CN112697855A - Method for detecting concentration of mercury ions based on photoelectrochemical sensor - Google Patents
Method for detecting concentration of mercury ions based on photoelectrochemical sensor Download PDFInfo
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- G—PHYSICS
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- 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 application relates to a method for detecting mercury ion concentration based on a photoelectrochemical sensor. The method comprises the following steps: adding the solution to be detected into a photoelectrochemical sensor with a composite electrode, identifying mercury ions through a specific modifier, and calculating the concentration of the mercury ions according to the change quantity of the photocurrent value generated by the photoelectrochemical sensor before and after the mercury ions in the solution to be detected react with sulfur ions. The scheme provided by the application can realize high specificity and high sensitivity photoelectrochemistry sensing detection of mercury ions.
Description
Technical Field
The application relates to the technical field of photoelectrochemistry detection, in particular to a mercury ion concentration detection method based on a photoelectrochemical sensor.
Background
Heavy metal poisoning is a serious worldwide problem related to human health and the environment. Mercury ions, one of the most toxic heavy metal elements, even at very low concentrations, can have a tremendous impact on human health and the natural environment. As the mercury ions have the characteristics of nondegradable and easy accumulation in organisms, the mercury ions are easily transmitted by a human body through a food chain to be enriched in the human body, so that the problems of cardiovascular diseases, serious cognitive impairment and the like are caused, and the health of the human body is threatened. Therefore, it is necessary to detect mercury ions in the daily environment, particularly in water.
In the related art, a commonly used mercury ion detection method includes atomic absorption spectrometry, which converts mercury into an ionic state by acid digestion or catalytic acid digestion, reduces stannous chloride into elemental mercury in a strong acid medium, blows the elemental mercury into a mercury tester by taking nitrogen or dry air as a carrier, measures an atomic absorption value, and calculates the mercury content based on the absorption value. The method can carry out high-sensitivity detection on the mercury ions, but the method has the disadvantages of complex operation, high cost, expensive equipment and long detection time, and is not suitable for the field detection of the mercury ions.
Based on the above situation, the prior art proposes a photoelectrochemical sensor technology based on the principle that mercury ions and an organic reagent are directly or indirectly complexed to generate absorbance change and based on the redox property of the mercury ions to detect the mercury ions, the method is simple, economical and rapid, but because the mercury ions in an ecological environment always exist along with a large amount of other ions, and a single-material photoelectric sensor has poor photoelectric conversion efficiency and small photocurrent, in practical application, the following defects still exist:
1. the specificity recognition mechanism for mercury ions is lacked, and specificity detection cannot be carried out;
2. the photoelectric conversion capability of the sensor is not enough, so that the sensitivity of the photoelectrochemical sensor is low, and the detection result is inaccurate and unstable.
Disclosure of Invention
In order to overcome the problems in the related art, the application provides a mercury ion concentration detection method based on a photoelectrochemical sensor, and the method is used for detecting the mercury ion concentration of an object to be detected based on the photoelectrochemical sensor with a composite electrode and a modifier capable of being specifically combined with mercury ions, so that the photoelectrochemical sensing detection with high specificity and high sensitivity to mercury ions can be realized.
The application provides a method for detecting mercury ion concentration based on a photoelectrochemical sensor, which comprises the following steps:
adding the solution of the substance to be detected into a photoelectrochemical sensor; the photoelectrochemical sensor includes: a composite electrode and an electrolyte solution; the composite electrode is a modified titanium dioxide TiO2 electrode obtained by modifying carbon quantum dots CQDs; a specific modifier is added on the surface of the modified TiO2 electrode;
detecting the current change value of the composite electrode after the solution of the object to be detected is added into the photoelectrochemical sensor;
and determining the concentration of mercury ions in the object to be detected according to the current change value.
In one embodiment, before the adding the analyte solution into the photoelectrochemical sensor, the method comprises the following steps:
preparing a TiO2 electrode of the photoelectrochemical sensor;
modifying the TiO2 electrode to obtain a composite electrode; the composite electrode is a TiO2-CQDs composite electrode;
modifying the composite electrode with a specific modifying agent;
preparing an electrolyte solution, wherein the electrolyte solution and the composite electrode form a photoelectric chemical sensor.
In one embodiment, the TiO2 electrode for preparing a photoelectrochemical sensor includes:
cleaning the cut fluorine-doped tin dioxide conductive glass;
and preparing nano TiO2 on the conductive surface of the fluorine-doped tin dioxide conductive glass by a hydrothermal method to obtain the TiO2 electrode.
In one embodiment, the modifying the TiO2 electrode to obtain a composite electrode comprises:
preparing CQDs solution;
and carrying out electrochemical deposition on the TiO2 electrode by taking the CQDs solution as electrolyte to obtain the composite electrode.
In one embodiment, the preparation of the CQDs solution comprises:
preparing CQDs solution by using citric acid as a carbon source by a hydrothermal method.
In one embodiment, the specificity modifying agent comprises: a thymine oligonucleotide solution;
the modification of the composite electrode with a specific modifying agent comprises:
dripping glutaraldehyde solution on the surface of the composite electrode to obtain a first composite electrode;
dripping thymine oligonucleotide solution on the surface of the first composite electrode to obtain a second composite electrode;
and blocking the second composite electrode by using bovine serum albumin BSA blocking solution.
In one embodiment, the thymine oligonucleotide solution, comprises:
a thymine oligonucleotide chain of sequence 10D and ultrapure water.
