Mercury ion detection method based on paper chip

Abstract

The invention provides a mercury ion detection method based on a paper chip, and belongs to the technical field of mercury ion detection. The mercury ion detection method based on the paper chip comprises the following steps: firstly preparing nanogold, then preparing graphene quantum dots, mixing the nanogold and the graphene quantum dots to obtain a nanogold-graphene quantum dot compound, and then dropwise adding the nanogold-graphene quantum dot compound to filter paper to obtain a nanogold-graphene quantum dot paper chip, the paper chip is used for detecting the mercury ion concentration of a to-be-detected sample. According to the invention, sodium borohydride is used as a reducing agent and sodium citrate is used as a stabilizer to prepare nanogold, so that the particle size of the nanogold is more controllable, the particle size of the nanogold-graphene quantum dot compound obtained by combining with the graphene quantum dots is smaller, and the nanogold-graphene quantum dot compound is more tightly combined with mercury ions during detection; and finally, the result of measuring the mercury ion concentration by adopting the paper chip is more accurate.

Description

Technical Field

[0001] The invention relates to the technical field of mercury ion detection, and in particular to a mercury ion detection method based on a paper chip. Background Art

[0002] Mercury is a highly toxic heavy metal element that poses a serious threat to both the human body and the environment. 2+ ) accumulates in the human body and can cause damage to multiple systems, including the central nervous system, cardiovascular system, and immune system, and may even lead to serious health problems, such as neurological diseases and kidney damage. In addition, mercury ions can easily accumulate through the food chain, causing harm to aquatic and terrestrial organisms, and then damage the entire ecosystem. Given the high toxicity and easy accumulation of mercury ions, accurate and rapid detection of mercury ions is of great significance for environmental protection and human health. By detecting the concentration of mercury ions in the environment, the extent of mercury pollution can be assessed, and timely control measures can be taken to prevent mercury pollution from causing further harm to the ecosystem and human health. At the same time, mercury ion detection is also an important part of food safety testing, which can ensure that the content of mercury ions in food is within a safe range and protect the health of consumers.

[0003] Paper chip is a paper-based microfluidic analysis platform with the advantages of low cost, biodegradability, and good biocompatibility. It uses the capillary action of paper to achieve automatic transmission and mixing of liquids, thereby completing various chemical reactions and detection processes. In addition, paper chips can also be combined with various nanomaterials and optical detection technologies to improve detection sensitivity and accuracy. Existing detection methods based on paper chips have problems such as being affected by environmental fluorescence and low detection accuracy. Therefore, it is of great practical significance to provide a mercury ion detection method with high detection accuracy based on paper chips. Summary of the invention

[0004] The object of the present invention is to provide a mercury ion detection method based on a paper chip, in which sodium borohydride is used as a reducing agent and sodium citrate is used as a stabilizer to prepare nanogold, so that the particle size of the nanogold is more controllable, and the particle size of the complex obtained by combining with graphene quantum dots can be made smaller, ultimately making the result of measuring mercury ion concentration using a paper chip more accurate.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a method for detecting mercury ions based on a paper chip, comprising the following steps:

[0007] The sodium citrate solution, the chloroauric acid solution and the sodium borohydride solution are first mixed to obtain a seed solution;

[0008] Mixing the chloroauric acid solution with CTAB to obtain a CTAB growth solution;

[0009] The CTAB growth solution, the seed solution and the ascorbic acid are mixed for a second time, and then stirred to obtain nano-gold;

[0010] The citric acid is heated, and then a NaOH solution is added to obtain graphene quantum dots;

[0011] The graphene quantum dots are mixed with nano-gold for a third time to obtain nano-gold-graphene quantum dots;

[0012] Adding the nano-gold-graphene quantum dots dropwise onto filter paper to obtain a nano-gold-graphene quantum dot paper chip;

[0013] Dropping mercury ion solutions of different concentrations on the nanogold-graphene quantum dot paper chip in sequence, recording the colors of mercury ions of different concentrations dropped on the nanogold-graphene quantum dot paper chip, and preparing a standard colorimetric card based on the recorded colors;

[0014] The sample to be tested is added dropwise onto the nanogold-graphene quantum dot paper chip, and after the color no longer changes, it is compared with a standard colorimetric card to obtain the concentration of mercury ions in the sample to be tested;

[0015] The nanogold-graphene quantum dots can also be obtained by mixing nanogold and carboxyl graphene quantum dots; when the nanogold-graphene quantum dots are obtained by mixing nanogold and carboxyl graphene quantum dots, the filter paper is infiltrated with a crosslinking agent before preparing the nanogold-graphene quantum dot paper chip.

