Preparation method and application of magnetic enrichment composite SERS (Surface Enhanced Raman Scattering) detection chip

Abstract

The invention discloses a preparation method and application of a magnetic enrichment composite SERS (Surface Enhanced Raman Scattering) detection chip, gold nanoparticles are electrostatically adsorbed on the surface of a magnetic ferroferric oxide nanoring, the prepared material is subjected to cyclodextrin modification, nanogaps among the gold nanoparticles form hot spots, a local electromagnetic field enhancement effect is generated, and the magnetic enrichment composite SERS detection chip is obtained. The cyclodextrin molecules adsorb PAHs in the environment through a hydrophobic effect and are fixed in an electromagnetic field enhancement area, amplification of Raman signals is achieved, the magnetic material serves as a carrier, aggregation of gold nanoparticles can be effectively prevented, SERS signals can be further enhanced through a magnetic enrichment effect, and therefore, the method has the advantages that the method is simple, and the application prospect is wide. The high-sensitivity and high-selectivity detection of PAHs in the tail gas of the engineering machinery vehicle is realized by constructing the magnetic composite SERS nano sensing chip.

Description

Technical Field

[0001] The invention relates to the technical field of SERS detection, and in particular to a method for preparing a magnetic enrichment composite SERS detection chip. Background Art

[0002] Diesel engines are widely used in various construction machinery due to their excellent thermal efficiency and fuel economy, but the amount of gaseous pollutants and particulate matter in diesel engine exhaust emissions far exceeds that of gasoline engines. These exhaust gases are quite complex, containing particulate matter and various toxic gaseous substances, such as heavy metals, elemental carbon, organic carbon, inorganic salts, etc. Among them, polycyclic aromatic hydrocarbons (PAHs) are an important component in the exhaust of construction machinery vehicles. PAHs are mainly produced by incomplete combustion of organic matter. They have stable chemical properties and have significant carcinogenic, teratogenic and mutagenic properties. These pollutants pose a serious threat to human health and the ecological environment.

[0003] As an efficient and sensitive detection method, SERS technology has the advantages of simple operation, rich spectral fingerprint information, high sensitivity and no interference from water. Therefore, it is widely used in the field of pollutant analysis. For the detection of PAHs, SERS technology also shows great potential.

[0004] To achieve this goal, the key is to construct a SERS substrate with a strong electromagnetic field enhancement effect and ensure that PAHs can be effectively adsorbed onto the substrate to improve the sensitivity of detection. However, for PAHs with a benzene ring structure, since they have fewer substituents that can undergo chemical reactions, it becomes very difficult to directly fix them near the substrate through covalent bonds. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing a magnetic enrichment composite SERS detection chip to solve the problems raised in the above background technology.

[0006] To achieve the above object, the present invention provides the following technical solution: a method for preparing a magnetic enrichment composite SERS detection chip, comprising the following steps:

[0007] S1. Preparation of ferric oxide nanorings: dissolving anhydrous ferric chloride, ammonium dihydrogen phosphate and anhydrous sodium sulfate in deionized water to obtain a mixed solution, transferring the mixed solution to a stainless steel autoclave, heating, cooling and washing, and obtaining ferric oxide nanoring powder after drying;

[0008] S2. Preparation of ferroferric oxide nanorings: placing ferroferric oxide nanoring powder into a tube furnace for vacuum treatment, then calcining at 450° C. for 10 hours in a hydrogen atmosphere, and finally cooling to room temperature to obtain ferroferric oxide nanorings;

[0009] S3, preparation of gold nanoparticles: ultrapure water and chloroauric acid solution were added to a round-bottom flask, a condensation reflux device was set up and heated to boiling, then sodium citrate solution was added, and the mixture was boiled for 20 minutes, and the heating was stopped and stirred to room temperature to obtain gold nanoparticles;

[0010] S4. Preparation of amino-functionalized ferroferric oxide: adding ferroferric oxide nanorings to anhydrous ethanol, subjecting to ultrasonic treatment for 5 minutes, then adding 3-aminopropyltriethoxysilane, reacting under ultrasonic stirring and mechanical stirring, washing twice by magnetic separation, and redispersing in deionized water to obtain amino-functionalized ferroferric oxide;

[0011] S5. Preparation of gold nanoparticles / amino-functionalized ferroferric oxide: adding amino-functionalized ferroferric oxide to gold nanoparticles, stirring for 3 hours, washing by centrifugation, and redispersing in deionized water to obtain gold nanoparticles / amino-functionalized ferroferric oxide;

[0012] S6. Prepare a thiol-cyclodextrin-gold nanomagnetic enrichment SERS detection chip: prepare a thiol-cyclodextrin solution, add gold nanoparticles / amino-functionalized ferrosoferric oxide thereto and incubate for 30 minutes, then centrifuge and wash to remove unmodified thiol-cyclodextrin, and obtain a thiol-cyclodextrin-gold nanomagnetic enrichment SERS detection chip.

