CN114891349B - Composite with SERS effect and preparation method and application thereof - Google Patents

Composite with SERS effect and preparation method and application thereof Download PDF

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CN114891349B
CN114891349B CN202210380419.9A CN202210380419A CN114891349B CN 114891349 B CN114891349 B CN 114891349B CN 202210380419 A CN202210380419 A CN 202210380419A CN 114891349 B CN114891349 B CN 114891349B
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sers
res
noble metal
nano particles
polydopamine layer
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CN114891349A (en
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胡玉斐
胡文尧
李攻科
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Sun Yat Sen University
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Sun Yat Sen University
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L79/00—Compositions of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing nitrogen with or without oxygen or carbon only, not provided for in groups C08L61/00 - C08L77/00
    • C08L79/04—Polycondensates having nitrogen-containing heterocyclic rings in the main chain; Polyhydrazides; Polyamide acids or similar polyimide precursors
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
    • G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
    • G01N21/65—Raman scattering
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/02—Elements
    • C08K3/08—Metals
    • C08K2003/0806—Silver
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/30—Sulfur-, selenium- or tellurium-containing compounds
    • C08K2003/3009—Sulfides
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K2201/00—Specific properties of additives
    • C08K2201/011—Nanostructured additives
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
    • Y02A50/30—Against vector-borne diseases, e.g. mosquito-borne, fly-borne, tick-borne or waterborne diseases whose impact is exacerbated by climate change

Abstract

The invention discloses a compound with SERS effect, a preparation method and application thereof, wherein the compound comprises ReS 2 A material, a polydopamine layer and noble metal nanoparticles; the ReS 2 The surface of the material is coated with a polydopamine layer; the polydopamine layer has positive charges; the noble metal nano particles are adsorbed on the polydopamine layer. The compound of the invention has both electromagnetic enhancement and ReS of noble metal nano particles 2 Chemical enhancement of the material, remarkable SERS signal enhancement effect and ReS 2 The polydopamine layer on the surface layer of the material enables the compound to have stronger adsorption effect on noble metal nano particles and targets.

Description

Composite with SERS effect and preparation method and application thereof
Technical Field
The invention belongs to the field of materials, and particularly relates to a compound with a SERS effect, and a preparation method and application thereof.
Background
Surface Enhanced Raman Scattering (SERS) is a spectroscopic detection technique based on molecular feature fingerprints. SERS has the advantages of rapidness, convenience, no damage, good sensitivity and the like, and is widely applied to various fields such as food safety, environment monitoring, medical analysis, reaction monitoring and the like. The raman signal of a molecule can be greatly enhanced on SERS substrates, and therefore high performance SERS substrates are critical for SERS applications. The noble metal sol substrate is a commonly used SERS substrate at present, has the advantages of simple preparation, low cost and controllable size, but has the defects of easy agglomeration and coagulation, poor stability and dispersibility, weak enrichment and the like. Meanwhile, the matrix components of the actual sample are complex, the matrix interference is serious, and the SERS detection of target molecules in the actual sample is directly affected. Therefore, developing a high performance SERS substrate is an effective way to improve the sensitivity and accuracy of SERS analysis.
6-benzyl adenine is used as a plant growth regulator, and is applied to vegetable and fruit such as mung bean sprouts, soybean sprouts, green bean sprouts, alfalfa sprouts, chinese toon sprouts and the like, thereby being beneficial to cell division, shortening the growth cycle, increasing the yield and improving the appearance. However, excessive addition of the additive to human body can cause damage to eyes, lungs and other organs, and harm human health. At present, the detection of 6-benzyl adenine is mainly based on a liquid chromatography method, but the time consumption is long, and the pretreatment process is complicated. Therefore, the establishment of a rapid, accurate and efficient quantitative analysis method for 6-benzyl adenine has important significance for food safety.
Rhenium disulfide (ReS) 2 ) Belongs to transition metal chalcogenide, has low symmetrical distorted octahedral crystal structure, weak interlayer coupling effect, anisotropy, unique band gap structure and good electron transfer performance, and is widely used in the fields of optics, optoelectronics and the like. The unique band gap structure and electronic properties also allow ReS2 to have excellent chemical enhancement properties.
