Paper-based sensors modified with metal-organic frameworks exhibiting aggregation-induced emission effect and their application in formaldehyde detection.

Abstract

This invention discloses a paper-based sensor modified with a metal-organic framework (MOF) exhibiting aggregation-induced emission (AIE) and its application in formaldehyde detection. The paper-based sensor is prepared by in-situ growth of an AIE on a paper substrate. The AIE is formed by complexing zinc chloride with tetra(4-pyridinebiphenyl)ethylene in a mixed solvent of tetrachloroethylene and methanol. This paper-based sensor features low cost, minimal environmental pollution, small size for handheld use, and high stability. It can detect volatile formaldehyde using both fluorescence and chemiluminescence methods, exhibiting high sensitivity, a wide linear range, and rapid response. This not only provides a new approach for the real-time detection of gaseous formaldehyde but also enriches and expands the application of AIE-modified MOFs on paper substrates.

Description

Technical Field

[0001] This invention belongs to the field of chemical detection technology, specifically relating to a paper-based sensor modified with a metal-organic framework material that exhibits aggregation-induced emission effect, and its application in detecting gaseous formaldehyde. Background Technology

[0002] Metal-organic frameworks (MOFs) are a new class of materials formed by the complexation of metal nodes and organic ligands. Due to their high surface area and ultra-high porosity, they have been widely used in gas adsorption and chemical sensing. However, the application of traditional luminescent MOFs is greatly limited by aggregation-induced quenching. Unlike traditional luminescent molecules that suffer from aggregation-induced quenching, aggregation-induced emitting molecules produce strong luminescence when aggregated in chromophores. Tetraphenylethylene and its derivatives (e.g., tetra(4-pyridinylbiphenyl)ethylene) are typical examples of aggregation-induced luminescent molecules; their aggregation-induced luminescence process can be attributed to restricted intramolecular rotation and highly distorted molecular conformation. By preparing MOFs with aggregation-induced luminescence effects, the intramolecular motion of aggregation-induced luminescent molecules can be further restricted by the rigid structure of the MOF, thereby improving luminescence efficiency and facilitating trace analysis.

[0003] Paper-based sensors offer advantages such as low cost, ease of modification, foldability, and small, handheld size, making them suitable as carriers for point-of-care testing devices. Combining solid-phase metal-organic frameworks (MOFs) with aggregation-induced emission (AIE) effects with a paper matrix allows for the integration of a rigid crystalline framework structure with a flexible matrix. Furthermore, the strong emission characteristics of AIEs in the solid phase facilitate chemiluminescence sensing, further expanding the applications of fluorescent materials. While AIEs have been widely used in liquid-phase fluorescence sensing, their application in chemiluminescence for gas-phase analytes is limited. Moreover, for specific analytes, a single detection method is often employed. To date, no literature reports on using AIEs for multi-mode detection of a specific analyte. Summary of the Invention

[0004] The purpose of this invention is to provide a paper-based sensor modified with a metal-organic framework material that exhibits aggregation-induced emission effect. This sensor can achieve dual detection of gaseous formaldehyde using both fluorescence and chemiluminescence methods.

[0005] To achieve the above objectives, the paper-based sensor of the present invention is a metal-organic framework material with aggregation-induced emission effect grown in situ on the surface of a paper matrix; the metal-organic framework material is formed by complexing zinc chloride and tetra(4-pyridinebiphenyl)ethylene in a mixed solvent of tetrachloroethylene and methanol, and its chemical formula is ZnCl2Py-TPE·4(TCE), where Py-TPE represents tetra(4-pyridinebiphenyl)ethylene and TCE represents tetrachloroethylene.

[0006] The above-mentioned paper-based sensor is prepared as follows: zinc chloride is dissolved in methanol, and tetra(4-pyridinebiphenyl)ethylene is dissolved in a mixed solvent of tetrachloroethylene and methanol in a volume ratio of 3:1. After the two are mixed evenly, they are transferred to a beaker containing paper matrix and left to stand at room temperature for 1 to 5 days. Then, they are activated by soaking in ethanol for 1 to 5 days, during which the ethanol is replaced every 3 to 6 hours. Finally, they are vacuum dried at 60 to 100°C.

[0007] In the above preparation method, the preferred molar ratio of zinc chloride to tetra(4-pyridinebiphenyl)ethylene is 2:1 to 6:1.

[0008] In the above preparation method, it is preferable to allow the reaction to stand at room temperature for 1 to 5 days.

[0009] In the above preparation method, it is preferable to activate the product by soaking in ethanol for 1 to 5 days.

