A portable fluorescent test paper for detecting sewage and its preparation method and application

Abstract

The present invention discloses a portable fluorescent test paper for detecting sewage, its preparation method and application, which belongs to the field of chemical analysis technology. The fluorescent probe uses an organic carbon source and a nitrogen source as precursors, is rapidly prepared and synthesized by a reaction heat release method, and the product size is screened by a dialysis membrane to obtain nitrogen-doped carbon quantum dots. Finally, the nitrogen-doped carbon quantum dots are loaded on a pH test paper by soaking or ultrasonic atomization spraying. The present invention adopts the above-mentioned portable fluorescent test paper for detecting sewage, its preparation method and application, and the prepared fluorescent test paper loaded with nitrogen-doped carbon quantum dot fluorescent probe can conveniently and quickly detect Pb in actual sewage. 2+ Qualitative detection; the loaded fluorescent probe is nitrogen-doped carbon quantum dots for Pb 2+ The detection is highly specific, the detection process will not be interfered by other ionic components, and it has high sensitivity. The synthesis process of the fluorescent probe is simple and easy, with low cost, and it is used to detect Pb 2+ Fluorescent test paper can quickly detect Pb in sewage environment 2+ .

Description

Technical Field

[0001] The present invention relates to the technical field of chemical analysis, in particular to a portable fluorescent test paper for detecting sewage, and a preparation method and application thereof. Background Art

[0002] With the development of industrialization, an increasing amount of untreated organic and inorganic pollutants are being released into the natural environment, causing environmental pollution and ecological damage. Among these, heavy metal pollution, as a serious health hazard to animals, plants, and humans, has garnered widespread attention. Lead (Pb) is a widely used heavy metal. Once released into the environment, it persists for a long time and can accumulate through the food chain, posing a significant potential threat to humans, animals, and plants. Severe lead pollution exists in many regions around the world, accompanied by a series of health risks, such as excessive blood lead levels. Common methods for detecting heavy metal ions include atomic absorption spectrometry (AAS), atomic emission spectrometry (AES), atomic fluorescence spectrometry (AFS), inductively coupled plasma-mass spectrometry (ICP-MS), X-ray fluorescence spectrometry (XRF), and electrochemical analysis. These methods struggle to be cost-effective, simple to operate, and rapid, making the development of commercially available analytical equipment or supplies that can meet the needs of the general public for rapid lead ion detection crucial. With the recent advancement of nanotechnology, the detection of trace heavy metal ions in wastewater has become a research hotspot. Quantum dots (QDs), due to their excellent optical properties, have been widely used in the preparation of fluorescence sensors. However, traditional QDs contain heavy metals that can cause secondary environmental pollution, and the complex and time-consuming surface modification process limits their practical application in detection.

[0003] Carbon quantum dots (CQDs) are a widely used carbon nanomaterial, following fullerenes, carbon nanotubes, and graphene. Compared to traditional semiconductor QDs, they offer advantages such as improved water solubility, fluorescence stability, biocompatibility, and environmental friendliness. In recent years, they have become a new research hotspot, with applications in fluorescence sensors, bioimaging, drug delivery, and photocatalysis. A high quantum yield is crucial for the application of CQDs. Traditional CQD synthesis processes can be categorized into two types: top-down and bottom-up. The top-down method primarily involves exfoliation or pulverization of large carbon materials through mechanical, physical, or chemical methods. The resulting QDs have low yields, are non-uniform in size, and are unstable due to stacking. The bottom-up method primarily involves preparing precursor materials and then using physical and chemical methods to synthesize uniformly sized CQDs in high yield. In recent years, there have been many reports that doping nitrogen atoms into carbon quantum dots can have a higher quantum yield, and at the same time, it can have a strong binding affinity with heavy metal ions and is used in the detection of heavy metal ions.

[0004] Currently, the fluorescence detection of Pb based on nitrogen-doped carbon quantum dots is 2+ There are few reports on this topic, and the method mainly relies on the use of fluorescence spectrophotometers. Although the sensitivity can reach a high level, it is not suitable for market popularization and on-site testing. Test strips are a relatively mature and convenient detection method, such as pH test strips and starch potassium iodide test strips, but there is no information on the fluorescence analysis mechanism for the detection of Pb 2+ The test paper has not been reported yet. Summary of the Invention

[0005] The purpose of the present invention is to provide a portable fluorescent test paper for detecting sewage and its preparation method and application. The loaded fluorescent probe is nitrogen-doped carbon quantum dots, whose fluorescence emission spectrum is 400-550nm and is effective for Pb 2+ The detection of Pb is highly specific and will not be interfered by other ionic components. It has high sensitivity. In addition, the synthesis process of the fluorescent probe is simple and easy, with low cost. 2+ The fluorescent test paper is easy to prepare and use, and can quickly detect Pb in sewage environment. 2+ .

