Fluorescent material for rapidly detecting cesium ions in water body

Abstract

The invention discloses a fluorescent material for rapidly detecting cesium ions in a water body, and a preparation method of the fluorescent material comprises the following steps: firstly, synthesizing a carbon quantum dot (NCD) with positive charges on the surface through a hydrothermal method, and then preparing an aqueous solution containing 0.1-100 mg.mL <-1 > of nitrogen-doped carbon quantum dots and 0.02-100 mg.mL <-1 > of heteropolyacid. The surface of the formed composite material presents negative charges, the original strong fluorescence effect is inhibited, and the composite material presents weak fluorescence, when a water body contains cesium ions capable of forming associates with heteropolyacid anions, the heteropolyacid anions are captured by the cesium ions, the strong fluorescence performance of the material is recovered, and it is indicated that the water body contains the cesium ions and is polluted. When the fluorescent material is used for detecting cesium ions, the sensitivity is high, the detection limit is low, rapidness is achieved, operation is easy, and the fluorescent material is especially suitable for monitoring seawater cesium ion pollution.

Description

Technical Field

[0001] The invention belongs to the field of rapid ion detection and analysis, in particular to a fluorescent material for rapid detection of cesium ions in water. Background Art

[0002] Nuclear contaminated water contains a large amount of radioactive pollutants—— 134 Cs, 137 Cs, 131 I and 90 Sr, where 137 Cs has a half-life of 30.2 years. After entering the human body, it will bind to the myocardium, causing major myocardial dysfunction and leading to death. In order to respond to possible pollution risks in a timely manner, it is very important to quickly and accurately measure the concentration of cesium ions in water.

[0003] There are three main methods currently used to monitor seawater pollution: 1. Using laboratory instruments such as atomic emission spectroscopy, atomic absorption spectroscopy, and inductively coupled plasma emission spectrometry to detect specific metal ions. This method is accurate and sensitive, but time-consuming and not conducive to real-time sampling and observation; 2. Detecting the radioactive radiation value of water bodies. This method has a high detection limit and is not conducive to risk prevention and control; 3. Detecting the concentration of metal ions in organisms in the ocean. This method is time-consuming and is also not conducive to risk prevention and control.

[0004] Carbon quantum dots refer to monodisperse fluorescent carbon materials with a size of less than 10 nm. They have the characteristics of good biocompatibility, high chemical and optical stability, and easy functionalization. They are widely used as fluorescent probes to detect Cu 2+ , Hg + and Fe 3+ Inorganic metal ions such as cesium, antibiotic molecules, pigment molecules, pesticide molecules, and organic molecules such as melamine. Polyoxometalates (POMs) are a class of metal-oxygen clusters composed of transition metals, and heteropolyacids are formed by the condensation of different oxygen-containing acids. However, there has been no report on the use of fluorescent materials of nitrogen-doped carbon quantum dots in situ composited with heteropolyacid anions for the detection of trace cesium ions. Summary of the invention

[0005] The present invention aims to solve the above technical problems existing in the prior art and provide a fluorescent material for rapid detection of cesium ions in water.

[0006] The present invention and technical solution are: a fluorescent material for rapid detection of cesium ion concentration in water, which is a fluorescent material of nitrogen-doped carbon quantum dots with positive charges on the surface in situ composite heteropoly acid anions. The nitrogen-doped carbon quantum dots with positive charges on the surface are nitrogen-doped carbon quantum dots containing positive ions such as aliphatic amine salts, pyridine carbon cations and pyrrole carbon, and the heteropoly acid can be H4SiW 12 O 40 (SiW 12 )、H4PW 12 O 40 (PW 12 )、H4SiMo 12 O 40 (SiMo 12 ) and H4PMo 12 O 40 (PMo 12 )wait.

[0007] Preferably, the aqueous solution contains nitrogen-doped carbon quantum dots and heteropoly acid, wherein the concentration of nitrogen-doped carbon quantum dots in the aqueous solution is 0.1-100 mg.mL -1 , the concentration of heteropoly acid is 0.02-100mg.mL -1 .

