Preparation method and application of a flexible TiO2 surface-enhanced Raman scattering active substrate

Abstract

A preparation method and application of a flexible TiO2 surface-enhanced Raman scattering active substrate, which relates to the preparation and application of a surface-enhanced Raman scattering active substrate. It aims to solve the technical problems of the existing method of preparing TiO2 nanoparticles on cotton fabrics, which is complicated in operation and expensive in equipment. This method: After the cotton fabric is hydroxylated, tetrabutyl titanate is filtered and dried, and then placed in a hydrothermal kettle for hydrothermal treatment and then dried, and the filtration-hydrothermal treatment operation is repeated to obtain a flexible TiO2 surface-enhanced Raman scattering active substrate. The flexible TiO2 surface-enhanced Raman scattering active substrate of the present invention has good stability in acid, alkali, high temperature, low temperature, fresh state and after long-term storage. The minimum concentration of enrofloxacin residue detected on the surface of fish by the flexible TiO2 substrate is 1×10 ‑6 mol / L, and can be rapidly and in situ detected. This flexible TiO2 surface-enhanced Raman scattering active substrate can be used in the detection field.

Description

Technical Field

[0001] The invention relates to a preparation and application method of a surface enhanced Raman scattering active substrate. Background Art

[0002] Surface-enhanced Raman scattering (SERS) technology utilizes SERS-active substrates to achieve highly sensitive detection of adsorbed molecules. It has become a powerful advanced analytical technique, widely used in high-sensitivity detection, trace analysis, rapid detection, and other fields. Currently, there are two widely accepted enhancement mechanisms: electromagnetic field enhancement and chemical enhancement. The former is mainly due to the contribution of localized surface plasmon resonance of plasmon nanostructures, while the latter is mainly due to the contribution of charge transfer between the substrate and the adsorbate. Currently, noble metal (Au and Ag) plasmon nanostructures have been developed as SERS substrates for trace detection of analytes. To achieve rapid and convenient in situ analysis and detection, researchers have developed flexible SERS substrates by immobilizing noble metals on flexible support materials. Loading Au or Ag onto flexible support materials enables on-site detection of analytes in solution or on solid surfaces by dipping or wiping methods. However, the preparation of flexible SERS substrates of noble metals requires complex processes and preparation steps, which increases the cost and time of preparation. In addition, noble metal materials Au or Ag as flexible SERS substrates also have the disadvantages of high cost and low stability, which limit their practical applications.

[0003] Compared with noble metals, semiconductor substrates that mainly contribute to charge transfer have the advantages of low cost, good chemical stability, good biocompatibility, and high selectivity, and have excellent application prospects in actual detection. Therefore, researchers have begun to pay attention to the development of semiconductor nanomaterials as SERS substrates, especially wide-bandgap semiconductors with excellent optical, electromagnetic and sensing properties. TiO2, as an important wide-bandgap semiconductor inorganic functional material, has the advantages of being non-toxic, cheap, easily available and chemically stable, and has important applications in many fields. As a semiconductor SERS substrate, TiO2 can reflect information such as the adsorption configuration and interface of the detected molecules, but the semiconductor TiO2 SERS substrates reported so far are all in powder form, which cannot achieve rapid in-situ analysis and detection in actual systems.

[0004] The article "Hybrid cotton–anatase prepared under mild conditions with high photocatalytic activity under sunlight," published in the 2016 issue of the Royal Society of Chemistry (RSC Adv.) journal, issue 6, pages 58957-58969, reported coating cotton fibers with anatase titanium dioxide nanoparticles using a non-hydrolytic sol-gel process followed by a mild hydrothermal treatment. While this method successfully coated the cotton fabric with TiO2, it required extremely acidic conditions (pH < 1.5) to achieve this, and the thickness of the deposited layer and the size of the anchored TiO2 nanoparticles were difficult to control.

[0005] The article "Ultrasound and microwave technology for flake-TiO2 growth and immobilization on cotton fabrics in micro-dissolution process" published in the journal Mater. Chem. Phys. (2020), pp. 6, 58957-58969, reports the use of ultrasound and microwave technology to grow and immobilize flake TiO2 on cotton fabrics. While this innovative micro-dissolution process yields functional cotton fabrics with satisfactory photocatalytic activity and good durability, the preparation method is complex and requires specialized equipment and facilities, which increases production costs.

