Gold particle transfer method for preparing PDMS flexible substrate

Abstract

The invention relates to the technical field of high-sensitivity trace substance detection, in particular to a gold particle transfer method for preparing a PDMS (polydimethylsiloxane) flexible substrate, which comprises the following steps: step 1, preparing a gold nanoparticle solution; as the ethanol is injected into the gold nanoparticle solution, a layer of gold nanoparticle film is gradually formed on a water-oil interface; and step 3, preparing the flexible SERS substrate. According to the method, the gold nanoparticles can be successfully transferred to the flexible substrate; naturally settling a gold particle film formed by liquid-liquid self-assembly on the surface of PDMS in an original compact arrangement mode; the substrate prepared by the preparation method has a good detection effect on an object to be analyzed, rhodamine 6G is used as a Raman active probe, and the limit can be measured to be 1 * 10 <-8 > mol / L.

Description

Technical Field

[0001] The invention relates to the technical field of high-sensitivity trace substance detection, and in particular to a gold particle transfer method for preparing a PDMS flexible substrate. Background Art

[0002] Surface enhanced Raman scattering (SERS) is a molecular level detection technology developed from Raman scattering, which can realize the analysis and detection of substances at extremely low concentrations. Testing Raman spectroscopy requires that the concentration of the substance to be tested is not less than 10 -3 mol / L. To detect the Raman spectrum of trace adsorbents on the surface, almost all of them must use the enhancement effect of SERS substrate. Therefore, the design and preparation of high-performance SERS substrate is the key.

[0003] The flexible SERS substrate has good mechanical flexibility, which makes it easy to wipe and obtain probe molecules, and can be cut to fit and wrap irregular sample surfaces. Combined with the use of portable Raman spectrometers, the flexible SERS substrate meets the requirements of instant diagnosis and is expected to be applied to on-site detection in daily life.

[0004] The document with application number "201510180681.9" discloses "a transparent and flexible surface enhanced Raman spectroscopy substrate, preparation method and application". Gold nanoparticles are first prepared by sodium citrate method, and then a monolayer of gold nanoparticles loaded on a silicon wafer or a glass slide is obtained by aminopropyltrimethoxysilane self-assembly method or liquid-liquid two-phase film formation method; finally, a sticky transparent film is covered on the gold nanoparticles, and after peeling off, a flexible transparent SERS substrate with a monolayer of gold nanoparticles attached can be obtained. This patent uses the viscosity of the transparent film to stick the gold nanoparticles to the transparent film, and there is a problem that the nanoparticles cannot be completely transferred to the transparent film, which results in a sparse arrangement of particles on the transparent film.

[0005] The document with application number "CN202110324174" discloses the preparation of a double-layer gold nanoparticle-modified flexible SERS substrate by pulling the substrate. The sample has good mechanical flexibility, and the two-layer nanoparticle arrangement can reduce the gap between the nanoparticles, so that the electromagnetic field is enhanced. However, during the preparation process, when the silicon wafer is immersed in the nanoparticle solution and slowly pulled out, the nanoparticle film formed at the liquid-liquid interface is broken and dispersed due to the disturbance of the liquid surface, and the nanoparticles no longer maintain their original dense state. Therefore, the gold particles finally pulled onto the silicon wafer are not dense enough. Summary of the invention

[0006] The invention provides a gold particle transfer method for preparing a PDMS flexible substrate, so as to overcome the shortcomings of the prior art that nanoparticles cannot be completely transferred and it is difficult for them to completely maintain a dense state on the flexible substrate.

[0007] In order to achieve the above object, the technical solution provided by the present invention is: a method for transferring gold particles to prepare a PDMS flexible substrate, comprising the following steps:

[0008] Step 1: Prepare gold nanoparticle solution:

[0009] 1.1 Add HAuCl4 solution to deionized water, heat to boiling, add trisodium citrate solution while stirring rapidly, and continue heating for 15-20 minutes to obtain a solution;

[0010] 1.2 Centrifuge the solution, aspirate the supernatant, and redisperse the concentrated particles at the bottom of the test tube in deionized water to obtain a gold nanoparticle solution;

[0011] Step 2: Self-assembly into a thin film: Through the liquid-liquid interface self-assembly method, a water-oil interface is constructed with a gold nanoparticle solution and n-hexane. As ethanol is injected into the gold nanoparticle solution, a layer of gold nanoparticle film will gradually form at the water-oil interface;

[0012] Step 3: Preparation of flexible SERS substrate:

[0013] First, retain the film;

[0014] Then, by evaporating the solvent, a gold film was deposited on the PDMS at the bottom of the beaker, and the flexible SERS substrate was prepared.

