Application of acid discoloration carbon dots in formaldehyde visual detection

Abstract

The application relates to an application of acid discoloration carbon dots in visual detection of formaldehyde. The detection method utilizes the reaction of formaldehyde and ammonium chloride to generate free protons, so that the acid discoloration carbon dots obviously change colors, thereby indicating whether formaldehyde is contained. The method has good selectivity, can realize detection of formaldehyde with a concentration of 10 mmol / L and above in a solution, and can realize detection of formaldehyde with a concentration of 50 mmol / L and above on a solid matrix such as filter paper. The color change is from pink to blue, the discoloration is obvious, and the discoloration is easy to observe. The acid discoloration carbon dots used in the method have good biocompatibility, do not volatilize, and have no toxic and harmful side effects on the human body.

Description

Technical Field

[0001] This invention belongs to the field of visual detection technology, specifically relating to the application of acid-induced color-changing carbon dots in the visual detection of formaldehyde. Background Technology

[0002] Formaldehyde is a colorless, irritating gas that is soluble in water. It damages the human sense of smell, lung function, liver function, and immune system, and can cause symptoms such as coma, shock, internal bleeding, and leukemia. The International Agency for Research on Cancer (IARC) of the World Health Organization classifies formaldehyde as a Group 1 carcinogen. However, due to its widespread use in industrial production, textile dyeing, and food preservation and sterilization, formaldehyde is ubiquitous in people's daily lives. For example, furniture boards, wall paints, wooden door varnishes, clothing, and some seafood products gradually release formaldehyde, exposing the human body to a dangerous environment. Therefore, rapid and convenient formaldehyde detection is of paramount importance for protecting human health.

[0003] Currently, the main methods for formaldehyde detection are spectrophotometry, fluorescence spectroscopy, and colorimetry. Colorimetry, in particular, requires less sophisticated equipment and is relatively simple to operate, making it more widely used for rapid on-site formaldehyde detection. Formaldehyde test strips and reagents based on colorimetric methods are already available on the market. However, most of these colorimetric methods still require the use of phenol reagents, acetylacetone, or other chemical reagents that are highly toxic to humans. Therefore, developing new colorimetric methods and corresponding reagents to reduce the harm to humans from the detection methods themselves is essential for rapid and visual formaldehyde detection. Summary of the Invention

[0004] This invention aims to provide a visual detection method for formaldehyde using acid-induced color-changing carbon dots. The chemical reagents and materials used in the method are non-toxic to the human body, the method is simple to operate, and the detection has good selectivity, thus solving the problem of using toxic and harmful chemical reagents in existing visual detection methods for formaldehyde.

[0005] The detection method of this invention utilizes the reaction of formaldehyde with ammonium chloride to synthesize hexamethylenetetramine and hydrogen ions, which are relatively strong acids. The reaction equation is shown below:

[0006] 6HCHO+4NH4 + =(CH2)6N4H + +6H2O+3H +

[0007] Stronger acids cause a noticeable color change in acid-induced color-changing carbon dots, enabling the visual detection of formaldehyde based on this color change.

[0008] Acid-induced color-changing materials can be organic molecules, nanomaterials, polymers, etc., and must exhibit a visible color change under desired acidic conditions while possessing low biotoxicity. Based on this, we selected an acid-induced color-changing carbon dot.

[0009] The technical solution adopted in this invention is:

[0010] An application of acid-induced color-changing carbon dots in the visual detection of formaldehyde, wherein the preparation method of the acid-induced color-changing carbon dots includes the following steps:

[0011] 1) Dissolve 0.2g o-phenylenediamine and 0.13g urea in 10mL deionized water, then mix with 20mL 3.0mol / L sulfuric acid solution. Add the resulting mixture to a polytetrafluoroethylene reactor and place the reactor in an oven. Perform a hydrothermal reaction at 210℃ for 10h. Cool to room temperature to obtain the crude product.

[0012] 2) The crude product obtained was filtered through a 0.22 μm filter membrane and washed three times with deionized water. The washed product was placed in a dialysis bag with MW=5000 and dialyzed until the exudate was colorless and neutral.

[0013] 3) The dialyzed product was rotary evaporated at 60°C to remove most of the water, and then vacuum dried at 60°C for 24 hours to obtain a black powder, which is the target product.

[0014] Furthermore, the above-mentioned application of the formaldehyde visualization detection method includes the following steps:

[0015] 1) Preparation of standard colorimetric solutions: Mix 20 μL of ammonium chloride solution with 20 μL of formaldehyde solutions with concentrations of 0, 0.01, 0.05, 0.1, and 0.5 mol / L respectively. After standing for 5 minutes, add 2 mL of acid-induced color-changing carbon dot solution to each solution to obtain standard colorimetric solutions that display different colors.

