A protonated guanidinium group-containing molecular material, a complex, and preparation and application thereof

Abstract

The present application relates to a kind of containing protonated guanidino group structure molecular material, complex and its preparation and application, mainly utilize guanidino group aromatic hydrocarbon structure as base, by guanidino functional group protonation obtains high activity ionic type sensitive material, and with carbon nanotube is non-covalent combination and forms composite film, forms chemical resistance type sensor, and with the carbon nanotube composite sensing film as core constructs chemical resistance type gas sensor, can realize SO2 capture and sensing, it is expected to be used to improve the detection sensitivity and detection limit of sulfur dioxide sensor.

Description

Technical Field

[0001] This invention belongs to the field of sensing materials, and specifically relates to a protonated guanidine group-containing molecular material, composite, and its preparation and application. Background Technology

[0002] Sulfur dioxide is a common hazardous pollutant in workplace air. Traditional sulfur dioxide collection methods include solution absorption, with commonly used absorbent solutions including sodium bisulfite (NaHSO3), sodium thiosulfate (Na2S2O3), or potassium iodide (KI) solution. Subsequent analytical methods include spectrophotometry, electrochemical methods, chromatography, chemiluminescence, and capillary electrophoresis. Solution absorption is relatively inexpensive and simple to operate, making it suitable for sulfur dioxide monitoring in various environments. However, this method is limited by its suitability for real-time or continuous monitoring and its complexity, requiring large-scale chemical detection instruments for testing, processing, and analysis.

[0003] The national occupational health standard testing methods are formaldehyde buffer solution, pararosaniline hydrochloride spectrophotometric method, and potassium tetrachloromercurate, pararosaniline hydrochloride spectrophotometric method. Although these two methods are accurate and reliable, they require the use of highly toxic formaldehyde or the highly toxic chemical mercuric chloride. Furthermore, they necessitate sample collection with an absorption solution, followed by bringing the samples back to the laboratory for spectrophotometric analysis. The color development process is subject to strict requirements regarding time and temperature. Moreover, when dealing with a large number of samples, spectrophotometry is insufficient to meet quality requirements, and the operation is complex and inefficient.

[0004] Therefore, using gas sensors has become an effective method for real-time detection of sulfur dioxide. Traditional metal-oxide-semiconductor (MODS) chemiluminescence resistivity sensors (COSTS) lack specificity, making it difficult to distinguish certain common gases such as SO2 and NO2; furthermore, their high operating temperature prevents them from operating at room temperature, resulting in extremely high power consumption, which is unsuitable for the real-time monitoring requirements of the Internet of Things (IoT). Currently, commercially available sulfur dioxide sensors mainly include the SO2-BF sulfur dioxide sensor from Alphasense (UK) and the FECS43-20 gas sensor from Figaro (Japan). The SO2-BF sulfur dioxide sensor has a detection limit of 20 ppm, while the FECS43-20 gas sensor has a detection limit of 0.5 ppm for sulfur dioxide. Existing sulfur dioxide sensors still struggle to achieve high sensitivity detection of SO2 at the ppb level. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a protonated guanidine-based molecular material, composite material, preparation and application thereof, and in particular, it relates to a material and preparation method of a composite sensing film of protonated guanidine-based molecular material and carbon nanotube.

[0006] The present invention discloses a guanidine-containing compound, wherein the compound has an aromatic ring structure as the main structure, and a guanidine group or a guanidine-derived functional group is connected to the aromatic ring structure in the form of more than one substitution site.

[0007] The aromatic ring structure serves as the main structure and is used as the substitution site for constructing guanidine groups and their derived functional groups.

[0008] The aromatic ring structure includes, but is not limited to,

[0009]

[0010] One or more of them.

[0011] The structural formula is:

[0012]

[0013] The side chain substituents R1 to R8 are one or more of the following groups A1 to A12, where n is an integer from 0 to 20, and further n is from 1 to 20;

[0014] A1 = —H;

[0015] A2=—O(CH2) n CH3;

[0016] A3 = —(CH2) n CH3;

[0017] A4 = —(CH2) n CH(CH3)2;

[0018]

[0019]

[0020] The present invention provides a probe molecule comprising an anion and a protonated compound thereof; wherein the protonation is a protonated guanidine group.

[0021] Preferably, the negative ion is a negative ion with strong electron-withdrawing properties.

