Cyano-functionalized tetraphenylstyryl crosslinked fluorescent nanofilms, template-free preparation method and gaseous hydrazine detection applications

Abstract

The application discloses a cyan-functionalized tetraphenylethene cross-linked fluorescent nanofilm, a template-free preparation method and gaseous hydrazine detection application, and belongs to the field of gas-phase sensing materials. In the application, 4-(isocyanomethyl) benzhydrazide and tetraaldehyde tetraphenylethene are used as comonomers, and a cross-linked fluorescent nanofilm with acylhydrazone bonds and carbon-carbon double bonds is constructed in situ through Knoevenagel condensation reaction and Schiff base reaction at a gas-liquid interface. The cyan group in the film can effectively regulate π electron delocalization effect, providing a specific reaction site for hydrazine molecules, and combining the aggregation-induced emission characteristics of tetraphenylethene, the film is endowed with strong fluorescence emission and high sensing activity. The film shows super-sensitivity, high selectivity and rapid response to hydrazine vapor, and the detection limit is as low as 130 ppt, and the film has good anti-interference ability to common volatile organic compounds and water. The film preparation method is template-free, simple in process and controllable in film area, and has wide application prospect.

Description

Technical Field

[0001] This invention belongs to the field of gas phase sensing materials technology, specifically relating to a fluorescent nanofilm for high-performance detection of gaseous hydrazine, its template-free preparation method, and its application. Background Technology

[0002] Fluorescence sensing technology is a detection method based on changes in fluorescence signals. It has advantages such as high sensitivity, fast response speed, and simple operation, and has important application value in environmental monitoring, public safety, and industrial process control. Among them, film-based fluorescence sensors (FSSs) have become a research hotspot in the field of gas phase sensing in recent years due to their simple structure, ease of integration, and portability for in-situ detection.

[0003] Gaseous hydrazine (N₂H₄) is an important industrial raw material widely used in rocket propellants, pesticide synthesis, and pharmaceutical intermediates. However, hydrazine is highly volatile and toxic, and has been classified as a possible human carcinogen by the International Agency for Research on Cancer. The U.S. Environmental Protection Agency (EPA) sets its indoor exposure limit at 3 × 10⁻⁶. -3 mg / m 3 Therefore, developing sensing materials capable of efficiently and sensitively detecting gaseous hydrazine is of significant practical importance.

[0004] Currently, fluorescent sensing materials for hydrazine detection mainly focus on hydrazine molecule recognition in liquid-phase systems, with relatively little research on gas-phase hydrazine sensing based on solid-film forms. Existing thin-film sensing materials mostly use small organic molecule dyes, conjugated polymers, or metal-organic frameworks as sensing layers, and are formed by methods such as spin coating, vapor deposition, or layer-by-layer self-assembly. For example, Lee et al. (MH Lee, et al., Chem. Sci., 2013, 4, 4121) reported a fluorescent probe based on a naphthalimide derivative, which can detect gas-phase hydrazine, but its film preparation relies on solid matrices such as TLC plates, making the process relatively complex and the film uniformity difficult to control precisely. Thomas et al. (SW Thomas III, et al., Adv. Mater., 2006, 18, 1047) used conjugated polymer films to achieve a fluorescent "turn-on" response to hydrazine vapor, but the random stacking of polymer chains may lead to defects inside the film, affecting the stability of the fluorescence signal and the long-term reliability of the sensor.

[0005] Furthermore, most of the aforementioned film-forming methods rely on templates or complex interface assembly processes, limiting the film area to the template size and hindering large-area, low-cost fabrication. Simultaneously, traditional fluorescent molecules often exhibit aggregation-caused quenching (ACQ) in the solid state, significantly reducing the film's fluorescence emission efficiency and hindering improved detection sensitivity. Therefore, developing a novel fluorescent nanofilm that requires no template assistance, possesses a complete film structure, exhibits high fluorescence emission efficiency, and demonstrates high sensitivity to gaseous hydrazine remains a pressing technical challenge in this field. Summary of the Invention

[0006] To address the shortcomings of existing gaseous hydrazine fluorescent sensing materials, such as insufficient sensitivity and poor selectivity, as well as the technical bottlenecks of complex thin-film preparation processes and reliance on template assistance, this invention provides a cyano-functionalized tetraphenylethylene crosslinked fluorescent nanofilm and its template-free preparation method. This film exhibits advantages such as strong fluorescence emission, high sensitivity, excellent anti-interference ability, and simple preparation.

