CN112525878B - Preparation method and application of SERS substrate with filtering function - Google Patents

Abstract

A preparation method and application of a SERS substrate with a filtering function belong to the technical field of analytical chemistry, and comprise the following steps: step 1: preparation of HCl-SnCl ₂ Mixing the solutions; step 2: contacting a solid-liquid interface on one side of filter paper with HCl-SnCl prepared in advance ₂ Mixing the solutions; step 3: taking out the filter paper, sequentially washing with ultrapure water and acetone, naturally airing the filter paper, and soaking the dried filter paper in AgNO ₃ Soaking in the solution for a certain time, taking out filter paper with white side and dark brown side, and flushing with ultrapure water; step 4: soaking the filter paper in AgNO ₃ Adding ascorbic acid solution into the solution, soaking for a certain time, taking out, and taking out againAnd cleaning with pure water to obtain the SERS substrate with the filtering function. The SERS substrate has the advantages of high filtering speed, high sensitivity, simple preparation, low cost and the like, and is suitable for quickly separating and detecting harmful substances in food.

Description

A kind of preparation method and application of SERS substrate with filtering function

technical field

The invention belongs to the technical field of analytical chemistry, and in particular relates to a preparation method and application of a SERS substrate with a filtering function.

Background technique

Methods for separating analytes in food include liquid chromatography, gas chromatography, thin chromatography, and solvent extraction. These processing methods are not only complicated, but also costly and time-consuming. Surface-enhanced Raman scattering (SERS) spectroscopy was discovered in 1974. It is a technique for detecting trace substances. It is a highly sensitive, non-destructive, simple and fast analysis method. The field of application testing has broad prospects. In SERS detection, the SERS active substrate plays a decisive role in the detection results. Traditional solid-phase supports also have high repeatability and sensitivity, and have suitable nanostructures, such as glass, silicon and anodized aluminum, etc. However, the overall process of manufacturing these substrates is complex, environmentally unfriendly, and expensive, in addition to failing to adequately pick up analyte molecules when detecting complex analytes. Inexpensive flexible substrates can be more adaptable to the pick-up and detection of substances in different environments, so they are widely used to construct active SERS substrates. At present, most flexible SERS substrates include filter paper, cotton, adhesive tape, etc.

Contents of the invention

Based on the above technical background, the purpose of the present invention is to propose a method for preparing a SERS substrate with a filtering function. Through the selection and surface functionalization of the SERS substrate carrier material, the filter paper is firstly adsorbed on one side of the SnCl ₂ +HCl solution through solid-liquid interface contact. , so that one side of the filter paper has reducibility, the _AgNO3 is reduced to small particles of nano-silver and deposited on the surface of one side of the filter paper by potential deposition, and the filter paper is continued to be soaked in silver nitrate and ascorbic acid solution, and the size and density of silver nanoparticles can be prepared. Controlled filtering capabilities of SERS substrates. Also proposed here is an operating method for rapid filtration separation and SERS detection of harmful substances in food. The SERS substrate has the advantages of fast filtration speed, high sensitivity, simple preparation and low cost, and is suitable for rapid separation and detection of harmful substances in food.

In order to achieve the above-mentioned technical purpose, technical scheme of the present invention is:

A method for preparing a SERS substrate with a filtering function, the method comprising preparing a flexible SERS substrate with a filtering function, using a medium-speed qualitative filter paper to provide adsorption and filtering properties for the substrate, and loading nano-silver particles into the substrate by an in-situ synthesis method One-sided surface of quick-fixing filter paper forms a filter paper-silver SERS substrate with filtering function; it includes the following preparation steps:

Step 1: Prepare HCl-SnCl ₂ mixed solution:

Weigh _SnCl2 powder, ultrapure water, HCl solution, dissolve the powder to obtain HCl- _SnCl2 mixed solution;

Step 2: Using the in-situ synthesis method, contact the solid-liquid interface on one side of the filter paper with the pre-prepared HCl-SnCl ₂ mixed solution;

Step 3: Take out the filter paper, rinse it with ultrapure water and acetone in turn, let the filter paper dry naturally, soak the dry filter paper in the AgNO ₃ solution for a certain period of time, take out the filter paper with white on one side and dark brown on the other. Rinse with pure water;

Step 4: Soak the filter paper at this time in AgNO ₃ solution, then add ascorbic acid solution, soak for a certain period of time, take it out and wash it with ultrapure water again to obtain a SERS substrate with filtering function.

