Acridine fluorescent nanofilm, preparation method thereof and application of fluorescent nanofilm in sensing and detecting ethylenediamine

Abstract

This invention discloses an acridine-based fluorescent nanofilm, its preparation method, and its application in the fluorescence sensing detection of ethylenediamine, belonging to the field of gas phase sensing materials. The fluorescent nanofilm is prepared by the self-assembly reaction of an aldehyde-modified acridine derivative and calix[4]pyrroletetrahydrazine at the gas-liquid interface via acylhydrazone bonds. By controlling the precursor concentration and reaction time, this invention can achieve precise control of the nanofilm thickness. The prepared nanofilm has excellent self-supporting properties and a uniform porous network structure, effectively suppressing the aggregation-induced quenching effect. When this nanofilm is used as a fluorescent sensing material for the detection of ethylenediamine, it exhibits a ratiometric fluorescence response, with advantages such as fast response speed, rapid recovery, low detection limit, high selectivity, and good stability, which can meet the needs of rapid on-site visualization detection. The preparation method of this invention is simple, the reaction conditions are mild, and no template is required, which has important application prospects in the field of on-site visualization detection of ethylenediamine.

Description

Technical Field

[0001] This invention belongs to the field of gas phase sensing materials, specifically relating to an acridine-based fluorescent nanofilm prepared by template-free gas-liquid interface self-assembly, and the application of this nanofilm in the fluorescence sensing detection of ethylenediamine. Background Technology

[0002] Ethylenediamine (EDA) is an important industrial raw material in pharmaceuticals, pesticides, dyes, and coatings, but it is highly corrosive and systemically toxic, capable of irritating the skin and respiratory tract, and even causing irreversible damage. According to the World Health Organization, exposure to 10 ppm of EDA can induce vomiting, dizziness, and even acute kidney injury. Therefore, developing real-time, rapid, highly sensitive EDA technologies suitable for on-site detection is of great significance.

[0003] Currently, EDA detection methods mainly include high-performance liquid chromatography (HPLC), electrochemical methods, colorimetry, and fluorescence methods. Among these, fluorescence sensing has attracted widespread attention due to its high sensitivity, fast response, and rich signal modes. However, traditional solution-based fluorescent probes suffer from difficulties in integration and waste disposal, limiting their application in practical scenarios. In contrast, solid-state fluorescent sensing materials can be loaded onto various substrates, facilitating device integration and promoting the development of portable on-site detection technologies.

[0004] Thin-film fluorescent sensors, with their advantages of high sensitivity, fast response, ease of integration, and low power consumption, have shown great potential in fields such as environmental monitoring and industrial safety. Interfacial confined polymerization is one of the effective methods for constructing functional nanofilms. The prepared films possess excellent uniformity and transmittance, effectively overcoming common problems in film preparation such as the coffee ring effect and coating inhomogeneity. Through rational molecular design, specific recognition sites can be precisely introduced into the films, achieving highly selective recognition of target analytes. Furthermore, most thin-film fluorescent sensors exhibit good reversibility and regeneration capabilities, requiring only simple treatments such as air purging and acid / alkali adjustment to return to their initial state. This not only enables the reuse of the devices but also effectively reduces detection costs.

[0005] Chinese patent CN111499904B discloses a self-supporting cup[4]pyrrole nanofilm and its template-free preparation method. The film is prepared by Schiff base condensation reaction at the gas-liquid interface using cup[4]pyrrole tetrahydrazide and aromatic aldehyde compounds as building blocks. It has good mechanical properties and water flux and can be used in water purification and drug concentration. However, this film is mainly used for liquid phase separation and does not have fluorescence sensing function, making it difficult to directly apply to gas phase fluorescence sensing detection.

[0006] Therefore, developing a nanofilm material that combines excellent fluorescence properties and gas-phase sensing performance, and achieving highly sensitive and visual detection of ethylenediamine, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0007] The purpose of this invention is to address the lack of nanofilm materials with both excellent fluorescence properties and gas-phase sensing performance in the prior art, as well as the technical problems that existing ethylenediamine detection methods are difficult to implement in-situ rapid and visual detection. This invention provides an acridine-based fluorescent nanofilm, its preparation method, and its application in fluorescence sensing detection of ethylenediamine.

