CN115184424A - Method for detecting lead, detection electrode, electrochemical sensor and preparation - Google Patents
Method for detecting lead, detection electrode, electrochemical sensor and preparation Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 22
- 238000002360 preparation method Methods 0.000 title claims abstract description 15
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- 239000010931 gold Substances 0.000 claims abstract description 73
- 229910052737 gold Inorganic materials 0.000 claims abstract description 69
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 claims abstract description 67
- 229910002804 graphite Inorganic materials 0.000 claims abstract description 61
- 239000010439 graphite Substances 0.000 claims abstract description 61
- 239000002103 nanocoating Substances 0.000 claims abstract description 36
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- FOIXSVOLVBLSDH-UHFFFAOYSA-N Silver ion Chemical compound [Ag+] FOIXSVOLVBLSDH-UHFFFAOYSA-N 0.000 claims abstract description 20
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- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 14
- 230000008021 deposition Effects 0.000 claims description 14
- SQGYOTSLMSWVJD-UHFFFAOYSA-N silver(1+) nitrate Chemical compound [Ag+].[O-]N(=O)=O SQGYOTSLMSWVJD-UHFFFAOYSA-N 0.000 claims description 14
- 239000004927 clay Substances 0.000 claims description 12
- 238000003950 stripping voltammetry Methods 0.000 claims description 11
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 claims description 10
- 150000002500 ions Chemical class 0.000 claims description 9
- 239000002253 acid Substances 0.000 claims description 7
- BFNBIHQBYMNNAN-UHFFFAOYSA-N ammonium sulfate Chemical compound N.N.OS(O)(=O)=O BFNBIHQBYMNNAN-UHFFFAOYSA-N 0.000 claims description 7
- 229910052921 ammonium sulfate Inorganic materials 0.000 claims description 7
- 235000011130 ammonium sulphate Nutrition 0.000 claims description 7
- 229910001961 silver nitrate Inorganic materials 0.000 claims description 7
- 238000004070 electrodeposition Methods 0.000 claims description 6
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 5
- 239000008151 electrolyte solution Substances 0.000 claims description 5
- 229910017604 nitric acid Inorganic materials 0.000 claims description 5
- 238000004140 cleaning Methods 0.000 claims description 4
- 238000005498 polishing Methods 0.000 claims description 4
- 238000003756 stirring Methods 0.000 claims description 3
- 230000000694 effects Effects 0.000 abstract description 7
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 45
- 235000014653 Carica parviflora Nutrition 0.000 description 27
- 241000243321 Cnidaria Species 0.000 description 27
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- 238000004090 dissolution Methods 0.000 description 10
- 238000001075 voltammogram Methods 0.000 description 10
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 8
- 238000005259 measurement Methods 0.000 description 6
- 238000001878 scanning electron micrograph Methods 0.000 description 6
- 229940075397 calomel Drugs 0.000 description 4
- ZOMNIUBKTOKEHS-UHFFFAOYSA-L dimercury dichloride Chemical compound Cl[Hg][Hg]Cl ZOMNIUBKTOKEHS-UHFFFAOYSA-L 0.000 description 4
- 238000000835 electrochemical detection Methods 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 229910052697 platinum Inorganic materials 0.000 description 4
- LDXJRKWFNNFDSA-UHFFFAOYSA-N 2-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)-1-[4-[2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidin-5-yl]piperazin-1-yl]ethanone Chemical compound C1CN(CC2=NNN=C21)CC(=O)N3CCN(CC3)C4=CN=C(N=C4)NCC5=CC(=CC=C5)OC(F)(F)F LDXJRKWFNNFDSA-UHFFFAOYSA-N 0.000 description 3
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- YLZOPXRUQYQQID-UHFFFAOYSA-N 3-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)-1-[4-[2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidin-5-yl]piperazin-1-yl]propan-1-one Chemical compound N1N=NC=2CN(CCC=21)CCC(=O)N1CCN(CC1)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F YLZOPXRUQYQQID-UHFFFAOYSA-N 0.000 description 1
- 229910003771 Gold(I) chloride Inorganic materials 0.000 description 1
- 230000003213 activating effect Effects 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 238000003968 anodic stripping voltammetry Methods 0.000 description 1
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- FDWREHZXQUYJFJ-UHFFFAOYSA-M gold monochloride Chemical compound [Cl-].[Au+] FDWREHZXQUYJFJ-UHFFFAOYSA-M 0.000 description 1
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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
