JP6549598B2 - Photoelectric field enhancement device for carbon dioxide gas sensing - Google Patents

Description

  The present invention relates to an optical electric field enhancement device for carbon dioxide gas sensing, and more particularly to a high sensitivity optical electric field enhancement device capable of detecting a trace amount of carbon dioxide gas.

One of the gas detection methods such as carbon dioxide (CO _2), include 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. Discloses an optical gas sensor capable of obtaining the concentration of

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

  Also, in order to enhance weak Raman scattering light, Raman spectroscopy using an optical electric field enhanced by localized plasmon resonance, which is called surface enhanced Raman scattering (SERS), is known. This is because, when light is irradiated in a state in which the sample is in contact with a metal body, particularly a metal body having irregularities of nano order on the surface, optical electric field enhancement occurs by localized plasmon resonance, and Raman of the sample in contact with the metal body surface It utilizes the principle that the scattered light intensity is enhanced. Surface enhanced Raman spectroscopy can be implemented by using a substrate (optical electric field enhanced device) provided with a metal concavo-convex structure on the surface as a carrier (substrate) for supporting an analyte.

  Then, as an optical electric field enhancing device that more effectively generates optical electric field enhancement, a fine uneven structure made of boehmite is provided on a transparent substrate, and a metal fine film is formed on the fine uneven structure by depositing a metal film. And the like have been proposed (see Patent Document 2).

  In addition, Patent Document 3 proposes a method for quantitative detection of gas molecules of extremely small concentration using enhanced Raman spectroscopy. A method of calculating the average value by dividing the sum of Raman signals output within a predetermined measurement time by the measurement time in order to reduce the blinking phenomenon that occurs when the gas molecules are quantitatively detected and to improve the quantitative detection accuracy. Has been proposed.

  On the other hand, Patent Document 4 discloses that at least two types of self-assembled monolayers are formed as a method of adsorbing a target molecule on the metal surface of an optical electric field enhancement device to improve detection sensitivity, and a space for capturing the target molecule. A method of controlling the

JP 2012-37344 A JP, 2012-198090, A JP, 2013-238479, A JP, 2014-119263, A

  In recent years, enhanced Raman spectroscopy has been considered for application to the detection of metabolites from cells. However, even if it is going to measure a very slight amount of carbon dioxide gas produced as a metabolite from cells using enhanced Raman spectroscopy, the Raman scattering cross section of carbon dioxide gas is small, and the affinity with a metal substrate is small. As a result, it is difficult to detect, and no adequate study has been made on measuring such a very small amount of carbon dioxide gas in the first place. Also in Patent Documents 2 to 4, carbon dioxide is not mentioned as an inspection object, and application to carbon dioxide is not mentioned.

  In Patent Document 1, since the cell filled with gas is irradiated with laser light to collect Raman scattered light without using a substrate, this method only complicates the apparatus configuration very much. 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 it is an object of the present invention to provide an optical electric field enhancing device for carbon dioxide gas sensing which can detect very little carbon dioxide gas produced as a metabolite from cells S / N well. With the goal.

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

Here, adsorption means physical adsorption and bonding means chemical bonding.
When the molecule length is 5 nm or less, when the molecule is a linear molecule, it means that 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 (calculated value) theoretically derived from the structural formula. Detailed calculation methods will be described in the section of Examples described later.

In the photoelectric field enhancement device for carbon dioxide gas sensing of the present invention, the molecule having an amino group can be composed of 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 consisting of the above structural formula is bound to a region between convex portions as a self-assembled film, the molecular length is preferably 2 nm or less, and 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 15,000 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.

  It is preferable that the fine concavo-convex structure is made of Bayerite or boehmite.

  In the optical electric field enhancing device for sensing carbon dioxide gas of the present invention, a molecule having an amino group and having a molecular length of 5 nm or less is adsorbed or bonded to a region between convex portions adjacent to a metal microrelief structure at a distance of 10 nm or less. Since carbon dioxide gas easily bonds to amino groups, carbon dioxide gas can be retained on the device, so trace amounts of carbon dioxide gas can be detected efficiently.

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 a top 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, in order to make it easy to visually recognize, the scale of each component in the drawings and the like are appropriately changed from the actual ones.

