CN115290562A - A kind of SERS detection method of 5-hydroxymethyl furfural - Google Patents

Abstract

The invention discloses a SERS detection method of 5-hydroxymethylfurfural, which comprises PVP modified SiO ₂ Preparation of nanospheres and SiO ₂ And (3) preparing and detecting the @ Ag nanosphere. The invention has the beneficial effects that: by a simple method on SiO ₂ Completely coating the surfaces of the nanospheres with uniform AgNPs to obtain SiO ₂ @ Ag nanocomposite, which was then used as the SERS substrate for detection of 5-HMF. Due to SiO ₂ The @ Ag nanosphere has high surface uniformity and is in SiO ₂ Gaps among AgNPs coated on the surfaces of the nanospheres are smaller than 10nm, and a large number of hot spots can be formed, so that the SERS substrate has the advantages of good stability, good reproducibility and high sensitivity, and is suitable for detecting low concentration of 5-HMF and actual samples.

Description

A kind of SERS detection method of 5-hydroxymethylfurfural

technical field

The invention relates to a SERS detection method, in particular to a SERS detection method for 5-hydroxymethylfurfural, and belongs to the technical field of food safety detection.

Background technique

5-Hydroxymethylfurfural (5-HMF), a six-carbon heterocyclic organic compound containing aldehyde and alcohol (hydroxymethyl) functional groups, is considered to be a ubiquitous food contaminant. Many foods will undergo Maillard reaction and coking reaction during heat treatment. When this reaction is under acidic conditions, pentose sugar will be dehydrated to form furfural, and hexose sugar will be dehydrated to form 5-HMF. According to reports, 5-hydroxymethylfurfural exceeding the prescribed limit not only has cytotoxicity in the human body, but also irritates mucous membranes such as eyes, skin, and upper respiratory tract. In addition, 5-HMF accumulated in the human body for a long time will be converted into a carcinogen-5-sulfoxide methylfurfural (SMF). Although 5-HMF is not present in fresh and unprocessed foods, it accumulates rapidly in heat-treated carbohydrate-rich foods. There are many detection methods for 5-hydroxymethylfurfural, such as high performance liquid chromatography, liquid chromatography-tandem mass spectrometry, gas phase-liquid chromatography, spectrophotometry, capillary electrophoresis chromatography, enzyme-linked immunosorbent assay ( ELISA) and so on. However, these methods generally have the disadvantages of complex detection procedures, long time, high detection cost, and the need for professional knowledge and operating techniques. Their wide application is limited and they are not suitable for the direct on-site detection of 5-hydroxymethylfurfural, so it is very important to develop a simple, rapid and sensitive means to detect 5-HMF.

Surface-enhanced Raman scattering (SERS) emerges as a rapid and ultrasensitive detection technique, allowing highly sensitive biological and chemical detection. SERS mainly achieves Raman scattering enhancement of several orders of magnitude by adsorbing molecules on the surface of rough plasmonic nanostructures. Due to the sensitivity of single-molecule detection, SERS has a wide range of applications in biochemistry, pharmaceutical analysis, food safety and other fields.

Contents of the invention

The purpose of the present invention is to provide a SERS detection method for 5-hydroxymethylfurfural in order to solve at least one of the above technical problems.

The present invention achieves the above object through the following technical solutions: a SERS detection method of 5-hydroxymethylfurfural, comprising the following steps

Step 1, the preparation of PVP modified _SiO2 nanospheres

Add 4mL of ammonia water to 25mL ethanol and sonicate for 10min as liquid A, then add 2.5mL tetraethyl orthosilicate to 25mL of ethanol and sonicate for 10min as liquid B, then drop liquid B into liquid A for 40min, and finally Stir for 6h to obtain a pure white sol, wash with ethanol several times and dry to obtain SiO ₂ powder;

Mix 0.25g of _SiO2 powder and 13mL of pure water with ultrasonic for 30min to obtain _SiO2 dispersion, add 0.125g of PVP powder into 10mL of pure water, sonicate until no white powder can be seen in the upper layer of pure water, pour it into the _SiO2 dispersion, and stir for 2h Obtain PVP modified SiO ₂ nanospheres (PVP-SiO ₂ );

