Paper-based chip for detecting cadmium ions by LIBS (laser-induced breakdown spectroscopy) as well as preparation method and application of paper-based chip

Abstract

The invention relates to the technical field of substance detection, in particular to a paper-based chip for detecting cadmium ions by LIBS (Laser-induced Breakdown Spectroscopy) as well as a preparation method and application of the paper-based chip. The preparation method comprises the following steps: 1) mixing a zinc salt solution and a sodium sulfide solution, and reacting to obtain a ZnS nano-particle solution; (2) mixing the ZnS nano-particle solution, polyvinylpyrrolidone and an acid solution to obtain a ZnSNPs (zinc single nucleotide polymorphisms) modified solution; and 3) mixing the ZnSNPs modified solution with a filter paper sheet, oscillating, adding an alcoholic solution, cleaning and drying. The paper-based chip provided by the invention can efficiently enrich the heavy metal element cadmium in the water body so as to carry out LIBS detection, and high-sensitivity, rapid and efficient detection of the heavy metal Cd in the water body can be well realized by combining the LIBS technology with the provided paper-based chip.

Description

Technical Field

[0001] The present invention relates to the technical field of material detection, and in particular to a paper-based chip for detecting cadmium ions using LIBS, and a preparation method and application thereof. Background Art

[0002] Heavy metal pollution not only damages the environment, but also affects the ecosystem through the food chain. Cadmium (Cd) is a typical toxic element, and it is crucial to detect excessive cadmium in water bodies (such as environmental water and drinking water). Laser-induced breakdown spectroscopy (LIBS) is an elemental analysis technique. Its basic principle is to focus ultrashort pulse lasers on the surface of the sample to make its energy density high enough to form a plasma. The atoms in the plasma are excited and emit characteristic spectra, which can be analyzed by a spectrometer to determine the material composition and content of the sample. LIBS technology has shown great application potential in many fields due to its unique advantages. LIBS has been applied in various fields. However, since harmful metal elements in the environment are generally trace levels, the detection limit of LIBS is often at the sub-ppm level, which makes it difficult to directly detect trace heavy metal elements by LIBS. Paper-based chips are a paper-based detection device based on microfluidic technology. They have the advantages of environmental protection, low cost, easy transportation and storage, and are used in clinical diagnosis, environmental monitoring, food safety and other fields. Paper-based chips are microfluidic chips that use paper (such as filter paper, chromatography test paper, and various cellulose membranes) as chip manufacturing materials and biochemical analysis platforms. They have the advantages of fast detection speed, simple operation, portability, and low cost. They are often used as research hotspots in many fields such as basic scientific research and biochemical detection, and have promoted the development of low-cost analytical technology. In recent years, nanomaterials, as a multifunctional nanomaterial, have been widely used in medicine, sensors, and catalysis. Among them, biosensors based on metal nanoparticles have also been used in heavy metal detection. The principle is mainly to use the specific binding of heavy metal ions to certain nanomaterials to change the physical and chemical properties of nanomaterials (color development, fluorescence, catalytic activity, thermal effect, etc.). Finally, the changes in the physical and chemical properties of nanomaterials are collected through colorimetry, ultraviolet-visible spectroscopy, local plasma resonance, and fluorescence spectroscopy, thereby indirectly reflecting the content of heavy metal elements in the analyte.

[0003] At present, there are many detection technologies (such as atomic absorption spectroscopy, atomic fluorescence spectroscopy, and inductively coupled plasma spectroscopy) that are applied to the detection of heavy metal elements Cd. Although the above methods can achieve high-sensitivity detection of heavy metal elements, they can often only be used in laboratories and require professional operation. Sometimes they are affected by sample matrix effects, background interference, or scattered light interference with fluorescence signals, which makes the detection time-consuming, labor-intensive and costly, and difficult to be truly applied to the actual in-situ detection of environmental heavy metals. In order to be able to quickly detect trace heavy metal elements Cd in water, it is urgent to provide a new method that can quickly and efficiently detect heavy metal elements. Rapid Determination of Cr 3+ and Mn 2+ in Water Using Laser-Induced Breakdown Spectroscopy Combined with FilterPaper Modified with Gold Nanoclusters. Biosensors, 2024, 14 (6), 267. This paper introduces a LIBS-based paper-based gold nanocluster-modified Cr 3+ and Mn 2+ Although the literature currently has certain detection performance for some heavy metals such as Cr and Mn, it is unable to realize the analysis and detection of Cd in water.