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

  As shown in FIGS. 1A and 1B, the optical electric field enhancing substrate 1 comprises a transparent substrate 10 having a fine concavo-convex structure on the surface, and a metal fine concavo-convex structure layer 24 formed on the surface of the fine concavo-convex structure. Localized plasmon resonance is induced by light (hereinafter referred to as excitation light) irradiated to the metal microrelief structure layer 24, and photoelectricity enhanced on the surface of the metal microrelief structure layer 24 by the localized plasmon resonance It is what gives rise to a place. The molecule 30 having an amino group and having a molecular length of 5 nm or less is adsorbed or bonded to the region between the convex portions at a distance of at least 10 nm or less on the surface of the metal microrelief structure layer 24. The molecular length is preferably 0.4 nm or more, and more preferably 4.4 nm or less. Furthermore, the thickness is more preferably 2.0 nm or less, and most preferably 1.0 nm or less.

The amino group is easily bonded to carbon dioxide gas as shown by the following reaction formula.

  Carbon dioxide has a low affinity for metals and does not adsorb or bind to metal surfaces, but the surface of metal microrelief structure layer 24 of the present photoelectric field enhanced substrate is a molecule having an amino group. Since the carbon dioxide gas is surface-modified and carbon dioxide bonds with the amino groups on the substrate surface and remains on the substrate surface, the detection sensitivity of carbon dioxide gas can be significantly 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.
Moreover, as an alkyl chain length in the above structural formula, n is 2 ≦ n ≦ 10. When n is 2 or more, good surface modification is possible, and when 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- Propanethiol, 3-amino-1-propanethiol hydrochloride, 4-amino-1-propanethiol, 7-aminoheptanethiol, 8-aminooctanethiol, 8-aminooctanethiol hydrochloride and the like.

In the molecule 30 having an amino group of the above structural formula, when A is SH, the SH group is bonded to the metal constituting the metal microrelief structure layer to be surface-modified. On the other hand, when A is NH ₂ , since the NH ₂ group has high affinity to metal, surface modification is carried out by adsorption of the NH ₂ group onto the surface of the metal microrelief structure layer. The molecule of the above structural formula is modified on the surface of the metal microrelief structure as a self-assembled monolayer.
In addition, since the SH group exhibits a particularly high bondability to gold and silver, gold and silver are particularly preferable as the metal constituting the metal microrelief structure layer when performing surface modification by chemical bonding.

  Also, the molecule having an amino group may be a disulfide.

Furthermore, the molecule 30 having an amino group may be a dendrimer.
For example, generation 0 to 4 of polyamidoamine dendrimers can be used, and 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 , Dendrimers represented by molecular formulas such as C ₃₀₂ H ₆₀₈ N ₁₂₂ O ₆₀ and C ₆₂₂ H ₁₂₄₈ N ₂₅₀ O ₁₂₄ can be mentioned.
The weight average molecular weight of the dendrimer is preferably 500 to 15,000. 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, as shown in FIG. 1B, the metal micro-relief structure layer 24 is formed of a metal micro-structure composed of a large number of flat metal particles formed at the tip of the convex portion of the micro-relief structure layer 22. It is The metal fine structure composed of flat metal particles is formed by vapor deposition of metal from a direction oblique to the direction perpendicular to the plane of the substrate on which the fine concavo-convex structure layer 22 is formed. Although the shape of the tabular metal particles varies, it is desirable that the aspect ratio (average length / average thickness) of the average length to the average thickness is 2 or more.

  Further, the flat metal particles are formed separately, and a gap is provided between the flat metal particles. Therefore, in the present embodiment, the metal fine uneven structure layer 24 as a whole is in a state of being not conductive and insulated.

The metal fine uneven structure layer 24 is not limited to the form of flat metal particles shown in FIG. 1B, and at least the length in the direction perpendicular to the substrate and the length in the direction horizontal to the substrate It is fine as long as it has a fine uneven structure which has a length shorter than the wavelength of excitation light, and it can be any one that can generate localized plasmons on the surface of the metal fine uneven structure layer 24. The metal concavo-convex structure etc. may be connected as a whole and have conductivity.
When the gap (gap) G between adjacent convex parts (adjacent metal particles 25) of the metal fine concavo-convex structure layer is 10 nm or less, the space between the convex parts is very strong called a hot spot by light irradiation. Since an optical electric field enhancement field is generated, it is preferable that a large number of places have a distance of 10 nm or less between adjacent convex portions.
The adjacent convex portions may be in partial contact with each other.