[0007] To achieve the above objectives, the cyano-functionalized tetraphenylethylene crosslinked fluorescent nanofilm provided by the present invention has a covalently crosslinked network of repeating structural units as shown below:

[0008]

[0009] Preferably, the film is formed by crosslinking 4-(isocyanomethyl)benzoylhydrazine (CNHA) and tetraaldehyde tetraphenylethylene (TFPE) through acylhydrazone bonds (C=N-NH-CO) and carbon-carbon double bonds (C=C).

[0010] This invention also provides a template-free method for preparing the cyano-functionalized tetraphenylethylene crosslinked fluorescent nanofilm, comprising the following steps:

[0011] Step 1: At room temperature, CNHA and TFPE are added to dimethyl sulfoxide (DMSO) at a molar ratio of 2:1, and KOH is added as a catalyst. The resulting mixture is placed in an ultrasonic cleaner and ultrasonically treated for 20-30 min in a water bath at 20-30 ℃. Then, it is transferred to a constant temperature shaker and shaken at 20-30 ℃ and 2000-4000 rpm for 5-10 min. The above ultrasonic-shaking cycle is repeated 2-4 times until the solid phase is completely dissolved. After cooling to room temperature, the precursor solution is obtained.

[0012] Step 2: The precursor solution is dropped onto a clean glass substrate and spread evenly. The substrate is then allowed to stand for 3–8 hours at a temperature of 20–30°C and a relative humidity of 50%–70%. This allows the precursor to undergo both Kronowenger and Schiff base condensation reactions at the gas-liquid interface, forming a nanofilm cross-linked with carbon-carbon double bonds and acylhydrazone bonds. After thorough washing, the fluorescent nanofilm is obtained. The reaction equation is as follows:

[0013]

[0014]

[0015] In step 1 above, the CNHA is prepared by the following method: methyl 4-(cyanomethyl)benzoate (CNBZ) is dissolved in methanol, hydrazine hydrate is added, and the mixture is stirred and reacted at 65–75 °C for 16–20 h under nitrogen protection; after the reaction is completed, the mixture is cooled, concentrated, washed, and filtered to obtain CNHA; the reaction equation is as follows:

[0016]

[0017] In step 1, the concentration of 4-(isocyanomethyl)benzoyl hydrazide in the precursor solution is 0.01–0.05 mol / L.

[0018] In step 1, the amount of KOH added is 5% to 10% of the molar amount of 4-(isocyanomethyl)benzoylhydrazine.

[0019] The present invention also provides the use of the above-mentioned fluorescent nanofilm in the detection of gaseous hydrazine.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. The fluorescent nanofilm of this invention uses CNHA and TFPE as core building blocks. CNHA is an asymmetric molecule with cyanomethyl and hydrazide groups modified at its two ends, respectively, both of which can serve as reactive sites. TFPE is a polyaldehyde monomer with aggregation-induced emission (AIE) properties. The two form a covalent cross-linked network through a condensation reaction, and the resulting film combines the AIE fluorescence enhancement effect of TFPE with the hydrazide-specific response function of CNHA. Specifically, although the formation of carbon-nitrogen double bonds and carbon-carbon double bonds in the cross-linked structure may induce intramolecular charge transfer and lead to fluorescence quenching, the AIE properties of TFPE can effectively counteract this negative effect, allowing the film to maintain strong fluorescence emission.

