A simple and rapid quantitative visual detection method for chromium (VI) in water

Abstract

The application discloses a simple and rapid quantitative visual detection method for hexavalent chromium in water, which realizes etching reaction of gold core silver shell nanoparticles (Au@Ag NPs) and hexavalent chromium by adding hydrogen bromide solution and strictly controlling the amount of hydrogen bromide solution, and comprises the following steps: (1) preparing an Au@Ag NPs nanometer colorimetric probe solution; (2) configuring standard solutions of different concentrations of hexavalent chromium, adding the standard solutions of hexavalent chromium into a detection solution containing the Au@Ag NPs nanometer colorimetric probe solution and hydrogen bromide solution, and determining a blue channel intensity value I B of each standard solution according to a standard curve of hexavalent chromium and a detection limit; and (3) performing visual detection on actual water samples of hexavalent chromium. The detection method provided by the application has the advantages of mild detection conditions, good elimination of matrix interference, high stability and sensitivity, simple operation, rapid real-time quantification, low cost and wide application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to a simple and rapid quantitative visual detection method of Cr(VI) in water, belonging to the technical field of analytical chemistry. BACKGROUND

[0002] Cr(VI) is a chemical element with high oxidizing ability, commonly used in industrial applications such as metal plating, dye manufacturing, pigment production, etc. It is strictly regulated due to its toxicity and carcinogenicity. Cr(VI) can enter the human body through inhalation, ingestion or skin contact, and may cause respiratory problems, skin allergies and other health problems, and is listed as a class I carcinogen. Therefore, it is crucial to develop a simple, sensitive and rapid method for detecting Cr(VI).

[0003] There are many traditional methods for detecting Cr(VI), including atomic absorption spectrometry, chromatography, electrochemistry, colorimetry, chemiluminescence and fluorescence spectroscopy, etc. The above methods require the use of professional equipment, and the operation process is time-consuming, complicated and expensive. Therefore, it is of great significance to develop a method for real-time quantitative detection of Cr(VI) ions in ordinary laboratories or even in the field, which can overcome the problems of tedious operation and time-consuming in the existing image colorimetric method based on color recognition for detecting Cr(VI) ions. SUMMARY

[0004] The purpose of the present application is to provide a visual detection method for real-time quantitative detection of Cr(VI) in water in ordinary laboratories or even in the field, which can overcome the problems of tedious operation and time-consuming in the existing image colorimetric method based on color recognition for detecting Cr(VI) ions.

[0005] The technical solution of the present application is a simple and rapid quantitative visual detection method of Cr(VI) in water, which comprises using Au@Ag NPs as a colorimetric probe, reacting with Cr(VI) in the presence of HBr solution, and taking color images of the reacted solution by a shooting device, and identifying the RGB of each color image to obtain the blue channel intensity value I B , and using the linear relationship between the blue channel intensity value I B and the concentration of Cr(VI) to quantify Cr(VI).

[0006] The simple and rapid quantitative visual detection method of Cr(VI) in water according to the present application comprises the following steps:

[0007] (1) Prepare an Au@Ag NPs nanometer colorimetric probe solution;

[0008] (2) configure different concentrations of chromium (VI) standard solution, mix Au@Ag NPs nanometer colorimetric probe solution with hydrobromic acid solution to obtain a detection solution, add different concentrations of chromium (VI) standard solution to the detection solution to react, take color images of the reaction solution, and obtain blue channel intensity values I corresponding to different concentrations of chromium (VI) through RGB identification of each color image B， Utilize the blue channel intensity values I B and different concentrations of chromium (VI) to construct a standard curve.

[0009] (3) mix Au@Ag NPs nanometer colorimetric probe solution with hydrobromic acid solution to obtain a detection solution, add the water to be tested to the detection solution to react, and obtain a blue channel intensity value I B , and utilize the standard curve obtained in step (2) to obtain the concentration of chromium (VI) in the water to be tested.

[0010] Further, in step (1), the preparation method of the Au@Ag NPs nanometer colorimetric probe includes the following steps:

[0011] rapidly add trisodium citrate to the HAuCl4 solution, continue to maintain boiling reaction under rapid stirring, cool the solution to room temperature, and then sequentially add ascorbic acid and AgNO3 to the solution, and continuously stir, so that the color of the solution gradually changes from wine red to orange, thereby obtaining the Au@Ag NPs nanometer colorimetric probe solution.

