Preparation method of poly(4-vinylpyridine) grafted carbon nanotube / sea urchin gold nanonecklace structure and its SERS application

Abstract

The present invention discloses a preparation method of a poly (4-vinylpyridine) grafted carbon nanotube / sea urchin gold nanonecklace structure and its SERS application, which is a simple and effective method for preparing a necklace-like nanostructure, wherein sea urchin gold is uniformly and stably connected in series on polymer-grafted carbon nanotubes through template-assisted nanocrystal growth. First, the surface of the carbon nanotube is covalently functionalized by surface-initiated atom transfer radical polymerization. Then, sea urchin gold (SUGNPs) nanostructures are grown using the polymer-grafted carbon nanotubes as a template. This special structure can prevent the aggregation of SUGNPs and ensure the long-term stability of the obtained necklace-like SUG-CNT shish-kebab nanocomposite material. The reliability and sensitivity of the necklace-like SUG-CNT shish-kebab nanocomposite material as a SERS substrate are verified by Raman detection of malachite green.

Description

Technical Field

[0001] The present invention relates to a preparation method of a poly (4-vinylpyridine) grafted carbon nanotube / sea urchin gold nanonecklace structure as a SERS substrate and research on the detection of trace organic dye malachite green, belonging to the field of preparation and application of nanocomposite materials. Background Art

[0002] Over the past few decades, the emerging field of nanosynthesis has focused on the preparation of complex nanostructures with adjustable size, shape, and morphology. A large number of methods have been developed to synthesize gold nanoparticles (AuNPs) with various morphologies, such as spherical gold particles, gold cubes, gold rods, gold wires, gold cones, gold nanoflowers, and gold nanostars. Among these different structures, sea urchin-like gold nanoparticles (SUGNPs) with abundant surface tips can lead to higher enhancement factors due to the abundant interstitial hotspots on their adjacent tips. Therefore, in order to obtain strong SERS signals, people have explored methods to use SUGNPs as SERS substrates.

[0003] Past studies have proposed a series of methods for the controllable preparation of sea urchin-like gold nanostructures. However, due to the anisotropic growth characteristics of SUGNPs, they are inherently unstable and easily aggregated. For this reason, the random hot spots generated by their uncontrollable aggregation often lead to non-repeatable Raman signals. Currently, a large number of related studies have been devoted to the preparation of more stable sea urchin-like structures. One method is to protect SUGNPs with a coating, which can significantly prevent inter-particle aggregation, but at the same time the presence of the coating will have an inhibitory effect on the SERS signal.

[0004] Malachite green (MG) has been widely used in aquaculture to improve fish survival. However, MG and its metabolites are highly toxic and carcinogenic, causing a variety of diseases. Therefore, it is of great significance to develop nano-SERS substrates that are reproducible, stable, easy to fabricate, and provide satisfactory SERS signal enhancement for the rapid and sensitive detection of MG in aquatic products. Summary of the Invention

[0005] The purpose of the present invention is to provide a simple and effective method to prepare necklace-like nanostructures, in which sea urchin gold is uniformly and stably connected to poly (4-vinyl pyridine) grafted carbon nanotubes (CNTs) through template-assisted nanocrystal growth. First, the surface of the carbon nanotubes is covalently functionalized by surface-initiated atom transfer radical polymerization (SI-ATRP). Subsequently, SUGNPs are grown using poly (4-vinyl pyridine) grafted carbon nanotubes (CNT-g-P4VP) as a template. This special structure can prevent the aggregation of SUGNPs and ensure the long-term stability of the resulting necklace-like poly (4-vinyl pyridine) grafted carbon nanotube / sea urchin gold (SUG-CNTshish-kebab) nanocomposite material. The reliability and sensitivity of the SUG-CNT material as a SERS substrate were verified by Raman detection of malachite green, and the concentration level can reach 10 -8 M, and found no significant degradation in SERS performance over a 3-month period. The prepared necklace-like SUG-CNT shish-kebab nanocomposite exhibited excellent stability and could be reused as a SERS substrate. This versatile and robust templating strategy can easily yield unique necklace-like nanocomposites for efficient SERS detection applications.