[0016] 2) Sample detection: Mix 20 μL of ammonium chloride solution with 20 μL of sample solution containing formaldehyde evenly, let stand for 5 minutes, then add 2 mL of acid-induced color-changing carbon dot solution. Based on the color change of the sample solution, compare it with the standard colorimetric solution that shows different colors obtained in step 1) to achieve visual detection of formaldehyde.

[0017] Furthermore, the above-mentioned application of the formaldehyde visualization detection method includes the following steps:

[0018] 1) Preparation of filter paper discs: Cut the filter paper into small round discs of 12mm using a tablet press. Then, take 10μL of acid-induced color-changing carbon dot solution and drop it evenly onto the small round discs. Dry them in a vacuum drying oven at 60℃ for 2 hours to prepare filter paper discs.

[0019] 2) Preparation of standard colorimetric cards: Take nine filter paper pieces prepared in step 1), add 10 μL of ammonium chloride solution to each filter paper piece, and after the solution has soaked the filter paper pieces, add formaldehyde solutions with concentrations of 0, 50, 100, 150, 200, 300, 500, 800, and 1000 mmol / L to the nine filter paper pieces respectively, and wait for the color to develop to prepare a standard colorimetric card showing the change from red to blue;

[0020] 3) Sample detection: Add 10 μL of ammonium chloride solution to the filter paper obtained in step 1). After the solution wets the filter paper, add a sample solution containing formaldehyde to the filter paper. Based on the color change of the filter paper with the sample solution, compare it with the standard colorimetric card obtained in step 2) which shows a change from red to blue to achieve visual detection of formaldehyde.

[0021] Preferably, in the above application, the concentration of the ammonium chloride solution is 0.2 mol / L.

[0022] Preferably, in the above application, the concentration of the acid-induced color-changing carbon dot solution is 10 μg / mL.

[0023] The beneficial effects of this invention are as follows: The reagent used in this invention as a color-changing indicator of formaldehyde is a safe and non-toxic acid-induced color-changing carbon point. Under the stated conditions, the carbon point changes from red to blue upon the addition of formaldehyde, and the change is obvious and easy to observe. Therefore, the method used in this invention is expected to be applied to the visual detection of formaldehyde. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the color change of acid-induced chromogenic carbon dots in solution for visual detection of formaldehyde, where the formaldehyde concentrations in ae are 0, 0.01, 0.1, 0.5, and 1.0 mol / L.

[0025] Figure 2 This is a schematic diagram illustrating the color change of acid-induced color-changing carbon dots on filter paper for visual detection of formaldehyde. The left side of the dotted line represents filter paper with only ammonium chloride or formaldehyde added, while the right side of the dotted line represents filter paper with ammonium chloride added, followed by formaldehyde solutions with concentrations of 50, 100, 150, 200, 300, 500, 800, and 1000 mmol / L. Detailed Implementation

[0026] Example 1: Preparation of acid-induced color-changing carbon dots

[0027] 1) Dissolve 0.2g o-phenylenediamine and 0.13g urea in 10mL deionized water, then mix with 20mL 3.0mol / L sulfuric acid solution. Add the resulting mixture to a polytetrafluoroethylene reactor and place the reactor in an oven. Perform a hydrothermal reaction at 210℃ for 10h. Cool to room temperature to obtain the crude product.

[0028] 2) The crude product obtained was filtered through a 0.22 μm filter membrane and washed three times with deionized water. The washed product was placed in a dialysis bag with MW=5000 and dialyzed until the exudate was colorless and neutral.

[0029] 3) The dialyzed product was rotary evaporated at 60°C to remove most of the water, and then vacuum dried at 60°C for 24 hours to obtain a black powder, which is the target product.

[0030] Example 2: Visual detection of formaldehyde using acid-induced color-changing carbon dots in solution.

[0031] The detection method includes the following steps:

[0032] 1) Preparation of standard colorimetric solutions: Mix 20 μL of 0.2 mol / L ammonium chloride solution with 20 μL of formaldehyde solutions with concentrations of 0, 0.01, 0.05, 0.1, and 0.5 mol / L respectively. After standing for 5 minutes, add 2 mL of 10 μg / mL acid-induced color-changing carbon dot solution to each solution to obtain standard colorimetric solutions that display different colors.

[0033] 2) Sample detection: Mix 20 μL of 0.2 mol / L ammonium chloride solution with 20 μL of formaldehyde sample solution, let stand for 5 minutes, then add 2 mL of 10 μg / mL acid-induced color-changing carbon dot solution, observe the color change of the sample solution, and compare the color with the standard colorimetric solutions that show different colors obtained in step 1) to achieve visual detection of samples with unknown formaldehyde concentration.

[0034] Figure 1 This is a schematic diagram illustrating the results of visual detection of acid-induced color-changing carbon dots in formaldehyde solutions with concentrations of 0, 0.01, 0.05, 0.1, and 0.5 mol / L. (From...) Figure 1 It can be seen that a color change can be observed in the solution when the formaldehyde concentration is 0.01 mol / L, and the color change of the detection system is already very obvious when the formaldehyde concentration is 0.1 mol / L.

