A method for preparing CuI-based fluorescent probe material for gas sensors

Abstract

A method for preparing CuI-based fluorescent probe materials for gas sensors is disclosed. The synthesized CuI-based polymer crystal has the following simplified structure: {[(Cu4I4)(3-bpah)2]·3CHCl3·MeCN}n, where 3-bpah is N,N'-bis(3-pyridinecarboxamide)-1,2-cyclohexane. The synthesized crystal emits strong green phosphorescence with an internal quantum yield of 53.6%. After solvent removal via vacuum treatment at room temperature, a CuI-based fluorescent probe with an internal quantum yield of 7.46% is obtained. The probe is prepared by reacting CuI, 3-bpah, ethanol, acetonitrile, distilled water, and chloroform under diffusion conditions. The derived nanofiber composite membrane is obtained using polyacrylonitrile (PAN) and the CuI-based fluorescent probe via electrospinning. The CuI-based fluorescent probe can be used for sensing volatile organic gases, and its derived nanofiber composite membrane is used for the rapid detection of toluene.

Description

Technical Field

[0001] This invention relates to a method for preparing a gas sensor probe material, and more particularly to a method for preparing a CuI-based fluorescent probe material for a gas sensor. Background Technology

[0002] Volatile organic compounds (VOCs) refer to organic compounds that are easily volatilized at room temperature. They are widely present in many industries and daily life, including chemical, printing, coating, paint, cleaning agents, and automobile exhaust. When VOCs are emitted into the atmosphere, they participate in photochemical reactions, reacting with pollutants such as nitrogen oxides under sunlight to generate photochemical smog, which is harmful to the environment and human health. Photochemical smog can trigger respiratory diseases such as asthma and allergic rhinitis, and negatively impact plant growth. Short-term exposure to high concentrations of VOCs may cause strong irritation to the eyes, nose, and throat, as well as discomfort such as headaches, dizziness, and nausea. Long-term or chronic exposure to VOCs can have adverse effects on organs and systems such as the respiratory, nervous, and liver systems, and is closely related to health problems such as certain cancers, allergic reactions, and reproductive issues. Currently, gas chromatography remains the primary detection technology for VOCs pollutants, but this method still has some insurmountable drawbacks, such as the large and expensive size of the instruments, the difficulty of operation, and the complexity of sample transportation and handling.

[0003] CuI-based fluorescent probes, as emerging fluorescent materials, possess advantages such as low cost, excellent stability, rapid and sensitive sensing, and reusability. Their high fluorescence efficiency has also made them a focus of attention in the field of chemical sensors. However, to date, there are no reports on the use of CuI-based materials for sensing VOCs of different polarities, or for the detection of toluene by their derivatives. Summary of the Invention

[0004] This invention provides a method for preparing CuI-based fluorescent probe materials for gas sensors, a method for preparing CuI-based fluorescent probe materials and their derivatives, and their applications. The fluorescent probe materials exhibit strong sensitivity and stability for sensing VOCs of different polarities, and their derivatives demonstrate high sensitivity and stability for detecting toluene. Furthermore, the preparation method is simple, low-cost, low-polluting, provides rapid and sensitive detection, and is easy to operate.

[0005] The technical solution adopted in this invention is as follows:

[0006] A method for preparing CuI-based fluorescent probe material for a gas sensor, the method comprising the following preparation steps:

[0007] (a) Dissolve the ligand 3-bpah (0.2 mmol) in a small vial containing chloroform (4 mL) and anhydrous ethanol (2 mL), and add distilled water (1 mL) as another layer;

[0008] (ii) Slowly add a CuI (0.1 mmol) solution in acetonitrile (2 mL) to a vial; keep the reaction mixture at room temperature and allow it to form colorless, blocky, transparent single crystals after 96 hours; collect the crystals by scraping.

[0009] (iii) The yellow prismatic crystals obtained in step (ii) are filtered, washed, ground, and vacuum dried to obtain powdered CuI-based fluorescent probe material (solvent-free CP 2);

[0010] (iv) Mix the solvent-free CP 2 (0.5 g) and polyacrylonitrile (PAN) (0.5 g) from step (iii) and place them in a vial containing 5 mL of N,N-dimethylformamide (DMF). Maintain the temperature at 60 °C and stir for 6 hours. Finally, use electrospinning technology to obtain a nanofiber composite membrane.

