JP2000266667A - Surface plasmon sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the effect of an interference fringe generated by an interference between light beams totally reflected at the interface of a dielectric body and a metallic film and, light beams reflected at the other part. SOLUTION: The sensor has a dielectric 10 constituting a prism or the like, a metallic film 12 formed on one face of the dielectric and brought into contact with a sample 11, a light source 14 for generating light beams 13, and an optical system 15 for passing the light beams 13 through the dielectric body 10 to be incident on an interface of the dielectric body 10 and metallic film 12 with various angle of incidence. A light-detecting means 20 is set adjacent to a surface opposite to the interface side of the metallic film 12, which specifies and detects a position where a scattering light 25 is generated from the metallic film 12.

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, to a light incident on an interface between a dielectric and a metal film. The present invention relates to a surface plasmon sensor for detecting scattered light generated on the back side of a metal film and analyzing a sample when total reflection is eliminated.

[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 surface plasmon sensor using the above system basically includes, for example, a dielectric formed in a prism shape,
A metal film formed on one surface of the dielectric and brought into contact with a sample, a light source for generating a light beam, and passing the light beam through a dielectric to make various incidents on an interface between the dielectric and the metal film The optical system includes an optical system for making an incident light so as to obtain an angle, and light detecting means capable of detecting the intensity of the light beam totally reflected at the interface at each of various incident angles.

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 reflection 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 direction of the change in the reflection 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 reflected at various reflection angles can be received.

In the surface plasmon sensor having the above structure, when a light beam is made incident on a metal film at a specific incident angle θ _SP equal to or larger than the total reflection angle, an evanescent wave having an electric field distribution is formed in a sample in contact with the metal film. Is generated, and surface plasmons are excited at the interface between the metal film and the sample by the evanescent wave. 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, both are in a resonance state, and the light energy is transferred to the surface plasmon, so that total reflection occurs at the interface between the dielectric and the metal film. The intensity of the light is sharply reduced.

When the wave number of the surface plasmon is known from the incident angle θ _{SP at} which this phenomenon occurs (this is generally called the angle for eliminating total reflection), 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. Therefore, by knowing the incident angle θ _{SP at} which the reflected light intensity decreases, The specific substance in the sample can be quantitatively analyzed.

[0010]

In a conventional surface plasmon sensor of the type described above, the interference between the light beam totally reflected at the interface between the dielectric and the metal film and the light beam reflected at other parts is caused. Interference fringes may occur. Such interference fringes hinder the detection of the totally reflected light beam, which may impair the accuracy of the sample analysis.

Accordingly, an object of the present invention is to provide a surface plasmon sensor capable of ensuring high accuracy of sample analysis without being affected by the interference fringes.

[0012]

According to the surface plasmon sensor of the present invention, as described above, when the total reflection is eliminated in the light beam incident on the interface between the dielectric and the metal film at the incident angle θ _SP , This is based on the new finding that scattered light is generated on the back side of the metal film (opposite to the interface) at the beam incident position, and total reflection is eliminated by detecting the position where the scattered light is generated. The angle θ _SP can be obtained.

More specifically, the surface plasmon sensor according to the present invention comprises, for example, a dielectric formed in a prism shape, a metal film formed on one surface of the dielectric and brought into contact with a sample, and a light beam. A light source that generates
An optical system for passing this light beam through the dielectric and entering the interface between the dielectric and the metal film so as to obtain various incident angles, and an opposite side of the interface between the metal film and the metal film And a light detecting means disposed close to the surface and capable of specifying a position where the scattered light emitted from the metal film is generated and detecting the scattered light.

In this surface plasmon sensor, more preferably, there is provided means for calculating the angle of incidence of the light beam incident on this position from the position of the scattered light indicated by the output of the light detecting means.

[0015]

According to the surface plasmon sensor of the present invention, if the position where the scattered light emitted from the metal film is generated is specified and detected, the incident angle of the light beam incident on the position where the scattered light is generated is determined by the optical angle. For example, it can be obtained by calculation based on the configuration of the system. Since the incident angle is the total reflection elimination angle θ _SP , the specific substance in the sample can be quantitatively analyzed based on the total reflection elimination angle θ _{SP as} in the related art.