- G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
- G01N27/28—Electrolytic cell components
- G01N27/30—Electrodes, e.g. test electrodes; Half-cells
- G01N27/308—Electrodes, e.g. test electrodes; Half-cells at least partially made of carbon
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- G—PHYSICS
- 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
- G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
- G01N27/416—Systems
- G01N27/48—Systems using polarography, i.e. measuring changes in current under a slowly-varying voltage
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Abstract
The invention provides a method for detecting lead, a detection electrode, an electrochemical sensor and a preparation method. The detection electrode comprises a graphite core and a nano-coating. The graphite core surface has a graphite surface layer, and the graphite surface layer comprises a plurality of graphite layers. The nano coating covers the graphite surface layer, the nano coating comprises a plurality of three-dimensional nano gold particles and a plurality of three-dimensional nano silver particles, the nano silver particles and the nano gold particles are uniformly dispersed, and the number ratio of the nano gold particles to the nano silver particles is 15-25: 1. the nano gold particles and the nano silver particles are of three-dimensional structures, and the specific surface area of the nano gold particles and the nano silver particles is larger. Therefore, the specific surface area of the whole nano coating is large, and the electrochemical activity of the detection electrode is high. In addition, the contact area between the three-dimensional structure of the gold nanoparticles and the silver nanoparticles and the surface layer of the graphite is increased, so that the nano coating and the graphite core are firmly combined, the stability of the detection electrode is good, the service life is long, and the data repeatability is good.
Description
Technical Field
The invention relates to the technical field of electrochemical sensing, in particular to a method for detecting lead, a detection electrode, an electrochemical sensor and a preparation method.
Background
Drinking water health and safety are a major problem for human health. Lead, one of the toxic and harmful water pollutants, poses a great hazard to the human body. According to the World Health Organization (WHO) regulations, the total lead concentration in drinking water should be less than 10ppb. Various methods have been developed to detect trace lead, including inductively coupled plasma mass spectrometry (ICP-MS), atomic Absorption Spectroscopy (AAS), etc. However, these methods are generally expensive in terms of equipment cost and are bulky and therefore cannot be used in the field. In contrast, electroanalytical techniques offer a low cost, fast and portable option for routine on-site monitoring of large numbers of samples. The most promising electroanalytical technique is Anodic Stripping Voltammetry (ASV), which is a highly sensitive analytical method.
However, the electrochemical detection usually uses noble metals as electrodes, such as gold electrodes, silver electrodes, etc., but the noble metals are expensive, so that the popularization cannot be realized.
Disclosure of Invention
In view of the above, it is necessary to provide a method for detecting lead, a detection electrode, an electrochemical sensor, and a method for manufacturing the same, which address the problem of using a noble metal as an electrode for electrochemical detection.
In a first aspect, the invention provides a detection electrode comprising a graphite core and a nano-coating.
The graphite core surface has a graphite surface layer, and the graphite surface layer comprises a plurality of graphite layers.
The nano coating covers on the graphite surface layer, the nano coating comprises a plurality of three-dimensional nano gold particles and a plurality of three-dimensional nano silver particles, the nano silver particles and the nano gold particles are uniformly dispersed, and the number ratio of the nano gold particles to the nano silver particles is 15-25: 1.
optionally, the number ratio of the gold nanoparticles to the silver nanoparticles is 19:1.
alternatively, the graphite core is a pencil core with the surface layer of wax and clay removed.
The second aspect of the present invention provides a method for preparing a detection electrode, comprising the following steps:
providing a graphite core, wherein the surface of the graphite core is provided with a graphite surface layer, and the graphite surface layer comprises a plurality of graphite layers.
