Cu / CuO / Ag nanoparticles and preparation method and application thereof

Abstract

The invention discloses Cu / CuO / Ag nano-particles and a preparation method and application thereof, and the method successfully prepares the Cu / CuO / Ag nano-particles with regular morphology and uniform dispersion by optimizing a dual-stabilizer system and a step-by-step reduction-replacement process. The material has dual functions of SERS enhancement and catalysis: as an SERS substrate, the enhancement factor of rhodamine 6G reaches 5.3 * 10 < 8 >, the detection limit is as low as 5.0 * 10 <-13 > mol / L, and the reproducibility is good (RSD = 6.2%); meanwhile, as a catalyst for hydrazinolysis and reduction reaction, by optimizing a reaction solvent and the pH value of a system, the reaction efficiency is remarkably improved, and an additional incubation step is not needed. The detection limit on the plasticizer DOTP can reach 2.0 * 10 <-9 > mol / L, and the method has the advantages of simplicity and convenience in operation, good reproducibility, high analysis speed and the like, and is suitable for rapid screening and quantitative analysis of plasticizers in food packaging, environmental water bodies and medical instruments.

Description

Technical Field

[0001] This invention belongs to the field of trace substance detection technology, specifically relating to a Cu / CuO / Ag nanoparticle, its preparation method, and its application. Background Technology

[0002] Surface-enhanced Raman scattering (SERS) is an analytical technique based on the surface plasmon resonance effect of metal nanostructures. When target molecules are adsorbed on rough metal surfaces or near nanostructures, their Raman scattering signals can be significantly enhanced, by millions to billions of times. SERS technology not only provides molecular vibrational fingerprint information for highly specific identification but also offers advantages such as narrow spectral bands, strong resistance to water interference, and no need for complex pretreatment. It has been widely applied in trace substance detection in fields such as environmental monitoring, biomedicine, and food safety.

[0003] Dioctyl terephthalate (DOTP), as a novel environmentally friendly plasticizer, is gradually replacing traditional phthalate (PAE) plasticizers due to its good heat resistance, low volatility, and excellent electrical insulation properties. It is widely used in PVC products such as food packaging, medical devices, and children's toys. However, the potential risks of long-term low-dose exposure to DOTP are not fully understood, and its chronic toxicity, endocrine disruption effects, and environmental residues have attracted widespread attention. Therefore, establishing a highly sensitive, rapid, and reliable method for detecting DOTP is of great significance.

[0004] Currently, the main conventional detection methods for DOTP include gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-tandem mass spectrometry (LC-MS / MS). Although these methods have high sensitivity and accuracy, they have limitations such as complex sample pretreatment, high instrument cost, long detection cycle, and difficulty in rapid on-site detection, which limits their application in large-scale screening and real-time monitoring.

[0005] In recent years, surface-enhanced Raman spectroscopy (SERS) technology has shown great promise in the field of plasticizer detection due to its high sensitivity, rapid response, and potential on-site detection capabilities. Existing SERS research largely focuses on using precious metal nanomaterials such as gold and silver as reinforcing substrates. For example, CN107290331A reports a hydrophobic PET-gold nanoparticle composite film for the detection of 2-mercaptopyridine; Huang Yiwei et al. (Rapid Surface-Enhanced Raman Spectroscopy Detection of Phthalate Esters in Textiles [J]. Spectroscopy and Spectral Analysis, 2020, 40(03): 760-764.) used nano-gold sol as a SERS substrate to achieve rapid detection of various phthalate esters, with a detection limit of 5 mg / L. However, there is still room for improvement in the enhancement performance, stability, cost, and functional integration of this type of substrate. Especially for nonpolar, low-affinity molecules such as DOTP, direct SERS detection is difficult, often requiring functionalized substrates or derivatization reactions to enhance the signal.

[0006] Therefore, developing a novel SERS substrate that integrates high enhancement performance, good stability, catalytic function, and detection to achieve rapid and highly sensitive SERS detection of plasticizers such as DOTP has significant scientific research value and practical application potential. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides Cu / CuO / Ag nanoparticles, their preparation method, and applications. By constructing a novel Cu / CuO / Ag composite nanomaterial as a surface-enhanced Raman scattering (SERS) substrate and integrating catalytic functions, it achieves highly sensitive, rapid, and repeatable detection of plasticizers such as terephthalic acid esters. This invention is innovative not only in material design and preparation process but also demonstrates significant advantages in detection performance, functional integration, and practical application, providing a reliable, economical, and efficient solution for rapid and highly sensitive SERS detection of plasticizers and their analogues.

