A luminescent sulfur-phosphorus quantum dot is used for fluorescence detection of iron ions in a water sample

Abstract

The application relates to a method for fluorescent detection of iron ions in a water sample by using luminescent sulfur-phosphorus quantum dots, and the method specifically comprises the following steps: dissolving appropriate luminescent sulfur-phosphorus quantum dots in a buffer solution to obtain a detection mother liquor, the detection mother liquor can be prepared into different concentrations according to needs, and the detection mother liquor is added into a sample to be detected, and the detection mother liquor is used for detecting the iron ions in the water sample through a fluorescence quenching method. The application utilizes the fluorescence characteristics of the sulfur-phosphorus quantum dots to quickly (less than 60s) detect the iron ions, and the material has good selectivity for the iron ions in different water samples.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterial application technology and relates to a fluorescence detection method for iron ions in water samples using luminescent sulfur-phosphorus quantum dots. Background Technology

[0002] Iron, as one of the essential trace elements for the human body, is the most abundant trace element in the body, and its content in the body is directly related to its effective functions. Therefore, mastering the key technologies for iron ion detection and improving its selectivity and sensitivity is the primary task for accurately understanding the balance of trace elements in the human body. When iron ions (a common metal ion) accumulate in water to a level exceeding 0.3 M, they are harmful to the human body and the natural aquatic environment. If the iron ion content in the human body is too high, people will suffer from methemoglobinemia, which reduces the blood's oxygen transport capacity and endangers human health. At the same time, when the iron ion content in natural water is too high, the water color will darken significantly, causing water pollution. Therefore, it is very important to detect the iron ion content in water. Traditional methods for detecting iron ions include inductively coupled plasma atomic emission spectrometry (ICP-AES), atomic emission spectrometry (AES), and atomic absorption spectrometry (AES). These methods mostly require sophisticated analytical instruments and equipment, and the sample preparation process is cumbersome, making them inconvenient for widespread use.

[0003] Patent CN108226119A discloses a method for detecting the concentration of ferric ions using carbon quantum dot phosphorescence, comprising the following steps: preparing multiple standard solutions of ferric ions with different concentrations, adding carbon quantum dots and cyanuric acid respectively, and mixing them evenly; placing the resulting solutions into a fluorescence spectrophotometer, recording the phosphorescence intensity value in phosphorescence mode, and plotting a linear regression curve; detecting the solution to be tested according to the above method, substituting the obtained phosphorescence intensity data into the regression curve to obtain the concentration of ferric ions in the solution to be tested. However, the shortcomings of this patent are that the phosphorescence mode detection instrument is expensive, the operation is complex, the conditions are harsh, and the detection range of this patent is relatively narrow. Patent CN108333158A discloses a double-doped fluorescent carbon quantum dot. The optimal excitation and emission wavelengths of the double-doped fluorescent carbon quantum dot are located at 325 nm and 390 nm, respectively. The size of the atomic clusters of the double-doped fluorescent carbon quantum dot is 3-6 nm. It also discloses a simple and convenient synthesis method for the double-doped fluorescent carbon quantum dot and a method for detecting iron content in serum using a standard curve method. However, the patent's limitation is that its detection is not applicable to the more common aquatic environment, and its practicality in aquatic environments is weak, as is its applicability to strong acid and alkaline environments. Patent CN107764788A discloses a synthesis method for carbon quantum dots, carbon quantum dots, and the detection of Fe. 3+ This method utilizes carrot as the carbon source and citric acid as the dispersant to synthesize carbon quantum dots with abundant functional groups on their surface via hydrothermal synthesis. These carbon quantum dots exhibit good dispersibility in water and show good resistance to Fe.3+ It exhibits good selective fluorescence detection, but a drawback of this patent lies in the functional groups on the surface of its carbon quantum dots and Fe. 3+ Coordination is more susceptible to pH effects. For example, when the environment is alkaline, hydroxyl groups in the environment will compete with it, causing the coordination to fail, which is not conducive to use in extreme environments. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a fluorescence detection method for iron ions in water samples using luminescent sulfur-phosphorus quantum dots. This invention utilizes the fluorescence characteristics of luminescent sulfur-phosphorus quantum dots to detect iron ions rapidly (in less than 60 seconds), and it has good selectivity for iron ions in different water environments, with minimal interference from other common metal cations.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] This invention provides a method for the fluorescence detection of iron ions in water samples using luminescent sulfur-phosphorus quantum dots. The method specifically involves dissolving an appropriate amount of luminescent sulfur-phosphorus quantum dots in a buffer solution to obtain a detection stock solution. This detection stock solution can be prepared into different concentrations as needed for application. The detection stock solution is then added to the water sample to be tested, and detection is performed by fluorescence quenching.