[0013] Preferably, in S1, the mixed solution is heated at 220° C. for 48 hours in a stainless steel autoclave, washed after cooling and dried at 80° C. for 6 hours.

[0014] Preferably, in S3, the particle size of the gold nanoparticles obtained is 16 nm.

[0015] Preferably, in S1, the inner diameter of a single particle of the ferric oxide nano-ring powder is 66 nm, and the outer diameter is 36 nm.

[0016] Preferably, in S4, the ultrasonic stirring reaction time is 30 minutes, and the mechanical stirring time is continued for 6 hours.

[0017] Preferably, in S6, the volume of the configured thiol cyclodextrin is 10 mL, and the concentration of the solute is 1 μm.

[0018] Preferably, the structure and magnetism of the mercaptocyclodextrin-gold nanomagnetic enrichment SERS detection chip prepared by S1 to S6 are analyzed and characterized by SEM, TEM and XRD.

[0019] The present invention also provides an application of a magnetic enrichment composite SERS detection chip in PAHs detection, comprising the following steps:

[0020] S1. Use R6G and p-ATP as two probe molecules to evaluate the sensitivity of the mercaptocyclodextrin-gold nanomagnetic enrichment SERS detection chip to different PAHs by SERS detection, and calculate the detection limits of the corresponding PAHs, and calculate the linear relationship corresponding to the detection limits of each PAH;

[0021] S2, continue to use SERS detection, and detect the mercaptocyclodextrin-gold nanomagnetic enrichment SERS detection chip at different times to observe the spectral changes;

[0022] S3. Detect polycyclic aromatic hydrocarbons produced in the exhaust gas of construction machinery in simulated and actual environments, use mercaptocyclodextrin-gold nanomagnetic enrichment SERS detection chip to capture mixed aromatic hydrocarbons and use SERS to detect spectral changes.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. The present invention achieves physical enhancement by electrostatically adsorbing gold nanoparticles on the surface of magnetic ferroferric oxide nanorings and modifying the prepared material with cyclodextrin. The nanogaps between the gold nanoparticles form hot spots, which produce a local electromagnetic field enhancement effect. The cyclodextrin molecules adsorb PAHs in the environment through hydrophobic action and fix them in the electromagnetic field enhancement area, thereby amplifying their Raman signals.

[0025] 2. Magnetic materials as carriers can not only effectively prevent the aggregation of gold nanoparticles, but also further enhance the SERS signal through magnetic enrichment. Therefore, by constructing a magnetic composite SERS nanosensor chip, high-sensitivity and high-selectivity detection of PAHs in the exhaust of construction machinery vehicles is achieved, providing a simple, fast and sensitive method for dynamically capturing and detecting trace PAHs molecules and other volatile pollutants in the exhaust of construction machinery. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the preparation process of the magnetic enrichment composite SERS detection chip according to an embodiment of the present invention;

[0027] Figure 2 Schematic diagram of characterization of the mercaptocyclodextrin-gold nanomagnetic enrichment SERS detection chip by SEM, TEM and XRD in an embodiment of the present invention (Figure A: SEM image of gold nanoparticles; Figure B: SEM image of a large batch of gold nanoparticles; Figure C: SEM image of ferric oxide nanorings; Figure D: SEM image of ferric oxide nanorings; Figure E: TEM image of gold nanoparticles / amino-functionalized ferric oxide; Figure F: HRTEM image of gold nanoparticles / amino-functionalized ferric oxide);

[0028] Figure 3Schematic diagram of EDS images of O, Fe and Au in an embodiment of the present invention;

[0029] Figure 4 Schematic diagram of characterizing the mercaptocyclodextrin-gold nanomagnetic enrichment SERS detection chip by XRD in an embodiment of the present invention (Figure H: XRD images of amino-functionalized ferroferric oxide and gold nanoparticles / amino-functionalized ferroferric oxide; Figure I: hysteresis regression curves of amino-functionalized ferroferric oxide and gold nanoparticles / amino-functionalized ferroferric oxide);

