A V5S4 nanoflower SERS substrate with SERS activity, its preparation method and application

Abstract

The application relates to a V5S4 nanoflower SERS substrate with SERS activity and a preparation method and application thereof. The V5S4 nanoflower SERS substrate is composed of V5S4 nanosheet cross growth; and the exposed crystal face of the V5S4 nanoflower SERS substrate is a (110) face.

Description

Technical Field

[0001] This invention relates to a V5S4 nanoflower SERS substrate, its preparation method, and its application. Specifically, it relates to a method for preparing a V5S4 nanoflower surface-enhanced Raman scattering (SERS) substrate with a size of 200-1000 nm by cross-growing of nanosheets using a hydrothermal method, belonging to the field of laser Raman spectroscopy and detection technology. Background Technology

[0002] Surface-enhanced Raman scattering (SERS) refers to the phenomenon where the Raman signal of molecules adsorbed on a rough substrate surface is significantly enhanced. Discovered in 1973 and formally proposed in 1977, SERS spectroscopy, as a sensitive vibrational spectroscopy technique, can provide information on material structure and chemical composition down to the single-molecule level, thus enabling trace detection of analytes. Compared to traditional atomic absorption spectroscopy, colorimetry, fluorescence, nuclear magnetic resonance, and immunochromatography, SERS spectroscopy offers advantages such as speed, sensitivity, and non-destructive testing. Therefore, SERS technology has attracted considerable interest from researchers, and numerous substrate materials and detection methods related to SERS have been reported. It is currently widely used in environmental pollutant detection, food safety testing, and biosensing, especially in virus detection, tumor identification, and even the currently popular field of bioimaging, where its specificity and non-destructive nature offer broad application prospects.

[0003] The core of SERS detection lies in the selection of the substrate material. Traditional SERS substrate materials are mainly noble metal nanoparticles such as Au and Ag. Through the electromagnetic enhancement mechanism, when the frequency of the incident light is close to the plasma vibration frequency on the surface of the metal nanospheres, a strong local electric field is formed on the surface of the metal particles, which significantly enhances the Raman signal of the analyte in this region. Noble metals have high carrier concentrations, and their unique plasmon resonance effect allows their enhancement factor (EF) to reach 10. 14 However, noble metal substrates suffer from drawbacks such as high manufacturing costs, limited variety, poor chemical stability, poor biocompatibility, and poor reproducibility due to uneven hotspot distribution. These intractable problems severely limit their application. Conversely, semiconductor substrates offer advantages such as easily tunable band structure, low manufacturing costs, good biocompatibility, high spectral stability, and good reproducibility, overcoming the shortcomings of noble metal substrates. Furthermore, semiconductor substrates exhibit selective enhancement of molecules and molecular Raman peaks, which holds broad application prospects in bioanalysis. Therefore, we need semiconductor materials with high SERS activity.

[0004] The high SERS activity of noble metal nanoparticles such as Au and Ag originates from the surface plasmon resonance effect brought about by their abundant carrier concentration. Semiconductor materials, however, lack sufficient carrier concentration and are unlikely to produce the same plasmon resonance effect as noble metals. At 300K, the intrinsic carrier concentration of Si is 1.5 × 10⁻⁶. 10 cm -3 The carrier concentration of Au can reach 10⁻⁶. 22 cm -3 This results in the insignificance of the plasma-dominated electromagnetic enhancement effect. Therefore, the SERS phenomenon in semiconductor materials is explained by charge transfer-dominated chemical enhancement. Charge transfer refers to the interaction between molecules and other adsorbed materials on the SERS substrate surface after molecules are adsorbed, which affects the charge density distribution of the molecules, changes the polarizability of the molecules, increases the Raman scattering cross section of the molecules, and enhances the Raman signal of the molecules. Currently, a large number of SERS-active semiconductor substrate materials have been reported, and transition metal sulfides (TMDS), as a special class of two-dimensional materials that have emerged in recent years, possess unique photoelectric properties and high stability, while exhibiting strong in-plane bonds and weak out-of-plane interactions, showing great application potential in SERS detection. The reported SERS detection limit of pure-phase MoS2 microspheres can reach 10⁻⁶. -8 M, its enhancement factor can reach 5.3×10 5 By modulating the morphology, the SERS detection limit of MoS2 nanocages can be reduced to 10. -10 M; while the SERS detection limit for SnS2 microspheres with a size of micrometer can reach 10. -13 M, its enhancement factor can reach 3×10 8 Considering that transition metals can provide abundant excited-state electrons, they are often used to combine with nonmetals to form compounds. Currently reported Ta₂O₅ and Nb₂O₅ semiconductor SERS substrate materials have detection limits of 9 × 10⁻⁶. -9 M and 10 -7 M. Summary of the Invention

