Dual-signal detection method for sulfur ions by an er-tcpp metal-organic framework nanoprobe

Abstract

The application discloses a kind of dual signal detection methods of Er-TCPP metal organic framework nanoprobes to sulphur ion, belong to environmental detection and food safety field.The method of the present application first utilizes TCPP, Er (NO3) 3 Synthesis Er-TCPP MOFs;Then Er-TCPP MOFs is dispersed into Tris-HCl buffer, and preparation is obtained in Er-TCPP MOFs probe dispersion liquid, then with Tris-HCl buffer, a series of known concentration S 2‑ Standard liquid is mixed, incubated for a period of time, after ending, fluorescence spectrometer and ultraviolet-visible spectrometer are determined using microwell enzyme label instrument, obtain fluorescence intensity value and absorbance value, respectively with the concentration of S 2 Linear correlation is carried out, and the quantitative detection model of fluorescence and ultraviolet-visible light is obtained correspondingly.The method of the present application does not need to be pretreated to the detection sample, directly to S 2‑ Fast detection is carried out;S 2‑ Detection specificity, exclude the interference of other heavy metal ions;Realization is detected to low concentration S 2‑ , ensure high sensitivity.

Description

Technical Field

[0001] This invention relates to a dual-signal detection method for sulfur ions using Er-TCPP metal-organic framework nanoprobes, belonging to the fields of environmental monitoring and food safety. Background Technology

[0002] Sulfide ions (S) 2- As an important anion in biology and the environment, sulfur dioxide (S₂) is widely used in industry, including the production of sulfur, sulfuric acid, dyes, and cosmetics. It is also widely present in natural water, domestic sewage, industrial wastewater, and biological systems. Sulfide ions are a traditional toxic pollutant; once protonated, S₂... 2- It can even transform into hydrogen sulfide (H2S). Protonated sulfur participates in various physiological processes, including regulating blood pressure, myocardial contraction, neurotransmission, and insulin secretion. Long-term exposure to sulfides can induce serious physiological and biological problems, such as Alzheimer's disease, Down syndrome, hyperglycemia, and respiratory paralysis. Therefore, the development of convenient, sensitive, and reliable sulfur compounds is crucial. 2- Detection methods are of great significance and value for exploring biological functions and for environmental protection. Currently, the detection of S... 2- The main methods include titration, ion chromatography, inductively coupled plasma spectroscopy, and electrochemical methods. These traditional methods require large and expensive equipment and specialized operators, involve lengthy sample pretreatment, are complex to operate, and have high detection costs, making it difficult to achieve rapid, specific, real-time online detection. There is an urgent need to develop new sulfide ion detection methods that simplify the detection procedure and reduce instrumentation. Summary of the Invention

[0003] For existing S 2- To address the aforementioned shortcomings of existing detection technologies, this invention proposes a fluorescence / colorimetric dual-mode MOF probe for S 2- The detection method has advantages such as high sensitivity, simplicity, speed, low cost, and visualization.

[0004] The present invention adopts the following technical solution:

[0005] A dual-signal detection method for sulfur ions using Er-TCPP metal-organic framework nanoprobes includes the following steps:

[0006] (1) Synthesis of Er-TCPP MOFs: TCPP and Er(NO3)3 were dissolved in DMF to obtain TCPP solution and Er(NO3)3 solution respectively; Er(NO3)3 solution was quickly added to TCPP solution and heated to react. After the reaction was completed, the precipitate was collected by centrifugation, washed and dried to obtain Er-TCPP MOFs.

[0007] (2) Er-TCPP MOFs were dispersed in buffer to prepare Er-TCPP MOFs probe dispersion, and then reacted with Tris-HCl buffer and a series of S solutions of known concentrations. 2- The standard solution was mixed and incubated for a period of time. After incubation, the fluorescence spectrum and UV-Vis spectrum were measured using a microplate reader to obtain the fluorescence intensity and absorbance values, which were then compared with S. 2 A linear correlation was established between the concentrations to obtain quantitative detection models for fluorescence and ultraviolet-visible light.

[0008] In one embodiment of the present invention, the mass ratio of TCPP to Er(NO3)3 is 1:1.

[0009] In one embodiment of the present invention, the concentration of the TCPP solution is 0.3-0.5 mg / mL.

[0010] In one embodiment of the present invention, the concentration of the Er(NO3)3 solution is 3-5 mg / mL.

[0011] In one embodiment of the present invention, in step (1), the reaction temperature is 100°C and the time is 4 hours.

[0012] In one embodiment of the present invention, in step (2), the concentration of the Er-TCPP MOFs probe dispersion is 0.1-1.0 mg / mL. Specifically, 0.5 mg / mL may be selected.

