Surface-modified silver nanoparticles, method for their production and use thereof

Abstract

The application belongs to the technical field of mycotoxin detection, and particularly relates to a surface-modified nano-silver solution and a preparation method and application thereof. The nano-silver solution contains nano-silver particles with nano-silver as a core and 1-thiodecane as surface modification. After the solution is used to treat the surface of a to-be-detected object and then added to the surface of an aluminum foil, SERS determination of mycotoxins such as DON on the surface of the to-be-detected object can be realized, without the need of additional preparation of a SERS substrate, and the operation is simple and fast. According to the characteristic Raman fingerprint spectrum of the to-be-detected object, the surface-modified nano-silver solution can be used for rapid on-site detection of DON on the surface of objects such as grains, vegetables and fruits through a portable Raman spectrometer, thereby providing a new analysis means for rapid on-site detection of mycotoxins such as DON, and providing strong technical support for food safety.

Description

Technical Field

[0001] This invention belongs to the field of fungal toxin detection technology, specifically relating to a surface-modified silver nanoparticle, its preparation method, and its application. Background Technology

[0002] Trichothecenes are a class of fungal toxins that pose serious threats to human health and livestock production. Trichothecenes can be classified into four groups: A, B, C, and D. Among them, deoxynivalenol (DON) in group B is the most widely distributed and most serious contaminant fungal toxin, with contamination occurring globally, frequently in the production or storage of grains such as wheat, corn, rice, and barley. Consuming DON-contaminated products in humans and animals can easily cause digestive disorders such as vomiting, stomach upset, and diarrhea, and may also produce acute and chronic effects such as neurotoxicity and immunosuppression. Due to the harmfulness of DON and its unavoidable occurrence, this class of toxins is considered one of the most dangerous naturally occurring contaminants. Therefore, developing a simple and sensitive method for rapid on-site detection of this class of fungal toxins in food matrices is of great significance for human health and socio-economic development.

[0003] Currently, detection methods for such toxins mainly include instrumental analysis methods and immunoassay methods. Instrumental analysis methods such as high-performance liquid chromatography (HPLC), gas chromatography (GC), and liquid chromatography-tandem mass spectrometry (LC-MS / MS) can accurately quantify the target analytes and achieve high sensitivity. However, these methods are expensive, complex to operate, require complex pretreatment processes, and have high requirements for personnel and environment, resulting in high detection costs and long turnaround times, and cannot meet the requirements for large-scale screening of such contaminants in grain and feed samples. Immunoassay methods mainly include lateral flow immunochromatography (LFIA) and enzyme-linked immunosorbent assay (ELISA). However, ELISA is complex to operate, requires laboratory analysis, and is not suitable for online sample detection; LFIA is not suitable for high-throughput sample screening.

[0004] Surface-enhanced Raman scattering (SERS) technology, by introducing a metal substrate, offers high sensitivity and is characterized by ease of operation, short sample preparation time, and non-destructive testing. It has become one of the most sensitive on-site detection technologies in fields such as analytical chemistry, environmental monitoring, food safety, and life sciences. Current research utilizes SERS for the detection of mycotoxins such as DON. However, there is still significant room for improvement in the enhancement effect of using silver nanoparticles as a SERS substrate for DON, and further enhancement of the SERS enhancement effect for mycotoxins such as DON is needed to achieve higher detection sensitivity. Summary of the Invention

[0005] To address the above technical problems, this invention provides surface-modified silver nanoparticles, their preparation method, and applications. These surface-modified silver nanoparticles exhibit a high SERS enhancement effect against mycotoxins such as DON, improving the detection sensitivity of DON and other mycotoxins using SERS technology. They can be used to prepare SERS substrates with high enhancing activity against DON and other mycotoxins, enabling rapid on-site detection of DON and other mycotoxins.

[0006] To solve the above-mentioned technical problems, the embodiments of the present invention adopt the following technical solutions:

[0007] In a first aspect, the present invention provides a surface-modified nano-silver solution, wherein the nano-silver solution contains nano-silver particles with a nano-silver core and a surface modified with 1-thiodecane.

