CN115015202A

CN115015202A - Preparation method and application of fluorescent sensor array for detecting heavy metal ions

Info

Publication number: CN115015202A
Application number: CN202210697836.6A
Authority: CN
Inventors: 汪溪远; 陈娇; 许紫峻; 刘玉莹
Original assignee: Xinjiang University
Current assignee: Xinjiang University
Priority date: 2022-06-20
Filing date: 2022-06-20
Publication date: 2022-09-06

Abstract

The invention provides a preparation method of a fluorescence sensor array for detecting heavy metal ions, which comprises the following steps: mixing a cetylpyridinium chloride solution with a sodium hydroxide solution, performing water bath ultrasound, purifying by using dichloromethane, and dialyzing by using a dialysis bag to obtain a CPC-CDs solution; and adding heavy metal ion solutions with different concentrations into two groups of CPC-CDs/XO sensing solutions under the pH environment to obtain the fluorescence sensor array. Also provides application of the heavy metal ion Cr ⁶⁺ 、Fe ²⁺ 、Fe ³⁺ And Hg ²⁺ Is examinedAnd (6) measuring. The invention simplifies the array construction steps by adjusting the pH environment of the system, effectively improves the defect of lack of affinity between carbon and heavy metal ions by adding xylenol, and can simultaneously detect a plurality of metal ions (Cr) ⁶⁺ 、Fe ²⁺ 、Fe ³⁺ And Hg ²⁺ ) The method has high sensitivity and good selectivity, and is used for detecting heavy metals in the environment.

Description

Preparation method and application of fluorescent sensor array for detecting heavy metal ions

Technical Field

The invention belongs to the technical field of heavy metal detection, and particularly relates to a preparation method and application of a fluorescent sensor array for detecting heavy metal ions.

Background

Heavy metal pollution is a serious problem in current environmental governance research, causing extensive concentration of numerous scholars. Under the social background of the rapid development of modern industry, a large amount of carcinogenic, teratogenic and mutagenic heavy metal ions are released into the environment, so that the environmental quality is greatly reduced, or the human health is endangered. The selection of a rapid and accurate detection method is a necessary condition for developing the prevention and treatment of heavy metal pollutants. The traditional detection methods such as enzyme analysis, chemical color development, biochemical method and the like generally have the defects of relatively high detection limit, expensive instrument, complex operation and low accuracy. The fluorescence sensor array as a method in the optical sensor array has the advantages of high brightness, no need of a reference system, abundant output signals, capability of imaging and the like. However, so far, the research report of constructing an array based on carbon spots to detect heavy metals is relatively blank. Therefore, in the existing research, based on the advantages of the fluorescence sensing array, it is necessary to develop a detection method with stronger specificity.

Carbon quantum dots (CDs) are quasi-spherical nano materials with the size of about 10nm and fluorescence, and are widely concerned in the research field due to wide raw material sources and simple preparation methods. The carbon quantum dots are used as sensing units to construct a fluorescence sensing array, and information is conducted in a fluorescence signal mode by utilizing the interaction between molecules and ions through a molecular recognition process. The array sensing platform has the advantages of accuracy, diversity, simplicity, time saving, high selectivity and the like. At present, the research of utilizing the carbon quantum dot specificity to detect the heavy metal pollutants is relatively extensive, the research of constructing a fluorescent sensor array for detection is less, and the research of detecting the heavy metal pollutants based on the array is relatively blank. At present, the research of the fluorescence sensing array based on the carbon dots mainly focuses on the enhancement or the weakening of the fluorescence intensity of a single fluorophore as a response signal, and on the basis, functional groups on the surface of the carbon dots are functionally modified, or fluorescent dyes are used as raw materials to artificially synthesize the fluorescent probes.

Disclosure of Invention

The invention aims to solve the technical problem of providing a preparation method and application of a fluorescent sensor array for detecting heavy metal ions aiming at the defects of the prior art, wherein the method comprises the steps of constructing the fluorescent sensor array by adjusting the pH environment of a system, and combining carbon quantum dots with the heavy metal ions (Cr) by adding xylenol orange as a receptor ⁶⁺ 、Fe ²⁺ 、Fe ³⁺ And Hg ²⁺ ) The method has the advantages of high detection sensitivity, high accuracy and good stability, and can be applied to detection of heavy metals in the environment.

