Method for constructing SERS (Surface Enhanced Raman Scattering) substrate with high-density hot spots based on capillary force for TNT (Trinitrotoluene) detection
By constructing a capillary force-driven SERS hotspot, the problem of cumbersome process in existing SERS technology for TNT detection is solved, achieving efficient and rapid TNT detection with significantly improved sensitivity.
Patent Information
- Application Number
- CN202511511165.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-22
- Publication Date
- 2026-01-09
AI Technical Summary
Existing SERS technology for detecting TNT is cumbersome, inefficient, and makes it difficult to efficiently detect TNT molecules.
By constructing a SERS substrate based on capillary forces, the capillary forces generated by solvent evaporation are used to pull the tops of nanorods together and aggregate them, forming high-density SERS hotspots, eliminating the need for the step of re-adsorbing Ag nanoparticles.
Significantly improves detection efficiency, shortens detection time to within 3 hours, and has a sensitivity enhancement factor of over 10⁹, enabling the detection of femtomolar levels of TNT.
Smart Images
Figure CN121298697A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application belongs to the field of surface-enhanced Raman scattering trace detection, and particularly relates to a method for constructing a SERS substrate with high-density hot spots based on capillary force for TNT detection. BACKGROUND
[0002] 2, 4, 6-trinitrotoluene (TNT) not only has highly dangerous explosion characteristics and huge destructive power, but also has different degrees of toxicity and environmental pollution. In the face of the dual challenges of terrorist threats and environmental pollution, developing ultra-sensitive and highly reliable TNT trace detection technology has become one of the research hotspots in the current public safety field. Among numerous trace chemical sensing technologies, surface-enhanced Raman spectroscopy (SERS) has become one of the most promising analysis technologies due to its fingerprint recognition ability, high sensitivity, excellent selectivity, and rich spectral information.
[0003] The Raman scattering cross section of TNT is low, and there is no significant chemical adsorption with the surface of metal particles, which makes it difficult to detect directly. Indirect detection is to load specific receptor molecules (4-aminobenzenethiol, cysteine, etc.) on the surface of metal particles to construct a functionalized SERS probe. When the SERS probe interacts with TNT, the change in its SERS spectrum characteristics can be used as an indication signal for detecting TNT.
[0004] Currently, the methods for detecting TNT using SERS technology mainly include three steps: the first step is to modify the SERS substrate with receptor molecules to form a SERS probe, and by gradually reducing the concentration of receptor molecules, the Raman signal of the SERS probe cannot be detected; the second step is to use the SERS probe to adsorb TNT in the solution, and due to the low concentration of TNT, this process generally requires adsorption time of more than several hours; the third step is to immerse the substrate after adsorbing TNT in the solution of Ag nanoparticles modified by receptor molecules, and under the action of TNT, Ag nanoparticles are fixed on the surface of the SERS substrate to form SERS gap hot spots, so that the Raman signal of the SERS probe is significantly enhanced, thereby achieving the purpose of indirectly detecting TNT. Due to the weak interaction between molecules, the time required for re-adsorbing Ag nanoparticles is more than 10 hours, making the entire detection process extremely tedious and inefficient. SUMMARY
[0005] The present application aims to improve the efficiency of the whole detection process, and aims to a method for constructing a SERS substrate with high-density hot spots based on capillary force for TNT detection.
[0006] In order to achieve the purpose of the present application, the present application provides a method for constructing a SERS substrate with high-density hot spots based on capillary force for TNT detection.
[0007] The present application indirectly recognizes TNT molecules by using a Raman spectrometer to detect the signal of SERS probes, and it is difficult to detect the Raman signal of SERS probes even if gap hot spots are constructed without adsorbing TNT molecules; only after adsorbing TNT molecules can the Raman signal of SERS probes be obviously enhanced.
[0008] Firstly, a periodic Ag-coated silicon nanorod array is constructed based on a single-layer polystyrene microsphere template, and the periodic order and openness thereof are used to significantly enhance the adsorption efficiency of target molecules. Secondly, after the substrate adsorbs TNT molecules, the capillary force generated by solvent evaporation pulls and agglomerates the top of the nanorod to form SERS gap hot spots, thereby eliminating the cumbersome step of re-adsorbing Ag nanoparticles, and significantly improving the overall efficiency.
