JP6941344B2 - Substrate for surface-enhanced Raman spectroscopy and its manufacturing method - Google Patents

Description

The present invention relates to a method for producing a substrate for surface-enhanced Raman spectroscopy and the like.

In surface-enhanced Raman spectroscopy (hereinafter referred to as "SERS") and other surface-enhanced Raman spectroscopy, the use of metal nanostructures is indispensable. For example, various nanostructures are used, such as noble metal colloids synthesized in the liquid phase, noble metal-coated nanostructures, and noble metal nanostructures produced by an electron beam drawing system.

In recent years, the utilization of nanostructures found in living organisms has also been reported (see Non-Patent Document 1). As one specific example, the use of scales of the wing 103 of the butterfly X as shown in FIG. 1A is mentioned. A complex three-dimensional structure is formed on the scale surface of the butterfly wing. It has been confirmed that the SERS effect is exhibited by coating the surface with a colloid or a thin-film noble metal.

Zhongde Mu, Xiangwei Zhao, Zhuoying Xie, Yuanjin Zhao, Qifeng Zhong, Ling Boand Zhongze Gu, “In situ synthesis of gold nanoparticles (AuNPs) in butterfly wings for surface enhanced Raman spectroscopy (SERS),” Journal of Materials Chemistry B, 2013 , 1, 1607-1613.

As described above, butterfly scale powder has potential as a SERS substrate.
However, there are the following problems in using it in a state of being integrated with the wing. FIG. 1B is a diagram schematically showing a cross section of a wing. As shown in FIG. 1 (b), scales 103a, 103b, 103c obtained from the butterfly wing 103 are placed on a substrate such as a slide glass 101. Since each scale is inclined, it is necessary to focus the excitation laser light at different heights even within the same scale. When irradiating the scales further apart with the excitation laser beams 105a and 105b, it is even more necessary to adjust the focus position.

The problem (first problem) in this case is the problem of flatness of the wing 103. The wing 103 undulates within a range of several tens of microns, and the scales 103a, 103b, 103c are not parallel to the wing 103. Therefore, there is a problem that it is necessary to adjust the focal points of the excitation laser beams 105a and 105b for each location.

FIG. 1 (c) is a diagram showing nanostructures on the surface of scales.
The second issue is as follows.
That is, as shown in FIG. 1 (c), the structure differs depending on the front and back of the scales. Therefore, since the SERS effect differs depending on the front and back, it is preferable to selectively turn either the front side or the back side upward for transfer in order to obtain the desired SERS effect. At that time, it is necessary not to damage the nanostructure on the surface.

A third challenge is, for example, that the secretions of butterflies may have an effect and the scales themselves may have a Raman active substance, in which case the signal is suppressed.
An object of the present invention is to solve the above problems.

According to one aspect of the present invention, there is a method for producing a substrate for surface-enhanced spectroscopy using microstructures in lepidopteran scales, which comprises a step of arranging the scales on the surface of the first substrate and at least. The microstructure is brought closer to one surface side by bringing a second substrate having a higher adhesiveness than the surface of the first substrate to the surface of the first substrate so as to face the surface of the first substrate. Provided is a method for producing a substrate for surface-enhanced spectroscopy, which comprises a step of transferring to the surface of the substrate of the above.
According to this method, it is possible to obtain a substrate for surface-enhanced spectroscopy aligned on the back surface of scales.

The size of the scale itself is about 50 to 100 μm, and the size of the nanostructure existing on the surface thereof is about 1 nm to 1 μm.

Further, the present invention is a method for producing a substrate for surface-enhanced spectroscopy using a microstructure in lepidopteran wing scales, which is a step of arranging the scales on the surface of a first substrate and at least one surface. By bringing a transfer substrate having a higher adhesiveness than the surface of the first substrate to the side in a state of facing the surface of the first substrate, the microstructure is brought closer to the transfer substrate. A state in which the first transfer step of transferring to the surface and a second substrate having a higher adhesiveness to the surface of the transfer substrate than the surface of the transfer substrate are opposed to the surface of the transfer substrate. This is a method for manufacturing a substrate for surface-enhanced spectroscopy, which comprises a second transfer step of transferring the microstructure to the surface of the second substrate by bringing the microstructures closer to each other.
According to this method, a substrate for surface-enhanced spectroscopy can be obtained that is aligned with the surface of scales.