In one embodiment, the electrolyte solution comprises:
phosphate buffered saline PBS buffer.
In one embodiment, the adding the analyte solution to the photoelectrochemical sensor includes:
mixing the object to be detected with the adenine oligonucleotide solution to obtain an object solution to be detected;
and adding the solution of the substance to be detected to the composite electrode of the photoelectrochemical sensor.
In one embodiment, the detecting the current change value of the composite electrode after the solution of the analyte is added into the photoelectrochemical sensor comprises:
before the solution of the object to be detected is added into the photoelectrochemical sensor, detecting the composite electrode in an electrolyte solution to obtain a first current value;
adding the photoelectrochemical sensor added with the solution of the substance to be detected into a sulfur-containing solution for chemical amplification; the sulfur-containing solution comprises: a PBS solution containing sulfide ions;
detecting the chemically amplified composite electrode in an electrolyte solution to obtain a second current value;
a current variation value is obtained based on a difference between the first current value and the second current value.
In one embodiment, the detecting the current change value of the composite electrode after the solution of the analyte is added into the photoelectrochemical sensor comprises:
A10W LED white lamp is used as an excitation light source, a three-electrode system is adopted, a composite electrode is used as a working electrode, a silver chloride electrode is used as a reference electrode, a platinum electrode is used as an auxiliary electrode, a PBS buffer solution is used as an electrolyte, the photocurrent values of the photoelectrochemical sensors before and after the solution of a substance to be detected reacts with a sulfur-containing solution are respectively measured in an electrochemical workstation, and the photocurrent change value is used as the current change value of the composite electrode.
In one embodiment, the determining the concentration of mercury ions in the analyte according to the current variation value includes:
calculating the concentration of mercury ions in the object to be measured according to the following calculation formula;
y = 0.2785lnx+ 4.6178；
wherein y is the current change value, and x is the mercury ion concentration.
In one embodiment, the calculation formula is applied to the analyte with the mercury ion concentration of 0.5 mu mol ∙ L-1 to 50 mu mol ∙ L-1.
The technical scheme provided by the application comprises the following beneficial effects:
the method is based on that a photoelectrochemical sensor which is processed by a specific modifier and is provided with a TiO2-CQDs composite electrode detects the object to be detected, and the concentration of mercury ions in the object to be detected is calculated based on the current change value before and after the object to be detected reacts with an electrolyte solution. The TiO2-CQDs composite electrode effectively inhibits the combination of photo-generated electrons and holes, and enhances the absorption of the photoelectrochemical sensor to ultraviolet light, so that the photoelectric property of the photoelectrochemical sensor is improved, and mercury ions can be specifically combined with effective components in a specific modifier to form a stable structure, and therefore, the photoelectrochemical sensor can realize specific photoelectrochemical sensing detection of the mercury ions. In addition, because the photocurrent change value and the mercury ion concentration show good linear relation in a certain mercury ion concentration range, the mercury ion concentration in the object to be detected can be calculated according to the photoelectrochemistry sensing detection result, and the method has good stability and accuracy.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the application.
Drawings
The foregoing and other objects, features and advantages of the application will be apparent from the following more particular descriptions of exemplary embodiments of the application, as illustrated in the accompanying drawings wherein like reference numbers generally represent like parts throughout the exemplary embodiments of the application.
Fig. 1 is a schematic flow chart of a method for detecting mercury ion concentration based on a photoelectrochemical sensor according to an embodiment of the present application;
FIG. 2 is a schematic flow chart illustrating a method for manufacturing a photoelectrochemical sensor according to an embodiment of the present application;
FIG. 3 is a schematic flow chart of a method of making a composite electrode according to an embodiment of the present disclosure;
FIG. 4 is a schematic flow chart illustrating a method of modifying the composite electrode according to an embodiment of the present disclosure;
fig. 5 is a schematic flowchart of a method for calculating a mercury ion concentration based on a current variation value according to an embodiment of the present disclosure;
FIG. 6 is a graph showing the results of experiments in which the concentration of a thymine oligonucleotide solution affects the detection, which is shown in the examples of the present application;
FIG. 7 is a graph of experimental results of photo-electrochemical sensing effect on different metal ions according to the present application;
FIG. 8 is a graph of experimental results on the effect of time of electrochemical deposition on modification treatment as shown in the examples of the present application;
FIG. 9 is a graph showing the photoelectric response of the photoelectric chemical sensor for different concentrations of mercury ions according to the embodiment of the present application;
fig. 10 is a schematic diagram showing a relationship between the mercury ion concentration and the current variation value according to the embodiment of the present application.
Detailed Description
Preferred embodiments of the present application will be described in more detail below with reference to the accompanying drawings. While the preferred embodiments of the present application are shown in the drawings, it should be understood that the present application may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in this application and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should also be understood that the term "and/or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.
It should be understood that although the terms "first," "second," "third," etc. may be used herein to describe various information, these information should not be limited to these terms. These terms are only used to distinguish one type of information from another. For example, first information may also be referred to as second information, and similarly, second information may also be referred to as first information, without departing from the scope of the present application. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present application, "a plurality" means two or more unless specifically limited otherwise.
