CN106645087A - PDMS-base single-layer SERS substrate not requiring surface modification and preparation method thereof - Google Patents

Abstract

The invention discloses a PDMS-based single-layer SERS substrate without surface modification and a preparation method thereof. The preparation method of the PDMS-based SERS substrate without surface modification comprises the following steps: preparing uniform metal sol particles; A dense metal nanoparticle film; transfer the metal nanoparticle film to the PDMS surface without surface treatment and form a dense and uniform SERS substrate. This method omits the hydrophilization treatment of PDMS and the subsequent modification of specific groups, greatly simplifies the production process, improves the reliability of production, and does not need to be implemented in a clean room, reducing the requirements for the production environment; The metal nanoparticle film prepared by the method is spontaneously formed, and the distance between the metal nanoparticle is extremely small, so the SERS enhancement effect and uniformity are extremely high.

Description

PDMS-based monolayer SERS substrate without surface modification and preparation method thereof

technical field

The invention belongs to the technical field of measurement, testing or detection, in particular to a method for preparing a hydrophobic surface solid-phase SERS substrate.

Background technique

Surface-enhanced Raman scattering (SERS) detection technology is a highly sensitive detection method that can characterize the structural characteristics of low-concentration analytes; microfluidic devices can observe biological and chemical reactions in real time in a flowing state. Therefore, microfluidic devices with SERS activity are of great significance for the study of biological and chemical reaction kinetics. Polydimethylsiloxane (PDMS) is currently the most commonly used material for the preparation of microfluidic devices. The preparation of highly uniform PDMS-based SERS substrates is the basis for the development of functionalized SERS active microfluidic devices.

The most common fabrication method for solid-phase SERS substrates is to uniformly deposit prepared metal nanoparticle colloids on the substrate. However, PDMS is strongly hydrophobic, and it is difficult to uniformly deposit metal nanoparticles on it. The usual method is to modify the surface of PDMS first, and then graft some specific groups or polymer layers (such as modifying APTMS or PDDA, etc.) to make the surface positively charged. Finally, the metal nanoparticles were deposited on the PDMS surface.

It can be seen that the current fabrication of SERS substrates on hydrophobic PDMS surfaces has the following problems: 1. The steps are cumbersome, which reduces the reliability of preparing SERS substrates with high uniformity, making it difficult to guarantee the uniformity; 2. The cycle is long, the cost is high, and the Use large-scale equipment such as oxygen plasma cleaning machines; 3. The cleanliness of the production environment is high, and surface hydrophilic modification needs to be carried out in an ultra-clean room; 4. Due to the repulsion between metal nanoparticles, the distance between the particles adsorbed on the substrate is relatively small. big.

Therefore, it is necessary to develop a simple and reliable method for fabricating single-layer dense SERS substrates on PDMS.

Contents of the invention

Purpose of the invention: To directly self-assemble a single-layer dense metal nanoparticle film on the surface of a hydrophobic material (PDMS) without surface modification, to obtain a SERS substrate with good SERS activity and high repeatability.

Technical solution: Provide a method for preparing a PDMS-based SERS substrate without surface modification, including the following steps:

Step 1, preparing uniform metal sol particles;

Step 2, self-assembling a single-layer dense metal nanoparticle film at the water-oil interface;

Step 3, transferring the metal nanoparticle film to the PDMS surface without surface treatment and forming a dense and uniform SERS substrate.

Preferably, said step 1 further includes:

Step 11, prepare 0.2-2mol/L silver nitrate solution, place in boiling water for preheating; prepare 0.3-1.5mol/L sodium citrate solution, adjust the pH value to 8.7-12, place in boiling water for preheating, and Put it in an ultrasonic machine for ultrasonic treatment; measure the silver nitrate solution according to the molar ratio of silver nitrate and sodium citrate being 0.125-1.5, and inject the silver nitrate solution into the sodium citrate solution until the mixed solution becomes milky white. Obtain the seed solution;

Step 12, prepare an aqueous solution with a pH of 3.5-7.5, put the aqueous solution in an oil bath, boil it, condense and reflux; inject the seed solution obtained in step 11 into the aqueous solution, and continue heating for 0.5-2 hours to obtain silver nanoparticles solution;

Step 13. Centrifuge the silver nanoparticle solution obtained in step 12 at a centrifugal rate of 1500-5000 rpm; the number of centrifugations is 1-8 times; obtain a spherical silver nanoparticle solution of 65×(1±0.07) nm.

Preferably, said step 2 further includes:

Step 21, process the reaction vessel with piranha solution, inject the spherical silver nanoparticle solution obtained in step 13 into the reaction vessel, then inject the oil phase solution into the reaction vessel, let stand, the oil phase solution and the spherical silver nanoparticle solution The volume ratio is 0.5-2;

Step 22. Inject a certain amount of hydrophilic ligand substituting agent into the water phase side of the water-oil interface at a uniform speed of 0.01-2ml/min, and the silver nanoparticles are precipitated at the water-oil interface.

