A perovskite-metal organic framework-based electrospun film and a preparation method and application thereof

Abstract

The application discloses a kind of ammonia sensing electrospinning films based on perovskite-metal organic framework. Porous fiber film containing perovskite and metal organic framework is prepared by electrospinning, and perovskite is in-situ grown and enriched in metal organic framework during electrospinning process. The application embeds metal organic framework in electrospinning fiber, improves the perovskite ammonia sensing performance. The application uses a method of repairing and enhancing perovskite fluorescence intensity after using ammonia, which is a new type of fluorescence sensing method, and can realize non-real-time recording function of ammonia concentration. The new ammonia sensing film and non-real-time ammonia concentration recording method provided by the application have the advantages of low cost, large-area preparation, simple detection, etc.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of gas sensors, and relates to a static electrospinning film based on a perovskite-metal organic framework. BACKGROUND

[0002] Ammonia gas, as an important biomarker for monitoring food quality, is usually generated from the degradation of amino acids caused by exogenous microbial activity or endogenous metabolism of body tissues during food spoilage. In the field of food safety, improper handling of seafood and meat products during storage, transportation and sales can lead to spoilage, thereby producing biogenic amine metabolites with unpleasant odor. However, some businesses sell expired and rotten food after treating it with chemical additives to mask the ammonia gas generated during the spoilage process, while the toxic amine metabolites inside the food remain and are not easily detected by consumers, leading to food safety problems. In order to avoid such situations, it is necessary to record the quality of food during storage and transportation. Therefore, it is an urgent and necessary technical requirement to develop a simple, rapid, low-cost and accurate ammonia gas concentration recording sensor.

[0003] In order to realize the recording of gas concentration, a gas sensor usually includes a power supply, an electrical signal transmission system, a signal analysis and processing system, etc., which is large in size and involves complex systems, and cannot meet the needs of the new generation of sensors for miniaturization, energy saving and long-term stable operation. At present, the gas sensing methods for ammonia gas include metal oxide sensors, conductive polymer sensors, biological sensors, mass spectrometry sensors, electrochemical sensors, fluorescent sensors, etc. Among them, fluorescent sensors have become a research hotspot due to their rapid and low-cost characteristics. In the field of gas sensing, fluorescent sensors mainly rely on the reaction between the gas to be detected and the fluorescent material of the sensor in the gas environment to realize real-time fluorescence signal change. However, ammonia gas is volatile, and if it is separated from the gas environment to be detected, the signal change of the fluorescent material will be disturbed or completely disappeared, making it difficult to realize long-time recording of the fluorescent signal. The detection of such signals requires real-time detection or acquisition of real-time images by building an optical path, which still cannot meet the needs of simple detection, low cost and non-real-time signal recording. SUMMARY

[0004] In view of the above problems, the purpose of the present application is to provide an ammonia gas sensing electrospinning film based on a perovskite-metal organic framework, which can realize non-real-time recording of ammonia gas concentration, and achieve low cost, large-area preparation, simple detection and information recording effects.

[0005] To achieve the above purpose, the technical solution adopted by the present application is as follows: a preparation method of a static electrospinning film based on a perovskite-metal organic framework, comprising the following steps:

[0006] (1) Preparation of metal organic framework: dissolve indium nitrate and terephthalic acid in N,N-dimethylformamide, and carry out the reaction in an oil bath; after the reaction is completed, centrifuge and remove the supernatant; the product after centrifugation is re-dispersed in anhydrous ethanol, centrifuged and the supernatant is removed, and the washing step is repeated until the separated supernatant is colorless and transparent; the washed product is dried in an oven; and a metal organic framework is obtained;

[0007] (2) Preparation of perovskite-metal organic framework precursor solution: dissolve cesium bromide in deionized water and ultrasonic until completely dissolved; add N,N-dimethylformamide to the mixed solution, and then add lead bromide and ultrasonic until completely dissolved to obtain a perovskite precursor solution; thermoplastic polyurethane elastomer is used as an electrospinning polymer and dissolved in the perovskite precursor solution, and magnetic stirring is carried out to obtain a homogeneous and transparent polymer-perovskite precursor solution; the metal organic framework is added to the polymer-perovskite precursor solution and magnetic stirring is carried out until the metal organic framework is uniformly dispersed in the polymer solution to obtain a perovskite-metal organic framework precursor solution;

[0008] (3) Preparation of perovskite-metal organic framework electrospinning film: electrospinning the perovskite-metal organic framework precursor solution to obtain a perovskite-metal organic framework electrospinning film.