[0008] The surface-modified silver nanoparticle solution provided by this invention allows the silver nanoparticles to serve as a SERS-enhancing substrate material. The hydroxyl groups on the 1-thiodecane nanoparticles on their surface can form hydrogen bonds with the hydroxyl groups of fungal toxins such as DON, making it easier for these toxins to accumulate on the surface. Furthermore, the exposed alkyl chains of the 1-thiodecane nanoparticles can reduce the aggregation between the silver nanoparticles, allowing for better capture of the target analyte when dispersed on the analyte surface. This enables rapid capture of DON and other fungal toxin molecules from the analyte surface onto the SERS substrate, improving the SERS detection efficiency for DON and other fungal toxins to a certain extent. The cumbersome extraction process for DON and other fungal toxins can be avoided during the detection process. Therefore, by treating the analyte surface with a solution containing these surface-modified silver nanoparticles and then dropping it onto an aluminum foil surface, SERS determination of DON and other fungal toxins on the analyte surface can be achieved without the need for additional SERS substrate preparation, making the operation simple and rapid. Based on the characteristic Raman fingerprint spectrum of the analyte, the surface-modified silver nanoparticles can be used for rapid on-site detection of fungal toxins such as DON on the surface of grains, fruits and vegetables using a portable Raman spectrometer. This is of great significance for rapidly screening the contamination status of such fungal toxins in food and accurately assessing their health risks.

[0009] This invention has found that, compared to other hydrophobic functional groups, 1-thiodecane can significantly improve the detection sensitivity of fungal toxins such as DON using SERS technology, enabling the modified silver nanoparticles to accurately quantify low doses of fungal toxins such as DON.

[0010] Secondly, the present invention provides a method for preparing a surface-modified nano-silver solution, specifically comprising the following steps:

[0011] S1. Boil the silver nitrate aqueous solution, add a reducing agent to carry out the reduction reaction, and filter after the reaction is complete.

[0012] S2. Add 1-thiodecane solution to the filtrate obtained from filtering in S1, mix well, and let stand at room temperature for at least 10 hours to obtain the final product.

[0013] The preparation method of the present invention first uses a reducing agent to reduce silver nitrate. The particle size of the obtained silver nanoparticles can be controlled by controlling the amount of reducing agent. Then, a 1-thiodecane solution is added, mixed, and left to stand for at least 10 hours to allow the thiol group of 1-thiodecane to fully contact the surface of the silver nanoparticles and form silver-sulfur bonds. This allows the outer layer of the silver nanoparticles to be connected to the hydrophobic 1-thiodecane group, thereby obtaining surface-modified silver nanoparticles with the best reinforcing effect on DON.

[0014] The preparation method of the present invention is simple to operate, requires little equipment, and is feasible for mass production of the above-mentioned surface-modified silver nanoparticles.

[0015] Preferably, the reducing agent in S1 is an aqueous solution of trisodium citrate or an aqueous solution of sodium borohydride. Since trisodium citrate has relatively weak reducing properties, it is easier to control the reaction process and the particle size of the resulting silver nanoparticles; therefore, an aqueous solution of trisodium citrate is preferred as the reducing agent.

[0016] Preferably, the molar ratio of trisodium citrate to silver nitrate is 0.7–0.9:1, within which nanoparticles with a particle size of approximately 30–40 nm can be obtained. A more preferred molar ratio is 0.8:1.

[0017] Preferably, the molar ratio of sodium borohydride to silver nitrate is 2.1 to 2.7:1, within which nanoparticles with a particle size of approximately 30 to 40 nm can be obtained. A more preferred molar ratio is 2.4:1.

[0018] When the molar ratios of trisodium citrate and sodium borohydride to silver nitrate are within the ranges described above, the molar ratio of 1-thiodecane in S2 to silver nitrate in S1 is 0.9 to 1.1:10000, so that the surface of the silver nanoparticles with a particle size of about 30 to 40 nm is basically completely coated by 1-thiodecane.

[0019] Preferably, the boiling time of the silver nitrate aqueous solution in S1 is 4 to 6 minutes to keep the silver nitrate aqueous solution in a stable state.

[0020] Preferably, when the reducing agent in S1 is an aqueous solution of trisodium citrate, the mixture is boiled after addition for ≥13 minutes to ensure that silver nitrate and trisodium citrate react fully. After the reaction is complete, the mixture is allowed to cool to room temperature before filtration. The reaction time should not be too long to avoid reducing work efficiency; 13–17 minutes is preferred.