Preferably, said step 3 further includes:

Step 31, remove the upper oil phase solution, the surface of the spherical silver nanoparticle solution forms a dense and flexible silver nanoparticle monolayer film with metallic luster;

Step 32, lightly place the PDMS substrate on the silver nanoparticle film, and transfer the silver film to the PDMS substrate for 0.5-5 minutes, and tightly bond the single-layer silver nanoparticle film on the PDMS surface;

Step 33, taking out the PDMS coated with the metal nanoparticle film, washing with water, and blowing dry with nitrogen.

A method for preparing a PDMS-based SERS substrate without surface modification, comprising:

A single-layer metal nanoparticle film is formed at the water-oil two-phase interface; the upper oil phase solvent is volatilized; untreated PDMS is lightly placed on the surface of the film, and the metal nanoparticle film is automatically transferred to the PDMS to form a SERS substrate.

Preferably, the process of generating a single-layer metal nanoparticle film at the water-oil two-phase interface specifically includes the following steps:

Inject the prepared concentrated uniform metal sol into a clean glass container first, then inject the oil phase solvent with a density lower than water, and let it stand; inject a hydrophilic ligand substituent into the water phase of the water-oil interface at a predetermined speed, and the metal nano The particles spontaneously precipitated at the water-oil interface, forming a single-layer metal nanoparticle film.

Preferably, the oil phase solvent includes toluene, ethyl acetate and n-hexane. Metal nanoparticles include gold nanoparticles and silver nanoparticles. The hydrophilic ligand substituting agent includes alcohols, concentrated silver nitrate solution, acetone and protein solution.

The PDMS-based SERS substrate obtained by the preparation method of any of the above examples.

Working principle: After in-depth and creative research, the applicant found that growing on the water-oil interface greatly reduces the potential of the metal nanoparticle film, and it can be closely adsorbed to the surface of PDMS through strong electrostatic interaction, so that no surface modification of PDMS is required. A single layer of dense metal nanoparticle film can be deposited on it, thus forming a uniform and highly enhanced SERS substrate.

Beneficial effects: the preparation method of the present invention can prepare a dense single-layer metal nanoparticle film on PDMS without any surface modification, and the method is simple and easy; and the metal nanoparticle film produced by this method is dense and flexible, which is comparable to PDMS Tightly combined, with extremely high SERS enhancement and uniformity. This method omits the hydrophilization treatment of PDMS and the subsequent modification of specific groups, greatly simplifies the production process, improves the reliability of production, and does not need to be implemented in a clean room, reducing the requirements for the production environment; The metal nanoparticle film prepared by the method is spontaneously formed, and the distance between the metal nanoparticle is extremely small, so the SERS enhancement effect and uniformity are extremely high.

Description of drawings

Fig. 1 is a flowchart of the present invention.

Fig. 2a and Fig. 2b are the topography diagrams of the PDMS-based SERS substrate prepared in Example 8.

Figure 3 is the SERS spectrum of R6G detected at any 20 points on the prepared SERS substrate.

Figure 4 is the homogeneity characterization of the 1510cm ^-1 characteristic peak of R6G.

Fig. 5 is a topography diagram of the PDMS-based SERS substrate prepared in Example 9.

Fig. 6 is a topography diagram of the PDMS-based SERS substrate prepared in Example 10.

detailed description

In order to solve the problems existing in the prior art, such as cumbersome steps, low repeatability, high requirements on the cleanliness of the production environment, and large spacing between metal nanoparticles, the applicant proposed the following scheme:

The preparation method of the PDMS-based SERS base without surface modification of the present invention includes the following steps: preparing uniform metal sol particles; self-assembling a single-layer dense metal nanoparticle film at the water-oil interface; PDMS surface and form a dense and uniform SERS substrate.

Wherein, the step 1 specifically includes:

Step 11, prepare 0.2-2mol/L silver nitrate solution, place in boiling water for preheating; prepare 0.3-1.5mol/L sodium citrate solution, adjust the pH value to 8.7-12, place in boiling water for preheating, and Put it in an ultrasonic machine for ultrasonic treatment; measure the silver nitrate solution according to the molar ratio of silver nitrate and sodium citrate being 0.125-1.5, and inject the silver nitrate solution into the sodium citrate solution until the mixed solution becomes milky white. Obtain the seed solution;

Step 12, prepare an aqueous solution with a pH of 3.5-7.5, put the aqueous solution in an oil bath, boil it, condense and reflux; inject the seed solution obtained in step 11 into the aqueous solution, and continue heating for 0.5-2 hours to obtain silver nanoparticles solution;

Step 13. Centrifuge the silver nanoparticle solution obtained in step 12 at a centrifugal rate of 1500-5000 rpm; the number of centrifugations is 1-8 times; obtain a spherical silver nanoparticle solution of 65×(1±0.07) nm.

