Preparation method of barium acetate open-framework based probe material and application thereof in detection of l-glutamic acid

Abstract

This invention belongs to the field of chemical / biological sensing technology, and relates to the preparation method of barium acetate open framework-based probe materials and their application in L-glutamic acid detection. This invention prepares the host-guest doped material P@1 (P is 1,4-naphthalenedicarboxylic acid, and 1 is C4H6BaO4) via a solvothermal evaporation method. P@1 exhibits a visible green RTP with a duration of approximately 3 s. In terms of detection, P@1 shows a selective phosphorescence-enhanced response to L-Glu, with a detection limit of 0.938 μmol·L⁻¹. ‑1 The detection mechanism primarily involves hydrogen bonding between L-glutamic acid and P@1, which restricts the movement of guest molecules, thereby reducing non-radiative transition pathways and promoting radiative transitions, ultimately leading to enhanced phosphorescence intensity. Finally, this method was developed into a pH test strip, which exhibits significant advantages in amino acid detection, including high sensitivity, speed, simplicity, and low cost, providing a new method for efficient amino acid detection.

Description

Technical Field

[0001] This invention belongs to the field of chemical / biological sensing technology, and relates to the preparation method of barium acetate open framework probe material and its application in L-glutamic acid detection. Background Technology

[0002] L-Glutamate, a non-essential amino acid, is an indispensable physiologically active substance in the human body, participating in key physiological processes such as nerve signal transmission, energy metabolism, and immune regulation. Its deficiency can lead to dysfunction of multiple systems, including nervous system disorders, metabolic imbalances, and immunodeficiency. Therefore, its detection is of great significance in food nutrition assessment and clinical disease diagnosis. Currently, methods for detecting L-glutamate mainly include high-performance liquid chromatography (HPLC), capillary electrophoresis, enzyme-linked immunosorbent assay (ELISA), and electrochemical sensor methods. Although traditional L-glutamate detection methods have the advantages of high sensitivity and specificity, they often rely on expensive equipment and have stringent experimental conditions, which limits their widespread application. In contrast, luminescent detection methods have attracted widespread attention due to their rapid response, high selectivity, low cost, and ease of operation. In recent years, various luminescent probes have been used for L-glutamate detection. However, most of the reported probes are fluorescent probes, which are easily interfered with by background luminescence in practical applications, leading to limited detection accuracy. Phosphorescent probes can effectively avoid this problem, but the construction of phosphorescent probes still faces significant challenges.

[0003] Room-temperature phosphorescence (RTP) materials have important applications in information encryption, bioimaging, and sensing due to their long emission lifetime, high signal-to-noise ratio, absence of background fluorescence interference, and large Stokes shift. To date, several room-temperature phosphorescent materials for sensing have been developed, including organic materials, carbon dots, and coordination polymers (CPs), but short lifetimes remain a concern. CP-based host-guest RTP materials have attracted widespread attention in sensing due to their efficient phosphorescence emission and long-lifetime phosphorescence enhancement. However, while CP-based host-guest doped RTP materials hold great potential in sensing, reports on their application in this field are scarce. Researchers urgently need to increase their efforts to explore their underlying mechanisms, expand their applications, and promote the rapid development of this field. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, this invention provides a method for preparing a novel barium acetate open-framework material, C4H6BaO4 (denoted as 1). Based on this, a host-guest doping strategy was employed to introduce trace amounts of the organic molecule 1,4-naphthalenedicarboxylic acid (denoted as P) into material 1, successfully preparing the composite material P@1. This material exhibits visible room-temperature phosphorescence in the solid state. Notably, it retains its phosphorescence emission characteristics even in an ethanol / water suspension, laying the foundation for phosphorescence detection in solution systems. Based on this, the P@1 system was further used as a phosphorescent sensor to detect amino acids. The results showed that this material can achieve specific detection of L-glutamic acid through enhanced luminescence response, with a detection limit as low as 0.938 μmol·L⁻¹. -1 Detailed characterization revealed its luminescence mechanism, and this method provides a new approach for the efficient and rapid detection of L-glutamate.