Placing a graphite core in an electrolyte, preparing a nano coating through electrodeposition, wherein the nano coating covers on a graphite surface layer, the nano coating comprises a plurality of three-dimensional nano gold particles and a plurality of three-dimensional nano silver particles, the nano silver particles and the nano gold particles are uniformly dispersed, and the number ratio of the nano gold particles to the nano silver particles is 15-25: 1.
optionally, the electrolyte in the electrolyte comprises chloroauric acid, silver nitrate and ammonium sulfate, the concentration of the chloroauric acid is 1mmol/L, the concentration of the silver nitrate is 0.1mmol/L, and the concentration of the ammonium sulfate is 10mmol/L.
Optionally, the conditions of electrodeposition are: depositing for 40-60 min under the constant voltage of-1.5V.
Optionally, the preparation method of the graphite core comprises:
polishing the pencil core, cleaning the pencil core by using acetone and nitric acid solution, and applying voltage in sulfuric acid solution to obtain the graphite core.
In a third aspect, the present invention provides an electrochemical sensor for detecting lead, the electrochemical sensor includes a working electrode, a counter electrode and a reference electrode, and the working electrode is the detection electrode or the detection electrode obtained by the preparation method.
The fourth aspect of the present invention provides a method for detecting lead, comprising the steps of:
and placing the electrochemical sensor in a solution to be detected, wherein the solution to be detected is an electrolyte solution and comprises lead ions.
The deposition was carried out for 500s under the conditions of stirring and detection voltage of-0.3 v, and the stripping peak current value of the electrochemical sensor was detected by square wave stripping voltammetry.
Optionally, the solution to be tested further comprises 0.5mol/L sulfuric acid solution.
The detection electrode comprises a graphite core and a nano coating. The graphite surface layer comprises a plurality of graphite layers, so that the graphite surface layer has a larger specific surface area, and can provide a larger accommodating space for the nano coating, namely more nano gold particles and nano silver particles can be accommodated. And the nano gold particles and the nano silver particles are of three-dimensional structures, and the specific surface area of the nano gold particles and the nano silver particles is larger. Therefore, the specific surface area of the whole nano coating is large, and the electrochemical activity of the detection electrode is high. In addition, the contact area between the three-dimensional structure of the gold nanoparticles and the silver nanoparticles and the surface layer of the graphite is increased, so that the nano coating and the graphite core are firmly combined, the stability of the detection electrode is good, the service life is long, and the data repeatability is good.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the structures shown in the drawings without creative efforts.
Fig. 1A is an SEM image of the nano silver/graphite core at 5k times magnification in the first detection electrode prepared in example 3, and fig. 1B is an SEM image of the nano silver/graphite core at 10k times magnification; FIG. 1C is an SEM image of the nano coral gold/graphite core at 10k times magnification, and FIG. 1D is an SEM image of the nano coral gold/graphite core at 20k times magnification; FIG. 1E is an SEM image of the nano coral gold and silver/graphite core magnified 10k times, and FIG. 1F is an SEM image of the nano coral gold and silver/graphite core magnified 20k times (wherein the nano silver in the yellow circle is dispersed on the nano gold).
Fig. 2 is an EDS spectrum of the first detection electrode prepared in example 3;
FIG. 3 is a graph showing that the first, second, and third detection electrodes prepared in example 3 measure 100ppb of Pb 2+ Anodic dissolution voltammogram;
FIG. 4A is a graph showing the measurement of different concentrations of Pb by the first detection electrode obtained in example 3 2+ The square wave dissolution voltammogram of (1); FIG. 4B shows the peak current value and Pb of square wave stripping voltammetry 2+ A current response line plot of concentration;
FIG. 5 shows a repeated measurement of 100ppb of Pb for the first detection electrode obtained in example 3 2+ Anodic dissolution voltammogram;
FIG. 6A shows the measurement of 100ppb of Pb for different detection electrodes fabricated at different deposition times in example 2 2+ Anodic dissolution voltammogram; FIG. 6B shows the peak current value and Pb of the square wave stripping voltammetry shown in FIG. 6A 2+ A current response line plot of concentration; FIG. 6C shows the measurement of 100ppb Pb for different detection electrodes made of different compositions in example 3 2+ Anodic dissolution voltammogram; FIG. 6C shows the peak current value and Pb of the square wave stripping voltammetry shown in FIG. 6D 2+ Current response line graph of concentration.