[0011] The structural formula of the CuI-based fluorescent probe material is: {[(Cu4I4)(3-bpah)2]·3CHCl3·MeCN}n (CP2). 3-bpah is N,N'-bis(3-pyridinecarboxamide)-1,2-cyclohexane; the crystalline compound is monoclinic, crystallized in space group P1 21 / c 1, with unit cell parameters a = 24.0552(16) Å, b = 9.5569(6) Å, c = 25.9626(17) Å, α = 90 º, β = 90.2(2) º, γ = 90 º, Z = 4, V = 5968.6(7) Å3;

[0012] CuI-based fluorescent probe materials are used as fluorescent sensors to detect volatile organic compounds (VOCs) of different polarities and to rapidly detect low concentrations of toluene in the air.

[0013] The method for preparing CuI-based fluorescent probe material for gas sensors involves placing the CuI-based fluorescent probe material under 365 nm ultraviolet light irradiation in a moderately polar VOCs atmosphere. The fluorescence color of the fluorescent probe rapidly shifts from yellow to blue to bright green. When placed in a weakly polar or non-polar VOCs atmosphere, the fluorescence color rapidly shifts from yellow to blue to bright blue (moderately polar volatile organic compounds include chloroform, dichloromethane, and acetone; weakly polar or non-polar volatile organic compounds include toluene, hexane, and cyclohexane). The probe exhibiting fluorescence color change recovers its initial fluorescence after vacuum drying and can be reused.

[0014] The method for preparing CuI-based fluorescent probe material for gas sensors involves doping the probe with polyacrylonitrile polymer and then preparing a nanofiber composite membrane by electrospinning for rapid detection of toluene in the air. Furthermore, the material can be reused after vacuum treatment. Attached Figure Description

[0015] Figure 1 Here is the molecular structure diagram of CP2;

[0016] Figure 2 PXRD diffraction patterns of single-crystal CP2 and CuI-based fluorescent probe (solvent-free CP2);

[0017] Figure 3 Mapping diagram for single-crystal CP 2;

[0018] Figure 4 This is the X-ray diffraction pattern of a CuI-based fluorescent probe;

[0019] Figure 5 Thermogravimetric analysis diagram of CP 2;

[0020] Figure 6 Fluorescence spectra, CIE color gamut information, and internal quantum yield of CP2 and CuI-based fluorescent probes under 365 nm ultraviolet light irradiation;

[0021] Figure 7 The emission gamut, fluorescence emission spectrum, and internal quantum yield of CuI-based fluorescent probes in chloroform and toluene under VOC atmospheres of different polarities are shown.

[0022] Figure 8 PXRD diffraction patterns of CuI-based fluorescent probes in chloroform and toluene atmospheres;

[0023] Figure 9 Infrared spectra of a composite membrane containing ligand 3-bpah, CuI-based fluorescent probe, polyacrylonitrile (PAN), and derivative nanofibers.

[0024] Figure 10 SEM and mapping spectra of the derivative nanofiber composite membrane;

[0025] Figure 11 The fluorescence emission patterns, detection limit linearity, and luminescence color gamut of the composite membrane under different toluene contents in the air were obtained for the derivative nanofiber composite membrane. Detailed Implementation

[0026] The present invention will now be described in detail with reference to specific embodiments and accompanying drawings. These embodiments are based on the technical solutions of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments. In the embodiments, the original or processing technology used is a conventional commercially available product or conventional processing technology in the art.