Described step 2 specifically comprises:

Step 21, process the reaction vessel with piranha solution, inject the spherical silver nanoparticle solution obtained in step 13 into the reaction vessel, then inject the oil phase solution into the reaction vessel, let stand, the oil phase solution and the spherical silver nanoparticle solution The volume ratio is 0.5-2;

Step 22. Inject a certain amount of hydrophilic ligand substituting agent into the water phase side of the water-oil interface at a uniform speed of 0.01-2ml/min, and the silver nanoparticles are precipitated at the water-oil interface.

The step 3 specifically includes:

Step 31, remove the upper oil phase solution, the surface of the spherical silver nanoparticle solution forms a dense and flexible silver nanoparticle monolayer film with metallic luster;

Step 32, lightly place the PDMS substrate on the silver nanoparticle film, and transfer the silver film to the PDMS substrate for 0.5-5 minutes, and tightly bond the single-layer silver nanoparticle film on the PDMS surface;

Step 33, taking out the PDMS coated with the metal nanoparticle film, washing with water, and blowing dry with nitrogen.

Example 1

A method for preparing a PDMS-based SERS base without surface modification, comprising the steps of:

Step 1, preparing uniform metal sol particles, specifically including:

Step 11, prepare a 1.6mol/L silver nitrate solution, preheat in boiling water; prepare a 1.4mol/L sodium citrate solution, adjust the pH to 12, preheat in boiling water, and place in an ultrasonic machine Carry out ultrasonic treatment; Measure the silver nitrate solution according to the molar ratio of silver nitrate and sodium citrate being 0.13, and inject the silver nitrate solution into the sodium citrate solution, and obtain the seed solution after the mixed solution becomes milky white;

Step 12, prepare an aqueous solution with a pH of 3.5, put the aqueous solution in an oil bath, add to boil, condense and reflux; inject the seed solution obtained in step 11 into the aqueous solution, and continue heating for 0.5 hours to obtain a silver nanoparticle solution;

Step 13. Centrifuge the silver nanoparticle solution obtained in step 12 at a centrifugal rate of 5000 rpm; the number of centrifugations is 6 times; obtain a spherical silver nanoparticle solution of 65×(1±0.07) nm.

Step 2. Self-assemble a single-layer dense metal nanoparticle film at the water-oil interface, specifically including:

Step 21, process the reaction vessel with piranha solution, inject the spherical silver nanoparticle solution obtained in step 13 into the reaction vessel, then inject the oil phase solution into the reaction vessel, let stand, the oil phase solution and the spherical silver nanoparticle solution The volume ratio is 2;

Step 22. Inject a certain amount of hydrophilic ligand substituting agent into the water phase side of the water-oil interface at a uniform speed of 0.01 ml/min, and the silver nanoparticles are precipitated at the water-oil interface.

Step 3, transferring the metal nanoparticle film to the PDMS surface without surface treatment and forming a dense and uniform SERS substrate, specifically including:

Step 31, remove the upper oil phase solution, the surface of the spherical silver nanoparticle solution forms a dense and flexible silver nanoparticle monolayer film with metallic luster;

Step 32, lightly place the PDMS substrate on the silver nanoparticle film, and transfer the silver film to the PDMS substrate for 5 minutes, and tightly bond the single-layer silver nanoparticle film on the PDMS surface;

Step 33, taking out the PDMS coated with the metal nanoparticle film, washing with water, and blowing dry with nitrogen.

Example 2

A method for preparing a PDMS-based SERS substrate without surface modification, comprising the steps of:

Step 1, preparing uniform metal sol particles, specifically including:

Step 11, prepare a 0.6mol/L silver nitrate solution, preheat in boiling water; prepare a 1mol/L sodium citrate solution, adjust the pH to 11.0, preheat in boiling water, and place in an ultrasonic machine Ultrasonic treatment: measure the silver nitrate solution according to the molar ratio of silver nitrate and sodium citrate being 1.25, and inject the silver nitrate solution into the sodium citrate solution, and obtain the seed solution after the mixed solution becomes milky white;

Step 12, prepare an aqueous solution with a pH of 4.5, put the aqueous solution in an oil bath, add to boil, condense and reflux; inject the seed solution obtained in step 11 into the aqueous solution, and continue heating for 1 hour to obtain a silver nanoparticle solution;

Step 13, centrifuging the silver nanoparticle solution obtained in step 12, the centrifugal rate is 4000 rpm; the number of centrifugation is 3 times; a spherical silver nanoparticle solution of 65×(1±0.07) nm is obtained.