[0009] The specific technical solution is:
[0010] A method for constructing a SERS substrate with high-density hot spots based on capillary force for TNT detection, the SERS hot spots are constructed based on a periodic Ag-coated silicon nanorod array, after the nanorod array substrate adsorbs target molecules, the capillary force generated by solvent evaporation pulls the nanorods together to form clusters, thereby generating gap SERS hot spots.
[0011] Further, the specific steps include:
[0012] Step 1: A single-layer PS microsphere template is assembled at the air / water interface by using the Malan-Goni effect, and then the single-layer PS microsphere template is transferred to the surface of a silicon wafer by lifting the silicon wafer previously placed under water;
[0013] Step 2: The diameter and spacing of the PS microspheres are controlled by reactive ion etching (RIE), and then a Ti / Au composite double-layer film is deposited on the surface of the substrate by an electron beam evaporation system; this step mainly controls the structure of the Ti / Au composite double-layer film by controlling the diameter and spacing of the PS microspheres.
[0014] Step 3: Remove PS microspheres by high-temperature decomposition, and then prepare silicon nanorod array substrate based on metal-assisted chemical etching (MACE) process; the diameter and spacing of nanorods are mainly controlled by the structure of Ti / Au composite bilayer film, and the length is controlled by MACE reaction time.
[0015] Step 4: Immerse the array substrate in aqua regia to remove the Ti / Au film, and deposit an Ag film with a thickness of 10-15 nm on the surface of the nanorods using magnetron sputtering to obtain a periodically Ag-plated silicon nanorod array substrate.
[0016] Step 5: Use a concentration of 10 -7 M's 4-aminothiophenol 4-ATP molecule modified the substrate to form a SERS probe, and then the SERS probe was immersed in TNT ethanol solution of different concentrations;
[0017] Step 6: Place the substrate in a constant temperature (25℃) experimental chamber and allow the ethanol to slowly evaporate. The nanorods will then approach each other to form a cluster structure. Use a Raman spectrometer to detect the signal of the SERS probe to indirectly identify TNT molecules.
[0018] Furthermore, the RIE etching time should be controlled between 90 and 120 s, that is, the diameter of the nanorod array after Ag deposition should be controlled between 90 and 120 nm.
[0019] Furthermore, the MACE reaction time should be controlled between 120 and 180 s, that is, the length of the nanorod array should be controlled between 1000 and 1500 nm.
[0020] Furthermore, the soaking process should be carried out under gentle stirring conditions to accelerate the adsorption rate. In addition, the soaking time should be adjusted appropriately according to the different concentrations of TNT solution, and the soaking time should be controlled within 1 to 2 hours.
[0021] Furthermore, the substrate was placed in a constant temperature environment at 25°C.
[0022] Another aspect of the present invention provides a SERS substrate with high-density hotspots constructed based on capillary forces. This SERS substrate is obtained through the above steps 1-5 to form a SERS probe.
[0023] The innovation of this invention compared to existing technologies lies in:
[0024] (1) The SERS hotspots constructed by capillary forces have extremely high sensitivity, with an enhancement factor exceeding 10. 9 It can detect femtomolar levels of TNT.
[0025] (2) Compared with the existing technology, the tedious step of re-adsorbing Ag nanoparticles is eliminated, and the detection time is shortened to less than 3 hours. Attached Figure Description
[0026] Figure 1 SEM image of a single-layer polystyrene microsphere template with a particle size of 250 nm;
[0027] Figure 2 SEM image of the template after RIE etching for 90 s;
[0028] Figure 3 The image shows a SEM image of a silicon nanorod array formed after MACE etching for 150 s.
[0029] Figure 4 SEM image of the array substrate formed after Ag deposition by magnetron sputtering;
[0030] Figure 5 The left side shows the SEM image of the Ag-silicon nanorod array after top gathering and aggregation, while the right side shows the SEM image after top gathering when the array length exceeds 2 µm and the diameter is less than 80 nm.