[0008] To achieve the above objectives, the acridine-based fluorescent nanofilm provided by the present invention is a nanofilm material with fluorescent properties formed by the self-assembly reaction of aldehyde-modified acridine derivatives and calix[4]pyrroletetrahydrazine at the gas-liquid interface through acylhydrazone bonds.

[0009] Preferably, the acridine-based fluorescent nanofilm has a porous network structure and a thickness of 30–120 nm.

[0010] The preparation method of the above-mentioned acridine-based fluorescent nanofilm includes the following steps:

[0011] Step 1: Preparation of aldehyde-modified acridine derivatives

[0012] Under an inert atmosphere, 9,9-diphenyl-9,10-dihydroacridine and N-bromosuccinimide (NBS) were reacted in anhydrous tetrahydrofuran (THF) with stirring for 5–7 hours. The reaction mixture was then purified to obtain 2,7-dibromo-9,9-diphenyl-9,10-dihydroacridine (ACR-2Br). Subsequently, 2,7-dibromo-9,9-diphenyl-9,10-dihydroacridine was reacted with 4-formylphenylboronic acid in toluene under reflux for 10–12 hours in the presence of tetrabutylammonium bromide (TBAB), aqueous potassium carbonate solution, and tetrakis(triphenylphosphine)palladium (Pd(PPh3)4). The reaction mixture was then purified to obtain an aldehyde-modified acridine derivative (ACR-2CHO). The reaction equation is as follows:

[0013]

[0014] Step 2: Preparation of precursor solution

[0015] The aldehyde-modified acridine derivative obtained in step 1 was completely dissolved in dimethyl sulfoxide (DMSO) at a molar ratio of 2:1 with calix[4]pyrroletetrahydrazine to obtain a precursor solution.

[0016] Step 3: Dynamic assembly of nanofilms at the gas-liquid interface

[0017] The precursor solution from step 2 was dropped onto a clean glass substrate to spread it evenly. An acylhydrazone condensation reaction was carried out under environmental conditions of 25–30°C and 60%–65% relative humidity to form a nanofilm at the gas-liquid interface. The acridine-based fluorescent nanofilm was obtained after washing.

[0018] Preferably, in step 1 above, the molar ratio of 9,9-diphenyl-9,10-dihydroacrylidine to N-bromosuccinimide is 1:2 to 4.

[0019] Preferably, in step 1 above, the molar ratio of 2,7-dibromo-9,9-diphenyl-9,10-dihydroacridine to 4-formylphenylboronic acid, tetrabutylammonium bromide, tetra(triphenylphosphine)palladium, and potassium carbonate is preferably 1:5~7:1~1.5:0.1~0.2:8~15.

[0020] Preferably, in step 2 above, the total concentration of the aldehyde-modified acridine derivative and calix[4]pyrroletetrahydrazine in the precursor solution is 5 to 25 mg / mL.

[0021] Preferably, in step 3 above, the acylhydrazone bond condensation reaction takes 4 to 5 hours.

[0022] The present invention also provides a fluorescence sensing unit comprising the above-mentioned acridine-based fluorescent nanofilm.

[0023] The present invention further provides the application of the above-mentioned acridine-based fluorescent nanofilm or fluorescent sensing unit in the fluorescence sensing detection of ethylenediamine.

[0024] The beneficial effects of this invention are as follows:

[0025] 1. This invention uses aldehyde-modified acridine derivatives (ACR-2CHO) and calix[4]pyrroletetrahydrazide (CPTH) as building blocks to prepare fluorescent nanofilms through dynamic confined polymerization at the air / DMSO interface. Among them, the multiple hydrazide groups of CPTH are easily enriched at the interface, react with ACR-2CHO to crosslink and form nanofilms, and its non-planar three-dimensional structure can enhance the porosity of the nanofilm at the molecular level and promote the contact response between the nanofilm and the analyte molecules.

