An organic small molecule modified based on green natural products, its preparation method and application in the viscosity detection of metal cleaning agents

Abstract

The present invention relates to the field of photophysical molecular detection technology, and provides an organic small molecule modified based on green natural products, a preparation method thereof, and an application in the viscosity detection of metal cleaning agents. The organic small molecule provided by the present invention is obtained by condensing a strong electron-donating group triphenylamine derivative and a natural cinnamaldehyde derivative, which is green and environmentally friendly, and has a simple preparation method and low energy consumption in the process, meeting the social concept of low-carbon development; the fluorescence intensity of the organic small molecule can increase with the increase of the viscosity of the metal cleaning agent, and then the physical viscosity of the metal cleaning agent can be judged by the strength of the apparent fluorescence signal, realizing the visual detection of the viscosity of the metal cleaning agent; by using the organic small molecule of the present invention, the micro-region viscosity of the metal cleaning agent can be tested, different types of metal cleaning agents can be distinguished, providing necessary reference for the formulation of metal cleaning agents, and at the same time, the wetting effect of metal cleaning can be indirectly predicted and judged, having broad application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of photophysical analysis and detection, and in particular to an organic small molecule modified based on a green natural product, a preparation method thereof, and an application thereof in the viscosity detection of a metal cleaning agent. Background Art

[0002] A metal cleaning agent is an industrial and public general-purpose hard surface cleaning agent that can remove oil stains, dust, and some oxidized substances on the metal surface. In order to ensure the cleanliness of the metal surface in many technological processes, various types of surface cleaning products have been developed according to different requirements. Currently, there are mainly solvent-based cleaning agents, semi-solvent-based cleaning agents, and water-based metal cleaning agents, including many specific types such as acidic metal cleaning agents, alkaline metal cleaning agents, and environmentally friendly metal cleaning agents, and their usage in modern industrial washing is also increasing. In order to enhance the capabilities of various metal cleaning agents in aspects such as adsorption, wetting, solubilization, emulsification, dispersion, anti-deposition, and chelation, the relative contents of auxiliary agents such as corrosion inhibitors, solubilizers, defoamers, and rust inhibitors are usually adjusted in the cleaning agent to achieve the above goals. The addition of the above components makes the viscosity of the cleaning agent show a large fluctuation range, and viscosity, as one of the key physical indicators of the cleaning agent, plays a crucial role in the preparation process and subsequent application process of the cleaning agent. The current viscosity detection methods mainly focus on testing the macroscopic viscosity of liquids through viscometers, which not only require complex pretreatment processes, time-consuming detection procedures, and a large amount of liquid samples, but also are not suitable for measuring the viscosity of liquid micro-regions, and their applications are limited. Therefore, it is imperative to develop a detection tool with high sensitivity, fast result output, easy operation, and preferably also with a visualization function.

[0003] The analysis technology based on photoluminescence has become one of the powerful means for viscosity sensing, and luminescent materials have become an advantageous tool for improving the detection quality, efficiency, and ease of use. However, at the present stage, many molecular probes developed for micro-region viscosity detection mostly rely on complex artificial synthesis, which not only consumes a large amount of reagents, but also goes against the current trend of low-carbon environmental protection. More importantly, the cost is relatively high. In contrast, natural products are a very promising material, which can be artificially purified and applied in many fields, and are environmentally friendly and are one of the typical renewable resources. Many plant extracts from nature have been widely used in the field of traditional medicine, especially in traditional Chinese medicine. If certain specific natural products are modified, not only can molecular devices with better luminescent properties be obtained, but also the application scope of natural products can be greatly expanded. More importantly, through simple chemical modification, the complicated organic synthesis process can be avoided, and its added value can be increased, enabling it to become a more potential molecular tool.

[0004] In summary, there is an urgent need to develop a molecular rotor that can be used for the micro-region viscosity detection of metal cleaning agents and is modified based on green natural products. Summary of the Invention

[0005] In view of this, the present invention provides an organic small molecule modified based on green natural products, its preparation method, and its application in the viscosity detection of metal cleaning agents. The organic small molecule provided by the present invention is modified by a natural cinnamaldehyde derivative, and can emit fluorescence signals with different intensities for metal cleaning agents with different viscosities. Therefore, it can be directly used for the detection of the physical viscosity of different types of metal cleaning agents, with simple operation and visual detection achievable.

[0006] In order to achieve the above-mentioned invention objectives, the present invention provides the following technical solutions:

[0007] An organic small molecule has the structure shown in Formula I:

[0008]

[0009] In Formula I: X is a formyl group, a hydroxyl group, a methyl group, an ethyl group, a methoxy group, an ethoxy group, or a hydrogen atom, and R is any one of the following structures:

[0010]

[0011] Preferably, the organic small molecule has the structure shown in Formula I-1:

[0012]

[0013] The present invention also provides a preparation method for the organic small molecule described in the above solution, including the following steps:

[0014] Mix a triphenylamine derivative, a cinnamaldehyde derivative, an inorganic salt, a palladium catalyst, and an organic solvent for a condensation reaction to obtain an organic small molecule with the structure shown in Formula I; the structure of the triphenylamine derivative is shown in Formula II; the structure of the cinnamaldehyde derivative is: Br-R, where the type of the R group is the same as that in Formula I;

[0015] The type of X in Formula II is the same as that in Formula I.