Step 2. Self-assemble a single-layer dense metal nanoparticle film at the water-oil interface, specifically including:

Step 21, process the reaction vessel with piranha solution, inject the spherical silver nanoparticle solution obtained in step 13 into the reaction vessel, then inject the oil phase solution into the reaction vessel, let stand, the oil phase solution and the spherical silver nanoparticle solution The volume ratio is 1.2;

Step 22. Inject a certain amount of hydrophilic ligand substituting agent into the water phase side of the water-oil interface at a uniform speed of 0.5 ml/min, and the silver nanoparticles are precipitated at the water-oil interface.

Step 3, transferring the metal nanoparticle film to the PDMS surface without surface treatment and forming a dense and uniform SERS substrate, specifically including:

Step 31, remove the upper oil phase solution, the surface of the spherical silver nanoparticle solution forms a dense and flexible silver nanoparticle monolayer film with metallic luster;

Step 32, lightly place the PDMS substrate on the silver nanoparticle film, and within 4 minutes, the silver film is transferred to the PDMS substrate, and a single layer of silver nanoparticle film is tightly bonded on the PDMS surface;

Step 33, taking out the PDMS coated with the metal nanoparticle film, washing with water, and blowing dry with nitrogen.

Example 3

A method for preparing a PDMS-based SERS base without surface modification, comprising the steps of:

Step 1, preparing uniform metal sol particles, specifically including:

Step 11, prepare a 0.3mol/L silver nitrate solution, preheat in boiling water; prepare a 0.4mol/L sodium citrate solution, adjust the pH to 10.0, preheat in boiling water, and place in an ultrasonic machine Carry out ultrasonic treatment; Measure the silver nitrate solution according to the molar ratio of silver nitrate and sodium citrate being 0.8, and inject the silver nitrate solution into the sodium citrate solution, and obtain the seed solution after the mixed solution becomes milky white;

Step 12, prepare an aqueous solution with a pH of 5.5, put the aqueous solution in an oil bath, add to boil, condense and reflux; inject the seed solution obtained in step 11 into the aqueous solution, and continue heating for 1.5 hours to obtain a silver nanoparticle solution;

Step 13. Centrifuge the silver nanoparticle solution obtained in step 12 at a centrifugal rate of 3000 rpm; the number of centrifugations is 5 times; obtain a spherical silver nanoparticle solution of 65×(1±0.07) nm.

Step 2. Self-assemble a single-layer dense metal nanoparticle film at the water-oil interface, specifically including:

Step 21, process the reaction vessel with piranha solution, inject the spherical silver nanoparticle solution obtained in step 13 into the reaction vessel, then inject the oil phase solution into the reaction vessel, let stand, the oil phase solution and the spherical silver nanoparticle solution The volume ratio is 4;

Step 22. Inject a certain amount of hydrophilic ligand substituting agent into the water phase side of the water-oil interface at a uniform speed of 1 ml/min, and the silver nanoparticles are precipitated at the water-oil interface.

Step 3, transferring the metal nanoparticle film to the PDMS surface without surface treatment and forming a dense and uniform SERS substrate, specifically including:

Step 31, remove the upper oil phase solution, the surface of the spherical silver nanoparticle solution forms a dense and flexible silver nanoparticle monolayer film with metallic luster;

Step 32, lightly place the PDMS substrate on the silver nanoparticle film, and within 3 minutes, the silver film is transferred to the PDMS substrate, and a single layer of silver nanoparticle film is tightly bonded on the PDMS surface;

Step 33, taking out the PDMS coated with the metal nanoparticle film, washing with water, and blowing dry with nitrogen.

Example 4

A method for preparing a PDMS-based SERS base without surface modification, comprising the steps of:

Step 1, preparing uniform metal sol particles, specifically including:

Step 11, prepare a 1.9mol/L silver nitrate solution, preheat in boiling water; prepare a 0.4mol/L sodium citrate solution, adjust the pH to 8.7, preheat in boiling water, and place in an ultrasonic machine Carry out ultrasonic treatment; Measure the silver nitrate solution according to the ratio that the molar ratio of silver nitrate and sodium citrate is 0.15, and inject the silver nitrate solution into the sodium citrate solution, after the mixed solution becomes milky white, obtain the seed solution;

Step 12, prepare an aqueous solution with a pH of 6.5, put the aqueous solution in an oil bath, add to boil, condense and reflux; inject the seed solution obtained in step 11 into the aqueous solution, and continue heating for 2 hours to obtain a silver nanoparticle solution;

Step 13. Centrifuge the silver nanoparticle solution obtained in step 12 at a centrifugal rate of 2500 rpm; the number of centrifugations is 8 times; obtain a spherical silver nanoparticle solution of 65×(1±0.07) nm.

Step 2. Self-assemble a single-layer dense metal nanoparticle film at the water-oil interface, specifically including:

Step 21, process the reaction vessel with piranha solution, inject the spherical silver nanoparticle solution obtained in step 13 into the reaction vessel, then inject the oil phase solution into the reaction vessel, let stand, the oil phase solution and the spherical silver nanoparticle solution The volume ratio is 0.6;

Step 22. Inject a certain amount of hydrophilic ligand substituting agent into the water phase side of the water-oil interface at a uniform speed of 1.2ml/min, and silver nanoparticles are precipitated at the water-oil interface.