[0006] To achieve the above object, the present invention provides a method for preparing a portable fluorescent test paper for detecting sewage, comprising the following steps:

[0007] S1. Add dopamine hydrochloride powder to ethylenediamine, dissolve under ultrasonication, and mix thoroughly to obtain a precursor mixture solution. Weigh phosphoric acid and add it to the precursor mixture solution, stirring to obtain a yellow mixture.

[0008] S2. Add ethanol to the yellow mixture in S1 and centrifuge to desalt, retain the supernatant, further separate and purify it through a water membrane, and then rotary evaporate to remove excess ethylenediamine to obtain a nitrogen-doped carbon quantum dot solution. The obtained nitrogen-doped carbon quantum dot solution is dialyzed using a dialysis membrane, and then the supernatant is collected by centrifugation. The supernatant is freeze-dried to obtain nitrogen-doped carbon quantum dot powder, which is stored in the dark;

[0009] S3. The nitrogen-doped carbon quantum dots are loaded on the surface of the pH test paper by immersion or ultrasonic atomization spraying, and vacuum drying is performed to obtain the fluorescent test paper.

[0010] Preferably, the amount of dopamine in S1 is 200-400 mg, the amount of ethylenediamine is 10-20 mL, the ultrasonication time is 10-20 min, and the amount of phosphoric acid is 5-10 mL.

[0011] Preferably, the centrifugal desalination speed in S2 is 10000-15000 rpm, the centrifugation time is 5-20 min, the rotary evaporation temperature is 50-70° C., the centrifugal speed for collecting the supernatant is 10000-15000 rpm, and the centrifugation time is 5-20 min.

[0012] Preferably, the dialysis membrane in S2 is 100 MW and the dialysis time is 6-12 hours.

[0013] Preferably, the soaking time in S3 is 5-10 minutes.

[0014] The present invention provides a rapid detection of Pb prepared by the above preparation method. 2+ The fluorescent test paper is composed of fluorescent whitening agent-free test paper loaded with nitrogen-doped carbon quantum dots.

[0015] Preferably, the fluorescent test paper is light yellow, and its dimensions are length×width×thickness=80mm×10mm×0.5mm. The amount of nitrogen-doped carbon quantum dots loaded on each fluorescent test paper is at least in the milligram level.

[0016] The present invention also provides an application of a portable fluorescent test paper for detecting sewage, wherein the portable fluorescent test paper for detecting sewage is used to detect Pb in sewage. 2+ .

[0017] Therefore, the present invention adopts the above-mentioned portable fluorescent test paper for detecting sewage and its preparation method and application, which has the following beneficial effects:

[0018] (1) The prepared fluorescent test paper loaded with nitrogen-doped carbon quantum dots fluorescent probe can react with Pb 2+ The fluorescence quenching reaction is a fast and specific reaction. The fluorescence signal can be quenched to Pb 2+ Qualitative testing can be carried out to quickly and easily detect Pb in actual sewage. 2+ Perform qualitative testing.

[0019] (2) The loaded fluorescent probe is nitrogen-doped carbon quantum dots, whose fluorescence emission spectrum is 400-550nm, and is sensitive to Pb 2+ The detection of Pb is highly specific and will not be interfered by other ionic components. It has high sensitivity. In addition, the synthesis process of the fluorescent probe is simple and easy, with low cost. 2+ The fluorescent test paper is easy to prepare and use, and can quickly detect Pb in sewage environment. 2+ .

[0020] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a TEM image of quantum dots doped with a portable fluorescent test paper for detecting sewage and its preparation method and application embodiment of the present invention;

[0022] Figure 2 The portable fluorescent test paper for detecting sewage and its preparation method and application embodiment of the present invention are fluorescence selective detection spectra of nitrogen-doped carbon quantum dots for different ions;

[0023] Figure 3 The invention is a portable fluorescent test paper for detecting sewage and its preparation method and application embodiment of nitrogen-doped carbon quantum dots and Pb 2+ The linear relationship data of fluorescence intensity;

[0024] Figure 4 The invention discloses a portable fluorescent test paper for detecting sewage and its preparation method and application embodiment. 2+ Actual detection picture. DETAILED DESCRIPTION

[0025] The technical solution of the present invention is further described below with reference to the accompanying drawings and embodiments.

[0026] Unless otherwise defined, technical or scientific terms used in the present invention shall have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs.