The mercury ions, as one of the most toxic heavy metal elements, bring great influence on human health and natural environment, so it is necessary to detect the mercury ions in the daily environment, especially in the water body. In practical application, atomic absorption spectrometry is mostly adopted to detect mercury ions, however, the method has the problems of complex operation, high cost, expensive equipment, long detection time and the like, and the photoelectrochemistry sensing detection method provided in the prior art can simply, economically and rapidly detect the content of the mercury ions, but the technology has the defects that the mercury ions cannot be subjected to specific detection and the sensitivity is low, so that the detection result is inaccurate and unstable.
Example 1
In order to solve the above problem, an embodiment of the present application provides a method for detecting a mercury ion concentration based on a photoelectrochemical sensor, which can implement high-specificity and high-sensitivity photoelectrochemical sensing detection on a mercury ion.
The technical solutions of the embodiments of the present application are described in detail below with reference to the accompanying drawings.
Fig. 1 is a schematic flow chart of a method for detecting mercury ion concentration based on a photoelectrochemical sensor according to an embodiment of the present application.
Referring to fig. 1, a method for detecting mercury ion concentration based on a photoelectrochemical sensor includes:
101. adding the solution of the substance to be detected into a photoelectrochemical sensor;
the photoelectrochemical sensor includes: a composite electrode and an electrolyte solution; the composite electrode is a modified titanium dioxide TiO2 electrode obtained by modifying carbon quantum dots CQDs; a specific modifier is added on the surface of the modified TiO2 electrode;
in the embodiment of the application, the solution of the substance to be detected is a solution obtained by uniformly mixing the substance to be detected and an adenine oligonucleotide solution according to the proportion of 1: 1; the adenine oligonucleotide solution is prepared by diluting an adenine oligonucleotide chain with a sequence of 10D to a concentration of 2 mu mol of ∙ L-1 with ultrapure water.
The mixing ratio of the sample and the adenine oligonucleotide solution is merely an example, and in practical applications, the mixing ratio may be adjusted according to circumstances, that is, the mixing ratio is not a limitation of the present invention.
In the embodiment of the present application, the specific implementation steps of this step in the experimental stage include: dripping 180uL of the solution of the substance to be detected on the surface of a prepared composite electrode of the photoelectrochemical sensor, reacting for 1 hour in a water bath at 37 ℃, and then cleaning with ultrapure water and drying; and immersing the electrode of the sensor after treatment in a sulfur-containing solution for 20min, and then cleaning with ultrapure water and drying.
It should be noted that the above description of this step is only an example of the operation in the experimental stage, and during the practical application, the operation may be adjusted based on the structure and the using method of the photoelectrochemical sensor, for example, during the practical application of the photoelectrochemical sensor, the composite electrode of the photoelectrochemical sensor may be directly inserted into the solution of the substance to be detected for the identification of the mercury ions.
It should be understood that the above description is only an example of the embodiments of the present application, and should not be construed as limiting the present invention.
102. Detecting the current change value of the composite electrode after the solution of the object to be detected is added into the photoelectrochemical sensor;
in the embodiment of the present application, the detection process specifically includes: firstly, detecting the prepared photoelectrochemical sensor to obtain an initial photocurrent value; then, putting the photoelectrochemical sensor processed in the step 101 into a sulfur-containing solution, and detecting the reacted photoelectrochemical sensor to obtain a final photocurrent value; and obtaining the current change value of the composite electrode based on the difference value of the initial and final light current values.
It should be noted that, because mercury ions react with sulfur ions to form mercury sulfide precipitates, the mercury sulfide precipitates can block absorption of light and photoelectron transfer by the photoelectrochemical sensor, so that photocurrent in the photoelectrochemical sensor changes, and thus a current change value of the composite electrode is obtained.
In practical application, the above steps 101 and 102 may be adjusted to obtain another scheme for detecting the current variation value. For example, the specific modifier in step 101 is mixed with adenine oligonucleotide solution 1:1 for reaction, and then dropped onto the composite electrode to form a photoelectric chemical sensor with the specific modifier and detect the photocurrent value; then inserting the photoelectric chemical sensor into a solution containing mercury ions for reaction for a period of time; then extending into a sulfur-containing solution for amplification; and then inserting the electrode into an electrolyte solution to detect the changed photocurrent value to obtain a current change value.
It should be understood that the above description of the detection process is only an example of the embodiment of the present application, and is not intended to limit the present invention.
103. And determining the concentration of mercury ions in the object to be detected according to the current change value.
In the embodiment of the present application, the current variation value is a photocurrent variation value of the photoelectric chemical sensor before and after the reaction between the mercury ions and the sulfur ions in the analyte solution. In the practical application process, the current change value and the mercury ion concentration are mapped one by one, and the mercury ion concentration in the object to be measured can be obtained in the mapping relation based on the obtained current change value.
In the embodiment of the application, a photoelectrochemical sensor which is processed by a specific modifier and is provided with a TiO2-CQDs composite electrode is used for detecting the object to be detected, and the concentration of mercury ions in the object to be detected is calculated based on the current change value before and after the object to be detected reacts with sulfur ions. The TiO2-CQDs composite electrode effectively inhibits the combination of photo-generated electrons and holes, and enhances the absorption of the photoelectrochemical sensor to ultraviolet light, so that the photoelectric property of the photoelectrochemical sensor is improved, and mercury ions can be specifically combined with effective components in a specific modifier to form a stable structure, and therefore, the photoelectrochemical sensor can realize specific photoelectrochemical sensing detection of the mercury ions. In addition, because the photocurrent change value and the mercury ion concentration show good linear relation in a certain mercury ion concentration range, the mercury ion concentration in the object to be detected can be calculated according to the photoelectrochemistry sensing detection result, and the method has good stability and accuracy.