[0013] In one embodiment of the present invention, in step (2), the buffer in which Er-TCPP MOFs are dispersed is a 10 mM Tris-HCl solution with pH 7.

[0014] In one embodiment of the present invention, in step (2), the volume ratio of Er-TCPP MOFs probe dispersion to Tris-HCl buffer is 1:99.

[0015] In one embodiment of the present invention, in step (2), the concentration of Tris-HCl buffer is 20 mM and the pH is 7.

[0016] In one embodiment of the present invention, in step (2), the incubation time is 10 min.

[0017] In one embodiment of the present invention, in step (2), the optimal fluorescence excitation wavelength is 415 nm and the optimal emission wavelength is 645 nm for the ultraviolet-visible spectrum and fluorescence spectrum, respectively.

[0018] In one embodiment of the present invention, the detection method specifically includes:

[0019] (1) Synthesis of Er-TCPP MOFs

[0020] First, two stock solutions were prepared: Solution A: 40 mg TCPP was fully dissolved in 90 mL of NN-dimethylformamide (DMF); Solution B: 40 mg Er(NO3)3 was fully dissolved in 10 mL of DMF. Under vigorous stirring, Solution B was rapidly added to Solution A, and the mixture was heated in a 100 °C water bath for 4 h. After cooling, the reactants were centrifuged at 13000 rpm for 30 min, and the supernatant was removed. The resulting precipitate was washed twice with anhydrous ethanol by centrifugation (13000 rpm, 30 min), and then dried in a 60 °C oven for 12 h. The final product was a brown Er-TCPP MOF powder, and the morphology of Er-TCPP MOFs was observed using scanning electron microscopy.

[0021] (2) Dual-signal mode detection of Er-TCPP MOF nanoprobe pairs

[0022] Er-TCPP MOFs were dispersed in Tris-HCl (10 mM, pH 7) buffer to a final concentration of 0.5 mg / mL. The mixture was sonicated for 30 min to ensure complete dissolution, resulting in a homogeneous suspension of Er-TCPP MOF probe stock solution, which was stored at 4°C. 10 μL of the Er-TCPP MOF probe stock solution was added to 990 μL of Tris-HCl buffer (20 mM, pH 7), followed by the addition of 1 mL of different concentrations of S... 2- After thorough mixing, the mixture was incubated at room temperature for 10 min. The UV-Vis and fluorescence spectra of the Er-TCPP MOF nanoprobes under different sulfur ion concentrations were recorded using a Bio-Tek Synergy H4 microplate reader. The optimal fluorescence excitation wavelength was 415 nm, and the optimal emission wavelength was 645 nm. The fluorescence / absorbance response value and S were calculated. 2- The linear relationship between concentrations was determined, a standard curve was fitted, the fitting equation was determined, and the detection limit was calculated.

[0023] Advantages and effects of the present invention:

[0024] The detection system constructed in this invention has dual recognition modes of fluorescence and visualization; it eliminates the need for sample pretreatment and directly detects S. 2- Perform rapid detection; for S 2- Detection specificity, eliminating interference from other heavy metal ions; achieving detection of low concentrations of S 2- This invention provides a fluorescence / visualization dual-signal nanoprobe for detecting sulfur in aqueous media, ensuring high sensitivity. 2- Detection was performed in fluorescence detection mode for S at concentrations ranging from 1 to 500 μM.2- It exhibits good linear response and a detection limit of 0.23 μM; in colorimetric detection mode, it can detect S at concentrations ranging from 25 to 500 μM. 2- It exhibits good linear response and a detection limit of 4.33 μM, significantly lower than the maximum concentration of sulfides in drinking water stipulated by the World Health Organization (approximately 500 μg / L or 15 μM). Furthermore, the Er-MOF nanoprobe also yielded satisfactory results in practical applications with real water samples. Attached Figure Description

[0025] Figure 1 For the detection of S by Er-TCPP MOF nanoprobes 2- flow chart.

[0026] Figure 2 SEM image (A) and infrared spectrum (B) of Er-TCPP MOFs.

[0027] Figure 3 (A) Fluorescence and UV-Vis absorption optical properties of Er-TCPP MOFs and ligand TCPP; (B) Detection of S by Er-TCPP MOF nanoprobes. 2- feasibility.

[0028] Figure 4 The response time (A, B) and pH (C, D) of Er-TCPP MOF nanoprobes for detecting S 2- The impact of condition optimization.

