Organic ion pair charge transfer nano-particles based on fluorescent viologen and preparation method and application of organic ion pair charge transfer nano-particles

Abstract

The invention discloses a fluorescent viologen-based organic ion pair charge transfer nanoparticle and a preparation method and application thereof.The method comprises the steps that firstly, dithio-oxamide and 4-pyridylaldehyde react under the water-free and oxygen-free condition, and thiazolothiazole bipyridine is prepared; then, under the argon protection state, the thiazolothiazole bipyridine reacts with an alkylating reagent, and N-ionized thiazolothiazole bridged viologen is prepared; and finally, mixing the N-ionized thiazolothiazole bridged viologen with sodium tetraphenylborate and polyvinylpyrrolidone to react, so as to prepare the organic ion pair charge transfer nanoparticles based on the fluorescent viologen. According to the invention, the progressive design from molecular skeleton reconstruction to supramolecular assembly reinforcement systematically breaks the core technical bottleneck of viologen photochromic materials in the aspects of electronic structure and environmental stability.

Description

Technical Field

[0001] The invention belongs to the technical field of viologen fluorescent materials and relates to fluorescent viologen-based organic ion-pair charge transfer nanoparticles and a preparation method and application thereof. Background Art

[0002] Photochromic materials are a booming field with a wide range of potential applications in display, decoration, switching, storage, photography, etc. So far, smart materials with light-induced electron transfer properties have led to optical changes in the visible spectrum. These materials show visible color changes to the naked eye, providing a wide range of potential applications in the macroscopic field.

[0003] Viologens are ionic compounds with electron-deficient systems that exhibit distinct color changes when exposed to external light stimuli (such as Xe lamps). Based on specific light irradiation, they can be used for information encryption, display reading, toxic amine detection, and ultraviolet detection. Light stimulation causes visible color changes in materials, broadens the spectral response, and improves light absorption efficiency. Their unique photoresponse properties and tunability have attracted the interest of researchers. However, viologen derivatives also have some significant disadvantages, such as a wide energy gap, low degree of conjugation, poor luminescence properties, and easy fading in air, which greatly limit their application in the field of photochromism.

[0004] In the viologen system, its divalent cations act as efficient electron acceptors, capable of forming ion-pair charge transfer (IPCT) complexes with a variety of electron donors (such as tetraphenylboron derivatives). Although these IPCT complexes have achieved breakthroughs such as "broad absorption bands in the UV-visible region and retention of photochromic behavior at the nanoscale," providing theoretical support for applications such as optical recording and switching, this approach does not address the inherent defects of viologens, such as "wide energy gap, weak conjugation, poor luminescence, and easy fading," from the molecular skeleton. Furthermore, limited progress has been made in the multifunctional integration of macroscopic materials (such as flexibility and multi-stimulus response coordination), limiting the application of viologen-based photochromic materials towards high performance and diversification. Summary of the Invention

[0005] In response to the problems existing in the prior art, the present invention provides a fluorescent viologen-based organic ion pair charge transfer nanoparticle and its preparation method and application, thereby solving the technical problems of viologen-based photochromic materials in the prior art, such as wide energy gap, low degree of conjugation, poor luminescence performance, and easy fading in air environment.

[0006] The present invention is achieved through the following technical solutions:

[0007] A method for preparing fluorescent viologen-based organic ion-pair charge transfer nanoparticles comprises the following steps:

[0008] S1: reacting dithiooxalylamine with 4-pyridinecarboxaldehyde under anhydrous and oxygen-free conditions to prepare thiazolothiazole bipyridine;

[0009] S2: Under argon protection, reacting the thiazolothiazole bipyridine with an alkylating agent to obtain an N-ionized thiazolothiazole bridged viologen;

[0010] S3: mixing the N-ionized thiazolothiazole bridged viologen with sodium tetraphenylborate and polyvinylpyrrolidone to react, so as to prepare the fluorescent viologen-based organic ion pair charge transfer nanoparticles.

[0011] Preferably, in step S1, the molar ratio of dithiooxalylamine to 4-pyridinecarboxaldehyde is 1:(3-4).

[0012] Preferably, in step S2, the molar ratio of the thiazolothiazole bipyridine to the alkylating agent is 1:(2-4).

[0013] Preferably, in step S2, the alkylating agent is methyl bromide, benzyl bromide, 9-bromomethylanthracene, 1-(bromomethyl)pyrene, 2-bromomethylnaphthalene, 1,3-propanesultone, 9-(bromomethyl)phenanthrene or 3-(bromomethyl)perylene.

[0014] Preferably, in step S3, the molar ratio of the N-ionized thiazolothiazole-bridged viologen to sodium tetraphenylborate is 1:(2-8).

[0015] Preferably, in step S3, the concentration of polyvinyl pyrrolidone in the reaction system is 0.4-0.45 mg / mL.

[0016] A fluorescent viologen-based organic ion pair charge transfer nanoparticle is prepared by the above method.

[0017] A photochromic test paper is prepared by using the above-mentioned fluorescent viologen-based organic ion-pair charge transfer nanoparticles.

[0018] A photochromic film is prepared by using the above-mentioned fluorescent viologen-based organic ion-pair charge transfer nanoparticles.

[0019] Application of the above-mentioned photochromic test paper or photochromic film in the detection of ethylenediamine.

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

[0021] The invention discloses a preparation method of fluorescent viologen-based organic ion-pair charge transfer nanoparticles. First, a thiazole ring and a viologen pyridine ring are fused to form a "thiazole-thiazole-pyridine" hyperconjugated skeleton, which expands the electron delocalization range from a single pyridine ring to a multi-heterocyclic π system, effectively reducing the energy gap and red-shifting the optical absorption from the ultraviolet region to the visible light region. In addition, the π-π stacking effect of the fused ring structure and the orbital delocalization of heteroatoms (S, N) in the thiazole ring also enhance the electron transition efficiency and fluorescence quantum yield, solving the problem of "poor luminescence performance" of viologen molecules. Secondly, the viologen cation (electron-deficient acceptor) and tetraphenylborate form an ion pair through electrostatic / charge transfer. The large-volume tetraphenylborate physically wraps the viologen cation, isolating it from air, and effectively inhibiting oxidative decomposition after photochromism. At the same time, polyvinylpyrrolidone (PVP) is introduced as a stabilizer, so that long PVP chains are adsorbed on the surface of the IPCT nanoparticles, preventing agglomeration by steric hindrance, further improving the dispersion stability and cycle durability. The present invention adopts a progressive design from molecular skeleton reconstruction (conjugation expansion) to supramolecular assembly enhancement (stability improvement), which systematically breaks the core technical bottlenecks of viologen-based photochromic materials in terms of electronic structure and environmental stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 for Figure 1 Figure 1 is a particle size dispersion diagram of the viologen derivative-based organic ion-pair charge transfer nanoparticles prepared in Examples 1 and 2 of the present invention, wherein (A) is the sample in Example 1 and (B) is the sample in Example 2;

[0024] Figure 2 UV spectra of an aqueous solution of sodium tetraphenylborate, an aqueous solution of N-ionized thiazolothiazole-bridged viologen (BTV) prepared in Example 1, and an aqueous dispersion of organic ion-pair charge transfer nanoparticles based on viologen derivatives;

[0025] Figure 3 These are ultraviolet absorption spectra of suspensions of viologen derivative-based organic ion-pair charge transfer nanoparticles prepared in Examples 1 and 2 of the present invention under ultraviolet light irradiation, wherein (A) is the sample in Example 1 and (B) is the sample in Example 2;

[0026] Figure 4These are UV absorption spectra of suspensions of viologen derivative-based organic ion-pair charge-transfer nanoparticles prepared in Examples 1 and 2 of the present invention, after the colors reached saturation under UV light, in the dark. (A) is the sample in Example 1, and (B) is the sample in Example 2.

