JP2020134133A - Electric measurement type surface plasmon resonance sensor, electric measurement type surface plasmon resonance sensor chip, and surface plasmon polariton change detection method - Google Patents

Abstract

To provide an electric measurement type surface plasmon resonance sensor that achieves easily miniaturization and high throughput, and has sufficient sensor sensitivity.SOLUTION: An electric measurement type surface plasmon resonance sensor comprises: a sensor chip that has a transparent substrate provided with a light incident port in an edge part, a transparent electrode, an n-type transparent semiconductor film, and a plasmon resonance film electrode arranged in this order; a reflection plane that can reflect light reflected between the n-type transparent semiconductor film and the plasmon resonance film electrode; and an electrical measurement device that directly measures a current value or voltage value from the transparent electrode and plasmon resonance film electrode.SELECTED DRAWING: Figure 1A

Description

The present invention relates to an electric measurement type surface plasmon resonance sensor, an electric measurement type surface plasmon resonance sensor chip, and a surface plasmon polariton change detection method. More specifically, the electric measurement type surface plasmon resonance sensor and an electric measurement type surface plasmon resonance used therein. The present invention relates to a sensor chip and a method for detecting a change in surface plasmon polariton using these.

Surface plasmon resonance (SPR) is a state in which free electrons undergo collective oscillation motion (plasma oscillation) on the surface of a metal, and is a propagating surface plasmon resonance (PSPR) that propagates on the metal surface. There are Surface Plasma Resonance (LSPR) and Localized Surface Plasmon Resonance (LSPR) localized in nanometer-sized metal structures. Propagation-type surface plasmon resonance is a state in which resonance is generated by the interaction between an electric field generated around a free electron that has caused plasma oscillation and incident light, and the plasma oscillation and an electromagnetic wave traveling along an interface are combined. Electromagnetic waves (surface plasmon polariton, SPP: Surface Plasma Polariton) propagate along the metal surface. On the other hand, localized surface plasmon resonance is a state in which metal nanostructures such as metal nanoparticles are polarized and induced by the plasma oscillation to generate electric dipoles.

Surface plasmon resonance is used in sensors such as affinity sensors that detect the presence or absence of adsorption of target substances and the strength of the interaction. For example, Japanese Patent Application Laid-Open No. 2011-141265 (Patent Document 1) describes a flat surface. Described is a sensor chip comprising a substrate having a portion and a diffraction grating having a surface formed on the flat surface portion and formed of a metal and including a specific protrusion on which a target substance is arranged. However, in the sensor chip as described in Patent Document 1, the device becomes expensive because it is necessary to detect the change in the surface plasmon resonance angle due to the change in the concentration of the target substance existing on the metal surface by the optical system. There is a tendency for the size to increase, and there is a problem that it is difficult to integrate and increase the throughput for processing a large number of samples at the same time.

Further, Japanese Patent Application Laid-Open No. 2000-356587 (Patent Document 2) is configured to include a substrate and metal fine particles fixed as a single film in a state of being separated from each other without being aggregated on the surface of the substrate. A localized plasmon resonance sensor having a sensor unit is described. However, the localized plasmon resonance sensor described in Patent Document 2 measures the change in the refractive index of the medium near the surface of the metal fine particles due to the adsorption or deposition of the target substance on the metal fine particles, and the absorbance of the light transmitted between the metal fine particles. Since it is detected by measurement, it is necessary to strictly control the size and arrangement of the metal fine particles, and it is difficult to sufficiently increase its intensity because the detection signal is absorbance. Was there.

Surface plasmon resonance is also used in photoelectric conversion elements to improve photoelectric conversion efficiency. For example, Japanese Patent Application Laid-Open No. 2012-38541 (Patent Document 3) describes a transparent substrate, a transparent electrode layer, and the like. A plasmon resonance type photoelectric conversion including an anode electrode in which a metal fine particle layer, a semiconductor thin film made of an n-type semiconductor, and an adsorption layer of a dye are laminated in this order, and a cathode electrode arranged therein via an electrolyte containing an oxidation-reduced species. The elements are described.

In addition, the Applicant has a sensor chip in which a transparent electrode, an n-type transparent semiconductor film, and a plasmon resonance film electrode are arranged in this order, a plasmon polariton augmented sensor chip in which a prism is arranged, the transparent electrode, and the transparent electrode. An international application was filed on August 9, 2018 for an electrically measuring surface plasmon resonance sensor including an electrical measuring device for directly measuring a current value or a voltage value from the plasmon resonance membrane electrode (PCT / JP2018 / 29979). According to such an electric measurement type surface plasmon resonance sensor, an electric measurement type surface plasmon resonance sensor which can be easily miniaturized and high throughput and has sufficient sensor accuracy and an electric measurement type surface plasmon resonance sensor chip used therein can be obtained. It will be possible to provide.

Japanese Unexamined Patent Publication No. 2011-141265 Japanese Unexamined Patent Publication No. 2000-356587 Japanese Unexamined Patent Publication No. 2012-38541

However, when the photoelectric conversion element as described in Patent Document 3 is applied to the sensor, the present inventors need to control the metal fine particles, and it is difficult to improve the sensor sensitivity. In addition, it has been found that there is a problem that the sample itself to be measured is redoxed and reduced due to the oxidation / reduction reaction of the electrolyte, which affects the sensor accuracy.

Furthermore, as a result of further studies by the present inventors, a higher level of sensitivity may be required for an electrically measuring surface plasmon resonance sensor chip including a plasmon polariton augmented sensor chip and an electrical measuring device. I found that.

The present invention has been made in view of the above-mentioned problems of the prior art, and is an electric measurement type surface plasmon resonance sensor which is easy to miniaturize and increase the throughput and has sufficient sensor sensitivity, and the electric measurement used therefor. It is an object of the present invention to provide a mold surface plasmon resonance sensor chip.

As a result of diligent research to achieve the above object, the present inventors have made a chip in which a transparent electrode, an n-type transparent semiconductor film, and a plasmon resonance film electrode are combined and arranged in this order, within a specific range. By causing the incident light incident at the incident angle to reach the plasmon resonance film electrode, the reached light is converted into a surface plasmon polariton propagating through the plasmon resonance film electrode, which is converted from the transparent electrode and the plasmon resonance film electrode. We found that it could be detected directly as an electrical signal. Further, the magnitude of the detected electric signal changes with high accuracy according to the refractive index of the sample in the vicinity of the plasmon resonance film electrode, and in addition, the n-type transparent semiconductor film and the plasmon resonance film electrode It has been found that particularly excellent sensor sensitivity is achieved by reflecting the light reflected between them on the reflecting surface, using it again as incident light, and integrating the detected current values. Furthermore, since the refractive index of the sample corresponds to the concentration and state of the sample, it was found that the chip having the above configuration can be used as a sensor chip capable of measuring the concentration change and state change of the sample. The present invention has been completed.

That is, the electromeasurement type surface plasmon resonance sensor of the present invention is
A sensor chip in which a transparent substrate having a light incident port at the end, a transparent electrode, an n-type transparent semiconductor film, and a plasmon resonance film electrode are arranged in this order.
A reflective surface capable of reflecting light reflected between the n-type transparent semiconductor film and the plasmon resonance film electrode,
An electrical measuring device that directly measures a current value or a voltage value from the transparent electrode and the plasmon resonance membrane electrode.
To prepare
It is characterized by that.

Further, the electromeasurement type surface plasmon resonance sensor of the present invention is
A transparent substrate with a light incident port at the end that allows light to enter,
Plasmon resonance membrane electrode capable of converting incident light into surface plasmon polaritons,
It is arranged on the incident light side of the plasmon resonance film electrode, transmits the incident light, and is emitted from the plasmon resonance film electrode by interacting with the plasmon resonance film electrode. An n-type transparent semiconductor film capable of receiving hot electrons, and a transparent electrode capable of extracting hot electrons transferred from the n-type transparent semiconductor film as an electric signal.
With a sensor chip
A reflective surface capable of reflecting light reflected between the n-type transparent semiconductor film and the plasmon resonance film electrode,
An electrical measuring device capable of directly measuring a current value or a voltage value from the transparent electrode and the plasmon resonance membrane electrode.
With
The incident light includes incident light incident from the light incident port and reflected light reflected by the reflecting surface.
It is characterized by that.

As a preferable form of the above-mentioned electrical measurement type surface plasmon resonance sensor, it is preferable that the reflective surface is a boundary surface between the surface of the transparent substrate opposite to the transparent electrode and the inside of the transparent substrate.

Further, as another preferable form of the electric measurement type surface plasmon resonance sensor, a second transparent electrode, a second n-type transparent semiconductor film, and a second n-type transparent semiconductor film are provided on the surface of the transparent substrate opposite to the transparent electrode. A second photoelectric conversion unit in which the second plasmon resonance film electrode is arranged in this order, and a second that directly measures a current value or a voltage value from the second transparent electrode and the second plasmon resonance film electrode. It is further equipped with an electrical measuring device of
It is also preferable that the reflective surface is a surface between the second n-type transparent semiconductor film and the second plasmon resonance film electrode.

As a preferable form of the above-mentioned electrical measurement type surface plasmon resonance sensor, it is preferable that the combination of the n-type transparent semiconductor film and the plasmon resonance film electrode forms a Schottky barrier in the sensor chip. ..

Further, as a preferable form of the electromeasurement type surface plasmon resonance sensor, it is preferable that the thickness of the plasmon resonance film electrode in the sensor chip is 200 nm or less (however, 0 is not included).

