Precious metal-semiconductor composite nanomaterial with Raman enhancement effect as well as preparation method and application of precious metal-semiconductor composite nanomaterial

Abstract

The invention belongs to the technical field of nanometer materials, and particularly relates to a precious metal-semiconductor composite nanometer material with a Raman enhancement effect and a preparation method and application of the precious metal-semiconductor composite nanometer material. The noble metal-semiconductor composite nanomaterial comprises a cerium dioxide carrier with a tubular structure and a gold nanoparticle load. The preparation method comprises the following steps: preparing white rod-shaped alkaline cerium carbonate by taking cerium nitrate hexahydrate and urea as reactants; and mixing the white rod-like alkaline cerium carbonate with sodium hydroxide in water, and carrying out hydrothermal reaction to obtain the cerium dioxide nanotube, hAuCl4 is used as a load precursor, a cerium dioxide nanotube is used as a carrier, under the action of PVP and L-ascorbic acid, a reduction reaction is carried out, the cerium dioxide nanotube is prepared, the diameter of the cerium dioxide nanotube is 400-450 nm, the wall thickness of the cerium dioxide nanotube is 15-20 nm, the diameter of gold nanoparticles is 10-20 nm, and the cerium dioxide nanotube / gold nanoparticles composite material has a strong surface Raman enhancement effect, can detect various organic matters, and can be used for detecting various organic matters. And the detection of part of organic matters can reach a lower detection limit.

Description

Technical Field

[0001] The present invention belongs to the technical field of nanomaterials, and more specifically relates to a noble metal-semiconductor composite nanomaterial with Raman enhancement effect, and its preparation method and application. Background Art

[0002] Surface-Enhanced Raman Spectroscopy (SERS) has developed into a powerful spectroscopic analysis technology due to its non-destructive property, which will not affect the measured object during the actual test process, and its high sensitivity, fast detection and other characteristics. As an advanced spectroscopic analysis technology, SERS has been widely applied in many fields such as pesticide residue detection, surface science analysis, biochemical analysis and environmental monitoring. Due to its unique fingerprint analysis, it has developed into an important technical means for in-situ analysis on the surface or interface, and plays an important role in trace detection and ultra-trace detection due to its excellent detection sensitivity. At present, a large number of noble metal / semiconductor composite nanomaterials are used as SERS substrates. Liu Yang et al. designed and prepared ternary Au@Cu 2 O-AgNCs by electroplating substitution method, realizing high-sensitivity SERS detection of malachite green (MG), with a detection limit as low as 10 -9 M. Sun Dawen et al. prepared molybdenum disulfide-coated titanium dioxide modified with gold nanoparticles (MoS 2 @TiO 2 @Au) as a recyclable SERS substrate for repeatable and sensitive SERS analysis and in-situ monitoring of the photodegradation process of three fungicides (methylene blue, malachite green and crystal violet). In the determination experiment of methylene blue in shrimp protein solution, the detection limit reached 1.509 μg / L. Zhang Xia et al. synthesized Ag / CeO 2 nanomaterials with dual enzyme-like activities to detect thiourea, and found that Ag / CeO 2 nanoenzymes showed strong peroxidase-like activity and oxidase-like activity, and were able to accelerate and catalyze the enzyme reaction of 3,3',5,5'-tetramethylbenzidine, significantly enhancing the Raman signal. The Raman intensity showed a good linear relationship with the thiourea concentration in the range of 10 -11 M~10 -1 M, and the detection limit was 2.4×10 -13 M. Due to the strong selectivity of SERS substrates, different substrate materials have different detection effects on different substances. At present, a large number of SERS substrate materials have not been prepared, which leads to the inability to detect some organic substances and hinders their application. At the same time, the insufficient SERS detection sensitivity of the substrate will also affect the practical application of SERS. Summary of the Invention

[0003] The object of the present invention is to provide a noble metal-semiconductor composite nanomaterial with Raman enhancement effect, which has high SERS detection sensitivity for organic substances and can be used for the detection of organic substances. The present invention provides the following solutions:

[0004] One of the technical solutions of the present invention: A preparation method of cerium dioxide nanotubes, the steps include:

[0005] Using cerium nitrate hexahydrate and urea as reactants to prepare white rod-shaped basic cerium carbonate (Ce(OH)CO 3 );

[0006] After mixing the white rod-shaped basic cerium carbonate with sodium hydroxide in water, the cerium dioxide (CeO 2 ) nanotubes are obtained through hydrothermal reaction.