[0006] The SUG-CNT shish-kebab nanocomposite prepared in the present invention can stably provide high-density hot spots, and thus can be used as an active substrate material for SERS applications to sensitively and quickly detect MG, thereby achieving an efficient SERS effect.

[0007] To address the above technical issues, a technical solution is proposed: a method for preparing a SERS substrate based on a poly(4-vinylpyridine)-grafted carbon nanotube / sea urchin gold nanoparticle composite material, which uses a simple template-assisted in situ growth method to prepare a necklace-shaped carbon nanotube / sea urchin gold nanoparticle composite material with controllable structure and orderly arrangement. The specific steps include:

[0008] (1) Initiating the reaction sites of atom transfer radical reaction (ATRP) on the surface modification of carbon nanotubes (CNTs) through chemical reaction, acting as a carbon nanotube macromolecular initiator;

[0009] (2) using the carbon nanotube macromolecular initiator through an active atom transfer radical reaction to prepare a poly (4-vinylpyridine) grafted carbon nanotube CNT-g-P4VP as a carrier;

[0010] (3) Regular and continuous sea urchin gold nanoparticles (SUGNPs) were grown on polymer-based carbon nanotubes by a template-assisted in situ growth method to obtain necklace-shaped poly (4-vinylpyridine) grafted carbon nanotubes / sea urchin gold SUG-CNT shish-kebab nanocomposites; silver / gold seeds were anchored on the surface of P4VP grafted CNTs through Au-N coordination, and then HAuCl4 was added for secondary growth into a necklace-shaped sea urchin gold string structure, where the precursors were chloroauric acid (HAuCl4·3H2O) and silver nitrate (AgNO3), and ascorbic acid (AA) was selected as the reducing agent. The gold precursor added for further growth was HAuCl4·3H2O.

[0011] Preferably, the carbon nanotubes include single-walled carbon nanotubes, double-walled carbon nanotubes or multi-walled carbon nanotubes.

[0012] Preferably, the structural formula of the carbon nanotube macroinitiator is:

[0013]

[0014] is a carbon nanotube-based group; X is Br l.

[0015] Preferably, regular and continuous sea urchin gold nanoparticles SUGNPs are grown on polymer-based carbon nanotubes by a template-assisted in situ growth method;

[0016] Preparation of the necklace-shaped SUG-CNT shish-kebab nanocomposite material in step (3):

[0017] 1 mg of CNT-g-P4VP was dissolved in 10 mL of ethanol solution to maintain the concentration of CNT-g-P4VP at 0.1 mg / mL; a seed solution was prepared by sequentially adding 20 μL of HAuCl4·3H2O (10 mM) and 20 μL of AgNO3 (10 mM) as precursors and 300 μL of ascorbic acid AA (10 mM) as a reducing agent to 300 μL of CNT-g-P4VP solution; the resulting reaction mixture was vigorously stirred under the action of a magnetic field for 20 s, and then 300 μL of HAuCl4·3H2O (3 mM) was added and stirred for another 1 min. The reaction was stopped by centrifugation at 6000 rpm for 10 min, and the final product was redispersed in 3 mL of deionized water in the form of a black solution.

[0018] Preferably, the gold nanostructures are uniformly anchored on the polymer-based carbon nanotubes through Au-N interactions with the functional groups without obvious agglomeration.

[0019] In order to solve the above technical problems, another technical solution is proposed: prepare the poly (4-vinyl pyridine) grafted carbon nanotube / sea urchin gold nanocomposite material by any method.

[0020] In order to solve the above technical problems, another technical solution is proposed: a method for detecting the organic dye malachite green using the poly (4-vinylpyridine) grafted carbon nanotube / sea urchin gold nanocomposite SERS substrate. In order to quantify the SERS performance of the prepared substrate, we use the organic dye malachite green as a probe molecule, disperse the nanocomposite obtained by centrifugation in a malachite green aqueous solution and fully sonicate it, so that the analyte molecules are effectively captured on the surface of the substrate material, and then Raman detection is performed.