Then, when an object to be detected is present at this hot spot, the Raman signal from the object to be detected can be effectively enhanced. Therefore, in the present invention, the surface modification with the above-mentioned molecule having an amino group is performed between the convex portions adjacent to each other at 10 nm or less which constitute the hot spot of the metal fine uneven structure layer 24. As described above, the hot spots are formed in the area where the convex portions are close to each other at 10 nm or less, but in the device manufactured by the manufacturing method described later, the intervals of the metal fine particles are not uniform. That is, the gap constituting the hot spot in the device may be 10 nm or several nm at the same time. If the molecular length is 10 nm or less, it can be modified to a gap of 10 nm, but a gap smaller than the molecular length can not be well modified. The molecular length is 5 nm or less in order to modify a molecule having an amino group for so many gaps that can sufficiently improve the CO ₂ detection sensitivity among many gaps constituting the hot spot I need to If the molecular weight is 5 nm or less, surface modification can be performed on a gap of 5 nm or more, and the effect of CO ₂ adsorption on 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 is possible.

In addition, when the molecule | numerator which has an amino group is modified by the microparticles | fine-particles 25 which comprise the metal fine concavo-convex structure layer 24 as a self-assembled monolayer, it is modified by both of two microparticles | fine-particles which comprise a hot spot. It is necessary. In order to modify well to both of two particles close to 10 nm or less (to the extent that the CO ₂ detection sensitivity can be sufficiently improved among the 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, in the case where the molecule having an amino group is a dendrimer, sufficient effect can be obtained if it is modified to one of the two microparticles constituting the hot spot, in this case the diameter of the dendrimer Should be 5 nm or less. The diameter of the dendrimer is preferably 4.4 nm or less, more preferably 2 nm or less.

  Further, the metal fine concavo-convex structure layer 24 of the present embodiment is formed so that the convex part thereof extends granularly from the tip of the convex part of the fine concavo-convex structure of the transparent substrate 10, and the surface area becomes large if granular. The number of analytes attached to the metal surface can be increased, which is preferable because it leads to an increase in detection light.

  The metal constituting the metal microrelief structure layer 24 may be any metal capable of generating localized plasmons upon irradiation with excitation light, and for example, Au, Ag, Cu, Al, Pt, or a main component thereof Alloy. In particular, Au or Ag is preferred. Here, the main component is a component that occupies 80% or more of all components.

  In the present embodiment, the transparent substrate 10 is a transparent substrate main body 11 made of glass or the like, and a transparent concavoconvex structure which is provided on the surface of the transparent substrate main body 11 and which is different from the transparent substrate main body 11. It consists of the fine uneven structure layer 22. The fine uneven structure layer 22 is preferably a boehmite layer, but the fine uneven structure layer 22 may be made of Bayerite other than boehmite. Also, it may be composed of hydroxides of other metals or hydroxides of metal oxides.

  Further, the fine concavo-convex structure may be made of the same substance as the substrate main body by processing the surface of the transparent substrate main body, as well as the one made of the substance different from the transparent substrate main body. For example, the surface of a glass substrate may be subjected to dry etching with any of lithography, ion beam lithography, and nanoimprinting to form a fine uneven structure on the surface, which may be used as a transparent substrate.

  In addition, it is most preferable to comprise the fine concavo-convex structure by the boehmite layer 22 from the formation method being easy.

  As shown in FIG. 1B, a transparent fine uneven structure made of metal hydroxide or metal oxide hydroxide such as a boehmite layer generally has various sizes (apex angles) and directions, although it has various shapes. It has a sawtooth cross section. This fine concavo-convex structure may be any one on which the fine metal concavo-convex structure layer 24 can be formed, but the distance between the convex parts and the depth are generally less than the wavelength of the excitation light. Here, in the fine concavo-convex structure, the distance between the projections is the distance between the apexes of the nearest adjacent projections separated by the depressions, and the depth is the distance from the apex of the projections to the bottom of the adjacent depressions. The distance between the convex portions and the depth can be determined by image processing from a scanning electron microscope image.

  A method of manufacturing the photoelectric field enhanced substrate 1 according to the present embodiment will be described with reference to FIG.