[0016] Furthermore, the concentrations of the sodium citrate solution and the chloroauric acid solution are both 2.0×10 -4 ~3.0×10 -4 M, the concentration of the sodium borohydride is 0.1-0.3M.

[0017] Furthermore, the dosage ratio of the sodium citrate solution, the chloroauric acid solution and the sodium borohydride in the first mixture is 200:200:1-3.

[0018] Furthermore, the concentration of the CTAB growth solution is 0.08-0.1M.

[0019] Furthermore, in the second mixture, the ratio of CTAB growth solution to seed solution is 2-3:1-2, and the ratio of seed solution to ascorbic acid is 100-120:1-1.5.

[0020] Furthermore, the heating temperature is 160-200° C. and the heating time is 25-30 minutes.

[0021] Furthermore, the usage ratio of graphene quantum dots to nano-gold in the third mixture is 1:50-100.

[0022] Furthermore, the cross-linking agent is 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride.

[0023] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0024] The invention uses sodium borohydride as a reducing agent and sodium citrate as a stabilizer to prepare nano gold, so that the particle size of the nano gold is more controllable, and the particle size of the complex obtained by combining with graphene quantum dots can be smaller, so that the final test result is more accurate; in addition, the invention also limits that carboxylated graphene quantum dots can be used to prepare nano gold-graphene quantum dots, and a cross-linking agent is used to improve the luminescence performance of the graphene quantum dots, so that the color change is more obvious when mercury ions are detected, and the detection result can be more accurate; in addition, the invention adopts a method of preparing a colorimetric card to detect the concentration of mercury ions, which is more convenient and quick, and is easy to be applied in actual production and life. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic diagram of the process of the mercury ion detection method based on paper chip in Example 1. DETAILED DESCRIPTION

[0026] The present invention provides a method for detecting mercury ions based on a paper chip, comprising the following steps:

[0027] The sodium citrate solution, the chloroauric acid solution and the sodium borohydride solution are first mixed to obtain a seed solution;

[0028] Mixing the chloroauric acid solution with CTAB to obtain a CTAB growth solution;

[0029] The CTAB growth solution, the seed solution and the ascorbic acid are mixed for a second time, and then stirred to obtain nano-gold;

[0030] The citric acid is heated, and then a NaOH solution is added to obtain graphene quantum dots;

[0031] The graphene quantum dots are mixed with nano-gold for a third time to obtain nano-gold-graphene quantum dots;

[0032] Adding the nano-gold-graphene quantum dots dropwise onto filter paper to obtain a nano-gold-graphene quantum dot paper chip;

[0033] Dropping mercury ion solutions of different concentrations on the nanogold-graphene quantum dot paper chip in sequence, recording the colors of mercury ions of different concentrations dropped on the nanogold-graphene quantum dot paper chip, and preparing a standard colorimetric card based on the recorded colors;

[0034] The sample to be tested is added dropwise onto the nanogold-graphene quantum dot paper chip, and after the color no longer changes, it is compared with a standard colorimetric card to obtain the concentration of mercury ions in the sample to be tested;

[0035] The nanogold-graphene quantum dots can also be obtained by mixing nanogold and carboxyl graphene quantum dots; when the nanogold-graphene quantum dots are obtained by mixing nanogold and carboxyl graphene quantum dots, the filter paper is infiltrated with a crosslinking agent before preparing the nanogold-graphene quantum dot paper chip.

[0036] The CTAB described in the present invention is hexadecyltrimethylammonium bromide.

[0037] The sodium citrate solution, the chloroauric acid solution and the sodium borohydride solution are first mixed to obtain a seed solution.

[0038] The present invention first prepares a sodium citrate solution and a chloroauric acid solution of target concentrations, mixes the sodium citrate solution and the chloroauric acid solution evenly, then adds a sodium borohydride solution, and continues to stir evenly to obtain the seed solution;

[0039] In the present invention, the concentrations of the sodium citrate solution and the chloroauric acid solution are preferably 2.0×10 -4 ~3.0×10 -4 M is more preferably 2.5×10 -4 M; the concentration of the sodium borohydride is 0.1-0.3M, more preferably 0.1M.

[0040] In the present invention, the dosage ratio of the sodium citrate solution, the chloroauric acid solution and the sodium borohydride in the first mixture is preferably 200:200:1-3.