[0021] Carbon nanotubes are ultrasonically dispersed in concentrated nitric acid, followed by an acidification reaction to obtain carbon nanotubes (CNT-COOH) with numerous surface carboxyl sites, which are then functionalized. The acidified carbon nanotubes are reacted with thionyl chloride to obtain acylated carbon nanotubes (CNT-COCl). The acylated carbon nanotubes are ultrasonically dispersed in a diol compound, where the acyl groups on the surface of the carbon nanotubes are replaced by hydroxyl groups, yielding hydroxylated carbon nanotubes (CNT-OH). The hydroxylated carbon nanotubes are dispersed in N-methylpyrrolidone (NMP), and 2-bromoisobutyryl bromide is added to further modify the carbon nanotubes (CNTs) with active initiating groups, yielding brominated carbon nanotubes (CNT-Br), which are used as initiators for atom transfer radical polymerization (ATRP).

[0022] The brominated carbon nanotubes (CNT-Br), polymer monomer 4-vinylpyridine (4VP), active polymerization catalyst, co-catalyst and solvent were ultrasonically mixed to obtain functionalized carbon nanotubes grafted with complex poly(4-vinylpyridine) (CNT-g-P4VP), which were dissolved in ethanol and used as a template for subsequent sea urchin gold growth.

[0023] The seed solution was prepared by adding precursors and reducing agents to the ethanol solution of poly(4-vinylpyridine) grafted carbon nanotubes (CNT-g-P4VP) via the template-assisted in situ growth method, and gold precursor was subsequently added to grow regular and continuous sea urchin gold nanoparticles (SUGNPs).

[0024] The SUG-CNT shish-kebab nanocomposite obtained by centrifugation was dispersed in an aqueous solution of probe molecules and then thoroughly sonicated, effectively trapping the probe molecules on the substrate surface for Raman detection. This versatile and robust templating strategy can easily produce unique necklace-like nanocomposites for efficient SERS detection applications.

[0025] In the step (1), the carbon nanotubes include single-walled carbon nanotubes, double-walled carbon nanotubes, or multi-walled carbon nanotubes.

[0026] In the step (2), the temperature of the active polymerization reaction is 50° C., and the reaction time can be adjusted according to the situation. Different reaction times can obtain polymer layers of different thicknesses. The reaction time is preferably 24 h.

[0027] In the step (3), the average diameter of the necklace-shaped sea urchin gold strings uniformly grown on the carbon nanotubes by the template-assisted in-situ growth method is 100±20nm, the tip length is about 10-30nm, and there is no obvious agglomeration phenomenon.

[0028] In step (4), to quantify the SERS performance of the prepared substrate, 4-MBA, which has excellent vibrational properties, was used as a probe molecule. The nanocomposite obtained by centrifugation was dispersed in a 4-MBA aqueous solution and then fully sonicated to effectively capture the 4-MBA molecules on the surface of the substrate, followed by Raman detection.

[0029] In step (4), in order to quantify the SERS performance of the prepared substrate, MG was used as a probe molecule. The nanocomposite obtained by centrifugation was dispersed in a MG aqueous solution and then fully sonicated to effectively capture the analyte molecules on the surface of the substrate material, and then Raman detection was performed.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) The preparation of the necklace-shaped SUG-CNT shish-kebab nanocomposite developed in this invention involves the initial synthesis of CNT-g-P4VP, the preparation of a seed solution, and the further addition of a gold precursor to grow the SUGNPs structure. The principle is to anchor the silver / gold seeds on the surface of the P4VP-grafted CNT through Au-N coordination, followed by the addition of HAuCl4 for secondary growth into a necklace-shaped sea urchin gold string structure. This unique structure effectively prevents the aggregation of SUGNPs, provides good dispersion, and exhibits long-term stability.