[0031] Figure 6 The left side shows the Raman spectrum of R6G molecules in a 0.1 M solution, and the right side shows the SERS spectrum of R6G molecules before and after aggregation at the top of the array substrate (R6G solution concentration is 10). -6 M);
[0032] Figure 7 Raman spectra of different molecules adsorbed on different substrates were used to verify the feasibility of constructing SERS hotspots through capillary forces and using them to detect TNT.
[0033] Figure 8 60×60 µm on the substrate 2 The measured Raman mapping is used to verify the uniformity of the Raman signal. Detailed Implementation
[0034] The present invention will be further described in detail below with reference to embodiments, and the technical solutions in the embodiments of the present invention will be clearly and completely described. The implementation of the present invention is not limited thereto.
[0035] This invention provides a method for constructing a SERS substrate with high-density hotspots based on capillary forces for TNT detection, mainly comprising two parts.
[0036] The first step involved constructing a periodically ordered silicon nanorod array substrate. First, a tightly packed monolayer of PS microspheres was self-assembled on the silicon wafer surface. Reactive ion etching was then used to reduce the diameter of the PS microspheres, resulting in a loosely packed monolayer PS microsphere template. Next, a 3 nm titanium and 30 nm gold bilayer film was deposited on the silicon wafer surface using a KJL PVD75 electron beam evaporator. The substrate was then heated at 250°C for 1 hour in a vacuum tube furnace to remove the PS microspheres, followed by ultrasonic cleaning in chloroform solution for 10 min to thoroughly remove residual organic matter. Subsequently, a silicon nanorod array was obtained through metal-assisted chemical etching, and the substrate was immersed in aqua regia to completely remove the gold catalyst. Finally, a 10-15 nm thick Ag layer was deposited on the silicon nanorod surface using a KJL PVD75 magnetron sputtering system to obtain a periodically Ag-plated silicon nanorod array.
[0037] The second step is to construct SERS hotspots using capillary forces and detect trace amounts of TNT. Specifically, the Ag-coated silicon nanorod array substrate is immersed in a solution with a concentration of 10... -7 In a 4-ATP ethanol solution of M for 30 min, 4-ATP molecules are fixed on the surface of Ag particles by forming stable Ag-S bonds. Subsequently, the substrate is immersed in TNT ethanol solutions of different concentrations for 1-2 hours, rinsed three times with anhydrous ethanol, and placed in a quiet environment. The capillary force generated by ethanol evaporation pulls the top of the nanorods together and aggregates, forming SERS gap hotspots, thereby enhancing the Raman signal of molecules within the gap and achieving the purpose of selective detection of TNT.
[0038] The parameters for reactive ion etching are: power 100 W, O2 flow rate 10 sccm, and etching time between 90 and 120 s, thereby controlling the diameter of the subsequent Ag silicon nanorods to be between 90 and 120 nm.
[0039] The etching solution used in the metal-assisted chemical etching process consisted of 76 mL of deionized water, 22 mL of 40% HF acid, and 2 mL of 30% H2O2. The etching time was controlled between 120 and 180 s, thereby controlling the length of the subsequently deposited Ag silicon nanorods to be between 1000 and 1500 nm.
[0040] The parameters for magnetron sputtering deposition of Ag particles are: power 80 W, bias voltage 50 V, Ar gas flow 50 sccm, and time 100~150 s, thereby controlling the thickness of the subsequent Ag layer to be between 10-15 nm.
[0041] The specific conditions for 4-ATP modification of the SERS substrate were as follows: the concentration of the 4-ATP ethanol solution was 10... -7M. Immerse the substrate in the solution for 30 min. After the substrate modification is completed, rinse it three times with deionized water to remove free 4-ATP molecules. The above process must ensure that the substrate is always in a wet state.
[0042] The step of constructing SERS hotspots using capillary forces is as follows: immersing the 4-ATP-modified SERS substrate in a TNT ethanol solution for 1-2 hours, with a TNT concentration of 10... -9 -10 -14 M. The soaking process needs to be carried out under gentle stirring conditions to accelerate the adsorption rate. After adsorption is completed, the substrate is placed in a quiet environment, and the capillary force generated by the evaporation of ethanol is used to pull the top of the nanorods together and aggregate them.