[0009] In the step (1), the addition amount of terephthalic acid is 0.03 g-0.012 g, the addition amount of indium nitrate is 0.015 g-0.06 g, and the molar ratio of terephthalic acid to indium nitrate is 1:0.9-1.1. The addition amount of N,N-dimethylformamide is 2-8 mL.

[0010] In the step (1), the oil bath reaction conditions are 130-140℃ for 20-30 minutes. The oven drying temperature is 55-75℃, and the time is 4-8 hours.

[0011] In the step (2), the addition amount of cesium bromide is 1.064 mg-17.024 mg, the addition amount of lead bromide is 3.67 mg-58.72 mg, and the molar ratio of cesium bromide to lead bromide is 1:1.9-2.1. The addition amount of deionized water is 0.2-0.4 mL. The addition amount of N,N-dimethylformamide is 3-5 mL.

[0012] In the step (2), the electrospinning polymer is thermoplastic polyurethane elastomer, and the addition amount is 0.9-1.1 g. The addition amount of metal organic framework is 20-80 mg.

[0013] In the step (3), the parameter conditions of the electrospinning system are: voltage 12-14 kV, needle-collector distance 10-14 cm, and polymer flow rate 0.5-0.7 mL / h.

[0014] In the perovskite-metal organic framework electrospinning film, due to the existence of a porous structure suitable for perovskite growth in the metal organic framework, CsPb2Br5 tends to grow in the porous structure in the metal organic framework in situ during the electrospinning process; and when the metal organic framework is not added, CsPb2Br5 grows on the surface of the polymer. Due to the special porous structure, the CsPb2Br5 recrystallized in the metal organic framework has higher quality, and its fluorescence intensity is much greater than that of the film without adding the metal organic framework.

[0015] The sensing principle of the perovskite-metal organic framework electrospinning film is as follows: the perovskite in the electrospinning fiber is treated with ammonia gas to liquefy the perovskite, and after the perovskite is removed from the ammonia atmosphere, the perovskite is recrystallized into a higher quality crystal, and the fluorescence intensity is significantly increased; according to the ratio of the fluorescence intensity of the film before and after ammonia treatment, the concentration of ammonia in the environment to be measured is calculated through a standard fitting curve, so as to realize the non-real-time recording function of the ammonia concentration in the environment to be measured.

[0016] The application uses ammonia gas to treat the in-situ grown CsPb2Br5 perovskite in the electrospinning fiber to liquefy the perovskite, and after the perovskite is removed from the ammonia atmosphere, the perovskite is recrystallized into a higher quality crystal, and the fluorescence intensity is significantly increased. The enhancement of the perovskite fluorescence signal occurs only after the ammonia gas is removed, so as to realize the non-real-time recording function of the ammonia concentration in the past environment, and it is a new type of fluorescence sensing method.

[0017] In the application, the metal organic framework is embedded in the electrospinning fiber by adding the metal organic framework into the electrospinning precursor solution. Due to the existence of a porous structure suitable for perovskite growth in the metal organic framework, CsPb2Br5 tends to grow in the porous structure in the metal organic framework in situ during the electrospinning process; and when the metal organic framework is not added, CsPb2Br5 grows on the surface of the polymer. Due to the special porous structure, after ammonia treatment, the CsPb2Br5 recrystallized in the metal organic framework has higher quality, and its fluorescence intensity is much greater than that of the film without adding the metal organic framework. The addition of the metal organic framework improves the fluorescence response intensity of the film and enhances the ammonia sensing performance.

[0018] Compared with the prior art, the application has the following beneficial effects:

[0019] 1. The application uses the method of ammonia post-repairing and enhancing the fluorescence intensity of perovskite, which is a new type of fluorescence sensing method, and can realize the non-real-time recording function of the ammonia concentration.