[0027] Figure 5 The transmittance of suspensions of organic ion-pair charge transfer nanoparticles based on viologen derivatives prepared in Examples 1 and 2 of the present invention changes over time, wherein (A) is the sample in Example 1 and (B) is the sample in Example 2;

[0028] Figure 6 Graphs showing changes in the ultraviolet absorption spectra of the viologen derivative-based organic ion-pair charge transfer nanoparticles prepared in Examples 1 and 2 of the present invention under ethylenediamine titration, wherein (A) is the sample in Example 1 and (B) is the sample in Example 2;

[0029] Figure 7 Spectra showing changes in fluorescence intensity of viologen derivative-based organic ion-pair charge transfer nanoparticles prepared in Examples 1 and 2 of the present invention under ethylenediamine titration, wherein (A) is the sample in Example 1 and (B) is the sample in Example 2;

[0030] Figure 8 The figure shows the changes in the ultraviolet absorption spectra of the viologen derivative-based organic ion-pair charge transfer nanoparticle films prepared in Examples 1 and 2 of the present invention under ultraviolet light irradiation, wherein (A) is the sample in Example 1 and (B) is the sample in Example 2;

[0031] Figure 9 The figure shows the changes in the ultraviolet absorption spectra of the viologen derivative-based organic ion-pair charge transfer nanoparticle films prepared in Examples 1 and 2 of the present invention before and after exposure to ethylenediamine gas, wherein (A) is the sample in Example 1 and (B) is the sample in Example 2;

[0032] Figure 10 Figure 3 is a particle size dispersion diagram of the viologen derivative-based organic ion-pair charge transfer nanoparticles prepared in Examples 3 and 4 of the present invention, wherein (A) is the sample in Example 3, and (B) is the sample in Example 3;

[0033] Figure 11 UV spectra of an aqueous solution of sodium tetraphenylborate, an aqueous solution of N-ionized thiazolothiazole-bridged viologen (NTV) prepared in Example 3, and an aqueous dispersion of organic ion-pair charge transfer nanoparticles based on viologen derivatives prepared in Example 3;

[0034] Figure 12These are ultraviolet absorption spectra of suspensions of viologen derivative-based organic ion-pair charge transfer nanoparticles prepared in Examples 3 and 4 of the present invention under ultraviolet light irradiation, wherein (A) is the sample in Example 3, and (B) is the sample in Example 3;

[0035] Figure 13 These are UV absorption spectra of suspensions of viologen derivative-based organic ion-pair charge transfer nanoparticles prepared in Examples 3 and 4 of the present invention, after the colors reached saturation under UV light, in the dark. (A) is the sample in Example 3, and (B) is the sample in Example 3;

[0036] Figure 14 The transmittance of suspensions of organic ion-pair charge transfer nanoparticles based on viologen derivatives prepared in Examples 3 and 4 of the present invention changes over time, wherein (A) is the sample in Example 3, and (B) is the sample in Example 3;

[0037] Figure 15 The UV absorption and visible light spectra of the organic ion-pair charge transfer nanoparticle suspensions based on viologen derivatives prepared in Examples 3 and 4 of the present invention under ethylenediamine titration, wherein (A) is the sample in Example 3, and (B) is the sample in Example 3;

[0038] Figure 16 Spectra showing changes in fluorescence intensity of suspensions of viologen derivative-based organic ion-pair charge transfer nanoparticles prepared in Examples 3 and 4 of the present invention under ethylenediamine titration, wherein (A) is the sample in Example 3, and (B) is the sample in Example 3;

[0039] Figure 17 The figure shows the changes in the ultraviolet absorption spectra of the viologen derivative-based organic ion-pair charge transfer nanoparticle films prepared in Examples 3 and 4 of the present invention under ultraviolet light irradiation, wherein (A) is the sample in Example 3, and (B) is the sample in Example 3;

[0040] Figure 18 The figure shows the changes in the ultraviolet absorption spectra of the viologen derivative-based organic ion-pair charge transfer nanoparticle films prepared in Examples 3 and 4 of the present invention before and after exposure to ethylenediamine gas, wherein (A) is the sample in Example 3, and (B) is the sample in Example 3;

[0041] Figure 19 Figures 1 and 2 are particle size dispersion diagrams of the viologen derivative-based organic ion-pair charge transfer nanoparticles prepared in Examples 5 and 6 of the present invention, wherein (A) is the sample in Example 5 and (B) is the sample in Example 6;

[0042] Figure 20UV spectra of an aqueous solution of sodium tetraphenylborate, an aqueous solution of N-ionized thiazolothiazole-bridged viologen (STV) prepared in Example 5, and an aqueous dispersion of organic ion-pair charge transfer nanoparticles based on viologen derivatives prepared in Example 5;

[0043] Figure 21 These are ultraviolet absorption spectra of suspensions of viologen derivative-based organic ion-pair charge transfer nanoparticles prepared in Examples 5 and 6 of the present invention under ultraviolet light irradiation, wherein (A) is the sample in Example 5 and (B) is the sample in Example 6;

[0044] Figure 22 These are UV absorption spectra of suspensions of viologen derivative-based organic ion-pair charge-transfer nanoparticles prepared in Examples 5 and 6 of the present invention, after the colors reached saturation under UV light, in the dark. (A) is the sample in Example 5, and (B) is the sample in Example 6.

[0045] Figure 23 The transmittance of suspensions of organic ion-pair charge transfer nanoparticles based on viologen derivatives prepared in Examples 5 and 6 of the present invention changes over time, wherein (A) is the sample in Example 5 and (B) is the sample in Example 6;

[0046] Figure 24 UV absorption and visible light spectra of the organic ion-pair charge transfer nanoparticle suspensions based on viologen derivatives prepared in Examples 5 and 6 of the present invention under ethylenediamine titration, wherein (A) is the sample in Example 5 and (B) is the sample in Example 6;

[0047] Figure 25 Spectra showing changes in fluorescence intensity of suspensions of viologen derivative-based organic ion-pair charge transfer nanoparticles prepared in Examples 5 and 6 of the present invention under ethylenediamine titration, wherein (A) is the sample in Example 5 and (B) is the sample in Example 6;

[0048] Figure 26 The figure shows the changes in the ultraviolet absorption spectra of the viologen derivative-based organic ion-pair charge transfer nanoparticle films prepared in Examples 5 and 6 of the present invention under ultraviolet light irradiation, wherein (A) is the sample in Example 5 and (B) is the sample in Example 6;

[0049] Figure 27 The figure shows the changes in the UV absorption spectra of the viologen derivative-based organic ion-pair charge transfer nanoparticle films prepared in Examples 5 and 6 of the present invention before and after exposure to ethylenediamine gas, wherein (A) is the sample in Example 5 and (B) is the sample in Example 6;

[0050] Figure 28These are the photochromic test results of viologen derivative-based organic ion-pair charge-transfer nanoparticle films prepared in Examples 1, 3, and 5 of the present invention. The first column in (A) shows photochromic test papers using viologen derivative-based organic ion-pair charge-transfer nanoparticle films prepared in Examples 1, 3, and 5 of the present invention. The second column in (A) shows tin foil used as a mask with different patterns set on the mask. After exposure to light, the color of the area on the test paper not covered by the mask changes. The third column in (A) shows patterns of different shapes used as masks to cover a portion of the photochromic test paper. The color of the uncovered area changes after exposure to light. The fourth column in (A) shows the use of a laser to write corresponding content on the photochromic test paper to achieve inkless printing. The first row in (B) shows the use of a mask with a specific pattern set on the photochromic film. After exposure to light, the color of the uncovered area changes. The picture on the left in the second row in B) shows the use of a laser to write specific content on the photochromic film to achieve inkless printing. The picture on the right shows that the photochromic film has flexibility.