[0026] 2. The nanofilm prepared in this invention possesses a unique three-dimensional network structure. This structure allows for effective spatial isolation of the fluorescent units within the film, significantly suppressing aggregation-induced quenching effects. When used as a sensing active layer, the prepared nanofilm exhibits a ratiometric response to ethylenediamine, accompanied by a clear change in fluorescence color from green to yellow-orange, which is beneficial for on-site visual identification.

[0027] 3. The nanofilm prepared in this invention is integrated into a sensing platform. This nanofilm sensor exhibits excellent response and recovery performance to ethylenediamine, with a response time as low as 3.0 seconds, a recovery time as low as 3.5 seconds, and a detection limit of 1.2 ppm, while also possessing good stability and repeatability. Its high specificity recognition capability stems from the porous adsorption structure of the nanofilm and the uniform distribution of active recognition sites. This sensor has been successfully applied to the real-time detection of ethylenediamine in practical scenarios such as hazardous chemical screening and leak detection.

[0028] 4. This invention successfully constructs a high-performance fluorescent sensing film by combining molecular structure design with an interface confined polymerization strategy. This not only provides an effective solution for the real-time on-site detection of ethylenediamine, but also provides experimental basis for the rational design of functionalized active layer materials, and offers useful reference for the development of an intelligent fluorescent sensing platform for rapid on-site detection. Attached Figure Description

[0029] Figure 1 These are photographs of the acridine-based fluorescent nanofilm prepared in Example 5; the upper image is a fluorescence photograph under 365 nm light, and the lower image is a demonstration photograph of the nanofilm being squeezed with a dropper.

[0030] Figure 2 These are electron microscope images of the acridine-based fluorescent nanofilm prepared in Example 5; wherein, (a) is a scanning electron microscope image of the nanofilm loaded on a copper grid; and (b) is a high-resolution transmission electron microscope image of the nanofilm loaded on a microgrid.

[0031] Figure 3 The following are the elemental distribution diagram and X-ray photoelectron spectrum of the acridine-based fluorescent nanofilm prepared in Example 5; wherein, (a) is the elemental distribution diagram of the nanofilm; (b) is a comparison diagram of the Fourier transform infrared spectra of the nanofilm, CPTH and ACR-2CHO; (c) is the C1s high-resolution XPS spectrum of the nanofilm; and (d) is the N1s high-resolution XPS spectrum of the nanofilm.

[0032] Figure 4 These are atomic force microscopy images (AFM images) of the acridine-based fluorescent nanofilms prepared in Examples 1-5. q R represents the root mean square roughness. a (representing average roughness); where a is the surface morphology and b is the cross-sectional morphology.

[0033] Figure 5 The response behavior of the acridine-based fluorescent nanofilm prepared in Example 5 to different concentrations of ethylenediamine gas (0-1500 ppm) is shown in (a) for fluorescence spectrum and (b) for CIE 1931 chromaticity coordinate change of nanofilm in response to ethylenediamine gas.

[0034] Figure 6The response curve (t) of the thin-film-based sensing unit to ethylenediamine based on the acridine-based fluorescent nanofilm prepared in Example 5 is shown. res t represents the response time. rec (Indicates recovery time).

[0035] Figure 7 The sensing response behavior of the thin-film based sensing unit of the acridine-based fluorescent nanofilm prepared in Example 5 to ethylenediamine vapor is shown; where (a) is the selectivity; (b) is the concentration effect, and the inset shows the relationship curve between the fluorescence response intensity and the ethylenediamine concentration; (c) is the cycle stability test. Detailed Implementation

[0036] To enable those skilled in the art to better understand the present invention, the technical solution of the present invention will be clearly and completely described below with reference to embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0037] Example 1