[0043] Combination Figures 1-8 As shown, a method for constructing SERS hotspots based on capillary force and using them for TNT detection is described, with the following specific implementation steps:
[0044] Step 1: Reactive ion etching (RIE) is used to reduce the diameter of PS microspheres, resulting in a non-closely packed monolayer PS microsphere template. The diameter of the PS microspheres can be controlled by adjusting the RIE time, which directly determines the diameter of the silicon nanorods. In this embodiment, the RIE time is 90 s, reducing the PS microsphere diameter to 90 nm.
[0045] Step 2: A 30 nm thick Au layer is deposited on the silicon wafer surface using a KJL PVD75 electron beam evaporator as a catalyst for metal-assisted chemical etching. To prevent the Au layer from peeling off, a Ti layer of approximately 3 nm is first deposited as a bonding layer.
[0046] Step 3: Remove PS microspheres by high-temperature sintering. Place the substrate in a vacuum tube furnace and heat at 250°C for 1 hour. Then, ultrasonically clean the substrate in a chloroform solution for 10 minutes to thoroughly remove residual organic matter.
[0047] Step 4: Prepare silicon nanorod arrays via metal-assisted chemical etching. Place the substrate in the etching solution for 150 s. The length of the silicon nanorods is 1200 nm. Immediately after etching, transfer the substrate to deionized water and rinse three times to remove residual etching solution. Then, transfer it to aqua regia to completely remove the gold catalyst.
[0048] Step 5: Use a critical point dryer to dry the wetted substrate to ensure that the silicon nanorod array is in a vertical position after drying.
[0049] Step 6: Deposit Ag particles on the surface of silicon nanorods using a magnetron sputtering system. In this embodiment, the magnetron sputtering power is 80 W, the bias voltage is 50 V, the Ar gas flow is 50 sccm, and the time is 150 s. The average thickness of the deposited Ag layer is 15 nm.
[0050] Step 7: Immerse the substrate in a solution with a concentration of 10. -7 The 4-ATP molecules were immobilized on the silver particles on the surface of the nanorods by forming Ag-S bonds in an ethanol solution of M for 30 min. The substrate was then rinsed three times with deionized water to remove free 4-ATP molecules, keeping the substrate in a wetted state for later use.
[0051] Step 8: Place the above substrate in a solution with a concentration of 10... -10 Incubation was performed in a TNT ethanol solution of M for 2 h to capture TNT molecules, with a stirring speed of 50 rpm. After adsorption, the mixture was rinsed three times with anhydrous ethanol and then placed in a quiet environment to slowly evaporate and dry.
[0052] Step 10: The specific method for detecting TNT using the above strategy is as follows: First, for the vertical Ag-coated nanorod array, after adsorbing 4-ATP molecules, it is difficult to detect the Raman signal due to the low concentration of 4-ATP solution. Even after further adsorbing TNT, it is still difficult to detect the Raman signal. This is mainly due to the poor enhancement effect of the vertical Ag-coated nanorod array. Figure 7 As shown, when the tops of the nanorods are pulled together and aggregated by capillary forces to form SERS gap hotspots, a significant Raman signal can be detected, although the signal is weak at this stage. Upon further adsorption of TNT, the Raman signal increases dramatically; therefore, the presence of TNT molecules can be determined by the dramatic increase in the Raman signal detected under the influence of TNT. Furthermore, to demonstrate the uniformity of the Raman signal, mapping tests were performed on the Raman signal intensity of the probe molecules on the SERS substrate. Figure 8 The spectrum is 1141.6 cm⁻¹ -1 The Raman mapping test results for the location showed a relative standard deviation of only 4.8%, which fully demonstrates that the invention has excellent uniformity and consistency for TNT detection.
[0053] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.
Claims
1. A method for constructing a SERS substrate with high-density hotspots based on capillary forces for TNT detection, characterized in that, This SERS hotspot is constructed based on a periodically coated Ag-silicon nanorod array. After the target molecule TNT is adsorbed onto the nanorod array substrate, the capillary force generated by solvent evaporation pulls the nanorods together to form clusters, thereby generating interstitial SERS hotspots. TNT is identified by detecting the signal of the SERS probe.
