CN107389755B - Electrochemical sensor for detecting mercury, and preparation method and application thereof - Google Patents
Electrochemical sensor for detecting mercury, and preparation method and application thereof Download PDFInfo
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- 238000001514 detection method Methods 0.000 claims abstract description 42
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- QJXJWGINTRVDEA-UHFFFAOYSA-N mercury;5-methyl-1h-pyrimidine-2,4-dione Chemical compound [Hg].CC1=CNC(=O)NC1=O.CC1=CNC(=O)NC1=O QJXJWGINTRVDEA-UHFFFAOYSA-N 0.000 claims description 6
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- 239000012279 sodium borohydride Substances 0.000 claims description 6
- 229910000033 sodium borohydride Inorganic materials 0.000 claims description 6
- 239000001509 sodium citrate Substances 0.000 claims description 6
- NLJMYIDDQXHKNR-UHFFFAOYSA-K sodium citrate Chemical compound O.O.[Na+].[Na+].[Na+].[O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O NLJMYIDDQXHKNR-UHFFFAOYSA-K 0.000 claims description 6
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- 125000003396 thiol group Chemical group [H]S* 0.000 claims description 4
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- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
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Abstract
The invention provides an electrochemical sensor for detecting mercury and a preparation method and application thereof, wherein the electrochemical sensor comprises a glassy carbon electrode, a probe P2 and a mercapto-modified probe P3 fixed on a nano gold particle; the surface of the detection end of the glassy carbon electrode is modified with carbon-doped graphene-like carbon nitride, gold nanoparticles are deposited on the carbon-doped graphene-like carbon nitride, a sulfhydryl-modified probe P1 is connected to the gold nanoparticles, part of deoxyribonucleotide of the probe P2 and part of deoxyribonucleotide of the sulfhydryl-modified probe P1 are complementarily paired to form a double-chain structure, and unpaired deoxyribonucleotide of the probe P1 and the probe P2 and sulfhydryl-modified probe P3 fixed on the gold nanoparticles can form the double-chain structure. The preparation method comprises the steps of modifying carbon-doped graphene-phase carbon nitride, modifying nanogold, modifying a probe P1 and the like. The electrochemical sensor has strong heavy metal ion interference resistance and can be applied to detecting mercury ions.
Description
Technical Field
The invention relates to the technical field of genes, in particular to an electrochemical sensor for detecting mercury and a preparation method and application thereof.
Background
At present, methods for determining pollutants in the environment are mainly chromatograms, uv spectroscopy, simultaneous fluorescence spectroscopy, spectrophotometry, derivative photometry, flow injection analysis, and the like. The methods have the defects of complex pretreatment, long time consumption, large sample matrix effect, long analysis period and the like, have higher requirements on the operation water average of instruments and workers, and are difficult to popularize and apply in small and medium-sized enterprises. For example: when the spectrophotometry is adopted to detect the pollutants, the accuracy and the application range of the pollutants are limited due to the requirements on the turbidity of the substrate and the influence of light interference substances; and liquid chromatography and gas chromatography are adopted for detection, a sample needs to be separated before detection, the separation process usually needs pretreatment, the operation steps are relatively complicated and time-consuming, and a detection instrument is relatively expensive, is inconvenient to carry and cannot carry out real-time detection.
The electrochemical biosensor is a new technology for quantitatively detecting substances to be detected by specifically identifying the substances to be detected based on biological organic components (such as enzyme, antibody, nucleic acid, cells, microorganisms and the like) and converting generated signals into electric signals and optical signals through a signal conductor. The electrochemical biosensor is used for detecting heavy metals, pathogenic microorganisms and harmful organic matters in the environment, and has the characteristics of strong specificity, high detection sensitivity, high detection efficiency and low cost, so the electrochemical biosensor becomes a research hotspot in the environment protection work.
Currently, researchers modify electrochemical biosensors using various novel materials to improve the stability, reproducibility, and structural reliability of electrochemical biosensors. The key to making an electrochemical DNA sensor is how to efficiently immobilize a DNA probe on gold and maintain its activity, which is a prerequisite for the sensor to be able to detect. In general, there are two methods of fixing a DNA probe on a gold surface, i.e., fixing the DNA probe by modifying the DNA probe and fixing the DNA probe directly without modifying the DNA probe. These methods have disadvantages such as weak immobilization, use of various affinity substances for immobilization, influence on the activity of DNA, and easy use of substances harmful to the environment.
Disclosure of Invention
The technical problem to be solved by the invention is to overcome the defects of the prior art, provide an electrochemical sensor for detecting mercury, which has the advantages of simple manufacture, good stability, high sensitivity and detection precision and strong capability of resisting the interference of other common heavy metal ions in the environment, and correspondingly provide a preparation method of the electrochemical biosensor, so that a preparation method which has the advantages of simple process and rapid manufacture is used for ensuring that a fixed DNA probe has better stability and high activity; on the basis, the application of the electrochemical sensor is further provided, and the high-efficiency detection of the lead in the water body can be realized by the characteristics of simplified operation, quick response, high detection precision, strong anti-interference performance and the like.