[0051] Figure 29 The color of the organic ion-pair charge transfer nanoparticle film based on viologen derivatives prepared in Example 1 of the present invention changes with the sunlight irradiation time at an ambient temperature of 30°C. DETAILED DESCRIPTION

[0052] To facilitate understanding of the features and effects of the present invention by those skilled in the art, the following provides a general description and definition of the terms and expressions used in the specification and claims. Unless otherwise indicated, all technical and scientific terms used herein have the ordinary meanings as understood by those skilled in the art regarding the present invention. In the event of conflict, the definitions in this specification shall prevail.

[0053] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0054] Herein, all features such as values, amounts, amounts, and concentrations defined in numerical ranges or percentage ranges are for brevity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to include and specifically disclose all possible subranges and individual values ​​within the range (including integers and fractions).

[0055] In this document, unless otherwise specified, “include,” “including,” “contains,” “has” or similar terms cover the meanings of “consisting of” and “mainly consisting of,” for example, “A includes a” covers the meanings of “A includes a and other” and “A only includes a.”

[0056] In this document, for the sake of brevity, not all possible combinations of the various technical features in each embodiment or example are described. Therefore, as long as there are no contradictions in the combination of these technical features, the various technical features in each embodiment or example can be combined in any way, and all possible combinations should be considered to be within the scope of this specification.

[0057] The first object of the present invention is to provide an organic ion-pair charge transfer nanoparticle based on a thiazolothiazole viologen derivative, wherein the composite has unique photochromic behavior and ethylenediamine response characteristics based on changes in fluorescence intensity.

[0058] The second object of the present invention is to provide a method for preparing organic ion-pair charge transfer nanoparticles based on thiazolothiazole viologen derivatives.

[0059] The third object of the present invention is to provide applications of organic ion-pair charge transfer nanoparticles based on thiazolothiazole viologen derivatives in the field of photochromism and ethylenediamine detection.

[0060] Specifically, the present invention provides a thiazolothiazole viologen derivative, the structural formula of which is as follows:

[0061]

[0062] Wherein, R is methyl, benzyl, methylanthracene, methylpyrene, methylenenaphthalene, 3-sulfonylpropyl, methylphenanthrene or methylperylene, X - Br - ;

[0063] The present invention provides a method for preparing thiazolothiazole viologen derivative organic ion pair charge transfer nanoparticles, comprising the following steps:

[0064] Step 1, preparing thiazolothiazole bipyridine TTz;

[0065] Specifically, under argon protection, dithiooxamide, 4-pyridinecarboxaldehyde, and ultra-dry N,N-dimethylformamide (DMF) are mixed and refluxed at 100-130°C in a pressure tube for 48-72 hours, preferably, refluxed at 130°C for 48 hours. After the reaction is completed, the reaction system is allowed to cool to room temperature, and the precipitated product is then centrifuged and rinsed with DMF and acetonitrile to obtain thiazolothiazolopyridine (TTz). The molar ratio of dithiooxamide to 4-pyridinecarboxaldehyde is 1:(3-4), preferably, the molar ratio of dithiooxamide to 4-pyridinecarboxaldehyde is 1:4.

[0066] The reaction process of the above step 1 is specifically as follows:

[0067]

[0068] Step 2, preparing N-ionized thiazolothiazole-bridged viologen;

[0069] Specifically, under argon protection, thiazolothiazole bipyridine TTz, an alkylating agent, and ultra-dry DMF are mixed and stirred in a pressure tube at 80-100°C for 24-48 hours. After the reaction is completed, the reaction system is allowed to stand at room temperature, and the precipitated product is separated by centrifugation to obtain N-ionized thiazolothiazole bridged viologen.

[0070] wherein the alkylating agent is methyl bromide, benzyl bromide, 9-bromomethylanthracene, 1-(bromomethyl)pyrene, 2-bromomethylnaphthalene, 1,3-propanesultone, 9-(bromomethyl)phenanthrene or 3-(bromomethyl)perylene;

[0071] When the alkylating agent is benzyl bromide, the product is N,N'-bis(benzyl)-4,4'-thiazolothiazolopyridinium viologen (Benzyl-Thiazolothiazolopyridinium Viologen, BTV). A specific reaction process is as follows:

[0072]

[0073] When the alkylating agent is 2-bromomethylnaphthalene, the product is naphthylmethyl-thiazolothiazolopyridinium viologen (NTV). A specific reaction process is as follows:

[0074]

[0075] When the alkylating agent is 1,3-propane sultone, the product is sulfonatopropyl-Thiazolothiazolopyridinium viologen (STV). A specific reaction process is as follows:

[0076]

[0077] The molar ratio of thiazolothiazole bipyridine to the alkylating agent is 1:(2-4), preferably 1:4.

[0078] Step 3, preparing organic ion-pair charge transfer nanoparticles based on viologen derivatives;

[0079] Specifically, N-ionized thiazolothiazole-bridged viologen was dissolved in a solvent to form a 1 mM solution A, sodium tetraphenylborate was dissolved in water to form a 2 mM solution B, and an appropriate amount of polyvinylpyrrolidone (PVP) was added to solution B. Under ultrasonic conditions, solution A was quickly added to solution B, and then ultrasonicated for 15 minutes to ensure uniform dispersion. During this process, the final concentration of PVP after solution mixing was ensured to be 0.4-0.45 mg / mL. The product should be stored in the dark. Sodium tetraphenylborate was used to provide tetraphenylborate (BPh4 - ) acts as an anion, electrostatically bonding with the viologen cation to form an ion pair (IPCT). PVP prevents nanoparticle aggregation. During the reaction, the molar ratio of the N-ionized thiazolothiazole-bridged viologen to sodium tetraphenylborate is 1:(2-8).

[0080] The solvent used to dissolve the N-ionized thiazolothiazole-bridged viologen is water or a mixed solvent of water and N,N-dimethylformamide. When NTV is used to prepare organic ion-pair charge transfer nanoparticles based on viologen derivatives, the solvent is a mixed solvent of water and N,N-dimethylformamide, wherein the volume ratio of water to N,N-dimethylformamide is 3:1.

[0081] The present invention also discloses the application of organic ion-pair charge transfer nanoparticles based on thiazolothiazole viologen derivatives in photochromism, specifically including photochromic test paper and photochromic film:

[0082] The preparation of the above-mentioned photochromic test paper is as follows: the filter paper is cut into corresponding sizes, preferably 2×5 cm 2 , using a dropper to wet filter paper with a sample of the organic ion-pair charge-transfer nanoparticles based on the thiazolothiazole viologen derivative of the present invention, and then drying in an 80°C oven to produce photochromic test paper. This photochromic test paper exhibits excellent light response and can display specific visual content when illuminated or written on with a UV laser pen.

[0083] The above-mentioned photochromic film is prepared by adding the organic ion-pair charge-transfer nanoparticles based on the thiazolothiazole viologen derivative of the present invention to polyvinyl alcohol. The temperature is gradually raised to 90°C in a metal bath until the polymer is completely dissolved to form a viscous liquid. The liquid is then poured into a petri dish while still hot and allowed to evaporate naturally to form a photochromic film. This photochromic film exhibits excellent light response properties and can display specific visual content when illuminated or written with a UV laser pen.

[0084] In addition, the fluorescent viologen organic ion-pair charge transfer nanoparticles of the present invention can also be used for the rapid detection of ethylenediamine, specifically:

[0085] Ethylenediamine is dropped onto the above-mentioned photochromic test paper or photochromic film, and the area where the ethylenediamine is dropped changes color, thereby realizing rapid detection of ethylenediamine.

[0086] The present invention introduces a thiazolothiazole group into a viologen compound and combines it with a large, hyperconjugated tetraphenylborate anion to prepare organic ion-pair charge transfer nanoparticles. The thiazolothiazole group in the composite effectively extends the conjugation of the viologen compound, red-shifting its optical absorption to the visible light region, enhancing electron delocalization, reducing the energy gap, and exhibiting strong fluorescence properties. The viologen compound with the expanded thiazolothiazole group exhibits significant photochromic behavior after combining with the tetraphenylborate anion. In addition, the viologen is introduced into polyvinyl alcohol, which, while retaining its photochromic and toxic amine detection applications, also exhibits thermochromic behavior, effectively increasing its application in flexible fields and having greater application prospects.

