JP2019168357A - Reflection structure and optical analyzer using reflection structure - Google Patents

Abstract

To provide a reflection structure which can increase the intensity of optical absorption.SOLUTION: The reflection structure according to the present invention is a reflection structure 3 reflecting light, and includes: a body 31 with a reflection surface 31a made of gold; and metal nanoparticles 32 provided on the reflection surface 31a of the body 31 so that light emission will generate a localized surface plasmon resonance.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a reflection structure and an optical analyzer using the reflection structure.

  Conventionally, for example, a non-dispersive infrared analysis (NDIR) type gas sensor as disclosed in Patent Document 1 is used as an optical analysis device for detecting a detection target such as a detection target gas in an atmospheric gas. The NDIR gas sensor detects the detection target gas by measuring the absorption intensity of the infrared of the specific wavelength that has passed through the detection target gas, using the characteristic that the detection target gas absorbs the infrared of the specific wavelength.

  In the NDIR gas sensor, in order to increase the absorption intensity of the detection target gas, it is necessary to secure the infrared optical path length as long as possible and increase the amount of infrared absorption by the detection target gas. However, there is a problem that the sensor becomes larger by increasing the optical path length of infrared rays. In order to solve such a problem, for example, as shown in Patent Document 2, a plurality of reflecting mirrors are arranged in a measurement cell, and multiple reflections of infrared rays are used to increase the size of the sensor. It has been proposed to secure a long optical path length of infrared rays while suppressing the above.

JP2015-219101A JP 2014-238307 A

  However, in the case of using a reflecting mirror in the optical path in an optical analyzer using light absorption, such as an infrared spectroscopic device or a Raman spectroscopic device, as well as an NDIR gas sensor, it is difficult to accurately position the focal point of the reflecting mirror. It is difficult to receive the entire light passing through the optical path, and as a result, the absorption intensity of the light to be measured is reduced. Further, in addition to the difficulty in condensing light by the reflecting mirror, there is a possibility that reflection loss due to light absorption by the reflecting mirror itself may occur, and in this case, the intensity of the light to be measured is reduced. Furthermore, since the arrangement of the reflecting mirrors is also restricted due to restrictions on the housing of the optical analyzer, there is a limit to extending the optical path length by increasing the number of reflecting mirrors and increasing the number of reflections. Therefore, in an optical analyzer, it is required to increase the light absorption intensity while extending the optical path length using a minimum number of reflecting mirrors.

  The present invention has been made in view of the above problems, and an object thereof is to provide a reflective structure capable of increasing the light absorption intensity and an optical analyzer using the reflective structure.

  The reflecting structure of the present invention is a reflecting structure that reflects light, and a main body having a reflecting surface formed of gold and the main body so that localized surface plasmon resonance occurs when light is irradiated. And gold nanoparticles provided on the reflecting surface.

  Moreover, it is preferable that the said gold nanoparticle is connected with the said reflective surface through the linker.

  Moreover, it is preferable that the said gold nanoparticle is connected with the said reflective surface through the linker formed by self-organization.

  The gold nanoparticles are preferably formed in a rod shape.

  The optical analyzer of the present invention is an optical analyzer using the reflective structure.

  Moreover, it is preferable to use infrared rays in the middle infrared region.

  According to the present invention, it is possible to provide a reflection structure capable of increasing the light absorption intensity and an optical analyzer using the reflection structure.

It is the schematic which shows the structure of the optical analyzer which concerns on one Embodiment of this invention. It is the schematic of the reflective structure used with the optical analyzer of FIG.

  Hereinafter, with reference to the accompanying drawings, a reflection structure according to an embodiment of the present invention and an optical analyzer using the reflection structure will be described. However, the embodiment shown below is an example, and the reflection structure and the optical analyzer of the present invention are not limited to the following example.

  The reflective structure of the present embodiment is used for reflecting light. The reflective structure of this embodiment can be used for an optical analyzer, for example. Hereinafter, an example in which the reflective structure is applied to a gas detector using an optical analyzer, particularly a non-dispersive infrared analysis (NDIR) gas sensor will be described. However, the reflective structure of the present invention is not limited to an optical analyzer, but can be applied to other uses that require light reflection.

