CN107674003B - Tetrahydroxy-modified diurea compounds and their gels and gel-based methods for detecting mercury ions - Google Patents

Abstract

The invention discloses a tetrahydroxy-modified diurea compound, its gel and a method for detecting mercury ions based on the gel. The compound has the following structural formula:

where R stands for

The compound and borate in the mixed solvent of dimethyl sulfoxide and water can form a reversible covalent bond gel through the hydrogen bond between the boron-oxygen bond and the urea group. Gold nanoparticles are prepared from chloroauric acid, and the resulting gel and gold nanocomposite can detect mercury ions with high sensitivity and selectivity, and have the advantages of short time consumption, low cost, and simple operation.

Description

Tetrahydroxy-modified diureas and their gel and gel-based detection of mercury ions Methods

technical field

The invention belongs to the technical field of mercury ion detection, in particular to a tetrahydroxy-modified diurea compound, a reversible covalent bond molecular gel prepared by using the compound, and a method for detecting mercury ions based on the gel.

Background technique

Toxic metal ions have a very serious impact on human health and the environment. Therefore, the detection of these pollutants in water ecosystems has become the focus of attention. Mercury is one of the most harmful toxic metal ions in the environment. It is generally produced through the combustion of coal, power plants, oceans, volcanic eruptions, gold mines and the incineration of solid waste. The most stable form of mercury ion (Hg ²⁺ ) is the formation of inorganic mercury, which has high cytotoxicity such as corrosiveness and carcinogenicity. It can seriously damage the brain, nervous system, kidney and endocrine system. Long-term exposure to inorganic mercury can cause Diseases of the autoimmune system. Therefore, it is of great significance to detect mercury ions with high sensitivity and selectivity in environmental and biological samples. At present, the commonly used detection methods for Hg ²⁺ mainly include atomic absorption spectrometry (Atomic absorption spectrometry, AAS), atomic fluorescence spectrometry (Atomic fluorescence spectrometry, AFS), inductively coupled plasma mass spectrometry (Inductively coupled plasma mass spectrometry, ICPMS) ) and high-performance liquid chromatography (High-performance liquid chromatography, HPLC). Although these methods have many advantages, they usually require expensive equipment, cumbersome sample preparation, and the need to separate and enrich the samples, thus requiring a lot of time. Therefore, establishing a method for the determination of Hg ²⁺ with high sensitivity, high selectivity, short time-consuming and low cost has become a hot research topic. Optical sensors do not require special instruments and can also visually detect Hg ²⁺ , which has attracted widespread attention. Today, ^Hg sensors based on organic chromophores and fluorophores, conjugated polymers, nucleic acids, DNases, proteins, thin films, and nanoparticles have been proposed. Although these optical sensors are much simpler than traditional methods, most of them have low sensitivity and selectivity, complicated synthesis steps of probe materials, or are not suitable for the inspection of actual samples, so their applications are greatly limited. Therefore, designing a simple, economical and practical method for the detection of Hg ²⁺ not only with high sensitivity and selectivity is still a frontier research hotspot.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide a tetrahydroxy-modified diurea compound, a reversible covalent bond molecular gel based on the compound, and a method for detecting mercury ions using the gel as a matrix.

The structural formula of the tetrahydroxy-modified diurea compound used to solve the above-mentioned technical problems is as follows:

where R stands for

The preparation method of the above-mentioned tetrahydroxy-modified diurea compound is as follows: 2-amino-1,3-propanediol is dissolved in methanol, and the dichloromethane solution of the diisocyanate shown in formula I is added dropwise to the above solution, wherein The molar ratio of 2-amino-1,3-propanediol to diisocyanate is 2:1; the volume ratio of methanol to dichloromethane is 1:75, the reaction is stirred at room temperature for 16 hours, filtered, washed with ethyl acetate, and dried to obtain Four hydroxyl modified diurea compounds, the specific synthetic route is as follows:

The reversible covalent bond molecular gel of the present invention is a hydrogen bond between the above-mentioned tetrahydroxy-modified diurea compound and borate in a mixed solvent of dimethyl sulfoxide and water through a reversible boron-oxygen bond and a urea group Form, wherein borate is any one in lithium borate, sodium borate, tetrabutylammonium borate, and described borate is generated by boric acid and hydroxide reaction, and wherein said hydroxide is hydroxide Lithium, sodium hydroxide or tetrabutylammonium hydroxide.