[0038] Step 1: Preparation of aldehyde-modified acridine derivatives

[0039] Under a nitrogen atmosphere, 1.0 g (3.0 mmol) of 9,9-diphenyl-9,10-dihydroacridine was placed in a dry three-necked flask, and 10 mL of anhydrous THF was added. The mixture was stirred until completely dissolved, and the reaction system was cooled to 0 °C. Subsequently, 1.60 g (9.0 mmol) of NBS was dissolved in 15 mL of anhydrous THF and slowly added dropwise to the three-necked flask over 30 minutes using a constant-pressure dropping funnel. After the addition was complete, the ice bath was removed, and the reaction mixture was allowed to rise naturally to room temperature. The reaction was stirred for another 6 hours. After the reaction was complete, excess NBS was quenched with a saturated sodium thiosulfate aqueous solution, and the mixture was stirred for 30 minutes before THF was removed by vacuum distillation. The residue was extracted three times with dichloromethane, and the organic phases were combined, dried over anhydrous sodium sulfate, filtered, and concentrated. The crude product was purified by silica gel column chromatography using n-hexane / dichloromethane = 3 / 1 (v / v) as the eluent to give 950 mg of a white solid, ACR-2Br. Its structural characterization data are as follows: 1H NMR (600 MHz, DMSO-d6, ppm): δ 9.50 (s, 1H), 7.38 - 7.29 (m, 6H), 7.26 (t, J = 7.3 Hz, 2H), 6.94 (d, J = 8.5 Hz, 2H), 6.86 (d, J = 7.4 Hz, 4H), 6.72(d, J = 1.9 Hz, 2H); HRMS (m / z, APCI-Orbitrap, [M+H] + ), C 25 H 18 Br2N + Theoretical value: 491.9782, measured value: 491.9778.

[0040] 950 mg (1.94 mmol) of ACR-2Br and 1.75 g (11.64 mmol) of 4-formylphenylboronic acid were dissolved in 15 mL of toluene. 625.40 mg (1.94 mmol) of TBAB and 10 mL of 2 mol / L K₂CO₃ aqueous solution were added sequentially. The mixture was stirred at room temperature for 30 minutes under nitrogen protection. Then, 231.12 mg (0.2 mmol) of Pd(PPh₃)₄ was added, and the reaction mixture was heated to 100 °C and refluxed for 12 hours. After the reaction was complete, it was cooled to room temperature, and the reaction was quenched with saturated ammonium chloride aqueous solution. The mixture was extracted three times with ethyl acetate, and the combined organic phases were washed with saturated brine, dried over anhydrous sodium sulfate, filtered, and concentrated. The crude product was purified by silica gel column chromatography using dichloromethane / n-hexane = 2 / 1 (v / v) as the eluent to give 841 mg of the pale yellow solid target product ACR-2CHO. The characterization data of the obtained product are as follows: 1 H NMR (600 MHz, DMSO-d6, ppm): δ 9.97 (s, 2H), 9.71 (s, 1H), 7.89 (d, J = 8.2 Hz, 4H), 7.66 (dd, J = 8.3, 1.9 Hz, 2H), 7.59(d, J = 8.2 Hz, 4H), 7.34 (t, J = 7.7 Hz, 4H), 7.27 (t, J = 7.2 Hz, 2H), 7.12(d, J = 8.3 Hz, 2H), 7.06 (d, J = 1.8 Hz, 2H), 7.01 (d, J = 7.7 Hz, 4H); 13CNMR (151 MHz, acetone-d6, ppm): δ 192.21, 147.50, 147.05, 141.30, 135.78,132.06, 131.07, 130.92, 129.96, 128.78, 115.66, 57.88. IR (KBr plates, cm -1 ):3335 (-NH), 1693 (C=O), 1481 (CN); HRMS (m / z, APCI-Orbitrap, [M+H] + ), C 39 H 28 NO2 + Theoretical value: 542.2115, measured value: 542.2114.