[0005] The technical solution of the present invention is as follows: (1) Synthesis of compound 1 In a 20 mL glass reaction vessel, barium acetate (Ba(CH3COO)2, 300-1000 μL) was added to 1-4 mL of dimethyl sulfoxide, heated to 70-120 °C and stirred continuously to obtain a clear solution. After 12-36 hours, the reaction mixture was removed from the heat source and cooled to room temperature to induce the precipitation of crystalline products from the solution.

[0006] (2) Preparation of P@1 Using a similar preparation method as compound 1, barium acetate (Ba(CH3COO)2, 300-1000 μL) was added to 1-4 mL of dimethyl sulfoxide, followed by the addition of organic molecule P (P = 1,4-naphthalenedicarboxylic acid). P reacted with Ba... 2+ The molar ratio of the reactants is 1:50. The mixture is heated to 70-120°C with continuous stirring to obtain a clear solution. After 12-36 hours, the reaction mixture is removed from the heat source and cooled to room temperature to induce the precipitation of crystalline products from the solution.

[0007] (3) L-Glutamate (L-Glu) detection In the L-glutamate sensing experiments, 0.5–3 mg of P@1 powder was dispersed in 2–5 mL of ethanol / water (EtOH / H2O) to form suspensions, and sonicated for at least 10 min to ensure homogeneity. Emission spectra were measured under 254 nm excitation. All experiments were performed in ethanol / water. The amino acids used in this experiment during the detection process include L-histidine (L-His), L-cysteine ​​(L-Cys), D-tryptophan (D-Trp), L-arginine (L-Arg), D-serine (D-Ser), DL-phenylalanine (DL-Phe), L-aspartic acid (L-Asp), glycine (Gly), L-glutamic acid (L-Glu), L-leucine (L-Leu), D-valine (D-Val), L-lysine (L-Lys), β-alanine (β-Ala), L-threonine (L-Thr), L-glutamine (L-Gln), and L-methionine (L-Met).

[0008] The volume ratio of ethanol to water can be any ratio, but preferably, the volume ratio of ethanol to water is 1:1 to 4:1.

[0009] Preferably, the power of the ultrasonic treatment is 50-200W.

[0010] Compared with the prior art, the beneficial effects of this application are as follows: 1. This material relies on the large Stokes shift and long lifetime characteristics of room temperature phosphorescence to effectively avoid background fluorescence interference, and significantly improves the signal-to-noise ratio and anti-interference ability in sensing, anti-counterfeiting and bioimaging scenarios.

[0011] 2. The host-guest doped P@1 was prepared by solvothermal evaporation method, which can obtain green room temperature phosphorescence visible to the naked eye with an afterglow lasting about 3 seconds, and has outstanding advantages in naked-eye recognition and visualization applications.

[0012] 3. Exhibits a specific phosphorescence-enhanced response to L-glutamate (L-Glu), with a detection limit as low as 0.938 μmol·L⁻¹. -1 It combines high selectivity and high sensitivity, and its detection performance is superior to most similar systems. Attached Figure Description