Further, as a preferable form of the electromeasurement type surface plasmon resonance sensor, in the sensor chip, the n-type transparent semiconductor film is thio ₂ , ZnO, SnO ₂ , SrTiO ₃ , Fe ₂ O ₃ , TaON, WO ₃ , And a film made of at least one n-type semiconductor selected from the group consisting of In ₂ O ₃ .

The electromeasurement type surface plasmon resonance sensor chip of the present invention is a sensor chip used for the above-mentioned electromeasurement type surface plasmon resonance sensor, and is a transparent substrate having a light incident port at an end, a transparent electrode, an n-type transparent semiconductor film, and an n-type transparent semiconductor film. It is characterized in that the plasmon resonance membrane electrodes are arranged in this order.

The surface plasmon polariton change detection method of the present invention
A sensor chip in which a transparent substrate having a light incident port at the end, a transparent electrode, an n-type transparent semiconductor film, and a plasmon resonance film electrode are arranged in this order.
A reflective surface capable of reflecting light reflected between the n-type transparent semiconductor film and the plasmon resonance film electrode,
An electrical measuring device that directly measures a current value or a voltage value from the transparent electrode and the plasmon resonance membrane electrode.
It is a method of detecting changes in surface plasmon polaritons using an electromeasurement type surface plasmon resonance sensor equipped with.
The first step of injecting light from the light incident port and totally reflecting the incident light between the plasmon resonance film electrode and the n-type transparent semiconductor film;
Due to the total reflection, the incident light interacts with the plasmon resonance film electrode to generate surface plasmon polaritons, and the hot electrons generated by the surface plasmon polaritons and transferred to the n-type transparent semiconductor film are electrically signaled from the transparent electrode. The second step of measuring the change in the current value or the voltage value between the transparent electrode and the plasmon resonance film electrode by the electric measuring device;
The light totally reflected between the plasmon resonance film electrode and the n-type transparent semiconductor film is reflected on a reflective surface that can be reflected to obtain incident light again, and this is used as the plasmon resonance film electrode and the n-type transparent semiconductor film. A third step in which total reflection is performed between the two and the second step is performed again;
The fourth step of repeating the third step a plurality of times, integrating the measured changes in the current value or the voltage value, and detecting the change in the surface plasmon polariton as the integrated value;
It is a method characterized by including.

The reason why the above object is achieved by the configuration of the present invention is not always clear, but the present inventors presume as follows. That is, in the electric measurement type surface plasmon resonance sensor (hereinafter, sometimes simply referred to as "sensor") using the electric measurement type surface plasmon resonance sensor chip (hereinafter, sometimes simply referred to as "sensor chip") of the present invention. When the plasmon resonance film electrode is irradiated with light from the transparent electrode side and the light passing through the transparent electrode and the n-type transparent semiconductor film is totally reflected between the plasmon resonance film electrode and the n-type transparent semiconductor film, Energy exudation (evanescent wave) occurs on the back side of the totally reflected surface. Therefore, when the incident angle of light with respect to the interface is equal to or greater than the critical angle (hereinafter referred to as "total reflection angle"), the evanescent wave generated at the place of total internal reflection and the plasmon resonance film electrode in contact with the back side thereof are mutually compatible. It acts to excite the above surface plasmon polaritons.

Next, the surface plasmon polariton sufficiently polarizes the plasmon resonance membrane electrode to release hot electrons and form hot holes, but the released hot electrons form the plasmon resonance membrane electrode and the Schottky barrier. It can smoothly move to the opposite transparent electrode through the n-type transparent semiconductor film. Therefore, in the sensor using the sensor chip of the present invention, the present inventors presume that the surface plasmon polariton can be sufficiently detected as an electric signal from the plasmon resonance film electrode and the transparent electrode.

Further, in the sensor using the sensor chip of the present invention, the incident angle (from the side of the transparent electrode) at which the change in the refractive index in the vicinity of the plasmon resonance film electrode causes the above-mentioned total internal reflection, that is, the surface plasmon polariton. The range of the incident angle of the incident light) and the intensity of the surface plasmon polaritons generated are changed. Further, since the electric field generated in the plasmon resonance film electrode by the incident light is enhanced by the surface plasmon polariton, the amount of current that changes according to the change in the electric field changes depending on the intensity of the surface plasmon polariton. Therefore, the present inventors presume that the change in the refractive index of the sample near the plasmon resonance membrane electrode can be measured with sufficient accuracy. Therefore, according to the sensor using the sensor chip of the present invention, by detecting the change in the surface plasmon polariton, the concentration change and the state change of the sample can be monitored with high accuracy, and the detection signal is electric. Since it is a signal, the present inventors presume that its strength can be easily increased electrically and can be easily measured as an electric current.

Further, at this time, as light (incident light) totally reflected between the plasmon resonance film electrode and the n-type transparent semiconductor film, the light is reflected between the n-type transparent semiconductor film and the plasmon resonance film electrode. By reflecting the light and reusing it as re-incident light, the light (re-incident light) that is affected by the plasmon resonance and whose intensity decreases with the intensity of the plasmon resonance is incident in the second and subsequent incidents. It will be. Therefore, in addition to increasing the current value by integrating the detected current values, the difference between the maximum value and the minimum value of the integrated current value is larger than that when the incident light is simply enhanced and irradiated. The present inventors speculate that the enhancement is made and excellent sensor sensitivity is achieved.

According to the present invention, it is possible to provide an electric measurement type surface plasmon resonance sensor which can be easily miniaturized and high throughput and has sufficient sensor sensitivity, and an electric measurement type surface plasmon resonance sensor chip used therein. Become.

It is a schematic vertical sectional view which shows the preferred Embodiment 1 of a sensor chip. It is a schematic vertical sectional view which shows preferred Embodiment 1 of an electric measurement type surface plasmon resonance sensor. It is a schematic vertical sectional view which shows the preferred Embodiment 2 of a sensor chip. It is a schematic vertical sectional view which shows the preferred Embodiment 3 of a sensor chip. It is a schematic vertical sectional view which shows the preferred Embodiment 4 of a sensor chip. It is a schematic cross-sectional view which shows the example of the incident light and the reflected light in preferable Embodiment 1 of a sensor chip. FIG. 5 is a schematic vertical sectional view showing a preferred embodiment 5 of the sensor chip. It is a schematic vertical sectional view which shows the preferred Embodiment 6 of a sensor chip. FIG. 5 is a schematic vertical sectional view showing a preferred embodiment 7 of the sensor chip. It is a schematic diagram which shows the incident angle (θ °) of the light incident on a sensor chip. It is a schematic diagram which shows the current value measuring method of Example 1. FIG. Reference Example 1. It is a graph which shows the relationship between the incident angle (θ [°]) in chip 1, the current value [μA] (left axis), and the output current ratio [%] (right axis). It is a graph which shows the relationship between the incident angle (θ [°]) of light in chip 1 and the intensity (reflected light intensity [%]) of each reflected light (R _{1 to} R ₆ ). It is a graph which shows the relationship between the incident angle (θ [°]) at the time of enhancing the incident light in chip 1 and the output current ratio [%]. It is a graph which shows the relationship between the incident angle (θ [°]) at the time of using the reflected light in chip 1 and the integrated value [%] of an output current ratio. It is a graph which shows the relationship between the refractive index and the output current ratio [%] of the sample solution at the time of enhancing the incident light in chip 1. It is a graph which shows the relationship between the refractive index of a sample solution at the time of using the reflected light in chip 1 and the integrated value [%] of an output current ratio.

Hereinafter, the present invention will be described in detail according to the preferred embodiment thereof. The electromeasuring surface plasmon resonance sensor of the present invention
A sensor chip in which a transparent substrate having a light incident port at the end, a transparent electrode, an n-type transparent semiconductor film, and a plasmon resonance film electrode are arranged in this order.
A reflective surface capable of reflecting light reflected between the n-type transparent semiconductor film and the plasmon resonance film electrode,
An electrical measuring device that directly measures a current value or a voltage value from the transparent electrode and the plasmon resonance membrane electrode.
To prepare
It is a thing.

Further, the electromeasurement type surface plasmon resonance sensor of the present invention is
A transparent substrate with a light incident port at the end that allows light to enter,
Plasmon resonance membrane electrode capable of converting incident light into surface plasmon polaritons,
It is arranged on the incident light side of the plasmon resonance film electrode, transmits the incident light, and is emitted from the plasmon resonance film electrode by interacting with the plasmon resonance film electrode. An n-type transparent semiconductor film capable of receiving hot electrons, and a transparent electrode capable of extracting hot electrons transferred from the n-type transparent semiconductor film as an electric signal.
With a sensor chip
A reflective surface capable of reflecting light reflected between the n-type transparent semiconductor film and the plasmon resonance film electrode,
An electrical measuring device capable of directly measuring a current value or a voltage value from the transparent electrode and the plasmon resonance membrane electrode.
With
The incident light includes incident light incident from the light incident port and reflected light reflected by the reflecting surface.
It is also a thing.

Further, the electric measurement type surface plasmon resonance sensor chip of the present invention is a sensor chip used for the electric measurement type surface plasmon resonance sensor of the present invention, and is a transparent substrate, a transparent electrode, and an n-type transparent having a light incident port at an end. The semiconductor film and the plasmon resonance film electrode are arranged in this order.

Hereinafter, with reference to the drawings, a preferable form of the electric measurement type surface plasmon resonance sensor (hereinafter, “sensor”) and the electric measurement type surface plasmon resonance sensor chip (hereinafter, “sensor chip”) will be cited as an example to be more specific. As described above, the present invention is not limited to this. In the following description and drawings, the same or corresponding elements are designated by the same reference numerals, and duplicate description will be omitted.