The implementation, functional features and advantages of the present invention will be further explained with reference to the accompanying drawings.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.
It should be noted that all directional indicators (such as upper and lower 8230; etc.) in the embodiments of the present invention are only used for explaining the relative positional relationship between the components at a certain posture (as shown in the attached drawings), the motion situation, etc., and if the certain posture is changed, the directional indicator is also changed accordingly.
In addition, the descriptions related to "first", "second", etc. in the present invention are only for descriptive purposes and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature.
Moreover, the technical solutions in the embodiments of the present invention may be combined with each other, but it is necessary to be based on the realization of the technical solutions by those skilled in the art, and when the technical solutions are contradictory to each other or cannot be realized, such a combination of the technical solutions should not be considered to exist, and is not within the protection scope claimed by the present invention.
The embodiment of the application provides a detection electrode, which comprises a graphite core and a nano coating. The graphite core surface has a graphite surface layer, and the graphite surface layer comprises a plurality of graphite layers. The nano coating covers on the graphite surface layer, the nano coating comprises a plurality of three-dimensional nano gold particles and a plurality of three-dimensional nano silver particles, the nano silver particles and the nano gold particles are uniformly dispersed, and the number ratio of the nano gold particles to the nano silver particles is 15-25: 1.
the surface of the graphite core is provided with a graphite surface layer, and the graphite is layered into graphite flakes or graphite particles with small volume. And a certain gap is reserved between two adjacent graphite layers or between one graphite layer and other graphite layers.
The gap may be formed in at least two ways: illustratively, the material of the surface of the graphite core is graphite, and fine grooves or holes are formed on the surface of the graphite core by machining. The wall body of the groove or the hole is a graphite layer, and the space of the groove or the hole is a gap between the graphite layers.
As another example, the material of the surface of the graphite core is graphite and a material that is easily eroded (such as wax and clay), and the material that is easily eroded is removed by solution erosion, so that fine grooves or holes are formed in the surface of the graphite core. The wall body of the groove or the hole is a graphite layer, and the space of the groove or the hole is a gap between the graphite layers.
Due to the existence of a plurality of graphite layers, the surface of the graphite core is uneven, and has larger specific surface area compared with a structure with a flat surface. Therefore, the graphite surface layer can provide a larger accommodating space for the nano coating, namely more nano gold particles and nano silver particles can be accommodated.
The nano-coating layer comprises a plurality of three-dimensional nano-gold particles and a plurality of three-dimensional nano-silver particles. The three-dimensional gold nanoparticles comprise small protrusions extending in multiple directions in a three-dimensional space. A plurality of three-dimensional nano gold particles are connected together, so that the whole nano coating has a three-dimensional network structure with multiple nano branches and multiple nano holes, and can be called Nano Coral Gold (NCG). The shape of the nano coral is three-dimensional and grows from bottom to top. The nano-branches have different orientations, which significantly increases the specific surface area. The nano silver particles are dispersed on the surface of the nano coral gold.
The nano-coating on the surface of the graphite core is very closely arranged in structure, and almost covers the whole surface of the pencil core.
The graphite surface layer can contain more nano gold particles. Therefore, the specific surface area of the whole nano coating is larger, more active sites are provided, more metal ions to be detected can be combined, and the electrochemical activity of the detection electrode is high.
In addition, the contact area of the nano coral gold and the graphite surface layer is increased, the nano coating is firmly combined with the graphite core, the stability of the detection electrode is better, the service life is long, and the data repeatability is good.
