A sers substrate for detecting malachite green and a preparation method thereof
By combining sandpaper polishing and oxygen plasma treatment on PET film, a micro-nano composite structure was constructed, which solved the problem of poor adhesion of silver nanoparticles in malachite green detection on PET film substrate, and achieved a highly sensitive, uniform and reusable SERS substrate.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- NANTONG UNIV
- Filing Date
- 2026-03-24
- Publication Date
- 2026-07-21
AI Technical Summary
When detecting malachite green, existing PET film substrates have smooth surfaces and strong chemical inertness, making it difficult to form nano-interstitial structures with high specific surface area. This results in poor adhesion of silver nanoparticles, poor mechanical stability, and difficulty in reusing them.
By combining sandpaper polishing and oxygen plasma treatment, a micro-nano composite structure is constructed on the surface of PET film, forming a maze-like nano-protrusion, which increases the adhesion sites of the silver layer, improves chemical activity, and enhances adhesion.
It significantly enhances the adhesion between the silver layer and the substrate, improves the substrate's sensitivity, uniformity, and mechanical stability, and achieves high sensitivity and reusability.
Smart Images
Figure CN122430299A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of Raman spectroscopy technology, specifically relating to a SERS substrate for detecting malachite green and its preparation method. Background Technology
[0002] Malachite green (MG) is prohibited from use in aquaculture due to its highly effective bactericidal and antiparasitic properties. However, its illegal use continues despite repeated bans because of its low price and significant therapeutic effects. Detecting MG in water can build a core defense line that integrates ecological, food, and economic security from the source.
[0003] Surface-enhanced Raman scattering (SERS) is a precise, non-destructive molecular detection method with fingerprint-like capabilities, making it a powerful tool for detecting MG in water. Currently, among solid-state SERS substrates used for MG detection, flexible materials have a wider range of applications due to their excellent elasticity.
[0004] Commercially available polyethylene terephthalate (PET) films are excellent flexible materials at low cost, but their surfaces are typically very smooth and chemically inert. On such flat surfaces, it is difficult to induce metal nanoparticles to form SERS hotspot structures with high specific surface area and high-density nano-interstic gaps through physical deposition (such as thermal evaporation or sputtering), limiting the substrate's reinforcing properties. Furthermore, due to the strong chemical inertness and lack of active sites on the PET surface, the metal layer mainly adheres through weak van der Waals forces. This makes silver nanostructures highly susceptible to detachment during bending deformation or liquid cleaning, severely restricting the substrate's mechanical stability and hindering reusability. Summary of the Invention
[0005] Technical problem to be solved: In view of the problems existing in the prior art, the present invention proposes a SERS substrate for detecting malachite green and its preparation method. The method constructs a micro-nano composite structure on the surface of a PET film through the synergistic effect of polishing and oxygen plasma treatment. This not only greatly improves the SERS activity of the subsequently deposited silver layer, but also significantly enhances the bonding force between the silver layer and the substrate, so that the substrate has high sensitivity, high uniformity, excellent mechanical stability and reusability.
[0006] Technical solution: The first objective of this invention is to provide a method for preparing a SERS substrate for detecting malachite green, the steps of which are as follows:
[0007] Step 1: Pre-treat the PET film by sanding it with sandpaper to create a micron-level groove structure on its surface;
[0008] Step 2: The PET film treated in Step 1 is subjected to oxygen plasma treatment to form nano-protrusions on the surface of the micron-level trench structure and to introduce oxygen-containing polar groups on the surface of the PET film.
[0009] Step 3: A silver layer is grown on the PET film treated in Step 2 by vacuum evaporation to obtain a SERS substrate with a micro-nano composite structure, which is used for malachite green detection.
[0010] Preferably, in step one, the polishing is performed by using sandpaper to polish in the same direction.
[0011] Preferably, in step one, the sandpaper has a grit of 2000 and the sanding is performed 20 times.
[0012] Preferably, in step one, the PET film has a thickness of 0.2 mm and a size of 1 cm × 1 cm.
[0013] Preferably, in step one, after the grinding pretreatment, the PET film is further cleaned and dried. The cleaning method is as follows: the ground PET film is immersed in anhydrous ethanol and deionized water in sequence for ultrasonic cleaning, and the drying method is to blow it dry with nitrogen gas.
[0014] Preferably, in step two, the conditions for oxygen plasma treatment are: power of 115-125 W, treatment time of 1-5 min, and oxygen flow rate of 2.8-3.2 mL / min.