[0029] Figure 5 For Er-TCPP MOFs nanoprobes to S 2- The fluorescence and UV-Vis dual-mode detection performance of Er-TCPPMOF nanoprobes for detecting different concentrations of S 2- The response fluorescence spectrum (A) and fitted standard curve (B) of Er-TCPP MOF nanoprobes for different concentrations of S 2- The UV-Vis response spectrum (C) and the fitted standard curve (D).

[0030] Figure 6 The fluorescence spectra (A) and UV-Vis response spectra (B) of Er-TCPP MOF nanoprobes to various interfering substances, and the corresponding net response histograms (C, D). Detailed Implementation

[0031] Figure 1 This invention demonstrates the synthesis of MOF probes and S... 2-In the detection process, erbium-based porphyrin metal-organic framework materials (Er-TCPP MOFs) were synthesized for the first time using rare-earth erbium ion (Er(III)) metal center and tetracarboxyphenylporphyrin (TCPP) as fluorescent ligand. TCPP exhibits strong red fluorescence with an optimal emission wavelength of 645 nm. After the formation of Er-TCPP MOFs, the fluorescence of the TCPP ligand is quenched by Er(III) due to the photoinduced electron transfer (PET) effect, resulting in no fluorescence in the TCPP MOF probe. Er-TCPP MOFs and S 2- There is a strong host-guest effect between them, which mainly manifests in the following aspects: (1) Erbium ions have a high coordination number and a large number of unsaturated coordination metal centers, providing S 2- The binding sites are beneficial for Er-TCPP MOFs to bind to S 2- The adsorption of S accelerated the process. 2- (2) Reaction frequency with Er(Ⅲ) clusters; (3) Compared to other anions, S 2- Low electronegativity, similar to Er 3+ The higher degree of covalent bonding results in the formation of Er2S3 compounds that are insoluble in water, promoting the reaction between Er(III) and S. 2- The reaction equilibrium between them shifts forward towards the formation of Er2S3; (3) Er(Ⅲ) is a Lewis base and belongs to Lewis acids. Er-TCPP MOFs and S 2- There is a strong Lewis acid-base reaction between them. The above Er-TCPP MOFs and S 2- The unique host-guest effect not only blocks the photoinduced electron transfer (PET) pathway from TCPP to Er(III), but also leads to the structural collapse of Er-TCPP MOFs, generating free TCPP ligand molecules. Therefore, Er-TCPP MOFs and S 2- After the reaction, the fluorescence of TCPP is restored, accompanied by the generation of a brown visible light signal, realizing the detection of sulfur ions in a dual-signal mode of fluorescence and visualization, thus improving detection accuracy. The whole process is an instantaneous direct reaction, which is simple, fast, low-cost, easy to operate, and shortens the detection time.

[0032] Example 1 Synthesis of Er-TCPP MOFs

[0033] Two stock solutions were first prepared: Solution A: 40 mg TCPP dissolved completely in 90 mL of N,N-dimethylformamide (DMF); Solution B: 40 mg Er(NO3)3 dissolved completely in 10 mL of DMF. Solution B was rapidly added to Solution A under vigorous stirring, and the mixture was heated in a 100°C water bath for 4 h. After cooling, the reactants were centrifuged at 13,000 rpm for 30 min, and the supernatant was removed. The resulting precipitate was washed twice with anhydrous ethanol by centrifugation (13,000 rpm, 30 min), and then dried in a 60°C oven for 12 h. The final product was a brown Er-TCPP MOF powder, and its morphology was observed using scanning electron microscopy.

[0034] Er-TCPP MOF characterization:

[0035] SEM images of Er-TCPP MOFs ( Figure 2 As shown in A), Er-TCPP MOFs exhibit good dispersibility and a rod-like structure, with a size range of approximately 350-500 nm along the length of the nanorods. Fourier transform infrared spectroscopy was used to determine the functional groups of Er-TCPP MOFs. Figure 2 B shows that 965cm -1 The peak appearing at 1415 cm⁻¹ is a characteristic peak of the in-plane vibration and stretching vibration of NH in the TCPP molecule. The fact that this peak can still be observed after the formation of Er-TCPP MOFs indicates that the hydrogen protons in TCPP cannot be replaced by Er(Ⅲ). -1 The absorption peak at 1679 cm⁻¹ corresponds to the bending vibration of the -OH bond. After the formation of Er-TCPP MOFs, due to the coordination effect between Er(Ⅲ) and TCPP, the 1679 cm⁻¹ peak does not appear in the infrared spectrum of Er-TCPP MOFs. -1 and 1181cm -1 The characteristic peak of C=O stretching vibration at [location missing]. Simultaneously, at 1582 cm⁻¹... -1 A new absorption peak appeared, which is related to the overall frame vibration of Er-TCPP MOFs.