Example 2
In practical applications, the embodiment of the present application designs a method for manufacturing a photoelectrochemical sensor in step 101 of embodiment 1, and fig. 2 is a schematic flow chart of the method for manufacturing a photoelectrochemical sensor, and specifically please refer to fig. 2, the method for manufacturing a photoelectrochemical sensor includes:
201. preparing a TiO2 electrode of the photoelectrochemical sensor;
in the examples of the present application, the preparation of the TiO2 electrode was carried out by hydrothermal method. TiO2 prepared by a hydrothermal method is rod-shaped, most of the TiO2 grows vertically on the surface of the photoelectrochemical sensor to form a rod-shaped array, the diameter of the rod-shaped array is about 100nm, and the rod-shaped array is favorable for transfer of carriers.
The method for producing the TiO2 electrode according to the present invention is not limited, and the TiO2 electrode may be produced by a precursor crystal sublimation film formation method, an electrodeposition method, or the like.
It is to be understood that the above description of preparing the TiO2 electrode is exemplary only and not limiting of the invention.
202. Modifying the TiO2 electrode to obtain a composite electrode;
the composite electrode is a TiO2-CQDs composite electrode;
in the present example, the TiO2 electrode was modified by electrochemical deposition of CQDs onto the TiO2 electrode.
It should be noted that, the method for modifying the TiO2 electrode is not limited in the present invention, and for example, in practical applications, a TiO2-CQDs composite electrode can be synthesized by a hydrothermal method to modify the TiO2 electrode.
It is to be understood that the above description of the method for modifying the TiO2 electrode is only exemplary and should not be construed as limiting the present invention.
203. Modifying the composite electrode with a specific modifying agent;
in the examples of the present application, the specific modifying agents include: a thymine oligonucleotide solution; the thymine oligonucleotide solution comprises: a thymine oligonucleotide chain with a sequence of 10D and ultrapure water; the specific preparation process of the thymine oligonucleotide solution comprises the following steps: centrifuging the thymine oligonucleotide chain with the sequence of 10D for 60 s; then 62. mu.L of ultrapure water was mixed with the centrifuged thymine oligonucleotide chain to prepare 100. mu. mol of ∙ L-1 stock solution which was refrigerated at-20 ℃.
The specific modifier can specifically bind to mercury ions in the analyte, and the specific component of the specific modifier is not strictly limited in the present invention, and any component capable of selectively enriching mercury ions in the analyte on the composite electrode can be used as the specific modifier, for example, an isothiocyanate-substituted ruthenium bipyridyl dye.
In the examples of the present application, the present invention was studied on the effect of the concentration of the thymine oligonucleotide solution on the detection at the experimental stage. In order to study the influence of the concentration of the thymine oligonucleotide solution on the detection, under the same other conditions, the coincidence electrode is modified by using 0.1 mu mol ∙ L-1, 0.4 mu mol ∙ L-1, 0.8 mu mol ∙ L-1, 1.0 mu mol ∙ L-1 and 1.6 mu mol ∙ L-1 of the thymine oligonucleotide solution respectively, the magnitude of the change value of the photocurrent of the photoelectric chemical sensor after the modification of different concentrations of the thymine oligonucleotide solution is tested, and the experimental result is shown in FIG. 6 in detail.
Wherein Δ I represents a current change value, and T-chain concentration represents the concentration of the thymine oligonucleotide solution.
It can be seen that the higher the concentration of the thymine oligonucleotide solution is, the larger the photocurrent variation value of the photoelectrochemical sensor is, because the higher the concentration of the thymine oligonucleotide solution is, the more mercury ions are bound to the composite electrode of the photoelectrochemical sensor, the more mercury sulfide precipitates are formed, and the electron transfer performance of the surface of the composite electrode is further reduced. Therefore, the higher the concentration of the thymine oligonucleotide solution is, the more accurate the detection result of the photoelectrochemical sensor on the concentration of the mercury ions in the substance to be detected is. For cost reasons, the examples of the present application employ a thymine oligonucleotide solution having a concentration of 1.0. mu. mol ∙ L-1.
It should be noted that the concentration of the thymine oligonucleotide solution in the embodiment of the present application is determined based on the data selection at the experimental stage, and in practical application, it can be adjusted according to the production conditions.
It is to be understood that the above description of specific modifying agents is exemplary only and should not be taken as a limitation of the present invention.
204. Preparing an electrolyte solution, wherein the electrolyte solution and the composite electrode form a photoelectric chemical sensor.
In an embodiment of the present application, the electrolyte solution includes: phosphate buffered saline PBS buffer. The concentration of the PBS buffer solution is 0.1mol ∙ L-1.
It should be noted that the above description of the electrolyte solution is only an example, and in practical applications, the content of the electrolyte solution may be adjusted according to production conditions, for example, Tris-HCL buffer solution, i.e., the above description of the electrolyte solution does not limit the present invention.
It should be noted that the concentration of the PBS buffer is only an example of the experimental stage in the embodiment of the present application, and in the practical application process, the concentration of the PBS buffer may be adjusted according to the actual situation, that is, the concentration of the PBS buffer is not limited to the present invention.