[0007] Luminescent sulfur-phosphorus quantum dots possess excellent luminescence properties and high photostability, and can continuously absorb the spectrum (from ultraviolet to visible light). They also exhibit high sensitivity and selectivity, making them highly valuable for applications in environmental monitoring, bioimaging, and medicine.

[0008] Furthermore, the luminescent sulfur-phosphorus quantum dots are first excited by an ultraviolet lamp source, exhibiting obvious blue fluorescence; iron ions have a significant tendency to gain electrons, thus causing the fluorescence of the luminescent sulfur-phosphorus quantum dots to be quenched.

[0009] Furthermore, the concentration of the detection mother solution is 0.05-2 mg / mL.

[0010] Furthermore, the buffer solution is a phosphate buffer solution (PBS).

[0011] Furthermore, the pH value of the phosphate buffer solution is 1-14.

[0012] As a preferred technical solution, the pH value of the phosphate buffer solution is 6.0.

[0013] Furthermore, the volume ratio of the detection mother liquor to the water sample to be tested is 1:(100-250).

[0014] Furthermore, the method includes the following steps:

[0015] (1) First, the luminescent sulfur-phosphorus quantum dots were dissolved in a buffer solution to obtain the detection stock solution. Multiple portions of the detection stock solution were added to iron ion solutions of known different concentrations. After stirring, the fluorescence spectrum was recorded. Then, the standard working curve of relative fluorescence intensity versus iron ion concentration was obtained by linear fitting.

[0016] (2) Add the test stock solution to the water sample to be tested, stir and record the fluorescence spectrum. According to the standard working curve, obtain the iron ion concentration in the sample to be tested.

[0017] Furthermore, the concentration of the iron ion solution is 0.2-3.2 mM.

[0018] Furthermore, the iron ion solution is an aqueous solution of ferric chloride dissolved in a buffer solution.

[0019] Furthermore, the volume ratio of the detection mother liquor to the iron ion solution is 1:(100-250).

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] (1) The present invention uses a fluorescence method. After adding iron ion solutions of different concentrations, the fluorescence intensity of the solution is gradually quenched.

[0022] (2) The detection mother liquor of the present invention only reacts with iron ions, while other common cations have little effect on its fluorescence, thus exhibiting excellent selectivity and specificity;

[0023] (3) The present invention can rapidly (less than 60s) detect iron ions in the water environment, and the detection process is simple and easy to perform, with sensitive response and good reproducibility. Attached Figure Description

[0024] Figure 1 This is a schematic diagram illustrating the principle of the fluorescence detection method for iron ions in water samples using luminescent sulfur-phosphorus quantum dots in Example 1 of the present invention.

[0025] Figure 2 The images show the ultraviolet absorption, fluorescence emission, and fluorescence excitation spectra of the aqueous solution of luminescent sulfur-phosphorus quantum dots in Example 1 of this invention.

[0026] Figure 3 This is a time diagram of the interaction between luminescent sulfur-phosphorus quantum dots and iron ions in Example 1 of the present invention;

[0027] Figure 4 The fluorescence spectra of luminescent sulfur-phosphorus quantum dots with different concentrations of iron ions in Example 1 of this invention are shown.