[0032] (2) The unique structure of the necklace-shaped SUG-CNT shish-kebab nanocomposite developed in this invention can be used as a highly active substrate for ultrasensitive SERS analysis. This enhanced SERS effect comes from multiple reasons: First, the dense spike-like structure on the SUGNPs naturally forms a large number of adjacent SERS hotspots, resulting in a stronger SERS response than that of pure noble metal particles; at the same time, the regular growth of necklace-shaped SUGNPs by functionalized carbon nanotubes causes a coupling effect between adjacent sea urchin gold, which also leads to a higher SERS effect. On the other hand, the surface plasmons of CNTs couple with the local surface plasmons of SUGNPs, which can have a physical enhancement effect; in addition, the charge transfer process between the CNT substrate and the target molecules can also provide additional SERS enhancement effects through chemical enhancement (CM). Finally, the spikes on the SUGNPs have a unique wedge-shaped structure that can load more probe molecules, providing a highly detectable molecular concentration environment for their good adsorption, which can effectively enhance the SERS signal through the physical enhancement (EM) mechanism.

[0033] (3) The SUG-CNT shish-kebab nanocomposite has excellent reliability, stability and sensitivity, and can be used as an effective sensitive SERS substrate for quantitative detection, with broad application prospects in environmental monitoring.

[0034] (4) Figure 2 As shown, by comparing the examples and comparative example 1, it can be found that when the growth time of the silver / gold seeds is doubled, a certain core-shell structure can be obtained instead of a string-like structure, and its tip is not obvious, which may not provide enough hot spots for Raman detection. Therefore, it is expected that the SERS enhancement effect will also be significantly weaker than that of the necklace-like SUG-CNT shish-kebab nanocomposite material.

[0035] (5) Figure 4 As shown, 4-MBA was used as the probe molecule to detect the SERS effect of the SUG-CNT material prepared in the experiment. -1 and 1582cm -1 The two strong peaks at the 4-MBA correspond to the aromatic ring vibration of 4-MBA. The SERS performance of the necklace-shaped SUG-CNT shish-kebab nanocomposite and two other nanocomposites were evaluated by control experiments. Compared with the core-shell structure obtained by doubling the growth time of the silver / gold seed in Comparative Example 1 and the SUG-CNT material prepared by using CNT-COOH instead of CNT-g-P4VP as the template in Comparative Example 2, the necklace-shaped SUG-CNT shish-kebab nanocomposite showed the highest SERS signal. Figure 5As shown in the figure, the SERS performance of SUG-CNT and pure SUGNPs was evaluated by control experiments using 4-MBA as a probe molecule. Compared with pure SUGNPs, the necklace-shaped SUG-CNT shish-kebab nanocomposite exhibited a higher SERS signal.

[0036] (6) Figure 6 As shown in a, the main characteristic Raman band of MG can be clearly identified. 1617cm -1 and 1400cm -1 The strong scattering band at 1175 cm is attributed to C—C stretching vibration. -1 1294cm -1 The band is attributed to CH stretching vibration, and the NC stretching band is located at 1369 cm -1 In addition, 917cm -1 The corresponding radial vibration of the ring bone can also be observed. Figure 6 As shown in b, with the decrease of MG concentration, the SERS intensity detected by necklace-shaped SUG-CNT shish-kebab nanocomposites gradually decreases, and its detection concentration level can be reduced to 10 -8 Therefore, the necklace-like SUG-CNT shish-kebab nanocomposite can be used as an effective sensitive SERS substrate for the quantitative detection of MG.

[0037] (7) Stability of necklace-like SUG-CNT shish-kebab nanocomposites

[0038] In order to evaluate the stability of necklace-shaped SUG-CNT shish-kebab nanocomposites as SERS substrates, the SERS spectra of necklace-shaped SUG-CNT shish-kebab nanocomposites labeled with 1.0 mM 4-MBA were tested over a long period of time. The Raman signals of the same batch of necklace-shaped SUG-CNT shish-kebab nanocomposites were monitored every other month. Figure 7 As shown in Figure 3, it was found that the SERS performance did not significantly decrease over a period of 3 months, indicating that the prepared necklace-like SUG-CNT shish-kebab nanocomposite has excellent stability and can be reused as a SERS substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a transmission electron microscope (TEM) characterization image of the necklace-shaped SUG-CNT shish-kebab nanocomposite material in Example 1, which is the product obtained in Example (3).

