WO2016051666A1 - Optical-electric field strengthening device for sensing carbon dioxide gas - Google Patents

Abstract

[Problem] To provide an optical-electric field strengthening device for sensing a carbon dioxide gas, the device enabling detection, with a good S/N ratio, of minute amounts of carbon dioxide gas generated as a metabolite from cells. [Solution] In the present invention, an optical-electric field strengthening device is provided with the following: a transparent substrate (10) having a microroughness structure on the surface thereof; and a metal microroughness structure layer (24) made of a metal and provided on the surface of the transparent microroughness structure. A molecule (30) having a molecular length of 5 nm or less and having an amino group is adsorbed or bonded to a region in the metal microroughness structure layer (24) between protrusions that are adjacent to each other at least at a distance of 10nm or less.

Description

Photoelectric field enhancement device for carbon dioxide sensing

The present invention relates to a photoelectric field enhancing device for carbon dioxide sensing, and more particularly to a highly sensitive photoelectric field enhancing device capable of detecting a small amount of carbon dioxide.

One of gas detection methods such as carbon dioxide (CO ₂ ) is Raman spectroscopy. For example, in Patent Document 1, as a gas sensing device using Raman spectroscopy, a gas cell filled with an observation target gas is irradiated with laser light, Raman scattered light from the gas cell is detected, and a specific gas in the gas cell is detected. An optical gas sensor that can obtain the concentration of the gas is disclosed.

Raman spectroscopy is a method of obtaining a spectrum of Raman scattered light (Raman spectrum) by dispersing scattered light obtained by irradiating a substance with single wavelength light, and is used for identification of a substance.

Also, in order to enhance weak Raman scattered light, Raman spectroscopy using a photoelectric field enhanced by localized plasmon resonance, called surface enhanced Raman (SERS), is known as “Surface” enhanced “Raman” Scattering. This is because when a sample is irradiated with a metal body, particularly a metal body having nano-order irregularities on the surface, the photoelectric field is enhanced by localized plasmon resonance, and the Raman of the sample in contact with the surface of the metal body is generated. This utilizes the principle that the scattered light intensity is enhanced. Surface-enhanced Raman spectroscopy can be carried out by using a substrate (photoelectric field enhancement device) having a metal concavo-convex structure on the surface as a carrier (substrate) for supporting an object.

Then, as a photoelectric field enhancement device that more effectively generates a photoelectric field enhancement, a fine concavo-convex structure made of boehmite is provided on a transparent substrate, and a metal film is formed on the fine concavo-convex structure to surface the metal fine structure. The thing etc. which were prepared for are proposed (refer patent document 2).

In addition, Patent Document 3 proposes a method for quantitative detection of a gas molecule having an extremely small concentration using enhanced Raman spectroscopy. In order to reduce the blinking phenomenon that occurs when quantitatively detecting gas molecules and improve the accuracy of quantitative detection, the average value is obtained by dividing the sum of the Raman signals output within the specified measurement time by the measurement time. Has been proposed.

On the other hand, in Patent Document 4, as a method for improving the detection sensitivity by adsorbing a target molecule on a metal surface of a photoelectric field enhancement device, at least two kinds of self-assembled monolayers are formed, and a target molecule supplementary space is formed. A method of controlling is disclosed.

JP 2012-37344 A JP2012-188090A JP 2013-238479 A JP 2014-119263 A

In recent years, application of enhanced Raman spectroscopy to the detection of metabolites from cells has been studied. However, even if we try to measure the very small amount of carbon dioxide produced as a metabolite from cells using enhanced Raman spectroscopy, the Raman scattering cross section of carbon dioxide is small and the affinity with the metal substrate is small. From the above, it is difficult to detect, and in the first place, sufficient studies have not been made to measure such a trace amount of carbon dioxide gas. Patent Documents 2 to 4 do not mention carbon dioxide as an inspection object, and do not mention application to carbon dioxide.

In Patent Document 1, since the Raman-scattered light is collected by irradiating a cell filled with gas without using a substrate, this method only makes the apparatus configuration very complicated. Alternatively, it is impossible to detect carbon dioxide gas discharged from the sample.

The present invention has been made in view of the above circumstances, and provides a photoelectric field enhancement device for carbon dioxide sensing capable of detecting a very small amount of carbon dioxide produced as a metabolite from a cell with a good S / N ratio. With the goal.

The photoelectric field enhancement device for carbon dioxide sensing according to the present invention is a photoelectric field enhancement device in which localized plasmons are induced on the surface by irradiation of excitation light, and an enhanced photoelectric field is generated on the surface,
A transparent substrate having a fine uneven structure on the surface, and a metal fine uneven structure layer made of metal provided on the surface of the transparent fine uneven structure,
The metal fine concavo-convex structure layer is formed by adsorbing or binding molecules having an amino group and a molecular length of 5 nm or less in a region between adjacent convex portions at a distance of at least 10 nm or less.

