JPH1078391A - Surface plasmon sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface plasmon sensor which can measure two-dimensional physical property information on a substance in a sample. SOLUTION: A metallic film 12 is formed on one surface of a transparent base board 10 having a uniform thickness, on the one hand, a light input means 15 and a light output means 16 such as two-dimensionally expanding grating are respectively formed on the other surface opposed to this one surface, and a light beam 13 incident on this light input means 15 is two-dimensionally scanned in the expanding direction of the light input means 15 by a light scanning means 17. The light beam 13 emitted outside the transparent base board 10 from the light output means 16 by being totally reflected by an interface 10a between the transparent base board 10 and a metallic film 12, is detected by a light detecting means 18.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface plasmon sensor for quantitatively analyzing a substance in a sample by utilizing the generation of surface plasmons, and more particularly, it can measure two-dimensional physical property information on a substance in a sample. And a surface plasmon sensor as described above.

[0002]

2. Description of the Related Art In a metal, free electrons vibrate collectively to generate a compression wave called a plasma wave. And, the quantization of this compression wave generated on the metal surface is
It is called surface plasmon.

Conventionally, various surface plasmon sensors for quantitatively analyzing a substance in a sample by utilizing the phenomenon that surface plasmons are excited by light waves have been proposed.
Among them, a particularly well-known one uses a system called a Kretschmann configuration (see, for example, JP-A-6-167443).

A conventional surface plasmon sensor using the above system basically includes a prism, a metal film formed on one surface of the prism and brought into contact with a sample, a light source for generating a light beam, and a light source for generating the light beam. An optical system that passes through the prism and enters the interface between the prism and the metal film so that various angles of incidence can be obtained, and the intensity of the light beam totally reflected at the interface can be detected at various angles of incidence And light detecting means.

In order to obtain various angles of incidence as described above, a relatively narrow light beam may be deflected and incident on the interface, or a component which is incident on the light beam at various angles may be included. As described above, a relatively thick light beam may be incident so as to be focused at the interface. In the former case, the light beam whose emission angle changes with the deflection of the light beam is detected by a small photodetector that moves synchronously with the deflection of the light beam, or by an area sensor extending along the change direction of the emission angle. Can be detected. On the other hand, the latter case can be detected by an area sensor extending in a direction in which all light beams emitted at various emission angles can be received.

In the surface plasmon sensor having the above-mentioned structure, when a light beam of P-polarized light (polarized light component perpendicular to the sensor surface) is incident on the metal film at a specific incident angle θ _SP equal to or larger than the total reflection angle, the metal film is An evanescent wave having an electric field distribution is generated in the sample in contact with the surface, and the evanescent wave excites surface plasmons at the interface between the metal film and the sample. When the wave number vector of the evanescent light is equal to the wave number of the surface plasmon and the wave number matching is established, the two are in a resonance state, and the light energy is transferred to the surface plasmon, so the intensity of the light totally reflected at the interface between the prism and the metal film Drops sharply.

When the wave number of the surface plasmon is known from the incident angle θ _{SP at} which this phenomenon occurs, the dielectric constant of the sample can be obtained.
That is, when the wave number of the surface plasmon is K _SP , the angular frequency of the surface plasmon is ω, c is the speed of light in vacuum, ε _m and ε _s are metal and the dielectric constant of the sample, respectively, the following relationship is obtained.

[0008]

(Equation 1)

If the dielectric constant ε _s of the sample is known, the concentration of the specific substance in the sample can be determined based on a predetermined calibration curve or the like, and eventually, the incident angle (the angle of elimination of total reflection) θ at which the reflected light intensity decreases. Knowing the _SP enables quantitative analysis of a specific substance in the sample.

[0010]

When analyzing a substance in a sample, it is sometimes necessary to obtain two-dimensional physical property information. However, with the above-described conventional surface plasmon sensor, it has been difficult to obtain two-dimensional physical property information of a substance in a sample. That is, when the light beam is two-dimensionally scanned at the interface between the prism and the metal film in order to obtain two-dimensional physical property information, the optical path length of the light beam in the prism changes, and, for example, In some cases, correct analysis cannot be performed due to a change in the position of the convergence point of the light beam that should be present.

The present invention has been made in view of the above circumstances, and has as its object to provide a surface plasmon sensor capable of measuring two-dimensional physical property information on a substance in a sample.

