An application for mercury ion detection in water environment based on a non-noble metal-doped Raman substrate

Abstract

This invention discloses an application for mercury ion detection in water environments based on a non-precious metal-doped Raman scattering substrate, belonging to the field of environmental monitoring technology. The invention involves preparing a non-precious metal-doped surface-enhanced Raman scattering substrate; preparing aminated closed-ring Rhodamine 6G; preparing mercury ion standard solutions of different concentrations; and using the prepared surface-enhanced Raman scattering substrate for detection. A standard curve is plotted based on the peak values ​​at characteristic Raman shifts of the obtained standard solutions at different concentrations and the concentrations of the mercury ion standard solutions. The obtained surface-enhanced Raman scattering substrate is used to detect pretreated water samples, and the peak values ​​at characteristic Raman shifts are compared with the standard curve to obtain the concentration of mercury ions in the water sample. This method exhibits high repeatability and stability under different pH values, different salt ion concentrations, different storage temperatures, and different solvents. It also shows specific selectivity for mercury ions, enabling rapid, accurate, and trace detection of mercury ions in water samples.

Description

Technical Field

[0001] This invention belongs to the field of environmental monitoring technology, and in particular relates to an application for the detection of mercury ions in aquatic environments based on a non-precious metal-doped Raman substrate. Background Technology

[0002] Mercury ions are a common environmental pollutant, frequently found in water and soil. Since water and soil are essential natural resources for humankind, they are often contaminated by various wastes. Among these pollutants, mercury ion pollution is a common type of water pollution, and drinking water contaminated with mercury ions poses a serious threat to the health of humans and livestock. Furthermore, mercury ions are raw materials for many electronic products, such as batteries, mobile phones, and computers. Driven by profit, some unscrupulous factories directly discharge industrial wastewater generated during production into water sources, significantly increasing the risk of mercury ion pollution in water bodies. Therefore, establishing a rapid, accurate, sensitive, and highly selective analytical method for the trace analysis and detection of mercury ions in the aquatic environment is of great significance.

[0003] Currently, the main method for detecting mercury ions in the domestic aquatic environment is atomic spectroscopy, but this method suffers from drawbacks such as high cost, long processing time, and complex pretreatment, thus failing to meet the needs of on-site and rapid detection. Surface-enhanced Raman spectroscopy (SERS) offers numerous advantages, including high sensitivity, fast analysis speed, and miniaturized instrumentation, thus enabling rapid on-site detection.

[0004] However, in applications, SERS-enhanced substrates are fundamental to achieving detection targets, but commonly used SERS substrates have shortcomings in selectivity, repeatability, and stability. Therefore, it is crucial to develop a SERS-enhanced substrate with high selectivity, high SERS activity, good stability, and ease of storage. Summary of the Invention

[0005] The purpose of this invention is to provide a quantitative analysis method for mercury ions in the aquatic environment, which aims to achieve quantitative detection of mercury ions in water samples using SERS, and has ideal sensitivity, selectivity, repeatability and stability.

[0006] This invention provides a method for preparing a non-noble metal-doped surface-enhanced Raman scattering substrate, the preparation process of which is as follows:

[0007] Step S1: Ammonium molybdate and thiourea are stirred and mixed with water to obtain an ammonium molybdate-thiourea solution. The ammonium molybdate-thiourea solution is transferred to a reaction vessel for reaction. Afterward, the reaction product is washed and dried to obtain molybdenum disulfide nanomaterials.

[0008] Step S2: Disperse molybdenum disulfide nanomaterials in water and ethanol to form a mixture A, dissolve tetrabutyl titanate in ethanol to form a mixture B, add mixture B to mixture A and stir to obtain mixture C, transfer mixture C to a reaction vessel for reaction, and then wash and dry the reaction product to obtain a non-noble metal doped surface-enhanced Raman scattering substrate.

[0009] Furthermore, in step S1, the molar ratio of ammonium molybdate to thiourea is 0.12:(3.5-4.5).

[0010] Preferably, the molar ratio of ammonium molybdate to thiourea in step S1 is 0.12:3.94.

[0011] Furthermore, the reaction conditions in step S1 of the reactor are a temperature of 150–250°C and a reaction time of 12–24 h.

[0012] Preferably, the reaction conditions in step S1 of the reactor are a temperature of 200°C and a reaction time of 18 hours.

[0013] Furthermore, in step S2, the mass-to-volume ratio of molybdenum disulfide nanomaterials to water is 30 mg: (5-15) mL.