[0027] This invention discloses a CuI-based fluorescent probe material, {[(Cu4I4)(3-bpah)2]·3CHCl3·MeCN}n (CP2). Wherein 3-bpah is N,N'-bis(3-pyridinecarboxamide)-1,2-cyclohexane. The crystal characteristics are: the compound is monoclinic, crystallizing in P1 21 / c 1, with unit cell parameters a = 24.0552(16) Å, b = 9.5569(6) Å, c = 25.9626(17) Å, α = 90 º, β = 90.2(2) º, γ = 90 º, Z = 4, V = 5968.6(7) Å3;

[0028] A typical method for preparing CuI-based fluorescent probe materials includes the following steps:

[0029] Step (1): Dissolve the ligand 3-bpah (0.2 mmol) in a small vial containing chloroform (4 mL) and anhydrous ethanol (2 mL), and carefully add distilled water (1 mL) as another layer;

[0030] Step (II): A CuI (0.1 mmol) solution in acetonitrile (2 mL) was slowly added to the vial. The reaction mixture was kept at room temperature, and after 96 hours, colorless, blocky, transparent single crystals of CP2 formed. The reaction mixture was collected by filtration, with a CuI-based crystal yield of 63%.

[0031] Step (3): The colorless blocky crystals obtained in Step (2) are filtered, washed, ground, and vacuum dried to obtain yellow powdered CuI-based fluorescent probe material (solvent-free CP 2);

[0032] Step (IV): Mix the solvent-free CP 2 (0.5 g) from step (III) with polyacrylonitrile (PAN) (0.5 g) and place it in a vial containing 5 mL of N,N-dimethylformamide (DMF). Maintain the temperature at 60 °C and stir for 6 hours. Finally, use electrospinning technology to obtain a nanofiber composite membrane with VOCs detection function.

[0033] In step (1), the volume ratio of chloroform to anhydrous ethanol is 2:1.

[0034] In step (ii), the molar ratio of cuprous iodide to ligand is 1:2.

[0035] The volume of distilled water added in step (II) is 1 mL, and it should be added in small batches.

[0036] The reaction time in step (ii) is 96 hours.

[0037] In step (iii), the vacuum drying temperature is room temperature.

[0038] In step (iv), the mass ratio of solvent-free CP 2 to polyacrylonitrile (PAN) is 1:1.

[0039] In step (iv), the mass ratio of solution-free CP 2 to polyacrylonitrile (PAN) in the vial is 1:1.

[0040] In step (iv), the electrospinning temperature is 25 ℃, the spinning humidity is 16%, the applied positive voltage is 10.0 ~ 15.0 kV, and the applied negative voltage is -2.0 ~ -0.5 kV. The volume of DMF solvent used is 5.0 mL.

[0041] Figure 1 The molecular structure is CP 2, in which copper and iodine adopt a tetrameric configuration similar to cuboethane, and 3-bpah forms a tetranuclear cuprous iodide polymer through copper-nitrogen covalent bonds;

[0042] Figure 2 The PXRD diffraction patterns of single-crystal CP 2 and CuI-based fluorescent probe (solvent-free CP 2) are shown. The diffraction peaks of the synthesized crystal almost overlap with the simulated pattern, while the diffraction peaks of the CuI-based fluorescent probe shift after losing the solvent.

[0043] Figure 3 The mapping diagram of single-crystal CP2 shows that chloroform participated in crystal formation;

[0044] Figure 4 This is the X-ray diffraction pattern of a CuI-based fluorescent probe, containing elements such as Cu, I, C, N, and O; the copper element is in the +1 valence.

[0045] Figure 5 The thermogravimetric analysis (TGA) plot of CP2 shows a mass loss of approximately 7% at 100 °C, attributed to the evaporation of acetonitrile and chloroform in CP2. A sharp mass drop begins at 325 °C, attributed to the collapse of the solvent-free CP2 framework and the initiation of ligand degradation.

[0046] Figure 6The fluorescence spectra, CIE color gamut information, and internal quantum yields of CP₂ and CuI-based fluorescent probes under 365 nm UV irradiation are presented. CP₂ emits strong green light near 510 nm, with color coordinates calculated according to CIE 1931 as (0.2808, 0.5136), and an internal quantum yield of 53.22%. The CuI-based fluorescent probe emits warm yellow light near 560 nm, with color coordinates of (0.3652, 0.4453), and an internal quantum yield of 7.46%.