Step 3, transferring the metal nanoparticle film to the PDMS surface without surface treatment and forming a dense and uniform SERS substrate, specifically including:

Step 31, remove the upper oil phase solution, the surface of the spherical silver nanoparticle solution forms a dense and flexible silver nanoparticle monolayer film with metallic luster;

Step 32, lightly place the PDMS substrate on the silver nanoparticle film, and transfer the silver film to the PDMS substrate in 2 minutes, and tightly bond the single-layer silver nanoparticle film on the PDMS surface;

Step 33, taking out the PDMS coated with the metal nanoparticle film, washing with water, and blowing dry with nitrogen.

Example 5

A method for preparing a PDMS-based SERS base without surface modification, comprising the steps of:

Step 1, preparing uniform metal sol particles, specifically including:

Step 11, prepare a 0.2mol/L silver nitrate solution, preheat in boiling water; prepare a 0.3mol/L sodium citrate solution, adjust the pH to 11.0, preheat in boiling water, and place in an ultrasonic machine Carry out ultrasonic treatment; Measure the silver nitrate solution according to the molar ratio of silver nitrate and sodium citrate being 0.6, and inject the silver nitrate solution into the sodium citrate solution, and obtain the seed solution after the mixed solution becomes milky white;

Step 12, prepare an aqueous solution with a pH of 7.5, place the aqueous solution in an oil bath, add to boil, condense and reflux; inject the seed solution obtained in step 11 into the aqueous solution, and continue heating for 1.5 hours to obtain a silver nanoparticle solution;

Step 13. Centrifuge the silver nanoparticle solution obtained in step 12 at a centrifugal rate of 2000 rpm; the number of centrifugations is 6 times; obtain a spherical silver nanoparticle solution of 65×(1±0.07) nm.

Step 2. Self-assemble a single-layer dense metal nanoparticle film at the water-oil interface, specifically including:

Step 21, process the reaction vessel with piranha solution, inject the spherical silver nanoparticle solution obtained in step 13 into the reaction vessel, then inject the oil phase solution into the reaction vessel, let stand, the oil phase solution and the spherical silver nanoparticle solution The volume ratio is 1.5;

Step 22. Inject a certain amount of hydrophilic ligand substituting agent into the water phase side of the water-oil interface at a uniform speed of 2 ml/min, and the silver nanoparticles are precipitated at the water-oil interface.

Step 3, transferring the metal nanoparticle film to the PDMS surface without surface treatment and forming a dense and uniform SERS substrate, specifically including:

Step 31, remove the upper oil phase solution, the surface of the spherical silver nanoparticle solution forms a dense and flexible silver nanoparticle monolayer film with metallic luster;

Step 32, lightly place the PDMS substrate on the silver nanoparticle film, and transfer the silver film to the PDMS substrate for 1 minute, and tightly bond the single-layer silver nanoparticle film on the PDMS surface;

Step 33, taking out the PDMS coated with the metal nanoparticle film, washing with water, and blowing dry with nitrogen.

Example 6

A method for preparing a PDMS-based SERS base without surface modification, comprising the steps of:

Step 1, preparing uniform metal sol particles, specifically including:

Step 11, prepare 0.8mol/L silver nitrate solution, preheat in boiling water; prepare 1.1mol/L sodium citrate solution, adjust the pH to 11.0, preheat in boiling water, and place in an ultrasonic machine Carry out ultrasonic treatment; Measure the silver nitrate solution according to the ratio that the molar ratio of silver nitrate and sodium citrate is 0.65, and inject the silver nitrate solution into the sodium citrate solution, after the mixed solution becomes milky white, obtain the seed solution;

Step 12, prepare an aqueous solution with a pH of 4.5, put the aqueous solution in an oil bath, add to boil, condense and reflux; inject the seed solution obtained in step 11 into the aqueous solution, and continue heating for 1.5 hours to obtain a silver nanoparticle solution;

Step 13. Centrifuge the silver nanoparticle solution obtained in step 12 at a centrifugal rate of 1500 rpm; the number of centrifugations is 5 times; obtain a spherical silver nanoparticle solution of 65×(1±0.07) nm.

Step 2. Self-assemble a single-layer dense metal nanoparticle film at the water-oil interface, specifically including:

Step 21, process the reaction vessel with piranha solution, inject the spherical silver nanoparticle solution obtained in step 13 into the reaction vessel, then inject the oil phase solution into the reaction vessel, let stand, the oil phase solution and the spherical silver nanoparticle solution The volume ratio is 0.6;

Step 22. Inject a certain amount of hydrophilic ligand substituting agent into the water phase side of the water-oil interface at a uniform speed of 1.0 ml/min, and silver nanoparticles are precipitated at the water-oil interface.