FIG. 1A shows a first preferred embodiment of the sensor chip (preferable embodiment 1; sensor chip 11). As shown in FIG. 1A, in the preferred embodiment 1, the sensor chip 11 has a transparent electrode (hereinafter, “transparent electrode 3”) and an n-type transparent semiconductor film on a transparent substrate (hereinafter, “transparent substrate 2”). (Hereinafter, "n-type transparent semiconductor film 4") and plasmon resonance film electrode (hereinafter, "plasmon resonance film electrode 5") are a transparent substrate 2, a transparent electrode 3, an n-type transparent semiconductor film 4, and a plasmon resonance film electrode. It is laminated in the order of 5. Further, at the end of the transparent substrate 2, a light incident port (hereinafter, “light incident port 1”) capable of incident light is provided.

Further, FIG. 1B shows a first preferred embodiment of the sensor (preferable embodiment 1; sensor 510). As shown in FIG. 1B, in a preferred embodiment 1, the sensor 510 is electrically connected through the sensor chip 11, the transparent electrode 3 of the sensor chip 11, the plasmon resonance film electrode 5, and an external circuit (external circuits 31 and 31'). (Electrical measuring device 21) connected to the above.

(Transparent board)
The transparent substrate 2 has a function of supporting the sensor chip 11 and has a light incident port 1 at an end thereof. Further, as shown below, in the transparent substrate 2, the interface between the surface of the transparent substrate 2 opposite to the transparent electrode 3 and the inside of the transparent substrate 2 is the n-type transparent semiconductor film 4 and the plasmon resonance film electrode 5. The light reflected between them may function as a reflective surface that can be reflected.

The material of the transparent substrate 2 is not particularly limited as long as it can transmit light, and examples thereof include high molecular weight organic compounds such as glass; plastic and film, and the transparent substrate 2 is at least one of these. It may be a single layer containing seeds or a multi-layer in which two or more such single layers are laminated.

The interface between the surface of the transparent substrate 2 opposite to the transparent electrode 3 and the inside of the transparent substrate 2 is used as a reflective surface capable of reflecting the light reflected between the n-type transparent semiconductor film 4 and the plasmon resonance film electrode 5. When functioning, the surface of the transparent substrate 2 opposite to the transparent electrode 3 is coated with a metal (for example, gold, silver, aluminum, copper, chromium, nickel, tin, etc.) or has a refractive index. A multi-layer reflective film in which a high refractive index and a low refractive index are alternately laminated, and a material having a refractive index lower than that of the transparent substrate 2 is coated. Can be used.

In the present invention, "a film, an electrode, a layer, a substrate, or the like can transmit light" means one surface of the film, the electrode, a layer, or a substrate (the transparent substrate 2 is not processed above). It means that the light transmittance when light of at least one of the wavelengths of 400 to 1500 nm is vertically incident is 40% or more, and the light transmittance is 50% or more. It is preferably 60% or more, and more preferably 60% or more.

The light incident port 1 has a function of incident light inside the sensor chip 11. The light incident port 1 is an end portion of the transparent substrate 2, preferably a side surface in contact with a plane on which the transparent electrode 3, the n-type transparent semiconductor film 4, and the plasmon resonance film electrode 5 are laminated (more preferably, the transparent substrate 2). The n-type transparent semiconductor film 4 and the plasmon resonance film electrode 5 are formed by forming an oblique plane or a curved shape such as a hemispherical or semi-cylindrical shape on the side surface forming the short side of the light by cutting, polishing, or the like. There is a structure processed so that light can be incident between them so that light is totally reflected between them. Further, as the light incident port 1, a prism such as a right triangle, a semi-cylinder, or a hemisphere may be arranged at the end of the transparent substrate 2 and used as the light incident port 1. In this case, the material of the light incident port 1 includes, for example, glass, high molecular weight polymer (methyl methacrylate, polystyrene, polyethylene, epoxy, polyester, etc.), sulfur, ruby, sapphire, diamond, zinc selenium (ZnSe), and sulfide. Zinc (ZnS), Germanium (Ge), Silicon (Si), Cesium iodide (CsI), Potassium bromide (KBr), Talium bromide, Calcium carbonate (CaCO ₃ ), Barium fluoride (BaF ₂ ), Sulfur Examples thereof include magnesium carbonate (MgF ₂ ) and lithium fluoride (LiF).

The light incident port 1 is arranged at the end of the transparent substrate 2, but more specifically, it is arranged on any surface of the transparent substrate 2, more preferably near the end of the surface, and is n-type transparent. From the viewpoint of repeating the reflection of the light reflected between the semiconductor film 4 and the plasmon resonance film electrode 5 a plurality of times, it is further arranged on the end face in the longitudinal direction (the end face constituting the short side) of the transparent substrate 2. preferable.

The thickness of the transparent substrate 2 is usually 0.01 to 2 mm, but the interface between the surface of the transparent substrate 2 opposite to the transparent electrode 3 and the inside of the transparent substrate 2 is the n-type transparent semiconductor film 4. When the light reflected from the plasmon resonance film electrode 5 functions as a reflective surface that can be reflected, the thickness thereof is preferably 0.01 to 10 mm, preferably 0.01 to 5 mm. More preferred. As the thickness of the transparent substrate 2 increases, it tends to be necessary to increase the size of the entire sensor.

(Transparent electrode)
The transparent electrode 3 has a function of extracting hot electrons (electrons) emitted along with the surface plasmon polaritone generated in the plasmon resonance film electrode 5 and moving through the n-type transparent semiconductor film 4 as an electric signal, and has a function of extracting plasmon. It functions as a counter electrode of the resonance film electrode 5, and is suitable for the plasmon resonance film electrode 5, an electrical measuring device (electric measuring device 21 in the preferred embodiment 1), and an external circuit (lead wire, current meter, etc.) as necessary. In the first embodiment, they are electrically connected via external circuits 31 and 31'). Further, the transparent electrode 3 needs to be able to transmit light.

The material of the transparent electrode 3 can be appropriately selected from those conventionally used as a transparent electrode in the semiconductor field, and can be used, for example, copper (Cu), gold (Au), silver (Ag), and platinum. (Pt), zinc (Zn), chromium (Cr), aluminum (Al), titanium (Ti), titanium nitride (TiN), ITO (Indium tin oxide), FTO (Fluorine-doped tin oxide), and other elements (Pt), zinc (Zn), chromium (Cr), aluminum (Al), titanium (Ti), titanium nitride (TiN), ITO (Indium tin oxide), and other elements ( Examples thereof include a transparent conductive material such as a metal oxide such as ZnO doped with (aluminum, gallium, etc.), and a thin film or a net-like shape composed of a laminate thereof. Further, as the material of the transparent electrode 3, the n-type semiconductor constituting the following n-type transparent semiconductor film can be mentioned, and in the sensor chip, the transparent electrode 3 and the n-type transparent semiconductor film 4 are made of the same material. It may be a layer.

The thickness of the transparent electrode 3 is usually 1 to 1000 nm. In the present invention, the thickness of the film, electrodes, layers and the like can be measured by observation with a scanning electron microscope (SEM) or a transmission electron microscope (TEM).

(N-type transparent semiconductor film)
The n-type transparent semiconductor film 4 has a function of receiving hot electrons emitted when the plasmon resonance film electrode 5 is sufficiently polarized by the surface plasmon polariton excited by the plasmon resonance film electrode 5. It is a film made of a type semiconductor. Further, the n-type transparent semiconductor film 4 needs to be able to transmit light.

Examples of the n-type semiconductor include inorganic oxide semiconductors, and one of them may be used alone or two or more kinds of composite materials may be used. Examples of the inorganic oxide semiconductor include titanium dioxide (TiO ₂ ), zinc oxide (ZnO), tin dioxide (SnO ₂ ), gallium nitride (GaN), gallium oxide (GaO), strontium oxide (SrTiO ₃ ), and oxidation. Examples thereof include iron (Fe ₂ O ₃ ), tantalum oxynitride (TaON), tungsten oxide (WO ₃ ), indium oxide (In ₂ O ₃ ), and composite oxides thereof. Among them, the n-type semiconductor is composed of TiO ₂ , ZnO, SnO ₂ , SrTIO ₃ , Fe ₂ O ₃ , TaON, WO ₃ and In ₂ O ₃ from the viewpoint of high transparency and high conductivity. It is preferably at least one type of semiconductor selected from the group, and is at least one type of semiconductor selected from the group consisting of TiO ₂ , ZnO, SnO ₂ , SrTIO ₃ , Fe ₂ O ₃ and In ₂ O _3. Is more preferable.

The thickness of the n-type transparent semiconductor film 4 is preferably 1 to 1000 nm, more preferably 5 to 500 nm, and even more preferably 10 to 300 nm. If the thickness is less than the lower limit, the n-type transparent semiconductor cannot exist as a film and tends to be unable to perform a sufficient function as a semiconductor. On the other hand, if the upper limit is exceeded, the light transmittance tends to decrease or the resistance tends to increase, making it difficult for current to flow.

(Plasmon resonance membrane electrode)
The plasmon resonance film electrode 5 has a function of converting incident light (incident light) into surface plasmon polaritons, and is a film made of a plasmonic material capable of generating surface plasmon polaritons by interacting with light. .. Further, it has a function of extracting the surface plasmon polaritone as an electric signal, functions as a counter electrode of the transparent electrode 3, the transparent electrode 3, the electric measuring device (the electric measuring device 21 in the preferred embodiment 1), and the electric measuring device 21. If necessary, they are electrically connected via an external circuit (lead wire, ammeter, etc .; external circuits 31 and 31'in the preferred embodiment 1). The incident light includes incident light incident from the light incident port and reflected light reflected by the reflecting surface.