[0004] At present, there is an urgent need to provide a new type of paper chip for detecting cadmium ions in water using LIBS. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a paper-based chip for LIBS detection of cadmium ions and its preparation method and application. The present invention synthesizes zinc sulfide nanoparticles (ZnS nanaparticles, ZnSNPs) in situ on the paper-based chip, which can detect Cd 2+ The solution can be specifically and efficiently adsorbed. The LIBS technology combined with the paper-based chip modified with ZnSNPs can better realize the rapid and efficient detection of heavy metal Cd in water bodies with high sensitivity.

[0006] In a first aspect, the present invention provides a method for preparing a paper-based chip for detecting cadmium ions by LIBS, comprising: 1) Mixing a zinc salt solution and a sodium sulfide solution and reacting them to obtain a ZnS nanoparticle solution.

[0007] 2) The ZnS nanoparticle solution, polyvinyl pyrrolidone and acid solution are mixed to obtain a ZnSNPs modified solution.

[0008] 3) Mix the ZnSNPs modified solution with the filter paper and shake it, add the alcohol solution, wash and dry it. The present invention uses LIBS technology and combines ZnSNPs modified paper-based chips to detect heavy metal Cd in water. Through the optimization of the preparation process, ZnSNPs are synthesized in situ on the paper-based chip, and the obtained paper-based chip can detect Cd-containing 2+ The solution was specifically and efficiently adsorbed, and the LIBS signal of the Cd element in the paper-based chip was collected by LIBS instrument. 2+ The quantitative relationship model established based on the concentration of Cd in water can well realize the 2+ Detection and analysis.

[0009] According to the present invention, by adopting the paper-based chip for detecting cadmium ions prepared by the present invention, the paper-based chip is capable of specifically adsorbing Cd 2+ The (ZnSNPs in situ modified) rapid paper-based sensor chip has a porous structure and a large specific surface area, which can more efficiently and specifically adsorb the heavy metal element Cd in water, and also increase the LIBS signal of the element Cd to be detected, improve the sensitivity of Cd detection, and can detect Cd in water. 2+ The invention can realize efficient and rapid detection, realize efficient and specific enrichment of heavy metal element Cd in water, and better perform LIBS detection of Cd in water. Moreover, the nanoparticle-modified paper base of the invention is simple to prepare, inexpensive, and easy to promote and use. The ZnSNPs-modified paper base chip prepared by the invention can efficiently and specifically adsorb the Cd element and has excellent effect of LIBS detection. The principle may be that the ZnSNPs-modified paper base chip itself has a porous structure and a large specific surface area, which can effectively adsorb the heavy metal Cd. 2+ At the same time, Cd 2+ and S 2- There is a stronger chemical bonding energy between them, which makes Cd 2+ With Zn 2+ Moreover, the nanomaterials increase the density of the number of particles in the plasma phase during the ablation process, which can further increase the LIBS signal of the element Cd to be detected and improve the sensitivity of Cd detection.

[0010] Preferably, in step 1), the zinc salt solution is a zinc nitrate solution, the concentration of the zinc nitrate solution is 8-12 mM, preferably 10-11 mM; and / or the concentration of the sodium sulfide solution is 10-14 mM, preferably 12-13 mM.