[0030] Figure 5 The thiol cyclodextrin-gold nanomagnetic enrichment SERS detection chip in the embodiment of the present invention is used to capture mixed aromatic hydrocarbons and detect spectra using SERS (a: SERS spectrum of PAHs captured from automobile exhaust; b SERS spectrum obtained in the presence of anthracene, fluoranthene, pyrene and fluorene). DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] See also Figure 1-Figure 4 The embodiment of the present invention provides a method for preparing a magnetic enrichment composite SERS detection chip, comprising the following steps:

[0033] S1. Dissolve 0.81g of anhydrous ferric chloride, 0.0052g of ammonium dihydrogen phosphate and 0.019g of anhydrous sodium sulfate in 10mL of deionized water and transfer to a 250mL volumetric flask to make up the volume. Then transfer the mixed solution to a 100mL stainless steel autoclave, heat at 220°C for 48 hours, cool, wash and dry at 80°C for 6 hours to obtain ferric oxide nanoring powder;

[0034] S2. Preparation of ferroferric oxide nanorings: The ferroferric oxide nanoring powder was placed in a tube furnace for vacuum treatment, and then calcined at 450° C. for 10 hours in a hydrogen atmosphere [H2 / (H2+Ar)) 10 / 100], and finally cooled to room temperature to obtain ferroferric oxide nanorings;

[0035] S3. Preparation of gold nanoparticles: Add 200 mL of ultrapure water and 2.42 mL of 1% chloroauric acid solution into a 250 mL round-bottom flask, set up a condensation reflux device and heat to boiling, then add 3 mL of 1% sodium citrate solution, continue boiling for 20 minutes, stop heating and stir to room temperature to obtain gold nanoparticles with a diameter of about 16 nm;

[0036] S4. Preparation of amino-functionalized ferroferric oxide: 6 mg of ferroferric oxide nanorings were added to 4 mL of anhydrous ethanol, and ultrasonic treatment was performed for 5 minutes. Subsequently, 0.2 mL of 3-aminopropyltriethoxysilane was added, and the mixture was reacted under ultrasonic stirring for 30 minutes. Mechanical stirring was continued for 6 hours, and the mixture was washed twice by magnetic separation, and redispersed in 3 mL of deionized water to obtain amino-functionalized ferroferric oxide.

[0037] S5. Preparation of gold nanoparticles / amino-functionalized ferroferric oxide: adding amino-functionalized ferroferric oxide to gold nanoparticles, stirring for 3 hours, washing by centrifugation, and redispersing in deionized water to obtain gold nanoparticles / amino-functionalized ferroferric oxide;

[0038] S6. Magnetic enrichment composite SERS detection chip modified with thiol cyclodextrin: prepare thiol cyclodextrin into a solution with a volume of 10 ml and a solute concentration of 1 μm, add magnetic gold nanoparticles / amino-functionalized ferrosoferric oxide and incubate for 30 minutes, and remove the unmodified thiol cyclodextrin by centrifugal washing to obtain the thiol cyclodextrin-gold nanomagnetic enrichment SERS detection chip.

[0039] Furthermore, the structure and magnetism of the mercaptocyclodextrin-gold nanomagnetic enrichment SERS detection chip prepared by S1 to S6 were analyzed and characterized by SEM, TEM and XRD.

[0040] Among them, gold nanoparticles with uniform size and a diameter of about 16 nm were obtained by trisodium citrate reduction method (refer to Figure 2 A and Figure 2 B).

[0041] The Fe2O3 nanoring powder was prepared by using anhydrous ferric chloride, ammonium dihydrogen phosphate and anhydrous sodium sulfate and hydrothermally treating at 220 °C for 48 h (ref. Figure 2 C), with an inner diameter of about 66 nm, an outer diameter of about 36 nm, and a height of about 110 nm. After further calcination in a hydrogen atmosphere for 10 hours, ferroferric oxide nanorings were obtained, and their structure was not destroyed at high temperatures (refer to Figure 2 D).

[0042] The ferroferric oxide nanorings were added to anhydrous ethanol and subjected to ultrasonic treatment, and then reacted with 3-aminopropyltriethoxysilane to obtain amino-functionalized ferroferric oxide. The functionalized ferroferric oxide was then mixed with the pre-prepared gold nanoparticles, mechanically stirred, centrifuged and washed, and finally dispersed in deionized water to obtain gold nanoparticles / amino-functionalized ferroferric oxide.