[0028] Figure 5 This is a standard working curve of relative fluorescence intensity versus iron ion concentration in Example 1 of the present invention;

[0029] Figure 6 This is a comparison chart of the selectivity of common cations in Example 1 and Comparative Examples 1 to 16 of the present invention;

[0030] Figure 7 The graphs show the response of luminescent sulfur-phosphorus quantum dots to iron ions and other cations under the coexistence conditions in Examples 1 to 2 and Comparative Example 11 of the present invention. Detailed Implementation

[0031] The present invention will now be described in detail with reference to specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0032] Unless otherwise specified, the equipment used in the following embodiments is conventional equipment in the art; unless otherwise specified, the reagents used are commercially available products or prepared by conventional methods in the art. In the following embodiments, unless otherwise described in detail, conventional experimental methods in the art can be used.

[0033] Example 1:

[0034] A method for plotting a standard working curve of iron ions in water samples using luminescent sulfur-phosphorus quantum dots includes the following steps:

[0035] First, prepare 50 mL of phosphate-buffered saline (PBS) (pH close to 6.0, 10 mM) and set aside. Then, prepare 10 mL of a sulfur-phosphorus quantum dot aqueous solution (2 mg / mL) as a detection stock solution and set aside. Next, add 2.0 mL of the PBS to a 4 mL quartz cuvette, then accurately transfer 10 μL of the detection stock solution into it. Stir rapidly and measure the fluorescence intensity in a fluorescence spectrometer, recording it as F0. Then, add 10 μL of the detection stock solution to 0.4, 0.8, 1.2, 1.6, 2.0, 2.4, 2.8, and 3.2 mM iron ion solutions obtained by dissolving ferric chloride aqueous solution in 2 mL of PBS, stirring rapidly until the fluorescence intensity no longer changes, and record the fluorescence intensity at each concentration as F. The excitation wavelength is 390 nm for all concentrations.

[0036] like Figure 1 As shown, the luminescent sulfur-phosphorus quantum dots were first excited by an ultraviolet lamp, and they exhibited a distinct blue fluorescence. Iron ions have a strong tendency to gain electrons, thus quenching the fluorescence of the luminescent sulfur-phosphorus quantum dots.

[0037] like Figure 2 As shown in the figure, a represents the ultraviolet absorption curve, b represents the optimal excitation curve, and c represents the optimal emission curve. It can be seen from the figure that the optimal excitation wavelength is 390nm, the optimal emission wavelength is 476nm, and there is a significant absorption between 310-375nm.

[0038] like Figure 3 As shown in the figure, the interaction between the luminescent sulfur-phosphorus quantum dots and iron ions tends to stabilize within 60 s.

[0039] like Figure 4 As shown, the fluorescence intensity of the luminescent sulfur-phosphorus quantum dots gradually decreases with increasing iron ion concentration.

[0040] like Figure 5 As shown, within the iron ion concentration range of 0-3.2 mM, the relative fluorescence intensity F / F0 (as the y-axis) of the luminescent sulfur-phosphorus quantum dots exhibits a linear relationship with the iron ion concentration (as the x-axis). A good standard working curve was obtained through linear fitting (y = 0.99156 + (-0.24333)*x, R0). 2 =0.998).

[0041] A fluorescence detection method for iron ions in water samples using luminescent sulfur-phosphorus quantum dots includes the following steps:

[0042] The collected river water samples were filtered through a 0.22 μm filter membrane to remove larger particles before use. Next, 2.5 mL of the treated river water was added to a 4 mL quartz cuvette, and then 10 μL of the detection stock solution was accurately transferred and dispersed into the river water in the cuvette. The mixture was stirred rapidly, and the fluorescence intensity was measured in a fluorescence spectrometer. The iron ion concentration in the river water was obtained by comparing the fluorescence intensity with a standard curve. The effectiveness of the fluorescence detection method was verified by the standard addition method combined with a standard working curve. The results are shown in Table 1. The experimental results show that the fluorescence detection method has good operability, further demonstrating the practicality of using this luminescent sulfur-phosphorus quantum dot fluorescence detection method for iron ions in the aquatic environment.