Examples of the plasmonic material include metals, metal nitrides, and metal oxides, and one of these may be used alone or in combination of two or more. Among them, preferred as the plasmonic material, the metal is gold (Au), silver (Ag), aluminum (Al), copper (Cu), platinum (Pt), palladium (Pd), zinc (Zn). , And sodium (Na), the metal nitride is titanium nitride (TiN), the metal oxide is ITO (aluminum tin oxide), FTO (Fluorine-topped tin oxide), and other elements. ZnOs doped with (aluminum, gallium, etc.) can be mentioned. Among them, the plasmonic material is preferably at least one selected from the group consisting of Au, Ag, Al, Cu, Pt, Pd, and TiN, and is composed of Au, Ag, Al, Cu, and Pt. More preferably, it is at least one selected from the group.

The thickness of the plasmon resonance membrane electrode 5 is preferably 200 nm or less (but not including 0), more preferably 1 to 150 nm, further preferably 5 to 100 nm, and preferably 10 to 60 nm. It is even more preferable to have. If the thickness is less than the lower limit, the plasmon resonance film electrode tends to be unable to exist as a film, while if the thickness exceeds the upper limit, an evanescent wave reaching the surface opposite to the surface on which light is incident. Becomes weaker and tends to be unable to excite sufficient surface plasmon polaritons.

From the viewpoint that the thickness of the plasmon resonance film electrode 5 tends to be able to measure a wider range of refractive index (preferably 1.33 to 1.40) as the refractive index of the sample to be measured, from the viewpoint. It is particularly preferably 10 to 34 nm, and particularly preferably 35 to 60 nm from the viewpoint of increasing the rate of change of the current value with respect to the change of the refractive index.

(Adhesive layer)
FIG. 2 shows a second preferred embodiment of the sensor chip (preferable embodiment 2). The main purpose of the sensor chip is to more firmly fix the plasmon resonance film electrode 5 between the n-type transparent semiconductor film 4 and the plasmon resonance film electrode 5, as shown in the sensor chip 12 shown in FIG. , The adhesive layer 6 may be further provided.

Examples of the material of the adhesive layer 6 include titanium (Ti), chromium (Cr), nickel (Ni), and titanium nitride (TiN), and the adhesive layer simply contains at least one of these. It may be a layer or a multi-layer in which two or more kinds of such single layers are laminated. Further, the adhesive layer 6 does not have to completely cover the boundary surface between the n-type transparent semiconductor film 4 and the plasmon resonance film electrode 5. However, since the evanescent wave reaching the surface opposite to the surface on which the light is incident tends to be weakened and the surface plasmon polariton having sufficient strength tends to be unable to be excited, the n-type transparent semiconductor film is used in the sensor chip. 4 and the plasmon resonance film electrode 5 are preferably arranged close to each other, and the distance between the n-type transparent semiconductor film 4 and the plasmon resonance film electrode 5 is preferably 25 nm or less, preferably 1 to 10 nm. More preferably. Therefore, when the adhesive layer 6 is further provided, the thickness thereof is preferably 25 nm or less, and more preferably 1 to 10 nm.

(Protective film)
FIG. 3 shows a third preferred embodiment of the sensor chip (preferable embodiment 3). In the sensor chip, as shown in FIG. 3, protection for the main purpose of protecting the exposed surface of the plasmon resonance film electrode 5 on the surface of the plasmon resonance film electrode 5 opposite to the n-type transparent semiconductor film 4. A film 7 may be further provided.

Examples of the material of the protective film 7 include glass, plastic, titanium oxide (TiO ₂ ), magnesium fluoride (MgF ₂ ), tantalum pentoxide (Ta ₂ O ₅ ), aluminum oxide (Al ₂ O ₃ ), and diamond-like material. Examples thereof include carbon and silicon carbide, and the protective film 7 may be a single layer containing one of these, or a plurality of layers in which two or more such single layers are laminated. However, since the range covered by the surface plasmon polariton generated in the plasmon resonance film electrode 5 is within about 300 nm from the surface of the plasmon resonance film electrode, when the protective film 7 is further provided, the thickness thereof is 300 nm or less. It is preferably 200 nm or less, and more preferably 100 nm or less.

(Sample layer)
FIG. 4 shows a fourth preferred embodiment of the sensor chip (preferable embodiment 4). In the sensor chip, as shown in FIG. 4, the protective film described above or on the surface of the plasmon resonance film electrode 5 opposite to the n-type transparent semiconductor film 4 for the main purpose of holding the sample to be measured. A sample layer 8 may be further provided on the 7. As the sample layer 8, even if the sample is arranged so as to be supplied at an arbitrary flow rate, the sample layer 8 is divided and arranged in a cell shape so that the sample is included in a constant volume. There may be.

In the sensor chip of the present invention, the combination of the n-type transparent semiconductor film 4 and the plasmon resonance film electrode 5 (the adhesive layer 6 if the adhesive layer 6 is further provided) forms a shotky barrier. Is preferable. The fact that the sensor chip forms a Schottky barrier means that the transparent electrode 3 of the sensor chip is connected to the working electrode of a voltage applying means such as a semiconductor analyzer, and the plasmon resonance film electrode 5 is connected to the counter electrode and the reference electrode of the voltage applying means, respectively. Then, it can be confirmed by measuring the current value when a voltage is applied to the working electrode in the range of −1.5 to + 1.5V. As for the current value, the maximum value of the absolute value of the current value at 0 V or more and + 1.5 V or less is 1/5 or less of the maximum value of the absolute value of the current value at -1.5 V or more and less than 0 V. It is more preferably 1/10 or less, and even more preferably 1/20 or less. When this ratio exceeds the upper limit value, the rectification characteristic is attenuated, so that noise during measurement tends to increase, and the sensitivity and accuracy of the sensor tend to decrease.

The combination forming such a Schottky barrier is obtained by the following equation: φS <, when the work function of the n-type transparent semiconductor film 4 is φS and the work function of the plasmon resonance film electrode 5 (or the adhesive layer 6) is φM. It is a combination that satisfies the conditions indicated by φM.

The value of the work function in each material is known, and examples of the work function (φS) of the n-type transparent semiconductor film 4 include (I) Akihito Imanishi et al., J. Mol. Phys. Chem. C, 2007, 111 (5), p. 2128-2132; (II) Min Wei et al., Energy Procedure, 2012, Volume 16, Part A, p. 76-80; (III) David Ginley et al., "Handbook of Transition Conducors", 2011; (IV) L. Ginley. F. Zagonel et al., J. Mol. Phys. : Condens. Matter, 2009, 21, 31; (V) E.I. R. Bautista et al., J. Mol. Phys. Chem. B, 2002, 106 (33), p. 8136-8141; (VI) Gy. Vida et al., 2003, Microsc. Microanal. , 9 (4), p. 337-342; (VII) W. J. Chu et al., J. Mol. Phys. Chem. B, 2003, 107 (8), p. In 1798-1803, titanium dioxide (TiO ₂ ): 4.0 to 4.2 (I), zinc oxide (ZnO): 4.71 to 5.08 (II), tin dioxide (SnO ₂ ): 5, respectively. .1 (III), Strontium Titanium (SrTIO ₃ ): 4.2 (IV), Diiron Trioxide (Fe ₂ O ₃ ): 5.6 (V), Titanium Oxide (WO ₃ ): 5.7 ( VI), strontium titanate (TaON): 4.4 (VII), indium oxide (In ₂ O ₃ ): 4.3 to 5.4 (III).

The work function (φM) of the plasmon resonance film electrode 5 (or the adhesive layer 6) is, for example, (VIII) edited by the Chemical Society of Japan, "Chemical Handbook Basic Edition Revised 4th Edition", II-489, respectively. (Au): 5.1 to 5.47, silver (Ag): 4.26 to 4.74, aluminum (Al): 4.06 to 4.41, copper (Cu): 4.48 to 4.94. , Platinum (Pt): 5.64 to 5.93, Palladium (Pd): 5.55, and (IX) Takashi Matsukawa et al., Jpn. J. Apple. Phys. , 2014, 53, 04EC11, it is described that titanium nitride (TiN): 4.4 to 4.6.

Therefore, the combination of the n-type transparent semiconductor film 4 forming the Schottky barrier and the plasmon resonance film electrode 5 (or the adhesive layer 6) is a combination satisfying the above conditions from among these work functions (φS, φM). Can be selected and adopted as appropriate. Among these, as a combination of the n-type transparent semiconductor film 4 and the plasmon resonance film electrode 5 (or the adhesive layer 6), any one of TiO ₂ and Au, Ag, Al, Cu, Pt, Pd, and TiN. Combination with one, combination of ZnO with any one of Au, Pt, Pd, combination of SnO ₂ with any one of Au, Pt, Pd, SrTIO ₃ and Au, Ag, Al, Cu, Combination with any one of Pt, Pd, TiN, combination of Fe ₂ O ₃ and Pt, combination of WO ₃ and Pd, any of TaON and Au, Ag, Cu, Pt, Pd, TiN A combination with one of them, a combination of In ₂ O ₃ with any one of Pt and Pd is preferable, and a combination of TiO ₂ with any one of Au, Ag, Cu, Pt and Pd, ZnO and Combination with Pt, combination of SnO ₂ and Pt, combination of SrTIO ₃ with any one of Au, Ag, Cu, Pt, Pd, TaON and any one of Au, Cu, Pt, Pd A combination with one, a combination of In ₂ O ₃ and Pt is more preferable.