[0008] This invention is achieved through the following technical solution:

[0009] A method for preparing Cu / CuO / Ag nanoparticles includes the following steps:

[0010] Step 1) Disperse copper salt in water, heat to 45℃~50℃, add NH3·H2O solution while stirring until the solution becomes clear, continue stirring and add nonionic surfactant nonylphenol polyoxyethylene ether and anionic surfactant sodium dodecyl sulfate; after stirring, add hydrazine hydrate dropwise; after the addition is complete, continue the reaction, centrifuge, collect the reaction product, wash, and vacuum dry to obtain Cu / CuO nanoparticles;

[0011] Step 2) Disperse the Cu / CuO nanoparticles obtained in Step 1) in water; add AgNO3 aqueous solution dropwise while stirring, centrifuge after reaction, wash, and vacuum dry to obtain the final product.

[0012] Preferably, the concentration of sodium dodecyl sulfate in step 1) is 0.1 mol / L, and the concentration ratio of nonylphenol polyoxyethylene ether to sodium dodecyl sulfate is 1:8 to 1:10.

[0013] Preferably, the specific operation of adding hydrazine hydrate dropwise in step 1) is as follows:

[0014] Divide 6 mL of hydrazine hydrate into three equal portions and dilute them to volumes of 8 mL, 12 mL, and 15 mL respectively. Add the hydrazine hydrate dropwise in three separate drops, each dropwise over a period of 30 min.

[0015] Preferably, the concentration of the AgNO3 aqueous solution in step 2) is 0.05 mol / L, and the volume is 10 mL; the specific operation of adding the AgNO3 aqueous solution is as follows:

[0016] The AgNO3 aqueous solution was added dropwise in two batches, with an interval of 0.5 h between each addition, and the reaction time was 2 h.

[0017] Cu / CuO / Ag nanoparticles were prepared by the above method.

[0018] The above-mentioned Cu / CuO / Ag nanoparticles are used as a substrate in surface-enhanced Raman scattering.

[0019] Preferably, the application is for detecting terephthalate plasticizers.

[0020] Preferably, the plasticizer is dioctyl terephthalate.

[0021] Preferably, the detection includes the following steps:

[0022] Step A) Dissolve the plasticizer to be tested in a solvent, add the above-mentioned Cu / CuO / Ag nanoparticles, disperse evenly, and adjust the pH of the solution to 4~6; add hydrazine hydrate solution while stirring, without adding an additional catalyst to convert the plasticizer into dihydrazine phthalate. After the reaction, separate the nanoparticles, rinse and dry them, and test the SERS signal of the sample.

[0023] Step B) Prepare standard solutions of different concentrations for the sample solutions, and plot the concentration against 1610 cm⁻¹. -1 Standard curve of Raman intensity at a given location;

[0024] Step C) Calculate the concentration of plasticizer in the sample using a standard curve.

[0025] Preferably, the solvent in step A) is a mixed solution of water and ethanol; the pH value of the adjusted solution is 4.5.

[0026] The beneficial effects of this invention are as follows:

[0027] (1) This invention employs a method combining mild chemical reduction and displacement reactions, and through the synergistic effect of dual stabilizers and a stepwise addition process, successfully prepares Cu / CuO / Ag nanoparticles with regular morphology and uniform particle size. This method is simple to operate, has good repeatability, avoids the large-scale use of precious metals (such as gold and silver), significantly reduces material costs, and has good potential for large-scale preparation.

[0028] (2) The Cu / CuO / Ag nanoparticles of the present invention exhibit excellent SERS enhancement performance under 532 nm laser excitation. The enhancement factors for rhodamine 6G (R6G) and thiophenol reach 5.3 × 10⁻⁶, respectively. 8 and 7.8×10 7 The lowest detectable concentration for R6G is as low as 5.0 × 10⁻⁶. -13 The concentration of mol / L demonstrates extremely high detection sensitivity. Furthermore, the relative standard deviation (RSD) of 50 random detection points is only 6.2%, indicating that the substrate exhibits good signal reproducibility and reliability.