[0020] 2. The application embeds the hexagonal columnar metal organic framework in the electrospinning fiber, improves the fluorescence response intensity of the film to ammonia, and enhances the ammonia sensing performance.

[0021] 3、The electrospun flexible film prepared by the application has unique ultrahigh specific surface area and open porous non-woven structure, and can provide a unique sensing platform, and exhibits extremely high fluorescence stability and sensitivity.

[0022] 4、The application adopts a fluorescence-on sensing method, and only in the presence of an analyte, a non-fluorescent precursor is converted into a fluorescent indicator. Due to higher sensitivity and selectivity, such fluorescence detection is more attractive than fluorescence quenching detection in actual sensing devices.

[0023] 5、The application selects a thermoplastic polyurethane elastomer as an electrospun polymer, and the polymer has a hydrophobic property, can improve the stability of perovskite in a wet environment, and improve the accuracy of ammonia gas sensing.

[0024] 6、The electrospun film of the application has simple raw materials, low cost, and short preparation time, and is conducive to large-scale synthesis and application. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 It is a schematic diagram of the morphology of the metal organic framework prepared in Example 1 under a scanning electron microscope.

[0026] Figure 2 It is a schematic diagram of the morphology of the perovskite electrospun film prepared in Example 2 under a scanning electron microscope.

[0027] Figure 3 It is a schematic diagram of the X-ray diffraction spectrum of the perovskite-metal organic framework electrospun film prepared in Example 3.

[0028] Figure 4 It is a schematic diagram of the morphology of the electrospun film prepared in Example 3 under a scanning electron microscope.

[0029] Figure 5 It is a schematic diagram of the EDS-Mapping element distribution of the perovskite-metal organic framework electrospun film prepared in Example 3.

[0030] Figure 6 It is a schematic diagram of the atomic force microscope comparison of the CsPb2Br5 film sample before and after ammonia treatment in Example 4.

[0031] Figure 7 It is a schematic diagram of the fluorescence emission spectrum comparison of the electrospun film before and after ammonia treatment in Example 5.

[0032] Figure 8 It is a schematic diagram of the change of the fluorescence intensity of the electrospun film after ammonia treatment in Example 5 after being placed in air for a certain period of time.

[0033] Figure 9 Figure 6 is a schematic diagram of fluorescence spectra of the electrospun film in Example 6 after treatment with different concentrations of ammonia.

[0034] Figure 10 Figure 7 is a schematic diagram of the linear relationship between the ratio of fluorescence intensity of the electrospun film established in Example 6 before and after treatment with ammonia and the concentration of ammonia. DETAILED DESCRIPTION

[0035] The application will be further described below in conjunction with the examples and drawings, and the following examples are only used to illustrate the application, but not to limit the scope of the application.

[0036] Example 1

[0037] Method for preparing metal organic framework:

[0038] 0.06 g of indium nitrate and 0.03 g of terephthalic acid were dissolved in 4 mL of N,N-dimethylformamide, and the reaction was carried out in an oil bath. The reaction conditions were 135 ℃ and 25 minutes. After the reaction was completed, centrifugation was performed and the supernatant was removed. The product after centrifugation was redispersed in 2 mL of anhydrous ethanol, centrifuged and the supernatant was removed, and this washing step was repeated three times. The washed product was dried in an oven at 65 ℃ for 6 hours. A white metal organic framework was obtained.

[0039] Figure 1 Figure 3 is a schematic diagram of the morphology of the metal organic framework prepared by this example under a scanning electron microscope. The metal organic framework prepared has a hexagonal column structure with a length of 2-4 μm and a diameter of about 600 nm.

[0040] Example 2

[0041] Method for preparing perovskite electrospun film:

[0042] 4.256 mg of cesium bromide was dissolved in 0.3 mL of deionized water and ultrasonicated until completely dissolved. 4 mL of N,N-dimethylformamide was added to the mixed solution, and 14.68 mg of lead bromide was added and ultrasonicated until completely dissolved to obtain a perovskite precursor solution. 1 g of a thermoplastic polyurethane elastomer was dissolved in the perovskite precursor solution, and magnetic stirring was performed for 6 hours to obtain a homogeneous and transparent polymer-perovskite precursor mixed solution. The polymer-perovskite precursor mixed solution was used for electrospinning, and the parameter conditions of the electrospinning system were set as follows: voltage 13 kV, needle-collector distance 12 cm, and flow rate 0.6 mL / h. After electrospinning was completed, a perovskite electrospun film was collected.

