A Zn(II)-Tb(III) complex ratio fluorescence sensor, a preparation method and application thereof

Abstract

The application belongs to the field of coordination chemistry and analytical sensing technology, and particularly relates to a Zn(II)-Tb(III) complex ratio fluorescence sensor and a preparation method and application thereof. The sensor is a double-metal coordination polymer formed by coordination of Zn(II) ions, Tb(III) ions, nitrogen-containing organic ligands and carboxylic acid organic ligands. Under excitation conditions, the sensor simultaneously generates an emission signal of ligand coordination with Zn(II) and a characteristic emission signal of Tb(III) ions, forming intrinsic double emission. By monitoring the fluorescence intensity ratio (I395 / I549) of the two characteristic emission peaks at 395 nm and 549 nm, ratio fluorescence detection of propyl gallate can be realized, and the detection limit is as low as 0.35 μM. The sensor of the application has a simple synthesis method, a rapid detection process, and realizes internal calibration by using a ratio signal, has strong anti-interference ability, and is suitable for detection of propyl gallate in edible oil and other actual samples.

Description

Technical Field

[0001] This invention belongs to the field of coordination chemistry and analytical sensing technology, specifically relating to a Zn(II)-Tb(III) complex ratio fluorescence sensor, its preparation method, and its application. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Propyl gallate (PG), a phenolic antioxidant, is widely used in food, cosmetics, and related products. Its core function is to delay the oxidative degradation of oils and lipids in these products, thereby extending shelf life. Studies have confirmed that high-dose PG exposure or long-term PG contact can easily lead to adverse effects such as chromosomal abnormalities, mitochondrial dysfunction, and abnormal cell physiological functions. Given these potential risks, many countries and regions worldwide have enacted regulations to strictly control the scope and dosage of PG as a food additive. Therefore, developing a highly sensitive, stable, and rapid PG detection method is of significant practical importance and application value for ensuring food safety, controlling the quality of related products, and implementing compliant supervision.

[0004] Currently, detection methods for prostaglandins (PGs) mainly include high-performance liquid chromatography (HPLC), chromatography-mass spectrometry (GC-MS), and electrochemical methods. While these methods are accurate, they typically require large-scale equipment, time-consuming procedures, and complex sample pretreatment steps, making them unsuitable for rapid on-site screening. Fluorescence detection methods have attracted attention due to their ease of operation and rapid response. However, most existing fluorescence sensors rely on a single fluorescence signal's "on-off" response mechanism, making them susceptible to changes in probe concentration, light source intensity, and environmental conditions. The stability and reliability of the detection results still need improvement.

[0005] Ratio fluorescence detection technology simultaneously monitors fluorescence signals at two different wavelengths and uses their intensity ratio as the analytical signal. This allows for internal self-calibration, effectively reducing the impact of environmental factors and instrument errors on the detection results, and offers significant advantages in trace analysis and practical applications. However, current reports on ratio fluorescence sensing systems based on bimetallic complexes are still relatively limited, and research on bimetallic complex-based ratio fluorescence sensing systems for PG detection is even more insufficient. A mature technical solution has not yet been developed, and further development is still necessary. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a Zn(II)-Tb(III) complex ratio fluorescence sensor, its preparation method, and its application.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A ratiometric fluorescence sensor constructed from a Zn(II)-Tb(III) complex, with the molecular formula [Zn(tpy)2][Tb4(DCA)] 14 [], where DCA represents 3,5-dichlorobenzoic acid and tpy represents tripyridine. The Zn(II)-Tb(III) complex crystallizes in the triclinic system with space group P-1.

[0008] Furthermore, the asymmetric units of the Zn(II)-Tb(III) complex exhibit ion-pair characteristics, with the Zn(II) ion coordinating with the nitrogen-containing organic ligand tpy, and the Tb(III) ion coordinating with the carboxylic acid organic ligand DCA. These two components synergistically construct a bimetallic complex structure. The cation [Zn(tpy)2] 2+ The component consists of a Zn(II) cation and two tpy ligands. The Zn(II) center is coordinated through the six nitrogen atoms (N1-N6) of the two tpy ligands, forming a distorted octahedral ZnN8 coordination geometry; the anion [Tb4(DCA)] 14 ] 2- The composition contains four Tb(III) cations and 14 DCA anions. The four Tb(III) ions exist in a linear arrangement of Tb1···Tb2···Tb3···Tb4.