[0041] Step 2: Preparation of precursor solution

[0042] 0.99 mg (1.84 × 10) -3 0.66 mg (0.92 × 10 mmol) ACR-2CHO and 0.92 × 10 mmol) ACR-2CHO -3 Add 300 μL of DMSO to CPTH (mmol), and repeatedly heat and shake to promote dissolution until the solid phase is completely dissolved to form a transparent and homogeneous solution. Allow the solution to cool to room temperature to obtain the precursor solution. The total concentration of ACR-2CHO and CPTH in the precursor solution is 5.5 mg / mL.

[0043] Step 3: Dynamic assembly of nanofilms at the gas-liquid interface

[0044] A 2 cm glass slide was sequentially washed with acetone and deionized water, dried with nitrogen, and then treated with plasma for 2 minutes. 100 μL of the precursor solution from step 2 was dropped onto the treated glass slide surface and allowed to spread evenly. The slide was then placed in a constant temperature and humidity chamber and incubated at 25°C and 65% RH for 4 hours to form a dense and transparent nanofilm at the air-DMSO interface. The nanofilm was carefully floated in deionized water and washed to remove randomly cross-linked nanoparticles and DMSO, yielding an acridine-based fluorescent nanofilm with the same area as the glass slide.

[0045] Example 2

[0046] Step 1: Preparation of aldehyde-modified acridine derivatives

[0047] This step is the same as step 1 in Example 1.

[0048] Step 2: Preparation of precursor solution

[0049] 1.49 mg (2.74 × 10) -3 mmol) ACR-2CHO and 0.98 mg (1.37×10 -3 Add 300 μL of DMSO to CPTH (mmol), and repeatedly heat and shake to promote dissolution until the solid phase is completely dissolved to form a transparent and homogeneous solution. Allow the solution to cool to room temperature to obtain the precursor solution. The total concentration of ACR-2CHO and CPTH in the precursor solution is 8.2 mg / mL.

[0050] Step 3: Dynamic assembly of nanofilms at the gas-liquid interface

[0051] This step is the same as step 3 in Example 1, and acridine-based fluorescent nanofilms are obtained.

[0052] Example 3

[0053] Step 1: Preparation of aldehyde-modified acridine derivatives

[0054] This step is the same as step 1 in Example 1.

[0055] Step 2: Preparation of precursor solution

[0056] 1.98 mg (3.66 × 10) -3 mmol) ACR-2CHO and 1.31 mg (1.83×10 -3 Add 300 μL of DMSO to CPTH (mmol), and repeatedly heat and shake to promote dissolution until the solid phase is completely dissolved to form a transparent and homogeneous solution. Allow the solution to cool to room temperature to obtain the precursor solution. The total concentration of ACR-2CHO and CPTH in the precursor solution is 11.0 mg / mL.

[0057] Step 3: Dynamic assembly of nanofilms at the gas-liquid interface

[0058] This step is the same as step 3 in Example 1, and acridine-based fluorescent nanofilms are obtained.

[0059] Example 4

[0060] Step 1: Preparation of aldehyde-modified acridine derivatives

[0061] This step is the same as step 1 in Example 1.

[0062] Step 2: Preparation of precursor solution

[0063] 2.97 mg (5.48 × 10) -3 mmol) ACR-2CHO and 1.96 mg (2.74 × 10 -3Add 300 μL of DMSO to CPTH (mmol), and repeatedly heat and shake to promote dissolution until the solid phase is completely dissolved to form a transparent and homogeneous solution. Allow the solution to cool to room temperature to obtain the precursor solution. The total concentration of ACR-2CHO and CPTH in the precursor solution is 16.4 mg / mL.

[0064] Step 3: Dynamic assembly of nanofilms at the gas-liquid interface

[0065] This step is the same as step 3 in Example 1, and acridine-based fluorescent nanofilms are obtained.

[0066] Example 5

[0067] Step 1: Preparation of aldehyde-modified acridine derivatives

[0068] This step is the same as step 1 in Example 1.