In order to solve the above technical problems, the present invention provides an electrochemical sensor for detecting mercury, comprising a glassy carbon electrode used as a working electrode in a three-electrode system, the surface of the detection end of the glassy carbon electrode is modified with carbon-doped graphene-like carbon nitride, nano-gold particles are deposited on the carbon-doped graphene-like carbon nitride, a mercapto-modified probe P1 is connected to the nano-gold particles, the electrochemical sensor also comprises a probe P2 and a mercapto-modified probe P3 fixed on the gold nanoparticles, the deoxyribonucleotide of the probe P2 can be complementarily paired with the deoxyribonucleotide of the sulfhydryl-modified probe P1 through thymine-mercury-thymine to form a double-stranded structure, the unpaired deoxyribonucleotide in the probe P1 and the probe P2 can form a double-stranded structure with the sulfhydryl-modified probe P3 immobilized on the gold nanoparticle through base complementary pairing.
In the above electrochemical sensor, preferably, the probe P1 has a nucleotide sequence shown in SEQ ID No. 1; the probe P2 is a nucleotide sequence shown in SEQ ID NO. 2; the probe P3 is a nucleotide sequence shown in SEQ ID NO. 3.
The electrochemical sensor preferably further comprises a signal indicator, wherein the signal indicator is embedded in the double-stranded structure formed by the probe P1 and the probe P2, the double-stranded structure formed by the probe P1 and the probe P3, and the double-stranded structure formed by the probe P2 and the probe P3.
In the electrochemical sensor, preferably, the signal indicator is methylene blue, and the concentration of the methylene blue is 0.1 to 0.5 mM.
As a general technical concept, the present invention also provides a method for manufacturing the electrochemical sensor as claimed above, comprising the steps of:
s1, preparing carbon-doped graphene-like carbon nitride into a suspension, and dropwise adding the suspension to the surface of the detection end of the glassy carbon electrode to obtain the glassy carbon electrode modified by the carbon-doped graphene-like carbon nitride;
s2, electrodepositing nano gold particles on the surface of the detection end of the glassy carbon electrode modified by the carbon-doped graphene-like phase carbon nitride to obtain a nano gold/carbon-doped graphene-like phase carbon nitride modified glassy carbon electrode;
s3, inserting a glassy carbon electrode modified by nano-gold/carbon-doped graphene-like carbon nitride into a mercapto-modified probe P1, wherein the mercapto-modified probe P1 is electrostatically adsorbed on nano-gold particles; and then inserting the probe into a mercaptoethanol solution to seal the unadsorbed nanogold by mercaptoethanol, thereby obtaining the probe P1/nanogold/carbon-doped graphene-phase carbon nitride modified glassy carbon electrode.
The preparation method preferably further comprises the steps of preparing a probe P2 solution and a thiol-modified probe P3 solution immobilized on the gold nanoparticles; the specific steps for preparing the sulfhydryl-modified probe P3 solution fixed on the gold nanoparticles are as follows: mixing ultrapure water, a chloroauric acid solution and a sodium citrate solution uniformly, adding a sodium borohydride solution while stirring, and then placing in a dark place for reaction to obtain a nano gold particle solution; and mixing the probe P3 with the nano-gold particle solution to obtain a sulfhydryl group modified probe P3 fixed on the nano-gold particles.
In the above preparation method, preferably, the mass ratio of the ultrapure water, the chloroauric acid solution, the sodium citrate solution and the sodium borohydride solution is 9.2: 0.0005-0.0011: 0.0007: 0.0011, and the concentration ratio of the probe P3 to the gold nanoparticle solution is 2: 0.001-0.002.
In the above preparation method, preferably, in the step S1, the carbon-doped graphene-like carbon nitride is prepared by the following method: reacting melamine with absolute ethyl alcohol at the temperature of 200-220 ℃ for 24-25 h, then heating to 520-530 ℃ at the rising speed of 2-3 ℃/min, and calcining at 520-530 ℃ for 4-4.5 h to obtain the carbon-doped graphene-like carbon nitride.
In the above preparation method, preferably, in the step S2, the specific steps of electrodeposition are: HAuCl with the mass fraction of 1 percent4And mixing the aqueous solution and perchloric acid to obtain a mixed solution, putting the glassy carbon electrode modified by the carbon-doped graphene-like phase carbon nitride into the mixed solution to perform current-time curve scanning, wherein the initial potential of an electrochemical deposition method is 0V, the sampling interval is 0.1s, and the time is 30-100 s, so that the glassy carbon electrode modified by the nano-gold/carbon-doped graphene-like phase carbon nitride is obtained.