The nano gold particles are more suitable for detection by binding with lead than silver, and the nano silver particles are less effective than the nano gold particles, so that the excessive nano silver particles may have adverse effects. But the addition of a small amount of nano silver particles is better, and the double nano gold particles have a synergistic effect or generate proton positions; or a change in the electronic structure caused by a change in the surface topography on the nanoparticle. Therefore, the number ratio of the gold nanoparticles to the silver nanoparticles is set to 15 to 25:1.
the detection electrode comprises a graphite core and a nano coating. The graphite surface layer comprises a plurality of graphite layers, so that the graphite surface layer has a larger specific surface area, and a larger accommodating space can be provided for the nano coating, namely, more nano gold particles and nano silver particles can be accommodated. And the nano gold particles and the nano silver particles are of three-dimensional structures, and the specific surface area of the nano gold particles and the nano silver particles is larger. Therefore, the specific surface area of the whole nano coating is larger, and the electrochemical activity of the detection electrode is high. In addition, the contact area between the three-dimensional structure of the gold nanoparticles and the silver nanoparticles and the surface layer of the graphite is increased, so that the nano coating and the graphite core are firmly combined, the stability of the detection electrode is good, the service life is long, and the data repeatability is good.
Optionally, the number ratio of the gold nanoparticles to the silver nanoparticles is 19:1.
alternatively, the graphite core is a pencil core (GPL) with the surface wax and clay removed. The lead of the pencil is made by mixing graphite, clay and wax according to a certain proportion. And removing the wax and the clay on the surface layer of the pencil lead by using a reagent to form a large amount of graphite layering. The graphite of the graphite core is uniformly distributed in a layered mode, and the manufacturing cost is low.
The second aspect of the present invention provides a method for preparing a detection electrode, comprising the following steps:
providing a graphite core, wherein the surface of the graphite core is provided with a graphite surface layer, and the graphite surface layer comprises a plurality of graphite layers.
Placing a graphite core in an electrolyte, preparing a nano coating through electrodeposition, wherein the nano coating covers on the surface layer of the graphite, the nano coating comprises a plurality of three-dimensional nano gold particles and a plurality of three-dimensional nano silver particles, the nano silver particles and the nano gold particles are uniformly dispersed, and the number ratio of the nano gold particles to the nano silver particles is 15-25: 1.
the preparation method has the technical characteristics corresponding to the detection electrode, so the preparation method has the corresponding technical effects, and the details are not repeated.
Optionally, the electrolyte in the electrolyte comprises chloroauric acid, silver nitrate and ammonium sulfate, the concentration of the chloroauric acid is 1mmol/L, the concentration of the silver nitrate is 0.1mmol/L, and the concentration of the ammonium sulfate is 10mmol/L.
The reaction formula is shown as follows:
AuCl 4 - +Ag + +4e - +4H + ＝Au+Ag+4HCl
the ratio of the amount of nano-gold particles to nano-silver particles is different from the ratio of chloroauric acid to silver nitrate for several reasons: 1. the electrolyte contains ammonium sulfate, and the sulfuric acid is slightly soluble with silver ions and can cause partial silver ion precipitation. 2. The combination of the ammonium ions and the nano-gold is better, so that the gold can grow upwards better to form coral gold, and the nano-silver is easier to agglomerate to form larger nano-particles.
Optionally, the conditions of electrodeposition are: depositing for 40-60 min under the constant voltage of-1.5V.
Optionally, the method of preparing the graphite core comprises:
polishing the pencil core, cleaning the pencil core by using acetone and nitric acid solution, and applying voltage in sulfuric acid solution to obtain the graphite core.
Since the surface of the pencil lead contains a large amount of wax and clay, it is necessary to remove the wax and clay on the surface by surface-polishing the GPL using sandpaper. Then GPL is treated by ultrasonic treatment in acetone solution and nitric acid solution respectivelyAnd (4) treating and cleaning residual wax and clay. For GPL at H 2 SO 4 The electrical conductivity of the GPL platform was maximized by applying a voltage of-1.5V to the solution by electrochemically dissolving the wax located between the graphite particles. After the steps, the wax and the clay on the surface of the pencil lead are removed, and fine grooves or holes are formed in the space occupied by the wax and the clay. The wall body of the groove or the hole is a graphite layer, and the space of the groove or the hole is a gap between the graphite layers.
