A method for gold particle transfer for the preparation of PDMS flexible substrates

Abstract

The present application relates to high sensitivity micro substance detection technical field, specifically is a kind of preparation PDMS flexible substrate gold particle transfer method, including the following steps: step one, preparation gold nanoparticles solution: step two, self-assembly into film: by liquid-liquid interface self-assembly method, with gold nanoparticles solution and n-hexane water oil interface is constructed, with ethanol injection into gold nanoparticles solution, water oil interface will gradually form a layer of nanometer gold particle film;Step three, preparation flexible SERS substrate.The present application can successfully transfer gold nanoparticles to flexible substrate;Gold particle film formed by liquid-liquid self-assembly is naturally settled on the surface of PDMS in keeping with the original close arrangement arrangement mode;The substrate prepared by the preparation method of the application has good detection effect on the analyte, and the limit can be measured 1×10 ‑8 mol / L with rhodamine 6G as raman active probe.

Description

Technical Field

[0001] The present 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. The Raman spectrum test requires that the concentration of the substance to be tested is not less than 10 -3 To detect trace amounts of adsorbed substances on the surface, Raman spectroscopy almost always requires the use of the enhanced effect of the SERS substrate. Therefore, the design and preparation of high-performance SERS substrates is crucial.

[0003] Flexible SERS substrates have excellent mechanical flexibility, making them easy to wipe and retrieve probe molecules, and can be cut to fit and wrap around irregular sample surfaces. Combined with portable Raman spectrometers, flexible SERS substrates meet the requirements of instant diagnosis and are expected to be applied to on-site detection in daily life.

[0004] Application number 201510180681.9 discloses a "transparent, flexible surface-enhanced Raman spectroscopy substrate, preparation method, and application." Gold nanoparticles are first prepared using the sodium citrate method. A monolayer of gold nanoparticles is then formed on a silicon wafer or glass slide using aminopropyltrimethoxysilane self-assembly or a liquid-liquid two-phase film formation method. Finally, a sticky transparent film is applied over the gold nanoparticles. This film is then removed to obtain a flexible, transparent SERS substrate with a monolayer of gold nanoparticles. This patent utilizes the stickiness of the film to adhere the gold nanoparticles to the substrate. However, this method suffers from the problem of incomplete transfer of the nanoparticles to the film, resulting in a sparse arrangement of the particles on the film.

[0005] The document with application number "CN202110324174" discloses the preparation of a flexible SERS substrate modified with double-layer gold nanoparticles by pulling the substrate. The sample has good mechanical flexibility, and the arrangement of the two layers of nanoparticles can reduce the gaps between the nanoparticles, thereby enhancing the electromagnetic field. 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 ruptured and dispersed due to the disturbance of the liquid surface. The nanoparticles no longer maintain their original dense state, so the gold particles finally pulled onto the silicon wafer are not dense enough. Summary of the Invention

[0006] The present 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 maintain a completely 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: Using the liquid-liquid interface self-assembly method, a water-oil interface is constructed using a gold nanoparticle solution and n-hexane. As ethanol is injected into the gold nanoparticle solution, a layer of gold nanoparticle film gradually forms 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 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 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 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; 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 PDMS.

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

[0020] 1. The present invention successfully transfers gold nanoparticles onto flexible substrates: Although liquid / liquid interfacial self-assembly can induce the formation of a dense gold particle film, improper transfer methods can prevent the gold nanoparticles from being fully transferred to the flexible substrate. The present invention allows the gold particle film formed by liquid-liquid self-assembly to naturally settle onto the PDMS surface while maintaining its original dense arrangement through solution evaporation, 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. Using rhodamine 6G as a Raman active probe, the maximum detection limit is 1×10 -8 mo l / 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 its surface;

[0024] Figure 3 The SEM scanning images of the present invention are as follows; (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 solutions and advantages of the present invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Obviously, the embodiments described are only part of the embodiments of the present invention and are only used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0027] Example 1: A gold particle transfer method for preparing 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 with rapid stirring, and continue heating for 16 minutes to obtain a solution; the concentration of the HAuCl4 solution is 25 mM, 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, respectively.

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

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

[0032] The specific method is to evenly mix the PDMS main agent and curing agent and then drip it into the bottom of the beaker and wait for it to solidify; drip the gold nanoparticle solution, and then add the gold nanoparticle solution in turn. 1 Parts by volume of n-hexane and 1 Parts by volume 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 n-hexane and wait for the n-hexane to completely evaporate. The gold particle film floats on the surface of the solution; continue to wait. As the solution below the gold particle film evaporates further, the gold particle film gradually falls. When the solution completely evaporates and dissipates, 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, a densely arranged gold film is deposited on the PDMS at the bottom of the beaker without external interference, and the gold nanoparticles remain tightly arranged, and the flexible SERS substrate is prepared.

[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 with 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, respectively.

[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 two, self-assemble into a film: through liquid-liquid interface self-assembly method, gold nanoparticles solution and n-hexane are used to construct water-oil interface, with ethanol injected into the gold nanoparticles solution, water-oil interface will gradually form a layer of gold nanoparticles film;

[0041] Specifically, the PDMS main agent and the curing agent are uniformly mixed and then dropped into the bottom of a beaker, and then the gold nanoparticles solution is dropped into the beaker, and then 1 volume part of n-hexane and 2 volume parts of ethanol are added into the gold nanoparticles solution in sequence, and a clear interface is formed at the junction of the two phases, and a layer of gold nanoparticles film with metallic luster can be seen.

[0042] Step three, preparation of a flexible SERS substrate:

[0043] First, the gold nanoparticles film is reserved: the upper n-hexane is absorbed, and the n-hexane is completely volatilized, and the gold nanoparticles film floats on the surface of the solution; continue to wait, and in the process of further volatilization of the solution below the gold nanoparticles film, the gold nanoparticles film gradually descends, and when the solution is completely volatilized and dispersed, the gold nanoparticles film is settled on the surface of the PDMS, and the gold nanoparticles film is completely attached to the surface of the PDMS, so that the gold nanoparticles film is successfully transferred to the PDMS.

[0044] Then, through evaporation of 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 still maintain close arrangement, and the preparation of the flexible SERS substrate is completed.

[0045] The above embodiment 1 is the best embodiment: the PDMS / Au composite substrate is characterized by a field emission scanning electron microscope, and scanning electron microscope images under different magnifications are obtained, as shown in Figure 3 (a) and (b) are images of the same sample under different magnifications, and the magnifications are 20,000 times and 100,000 times, respectively, and from the images, it can be seen that the gold nanoparticles on the substrate form a dense arrangement.

[0046] Rhodamine 6G is used as a Raman active probe, and the limit can be measured to be 1×10 -8 mo l / L, and the Raman spectrum is shown in Figure 4 .

[0047] The above detailed description of the preferred embodiments of the present application, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed by the present application, and all belong to the protection scope of the present application.

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 using 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; In the step two, the PDMS main agent and curing agent are evenly mixed and then dropped into the bottom of the beaker and allowed to solidify; the gold nanoparticle solution is added dropwise, and then the gold nanoparticle solution is successively added in parts by volume of 1:1-2 of n-hexane and ethanol; 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; 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.

2. The method for transferring gold particles to prepare a PDMS flexible substrate according to claim 1, wherein: In 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 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, wherein: In the step 1.2, the amount of deionized water used is 2-4 parts.

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