[0013] Figure 1 This is the structure of compound 1, (a) is Ba 2+ The coordination environment of the ions, (b) is the structure of the tetranuclear {Ba4} metal framework, and (c) is the one-dimensional chain structure based on the tetranuclear {Ba4} metal framework. Figure 2 This is the stacking structure of compound 1, (a) is along ab A two-dimensional layered structure extending in a plane, (b) is along... ac Axial three-dimensional structure; Figure 3 The following are characterizations of compounds 1 and P@1: (a) powder X-ray diffraction pattern; (b) ultraviolet-visible reflectance spectrum. Figure 4 (a) shows the transient and delayed emission spectra of P, L-glutamic acid and P@1 composite material under 254 nm excitation; (b) shows the time-resolved emission decay curve of P@1 composite material; (c) shows the corresponding luminescent photographs of P@1 composite material under 254 nm UV lamp irradiation and after the UV lamp is removed. Figure 5 (a) is 0.1 mM L -1 (a) Phosphorescence intensity of P@1 in ethanol / water suspensions of different amino acids; (b) Phosphorescence spectra of P@1 suspensions at different L-glutamic acid concentrations; (c) Phosphorescence intensity ratio of P@1 suspensions in the range of 0–0.12 mM (Ig). 515 (d) shows the linear relationship between (0.1 mM L) and L-glutamate concentration; (d) indicates the presence or absence of 0.1 mM L. -1 The phosphorescence intensity of interfering substances in the P@1 suspension when glutamic acid is present; Figure 6 (a) is a comparison of the infrared spectra of P@1 and P@1+L-Glu; (b) are the transient and delayed spectra of P@1 and P@1+L-Glu; (c) are the time-resolved phosphorescence decay curves of P@1 and P@1+L-Glu glutamic acid at the 515 nm emission peak; (d) is a schematic diagram of the synthesis route of P@1 and its detection mechanism against L-Glu. Figure 7 (a) shows the application of time-resolved multi-level information encryption between P@1 and P with different lifespans; (b) shows the detection of L-Glu by making P@1 into a test strip. Detailed Implementation

[0014] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0015] Example 1 Crystal structure of compound 1 X-ray single-crystal diffraction analysis showed that the crystal of 1 has a tetragonal crystal system. I 4 (1) / a Space group. This compound has a three-dimensional structure based on a tetranuclear {Ba4} metallic framework. The structure contains one independent Ba4 core. 2+ Ions, each individual Ba2+ The ion exhibits a 9-coordination configuration, with ions from 7 different acetate groups (CH3COO). - The oxygen atom of the group is coordinated. Each of the five acetate groups is monodentately linked to Ba through one oxygen atom. 2+ Coordination; the other two acetate ions each bind to Ba via a bidentate chelate mechanism through two oxygen atoms. 2+ Coordination; the corresponding Ba-O bond lengths range from 2.680(5) to 3.167(5) Å, and the ∠O-Ba-O bond angles range from 43.89(15) to 164.65(15)º. The acetate group in the structure acts as a bridging group. μ 3 - κ O 1 : κ O 1 : κ O 1 and μ 2 - κ O 1 : κ O 1 Two coordination modes are used to connect three and two Ba, respectively. 2+ ion.

[0016] Four adjacent Ba 2+ The ions, bridged by two acetate groups and assisted by other acetate groups, form a tetranuclear {Ba4} metal framework unit. Zn The Zn distance is 4.3253 Å. The four {Ba4} primitives are connected by sharing vertices, forming a line along... c One-dimensional linear chain extending in a direction ( Figure 1 c). Adjacent chains are linked by acetate groups, forming a chain-like structure. ab Two-dimensional layered structure extending in a plane ( Figure 2 a). These layers along c The axial direction is further connected by acetate groups, ultimately constructing a three-dimensional framework structure. Figure 2 b).

[0017] The resulting three-dimensional framework structure can effectively confine the trace-doped guest molecule P, enabling it to exhibit excellent phosphorescence performance and laying a solid foundation for subsequent detection applications.

[0018] Example 2 Characterization of Compound 1 and Complex P@1 The phase purity of compound 1's crystal structure was confirmed by powder X-ray diffraction (PXRD). PXRD characterization showed good agreement between the experimental and simulated diffraction patterns, indicating that the synthesized crystal is a pure phase. Figure 3 a) The PXRD spectrum of complex P@1 shows negligible deviation compared to that of compound 1. Furthermore, we also tested the solid-state UV-Vis diffuse reflectance spectra of 1, P, and P@1, and the results are as follows: Figure 3 As shown in b, compared to compound 1, the UV-Vis diffuse reflectance spectrum of P@1 exhibits a distinct shoulder peak in the 300 nm range, which can be attributed to the absorption band generated by 1,4-naphthalenedicarboxylic acid (P). This further indicates that P is doped in trace amounts in compound 1.