The preparation method of the above-mentioned reversible covalent bond molecular gel is as follows: the tetrahydroxy-modified diurea compound and boric acid are completely dissolved in dimethyl sulfoxide, then an aqueous solution of hydroxide is added, and the mixture is uniformly mixed, and the obtained mixed solution is allowed to stand at room temperature After 10-20 minutes, a reversible covalent bond molecular gel is obtained.

In the preparation method of the above-mentioned reversible covalent bond molecular gel, the molar ratio of the tetrahydroxy-modified biurea compound, boric acid and hydroxide is 1:1:1, and the tetrahydroxy-modified biurea in the mixed solution The concentration of the compound is 0.018-0.050 g/mL; the volume ratio of the dimethyl sulfoxide to water is 7:3-9:1.

The method for detecting mercury ions based on the reversible covalent bond molecular gel of the present invention consists of the following steps:

1. Completely dissolve the tetrahydroxy-modified biurea compound and boric acid in dimethyl sulfoxide, then add an aqueous solution containing hydroxide and chloroauric acid, mix evenly, and let stand in the dark at room temperature for 10 to 20 minutes to obtain a solution containing Colorless gel of chloroauric acid.

2. Add anhydrous ethanol solution of hydrazine hydrate on the colorless gel containing chloroauric acid, and place under sealing conditions in the dark for 12-48 hours to obtain a gel containing gold nanoparticles.

3. Add ultrapure water to the gel containing gold nanoparticles to destroy the gel, and then add dimethyl sulfoxide to make the solution clear and transparent to obtain a composite solution of gel and gold nanoparticles. The surface plasmon resonance absorption peak λ ₀ of the composite solution was added to the standard sample solution of mercury ions with different concentrations, and the surface plasmon resonance absorption peak λ of the corresponding system with different concentrations of mercury ions was measured by ultraviolet-visible spectrophotometer, and Δλ was plotted with mercury ions. Standard curve of concentration change, where Δλ = λ ₀ -λ.

4. According to the method of step 3 above, measure the surface plasmon resonance absorption peak λ of the corresponding system of the sample to be tested with an ultraviolet-visible spectrophotometer, calculate the corresponding Δλ of the sample to be tested according to the formula Δλ=λ ₀ -λ, and combine the The linear equation can identify mercury ions with high selectivity and determine the concentration of mercury ions in the sample to be tested.

In the above step 1, the concentration of chloroauric acid in the colorless gel containing chloroauric acid is 0.5-2.0 mmol/L.

Compared with the prior art, the present invention has the following beneficial effects:

1. The tetrahydroxy-modified diurea compound of the present invention has simple synthesis steps and high yield, and the compound and borate pass through the hydrogen bond between boron-oxygen bond and urea group in a mixed solvent of dimethyl sulfoxide and water A reversible covalent bond gel can be formed, and gold nanoparticles are prepared by in-situ reduction of chloroauric acid with the formed gel as a matrix. The three-dimensional network structure of the gel can prevent the agglomeration of gold nanoparticles, and the prepared gold nanoparticles Good stability, uniform size, good dispersibility, the average particle size is 20-30nm, and the gel has good compatibility with gold nanoparticles. .

2. The composite solution formed by the reversible covalent bond gel and the nano-gold of the present invention can realize the high-sensitivity and high-selectivity detection of mercury ions, the detection time is short, the cost is low, and the nano-gold particles in the composite solution are not easy to agglomerate. It has good stability and brings great convenience to the detection of mercury ions. It is of great significance to detect mercury ions in environmental and biological samples with high sensitivity and high selectivity. The present invention is supported by the National Natural Science Foundation of China (fund number 21473110).

Description of drawings

FIG. 1 is a photograph of the reversible covalently bonded molecular gels formed in Examples 4-12.

2 is the stress sweep curve of the reversible covalently bonded molecular gel formed in Examples 7-9.

FIG. 3 is a thixotropic behavior curve of the reversible covalently bonded molecular gel formed in Example 7. FIG.

FIG. 4 is the thixotropic behavior curve of the reversible covalent bond molecular gel formed in Example 8. FIG.

FIG. 5 is a thixotropic behavior curve of the reversible covalently bonded molecular gel formed in Example 9. FIG.

