CN112229828A

CN112229828A - SERS active substrate for high-selectivity capture of sudan dye and preparation method thereof

Info

Publication number: CN112229828A
Application number: CN202010798330.5A
Authority: CN
Inventors: 陈�峰; 赵健伟; 赵博儒; 程娜; 贺园园
Original assignee: Jiaxing University
Current assignee: Jiaxing University
Priority date: 2020-08-11
Filing date: 2020-08-11
Publication date: 2021-01-15
Anticipated expiration: 2040-08-11
Also published as: CN112229828B

Abstract

The invention relates to a SERS active substrate for capturing Sudan dye with high selectivity and a preparation method thereof, wherein the method comprises the steps of firstly adding epoxy azobenzene into HPEI solution for reaction to obtain HPEI @ AZ; adding propylene oxide into the HPEI @ AZ solution to react to obtain modified hyperbranched polyethyleneimine; finally, placing the electrodeposited silver SERS active substrate in a modified hyperbranched polyethyleneimine solution for reaction to prepare an SERS active substrate consisting of the electrodeposited silver SERS active substrate and the modified hyperbranched polyethyleneimine on the surface of the silver nanoparticles of the electrodeposited silver SERS active substrate, wherein the alkyl on the modified hyperbranched polyethyleneimine accounts for 40-50% of the molar amount of-NH-in the HPEI; the selectivity of the SERS active substrate to Sudan II in the mixed solution of Sudan I and Sudan II is 98.8% -99.1%, and the selectivity to Sudan IV in the mixed solution of Sudan III and Sudan IV is 98.9% -99.1%.

Description

SERS active substrate for high-selectivity capture of sudan dye and preparation method thereof

Technical Field

The invention belongs to the technical field of chemical analysis and detection, and relates to a SERS active substrate for capturing Sudan dye with high selectivity and a preparation method thereof.

Background

The high-selectivity capture response performance is always an important index for preparing a Surface Enhanced Raman Scattering (SERS) active substrate. Research in this regard is currently focused mainly in two directions: one type is a bioactive substrate mainly based on DNA, and the substrate selectively captures and detects target molecules mainly through antigen-antibody specific reaction (the selective capture principle of the bioactive substrate); the other type is an active substrate prepared based on molecular imprinting technology, and the substrate specifically captures target molecules mainly through holes formed in a polymer by the topological shape of the target molecules (the selective capture principle of the molecular imprinting active substrate). Both active substrates are designed and prepared based on the principle of accurate identification (similar to a key with a lock).

Although the active substrate prepared by the above method has achieved high selective capture of a portion of the target molecule; however, each specific active substrate is usually only specific to one specific target molecule, and cannot be simultaneously applied to the selective capture of different target molecules and interfering molecules; and there are some disadvantages: for example, in the preparation and use processes of the bioactive substrate, attention needs to be paid to changes of conditions such as temperature and pH value, and the preparation process of the molecular imprinting active substrate is relatively complicated because a corresponding substrate surface modification polymer needs to be prepared according to the topological structure or electronic structure characteristics of a specific target molecule. More importantly, the highest selectivity of the active substrates which can be achieved at present is only about 92%, and the actual analysis requirements are difficult to achieve in some trace analysis and detection fields.

Therefore, the development of the surface enhanced Raman scattering active substrate which has simple preparation process, universal applicable conditions, and can give consideration to the detection of various target molecules and higher selectivity and the preparation method thereof have very important significance.

Disclosure of Invention

In order to solve the problems in the prior art, the invention provides the SERS active substrate for capturing the Sudan dye with high selectivity and the preparation method thereof;

one of the purposes is to provide a SERS active substrate for capturing sudan dye with high selectivity, specifically: the device consists of an electrodeposited silver SERS active substrate and modified hyperbranched polyethyleneimine of the surface of nano silver particles of the electrodeposited silver SERS active substrate; the mass ratio of the electrodeposited silver SERS active substrate to the modified hyperbranched polyethyleneimine is 62.5-28.5: 1; the modified hyperbranched polyethyleneimine is prepared by grafting azobenzene and alkyl on Hyperbranched Polyethyleneimine (HPEI), and the alkyl on the modified hyperbranched polyethyleneimine accounts for 40-50% of the molar amount of-NH-in the HPEI (theoretically, as the alkyl content increases, the selectivity increases, therefore, the alkyl content is too low, the selectivity decreases, and when the molar ratio of the alkyl is increased to 50%, the highest selectivity is achieved, and the alkyl content does not need to be increased continuously).

The second purpose of the method is to provide a preparation method of the SERS active substrate for capturing Sudan dye with high selectivity, which comprises the following steps: firstly, adding epoxy azobenzene into an HPEI solution to react to obtain HPEI @ AZ; adding epoxypropane into the HPEI @ AZ solution to react to obtain modified hyperbranched polyethyleneimine; and finally, placing the electrodeposited silver SERS active substrate in a modified hyperbranched polyethyleneimine solution to react to obtain the SERS active substrate.

In order to achieve the purpose, the invention adopts the following scheme:

the SERS active substrate for capturing Sudan dye with high selectivity consists of an electrodeposited silver SERS active substrate and modified hyperbranched polyethyleneimine (HPEI @ AZ @ AL) deposited on the surface of nano silver particles;

the mass ratio of the electrodeposited silver SERS active substrate to the modified hyperbranched polyethyleneimine (HPEI @ AZ @ AL) is 62.5-28.5: 1;

the modified hyperbranched polyethyleneimine (HPEI @ AZ @ AL) is prepared by grafting azobenzene and alkyl on Hyperbranched Polyethyleneimine (HPEI);

the Alkyl (AL) on the modified hyperbranched polyethyleneimine (HPEI @ AZ @ AL) occupies-NH- (in the invention, -NH-is-NH-and-NH-in the Hyperbranched Polyethyleneimine (HPEI)₂) 40 to 50 percent of the molar weight of (A).

As a preferred technical scheme:

SERS Activity for highly selective capture of Sudan dyes as described aboveThe azobenzene on the modified hyperbranched polyethyleneimine (HPEI @ AZ @ AL) occupies-NH- (including-NH-and-NH-in the Hyperbranched Polyethyleneimine (HPEI)₂) 10 to 30 percent of the molar weight of (A).

The high-selectivity SERS active substrate for capturing Sudan dye has the advantages that the number average molecular weight of the Hyperbranched Polyethyleneimine (HPEI) is 5000-20000. When the molecular weight is too large, the trapped sudan dye is too far away from the active substrate, the intensity of the raman signal is weak, and the selectivity cannot be measured; when the molecular weight is too small, the density of functional groups is too low, the intensity of the statistic effect of the supermolecule hydrophobic multipoint is too weak, the selective capture capability is too weak, and meanwhile, the adsorbed sudan dye is too little, the intensity of a Raman signal is weak, so that the selectivity cannot be measured.

With regard to the selection of the number average molecular weight of the Hyperbranched Polyethyleneimine (HPEI), the present invention is determined by the following method:

(1) the preparation process of the electrodeposited silver SERS active substrate comprises the following steps: mixing 15X 15mm²The red copper sheet is taken as an electro-deposition silver substrate, and is subjected to absolute ethyl alcohol ultrasonic washing for 15min at the temperature of 45 ℃, and is washed by deionized water once. Under the heating condition of 40-50 ℃, the current density is 3-5A/dm²And (3) degreasing the cathode for 5min (the degreasing purpose is to remove grease on the surface of the copper sheet), and washing with deionized water for one time. Soaking the copper sheet substrate with 10% (volume fraction) dilute sulfuric acid solution at room temperature for 5min, taking out, and washing with deionized water. Then, the current density was set to 1.0A/dm²Cathode/anode area ratio of 1:10, plating bath (AgNO)₃The content of the complexing agent is 45g/L, the content of the complexing agent 5, 5' -dimethylhydantoin is 110g/L, and the conductive salt K₂CO₃The content is 45g/L, the pH value is 10.5), the temperature is 23 ℃, and the electrodeposited silver SERS active substrate is prepared by constant-current electrodeposition for 5 min.