[0014] Preferably, in step S2, the mass-to-volume ratio of molybdenum disulfide nanomaterials to water is 30 mg: 10 mL.

[0015] Furthermore, in step S2, the mass-to-volume ratio of molybdenum disulfide nanomaterials to ethanol is 30 mg: (5-15) mL.

[0016] Preferably, in step S2, the mass-to-volume ratio of molybdenum disulfide nanomaterials to ethanol is 30 mg: 10 mL.

[0017] Furthermore, in step S2, the volume ratio of tetrabutyl titanate to ethanol is 765.3 μL: (10–20) mL.

[0018] Preferably, in step S2, the mass-to-volume ratio of tetrabutyl titanate to ethanol is 765.3 μL: 15 mL.

[0019] Furthermore, the reaction conditions in step S2 are a temperature of 150–250°C and a reaction time of 6–18 h.

[0020] Preferably, the reaction conditions in step S2 are a temperature of 180°C and a reaction time of 12 hours.

[0021] This invention provides a non-noble metal-doped surface-enhanced Raman scattering substrate.

[0022] This invention provides an application of a non-precious metal-doped surface-enhanced Raman scattering substrate in the field of environmental monitoring.

[0023] This invention provides a method for quantitative analysis of mercury ions in an aquatic environment, comprising the following steps:

[0024] Step 1: Dissolve Rhodamine 6G in ethanol, add ethylenediamine, reflux, recrystallize the refluxed product, and dry it to obtain aminated cyclic Rhodamine 6G.

[0025] Step 2: Prepare mercury ion standard solutions of different concentrations, add the aminated closed-ring rhodamine 6G solution obtained in Step 1, incubate to obtain a treatment solution, take the treatment solution and add it to the non-noble metal doped surface-enhanced Raman scattering substrate obtained above, incubate, perform surface-enhanced Raman detection, and plot a standard curve based on the peak value at the characteristic Raman shift of mercury ions of different concentrations and the concentration of mercury ion standard solution.

[0026] Step 3: Add the aminated closed-ring Rhodamine 6G solution obtained in Step 1 to the test solution, incubate to obtain the treatment solution, take the treatment solution and add it to the non-noble metal doped surface-enhanced Raman scattering substrate obtained above, incubate, perform surface-enhanced Raman detection, compare the peak value at the characteristic Raman shift obtained with the standard curve obtained in Step (3), and obtain the concentration of mercury ions in the test solution.

[0027] Furthermore, in step 1, the molar volume ratio of rhodamine 6G to ethylenediamine is 4 mmol: (1-2) mL.

[0028] Preferably, in step 1, the molar volume ratio of rhodamine 6G to ethylenediamine is 4 mmol: 1.4 mL.

[0029] Furthermore, in step 1, the molar volume ratio of rhodamine 6G to ethanol is 4 mmol: (15–25) mL.

[0030] Preferably, in step 1, the molar volume ratio of rhodamine 6G to ethanol is 4 mmol: 20 mL.

[0031] Furthermore, the reflux condensation conditions in step 1 are reflux condensation at 85°C for 8 hours.

[0032] Furthermore, the recrystallization in step 1 is carried out using ethanol at 25°C.

[0033] Furthermore, in step 2, the concentrations of the mercury ion standard solutions are 0.5 μg / L, 10 μg / L, 50 μg / L, 100 μg / L, 500 μg / L, and 1000 μg / L, respectively.

[0034] Furthermore, the concentration of the aminated cyclic-closed rhodamine 6G solution in step 2 is (2-6) mg / L.

[0035] Preferably, the concentration of the aminated cyclic-closed rhodamine 6G solution in step 2 is 4 mg / L.

[0036] Furthermore, the volume ratio of the mercury ion standard solution and the aminated cyclic rhodamine 6G solution in step 2 is 1:(0.5-1.5).

[0037] Preferably, the volume ratio of the mercury ion standard solution and the aminated cyclic rhodamine 6G solution in step 2 is 1:1.

[0038] Furthermore, in step 2, the incubation time after adding the aminated cyclic-closed rhodamine 6G solution was 30 min.

[0039] Furthermore, the volume-to-mass ratio of the treatment solution in step 2 to the non-precious metal-doped surface-enhanced Raman scattering substrate is 20 μL: (0.5–2) mg.

[0040] Preferably, the volume-to-mass ratio of the treatment solution in step 2 to the non-noble metal-doped surface-enhanced Raman scattering substrate is 20 μL: 1 mg.