6 is a stress sweep curve of the reversible covalently bonded molecular gels formed in Examples 9, 13, and 14. FIG.

7 is a stress sweep curve of the reversible covalently bonded molecular gels formed in Examples 9, 15, and 16. FIG.

FIG. 8 is a transmission electron microscope image of gold particles separated from the gel containing gold nanoparticles in Example 17. FIG.

FIG. 9 is an ultraviolet absorption spectrogram of detecting mercury ions with different concentrations based on the reversible covalent bond molecular gel of Example 8 as a matrix.

10 is a standard curve of the change value Δλ of the surface plasmon resonance absorption peak of the composite solution in Example 17 as a function of the mercury ion concentration.

Figure 11 shows the effects of tetrahydroxy-modified diurea compound b, boric acid and sodium hydroxide on the detection results of mercury ions.

FIG. 12 is a photograph of using the method of Example 17 to detect different metal ions in the environment.

Detailed ways

The present invention is further described in detail below with reference to the accompanying drawings and embodiments, but the protection scope of the present invention is not limited to these embodiments.

Example 1

Preparation of tetrahydroxy-modified diurea compound a with the following structural formula

Dissolve 1.476 g (16.20 mmol) of 2-amino-1,3-propanediol in 2 mL of methanol, and dissolve 150 mL of 1.524 g (8.10 mmol) of 4,4'-diisocyanato-3,3'-dimethyl The dichloromethane solution of biphenyl was added dropwise to the above solution, the reaction was stirred at room temperature for 16 hours, filtered, washed with ethyl acetate, and dried under vacuum at room temperature to obtain the tetrahydroxy-modified biurea compound a.

The obtained compound a was confirmed by ¹ H NMR and FTIR characterization, and the specific data are as follows: ¹ H NMR (600MHz, DMSO-d ₆ , TMS), δ=2.17-2.28 (6H,s, 2-CH ₃ ), δ=3.40- 3.46; 3.49-3.55(8H,m,4-CH ₂ -),δ=3.59-3.66(2H,m,2-CH-),δ=4.72-4.76(4H,t,4-OH),δ= 6.59-6.66(2H,d,2-NH-),δ=7.32-7.36(2H,d,2-Ph),δ=7.37-7.41(2H,s,2-Ph),δ=7.83-7.88( 2H,s,2-NH-),δ＝7.91-7.95(2H,d,2-Ph).FTIR(KBr):υ＝3312cm ^-1 (OH),υ＝3041cm ^-1 (CH),υ＝ 2970cm ^-1 (NH), υ=2883cm ^-1 (CH), υ=1639cm ^-1 (C=O), υ=1593cm ^-1 (C=C).

Example 2

Preparation of tetrahydroxy-modified biurea compound b with the following structural formula

In this example, 4,4'-diisocyanato-3,3'-dimethylbiphenyl in Example 1 was replaced with equimolar 4,4'-diisocyanatodiphenylmethane, and other steps In the same manner as in Example 1, a tetrahydroxy-modified diurea compound b was obtained.

The obtained compound b was confirmed by ¹ H NMR and FTIR characterization, and the specific data are as follows: ¹ H NMR (600MHz, DMSO-d ₆ , TMS), δ=3.37-3.42; 3.45-3.50 (8H, m, 4-CH ₂ -) ,δ=3.55-3.61(2H,m,2-CH-),δ=3.72-3.75(2H,s,-CH-),δ=4.69-4.73(4H,t,4-OH),δ=5.79 -6.01(2H,d,2-NH-),δ=7.00-7.06(4H,d,2-Ph),δ=7.23-7.29(4H,s,2-Ph),δ=8.50-8.54(4H ,d,2-NH-).FTIR(KBr):υ＝3380cm ^-1 (OH),υ＝3290cm ^-1 (NH),υ＝3100,3031cm ^-1 (CH),υ＝2876cm ^-1 (CH ), υ=1630cm ^-1 (C=O), υ=1572cm ^-1 (C=C).

Example 3

Preparation of tetrahydroxy-modified diurea compound c with the following structural formula

In this example, the 4,4'-diisocyanato-3,3'-dimethylbiphenyl in Example 1 was replaced with equimolar 1,4-benzenediisocyanate, and other steps were the same as those in Example 1 , to obtain a tetrahydroxy-modified diurea compound c.

