CN105588824B - Application of the double-deck electrostatic spinning film sensor in the detection of nitro-aromatic substance - Google Patents

Abstract

The invention discloses the application of a double-layer electrospun film sensor in the detection of nitroaromatic substances. The sensor includes a double-layer film structure, and the bottom layer is a gelatin electrospun film (GEL), which is layered as a skeleton On the surface of the glass sheet; the top layer uses polystyrene as a carrier, and carries out blending with the fluorescent sensing polymer P described in claim 1 to prepare an electrospun film (PS-P), which is a sensing layer. The advantages are: i) gelatin has a large number of amino and hydroxyl groups, and nitroaromatics and gelatin are enriched through hydrogen bond interaction forces to enrich nitroaromatics so that nitroaromatics are gathered in the P-PS sensing layer to achieve The effect of increasing the quenching rate. ii) As a porous framework under the P‑PS layer, the gelatin layer can allow the simultaneous diffusion of nitroaromatic molecules up and down the P‑PS layer, greatly improving the permeability of the P‑PS layer.

Description

Application of double-layer electrospun film sensor in the detection of nitroaromatics

technical field

The invention relates to the application of a double-layer electrostatic spinning film sensor in the detection of nitroaromatic substances.

Background technique

Nitroaromatics such as 2,4,6-trinitrotoluene (TNT), 2,4-dinitrotoluene (DNT), picric acid (PA) etc. are all important explosive components, for the use and Transportation must be strictly managed, otherwise it will not only seriously affect social stability and national security, but also cause harm to human health because of its biological toxicity and potential carcinogenicity. Therefore, the detection of explosives has attracted great attention from all countries, and many countries have invested a lot of money in scientific research. The fluorescence sensing method has the characteristics of high sensitivity, many parameters that can be collected (such as fluorescence intensity, fluorescence spectrum shape, fluorescence anisotropy, fluorescence lifetime, etc.), fast response time and relatively mature instrument design, which has become the most promising detection method. .

The current fluorescent sensors generally prepare fluorescent compounds into thin films by spin coating to form fluorescent thin film sensors. In order to ensure that the film has a certain fluorescence intensity, the polymer film must have a certain thickness, and the dense structure of ordinary films often makes the diffusion of the analyte in the film slow, so the response speed is slow. Various methods have been used to improve the polymer structure and increase the permeability of the film, so as to increase the diffusion rate of nitroaromatics in the film and improve the quenching efficiency.

Electrospinning technology is a simple method to prepare nanomaterials, which can obtain high permeability thin film materials. Electrospun films have numerous advantages: large specific surface area, high porosity, good permeability, and controllable morphology. These advantages all facilitate the mutual contact between the analyte and the probe. In recent years, thin film sensing materials prepared by electrospinning technology have been gradually applied in the detection of various substances, such as the detection of various metal ions, the detection of nitroaromatics, and so on. The common electrospun film sensor is to form an electrospun film on the surface of a solid substrate with a fluorescent sensing material. When detecting a gas analyte, gas molecules permeate into the membrane from above the membrane, causing a change in the fluorescence of the sensing material.

At present, no application of double-layer electrospun thin film sensor materials in the detection of nitroaromatics has been found.

Contents of the invention

In this patented technology, a layer of electrospun film is firstly prepared with gelatin on the glass surface, and a layer of electrospun film is prepared with sensing material on the surface of the film. Compared with the single-layer film, this double-layer film fluorescence sensor has superior sensing performance. The gelatin electrospun membrane on the bottom layer can allow the gas analyte to permeate from the top and bottom of the sensing layer at the same time, which improves the sensing rate. On the other hand, gelatin molecules contain a large number of electron-rich groups such as hydroxyl and amino groups, which can generate hydrogen bonds with nitroaromatics, thus enriching nitroaromatics and improving the sensitivity of the sensor. in particular:

The purpose of the present invention is to provide an application of a double-layer electrospun film sensor in the detection of nitroaromatic substances.

The present invention adopts the following technical solutions in order to achieve the above object:

Application of a double-layer electrospun film sensor in the detection of nitroaromatics.