[0012] Further, in step (2), the concentration of the Au@Ag NPs nanometer colorimetric probe solution is 0.2-0.5 mmol / L, the concentration of the hydrobromic acid solution is 0.05-0.15 mol / L, and the volume ratio of the Au@Ag NPs nanometer colorimetric probe solution to the hydrobromic acid solution in the mixed solution is (500-1000):(10-50). Most preferably, the concentration of the Au@Ag NPs nanometer colorimetric probe solution is 0.2 mmol / L, the concentration of the hydrobromic acid solution is 0.15 mol / L, and the volume ratio of the Au@Ag NPs nanometer colorimetric probe solution to the hydrobromic acid solution in the mixed solution is 700:30.

[0013] Further, in step (2), the concentrations of different chromium (VI) standard solutions are 2.5 μmol / L, 5 μmol / L, 8 μmol / L, 10 μmol / L, 12 μmol / L, 15 μmol / L, 20 μmol / L, 25 μmol / L, 30 μmol / L, and 35 μmol / L.

[0014] Further, in step (2), the standard curve is y=4.209x+108.049, wherein x is the concentration of chromium (VI) ions (μM), and Y is the blue channel intensity value I B .

[0015] Further, in step (2), the linear range of the standard curve is 2.5-35 μmol / L.

[0016] Further, when taking the color developing image of the reaction solution, the distance between the camera of the shooting device and the reaction solution is 5-10 cm.

[0017] Further, when taking the color developing image of the reaction solution, the distance between the camera of the shooting device and the reaction solution is 5-10 cm.

[0018] Further, in steps (2) and (3), the reaction time is within 12 min.

[0019] The construction mechanism is as follows: Au@Ag NPs undergoes redox reaction with hexavalent chromium in the presence of hydrobromic acid (HBr) solution, leading to etching of Au@Ag NPs. Chromium changes from hexavalent state to trivalent state, and the silver shell of the core-shell structure Au@Ag NPs gradually thins until completely etched into gold nanospheres. In this process, the solution color of Au@Ag NPs presents a vivid change from orange to pink and then to light purple. The color change can be converted into RGB value by color block grabbing function in the camera of the smart phone, and a linear relationship is established between the RGB value and the concentration of hexavalent chromium to realize the quantification of hexavalent chromium.

[0020] The hexavalent chromium ions can oxidize and etch Au@Ag NPs in the presence of HBr solution, so that the solution color changes from orange to pink and then to light purple. The change of the solution color is closely related to the concentration of hexavalent chromium ions. The color of the solution is photographed by a smart phone, and then recognized and read, and finally converted into the concentration of hexavalent chromium ions. The obtained image is expressed as blue channel intensity value I B A standard curve is constructed for the concentration of hexavalent chromium ions, and the fitting correlation coefficient is very high. Moreover, this detection method can well exclude matrix interference, and has good stability and precision.

[0021] Advantages: Compared with the prior art, the present application has the following significant advantages:

[0022] (1) The present application realizes visual detection of hexavalent chromium ions by mobile phone shooting, which is simple and convenient, and has low detection cost, without the need for professional and expensive detection equipment and carefully trained operators.

[0023] (2) The present application uses Au@Ag NPs as a colorimetric probe, and the preparation process is simple. Unlike most colorimetric sensors based on metal nanoparticles, which only show a single color change when responding to the target. Different color changes correspond to different target concentrations, so the approximate concentration of the detection target can also be easily determined by the naked eye, which is considered as an efficient colorimetric sensor in actual detection.

[0024] (3) The colorimetric probe provided by the application has good selectivity and sensitivity for detecting hexavalent chromium, is hardly interfered by other ions, and has a linear relationship with the concentration of hexavalent chromium within a certain range, so that the content of hexavalent chromium in a water environment can be detected, and the application has a very broad application prospect.

[0025] (4) The colorimetric probe provided by the application has a short detection time, and the reaction can be quickly completed within 12 minutes, is simple to operate, and can be operated at room temperature. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 It is a schematic diagram for detecting the hexavalent chromium ion standard solution in Example 14.