In the embodiment of the application, in the experimental stage, the invention aims to verify that the photoelectrochemical sensor can be specifically selected for mercury ions. Under the condition that other conditions are not changed, a plurality of metal ions with the same concentration and including mercury ions are respectively and uniformly mixed with the adenine oligonucleotide solution and then detected by the photoelectrochemical sensor. The results of recording the photocurrent change value Δ I for each metal ion reaction are shown in fig. 7.
It can be seen that other ions have little influence on the change of the photocurrent response compared with the change value of the photocurrent of the mercury ions, indicating that the photoelectrochemical sensor has high specificity for the mercury ions.
The embodiment of the application provides a photoelectrochemical sensor based on a TiO2-CQDs composite electrode, a specific modifier capable of specifically selecting mercury ions and a PBS (phosphate buffer solution) containing sulfur ions, the photoelectrochemical sensor can be specifically connected with the mercury ions, so that a large amount of mercury ions are enriched on the composite electrode, and a composite material on the electrode of the photoelectrochemical sensor can effectively inhibit photo-generated electron-hole combination, so that the photoelectric performance of the photoelectrochemical sensor is enhanced. The photoelectric chemical sensor can accurately detect the photocurrent change value before and after the reaction of mercury ions and sulfur ions.
Example 3
In practical applications, the embodiment of the present application designs the preparation of the composite electrode, specifically referring to fig. 3, and in the embodiment of the present application, the preparation of the composite electrode includes:
301. cleaning the cut fluorine-doped tin dioxide conductive glass;
in the embodiment of the application, in the experimental stage, the specific step of cleaning the cut fluorine-doped tin dioxide conductive glass is to cut the fluorine-doped tin dioxide conductive glass into conductive glass with the length of 5cm and the width of 3cm, sequentially soak the conductive glass in acetone, absolute ethyl alcohol and deionized water, perform ultrasonic treatment for 15min, and then dry the conductive glass in an oven.
It should be noted that, in the actual application process, the cleaning process may be adjusted in steps according to the actual production conditions to achieve the purpose of saving the production cost or improving the production efficiency.
It should be understood that the above description is only one example of the embodiments of the present application and should not be taken as limiting the invention.
302. Preparing nano TiO2 on the conductive surface of the fluorine-doped tin dioxide conductive glass by a hydrothermal method to obtain a TiO2 electrode;
in the embodiment of the application, in the experimental stage, a hydrothermal method is adopted to prepare the TiO2 electrode, and the specific steps are that 0.8ml of n-butyl titanate is slowly dropped into a mixed solution of 10ml of deionized water and 20ml of concentrated hydrochloric acid and stirred to obtain a mixed solution, the mixed solution is transferred into a 50ml reaction kettle polytetrafluoroethylene lining, the cleaned conductive glass is placed into the reaction kettle, hydrothermal reaction is carried out in an oven for 5 hours, and after natural cooling, the conductive glass is placed into a muffle furnace to be calcined for 1 hour, so that the TiO2 electrode is obtained.
In practical application, the TiO2 electrode prepared by the above method can be adjusted in steps according to practical production conditions to save production cost or improve production efficiency.
It is understood that the above description of the TiO2 electrode preparation method is only an example provided in the examples of the present application and should not be construed as a limitation of the present invention.
303. Preparing CQDs solution;
in the embodiment of the application, in the experimental stage, a CQDs solution is prepared by using citric acid as a carbon source through a hydrothermal method, and the specific steps are that 2g of citric acid and 2g of urea are dissolved in 30ml of water and are stirred and mixed uniformly; then transferring the uniformly mixed solution into a polytetrafluoroethylene reaction kettle lining, putting the reaction kettle lining into a reaction kettle, and heating the reaction kettle lining in an oven to 180 ℃ for reaction for 6 hours; naturally cooling to room temperature to obtain a dark green mixture; and taking supernatant of the mixture and centrifuging the supernatant for 20min to obtain supernatant which is CQDs solution.
It should be noted that the above-mentioned preparation process of the CQDs solution is only an example of the experimental stage of the embodiment of the present application, and in the practical application process, the above-mentioned method for preparing the CQDs solution may be adjusted according to the production conditions, for example, in the practical production process, other methods such as arc discharge method or microwave synthesis method may also be used to synthesize the CQDs.
It is understood that the above-mentioned preparation method of CQDs solution is only an example and not a limitation of the present invention.
Further, the step 303 has no strict timing relationship with the steps 301 and 302, that is, the step 303 may be executed before the step 301, between the steps 301 and 302, or after the step 302.
It is understood that the above description of the sequence of step 301, step 302 and step 303 is only an example and is not intended to limit the present invention.
304. And carrying out electrochemical deposition on the TiO2 electrode by taking the CQDs solution as electrolyte to obtain the composite electrode.
In the embodiment of the application, in the experimental stage, the preparation process of the composite electrode specifically comprises the steps of diluting 2.5ml of the CQDs solution with deionized water to obtain 25ml of diluted CQDs solution as electrolyte; cutting the TiO2 electrode into electrodes with the length of 5cm and the width of 1cm by using a glass cutter, taking the electrodes as working electrodes, taking a silver chloride electrode as a reference electrode and a platinum electrode as an auxiliary electrode, and performing electrochemical deposition in the electrolyte by adopting an alternating current voltammetry; and after the deposition is finished, cleaning the composite electrode by using deionized water and drying the composite electrode by blowing to obtain the composite electrode.
It should be noted that the above-mentioned method for preparing the composite electrode is only an example of the experimental stage of the present invention, and in the actual production process, the preparation process can be adjusted according to the actual production conditions.