Here, adsorption means physical adsorption, and bond means chemical bond.
The molecular length of 5 nm or less means that when the molecule is a straight-chain molecule, the straight chain is 5 nm or less, and when the molecule has a branch, from the end that adsorbs or binds to the metal. It means that the length to the farthest amino group is 5 nm or less, and when the molecule is a spherical molecule, it means that its diameter is 5 nm or less.
Here, the molecular length is a value theoretically derived from the structural formula (calculated value). A detailed calculation method will be described in the section of the example below.

The photoelectric field enhancing device for carbon dioxide sensing according to the present invention can have an amino group-containing molecule having the following structural formula.

Here, A is SH or NH ₂ , R ₁ and R ₂ are H or CH ₃ , and n is 2 ≦ n ≦ 10.

When a molecule having an amino group having the above structural formula is bonded to a region between convex portions as a self-assembled film, the molecular length is preferably 2 nm or less, and the molecular length is more preferably 1 nm or less. .

The molecule having an amino group may be a disulfide.

Furthermore, the molecule having an amino group may be a dendrimer.

The molecular weight of the dendrimer is preferably 500 or more and 15000 or less.

The metal is preferably any of gold (Au), silver (Ag), copper (Cu), aluminum (Al) and platinum (Pt), and particularly preferably gold or silver.

The fine concavo-convex structure is preferably made of buyer light or boehmite.

The photoelectric field enhancing device for carbon dioxide sensing according to the present invention has an amino group and a molecule having a molecular length of 5 nm or less adsorbed or bonded in a region between adjacent convex portions at a distance of 10 nm or less of the metal fine uneven structure. Since carbon dioxide gas easily binds to an amino group, carbon dioxide gas can be retained on the device, so that a small amount of carbon dioxide gas can be efficiently detected.

It is a perspective view which shows typically the photoelectric field enhancement board | substrate for carbon dioxide gas sensing. It is an enlarged view which shows a part of FIG. 1A. It is a figure which shows the manufacturing process of the photoelectric field enhancement board | substrate for carbon dioxide gas sensing. It is an upper surface scanning electron microscope image of boehmite. It is a figure which shows schematic structure of a Raman spectroscopy apparatus.

Hereinafter, embodiments of the photoelectric field enhancement device of the present invention will be described with reference to the drawings. In addition, for easy visual recognition, the scale of each component in the drawings is appropriately changed from the actual one.

FIG. 1A is a perspective view showing a photoelectric field enhancement substrate 1 according to an embodiment of the photoelectric field enhancement device for carbon dioxide sensing of the present invention, and FIG. 1B is a side view of the photoelectric field enhancement substrate 1 shown in FIG. 1A. It is a partial enlarged view of IB.

As shown in FIGS. 1A and 1B, the photoelectric field enhancing substrate 1 is composed of a transparent substrate 10 having a fine uneven structure on the surface and a metal fine uneven structure layer 24 formed on the surface of the fine uneven structure. Local plasmon resonance is induced by the light (hereinafter referred to as excitation light) irradiated to the metal fine concavo-convex structure layer 24, and the photoelectric enhanced on the surface of the metal fine concavo-convex structure layer 24 by this local plasmon resonance. It creates a place. And the molecule | numerator 30 which has an amino group and whose molecular length is 5 nm or less is adsorbed or couple | bonded with the area | region between the convex parts of the metal fine concavo-convex structure layer 24 surface at least 10 nm or less of space | interval. The molecular length is preferably 0.4 nm or more, and more preferably 4.4 nm or less. Furthermore, it is more preferably 2.0 nm or less, and most preferably 1.0 nm or less.

The amino group easily binds to carbon dioxide as shown in the following reaction formula.

Carbon dioxide gas has low affinity for metals and does not adsorb or bind to the metal surface, but the surface of the metal fine uneven structure layer 24 of the photoelectric field enhancing substrate is made of molecules having amino groups. Since the surface is modified, carbon dioxide gas binds to the amino group on the substrate surface and stays on the substrate surface, so that the carbon dioxide gas detection sensitivity can be greatly improved.

Specific examples of the molecule 30 having an amino group include those represented by the following structural formula.

Here, A is SH or NH ₂ , and R ₁ and R ₂ are H or CH ₃ . In this _case, R 1, _{R 2} is, _{R 2} when _{R 1} is H _{R 2} is H or _CH 3, _{R 1} is CH ₃ may be any combination of H or CH _3.
In addition, as the length of the alkyl chain in the above structural formula, n is 2 ≦ n ≦ 10. If n is 2 or more, good surface modification is possible, and if n is 10 or less, the molecular length can be 5 nm or less.

