WO2022021662A1 - Azaanthracene derivative upconversion system, preparation method therefor and use thereof - Google Patents

Abstract

The present invention relates to an azaanthracene derivative upconversion system, a preparation method therefor and use thereof. The azaanthracene derivative free of noble metals and heavy atoms used as a photosensitizer material of TTA-UC can be effectively compounded with a 9,10-diphenylanthracene (DPA) light emitting agent to obtain TTA-UC, and a green-turn-blue upconversion efficiency of up to 9.69% can be obtained. Using the azaanthracene derivative as a light emitting agent material of single photon absorption upconversion, red light of 655 nm excitation can be achieved, a red-turn-yellow single photon absorption upconversion fluorescence color-changing effect of orange-yellow light at about 610 nm can be obtained, and upconversion color changes can be obtained without requiring oxygen removal, thereby enriching the types of light emitting agent materials in the field of single photon absorption upconversion.

Description

Upconversion system of azaanthene derivatives, preparation method and application thereof technical field

The invention relates to a heterocyclic compound, which is an azaanthene derivative, in particular to the application of an azaanthene derivative as a triplet-triplet annihilation upconversion (TTA-UC) photosensitizer material.

Background technique

Organic upconversion (UC) refers to a phenomenon in which organic molecular systems emit short-wavelength (high-energy) light by absorbing long-wavelength (low-energy) light. According to the excitation light source is divided into strong light and weak light, up-conversion is also called strong light up-conversion and weak light up-conversion. The former is such as strong two-photon absorption upconversion (TPA-UC), in the process of TPA-UC, the excitation light source intensity needs to be as high as MW·cm ^-2 or even GW·cm ^-2 order (that is, sunlight more than one million times the intensity), apparently, such high-intensity excitation light sources limit the practical application of strong two-photon absorption upconversion. Weak light upconversion refers to a phenomenon in which organic molecular systems emit high-energy light by absorbing low-energy light under the irradiation of an excitation light source of the order of mW~W·cm ^-2 . Since the intensity of the excitation light required for weak light upconversion is close to that of sunlight (100 mW·cm ^-2 ), this technique is widely used in upconversion lasing, 3D fluorescence microscopy/imaging, solar cells, photocatalysis and optoelectronic devices, etc. The high-tech field has potential application value, so it is widely favored by the scientific and technological circles, stimulates the great enthusiasm of researchers, and becomes a hot topic in the field of organic optoelectronics.

Organic weak light upconversion mechanisms include two, namely triplet-triplet annihilation upconversion (Triplet-triplet upconversion). annihilation upconversion, TTA-UC) and one-photon tropical absorption upconversion (One-photon hot band absorption upconversion, OPA-UC). TTA-UC The composition of weak light up-conversion material is composed of two parts, which are photosensitizer molecules (also known as donors) and luminescent molecules (also known as acceptors). exist Under the mechanism of TTA-UC, the up-conversion phenomenon can be generated by the cooperation of photosensitizers and luminescent agents through many microscopic mechanisms of intermolecular energy transfer.

At present, the photosensitizer materials used in the TTA-UC mechanism can be mainly divided into three categories: (1) noble metal complex sensitizers, such as RuII, IrIII, PtII, PdII sensitizers; (2) heavy atom effect organic sensitizers Triplet sensitizer; (3) Organic triplet sensitizer without heavy atom effect. There are many studies on noble metal complex sensitizers, and they are relatively mature. It has been reported that the efficiency of the TTA-UC system composed of noble metal complex sensitizers can reach about 30%; however, the price of noble metal sensitizers is high, and the preparation of The process is complex, and it is highly toxic to the environment and organisms, so it cannot be used in large-scale practical applications. Among the triplet sensitizers with heavy atom effect, due to the heavy atom effect of the halogenated elements bromine and iodine atoms, they can generate strong spin-orbit coupling and energy level crossing, thereby enhancing the ability of ISC, which also has potential research value; however, The price of photosensitizer materials with heavy atoms is also relatively high. Heavy atom-free pure organic triplet sensitizers are also a class of sensitizers being studied by researchers, but their structures are special, and their intersystem crossing ability cannot be effectively predicted, and there are few reports in the literature. This kind of sensitizer is relatively cheap, simple to prepare and easy to obtain; however, the TTA-UC efficiency obtained by pure organic photosensitizers reported so far is low, only about 3%.

