A smartphone-based method for detecting Hg 2+ Fluorescent carbon dots and test paper

Abstract

The invention discloses a method for detecting Hg based on a smart phone 2+ The fluorescent carbon dots and test paper are fluorescent carbon dots with o-phenylenediamine as the precursor, which are used as fluorescent probes to detect heavy metal ions of mercury in aqueous solution. This carbon dot fluorescent probe is prepared by a simple one-time green synthesis route and has the characteristics of low cost and easy synthesis. 2+ The quenching reaction can be generated, and the detection can be realized quickly. It can also be made into a portable fluorescent test paper, and can be detected by the color recognition software of the mobile phone. The method is simple to operate, convenient to carry, and a method for detecting mercury ions in real time and quickly.

Description

Technical Field

[0001] The invention belongs to the technical field of nano synthesis and detection, and specifically relates to the preparation of fluorescent carbon quantum dots and the application of fluorescent carbon quantum dots as a fluorescent detection probe for sensitively identifying heavy metal ions in aqueous solution. Background Art

[0002] Heavy metal pollution has become a serious problem worldwide. Even exposure to extremely low concentrations of these heavy metals can threaten human health and cause various diseases. What is more serious is that these heavy metal elements are difficult to be biodegraded and will gradually accumulate in the environment and organisms. They are enriched in higher organisms through the food chain and eventually enter the human body thousands of times, endangering human health. Mercury is a highly toxic heavy metal element that exists in every corner of the earth, posing a serious threat to the environment and human life. Mercury compounds generally exist in inorganic and organic forms. Hg 2+ It is one of the most stable inorganic forms of mercury. Long-term exposure to mercury compounds from different sources (such as water, food, soil and air) can have varying degrees of impact on the skin, cardiovascular, lung, urinary, gastrointestinal and nervous systems, causing symptoms such as tremors, mood changes, insomnia, weakness, muscle atrophy, convulsions, headaches, sensory disorders, changes in nerve responses and performance defects in cognitive function tests [Kim, KH; Kabir, E.; Jahan, SA A Review on the Distribution of Hg in the Environment and Its Human Health Impacts. J. Hazard. Mater. 2016, 306, 376–385.]. Therefore, it is of great significance to achieve real-time detection of mercury ions in the environment and rapid in-situ detection with high sensitivity.

[0003] There are many methods for the detection of mercury ions, such as inductively coupled plasma mass spectrometry, atomic absorption spectrometry, and high performance liquid chromatography. These methods have good detection results for mercury ions, but for the real-time in-situ rapid detection of mercury ions, these methods have more or less some problems, such as high price, long time consumption, complex operation and certain technical requirements for operators, and it is difficult to use them for online real-time detection of heavy metal ions. Fluorescence method has the advantages of convenient detection, fast response speed, high sensitivity, and the ability to perform in-situ monitoring in various environments. It has been widely studied and applied in the detection of food and biological samples. As a new type of hot spot material, carbon quantum dots have excellent optical properties and can be used as fluorescent probes for detection and supervision. Carbon dot fluorescent probes have the advantages of in situ, real-time and non-destructive detection of target molecules [Shen, B.; Zhu, W.; Zhi, X.; Qian, Y. A Lysosome Targeting ProbeBased on Fluorescent Protein Chromophore for Selectively Detecting GSH andCys in Living Cells. Talanta. 2020, 208, 120461; AT Townsend, KA Miller,S. Mc, S. Aldous, J. Anal. At. Spectrom. 13 (1998) 1213–1219; V. Iyengar, J.Wolttlez, Clin. Chem. (Washington, DC), 34 (1988) 474-481.]. Summary of the invention

[0004] The purpose of the present invention is to provide a fluorescent detection probe capable of detecting heavy metal mercury ions in aqueous solution.

[0005] Another object of the present invention is to provide a portable fluorescent test paper capable of detecting heavy metal mercury ions in aqueous solution, which can be combined with mobile phone software recognition to achieve in-situ rapid detection.