Specific molecular species satisfying the above structural formula include 2-aminoethanethiol, 2-dimethylaminoethanethiol, 6-amino-1-hexanethiol, 8-amino-1-octanethiol, 3-amino-1- Examples include propanethiol, 3-amino-1-propanethiol hydrochloride, 4-amino-1-propanethiol, 7-aminoheptanethiol, 8-aminooctanethiol, and 8-aminooctanethiol hydrochloride.

In the molecule 30 having the amino group of the above structural formula, when A is SH, the SH group is bonded to the metal constituting the metal fine concavo-convex structure layer and is surface-modified. On the other hand, when A is NH ₂ , the NH ₂ group has a high affinity with the metal, so that the surface modification is performed by adsorption of the NH ₂ group onto the surface of the metal fine uneven structure layer. In addition, the molecule | numerator of the said structural formula is modified to the metal fine concavo-convex structure surface as a self-assembled monolayer.
In addition, since SH group shows especially high bondability with gold | metal | money and silver, when performing surface modification by a chemical bond, gold | metal | money and silver are especially preferable as a metal which comprises a metal fine concavo-convex structure layer.

The molecule having an amino group may be a disulfide.

Further, the molecule 30 having an amino group may be a dendrimer.
For example, polyamidoamine dendrimer generations 0 to 4 can be used, specifically, C ₂₂ H ₄₈ N ₁₀ O ₄ , C ₆₂ H ₁₂₈ N ₂₆ O ₁₂ , C ₁₄₂ H ₂₈₈ N ₅₈ O ₂₈ , _{C 302 H 608 N 122 O 60} , dendrimers and the like represented by the molecular formula such as _{C 622 H 1248 N 250 O 124} .
The weight average molecular weight of the dendrimer is preferably 500 to 15000. If the weight average molecular weight is 500 or more, good surface modification is possible, and if it is 15000 or less, the molecular length (diameter) can be 5 nm or less. Here, the weight average molecular weight is a calculated value.

In the present embodiment, the metal fine concavo-convex structure layer 24 is composed of a metal fine structure composed of a large number of flat metal particles formed at the tips of the convex portions of the fine concavo-convex structure layer 22 as shown in FIG. 1B. Is. The metal microstructure composed of the flat metal particles is formed by evaporating metal from an oblique direction with respect to the vertical direction of the substrate plane on which the fine concavo-convex structure layer 22 is formed. Although the shape of the flat metal particles is various, it is desirable that the aspect ratio of the average length to the average thickness (average length / average thickness) is 2 or more.

Further, the flat metal particles are formed in isolation from each other, and a gap is provided between the flat metal particles. Therefore, in this embodiment, the metal fine concavo-convex structure layer 24 as a whole is in an insulated state without electrical conductivity.

The fine metal concavo-convex structure layer 24 is not limited to the form of the flat metal particles shown in FIG. 1B, and has at least the length of the concavo-convex convex portion in the direction perpendicular to the substrate and the length in the direction horizontal to the substrate. Any one having a fine concavo-convex structure that is shorter than the wavelength of the excitation light and capable of generating localized plasmons on the surface of the metal fine concavo-convex structure layer 24 may be used. As a whole, the metal uneven structure or the like may be connected to have conductivity.
When the gap (gap) G between adjacent convex portions (adjacent metal particles 25) of the metal fine concavo-convex structure layer is close to 10 nm or less, it is very strong called a hot spot in the gap between the convex portions due to light irradiation. Since a photoelectric field enhancement field is generated, it is preferable that there are many locations where the distance between adjacent convex portions is 10 nm or less.
In addition, adjacent convex parts may be contacting partially.

And when a detection target object exists in this hot spot, the Raman signal from a detection target object can be strengthened effectively. Therefore, in the present invention, the surface modification with the molecule having an amino group described above is performed between adjacent convex portions of 10 nm or less constituting the hot spot of the metal fine concavo-convex structure layer 24. As described above, hot spots are formed in adjacent regions with a convex portion of 10 nm or less. However, in a device manufactured by a manufacturing method described later, the interval between metal fine particles is not uniform. That is, the gap constituting the hot spot in the device may be 10 nm or about several nm at the same time. If the molecular length is 10 nm or less, the gap of 10 nm can be modified, but the gap smaller than the molecular length cannot be modified well. In order to modify a molecule having an amino group with respect to a large number of gaps constituting a hot spot so that CO ₂ detection sensitivity can be sufficiently improved, the molecular length is 5 nm or less. It takes a thing. When the molecular weight is 5 nm or less, surface modification is possible for a gap of 5 nm or more, and the effect of CO ₂ adsorption to a hot spot can be obtained. The molecular length is preferably 0.4 nm or more. If it is 0.4 nm or more, good surface modification becomes possible.