[0041] Furthermore, in step 2, the incubation after adding the non-noble metal-doped surface-enhanced Raman scattering substrate is carried out in the dark for 30 minutes.

[0042] Furthermore, in step 2, the surface-enhanced Raman detection was performed directly using an inVia laser confocal Raman spectrometer with an excitation intensity of 0.45 W and an integration time of 50 s. Each concentration of solution was detected three times consecutively, and the average value and relative deviation were taken.

[0043] Furthermore, in step 2, the characteristic Raman shift peak of mercury ions is 1650 cm⁻¹. -1 .

[0044] Furthermore, in step 3, the liquid to be tested is a water sample.

[0045] Preferably, the liquid to be tested in step 3 is one or more of the following: lake water, river water, tap water, groundwater, rainwater, seawater, industrial wastewater, and domestic sewage.

[0046] Specifically, the liquid to be tested in step 3 can be one or more of the following: lake water, river water, tap water, groundwater, and rainwater.

[0047] Furthermore, in step 3, the solution to be tested needs to be allowed to settle naturally before centrifugation to obtain the supernatant.

[0048] Furthermore, the concentration of the aminated cyclic-closed rhodamine 6G solution in step 3 is (2-6) mg / L.

[0049] Preferably, the concentration of the aminated cyclic-closed rhodamine 6G solution in step 3 is 4 mg / L.

[0050] Furthermore, the volume ratio of the test solution and the aminated cyclic rhodamine 6G solution in step 3 is 1:(0.5-1.5).

[0051] Preferably, the volume ratio of the test solution and the aminated cyclic rhodamine 6G solution in step 3 is 1:1.

[0052] Furthermore, in step 3, the incubation time after adding the aminated cyclic-closed rhodamine 6G solution was 30 min.

[0053] Furthermore, the volume-to-mass ratio of the treatment solution in step 3 to the non-precious metal-doped surface-enhanced Raman scattering substrate is 20 μL: (0.5–2) mg.

[0054] Preferably, the volume-to-mass ratio of the treatment solution in step 3 to the non-noble metal-doped surface-enhanced Raman scattering substrate is 20 μL: 1 mg.

[0055] Furthermore, in step 3, the incubation after adding the non-noble metal-doped surface-enhanced Raman scattering substrate is carried out in the dark for 30 minutes.

[0056] Furthermore, in step 3, the surface-enhanced Raman detection was performed directly using an inVia laser confocal Raman spectrometer with an excitation intensity of 0.45 W and an integration time of 50 s. Each concentration of solution was detected three times consecutively, and the average value and relative deviation were taken.

[0057] Furthermore, in step 3, the peak value at the characteristic Raman shift of mercury ions is 1650 cm⁻¹. -1 .

[0058] The present invention provides a quantitative analysis method for mercury ions in an aquatic environment, which is applied to the detection of mercury ions in water.

[0059] This invention provides a quantitative analysis method for mercury ions in an aquatic environment, which is applied in the field of environmental monitoring.

[0060] The beneficial effects of this invention are as follows:

[0061] Compared with existing technologies, the quantitative analysis method for mercury ions in the aquatic environment provided by this invention has the advantages of high SERS activity, selectivity, repeatability, and stability of the non-noble metal doped surface-enhanced Raman scattering substrate, as well as the excellent specificity of aminated closed-ring rhodamine 6G for mercury ions. It can achieve rapid, accurate, and trace detection of mercury ions in water samples.

[0062] Non-precious metal-doped surface-enhanced Raman scattering (SERS) substrates exhibit high SERS activity due to their high adsorption capacity and chemical enhancement. These substrates also demonstrate high selectivity, repeatability, and stability, with lower detection limits, making them more suitable for trace detection. Furthermore, the water sample pretreatment steps are simple and applicable to SERS detection. Additionally, the amination-modified closed-ring rhodamine 6G exhibits excellent specificity for mercury ions, demonstrating specific selectivity for mercury ions in water samples, enabling rapid, accurate, and trace detection of mercury ions in water. Attached Figure Description

[0063] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0064] Figure 1 This is a scanning electron microscope image of a molybdenum disulfide / titanium dioxide composite material in the quantitative analysis method for mercury ions in the aquatic environment provided by the present invention. The scale bar in the image is 100 nm.

[0065] Figure 2 These are X-ray diffraction patterns of different substrates in the quantitative analysis method for mercury ions in the aquatic environment provided by this invention. Curve 1 is the X-ray diffraction pattern of molybdenum disulfide, curve 2 is the X-ray diffraction pattern of Comparative Example 1, and curve 3 is the X-ray diffraction pattern of the molybdenum disulfide / titanium dioxide composite material.