[0016] Preferably, the mixing includes: first mixing the triphenylamine derivative, the cinnamaldehyde derivative, and a first organic solvent to obtain a first mixed solution; then mixing the first mixed solution, the inorganic salt, the palladium catalyst, and a second organic solvent.

[0017] Preferably, the concentration of the triphenylamine derivative in the first mixed solution is 1-20 M, and the concentration of the cinnamaldehyde derivative is 1-30 M; the molar ratio of the triphenylamine derivative to the cinnamaldehyde derivative is 1:1-30.

[0018] Preferably, the first organic solvent includes one or more of dichloromethane, tetrahydrofuran, acetone, ethyl acetate, ethanol, methanol, N,N-dimethylformamide, and dimethyl sulfoxide; the second organic solvent includes one or more of deionized water, ethanol, methanol, toluene, ethyl acetate, dimethyl sulfoxide, and tetrahydrofuran.

[0019] Preferably, the inorganic salt includes one or more of calcium carbonate, magnesium carbonate, cesium carbonate, and tin acetate; the molar ratio of the triphenylamine derivative to the inorganic salt is 1:10-50.

[0020] Preferably, the palladium catalyst includes one or more of palladium on carbon, palladium acetate, palladium trifluoroacetate, dichloropalladium (II) bis(ferrocenyldiphenylphosphine), palladium neopentanoate, bis(tri-tert-butylphosphine)palladium, tetrakis(triphenylphosphine)palladium, and bis(tri-tert-butylphosphine)palladium; the molar ratio of the triphenylamine derivative to the palladium catalyst is 1:0.01-0.3.

[0021] Preferably, the temperature of the condensation reaction is 25-100 °C, and the time is 1-72 h.

[0022] The present invention also provides an application of the organic small molecule prepared by the preparation method described above as a fluorescent rotor in the viscosity detection of metal cleaning agents.

[0023] The present invention provides an organic small molecule, the structural formula of which is shown in Formula I. The organic small molecule provided by the present invention is obtained by condensing a strong electron-donating group triphenylamine derivative and a natural cinnamaldehyde derivative, has a typical large conjugated molecular structure, and contains many conjugated single and double bonds and aromatic rings that can rotate freely. It has typical twisted intramolecular charge transfer (TICT) effect and aggregation-induced emission (AIE) effect, is suitable for application as a molecular rotor, and is also suitable for application as an aggregated molecular device, greatly expanding its use range in solid-state devices, and the detection signal can be amplified to a certain extent; the results of the examples show that the organic small molecule (DPABMA) provided by the present invention has a high light signal intensity, a Stokes shift of up to 173 nm, has good anti-light signal interference, strong light stability, and good chemical stability, and is suitable for use in a relatively complex metal cleaning agent atmosphere.

[0024] The present invention also provides a preparation method of the above-mentioned organic small molecule. The organic small molecule provided by the present invention is obtained by further modifying the green natural product cinnamaldehyde. The natural product itself has a wide source, has typical environmentally friendly characteristics, conforms to the current concept of green environmental protection, and the method steps of further modification are simple and easy to implement, with a high yield, without expensive equipment and complex processes, and low energy consumption during the process, which is extremely beneficial for low-carbon development and subsequent large-scale industrial promotion.

[0025] The present invention also provides an application of the above-mentioned organic small molecule as a fluorescent rotor in the viscosity detection of metal cleaning agents. The chemical structure of the organic small molecule provided by the present invention contains many conjugated single and double bonds and aromatic rings that can rotate freely. In a metal cleaning agent with low viscosity, it can rotate freely, enabling it to dissipate the energy after being excited by an external light source through mechanical motion, and the metal cleaning agent apparently exhibits a lower fluorescence signal. In contrast, when the viscosity of the metal cleaning agent increases, the structure of the organic small molecule is inhibited to varying degrees, and the originally freely rotating phenomenon significantly decreases, and instead dissipates the excited state energy through radiative transition, making the metal cleaning agent exhibit a stronger fluorescence signal (the specific principle is as Figure 1 shown, Figure 1 is a schematic diagram of the detection principle of physical viscosity taking the organic small molecule shown in Formula I-1 as an example); that is, the physical viscosity of the metal cleaning agent can be judged by the strength of the apparent fluorescence signal, and an effective visual monitoring of the viscosity change process during the preparation process of the metal cleaning agent can be realized. The organic small molecule of the present invention can be used to distinguish different types of metal cleaning agents, and can also provide necessary reference for the formulation of metal cleaning agents (control of the reasonable viscosity range); at the same time, the optical signal of the organic small molecule of the present invention can change with the change of the physical micro-region viscosity of the metal cleaning agent. As the viscosity increases, the optical signal intensity gradually increases, and the 'turn-on' detection effect can be realized in-situ, sensitively and efficiently, and the metal cleaning and wetting effect can be indirectly predicted and judged, and the physical viscosity range of the best wetting effect can be effectively determined. Description of the Drawings

