Preparation method of large-area and distance-adjustable gold nano single-layer superlattice film and product and application thereof

Abstract

The invention discloses a preparation method of a large-area and distance-adjustable gold nanoparticle single-layer superlattice film and a product and application thereof, and belongs to the technical field of nanomaterials, the method comprises the following steps: modifying the surfaces of gold nanoparticles by using sulfydryl polystyrene and 1, 8-octyldithiol to obtain double-ligand co-modified gold nanoparticles; an interface assembly strategy is adopted to enable the double-ligand co-modified gold nanoparticles to form a film at the interface of toluene and diethylene glycol, and after toluene volatilizes, the large-area gold nano single-layer superlattice film with the adjustable distance is obtained. According to the method disclosed by the invention, by accurately regulating and controlling double-ligand modification on the surfaces of the gold nanoparticles and optimizing interaction among the particles in the assembly process, accurate regulation and control of the particle spacing of the gold nanoparticle single-layer superlattice film from 1nm to 8nm are realized. The electromagnetic field intensity can be obviously enhanced by accurately regulating and controlling the particle gaps to the sub-nanometer scale, so that the material becomes an ideal SERS substrate, and possibility is provided for developing a metamaterial with a high optical index.

Description

Technical Field

[0001] The invention relates to the technical field of nanomaterials, and in particular to a preparation method of a large-area and space-adjustable gold nano-monolayer superlattice film, a product thereof and an application thereof. Background Art

[0002] Gold nanoparticle monolayer films exhibit excellent electrical, magnetic, optical and other physical and chemical properties due to the integration effect between particles, and have broad application prospects in optical nanodevices, nanomedicine, catalysis, biosensors and surface enhanced Raman scattering (SERS) detection. The methods for preparing gold nanoparticle monolayer films include: self-assembly method, solvent evaporation method and chemical vapor deposition method. However, the two-dimensional gold nano-monolayer superlattice films prepared by traditional methods have the disadvantages of poor order, poor spacing controllability and small area, which limit the development of their applications. Therefore, it is of great significance to develop a two-dimensional gold nano-monolayer superlattice film that can be prepared on a large area, is highly ordered, and has adjustable spacing between gold nanoparticles.

[0003] In recent years, two-dimensional superlattice films based on gold nanoparticles have attracted much attention in the preparation of SERS detection substrates. Gold nanoparticles are commonly used materials for preparing high-performance SERS substrates due to their superior plasma resonance properties. Studies have shown that the optimization and regulation of the spacing between plasmon nanoparticles is crucial to enhancing the uniformity and hotspot density of SERS signals. When the spacing between gold nanoparticles is as small as sub-nanometer spacing, the coupling between particles can significantly enhance the electromagnetic field on the surface of the gold nanoparticles, thereby enhancing their SERS effect. In addition, achieving a highly ordered arrangement of gold nanoparticles can improve the uniformity of the detection substrate and the density of electromagnetic field hotspots, thereby further enhancing the Raman scattering signal of the molecule. Therefore, it is crucial to accurately control the spacing of plasmon nanoparticles and the orderliness and uniformity of the particle arrangement.

[0004] The Chinese patent document with publication number CN104152897A discloses a method for preparing a SERS substrate monolayer film, the method comprising: preparing a gold nanorod aqueous solution, redissolving the gold nanorods in a CTAB aqueous solution, dropping a mercaptoalkane ethanol solution into the gold nanorod CTAB aqueous solution, stirring sufficiently, preparing a ligand replacement mixed solution, adding an organic solvent thereto, and standing the sample so that the gold nanorods are laid flat on the surface of the aqueous phase to form a self-assembled SERS substrate monolayer film. The Chinese patent document with publication number CN106645087A discloses a PDMS-based monolayer SERS substrate without surface modification and a preparation method thereof, comprising the following steps: preparing uniform metal sol particles; self-assembling a single layer of dense metal nanoparticle film at the water-oil interface; transferring the metal nanoparticle film to a PDMS surface that has not been surface treated and forming a dense and uniform SERS substrate. However, the above method has the problem that the adjustability and orderliness of the metal nanoparticle spacing need to be improved, and the existing technology is difficult to achieve large-area preparation of sub-nanometer spacing superlattices. Therefore, developing a new superlattice preparation method that can achieve adjustable spacing while ensuring highly ordered arrangement of gold nanoparticles, especially the preparation of sub-nanometer spacing superlattices, has become the key to promoting the application of SERS substrates and related technologies. Summary of the invention

[0005] The invention provides a method for preparing a large-area and space-adjustable gold nanometer single-layer superlattice film, which overcomes the shortcomings of the prior art such as poor space adjustability of gold nanometer particles, low orderliness and small superlattice area.