In addition, when the molecule | numerator which has an amino group is modified to the microparticles | fine-particles 25 which comprise the metal fine concavo-convex structure layer 24 as a self-organization monomolecular film, it is modified to both of two microparticles | fine-particles which comprise a hot spot. It is necessary. In order to modify both of the two fine particles adjacent to each other at 10 nm or less well (to the extent that the CO ₂ detection sensitivity can be sufficiently improved among many gaps constituting the hot spot), the modified self The molecular length of the organized monolayer is preferably less than 2.5 nm, more preferably 2 nm or less, and even more preferably 1 nm or less. On the other hand, when the molecule having an amino group is a dendrimer, a sufficient effect can be obtained if it is modified to one of two fine particles constituting a hot spot. In this case, the diameter of the dendrimer May be 5 nm or less. The diameter of the dendrimer is preferably 4.4 nm or less, and more preferably 2 nm or less.

In addition, the metal fine concavo-convex structure layer 24 of the present embodiment is formed so that the convex portions extend in a granular form from the tips of the convex portions of the fine concavo-convex structure of the transparent substrate 10. It is preferable because the number of analytes attached to the metal surface can be increased and the detection light can be increased.

The metal constituting the metal fine concavo-convex structure layer 24 may be any metal that can generate localized plasmon when irradiated with excitation light. For example, Au, Ag, Cu, Al, Pt, or these as a main component Alloy. In particular, Au or Ag is preferable. Here, the main component is a component that occupies 80% or more of all components.

In the present embodiment, the transparent substrate 10 is made of a transparent substrate body 11 made of glass or the like, and a transparent substrate made of a material different from the transparent substrate body 11 constituting the fine uneven structure provided on the surface of the transparent substrate body 11. The fine concavo-convex structure layer 22 is used. The fine concavo-convex structure layer 22 is preferably a boehmite layer, but the fine concavo-convex structure layer 22 may be made of Bayerlite in addition to boehmite. Moreover, you may be comprised from the hydroxide of another metal or the hydroxide of a metal oxide.

Further, the fine concavo-convex structure is not limited to a material made of a material different from that of the transparent substrate body, but may be made of the same material as the substrate body by processing the surface of the transparent substrate body. For example, a glass substrate having a surface with a fine concavo-convex structure formed by dry etching treatment with any of lithography, ion beam lithography, and nanoimprint may be used as the transparent substrate.

In addition, since the formation method is easy, it is most preferable that the fine concavo-convex structure is constituted by the boehmite layer 22.

The transparent fine concavo-convex structure made of a metal hydroxide such as a boehmite layer or a hydroxide of a metal oxide has various sizes (vertical angle sizes) and orientations as shown in FIG. It has a sawtooth cross section. The fine concavo-convex structure may be any structure as long as the metal fine concavo-convex structure layer 24 can be formed on the fine concavo-convex structure. Here, in the fine concavo-convex structure, the distance between the convex portions is a distance between the vertices of the nearest adjacent convex portions separated by the concave portions, and the depth is a distance from the convex portion vertex to the bottom portion of the adjacent concave portion. In addition, the distance and depth between convex parts can be calculated | required by image processing from a scanning electron microscope image.

A method for producing the photoelectric field enhancement substrate 1 according to the present embodiment will be described with reference to FIG.

A plate-like transparent substrate body 11 is prepared, and the transparent substrate body 11 is washed with acetone and methanol. Thereafter, the aluminum 20 is deposited on the surface of the substrate body 11 by a sputtering method to a thickness of about several tens of nm.

Thereafter, the transparent substrate body 11 with aluminum 20 is immersed in boiling pure water, and is taken out after a few minutes (about 5 minutes). By this boiling treatment (boehmite treatment), the aluminum 20 becomes transparent and becomes a boehmite layer 22 constituting a fine concavo-convex structure. FIG. 3 shows a scanning electron microscope image of the upper surface of the boehmite layer. As shown in FIG. 3, the boehmite layer is a structure in which thin-shaped petals (tapered petals) in a variety of sizes (vertical angle sizes) and orientations are randomly arranged. Here, each convex part of the fine concavo-convex structure has a structure in which the fine structure cross-sectional area of the plane parallel to the substrate surface decreases as the distance from the substrate surface increases. As shown in FIG. 3, it can be seen that the boehmite layer has a structure in which the petal structure is joined and the joined portion is the apex.

Boehmite has such a structure in which petals with thin tips are joined, and the cross section of boehmite decreases as the distance from the substrate body 11 decreases, and the effective refractive index continuously decreases. It also functions.

Next, by depositing a metal on the boehmite layer 22, a metal fine concavo-convex structure layer 24 is generated on the boehmite layer 22.

Thereafter, the surface of the metal fine concavo-convex structure layer 24 is modified with a molecule having an amino group by a surface modification treatment. For example, an amino group-containing molecule 30 is prepared in an ethanol solution to prepare a dipping solution, and the substrate provided with the metal fine concavo-convex structure layer 24 is immersed in the solution 40 to immerse the amino group-containing molecule 30 alone. A molecular film is formed on the surface of the metal fine concavo-convex structure layer 24.
The photoelectric field enhancing substrate 1 can be manufactured by the above processing.