Step 3, transferring the metal nanoparticle film to the PDMS surface without surface treatment and forming a dense and uniform SERS substrate, specifically including:

Step 31, remove the upper oil phase solution, the surface of the spherical silver nanoparticle solution forms a dense and flexible silver nanoparticle monolayer film with metallic luster;

Step 32, lightly place the PDMS substrate on the silver nanoparticle film, and transfer the silver film to the PDMS substrate for 0.5 minutes, and tightly bond the single-layer silver nanoparticle film on the PDMS surface;

Step 33, taking out the PDMS coated with the metal nanoparticle film, washing with water, and blowing dry with nitrogen.

Embodiment 7: The preferred PDMS-based single-layer SERS substrate preparation method of the present invention without surface modification comprises the following three steps:

The first step: preparing uniform metal sol particles, specifically including the following steps:

A. Dissolve 0.5418g of sodium citrate in 4ml of water, adjust its pH to 11, preheat it in boiling water, and put it in an ultrasonic machine for ultrasonication; dissolve 0.051g of silver nitrate in 1ml of water , preheat it in boiling water; inject the prepared silver nitrate aqueous solution into a sodium citrate solution with a pH value of 11, and obtain a seed solution after the solution is milky white;

B. Take 295ml of water and place it in a three-neck round bottom flask, adjust its pH value to 4.5, heat and boil in an oil bath, condense and reflux; quickly inject the seed solution obtained in step A into an aqueous solution with a pH value of 4.5, and continue heating After stirring for 1.5h, cool naturally during stirring to complete the preparation of silver nanoparticles;

C, the silver nanoparticle that makes is carried out repeatedly centrifugation, centrifugation speed 2500 rev/mins, extract the silver nanoparticle that settles on the centrifuge tube bottom, after 6 times of centrifugation, obtain about 65nm, relative standard deviation is only 7% Spherical silver nanoparticles.

The second step: a self-assembled single-layer dense metal nanoparticle film at the water-oil interface, as shown in Figure 1, specifically including

Follow the steps below:

A) Prepare a 10ml beaker processed with piranha solution, first inject 2ml of the silver colloid solution prepared in the first step into it as solution A, then inject 2ml of oil phase solution B, and let it stand;

B) Use a syringe pump to inject a certain amount of solution C into the water-oil interface (water phase side) at a constant speed of 1ml/min. The interface is violently disturbed, and silver nanoparticles are continuously precipitated at the water-oil interface until the interface is completely covered by the metal film. .

The third step: transfer the metal nanoparticle film to the PDMS surface without surface treatment and form a dense and uniform SERS substrate, including the following steps:

A) Remove the upper layer solution B until it is completely volatilized, and a dense and flexible silver nanoparticle monolayer film with metallic luster is formed on the water surface;

B) Lightly place the PDMS substrate on the dense silver nanoparticle film, and in about half a minute, the silver film is completely transferred to the PDMS substrate spontaneously, and a single layer of silver nanoparticle film is tightly bonded on the PDMS surface, as shown in Figure 2 ;

C) Take out the PDMS coated with the metal nanoparticle film, wash it with water, and blow it dry with nitrogen, then the preparation of the PDMS-based single-layer SERS substrate is completed;

D) SERS activity detection: soak the prepared SERS substrate in 1.0×10 ⁻⁶ M R6G solution for 3 hours, take it out, wash it with deionized water, dry it with nitrogen gas, and perform SERS detection at any 20 points.

Example 8:

Take the silver colloid prepared in the first step of the scheme and carry out centrifugation concentration, so that the peak intensity of the extinction spectrum of the concentrated solution is 1. Take 2ml of concentrated silver colloid solution and place it in a 10ml beaker treated with piranha solution, add 2ml of toluene solution, and let stand to separate layers. Use a syringe pump to inject a certain amount of ethanol solution to the water/toluene interface (water phase side) at a constant speed of 1ml/min. Silver nanoparticles are continuously precipitated and captured by the interface until the precipitated particles cover the caliber of the beaker and stop injecting ethanol. With the volatilization of toluene, the precipitated silver particles shrink into a dense silver film, and the TEM of the silver film is shown in Figure 2(a). The morphology of the SERS substrate formed by transferring the silver film onto the PDMS surface is shown in Figure 2(b). Soak the prepared SERS substrate in 1.0×10 ^-6 MR6G solution for 3 hours, take it out, wash it with deionized water, dry it with nitrogen, and perform SERS detection at any 20 points. The SERS spectrum is shown in Figure 3, and the enhancement factor is 1.7×10 ⁷ ; the homogeneity of the SERS substrate was analyzed with a peak of 1510 cm ^-1 , and the relative standard deviation was RSD=7.2%, as shown in Figure 4 .