[0021] When the reducing agent mentioned in S1 is an aqueous solution of sodium borohydride, boiling is not required after adding the aqueous solution of sodium borohydride, so as to avoid the reaction being too violent and making it difficult to control the reaction process and the purity and particle size of the obtained nano-silver.

[0022] Preferably, filtration in S1 is performed using a 30kD ultrafiltration tube.

[0023] Thirdly, the present invention also provides the application of the above-mentioned surface-modified nano-silver solution or the surface-modified nano-silver solution prepared by the above preparation method in the preparation of SERS substrate for detecting DON.

[0024] By dispersing the surface-modified silver nanoparticle solution onto the surface of the analyte, the functional groups modified on the surface of the silver nanoparticles can capture DON molecules attached to the surface of the analyte. The solution can then be collected and directly dropped onto the surface of aluminum foil to serve as a SERS substrate. Combined with a portable Raman spectrometer, the target analyte can be rapidly detected by SERS, enabling rapid analysis of DON on the surface of the analyte.

[0025] Preferably, the silver ion concentration in the surface-modified silver nanoparticle solution is 0.17–0.68 mg / L. After self-assembly on the aluminum foil surface, the surface-modified silver nanoparticles can enhance the SERS detection of DON on the substrate. Within this concentration range, at 850 cm⁻¹… -1 The enhancement effect at the wavenumber increases with increasing concentration of silver nanoparticles. However, at higher concentrations, the DON content adhering to the surface of each surface-modified silver nanoparticle decreases relatively. When SERS measurements are performed using Raman spectroscopy, the amount of DON is low within the measured spot range, resulting in a lower SERS spectrum at 850 cm⁻¹. -1 The signal strength decreases at the wavenumber.

[0026] Preferably, the silver ion concentration in the surface-modified silver nanoparticle solution is 0.34 mg / L. At this concentration, 850 cm⁻¹ -1 and 1560cm -1 The characteristic Raman peaks at the wavenumber are all quite strong.

[0027] Fourthly, the present invention also provides the application of the above-mentioned surface-modified nano-silver solution or the surface-modified nano-silver solution prepared by the above preparation method in the detection of DON on wheat surface.

[0028] DON is a secondary metabolite secreted by fungal cells. Fungal cells are aerobic microorganisms that typically attach and grow only on the surface of wheat when in contact with air. Therefore, the DON secreted by fungi outside their cell walls is present on the wheat surface. Furthermore, DON is a colorless, needle-like crystal at room temperature, not a liquid, and generally does not penetrate into the wheat interior. Therefore, the method described in this invention, using the surface-modified nano-silver solution or the surface-modified nano-silver solution prepared by the above method for rapid detection of DON on the wheat surface, is of research significance for monitoring DON contamination in wheat raw materials.

[0029] The surface-modified silver nanoparticle solution was dispersed onto the wheat surface. The hydrophobic functional groups on the surface of the silver nanoparticles could quickly capture DON molecules on the wheat surface without the need for pretreatment, thus avoiding the cumbersome DON extraction process. This method is more suitable for rapid on-site detection in grain storage warehouses and other similar locations. At the same time, the silver nanoparticles in the solution can also serve as a SERS-enhancing substrate material. By dropping them onto the surface of aluminum foil, rapid SERS determination of DON on the wheat surface can be achieved without the need for additional SERS substrate preparation. Attached Figure Description

[0030] Figure 1 Electron microscopy characterization and UV-Vis absorption spectrum of the silver nanoparticles prepared in Example 1 of this invention;

[0031] Figure 2 The results of SERS measurements on aluminum foil surfaces after mixing surface-modified nano-silver of different concentrations with DON in Example 1 of this invention are shown.

[0032] Figure 3 To test the effect of different modifiers on the determination of DON by SERS of nano-silver in Example 2 of this invention;

[0033] Figure 4 In Example 3 of this invention, the Raman signal intensity of different concentrations of DON was detected using the prepared SERS substrate.

[0034] Figure 5 The concentration of DON in Example 3 of this invention and 1560 cm⁻¹ -1 The linear relationship between the intensity of the characteristic spectral peaks at that location;

[0035] Figure 6 This is the SERS spectrum of wheat grains with different amounts of DON added in Example 2 of the present invention. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0037] Unless otherwise defined, all technical terms used in the following embodiments have the same meaning as commonly understood by those skilled in the art. The technical terms used in the following embodiments are for the purpose of describing particular embodiments only and are not intended to limit the scope of protection of the present invention.