(2) Firstly, 1g of Hyperbranched Polyethyleneimine (HPEI) with the molecular weight of 10000 is uniformly dissolved in deionized water (10 mL); standing a piece of electrodeposited silver SERS active substrate in the step (1) in the solution; finally, stirring the solution at room temperature for 3h, taking out, fully cleaning with ethanol, and naturally drying to obtain an HPEI SERS active substrate with molecular weight of 10000;

(3) selecting HPEI with the molecular weight of 5000 and different molecular weights, and repeating the step (2) to obtain an SERS active substrate of the HPEI with the molecular weight of 5000;

(4) selecting HPEI with molecular weight of 20000 and different molecular weight to repeat the step (2) to obtain an SERS active substrate of HPEI with molecular weight of 20000;

(5) selecting HPEI with the molecular weight of 40000 and different molecular weights, and repeating the step (2) to obtain a SERS active substrate of the HPEI with the molecular weight of 40000;

(6) respectively placing the above active substrates at a concentration of 1.0 × 10^-7Standing the solution of rhodamine 6G (R6G) at room temperature for 2h, taking out, leaching with deionized water, blowing the solution with small-flow nitrogen for drying, and then carrying out Raman spectrum detection, wherein the detection parameters are as follows: an excitation light source is argon ion laser with the wavelength of 532nm, the laser intensity is 2.0mW, the integration time is 0.02s, and the cycle is carried out for 13 times.

The test result is shown in fig. 1, and it can be seen from fig. 1 that after raman spectrum detection is performed on the electrodeposited silver SERS active substrate subjected to surface modification by HPEI with different molecular weights by using rhodamine 6G (R6G) as a probe molecule, when the molecular weight of the HPEI is 5000-10000, the SERS activity is gradually enhanced (the intensity of raman signal is continuously increased) along with the continuous increase of the molecular weight, which is caused by the increase of the number of capture functional groups on the HPEI for R6G; however, as the molecular weight is further increased, SERS activity gradually decreases because the molecular weight of HPEI is too large and the polymer layer is too thick, resulting in a considerable amount of R6G being captured further from the electrodeposited silver nano-layer and thus failing to generate SERS activity. Therefore, the desirable range of HPEI molecular weight is 5000-.

Before testing the active substrate which adsorbs the sudan dye or the rhodamine 6G (R6G), the SERS active substrate which does not adsorb is subjected to Raman spectrum testing under respective corresponding testing conditions, and background correction is performed to eliminate the influence of the Raman signal of the hyperbranched polymer on the Raman signal of the sudan dye or the rhodamine 6G (R6G).

In the invention, each Raman characteristic peak intensity used for comparison is the average value of the intensity values obtained from ten different test points, and the deviation range of the calculated average value and the intensity value of each test point used for calculation is within 1.5%.

The method for preparing the high-selectivity Sudan dye-capturing SERS-active substrate as described above has a selectivity of 98.8% to 99.1% for Sudan II in a mixed solution (solvent is ethanol) of Sudan I (Sudan I, interfering guest molecule) and Sudan II (Sudan II, target guest molecule), and a selectivity of 98.9% to 99.1% for Sudan IV in a mixed solution (solvent is ethanol) of Sudan III (Sudan III, interfering guest molecule) and Sudan IV (Sudan IV, target guest molecule). The specific process of the selectivity test is as follows: standing the SERS active substrate in the mixed solution at room temperature, stirring the solution for 2h, taking out, rinsing with deionized water, blowing with small-airflow nitrogen, and performing Raman spectrum detection. The excitation light source is argon ion laser with the wavelength of 532nm, the laser intensity is 1.0mW, the integration time is 0.03s, and the cycle is performed for 20 times. Wherein, the molecular structures of Sudan I, II, III and IV are as follows:

the preparation method of the SERS active substrate for capturing Sudan dye with high selectivity is as described above, and the concentration of all mixed solutions is 1.6 multiplied by 10^-10～1.0×10^-5mol/L; all solvents of the mixed solution are ethanol;

the saturated adsorption capacity A of each active substrate to different single-component sudan dyes is firstly tested, and as can be seen from Table 1, the saturated adsorption of the SERS active substrate for capturing the sudan dyes with high selectivity to different sudan dyes is generally lower, on one hand, the modified hyperbranched polymer loaded on the surface of the substrate has lower content, on the other hand, the modified hyperbranched polymer can generate obvious pi-pi stacking effect between benzene rings so as to prevent the sudan dyes from being captured into the polymer, and simultaneously, the rigid structure (conjugated structure formed by the benzene rings and azo groups in an alternating mode) of the sudan dyes also prevents the sudan dyes from being further transferred into the polymer. Wherein, the calculation formula of the saturated adsorption capacity A isA＝M_dye*V_dye/m_substrateWherein M is_dyeIs the molar concentration of the Sudan dye solution, V_dyeVolume of Sudan dye solution to reach saturation adsorption of active substrate, m_substrateIs the mass of the active substrate dosed.

Next, taking 10mL of the one-component sudan dye solution as an example, the saturated adsorption capacity in table 1 is converted into the lowest saturated adsorption concentration of the sudan dye (i.e. the minimum concentration of saturated adsorption of a certain mass of SERS-active substrates that can selectively capture the sudan dye (i.e. each SERS-active substrate tested contains 4.03g of electrodeposited silver) in 10mL of the one-component sudan dye solution), which is shown in table 2. It can be seen from table 2 that although the molecular weight of HPEI increases by a factor of 4 from 5000 to 20000, the lowest saturation adsorption concentration of sudan dye is still an order of magnitude. Converting the corresponding molar concentration when the substrate reaches saturated adsorption in 10mL of Sudan dye solution, wherein the calculation formula is A m_substrate/10^-2L, wherein A is the saturation adsorption capacity of the active substrate, m_substrateIs the mass of the active substrate.

TABLE 1 different molecular weights HPEI @ AZ₃₀@AL_40～50Saturated adsorption capacity of surface-loaded electrodeposited silver SERS active substrate

TABLE 2 different molecular weights HPEI @ AZ₃₀@AL_40～50Minimum saturated adsorption concentrations of surface-loaded electrodeposited silver SERS active substrates to 10mL of different sudan dye solutions

Sudan dye type	HPEI molecular weight is 5000	HPEI molecular weight is 10000	HPEI molecular weight is 20000
				Sudan I	2.5～2.4×10^-10mol/L	3.7～3.6×10^-10mol/L	2.8～2.7×10^-10mol/L
Sudan II	2.5～2.4×10^-10mol/L	3.6～3.5×10^-10mol/L	2.8～2.6×10^-10mol/L
				Sudan III	1.9～1.7×10^-10mol/L	2.5～2.4×10^-10mol/L	2.0～1.9×10^-10mol/L
Sudan IV	1.8～1.6×10^-10mol/L	2.4～2.3×10^-10mol/L	1.9～1.8×10^-10mol/L

