A flexible fluorescence / raman spectrum enhancement patch based on silver nanoparticles and a preparation method thereof

Abstract

The application belongs to the technical field of flexible display or light emitting or detecting device spectrum signal enhancement, and particularly discloses a flexible fluorescent / Raman spectrum enhancement patch based on silver nanoparticles and a preparation method thereof, wherein silver nanoparticles are evaporated directly on a flexible polydimethylsiloxane (PDMS) substrate, then pure water is spin-coated to induce self-assembly of the silver particles, the agglomeration state of the evaporated silver nanoparticles is changed, and uniformly distributed silver nanoparticles are obtained; for surface spectrum enhancement of different substances, the patch can be further strained to regulate the surface plasmon resonance wavelength of the silver nanoparticles, so that the flexible fluorescent / Raman spectrum enhancement patch has higher applicability to different substances; the patch with the silver nanoparticles on the surface can be directly pasted on the surface of a device or a sample, the silver nanoparticles are adsorbed on the substance whose spectrum needs to be enhanced, and spectrum signal enhancement of the light emitting or detected substance is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of flexible display or light-emitting device spectrum signal enhancement, and particularly to a flexible fluorescent / Raman spectrum enhancement patch based on silver nanoparticles and a preparation method thereof. BACKGROUND

[0002] Due to the particularity of the size of the metal nanoparticle structure, it will have some unique optical properties. Compared with other materials, the number of free electrons of noble metal nanoparticles is relatively large. When the incident light (the wavelength of the light is much larger than the size of the nanoparticle) irradiates the metal nanoparticle, the electric field of the light wave will cause the movement of the electrons, at this time the electrons have displacement relative to the nucleus, and the electrons will deviate from the equilibrium position; the electrons are also affected by the Coulomb force between the nucleus and the electrons, and a restoring force is generated. Under the joint action of the electric field and the restoring force, the electrons will oscillate. When the frequency of the incident light and the intrinsic frequency of the electron oscillation are close, resonance occurs, which is called localized surface plasmon resonance (LSPR for short). The result of this resonance is usually manifested as the enhancement of the surface local electric field intensity and the absorption and scattering of light of a specific wavelength, which is manifested as a plasmon resonance dip, or LSPR dip, in the transmission spectrum. Metal plasmon resonance is affected by many factors, such as the type, size, spacing and surrounding medium environment of the metal particles, which can change the metal plasmon resonance wavelength. For example, the resonance dip of a spherical nanoparticle has only one, while the resonance dip of a rod-shaped nanoparticle is split into two, corresponding to the longitudinal oscillation parallel to the axis of the nanoparticle rod and the oscillation perpendicular to the axis of the nanoparticle rod, and the resonance wavelengths corresponding to different oscillation modes are different; with the change of the size and spacing of the nanoparticle, the resonance wavelength will also have a blue shift or a red shift. Therefore, the metal plasmon resonance effect can be regulated by changing these factors of the nanoparticle.

[0003] Surface plasmon resonance can strongly amplify the local electric field on the surface of the metal nanoparticle, and improve the utilization rate of light. Theoretical simulation calculations can know that the electric field near it can be enhanced by 10-100 times, which depends on the shape of the material. In general, the local electric field at the tip is stronger. In addition to single metal particles, it has been found that when two or more nanoparticles are close together, the local electric field in the gap between them will be amplified more significantly, compared with single dispersed particles, the electric field in the gap can be enhanced by several hundred times or even thousands of times, and people call the area between the nanoparticles as "hot spot". The strong local electric field strength can cause an effect similar to "optical antenna" on the metal surface, enhancing the spectral intensity of the dye molecules near the metal surface, based on which people have developed metal-enhanced fluorescence, metal-enhanced Raman scattering, metal-enhanced second harmonic generation and other technologies.