[0007] Further, the step of using cerium nitrate hexahydrate and urea as reactants to prepare white rod-shaped basic cerium carbonate includes: dissolving cerium nitrate hexahydrate in water, adding urea, stirring until the solution becomes colorless and transparent, then stirring and reacting in an oil bath, collecting the solid product, and obtaining the white rod-shaped basic cerium carbonate through washing and drying.

[0008] Optionally, the mass ratio of cerium nitrate hexahydrate to urea is 0.9:2 to 1:2.

[0009] Optionally, the temperature of the stirring reaction in the oil bath is 80-100°C, and the time is 22-26h.

[0010] Further, the mass ratio of the white rod-shaped basic cerium carbonate to sodium hydroxide is 1:15 to 1:16.

[0011] Further, the temperature of the hydrothermal reaction is 115-125°C, and the time is 22-26h.

[0012] Another technical solution of the present invention: Provide a cerium dioxide nanotube prepared by the above preparation method, the diameter of the cerium dioxide nanotube is 400-450nm, and the wall thickness is 15-20nm.

[0013] Another technical solution of the present invention: Provide a composite nanomaterial with Raman enhancement effect, the composite nanomaterial uses the above cerium dioxide nanotube as a carrier and gold nanoparticles as a load;

[0014] The particle size of the gold nanoparticles is 10-20nm.

[0015] Further, the loading amount of gold nanoparticles in the composite nanomaterial is 5-6wt.%.

[0016] Fourth technical solution of the present invention: Provide a preparation method of the above composite nanomaterial, the steps include:

[0017] Using HAuCl 4 as the precursor of the loading substance, using the cerium dioxide nanotube as the carrier, under the action of polyvinylpyrrolidone (PVP) and L-ascorbic acid, through a reduction reaction, a gold / ceria composite tubular nanomaterial is prepared, which is the composite nanomaterial.

[0018] Furthermore, the mass ratio of the cerium dioxide nanotube, HAuCl 4 , polyvinylpyrrolidone (PVP) and L-ascorbic acid is 0.5:0.01:0.35:0.6.

[0019] Furthermore, the steps of the reduction reaction include:

[0020] Mix polyvinylpyrrolidone (PVP) and L-ascorbic acid with water, then add the cerium dioxide nanotube, heat to 80-100 °C under stirring conditions, and then add HAuCl 4 , react for 3-4 h, centrifuge, wash and dry to obtain the gold / ceria composite tubular nanomaterial.

[0021] The present invention uses polyvinylpyrrolidone (PVP) for surface modification. PVP acts as a dispersant in the present invention, which can fully disperse the reduced gold nanoparticles and prevent the aggregation of gold nanoparticles; at the same time, PVP also acts as an adhesive in the present invention, and it has excellent adhesion, which can adhere the dispersed gold nanoparticles with smaller sizes to the cerium dioxide tubes with larger sizes.

[0022] Optionally, the addition of HAuCl 4 is added in the form of an aqueous solution.

[0023] Optionally, the drying temperature is 50-70 °C and the time is 5-7 h.

[0024] Due to its tubular structure, cerium dioxide nanotubes have a high specific surface area and porosity, and they have more excellent performance in the fields of catalysis, sensing, etc. The special morphology of its pipeline structure also shows obvious optical absorption and scattering effects optically, and has good detection ability for organic substances, especially methylene blue and crystal violet, in surface Raman enhanced spectroscopy tests, and can reach a lower detection limit, and can be used for the detection of related organic substances.