In some embodiments, the sonication time in the graphite core preparation step is 15min.
In some embodiments, H in the graphite core preparation step 2 SO 4 The concentration was 0.5mol/L.
In some embodiments, the voltage in the graphite core preparation step is-1.5V and the treatment time is 300s.
The embodiment of the application also provides an electrochemical sensor for detecting lead, which comprises a working electrode, a counter electrode and a reference electrode, wherein the working electrode is the detection electrode or the detection electrode obtained by the preparation method. For example, a platinum electrode can be used as a counter electrode, a calomel electrode can be used as a reference electrode, the three electrodes form a three-electrode system, and Pb is completed on a CHI660D electrochemical workstation 2+ The electrochemical measurement of (1).
The fourth aspect of the present invention provides a method for detecting lead, comprising the steps of:
and placing the electrochemical sensor in a solution to be detected, wherein the solution to be detected is an electrolyte solution and comprises lead ions.
The deposition was carried out for 500s under the conditions of stirring and detection voltage of-0.3 v, and the stripping peak current value of the electrochemical sensor was detected by square wave stripping voltammetry.
Optionally, the solution to be tested further comprises 0.5mol/L sulfuric acid solution.
Example 1
Preparation of graphite core
Since the surface of the pencil lead contains a large amount of wax and clay, the pencil lead needs to be fed by using sandpaperThe row surface was polished and the pencil lead was then sonicated in acetone and nitric acid solutions for 15min, respectively. Then activating the pencil lead, namely H at 0.5mol/L 2 SO 4 And (3) applying a voltage of-1.5V to the solution, treating for 300s, and finally drying and storing to obtain the graphite core GPL.
Example 2
The GPL of example 1 was immersed in a solution containing HAuCl 4 And AgNO 3 、(NH 4 ) 2 SO 4 In solution (i.e., electrolyte) of (2), HAuCl 4 Is 1mmol/L of AgNO 3 Has a concentration of (NH) of 0.1mmol/L 4 ) 2 SO 4 The concentration of (2) is 10mmol/L.
The deposition time is an important parameter when the nano coral gold and silver are deposited. Therefore, the nano coral gold and silver modified pencil lead prepared under different deposition times is researched.
On the basis of the experimental conditions, under the condition that the deposition voltage is-1.5V, preparing the nano coral gold-silver modified pencil lead (namely the detection electrode) under the conditions that the deposition time is 15min, 30min, 45min and 60min respectively, washing the prepared detection electrode with ultrapure water respectively, and drying at room temperature for later use.
Electrochemical testing was performed using a three-electrode system: NCG/GPL is a working electrode, a calomel electrode is a reference electrode, and a platinum electrode is a counter electrode. To 0.5M H each containing 100ppb Pb 2 SO 4 The electrolyte solution is a test solution, a working electrode is applied with a voltage of-0.3V for 500s through an electrochemical workstation, scanning is carried out in a potential range of-0.3V to +0.3V by using a Square Wave Anodic Stripping Voltammetry (SWASV), so that zero-valent lead on the surface of the electrode is rapidly oxidized into divalent lead along with the increase of ion concentration, the stripping peak current value is gradually increased, and a working curve, namely a square wave stripping voltammogram, is drawn according to the peak current intensity and the ion concentration.
The detection results of the detection electrodes prepared by the different deposition times in the electrochemical detection manner are shown in fig. 6A and B. Therefore, under the experimental conditions, under the conditions that the deposition voltage is-1.5V and the deposition time is 45min, the prepared nano coral gold-silver modified pencil lead (first detection electrode) has the largest signal of the anode dissolution peak current for detecting Pb ions, and therefore, the performance of the pencil lead is best.
Example 3
HAuCl due to deposition of gold and silver from coral 4 And AgNO 3 The ratio of gold and silver ions of the two is a relatively important parameter. Therefore, the pencil lead modified by the nano coral gold and silver (or the nano coral gold and the nano coral silver) prepared under different concentrations is researched.