[0006] The mercury ion fluorescent detection probe of the present invention is a fluorescent carbon quantum dot with o-phenylenediamine as a precursor.

[0007] Fluorescent carbon quantum dots with o-phenylenediamine as a precursor can detect trace amounts of divalent mercury ions in aqueous solution samples through fluorescence detection.

[0008] The present invention aims to provide fluorescent carbon quantum dots Y-CDs capable of detecting heavy metal mercury ions in aqueous solution and a method for detecting Hg based on a smart phone.2+ method.

[0009] Fluorescent carbon quantum dots Y-CDs, which are prepared by the following method:

[0010] 1) 0.04-0.07 g of o-phenylenediamine and 1-5 ml of carbon source are heated at 120-200 °C with stirring for 0.5-4 h, and then cooled to room temperature;

[0011] 2) Add 5 ml of solvent to dissolve, and dialysis and purification to obtain Y-CDs;

[0012] The carbon source in step 1) is glycerol, thiourea, folic acid, uric acid or glutathione.

[0013] Step 1) is water, ethanol, acetone, acetonitrile or chloroform.

[0014] 0.05 g of the o-phenylenediamine and 1 ml of propylene glycol were stirred and heated at 180 °C for 1 h;

[0015] Carbon quantum dots Y-CDs as fluorescent probes for detecting Hg 2+ Application in this area.

[0016] The carbon quantum dot Y-CDs fluorescence detection test paper is prepared by the following method: diluting the carbon quantum dot Y-CDs solution according to claim 1, distributing the diluted Y-CDs on the paper, and drying it.

[0017] Fluorescence detection of Hg based on carbon quantum dots Y-CDs in smartphones 2+ The method comprises:

[0018] 1) Add Hg to the carbon quantum dot Y-CDs fluorescence detection test paper according to claim 6 2+ Sample solution;

[0019] 2) Place the test paper under a 365 nm UV lamp;

[0020] 3) Open the smartphone color recognition software, capture, obtain the fluorescence color data, and determine Hg based on the color data 2+ concentration.

[0021] The present invention provides a method for detecting Hg based on a smart phone. 2+ Fluorescent carbon dots and test papers are prepared by using o-phenylenediamine as a precursor of fluorescent carbon quantum dots, which are used as fluorescent probes to detect heavy metal ions of mercury in aqueous solution. This carbon dot fluorescent probe is prepared by a simple one-time green synthesis route and has the characteristics of low cost and easy synthesis. During the detection process, the fluorescent carbon dots react with Hg 2+The quenching reaction can be generated, and the detection can be realized quickly. It can also be made into a portable fluorescent test paper, and can be detected by the color recognition software of the mobile phone. The method is simple to operate, convenient to carry, and a method for detecting mercury ions in real time and quickly.

[0022] The present invention has the following advantages:

[0023] 1. The fluorescent detection probe and portable fluorescent test paper provided by the present invention have high sensitivity and good selectivity.

[0024] 2. No large instruments are required, and the test results can be identified through naked eye observation or smartphone software.

[0025] 3. The present invention is easy to prepare, has low cost, and the synthesis method is simple and environmentally friendly.

[0026] 4. The present invention is simple to operate, convenient to carry, and can be used for on-site rapid detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Fluorescence spectra of Y-CDs under excitation from 380 nm to 480 nm;

[0028] Figure 2 (a) Fluorescence spectra of Y-CDs mixed with different types of metal ions and (b) corresponding images under UV light;

[0029] Figure 3 Add different concentrations of Hg 2+ Post-Y-CDs: (a) fluorescence spectrum; (b) about Hg 2+ The detected fluorescence intensity-related concentration relationship corresponds to the image under ultraviolet light;

[0030] Figure 4 Portable smartphone platform for Hg detection based on test strip sensing 2+ Schematic diagram;

[0031] Figure 5 Capture the R, G, B values ​​of the color and add Hg 2+ Concentration relationship diagram. DETAILED DESCRIPTION

[0032] Example 1: Preparation of carbon quantum dots (Y-CDs)

[0033] Preparation of carbon quantum dots (Y-CDs): 0.05 g of o-phenylenediamine and 1 ml of propylene glycol were stirred and heated at 180 °C for 1 h, cooled to room temperature, and 5 ml of water was added to dissolve to obtain Y-CDs. The Y-CDs solution exhibited strong yellow light emission under ultraviolet light. At an excitation wavelength of 420 nm, Y-CDs had the strongest emission peak at 562 nm ( Figure 1).