[0022] Preferably, the negative ion is one or more of tetrafluoroborate ion, chloride ion, hexafluorophosphate ion, and bis(trifluoromethanesulfonyl)imide ion.

[0023] Preferably, the probe is a negative ion and the protonated compound in a molar ratio of 1:1 to 1:2.

[0024]

[0025] The present invention provides a method for preparing a probe molecule, comprising: reacting an acid with strong electron-withdrawing properties with a molecule having a guanidine group and performing an ion exchange process to obtain the target probe molecule.

[0026] The present invention provides a sensing material comprising any one of the aforementioned probes and carbon nanotubes. The mass ratio of the probe to the carbon nanotubes is 10:1 to 1:1.

[0027] Furthermore, the sensing material is a composite of probe molecules and carbon nanotubes.

[0028] Preferably, the carbon nanotubes are one or more of single-walled carbon nanotubes, double-walled carbon nanotubes, and multi-walled carbon nanotubes.

[0029] A method for preparing a sensing material according to the present invention includes: mixing any of the probe molecules and carbon nanotubes, and then ultrasonicating them to make them composite.

[0030] The ultrasound duration is 10-30 minutes.

[0031] The present invention provides a sensing film, wherein the sensing film is a thin film material formed from the sensing material.

[0032] The present invention provides a method for preparing a sensing thin film, comprising: preparing a precursor solution of the sensing material, coating the precursor solution, and evaporating the solvent to obtain the sensing thin film.

[0033] The precursor solution of the sensing material is prepared by combining probe molecules and carbon nanotubes with ultrasound to obtain the precursor solution.

[0034] The sensing material is a composite of probe molecules and carbon nanotubes.

[0035] The solvent of the precursor solution is one or more of toluene, xylene, chlorobenzene, dimethylformamide, dimethyl sulfoxide, and N-methylpyrrolidone.

[0036] The present invention provides a sensor, the sensor comprising a sensor element and a sensing film; wherein the sensing film is loaded on the surface of the sensor element; wherein the sensor element is an electrode.

[0037] The present invention provides a method for preparing a sensor, comprising: preparing a precursor solution of the sensing material, coating it on the surface of a sensor element (such as an electrode), and obtaining the sensor after the solvent evaporates.

[0038] The solvent of the precursor solution is one or more of toluene, xylene, chlorobenzene, dimethylformamide, dimethyl sulfoxide, and N-methylpyrrolidone; the volatilization is volatilization in a vacuum.

[0039] The precursor solution of the sensing material is a precursor solution of probe molecules and carbon nanotube composites.

[0040] This invention provides an application of the sensing material or the sensor in the detection of sulfur dioxide (SO2) gas, such as sulfur dioxide gas molecules in the air.

[0041] This invention discloses an SO2 sensor material and its preparation method based on a protonated guanidine aromatic molecule and a carbon nanotube composite film. It primarily utilizes guanidine aromatic hydrocarbon structures, represented by 1,8-bis(tetramethylguanidine)naphthalene, as a substrate. A highly active ionic sensitive material is obtained by protonating the guanidine functional groups, and then non-covalently bonded with carbon nanotubes to form a composite film, creating a chemielectric resistive sensor. This carbon nanotube composite sensing film serves as the core to construct a chemielectric resistive gas sensor, enabling SO2 capture and sensing. This technology holds promise for improving the detection sensitivity and detection limit of sulfur dioxide sensors.

[0042] Beneficial effects

[0043] This invention utilizes a guanidine aromatic hydrocarbon structure (represented by 1,8-bis(tetramethylguanidine)naphthalene) as a substrate. By protonating the guanidine functional group, a highly active ionic sensitive material is obtained, which is then non-covalently bonded with carbon nanotubes to form a composite film. In other words, after this type of probe molecule effectively functionalizes the carbon nanotubes, which serve as the electrical carrier, a chemielectric resistivity sensor is formed. A chemielectric resistivity gas sensor is constructed with this carbon nanotube composite sensing film as the core. In a normal temperature atmospheric environment, it can achieve high sensitivity and high selectivity for sulfur dioxide sensing and is not easily affected by interference from other gases.