It can be seen from the TTA-UC mechanism that the wavelengths of up-converted excitation light and emission light can be easily regulated by choosing different photosensitizers and luminescent agents. However, this regulation is based on the triplet energy levels of the photosensitizers and luminescent agents. a valid match. Most of the triplet energy levels of photosensitizers and luminescent agents are difficult to measure, which greatly increases the difficulty of material preparation and performance research. On the other hand, because the energy transfer between the photosensitizer and luminescent agent of TTA-UC needs to be carried out under the condition of deoxygenation, the practical application of its material is greatly limited; while OPA-UC can be carried out without deoxygenation, which is The application value of the up-conversion is greatly improved. At present, most of the research on the weak light up-conversion direction is carried out around TTA-UC, and the research on OPA-UC is rarely reported, and the research on the structure-property relationship of OPA-UC materials is still blank.

technical problem

The invention provides the application of an azaanthene derivative as a TTA-UC photosensitizer material, which is cheap, simple to prepare and easy to obtain. Using azaanthene derivatives as photosensitizers and compounding with DPA materials to obtain TTA-UC upconversion, the upconversion efficiency is significantly improved compared with the current efficiency of pure organic photosensitizers. Azaanthene derivative materials do not contain precious metals or heavy atoms. They are traditionally used as dyes, often used as biological dyeing reagents, and often used as acid-base indicators, but they have not been used in TTA-UC photosensitizers. material reports.

The invention provides the application of an azaanthene derivative as a single-photon absorption up-conversion luminescent agent, which does not require a deoxidizing environment, and can realize the fluorescence color change of red light irradiation and yellow light emission after low-power excitation, which further enriches the single photon The types of luminescent agent materials in the field of absorption upconversion materials provide reference for the molecular design of OPA-UC materials. Azaanthene derivative materials are traditionally used as dyes, often used as biological dyeing reagents, and often used as acid-base indicators, but there is currently no report of applying them to single-photon absorption upconversion luminescent materials. Three commercially available azaanthene derivatives are Phenosafranine (PSF), Safranine T (SFT) and Methylene Violet (MTV), which do not require deoxygenation and require low power. Excitation can realize the fluorescent color change of yellow light emission under red light irradiation, and it was applied to triplet-triplet annihilation upconversion (TTA-UC) photosensitizer for the first time, and achieved a conversion efficiency as high as 9.69%.

technical solutions

In order to achieve the purpose of the invention, the technical scheme adopted in the present invention is: a weak light up-conversion system of azaanthene derivatives, including azaanthene derivatives and a luminescent agent; further comprising a solvent. The single-photon weak light up-conversion system is composed of azaanthracene derivatives and a solvent. Application of azaanthene derivatives as photosensitizers for TTA-UC weak light upconversion system.

Application of azaanthene derivatives as single-photon weak light upconversion luminescent materials.

The preparation method of the azaanthene derivative weak light up-conversion system includes the following steps: the azaanthene derivative, the luminescent agent and the solvent are mixed, and then deoxygenated to obtain the azaanthene derivative weak light up-conversion system; the luminescent agent is anthracene A compound, such as DPA; the solvent is any one of DCM, DMSO, n-propanol and DMF, preferably DCM (dichloromethane); the concentration of the azaanthene derivative is 2-10 μM, and the luminescent agent The concentration of the material is 0.2~1.8 mM; preferably, the concentration of the azaanthene derivative is 6 μM, and the concentration of the luminescent material is 1.4 mM.

The preparation method of the above single-photon weak light up-conversion system is as follows: adding azaanthene derivatives into a solvent to obtain a single-photon weak light up-conversion system; the solvent is any one of DMSO, DMF and THF, preferably, The solvent is DMSO; the concentration of the azaanthene derivative is 1×10 ^-5 to 5×10 ^-3 M; preferably 1×10 ^-5 M.