[0015] Preferably, the processing time is 1-3 minutes. More preferably, the processing time is 3 minutes.
[0016] Preferably, the vacuum evaporation conditions in step three are as follows: a silver layer is deposited in a vacuum evaporation apparatus at a deposition rate of 0.5-1.2 Å / s and a deposition time of 2-12 min.
[0017] The second objective of this invention is to provide a SERS substrate for detecting malachite green prepared by the above method.
[0018] The third objective of this invention is to provide the application of the aforementioned SERS substrate for detecting malachite green in the detection of malachite green residues in pond water or aquatic products.
[0019] Beneficial effects:
[0020] 1. This invention provides a SERS substrate for detecting malachite green and its preparation method. The method first constructs a micron-scale rough structure on the PET surface through grinding, followed by fine etching using oxygen plasma bombardment, further inducing the formation of a labyrinthine nanoprotrusion structure on the micron-grooves. This micro / nano structure not only significantly increases the specific surface area of the substrate, providing abundant adhesion sites for the growth of silver nanoparticles, but also significantly improves the chemical inertness of the PET surface by introducing a large number of oxygen-containing polar groups such as CO and OC=O, providing abundant chemical binding sites for silver atoms. The synergistic effect of these two factors greatly enhances the adhesion between the silver layer and the substrate. This tight bond allows the silver layer to adapt to the flexible deformation of the substrate, maintaining structural integrity even under mechanical tests such as repeated bending or tape peeling, thus endowing the substrate with excellent flexibility and mechanical stability.
[0021] 2. The SERS substrate prepared by this invention exhibits excellent detection performance. The dense nanostructures on the substrate surface induce silver particles to form a high-density "hot spot" array, thereby achieving ultrasensitive detection of target molecules (such as malachite green). Simultaneously, the highly oriented parallel micron-scale trench structure ensures the high uniformity of the substrate surface properties, guaranteeing the uniformity of the Raman signal.
[0022] 3. The preparation method provided by this invention is simple, requires no complex equipment, is environmentally friendly, and has low cost. The resulting substrate not only has extremely high sensitivity and good uniformity, but also has excellent bending resistance and reusability, making it an economical and environmentally friendly flexible SERS substrate material. Attached Figure Description
[0023] Figure 1 This is a flowchart illustrating the preparation process of the Ag / PET SERS substrate of this invention;
[0024] Figure 2 SEM images of PET film surfaces at different processing stages are shown, where (a) is an untreated PET film, (b) is a PET film after polishing only, (c) is a PET film after oxygen plasma treatment only, and (d) is a PET film after polishing + oxygen plasma treatment.
[0025] Figure 3 SEM images of PET surfaces after different oxygen plasma treatment times (a) 1 min, (b) 3 min, and (c) 5 min, and (d) images of PET surfaces after 10 minutes of oxygen plasma treatment on the corresponding substrates. -5 SERS spectra of M CV;
[0026] Figure 4SEM images of PET surfaces after Ag deposition at different times: (a) 2 min, (b) 7 min, and (c) 12 min; and (d) images of 10 μL of Ag deposited on the corresponding substrates. -5 SERS spectrum of M CV.
[0027] Figure 5 The graph shows the changes in chemical properties of the PET surface before and after oxygen plasma treatment, where (a) is the high-resolution XPS spectrum of C1s on the PET surface before treatment and (b) is the spectrum after treatment; and (c) is the static contact angle photograph of the PET substrate surface before treatment and (d) is the spectrum after treatment.
[0028] Figure 6 SEM images of the substrates prepared with a deposition time of 7 min on different substrate surfaces are shown in the figures. (a) is untreated PET, (b) is PET treated only by polishing, (c) is PET treated only by oxygen plasma, and (d) is PET treated by polishing and oxygen plasma.
