WO2020186834A1 - Sers substrate for detecting synthetic pigment and raman detection method - Google Patents

Abstract

Disclosed are a SERS substrate for detecting synthetic pigments and a Raman detection method. The SERS substrate comprises a base plate, precious metal nanoparticles provided on the base plate, and a modification layer used for grabbing synthetic pigments on the surface of the precious metal nanoparticles. The modification layer is composed of modified molecules, and the modified molecules are a combination of one or more selected from among C₂-C₁₂ hydrocarbyl compounds substituted by thiol and amino groups and salts thereof. The SERS substrate above is used for a method for detecting synthetic pigments. The present invention does not require that a sample be pre-treated, may directly grab illegal additives (i.e., artificial synthetic pigments) in the sample for detection, and then obtain a surface enhanced Raman scattering pattern thereof. The present invention is quick and efficient and has high detection sensitivity.

Description

A SERS substrate and Raman detection method for detecting synthetic pigments Technical field

The invention belongs to the technical field of detection, and particularly relates to the detection of synthetic pigments in foods, and in particular to a SERS substrate and a Raman detection method for detecting synthetic pigments.

Background technique

At present, food safety has attracted more and more attention. Among them, synthetic pigments are cheaper than natural pigments, and they are not easy to fade. Some illegal vendors take risks and use illegal additives. The current detection methods are mostly high performance liquid chromatography (HPLC), or the combination of chromatography and mass spectrometry, and spectrophotometry. However, the pre-processing of large instruments is complicated, time-consuming and costly, which is not conducive to rapid detection.

SERS (Surface Enhanced Raman Scattering) as a highly sensitive detection method has been widely used in food safety, environmental analysis, drugs and explosives and other fields. Coupled with the rapid development of portable and handheld Raman spectrometers in recent years, SERS can be used as a means of rapid on-site detection. Based on this, some people in the prior art have proposed surface-enhanced Raman spectroscopy as a detection technique to detect synthetic pigments. For example, Chinese Patent CN108693297A discloses a combination of thin-layer chromatography and surface-enhanced Raman spectroscopy to detect synthetic pigments. Pigment method; this patent prepares a silver nanorod array surface-enhanced Raman scattering substrate, and then combines thin-layer chromatography technology as a fast pre-processing technology for detection, which can be used for the separation and detection of artificial synthetic pigments. It can be seen that although this patent Surface-enhanced Raman spectroscopy technology is used to detect synthetic pigments, but it requires pre-processing of the detected objects, which still does not meet the high requirements for rapid detection, the detection takes a long time and the detection speed is still relatively slow.

Therefore, those skilled in the art urgently seek a detection method that can quickly detect artificially synthesized pigments in food.

Summary of the invention

The technical problem to be solved by the present invention is to overcome the deficiencies in the prior art and provide an improved SERS substrate for detecting synthetic pigments. The improved SERS substrate does not require pre-treatment of the sample, and can directly grab the sample. Illegal additives (that is, synthetic pigments) are detected to obtain the surface enhanced Raman scattering pattern, which is not only fast and efficient, but also has high detection sensitivity.

To solve the above technical problems, a technical solution adopted by the present invention is as follows:

A SERS substrate for detecting synthetic pigments. The SERS substrate includes a substrate and precious metal nanoparticles arranged on the substrate. The SERS substrate also includes a surface modified on the precious metal nanoparticles for grabbing synthesis The modified layer of the pigment, the modified layer is composed of modified molecules, and the modified molecules are one or a combination of one or more selected from the group consisting of sulfhydryl and amino substituted C ₂ to C ₁₂ hydrocarbon-based compounds and their salts.

In the present invention, the synthetic pigments include sunset yellow, lemon yellow, amaranth, brilliant blue, carmine, alluring red and the like.

In the present invention, the modification refers to the connection of the modified molecule to the noble metal nanoparticles through the method of chemical bond connection, for example, covalent bond connection.

According to some preferred aspects of the present invention, the modified molecule is a linear hydrocarbon-based compound, and the mercapto group and the amino group are located at both ends of the linear hydrocarbon-based compound.

According to some specific and preferred aspects of the present invention, the modified molecule is selected from p-mercaptoaniline and its hydrochloride, mercaptoethylamine and its hydrochloride, 3-mercapto-1-propylamine and its hydrochloride, 4 One or more of mercapto-1-butylamine and its hydrochloride, 5-mercapto-1-pentylamine and its hydrochloride, 2-methyl-2-mercaptopropylamine and its hydrochloride.