[0011] Further preferably, in step 1), the volume ratio of the zinc nitrate solution to the sodium sulfide solution is 4-7:3-6, preferably 5-6:4-5. By optimizing the concentration and ratio of zinc nitrate and sodium sulfide, ZnS nanoparticles can be better generated, and ultimately a better modification effect can be achieved, which is helpful for improving the material performance of subsequent paper chips and enhancing the resistance to heavy metal ions Cd² + adsorption capacity.

[0012] Further preferably, in step 1), the reaction temperature may be room temperature; preferably, the reaction temperature is 25±2°C, the reaction time is 10±2min, and the stirring speed is 200±5 r / min.

[0013] Preferably, in step 2), the ratio of the ZnS nanoparticle solution, the polyvinyl pyrrolidone and the acid solution is 6-10 mL: 0.3-0.8 g: 0.05-0.2 mL, preferably 8-9 mL: 0.4-0.5 g: 0.08-0.1 mL.

[0014] More preferably, in step 2), the acid solution is hydrochloric acid, and the concentration of the hydrochloric acid is 0.05-0.15M, preferably 0.1-0.12M.

[0015] In the present invention, the ratio and concentration of the prepared ZnS nanoparticle solution, polyvinyl pyrrolidone and hydrochloric acid can enhance the adsorption performance, improve the LIBS sensitivity and optimize the detection effect. Especially under the preferred conditions, the distribution uniformity of the nanoparticles on the paper substrate can be further improved, and it is helpful to detect Cd² + The specific adsorption effect of Cd2 in water can be improved by further optimizing the ratio. + The detection effect can be further guaranteed, and the detection sensitivity and accuracy can be further guaranteed, while reducing possible background interference and the influence of other metal ions. Combined with the optimal hydrochloric acid concentration, the stability of ZnS particles can be ensured, the agglomeration and precipitation of particles can be avoided, and the stability and sensitivity of LIBS signals can be further improved.

[0016] Preferably, in step 3), the shaking time is 8 to 12 min, preferably 10 to 11 min; and / or the size of the filter paper is 0.5 to 1.5 cm × 0.5 to 1.5 cm, preferably 1 to 1.2 cm × 1 to 1.2 cm; and / or the alcohol solution is an ethanol solution, and the volume of the ethanol solution is preferably 2 to 3 mL.

[0017] Further preferably, in step 3), the washing is washing with deionized water for 2-3 times; and / or, the drying temperature is 35-40°C, preferably 37-38°C. In the present invention, the drying temperature is higher than room temperature and cannot be too high. Too low or too high a temperature will affect the effect. For example, if the temperature exceeds 50°C, it will cause the paper base to burn. The drying temperature selected in the present invention is preferably 37-38°C for the best effect.

[0018] In the second aspect, the LIBS paper-based chip for detecting cadmium ions provided by the present invention is prepared by the preparation method of the paper-based chip for detecting cadmium ions by LIBS. The paper-based chip for detecting cadmium ions prepared by the present invention can specifically enrich cadmium ions in water, and the combination of the paper-based chip and the LIBS technology can perform high-sensitivity rapid detection of heavy metal Cd in water.

[0019] In a third aspect, the present invention provides a paper-based chip for detecting cadmium ions prepared by the preparation method of the paper-based chip for detecting cadmium ions by LIBS or an application of the paper-based chip for detecting cadmium ions by LIBS, especially in detecting Cd in water by LIBS. 2+ Application in specific adsorption detection.

[0020] In the present invention, ZnSNPs are synthesized in situ on paper substrate to 2+ The water body was specifically and efficiently adsorbed, and the LIBS signal of Cd element was collected by LIBS instrument. 2+ The concentration of Cd in water is used to establish a quantitative relationship model. 2+ Detection and analysis.

[0021] Further preferably, the quantitative relationship model used is: Y=aX+b; where Y is the LIBS signal intensity at 226.56nm, X is Cd 2+ The concentration of a is 51.5±0.2, and b is 1869.6±0.2. The paper-based chip for LIBS detection of cadmium ions prepared by the present invention specifically enriches cadmium ions in water and uses LIBS technology to excite the spectral signal of metal ion Cd. By establishing a quantitative model between LIBS signal and Cd concentration, it can better achieve high-sensitivity, rapid and efficient detection of heavy metal Cd in water.