The photoelectric field enhancement device for carbon dioxide sensing according to the present invention improves the affinity between carbon dioxide and the outermost surface of the metal film by adsorbing or binding molecules having amino groups to the surface of the metal fine concavo-convex structure layer. Thus, it is possible to sense carbon dioxide at a concentration that could not be detected by conventional enhanced Raman spectroscopy. Specifically, in the case of using a conventional SERS substrate that does not include molecules having amino groups, carbon dioxide was hardly detected even when carbon dioxide was sprayed onto the substrate surface at 10 ml / min. If the photoelectric field enhancement device is used, carbon dioxide gas can be measured when carbon dioxide gas is sprayed at 10 ml / min.

(Raman spectroscopy and Raman spectrometer)
Below, the Raman spectroscopy and the Raman spectroscopy apparatus 100 are demonstrated as an example of the measuring method using the photoelectric field enhancement board | substrate 1 for the carbon dioxide gas sensing of the above-mentioned this invention.

FIG. 4 is a schematic diagram showing a configuration of the enhanced Raman spectroscopic device 100 including the photoelectric field enhancing substrate 1 according to the above-described embodiment.

As shown in FIG. 4, the Raman spectroscopic device 100 includes the above-described photoelectric field enhancement substrate 1, the excitation light irradiation unit 140 that irradiates the photoelectric field enhancement substrate 1 with the excitation light L1, and the photoelectric field enhancement substrate emitted from the subject. And a light detection unit 150 for detecting the Raman scattered light L2 enhanced by the above action.

The excitation light irradiation unit 140 transmits the semiconductor laser 141 that emits the excitation light L1, the mirror 142 that reflects the light L1 emitted from the semiconductor laser 141 toward the substrate 1, and the excitation light L1 reflected by the mirror 142. Then, the half mirror 144 that reflects light from the substrate 1 side including the enhanced Raman scattered light L2 generated from the subject by irradiation of the excitation light L1 to the light detection unit 150 side, and the excitation light L1 that has passed through the half mirror 144 And a lens 146 for condensing the light on the surface of the photoelectric field enhancement substrate 1.

The light detection unit 150 absorbs the excitation light L1 out of the light reflected by the half mirror 144 and transmits the other light, and a pin provided with a pinhole 152 for removing noise light. A hole 153, a lens 154 for condensing the enhanced Raman scattered light L2 emitted from the subject and transmitted through the lens 146 and the notch filter 151 to the pinhole 152, and the Raman scattered light passing through the pinhole 152 A lens 156 for collimating light and a spectroscope 158 for detecting enhanced Raman scattered light are provided.

A Raman spectroscopy method for measuring a Raman spectrum of a subject using the above-described Raman spectrometer 100 will be described.

Excitation light L1 is emitted from the semiconductor laser 141 of the light irradiation unit 140, the excitation light L1 is reflected to the substrate 1 side by the mirror 142, passes through the half mirror 144 and is collected by the lens 146, and the photoelectric field enhancement substrate 1 Irradiated on top.

The irradiation of the excitation light L1 induces localized plasmon resonance in the metal fine concavo-convex structure layer 24 of the photoelectric field enhancing substrate 1, and an enhanced photoelectric field is generated on the surface of the metal fine concavo-convex structure layer 24. The Raman scattered light L2 emitted from the subject enhanced by the enhanced photoelectric field is transmitted through the lens 146 and reflected by the half mirror 144 toward the spectroscope 158 side. At this time, the excitation light L1 reflected by the photoelectric field enhancement substrate 1 is also reflected by the half mirror 144 and reflected to the spectroscope 158 side, but the excitation light L1 is cut by the notch filter 151. On the other hand, light having a wavelength different from that of the excitation light passes through the notch filter 151, is condensed by the lens 154, passes through the pinhole 152, is collimated again by the lens 156, and enters the spectroscope 158. In the Raman spectroscopic device, the wavelength of Rayleigh scattered light (or Mie scattered light) is the same as that of the excitation light L 1, so that it is cut by the notch filter 151 and does not enter the spectroscope 158. The Raman scattered light L2 enters the spectroscope 158 and is subjected to Raman spectrum measurement.

The Raman spectroscopic device 100 of the present embodiment is configured using the photoelectric field enhancing substrate 1 of the above embodiment, and by combining a sample gas or carbon dioxide gas (CO ₂ ) in the sample liquid with an amino group. The Raman spectroscopic measurement with high carbon dioxide gas detection sensitivity can be performed.
Here, the analyte is CO ₂ , but on the substrate, CO ₂ is adsorbed by an electrostatic interaction with an amino group that binds to an amino group to form a carbamate. It is presumed that CO ₂ exists, and it is assumed that signals from both are detected.