In order to solve the technical problems, the invention adopts the technical scheme that: a preparation method of a fluorescence sensor array for detecting heavy metal ions comprises the following steps:

s1, preparation of CPC-CDs solution: at room temperature, transferring a sodium hydroxide solution into a cetylpyridinium chloride solution, and carrying out water bath ultrasound to obtain a reaction solution; adding dichloromethane into the reaction solution, extracting and purifying for 3 times, standing until the solution is colorless and transparent, dialyzing in deionized water by using a dialysis bag to obtain a CPC-CDs solution (cetyl pyridine carbon quantum dots), and storing in a dark place at 4 ℃;

s2, establishing a carbon quantum dot fluorescence sensor array with pH adjusted: two groups of pH detection environments are arranged, wherein the first group of pH detection environments are as follows: Tris-HCl buffer solution A with pH7.4 and concentration of 10 mM; the second set of pH test environments is: Tris-HCl buffer solution B with pH 8.8 and concentration of 10 mM;

uniformly mixing 950 mu L of Tris-HCl buffer solution, 20 mu L of CPC-CDs solution obtained from S1 and 2 mu L of xylenol orange solution with the concentration of 100 mu M, and standing for 7min to respectively obtain two groups of CPC-CDs/XO sensing solutions under the pH environment; the Tris-HCl buffer solutions are a Tris-HCl buffer solution A and a Tris-HCl buffer solution B respectively;

and respectively adding metal ions with different concentrations into the two groups of CPC-CDs/XO sensing solutions under the pH environment, uniformly mixing and standing for 10min to obtain a CPC-CDs/XO sensing system, and recording the fluorescence emission spectrum of the CPC-CDs under the excitation wavelength of 370nm to obtain the fluorescence sensor array.

Preferably, the volume ratio of the cetylpyridinium chloride solution to the sodium hydroxide solution in S1 is 2: 1, the concentration of the chlorohexadecyl pyridine solution is 50 mmol/L; the concentration of the sodium hydroxide solution is 330 mmol/L; the dosage ratio of the dichloromethane to the CPC-CDs solution is (1-3): 1.

preferably, the temperature of the water bath ultrasound in S1 is 20-40 ℃, and the time is 6-9 h.

Preferably, the MWCO membrane with the molecular weight cut-off of the dialysis bag in the S1 of 3000Da has the dialysis time of 24-72 h.

Preferably, the final concentration of the xylenol orange solution in the fluorescent sensor array in S2 is 0.2. mu. mol/L.

The invention also provides application of the prepared fluorescent sensor array for detecting the heavy metal ions, wherein the fluorescent sensor array is used for detecting the heavy metal ions; the heavy metal ions are Cr ⁶⁺ 、Fe ²⁺ 、Fe ³⁺ And Hg ²⁺ 。

Preferably, the final concentration of each heavy metal ion in the fluorescence sensor array ranges from 0 μmol/L to 50 μmol/L.

Compared with the prior art, the invention has the following advantages:

1. the invention solves the problem of poor affinity of the fluorescent probe and the analyte by adding the chelating agent. CPC-CDs solution is used as a fluorescent probe, a metal chelating agent is used as a receptor, and the CPC-CDs solution and the metal chelating agent are combined under the action of a connecting arm for detecting heavy metal ions, so that a standard indicator-connecting arm-receptor mode (ISR) is formed. Because the chelation degrees of different heavy metal ions and chelating agents are different, different metal ion complexes are formed, and the fluorescent sensor array successfully distinguishes Cr under the internal filtering effect ⁶⁺ 、Fe ² ⁺ 、Fe ³⁺ 、Hg ²⁺ Four heavy metals.

2、The invention constructs the fluorescent sensor array by designing and detecting the pH value of the environment, thereby simplifying the construction steps of the sensor array. According to the change I/I of fluorescence intensity under a Tris-hydrochloric acid buffer solution system with two pH values ₀ (I and I) ₀ Respectively representing the fluorescence intensity when heavy metal exists and does not exist), the fluorescence response spectra of the two groups of heavy metal ions can be obtained, and therefore, the fluorescence sensor array can be constructed by adjusting the pH value of the detection environment to detect the heavy metal ions.