  The optical analysis device is a device used for detecting a detection target using light. As shown in FIG. 1, the optical analyzer 1 includes a light source 2 and a reflective structure 3 that reflects light L from the light source 2. The optical analyzer 1 detects changes in the light L generated by interacting with the detection target or newly generated light in the process in which the light L emitted from the light source 2 is reflected and propagated by the reflecting structure 3. By doing so, the detection object is detected. In this embodiment, the optical analyzer 1 is a gas detector using a non-dispersive infrared analysis (NDIR) gas sensor N. Below, this gas detector 1 is mentioned as an example, and the optical analyzer of this invention is demonstrated. However, the optical analyzer of the present invention is not limited to a gas detector using an NDIR gas sensor, and other than detecting an object to be detected using light, such as an infrared spectrometer or a Raman spectrometer. The optical analyzer may be used.

  The gas detector 1 that is an optical analyzer is used to detect a detection target gas that is a detection target. As shown in FIG. 1, the gas detector 1 includes a non-dispersive infrared analysis (NDIR) type gas sensor N that detects a detection target gas. The gas detector 1 optionally further includes an operation unit C (for example, an operation button) for operating the NDIR type gas sensor N, and a display unit D (for example, a liquid crystal display or the like) for displaying a detection result obtained by the NDIR type gas sensor N. ). The gas detector 1 operates by being supplied with electric power from a power source (not shown) such as an internal battery or an external power source.

  The detection target gas of the gas detector 1 is a gas to be detected by the gas detector 1. Examples of the detection target gas include methane, butane, isobutane, water, ammonia, sulfur dioxide, sulfur trioxide, hydrogen sulfide, nitrous oxide, acetone, ozone, sulfur hexafluoride, octafluorocyclopentene, hexafluoro 1, 3 Examples thereof include gases having an absorption peak in the infrared wavelength region, such as butadiene. However, the detection target of the optical analyzer of the present invention is not limited to a gas having an absorption peak in the infrared wavelength region, and has absorption characteristics in other wavelength regions such as an ultraviolet wavelength region and a visible wavelength region. It may be a substance.

  The NDIR gas sensor N detects the detection target gas by irradiating the detection target gas with infrared rays and measuring the absorption intensity (attenuation intensity) of the infrared rays absorbed by the detection target gas. In the present embodiment, as shown in FIG. 1, the NDIR gas sensor N includes a housing H having an internal space S, a light source 2 that emits light L inside the housing H, and a light L from the light source 2. Are provided, a reflection structure 3 that reflects light, a light detection unit 4 that detects light L, and a circuit unit 5 that controls the light source 2 and the light detection unit 4. In the NDIR gas sensor N, the light source 2, the reflection structure 3, the light detection unit 4, and the circuit unit 5 are provided integrally with the housing H to form a module that can be handled as a single unit. However, in the NDIR gas sensor N, for example, the circuit unit 5 may be provided separately from the housing H, and the configuration is not limited to the illustrated example.

  The housing H is a member that supplies the detection target gas to the internal space S. As shown in FIG. 1, the housing H is formed in a substantially cylindrical shape in which both the upper and lower ends (the front and back directions in FIG. 1) are closed, and an internal space S is provided therein. The housing H includes a gas introduction part (not shown) for introducing the detection target gas into the internal space S and a gas discharge part (not shown) for discharging the detection target gas from the internal space S. Yes. In the housing H, the detection target gas is introduced from the gas introduction unit, the detection target gas is supplied into the internal space S, and the detection target gas is discharged from the gas discharge unit. The housing H is not particularly limited, and is formed of, for example, a resin material. The housing H is formed in a substantially cylindrical shape in the present embodiment, but may be formed in other shapes such as a substantially rectangular parallelepiped shape.