The invention also provides a method for preparing the SERS active substrate for capturing the Sudan dye with high selectivity, which comprises the steps of firstly adding epoxy azobenzene into a Hyperbranched Polyethyleneimine (HPEI) solution (a solvent is chloroform) to react to obtain HPEI @ AZ; adding epoxypropane into the HPEI @ AZ solution (solvent is chloroform) to react to obtain modified hyperbranched polyethyleneimine (HPEI @ AZ @ AL); finally, placing the electrodeposited silver SERS active substrate in a modified hyperbranched polyethyleneimine (HPEI @ AZ @ AL) solution (the solvent is chloroform, the concentration of the solution is 0.1-1 g/mL, and only after the surface of the active substrate is completely covered by the polymer and the polymer remains in the solution) to perform coordination reaction (the amino on the HPEI and the nano silver particles perform coordination action) to prepare the SERS active substrate for capturing the Sudan dye with high selectivity;

the mass ratio of the electrodeposited silver SERS active substrate to the modified hyperbranched polyethyleneimine in the solution before coordination reaction is 10-5: 1, so that the excessive modified hyperbranched polyethyleneimine is ensured;

when the propylene oxide is added for reaction, the molar ratio of the propylene oxide to-NH-on the HPEI is 4.21-5.26: 10. Wherein, the calculation method of the mole ratio of the propylene oxide to the-NH-on the HPEI comprises the following steps: (a/M)_AL):[(b/M_HPEI@AZ)*(M_HPEI/M_-NH-)]Wherein a and b are the masses of propylene oxide and HPEI @ AZ, respectively, M_ALIs the relative molecular mass of propylene oxide, M_HPEI@AZRelative molecular mass of HPEI @ AZ, M_HPEIRelative molecular mass of HPEI, M_-NH-Is a repeating unit (-CH) containing one-NH-in HPEI₂-CH₂-NH-).

As a preferred technical scheme:

the preparation method of the SERS active substrate for capturing Sudan dye with high selectivity comprises the following steps of adopting chloroform as a solvent of the Hyperbranched Polyethyleneimine (HPEI) solution, the HPEI @ AZ solution and the modified hyperbranched polyethyleneimine (HPEI @ AZ @ AL) solution.

In the method for preparing the SERS active substrate for capturing Sudan dye with high selectivity, the concentration of the Hyperbranched Polyethyleneimine (HPEI) solution is 0.01-0.5 g/mL (when the concentration is too high, the reaction raw materials are not uniformly dispersed, and the reaction process is not uniformUniformly mixing, when the concentration is too low, the reaction rate is reduced), when the epoxy azobenzene is added for reaction, the molar ratio of the epoxy azobenzene to-NH-in the HPEI is 1.05-3.16: 10, the temperature for reaction is 50-70 ℃, and the time is 2-4 days. Wherein, the calculation method of the molar ratio of the epoxy azobenzene to-NH-in the HPEI comprises the following steps: (a/M)_AZ):(b/M_-NH-) Wherein a and b are the masses of azoxybenzene and HPEI, respectively, M_AZRelative molecular mass of epoxyazobenzene, M_-NH-Is a repeating unit (-CH) containing one-NH-in HPEI₂-CH₂-NH-).

According to the preparation method of the SERS active substrate for capturing Sudan dye with high selectivity, the concentration of the HPEI @ AZ solution is 0.05-0.5 g/mL (when the concentration is too high, the reaction raw materials are not uniformly dispersed, the reaction process is not uniform, and when the concentration is too low, the reaction rate is reduced), the temperature for adding propylene oxide to carry out reaction is 20-40 ℃, and the time is 2-4 days.

According to the preparation method of the SERS active substrate for capturing the Sudan dye with high selectivity, the concentration of the modified hyperbranched polyethyleneimine (HPEI @ AZ @ AL) solution is 0.1-1 g/mL, and the time of coordination reaction after the modified hyperbranched polyethyleneimine (HPEI @ AZ @ AL) solution is added is 2-4 h.

The principle of the invention is as follows:

in the selective capture process of the sudan dye, the selective capture method is a supermolecule multipoint statistical effect in the host-guest effect, the effect form is generally dominated by non-specific effect, the strict host-guest proportion and the strict space direction requirement between the action points are not usually met, and the host-guest combination form has dynamic and time-varying characteristics. Typical multi-point statistical effects include electrostatic effects, van der waals forces, ion-dipole and dipole-dipole effects. Due to their high functional group density and relatively easily adjustable molecular conformation, dendrimers and hyperbranched polymers are often used as hosts for supramolecular multi-point statistical effects, which can be achieved by changing their functional group density and properties to achieve efficient capture of different guest molecules, and which exponentially increases with increasing number of functional groups of the host molecule.

In the supermolecule multipoint statistic effect, a host molecule is modified Hyperbranched Polyethyleneimine (HPEI), target guest molecules are neutral azo dyes Sudan II and Sudan IV containing methyl, and interfering guest molecules are neutral azo dyes Sudan I and Sudan III containing no methyl; according to the invention, Azobenzene (AZ) is covalently bonded to HPEI by utilizing the ring-opening reaction of amino and epoxy, and the supermolecule multipoint statistical action strength is improved by generating pi-pi accumulation action by a benzene ring on the HPEI @ AZ and a benzene ring on a target object molecule and generating hydrogen bonding action by amino and hydroxyl on the HPEI @ AZ and hydroxyl on the target object molecule.

Further according to the principle of supermolecule fuzzy recognition, the high-selectivity capture of target guest molecules can be realized by a method for amplifying the subtle differences among competing guests; the present invention covalently bonds propylene oxide to HPEI @ AZ by a ring-opening reaction of amino and epoxy, thereby changing the internal functional group of HPEI @ AZ, and thus changing the hydrophobicity of Hyperbranched Polyethyleneimine (HPEI), and causing a nonlinear change in the intensity of the complementary interaction between competing guest molecules (target guest molecules and interfering guest molecules) and host molecules (i.e., the change in the internal electronic properties of the host leads to an exponential increase in the multi-point statistical interaction of supramolecules between target guest molecules and host molecules, which is nonlinear), which can amplify the difference between competing guests, i.e., the alkyl group on HPEI @ AZ @ AL not only generates a certain hydrophobic interaction with the benzene rings on the target guest molecules and interfering guest molecules, but also generates a hydrophobic interaction with the methyl groups on the target guest molecules, and HPEI @ AZ @ AL does not generate such additional hydrophobic interaction with interfering guest molecules (not have methyl groups), the existence of hydrophobic interaction between the alkyl and the methyl is utilized, so that the high-selectivity capture of target guest molecules is realized.

The synthetic route of the modified hyperbranched polymer is as follows: (several hundreds to thousands of repeating units of HPEI, the following structural formula is only schematic)

Moreover, the modified hyperbranched polyethyleneimine adopted by the invention can easily adjust the molecular conformation thereof according to the topological shape of a guest molecule so as to realize better wrapping and capturing, so that as long as the neutral azo dye containing methyl is adopted, even if the molecular structure is slightly different, the host molecule can realize selective capturing, namely high-selective capturing can be realized on Sudan II and Sudan IV.

Advantageous effects

(1) The preparation method of the SERS active substrate for capturing the Sudan dye with high selectivity has simple preparation process and low preparation cost;

(2) the SERS active substrate for capturing the Sudan dye with high selectivity has common application conditions, can be simultaneously suitable for various target guest molecules, and further improves the selectivity.