[0041] The present invention uses sodium borohydride as a reducing agent and sodium citrate as a stabilizer to prepare nano-gold, so that the particle size of the nano-gold is more controllable, and the particle size of the composite obtained by combining with graphene quantum dots can be smaller, so that the final test result is more accurate.

[0042] The chloroauric acid solution was mixed with CTAB to obtain a CTAB growth solution.

[0043] The present invention adds CTAB into the chloroauric acid solution so that the concentration of CTAB is 0.08-0.1M, thereby obtaining the CTAB growth solution.

[0044] In the present invention, the concentration of the CTAB growth solution is preferably 0.08-0.1M, and more preferably 0.08M.

[0045] The CTAB growth solution, seed solution and ascorbic acid are mixed for a second time and stirred to obtain nano-gold.

[0046] The present invention first mixes CTAB growth solution and ascorbic acid, stirs them evenly, then adds seed solution, continues to stir evenly, and then stands to obtain nano gold precipitation;

[0047] In the present invention, the usage ratio of CTAB growth solution to seed solution in the second mixture is preferably 2-3:1-2, more preferably 2:1; the usage ratio of seed solution to ascorbic acid is preferably 100-120:1-1.5, more preferably 100:1.

[0048] The citric acid is heated, and then a NaOH solution is added to obtain graphene quantum dots.

[0049] The present invention places a certain amount of citric acid in a beaker and heats it. After the citric acid changes from colorless to light yellow and then to orange, a NaOH solution is added to adjust the pH value to 7.0. After stirring, the solution is allowed to stand to obtain light green transparent graphene quantum dots.

[0050] In the present invention, the heating temperature is preferably 160 to 200° C., more preferably 180 to 200° C.; the heating time is preferably 25 to 30 minutes.

[0051] The graphene quantum dots are mixed with the nano-gold for the third time to obtain the nano-gold-graphene quantum dots.

[0052] In the present invention, the usage ratio of graphene quantum dots to nano-gold in the third mixture is 1:50-100.

[0053] Adding nano-gold-graphene quantum dots dropwise onto filter paper to obtain a nano-gold-graphene quantum dot paper chip;

[0054] The invention drips the nano-gold-graphene quantum dots onto filter paper, and then places the filter paper in an oven for drying to obtain a nano-gold-graphene quantum dot paper chip that can be used to detect mercury ion concentration.

[0055] Then, mercury ion solutions of different concentrations are sequentially dripped onto the nanogold-graphene quantum dot paper chip, and the colors of mercury ions of different concentrations dripped onto the nanogold-graphene quantum dot paper chip are recorded. Based on the recorded colors, a standard colorimetric card is prepared;

[0056] The sample to be tested is dropped onto the nanogold-graphene quantum dot paper chip. After the color stops changing, it is compared with the standard colorimetric card to obtain the concentration of mercury ions in the sample to be tested.

[0057] In the present invention, the nanogold-graphene quantum dots can also be obtained by mixing nanogold and carboxylated graphene quantum dots; when the nanogold-graphene quantum dots are obtained by mixing nanogold and carboxylated graphene quantum dots, the filter paper is infiltrated with a crosslinking agent before preparing the nanogold-graphene quantum dot paper chip, and the crosslinking agent is preferably 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride.

[0058] The carboxylated graphene quantum dots described in the present invention are commercially available products, and products known to those skilled in the art may be used; in addition, products not limited in the present invention are all commercially available products known to those skilled in the art.

[0059] The present invention stipulates that carboxylated graphene quantum dots can also be combined with nanogold to obtain nanogold-graphene quantum dots, and at the same time, the filter paper is impregnated with a cross-linking agent to improve the luminescence performance of the carboxylated graphene quantum dots, so that when mercury ions are detected, the color change is more obvious and the detection result is more accurate.

[0060] In the present invention, unless otherwise specified, the required raw materials for preparation are all commercially available products well known to those skilled in the art.