[0069] Step 2: Preparation of precursor solution

[0070] 3.96 mg (7.30 × 10) -3 mmol) ACR-2CHO and 2.62 mg (3.65 × 10 -3 Add 300 μL of DMSO to CPTH (mmol), and repeatedly heat and shake to promote dissolution until the solid phase is completely dissolved to form a transparent and homogeneous solution. Allow the solution to cool to room temperature to obtain the precursor solution. The total concentration of ACR-2CHO and CPTH in the precursor solution is 21.9 mg / mL.

[0071] Step 3: Dynamic assembly of nanofilms at the gas-liquid interface

[0072] This step is the same as step 3 in Example 1, and acridine-based fluorescent nanofilms are obtained.

[0073] Depend on Figure 1 As can be seen, the obtained acridine-based fluorescent nanofilm exhibits bright yellow-green fluorescence, with a smooth surface, intact structure, and uniform thickness distribution, demonstrating excellent flexibility and self-supporting properties. Even under repeated compression from sharp objects, it maintains high structural integrity and mechanical flexibility.

[0074] The acridine-based fluorescent nanofilm prepared in Example 5 was transferred to a clean substrate, and its surface morphology and elemental composition were characterized by field emission scanning electron microscopy. Figure 2 As shown in Figure a, the nanofilm can completely cover the copper grid, and the entire surface of the nanofilm is free of cracks and pores, exhibiting excellent structural integrity and mechanical strength. (High-resolution transmission electron microscopy) Figure 2 b reveals that the nanofilm possesses a dense and porous microstructure, which is beneficial for achieving good mass transfer performance in sensing applications. Elemental distribution Figure 3The image shows that C (red), N (blue), and O (yellow) elements are uniformly distributed on the surface of the nanofilm, confirming the uniformity of the chemical composition of the prepared nanofilm. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy were used to confirm the chemical structure of the nanofilm. Figure 3 As shown in b, 3358 cm -1 The characteristic vibrational peak of -NH2 disappears at approximately 1660 cm⁻¹, while the peak at approximately 1660 cm⁻¹ also disappears. -1 A new absorption peak appeared, attributed to the stretching vibration of the C=N bond, confirming the successful formation of acylhydrazone bonds in the nanofilm. The elemental composition and bonding types of the nanofilm were characterized, such as... Figure 3 As shown in c and 3d, the C1s spectrum can be fitted to three components with binding energies of 284.8 eV (CC / C=C), 285.7 eV (CN), and 288.7 eV (C=O). The peaks at 399.8 eV and 401 eV in the N 1s spectrum correspond to C=N and CN bonds, respectively, clearly confirming that the nanofilm system is formed by cross-linking of acylhydrazone structures.

[0075] The surface roughness and interface thickness of the acridine-based fluorescent nanofilms prepared in Examples 1-5 were measured using atomic force microscopy. Figure 4 The results showed that the prepared acridine-based fluorescent nanofilms were uniform in thickness and structurally intact. When the total concentration of ACR-2CHO and CPTH in the precursor solution was 5.5 mg / mL, the nanofilm thickness was approximately 30.6 nm, and the surface roughness was 2.36 nm. When the total concentration of ACR-2CHO and CPTH in the precursor solution increased to 21.9 mg / mL, the nanofilm thickness was approximately 105.8 nm, and the surface roughness decreased to 0.70 nm. This demonstrates that the thickness and surface uniformity of the nanofilm can be effectively controlled by adjusting the concentration of ACR-2CHO and CPTH in the precursor solution, and the prepared nanofilms maintain good structural continuity over a wide concentration range.

[0076] Example 6

[0077] Application of acridine-based fluorescent nanofilms prepared in Example 5 in gas-phase EDA sensing.

[0078] The fluorescence response behavior of the acridine-based fluorescent nanofilm prepared in Example 5 to EDA vapor was investigated using a steady-state fluorescence system. Figure 5As shown in Figure a, after exposure to EDA vapor, the original fluorescence emission of the nanofilm at 510 nm was significantly quenched, while a new characteristic emission peak appeared near 630 nm. With the gradual increase of EDA concentration, the emission intensity at both wavelengths exhibited a clear ratioistic change trend. Accompanying this spectral change, the fluorescence color of the nanofilm under 365 nm UV light illumination gradually changed from initial green to pink; this color change can be directly observed with the naked eye. Figure 5 b). Significant CIE color coordinate shift further confirms that the nanofilm possesses the ability to perform semi-quantitative detection of EDA through color changes.