[0040] Figure 2This is a TEM image of the CNT-g-P4VP / Au core-shell structure prepared in Comparative Example 1 with a seed growth time of 40 s and the addition of HAuCl4·3H2O (3 mM, 300 μL), which is the product obtained in Comparative Example 1(3).

[0041] Figure 3 This is the TEM image of the necklace-like SUG-CNT structure prepared using CNT-COOH as a template in Comparative Example 2, which is the product obtained in Comparative Example 2(2).

[0042] Figure 4 Surface-enhanced Raman spectra of 4-MBA attached to three batches of nanocomposites in Example 1 and the comparative example.

[0043] Figure 5 These are the SERS spectra of SUG-CNT and SUGNPs in Example 1 and Comparative Example 3.

[0044] Figure 6 Surface-enhanced Raman spectra of MG attached to the necklace-shaped SUG-CNT shish-kebab nanocomposite in Example 1. a is the spectrum of the SUG-CNT shish-kebab nanocomposite labeled with a 1.0 mM MG aqueous solution, and b is the spectrum of the SUG-CNT shish-kebab nanocomposite labeled with different concentrations of MG aqueous solutions.

[0045] Figure 7 The SERS spectra of the necklace-shaped SUG-CNT shish-kebab nanocomposite prepared in Example 1 were measured every month over a period of three months after being adsorbed with 1.0 mM 4-MBA. DETAILED DESCRIPTION

[0046] The present invention will be further described below with reference to specific embodiments:

[0047] Example 1

[0048] A preparation method based on a carbon nanotube / sea urchin gold nanonecklace structure and its SERS application, comprising the following steps:

[0049] (1) Synthesis of ATRP initiator CNT-Br

[0050] First, pristine multi-walled carbon nanotubes (0.4 g) were treated with 10 mL of a 60% aqueous HNO₃ solution at 120°C for 13 hours. The pH was then adjusted to neutral with water, washed with ethanol, and filtered. The resulting CNT-COOH was vacuum-dried at 60°C overnight. Subsequently, the CNT-COOH was reacted with 8 mL of SOCl₂ at 65°C for 24 hours, and the product was centrifuged. The resulting CNT-COCl was then reacted with excess ethylene glycol at 120°C for 48 hours to produce CNT-OH, which was vacuum-dried at 50°C overnight. The CNT-OH was stirred in 15 mL of anhydrous NMP. Then, 10 mL of 2-bromoisobutyryl bromide was slowly added, stirred at 0°C for 2 hours, and continued to stir at room temperature for 48 hours. Finally, the black solid product, CNT-Br, was filtered and isolated, washed three times with appropriate amounts of chloroform, and vacuum-dried at 50°C overnight.

[0051] (2) Synthesis of P4VP-grafted CNTs (i.e., CNT-g-P4VP) by ATRP

[0052] In a dry reaction flask, ATRP macroinitiator CNT-Br (100 mg), 4VP (5 mL), DMF (5 mL), CuBr (35 mg), and Me6TREN (85 mg) were added and degassed with argon for 30 minutes. Polymerization was carried out at 50°C for 36 hours with vigorous stirring. The polymerization reaction was terminated by removing the reaction flask from the oil bath and allowing it to cool. The product was collected by centrifugation and washed three times with ethanol. The final product, CNT-g-P4VP, was dried under vacuum at 50°C for 24 hours.

[0053] (3) Preparation of necklace-shaped SUG-CNT shish-kebab nanocomposites

[0054] 1 mg of CNT-g-P4VP was dissolved in 10 mL of ethanol to maintain a CNT-g-P4VP concentration of 0.1 mg / mL. A seed solution was prepared by sequentially adding 20 μL of 10 mM HAuCl4·3H2O and 20 μL of 10 mM AgNO3 as precursors, along with 300 μL of 10 mM ascorbic acid (AA) as a reducing agent, to 300 μL of the CNT-g-P4VP solution. The resulting reaction mixture was vigorously stirred under a magnetic field for 20 seconds, followed by the addition of 300 μL of 3 mM HAuCl4·3H2O and stirring for an additional minute. The reaction was terminated by centrifugation at 6000 rpm for 10 minutes. The final product, a black solution, was redispersed in 3 mL of deionized water.