[0026] Figure 1 is a schematic diagram of the detection principle of physical viscosity of the organic small molecule provided by the present invention, taking DPABMA as an example;

[0027] Figure 2 is the high-resolution mass spectrum of the fluorescent rotor DPABMA prepared in Example 1;

[0028] Figure 3 is the absorption spectrum of DPABMA in different solvents;

[0029] Figure 4 is the fluorescence intensity change diagram of DPABMA in DMSO / water mixed solutions with different volume ratios;

[0030] Figure 5 Fluorescence intensity change diagram of DPABMA in glycerol / water mixed solutions with different volume ratios;

[0031] Figure 6 Linear fitting diagram of the logarithmic function of the measured fluorescence intensity and the corresponding viscosity of DPABMA;

[0032] Figure 7 Spectrum diagram and viscosity diagram of DPABMA in metal cleaning agent samples of different types. Detailed implementation manners

[0033] The present invention provides an organic small molecule having the structure shown in Formula I:

[0034]

[0035] In Formula I: X is a formyl group, a hydroxyl group, a methyl group, an ethyl group, a methoxy group, an ethoxy group or a hydrogen atom, and R is any one of the following structures:

[0036]

[0037] In the present invention, the organic small molecule structure includes a strong electron-donating group triphenylamine derivative part and a natural cinnamaldehyde derivative part; among them, the triphenylamine derivatives include 4,4'-dimethanoyl triphenylamine, 4,4'-dihydroxy triphenylamine, 4,4'-dimethyl triphenylamine, 4,4'-diethyl triphenylamine, 4,4'-dimethoxy triphenylamine, 4,4'-diethoxy triphenylamine, triphenylamine; the cinnamaldehyde derivatives include α-methyl cinnamaldehyde, cinnamaldehyde, 2-methoxy cinnamaldehyde, α-chloro cinnamaldehyde, α-hexyl cinnamaldehyde, 2-hydroxy cinnamaldehyde or 3-methoxy cinnamaldehyde.

[0038] In the present invention, the organic small molecule preferably has the structure shown in Formula I-1:

[0039]

[0040] In the present invention, the organic small molecule shown in Formula I-1 is denoted as DPABMA.

[0041] The present invention also provides a preparation method of the organic small molecule described in the above solution, including the following steps:

[0042] Mix a triphenylamine derivative, a cinnamaldehyde derivative, an inorganic salt, a palladium catalyst and an organic solvent to carry out a condensation reaction to obtain an organic small molecule having the structure shown in Formula I; the structure of the triphenylamine derivative is shown in Formula II; the structure of the cinnamaldehyde derivative is: Br-R, where the type of the R group is the same as that in Formula I;

[0043] The type of X in Formula II is the same as that in Formula I.

[0044] In the present invention, the mixing preferably includes: first mixing a triphenylamine derivative, a cinnamaldehyde derivative and a first organic solvent to obtain a first mixed solution; then mixing the first mixed solution, an inorganic salt, a palladium catalyst and a second organic solvent.

[0045] In the present invention, the concentration of the triphenylamine derivative in the first mixed solution is preferably 1 to 20 M, more preferably 3 to 15 M; the concentration of the cinnamaldehyde derivative in the first mixed solution is preferably 1 to 30 M, more preferably 5 to 25 M; the molar ratio of the triphenylamine derivative to the cinnamaldehyde derivative is preferably 1:1 to 30, more preferably 1:3 to 1:15; the first organic solvent preferably includes one or more of dichloromethane, tetrahydrofuran, acetone, ethyl acetate, ethanol, methanol, N,N-dimethylformamide and dimethyl sulfoxide; the mixing of the triphenylamine derivative, the cinnamaldehyde derivative and the first organic solvent is preferably carried out under stirring conditions, the rotation speed of the stirring is preferably 100 rpm to 1000 rpm, the stirring time is preferably 30 to 180 min, and the stirring temperature is preferably 20 to 50 °C; in a specific embodiment of the present invention, preferably, the triphenylamine derivative and the cinnamaldehyde derivative are respectively dissolved in the first organic solvent to obtain a triphenylamine derivative solution and a cinnamaldehyde derivative solution, and then the triphenylamine derivative solution and the cinnamaldehyde derivative solution are mixed. The types of the first organic solvents used to dissolve the triphenylamine derivative and the cinnamaldehyde derivative may be the same or different, and the present invention does not make specific limitations.