The obtained compound b was confirmed by ¹ H NMR and FTIR characterization, and the specific data are as follows: ¹ H NMR (600MHz, DMSO-d ₆ , TMS), δ=3.37-3.42; 3.46-3.51 (8H, m, 4-CH ₂ -) ,δ=3.55-3.61(2H,m,2-CH-),δ=4.68-4.73(4H,t,4-OH),δ=5.92-5.96(2H,d,2-NH-),δ= 7.18-7.22(4H,s,2-Ph),δ=8.37-8.43(2H,s,2-NH-).FTIR(KBr):υ=3312cm ^-1 (OH),υ=3041cm ^-1 (CH ), υ=2974cm ^-1 (NH), υ=2880cm ^-1 (CH), υ=1639cm ^-1 (C=O), υ=1579cm ^-1 (C=C).

Example 4

Dissolve 0.04 g (0.090 mmol) of tetrahydroxy-modified biurea compound a in 344 μL of dimethyl sulfoxide, sonicate until the solution is clear, then add 556 μL of 0.01 g/mL (0.090 mmol) boric acid in dimethyl sulfoxide and 100 μL of dimethyl sulfoxide. 0.022g/mL (0.090mmol) lithium hydroxide aqueous solution, shake uniformly at room temperature, and stand for 15 minutes to form an opaque reversible covalent bond molecular gel.

Example 5

Dissolve 0.04 g (0.090 mmol) of tetrahydroxy-modified biurea compound a in 344 μL of dimethyl sulfoxide, sonicate until the solution is clear, then add 556 μL of 0.01 g/mL (0.090 mmol) boric acid in dimethyl sulfoxide and 100 μL of dimethyl sulfoxide. 0.036g/mL (0.090mmol) sodium hydroxide aqueous solution, shake uniformly at room temperature, and stand for 15 minutes to form a colorless and transparent reversible covalent molecular gel.

Example 6

Dissolve 0.04 g (0.090 mmol) of tetrahydroxy-modified biurea compound a in 344 μL of dimethyl sulfoxide, sonicate until the solution is clear, then add 556 μL of 0.01 g/mL (0.090 mmol) boric acid in dimethyl sulfoxide and 100 μL of dimethyl sulfoxide. 0.232 g/mL (0.090 mmol) tetrabutylammonium hydroxide aqueous solution, shake uniformly at room temperature, and stand for 15 minutes to form an opaque reversible covalent molecular gel.

Example 7

Dissolve 0.04 g (0.092 mmol) of tetrahydroxy-modified biurea compound b in 330 μL of dimethyl sulfoxide, sonicate until the solution is clear, then add 570 μL of 0.01 g/mL (0.092 mmol) boric acid in dimethyl sulfoxide and 100 μL of dimethyl sulfoxide. 0.022g/mL (0.092mmol) lithium hydroxide aqueous solution, shake uniformly at room temperature, and stand for 15 minutes to form a colorless and transparent reversible covalent bond molecular gel.

Example 8

Dissolve 0.04 g (0.092 mmol) of tetrahydroxy-modified biurea compound b in 330 μL of dimethyl sulfoxide, sonicate until the solution is clear, then add 570 μL of 0.01 g/mL (0.092 mmol) boric acid in dimethyl sulfoxide and 100 μL of dimethyl sulfoxide. 0.037g/mL (0.092mmol) sodium hydroxide aqueous solution, shake evenly at room temperature, and stand for 15 minutes to form a colorless and transparent reversible covalent molecular gel.

Example 9

Dissolve 0.04 g (0.092 mmol) of tetrahydroxy-modified biurea compound b in 330 μL of dimethyl sulfoxide, sonicate until the solution is clear, then add 570 μL of 0.01 g/mL (0.092 mmol) boric acid in dimethyl sulfoxide and 100 μL of dimethyl sulfoxide. 0.240 g/mL (0.092 mmol) aqueous solution of tetrabutylammonium hydroxide, shake uniformly at room temperature, and stand for 15 minutes to form a translucent reversible covalent molecular gel.