[0044] This invention improves the detection sensitivity and detection limit of sulfur dioxide sensors. Attached Figure Description

[0045] Figure 1 The image shows the 1H NMR spectrum of 1,8-bis(tetramethylguanidine)naphthalene in CDCl3. 1 H NMR (600MHz, Chloroform-d) δ7.33–7.26(m,1H),7.19(t,J=7.3Hz,1H),6.37(d,J=7.2Hz,1H),2.68(d,J=41.7Hz,12H);

[0046] Figure 2 The image shows the 1H NMR spectrum of 1,8-bis(tetramethylguanidine)naphthalene-tetrafluoroborate in CDCl3. 1 H NMR (600MHz, Chloroform-d) δ7.36 (s, 1H), 7.28 (s, 1H), 6.40 (d, J = 7.4Hz, 1H), 2.94 (s, 13H);

[0047] Figure 3 Comparison of 1,8-bis(tetramethylguanidine)naphthalene and 1,8-bis(tetramethylguanidine)naphthalene-tetrafluoroborate 1H NMR spectra;

[0048] Figure 4 Here is a picture of the actual sensor electrode;

[0049] Figure 5 A scanning electron microscope image of a thin film formed by drop-coating 1,8-bis(tetramethylguanidine)naphthalene-tetrafluoroborate and single-walled carbon nanotubes onto a sensing electrode.

[0050] Figure 6 Infrared spectral analysis of the composite film of 1,8-bis(tetramethylguanidine)naphthalene-tetrafluoroborate and single-walled carbon nanotubes before and after sulfur dioxide sensing.

[0051] Figure 7 The graph shows the change in the sensing signal of sulfur dioxide for the composite film of 1,8-bis(tetramethylguanidine)naphthalene and single-walled carbon nanotubes.

[0052] Figure 8 The graph shows the change in the sensing signal of sulfur dioxide for the composite film of 1,8-bis(tetramethylguanidine)naphthalene-tetrafluoroborate and single-walled carbon nanotubes.

[0053] Figure 9 The sensor device prepared by 1,8-bis(tetramethylguanidine)naphthalene-tetrafluoroborate and single-walled carbon nanotube composite film exhibits selective sensing response to different gases at the same concentration (8 ppm). Detailed Implementation

[0054] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0055] Example 1

[0056] Synthesize 1,8-bis(tetramethylguanidine)naphthalene ionic liquid and carry out ion exchange process.

[0057] The steps are as follows: Under ice bath conditions, 177 mg of 1,8-bis(tetramethylguanidine)naphthalene (0.5 mmol) was dissolved in 20 mL of ethanol solution and stirred thoroughly. 70 μL of 98% fluoroboric acid aqueous solution (1.1 mmol) was added dropwise, and the mixture was stirred in an ice bath for 24 h to obtain a colorless and transparent solution. The solvent was removed by rotary evaporation, and the solution was vacuum dried at room temperature for 48 h to obtain a gray powdery solid, which is a 1,8-bis(tetramethylguanidine)naphthalene-tetrafluoroborate ionic liquid. The NMR spectrum was [missing value]. Figure 2 As shown, 1 ¹H NMR (600MHz, Chloroform-d) δ 7.36 (s, 1H), 7.28 (s, 1H), 6.40 (d, J = 7.4Hz, 1H), 2.94 (s, 13H), compared with the ¹H NMR spectrum of the raw material. Figure 3 As shown.

[0058] Example 2

[0059] Preparation of SO2 sensor thin films composed of small molecule ionic liquids and carbon nanotubes

[0060] Sensor electrodes were fabricated using a standard lift-off process on a 4-inch silicon wafer to create a 4mm × 8mm sensor device. A physical image is shown below. Figure 4 As shown, a 20 ml solution of 1 mg / ml TMGN-BF4 was prepared; 0.2 mg of single-walled carbon nanotube (SWCNT) powder was added to the solution, and the mixture was sonicated for 30 min to prepare an SO2 sensor precursor solution of SWCNTs-TMGN-BF4. Then, 2 μl of the solution was dropped onto each electrode, and after the solution evaporated in a vacuum, several thin-film-based SO2 chemical resistance sensors were fabricated. These sensors are characterized by a sensing film on the electrode surface, with two pins below for connecting to an external circuit.

[0061] Scanning electron microscope image of 1,8-bis(tetramethylguanidine)naphthalene-tetrafluoroborate composite with single-walled carbon nanotubes after drop-coating, as shown below. Figure 5 As shown.