[0087] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0088] The following examples were prepared using conventional instruments and equipment in the art. Experimental methods in the following examples, where specific conditions are not specified, were generally performed under conventional conditions or according to the conditions recommended by the manufacturer. The various raw materials used in the following examples, unless otherwise specified, were conventional commercially available products, with specifications conventional in the art. In the present specification and the following examples, unless otherwise specified, "%" indicates percentage by weight, "part" indicates parts by weight, and "ratio" indicates weight ratio.

[0089] Example 1

[0090] A method for preparing organic ion-pair charge transfer nanoparticles based on thiazolothiazole viologen derivatives comprises the following steps:

[0091] Step 1: Preparation of thiazolothiazole bipyridine (TTz)

[0092] First, dithiooxalylamine (0.9 g, 7.5 mmol) was added to a reactor, which was sealed with a rubber stopper. The air in the flask was exchanged with argon to create an anhydrous and oxygen-free reaction atmosphere. 4-Pyridinecarboxaldehyde (3.21 g, 2.825 ml, 30 mmol) and ultra-dry DMF (30 ml) were added to the reactor via a syringe through the rubber stopper. The reaction system was stirred at 130°C in an anhydrous and oxygen-free atmosphere for 48 hours. The reaction system was centrifuged, rinsed with DMF and acetonitrile, and vacuum-dried to obtain a pale yellow powder, namely thiazolothiazole bipyridine (TTz).

[0093] Step 2: Preparation of N-ionized Thiazolothiazole-bridged Viologen (BTV)

[0094] Pale yellow TTz (0.3 g, 1.5 mmol) was added to a pressure tube, and the air in the tube was replaced with argon to create a water-free and oxygen-free reaction atmosphere. Benzyl bromide (9 ml, 10.12 mmol) was then added via syringe through the stopper. The reaction system was placed in a metal bath and stirred at 100°C. After 24 hours, the reaction system became an orange-red turbid liquid. After cooling, it was centrifuged, rinsed with n-hexane, and then dried in a vacuum oven at 80°C to yield a bright yellow solid, N,N'-bis(benzyl)-4,4'-thiazolothiazole bipyridine, denoted as BTV.

[0095] Step 3: Preparation of organic ion-pair charge transfer nanoparticles based on viologen derivatives

[0096] Under ultrasound, 2 mL of 1 mM BTV transparent deionized water solution was quickly added to a colorless, transparent deionized water solution containing polyvinylpyrrolidone (PVP, Mw = 10000) and sodium tetraphenylborate (NaTPB, 2 mM). In the system, the final concentration of PVP was 0.4 mg / mL, and the molar ratio of NaTPB to BTV was 2:1, that is, the charge ratio ρ = [TPB - ] / (2×[BTV 2+ ])=1, achieving effective neutralization of charge, and preparing a yellow nanoparticle suspension, that is, organic ion pair charge transfer nanoparticles based on viologen derivatives, labeled as N1-TVP-1, where TVP stands for thiazolothiazole viologen-phenyl borate.

[0097] Preparation of organic ion-pair charge transfer nanoparticle films based on viologen derivatives

[0098] Dissolution of raw materials: Add polyvinyl alcohol (PVA) particles (100 mg) to the N1-TVP-1 nanoparticle suspension (2 mL), slowly raise the temperature to 90°C under stirring conditions, and continue stirring to ensure that the PVA is completely dissolved to form a uniform, transparent, particle-free viscous liquid.

[0099] Cast film: Pour the above-mentioned viscous liquid into a flat and clean cuvette, spread it evenly on the substrate to form a liquid film with relatively uniform thickness. Ensure that the casting process is always carried out in a clean, dry and well-ventilated environment to avoid impurities.

[0100] Drying film formation: Drying is carried out at room temperature. During the drying process, water gradually evaporates and the polymer molecules in the viscous liquid gradually aggregate into a continuous film. After complete drying, it is carefully peeled off from the cuvette base with tweezers to obtain an organic ion-pair charge transfer nanoparticle film based on viologen derivatives. The film has good flexibility, strength, rapid photochromism and unique amine response characteristics.

[0101] Example 2

[0102] The difference between this embodiment and embodiment 1 is that in step 3, the molar ratio of NaTPB to BTV is 8:1, that is, the charge ratio ρ = [TPB - ] / (2×[BTV 2+ ]) = 4. In the system, NaTPB is in excess, achieving full neutralization of the cations. The product is labeled N1-TVP-4.

[0103] At the same time, the same method as in Example 2 was used to prepare an organic ion-pair charge transfer nanoparticle film based on a viologen derivative.

[0104] In order to explore the application of the organic ion-pair charge-transfer nanoparticles based on thiazolothiazole viologen derivatives prepared in this example in photochromic and amine detection: In this example, filter paper is cut into the required size to prepare test paper, and a suspension of the prepared organic ion-pair charge-transfer nanoparticles based on thiazolothiazole viologen derivatives is dropped on the test paper, which is then dried in an oven to obtain a test paper to verify the photochromic properties and ethylenediamine response characteristics of the test paper.

[0105] Figure 1 The particle size dispersion diagram of the organic ion-pair charge transfer nanoparticles based on viologen derivatives prepared in Examples 1 and 2 of the present invention shows that the charge transfer complex has a nanometer-level size.

[0106] Figure 2 The UV spectra of the aqueous solution of sodium tetraphenylborate, the aqueous solution of the N-ionized thiazolothiazole-bridged viologen (BTV) prepared in Example 1, and the aqueous dispersion of organic ion-pair charge transfer nanoparticles based on viologen derivatives are shown. As can be seen from the figure, after the organic ion-pair charge transfer nanoparticles are formed, the UV-visible light absorption peak red-shifts to the visible light region, indicating that after the charge transfer complex is formed, intermolecular charge transfer occurs and a new charge transfer orbit is formed.

[0107] Figure 3 The ultraviolet absorption spectra of the suspensions of organic ion-pair charge-transfer nanoparticles based on viologen derivatives prepared in Examples 1 and 2 of the present invention under ultraviolet light can be seen. As can be seen from the figure, the change in charge ratio ρ does not change the position of the absorption peak. Under ultraviolet light, the sample liquids of organic ion-pair charge-transfer nanoparticles based on viologen derivatives will show color changes from yellow, green to blue, and the absorption spectra will gradually increase around 624 nm.

[0108] Figure 4 The ultraviolet absorption spectra of the suspensions of organic ion-pair charge-transfer nanoparticles based on viologen derivatives prepared in Examples 1 and 2 of the present invention are shown in the dark after the color reaches saturation under ultraviolet light irradiation. As can be seen from the figure, the sample solutions of organic ion-pair charge-transfer nanoparticles based on viologen derivatives will show a color change process from blue to green to close to the initial sample solution under light-proof conditions.

[0109] Figure 5 The transmittance of the suspension of organic ion-pair charge transfer nanoparticles based on viologen derivatives prepared in Examples 1 and 2 of the present invention changes with time. As can be seen from the figure, the nanoparticle sample liquid with a charge ratio of 1 (product of Example 1) has a longer charge transfer life.

[0110] Figure 6 The figure shows the change in the ultraviolet absorption spectrum of the organic ion-pair charge transfer nanoparticles based on viologen derivatives prepared in Examples 1 and 2 of the present invention under ethylenediamine titration. As can be seen from the figure, with the increase of the amount of ethylenediamine, the absorption peak at around 624nm gradually increases, and the color of the nanoparticle sample liquid gradually changes from yellow to blue. This is attributed to the fact that ethylenediamine is an electron-rich molecule, and the electrons on its HOMO orbital are transferred to the viologen derivative molecule, thereby inducing the generation of viologen free radicals and then the color change occurs.

