JPH09257697A - Surface plasmon resonance sensor apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface plasmon resonance snesor apparatus by which a surface pasmon resonance angle can be measured with high accuracy even by using a light source such as an LED lamp which radiates light which is not coherent. SOLUTION: Images of an LED lamp as a light source, i.e., the image 6 of an LED chip and the image 7 of an electrode in its circumference, are projected on the light reflection face of a sensor chip 3 at a surface plasmon resonance sensor apparatus. A small metal-thin-film spot 5 which is used to generate surface plasmon resonance is formed on the light reflection face. The metal-thin- film spot 5 is small to such an extent that it can be put completely inside the image 6 of the LED chip as the light source. Only the light, of the image 6 of the LED chip, which is incident on the metal-thin-film spot 5 out of light from the light source is reflected with a refractive index profile due to the surface plasmon resonance, and other light is reflected totally unformly. Instead of forming the small metal-thin-film spot 5, a metal thin film is formed over a wide area, the surface of the metal thin film is covered with a coating film whose refractive index is higher than that of the sensor chip 3, and a small spot window may be opened in the coating film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface plasmon resonance sensor device utilizing a surface plasmon resonance phenomenon, and more particularly to improvement of a sensor chip thereof.

[0002]

2. Description of the Related Art A surface plasmon resonance sensor is known which measures the refractive index of a solution or the like and its variation by utilizing the surface plasmon resonance phenomenon. Here, since the fluctuation of the refractive index of the solution reflects the fluctuation of the amount of the substance in the solution, for example, as a biosensor used in the fields of biochemistry, molecular biology, medical examination, etc., this surface plasmon resonance The sensor is being used.

The surface plasmon resonance sensor is basically composed of
A light source, a high refractive index light transmission medium having a light reflection surface having a metal thin film, and a photodetector are provided. The light transmission medium is generally made of a high refractive index material such as glass or acrylic and is called a sensor chip. With a sample such as blood or urine in contact with the outer surface of the metal thin film formed on the light-reflecting surface of the sensor chip, a light beam is incident on the light-reflecting surface from the light source to the light-reflecting surface through the sensor chip at a total reflection angle. The material state of the sample is inspected by receiving the reflected light with a photodetector and measuring the incident angle (plasmon resonance angle) at which extinction due to surface plasmon resonance occurs.

The light source of the surface plasmon resonance sensor device is generally an LED (light emitting diode) or LD.
(Laser diode) is used. When the LD is used, the beam diameter of the laser light can be narrowed down to about 1 μm. On the other hand, in the case of the LED, unlike the LD, it is not possible to emit coherent light. Therefore, the light emitted from the LED should be condensed to a level as small as the laser light from the LD by using any optical system. I can't. Also,
In a commonly used LED lamp, an LED wafer chip (LED chip) is mounted on an electrode having a high light reflectance. This is because the purpose of the electrode is to have a function as a reflecting mirror to improve the light extraction efficiency. Therefore, the light reflected by the electrodes is also emitted outside the lamp. As a result, when the light emitted from the LED lamp is focused on the light reflection surface of the sensor chip through the optical system, the light directly entering the lens from the LED chip of the lamp and reflected by the electrode are reflected. Each of the lights incident on the lens is focused on the focal point.

[0005]

FIG. 1 shows a plane layout of an LED lamp and an illuminance distribution of an LED lamp image projected on a light reflecting surface of a sensor chip.

As shown in FIG. 1, in an LED lamp, a small LED chip 1 is mounted on a large electrode 2. Therefore, the LED lamp image also includes the small LED chip image 1a and the large electrode image 2a. The illuminance distribution of this lamp image is a distribution having two peaks on both sides corresponding to the edges of the electrode image 2 in addition to the central peak corresponding to the LED chip image 1a.

FIG. 2 shows how plasmon excitation light enters and reflects on the light reflecting surface of the sensor chip when an LED lamp is used as the light source.

The sensor chip 3 is, for example, a glass plate 4 having a high refractive index and having a metal thin film 5 on the light reflecting surface. The light reflection surface of the sensor chip 3 has LEs as shown in FIG.
A D-lamp image is formed, and its illuminance distribution has three peaks at the center and on both sides as shown in the figure, and surface plasmon resonance can occur at each peak location. Therefore, a ray bundle having a reflectance distribution associated with surface plasmon resonance is reflected from each peak portion.