Nitroaromatic substances are 2,4,6-trinitrotoluene (TNT), 2,4-dinitrotoluene (DNT), picric acid (PA), 2,4-dinitrophenol (DNP) or its derivatives.

The double-layer electrospun film sensor is composed of a double-layer film structure, the bottom layer is a gelatin electrospun film (GEL), which is placed on the surface of the glass sheet as a skeleton layer; the top layer uses polystyrene as a carrier, and fluorescent The sensing polymer P is blended to prepare an electrospun film (PS-P), which is the sensing layer.

Wherein, the fiber diameter in the gelatin electrospinning film (GEL) is 20 to 35 microns, and the electrospinning film (PS-P) is an electrospinning film of polystyrene doped fluorescent sensing polymer P , the fiber is in a beaded structure, the diameter of the beaded structure is 5-15 microns, and the diameter of the fiber is 180nm-220nm, preferably 200nm.

Compared with the separate PS-P electrospun film sensor, the introduction of the gelatin electrospun layer GEL as the backbone layer has many advantages: i) The gelatin molecule contains a large number of electron-rich groups of amino and hydroxyl groups, which can be combined with nitric acid through them. The hydrogen bond interaction between the base aromatics can effectively attract the nitroarenes molecules, so that the nitroarenes molecules can be enriched around the sensing material and the sensitivity of the sensor can be improved. ii) The gelatin electrospun membrane is porous, which allows nitroaromatic molecules to enter from the top and bottom of the P-PS film layer at the same time, which improves the permeability of the P-PS sensing membrane; while ordinary P-PS The monolayer membrane sensor only allows nitroaromatic molecules to penetrate from above.

The double-layer electrospun film sensor of the present invention is represented by PS-P/GEL. The fluorescent sensing polymer P is a fluorescent conjugated polymer, and the fluorescent conjugated polymer is preferably a copolymer based on polyfluorene acetylene polymers, but its protection scope is not limited to polyfluorene acetylene polymers. Copolymers of things. It is further preferably the above-mentioned fluorescent sensing polymer P, whose structural formula is shown in Formula 1. After experimental verification and analysis, the performance of the double-layer electrospun thin film sensor prepared by using the above-mentioned fluorescent sensing polymer P is even better.

The fluorescent sensing polymer P has a structural formula such as formula 1:

Among them, x: (0.1-2), y: (0.1-2), z: (0.1-2).

The preparation method of the fluorescent sensing polymer P comprises the following steps: using 2,5-dibromothiophene, polyphenylene vinylene polymer and 2,7-dibromo-9,9-diphenylfluorene as raw materials , carry out polymerization to prepare the polymer with structural formula such as formula 1.

Concrete preparation method is as follows:

2,5-dibromothiophene, polyphenylene vinylene polymer and 2,7-dibromo-9,9-diphenylfluorene were dissolved in anhydrous diisopropylamine (DIPA) and anhydrous toluene under the protection of argon , adding PdCl ₂ (PPh ₃ ) ₂ , PPh ₃ and CuI, reacting at 90-110° C. for 18-36 hours, and then purifying to obtain the fluorescent sensing polymer P.

The structural formula of polyphenylene vinylene polymer is as formula 2:

Wherein, the molar ratio of the polyphenylene vinylene polymer, 2,5-dibromothiophene and 2,7-dibromo-9,9-diphenylfluorene is 1:(1～4):(1～ 4), the preferred molar ratio is 1:1:1. After experimental verification and analysis, the yield of fluorescent sensing polymer P obtained under this condition is relatively high.

The anhydrous diisopropylamine (DIPA) and anhydrous toluene are used as solvents to dissolve the raw materials so as to facilitate the smooth reaction of the reactants, and the consumption is determined according to the consumption of the raw materials. Preferably, the addition ratio of 2,5-dibromothiophene, anhydrous diisopropylamine (DIPA) and anhydrous toluene is 1g: (5-15)ml: (100-200)ml, and a more preferred ratio is 1g: 10ml: 150ml. After experimental verification and analysis, this condition is more conducive to the reaction.