[0111] Figure 7 This is a spectrum of changes in fluorescence intensity of the organic ion-pair charge transfer nanoparticles based on viologen derivatives prepared in Examples 1 and 2 of the present invention under ethylenediamine titration. As can be seen from the figure, as the amount of ethylenediamine increases, fluorescence quenching occurs and the fluorescence intensity gradually decreases.

[0112] Figure 8 The changes in the ultraviolet absorption spectra of the organic ion-pair charge transfer nanoparticle films based on viologen derivatives prepared in Examples 1 and 2 of the present invention under ultraviolet light irradiation show that as the irradiation time increases, the absorption peak at around 624 nm gradually increases, and the color of the film changes from yellow to blue.

[0113] Figure 9The changes in the ultraviolet absorption spectra of the organic ion-pair charge-transfer nanoparticle films based on viologen derivatives prepared in Examples 1 and 2 of the present invention before and after exposure to ethylenediamine gas are shown in the figure. As can be seen from the figure, with the extension of the steam fumigation time, the color of the film gradually changes from yellow to blue and then to brownish yellow. Therefore, the presence of ethylenediamine can be quickly detected by the change in film color.

[0114] Example 3

[0115] A method for preparing organic ion-pair charge transfer nanoparticles based on thiazolothiazole viologen derivatives comprises the following steps:

[0116] Step 1: Preparation of thiazolothiazole bipyridine (TTz)

[0117] First, dithiooxalylamine (0.9 g, 7.5 mmol) was added to a reactor, which was sealed with a rubber stopper. The air in the flask was exchanged with argon to create an anhydrous and oxygen-free reaction atmosphere. 4-Pyridinecarboxaldehyde (3.21 g, 2.825 ml, 30 mmol) and ultra-dry DMF (30 ml) were added to the reactor via a syringe through the rubber stopper. The reaction system was stirred at 130°C in an anhydrous and oxygen-free atmosphere for 48 hours. The reaction system was centrifuged, rinsed with DMF and acetonitrile, and vacuum-dried to obtain a pale yellow powder, namely thiazolothiazole bipyridine (TTz).

[0118] Step 2: Preparation of N-ionized Thiazolothiazole-bridged Viologen (NTV)

[0119] TTz (50 mg, 0.169 mmol) and 2-bromomethylnaphthalene (139.74 mg, 0.23 mmol) were added to a 25 mL pressure tube and sealed with a rubber stopper. The air in the reactor was then replaced with argon to create an anhydrous and oxygen-free reaction atmosphere. Ultra-dry acetonitrile (10 mL) was then added to the reactor via a syringe through the rubber stopper. The reaction system was stirred at 75°C under an anhydrous and oxygen-free atmosphere for 24 hours. After the reaction was terminated and the reaction solution cooled to room temperature, the reaction system was centrifuged to separate the lower solid layer. The solid was then washed with DMF to obtain a yellow solid, which was then dried under vacuum. This solid was N,N'-bis(methylenenaphthalene)-4,4'-thiazolothiazole bipyridine, designated NTV.

[0120] Step 3: Preparation of organic ion-pair charge transfer nanoparticles based on viologen derivatives

[0121] Under ultrasound, 2 mL of a 1 mM NTV transparent solution (the solvent in the transparent solution is a mixed solvent of N, N-dimethylformamide and water, with a volume ratio of N, N-dimethylformamide to water of 1:3) was quickly added to a colorless transparent solution containing polyvinylpyrrolidone (PVP, Mw = 10000) and sodium tetraphenylborate (NaTPB, 2 mM) (the solvent in the transparent solution is a mixed solvent of N, N-dimethylformamide and water, with a volume ratio of N, N-dimethylformamide to water of 1:3, 4 mL). The final concentration of PVP was adjusted to 0.4 mg / mL. The molar ratio of NaTPB to BTV was 2:1, i.e., the charge ratio ρ = [TPB - ] / (2×[NTV 2+ ])=1, a transparent yellow nanoparticle suspension was prepared, namely organic ion pair charge transfer nanoparticles based on viologen derivatives, labeled as N2-TVP-1, where TVP stands for thiazolothiazole viologen-phenyl borate.

[0122] Preparation of organic ion-pair charge transfer nanoparticle films based on viologen derivatives:

[0123] Dissolution of raw materials: Add polyvinyl alcohol (PVA) particles (100 mg) to the prepared N2-TVP-1 nanoparticle sample solution (2 mL), slowly raise the temperature to 90°C under stirring conditions, and continue stirring to ensure that the PVA is completely dissolved to form a uniform, transparent, particle-free viscous liquid.

[0124] Cast film: Pour the prepared PVA nanoparticle solution into a flat and clean cuvette and spread it evenly on the substrate to form a liquid film with relatively uniform thickness. Ensure that the casting process is always carried out in a clean, dry and well-ventilated environment to avoid the mixing of impurities.

[0125] Drying to film: Drying is performed at room temperature. During the drying process, the water gradually evaporates, and the polymer molecules in the PVA nanoparticle solution gradually aggregate into a continuous film. Once completely dry, the film is carefully peeled from the cuvette substrate with tweezers, resulting in a flexible and strong viologen-derivative-based organic ion-pair charge transfer nanoparticle film. This film exhibits rapid photochromism and unique amine-responsive properties.

[0126] Example 4

[0127] The difference between this embodiment and embodiment 3 is that in step 3, the molar ratio of NaTPB to NTV is 8:1, that is, the charge ratio ρ = [TPB - ] / (2×[NTV 2+ ]) = 4. In the system, NaTPB is in excess, achieving full neutralization of the cations. The product is labeled N2-TVP-4.

[0128] Figure 10 This is a particle size dispersion diagram of the organic ion-pair charge transfer nanoparticles based on viologen derivatives prepared in Examples 3 and 4 of the present invention. As can be seen from the figure, the particle size is not much different from that of Examples 1 and 2, and all have a particle size within 100 nanometers, which meets the requirements of nanoparticle size.

[0129] Figure 11 The UV spectra are of an aqueous solution of sodium tetraphenylborate, an aqueous solution of N-ionized thiazolothiazole-bridged viologen (NTV) prepared in Example 3, and an aqueous dispersion of organic ion-pair charge-transfer nanoparticles based on viologen derivatives prepared in Example 3. As can be seen from the figure, after the formation of organic ion-pair charge-transfer nanoparticles, the UV-visible light absorption peak red-shifts to the visible light region, and charge transfer occurs from the tetraphenylborate anion to the viologen derivative cation, forming a new electron transfer orbit.

[0130] Figure 12 The ultraviolet absorption spectra of the suspensions of organic ion-pair charge-transfer nanoparticles based on viologen derivatives prepared in Examples 3 and 4 of the present invention under ultraviolet light. As can be seen from the figure, the change in charge ratio will not change the position of the absorption peak. Under ultraviolet light, the sample liquids of organic ion-pair charge-transfer nanoparticles based on viologen derivatives will show color changes from yellow, green to blue, and the absorption spectra will gradually increase around 624 nm.

[0131] Figure 13 The ultraviolet absorption spectra of the suspensions of organic ion-pair charge-transfer nanoparticles based on viologen derivatives prepared in Examples 3 and 4 of the present invention are shown in the dark after the color reaches saturation under ultraviolet light irradiation. It can be seen from the figure that the sample liquids of organic ion-pair charge-transfer nanoparticles based on viologen derivatives will show a color change process from blue to green to close to the initial sample liquid under light-proof conditions.

[0132] Figure 14 The curves showing the change in transmittance over time of suspensions of organic ion-pair charge transfer nanoparticles based on viologen derivatives prepared in Examples 3 and 4 of the present invention show that the nanoparticle sample liquid with a charge ratio of 1 has a longer charge transfer life.

[0133] Figure 15 This is the UV absorption-visible light spectrum of the organic ion-pair charge transfer nanoparticle suspension based on viologen derivatives prepared in Examples 3 and 4 of the present invention under ethylenediamine titration. As can be seen from the figure, with the addition of ethylenediamine, a new absorption peak appears in the visible light region, and the color of the nanoparticle sample liquid gradually changes from yellow to blue.