[0008] Preferably, the nitrogen-doped carbon quantum dots are prepared according to the following method: dissolving citric acid and polyethyleneimine in water, wherein the amount ratio of citric acid, polyethyleneimine and water is (0.1-0.9) g: (0.1-0.9) g: 15 mL; after stirring evenly, transferring to a reactor, heating at a constant temperature of 140-180°C for 3-7 hours to obtain a dark brown solution; centrifuging the resulting solution in a centrifuge at a speed of 10000 rpm for 10 minutes, filtering with a 0.22 μm filter membrane and dialyzing in a dialysis bag for 24 hours, and freeze-drying to obtain a brown solid powder, namely nitrogen-doped carbon quantum dots.

[0009] The present invention adopts carbon quantum dots with positive surface charge and strong fluorescence effect under sunlight and in-situ composite heteropolyacid anions thereon, and the surface of the composite material formed is negatively charged and the original strong fluorescence effect is suppressed and weak fluorescence is presented. When the water body contains cesium ions that can form an association complex with the heteropolyacid anions, the heteropolyacid anions are "captured" by the cesium ions, and then the strong fluorescence performance of the material is restored, indicating that the water body contains cesium ions and is contaminated. The fluorescent material of the present invention is used to detect cesium ions, which has high sensitivity, low detection limit, rapidity and simple operation, and is particularly suitable for monitoring seawater cesium ion pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 The infrared spectra of the NCD solutions prepared in Examples 1 and 2 of the present invention are shown.

[0011] Figure 2 It is the fluorescence spectra of comparative example 1 and embodiment 1 of the present invention.

[0012] Figure 3 The fluorescence spectra of the aqueous solution of Example 1 of the present invention after adding cesium ions of different concentrations.

[0013] Figure 4 The fluorescence spectra of the aqueous solution of Example 2 of the present invention after adding cesium ions of different concentrations.

[0014] Figure 5 This is an experimental effect diagram of an embodiment of the present invention. DETAILED DESCRIPTION

[0015] Embodiment 1:

[0016] Step 1. Preparation of nitrogen-doped carbon quantum dots: Dissolve citric acid and polyethyleneimine (PEI) in water, wherein the amount ratio of citric acid, polyethyleneimine (PEI) and water is 0.225 g: 0.225 g: 15 mL; Stir evenly and transfer to a reactor, heat at 140°C for 7 hours to obtain a dark brown solution; Centrifuge the resulting solution in a centrifuge at a speed of 10000 rpm for 10 minutes, filter with a 0.22 μm filter membrane and dialyze in a dialysis bag for 24 hours, and freeze-dry to obtain a brown solid powder, namely nitrogen-doped carbon quantum dots (NCD);

[0017] Step 2. Take the NCD and PW prepared in step 1 12 Prepare aqueous solution with NCD concentration of 0.1mg.mL-1 and PW 12 Concentration: 0.14 mg.mL -1 .

[0018] Embodiment 2:

[0019] NCD and SiW were prepared according to the method of Example 1. 12 The final concentration of NCD is 0.1mg.mL-1, SiW 12 The final concentration is 0.14 mg.mL -1 .

[0020] The aqueous solutions of Examples 1 and 2 can be added to seawater to prepare solutions for use in seawater cesium ion detection.

[0021] Experiments and results:

[0022] Comparative Example: Configuration of NCD-control aqueous solution

[0023] The NCD prepared in Examples 1 and 2 of the present invention has a concentration of 0.1 mg L -1 NCD aqueous solution.

[0024] The specific method for detecting the fluorescence of cesium ions in water using the fluorescent material prepared in the embodiment of the present invention is as follows: take 0.5 mL of the aqueous solution containing NCD-POM prepared in the present invention, and add it to a 2 mL polyethylene sample tube; take 0.5 mL of the seawater solution to be tested and add it to the sample tube; observe the fluorescence intensity of the sample tube containing the sample to be tested under sunlight, and estimate the cesium ion concentration in the sample by comparing the fluorescence intensity.