[0005] Therefore, the purpose of this invention is to provide a V5S4 material with special morphology and high SERS activity, as well as its preparation method and application, so as to provide a material basis for the practical application of SERS technology.

[0006] On one hand, the present invention provides a V5S4 nanoflower SERS substrate, which is composed of V5S4 nanosheets grown in a cross-growth manner; the exposed crystal plane of the V5S4 nanoflower SERS substrate is the (110) plane.

[0007] Compared to existing methods for synthesizing vanadium sulfide, relatively uniform nanospheres were obtained by uniformly mixing ammonium metavanadate powder and sodium thiosulfate powder without adding any other surfactants, followed by hydrothermal reaction at 180°C for 14 hours, and then vacuum drying at 80°C. Nanorod-shaped vanadium sulfide nanoparticles of different lengths were obtained by uniformly mixing ammonium metavanadate powder and sodium thiosulfate powder, adding 10 mL of NH3·H2O as a surfactant, and then performing hydrothermal reactions at 180°C for 14 and 16 hours, followed by vacuum drying at 80°C. Nanosheets of different thicknesses were obtained by uniformly mixing sodium orthovanadate powder and ammonium thiosulfate powder, adding 2 mL of polyethylene glycol 400 as a surfactant, and then vacuum drying at 80°C. The vanadium sulfide nanoparticles with different morphologies synthesized by these methods generally exhibited poor SERS activity.

[0008] In this invention, V5S4 nanoflowers are directly synthesized via a simple one-step hydrothermal reaction. Polyvinylpyrrolidone K30 is added as a surfactant in the reaction. By adjusting the mass of the surfactant and the hydrothermal reaction time, V5S4 nanosheets can be cross-grown to form nanoflowers of 200-1000 nm. These nanoflowers have a large specific surface area and weak out-of-plane interactions, facilitating chemical bonding and promoting molecular adsorption. They also promote charge transfer between the substrate and molecules, significantly improving the intensity of the SERS signal. When the V5S4 nanoflowers are used as a SERS substrate, SERS detection of Rhodamine 6G (R6G) and methyl violet (MV) molecules is performed. When the concentrations of both are 10... -7 Even at time M, a relatively strong signal is still present. This invention synthesizes a two-dimensional semiconductor material, V5S4 nanoflowers, via a hydrothermal method, and investigates its SERS performance by varying the hydrothermal reaction time and the amount of surfactant added.

[0009] Preferably, the thickness of the nanosheets in the V5S4 nanoflower is 2-10 nm, and the diameter is 100-900 nm.

[0010] Preferably, the size of the V5S4 nanoflower SERS substrate is 200–1000 nm.

[0011] On the other hand, the present invention provides a method for preparing a V5S4 nanoflower SERS substrate, comprising:

[0012] (1) Add vanadium source, surfactant and sulfur source to deionized water and mix to obtain precursor solution;

[0013] (2) The obtained precursor solution was placed in a reaction vessel and subjected to hydrothermal reaction to obtain the V5S4 nanoflower SERS substrate.

[0014] In this invention, a certain amount of sodium orthovanadate is added to deionized water, followed by polyvinylpyrrolidone K30 powder. The mixture is stirred until a homogeneous and transparent solution is obtained. Thioacetamide powder is then dissolved in the above solution and stirred until homogeneous to obtain a precursor solution. The precursor solution is then placed in a 100 mL reaction vessel and reacted hydrothermally at 160 °C for 15-24 hours. After centrifugation, washing, and vacuum drying, the V5S4 substrate is obtained.