Example 10

Dissolve 0.04 g (0.120 mmol) of tetrahydroxy-modified biurea compound c in 178 μL of dimethyl sulfoxide, sonicate until the solution is clear, then add 722 μL of 0.01 g/mL (0.120 mmol) boric acid in dimethyl sulfoxide and 100 μL of dimethyl sulfoxide. 0.028g/mL (0.120mmol) lithium hydroxide aqueous solution, shake evenly at room temperature, and stand for 15 minutes to form a translucent reversible covalent bond molecular gel.

Example 11

Dissolve 0.04 g (0.120 mmol) of tetrahydroxy-modified biurea compound c in 178 μL of dimethyl sulfoxide, sonicate until the solution is clear, then add 722 μL of 0.01 g/mL (0.120 mmol) boric acid in dimethyl sulfoxide and 100 μL of dimethyl sulfoxide. 0.048g/mL (0.120mmol) sodium hydroxide aqueous solution, shake uniformly at room temperature, and stand for 15 minutes to form a colorless and transparent reversible covalent molecular gel.

Example 12

Dissolve 0.04 g (0.120 mmol) of tetrahydroxy-modified biurea compound c in 178 μL of dimethyl sulfoxide, sonicate until the solution is clear, then add 722 μL of 0.01 g/mL (0.120 mmol) boric acid in dimethyl sulfoxide and 100 μL of dimethyl sulfoxide. 0.303 g/mL (0.120 mmol) tetrabutylammonium hydroxide aqueous solution, shake uniformly at room temperature, and stand for 15 minutes to form a translucent reversible covalent molecular gel.

Example 13

Dissolve 0.04 g (0.092 mmol) of tetrahydroxy-modified biurea compound b in 230 μL of dimethyl sulfoxide, sonicate until the solution is clear, then add 570 μL of 0.01 g/mL (0.092 mmol) boric acid in dimethyl sulfoxide and 200 μL of dimethyl sulfoxide. 0.120 g/mL (0.092 mmol) aqueous solution of tetrabutylammonium hydroxide, shake uniformly at room temperature, and stand for 15 minutes to form a transparent reversible covalent molecular gel.

Example 14

Dissolve 0.04 g (0.092 mmol) of tetrahydroxy-modified biurea compound b in 130 μL of dimethyl sulfoxide, sonicate until the solution is clear, then add 570 μL of 0.01 g/mL (0.092 mmol) boric acid in dimethyl sulfoxide and 300 μL of dimethyl sulfoxide. 0.080g/mL (0.092mmol) aqueous solution of tetrabutylammonium hydroxide, shake evenly at room temperature, and stand for 30 minutes to form a transparent reversible covalent bond molecular gel.

Example 15

Dissolve 0.036 g (0.083 mmol) of tetrahydroxy-modified biurea compound b in 387 μL of dimethyl sulfoxide, sonicate until the solution is clear, then add 513 μL of 0.01 g/mL (0.083 mmol) boric acid in dimethyl sulfoxide and 100 μL of dimethyl sulfoxide. 0.217 g/mL (0.083 mmol) aqueous solution of tetrabutylammonium hydroxide, shake uniformly at room temperature, and stand for 15 minutes to form a transparent reversible covalent molecular gel.

Example 16

Dissolve 0.045 g (0.104 mmol) of tetrahydroxy-modified biurea compound b in 256 μL of dimethyl sulfoxide, sonicate until the solution is clear, then add 644 μL of 0.01 g/mL (0.104 mmol) boric acid in dimethyl sulfoxide and 100 μL of dimethyl sulfoxide. 0.271 g/mL (0.104 mmol) aqueous solution of tetrabutylammonium hydroxide, shake evenly at room temperature, and stand for 15 minutes to form a translucent reversible covalent molecular gel.

The photos of the reversible covalent bond molecular gels formed by the above examples 4 to 12 are shown in Figure 1. The inventors studied the mechanical strength and thixotropy of the reversible covalent bond molecular gels formed by the salt effect in Examples 7 to 9. The results are shown in Figures 2 to 5. It can be seen from Figure 2 that in the low shear range, the storage modulus G' of the reversible covalent bond molecular gels formed in Examples 7-9 is higher than the loss modulus G", showing typical soft solid properties, The elastic moduli and yield stress of the three gels are decreased according to Example 8 > Example 7 > Example 9. In addition, it can also be seen from Figure 2 that when the shear stress is higher than the yield value, the three gels are The values of G′ and G″ dropped sharply, and G″ was significantly higher than G′, indicating that the gel network structure was damaged under high shear and showed obvious liquid behavior. From the test results in Figures 3 to 5 , the gel formed in Example 9 exhibits a unique shear thixotropy, and the "gel-sol" phase transition of the system is almost completely reversible during the 10 cycles of destruction and recovery, all maintaining the original molecular gel. Viscoelasticity, while the gels formed in Examples 7 and 8 showed a decreasing trend in their "gel-sol" reversibility, which may be attributed to the fact that both gels would break into pieces under high shear forces.