The PdCl ₂ (PPh ₃ ) ₂ , PPh ₃ and CuI are used as catalysts to carry out the catalytic reaction, and the amount thereof is determined according to the amount of raw materials. Preferably, the mass ratio of 2,5-dibromothiophene, PdCl ₂ (PPh ₃ ) ₂ , PPh ₃ and CuI is 1:0.1-0.2:1-1.5:0.1-0.3. After experimental verification and analysis, this condition is more favorable for the catalyst to carry out the catalytic reaction.

Preferably, the time for feeding argon is 30 minutes, and the reaction is refluxed at 100°C for 24 hours. After experimental verification and analysis, this condition is an optimized experimental parameter. The yield of the fluorescent sensing polymer P obtained under this condition is higher.

The introduction of 9,9-diphenylfluorene units into polyphenylene vinylene polymers can weaken the π-π stacking between the skeletons and improve the permeability of the polymer due to its rigid steric hindrance. At the same time, the introduction of thiophene units makes the polymer electron-rich, which can promote the electron transfer between the polymer and nitroarenes, and promote the occurrence of fluorescence quenching. The synthesis equation is as follows:

A method for preparing an electrospun film P-PS using the fluorescent sensing polymer P, dissolving the fluorescent sensing polymer P and polystyrene (PS) in a mixed solution of DMF and THF, stirring , The obtained solution is subjected to electrospinning and dried to obtain an electrospun nanofiber membrane (electrospun film P-PS).

Wherein, the mass ratio of the fluorescent sensing polymer P to polystyrene (PS) is 1:1000-1500, preferably 1:1000. Stirring is preferably for 12 to 36 hours, more preferably for 15 hours. The effect of the electrospun nanofiber membrane obtained under the conditions is better.

The conditions of the electrospinning are: the diameter of the injection needle is 0.5-2 mm, the receiving distance is 20-30 cm, the voltage is 15-25 kV, and the flow rate of the solution is controlled by a syringe pump at a constant rate of 1 mL H ^-1 . The preferred receiving distance is 25cm and the voltage is 20kV. The above conditions make the electrospinning effect better, and the electrospun nanofiber membrane with ideal effect is obtained, and the thickness of the obtained electrospun P-PS film is 18-22 microns (preferably 20 microns).

The ratio of the mixed solution of DMF and THF to polystyrene (PS) is 1ml:(0.05-0.2)g, preferably 1ml:0.1g, wherein the volume ratio of DMF:THF is 3:1.

The drying condition is: 25-30° C. for 8-12 hours, preferably 10 hours, so as to remove the residual organic solvent.

A preparation method for gelatin electrospun film (GEL), comprising the following steps:

The gelatin was dissolved in a mixed solution of 2,2,2-trifluoroethanol and THF, stirred, and the obtained solution was subjected to electrospinning and dried to obtain a gelatin electrospun film (GEL).

Among them, preferably stirring for 18 to 36 hours, more preferably 24 hours. The effect of the gelatin film that described condition obtains is better.

The conditions of the electrospinning are: the diameter of the injection needle is 0.5-2 mm, the receiving distance is 20-30 cm, the voltage is 15-25 kV, and the flow rate of the solution is controlled at a constant rate of 1 mL H ^-1 by a syringe pump. The preferred receiving distance is 25cm and the voltage is 20kV. The above conditions make the effect of electrospinning better, and a gelatin film with ideal effect can be obtained, and the thickness of the obtained gelatin film is 18-22 microns (preferably 20 microns).

The volume ratio of the mixed solution of 2,2,2-trifluoroethanol and THF is 3:1.

The drying condition is: drying at 25-30°C for 10 hours to remove residual organic solvent.

Electrospinning in the present invention uses an electrospinning instrument. Electrospinning equipment is mainly composed of the following parts: receiving device, liquid storage device, high voltage DC power supply and injection device. The power supply generally has a maximum output voltage of 30-100kV DC high-voltage power supply to provide the electric field. The solution storage device is generally used to store the molten electrospinning solution. The diameter of the injection needle is generally 0.5-2mm, and the needle is connected to the high-voltage power supply. Discharge methods can generally be divided into the following two types: vertical and horizontal. The receiving device is usually a metal roller or a metal plate.