3. The pH-adjusted fluorescence sensor array constructed by the invention improves the defect of lack of affinity between CPC-CDs solution and heavy metal ions by adding the chelating agent, and improves the detection efficiency and accuracy of various metal ions. The sensor array is used for 4 heavy metal ions (Cr) in the range of 0 mu mol/L to 50 mu mol/L ⁶⁺ 、Fe ²⁺ 、Fe ³⁺ And Hg ²⁺ ) Has higher detection sensitivity, no response to other heavy metal ions, strong selectivity and simple detection operation.

The present invention will be described in further detail with reference to the drawings and examples.

Drawings

FIG. 1 is a microscopic view of CPC-CDs prepared in example 1 of the present invention.

FIG. 2 is a graph of the optical properties of CPC-CDs prepared in example 1 of the present invention.

FIG. 3 is a four metal ion complex (XO-Cr) of example 2 of the present invention ⁶⁺ ,XO-Fe ²⁺ ,XO-Fe ³⁺ ,XO-Hg ² ⁺ ) The absorption spectrum of (A) and the fluorescence emission spectrum of CPC-CDs (single metal ion concentration: 10. mu. mol/L).

FIG. 4 is UV absorption spectra (single metal ion concentration 10. mu. mol/L) of CPC-CDs, four metal ion complexes, CPC-CDs + metal ion complex and CPC-CDs and metal ion complex of example 2 of the present invention.

FIG. 5 shows the degree of fluorescence response between CPC-CDs and CPC-CDs-XO in buffer solutions of different pH according to example 2 of the present invention.

FIG. 6 shows the fluorescence response of the metal ions of example 2 of the present invention in the sensor array system under different pH conditions (all final metal ion concentrations are 0-50. mu. mol/L).

Figure 7 is an optimized graph of XO concentration in Tris-HCl buffered solution at pH7.4 for example 2 of the present invention.

FIG. 8 is a graph showing the optimization of the reaction time of CPC-CDs with XO in Tris-HCl buffer solution at pH7.4 in example 2 of the present invention.

Fig. 9 is an optimization graph of the incubation time of the CPC-CDs/XO sensing system of pH7.4 (single metal ion concentration 10 μmol/L) for example 2 of the present invention with respect to metal ions.

Detailed Description

Example 1

This example is the preparation of a carbon quantum dot CPC-CDs solution:

at room temperature, transferring 10mL of 330mmol/L sodium hydroxide solution into 20mL of 50mmol/L cetylpyridinium chloride solution (CPC), and carrying out ultrasonic treatment in water bath at 20 ℃ for 9h to obtain a reaction solution; adding dichloromethane into the reaction solution, extracting and purifying for 3 times, standing until the solution is colorless and transparent, dialyzing with dialysis bag (MWCO membrane, molecular weight cutoff is 3000Da) in deionized water for 72h to obtain carbon quantum dots (CDs), CPC-CDs solution for short, and storing at 4 deg.C in dark place; the dosage ratio of the dichloromethane to the CPC-CDs solution is 3: 1.

the condition of the water bath ultrasound in the embodiment can be 20-40 ℃ for 6-9 h; the dialysis time can be 24-72 h; the dosage ratio of the dichloromethane to the CPC-CDs solution can be (1-3): 1.

the fluorescence spectrum was recorded using a fluorescence spectrophotometer (F-4500 Hitachi, Japan). The UV-visible spectrum was obtained using a UV-3600 type UV absorption spectrometer (general analysis, China). Fourier transform infrared (FT-IR) spectra were recorded by a VERTEX 70 spectrometer (Bruker, Germany). X-ray photoelectron spectroscopy (XPS; ESCALB 250Xi, USA) was processed using an advanced Avantage data System. The morphological particle size of CPC-CDs, and the lattice fringes, etc. were observed with a high-resolution transmission electron microscope (HRTEM; JEM-2100 series, 200 kV).

As shown in FIG. 1, (a) TEM (inset: size distribution of CPC-CDs) in FIG. 1; (b) HRTEM images of CPC-CDs; (c) infrared spectroscopy of CPC-CDs; (d) XPS scan of CPC-CDs. High Resolution Transmission Electron Microscopy (HRTEM) showed good lattice striations for CPC-CDs, with a typical lattice spacing of 0.20nm (fig. 1a, fig. 1 b). The surface structure of the material was studied by FT-IR and XPS spectroscopy (FIG. 1c, FIG. 1d), and the O-H/N-H structure was determined at 3468ev, indicating that the water solubility was good.