[0022] 2. The fluorescent nanofilm of this invention employs a double-linked covalent network composed of acylhydrazone bonds and carbon-carbon double bonds. The dynamic acylhydrazone bonds (C=N-NH-CO) possess reversible exchange properties, automatically correcting structural defects during film formation and ensuring the film remains large-area intact and crack-free. The conjugated carbon-carbon double bonds (C=C) endow the film with excellent structural rigidity and thermodynamic stability, giving the material both good mechanical strength and photochemical stability.

[0023] 3. This invention utilizes the spontaneous aggregation and reaction of precursor solutions at the gas-liquid interface in a humid air / DMSO system to form a film. The entire process requires no template or external substrate support, and the film area is determined solely by the size of the reaction vessel, enabling large-area, controllable preparation from laboratory to industrial applications. This process is simple to operate, uses readily available raw materials, operates under mild reaction conditions, and allows for adjustable film thickness and size, enabling large-area preparation and demonstrating promising prospects for industrial application.

[0024] 4. The fluorescent nanofilm of this invention exhibits ultrasensitive, highly selective, and rapid response characteristics to gaseous hydrazine. The cyano functional group, as an electron-withdrawing group, can effectively modulate the π-electron delocalization effect of the system, providing a specific reaction site for hydrazine molecules; simultaneously, the dynamic acylhydrazone bond can also specifically interact with alkaline gases such as hydrazine. This synergistic effect of the above dual active sites endows the film with a detection limit as low as 130 ppt for hydrazine vapor and good resistance to interference from common volatile organic compounds and moisture. This sensing material has broad application prospects in industrial production safety, environmental monitoring, and public safety. Attached Figure Description

[0025] Figure 1 It is CNHA 1 H NMR spectrum.

[0026] Figure 2 It is CNHA 13 C10 NMR spectrum.

[0027] Figure 3 This is the HRMS spectrum of CNHA.

[0028] Figure 4 The images show the Fourier transform infrared (FT-IR) spectra of CNHA, TFPE, and the fluorescent nanofilms prepared in Example 1.

[0029] Figure 5 The image shows the high-resolution X-ray photoelectron spectroscopy (XPS) spectrum of the fluorescent nanoparticles prepared in Example 1; where a is the C 1s spectrum and b is the N 1s spectrum.

[0030] Figure 6These are optical images of the fluorescent nanofilm prepared in Example 1; where a is a photograph of the nanofilm under sunlight, and the upper right inset is a photograph of the nanofilm under ultraviolet light; b is a photograph of the nanofilm self-supported on an iron ring with a diameter of 1 cm; c is a photograph of a sharp object applying force to the surface of the film; d is a photograph of the nanofilm attached to different substrates.

[0031] Figure 7 These are images showing the microstructure of the fluorescent nanofilm prepared in Example 1; where a is an energy-dispersive X-ray elemental spectrum of the nanofilm taken under a scanning electron microscope; and b is a photograph of the nanofilm attached to a silicon wafer and observed under a transmission electron microscope.

[0032] Figure 8 The results of the fluorescent nanofilm prepared in Example 1 for sensing and detecting N2H4 vapor are shown below. In this figure, a represents the fluorescence response of the nanofilm to different concentrations of N2H4 vapor, with each measurement repeated 5 times. The inset shows the response intensity of the nanofilm to air and analyte vapor at a concentration of 130 ppt. b shows the linear relationship between the response intensity of the nanofilm and the N2H4 vapor concentration. c shows the response of the fluorescent nanofilm to N2H4 and some potential interferences. d shows the stability of the fluorescent sensing film after 15 consecutive tests.

[0033] Figure 9 These are the fluorescence response spectra of the fluorescent nanofilms of Example 1 and Comparative Example 1 to saturated N2H4 vapor (concentration approximately 13000 ppm); wherein, Figure 9 a is the fluorescence spectrum corresponding to Comparative Example 1. Figure 9 b is the fluorescence spectrum corresponding to Example 1. Detailed Implementation

[0034] To enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions of the present invention will be clearly and completely described below in conjunction with embodiments and accompanying drawings. Obviously, the embodiments described below are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all embodiments obtained by those skilled in the art without creative effort fall within the protection scope of the present invention.

