A Raman detection method for potassium permanganate based on an Au-Ag core-shell structure substrate

Abstract

A Raman detection method of potassium permanganate based on an Au-Ag core-shell structure substrate, which relates to the detection technology of KMnO4. In the present invention, Au-4MBA@Ag nanosol embedded with the Raman signal molecule 4-mercaptobenzoic acid (4MBA) is synthesized by a layer-by-layer coating method. The prepared Au-4MBA@Ag nanosol shows excellent SERS signals at 1074 cm ‑1 -1 by a 633 nm laser. In the presence of KMnO4, the Ag shell layer will be gradually consumed, resulting in the decrease of the SERS signal of 4MBA with the increase of the concentration of the KMnO4 solution. The present invention can achieve sensitive, time-saving and efficient Raman detection of KMnO4 without adding additional Raman signal molecules.

Description

Technical Field:

[0001] The present invention belongs to the technical field of Raman analysis, and particularly relates to a Raman detection method for potassium permanganate based on an Au-Ag core-shell structure substrate. Background Art:

[0002] Potassium permanganate is a strong oxidizing agent. In chemical production, it is widely used as an oxidizing agent, for example, as an oxidizing agent for producing saccharin, vitamin C, isoniazid, and benzoic acid; in medicine, it is used as an antiseptic, disinfectant, deodorant, and antidote; in water purification and wastewater treatment, it is used as a water treatment agent to oxidize various pollutants such as hydrogen sulfide, phenol, iron, manganese, and organic and inorganic substances, and to control odor and decolorization; in gas purification, it can remove trace amounts of sulfur, arsenic, phosphorus, silane, borane, and sulfides; in mining and metallurgy, it is used to separate molybdenum from copper, remove impurities from zinc and cadmium, and as an oxidizing agent for compound flotation; it is also used as a bleaching agent for special fabrics, waxes, oils, and resins, an adsorbent for gas masks, a coloring agent for wood and copper, etc.

[0003] Currently, the most commonly used methods for detecting KMnO4 include the sodium oxalate method and the iodometric method. However, both of these methods are chemical titration methods, with relatively large errors and long time consumption. Therefore, it is very necessary to explore a convenient, accurate, and rapid KMnO4 detection and analysis method. Summary of the Invention:

[0004] To solve the above technical problems, the present invention provides a Raman detection method for potassium permanganate based on an Au-Ag core-shell structure substrate. The Au-Ag core-shell structure embedded with 4MBA can provide excellent SERS signals, and can conveniently, accurately, and rapidly achieve quantitative detection of KMnO4 without adding external Raman signal molecules.

[0005] The object of the present invention is achieved through the following technical solutions:

[0006] A Raman detection method for potassium permanganate based on an Au-Ag core-shell structure substrate, characterized by comprising the following steps:

[0007] S1: Prepare gold nanosol;

[0008] S2: After adding Raman signal molecules and incubating, add a stabilizer, a reducing agent, and a silver ion solution and react for 20 - 50 min, and remove the unreacted completely reagents to obtain an Au-Ag core-shell structure nanosol;

[0009] S3: Adjust the pH value range of the Au-Ag core-shell structure nanosol in S2 to 10.2 - 12.3, respectively add a KMnO4 standard solution and a test solution, and perform Raman signal detection to achieve qualitative or quantitative detection of KMnO4.

[0010] Preferably, the method for preparing the gold nano-sol in step S1 is as follows: adding a reducing agent to a boiling gold source solution for full reaction, and removing the unreacted reagents after the reaction to obtain the gold nano-sol.

[0011] Preferably, the gold source solution described in step S1 is an aqueous solution of chloroauric acid with a concentration of 0.05 - 0.1 g / L; the reducing agent is an aqueous solution of sodium citrate dihydrate with a mass fraction of 1% ± 0.5%; the volume ratio of the gold source solution to the reducing agent is 122:1 - 40:1.

[0012] Preferably, the Raman signal molecule in step S2 is a methanol and water (v:v = 1:9) solution of 4-mercaptobenzoic acid with a concentration of 0.1 mM - 1 mM; the volume ratio of the gold nano-sol to the Raman signal molecule solution is 15:1 - 150:1.

[0013] Preferably, the incubation condition in step S2 is incubation at 30 - 50 °C for 1 - 3 h.