[0025] Fifth technical solution of the present invention: Provide an application of the above composite nanomaterial in the detection of organic substances.

[0026] Optionally, the application in the detection of organic substances includes the detection of methylene blue and / or crystal violet.

[0027] The present invention discloses the following technical effects:

[0028] The present invention prepares a gold / ceria composite tubular nanomaterial, wherein the ceria nanotubes have a diameter of about 400 - 450 nm, a wall thickness of 15 - 20 nm, and the gold nanoparticles have a diameter of 10 - 20 nm. The gold nanoparticles are successfully loaded on the ceria nanotubes, and then the gold / ceria composite tubular nanomaterial is used for surface-enhanced Raman spectroscopy detection. The detection results show that the composite tubular nanomaterial has a strong surface Raman enhancement effect, can detect a variety of organic substances, and the detection of some organic substances can reach a lower detection limit. Brief Description of the Drawings

[0029] The drawings constituting a part of this application are used to provide a further understanding of this application. The schematic embodiments and descriptions thereof of this application are used to explain this application and do not constitute an improper limitation to this application. In the drawings:

[0030] Figure 1 are TEM images of the gold / ceria composite tubular nanomaterial at different magnifications in Example 1, wherein a is at low magnification and b is at high magnification;

[0031] Figure 2 is the X-ray energy spectrum analysis image of the gold / ceria composite tubular nanomaterial in Example 1;

[0032] Figure 3 is the X-ray diffraction image of the gold / ceria composite tubular nanomaterial in Example 1;

[0033] Figure 4 is the X-ray photoelectron energy spectrum analysis image of the gold / ceria composite tubular nanomaterial in Example 1, wherein a is for cerium element and b is for gold element;

[0034] Figure 5 is the surface Raman enhancement spectroscopy detection result of methylene blue (MB) by the composite nanomaterial in Example 1;

[0035] Figure 6 is the surface Raman enhancement spectroscopy detection result of methylene blue (MB) by pure gold nanoparticles;

[0036] Figure 7 is the surface Raman enhancement spectroscopy detection result of crystal violet (CV) by the composite nanomaterial in Example 1. Detailed Description of the Invention

[0037] Now, various exemplary embodiments of the present invention will be described in detail. This detailed description should not be considered as a limitation to the present invention, but should be understood as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0038] It should be understood that the terms used in the present invention are only for describing particular embodiments and are not intended to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0039] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0040] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific embodiments of the present invention specification, which are obvious to those skilled in the art. Other embodiments obtained from the present invention specification are obvious to those skilled in the art. The present invention specification and examples are merely exemplary.

[0041] Regarding "comprising", "including", "having", "containing", etc. used herein, they are all open-ended terms, meaning including but not limited to.

[0042] Unless otherwise specified, "room temperature" and "normal temperature" referred to in the specific embodiments of the present invention both refer to 20 - 30 °C.

[0043] The raw materials and reagents used in the specific embodiments of the present invention are all commercially available products.