The azaanthene derivative of the present invention has the following chemical structural formula.

.

Wherein, R ₁ is NH ₂ or N(CH ₂ CH ₃ ) ₂ , R ₂ is NH ₂ or N(CH ₂ CH ₃ ) ₂ , R ₃ is H or CH ₃ , and R ₄ is H or CH ₃ . Preferably, in the chemical structural formula of the azaanthene derivative, at least one of R ₁ and R ₂ is NH ₂ , and at least one of R ₃ and R ₄ is H; preferably, R ₁ and R ₂ are both NH ₂ or N(CH ₂ CH ₃ ) ₂ , and R ₃ and R ₄ are both H or CH ₃ .

Preferably, the azaanthene derivative of the present invention has the following chemical structural formula:

.

Preferably, the above-mentioned TTA-UC solution is first subjected to deoxygenation operation, and then tested under green light irradiation.

Further preferably, the deoxygenation operation includes feeding nitrogen gas into the solution for 15-30 minutes or feeding argon gas for 15-30 minutes.

Further preferably, the power density of the green light is 5-500 mW/cm ² .

More preferably, the wavelength of the green light is 532 nm.

The power density of the excitation light of the single-photon weak light up-conversion system of the present invention is 500-2000 mW/cm ² , preferably 1000 mW/cm ² ; the excitation light wavelength is 655 nm.

beneficial effect

Azaanthene derivatives can be used as pure organic photosensitizer materials for triplet-triplet annihilation upconversion (TTA-UC). Compared with the prior art, the present invention has the following advancements: as pure organic photosensitizer materials, azaanthene derivatives can greatly reduce the cost of traditional TTA-UC photosensitizers, the structure is simple and easy to obtain, and the obtained upconversion efficiency is relatively high. High, the first public green-to-blue upconversion system. Using azaanthene derivatives as single-photon absorption up-conversion luminescent materials, up-conversion fluorescence color change can be performed without deoxygenation and only low-power optical excitation, which enriches OPA-UC A study of the structure-property relationship of materials.

Description of drawings

Figure 1 shows the up-conversion spectrum of the azaanthene derivative MTV as a photosensitizer (10 μM) and DPA (1 mM) (solvent: dichloromethane/n-propanol=1/1, λ _ex = 532 nm) .

Figure 2 shows the upconversion spectra of the azaanthene derivatives PSF and SFT as photosensitizers (10 μM) and DPA (1 mM) (solvent: dichloromethane/n-propanol = 1/1, λ _ex = 532 nm).

Figure 3 shows the ratio test of photosensitizer (a:PSF, b:SFT) and luminescent agent (DPA) ([photosensitizer]=10 μM, solvent: n-propanol, λ _ex = 532 nm).

Figure 4 shows the ratio test of photosensitizer (a:PSF, b:SFT) and luminescent agent (DPA) ([luminescent agent]=1.4 mM, solvent: n-propanol, λ _ex = 532 nm).

Figure 5 shows the upconversion spectra of photosensitizer (a:PSF, b:SFT) and luminescent agent (DPA) in different solvents (photosensitizer: 6 μM, luminescent agent: 1.4 mM, λ _ex = 532 nm).

Figure 6 is a graph showing the fluorescence quenching of photosensitizers (a:PSF, b:SFT) by luminescent agent (DPA) (photosensitizer: 6 μM, solvent: DCM, λ _ex =532 nm).

Figure 7 shows the Stern-Volmer fluorescence quenching curves of the two photosensitizers (solvent: DCM, λ _ex =532 nm).

Figure 8 shows the power density-upconversion spectra of photosensitizers PSF (a) and SFT (b) ([DPA]=1.4 mM, [photosensitizer]=6 μM, solvent: DCM, λ _ex = 532 nm).

Figure 9 shows the up-conversion efficiency test process of the two systems, absorption spectra (a) and up-conversion spectra (b) (photosensitizer: 6 μM, luminescent agent: 1.4 mM, solvent: DCM, λ _ex = 532 nm).

Figure 10 shows the UV-Vis absorption spectra of azaanthene derivatives in different solvents (a: PSF, b: SFT, c: MTV, concentration: 1×10 ^-5 M).