[0014] Preferably, the stabilizer in step S2 is an aqueous solution of sodium citrate with a mass fraction of 0.5% - 2%; the reducing agent is an aqueous solution of ascorbic acid, and the silver ion solution is an aqueous solution of silver nitrate; the reducing agent and the silver ion solution have the same molar concentration, with a concentration of 5 mM - 15 mM.

[0015] Preferably, the volume ratio of the gold nano-sol to the stabilizer in step S2 is 30:1 - 60:1; the reducing agent and the silver ion solution are added in equal volume, and the volume ratio of the gold nano-sol to the reducing agent or the silver ion solution is 16:1 - 30:1.

[0016] Preferably, the method for quantitative detection in S3 is as follows:

[0017] (1) Plot a standard curve: taking the natural logarithm value of the KMnO4 concentration as the abscissa and the Raman intensity at 1074 cm -1 as the ordinate to plot the standard curve for quantitative detection;

[0018] (2) Mix the KMnO4 sample with unknown concentration to be measured with the Au-Ag core-shell structure nano-sol, conduct Raman intensity detection, and calculate the concentration of the KMnO4 sample through the standard curve formula.

[0019] Preferably, the method for measuring the standard curve in step (1) is as follows: mixing the Au-Ag core-shell structure nano-sol with KMnO4 at different concentrations, reacting under ultrasonic for 20 - 50 s to make KMnO4 fully contact with the Ag shell surface to obtain a mixed liquid; collecting the mixed liquid with a capillary, and conducting Raman detection on the mixed liquid using a 633 nm laser source.

[0020] Preferably, the detectable concentration of the KMnO4 solution is 0.001 mg / ml to 20.0 mg / ml.

[0021] Compared with the prior art, the advantages of the present invention are as follows:

[0022] (1) The method provided by the present invention uses Raman detection technology to achieve convenient, accurate and rapid detection of the KMnO4 concentration. The Au-Ag core-shell structure nanomaterials are simply prepared, have excellent SERS performance, are sensitive to the KMnO4 solution, have a short reaction time, and are highly efficient in detection. The present invention provides a new idea for the detection of the KMnO4 concentration and has a very broad application prospect.

[0023] (2) The present invention uses the direct reaction between potassium permanganate and the silver shell layer to generate signal changes. The synthesis of the substrate is simpler, the detection object directly contacts the substrate surface to generate more direct hot spot changes, and the signal changes are more obvious. Description of the drawings:

[0024] In order to make the content of the present invention easier to be clearly understood, the following further details the present invention according to the specific embodiments of the present invention and in combination with the drawings, where

[0025] Figure 1 is the transmission electron microscope image of the Au-Ag core-shell structure nanomaterials in the second embodiment of the present invention.

[0026] Figure 2 is the Raman intensity at 1074 cm -1 in the second embodiment of the present invention when there are different concentrations of KMnO4.

[0027] Figure 3 is the standard curve of the concentration of the KMnO4 solution in the range of 0.001 mg / mL - 20 mg / mL in the second embodiment of the present invention. Specific embodiments:

[0028] Example 1:

[0029] 1. Synthesis of Au-Ag core-shell structure nanomaterials

[0030] Add 1 mL of 1% (w / v) HAuCl4·3H2O solution to 60 mL of ultrapure water, heat it under stirring and reflux. After the solution boils for 5 minutes, quickly add 600 μL of 1% (w / v) sodium citrate solution. Continue to stir and heat for 10 minutes, then remove the heat source and cool the solution to room temperature. Take 3 mL of the prepared gold nanoparticles obtained above, centrifuge them, redissolve them in ultrapure water, add 20 μL of 4-mercaptobenzoic acid (4MBA) with a concentration of 0.1 mM, incubate at 50 °C for 1 h. After centrifugation, redisperse the gold nanoparticles modified with 4MBA in 3 mL of ultrapure water. Under oscillation, add 60 μL of 1% (w / v) sodium citrate solution, 100 μL of ascorbic acid solution with a molar concentration of 10 mM and 100 μL of silver nitrate solution with a molar concentration of 10 mM, react for 30 minutes, centrifuge and wash twice with ultrapure water. Finally, redissolve the Au-Ag core-shell structured nanomaterials in 3 mL of ultrapure water.