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

  Thereafter, the aluminum 20-containing transparent substrate main body 11 is immersed in boiling pure water, and is taken out after several minutes (about 5 minutes). By the boiling treatment (boehmite treatment), the aluminum 20 is made transparent to become the boehmite layer 22 constituting the fine concavo-convex structure. The scanning electron microscope image of the upper surface of the boehmite layer is shown in FIG. As shown in FIG. 3, the boehmite layer is a structure in which thin petals (petal-shaped petals) having various sizes (apex angles) and directions with various sizes are randomly arranged. Here, each convex portion of the fine concavo-convex structure is a structure in which the microstructure 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 a petal structure is joined and the joined portion is at the top.

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

  Next, a metal is deposited on the boehmite layer 22 to form a metal fine uneven structure layer 24 on the boehmite layer 22.

Thereafter, the surface of the metal microrelief structure layer 24 is surface-modified with a molecule having an amino group by surface modification treatment. For example, a molecule having an amino group is prepared in an ethanol solution to prepare a solution for immersion, and the substrate having the metal fine uneven structure layer 24 is dipped in the solution 40 to form an amino group-containing molecule 30 alone. A molecular film is formed on the surface of the metal microrelief structure layer 24.
The optical electric field enhancing substrate 1 can be manufactured by the above process.

  The optical electric field enhancement device for carbon dioxide gas sensing of the present invention improves the affinity (affinity) between carbon dioxide gas and the outermost surface of the metal film by adsorbing or binding a molecule having an amino group to the surface of the metal microrelief structure layer. It is possible to sense carbon dioxide at a concentration that could not be detected by conventional enhanced Raman spectroscopy. Specifically, when a conventional SERS substrate not having a molecule having an amino group is used, carbon dioxide gas can hardly be detected even when carbon dioxide gas is sprayed on the substrate surface at 10 ml / min. The carbon dioxide gas can be measured when the carbon dioxide gas is blown at 10 ml / min using the optical electric field enhancement device of the above.

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

  FIG. 4 is a schematic view showing the configuration of an enhanced Raman spectroscopy apparatus 100 provided with the photoelectric field enhanced substrate 1 according to the above-described embodiment.

  As shown in FIG. 4, the Raman spectroscopy apparatus 100 includes the above-described optical electric field enhancement substrate 1, an excitation light irradiation unit 140 which irradiates the excitation light L 1 to the optical electric field enhancement substrate 1, and an optical electric field enhancement substrate And a light detection unit 150 for detecting the Raman scattered light L2 enhanced by the action of

  The excitation light irradiator 140 transmits the semiconductor laser 141 that emits 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 that is reflected by the mirror 142. And the half mirror 144 that reflects the light from the substrate 1 side including the Raman scattered light L 2 generated from the subject and enhanced by the irradiation of the excitation light L 1 to the light detection unit 150 side, and the excitation light L 1 transmitted through the half mirror 144 And a lens 146 for collecting light on the surface of the optical electric field enhancing substrate 1.

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

  A Raman spectroscopy method for measuring a Raman spectrum of an object using the above-described Raman spectroscopy apparatus 100 will be described.

  The excitation light L1 is emitted from the semiconductor laser 141 of the light irradiator 140, the excitation light L1 is reflected by the mirror 142 toward the substrate 1 and transmitted through the half mirror 144 and collected by the lens 146. Irradiated on top.

  Localized plasmon resonance is induced in the metal fine uneven structure layer 24 of the optical electric field enhancing substrate 1 by the irradiation of the excitation light L1, and an enhanced optical electric field is generated on the surface of the metal fine uneven structure layer 24. The Raman scattered light L 2 emitted from the subject, which is enhanced by the enhanced optical field, passes through the lens 146 and is reflected by the half mirror 144 toward the spectroscope 158. At this time, the excitation light L1 reflected by the optical electric field enhancement substrate 1 is also reflected by the half mirror 144 and reflected toward the spectroscope 158, 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 spectroscopy device, Rayleigh scattered light (or Mie scattered light) and the like have the same wavelength as the excitation light L 1, so they are cut by the notch filter 151 and do not enter the spectroscope 158. The Raman scattered light L2 is incident on the spectrometer 158 to perform Raman spectrum measurement.

