Preparation method of composite SERS substrate based on piezoelectric PVDF film

Abstract

The present invention discloses a preparation method of a composite SERS substrate based on a piezoelectric PVDF film, which is characterized by including the following steps: (1) dispersing massive black phosphorus in an N-methylpyrrolidone NMP solution and preparing a black phosphorus nanosheet BP NSs suspension through centrifugal exfoliation; (2) dispersing a GO suspension in the BP NSs suspension to prepare a graphene oxide / black phosphorus GOBP composite solution; (3) spin-coating the GOBP composite solution on the PVDF film to obtain the composite SERS substrate based on the piezoelectric PVDF film; the advantage is that it promotes the separation of electron-hole pairs in the semiconductor composite, improves the charge transfer rate, and significantly enhances the SERS performance of the semiconductor.

Description

Technical Field

[0001] The present invention relates to a preparation method of a composite SERS substrate, in particular to a preparation method of a composite SERS substrate based on a piezoelectric PVDF film. Background Art

[0002] Surface-enhanced Raman scattering (SERS) is a molecular sensing technology with high sensitivity, fast and non-destructive analysis, and is widely used in the fields of biomedicine, environmental monitoring, and food safety. Achieving accurate detection of low-concentration samples is the core of the progress of SERS technology, which also depends on the Raman signal enhancement effect of the SERS chip. Among many SERS signal enhancement technologies, electro-modulated SERS (E-SERS) has unique advantages. For example, an externally applied electric field can effectively adjust the electron density of metal nanostructures, further enhancing the plasmon resonance effect. However, traditional electro-modulated devices are complex and prone to energy loss, which limits on-site detection and portable applications.

[0003] Polyvinylidene fluoride (PVDF) is a portable and easily polarized flexible organic piezoelectric material. Due to its own insulation, most studies tend to mix conductive materials (such as Ag, Au, CuO, reduced graphene oxide rGO) as fillers with PVDF raw materials. However, this doping is prone to particle aggregation, greatly increasing the uncontrollability of the polarization process of the piezoelectric substrate and resulting in weakened SERS performance. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a preparation method of a composite SERS substrate based on a piezoelectric PVDF film that significantly enhances the SERS performance of semiconductors.

[0005] The technical solution adopted by the present invention to solve the above technical problems is: a preparation method of a composite SERS substrate based on a piezoelectric PVDF film, comprising the following steps:

[0006] (1) Prepare black phosphorus nanosheets (BPNSs)

[0007] Take bulk black phosphorus and disperse it evenly in an N-methylpyrrolidone NMP solution at a ratio of 1 mg / mL. After mixing evenly, transfer the solution to a probe-type ultrasonic instrument and strip it at a power of 150-250 W for 5-6 h. Then, centrifuge at 2000 rpm for 8-12 min to remove the unpeeled bulk black phosphorus BP. After that, centrifuge the obtained solution at 12000 rpm for 8-12 min to remove the supernatant. Wash the obtained precipitate with anhydrous ethanol and deionized water 3 times, and then redisperse the precipitate in an N-methylpyrrolidone NMP solution with the same volume as the initial addition amount to obtain a black phosphorus nanosheet BPNSs suspension;

[0008] (2) Preparation of graphene oxide / black phosphorus GOBP composite

[0009] Take monolayer graphene oxide GO and add it to NMP solution at a ratio of 0.5 mg / mL and ultrasonically treat for 30 min to obtain a GO suspension. Take 10 mL of the GO suspension and disperse it in 10 - 20 mL of BPNSs suspension, and add NaOH with the same mass as graphene oxide to prevent the oxidation of black phosphorus. After magnetic stirring for 10 min, transfer it to a stainless - steel autoclave with a polytetrafluoroethylene liner, and hydrothermally treat at 150 - 170 °C for 5 - 7 h. After cooling to room temperature, wash the solution with absolute ethanol several times until the supernatant is clear. Take the precipitate and dissolve it in absolute ethanol to obtain a graphene oxide / black phosphorus GOBP composite solution with a concentration of 1 mg / mL;

[0010] (3) Preparation of composite SERS substrate

[0011] Suspend and coat the GOBP composite solution prepared in step (2) on the PVDF film to obtain a composite SERS substrate based on the piezoelectric PVDF film.

[0012] Preferably, the volume ratio of the GO suspension to the BPNSs suspension is 1:1.5.