[0043] Through TEM images (ref. Figure 2 E), it can be seen that the gold nanoparticles are successfully modified on the inner and outer surfaces of the nanoring and are distributed in a single layer, and the size and morphology have not changed. Further HAADF characterization and EDS elemental imaging (refer to Figure 2 F and Figure 3 ) also confirmed the successful synthesis of gold nanoparticles / amino-functionalized ferroferric oxide.

[0044] In addition, XRD data (refer to Figure 4 H) shows that the synthesized amino-functionalized ferroferric oxide is a pure ferroferric oxide phase, and the saturation magnetization intensity is detected (refer to Figure 4 I) shows that the saturation magnetization intensity of gold nanoparticles / amino-functionalized ferroferric oxide is 42.3emu / g, indicating that even Au-coated R-Fe3O4 still exhibits good magnetic response. Due to the higher content, gold nanoparticles / amino-functionalized ferroferric oxide can be quickly separated from the sample solution within 30 seconds after an external magnetic field is applied.

[0045] The present invention also provides an application of a magnetic enrichment composite SERS detection chip in PAHs detection, comprising the following steps:

[0046] S1. Use R6G and p-ATP as two probe molecules to evaluate the sensitivity of the mercaptocyclodextrin-gold nanomagnetic enrichment SERS detection chip to different PAHs by SERS detection, and calculate the detection limits of the corresponding PAHs, and calculate the linear relationship corresponding to the detection limits of each PAH;

[0047] S2, continue to use SERS detection, and detect the mercaptocyclodextrin-gold nanomagnetic enrichment SERS detection chip at different times to observe the spectral changes;

[0048] S3. Detect polycyclic aromatic hydrocarbons produced in the exhaust gas of construction machinery in simulated and actual environments, use mercaptocyclodextrin-gold nanomagnetic enrichment SERS detection chip to capture mixed aromatic hydrocarbons and use SERS to detect spectral changes.

[0049] In another embodiment, when the simulated environment and the actual environment are detected, PAHs often appear in the form of a mixture. Therefore, in the actual detection, the PAHs mixture in the tail gas is collected by using an acetone solution, and the SERS spectrum of the extract is recorded on a mercaptocyclodextrin-gold nanomagnetic enrichment SERS detection chip by magnetic enrichment (refer to Figure 5 a) The results show that the acetone solution has almost no SERS sensing signal on the mercaptocyclodextrin-gold nanomagnetic enrichment SERS detection chip, which means that the acetone solution does not interfere with the actual detection.

[0050] Furthermore, in order to evaluate the effectiveness of the mercaptocyclodextrin-gold nanomagnetic enrichment SERS detection chip in SERS detection of PAHs mixture, anthracene, pyrene, fluoranthene and fluorene were added to the acetone solution, and the final concentration of the above four PAHs was 1.0×10-5M. According to the SERS spectrum (refer to Figure 5 b), the key SERS peaks that can distinguish each PAHs from the complex mixture can be observed. Figure 5 The SERS spectra showed that the mercaptocyclodextrin-gold nanomagnetic enrichment SERS detection chip can directly detect each PAH molecule in a complex system.

[0051] In summary: The present invention achieves highly sensitive and highly selective detection of PAHs in the exhaust of construction machinery vehicles by electrostatically adsorbing gold nanoparticles on the surface of magnetic ferroferric oxide nanorings and modifying the prepared materials with cyclodextrin. Hot spots are formed by the nanogaps between the gold nanoparticles, which produce local electromagnetic field enhancement, thereby achieving physical enhancement. Cyclodextrin molecules adsorb PAHs in the environment through hydrophobic interaction and fix them in the electromagnetic field enhancement area, thereby achieving the amplification of their Raman signals.

[0052] In addition, the chemical reaction between the surface of nanomaterials and adsorbed molecules will also produce a chemical enhancement effect. Magnetic materials as carriers can not only effectively prevent the aggregation of gold nanoparticles, but also further enhance the SERS signal through magnetic enrichment. Therefore, by constructing a magnetic composite SERS nanosensor chip as a signal sensing enhancement unit for the engineering machinery exhaust detection system, high-sensitivity and high-selectivity detection of PAHs in the exhaust of engineering machinery vehicles is achieved, providing a simple, fast and sensitive method for dynamically capturing and detecting trace PAHs molecules and other volatile pollutants in the exhaust of engineering machinery.