Figure 11 shows the UV-Vis absorption spectra of azaanthene derivatives at different concentrations (a: PSF, b: SFT, c: MTV, solvent: DMSO).

Figure 12 shows the fluorescence spectra of azaanthene derivatives in different solvents (a: PSF, b: SFT, c: MTV, concentration: 1×10 ^-5 M, λ _ex = maximum absorption peak position of each).

Figure 13 shows the fluorescence spectra of azaanthene derivatives at different concentrations (a: PSF, b: SFT, c: MTV, solvent: DMSO, λ _ex = maximum absorption peak position).

Figure 14 shows the power density-upconversion spectra of azaanthene derivatives (a and b) and the corresponding log-linear plots (c and d) (a: PSF, b: MTV, concentration: 50 μM, solvent: DMSO, λ _ex = 655 nm).

Figure 15 shows the OPA-UC spectrum of the azaanthene derivative (left) and the corresponding physical image (right).

Figure 16 shows up-conversion spectra of azaanthene derivatives at different concentrations (solvent: DMSO, λ _ex = 655 nm).

Figure 17 is the excitation spectrum of the azaanthene derivative (solvent: DMSO, ZnPc intensity reduced by a factor of 10).

Figure 18 is a graph of the up-conversion efficiency of azaanthene derivatives at different concentrations (solvent: DMSO).

Embodiments of the present invention

The present invention will be further described below with reference to the embodiments shown in the accompanying drawings. However, the present invention is not limited to the following examples. The implementation conditions adopted in the examples can be further adjusted according to different requirements of specific use, and the unremarked implementation conditions are the conventional conditions in the industry. The technical features involved in the various embodiments of the present invention can be combined with each other as long as they do not conflict with each other.

Three commercially available azaanthene derivatives are Phenosafranine (PSF), Safranine T (SFT) and Methylene Violet (MTV):

.

The UV-Vis absorption spectrum was measured on a UV-2600 UV-Vis spectrometer, Shimadzu Corporation, Japan; the fluorescence spectrum was measured at FLS, Edinburgh Company Measured on a 920 fluorescence/phosphorescence emission spectrometer. Diode-pumped 532 for testing upconversion spectra nm green laser and the PR655 SpectraScan spectrometer of PhotoResearch Company, USA.

The weak light up-conversion system of the azaanthene derivative of the present invention is composed of the azaanthene derivative, a luminescent agent and a solvent. Three azaanthenes (PSF, SFT and MTV) were used as photosensitizers, respectively mixed with the luminescent agent DPA in a solvent to obtain 3 kinds of photosensitizer/luminescent agent binary systems, and oxygen was removed to obtain azaanthene derivatives weak light Up conversion system.

Comparative Example 1 Figure 1 The triplet-triplet annihilation upconversion test was carried out with azaanthene derivative MTV as photosensitizer (concentration of 10 μM) and luminescent agent DPA (concentration of 1 mM), and the test solvent was dichloride Methane/n-propanol = 1/1 (v/v). It was found that TTA upconversion could not be generated when MTV was used as a photosensitizer with 532 nm wavelength light as excitation.

Example 1 Figure 2 Using azaanthene derivatives PSF and SFT as photosensitizers (concentration of 10 μM), respectively compounded with luminescent agent DPA (concentration of 1 mM), triplet-triplet annihilation upconversion test was carried out, and the solvent was tested. It is dichloromethane/n-propanol=1/1 (v/v). It was found that with 532 nm wavelength light as excitation, PSF and SFT can be combined with DPA to produce obvious TTA-UC upconversion.

As shown in Figure 3, in n-propanol solvent, with 532 nm wavelength light as excitation, the concentration of fixed photosensitizer (PSF/SFT) was 10 μM, and the concentration of luminescent agent was changed (increased from 0 mM to 1.8 mM), The upconversion spectra of the two photosensitizers compounded with different concentrations of the luminescent agent DPA were tested.