[0046] In the present invention, the second organic solvent preferably includes one or more of deionized water, ethanol, methanol, toluene, ethyl acetate, dimethyl sulfoxide and tetrahydrofuran; the volume ratio of the second organic solvent to the first solvent is preferably 1:1; the inorganic salt preferably includes one or more of calcium carbonate, magnesium carbonate, cesium carbonate and tin acetate; the molar ratio of the triphenylamine derivative to the inorganic salt is preferably 1:10 to 50, more preferably 1:20 to 40; in the present invention, the inorganic salt mainly plays a role of dehydrating to promote the reaction to proceed in the forward direction.

[0047] In the present invention, the palladium catalyst preferably includes one or more of palladium on carbon, palladium acetate, palladium trifluoroacetate, dichloropalladium (II) ferrocenyl diphenylphosphine, palladium neopentanoate, bis(tri-tert-butylphosphine)palladium, tetrakis(triphenylphosphine)palladium and bis(tri-tert-butylphosphine)palladium; the molar ratio of the triphenylamine derivative to the palladium catalyst is preferably 1:0.01 to 0.3, more preferably 1:0.05 to 0.25, and further preferably 1:0.1 to 0.2.

[0048] In the present invention, the temperature of the condensation reaction is preferably 25 to 100 °C, more preferably 40 to 80 °C, the time of the condensation reaction is preferably 1 to 72 h, more preferably 5 to 60 h, and further preferably 10 to 48 h; the condensation reaction is preferably carried out in an inert gas atmosphere, and the inert gas preferably includes helium, neon or argon.

[0049] In the present invention, taking the organic small molecule with the structure shown in Formula I-1 as an example, the reaction formula of the condensation reaction is shown in Formula III:

[0050]

[0051] After the condensation reaction is completed, the present invention preferably performs post-treatment on the obtained product liquid; the post-treatment preferably includes the following steps: extracting the obtained product liquid with an ethyl acetate-water mixed solvent, and collecting the organic phase; drying the organic phase and then distilling off the organic solvent under reduced pressure to obtain a crude product; subjecting the obtained crude product to column chromatography purification, and freeze-drying the obtained purified product to obtain an organic small molecule with the structure shown in Formula I. In the present invention, the volume ratio of ethyl acetate to water in the ethyl acetate-water mixed solvent is preferably 1:1; the desiccant for drying the organic phase is preferably anhydrous sodium sulfate; the temperature of the freeze-drying is preferably -40 °C.

[0052] The organic small molecule prepared by the present invention is an orange-yellow odorless solid powder, which is easily soluble in various common organic solvents, has a stable chemical structure, stable photoluminescence performance, is easy to store, convenient for weighing and packaging, and is suitable for subsequent large-scale production and large-scale industrial storage.

[0053] The present invention also provides the application of the organic small molecule described in the above solution or the organic small molecule prepared by the preparation method described in the above solution as a fluorescent rotor in the viscosity detection of metal cleaning agents. The fluorescence intensity of the organic small molecule provided by the present invention can change with the change of the physical micro-region viscosity of the metal cleaning agent, specifically manifested as the gradual increase of the optical signal intensity with the increase of the viscosity, and can realize the 'turn-on' detection effect in situ, sensitively and efficiently, and can indirectly predict and judge the metal cleaning wetting effect, as well as effectively determine the physical viscosity range of the best wetting effect. In the specific embodiments of the present invention, the organic small molecule of the present invention can be added to the metal cleaning agent, and the physical viscosity of the metal cleaning agent can be judged according to the strength of the fluorescence signal, so as to effectively visualize the monitoring of the viscosity change process during the preparation of the metal cleaning agent. In the specific embodiments of the present invention, it is preferably to detect the fluorescence signal at 553 nm at an excitation wavelength of 380 nm.

[0054] In the present invention, when detecting the viscosity of the metal cleaning agent, it is preferable to dissolve the organic small molecule in an organic solvent to prepare a test mother liquor. When performing the test, the test mother liquor is diluted and added to the metal cleaning agent, and the final concentration of the organic small molecule in the solution is controlled to be 1 μM to 100 μM, preferably 10 μM to 30 μM. By measuring the fluorescence intensity of the solution, the micro-region viscosity of different metal cleaning agents can be judged, and thus the effective control of the physical index of viscosity during the preparation of the metal cleaning agent can be realized, which is of great benefit to the formulation design and the improvement of the cleaning efficiency for different workpieces. In the present invention, the organic solvent for dissolving the organic small molecule is preferably one or more of dimethyl sulfoxide, tetrahydrofuran, dimethyl sulfoxide and ethanol; the solvent for diluting the mother liquor is preferably deionized water.