Further, the concentration of the HCl solution in the step 1 is 36%-38%; the concentration of the HCl-SnCl ₂ mixed solution is configured to be 5-30 mM.

Further, the filter paper in step 2 is pre-cut to a size of 10 mm×15 mm before synthesis, and the SnCl ₂ solution is adsorbed on one side in solid-liquid contact, and the contact time is 10 min.

Further, in step 3, the filter paper was dried naturally and soaked in 20 mM AgNO ₃ solution for 10 min, and the filter paper that had turned dark brown on one side was taken out and rinsed with ultrapure water.

Further, the step 4 is specifically: soak the filter paper at this time in 30 mM AgNO ₃ and 40 mM ascorbic acid solution again, soak for 10 min, take out and wash with ultrapure water again, and obtain the SERS substrate with filtering function .

The application of the SERS substrate with filtering function, the SERS substrate with filtering function is used for rapid separation and detection of harmful substances in food.

Further, the method for separating and detecting harmful substances in food is as follows: take a small amount of tomato paste and fruit juice respectively, add different concentrations of thiram respectively, place them on the blank surface of the freshly prepared flexible SERS substrate with filtering function, and stay for a period of time. Time, detect the target molecule thiram that has been filtered through the filter paper, use a portable Raman spectrometer to detect, and obtain the thiram Raman signal.

Further, the method for separating and detecting harmful substances in food is as follows: take 0.15 g of ketchup or fruit juice drinks containing different concentrations of thiram respectively, place the food sample on a blank surface of a SERS substrate with a filtering function, and filter by gravity for 1 min. Bimolecular permeation filter paper, adsorbed to the surface of substrate silver nanoparticles, was detected on-site using a portable Raman spectrometer.

Advantage and effect of the present invention are:

The invention prepares a flexible filter paper SERS substrate with filtering function for the first time, and further modifies the surface of the flexible filter paper SERS substrate with SERS active silver nanoparticles to prepare a single-side filter paper loaded Ag composite material with filtering function. The prepared Ag-loaded composite material on flexible filter paper was successfully applied to the rapid filtration separation and sensitive SERS detection of thiram in food. The substrate has the advantages of filterable separation, low cost, high density, and high sensitivity for detection of trace or trace substances. It is worth mentioning that the substrate has a self-filtering function, eliminating the need for separation steps, greatly The shortened SERS detection time.

The preparation method of the SERS substrate with the filtering function proposed by the present invention, and the application of the flexible SERS substrate with the filtering function to the filtration, separation and detection of pesticides in food. The new flexible SERS substrate, combined with a portable Raman spectrometer, is of great significance for on-site, rapid filtration and in-situ detection of pre-filtered and separated analytes.

The filter-type flexible SERS substrate designed in the present invention is used for the first time to detect thiram pesticide residues in tomato sauce and juice, and the filtration characteristics of the filter paper are conducive to the separation and detection of special substances. This new type of self-filtering flexible SERS substrate is used for the detection of thiram pesticide residues in food. It does not require special modification of laser instruments, and samples do not need to be pre-filtered and separated. It has high sensitivity, low cost, convenient method, simple manufacturing process, and easy mass production.

Description of drawings

Fig. 1 is a schematic diagram of the preparation and detection process of the present invention;

Figure 2 is the Raman spectrum of the filter paper substrate with different reaction times under the optimal concentration conditions in Example 1; (a) The Raman spectrum of the filter paper substrate when the reaction time of the first step and the second step is 5 min; (b) The Raman spectrum of the filter paper substrate when the reaction time of the first step is 10 min and the reaction time of the second step is 5 min; (c) The Raman spectrum of the filter paper substrate when the reaction time of the first step and the second step is 10 min;

Figure 3 is the Raman spectrum of the PATP probe molecular filter paper substrate with different concentrations of AgNO ₃ and ascorbic acid in Example 1; (a) the concentration of AgNO ₃ is 10 mM, and the concentration of ascorbic acid is 10-50 mM; (b) AgNO ₃ The concentration is 20 mM, and the concentration of ascorbic acid is 10-50 mM; (c) the concentration of AgNO ₃ is 30 mM, and the concentration of ascorbic acid is 10-50 mM; (d) the concentration of AgNO ₃ is 40 mM, and the concentration of ascorbic acid is 10-40 mM.;