Disclosure of Invention
In order to overcome the problems of the prior art, it is an object of the present invention to provide a complex having SERS effect.
The second object of the present invention is to provide a method for preparing a complex having SERS effect.
It is a further object of the present invention to provide a composite flexible SERS substrate.
The fourth object of the invention is to provide an application of a compound with SERS effect in pesticide residue detection.
The fifth purpose of the invention is to provide a method for detecting 6-benzyl adenine in vegetables and fruits.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
a first aspect of the present invention is to provide a complex having a SERS effect, the complex comprising ReS 2 A material, a polydopamine layer and noble metal nanoparticles; the ReS 2 The surface of the material is coated with a polydopamine layer; the polydopamine layer has positive charges; the noble metal nano particles are adsorbed on the polydopamine layer.
Preferably, the noble metal nanoparticles are electrostatically adsorbed on the polydopamine layer. The noble metal nano-particles are negatively charged, the polydopamine layer is positively charged, and the noble metal nano-particles and the polydopamine layer are adsorbed on the polydopamine layer through electrostatic action.
Preferably, the polydopamine layer has a positive charge after modification by a cationic polyelectrolyte.
The polydopamine is a polymer, contains amino and other functional groups, and can enhance the adsorption effect on noble metal nano particles. After the polydopamine is subjected to charge modification through the cationic polyelectrolyte, the polydopamine is positively charged, so that the electrostatic adsorption effect on negatively charged noble metal nanoparticles can be further improved, and more noble metal nanoparticles are adsorbed on the surface of the polydopamine layer. If the ReS is directly used 2 The material is combined with noble metal nano particles, then due to ReS 2 Belongs to transition metal sulfide, noble metal nano particles have weak affinity on the surface, are not easy to be combined on the surface, and are ReS 2 The surface of the material will not be loaded with a large amount of precious metal nanoparticles.
Preferably, the cationic polyelectrolyte is at least one of polydiallyl dimethyl ammonium chloride, cetyl trimethyl ammonium bromide.
The main function of the cationic polyelectrolyte in the invention is to provide a catalyst for ReS 2 The polydopamine layer coated on the surface of the material is subjected to charged modification to ensure that the surface of the polydopamine layer is positively charged, so that negatively charged noble metal nano particles can be assembled on the surface of the polydopamine layer through electrostatic action.
Preferably, the ReS 2 The material is formed by sheet ReS 2 And (5) assembling the honeycomb material. Sheet-like ReS 2 The surfaces of the honeycomb materials are formed with polydopamine layers, so that the adsorption quantity of noble metal nano particles can be increased, and the SERS effect is further enhanced.
Preferably, the polydopamine layer is formed in a sheet-like ReS 2 A surface.
Preferably, the ReS 2 The mass ratio of the material to the polydopamine layer to the noble metal nano particles is 1 (0.01-0.1) (0.1-1.0).
Preferably, the ReS 2 The mass ratio of the material to the polydopamine layer is 1: (0.02 to 0.08); further preferably, the ReS 2 The mass ratio of the material to the polydopamine layer is 1: (0.02-0.07); still further preferably, the ReS 2 The mass ratio of the material to the polydopamine layer is 1: (0.025-0.05).
Preferably, the ReS 2 The mass ratio of the material to the noble metal nano particles is 1 (0.2-0.8); further preferably, the ReS 2 The mass ratio of the material to the noble metal nano particles is 1 (0.3-0.6); still further preferably, the ReS 2 The mass ratio of the material to the noble metal nano particles is 1 (0.36-0.48).
Preferably, the noble metal nanoparticles include at least one of silver nanoparticles and gold nanoparticles; further preferably, the noble metal nanoparticles are silver nanoparticles.
Preferably, the particle size of the noble metal nano particles is 10-40 nm; further preferably, the noble metal nanoparticles have a particle diameter of 20 to 30nm.
A second aspect of the present invention provides a method for preparing a complex having SERS effect according to the first aspect of the present invention, comprising the steps of:
s1: reS is to 2 Mixing the material with dopamine for reaction to obtain ReS with the surface coated with polydopamine layer 2 A material;
s2: reS with the surface coated with polydopamine layer 2 The material is mixed and reacted with cationic polyelectrolyte and noble metal nano particles to prepare the compound with SERS effect.