[0055] In addition, the organic small molecule of the present invention can also be used to distinguish different types of metal cleaning agents. Specifically, the organic small molecule of the present invention can be added to metal cleaning agents with different viscosities. Due to the different formulation properties of the metal cleaning agents themselves, there are certain differences in their physical viscosities, which are reflected as different fluorescence intensities. For example, when in the low-viscosity metal cleaning agent sample 1, it can emit a relatively weak fluorescence signal at 553 nm under an excitation wavelength of 380 nm. When in the high-viscosity sample 2, its fluorescence intensity is significantly enhanced. When added to the sample 3 with a higher viscosity, it is found that its fluorescence intensity further increases; this may be because the molecular structure of the rotor is inhibited to different degrees, resulting in different energies for it to return to the ground state via radiative transition, and finally the intensities of the optical signals released are inconsistent, which is consistent with the test results of traditional viscometers. The specific mechanism is as shown in the appendix Figure 1 as follows.

[0056] Next, the technical solutions in the present invention will be clearly and completely described in conjunction with the embodiments in the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without making creative efforts shall fall within the protection scope of the present invention.

[0057] Example 1

[0058] 351 mg of 4-bromo-N,N-di-p-toluidine was dissolved in ethanol, and 3360 mg of 3-(4-bromophenyl)-2-methylacrolein was dissolved in ethanol. The concentration of 4-bromo-N,N-di-p-toluidine was controlled to be 1 M, the concentration of 3-(4-bromophenyl)-2-methylacrolein was 15 M, the molar ratio of 4-bromo-N,N-di-p-toluidine to 3-(4-bromophenyl)-2-methylacrolein was 1:15, the mixing and stirring time was 60 min, the stirring rate was 500 rpm, and the stirring temperature was 30 °C to obtain a first mixed solution;

[0059] Mix the first mixed solution, calcium carbonate, palladium acetate and deionized water. The amount of calcium carbonate added is 1500 mg, the amount of palladium acetate added is 22.4 mg, and the volume ratio of deionized water to the solvent in the first mixed solution is 1:1. When carrying out the condensation reaction, control the reaction temperature at 60 °C, the stirring rate at 800 rpm, the reaction atmosphere as helium, and the reaction time at 24 h to obtain the crude product. Use a mixed solvent of ethyl acetate and deionized water (V / V = 1:1) to extract the above crude product. After collecting the organic phase and drying it over Na2SO4, remove the organic solvent by vacuum distillation, then prepare a mixed solvent of petroleum ether and ethyl acetate (V / V = 1:1) for column chromatography purification, and finally dry it at low temperature (-40 °C) with a freeze dryer to obtain 371.3 mg of the fluorescent rotor DPABMA for measuring the viscosity of the metal cleaner, with a yield of 89%.

[0060] The relative molecular mass of DPABMA was verified by a high-resolution mass spectrometer, and MS(ESI): m / z 418.20964 [M+1] was obtained + , and the specific test results are as shown in the appendix Figure 2 as follows

[0061] Example 2

[0062] Dissolve 351 mg of 4-bromo-N,N-di-p-toluidine in methanol, and dissolve 224 mg of 3-(4-bromophenyl)-2-methylacrolein in ethanol. Control the concentration of 4-bromo-N,N-di-p-toluidine at 1 M and the concentration of 3-(4-bromophenyl)-2-methylacrolein at 1 M. The molar ratio of 4-bromo-N,N-di-p-toluidine to 3-(4-bromophenyl)-2-methylacrolein is 1:1. The mixing and stirring time is 30 min, the stirring rate is 1000 rpm, and the stirring temperature is 50 °C to obtain the first mixed solution;

[0063] Mix the first mixed solution, cesium carbonate, palladium trifluoroacetate and methanol. The amount of cesium carbonate added is 3258 mg, the amount of palladium trifluoroacetate added is 3.5 mg, and the volume ratio of methanol to the solvent in the first mixed solution is 1:1. When carrying out the condensation reaction, control the reaction temperature at 25 °C, the stirring rate at 200 rpm, the reaction atmosphere as neon, and the reaction time at 72 h to obtain the crude product. Use a mixed solvent of ethyl acetate and deionized water (V / V = 1:1) to extract the above crude product. After collecting the organic phase and drying it over Na2SO4, remove the organic solvent by vacuum distillation, then prepare a mixed solvent of petroleum ether and ethyl acetate (V / V = 1:1) for column chromatography purification, and finally dry it at low temperature (-40 °C) with a freeze dryer to obtain 325.4 mg of the fluorescent rotor DPABMA for measuring the viscosity of the metal cleaner, with a yield of 78%.

[0064] In this example, the characterization results of the fluorescent rotor DPABMA are the same as those obtained in Example 1.

