of the dissolved oxygen-sensitive thin film prepared in Example 1. A 367nm UV-LED was used as the excitation source, and a lock-in amplifier was used to detect the fluorescence intensity signal at 650nm. The oxygen concentration in the test chamber was controlled by adjusting the mixing ratio of nitrogen and air.

[0082] Figure 5 The figure shows a comparison of the Stern-Volmer response curves of the dissolved oxygen sensitive film prepared in Example 1. As can be seen from the figure, the fluorescence intensity of the sensor element prepared in the example has a good linear relationship with the oxygen concentration, which conforms to the Stern-Volmer equation, and exhibits a good linear response in the oxygen concentration range of 0% to 100%.

[0083] Figure 6The sensitivity comparison chart of the dissolved oxygen sensitive film prepared in Example 1 and the dissolved oxygen sensitive film prepared in Comparative Experiment 1 without EPS carrier. As can be seen from the chart, using EPS as the carrier of PtOEP dye can improve the sensitivity of the sensor to oxygen. The sensitivity (I0 / I 90 ) of the dissolved oxygen sensitive film prepared in Example 1 reaches 16.7±0.5, and the response ratio is at the same level as that of the commercial sensor cap, proving the excellent sensing performance thereof.

[0084] Figure 7 The chart of the normalized intensity of the dissolved oxygen sensitive film prepared in Example 1 and the dissolved oxygen sensitive films prepared in Comparative Experiments 1 to 3 changing with time. As can be seen from the chart, the stability of the film with PDMS packaging is much higher than that of the film without PDMS packaging. The reason is that the PDMS packaging layer effectively blocks water molecules, thereby enhancing the chemical stability and anti-photobleaching ability of the dye.

Claims

1. A method for preparing a dissolved oxygen sensitive film, characterized by It is carried out according to the following steps: I. Preparation of polystyrene nano / microparticle powder: ①EPS solution is obtained by dissolving foamed polystyrene waste in ethyl acetate; ②Under stirring, the EPS solution is added dropwise into the mixed anti-solvent of ethanol and water, and after the dropwise addition is completed, stirring is continued until complete precipitation to obtain a suspension; ③The suspension is centrifuged to collect the precipitate, which is then washed and dried to obtain polystyrene nano / microparticle powder; II. Preparation of oxygen-sensitive film: ①Dye solution is obtained by dissolving PtOEP dye in toluene; ②EPS particle solution is obtained by adding polystyrene nano / microparticle powder into ethyl acetate; ③The dye solution and the EPS particle solution are mixed to obtain a mixed solution; ④Under stirring, the mixed solution is added dropwise into the mixed anti-solvent of ethanol and water, and after the dropwise addition is completed, the precipitate is obtained by centrifugation and washing; ⑤The washed precipitate is uniformly coated on a substrate and dried to obtain a sensitive intermediate layer, and a layer of PDMS prepolymer is covered on the sensitive intermediate layer and solidified to form an encapsulating layer, thereby completing the preparation of the dissolved oxygen-sensitive film.

2. The method of claim 1, wherein the method further comprises The mass percentage of the EPS solution in step I ① is 1% to 5%.

3. The method of claim 1, wherein the method further comprises In step I ②, the EPS solution is added dropwise into the mixed anti-solvent of ethanol and water at a stirring speed of 1000 rpm to 2000 rpm and a dropwise addition speed of 10 drops / min to 20 drops / min, and after the dropwise addition is completed, stirring is continued at a stirring speed of 1000 rpm to 2000 rpm for 5 min to 15 min until complete precipitation; the volume ratio of the EPS solution to the mixed anti-solvent of ethanol and water in step I ② is 1:(10 to 25); and the volume percentage of water in the mixed anti-solvent of ethanol and water in step I ② is 40% to 60%.

4. The method of claim 1, wherein the method further comprises In step I ③, the suspension is centrifuged at a centrifugal speed of 8000 rpm to 12000 rpm to collect the precipitate, which is then washed multiple times with deionized water, and finally dried at a temperature of 50°C to 70°C for 10 h to 15 h.

5. The method of claim 1, wherein the method further comprises The concentration of PtOEP dye in the dye solution in step II ① is 0.1 mg / mL to 0.2 mg / mL.

6. The method of claim 1, wherein the method further comprises The concentration of polystyrene nano / microparticle powder in the EPS particle solution in step II ② is 1 mol / L to 5 mol / L.

7. The method of claim 1, wherein the method further comprises The volume ratio of the dye solution to the EPS particle solution in step II ③ is 1:(10 to 30).

8. The method of claim 1, wherein the method further comprises In step II ④, the mixed solution is added dropwise into the mixed anti-solvent of ethanol and water at a stirring speed of 2000 rpm to 3000 rpm and a dropwise addition speed of 20 drops / min to 30 drops / min, and after the dropwise addition is completed, the precipitate is obtained by centrifugation and washing with deionized water; the volume ratio of the mixed solution to the mixed anti-solvent of ethanol and water in step II ④ is 1:(25 to 50); and the volume percentage of water in the mixed anti-solvent of ethanol and water in step II ④ is 60% to 100%.

9. The method of claim 1, wherein the method further comprises the step of: The substrate in step two ⑤ is a circular soda-lime glass substrate with a diameter of 15mm-30mm and a thickness of 100μm-250μm; the thickness of the sensitive intermediate layer in step two ⑤ is 1μm-50μm; the thickness of the encapsulation layer in step two ⑤ is 1μm-50μm. ​ 10. The method of claim 1, wherein the method further comprises The drying in step two ⑤ is specifically drying for 15h-24h at a temperature of 70℃-90℃.

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