[0061] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0062] Example 1

[0063] (1) Preparation of seed solution: Use a pipette to measure 10 mL of water into round-bottom flask A, and add chloroauric acid to make the concentration of the resulting chloroauric acid solution 2.5×10 -4 M; then measure 10 mL of water into round-bottom flask B, add sodium citrate to make the concentration of sodium citrate 2.5×10 -4 M; after mixing the round-bottom flask A and the round-bottom flask B, add 0.3 mL of 0.1 M sodium borohydride and stir evenly to obtain the seed solution;

[0064] (2) Prepare CTAB growth solution: 50 mL of 2.5×10 -4 Add CTAB to the 10M chloroauric acid solution and stir evenly to obtain a 0.08M CTAB growth solution;

[0065] (3) Using a pipette, measure 10 mL of CTAB growth solution and mix with 50 μL of ascorbic acid, stir evenly, add 5 mL of seed solution, stir evenly again, and let stand for a period of time to obtain a precipitate, which is nano-gold;

[0066] (4) Add 5 g of citric acid into a beaker and heat at 180° C. for 30 min. The colorless citric acid first turns into a light yellow liquid and then turns into orange. After the solution turns into orange, add 15 mg / mL of NaOH solution to adjust the pH of the solution to 7.0, stir, and stand to obtain light green transparent graphene quantum dots.

[0067] (5) Mix 10 μL of graphene quantum dots and 1 mL of nanogold to obtain nanogold-graphene quantum dots;

[0068] (6) adding 10 μL of nanogold-graphene quantum dots onto a circular filter paper with a diameter of 5 mm to obtain a nanogold-graphene quantum dot paper chip, and drying the obtained paper chip in an oven at 35° C. to obtain a nanogold-graphene quantum dot paper chip that can be used to detect mercury ions;

[0069] (7) dropping mercury ion solutions of different concentrations onto the nanogold-graphene quantum dot paper chip in sequence, recording the colors of mercury ions of different concentrations dropped onto the nanogold-graphene quantum dot paper chip, and preparing a standard colorimetric card based on the recorded colors;

[0070] (8) The sample to be tested is added dropwise onto the nanogold-graphene quantum dot paper chip. After the color no longer changes, it is compared with a standard colorimetric card to obtain the concentration of mercury ions in the sample to be tested.

[0071] Example 2

[0072] (1) Preparation of seed solution: Use a pipette to measure 10 mL of water into round-bottom flask A, and add chloroauric acid to make the concentration of the resulting chloroauric acid solution 3.0 × 10 -4 M; then measure 10 mL of water into round-bottom flask B, add sodium citrate to make the concentration of sodium citrate 3.0×10 -4 M; after mixing the round-bottom flask A and the round-bottom flask B, add 0.1 mL of 0.3 M sodium borohydride and stir evenly to obtain the seed solution;

[0073] (2) Prepare CTAB growth solution: 50 mL of 3.0×10 -4 Add CTAB to the 10M chloroauric acid solution and stir evenly to obtain a 0.1M CTAB growth solution;

[0074] (3) Using a pipette, measure 10 mL of CTAB growth solution and mix with 50 μL of ascorbic acid, stir evenly, add 10 mL of seed solution, stir evenly again, and let stand for a period of time to obtain a precipitate, which is nano-gold;

[0075] (4) Add 10 g of citric acid into a beaker and heat at 180° C. for 30 min. The colorless citric acid first turns into a light yellow liquid and then turns into orange. After the solution turns into orange, add 15 mg / mL of NaOH solution to adjust the pH of the solution to 7.0, stir, and stand to obtain light green transparent graphene quantum dots.

[0076] (5) Mix 10 μL of graphene quantum dots and 1 mL of nanogold to obtain nanogold-graphene quantum dots;

[0077] (6) adding 10 μL of nanogold-graphene quantum dots onto a circular filter paper with a diameter of 5 mm to obtain a nanogold-graphene quantum dot paper chip, and drying the obtained paper chip in an oven at 35° C. to obtain a nanogold-graphene quantum dot paper chip that can be used to detect mercury ions;

[0078] (7) dropping mercury ion solutions of different concentrations onto the nanogold-graphene quantum dot paper chip in sequence, recording the colors of mercury ions of different concentrations dropped onto the nanogold-graphene quantum dot paper chip, and preparing a standard colorimetric card based on the recorded colors;

[0079] (8) The sample to be tested is added dropwise onto the nanogold-graphene quantum dot paper chip. After the color no longer changes, it is compared with a standard colorimetric card to obtain the concentration of mercury ions in the sample to be tested.