[0065] Example 3

[0066] Dissolve 351 mg of 4-bromo-N,N-di-p-toluidine in ethyl acetate, and dissolve 6720 mg of 3-(4-bromophenyl)-2-methylacrolein in ethanol. Control the concentration of 4-bromo-N,N-di-p-toluidine to be 1 M, the concentration of 3-(4-bromophenyl)-2-methylacrolein to be 30 M, the molar ratio of 4-bromo-N,N-di-p-toluidine to 3-(4-bromophenyl)-2-methylacrolein to be 1:30, the mixing and stirring time to be 180 min, the stirring rate to be 100 rpm, and the stirring temperature to be 20 °C to obtain a first mixed solution;

[0067] Mix the first mixed solution, tin acetate, diphenylphosphinoferrocene dichloropalladium, and dimethyl sulfoxide. The amount of tin acetate added is 17740 mg, the amount of diphenylphosphinoferrocene dichloropalladium added is 217.7 mg, and the volume ratio of dimethyl sulfoxide to the solvent in the first mixed solution is 1:1. When carrying out the condensation reaction, control the reaction temperature to be 100 °C, the stirring rate to be 1200 rpm, the reaction atmosphere to be argon, and the reaction time to be 1 h to obtain a crude product; use a mixed solvent of ethyl acetate and deionized water (V / V = 1:1) to extract the above crude product. After collecting the organic phase and drying it over Na2SO4, remove the organic solvent by reduced pressure distillation, then prepare a mixed solvent of petroleum ether and ethyl acetate (V / V = 1:1) for column chromatography purification, and finally dry it at low temperature (-40 °C) with a freeze dryer to obtain 312.9 mg of the fluorescent rotor DPABMA for measuring the viscosity of the metal cleaning agent, with a yield of 75%.

[0068] In this example, the characterization results of the fluorescent rotor DPABMA are the same as those obtained in Example 1.

[0069] The test samples in Examples 4 to 5 are all DPABMA prepared in Example 1.

[0070] Spectroscopic test of DPABMA in Example 4

[0071] (1) Luminescence performance test of the fluorescent rotor in different solvents:

[0072] Prepare a 1 mM stock solution of the fluorescent rotor (with dimethyl sulfoxide as the solvent). Before testing, fully dilute the fluorescent rotor prepared in Example 1 in the solvent (deionized water), and then add it to six common solvents respectively, including toluene, ethyl acetate, tetrahydrofuran, N,N-dimethylformamide, methanol, and dimethyl sulfoxide. Control the final concentration of DPABMA to be 10 μM, and test its absorption spectra in various solvents. The obtained spectra are as shown in Appendix Figure 3 as follows, and the specific test data are shown in Table 1.

[0073] Table 1 Absorbance of the test group

[0074] Solvent type Peak wavelength of absorption spectrum (nm) Absorbance Toluene 375.6 0.50 Ethyl acetate 378.8 0.53 Tetrahydrofuran 380.1 0.42 N,N-Dimethylformamide 382.6 0.49 Methanol 384.3 0.41 Dimethyl sulfoxide 386.7 0.49

[0075] The above test results show that the absorption spectral peaks of the fluorescent rotor in various solvents are similar, with a slight tendency of red shift, indicating that when using the fluorescent rotor in solvents with different polarities, it will not have an adverse effect on the normal light signal release of the fluorescent rotor, having a certain universality, and just being very close to the emission wavelength of 365 nm of a common portable ultraviolet lamp. It is suitable for exciting light signals through the light emitted by the ultraviolet lamp, and has the effects of being portable and quickly detecting in various occasions, which is very convenient.

[0076] (2) Test on the aggregation-induced emission property of DPABMA:

[0077] Dissolve 0.83 mg of DPABMA in dimethyl sulfoxide to prepare a 1 mM stock solution to be tested, and the test is carried out at room temperature; then prepare mixed solutions of deionized water and dimethyl sulfoxide with different volume ratios, where the volume percentages of deionized water are 0%, 10%, 30%, 50%, 70%, 90%, and 99% respectively. Then add DPABMA to the above solutions with different volume fractions, control the final concentration of DPABMA to be 10 μM, set the excitation wavelength to 380 nm, and test the fluorescence intensity. The test results are shown in Appendix Figure 4 as follows, and the specific results are shown in Table 2.

[0078] Table 2 Fluorescence intensity of deionized water / dimethyl sulfoxide with different volume fractions

[0079] Volume fraction of deionized water Fluorescence intensity 0％ 11.3 10％ 15.3 30％ 21.2 50％ 60.1 70％ 317.9 90％ 336.3 99％ 358.7

[0080] From Appendix Figure 4As can be seen from the results in Table 2, when the volume fraction of deionized water in the solution is less than 70%, the fluorescence intensity of the solution increases limitedly. This may be because the fluorescent rotor can dissolve fully in dimethyl sulfoxide, and the energy in the excited state can be dissipated through free rotation, with a relatively low proportion of energy for radiative transition, resulting in a weak overall optical signal. In contrast, as the volume fraction of the poor solvent deionized water gradually increases, the solubility of the fluorescent rotor gradually decreases, showing an aggregated state with an increasing degree. This makes the proportion of the way to dissipate the energy in the excited state through free rotation decrease, and the proportion of the way to dissipate the energy in the excited state through radiative transition become larger, with an obvious release of optical signal. The above phenomena fully illustrate that the fluorescent rotor has a typical aggregation-induced emission effect.