Figure 4 shows (a) Ag-seed/(b) Ag particles when AgNO ₃ concentration is 20 mM/(c) Ag particles at 30 mM/(d) Ag particles at 40 mM/(e) filter paper loaded with AgNPs Cross section (f) SEM image under the optimal concentration of 30 mM;

Fig. 5 is the X-ray diffraction before and after filter paper loading metal nanoparticles;

Fig. 6 is the infrared spectrogram before and after the filter paper is loaded with metal nanoparticles;

Figure 7 is the SERS spectrum of flexible SERS substrate detection of thiram in fruit juice;

Fig. 8 is a SERS spectrum of detecting thiram in tomato paste by a flexible SERS substrate.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments.

The present invention is a method for preparing a SERS substrate with a filtering function. The method includes preparing a flexible SERS substrate with a filtering function, using medium-speed qualitative filter paper as the substrate to provide adsorption and filtering performance, and preparing nano-silver particles by an in-situ synthesis method. Loaded onto the surface of one side of medium-speed qualitative filter paper to form a filter paper-silver SERS substrate with filtering function. Contains following preparation steps:

Step 1: Prepare HCl-SnCl ₂ mixed solution.

Weigh SnCl ₂ powder, ultrapure water, HCl solution, dissolve the powder to make HCl-SnCl ₂ mixed solution

Step 2: Using the in-situ synthesis method, the filter paper is pre-cut to a suitable size, and the solid-liquid interface on one side of the filter paper is in contact with the pre-prepared HCl-SnCl ₂ mixed solution.

Step 3: Take out the filter paper, rinse it with ultrapure water and acetone in turn, and let the filter paper dry naturally. Soak the dry filter paper in the _AgNO3 solution for a certain period of time, take out the filter paper with white on one side and dark brown on the other, and rinse it with ultrapure water.

Step 4: Soak the filter paper at this time in AgNO ₃ solution, then add ascorbic acid solution, soak for a certain period of time, take it out and wash it with ultrapure water again to obtain a SERS substrate with filtering function.

The strength of ultrapure water and acetone flushing in steps 1-4 does not need to be too strong.

The specific process of preparing the SERS substrate with filtering function by the in-situ synthesis method is as follows:

Step 1: Prepare HCl-SnCl ₂ mixed solution.

Weigh about 0.09g of SnCl ₂ powder, measure 20 ml of ultrapure water, add 33 ul of HCl solution with a concentration of 36%-38%, dissolve the powder in aqueous hydrochloric acid solution to prepare 5-30 mM HCl-SnCl ₂ mixture

Step 2: Using the in situ synthesis method, pre-cut the filter paper with a size of 10 mm × 15 mm, and adsorbed the SnCl ₂ solution by solid-liquid contact on one side.

Step 3: Take out the filter paper after 10 min, and rinse it with ultrapure water and acetone in turn to remove residual molecules on the surface. After drying the filter paper naturally, soak it in 20 mM AgNO ₃ solution for 10 min, take out the filter paper that has turned dark brown on one side, and rinse it with ultrapure water. Since the Ag seeds had grown to the surface of the filter paper, the color turned dark brown.

Step 4: Soak the filter paper again in 30 mM AgNO ₃ and 40 mM ascorbic acid solution for 10 min, take it out and wash it with ultrapure water again to obtain a SERS substrate with filtering function.

An application of SERS substrate with filtering function, take a small amount of tomato paste and fruit juice respectively, add different concentrations of thiram respectively, place the food sample on the blank surface of the flexible SERS substrate with filtering function, and after 1 min, it is detected that it has been filtered The target molecule thiram through the filter paper is detected by a portable Raman spectrometer, and a lower concentration of thiram Raman signal is obtained.

Specifically, take 0.15 g of ketchup and juice drinks containing different concentrations of thiram, put the food samples on the blank surface of the SERS substrate with filtering function, and filter by gravity for 1 min. The thiram bimolecular permeation filter paper is adsorbed to the substrate silver nanoparticles Surface, using a portable Raman spectrometer for on-site detection.