[0009] Furthermore, the adjacent anion [Tb4(DCA)] 14 ] 2- Units are connected along the a-axis through DCA ligands to form one-dimensional linear chains. The one-dimensional chains are further connected along the b-axis through hydrogen bonds to form two-dimensional layers. The two-dimensional layers are extended to form a three-dimensional supramolecular structure through hydrogen bonds and interactions between chlorine atoms.

[0010] Furthermore, the Zn(II)-Tb(III) complex, under 300 nm excitation light, simultaneously generates an emission signal (395 nm) from the coordination of the ligand with Zn(II) ions and a characteristic emission signal (549 nm) from Tb(III) ions, forming an intrinsic dual-emission system; wherein, the characteristic emission peaks of Tb(III) ions also include 495 nm, 590 nm, and 626 nm, corresponding to the emission peaks of Tb(III) ions, respectively. 5 D4→ 7The F_J (J=6,5,4,3) transition has the strongest fluorescence emission peak at 549 nm, indicating that the ligand sensitizes Tb(III) ions to emit light through the "antenna effect". The emission band at 395 nm is attributed to the emission peak generated by the coordination of tpy with Zn(II) ions. Compared with the emission band of the free ligand, there is a significant blue shift, which confirms that the ligand coordinates with the metal center.

[0011] Furthermore, by monitoring the fluorescence intensity ratio I of the dual emission signals 395 / I 549 This invention enables the quantitative detection of propyl gallate (PG). The sensor's quenching constant Ksv for PG is 4.88 × 10⁻⁶. 3 M -1 The detection limit is as low as 0.35 μM.

[0012] Furthermore, the preparation method of the Zn(II)-Tb(III) complex ratio fluorescence sensor adopts the following steps: 1. Weigh 0.40-0.41 g of 3,5-dichlorobenzoic acid (DCA), 0.018-0.022 g of ZnCl2, 0.26-0.28 g of Tb(NO3)3·6H2O, and 0.06-0.08 g of tripyridine (tpy), add them to 8 mL of deionized water, and stir at room temperature to form a mixed solution.

[0013] 2. Under stirring conditions, add 0.25 M sodium carbonate aqueous solution dropwise to the above mixed solution to adjust the pH of the system to 5-6.

[0014] 3. Transfer the resulting mixed solution to a 25 mL polytetrafluoroethylene-lined stainless steel high-pressure reactor and heat it at 150-170 °C for 2-4 days.

[0015] 4. After the reaction is complete, the reactor is cooled to room temperature at a rate of 2 °C / hour, filtered and washed with deionized water to obtain purple blocky crystals, which are the target Zn(II)-Tb(III) complex. The yield can reach 67% based on the amount of Tb(III) salt fed.

[0016] Furthermore, the preferred reaction temperature for the hydrothermal reaction in step (3) is 160 °C, and the reaction time is 3 days.

[0017] Furthermore, the sensing material is stored in the form of solid crystal powder and is uniformly dispersed in a solvent when used.

[0018] Furthermore, the Zn(II)-Tb(III) complex ratio fluorescence sensor can be used for ratio fluorescence detection of PG, especially suitable for the detection of trace PG and PG in actual samples such as edible oil. It needs to be pretreated by organic solvent extraction before detection.

[0019] Furthermore, the detection process is as follows: The Zn(II)-Tb(III) complex was dispersed in an ethanol system to prepare a fluorescence sensing system with a concentration of 0.50 mg / mL. Under 300 nm excitation conditions, different concentrations of PG were gradually added to the sensing system, and the mixture was mixed and the fluorescence emission spectrum was recorded after each addition. As the PG concentration increased, the fluorescence intensity of the sensing system at 395 nm and 549 nm gradually decreased, exhibiting significant fluorescence quenching behavior. The fluorescence intensity ratio I... 395 / I 549 As an analytical signal, the PG content in the sample is calculated in conjunction with the standard curve.