[0081] (3) Response test of the fluorescent rotor DPABMA to the viscosity of the solution

[0082] Prepare glycerol / deionized water mixed solutions with different volume fractions respectively, where the volume fractions of glycerol are 0%, 10%, 30%, 50%, 70%, and 90% respectively. During the specific test, control the addition concentration of the fluorescent rotor DPABMA to be 10 μM, set the excitation wavelength to 380 nm, and test the fluorescence intensity at room temperature. The specific test results are as shown in the appendix Figure 5 shown. As can be seen from the appendix Figure 5 , as the volume fraction of glycerol in the mixed solution gradually increases, its fluorescence intensity gradually increases. Especially when the volume fraction of glycerol reaches 90%, its fluorescence intensity reaches the maximum value. Compared with when the volume fraction of glycerol is 0%, the fluorescence intensity increases by about 13 times, and the response effect is significant. This may be because as the volume fraction of glycerol increases, the viscosity of the mixed solution gradually increases, and the inhibitory effect on the fluorescent rotor gradually enhances. The conjugated structure that could originally rotate freely is inhibited, resulting in a gradually increasing proportion of the energy dissipated through radiative transition in the excited state, and thus releasing a stronger optical signal.

[0083] Furthermore, through the equation, the logarithmic function of viscosity can be fitted with the logarithmic function of fluorescence intensity. The final fitting result is as shown in the appendix Figure 6 shown. Through this linear equation, the sensitivity coefficient to viscosity can be calculated to be 0.43, and the coefficient of determination of the fitting is 0.99. The above test results show that the fluorescent rotor has a sensitive response effect to viscosity and can be used for the determination of the micro-region viscosity of various metal cleaning agents.

[0084] Example 5 Detection application of DPABMA in different types of metal cleaning agents

[0085] 4.17 mg of the fluorescent rotor DPABMA prepared in Example 1 was dissolved in dimethyl sulfoxide. Three kinds of metal cleaning agents (mainly composed of surfactants, co-cleaning agents, chelating agents, rust inhibitors, etc.) were selected, and the DPABMA solution was added to the three cleaning agents. The final concentration was controlled to be 10 μM, the excitation wavelength was set to 380 nm, and the room temperature was controlled at 25 °C to measure the fluorescence intensity. The rules of the obtained fluorescence intensity and viscosity are as shown in Figure 7 and the specific results are shown in Table 3.

[0086] Table 3 Fluorescence intensity of the fluorescent rotor DPABMA in different kinds of metal cleaning agents and viscosities of different kinds of metal cleaning agents

[0087] Type of metal cleaning agent Fluorescence intensity Viscosity Sample 1 630.9 3.6 Sample 2 781.6 6.1 Sample 3 887.5 8.0

[0088] As can be seen from Figure 7 , the viscosities of these three metal cleaning agents (Sample 1, Sample 2, Sample 3) are different. Through viscosity measurement, it is found that their viscosities show a gradually increasing trend. Through spectroscopic research, it is found that the fluorescence intensity also gradually increases. It can be seen that the fluorescence intensity and viscosity show a positive correlation, indicating that the fluorescent rotor DPABMA can fully sense the viscosity change in the micro-region of the metal cleaning agent and visualize the viscosity change of the metal cleaning agent through the intensity of the optical signal released, realizing the determination of the physical viscosity range of the metal cleaning agent. Combining the results in Table 3 and Figure 7 , it can be seen that due to the different viscosities of different metal cleaning agents, their fluorescence intensities also show inconsistent phenomena, achieving the visual detection effect of viscosity through the release of optical signals, which is of great significance for the determination of the optimal physical viscosity of metal cleaning agents.

[0089] Example 6

[0090] Other conditions were the same as in Example 1, except that 4-bromo-N,N-di-p-toluidine was replaced with 4-bromo-N,N-bis(4-methoxyphenyl)aniline, and 3-(4-bromophenyl)-2-methylacrolein was replaced with p-bromocinnamaldehyde to obtain an organic small molecule.

[0091] Example 7

[0092] Other conditions were the same as in Example 1, except that 4-bromo-N,N-di-p-toluidine was replaced with 4,4'-((4-bromophenyl)azanediyl)diphenol, and 3-(4-bromophenyl)-2-methylacrolein was replaced with 3-(4-bromo-2-methoxyphenyl)acrolein to obtain an organic small molecule.

[0093] Example 8

[0094] Other conditions are the same as in Example 1, except that 4-bromo-N,N-di-p-toluidine is replaced with 4,4'-((4-bromophenyl)azanediyl)dibenzaldehyde, and 3-(4-bromophenyl)-2-methylacrolein is replaced with 3-(4-bromophenyl)-2-chloroacrolein to obtain an organic small molecule.