[0066] Figure 3 The SERS signal response diagram; Figure 3 a and 3b are SERS signal response diagrams of different substrates for Rhodamine 6G and aminated closed-ring Rhodamine 6G in the quantitative analysis method of mercury ions in the water environment provided by the present invention. Curve 1 is the molybdenum disulfide substrate of Comparative Example 2, curve 2 is Comparative Example 1, curve 3 is Comparative Example 3, and curve 4 is the molybdenum disulfide / titanium dioxide composite material.

[0067] Figure 4 The SERS signal response diagram; Figure 4 a and 4b are SERS spectra of different concentrations of rhodamine 6G and aminated closed-ring rhodamine 6G obtained by the molybdenum disulfide / titanium dioxide composite material in the quantitative analysis method of mercury ions in the water environment provided by the present invention.

[0068] Figure 5In the quantitative analysis method for mercury ions in the aquatic environment provided by this invention, Figure a shows the UV-Vis absorption spectra of Rhodamine 6G on the molybdenum disulfide / titanium dioxide composite material, Figure b shows the amination of closed-ring Rhodamine 6G, and Figure c shows the UV-Vis absorption spectra of the reaction solution of amination-closed-ring Rhodamine 6G and mercury ions before and after adsorption.

[0069] Figure 6 This invention provides a quantitative analysis method for mercury ions in an aquatic environment, showing the UV-Vis absorption spectra before and after the reaction of aminated cyclic rhodamine 6G with mercury ions.

[0070] Figure 7 This invention provides a quantitative analysis method for mercury ions in an aquatic environment, showing the SERS response of a non-noble metal-doped surface-enhanced Raman scattering substrate to a series of mercury ion structural analogs.

[0071] Figure 8 This invention provides a quantitative analysis method for mercury ions in an aquatic environment, which uses a non-noble metal-doped surface-enhanced Raman scattering substrate to obtain SERS response diagrams of a series of mercury ion structural analogs coexisting with mercury ions.

[0072] Figure 9 This is the SERS response diagram of mercury ion analysis in the quantitative analysis method for mercury ions in the aquatic environment provided by the present invention.

[0073] Figure 10 In the quantitative analysis method for mercury ions in the aquatic environment provided by this invention, the mercury ion concentrations are at 1650 cm⁻¹. -1 Peak value versus standard curve of response concentration.

[0074] Figure 11 This invention provides a quantitative analysis method for mercury ions in an aquatic environment. The SERS test response diagrams of a non-precious metal-doped surface-enhanced Raman scattering substrate under different conditions are shown in Figure a (11 consecutive tests), Figure b (11 random point tests), Figure c (11 batch tests), Figure d (17 consecutive weeks of tests), Figure e (tests with pH ranging from 3 to 11), Figure f (tests with sodium chloride concentration ranging from 1 to 100 mmol / L), Figure g (tests with temperature ranging from -20 to 100°C), and Figure h (tests with different solvents, specifically methanol, ethanol, acetonitrile, acetone, ethyl acetate, n-hexane, toluene, dichloromethane, and chloroform). Detailed Implementation

[0075] To make the technical problem to be solved, the technical solution, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0076] To better illustrate the technical solution of the present invention, specific embodiments are described below.

[0077] Source of raw materials

[0078] Rhodamine 6g (95%) was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. Ammonium molybdate tetrahydrate (99%), thiourea (99%), and tetrabutyl titanate (99%) were purchased from Leyan Biochemical Technology Co., Ltd. Ethylenediamine was from Guangzhou Chemical Reagent Company (Guangzhou, China). Mercuric nitrate was purchased from Sinopharm Chemical Reagent Co., Ltd.

[0079] Example 1

[0080] A method for preparing a non-noble metal-doped surface-enhanced Raman scattering substrate includes the following steps:

[0081] S1. Add 0.12 mmol ammonium molybdate and 3.94 mmol thiourea to a 100 mL beaker, followed by 50 mL ultrapure water. Sonicate and stir for 30 min each. Then mix the ammonium molybdate solution and thiourea solution and stir for 30 min to obtain a mixture. Transfer the mixture to a 100 mL polytetrafluoroethylene reactor and react at 200 °C for 18 h. After that, wash the reaction product three times with anhydrous ethanol and ultrapure water, and then dry it to obtain molybdenum disulfide nanomaterials with a diameter of about 2 μm.