[0029] (3) The Cu / CuO / Ag composite nanomaterial of the present invention not only serves as a SERS-enhancing substrate, but also possesses dual catalytic functions for hydrazine hydrolysis and reduction reactions. By optimizing the reaction solvent and system pH, the conversion rate and detection sensitivity of the hydrazine hydrolysis reaction are significantly improved. This design eliminates the additional incubation or derivatization steps required in traditional methods, realizing the integration of "detection-catalysis" and greatly improving analytical efficiency.

[0030] (4) For the target analyte diterephthalate, the detection limit of the method of the present invention can reach 2.0 × 10⁻⁶. -9 With a detection limit of mol / L, it is far superior to that of conventional chromatographic methods, meeting the needs for trace and even ultra-trace detection, and is especially suitable for rapid screening and risk assessment in fields such as environment, food, and medical devices.

[0031] (5) The SERS substrate and detection method developed in this invention are not only applicable to the detection of plasticizers, but can also be extended to the rapid analysis of other harmful organic compounds or environmental pollutants. Its high throughput and on-site application characteristics provide broad application prospects for real-time monitoring, portable device integration, and other fields. Attached Figure Description

[0032] Figure 1The following are SEM, TEM, and EDX elemental images of the nanoparticles prepared in Example 1: a) SEM image of Cu / CuO nanoparticles; b) SEM image of Cu / CuO / Ag nanoparticles; c) TEM image of Cu / CuO / Ag nanoparticles; d) Dark-field image of Cu / CuO / Ag nanoparticles; e) Elemental image of Cu; f) Elemental image of Ag; g) Elemental image of O.

[0033] Figure 2 The Cu / CuO / Ag nanoparticles prepared in Example 1 were used to detect the standard curve of dihydrazine terephthalate;

[0034] Figure 3 SEM image of Cu / CuO / Ag nanoparticles prepared in Example 2;

[0035] Figure 4 SEM image of Cu / CuO / Ag nanoparticles prepared in Example 3;

[0036] Figure 5 The two-dimensional SERS spectra of rhodamine 6G (a) and thiophenol (b) on the surface of Cu / CuO / Ag nanoparticles in Example 3 are shown.

[0037] Figure 6 The SERS curves of the products from hydrazine hydrolysis in different solvents in Examples 1, 4, and 5 are shown.

[0038] Figure 7 The liquid chromatograms of the products of the hydrazinolysis reaction using Cu / CuO / Ag nanoparticles as a catalyst and without a catalyst in Example 6 are shown. Detailed Implementation

[0039] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0040] Unless otherwise specified, the technical means used in the following embodiments are all conventional means well known to those skilled in the art, and the experimental methods without specific conditions are all conventional methods in the art.

[0041] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0042] Example 1

[0043] 1. Preparation of Cu / CuO / Ag composite nanomaterials

[0044] A method for preparing Cu / CuO / Ag nanoparticles, the specific steps of which are as follows:

[0045] (1) 6.25 g CuSO4 was dispersed in 100 mL of ultrapure water and heated to 50 °C. 12 mL of NH3·H2O solution was slowly added under vigorous stirring until the solution became clear. Then, nonionic surfactant nonylphenol polyoxyethylene ether (NP-10) and anionic surfactant sodium dodecyl sulfate (SDS) were added under stirring, with the SDS concentration maintained at 0.1 mol / L and the NP-10 to SDS concentration ratio determined to be 1:10. After stirring for 15 min, N2H4·H2O (hydrazine hydrate) was added dropwise. After the addition was complete, the reaction was continued for 0.5 h. The product was then centrifuged, washed several times with water and ethanol, and dried under vacuum to obtain Cu / CuO nanoparticles.

[0046] In this invention, the selection and dosage of surfactants are crucial. Two different types of surfactants are used in combination to leverage their respective effects. SDS can more effectively control the growth of copper crystal nuclei, generating uniformly shaped nano-copper and avoiding agglomeration at low temperatures. Nonylphenol polyoxyethylene ether interacts with crystal faces through electrostatic forces, influencing the selection of crystal faces and the growth direction.

[0047] The specific procedure for adding the reducing agent hydrazine hydrate (6 mL in total) is as follows:

[0048] Divide 6 mL of hydrazine hydrate into three equal portions, dilute to different volumes, and add in three separate portions.