[0022] The beneficial effects of the present invention are at least that: the present invention realizes for the first time the detection of Cd in water by using LIBS technology combined with ZnSNPs modified paper-based chips. 2+ Enrichment is carried out to achieve the Cd 2+ The method is applicable to the detection of excessive heavy metal Cd in water. 2+The detection linear range is 0~100μg / L, and the sensitivity is 1.10μg / L. The recovery rate of actual sample detection is between 95% and 115%. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 This is a laser induced breakdown spectroscopy instrument device in an embodiment of the present invention.

[0025] Figure 2 A schematic diagram of the production process of a paper-based chip modified with ZnSNPs provided in an embodiment of the present invention.

[0026] Figure 3 These are the adsorption results of some common metal ions by the ZnSNPs modified paper-based chip provided in Example 1 of the present invention.

[0027] Figure 4 The ZnSNPs modified paper-based chip provided in Example 1 of the present invention is used to detect Cd in water 2+ LIBS spectrum of adsorption detection.

[0028] Figure 5 The ZnSNPs modified paper-based chip provided in Example 1 of the present invention is used to detect Cd in water 2+ A quantitative model for detection in the concentration range (0~100μg / L) was established.

[0029] Figure 6 The ZnSNPs modified paper-based chip provided in Example 2 of the present invention is used to detect Cd in water 2+ Optimal enrichment time for detection.

[0030] Figure 7 The ZnSNPs modified paper-based chip provided in Example 2 of the present invention is used to detect Cd in water 2+ Optimal pH conditions of the test solution.

[0031] In the figure, 1-signal delay generator; 2-laser; 3-plasma; 4-3D detection platform; 5-paper-based chip; 6-optical fiber; 7-spectrometer; 8-focusing mirror; 9-mirror; 10-reaction container; 11-zinc ion; 12-sulfur ion; 13-filter paper; 14-ZnSNPs modified nanopaper; 15-cadmium ion; 16-adsorbed Cd 2+ Nanopaper-based; 17-Laser induced breakdown spectroscopy instrument. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] The endpoints and any values ​​of the ranges disclosed in the present invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed in the present invention.

[0034] If no specific technology or conditions are specified in the examples of the present invention, the technology or conditions described in the literature in the field or the product instructions shall be followed. If the manufacturer of the devices, instruments, reagents, etc. is not specified, they are all conventional products that can be purchased through regular channels. The experimental reagents and raw materials involved are all commercially available, and the reagents are all analytically pure products. In the following examples, zinc nitrate (Zn(NO 3 ) 2 ) (purchased from McLean, model: 228737-100g), sodium sulfide (Na 2 S standard solution, 0.1M, purchased from Guangzhou Hewei Pharmaceutical Technology Co., Ltd.) Cd 2+ Standard solution and other conventional metal ion standard solutions (initial concentration of 1000ppm, purchased from the National Standard Material Platform), ethanol (purchased from Beijing Jintong Letai Chemical Products Co., Ltd.), polyvinyl pyrrolidone (purchased from McLean, reagent number: 81440-250G), hydrochloric acid (purchased from McLean, reagent number: 1.09063, 2M). In the following examples, the main experimental equipment involved: the laser induced breakdown spectroscopy instrument device is a feasibility-level LISB device built by the laboratory itself.