In terms of optical properties, as shown in FIG. 2, the fluorescence excitation (line a) and emission (line b) spectra of CPC-CDs are shown (inset: photographs of CPC-CDs solutions under natural light (right) and 365nm ultraviolet light (left)). CPC-CDs were pale yellow solutions in ambient light and emitted intense yellow fluorescence under 365nm UV excitation (FIG. 2). The maximum emission wavelength was 535nm and the excitation wavelength was 370 nm. The quantum yield was found to be 26.2% in aqueous solution.

Example 2

This example is the establishment of a pH-adjusted carbon quantum dot fluorescence sensor array:

with four heavy metals (Cr) ⁶⁺ 、Fe ²⁺ 、Fe ³⁺ 、Hg ²⁺ ) An array sensing platform was established with Tris-hydrochloric acid buffer solutions (pH 7.4 and 8.8), XO (metal chelator xylenol orange) and CPC-CDs solution prepared in example 1.

Heavy metal ion solution (Cr) provided with different heavy metal ions ⁶⁺ 、Fe ²⁺ 、Fe ³⁺ 、Hg ²⁺ ) And the final concentration of each heavy metal ion solution in the fluorescence sensor array is set to different concentration gradients (0, 1 μ M, 10 μ M, 20 μ M, 30 μ M, 40 μ M, 50 μ M);

reacting CPC-CDs with XO in Tris-hydrochloric acid buffer solution (pH of 7.4 and 8.8) for 7 min; on the basis, a metal ion solution is added to obtain the incubation time of the CPC-CDs/XO sensing system to the metal ions for 10min (figure 9).

Diluting 5mL of Tris-HCl solution with the pH of 7.4 and the initial concentration of 1M and 3.3mL of Tris-HCl solution with the pH of 8.8 and the initial concentration of 1.5M with deionized water respectively to obtain two groups of pH detection environments;

the first set of pH test environments was: a Tris-HCl buffer solution with pH of 7.4 and concentration of 10 mM;

the second set of pH test environments is: a Tris-HCl buffer solution with the pH of 8.8 and the concentration of 10 mM;

then, 950. mu.L of Tris-HCl buffer solution (10 mM, pH7.4, 950. mu.L/10 mM, pH 8.8, 950. mu.L, respectively), 20. mu.L of CPC-CDs solution and 2. mu.L of XO with the concentration of 100. mu.M are mixed in a 1mL centrifuge tube, and the mixture is uniformly mixed and then kept stand for 7min to obtain two sets of CPC-CDs/XO sensing solutions under the pH environment;

respectively adding metal ions with different concentrations into two groups of CPC-CDs/XO sensing solutions under a pH environment, uniformly mixing and standing for 10min to obtain a CPC-CDs/XO sensing system, and recording the fluorescence emission spectrum of CPC-CDs under the excitation wavelength of 370nm to obtain the fluorescence sensor array.

In the detection system, FIG. 3 shows that the absorption spectra of the four metal ion complexes overlap well with the excitation spectra of CPC-CDs. Therefore, when the heavy metal ion complex is added into two pH detection systems, the fluorescence intensity of CPC-CDs can be effectively reduced. FIG. 4 measures the UV absorption spectra and the sum of the amounts of CPC-CDs, four metal ion complexes, CPC-CDs + metal ion complex, and CPC-CDs and metal ion complex, indicating that the test curve (absorption spectrum of CPC-CDs/metal ion complex) closely coincides with the theoretical curve (physical superposition of the curves for CPC-CDs solution and metal ion complex solution), indicating that no complex is formed between CPC-CDs and metal ion complex.