[0053] Parts not involved in the present invention are the same as the prior art or can be implemented by the prior art. Although the embodiments of the present invention have been shown and described, it is understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a magnetic enrichment composite SERS detection chip, characterized in that: The following steps are involved: S1. Preparation of ferric oxide nanorings: dissolving anhydrous ferric chloride, ammonium dihydrogen phosphate and anhydrous sodium sulfate in deionized water to obtain a mixed solution, transferring the mixed solution to a stainless steel autoclave, heating, cooling and washing, and obtaining ferric oxide nanoring powder after drying; S2. Preparation of ferroferric oxide nanorings: placing ferroferric oxide nanoring powder into a tube furnace for vacuum treatment, then calcining at 450° C. for 10 hours in a hydrogen atmosphere, and finally cooling to room temperature to obtain ferroferric oxide nanorings; S3, preparation of gold nanoparticles: ultrapure water and chloroauric acid solution were added to a round-bottom flask, a condensation reflux device was set up and heated to boiling, then sodium citrate solution was added, and the mixture was boiled for 20 minutes, and the heating was stopped and stirred to room temperature to obtain gold nanoparticles; S4. Preparation of amino-functionalized ferroferric oxide: adding ferroferric oxide nanorings to anhydrous ethanol, subjecting to ultrasonic treatment for 5 minutes, then adding 3-aminopropyltriethoxysilane, reacting under ultrasonic stirring and mechanical stirring, washing twice by magnetic separation, and redispersing in deionized water to obtain amino-functionalized ferroferric oxide; S5. Preparation of gold nanoparticles / amino-functionalized ferroferric oxide: adding amino-functionalized ferroferric oxide to gold nanoparticles, stirring for 3 hours, washing by centrifugation, and redispersing in deionized water to obtain gold nanoparticles / amino-functionalized ferroferric oxide; S6. Preparation of thiol-cyclodextrin-gold nanomagnetic enrichment SERS detection chip: prepare thiol-cyclodextrin into a solution, add gold nanoparticles / amino-functionalized ferrosoferric oxide thereto and incubate for 30 min, then centrifuge and wash to remove unmodified thiol-cyclodextrin, and obtain thiol-cyclodextrin-gold nanomagnetic enrichment SERS detection chip.

2. The method for preparing a magnetic enrichment composite SERS detection chip according to claim 1, characterized in that: In S1, the mixed solution was heated at 220°C for 48 hours in a stainless steel autoclave, washed after cooling and dried at 80°C for 6 hours.

3. The method for preparing a magnetic enrichment composite SERS detection chip according to claim 1, characterized in that: In S3, the particle size of the gold nanoparticles obtained is 16 nm.

4. The method for preparing a magnetic enrichment composite SERS detection chip according to claim 2, characterized in that: In the S1, the inner diameter of a single particle of the iron oxide nanoring powder is 66 nm, and the outer diameter is 36 nm.

5. The method for preparing a magnetic enrichment composite SERS detection chip according to claim 1, characterized in that: In S4, the ultrasonic stirring reaction time is 30 minutes, and the mechanical stirring time is continued for 6 hours.

6. The method for preparing a magnetic enrichment composite SERS detection chip according to claim 1, characterized in that: In the S6, the volume of the configured thiocyclodextrin is 10 mL, and the concentration of the solute is 1 μM.

7. The method for preparing a magnetic enrichment composite SERS detection chip according to claim 1, characterized in that: The structure and magnetism of the mercaptocyclodextrin-gold nanomagnetic enrichment SERS detection chips prepared by S1-S6 were analyzed and characterized by SEM, TEM and XRD.

8. Application of a magnetic enrichment composite SERS detection chip in PAHs detection, characterized in that: The following steps are involved: S1. Use R6G and p-ATP as two probe molecules to evaluate the sensitivity of the mercaptocyclodextrin-gold nanomagnetic enrichment SERS detection chip to different PAHs by SERS detection, and calculate the detection limits of the corresponding PAHs, and calculate the linear relationship corresponding to the detection limits of each PAH; S2, continue to use SERS detection, and detect the mercaptocyclodextrin-gold nanomagnetic enrichment SERS detection chip at different times to observe the spectral changes; S3. Detect polycyclic aromatic hydrocarbons produced in the exhaust gas of construction machinery in simulated and actual environments, use mercaptocyclodextrin-gold nanomagnetic enrichment SERS detection chip to capture mixed aromatic hydrocarbons and use SERS to detect spectral changes.

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