In the preparation method, preferably, the step S3 specifically includes: inserting a glassy carbon electrode modified by nano-gold/carbon-doped graphene-like carbon nitride into a probe P1 with the concentration of 1.0 mu M, and adsorbing the probe P1 on nano-gold particles through chemistry and static electricity; and then inserting the membrane into a mercaptoethanol solution with the concentration of 2.0mM to seal the unadsorbed nanogold by mercaptoethanol, thereby obtaining the probe P1/nanogold/carbon-doped graphene-like carbon nitride modified glassy carbon electrode.
As a general technical concept, the invention also provides an application of the electrochemical sensor or the electrochemical sensor prepared by the preparation method in detection of mercury ions.
The application method comprises the following steps:
(1) soaking the probe P1/nanogold/carbon-doped graphene-like carbon nitride modified glassy carbon electrode in a mixed solution of mercury and a probe P2, and carrying out thymine-mercury-thymine complementary pairing on the probe P1, the mercury and the probe P2 to obtain a probe P2/probe P1/nanogold/carbon-doped graphene-like carbon nitride modified glassy carbon electrode;
(2) reacting the probe P2/probe P1/nanogold/carbon-doped graphene-like carbon nitride modified glassy carbon electrode with a probe P3 fixed on nanogold particles, so that the probe P3 forms double chains with the probe P1 and the probe P2 respectively to obtain a probe P3/probe P2/probe P1/nanogold/carbon-doped graphene-like carbon nitride modified glassy carbon electrode;
(3) soaking the probe P3/probe P2/probe P1/nanogold/carbon-doped graphene-like carbon nitride modified glassy carbon electrode in a signal indicator for reaction; cleaning, air drying, soaking in 10mM Tris-HCl buffer solution,
(4) detecting a current value in an electrolytic cell accessed to the three-electrode system, and establishing a linear regression equation according to the concentration and the current value of lead ions:
Y＝(2.288±0.0.085)χ+(1.072±0.042)
wherein, Y is the average value of current when detecting mercury ions, and the unit is muA; chi is the concentration of mercury ions in the solution to be measured, and the concentration unit of the mercury ions is nM; r20.993, the detection range of 0.01-1 nM, and the lowest detection concentration of 3.7X 10- 11M。
In the above application, preferably, in the step (1), the reaction time of the probe P1, mercury and the probe P2 is 10-50 min.
In the above application, preferably, in the step (2), the reaction temperature of the probe P2/the probe P1/the nanogold/carbon-doped graphene-like carbon nitride modified glassy carbon electrode and the probe P3 fixed on the nanogold particles is 37 ℃, and the reaction time is 30-90 min.
In the above application, preferably, in the step (3), the probe P3/the probe P2/the probe P1/the nanogold/carbon-doped graphene-like carbon nitride modified glassy carbon electrode is soaked in the signal indicator for a reaction time of 10 to 30 min.
In the above application, preferably, in the step (4), Tris-HCl with pH of 5.5 to 9.0 is used as an electrolyte solution.
Compared with the prior art, the invention has the advantages that:
(1) the invention provides an electrochemical sensor for detecting mercury, which is characterized in that a glassy carbon electrode is modified by carbon-doped graphene-like carbon nitride and nano gold particles, and the surface of a detection end of the glassy carbon electrode is modified in a nano gold/carbon-doped graphene-like carbon nitride multilayer material combination mode, so that the microstructure of the surface of a reaction end is optimized. The carbon-doped graphene-phase carbon nitride is a stable nano material, has good dispersibility and biocompatibility, can effectively maintain the bioactivity, is simple and convenient to manufacture, has low cost and the like, and is an excellent electric signal transmission medium; the nano gold particles have good affinity and biocompatibility to biological molecules, can remarkably improve the transfer speed of electrons between the biosensor and a solution to be detected, and can quickly obtain stable response current. The electrochemical sensor of the invention can improve the high efficiency and sensitivity of detection by utilizing the characteristics of the material. The invention fully considers the respective properties of the carbon-doped graphene-phase carbon nitride, the nanogold, the methylene blue and the DNA, and utilizes the composite film formed by the carbon-doped graphene-phase carbon nitride, the nanogold, the methylene blue and the DNA, thereby having the characteristics of high sensitivity, quick response, high detection precision, strong anti-interference performance and the like.
(2) The invention provides an electrochemical sensor for detecting mercury, which adopts a probe P3 to seal P1 and P2, generates hybridization reaction and improves current signals; the reason why P3 is immobilized on the gold nanoparticles is that the gold nanoparticles have excellent conductivity and can enhance the electrical signal of the hybridization reaction.