[0082] S2. Disperse 30 mg of molybdenum disulfide nanomaterials into a mixture of 10 mL ultrapure water and 10 mL anhydrous ethanol to form mixture A. Then, add 765.3 μL of tetrabutyl titanate to 15 mL anhydrous ethanol dropwise to form mixture B. Immediately add mixture B dropwise to mixture A and stir for 30 min to obtain mixture C. Transfer mixture C to a 100 mL polytetrafluoroethylene reactor and react at 180 °C for 12 h. Afterward, wash the reaction product three times each with anhydrous ethanol and ultrapure water, and then dry to obtain the molybdenum disulfide / titanium dioxide composite material, i.e., a non-noble metal doped surface-enhanced Raman scattering substrate.

[0083] The molybdenum disulfide / titanium dioxide composite material was characterized using scanning electron microscopy. Figure 1 It can be seen that titanium dioxide nanoparticles are uniformly modified on the surface of molybdenum disulfide, thus ensuring a good SERS enhancement effect. Furthermore, X-ray diffraction was used to characterize molybdenum disulfide, Comparative Example 1, and the molybdenum disulfide / titanium dioxide composite material, as shown in the figure. Figure 2 As shown, compared with molybdenum disulfide and Comparative Example 1, the molybdenum disulfide / titanium dioxide composite material has the crystal diffraction peaks of molybdenum disulfide and Comparative Example 1, indicating the successful synthesis of the molybdenum disulfide / titanium dioxide composite material.

[0084] Example 2

[0085] (1) Preparation of amination-closed-ring rhodamine 6G

[0086] 4 mmol of rhodamine 6G was dissolved in 20 mL of ethanol at 50 °C, and then 1.4 mL of ethylenediamine was added. The mixture was refluxed at 85 °C for 8 h. The product was recrystallized from 20 mL of ethanol at 25 °C and dried to obtain aminated cyclic rhodamine 6G.

[0087] (2) Detection method for non-noble metal doped surface-enhanced Raman scattering substrates

[0088] Take 20 μL of the liquid to be tested and add it to 1.0 mg of the molybdenum disulfide / titanium dioxide composite material prepared in Example 1. After incubating in the dark for 30 minutes, it is directly detected by an inVia laser confocal Raman spectrometer with an excitation intensity of 0.45 W and an integration time of 50 s. Each concentration of solution is detected three times consecutively, and the average value and relative deviation are taken.

[0089] (3) Construction of the mercury ion standard curve

[0090] Mercury ion (mercuric nitrate) standard solutions with concentrations of 0.5 μg / L, 10 μg / L, 50 μg / L, 100 μg / L, 500 μg / L, and 1000 μg / L were prepared respectively. 0.5 mL of 4 mg / L aminated cyclic rhodamine 6G was added to each 0.5 mL mercury ion standard solution, and the mixture was incubated for 30 min to obtain the test liquid. The test was then performed according to the method in step (2) of Example 2. Afterwards, a 1650 cm⁻¹ plot was drawn. -1 The standard curve of peak value at Raman shift versus mercury ion concentration is shown in the figure. Figure 9 and Figure 10 As shown, the detection limit is set at the lowest concentration that can detect a signal with a signal-to-noise ratio of 3, which is 0.2 μg / L (S / N = 3). The linear range and detection limit of this method can meet the needs of actual sample analysis.

[0091] (4) Detection of mercury ions in water samples

[0092] Take 10 mL of lake water, river water, and tap water respectively, let them settle naturally for 24 h, then centrifuge them at 4000 rpm for 8 min, take the supernatant, and then take 0.5 mL of the supernatant of each of the three water samples and incubate them with 0.5 mL of 4 mg / L aminated cyclic rhodamine 6 G for 30 min to obtain three liquids to be tested. Then, each liquid is tested according to the method in step (2) of Example 2.

[0093] Subsequently, three water samples—lake water, river water, and tap water—were spiked. The spiked samples were prepared by adding 1 μg / L, 50 μg / L, and 500 μg / L of mercury ion standard solution, respectively. SERS analysis was then performed, with three consecutive tests conducted, and the 1650 cm⁻¹ value was calculated for each of the three data points.-1 The peak average and relative deviation were substituted into the standard curve to obtain the mercury ion concentration in the spiked sample. The calculated sample spiked recoveries were 82.3-106.7%, and the relative standard deviations were 2.1-6.3%.