Further, a step of coating the surface of the second substrate on which the scales are transferred with a noble metal can be included. Alternatively, a step of coating the surface of the second substrate on which the scales have been transferred with a noble metal nanostructure may be further included.

Further, the present invention is a method for producing a substrate for surface-enhanced spectroscopy using microstructures in scales of lepidopteran wings, wherein the scales are arranged on the surface of the first substrate, and the first. A step of pressing a flat filter or a porous substance having finer pores than the scales against the scales fixed on the surface of the substrate, and the scales, for example, by a negative pressure of 0.01 MPa to 0.2 MPa. Is a method for producing a substrate for surface-enhanced spectroscopy, which comprises a step of stopping suction after pressing the scales onto the second substrate and transferring the scales to the second substrate.

According to another aspect of the present invention, a surface-enhanced spectroscopic substrate having a surface on which microstructures in lepidopteran scales are arranged, characterized in that the surfaces are aligned upward. A spectroscopic substrate is provided.

Also provided is a surface-enhanced spectroscopy substrate having a surface on which microstructures in lepidopteran scales are arranged, characterized in that the surfaces are aligned downward. Can be done.

Further, it is preferable to have a noble metal layer that covers the surface of the second substrate. Alternatively, it may further have a noble metal nanoparticle layer that covers the surface of the second substrate.

Further, the present invention is a surface-enhanced spectroscopy substrate having a surface on which microstructures in lepidopteran scales are arranged, and the surfaces are aligned upward and formed on the microstructures. A substrate for surface-enhanced spectroscopy, which comprises a dielectric layer and a noble metal layer formed on the dielectric layer.

Further, the present invention is a surface-enhanced spectroscopy substrate having a surface on which microstructures in lepidopteran scales are arranged, and the surfaces are aligned downward and formed on the microstructures. A substrate for surface-enhanced spectroscopy, which comprises a dielectric layer and a noble metal layer formed on the dielectric layer.

The noble metal layer preferably has a thickness that suppresses the influence of the SERS signal of the scale-derived substance.

According to the present invention, in a substrate having microstructures having different structures on the front and back surfaces, it is possible to control only one of the front and back surfaces. Further, in a substrate having microstructures having different structures on the front and back surfaces, it is possible to suppress signals of Raman active substances caused by secretions and the like.

It is a figure which shows the structure of the substrate which has the nanostructure of the scale surface using a wing on the surface. FIG. 1 (a) is a side view of a butterfly (Japanese emperor butterfly), and FIG. 1 (b) is a view showing a cross section of a part of a butterfly wing and a state in which scales are placed on a substrate, and FIG. 1 (c). ) Is a diagram showing the front surface (left figure) and the back surface (right figure) of the scale powder. It is a figure which shows one step example of the manufacturing method of the substrate for surface-enhanced Raman spectroscopy by 1st Embodiment of this invention. It is a figure which shows one step example of the manufacturing method of the substrate for surface-enhanced Raman spectroscopy by the 2nd Embodiment of this invention. It is a figure which shows the process which follows FIG.2 and FIG. It is a figure which shows an example of the transfer process by the 3rd Embodiment of this invention. FIG. 6 is a diagram showing SERS signals from rhodamine 6G molecules adsorbed on the front surface (front surface) and the back surface (uramen) of scales. It is a figure which shows the appearance that the insulating layer and the noble metal nanostructure were formed on the scale which was transferred from the wing to the substrate. FIG. 8A is a diagram showing an example of a SERS signal of a substance derived from scales. FIG. 8B is a diagram showing an example in which the SERS signal of the scale-derived substance is suppressed by the dielectric layer.

Scales are small, flat leaf-like objects that cover the surface of insects and the surface of the body, and are attached to the surface at one end of the stalk. Typical ones are found in the splashes of butterflies and moths belonging to the lepidoptera, and the surface is covered with tiles to create a color pattern. Scales are also called scales, but they vary in shape from discs to hairs, and those that are elongated and close to hairs are called scales. Embryologically homologous to bristles, scaly cells in the epithelial cell layer produce club-like processes after division, which spread flat and form internal cavities, with numerous parallel ridges on the surface.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following, an example of using scales of butterfly wings will be described, but moths and the like may also be used. Examples of butterflies performed by the inventor include, but are not limited to, the Japanese emperor butterfly, the bluebottle butterfly, the morpho butterfly, and the cabbage white butterfly. In the following, a description will be given using the Japanese emperor as an example.