As in the Raman spectroscopic device 100 of the present embodiment, by detecting from the back surface of the photoelectric field enhancing substrate 1, the enhanced Raman scattered light that occurs most strongly at the interface between the metal fine concavo-convex structure layer and the object is sample fluid. It can detect from the back surface side of a transparent substrate, without being shielded by.

The Raman spectroscopic apparatus 100 according to the above-described embodiment is configured so that excitation light is incident from the side opposite to the sample holding surface (front surface) of the photoelectric field enhancing device 1 (back surface of the device) and Raman scattered light is detected. However, like the conventional apparatus, the excitation light L1 may be incident from the surface side (sample holding surface) of the metal fine concavo-convex structure layer 24 and the Raman scattered light L2 may be detected.

Furthermore, either the excitation light irradiation part or the light detection part may be arranged on the surface side of the metal fine concavo-convex structure layer 24 and the other may be arranged on the back side of the substrate 1.

Thus, since the photoelectric field enhancement device of the present invention uses a transparent substrate, light can be irradiated from either the surface side of the metal fine concavo-convex structure layer or the back side of the transparent substrate, Light generated from the sample by this light irradiation can also be detected from either the surface side of the metal fine concavo-convex structure layer or the back side of the transparent substrate.

Hereinafter, examples and comparative examples of the present invention will be described.

[Example 1]
"Method for producing photoelectric field enhancement substrate"
As the transparent substrate body 11, a glass substrate (BK-7; Eagle 2000 manufactured by Corning) was used.
After ultrasonic cleaning (45 kHz) for 5 minutes with acetone and 5 minutes with methanol, 25 nm of aluminum 20 was laminated on the glass substrate 11 using a sputtering apparatus (manufactured by Canon Anelva). In addition, the aluminum thickness was measured using the surface shape measuring device (made by TENCOR), and it confirmed that thickness was 25 nm (+/- 10%).

Thereafter, pure water was prepared in a water bath (Nishi Seiki Co., Ltd.) and boiled.
The glass substrate 11 with aluminum 20 was submerged in boiling water and taken out after 5 minutes. At this time, it was confirmed that the glass substrate 11 with aluminum 20 was immersed in boiling water and the aluminum became transparent in about 1-2 minutes. The aluminum 20 became a boehmite layer 22 by this boiling treatment (boehmite treatment). The result of observing the surface of the boehmite layer 22 with SEM (Hitachi S4100) is as shown in FIG.

Next, Au was deposited on the surface of the boehmite layer 22 by 110 nm to form a metal fine concavo-convex structure layer. In addition, the thickness at this time means that it is vapor-deposited by the vapor deposition amount required when vapor-depositing gold by the thickness on a flat substrate. The same applies to the following.

2-aminoethanethiol (manufactured by Tokyo Chemical Industry Co., Ltd.) was prepared to 1 mM with an ethanol solution. The pH at that time was 8.3. In the prepared 2-aminoethanethiol solution, the surface of the metal fine concavo-convex structure layer was subjected to plasma treatment to remove dust. A substrate whose surface was hydrophilized by this plasma treatment was immersed for 24 hours, thereby forming a monomolecular film of 2-aminoethanethiol on the surface of the metal fine concavo-convex structure layer.
Thus, the photoelectric field enhancing substrate of Example 1 was produced.

[Example 2]
In Example 1, the photoelectric field enhancement substrate of Example 2 was produced in the same manner except that Ag was used instead of Au when the metal fine concavo-convex structure layer was formed and vapor deposition was performed for 150 nm.

[Example 3]
In Example 1, the photoelectric field enhancement substrate of Example 3 was produced in the same manner except that Cu was used instead of Au when the metal fine concavo-convex structure layer was formed, and vapor deposition was performed for 150 nm.

[Example 4]
In Example 1, the photoelectric field enhancement substrate of Example 4 was produced in the same manner except that Pt was used instead of Au when the metal fine concavo-convex structure layer was formed, and vapor deposition was performed for 150 nm.

[Example 5]
In Example 1, the photoelectric field enhancement substrate of Example 5 was produced in the same manner except that Al was used instead of Au at the time of forming the metal fine concavo-convex structure layer and vapor deposition was performed for 150 nm.

[Example 6]
In the same manner as in Example 1, except that a surface treatment liquid (pH 9.6) having a 2-aminoethanethiol concentration of 20 mM was used and the immersion time in the treatment liquid was 1 hour, the photoelectric field of Example 6 was used. An enhanced substrate was produced. The pH of the surface treatment solution was 9.6.

[Example 7]
In the same manner as in Example 1, except that the surface treatment solution (pH 4.3) was replaced with 2-aminoethanethiol hydrochloride (manufactured by Tokyo Chemical Industry Co., Ltd.) instead of 2-aminoethanethiol. A field-enhanced substrate was fabricated.

[Example 8]
The photoelectric field enhancing substrate of Example 8 was prepared in the same manner as in Example 7 except that the surface treatment solution (pH 4.5) had a concentration of 2-aminoethanethiol hydrochloride of 20 mM and the immersion time was 1 hour. Produced.