Figure 4 shows that in n-propanol solvent, the light of 532 nm wavelength was used as excitation, the concentration of luminescent agent DPA was fixed at 1.4 mM, and the concentration of photosensitizer was changed (increased from 2 μM to 10 μM). Upconversion spectra of a combination of photosensitizers.

Figure 5 tests the upconversion spectra of the TTA-UC system (photosensitizer: 6 μM, luminescent agent: 1.4 mM, λ _ex = 532 nm) under the excitation of 532 nm light in different solvents. It can be seen from the figure that the up-conversion intensities of the two TTA-UC systems in the dichloromethane solvent are the largest, which are about tens of times higher than those in other solvents. It can be seen that when tested under optimal conditions, when SFT is used as photosensitizer, its upconversion intensity is about 3 times higher than that in the system with PSF as photosensitizer.

As shown in Figure 6, the concentration of the photosensitizer was fixed at 6 µM. Under the excitation of a 532 nm laser, the fluorescence quenching spectra of the photosensitizers by adding different concentrations of luminescent agents were tested after the solution was deoxygenated. It can be seen from the figure that with the increase of the concentration of the luminescent agent, the fluorescence of the photosensitizer is weakened, and the up-conversion fluorescence of the luminescent agent is enhanced, which clearly reflects the energy transfer process of the triplet energy of the photosensitizer to the luminescent agent.

In triplet-triplet annihilation upconversion, the energy transfer process between the triplet states of the photosensitizer and the luminescent agent is usually measured by the Stern-Volmer equation. The quenching constant is obtained by measuring the quenching of the donor by the triplet energy acceptor (the test needs to pass argon for 15 min to deoxygenate), and then use the Stem-Volmer formula to calculate the quenching constant. where I ₀ and I _Q are the luminescence intensity of the photosensitizer without quencher and with different concentrations of quencher, respectively, τ ₀ is the luminescence lifetime of the photosensitizer without quencher, k _q is the quenching constant, and k _SV is the Stern-Volmer constant.

.

The obtained data was calculated according to formula 1, and the Stern-Volmer quenching curves of the two photosensitizers were obtained, and the results were shown in Figure 7. The quenching constants of different luminescent agents to photosensitizers can be obtained from the Stern-Volmer quenching curve (the K _sv of the PSF system is 0.00122, and the K _sv of the SFT system is 0.00123).

Figure 8 tests the power density-upconversion spectra of two azaanthene compounds as photosensitizers and luminescent agent DPA, respectively. It can be seen that in the process of increasing the power density from 5 mW/cm ² to 400 mW/cm ² , the strength of the two upconversion systems also increases. Among them, the upconversion intensity of SFT(b) as a photosensitizer is 4.4 times higher than that of PSF(a).

Using Rh6G as a reference material, the TTA-UC efficiency of two azaanthene derivatives as photosensitizers was tested under the excitation of 532 nm light. As shown in Figure 9, a is the UV-Vis spectra under the same test conditions, and b is their respective up-conversion spectra. Substitute the corresponding data into the calculation formula 2 of TTA-UC efficiency. where Φ _r is the fluorescence quantum yield of the reference substance; F _s and F _r represent the up-conversion peak integral area of the analyte and the down-conversion fluorescence integral area of the reference substance at the excitation wavelength, respectively _; As and _Ar respectively represents the absorbance of the test substance and the reference substance at the excitation wavelength; n _s and n _r represent the refractive index of the test substance and the reference substance solution, respectively; when the solution is a dilute solution, it can be directly replaced by the refractive index of the solvent.

.

The calculation process of TTA-UC efficiency of azaanthene derivatives as photosensitizers is shown in Table 1. It can be seen that the upconversion efficiency of SFT/DPA (9.69 %) is 3 times that of PSF/DPA (3.16 %).

When triplet-triplet annihilation upconversion (TTA-UC) occurs, the three azaanthene derivatives as photosensitizers show different sensitization behaviors, but the measured green-to-blue upconversion efficiency is SFT/DPA (9.69 %) > PSF/DPA (3.16 %), while MTV cannot achieve up-conversion at all. The green-to-blue up-conversion efficiency obtained by the currently reported photosensitizer (C ₇₀ ) without heavy atoms is much lower than that of the present invention, and the photosensitizer is difficult to prepare and expensive. The present invention uses the azaanthene photosensitizer to obtain higher up-conversion efficiency, is cheap and convenient to obtain, and has certain practical significance.