The test method of the fluorescence quenching rate of the sensor:

First measure the fluorescence intensity F0 of the sensing material when nitroaromatics do not exist, then measure the fluorescence intensity F of the sensing material when nitroaromatics exist, make a working curve of fluorescence intensity and time, and draw a double-layer electrostatic Comparison chart of spun film sensor for different nitroaromatics.

The specific operation method is: taking DNT as an example, the quenching efficiency of the sensor in saturated nitroaromatics vapor is measured according to the following method: add 100 mg of DNT to a cuvette and cover it with a piece of filter paper to Prevent direct contact between DNT and sensor. The cuvette was then left at room temperature for 3 hours to allow it to reach gas equilibrium. Then, the cuvette was placed in the spectrofluorometer, and the sensor of the invention was immediately inserted into the cuvette, with the sensor facing the laser source. Fluorescence spectra were measured every 30 seconds.

The beneficial effects of the present invention are:

(1) In the present invention, a novel double-layer electrospun film sensor was synthesized by electrospinning technology for the detection of nitroaromatic compounds. The upper P-PS layer has a fluorescence quenching effect on nitroaromatic compounds and is the sensing material layer; the bottom GEL layer is a gelatin skeleton layer, which improves the sensing performance of the double-layer sensor through the following multiple functions: ⅰ ) Gelatin has a large number of amino and hydroxyl groups, which can generate hydrogen bond interactions with gelatin, so that nitroaromatics can be enriched near the sensor, which can reduce the detection limit and improve the response sensitivity. ii) The GEL layer acts as a porous framework under the P-PS layer, which can allow the simultaneous diffusion of nitroaromatic molecules from above and below the P-PS layer, thereby greatly improving the permeability of the P-PS layer. Therefore, the P-PS/GLE of the double-layer sensor exhibited better sensing performance for nitroaromatics compared to the single-layer P-PS film double-layer sensor.

(2) The fluorescent conjugated polymer in the present invention is preferably a copolymer based on a polyfluorene acetylene polymer, but its scope of protection is not limited to a copolymer based on a polyfluorene acetylene polymer. In the polymer P of the present invention, the thiophene monomer is an electron-rich unit, and its introduction can effectively promote the electron transfer between the polymer and the nitroaromatic molecule, thereby improving the fluorescence quenching efficiency of the polymer to the nitroaromatic; 9 , 9-diphenylfluorene has a rigid three-dimensional space structure, which can effectively prevent the accumulation of polymer chains and self-quenching of polymer fluorescence. In addition, it can also increase the gas permeability of the membrane and increase the concentration of nitroaromatic molecules in the membrane. Diffusion rate, improve response sensitivity.

Description of drawings

Figure 1 is a schematic diagram of a double-layer electrospun thin film sensor material.

Figure 2 is a schematic diagram of the electrospinning process.

Fig. 3 is the fluorescence spectrum of THF solution of polymer P, electrospun film P-PS, double-layer electrospun film P-GLE/PS (excitation wavelength is 390nm).

Figure 4a is a scanning electron microscope spectrum of gelatin.

Figure 4b is the scanning electron microscope spectrum of the electrospun film P-PS.

Figure 4c is the SEM spectrum of the double-layer electrospun membrane P-PS/GLE.

Figure 4d is a diagram of the diameter distribution of the electrospun film P-PS.

Figure 5a is the change of fluorescence spectrum of electrospun film P-PS in DNT saturated vapor with time.

Figure 5b is the change of the fluorescence spectrum of the double-layer electrospun membrane P-PS/GLE in DNT saturated vapor with time.

Figure 5c shows the quenching rate of the electrospun film P-PS and the double-layer electrospun film P-PS/GLE as a function of time.

Figure 5d is the change curve of I ₀ /I-1 of the electrospun film P-PS and the double-layer electrospun film P-PS/GEL within forty minutes, where I ₀ is the P-PS/GEL without DNT Fluorescence intensity in presence, I is the fluorescence intensity of P-PS/GEL in saturated DNT vapor at a certain moment.

