A colorimetric-luminescent dual-mode sensing system based on three-component supramolecular self-assembly behavior and use thereof

Abstract

The application discloses a colorimetric-luminescent dual-mode sensing system based on three-component supramolecular self-assembly behavior and application thereof in zinc ion detection, wherein the platinum (II) complex in the colorimetric-luminescent platinum (II) complex / oxalate / zinc ion three-component system is isothiocyanate·(terpyridine) platinum (II), by adding zinc ions into the mixed solution of the platinum (II) complex / oxalate, the solution changes from yellow to orange, and from no luminescence to strong orange luminescence. The process utilizes the coordination of zinc ions and oxalate during the detection process to induce the supramolecular self-assembly behavior of the platinum (II) complex to cause the sharp change of ultraviolet-visible absorption and luminescence, thereby realizing the sensitive, rapid and intuitive detection of zinc ions, and meanwhile, the process has the advantages of high detection selectivity and good anti-interference property.

Description

Technical Field

[0001] This invention belongs to the field of chemical sensing technology and relates to a colorimetric-luminescent platinum(II) complex / oxalate / zinc ion three-component supramolecular self-assembly system for zinc ion detection. Background Technology

[0002] Zinc ions (Zn) 2+ Zinc is an indispensable trace element in the human body, playing a crucial role in many biological processes, including pathological mechanisms, brain function, gene transcription, immune responses, DNA binding, apoptosis, mammalian reproduction, and muscle contraction. As the second most abundant metallic ion in the body after iron, abnormal zinc concentrations can lead to various health problems, including growth retardation, prostate cancer, diabetes, stroke, Alzheimer's disease, and Parkinson's disease. Furthermore, zinc ions are ubiquitous in daily life, ranking among the top ten most common non-ferrous metals and third in consumption. Improper handling leading to leaks can cause environmental pollution and allow zinc ions to enter the human body through the food chain. Therefore, achieving highly specific detection of zinc ions in complex environments is crucial for human health protection and ecological balance.

[0003] According to previous reports, many analytical techniques have been used to detect zinc ions, such as atomic absorption spectrometry, inductively coupled plasma mass spectrometry, atomic emission spectrometry, and inductively coupled plasma electroanalysis. However, these methods are not suitable for rapid on-site detection due to significant drawbacks such as expensive instruments, empirical operation, and time-consuming pretreatment. In contrast, optical sensing methods based on color or emission changes offer advantages such as simple operation, low cost, visualization, fast response, and high sensitivity. To date, many probes for detecting zinc ions have been developed. However, these probes show significant limitations in specific detection of zinc ions under complex environments. This lack of specificity can be attributed to single-mode optical signals and insufficient recognition capabilities. On the one hand, single-mode optical signals are easily interfered with by inherent color or autofluorescence. On the other hand, insufficient recognition capabilities can lead to false alarms from other coexisting competing cations / anions. Therefore, it is essential to develop an effective zinc ion optical sensing system with dual-mode optical signals and high recognition capabilities.

[0004] Supramolecular platinum(II) complexes have been reported as promising colorimetric and luminescent dual-mode probes. These complexes exhibit rich luminescence and colorimetric properties due to the formation of Pt-Pt interactions between non-radiative monomers during supramolecular self-assembly, leading to low-energy metal-metal-ligand charge transfer (MMLCT) excited states. Based on their unique optical properties and supramolecular self-assembly behavior, platinum(II) complexes have been successfully applied to the dual-mode detection of various ions. However, these supramolecular sensing systems based on Pt-Pt interactions involve only two components and cannot completely eliminate interference from competing ions or molecules. Three-component supramolecular self-assembly is an effective strategy to further enhance recognition capabilities. This is because the introduction of additional components can generate additional interactions with the target ion, which not only enhances the strength of the recognition but also enriches the types of recognition interactions. Therefore, to achieve colorimetric-luminescence dual-mode detection of the target zinc ion through three-component supramolecular self-assembly, oxalate ions with strong coordination ability with zinc ions are first selected. The coordination of zinc ions with oxalate ions forms a complex anion, which then triggers ion association and assembly reactions with platinum(II) complexes, generating significant colorimetric and luminescence signal responses. The dual-mode response originates from interlattice Pt-Pt and π-π interactions, which produce absorption and emission of low-energy metal-metal-ligand charge transfer (MMLCT), thereby achieving colorimetric-fluorescence detection of the target zinc ion. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of current zinc ion detection methods by providing a colorimetric-luminescence dual-mode sensing system based on the supramolecular self-assembly behavior of a platinum(II) complex / oxalate / zinc ions ternary system. In this ternary system, the platinum(II) complex is isothiocyanate·(terpyridine)platinum(II), whose aqueous solution is pale yellow and non-luminescent. Even when mixed with oxalate, it still exhibits a pale yellow color and no luminescence. With the addition of different concentrations of zinc ions, the zinc ions first form a complex anion with the oxalate, which then forms an anion-cation pair through ion association with the terpyridine platinum(II) complex monomer. Subsequently, the ion pair undergoes self-assembly and aggregation, causing the solution to turn orange and produce a distinct orange luminescence, thereby achieving visual detection of zinc ions. This system utilizes the dramatic changes in UV-Vis absorption and luminescence caused by the supramolecular self-assembly of the platinum(II) complex / oxalate / zinc ions to achieve sensitive, rapid, and intuitive detection of zinc ions, while also possessing advantages such as high detection selectivity and good anti-interference capabilities.