(Reflective surface)
As one of the preferred embodiments of the reflective surface capable of reflecting the light reflected between the n-type transparent semiconductor film and the plasmon resonance film electrode, the surface of the transparent substrate 2 opposite to the transparent electrode 3 is transparent. The boundary surface with the inside of the substrate 2 can be mentioned.

FIG. 5 shows a schematic cross-sectional view showing an example of incident light and reflected light as an embodiment of the sensor chip 11. In the embodiment shown in FIG. 5, the interface between the surface of the transparent substrate 2 of the sensor chip 11 opposite to the transparent electrode 3 and the inside of the transparent substrate 2 is the n-type transparent semiconductor film 4 and the plasmon resonance film electrode 5. The light reflected between them functions as a reflective surface that can be reflected. At this time, the incident light (“incident light 401”, incident light I ₁ ) incident from the light incident port 1 passes through the transparent substrate 2, the transparent electrode 3, and the n-type transparent semiconductor film 4, and becomes the plasmon resonance film electrode 5. The surface plasmon polaritone is generated by interacting with the plasmon resonance film electrode 5 by total reflection with the n-type transparent semiconductor film 4. Further, the totally reflected reflected light (R ₁ ) at this time is reflected at the interface between the surface of the transparent substrate 2 opposite to the transparent electrode 3 and the inside of the transparent substrate 2 and is reflected again as the incident light (re-incident light I ₂ ). Then, the surface plasmon polaritone is generated again by transmitting through the transparent substrate 2, the transparent electrode 3, and the n-type transparent semiconductor film 4 and completely reflecting between the plasmon resonance film electrode 5 and the n-type transparent semiconductor film 4. In the sensor chip 11, by repeating this process (6 times in FIG. 5), the subsequent reflected light (reflected light R ₂ to 5 in FIG. 5) is used again as incident light ( _reincident light I _{3 to 6 in} FIG. 5). However, surface plasmon polaritons can be continuously generated.

Further, one of the preferred embodiments of the reflective surface is a surface existing between the plasmon resonance film electrode of the other photoelectric conversion unit and the n-type transparent semiconductor film.

FIG. 6 shows a schematic cross-sectional view showing an example of a fifth preferred embodiment of the sensor chip (preferable embodiment 5) and its incident light and reflected light. As the sensor chip, as shown in the sensor chip 15 shown in FIG. 6, a second transparent electrode (hereinafter, “second transparent electrode 3'”) is placed on the surface of the transparent substrate 2 opposite to the transparent electrode 3. The second n-type transparent semiconductor film (hereinafter, "second n-type transparent semiconductor film 4'") and the second plasmon resonance film electrode (hereinafter, "second plasmon resonance film electrode 5'") are the same. A second photoelectric conversion unit (hereinafter, "second photoelectric conversion unit 11'") arranged in order is further provided, and a second n-type transparent semiconductor film 4'and a second plasmon resonance film electrode are provided. The surface between 5'may function as the reflective surface. As a sensor using the sensor chip 15, a second electrical measuring device (not shown) that directly measures a current value or a voltage value from a second transparent electrode 3'and a second plasmon resonance film electrode 5'(not shown). ), And the second electrical measuring device may be the same as or different from the electrical measuring device 21.

The surface existing between the plasmon resonance film electrode and the n-type transparent semiconductor film of the other photoelectric conversion unit includes an interface between the second n-type transparent semiconductor film 4'and the second plasmon resonance film electrode 5'. Alternatively, when a second adhesive layer is provided between the second n-type transparent semiconductor film 4'and the second plasmon resonance film electrode 5', the second plasmon resonance film electrode 5'and the second adhesive layer are provided. When the interface with, or the interface between the second adhesive layer and the second n-type transparent semiconductor film 4', or the second adhesive layer consists of two or more layers, the second plasmon resonance film electrode 5' The interface between the second adhesive layer and the second adhesive layer, the interface between the second adhesive layer and the second n-type transparent semiconductor film 4', or the interface between two adjacent layers in the second adhesive layer can be mentioned.

At this time, the incident light 401 incident from the light incident port 1 passes through the transparent substrate 2, the transparent electrode 3, and the n-type transparent semiconductor film 4, and is totally between the plasmon resonance film electrode 5 and the n-type transparent semiconductor film 4. By reflecting, it interacts with the plasmon resonance film electrode 5 to generate surface plasmon polaritons. Further, the totally reflected reflected light at this time passes through the n-type transparent semiconductor film 4, the transparent electrode 3, the transparent substrate 2, the second transparent electrode 3', and the second n-type transparent semiconductor film 4', and is the second. Surface plasmon polaritone is generated by total internal reflection between the plasmon resonance film electrode 5'and the second n-type transparent semiconductor film 4'. Further, the light totally reflected between the second plasmon resonance film electrode 5'and the second n-type transparent semiconductor film 4'becomes the re-incident light to the photoelectric conversion part on the opposite side, and the surface plasmon polaritons are again generated. Generate it. By repeating this process, the sensor chip 15 can use the reflected light again as incident light to continuously generate surface plasmon polaritons.

The distance between the surface on which the incident light is totally reflected between the n-type transparent semiconductor film 4 and the plasmon resonance film electrode 5 and the reflection surface increases, that is, it is laminated on the transparent substrate 2. When the length of the transparent electrode 3, the n-type transparent semiconductor film 4, and the plasmon resonance film electrode 5 with respect to the incident direction becomes long, the entire sensor is enlarged in order to exceed the number of reflections required to achieve high sensitivity. From the viewpoint that the need tends to occur, it is preferably 0.01 to 10 mm, and more preferably 0.01 to 5 mm.

Further, the reflecting surface needs to be a surface capable of reflecting the light reflected between the n-type transparent semiconductor film 4 and the plasmon resonance film electrode 5. As a condition of such a surface, the light reflectance when light of at least one wavelength of 400 to 1500 nm is vertically incident is preferably 50% or more, and is preferably 60% or more. Is more preferable. Such a reflective surface is, for example, a metal coating such as gold, silver, aluminum, copper, chromium, nickel, tin; titanium dioxide (TiO ₂ ), tantalum oxide (V) (Ta ₂ O ₅ ), aluminum oxide (Al). _It can be obtained by laminating a multilayer thin film in which at least two types of ₂ O ₃ ), silicon dioxide (SiO ₂ ), and magnesium fluoride (MgF ₂ ) are alternately laminated.

Further, the reflecting surface may be a totally reflecting surface capable of totally reflecting the reflected light. As a condition of such a surface, the surface of the transparent substrate 2 opposite to the transparent electrode 3 is refracted. A surface coated with a material having a refractive index lower than that of the transparent substrate 2 can be mentioned, and the refractive index of the material is preferably a material having a total reflection angle of 80 ° or less caused by a difference in the refractive index from the transparent substrate 2. , 70 ° or less is more preferable, and 60 ° or less is further preferable. Such a total reflection surface can be obtained by adhering or coating a solid material having a refractive index different from that of the solid material to the transparent substrate 2 when the transparent substrate 2 is a solid material such as glass or plastic. Is. Further, by arranging an encapsulation tank capable of sealing the air layer and the liquid layer on the surface of the transparent substrate 2 opposite to the transparent electrode 3, the encapsulation tank can be filled with gas or solution to obtain a total reflection surface. It is possible.

Further, as the reflection surface, the angle at which the incident light is totally reflected between the n-type transparent semiconductor film 4 and the plasmon resonance film electrode 5 and the reflected light (re-incident light) are again the n-type transparent semiconductor film. It is necessary that the angle of total reflection between 4 and the plasmon resonance film electrode 5 is the same angle. As the arrangement condition of such a reflective surface, the surface formed between the n-type transparent semiconductor film 4 and the plasmon resonance film electrode 5 is optically flat, and the reflective surface is the n-type transparent semiconductor film 4 and It is mentioned that it is arranged in parallel with the plasmon resonance film electrode 5 and is optically flat. However, in the n-type transparent semiconductor film 4, the plasmon resonance film electrode 5, and the reflective surface, all the surfaces need not be parallel or all the surfaces need not be optically flat, and light is emitted from each of them. These conditions may be satisfied in the reflected region. Further, such an optically flat surface can be obtained by optical polishing after cutting.

Further, as the reflecting surface, the light reflected between the n-type transparent semiconductor film 4 and the plasmon resonance film electrode 5 can be reflected at least 3 times, preferably 3 to 20 times, more preferably 3 to 10 times. A reflective configuration is preferred. Even if the number of reflections exceeds the upper limit, there is a tendency that no further improvement in sensitivity is achieved. Further, in this case, in order to realize such a number of reflections, the length in the longitudinal direction of the three transparent electrodes of the photoelectric conversion unit including the transparent electrode 3, the n-type transparent semiconductor 4, and the plasmon resonance film electrode 4, that is, The length in the traveling direction of light is preferably 5 mm or more, more preferably 5 to 200 mm, and even more preferably 5 to 50 mm.

The sensor chip of the present invention is not limited to the above-mentioned sensor chip embodiments 1 to 5 (sensor chips 11 to 15), and any of these may be provided, for example, both the adhesive layer 6 and the sample layer 8 are provided. It may be a combination of (not shown). Further, as the sensor chip of the present invention, one may be used alone, or a plurality of sensor chips may be arranged side by side in a row or a plane.