[0015] Preferably, in step (1): first add the vanadium source to deionized water, then add a surfactant and mix to obtain a mixed transparent solution; then add the sulfur source and mix to obtain a precursor solution.

[0016] Preferably, in step (1): the sulfur source is at least one of thioacetamide, sodium thiosulfate and potassium thiosulfate;

[0017] The vanadium source is at least one of sodium orthovanadate, ammonium metavanadate, and potassium orthovanadate.

[0018] The surfactant includes at least one of polyvinylpyrrolidone K30, polyethylene glycol 400, and ammonia.

[0019] Preferably, in step (1): the mixing method is electromagnetic stirring, with a rotation speed of 500-600 rpm and a time of 10-30 minutes;

[0020] The molar ratio of the sulfur source to the vanadium source is (2-7):1, preferably 5:1.

[0021] Preferably, in step (1): the ratio of the sulfur source to deionized water is 20 mmol: (50-80) mL;

[0022] The ratio of the vanadium source to deionized water is 4 mmol: (50–80) mL;

[0023] The ratio of the vanadium source to the surfactant is 4 mmol: (0.25–1.0) g.

[0024] Preferably, in step (2), the temperature of the hydrothermal reaction is 140-180°C, and the time of the hydrothermal reaction is 15-24 hours.

[0025] Preferably, after the hydrothermal reaction, the product is centrifuged, washed, and dried.

[0026] The centrifugation is performed at a speed of 9000-11000 rpm for 4-8 minutes; preferably, the centrifugation is performed at a speed of 10000 rpm for 5 minutes.

[0027] The solvents used for washing are anhydrous ethanol and deionized water, and the number of washing cycles is 5 or more.

[0028] The drying method is vacuum drying, and the vacuum drying temperature is 60-80℃, and the time is 24-48h.

[0029] In another aspect, the present invention provides an application of V5S4 nanoflower SERS substrate in laser Raman spectroscopy and detection.

[0030] The beneficial effects of this invention are:

[0031] In this invention, V5S4 nanoflowers with high SERS activity were prepared, which are effective against concentrations of 10... -7 The probe molecules of Rhodamine 6G (R6G) and Methyl Violet (MV) still have high signals and can be directly used for the detection of various biomolecules. It is believed that the discovery of a SERS substrate V5S4 nanoflower shows great potential for practical applications such as biosensing. Attached Figure Description

[0032] Figure 1 SEM morphology (scale bar 500 nm) of V5S4 nanoflowers obtained by adding 0.50 g of surfactant polyvinylpyrrolidone K30 and hydrothermally reacting at 160 °C for different times: (a) 15 h; (b) 20 h; (c) 24 h. Figure 2 XRD patterns of V5S4 nanoflowers were obtained by adding 0.50 g of polyvinylpyrrolidone K30 and carrying out hydrothermal reactions at 160 °C for 15, 20 and 24 hours, respectively.

[0033] Figure 3 Adding 0.50 g of polyvinylpyrrolidone K30 and carrying out hydrothermal reactions at 160 °C for 15, 20, and 24 hours respectively yielded 10 pairs of V5S4 nanoflowers. -7 Raman spectra of different dye molecules of M, where (a) R6G molecule and (b) MV molecule;

[0034] Figure 4 In Examples 10 and 11, after adding 0.5g of surfactant polyvinylpyrrolidone K30 and adjusting different sulfur-vanadium ratios, a hydrothermal reaction was carried out at 160°C for 15h to obtain the XRD patterns of V5S4 nanoflowers.

[0035] Figure 5 In Examples 10 and 11, after adding 0.5g of surfactant polyvinylpyrrolidone K30 and adjusting different sulfur-vanadium source ratios, a hydrothermal reaction was carried out at 160°C for 15h to obtain the SERS performance test chart of V5S4 nanoflowers.

[0036] Figure 6In Examples 10 and 11, after adding 0.5g of surfactant polyvinylpyrrolidone K30 and adjusting different sulfur-vanadium source ratios, a hydrothermal reaction was carried out at 160°C for 15h to obtain the XRD patterns of V5S4 nanoflowers.