[0006] The specific technical solutions adopted are as follows:

[0007] A method for preparing a large-area and space-adjustable gold nano-monolayer superlattice film comprises the following steps:

[0008] (1) preparing a gold nanoparticle solution;

[0009] (2) The gold nanoparticles were modified with mercapto polystyrene (PSSH) to obtain mercapto polystyrene-modified gold nanoparticles Au NP@PSSH; Au NP@PSSH was further treated with 1,8-octanedithiol to obtain mercapto polystyrene and 1,8-octanedithiol-co-modified gold nanoparticles Au NP@PSSH@OCT;

[0010] (3) Forming Au NP@PSSH@OCT at the interface of toluene and diethylene glycol, and preparing the large-area and spacing-adjustable gold nano-monolayer superlattice film after the toluene is volatilized.

[0011] The present invention achieves the preparation of a large-area spacing-adjustable superlattice film by modifying the surface of gold nanoparticles with mercapto polystyrene and 1,8-octanedithiol dual ligands, precisely controlling the interaction between particles during the film-forming process. The gold nanoparticles in the gold nano-monolayer superlattice film obtained by this method are highly ordered, and the spacing between the gold nanoparticles is precisely adjustable within the range of 1nm-8nm, thereby greatly improving the electromagnetic field enhancement effect of the substrate. In particular, when the spacing between the nanoparticles is 1 nanometer, the SERS enhancement factor of the resulting superlattice film is as high as 95429, which greatly promotes the application of SERS substrates in various types of sensors.

[0012] The method of the present invention is to graft thiol molecules onto gold nanoparticles in a gold-sulfur bond connection mode to achieve the purpose of modifying the particles, and gold nanoparticles with different grafting densities can be obtained by changing the molar amount of the modified molecules. During the assembly process, as the particles approach each other, the particles grafted with two ligands will undergo nanophase separation, so that the distance between the nanoparticles is reduced.

[0013] Optionally, in step (1), a nano-gold seed solution is prepared using chloroauric acid, sodium borohydride and cetyltrimethylammonium bromide (CTAB) as raw materials, and then the nano-gold seed solution, ascorbic acid, cetyltrimethylammonium chloride (CTAC) and chloroauric acid are used as raw materials to further grow the nano-gold seeds to prepare a gold nanoparticle solution.

[0014] Most preferably, the particle size of the gold nanoparticles in step (1) is 30 nm.

[0015] The seed growth method is adopted, with chloroauric acid as the gold precursor, sodium borohydride reducing chloroauric acid as seeds, and the seeds as cores, ascorbic acid AA as a weak reducing agent to continue reducing chloroauric acid to enlarge the gold nanoparticles. The gold nanoparticles obtained by this method have controllable morphology and good uniformity.

[0016] Preferably, the average molecular weight of the mercapto polystyrene PSSH is 5000-20000 g / mol.

[0017] In step (2), the gold nanoparticle solution is reacted with mercapto polystyrene PSSH in tetrahydrofuran to modify the gold nanoparticles with mercapto polystyrene PSSH. The concentration of the gold nanoparticle solution is 6.0×10 -11 mol / L-1.6×10 - 8 mol / L; preferably, the concentration of the gold nanoparticle solution is 2×10 -9 mol / L-8×10 -9 mol / L.

[0018] The molar ratio of mercapto polystyrene PSSH to gold nanoparticles was 3.0×10 2 -8.0×104 :1; Preferably, the molar ratio of mercapto polystyrene PSSH and gold nanoparticles is 650-13000:1.

[0019] Furthermore, the reaction time is 12-24 h, and the free ligands are removed after the reaction to obtain mercaptopolystyrene-modified gold nanoparticles Au NP@PSSH.