[0049] ① Initial addition: Take 2 mL of hydrazine hydrate solution, dilute with deionized water to a total volume of 8 mL, control the addition rate, and complete the addition in 30 min;

[0050] ② Second addition: Take 2 mL of hydrazine hydrate solution, dilute it with deionized water to a total volume of 12 mL, control the addition rate, and complete the addition in 30 min;

[0051] ③ Third addition: Take 2 mL of hydrazine hydrate solution, dilute it with deionized water to a total volume of 15 mL, control the addition rate, and complete the addition in 30 min.

[0052] In this invention, the batch addition of the reducing agent hydrazine hydrate is crucial. In the initial stage of the reaction, the reactant concentration is high and the reaction rate is fast, but incomplete reaction or the presence of side reactions may result in lower product formation efficiency compared to the intermediate stage. As the reaction approaches equilibrium, the amount of reducing agent added per unit time should be gradually reduced to ensure a stable reaction, thereby improving the conversion rate of nano-copper and achieving effective morphology control.

[0053] (2) The prepared Cu / CuO nanoparticles were redispersed in 50 mL of ultrapure water. AgNO3 (0.05 mol / L, 10 mL) aqueous solution was added dropwise to the suspension in two portions (0.5 h apart) with stirring, and the reaction was allowed to proceed for 2 h. After centrifugation, washing with water and ethanol, and vacuum drying, the resulting solid was the Cu / CuO / Ag composite nanomaterial. Samples were taken and Raman enhancement of the product under different conditions was tested.

[0054] like Figure 1 As shown in Figure a, the Cu / CuO nanoparticles exhibit a uniform particle size distribution, with a particle size of approximately 200–300 nm. Figure 1 As shown in Figure b, it can be clearly observed that the surface of the particle center is covered with Ag nanoparticles of about 50 nm. Figure 1 Image c in the image is a transmission electron microscope (TEM) image of Cu / CuO / Ag nanoparticles after thorough ultrasonic dispersion. Figure 1 The image in dg shows a dark-field photograph of Cu / CuO / Ag nanoparticles and elemental images of Cu, Ag, and O. In the image, Ag is uniformly distributed on the surface of the Cu / CuO particles, fused together as a whole, rather than simply being physically stacked from Cu and Ag nanoparticles.

[0055] 2. Testing of plasticizers

[0056] Using the Cu / CuO / Ag composite nanomaterials prepared above as a SERS substrate, the analysis and detection of plasticizers (terephthalic acid esters) were performed. The specific steps are as follows:

[0057] A precise amount of dioctyl terephthalate (DOTP) was accurately weighed and dissolved in 20 mL of a solvent system prepared by mixing deionized water and ethanol at a volume ratio of 4:6, resulting in a concentration of 1 mmol / L. 20 mg of the prepared Cu / CuO / Ag nanoparticles were added and ultrasonically dispersed until homogeneous. The pH of the solution was adjusted to 4.5. Three times the stoichiometric amount of hydrazine hydrate solution was added with stirring, and the mixture was refluxed for 4 h. After centrifugation, the Cu / CuO / Ag nanoparticles were washed with deionized water and dried. Samples were taken and the SERS signals of different samples were measured. Standard solutions of hydrazine terephthalate at different concentrations were prepared. Using Cu / CuO / Ag nanoparticles as the reinforcing substrate, plots were plotted as concentration versus 1610 cm⁻¹. -1 A standard curve of Raman intensities was generated. The concentration of DOTP in the sample was calculated using the standard curve.

[0058] The Cu / CuO / Ag nanoparticles prepared in this embodiment achieve a detection limit of 2.0 × 10⁻⁶ for DOTP detection. -9 mol / L, its standard curve is as follows Figure 2 As shown.

[0059] In this invention, the pH value of the reaction system has a crucial impact on the reducing performance of hydrazine hydrate. Experimental studies show that hydrazine hydrate exhibits optimal reducing efficiency when the system pH is maintained in the range of 4–6—this condition not only enhances its reduction reaction rate but also ensures optimal reduction performance for various target compounds. In contrast, if the system pH deviates from the suitable range (too high or too low), the reducing activity of hydrazine hydrate is significantly inhibited. Specifically, in a strongly acidic environment, hydrazine hydrate is prone to decomposition, leading to a reduction in its effective reducing components and thus lowering the overall reduction efficiency; while in a strongly alkaline environment, the nitrogen atoms in the hydrazine hydrate molecule undergo protonation, disrupting its reducing active center structure and ultimately weakening its reducing power.

