An amino acid coordination polymer with ultralong room-temperature phosphorescence emission and a preparation method thereof

Abstract

The application discloses an amino acid coordination polymer with super-long room-temperature phosphorescence emission and a preparation method thereof. Zn(NO3)2.6H2O, amino acid, deionized water and a mixed solvent of DMF are added into a polytetrafluoroethylene reaction kettle liner, concentrated ammonia water is then added, and stirring is performed until the pH of the solution is weak alkaline, so that a mixed solution is obtained; the mixed solution is placed in an oven for reaction to obtain a solid powder; then, the solid powder is naturally cooled to room temperature, washed with DMF and deionized water alternately, and vacuum dried to obtain the amino acid coordination polymer. The polymer exhibits significant phosphorescence emission enhancement, and after the excitation light source is turned off, the afterglow time can reach 0.5-20 s under naked eye observation. The application effectively overcomes the limitation that traditional amino acid molecules need to be in a low-temperature condition to realize afterglow light emission, and has the advantages of easy availability of reaction raw materials, mild reaction condition, good chemical stability of the product and the like, and has a wide application prospect in the fields of biological imaging, sensing and anti-counterfeiting.

Description

Technical Field

[0001] This invention relates to the field of long afterglow luminescence technology, specifically to an amino acid coordination polymer with ultralong room temperature phosphorescence emission and its preparation method. Background Technology

[0002] Room-temperature phosphorescent (RTP) materials, due to their long-lived triplet excited states, large Stokes shifts, and high exciton utilization, have found wide applications in cell imaging, light-emitting devices, information storage, and encryption. However, achieving efficient and sustained RTP emission remains extremely challenging due to the inherent spin-forbidden transitions and easy deactivation of triplet excitons. As an emerging class of light-emitting materials, metal-organic coordination polymers can significantly enhance the rigidity of phosphorescent molecular conformations, restricting molecular motion and effectively reducing non-radiative decay. Furthermore, the heavy atom effect of metal ions can enhance spin-orbit coupling, thereby effectively promoting RTP emission. In recent years, coordination polymers have been widely used to develop various RTP materials, showing promising prospects in information encryption and optoelectronic devices. However, coordination polymer phosphorescent materials with tunable ultralong afterglow remain relatively rare.

[0003] Amino acids, as the basic building blocks of proteins, play a crucial role in various physiological activities. Research on amino acid luminescent materials not only provides a deeper understanding of protein emission characteristics but also has significant scientific implications for further elucidating the mechanism of autofluorescence in biological tissues. Currently, most amino acid luminescent materials are based on their fluorescence properties, and the synthesis of amino acid RTP materials with ultralong afterglow shows great potential. Yan Dongpeng's research group reported a zinc-based histidine supramolecular glass material that achieved multicolor circularly polarized afterglow emission from blue to red light at room temperature. Nat. Commun. 2023, 14 (1654). However, long-afterglow RTP complexes for other types of amino acids, especially non-aromatic amino acids, are rarely reported. Therefore, developing a simple and universal method to prepare amino acid RTP materials will help deepen our understanding of the protein RTP luminescence mechanism. Summary of the Invention

[0004] Based on the aforementioned research background, the purpose of this invention is to provide an amino acid coordination polymer with ultralong room-temperature phosphorescence emission and its preparation method, offering new ideas and feasible solutions for the design and synthesis of long-afterglow luminescent materials. This method utilizes low-cost raw materials, employs a simple preparation process, and consumes minimal energy, thus demonstrating promising industrial applications.

[0005] The technical method of this invention is as follows: This method is simple to operate, requires low experimental equipment, produces stable products, and has good reproducibility.

[0006] Using Zn(NO3)2·6H2O as the zinc source, amino acids as ligands, H2O and DMF as solvents, and concentrated ammonia as a pH adjuster, the zinc-based amino acid coordination polymer was obtained by drying in an oven and washing and drying.

[0007] A method for preparing an amino acid coordination polymer with ultralong room temperature phosphorescence emission, the specific steps of which are as follows:

[0008] (1) Add Zn(NO3)2·6H2O, amino acids, and a mixture of deionized water and DMF to the liner of a polytetrafluoroethylene reactor, then add concentrated ammonia and stir until the pH of the solution is weakly alkaline to obtain a mixed solution.

[0009] (2) The mixed solution is placed in an oven to react and obtain a solid powder; then it is naturally cooled to room temperature, and the solid powder is washed alternately with DMF and deionized water, and then vacuum dried to obtain a zinc-based amino acid coordination polymer with RTP properties.

