JP2006105670A - Surface plasmon resonance sensor probe and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface plasmon resonance sensor probe capable of detecting a micro change of refractive index by curving completely an optical fiber or by folding back at 180° of angle, and a method for manufacturing the surface plasmon resonance sensor probe. <P>SOLUTION: This surface plasmon resonance sensor probe is provided with a curved part with a U-shapedly bent intermediate portion of the the optical fiber comprising a core and a clad, and a metal thin film layer comprising conductive metal to cover a core surface exposed by removing the clad in the curved part, and the refractive index of light propagated inside the core of the optical fiber is varied with actions of an evanescent wave and surface plasmon by forming the surface plasmon resonance sensor probe, to be output from the other end of the optical fiber as a change of emission light intensity. The maximum resonance wavelength where the emission light intensity is most attenuated is obtained to specify a measured sample. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a surface plasmon resonance sensor probe that can detect a reaction of a sample to be measured, a concentration change, and the like using a surface plasmon resonance phenomenon, and a method for manufacturing the same.

  As a sensor that can monitor an antigen-antibody reaction in a non-labeled manner in real time, a sensor that electrically analyzes various molecular interactions occurring in a living body using surface plasmon resonance (SPR) has been developed. Since the sensor using this SPR is sensitive to the surface state (refractive index) of the sensor surface, the reaction occurring on the sensor surface can be detected in real time, and the types of components such as a medium (gas, liquid) in contact with the sensor surface Because it can detect minute changes due to differences in concentration, it is also expected to be used as a sensor for substance identification and substance concentration measurement.

  FIG. 9 shows a sensor using the most common SPR. In this sensor, gold (Au) is deposited on a glass substrate 101 by vapor deposition or the like, and an organic compound (medium 103 (refractive index n)) such as protein, peptide, DNA, hormone, etc. is used as a sample to be measured on the metal thin film 102. ) Is fixed. The surface of the metal thin film 102 on which the medium 103 is fixed is used as a front surface, laser light is incident on the glass substrate 101 from the back surface at an incident angle θ, and the amount of reflected light is measured by a light receiving element (not shown). Only when the medium 103 reacts, the reflected light of the light abruptly attenuates. Therefore, the presence or absence of the reaction can be known by measuring the reflected light.

  In this phenomenon, when laser light is incident from the back surface of the glass substrate 101, an evanescent wave is generated at the interface between the glass substrate 101 and the metal thin film 102, and surface plasmons are generated at the interface between the metal thin film 102 and the medium 103 due to the evanescent wave. When excited, the wave number in the plane direction of the evanescent wave and the wave number in the plane direction of the surface plasmon coincide with each other as a resonance phenomenon.

  Therefore, when an antigen-antibody reaction occurs on the medium 103, the dielectric constant ε of the medium 103 changes, a resonance phenomenon occurs, and the resonance angle also changes. Since the refractive index also changes with this, the presence or absence of reaction can be known by measuring the reflected light.

  By utilizing this, it is possible to analyze the intermolecular interaction by measuring the change in resonance angle over time by selectively mixing the sample while flowing the solution on the sensor surface.

  Here, as an example, when an arbitrary protein is immobilized on the metal thin film 102 and a ligand assay that acts on this receptor flows on the sensor surface, the resonance angle changes greatly. Using such a phenomenon, it is possible to investigate receptor / ligand pairs from various protein and compound groups, and to analyze the reaction rate of the combination.

  However, since such an SPR sensor uses a two-dimensional thin film, there is a problem that an optical system for measurement becomes complicated, and the apparatus becomes large and expensive. Therefore, in recent years, sensors using optical fibers have been developed as solutions to such problems. As a sensor using this optical fiber, there are a reflection type (for example, Patent Document 1) and a transmission type (for example, Patent Documents 2 and 3).

  The sensors shown in FIGS. 10A, 10B, and 11 are examples of transmissive sensors. The biosensor 110a shown in FIG. 10 (a) is obtained by connecting two types of optical fibers having different core diameters and providing a metal thin film layer on the outer periphery of the optical fiber to be a sensor portion. That is, a first optical fiber composed of a core 111 and a clad 112 and a second optical fiber composed of a core 113 and a clad 114 are prepared, and the first optical fiber is fused and connected to both ends of the second optical fiber. The metal thin film 115 is provided on the outer periphery of the fusion splicing portion and the second optical fiber.