Preferably, in the step S2, the mixing reaction is performed in the presence of a cationic polyelectrolyte.
Preferably, the cationic polyelectrolyte is at least one of polydiallyl dimethyl ammonium chloride, cetyl trimethyl ammonium chloride and cetyl trimethyl ammonium bromide; further preferably, the cationic polyelectrolyte is polydiallyl dimethyl ammonium chloride.
Preferably, the polydiallyl dimethyl ammonium chloride is prepared into polydiallyl dimethyl ammonium chloride solution for use; further preferably, the volume fraction of the polydiallyl dimethyl ammonium chloride solution is 1.0-3.0%; still further preferably, the volume fraction of the polydiallyl dimethyl ammonium chloride solution is 1.75%.
Preferably, in the step S2, the mixing reaction time is 4 to 10 hours; further preferably, in the step S2, the mixing reaction time is 5 to 8 hours; still more preferably, in the step S2, the mixing reaction time is 6 to 8 hours.
Preferably, in the step S2, the mixing reaction temperature is 15 to 35 ℃; further preferably, in the step S2, the mixing reaction temperature is 25 to 35 ℃.
Preferably, the ReS 2 The preparation method of the material comprises the following steps: mixing hydroxylamine hydrochloride, ammonium perrhenate and thiourea for reaction to obtain the ReS 2 A material.
Preferably, the ReS 2 In the preparation method of the material, the mixing reaction temperature is 180-240 ℃; further preferably, the ReS 2 In the preparation method of the material, the mixing reaction temperature is 200-240 ℃; still further preferably, the ReS 2 In the preparation method of the material, the mixing reaction temperature is 220-240 ℃.
Preferably, the ReS 2 In the preparation method of the material, the mixing reaction time is 20-30 h; further preferably, the ReS 2 In the preparation method of the material, the mixing reaction time is 22-28 h; still further preferably, the ReS 2 In the preparation method of the material, the mixing reaction time is 24-26 h.
Preferably, the ReS 2 In the preparation method of the material, the mass ratio of the hydroxylamine hydrochloride to the ammonium perrhenate to the thiourea is 1 (1-2) to 1-3.
Preferably, the mass ratio of the hydroxylamine hydrochloride to the ammonium perrhenate is 1 (1-1.5); further preferably, the mass ratio of the hydroxylamine hydrochloride to the ammonium perrhenate is 1 (1-1.4); still more preferably, the mass ratio of the hydroxylamine hydrochloride to the ammonium perrhenate is 1 (1-1.3).
Preferably, the mass ratio of the hydroxylamine hydrochloride to the thiourea is 1 (1-3); further preferably, the mass ratio of the hydroxylamine hydrochloride to the thiourea is 1 (1-2.5); still more preferably, the mass ratio of the hydroxylamine hydrochloride to the thiourea is 1 (1-1.5).
Preferably, in the step S1, the mixing reaction time is 2-6 hours; further preferably, in the step S1, the mixing reaction time is 2 to 5 hours; still more preferably, in the step S1, the mixing reaction time is 3 to 4 hours.
Preferably, in the step S1, the mixing reaction temperature is 15 to 35 ℃; further preferably, in the step S1, the mixing reaction temperature is 25 to 35 ℃.
Preferably, the preparation method of the noble metal nanoparticle specifically comprises the following steps: mixing noble metal salt, sodium citrate and water, reacting for 1-2 h at 100-120 ℃, and cooling to obtain the noble metal nano particles.
Preferably, the step S1 further comprises the step of adding Tris-HCl buffer.
Preferably, the step S1 further includes a step of ultrasonic mixing.
Preferably, in the step S1, the ultrasonic mixing time is 20-50 min; further preferably, in the step S1, the ultrasonic mixing time is 20 to 40 minutes; still further preferably, in the step S1, the ultrasonic mixing time is 20 to 30 minutes.
A third aspect of the present invention is to provide a composite flexible SERS substrate comprising a substrate and a composite having SERS effect provided in the first aspect of the present invention; the complex with SERS effect is supported on a substrate.