[0044] Composite nanomaterials are materials composed of two or more different nanomaterials, which can achieve a synergistic effect by combining the characteristics and functions of different nanomaterials. Currently, they have shown broad application prospects in the fields of energy, sensors, catalysts, biomedicine, etc. Among them, noble metal / semiconductor composite nanomaterials can obtain materials with unique physical and chemical properties by combining noble metals (such as gold, silver, and platinum) with semiconductor materials (such as titanium dioxide, zinc oxide, and molybdenum disulfide, etc.). Such composite nanomaterials can regulate electron transport properties, optoelectronic properties, and catalytic properties, and expand the application fields of the materials. Gold / ceria (Au / CeO 2)Composite nanomaterials have a high surface area, excellent chemical stability, and tunable structural morphology. Gold / ceria composite nanomaterials have broad application potential, but there are also some potential disadvantages and challenges. In the prior art, the process of preparing gold / ceria composite nanomaterials is complex, requiring the control of multiple steps and process parameters, which increases the complexity of synthesis. In addition, some preparation methods may use expensive materials or require special equipment, resulting in high costs. During the material composite process, there are challenges in the interfacial compatibility between materials, which may lead to interfacial defects and interaction problems. Moreover, the proportion of gold / ceria composite nanomaterials and the particle size of gold nanoparticles are not appropriate, making it difficult to achieve the optimal performance. Based on the problems of the existing gold / ceria composite nanomaterials, such as complex preparation process, high cost, poor interfacial compatibility, and the need for further optimization of the ratio of gold nanoparticles to ceria and the size of gold nanoparticles, the present invention provides a noble metal-semiconductor composite nanomaterial with Raman enhancement effect, its preparation method, and application. Using a small amount of chloroauric acid solution (HAuCl 4 ), gold nanoparticles are successfully loaded onto the surface of ceria nanotubes to obtain a gold / ceria composite tubular nanomaterial with a large loading amount and gold nanoparticle diameters between 10 and 20 nm.

[0045] Gold plays an important role in SERS detection research and has made remarkable progress. Current research mainly focuses on the design of gold nanostructures, surface modification and functionalization, the study of surface enhancement effect mechanisms, and the exploration of new gold-based SERS materials. The present invention realizes a higher SERS enhancement effect by controlling the shape, size, and structure of gold nanoparticles.

[0046] Ceria (CeO 2 ) has also been widely studied in the field of SERS detection. As a SERS substrate material, CeO 2 nanoparticles or thin films have a high surface area, optical properties, and chemical stability, and can provide a relatively high SERS enhancement effect. The catalytic activity of CeO 2 can enhance the chemical reaction of target molecules in SERS detection and improve the SERS signal. The present invention uses the functionalization modification of the surface of CeO 2 with gold nanoparticles to further enhance its SERS performance.

[0047] The present invention optimizes the SERS enhancement effect and catalytic performance of the composite material by designing the morphology of ceria, changing the particle size and loading amount of gold nanoparticles. The prepared Au / CeO 2 composite material shows broad application prospects in the fields of SERS detection, catalytic conversion, and biomedicine, providing new solutions for improving analysis sensitivity, enhancing catalytic efficiency, and realizing biomedical applications. The Au / CeO disclosed in the prior art2 The technical solutions of the composite materials are different from the morphology and applications of the present invention. For example, the Huang Peixiang team has prepared a Au / CeO₂ rod-shaped catalyst for CO oxidation reaction, and the synthesized Au / CeO₂ has higher catalytic activity than pure CeO₂ nanorods; the Ruan Wendao team has prepared Au@CeO₂ core-shell nanospheres for photocatalytic hydrogen evolution reaction, and the hydrogen evolution rate of 4.05 μmol mg -1 h -1 is achieved under visible light, which is 10 times that of pure CeO 2 and has long-term stability; the Ouyang team has prepared a Au / CeO₂ / gC 3 N 4 heterostructure for the detection of microcystin by a sensor, and the sensor has excellent detection performance, with a linear response range of 0.05 - 10 5 pM and a detection limit of 0.01 pM.

[0048] Example 1

[0049] The preparation steps of the composite nanomaterial (Au / CeO₂ composite tubular nanomaterial) are as follows:

[0050] S1. Weigh 1.700 g of cerium nitrate hexahydrate and dissolve it in 80 mL of distilled water. Then weigh 3.600 g of urea and slowly add it under magnetic stirring until the solution becomes colorless and transparent. Subsequently, stir the solution at 80 °C in an oil bath for 24 h for the reaction. After the reaction is completed and cooled, centrifuge and wash with distilled water, and dry overnight to obtain white rod-shaped cerium basic carbonate.