[0034] Example 2 Detection of Hg using carbon quantum dots Y-CDs as a fluorescent probe 2+

[0035] Detection of Hg using Y-CDs as a fluorescent probe 2+ When the Y-CDs were diluted 100 times as the detection probe, they were added into the sample solution to be tested. Under ultraviolet light, the fluorescence changes were observed. 2+ When Hg is present, Y-CDs will be quenched. At the same time, the fluorescence spectrum test is carried out to observe the change of Y-CDs fluorescence spectrum intensity. 2+ When the solution contains Hg 2+ When the concentration is high, the Y-CDs fluorescent probe will be completely quenched. The fluorescence intensity of Y-CDs as a fluorescent detection probe is related to Hg 2+ There is a good linear relationship between the concentration of Hg and 2+ existence.

[0036] 1. Carbon quantum dots Y-CDs as fluorescent probes for detecting Hg 2+ Selectivity

[0037] Detection of Hg using Y-CDs as a fluorescent probe 2+ It is necessary to investigate its effect on Hg among other similar heavy metals. 2+ Under the same conditions, Ag at a concentration of 100 µM + , Ba 2+ , Ca 2+ , Cd 2+ , Co 2+ , Cr 3+ , Cu 2+ , Fe 2+ , Hg 2+ Mg 2+ , Mn 2+ , Ni 2+ , Pb 2+ , Zn 2+ The solutions were mixed with fluorescent probes to observe the experimental phenomena and test the fluorescence spectra of the samples. Figure 2 a Fluorescence spectrum shows that, except Hg 2+ Other ions cannot quench Y-CDs. Figure 2 It can be seen from b that when different metal ions are added, Hg 2+After mixing with the fluorescent probe, the Y-CDs fluorescent detection probe was completely quenched under ultraviolet light, producing an experimental phenomenon that was significantly different from that of the blank sample, while the colors of the other groups of samples under ultraviolet light were almost the same as those of the blank sample, which was consistent with the results of the fluorescence spectrum. By comparing the fluorescence spectrum and its emission under ultraviolet light, it can be shown that the Y-CDs fluorescent detection probe is effective for Hg 2+ Highly selective ( Figure 2 ).

[0038] 2. Carbon quantum dots Y-CDs as fluorescent probes for detecting Hg 2+ Sensitivity

[0039] Detection sensitivity

[0040] Detection of Hg using Y-CDs as a fluorescent probe 2+ When Hg 2+ The concentrations of the solution samples ranged from 0.4 µM to 100 µM and were reacted with the Y-CDs fluorescent probe. The fluorescence spectra of the samples were then tested to verify the sensitivity of the probe. It can be seen from the fluorescence spectra that the fluorescence emission peaks of all mixed solutions increased with the increase of Hg 2+ As the concentration increases, the fluorescence intensity gradually decreases. Y-CDs was used as a fluorescent probe to detect Hg in the range of 0.4 µM to 100 µM. 2+ It can be observed from the experimental phenomenon picture that the fluorescence intensity of the mixed solution increases with the Hg 2+ The concentration decreases from 0.4 µM to 100 µM. 2+ When the concentration is 100 μM, the fluorescence of Y-CDs fluorescent probe is completely quenched. 2+ The absorption peak of Y-CDs as the detection probe is closely related to Hg 2+ There is a good linear relationship with the concentration of mercury. Therefore, Y-CDs can be used as a fluorescent probe to detect mercury ions to quickly and quantitatively detect the presence of mercury ions in aqueous solution ( Figure 3 ), with a detection limit of 10.15 nM.