[0038] The experimental materials used in the following examples were: DON, 1-thiodecane (analytical grade, Shanghai Aladdin Biochemical Technology Co., Ltd.); hepta(6-mercapto-6-deoxy)-β-cyclodextrin (SH-CD) (chemically pure, Shandong Binzhou Zhiyuan Biotechnology Co., Ltd.); silver nitrate (analytical grade, Shanghai Reagent Factory No. 1, China); trisodium citrate, sodium chloride, methanol, dimethyl sulfoxide (DMSO) (analytical grade, Sinopharm Chemical Reagent Co., Ltd.). All reagent solutions were prepared with ultrapure water. All glassware used in the experiments was treated with aqua regia (V). HCL :V HNO3 Soak in a solution of 3:1 and rinse thoroughly with deionized water.

[0039] Unless otherwise specified, all other experimental materials used in the following examples were either commercially available or prepared using existing methods. The instruments and equipment used in the following examples were also commercially available.

[0040] The solutions used in the following examples were prepared according to the following methods:

[0041] DON solution: Dissolve deoxyfusinol in methanol solution to obtain 1000 ppm DON solution, then dilute stepwise with ultrapure water to obtain a series of DON stock solutions of different concentrations, and store at 4°C for later use.

[0042] 1-Thiodecane solution: First, dilute 1-thiodecane with an appropriate amount of methanol (dissolve 10 μL of 1-thiodecane in 1 mL of methanol), then dilute stepwise with ultrapure water to a final concentration of 10 μL. -5 M, store in a refrigerator at 4℃ for later use.

[0043] SH-CD solution: First, dissolve SH-CD in dimethyl sulfoxide (DMSO) (dissolve at a ratio of 0.0125 g SH-CD to 1 mL DMSO), then dilute stepwise with ultrapure water to a concentration of 10. -5 M, store in a refrigerator at 4℃ for later use.

[0044] In the following examples, inductively coupled plasma mass spectrometry (ICP-MS) was used to quantify the nano-silver in solution. The concentration of nano-silver was expressed as the concentration of silver ions in the solution.

[0045] Example 1

[0046] This embodiment provides a surface-modified nano-silver solution, the preparation method of which is as follows:

[0047] Add 25.5 mg of silver nitrate and 150 mL of deionized water to a 250 mL Erlenmeyer flask, stir well and heat to boiling. After boiling for 5 min, quickly add 3 mL of 1% wt trisodium citrate aqueous solution while stirring at 600 rpm, continue boiling for 15 min, then let it cool to room temperature and filter using a 30 kD ultrafiltration tube. Collect the filtrate.

[0048] Add 10 μL of 10 to 1 mL of filtrate. -5 Mix thoroughly with a mol / L solution of 1-thiodecane and let stand at room temperature for 12 hours for later use.

[0049] Electron microscopy characterization and UV-Vis absorption spectrum of the obtained silver nanoparticles are shown in the figure. Figure 1 .

[0050] Example 2

[0051] This embodiment provides a surface-modified nano-silver solution, the preparation method of which is as follows:

[0052] Add 25.5 mg of silver nitrate and 150 mL of deionized water to a 250 mL Erlenmeyer flask, stir well and heat to boiling. After boiling for 4 min, quickly add 2.7 mL of 1% wt trisodium citrate aqueous solution while stirring at 600 rpm, continue boiling for 13 min, then let it cool to room temperature and filter it using a 30 kD ultrafiltration tube. Collect the filtrate.

[0053] Add 9 μL of 10 to 1 mL of filtrate. -5 Mix thoroughly with a mol / L solution of 1-thiodecane and let stand at room temperature for 10 hours for later use.

[0054] Example 3

[0055] This embodiment provides a surface-modified nano-silver solution, the preparation method of which is as follows:

[0056] Add 25.5 mg of silver nitrate and 150 mL of deionized water to a 250 mL Erlenmeyer flask, stir well and heat to boiling. After boiling for 6 min, quickly add 3.5 mL of 1% wt trisodium citrate aqueous solution while stirring at 600 rpm, continue boiling for 17 min, then let it cool to room temperature and filter it using a 30 kD ultrafiltration tube. Collect the filtrate.