[0055] like Figure 1As shown in the figure, a necklace-like SUG-CNT shish-kebab structure can be clearly observed, accompanied by the sharp tips of SUGNPs. The average diameter of the SUGNPs calculated from TEM images is 100±20nm, and the tip length is about 10-30nm.

[0056] Comparative Example 1

[0057] Preparation of nanocomposites by extending the reaction time of growing silver / gold seeds on CNT-g-P4VP

[0058] The preparation method is the same as that of Example 1 except step (3).

[0059] Step (3) of this example is as follows: 1 mg of CNT-g-P4VP was dissolved in 10 mL of ethanol solution to maintain a CNT-g-P4VP concentration of 0.1 mg / mL. A seed solution was prepared by sequentially adding 20 μL of HAuCl4·3H2O (10 mM) and 20 μL of AgNO3 (10 mM) as precursors, and 300 μL of AA (10 mM) as a reducing agent to 300 μL of CNT-g-P4VP solution. The resulting reaction mixture was vigorously stirred under a magnetic field for 40 seconds, and then 300 μL of HAuCl4·3H2O (3 mM) was added and stirred for another 1 minute. The reaction was stopped by centrifugation at 6000 rpm for 10 minutes. The final product was redispersed in 3 mL of deionized water as a black solution.

[0060] like Figure 2 As shown, by comparing the examples and comparative example 1, it can be found that when the growth time of the silver / gold seeds is doubled, a certain core-shell structure can be obtained instead of a string-like structure, and its tip is not obvious, which may not provide enough hot spots for Raman detection. Therefore, it is expected that the SERS enhancement effect will also be significantly weaker than that of the necklace-like SUG-CNT shish-kebab nanocomposite material.

[0061] Comparative Example 2: Using CNT-COOH instead of CNT-g-P4VP as a template to prepare a nanocomposite material, comprising the following steps:

[0062] (1) Synthesis of CNT-COOH

[0063] First, pristine carbon nanotubes (0.4 g) were treated with 10 mL of 60% HNO3 aqueous solution at 120°C for 13 h, then the pH was adjusted to neutral with water, washed with ethanol, and filtered. The resulting CNT-COOH was dried in vacuum at 60°C overnight.

[0064] (2) Preparation of nanocomposites

[0065] 1 mg of CNT-COOH was dissolved in 10 mL of ethanol to maintain a concentration of 0.1 mg / mL. A seed solution was prepared by sequentially adding 20 μL of 10 mM HAuCl4·3H2O and 20 μL of 10 mM AgNO3 as precursors, along with 300 μL of 10 mM AA as a reducing agent, to 300 μL of CNT-g-COOH solution. The resulting reaction mixture was vigorously stirred under a magnetic field for 20 seconds, followed by the addition of 300 μL of 3 mM HAuCl4·3H2O and stirring for an additional minute. The reaction was terminated by centrifugation at 6000 rpm for 10 minutes. The final product, a black solution, was redispersed in 3 mL of deionized water.

[0066] like Figure 3 As shown, a comparison between Example 1 and Comparative Example 2 reveals that, when carboxyl-functionalized carbon nanotubes are used instead of CNT-g-P4VP, only a small amount of SUGNPs grow on the CNT-COOH in the SUG-CNT nanocomposite prepared under the same conditions. Furthermore, the size of the SUG strings is much larger than that of the SUGNPs in the necklace-like SUG-CNT shish-kebab nanocomposite, and the ends of the SUGNPs appear blunt, which may not provide sufficient hotspots for Raman detection. Therefore, the SERS enhancement effect is expected to be significantly weaker than that of the necklace-like SUG-CNT shish-kebab nanocomposite.