Step 2. Preparation of SiO ₂ @Ag nanospheres

First prepare the silver ammonia solution, mix 0.105gAgNO ₃ and 10mL pure water and ultrasonically until completely dissolved, then slowly drop in 10% ammonia water until the precipitate is formed and then disappear, pour the silver ammonia solution into the PVP-SiO ₂ dispersion, and stir for 30min ;Heat up the water bath to 80°C, put it into the water bath and stir, when the temperature of the solution rises to 80°C, add 0.1g/mL glucose solution, the solution changes from white to brown after 4 hours of reaction, indicating that the SiO ₂ Silver nanoparticles are generated on the surface, and finally washed several times with pure water;

Step 3. Detection

Take 20 μL of SiO ₂ @Ag solution, drop it evenly on the glass slide, and let it dry naturally; take 20 μL of 5-HMF standard solution with a concentration of 10 ^-1 M ~ 10 ^{- 8} M, drop it on the dried substrate, and wait for it to naturally dry. After drying, test with Raman spectroscopy;

After diluting honey, red wine and other samples by a certain number of times, perform the test according to the above operation, and calculate the content of 5-hydroxymethylfurfural in the sample to be tested according to the standard curve.

As a further solution of the present invention: in the second step, the preparation process of SiO ₂ @Ag nanospheres with uniform shape and size is:

First, PVP (polyvinylpyrrolidone), which acts as a protective agent and stabilizer, is coated on the surface of SiO ₂ nanospheres, and then the positively charged silver ammonium ions as a silver source are electrostatically adsorbed on the electronegative PVP-SiO ₂ , and finally the glucose solution reduced silver ammonium ions to generate AgNPs coated on the surface of SiO ₂ nanospheres.

As a further solution of the present invention: in the third step, the SiO ₂ @Ag solution is used for SERS detection of 5-HMF solutions with different concentrations, specifically including:

When SiO ₂ @Ag was used as the SERS substrate, the SERS spectra of 5-HMF solutions with different concentrations were analyzed. When 5-HMF molecules were adsorbed on the SERS substrate, the Raman characteristic peaks that showed significant changes were used as quantitative analysis5 - The standard peak of HMF, there is a linear relationship between the Raman signal intensity of the standard peak and the negative logarithm of the 5-HMF concentration, and the linear correlation coefficient (R ² ) is 0.9918, and the detection limit is obtained by calculation.

As a further solution of the present invention: when the SiO ₂ @Ag solution is used for SERS detection of 5-HMF solutions of different concentrations, pure water (without 5-HMF) and SiO ₂ @Ag powder are directly mixed and dried to obtain The SERS spectrum was used as a blank control group.

As a further solution of the present invention: in the third step, SiO ₂ @Ag is used to detect the reproducibility and stability of 5-HMF SERS, and the reproducibility of SERS signal is used to evaluate the practical application of SERS substrate An important indicator in , the Raman spectrum was obtained by randomly detecting 5-HMF molecules at 15 different positions on the SiO ₂ @Ag SERS substrate to prove its reproducibility.

The beneficial effect of the invention is that the SiO ₂ @Ag nanocomposite material is obtained by completely covering the surface of the SiO ₂ nanosphere with uniform AgNPs by a simple method, and then using it as a SERS substrate for detecting 5-HMF. Since SiO ₂ @Ag nanospheres have a high degree of surface uniformity, and the gap between AgNPs coated on the surface of SiO ₂ nanospheres is less than 10 nm, a large number of hot spots can be formed, so this SERS substrate has good stability and reproducibility. The advantages of good and high SERS enhancement performance are suitable for low concentration of 5-HMF and detection in real samples.