According to some preferred aspects of the present invention, a plurality of pits are provided on the substrate, and the precious metal nanoparticles are self-assembled in each of the pits; wherein, nanoimprinting, plasma etching, and ultraviolet etching can be used. The pits are prepared by etching, chemical etching, laser etching, mechanical drilling, mechanical punching or electrochemical methods.

According to some specific aspects of the present invention, the self-assembly method includes dropping, spin coating, printing, injecting or spraying a dispersion containing precious metal nanoparticles onto the surface of the substrate, or applying the substrate The surface is immersed in the dispersion of the precious metal nanoparticles, and the solvent of the dispersion is removed by volatilization.

There are many ways of immersing, for example, immersing the substrate in the dispersion liquid, taking out the substrate, and volatilizing the solvent; or immersing the surface of the substrate in the dispersion liquid and removing the substrate to volatilize the solvent; or, Drop a layer of dispersion on the surface of the substrate, and then volatilize the solvent. The above spin coating refers to the spin coating of the dispersion liquid on the surface of the substrate through the equipment.

According to some preferred aspects of the present invention, the depth of the pits ranges from 30 nm to 500 nm, and the mouth diameter ranges from 50 nm to 500 nm.

According to some preferred aspects of the present invention, the density of the pits is 10 ⁸ to 10 ¹⁰ per cm ² , and the minimum separation distance between two adjacent pits is 1 to 50 nm, preferably 5 to 50 nm, More preferably, it is 10 to 30 nm.

According to some preferred aspects of the present invention, each of the pits has 2-15 of the noble metal nanoparticles, preferably 3-6.

According to some preferred aspects of the present invention, the particle size of the noble metal nanoparticles is 2 nm to 800 nm, preferably 30 nm to 120 nm.

According to some preferred aspects of the present invention, the SERS substrate includes at least two specifications of noble metal nanoparticles, and the two specifications of noble metal nanoparticles have at least one specification difference in element composition, particle size, and shape.

According to some specific and preferred aspects of the present invention, the noble metal nanoparticles are selected from nano-sized gold particles and/or silver particles.

According to some preferred aspects of the present invention, the SERS substrate includes at least two types of pits, and the two types of pits have at least one size difference in the diameter of the pit opening, the pit pitch, and the pit depth. .

According to some preferred aspects of the present invention, the pitch of the pits differs from 0 to 500 nm.

In the present invention, the pit pitch refers to the minimum separation distance between two adjacent pits, and more specifically refers to any point on the upper edge of a pit and any point on the upper edge of an adjacent pit. The smallest distance among the multiple distances that exist between points. The diameter of the pit mouth refers to the largest distance among the multiple distances between any two points on the upper edge of the pit. When the surface enclosed by the upper edge of the pit is circular, the diameter of the pit mouth is the circle When the surface enclosed by the upper edge of the pit is square, the diameter of the pit mouth is the diagonal of the square; when the surface enclosed by the upper edge of the pit is triangle, the diameter of the pit mouth is this The longest side of a triangle; when the surface enclosed by the upper edge of the pit is an ellipse, the diameter of the mouth of the pit is the long axis of the ellipse.

According to some specific and preferred aspects of the present invention, the SERS substrate is subjected to hydrophobic treatment before modification. In the present invention, the hydrophobic treatment used can adopt the hydrophobic modification methods commonly used in the art.

According to some preferred aspects of the present invention, the upper surface area of the substrate is 4-400 mm ² ; more preferably, the upper surface area of the substrate is 16-100 mm ² ; further preferably, the upper surface area of the substrate is 16-36mm ² .

According to some specific aspects of the present invention, the substrate is an inorganic substrate, an organic substrate, or an inorganic/organic composite substrate, and specifically can be glass, silicon wafer, plastic, polytetrafluoroethylene material, polystyrene material, metal , Metal oxides, etc., preferably alumina, titanium oxide, silicon, etc.

Another technical solution provided by the present invention: a Raman detection method for synthetic pigments, the Raman detection method comprising the following steps: using the above-mentioned SERS substrate, immersing the SERS substrate or the surface of the SERS substrate In the sample liquid for 5-30 minutes, take out the SERS substrate, clean it with organic solvent and dry it, and test it on a Raman instrument.