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

  As in the Raman spectroscopy apparatus 100 of the present embodiment, the enhanced Raman scattering light generated most strongly at the interface between the metal fine concavo-convex structure layer and the object is detected as a sample fluid by using the configuration to detect from the back surface of the optical electric field enhancement substrate 1 It can detect from the back side of a transparent substrate, without being shielded.

  The Raman spectroscopy apparatus 100 according to the above-described embodiment is configured to inject excitation light from the opposite side (back side of the device) to the sample holding surface (front surface) of the optical electric field enhancement device 1 and to detect Raman scattered light. However, as in the conventional device, 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, one of the excitation light irradiation unit and the light detection unit may be disposed on the surface side of the metal fine concavo-convex structure layer 24, and the other may be disposed on the back surface side of the substrate 1.

  As described above, since the optical electric field enhancing device of the present invention uses a transparent substrate, light can be emitted from either the surface side of the metal fine uneven structure layer or the back surface side of the transparent substrate, and The light generated from the sample by this light irradiation can also be detected from either the surface side of the metal fine uneven structure layer or the back surface side of the transparent substrate.

  Examples of the present invention and comparative examples will be described below.

Example 1
"Method of making optical electric field enhanced substrate"
A glass substrate (BK-7; Eagle 2000 manufactured by Corning) was used as the transparent substrate main body 11.
After ultrasonic cleaning (45 kHz) for 5 minutes in acetone and 5 minutes in methanol, 25 nm of aluminum 20 was laminated on the glass substrate 11 using a sputtering apparatus (manufactured by Canon Anerva). In addition, 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 immersed in boiling water and removed after 5 minutes. At this time, it was confirmed that the aluminum was made transparent in about 1 to 2 minutes by immersion of the aluminum 20-attached glass substrate 11 in boiling water. The aluminum 20 became a boehmite layer 22 by this boiling process (boehmite process). The surface of the boehmite layer 22 was observed by SEM (S4100 manufactured by Hitachi, Ltd.). The result is as shown in FIG.

  Next, 110 nm of Au was vapor-deposited on the surface of the boehmite layer 22 to form a metal fine uneven structure layer. In addition, the thickness at this time means that it vapor-deposits with the vapor deposition amount required when vapor-depositing gold only by the thickness on a flat board | 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 microrelief structure layer was subjected to plasma treatment to remove dust. By immersing the substrate having the surface hydrophilized by this plasma treatment for 24 hours, a monomolecular film of 2-aminoethanethiol was formed on the surface of the metal microrelief structure layer.
Thus, the photoelectric field enhanced substrate of Example 1 was produced.

Example 2
The optical electric field enhanced substrate of Example 2 was produced in the same manner as Example 1 except that Ag was used instead of Au when forming the metal fine uneven structure layer, and vapor deposition was performed for 150 nm.

[Example 3]
The optical electric field enhanced substrate of Example 3 was produced in the same manner as in Example 1 except that Cu was used instead of Au at the time of formation of the metal microrelief structure layer and vapor deposition was carried out for 150 nm.

Example 4
The optical electric field enhanced substrate of Example 4 was produced in the same manner as in Example 1 except that Pt was used instead of Au when forming the metal fine uneven structure layer and vapor deposition was carried out for 150 nm.

[Example 5]
The optical electric field enhanced substrate of Example 5 was produced in the same manner as Example 1 except that Al was used in place of Au when forming the metal micro-relief structure layer and vapor deposition was performed for 150 nm.

[Example 6]
The optical electric field of Example 6 is the same as Example 1 except that the surface treatment solution (pH 9.6) in which the concentration of 2-aminoethanethiol is 20 mM is used and the immersion time in the treatment solution is 1 hour. An enhanced substrate was made. The pH of the surface treatment solution was 9.6.

[Example 7]
The photoelectric conversion of Example 7 was repeated except that a surface treatment solution (pH 4.3) was used in place of 2-aminoethanethiol instead of 2-aminoethanethiol hydrochloride (manufactured by Tokyo Chemical Industry Co., Ltd.). A field enhanced substrate was made.

[Example 8]
The optical field enhanced substrate of Example 8 is the same as Example 7 except that the surface treatment solution (pH 4.5) in which the concentration of 2-aminoethanethiol hydrochloride is 20 mM is used, and the immersion time is 1 hour. Made.