[0062] Example 3

[0063] Infrared characterization of SO2 sensor thin film composed of small molecule ionic liquid and carbon nanotube composite

[0064] exist Figure 6 In the study, the sensing film of the 1,8-bis(tetramethylguanidine)naphthalene-tetrafluoroborate and single-walled carbon nanotube composite was characterized by infrared spectroscopy before and after sensing SO2, showing a spectral density of 10¹³ cm⁻¹. -1 Vibration of the BF bond at position 1060–1320 cm -1 CN vibration at position, 1460–1550 cm -1The NH vibration at the position demonstrates the crucial role of the protonated guanidine structure in the sensing process.

[0065] Example 4

[0066] Chemical resistance sensor testing

[0067] 4.1 Preparation of sulfur dioxide gas

[0068] At 25℃, a 50ml glass syringe was used to extract 50ml of SO2 gas from a commercially available 200ppm SO2 standard gas sample. 40ml of the extracted SO2 gas was used as the test sample for this concentration. 40ml of clean air was added and mixed with the remaining 10ml of SO2 gas in the syringe to achieve a five-fold dilution of the gas concentration, resulting in a 40ppm SO2 gas sample. This method was used to obtain the 200ppm-12.8ppb SO2 gas required for detection.

[0069] 4.2 Sensor Device Setup

[0070] For SO2 sensing testing, a Keysight 34461A digital multimeter was used. At 25°C, 40 ml of SO2 gas of various concentrations obtained in Example 4.1 was injected uniformly at a flow rate of 60 ml / min into a relatively sealed test chamber using a glass syringe. The resistance signal changes during the SO2 adsorption process were collected using the digital multimeter. The gas concentration changes can be monitored through the resistance signal. The time curve of the resistance signal change is shown below. Figure 7 As shown, the concentration of sulfur dioxide gas that could be directly detected was as low as 12.8 ppb.

[0071] 4.3 Selectivity Testing of Protonated Guanidine Aromatic Hydrocarbon Structured Single-Walled Carbon Nanotube Composite Thin-Film Sensor

[0072] This invention detects several typical sulfur dioxide gaseous interfering substances: nitrogen dioxide, hydrogen sulfide, carbon monoxide, carbon dioxide, etc. The response is as follows: Figure 8 As shown, for different gases at the same concentration of 8 ppm, the SWCNTs-TMGN-BF4 sensing film has the highest response value for sulfur dioxide, proving that it has a significant specific sensing effect for sulfur dioxide gas.

Claims

1. A compound containing a guanidine group, characterized in that, The structural formula of the guanidine-containing compound is as follows: ； Wherein, the side chain substituents R1~R8 are one or more of A3 and A4 groups, where n is an integer from 1 to 20; and where A3 = —(CH2). n CH3; A4 = —(CH2) n CH(CH3)2.

2. A probe, characterized in that, The probe comprises an anion and a protonated compound of claim 1; wherein the protonation is a protonated guanidine group; wherein the anion is one or more of tetrafluoroborate ion, chloride ion, hexafluorophosphate ion, and bis(trifluoromethanesulfonyl)imide ion.

3. The probe according to claim 2, characterized in that, The probe is 。 4. A sensing material, characterized in that, The sensing material comprises the probe and carbon nanotubes as described in any one of claims 2-3; wherein the carbon nanotubes are one or more of single-walled carbon nanotubes, double-walled carbon nanotubes, and multi-walled carbon nanotubes.

5. A method for preparing a sensing material, comprising: The probe molecules described in any one of claims 2-3 and carbon nanotubes are mixed and ultrasonically composited. The carbon nanotubes mentioned therein are one or more of single-walled carbon nanotubes, double-walled carbon nanotubes, and multi-walled carbon nanotubes.

6. A sensing thin film, characterized in that, The sensing film is a thin film material formed from the sensing material described in claim 4.

7. A method for preparing a sensing thin film, comprising: Prepare a precursor solution of the sensing material according to claim 4, coat it, and allow the solvent to evaporate to obtain a sensing film.

8. The preparation method according to claim 7, characterized in that, The solvent of the precursor solution is one or more of toluene, xylene, chlorobenzene, dimethylformamide, dimethyl sulfoxide, and N-methylpyrrolidone.

9. A sensor, characterized in that, The sensor includes a sensor element and the sensing film of claim 6; wherein the sensing film is loaded on the surface of the sensor element.

10. The application of the sensing material of claim 4, the sensing film of claim 6, or the sensor of claim 9 in the detection of sulfur dioxide gas.

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