[0012]

According to the surface plasmon sensor of the present invention, a transparent substrate having a uniform thickness is used in place of the prism used in the conventional surface plasmon sensor, and a metal film is formed on one surface of the transparent substrate. On the other surface facing the one surface, a light input means and a light output means which are respectively spread two-dimensionally are formed, and the light beam incident on the light input means is scanned by the light scanning means to form the light beam. The light beam is made to scan two-dimensionally in the spreading direction of the input means, and the light beam emitted from the light output means to the outside of the transparent substrate after being totally reflected at the interface between the transparent substrate and the metal film is detected by the light detection means. Things.

As the light input means and light output means which spread two-dimensionally as described above, for example, a grating (diffraction grating) can be suitably used.

[0014]

According to the surface plasmon sensor of the present invention having the above structure, the sample in contact with the metal film can be analyzed by the same mechanism as in the conventional surface plasmon sensor.

When the light beam incident on the light input means is scanned as described above, the light beam scans two-dimensionally at the interface between the transparent substrate and the metal film. Therefore, if a light beam totally reflected at the interface and emitted from the light output means to the outside of the transparent substrate is detected by the light detection means, the two-dimensional material of the sample in contact with the metal film is detected from the light detection means. A signal indicating physical property information can be obtained.

The two-dimensional scanning of the light beam is performed in the direction in which the light input means spreads, that is, in a direction parallel to the surface of the transparent substrate. On the other hand, since the thickness of the transparent substrate is uniform, even if the two-dimensional scanning is performed. The optical path length of the light beam in the transparent substrate does not change. Therefore, the analysis is not hindered by the change in the optical path length.

[0017]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a side surface shape of a surface plasmon sensor according to a first embodiment of the present invention, and FIG. 2 is an exploded perspective view thereof. As shown, the surface plasmon sensor includes a transparent substrate 10 having a uniform thickness, for example, made of glass,
A metal film 12 made of, for example, gold, silver or the like formed on one surface (upper surface in the figure) and brought into contact with the sample 11 and a light source 14 made of a semiconductor laser or the like for generating one thin light beam 13 And

On the other surface of the transparent substrate 10, that is, on the lower surface in the figure, a light input grating (diffraction grating) 15 and a light output grating 16 extending two-dimensionally along the surface are formed. I have. On the other hand, the light source 14 is fixed to the XY scanner stage 17 in a predetermined direction. On the XY scanner stage 17, a light detecting means 18 such as a photodiode is fixed in a predetermined direction.

The XY scanner stage 17 includes a driver 20
Driven by, in a plane parallel to the surface of the transparent substrate 10,
The substrate 10 moves in the vertical and horizontal directions (XY directions). On the other hand, the photodetection signal S output from the photodetection means 18 is amplified by an amplifier 21, digitized by an A / D converter 22, and input to a data processing and control unit 23 composed of, for example, a computer system. The operation of the driver 20 described above is controlled by the data processing and control unit 23. The data processing and control unit 23 is connected to an image display means 24 such as a CRT display device.

For example, a sample 11 such as a gel sheet used for electrophoresis is placed on a metal film 12 at the time of analysis.
Then, the light beam 13 set to P-polarized light is made incident on the light input grating 15 at a predetermined incident angle. The light beam 13 is diffracted by the light input grating 15 and is incident on the transparent substrate 10, and is incident on the interface 10 a between the transparent substrate 10 and the metal film 12. The light beam 13 is totally reflected at the interface 10a, enters the light output grating 16, diffracts there, and exits the transparent substrate 10. The emitted light beam 13 is
The light is detected by the light detecting means 18.

When the intensity of the light beam 13 is measured by the light detecting means 18, based on the light detection signal S output from the light detecting means 18, the substance 30 in the sample 11 and in contact with the metal film 12 is detected. Can be detected and analyzed. In the present embodiment, the analysis is specifically performed as follows.

The incident angle θ of the light beam 13 with respect to the interface 10a
The relationship between the intensity of the light detection signal S output from the light detection means 18 (the intensity of the light beam 13 totally reflected) is substantially as shown in FIG. That is, the light beam 13 incident at a specific incident angle θ _SP excites surface plasmons at the interface between the metal film 12 and the sample 11, so that the intensity of the reflected light sharply decreases at this time. If the incident angle (the angle of total reflection elimination) θ _SP is known, the substance 30 in the sample 11 can be quantitatively analyzed based on the angle. In this example, the total reflection elimination angle θ _SP is obtained indirectly. ing.