Fig. 6: The time-dependent curves of the quenching rate of DNP, DNT, PA and TNT by P-PS/GLE in double-layer electrospun films.

Figure 7: Reversibility of the fluorescence quenching process of P-PS/GLE in double-layer electrospun films.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

Reagents and instruments:

Example 1

A synthetic method for fluorescent sensing polymer P, comprising the following steps:

2,5-dibromothiophene (200mg, 0.9mmol), polyphenylene vinylene polymer (376mg, 0.9mmol) and 2,7-dibromo-9,9-diphenylfluorene (426.6mg, 0.9mol) Dissolve in anhydrous diisopropylamine (DIPA, 2mL) and anhydrous toluene (30mL), place in a 50ml three-necked flask. Pass through argon for 30 minutes, add PdCl ₂ (PPh ₃ ) ₂ (36mg, 2.6×10 ^{- 2} mmol), PPh ₃ (270 mg, 0.90 mmol) and CuI (40.5 mg, 0.3 mmol). 100 ° C reflux reaction for 24h. Then, according to the purification, the fluorescent sensor polymer P is obtained, and the structural formula is shown in Formula 1 of the present invention.

Fluorescence sensor polymer P: dark yellow solid (400mg, 69%). ¹ H NMR: (CDCl ₃ , 400MHz), δ (ppm): 0.0-2.0 (m, 20H), 7.0-7.2 (m, 3H), 7.4(d,1H,J=7.2HZ),6.0(d,3H,J=5.5HZ),7.6-7.9(m,2H).FT-IR(KBr):3060,2967,2921,2850,2198, ⁽ _{_ _ _ _ _} THF): _Mn = 4426, _Mw = 7852, PDI = 1.7.

Embodiment 2 A synthetic method of fluorescent sensing polymer P, comprising the following steps:

2,5-dibromothiophene (210mg), polyphenylene vinylene polymer (378mg) and 2,7-dibromo-9,9-diphenylfluorene (438mg) were dissolved in anhydrous diisopropylamine (DIPA, 2.5mL) and anhydrous toluene (22mL), placed in a 50ml three-neck flask. Argon protection was passed through for 40 minutes, and PdCl ₂ (PPh ₃ ) ₂ (21mg), PPh ₃ (252mg) and CuI (63mg) were added. 90 ° C reflux reaction for 36h. Then, according to the purification, the fluorescent sensor polymer P is obtained, and the structural formula is shown in Formula 1 of the present invention.

Implementation 3

Preparation of electrospun P-PS films: Fluorescent sensing polymers P (0.4 mg) and PS (0.4 g) were dissolved in 4 mL of mixed solution (DMF:THF=3:1) and stirred for 24 hours. Transfer the resulting solution to the syringe of the electrospinning device. Electrospinning was performed with a spinning voltage of 20 kV and a receiving distance of 25 cm. The flow rate of the solution was controlled at a constant rate by a syringe pump with 1 mL ^of H. Finally, an electrospun nanofibrous membrane was formed on a glass slide (1.0 cm×1.7 cm). The electrospun nanofibrous membrane (20 μm) was vacuum dried at 30° C. for 10 hours to remove residual organic solvent.

Example 4

Preparation of electrospun P-PS films: Fluorescent sensing polymers P (0.4 mg) and PS (0.5 g) were dissolved in 5 mL of mixed solution (DMF:THF=3:1) and stirred for 36 hours. Transfer the resulting solution to the syringe of the electrospinning device. Electrospinning was performed with a spinning voltage of 20 kV and a receiving distance of 25 cm. The flow rate of the solution was controlled at a constant rate by a syringe pump with 1 mL ^of H. Finally, an electrospun nanofibrous membrane was formed on a glass slide (1.0 cm×1.7 cm). The electrospun nanofibrous membrane (20 μm) was vacuum dried at 30° C. for 12 hours to remove residual organic solvent.

Example 5

Fabrication of bilayer electrospun film sensors: The bilayer nanofibrous membrane is fabricated by two consecutive spinning methods.