[0006] The present invention discloses a colorimetric-luminescence dual-mode sensing system based on the three-component supramolecular self-assembly behavior of platinum(II) complex / oxalate / zinc(II) ions. The chemical name of the platinum(II) complex isothiocyanate·(terpyridine)platinum(II), and its structural formula (1) is as follows:

[0007]

[0008] The application of the platinum(II) complex / oxalate / zinc ion system based on the three-component supramolecular self-assembly behavior in the detection of zinc ions.

[0009] The colorimetric-luminescence dual-mode sensing system based on the three-component supramolecular self-assembly behavior and its applications described in this invention, wherein the preparation method of the platinum(II) complex / oxalate / zinc ion colorimetric-luminescence sensing system is as follows:

[0010] a. Add 1 g of potassium tetrachloroplatinate to a 250 mL three-necked flask, followed by 20 mL of deionized water to completely dissolve it. Then, add 24 mL of glacial acetic acid and 2.4 mL of 1,5-cyclooctadiene sequentially. Heat the mixture to 80-90 °C and stir for 3 h. Finally, cool the solution to room temperature to obtain a bright gray solid precipitate. Filter the bright gray solid precipitate, then wash it sequentially with water, ethanol, and diethyl ether, and then dry it in an oven at 40 °C for 30 min to obtain 1,5-cyclooctadiene platinum(II) dichloride.

[0011] b. Add 0.8 g of 1,5-cyclooctadiene platinum(II) dichloride obtained in step a) to a 100 mL single-necked flask, then add 40 mL of deionized water to completely dissolve it. Next, add 0.504 g of terpyridine. Heat the mixture to 40-50 °C and stir for 15 min. Filter the cooled reaction solution to remove unreacted 1,5-cyclooctadiene platinum(II) dichloride. The filtrate is then evaporated by rotary evaporation to obtain solid chloro-terpyridine platinum(II) chloride. The solid is then washed three times with diethyl ether and finally dried in air.

[0012] c. Dissolve 0.4 g of chloro-(4'-methyl-terpyridine)platinum(II) obtained in step b in 20 mL of deionized water, then add excess potassium thiocyanate and stir at room temperature until an orange precipitate is formed.

[0013] d. Dissolve a portion of the orange precipitate obtained in step c in as little dimethyl sulfoxide solution as possible, then add diethyl ether to produce an orange-red precipitate. Filter the precipitate and dry it in an oven at 60°C for 1 hour to finally obtain platinum(II) isothiocyanate·(terpyridine) thiocyanate purified by recrystallization.

[0014] e. Prepare a mixed solution of isothiocyanate-(terpyridine)platinum(II) obtained in step d with oxalate to form isothiocyanate-(terpyridine)platinum(II) (0.8 mM) / oxalate (10 mM). Then add zinc ions of different concentrations to 3 mL of the mixed solution to obtain the platinum(II) complex / oxalate / zinc ion colorimetric-luminescent sensing system.