[0019] Example 3: Luminescent properties of compound 1, P, L-glutamic acid (L-Glu), and complex P@1 The solid-state luminescence properties of compounds 1, P, and L-glutamic acid (L-Glu) were investigated at room temperature. Figure 4 As shown in Figure a, the maximum values ​​of the transient photoluminescence (PL) spectra of compounds 1, P, and L-Glu are located at 399 nm, 416 nm, and 324 nm, respectively. However, under ambient conditions, neither in dilute solution nor in solid powder form did they exhibit phosphorescence emission. Surprisingly, P@1 exhibited a green afterglow lasting for more than 3 seconds that was observable to the naked eye. Figure 4 The photoluminescence (PL) spectrum of compound a shows emission peaks at 397 nm and 550 nm, corresponding to the emission of compounds 1 and P, respectively. Simultaneously, P@1 exhibits green afterglow emission at 515 nm and 546 nm. Further time-resolved photoluminescence decay curves were tested to determine the photophysical properties of the newly emerging emission peak at 515 nm, showing a lifetime of 229.41 ms. Figure 4 b). The above results indicate that compound 1 can restrict the vibration of guest P, thereby suppressing the nonradiative energy loss of triplet excitons and ultimately enhancing room-temperature phosphorescence.

[0020] Example 5: Detection of L-glutamic acid P@1 also exhibited similar long-lifetime luminescence behavior to its solid sample in an ethanol / water (9:1) solution, with a decay lifetime of 99.11 ms. Figure 6c). Based on its excellent long-lifetime luminescence performance in aqueous solution, the potential of P@1 in the detection of amino acids in an ethanol / water system was further explored. We used an ethanol / water suspension of P@1 to detect a variety of amino acids via luminescence sensing, including L-histidine (L-His), L-cysteine ​​(L-Cys), D-tryptophan (D-Trp), L-arginine (L-Arg), D-serine (D-Ser), DL-phenylalanine (DL-Phe), L-aspartic acid (L-Asp), glycine (Gly), L-glutamic acid (L-Glu), L-leucine (L-Leu), D-valine (D-Val), L-lysine (L-Lys), β-alanine (β-Ala), L-threonine (L-Thr), L-glutamine (L-Gln), and L-methionine (L-Met). The aforementioned amino acids were added to the P@1 suspension, and the system's selectivity for amino acid recognition was investigated. Based on this, their phosphorescence spectra were measured (Figure 5). The concentration of amino acids in the suspension was maintained at 0.1 mmol·L⁻¹. -1 When L-glutamic acid was added to the aqueous solution, the luminescence intensity of P@1-L+Glu increased by approximately 18 times compared to the initial state. Figure 5 a) In contrast, the introduction of amino acids other than L-Glutamate had negligible effects on emission intensity, indicating that P@1 is selective for L-Glutamate. These results collectively confirm that P@1 can selectively detect L-Glu through phosphorescence enhancement. This phosphorescence detection method avoids interference from short-lived fluorescence background, thus possessing higher sensitivity and a better signal-to-noise ratio, an advantage that creates opportunities for reliable detection in complex media.

[0021] To gain a deeper understanding of the luminescence response of P@1 to L-Glu, we conducted a phosphorescence titration experiment. Figure 5 (b, c) L-Glu was added to the suspension of compound P@1. The phosphorescence emission intensity at 515 nm increased with increasing L-Glu concentration. (0–0.1176 mmol·L⁻¹) -1 Within the range, the phosphorescence intensity of P@1 suspension at 515 nm showed a good linear correlation with L-Glu concentration, and the correlation coefficient (R0) was [value missing]. 2 The value is 0.9930. Figure 5 c). Based on the detection limit formula LOD = 3σ / k (where σ is the standard deviation of 8 blank measurements and k is the slope of the fitted line), the detection limit (LOD) of L-glutamic acid was calculated to be 0.938 μmol·L⁻¹. -1 .