[0094] Comparative Example 1

[0095] This comparative example provides a substrate that differs from the molybdenum disulfide / titanium dioxide composite material in Example 1 in that the substrate contains only titanium dioxide nanoparticles. The specific preparation process is as follows:

[0096] 765.3 μL of tetrabutyl titanate was added dropwise to 15 mL of anhydrous ethanol to form a mixture, which was then transferred to a 100 mL polytetrafluoroethylene reactor and reacted at 180 °C for 12 h. The reaction product was then washed three times with anhydrous ethanol and ultrapure water, and dried to obtain titanium dioxide nanoparticles.

[0097] Comparative Example 2

[0098] This comparative example provides a substrate that differs from the molybdenum disulfide / titanium dioxide composite material in Example 1 in that the substrate contains only molybdenum disulfide nanoparticles, and the preparation process is step S1 in Example 1.

[0099] Comparative Example 3

[0100] This comparative example prepares a substrate that differs from the molybdenum disulfide / titanium dioxide composite material in Example 1 in that the molybdenum disulfide and titanium dioxide are prepared by mechanical mixing. The specific preparation process is as follows:

[0101] S1. Add 0.12 mmol ammonium molybdate and 3.94 mmol thiourea to a 100 mL beaker, then add 50 mL ultrapure water. Sonicate and stir for 30 min each, then transfer to a 100 mL polytetrafluoroethylene reactor and react at 200 °C for 18 h. After that, wash the reaction product three times with anhydrous ethanol and ultrapure water, and then dry it to obtain molybdenum disulfide nanomaterials with a diameter of about 2 μm.

[0102] S2. Add 765.3 μL of tetrabutyl titanate dropwise to 15 mL of anhydrous ethanol to form a mixture, then transfer it to a 100 mL polytetrafluoroethylene reactor and react at 180 °C for 12 h. The reaction product is then washed three times each with anhydrous ethanol and ultrapure water, and dried to obtain titanium dioxide nanoparticles. Disperse 30 mg of molybdenum disulfide nanomaterials in 10 mL of anhydrous ethanol to form mixture A, and disperse 960 mg of titanium dioxide nanoparticles in 10 mL of anhydrous ethanol to form mixture B. Add mixture A dropwise to mixture B and stir at 60 °C until dry to obtain a mechanically mixed molybdenum disulfide / titanium dioxide composite material.

[0103] Comparative Example 4

[0104] SERS detection of Rhodamine 6G and amination-closed-ring Rhodamine 6G was performed using the substrates of Example 1, Comparative Example 1, Comparative Example 2 (molybdenum disulfide substrate), and Comparative Example 3, respectively. The specific steps are as follows:

[0105] 1.0 mg of the non-noble metal-doped surface-enhanced Raman scattering (SERS) substrate prepared in Example 1 was thoroughly mixed with 20 μL of a 0.1 mg / L solution of rhodamine 6G and aminated cyclic rhodamine 6G, and incubated in the dark for 30 minutes before SERS detection. An inVia laser confocal Raman spectrometer was used with an excitation intensity of 0.45 W and an integration time of 50 s. Each concentration was tested three times consecutively, and the three data points were statistically analyzed to obtain the average value and relative deviation. For the analyte, values ​​at 1646 and 1650 cm⁻¹ were taken respectively. -1 The SERS response is examined by analyzing the peak intensity of the characteristic peak.

[0106] from Figure 3 It can be seen that the non-noble metal-doped surface-enhanced Raman scattering substrate prepared in Example 1 of the present invention has the best enhancement effect on both Rhodamine 6G and aminated closed-ring Rhodamine 6G.

[0107] Example 3

[0108] Rhodamine 6G and aminated ring-closed rhodamine 6G were subjected to SERS detection using the non-noble metal-doped surface-enhanced Raman scattering substrate prepared in Example 1. The specific procedure is as follows:

[0109] 1.0 mg of the non-noble metal-doped surface-enhanced Raman scattering (SERS) substrate prepared in Example 1 was thoroughly mixed with 20 μL of solutions of 1.0 μg / L, 10.0 μg / L, 100.0 μg / L, 1.0 mg / L, and 1.5 mg / L rhodamine 6G and aminated cyclic rhodamine 6G. The mixture was then incubated in the dark for 30 minutes before SERS detection. An inVia laser confocal Raman spectrometer was used with an excitation intensity of 0.45 W and an integration time of 50 s. Each concentration was tested three times consecutively, and the three data points were statistically analyzed to obtain the average value and relative deviation. For the analyte, the peak intensities of its characteristic peaks at 1646 and 1650 cm⁻¹ were used to examine its SERS response.