[0029] Figure 7 To detect 10 on four different substrates -5 Comparison of SERS spectra of M CV;
[0030] Figure 8 To detect different concentrations (10) on the Ag / PET substrate surface of this invention -5 -10 -9 SERS spectrum of M)CV;
[0031] Figure 9 The detection concentration on the Ag / PET substrate surface of this invention is 10. -8 The CV of M is compared with the concentration of 10 measured on the silicon wafer surface. -1 SERS spectrum of M CV;
[0032] Figure 10 This is a uniformity evaluation diagram of the Ag / PET substrate of the present invention, wherein (a) is a sample taken from 50 random locations on the Ag / PET substrate. -8 SERS spectral intensity mapping of M CV, (b) is 1162 cm⁻¹ -1 The intensity distribution of the characteristic peak;
[0033] Figure 11 This invention relates to the detection of different concentrations (10) of Ag / PET substrates on pond water. -5 -10 -8 (a) SERS spectrum of M)MG and (b) at 1158 cm⁻¹ -1 Linear correlation curve between characteristic peak intensity and concentration;
[0034] Figure 12This is a graph showing the reusability evaluation of the Ag / PET substrate of the present invention, where (a) represents the results of 5 cycles of testing at 10... -7 M MG at 1158 cm -1 The intensity change of the characteristic peak at (b) is the result of 10 measurements after the substrate has undergone one repeated use. -7 SERS spectrum of MMG;
[0035] Figure 13 The diagrams show the mechanical stability evaluation of the Ag / PET substrate of this invention, including (a) a schematic diagram of bending and (b) peeling once; (c) SEM images after bending and (d) peeling 20 times; and (e) SEM images after bending and (f) peeling 20 times. -8 M CV at 1162 cm -1 The intensity variation of the characteristic peak. Detailed Implementation
[0036] The present invention will be further described below with reference to specific embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention in any way. Modifications, equivalent substitutions, or improvements made by those skilled in the art based on their understanding of the technical solutions of the present invention should all fall within the scope of protection of the present invention. Experimental methods not specified in the embodiments are generally performed under conventional conditions or as recommended by the manufacturer.
[0037] Unless otherwise specified, all raw materials used in this application are from commercially available products. Among them, the polyethylene terephthalate (PET) film has a thickness of 0.2 mm and a size of 1 cm × 1 cm; the sandpaper has a mesh size of 2000.
[0038] Example 1
[0039] This embodiment provides a method for preparing a SERS substrate for detecting malachite green. See [link to previous document]. Figure 1 The specific steps are as follows:
[0040] (1) Pretreatment of PET film: Sand the PET film 20 times in the same direction with 2000 grit sandpaper. Soak it in anhydrous ethanol and deionized water in sequence, ultrasonically clean it for 5 min, and dry it with nitrogen gas.
[0041] (2) Oxygen plasma treatment: The cleaned PET film was placed flat in a glass dish and subjected to OP treatment in a plasma cleaner to obtain a PET substrate with a labyrinthine nano-protrusion structure on the surface. The oxygen plasma power was 120W, the treatment time was 3 min, and the oxygen flow rate was 3 mL / min.
[0042] (3) Thermal evaporation deposition of silver: Ag nanostructures were grown on a PET substrate with micro-nano structures by evaporation using a vacuum evaporation apparatus. The silver source was 99.99% silver particles, the evaporation rate was set to 1 Å / s, and the deposition time was 7 min, resulting in a highly sensitive Ag / PET substrate.
[0043] Example 2
[0044] Similar to Example 1, except that the oxygen plasma treatment time in step (2) of Example 1 was adjusted to 1 min and 5 min respectively, and Ag / PET substrates with different treatment times were prepared.
[0045] The surface morphology of PET after different treatment times was characterized using scanning electron microscopy (SEM), and the results are as follows: Figure 3 As shown in (a)-(c). Figure 3 (a) The surface nanostructures were not fully formed after 1 min of treatment; Figure 3 (c) This shows that after 5 min of treatment, the nanostructure was over-etched, resulting in poor morphology. In contrast, after 3 min of treatment ( Figure 3 (b) A uniform and dense nanoprotrusion structure was successfully obtained. The three substrates described above were immersed in 10... -5 The Raman spectra of the crystal violet (CV) were collected after being immersed in a mol / L (M) crystal violet (CV) solution for 30 min and then allowed to air dry at room temperature. The results are as follows: Figure 3 As shown in (d), Raman spectroscopy measurements were performed using a Raman spectrometer (Advantage 785, DeltaNu) with a laser wavelength of 785 nm. The laser power was 36 mW, and the integration time was 10 s. The substrate treated for 3 min exhibited the highest SERS signal intensity. Therefore, 3 min was determined to be the optimal oxygen plasma treatment time.
[0046] Example 3
[0047] Similar to Example 1, except that the silver deposition time in step (3) of Example 1 was adjusted to 2 min and 12 min respectively, and Ag / PET substrates with different deposition times were prepared.