(3) The invention provides a preparation method of an electrochemical sensor for detecting mercury, which has simple process and rapid preparation, and ensures that the fixed DNA probe has better stability and high activity.
(4) The application of the electrochemical sensor in detecting mercury ions provided by the invention is simple and convenient to operate, high in efficiency and low in detection cost, and an effective molecular biological detection method is provided for the monitoring and control process of mercury in a water body.
Drawings
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention.
Fig. 1 is a flow chart illustrating the structure and fabrication of an electrochemical sensor according to example 1.
Fig. 2 is a scanning electron microscope image of the detection end surface of the glassy carbon electrode modified by carbon-doped graphene-like carbon nitride in example 2.
Fig. 3 is a carbon content energy spectrum of the detection end surface of the glassy carbon electrode modified by carbon-doped graphene-like phase carbon nitride in example 2.
Fig. 4 is a scanning electron microscope image of the surface of the detection end of the glassy carbon electrode modified by the nanogold/carbon-doped graphene-like phase carbon nitride in example 2.
FIG. 5 is a graph showing the change in current obtained by measuring different concentrations of mercury using square wave voltammetry in example 3.
FIG. 6 is a linear regression plot of mercury content versus current change for example 3.
FIG. 7 is a graph comparing the selectivity of the electrochemical sensor in example 3.
Detailed Description
The invention is further described below with reference to the drawings and specific preferred embodiments of the description, without thereby limiting the scope of protection of the invention.
The materials and equipment used in the following examples are commercially available.
Example 1
An electrochemical sensor for detecting mercury of the present invention, see fig. 1: the device comprises a glassy carbon electrode used as a working electrode in a three-electrode system, wherein the surface of the detection end of the glassy carbon electrode is modified with carbon-doped graphene-like carbon nitride, and nano gold particles are deposited on the carbon-doped graphene-like carbon nitride. Because the gold nanoparticles have available adsorption sites, a sulfhydryl-modified probe P1 is added on the glassy carbon electrode, sulfhydryl is adsorbed on the sites of the gold nanoparticles, and then mercaptoethanol is added to seal the sites of the gold nanoparticles which are not adsorbed by sulfhydryl. Then adding a probe P2, wherein the deoxyribonucleotide of the probe P2 and the deoxyribonucleotide of the sulfhydryl-modified probe P1 can form a double-chain structure through thymine-mercury-thymine complementary pairing, and the unpaired deoxyribonucleotide of the probe P1 and the unpaired deoxyribonucleotide of the probe P2 are respectively subjected to base complementary pairing with the sulfhydryl-modified probe P3 fixed on the gold nanoparticle (the gold nanoparticle fixed with the probe P3 is the gold nanoparticle manufactured by a chemical reduction method).
Wherein, the probe P1 preferably has a deoxyribonucleotide sequence shown in SEQ ID NO.1, and specifically comprises the following components:
5’-SH-CTGTTTCGTTCCCGAAAGAGGAAG-3’；
the probe P2 preferably has a nucleotide sequence shown in SEQ ID NO.2, and specifically comprises the following components:
5’-AAAGAGGAAGGCCCTTCGTTTCTG-3’；
the probe P3 preferably has a nucleotide sequence shown in SEQ ID NO.3, and specifically comprises the following components:
5’-SH-CTTCCTCTTT-3’
when mercury ions exist in the detected water body, the mercury ions and thymine in the probe have stronger binding force, so that the probe P1 and the probe P2 are subjected to hybridization reaction to form a DNA double-helix structure, namely: wherein the "CTGTTTCGTT" at the 5 'end of probe P1 is complementarily paired with the "TTCGTTTCTG" at the 3' end of probe P2. While some unpaired deoxyribonucleotides also exist in probe P1 and probe P2, probe P3 forms a DNA double helix structure by complementary pairing with "AAAGAGGAAG" at the 3 'end of probe P1 and "AAAGAGGAAG" at the 5' end of probe P2, respectively.
Methylene blue is embedded in the gaps of the double helix structure of DNA. Current change is generated in the process of forming double chains by DNA, and simultaneously, the change of the current is expanded by the nano gold particles, and methylene blue is an electric signal indicator. Because the magnitude of the current change is related to the concentration of the DNA double strands, and the concentration of the DNA double strands is related to the concentration of the mercury ions, the electrochemical sensor is prepared according to the current change principle, and the concentration of the mercury ions in the water body can be effectively detected.
Example 2
A method of making the electrochemical sensor of embodiment 1, comprising:
(1) preparing carbon-doped graphene-like phase carbon nitride:
1g of melamine is put into a reaction kettle with the volume of 100mL, 80mL of absolute ethyl alcohol is injected, and the reaction is carried out for 24 hours at the temperature of 200 ℃ to obtain a colorless transparent product. And drying the colorless transparent product at room temperature, wrapping the product by using tinfoil, transferring the product into a muffle furnace, heating the product to 520 ℃ at the speed of 2 ℃/min, and calcining the product for 4 hours at 520 ℃ to obtain the carbon-doped graphene-like carbon nitride.