[0013] Compared with the prior art, the advantages of the present invention are as follows: The preparation method of the SERS substrate based on the piezoelectric PVDF film in the present invention improves the SERS performance of the semiconductor substrate by means of the piezoelectric effect of PVDF. It directly loads the graphene oxide / black phosphorus GOBP semiconductor composite with excellent electrical conductivity on the PVDF film substrate. Due to the piezoelectric effect of PVDF itself, the separation of electron - hole pairs in the semiconductor composite is promoted, the charge transfer rate is increased, and the SERS performance of the semiconductor is significantly enhanced. At the same time, it provides an effective path for improving the SERS activity of the semiconductor substrate. Description of the drawings

[0014] Figure 1 It is the scanning electron microscope photograph of GOBP1:1 prepared in Example 1 of Specific Example 1;

[0015] Figure 2 It is the scanning electron microscope photograph of GOBP1:1.5 prepared in Example 2 of Specific Example 1;

[0016] Figure 3 It is the scanning electron microscope photograph of the GOBP1:2 composite prepared in Example 3 of Specific Example 1;

[0017] Figure 4 It is the Raman detection result of different ratios of GOBP composites to RhB in Specific Example 2;

[0018] Figure 5 Raman detection results of GOBP1:1.5 before and after pressing of crystal violet (CV) in Specific Example 3;

[0019] Figure 6 Raman detection results of GOBP1:1.5 before and after pressing of rhodamine 6G (R6G) in Specific Example 3;

[0020] Figure 7 Raman detection results of GOBP1:1.5 before and after pressing of malachite green (MG) in Specific Example 3;

[0021] Figure 8 Raman detection results of GOBP1:1.5 before and after pressing of rhodamine B (RhB) in Specific Example 3. Specific Embodiment

[0022] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. Specific Example 1

[0024] Example 1

[0025] A preparation method of a composite E-SERS substrate based on a piezoelectric PVDF film, which is characterized by including the following steps:

[0026] (1) Preparation of black phosphorus nanosheets (BPNSs)

[0027] Take 40 mg of bulk black phosphorus and disperse it in 40 mL of N-methylpyrrolidone (NMP) solution. After mixing evenly, transfer the solution to a probe-type ultrasonic instrument and exfoliate it at a power of 200 W for 4 h. Then, centrifuge the solution at 2000 rpm for 10 min to remove the unexfoliated precipitate of bulk BP. After that, centrifuge the obtained solution at 12000 rpm for 10 min to remove the supernatant. Wash the obtained precipitate with anhydrous ethanol and deionized water 3 times, and then redisperse the precipitate in 40 mL of NMP solution to obtain a black phosphorus nanosheet BPNSs suspension;

[0028] (2) Preparation of graphene oxide / black phosphorus composite

[0029] 10 mg of high-purity single-layer graphene oxide (GO) was added to 20 mL of NMP solution and ultrasonicated for 30 min to obtain a GO suspension. 10 mL of the GO suspension was dispersed in 10 mL of BP NSs suspension (GOBP 1:1), and 10 mg of NaOH was added to prevent the oxidation of black phosphorus. After magnetic stirring for 10 min, the mixture was transferred to a stainless-steel autoclave with a polytetrafluoroethylene liner and hydrothermally treated at 160 °C for 6 h. After cooling to room temperature, the solution was washed several times with absolute ethanol until the supernatant was clear. The precipitate was dissolved in absolute ethanol to obtain a graphene oxide / black phosphorus (GOBP) composite solution with a concentration of 1 mg / mL. Figure 1 For the preparation of the scanning electron microscope image of graphene oxide / black phosphorus (GOBP); from Figure 1 it can be seen that the bulk BP was successfully exfoliated into thinner BP nanosheets with a larger specific surface area, and was tightly combined with GO; (3) Preparation of the composite SERS substrate

[0030] The GOBP composite solution prepared in step (2) was dropped onto a PVDF film, and a composite SERS substrate based on the piezoelectric PVDF film was obtained.

[0031] Example 2

[0032] Same as the above specific Example 1, the difference is that in step (2), 10 mL of the GO suspension was mixed with 15 mL of the BP NSs suspension, denoted as GOBP 1:1.5. From Figure 2 it can be seen that in the prepared graphene oxide / black phosphorus (GOBP) composite material, the bulk BP was successfully exfoliated into thinner BP nanosheets with a larger specific surface area, and was tightly combined with GO.