[0036] Example 2: Dual-signal mode detection of Er-TCPP MOF nanoprobe pairs

[0037] Er-TCPP MOFs were dispersed in Tris-HCl (10 mM, pH 7) buffer to a final concentration of 0.5 mg / mL. The mixture was sonicated for 30 min to ensure complete dissolution, resulting in a homogeneous suspension of Er-TCPP MOF probe stock solution, which was stored at 4°C. 10 μL of the Er-TCPP MOF probe stock solution was added to 990 μL of Tris-HCl buffer (20 mM, pH 7), followed by the addition of 1 mL of S at different concentrations. 2- Mix thoroughly with Na2S solution and incubate at room temperature for 10 min. Record the UV-Vis and fluorescence spectra of Er-TCPP MOF nanoprobes under different sulfur ion concentrations using a Bio-Tek Synergy H4 microplate reader. The optimal fluorescence excitation wavelength was 415 nm, and the optimal emission wavelength was 645 nm. Calculate the fluorescence / absorbance response value and S. 2- The linear relationship between concentrations was determined, a standard curve was fitted, the fitting equation was determined, and the detection limit was calculated.

[0038] Test results as follows Figure 5 A and Figure 5 As shown in C, with S 2- With increasing concentration, the fluorescence intensity and absorbance of the Er-TCPP MOFs detection system continuously increased, and the difference in dual optical signal response correlated with S. 2- There is a good linear relationship between concentrations. Figure 5 B and Figure 5 D). In fluorescence mode, the detection linear range is 1 μM–500 μM, and the fitted linear equation is F–F0 = 141.6 * C + 1752, R0 2 =0.9947, the calculated detection limit is 0.23 μM (3σ / S), significantly lower than the maximum concentration of sulfides in drinking water stipulated by the World Health Organization (approximately 500 μg / L or 15 μM). In colorimetric mode, the linear range of detection is 25 μM–500 μM, and the fitted linear equation is F - F0 = 0.0007720 * C - 0.007155, R0. 2 =0.9805, the calculated detection limit is 4.33 μM.

[0039] Optical properties and detection of Er-TCPP MOFs 2- The principle:

[0040] from Figure 3As can be seen from A, TCPP is brownish-yellow, exhibits strong UV-Vis absorption at 415 nm, and emits red fluorescence under excitation at this wavelength, with the optimal emission wavelength being 645 nm. In contrast, the dispersed Er-TCPP MOFs at low concentrations are almost colorless, show no significant absorbance at 415 nm, and exhibit no fluorescence under excitation. This indicates that the formation of Er-TCPP MOFs causes photo-induced electron transfer (PET) from TCPP to the Er(III) metal center, leading to the fluorescence quenching of TCPP. When Er-TCPP MOFs react with S... 2- After the reaction, a significant UV-Vis absorption was observed at 415 nm, the solution turned brown, and it emitted red fluorescence at 645 nm in the excited state. According to the Lewis acid-base theory, S... 2- It can replace the solvent H2O in the solvation shell of the Er(Ⅲ) cluster. Furthermore, S 2- Can be with Er 3+ The Er2S3 compound formed by the combination is insoluble in water, which promotes the reaction of Er(III) with S. 2- The reaction equilibrium shifts forward towards Er2S3 formation, disrupting the Er-TCPP MOF structure and generating free TCPP ligand molecules. Both of these effects alter the electron transfer pathway of Er-TCPP MOFs, causing the recovery of TCPP fluorescence at 645 nm.

[0041] Example 3: Optimization of Detection Conditions

[0042] Depend on Figure 4 As can be seen from A and 4B, the Er-TCPP MOF nanoprobes and S 2- The reaction rate was relatively fast; after 5 minutes, there was no significant increase in fluorescence or absorbance. To ensure a complete reaction, 10 minutes was selected as the optimal detection time. Furthermore, pH is also a key factor affecting detection; as pH increases, the Er-TCPP MOF nanoprobes show reduced activity against S... 2- The net response values ​​of fluorescence and absorbance showed a trend of first increasing and then decreasing, reaching the maximum response value at pH 7. This is because the Er-TCPP MOF nanoprobe is sensitive to alkaline conditions, and under high pH conditions, there is a strong background fluorescence signal, which affects the detection effect. Therefore, pH 7 was selected for subsequent detection.