[0134] Figure 16This is a spectrum showing the change in fluorescence intensity of the suspension of organic ion-pair charge transfer nanoparticles based on viologen derivatives prepared in Examples 3 and 4 of the present invention under ethylenediamine titration. As can be seen from the figure, with the addition of ethylenediamine, fluorescence quenching occurs and the fluorescence intensity gradually decreases.

[0135] Figure 17 The figure shows the changes in the ultraviolet absorption spectra of the organic ion-pair charge transfer nanoparticle films based on viologen derivatives prepared in Examples 3 and 4 of the present invention under ultraviolet light irradiation. As can be seen from the figure, with the increase of irradiation time, the absorption peak at around 624nm gradually increases, and the color of the film changes from yellow to blue.

[0136] Figure 18 The changes in the ultraviolet absorption spectra of the organic ion-pair charge-transfer nanoparticle films based on viologen derivatives prepared in Examples 3 and 4 of the present invention before and after exposure to ethylenediamine gas are shown in the figure. As can be seen from the figure, as the steam fumigation time increases, the color of the film gradually changes from yellow to blue and then to brownish yellow. Therefore, the presence of ethylenediamine can be quickly detected by the change in film color.

[0137] Example 5

[0138] A method for preparing organic ion-pair charge transfer nanoparticles based on thiazolothiazole viologen derivatives comprises the following steps:

[0139] Step 1: Preparation of thiazolothiazole bipyridine (TTz)

[0140] First, dithiooxalylamine (0.9 g, 7.5 mmol) was added to a reactor, which was sealed with a rubber stopper. The air in the flask was exchanged with argon to create an anhydrous and oxygen-free reaction atmosphere. 4-Pyridinecarboxaldehyde (3.21 g, 2.825 ml, 30 mmol) and ultra-dry DMF (30 ml) were added to the reactor via a syringe through the rubber stopper. The reaction system was stirred at 130°C in an anhydrous and oxygen-free atmosphere for 48 hours. The reaction system was centrifuged, rinsed with DMF and acetonitrile, and vacuum-dried to obtain a pale yellow powder, namely thiazolothiazole bipyridine (TTz).

[0141] Step 2: Preparation of N-ionized Thiazolothiazole-bridged Viologen (STV)

[0142] TTz (50 mg, 0.169 mmol) and 1,3-propane sultone (61.9 mg, 0.121 mmol) were added separately to a 25 mL pressure tube. After evacuating and inflating the reaction system with argon three times, 6 mL of ultra-dry DMF was added to the reaction system. The mixture was stirred at 100°C for 24 hours. After cooling to room temperature, the mixture was centrifuged and washed three times with acetonitrile. Finally, the product was dried in a vacuum oven to obtain a pale yellow solid (63.8 mg, 0.125 mmol), which is N,N'-bis(3-sulfonylpropyl)-2,5-di(4-pyridyl)thiazolo[5,4-d]thiazole, denoted as STV.

[0143] Step 3: Preparation of organic ion-pair charge transfer nanoparticles based on viologen derivatives

[0144] Under ultrasound, 2 mL of a 1 mM solution of STV in a transparent deionized water solution was quickly added to a colorless, transparent deionized water solution containing polyvinylpyrrolidone (PVP, Mw = 10,000) and sodium tetraphenylborate (NaTPB, 2 mM). PVP is used to prevent nanoparticle aggregation, and its final concentration was adjusted to 0.4 mg / mL. The molar ratio of NaTPB to STV was 2:1, i.e., the charge ratio ρ = [TPB - ] / (2×[STV 2+ ])=1, a transparent yellow nanoparticle suspension was prepared, namely organic ion pair charge transfer nanoparticles based on viologen derivatives, labeled as N3-TVP-1, where TVP stands for thiazolothiazole viologen-phenyl borate.

[0145] Preparation of organic ion-pair charge transfer nanoparticle films based on viologen derivatives

[0146] Dissolution of raw materials: Add polyvinyl alcohol (PVA) particles (100 mg) to the prepared N3-TVP-1 nanoparticle sample solution (2 mL), slowly raise the temperature to 90°C under stirring conditions, and continue stirring to ensure that the PVA is completely dissolved to form a uniform, transparent, particle-free viscous liquid.

[0147] Cast film: Pour the prepared PVA nanoparticle solution into a flat and clean cuvette and spread it evenly on the substrate to form a liquid film with relatively uniform thickness. Ensure that the casting process is always carried out in a clean, dry and well-ventilated environment to avoid the mixing of impurities.

[0148] Drying to film: Drying is performed at room temperature. During the drying process, the water gradually evaporates, and the polymer molecules in the PVA nanoparticle solution gradually aggregate into a continuous film. Once completely dry, the film is carefully peeled from the cuvette substrate with tweezers, resulting in a flexible and strong viologen-derivative-based organic ion-pair charge transfer nanoparticle film. This film exhibits rapid photochromism and unique amine-responsive properties.

[0149] Example 6

[0150] The difference between this embodiment and embodiment 5 is that in step 3, the molar ratio of NaTPB to STV is 8:1, that is, the charge ratio ρ = [TPB - ] / (2×[STV 2+ ]) = 4. In the system, NaTPB is in excess, achieving full neutralization of the cations. The product is labeled N3-TVP-4.

[0151] Figure 19 The particle size dispersion diagram of the organic ion-pair charge transfer nanoparticles based on viologen derivatives prepared in Examples 5 and 6 of the present invention shows that N3-TVP has a size distribution within one thousand nanometers, which is larger than that of Examples 1 to 4. This is attributed to the sulfonyl group on the alkylation of viologen, which is itself an anion, neutralizing the charge of the small molecule of the viologen derivative. Therefore, in the subsequent ion association to form a charge transfer complex, the interaction force between the anion and the cation is not obvious, the distance between the molecules may be far, and the aggregate is larger overall.

[0152] Figure 20 The UV spectra of the aqueous solution of sodium tetraphenylborate, the aqueous solution of the N-ionized thiazolothiazole-bridged viologen (STV) prepared in Example 5, and the aqueous dispersion of the organic ion-pair charge transfer nanoparticles based on the viologen derivative prepared in Example 5 are shown. As can be seen from the figure, after the organic ion-pair charge transfer nanoparticles are formed, the UV-visible light absorption peak red-shifts to the visible light region, indicating that there is a charge transfer phenomenon between molecules and a new electron transfer orbit is formed.

[0153] Figure 21 The ultraviolet absorption spectra of the suspensions of organic ion-pair charge-transfer nanoparticles based on viologen derivatives prepared in Examples 5 and 6 of the present invention under ultraviolet light irradiation. As can be seen from the figure, the change in charge ratio will not change the position of the absorption peak. Under ultraviolet light irradiation, the sample liquids of organic ion-pair charge-transfer nanoparticles based on viologen derivatives will show color changes from light yellow, purple to light brown, and the absorption spectra will gradually increase at around 590nm.

[0154] Figure 22 The ultraviolet absorption spectra of the suspensions of organic ion-pair charge-transfer nanoparticles based on viologen derivatives prepared in Examples 5 and 6 of the present invention are shown in the dark after the color reaches saturation under ultraviolet light irradiation. As can be seen from the figure, the sample liquids of organic ion-pair charge-transfer nanoparticles based on viologen derivatives will show a color change process from light yellow, light purple to close to the initial sample liquid under light-proof conditions.

[0155] Figure 23The curves showing the change in transmittance over time of suspensions of organic ion-pair charge transfer nanoparticles based on viologen derivatives prepared in Examples 5 and 6 of the present invention show that the nanoparticle sample liquid with a charge ratio of 1 has a longer charge transfer life.

[0156] Figure 24 This is the UV absorption-visible light spectrum of the organic ion-pair charge transfer nanoparticle suspension based on viologen derivatives prepared in Examples 5 and 6 of the present invention under ethylenediamine titration. As can be seen from the figure, with the addition of ethylenediamine, a new absorption peak appears in the visible light region, and the color of the nanoparticle sample liquid gradually changes from light color to cyan.