[0035] In the embodiment of the present invention, Figure 1 This is a schematic diagram of a laser induced breakdown spectroscopy instrument device, which includes a signal delay generator 1, a laser 2, a plasma 3, a 3D detection platform 4, a paper-based chip 5, an optical fiber 6, a spectrometer 7, a focusing mirror 8 and a mirror 9. Figure 2The production process of the ZnSNPs-modified paper-based chip provided in the embodiment of the present invention is as follows: first, the zinc nitrate solution and the sodium sulfide solution are mixed and shaken, and after 2 minutes, PVP and hydrochloric acid solution are added and mixed, and then the filter paper is placed in the above solution and shaken at room temperature for 10 minutes, and ethanol is added to terminate the reaction. Finally, the ZnSNPs-modified paper-based chip is taken out and washed twice with deionized water, and then dried at 37°C for use. By in-situ synthesizing ZnSNPs on the paper-based chip, the paper-based chip modified with the nanoparticles can specifically enrich the cadmium ions in the water body, and finally the spectral signal of the metal ion Cd is excited by the LIBS technology, and a quantitative model between the LIBS signal and the Cd concentration is established to achieve high-sensitivity, rapid and efficient detection of heavy metal Cd in water bodies; in the figure, reaction container 10 (centrifuge tube), zinc ions 11, sulfide ions 12, filter paper 13, ZnSNPs-modified nanopaper 14, cadmium ions 15, adsorbed Cd 2+ Nanopaper substrate 16, laser induced breakdown spectroscopy instrument 17.

[0036] Example 1 This embodiment provides a ZnSNPs modified paper-based chip and a preparation method thereof, and uses LIBS technology combined with ZnSNPs modified paper-based chip to detect Cd in water. 2+ Enrichment and efficient and rapid detection were carried out, specificity experiments on the ZnSNPs modified paper-based chip prepared in this embodiment, adsorption detection of Cd elements, LIBS signal acquisition and establishment of quantitative relationship model, and performance testing such as actual sample detection were performed.

[0037] (1) Preparation of ZnSNPs-modified paper-based microarray Take 5mL zinc nitrate solution (10mM) and 4mL sodium sulfide solution (12mM) and mix them for 2min, then add 0.5g polyvinyl pyrrolidone, add hydrochloric acid (0.1mL, 0.1M) dropwise and mix, then place 50 filter papers (1cm×1cm) in it and shake for 10min, then add 2mL ethanol solution to terminate the reaction of the solution, finally take out the filter paper, wash it twice with deionized water and dry it at 37℃ for use, to obtain the ZnSNPs modified paper substrate (chip).

[0038] (2) Specificity detection This example verifies and proves that ZnSNPs modified paper substrate has a positive effect on Cd 2+ The present invention compares the adsorption of various conventional metal ions by ZnSNPs-modified paper substrates, and prepares other metal ions at a concentration of 0.2 mg / L. After shaking for 15 minutes, the paper substrate chip is taken out and washed twice with deionized water. The LIBS signal of the characteristic peaks of adsorbed metal ions corresponding to different paper substrates is collected by LIBS technology, and then data processing and comparative analysis are performed. Figure 3As shown in the bar graph, it can be seen that the signal of cadmium ions collected by LIBS is 1000, the signal of copper ions is 100, and the signals of other metal elements are basically 0. Based on the test results, the present invention concludes that the paper substrate modified with ZnSNPs has a very high specific adsorption performance for insulators and can well realize the detection of insulators.

[0039] (3) Cd 2+ Establishment of quantitative relationship model for detection Prepare 5 mL of different concentration gradients of Cd 2+ Solution (0, 5, 10, 50, 100, 200, 500, 1000 μg / L), and then add a prepared ZnSNPs modified paper chip to each solution. After shaking for 15 minutes, take out the paper chip and wash it twice with deionized water. Finally, detect the LIBS signal of Cd element on the paper chip. 2+ Quantitative relationship model between concentration and its LIBS signal.

[0040] (4) Cd in pond and river water 2+ Analytical testing and recovery calculation The pond water and river water were taken and the concentration of Cd in them was first detected by ICP-MS. The detection results showed that the concentration of Cd in the pond water and river water was 0.003μg / L and 0.002μg / L respectively. Then, the spike experiment was carried out (10μg / L and 50μg / L of Cd concentration were spiked respectively), and the concentration value and recovery rate were calculated by linearity.