[0057] Add 11 μL of 10 to 1 mL of filtrate. -5 Mix thoroughly with a mol / L solution of 1-thiodecane and let stand at room temperature for 14 hours for later use.

[0058] Example 4

[0059] This embodiment provides a surface-modified nano-silver solution, the preparation method of which is as follows:

[0060] Add 25.5 mg of silver nitrate and 150 mL of deionized water to a 250 mL Erlenmeyer flask, stir well and heat to boiling. After boiling for 5 min, quickly add 1.4 mL of 1% wt sodium borohydride aqueous solution while stirring at 600 rpm. After the reaction is complete, filter through a 30 kD ultrafiltration tube and collect the filtrate.

[0061] Add 10 μL of 10 to 1 mL of filtrate. -5 Mix thoroughly with a mol / L solution of 1-thiodecane and let stand at room temperature for 12 hours for later use.

[0062] Example 5

[0063] This embodiment provides a surface-modified nano-silver solution, the preparation method of which is as follows:

[0064] Add 25.5 mg of silver nitrate and 150 mL of deionized water to a 250 mL Erlenmeyer flask, stir well and heat to boiling. After boiling for 4 min, quickly add 1.2 mL of 1% wt sodium borohydride aqueous solution while stirring at 600 rpm. After the reaction is complete, filter through a 30 kD ultrafiltration tube and collect the filtrate.

[0065] Add 9 μL of 10 to 1 mL of filtrate. -5 Mix thoroughly with a mol / L solution of 1-thiodecane and let stand at room temperature for 10 hours for later use.

[0066] Example 6

[0067] This embodiment provides a surface-modified nano-silver solution, the preparation method of which is as follows:

[0068] Add 25.5 mg of silver nitrate and 150 mL of deionized water to a 250 mL Erlenmeyer flask, stir well and heat to boiling. After boiling for 6 min, quickly add 1.5 mL of 1% wt sodium borohydride aqueous solution while stirring at 600 rpm. After the reaction is complete, filter through a 30 kD ultrafiltration tube and collect the filtrate.

[0069] Add 11 μL of 10 to 1 mL of filtrate. -5 Mix thoroughly with a mol / L solution of 1-thiodecane and let stand at room temperature for 14 hours for later use.

[0070] Comparative Example 1

[0071] This comparative example provides a surface-modified silver nanoparticle solution, the preparation method of which is as follows:

[0072] Add 25.5 mg of silver nitrate and 150 mL of deionized water to a 250 mL Erlenmeyer flask, stir well and heat to boiling. After boiling for 5 min, quickly add 3 mL of 1% wt trisodium citrate aqueous solution while stirring at 600 rpm, continue boiling for 15 min, then let it stand at room temperature and filter it using a 30 kD ultrafiltration tube. Collect the filtrate.

[0073] Add 10 μL of 10 to 1 mL of filtrate. -5 Mix mol / L SH-CD thoroughly and let stand at room temperature for 12 hours for later use.

[0074] Test Example 1

[0075] This test case examines the effect of the surface-modified nano-silver solution obtained in Example 1 above on the uniformity and enhancement effect of the SERS substrate formed on the aluminum foil surface.

[0076] The surface-modified silver nanoparticle solution obtained in Example 1 was diluted to 0.05, 0.09, 0.14, 0.17, 0.34, 0.68, and 1.02 mg / L (concentration based on silver ions). 2 μL of each diluted solution was mixed with 2 μL of a 50 mg / L DON aqueous solution. The mixture was then dropped onto the surface of an aluminum foil. After air drying at room temperature, the foil was placed on the microscopic platform of a Raman spectrometer. SERS detection was performed at different locations by moving the platform. Each sample was randomly measured five times, with the sample at 850 cm⁻¹. -1 and 1560cm -1 The intensity of the characteristic Raman peak at the wavenumber is used as the quantitative basis; the experimental results are shown in […]. Figure 2 As shown.

[0077] As shown in the figure, surface-modified silver nanoparticles, after self-assembly on the aluminum foil surface, can serve as an enhanced substrate for SERS detection of DON. Within a certain concentration range, the enhancement effect continuously increases with increasing silver nanoparticle concentration. However, when the concentration of surface-modified silver nanoparticles continues to increase, the effect drops below 850 cm⁻¹. -1 The enhancement effect at the wavenumber no longer increased but instead gradually began to decrease. At a concentration of 0.34 mg / L, at 850 cm⁻¹... -1 and 1560cm -1 The characteristic Raman peaks at the wavenumber are all quite strong.