In the examples of the present application, the present invention also investigated the time of electrochemical deposition during the experimental phase. Under the same other conditions, the magnitude of the increase in the photocurrent response value of the TiO2 electrode after deposition in the CQDs solution for 30s, 60s, 90s, 120s, and 180s, respectively, was tested. The test results are shown in detail in FIG. 8.
Wherein I0 represents the magnitude of the photocurrent response value of the TiO2 electrode before electrochemical deposition, I represents the magnitude of the photocurrent response value of the TiO2 electrode after electrochemical deposition, and t represents the time of electrochemical deposition.
It can be seen that the photocurrent response value is increased to the maximum intensity when the electrochemical deposition time is 120 s. When the deposition time is too short, the carbon spots deposited on the electrode are less, and the improvement of the photoelectric conversion performance is not obvious enough. When the deposition time is too long, the deposited carbon dots are too dense, resulting in the inhibition of the transport of photo-generated electrons and holes between the TiO2 electrodes, affecting the photocurrent. Based on the above tests, the composite electrode was obtained by electrochemical deposition in an electrolyte for 120s in the examples of the present application.
It should be noted that, in the embodiment of the present application, the preparation of the composite electrode is designed based on the experimental result in the experimental stage, and in the actual application process, due to the limitations of the actual production environment and the production equipment, the parameters and the steps of the preparation process of the composite electrode can be adjusted.
It is to be understood that the above description of the preparation of the composite electrode is merely exemplary and should not be construed as limiting the invention.
The embodiment of the application provides a preparation method of a composite electrode, which uses CQDs to modify a TiO2 electrode to obtain the composite electrode. Because TiO2 has wider band gap and smaller photoresponse range and has weaker inhibition on the combination of photo-generated electrons and holes, the photoelectrochemical sensor adopting TiO2 as an electrode material has lower photoelectric conversion efficiency, and CQDs have excellent electron transfer capability and have a little absorption capability on ultraviolet light and visible light, and after the TiO2 electrode is modified by adopting the CQDs, the photoelectrochemical sensor not only can effectively inhibit the combination of the photo-generated electrons and the holes and enhance the photocurrent, but also can enhance the absorption of the TiO2 electrode on the ultraviolet light and broaden the photoresponse range of the photoelectrochemical sensor, so that the sensitivity of the photoelectrochemical sensor with the composite electrode is improved, and the accuracy of a detection result is improved.
Example 4
In practical applications, the present application embodiment designs step 203 in embodiment 2, specifically referring to fig. 4, and an embodiment of modifying the composite electrode in the present application embodiment includes:
401. dripping glutaraldehyde solution on the surface of the composite electrode to obtain a first composite electrode;
in the embodiment of the application, in the experimental stage, the preparation process of the first composite electrode specifically comprises the steps of dropwise adding 180 μ L of diluted glutaraldehyde solution onto the surface of the composite electrode, reacting for 1h in a refrigerator at 4 ℃, cleaning with ultrapure water, and drying.
It should be noted that the above-mentioned preparation process for the first composite electrode is only an example of the experimental stage, and does not limit the present invention.
402. Dripping thymine oligonucleotide solution on the surface of the first composite electrode to obtain a second composite electrode;
in the embodiment of the application, in the experimental stage, the second composite electrode is specifically prepared by dropping 180uL of a thymine oligonucleotide solution with a concentration of 1 μmol ∙ L-1 onto the surface of the first composite electrode, reacting for 1h in a water bath at 37 ℃, then washing with ultrapure water, and drying.
It should be noted that the above-mentioned process for preparing the second composite electrode is only an example of the experimental stage, and does not limit the present invention.
403. And blocking the second composite electrode by using bovine serum albumin BSA blocking solution.
In the embodiment of the application, in the experimental stage, the blocking treatment is specifically to immerse the second composite electrode into 180uL of 1% BSA blocking solution to block for 1h at 37 ℃, and then to dry after washing with ultrapure water.
It should be noted that the above description of the sealing process is only an example of the experimental stage, and does not limit the present invention.
In the embodiment of the application, thymine oligonucleotide solution is used for modifying the composite electrode. Based on the characteristic that mercury ions can form specific binding with thymine oligonucleotide chains, the composite electrode can bind a large amount of mercury ions in an object to be detected, so that the photoelectrochemical sensor can realize specific detection of the mercury ions.
Example 5
In practical application, the embodiment of the present application designs step 102 and step 103 in embodiment 1, specifically referring to fig. 5, and the method for calculating the mercury ion concentration based on the current variation value in the embodiment of the present application includes:
501. before the solution of the object to be detected is added into the photoelectrochemical sensor, detecting the composite electrode in an electrolyte solution to obtain a first current value;
in the embodiment of the present application, the step of detecting the first current value specifically includes using a 10W LED white lamp as an excitation light source, using a three-electrode system, using a composite electrode as a working electrode, a silver chloride electrode as a reference electrode, a platinum electrode as an auxiliary electrode, and a PBS buffer solution as an electrolyte, and measuring a photocurrent value on the composite electrode before a solution to be measured reacts with a sulfur-containing solution in an electrochemical workstation, and recording the photocurrent value as the first current value.
It should be noted that, the excitation light source used in the present invention is not strictly limited, and in the practical application process, an ultraviolet single-band light source may also be used as the excitation light source for detection.
It is to be understood that the above description of the detection process of the first current value is only an example, and should not be construed as limiting the present invention.