Description of drawings

Fig. 1 is a schematic flow chart of the present invention;

Fig. 2 is the SEM figure of large-area SiO of the present invention ₂ nanospheres;

Fig. 3 is that diffraction peak of the present invention and amorphous SiO _The corresponding figure of characteristic peak;

Fig. 4 is the ultraviolet diagram of Ag and SiO ₂ @Ag of the present invention;

Fig. 5 is the SERS spectrum of the 5-HMF solution with a concentration of 10 ^-8 ~ 10 ^-1 M in the present invention and a good linear relationship between the Raman signal intensity and the negative logarithm of the 5-HMF concentration;

Fig. 6 is a Raman spectrum obtained by randomly detecting 5-HMF molecules at 15 different positions on the SiO ₂ @Ag SERS substrate according to the present invention.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

Embodiment one

As shown in Figure 1, a kind of SERS detection method of 5-hydroxymethylfurfural, comprises the following steps

Step 1, the preparation of PVP modified _SiO2 nanospheres

Add 4mL of ammonia water to 25mL of ethanol and sonicate for 10min as solution A, then add 2.5mL tetraethyl orthosilicate into 25mL of ethanol and sonicate for 10min as solution B, then drop B into solution A for 40min, and finally stir After 6h, a pure white sol was obtained, which was washed several times with ethanol and then dried to obtain SiO ₂ powder;

Mix 0.25g of _SiO2 powder and 13mL of pure water with ultrasonic for 30min to obtain _SiO2 dispersion, add 0.125g of PVP powder into 10mL of pure water, sonicate until no white powder can be seen in the upper layer of pure water, pour it into the _SiO2 dispersion, and stir for 2h Obtain PVP modified SiO ₂ nanospheres (PVP-SiO ₂ );

Step 2. Preparation of SiO ₂ @Ag nanospheres

First prepare the silver ammonia solution, mix 0.105gAgNO ₃ and 10mL pure water and ultrasonically until completely dissolved, then slowly drop in 10% ammonia water until the precipitate is formed and then disappear, pour the silver ammonia solution into the PVP-SiO ₂ dispersion, and stir for 30min ;Heat up the water bath to 80°C, put it into the water bath and stir, when the temperature of the solution rises to 80°C, add 0.1g/mL glucose solution, the solution changes from white to brown after 4 hours of reaction, indicating that the SiO ₂ Silver nanoparticles were formed on the surface, and finally washed several times with pure water.

Step 3. Detection

Take 20 μL of SiO ₂ @Ag solution, drop it evenly on the glass slide, and let it dry naturally; take 20 μL of 5-HMF standard solution with a concentration of 10 ^-1 M ~ 10 ^{- 8} M, drop it on the dried substrate, and wait for it to naturally dry. After drying, test with Raman spectroscopy;

After diluting honey, red wine and other samples by a certain number of times, perform the test according to the above operation, and calculate the content of 5-hydroxymethylfurfural in the sample to be tested according to the standard curve.

In the embodiment of the present invention, in the second step, the preparation process of SiO ₂ @Ag nanospheres with uniform shape and size is as follows:

First, PVP (polyvinylpyrrolidone), which acts as a protective agent and stabilizer, is coated on the surface of SiO ₂ nanospheres, and then the positively charged silver ammonium ions as a silver source are electrostatically adsorbed on the electronegative PVP-SiO ₂ , and finally the glucose solution reduced silver ammonium ions to generate AgNPs coated on the surface of SiO ₂ nanospheres.

In the embodiment of the present invention, in the third step, the SiO ₂ @Ag solution is used for SERS detection of 5-HMF solutions with different concentrations, specifically including:

When SiO ₂ @Ag was used as the SERS substrate, the SERS spectra of 5-HMF solutions with different concentrations were analyzed. When 5-HMF molecules were adsorbed on the SERS substrate, the Raman characteristic peaks that showed significant changes were used as quantitative analysis5 - The standard peak of HMF, there is a linear relationship between the Raman signal intensity of the standard peak and the negative logarithm of the 5-HMF concentration, and the linear correlation coefficient (R ² ) is 0.9918, and the detection limit is obtained by calculation.

In the embodiment of the present invention, when the SiO ₂ @Ag solution is used for SERS detection of 5-HMF solutions with different concentrations, it is obtained by directly mixing and drying pure water (without 5-HMF) and SiO ₂ @Ag powder SERS spectrum was used as a blank control group.