[0078] Test Example 2

[0079] This test case examines the effect of the surface-modified nano-silver solution obtained in Example 1 and Comparative Example 1 on the uniformity and enhancement effect of the SERS substrate formed on the aluminum foil surface.

[0080] The surface-modified silver nanoparticle solutions obtained in Example 1 and Comparative Example 1 were diluted to 0.34 mg / L (concentration based on silver ions). 2 μL of the diluted solution was mixed with 2 μL of a 50 mg / L DON aqueous solution. The mixture was then dropped onto the surface of an aluminum foil. After air drying at room temperature, the foil was placed on the microscopic platform of a Raman spectrometer. SERS detection was performed at different locations by moving the platform. Each sample was randomly measured 5 times, with the sample at 850 cm⁻¹. -1 and 1560cm -1 The intensity of the characteristic Raman peak at the wavenumber is used as the quantitative basis; the experimental results are shown in […]. Figure 3 As shown in the figure (A represents unmodified AgNPs; B represents SH-CD modified AgNPs, i.e., Comparative Example 1; C represents 1-thiodecane modified AgNPs, i.e., Example 1).

[0081] Experimental results show that both modified and unmodified silver nanoparticles can self-assemble on the aluminum foil surface to form SERS substrates, but from... Figure 3 As can be seen, although all of these types of silver nanoparticles can be used as SERS substrates to detect DON, the Raman signal intensity of the SERS substrate assembled on the aluminum foil surface after modification with 1-thiodecane is significantly higher than that of the other two SERS substrates when detecting DON. Figure 3 Analysis of variance was performed on the data, and pairwise post-hoc tests were conducted using Turkey (where a and b represent different significance levels). Due to the hydrogen bonding between the hydroxyl groups on the modifiers 1-thiodecane and SH-CD and the hydroxyl groups on DON, DON is more easily enriched on their surface. Therefore, nanosilver using these two modifiers can improve the capture ability of the target analyte DON to a certain extent, thereby improving the SERS detection effect. Furthermore, after modification with 1-thiodecane, the exposed alkyl chains of the nanosilver can reduce the aggregation between nanosilver particles, allowing for better capture of the target analyte and more analyte molecules when dispersed on the wheat surface.

[0082] Test Example 3

[0083] This test case examines the linearity of the determination of different concentrations of DON using the surface-modified nano-silver solution obtained in Example 1.

[0084] The surface-modified silver nanoparticle solution obtained in Example 1 was diluted to 0.34 mg / L (concentration based on silver ions). 2 μL of the diluted solution was mixed with 2 μL of DON aqueous solutions of different concentrations. The mixture was then dropped onto the surface of an aluminum foil. After air drying at room temperature, the foil was placed on the microscopic platform of a Raman spectrometer. SERS detection was performed at different locations by moving the platform. Each sample was randomly measured 5 times, with the sample at 850 cm⁻¹. -1and 1560cm -1 The intensity of the characteristic Raman peak at the wavenumber is used as the quantitative basis; the experimental results are shown in […]. Figure 4 and Figure 5 As shown, Figure 4 The concentrations of a to g in the solution were 0, 3.3, 16.7, 33, 84, 167, and 333 mg / L, respectively.

[0085] from Figure 4 Three characteristic spectral peaks of DON can be clearly observed, with wavenumbers located at 850 cm⁻¹. -1 1050cm -1 and 1560cm -1 Furthermore, its signal strength increases continuously with the increase of DON concentration.

[0086] Figure 5 Therefore, DON is located at 1560cm. -1 The intensity of the characteristic spectral peaks at the specified locations was used as the quantitative basis for plotting. It is evident from this plot that the SERS signal intensity of DON exhibits a good linear relationship with its concentration in the range of 3.3–333 mg / L. The linear equation is Y = -931 + 11704 × lgX (where Y is the Raman signal intensity and X is the concentration of DON), with a correlation coefficient r. 2 =0.9879, and the limit of detection (S / N = 3) is 1.7 mg / L. These results indicate that this method can be used for rapid SERS detection of DON.