[0004] The related researches on the enhancement of the luminescence intensity of fluorescent substances and the enhancement of Raman scattering by using the plasmonic resonance effect of nano-metal particles are widely considered to have very good application prospects, and have important research significance in the fields of biochemical detection, food safety, environmental protection and optoelectronic devices. At present, most of the strategies for enhancing the spectral signal by using nano-metal particles are to mix the substance that needs to enhance the spectral signal and the nano-metal particles in the sample preparation process, so that the nano-metal particles are embedded in the sample, or the metal nano-particles are prepared on a rigid substrate, and then the substance that needs to enhance the spectral signal is covered on the metal nano-particles. The flexibility and application range of these strategies are limited, for example: it is difficult to enhance the spectrum of the previously prepared film sample; the nano-metal particles based on the plane rigid substrate are not suitable for flexible detection, display or luminescent devices. Therefore, it is of great significance to propose a relatively simple metal nano-particle structure that can be applied to flexible devices. Polydimethylsiloxane (Polydimethylsiloxane, abbreviated as PDMS) is low in price, non-toxic, simple in molding process, has good optical properties and chemical inertness, and is easy to adhere to various curved surfaces. The preparation of silver nano-particles on the PDMS flexible substrate can meet the needs of flexible use and be suitable for non-planar devices. SUMMARY

[0005] In order to solve the above technical problems, the present application provides a flexible fluorescent / Raman spectrum enhancement patch based on silver nano-particles and a preparation method thereof.

[0006] In order to achieve the above purpose, the present application is implemented according to the following technical solutions:

[0007] The first object of the present application is to provide a preparation method of a flexible fluorescent / Raman spectrum enhancement patch based on silver nano-particles, comprising the following steps:

[0008] S1, evaporating silver nano-particles on the prepared flexible polydimethylsiloxane (PDMS) substrate;

[0009] S2, after the silver nano-particles are evaporated on the flexible substrate, the silver nano-particles are induced to self-assemble by using the weak bonding force between the silver nano-particles and the flexible polydimethylsiloxane (PDMS) substrate, and pure water is spin-coated on the surface of the silver particles by using a spin coater, so that the agglomerated silver nano-particles are rearranged and self-assembled into closely arranged silver nano-particles, that is, a flexible fluorescent / Raman spectrum enhancement patch based on silver nano-particles is obtained.

[0010] Further, the step S1 is specifically:

[0011] The prepared flexible polydimethylsiloxane (PDMS) substrate is cut into a desired shape and attached to a clean glass substrate, and then silver particles are evaporated on the flexible polydimethylsiloxane (PDMS) substrate by a high-vacuum evaporation coating equipment, with the evaporation condition being a pressure of 5*10 -5 Pa and a current size controlled to be 100 A. In the case of ensuring that other experimental conditions are completely the same, the amount of material in the evaporation source is changed to adjust the LSPR resonance peak.

[0012] Specifically, the flexible polydimethylsiloxane (PDMS) substrate in the step S1 is prepared in the following process:

[0013] First, the Sylgard 184 PDMS prepolymer and the curing agent are mixed by a disposable syringe at a mass ratio of 10:1, and a glass rod is used to stir the prepolymer and the curing agent until they are uniformly mixed; then, the uniformly mixed gluey liquid is poured into a clean culture dish, and the culture dish is horizontally placed in an electric heating constant-temperature drying box with a temperature of 80 DEG C for about 2 hours. The gluey liquid is solidified to obtain a flexible polydimethylsiloxane (PDMS) substrate with a smooth surface and uniform thickness.

[0014] A second object of the present application is to provide a flexible fluorescent / Raman spectrum enhancement patch based on silver nanoparticles prepared by the above method.

[0015] Compared with the prior art, the present application has the following beneficial effects:

[0016] In the present application, silver is directly evaporated on a flexible PDMS substrate, the flexible PDMS substrate is easy to be adsorbed to various surfaces, and can be attached to any surface with a desired shape like a tape, so that the use method is simple and has high universality.

[0017] In the present application, silver is evaporated on a flexible PDMS substrate by evaporation, which is a new method for combining nanoparticles and a flexible substrate, and as a physical preparation method, the grown silver particles are more pure and pollution-free, and the present application provides a new idea for the production of flexible plasmonic devices.