Preferably, the substrate comprises at least one of a filter membrane, a filter paper, a silicon wafer.
Preferably, the filter membrane is a microporous filter membrane.
Preferably, the preparation method of the composite flexible SERS substrate comprises the following steps: and concentrating and loading the compound with the SERS effect on the surface of a matrix to obtain the SERS substrate.
The compound with SERS effect is concentrated on the matrix, the noble metal nano particles are adsorbed on the polydopamine layer through electrostatic acting force, the adsorption acting force is strong, the noble metal nano particles are not easy to agglomerate and sink, the noble metal nano particles have good dispersibility and strong enrichment, and the problems that the noble metal sol substrate in the prior art is easy to agglomerate and sink, the dispersibility is poor and the enrichment is weak are solved.
A fourth aspect of the present invention is to provide an application of the complex with SERS effect provided in the first aspect of the present invention in detecting pesticide residues.
The fifth aspect of the present invention provides a method for detecting 6-benzyl adenine in vegetable and fruit, mixing a vegetable and fruit liquid to be detected with the composite flexible SERS substrate provided in the third aspect of the present invention, and performing SERS test to calculate the content of 6-benzyl adenine in the vegetable and fruit liquid to be detected.
Preferably, the method further comprises mixing different concentrations of 6-benzyladenine standard solution with the composite flexible SERS substrate; performing SERS test to obtain the relationship between the characteristic Raman shift intensity of the 6-benzyl adenine and the standard concentration.
Preferably, the method specifically comprises the following steps: and (3) dropwise adding the vegetable and fruit to be detected onto the composite flexible SERS substrate provided by the third aspect of the invention, performing SERS detection to obtain the characteristic Raman displacement intensity of the 6-benzyl adenine, and then calculating the concentration of the 6-benzyl adenine in the vegetable and fruit to be detected according to the relation between the characteristic Raman displacement intensity of the 6-benzyl adenine and the standard concentration.
Preferably, the concentration of the 6-benzyl adenine standard solution is 0.065-1.0 mg/L.
The beneficial effects of the invention are as follows: the compound of the invention has both electromagnetic enhancement and ReS of noble metal nano particles 2 Chemical enhancement of the material, remarkable SERS signal enhancement effect and ReS 2 The polydopamine layer on the surface layer of the material enables the compound to have stronger adsorption effect on noble metal nano particles.
In addition, the composite flexible SERS substrate is used for carrying out SERS detection on target molecules, and because enrichment and detection are concentrated on the substrate, the analysis speed is high, the analysis efficiency is high, and the accuracy is high. The composite flexible SERS substrate has good uniformity and reproducibility, the Relative Standard Deviation (RSD) of the test results of the substrate in different positions in the same batch and the test results of the substrate in different batches is less than 10% for the 6-benzyl adenine detection of the same concentration, and the relative standard deviation of the test results of the 6-benzyl adenine detection of the composite flexible SERS substrate in the invention is less than 10% after the composite flexible SERS substrate is placed for different days.
The method for detecting 6-benzyl adenine in vegetables and fruits has the advantages of simplicity in operation, high sensitivity, good stability and the like, the detection limit is as low as 24.4 mug/L, and the method is high in accuracy and high in practicability in actual sample measurement.
Drawings
FIG. 1 is a ReS in example 1 2 Scanning electron microscope images of (2);
FIG. 2 is a ReS in example 1 2 Scanning electron microscope of PDA;
FIG. 3 is a scanning electron microscope image of a complex with SERS effect in example 1;
FIG. 4 is a physical diagram of the composite flexible SERS substrate of example 1;
FIG. 5 is a SERS test spectrum of the substrates of example 1, comparative example 2;
FIG. 6 is a chart of SERS response tests at different locations on the same substrate;
FIG. 7 is a chart of SERS response tests for different batches of substrates;
FIG. 8 is a graph of stability testing for various times of the composite flexible SERS substrate of example 1;
FIG. 9 is a SERS test spectrum of different plant growth regulators on the composite flexible SERS substrate in example 1;
FIG. 10 is a SERS test spectrum of 6-benzyladenine standard solutions of different concentrations;
FIG. 11 is a graph at 1000cm -1 A plot of 6-benzyladenine concentration at raman signal intensity versus raman signal intensity;
FIG. 12 is a SERS test spectrum of bean sprout samples, 6-benzyladenine and labeled samples.
