Preparation method of uniform and stable Raman substrate

Abstract

The invention discloses a preparation method of a uniform and stable Raman substrate, which comprises the following steps: filtering precious metal nanoparticle sol for 3-5 times by using a filter membrane with a determined pore size to obtain standby sol; the circular perforated substrate is arranged on an ink-jet device of the ink-jet printer, and the distance between arrays of the circular perforated substrate is determined, and the diameter is determined. And setting the number of printing times to obtain a uniform and stable nano-particle array with a determined diameter and a determined distance. The method has the advantages that the uniformly-arranged nanoparticle array with the same diameter can be stably printed, the agglomeration phenomenon of nanoparticles is effectively avoided, the preparation method is simple, the cost is low, the preparation process can be accurately controlled through a computer, and the controllability is high.

Description

Technical Field

[0001] The invention relates to a method for preparing a Raman substrate, and in particular to a method for preparing a uniform and stable Raman substrate. Background Art

[0002] Surface enhanced Raman spectroscopy (SERS) is a powerful analytical technique that is widely used for ultra-low concentration molecular analysis and can even analyze single molecules. The development of low-cost, highly active SERS substrates is a research hotspot in this field. At present, the most common SERS substrates are noble metal SERS substrates. Existing methods for preparing noble metal SERS substrates include noble metal sol method, nanoparticle self-assembly technology, etc., but their disadvantages are that the particles of the noble metal sol method are not evenly distributed, and agglomeration is easily generated, and the self-assembly technology cannot prepare periodic structures. Therefore, it is particularly important to prepare a low-cost and evenly distributed periodic SERS substrate. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a low-cost method for preparing a uniform and stable Raman substrate using inkjet printing. By controlling the pattern on the inkjet printing nozzle, the particle size of the precious metal nanoparticles is screened in advance to ensure that the particle size of the printed nanoparticles is equal within the error range and effectively avoid the phenomenon of nanoparticle agglomeration caused by traditional inkjet printing methods.

[0004] The technical solution adopted by the present invention to solve the above technical problems is: a method for preparing a uniform and stable Raman substrate, characterized in that a uniform and stable nanoparticle array can be prepared by controlling the number of printing times and replacing circular openings with different diameters and spacings; the preparation method comprises the following steps:

[0005] Step 1: Filter the noble metal nanoparticle sol 3-5 times with a filter membrane with a determined pore size to obtain a standby sol;

[0006] Step 2: The inkjet device of the inkjet printer has a substrate with circular openings with uniformly arranged intervals and a certain diameter;

[0007] Step 3: Set the number of prints to obtain a uniform and stable array of nanoparticles with a certain diameter and spacing.

[0008] In the step 1, the filter membrane with a determined diameter has a pore size that is the same as the diameter of the circular opening in the step 2.

[0009] In the step 1, the noble metal nanoparticle sol is a gold nanoparticle sol or a silver nanoparticle sol.

[0010] In the step 2, the circular openings can be replaced, and the spacing and diameter thereof can be set according to the requirements for enhancing the Raman substrate signal.

[0011] In the step 2, the spacing between the circular openings is 5-10 nm, that is, the distance between the edges of every two circular openings is 5-10 nm.

[0012] In the step 3, the size of the nanoparticles is 20-100 nm.

[0013] In the step 2, the preparation method of the circular opening is electron beam etching, and the specific steps are as follows: the first step is to first grind the substrate flat, then clean the surface with a chemical solution, and finally rinse with deionized water and dry; the second step is to preheat the substrate and apply photoresist by spin coating; the third step is to electron beam expose the photoresist, develop and clean after forming a pattern, and remove the uncured photoresist; the fourth step is to bake the substrate to evaporate the developer and fixer remaining in the photoresist mold; the fifth step is to heat the etching solution to a certain temperature, put the substrate into an etching tank for etching, and after etching, clean and deionize the substrate to remove the etching solution remaining on the surface.

[0014] In step 2, the solution to the blockage of the inkjet device of the printer is air cleaning technology. The specific steps are as follows: first connect the printer to a power source, and then use an air cleaner to blow air at the nozzle to clear the blockage on the surface and inside of the nozzle.