[0047] Figure 7 The emission gamut, fluorescence emission spectrum, and internal quantum yield of CuI-based fluorescent probes in VOC atmospheres of different polarities are shown. In moderately polar VOCs (chloroform, dichloromethane, acetone), the emission gamut of CuI-based fluorescent probes is in the green region, with emission wavelengths between 500-510 nm; in weakly polar or non-polar VOC gases (toluene, hexane, cyclohexane), the emission gamut of CuI-based fluorescent probes is in the blue region, with emission wavelengths between 460-480 nm; in a chloroform atmosphere, the internal quantum yield of the probe increases from the initial 7.46% to 18.58%, and in a toluene atmosphere, the internal quantum yield surges from 7.46% to 28.00%.

[0048] Figure 8 The images show the PXRD diffraction patterns of a CuI-based fluorescent probe in chloroform and toluene atmospheres. It can be seen that under the influence of a weakly polar volatile gas (toluene), the PXRD diffraction peaks of the probe show significant recovery, indicating that the probe's crystal phase and crystallinity have been restored. Under the influence of a moderately polar volatile gas (chloroform), the crystal phase recovery is poor, but the crystallinity is restored to some extent.

[0049] Figure 9 The image shows the infrared spectrum of a composite film containing ligand 3-bpah, CuI-based fluorescent probe, polyacrylonitrile (PAN), and derivative nanofibers. The characteristic peaks in the image clearly indicate successful doping of the derivative.

[0050] Figure 10 The SEM and mapping spectra of the derivative nanofiber composite film show that the fiber diameter is around 300 nm, and the CuI-based fluorescent probe is uniformly attached to the nanofiber surface.

[0051] Figure 11The fluorescence emission patterns, detection limits, and color gamut of the composite membrane under different toluene concentrations in the air were determined for the derivative nanofiber composite membrane. Keeping the fluorescence testing conditions constant, the fluorescence intensity of the composite membrane in contact with mixed gases of different toluene concentrations was rapidly measured. The graph shows a blue shift in the fluorescence of the composite membrane, and the fluorescence intensity increases with increasing toluene concentration. A good linear enhancement relationship was observed within the toluene concentration range of 0.5–1.0 μL / L in the air. Example 1

[0052] A method for preparing a CuI-based fluorescent probe includes the following steps:

[0053] Commercially available cuprous iodide and N,N'-bis(3-pyridinecarboxamide)-1,2-cyclohexane (3-bpah) were used as reactants, polyacrylonitrile (PAN) was used as spinning material, and anhydrous ethanol, DMF, acetonitrile, chloroform and distilled water were used as reactants or solvents.

[0054] The CuI-based material synthesized in this invention exhibits strong fluorescence and a high internal quantum yield of 53.22%. Even after solvent-free CP2 loses its solvent, it still displays yellow fluorescence with an internal quantum yield of 7.46%. The CuI-based fluorescent probe demonstrates the ability to identify and sense VOCs of different polarities. The prepared nanofiber composite membrane exhibits excellent detection performance for toluene in the air. Compared with existing detection methods (gas chromatography analysis), it demonstrates speed, convenience, and high sensitivity. Furthermore, the preparation method is simple, low-cost, low-polluting, and easy to operate, and all the materials can be reused.

[0055] Synthesis step (1): Dissolve the ligand 3-bpah (0.2 mmol) in a small vial containing chloroform (4 mL) and anhydrous ethanol (2 mL), and carefully add distilled water (1 mL) as another layer;

[0056] Synthesis Step (II): A CuI (0.1 mmol) solution in acetonitrile (2 mL) was slowly added to a vial. The reaction mixture was kept at room temperature, and after 72 hours, colorless, blocky, transparent single crystals of CP2 were formed. The reaction mixture was collected by filtration, with a CuI-based crystal yield of 63%.