[0043] Table 1. Detection of iron ions in the campus river water

[0044]

[0045] Comparative Examples 1 to 16:

[0046] A fluorescence detection method for cations in water samples using luminescent sulfur-phosphorus quantum dots includes the following steps:

[0047] Prepare 0.2M cationic PBS buffer (pH 6.0) separately. Common cations are selected as shown in Table 2 and are prepared from the corresponding chloride salts. Take 2 mL of each buffer and add 10 μL of the detection stock solution prepared in Example 1. Stir and measure the fluorescence intensity.

[0048] The fluorescence intensity was compared with that under the conditions of Example 1 with the effect of 3.2 mM iron ions, such as Figure 6As shown, common cations do not exhibit significant fluorescence quenching ability even at concentrations many times higher than that of iron ions, indicating that iron ions have a good fluorescence quenching ability for sulfur-phosphorus luminescent quantum dots.

[0049] Table 2 Selection of cations in Comparative Examples 1 to 16

[0050]

[0051]

[0052] Example 2:

[0053] A fluorescent detection method for iron ions in water samples using luminescent sulfur-phosphorus quantum dots differs from Comparative Example 1 in that it is effective against iron ions and other coexisting cation interferences (NH4+). 4+ Na + Mg 2+ K + Zn 2+ Ca 2+ Ag + Cu 2+ Fe 2+ 、Sr 2+ Co 2 + Hg 2+ Mn 2+ Ni 2+ Co 3+ Cr 3+ The test was conducted with an added iron ion concentration of 3.2 mM and other ion concentrations of 0.2 mM.

[0054] like Figure 7 As shown, column a represents the response of the luminescent sulfur-phosphorus quantum dot without the addition of iron ions; column b represents the fluorescence response of the luminescent sulfur-phosphorus quantum dot with the addition of iron ions only; and column c represents the response of the luminescent sulfur-phosphorus quantum dot under the condition of coexistence of iron ions and other cations. Compared with the tested iron ion concentration, the concentration of these interfering cations is many times higher. In the presence of these interfering cations, the sulfur-phosphorus luminescent material exhibits high selectivity for iron ions, and the influence of the coexisting interfering cations on the optical response of the luminescent quantum dot is negligible.

[0055] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for fluorescence detection of iron ions in water samples using luminescent sulfur-phosphorus quantum dots, characterized in that, The method specifically involves dissolving luminescent sulfur-phosphorus quantum dots in a buffer solution to obtain a detection stock solution, adding the detection stock solution to the water sample to be tested, and detecting the sample by fluorescence quenching. Luminescent sulfur-phosphorus quantum dots exhibit blue fluorescence upon excitation; iron ions quench the fluorescence of the luminescent sulfur-phosphorus quantum dots. The concentration of the test stock solution is 0.05-2 mg / mL; The volume ratio of the detection mother liquor to the water sample to be tested is 1:(100-250); The method includes the following steps: (1) The luminescent sulfur-phosphorus quantum dots were dissolved in a buffer solution to obtain the detection stock solution. Multiple portions of the detection stock solution were added to iron ion solutions of different concentrations. After stirring, the fluorescence spectrum was recorded. Then, the standard working curve of relative fluorescence intensity versus iron ion concentration was obtained by linear fitting. (2) Add the test stock solution to the water sample to be tested, stir and record the fluorescence spectrum. According to the standard working curve, obtain the iron ion concentration in the sample to be tested; The concentration of the iron ion solution is 0.2-3.2 mM; The volume ratio of the detection mother liquor to the iron ion solution is 1:(100-250).

2. The method for fluorescence detection of iron ions in water samples using luminescent sulfur-phosphorus quantum dots according to claim 1, characterized in that, The buffer solution is a phosphate buffer solution.

3. The method for fluorescence detection of iron ions in water samples using luminescent sulfur-phosphorus quantum dots according to claim 2, characterized in that, The pH value of the phosphate buffer solution is 1-14.

4. The method for fluorescence detection of iron ions in water samples using luminescent sulfur-phosphorus quantum dots according to claim 1, characterized in that, The iron ion solution is an aqueous solution of ferric chloride dissolved in a buffer solution.

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