[0015] The advantages and beneficial effects of this invention are:

[0016] This invention discloses a colorimetric-luminescence dual-mode sensing system based on three-component supramolecular self-assembly and its application in zinc ion detection. The system utilizes the coordination of zinc ions with oxalate ions to form zinc anions, which then associate with platinum(II) complex ions to form ion pairs. These ion pairs subsequently undergo self-assembly and aggregation, achieving highly efficient optical detection of zinc ions. Adding zinc ions to a mixed solution of platinum(II) complex / oxalate ions induces ternary supramolecular self-assembly, causing the solution color to change from pale yellow to orange and from non-luminescent to emitting strong orange light. Other common metal cations do not alter the solution's color or luminescence, and the mixing of metal cations with zinc ions does not significantly interfere with zinc ion detection. Therefore, this system exhibits fast response speed, high sensitivity, good selectivity, and good anti-interference capabilities for zinc ion detection. Furthermore, its colorimetric-luminescence dual-mode detection method and three-component supramolecular self-assembly enhance its reliability under complex environmental conditions.

[0017] This invention discloses a colorimetric-luminescence dual-mode sensing system based on the self-assembly behavior of a three-component supramolecular system and its application in zinc ion detection. The platinum(II) complex in this colorimetric-luminescence platinum(II) complex / oxalate / zinc ion three-component system is isothiocyanate·(terpyridine)platinum(II). By adding zinc ions to the mixed solution of platinum(II) complex / oxalate, the solution undergoes a color change from yellow to orange, and from no luminescence to strong orange luminescence. This is because the oxalate ion forms a complex anion with the zinc ion, which can ion-associate with the platinum(II) complex, inducing self-assembly behavior of the platinum(II) complex under metal-metal and π-π interactions. The colorimetric-luminescence platinum(II) complex / oxalate / zinc ion three-component system of this invention exhibits fast detection response for zinc ions; high detection sensitivity (detection limit of 0.199 μM); good selectivity; and good anti-interference performance. Attached Figure Description

[0018] Figure 1 The detection performance of zinc ions in the platinum(II) complex / oxalate / zinc ion three-component system of thiocyanate isothiocyanate·(terpyridine)platinum(II) / oxalate / zinc ion is shown in Figure a, where a is the emission spectrum image and the inset is the emission image under a 356nm ultraviolet lamp; b is the ultraviolet-visible absorption spectrum image and the inset is the color development image under sunlight.

[0019] Figure 2The selectivity of the platinum(II) complex / oxalate / zinc ion three-component system of thiocyanate isothiocyanate·(terpyridine)platinum(II) / oxalate / zinc ion for zinc ion detection is expressed as a) by the intensity of the UV-Vis absorption peak at 508 nm and b) by the intensity of the emission spectrum at 564 nm, with excitation by 356 nm light.

[0020] Figure 3 The anti-interference effect of the platinum(II) complex / oxalate / zinc ion three-component system of the present invention, thiocyanate isothiocyanate·(terpyridine)platinum(II) / oxalate / zinc ion, on the detection of zinc ions is expressed as a) the intensity of the ultraviolet-visible absorption peak at 508 nm and b) the intensity of the emission spectrum at 564 nm, with excitation by 356 nm light.

[0021] Figure 4 The ultraviolet absorption and emission spectra of zinc ions in the platinum(II) complex / oxalate / zinc ion three-component system of the present invention, isothiocyanate·(terpyridine)platinum(II) / oxalate / zinc ion, are used to detect the changes in zinc ion content.

[0022] Figure 5 The changes in the intensity of the UV-Vis absorption peak at 508 nm and the intensity of the emission peak at 564 nm of the platinum(II) complex / oxalate / zinc ion three-component system of thiocyanate isothiocyanate·(terpyridine)platinum(II) / oxalate / zinc ion under different initial pH conditions of the thiocyanate isothiocyanate·(terpyridine)platinum(II) / oxalate mixed solution for zinc ion detection are shown.

[0023] The present invention will be further described below through specific embodiments, but the invention is not limited to these embodiments.