[0043] Figure 2Morphology of the perovskite electrospun film prepared in this example under scanning electron microscope. The diameter of the electrospun fiber prepared is about 0.5-1 μm, and the fiber thickness distribution is relatively uniform. The perovskite CsPb2Br5 grows in situ on the surface of the fiber, showing a crystal morphology with sharp corners.

[0044] Example 3

[0045] Method for preparing a perovskite-metal organic framework electrospun film

[0046] Dissolve 4.256 mg of cesium bromide in 0.3 mL of deionized water, and ultrasonic until completely dissolved; add 4 mL of N,N-dimethylformamide to the mixed solution, and then add 14.68 mg of lead bromide, and ultrasonic until completely dissolved, to obtain a perovskite precursor solution; dissolve 1 g of a thermoplastic polyurethane elastomer in the perovskite precursor solution, and magnetically stir for 6 hours, to obtain a homogeneous and transparent polymer-perovskite precursor mixed solution;

[0047] Add 50 mg of metal organic framework powder to the polymer-perovskite precursor mixed solution, and magnetically stir for 1 hour, to obtain an electrospinning precursor solution.

[0048] Electrospin the electrospinning precursor solution, and set the parameter conditions of the electrospinning system as follows: voltage 13 kV, needle-collector distance 12 cm, and flow rate 0.6 mL / h. After the electrospinning is completed, collect the perovskite-metal organic framework electrospun film.

[0049] Figure 3 X-ray diffraction spectrum of the perovskite-metal organic framework electrospun film prepared in this example. The diffraction peaks in the "*" part belong to the metal organic framework, and the diffraction peaks in the "▲" part belong to the CsPb2Br5 perovskite, proving that the perovskite grows in situ in the electrospun film.

[0050] Figure 4 Morphology of the electrospun film prepared in this example under scanning electron microscope. The diameter of the electrospun fiber prepared is about 500 nm-1 μm. Some fibers incorporate hexagonal columnar metal organic frameworks, showing a discontinuous truncated morphology. Compared with the perovskite electrospun film prepared in Example 2, the method of adding a metal organic framework to the electrospinning precursor solution in this example embeds a hexagonal columnar metal organic framework in the electrospun fiber. Since there is a porous structure suitable for perovskite growth inside the metal organic framework, CsPb2Br5 tends to grow in situ in the porous structure inside the metal organic framework during the electrospinning process; while CsPb2Br5 grows on the surface of the polymer when no metal organic framework is added.

[0051] Figure 5 EDS-Mapping element distribution map of the perovskite-metal organic framework electrospinning film prepared by the present embodiment. The element scanning range corresponds to Figure 4 the middle white box part. Among them, the indium element belongs to the metal organic framework, and the cesium lead bromide belongs to the CsPb2Br5 perovskite. The element distribution map proves that the CsPb2Br5 perovskite is in-situ grown inside the metal organic framework.

[0052] Example 4

[0053] Verification of the mechanism of CsPb2Br5 applied to ammonia sensing:

[0054] Dissolve 21.28 mg of cesium bromide in 0.3 mL of deionized water, and ultrasonic until completely dissolved; add 4 mL of N,N-dimethylformamide to the mixed solution, and then add 73.4 mg of lead bromide, and ultrasonic until completely dissolved, to obtain a perovskite precursor solution; spin-coat 0.3 mL of the perovskite precursor solution on glass to obtain a uniform perovskite precursor film, and the spin-coating conditions are 4000 rpm and 20 s; anneal the glass sheet at 120°C for 20 minutes to obtain a CsPb2Br5 film; fix the CsPb2Br5 film sample on the inner wall of a 1.5 L gas container, add ammonia water at the bottom of the container, and seal the container; place the container on a 50°C heating platform for 1 minute to make the internal ammonia water completely volatilize, and take out the container and place it in a room temperature environment; after 5 minutes of reaction, take out the CsPb2Br5 film sample; respectively, perform atomic force microscope (AFM) characterization on the CsPb2Br5 film samples before and after ammonia treatment in the present embodiment.