  The light source 2 emits light that can be used to detect the detection object. In the present embodiment, the light source 2 emits light having a wavelength that is absorbed by the detection target gas that is the detection target (for example, light having energy that excites molecular vibrations of the detection target gas). The light emitted from the light source 2 only needs to include at least light having a wavelength of an absorption peak in the absorption spectrum of the detection target gas. Even if the light is monochromatic light of that wavelength, light in a wide wavelength range including that wavelength. It may be. For example, when combustible gases such as methane and butane are used as detection target gases, these combustible gases have an absorption peak at a wavelength in the mid-infrared region (for example, 2.5 to 4 μm). In the case of detecting a combustible gas, infrared light in the middle infrared region is used. As shown in FIG. 1, the light source 2 is communicably connected to the circuit unit 5, and its output is controlled by the circuit unit 5. For example, a light emitting diode (LED) or an infrared lamp can be used as the light source 2. For example, the light source 2 emits continuous light or pulsed light. In the present embodiment, the light source 2 is configured to emit infrared rays. However, the light source 2 only needs to be able to emit light having a wavelength necessary for detecting a detection target. It may be configured to emit light of other wavelengths.

  The light detection unit 4 detects the light L and measures the intensity of the light L. In this embodiment, the light detection unit 4 detects the light L after being radiated from the light source 2 and propagating through the internal space S of the housing H, as shown in FIG. The light detection unit 4 is aligned so as to detect the light L reflected from the reflection structure 3. The light detection unit 4 is communicably connected to the circuit unit 5 and transmits the measured intensity data of the light L to the circuit unit 5. The light detection unit 4 is not particularly limited as long as it can detect light and measure the light intensity, and is a photodiode that is a known quantum light receiving element or a thermopile that is a known thermal light receiving element. A bolometer, a pyroelectric sensor, or the like can be employed. Examples of photodiodes include MCT (tellurium) used in the far-infrared region, such as PbSe elements, InAsSb devices, and Al-InAsSb devices used in the mid-infrared region, such as PbS elements and InGaAs devices used in the near-infrared region. Cadmium mercury fluoride) element and the like are exemplified.

  As shown in FIG. 1, the circuit unit 5 is communicably connected to the light source 2 and the light detection unit 4, and controls the light source 2 and the light detection unit 4. Further, the circuit unit 5 determines the presence or absence of the detection target gas by comparing the intensity of the light L emitted from the light source 2 with the intensity of the light L measured by the light detection unit 4, or detects the detection target. Calculate the gas concentration. The circuit unit 5 can be constituted by a known central processing unit (CPU), for example.

  The reflective structure 3 reflects the light L and promotes absorption of the light L by the detection target. As shown in FIG. 2, the reflective structure 3 includes a main body 31 having a reflective surface 31a formed of gold, and a reflective surface of the main body 31 so that localized surface plasmon resonance occurs when the light L is irradiated. And gold nanoparticles 32 provided on 31a. The reflection structure 3 reflects the light L by the reflection surface 31a of the main body 31, and promotes the absorption of the light L by the detection target object by the gold nanoparticles 32 provided on the reflection surface 31a.

  In the present embodiment, the reflection structure 3 is, as shown in FIG. 1, the light L emitted from the light source 2 or the light reflected from another reflection structure 3 in the internal space S of the housing H. It is provided on the side surface of the housing H adjacent to the internal space S so as to reflect L and further guide the light L to another reflection structure 3 or the light detection unit 4. In the gas detector 1, since the light L is reflected and propagated by the reflecting structure 3 in the internal space S of the housing H to which the detection target gas is supplied, the light source 2 does not increase the internal space S. The path of the light L reaching the light detection unit 4 can be lengthened. Since the gas detector 1 can lengthen the path of the light L, the light absorption intensity (detection signal intensity) by the detection target gas can be increased without increasing the internal space S. In this embodiment, the reflecting structures 3 are separated from each other so that the light L is reflected a plurality of times (four times in the illustrated example) in the internal space S and guided from the light source 2 to the light detection unit 4. However, there are no particular limitations on the number or positions provided, and for example, one may be provided, or a housing adjacent to the internal space S may be provided. It may be provided continuously on the side surface of the body H.