  According to this configuration, when a sample to be measured is arranged on the metal thin film 115 and inspection light is incident on the optical fiber, an evanescent wave is generated at the boundary surface 116 between the clad 114 and the metal thin film 115, and the object to be measured is generated by the evanescent wave. Surface plasmons are generated at the interface between the sample and the metal thin film 115. A resonance phenomenon occurs due to the coincidence of these wave numbers, and the resonance angle changes. Accordingly, the refractive index also changes, so that the presence or absence of reaction can be known from this characteristic. Further, according to this configuration, there is an advantage that the concentration of the sample to be measured can be detected from the change in refractive index characteristics, and a biosensor can be realized by a simple and easy manufacturing method.

  In addition, the biosensor 110b shown in FIG. 10B is obtained by removing a part of the clad layer 112 of the long optical fiber to expose the core 111 and providing a metal thin film 115 on the surface of the core 111. . Similar to the biosensor 110a, such a biosensor 110b also attenuates the reflected light intensity with respect to a predetermined incident angle due to the surface plasmon resonance phenomenon generated at the interface between the sample to be measured and the metal thin film 115. From this, it is possible to know the refractive index of the sample to be measured, and thus the presence or absence of the antigen-antibody reaction.

  Further, the biosensor 120 shown in FIG. 11 removes a part of the cladding layer of the long optical fiber 121 to expose the core, and covers the exposed core fiber part with the metal layer 122 to form a detection part, A sample for measuring a biochemical reaction is placed on the detection unit, and the plasmon resonance that is excited by the metal layer 122 of the detection unit when laser light is incident from the end of the optical fiber 121 is used in the sample. It detects the presence or absence of a chemical reaction. According to this configuration, it is possible to accurately determine the presence or absence of a biochemical reaction with a simple structure.

  On the other hand, as a reflective sensor, there is a biosensor 130 shown in FIG. This sensor 130 is an optical fiber composed of a core fiber portion 134 and a cladding layer 133 covering the outer periphery, and the tip cladding layer 133 of the optical fiber is removed, and the exposed outer periphery of the core fiber portion 134 is thereby removed. A metal layer 135 is provided. On the outer periphery of the metal layer 135, a sensitive dielectric layer 132 and a non-sensitive dielectric layer 131 having sensitivity to the detection target are further provided in parallel with the axial direction of the optical fiber.

According to this configuration, as in the transmission type sensor shown in FIGS. 10 and 11, by immobilizing an antigen or an antibody on the sensitive dielectric layer 132, when the sample to be tested reacts, plasmon resonance occurs. Since the reflected light intensity changes, it is possible to know the refractive index of the sample to be measured from this change, and thus the presence or absence of the antigen-antibody reaction. In addition, there is an advantage that the sensor portion can be made smaller than the transmission type sensor.
Japanese Patent Application Laid-Open No. 11-223597 JP 2002-350335 A JP 2003-57175 A

  As described above, many proposals relating to biosensors have already been made, but the transmission-type biosensors 110a, 110b, and 120 shown in FIGS. 10 and 11 are in a straight line state of an inspection unit provided with a metal thin film 115. There is a problem that it is necessary to perform inspection while maintaining the size of the inspection unit. In addition, since a special measurement container that covers the inspection section is required, there is a problem that the entire apparatus is enlarged.

  When the inspection portion is large in this way, for example, when it is desired to inspect a liquid sample in a test tube or when the inspection is performed by inserting the sample into a human body, the sensor cannot be inserted and the use range is limited.

  On the other hand, since the reflective biosensor 130 shown in FIG. 12 detects the laser light reflected a plurality of times within the core fiber part 134, it is difficult to measure the light intensity, and how light absorption by plasmon resonance is observed. There is also a problem that it is difficult to determine whether the problem occurs under different conditions.