(First Embodiment)
The problem of scale flatness may be solved by transferring individual scales to a flat substrate.

First, the first embodiment of the present invention will be described. FIG. 2 is a diagram showing an example of one step of a method for manufacturing a substrate for surface-enhanced Raman spectroscopy according to the first embodiment of the present invention.

As shown in FIG. 2A, scales 3a, 3b, and 3c having a size of, for example, about 100 μm are placed on a flat slide glass (first substrate) 1. Here, the scale powder 3c is a microstructure having different nanostructures on the front surface side 3c-1 and the back surface side 3c-2. The structures of the scale 3c on the front surface side 3c-1 and the back surface side 3c-2 are schematically shown.

In order to solve the problem of flatness of the wing 3, as shown in FIG. 2B, a tape or a slide glass (second substrate) 11 having adhesiveness at least on the surface side 11a is made to face the slide glass 1. Bring closer in a vertical state. Then, as shown in FIG. 2C, scales 3a, 3b, and 3c adhere to the tape having a stronger adhesiveness than the slide glass 1 side or the slide glass 11 side. As shown in FIG. 2D, a nanostructured substrate in which scales 3a, 3b, and 3c are adhered on the surface 11a of the tape or the slide glass 11 can be used. At this time, the height of all the scales transferred to the slide glass 11 is constant, and the plane of the scales is parallel to the tape or the slide glass 11 which is the second substrate.

In the above step, the back surface side 3c-2 of the scale powder 3c is aligned with the front surface side. By covering the surface of the nanostructured substrate thus formed with a noble metal or the like as described later, a substrate for surface-enhanced Raman spectroscopy can be manufactured.

According to the present embodiment, the plane of the scales is parallel to the tape or slide glass 11 which is the second substrate, and the surface enhancement is such that only the back surface side 3c-2 of the scales is aligned on the surface of the substrate. A substrate for spectroscopy can be manufactured.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. FIG. 3 is a diagram showing an example of one step of a method for manufacturing a substrate for surface-enhanced Raman spectroscopy according to the second embodiment of the present invention.

As shown in FIG. 3A, for example, scales 3a, 3b, and 3c (pieces of butterfly wings) are fixed on a slide glass 1 to which double-sided tape 1a is attached to the surface.

Next, as shown in FIG. 3B, for example, a rubber sheet 21 having a thickness of 1 mm to 10 mm or one side 21a of a rubber rod is pressed against the wing.

As shown in FIG. 3C, carefully separate the slide glass 1 and the rubber sheet 21. Then, the scales 3a, 3b, and 3c are transferred to the surface 21a of the rubber sheet 21 having a higher adhesive force on the surface than the slide glass 1. At this time, the scales 3a, 3b and 3c are flattened.

As shown in FIG. 3D, the surface 21a of the rubber sheet 21 is pressed against the surface of the slide glass 11 to which, for example, the double-sided tape 11a, which is prepared separately, is attached.

As shown in FIG. 3E, when the rubber sheet 21 is separated from the slide glass 11, scales 3a, 3b, and 3c can be transferred to the surface side of the slide glass 11 having higher adhesive strength.

At this time, the directions of the scales 3a, 3b, and 3c can be fixed upward in the same manner as the surface of the wing. The heights of all the scales 3a, 3b, and 3c transferred to the slide glass 11 are substantially constant, and the planes of the scales 3a, 3b, and 3c are parallel to the slide glass 11, so the height is also constant.

In this way, 1) there is a difference in the height of the scales depending on the part of the wing based on the gentle undulations of the butterfly wing, and 2) the scales are inclined with respect to the wing, so even the same scales have the same height. Can solve the problem of not being constant. Further, unlike the first embodiment, only the surface side of the scales can be used.

That is, only the back side of the scales can be used in the method according to the first embodiment, and only the front side of the scales can be used in the method according to the second embodiment. Any surface structure can be obtained.

FIG. 4 is a diagram showing a process following FIG.
The slide glass 11 shown in FIG. 4A is loaded into a vacuum vapor deposition apparatus or a sputtering apparatus (not shown), and the surface is coated with a precious metal 31 such as gold or silver having a thickness of, for example, about 5 nm to 500 nm (FIG. 4 (a). b)). Alternatively, as shown in FIG. 4C, the noble metal nanoparticles 33 may be added to and adhered to the surface.
This makes it possible to form a substrate for surface-enhanced Raman spectroscopy.