Drawings

FIG. 1 is a SERS spectrum of R6G after different molecular weight HPEI is loaded on the surface of a silver-electrodeposited SERS active substrate; raman spectrum testing conditions are as follows: [ R6G]＝1.0×10^-7mol/L, excitation wavelength of 532nm and laser intensity of 2.0 mW;

FIG. 2 is a SERS spectrogram of a Sudan IV/Sudan III adsorbed on the surface of the SERS active substrate in examples 2-3 and comparative examples 2-3; raman spectrum testing conditions are as follows: [ Sudan III)]═ Sudan IV]＝1.0×10^-7mol/L, excitation wavelength 532nm, laser intensity 1.0 mW.

Detailed Description

The invention will be further illustrated with reference to specific embodiments. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Further, it should be understood that various changes or modifications of the present invention may be made by those skilled in the art after reading the teaching of the present invention, and such equivalents may fall within the scope of the present invention as defined in the appended claims.

When the SERS active substrate for capturing the Sudan dye with high selectivity is respectively placed in an ethanol mixed solution of Sudan I and Sudan II and an ethanol mixed solution of Sudan III and Sudan IV, the mass-to-volume ratio of the SERS active substrate for capturing the Sudan dye with high selectivity to the Sudan dye mixed solution is 4.09-4.17 g/10 mL.

In the present invention, when only HPEI appears, the only HPEI appears refers to Hyperbranched Polyethyleneimine (HPEI) before azobenzene grafting.

Example 1

The preparation process of the electrodeposited silver SERS active substrate comprises the following steps:

mixing 15X 15mm²The red copper sheet is taken as an electro-deposition silver substrate, and is subjected to absolute ethyl alcohol ultrasonic washing for 15min at the temperature of 45 ℃, and is washed by deionized water once. Under the heating condition of 40-50 ℃, the current density is 3-5A/dm²And (3) degreasing the cathode for 5min (the degreasing purpose is to remove grease on the surface of the copper sheet), and washing with deionized water for one time. Soaking the copper sheet substrate with 10% (volume fraction) dilute sulfuric acid solution at room temperature for 5min, taking out, and washing with deionized water. Then, the current density was set to 1.0A/dm²Cathode/anode area ratio of 1:10, plating bath (AgNO)₃The content of the complexing agent is 45g/L, the content of the complexing agent 5, 5' -dimethylhydantoin is 110g/L, and the conductive salt K₂CO₃The content is 45g/L, the pH value is 10.5), the temperature is 23 ℃, and the electrodeposited silver SERS active substrate is prepared by constant-current electrodeposition for 5 min.

Example 2

The preparation method of the SERS active substrate for capturing the Sudan dye with high selectivity comprises the following steps:

(1) adding epoxy azobenzene into chloroform solution of hyperbranched polyethyleneimine (HEPI) with the number average molecular weight of 10000 to react to obtain HPEI @ AZ; wherein the concentration of the HPEI solution is 0.1g/mL, the molar ratio of epoxy azobenzene to-NH-in the HPEI is 3.16:10, the reaction temperature is 60 ℃, and the reaction time is 3 days;

(2) adding epoxypropane into a chloroform solution of HPEI @ AZ to react to obtain modified hyperbranched polyethyleneimine; wherein the concentration of the HPEI @ AZ solution is 0.1g/mL, the molar ratio of the propylene oxide to-NH-on the HPEI is 4.21:10, the reaction temperature is 25 ℃, and the reaction time is 3 days;

(3) then placing the electrodeposited silver SERS active substrate prepared in the embodiment 1 into a chloroform solution of modified hyperbranched polyethyleneimine to perform a coordination reaction to prepare a high-selectivity SERS active substrate for capturing Sudan dye; the concentration of the modified hyperbranched polyethyleneimine solution is 0.5g/mL, the mass ratio of the electrodeposited silver SERS active substrate to the modified hyperbranched polyethyleneimine in the solution is 7:1, and the coordination reaction time is 3 hours;

the prepared SERS active substrate for capturing the Sudan dye with high selectivity consists of an electrodeposited silver SERS active substrate with the mass ratio of 41.6:1 and modified hyperbranched polyethyleneimine on the surface of nano silver particles of the electrodeposited silver SERS active substrate; wherein, the alkyl on the modified hyperbranched polyethyleneimine accounts for 40 percent of the molar amount of-NH-in the HPEI, and the azobenzene on the modified hyperbranched polyethyleneimine accounts for 30 percent of the molar amount of-NH-in the HPEI.

4.13g of the SERS active substrate for capturing the Sudan dye with high selectivity is respectively placed in 10mL of ethanol mixed solution of Sudan I and Sudan II and 10mL of ethanol mixed solution of Sudan III and Sudan IV, and the concentrations of the Sudan I and the Sudan II in the ethanol mixed solution of the Sudan I and the Sudan II are both 1.0 multiplied by 10^-7The concentration of Sudan III and Sudan IV in the ethanol mixed solution of mol/L, Sudan III and Sudan IV is 1.0 × 10^-7And (3) mol/L, stirring the solution for 2 hours, taking out, leaching with deionized water, blowing the solution with small-flow nitrogen, and then performing Raman spectrum detection under the following test conditions: an excitation light source is 532nm argon ion laser, the laser intensity is 1.0mW, the integration time is 0.03s, and the cycle is performed for 20 times.

Selective assayThe test method comprises the following steps: firstly, the SERS active substrate for capturing the Sudan dye with high selectivity is tested to have the concentration of 1.0 multiplied by 10 under the same condition^-7Raman spectra of single-component ethanol solutions of Sudan I, Sudan II, Sudan III and Sudan IV in mol/L (namely, only replacing the mixed solution with the single-component ethanol solution, and keeping consistent dye concentration, solution volume, substrate quality, Raman test conditions and the like); and then determining the content of each of Sudan I, Sudan II, Sudan III and Sudan IV in the mixed solution on the surface of the active substrate by comparing the Raman characteristic peak intensities of the ethanol mixed solution and the corresponding single-component solution, thereby converting the selectivity of the substrate to the target guest molecule. The test results are: the selectivity to sudan II was 98.8%, while the selectivity to sudan IV was 99.1%.

Comparative example 1

A method for preparing a SERS active substrate, which is substantially the same as example 2 except that in the step (2), the molar ratio of propylene oxide to-NH-in HPEI is 1.05:10, to obtain a SERS active substrate, wherein alkyl groups on the modified hyperbranched polyethyleneimine account for 10% of the molar amount of-NH-in HPEI, and azobenzene on the modified hyperbranched polyethyleneimine accounts for 30% of the molar amount of-NH-in HPEI;

the selectivity of the active substrate to sudan II in the mixed solution of sudan I and sudan II in example 2 was 49.2%, and the selectivity to sudan IV in the mixed solution of sudan III and sudan IV was 50.6%; it is known that the active substrate can adsorb sudan dye, but does not have high selectivity for capturing sudan II and sudan IV.

Comparative example 2

A method for preparing the SERS active substrate is substantially the same as that in example 2, except that in the step (2), the molar ratio of the epoxy propane to the-NH-in the HPEI is 2.10:10, and the SERS active substrate is prepared, wherein on the active substrate, the alkyl on the modified hyperbranched polyethyleneimine accounts for 20% of the molar amount of the-NH-in the HPEI, and the azobenzene on the modified hyperbranched polyethyleneimine accounts for 30% of the molar amount of the-NH-in the HPEI.