[0060] Example 2

[0061] A method for preparing Cu / CuO / Ag nanoparticles, the specific steps of which are as follows:

[0062] 6.25 g of CuSO4 was dispersed in 100 mL of ultrapure water and heated to 50 °C. While stirring vigorously, 12 mL of NH3·H2O solution was slowly added until the solution became clear. Then, the nonionic surfactant nonylphenol polyoxyethylene ether (NP-10) was added while stirring. After stirring for 15 min, hydrazine hydrate was added dropwise. 6 mL of hydrazine hydrate was divided into three equal portions and diluted to volumes of 8 mL, 12 mL, and 15 mL, respectively. These portions were then slowly added dropwise to the solution system in three separate additions, each over a period of 30 min. After the addition was complete, the reaction was continued for 0.5 h. The mixture was then centrifuged, and the product was collected, washed several times with water and ethanol, and dried to obtain Cu / CuO nanoparticles.

[0063] The prepared Cu / CuO nanoparticles were redispersed in 50 mL of ultrapure water. AgNO3 (0.05 mol / L, 10 mL) aqueous solution was added dropwise to the suspension in two portions (0.5 h apart) with stirring, and the reaction was allowed to proceed for 2 h. After centrifugation, washing, and vacuum drying, a solid (Cu / CuO / Ag) was obtained.

[0064] The selection of suitable surfactants and their amounts is crucial for the successful preparation of nanoparticles. Simultaneously selecting nonionic surfactants such as octylphenyl ether (TX-100) and nonylphenol polyoxyethylene ether (NP-10), as well as anionic surfactants such as sodium dodecyl sulfate (SDS) and sodium dodecylbenzene sulfonate (SDSA), especially when the concentration ratio of the two is set between 1:8 and 1:10, allows for the orderly formation of nanoparticles. Figure 3The image shown is a SEM image of the Cu / CuO / Ag nanoparticles obtained in this embodiment using only a nonionic surfactant. Compared with Examples 1 and 2, due to the lack of SDS control over the growth rate, the nanoparticles obtained in Example 2 no longer have a uniform particle size distribution, and the nanoparticle shape is no longer regular.

[0065] Example 3

[0066] A method for preparing Cu / CuO / Ag nanoparticles, the specific steps of which are as follows:

[0067] 6.25 g of CuSO4 was dispersed in 100 mL of ultrapure water and heated to 50 °C. While stirring vigorously, 12 mL of NH3·H2O solution was slowly added until the solution became clear. Then, while stirring, the nonionic surfactant nonylphenol polyoxyethylene ether (NP-10) and the anionic surfactant sodium dodecyl sulfate (SDS) were added, maintaining the SDS concentration at 0.1 mol / L and the NP-10 to SDS concentration ratio at 1:10. After stirring for 15 min, hydrazine hydrate was added dropwise. 6 mL of hydrazine hydrate was diluted to a volume of 35 mL and slowly added dropwise to the solution over 90 min. After the addition was complete, the reaction was continued for 0.5 h. The mixture was then centrifuged, and the product was collected, washed several times with water and ethanol, and dried to obtain Cu / CuO nanoparticles.

[0068] The prepared Cu / CuO nanoparticles were redispersed in 50 mL of ultrapure water. AgNO3 (0.05 mol / L, 10 mL) aqueous solution was added dropwise to the suspension in two portions (0.5 h apart) with stirring, and the reaction was allowed to proceed for 2 h. After centrifugation, washing, and vacuum drying, a solid (Cu / CuO / Ag) was obtained.

[0069] The method of adding the reducing agent hydrazine hydrate solution is crucial. Comparing Examples 1 and 3, under identical reaction conditions, Cu / CuO / Ag nanoparticles were obtained by slowly adding hydrazine hydrate in batches with varying intervals. Figure 1 ) and continuous dripping without intervals ( Figure 4 Compared to the previous method, the particle size decreased significantly.