502. Adding the photoelectrochemical sensor added with the solution of the substance to be detected into a sulfur-containing solution for chemical amplification;
the sulfur-containing solution comprises: a PBS solution containing sulfide ions;
in practical application, the sulfur-containing solution is any solution that can form a precipitate with mercury ions, and the precipitate is formed on the surface of the electrode by combining with the mercury ions in the substance to be detected, so that the photocurrent intensity is further reduced, and the signal is amplified.
In the examples of the present application, the sulfur-containing solution was a PBS buffer solution containing sulfur ions at a concentration of 0.1mol ∙ L-1.
It is to be understood that the above description of the sulfur-containing solution is merely an example and should not be construed as limiting the present invention.
503. Detecting the chemically amplified composite electrode in an electrolyte solution to obtain a second current value;
in the embodiment of the present application, the step of detecting the second current value specifically includes using a 10W LED white lamp as an excitation light source, using a three-electrode system, using a composite electrode as a working electrode, a silver chloride electrode as a reference electrode, a platinum electrode as an auxiliary electrode, and a PBS buffer solution as an electrolyte, and measuring a photocurrent value on the composite electrode after a solution to be measured reacts with a sulfur-containing solution in an electrochemical workstation, and recording the photocurrent value as the second current value.
It should be noted that, the excitation light source used in the present invention is not strictly limited, and in the practical application process, an ultraviolet single-band light source may also be used as the excitation light source for detection.
It is to be understood that the above description of the detection process of the second current value is only an example, and should not be construed as limiting the present invention.
504. Obtaining a current change value based on a difference value between the first current value and the second current value;
in the embodiment of the present application, the difference value is obtained by subtracting a second current value from the first current value, and the difference value is the current variation value; the difference value may be obtained by subtracting the first current value from the second current value, and an absolute value of the difference value may be taken as the current variation value.
It is to be understood that the above description of obtaining the current variation value is only exemplary and is not to be construed as limiting the present invention.
505. And calculating the concentration of mercury ions in the object to be detected according to the current change value.
In the embodiment of the present application, the mercury ion concentration in the analyte is calculated according to the following calculation formula:
y = 0.2785lnx+ 4.6178；
wherein y is the current change value, and x is the mercury ion concentration.
The detection limit is the lowest detection concentration at which a biological sample is extracted and detected according to the requirements of the analysis method and can be distinguished from noise.
In the embodiment of the application, the detection limit refers to the lowest concentration of mercury ions which can be detected in an object to be detected based on the photoelectrochemical sensor and can be distinguished from other metal ions.
In the examples of the present application, the linearity and detection limit of mercury ion detection were studied, and the results are as follows:
under the optimized conditions, the photoelectric response results of the photoelectrochemical sensor for different concentrations of mercury ions are shown in FIG. 9.
Wherein a represents 0 of mercury ion, b represents ∙ L-1 of mercury ion concentration of 0.5 mu mol, c represents ∙ L-1 of mercury ion concentration of 1 mu mol, d represents ∙ L-1 of mercury ion concentration of 5 mu mol, e represents ∙ L-1 of mercury ion concentration of 10 mu mol, and f represents ∙ L-1 of mercury ion concentration of 50 mu mol.
It can be seen that, as the concentration of mercury ions increases, the absorption of light and the blocking of photoelectron transfer increase, the current variation value increases, and the concentration of mercury ions and the current variation value are in positive correlation.
Further, the relationship between the mercury ion concentration and the current change value was investigated, and the results are shown in fig. 10.
Wherein x represents the concentration of mercury ions and y represents the change value delta I of current.
It can be known that, in the concentration range of 0.5-50 μmol ∙ L-1, the variation value of the photocurrent and the mercury ion concentration show good linear relationship, and the corresponding linear equation is y = 0.2785lnx + 4.6178, the coefficient of the linear relationship R = 0.99201, and the detection limit is about 0.1 μmol ∙ L-1.
It should be noted that the above calculation formula for the mercury ion concentration in the analyte is obtained based on data in the experimental stage, and in the practical application process, due to the adjustment of steps and parameters in the production process, the coefficients in the calculation formula may be different from the experimental data, but do not affect the good linear relationship between the change value of the photocurrent and the mercury ion concentration.
It is to be understood that the above description of the mercury ion concentration calculation process is only an example of the embodiment of the present application, and should not be construed as limiting the present invention.
The embodiment of the application calculates the concentration of the mercury ions in the object to be measured based on the current change value measured by the photoelectrochemical sensor, and the experiment proves that in a certain concentration range, the concentration of the mercury ions and the current change value show a good linear relation, and the concentration of the mercury ions in the object to be measured is calculated based on the linear relation, so that the accuracy and reliability are realized.
The aspects of the present application have been described in detail hereinabove with reference to the accompanying drawings. In the above embodiments, the descriptions of the respective embodiments have respective emphasis, and for parts that are not described in detail in a certain embodiment, reference may be made to related descriptions of other embodiments. Those skilled in the art should also appreciate that the acts or modules referred to in the specification are not necessarily required in the present application. In addition, it can be understood that the steps in the method of the embodiment of the present application may be sequentially adjusted, combined, and deleted according to actual needs.
Having described embodiments of the present application, the foregoing description is intended to be exemplary, not exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen in order to best explain the principles of the embodiments, the practical application, or improvements made to the technology in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.