[0055] Figure 6 The AFM comparison chart of the CsPb2Br5 film samples before and after ammonia treatment. Among them, the root mean square of the surface roughness of the film before ammonia treatment is 21 nm, and the root mean square of the surface roughness of the film after ammonia treatment is 6 nm, indicating that the CsPb2Br5 has undergone a liquefaction and recrystallization process after ammonia treatment, verifying the sensing mechanism of the post-ammonia repair enhancing the perovskite fluorescence intensity. The present embodiment proves that ammonia can cause CsPb2Br5 to liquefy, and after leaving the ammonia atmosphere, CsPb2Br5 recrystallizes into a crystal with a smooth surface and higher quality.

[0056] Example 5

[0057] Verification of the enhancement effect of adding a metal organic framework on the ammonia sensing performance of the electrospinning film:

[0058] The perovskite electrospinning film prepared in Example 2 and the perovskite-metal organic framework electrospinning film prepared in Example 3 were respectively cut into small pieces of 1 cm*1 cm, and the fluorescence spectra of the films were detected; a glass reagent bottle with a volume of 1.5 L and good air tightness was prepared as a gas container; the cut electrospinning film was fixed to the inner wall of the container, 50 μL of 1% ammonia water was added at the bottom of the container, and the container was sealed; the container was placed on a 50 ℃ heating table for 1 minute to make the internal ammonia water completely volatilize, and the container was taken out and placed in a room temperature environment; after 5 minutes of reaction, the electrospinning film treated by ammonia gas was taken out, and the fluorescence spectrum of the film was detected; the fluorescence spectrum changes of the perovskite of the film without adding metal organic framework in Example 2 and the film adding metal organic framework in Example 3 before and after ammonia gas treatment were compared.

[0059] Figure 7 The fluorescence emission spectra of the electrospinning film before and after ammonia gas treatment were compared. After ammonia gas treatment, the fluorescence intensity of the film without adding metal organic framework was enhanced to 24.3 times that before ammonia gas treatment; the fluorescence intensity of the film adding metal organic framework was enhanced to 113.8 times that before ammonia gas treatment. This embodiment proves that due to the special porous structure, the CsPb2Br5 recrystallized in the metal organic framework has higher quality after ammonia gas treatment, and the fluorescence intensity enhancement amplitude is much larger than that of the film without adding metal organic framework. The addition of metal organic framework improves the fluorescence response intensity of the film and enhances the ammonia gas sensing performance.

[0060] Figure 8 The change of fluorescence intensity of the film after ammonia gas treatment and after being placed in air for a certain time was compared. Within ten days of testing time, in the film without adding metal organic framework, the fluorescence intensity of the perovskite decreased to 83.8% of that just after treatment; in the film adding metal organic framework, the fluorescence intensity of the perovskite decreased to 94.5% of that just after treatment. The results show that the CsPb2Br5 recrystallized in the metal organic framework has better stability.

[0061] Example 6

[0062] Method for establishing ammonia gas concentration sensing standard curve:

[0063] The electrospun film prepared in Example 3 was cut into small pieces of 1 cm*1 cm, and the fluorescence spectrum of the film was detected; a glass reagent bottle with a volume of 1.5 L and good air tightness was prepared as a gas container; the cut electrospun film was fixed to the inner wall of the container, and ammonia was added to the bottom of the container, and the container was sealed; the container was placed on a 50℃ heating table for 1 minute to make the internal ammonia completely volatilize, and the container was taken out and placed in a room temperature environment; after 5 minutes of reaction, the electrospun film treated by ammonia gas was taken out, and the fluorescence spectrum of the film was detected; the volume of ammonia added to the container (6-50 μL) was adjusted to change the ammonia concentration in the container, and the fluorescence spectrum of the electrospun film treated by ammonia gas with different concentrations was detected respectively; according to the linear relationship between the fluorescence intensity ratio of the electrospun film before and after ammonia treatment and the ammonia concentration, a standard fitting curve was established, and the linear range was calculated.

[0064] Figure 9 The fluorescence spectrum of the electrospun film after treatment by ammonia gas with different concentrations is shown in FIG. 3. As the ammonia concentration increases, the fluorescence emission peak intensity gradually increases.