[0070] Comparing the SERS enhancement effects of the nanoparticles prepared in Examples 1 and 3, using rhodamine 6G molecules as probe molecules, its SERS enhancement effect at 1634 cm⁻¹ was observed. -1 By comparing the characteristic peak intensity at the location, the material effect of Example 1 was nearly 7 times greater than that of Example 3.

[0071] like Figure 5The image shows two-dimensional SERS patterns of rhodamine 6G and thiophenol molecules on the surface of Cu / CuO / Ag nanoparticles. As can be seen from the image, the Cu / CuO / Ag nanoparticles prepared in Example 1 exhibit a significant SERS enhancement effect. Calculations show that at an excitation wavelength of 532 nm, the Cu / CuO / Ag nanoparticles enhance the SERS of rhodamine 6G (… Figure 5 a) and thiophenol ( Figure 5 The enhancement factor for (b) can reach 5.3 × 10⁻⁶. 8 and 7.8×10 7 Order of magnitude. When the detection concentration of Rhodamine 6G is as low as 5.0 × 10⁻⁶. -13 At mol / L, it is located at 1634 cm⁻¹. -1 The characteristic Raman peak at this location can still be clearly detected. Fifty data points were randomly selected, and the value was calculated to be 1634 cm⁻¹. -1 The relative standard deviation of the characteristic Raman peak intensity at that location is only 6.2%.

[0072] Example 4

[0073] Using the Cu / CuO / Ag composite nanomaterial prepared in Example 1 as a SERS substrate, the plasticizer DOTP was analyzed and detected. The specific steps are as follows:

[0074] A precise amount of DOTP was weighed and dissolved in 20 mL of deionized water to a concentration of 1 mmol / L. 20 mg of the Cu / CuO / Ag nanoparticles prepared in Example 1 were added, and the mixture was ultrasonically dispersed until homogeneous. The pH of the solution was adjusted to 4.5. Three times the stoichiometric amount of hydrazine hydrate solution was added with stirring, and the mixture was refluxed for 4 h. After centrifugation, the Cu / CuO / Ag nanoparticles were rinsed with deionized water, dried, and samples were taken to test the SERS signals of different samples.

[0075] Example 5

[0076] Using the Cu / CuO / Ag composite nanomaterial prepared in Example 1 as a SERS substrate, the plasticizer DOTP was analyzed and detected. The specific steps are as follows:

[0077] A precise amount of DOTP was weighed and dissolved in 20 mL of ethanol to a concentration of 1 mmol / L. 20 mg of the Cu / CuO / Ag nanoparticles prepared in Example 1 were added, and the mixture was ultrasonically dispersed until homogeneous. The pH of the solution was adjusted to 4.5. Three times the stoichiometric amount of hydrazine hydrate solution was added with stirring, and the mixture was refluxed for 4 h. After centrifugation, the Cu / CuO / Ag nanoparticles were washed with deionized water, dried, and samples were taken to test the SERS signal of different samples.

[0078] The SERS curves of the products from hydrazinolysis in different solvents in Examples 1, 4, and 5 above are as follows: Figure 6 As shown, using a water / ethanol mixture as the solvent, the hydrazine hydrolysis efficiency and the corresponding SERS spectrum are significantly superior in terms of peak shape and intensity compared to using water or ethanol alone. This is mainly because the solubility of reactants and products differs greatly in solvents of different polarities. Dioctyl terephthalate has extremely poor solubility in water; if water is used as the solvent, the reaction proceeds almost in a two-phase state, resulting in a low conversion rate. Therefore, it is necessary to add ethanol to form a mixed solvent, while controlling the ratio of the two to ensure the hydrazine hydrolysis conversion rate, thereby improving the detection sensitivity and lowering the detection limit of the method. It is evident that the choice of solvent in the detection system of this invention has a crucial impact on the conversion rate and detection sensitivity of the subsequent products.

[0079] Example 6

[0080] The Cu / CuO / Ag composite nanomaterials prepared in Example 1 were used as catalysts for the hydrazinolysis reaction of the plasticizer DOTP. The specific steps are as follows:

[0081] A precise amount of DOTP was weighed and dissolved in 20 mL of a solvent system prepared by mixing deionized water and ethanol at a volume ratio of 4:6, resulting in a concentration of 1 mmol / L. The pH of the solution was adjusted to 4.5, and 3 times the stoichiometric amount of hydrazine hydrate solution was added with stirring. The mixture was then refluxed for 4 h. After the reaction was complete, 20 mg of Cu / CuO / Ag nanoparticles prepared in Example 1 were added, ultrasonically dispersed, and continuously stirred and incubated for adsorption for 4 h. After centrifugation, washing, and drying, samples were taken and the SERS signal was measured.