[0037] Figure 7 In Examples 12 and 13, after adding 0.5g of surfactant polyvinylpyrrolidone K30 and adjusting different sulfur-vanadium source ratios, a hydrothermal reaction was carried out at 160°C for 15h to obtain the SERS performance test chart of V5S4 nanoflowers. Detailed Implementation

[0038] The present invention will be further illustrated by the following embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the present invention.

[0039] In this disclosure, the V5S4 nanoflower SERS substrate is formed by the cross-growth of V5S4 nanosheets, with uniform particle size. Each nanoflower has a size of about 200-1000 nm and exhibits high SERS activity.

[0040] The method for preparing the V5S4 nanoflower SERS substrate in this invention includes: mixing reactants to form a homogeneous solution, performing a hydrothermal reaction, and vacuum drying to collect the product. Preferably, the hydrothermal reaction is carried out at 160°C, and the growth process of V5S4 grains is controlled by adjusting the hydrothermal reaction time to 15-24 hours to obtain the V5S4 nanoflower substrate.

[0041] The following is an example illustrating the preparation method of V5S4 nanoflowers.

[0042] A certain amount of commercially available sodium orthovanadate was dissolved in deionized water. Specifically, 4 mmol of sodium orthovanadate powder was added to 60 mL of deionized water, followed by the addition of a certain amount of polyvinylpyrrolidone K30 as a surfactant. As an example, 0.25 g of polyvinylpyrrolidone K30 was added as a surfactant, and the mixture was electromagnetically stirred at approximately 40°C until a homogeneous solution was formed. In this reaction, sodium orthovanadate served as the vanadium source.

[0043] A certain amount of thioacetamide (TAA) is then dissolved in the above solution. As an example, 20 mmol of thioacetamide (TAA) powder is added to the above solution, and the mixture is stirred at approximately 40°C for about 20 minutes (e.g., at a speed of 400–600 rpm for 10–30 minutes, preferably 20 minutes) until a yellow, transparent solution is formed, thus obtaining the desired precursor solution. In this reaction, thioacetamide powder (TAA) serves as the sulfur source.

[0044] V5S4 nanoflowers were prepared from the above precursor solution via a hydrothermal reaction. As an example, the precursor solution was transferred to a 100 mL reactor and hydrothermally reacted at 160°C for 15-24 hours to obtain a black solution. This solution was then centrifuged, washed, and vacuum dried to obtain the black V5S4 nanoflower powder. The centrifugation speed was 10,000–12,000 rpm for 5–10 minutes. For example, a centrifugation speed of 10,000 rpm for 10 minutes was used.

[0045] In this invention, the lining material of the hydrothermal reactor used in the above-mentioned hydrothermal reaction process is polytetrafluoroethylene (PTFE) or para-polystyrene (PPL).

[0046] The following examples further illustrate the present invention in detail. It should also be understood that the following examples are only for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are all within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make selections within a suitable range based on the description herein, and are not intended to be limited to the specific values ​​in the examples below. In the following examples and comparative examples, unless otherwise specified, the centrifugation speed is 10000 rpm / min and the time is 10 min.

[0047] Example 1:

[0048] First, 0.74 g (4 mmol) of sodium orthovanadate powder was added to 60 mL of deionized water, followed by 0.25 g of polyvinylpyrrolidone K30 powder. The mixture was then stirred electromagnetically at approximately 40 °C for 10-15 minutes to rapidly dissolve the powder and obtain a mixed transparent solution. Next, 1.5 g of TAA powder (20 mmol) was added to the above solution, and the mixture was stirred electromagnetically at 60 °C for 20 minutes to rapidly dissolve the powder and form a yellow, transparent, and homogeneous solution. The precursor solution was then transferred to a 100 mL hydrothermal reactor lined with polytetrafluoroethylene (PTFE) or para-polystyrene (PPL) and subjected to hydrothermal reaction at 160 °C for 15 hours to obtain a black precipitate. Finally, the precipitate was centrifuged, washed repeatedly with anhydrous ethanol and deionized water, and vacuum dried at 80 °C for 24 hours to obtain black V5S4 nanoflower powder.