[0010] The paper substrate mentioned above is Whatman No. 1 filter paper or Whatman No. 3 filter paper.

[0011] The paper-based sensor modified with metal-organic framework material of this invention can be used to detect trace amounts of volatile formaldehyde, and the detection method can be either fluorescence or chemiluminescence. The fluorescence method uses an excitation wavelength of 250–500 nm and a detection wavelength of 375–700 nm. The chemiluminescence method uses a bis(2,4,6-trichlorophenyl)oxalate-hydrogen peroxide chemiluminescence system, without the addition of hydrogen peroxide; wherein the concentration of bis(2,4,6-trichlorophenyl)oxalate is 5 mmol / L.

[0012] This invention relates to a paper-based sensor modified with a metal-organic framework material exhibiting aggregation-induced emission (AIE) for the detection of volatile formaldehyde. The detection method can be either fluorescence or chemiluminescence. Specifically, the fluorescence excitation wavelength of the fluorescence detection method is 250–500 nm, and the detection wavelength is 375–700 nm. The chemiluminescence detection method employs a bis(2,4,6-trichlorophenyl)oxalate-hydrogen peroxide chemiluminescence system, and trace detection of volatile formaldehyde can be achieved without the addition of hydrogen peroxide. The concentration of bis(2,4,6-trichlorophenyl)oxalate is 5 mmol / L.

[0013] The mechanism by which the paper-based sensor modified with a metal-organic framework material exhibiting aggregation-induced emission effect detects volatile formaldehyde is as follows: Because the dynamic diameter of formaldehyde is... The metal-organic framework (MOF) material exhibiting aggregation-induced emission (AIE) has a large number of microporous structures and a high specific surface area, allowing formaldehyde to be adsorbed into the pores. The entry of formaldehyde molecules hinders the rotation of the benzene and pyridine rings, further increasing the aggregation degree of the MOF material on paper. Therefore, fluorescence enhancement can be used to detect gaseous formaldehyde with a detection limit of 3.4 ppb. To further reduce the detection limit and achieve the detection of even lower concentrations of gaseous formaldehyde, a chemiluminescence resonance energy transfer platform can be used for signal amplification. Since the bis(2,4,6-trichlorophenyl)oxalate-hydrogen peroxide chemiluminescence system is an excellent energy transfer donor, its released energy can be used to excite the MOF material to produce chemiluminescence. Due to the presence of dissolved oxygen in the system, strong chemiluminescence can be produced even without the addition of hydrogen peroxide, with a detection limit of 0.05 ppb.

[0014] This invention applies metal-organic frameworks (MOFs) exhibiting aggregation-induced emission (AIE) to paper to fabricate paper-based sensors. It was discovered that these MOFs aggregate on paper and produce strong chemiluminescence even without the addition of hydrogen peroxide, i.e., only with the addition of bis(2,4,6-trichlorophenyl)oxalate. Compared with existing technologies, the advantages of this invention are as follows:

[0015] 1. The paper-based sensor modified with metal-organic framework material with aggregation-induced emission effect of the present invention has the characteristics of low cost, low environmental pollution, small size and handheld design, and high stability.

[0016] 2. The paper-based sensor modified with metal-organic framework material with aggregation-induced emission effect of the present invention can detect volatile formaldehyde by fluorescence and chemiluminescence detection methods. Both methods have the advantages of high sensitivity, wide linear range and fast response.

[0017] 3. The paper-based sensor of this invention can detect trace amounts of gaseous formaldehyde with good selectivity. This not only provides a new approach for the real-time detection of gaseous formaldehyde, but also enriches and expands the application of metal-organic framework materials with aggregation-induced emission effect on paper substrates.

[0018] 4. This invention is the first to apply metal-organic framework materials with induced emission effect to the field of solid-phase chemiluminescence, and it also performs dual-mode detection for formaldehyde as an analyte. Attached Figure Description

[0019] Figure 1This is an SEM image of the paper-based sensor modified with a metal-organic framework material that exhibits induced light emission in Example 1.

[0020] Figure 2 This is the chemiluminescence analysis curve of the paper-based sensor modified with a metal-organic framework material that has an induced emission effect in Example 2 for detecting volatile formaldehyde.

[0021] Figure 3 This is the chemiluminescence analysis standard curve for detecting volatile formaldehyde using a paper-based sensor modified with a metal-organic framework material that incorporates induced emission effect, as described in Example 2.