Detailed Description
Specific embodiments of the present invention will be described in further detail below with reference to the drawings and examples, but the practice and protection of the present invention are not limited thereto. It should be noted that the following processes, unless otherwise specified, are all realized or understood by those skilled in the art with reference to the prior art. The reagents, methods and apparatus employed in the present invention, unless otherwise specified, are all conventional in the art.
The following examples and comparative examples were prepared from the following raw materials:
6-Benzylacradenine was purchased from: shanghai Ala Biochemical technology Co., ltd;
bean sprouts, tomatoes, cucumbers were purchased from: a local market;
surface enhanced raman spectroscopy was purchased from: deltaNu, USA;
high performance liquid chromatography was purchased from: shimadzu corporation of Japan.
Example 1
The composite flexible SERS substrate in the embodiment consists of a composite with SERS effect and a nylon microporous filter membrane, wherein the composite with SERS effect is loaded on the nylon microporous filter membrane. Res in the complex with SERS effect 2 The mass ratio of the dopamine to the nano silver is 1:0.05:0.36.
The composite flexible SERS substrate in the embodiment is prepared by adopting the following preparation method, and comprises the following steps:
s1: 18.0mg AgNO 3 Dissolved in 100.0mL deionized water, heated to boiling, rapidly added with 5.3mL of a 2.0% (mass fraction) sodium citrate solution, and heated under reflux with stirring for 1.5h. And then finishing the reaction, naturally cooling to room temperature to obtain silver nano sol, and placing the silver nano sol at the temperature of 4 ℃ for standby.
S2: 0.414g hydroxylamine hydrochloride, 0.536g ammonium perrhenate, and 0.608g thiourea were mixed, and 60.0mL deionized water was added thereto, and the mixture was thoroughly stirred and dissolved. Transferring the mixed solution into a hydrothermal reaction kettle, reacting at 200 ℃ for 24 hours, naturally cooling, washing the product with ethanol and deionized water for three times respectively, and vacuum drying at 60 ℃ for 12 hours to obtain ReS 2 ，ReS 2 Scanning electron microscope patterns such asShown in fig. 1.
S3: 30.0mg of ReS in step S2 was taken 2 Dispersing in 3.0mL Tris-HCl buffer solution, and performing ultrasonic treatment for 30min to obtain ReS 2 A dispersion; then 60.0mL of 0.025mg/mL dopamine Tris-HCl solution is added, the mixture is stirred for 4 hours at room temperature, the reaction is finished, the mixture is centrifugally washed with water for 3 times, and the mixture is dried in vacuum for 12 hours at 60 ℃ to obtain the ReS 2 /PDA；ReS 2 A scanning electron microscope of the PDA is shown in FIG. 2.
S4: 15.0mg of ReS in step S3 was taken 2 PDA was dispersed in 5.0mL of ethanol, sonicated for 10min, 30.0mL of polydiallyl dimethyl ammonium chloride solution was added and stirred for 10h, then centrifuged and water washed 2 times. Dispersing in 5.0mL water, ultrasonic treating for 10min, adding into 30.0mL silver sol, stirring for 6h, centrifuging, washing for 3 times, and dispersing in 15.0mL water to obtain compound with SERS effect, namely ReS 2 A scanning electron microscope image of the/PDA/AgNPs complex is shown in FIG. 3.
S5: taking 5.0mL (concentration of 1.0 mg/mL) of ReS in step S3 2 And concentrating the PDA/AgNPs compound dispersion liquid on the surface of the nylon microporous filter membrane to obtain the compound flexible SERS substrate in the example. A physical diagram of the prepared composite flexible SERS substrate is shown in fig. 4.
Example 2
The preparation method of the composite flexible SERS substrate in this example is the same as that of example 1, and the composite flexible SERS substrate in this example is different from that of example 1 in that: res in complexes with SERS effect 2 The mass ratio of the dopamine to the silver nanoparticles is 1:0.05:0.48.