According to some preferred aspects of the present invention, in the Raman detection method, the temperature of the sample liquid is 2°C to 80°C.

In some specific embodiments of the present invention, in the Raman detection method, when the sample is a liquid, the SERS substrate or the surface of the SERS substrate is directly immersed in the liquid sample to grab the sample containing When the sample is solid or paste, first disperse the sample in a dispersion solvent to make a dispersion solution, and then directly immerse the SERS substrate or the surface of the SERS substrate in the dispersion solution to grab Synthetic pigments contained in the sample.

Due to the adoption of the above technical solutions, the present invention has the following advantages compared with the prior art:

The present invention uses specific molecules to modify the SERS substrate, thereby giving the obtained modified SERS substrate the ability to directly grab the illegal additives (ie artificially synthesized pigments) in the sample, thereby achieving the advantage of not requiring pre-treatment of the test object , Simplifying the actual operation detection steps on site, and then can quickly obtain its surface enhanced Raman scattering spectrum, which is fast and efficient, and has the advantages of high detection sensitivity.

Description of the drawings

In order to explain the embodiments of the present invention or the technical solutions in the prior art more clearly, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only These are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative labor;

Figure 1 shows the 0.5ppm sunset yellow (A), amaranth (B), lemon yellow (C), allure red (D) standard map;

Figure 2 is the Raman spectra of standard sample sunset yellow (A) and blank sample (B) obtained in Example 1;

Figure 3 shows the Raman spectra of standard amaranth (A) and blank (B) obtained in Example 2;

Figure 4 shows the Raman spectra of standard sample lemon yellow (A) and blank sample (B) obtained in Example 3;

Figure 5 shows the Raman spectra of the standard sample Allure Red (A) and the blank sample (B) obtained in Example 4;

Figure 6 is the SERS substrate I prepared by the present invention;

Figure 7 shows the SERS substrate II prepared by the present invention;

Figure 8 shows the SERS substrate Ⅲ prepared by the present invention;

Figure 9 shows the SERS substrate IV prepared by the present invention;

Figure 10 shows the SERS substrate V prepared by the present invention.

detailed description

The above solutions are further described below in conjunction with specific embodiments; it should be understood that these embodiments are used to illustrate the basic principles, main features and advantages of the present invention, and the present invention is not limited by the scope of the following embodiments; Implementation conditions can be further adjusted according to specific requirements, and implementation conditions that are not specified are usually the conditions in routine experiments.

In the following examples, unless otherwise specified, all raw materials are commercially available or prepared by conventional methods in the art.

Preparation of nano silver sol:

Add 1 mL of 1% silver nitrate aqueous solution with a mass concentration of 1% in a 100 mL three-necked flask and dilute to 100 mL; heat this solution to boiling, add 1% sodium citrate solution under constant reflux and vigorous stirring, the solution gradually changes from nothing The color changed to light blue. After the color changed, a timer was started. The system was kept in a boiling state for 15 minutes under stirring, and then naturally cooled to room temperature to obtain a silver sol.

Preparation of nano gold sol:

Add 1 mL of 1% chloroauric acid aqueous solution with a mass concentration of 1% to a 100 mL three-necked flask and dilute to 100 mL; heat this solution to boiling, add 1% sodium citrate solution under constant reflux and vigorous stirring, the solution gradually Turn from light yellow to wine red, start timing after the color changes, keep the system in a boiling state for 15 minutes under stirring, and then naturally cool to room temperature to obtain a gold sol.

Nanosol self-assembly:

Cut the glass slides into 2cm*2cm square pieces, clean them with detergent, dry with N ₂ , and then treat them with O ₂ plasma cleaner for 5 min. After soaking in 5% 3-aminopropyltriethoxysilane aqueous solution for 1 minute, rinse with ultrapure water twice, dry with N ₂ and place in silver sol for 3 hours. After taking it out, wash with plenty of water to obtain SERS Base I, as shown in Figure 6.

Nanosol self-assembly:

Nanoimprint a 0.3cm*0.3cm square chip with regular holes, with a hole diameter of 90nm, a hole depth of 80nm, and a hole spacing of 90nm. Clean it with detergent, dry it with N ₂ , then treat it with O ₂ plasma cleaner for 5 minutes, then soak it in gold sol for 2 hours, take it out and wash it with plenty of water to obtain SERS substrate II, as shown in Figure 7.