[0015] Furthermore, in the above step 1.1, the concentration of HAuCl4 solution is 25 mM, the mass concentration of trisodium citrate solution is 1-2%, and the volume ratio of HAuCl4 solution, deionized water and trisodium citrate solution is 1:98-100:1-2.

[0016] Furthermore, in the above step 1.2, the amount of deionized water used is 2-4 parts.

[0017] Furthermore, in the above step 2, the PDMS main agent and the curing agent are uniformly mixed and then dripped into the bottom of the beaker to be solidified; the gold nanoparticle solution is dripped into it, and then n-hexane and ethanol are successively added to the gold nanoparticle solution in a volume ratio of 1:1-2.

[0018] Furthermore, in the above step three, the method of retaining the film is: absorbing the upper layer of n-hexane, waiting for the n-hexane to completely evaporate, and the gold particle film floats on the surface of the solution; continue to wait for the aqueous solution under the gold particle film to evaporate and disappear, until the gold particle film settles on the surface of PDMS.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. The present invention can successfully transfer gold nanoparticles to a flexible substrate: Although liquid / liquid interface self-assembly can induce the formation of a dense gold particle film, improper transfer methods will prevent the gold nanoparticles from being completely transferred to the flexible substrate. The present invention allows the gold particle film formed by liquid-liquid self-assembly to naturally settle on the PDMS surface while maintaining the original tightly arranged arrangement by evaporating the solution without disturbing the dispersed state of the gold particle film.

[0021] 2. The substrate prepared by the invention has a good detection effect on the analyte. With rhodamine 6G as the Raman active probe, the maximum detection value can be 1×10 -8 mol / L. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The production process of the present invention;

[0023] Figure 2 The PDMS flexible substrate of the present invention has gold nanoparticles attached to the surface;

[0024] Figure 3 The SEM scanning images of the present invention; wherein (a) is a SEM image magnified 20,000 times; (b) is a SEM image magnified 100,000 times;

[0025] Figure 4 This is the SERS test spectrum on the PDMS / Au substrate of the present invention. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention and are only used to illustrate the present invention, but not to limit the scope of the present invention.

[0027] Example 1: A method for transferring gold particles to prepare a PDMS flexible substrate, see Figure 1 , including the following steps:

[0028] Step 1: Prepare gold nanoparticle solution:

[0029] 1.1 Add HAuCl4 solution to deionized water, heat to boiling, add trisodium citrate solution under rapid stirring, and continue heating for 16 minutes to obtain a solution; the concentration of the HAuCl4 solution is 25mM, the mass concentration of the trisodium citrate solution is 1%, and the volume proportions of HAuCl4 solution, deionized water and trisodium citrate solution are 1 part, 100 parts and 1 part.

[0030] 1.2 Centrifuge the solution, aspirate the supernatant, and redisperse the concentrated particles at the bottom of the test tube in 3 portions of deionized water to obtain a gold nanoparticle solution.

[0031] Step 2: Self-assembly into a thin film: Through the liquid-liquid interface self-assembly method, a water-oil interface is constructed with a gold nanoparticle solution and n-hexane. As ethanol is injected into the gold nanoparticle solution, a layer of gold nanoparticle film will gradually form at the water-oil interface;

[0032] The specific method is to evenly mix the PDMS main agent and curing agent and drip them into the bottom of the beaker to wait for them to solidify; drip the gold nanoparticle solution, and then add the gold nanoparticle solution in turn. 1 Volume parts of n-hexane and 1 Volume parts of ethanol can form a clear interface at the junction of the two phases, and a layer of nano-gold particle film with metallic luster can be seen.

[0033] Step 3: Preparation of flexible SERS substrate:

[0034] First, retain the gold nanoparticle film: absorb the upper layer of n-hexane, wait for the n-hexane to completely evaporate, and the gold particle film floats on the surface of the solution; continue to wait, and as the solution below the gold particle film further evaporates, the gold particle film gradually drops, and wait until the solution completely evaporates and dissipates until the gold particle film settles on the surface of PDMS. The gold nanoparticle film can be completely attached to the surface of PDMS (see Figure 2 ), thus successfully transferring the gold particle film completely onto PDMS.

[0035] Then, by evaporating the solvent, the densely arranged gold film is deposited on the PDMS at the bottom of the beaker without external interference, and the gold nanoparticles remain densely arranged, and the preparation of the flexible SERS substrate is completed.

[0036] Example 2: A method for transferring gold particles to prepare a PDMS flexible substrate, comprising the following steps:

[0037] Step 1: Prepare gold nanoparticle solution:

[0038] 1.1 Add HAuCl4 solution to deionized water, heat to boiling, add trisodium citrate solution under rapid stirring, and continue heating for 20 minutes to obtain a solution; the concentration of the HAuCl4 solution is 25mM, the mass concentration of the trisodium citrate solution is 2%, and the volume proportions of HAuCl4 solution, deionized water and trisodium citrate solution are 1 part, 98 parts and 2 parts.