As a result, in the photodetector, as shown in FIG. 3, the reflectance distributions (dotted lines) of the reflected ray bundles are combined,
As a whole, a reflectance curve (solid line) having a broad peak is observed. However, in order to measure the plasmon resonance angle with high accuracy, a waveform having a sharper peak is required.

Therefore, the present invention provides a surface plasmon resonance sensor device capable of measuring the plasmon resonance angle with high accuracy even when using a light source that emits non-coherent light such as an LED lamp. With the goal.

[0011]

The surface plasmon resonance sensor device of the present invention is configured such that the metal thin film causes surface plasmon resonance only on the spot area smaller than the light source image on the light reflecting surface of the sensor chip. It is characterized by

In one embodiment, the metal thin film is formed only in the spot area on the light reflecting surface. In another embodiment, the metal thin film is formed over a large area, but its surface is covered with an overcoat film having a refractive index higher than that of the light transmission medium of the sensor chip. Moreover, the overcoat film has a small spot window corresponding to the spot area. Therefore,
Only the part corresponding to the spot area on the surface of the metal thin film,
The sample can be exposed to the outside through the spot window to contact the sample. In still another embodiment, a light shielding film is arranged on the optical path near the light reflecting surface, and the light shielding film has a small spot window corresponding to the spot area. Therefore, of the light forming the light source image, only the light of the image portion corresponding to the spot region passes through the spot window and can participate in the surface plasmon resonance.

According to the present invention, the surface plasmon resonance is generated in the metal thin film only in the spot area smaller than the light source image. Therefore, a sufficiently small light source image cannot be formed by using a light source that emits non-coherent light. Even in this case, only the light in the spot area having the desired small size is reflected with the reflectance distribution associated with the surface plasmon resonance,
The photodetector can observe the reflectance distribution with a sharp peak. Therefore, high measurement accuracy can be obtained.

For example, when the LED lamp as shown in FIG. 1 is used, it is desirable that the spot area has a small size so as to fit within the LED chip image 1a. Thereby, only the light forming the LED chip image 1a excites the surface plasmon wave, and the light forming the electrode image 2a does not excite the surface plasmon wave, so that the measurement accuracy is improved.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 4 is a plan view showing the structure of the reflecting surface of the sensor chip of the surface plasmon resonance sensor according to the first embodiment of the present invention.

The sensor chip 3 comprises a transparent glass plate 4 having a high refractive index and a metal thin film spot 5 deposited on the light reflecting surface of the glass plate 3. Note that an acrylic resin plate is also suitable instead of the glass plate 4. The metal thin film spot 5 is a thin film of gold or silver for causing surface plasmon resonance, and has a film thickness of about 50 nm.

FIG. 4 also shows an image of an LED lamp, which is a light source, projected on the light-reflecting surface of the sensor chip 3, that is, an LED chip image 6 and an electrode image 7 on the periphery thereof.

The important point here is the metal thin film spot 5
Is the same size as or smaller than the LED chip image 6 and is accommodated in the area of the LED chip image 6. The shape of the thin film spot 5 is preferably circular, but may be other shape such as square. As a patterning method of the thin film spot 5, there are a method using a photolithography technique, a method of covering with a mask at the time of vapor deposition of gold, and the like.

As described above, the metal thin film spot 5 is the LED.
Since it falls within the area of the chip image 6, the light flux forming the electrode image 7 does not excite surface plasmon waves. Therefore, since only the light flux forming the LED chip image 6 excites the surface plasmon wave, a sharp reflectance curve due to a single light flux is observed in the photodetector, and the plasmon resonance angle can be measured with high accuracy.

FIG. 5 is a configuration diagram of a sensor chip according to the second embodiment, (a) is a plan view of a light reflecting surface, and (b) is a plan view.
FIG. 4 is a vertical sectional view of a sensor chip.

The sensor chip 13 has a glass plate 14, a metal thin film 15 formed on a light reflecting surface of the glass plate 14 over a wide area (for example, the entire surface) by vapor deposition, and the surface of the metal thin film 15 has a small spot-like shape. It is provided with an overcoat film 18 which covers only the window. Therefore, only the spot window portion 15a of the surface of the metal thin film 15 is exposed to the outside. The size of the spot exposed portion 15a of the metal thin film 15 is the same as that of the metal thin film spot 5 shown in FIG.
It is small enough to fit within the area of the D-chip image 6. The refractive index of the overcoat film 18 is equal to or higher than the refractive index of the glass plate 4. As a method for patterning the overcoat film 18, there are a photolithography technique and a method of vapor deposition using a mask.