[0041] Table 1 Cd 2+ Actual sample testing

[0042] (5) Specificity analysis In order to verify the effect of the present invention on Cd 2+ The ZnSNPs modified paper-based chip provided in this embodiment showed strong adsorption specificity for Cd (LIBS signal was 1000), but had almost no adsorption capacity for other metal elements or had weak signals (LIBS signal for copper ions was only 100, and LIBS signals for other metal ions were basically 0). The ZnSNPs modified paper-based chip provided by the present invention can realize the adsorption of Cd in water. 2+ Specific adsorption detection.

[0043] (6) Sensitivity analysis from Figure 4 It can be seen that after the ZnSNPs modified paper-based chip adsorbed different concentrations (0-1000 μg / L) of Cd, the LIBS spectrum changed with the increase of Cd2+ The signal at 226.56 nm increases with the increase of Cd 2+ The concentration increases and Figure 5 It can also be seen that the LIBS signal intensity is similar to that of Cd 2+ In a certain concentration range, there is a positive correlation. In order to establish a better quantitative model and calculate the best detection limit, such as Figure 5 As shown, the present invention establishes a corresponding quantitative relationship model (Y=51.5887X+1869.6045, R 2 =0.9922), which can achieve more accurate quantitative detection, and the Cd 2+ The detection limit was 1.10 μg / L.

[0044] (7) Analysis of test results In order to verify the practicability of this method, this example conducted Cd 2+ The spiked water samples were analyzed and tested. Table 1 shows the results of the actual sample spike test and the recovery rate calculation. The recovery rate can be maintained between 95% and 115%.

[0045] Comparative Example 1 This comparative example provides a paper substrate modified with zinc sulfide nanoparticles for detecting cobalt ions, and the preparation method thereof is as follows: (1) Preparation of zinc sulfide nanoparticle dispersion: zinc salt and sodium sulfide in a molar ratio of 0.3:1 are dissolved in deionized water to obtain a zinc salt solution and a sodium sulfide solution, respectively; the zinc salt solution is heated to 80°C, and then thioglycolic acid is added dropwise, and stirred for 30 minutes, wherein the volume ratio of thioglycolic acid to the zinc salt solution is 0.05:1; then the sodium sulfide solution is added dropwise, and the stirring is continued for 90 minutes and then cooled to obtain a zinc sulfide nanoparticle dispersion.

[0046] (2) Preparation of test paper: The adsorption layer is soaked in the zinc sulfide nanoparticle dispersion obtained in step (1) to fully infiltrate, and then the soaked adsorption layer is taken out and dried to obtain a cobalt ion detection test paper. This comparative example provides a different preparation method, using thioglycolic acid as a stabilizer, which is different from the polyvinyl pyrrolidone used in the present invention. Its final detection specificity is poor. Comparative Example 1 cannot achieve specific adsorption of Cd element, and cannot achieve accurate and efficient testing of Cd element using LIBS.

[0047] Comparative Example 2 The comparative example provides a gold nanocomposite particle synthesized based on the principle of click chemistry as a labeling probe of a lateral flow test strip and a signal output probe of LIBS technology, and realizes the detection of the insulator by combining the immunological principle. The preparation method is as follows: firstly, gold nanoparticles are prepared according to the traditional method, and then the nanoparticles are modified with Tz molecules and TCO-Ab respectively, and then the modified nanoparticles are subjected to a click reaction between TCO and Tz to obtain gold nanocomposite particles, and the nanocomposite particles are used as the labeling probe and signal output probe of the lateral flow test strip, and then the immunological detection of Cd 2+ The reaction was carried out, and finally the LIBS signal of the gold nanocomposite particles gathered at the T line of the test strip was combined with the Cd 2+ The concentration of Cd was used to establish a quantitative model, thereby achieving 2+ The comparative example provides a method of combining a lateral chromatography test strip with LIBS and using gold nanocomposite particles as probes. Although the Cd element can be tested by LIBS, the cost is relatively high and the preparation process of the gold nanocomposite particles is relatively complicated. In comparison, the ZnS nanoparticles provided by the present invention as enrichment probes are simple to prepare, low in cost, and easy to promote.