[0027] Figure 2 It is a broken line graph of RGB three groups of values and hexavalent chromium concentration and a standard curve graph, wherein the large graph is a broken line graph of RGB three groups of values and hexavalent chromium concentration, and the small graph is a standard curve graph. DETAILED DESCRIPTION

[0028] The technical solutions of the application will be further described below with reference to the drawings.

[0029] The components of the following detection solution include: the amount of Au@Ag NPs is 0.5-1.0 mL, and the amount of HBr is 10-50 μL. The implementation conditions not mentioned are usually the conditions in the conventional experiments. In addition, it should be noted that the numerical values given in the following examples are as accurate as possible, but due to the inevitable measurement errors and experimental operation problems of the person skilled in the art, each number should be understood as an approximate number rather than an absolutely accurate number.

[0030] Example 1: Preparation of Au@Ag NPs as a colorimetric probe:

[0031] 1.5 mL of trisodium citrate is quickly added to 100 mL of HAuCl4 solution, and the boiling reaction is continued for 15 minutes under rapid stirring. After the solution is cooled to room temperature, 3 mL of 0.1 mol / L ascorbic acid solution and 3 mL of 1 mmol / L AgNO3 solution are sequentially added to the solution, and the stirring is continued for 30 minutes. The color of the solution gradually changes from wine red to orange, and the Au@Ag NPs colorimetric probe solution is obtained. The concentration of Au@Ag NPs is measured by UV-Vis spectroscopy, that is, the absorbance of UV-Vis is combined with Beer-Lambert law to measure the concentration of the Au@Ag NPs colorimetric probe solution, and the concentration is 0.2 mmol / L.

[0032] Example 2

[0033] (1) Mix 0.5 mL of 0.2 mmol / L Au@Ag NPs colorimetric probe solution with 10 μL of 0.15 mol / L HBr solution, and add ultrapure water to obtain 1.1 mL of detection solution.

[0034] (2) Take 0.4 mL of 20 μmol / L hexavalent chromium solution to be detected and mix with the detection solution, shake well, and stand for 10 minutes; use ultrapure water instead of hexavalent chromium solution for the blank experiment;

[0035] Rough determination: observe with the naked eye, if the solution changes from orange to pink or purple, it indicates the presence of hexavalent chromium;

[0036] Accurate identification: use a smartphone camera to take an image of the solution and then perform RGB identification to obtain the blue channel intensity value I B , and the blue channel intensity value I B0 obtained from the blank experiment are compared, if the two values change significantly, it indicates the presence of hexavalent chromium.

[0037] Examples 3-8

[0038] The detection process is the same as that of Example 2, and the components of the detection solution are shown in Table 1.

[0039] Table 1 Components of the detection solution of Examples 3-8

[0040] Ingredients Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Au@Ag NPs 0.5 mL 0.6 mL 0.7 mL 0.8 mL 0.9 mL 1.0 mL HBr 20 μL 20 μL 20 μL 20 μL 20 μL 20 μL ultra-pure water balance balance balance balance balance balance

[0041] The detection solution for metal hexavalent chromium of Examples 3-8 is determined by color change, I B intensity value change degree, and color change time, and the determination results are shown in Table 2.

[0042] Table 2 Determination results of Examples 3-8

[0043] Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Color change Orange→pink Orange→pink Orange→pink Orange→pink Orange→pink Orange→pink I B degree of intensity value change 107→170 obvious 103→175 obvious 98→190 obvious 94→182 obvious 91→176 obvious 87→170 obvious Color changing time 12 min 11.5 min 10.8 min 11.3 min 11.6 min 11.9 min

[0044] As can be seen from Table 2, in Examples 3-8, the color of the solution changes from orange to pink, the I B intensity value change degree is obvious, and the presence of hexavalent chromium can be determined. Among them, the I B intensity value change degree in Example 5 is the largest, the color change time is the shortest, and the effect is the best. It also shows that the amount of Au@Ag NPs has an effect on the detection effect.

[0045] Examples 9-13

[0046] The detection process is the same as that of Example 2, and the components of the detection solution are shown in Table 3.