[0020] Furthermore, this sensor exhibits good selectivity and anti-interference properties for PGs, as well as phenolic antioxidants such as butylated hydroxyanisole, 2,6-di-tert-butyl-4-methylphenol, and tert-butylhydroquinone; oil components such as oleic acid and palmitic acid; vitamins such as tocopherol and ascorbic acid; food additives such as glucose, lactose, and calcium propionate; and K. + Na + Mg 2+ I - Even in the presence of representative ions, PG can still be accurately detected, and the fluorescence intensity ratio remains basically stable. Significant changes in the ratio signal can be observed after the addition of PG.

[0021] Furthermore, when used for PG detection in edible oil samples, the sample pretreatment steps are as follows: Weigh 0.5 g of edible oil sample into a centrifuge tube, add 15 mL of chromatographic grade methanol, mix well, sonicate for 30 min, centrifuge at 10000 r / min for 20 min, collect the supernatant, and repeat the extraction twice; combine the supernatants and remove the organic solvent by rotary evaporation, dilute the obtained extract with an appropriate amount of ethanol, add it to the sensing system for detection, the recovery rate is 96.75%-102.21%, and the relative standard deviation is less than 2.65%, which meets the actual sample analysis requirements.

[0022] The beneficial effects of the technical solution provided by this invention are: 1. The Zn(II)-Tb(III) complex provided by this invention can be directly synthesized by a simple one-pot hydrothermal method without the need for complicated post-synthesis modification steps. The preparation process is simple to operate, has good reproducibility, and the yield can reach 67%, which has good potential for practical application.

[0023] 2. The Zn(II)-Tb(III) complex provided by this invention adopts a ratio fluorescence detection strategy. Compared with the traditional single-signal "on-off" fluorescence sensor, it can achieve internal self-calibration through the ratio of dual emission signals, which significantly reduces the impact of environmental factors, instrument errors and probe concentration fluctuations on the detection results, and greatly improves the stability and reliability of the detection results. At the same time, the detection limit is as low as 0.35 μM, which can realize the accurate detection of trace PG.

[0024] 3. This ratiometric fluorescence sensor exhibits specific recognition capability for PG, accurately detecting it even under conditions where various interfering substances associated with the actual sample matrix coexist. This makes it suitable for detecting PG in complex matrix samples, broadening its application scenarios. The sensor can be directly used for PG detection in edible oil samples, achieving a reasonable recovery rate and low relative standard deviation, meeting the practical needs of food safety testing. Furthermore, it expands the application scope of bimetallic complexes in fluorescence sensing, providing a new technical solution for rapid and reliable PG detection, and possesses significant value for technological promotion. Attached Figure Description

[0025] Figure 1 The image shows the crystal morphology of the Zn(II)-Tb(III) complex prepared in Example 1 of this invention. The crystal shown is a purple blocky crystal. Figure 2 This is a schematic diagram of the asymmetric unit and metal-center coordination environment structure of the Zn(II)-Tb(III) complex prepared in Example 1 of this invention. Figure 2 (a) is a schematic diagram of the coordination environment of the Zn(II) center. Figure 2 (b) is a schematic diagram of the coordination environment of the Tb(III) center.

[0026] Figure 3 These are schematic diagrams of the one-dimensional, two-dimensional, and three-dimensional structures of the Zn(II)-Tb(III) complex prepared in Example 1 of this invention. Figure 3 (a) is a one-dimensional chain structure. Figure 3 (b) is a two-dimensional layered structure formed by a one-dimensional chain. Figure 3 (c) is a three-dimensional supramolecular structure formed by the expansion of a two-dimensional layered structure; Figure 4 Solid-state excitation and emission spectra of DCA ligand, tpy ligand, and Zn(II)-Tb(III) complexes prepared in Example 1 of this invention; Figure 5 This is a schematic diagram showing the ratio fluorescence detection results of the Zn(II)-Tb(III) complex prepared in Example 1 against PG. Figure 5 (a) shows the fluorescence emission spectra of the complexes under different PG concentrations. Figure 5(b) is the fluorescence intensity ratio I 395 / I 549 A linear relationship curve between PG concentration and PG concentration; Figure 6 This is a schematic diagram showing the test results of the selectivity and anti-interference performance of the Zn(II)-Tb(III) complex prepared in Example 1 against PG. Figure 6 (a) The fluorescence intensity changes of the complex under the presence of multiple potential interfering substances. Figure 6 (b) The fluorescence intensity change of the complex after adding PG under the condition of coexistence of interfering substances; Figure 7 A schematic diagram showing the overlap between the excitation and emission spectra of the Zn(II)-Tb(III) complex prepared in Example 1 and the ultraviolet absorption spectrum of PG; Figure 8 The infrared spectra of the Zn(II)-Tb(III) complex prepared in Example 1 before and after the addition of PG are compared. Detailed Implementation