[0079] The acridine-based fluorescent nanofilm, washed in step 3 of Example 5, was retrieved using a 10 mm diameter high-transmittance quartz glass disc, ensuring uniform adhesion of the film to the disc surface. The disc was then placed in a clean, dust-proof sample container and allowed to air dry at room temperature for 24 hours, yielding the thin-film-based sensing unit. The dried sensing unit was then fixed to a gas-sensitive sensing platform (fluorescence detection mode). Parameters were set based on the optical properties of the thin-film material: excitation wavelength 400 nm, emission wavelength (peak intensity at 510 nm). The analyte EDA liquid was injected into a pre-vacuumed gas bag (1 L volume), allowing it to evaporate naturally to saturation vapor (diluted with dry air to obtain the desired ppm concentration). To ensure stable signal acquisition and enable multiple real-time detections, an alternating flow of analyte and recovery gas (air) was used. Figure 6 The real-time response curves show that the fluorescence signal of the thin-film substrate sensing unit decreases rapidly after exposure to EDA gas, reaching 90% of the steady-state response value from the initial baseline in only about 3 seconds, demonstrating an extremely fast response speed. The fluorescence signal can recover to 90% of its initial state within 3.5 seconds. To ensure the stability of continuous cycle testing, the recovery time was appropriately extended to 5 seconds in subsequent experiments to ensure that the thin-film substrate sensing unit can fully recover to the baseline state before each test.

[0080] To systematically evaluate the selective recognition capability of the aforementioned thin-film-based sensing unit for EDA, 13 interfering substances were selected for specificity testing. These interfering substances included cadaverine, hydrazine hydrate, tert-butylamine, aniline, ammonia, triethylamine, and water. Under the same experimental conditions, the saturated vapors of both the interfering substances and the target analyte EDA were tested, and the fluorescence response behavior of the thin-film-based sensing unit was recorded. Figure 7 As shown in Figure a, the fluorescence emission intensity of the thin-film-based sensing unit significantly decreases in the presence of EDA; while other interfering substances do not cause significant changes in fluorescence intensity. These results demonstrate that the thin-film-based sensing unit exhibits excellent selective recognition capability for EDA.

[0081] To investigate the quantitative detection capability of the aforementioned thin-film-based sensing unit for EDA, the fluorescence response under different concentrations of EDA vapor was tested. Figure 7 As shown in b, within the low concentration range of 1.2–400 ppm, the fluorescence quenching intensity exhibits a good linear relationship with the EDA concentration, and the linear regression equation is ΔI = -1.81c. EDA +141.87, correlation coefficient R 2 ≥0.99. The detection limit of this thin-film-based sensing unit for EDA is as low as 1.2 ppm, which is significantly lower than the occupational exposure limit for EDA set by the World Health Organization (10 ppm).

[0082] To evaluate the reliability of the aforementioned thin-film-based sensing unit in practical applications, its long-term operational stability, reversibility, and environmental tolerance were further tested. The same thin-film-based sensing unit was subjected to 80 consecutive exposure-recovery cycles at a 600 ppm EDA concentration. Figure 7 As shown in Figure c, the fluorescence response signal of the thin-film-based sensing unit remained stable throughout the entire 80 cycles, without significant attenuation. This result demonstrates that the aforementioned thin-film-based sensing unit possesses excellent reversible response performance and long-term durability, making it suitable for repeated use in practical monitoring scenarios.