According to this sensor chip 13, since only the spot exposed portion 15a of the metal thin film 15 can contact the external sample, surface plasmon wave resonance occurs at this spot exposed portion 15a, but other overcoats are formed. In the portion covered with the film 18, the surface plasmon resonance does not occur because the refractive index of the overcoat film 18 is higher than that of the glass plate 14. As a result, only the light flux of the LED chip image 6 reflected by the spot exposed portion 15a shows the reflectance distribution due to the surface plasmon resonance, so that a sharp reflectance curve is observed in the photodetector, and it is highly accurate. The plasmon resonance angle can be measured.

If the overcoat film 18 is too thin, the evanescent wave that oozes from the surface of the metal thin film 15 permeates the overcoat film 18 and oozes into the sample, so that surface plasmon resonance occurs. appear. FIG. 6 shows the thickness of the overcoat film 18 and this overcoat film 1.
8 is a characteristic diagram showing the relationship of the reflectance of the excitation light from the light reflecting surface in the place where 8 exists. In addition, this characteristic curve shows that the wavelength of the light source = 660 nm, the film thickness of the metal thin film 15 = 5.
0 nm, refractive index of glass plate = 1.523, refractive index of external sample (water) = 1.3325, overcoat film 1
8 was measured under the condition of dielectric constant = 2.32.

As shown in FIG. 6, the overcoat film 18
The light reflectance increases as the film thickness increases. This means that as the film thickness increases, the occurrence of surface plasmon resonance decreases and the absorption of light energy decreases. From this result, when the thickness of the overcoat film 18 is 50 nm or more, the occurrence of surface plasmon resonance is substantially suppressed,
It can be seen that the measurement can be performed only in the spot area portion 15a.

FIG. 7 is an exploded perspective view of the sensor chip according to the third embodiment.

The sensor chip 23 comprises a glass plate 24 and a metal thin film 25 deposited on its light reflecting surface. Furthermore,
On the light incident surface of the glass 24, a triangular prism 3 for guiding light from an LED lamp (not shown) to a light reflecting surface and guiding light reflected from the light reflecting surface to a photodetector (not shown).
0 is joined. A light-shielding film 31 of chromium or the like is vapor-deposited on the surface of the triangular prism 30 that is joined to the glass plate 24, leaving only a small spot-shaped window 31a. The film thickness of the light shielding film 31 is thick enough not to transmit light. The spot window 31a is the LED of the light from the LED lamp.
Only the light forming the chip image 6 (see FIG. 4) is passed. The patterning method of the light shielding film 31 includes a photolithography technique and the like. Instead of the triangular prism 30, various types of optical elements such as prisms of other shapes and light guide plates can be used.

Also in this sensor chip 23, the LED
Since only the light forming the chip image 6 excites the surface plasmon wave, it is possible to perform highly accurate measurement with a sharp reflectance curve.

It is a sectional view of a sensor chip according to a fourth embodiment.

In this sensor chip, a fluororesin layer 46 is formed on the surface of the glass plate 44, and a spot window 46a smaller than the LED chip image 6 is opened in the fluororesin layer 46, and the spot window 46a is formed thereon. A metal thin film 45 is formed. Therefore, the metal thin film 45 is in contact with the glass plate 44 only in the area of the spot window 46a, and is in contact with the fluororesin layer 46 in other areas. This sensor chip is used for inspection of an aqueous solution, but the refractive index of the fluorine resin layer 46 is slightly smaller than that of water. Therefore, the spot window 46a
Since surface plasmon resonance occurs only in the area of
Highly accurate measurement using only the light forming the D-chip image 6 is possible.

The present invention is not limited to the embodiment described above,
It can be implemented in various modes with variations, improvements, and modifications. For example, the light source image formed on the light-reflecting surface of the sensor chip does not need to have the form shown in FIGS. 1 and 4, and may have another form, such as an image having only a single illuminance peak. However, the present invention can be applied. Further, the form of the light transmission medium forming the sensor chip is not limited to the glass or acrylic plate as in the embodiment, but a light transmission medium of any form such as a block like a prism or a light guide plate is used. The present invention can be applied to a sensor chip.

[0032]

According to the present invention, the surface plasmon resonance angle can be measured with high accuracy even when a light source that emits light that is not coherent is used.

[Brief description of drawings]

FIG. 1 is a plan view of a general LED lamp and its LE.
It is explanatory drawing which shows the illuminance distribution of the image of D lamp.