[Example 9]
The photoelectric field of Example 9 was the same as in Example 1 except that the surface treatment solution (pH 4.4) was replaced with 2-dimethylaminoethanethiol (manufactured by Tokyo Chemical Industry Co., Ltd.) instead of 2-aminoethanethiol. An enhanced substrate was produced.

[Example 10]
The same procedure as in Example 10 was performed except that the surface treatment solution (pH 4.4) was replaced with 2-aminoethanethiol instead of 2-aminoethanethiol using 6-amino-1-hexanethiol (manufactured by Dojindo). A photoelectric field enhancement substrate was prepared.

[Example 11]
Example 11 was conducted in the same manner as in Example 1 except that the surface treatment solution (pH 4.3) was replaced with 8-amino-1-octanethiol (manufactured by Wako Pure Chemical Industries, Ltd.) instead of 2-aminoethanethiol. A photoelectric field enhancement substrate was prepared.

[Example 12]
In Example 1, instead of 2-aminoethanethiol, 12-amino-1-dodecanethiol (manufactured by Dojin Chemical Co., Ltd.) was used, a surface treatment solution (pH 5.1) with a concentration of 1 mM was used, and the immersion time was 6 A photoelectric field enhancement substrate of Example 12 was produced in the same manner except for the time.

[Example 13]
In Example 1, instead of 2-aminoethanethiol, a surface treatment solution (pH 5.3) having a concentration of 0.1 mM Dendrimer_Gene0 (0th generation) (Aldrich) was used, and the immersion time was 6 hours. A photoelectric field enhancement substrate of Example 13 was produced in the same manner except for the points described above.

[Example 14]
Example 13 is the same as Example 13 except that the surface treatment solution (pH 5.3) using dendrimer_Gene1 (first generation) (manufactured by Aldrich) is used instead of dendrimer_Gene0 (0th generation). 14 photoelectric field enhancement substrates were prepared.

[Example 15]
Example 13 is the same as Example 13 except that the surface treatment solution (pH 5.2) using dendrimer_Gene4 (4th generation) (manufactured by Aldrich) is used instead of dendrimer_Gene0 (0th generation). Fifteen photoelectric field enhancing substrates were prepared.

[Comparative Example 1]
After forming the metal fine concavo-convex structure layer made of gold, the substrate without surface modification was used as the photoelectric field enhancing substrate of Comparative Example 1.

[Comparative Example 2]
In Example 13, instead of dendrimer_Gene0 (0th generation), a surface treatment solution (pH 5.1) using dendrimer_Gene9 (9th generation) (manufactured by Aldrich) was used, and the immersion time was 12 hours. A photoelectric field enhancing substrate of Comparative Example 2 was produced in the same manner except for the above.

(Measurement of Raman scattered light)
Raman spectra were measured before and after carbon dioxide was sprayed on the photoelectric field enhancement substrates of each Example and each Comparative Example prepared by the above method. Carbon dioxide was sprayed in an environment of 25 ° C. and 50% RH at 10 sccm (ml / min) for 1 minute, and after standing for 1 minute, a Raman spectrum was measured under the same conditions as before spraying.
About signal of 1280 cm ⁻¹ [(Signal strength after spraying−signal strength before spraying) / signal strength before spraying] × 100 (%)
When the amount of change was 20% or more, it was evaluated as good when it was 5% or more but less than 20%, and when it was less than 5%, it was evaluated as defective.
The signal at 1280 cm ⁻¹ is generally known as a CO ₂ Raman peak, but here, as described above, it is a signal of both CO ₂ and a carbamate formed by bonding CO ₂ to an amino group. It is estimated that there is.

The Raman scattered light was detected using a micro Raman spectroscope (HR800). As the excitation light, laser light having a peak wavelength of 785 nm was used and observed at a magnification of 20 times.
Table 1 summarizes the metal species constituting the fine metal concavo-convex structure layers of each Example and Comparative Example, details of the surface treatment solution for surface modification, treatment time, and evaluation. In addition, the molecular length in Table 1 is a calculated value from the structural formula of each molecular species. In Examples 13 to 15 and Examples 1 to 12 other than Comparative Example 2 in which dendrimers are used as molecules having an amino group among the examples subjected to surface modification, self-assembled monolayers are formed. .

In the present invention, the molecular length of a molecule having an amino group is calculated by applying a typical bond distance (listed below) to the molecular structure.
CC: 0.154 nm
CN: 0.147 nm
C—H: 0.108 nm
NH: 0.1012 nm
CS: 0.18 nm
Au-S: 0.267 nm
Ag-S: 0.282 nm
Cu-S: 0.247 nm
Al-S: 0.239 nm
Pt-S: 0.231 nm
For example, when aminoethanethiol or aminoethanethiol hydrochloride is modified in the Au layer or the Ag layer, the structure constituting the molecular length is Au (or Ag) -S—C—C—N—H It is. Therefore, when aminoethanethiol or aminoethanethiol hydrochloride is modified in the Au layer, their molecular length is 0.267 + 0.18 + 0.154 + 0.147 + 0.1012 = 0.492 (nm), and the Ag layer If modified, their molecular length is 0.282 + 0.18 + 0.154 + 0.147 + 0.1012 = 0.642 (nm).