In the embodiment of the present invention, in the third step, SiO ₂ @Ag is used to detect the reproducibility and stability of 5-HMF SERS, and the reproducibility of the SERS signal is used to evaluate the SERS substrate in practical applications An important indicator of , the Raman spectrum was obtained by randomly detecting 5-HMF molecules at 15 different positions on the SiO ₂ @Ag SERS substrate to prove its reproducibility.

Embodiment two

As shown in Figure 2 to Figure 6, a kind of SERS detection method of 5-hydroxymethylfurfural, comprises the following steps

Step 1, the preparation of PVP modified _SiO2 nanospheres

Add 4mL of ammonia water to 25mL ethanol and sonicate for 10min as liquid A, then add 2.5mL tetraethyl orthosilicate to 25mL of ethanol and sonicate for 10min as liquid B, then drop liquid B into liquid A for 40min, and finally Stir for 6h to obtain a pure white sol, wash with ethanol several times and dry to obtain SiO ₂ powder;

Mix 0.25g of _SiO2 powder and 13mL of pure water with ultrasonic for 30min to obtain _SiO2 dispersion, add 0.125g of PVP powder into 10mL of pure water, sonicate until no white powder can be seen in the upper layer of pure water, pour it into the _SiO2 dispersion, and stir for 2h Obtain PVP modified SiO ₂ nanospheres (PVP-SiO ₂ );

Step 2. Preparation of SiO ₂ @Ag nanospheres

First prepare the silver ammonia solution, mix 0.105gAgNO ₃ and 10mL pure water and ultrasonically until completely dissolved, then slowly drop in 10% ammonia water until the precipitate is formed and then disappear, pour the silver ammonia solution into the PVP-SiO ₂ dispersion, and stir for 30min ;Heat up the water bath to 80°C, put it into the water bath and stir, when the temperature of the solution rises to 80°C, add 0.1g/mL glucose solution, the solution changes from white to brown after 4 hours of reaction, indicating that the SiO ₂ Silver nanoparticles are generated on the surface, and finally washed several times with pure water;

Step 3. Detection

Take 20 μL of SiO ₂ @Ag solution, drop it evenly on the glass slide, and let it dry naturally; take 20 μL of 5-HMF standard solution with a concentration of 10 ^-1 M ~ 10 ^{- 8} M, drop it on the dried substrate, and wait for it to naturally dry. After drying, test with Raman spectroscopy;

After diluting honey, red wine and other samples by a certain number of times, perform the test according to the above operation, and calculate the content of 5-hydroxymethylfurfural in the sample to be tested according to the standard curve.

Among them, Figure 2 (a) and (b) are the SEM images of the prepared large-area _SiO2 nanospheres, from which it can be seen that the size is highly uniform, and the particle size of more than 100 nanoparticles is counted using Nano Measurer software The particle size distribution diagram was obtained, and the average particle size of SiO ₂ nanospheres was calculated to be 471nm; Figure 2(c) and (d) are SEM images of SiO ₂ @Ag composite nanospheres, where SiO ₂ @Ag nanospheres can be seen The surface of the SiO 2 @Ag nanosphere is relatively rough, although the SiO ₂ @Ag nanosphere is a composite material obtained by in-situ growth of AgNPs on the SiO ₂ surface, but the size of the nanosphere is still uniform, and the calculated average particle size is 500 nm.

XRD

SiO ₂ nanospheres and SiO ₂ @Ag composite nanospheres were characterized by XRD. It can be seen in Fig. 3 that the diffraction peaks appearing at the 2θ value of 21.8° correspond to the characteristic peaks of amorphous _SiO2 . The four diffraction peaks appearing at 2θ values of 38.1°, 44.3°, 64.4°, and 77.5° correspond to (111), (200), (220) of face-centered cubic silver (JCPDS card no.04-0783), respectively ), (311) crystal plane reflections, indicating that AgNPs were successfully synthesized in situ on the surface of SiO ₂ nanospheres, and it can be seen that the characteristic peaks of amorphous SiO ₂ are relatively weakened after the formation of silver nanoparticles.