[0024] Example 1

[0025] This embodiment verifies the detection performance of the platinum(II) complex / oxalate / zinc ion three-component system of the present invention, thiocyanate isothiocyanate·(terpyridine)platinum(II) / oxalate / zinc ion, for zinc ions. Figure 1 As shown:

[0026] A mixed solution of isothiocyanate-(terpyridine)platinum(II) and oxalate was prepared, with a platinum(II) complex concentration of 0.8 mM and an oxalate concentration of 10 mM. The mixed solution appeared pale yellow under sunlight but did not emit light under a 365 nm UV lamp. Subsequently, 130 μL of a 100 mM zinc ion solution was added dropwise, and a distinct orange precipitate was formed in the test tube within 3 seconds. This precipitate emitted a bright orange light under a 365 nm UV lamp. The UV-Vis absorption spectrum showed a distinct absorption peak at 508 nm, and the emission spectrum showed a distinct emission peak at 564 nm.

[0027] Example 2

[0028] This embodiment verifies the selectivity of the platinum(II) complex / oxalate / zinc ion three-component system of the present invention, thiocyanate isothiocyanate·(terpyridine)platinum(II) / oxalate / zinc ion, for zinc ion detection. Figure 2 As shown:

[0029] At room temperature, several 3 mL aliquots of a 0.8 mM thiocyanate-(terpyridine)platinum(II) (oxalate) (10 mM) mixed solution were taken, and then 390 μL of a 100 mM common cation solution, such as aluminum ion, calcium ion, cadmium ion, cobalt ion, chromium ion, copper ion, iron ion, mercury ion, lithium ion, magnesium ion, manganese ion, and nickel ion, were added dropwise to each solution. None of these ions could induce self-assembly behavior or produce obvious changes in colorimetric and luminescent phenomena, indicating that the platinum(II) complex / oxalate / zinc ion three-component system has good selectivity for zinc ions.

[0030] Example 4

[0031] This embodiment verifies the anti-interference ability of the platinum(II) complex / oxalate / zinc ion three-component system of the present invention, thiocyanate isothiocyanate·(terpyridine)platinum(II) / oxalate / zinc ion, for zinc ion detection. Figure 3 As shown:

[0032] At room temperature, several 3 mL aliquots of a 0.8 mM (0.8 mM) / 10 mM (10 mM) mixed solution of isothiocyanate·(terpyridine)platinum(II) / oxalate were taken. Then, 130 μL of 100 mM zinc ion solution and 390 μL of 100 mM common cation solution, such as aluminum ion, calcium ion, cadmium ion, cobalt ion, chromium ion, copper ion, iron ion, mercury ion, lithium ion, magnesium ion, manganese ion and nickel ion were added to the solution simultaneously. The presence of these ions did not significantly affect the colorimetric and luminescent response of zinc ions, indicating that the solution has good anti-interference ability for zinc ion detection.

[0033] Example 5

[0034] This embodiment verifies the sensitivity of the platinum(II) complex / oxalate / zinc ion three-component system of the present invention, isothiocyanate·(terpyridine)platinum(II) / oxalate / zinc ion, to the detection of zinc ions. The ultraviolet titration experiment is as follows: Figure 4 As shown in a and 4b, the luminescent titration experiments are shown in 4c and 4d:

[0035] At room temperature, after adding zinc ion solutions of concentrations ranging from 0 to 4.29 mM to 3 mL of a mixed solution of isothiocyanate·(terpyridine)platinum(II) (0.8 mM) / oxalate (10 mM), a new absorption peak appeared at 508 nm, and this absorption peak continuously increased with the increase of zinc ion concentration. Figure 4 a), Figure 4 b shows the change in UV absorption at 508 nm under different zinc ion concentrations. It can be seen that when the zinc ion concentration is between 1.32 and 3.3 mM, the absorption peak is linearly correlated with the zinc ion concentration. Based on the detection limit calculation formula 3σ / k, where σ is the standard deviation of 11 blank samples and k is the slope of the fitted line, the UV absorption detection limit is calculated to be 1.175 μM. Similarly, in the luminescent titration experiment, at room temperature, after adding zinc ion solutions with concentrations of 0-4.29 mM to 3 mL of a mixed solution of isothiocyanate·(terpyridine)platinum(II) (0.8 mM) / oxalate (10 mM), and exciting with 365 nm light, an emission peak appeared at 564 nm, and this emission peak continuously increased with increasing zinc ion concentration. Figure 4 c), Figure 4 d represents the change in emission peak intensity at 564 nm under different zinc ion concentrations. It can be seen that when the uranyl ion concentration is between 0.66 and 3.63 mM, the emission peak is linearly correlated with the zinc ion concentration. Based on the detection limit calculation formula 3σ / k, where σ is the standard deviation of 11 blank samples and k is the slope of the fitted line, the detection limit of luminescence is calculated to be 0.199 μM.