[0087] Test Example 4

[0088] This embodiment examines the spiked experimental data of the surface-modified nano-silver solution prepared in Example 1 when detecting the DON content on the surface of wheat.

[0089] Three wheat samples were purchased from the market. To ensure uniform sampling, 1.0g (approximately 20 grains) of wheat was placed on the surface of aluminum foil using the quartering method (the average weight of each wheat grain, m0, was approximately 50 × 10⁻⁶). -6 For each wheat grain, 5 μL of a methanol / water (1:1, V:V) mixture was pipetted onto the surface to thoroughly wet the wheat grain. After standing for 5 min, 5 μL of the surface-modified silver nanoparticle solution prepared in Example 1 was taken and dispersed-absorbed-redispersed-absorbed on the wheat surface, repeated 5 times. The silver nanoparticle solution from each wheat grain was then mixed, and 4 μL of this mixture was dropped onto a clean aluminum foil surface, dried, and detected using Raman spectroscopy. No SERS signal of DON was detected in the purchased wheat samples.

[0090] DON addition and recovery experiments were conducted on wheat samples:

[0091] (1) Calculation of theoretical DON content on wheat surface in spiked recovery experiment

[0092] Wheat samples were immersed in solutions containing different concentrations of DON (250 mg / L, 100 mg / L, and 50 mg / L). After 5 minutes, the wheat was removed, placed on aluminum foil, and air-dried. The mass difference of the DON solution before and after immersion was measured. The mass of 1 mL of DON solution was weighed using a balance, and the density was calculated. Assuming that the concentration of the DON solution does not change before and after immersion, and that all the lost DON adheres to the surface of the wheat, the DON content (χ, μg / g) on ​​the surface of each wheat grain is calculated using the following formula.

[0093]

[0094] In the formula: χ represents the DON content on the wheat surface, in μg / g;

[0095] △m represents the mass difference of the DON solution before and after wheat soaking, in mg;

[0096] ρ represents the density of the DON solution, in mg / mL;

[0097] c represents the concentration of the DON solution, in mg / mL;

[0098] m0 represents the mass of wheat grains, in grams.

[0099] (2) Measurement of the actual DON content on the surface of wheat in the spiked recovery experiment

[0100] Take 1.0g of wheat soaked in DON solution and place it on the surface of aluminum foil. Disperse-absorb-redisperse-absorb the surface-modified nano silver solution prepared in Example 1 on the surface of each wheat grain. Repeat this process 5 times. Then, absorb the nano silver solution from the surface of each wheat grain and mix them. Take 4μL of the mixture and drop it onto a clean aluminum foil surface. Let it dry and then use a Raman spectrometer to detect its SERS.

[0101] In the experiment, all Raman spectra were processed by background subtraction and data smoothing using the instrument's built-in analysis software (Uspectra PLUS). The characteristic peaks of each Raman spectrum were automatically identified and their areas were calculated by the software. Each sample was randomly measured five times at different locations, and the average of the five measurements was used for quantitative analysis. In the experiment, Origin was used to process and plot the Raman data.

[0102] Based on DON's Raman spectrum, three characteristic Raman peaks were selected, located at 850 cm⁻¹. -1 1050cm -1 and 1560cm -1Using one of the characteristic spectral peaks (e.g., 1560 cm⁻¹) -1 The Raman signal intensity (peak area, automatically calculated using Uspectra PLUS software) of the sample was used as the quantitative basis for analysis. The concentration detection curve of DON was established (this experiment was conducted under the same experimental conditions as Example 3, using...). Figure 5 The linear equation is Y = -931 + 11704 × lgC DON Correlation coefficient r 2 =0.9879). For samples with unknown DON concentration, the corresponding concentration c can be found on the curve based on the signal intensity of its characteristic Raman spectrum, thereby realizing the detection of the DON content (X, μg / g) on ​​the surface of the unknown sample. The specific calculation formula is as follows:

[0103]

[0104] In the formula:

[0105] c represents the concentration value on the horizontal axis obtained from the curve, in mg / L;

[0106] m0 represents the average weight of each wheat grain, in mg.

[0107] The experimental results are shown in Figure 6 As shown in Table 1, Raman signals of DON were detected on the surface of wheat at three different addition levels, indicating that this method can effectively detect it. The spiked experiments at the three concentrations showed recoveries greater than 80% in all cases.

