CN107674003B

CN107674003B - Tetrahydroxyl modified diurea compound, gel thereof and method for detecting mercury ions based on gel

Info

Publication number: CN107674003B
Application number: CN201710832006.9A
Authority: CN
Inventors: 刘凯强; 王酸酸; 王今强; 高升; 房喻
Original assignee: Shaanxi Normal University
Current assignee: Shaanxi Normal University
Priority date: 2017-09-15
Filing date: 2017-09-15
Publication date: 2020-02-21
Anticipated expiration: 2037-09-15
Also published as: CN107674003A

Abstract

The invention discloses a tetrahydroxy modified diurea compound, gel thereof and a method for detecting mercury ions based on the gel, wherein the structural formula of the compound is shown in the specification

In the formula, R represents

The compound and borate can form reversible covalent bond gel in a mixed solvent of dimethyl sulfoxide and water through a hydrogen bond between a boron-oxygen bond and carbamido, the formed gel is used as a matrix, gold nanoparticles are prepared by in-situ reduction of chloroauric acid, and the obtained gel and the nano-gold compound can detect mercury ions with high sensitivity and high selectivity, and have the advantages of short time consumption, low cost, simple operation and the like.

Description

Tetrahydroxyl modified diurea compound, gel thereof and method for detecting mercury ions based on gel

Technical Field

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

Background

Toxic metal ions have a very serious impact on human health and the environment, and therefore, the detection of these contaminants in water ecosystem is a focus of attention. Mercury is one of the most harmful toxic metal ions in the environment and is generally produced by coal combustion, power plants, oceans, volcanic eruptions, burning of gold ores and solid wastes, and the like. Mercury ion (Hg)²⁺) The most stable form is the formation of inorganic mercury, which has high cytotoxicity such as corrosiveness and carcinogenicity, and can cause serious damage to the brain, nervous system, kidney and endocrine system, and diseases of autoimmune system can be caused by long-term exposure to inorganic mercury. Therefore, the method has great significance for detecting mercury ions in environmental and biological samples with high sensitivity and high selectivity. At present, the commonly used method for detecting Hg²⁺The methods of (1) mainly include Atomic Absorption Spectrometry (AAS), Atomic Fluorescence Spectrometry (AFS), Inductively Coupled Plasma Mass Spectrometry (ICPMS), High-performance liquid chromatography (HPLC), and the like. Although these methods have many advantages, they generally require expensive instrumentation, cumbersome sample preparation, separation and enrichment of the sample, and thus require a significant amount of time. Therefore, the method for measuring Hg with high sensitivity, high selectivity, short time consumption and low cost is established²⁺Become a hot spot of research today. The optical sensor does not need special instruments and can also be used for Hg²⁺The visual detection is carried out, thereby arousing the wide attention of people. Nowadays, Hg based on organic chromophores and fluorophores, conjugated polymers, nucleic acids, dnases, proteins, films and nanoparticles are proposed²⁺A sensor. Although these optical sensors are much simpler than conventional methods, most of them have low sensitivity and selectivity, and the synthesis steps of the probe materials are complicated or unsuitable for the examination of actual samples, so that their applications are greatly limited. Therefore, the Hg is detected simply, economically and practically with high sensitivity and selectivity²⁺Is still the leading edge of current researchA hot spot.

Disclosure of Invention

The invention aims to provide a tetrahydroxy modified diurea compound, a reversible covalent bond molecular gel based on the compound and a method for detecting mercury ions by taking the gel as a matrix.

The structural formula of the tetrahydroxy modified diurea compound adopted for solving the technical problems is as follows:

in the formula, R represents

The preparation method of the tetrahydroxy modified diurea compound comprises the following steps: dissolving 2-amino-1, 3-propanediol in methanol, and dropwise adding a methylene chloride solution of diisocyanate shown in formula I into the 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, stirring and reacting for 16 hours at normal temperature, filtering, washing with ethyl acetate, and drying to obtain the tetrahydroxy modified diurea compound, wherein the specific synthetic route is as follows:

the reversible covalent bond molecular gel is formed by the double urea compound modified by the tetrahydroxy and borate through hydrogen bonds between reversible boron-oxygen bonds and carbamido in a mixed solvent of dimethyl sulfoxide and water, wherein the borate is any one of lithium borate, sodium borate and tetrabutylammonium borate, the borate is generated by the reaction of boric acid and hydroxide, and the hydroxide is lithium hydroxide, sodium hydroxide or tetrabutylammonium hydroxide.