[0020] In step (2), the process of treating Au NP@PSSH with 1,8-octanedithiol is as follows: Au NP@PSSH is mixed with a tetrahydrofuran solution of 1,8-octanedithiol, and after at least 24 hours, the solution is redispersed in toluene, and washed with water and ethanol to obtain AuNP@PSSH@OCT.

[0021] Furthermore, the molar ratio of 1,8-octanedithiol to gold nanoparticles in Au NP@PSSH was 1.0×10 3 -1.0×10 4 :1; Preferably, the molar ratio of 1,8-octanedithiol to the gold nanoparticles in Au NP@PSSH is 1300-6500:1.

[0022] The invention also provides a gold nanometer single layer super lattice film prepared by the method for preparing the gold nanometer single layer super lattice film with large area and adjustable spacing.

[0023] The basic unit of the gold nanometer single-layer superlattice film is gold nanometer particles with a particle size of 10-60nm. The arrangement of the gold nanometer particles is long-range orderly, and the surface thereof is complete and has a yellow metallic luster.

[0024] The present invention also provides the application of the gold nanometer single layer super lattice film in SERS detection. The gold nanometer single layer super lattice film can be directly used as a SERS substrate for sample detection.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) The method of the present invention can form a single-layer and orderly arranged gold nano-superlattice. The prepared gold nano-monolayer superlattice film has the characteristics of long-range order, large area and controllable spacing, and has a wide range of applications in the fields of surface enhanced Raman, photovoltaic enhancement, fluorescence enhancement and light-emitting diodes.

[0027] (2) The gold nanoparticles in the gold nano-monolayer superlattice film prepared by the method of the present invention are evenly distributed, and the spacing between the gold nanoparticles is precisely adjustable within the range of 8nm-1nm, with the minimum spacing being 1 nanometer; by regulating the nanogaps in the gold nanoparticle superlattice, extreme electromagnetic field confinement and enhancement can be achieved. The metasurface composed of gold nanoparticles exhibits an effective refractive index that is adjustable over a wide wavelength range. By rationally designing the size of the nanogaps, the plasma near-field coupling can be precisely adjusted, thereby realizing a large-scale metasurface with an engineered refractive index. The reduction in spacing can increase the density of "hot spots", enhance the coupling interaction, and help improve the intensity of the SERS signal.

[0028] (3) The method of the present invention has the characteristics of wide applicability, simple preparation process and can prepare a large-area gold nano-monolayer superlattice film. The prepared gold nano-monolayer superlattice film has long-range order and the maximum area can reach 3cm 2 , has excellent optical properties in the visible and near-infrared bands, and is suitable for optical sensors, photonic crystals, and Raman detection.

[0029] (4) The gold nano-monolayer superlattice film prepared by the method of the present invention is used as a SERS substrate to detect 4-aminobenzenethiol, and the SERS enhancement factor can reach 95429, which has an excellent technical effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic flow chart of the method for preparing a large-area and spacing-adjustable gold nano-monolayer superlattice film in the present invention.

[0031] Figure 2 This is a SEM image of the gold nano-monolayer superlattice film prepared in Example 3, and the upper right corner is a macroscopic image of the actual object.

[0032] Figure 3 TEM images of the gold nano-monolayer superlattice films prepared in Examples 1-4, a) is Example 1, b) is Example 2, c) is Example 3, and d) is Example 4.

[0033] Figure 4 This is a Raman spectrum diagram of detecting 4-ATP using the gold nano monolayer superlattice film of Example 1-4 as the SERS substrate in Application Example 1-4.

[0034] Figure 5 The SERS enhancement factor bar graph of gold nanolayer superlattices with different spacings (at 1078 cm -1 as an example). DETAILED DESCRIPTION

[0035] In order to make the purpose, features and advantages of the present invention more obvious and easy to understand, the following is a detailed description through specific embodiments. In the following description, many specific details are set forth in order to fully understand the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed below. The technical features in each embodiment of the present invention can be combined accordingly without conflicting with each other.