Nanoimprint a 0.3cm*0.3cm square chip with regular holes, with a hole diameter of 90nm, a hole depth of 80nm, and a hole spacing of 90nm. It was cleaned with detergent, dried with N ₂ , and then treated with an O ₂ plasma cleaner for 5 minutes, then immersed in silver sol for 2 hours, and washed with a large amount of water after taking it out to obtain SERS substrate III, as shown in FIG. 8.

Nanoimprint a 0.3cm*0.3cm square chip with regular holes, with a hole diameter of 90nm, a hole depth of 80nm, and a hole spacing of 90nm. Clean it with detergent, dry it with N ₂ , then treat it with O ₂ plasma cleaner for 5 min, then soak it in gold sol for 2 h, take it out and wash it with a large amount of water to obtain SERS substrate IV, as shown in Figure 9.

Modification of SERS substrate

The SERS substrate I was soaked in a 10 mM 3-mercapto-1-propanamine solution for 10 minutes at room temperature to obtain a modified SERS substrate I.

The SERS substrate II was immersed in a 1 mM 4-mercapto-1-butylamine solution for 5 minutes at 30°C to obtain a modified SERS substrate II.

The SERS substrate III was immersed in 20 mM 3-mercapto-1-propanamine solution for 10 minutes at 0°C to obtain the modified SERS substrate III.

The SERS substrate IV was immersed in 10mM p-mercaptoaniline solution for 10 minutes at room temperature to obtain the modified SERS substrate IV.

Example 1

This embodiment provides a Raman detection method for synthetic pigments, including the following steps:

Take 200 μL of fruit orange beverage (sunset yellow 0.5 ppm) in a test tube, soak the modified SERS substrate I in the above solution, after soaking for 10 minutes, take it out, wash it with ethanol and dry it, and test it with a Raman spectrometer. The surface enhanced Raman spectrum as shown in Figure 2 is obtained.

Example 2

This embodiment provides a Raman detection method for synthetic pigments, including the following steps:

Take 200 μL of red wine (Amaranth 1ppm) in a test tube, soak the modified SERS substrate II in the above solution, soak for 10 minutes, take it out, wash it with ethanol, dry it, and test it with a Raman spectrometer. The surface-enhanced Raman spectrum as shown in Figure 3 is obtained.

Example 3

This embodiment provides a Raman detection method for synthetic pigments, including the following steps:

Take 200 μL of Fanta beverage (lemon yellow 0.1 ppm) in a test tube, soak the modified SERS substrate III in the above solution, soak for 10 minutes, take it out, wash it with ethanol, and dry it, and test it with a Raman spectrometer. The surface enhanced Raman spectrum as shown in Figure 4 is obtained.

Example 4

This embodiment provides a Raman detection method for synthetic pigments, including the following steps:

Take 200 μL of red wine (Allure Red 1ppm) in a test tube, soak the modified SERS substrate IV in the above solution, soak for 10 minutes, take it out, wash it with ethanol, and dry it, and test it with a Raman spectrometer. The surface-enhanced Raman spectrum as shown in Figure 5 is obtained.

Example 5

Preparation of SERS substrate: use chemical etching to prepare pits, 1) use electron beam etching and other means to process the required structure on silicon or other substrates as a template; 2) transfer the pattern to the material to be processed The surface is coated with photoresist, and then the template is pressed on the surface, and the pattern is transferred to the photoresist by pressure; 3) The processing of the substrate, the photoresist is cured with ultraviolet light, after removing the template, The etching solution etches away the photoresist that was not completely removed in the previous step, exposing the surface of the material to be processed, and then uses a chemical etching method for processing. After completion, all the photoresist is removed, and finally a high-precision substrate with pits is obtained. The sheet was cleaned with detergent, dried with N ₂ , and then treated with an O ₂ plasma cleaner for 5 minutes, then immersed in the gold sol prepared according to the above-mentioned nano gold sol preparation method for 2 hours, and then washed with a large amount of water after taking it out. SERS substrate V, this immersion of a single particle size nanomaterial, the resulting structure is shown in Figure 10. This SERS substrate V has high SERS activity and can be used for SERS trace detection.

The above-prepared SERS substrate V avoids the defect that the uniform SERS substrate can only act on a single substance in the prior art, and cannot perform rapid detection, catalysis and other operations under unknown substance types and micro contents; the use of a variable SERS substrate provides In this case, the SERS substrate has the advantages of wide matching range and strong universality, so that it can catalyze, detect, and degrade multiple substances at the same time, which greatly reduces the workload and cost.