[0031] 2. Establishment of Raman analysis method for KMnO4

[0032] Adjust the pH value of the Au-Ag core-shell structured nanomaterial solution to 10.5 with 1 mol / l sodium hydroxide solution, mix it with KMnO4 at different concentrations (0.001 mg / mL, 0.005 mg / mL, 0.01 mg / mL, 0.05 mg / mL, 0.1 mg / mL, 0.5 mg / mL, 1.0 mg / mL, 5.0 mg / mL, 10.0 mg / mL, 20.0 mg / mL) under ultrasonic treatment, react ultrasonically for 20 s, collect the mixed liquid with a capillary tube, and detect the Raman intensity at room temperature using a 633 nm laser source through a Raman spectrometer to obtain a standard for quantitative detection with the natural logarithm of the KMnO4 concentration as the abscissa and the Raman intensity at 1074 cm 1 as the ordinate.

[0033] Example 2:

[0034] 1. Synthesis of Au-Ag core-shell structured nanomaterials

[0035] Add 1 mL of 1% (w / v) HAuCl4·3H2O solution to 60 mL of ultrapure water, heat it under stirring and reflux. After the solution boils for 4 minutes, quickly add 700 μL of 1% (w / v) sodium citrate solution. Continue stirring and heating for 8 minutes, then remove the heat source and cool the solution to room temperature. Take 3 mL of the prepared gold nanoparticles, centrifuge them and redissolve them in ultrapure water. Add 50 μL of 4MBA with a concentration of 0.1 mM, incubate at 40 °C for 2 h, centrifuge and redisperse the gold nanoparticles modified with 4MBA in 3 mL of ultrapure water. Under oscillation, add 60 μL of 1% (w / v) sodium citrate solution, 120 μL of ascorbic acid solution with a molar concentration of 10 mM and 100 μL of silver nitrate solution with a molar concentration of 10 mM, react for 20 minutes, centrifuge and wash twice with ultrapure water. Finally, redissolve the Au-Ag core-shell structured nanomaterials in 3 mL of ultrapure water.

[0036] 2. Establishment of the Raman analysis method for KMnO4

[0037] Adjust the pH value of the Au-Ag core-shell structured nanomaterials to 11.2 with 1 mol / L sodium hydroxide solution, mix them with KMnO4 at different concentrations (0.001 mg / mL, 0.005 mg / mL, 0.01 mg / mL, 0.05 mg / mL, 0.1 mg / mL, 0.5 mg / mL, 1.0 mg / mL, 5.0 mg / mL, 10.0 mg / mL, 20.0 mg / mL) under ultrasonic treatment for 30 s. Collect the mixed liquid with a capillary tube and detect the Raman intensity at room temperature using a 633 nm laser source through a Raman spectrometer to obtain the standard for quantitative detection with the natural logarithm of the KMnO4 concentration as the abscissa and the Raman intensity at 1074 cm -1 as the ordinate. The results are shown in Figure 2 , and it can be seen from Figure 2 that there is a linear relationship between the natural logarithm of the KMnO4 concentration and the Raman intensity at 1074 cm -1 in this method, which can be used to detect the KMnO4 concentration in the sample.

[0038] Example 3:

[0039] 1. Synthesis of Au-Ag core-shell structured nanomaterials

[0040] Add 1 mL of 1% (w / v) HAuCl4·3H2O solution to 60 mL of ultrapure water, heat under stirring and reflux. When the solution boils for 8 minutes, quickly add 800 μL of 1% (w / v) sodium citrate solution. Continue to stir and heat for 12 minutes, then remove the heat source and cool the solution to room temperature. Take 3 mL of the prepared gold nanoparticles obtained above, centrifuge and redissolve them in ultrapure water. Add 80 μL of 4MBA with a concentration of 0.1 mM, incubate at 30 °C for 3 h, centrifuge, and redisperse the gold nanoparticles modified with 4MBA in 3 mL of ultrapure water. Under oscillation, add 60 μL of 1% (w / v) sodium citrate solution, 150 μL of ascorbic acid solution with a molar concentration of 10 mM, and 100 μL of silver nitrate solution with a molar concentration of 10 mM, react for 40 minutes, centrifuge and wash twice with ultrapure water, and finally redissolve the Au-Ag core-shell structured nanomaterials in 3 mL of ultrapure water.