Figure 10 shows the solvent-effect UV-Vis absorption spectra of azaanthene derivatives. At the same concentration (1×10 ^-5 M), the absorption peaks of the three compounds are red-shifted, with PSF from 530 nm to 537 nm Red-shifted by 7 nm, SFT by 6 nm from 532 nm to 538 nm, and MTV by 4 nm from 556 nm to 560 nm, it can be seen that π-π ^* transitions occurred in all three azaanthene derivatives .

Figure 11 tests the UV-Vis absorption spectra of azaanthene derivatives at different concentrations. In the solvent DMSO, the absorption values of the three azaanthene derivatives increased with the increase of the concentration. When the concentration increased to 1×10 ^-4 M, a plateau peak appeared, and the characteristics of aggregates appeared. When testing the molecular properties A concentration of 1 x ^10-5 M was chosen.

As shown in Figure 12, the fluorescence spectra of azaanthene derivatives in different solvents were tested. Three solutions of azaanthene derivatives with a concentration of 1×10 ^-5 M were prepared, and the three solutions were excited with light of 530 nm, 535 nm and 556 nm wavelengths (respectively their respective maximum absorption wavelengths) to test their performance. Fluorescence spectral properties.

Figure 13 tests the fluorescence spectra of azaanthene derivatives at different concentrations. In the solvent DMSO, the fluorescence spectra of the three were excited and tested with light at wavelengths of 537 nm, 539 nm and 560 nm (the respective maximum absorption wavelengths). It can be seen from the figure that the fluorescence peak positions of the three azaanthracene derivatives all undergo a red shift with the increase of concentration. When the concentration increased from 1×10 ^-6 M to 1×10 ^-5 M, the fluorescence intensities of the three azaanthene derivatives increased with the increase of the concentration. As the concentration continued to increase to 1×10 ^-4 M, the fluorescence intensity of the three azaanthene derivatives gradually weakened.

Example 2 One-component up-conversion (OPA-UC) spectroscopy was performed on azaanthene derivatives. In this embodiment, the diode-pumped solid-state red laser of Changchun New Industry Optoelectronics Technology Co., Ltd. and the U.S. PhotoResearch's PR655 SpectraScan Spectrometer for testing. Comparative tests were performed with PSF and MTV to study the effect on OPA-UC, and the solvent was DMSO (dimethyl sulfoxide).

Using a 655 nm CW semiconductor laser as the light source, the upconversion spectra of the two azaanthene derivatives were measured (at a concentration of 50 μM), as shown in Figure 14. Figure 14(a and b) are the power density-upconversion spectra of PSF and MTV, respectively. It can be seen that the upconversion intensity of each azaanthene derivative increases with the increase of power density. Figure 14(c and d) are log-linear plots of upconverted integrated intensity-power density for PSF and MTV, respectively. In the process of increasing the power density from 500 mW·cm ^-2 to 2 W·cm ^-2 , their integrated upconversion intensity and the logarithm of the power density show a linear relationship, with slopes of 0.98 and 0.99, which are close to 1, respectively. It is proved that the upconversion process of this azaanthene derivative is a direct single-photon absorption process.

In the same concentration (1×10 ^-5 M) and the same solvent (DMSO), two azaanthene derivatives were excited with 655 nm light, and their OPA-UC structure effect spectra were obtained (Fig. 15). It can be seen from the figure that the order of up-conversion intensity is MTV > PSF. It can be demonstrated that strong intramolecular charge transfer (ICT) is beneficial for the enhancement of single-photon absorption upconversion. From the physical map, the OPA-UC process of these two azaanthene derivatives can be observed with the naked eye for the change of red-to-yellow, and the yellow light of MTV is more obvious.