  Furthermore, since a beam splitter, a coupler, or the like is required as a detection element for detecting light output from the output end of the optical fiber, the sensitivity is reduced due to light attenuation caused by using these detection elements, and the entire apparatus is There is a problem that it cannot be miniaturized.

  The present invention has been made to solve the above-described problems of the prior art. The object of the present invention is to reduce the size of the sensor unit, realize the entire apparatus with a simple configuration, and enable high-sensitivity measurement. The object is to provide a surface plasmon resonance sensor probe and a method of manufacturing the surface plasmon resonance sensor probe.

  In order to solve the above-mentioned object, the surface plasmon resonance sensor probe according to the first aspect of the present invention has a curved core formed by bending an optical fiber comprising a core and a clad into a U shape, and the exposed portion. The gist of the present invention is to have a detection part formed with a thin film of conductive metal.

  A surface plasmon resonance sensor probe according to a second aspect of the present invention is the surface plasmon resonance sensor probe according to the first aspect, wherein the bending portion is formed by softening and melting an optical fiber. To do.

  The surface plasmon resonance sensor probe according to the present invention described in claim 3 is the surface plasmon resonance sensor probe according to claim 1 or 2, wherein the detection unit includes a bending portion and a linear portion having a predetermined length following the bending portion. It consists of the following.

  A surface plasmon resonance sensor probe according to a fourth aspect of the present invention is the surface plasmon resonance sensor probe according to the first aspect, wherein the optical fiber has an outer diameter of the core of 10 μm or less and an outer diameter of the cladding is the core. The gist is that it is 3 times or less of the outer diameter of the.

  A surface plasmon resonance sensor probe according to a fifth aspect of the present invention is the surface plasmon resonance sensor probe according to any one of the first to third aspects, wherein the bending portion is 180 degrees around the bending portion. The gist of the present invention is that the optical fiber has a configuration folded in the direction, and the incident end face and the outgoing end face of the optical fiber are located on the same plane.

  The surface plasmon resonance sensor probe according to the present invention described in claim 6 is a method of manufacturing a surface plasmon resonance sensor probe according to the present invention, wherein the optical fiber comprising a core and a clad is softened and melted and bent into a U shape. A step of removing a clad layer by immersing an optical fiber including at least a bent portion bent into a U shape in an etching solution, and removing the clad layer; And a conductive metal coating step for forming a thin layer of material.

  A surface plasmon resonance sensor probe according to the present invention described in claim 7 is a method of manufacturing the surface plasmon resonance sensor probe according to claim 6, wherein the plastic clad silica fiber is heated to decompose and disappear the clad layer; A bending process in which the exposed core is softened and melted by decomposing and disappearing the clad layer and bent into a U-shape, and a conductive metal thin film is formed on the surface of the core including at least a curved portion bent into a U-shape. And having a conductive metal coating step for forming a layer.

  According to the surface plasmon resonance sensor probe 1 of the present invention, the entire surface plasmon resonance sensor probe can be miniaturized and the plasmon resonance can be reduced in a small space because the surface plasmon resonance sensor probe 1 is composed of an optical fiber having a curved portion 14 bent to a small diameter. Can be easily formed, and as a result, a highly sensitive sensor can be obtained.

  Further, according to the present invention, since the sensor portion has a curved portion bent to a small diameter, when a multimode optical fiber is used, the plasmon resonance effect is also exerted on the transmitted low-order mode light. can get. For this reason, highly sensitive measurement can be performed with an optical fiber having a shorter length. Furthermore, sharper resonance absorption can be obtained on the short wavelength side of visible light than the conventional linear optical fiber sensor.

  Furthermore, according to the present invention, in the case where the sensor portion is configured by a curved portion and a straight portion bent to a small diameter, for example, in a U shape, the wavelength range of visible light (400 to 700 nm) in which plasmon resonance occurs. Stable and sharp resonance absorption can be obtained, so that stable and highly sensitive measurement can be performed in a wide wavelength range.

  Furthermore, according to the present invention, a predetermined sensor shape can be obtained simply by softening and melting the optical fiber and bending it, so that mass production can be facilitated.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 is a cross-sectional configuration diagram of a surface plasmon resonance sensor probe 1 according to the present invention.