[0022] Figure 4 This is the chemiluminescence analysis standard curve for detecting volatile formaldehyde using a paper-based sensor modified with a metal-organic framework material that incorporates induced emission effect, as described in Example 2.

[0023] Figure 5 This is an interference bar chart of the paper-based sensor modified with a metal-organic framework material having aggregation-induced emission effect in Example 2 for detecting volatile formaldehyde.

[0024] Figure 6 This is the fluorescence analysis standard curve of the paper-based sensor modified with a metal-organic framework material that exhibits aggregation-induced emission effect in Example 3 for detecting gaseous formaldehyde. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, but the scope of protection of the present invention is not limited to these embodiments.

[0026] Example 1

[0027] 10 mg (0.0156 mmol) of tetrakis(4-pyridinebiphenyl)ethylene was dissolved in a mixed solvent of 11.25 mL tetrachloroethylene and 3.75 mL methanol, and 8.7 mg (0.0638 mmol) of ZnCl2 was dissolved in 10 mL methanol. The two solutions were then mixed thoroughly and poured into a beaker pre-lined with 5 cm × 5 cm circular Whatman No. 1 filter paper. After standing at room temperature for 3 days, the filter paper was removed and immersed in ethanol for 2 days for activation, with the ethanol being replaced every 4 hours during this period. Finally, the paper was vacuum dried at 80 °C for 12 hours to obtain a paper-based sensor modified with a metal-organic framework material exhibiting aggregation-induced emission. Figure 1 As shown, metal-organic framework materials with aggregation-induced emission effect grow on the paper surface and aggregate along the fibers.

[0028] Example 2

[0029] The paper-based sensor in Example 1 is used for the detection of volatile formaldehyde by chemiluminescence immunoassay. The specific method is as follows:

[0030] The paper-based sensor was cut into 1cm × 1cm circular pieces. To prepare a standard gas of volatile formaldehyde, the liquid formaldehyde concentration was first converted to a percentage, and then to a gaseous formaldehyde concentration. Before using the paper-based sensor to sense gaseous formaldehyde, a slit was cut at the top of a Tedlar bag. Double-sided tape was applied to the side of the paper-based sensor that was not modified with the metal-organic framework. Then, using tweezers, the paper-based sensor was inserted through the slit and attached to the top of the Tedlar bag. The slit was then sealed with tape, and the air in the bag was extracted using a vacuum pump. To accurately prepare volatile formaldehyde, nitrogen gas was blown into a 200 mL Tedlar gas sampling bag to precisely control the gas volume. Then, a series of liquid formaldehyde solutions were injected into the bag without the paper sensor. The Tedlar gas sampling bag was placed at 37°C for 2 hours until the liquid formaldehyde completely evaporated and formed a uniform gaseous formaldehyde, resulting in gaseous formaldehyde concentrations of 1, 2, 4, 6, 8, 10, 20, 40, 60, 80, and 100 ppb in the bag. After 0.5 hours of sensing, the paper sensor was removed from the bag and placed in the detection area of ​​the chemiluminescence analyzer. Then, 2.5 μL of a 5 mmol / L bis(2,4,6-trichlorophenyl)oxalate solution in acetone was dropped onto the paper sensor, and the chemiluminescence signal data was recorded.

[0031] like Figure 2 As shown, within the gaseous formaldehyde concentration range of 1–100 ppb, the chemiluminescence intensity gradually increases with increasing volatile formaldehyde concentration. Figure 3 As shown, when the concentration of gaseous formaldehyde is in the range of 1–10 ppb, the linear equation is I = 51C + 32(R). 2 =0.998). For example... Figure 4 As shown, when the concentration of gaseous formaldehyde is in the range of 10–100 ppb, the linear equation is I = 3C + 505(R). 2 =0.997). According to the 3σ rule, the detection limit of the paper-based sensor in Example 1 for the chemiluminescence method to detect volatile formaldehyde is 0.05 ppb.

[0032] To demonstrate the specific response of the metal-organic framework-modified paper-based sensor of this invention to volatile formaldehyde, acetaldehyde, isopropanol, and toluene at 20 times the concentration, methanol, ethanol, and ammonia at 50 times the concentration, and carbon dioxide, hydrogen sulfide, and acetone at 500 times the concentration were added to 1.5 ppb gaseous formaldehyde as interfering compounds. The paper-based sensor prepared in Example 1 was subjected to chemiluminescence detection according to the above method, and the results are as follows. Figure 5 As shown, the influence of interfering compounds on the measurement signal is negligible, indicating that other volatile organic compounds have no effect on the detection of formaldehyde.