[0047] Table 3 Components of the detection solution of Examples 9-13

[0048] Ingredients Example 9 Example 10 Example 11 Example 12 Example 13 Au@Ag NPs 0.7 mL 0.7 mL 0.7 mL 0.7 mL 0.7 mL HBr 10 μL 20 μL 30 μL 40 μL 50 μL ultra-pure water balance balance balance balance balance

[0049] The detection solution for hexavalent chromium metal of Examples 9-13 was determined by color change, I B intensity value change degree, discoloration time, and the determination results are shown in Table 4.

[0050] Table 4 Determination results of Examples 9-13

[0051] Example 9 Example 10 Example 11 Example 12 Example 13 Color change Orange→pink Orange→pink Orange→pink Orange→pink Orange→pink I B degree of intensity value change 100→158 obvious 100→175 obvious 100→197 obvious 100→190 obvious 100→182 obvious Color changing time 11.8 min 11.2 min 10.1 min 10.9 min 10.6 min

[0052] As can be seen from Table 4, in Examples 9-13, the color change of the solution is from orange to pink, I B intensity value change degree is obvious, which can be judged to exist hexavalent chromium. Among them, the I B intensity value change degree of Example 11 is the largest, and the discoloration time is the shortest, so it is determined that the effect is the best. This also shows that the amount of HBr is crucial in the simple and rapid visual detection method of hexavalent chromium.

[0053] Comparative Examples 1-6

[0054] The detection process is the same as Example 6, and the components of the detection solution are shown in Table 5.

[0055] Table 5 Components of the detection solution of Comparative Examples 1-6

[0056] Ingredients Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Au@Ag NPs 0.7 mL 0 0.3 mL 0.4 mL 0.7 mL 0.7 mL HBr 0 20 μL 20 μL 20 μL 60 μL 70 μL ultra-pure water balance balance balance balance balance balance

[0057] The detection solution for hexavalent chromium metal of Examples 9-13 was determined by color change, I B intensity value change degree, discoloration time, and the determination results are shown in Table 6.

[0058] Table 6 Determination results of Comparative Examples 1-6

[0059] Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Color change Orange→orange Colorless→colorless Pink→light purple Light orange→light purple Light orange→light purple Pink→light purple I B degree of intensity value change 98→99 not obvious Not obvious 169→216 obvious 158→195 obvious 160→228 obvious 175→242 obvious

[0060] In combination with Examples 2-13 and Comparative Example 1, it can be shown that the presence of HBr is crucial in the simple and rapid visual detection method of hexavalent chromium. In combination with Examples 2-13 and Comparative Example 2, it is shown that Au@Ag NPs play a key role in the simple and rapid visual detection method of hexavalent chromium. In combination with Example 2 and the above two comparative examples, it can be seen that Au@Ag NPs and HBr are indispensable in the simple and rapid visual detection method of hexavalent chromium.

[0061] Comparative Example 5-8, before adding the hexavalent chromium solution, the detection solution of Comparative Examples 3 and 4 respectively presents pink and light orange, which indicates that the amount of HBr is excessive relative to the amount of Au@Ag NPs, so that the system is in an unstable state. These two examples will affect the quantitative detection result of hexavalent chromium, and are judged as invalid detection solution.

[0062] Comparative Example 9-13, the detection solution of Comparative Examples 5 and 6 respectively presents light orange and pink at the beginning, which indicates that too much HBr will affect the stability of Au@Ag NPs, resulting in the detection solution starting to change color before the hexavalent chromium solution is added, which is judged as invalid detection solution.

[0063] In summary, from the color change time of the above examples, it can be considered that the detection solution of the present application can quickly and accurately determine the presence of hexavalent chromium. The effective volume ratio of the components of the detection solution is (500-1000):(10-50), and the most preferred volume ratio is 700:30.

[0064] Example 14 Construction of hexavalent chromium ion standard curve and detection limit

[0065] (1) The hexavalent chromium ion standard substance was configured into a 100 μM stock solution with pure water. 1.25 mL, 2.5 mL, 4 mL, 5 mL, 6 mL, 7.5 mL, 10 mL, 12.5 mL, 15 mL, 17.5 mL of the stock solution were taken into a 50 mL volumetric flask, and diluted to the mark with pure water, to prepare 2.5 μM, 5 μM, 8 μM, 10 μM, 12 μM, 15 μM, 20 μM, 25 μM, 30 μM, 35 μM of hexavalent chromium ion standard solution.