[0049] Example 2:

[0050] First, 0.74 g (4 mmol) of sodium orthovanadate powder was added to 60 mL of deionized water, followed by 0.50 g of polyvinylpyrrolidone K30 powder. The mixture was then stirred electromagnetically at approximately 40 °C for 10-15 minutes to rapidly dissolve the powder and obtain a mixed transparent solution. Next, 1.5 g of TAA powder (20 mmol) was added to the above solution, and the mixture was stirred electromagnetically at 60 °C for 20 minutes to rapidly dissolve the powder and form a yellow, transparent, and homogeneous solution. The precursor solution was then transferred to a 100 mL hydrothermal reactor lined with polytetrafluoroethylene (PTFE) or para-polystyrene (PPL) and subjected to hydrothermal reaction at 160 °C for 15 hours to obtain a black precipitate. Finally, the precipitate was centrifuged, washed repeatedly with anhydrous ethanol and deionized water, and vacuum dried at 80 °C for 24 hours to obtain black V5S4 nanoflower powder.

[0051] Example 3:

[0052] First, 0.74 g (4 mmol) of sodium orthovanadate powder was added to 60 mL of deionized water, followed by 1.00 g of polyvinylpyrrolidone K30 powder. The mixture was then stirred electromagnetically at approximately 40 °C for 10-15 minutes to rapidly dissolve the powder and obtain a mixed transparent solution. Next, 1.5 g of TAA powder (20 mmol) was added to the above solution, and the mixture was stirred electromagnetically at 60 °C for 20 minutes to rapidly dissolve the powder and form a yellow, transparent, and homogeneous solution. The precursor solution was then transferred to a 100 mL hydrothermal reactor lined with polytetrafluoroethylene (PTFE) or para-polystyrene (PPL) and subjected to hydrothermal reaction at 160 °C for 15 hours to obtain a black precipitate. Finally, the precipitate was centrifuged, washed repeatedly with anhydrous ethanol and deionized water, and vacuum dried at 80 °C for 24 hours to obtain black V5S4 nanoflower powder.

[0053] Example 4:

[0054] First, 0.74 g (4 mmol) of sodium orthovanadate powder was added to 60 mL of deionized water, followed by 0.25 g of polyvinylpyrrolidone K30 powder. The mixture was then stirred electromagnetically at approximately 40 °C for 10-15 minutes to rapidly dissolve the powder and obtain a mixed transparent solution. Next, 1.5 g of TAA powder (20 mmol) was added to the above solution, and the mixture was stirred electromagnetically at 60 °C for 20 minutes to rapidly dissolve the powder and form a yellow, transparent, and homogeneous solution. The precursor solution was then transferred to a 100 mL hydrothermal reactor lined with polytetrafluoroethylene (PTFE) or para-polystyrene (PPL) and subjected to a hydrothermal reaction at 160 °C for 20 hours to obtain a black precipitate. Finally, the precipitate was centrifuged, washed repeatedly with anhydrous ethanol and deionized water, and vacuum dried at 80 °C to obtain black V5S4 nanoflower powder.

[0055] Example 5:

[0056] First, 0.74 g (4 mmol) of sodium orthovanadate powder was added to 60 mL of deionized water, followed by 0.50 g of polyvinylpyrrolidone K30 powder. The mixture was then stirred electromagnetically at approximately 40 °C for 10-15 minutes to rapidly dissolve the powder and obtain a mixed transparent solution. Next, 1.5 g of TAA powder (20 mmol) was added to the above solution, and the mixture was stirred electromagnetically at 60 °C for 20 minutes to rapidly dissolve the powder and form a yellow, transparent, and homogeneous solution. The precursor solution was then transferred to a 100 mL hydrothermal reactor lined with polytetrafluoroethylene (PTFE) or para-polystyrene (PPL) and subjected to hydrothermal reaction at 160 °C for 20 hours to obtain a black precipitate. Finally, the precipitate was centrifuged, washed repeatedly with anhydrous ethanol and deionized water, and vacuum dried at 80 °C for 24 hours to obtain black V5S4 nanoflower powder.