[0006] The article "Fabrication and characterization of infrared-insulating cotton fabrics by ALD" published in Cellulose, Issue 24, 2017, pages 3981-3990, reported that TiO2 nanoparticles were coated on cotton fabrics by atomic layer deposition technology. However, the thickness of the TiO2 layer in this method is controlled by the number of atomic layer deposition cycles, and the technology requires expensive equipment and is complicated to operate.

[0007] The article "One-step hydrothermal method to preparesuperhydrophobic cotton fabric with antibacterial properties" published in the 2021 issue of J. Eng. Fibers Fabr., No. 16, p. 15589250211066095, reported that a mixed solution of tetrabutyl titanate (TBT) and tridecafluorooctyl triethoxysilane (PEOTES) was hydrolyzed on the fiber surface using a one-step sol-gel method to form TiO2 nanoparticles on the fiber. However, this method requires the preparation of a sol in advance during the preparation process, which is complicated and cumbersome. Summary of the Invention

[0008] The present invention aims to address the technical issues of complex operations and expensive equipment in existing methods for preparing TiO2 nanoparticles on cotton fabrics. Instead, it provides a method for preparing and applying a flexible TiO2 surface-enhanced Raman scattering (SERS)-active substrate. Using a filtration-hydrothermal method, the present invention densely grows TiO2 nanoparticles of controllable size and distribution in situ on the surface of cotton fabrics. These nanoparticles serve as a flexible surface-enhanced Raman scattering (SERS)-active substrate, resolving the problem of conventional TiO2 powders hindering rapid, in-situ detection in practical applications and achieving a diverse range of TiO2 substrate forms.

[0009] The method for preparing a flexible TiO2 surface-enhanced Raman scattering active substrate of the present invention is carried out according to the following steps:

[0010] First, the cotton fabric is sequentially placed in acetone, anhydrous ethanol, hydrogen peroxide, and water and ultrasonically treated for 10 to 15 minutes, and then the cotton fabric is placed in an oven and dried at 60 to 80° C. for 2 to 3 hours to obtain a hydroxylated cotton fabric; this step removes impurities on the surface of the cotton fabric and completes the hydroxylation treatment;

[0011] 2. Add tetrabutyl titanate to the hydroxylated cotton fabric and filter it, then put the cotton fabric with tetrabutyl titanate into an oven and dry it at 60-80°C for 2-3 hours;

[0012] 3. Transfer the dried cotton fabric to a hydrothermal kettle filled with a mixed solvent of water and tert-butyl alcohol, place the hydrothermal kettle in an oven, and perform a hydrothermal reaction at a temperature of 110-130°C for 3-5 hours. Cool it naturally to room temperature, take out the cotton fabric, rinse it with deionized water, place it in a watch glass, and dry it in an oven at 50-70°C for 2-3 hours.

[0013] 4. Repeat the filtration-hydrothermal treatment operations of steps 2 and 3 1 to 4 times to obtain a flexible TiO2 surface-enhanced Raman scattering active substrate.

[0014] Furthermore, in step 1, the cotton fabric is pure white cotton cloth.

[0015] Furthermore, in step three, the mixed solvent is water and tert-butanol in a volume ratio of 1:(0.2-5).

[0016] Furthermore, in step three, the volume of the mixed solvent is two-thirds of the volume of the hydrothermal reactor.

[0017] The application of the flexible TiO2 surface-enhanced Raman scattering active substrate is to use the flexible TiO2 surface-enhanced Raman scattering active substrate in surface-enhanced Raman detection of antibiotics.

[0018] Furthermore, the antibiotics are attached to the surface of animal-derived food and can be wiped with a flexible TiO2 surface-enhanced Raman scattering active substrate to achieve rapid, in-situ detection.

[0019] Furthermore, the antibiotic is the quinolone antibiotic enrofloxacin.

[0020] The present invention adopts a simple and direct strategy, namely a filtration-hydrothermal synthesis scheme. The abundant surface hydroxyl groups on cotton fabric enable the titanium source (tetrabutyl titanate) to tightly bind to the cotton fabric surface. Through repeated filtration-hydrothermal operations, in situ nucleation and regrowth of titanium dioxide are achieved. Tightly arranged and evenly distributed TiO2 nanoparticles are in situ grown on the cotton fabric surface under mild conditions. As a new type of flexible TiO2 SERS active substrate, by wiping the surface of animal-derived food or vegetables, the semiconductor SERS active substrate can be used for rapid, in situ detection in practical applications.