[0057] Synthesis Step (3): The colorless bulk crystals obtained in Step (2) were filtered, washed, ground, and vacuum dried to obtain a yellow powdered CuI-based fluorescent probe material (solvent-free CP 2);

[0058] Synthesis step (four): The solvent-free CP 2 (0.5 g) from step (three) was mixed with polyacrylonitrile (PAN) (0.5 g) and placed in a vial containing 5 mL of N,N-dimethylformamide (DMF). The mixture was kept at 60 °C and stirred for 6 hours. Finally, the nanofiber composite membrane with VOCs detection function was obtained by electrospinning. Example 2

[0059] Performance testing of CuI-based fluorescent probe

[0060] 1. Photoluminescence performance test

[0061] The photoluminescence properties of the prepared CP 2, vacuum-treated CuI-based fluorescent probe, and derivative nanofiber composite film were tested on an F-4600 FL Spectrophotometer, with the slit width maintained at 5 nm. The internal quantum yield of the CP 2 and vacuum-treated CuI-based fluorescent probe was tested using an FS5 Spectrofluorometer. The fluorescence lifetime of the CP 2 and vacuum-treated CuI-based fluorescent probe was tested using The Edinburgh Instruments FS-C05, and the tests showed that the lifetime of emission at the corresponding position was in the microsecond range, proving that it was phosphorescent emission.

[0062] 2. Sensing and identification of VOCs of different polarities

[0063] After thoroughly grinding the vacuum-treated CuI-based fluorescent probe, a small amount was placed in a solid fluorescence test cell. 0.5 mL of organic volatile liquids of different polarities were added (chloroform, dichloromethane, and acetone for moderately polar organic volatile liquids; toluene, hexane, and cyclohexane for weakly polar or non-polar organic volatile liquids). The sample was kept under saturated vapor pressure and covered with a glass slide. Throughout the fluorescence sensing test, the sample cell remained stationary, the spectral test conditions remained consistent, and the slit width was 5 nm. After vacuum treatment of the CuI-based fluorescent probe with altered fluorescence, the fluorescence color could be restored.

[0064] 3. Toluene detection in derivative nanofiber composite membranes

[0065] Six nanofiber composite membranes of relatively uniform thickness were cut into pieces similar in size to the solid sample cell. These membranes were carefully laid flat in the solid sample cell and covered with a glass slide, allowing for similar fluorescence data to be measured. Toluene was then pipetted into syringes at concentrations of 0.5, 0.6, 0.7, 0.8, 0.9, and 1.0 μL, respectively. After thorough mixing with air in the syringe, the syringe tip was kept 1 cm away from the composite membrane. The plunger was quickly pushed to rapidly spray the mixed gas onto the composite membrane surface. The membrane was then quickly covered with a glass slide, and the fluorescence intensity was rapidly measured. Figure 11 It can be seen that the prepared nanofiber composite membrane has linear detection results for toluene in the range of 0.5-1.0 μL / L.

Claims

1. A method for preparing CuI-based fluorescent probe material for gas sensors, characterized in that, The method includes the following preparation process: (a) Dissolve 0.2 mmol of ligand 3-bpah in a small vial containing 4 mL of chloroform and 2 mL of anhydrous ethanol, and add 1 mL of distilled water as another layer; (ii) Slowly add a solution of 0.1 mmol CuI and 2 mL acetonitrile into a vial; keep the reaction mixture at room temperature, and after 96 hours, a colorless, blocky, transparent single crystal will form; (iii) The colorless block crystals obtained in step (ii) are filtered, washed, ground, and vacuum dried to obtain yellow powder CuI-based fluorescent probe material; (iv) Mix 0.5 g of powdered CuI-based fluorescent probe material from step (iii) with 0.5 g of polyacrylonitrile and place it in a vial containing 5 mL of N,N-dimethylformamide. Maintain 60°C and stir for 6 hours. Finally, use electrospinning technology to obtain a nanofiber composite membrane. The structural formula of CuI-based fluorescent probe materials is: {[(Cu₄I₄)(3-bpah)₂]·3CHCl₃·MeCN} n (CP 2); where 3-bpah is N,N'-bis(3-pyridinecarboxamide)-1,2-cyclohexane; the crystalline compound is monoclinic, crystallizing in space group P1 21 / c 1, with unit cell parameters a = 24.0552(16) Å, b = 9.5569(6) Å, c = 25.9626(17) Å, α = 90 o , β = 90.2(2) o , γ = 90 o Z = 4, V = 5968.6(7) Å 3 ; CuI-based fluorescent probe materials are used as fluorescent sensors to detect volatile organic compounds (VOCs) of different polarities and to rapidly detect low concentrations of toluene in the air.

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