[0057] Example 6:

[0058] First, 0.74 g (4 mmol) of sodium orthovanadate powder was added to 60 mL of deionized water, followed by 1.00 g of polyvinylpyrrolidone K30 powder. The mixture was then stirred electromagnetically at approximately 40 °C for 10-15 minutes to rapidly dissolve the powder and obtain a mixed transparent solution. Next, 1.5 g of TAA powder (20 mmol) was added to the above solution, and the mixture was stirred electromagnetically at 60 °C for 20 minutes to rapidly dissolve the powder and form a yellow, transparent, and homogeneous solution. The precursor solution was then transferred to a 100 mL hydrothermal reactor lined with polytetrafluoroethylene (PTFE) or para-polystyrene (PPL) and subjected to hydrothermal reaction at 160 °C for 20 hours to obtain a black precipitate. Finally, the precipitate was centrifuged, washed repeatedly with anhydrous ethanol and deionized water, and vacuum dried at 80 °C for 24 hours to obtain black V5S4 nanoflower powder.

[0059] Example 7:

[0060] First, 0.74 g (4 mmol) of sodium orthovanadate powder was added to 60 mL of deionized water, followed by 0.25 g of polyvinylpyrrolidone K30 powder. The mixture was then stirred electromagnetically at approximately 40 °C for 10-15 minutes to rapidly dissolve the powder and obtain a mixed transparent solution. Next, 1.5 g of TAA powder (20 mmol) was added to the above solution, and the mixture was stirred electromagnetically at 60 °C for 20 minutes to rapidly dissolve the powder and form a yellow, transparent, and homogeneous solution. The precursor solution was then transferred to a 100 mL hydrothermal reactor lined with polytetrafluoroethylene (PTFE) or para-polystyrene (PPL) and subjected to hydrothermal reaction at 160 °C for 24 hours to obtain a black precipitate. Finally, the precipitate was centrifuged, washed repeatedly with anhydrous ethanol and deionized water, and vacuum dried at 80 °C for 24 hours to obtain black V5S4 nanoflower powder.

[0061] Example 8:

[0062] First, 0.74 g (4 mmol) of sodium orthovanadate powder was added to 60 mL of deionized water, followed by 0.50 g of polyvinylpyrrolidone K30 powder. The mixture was then stirred electromagnetically at approximately 40 °C for 10-15 minutes to rapidly dissolve the powder and obtain a mixed transparent solution. Next, 1.5 g of TAA powder (20 mmol) was added to the above solution, and the mixture was stirred electromagnetically at 60 °C for 20 minutes to rapidly dissolve the powder and form a yellow, transparent, and homogeneous solution. The precursor solution was then transferred to a 100 mL hydrothermal reactor lined with polytetrafluoroethylene (PTFE) or para-polystyrene (PPL) and subjected to hydrothermal reaction at 160 °C for 24 hours to obtain a black precipitate. Finally, the precipitate was centrifuged, washed repeatedly with anhydrous ethanol and deionized water, and vacuum dried at 80 °C for 24 hours to obtain black V5S4 nanoflower powder.

[0063] Example 9:

[0064] First, 0.74 g (4 mmol) of sodium orthovanadate powder was added to 60 mL of deionized water, followed by 1.00 g of polyvinylpyrrolidone K30 powder. The mixture was then stirred electromagnetically at approximately 40 °C for 10-15 minutes to rapidly dissolve the powder and obtain a mixed transparent solution. Next, 1.5 g of TAA powder (20 mmol) was added to the above solution, and the mixture was stirred electromagnetically at 60 °C for 20 minutes to rapidly dissolve the powder and form a yellow, transparent, and homogeneous solution. The precursor solution was then transferred to a 100 mL hydrothermal reactor lined with polytetrafluoroethylene (PTFE) or para-polystyrene (PPL) and subjected to hydrothermal reaction at 160 °C for 24 hours to obtain a black precipitate. Finally, the precipitate was centrifuged, washed repeatedly with anhydrous ethanol and deionized water, and vacuum dried at 80 °C for 24 hours to obtain black V5S4 nanoflower powder.