The inventors further studied the effect of solvent effects on the rheological properties of the formed reversible covalently bonded molecular gels in Examples 9, 13 and 14, and the results are shown in Figure 6 . It can be concluded from Figure 6 that when the volume ratio of dimethyl sulfoxide and water is 9:1 (Example 9), 8:2 (Example 13), and 7:3 (Example 14), respectively, the gel The yield values were 1778.0Pa, 891.2Pa, and 630.9Pa in turn, while the G' and G" of the gel did not change significantly. The results showed that a slight change in the solvent would lead to a significant change in the mechanical strength of the gel.

The mechanical strength and viscoelasticity of the gel are closely related to the concentration of the gelling agent, so the inventors also studied the effect of the concentration in Examples 9, 15, 16 on the rheological properties of the formed reversible covalent molecular gels. , and the results are shown in Figure 7. As can be seen from Figure 7, when the concentrations of the tetrahydroxy-modified diurea compound b were 0.036 g/mL (Example 15), 0.040 g/mL (Example 9) and 0.045 g/mL (Example 16), respectively, the obtained The yield value of the gel is 223.8Pa, 777.0Pa, 6010.2Pa in turn, indicating that the mechanical strength of the gel increases with the increase of the gelling agent concentration.

Example 17

Detecting mercury ions based on the reversible covalent molecular gel of Example 8 as a matrix

1. Dissolve 0.04g (0.092mmol) of tetrahydroxy-modified diurea compound b in 330μL of dimethyl sulfoxide, sonicate until the solution is clear, and then add 570μL of 0.1g/mL (0.092mmol) boric acid in dimethyl sulfoxide solution , 100 μL of an aqueous solution containing 3.7 mg (0.092 mmol) of sodium hydroxide and 1.26 mg (1.5 × 10 ^-3 mmol) of chloroauric acid, mixed well, and allowed to stand for 15 minutes at room temperature in the dark to obtain a colorless gel containing chloroauric acid .

2. Add 250 μL of 88% hydrazine hydrate solution in absolute ethanol to the colorless gel containing chloroauric acid, seal the bottle, and place it in the dark at room temperature for 24 hours to obtain a purple gel containing gold nanoparticles. glue. It can be seen from FIG. 8 that the average particle size of the gold particles in the obtained gel is 20-30 nm.

3. Pour off the remaining hydrazine hydrate solution in absolute ethanol on the top of the gel containing gold nanoparticles, then add 150 μL of ultrapure water to destroy the gel, and then add 350 μL of dimethyl sulfoxide to make the solution clear and transparent to obtain gel and The composite solution of nano-gold, the surface plasmon resonance absorption peak λ ₀ of the composite solution was measured by ultraviolet-visible spectrophotometer, and then mercuric chloride aqueous solutions with concentrations of 1, 2, 3...18, 19, 20 μmol/L were added respectively, The surface plasmon resonance absorption peak λ of the corresponding system with different concentrations of mercury ions was measured by UV-visible spectrophotometer, the results are shown in Figure 9, and the standard curve of Δλ with the concentration of mercury ions was drawn, where Δλ=λ ₀ -λ, the results are shown in Figure 9 10.

It can be seen from Figure 9 that with the increase of mercury ion concentration, the surface plasmon resonance absorption peak exhibits a blue shift, the absorption intensity increases slightly, and an iso-extinction point is observed at 556 nm. It can be seen from Figure 10 that when the mercury ion concentration is in the lower concentration range (0-6 μmol/L), Δλ has a linear relationship with the mercury ion concentration. The linear equation is: Y=0.07143+2X, where Y represents Δλ, and X is mercury Ion concentration, its correlation coefficient R=0.9977. According to S/N=3, the detection limit of this method was calculated to be 0.2 μmol/L.