[0110] Figure 4The numbers 1 to 5 in the figure correspond to 1.0 μg / L, 10.0 μg / L, 100.0 μg / L, 1.0 mg / L, and 1.5 mg / L, respectively. According to the results in the figure, the detection range of the prepared non-noble metal doped surface-enhanced Raman scattering substrate for Rhodamine 6G and aminated closed-ring Rhodamine 6G is 1 μg / L-1.5 mg / L, indicating that the prepared non-noble metal doped surface-enhanced Raman scattering substrate has excellent SERS activity.

[0111] Example 4

[0112] This embodiment verifies the adsorption properties of a non-noble metal-doped surface-enhanced Raman scattering (SERS) substrate. The non-noble metal-doped SERS substrate prepared according to this invention was used to perform adsorption tests on Rhodamine 6G, aminated cyclic Rhodamine 6G, and a solution of aminated cyclic Rhodamine 6G reacted with mercury ions. The test procedure was as follows: 1.0 mg of the non-noble metal-doped SERS substrate prepared in Example 1 was mixed with 1.0 mL of 1.0 mg / L Rhodamine 6G, aminated cyclic Rhodamine 6G, and 0.5 mL of a solution of 2.0 mg / L aminated cyclic Rhodamine 6G + 0.5 mL of 2.0 mg / L mercury ions. The mixture was incubated at 200 rpm in the dark for 2 hours, and then UV-Vis absorption spectroscopy was performed. Figure 5 It can be seen that the non-noble metal-doped surface-enhanced Raman scattering substrate prepared in this invention has good adsorption performance for all three solutions.

[0113] Example 5

[0114] This embodiment verifies the feasibility of the reaction between aminated cyclic rhodamine 6G and mercury ions. 1.0 mL of 4.0 mg / L aminated cyclic rhodamine 6G was mixed with 1.0 mL of 1.0 mg / L mercury ions, and then UV-Vis absorption spectroscopy was performed for detection. Figure 6 As shown, the addition of mercury ions can significantly increase the UV-Vis absorbance of the aminated cyclic rhodamine 6G, indicating that the reaction between the two can be achieved.

[0115] Example 6

[0116] This embodiment verifies that the non-noble metal-doped surface-enhanced Raman scattering substrate exhibits specific selectivity and anti-interference properties for mercury ions.

[0117] The specificity selection test was performed by replacing mercury ions with ions with similar structures (all nitrates): potassium ions, sodium ions, calcium ions, magnesium ions, copper ions, zinc ions, manganese ions, aluminum ions, iron ions, and a blank solution (water). Specifically, 20 μL of the above-mentioned 2.0 mg / L salt ion solution was used as the test solution. 1.0 mg of the non-noble metal-doped surface-enhanced Raman scattering substrate prepared in Example 1 was added and incubated in the dark for 30 minutes. Then, SERS detection was performed according to step (2) of Example 2. The SERS spectrum is shown below. Figure 7 As shown.

[0118] The anti-interference test involved mixing mercury ions with the aforementioned salt ions as the test solution. Specifically, 10 μL of a 40.0 μg / L mercury ion solution was mixed with 10 μL of a 4.0 mg / L salt ion solution as the test solution. 1.0 mg of the non-noble metal-doped surface-enhanced Raman scattering substrate prepared in Example 1 was added and incubated in the dark for 30 minutes. Then, SERS detection was performed according to step (2) of Example 2. The SERS spectrum is shown below. Figure 8 As shown.

[0119] from Figure 7 It can be seen that, when using the non-noble metal-doped surface-enhanced Raman scattering substrate of the present invention to detect the above eight substances, the SERS responses of potassium ions, sodium ions, calcium ions, magnesium ions, copper ions, zinc ions, manganese ions, aluminum ions, iron ions, and blank solution are weak. Furthermore, from... Figure 8 It is known that when mercury ions coexist with interfering substances such as potassium ions, sodium ions, calcium ions, magnesium ions, copper ions, zinc ions, manganese ions, aluminum ions, iron ions, and chromium ions, the SERS response shows almost no change. Therefore, the method of this invention can accurately determine the content of mercury ions.