[0027] The specific embodiments of the present invention are described in detail below. These embodiments are intended to more fully demonstrate the technical content of the present invention and help to understand the specific implementation process of the present invention, but their content should not be construed as limiting the scope of the claims of the present invention in any way. For those skilled in the art, various adjustments, modifications, and substitutions made to the embodiments without departing from the spirit and scope of the present invention are all within the scope of protection sought by the present invention.

[0028] Example 1 Preparation of Zn(II)-Tb(III) complexes: (1) Weigh 0.405 g of 3,5-dichlorobenzoic acid (DCA), 0.020 g of ZnCl2, 0.272 g of Tb(NO3)3·6H2O and 0.070 g of tripyridine ligand (tpy). Add the above raw materials to 8 mL of distilled water and stir at room temperature to mix them thoroughly.

[0029] (2) Under stirring conditions, 3.6 mL of 0.25 M Na2CO3 aqueous solution was added dropwise to the reaction mixture obtained in step (1) to adjust the pH of the reaction system to 5.

[0030] (3) Transfer the solution obtained in step (2) to a 25 mL polytetrafluoroethylene-lined stainless steel autoclave, seal it, and place it in an oven to heat and react at 160 °C for 3 days.

[0031] (4) After the reaction was completed, the reactor was cooled to room temperature at a rate of 2 °C / hour, and the reactor was opened to obtain purple crystals. The obtained crystals were filtered, washed, and then naturally dried to obtain the target Zn(II)-Tb(III) bimetallic complex. The yield was 67% based on the amount of Tb(III) salt fed.

[0032] Crystal structure characterization: Figure 1 This is the crystal morphology of the Zn(II)-Tb(III) complex prepared in Example 1. It appears as purple, blocky crystals. The structural characterization of the Zn(II)-Tb(III) complex is as follows: The Zn(II)-Tb(III) complex is a triclinic crystal system, space group P-1. The cation is [Zn(tpy)2]. 2+ The composition consists of a Zn(II) cation and two tpy ligands. The Zn(II) center is coordinated to the six nitrogen atoms (N1-N6) of the two tpy ligands, forming a twisted octahedral ZnN6 coordination geometry. The Zn-N bond length ranges from 2.079(4) to 2.228(4) Å, and the N-Zn-N bond angle is between 75.21(17) and 171.03(17)°.

[0033] Anion [Tb4(DCA)] 14 ] 2- The composition contains four Tb(III) cations and 14 DCA anions. The four Tb(III) ions exist in a linear arrangement of Tb1···Tb2···Tb3···Tb4. The distances between adjacent Tb atoms are as follows: Tb1-Tb2 is 4.283(4) Å, Tb2-Tb3 is 4.356(4) Å, Tb3-Tb4 is 5.054(4) Å, and Tb4-Tb1#1 is 4.200(4) Å. The Tb-O bond length ranges from 2.234(3) to 2.725(3) Å, and the O-Tb-O bond angle is between 50.17(11) and 159.67(14)°. The adjacent anions [Tb4(DCA)]... 14 ] 2- The units are connected along the a-axis via DCA ligands to form a one-dimensional linear chain. The one-dimensional chain is further connected along the b-axis via C98-H98···Cl7 hydrogen bonds to form a two-dimensional layer. The two-dimensional layer is extended to form a three-dimensional supramolecular structure through C49-H49···Cl12 and C105-H105···Cl14 hydrogen bonds and Cl2···Cl25 interactions.