[0108] Table 1. Results of the DON recovery experiment in wheat.

[0109]

[0110] Furthermore, when linear detection of DON on the aluminum foil surface is achieved within the range of 3.3–333 mg / L, the corresponding DON concentration range on the wheat surface is calculated to be 0.264–26.64 mg / kg. According to GB 2761-2017, "National Food Safety Standard - Limits of Mycotoxins in Food," the limit for DON in wheat is 1000 μg / kg. Therefore, this method meets the needs of practical detection.

[0111] Example 2

[0112] This embodiment provides the application of the surface-modified nano-silver solution prepared in Example 1 in detecting the DON content on wheat surfaces.

[0113] 1.0 g (about 20 grains) of wheat was placed on the surface of aluminum foil using the quartering method. 5 μL of methanol / water (1:1, V:V) mixed solution was pipetted onto the surface of each wheat grain to fully wet it. After standing for 5 min, 5 μL of the surface-modified silver nanoparticle solution prepared in Example 1 was taken and dispersed-absorbed-redispersed-absorbed on the wheat surface, repeated 5 times. The silver nanoparticle solution on the surface of each wheat grain was then aspirated and mixed. 4 μL of the silver nanoparticle solution was taken and dropped onto a clean aluminum foil surface, dried, and detected using a Raman spectrometer. The Raman data were processed and plotted using Origin.

[0114] Based on DON's Raman spectrum, three characteristic Raman peaks were selected, located at 850 cm⁻¹. -1 1050cm -1 and 1560cm -1 Using one of the characteristic spectral peaks (e.g., 1560 cm⁻¹) -1 The Raman signal intensity (peak area, automatically calculated using Uspectra PLUS software) of DON is used as the quantitative basis for sample analysis. Based on the established DON concentration detection curve (each slight change in experimental conditions will cause a slight change in the linear equation; therefore, the linear equation should be calculated for each experiment to reduce errors caused by experimental conditions and improve experimental accuracy), the corresponding concentration c is found on the curve according to the signal intensity of its characteristic Raman spectrum, thus realizing the detection of the DON content (X, μg / g) on ​​the surface of the unknown sample. The specific calculation formula is as follows:

[0115]

[0116] In the formula:

[0117] c represents the concentration value on the horizontal axis obtained from the curve, in mg / L;

[0118] m0 represents the average weight of each wheat grain, in mg.

[0119] 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 or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. Use of a surface-modified nanosilver solution for detecting deoxynivalenol on the surface of wheat, characterized in that The nano-silver solution contains nano-silver particles with nano-silver as the core and 1-thiodecane as the surface modification, and the nano-silver solution is added dropwise to the surface of the aluminum foil to realize rapid SERS determination of deoxynivalenol on the surface of the wheat. The silver ion concentration in the surface-modified nano-silver solution is 0.34 mg / L.

2. Use according to claim 1, characterized in that, The silver ion concentration in the surface-modified nano-silver solution is 0.34 mg / L.

3. The method for preparing the surface-modified nanosilver solution as claimed in claim 1, characterized by, Specifically, the following steps are included: S1, boiling the silver nitrate aqueous solution, adding a reducing agent for reduction reaction, after the reaction is completed, placing at room temperature, and filtering; S2, adding 1-thiodecane solution to the filtrate obtained in S1, mixing uniformly, and placing at room temperature for at least 10 h, and obtaining the surface-modified nano-silver solution.

4. The method for preparing the surface-modified nano-silver solution according to claim 3, characterized in that, The reducing agent in S1 is a trisodium citrate aqueous solution or a sodium borohydride aqueous solution.

5. The method for preparing the surface-modified nano-silver solution according to claim 4, characterized in that, The molar ratio of trisodium citrate to silver nitrate is 0.7-0.9:1, and the molar ratio of sodium borohydride to silver nitrate is 2.1-2.7:

1.

6. The method for preparing the surface-modified silver nanoparticle solution according to claim 3, characterized in that, The molar ratio of 1-thiodecane in S2 to silver nitrate in S1 is 0.9-1.1:10000.

7. The method for preparing the surface-modified nano-silver solution according to claim 3, characterized in that, The boiling time of the silver nitrate aqueous solution in S1 is 4-6 min; and / or In S1, the filtration is performed by using a 30 kD ultrafiltration tube.

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