  The main body 31 of the reflective structure 3 reflects the light L and supports the gold nanoparticles 32. In the present embodiment, as shown in FIG. 2, the main body 31 includes a reflective surface 31a formed of gold, a base portion 31b provided with the reflective surface 31a, and a support base 31c formed integrally with the base portion 31b. have. As shown in FIG. 1, the main body 31 is provided on the housing H by attaching a support base 31 c to the side surface of the housing H so that the reflecting surface 31 a faces the inside space S of the housing H. .

  The reflection surface 31 a of the main body 31 reflects the light L emitted from the light source 2. In this embodiment, as shown in FIG. 2, the reflecting surface 31a is formed in a concave shape so that the reflected light L is collected, thereby forming a concave mirror. However, the reflecting surface 31a is not limited to a concave shape as long as it can reflect the light L and guide the light L to the reflecting surface 31a of another reflecting structure 3 or the light detection unit 4. It may be formed in other shapes. The reflecting surface 31a can be formed, for example, by forming the base 31b of gold and polishing the surface of the base 31b, or by providing a gold film on the surface of the base 31b by a known film formation method such as vapor deposition. Can also be formed. Since the reflecting surface 31a is formed of gold and can maintain a more stable surface without being oxidized, the reflecting surface 31a can stably reflect light. Furthermore, gold has a high reflectance with respect to infrared rays, and the reflection surface 31a can reflect light more effectively when infrared rays are used as the light L.

  In the present embodiment, the base 31b and the support base 31c of the main body 31 are formed in substantially cylindrical shapes having different diameters. However, the reflecting surface 31b may be provided and attached to the housing H, and the shape thereof is as follows. There is no particular limitation. The base 31b and the support base 31c are not particularly limited, and can be formed of, for example, a metal (such as aluminum) or a resin. The base 31b, the support base 31c, and the reflecting surface 31a may be formed of different materials or may be formed of the same material.

The gold nanoparticles 32 of the reflective structure 3 are particles that cause localized surface plasmon resonance when irradiated with light L having a wavelength that satisfies the resonance condition. When the gold nanoparticle 32 is irradiated with light L, free electron plasmon oscillation is excited on the surface of the gold nanoparticle 32, and free electron density is generated in the gold nanoparticle 32, thereby polarizing the gold nanoparticle 32. A state arises. When the wavelength of the irradiated light L and the dielectric constant of the gold nanoparticle 32 satisfy the resonance conditions, the polarization excited by the light nanoparticle 32 by the light L becomes very large, and the gold nanoparticle 32 is localized. Surface plasmon resonance occurs. The polarization at this time oscillates at the frequency of the light L that satisfies the resonance condition, and as a result, strong near-field light is generated in the very vicinity of the gold nanoparticle 32. The detection target gas that passes in the very vicinity of the gold nanoparticle 32 absorbs the near-field light, for example, when molecular vibration is excited by the near-field light. In this case, the interaction time is increased light and molecules (10 ⁴ times), the interaction of light with molecules is considerably amplified, excitation of molecular vibration is promoted. The wavelength of the light L emitted from the light source 2 corresponds (or substantially coincides) with the wavelength of the light L for causing localized surface plasmon resonance in the gold nanoparticle 32, and is generated by the localized surface plasmon resonance. When the wavelength of the field light corresponds to (or substantially coincides with) the wavelength of an absorption peak (for example, the wavelength of light for exciting molecular vibrations) in the absorption spectrum of the detection target gas, the localized surface plasmon on the gold nanoparticle 32 As resonance occurs, for example, the molecular vibration of the detection target gas is very much generated, and as a result, the absorption of the light L by the detection target gas increases. Therefore, the reflective structure 3 can increase the absorption intensity of the light L by providing the gold nanoparticles 32 on the reflective surface 31a. And in the gas detector 1, since the absorption of the light L by detection object gas becomes large by using the reflective structure 3 in which the gold nanoparticle 32 was provided in the reflective surface 31a for reflection of the light L, detection object Gas detection signal intensity increases.