Example 3
The preparation method of the composite flexible SERS substrate in this example is the same as that of example 1, and the composite flexible SERS substrate in this example is different from that of example 1 in that: res in complexes with SERS effect 2 The mass ratio of the dopamine to the silver nanoparticles is 1:0.025:0.36.
Comparative example 1:
the SERS substrate in this example comprises ReS 2 Dispersion liquid and nylon microporous filter membrane; reS (ReS) 2 The dispersion liquid is loaded on a nylon microporous filter membrane; the ReS 2 The amount of the dispersion was 5.0mg。ReS 2 The dispersion was derived from ReS prepared in example 1 2 And (3) a dispersion.
Comparative example 2:
the SERS substrate in this example comprises silver nanosol and nylon microporous filter membrane; silver nano sol is loaded on a nylon microporous filter membrane; the dosage of the silver nano sol is 5.0mg.
Test example 1
The composite flexible SERS substrates prepared in examples 1 to 2 and SERS substrates in comparative examples 1 to 2 were evaluated for enhancement performance test, and the specific test methods were as follows:
using 6-benzyladenine as a target, 50.0. Mu.L of a 1 mg/L6-benzyladenine solution was dropped onto the substrate of example 1, the substrate of comparative example 1 and the substrate of comparative example 2, respectively, and SERS test was performed using 785nm laser as a light source with an integration time of 7s at 1000cm -1 The characteristic peak intensities are used as reference, and the test results are shown in fig. 5. As can be seen from fig. 5, the strength of 6-benzyladenine on the substrate in example 1 is significantly higher than that of the substrates in comparative examples 1 and 2, and the results indicate that the composite flexible SERS substrate of the present invention has a significant SERS enhancing effect on 6-benzyladenine.
Test example 2
The uniformity and reproducibility of the composite flexible SERS substrate prepared in example 1 was evaluated by the following test methods:
using 6-benzyladenine as a target, 50.0 μl of a 6-benzyladenine solution at a concentration of 0.75mg/L was added dropwise to the composite flexible SERS substrate of example 1, and the SERS response at 11 different positions on the same substrate was tested; 11 different batches of composite flexible SERS substrates were prepared according to the preparation method in example 1, and SERS responses on the different batches of composite flexible SERS substrates were tested. 785nm lasers are used as light sources for SERS tests at different positions of the same substrate and SERS tests of different batches of substrates, integration time is 7s, obtained SERS spectrograms are shown in fig. 6 and 7, fig. 6 shows SERS response test charts at different positions on the same substrate, and fig. 6 (a) shows SERS response charts at different positions on the same substrate;
FIG. 6 (b) is a graph of SERS response intensity at different locations on the same substrate; FIG. 7 is a chart of SERS response tests for different batches of substrates; wherein FIG. 7 (a) is a SERS response plot for different batches of substrates; fig. 7 (b) is a plot of SERS response intensity for different batches of substrates. At 1000cm -1 The RSD value was calculated by scanning 3 times continuously with the characteristic peak intensity as a reference. The relative standard deviation of SERS analysis signal intensities at different locations on the same substrate in fig. 6 was calculated to be 4.5% (n=11); the relative standard deviation of SERS analysis signal intensities for the different batches of substrates in fig. 7 was calculated to be 5.5% (n=11). Therefore, the composite flexible SERS substrate has good uniformity and reproducibility, and can meet the requirements of SERS quantitative analysis precision.
Test example 3
The composite flexible SERS substrate prepared in example 1 was subjected to stability test evaluation, and the specific test method is as follows:
a50.0. Mu.L solution of 6-benzyladenine at a concentration of 0.75mg/L was infiltrated onto the composite flexible SERS substrate of example 1 for different days, and SERS test was performed using 785nm laser as light source with an integration time of 7s. At 1000cm -1 The characteristic peak intensity is used as a reference, the relative standard deviation is calculated by scanning three times continuously, the result is shown in fig. 8, and the relative standard deviation of the SERS detection results of different days is 8.9% (n=3), so that the composite flexible SERS substrate has good storage stability.