4.13g of SERS active substrate is respectively placed in 10mL of solution with concentration of 1.010^-7The mol/L mixed solution of Sudan I and Sudan II and 10mL concentration are both 1.0X 10^-7Stirring the solution for 2 hours in a mixed solution of Sudan III and Sudan IV of mol/L, taking out, leaching with deionized water, blowing dry with small-airflow nitrogen, and performing Raman spectrum detection under the following test conditions: an excitation light source is 532nm argon ion laser, the laser intensity is 1.0mW, the integration time is 0.03s, and the cycle is performed for 20 times. The selectivity test method was the same as in example 2; the test results are: the selectivity to sudan II was 77.3% while the selectivity to sudan IV was 76.8%.

Comparative example 3

A method for preparing a SERS-active substrate, substantially the same as in example 2, except that in step (2), the molar ratio of propylene oxide to-NH-in HPEI is 3.16:10, to obtain a SERS-active substrate in which the alkyl groups on the modified hyperbranched polyethyleneimine account for 30% of the molar amount of-NH-in HPEI, and the azobenzene on the modified hyperbranched polyethyleneimine accounts for 30% of the molar amount of-NH-in HPEI.

4.13g of the SERS active substrate is respectively placed in 10mL of ethanol mixed solution of Sudan I and Sudan II and 10mL of ethanol mixed solution of Sudan III and Sudan IV, wherein the concentrations of the Sudan I and the Sudan II in the ethanol mixed solution of the Sudan I and the Sudan II are both 1.0 multiplied by 10^-7The concentration of Sudan III and Sudan IV in the ethanol mixed solution of mol/L, Sudan III and Sudan IV is 1.0 × 10^-7And (3) mol/L, stirring the solution for 2 hours, taking out, leaching with deionized water, blowing the solution with small-flow nitrogen, and then performing Raman spectrum detection under the following test conditions: an excitation light source is 532nm argon ion laser, the laser intensity is 1.0mW, the integration time is 0.03s, and the cycle is performed for 20 times. The selectivity test method was the same as in example 2; the test results are: the selectivity to sudan II was 86.9% while the selectivity to sudan IV was 87.3%.

Comparing comparative examples 1-3 with example 2, it can be seen that, in the process of increasing the content of AL (alkyl) from 10% to 40%, the SERS active substrate for highly selectively capturing sudan dye prepared by the present invention can simultaneously achieve highly selective capture responses to sudan II and sudan IV as the content of AL continuously increases, because the method of the present invention achieves highly selective capture of target guest molecules (sudan II and sudan IV) by amplifying subtle differences between competing guests according to the principle of supramolecular fuzzy recognition; when the alkyl on the modified hyperbranched polyethyleneimine accounts for more than 40 percent of the molar amount of-NH-in the HPEI, the competition difference can be sufficiently amplified, and the ideal selective capture effect is achieved.

Example 3

(1) adding epoxy azobenzene into a chloroform solution of HPEI with the number average molecular weight of 10000 to react to obtain HPEI @ AZ; wherein the concentration of the HPEI solution is 0.1g/mL, the molar ratio of epoxy azobenzene to-NH-in the HPEI is 3.16:10, the reaction temperature is 60 ℃, and the reaction time is 3 days;

(2) adding epoxypropane into a chloroform solution of HPEI @ AZ to react to obtain modified hyperbranched polyethyleneimine; wherein the concentration of the HPEI @ AZ solution is 0.1g/mL, the molar ratio of the propylene oxide to-NH-on the HPEI is 5.26:10, the reaction temperature is 25 ℃, and the reaction time is 3 days;

the prepared SERS active substrate for capturing the Sudan dye with high selectivity consists of an electrodeposited silver SERS active substrate with the mass ratio of 41.6:1 and modified hyperbranched polyethyleneimine on the surface of nano silver particles of the electrodeposited silver SERS active substrate; wherein, the alkyl on the modified hyperbranched polyethyleneimine accounts for 50 percent of the molar weight of-NH-in the HPEI, and the azobenzene on the modified hyperbranched polyethyleneimine accounts for 30 percent of the molar weight of-NH-in the HPEI.

4.13g of the SERS active substrate for capturing the Sudan dye with high selectivity is respectively placed in 10mL of ethanol mixed solution of Sudan I and Sudan II and 10mL of Sudan III and Sudan IIIIn the ethanol mixed solution of Sudan IV, the concentrations of Sudan I and Sudan II in the ethanol mixed solution of Sudan I and Sudan II are both 1.0 × 10^-7The concentration of Sudan III and Sudan IV in the ethanol mixed solution of mol/L, Sudan III and Sudan IV is 1.0 × 10^-7And (3) mol/L, stirring the solution for 2 hours, taking out, leaching with deionized water, blowing the solution with small-flow nitrogen, and then performing Raman spectrum detection under the following test conditions: an excitation light source is 532nm argon ion laser, the laser intensity is 1.0mW, the integration time is 0.03s, and the cycle is performed for 20 times.

The selective test method comprises the following steps: firstly, the SERS active substrate for capturing the Sudan dye with high selectivity is tested to have the concentration of 1.0 multiplied by 10 under the same condition^-7Raman spectra of single-component ethanol solutions of Sudan I, Sudan II, Sudan III and Sudan IV in mol/L (namely, only replacing the mixed solution with the single-component ethanol solution, and keeping consistent dye concentration, solution volume, substrate quality, Raman test conditions and the like); and then determining the content of each of Sudan I, Sudan II, Sudan III and Sudan IV in the mixed solution on the surface of the active substrate by comparing the Raman characteristic peak intensities of the ethanol mixed solution and the corresponding single-component solution, thereby converting the selectivity of the substrate to the target guest molecule. The test results are: the selectivity to sudan II was 99% while the selectivity to sudan IV was 98.9%.

As can be seen from fig. 2, the raman characteristic peak of sudan III gradually decreased as the AL content increased from 20% to 40%, indicating that the substrate had an increased selective capture capacity for sudan IV. When the content of AL is 40%, the Raman characteristic signal peak of Sudan III can not be basically detected; the AL content is further improved, and still no characteristic signal peak of Sudan III is detected, which indicates that the ideal AL content range is 40-50%.

Example 4

(1) adding epoxy azobenzene into a chloroform solution of HPEI with the number average molecular weight of 5000 to react to obtain HPEI @ AZ; wherein the concentration of the HPEI solution is 0.5g/mL, the molar ratio of epoxy azobenzene to-NH-in the HPEI is 3.16:10, the reaction temperature is 50 ℃, and the reaction time is 4 days;

(2) adding epoxypropane into a chloroform solution of HPEI @ AZ to react to obtain modified hyperbranched polyethyleneimine; wherein the concentration of the HPEI @ AZ solution is 0.5g/mL, the molar ratio of the propylene oxide to-NH-on the HPEI is 4.21:10, the reaction temperature is 20 ℃, and the reaction time is 4 days;

(3) then placing the electrodeposited silver SERS active substrate prepared in the embodiment 1 into a chloroform solution of modified hyperbranched polyethyleneimine to perform a coordination reaction to prepare a high-selectivity SERS active substrate for capturing Sudan dye; the concentration of the modified hyperbranched polyethyleneimine solution is 1g/mL, the mass ratio of the electrodeposited silver SERS active substrate to the modified hyperbranched polyethyleneimine in the solution is 10:1, and the coordination reaction time is 4 hours;

the prepared SERS active substrate for capturing the Sudan dye with high selectivity consists of an electrodeposited silver SERS active substrate with the mass ratio of 62.5:1 and modified hyperbranched polyethyleneimine on the surface of nano silver particles of the electrodeposited silver SERS active substrate; wherein azobenzene on the modified hyperbranched polyethyleneimine accounts for 30% of the molar amount of-NH-in the HPEI, and alkyl on the modified hyperbranched polyethyleneimine accounts for 40% of the molar amount of-NH-in the HPEI.