(2) Pretreating a glassy carbon electrode:
polishing the surface of a Glassy Carbon Electrode (GCE), washing the surface of the glassy carbon electrode with water, sequentially washing with nitric acid, acetone and ultrapure water, finally washing with a Tris-HCl buffer solution (containing 1.0M KCl in the Tris-HCl buffer solution) with the pH value of 7.4 and the concentration of 10mM, and naturally drying to obtain the pretreated glassy carbon electrode.
(3) Preparing a glassy carbon electrode modified by carbon-doped graphene-like carbon nitride:
3.1, dissolving the carbon-doped graphene-like phase carbon nitride prepared in the step 1 in ultrapure water, performing ultrasonic treatment for 10 hours, centrifuging, filtering, and performing vacuum drying at the temperature of 60 ℃ for 24 hours to obtain the stripped flaky carbon-doped graphene-like phase carbon nitride. The carbon-doped graphene-like carbon nitride is of a blocky structure after being calcined, the conductivity is poor, and the conductivity of the stripped flaky structure is greatly improved.
And 3.2, putting the flake carbon-doped graphene-phase carbon nitride into N, N-dimethylformamide to prepare a suspension with the concentration of 0.05mg/mL, then dropwise adding the suspension onto the surface of the detection end of the glassy carbon electrode, and carrying out air drying at normal temperature to obtain the glassy carbon electrode modified by the carbon-doped graphene-phase carbon nitride.
(4) And (3) electrodeposition of nano gold particles:
to 5mL of HAuCl with the mass fraction of 1%4Adding 200 mu L of perchloric acid into the aqueous solution to prepare a mixed solution, putting the glassy carbon electrode modified by the carbon-doped graphene-like phase carbon nitride into the mixed solution, and scanning by a current-time curve (I-T) method, wherein the initial potential of an electrochemical deposition method is 0V, the sampling interval is 0.1s, and the time is 30-100 s, so as to obtain the glassy carbon electrode modified by the nano-gold/carbon-doped graphene-like phase carbon nitride, and airing for later use.
(5) Modified probe P1:
inserting a glassy carbon electrode modified by nano-gold/carbon-doped graphene-like carbon nitride into a probe P1 (a probe P1 is a deoxyribonucleotide sequence shown in SEQ ID NO. 1) with the concentration of 1.0 mu M (the probe P1 is a mercapto-modified probe P1), and adsorbing the probe P1 on nano-gold particles through chemistry and static electricity; and then inserting the membrane into a mercaptoethanol solution with the concentration of 2.0mM to seal the unadsorbed nanogold by mercaptoethanol, thereby obtaining the probe P1/nanogold/carbon-doped graphene-like carbon nitride modified glassy carbon electrode.
(6) Adding chloroauric acid solution and sodium citrate solution into ultrapure water respectively, adding sodium borohydride solution while stirring, and then placing in the dark for reaction. The mass ratio of the ultrapure water to the chloroauric acid solution to the sodium citrate solution to the sodium borohydride solution is 9.2: 0.0010: 0.0007: 0.0011, and then the nano-gold particle solution is obtained. Mixing the probe P3 with the nano-gold particle solution, wherein the concentration ratio is 2: 0.025; and finishing the preparation of the electrochemical sensor.
And (3) respectively carrying out electron microscope and energy spectrum scanning on the glassy carbon electrode modified by the carbon-doped graphene-like phase carbon nitride prepared in the step (3) and the nano-gold/glassy carbon electrode modified by the carbon-doped graphene-like phase carbon nitride prepared in the step (4), wherein the scanning results are shown in figures 2, 3 and 4.
As can be seen from fig. 2 and 3: the surface of the detection end of the glassy carbon electrode is modified with carbon-doped graphene-phase carbon nitride, and carbon is successfully doped in the graphene-phase carbon nitride (figures 2 and 3);
the gold nanoparticles are electrodeposited on the detection end surface of the glassy carbon electrode modified by the carbon-doped graphene-like phase carbon nitride (fig. 4).
Example 3
An application of the electrochemical sensor of embodiment 1 in detecting mercury ions is as follows:
(1) the probes P2 were separately contacted with a gradient concentration of mercury ions (concentration of mercury ions was 10, respectively)-7M、5.0×10-8M、1.0×10-8M、5.0×10-9M、1.0×10-9M、5.0×10-10M、1.0×10-10M、5.0×10-11M、2.0×10-11M、1.0×10-11M) was mixed well and the concentration of probe P2 was 1. mu.M.
(2) And soaking the probe P1/nano-gold/carbon-doped graphene-like carbon nitride modified glassy carbon electrode in a mixed solution of mercury and the probe P2, so that the probe P1, the mercury and the probe P2 react for 30min at normal temperature.