  The gold nanoparticles 32 include gold particles having an arbitrary shape such as a spherical shape, a rod shape, a wire shape, or a plate shape, and having a longest length of less than 5 μm. The shape and size of the gold nanoparticle 32 are not particularly limited, and are set so as to cause localized surface plasmon resonance in the gold nanoparticle 32 corresponding to the wavelength of light absorbed by the detection target gas. Is done. Conventionally, it is known that the dielectric constant of a gold nanoparticle changes depending on the shape and size of the gold nanoparticle, thereby changing the wavelength of light that causes localized surface plasmon resonance. For example, as the gold nanoparticle size increases, the wavelength of light that causes localized surface plasmon resonance increases. Also, by changing the gold nanoparticles from spherical to rod-like or plate-like, the wavelength of light that causes localized surface plasmon resonance increases. When gold nanoparticles are formed in a rod shape, when the aspect ratio (long side length / short side length) of the rod-shaped gold nanoparticles is small, the size of the gold nanoparticles ( For example, the wavelength of light that causes localized surface plasmon resonance increases depending on the length of the long side), but when the aspect ratio of rod-shaped gold nanoparticles increases, it mainly depends on the aspect ratio. Thus, the wavelength of light that causes localized surface plasmon resonance increases. By forming the gold nanoparticles in the form of a wire having a further increased aspect ratio, the wavelength of light is further increased. As described above, since the wavelength of light that causes the localized surface plasmon resonance depends on the shape and size of the gold nanoparticle 32, the localized surface plasmon resonance is caused in the gold nanoparticle 32, thereby depending on the detection target gas. The shape and size of the gold nanoparticles can be set according to the wavelength of the light L necessary for the light L to be absorbed.

  In the gas detector 1 of the present embodiment, the light L including the wavelength at which the absorption peak in the absorption spectrum of the detection target gas to be detected is selected, and the shape and the size of the local surface plasmon resonance is generated by the light L. Gold nanoparticles 32 are selected. For example, when a combustible gas such as methane or butane is used as a detection target gas, since the combustible gas has an absorption peak at a wavelength in the mid-infrared region (for example, 2.5 to 4 μm), the light L For example, it is preferable to use infrared rays in the mid-infrared region, and the gold nanoparticles 32 are preferably formed in a rod shape or a plate shape. Or when using the infrared rays of a far-infrared area | region as the light L, it is preferable that the gold nanoparticle 32 is formed in the wire shape which made the aspect ratio of the rod larger. Since the gold nanoparticles 32 are formed in a rod shape, even if the wavelength of the light L is changed, it is possible to cause localized surface plasmon resonance by changing the aspect ratio. The design can be easily changed accordingly. The aspect ratio and size of the gold nanoparticles 32 formed in a rod shape can be set according to the wavelength of the light L, the distance between the gold nanoparticles 32 and the reflecting surface 31a, and the like. The aspect ratio of the gold nanoparticles 32 is set, for example, in a range of about 1/1 to about 200/1. When light having a wavelength from the visible range to the near infrared range is used, the aspect ratio is about 1/1 to about 5/1. About 5/1 to about 25/1 when using light in the mid-infrared region (about 15/1 to about 25/1 when using light with a wavelength of 3 to 4.5 μm), far infrared When light having a wavelength in the region is used, the range is set to about 25/1 to about 200/1. The length of the long side of the gold nanoparticle 32 is set, for example, in the range of about 5 to about 5000 nm. When light having a wavelength in the visible range is used, the light in the near infrared range is about 5 to about 20 nm. When using, it is set in the range of about 20 to about 100 nm, about 100 to about 1000 nm when using mid-infrared light, and about 1000 to about 5000 nm when using far-infrared light.