As described above, the means for calculating the incident angle (the angle of elimination of total reflection) θ _SP of the light beam incident on this position from the scattered light generation position indicated by the output of the light detecting means is provided. Without the need for manual calculations,
The total reflection elimination angle θ _SP can be automatically obtained.

[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, partially cut away. As shown in the figure, this surface plasmon sensor includes a prism 10 having a triangular cross section made of glass as a dielectric, and a prism 10 formed on one surface (upper surface in the figure) 10 a of the prism 10 and brought into contact with a sample 11. , A metal film 12 made of silver or the like, a light source 14 made of a semiconductor laser or the like for generating one light beam 13, and a light beam 13 emitted from this light source 14 in a divergent light state in one direction (A right angle direction) only, and a cylindrical lens 15
A polarizing plate 16 arranged on the optical path of the light beam 13 that has passed through, and a container 17 for storing the liquid sample 11.

Further, this surface plasmon sensor has a structure in which the metal film 12 is exposed from the side opposite to the prism 10.
CCD camera 20 as light detecting means arranged in close proximity to
An imaging lens 21 disposed between the CCD camera 20 and the metal film 12, a personal computer 22 to which an image signal S output from the CCD camera 20 is input, and a CRT connected to the personal computer 22. And an image monitor 23 such as a display device.

The light source 14 and the polarizing plate 16 are arranged so that the light beam 13 is incident on the one surface 10a of the prism 10 in a p-polarized state. The light beam 13 is incident on one surface 10a of the prism 10 in a diverging state in a plane parallel to the plane of the drawing. That is, the light beam 13 incident on the prism surface 10a is composed of components incident at various incident angles θ.

The operation of the surface plasmon sensor according to the present embodiment having the above configuration will be described below. The sample 11 to be analyzed is stored in the container 17 as shown in the drawing, and comes into contact with the metal film 12. In this state, the light source 14 is driven, and the light beam 13 is incident on one surface 10a of the prism 10. The light beam 13 is basically totally reflected at the interface between the metal film 12 and the prism 10, but for a component incident on the interface at a specific incident angle θ, the reflected light intensity sharply decreases, which is called total reflection elimination. A phenomenon can occur.

Since the incident angle θ _{SP at} which this phenomenon occurs corresponds to the dielectric constant of the sample 11, the specific substance in the sample 11 can be quantitatively analyzed if the total reflection cancellation angle θ _SP is known. As described above, in this example, the total reflection elimination angle θ _SP is obtained as described below.

When total reflection is eliminated in the light beam 13 incident at the incident angle θ _SP , scattered light 25 is generated on the back side of the metal film 12 (on the side opposite to the interface) at the incident position of the light beam 13. The situation on the metal film 12 is represented by C
An image is formed on the imaging surface of the CD camera 20 and the scattered light 25
Is imaged by the CCD camera 20.

The image signal S output from the CCD camera 20 is
For example, by directly inputting the image to the image monitor 23 and reproducing the image, it is possible to observe from which position on the metal film 12 the scattered light 25 is generated. In this way, the position where the scattered light 25 is generated is known, and the total reflection elimination angle θ _SP can be obtained by manual calculation based on this and the configuration of the optical system.

In this embodiment, in addition to the above, an image signal S indicating the position where the scattered light 25 is generated is input to the personal computer 22, and the total reflection elimination angle θ _SP is automatically calculated by the personal computer 22. It is also possible to ask for. Still further, personal computers
According to 22, it is also possible to automatically analyze a sample from the total reflection elimination angle θ _SP based on a predetermined program.

Next, a second embodiment of the present invention will be described. FIG. 2 is a partially cutaway side view of a surface plasmon sensor according to a second embodiment of the present invention. In FIG. 2, elements that are the same as the elements in FIG. 1 are given the same reference numerals, and descriptions thereof will be omitted unless otherwise necessary (the same applies hereinafter).

As shown, the surface plasmon sensor includes a light source 14 having a collimator lens,
A cylindrical lens 30 that converges the light beam 13 in a parallel light state emitted from the plane only in a plane parallel to the drawing plane, and a light beam 13 that diverges in the plane after passing through the cylindrical lens lens 30 Cylindrical lens 31 and a plurality of slits 32 arranged regularly in the vertical and horizontal directions
And a plurality of recesses 34 for storing the sample 11
a, each of which has a cylindrical well 35 without a bottom therein. In the container 34, the same metal film 12 as described above is disposed at the bottom of each recess 34a.