  The surface plasmon resonance sensor probe 1 removes the clad layer of the curved portion 14 formed by bending a transmission optical fiber into a U shape, exposes the core 11, and exposes the conductive metal thin film layer to the exposed portion. Is a surface plasmon resonance sensor probe.

  Here, examples of the optical fiber include a single mode optical fiber (SMF) and a multimode optical fiber, and both optical fibers can be applied to the present invention. There are various types of optical fibers, such as quartz, multicomponent, plastic clad, and all plastic, but any optical fiber can be applied. There are two types of refractive index distributions such as graded index type and step index type in the refractive index distribution of such an optical fiber, and an optical fiber having any distribution may be applied. In the present embodiment, an optical fiber is taken as an example, but not limited to an optical fiber, an optical waveguide may be applied.

  On the other hand, when any one of the above optical fibers is used, the bending portion 14 softens and melts a predetermined portion of the optical fiber, that is, a part of the long optical fiber, or is completely 180 degrees. It is obtained by folding back and forming into a U-shape. In the case of using an optical waveguide, a core layer is formed on a flat glass substrate, a U-shaped mask is put on the core layer, and other cores are etched away to form a U-shaped core. The curved portion 14 can be formed by providing the metal thin film layer 2 made of a material.

  The bending angle of the bending portion 14 is not particularly limited, but it is desirable that the bending portion 14 be bent to an angle centered at 180 degrees. By bending to such an angle, the incident end and the emission end can be arranged close to each other, so that the overall shape of the surface plasmon resonance sensor probe can be further reduced.

  Also, the bending radius at that time varies depending on the type of optical fiber to be used, but the limit is the minimum radius of a physical optical fiber in which light propagating in the core can propagate with low loss. For example, in the case of a single mode optical fiber, the bending diameter R due to softening and melting is 5 mm.

  The conductive material 2 covering the exposed core is preferably gold (Au), silver (Ag), or the like. These may be laminated as a single layer or may be deposited in combination. Further, chromium (Cr) may be deposited as a base treatment to facilitate the deposition of these metals. Thereby, the adhesiveness of a core and a metal can be improved. Examples of the deposition method for depositing on the core surface include vapor deposition, sputtering, CVD, and thermal oxidation.

  According to the surface plasmon resonance sensor probe 1 having the above-described configuration, the bending portion 14 of the surface plasmon resonance sensor probe 1 is immersed in the sample to be measured (liquid), or the sample to be measured is directly applied to the metal thin film layer 2. When light is incident from one end of the optical fiber and the transmitted light intensity emitted from the other end is measured while in contact or placed, the evanescent wave is generated at the interface between the core 11 and the metal thin film layer 2 by the light propagating through the core. As a result, surface plasmons are excited at the interface between the metal thin film layer 2 and the sample to be measured. The intensity of transmitted light emitted from the other end abruptly attenuates due to the resonance phenomenon that occurs when the wave number in the plane direction of the evanescent wave matches the wave number in the plane direction of the surface plasmon due to the concentration of the sample to be measured and the antigen-antibody reaction. The characteristics can be obtained.

  Further, according to the surface plasmon resonance sensor probe 1 of the present invention, the surface plasmon resonance sensor probe 1 is constituted by the optical fiber having the curved portion 14 bent to a small diameter, so that the entire surface plasmon resonance sensor probe can be miniaturized and the plasmon can be formed in a small space. A sensor in which the length of the reflective portion of the surface where resonance is obtained can be easily formed, and as a result, a highly sensitive sensor can be obtained.

  Next, a method for manufacturing the surface plasmon resonance sensor probe 1 according to the present invention will be described with reference to the process diagrams of FIGS. 2 (A) to 2 (F).

  First, as shown in FIG. 2A, an optical fiber 10 comprising a core 11, a clad 12, and a primary coating 13, or an optical fiber core wire having a secondary coating on the outer periphery of the primary coating 13 is prepared. Then, as shown in FIG. 2B, the primary coating and the secondary coating having a predetermined width are removed by immersing them in a chemical solution or removed with a nipper or the like.