[0035] The CNHA used in the following examples was prepared as follows: 900 mg (5.0 mmol) of CNBZ was dissolved in 20 mL of methanol, and then 3.0 mL of 80% (w / w) hydrazine hydrate was added dropwise. Under nitrogen protection, the reaction system was stirred at 70 °C for 18 h. After the reaction was completed, the solution was cooled to room temperature, concentrated under reduced pressure, and the residue was repeatedly washed with dichloromethane. The suspension was then filtered and dried under vacuum at 50 °C to obtain 556 mg of a pale yellow solid product, CNHA. The structural characterization results of the obtained CNHA are shown in the figure below. Figures 1-3 The NMR and mass spectrometry data are as follows: 1 H NMR (600 MHz, DMSO- d 6) δ : 9.82 (s, 1H), 7.92 (d, J = 8.0 Hz, 2H), 7.48 (d, J = 7.9 Hz, 2H), 4.49 (s, 2H), 4.11(s, 2H); 13 C NMR (151 MHz, DMSO- d 6) δ :165.84, 134.77, 133.12, 129.30, 128.88,128.66, 128.50, 128.05, 127.55, 119.41, 29.94, 22.75; HRMS C9H9N3O (APCI, m / z ):[M+Na] + Theoretical value: 198.0638; measured value: 198.0634.

[0036] Example 1

[0037] Step 1: At room temperature, 0.88 mg (0.005 mmol) CNHA and 1.12 mg (0.0025 mmol) TFPE were added to 0.4 mL DMSO, and 1 μL of 0.5 mmol / L (0.0005 mmol) KOH solution in DMSO was added. The resulting mixture was placed in an ultrasonic cleaner and ultrasonically treated for 30 min in a water bath at 25 °C. Then it was transferred to a constant temperature shaker and shaken at 25 °C and 3000 rpm for 5 min. The above ultrasonic-shaking cycle was repeated 3 times until the solid phase was completely dissolved. The solution was then cooled to room temperature to obtain the precursor solution.

[0038] Step 2: Clean a 3 cm diameter glass culture dish three times ultrasonically with acetone, ethanol, and deionized water respectively, then dry it with nitrogen gas. Next, treat it with a plasma cleaner (air atmosphere) for 2 minutes. Then, add 0.4 mL of the precursor solution from Step 1 to the surface of the glass culture dish, spreading the liquid evenly. Place the glass culture dish covered with the precursor solution in a constant temperature and humidity incubator and allow it to react for 5 hours at 25°C and 65% relative humidity. After the reaction is complete, a flat, dense, transparent 3 cm diameter circular nanofilm can be observed at the solution-air interface. Slowly inject ultrapure water into the glass culture dish; the nanofilm will detach from the glass culture dish and float on the water surface. After repeated washing with ultrapure water, a fluorescent nanofilm is obtained.

[0039] The composition and structure of the obtained fluorescent nanofilms were characterized by Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS), respectively. The results are shown in the figure. Figure 4 and Figure 5 .exist Figure 4 The Fourier transform infrared spectra of the fluorescent nanofilm (TFPE-CN) before and after the reaction can be clearly observed in the infrared spectrum at 1660 cm⁻¹. -1 A stretching vibration absorption peak appears at 3475 cm⁻¹, which is attributed to the carbon-nitrogen double bond (-C=N). It is noteworthy that the peak at 3475 cm⁻¹ is absent from the spectrum, indicating the presence of the starting material CNHA. -1 The corresponding amino (-NH2) stretching vibration peak at 2200 cm⁻¹ confirms the formation of an acylhydrazone bond in the reaction; simultaneously, at 2200 cm⁻¹... -1 The characteristic absorption peak of the cyano group (-CN) can be observed nearby, at 950 cm⁻¹. -1 An out-of-plane bending vibration absorption peak of hydrogen (-CH=C) on the carbon-carbon double bond was observed, confirming the presence of cyano groups and carbon-carbon double bonds in the film structure. Figure 5 The XPS spectra data show that fine peak fitting was performed on C and N elements to analyze the chemical bond composition inside the film. The XPS analysis results are consistent with the infrared spectroscopy analysis results, indicating that acylhydrazone bonds and carbon-carbon double bonds were formed during the formation of the film. The above characterization results together show that the fluorescent nanofilm of this embodiment has been successfully prepared and possesses the complete target molecular structure.