[0033] Example 3

[0034] Same as the above specific Example 1, the difference is that in step (2), 10 mL of the GO suspension was mixed with 20 mL of the BP NSs suspension, denoted as GOBP 1:2. From Figure 3 it can be seen that in the prepared graphene oxide / black phosphorus (GOBP) composite material, the bulk BP was successfully exfoliated into thinner BP nanosheets with a larger specific surface area, and was tightly combined with GO.

[0035] Combined Figure 1 、 Figure 2 and Figure 3 it can be seen that with the increase of the proportion of black phosphorus, there is a gradually stacking trend on the GO substrate.

[0036] Example 4

[0037] Same as the above specific Example 1, the difference is that: in step (1), after peeling for 6 h at a power of 150 W in a probe-type ultrasonic instrument, centrifuging at 2000 rpm for 8 min to remove the unpeeled bulk black phosphorus BP, and then centrifuging the obtained solution at 12000 rpm for 8 min to remove the supernatant; in step (2), hydrothermally treating at 150 °C for 7 h.

[0038] Example 5

[0039] Same as the above specific Example 1, the difference is that: in step (1), after peeling for 5 h at a power of 250 W in a probe-type ultrasonic instrument, centrifuging at 2000 rpm for 12 min to remove the unpeeled bulk black phosphorus BP, and then centrifuging the obtained solution at 12000 rpm for 12 min to remove the supernatant; in step (2), hydrothermally treating at 170 °C for 5 h. Specific Example Two

[0041] Take 10 μL of the GOBP composite solution prepared in Examples 1-3 of the above specific Example 1 and drop it on a 0.5×0.5 cm silicon wafer. After drying at 60 °C, drop 10 μL of rhodamine B solution (Rhodamine B, abbreviated as RhB), and dry again. Use a Raman laser with a laser wavelength of 532 nm as the excitation source, the laser spot diameter is 12.5 μm, the numerical aperture is 0.55, the laser power is set to 1 mw, and the integration time is 10 s. Test the sample, draw a Raman spectrum, and analyze the Raman data; the results are as Figure 4 shown, the SERS spectra of GOBP1:1, GOBP1:1.5 and GOBP1:2 for RhB (10 -3 M), and the Raman intensities at 1641 cm -1 are 4317, 5607 and 5526 respectively. Among them, the SERS signal of GOBP1:1.5 is the strongest, and the enhancement factor reaches 3.32×10 4 . Specific Example Three

[0043] Use a 532 nm Raman laser to test the SERS performance of GOBP before and after pressing on a PVDF film. Take 10 μL of the GOBP composite solution with the best SERS performance obtained in the test of Specific Example Two and drop it on 4 silicon wafers of 0.5×0.5 cm and 4 commercial PVDF films with a cut size of 4×4 cm respectively. After drying, obtain GOBP / Si substrates and GOBP / PVDF composite SERS substrates.

[0044] 1. Add 10 μL of crystal violet solution (CV 10 -3M) was separately dropped onto the GOBP / Si substrate and the GOBP / PVDF substrate. When collecting the SERS spectra of the SERS substrate under pressure, a 100 g weight was placed 1 cm away from the incident laser spot, and the SERS spectral data was quickly collected. After an interval of 10 s, the weight was removed, and the SERS spectra were collected from the discharged substrate. Figure 5 For the SERS substrate to CV (10 -3 SERS spectra before and after pressing, from Figure 5 it can be seen that the intensities at 801, 909, 1177, 1370, 1533, and 1616 cm -1 are significantly enhanced. The Raman intensity (I Press ) of the GOBP / PVDF composite SERS substrate after pressing is 2.8 times that of the GOBP / Si substrate.

[0045] 2. 10 μL of rhodamine 6G solution (R6G 10 -3 M) was separately dropped onto the GOBP / Si substrate and the GOBP / PVDF composite SERS substrate. When collecting the SERS spectra of the SERS substrate under pressure, a 100 g weight was placed 1 cm away from the incident laser spot, and the SERS spectral data was quickly collected. After an interval of 10 s, the weight was removed, and the SERS spectra were collected from the discharged substrate. Figure 6 For the SERS substrate to R6G (10 -3 M) SERS spectra before and after pressing, from Figure 6 it can be seen that the intensities at 608, 772, 1182, 1301, 1360, 1502, and 1645 cm -1 are significantly enhanced. The Raman intensity (I Press ) of the GOBP / PVDF composite SERS substrate after pressing is 2.5 times that of the GOBP / Si substrate.