4.09g of the SERS active substrate for capturing the Sudan dye with high selectivity is respectively placed in 10mL of ethanol mixed solution of Sudan I and Sudan II and 10mL of ethanol mixed solution of Sudan III and Sudan IV, and the concentrations of the Sudan I and the Sudan II in the ethanol mixed solution of the Sudan I and the Sudan II are both 1.0 multiplied by 10^-5The concentration of Sudan III and Sudan IV in the ethanol mixed solution of mol/L, Sudan III and Sudan IV is 1.0 × 10^-5And (3) mol/L, stirring the solution for 2 hours, taking out, leaching with deionized water, blowing the solution with small-flow nitrogen, and then performing Raman spectrum detection under the following test conditions: an excitation light source is 532nm argon ion laser, the laser intensity is 1.0mW, the integration time is 0.03s, and the cycle is performed for 20 times.

The selective test method comprises the following steps: firstly, the SERS active substrate for capturing the Sudan dye with high selectivity is tested to have the concentration of 1.0 multiplied by 10 under the same condition^-5One-component ethanol of Sudan I, Sudan II, Sudan III and Sudan IV in mol/LThe Raman spectrum of the solution (namely, the mixed solution is replaced by a single-component ethanol solution, and the concentration of the dye, the volume of the solution, the quality of the substrate, the Raman test conditions and the like are kept consistent); and then determining the content of each of Sudan I, Sudan II, Sudan III and Sudan IV in the mixed solution on the surface of the active substrate by comparing the Raman characteristic peak intensities of the ethanol mixed solution and the corresponding single-component solution, thereby converting the selectivity of the substrate to the target guest molecule. The test results are: the selectivity to sudan II was 99.1%, while the selectivity to sudan IV was 99%.

Example 5

(1) adding epoxy azobenzene into a chloroform solution of HPEI with the number average molecular weight of 5000 to react to obtain HPEI @ AZ; wherein the concentration of the HPEI solution is 0.5g/mL, the molar ratio of epoxy azobenzene to-NH-in the HPEI is 1.05:10, the reaction temperature is 50 ℃, and the reaction time is 4 days;

the prepared SERS active substrate for capturing the Sudan dye with high selectivity consists of an electrodeposited silver SERS active substrate with the mass ratio of 62.5:1 and modified hyperbranched polyethyleneimine on the surface of nano silver particles of the electrodeposited silver SERS active substrate; wherein azobenzene on the modified hyperbranched polyethyleneimine accounts for 10% of the molar amount of-NH-in the HPEI, and alkyl on the modified hyperbranched polyethyleneimine accounts for 40% of the molar amount of-NH-in the HPEI.

The selective test method comprises the following steps: firstly, the SERS active substrate for capturing the Sudan dye with high selectivity is tested to have the concentration of 1.0 multiplied by 10 under the same condition^-5Raman spectra of single-component ethanol solutions of Sudan I, Sudan II, Sudan III and Sudan IV in mol/L (namely, only replacing the mixed solution with the single-component ethanol solution, and keeping consistent dye concentration, solution volume, substrate quality, Raman test conditions and the like); and then determining the content of each of Sudan I, Sudan II, Sudan III and Sudan IV in the mixed solution on the surface of the active substrate by comparing the Raman characteristic peak intensities of the ethanol mixed solution and the corresponding single-component solution, thereby converting the selectivity of the substrate to the target guest molecule. The test results are: the selectivity to sudan II was 98.9%, while the selectivity to sudan IV was 99.1%.

Example 6

(2) adding epoxypropane into a chloroform solution of HPEI @ AZ to react to obtain modified hyperbranched polyethyleneimine; wherein the concentration of the HPEI @ AZ solution is 0.5g/mL, the molar ratio of the propylene oxide to-NH-on the HPEI is 5.26:10, the reaction temperature is 20 ℃, and the reaction time is 4 days;

the prepared SERS active substrate for capturing the Sudan dye with high selectivity consists of an electrodeposited silver SERS active substrate with the mass ratio of 62.5:1 and modified hyperbranched polyethyleneimine on the surface of nano silver particles of the electrodeposited silver SERS active substrate; wherein azobenzene on the modified hyperbranched polyethyleneimine accounts for 30% of the molar amount of-NH-in the HPEI, and alkyl on the modified hyperbranched polyethyleneimine accounts for 50% of the molar amount of-NH-in the HPEI.

4.09g of the SERS active substrate for capturing the Sudan dye with high selectivity is respectively placed in 10mL of ethanol mixed solution of Sudan I and Sudan II and 10mL of ethanol mixed solution of Sudan III and Sudan IV, and the concentrations of the Sudan I and the Sudan II in the ethanol mixed solution of the Sudan I and the Sudan II are both 2.4 multiplied by 10^-10The concentration of Sudan III and Sudan IV in the ethanol mixed solution of mol/L, Sudan III and Sudan IV is 1.6 multiplied by 10^-10And (3) mol/L, stirring the solution for 2 hours, taking out, leaching with deionized water, blowing the solution with small-flow nitrogen, and then performing Raman spectrum detection under the following test conditions: an excitation light source is 532nm argon ion laser, the laser intensity is 2.0mW, the integration time is 0.03s, and the cycle is performed for 20 times.

The selective test method comprises the following steps: firstly, the SERS active substrate for capturing the Sudan dye with high selectivity is tested to respectively capture the Sudan I (the concentration is 2.4 multiplied by 10) under the same condition^-10mol/L), Sudan II (concentration of 2.4X 10)^-10mol/L), Sudan III (concentration 1.6X 10)^-10mol/L) and Sudan IV (concentration 1.6X 10)^-10mol/L) of the single-component ethanol solution (i.e., only replacing the mixed solution with the single-component ethanol solution, dye concentration, solution volume, substrate quality, Raman test conditionsEtc. all remain consistent); and then determining the content of each of Sudan I, Sudan II, Sudan III and Sudan IV in the mixed solution on the surface of the active substrate by comparing the Raman characteristic peak intensities of the ethanol mixed solution and the corresponding single-component solution, thereby converting the selectivity of the substrate to the target guest molecule. The test results are: the selectivity to sudan II was 98.9%, while the selectivity to sudan IV was 99.0%.

Example 7

4.09g of the SERS active substrate for capturing the Sudan dye with high selectivity is respectively placed in 10mL of ethanol of Sudan I and Sudan II to be mixedThe concentration of Sudan I and Sudan II in the solution and 10mL of the ethanol mixed solution of Sudan III and Sudan IV are both 2.5 × 10^-10The concentration of Sudan III and Sudan IV in the ethanol mixed solution of mol/L, Sudan III and Sudan IV is 1.8 multiplied by 10^-10And (3) mol/L, stirring the solution for 2 hours, taking out, leaching with deionized water, blowing the solution with small-flow nitrogen, and then performing Raman spectrum detection under the following test conditions: an excitation light source is 532nm argon ion laser, the laser intensity is 2.0mW, the integration time is 0.03s, and the cycle is performed for 20 times.