[0034] Example 2 (1) Weigh 0.400 g of DCA, 0.018 g of ZnCl2, 0.260 g of Tb(NO3)3·6H2O and 0.060 g of tpy, add the above raw materials to 8 mL of distilled water, and stir at room temperature to mix them thoroughly.

[0035] (2) Under stirring conditions, add 0.25 M Na2CO3 aqueous solution dropwise to the reaction mixture obtained in step (1) to adjust the pH of the reaction system to 6.

[0036] (3) Transfer the solution obtained in step (2) to a 25 mL polytetrafluoroethylene-lined stainless steel autoclave, seal it, and place it in an oven to heat and react at 150 °C for 4 days.

[0037] (4) After the reaction was completed, the reactor was cooled to room temperature at a rate of 2°C / hour. The reactor was then opened, and purple crystals were obtained. The obtained crystals were filtered, washed, and then naturally dried to obtain the target Zn(II)-Tb(III) bimetallic complex. The yield was 68% based on the amount of Tb(III) salt fed.

[0038] Example 3 (1) Weigh 0.410 g of DCA, 0.022 g of ZnCl2, 0.280 g of Tb(NO3)3·6H2O and 0.080 g of tpy, add the above raw materials to 8 mL of distilled water, and stir at room temperature to mix them thoroughly.

[0039] (2) Under stirring conditions, add 0.25 M Na2CO3 aqueous solution dropwise to the reaction mixture obtained in step (1) to adjust the pH of the reaction system to 5.

[0040] (3) Transfer the solution obtained in step (2) to a 25 mL polytetrafluoroethylene-lined stainless steel autoclave, seal it, and place it in an oven to heat and react at 170 °C for 2 days.

[0041] (4) After the reaction was completed, the reactor was cooled to room temperature at a rate of 2°C / hour. The reactor was then opened, and purple crystals were obtained. The obtained crystals were filtered, washed, and then naturally dried to obtain the target Zn(II)-Tb(III) bimetallic complex. The yield was 68% based on the amount of Tb(III) salt fed.

[0042] Example 4 Dual emission sources confirmed for Zn(II)-Tb(III) complexes: Figure 4As shown, the solid-state excitation and emission spectra of DCA, tpy ligands, and the Zn(II)-Tb(III) complex prepared in Example 1 were recorded at room temperature. With excitation wavelengths of 385 nm and 375 nm, respectively, strong emission bands appeared at 444 nm and 432 nm for DCA and tpy, respectively. This emission is attributed to electronic transitions within the ligands.

[0043] Under 300 nm excitation, the Zn(II)-Tb(III) complex prepared in Example 1 emitted strong green fluorescence and exhibited characteristic emission peaks of Tb(III) ions: fluorescence emission peaks at 495 nm, 549 nm, 590 nm, and 626 nm corresponded to the Tb(III) ions, respectively. 5 D4→ 7 F J The transitions (J = 6, 5, 4, 3) with the strongest fluorescence emission peak at 549 nm indicate that the ligand can sensitize Tb(III) ion luminescence through the "antenna effect".

[0044] In addition to the characteristic emission of Tb(III) ions, the Zn(II)-Tb(III) complex prepared in Example 1 also exhibits a broad but weak emission band around 395 nm. Compared to the emission of free DCA and tpy ligands, this emission band shows a significant blue shift, indicating coordination between the ligands and the metal center. Combining the structural and luminescence characteristics, the emission band around 395 nm is attributed to the emission peak generated by the coordination of tpy with Zn(II) ions.

[0045] Therefore, the Zn(II)-Tb(III) complex prepared in Example 1 has two intrinsic emission signals that can be used for ratio detection: the first emission peak is the emission signal at 395 nm generated by the coordination of the ligand with the Zn(II) ion, and the second emission peak is the strongest characteristic emission signal of the Tb(III) ion at 549 nm.

[0046] Example 5 Detection of PG using a Zn(II)-Tb(III) complex ratio fluorescence sensor: An ethanol suspension of the Zn(II)-Tb(III) complex was prepared as a fluorescence sensing system. Its initial fluorescence emission spectrum was recorded under 300 nm excitation, and the fluorescence intensities at 395 nm and 549 nm were denoted as IL and IL, respectively. 395 with I 549 .