[0022] For practical applications, sensors not only need excellent sensitivity but also superior selectivity. Therefore, we conducted interference experiments to evaluate the response of P@1 to potentially coexisting amino acids. Adding an equivalent amount of L-Glu to the P@1 suspension significantly enhanced phosphorescence emission intensity. However, subsequent additions of equivalent amounts of L-histidine, L-cysteine, D-tryptophan, L-arginine, D-serine, DL-phenylalanine, L-aspartic acid, glycine, L-leucine, D-valine, L-lysine, β-alanine, L-threonine, L-glutamine, and L-methionine resulted in negligible changes in phosphorescence emission intensity. This confirms that the luminescence intensity of P@1 only changes in the presence of L-Glu.

[0023] Response time is a key parameter for evaluating sensor performance. To determine the response kinetics of P@1 to L-Glu, we added 0.1 mmol·L⁻¹ of Glu. -1 Following the addition of L-Glu, the phosphorescence spectrum of the P@1 suspension was dynamically monitored. Within 15 seconds of L-Glu addition, the phosphorescence intensity of P@1 at 515 nm increased sharply, reached a stable plateau after 10 minutes, and remained in a negligible fluctuation state for 45 minutes. These results indicate that P@1 can serve as a fast-responding L-Glu phosphorescence probe.

[0024] To investigate the sensing mechanism of P@1 for L-Glu, we conducted a series of experiments. The study found that the fluorescence and phosphorescence emission spectra of P@1 did not overlap with the absorption spectrum of L-Glu, ruling out the possibility of photoinduced energy transfer. The L-Glu molecule contains carboxyl groups (–COOH) and amino groups (–NH2), and its oxygen and nitrogen atoms can form hydrogen bonds with the carboxyl groups of P@1, thereby enhancing the phosphorescence properties of the composite material. Figure 6 As shown in a, 3450 cm -1 The nearby absorption peak corresponds to the stretching vibration of the hydroxyl group (-OH) in P@1; after interaction with L-Glu, this characteristic peak shifts, indicating the existence of non-covalent interactions such as N–H–O hydrogen bonds between the amino acid and P@1. Furthermore, the addition of L-Glu significantly enhances the phosphorescence intensity of the system. Figure 6 (b) and the phosphorescence lifetime of P@1 increased from 99.11 ms to 130.44 ms. Figure 6 c). This indicates that the hydrogen bonding between L-Glu and P@1 restricts the movement of guest molecules, thereby reducing non-radiative transition paths, promoting radiative transitions, and ultimately enhancing phosphorescence intensity. All the above data suggest that this phosphorescence enhancement effect is attributed to the formation of hydrogen bonds between them.

[0025] The detection mechanism of P@1 for L-Glu is as follows: Figure 6As shown in d, excited-state molecules of P@1 readily undergo nonradiative transitions via molecular vibration and rotation, and lack efficient spin-orbit coupling to promote intersystem crossing (S1→T1), resulting in a low number and short lifetime of triplet excitons. Therefore, P@1 solutions produce only weak phosphorescence. L-Glu is an acidic amino acid containing two carboxyl groups (-COOH) and one amino group (-NH2). Its carboxyl and amino groups can form a multidimensional hydrogen bond network with the carboxyl groups in P@1, further "locking" the motion of the guest molecule P and reducing vibrational and rotational energy loss in the excited state. Therefore, when L-Glu is added to the P@1 solution, the system exhibits enhanced phosphorescence. The change in luminescence intensity is related to the L-Glu content and can be used as a sensing signal for detecting L-glutamic acid.

[0026] Based on the unique afterglow properties of P@1 composite materials, their potential applications in the field of anti-counterfeiting technology were further explored. For example... Figure 7 As shown in Figure a, under natural light, all patterns are the same color, with the letter patterns "H" and "U" appearing white. Under 254 nm ultraviolet light, "H" remains white, while "U" appears blue-green. After the ultraviolet light source is turned off, only the green "H" letter pattern can be observed, and the afterglow of this green "H" disappears completely after 3.0 seconds. The above phenomena confirm that the P@1 composite material possesses time-resolved multi-level information encryption capabilities.