[0043] Example 4 Ion Interference

[0044] Add 10 μL of Er-TCPP MOFs probe stock solution to 990 μL of Tris-HCl buffer (20 mM, pH 7), then add 1 mL of 500 μM of other interfering substances (aspartic acid (Asp), folic acid (FA), tryptophan (Trp), glutathione (GSH), Na+). + K+ HCO 3- SO4 2- Ca 2+ ATP, Co 2+ Zn 2+ Ag + Cu 2+ Al 3+ Fe 3+ Ni 2+ Ce 3+ Pb 2+ Mn 2+ Cr2O7 2- SCN - I - ,Br - NH 4+ NO 2- Cd 2+ ,ClO - Mix thoroughly, incubate at room temperature for 10 minutes, and record the UV-Vis and fluorescence spectra.

[0045] Specificity is another key indicator for evaluating sensors, using S 2- and high concentrations of interfering ions (5 times S) 2- The concentrations of the Er-TCPP MOF nanoprobes were applied to the Er-TCPP MOF nanoprobes, and the detection of S by the Er-TCPP MOF nanoprobes was evaluated based on the fluorescence and absorbance signal responses. 2- Its specificity. (By) Figure 6 It can be seen that only S 2- It can induce strong fluorescence and UV-Vis signal enhancement, while the changes in fluorescence and UV-Vis signals caused by other high-concentration interfering substances are almost negligible, indicating that Er-TCPP MOF nanoprobes enhance S 2- The detection has strong selectivity and anti-interference ability.

[0046] Example 5: Actual Sample Detection

[0047] Commercially available mineral water and tap water were selected as actual samples to evaluate the practicality of Er-TCPP MOF nanoprobes. Different concentrations of S were then used. 2- (50, 100, 200 μM) were added to untreated mineral water and tap water to serve as actual sample test solutions. 1 mL of the actual sample test solution, 10 μL of Er-TCPP MOFs probe stock solution, and 990 μL of Tris-HCl buffer (20 mM, pH 7) were thoroughly mixed and incubated at room temperature for 10 min. UV-Vis and fluorescence spectra were recorded. The measurement results were substituted into the standard curve to calculate the concentration measurements and spiked recoveries, thus evaluating the practicality of the method.

[0048] The results are shown in Table 1. The spiked recoveries in mineral water and tap water samples ranged from 96.26% to 104.03%, and the RSD values ​​ranged from 0.98% to 3.11%, indicating that the Er-TCPP MOF nanoprobes have good practicality.

[0049] Table 1. Determination of sulfur ions in tap water and mineral water using Er-TCPP MOF nanoprobes (n=3)

[0050]

Claims

1. A dual-signal detection method for sulfur ions using Er-TCPP metal-organic framework nanoprobes, comprising the following steps: (1) Synthesis of Er-TCPP MOFs: TCPP and Er(NO3)3 were dissolved in DMF to obtain TCPP solution and Er(NO3)3 solution respectively; Er(NO3)3 solution was quickly added to TCPP solution and heated to react. After the reaction was completed, the precipitate was collected by centrifugation, washed and dried to obtain Er-TCPP MOFs. (2) Disperse Er-TCPP MOFs in buffer to prepare Er-TCPP MOFs probe dispersion, and then mix with Tris-HCl buffer and a series of S solutions of known concentrations. 2- The standard solution was mixed and incubated for a period of time. After incubation, the fluorescence spectrum and UV-Vis spectrum were measured using a microplate reader to obtain the fluorescence intensity and absorbance values, which were then compared with S. 2- A linear correlation was established between the concentrations to obtain quantitative detection models for fluorescence and ultraviolet-visible light.

2. The method according to claim 1, characterized in that, The mass ratio of TCPP to Er(NO3)3 is 1:

1.

3. The method according to claim 1, characterized in that, The concentration of TCPP solution is 0.3-0.5 mg / mL.

4. The method according to claim 1, characterized in that, The concentration of Er(NO3)3 solution is 3-5 mg / mL.

5. The method according to claim 1, characterized in that, The reaction was carried out at a temperature of 100 °C for 4 h.

6. The method according to claim 1, characterized in that, In step (2), the concentration of the Er-TCPP MOFs probe dispersion is 0.1-1.0 mg / mL.

7. The method according to claim 1, characterized in that, In step (2), the buffer in which Er-TCPP MOFs are dispersed is a 10 mM Tris-HCl solution at pH 7.

8. The method according to claim 1, characterized in that, In step (2), the volume ratio of Er-TCPP MOFs probe dispersion to Tris-HCl buffer is 1:

99.

9. The method according to claim 1, characterized in that, In step (2), the concentration of Tris-HCl buffer is 20 mM and the pH is 7.

10. The method according to any one of claims 1-9, characterized in that... In step (2), the incubation time is 10 minutes.

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