[Example 9]
The optical electric field of Example 9 is the same as Example 1 except that a surface treatment solution (pH 4.4) is used in place of 2-aminoethanethiol and 2-dimethylaminoethanethiol (manufactured by Tokyo Chemical Industry Co., Ltd.). An enhanced substrate was made.

[Example 10]
The same procedure as in Example 10 was repeated except that a surface treatment solution (pH 4.4) was used in place of 2-aminoethanethiol in place of 6-amino-1-hexanethiol (manufactured by Dojin Chemical Co., Ltd.). An optical electric field enhanced substrate was prepared.

[Example 11]
Example 11 is the same as Example 11, except that in place of 2-aminoethanethiol, a surface treatment solution (pH 4.3) is used using 8-amino-1-octanethiol (manufactured by Wako Pure Chemical Industries, Ltd.). An optical electric field enhanced substrate of

[Example 12]
In Example 1, in place of 2-aminoethanethiol, using 12-amino-1-dodecanethiol (manufactured by Dojin Chemical Co., Ltd.), using a surface treatment solution (pH 5.1) having a concentration of 1 mM, the immersion time is 6 The photoelectric field enhanced substrate of Example 12 was produced in the same manner except that time was taken.

[Example 13]
In Example 1, in place of 2-aminoethanethiol, using a surface treatment solution (pH 5.3) having dendrimer Gene 0 (generation 0) (manufactured by Aldrich) at a concentration of 0.1 mM, the immersion time is 6 hours The photoelectric field enhanced substrate of Example 13 was produced in the same manner as described above.

Example 14
Example 13 is the same as Example 13, except that dendrimer Gene 0 (generation 0) is replaced with dendrimer Gene 1 (generation 1) (manufactured by Aldrich) to form a surface treatment solution (pH 5.3). Fourteen optical field enhanced substrates were prepared.

[Example 15]
Example 13 is the same as Example 13, except that dendrimer Gene 0 (generation 0) is replaced with dendrimer Gene 4 (generation 4) (manufactured by Aldrich) to form a surface treatment solution (pH 5.2). Fifteen optical field enhanced substrates were fabricated.

Comparative Example 1
A substrate not subjected to surface modification after formation of the metal fine uneven structure layer made of gold was used as the photoelectric field enhanced substrate of Comparative Example 1.

Comparative Example 2
In Example 13, instead of dendrimer Gene0 (generation 0), a surface treatment solution (pH 5.1) was used in which dendrimer Gene9 (generation 9) (manufactured by Aldrich) was used, and the immersion time was 12 hours. The photoelectric field enhanced substrate of Comparative Example 2 was produced in the same manner except for the above.

(Measurement of Raman scattered light)
The Raman spectrum was measured before and after the carbon dioxide gas was blown to the photoelectric field enhanced substrates of each of the examples and the comparative examples manufactured by the above method. The carbon dioxide was sprayed at 10 sccm (ml / min) for 1 minute in an environment of 25 ° C. and 50% RH, and then allowed to stand for 1 minute, and then a Raman spectrum was measured under the same conditions as before spraying.
About the signal of 1280 cm ^-1
[(Signal strength after spraying-Signal strength before spraying) / Signal strength before spraying] × 100 (%)
Were evaluated as good when the change amount was 20% or more, acceptable when the change amount was 5% or more and less than 20%, and poor when it was less than 5%.
In addition, although the signal of 1280 cm ^-1 is generally known as a Raman peak of CO ₂ , here, as described above, it is a signal of both of CO ₂ and a carbamate formed by bonding CO ₂ to an amino group. It is estimated that there is.

Raman scattered light was detected using a microscopic Raman spectrometer (HR800). As excitation light, laser light with a peak wavelength of 785 nm was used and observed at a magnification of 20 times.
Table 1 collectively shows the metal species constituting the metal fine relief structure layer 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 addition, in Examples 1 to 12 in which a dendrimer is used as the molecule having an amino group among Examples subjected to surface modification and Examples 1 to 12 except Comparative Example 2, a self-assembled monolayer is formed. .