[0082] The Cu / CuO / Ag nanoparticles of this invention can not only be used as an enhancing substrate for Raman detection, but more importantly, these nanoparticles can be used as a catalyst for the hydrazinolysis reaction of the plasticizer DOTP, greatly improving the conversion rate of the reaction. For example... Figure 7 The figures show the liquid chromatograms of the products obtained by hydrazolysis using Cu / CuO / Ag nanoparticles as catalysts and without catalysts. As can be seen from the figures, the hydrazolysis reaction catalyzed by Cu / CuO / Ag nanoparticles not only has a high conversion rate but also fewer side reactions.

[0083] The embodiments described above are only some, not all, of the embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. The scope of protection of the present invention is determined by the scope claimed in the claims. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A method for preparing Cu / CuO / Ag nanoparticles, characterized in that, Includes the following steps: Step 1) Disperse copper salt in water, heat to 45℃~50℃, add NH3·H2O solution while stirring until the solution becomes clear, and continue stirring while adding nonionic surfactant nonylphenol polyoxyethylene ether and anionic surfactant sodium dodecyl sulfate. After stirring, add hydrazine hydrate dropwise in several portions; After the addition was complete, the reaction continued, followed by centrifugation. The product was collected, washed, and vacuum dried to obtain Cu / CuO nanoparticles. Step 2) Disperse the Cu / CuO nanoparticles obtained in Step 1) in water; add AgNO3 aqueous solution dropwise while stirring, centrifuge after reaction, wash, and vacuum dry to obtain the final product.

2. The method for preparing Cu / CuO / Ag nanoparticles according to claim 1, characterized in that, Step 1) The concentration of sodium dodecyl sulfate is 0.1 mol / L, and the concentration ratio of nonylphenol polyoxyethylene ether to sodium dodecyl sulfate is 1:8 to 1:

10.

3. The method for preparing Cu / CuO / Ag nanoparticles according to claim 1, characterized in that, The specific operation of adding hydrazine hydrate dropwise in step 1) is as follows: Divide 6 mL of hydrazine hydrate into three equal portions and dilute them to volumes of 8 mL, 12 mL, and 15 mL respectively. Add the hydrazine hydrate dropwise in three separate drops, each dropwise over a period of 30 min.

4. The method for preparing Cu / CuO / Ag nanoparticles according to claim 1, characterized in that, Step 2) The concentration of the AgNO3 aqueous solution is 0.05 mol / L, and the volume is 10 mL; the specific operation of adding the AgNO3 aqueous solution is as follows: The AgNO3 aqueous solution was added dropwise in two batches, with an interval of 0.5 h between each addition, and the reaction time was 2 h.

5. Cu / CuO / Ag nanoparticles prepared by the preparation method according to any one of claims 1-4.

6. The application of Cu / CuO / Ag nanoparticles as described in claim 5 as a substrate in surface-enhanced Raman scattering.

7. The application according to claim 6, characterized in that, The application is for detecting terephthalate plasticizers.

8. The application according to claim 7, characterized in that, The plasticizer is dioctyl terephthalate.

9. The application according to claim 7, characterized in that, The detection includes the following steps: Step A) Dissolve the plasticizer to be tested in a solvent, add the Cu / CuO / Ag nanoparticles as described in claim 5, disperse evenly, and adjust the pH of the solution to 4-6; add hydrazine hydrate solution while stirring, without adding an additional catalyst to convert the plasticizer into dihydrazine phthalate. After the reaction, separate the nanoparticles, rinse and dry them, and test the SERS signal of the sample. Step B) Prepare standard solutions of different concentrations for the sample solutions, and plot the concentration against 1610 cm⁻¹. -1 Standard curve of Raman intensity at a given location; Step C) Calculate the concentration of plasticizer in the sample using a standard curve.

10. The application according to claim 9, characterized in that, Step A) The solvent is a mixed solution of water and ethanol; the pH value of the adjusted solution is 4.5.

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