[0047] Different concentrations of PG were gradually added to the fluorescence sensing system. After each addition, the mixture was stirred and the corresponding fluorescence emission spectrum was recorded. Figure 5(a) As the PG concentration increases, the fluorescence intensity of the Zn(II)-Tb(III) complex at 395 nm and 549 nm gradually decreases, exhibiting significant fluorescence quenching behavior.

[0048] I recorded at different concentrations of PG 395 / I 549 As an analytical signal. Results showed that within the PG concentration range of 0-40 μM, I... 395 / I 549 It showed a good linear relationship with PG concentration, and the linear fitting equation was: y = 0.00488x + 0.11494, with a correlation coefficient R. 2 =0.995.

[0049] Analysis revealed that the Ksv of the Zn(II)-Tb(III) complex to PG was 4.88 × 10³ M. -1 To calculate the limit of detection (LOD), the standard deviation σ was obtained by performing 10 parallel measurements of the fluorescence intensity of the blank system. Based on LOD = 3σ / Ksv, the detection limit of the Zn(II)-Tb(III) complex for PG was calculated to be 0.35 μM.

[0050] Example 6 Selectivity and anti-interference experiments of Zn(II)-Tb(III) complexes for PG: To evaluate the selectivity and anti-interference ability of the Zn(II)-Tb(III) complex for PG, the effects of various potential interfering substances on the ratiometric signal of this fluorescence sensing system were investigated. These potential interfering substances included: (1) Phenolic antioxidants with structures similar to PG: butylated hydroxyanisole (BHA), 2,6-di-tert-butyl-4-methylphenol (BHT) and tert-butylhydroquinone (TBHQ); (2) Common oil components: oleic acid (OA), palmitic acid (PA) and lecithin (CSL); (3) Vitamins: Tocopherol (VE) and ascorbic acid (VC); (4) Commonly used food additives: glucose (Glc), lactose (Lac), propylparaben (PP), calcium propionate (CaP), sodium phenolate (SP) and potassium persulfate (KPS); (5) Representative ion: K + Na + Mg 2+ , I - .

[0051] like Figure 6As shown in (a), under the conditions of adding the above interfering substances respectively, the fluorescence intensity and I of the Zn(II)-Tb(III) complex at 395 nm and 549 nm are... 395 / I 549 The ratio remained relatively stable; significant fluorescence quenching and ratio signal changes were observed only upon the addition of PG. The quenching rate at 395 nm was 82%, while the quenching at 549 nm was more severe, reaching 93%.

[0052] Furthermore, when PG was added to the system containing the aforementioned interfering substances for anti-interference experiments, a significant fluorescence quenching phenomenon of PG by the Zn(II)-Tb(III) complex was still observed, and I 395 / I 549 The trend of change is consistent with that of the system containing only PG, I 395 / I 549 The intensity ratio values ​​are between 0.31 and 0.38, indicating that the Zn(II)-Tb(III) complex has good anti-interference ability for the detection of PG and is suitable for complex sample environments.

[0053] Example 7 The peanut oil sample was purchased from a local supermarket.

[0054] Application steps of Zn(II)-Tb(III) complexes for the detection of PG in peanut oil: (1) Peanut oil sample pretreatment: Weigh 0.5 g of peanut oil sample and add it to a centrifuge tube. Add 15 mL of chromatographic grade methanol, mix well and then sonicate for 30 min.

[0055] (2) Centrifuge the mixture obtained in step (1) at 10000 r / min for 20 min and collect the supernatant; repeat the above extraction steps twice to improve the extraction adequacy.

[0056] (3) Combine the supernatants obtained from multiple extractions into a distillation flask, remove the organic solvent by rotary evaporation, and obtain peanut oil extract; dilute the extract with an appropriate amount of ethanol for later use.

[0057] (4) Peanut oil sample determination: A certain concentration of PG (14, 24, 34 μM) was added to the pretreated peanut oil sample, and then the spiked sample was added to the fluorescence sensing system constructed by the Zn(II)-Tb(III) complex in Example 1. I was measured under 300 nm excitation. 395 with I 549 And by I 395 / I 549 Calculate the PG content.