[0067] Comparative Example 3: A pure SUGNPs solution and a necklace-shaped SUG-CNT shish-kebab nanocomposite were prepared under the same conditions, comprising the following steps:

[0068] (1) First, 300 μL of ethanol, 20 μL of HAuCl4 (10 mM), and 20 μL of AgNO3 (10 mM) were added sequentially to a flask as reaction precursors. Then, 300 μL of AA (10 mM) was added as a reducing agent and stirred vigorously for 20 seconds to prepare a seed solution. Then, 300 μL of AA HAuCl4·3H2O (3 mM) was added to the flask and stirred for another 1 minute. The reaction was stopped to obtain a dark blue solution, which was centrifuged at 6000 rpm for 10 minutes and redispersed in 3 mL of deionized water.

[0069] SERS performance test of Example 1 and comparative example

[0070] (1) 4-MBA as a probe molecule to detect the SERS properties of nanocomposites

[0071] To quantify the SERS performance of the prepared substrate, we used 4-MBA, a molecule with excellent vibrational properties, as a probe molecule. The centrifuged material was dispersed in 2 mL of 4-MBA aqueous solution and thoroughly sonicated for 30 minutes, effectively trapping the 4-MBA molecules on the substrate surface. Raman spectroscopy was then performed.

[0072] like Figure 4 As shown, 4-MBA was used as the probe molecule to detect the SERS effect of the SUG-CNT material prepared in the experiment. -1 and 1582cm -1 The two strong peaks at 4-MBA correspond to the aromatic ring vibrations of 4-MBA. A control experiment evaluated the SERS performance of the necklace-shaped SUG-CNT shish-kebab nanocomposite compared with two other nanocomposites. Compared with the core-shell structure obtained in Comparative Example 1, where the growth time of the silver / gold seeds was doubled, and the SUG-CNT material prepared in Comparative Example 2 using CNT-COOH instead of CNT-g-P4VP as a template, the necklace-shaped SUG-CNT shish-kebab nanocomposite exhibited the highest SERS signal.

[0073] like Figure 5 As shown in the figure, the SERS performance of SUG-CNT and pure SUGNPs was evaluated by control experiments using 4-MBA as a probe molecule. Compared with pure SUGNPs, the necklace-shaped SUG-CNT shish-kebab nanocomposite exhibited a higher SERS signal.

[0074] (2) Detection of the SERS effect of necklace-shaped SUG-CNT shish-kebab nanocomposites on MG

[0075] To quantify the SERS performance of the prepared substrate, we used the organic dye MG as a probe molecule. The necklace-shaped SUG-CNT shish-kebab nanocomposite obtained by centrifugation was dispersed in 2 mL of MG aqueous solution and thoroughly sonicated for 30 minutes. This effectively trapped the MG molecules on the surface of the necklace-shaped SUG-CNT shish-kebab substrate, and then subjected to Raman spectroscopy.

[0076] like Figure 6 As shown in a, the main characteristic Raman band of MG can be clearly identified. 1617cm -1 and 1400cm -1 The strong scattering band at 1175 cm is attributed to C—C stretching vibration. -1 1294cm -1 The band is attributed to CH stretching vibration, and the NC stretching band is located at 1369 cm -1 In addition, 917cm-1 The corresponding radial vibration of the ring bone can also be observed. Figure 6 As shown in b, with the decrease of MG concentration, the SERS intensity detected by necklace-shaped SUG-CNT shish-kebab nanocomposites gradually decreases, and its detection concentration level can be reduced to 10 -8 Therefore, the necklace-like SUG-CNT shish-kebab nanocomposite can be used as an effective sensitive SERS substrate for the quantitative detection of MG.

[0077] (3) Stability of necklace-shaped SUG-CNT shish-kebab nanocomposites

[0078] In order to evaluate the stability of necklace-shaped SUG-CNT shish-kebab nanocomposites as SERS substrates, the SERS spectra of necklace-shaped SUG-CNT shish-kebab nanocomposites labeled with 1.0 mM 4-MBA were tested over a long period of time. The Raman signals of the same batch of necklace-shaped SUG-CNT shish-kebab nanocomposites were monitored every other month. Figure 7 As shown in Figure 3, it was found that the SERS performance did not significantly decrease over a period of 3 months, indicating that the prepared necklace-like SUG-CNT shish-kebab nanocomposite has excellent stability and can be reused as a SERS substrate.