[0041] 2. Establishment of Raman analysis method for KMnO4

[0042] Adjust the pH value of the Au-Ag core-shell structured nanomaterials to 12.3 with 1 mol / l sodium hydroxide solution, mix them with KMnO4 at different concentrations (0.001 mg / mL, 0.005 mg / mL, 0.01 mg / mL, 0.05 mg / mL, 0.1 mg / mL, 0.5 mg / mL, 1.0 mg / mL, 5.0 mg / mL, 10.0 mg / mL, 20.0 mg / mL) under ultrasonic treatment for 50 s, collect the mixed liquid with a capillary tube, and detect the Raman intensity at room temperature using a 633 nm laser source through a Raman spectrometer to obtain a standard for quantitative detection with the natural logarithm value of the KMnO4 concentration as the abscissa and the Raman intensity at 1074 cm -1 as the ordinate.

[0043] The above embodiments are only explanations of the present invention, but the embodiments of the present invention are not limited by the described embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A Raman detection method for potassium permanganate based on an Au-Ag core-shell structure substrate, characterized in that, It includes the following steps: S1: Prepare gold nanosol; S2: After adding Raman signal molecules and incubating, add a stabilizer, a reducing agent and a silver ion solution and react for 20 - 50 min, and remove the unreacted reagents completely to obtain Au - Ag core - shell structured nanosol; S3: Adjust the pH value range of the Au - Ag core - shell structured nanosol in S2 to 10.2 - 12.3, add KMnO4 standard solution and the solution to be measured respectively, and conduct Raman signal detection to achieve qualitative or quantitative detection of KMnO4; The Raman signal molecules described in step S2 are methanol and aqueous solutions of 4 - mercaptobenzoic acid, the volume ratio of methanol to water is 1:9, and the concentration is 0.1 mM - 1 mM; the volume ratio of gold nanosol to Raman signal molecule solution is 15:1 - 150:1; the incubation conditions described in step S2 are incubation at 30 - 50 °C for 1 - 3 h; The method for quantitative detection in S3 is: (1) Plot the standard curve: Take the natural logarithm of the KMnO4 concentration as the abscissa and the Raman intensity at 1074 cm -1 as the ordinate to plot the standard curve for quantitative detection; (2) Mix the KMnO4 sample with unknown concentration to be measured with the Au - Ag core - shell structured nanosol, conduct Raman intensity detection, and calculate the concentration of the KMnO4 sample through the standard curve formula.

2. The method according to claim 1, characterized in that, The method for preparing gold nanosol in step S1 is: Add a reducing agent to the boiling gold source solution and react fully. After the reaction ends, remove the unreacted reagents completely to obtain gold nanosol.

3. The method according to claim 2, characterized in that, The gold source solution described in step S1 is an aqueous solution of chloroauric acid, with a concentration of 0.05 - 0.1 g / L; the reducing agent is an aqueous solution of sodium citrate dihydrate, with a mass fraction of 1% ± 0.5%; the volume ratio of the gold source solution to the reducing agent is 122:1 - 40:

1.

4. The Raman detection method according to claim 1, characterized in that, The stabilizer described in step S2 is an aqueous solution of sodium citrate, with a mass fraction of 0.5% - 2%; the reducing agent is an aqueous solution of ascorbic acid, and the silver ion solution is an aqueous solution of silver nitrate; the reducing agent and the silver ion solution have the same molar concentration, and the concentration is 5 mM - 15 mM.

5. The Raman detection method according to claim 4, characterized in that, In step S2, the volume ratio of gold nanosol to the stabilizer is 30:1 - 60:1; the reducing agent and the silver ion solution are added in equal volume, and the volume ratio of gold nanosol to the reducing agent or silver ion solution is 16:1 - 30:

1.

6. The Raman detection method according to claim 1, characterized in that, The method for measuring the standard curve described in step (1) is: Mix the Au - Ag core - shell structured nanosol with KMnO4 of different concentrations, react under ultrasonic for 20 - 50 s to make KMnO4 fully contact with the Ag shell surface to obtain a mixed liquid; collect the mixed liquid with a capillary tube and conduct Raman detection on the mixed liquid using a 633 nm laser source.

7. The Raman detection method according to claim 1, characterized in that, The detectable concentration of the KMnO4 solution is 0.001 mg / mL - 20.0 mg / mL.

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