[0036] The operating methods in the following examples without specifying specific conditions are usually carried out under conventional conditions or according to the conditions recommended by the manufacturer. The contents not described in detail in this specification belong to the prior art known to professionals in the field. The experimental materials used in the following examples, unless otherwise specified, can be purchased from conventional biochemical reagent companies.

[0037] Specifically, in the embodiment, gold nanoparticles are first prepared by a classical seed growth method, and then the original hexadecyltrimethylammonium chloride ligand is removed by centrifugation, and then the gold nanoparticles are modified with thiol-terminated polystyrene to obtain Au NP@PSSH, and then the gold nanoparticles are further modified with 1,8-octanedithiol to obtain Au NP@PSSH@OCT, and Au NP@PSSH@OCT is dissolved in toluene, and an interfacial film is formed on a diethylene glycol subphase. After the toluene evaporates, a gold nano monolayer superlattice film is obtained at the diethylene glycol interface. The schematic flow chart of the preparation method of the large-area and spacing-adjustable gold nano monolayer superlattice film is as shown in FIG. Figure 1 shown.

[0038] Example 1

[0039] In this embodiment, the method for preparing a large-area and space-adjustable gold nano-monolayer superlattice film comprises the following steps:

[0040] S1: The newly prepared NaBH4 solution (600 μL, 0.010 mol / L) was quickly injected into a mixed solution of CTAB (9.9 mL, 0.10 mol / L) and HAuCl4 (0.0250 mol / L). After stirring at 300 r / min for 3 h, the reaction mixture was placed in a water bath at 30 °C for 3 h to obtain a nanogold seed solution.

[0041] S2: 500 μL of gold nanoparticle seed solution (gold seeds stabilized with CTAB) was mixed with ascorbic acid AA (15.0 mL, 0.10 mol / L) and CTAC (20.0 mL, 0.20 mol / L), stirred at 600 r / min for 1 min, and then HAuCl4 (20 mL, 0.000050 mol / L) was injected. After continuous stirring for 15 min (300 rpm), 15 mL of the solution after the first growth was collected, initially purified by centrifugation (16000 r / min × 20 min), and the gold nanoparticles were redispersed in CTAC (2.5 mL, 0.020 mol / L) solution.

[0042] S3: CTAC (20 mL, 0.10 mol / L) and gold nanoparticles (750 μL, purified and dispersed in 0.020 mol / L CTAC) were mixed and ultrasonicated for 10 min. The mixture was then stirred in a 30 °C water bath (400 r / min), and then AA (1.3 mL, 0.010 mol / L) was added and stirred for 1 min. Then, HAuCl4 (50 mL, 0.00050 mol / L) was dripped into it at a concentration of 20 mL / h using a syringe pump. Finally, the mixture was stirred at 30 °C for another 5 minutes (400 r / min) and then refrigerated to obtain the final gold nanoparticle solution (containing Au NP@CTAC, the concentration of the gold nanoparticle solution was 7.69×10 -10 mol / L), and the diameter of gold nanoparticles was 30 nanometers.

[0043] S4: Centrifuge 10 ml of the gold nanoparticle solution obtained in the above step twice to remove excess CTAC. After the second round of centrifugation, reduce the volume of the solution to <100 μL, and then add the concentrated solution dropwise to a vigorously stirred (1000 rpm) THF solution of PSSH ligand (2 ml, 0.00000050 mol / L) (the average molecular weight of PSSH is 12000 g / mol, and the molar ratio of PSSH to gold nanoparticles is 1300:1). Stir the resulting mixture at 300 rpm for at least 24 hours so that PSSH completely replaces CTAC to obtain mercapto polystyrene-modified gold nanoparticles Au NP@PSSH, centrifuge the Au NP@PSSH solution, remove the supernatant, and reduce the volume of the solution to <100 μL to obtain a concentrated Au NP@PSSH solution.

[0044] S5: The concentrated Au NP@PSSH solution was redispersed in 1 mL of toluene under vigorous ultrasonic treatment. Then, equal volumes of water and ethanol were added to form a 1:1:1 mixture with the toluene solution, the upper toluene solution was extracted and the washing and extraction process was repeated to obtain Au NP@PSSH.