[0040] The obtained fluorescent nanofilm was transferred to various substrates, including quartz glass, silicon wafers, filter paper, and polytetrafluoroethylene. The film adhered completely to all of them and exhibited excellent mechanical strength. It not only achieved a self-supporting structure using iron rings but also withstood punctures from sharp objects without breaking. Figure 6 As shown.

[0041] The obtained fluorescent nanofilms were characterized using a SU8220 field emission scanning electron microscope and a Tecnai G2 F20 transmission electron microscope. The results are shown in the figure. Figure 7 .Depend on Figure 7 As can be seen, the fluorescent nanofilm has a complete and uniform structure, a smooth and uniform surface, and no visible pores or cracks.

[0042] Example 2

[0043] Step 1: At room temperature, 1.76 mg (0.010 mmol) CNHA and 2.24 mg (0.005 mmol) TFPE were added to 0.4 mL DMSO, and 2 μL of 0.5 mmol / L (0.001 mmol) KOH DMSO solution was added. The resulting mixture was placed in an ultrasonic cleaner and ultrasonically treated for 30 min at 25 ℃ in a water bath. Then it was transferred to a constant temperature shaker and shaken at 25 ℃ and 3000 rpm for 5 min. The above ultrasonic-shaking cycle was repeated 3 times until the solid phase was completely dissolved. The solution was then cooled to room temperature to obtain the precursor solution.

[0044] Step 2: Clean the 3 cm diameter glass culture dish three times with acetone, ethanol, and deionized water respectively using ultrasonic cleaning and then dry it with nitrogen. Then treat it with plasma cleaning agent (air atmosphere) for 2 minutes. Then add 0.4 mL of the precursor solution from Step 1 to the surface of the glass culture dish to spread the liquid evenly. Place the glass culture dish covered with the precursor solution in a constant temperature and humidity incubator and let it stand for 6 h at a temperature of 25 ℃ and a relative humidity of 65%. The other steps are the same as Step 2 in Example 1 to obtain a circular fluorescent nanofilm with a diameter of 3 cm.

[0045] Example 3

[0046] Step 1: At room temperature, 1.76 mg (0.010 mmol) CNHA and 2.24 mg (0.005 mmol) TFPE were added to 0.8 mL DMSO, and 2 μL of 0.5 mmol / L (0.001 mmol) KOH DMSO solution was added. The resulting mixture was placed in an ultrasonic cleaner and ultrasonically treated for 30 min at 25 ℃ in a water bath. Then it was transferred to a constant temperature shaker and shaken at 25 ℃ and 3000 rpm for 5 min. The above ultrasonic-shaking cycle was repeated 3 times until the solid phase was completely dissolved. The solution was then cooled to room temperature to obtain the precursor solution.

[0047] Step 2: Clean the 3 cm diameter glass culture dish three times with acetone, ethanol, and deionized water respectively, and dry it with nitrogen. Then treat it with plasma cleaner (air atmosphere) for 2 minutes. Then add 0.8 mL of the precursor solution from Step 1 to the surface of the glass culture dish to spread the liquid evenly. Place the glass culture dish covered with the precursor solution in a constant temperature and humidity incubator and let it stand for 6 h at a temperature of 26 ℃ and a relative humidity of 60%. The other steps are the same as Step 2 in Example 1 to obtain a circular fluorescent nanofilm with a diameter of 3 cm.

[0048] Example 4

[0049] Step 1: At room temperature, 3.52 mg (0.020 mmol) CNHA and 4.48 mg (0.010 mmol) TFPE were added to 0.8 mL DMSO, and 4 μL of 0.5 mmol / L (0.002 mmol) KOH DMSO solution was added. The resulting mixture was placed in an ultrasonic cleaner and ultrasonically treated for 30 min at 25 ℃ in a water bath. Then it was transferred to a constant temperature shaker and shaken at 25 ℃ and 3000 rpm for 5 min. The above ultrasonic-shaking cycle was repeated 3 times until the solid phase was completely dissolved. The solution was then cooled to room temperature to obtain the precursor solution.