(3) And (3) reacting the glassy carbon electrode obtained in the step (2) with P3 fixed on the surface of the nano gold particles at 37 ℃ for 60min (the reaction time can be implemented within 30-90 min), wherein the concentration of a probe P3 is 2 mu M.
(4) Soaking the glassy carbon electrode of the assembled electrochemical sensor obtained in the step (3) in methylene blue solution (the concentration of the methylene blue is 2 multiplied by 10)-5M) fully reacting for 15min (the reaction time can be implemented for 10-30 min), cleaning, airing, and then soaking in 10mM Tris-HCl buffer solution for 15 min. (the reaction time can be implemented within 10-30 min), then the sample is connected into an electrolytic cell of a three-electrode system, Tris-HCl with the pH value of 7.4 is used as an electrolyte solution, and the current value is detected.
FIG. 5 shows that the concentrations of mercury ions are 10-7M(a)、5.0×10-8M(b)、1.0×10-8M(c)、5.0×10-9M(d)、1.0×10-9M(e)、5.0×10-10M(f)、1.0×10-10M(g)、5.0×10-11M(h)、2.0×10-11M(i)、1.0×10-11M (j) square wave voltammograms (SWV curves) of the test solutions. Fig. 6 is a linear regression equation of mercury ion concentration versus current change. As can be seen from fig. 5 and 6, the linear regression equation of the concentration of mercury ions and the current value is:
Y＝(2.288±0.0.085)χ+(1.072±0.042)
wherein, Y is the average value of current when detecting mercury ions, and the unit is muA; chi is the concentration of mercury ions in the solution to be measured, and the concentration unit of the mercury ions is nM; r20.993, the detection range of 0.01-1 nM, and the lowest detection concentration of 3.7X 10- 11M。
In the application process, the electrolyte solution in the electrolytic cell is preferably Tris-HCl buffer solution with the pH value of 5.5-9.0.
As can be seen from fig. 5 and 6: the electrochemical sensor of example 1 had a minimum detectable concentration of 1.0X 10-14M mercury solution has high sensitivity and high detection accuracy.
Experiment 1:
to further verify the detection effect of the electrochemical sensor and the detection method of the present example, a recovery rate test was performed using the electrochemical sensor of example 1 for a solution to be measured of tap water, Yuenu mountain spring water, and Xiangjiang water (the measurement method was referred to in example 3).
Pretreatment of the solution to be detected: taking an environmental water sample, filtering, centrifuging the filtrate for 5min under the condition of 10000r/min, taking supernatant, and filtering to obtain a solution to be detected.
A detection step: the electrochemical sensor of example 1 was used to detect the solution to be measured.
Dripping 1 mu M of probe P2 and mercury mixed solution on the reaction end surface of a glassy carbon electrode of an electrochemical sensor, reacting for 30 minutes at room temperature, dripping 2 mu M of probe P3 (needing to be fixed by nano-gold particles) on the reaction end surface of the glassy carbon electrode, and reacting for 60 minutes at 37 ℃; and then soaking the assembled glassy carbon electrode of the electrochemical sensor in a methylene blue solution for sufficient reaction for 15min, washing, airing, soaking in a 10mM Tris-HCl buffer solution, then inoculating into a 20mL electrolytic cell of a three-electrode system, and detecting the current value by taking Tris-HCl with the pH of 7.4 as an electrolyte solution. And according to the strength of the generated current signal, the concentration and the content of the mercury ions in the environmental water sample to be detected correspond. The results are shown in Table 1.
Table 1: recovery rate verification results of three groups of environmental samplesa
| mol.L of sample to be measured-1 | Adding the mercury with the concentration of nmol.L-1 | Test results (10) | Recovery (%) |
| |
10 | 98.58±0.24 | 98.7 |
| Spring water of Yuenu mountain | 50 | 50.04±0.12 | 100.3 |
| |
100 | 104.01±0.31 | 106.3 |
Note: a represents the measured average concentration.
As can be seen from the results in table 1, the electrochemical sensor of example 1 has a high recovery rate and high accuracy in detecting mercury ions.
Experiment 2:
to verify the selectivity of the electrochemical sensor of this example, K is now applied at a concentration of 20nM+、Ca2+、Mg2+、Al3 +、Zn2+、Fe3+、Cu2+、Pb2+、Cd2+、Cr2+、Ni+With Hg2+The metal ion test solution was measured by using the electrochemical sensor of example 1.
A detection step: see example 3.
The detection results are shown in fig. 7, and it can be seen from fig. 7 that: the electrochemical sensor has high selectivity to mercury ions and strong anti-interference capability.