UV-vis

Figure 4 shows the UV images of Ag and SiO ₂ @Ag. From the UV-vis images, it can be seen that AgNPs and SiO ₂ @Ag nanospheres show typical surface plasmon resonance of metal nanoparticles at 412nm and 436nm, respectively. (SPR) absorption band, the half width of the surface plasmon resonance absorption peak of AgNPs is very narrow, and the symmetry is high, indicating that the particle size distribution of AgNPs synthesized by this method is uniform. The maximum absorption wavelength of SiO ₂ @Ag nanospheres is red-shifted compared with that of AgNPs, and the peak shape is obviously broadened, which is because the reduction generates localized plasmons between AgNPs on the surface of SiO ₂ nanospheres Exciton coupling effect, so it can also be concluded that AgNPs are coated on the surface of SiO ₂ nanospheres.

SERS Detection of SiO ₂ @Ag on 5-HMF

SERS detection of different concentrations of 5-HMF solutions using SiO ₂ @Ag

When SiO ₂ @Ag is used as the SERS substrate, the SERS spectrum of the 5-HMF solution with a concentration of 10 ^-8 ~10 ^-1 M is shown in Fig. 5 .

It can be seen that when 5 ^- HMF molecules are adsorbed on the SERS substrate, the Raman characteristic peak at 1509 cm shows a significant change, so the Raman peak at 1509 cm is selected here as the standard for quantitative analysis of 5 ^- HMF peak. Even when the concentration of 5-HMF solution is as low as 10 ^-8 M, it can be seen in the insert of Fig. 5(a) that distinguishable Raman characteristic peaks can be seen, indicating that this SERS substrate can detect 5 as low as 10 nM -HMF, blank refers to the SERS spectrum obtained after direct mixing and drying of pure water (without 5-HMF) and SiO ₂ @Ag powder. It can be seen from Figure 5(b) that there is a good linear relationship between the Raman signal intensity of the standard peak and the negative logarithm of the 5-HMF concentration, and the linear correlation coefficient (R ² ) reaches 0.9918. The detection limit of this method was calculated to be 4.8nM (3N/S).

Fig. 5(a) SERS spectra of 5-HMF solution with a concentration of 10 ^-8 ~ 10 ^-1 M; (b) there is a good linear relationship between the Raman signal intensity and the negative logarithm of the 5-HMF concentration. (Inset: SERS spectrum of 5-HMF solution with a concentration of 10 ^-8 M)

Reproducibility and stability of SiO ₂ @Ag for 5-HMF SERS detection

The reproducibility of SERS signal is an important index for evaluating SERS substrates in practical applications. Raman spectra were obtained by randomly detecting 5-HMF molecules at 15 different positions on the SiO ₂ @Ag SERS substrate to demonstrate its reproducibility. It can be seen from Fig. 6 that the relative standard deviation (RSD) at the peak position of 1509 cm ^-1 is only 2.2%, indicating that the SERS substrate has very good uniformity.

Working principle: Firstly, the SiO ₂ @Ag nanocomposite material is obtained by completely coating uniform AgNPs on the surface of SiO ₂ nanospheres by a simple method, and then it is used as a SERS substrate for detecting 5-HMF. Since SiO ₂ @Ag nanospheres have a high degree of surface uniformity, and the gap between AgNPs coated on the surface of SiO ₂ nanospheres is less than 10 nm, a large number of hot spots can be formed, so this SERS substrate has good stability and reproducibility. The advantages of good and high SERS enhancement performance are suitable for low concentration of 5-HMF and detection in real samples.

It will be apparent to those skilled in the art that the invention is not limited to the details of the above-described exemplary embodiments, but that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Accordingly, the embodiments should be regarded in all points of view as exemplary and not restrictive, the scope of the invention being defined by the appended claims rather than the foregoing description, and it is therefore intended that the scope of the invention be defined by the appended claims rather than by the foregoing description. All changes within the meaning and range of equivalents of the elements are embraced in the present invention. Any reference sign in a claim should not be construed as limiting the claim concerned.

In addition, it should be understood that although this specification is described according to implementation modes, not each implementation mode only contains an independent technical solution, and this description in the specification is only for clarity, and those skilled in the art should take the specification as a whole , the technical solutions in the various embodiments can also be properly combined to form other implementations that can be understood by those skilled in the art.

