CN114890914B - High-efficiency red light emitting organic crystal and application thereof in low-temperature fluorescence sensing - Google Patents

Abstract

The invention discloses an organic high-efficiency red light emitting organic crystal with linear response to extremely low temperature and application thereof in low-temperature fluorescence sensing, belonging to the technical field of temperature sensing. The invention obtains a strong red light emitting organic crystal by a solvent volatilization method, the maximum emission wavelength of the crystal is 693nm, the fluorescence quantum efficiency is up to 73 percent, and the structural formula is shown as the formula (I). The invention also discloses application of the crystal emitting red light in low-temperature fluorescence sensing. Experiments prove that the maximum emission wavelength of the crystal has good linear response to extremely low temperature which is difficult to measure under the traditional condition, can sensitively react to temperature change at the extremely low temperature, and has wide application prospect in the aspect of low-temperature fluorescence sensing.

Description

An organic crystal with high-efficiency red light emission and its application in low-temperature fluorescence sensing application

technical field

The invention belongs to the technical field of temperature sensing, and in particular relates to an organic crystal emitting red light with high efficiency and its application in low-temperature fluorescence sensing.

Background technique

As one of the important basic thermodynamic parameters, temperature is closely related to people's production and life. How to achieve accurate temperature measurement under different conditions, including extreme environments, has always been a problem that we must solve. The traditional temperature measurement principle is to measure the value of temperature according to the temperature-related volume, conductance and resistance changes, but from the perspective of practical application, the temperature measurement instrument developed based on this principle cannot meet the needs of micro-electromechanical systems, oceans, etc. In-situ measurements required by industries such as research and the aerospace industry. Therefore, the development of temperature sensors suitable for in-situ temperature measurement in extreme environments has very broad application prospects.

Because some temperature-sensitive fluorescent materials can respond well to temperature changes, temperature sensors based on fluorescent responses are being developed to detect temperature accurately. At present, researchers' interests are mainly focused on the development of materials such as temperature-sensitive luminescent organic dyes, polymers, nanocrystals and lanthanide materials, but the performance of these materials under extreme conditions, especially at extremely low temperatures It seems a little unsatisfactory. Due to the high price and low solubility of rare earth metals, the complexity of polymer and nanocrystal operation, we focus on small molecules of luminescent organic dyes that are sensitive to temperature. Most of the organic dye fluorescence sensors reported so far are in solution, The temperature is measured in the polymer-doped film. At extremely low temperatures, the above-mentioned solutions and polymer-doped films cannot effectively measure the temperature due to solidification and freezing cracks. Therefore, there is an urgent need for an organic light-emitting small molecule fluorescent sensor that can measure extremely low temperatures.

Contents of the invention

Aiming at the deficiency of existing low-temperature sensing materials, the problem to be solved by the present invention is to provide an organic crystal with high-efficiency red light emission and its application in low-temperature fluorescence sensing.

The high-efficiency red light-emitting organic crystal of the present invention has simple molecular structure, simple synthesis steps, and is easy to crystallize. It is prepared from the compound represented by formula (I) by solvent evaporation. The standard name of the compound is ( 2Z,2'Z)-3,3'-(2,5-bis(diphenylamino)-1,4-phenylene)bis(2-(4-(dibutylamino)phenyl)acrylonitrile ).

The preparation reaction formula of compound shown in formula (I) is as follows:

Aiming at the shortcomings of the existing low-temperature fluorescent sensing materials in detecting extremely low temperatures, the present invention develops a red-light organic crystal with high fluorescence quantum efficiency and which can accurately measure extremely low temperatures. The red-light organic crystals prepared in the present invention achieve strong red-light emission, which is very rare, because most of the red-light-emitting fluorescent molecules, especially in the crystal state, usually aggregate to induce fluorescence quenching, which greatly reduces the fluorescence quantum efficiency, it is difficult to achieve strong red emission. However, the high-efficiency red-light organic crystal prepared by the present invention, because of its unique structure, can achieve very good measurement of extremely low temperatures while achieving strong red light emission. At present, there are few literature reports on high-efficiency red light-emitting organic crystals for precise low-temperature measurement. Due to the above advantages, high-efficiency red light-emitting organic crystals have very broad application prospects for extremely low temperature detection.