The preparation method of the reversible covalent bond molecular gel comprises the following steps: and completely dissolving the tetrahydroxy modified diurea compound and boric acid in dimethyl sulfoxide, adding an aqueous solution of hydroxide, uniformly mixing, and standing the obtained mixed solution at normal temperature for 10-20 minutes to obtain the reversible covalent bond molecular gel.

In the preparation method of the reversible covalent bond molecular gel, 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 0.018-0.050 g/mL; the volume ratio of the dimethyl sulfoxide to the water is 7: 3-9: 1.

The method for detecting mercury ions based on the reversible covalent bond molecular gel comprises the following steps:

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

2. And adding an absolute ethanol solution of hydrazine hydrate to the colorless gel containing the chloroauric acid, and placing for 12-48 hours in a dark place under a sealed condition to obtain the 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 mercury ion standard sample solutions with different concentrations, measuring surface plasma resonance absorption peak lambda of a mercury ion corresponding system with different concentrations by using an ultraviolet-visible spectrophotometer, and drawing a standard curve of delta lambda changing along with the concentration of mercury ions, wherein the delta lambda is equal to the lambda₀-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 according to the formula delta lambda, changing to lambda₀And (4) calculating delta lambda corresponding to 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.

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.

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

1. the synthetic steps of the tetrahydroxy modified diurea compound are simple, the yield is high, the compound and borate can form reversible covalent bond gel in a mixed solvent of dimethyl sulfoxide and water through hydrogen bonds between boron-oxygen bonds and carbamido groups, the formed gel is used as a matrix, gold nanoparticles are prepared by reducing chloroauric acid in situ, the three-dimensional network structure of the gel can prevent the gold nanoparticles from agglomerating, the prepared gold nanoparticles are good in stability, uniform in size and good in dispersity, the average particle size is 20-30 nm, the compatibility of the gel and the gold nanoparticles is good, and the gold nanoparticles cannot cause great influence on the gelling speed and the gelling condition.

2. The composite solution formed by the reversible covalent bond gel and the nanogold can realize high-sensitivity and high-selectivity detection of mercury ions, the detection time is short, the cost is low, nanogold particles in the composite solution are not easy to agglomerate, the stability is good, great convenience is brought to the detection of the mercury ions, and the composite solution has great significance for the high-sensitivity and high-selectivity detection of the mercury ions in environment and biological samples. The invention obtains the support of the national science fund (the fund number is 21473110) in China.

Drawings

FIG. 1 is a photograph of a reversible covalent bond molecular gel formed in examples 4 to 12.

FIG. 2 is a stress scan curve of the reversible covalent bond molecular gels formed in examples 7-9.

FIG. 3 is a thixotropic behavior curve of the reversible covalent bond molecular gel formed in example 7.

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

FIG. 5 is a thixotropic behavior curve of the reversible covalent bond molecular gel formed in example 9.

FIG. 6 is a stress scan curve of the reversible covalent bond molecular gels formed in examples 9, 13, and 14.

FIG. 7 is a stress scan curve of the reversible covalent bond molecular gels formed in examples 9, 15, 16.

FIG. 8 is a transmission electron micrograph of gold particles separated from the gel containing gold nanoparticles of example 17.

FIG. 9 is a graph of UV absorption spectra for detecting different concentrations of mercury ions based on the reversible covalent bond molecular gel of example 8 as a matrix.

FIG. 10 is a calibration curve showing the variation of the surface plasmon resonance absorption peak Δ λ with the mercury ion concentration of the composite solution in example 17.