[0048] The surface morphology of PET after different treatment times was characterized using scanning electron microscopy (SEM), and the results are as follows: Figure 4 As shown in (a)-(c). Figure 4 (a) It shows that when the deposition time is 2 min, the electromagnetic field coupling cannot be generated due to insufficient deposition. Figure 4 (b) It shows that when the deposition time is 7 min, the Ag layer thickens and the compact nano-interstices form dense "hot spots" on the substrate. Figure 4(c) The deposition time of 12 min shows that excessive deposition disrupted the originally dense interstices, leading to "hot spot" attenuation and a significant decrease in the SERS signal. The Raman test method was the same as in Example 2. The results are as follows: Figure 4 As shown in (d), the substrate with a deposition time of 7 min exhibited the highest SERS signal intensity. Therefore, a deposition time of 7 min was determined to be the optimal deposition time.
[0049] Example 4
[0050] This embodiment verifies the effectiveness of the preparation method of the present invention through comparative experiments:
[0051] Ag / PET substrates were prepared according to the method of Example 1, which involved polishing and oxygen plasma co-treatment. Meanwhile, PET substrates without any treatment, PET substrates with polishing treatment only (using only step (1)), and PET substrates with oxygen plasma (OP) treatment only (without polishing treatment, directly using the oxygen plasma treatment of step (2)) were prepared as controls and silver was deposited under the same conditions.
[0052] Figure 2 The surface microstructure of PET films at different processing stages is shown. Figure 2 As can be seen in (a) and (b), the polishing process creates micron-level rough grooves on the smooth PET surface. For example... Figure 2 As shown in (c) and (d), further OP treatment produces nanoscale labyrinthine protrusions on the surface. Figure 2 (d) It was confirmed that the combined grinding and oxygen plasma treatment successfully constructed micro-nano structures.
[0053] Figure 5 The changes in the chemical properties of the substrate surface before and after OP treatment are shown. Figure 5 The comparison results of (a) and (b) show that the content of C-C bonds decreased significantly after treatment, while the content of oxygen-containing polar groups such as CO and OC=O increased significantly. Figure 5 The comparison results in (c) and (d) show that the static contact angle decreased significantly. This indicates that the OP treatment improved the chemical activity of the substrate surface and enhanced the adhesion between the silver layer and the substrate.
[0054] Figure 6 The microstructures of Ag deposited on different treated substrates are shown. Figure 6 As shown in (d), on the surface treated with polishing and oxygen plasma, the Ag layer is tightly attached to and continuously wrapped around the micro-nano structure surface of the substrate, successfully constructing a high-density, uniformly distributed "hot spot" array.
[0055] Figure 7 Comparison of SERS intensity for four substrates (using 10) -5M CV was tested, using the same testing method as above. From Figure 7 As can be seen, the micro-nano structures introduced by the combined grinding and oxygen plasma treatment on the PET film surface significantly improve the SERS performance of the substrate. The signal intensity of the substrate treated with the combined grinding and oxygen plasma treatment is much higher than that of the other three substrates, demonstrating the superiority of the combined treatment.
[0056] Example 5
[0057] The performance of the Ag / PET substrate prepared in Example 1 was tested:
[0058] (a) Minimum Detection Concentration Test:
[0059] Using this substrate to detect different concentrations (10 -5 M to 10 -9 The CV solution of M) was detected using the same method as above, and the resulting SERS spectrum is as follows: Figure 8 As shown in the figure. The results indicate that the substrate can achieve a minimum detection concentration of 10 for CV. -9 M.
[0060] Meanwhile, to calculate the enhancement factor of the Ag / PET substrate, the detection performance of this substrate was compared with that of 10... -8 M CV's SERS signal and silicon wafer detection 10 -1 The Raman signal of M CV, the results are as follows Figure 9 As shown. According to the formula, the enhancement factor EF = (I SERS *C0) / (I0*C SERS (where I) SERS I0 and I0 represent the CV measured on Ag / PET substrate and silicon wafer, respectively. -1 Peak intensity, C SERS (where C0 represents the corresponding CV concentration) The enhancement factor of the Ag / PET substrate prepared in Example 1 was calculated to be 1.13 × 10⁻⁶. 7 .
[0061] (ii) Uniformity test:
[0062] Fifty points were randomly selected on the Ag / PET substrate, and 10 samples were collected. -8 The SERS spectrum of M CV, the results are as follows: Figure 10 As shown. Figure 10 (a) is the intensity mapping diagram of 50 spectra. Figure 10 (b) 1162 cm⁻¹ in these 50 spectra -1 The intensity distribution of the characteristic peaks is shown. The calculated relative standard deviation (RSD) is 9.8%, indicating that the substrate exhibits excellent signal uniformity.