[0045] S6: The Au NP@PSSH in 1 mL of toluene was slowly transferred into a polytetrafluoroethylene test tube (~2 cm inner diameter, maximum volume = 30.0 mL) containing 20 mL of diethylene glycol DEG. The mouth of the test tube was covered with a glass petri dish to control the evaporation rate of toluene. After the toluene evaporated, a gold nanomonolayer superlattice film was formed on the surface of the DEG phase.

[0046] S7: The gold nano-monolayer superlattice film is transferred onto a silicon wafer to obtain a gold nano-superlattice SERS substrate with an average nanoparticle spacing of 8 nanometers.

[0047] Example 2

[0048] The difference between Example 2 and Example 1 is that in step S5, the concentrated Au NP@PSSH solution is added dropwise to the OCT solution (THF, 2 mL, 0.0000050 mol / L) under severe ultrasonic treatment (the molar ratio of 1,8-octanedithiol to the gold nanoparticles in Au NP@PSSH is 1300:1). The resulting mixture is further mixed for at least 24 hours to allow sufficient interaction between OCT and the residual active sites on the gold nanoparticles. The solution is centrifuged 3 times, concentrated, and redispersed in 1 mL of toluene under ultrasonic treatment. Then, an equal volume of water and ethanol is added to form a 1:1:1 mixture with the toluene solution, the upper toluene solution is extracted, and the washing and extraction process is repeated to obtain Au NP@PSSH@OCT.

[0049] Au NP@PSSH@OCT in 1 mL of toluene was slowly transferred into a polytetrafluoroethylene test tube (∼2 cm inner diameter, maximum volume = 30.0 mL) containing 20 mL of diethylene glycol (DEG), and after toluene volatilized, a gold nanomonolayer superlattice film with an average nanoparticle spacing of 5 nm was formed on the surface of the DEG phase.

[0050] Example 3

[0051] The only difference between Example 3 and Example 2 is that the concentration of the OCT solution is 0.000010 mol / L, the molar ratio of 1,8-octanedithiol to the gold nanoparticles in Au NP@PSSH is 2600:1, and the other processes and parameters are the same as those in Example 2. A gold nano-monolayer superlattice film with an average nanoparticle spacing of 3 nanometers was prepared.

[0052] Example 4

[0053] The only difference between Example 4 and Example 2 is that the concentration of the OCT solution is 0.000015 mol / L, the molar ratio of 1,8-octanedithiol to the gold nanoparticles in Au NP@PSSH is 3900:1, and the other processes and parameters are the same as those in Example 2. A gold nano-monolayer superlattice film with an average nanoparticle spacing of 1 nm is prepared.

[0054] Application Example 1

[0055] The Raman detection of 4-aminothiophenol (4-ATP) was performed using the gold nanosuperlattice SERS substrate prepared in Example 1. The method comprises the following steps: taking 10 μL of a 10 -5 mol / L 4-ATP solution was dropped onto the surface of the gold nanosuperlattice SERS substrate of Example 1 and then dried naturally; at an excitation wavelength of 785 nm, the detection power was set to 100 mW, the integration time was set to 10000 ms, and a Raman instrument was used to perform SERS detection on 4-ATP.

[0056] Application Example 2

[0057] The only difference between Application Example 2 and Application Example 1 is that the gold nanosuperlattice SERS substrate prepared in Example 2 is used, and the other processes and parameters are the same as those in Application Example 1.

[0058] Application Example 3

[0059] The only difference between Application Example 3 and Application Example 1 is that the gold nanosuperlattice SERS substrate prepared in Example 3 is used, and the other processes and parameters are the same as those in Application Example 1.

[0060] Application Example 4

[0061] The only difference between Application Example 4 and Application Example 1 is that the gold nanosuperlattice SERS substrate prepared in Example 4 is used, and the other processes and parameters are the same as those in Application Example 1.

[0062] Sample analysis

[0063] Figure 2 This is the SEM image of the gold nano-monolayer superlattice film prepared in Example 3. The upper right corner is a macroscopic real-life image, showing that the gold nano-monolayer superlattice film has a large area and long-range order. The area of ​​the gold nano-monolayer superlattice film is 1-3 cm 2 , up to 3cm 2 , the particle size of gold nanoparticles is 30nm.