[0018] In the present application, silver nanoparticles are directly evaporated on a flexible PDMS substrate, and then water without nanoparticles is used for spin coating to induce self-assembly of the silver particles, change the agglomeration of the silver nanoparticles, and obtain uniformly distributed silver nanoparticles; and for the surface spectrum enhancement of different substances, a strain can be further applied to the sample to change the arrangement of the silver nanoparticles and adjust the resonance peak, so that the flexible fluorescent / Raman enhancement patch has higher applicability to different substances. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 A flexible PDMS substrate prepared in the present application is shown in the figure.

[0020] Figure 2 A scanning electron microscope image of silver nanoparticles evaporated on a flexible PDMS substrate.

[0021] Figure 3 A scanning electron microscope image of silver nanoparticles spin-coated on a flexible PDMS substrate after self-assembly in pure water.

[0022] Figure 4 A transmission spectrum of silver nanoparticles spin-coated on a flexible PDMS substrate after self-assembly in pure water.

[0023] Figure 5 A transmission spectrum of the LSPR resonance wavelength adjusted to 430 nm by changing the mass of silver in the evaporation source.

[0024] Figure 6 A transmission spectrum of the LSPR resonance wavelength adjusted to 500 nm by changing the mass of silver in the evaporation source

[0025] Figure 7 A schematic diagram of the use of a flexible fluorescence / Raman spectrum enhancement patch based on silver nanoparticles prepared according to the present application. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solutions and advantages of the present application clearer and more apparent, the present application will be further described in detail below in conjunction with examples. The specific examples described herein are only used to explain the present application and do not limit the present application. EXAMPLE

[0027] First, the Sylgard 184 polydimethylsiloxane (PDMS) prepolymer and the curing agent were mixed in a mass ratio of 10:1 using a disposable syringe, and the prepolymer and the curing agent were stirred with a glass rod for about 30 min until they were uniformly mixed. Then, the uniformly mixed gelatinous liquid was poured into a clean petri dish, and the petri dish was placed horizontally in an electric heating constant temperature drying oven at a temperature of 80°C for about 2 hours, and the gelatinous liquid was cured to obtain a flexible polydimethylsiloxane PDMS substrate with a smooth surface and uniform thickness.

[0028] The prepared flexible polydimethylsiloxane PDMS substrate was cut into the desired shape and attached to a clean glass substrate, and then silver particles were evaporated on the flexible PDMS substrate by a high vacuum evaporation coating equipment. The deposition film thickness of the evaporation coating was determined by the amount of charge, and was related to the distance between the evaporation source and the substrate. Different sizes of silver nanoparticles were obtained by controlling the appropriate experimental conditions, i.e. silver nanoparticles with different LSPR resonance peaks were obtained by adjusting the experimental conditions during evaporation. In some embodiments, the specific parameters of the high vacuum evaporation coating equipment were: pressure: 5 x 10 -5 Pa, and the current size was controlled to 100 A. The resonance peak of the evaporated silver particles is shown in Figure 4 ​

[0029] Then, after silver nanoparticles are obtained by evaporation on a flexible polydimethylsiloxane (PDMS) substrate, pure water is spin-coated on the surface of the silver particles by using a spin coater, so that the silver nanoparticles which are not very tightly combined with the flexible substrate are rearranged and self-assembled into closely arranged silver nanoparticles, thereby obtaining a flexible fluorescence / Raman enhancement patch based on silver nanoparticles.

[0030] For surface-enhanced fluorescence technology, the local enhancement effect is most prominent when the plasmonic resonance peak of the nanoparticles overlaps with the fluorescence peak of the dye; different substances require different plasmonic resonance peaks of the nanoparticles to enhance the Raman signal. Therefore, the resonance peak of the silver nanoparticles can be flexibly regulated, which is of great significance for the enhancement of different substances. The shape, size and spacing between the nanoparticles will affect the plasmonic resonance coupling effect of the nanoparticles, thereby changing the spectrum of the periodic nanostructure. On the one hand, different sizes of silver particles can be obtained by changing the experimental conditions during evaporation. In addition, for the silver nanoparticles which have been evaporated, the spacing between the nanoparticles can be dynamically regulated to effectively regulate the LSPR resonance peak. Therefore, the silver nanoparticles are regulated in real time by using the dynamic method of strain, so as to realize the surface fluorescence / Raman enhancement for different substances. The regulation of the resonance peak of the silver nanoparticles by strain is shown in Figure 4 As can be seen from Figure 4 , the transmission spectrum has a concave section with a width of more than 100 nm, corresponding to the resonance absorption of LSPR. As can be seen from Figure 2 , the silver nanoparticles obtained by evaporation are spherical, because the bonding energy between the flexible PDMS substrate and silver is small, so during the evaporation process, silver is more likely to grow into particles rather than tightly adhere to the substrate to form a film. These particles can still be attached to the substrate when the flexible substrate is deformed.