[0065] The main difference between Examples 1-3, 4-6, and 7-9 is that the hydrothermal reaction time is extended to allow the reactants to react fully; the main difference between Examples 1, 4, and 7 is that the mass of the surfactant is changed to explore the effect of the surfactant mass on the reactants.

[0066] Example 10:

[0067] The preparation process of the nanoflower powder in Example 10 is the same as in Example 2, except that the molar ratio of sulfur source to vanadium source is 4:1. That is, 1.5g (20mmol) of TAA powder and 0.74g (5mmol) of sodium orthovanadate are added.

[0068] Example 11

[0069] The preparation process of the nanoflower powder in Example 11 is the same as in Example 2, except that the molar ratio of sulfur source to vanadium source is 3:1. That is, 1.57g (21mmol) of TAA powder and 1.28g (7mmol) of sodium orthovanadate are added.

[0070] Example 12

[0071] The preparation process of the nanoflower powder in Example 12 is the same as in Example 2, except that the molar ratio of sulfur source to vanadium source is 6:1. That is, 1.35g (18mmol) of TAA powder and 0.55g (3mmol) of sodium orthovanadate are added.

[0072] Example 13

[0073] The preparation process of the nanoflower powder in Example 13 is the same as in Example 2, except that the molar ratio of sulfur source to vanadium source is 7:1. That is, 1.57g (21mmol) of TAA powder and 0.55g (3mmol) of sodium orthovanadate are added.

[0074] Figure 1 The microstructure of V5S4 nanoflowers generated by hydrothermal reaction at 160℃ with 0.5g of surfactant polyvinylpyrrolidone K30 for different times is shown in Figure a, where hydrothermal reaction time is 15h, b, and c are 20h.

[0075] Figure 2 The microstructure of V5S4 nanoflowers prepared in Examples 4, 5, and 6, obtained by adding the same mass of surfactant polyvinylpyrrolidone K30 and adjusting the hydrothermal reaction time at 160°C, is shown. Under the condition of the same mass of surfactant, it can be seen that the characteristic peak of V5S4 shifts towards a larger angle as the hydrothermal reaction is prolonged.

[0076] Figure 3 To test the SERS performance of hydrothermal reactions at 160℃ for 15h, 20h, and 24h after adding 0.50g of polyvinylpyrrolidone K30 surfactant, two probe molecules, R6G and MV, were used as markers. The results showed that when the probe molecule concentration was as low as 10... -7 At time M, the SERS intensity is still relatively high. When the hydrothermal reaction time is 15h, the SERS intensity reaches its peak. As the reaction time increases, the SERS intensity of the probe molecules gradually decreases.

[0077] Figure 4In Examples 10 and 11, V5S4 nanoflowers were obtained by adding 0.5g of surfactant polyvinylpyrrolidone K30 and adjusting the sulfur-vanadium ratio to different values, followed by a hydrothermal reaction at 160°C for 15 hours. The results showed that although the peak positions of the crystal planes corresponding to V5S4 remained essentially unchanged as the sulfur-vanadium ratio decreased, their intensity decreased significantly.

[0078] Figure 5 In Examples 10 and 11, after adding 0.5 g of surfactant polyvinylpyrrolidone K30 and adjusting the sulfur-vanadium source ratio, a hydrothermal reaction was carried out at 160°C for 15 h to obtain the SERS performance test charts of V5S4 nanoflowers. R6G and MV probe molecules were used as markers. The results showed that when the probe molecule concentration was as low as 10... -7 At a sulfur-vanadium ratio (M), significant SERS activity was still observed. However, the SERS activity decreased significantly with decreasing sulfur-vanadium ratio. The highest SERS activity was observed at a sulfur-vanadium ratio of 5:1. This is consistent with the peak intensity corresponding to the XRD pattern.

[0079] Figure 6 In Examples 10 and 11, V5S4 nanoflowers were obtained by adding 0.5g of surfactant polyvinylpyrrolidone K30 and adjusting the sulfur-vanadium source ratio to a certain extent, followed by a hydrothermal reaction at 160°C for 15 hours. The results showed that although the peak positions of the V5S4 crystal planes remained essentially unchanged with increasing sulfur-vanadium ratio, their intensity decreased significantly. Furthermore, when the sulfur-vanadium ratio reached 7:1, a significant amorphization phenomenon occurred.