Example 1

The preparation and screening steps of a flexible SERS substrate with filtering function are as follows:

1) In the first step, one side of the filter paper is adsorbed in the SnCl ₂ +HCl solution by solid-liquid contact. The contact time is 5 minutes for the first time and 10 minutes for the second time. The solution volume is 1.0 ml. When the soaking time in the second step is fixed Corresponding to Figure 2 at 5 minutes, it can be seen that (b) is obviously stronger than (a) Raman peak. Take out the filter paper, wash both sides slowly with ultrapure water first, then wash slowly with acetone, and then let it dry freely in the air.

2) In the second step, soak the filter paper in 20 mM AgNO ₃ , when the soaking time is 10 min and the solution volume is 1.0 ml. When the optimal condition of the first step of fixation is 10 min, corresponding to Figure 2(c) showing the Raman characteristic peaks with obvious intensity, take out the filter paper and rinse it slowly with ultrapure water.

3) In the third step, pre-soak the filter paper in 1 ml AgNO ₃ solution with a concentration of 10 mM, 20 mM, 30 mM (optimum concentration) 40 mM, and then add the concentration of 10 mM, 20 mM, 30 mM , 40 mM (optimum concentration) and 50 mM 0.5 ml ascorbic acid, the soaking time was fixed at 10 min. As shown in Figure 3(c), the optimal conditions were 30 mM AgNO ₃ solution and 40 mM ascorbic acid, and a flexible SERS substrate with filtering function was prepared.

The silver nanoparticles on the surface of the synthesized filter paper in the present invention have an average size of about 100 nm. It can be seen from the figure (referring to Fig. 4a that the scanning electron microscope image of silver nanoparticles at the moment of finishing the second step; 4b is that the _AgNO3 concentration is 20 mM and the ascorbic acid concentration is 40 mM; 4c is that the _AgNO3 concentration is 30 mM and the ascorbic acid concentration is 40 mM; 4d is The concentration of AgNO ₃ is 40 mM; the concentration of ascorbic acid is 40 mM); 4e is a cross-sectional view of loaded silver nanoparticles; 4f is an enlarged view of silver nanoparticles; in 4c, the silver nanoparticles have uniform size and high density, which is consistent with the optimal conditions for SERS detection.

See Figure 5 for X-ray diffraction spectra of filter paper before and after loading metal nanoparticles

The infrared spectra of the filter paper before and after loading metal nanoparticles are shown in Figure 6

Example 2

Preparation of flexible SERS substrate with filtering function and detection of pesticide residues in tomato paste:

For the flexible SERS substrate with filtering function prepared in Example 1 to be used in the detection of pesticide residues in tomato paste, 10 ul of thiram with a concentration of 1000, 100, 10, 1, and 0.1 ppm were added to the tomato paste in advance, and 0.15 g was taken. The tomato sauce was placed on the blank surface of the SERS substrate with filtering function, and it was gravity filtered for 1 min. The thiram bimolecular permeation filter paper was adsorbed to the surface of the silver nanoparticles on the substrate, and a portable Raman spectrometer was used for on-site detection.

Using a portable Raman spectrometer for detection, the Raman signal increases proportionally with the increase of thiram concentration. As shown in Figure 7.

For the SERS detection of the sample, a portable Raman spectrometer was used for detection, using the BWS465 iRmanplus portable Raman spectrometer of Bida Tech. The laser wavelength of this instrument is 785 nm, the spectral resolution is 5 cm ^-1 , and the beam diameter is 105 microns. The Raman probe with a quartz glass sealed window with a fiber length of 1.5 meters collects spectral signals, and the signal scans are accumulated 8 times.

Example 3

Preparation of a flexible SERS substrate with filtering function and detection of pesticide residues in fruit juice:

For the application of the flexible SERS substrate with filtering function prepared in Example 1 in the detection of pesticide residues in fruit juice, 10 ul of thiram with a concentration of 100, 10, 1, and 0.1 ppm were added to the fruit juice, and 0.15 g of fruit particles were taken The fruit juice was placed on the blank surface of the SERS substrate with filtering function, and was gravity filtered for 1 min. The thiram bimolecular permeation filter paper was adsorbed to the surface of the substrate silver nanoparticles, and a portable Raman spectrometer was used for on-site detection. Using a portable Raman spectrometer for detection, the Raman signal increases proportionally with the increase of thiram concentration. As shown in Figure 8.