[0050] Step 2: Clean the 3 cm diameter glass culture dish three times with acetone, ethanol, and deionized water respectively using ultrasonic cleaning and then dry it with nitrogen. Then treat it with plasma cleaning agent (air atmosphere) for 2 minutes. Then add 0.8 mL of the precursor solution from Step 1 to the surface of the glass culture dish to spread the liquid evenly. Place the glass culture dish covered with the precursor solution in a constant temperature and humidity incubator and let it stand for 3 h at a temperature of 26 ℃ and a relative humidity of 66%. The other steps are the same as Step 2 in Example 1 to obtain a circular fluorescent nanofilm with a diameter of 3 cm.

[0051] Example 5

[0052] Step 1: At room temperature, 5.28 mg (0.030 mmol) CNHA and 6.72 mg (0.015 mmol) TFPE were added to 1.6 mL DMSO, and 6 μL of 0.5 mmol / L (0.003 mmol) KOH DMSO solution was added. The resulting mixture was placed in an ultrasonic cleaner and ultrasonically treated for 30 min at 25 ℃ in a water bath. Then it was transferred to a constant temperature shaker and shaken at 25 ℃ and 3000 rpm for 5 min. The above ultrasonic-shaking cycle was repeated 3 times until the solid phase was completely dissolved. The solution was then cooled to room temperature to obtain the precursor solution.

[0053] Step 2: Clean the 5 cm diameter glass culture dish three times with acetone, ethanol, and deionized water respectively using ultrasonic cleaning and then dry it with nitrogen. Then treat it with plasma cleaning agent (air atmosphere) for 2 minutes. Then add 1.6 mL of the precursor solution from Step 1 to the surface of the glass culture dish to spread the liquid evenly. Place the glass culture dish covered with the precursor solution in a constant temperature and humidity incubator and let it stand for 6 h at a temperature of 25 ℃ and a relative humidity of 63%. The other steps are the same as Step 2 in Example 1 to obtain a circular fluorescent nanofilm with a diameter of 5 cm.

[0054] Example 6

[0055] Step 1: At room temperature, 10.56 mg (0.060 mmol) CNHA and 13.44 mg (0.030 mmol) TFPE were added to 3.2 mL DMSO, and 12 μL of 0.5 mmol / L (0.006 mmol) KOH DMSO solution was added. The resulting mixture was placed in an ultrasonic cleaner and ultrasonically treated for 30 min at 25 ℃ in a water bath. Then it was transferred to a constant temperature shaker and shaken at 25 ℃ and 3000 rpm for 5 min. The above ultrasonic-shaking cycle was repeated 3 times until the solid phase was completely dissolved. The solution was then cooled to room temperature to obtain the precursor solution.

[0056] Step 2: Clean the 7 cm diameter glass culture dish three times with acetone, ethanol, and deionized water respectively, and dry it with nitrogen. Then treat it with plasma cleaner (air atmosphere) for 2 minutes. Then add 3.2 mL of the precursor solution from Step 1 to the surface of the glass culture dish to spread the liquid evenly. Place the glass culture dish covered with the precursor solution in a constant temperature and humidity incubator and let it stand for 8 h at a temperature of 23 ℃ and a relative humidity of 64%. The other steps are the same as Step 2 in Example 1 to obtain a circular fluorescent nanofilm with a diameter of 7 cm.

[0057] Comparative Example 1

[0058] Step 1: At room temperature, 0.92 mg (0.005 mmol) Thz and 1.08 mg (0.0025 mmol) TFPE were added to 0.4 mL DMSO, and 1 μL (0.0005 mmol) formic acid was added. The mixture was placed in an ultrasonic cleaner and ultrasonically treated for 30 min at 25 ℃ in a water bath. Then it was transferred to a constant temperature shaker and shaken at 25 ℃ and 3000 rpm for 5 min. The above ultrasonic-shaking cycle was repeated 3 times until the solid phase was completely dissolved. The solution was cooled to room temperature to obtain the precursor solution.