[0021] The novel flexible TiO2 SERS substrate prepared by the present invention has a simple synthesis process, low raw material cost, is non-toxic and harmless, is environmentally friendly, has good SERS enhancement capability, and can realize rapid in situ detection of TiO2 as a flexible SERS substrate, which provides a new approach and idea for the application of semiconductor SERS in practical systems.

[0022] The novel flexible TiO2 SERS substrate of the present invention has no effect on detection accuracy when in a fresh state, stored in the air for a long time, soaked in hydrochloric acid, soaked in sodium hydroxide solution, soaked in hydrochloric acid and then in sodium hydroxide solution, and stored at high temperature or low temperature. The minimum concentration of enrofloxacin (ENR) residues detected on the surface of fish by the flexible TiO2 substrate is 1×10 - 6mol / L, which is the same as the sensitivity of ENR adsorbed on the flexible TiO2 substrate by conventional sampling (immersion solution adsorption sampling). The flexible TiO2 surface enhanced Raman scattering active substrate of the present invention can be used in the detection field. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a scanning electron microscope photograph of the flexible TiO2 surface-enhanced Raman scattering active substrate prepared in Examples 1 to 5;

[0024] Figure 2 Surface-enhanced Raman spectra of the flexible TiO2 surface-enhanced Raman scattering active substrates prepared in Examples 1 to 5;

[0025] Figure 3 The scanning electron microscope photographs of the flexible TiO2 surface-enhanced Raman scattering active substrates prepared in Examples 1 and 6 to 9 are shown;

[0026] Figure 4 Surface-enhanced Raman spectra of the flexible TiO2 surface-enhanced Raman scattering active substrates prepared in Examples 1 and 6 to 9;

[0027] Figure 5 Surface-enhanced Raman spectra of the flexible TiO2 surface-enhanced Raman scattering active substrate prepared in Example 1 in a fresh state and after being placed in air for 40 days, after being soaked in 5M hydrochloric acid for 5 hours, after being soaked in 5M sodium hydroxide solution for 5 hours, after being soaked in 5M hydrochloric acid for 2.5 hours and then in 5M sodium hydroxide solution for 2.5 hours, after being placed at a high temperature of 100°C for 5 hours, and after being placed at a low temperature of -20°C for 5 hours;

[0028] Figure 6 This is a surface-enhanced Raman spectrum of the flexible TiO2 surface-enhanced Raman scattering active substrate prepared in Example 1 after being wiped and sampled on the surface of a fish body;

[0029] Figure 7 The flexible TiO2 surface enhanced Raman scattering active substrate prepared in Example 1 was used to detect ENR residues on the surface of fish. In the surface enhanced Raman spectrum, ENR1388 cm -1 The relationship curve between the SERS peak intensity and the logarithm of its concentration;

[0030] Figure 8 Surface-enhanced Raman spectra of the flexible TiO2 surface-enhanced Raman scattering active substrates prepared in Examples 1, 10, and 11. DETAILED DESCRIPTION

[0031] The beneficial effects of the present invention are demonstrated with the following examples.

[0032] Example 1: The preparation method of the flexible TiO2 surface-enhanced Raman scattering active substrate of this embodiment is carried out according to the following steps:

[0033] 1. First, divide the pure cotton white cloth into 1×1cm 2 The cotton cloth was then placed in 5 mL of acetone, 10 mL of anhydrous ethanol, 10 mL of hydrogen peroxide, and 20 mL of water and ultrasonically treated for 15 minutes, and then placed in an oven and dried at 60°C for 2 hours. This step removed impurities on the surface of the cotton cloth and completed the hydroxylation treatment.

[0034] 2. Add 1.25 mL of tetrabutyl titanate to pure white cotton cloth for filtration, then place the cotton fabric with tetrabutyl titanate in an oven and dry it at 60°C for 2 hours;

[0035] 3. Then, the dried pure cotton white cloth was transferred to a hydrothermal kettle filled with 30 mL of a mixed solvent, wherein the mixed solvent was a mixture of water and tert-butanol in a volume ratio of 1:1. The hydrothermal kettle was placed in an oven and hydrothermally reacted at a temperature of 110°C for 3 hours. After cooling naturally to room temperature, the pure cotton white cloth was taken out and rinsed with deionized water, transferred to a watch glass, and placed in an oven to dry at 50°C for 2 hours.