[0058] Recovery results showed that the Zn(II)-Tb(III) complex had a recovery rate of 96.75%-102.21% for the detection of PG in peanut oil samples, with a relative standard deviation (RSD) of less than 2.65%, indicating that the detection method has good accuracy and repeatability and meets the needs of actual sample analysis.

[0059] To clarify the fluorescence sensing mechanism of the complex for PG, the ultraviolet absorption spectrum of PG and the excitation spectrum of the complex, as well as the infrared spectra of the complex before and after the addition of PG, were measured. The results showed that the ultraviolet absorption spectrum of PG effectively overlapped with the excitation spectrum of the Zn(II)-Tb(III) complex, thereby inducing an internal filtering effect (IFE). PG competitively absorbed the excitation light of the complex, ultimately leading to quenching of the complex's fluorescence signal. Furthermore, the infrared characteristic peaks of the complex did not change significantly before and after the addition of PG, confirming that PG did not coordinate with the Zn(II) and Tb(III) metal centers in the complex. Therefore, the core mechanism of the ratiometric fluorescence detection of PG by this complex is the internal filtering effect.

[0060] In summary, this invention constructs a Zn(II)-Tb(III) complex, realizing a ratiometric fluorescence detection system based on intrinsic dual emission signals. Under ultraviolet light excitation, the Zn(II)-Tb(III) complex simultaneously generates an emission signal from the coordination of the ligand with Zn(II) ions and a characteristic emission signal from Tb(III) ions. The ratio of their fluorescence intensities can be used for sensitive and stable quantitative detection of PG. This detection system exhibits good selectivity and anti-interference capabilities, making it suitable for complex real-world sample environments. Furthermore, it demonstrates a recovery rate of 96.75%-102.21% for PG detection in peanut oil, a real-world sample. The preparation method of the Zn(II)-Tb(III) complex is simple, obtained through a one-pot hydrothermal reaction, and exhibits good repeatability and practicality. Therefore, this invention provides a new technical solution for the rapid and reliable detection of propyl gallate in real-world samples such as peanut oil, and has promising application prospects.

[0061] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A Zn(II)-Tb(III) complex ratio fluorescence sensor, characterized in that, The molecular formula of the sensor is [Zn(tpy)2][Tb4(DCA)] 14 [], where DCA is 3,5-dichlorobenzoic acid and tpy is tripyridine.

2. A method for preparing the Zn(II)-Tb(III) complex ratio fluorescence sensor according to claim 1, characterized in that, The preparation method comprises the following steps: 3,5-dichlorobenzoic acid, ZnCl2, Tb(NO3)3·6H2O and tripyridine ligand are mixed with water, the pH is adjusted, and a hydrothermal reaction is carried out to obtain the Zn(II)-Tb(III) complex ratio fluorescence sensor.

3. The preparation method according to claim 2, characterized in that, The pH is adjusted using an aqueous solution of Na2CO3; the pH is adjusted to 5-6.

4. The preparation method according to claim 2, characterized in that, The hydrothermal reaction is carried out at a temperature of 150-170 ℃ for 2-4 days.

5. The preparation method according to claim 2, characterized in that, The mass-to-volume ratio of 3,5-dichlorobenzoic acid, ZnCl2, Tb(NO3)3·6H2O, tripyridine ligand, and water is: (0.05~0.05125) g : (0.00225~0.00275) g : (0.0325~0.035) g : (0.0075~0.01) g : 1 mL.

6. The preparation method according to claim 2, characterized in that, After the hydrothermal reaction is completed, cooling, separation, washing, and drying are required to obtain the Zn(II)-Tb(III) complex ratio fluorescence sensor.

7. The application of the sensor according to claim 1 or the sensor prepared by the preparation method according to claims 2-6, characterized in that, The application is for the detection of propyl gallate.

8. The application according to claim 7, characterized in that, The method for using the ratio fluorescence sensor to detect propyl gallate is as follows: using the intensity ratio I of the two fluorescence emission signals... 395 / I 549 As an analytical signal, the content of propyl gallate in the sample to be tested is determined.

9. The application according to claim 8, characterized in that, The samples to be tested are food, cosmetics and related products containing propyl gallate, and must undergo organic solvent extraction pretreatment before testing.

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