The results show that four heavy metals (Cr) ⁶⁺ 、Fe ²⁺ 、Fe ³⁺ 、Hg ²⁺ ) Under the action of the small molecule connecting arm, the IFE fluorescence intensity of CPC-CDs can be effectively quenched. Therefore, the metal chelating agent is used as the micromolecule connecting arm, and the fluorescence response change of the CPC-CDs is monitored while the metal chelating reaction is carried out under the environment of adjusting the pH value of the system. The sensor array with strong specificity and high sensitivity is manufactured. To verify the detection performance of the sensor array. First, we tested the extent of the fluorescence response of CPC-CDs in the pH range of 5-10 to find the optimal pH for array detection. FIG. 5 shows CPC-The fluorescence response degree of CDs and CPC-CDs-XO shows that the difference of fluorescence emission intensity at 535nm of CPC-CDs and CPC-CDs-XO is small in the pH range of 5-10, so that the influence of XO on the fluorescence emission intensity of CPC-CDs is small, the method can be used for connecting an analyte and a carbon dot, and the method has the advantage of enhancing the specificity of a detection system. We have chosen Tris-buffered solutions at two phs (7.4 and 8.8) and used XO as the small molecule linker arm to fabricate an array of sensors for the detection of heavy metals by monitoring the fluorescence change of CPC-CDs. First, the fluorescent response of the sensor array to a single analyte was tested to verify the performance of the sensor system. Then, 4 heavy metals at a concentration of 10 μ M were added to both pH sensing cells. As a result, the fluorescence intensity of CPC-CDs was quenched to different degrees at both pH sensing units. As shown in FIG. 6, the fluorescence response of the metal ions reacting with the sensor array system under different pH (left pH7.4 and right pH 8.8) environments shows that the relative fluorescence response change I/I of the four heavy metals ₀ In contrast, it is shown that the sensor array can be used for the identification of heavy metals.

And then optimizing detection conditions to improve the detection performance of the sensor. First, a fluorescence titration experiment was performed to adjust the optimum concentration of XO in the array system (fig. 7), and XO with different concentrations was added to Tris-HCl buffer solution with pH7.4, and as the concentration of XO increased, fluorescence of CPC-CDs began to quench, but when the concentration of XO was too low, the effect of chelating reaction with metal ions was poor, and it was difficult to improve the specificity of the detection system, so XO with a final concentration of 0.2 μ M in the fluorescence sensor array was selected as the optimum reaction concentration. Secondly, the reaction time was optimized (FIG. 8), and the fluorescence intensity of CPC-CDs-XO at 535nm increased with the increase of the reaction time, and finally the optimal reaction time was 7 min.

The above description is only for the preferred embodiment of the present invention, and is not intended to limit the present invention in any way. Any simple modification, change and equivalent changes of the above embodiments according to the technical essence of the invention are still within the protection scope of the technical solution of the invention.

Claims

1. A preparation method of a fluorescence sensor array for detecting heavy metal ions is characterized by comprising the following steps:

s1, preparation of CPC-CDs solution: at room temperature, transferring a sodium hydroxide solution into a cetylpyridinium chloride solution, and carrying out water bath ultrasound to obtain a reaction solution; adding dichloromethane into the reaction solution, extracting and purifying for 3 times, standing until the solution is colorless and transparent, dialyzing in deionized water by using a dialysis bag to obtain a CPC-CDs solution, and storing at 4 ℃ in the dark;

s2, establishing a carbon quantum dot fluorescence sensor array with pH adjusted:

two groups of pH detection environments are arranged, wherein the first group of pH detection environments are as follows: Tris-HCl buffer solution A with pH7.4 and concentration of 10 mM; the second set of pH test environments was: Tris-HCl buffer solution B with pH 8.8 and concentration of 10 mM;

2. The method according to claim 1, wherein the volume ratio of the cetylpyridinium chloride solution to the sodium hydroxide solution in S1 is 2: 1, the concentration of the chlorohexadecyl pyridine solution is 50 mmol/L; the concentration of the sodium hydroxide solution is 330 mmol/L; the dosage ratio of the dichloromethane to the CPC-CDs solution is (1-3): 1.

3. the method for preparing a fluorescence sensor array for detecting heavy metal ions according to claim 1, wherein the temperature of the water bath ultrasound in S1 is 20-40 ℃ and the time is 6-9 h.

4. The method of claim 1, wherein the dialysis bag of S1 has MWCO membrane with molecular weight cutoff of 3000Da, and the dialysis time is 24-72 h.

5. The method of claim 1, wherein a final concentration of xylenol orange solution in the fluorescence sensor array of S2 is 0.2 μmol/L.

6. Use of a fluorescent sensor array prepared according to any one of claims 1 to 5 for the detection of heavy metal ions, wherein the fluorescent sensor array is used for the detection of heavy metal ions, and the heavy metal ions are Cr ⁶⁺ 、Fe ²⁺ 、Fe ³⁺ And Hg ²⁺ 。

7. The use of claim 6, wherein the final concentration of each heavy metal ion in the fluorescent sensor array is in the range of 0 μmol/L to 50 μmol/L.