[0036] Example 6

[0037] This embodiment verifies the detection performance of the platinum(II) complex / oxalate / zinc ion three-component system of the present invention, isothiocyanate·(terpyridine)platinum(II) / oxalate / zinc ion, under different initial pH conditions:

[0038] First, the pH of a mixed solution of isothiocyanate-(terpyridine)platinum(II) (0.8 mM) / oxalate (10 mM) was adjusted to within the range of 1-11 using dilute hydrochloric acid and sodium hydroxide. Then, 130 μL of a 100 mM zinc ion solution was added dropwise to the mixed solutions of isothiocyanate-(terpyridine)platinum(II) (0.8 mM) / oxalate (10 mM) under different pH conditions. It was found that when the pH was below 7 or above 10, the fluorescence intensity at 564 nm and the absorption intensity at 508 nm of the supramolecular system were significantly reduced. In particular, at pH 1-2, the fluorescence and colorimetric signals were almost undetectable, possibly because the oxalate ion is protonated under strongly acidic conditions, making it difficult for it to coordinate with zinc ions. The emission and color of the aggregates were relatively stable within the pH range of 7-9. Therefore, the detection of zinc ions in the three-component supramolecular system of isothiocyanate·(terpyridine)platinum(II) / oxalate / zinc ions should be carried out under neutral or weakly alkaline conditions.

Claims

1. A colorimetric-luminescence dual-mode sensing system based on the supramolecular self-assembly behavior of a platinum(II) complex / oxalate / zinc ions, wherein the chemical name of the platinum(II) complex isothiocyanate·(terpyridine)platinum(II) isothiocyanate, and its structural formula (1) is as follows:

2. The preparation method of the platinum(II) complex / oxalate / zinc ion colorimetric-luminescent sensing system according to claim 1 is as follows: a. Add 1 g of potassium tetrachloroplatinate to a 250 mL three-necked flask, followed by 20 mL of deionized water to completely dissolve it. Then, add 24 mL of glacial acetic acid and 2.4 mL of 1,5-cyclooctadiene sequentially. Heat the mixture to 80-90 °C and stir for 3 h. Finally, cool the solution to room temperature to obtain a bright gray solid precipitate. Filter the bright gray solid precipitate, then wash it sequentially with water, ethanol, and diethyl ether, and then dry it in an oven at 40 °C for 30 min to obtain 1,5-cyclooctadiene platinum(II) dichloride. b. Add 0.8 g of 1,5-cyclooctadiene platinum(II) dichloride obtained in step a) to a 100 mL single-necked flask, then add 40 mL of deionized water to completely dissolve it. Next, add 0.504 g of terpyridine. Heat the mixture to 40-50 °C and stir for 15 min. Filter the cooled reaction solution to remove unreacted 1,5-cyclooctadiene platinum(II) dichloride. The filtrate is then evaporated by rotary evaporation to obtain solid chloro-terpyridine platinum(II) chloride. The solid is then washed three times with diethyl ether and finally dried in air. c. Dissolve 0.4 g of chloro-(4'-methyl-terpyridine)platinum(II) obtained in step b in 20 mL of deionized water, then add excess potassium thiocyanate and stir at room temperature until an orange precipitate is formed. d. Dissolve a portion of the orange precipitate obtained in step c in as little dimethyl sulfoxide solution as possible, then add diethyl ether to produce an orange-red precipitate. Filter the precipitate and dry it in an oven at 60°C for 1 hour to finally obtain platinum(II) isothiocyanate·(terpyridine) thiocyanate purified by recrystallization. e. Prepare a mixed solution of isothiocyanate-(terpyridine)platinum(II) obtained in step d with oxalate to form isothiocyanate-(terpyridine)platinum(II) (0.8 mM) / oxalate (10 mM). Then add zinc ions of different concentrations to 3 mL of the mixed solution to obtain the platinum(II) complex / oxalate / zinc ion colorimetric-luminescent sensing system as described in requirement 1.

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