[0051] S2. Weigh 0.250 g of the white rod-shaped cerium basic carbonate obtained in step S1 and add it to 40 mL of distilled water. Then add 3.840 g of NaOH and stir at room temperature for half an hour to obtain a milky white solution. React the solution in an oven at 120 °C for 24 h. After the reaction is completed, cool it to room temperature, centrifuge it, and wash it successively with distilled water and ethanol, and dry it at 100 °C for 24 h to obtain CeO₂ nanotubes.

[0052] S3. Weigh 0.350 g of polyvinylpyrrolidone (PVP) and 0.600 g of L-ascorbic acid and add them to 60 mL of distilled water. After complete dissolution, weigh 0.050 g of the CeO₂ nanotubes obtained in step S2 and add it to the solution. Heat the mixture to 90 °C and keep stirring for 10 minutes to obtain a mixed solution.

[0053] S4. Subsequently, take 0.2 mL of HAuCl 4 (0.05 g / mL), add it to 10 mL of distilled water and mix well, then introduce it into the mixed solution obtained in step S3. React for 3 h, centrifuge, wash it 3 times with distilled water and absolute ethanol, and place it in an oven at 60 °C to dry for 6 h to obtain the Au / CeO₂ composite tubular nanomaterial (composite nanomaterial).

[0054] Figure 1 TEM images of the Au / CeO₂ composite tubular nanomaterials at different magnifications in Example 1, where a is at low magnification and b is at high magnification. It can be seen from the figure the diameters of the CeO₂ nanotubes and the Au nanoparticles in the Au / CeO₂ composite tubular nanomaterials.

[0055] Figure 2 X-ray energy spectrum analysis image of the Au / CeO₂ composite tubular nanomaterials in Example 1. It can be seen from the figure the distribution of Au, O, and Ce elements in the Au / CeO₂ composite tubular nanomaterials.

[0056] Figure 3 X-ray diffraction image of the Au / CeO₂ composite tubular nanomaterials in Example 1. It can be seen from the figure that, compared with the standard card, the peak positions match exactly, proving the successful preparation of the Au / CeO₂ composite tubular nanomaterials by the method of the present invention.

[0057] Figure 4 X-ray photoelectron spectroscopy analysis image of the Au / CeO₂ composite tubular nanomaterials in Example 1, where a is for Ce element and b is for Au element. It can be seen from the figure that Ce element exists in +3 and +4 valences, and Au element exists in Au nanoparticles, +1 and +3 valences. This situation is due to the charge transfer between Au and CeO₂, which can further prove the successful synthesis of the Au / CeO₂ composite nanotubular materials.

[0058] Comparative Example 1

[0059] The preparation steps of the composite nanomaterials (Au / CeO₂ composite tubular nanomaterials) are as follows:

[0060] S1. Weigh 1.700 g of cerium nitrate hexahydrate and dissolve it in 80 mL of distilled water. Then weigh 3.600 g of urea and slowly add it under magnetic stirring until the solution becomes colorless and transparent. Subsequently, stir for 24 h under oil bath conditions at 80 °C for reaction. After the reaction is completed and cooled, wash it by centrifugation with distilled water and dry it overnight to obtain white rod-shaped cerium basic carbonate.

[0061] S2. Weigh 0.250 g of the white rod-shaped cerium basic carbonate obtained in step S1 and add it to 40 mL of distilled water. Then add 3.840 g of NaOH and stir at room temperature for half an hour to obtain a milky white solution. React in an oven at 120 °C for 24 h. After the reaction is completed, cool it to room temperature, centrifuge it with a centrifuge and wash it successively with distilled water and ethanol, and dry it at 100 °C for 24 h to obtain CeO₂ nanotubes.

[0062] S3. Uniformly disperse 0.05 g of CeO₂ nanotubes into 60 mL of deionized water and add 0.2 mL of HAuCl 4A solution (0.05 g / mL) was impregnated for 1 h, and then NaBH 4 solution was added as a reducing agent (NaBH 4 :Au = 10:1), and it was vigorously stirred. After reduction, the suspension was continuously stirred and dried at 80 °C. Finally, the sample was heated in air at 120 °C for 4 hours to prepare the Au / CeO 2 composite tubular nanomaterial.