[0027] Example 1

[0028] The present invention provides a method for preparing a portable fluorescent test paper for detecting sewage, comprising the following steps:

[0029] S1. Add 200-400 mg of dopamine hydrochloride powder to 10-20 mL of ethylenediamine, dissolve under ultrasonication for 10-20 min and mix thoroughly to prepare a precursor mixture solution. Weigh 5-10 mL of phosphoric acid and add it to the precursor mixture solution. Stir to obtain a yellow mixture.

[0030] S2. Add ethanol to the yellow mixture in S1 and centrifuge for desalination at 10,000-15,000 rpm for 5-20 minutes. Retain the supernatant, further separate and purify it through a water membrane, and then remove excess ethylenediamine by rotary evaporation at 50-70°C to obtain a nitrogen-doped carbon quantum dot solution. The obtained nitrogen-doped carbon quantum dot solution is dialyzed through a dialysis membrane (100MW) for 6-12 hours, and the supernatant is collected by centrifugation at a speed of 10,000-15,000 rpm for 5-20 minutes. The supernatant is freeze-dried to obtain nitrogen-doped carbon quantum dot powder, which is stored in the dark.

[0031] Nitrogen doping can effectively tune the fluorescence emission wavelength of carbon quantum dots and enhance their fluorescence quantum yield, making them more promising for applications in fields such as bioimaging and sensors. Nitrogen doping forms more nitrogen-related functional groups on the surface of carbon quantum dots, such as amino and amide groups. These groups can enhance the interaction between quantum dots and target molecules, improving their performance in applications such as adsorption and sensing.

[0032] The TEM spectrum of the synthesized nitrogen-doped carbon quantum dots is shown in Figure 1 It can be clearly seen from the figure that the synthesized nitrogen-doped carbon quantum dots have a uniform morphology, with a size of about 2-3nm and an average particle size of 2.34nm. The lattice spacing of 0.24nm in the high-magnification transmission electron microscope shows that the height of the nitrogen-doped carbon quantum dots is sp 2 Hybrid structure.

[0033] S3. Use immersion or ultrasonic atomization spraying to load nitrogen-doped carbon quantum dots on the surface of pH test paper, and vacuum dry to obtain fluorescent test paper. When immersion is used, the immersion time is 5-10 minutes. Immersion and ultrasonic atomization spraying are essentially to load nitrogen-doped carbon dots on the surface of pH test paper, and both can achieve the effect of preparing fluorescent test paper. The purpose of ultrasonic atomization spraying itself is to prepare different nitrogen-doped carbon quantum dot loading amounts on the surface.

[0034] The present invention provides portable fluorescent test paper for detecting wastewater, produced using the aforementioned preparation method. The fluorescent test paper comprises fluorescent whitening agent-free test paper loaded with nitrogen-doped carbon quantum dots. The fluorescent test paper is light yellow and measures 80 mm (length x width x thickness) by 10 mm (height x depth) by 0.5 mm. Each sheet of fluorescent test paper is loaded with at least milligrams of nitrogen-doped carbon quantum dots.

[0035] The present invention also provides a portable fluorescent test paper for detecting Pb in sewage. 2+ Applications containing Pb 2+ Drop the aqueous solution onto the fluorescent test paper, then place it under ultraviolet light at a wavelength of 365nm to observe whether it has yellow-green fluorescence. The presence or absence of fluorescence can be used to determine whether the sewage contains Pb. 2+ It is also possible to convert a certain amount of Pb into 2+ The solution was dropped into a system containing specific probes, and the fluorescence intensity of the solution was measured. The measured data was used as the Pb 2+ The content of Pb is evaluated by detecting the fluorescence intensity of the metal complex to determine the Pb content in the test object. 2+ content.

[0036] Depend on Figure 2 It can be seen from the figure that the fluorescence responses of nitrogen-doped carbon quantum dots to different ions are different. Among them, lead ions (Pb 2+ ) decreased significantly, indicating that nitrogen-doped carbon quantum dots have a high selectivity for lead ions. The fluorescence intensity changes of other ions were relatively small, indicating that nitrogen-doped carbon quantum dots have a low selectivity for these ions.

[0037] Depend on Figure 3 It can be seen that the figure shows nitrogen-doped carbon quantum dots and Pb 2+ The linear relationship data of fluorescence intensity. The horizontal axis represents Pb 2+ The figure shows the concentration of Pb at different concentrations (μM). 2+ The corresponding fluorescence intensity values ​​are plotted and a curve is fitted to these data points. 2+ As the concentration increases, the fluorescence intensity gradually decreases. The distribution of data points in the figure shows that the fluorescence intensity is closely related to the Pb 2+ There is a certain linear relationship between the concentrations.