(Third Embodiment)
Next, a third embodiment of the present invention will be described.
FIG. 5 is a diagram showing an example of a transfer step according to the third embodiment of the present invention, and is a diagram corresponding to FIGS. 3 (b) to 3 (d).

First, a flat polycarbonate porous substrate 31 (hole 31a) is prepared.
The state of FIG. 3A, that is, a flat filter (porous material) having holes 31a (pores smaller than scales) having a size of, for example, 0.1 μm to 80 μm, in the butterfly wing 3 fixed to the slide glass 1. ) 32 is pressed against the suction jig 41. In this way, scales (wings) 3a, 3b, and 3c are arranged on one side, and suction (51) is performed from the other side by a suction device 41 or the like. For example, the scales 3a, 3b, and 3c are exfoliated from the wing 3 by a negative pressure of 0.01 MPa to 0.2 MPa. The scales 3a, 3b, and 3c are pressed against the slide glass 11 (FIG. 3D), and then the suction is stopped. As a result, the scales 3a, 3b, and 3c can be transferred to the surface of the slide glass 11.

(Evaluation results)
The following is an example of the results of Raman analysis using a substrate for surface-enhanced Raman spectroscopy using scales.

FIG. 6 is a diagram showing an example of SERS signals from the front surface (left figure) and the back surface (right figure) of the scale powder. As shown in the figure on the left, when a substrate for surface-enhanced Raman spectroscopy in which the surface (front noodles) of scales is aligned is used, the Raman scattered light intensity is increased. However, the fluorescent background is also high. As shown in the right figure, when a substrate for surface-enhanced Raman spectroscopy in which the back surfaces (uramen) of scales are aligned is used, the Raman scattered light intensity is lower than that in the left figure. However, the fluorescent background is also low.

It should be noted that the relationship between the front surface and the back surface does not show such a tendency in all species, and is an exemplary explanation of the case of Japanese emperor. However, since the front and back structures are basically different in all species, it is clear that there are some differences in the SERS effect.

As described above, according to the present embodiment, it is possible to provide two types of SERS substrates having different intensities and fluorescence backgrounds in surface-enhanced Raman spectroscopy.

(Fourth Embodiment)
FIG. 7 is a fourth embodiment of the present invention and is a diagram showing a further step following the steps of FIGS. 2 and 3.

The slide glass 11 shown in FIG. 7 (a) is loaded into a vacuum vapor deposition apparatus or a sputtering apparatus (not shown), and the surface is coated with a precious metal 31 such as gold or silver having a thickness of, for example, about 5 nm to 500 nm (FIG. 7 (a). b)). Alternatively, as shown in FIG. 7 (c), the noble metal nanoparticles 33 may be added to and adhered to the surface.

When precious metals are vacuum-deposited directly on scales or when precious metal nanoparticles are adsorbed, SERS signals from substances adsorbed on the surface of scales, such as secretory substances, are detected.

Therefore, in the present embodiment, the scale surface is first coated with a dielectric 35, for example, SiO ₂ (FIG. 7 (b)), and further coated with a noble metal. The Raman active substance exists outside the near-field region of the noble metal nanostructure, and Raman scattered light from other than the measurement target can be suppressed. The film thickness of the dielectric is in the range of 5 nm to 1 μm, preferably about 20 nm to 100 nm.

Instead of vacuum deposition, noble metal nanostructures may be attached to the surface (FIG. 7 (c)).
This makes it possible to suppress the influence of secretions and the like on the substrate for surface-enhanced Raman spectroscopy.

FIG. 8A is a diagram showing an example of the SERS signal of the scale-derived substance, which is an example on the surface side. In the SERS spectrum from the Japanese emperor (orange) in FIG. 8 (a), the two peaks surrounded by the broken line are not signals derived from rhodamine 6G but signals of a substance peculiar to orange scales. The intensity of these peaks is about 5000. In FIG. 8B, it is a spectrum obtained when magnesium fluoride, which is a dielectric, is vapor-deposited at 100 nm to further form silver. Since Rhodamine 6G was not added dropwise, there was no peak derived from Rhodamine 6G, but it was found that the peak peculiar to orange scales was suppressed.