[0033] Example 3

[0034] The paper-based sensor in Example 1 is used for the fluorescence detection of volatile formaldehyde. The specific method is as follows:

[0035] The paper-based sensor was cut into 1cm × 1cm circular pieces. To prepare a standard gas of volatile formaldehyde, the liquid formaldehyde concentration was first converted to a percentage, and then to a gaseous formaldehyde concentration. Before using the paper-based sensor to sense gaseous formaldehyde, a slit was cut at the top of a Tedlar bag. Double-sided tape was applied to the side of the paper-based sensor that was not modified with the metal-organic framework. Then, using tweezers, the paper-based sensor was inserted through the slit and attached to the top of the Tedlar bag. The slit was then sealed with tape, and the air in the bag was evacuated using a vacuum pump. To ensure accurate preparation of volatile formaldehyde, nitrogen gas was blown into a 200mL Tedlar gas sampling bag to precisely control the gas volume. A series of liquid formaldehyde solutions were then injected into the bag without the paper-based sensor. The Tedlar gas sampling bag was placed at 37°C for 2 hours until the liquid formaldehyde completely evaporated and formed a uniform gaseous formaldehyde, resulting in gaseous formaldehyde concentrations of 10, 20, 40, 60, 80, and 100 ppb in the bag. After 0.5 hours of sensing, the paper-based sensor was removed from the bag and fixed in a fluorometer using a solid support. The metal-organic framework-modified paper-based sensor exhibited fluorescence at 360 nm excitation wavelength, further enhanced by formaldehyde, with fluorescence signal data recorded at 530 nm. Figure 6 As shown, within the concentration range of 10–100 ppb, the fluorescence intensity gradually increases with increasing gaseous formaldehyde concentration, and the linear equation is I = 20.3C + 2480.4(R). 2 =0.996). According to the 3σ rule, the detection limit of the paper-based sensor in Example 1 for the fluorescence method to detect volatile formaldehyde is 3.4 ppb.

Claims

1. The application of a paper-based sensor modified with a metal-organic framework material in the detection of trace volatile formaldehyde, wherein the detection method is either fluorescence or chemiluminescence, and the chemiluminescence detection uses a bis(2,4,6-trichlorophenyl)oxalate-hydrogen peroxide chemiluminescence system, without the addition of hydrogen peroxide during detection; wherein, The concentration of bis(2,4,6-trichlorophenyl)oxalate was 5 mmol / L; The paper-based sensor is a metal-organic framework material with aggregation-induced emission effect grown in situ on the surface of a paper matrix. The metal-organic framework material is formed by complexing zinc chloride with tetra(4-pyridinebiphenyl)ethylene in a mixed solvent of tetrachloroethylene and methanol, and its chemical formula is ZnCl2Py-TPE•4(TCE), where Py-TPE represents tetra(4-pyridinebiphenyl)ethylene and TCE represents tetrachloroethylene. The paper-based sensor is prepared by dissolving zinc chloride in methanol and dissolving tetra(4-pyridinebiphenyl)ethylene in a mixed solvent of tetrachloroethylene and methanol in a volume ratio of 3:

1. After the two are mixed evenly, the mixture is transferred to a beaker containing paper matrix and left to stand at room temperature for 1 to 5 days. Then, it is activated by soaking in ethanol for 1 to 5 days, during which the ethanol is replaced every 3 to 6 hours. Finally, it is vacuum dried at 60 to 100°C.

2. The application of the paper-based sensor modified with metal-organic framework material according to claim 1 in the detection of trace volatile formaldehyde, characterized in that, The molar ratio of zinc chloride to tetra(4-pyridinebiphenyl)ethylene is 2:1 to 6:

1.

3. The application of the paper-based sensor modified with metal-organic framework material according to claim 1 in the detection of trace volatile formaldehyde, characterized in that, The paper substrate is Whatman No. 1 filter paper or Whatman No. 3 filter paper.

4. The application of the paper-based sensor modified with metal-organic framework material according to claim 1 in the detection of trace volatile formaldehyde, characterized in that: Let the reaction stand at room temperature for 1 to 5 days.

5. The application of the paper-based sensor modified with metal-organic framework material according to claim 1 in the detection of trace volatile formaldehyde, characterized in that: Activate by soaking in ethanol for 1 to 5 days.

6. The application of the paper-based sensor modified with a metal-organic framework material exhibiting aggregation-induced emission effect according to claim 1 in the detection of trace volatile formaldehyde, characterized in that: The excitation wavelength for fluorescence detection is 250–500 nm, and the detection wavelength is 375–700 nm.

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