Experimental results confirm that the ultra-low temperature-sensitive red light organic crystals of the present invention realize high-efficiency red light emission due to their structural specificity, and it is very easy to obtain high-efficiency red light due to the easy crystallization of the organic molecules. Optical organic crystals. The crystal overcomes the inability of organic dyes to accurately measure extremely low temperatures in the state of solution and thin film, which provides a powerful tool for organic dyes in the field of low-temperature sensing, and more importantly, the design of the crystal can be used for efficient Red light crystals and extremely low temperature sensing designs provide a general guideline.

In a word, the ultra-low temperature sensing material described in the present invention is a brand-new red light organic crystal. Compared with other temperature sensing materials, the crystal does not require redundant preparation process, can realize high-efficiency red light emission, and is relatively easy to detect To the change of the optical signal, the maximum emission wavelength has a good linear response to the extremely low temperature that is difficult to measure under traditional conditions, and can sensitively respond to temperature changes at extremely low temperatures. In view of the above advantages, its application in low-temperature fluorescence sensing has broad prospects.

Description of drawings

Fig. 1: the nuclear magnetic hydrogen spectrum of the organic fluorescent dye crystal prepared in the embodiment 1 of the present invention;

Fig. 2: the carbon nuclear magnetic spectrum of the organic fluorescent dye crystal prepared in the embodiment 1 of the present invention;

Figure 3: Absorption (a) and emission spectrum (b) of the organic fluorescent dye crystal prepared in Example 1 of the present invention; show that the maximum emission wavelength of the crystal is 693nm, and the fluorescence quantum efficiency is as high as 73%;

Figure 4: Structural analysis diagram of the organic fluorescent dye crystal prepared in Example 1 of the present invention; it shows that the obtained crystal is a triclinic crystal system;

Fig. 5: Optical photo of the organic fluorescent dye crystal prepared in Example 1 of the present invention under sunlight (a) and 365nm ultraviolet lamp (b); illustrates the easy crystallization (a in- Fig. 5) and high efficiency of the crystal Red light emitting properties (- b in Figure 5);

Fig. 6: Fluorescence spectrum curve (a in Fig. 6, b in Fig. 6) and the ratio of fluorescence intensity at 665nm and 697nm at 77 to 295K of the organic fluorescent dye crystal prepared in Example 1 of the present invention and the temperature change The relationship curve (- c in Figure 6);

Detailed ways

Example 1: (2Z,2'Z)-3,3'-(2,5-bis(diphenylamino)-1,4-phenylene)bis(2-(4-(dibutylamino) Synthesis of phenyl)acrylonitrile)

Add 2-(4-(dibutylamino)phenyl)acetonitrile (153mg 0.626mmol), 2,5-bis(diphenylamino)terephthalaldehyde (117mg, 0.250mmol) to the two-necked flask, tert Potassium butoxide (71mg, 0.63mmol) and tetrabutylammonium hydroxide (214mg, 0.63mmol), and 10mL of tert-butanol and 5mL of tetrahydrofuran were added as solvents, and the resulting mixture was stirred at 50°C for 4h. After cooling to room temperature, the mixture was poured into 50 mL of methanol, and the precipitate was filtered and further purified by silica gel chromatography to obtain 177 mg (0.200 mmol, 77%) of the product as a red-black solid, namely (2Z,2'Z)-3 ,3'-(2,5-bis(diphenylamino)-1,4-phenylene)bis(2-(4-(dibutylamino)phenyl)acrylonitrile).