[0059]

[0060] Thz

[0061] Step 2: A 3 cm diameter glass culture dish was ultrasonically cleaned three times each with acetone, ethanol, and deionized water, and then dried with nitrogen. It was then treated with a plasma cleaner (air atmosphere) for 2 minutes. Next, 0.4 mL of the precursor solution from Step 1 was added dropwise to the surface of the glass culture dish, spreading it evenly. The culture dish covered with the precursor solution was placed in a constant temperature and humidity incubator and allowed to react for 7 hours at 22 ℃ and 60% relative humidity. After the reaction was complete, a flat, dense, and transparent 3 cm diameter circular nanofilm was observed at the solution-air interface. When ultrapure water was slowly injected into the glass culture dish, the nanofilm detached from the glass and floated on the water surface. After repeated washing with ultrapure water, a cyanide-free fluorescent nanofilm was obtained.

[0062] Application Example 1

[0063] Application of the fluorescent nanofilm prepared in Example 1 for detecting gaseous hydrazine

[0064] Experiment 1: Sensing and Detection of N2H4 Vapor of Different Concentrations by Fluorescent Nanofilms

[0065] The fluorescent nanofilm from Example 1 was floated on water, and retrieved from the water using a high-transmittance quartz plate. The film was then naturally air-dried in an indoor dry environment to obtain a dried film sensing unit. The film sensing unit was connected to a sensing platform, and the excitation wavelength of the sensor was adjusted to 365 nm, and the detection wavelength to 550 nm. Saturated N2H4 vapor was diluted with air to produce N2H4 vapor of different concentrations. The diluted gas was injected into a gas bag and connected to the sensor's air inlet. A small air pump was connected to the sensor's air outlet to allow gas to pass through the film sensing unit. Exhaust gas was introduced into an exhaust gas cylinder and treated using a bubbling method. Simultaneously, the sensor was connected to a computer to receive sensing signals. The sensing signals were calculated to obtain sensing data, which is shown below. Figure 8 a and Figure 8 b.

[0066] Depend on Figure 8 As can be seen from Figure 8b, the fluorescence intensity of the film gradually decreases with increasing N2H4 vapor concentration, exhibiting a typical concentration-dependent fluorescence quenching response. The lowest detectable concentration of N2H4 vapor for this sensing film is 130 ppt, which is far below the workplace safety concentration limit (10 ppb) set by the US Environmental Protection Agency (EPA), indicating that the fluorescent sensing film of this invention possesses ultrasensitive hydrazine detection capability. The standard curve fitting results in Figure 8b show that its linear correlation coefficient R... 2 = 0.984, which proves that there is a good linear relationship between the sensing response intensity and the hydrazine concentration.

[0067] Experiment 2: Sensing of N2H4 vapor interference gas by fluorescent nanofilms (monitoring wavelength 550 nm)

[0068] Saturated vapors of N2H4 (diluted with air to a concentration of 130 ppb), saturated vapors of common amines (triethylamine, ammonia, diethylamine, pyridine, piperidine, aniline), and saturated vapors of organic solvents (ethanol, tetrahydrofuran, chloroform, methanol, and water) were respectively filled into gas bags. Each gas bag was connected to the air inlet of the sensor, and sensing was performed one by one according to the method in Experiment 1 above. The sensing results are shown in Figure 8c.

[0069] Depend on Figure 8 As can be seen, under the same test conditions, N2H4 vapor can induce a significant fluorescence quenching effect, and its response intensity is significantly higher than that of other interfering gases, indicating that the fluorescent nanofilm of the present invention has good selective recognition ability for N2H4 vapor.