Example 9:

Take the silver colloid prepared in the first step of the scheme and carry out centrifugation concentration, so that the peak intensity of the extinction spectrum of the concentrated solution is 1. Take 2ml of concentrated silver colloid solution and place it in a 10ml beaker treated with piranha solution, add 2ml of n-hexane solution, and let stand to separate layers. Use a syringe pump to inject a certain amount of ethanol solution to the water/n-hexane interface (water phase side) at a constant speed of 1ml/min. Silver nanoparticles are continuously precipitated and captured by the interface until the precipitated particles cover the caliber of the beaker and stop injecting ethanol. With the volatilization of n-hexane, the precipitated silver particles shrink into a silver film, and the morphology of the SERS substrate formed by transferring the silver film to the PDMS surface. As shown in Figure 5.

Example 10:

Take the silver colloid prepared in the first step of the scheme and carry out centrifugation concentration, so that the peak intensity of the extinction spectrum of the concentrated solution is 1. Take 2ml of concentrated silver colloid solution and place it in a 10ml beaker treated with piranha solution, add 2ml of toluene solution, and let stand to separate layers. Use a syringe pump to inject a certain amount of concentrated silver nitrate salt solution to the water/toluene interface (water phase side) at a constant speed of 1ml/min. Silver nanoparticles are continuously precipitated and captured by the interface until the precipitated particles are covered with the beaker. Stop injection concentrated silver nitrate solution. With the volatilization of toluene, the precipitated silver particles shrink into a silver film, and the morphology of the SERS substrate formed by transferring the silver film to the PDMS surface is shown in Figure 6.

It can be seen from the above examples that this scheme can deposit a single layer of metal nanoparticle film on PDMS without any surface treatment to form a uniform SERS substrate. The method is simple and easy, and the SERS enhancement effect is good, and by selecting different solution groups, SERS substrates with different densities can be obtained.

Example 11

Other steps in this embodiment are similar to the above-mentioned embodiment, and the emphasis is on:

Take the silver colloid prepared in the first step of the scheme and carry out centrifugal concentration, so that the peak intensity of the extinction spectrum of the concentrated solution is 0.6-0.7. Take 2ml of concentrated silver colloid solution and place it in a 10ml beaker treated with piranha solution, add 2ml of n-hexane solution, and let stand to separate layers. Use a syringe pump to inject 1-1.5ml of ethanol solution to the water/n-hexane interface (water phase side) at a constant speed of 1ml/min. Silver nanoparticles are continuously precipitated and captured by the interface until the precipitated particles are covered with the beaker. Inject ethanol. With the volatilization of n-hexane, the precipitated silver particles shrink into a silver film, and the morphology of the SERS substrate formed by transferring the silver film to the PDMS surface.

In the experiment, it was found that the extinction spectrum intensity of silver colloid changed from 0.15 to 0.9, and the formed silver film became larger and larger. Due to the limitation of the container caliber, the silver film became denser, and the extinction spectrum intensity exceeded 0.7, and even multi-layer particles appeared, so the best Jiayin colloidal spectral intensity should be around 0.6-0.7.

When the concentration of silver colloid is 0.65, the ethanol injection volume is 0, 0.5, 1, 1.5, 2, 2.5, 3, 3.5ml respectively, the silver film first increases and then decreases, and the silver film is the largest when the ethanol injection volume is 1-1.5ml .

The concentration of silver colloid is 0.65, and the same amount (1.5ml) of ethanol is injected into the water phase at different speeds (0.05, 0.25, 0.5, 1, 1.5, 1.75, 2ml/min). The silver film is broken, so the speed is controlled at 1ml/min.

In conclusion, the present invention discloses a method for preparing a PDMS-based single-layer SERS substrate without surface modification, including generating a single-layer metal nanofilm at the water-oil two-phase interface and transferring the film to PDMS without any surface treatment, A PDMS-based monolayer SERS substrate was formed. The specific steps for forming a single-layer metal nano-film at the water-oil two-phase interface are as follows: sequentially add concentrated metal sol and an oil phase solvent with a density lower than water in the container, and then inject a hydrophilic ligand at the near-water phase of the two-phase interface to replace The metal nanoparticles spontaneously precipitate at the water-oil interface to form a thin film; transfer the generated metal nanofilm to PDMS without any surface treatment to form a PDMS-based single-layer SERS substrate, including standing to volatilize all the oil phase solvent , and then lightly place the PDMS without any treatment on the generated metal nanoparticle film, then the film is spontaneously transferred to the PDMS to form a PDMS-based single-layer SERS substrate. The invention greatly simplifies the production process for preparing the PDMS-based SERS substrate, reduces the requirements for the preparation environment, and the prepared SERS substrate metal nanoparticles have extremely small spacing, high uniformity, and high SERS enhancement and repeatability.