[0036] 4. Repeat the filtration-hydrothermal treatment operations of steps 2 and 3 three times to obtain a flexible TiO2 surface-enhanced Raman scattering active substrate.

[0037] Example 2: This example differs from Example 1 in that the mixed solvent in step 3 is a mixture of water and tert-butanol in a volume ratio of 1:5, and the other steps and parameters are the same as those in Example 1.

[0038] Example 3: This example differs from Example 1 in that the mixed solvent in step 3 is a mixture of water and tert-butanol in a volume ratio of 1:2, and the other steps and parameters are the same as those in Example 1.

[0039] Example 4: This example differs from Example 1 in that the mixed solvent in step 3 is a mixture of water and tert-butanol in a volume ratio of 2:1, and the other steps and parameters are the same as those in Example 1.

[0040] Example 5: This example differs from Example 1 in that the mixed solvent in step 3 is a mixture of water and tert-butanol in a volume ratio of 5:1, and the other steps and parameters are the same as those in Example 1.

[0041] The flexible TiO2 surface enhanced Raman scattering active substrates prepared in Examples 1 to 5 were tested by scanning electron microscopy, and the obtained scanning electron microscopy images are as follows: Figure 1 As shown, from Figure 1It can be seen that the SEM images of the flexible TiO2 SERS substrate obtained at different water-alcohol ratios (1:5, 1:2, 1:1, 2:1, 5:1) are clearly different from those at lower water-alcohol ratios ( Figure 1 a and b) and higher water-to-alcohol ratios ( Figure 1 d and e), only when the water-alcohol ratio is 1:1, the size of TiO2 nanoparticles is the smallest, and the diameter of TiO2 nanoparticles is about 8.5nm, showing a denser, more uniform and smoother distribution ( Figure 1 c).

[0042] The flexible TiO2 surface enhanced Raman scattering active substrates prepared in Examples 1 to 5 were immersed in 8 mL of 1×10 -3 mol / L 4-mercaptobenzoic acid (4-MBA) ethanol solution, magnetically stirred at room temperature for 30 minutes; then, the sample was rinsed three times with deionized water and dried at 60°C to obtain the flexible TiO2 surface modified with the probe molecule 4-MBA. Raman spectra were measured using a LabRAM ARAMIS confocal Raman microscope from Jobin Yvon, France, with an excitation light source wavelength of 633nm. The surface-enhanced Raman spectra of the flexible TiO2 SERS substrate for 4-MBA obtained at different water-to-alcohol ratios were as follows: Figure 2 As shown. Figure 2 It can be seen that compared with substrates with other water-alcohol ratios, the SERS enhancement ability of the prepared flexible TiO2 is significantly improved when the water-alcohol ratio is 1:1. This should be attributed to the fact that the TiO2 nanoparticles generated when the water-alcohol ratio is 1:1 are the smallest in size, and the small TiO2 nanoparticles have abundant surface defects. X-ray photoelectron spectroscopy tests show that the TiO2 nanoparticles prepared when the water-alcohol ratio is 1:1 have more abundant surface oxygen vacancies, and the ratio of defective oxygen to lattice oxygen is 1.41:1, which is much larger than the TiO2 nanoparticles prepared with other water-alcohol ratios. Abundant surface defects mean more abundant surface state energy levels, which are both a medium for charge transfer (CT) and an effective adsorption active site, providing more charge transfer channels for SERS enhancement.

[0043] Example 6: This example differs from Example 1 in that the number of repetitions in step 4 is 0, and the other steps and parameters are the same as those in Example 1.

[0044] Example 7: This example differs from Example 1 in that the number of repetitions in step 4 is 1, and the other steps and parameters are the same as those in Example 1.

[0045] Example 8: This example differs from Example 1 in that the number of repetitions in step 4 is 2, and the other steps and parameters are the same as those in Example 1.

[0046] Example 9: This example differs from Example 1 in that the number of repetitions in step 4 is 4, and the other steps and parameters are the same as those in Example 1.