Claims (5)

1. a SERS detection method of 5-hydroxymethylfurfural, is characterized in that: comprise the following steps Step 1, the preparation of PVP modified _SiO2 nanospheres Add ammonia water to ethanol for ultrasonic treatment as liquid A, then add tetraethyl orthosilicate to ethanol for ultrasonic treatment as liquid B, then drop liquid B into liquid A, and finally stir to obtain a pure white sol, wash with ethanol and dry Dry to obtain SiO ₂ powder; Mix SiO ₂ powder and pure water with ultrasonic to obtain SiO ₂ dispersion liquid, add PVP powder into pure water, ultrasonically until no white powder can be seen in the upper layer of pure water, pour it into SiO ₂ dispersion liquid, stir to obtain PVP modified SiO 2 ₂ nanospheres; Step 2. Preparation of SiO ₂ @Ag nanospheres Prepare silver ammonia solution, mix AgNO ₃ and pure water and ultrasonically dissolve until completely dissolved, then slowly drop ammonia water until the precipitate is formed and then disappear, pour the silver ammonia solution into the PVP-SiO ₂ dispersion, stir; heat up the water bath, put Put it in a water bath and stir it. When the temperature of the solution rises to 80°C, add glucose solution. After the reaction, the solution changes from white to brownish yellow, indicating that silver nanoparticles have been formed on the surface of _SiO2 . Finally, wash it several times with pure water. ; Step 3. Detection Take the SiO ₂ @Ag solution, drop it evenly on the glass slide, and let it dry naturally; take 20 μL of 5-HMF standard solution with a concentration of 10 ^-1 M ~ 10 ^-8 M, drop it on the dried substrate, and wait for it to naturally dry. After drying, test with Raman spectroscopy; After diluting the sample by a certain number of times, perform the test according to the above operation, and calculate the content of 5-hydroxymethylfurfural in the sample to be tested according to the standard curve. 2. the SERS detection method of a kind of 5-hydroxymethylfurfural according to claim 1, is characterized in that: in described step 2, the preparation process of SiO ₂ @Ag nanospheres with uniform appearance and uniform size is: First, PVP, polyvinylpyrrolidone, which acts as a protective agent and stabilizer, is coated on the surface of _SiO2 nanospheres, and then positively charged silver ammonium ions as a silver source are electrostatically adsorbed on the electronegative PVP-SiO ₂ , and finally the glucose solution reduced silver ammonium ions to generate AgNPs coated on the surface of SiO ₂ nanospheres. 3. the SERS detection method of a kind of 5-hydroxymethylfurfural according to claim 1, is characterized in that: in described step 3, SiO ₂ @Ag solution is used for carrying out SERS detection to the 5-HMF solution of different concentrations , including: When SiO ₂ @Ag was used as the SERS substrate, the SERS spectra of 5-HMF solutions with different concentrations were analyzed. When 5-HMF molecules were adsorbed on the SERS substrate, the Raman characteristic peaks that showed significant changes were used as quantitative analysis5 -the standard peak of HMF, there is a linear relationship between the Raman signal intensity of the standard peak and the negative logarithm of the 5-HMF concentration, and the linear correlation coefficient R is ^0.9918 , and the detection limit is obtained by calculation. 4. the SERS detection method of a kind of 5-hydroxymethylfurfural according to claim 4, is characterized in that: described SiO ₂ @Ag solution is used for the 5-HMF solution of different concentration when carrying out SERS detection, adopts pure The SERS spectrum obtained after direct mixing and drying of water (without 5-HMF) and SiO ₂ @Ag powder was used as a blank control group. 5. the SERS detection method of a kind of 5-hydroxymethylfurfural according to claim 1, is characterized in that: in described step 3, SiO ₂ @Ag is used for the reproducibility and stability to 5-HMF SERS The reproducibility of the SERS signal is an important indicator for evaluating the practical application of the SERS substrate. The 5-HMF molecule was randomly detected at 15 different positions on the SiO ₂ @Ag SERS substrate to obtain a Raman spectrum. demonstrate its reproducibility.

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