  Next, as shown in FIG. 2C, the outer periphery of the cladding 12 exposed by coating removal is softened and melted with a heat source (for example, a gas burner), and the optical fiber is bent into a U-shape. At this time, it is desirable that the bending angle of the U-shaped bending portion 14 be bent at an angle centered at 180 °. Then, as shown in FIG. 2D, the curved portion 14 is immersed in a predetermined etching solution for a predetermined time. Here, the etching solution is a hydrofluoric acid aqueous solution, and by immersing in this aqueous solution, only the clad 12 is removed and the core 11 is exposed as shown in FIG.

  Next, as shown in FIG. 2F, a conductive material is deposited on the exposed surface of the core 11 to a thickness of 0.1 μm or less on the surface of the core 11 using, for example, a vacuum evaporation method. The conductive material is a metal such as gold (Au) or silver (Ag). The deposition method is not limited to the vacuum evaporation method, and a deposition method such as a sputtering method, a CVD method, or a thermal oxidation method may be used. Through the above steps, the surface plasmon resonance sensor probe 1 shown in FIG. 1 can be manufactured.

  Furthermore, another example of the structure of the surface plasmon resonance sensor probe 1 is a surface plasmon resonance sensor probe 3 shown in FIG. This surface plasmon resonance sensor probe 3 is different from the surface plasmon resonance sensor probe 1 shown in FIG. 1 in that the bending portion 14 is composed of a curved portion and a linear portion 15 having a predetermined length. By providing the straight portion 15, it is possible to obtain an effect that a sharper and more sensitive absorption peak can be obtained than in the surface plasmon resonance sensor probe 1 in which most of the curved portion is a curved portion.

  When the surface plasmon resonance sensor probe 3 is manufactured, in the coating removal process of FIG. 2 (B), a large amount of coating is removed in advance in consideration of the straight line portion 15, and in FIG. The part is melted and softened to form a U-shape. Then, in FIG. 2D, the curved portion 14 and the straight portion 15 are immersed in an aqueous solution to remove the cladding 12, and the conductive material 2 is deposited only on the exposed core 11. Thereby, the surface plasmon resonance sensor probe 3 having the straight portion 15 can be manufactured.

  By using such surface plasmon resonance sensor probes 1 and 3 to constitute the refractive index measuring apparatus shown in FIG. 4, the type of the sample to be measured can be specified. The refractive index measuring device includes a surface plasmon resonance sensor probe 1 according to the present invention, a white light source 17 connected to one end of an optical fiber 13 of the surface plasmon resonance sensor probe 1 and outputting light of 400 to 900 nm, and the white light source. A spectroscope 18 that divides the output wavelength of light 17, a light receiving element (photomultiplier 19) that is connected to the other end of the optical fiber, converts the intensity of transmitted light emitted through the core, and converts it into an electrical signal, and the wavelength of incident light. And at least a personal computer (PC) 20 for measurement, which stores the electrical signal of the transmitted light intensity in association with each other and adjusts the output intensity of the white light source 17, controls the light receiving element, stores, and processes data. . In the figure, the fixture 16 is a jig for bundling the optical fibers 13. The operation of the apparatus will be described in conjunction with the measurement method in the following examples.

  Next, referring to FIGS. 2A to 2F again, a first embodiment of the present invention will be described. In this embodiment, a surface plasmon resonance sensor probe is manufactured by the manufacturing method of FIG. 2 using a single mode optical fiber for a wavelength of 1.5 μm, and the refractive index measurement shown in FIG. 4 is performed using this surface plasmon resonance sensor probe 1. The apparatus was configured and a measurement test was performed. The measurement results are shown in FIG.

  First, as shown in FIG. 2 (A), a single-mode optical fiber for a wavelength of 1.3 μm having a core diameter of 10 μm and a cladding diameter of 125 μm is prepared, and as shown in FIG. The UV coating resin was removed.

  Next, as shown in FIG. 2C, the exposed clad 12 was heated with a microtroch to form a U-shaped curved portion 14.

  Then, as shown in FIG. 2D, the entire curved fiber 13 was immersed in an aqueous hydrofluoric acid solution, and the cladding was etched until the outer diameter became 25 μm (FIG. 2E).