As described above, according to the present embodiment, in the surface-enhanced Raman spectroscopy, the SERS signal of the scale-derived substance can be suppressed by providing an insulating film or the like between the scale and the noble metal layer.

In addition to the secretion, sprayed pesticides may adhere to flying butterflies. Therefore, the effect of the dielectric layer extends to the sprayed pesticides. The sprayed pesticide is not preferable when it is removed by washing because the scale surface is delicate and delicate.

According to each of the above embodiments, nanostructures existing in nature such as butterfly scales can be utilized for the SERS substrate.

In particular, in a substrate having microstructures having different structures on the front and back surfaces, it is possible to control only one of the front and back surfaces.

There are a wide variety of butterflies on Earth, often suitable for preparing SERS substrates. The size of a typical scale is about 100 μm, which is necessary and sufficient for one SERS measurement.

Then, the influence of secretions and the like on the substrate for surface-enhanced Raman spectroscopy can be suppressed.

In the above embodiment, the configuration and the like shown in the accompanying drawings are not limited to these, and can be appropriately changed within the range in which the effects of the present invention are exhibited. In addition, it can be appropriately modified and implemented as long as it does not deviate from the scope of the object of the present invention.

In addition, each component of the present invention can be arbitrarily selected, and an invention having the selected configuration is also included in the present invention.

The present invention can be used as a method for producing a substrate for surface-enhanced Raman spectroscopy.

1 ... Slide glass (first substrate), 3a, 3b, 3c ... Scale powder, 3c-1 ... Front side, 3c-2 ... Back side, 11 ... Slide glass (second substrate), 21 ... Rubber sheet, 32 ... Polycarbonate porous substrate, 33 ... Precious metal nanoparticles, 35 ... Dielectric layer.

Claims (8)

A method for producing a substrate for surface-enhanced spectroscopy using microstructures in lepidopteran scales.
The process of arranging the scales on the surface of the first substrate,
The microstructure is brought closer to at least one surface side by bringing a second substrate having a higher adhesiveness than the surface of the first substrate to the surface of the first substrate so as to face the surface of the first substrate. 2. A method for manufacturing a substrate for surface-enhanced spectroscopy, which comprises a step of transferring to the surface of the substrate. A method for producing a substrate for surface-enhanced spectroscopy using microstructures in lepidopteran scales.
The process of arranging the scales on the surface of the first substrate,
The microstructure is transferred by bringing a transfer substrate having a higher adhesiveness than the surface of the first substrate to at least one surface side in a state of facing the surface of the first substrate. The first transfer step of transferring to the surface of the substrate for
The microstructure is brought close to the surface of the transfer substrate by bringing a second substrate having a higher adhesiveness than the surface of the transfer substrate so as to face the surface of the transfer substrate. A method for producing a substrate for surface-enhanced spectroscopy, which comprises a second transfer step of transferring to the surface of the second substrate. Moreover,
The method for producing a substrate for surface-enhanced spectroscopy according to claim 1 or 2, which comprises a step of coating the surface of the second substrate on which the scales are transferred with a noble metal. Moreover,
The method for producing a substrate for surface-enhanced spectroscopy according to claim 1 or 2, which comprises a step of coating the surface of the second substrate on which the scales are transferred with a noble metal nanostructure. A method for producing a substrate for surface-enhanced spectroscopy using microstructures in lepidopteran scales.
The process of arranging the scales on the surface of the first substrate and
A step of pressing a flat filter or a porous substance having finer pores than the scales against the scales fixed on the surface of the first substrate.
A method for producing a substrate for surface-enhanced spectroscopy, which comprises a step of pressing the scales against a second substrate by a negative pressure, stopping suction, and transferring the scales to the second substrate. A surface-enhanced spectroscopy substrate having a surface on which microstructures in lepidopteran scales are arranged.
The surface is aligned upwards,
A dielectric layer formed on the microstructure and
A substrate for surface-enhanced spectroscopy, which comprises a noble metal layer formed on the dielectric layer. A surface-enhanced spectroscopy substrate with a surface on which microstructures of lepidopteran scales are placed, with the surfaces aligned downwards.
A dielectric layer formed on the microstructure and
A substrate for surface-enhanced spectroscopy, which comprises a noble metal layer formed on the dielectric layer. The substrate for surface-enhanced spectroscopy according to claim 6 or 7 , wherein the noble metal layer has a thickness that suppresses the influence of the SERS signal of the scale-derived substance.

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