[0035] Example 3: Visual detection of formaldehyde using acid-induced color-changing carbon dots on a solid support such as filter paper.

[0036] The detection method includes the following steps:

[0037] 1) Preparation of filter paper discs: Cut the filter paper into small round discs of 12mm using a tablet press. Then, take 10μL of acid-induced color-changing carbon dot solution with a concentration of 10μg / mL and drop it evenly onto the small round discs. Dry them in a vacuum drying oven at 60℃ for 2 hours to prepare filter paper discs.

[0038] 2) Preparation of standard colorimetric cards: Take nine filter paper pieces prepared in step 1), and add 10 μL of 0.2 mol / L ammonium chloride solution to each filter paper piece. After the solution has soaked the filter paper pieces, add formaldehyde solutions with concentrations of 0, 50, 100, 150, 200, 300, 500, 800, and 1000 mmol / L to the nine filter paper pieces respectively. After the color develops, a standard colorimetric card showing the change from red to blue is prepared.

[0039] 3) Sample detection: Add 10 μL of 0.2 mol / L ammonium chloride solution to the filter paper obtained in step 1). After the solution wets the filter paper, add the sample solution containing formaldehyde to the filter paper and observe the color change of the sample solution on the filter paper. Compare the color with the standard colorimetric card obtained in step 2), which shows a change from red to blue, to achieve visual detection of samples with unknown formaldehyde concentration.

[0040] Figure 2 This is a schematic diagram illustrating the results of visually detecting acid-induced color-changing carbon dots on filter paper using formaldehyde solutions with concentrations of 0, 50, 100, 150, 200, 300, 500, 800, and 1000 mmol / L. Figure 2 It is known that a formaldehyde concentration of 50 mmol / L can cause a significant change in the color of the filter paper.

Claims

1. The application of acid-induced color-changing carbon dots in the visual detection of formaldehyde, characterized in that, The method for preparing the acid-induced color-changing carbon dots includes the following steps: 1) Dissolve 0.2 g o-phenylenediamine and 0.13 g urea in 10 mL deionized water, then mix with 20 mL 3.0 mol / L sulfuric acid solution. Add the resulting mixture to a polytetrafluoroethylene reactor, place the reactor in an oven, and perform a hydrothermal reaction at 210 °C for 10 h. Cool to room temperature to obtain the crude product. 2) The crude product obtained was filtered through a 0.22 μm filter membrane and washed three times with deionized water. The washed product was placed in a dialysis bag with MW=5000 and dialyzed until the exudate was colorless and neutral. 3) The dialyzed product was rotary evaporated at 60 °C to remove most of the water, and then vacuum dried at 60 °C for 24 h to obtain a black powder, which is the target product. The method for visualizing formaldehyde detection includes the following steps: 1) Preparation of standard colorimetric solutions: Mix 20 μL of ammonium chloride solution with 20 μL of formaldehyde solutions with concentrations of 0, 0.01, 0.05, 0.1, and 0.5 mol / L respectively. After standing for 5 minutes, add 2 mL of acid-induced color-changing carbon dot solution to each solution to obtain standard colorimetric solutions that display different colors. 2) Sample detection: Mix 20 μL of ammonium chloride solution with 20 μL of sample solution containing formaldehyde evenly, let stand for 5 minutes, then add 2 mL of acid-induced color-changing carbon dot solution. Based on the color change of the sample solution, compare the color with the standard colorimetric solution that displays different colors to achieve visual detection of formaldehyde. Alternatively, methods for visualizing formaldehyde detection may include the following steps: 1) Preparation of carbon dot filter paper discs: Cut the filter paper into small round discs of 12 mm using a tablet press, then take 10 μL of acid-induced color-changing carbon dot solution and drop it evenly onto the small round discs, and dry them in a vacuum drying oven at 60 ℃ for 2 h to prepare carbon dot filter paper discs. 2) Preparation of standard colorimetric cards: Take nine carbon dot filter paper discs and add 10 μL of ammonium chloride solution to each disc. After the solution has soaked the filter paper discs, add formaldehyde solutions with concentrations of 0, 50, 100, 150, 200, 300, 500, 800, and 1000 mmol / L to the nine discs respectively. After the color develops, a standard colorimetric card showing the change from red to blue is prepared. 3) Sample detection: Add 10 μL of ammonium chloride solution to the prepared carbon dot filter paper. After the solution wets the filter paper, add a sample solution containing formaldehyde to the filter paper. Based on the color change of the sample solution on the filter paper, compare it with the standard colorimetric card that shows the change from red to blue to achieve visual detection of formaldehyde.

2. The application according to claim 1, characterized in that, The concentration of the ammonium chloride solution is 0.2 mol / L.

3. The application according to claim 1, characterized in that, The concentration of the acid-induced color-changing carbon dot solution was 10 μg / mL.

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