In the present invention, the molecular length of the molecule having an amino group is calculated by applying the binding distances (listed below) typically shown to the molecular structure.
C-C: 0.154 nm
C-N: 0.147 nm
C-H: 0.108 nm
N-H: 0.1012 nm
C-S: 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 to Au layer or Ag layer, the structure constituting the molecular length is Au (or Ag) -S-C-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 = 0.8492 (nm), and the Ag layer is When modified, their molecular length is 0.282 + 0.18 + 0.154 + 0.147 + 0.1012 = 0.8642 (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 is Au or Ag, the sensitivity is higher than that of Cu, Pt or Al. Was high. It is considered that this is because the bonding property of 2-aminoethanethiol, which is a molecule having an amino group, to Au and Ag is large as compared to the bonding property to Cu, Pt and Al, and the surface modification rate is high.

  In the case of surface modification of molecules having the same amino group, which is a metal fine concavo-convex structure layer composed of the same metal, when the concentration of the surface treatment solution is increased, damage to the substrate becomes large and the surface modification rate is inferior. It is presumed that was acceptable.

  In the evaluation results for Examples 1 and 6 to 15 and Comparative Examples 1 and 2 in which molecular species differ with respect to the same metal species, as in Examples 1, 7, 9, 13 and 14, 2-aminoethanethiol. When 2-aminoethanethiol hydrochloride, 2-dimethylaminoethanethiol, generation 0, 1 dendrimer were used, they showed good sensitivity for carbon dioxide gas detection.

  In Examples 1 and 6 to 12, the molecule having each amino group is modified to a metal structure as a self-assembled monolayer, but in Examples 1 to 9, the molecular length is 1.0 nm or less Therefore, it is considered that good modification is also performed on both of the adjacent convex portions (particularly, the region facing the gap) which constitutes the gap between the metal convex portions (metal particles).

  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 forming the gap between the metal convex portions (metal particles) (in particular, a region facing the gap) It is considered that good modification to On the other hand, in Example 14, the molecular length is 4.4 nm, and it is considered that the modification to the region facing the gap of the metal convex portion is smaller than in Examples 12 and 13. Moreover, in Comparative Example 2, the molecular length is too large, 11.4 nm, and it is considered that the region facing the gap of the metal convex portion could not be modified.

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

Claims (10)

An optical electric field enhancing device that induces localized plasmons on a surface by irradiation of excitation light and generates an enhanced optical electric field on the surface,
Comprising a transparent substrate made comprises a transparent fine unevenness on the surface, and a metal micro-relief structure layer comprising a plurality of flat metal particles formed on the tip portion of the projecting portion of the transparent fine concavo-convex structure,
The metal particles are arranged so as to be isolated from one another, and the shape thereof has an aspect ratio of average length to average thickness of 2 or more,
Between the metal particles, there is a close region of a distance of at least 10 nm or less ,
Wherein the surface of the metal particles definitive proximity area, the following molecular molecular length 5nm having an amino group is adsorbed or bonded,
Photoelectric field enhancement device for carbon dioxide gas sensing. The photoelectric field enhancement device for carbon dioxide gas sensing according to claim 1, wherein the molecule having an amino group is represented by the following structural formula.

Here, A is SH or NH ₂ , R ₁ and R ₂ are H or CH ₃ ,
n is 2 ≦ n ≦ 10. The photoelectric field enhancement device for carbon dioxide gas sensing according to claim 2 , wherein the molecule having an amino group is a self-assembled film , and the molecular length is 2 nm or less. Before SL molecular length optical field amplifying device for carbon dioxide sensing according to claim 3, wherein at 1nm or less.   The photoelectric field enhancement device for carbon dioxide gas sensing according to claim 1, wherein the molecule having an amino group is a disulfide.   The photoelectric field enhancement device for carbon dioxide gas sensing according to claim 1, wherein the molecule having an amino group is a dendrimer.   The photoelectric field enhancement device for carbon dioxide gas sensing according to claim 6, wherein the molecular weight of the dendrimer is 500 or more and 15,000 or less. The optical electric field enhancing device for carbon dioxide gas sensing according to any one of claims 1 to 7, wherein the metal particles are any of gold, silver, copper, aluminum and platinum. The optical electric field enhancing device for carbon dioxide gas sensing according to claim 8, wherein the metal particles are any one of gold and silver. The optical electric field enhancing device for carbon dioxide gas sensing according to any one of claims 1 to 9, wherein the transparent fine uneven structure comprises Bayerite or boehmite.