FIG. 2 is an explanatory diagram showing a form of excitation light on a light reflecting surface of a sensor chip of a surface plasmon resonance sensor device using an LED lamp as a light source.

FIG. 3 is a characteristic diagram showing a reflectance distribution curve of reflected light of a surface plasmon resonance sensor device using an LED lamp as a light source.

FIG. 4 is a plan view showing a configuration of a light reflecting surface of the sensor chip according to the first embodiment of the present invention and an LED lamp image.

FIG. 5 is a plan view (a) and a sectional view (b) showing a configuration of a sensor chip according to a second embodiment.

FIG. 6 is a characteristic diagram showing the relationship between the thickness of an overcoat film and the reflectance of excitation light.

FIG. 7 is an exploded perspective view of a sensor chip according to a third embodiment.

FIG. 8 is a sectional view of a sensor chip according to a fourth embodiment.

[Explanation of symbols]

 1 LED chip 2 Electrodes 3, 13, 23 Sensor chip 4, 14, 24, 44 Glass plate 5 Metal thin film spot 6 LED chip image 7 Electrode image 15, 25, 45 Metal thin film 15a Metal thin film spot exposed portion 18 Overcoat film 31 Light-shielding film 31a Light-shielding film spot window 46 Fluoro resin layer 46a Fluoro resin layer spot window

Claims (13)

[Claims] 1. A surface plasmon resonance sensor device comprising a light source, a sensor chip including a light transmitting medium having a light reflecting surface having a metal thin film, and a photodetector, comprising: a light source image on the light reflecting surface; A surface plasmon resonance sensor device, wherein the metal thin film is configured to generate surface plasmon resonance only in a small spot region. 2. The surface plasmon resonance sensor device according to claim 1, wherein the metal thin film is formed only in the spot region. 3. The apparatus according to claim 1, further comprising an overcoat film that covers the surface of the metal thin film and has a refractive index that is equal to or higher than the refractive index of the light transmission medium, and the overcoat film is the metal. A surface plasmon resonance sensor device having a spot window for exposing only a portion of the surface of the thin film corresponding to the spot region. 4. The surface plasmon resonance sensor device according to claim 3, wherein the overcoat film has a thickness of 50 nm or more. 5. The apparatus according to claim 1, further comprising a light-shielding film arranged on an optical path in the vicinity of the light-reflecting surface, wherein the light-shielding film corresponds to the spot area of the light source image. A surface plasmon resonance sensor device having a spot window for allowing only the light forming the light to pass therethrough. 6. The apparatus according to claim 1, wherein a region other than the spot region on the light reflecting surface of the light transmitting medium has a refractive index equal to or lower than a refractive index of a sample in contact with the metal thin film. Surface plasmon resonance sensor device. 7. The apparatus according to claim 1, wherein the light source is an LED lamp, and the spot area is an LED in an image of the LED lamp.
A surface plasmon resonance sensor device having the same size as or smaller than the image of the chip. 8. A sensor chip for a surface plasmon resonance sensor device, comprising a light transmitting medium having a light reflecting surface having a metal thin film, and reflecting light from a light source at a reflectance associated with surface plasmon resonance. A sensor chip for a surface plasmon resonance sensor device, wherein the metal thin film is configured to generate surface plasmon resonance only in a spot area smaller than a light source image on a light reflecting surface. 9. The sensor chip according to claim 8, wherein
A sensor chip for a surface plasmon resonance sensor device, wherein the metal thin film is formed only in the spot region. 10. The sensor chip according to claim 8, further comprising an overcoat film covering the surface of the metal thin film, the overcoat film having a refractive index higher than that of the light transmitting medium. A sensor chip for a surface plasmon resonance sensor device, comprising a spot window for exposing only a portion corresponding to the spot region on the surface of the metal thin film. 11. The sensor chip for a surface plasmon resonance sensor device according to claim 10, wherein the overcoat film has a thickness of 50 nm or more. 12. The sensor chip according to claim 8, further comprising a light shielding film arranged on an optical path near the light reflecting surface, wherein the light shielding film corresponds to the spot region of the light source image. A sensor chip for a surface plasmon resonance sensor device, comprising a spot window for passing only light forming a part. 13. The sensor chip according to claim 8, wherein a refractive index of a region of the light reflecting surface of the light transmitting medium other than the spot region is less than or equal to a refractive index of a sample in contact with the metal thin film. Surface plasmon resonance sensor device.