[0064] Figure 3 a)-d) in the figure are TEM images of the gold nano-monolayer superlattice films obtained in Examples 1-4, respectively. It can be seen that the spacing between the gold nanoparticles (superlattice spacing) is 8nm, 5nm, 3nm and 1nm, respectively. It can be seen that as the concentration of 1,8-octanedithiol in the mixed solution increases, the spacing between the gold nanoparticles in the prepared gold nano-monolayer superlattice film decreases.

[0065] Figure 4 The Raman spectrum shows that as the superlattice spacing decreases, the Raman signal of 4-ATP gradually increases, and the Raman intensity increases from 1685 to 5702.

[0066] Figure 5 The SERS enhancement factor bar chart shows that as the superlattice spacing decreases, the enhancement factor increases from 28200 to 95429.

[0067] The embodiments described above provide a detailed description of the technical solutions of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, supplements or similar substitutions made within the scope of the principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a large-area and space-adjustable gold nano-monolayer superlattice film, characterized in that: The following steps are involved: (1) preparing a gold nanoparticle solution; (2) The gold nanoparticles were modified with mercapto polystyrene (PSSH) to obtain mercapto polystyrene-modified gold nanoparticles Au NP@PSSH; Au NP@PSSH was further treated with 1,8-octanedithiol to obtain mercapto polystyrene and 1,8-octanedithiol-co-modified gold nanoparticles Au NP@PSSH@OCT; (3) Forming Au NP@PSSH@OCT at the interface of toluene and diethylene glycol, and preparing the large-area and spacing-adjustable gold nano-monolayer superlattice film after the toluene is volatilized.

2. The method for preparing a large-area and space-adjustable gold nano-monolayer superlattice film according to claim 1, characterized in that: In step (1), chloroauric acid, sodium borohydride and cetyltrimethylammonium bromide (CTAB) are used as raw materials to prepare a nano-gold seed solution, and then the nano-gold seed solution, ascorbic acid, cetyltrimethylammonium chloride (CTAC) and chloroauric acid are used as raw materials to further grow the nano-gold seeds to prepare a gold nanoparticle solution.

3. The method for preparing a large-area and spacing-adjustable gold nano-monolayer superlattice film according to claim 1, characterized in that: The average molecular weight of mercapto polystyrene PSSH is 5000-20000 g / mol.

4. The method for preparing a large-area and space-adjustable gold nano-monolayer superlattice film according to claim 1, characterized in that: In step (2), the gold nanoparticle solution is reacted with mercapto polystyrene PSSH in tetrahydrofuran to modify the gold nanoparticles with mercapto polystyrene PSSH. The concentration of the gold nanoparticle solution is 6.0×10 -11 mol / L-1.6×10 - 8 mol / L, and the molar ratio of mercaptopolystyrene PSSH to gold nanoparticles was 3.0×10 2 -8.0×10 4 :

1.

5. The method for preparing a large-area and space-adjustable gold nano-monolayer superlattice film according to claim 4, characterized in that: The reaction time is 12-24h.

6. The method for preparing a large-area and space-adjustable gold nano-monolayer superlattice film according to claim 1, characterized in that: In step (2), the process of treating Au NP@PSSH with 1,8-octanedithiol is as follows: Au NP@PSSH is mixed with a tetrahydrofuran solution of 1,8-octanedithiol, and after at least 24 hours, the solution is redispersed in toluene, and washed with water and ethanol to obtain AuNP@PSSH@OCT.

7. The method for preparing a large-area and spacing-adjustable gold nano-monolayer superlattice film according to claim 6, characterized in that: The molar ratio of 1,8-octanedithiol to gold nanoparticles in Au NP@PSSH is 1.0×10 3 -1.0×10 4 :

1.

8. A gold nano-monolayer superlattice film prepared according to the method for preparing a large-area and spacing-adjustable gold nano-monolayer superlattice film according to any one of claims 1 to 7.

9. The gold nano-monolayer superlattice film according to claim 8, characterized in that: Its basic unit is gold nanoparticles with a particle size of 10-60nm, and the arrangement of gold nanoparticles is long-range orderly.

10. Use of the gold nano-monolayer superlattice film according to claim 8 in SERS detection.

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