[0066] (2) 0.7 mL of 0.2 mmol / L Au@Ag NPs colorimetric probe solution was mixed with 30 μL of 0.15 mol / L HBr solution, and 1.1 mL of detection solution was obtained by adding ultrapure water.

[0067] (3) 0.4 mL of different concentrations of hexavalent chromium ion standard solution to be detected was mixed with the detection solution, shaken and placed for 10 minutes; the blank experiment used ultrapure water instead of hexavalent chromium solution; the detection schematic diagram is as shown in Figure 1

[0068] (4) The RGB identification of the smartphone camera was performed on different color standard sample solutions to obtain the blue channel intensity value I B , I B0 and I B’ , respectively, which were the blue channel color intensity values of the blank sample and different concentrations of hexavalent chromium ion standard solution. The blue channel intensity value I B ​The linear range, regression equation, correlation coefficient, detection limit and relative standard deviation of the standard curve are shown in Table 7, and the standard curve graph is shown in Figure 2 .

[0069] Table 7 Regression equation, linear range, correlation coefficient, detection limit and relative standard deviation of the standard curve

[0070] Detection target Regression equation Linear range Correlation coefficient Detection limit Relative standard deviation Hexavalent chromium ion y=4.209x+108.049 2.5-35 μM 0.991 1.57 μM 5.47%

[0071] In Table 7, x is the concentration of hexavalent chromium ions, μM; Y is the blue channel intensity value, I B ; b: S / N ratio = 3;

[0072] From the results in Table 7 and Figure 2 , it can be seen that the fitting linear correlation coefficient of the standard curve constructed by the method provided by the present application is very high.

[0073] Example 15 Single metal ion interference effect experiment

[0074] (1) Prepare single metal ion interference hexavalent chromium solution: sequentially take 1 mL of 1000 mg / L trivalent chromium standard solution, total nickel standard solution, total cadmium standard solution, total lead standard solution, total copper standard solution, total zinc standard solution, trivalent iron standard solution, and total aluminum standard solution into a single 500 mL volumetric flask; use the prepared 20 μM (1.04 mg / L) hexavalent chromium standard solution to make up to the mark; that is, 8 groups of single metal interference ion 20 μM hexavalent chromium solutions containing 2 mg / L of trivalent chromium ions, total arsenic ions, total nickel ions, total cadmium ions, total lead ions, total copper ions, total zinc ions, and total aluminum ions are obtained;

[0075] (2) Mix 0.7 mL of 0.2 mmol / L Au@Ag NPs colorimetric probe solution with 30 μL of 0.15 mol / L HBr solution, and add ultrapure water to obtain 1.1 mL of detection solution.

[0076] (3) Take 0.4 mL of the 8 groups of single metal interference ion 20 μM hexavalent chromium solution to be tested and mix with the detection solution, shake well, and then stand for 10 minutes.

[0077] (4) Use a shooting device to take images of the reacted solution, use the color picking function of a smartphone camera to perform RGB identification on each color development image, and obtain the blue channel intensity value I B . According to the blue channel intensity value I B and the standard curve established in Example 14, the content of hexavalent chromium ions in each group of samples is calculated. The results are shown in Table 8.

[0078] Table 8 Results of detecting the content of hexavalent chromium ions in the hexavalent chromium solution interfered by eight single metal ions

[0079] Single metal ion interference sample Hexavalent chromium concentration (μM) Ion interference effect Trivalent chromium ion 19.534 2.33% Arsenic ion 19.378 3.11% Cadmium ion 18.733 6.34% Lead ion 18.962 5.19% Copper ion 19.293 3.54% Zinc ion 19.267 3.67% Nickel ion 18.569 7.16% Aluminum ion 19.479 2.61%

[0080] From Table 8, it can be seen that the calculated interference of the ions meets the national requirement of ion interference index requirement ≤ ± 15%, so the presence of the above-mentioned interfering ions will not interfere with the quantitative detection of hexavalent chromium.