[0039] 1.2 Centrifuge the solution, aspirate the supernatant, and redisperse the concentrated particles at the bottom of the test tube in 3 volumes of deionized water to obtain a gold nanoparticle solution.

[0040] Step 2: Self-assembly into a thin film: Through the liquid-liquid interface self-assembly method, a water-oil interface is constructed with a gold nanoparticle solution and n-hexane. As ethanol is injected into the gold nanoparticle solution, a layer of gold nanoparticle film will gradually form at the water-oil interface;

[0041] The specific method is to evenly mix the PDMS main agent and the curing agent and then drip them into the bottom of the beaker to wait for them to solidify; drip in the gold nanoparticle solution, and then add 1 volume part of n-hexane and 2 volume parts of ethanol to the gold nanoparticle solution in succession. A clear interface can be formed at the junction of the two phases, and a layer of nano-gold particle film with metallic luster can be seen.

[0042] Step 3: Preparation of flexible SERS substrate:

[0043] First, retain the gold nanoparticle film: absorb the upper layer of n-hexane and wait for the n-hexane to evaporate completely, and the gold particle film floats on the surface of the solution; continue to wait, and as the solution below the gold particle film evaporates further, the gold particle film gradually drops, and wait until the solution evaporates completely until the gold particle film settles on the surface of PDMS. The gold nanoparticle film can be completely attached to the surface of PDMS, thereby successfully transferring the gold particle film to PDMS.

[0044] Then, by evaporating the solvent, the densely arranged gold film is deposited on the PDMS at the bottom of the beaker without external interference, and the gold nanoparticles remain densely arranged, and the preparation of the flexible SERS substrate is completed.

[0045] The above-mentioned embodiment 1 is the best embodiment: the PDMS / Au composite substrate was characterized by field emission scanning electron microscopy, and scanning electron microscopy images at different magnifications were obtained. The results are as follows: Figure 3 As shown, (a) and (b) are images of the same sample at different magnifications, 20,000 times and 100,000 times respectively. It can be seen from the figures that the gold nanoparticles on the substrate form a dense arrangement.

[0046] Using rhodamine 6G as a Raman active probe, the maximum detectable -8 mo l / L, Raman spectrum Figure 4 shown.

[0047] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for transferring gold particles to prepare a PDMS flexible substrate, characterized in that: The steps include: Step 1: Prepare gold nanoparticle solution: 1.1 Add HAuCl4 solution to deionized water, heat to boiling, add trisodium citrate solution while stirring rapidly, and continue heating for 15-20 minutes to obtain a solution; 1.2 Centrifuge the solution, aspirate the supernatant, and redisperse the concentrated particles at the bottom of the test tube in deionized water to obtain a gold nanoparticle solution; Step 2: Self-assembly into a thin film: Through the liquid-liquid interface self-assembly method, a water-oil interface is constructed with a gold nanoparticle solution and n-hexane. As ethanol is injected into the gold nanoparticle solution, a layer of gold nanoparticle film will gradually form at the water-oil interface; Step 3: Preparation of flexible SERS substrate: First, retain the film; Then, by evaporating the solvent, a gold film was deposited on the PDMS at the bottom of the beaker, and the flexible SERS substrate was prepared.

2. The method for transferring gold particles to prepare a PDMS flexible substrate according to claim 1, characterized in that: In the step 1.1, the concentration of the HAuCl4 solution is 25 mM, the mass concentration of the trisodium citrate solution is 1-2%, and the volume ratio of the HAuCl4 solution, deionized water and the trisodium citrate solution is 1:98-100:1-2.

3. The method for transferring gold particles to prepare a PDMS flexible substrate according to claim 2, characterized in that: In the step 1.2, the amount of deionized water used is 2-4 parts.

4. The method for transferring gold particles to prepare a PDMS flexible substrate according to claim 3, characterized in that: In the step 2, the PDMS main agent and the curing agent are uniformly mixed and then dripped into the bottom of the beaker to be solidified; The gold nanoparticle solution was dropped, and then n-hexane and ethanol were successively added in a volume ratio of 1:1-2 to the gold nanoparticle solution.

5. The method for transferring gold particles to prepare a PDMS flexible substrate according to claim 4, characterized in that: In step three, the method of retaining the film is: absorbing the upper layer of n-hexane, waiting for the n-hexane to completely evaporate, and the gold particle film to float on the surface of the solution; and continuing to wait for the aqueous solution below the gold particle film to evaporate and disappear until the gold particle film settles on the surface of the PDMS.

Images