Take 10 mg of the product and place it in a test tube, add 5 mL of dichloromethane to completely dissolve the compound, slowly add 10 mL of petroleum ether solvent on the dichloromethane solvent layer to separate layers of dichloromethane and petroleum ether, and seal the test tube mouth with cotton , red light organic crystals were obtained by solvent evaporation. ¹ H NMR (400MHz, CDCl3): δ7.86(s,2H),7.30–7.26(m,7H),7.25(s,3H),7.09(t,12H),6.97(t,J＝7.3Hz, ¹³ C NMR (101MHz, CDCl3): δ148.65, 147.62, 143.24, 134.33, 132.72, 129.54, 129.41, 127.08, 122.65, 122.49, 120.63, 117.56, 113.88, 111.16, 50.64, 29.38, 13.9 The unit cell parameters in the crystal are a=8.4810(3), b=11.4818(5), c=14.0570(6), α=89.7366(15), β=87.7218(16), γ=86.1781(15), triclinic Tie. Figure 1, Figure 2, Figure 4 and the above data show that the product of the structure is obtained.

Embodiment 2: the measurement of the absorption of the organic crystal prepared in embodiment 1, emission spectrum

The crystals obtained in Example 1 were dispersed on the barium sulfate substrate, and the absorption spectrum was obtained by scanning in the 300-900 nm band with a UV-visible spectrophotometer. Use a fluorescence spectrometer to scan under 405nm excitation to obtain the fluorescence emission spectrum, and use the Origin software to map the two groups of data to obtain the absorption-emission spectrum of the organic crystal as shown in Figure 3 (the left part is the absorption spectrum, and the right part is the emission spectrum. spectrum). The absorption-emission peak position and its large Stokes shift of the red organic crystal are illustrated.

Embodiment 3: Fluorescence test of the variable temperature (77～295K) of the organic crystal prepared in embodiment 1

The crystal obtained in Example 1 is sample-prepared, placed in a sample chamber, poured into a cooling device with 77K liquid nitrogen, and a 375nm LED excitation light source is used to excite the crystal sample, and the fluorescence emission spectrum is collected, and then passed The temperature of the control system is programmed to rise, and the fluorescence emission spectrum is collected once every time the temperature rises by 20K. Process the data with Origin software to obtain the fluorescence test results of crystals with variable temperature (77-295 K) as shown in Figure 6, - (a) in Figure 6 is the fluorescence test results of 175-295K (with the increase of temperature , the intensity of the fluorescence emission peak becomes weaker), - (b) in Figure 6 is the fluorescence test result of 77 ~ 175K (as the temperature increases, the intensity of the fluorescence emission peak at 665nm becomes weaker, and the fluorescence emission at 697nm The intensity of the peak is enhanced); -c in Figure 6 is the relationship curve obtained by processing the data processing of the fluorescence intensity ratio at 665nm and 697nm in -a in Figure 6 and -b in Figure 6 with the temperature change ( Curve equation y=1.37-0.00689x, R ² =0.9999, where y represents the fluorescence intensity ratio at 665 nm and 697 nm, and x represents temperature). Further measure the fluorescence emission spectrum of the above-mentioned red-light organic crystal at an unknown ambient temperature, calculate the fluorescence intensity ratio at 665nm and 697nm, and substitute the above relationship curve, the ambient temperature can be calculated, so as to realize the accurate measurement in the range of low temperature (77-175 K) Measurement.

Claims (3)

1. A red light-emitting organic crystal prepared from a compound represented by formula (I) by a solvent evaporation method is a triclinic system, and the unit cell parameters in the crystal are a =8.4810 (3), b =11.4818 (5), c =14.0570 (6), α =89.7366 (15), β =87.7218 (16), γ =86.1781 (15),

2. use of a red-emitting organic crystal according to claim 1 in low temperature fluorescence sensing.

3. Use of a red-emitting organic crystal according to claim 2 in low temperature fluorescence sensing, wherein: the low-temperature sensing range is 77-175K.

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