[0038] Depend on Figure 4 It can be seen that Figure 4 The left test paper in A is the control group, and the right test paper is the experimental group. The fluorescent test paper in the experimental group contains Pb 2+ of aqueous solution, Figure 4 The left test paper of B in the figure is the test picture of the control group under ultraviolet light. Figure 4 The test paper on the right side of B is the test picture of the experimental group under ultraviolet light. As can be seen from the figure, the control group shows fluorescence under ultraviolet light, while the one containing Pb 2+ When the aqueous solution is added to the fluorescent test paper, no fluorescence is shown under ultraviolet light, indicating that Pb in sewage can be detected. 2+ , when there is no Pb 2+ When the fluorescent test paper shows fluorescence, it proves that the fluorescent test paper can be used to quickly and easily detect Pb in actual sewage. 2+ Perform qualitative testing.

[0039] Therefore, the present invention adopts the portable fluorescent test paper for detecting sewage and its preparation method and application. The prepared fluorescent test paper loaded with nitrogen-doped carbon quantum dot fluorescent probe can react with Pb 2+ The fluorescence quenching reaction is a fast and specific reaction. The fluorescence signal can be quenched to Pb 2+ Qualitative testing can be carried out to quickly and easily detect Pb in actual sewage. 2+ For qualitative detection, the loaded fluorescent probe is nitrogen-doped carbon quantum dots, whose fluorescence emission spectrum is 400-550nm, and the Pb 2+ The detection of Pb is highly specific and will not be interfered by other ionic components. It has high sensitivity. In addition, the synthesis process of the fluorescent probe is simple and easy, with low cost. 2+ The fluorescent test paper is easy to prepare and use, and can quickly detect Pb in sewage environment. 2+ .

[0040] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a portable fluorescent test paper for detecting sewage, characterized in that: The following steps are involved: S1. Add dopamine hydrochloride powder to ethylenediamine, dissolve under ultrasonication, and mix thoroughly to obtain a precursor mixture solution. Weigh phosphoric acid and add it to the precursor mixture solution, stirring to obtain a yellow mixture. S2. Add ethanol to the yellow mixture in S1 and centrifuge to desalt, retain the supernatant, further separate and purify it through a water membrane, and then rotary evaporate to remove excess ethylenediamine to obtain a nitrogen-doped carbon quantum dot solution. The obtained nitrogen-doped carbon quantum dot solution is dialyzed using a dialysis membrane, and then the supernatant is collected by centrifugation. The supernatant is freeze-dried to obtain nitrogen-doped carbon quantum dot powder, which is stored in the dark; S3. The nitrogen-doped carbon quantum dots are loaded on the surface of the pH test paper by immersion or ultrasonic atomization spraying, and vacuum drying is performed to obtain the fluorescent test paper.

2. The method for preparing a portable fluorescent test paper for detecting sewage according to claim 1, wherein: The amount of dopamine hydrochloride powder in S1 is 200-400 mg, the amount of ethylenediamine is 10-20 mL, the ultrasonic time is 10-20 min, and the amount of phosphoric acid is 5-10 mL.

3. The method for preparing a portable fluorescent test paper for detecting sewage according to claim 2, wherein: The centrifugal desalting speed in S2 is 10000-15000 rpm, the centrifugal time is 5-20 min, the rotary evaporation temperature is 50-70° C., the centrifugal speed for collecting the supernatant is 10000-15000 rpm, and the centrifugal time is 5-20 min.

4. The method for preparing a portable fluorescent test paper for detecting sewage according to claim 3, wherein: The dialysis membrane in S2 is 100MW, and the dialysis time is 6-12h.

5. The method for preparing a portable fluorescent test paper for detecting sewage according to claim 4, wherein: The soaking time in S3 is 5-10 minutes.

6. A portable fluorescent test paper for detecting sewage, prepared by the preparation method of claim 5, characterized in that: The fluorescent test paper is composed of fluorescent whitening agent-free test paper loaded with nitrogen-doped carbon quantum dots.

7. A portable fluorescent test paper for detecting sewage according to claim 6, characterized in that: The fluorescent test paper is light yellow in color, and has dimensions of length×width×thickness=80 mm×10 mm×0.5 mm. The amount of nitrogen-doped carbon quantum dots loaded on each fluorescent test paper is at least in the milligram level.

8. An application of portable fluorescent test paper for detecting sewage, characterized by: The portable fluorescent test paper for detecting sewage according to claim 7 is used to detect Pb in sewage 2+ .

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