The determination result shows that the method has high sensitivity, good selectivity and good stability, can measure the lead content on line with high efficiency and low cost, and provides technical support for the monitoring and control process of mercury in the water body.
The foregoing is merely a preferred embodiment of the invention and is not intended to limit the invention in any manner. Although the present invention has been described with reference to the preferred embodiments, it is not intended to be limited thereto. Those skilled in the art can make many possible variations and modifications to the disclosed embodiments, or equivalent modifications, without departing from the spirit and scope of the invention, using the methods and techniques disclosed above. Therefore, any simple modification, equivalent replacement, equivalent change and modification made to the above embodiments according to the technical essence of the present invention are still within the scope of the protection of the technical solution of the present invention.
Claims (9)
1. An electrochemical sensor for the detection of mercury comprising a glassy carbon electrode as the working electrode in a three-electrode system, the surface of the detection end of the glassy carbon electrode is modified with carbon-doped graphene-like carbon nitride, nano-gold particles are deposited on the carbon-doped graphene-like carbon nitride, a mercapto-modified probe P1 is connected to the nano-gold particles, the electrochemical sensor also comprises a probe P2 and a mercapto-modified probe P3 fixed on the gold nanoparticles, the deoxyribonucleotide of the probe P2 can be complementarily paired with the deoxyribonucleotide of the sulfhydryl-modified probe P1 through thymine-mercury-thymine to form a double-stranded structure, the unpaired deoxyribonucleotide in the probe P1 and the probe P2 can form a double-stranded structure with the sulfhydryl-modified probe P3 fixed on the gold nanoparticle through base complementary pairing; the probe P1 has a nucleotide sequence shown in SEQ ID NO. 1; the probe P2 is a nucleotide sequence shown in SEQ ID NO. 2; the probe P3 is a nucleotide sequence shown in SEQ ID NO. 3;
the deoxyribonucleotide sequence shown by SEQ ID NO.1 is as follows: 5 '-SH-CTGTTTCGTTCCCGAAAGAGGAAG-3';
the nucleotide sequence shown by SEQ ID NO.2 is as follows: 5'-AAAGAGGAAGGCCCTTCGTTTCTG-3', respectively;
the nucleotide sequence shown in SEQ ID NO.3 is as follows: 5 '-SH-CTTCCTCTTT-3'.
2. The electrochemical sensor according to claim 1, further comprising a signal indicator embedded in the double-stranded structure formed by the probe P1 and the probe P2, the double-stranded structure formed by the probe P1 and the probe P3, and the double-stranded structure formed by the probe P2 and the probe P3.
3. The electrochemical sensor according to claim 2, wherein the signal indicator is methylene blue, and the concentration of the methylene blue is 0.1 to 0.5 mM.
4. A method of manufacturing an electrochemical sensor according to any one of claims 1 to 3, comprising the steps of:
s1, preparing carbon-doped graphene-like carbon nitride into a suspension, and dropwise adding the suspension to the surface of the detection end of the glassy carbon electrode to obtain the glassy carbon electrode modified by the carbon-doped graphene-like carbon nitride;
s2, electrodepositing nano gold particles on the surface of the detection end of the glassy carbon electrode modified by the carbon-doped graphene-like phase carbon nitride to obtain a nano gold/carbon-doped graphene-like phase carbon nitride modified glassy carbon electrode;
s3, inserting a glassy carbon electrode modified by nano-gold/carbon-doped graphene-like carbon nitride into a mercapto-modified probe P1, wherein the mercapto-modified probe P1 is chemically and electrostatically adsorbed on nano-gold particles; then inserting the probe into a mercaptoethanol solution to seal the unadsorbed nanogold by mercaptoethanol to obtain a probe P1/nanogold/carbon-doped graphene-phase carbon nitride modified glassy carbon electrode;
s4, soaking the probe P1/nanogold/carbon-doped graphene-like phase carbon nitride modified glassy carbon electrode in a mixed solution of mercury and a probe P2, and carrying out thymine-mercury-thymine complementary pairing on the probe P1, the mercury and the probe P2 to obtain a probe P2/probe P1/nanogold/carbon-doped graphene-like phase carbon nitride modified glassy carbon electrode;
s5, reacting the probe P2/probe P1/nanogold/carbon-doped graphene-like carbon nitride modified glassy carbon electrode with the probe P3 fixed on nanogold particles, and enabling the probe P3 to form double chains with the probe P1 and the probe P2 respectively to obtain the electrochemical sensor.
5. The method according to claim 4, further comprising preparing a probe P2 solution and a thiol-modified probe P3 solution immobilized on the gold nanoparticles; the specific steps for preparing the sulfhydryl-modified probe P3 solution fixed on the gold nanoparticles are as follows: mixing ultrapure water, a chloroauric acid solution and a sodium citrate solution uniformly, adding a sodium borohydride solution while stirring, and then placing in a dark place for reaction to obtain a gold nanoparticle solution; and mixing the probe P3 with the nano-gold particle solution to obtain a sulfhydryl group modified probe P3 fixed on the nano-gold particles.