For the SERS detection of the sample, a portable Raman spectrometer was used for detection, using the BWS465 iRmanplus portable Raman spectrometer of Bida Tech. The laser wavelength of this instrument is 785 nm, the spectral resolution is 5 cm ^-1 , and the beam diameter is 105 microns. The Raman probe with a quartz glass sealed window with a fiber length of 1.5 meters collects spectral signals, and the signal scans are accumulated 8 times.

To sum up, the present invention designs and prepares a flexible SERS substrate with filtering function for detecting thiram pesticide residues in special foods such as tomato sauce and fruit juice. This new flexible SERS substrate is used to detect thiram pesticide residues in tomato sauce and fruit juice. It has self-filtering properties, high sensitivity, low cost, simple manufacturing process, and is easy for industrial batch production. It can quickly filter impurities to achieve the purpose of detecting target molecules.

Claims (8)

1. A preparation method of a SERS substrate with a filtering function is characterized by comprising the following steps: preparing a flexible SERS substrate with a filtering function, providing adsorption and filtering performances by taking medium-speed qualitative filter paper as a substrate, and loading nano silver particles on the surface of one side of the medium-speed qualitative filter paper by an in-situ synthesis method to form the filter paper-silver SERS substrate with the filtering function; comprises the following preparation steps:

step 1: preparation of HCl-SnCl ₂ Mixing solution:

weighing SnCl ₂ Dissolving the powder, ultrapure water and HCl solution to obtain HCl-SnCl ₂ Mixing the solutions;

step 2: adopting an in-situ synthesis method to contact a solid-liquid interface on one side of the filter paper with HCl-SnCl prepared in advance ₂ Mixing the solutions;

step 3: taking out the filter paper, sequentially washing with ultrapure water and acetone, naturally airing the filter paper, and soaking the dried filter paper in AgNO ₃ Soaking in the solution for a certain time, taking out filter paper with white side and dark brown side, and flushing with ultrapure water;

step 4: soaking the filter paper in AgNO ₃ And adding an ascorbic acid solution into the solution, soaking for a certain time, taking out, and cleaning with ultrapure water again to obtain the SERS substrate with the filtering function.

2. The method for preparing the SERS substrate with the filtering function according to claim 1, wherein: the concentration of the HCl solution in the step 1 is 36% -38%; configured as HCl-SnCl ₂ The concentration of the mixed solution is 5-30 mM.

3. The method for preparing the SERS substrate with the filtering function according to claim 1, wherein: the filter paper in the step 2 is pre-cut into 10 mm multiplied by 15 mm before synthesis, and single-sided solid-liquid contact adsorption of SnCl ₂ The contact time of the solution was 10 min.

4. The method for preparing the SERS substrate with the filtering function according to claim 1, wherein: the filter paper in the step 3 is naturally dried and then soaked in AgNO of 20 mM ₃ Soaking in the solution for 10min, taking out the filter paper with dark brown color on one side, and flushing with ultrapure water.

5. The method for preparing the SERS substrate with the filtering function according to claim 1, wherein: the step 4 specifically comprises the following steps: the filter paper at this time was again soaked in 30 mM AgNO ₃ Soaking in ascorbic acid solution of 40 mM for 10min, taking out, and cleaning with ultrapure water again to obtain SERS substrate with filtering function.

6. The use of a SERS substrate having a filtering function according to any one of claims 1 to 5, wherein: the SERS substrate with the filtering function is used for rapidly separating and detecting harmful substances in food.

7. The use of a SERS substrate having a filtering function according to claim 6, wherein: the method for separating and detecting the harmful substances in the food comprises the following steps: and respectively taking a small amount of tomato sauce or fruit juice, respectively adding thiram with different concentrations, placing a food sample on the blank surface of the SERS substrate with the filtering function, and detecting the substrate by using a portable Raman spectrometer after 1 minute to obtain the thiram Raman signal.

8. The use of a SERS substrate having a filtering function according to claim 7, wherein: the method for separating and detecting the harmful substances in the food comprises the following steps: respectively taking 0.15 g tomato catsup or fruit juice beverage containing different concentrations of thiram, placing a food sample on a blank surface of a SERS substrate with a filtering function, carrying out gravity filtration for 1 min, adsorbing the thiram molecules on the surface of silver nanoparticles of the substrate, and detecting by using a portable Raman spectrometer.

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