[0157] Figure 25 This is a spectrum showing the change in fluorescence intensity of the suspension of organic ion-pair charge transfer nanoparticles based on viologen derivatives prepared in Examples 5 and 6 of the present invention under ethylenediamine titration. As can be seen from the figure, with the addition of ethylenediamine, fluorescence quenching occurs and the fluorescence intensity gradually decreases.

[0158] Figure 26 The figure shows the changes in the ultraviolet absorption spectra of the organic ion-pair charge transfer nanoparticle films based on viologen derivatives prepared in Examples 5 and 6 of the present invention under ultraviolet light irradiation. As can be seen from the figure, with the increase of irradiation time, the absorption peak at around 590nm gradually increases, and the color of the film changes from yellow to purple.

[0159] Figure 27 The changes in the ultraviolet absorption spectra of the organic ion-pair charge transfer nanoparticle films based on viologen derivatives prepared in Examples 5 and 6 of the present invention before and after exposure to ethylenediamine gas show that, as the steam fumigation time increases, the color of the films gradually changes from yellow to purple and then to brownish yellow. Therefore, the presence of ethylenediamine can be quickly detected by the change in film color.

[0160] Figure 28 The photochromic test results of the organic ion-pair charge transfer nanoparticle films based on viologen derivatives prepared in Examples 1, 3 and 5 of the present invention are shown. As can be seen from the figure, after the nanoparticles in this work are made into films, they retain their fast light response behavior while also having good flexibility. This lays a certain foundation for the application of organic ion-pair charge transfer nanoparticles based on viologen derivatives in the field of flexible sensing.

[0161] Figure 29 The color of the organic ion-pair charge transfer nanoparticle film based on viologen derivatives prepared in Example 1 of the present invention changes with the exposure time to sunlight at an ambient temperature of 30°C. As can be seen from the figure, with the exposure to sunlight, the color of the film quickly changes from yellow to blue in a short period of time, which creates potential for detecting sunlight intensity and has application prospects in daily life.

[0162] Example 7

[0163] A method for preparing fluorescent viologen-based organic ion-pair charge transfer nanoparticles comprises the following steps:

[0164] S1: Under argon protection, dithiooxamide, 4-pyridinecarboxaldehyde, and ultra-dry N,N-dimethylformamide (DMF) were mixed and reacted at 100°C in a pressure tube under condensation reflux for 72 hours. After the reaction was completed, the reaction system was allowed to cool to room temperature, and the precipitated product was centrifuged and rinsed with DMF and acetonitrile to obtain thiazolothiazole bipyridine. The molar ratio of dithiooxamide to 4-pyridinecarboxaldehyde was 2:7;

[0165] S2: Under argon protection, thiazolothiazole bipyridine TTz, an alkylating agent, and ultra-dry DMF are mixed and stirred in a pressure tube at 80°C for 72 hours. After the reaction is completed, the reaction system is allowed to stand at room temperature, and the precipitated product is separated by centrifugation to obtain N-ionized thiazolothiazole bridged viologen;

[0166] The alkylating agent is methyl bromide, and the molar ratio of thiazolothiazole bipyridine to the alkylating agent is 1:2.

[0167] S3: Take N-ionized thiazolothiazole-bridged viologen and dissolve it in a solvent to form a solution A with a concentration of 1 mM, dissolve sodium tetraphenylborate in water to form a 2 mM solution B, and add an appropriate amount of polyvinylpyrrolidone (PVP) to solution B. Under ultrasonic conditions, solution A is quickly added to solution B, and then ultrasonicated for 15 minutes to ensure uniform dispersion. During this process, the final concentration of PVP after the solution is mixed is ensured to be 0.45 mg / mL, and the product needs to be stored in the dark; in the above reaction process, the molar ratio of N-ionized thiazolothiazole-bridged viologen to sodium tetraphenylborate is 1:4.

[0168] Example 8

[0169] A method for preparing fluorescent viologen-based organic ion-pair charge transfer nanoparticles comprises the following steps:

[0170] S1: Under argon protection, dithiooxamide, 4-pyridinecarboxaldehyde, and ultra-dry N,N-dimethylformamide (DMF) were mixed and reacted at 120°C under condensation reflux in a pressure tube for 60 hours. After the reaction, the reaction system was allowed to cool to room temperature, and the precipitated product was centrifuged and rinsed with DMF and acetonitrile to obtain thiazolothiazole bipyridine. The molar ratio of dithiooxamide to 4-pyridinecarboxaldehyde was 1:4.

[0171] S2: Under argon protection, thiazolothiazole bipyridine TTz, an alkylating agent, and ultra-dry DMF are mixed and stirred in a pressure tube at 90°C for 35 hours. After the reaction is completed, the reaction system is allowed to stand at room temperature, and the precipitated product is separated by centrifugation to obtain N-ionized thiazolothiazole bridged viologen;

[0172] The alkylating agent is 9-bromomethylanthracene, and the molar ratio of thiazolothiazole bipyridine to the alkylating agent is 1:4.

[0173] S3: Take N-ionized thiazolyl and thiazole-bridged viologen and dissolve it in a solvent to form a solution A with a concentration of 1mM, dissolve sodium tetraphenylborate in water to form a 2mM solution B, and add an appropriate amount of polyvinylpyrrolidone (PVP) to solution B. Under ultrasonic conditions, solution A is quickly added to solution B, and then ultrasonicated for 15 minutes to ensure uniform dispersion. During this process, the final concentration of PVP after the solution is mixed is ensured to be 0.4mg / mL, and the product needs to be stored in the dark; in the above reaction process, the molar ratio of N-ionized thiazolyl and thiazole-bridged viologen to sodium tetraphenylborate is 1:6.

[0174] Example 9

[0175] The difference between this embodiment and embodiment 1 is that the alkylating agent is 1-(bromomethyl)pyrene.

[0176] S1: Under argon protection, dithiooxamide, 4-pyridinecarboxaldehyde, and ultra-dry N,N-dimethylformamide (DMF) were mixed and reacted at 120°C under condensation reflux in a pressure tube for 48 hours. After the reaction, the reaction system was allowed to cool to room temperature, and the precipitated product was centrifuged and rinsed with DMF and acetonitrile to obtain thiazolothiazole bipyridine. The molar ratio of dithiooxamide to 4-pyridinecarboxaldehyde was 1:4;

[0177] S2: Under argon protection, thiazolothiazole bipyridine TTz, an alkylating agent, and ultra-dry DMF are mixed and stirred in a pressure tube at 110°C for 36 hours. After the reaction is completed, the reaction system is allowed to stand at room temperature, and the precipitated product is separated by centrifugation to obtain N-ionized thiazolothiazole bridged viologen;

[0178] The alkylating agent is 1-(bromomethyl)pyrene, and the molar ratio of thiazolothiazole bipyridine to the alkylating agent is 1:6.

[0179] S3: Take N-ionized thiazolylthiazole-bridged viologen and dissolve it in a solvent to form a solution A with a concentration of 1 mM, dissolve sodium tetraphenylborate in water to form a 2 mM solution B, and add an appropriate amount of polyvinylpyrrolidone (PVP) to solution B. Under ultrasonic conditions, solution A is quickly added to solution B, and then ultrasonicated for 15 minutes to ensure uniform dispersion. During this process, the final concentration of PVP after the solution is mixed is ensured to be 0.4 mg / mL, and the product needs to be stored in the dark; in the above reaction process, the molar ratio of N-ionized thiazolylthiazole-bridged viologen to sodium tetraphenylborate is 1:8.

[0180] Example 10

[0181] The difference between this embodiment and embodiment 1 is that the alkylating agent is 2-bromomethylnaphthalene.