The selective test method comprises the following steps: firstly, the SERS active substrate for capturing the Sudan dye with high selectivity is tested to respectively capture the Sudan I (the concentration is 2.5 multiplied by 10) under the same condition^-10mol/L), Sudan II (concentration of 2.5X 10)^-10mol/L), Sudan III (concentration of 1.8X 10)^-10mol/L) and Sudan IV (concentration 1.8X 10)^-10mol/L) of the single-component ethanol solution (i.e., only replacing the mixed solution with the single-component ethanol solution, the concentration of the dye, the volume of the solution, the quality of the substrate, the Raman test conditions, etc. are all kept consistent); and then determining the content of each of Sudan I, Sudan II, Sudan III and Sudan IV in the mixed solution on the surface of the active substrate by comparing the Raman characteristic peak intensities of the ethanol mixed solution and the corresponding single-component solution, thereby converting the selectivity of the substrate to the target guest molecule. The test results are: the selectivity to sudan II was 98.8%, while the selectivity to sudan IV was 98.9%.

Example 8

(1) adding epoxy azobenzene into a chloroform solution of HPEI with the number average molecular weight of 20000 to react to obtain HPEI @ AZ; wherein the concentration of the HPEI solution is 0.01g/mL, the molar ratio of epoxy azobenzene to-NH-in the HPEI is 3.16:10, the reaction temperature is 70 ℃, and the reaction time is 2 days;

(2) adding epoxypropane into a chloroform solution of HPEI @ AZ to react to obtain modified hyperbranched polyethyleneimine; wherein the concentration of the HPEI @ AZ solution is 0.05g/mL, the molar ratio of the propylene oxide to-NH-on the HPEI is 5.26:10, the reaction temperature is 40 ℃, and the reaction time is 2 days;

(3) then placing the electrodeposited silver SERS active substrate prepared in the embodiment 1 into a chloroform solution of modified hyperbranched polyethyleneimine to perform a coordination reaction to prepare a high-selectivity SERS active substrate for capturing Sudan dye; the concentration of the modified hyperbranched polyethyleneimine solution is 0.1g/mL, the mass ratio of the electrodeposited silver SERS active substrate to the modified hyperbranched polyethyleneimine in the solution is 5:1, and the coordination reaction time is 2 hours;

the prepared SERS active substrate for capturing the Sudan dye with high selectivity consists of an electrodeposited silver SERS active substrate with the mass ratio of 28.5:1 and modified hyperbranched polyethyleneimine on the surface of nano silver particles of the electrodeposited silver SERS active substrate; wherein azobenzene on the modified hyperbranched polyethyleneimine accounts for 30% of the molar amount of-NH-in the HPEI, and alkyl on the modified hyperbranched polyethyleneimine accounts for 50% of the molar amount of-NH-in the HPEI.

4.17g of the SERS active substrate for capturing the Sudan dye with high selectivity is respectively placed in 10mL of ethanol mixed solution of Sudan I and Sudan II and 10mL of ethanol mixed solution of Sudan III and Sudan IV, and the concentrations of the Sudan I and the Sudan II in the ethanol mixed solution of the Sudan I and the Sudan II are both 1.0 multiplied by 10^-5The concentration of Sudan III and Sudan IV in the ethanol mixed solution of mol/L, Sudan III and Sudan IV is 1.0 × 10^-5And (3) mol/L, stirring the solution for 2 hours, taking out, leaching with deionized water, blowing the solution with small-flow nitrogen, and then performing Raman spectrum detection under the following test conditions: an excitation light source is 532nm argon ion laser, the laser intensity is 1.0mW, the integration time is 0.03s, and the cycle is performed for 20 times.

The selective test method comprises the following steps: firstly, the SERS active substrate for capturing the Sudan dye with high selectivity is tested to have the concentration of 1.0 multiplied by 10 under the same condition^-5The raman spectra of the single-component ethanol solutions of sudan I, sudan II, sudan III and sudan IV (i.e. only the above mixed solution is replaced by the single-component ethanol solution, and the dye concentration, the solution volume, the substrate quality, the raman test conditions, etc. are consistent); then determining the mixed solution by comparing the Raman characteristic peak intensities of the ethanol mixed solution and the corresponding single-component solutionThe content of each of Sudan I, Sudan II, Sudan III and Sudan IV in the liquid on the surface of the active substrate, thereby converting the selectivity of the substrate to the target guest molecule. The test results are: the selectivity to sudan II was 99.1%, while the selectivity to sudan IV was 98.9%.

Example 9

(1) adding epoxy azobenzene into a chloroform solution of HPEI with the number average molecular weight of 20000 to react to obtain HPEI @ AZ; wherein the concentration of the HPEI solution is 0.01g/mL, the molar ratio of epoxy azobenzene to-NH-in the HPEI is 2.10:10, the reaction temperature is 70 ℃, and the reaction time is 2 days;

the prepared SERS active substrate for capturing the Sudan dye with high selectivity consists of an electrodeposited silver SERS active substrate with the mass ratio of 28.5:1 and modified hyperbranched polyethyleneimine on the surface of nano silver particles of the electrodeposited silver SERS active substrate; wherein azobenzene on the modified hyperbranched polyethyleneimine accounts for 20% of the molar weight of-NH-in the HPEI, and alkyl on the modified hyperbranched polyethyleneimine accounts for 50% of the molar weight of-NH-in the HPEI.

4.17g of the SERS active substrate for capturing the Sudan dye with high selectivity is respectively placed in 10mL of ethanol mixed solution of Sudan I and Sudan II and 10mL of ethanol mixed solution of Sudan III and Sudan IV, and the concentrations of the Sudan I and the Sudan II in the ethanol mixed solution of the Sudan I and the Sudan II are respectively1.0×10^-5The concentration of Sudan III and Sudan IV in the ethanol mixed solution of mol/L, Sudan III and Sudan IV is 1.0 × 10^-5And (3) mol/L, stirring the solution for 2 hours, taking out, leaching with deionized water, blowing the solution with small-flow nitrogen, and then performing Raman spectrum detection under the following test conditions: an excitation light source is 532nm argon ion laser, the laser intensity is 1.0mW, the integration time is 0.03s, and the cycle is performed for 20 times.

The selective test method comprises the following steps: firstly, the SERS active substrate for capturing the Sudan dye with high selectivity is tested to have the concentration of 1.0 multiplied by 10 under the same condition^-5The raman spectra of the single-component ethanol solutions of sudan I, sudan II, sudan III and sudan IV (i.e. only the above mixed solution is replaced by the single-component ethanol solution, and the dye concentration, the solution volume, the substrate quality, the raman test conditions, etc. are consistent); and then determining the content of each of Sudan I, Sudan II, Sudan III and Sudan IV in the mixed solution on the surface of the active substrate by comparing the Raman characteristic peak intensities of the ethanol mixed solution and the corresponding single-component solution, thereby converting the selectivity of the substrate to the target guest molecule. The test results are: the selectivity to sudan II was 99.0% while the selectivity to sudan IV was 99.1%.

Example 10

(2) adding epoxypropane into a chloroform solution of HPEI @ AZ to react to obtain modified hyperbranched polyethyleneimine; wherein the concentration of the HPEI @ AZ solution is 0.05g/mL, the molar ratio of the propylene oxide to-NH-on the HPEI is 4.21:10, the reaction temperature is 40 ℃, and the reaction time is 2 days;

the prepared SERS active substrate for capturing the Sudan dye with high selectivity consists of an electrodeposited silver SERS active substrate with the mass ratio of 28.5:1 and modified hyperbranched polyethyleneimine on the surface of nano silver particles of the electrodeposited silver SERS active substrate; wherein azobenzene on the modified hyperbranched polyethyleneimine accounts for 30% of the molar amount of-NH-in the HPEI, and alkyl on the modified hyperbranched polyethyleneimine accounts for 40% of the molar amount of-NH-in the HPEI.