[0083] In summary, this invention successfully prepared acridine-based fluorescent nanofilms with both flexibility and size tunability via gas-liquid interfacial polymerization using building block units ACR-2CHO and CPTH as precursors. The sensing unit based on this nanofilm exhibits a highly selective fluorescence response to EDA, with a detection limit as low as 1.2 ppm, significantly better than occupational exposure limits. Furthermore, this thin-film-based sensing unit demonstrated excellent stability, reversibility, and long-term durability in 80 consecutive exposure-recovery cycles, meeting the requirements for real-time and repetitive detection of EDA vapor in practical monitoring scenarios. These results indicate that the described thin-film-based sensing unit has clear practical value and promising prospects in environmental monitoring, public safety, and occupational health protection.

[0084] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. An acridine-based fluorescent nanofilm, characterized in that, The acridine-based fluorescent nanofilm is a nanofilm material with fluorescent properties formed by the self-assembly reaction of aldehyde-modified acridine derivatives and calix[4]pyrroletetrahydrazine at the gas-liquid interface through acylhydrazone bonds. The structural formula of the aldehyde-modified acridine derivative is shown below: The structural formula of the cup[4]pyrroletetrahydrazine is shown below: 。 2. The acridine-based fluorescent nanofilm according to claim 1, characterized in that, The acridine-based fluorescent nanofilm has a porous network structure with a thickness of 30–120 nm.

3. A method for preparing the acridine-based fluorescent nanofilm according to claim 1, characterized in that, Includes the following steps: Step 1: Preparation of aldehyde-modified acridine derivatives Under an inert atmosphere, 9,9-diphenyl-9,10-dihydroacridine and N-bromosuccinimide were reacted in anhydrous tetrahydrofuran with stirring for 5–7 hours, and the mixture was purified to obtain 2,7-dibromo-9,9-diphenyl-9,10-dihydroacridine. Then, 2,7-dibromo-9,9-diphenyl-9,10-dihydroacridine and 4-formylphenylboronic acid were reacted in toluene under reflux for 10–12 hours in the presence of tetrabutylammonium bromide, potassium carbonate aqueous solution, and tetra(triphenylphosphine)palladium, and the aldehyde-modified acridine derivative was purified. Step 2: Preparation of precursor solution The aldehyde-modified acridine derivative obtained in step 1 and calix[4]pyrroletetrahydrazine were completely dissolved in dimethyl sulfoxide at a molar ratio of 2:1 to obtain a precursor solution; Step 3: Dynamic assembly of nanofilms at the gas-liquid interface The precursor solution from step 2 was dropped onto a clean glass substrate to spread it evenly. An acylhydrazone condensation reaction was carried out under environmental conditions of 25–30°C and 60%–65% relative humidity to form a nanofilm at the gas-liquid interface. The acridine-based fluorescent nanofilm was obtained after washing.

4. The method for preparing acridine-based fluorescent nanofilms according to claim 3, characterized in that, In step 1, the molar ratio of 9,9-diphenyl-9,10-dihydroacrylidine to N-bromosuccinimide is 1:2 to 4.

5. The method for preparing acridine-based fluorescent nanofilms according to claim 3, characterized in that, In step 1, the molar ratio of 2,7-dibromo-9,9-diphenyl-9,10-dihydroacridine to 4-formylphenylboronic acid, tetrabutylammonium bromide, tetra(triphenylphosphine)palladium, and potassium carbonate is 1:5-7:1-1.5:0.1-0.2:8-15.

6. The method for preparing acridine-based fluorescent nanofilms according to claim 3, characterized in that, In step 2, the total concentration of aldehyde-modified acridine derivatives and calix[4]pyrroletetrahydrazine in the precursor solution is 5-25 mg / mL.

7. The method for preparing acridine-based fluorescent nanofilms according to claim 3, characterized in that, In step 3, the acylhydrazone condensation reaction takes 4 to 5 hours.

8. A fluorescence sensing unit, characterized in that, It comprises the acridine-based fluorescent nanofilm as described in claim 1 or 2.

9. The application of the acridine-based fluorescent nanofilm of claim 1 or 2 or the fluorescent sensing unit of claim 8 in the fluorescent sensing detection of ethylenediamine.

Images