6. The method according to claim 5, wherein the mass ratio of the ultrapure water to the chloroauric acid solution to the sodium citrate solution to the sodium borohydride solution is 9.2: 0.0005 to 0.0011: 0.0007: 0.0011, and the concentration ratio of the probe P3 to the gold nanoparticle solution is 2: 0.001 to 0.002.
7. The production method according to any one of claims 4 to 6,
in the step S1, the carbon-doped graphene-like carbon nitride is prepared by the following method: reacting melamine with absolute ethyl alcohol at the temperature of 200 ℃ for 24h, then heating to 520 ℃ at the speed of 2 ℃/min, and calcining at 520 ℃ for 4h to obtain carbon-doped graphene-like carbon nitride;
and/or in the step S1, the specific step of preparing the carbon-doped graphene-like phase carbon nitride into a suspension comprises: peeling the carbon-doped graphene-like phase carbon nitride into flaky carbon-doped graphene-like phase carbon nitride, and dispersing the flaky carbon-doped graphene-like phase carbon nitride in N, N-dimethylformamide to prepare a suspension;
and/or in the step S2, the specific steps of electrodeposition are: HAuCl with the mass fraction of 1 percent4Mixing the aqueous solution and perchloric acid to obtain a mixed solution, putting the glassy carbon electrode modified by the carbon-doped graphene-like phase carbon nitride into the mixed solution to perform current-time curve scanning, wherein the initial potential of an electrochemical deposition method is 0V, the sampling interval is 0.1s, and the time is 30-100 s, so that the glassy carbon electrode modified by the nano-gold/carbon-doped graphene-like phase carbon nitride is obtained;
and/or the step of S3 is specifically: inserting a glassy carbon electrode modified by nano-gold/carbon-doped graphene-like carbon nitride into a probe P1 with the concentration of 1.0 mu M, and adsorbing the probe P1 on nano-gold particles through chemistry and static electricity; and then inserting the membrane into a mercaptoethanol solution with the concentration of 2.0mM to seal the unadsorbed nanogold by mercaptoethanol, thereby obtaining the probe P1/nanogold/carbon-doped graphene-like carbon nitride modified glassy carbon electrode.
8. The use of the electrochemical sensor according to any one of claims 1 to 3 or the electrochemical sensor prepared by the preparation method according to any one of claims 4 to 7 in the detection of mercury ions, characterized in that the application method comprises the following steps:
(1) soaking the probe P1/nanogold/carbon-doped graphene-like carbon nitride modified glassy carbon electrode in a mixed solution of mercury and the probe P2, and carrying out thymine-mercury-thymine complementary pairing on the probe P1, the mercury and the probe P2 to obtain a probe P2/probe P1/nanogold/carbon-doped graphene-like carbon nitride modified glassy carbon electrode;
(2) reacting the probe P2/probe P1/nanogold/carbon-doped graphene-like carbon nitride modified glassy carbon electrode with a probe P3 fixed on nanogold particles, so that the probe P3 forms double chains with the probe P1 and the probe P2 respectively to obtain a probe P3/probe P2/probe P1/nanogold/carbon-doped graphene-like carbon nitride modified glassy carbon electrode;
(3) soaking the probe P3/probe P2/probe P1/nanogold/carbon-doped graphene-like carbon nitride modified glassy carbon electrode in a signal indicator for reaction; cleaning, airing and then soaking in 10mM Tris-HCl buffer solution;
(4) detecting a current value in an electrolytic cell accessed to the three-electrode system, and establishing a linear regression equation according to the concentration and the current value of mercury ions:
Y = (2.288± 0.085) χ+ (1.072 ± 0.042)
wherein, Y is the average value of current when detecting mercury ions, and the unit is muA; chi is the concentration of mercury ions in the solution to be measured, and the concentration unit of the mercury ions is nM; r20.993, the detection range of 0.01-1 nM, and the lowest detection concentration of 3.7X 10-11M。
9. The use according to claim 8, wherein in the step (1), the probe P1, mercury and the probe P2 are reacted for 10-50 min;
and/or in the step (2), the reaction temperature of the probe P2/probe P1/nanogold/carbon-doped graphene-like carbon nitride modified glassy carbon electrode and the probe P3 fixed on the nanogold particles is 37 ℃, and the reaction time is 30-90 min;
and/or, in the step (3), the probe P3/the probe P2/the probe P1/the nanogold/carbon-doped graphene-like carbon nitride modified glassy carbon electrode is soaked in a signal indicator for reaction for 10-30 min;
and/or, in the step (4), Tris-HCl with the pH value of 5.5-9.0 is used as an electrolyte solution.
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