[0079] The present invention is not limited to the specific technical solutions described in the above embodiments, and all technical solutions formed by equivalent replacement are within the protection scope required by the present invention.

Claims

1. A method for preparing a SERS substrate based on poly (4-vinylpyridine) grafted carbon nanotubes / sea urchin gold nanocomposite material, characterized by: A necklace-shaped carbon nanotube / sea urchin gold nanoparticle composite material with controllable and orderly arrangement was prepared by a simple template-assisted in-situ growth method, which specifically includes the following steps: (1) Initiate the reaction site of atom transfer radical reaction (ATRP) on the surface modification of carbon nanotubes (CNTs) through chemical reaction, acting as a carbon nanotube macromolecular initiator; (2) This carbon nanotube macromolecular initiator is used to prepare a poly (4-vinylpyridine) grafted carbon nanotube CNT- g -P4VP, as a carrier; (3) Regular and continuous sea urchin gold nanoparticles (SUGNPs) were grown on polymer-based carbon nanotubes by template-assisted in situ growth to obtain necklace-shaped poly (4-vinylpyridine) grafted carbon nanotubes / sea urchin gold SUG-CNT shish-kebab nanocomposites; silver / gold seeds were anchored on the surface of P4VP grafted CNTs through Au-N coordination, and then HAuCl4 was added for secondary growth into a necklace-shaped sea urchin gold string structure, wherein the precursors were chloroauric acid HAuCl4·3H2O and silver nitrate AgNO3, and ascorbic acid AA was selected as the reducing agent. The gold precursor added for further growth was HAuCl4·3H2O; Preparation of necklace-shaped SUG-CNT shish-kebab nanocomposite in step (3): 1 mg CNT- g -P4VP was dissolved in 10 mL of ethanol solution to make CNT- g The concentration of CNT-g-P4VP was maintained at 0.1 mg / mL. A seed solution was prepared by sequentially adding 20 μL of 10 mM HAuCl4·3H2O and 20 μL of 10 mM AgNO3 as precursors, and 300 μL of 10 mM ascorbic acid (AA) as a reducing agent to 300 μL of CNT-g-P4VP solution. The resulting reaction mixture was vigorously stirred under a magnetic field for 20 s, followed by the addition of 300 μL of 3 mM HAuCl4·3H2O and stirring for another 1 min. The reaction was stopped by centrifugation at 6000 rpm for 10 min, and the final product was redispersed in 3 mL of deionized water as a black solution.

2. The method for preparing a poly (4-vinylpyridine) grafted carbon nanotube / sea urchin gold nanocomposite SERS substrate according to claim 1, characterized in that: The carbon nanotubes include single-walled carbon nanotubes, double-walled carbon nanotubes or multi-walled carbon nanotubes.

3. The method for preparing a poly (4-vinylpyridine) grafted carbon nanotube / sea urchin gold nanocomposite SERS substrate according to claim 1, characterized in that: The structural formula of the carbon nanotube macroinitiator is: ， is a carbon nanotube-based group; X is Br.

4. The method for preparing a poly (4-vinylpyridine) grafted carbon nanotube / sea urchin gold nanocomposite SERS substrate according to claim 2, characterized in that: The gold nanostructures are uniformly anchored on the polymer-based carbon nanotubes through Au-N interactions with functional groups without obvious agglomeration.

5. A poly(4-vinylpyridine) grafted carbon nanotube / sea urchin gold nanocomposite material prepared according to any one of claims 1 to 4.

6. The method for detecting the organic dye malachite green using a poly (4-vinylpyridine) grafted carbon nanotube / sea urchin gold nanocomposite SERS substrate according to claim 5, characterized in that: In order to quantify the SERS performance of the prepared substrate, we used the organic dye malachite green as the probe molecule. The nanocomposite obtained by centrifugation was dispersed in a malachite green aqueous solution and then fully sonicated to effectively capture the analyte molecules on the surface of the substrate material, and then Raman detection was performed.

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