  The arrangement of the gold nanoparticles 32 is not particularly limited as long as localized surface plasmon resonance occurs when the light L is irradiated. In the present embodiment, as shown in FIG. 2, the gold nanoparticles 32 formed in a rod shape are in a direction in which the longitudinal direction intersects the reflecting surface 31 a (a direction substantially orthogonal in the illustrated example). It is arranged to extend. When the longitudinal direction of the gold nanoparticle 32 extends in a direction intersecting the reflecting surface 31a, the spectrum of the localized surface plasmon resonance shifts to the long wavelength side due to the influence of the dielectric function of gold forming the reflecting surface 31a. Therefore, the aspect ratio of the gold nanoparticles 32 can be kept small. The closer the distance between the gold nanoparticle 32 and the reflecting surface 31a is within the range where they do not contact each other, the more the spectrum of localized surface plasmon resonance is shifted to the longer wavelength side, and the aspect ratio of the gold nanoparticle 32 is increased. Further, it can be kept small. In terms of physical properties, when an electron-electron interaction (for example, Coulomb interaction) occurs between the gold nanoparticle 32 and the reflection surface 31a, when the gold nanoparticle 32 is irradiated with light L, the gold nanoparticle 32 is Since the polarization is performed while being affected by the reflecting surface 31a, the polarization is performed such that the length in the longitudinal direction is longer than the actual length, and the apparent aspect ratio of the gold nanoparticles 32 is increased. Thereby, the aspect ratio required of the gold nanoparticles 32 with respect to the wavelength of the light L used is satisfied by the increased apparent aspect ratio of the gold nanoparticles 32, so that the aspect of the gold nanoparticles 32 themselves. The ratio can be kept small.

  In the present embodiment, a plurality of gold nanoparticles 32 are provided on the reflecting surface 31a as shown in FIG. However, the number of gold nanoparticles 32 is not particularly limited, and may be a number that covers substantially the entire reflective surface 31a, or a number that covers a part of the reflective surface 31a. Alternatively, it can be appropriately set according to the required absorption intensity of the light L by the detection target gas and the reflection intensity of the light L by the reflecting surface 31a. For example, the density of the gold nanoparticles 32 on the reflective surface 31a can be set in a range in which the gold nanoparticles 32 are arranged by self-assembly described later. The interval between the gold nanoparticles 32 is not particularly limited, but is within a range in which metal quenching (disappearance of excitons accompanying energy transfer to the adjacent gold nanoparticles) is suppressed. It is preferably within the range affected by the electric field enhanced by the surface plasmon, for example, preferably 3 to 10 nm. However, as a range in which the metal quenching is suppressed, plasmon resonance disappears when the gold nanoparticles 32 come into contact with each other. In addition, since the range affected by the electric field enhanced by the localized surface plasmon is determined by the shape and resonance wavelength of the gold nanoparticles 32, the interval between the gold nanoparticles 32 is determined by the shape and resonance wavelength of the gold nanoparticles 32. For example, the range may be about 100 nm. Therefore, the interval between the gold nanoparticles 32 can be in the range of 1 to 100 nm.

  The arrangement method of the gold nanoparticles 32 on the reflection surface 31a is not particularly limited as long as it is provided on the reflection surface 31a of the main body 31 so that localized surface plasmon resonance occurs when the light L is irradiated. However, in this embodiment, as shown in FIG. 2, the gold nanoparticles 32 are connected to the reflecting surface 31 a via the linker 33. The linker 33 suppresses the transfer of free electrons between the gold nanoparticles 32 and the reflection surface 31a when the light L is irradiated, and causes the gold nanoparticles 32 to be polarized from the reflection surface 31a. The gold nanoparticles 32 are arranged on the reflecting surface 31a so as to be separated from each other. In the present embodiment, the gold nanoparticles 32 and the reflection surface 31a are connected via the linker 33, but the gold nanoparticles 32 may be connected via the linker.

  Although the space | interval between the gold nanoparticle 32 and the reflective surface 31a is not specifically limited, As long as metal quenching (disappearance of the exciton accompanying energy transfer to the adjacent reflective surface 31a) is suppressed. Thus, it is preferably within the range affected by the electric field enhanced by the localized surface plasmon, for example, 3 to 10 nm. However, as a range in which the metal quenching is suppressed, plasmon resonance disappears when the gold nanoparticles 32 and the reflection surface 31a come into contact with each other, so that the gold nanoparticles 32 and the reflection surface 31a do not come into contact with each other, for example, about 1 nm. It can also be a range. In addition, since the range affected by the electric field enhanced by the localized surface plasmon is determined by the shape of the gold nanoparticle 32, the resonance wavelength, and the like, the interval between the gold nanoparticle 32 and the reflecting surface 31a is determined by the gold nanoparticle. Depending on the shape of 32, the resonance wavelength, etc., for example, a range of about 100 nm is possible. Therefore, the interval between the gold nanoparticles 32 and the reflecting surface 31a can be in the range of 1 to 100 nm.