Test example 4
The composite flexible SERS substrate prepared in example 1 was subjected to selective test evaluation, and the specific test method is as follows:
the composite flexible SERS substrate prepared in the example 1 is adopted to carry out SERS test on common plant growth regulators with similar structures, the selected plant growth regulators comprise sodium p-chlorophenylacetate, paclobutrazol, thidiazuron, forchlorfenuron and 2,4-D (2, 4-dichlorophenoxyacetic acid), the concentrations of the plant growth regulators are all 0.75mg/L, and the SERS spectrum obtained by the test is shown in figure 9. As can be seen from fig. 9, the composite flexible SERS substrate in example 1 has a better enhancement effect on 6-benzyladenine, but has no obvious SERS enhancement effect on other common plant growth regulators with similar structures, which indicates that the composite flexible SERS substrate prepared in the invention has selectivity on 6-benzyladenine, and can be used for accurate measurement of 6-benzyladenine.
Test example 5
The 6-benzyl adenine in vegetables was detected using the composite flexible SERS substrate prepared in example 1, and the specific test method and procedure were as follows:
(1) Drawing of a Standard Curve
6-benzyl adenine standard solutions (0.065 mg/L, 0.125mg/L, 0.375mg/L, 0.5mg/L, 0.75mg/L, 1.0 mg/L) were prepared at various concentrations. 50.0 mu L of 6-benzyl adenine standard solution with different concentrations is soaked on the composite flexible SERS substrate prepared in the embodiment 1, SERS test is carried out, 785nm laser is adopted as a light source, the integral time is 7s, the obtained SERS spectrogram is shown in figure 10, each concentration is continuously tested for 3 times, and the relative standard deviation is calculated. As can be seen from FIG. 10, there is a linear relationship between the SERS signal and concentration of 6-benzyladenine at 1000cm on the composite flexible SERS substrate in example 1 -1 The intensity at the raman shift is used as a reference to establish a standard curve of raman signal intensity versus 6-benzyladenine concentration, as shown in fig. 11. The detection limit of the 6-benzyl adenine is 24.4 mug/L (n=3) by taking the lowest concentration capable of detecting a signal with 3 times of signal to noise ratio as the detection limit, and the result shows that the linear range and the detection limit of the detection method of the composite flexible SERS substrate prepared by the invention can meet the requirement of actual sample analysis.
(2) Detection of actual samples
Weighing 20.0g of bean sprouts, cucumber and tomato samples, putting into a centrifuge tube, fully grinding, adding 20.0mL of methanol, swirling for 2min, performing ultrasonic extraction for 15min, centrifuging for 10min at 6000rpm/min, and removing the supernatant. Spin concentration was performed at 40 ℃ using a rotary evaporator, then nitrogen blow-dried, redissolved with 2.0mL of methanol/water (volume ratio of methanol to water 1:1), and filtered using a filtration membrane to obtain the liquid to be tested. Soaking the test solution on the composite flexible SERS substrate prepared in the embodiment 1 for SERS test, wherein the SERS test result of the test solution of the bean sprout sample is shown in FIG. 12, and the test is continuously performed for 3 times, and 3 data are calculated1000cm -1 The average value of the intensity and the relative standard deviation are substituted into a 6-benzyl adenine standard curve, the content of 6-benzyl adenine in the actual sample is calculated, and the measurement results are shown in Table 1.
Then, the reliability of the method is verified by a labeling experiment on the sample, SERS detection is carried out by adopting the same pretreatment step, the test is carried out for 3 times continuously, and 1000cm of the test is calculated -1 The peak value relative standard deviation is substituted into the 6-benzyl adenine standard curve, the concentration of 6-benzyl adenine in the labeled sample is calculated, and the measurement result of the labeled experiment is shown in table 1.