[0010] Preferably, the amino acids in step (1) are L-histidine, L-tyrosine, L-tryptophan, L-homoserine, L-lysine, L-serine, L-glutamine, L-valine, L-isoleucine, L-proline, L-arginine, L-threonine, L-alanine, and L-leucine.

[0011] Preferably, in step (1), the Zn(NO3)2·6H2O is 4 mmol, the amino acid is 4 mmol, the deionized water is 10 ml, the DMF is 10 ml, and the concentrated ammonia is 1~1.5 ml.

[0012] Preferably, the stirring time in step (1) is 8 to 12 minutes.

[0013] Preferably, the pH value in step (1) is 7.0 to 8.0.

[0014] Preferably, the oven reaction temperature in step (2) is 130~170 ℃ and the reaction time is 36~48 h.

[0015] Preferably, the drying temperature in step (2) is 60~90 ℃ and the drying time is 3~6 h.

[0016] According to the method of the present invention, a variety of zinc-based amino acid coordination polymers with different RTP properties can be synthesized. These zinc-based amino acid coordination polymers with different RTP properties can be widely used in various industries, such as as bioimaging agents, sensors, anti-counterfeiting inks, and spray coating materials.

[0017] The beneficial effects of this invention are:

[0018] The synthesized amino acid coordination polymers exhibited significant enhanced phosphorescence emission, and the afterglow time could reach 0.5-20 s under naked-eye observation after the excitation source was turned off.

[0019] This invention effectively overcomes the limitation that traditional amino acid molecules can only achieve afterglow luminescence under low temperature conditions, and has the advantages of readily available reaction raw materials, mild reaction conditions, and good chemical stability of products.

[0020] (3) Adding ammonia will not introduce other impurity cations and impurity anions that participate in coordination. Attached Figure Description

[0021] Figure 1 The image shown is the FT-IR spectrum of Example 1.

[0022] Figure 2 The PXRD patterns are for Example 1 and other zinc-based amino acid coordination polymer powders.

[0023] Figure 3 The steady-state and delayed PL plots are for Example 1.

[0024] Figure 4 The phosphorescence lifetime spectrum of Example 1 is shown. Detailed Implementation

[0025] 4 mmol of zinc nitrate hexahydrate and 4 mmol of amino acids were dissolved in a mixed solvent of 10 mL of deionized water and 10 mL of DMF. The solution was added to a polytetrafluoroethylene (PTFE) reactor liner, and the pH was adjusted to a weakly alkaline state (7-8) with 1-1.5 mL of concentrated ammonia. After stirring at room temperature for 10 minutes, the mixture was placed in an oven at 130-170 °C and reacted for 36-48 h. After cooling, a solid powder was obtained, which was then washed three times each with alternating amounts of DMF and deionized water, and dried in a vacuum oven at 60-90 °C for 3-6 h to obtain the zinc-based amino acid coordination polymer.

[0026] The specific implementation of the present invention will be described in detail below. It should be noted that the following implementation is only for further illustration of the present invention and should not be construed as a limitation on the scope of protection of the invention. Some non-essential improvements and adjustments made to the present invention by those skilled in the art based on the above-described content of the present invention still fall within the scope of protection of the present invention. Example 1:

[0027] 4 mmol of zinc nitrate hexahydrate and 4 mmol of L-His were dissolved in a mixed solvent of 10 mL of deionized water and 10 mL of DMF. The solution was added to a polytetrafluoroethylene (PTFE) reactor liner, and 1–1.5 mL of concentrated ammonia was added to adjust the pH to 7.0–8.0. The mixture was stirred at room temperature for 10 minutes and then reacted in an oven at 150 °C for 36 h. After cooling, a pale yellow solid was obtained, which was then washed three times each with alternating amounts of DMF and deionized water, and dried in a vacuum oven at 60 °C for 6 h to obtain the zinc-based histidine coordination polymer, which exhibited a yellow-green afterglow visible to the naked eye for approximately 20 seconds. Example 2:

[0028] 4 mmol of zinc nitrate hexahydrate and 4 mmol of L-Ser were dissolved in a mixed solvent of 10 mL of deionized water and 10 mL of DMF. The pH was adjusted to 7.0–8.0 by adding 1–1.5 mL of concentrated ammonia. After stirring at room temperature for 10 minutes, the mixture was placed in an oven at 150 °C and reacted for 36 h. The mixture was cooled to obtain a pale yellow solid, which was then washed three times each with alternating amounts of DMF and deionized water. The solid was dried in a vacuum oven at 60 °C for 6 h to obtain the zinc-based serine coordination polymer, which exhibited a yellow-green afterglow visible to the naked eye for approximately 6 seconds.