  The material constituting the linker 33 is not particularly limited as long as the gold nanoparticles 32 can be arranged on the reflecting surface 31a so as to suppress the exchange of free electrons with each other. For example, a protein cross-linking agent is used. Alternatively, a terephthalic acid dianion that stabilizes the metal organic structure can be used. However, the gold nanoparticles 32 are preferably connected to the reflecting surface 31a via a linker 33 formed by self-assembly. In this embodiment, the linker 33 is self-assembled to form a self-assembled monolayer. Then, the linker 33 formed by self-assembly and the gold nanoparticles 32 are connected to form a self-assembled film. Since the self-assembled monolayer can be formed on the reflective surface 31a with a relatively uniform film thickness, the gold nanoparticles 32 are connected to the reflective surface 31a via the linker 33 formed by self-assembly. By doing so, it can arrange | position so that a space | interval with the reflective surface 31a may become more uniform.

  The monomolecule of the self-assembled monolayer formed by the linker 33 is not particularly limited, and one end of the self-assembled monolayer such as one having a thiol group, one having a phosphate group, or one having a phosphone group has a reflecting surface 31a. And the other end of which is bonded to the gold nanoparticle 32 can be used. It does not specifically limit as what has a thiol group, Alkane dithiol, octadecyl dithiol, etc. are illustrated. As alkanedithiol, those having 5 to 50 carbon atoms are preferable, those having 5 to 30 carbon atoms are more preferable, and those having 10 to 20 carbon atoms are more preferable.

  A known method can be adopted as a method for forming the self-assembled monolayer. For example, when alkanedithiol is used as a single molecule, a self-assembled monolayer film is formed on the reflective surface 31a by immersing the reflective surface 31a of the reflective structure 3 in a solution containing alkanedithiol having a predetermined carbon number. Can be formed. By immersing the reflective surface 31a on which the self-assembled monolayer is formed in a solution in which the gold nanoparticles 32 are dispersed, the gold nanoparticles 32 are connected to the reflective surface 31a via the self-assembled monolayer. Is done. Alternatively, the self-assembled monolayer can be formed on the reflective surface 31a by immersing the reflective surface 31a of the reflective structure 3 in a solution in which alkanedithiol having a predetermined number of carbon atoms and gold nanoparticles 32 are dispersed in advance. The gold nanoparticles 32 can be connected to the reflecting surface 31a.

  In addition to the chrome film (for example, a film thickness of 1 to 2 nm) and the silicon oxide film (for example, a film thickness of 2 to 3 nm) provided on the reflective surface 31a, for example, one of the materials constituting the linker is silane. By using a coupling provided with a surface modifier formed on the other side by thiol, the distance between the gold nanoparticles 32 and the reflecting surface 31a can be precisely controlled. Further, even when the reverse core-shell type, for example, rod-shaped gold nanoparticles 32 whose surface is covered with silicon oxide is used, the interval between the gold nanoparticles 32 and the reflecting surface 31a can be secured.

1 Optical analyzer (gas detector)
2 Light source 3 Reflective structure 31 Main body 31a Reflective surface 31b Base 31c Support base 32 Gold nanoparticle 33 Linker 4 Photodetection unit 5 Circuit unit C Operation unit D Display unit H Housing L Light N Non-dispersive infrared analysis (NDIR) type Gas sensor S Internal space

Claims (6)

A reflective structure that reflects light,
A body having a reflective surface formed of gold;
A reflective structure comprising: gold nanoparticles provided on the reflective surface of the main body so that localized surface plasmon resonance occurs when irradiated with light. The gold nanoparticles are connected to the reflective surface via a linker;
The reflective structure according to claim 1. The gold nanoparticles are connected to the reflective surface via a linker formed by self-assembly,
The reflective structure according to claim 1. The gold nanoparticles are formed in a rod shape,
The reflective structure of any one of Claims 1-3. An optical analyzer using the reflective structure according to claim 1. The optical analyzer according to claim 5, wherein infrared light in the middle infrared region is used.

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