The SERS substrate V was soaked in a 10mM 5-mercapto-1-pentylamine solution for 10 minutes at room temperature to obtain a modified SERS substrate V. With the above advantages, it can also have the ability to directly grab illegal additives (ie artificially synthesized pigments) in the sample, thereby realizing the advantage of not requiring pre-treatment of the object to be tested, simplifying the actual operation and detection steps on site, Furthermore, its surface-enhanced Raman scattering spectrum can be obtained quickly, which is fast and efficient, and has high detection sensitivity; in particular, the SERS substrate with the above-mentioned specific structure can be quickly detected under unknown substance types and micro content, and can be used for micro-content fruit juice drinks, etc. The limit grab detection of synthetic pigments in products is beneficial to control the improper use of illegal additives, indirectly protects human health, and has positive social significance.

Take 200μL of red wine (allure red 0.5ppm) in a test tube, soak the modified SERS substrate V in the above solution, soak for 10 minutes, take it out, clean it with ethanol, and dry it, test it with a Raman spectrometer to get a clear surface enhancement Raman spectroscopy.

The above-mentioned embodiments are only to illustrate the technical concept and features of the present invention, and their purpose is to enable those skilled in the art to understand the content of the present invention and implement them accordingly, and cannot limit the scope of protection of the present invention. The equivalent changes or modifications made by the spirit essence should all be covered within the protection scope of the present invention.

Claims (10)

1. A SERS substrate for detecting synthetic pigments. The SERS substrate includes a substrate and precious metal nanoparticles arranged on the substrate. The SERS substrate is characterized in that the SERS substrate further includes a surface of the precious metal nanoparticles. For grabbing the modified layer of synthetic pigments, the modified layer is composed of modified molecules, and the modified molecules are one or a combination of one or more selected from the group consisting of sulfhydryl and amino substituted C ₂ to C ₁₂ hydrocarbon-based compounds and their salts.
2. The SERS substrate according to claim 1, wherein the modified molecule is a linear hydrocarbon-based compound, and the mercapto group and the amino group are located at both ends of the linear hydrocarbon-based compound.
3. The SERS substrate of claim 1, wherein the modified molecule is selected from the group consisting of p-mercaptoaniline and its hydrochloride, mercaptoethylamine and its hydrochloride, 3-mercapto-1-propanamine and its hydrochloride One or more of salt, 4-mercapto-1-butylamine and its hydrochloride, 5-mercapto-1-pentylamine and its hydrochloride, 2-methyl-2-mercaptopropylamine and its hydrochloride Kind.
4. The SERS substrate according to claim 1, wherein a plurality of pits are provided on the substrate, and the noble metal nanoparticles are self-assembled in each of the pits.
5. The SERS substrate of claim 4, wherein the depth of the pits is in the range of 30 nm to 500 nm, and the diameter of the mouth is in the range of 50 nm to 500 nm; the density of the pits is 10 ⁸ to 10 ¹⁰ per cm ^2. The minimum separation distance between two adjacent pits is 1-50nm, preferably 5-50nm, more preferably 10-30nm; and/or, each pit has 2-15 pits The noble metal nanoparticles preferably have 3 to 6.
6. The SERS substrate according to claim 1 or 4, wherein the particle size of the noble metal nanoparticles is 2 nm to 800 nm, preferably 30 nm to 120 nm.
7. The SERS substrate according to claim 1 or 4, wherein the SERS substrate comprises at least two specifications of precious metal nanoparticles, and the two specifications of precious metal nanoparticles have elements in composition, particle size and shape. At least one specification is different.
8. The SERS substrate according to claim 4, wherein the SERS substrate includes at least two types of pits, and the two types of pits are in the pit opening diameter, pit pitch, and pit depth. Have at least one different specification.
9. A Raman detection method for synthetic pigments, characterized in that the Raman detection method comprises the following steps: using the SERS substrate according to any one of claims 1-8, and combining the SERS substrate or the The surface of the SERS substrate is immersed in the sample liquid for 5-30 minutes, the SERS substrate is taken out, washed with organic solvent and dried, and tested on a Raman instrument.
10. The Raman detection method of synthetic pigments according to claim 9, wherein in the Raman detection method, the temperature of the sample liquid is 2°C-80°C.

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