[0081] Example 16 Interference of mixed metal ions

[0082] (1) Preparation of a mixed metal ion interfered hexavalent chromium solution: 100 μL of each of 1000 mg / L trivalent chromium standard solution, total nickel standard solution, total cadmium standard solution, total lead standard solution, total copper standard solution, total zinc standard solution, trivalent iron standard solution and total aluminum standard solution were sequentially transferred into the same 50 mL volumetric flask; the prepared 20 μM (1.04 mg / L) hexavalent chromium standard solution was used for constant volume to the mark; thus a mixed metal interference ion 20 μM hexavalent chromium solution containing 2 mg / L of each of trivalent chromium ions, total arsenic ions, total nickel ions, total cadmium ions, total lead ions, total copper ions, total zinc ions and total aluminum ions was obtained;

[0083] (2) 0.7 mL of 0.2 mmol / L Au@Ag NPs colorimetric probe solution was mixed with 30 μL of 0.15 mol / L HBr solution, and ultrapure water was added to obtain 1.1 mL of detection solution.

[0084] (3) 0.4 mL of the mixed metal interference ion 20 μM hexavalent chromium solution to be detected was mixed with the detection solution, shaken and placed for 10 minutes. Three parallel tests were performed.

[0085] (4) The image of the reacted solution was captured by using the camera of a smart phone, the color of each developed image was recognized by using the color picking function of the camera of the smart phone, and the blue channel intensity value I B was obtained. The content of hexavalent chromium ions in the sample was calculated according to the blue channel intensity value I B and the standard curve. The results are shown in Table 9.

[0086] Table 9 Results of detecting the content of hexavalent chromium ions in the mixed metal ion interfered hexavalent chromium solution

[0087] Mixed metal ion interference sample Hexavalent chromium concentration (μM) Ion interference effect 1 19.628 1.86% 2 19.597 2.02% 3 19.466 2.67%

[0088] It is further verified from the results in Table 9 that the method of the present application is suitable for detecting hexavalent chromium in water under the condition of coexistence of multiple mixed ions.

[0089] Example 17 Detection of hexavalent chromium content in environmental water samples and recovery rate experiment

[0090] (1) Collect a freshwater lake water sample in Nanjing, Jiangsu, and filter it through a 0.22 μm water phase filter to remove particulates. Measure as soon as possible after collection, no more than 24 h.

[0091] (2) Mix 7 mL of 0.2 mmol / L Au@Ag NPs colorimetric probe solution with 300 μL of 0.15 mol / L HBr solution, and add ultrapure water to obtain 1.1 mL of detection solution.

[0092] (3) Take 4 mL of the three groups of lake water samples to be tested and mix with the detection solution, shake well, and then place for 10 minutes.

[0093] (4) Take an image of the water sample solution using a smartphone camera; identify the blue channel intensity value I B of the lake water sample image; and calculate the content of hexavalent chromium ions in the lake water sample according to the blue channel intensity value I B and the standard curve obtained in Example 14, see the initial detection value in Table 10.

[0094] (5) Take 1 mL, 2 mL, and 2.5 mL of 100 μM hexavalent chromium stock solution in Example 14 and add to 9 mL, 8 mL, and 7.5 mL of filtered lake water samples, respectively, to prepare the spiked water samples; re-determine the content of hexavalent chromium ions in the spiked water samples; and perform the matrix spike recovery rate experiment, see the results in Table 8. The recovery rate = spiked detection value / (initial detection value + added value).

[0095] Table 10 Spiked detection results

[0096] Sample Initial detection value (μM) Added value (μM) Spiked detection value (μM) Recovery rate (%) 1 7.96 10 17.35 96.60 2 7.07 20 27.14 100.26 3 7.98 25 32.16 97.51

[0097] The detection limit of hexavalent chromium in the method of the application can reach 1.57 μM, meeting the limit standard for drinking water, and has good linear correlation in the detection range of 2.5-35 μM.

[0098] The above examples are only optimized implementation methods of the application, used to exemplarily illustrate the principles and effects of the application, and are not intended to limit the application. It should be noted that, for those skilled in the art, without departing from the concept of the application, several modifications and improvements can be made, which are all within the protection scope of the application.