[0080] Example 3

[0081] (1) Preparation of seed solution: Use a pipette to measure 10 mL of water into round-bottom flask A, and add chloroauric acid to make the concentration of the resulting chloroauric acid solution 2.0 × 10 -4 M; then measure 10 mL of water into round-bottom flask B, add sodium citrate to make the concentration of sodium citrate 2.0×10 -4 M; after mixing the round-bottom flask A and the round-bottom flask B, add 0.3 mL of 0.3 M sodium borohydride and stir evenly to obtain the seed solution;

[0082] (2) Prepare CTAB growth solution: 50 mL of 3.0×10 -4 Add CTAB to the 10M chloroauric acid solution and stir evenly to obtain a 0.08M CTAB growth solution;

[0083] (3) Using a pipette, measure 10 mL of CTAB growth solution and mix with 50 μL of ascorbic acid, stir evenly, add 5 mL of seed solution, stir evenly again, and let stand for a period of time to obtain a precipitate, which is nano-gold;

[0084] (4) 10 μL of commercially available carboxylated graphene quantum dots and 1 mL of nanogold were mixed evenly to obtain nanogold-graphene quantum dots;

[0085] (5) impregnating the filter paper with a cross-linking agent, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, and then drying it in an oven for later use;

[0086] (6) adding 10 μL of nanogold-graphene quantum dots onto a circular filter paper with a diameter of 5 mm to obtain a nanogold-graphene quantum dot paper chip, and drying the obtained paper chip in an oven at 35° C. to obtain a nanogold-graphene quantum dot paper chip that can be used to detect mercury ions;

[0087] (7) dropping mercury ion solutions of different concentrations onto the nanogold-graphene quantum dot paper chip in sequence, recording the colors of mercury ions of different concentrations dropped onto the nanogold-graphene quantum dot paper chip, and preparing a standard colorimetric card based on the recorded colors;

[0088] (8) The sample to be tested is added dropwise onto the nanogold-graphene quantum dot paper chip. After the color no longer changes, it is compared with a standard colorimetric card to obtain the concentration of mercury ions in the sample to be tested.

[0089] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for detecting mercury ions based on a paper chip, characterized in that: The following steps are involved: The sodium citrate solution, the chloroauric acid solution and the sodium borohydride solution are first mixed to obtain a seed solution; Mixing the chloroauric acid solution with CTAB to obtain a CTAB growth solution; The CTAB growth solution, the seed solution and the ascorbic acid are mixed for a second time, and then stirred to obtain nano-gold; The citric acid is heated, and then a NaOH solution is added to obtain graphene quantum dots; The graphene quantum dots are mixed with nano-gold for a third time to obtain nano-gold-graphene quantum dots; Adding the nano-gold-graphene quantum dots dropwise onto filter paper to obtain a nano-gold-graphene quantum dot paper chip; Dropping mercury ion solutions of different concentrations on the nanogold-graphene quantum dot paper chip in sequence, recording the colors of mercury ions of different concentrations dropped on the nanogold-graphene quantum dot paper chip, and preparing a standard colorimetric card based on the recorded colors; The nanogold-graphene quantum dots can also be obtained by mixing nanogold and carboxyl graphene quantum dots; when the nanogold-graphene quantum dots are obtained by mixing nanogold and carboxyl graphene quantum dots, the filter paper is infiltrated with a crosslinking agent before preparing the nanogold-graphene quantum dot paper chip.

2. The method for detecting mercury ions based on a paper chip according to claim 1, characterized in that: The concentrations of the sodium citrate solution and the chloroauric acid solution are both 2.0×10 -4 ~3.0×10 -4 M, the concentration of the sodium borohydride is 0.1-0.3M.

3. The method for detecting mercury ions based on a paper chip according to claim 1, characterized in that: The dosage ratio of the sodium citrate solution, the chloroauric acid solution and the sodium borohydride in the first mixture is 200:200:1-3.

4. The method for detecting mercury ions based on a paper chip according to claim 1, characterized in that: The concentration of the CTAB growth solution is 0.08-0.1M.

5. The method for detecting mercury ions based on a paper chip according to claim 1, characterized in that: In the second mixture, the usage ratio of CTAB growth solution to seed solution is 2-3:1-2, and the usage ratio of seed solution to ascorbic acid is 100-120:1-1.

5.

6. The method for detecting mercury ions based on a paper chip according to claim 1, characterized in that: The heating temperature is 160-200° C. and the heating time is 25-30 minutes.

7. The method for detecting mercury ions based on a paper chip according to claim 1, characterized in that: The usage ratio of graphene quantum dots to nano-gold in the third mixture is 1:50-100.

8. The method for detecting mercury ions based on a paper chip according to claim 1, characterized in that: The cross-linking agent is 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride.

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