[0025] 1. The infrared spectrum of Comparative Example 1 is as follows Figure 1 As shown. Figure 1 It can be seen that at 3438cm -1 The absorption peak at 2920 cm is attributed to the stretching vibration of -OH. -1 and 2854cm -1 The absorption peaks at 1709 cm-1 are the antisymmetric and symmetric stretching vibrations of the alkyl group. -1 The absorption peak at 1649 cm is attributed to the stretching vibration of C=O. -1 The absorption peak at 1561 cm is attributed to the carbonyl stretching vibration of the amide bond. -1 The absorption peak at is attributed to the C=C stretching vibration of the aromatic skeleton, mainly due to the dehydration carbonization of citric acid to generate sp 2 Delocalized structure, 1409cm -1 The absorption peak at 1164 cm is attributed to the in-plane bending vibration of CN. -1 The absorption peak is attributed to the stretching vibration of COC.

[0026] 2. The fluorescence spectra of the NCD prepared in the comparative example of the present invention and Example 1 are as follows: Figure 2 As shown, Figure 2 The black line in the figure represents the fluorescence spectrum of the comparative example, and the red line represents the fluorescence spectrum of Example 1. Figure 2 It can be seen that the fluorescence performance of NCD has a maximum excitation wavelength of 360nm and a corresponding emission wavelength of 455nm; after in-situ composite heteropolyacid anion, the original strong fluorescence effect is suppressed and weak fluorescence is presented.

[0027] 3. The fluorescence spectra of the aqueous solution of Example 1 of the present invention after adding different concentrations of cesium ions are shown in the figure below: Figure 3 As shown. Figure 3 It can be seen that the fluorescence intensity of the fluorescence spectrum of Example 1 at a wavelength of 360 nm increases with the concentration of cesium ions. -1 ___ 0.01 μmol L -1 The range is linear, and the linear equation is Y=16.0064x+0.98609.

[0028] 4. The fluorescence spectra of the aqueous solution of Example 2 of the present invention after adding different concentrations of cesium ions are shown in the figure below. Figure 4 As shown. Figure 4 It can be seen that the fluorescence intensity of the fluorescence spectrum of Example 2 at a wavelength of 360 nm increases with the concentration of cesium ions. -1 ___ 0.01 μmol L -1 The range is linear, and the linear equation is Y=188.75391x+1.05063

[0029] 5. The photos of the detection effect of Example 1 of the present invention are as follows Figure 5 As shown, Figure 5 The left side is Comparative Example 1, the middle is Example 1, and the right side is Example 1 with CsCl added. Figure 5 It can be clearly seen that NCD exhibits strong fluorescence. 12 ) fluorescence weakened, and the fluorescence was restored by adding cesium ions.

Claims

1. A fluorescent material for rapid detection of cesium ion concentration in water, characterized in that Fluorescent material of nitrogen-doped carbon quantum dots with positive charge on the surface in situ complexed with heteropolyacid anions.

2. The fluorescent material for rapid detection of cesium ion concentration in water according to claim 1, characterized in that: It is an aqueous solution containing nitrogen-doped carbon quantum dots and heteropoly acid, wherein the concentration of nitrogen-doped carbon quantum dots in the aqueous solution is 0.1-100 mg.mL -1 , the concentration of heteropoly acid is 0.02-100mg.mL -1 .

3. The fluorescent material for rapid detection of cesium ion concentration in water according to claim 2, characterized in that: The heteropoly acid is phosphotungstic acid or silicotungstic acid, and the mass ratio of the nitrogen-doped carbon quantum dots to the heteropoly acid is 1:

14.

4. The fluorescent material for rapid detection of cesium ion concentration in water according to claim 1 or 2, characterized in that: The nitrogen-doped carbon quantum dots are prepared according to the following method: dissolving citric acid and polyethyleneimine in water, wherein the amount ratio of citric acid, polyethyleneimine and water is 0.1-0.9 g: 0.1-0.9 g: 15 mL; transferring the mixture into a reactor after stirring evenly, and heating the mixture at a constant temperature of 140-180° C. for 3-7 hours to obtain a dark brown solution; centrifuging the obtained solution in a centrifuge at a speed of 10,000 rpm for 10 minutes, filtering the solution with a 0.22 μm filter membrane and dialyzing the solution in a dialysis bag for 24 hours, and freeze-drying the solution to obtain a brown solid powder, namely the nitrogen-doped carbon quantum dots.

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