First, a layer of gelatin film was prepared on a glass slide, and gelatin (0.4 mg) was dissolved in 4 mL of a mixed solution (2,2,2-trifluoroethanol:THF=3:1) and stirred for 24 hours. Transfer the resulting solution to the syringe of the electrospinning device. Electrospinning was performed with a spinning voltage of 20 kV and a receiving distance of 25 cm. The flow rate of the solution was controlled by a syringe pump at a constant rate of 1 mL ^H. Finally, an electrospun nanofibrous membrane was formed on a glass slide (1.0 cm×1.7 cm). The reception time was 30 seconds and at the end, the thickness of the gelatin film was 20 microns.

Then, a glass slide covered with a gelatin film was used as a carrier to receive a film of P-PS, which was prepared by dissolving polymer P (0.4 mg) and PS (0.4 g) in 4 ml The solution was mixed (DMF:THF=3:1) and stirred for 24 hours. Transfer the resulting solution into the syringe of the electrospinning device. Electrospinning was performed with a spinning voltage of 20 kV and a receiving distance of 25 cm. The flow rate of the solution was controlled at a constant rate by a syringe pump with 1 mL ^of H. Finally, an electrospun nanofiber membrane was formed on a glass slide (1.0 cm×1.7 cm) covered with a gelatin film, and the receiving time was controlled at 1 minute.

After the spinning process was completed, the bilayer membrane was vacuum-dried at 25 °C for 10 h to remove residual organic solvents.

Adopt embodiment 1,3 and 5 to carry out effect experiment:

Experimental example 1 Fluorescence spectra of polymer P in THF, film P-PS/GLE and P-PS film

To better understand the effect of electrospun films on polymer P. Fluorescence spectra of polymer P in THF (C _P =1×10 ⁻³ g/L), P-PS/GLE film and P-PS film are given. As shown in Figure 3, the wavelengths of the fluorescence emission peaks of P-PS/GLE and P-PS of the film are 444 nm and 447 nm, both of which are not much different from the THF solution (442 nm) of this polymer P . These data show that polymer P has good dispersion in the PS matrix, and there is no strong π-π stacking between polymer P, so it can be explained that the large porosity of the electrospun fiber film is beneficial to prevent π-π stacking. accumulation.

Experimental example 2 Morphology of double-layer electrospun membrane P-PS/GLE

In order to display the morphology of the double-layer structure sensor more vividly, the present invention provides the morphology of gelatin and P-PS membranes respectively. As shown in Figure 4a and Figure 4b. The diameters of gelatin fibers were mainly concentrated in the range of 20–35 μm (Fig. 4a). On top of the gelatin film is a layer of P-PS electrospun nanofiber film. In this double-layer structure (Figure 4c), the upper layer is an electrospun film of polystyrene-doped polymer P, and the fibers are in a beaded structure (the diameter of the beads is between 5 μm and 15 μm). The diameter distribution of the fibers is Around 200 nanometers. As can be seen from the diameter size scatter diagram in Fig. 4d, the bottom layer is a layer of GLE, which is used as a sensor structural scaffold due to its thicker diameter and stronger gelatin fibers. In addition, the GLE layer provides a large number of porous structures that allow the diffusion of nitroaromatic molecules up and down the p-ps electrospun film. Apparently, these bilayer films of P-PS/GLE exhibited greater advantages than conventional electrospun films because conventional nanofibrous films were in direct contact with the glass substrate and nitroaromatics only diffused from above to below. For the same thickness of the sensing layer, this double-layer structure can speed up the transmission rate of DNT vapor, so to a certain extent, it also solves the problem that the thickness of the sensor has a great influence on the quenching rate.