Further, for example, FIG. 7 shows a schematic cross-sectional view showing an example of a sixth preferred embodiment (preferable embodiment 6) of the sensor chip and its incident light and reflected light. As the sensor chip, as shown in the sensor chip 16 shown in FIG. 7, a plurality of photoelectric conversion units including the transparent electrode 3, the n-type transparent semiconductor film 4, and the plasmon resonance film electrode 5 are divided on the transparent substrate 2. It may be arranged.

Further, for example, FIG. 8 shows a schematic cross-sectional view showing an example of a seventh preferred embodiment (preferable embodiment 7) of the sensor chip and its incident light and reflected light. As the sensor chip, as shown in the sensor chip 17 shown in FIG. 8, the surface of at least one plasmon resonance film electrode 5 of the divided photoelectric conversion part of the sensor chip 16 on the surface opposite to the n-type transparent semiconductor film 4 or A reference 9 may be further provided on the protective film 7 for the main purpose of comparing the performance with other sensors and confirming the deterioration state of the sensor at the time of measurement.

Reference 9 includes, for example, glass, high molecular weight polymer (methyl methacrylate, polystyrene, polyethylene, epoxy, polyester, etc.), sulfur, ruby, sapphire, diamond, zinc selenide (ZnSe), zinc sulfide (ZnS), germanium (ZnS). Ge), silicon (Si), cesium iodide (CsI), potassium bromide (KBr), tarium bromide, calcium carbonate (CaCO ₃ ), barium fluoride (BaF ₂ ), magnesium fluoride (MgF ₂ ), Examples include lithium fluoride (LiF).

(Electrical measuring device (electrical measuring means))
The sensor of the present disclosure is an electrical measurement that directly measures a current value or a voltage value from the sensor chip (for example, the sensor chip 11 in the preferred embodiment 1) and the transparent electrode 3 and the plasmon resonance film electrode 5 of the sensor chip. A device (for example, an electrical measuring device 21 in the preferred embodiment 1) is provided. The transparent electrode 3 and the plasmon resonance film electrode 5 and the electrical measuring device are connected to each other through an external circuit (for example, external circuits 31 and 31'in the preferred embodiment 1).

The material of the external circuit is not particularly limited, and a known material for the conducting wire can be appropriately used, and examples thereof include metals such as platinum, gold, palladium, iron, copper, and aluminum. Further, the electrical measuring device is not particularly limited as long as it can measure a voltage value or a current value, and examples thereof include a semiconductor device analyzer, a current measuring device, and a voltage measuring device.

(Surface plasmon polariton change detection method)
The surface plasmon polariton change detection method of the present invention is a method for detecting a change in surface plasmon polariton using the above-mentioned electromeasurement type surface plasmon resonance sensor (sensor).
The first step of injecting light from the light incident port and totally reflecting the incident light between the plasmon resonance film electrode and the n-type transparent semiconductor film;
Due to the total reflection, the incident light interacts with the plasmon resonance film electrode to generate surface plasmon polaritons, and the hot electrons generated by the surface plasmon polaritons and transferred to the n-type transparent semiconductor film are electrically signaled from the transparent electrode. The second step of measuring the change in the current value or the voltage value between the transparent electrode and the plasmon resonance film electrode by the electric measuring device;
The light totally reflected between the plasmon resonance film electrode and the n-type transparent semiconductor film is reflected on a reflective surface that can be reflected to obtain incident light again, and this is used as the plasmon resonance film electrode and the n-type transparent semiconductor film. A third step in which total reflection is performed between the two and the second step is performed again;
The fourth step of repeating the third step a plurality of times, integrating the measured changes in the current value or the voltage value, and detecting the change in the surface plasmon polariton as the integrated value;
including,
The method.

For example, in a sensor using the sensor chip 11, light is incident from the light incident port 1 and passes through the transparent substrate 2, the transparent electrode 3, and the n-type transparent semiconductor film 4 (incident light, I ₁ ). By total internal reflection between the plasmon resonance film electrode 5 and the n-type transparent semiconductor film 4 (first step), the incident light can interact with the plasmon resonance film electrode 5 to generate surface plasmon polaritons. it can. More specifically, the light passing through the n-type transparent semiconductor film 4 adheres to the interface between the n-type transparent semiconductor film 4 and the plasmon resonance film electrode 5, or to the plasmon resonance film electrode 5 when the adhesive layer 6 is provided. The interface with the layer 6, the interface between the adhesive layer 6 and the n-type transparent semiconductor film 4, or the interface between the plasmon resonance film electrode 5 and the adhesive layer 6 when the adhesive layer 6 consists of two or more layers, or adhesion. Total reflection occurs at the interface between the layer 6 and the n-type transparent semiconductor film 4 or at the interface between two adjacent layers in the adhesive layer 6, and the evanescent wave generated by the total reflection interacts with the plasmon resonance film electrode 5 on the surface. Plasmon polaritons occur.

Since the generated surface plasmon polariton sufficiently polarizes the plasmon resonance film electrode 5 to generate hot electrons, the hot electrons can move to the n-type transparent semiconductor film 4 and be extracted as an electric signal from the transparent electrode 3. .. At this time, since the transparent electrode 3 is electrically connected to the plasmon resonance film electrode 5 through the external circuit, the change in the current value between the transparent electrode 3 and the plasmon resonance film electrode 5 is measured by the electrical measuring device. Can be done (second step). The hot electron observed as an electric signal in this way is considered to be a hot electron generated in the vicinity of the interface inside the plasmon resonance membrane electrode 5, and the hot electron observable as an electric signal in this way is considered to be a plasmon resonance. It is presumed that the hot electrons are generated in a region of about 20% of the thickness of the plasmon resonance membrane electrode 5 at a distance from the n-type transparent semiconductor membrane 3 inside the membrane electrode 5.

Further, the reflected light (R1 to _n ) totally reflected between the plasmon resonance film electrode 5 and the n-type transparent semiconductor film 4 is transparent to the surface of the transparent substrate 2 opposite to the transparent electrode 3 of the transparent substrate 2. Reflected at the interface with the inside of the substrate 2 or, in the case of the sensor chip 15, the surface between the second n-type transparent semiconductor film 4'and the second plasmon resonance film electrode 5') and re-entered. Light (I _{2 to (n + 1)} ) is transmitted through the transparent substrate 2, the transparent electrode 3, and the n-type transparent semiconductor film 4, and is totally reflected between the plasmon resonance film electrode 5 and the n-type transparent semiconductor film 4. , Again generate surface plasmon polaritons (third step).

By repeating such a third step a plurality of times, surface plasmon polaritons are continuously generated, each current value change is measured by the electrical measuring device, and the measured current value change is integrated. Changes in surface plasmon polaritons can be detected as integrated values (fourth step). By detecting the change in surface plasmon polariton as an integrated value, the current value is increased, and in addition, the maximum and minimum values of the integrated current value are higher than when the incident light is simply enhanced and irradiated. The difference is enhanced and excellent sensor sensitivity can be achieved. The number of times of the third step is preferably 3 times or more, more preferably 3 to 20 times, and further preferably 3 to 10 times. Even if the number of reflections exceeds the upper limit, there is a tendency that no further improvement in sensitivity is achieved.

When the wavelength of the light incident from the light incident port 1 becomes longer, the range of the incident angle of the incident light that causes the surface plasmon polariton becomes narrower, while the intensity of the surface plasmon polariton that is generated is increased. Therefore, in the first step, the light incident on the light incident port 1 is not particularly limited depending on the purpose, but examples thereof include light in the wavelength region of visible light and light in the wavelength region of near infrared light. The wavelength is preferably ~ 1500 nm, more preferably 500 to 1000 nm, and even more preferably 600 to 900 nm.

Further, as the intensity of the light incident from the light incident port 1 becomes stronger, the amount of current generated by the surface plasmon polariton increases. Therefore, in the first step, the intensity of the light incident from the light incident port 1 is not particularly limited depending on the purpose, but is preferably 0.01 to 500 mW, preferably 0.1 to 50 mW. More preferably, it is more preferably 0.1 to 5 mW. If the light intensity is less than the lower limit, the amount of current generated by the surface plasmon polaritons tends to be too small to obtain sufficient sensor accuracy, while if the light intensity exceeds the upper limit, the plasmon resonance film electrode 5 tends to be obtained. There is a tendency that heat is generated in the water and the measurement sensitivity is lowered.

Further, in the first step, the light incident from the light incident port 1 is between the plasmon resonance film electrode 5 and the n-type transparent semiconductor film 4, and the second plasmon resonance film electrode 5'and the second. Reflects between the n-type transparent semiconductor film 4'or at the interface between the surface of the transparent substrate 2 opposite to the transparent electrode 3 and the inside of the transparent substrate 2, and is reflected between the plasmon resonance film electrode 5 and the n-type transparent semiconductor film 4. The angle at which the light is incident again is the light that is incident from the light incident port 1 and can be the angle that is incident between the plasmon resonance film electrode 5 and the n-type transparent semiconductor film 4, and is the case of the sensor chip 15. Can be incident at the same angle between the plasmon resonance film electrode 5 and the n-type transparent semiconductor film 4 and between the second plasmon resonance film electrode 5'and the second n-type transparent semiconductor film 4'. It is necessary that the light is bright, and the condition of such light is that the light has a small spread angle. Such light can be obtained by passing light emitted from a light source such as a laser; LED; a halogen lamp or a mercury lamp through an optical member such as a lens.