  Next, as shown in FIG. 2F, an optical fiber that has been reduced in diameter by etching is mounted on a sputtering apparatus, and after depositing 2 nm of chromium (Cr) as a base metal, 50 nm of gold (Au) is evaporated. Thus, the head portion of the surface plasmon resonance sensor probe 1 was obtained. Then, one end of the obtained surface plasmon resonance sensor probe 1 was connected to the incident port, and the other end was connected to the emission port. Light incident in the range of 400 nm to 900 nm was incident from the incident port, and the other end was connected to a photomal sensor, and the transmitted light intensity with respect to the wavelength of the incident light was measured.

  As a modification of the above embodiment, a method for manufacturing a surface plasmon resonance sensor probe using a single mode optical fiber for a wavelength of 0.63 μm is also shown.

  Also in this case, first, as shown in FIG. 2A, a single mode optical fiber for a wavelength of 0.63 μm having a core diameter of 6 μm and a cladding diameter of 125 μm was prepared, and about 7 mm of UV coating resin in the middle portion was removed. .

  Next, as shown in FIG. 2C, the exposed clad 12 was heated with a microtroch to form a curved portion 14.

  Then, as shown in FIG. 2D, the entire curved fiber 13 was immersed in an aqueous hydrofluoric acid solution, and the cladding was etched until the outer diameter became 15 μm (FIG. 2E).

  Subsequently, as shown in FIG. 2 (F), after the optical fiber thinned by etching is mounted on the sputtering apparatus as in the first embodiment, 2 nm of chromium (Cr) is deposited as a base metal. Then, gold (Au) was deposited to a thickness of 50 nm to obtain a head portion of the surface plasmon resonance sensor probe 1.

  As described above, two types of surface plasmon resonance sensor probes were manufactured by the manufacturing method of FIG. Among the two surface plasmon resonance sensor probes 1, a surface plasmon resonance sensor probe manufactured with a single mode optical fiber for 1.5 μm was used to configure the refractive index measurement device of FIG. 4 and perform a measurement test. The result is shown in FIG.

  FIG. 5 is a graph showing an absorption curve obtained by measuring the intensity of outgoing light with respect to incident light (wavelength) in each solution using the spectral intensity in air as a reference.

  First, after measuring a spectrophotometric curve in the air, the head of the surface plasmon resonance sensor probe 1 is moved to the following four kinds of solutions to be measured: (1) pure water], (2) acetone, (3) ethanol, (4) It was immersed in a glycerin aqueous solution, and each spectral intensity curve was measured.

  As a result, (1) in the case of pure water, a peak characteristic with the lowest emission light intensity is obtained near the wavelength of 640 nm, and (2) in the case of acetone, the peak characteristic in which the emission light intensity becomes the lowest near the wavelength of 690 nm. was gotten. In the case of (3) ethanol, a peak characteristic with the lowest output light intensity is obtained near the wavelength of 700 nm, and (4) in the case of the glycerin aqueous solution, a peak characteristic with the lowest output light intensity is obtained near the wavelength of 780 nm. It was. That is, acetone and ethanol could be distinguished from the result of the absorption curve resulting from the difference in refractive index.

  Further, the refractive index change when these characteristics are obtained is summarized in the table of FIG. As a result, in the case of pure water, the refractive index at the curved portion is 1.333, in the case of acetone, the refractive index at the curved portion is 1.359, and in the case of ethanol, the refractive index at the curved portion is 1.362. In the case of an aqueous glycerin solution, the refractive index at the curved portion was measured to be 1.380.

  That is, as described above, it was shown that the type of aqueous solution can be identified using the surface plasmon resonance sensor probe 1 of the present invention. As a result, the surface plasmon resonance sensor probe 1 can be easily manufactured, and a surface plasmon resonance sensor probe capable of easily measuring the sample to be measured can be provided.

  Next, instead of the silica-based optical fiber constituting the surface plasmon resonance sensor probe, a manufacturing method and a refractive index measurement result when the surface plasmon resonance sensor probe is made of a plastic fiber are shown.