Experimental Example 3 Sensing performance of double-layer film P-PS/GLE

In the study of the DNT sensing performance of the P-PS/GLE double-layer film sensor, the sensor was tested in the saturated vapor pressure of DNT. As shown in Figures 5a–5b, the fluorescence intensity of the sensor decreased with the prolonged exposure time in DNT vapor (Figure 5a and Figure 5b). As shown in Figure 5c, the quenching rates of both sensors increased significantly within 5 min, and then the rate of increase increased slowly until an equilibrium was reached after 40 min. Compared with the conventional single-layer P-PS sensor, the bilayer P-PS/GLE exhibited higher quenching efficiency within 40 min. In Fig. 5d, the I0/I-1 curve of the bilayer sensor in DNT gas as a function of time. It can be seen from the figure that the value of the sensor P-PS/GLE is greater than that of the traditional sensor P-PS. From the above results, it can be seen that the sensor P-PS/GLE has a stronger sensing performance for DNT, which is mainly due to the following reasons (i) because the gelatin layer contains a large number of amino groups and hydroxyl groups, it can effectively make DNT molecules pass through hydrogen The bond interaction is enriched on the sensor surface, increasing the contact opportunities between nitroaromatics and the sensor. (ii) Gelatin as the porous framework at the bottom of the bilayer membrane can further enhance the permeability of the sensor. Therefore, the sensor P-PS/GLE exhibited a higher quenching rate.

Experimental Example 4 Selectivity of P-PS/GLE Membrane to Nitroaromatics

The quenching mechanism of conjugated polymer sensors is generally considered to be determined by the electron donor-acceptor mechanism, the fluorophore acts as the electron donor, and the nitroarene acts as the electron acceptor, and electrons are transferred from the fluorophore to the nitroarene. In principle, this mechanism allows the sensor to respond to several types of electron-deficient compounds. However, the fluorescence quenching is determined by many factors, such as vapor pressure, reduction potential, and the binding constant (KB) of the analyte can also affect the sensing performance.

The P-PS/GLE electrospun film was tested for its sensing performance on four different nitro-explosives, including DNP, DNT, PA, and TNT. The procedure is as follows: the bilayer sensor is placed in a saturated nitroaromatic vapor at room temperature. The quenching rate was measured after 40 minutes. The results are shown in Fig. 6, the electrospun films have distinctly different quenching rates for the four nitroaromatic explosives. The order of quenching efficiency is DNT>DNP>TNT>PA. Within 30 minutes, the quenching rate of the sensor to DNT reaches 70%, and the quenching rate of the sensor to DNT is far greater than that of other nitroaromatics. Although the redox potential of DNT (-1.0V) is smaller than that of TNT (-0.7V), its saturated vapor pressure is 18 times that of TNT, which may be one of the reasons for the higher quenching rate of DNT . DNT and DNP have similar vapor pressures, but DNT still shows a higher quenching rate compared to DNP. This may be due to the presence of hydroxyl groups in DNP, which makes DNP have a lower reduction potential. PA has the lowest quenching efficiency, which can be attributed to the dual effects of hydroxyl groups: on the one hand, the electron-driven effect makes the redox potential of PA smaller, and on the other hand, the intermolecular hydrogen bond interaction reduces the saturation vapor pressure of PA.

Experimental example 5 Reversibility of P-PS/GLE electrostatic membrane for detection of nitroaromatics

Reversibility is an important parameter in the practical application of sensors. In the reversibility test experiment, DNT was selected as the analyte, and the reversibility of the electrospun film was checked by detecting the DNT molecule, and the results were as shown in FIG. 7 . Put the P-PS/GLE electrospun film in DNT vapor. When the quenching is complete, take out the sensor and soak it in methanol solution for 1 hour to wash off the absorbed DNT vapor, and then dry it in a vacuum oven at 30 °C for 2 hours. Through the above process, the fluorescence intensity of the membrane can be almost recovered. After repeated five cycles, the signal intensity of the electrospun film did not decrease significantly, which indicated that the sensor had good reversibility. This conclusion has important implications for the fabrication of sensors.

In the above research process, a novel double-layer nanofiber membrane sensor was synthesized by electrospinning technology and used to test nitroaromatic compounds, the upper P-PS layer was used as the main sensor material to detect nitroaromatics and the bottom gelatin skeleton There are the following multiple functions to improve the sensing performance of the double-layer sensor: i) gelatin has a large number of amino and hydroxyl groups, and the nitroaromatics and gelatin are enriched by hydrogen bond interaction forces, The nitroaromatic compounds are gathered in the P-PS sensing layer to increase the quenching rate. ii), which acts as a porous framework under the P-PS layer, the gelatin layer can allow the simultaneous diffusion of nitroaromatic molecules above and below the P-PS layer, greatly improving the permeability of the P-PS layer. Therefore, the P-PS/GLE of the double-layer sensor exhibited better sensing performance for nitroaromatics compared to the single-layer P-PS film double-layer sensor.