[0029] Two mg each of levorotatory histidine and zinc-based histidine coordination polymer (Example 1) were taken and FT-IR was performed using the KBr pellet method.

[0030] FT-IR ( Figure 1 Proof 581 cm -1 and 615 cm -1 The new peak at L-His is attributed to the coordination of Zn(II) with the N atom on the amino and imidazole groups, and the stretching vibration of the carboxylic acid group relative to the original L-His C=O at 1590 cm⁻¹. -1 A displacement of 1485 cm occurred. -1 This is attributed to the coordination of Zn(II) with the carboxylic acid group. The relative L-His at 3479 cm⁻¹ -1 The peak of Zn-L-His is at 3258 cm⁻¹. -1 The peak at that location is wider and weaker, which may be due to the formation of more hydrogen bonds after the formation of the Zn-L-His coordination polymer.

[0031] Figure 1 The image shown is the FT-IR spectrum of Example 1.

[0032] Take 10 mg of Example 1 and perform PXRD determination.

[0033] Narrow and sharp peaks indicate that the prepared powder sample has certain crystalline characteristics.

[0034] Figure 2The PXRD patterns are for Example 1 and other zinc-based amino acid coordination polymer powders.

[0035] Photoluminescence spectroscopy characterization of Example 1 was performed on an Edinburgh FLS-980 fluorescence spectrometer equipped with a xenon arc lamp and a microsecond flash lamp. The PL lifetime (τ) of the sample was obtained by fitting the decay curve using a multi-exponential decay function I(t) = A1exp(−t / τ1) A2exp(−t / τ2) ...Aiexp(−t / τi). Here, Ai and τi represent the amplitude and lifetime of each component of the multi-exponential decay characteristic, respectively. The absolute PL quantum yield of the powder was measured at room temperature using an integrating sphere (F-M101, Edinburgh) attachment in the FLS-980 fluorescence spectrometer.

[0036] The optimal excitation and emission wavelengths for Example 1 are 388 nm and 470 nm, respectively. Its delayed spectrum shows a strong RTP band at 550 nm under an excitation wavelength of 360 nm, and the fluorescence and phosphorescence decay lifetimes are 5.24 ns and 330.8 ms, respectively.

[0037] Figure 3 The steady-state and delayed PL plots are for Example 1.

[0038] Figure 4 The phosphorescence lifetime spectrum of Example 1 is shown.

[0039] In summary, this invention uses a solvothermal method to synthesize zinc-based amino acid coordination polymers, which has simple synthesis steps and excellent performance.

[0040] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing an amino acid coordination polymer with ultralong room temperature phosphorescence emission, characterized in that: (1) Add Zn(NO3)2·6H2O, amino acids, and a mixture of deionized water and DMF into the liner of a polytetrafluoroethylene reactor, then add concentrated ammonia and stir until the pH of the solution is weakly alkaline to obtain a mixed solution; wherein the amino acid is levorotatory histidine. (2) The mixed solution is placed in an oven to react and obtain a solid powder; then it is naturally cooled to room temperature, and the solid powder is washed alternately with DMF and deionized water, and then vacuum dried to obtain a zinc-based amino acid coordination polymer with RTP properties.

2. The method according to claim 1, characterized in that, In step (1), the Zn(NO3)2·6H2O is 4 mmol, the amino acid is 4 mmol, the deionized water is 10 ml, the DMF is 10 ml, and the concentrated ammonia is 1~1.5 ml.

3. The method according to claim 1, characterized in that, The stirring time in step (1) is 8 to 12 minutes.

4. The method according to claim 1, characterized in that, The pH value in step (1) is 7.0~8.

0.

5. The method according to claim 1, characterized in that, The oven reaction temperature in step (2) is 130~170℃, and the reaction time is 36~48 h.

6. The method according to claim 1, characterized in that, The drying temperature in step (2) is 60~90 ℃ and the drying time is 3~6 h.

7. An amino acid coordination polymer with ultralong room temperature phosphorescence emission, characterized in that, Prepared by the method according to any one of claims 1 to 6.

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