[0015] Compared with the prior art, the advantages of the present invention are:

[0016] 1) It can stably print uniform and stable nanoparticle structures with the same diameter, effectively avoiding the agglomeration of nanoparticles;

[0017] 2) Compared with traditional micro-nano structure preparation methods such as laser processing and template method, the preparation method of the present invention is simple, and the raw materials are cheap and easy to obtain. The preparation process can be accurately controlled by computer, with good reproducibility and strong controllability. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0019] Figure 1 This is the local electric field distribution diagram of the silver nanoparticle array with a simulated diameter of 50nm and a spacing of 5nm as described in the present invention;

[0020] Figure 2 This is the local electric field distribution diagram of the gold nanoparticles with a simulated diameter of 60nm and a spacing of 10nm as described in the present invention;

[0021] Figure 3 A schematic diagram of a method for preparing a uniform and stable Raman substrate according to the present invention; DETAILED DESCRIPTION

[0022] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. The specific embodiments listed below are not intended to limit the scope of rights of the present invention.

[0023] Implementation Example 1:

[0024] Step 1: Preparation of silver nanoparticle sol: 90 mg of silver nitrate was weighed and added to 250 mL of ultrapure water, heated to boiling under stirring, and then 10 mL of a 1% sodium citrate aqueous solution was quickly injected, and refluxed for one hour under boiling conditions, and the solution gradually turned yellow-green, thereby obtaining a silver nanoparticle sol with a particle size of 35-60 nm;

[0025] Furthermore, the silver nanoparticle sol is filtered 3-5 times with a filter membrane having a pore size of 50 nm to remove relatively small particles to obtain a standby sol.

[0026] Step 2: Clean the ink cartridge: Use deionized water to clean the ink cartridge of the inkjet printer repeatedly for several times until the residual ink in the cartridge is completely and thoroughly cleaned, and then put the cleaned ink cartridge into a 60-80℃ oven to dry to obtain a blank ink cartridge;

[0027] Step 3: Inkjet printing: Take 2-4 mL of the silver nanoparticle sol prepared in step 1 and inject it into a blank ink cartridge with a syringe to complete the refilling process of the ink cartridge. Install a circular perforated substrate with a spacing of 5 nm and a diameter of 50 nm on the inkjet device of the inkjet printer. Use a computer to set the printing parameters to obtain a silver nanoparticle array with a diameter of 50 nm and a spacing of 5 nm.

[0028] Here, the circular openings on the inkjet device can screen out the nanoparticles with a particle size greater than 50 nm or agglomerated in the silver nanoparticle sol, ensuring that a uniform and stable silver nanoparticle array with the same diameter can be stably printed.

[0029] Figure 1 The simulation of the local electric field distribution of the silver nanoparticle array using the finite difference time domain method in this embodiment is given. It can be seen from the figure that hot spots are generated between the silver nanoparticles, and the local electric field enhancement coefficient [(E:E0) 2 ] is 19.99.

[0030] Implementation Example 2:

[0031] Step 1: Preparation of gold nanoparticle sol: Add 250 ml of 1 mM chloroauric acid to a round-bottom flask equipped with a reflux condenser and a stirring paddle, heat to boiling while stirring, then quickly pour in 25 ml of a 1% sodium citrate aqueous solution, continue to reflux for 15 minutes, the color of the solution changes from light yellow to dark red, then stop heating, cool to room temperature, and filter with a filter membrane to obtain 13 nm gold nanoparticles as seeds.

[0032] Further, 125 ml of freshly prepared 0.296 mM chloroauric acid was heated to boiling, and then 1.125 ml of freshly prepared 13 nm gold nanoparticle solution and 0.56 ml of 1% sodium citrate aqueous solution were injected under stirring, and the stirring reaction was continued for 30 minutes, and 5 ml of 1% sodium citrate aqueous solution was injected as an additional stabilizer, and the heating reaction was continued for one hour to obtain a gold nanoparticle sol with a particle size of 50-80 nm;

[0033] Furthermore, the gold nanoparticle sol is filtered 3-5 times with a filter membrane with a pore size of 60 nm to remove relatively small particles to obtain a standby sol.