The GPL of example 1 was immersed in different electrolytes at a deposition voltage of-1.5V for a deposition time of 45min to prepare corresponding detection electrodes.
The compositions of the different electrolytes are shown in the table below.
The detection electrode prepared from the electrolyte with the Au/Ag ratio of 90% is a first detection electrode, the detection electrode prepared from the electrolyte with the Au/Ag ratio of 100% is a second detection electrode, and the detection electrode prepared from the electrolyte with the Au/Ag ratio of 0% is a third detection electrode.
The corresponding detection electrode prepared was detected in the electrochemical detection mode of example 2, and the detection results are shown in fig. 6C and D. Therefore, under the experimental conditions and under the condition that the Au/Ag ratio is 90%, the prepared nano coral gold-silver modified pencil lead has the largest signal of the anode dissolution peak current for detecting Pb ions, and therefore, the performance of the pencil lead is the best.
Example 4
The first detection electrode is characterized, and fig. 1 is a scanning electron microscope image of the first detection electrode (pencil lead modified by nano coral gold and silver) at different magnifications. It can be seen from fig. 1 that coral-shaped nanogold was successfully prepared, in which nanosilver was dispersed on the surface of coral-shaped nanogold (fig. 1 (F) yellow part). The structure of the coating on the surface of the pencil lead is arranged very tightly, and almost covers the whole surface of the pencil lead. The shape of the nano coral is three-dimensional and grows from bottom to top. The branches have different orientations, which significantly increases the specific surface area.
Fig. 2 is the EDS analysis result of the first detection electrode. The characteristic peaks of the elements of Au and Ag can be seen from the figure, which further indicates that the nano coral gold and silver is successfully plated on the pencil lead.
Example 5
Electrochemical testing was performed using a three-electrode system: the first detection electrode is a working electrode, the calomel electrode is a reference electrode, and the platinum electrode is a counter electrode. To 0.5M H each containing 100ppb Pb 2 SO 4 An electrolyte solution is a test solution, a working electrode is applied with a voltage of-0.3V for 500s through an electrochemical workstation, scanning is carried out in a potential range of-0.3V to +0.3V by using a Square Wave Anodic Stripping Voltammetry (SWASV), so that zero-valent lead on the surface of the electrode is rapidly oxidized into divalent lead, the stripping peak current value is gradually increased along with the increase of the ion concentration, and a working curve, namely a square wave stripping voltammogram, is drawn according to the peak current intensity and the ion concentration.
And (3) replacing the first detection electrode with the second detection electrode, keeping the other conditions unchanged, and recording a square wave dissolution voltammogram.
And replacing the first detection electrode with the third detection electrode, keeping the other conditions unchanged, and recording a square wave dissolution voltammogram.
The results are shown in FIG. 3. FIG. 3 shows Pb at a concentration of 100ppb each 2+ Square wave stripping voltammetry curves on the nano coral silver modified pencil lead (a), the nano coral gold modified pencil lead (b) and the nano coral gold modified pencil lead (c). As can be seen from FIG. 3, the pencil lead modified by the nano coral silver only shows a very weak peak; after the lead of the pencil is decorated with nano coral gold, pb 2+ The square wave stripping voltammetry peak current is obviously increased, which shows that the conductivity of the nano gold is better; and Pb when the pencil lead is further modified by the nano coral gold and silver 2+ The square wave stripping voltammetry peak current is higher, and compared with pure metal, the activity of the bimetallic nanoparticles is higher.
Example 6
The obtained first detection electrode is used as a working electrode, a platinum electrode is used as a counter electrode, a calomel electrode is used as a reference electrode to form a three-electrode system, and Pb is finished on a CHI660D electrochemical workstation 2+ Electrochemical (c) ofPerforming chemical determination; the electrochemical measurement method is as follows: in the presence of different concentrations of Pb 2+ 0.5mol/L H 2 SO 4 In the solution, before each measurement, the solution is deposited for 500s under constant potential at-0.3V, and then a square wave dissolution voltammogram within the range of-0.3V is recorded.