[0070] Experiment 3: Reproducibility of Fluorescent Nanofilm Sensing N2H4 Vapor

[0071] N2H4 vapor with a concentration of 130 ppb was injected into the gas bag and connected to the sensor inlet. Sensing was performed according to the method described in Experiment 1 above, and the sensing data are shown below. Figure 8 d. By Figure 8 As can be seen, the fluorescent nanofilm of Example 1 can detect N2H4 vapor 15 times consecutively, demonstrating the stability of the film in use.

[0072] Experiment 4: Comparison of the sensing and detection of N2H4 vapor by fluorescent nanofilms in Example 1 and Comparative Example 1

[0073] The fluorescent nanofilms prepared in Example 1 and Comparative Example 1 were placed in 3.5 mL cuvettes, respectively. 3.5 mL of saturated hydrazine vapor (approximately 13000 ppm) was injected into the cuvettes using a syringe. The fluorescence response was measured under the same conditions (excitation wavelength 365 nm), and the results are shown below. Figure 9 .

[0074] As shown in Figure 9, under the same hydrazine vapor concentration, the fluorescence quenching efficiency of the cyano-containing fluorescent nanofilm prepared in Example 1 reached 82%, while the fluorescence quenching efficiency of the cyano-free fluorescent nanofilm in Comparative Example 1 was only 23%, representing an improvement of approximately 60%. This significant performance difference stems from the fact that the cyano functional group in CNHA provides an interaction site that can specifically react with hydrazine; the Thz molecule in Comparative Example 1 lacks cyano modification, making it difficult for the resulting fluorescent nanofilm to effectively capture hydrazine molecules. These results confirm that the cyano functional group plays a crucial role in enhancing the sensing sensitivity of this sensor film.

Claims

1. A cyano-functionalized tetraphenylethylene crosslinked fluorescent nanofilm, characterized in that, The thin film has a covalently cross-linked network of repeating structural units as shown below: 。 2. The cyano-functionalized tetraphenylethylene crosslinked fluorescent nanofilm according to claim 1, characterized in that, The film is formed by cross-linking 4-(isocyanomethyl)benzoylhydrazine and tetraaldehyde tetraphenylethylene through acylhydrazone bonds and carbon-carbon double bonds.

3. A template-free method for preparing the cyano-functionalized tetraphenylethylene crosslinked fluorescent nanofilm according to claim 1 or 2, characterized in that, Includes the following steps: Step 1: At room temperature, 4-(isocyanomethyl)benzoylhydrazine and tetraaldehyde tetraphenylethylene were added to dimethyl sulfoxide at a molar ratio of 2:1, and KOH was added as a catalyst. The resulting mixture was placed in an ultrasonic cleaner and ultrasonically treated for 20-30 min in a water bath at 20-30 °C. Then, it was transferred to a constant temperature shaker and shaken at 20-30 °C and 2000-4000 rpm for 5-10 min. The above ultrasonic-shaking cycle was repeated 2-4 times until the solid phase was completely dissolved. The mixture was then cooled to room temperature to obtain the precursor solution. Step 2: The precursor solution is dropped onto a clean glass substrate and spread evenly. The substrate is allowed to stand for 3 to 8 hours in an environment with a temperature of 20 to 30 °C and a relative humidity of 50% to 70%. Krono Wenger condensation and Schiff base reaction occur at the gas-liquid interface to generate a nanofilm. After washing, the fluorescent nanofilm is obtained.

4. The template-free preparation method of cyanofunctionalized tetraphenylethylene crosslinked fluorescent nanofilm according to claim 3, characterized in that, In step 1, the concentration of 4-(isocyanomethyl)benzoyl hydrazide in the precursor solution is 0.01–0.05 mol / L.

5. The template-free preparation method of the cyano-functionalized tetraphenylethylene crosslinked fluorescent nanofilm according to claim 3, characterized in that, In step 1, the amount of KOH added is 5% to 10% of the molar amount of 4-(isocyanomethyl)benzoylhydrazine.

6. Use of the fluorescent nanofilm according to claim 1 or 2 in the detection of gaseous hydrazine.

7. Use of the fluorescent nanofilm prepared by the method according to any one of claims 3 to 5 in the detection of gaseous hydrazine.

Images