[0034] Step 2: Clean the ink cartridge: Use deionized water to clean the ink cartridge of the inkjet printer repeatedly for several times until the residual ink in the cartridge is completely and thoroughly cleaned, and then put the cleaned ink cartridge into a 60-80℃ oven to dry to obtain a blank ink cartridge;

[0035] Step 3: Inkjet printing: Take 2-4 mL of the gold nanoparticle sol prepared in step 1 and inject it into a blank ink cartridge with a syringe to complete the refilling process of the ink cartridge. Install a circular perforated substrate with a spacing of 10 nm and a diameter of 60 nm on the inkjet device of the inkjet printer. Use a computer to set the printing parameters to obtain a gold nanoparticle array with a diameter of 60 nm and a spacing of 10 nm.

[0036] Here, the circular openings on the inkjet device can screen out nanoparticles with a particle size greater than 60 nm or agglomerated nanoparticles in the gold nanoparticle sol, ensuring that a uniform and stable array of gold nanoparticles with the same diameter can be stably printed.

[0037] Figure 2 The simulation of the local electric field distribution of the gold nanoparticle array using the finite difference time domain method in this embodiment is given. It can be seen from the figure that hot spots are generated between the gold nanoparticles, and the local electric field enhancement coefficient [(E:E0) 2 ] is 324.63.

[0038] Although the present invention has been described above in conjunction with the accompanying drawings, the present invention is not limited to the above-mentioned specific embodiments, which are merely illustrative rather than restrictive. Under the guidance of the present invention, ordinary technicians in this field can make many modifications without departing from the purpose of the present invention, all of which are within the protection of the present invention.

Claims

1. A method for preparing a uniform and stable Raman substrate, characterized in that The inkjet printing technology can be used to print a uniform and stable nanoparticle array, comprising the following steps: Step 1: Filter the noble metal nanoparticle sol 3-5 times with a filter membrane with a determined pore size to obtain a standby sol; Step 2: The inkjet device of the inkjet printer has a circular perforated substrate with a determined diameter and an array spacing determined. Step 3: Set the number of prints to obtain a uniform and stable array of nanoparticles with a certain diameter and spacing.

2. The method for preparing a uniform and stable Raman substrate according to claim 1, characterized in that A uniform and stable nanoparticle array can be prepared by controlling the number of printing times and replacing circular openings with different diameters and spacings.

3. The method for preparing a uniform and stable Raman substrate according to claim 1, characterized in that The pore size of the filter membrane in step 1 is the same as the diameter of the circular opening.

4. The method for preparing a uniform and stable Raman substrate according to claim 1, characterized in that In the step 1, the noble metal nanoparticle sol is gold nanoparticle sol or silver nanoparticle sol.

5. The method for preparing a uniform and stable Raman substrate according to claim 1, characterized in that The circular openings in step 2 can be replaced, and their spacing and diameter can be set according to the needs of Raman substrate signal enhancement.

6. The method for preparing a uniform and stable Raman substrate according to claim 1, characterized in that The spacing between the circular openings in step 2 is 5-10 nm.

7. The circular opening spacing according to claim 6 is characterized in that The spacing is the distance between the edges of every two circular openings.

8. The method for preparing a uniform and stable Raman substrate according to claim 1, characterized in that The size of the nanoparticles in step three is 20-100 nm.

9. The method for preparing a uniform and stable Raman substrate according to claim 1, characterized in that The method for preparing the circular opening in step 2 is electron beam etching, and the specific steps are as follows: Step 1: first grind the substrate flat, then clean the surface with a chemical solution, then rinse with deionized water and dry; Step 2, preheating the substrate and applying photoresist by spin coating; Step 3, electron beam exposure of the photoresist, development and cleaning after forming a pattern, to remove uncured photoresist; Step 4, baking the substrate to volatilize the developer and fixer remaining in the photoresist mold; Step 5: Heat the etching solution to a certain temperature, place the substrate in an etching tank for etching, and clean and deionize the substrate after etching to remove the etching solution remaining on the surface.

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