[0031] As shown in Figure 4 , the sample with silver nanoparticles which have been evaporated is stretched, thereby changing the spacing between the silver nanoparticles and successfully regulating the resonance peak of the silver nanoparticles, thereby providing more possibilities for surface-enhanced spectroscopy technology. Embodiment

[0032] By changing the evaporation conditions, the LSPR resonance wavelength of the silver nanoparticles can be regulated, for example, when the mass of silver in the evaporation source is 0.02 g and 0.15 g, the LSPR resonance wavelength is 430 nm and 500 nm, respectively, and the corresponding transmission spectra are shown in Figure 5 and Figure 6 .

[0033] The silver nanoparticle-based flexible fluorescence / Raman enhancement patch prepared by the present application is used when a substance needs to enhance the fluorescence intensity / Raman signal. Only the silver particle patch with a suitable resonance peak is selected and pasted on the surface of the substance, and then the flexible PDMS substrate is removed. Since the adsorption force between the silver nanoparticles and the PDMS substrate is small, the silver nanoparticles remain on the surface of the substance that needs to enhance the spectral signal, as shown in Figure 7 The silver nanoparticles on the flexible PDMS substrate can be pasted on the surface of any substance that needs to enhance the spectral signal at will, and the operation method is very simple.

[0034] The technical scheme of the present application is not limited to the above specific embodiments, and any technical modification made according to the technical scheme of the present application falls within the protection scope of the present application.

Claims

1.A method for preparing a flexible silver nanoparticle-based fluorescence / Raman spectrum enhancement patch, comprising the following steps: S1.Evaporating silver nanoparticles on a prepared flexible polydimethylsiloxane (PDMS) substrate with smooth surface and uniform thickness; S2.After the silver nanoparticles are obtained by evaporation on the flexible PDMS substrate, a spin coater is used to spin-coat pure water on the surface of the silver nanoparticles, to induce the self-assembly process of the silver nanoparticles, so that the agglomerated silver nanoparticles are rearranged and self-assembled into closely arranged silver nanoparticles, thereby obtaining the flexible silver nanoparticle-based fluorescence / Raman spectrum enhancement patch. 2.The method for preparing the flexible silver nanoparticle-based fluorescence / Raman spectrum enhancement patch according to claim 1, wherein the step S1 is specifically as follows: The prepared flexible polydimethylsiloxane PDMS substrate is cut into the desired shape and attached to a clean glass substrate, and then silver particles are evaporated on the flexible polydimethylsiloxane PDMS substrate by a high-vacuum evaporation coating equipment, and the specific evaporation conditions are: pressure: 5x10 -5 Pa, current: 100 A. 3.The method for preparing the flexible silver nanoparticle-based fluorescence / Raman spectrum enhancement patch according to claim 1, wherein the flexible PDMS substrate with smooth surface and uniform thickness is prepared by the following process: First, a disposable syringe is used to mix Sylgard 184 PDMS prepolymer and curing agent at a mass ratio of 10:1, and a glass rod is used to stir the prepolymer and curing agent for 30 min until they are uniformly mixed; then, the uniformly mixed gelatinous liquid is poured into a clean culture dish, and the culture dish is horizontally placed in an electric heating constant temperature drying oven at a temperature of 80 ℃ for 2 hours, so that the gelatinous liquid is solidified to obtain the flexible PDMS substrate with smooth surface and uniform thickness. 4.A flexible silver nanoparticle-based fluorescence / Raman spectrum enhancement patch prepared by the method according to claim 1.

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