[0027] To simplify and facilitate detection, a portable test strip was prepared by depositing the P@1 sample onto the surface of the test strip (a suitable amount of P@1 powder sample was weighed and placed in a beaker, a certain volume of ethanol / water mixed solvent was added, and the sample was ultrasonically treated to fully disperse it and form a uniform suspension; then the test strip was immersed in the suspension to ensure that the P@1 sample was uniformly deposited on the surface of the test strip). Figure 7 (b) Under ultraviolet light, it emits blue-white light; when the ultraviolet light is turned off, a weak phosphorescence is produced. Subsequently, L-Glu was detected using a test strip. When an EtOH / H2O solution of L-Glu was dropped onto the test strip, its fluorescence did not change significantly under ultraviolet light, but after the ultraviolet light was turned off, its phosphorescence intensity and lifetime increased significantly. Therefore, the portable test strip based on P@1 can achieve portable and rapid detection of L-Glu.

[0028] In summary, the complex P@1, formed by trace doping of 1,4-naphthalenedic acid into matrix 1, exhibits visible green phosphorescence for up to 3 seconds. P@1 shows weak phosphorescence in its ethanol / water solution. Adding L-Glu to the ethanol / water solution of P@1 significantly enhances its phosphorescence, while the addition of other amino acids has almost no effect on the phosphorescence. This indicates that P@1 has excellent detection properties for L-Glu. Its detection limit can reach 0.938 μmol·L⁻¹. -1The main reason is that glutamic acid can form a multidimensional hydrogen bond network with the carboxyl group in P@1, further "locking in" the motion of the guest molecule P and reducing vibrational / rotational losses in the excited state. Therefore, when L-Glu is added to the P@1 solution, phosphorescence enhancement occurs. Thus, the above results open up new avenues for developing phosphorescent probes with high detection performance.

[0029] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a barium acetate open-framework material, characterized in that, Includes the following steps: Add 300-1000 μL of barium acetate (Ba(CH3COO)2) to 1-4 mL of dimethyl sulfoxide, then add the organic molecule 1,4-naphthalenedicarboxylic acid (P). P reacts with Ba... 2+ The molar ratio is 1:

50. The mixture is heated to 70-120 °C and stirred continuously to obtain a transparent solution. After 12-36 hours, the reaction mixture is removed from the heat source and cooled to room temperature to promote the precipitation of crystalline products from the solution.

2. The barium acetate open framework material prepared by the method according to claim 1.

3. The application of the barium acetate open-frame material according to claim 2 in the preparation of phosphorescent sensors.

4. The application of the barium acetate open-frame composite material of claim 3 in the preparation of a phosphorescent sensor for the specific detection of L-glutamic acid.

5. A method for detecting L-glutamic acid using the barium acetate open-framework composite material as described in claim 4, characterized in that, Includes the following steps: 0.5-3 mg of P@1 powder was dispersed in 2-5 mL of ethanol / water to form a suspension, and ultrasonic treatment was performed to ensure homogeneity. The emission spectrum was measured under 254 nm excitation, and L-glutamic acid was detected based on the changes in the emission spectrum.

6. The method for detecting L-glutamic acid according to claim 5, characterized in that, The volume ratio of ethanol to water is 1:1 to 4:

1.

7. The method for detecting L-glutamic acid according to claim 5, characterized in that, The power of the ultrasonic treatment is 50-200W.

8. The method for detecting L-glutamic acid according to claim 5, characterized in that, The amino acids used in the testing process include L-histidine (L-His), L-cysteine ​​(L-Cys), D-tryptophan (D-Trp), L-arginine (L-Arg), D-serine (D-Ser), DL-phenylalanine (DL-Phe), L-aspartic acid (L-Asp), glycine (Gly), L-glutamic acid (L-Glu), L-leucine (L-Leu), D-valine (D-Val), L-lysine (L-Lys), β-alanine (β-Ala), L-threonine (L-Thr), L-glutamine (L-Gln), and L-methionine (L-Met).

Images