That is, here, the incident angle θ of the light beam 13
Is a constant angle θ _S smaller than the total reflection elimination angle θ _SP
Is set to The intensity I _S of the light detection signal S when the incident angle is theta _S, since changes in accordance with the value of total reflection eliminated angle theta _SP, the total reflection eliminate angle theta _SP on the basis of the signal intensity I _S Knowing that, the substance 30 in the sample 11 can be quantitatively analyzed.

In this apparatus, the XY scanner stage 17
Move in the XY directions, the light beam 13 moves two-dimensionally in the spreading direction of the light input grating 15,
Two-dimensional scanning is performed on the interface 10a. Therefore, the light detection signal S continuously output from the light detection means 18 during this scanning indicates two-dimensional physical property information of the analysis target substance 30 distributed in the sample 11. Therefore, after the light detection signal S is digitized as described above, if predetermined data processing is performed in the data processing and control unit 23, the two-dimensional physical property information is imaged based on the light detection signal S, The image can be displayed on the image display means 24.

Here, the two-dimensional scanning of the light beam 13 is performed in a direction parallel to the surface of the transparent substrate 10, and the thickness of the transparent substrate 10 is uniform. The optical path length of the light beam 13 in 10 does not change. Therefore, correct analysis is not hindered by this change in optical path length.

In order to scan the light beam 13, in addition to the above, the light source 14 and the light detecting means 18 may be fixed and the transparent substrate 10 may be moved.

As shown in FIG. 4, a plurality of regions 12a, 12a, 12a... Are set in the metal film 12 and different functional thin films are formed in each region, so that each region has a different function. An analysis can be performed for each region by causing an immune reaction or the like.

Further, as in the second embodiment shown in FIG. 5, a lens 32 for converting the light beam 13 emitted from the light source 14 into divergent light, and a cylindrical lens for converging the light beam 13 only in a plane parallel to the paper surface. An optical system including the lens 33 may be provided so that the light beam 13 includes components incident on the interface 10a at various incident angles. In that case, a CCD or a photodiode array extending in a direction in which each light beam 13 emitted from the interface 10a at various emission angles can be received, a photodiode array, a two-division photodiode, or the like is used as the light detection means 18 and based on the output thereof. What is necessary is _just to detect the total reflection elimination angle θ _SP described above.

[Brief description of the drawings]

FIG. 1 is a side view of a surface plasmon sensor according to a first embodiment of the present invention.

FIG. 2 is an exploded perspective view of the surface plasmon sensor.

FIG. 3 is a graph showing a schematic relationship between an incident angle of a light beam on an interface between a transparent substrate and a metal film and a total reflection light intensity in a surface plasmon sensor.

FIG. 4 is a perspective view showing another example of the metal film in the surface plasmon sensor of the present invention.

FIG. 5 is a side view showing a part of the second embodiment of the present invention.

[Explanation of symbols]

 10 Transparent substrate 10a Interface between transparent substrate and metal film 11 Sample 12 Metal film 13 Light beam 14 Light source 15 Light input grating 16 Light output grating 17 XY scanner stage 18 Light detection means 20 Driver 21 Amplifier 22 A / D converter 23 Data processing and control unit 24 Image display means 30 Analyte 32 Lens 33 Cylindrical lens

Claims (2)

[Claims] 1. A transparent substrate having a uniform thickness, a metal film formed on one surface of the transparent substrate and brought into contact with a sample, a light source for generating a light beam, and a transparent substrate facing the one surface. A light input unit that spreads two-dimensionally on another surface and guides the irradiated light beam to an interface between the transparent substrate and the metal film; and two-dimensionally spreads on the other surface and totally reflects at the interface. Light output means for emitting the light beam emitted out of the transparent substrate; light detection means for detecting the intensity of the light beam emitted out of the transparent substrate; and light input means for inputting the light beam incident on the light input means. A surface scanning plasmon sensor comprising: a light scanning unit for performing two-dimensional scanning in a spreading direction of the object. 2. The surface plasmon sensor according to claim 1, wherein said light input means or light output means comprises a grating.