[0063] In Comparative Example 1, a different scheme from the present invention was adopted in the step of loading gold. After detection, it was found that the diameter of the gold nanoparticles was 4 - 20 nm, and the mass ratio of the gold nanoparticles loaded on the surface of cerium dioxide was 0.23%, which proved that by different methods of loading gold, the size of the gold loaded on the surface of cerium dioxide would change significantly, and the loading amount would be significantly reduced.

[0064] Comparative Example 3

[0065] The preparation steps of the gold / titanium dioxide composite nanomaterial are as follows:

[0066] S1. Weigh 0.350 g of polyvinylpyrrolidone (PVP) and 0.600 g of L-ascorbic acid and add them to 60 mL of distilled water. After fully dissolving, weigh 0.050 g of titanium dioxide and add it to the solution. The mixture was heated to 90 °C and stirred for 10 minutes to obtain a mixed solution; among them, the titanium dioxide was prepared by the method in "Ding D, Zhang L, Fan Q, et al. Assemble of high-density gold nanodots on TiO 2 substrate for surface-enhanced Raman spectroscopy[J]. Applied Surface Science, 2016, 379:462 - 466.";

[0067] S2. Subsequently, take 0.2 mL of HAuCl 4 (0.05 g / mL) and add it to 10 mL of distilled water and mix well, then introduce it into the mixed solution in step S1, react for 3 h, centrifuge, wash it 3 times with distilled water and absolute ethanol, and dry it in an oven at 60 °C for 6 h to obtain the gold / titanium dioxide composite nanomaterial.

[0068] The effect of detecting the surface Raman enhanced spectrum of crystal violet (CV) by the obtained gold / titanium dioxide composite nanomaterial in the literature is inferior to that of the composite nanomaterial prepared in Example 1 of the present invention.

[0069] Test Example

[0070] Surface Raman Enhancement Spectroscopy Detection of Methylene Blue (MB) by Composite Nanomaterials:

[0071] Four treatments were set up, namely Example 1 and Comparative Examples 1-3. Take 1 mg of the composite material in Example 1 and Comparative Examples 1-3 and put it into a cell culture dish. Set up seven groups for each treatment, and then take 50 μL of methylene blue (MB) solutions with concentrations of 10 -3 、10 -4 、10 -5 、10 -6 、10 -7 、10 -8 、10 -9 mol / L and add them into the cell culture dish. After fully dispersing, take 10 μL from each and drop it onto a silicon wafer, put it into a sample box, and then put it into a vacuum oven to dry. Subsequently, surface Raman enhancement spectroscopy testing was carried out, and the results are as shown in Figures 5 - 6 .

[0072] Figure 5 are the surface Raman enhancement spectroscopy detection results of methylene blue (MB) by the composite nanomaterial in Example 1.

[0073] Figure 6 are the surface Raman enhancement spectroscopy detection results of methylene blue (MB) by pure gold nanoparticles.

[0074] It can be seen from Figures 5 - 6 that the gold / ceria composite tubular nanomaterial in Example 1 has a detection effect on methylene blue (MB), and the detection limit reaches 10 -8 mol / L; the pure ceria nanotubes without loaded gold nanoparticles have no detection effect on methylene blue (MB) at all; pure gold nanoparticles have a detection effect on methylene blue (MB), but the lowest detection limit is only 10 -5 mol / L.

[0075] Surface Raman Enhancement Spectroscopy Detection of Crystal Violet (CV) by Composite Nanomaterials

[0076] Four treatments were set up, namely Example 1 and Comparative Examples 1-3. Take 1 mg of the composite material in Example 1 and Comparative Examples 1-3 and put it into a cell culture dish. Set up 4 groups for each treatment, and then take 50 μL of crystal violet (CV) solutions with concentrations of 10 -6 、10 -7 、10 -8 、10 - 9 mol / L and add them into each cell culture dish. After fully dispersing, take 10 μL from each and drop it onto a silicon wafer, put it into a sample box, and then put it into a vacuum oven to dry. Subsequently, surface Raman enhancement spectroscopy testing was carried out, and the results are as shown in Figure 7 .