[0120] Example 7

[0121] This embodiment verifies that the non-precious metal-doped surface-enhanced Raman scattering (SERS) substrate has good repeatability and reproducibility for mercury ion detection. Following the procedure in step (2) of Example 2, SERS tests were performed on the non-precious metal-doped surface-enhanced Raman scattering substrate for 11 consecutive times, 11 random SERS tests, 11 batches of SERS tests, and 17 consecutive weeks. SERS tests were conducted with pH values ​​ranging from 3 to 11, sodium chloride concentrations ranging from 1 to 100 mmol / L, and temperatures ranging from -20 to 100°C. Figure h shows the SERS tests with different solvents, including methanol, ethanol, acetonitrile, acetone, ethyl acetate, n-hexane, toluene, dichloromethane, and chloroform. The results are as follows: Figure 11 As shown in a-11d. From Figure 11It is known that the non-noble metal-doped surface-enhanced Raman scattering substrate of the present invention has good repeatability and reproducibility for mercury ion detection, and can be used for testing the mercury ion content in the water environment.

[0122] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a non-noble metal-doped surface-enhanced Raman scattering substrate, characterized in that, It is prepared according to the following process: S1. Ammonium molybdate and thiourea are mixed with water to obtain an ammonium molybdate-thiourea solution. The ammonium molybdate-thiourea solution is transferred to a reaction vessel for reaction. Afterward, the reaction product is washed and dried to obtain molybdenum disulfide nanomaterials. S2. Molybdenum disulfide nanomaterials are dispersed in water and ethanol to form a mixture A. Tetrabutyl titanate is dissolved in ethanol to form a mixture B. Mixture B is added to mixture A and stirred to obtain mixture C. Mixture C is transferred to a reaction vessel for reaction. The reaction product is then washed and dried to obtain a non-noble metal doped surface-enhanced Raman scattering substrate. The molar ratio of ammonium molybdate to thiourea in S1 is 0.12:3.5~4.5; the reaction conditions in the S1 reactor are a temperature of 150~250℃ and a reaction time of 12~24h. The mass-to-volume ratio of molybdenum disulfide nanomaterials to water in S2 is 30 mg: 5~15 mL; the mass-to-volume ratio of molybdenum disulfide nanomaterials to ethanol in S2 is 30 mg: 5~15 mL; the volume ratio of tetrabutyl titanate to ethanol in S2 is 765.3 μL: 10~20 mL.

2. A non-noble metal-doped surface-enhanced Raman scattering substrate prepared by the method of claim 1.

3. The method for quantitative analysis of mercury ions in an aqueous environment using the Raman scattering substrate described in claim 2, characterized in that, Includes the following steps: Step 1: Dissolve Rhodamine 6G in ethanol, add ethylenediamine, reflux, recrystallize the refluxed product, and dry it to obtain aminated cyclic Rhodamine 6G. Step 2: Prepare mercury ion standard solutions of different concentrations, add the aminated closed-ring rhodamine 6G solution obtained in Step 1, incubate to obtain a treatment solution, add the treatment solution to the Raman scattering substrate, incubate, perform surface-enhanced Raman detection, and plot a standard curve based on the peak values ​​at the characteristic Raman shifts of mercury ions of different concentrations and the concentration of the mercury ion standard solution. Step 3: Add the aminated closed-ring rhodamine 6G solution obtained in Step 1 to the test solution, incubate to obtain the treatment solution, add the treatment solution to the Raman scattering substrate, incubate, perform surface-enhanced Raman detection, compare the peak value at the characteristic Raman shift obtained with the standard curve obtained in Step 2, and obtain the concentration of mercury ions in the test solution. In step 1, the molar volume ratio of rhodamine 6G to ethylenediamine is 4 mmol: 1~2 mL; in step 1, the molar volume ratio of rhodamine 6G to ethanol is 4 mmol: 15~25 mL. The concentration of the aminated cyclic Rhodamine 6G solution in step 2 is 2~6 mg / L; the volume ratio of the mercury ion standard solution and the aminated cyclic Rhodamine 6G solution in step 2 is 1:0.5~1.5; the volume-to-mass ratio of the treatment solution and the non-noble metal-doped surface-enhanced Raman scattering substrate in step 2 is 20 μL:0.5~2 mg.

4. The quantitative analysis method according to claim 3, characterized in that, The characteristic Raman shift peak of mercury ions in steps 2 and 3 is 1650 cm⁻¹. -1 .

5. The quantitative analysis method according to claim 3, characterized in that, In step 3, the test solution is a water sample; the test solution in step 3 needs to be allowed to settle naturally before centrifugation to obtain the supernatant.

6. The application of the quantitative analysis method for mercury ions in the aquatic environment as described in any one of claims 3 to 5 in the field of environmental monitoring.

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