The accuracy of the SERS analysis method is verified through High Performance Liquid Chromatography (HPLC) comparison experiments. Weighing 20.0g of bean sprout sample, cucumber sample and tomato sample in a centrifuge tube, fully grinding, adding 20.0mL of methanol, swirling for 2min, ultrasonically extracting for 15min, centrifuging for 10min at 6000rpm/min, and removing supernatant. Spin concentration was performed at 40 ℃ using a rotary evaporator, then nitrogen blow-dried, redissolved with 2.0mL of methanol/water (volume ratio 1:1), filtered using a filter membrane to obtain the liquid to be tested, and subjected to HPLC testing. The HPLC was equipped with an ultraviolet detector (Shimadzu corporation) at 267nm, the column temperature was 30℃and the mobile phase was methanol-ammonium acetate solution (volume ratio of methanol to ammonium acetate solution: 70:30) at a flow rate of 1.0mL/min, with ODS C18 column (250 mm. Times.4.5 mm,5.0 μm) as the selected column, and the test results were shown in Table 1 below.
TABLE 1 determination of 6-Benzylamines in actual samples and labeling experiments
Figure BDA0003592690810000091
Figure BDA0003592690810000101
As shown in Table 1, the content of 6-benzyl adenine in the bean sprout sample is 6.9 mug/kg, the recovery rate of 6-benzyl adenine is 87.5% -97.1%, and the RSD is 2.5% -3.0%; 6-benzyl adenine is not detected in the cucumber sample, the recovery rate of 6-benzyl adenine is 87.6-93.3%, and RSD is 3.9-6.1%; 6-benzyl adenine in tomato samples is not detected, the recovery rate of 6-benzyl adenine in tomato samples in cucumber samples is 98.1% -106.7%, and RSD is 5.1% -6.6%. Through HPLC detection, the content of 6-benzyl adenine in the bean sprout sample is 6.7 mug/kg, and the relative deviation of the detection result detected by using the composite flexible SERS substrate is 3.0%, which shows that the composite flexible SERS substrate is adopted to analyze the actual sample, so that the analysis reliability and accuracy are high, and meanwhile, compared with an HPLC detection method, the detection method is short in time consumption and high in efficiency.
While the embodiments of the present invention have been described in detail, the present invention is not limited to the above embodiments, and various changes may be made without departing from the spirit of the present invention within the knowledge of those skilled in the art. Furthermore, embodiments of the invention and features of the embodiments may be combined with each other without conflict.

Claims (8)

1. A complex having SERS effect, characterized by: the complex comprises ReS 2 A material, a polydopamine layer and noble metal nanoparticles; the ReS 2 The surface of the material is coated with a polydopamine layer; the polydopamine layer has positive charges; the noble metal nano particles are adsorbed on the polydopamine layer;
the ReS 2 The material is formed by sheet ReS 2 The honeycomb material is assembled;
the noble metal nano particles comprise at least one of silver nano particles and gold nano particles;
the polydopamine layer has positive charges after being modified by a cationic polyelectrolyte.
2. The complex with SERS effect according to claim 1, wherein: the particle size of the noble metal nano particles is 10-40 nm.
3. A complex having a SERS effect according to claim 1 or 2,the method is characterized in that: the ReS 2 The mass ratio of the material to the polydopamine layer to the noble metal nano particles is 1 (0.01-0.1) (0.1-1.0).
4. A method for preparing a complex with SERS effect according to any one of claims 1 to 3, characterized in that: the method comprises the following steps:
s1: reS is to 2 Mixing the material with dopamine for reaction to obtain ReS with the surface coated with polydopamine layer 2 A material;
s2: reS with the surface coated with polydopamine layer 2 The material is mixed and reacted with cationic polyelectrolyte and noble metal nano particles to prepare the compound with SERS effect.
5. The method for preparing a complex with SERS effect according to claim 4, wherein: the cationic polyelectrolyte is at least one of polydiallyl dimethyl ammonium chloride, cetyl trimethyl ammonium chloride and cetyl trimethyl ammonium bromide.
6. A composite flexible SERS substrate, characterized by: a composite comprising a matrix and the SERS effect of any one of claims 1 to 3; the complex with SERS effect is supported on a substrate.
7. The use of a complex with SERS effect according to any one of claims 1 to 3 for detecting pesticide residues.
8. A method for detecting 6-benzyl adenine in vegetables and fruits is characterized by comprising the following steps: mixing the vegetable and fruit to-be-detected liquid with the composite flexible SERS substrate in claim 6, and then carrying out SERS test to calculate the content of 6-benzyl adenine in the vegetable and fruit to-be-detected liquid.
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