2. The method for constructing a SERS substrate with high-density hotspots based on capillary force for TNT detection according to claim 1, characterized in that, The specific steps are as follows: Step 1: Assemble a monolayer PS microsphere template at the air / water interface using the Marangoni effect, and then transfer the monolayer PS microsphere template to the surface of the silicon wafer by lifting the silicon wafer that was previously placed underwater. Step 2: The diameter and spacing of PS microspheres are controlled by reactive ion etching (RIE), and then Ti / Au composite bilayer films are deposited on the substrate surface by electron beam evaporation system; Step 3: Remove PS microspheres by high-temperature decomposition, and then prepare silicon nanorod array substrate based on metal-assisted chemical etching (MACE) process; Step 4: Immerse the array substrate in aqua regia to remove the Ti / Au film, and deposit an Ag film with a thickness of 10-15 nm on the surface of the nanorods using magnetron sputtering to obtain a periodically Ag-plated silicon nanorod array substrate. Step 5: Use a concentration of 10 -7 The substrate was modified with 4-aminothiophenol 4-ATP molecules of M to form a SERS probe, which was then immersed in the TNT ethanol solution to be tested. Step 6: Place the substrate in a constant temperature chamber and allow the ethanol to slowly evaporate. The nanorods will then approach each other to form a cluster structure. Use a Raman spectrometer to detect the signal of the SERS probe to indirectly identify TNT molecules.
3. The method for constructing a SERS substrate with high-density hotspots based on capillary force for TNT detection according to claim 2, characterized in that, In step 2, the structure of the Ti / Au composite bilayer film is controlled by controlling the diameter and spacing of the PS microspheres.
4. The method for constructing a SERS substrate with high-density hotspots based on capillary force for TNT detection according to claim 2 or 3, characterized in that, The RIE etching time should be controlled between 90 and 120 seconds.
5. The method for constructing a SERS substrate with high-density hotspots based on capillary force for TNT detection according to claim 2, characterized in that, In step 3, the diameter and spacing of the nanorod array are achieved by controlling the diameter of the PS microspheres through RIE in step 2. After Ag plating, the diameter of the nanorod array is controlled at 90~120 nm.
6. The method for constructing a SERS substrate with high-density hotspots based on capillary force for TNT detection according to claim 2, characterized in that, In step 3, the length of the nanorod array is controlled by the MACE etching time, which should be controlled between 120 and 180 s.
7. The method for constructing a SERS substrate with high-density hotspots based on capillary force for TNT detection according to claim 2 or 6, characterized in that, In step 3, the length of the nanorod array is controlled between 1000 and 1500 nm.
8. The method for capturing TNT molecules in solution using a SERS probe according to claim 2, characterized in that, In step 5, the soaking process requires stirring at a speed of 20-200 rpm to accelerate the adsorption rate; in addition, the soaking time should be adjusted according to the concentration of the TNT solution to be tested, and the soaking time should be controlled at 1-2 hours.
9. The method for capturing TNT molecules in solution using a SERS probe according to claim 1, characterized in that, In step 6, the substrate is placed in a constant temperature environment at 25°C.
10. A SERS substrate with high-density hotspots constructed based on capillary forces, characterized in that, The SERS substrate is obtained through the following steps: Step 1: Assemble a monolayer PS microsphere template at the air / water interface using the Marangoni effect, and then transfer the monolayer PS microsphere template to the surface of the silicon wafer by lifting the silicon wafer that was previously placed underwater. Step 2: The diameter and spacing of PS microspheres are controlled by reactive ion etching (RIE), and then Ti / Au composite bilayer films are deposited on the substrate surface by electron beam evaporation system; Step 3: Remove PS microspheres by high-temperature decomposition, and then prepare silicon nanorod array substrate based on metal-assisted chemical etching (MACE) process; Step 4: Immerse the array substrate in aqua regia to remove the Ti / Au film, and deposit an Ag film with a thickness of 10-15 nm on the surface of the nanorods using magnetron sputtering to obtain a periodically Ag-plated silicon nanorod array substrate. Step 5: Use a concentration of 10 -7 M-aminothiophenol 4-ATP molecules were used to modify the substrate to form a SERS probe.