The number of the slits 32 is equal to the number of the concave portions 34a (for example, 96) corresponding to each of the concave portions 34a of the container 34 made of dielectric plastic.

In the surface plasmon sensor according to the present embodiment, the light beam 13 incident on the slit plate 33 via the cylindrical lens 31 is applied to each slit 32 of the slit plate 33.
Out in a divergent light state in a plane parallel to the plane shown,
Each irradiates the metal film 12. That is, the light beam 13 incident on the metal film 12 is composed of components incident at various incident angles θ.

Also in this case, a specific incident angle θ is applied to each metal film 12.
, Total reflection can be eliminated. Then, the incident angle θ _{SP at which} this phenomenon occurs (total reflection elimination angle)
Corresponds to the dielectric constant of the sample 11 stored in each of the recesses 34a, so that the specific substance in each sample 11 can be quantitatively analyzed by measuring the total reflection elimination angle θ _SP for each of the recesses 34a. is there.

In this example, similarly to the first embodiment, the scattered light 25 generated on the back side of the metal film 12 when the total reflection is eliminated is measured to measure the total reflection elimination angle θ _SP. Recess
All the scattered light 25 generated for each of the concave portions 34a are simultaneously detected by the CCD camera 20, and the analysis of the sample 11 stored in each concave portion 34a can be performed in parallel.

FIG. 3 schematically shows a photographed image of the CCD camera 20. The generation position of the captured scattered light 25 in the left-right direction in the figure (this coincides with the left-right direction in FIG. 2) corresponds to the total reflection elimination angle θ _SP, and based on these scattered light generation positions The total reflection elimination angle θ _SP can be obtained by

Next, a third embodiment of the present invention will be described. FIG. 4 is a partially cutaway side view of a surface plasmon sensor according to a third embodiment of the present invention. In this embodiment, a glass block 50 is used as an alternative to the prism 10 in the apparatus of FIG. A bubble 51 is formed in the glass block 50, and the light beam 13 emitted from the light source 14 is incident on the bubble 51.

The bubble 51 in the glass block 50 acts like a concave lens and diverges the light beam 13. Therefore, also in this case, the light beam 13 enters the interface between the metal film 12 and the glass block 50 at various incident angles θ.

In this embodiment, as in the first embodiment, the position where the scattered light 25 is generated is specified and detected to measure the total reflection elimination angle θ _SP, and the total reflection elimination angle θ _SP is measured. The specific substance in the sample 11 can be quantitatively analyzed based on the _SP .

[Brief description of the drawings]

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

FIG. 2 is a partially cutaway side view of a surface plasmon sensor according to a second embodiment of the present invention.

FIG. 3 is a schematic diagram showing a scattered light detection image in the surface plasmon sensor of FIG. 2;

FIG. 4 is a partially cutaway side view of a surface plasmon sensor according to a third embodiment of the present invention.

[Explanation of symbols]

 10 Prism 10a One side of prism 11 Sample 12 Metal film 13 Light beam 14 Light source 15 Cylindrical lens 16 Polarizer 17 Sample container 20 CCD camera 21 Imaging lens 22 Image monitor 25 Scattered light 30, 31 Cylindrical lens 32 Slit 33 Slit plate 34 Container 34a Container recess 50 Glass block 51 Bubbles

Claims (3)

[Claims] 1. A dielectric, a metal film formed on one surface of the dielectric and brought into contact with a sample, a light source for generating a light beam, and passing the light beam through the dielectric, An optical system for entering the interface with the metal film so that various angles of incidence are obtained; and an optical system disposed close to the surface of the metal film opposite to the interface, and emitting from the metal film. A surface plasmon sensor comprising light detection means capable of detecting a scattered light to be generated by specifying its generation position. 2. The apparatus according to claim 1, further comprising means for calculating an incident angle of the light beam incident on the position from the position where the scattered light is indicated by the output of the light detecting means.
Surface plasmon sensor as described. 3. The surface plasmon sensor according to claim 1, wherein the dielectric forms a prism.