In the sensor of the present disclosure, the refractive index of the sample is arranged by arranging the sample to be measured in the vicinity of the plasmon resonance membrane electrode (preferably within 300 nm from the surface of the plasmon resonance membrane electrode, for example, in the sample layer 8). Since the change in surface plasmon polariton due to the change (concentration change, state change) can be detected as an electric signal, the state change of the sample can be monitored by measuring the electric signal.

Further, the sensor accuracy can be further sufficiently improved by changing the incident angle of light with respect to the sensor chip according to the sample to be measured. In the present invention, the incident angle of light is defined as the incident angle of the transparent electrode 3 with respect to the surface, as shown in FIG.

According to the sensors of the present disclosure, for example, the target substance and the target substance held on the surface of the plasmon resonance film electrode 5 opposite to the n-type transparent semiconductor film 4 or on the protective film 7, preferably in the sample layer 8. For a sample containing a medium, changes in surface plasmon polaritons due to changes in the concentration or state of the target substance can be detected as electrical signals. In this case, the target substance is not particularly limited, and small molecule compounds such as antibodies, nucleic acids (DNA, RNA, etc.), proteins, bacteria, drugs; ions; small molecule compounds in a gaseous state, volatile substances, etc. Can be mentioned. Examples of the medium include solutions and gases, examples of the solution include water; an electrolyte solution such as a buffer solution and a strong electrolyte solution, and examples of the gas include an inert gas such as nitrogen gas and helium gas. Be done.

(Manufacturing method of electrical measurement type surface plasmon resonance sensor)
The manufacturing method of the sensor and the sensor chip of the present disclosure is not particularly limited, but preferably, the transparent electrode 3, the n-type transparent semiconductor film 4, and the plasmon resonance film electrode 5 are sequentially formed on the transparent substrate 2 in this order. The method of laminating is preferable. The forming method is not particularly limited, but as a method for forming the transparent electrode 3, the n-type transparent semiconductor film 4, and the plasmon resonance film electrode 5, for example, the sputtering method, the ion plating method, and the electron are independently formed. Beam vapor deposition, vacuum vapor deposition, chemical vapor deposition, spin coating, atomic layer deposition (ALD), and plating methods can be mentioned. When the sputtering method is used, when the n-type transparent semiconductor film 2 made of a metal oxide is formed, a metal may be targeted and a film may be formed while being oxidized (reactive sputtering).

Further, the method for manufacturing the sensor is not particularly limited as a method for electrically connecting the transparent electrode 3 and the plasmon resonance film electrode 5 of the sensor chip and the electrical measuring device through an external circuit, and a conventionally known method is appropriately used. Can be adopted and connected.

Hereinafter, examples will be described in more detail, but the present invention is not limited to the following examples.

(Example 1)
Discontinuous Galerkin Time Domain Method (DGTD), using software (“DEVICE”, Thermal Inc. https: //www.luminical.com/jp/) by the “stuckfield” command in it. An electromagnetic field simulation was carried out under the following conditions.

[Chip configuration]
The electromagnetic field simulation was performed on a chip 1 in which a glass substrate, an n-type transparent semiconductor film (TiO ₂ film), a plasmon resonance film electrode (Au film), and a sample layer were laminated in this order. Incidentally, in the electromagnetic simulation, the light source is conducted as within a glass substrate and, at the boundary surface between the n-type transparent semiconductor layer and plasmon resonance membrane electrode, the incident light (I _n) is totally reflected, and , total reflection the light (reflected light: R _n) includes an inner glass substrate, the total reflection to incident again at the interface between the n-type transparent semiconductor film opposite to the surface of the glass substrate (surface in contact with air) The light (re-incident light: In _{+ 1} ) was used, and n was set to 1 to 6.

[Parameter]
Each parameter required by the stackfield command is as follows.
n: Refractive index of each layer As the refractive index of each layer, the complex refractive index (n: refractive index, k: extinction coefficient) shown in Table 1 below was used from the refractive index of the materials constituting each layer. In the sample layer, the refractive index (RI) was changed between 1.33 and 1.40 as the refractive index of the sample solution.
d: Thickness of each layer The thickness of each layer is the thickness shown in Table 1 below.
f: the frequency wavelength l = 670 nm of the incident light, the frequency f = c / l (c: calculated by the speed of light ^{(2.99 × 10 8 m / s} ).
theta: Incident angle of light (θ)
The range was 0 to 90 °.
res: Resolution In the stackfield command, the resolution is equal to the number of divisions in the simulation range, so if the thickness of each layer is changed, the size of each calculation cell may change. Therefore, the resolution res = (1 + total thickness of each layer) / calculated cell size (rounded, calculated cell size = 0.01 nm ³ ).

After the simulation, the absorption amount of p-polarized light in the region of 20% (10 nm) thickness from the surface on the n-type transparent semiconductor film (TiO ₂ film) side of the plasmon resonance film electrode (Au film) was calculated. Also, regarding the reflected light, only the p-polarized light component was acquired.

[Confirmation of simulation]
(Reference example 1)
First, an ITO substrate (glass substrate: S-TIH11, glass substrate thickness: 1.1 mm, area: 19 × 19 mm) in which a transparent electrode made of an ITO film (indium tin oxide) is formed on one surface of the glass substrate. , ITO film: Highly durable transparent conductive film 5Ω, manufactured by Geomatec Co., Ltd.) was prepared. Then, a sputtering apparatus (QAM-4-ST, ULVAC Kyushu Co., Ltd.) was used, _TiO 2 as a target (Titanium Dioxide, 99.9%, Furuuchi Chemical Co., Ltd.) using, TiO ₂ on the ITO film A film having a thickness of 200 nm (n-type transparent semiconductor film (TiO ₂ film)) was formed. Next, using the sputtering apparatus and using Au (99.99%, manufactured by High Purity Chemical Laboratory Co., Ltd.) as a target, a 50 nm-thick film (plasmon resonance film electrode) made of Au is placed on the TiO ₂ film. (Au film)) was formed, and a chip (sensor chip) in which a glass substrate, an ITO film, an n-type transparent semiconductor film (TiO ₂ film), and a plasmon resonance film electrode (Au film) were laminated in this order was obtained.

Next, diiodomethane (first grade, manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) was applied to the surface of the obtained chip opposite to the ITO film of the glass substrate, and a right angle prism (S-TIH11, manufactured by Tokiwa Optical Co., Ltd.) was applied. The slopes having a refractive index of 1.77) were brought into close contact with each other to obtain a chip (chip with a prism) in which a prism, a glass substrate, an ITO film, a TiO ₂ film, and a plasmon resonance film electrode (Au film) were laminated in this order.

Next, the ITO film of the obtained chip with a prism and the working electrode of the current measuring device (Electrochemical Analyzer Model 802D, manufactured by ALS / CH Instruments Inc.) were used as the counter electrode and the reference electrode of the plasmon resonance film electrode and the current measuring device. Were electrically connected via the conductors. Next, a laser beam of 670 nm (light source: CPS670F, manufactured by Thorlabs) was converted into p-polarized laser light through a polarizer (CMM1-PBS251 / M, manufactured by Thorlabs), and this intensity was measured by a power meter (Model 843-R, manufactured by Thorlabs). It was measured with (manufactured by) and adjusted to 4.0 mW. Next, as shown in FIG. 10, the p-polarized laser light (4.0 mW) was irradiated from the prism side of the photoelectric conversion unit (sensor chip 18) of the obtained chip. The incident angle (θ [°]) of the p-polarized laser light (incident light) with respect to the glass substrate surface is changed between 23 ° and 37 °, and the current value between the ITO film and the plasmon resonance film electrode at each incident angle [ μA] was measured. The output current ratio [%] (right axis), which is the ratio of the incident angle (θ [°]) of the obtained light, the current value [μA] (left axis), and the current value (output current energy) to the energy of the incident light. ) Is shown in FIG. 11 (solid line (reference example 1: measured value)). On the other hand, for chip 1, the relationship between the incident angle (θ [°]) of light obtained by simulation and the current value [μA] (left axis) and output current ratio [%] (right axis) is also shown in FIG. (Dotted line (simulation)).

As shown in FIG. 11, the relationship between the light incident angle (θ), the current value (A), and the output current ratio (CA) is similar between the measured value (solid line) and the simulated value (dotted line). It was confirmed that this simulation can be performed with high accuracy.

[1] Angle dependence of reflected light intensity For chip 1, the incident light (incident light I ₁ ) obtained by simulation and the incident light are totally reflected 6 times at the interface between the n-type transparent semiconductor film and the plasmon resonance film electrode. Then, the intensity (reflected light intensity [%], incident light intensity of each reflected light (R _{1 to} R ₆ ) when the incident light (re-incident light I _{2 to} I ₆ ) that was incident again is reflected again is 100%. The result of plotting the relationship between the intensity of the reflected light and the incident angle of the light (θ [°]) is shown in FIG. In FIG. 12, the solid line at the top of the figure indicates R1, and R2, R3, R4, R5, and R6 are shown in order from the lower side.

As shown in FIG. 12, it was confirmed that the reflected light intensity decreases every time light is totally reflected at the interface between the n-type transparent semiconductor film and the plasmon resonance film electrode, that is, every time plasmon resonance occurs. ..

[2] Angle dependence of current value when enhancing incident light and current value when using reflected light For chip 1, the intensity of incident light is shown on the interface between the n-type transparent semiconductor film and the plasmon resonance film electrode in Table 2 below. The result of plotting the relationship between the incident angle (θ [°]) of the light obtained by the simulation and the output current ratio [%] when the intensity is increased to the intensity of , FIG. 13. In FIG. 13, the solid line at the bottom of the figure shows the case where the incident light intensity is 100.0%, and is 174.3%, 229.6%, 270.7%, and 301.3% in order from the upper side. It shows the time of 324.0%. In addition, Table 2 below shows the maximum and minimum values of the output current ratio [%] at each incident light intensity, and their differences (differences).