Claims

1. A simple, rapid and quantitative visual detection method for Cr(VI) in water, characterized in that, The application relates to a method for detecting hexavalent chromium ions, which comprises taking gold core silver shell nanoparticles Au@Ag NPs as a colorimetric probe, reacting with hexavalent chromium in the presence of hydrobromic acid HBr solution, taking color images of the reacted solution by a shooting device, carrying out RGB identification on each color image, and obtaining a blue channel intensity value I B The application also relates to a method for quantifying hexavalent chromium ions, which utilizes the linear relationship between the blue channel intensity value I B and the concentration of hexavalent chromium; hexavalent chromium ions can oxidize and etch Au@Ag NPs in the presence of HBr solution, so that the color of the solution changes from orange to light pink and finally to light purple. The preparation method of the Au@Ag NPs nanometer colorimetric probe comprises the following steps: The trisodium citrate is quickly added into the HAuCl4 solution, and the boiling reaction is continuously kept under the condition of rapid stirring. After the solution is cooled to room temperature, the ascorbic acid and AgNO3 are sequentially added into the solution, and the stirring is continuously performed. The solution color is gradually changed from wine red to orange, and the Au@Ag NPs nanometer colorimetric probe solution is obtained.

2. The method for simple and rapid quantitative visual detection of Cr(VI) in water according to claim 1, characterized in that, The method comprises the following steps: (1) preparing the Au@Ag NPs nanometer colorimetric probe solution; (2) configure different concentrations of hexavalent chromium standard solution, mix Au@Ag NPs nanometer colorimetric probe solution with hydrobromic acid solution to obtain detection liquid, add different concentrations of hexavalent chromium standard solution in the detection liquid to react, take color developing image of the reaction liquid, and obtain blue channel intensity value I corresponding to different concentrations of hexavalent chromium through RGB identification of each color developing image B , and construct standard curve by using blue channel intensity value I B and different concentrations of hexavalent chromium. (3) The Au@Ag NPs nanometer colorimetric probe solution is mixed with a hydrobromic acid solution to obtain a detection liquid, and the blue channel intensity value I is obtained by adding the water to be detected into the detection liquid and reacting B The concentration of hexavalent chromium in the water to be detected is obtained by using the standard curve obtained in step (2).

3. The method for simple and rapid quantitative visual detection of Cr(VI) in water according to claim 2, characterized in that, In step (2), the concentration of the Au@Ag NPs nanometer colorimetric probe solution is 0.2-0.5 mmol / L, the concentration of the hydrobromic acid solution is 0.05-0.15 mol / L, and the volume ratio of the Au@Ag NPs nanometer colorimetric probe solution to the hydrobromic acid solution in the mixed solution is (500-1000):(10-50).

4. The method for simple and rapid quantitative visual detection of Cr(VI) in water according to claim 2, characterized in that, In step (2), the concentrations of different standard solutions of hexavalent chromium are respectively 2.5 μmol / L, 5 μmol / L, 8 μmol / L, 10 μmol / L, 12 μmol / L, 15 μmol / L, 20 μmol / L, 25 μmol / L, 30 μmol / L and 35 μmol / L.

5. The method for simple and rapid quantitative visual detection of Cr(VI) in water according to claim 2, characterized in that, In step (2), the standard curve is y = 4.209x + 108.049, where x is the concentration of hexavalent chromium ions in μM and y is the blue channel intensity value I B .

6. The method for simple and rapid quantitative visual detection of Cr(VI) in water according to claim 2, characterized in that, The linear range of the standard curve is 2.5-35 μmol / L.

7. The method for simple and rapid quantitative visual detection of Cr(VI) in water according to claim 2, characterized in that, When the color developing images of the reaction solution are taken, the distance between the camera of the shooting device and the reaction solution is 5-10 cm.

8. The method for simple and rapid quantitative visual detection of Cr(VI) in water according to claim 2, characterized in that, When the RGB identification of each color developing image is performed, the color picking function in the camera of the smart phone is adopted.

9. The method for simple and rapid quantitative visual detection of Cr(VI) in water according to claim 2, characterized in that, In steps (2) and (3), the reaction time is within 12 min.

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