[0065] Figure 10 The linear relationship between the fluorescence intensity ratio of the electrospun film before and after ammonia treatment and the ammonia concentration established in this embodiment is shown in FIG. 4. In the range of 50-400 ppm, the film has a good linear response of fluorescence intensity to ammonia, and the correlation coefficient can reach 0.994.

[0066] Example 7

[0067] Method for applying the electrospun film to ammonia concentration sensing in actual environment:

[0068] The small piece of film cut in Example 3 was prepared, and the fluorescence spectrum of the film was detected; the film was placed in the environment to be measured, and after 5 minutes of reaction, the film was taken out and the fluorescence spectrum of the film was detected again; the fluorescence peak intensity of the film before and after ammonia treatment was compared, the value of the fluorescence intensity after treatment / the fluorescence intensity before treatment was calculated, and the concentration of ammonia in the environment to be measured was calculated according to the standard fitting curve in Example 6.

[0069] The above only describes the preferred embodiments of the present application, and it should be noted that for ordinary skilled persons in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A method for preparing a perovskite-metal organic framework based electrospun thin film, characterized by, Comprising the following steps: Step (1) preparation of metal organic framework: Indium nitrate and terephthalic acid are dissolved in N,N-dimethylformamide, and the reaction is carried out in an oil bath; after the reaction is completed, centrifugation is performed and the supernatant is removed; the product after centrifugation is redispersed in anhydrous ethanol, centrifuged and the supernatant is removed, and the washing step is repeated until the separated supernatant is colorless and transparent; the washed product is dried in an oven; and a metal organic framework is obtained; Step (2) preparation of perovskite-metal organic framework precursor solution: Cesium bromide is dissolved in deionized water and ultrasonicated until completely dissolved; N,N-dimethylformamide is added to the mixed solution, and then lead bromide is added and ultrasonicated until completely dissolved, to obtain a perovskite precursor solution; the electrospinning polymer is dissolved in the perovskite precursor solution and magnetically stirred to obtain a homogeneous and transparent polymer-perovskite precursor solution; the metal organic framework is added to the polymer-perovskite precursor solution and magnetically stirred until the metal organic framework is uniformly dispersed in the polymer solution, to obtain a perovskite-metal organic framework precursor solution; Step (3) preparation of perovskite-metal organic framework-based electrospinning film: The perovskite-metal organic framework precursor solution is electrospun, and a perovskite-metal organic framework electrospinning film is obtained after electrospinning is completed; In the step (1), the addition amount of terephthalic acid is 0.03 g-0.012 g, the addition amount of indium nitrate is 0.015 g-0.06 g, and the molar ratio of terephthalic acid to indium nitrate is 1:(0.9-1.1); the addition amount of N,N-dimethylformamide is 2-8 mL; In the step (1), the oil bath reaction conditions are temperature 130-140℃ and time 20-30 minutes; the oven drying temperature is 55-75℃ and the time is 4-8 hours; In the step (1), the prepared metal organic framework is a hollow hexagonal column structure; In the step (2), the addition amount of cesium bromide is 1.064 mg-17.024 mg, the addition amount of lead bromide is 3.67 mg-58.72 mg, the molar ratio of cesium bromide to lead bromide is 1:(1.9-2.1), the addition amount of deionized water is 0.2-0.4 mL, and the addition amount of N,N-dimethylformamide is 3-5 mL; In the step (2), the electrospinning polymer is a thermoplastic polyurethane elastomer, and the addition amount is 0.9-1.1 g; In the step (2), the addition amount of the metal organic framework is 20-80 mg.

2. The method for preparing a perovskite-metal organic framework based electrospun thin film according to claim 1, characterized in that: In the step (3), the parameter conditions of the electrospinning system are: voltage 12-14 kV, needle-collector distance 10-14 cm, and polymer flow rate 0.5-0.7 mL / h.

3. A perovskite-metal organic framework based electrospun thin film, characterized in that: Prepared by using the preparation method of any one of claims 1-2.

4. Use of the perovskite-metal organic framework-based electrospinning film of claim 3 in an ammonia gas sensor.

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