[0182] S1: Under argon protection, dithiooxamide, 4-pyridinecarboxaldehyde, and ultra-dry N,N-dimethylformamide (DMF) were mixed and reacted at 100°C in a pressure tube under condensation reflux for 72 hours. After the reaction was completed, the reaction system was allowed to stand at room temperature, and the precipitated product was then centrifuged and rinsed with DMF and acetonitrile to obtain thiazolothiazole bipyridine. The molar ratio of dithiooxamide to 4-pyridinecarboxaldehyde was 1:4;

[0183] S2: Under argon protection, thiazolothiazole bipyridine TTz, an alkylating agent, and ultra-dry DMF are mixed and stirred in a pressure tube at 110°C for 30 hours. After the reaction is completed, the reaction system is allowed to stand at room temperature, and the precipitated product is separated by centrifugation to obtain N-ionized thiazolothiazole bridged viologen;

[0184] The alkylating agent is 2-bromomethylnaphthalene, and the molar ratio of thiazolothiazole bipyridine to the alkylating agent is 1:4.

[0185] S3: Take N-ionized thiazolyl and thiazole-bridged viologen and dissolve it in a solvent to form a solution A with a concentration of 1mM, dissolve sodium tetraphenylborate in water to form a 2mM solution B, and add an appropriate amount of polyvinylpyrrolidone (PVP) to solution B. Under ultrasonic conditions, solution A is quickly added to solution B, and then ultrasonicated for 15 minutes to ensure uniform dispersion. During this process, the final concentration of PVP after the solution is mixed is ensured to be 0.4mg / mL, and the product needs to be stored in the dark; in the above reaction process, the molar ratio of N-ionized thiazolyl and thiazole-bridged viologen to sodium tetraphenylborate is 1:2.

[0186] Example 11

[0187] The difference between this embodiment and embodiment 1 is that the alkylating agent is 9-(bromomethyl)phenanthrene.

[0188] S1: Under argon protection, dithiooxamide, 4-pyridinecarboxaldehyde, and ultra-dry N,N-dimethylformamide (DMF) were mixed and reacted under condensation reflux at 120°C in a pressure tube for 72 hours. After the reaction, the reaction system was allowed to cool to room temperature, and the precipitated product was centrifuged and rinsed with DMF and acetonitrile to obtain thiazolothiazole bipyridine. The molar ratio of dithiooxamide to 4-pyridinecarboxaldehyde was 1:4.

[0189] S2: Under argon protection, thiazolothiazole bipyridine TTz, an alkylating agent, and ultra-dry DMF are mixed and stirred in a pressure tube at 130°C for 48 hours. After the reaction is completed, the reaction system is allowed to stand at room temperature, and the precipitated product is separated by centrifugation to obtain N-ionized thiazolothiazole bridged viologen;

[0190] The alkylating agent is 9-(bromomethyl)phenanthrene, and the molar ratio of thiazolothiazole bipyridine to the alkylating agent is 1:5.

[0191] S3: Take N-ionized thiazolylthiazole-bridged viologen and dissolve it in a solvent to form a solution A with a concentration of 1 mM, dissolve sodium tetraphenylborate in water to form a 2 mM solution B, and add an appropriate amount of polyvinylpyrrolidone (PVP) to solution B. Under ultrasonic conditions, solution A is quickly added to solution B, and then ultrasonicated for 15 minutes to ensure uniform dispersion. During this process, the final concentration of PVP after the solution is mixed is ensured to be 0.42 mg / mL, and the product needs to be stored in the dark; in the above reaction process, the molar ratio of N-ionized thiazolylthiazole-bridged viologen to sodium tetraphenylborate is 1:6.

[0192] Example 12

[0193] The difference between this embodiment and embodiment 1 is that the alkylating agent is 3-(bromomethyl)perylene.

[0194] S1: Under argon protection, dithiooxamide, 4-pyridinecarboxaldehyde, and ultra-dry N,N-dimethylformamide (DMF) were mixed and reacted at 100°C in a pressure tube under condensation reflux for 50 hours. After the reaction was completed, the reaction system was allowed to stand at room temperature, and the precipitated product was then centrifuged and rinsed with DMF and acetonitrile to obtain thiazolothiazole bipyridine. The molar ratio of dithiooxamide to 4-pyridinecarboxaldehyde was 1:4;

[0195] S2: Under argon protection, thiazolothiazole bipyridine TTz, an alkylating agent, and ultra-dry DMF are mixed and stirred in a pressure tube at 90°C for 48 hours. After the reaction is completed, the reaction system is allowed to stand at room temperature, and the precipitated product is separated by centrifugation to obtain N-ionized thiazolothiazole bridged viologen;

[0196] The alkylating agent is 3-(bromomethyl)perylene, and the molar ratio of thiazolothiazole bipyridine to the alkylating agent is 1:4.

[0197] S3: Take N-ionized thiazolyl and thiazole-bridged viologen and dissolve it in a solvent to form a solution A with a concentration of 1mM, dissolve sodium tetraphenylborate in water to form a 2mM solution B, and add an appropriate amount of polyvinylpyrrolidone (PVP) to solution B. Under ultrasonic conditions, solution A is quickly added to solution B, and then ultrasonicated for 15 minutes to ensure uniform dispersion. During this process, the final concentration of PVP after the solution is mixed is ensured to be 0.42mg / mL, and the product needs to be stored in the dark; in the above reaction process, the molar ratio of N-ionized thiazolyl and thiazole-bridged viologen to sodium tetraphenylborate is 1:8.

[0198] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing fluorescent viologen organic ion-pair charge transfer nanoparticles, characterized in that: The following steps are involved: S1: reacting dithiooxalylamine with 4-pyridinecarboxaldehyde under anhydrous and oxygen-free conditions to prepare thiazolothiazole bipyridine; S2: Under argon protection, reacting the thiazolothiazole bipyridine with an alkylating agent to obtain an N-ionized thiazolothiazole bridged viologen; S3: mixing the N-ionized thiazolothiazole bridged viologen with sodium tetraphenylborate and polyvinylpyrrolidone to react, so as to prepare the fluorescent viologen-based organic ion pair charge transfer nanoparticles.

2. The method for preparing fluorescent viologen organic ion-pair charge transfer nanoparticles according to claim 1, characterized in that: In step S1, the molar ratio of dithiooxalylamine to 4-pyridinecarboxaldehyde is 1:(3-4).

3. The method for preparing fluorescent viologen organic ion-pair charge transfer nanoparticles according to claim 1, characterized in that: In step S2, the molar ratio of the thiazolothiazole bipyridine to the alkylating agent is 1:(2-4).

4. The method for preparing fluorescent viologen organic ion-pair charge transfer nanoparticles according to claim 1, characterized in that: In step S2, the alkylating agent is methyl bromide, benzyl bromide, 9-bromomethylanthracene, 1-(bromomethyl)pyrene, 2-bromomethylnaphthalene, 1,3-propanesultone, 9-(bromomethyl)phenanthrene or 3-(bromomethyl)perylene.

5. The method for preparing fluorescent viologen organic ion-pair charge transfer nanoparticles according to claim 1, characterized in that: In step S3, the molar ratio of the N-ionized thiazolothiazole-bridged viologen to sodium tetraphenylborate is 1:(2-8).

6. The method for preparing fluorescent viologen organic ion-pair charge transfer nanoparticles according to claim 1, characterized in that: In step S3, the concentration of polyvinyl pyrrolidone in the reaction system is 0.4-0.45 mg / mL.

7. A fluorescent viologen-based organic ion-pair charge transfer nanoparticle, characterized in that: It is prepared by the method according to any one of claims 1 to 6.

8. A photochromic test paper, characterized in that The nanoparticles are prepared by the fluorescent viologen organic ion pair charge transfer nanoparticles described in claim 7.

9. A photochromic film, characterized in that: The nanoparticles are prepared by the fluorescent viologen organic ion pair charge transfer nanoparticles described in claim 7.

10. Use of the photochromic test paper of claim 8 or the photochromic film of claim 9 in the detection of ethylenediamine.

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