In the presence of Pb in various concentrations 2+ In solution, square wave stripping voltammetry measurements were performed in the range of-0.3 to 0.3V (FIG. 4 (A)), and a standard curve was plotted. As shown in FIG. 4 (B), the results are shown at Pb 2+ In the concentration range of 5-300 ppb, the current value of square wave stripping voltammetric peak and the concentration present a linear relation, and the linear correlation coefficient R 2 =0.998, detection limit is 0.04ppb (S/N = 3).
Example 7
Under the conditions of example 2, the same first detection electrode was placed at a concentration of 100ppb Pb 2+ 0.5mol/L H 2 SO 4 In the solution, the parallel determination is carried out for 12 times, referring to fig. 5, the Relative Standard Deviation (RSD) of the square wave stripping voltammetry peak current is 3.17 percent, which shows that the electrochemical determination of Pb by the nano coral gold and silver modified pencil lead electrode 2+ Has good stability.
In the above technical solutions, the above are only preferred embodiments of the present invention, and the technical scope of the present invention is not limited thereby, and all the technical concepts of the present invention include the claims of the present invention, which are directly or indirectly applied to other related technical fields by using the equivalent structural changes made in the content of the description and the drawings of the present invention.
Claims (10)
1. A detection electrode, comprising:
the graphite core is provided with a graphite surface layer on the surface, and the graphite surface layer comprises a plurality of graphite layers;
the nano coating covers the graphite surface layer, the nano coating comprises a plurality of three-dimensional nano gold particles and a plurality of three-dimensional nano silver particles, the nano silver particles and the nano gold particles are uniformly dispersed, and the number ratio of the nano gold particles to the nano silver particles is (15-25): 1.
2. the detection electrode according to claim 1, wherein the ratio of the number of the gold nanoparticles to the silver nanoparticles is 19:1.
3. the detection electrode according to claim 1 or 2, wherein the graphite core is a pencil core from which wax and clay on the surface layer are removed.
4. The preparation method of the detection electrode is characterized by comprising the following steps of:
providing a graphite core, wherein the surface of the graphite core is provided with a graphite surface layer, and the graphite surface layer comprises a plurality of graphite layers;
placing the graphite core in an electrolyte, preparing a nano coating through electrodeposition, wherein the nano coating covers the graphite surface layer, the nano coating comprises a plurality of three-dimensional nano gold particles and a plurality of three-dimensional nano silver particles, the nano silver particles and the nano gold particles are uniformly dispersed, and the number ratio of the nano gold particles to the nano silver particles is 15-25: 1.
5. the method for preparing a detection electrode according to claim 4, wherein the electrolyte in the electrolyte comprises chloroauric acid, silver nitrate and ammonium sulfate, the concentration of the chloroauric acid is 1mmol/L, the concentration of the silver nitrate is 0.1mmol/L, and the concentration of the ammonium sulfate is 10mmol/L.
6. The method for preparing a detection electrode according to claim 4, wherein the electrodeposition conditions are: depositing for 40-60 min under the constant voltage of-1.5V.
7. The method for preparing the detection electrode according to claim 3, wherein the method for preparing the graphite core comprises the following steps:
polishing the pencil core, cleaning the pencil core by using an acetone and nitric acid solution, and applying voltage in a sulfuric acid solution to obtain the graphite core.
8. An electrochemical sensor for detecting lead, comprising a working electrode, a counter electrode and a reference electrode, wherein the working electrode is the detection electrode according to any one of claims 1 to 3 or the detection electrode obtained by the preparation method according to any one of claims 4 to 7.
9. A method of detecting lead, comprising the steps of:
placing the electrochemical sensor of claim 8 in a solution to be tested, wherein the solution to be tested is an electrolyte solution, and the solution to be tested comprises lead ions;
and (3) carrying out deposition for 500s under the conditions of stirring and detection voltage of-0.3 v, and detecting the stripping peak current value of the electrochemical sensor by using square wave stripping voltammetry.
10. The method for detecting lead according to claim 9, wherein the solution to be detected further comprises a 0.5mol/L sulfuric acid solution.
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