FIG. 11 shows the effect of tetrahydroxy-modified diurea compounds (b), boric acid, and sodium hydroxide on the results of mercury ion detection.

FIG. 12 is a photograph of the detection of different metal ions in an environment using the method of example 17.

Detailed Description

The invention will be further described in detail with reference to the following figures and examples, but the scope of the invention is not limited to these examples.

Example 1

Preparing tetrahydroxy modified diurea compound a with the structural formula

Dissolving 1.476g (16.20mmol) of 2-amino-1, 3-propanediol in 2mL of methanol, dropwise adding 150mL of dichloromethane solution containing 1.524g (8.10mmol) of 4,4 '-diisocyanato-3, 3' -dimethylbiphenyl into the solution, stirring at normal temperature for reaction for 16 hours, filtering, washing with ethyl acetate, and drying at normal temperature in vacuum to obtain the tetrahydroxy modified diurea compound a.

The obtained compound a is subjected to¹H NMR and FTIR characterization confirm, and the specific data are as follows:¹H NMR(600MHz,DMSO-d₆,TMS),δ＝2.17-2.28(6H,s,2-CH₃),δ＝3.40-3.46；3.49-3.55(8H,m,4-CH₂-),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(O-H),υ＝3041cm^-1(C-H),υ＝2970cm^-1(N-H),υ＝2883cm^-1(C-H),υ＝1639cm^-1(C＝O),υ＝1593cm^-1(C＝C)。

example 2

Preparing tetrahydroxy modified diurea compound b with the structural formula

In this example, 4' -diisocyanato-3, 3' -dimethylbiphenyl in example 1 was replaced with 4,4' -diisocyanatodiphenylmethane in an equimolar amount, and the other steps were the same as in example 1 to obtain a tetrahydroxy-modified diurea compound b.

The compound b is obtained by¹H NMR and FTIR characterization confirm, and the specific data are as follows:¹H NMR(600MHz,DMSO-d₆,TMS),δ＝3.37-3.42；3.45-3.50(8H,m,4-CH₂-),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(O-H),υ＝3290cm^-1(N-H),υ＝3100,3031cm^-1(C-H),υ＝2876cm^-1(C-H),υ＝1630cm^-1(C＝O),υ＝1572cm^-1(C＝C)。

example 3

Preparing tetrahydroxy modified diurea compound c with the structural formula

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

The compound b is obtained by¹H NMR and FTIR characterization confirmation, specificallyThe data are as follows:¹H NMR(600MHz,DMSO-d₆,TMS),δ＝3.37-3.42；3.46-3.51(8H,m,4-CH₂-),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(O-H),υ＝3041cm^-1(C-H),υ＝2974cm^-1(N-H),υ＝2880cm^-1(C-H),υ＝1639cm^-1(C＝O),υ＝1579cm^-1(C＝C)。

example 4

Dissolving 0.04g (0.090mmol) of tetrahydroxy modified diurea compound a in 344 mu L of dimethyl sulfoxide, performing ultrasonic treatment until the solution is clear, adding 556 mu L of 0.01g/mL (0.090mmol) of boric acid dimethyl sulfoxide solution and 100 mu L of 0.022g/mL (0.090mmol) of lithium hydroxide aqueous solution, shaking uniformly at normal temperature, and standing for 15 minutes to obtain opaque reversible covalent bond molecular gel.

Example 5

Dissolving 0.04g (0.090mmol) of tetrahydroxy modified diurea compound a in 344 mu L of dimethyl sulfoxide, carrying out ultrasonic treatment until the solution is clear, then adding 556 mu L of 0.01g/mL (0.090mmol) of boric acid dimethyl sulfoxide solution and 100 mu L of 0.036g/mL (0.090mmol) of sodium hydroxide aqueous solution, shaking uniformly at normal temperature, and standing for 15 minutes to obtain colorless and transparent reversible covalent bond molecular gel.