Several implementations of the present invention have been described in detail above, but the present invention is not limited to several options in the above-mentioned implementations. Within the scope of the technical concept of the present invention, various equivalent transformations can be performed on the technical solutions of the present invention. Equivalent transformations all belong to the protection scope of the present invention.

Claims (10)

1. a kind of PDMS base SERS substrate preparation methods without the need for surface modification, it is characterised in that comprise the steps：

Step 1, prepare homogeneous metal sol particle；

Step 2, in the fine and close film of metal nano-particles of water-oil interface self-assembled monolayer；

Step 3, the SERS that film of metal nano-particles is transferred to the PDMS surfaces of non-surface treated and dense uniform is formed Substrate.

2. as claimed in claim 1 without the need for the PDMS base SERS substrate preparation methods of surface modification, it is characterised in that the step Rapid 1 further includes：

Step 11, the silver nitrate solution for preparing 0.2-2mol/L, are placed in boiling water and preheat；Prepare the citric acid of 0.3-1.5mol/L Sodium solution, adjust pH value to 8.7-12, be placed in boiling water preheat, and be placed in ultrasonic machine carry out it is ultrasonically treated；According to silver nitrate Silver nitrate solution is measured for the ratio of 0.125-1.5 with the mol ratio of sodium citrate, and silver nitrate solution is injected into sodium citrate In solution, liquid to be mixed obtains seed solution into after milky；

Step 12, prepare pH be 3.5-7.5 the aqueous solution, and by the aqueous solution be placed in oil bath add boil, condensing reflux；Will The seed solution that step 11 is obtained is injected in the aqueous solution, continues to heat 0.5-2 hours, obtains silver nanoparticle solution；

Step 13, the silver nanoparticle solution to step 12 acquisition are centrifuged, and centrifugation rate is 1500-5000 rev/min；From Heart number of times is 1-8 time；Obtain 65 ×（1±0.07）The spherical silver nanoparticle solution of nm.

3. as claimed in claim 2 without the need for the PDMS base SERS substrate preparation methods of surface modification, it is characterised in that the step Rapid 2 further include：

Step 21, with Piranha solution process reaction vessel, in the reaction vessel implantation step 13 obtain spherical silver nanoparticle Particle solution, then inject oil-phase solution into the reaction vessel, stands, the volume of oil-phase solution and spherical silver nanoparticle solution Than for 0.5-2；

Step 22, a certain amount of metal Ion-hydrophilic Ligand is at the uniform velocity injected to the water phase side of water-oil interface with the speed of 0.01-2ml/min take For agent, silver nano-grain is separated out in water-oil interface.

4. as claimed in claim 3 without the need for the PDMS base SERS substrate preparation methods of surface modification, it is characterised in that the step Rapid 3 further include：

Step 31, upper oil phase solution is removed, the surface of spherical silver nanoparticle solution forms fine and close flexible with metal light The silver nano-grain single thin film in pool；

Step 32, PDMS substrates are gently placed in silver nanometer particle film, 0.5-5 minutes, silverskin is transferred on PDMS substrates, PDMS combines closely on surface individual layer silver nanometer particle film；

Step 33, the PDMS that will be coated with film of metal nano-particles take out, washing, and are dried up with nitrogen.

5. a kind of PDMS base SERS substrate preparation methods without the need for surface modification, it is characterised in that comprise the steps：

Single-layer metal nanometer particle film is generated at water phase and an oil phase interface；

Volatilization upper oil phase solvent；

Undressed PDMS is gently placed in into film surface, film of metal nano-particles is automatically transferred on PDMS, is formed SERS substrates.

6. as claimed in claim 5 without the need for the PDMS base SERS substrate preparation methods of surface modification, it is characterised in that in water oil Two-phase interface generates the process of single-layer metal nanometer particle film and specifically includes following steps：

The homogeneous metal colloidal sol of the concentration for preparing first is injected in clean glass container, oil phase of the density less than water is reinjected Solvent, stands；

At the uniform velocity get along to water-oil interface water at a predetermined velocity and inject metal Ion-hydrophilic Ligand substituting agent, metal nanoparticle is spontaneous in Shui Youjie Face separates out, and forms single-layer metal nanometer particle film.

7. as claimed in claim 5 without the need for the PDMS base SERS substrate preparation methods of surface modification, it is characterised in that described Oil phase solvent includes toluene, ethyl acetate and n-hexane.

8. as claimed in claim 5 without the need for the PDMS base SERS substrate preparation methods of surface modification, it is characterised in that metal is received Rice grain includes gold nano grain and silver nano-grain.

9. as claimed in claim 6 without the need for the PDMS base SERS substrate preparation methods of surface modification, it is characterised in that the parent The agent of water ligand substituting includes alcohols, red fuming nitric acid (RFNA) silver salt solution, acetone and protein buffer solution.

10. the PDMS base SERS for being prepared using the method described in any one of Claims 1-4 or any one of claim 5 to 9 Substrate.