[0080] Figure 7 In Examples 12 and 13, after adding 0.5 g of surfactant polyvinylpyrrolidone K30 and adjusting the sulfur-vanadium source ratio, a hydrothermal reaction was carried out at 160°C for 15 h to obtain SERS performance test images of V5S4 nanoflowers. R6G and MV probe molecules were used as markers. The results showed that when the probe molecule concentration was as low as 10... -7 At a sulfur-vanadium ratio (M), significant SERS activity was still observed. However, the SERS activity decreased significantly with increasing sulfur-vanadium ratio. The highest SERS activity was observed at a sulfur-vanadium ratio of 5:1. At a sulfur-vanadium ratio of 7:1, the SERS signal was very weak. Figure 5 and Figure 7 The SERS signal strength from strongest to weakest is: 5:1 > 6:1 > 4:1 > 7:1 > 3:1. This indicates that amorphization actually leads to a decrease in performance. This is consistent with the intensity corresponding to XRD.

Claims

1. A V5S4 nanoflower SERS substrate, characterized in that, The V5S4 nanoflower SERS substrate is composed of V5S4 nanosheet cross growth; and the exposed crystal face of the V5S4 nanoflower SERS substrate is a (110) face.

2. The V5S4 nanoflower SERS substrate of claim 1, wherein, The thickness of the nanosheet in the V5S4 nanoflower is 2-10 nm, and the diameter is 100-900 nm.

3. The V5S4 nanoflower SERS substrate of claim 2, wherein, The size of the V5S4 nanoflower SERS substrate is 200-1000 nm.

4. A method of preparing a V5S4 nanoflower SERS substrate according to any one of claims 1-3, characterized in that, Comprising: (1) adding a vanadium source, a surfactant and a sulfur source into deionized water and mixing to obtain a precursor solution; the surfactant is polyvinylpyrrolidone K30; the ratio of the sulfur source to deionized water is 20 mmol:(50-80) mL; the ratio of the vanadium source to deionized water is 4 mmol:(50-80) mL; and the ratio of the vanadium source to the surfactant is 4 mmol:(0.25-1.0) g; (2) placing the obtained precursor solution in a reaction kettle and performing hydrothermal reaction to obtain the V5S4 nanoflower SERS substrate; the temperature of the hydrothermal reaction is 140-180°C; and the time of the hydrothermal reaction is 15-24 hours.

5. The preparation method according to claim 4, characterized in that, In step (1), first, the vanadium source is added into deionized water, then the surfactant is added for mixing to obtain a mixed transparent solution; and then the sulfur source is added and mixed to obtain a precursor solution.

6. The preparation method according to claim 4, characterized in that, In step (1), the sulfur source is at least one of thioacetamide, sodium thiosulfate and potassium thiosulfate; The vanadium source is at least one of sodium orthovanadate, ammonium metavanadate and potassium orthovanadate.

7. The preparation method according to claim 4, characterized in that, In step (1), the mixing mode is electromagnetic stirring at a speed of 500-600 rpm for 10-30 minutes. The molar ratio of the sulfur source to the vanadium source is (2-7):

1.

8. The preparation method according to claim 7, characterized in that, In step (1), the molar ratio of the sulfur source to the vanadium source is 5:

1.

9. The production method according to any one of claims 4 to 8, characterized by, After the hydrothermal reaction, centrifugation, washing and drying are further performed; The centrifugation is performed at a speed of 9000-11000 rpm for 4-8 minutes. The washing solvent is anhydrous ethanol and deionized water, and the washing is performed for more than 5 times; The drying mode is vacuum drying, the temperature of the vacuum drying is 60-80°C, and the time is 24-48 h.

10. The method of claim 9, wherein, The centrifugation is performed at a speed of 10000 rpm for 5 minutes.

11. A V5S4 nanoflower SERS substrate as claimed in any one of claims 1-3 for use in laser Raman spectroscopy and detection.

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