Example 6

Dissolving 0.04g (0.090mmol) of tetrahydroxy modified diurea compound a in 344 mu L of dimethyl sulfoxide, performing ultrasonic treatment until the solution is clear, adding 556 mu L of 0.01g/mL (0.090mmol) of boric acid in dimethyl sulfoxide solution and 100 mu L of 0.232g/mL (0.090mmol) of tetrabutylammonium hydroxide aqueous solution, uniformly shaking at normal temperature, and standing for 15 minutes to obtain opaque reversible covalent bond molecular gel.

Example 7

Dissolving 0.04g (0.092mmol) of tetrahydroxy modified diurea compound b in 330 mu L of dimethyl sulfoxide, performing ultrasonic treatment until the solution is clear, adding 570 mu L of 0.01g/mL (0.092mmol) of boric acid dimethyl sulfoxide solution and 100 mu L of 0.022g/mL (0.092mmol) of lithium hydroxide aqueous solution, shaking uniformly at normal temperature, and standing for 15 minutes to form colorless and transparent reversible covalent bond molecular gel.

Example 8

Dissolving 0.04g (0.092mmol) of tetrahydroxy modified diurea compound b in 330 mu L of dimethyl sulfoxide, performing ultrasonic treatment until the solution is clear, adding 570 mu L of 0.01g/mL (0.092mmol) of boric acid dimethyl sulfoxide solution and 100 mu L of 0.037g/mL (0.092mmol) of sodium hydroxide aqueous solution, shaking uniformly at normal temperature, and standing for 15 minutes to form colorless and transparent reversible covalent bond molecular gel.

Example 9

Dissolving 0.04g (0.092mmol) of tetrahydroxy modified diurea compound b in 330 mu L of dimethyl sulfoxide, performing ultrasonic treatment until the solution is clear, adding 570 mu L of 0.01g/mL (0.092mmol) of boric acid dimethyl sulfoxide solution and 100 mu L of 0.240g/mL (0.092mmol) of tetrabutylammonium hydroxide aqueous solution, uniformly shaking at normal temperature, and standing for 15 minutes to form semitransparent reversible covalent bond molecular gel.

Example 10

Dissolving 0.04g (0.120mmol) of tetrahydroxy modified diurea compound c in 178 mu L of dimethyl sulfoxide, carrying out ultrasonic treatment until the solution is clear, then adding 722 mu L of 0.01g/mL (0.120mmol) of boric acid dimethyl sulfoxide solution and 100 mu L of 0.028g/mL (0.120mmol) of lithium hydroxide aqueous solution, uniformly shaking at normal temperature, and standing for 15 minutes to form semitransparent reversible covalent bond molecular gel.

Example 11

Dissolving 0.04g (0.120mmol) of tetrahydroxy modified diurea compound c in 178 mu L of dimethyl sulfoxide, carrying out ultrasonic treatment until the solution is clear, then adding 722 mu L of 0.01g/mL (0.120mmol) of boric acid dimethyl sulfoxide solution and 100 mu L of 0.048g/mL (0.120mmol) of sodium hydroxide aqueous solution, shaking uniformly at normal temperature, and standing for 15 minutes to form colorless and transparent reversible covalent bond molecular gel.

Example 12

Dissolving 0.04g (0.120mmol) of tetrahydroxy modified diurea compound c in 178 mu L of dimethyl sulfoxide, carrying out ultrasonic treatment until the solution is clear, then adding 722 mu L of 0.01g/mL (0.120mmol) of boric acid dimethyl sulfoxide solution and 100 mu L of 0.303g/mL (0.120mmol) of tetrabutylammonium hydroxide aqueous solution, shaking uniformly at normal temperature, and standing for 15 minutes to form semitransparent reversible covalent bond molecular gel.

Example 13

Dissolving 0.04g (0.092mmol) of tetrahydroxy modified diurea compound b in 230 mu L of dimethyl sulfoxide, performing ultrasonic treatment until the solution is clear, then adding 570 mu L of 0.01g/mL (0.092mmol) of boric acid dimethyl sulfoxide solution and 200 mu L of 0.120g/mL (0.092mmol) of tetrabutylammonium hydroxide aqueous solution, uniformly shaking at normal temperature, and standing for 15 minutes to form transparent reversible covalent bond molecular gel.