[0047] The flexible TiO2 surface enhanced Raman scattering active substrates prepared in Examples 1 and 6 to 9 were subjected to scanning electron microscopy testing, and the obtained scanning electron microscopy photos are as follows: Figure 3 As shown, from Figure 3 SEM images of the flexible TiO2 SERS substrate obtained after different filtration-hydrothermal cycles (1, 2, 3, 4, and 5) are shown. The figure shows that the density and uniformity of the TiO2 nanoparticles on the cotton fabric increase with increasing filtration-hydrothermal cycles. Like the water-alcohol ratio, the number of filtration-hydrothermal cycles also has a significant impact on the SERS enhancement of the flexible TiO2 substrate.

[0048] The flexible TiO2 surface-enhanced Raman scattering active substrates prepared in Examples 1 and 6 to 9 were immersed in 8 mL of a 1×10 -3 mol / L 4-mercaptobenzoic acid (4-MBA) ethanol solution, magnetically stirred at room temperature for 30 minutes; then, the sample was rinsed three times with deionized water and dried at 60 ° C to obtain the flexible TiO2 surface modified with the probe molecule 4-MBA. The Raman spectrum was measured using a LabRAM ARAMIS confocal Raman microscope from Jobin Yvon, France, with an excitation light source wavelength of 633 nm. The SERS spectra of the probe molecule 4-MBA adsorbed on the flexible TiO2 prepared with different filtration-hydrothermal cycles were shown in the figure below. Figure 4 As shown. Figure 4 As can be seen in the figure, the maximum SERS enhancement is observed when 4-MBA molecules are adsorbed on a substrate that has undergone four filtration-hydrothermal cycles. This is due to the dense and uniform distribution of TiO2 nanoparticles on the cotton fabric, which increases the number of TiO2 particles and enriches the surface defects, thereby enhancing the SERS signal of the probe molecule.

[0049] The stability of the flexible TiO2 surface-enhanced Raman scattering active substrate prepared in Example 1 was tested. The specific operation was as follows: the flexible TiO2 surface-enhanced Raman scattering active substrate prepared in Example 1 was immersed in 8 mL of 1×10 -3mol / L 4-mercaptobenzoic acid (4-MBA) ethanol solution, magnetic stirring at room temperature for 30 minutes; then, the sample was rinsed three times with deionized water and dried at 60 ° C to obtain the flexible TiO2 surface modified with the probe molecule 4-MBA. Figure 5 As shown, from Figure 5 As can be seen, even after 40 days of storage, the substrate still exhibited SERS activity similar to that of a fresh substrate. Furthermore, the substrate was resistant to corrosion by strong acids or bases, or even alternating strong acids and bases, as well as high temperatures up to 100°C and low temperatures as low as -20°C. This demonstrates that this novel flexible TiO2 SERS-active substrate has excellent stability and can be widely used as a reliable, low-cost SERS-active substrate for rapid, in-situ SERS detection.

[0050] The rapid in-situ detection capability of the flexible TiO2 surface-enhanced Raman scattering active substrate prepared in Example 1 was tested. The specific operation was as follows: First, five fish were immersed in aqueous solutions of enrofloxacin (ENR) with different concentrations. After a few minutes, the fish samples were taken out and placed in a 1×1 cm 2 The flexible TiO2 substrate is 2×2cm on the surface of the fish body. 2 The fish body surface was wiped 5 times along the square track in the counterclockwise or clockwise direction within the area. By wiping the sample from the fish body surface, the SERS spectra of different concentrations of ENR (enrofloxacin) adsorbed on the flexible TiO2 substrate are shown in Figure 6. Figure 6 It can be seen that the intensity of the ENR characteristic peak weakened with the decrease of ENR spike concentration when the ENR spike concentration was as low as 1×10 -7 mol / L, it is difficult to observe obvious SERS signals. -6 mol / L is the lowest concentration of ENR residue on the surface of fish body detected by flexible TiO2 substrate, which is the same as the sensitivity of ENR adsorbed on flexible TiO2 substrate by conventional sampling (immersion solution adsorption sampling). It can be seen that this new flexible TiO2 SERS active substrate can achieve rapid in situ detection without losing sensitivity. In addition, at ENR1388 cm -1 The relationship curve between the SERS peak intensity and its concentration logarithm is as follows: Figure 7 As shown, from Figure 7 It can be seen that ENR1388 cm -1 There is a good linear relationship between the SERS peak intensity and its concentration logarithm, which can be used for quantitative detection. 2 The value is 0.99154.