Experimental example 6

Spin-coated film: For comparison, the same mixture was spin-coated onto a glass slide to form a film. 0.4 mg of polymer P and 0.4 g of polystyrene were dissolved in 4 ml of a mixed solution (DMF:THF=3:1), followed by stirring for 24 hours. Spin-coated films on glass slides (10×20×1 mm) were prepared using a spin coater KW-4A instrument with a spin rate of 2000 rpm. The film was dried under vacuum. The film thickness was determined to be 50 nm using environmental scanning electron microscopy (SEM).

It has been verified by experiments that the effect of the spin-coated membrane is not as good as that of the electrospun membrane for detecting nitroaromatics.

Although the specific implementation of the present invention has been described above in conjunction with the accompanying drawings, it does not limit the protection scope of the present invention. Those skilled in the art should understand that on the basis of the technical solution of the present invention, those skilled in the art do not need to pay creative work Various modifications or variations that can be made are still within the protection scope of the present invention.

Claims (5)

1. a kind of application of bilayer electrostatic spinning film sensor in nitro-aromatic class analyte detection, it is characterized in that：The double-deck electrostatic Spinning thin film sensor is made of double membrane structure, and bottom is gelatin electrostatic spinning film, this layer is placed on as skeleton Glass sheet surface；For top layer using polystyrene as carrier, the progress of fluorescence sense polymer P is blended to be prepared into electrostatic spinning film, The layer is sensing layer；

The preparation method of the gelatin electrostatic spinning film is：Mixing by Gelatin in 2,2,2 tfifluoroethyl alcohol and THF is molten In liquid, obtained solution is carried out electrostatic spinning, is used for receiving the film of electrostatic spinning using sheet glass as carrier, obtains by stirring The gelatin film of load on the glass sheet；

The fluorescence sense polymer P is fluorescent conjugated polymer, and structural formula is：

Wherein x:(0.1~2), y:(0.1~2), z:(0.1~2).

2. application as described in claim 1, it is characterized in that：Gelatin fiber in the gelatin electrostatic spinning film it is a diameter of 20~35 microns, the electrostatic spinning film be polystyrene doping fluorescent sensing polymer P electrostatic spinning film, fiber at Beading structure, a diameter of 5~15 microns of the pearlitic texture, a diameter of 180nm~220nm of fiber.

3. application as described in claim 1, characterized in that the preparation method of the double-deck electrostatic spinning film sensor, including such as Lower step：

(1) gelatin electrostatic spinning film is prepared：By Gelatin in the mixed solution of 2,2,2- trifluoroethanols and THF, stirring, Obtained solution is subjected to electrostatic spinning, is used for receiving the film of electrostatic spinning using sheet glass as carrier, obtains and be supported on glass The gelatin film of on piece；

(2) fluorescence sense polymer P and polystyrene are dissolved in DMF and THF mixed solutions, are stirred, the solution that will be obtained Electrostatic spinning is carried out, is used for receiving the film of electrostatic spinning with the sheet glass of the covering gelatin film in step (1), after the completion of spinning, It is dried to get the double-deck electrostatic spinning film sensor.

4. application as claimed in claim 3, characterized in that in step (1) and (2), the condition of the electrostatic spinning is：Receive Distance is 20~30cm, and 15~25kV of voltage, the flow velocity of solution is by syringe pump with 1mL H^-1Constant rate of speed controlled.

5. application as described in claim 1, characterized in that the preparation method of the fluorescence sense polymer P, including walk as follows Suddenly：

Type of Collective object and 2 is supportted with 2,5- dibromo thiophenes, polyphenylacetylene, bis- bromo- 9,9- diphenylfluorenes of 7- are raw material, carry out polymerization system Obtain the polymer of structural formula such as formula 1；Wherein, the structural formula such as formula 2 of the polyphenylacetylene support Type of Collective object：