[0095] Example 9

[0096] Other conditions are the same as in Example 1, except that 4-bromo-N,N-di-p-toluidine is replaced with 4-bromo-N,N-bis(4-ethylphenyl)aniline, and 3-(4-bromophenyl)-2-methylacrolein is replaced with 2-(3-bromobenzylidene)octanal to obtain an organic small molecule.

[0097] Example 10

[0098] Other conditions are the same as in Example 1, except that 4-bromo-N,N-di-p-toluidine is replaced with 4-bromo-N,N-bis(4-ethoxyphenyl)aniline, and 3-(4-bromophenyl)-2-methylacrolein is replaced with 3-(4-bromo-2-hydroxyphenyl)acrolein to obtain an organic small molecule.

[0099] Example 11

[0100] Other conditions are the same as in Example 1, except that 4-bromo-N,N-di-p-toluidine is replaced with 4-bromo-N,N-dianiline, and 3-(4-bromophenyl)-2-methylacrolein is replaced with 3-(4-bromo-3-methoxyphenyl)acrolein to obtain an organic small molecule.

[0101] The performance of the organic small molecules prepared in Examples 6 - 11 was tested according to the methods in Examples 4 - 5. The results obtained were similar to those of DPABMA, indicating that the organic small molecules prepared by the present invention can be used for the viscosity detection of metal cleaning agents and achieve visualization.

[0102] The results of the above examples show that the organic small molecules provided by the present invention are prepared by further modifying natural products, and have the characteristics of simple preparation, low cost, and low energy consumption in the process, which conforms to the current development concept of green and low-carbon. Its chemical structure is stable, the photostability is good, it has strong adaptability to various polar solvents, and at the same time has TICT and AIE effects. It has good response characteristics to the physical marker of micro-region viscosity, which is a metal cleaning agent, and shows great application prospects in determining the optimal viscosity range of metal cleaning agents for cleaning different workpieces in industry.

[0103] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. Application of organic small molecules as fluorescence rotors in viscosity detection of metal cleaning agents, characterized in that, The excitation wavelength of the detection is 380 nm; the organic small molecule has the structure shown in Formula I: Formula I; In Formula I: X is formyl, hydroxyl, methyl, ethyl, methoxy or ethoxy, and R has the following structure: ； The organic small molecule is modified based on the green natural product cinnamaldehyde.

2. The application according to claim 1, wherein The organic small molecule has the structure shown in Formula I-1: Formula I-1.

3. The application according to claim 2, wherein The preparation method of the organic small molecule includes the following steps: Mix a triphenylamine derivative, a cinnamaldehyde derivative, an inorganic salt, a palladium catalyst and an organic solvent for a condensation reaction to obtain an organic small molecule having the structure shown in Formula I; the structure of the triphenylamine derivative is shown in Formula II; the structure of the cinnamaldehyde derivative is: Br-R, where the type of the R group is the same as that in Formula I; Formula II; In Formula II, X is methyl; The inorganic salt is one or more of calcium carbonate, magnesium carbonate, cesium carbonate and tin acetate.

4. The application according to claim 3, characterized in that, The mixing includes: first mixing the triphenylamine derivative, the cinnamaldehyde derivative and a first organic solvent to obtain a first mixed solution; then mixing the first mixed solution, the inorganic salt, the palladium catalyst and a second organic solvent.

5. The application according to claim 4, wherein The concentration of the triphenylamine derivative in the first mixed solution is 1-20 M, and the concentration of the cinnamaldehyde derivative is 1-30 M; the molar ratio of the triphenylamine derivative to the cinnamaldehyde derivative is 1:1-30.

6. The application according to claim 4, wherein The first organic solvent includes one or more of dichloromethane, tetrahydrofuran, acetone, ethyl acetate, ethanol, methanol, N,N-dimethylformamide and dimethyl sulfoxide; the second organic solvent includes one or more of deionized water, ethanol, methanol, toluene, ethyl acetate, dimethyl sulfoxide and tetrahydrofuran.

7. The application according to claim 3 or 4, characterized in that The molar ratio of the triphenylamine derivative to the inorganic salt is 1:10-50.

8. The application according to claim 3 or 4, characterized in that, The palladium catalyst includes one or more of palladium on carbon, palladium acetate, palladium trifluoroacetate, diphenylphosphinoferrocene dichloropalladium, palladium neopentanoate, bis(tri-tert-butylphosphine)palladium, tetrakis(triphenylphosphine)palladium and bis(tri-tert-butylphosphine)palladium; the molar ratio of the triphenylamine derivative to the palladium catalyst is 1:0.01-0.

3.

9. The application according to any one of claims 4 to 6, characterized in that, The temperature of the condensation reaction is 25-100 °C, and the time is 1-72 h.

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