[0048] Example 2 This example adopts the same method as Example 1, except that the ZnSNPs-modified paper substrate is used to modify Cd 2+ The detection adsorption time was adjusted to 15min. According to experimental analysis (such as Figure 6 As shown in FIG. 1 ), the enrichment saturation is reached in 15 minutes. The optimal time for adsorption enrichment of the present invention is 15 minutes.

[0049] Example 3 This example adopts the same method as Example 1, except that the ZnSNPs-modified paper substrate is used to modify Cd 2+ The pH of the enrichment solution should be changed to 6-8 (optimal). If it is too acidic, Cd 2+ More active, not good for Cd 2+ The enrichment on the paper base, and the alkalinity is too strong, then Cd 2+ Easy to generate Cd(OH) 2 precipitation, which is also not conducive to Cd 2+ The enrichment ( Figure 7 ).

[0050] 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 it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a paper-based chip for LIBS detection of cadmium ions, characterized in that: include: 1) mixing a zinc salt solution and a sodium sulfide solution and reacting them to obtain a ZnS nanoparticle solution; 2) mixing the ZnS nanoparticle solution, polyvinyl pyrrolidone and acid solution to obtain a ZnSNPs modified solution; 3) The ZnSNPs modified solution is mixed with the filter paper and shaken, an alcohol solution is added, and the mixture is washed and dried.

2. The method for preparing a paper-based chip for LIBS detection of cadmium ions according to claim 1, characterized in that: In step 1), the zinc salt solution is a zinc nitrate solution, and the concentration of the zinc nitrate solution is 8-12 mM; and / or the concentration of the sodium sulfide solution is 10-14 mM.

3. The method for preparing a paper-based chip for LIBS detection of cadmium ions according to claim 2, characterized in that, In step 1), the volume ratio of the zinc nitrate solution to the sodium sulfide solution is 4-7:3-6.

4. The method for preparing a paper-based chip for LIBS detection of cadmium ions according to claim 1, characterized in that, In step 2), the ratio of the ZnS nanoparticle solution, the polyvinyl pyrrolidone and the acid solution is 6-10 mL: 0.3-0.8 g: 0.05-0.2 mL.

5. The method for preparing a paper-based chip for LIBS detection of cadmium ions according to claim 4, characterized in that, In step 2), the acid solution is hydrochloric acid, and the concentration of the hydrochloric acid is 0.05-0.15M.

6. A method for preparing a paper-based chip for LIBS detection of cadmium ions according to any one of claims 1 to 5, characterized in that: In step 3), the shaking time is 8 to 12 minutes, and the alcohol solution is ethanol solution.

7. The method for preparing a paper-based chip for LIBS detection of cadmium ions according to claim 6, characterized in that: In step 3), the cleaning is performed by washing with deionized water for 2 to 3 times, and the drying temperature is 35 to 40°C.

8. A paper-based chip for LIBS detection of cadmium ions, characterized in that: The paper-based chip is prepared by the preparation method of the LIBS paper-based chip for detecting cadmium ions according to any one of claims 1 to 7.

9. The use of the paper-based chip for detecting cadmium ions by LIBS prepared by the method for preparing the paper-based chip for detecting cadmium ions by LIBS according to any one of claims 1 to 7 or the paper-based chip for detecting cadmium ions by LIBS according to claim 8, characterized in that: Using LIBS to analyze Cd in water 2+ Application in specific adsorption detection.

10. The use according to claim 9, characterized in that: The quantitative relationship model used is: Y=aX+b; where Y is the LIBS signal intensity at 226.56nm, X is Cd 2+ Concentration, a is 51.5±0.2, b is 1869.6±0.2.

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