[0063] (III) Detection of trace pollutants (MG) in complex real-world samples (pond water):
[0064] Using pond water collected from local ponds in Nantong as a solvent, different concentrations (10) were prepared. -5 M to 10 -8 A malachite green (MG) solution (M) was used. The SERS spectrum obtained using this substrate is shown below. Figure 11 As shown in (a). Figure 11 (b) Shows MG at 1158cm -1 The linear relationship between the characteristic peak intensity and the logarithm of the concentration is shown by the linear fitting equation y = 931x + 7624 (where y is the SERS intensity in arbitrary units and x is the logarithm of the MG concentration), R0. 2 =0.951 proves that this substrate can be used for the quantitative analysis of trace amounts of malachite green in complex real-world samples.
[0065] (iv) Reusability test:
[0066] Detection using Ag / PET substrate 10 -7 The solution of M and MG was then ultrasonically washed with ethanol for 15 min, dried, and detected again. This process was repeated 5 times, and the 1158 cm⁻¹ value was recorded for each detection. -1 The intensity of the characteristic peak is shown in the following results. Figure 12 As shown in (a), after 5 cycles, no significant attenuation of signal strength was observed. Figure 12 (b) No residual MG signal is shown on the cleaned substrate. The results indicate that the substrate has good chemical stability and reusability, which is beneficial for reducing detection costs.
[0067] (v) Mechanical stability test:
[0068] The Ag / PET substrate was subjected to 20 repeated bending cycles and 20 tape peeling cycles, respectively. After the tests, the surface morphology was observed by SEM. Figure 13 (a) and (b) respectively demonstrate the process of a bending and peeling test. Figure 13 (c) and (d) show the microstructure after 20 tests. Samples were collected every 5 tests at a depth of 10 μm. -8 The SERS signal of M CV, the results are as follows Figure 13 As shown in (e) and (f), the reinforcing properties of the substrate did not change significantly, indicating that the Ag / PET substrate exhibits good flexibility and mechanical stability.
[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method for preparing a SERS substrate for detecting malachite green, characterized in that, The steps are as follows: Step 1: Pre-treat the PET film by sanding it with sandpaper to create a micron-level groove structure on its surface; Step 2: The PET film treated in Step 1 is subjected to oxygen plasma treatment to form nano-protrusions on the surface of the micron-level trench structure and to introduce oxygen-containing polar groups on the surface of the PET film. Step 3: A silver layer is grown on the PET film treated in Step 2 by vacuum evaporation to obtain a SERS substrate with a micro-nano composite structure, which is used for malachite green detection.
2. The method for preparing a SERS substrate for detecting malachite green according to claim 1, characterized in that, In step one, sanding involves using sandpaper to sand in the same direction.
3. The method for preparing a SERS substrate for detecting malachite green according to claim 1, characterized in that, In step one, the sandpaper is 2000 grit and the sanding is done 15-20 times.
4. The method for preparing a SERS substrate for detecting malachite green according to claim 1, characterized in that, In step one, the PET film has a thickness of 0.2 mm and a size of 1 cm × 1 cm.
5. The method for preparing a SERS substrate for detecting malachite green according to claim 1, characterized in that, In step one, after the grinding pretreatment, the PET film is further cleaned and dried. The cleaning method is as follows: the ground PET film is immersed in anhydrous ethanol and deionized water in sequence for ultrasonic cleaning, and the drying method is to blow it dry with nitrogen.
6. The method for preparing a SERS substrate for detecting malachite green according to claim 1, characterized in that, In step two, the conditions for oxygen plasma treatment are: power of 115-125 W, treatment time of 1-5 min, and oxygen flow rate of 2.8-3.2 mL / min.
7. A method for preparing a SERS substrate for detecting malachite green according to claim 6, characterized in that, The processing time is 1-3 minutes.
8. The method for preparing a SERS substrate for detecting malachite green according to claim 1, characterized in that, The vacuum evaporation conditions in step three are as follows: a silver layer is deposited in a vacuum evaporation apparatus at a rate of 0.5-1.2 Å / s and a deposition time of 2-12 min.
9. A SERS substrate for detecting malachite green prepared by the method of any one of claims 1-8.
10. The application of the SERS substrate for detecting malachite green as described in claim 9 in the detection of malachite green residues in pond water or aquatic products.