Example 14

Dissolving 0.04g (0.092mmol) of tetrahydroxy modified diurea compound b in 130 mu L of dimethyl sulfoxide, performing ultrasonic treatment until the solution is clear, then adding 570 mu L of 0.01g/mL (0.092mmol) of boric acid dimethyl sulfoxide solution and 300 mu L of 0.080g/mL (0.092mmol) of tetrabutylammonium hydroxide aqueous solution, uniformly shaking at normal temperature, and standing for 30 minutes to form transparent reversible covalent bond molecular gel.

Example 15

Dissolving 0.036g (0.083mmol) of tetrahydroxy modified diurea compound b in 387 mu L of dimethyl sulfoxide, carrying out ultrasonic treatment until the solution is clear, then adding 513 mu L of 0.01g/mL (0.083mmol) of boric acid dimethyl sulfoxide solution and 100 mu L of 0.217g/mL (0.083mmol) of tetrabutylammonium hydroxide aqueous solution, uniformly shaking at normal temperature, and standing for 15 minutes to form transparent reversible covalent bond molecular gel.

Example 16

Dissolving 0.045g (0.104mmol) of tetrahydroxy modified diurea compound b in 256 mu L of dimethyl sulfoxide, performing ultrasonic treatment until the solution is clear, then adding 644 mu L of 0.01g/mL (0.104mmol) of boric acid dimethyl sulfoxide solution and 100 mu L of 0.271g/mL (0.104mmol) of tetrabutylammonium hydroxide aqueous solution, shaking uniformly at normal temperature, and standing for 15 minutes to form semitransparent reversible covalent bond molecular gel.

The photographs of the reversible covalent bond molecular gels formed in examples 4 to 12 are shown in fig. 1, and the inventors studied the influence of the salt effect on the mechanical strength and thixotropy of the reversible covalent bond molecular gels formed in examples 7 to 9, and the results are shown in fig. 2 to 5. As can be seen from FIG. 2, in the low shear range, the storage modulus G 'of the reversible covalent bond molecular gels formed in examples 7-9 is higher than that of the loss mode G', the gel shows typical soft solid characteristics, the elastic modulus and yield stress of the three gels are reduced according to example 8> example 7> example 9, and in addition, as can be seen from FIG. 2, when the shear stress is higher than the yield value, the values of G 'and G' of the three gels are sharply reduced, and G 'is obviously higher than G', which indicates that the gel network structure is damaged under the action of high shear to show obvious liquid behavior. From the test results of fig. 3-5, the gel formed in example 9 shows unique shear thixotropy, and the phase change of the "gel-sol" is almost completely reversible in 10 action cycles of destruction and recovery, and the original viscoelasticity of the molecular gel is maintained. While the gels formed in examples 7 and 8 exhibited a decreasing tendency for their "gel-sol" reversibility, which may be attributed to the fact that both gels fragmented under high shear.

The inventors further investigated the effect of solvent effect on the rheological properties of the reversible covalent bond molecular gel formed in examples 9, 13, 14, and the results are shown in fig. 6. As can be seen from FIG. 6, the yield values of the gels were 1778.0Pa, 891.2Pa and 630.9Pa in the order of the volume ratio of dimethyl sulfoxide to water of 9:1 (example 9), 8:2 (example 13) and 7:3 (example 14), respectively, while the G 'and G' of the gels did not change significantly. The results show that: a small change in solvent will result in 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 investigated the effect of the concentration effect in examples 9, 15, 16 on the rheological properties of the formed reversible covalent bond molecular gel, and the results are shown in fig. 7. As can be seen from FIG. 7, when the concentrations of the tetrahydroxy-modified diurea compounds b were 0.036g/mL (example 15), 0.040g/mL (example 9) and 0.045g/mL (example 16), the obtained gels had yield values of 223.8Pa, 777.0Pa and 6010.2Pa, respectively, indicating that the mechanical strength of the gels increased with increasing concentration of the gelling agent.