4.17g of the SERS active substrate for capturing the Sudan dye with high selectivity is respectively placed in 10mL of ethanol mixed solution of Sudan I and Sudan II and 10mL of ethanol mixed solution of Sudan III and Sudan IV, and the concentrations of the Sudan I and the Sudan II in the ethanol mixed solution of the Sudan I and the Sudan II are both 2.8 multiplied by 10^-10The concentration of Sudan III and Sudan IV in the ethanol mixed solution of mol/L, Sudan III and Sudan IV is 1.9 multiplied by 10^-10And (3) mol/L, stirring the solution for 2 hours, taking out, leaching with deionized water, blowing the solution with small-flow nitrogen, and then performing Raman spectrum detection under the following test conditions: an excitation light source is 532nm argon ion laser, the laser intensity is 2.0mW, the integration time is 0.03s, and the cycle is performed for 20 times.

The selective test method comprises the following steps: firstly, the SERS active substrate for capturing the Sudan dye with high selectivity is tested to respectively capture the Sudan I (the concentration is 2.8 multiplied by 10) under the same condition^-10mol/L), Sudan II (concentration of 2.8X 10)^-10mol/L), Sudan III (concentration 1.9X 10)^-10mol/L) and Sudan IV (concentration 1.9X 10)^-10mol/L) of the single-component ethanol solution (i.e., only replacing the mixed solution with the single-component ethanol solution, the concentration of the dye, the volume of the solution, the quality of the substrate, the Raman test conditions, etc. are all kept consistent); then, the content of Sudan I, Sudan II, Sudan III and Sudan IV in the mixed solution on the surface of an active substrate is determined by comparing the Raman characteristic peak intensity of the ethanol mixed solution with that of the corresponding single-component solution, so as to convert the content of the substrate on the target guest moleculeAnd (4) selectivity. The test results are: the selectivity to sudan II was 98.9%, while the selectivity to sudan IV was 99.0%.

Example 11

4.17g of the SERS active substrate for capturing the Sudan dye with high selectivity is respectively placed in 10mL of ethanol mixed solution of Sudan I and Sudan II and 10mL of ethanol mixed solution of Sudan III and Sudan IV, and the concentrations of the Sudan I and the Sudan II in the ethanol mixed solution of the Sudan I and the Sudan II are both 2.6 multiplied by 10^-10The concentration of Sudan III and Sudan IV in the ethanol mixed solution of mol/L, Sudan III and Sudan IV is 1.8 multiplied by 10^-10moland/L, stirring the solution for 2 hours, taking out, leaching with deionized water, blowing the solution with small-flow nitrogen, and performing Raman spectrum detection under the following test conditions: an excitation light source is 532nm argon ion laser, the laser intensity is 2.0mW, the integration time is 0.03s, and the cycle is performed for 20 times.

The selective test method comprises the following steps: firstly, the SERS active substrate for capturing the Sudan dye with high selectivity is tested to respectively capture the Sudan I (the concentration is 2.6 multiplied by 10) under the same condition^-10mol/L), Sudan II (concentration of 2.6X 10)^-10mol/L), Sudan III (concentration of 1.8X 10)^-10mol/L) and Sudan IV (concentration 1.8X 10)^-10mol/L) of the single-component ethanol solution (i.e., only replacing the mixed solution with the single-component ethanol solution, the concentration of the dye, the volume of the solution, the quality of the substrate, the Raman test conditions, etc. are all kept consistent); and then determining the content of each of Sudan I, Sudan II, Sudan III and Sudan IV in the mixed solution on the surface of the active substrate by comparing the Raman characteristic peak intensities of the ethanol mixed solution and the corresponding single-component solution, thereby converting the selectivity of the substrate to the target guest molecule. The test results are: the selectivity to sudan II was 99.1%, while the selectivity to sudan IV was 98.9%.

Claims

1. The SERS active substrate for capturing Sudan dye with high selectivity is characterized in that: the SERS active substrate consists of an electrodeposited silver SERS active substrate and modified hyperbranched polyethyleneimine deposited on the surface of nano silver particles of the substrate;

the mass ratio of the electrodeposited silver SERS active substrate to the modified hyperbranched polyethyleneimine is 62.5-28.5: 1;

the modified hyperbranched polyethyleneimine is prepared by grafting azobenzene and alkyl on HPEI;

the alkyl on the modified hyperbranched polyethyleneimine accounts for 40-50% of the molar amount of-NH-in the HPEI.

2. The SERS-active substrate for highly selective capture of sudan dyes according to claim 1, wherein azobenzene on the modified hyperbranched polyethyleneimine accounts for 10% to 30% of the molar amount of-NH "in the HPEI.

3. The SERS active substrate for capturing Sudan dye with high selectivity as claimed in claim 2, wherein the number average molecular weight of the HPEI is 5000-20000.

4. The method for preparing a high-selectivity Sudan dye-capturing SERS active substrate as claimed in claim 3, wherein the high-selectivity Sudan dye-capturing SERS active substrate has a Sudan II selectivity of 98.8% -99.1% in a mixed solution of Sudan I and Sudan II, and a Sudan IV selectivity of 98.9% -99.1% in a mixed solution of Sudan III and Sudan IV.

5. The method for preparing a SERS-active substrate capable of capturing Sudan dye with high selectivity as claimed in claim 4, wherein the concentration of all mixed solutions is 1.6 x 10^-10～1.0×10^-5mol/L; the solvent of all mixed solutions was ethanol.

6. A method for preparing the SERS active substrate for capturing Sudan dye with high selectivity according to any one of claims 1 to 5, which is characterized in that: firstly, adding epoxy azobenzene into an HPEI solution to react to obtain HPEI @ AZ; adding epoxypropane into the HPEI @ AZ solution to react to obtain modified hyperbranched polyethyleneimine; finally, placing the electrodeposited silver SERS active substrate in a modified hyperbranched polyethyleneimine solution for carrying out coordination reaction to prepare a high-selectivity SERS active substrate for capturing Sudan dye;

the mass ratio of the electrodeposited silver SERS active substrate to the modified hyperbranched polyethyleneimine in the solution before coordination reaction is 10-5: 1;

when the propylene oxide is added for reaction, the molar ratio of the propylene oxide to-NH-on the HPEI is 4.21-5.26: 10.

7. The method for preparing a SERS active substrate capable of capturing Sudan dye with high selectivity as claimed in claim 6, wherein the solvent of the HPEI solution, the HPEI @ AZ solution and the modified hyperbranched polyethyleneimine solution is chloroform.

8. The method for preparing a SERS active substrate capable of capturing Sudan dye with high selectivity as claimed in claim 7, wherein the concentration of HPEI solution is 0.01-0.5 g/mL, and the molar ratio of epoxy azobenzene to-NH-on HPEI is 1.05-3.16: 10 when epoxy azobenzene is added for reaction; and adding epoxy azobenzene to react at the temperature of 50-70 ℃ for 2-4 days.

9. The method for preparing a SERS active substrate for capturing Sudan dye with high selectivity as claimed in claim 8, wherein the concentration of HPEI @ AZ solution is 0.05-0.5 g/mL, the temperature for adding propylene oxide to carry out reaction is 20-40 ℃, and the time is 2-4 days.

10. The preparation method of the SERS active substrate for capturing Sudan dye with high selectivity according to claim 9, wherein the concentration of the modified hyperbranched polyethyleneimine solution is 0.1-1 g/mL, and the coordination reaction time is 2-4 h.