On the other hand, for chip 1, as in [1], the incident light is totally reflected 6 times at the interface between the n-type transparent semiconductor film and the plasmon resonance film electrode, and the incident light (I ₁ ) and each reflected light (R ₁ ) are reflected. When ~ R ₅ ) is used as incident light again (re-incident light I _{2 to} I ₆ ), the integrated value (output current ratio [output current ratio]) of the incident angle (θ [°]) of the light obtained by the simulation and the output current ratio. The result of plotting the relationship with%]) is shown in FIG. In FIG. 14, the solid line at the bottom of the figure shows the case where the incident light condition is I1, and shows the case of I1 + I2, I1 + I2 + I3, I1 + I2 + I3 + I4, I1 + I2 + I3 + I4 + I5, I1 + I2 + I3 + I4 + I5 + I6 in order from the upper side. In addition, Table 3 below shows the maximum and minimum values of the integrated value [%] of the output current ratio under each incident light condition, and their differences (differences).

[3] Change in the amount of current with respect to the change in the refractive index when the incident light is enhanced and the change in the refractive index when the reflected light is used. Refraction of the sample solution obtained by simulation when the intensity is increased to the intensity shown in Table 4 and the light is independently incident from the inside of the glass at an incident angle (θ) of 57.2 ° with respect to the plasmon resonance film electrode. The result of plotting the relationship between the rate and the output current ratio [%] is shown in FIG. In Table 4 below, the maximum value (when RI = 1.33), the minimum value (when RI = 1.38) of the output current ratio [%] at each incident light intensity, and their differences (differences) ) Is shown.

On the other hand, for chip 1, as in [1], the incident light is totally reflected 6 times at the interface between the n-type transparent semiconductor film and the plasmon resonance film electrode, and the incident angle (θ) from the inside of the glass to the plasmon resonance film electrode. The sample solution obtained by simulation when the incident light (I ₁ ) and each reflected light (R _{1 to} R ₅ ) were used as incident light (re-incident light I _{2 to} I ₆ ) again at 53.5 °. The result of plotting the relationship between the refractive index and the integrated value [%] of the output current ratio is shown in FIG. Further, in Table 5 below, the maximum value (when RI = 1.33) and the minimum value (when RI = 1.40) of the integrated value (output current ratio [%]) of the output current ratio under each incident light condition are shown. ), And their difference (difference).

As shown in FIGS. 12 to 16 and Tables 2 to 5, the current value is the light that is totally reflected at the interface between the n-type transparent semiconductor film and the plasmon resonance film electrode and is re-incident light (re-incident light I _2). It is enhanced by using it as ~ I ₆ ) and integrating it. In addition, the difference between the maximum and minimum integrated current values is enhanced compared to the case where the incident light is simply enhanced and irradiated. It was confirmed that excellent sensor sensitivity was achieved.

As described above, according to the electric measurement type surface plasmon resonance sensor and the sensor chip used therefor, it is possible to provide an electric measurement type surface plasmon resonance sensor having excellent sensor sensitivity and a sensor chip used therefor. Become. Further, since the sensor and the sensor chip of the present disclosure can detect the surface plasmon polariton as an electric signal, it is easy to reduce the size and increase the throughput. Further, the sensor and the sensor chip of the present disclosure do not affect the sample, so that more accurate measurement is possible. Therefore, the sensors and sensor chips of the present disclosure are very useful in the future development of medical care, foods, and environmental technologies.

1 ... light incident port, 2 ... transparent substrate, 3 ... transparent electrode, 3'... second transparent electrode, 4 ... n-type transparent semiconductor film, 4'... second n-type transparent semiconductor film, 5 ... plasmon resonance film Electrode, 5'... second plasmon resonance film electrode, 6 ... adhesive layer, 7 ... protective film, 8 ... sample layer, 9 ... reference, 10 ... prism, 11-18 ... sensor chip, 11'... second photoelectric Conversion unit, 21 ... Electrical measuring device, 31, 31'... External circuit, 200 ... Light source, 300 ... Polarizer, 401 ... Incident light, 402 ... Reflected light, 510 ... Sensor.

Claims (10)

A sensor chip in which a transparent substrate having a light incident port at the end, a transparent electrode, an n-type transparent semiconductor film, and a plasmon resonance film electrode are arranged in this order.
A reflective surface capable of reflecting light reflected between the n-type transparent semiconductor film and the plasmon resonance film electrode,
An electrical measuring device that directly measures a current value or a voltage value from the transparent electrode and the plasmon resonance membrane electrode.
To prepare
An electromeasuring surface plasmon resonance sensor characterized by this. The electromeasurement type surface plasmon resonance sensor according to claim 1, wherein the reflective surface is a boundary surface between the surface of the transparent substrate opposite to the transparent electrode and the inside of the transparent substrate. A second photoelectric in which a second transparent electrode, a second n-type transparent semiconductor film, and a second plasmon resonance film electrode are arranged in this order on the surface of the transparent substrate opposite to the transparent electrode. It further includes a conversion unit and a second electrical measuring device that directly measures a current value or a voltage value from the second transparent electrode and the second plasmon resonance film electrode.
The reflective surface is a surface between the second n-type transparent semiconductor film and the second plasmon resonance film electrode.
The electromeasurement type surface plasmon resonance sensor according to claim 1, wherein the surface plasmon resonance sensor is characterized in that. The sensor chip, wherein the combination of the n-type transparent semiconductor film and the plasmon resonance film electrode is a combination forming a shotky barrier, according to any one of claims 1 to 3. The electromeasuring surface plasmon resonance sensor described. The electromeasurement type surface according to any one of claims 1 to 4, wherein in the sensor chip, the thickness of the plasmon resonance film electrode is 200 nm or less (however, 0 is not included). Plasmon resonance sensor. In the sensor chip, the n-type transparent semiconductor film is at least one selected from the group consisting of TiO ₂ , ZnO, SnO ₂ , SrTIO ₃ , Fe ₂ O ₃ , TaON, WO ₃ , and In ₂ O ₃ . The electromeasurement type surface plasmon resonance sensor according to any one of claims 1 to 5, which is a film made of an n-type semiconductor. A sensor chip used for the electrometric surface plasmon resonance sensor according to any one of claims 1 to 6, which comprises a transparent substrate having a light incident port at an end, a transparent electrode, an n-type transparent semiconductor film, and an n-type transparent semiconductor film. An electromeasuring surface plasmon resonance sensor chip, characterized in that the plasmon resonance membrane electrodes are arranged in this order. A transparent substrate with a light incident port at the end that allows light to enter,
Plasmon resonance membrane electrode capable of converting incident light into surface plasmon polaritons,
It is arranged on the incident light side of the plasmon resonance film electrode, transmits the incident light, and is emitted from the plasmon resonance film electrode by interacting with the plasmon resonance film electrode. An n-type transparent semiconductor film capable of receiving hot electrons, and a transparent electrode capable of extracting hot electrons transferred from the n-type transparent semiconductor film as an electric signal.
With a sensor chip
A reflective surface capable of reflecting light reflected between the n-type transparent semiconductor film and the plasmon resonance film electrode,
An electrical measuring device capable of directly measuring a current value or a voltage value from the transparent electrode and the plasmon resonance membrane electrode.
With
The incident light includes incident light incident from the light incident port and reflected light reflected by the reflecting surface.
An electromeasuring surface plasmon resonance sensor characterized by this. The sensor chip used for the electromeasurement type surface plasmon resonance sensor according to claim 8, wherein a transparent substrate having a light incident port at an end, a transparent electrode, an n-type transparent semiconductor film, and a plasmon resonance film electrode are arranged in this order. An electrometric surface plasmon resonance sensor chip that is characterized by being A sensor chip in which a transparent substrate having a light incident port at the end, a transparent electrode, an n-type transparent semiconductor film, and a plasmon resonance film electrode are arranged in this order.
A reflective surface capable of reflecting light reflected between the n-type transparent semiconductor film and the plasmon resonance film electrode,
An electrical measuring device that directly measures a current value or a voltage value from the transparent electrode and the plasmon resonance membrane electrode.
It is a method of detecting changes in surface plasmon polaritons using an electromeasurement type surface plasmon resonance sensor equipped with.
The first step of injecting light from the light incident port and totally reflecting the incident light between the plasmon resonance film electrode and the n-type transparent semiconductor film;
Due to the total reflection, the incident light interacts with the plasmon resonance film electrode to generate surface plasmon polaritons, and the hot electrons generated by the surface plasmon polaritons and transferred to the n-type transparent semiconductor film are electrically signaled from the transparent electrode. The second step of measuring the change in the current value or the voltage value between the transparent electrode and the plasmon resonance film electrode by the electric measuring device;
The light totally reflected between the plasmon resonance film electrode and the n-type transparent semiconductor film is reflected on a reflective surface that can be reflected to obtain incident light again, and this is used as the plasmon resonance film electrode and the n-type transparent semiconductor film. A third step in which total reflection is performed between the two and the second step is performed again;
The fourth step of repeating the third step a plurality of times, integrating the measured changes in the current value or the voltage value, and detecting the change in the surface plasmon polariton as the integrated value;
A method for detecting changes in surface plasmon polaritons, which comprises.