Example 17

Mercury ion detection based on reversible covalent bond molecular gel as matrix in example 8

1. 0.04g (0.092mmol) of bishydrazide modified with tetrahydroxy groupb dissolved in 330. mu.L of dimethyl sulfoxide, sonicated until the solution is clear, and then 570. mu.L of a 0.1g/mL (0.092mmol) solution of boric acid in dimethyl sulfoxide, 100. mu.L of 3.7mg (0.092mmol) sodium hydroxide and 1.26mg (1.5X 10mmol) of boric acid are added^-3mmol) chloroauric acid aqueous solution, mixing well, standing at normal temperature in dark place for 15 minutes to obtain colorless gel containing chloroauric acid.

2. Adding 250 mu L of anhydrous ethanol solution of hydrazine hydrate with the volume concentration of 88% on colorless gel containing chloroauric acid, sealing the bottle mouth, and standing at room temperature in a dark place for 24 hours to obtain purple gel containing the nano gold particles. As can be seen from FIG. 8, the average particle size of the gold particles in the obtained gel is 20-30 nm.

3. Pouring off the residual hydrazine hydrate absolute ethanol solution on the upper part of the gel containing the nano-gold particles, adding 150 mu L of ultrapure water to destroy the gel, adding 350 mu L of dimethyl sulfoxide to clarify and transparent the solution 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 aqueous solution of mercuric chloride with concentration of 1, 2, 3 … 18, 19, 20 μmol/L, measuring surface plasmon resonance absorption peak λ of corresponding system of mercury ions with different concentrations by ultraviolet-visible spectrophotometer, and plotting standard curve of Δ λ with variation of mercury ion concentration, wherein Δ λ ═ λ₀λ, see FIG. 10 for the results.

As can be seen from FIG. 9, the surface plasmon resonance absorption peak appears blue-shifted with a slight increase in absorption intensity with an increase in mercury ion concentration, and an isoextinction point is observed at 556 nm. As can be seen from FIG. 10, when the concentration of mercury ions is in a lower range (0-6. mu. mol/L), Δ λ and the concentration of mercury ions are in a linear relationship, and the linear equation is: y is 0.07143+2X, where Y represents Δ λ and X is the mercury ion concentration, and its correlation coefficient R is 0.9977. The detection limit of this method was calculated from S/N-3 to be 0.2 μmol/L.

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 according to the formula delta lambda, changing to lambda₀Calculating the corresponding delta lambda of the sample to be detected, and combining the linear equation of the standard curve to obtain the high selectivityAnd identifying the mercury ions and determining the concentration of the mercury ions in the sample to be detected.

The inventors examined the influence of the tetrahydroxy-modified diurea compound b, boric acid, and sodium hydroxide on the results of detection of mercury ions (6. mu. mol/L) in example 17 as shown in Table 1, and the results are shown in FIG. 11.

TABLE 1 control experiment

Note: in the table, "-" indicates that the cell does not contain any substance, and "√" indicates that the cell contains any substance.

Experimental results show that in the method for detecting mercury ions, three substances, namely the tetrahydroxy modified diurea compound b, boric acid and sodium hydroxide, are absent, and the method shows that the reversible covalent bond molecular gel plays an important role in the detection process of mercury ions.

To prove the beneficial effects of the present invention, the inventors used the method of example 17 to detect the aqueous solutions of other metal ions in the environment, such as iron ions, chromium ions, magnesium ions, cobalt ions, barium ions, nickel ions, calcium ions, cadmium ions, lead ions, zinc ions, and copper ions, respectively. The experimental result shows that even if the concentrations of iron ions, chromium ions, magnesium ions, cobalt ions, barium ions, nickel ions, calcium ions, cadmium ions, lead ions, zinc ions and copper ions are increased to 100 mu mol/L, the color of the system does not change, and when the concentration of mercury ions is 6 mu mol/L, the color of the system is immediately changed from original purple to red (see figure 12), which indicates that the method can realize the selective detection of the mercury ions.

Claims

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.