[0051] Example 10: This example differs from Example 1 in that the mixed solvent in step 3 is a mixture of water and ethanol in a volume ratio of 1:1, and the other steps and parameters are the same as those in Example 1.

[0052] Example 11: This example differs from Example 1 in that the mixed solvent in step 3 is a mixture of water and isopropyl alcohol in a volume ratio of 1:1. Other steps and parameters are the same as those in Example 1.

[0053] The flexible TiO2 surface-enhanced Raman scattering active substrates prepared in Examples 1, 10, and 11 were immersed in 8 mL of a 1×10 -3 mol / L 4-mercaptobenzoic acid (4-MBA) ethanol solution, magnetically stirred at room temperature for 30 minutes; then, the sample was rinsed three times with deionized water and dried at 60 ° C to obtain the probe molecule 4-MBA surface modified flexible TiO2. Raman spectra were measured using a LabRAM ARAMIS confocal Raman microscope from JobinYvon, France, with an excitation light source wavelength of 633 nm. The surface enhanced Raman spectrum is shown in Figure 2. Figure 8 As shown, from Figure 8 It can be seen that the SERS spectral intensities on the substrates obtained by hydrothermal treatment with different alcohol and water mixed solvents are different. When tert-butanol and water are used as the mixed solvent, the flexible TiO2 substrate shows the best SERS performance. This is mainly attributed to the different effects of different types of alcohol and water mixed solvents on the hydrolysis reaction of the titanium source (tetrabutyl titanate) (that is, the nucleation-regrowth of TiO2). Tert-butanol has greater steric hindrance and moderate viscosity. It can effectively control the degree of contact between the titanium source and water and thus control the hydrolysis reaction rate. In other words, it can effectively control the nucleation rate and regrowth rate of TiO2, so that a kinetic equilibrium is achieved between the two, thereby preparing a TiO2 flexible substrate with controllable particle size, distribution morphology, and density, while ensuring that the flexible TiO2 has abundant surface defects so that it has high SERS activity and spectral stability.

Claims

1. A method for preparing a flexible TiO2 surface-enhanced Raman scattering active substrate, characterized in that The method proceeds as follows: First, the cotton fabric was placed in acetone, anhydrous ethanol, hydrogen peroxide and water for ultrasonic treatment for 10 to 15 minutes respectively, and then the cotton fabric was placed in an oven and dried at 60 to 80 degrees Celsius for 2 to 3 hours to obtain hydroxylated cotton fabric; Second, tetrabutyl titanate was added to the hydroxylated cotton fabric for filtration, and then the cotton fabric with tetrabutyl titanate was placed in an oven and dried at 60-80°C for 2-3 hours; 3. Transfer the dried cotton fabric to a hydrothermal kettle filled with a mixed solvent of water and tert-butyl alcohol in a volume ratio of 1:

1. Place the hydrothermal kettle in an oven and perform a hydrothermal reaction at a temperature of 110-130°C for 3-5 hours. Cool it naturally to room temperature. Take out the cotton fabric and rinse it with deionized water. Place it in a watch glass and dry it in an oven at 50-70°C for 2-3 hours.

4. Repeat the filtration-hydrothermal treatment operations of steps 2 and 3 1 to 4 times to obtain a flexible TiO2 surface-enhanced Raman scattering active substrate.

2. The method for preparing a flexible TiO2 surface-enhanced Raman scattering active substrate according to claim 1, characterized in that: The cotton fabric described in step 1 is pure cotton white cloth.

3. The method for preparing a flexible TiO2 surface-enhanced Raman scattering active substrate according to claim 1 or 2, characterized in that: The volume of the mixed solvent is two-thirds of the volume of the hydrothermal reactor.

4. Application of the flexible TiO2 surface-enhanced Raman scattering active substrate prepared by the method of claim 1, characterized in that: This application is to use a flexible TiO2 surface-enhanced Raman scattering active substrate in the surface-enhanced Raman detection of antibiotics.

5. The use of the flexible TiO2 surface-enhanced Raman scattering active substrate according to claim 4, characterized in that: The antibiotics are attached to the surface of animal-derived food.

6. The use of the flexible TiO2 surface-enhanced Raman scattering active substrate according to claim 4, characterized in that: The antibiotic is enrofloxacin.

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