[0077] Figure 7 Raman surface-enhanced spectroscopy detection results of the composite nanomaterial in Example 1 for crystal violet (CV). As can be seen from the figure, the Au / CeO₂ composite tubular nanomaterial in Example 1 has a detection effect on crystal violet (CV), and the detection limit reaches 10 -8 mol / L, while the pure CeO₂ nanotubes without loaded Au nanoparticles have no detection effect on crystal violet (CV), and the pure Au nanoparticles also have no detection effect on crystal violet (CV).

[0078] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. The same or similar parts among the various embodiments can be referred to each other.

[0079] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing cerium dioxide nanotubes, characterized in that the steps include: White rod-shaped basic cerium carbonate was prepared by using cerium nitrate hexahydrate and urea as reactants; The white rod-shaped alkaline cerium carbonate and sodium hydroxide are mixed in water and then subjected to a hydrothermal reaction to obtain the cerium dioxide nanotubes.

2. The preparation method according to claim 1, characterized in that The step of preparing white rod-shaped alkaline cerium carbonate using hexahydrate cerium nitrate and urea as reactants comprises: dissolving hexahydrate cerium nitrate in water, adding urea, stirring until the solution is colorless and transparent, then stirring and reacting in an oil bath, collecting solid products, washing and drying to obtain the white rod-shaped alkaline cerium carbonate.

3. The preparation method according to claim 2, characterized in that: The mass ratio of the cerium nitrate hexahydrate to urea is 0.9:2 to 1:2; and / or, The stirring reaction in the oil bath is carried out at a temperature of 80 to 100° C. and for a time of 22 to 26 hours.

4. The preparation method according to claim 1, characterized in that: The mass ratio of the white rod-shaped basic cerium carbonate to sodium hydroxide is 1:15 to 1:16; and / or, The temperature of the hydrothermal reaction is 115-125° C. and the time is 22-26 hours.

5. A cerium dioxide nanotube obtained by the preparation method according to any one of claims 1 to 4, characterized in that: The diameter of the cerium dioxide nanotube is 400-450nm, and the wall thickness is 15-20nm.

6. A composite nanomaterial with Raman enhancement effect, characterized in that: The composite nanomaterial uses the cerium dioxide nanotubes as claimed in claim 5 as carriers and gold nanoparticles as loads; The particle size of the gold nanoparticles is 10 to 20 nm; The loading amount of the gold nanoparticles in the composite nanomaterial is 5-6 wt.%.

7. A method for preparing a composite nanomaterial according to claim 6, characterized in that the steps include: The composite nanomaterial is prepared by using HAuCl4 as a load precursor and the cerium dioxide nanotube as a carrier through a reduction reaction under the action of polyvinyl pyrrolidone and L-ascorbic acid.

8. The preparation method according to claim 7, characterized in that: The mass ratio of the cerium dioxide nanotubes, HAuCl4, polyvinyl pyrrolidone and L-ascorbic acid is 0.5:0.01:0.35:0.6; and / or, The reduction reaction steps include: mixing polyvinyl pyrrolidone and L-ascorbic acid with water, then adding the cerium dioxide nanotubes, heating to 80-100° C. under stirring conditions, then adding HAuCl4, reacting for 3-4 hours, centrifuging, washing and drying to obtain the gold / cerium dioxide composite tubular nanomaterial.

9. The preparation method according to claim 8, characterized in that: The HAuCl4 is added in the form of an aqueous solution; and / or, The drying temperature is 50-70° C. and the drying time is 5-7 hours.

10. Use of the composite nanomaterial with Raman enhancement effect as claimed in claim 6 in organic matter detection.

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