[0046] 3. 10 μL of malachite green solution (MG 10 -3 M) was separately dropped onto the GOBP / Si substrate and the GOBP / PVDF composite SERS substrate. When collecting the SERS spectra of the SERS substrate under pressure, a 100 g weight was placed 1 cm away from the incident laser spot, and the SERS spectral data was quickly collected. After an interval of 10 s, the weight was removed, and the SERS spectra were collected from the discharged substrate. Figure 7 For the SERS substrate to MG (10 -3 M) SERS spectra before and after pressing, from Figure 7 it can be seen that the intensities at 915, 1171, 1290, 1486, and 1610 cm -1 are significantly enhanced. The Raman intensity (IPress ) It is 2.9 times that of the GOBP / Si substrate.

[0047] 4. Drop 10 μL of rhodamine B solution (RhB 10 -3 M) onto the GOBP / Si substrate and the GOBP / PVDF composite SERS substrate respectively. When collecting the SERS spectra of the SERS substrate under pressure, place a 100 g weight 1 cm away from the incident laser spot, and quickly collect the SERS spectral data. After 10 s, remove the weight and collect the SERS spectra from the discharged substrate. Figure 7 are the SERS spectra of the SERS substrate before and after pressing RhB (10 -3 M). It can be seen from Figure 8 that the intensities at 621, 1193, 1280, 1355, 1502 and 1641 cm -1 after pressing are significantly increased, and a new peak appears at 1078 cm -1 . The Raman intensity (I Press ) of the GOBP / PVDF composite SERS substrate after pressing is 3 times that of the GOBP / Si substrate.

[0048] In summary, the enhancement factor can reach 1.01×10 5 . It can be seen that due to the piezoelectric effect of PVDF, the charge transfer efficiency is improved, and the SERS performance of the semiconductor is significantly enhanced.

[0049] The above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by those of ordinary skill in the art within the scope of the essence of the present invention shall also fall within the protection scope of the present invention.

Claims

1. A method for preparing a composite SERS substrate based on a piezoelectric PVDF film, characterized in that The following steps are involved: (1) Preparation of black phosphorus nanosheets Block black phosphorus was dispersed in an N-methylpyrrolidone (NMP) solution at a ratio of 1 mg / mL and mixed evenly. The solution was then transferred to a probe ultrasonic instrument and stripped at a power of 150-250 W for 5-6 hours. The unstripped block black phosphorus BP was removed by centrifugation at 2000 rpm for 8-12 minutes. The resulting solution was then centrifuged at 12000 rpm for 8-12 minutes to remove the supernatant. The resulting precipitate was washed three times with anhydrous ethanol and deionized water, and then redispersed in the same volume of N-methylpyrrolidone (NMP) solution as the initial addition amount to obtain a black phosphorus nanosheet BP NSs suspension. (2) Preparation of graphene oxide / black phosphorus GOBP composite A single layer of graphene oxide (GO) was added to an NMP solution at a ratio of 0.5 mg / mL and ultrasonically treated for 30 minutes to obtain a GO suspension. 10 mL of the GO suspension was dispersed in a 10-20 mL BP NSs suspension, and NaOH was added in an amount equal to the mass of the graphene oxide. After magnetic stirring for 10 minutes, the mixture was transferred to a polytetrafluoroethylene-lined stainless steel autoclave and hydrothermally treated at 150-170°C for 5-7 hours. After cooling to room temperature, the solution was washed several times with anhydrous ethanol until the supernatant was clear. The precipitate was dissolved in anhydrous ethanol to obtain a graphene oxide / black phosphorus GOBP complex solution with a concentration of 1 mg / mL. (3) Preparation of composite SERS substrate The GOBP complex solution prepared in step (2) is suspended and coated on the PVDF film to obtain a composite SERS substrate based on the piezoelectric PVDF film.

2. The method for preparing a composite SERS substrate based on a piezoelectric PVDF film according to claim 1, characterized in that: The volume ratio of the GO suspension to the BP NSs suspension is 1:1.5.

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