As shown in Table 1, in Examples 1 to 5 in which the same surface modification treatment was performed, when the metal constituting the metal fine concavo-convex structure layer was Au or Ag, the sensitivity was higher than that of Cu, Pt, or Al. Was expensive. This is presumably because the binding property of 2-aminoethanethiol, which is a molecule having an amino group, to Au and Ag is larger than that to Cu, Pt and Al, and the surface modification rate is high.

It is a metal fine concavo-convex structure layer made of the same metal. When surface-modifying molecules having the same amino group, if the concentration of the surface treatment liquid is increased, damage to the substrate increases and the surface modification rate is inferior. It is inferred that this was possible.

In the evaluation results of Examples 1, 6 to 15 and Comparative Examples 1 and 2 having different molecular species with respect to the same metal species, as in Examples 1, 7, 9, 13 and 14, 2-aminoethanethiol , 2-aminoethanethiol hydrochloride, 2-dimethylaminoethanethiol, generations 0 and 1 dendrimers showed good sensitivity for carbon dioxide detection.

In Examples 1 and 6 to 12, each amino group-containing molecule is modified to a metal structure as a self-assembled monolayer, but Examples 1 to 9 have a molecular length of 1.0 nm or less. For this reason, it is considered that both the adjacent convex portions constituting the gap between the metal convex portions (metal particles) (particularly, the region facing the gap) are well modified.

In Examples 12 to 14 and Comparative Example 2, the molecule having an amino group is a dendrimer. Here, in Examples 12 and 13, the molecular length (diameter) is 2.0 nm or less, and at least one of the adjacent convex portions constituting the gap between the metal convex portions (metal particles) (particularly, the region facing the gap). It is considered that a good modification has been made. On the other hand, the molecular length of Example 14 is 4.4 nm, and it is considered that the modification to the region facing the gap of the metal convex portion is less than that of Examples 12 and 13. In Comparative Example 2, it is considered that the molecular length was too large as 11.4 nm, and the region facing the gap of the metal convex portion could not be modified.

Further, as in Comparative Example 1, when the surface modification was not performed, almost no carbon dioxide gas could be detected. When the surface is not modified, it is considered that carbon dioxide hardly remains on the metal surface.

Claims (10)

1. A photoelectric field enhancement device in which localized plasmon is induced on a surface by irradiation of excitation light and generates an enhanced photoelectric field on the surface,
   A transparent substrate having a fine uneven structure on the surface, and a metal fine uneven structure layer made of metal provided on the surface of the transparent fine uneven structure,
   A photoelectric field enhancement device for carbon dioxide sensing, wherein an amino group-containing molecule having a molecular length of 5 nm or less is adsorbed or bonded to a region between adjacent convex portions at a distance of at least 10 nm or less of the metal fine concavo-convex structure layer. .
2. The photoelectric field enhancement device for carbon dioxide sensing according to claim 1, wherein the molecule having an amino group has the following structural formula.
   

   

   Here, A is SH or NH ₂ , R ₁ and R ₂ are H or CH ₃ , and n is 2 ≦ n ≦ 10.
3. 3. The photoelectric field enhancement device for carbon dioxide sensing according to claim 2, wherein the molecule having an amino group is bonded to a region between the convex portions as a self-assembled film, and the molecular length is 2 nm or less.
4. The photoelectric field enhancing device for carbon dioxide sensing according to claim 3, wherein the molecule having an amino group is bonded to a region between the convex portions as a self-assembled film, and the molecular length is 1 nm or less.
5. The photoelectric field enhancing device for carbon dioxide sensing according to claim 1, wherein the molecule having an amino group is disulfide.
6. The photoelectric field enhancing device for carbon dioxide sensing according to claim 1, wherein the molecule having an amino group is a dendrimer.
7. The photoelectric field enhancing device for carbon dioxide sensing according to claim 6, wherein the molecular weight of the dendrimer is 500 or more and 15000 or less.
8. The photoelectric field enhancement device for carbon dioxide sensing according to any one of claims 1 to 7, wherein the metal is any one of gold, silver, copper, aluminum, and platinum.
9. 9. The photoelectric field enhancement device for carbon dioxide sensing according to claim 8, wherein the metal is gold or silver.
10. The photoelectric field enhancement device for carbon dioxide sensing according to any one of claims 1 to 9, wherein the fine concavo-convex structure is made of buyer light or boehmite.

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