4. According to the method of step 3 above, measure the surface plasmon resonance absorption peak λ of the corresponding system of the sample to be tested with an ultraviolet-visible spectrophotometer, calculate the corresponding Δλ of the sample to be tested according to the formula Δλ=λ ₀ -λ, and combine the The linear equation can identify mercury ions with high selectivity and determine the concentration of mercury ions in the sample to be tested.

As shown in Table 1, the inventors investigated the effects of the tetrahydroxy-modified diurea compound b, boric acid, and sodium hydroxide on the detection results of mercury ions (6 μmol/L) in Example 17. The experimental results are shown in Figure 11 .

Table 1 Control experiment

Note: "-" in the table means not containing the substance in the cell, and "√" means containing the substance in the cell.

The experimental results show that in the method for detecting mercury ions of the present invention, tetrahydroxy-modified diurea compounds b, boric acid and sodium hydroxide are indispensable, indicating that the reversible covalent bond molecular gel of the present invention is in the presence of mercury ions. played an important role in the detection process.

In order to prove the beneficial effect of the present invention, the inventor adopts the method of Example 17 to treat other metal ions in the environment, such as iron ion, chromium ion, magnesium ion, cobalt ion, barium ion, nickel ion, calcium ion, cadmium ion, lead ion, respectively. Aqueous solutions of ions, zinc ions, and copper ions are used for detection. The experimental results show that even if the concentration of iron ion, chromium ion, magnesium ion, cobalt ion, barium ion, nickel ion, calcium ion, cadmium ion, lead ion, zinc ion, and copper ion is increased to 100 μmol/L, the color of the system will not change. No change occurred, and when the mercury ion concentration was 6 μmol/L, the color of the system immediately changed from the original purple to red (see Figure 12), indicating that this method can realize the selective detection of mercury ions.

Claims (4)

1. A method for detecting mercury ions based on reversible covalent bond molecular gel is characterized in that:

(1) completely dissolving a tetrahydroxy modified diurea compound and boric acid in dimethyl sulfoxide, adding an aqueous solution containing hydroxide and chloroauric acid, uniformly mixing, and standing the obtained mixed solution at normal temperature in a dark place for 10-20 minutes to obtain a colorless gel containing chloroauric acid;

the structural formula of the tetrahydroxy modified diurea compound is shown as follows:

in the formula, R represents

、

Or；

The hydroxide is lithium hydroxide, sodium hydroxide or tetrabutylammonium hydroxide;

(2) adding an absolute ethanol solution of hydrazine hydrate to the colorless gel containing the chloroauric acid, and placing the mixture for 12-48 hours in a dark place under a sealed condition to obtain gel containing the nano-gold particles;

(3) adding ultrapure water on the gel containing the nano-gold particles to destroy the gel, then adding dimethyl sulfoxide to make the solution clear and transparent to obtain a composite solution of the gel and the nano-gold, and measuring the surface plasma resonance absorption peak lambda of the composite solution by adopting an ultraviolet-visible spectrophotometer₀Adding standard sample solutions of mercury ions with different concentrations, measuring surface plasmon resonance absorption peak λ of mercury ion corresponding system with different concentrations by ultraviolet-visible spectrophotometer, and drawing a standard curve of λ varying with mercury ion concentration, wherein λ = λ₀-λ；

(4) Measuring the surface plasma resonance absorption peak lambda of the corresponding system of the sample to be measured by using an ultraviolet-visible spectrophotometer according to the method of the step (3), and obtaining the equivalent system of the formula lambda = lambda₀And (4) calculating the corresponding Δ λ of the sample to be detected, and combining a linear equation of the standard curve to identify the mercury ions with high selectivity and determine the concentration of the mercury ions in the sample to be detected.

2. The method of detecting mercury ions according to claim 1, wherein: in the step (1), the concentration of the chloroauric acid in the colorless gel containing the chloroauric acid is 0.5-2.0 mmol/L.

3. The method of detecting mercury ions according to claim 1, wherein: in the step (1), the molar ratio of the tetrahydroxy modified diurea compound to the boric acid to the hydroxide is 1:1:1, and the concentration of the tetrahydroxy modified diurea compound in the mixed solution is 0.018 to 0.050 g/mL.

4. The method of detecting mercury ions according to claim 1, wherein: in the step (1), the volume ratio of the dimethyl sulfoxide to the water is 7: 3-9: 1.

Images