Figure 16 tests the OPA-UC spectra of different concentrations of azaanthene derivatives in DMSO solvent. In the process of increasing concentration, their upconversion peaks are continuously red-shifted. Among them, PSF is red-shifted by 4 nm from 615 nm to 619 nm, and MTV is red-shifted by 4 nm from 613 nm to 617 nm. In addition, as the concentration increased from 1 × 10 ^-5 M to 1 × 10 ^-3 M, their upconversion intensities continued to increase, PSF and MTV were enhanced by 9.2 times and 15.7 times, respectively, when the concentration continued to increase to 5 × At 10 ^-3 M, the upconversion intensity decreases rapidly (black dotted line in the figure).

Example 3 One-component up-conversion (OPA-UC) efficiency and performance comparison of azaanthene derivatives.

Taking ZnPc as a reference, the fluorescence quantum yield in DMF solvent is Φ _r =32%. The excitation spectra of the azaanthene derivatives were tested through Fig. 17, and their respective excitation intensity values at 655 nm were obtained. Substitute into the following formula to calculate their respective upconversion efficiencies at different concentrations.

Table 2 lists various parameters of the OPA-UC efficiency calculation of the azaanthene derivatives at different concentrations (1×10 ^-5 M at low concentration and 1 × 10 ^-3 M at high concentration). Combining with the concentration-upconversion efficiency curve in Figure 18, it can be seen that with the increase of the solution concentration of the azaanthene derivative, the upconversion efficiency increases significantly. From low to high concentration, the OPA-UC efficiency of PSF increased 1.6-fold and MTV increased 4.0-fold. It can be proved that in a certain concentration range, as the concentration of the solution increases, it is beneficial to increase the single-photon absorption upconversion efficiency.

In Table 3, the basic properties of OPA-UC of azaanthene derivatives at different concentrations are listed. Comparing their respective upconversion efficiencies at different concentrations, it can be found that their respective upconversion efficiencies are obtained at high concentrations. This is due to the enhanced intermolecular interaction, which may activate the thermal vibrational energy level of the molecular ground state, thereby promoting the electronic transition and increasing the upconversion efficiency.

Claims (10)

1. An azaanthene derivative weak light up-conversion system is characterized in that it comprises an azaanthene derivative and a luminescent agent, and the azaanthene derivative has the following chemical structural formula:

   

   Wherein, R ₁ is NH ₂ or N(CH ₂ CH ₃ ) ₂ , R ₂ is NH ₂ or N(CH ₂ CH ₃ ) ₂ , R ₃ is H or CH ₃ , and R ₄ is H or CH ₃ .
2. The weak light up-conversion system of the azaanthene derivative according to claim 1, wherein the azaanthene derivative has the following chemical structural formula:

   

   .
3. The weak light up-conversion system of the azaanthene derivative according to claim 1, further comprising a solvent.
4. The weak light up-conversion system of the azaanthene derivative according to claim 1, wherein the concentration of the azaanthene derivative is 2-10 μM, the concentration of the luminescent agent is 0.2-1.8 mM.
5. The preparation method of the azaanthene derivative weak light up-conversion system according to claim 1, characterized in that: the azaanthene derivative, a luminescent agent and a solvent are mixed, and then oxygen is removed to obtain the azaanthene derivative weak light up-conversion system .
6. Application of azaanthene derivatives as photosensitizers in TTA-UC weak light up-conversion system; the azaanthene derivatives have the following chemical structural formula:

   

   .
7. The application of the weak-light up-conversion system of the azaanthene derivative according to claim 1 in the preparation of green-to-blue up-conversion materials.
8. The application of the azaanthene derivative as a single-photon weak light up-conversion luminescent material is characterized in that: the azaanthene derivative has the following chemical structural formula:

   

   Wherein, R ₁ is NH ₂ or N(CH ₂ CH ₃ ) ₂ , R ₂ is NH ₂ or N(CH ₂ CH ₃ ) ₂ , R ₃ is H or CH ₃ , and R ₄ is H or CH ₃ .
9. The application according to claim 8, wherein when the azaanthene derivative is used as a single-photon weak light up-conversion luminescent material, the solvent is any one of DMSO, DMF and THF.
10. Application of the azaanthene derivative described in claim 8 in the preparation of a red-to-yellow up-conversion material.