[0041] Example 3 Preparation of carbon quantum dot Y-CDs fluorescence test paper and detection of Hg 2+ method

[0042] 1. Preparation of fluorescent test paper

[0043] The detection of Y-CDs was expanded to prepare fluorescent test strips and to detect Hg 2+The Y-CDs solution was diluted, and the cut filter paper (cellulose acetate paper, printing paper) was soaked or inkjet printed to distribute the diluted Y-CDs on the paper. After drying, the Y-CDs fluorescent detection test paper with fluorescence emission was obtained. The prepared Y-CDs fluorescent detection test paper showed bright fluorescence under ultraviolet light and was sensitive to Hg 2+ It has good selectivity and sensitivity.

[0044] 2. Detection of Hg 2+ method

[0045] Detection of Hg using Y-CDs fluorescent test paper 2+ When Hg 2+ When Hg 2+ When the concentration is high, the yellow fluorescence of the Y-CDs fluorescent test paper will be quenched and visible to the naked eye. Therefore, the Y-CDs fluorescent test paper can easily and quickly detect whether the sample contains Hg 2+ existence.

[0046] 3. Detect Hg based on smartphones 2+ Methods

[0047] 1. Add 3 to 5 drops of Hg to the Y-CDs fluorescent test paper. 2+ Sample solution, concentration gradient is Hg 2+ (0~100μM) After one minute, use clean filter paper to absorb the excess liquid on the surface of the test paper; place the test paper under ultraviolet light

[0048] 2. Make a standard curve

[0049] A smartphone with the Color Grab (version v3.9.2 Android) software installed

[0050] Place the test paper under UV light (365 nm), turn on color grab, use the instant recognition camera to select, capture and confirm the color, and obtain the captured color and the RGB value of the color in the list of recorded color information. 2+ It can be observed that the color G value is in a certain concentration range (1~100 μM) and is related to the addition of Hg 2+ The detection limit of mobile phone-assisted detection is 1 μM. Figure 4 , Figure 5 ).

[0051] 3. Sample testing

[0052] 1) Add Hg to the carbon quantum dot Y-CDs fluorescence detection test paper of claim 6 2+ Sample solution;

[0053] 2) Place the test paper under 365 nm ultraviolet light;

[0054] 3) Open the smartphone color recognition software, capture and obtain the fluorescence color data, and determine Hg based on the G value of the color data. 2+ concentration.

Claims

1. Carbon quantum dots Y-CDs, which are prepared by the following method: 1) 0.04-0.07 g of o-phenylenediamine and 1-5 ml of propylene glycol are stirred and heated at 120-200 °C for 0.5-4 h, and then cooled to room temperature; 2) Add 5 ml of solvent to dissolve, and purify by dialysis to obtain Y-CDs.

2. The carbon quantum dot Y-CDs according to claim 1, characterized in that: The solvent in step 2) is water, ethanol, acetone, acetonitrile or chloroform.

3. The carbon quantum dot Y-CDs according to claim 1 or 2, characterized in that: 0.05 g of the o-phenylenediamine and 1 ml of propylene glycol were stirred and heated at 180 °C for 1 h.

4. The carbon quantum dots Y-CDs described in claim 1 are used as fluorescent probes in detecting Hg 2+ Application in this area.

5. Carbon quantum dot Y-CDs fluorescence detection test paper, which is prepared by the following method: diluting the carbon quantum dot Y-CDs solution described in claim 1, distributing the diluted Y-CDs on paper, and drying.

6. Detection of Hg based on smartphones 2+ The method comprises: 1) Add Hg to the carbon quantum dot Y-CDs fluorescence detection test paper of claim 5 2+ Sample solution; 2) Place the test paper under ultraviolet light; 3) Open the smartphone color recognition software, capture, obtain the fluorescence color data, and determine Hg based on the color data 2+ concentration.

7. The method for detecting Hg based on a smart phone according to claim 6. 2+ The method is characterized in that: The UV lamp is 365 nm.

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