Claims (13)
1. A method for detecting the concentration of mercury ions based on a photoelectrochemical sensor is characterized by comprising the following steps:
adding the solution of the substance to be detected into a photoelectrochemical sensor; the photoelectrochemical sensor includes: a composite electrode and an electrolyte solution; the composite electrode is a modified titanium dioxide TiO2 electrode obtained by modifying carbon quantum dots CQDs; a specific modifier is added on the surface of the modified TiO2 electrode;
detecting the current change value of the composite electrode after the solution of the object to be detected is added into the photoelectrochemical sensor;
and determining the concentration of mercury ions in the object to be detected according to the current change value.
2. The method for detecting the concentration of mercury ions based on the photoelectric chemical sensor as claimed in claim 1, wherein before the step of adding the analyte solution to the photoelectric chemical sensor, the method comprises:
preparing a TiO2 electrode of the photoelectrochemical sensor;
modifying the TiO2 electrode to obtain a composite electrode; the composite electrode is a TiO2-CQDs composite electrode;
modifying the composite electrode with a specific modifying agent;
preparing an electrolyte solution, wherein the electrolyte solution and the composite electrode form a photoelectric chemical sensor.
3. The method for detecting the concentration of mercury ions based on the photoelectrochemical sensor according to claim 2, wherein the preparing of the TiO2 electrode of the photoelectrochemical sensor comprises:
cleaning the cut fluorine-doped tin dioxide conductive glass;
and preparing nano TiO2 on the conductive surface of the fluorine-doped tin dioxide conductive glass by a hydrothermal method to obtain the TiO2 electrode.
4. The method for detecting the concentration of mercury ions based on the photoelectrochemical sensor according to claim 2, wherein the modifying the TiO2 electrode to obtain a composite electrode comprises:
preparing CQDs solution;
and carrying out electrochemical deposition on the TiO2 electrode by taking the CQDs solution as electrolyte to obtain the composite electrode.
5. The method for detecting the concentration of mercury ions based on a photoelectrochemical sensor according to claim 4, wherein the preparing of the CQDs solution comprises:
preparing CQDs solution by using citric acid as a carbon source by a hydrothermal method.
6. The method for detecting the concentration of mercury ions based on a photoelectrochemical sensor according to claim 2, wherein the specific modifier comprises: a thymine oligonucleotide solution;
the modification of the composite electrode with a specific modifying agent comprises:
dripping glutaraldehyde solution on the surface of the composite electrode to obtain a first composite electrode;
dripping thymine oligonucleotide solution on the surface of the first composite electrode to obtain a second composite electrode;
and blocking the second composite electrode by using bovine serum albumin BSA blocking solution.
7. The method for detecting the concentration of mercury ions based on a photoelectrochemical sensor according to claim 6, wherein the thymine oligonucleotide solution comprises:
a thymine oligonucleotide chain of sequence 10D and ultrapure water.
8. The method for detecting the concentration of mercury ions based on a photoelectrochemical sensor according to claim 1, wherein the electrolyte solution comprises:
phosphate buffered saline PBS buffer.
9. The method for detecting the concentration of mercury ions based on the photoelectrochemical sensor according to claim 1, wherein the step of adding the analyte solution to the photoelectrochemical sensor comprises:
mixing the object to be detected with the adenine oligonucleotide solution to obtain an object solution to be detected;
and adding the solution of the substance to be detected to the composite electrode of the photoelectrochemical sensor.
10. The method for detecting the concentration of mercury ions based on the photoelectrochemical sensor according to claim 1, wherein the detecting the current change value of the composite electrode after the solution of the analyte is added to the photoelectrochemical sensor comprises:
before the solution of the object to be detected is added into the photoelectrochemical sensor, detecting the composite electrode in an electrolyte solution to obtain a first current value;
adding the photoelectrochemical sensor added with the solution of the substance to be detected into a sulfur-containing solution for chemical amplification; the sulfur-containing solution comprises: a PBS solution containing sulfide ions;
detecting the chemically amplified composite electrode in an electrolyte solution to obtain a second current value;
a current variation value is obtained based on a difference between the first current value and the second current value.
11. The method for detecting the concentration of mercury ions based on the photoelectrochemical sensor according to claim 1, wherein the detecting the current change value of the composite electrode after the solution of the analyte is added to the photoelectrochemical sensor comprises:
A10W LED white lamp is used as an excitation light source, a three-electrode system is adopted, a composite electrode is used as a working electrode, a silver chloride electrode is used as a reference electrode, a platinum electrode is used as an auxiliary electrode, a PBS buffer solution is used as an electrolyte, the photocurrent values of the photoelectrochemical sensors before and after the solution of a substance to be detected reacts with a sulfur-containing solution are respectively measured in an electrochemical workstation, and the photocurrent change value is used as the current change value of the composite electrode.
12. The method for detecting the concentration of mercury ions based on the photoelectrochemical sensor according to claim 1, wherein the determining the concentration of mercury ions in the analyte according to the current change value comprises:
calculating the concentration of mercury ions in the object to be measured according to the following calculation formula;
y = 0.2785lnx+ 4.6178；
wherein y is the current change value, and x is the mercury ion concentration.
13. The method for detecting the concentration of mercury ions based on a photoelectrochemical sensor according to claim 11, wherein the calculation formula is applied to the analyte having the concentration of mercury ions of 0.5 μmol ∙ L-1 to 50 μmol ∙ L-1.
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Application publication date: 20210423 |