  The manufacturing method in this case is to first heat the plastic clad silica fiber to decompose and disappear the clad layer, to decompose and disappear the clad layer, to soften and melt the exposed core, and to bend it into a U shape. The method includes a step of forming a thin layer of conductive metal on the surface of the core including at least a curved portion bent into a mold. Here, the step of decomposing and disappearing the cladding layer and the step of softening and melting the core may be performed simultaneously.

  The surface plasmon resonance sensor probe 1 shown in FIG. 1 was produced by the above manufacturing method. Further, the refractive index measuring apparatus shown in FIG. 4 was constructed using the surface plasmon resonance sensor probe 1, and the measurement results are summarized in FIG.

  FIG. 6 is an absorption curve obtained by measuring the intensity of emitted light with respect to incident light (wavelength) in each solution using the spectral intensity (a) in the air as a reference.

  The concentration of each aqueous solution is (b) glycerol concentration 0% (pure), (c) glycerol concentration 10%, (d) glycerol concentration 20%, (e) glycerol concentration 30%, (f) glycerol concentration 40%. . The surface plasmon resonance sensor probe 1 made of a plastic clad silica fiber was immersed in this aqueous solution, and light emitted from the white light source 17 was incident from one end of the optical fiber and propagated through the core. In the surface plasmon resonance sensor probe 1 immersed in the glycerin aqueous solution, the refractive index inside the core changes due to the change in the dielectric constant of the metal thin film accompanying the reaction between the aqueous solution and the metal thin film. The emitted light was detected by a light receiving element (Photomal 19), and the intensity of the emitted light with respect to the incident light was measured. At this time, the wavelength of the light output from the light source 17 was varied between 400 and 900 nm, and the intensity of light emitted from the optical fiber output end corresponding to this wavelength change was measured.

  As a result, as shown in FIG. 6, when (b) the glycerin concentration was 0%, attenuation of light intensity was observed from around the wavelength of 610 nm, and the light intensity was lowest at around the wavelength of 630 nm. In the case of (c) glycerin concentration of 10%, the light intensity was lowest at a wavelength of about 650 nm. Further, (d) when the glycerin concentration was 20%, the light intensity was the lowest in the vicinity of the wavelength of 670 nm. Further, (e) when the glycerin concentration was 30%, the light intensity was lowest at around the wavelength of 700 nm, and (f) when the disadvantageous serine concentration was 40%, the light intensity was around at the wavelength of 750 nm.

  From the above results, it was shown that the maximum resonance wavelength shifts to the longer wavelength side as the concentration increases. That is, it was confirmed that the absorption peak shifted to the long wavelength side corresponding to the refractive index difference.

  When such a surface plasmon resonance sensor probe is actually used, a spectrophotometric curve measured at a prescribed concentration is stored in a storage device in advance, and when an aqueous solution of unknown concentration is measured, its attenuation characteristics and measured characteristics And select matching characteristics from the spectrophotometric curve. The concentration of the aqueous solution whose concentration is unknown is specified from the degree of coincidence or difference.

  Next, using the plastic clad silica fiber again, the surface plasmon resonance sensor probe 3 shown in FIG. 3 was produced. The manufacturing method is the same as the plastic fiber processing method described above. The surface plasmon resonance sensor probe 3 was used to constitute the refractive index measurement device of FIG. 4 and measurement was performed using the same glycerin aqueous solution as described above. The measurement results are shown in FIG.

  As a result, when the straight portion 15 is provided on the extension of the curved portion 14 with a fixed length (9 mm in this embodiment), the spectrophotometric curve is shifted downward (lower light intensity) and The light curve was characterized. That is, in the process of rising from the vicinity beyond the peak, the difference from the peak is large. In particular, focusing on (f) glycerin 40%, (f) glycerin 40% in FIG. 6 has a gradual change in the curve and no difference between the peak peak and the following points. For 40%, the peak is clarified with a large difference from the peak top to the subsequent peak. This can be said that the sensitivity of the surface plasmon resonance sensor probe 3 is more improved than that of the surface plasmon resonance sensor probe 1.

  On the other hand, as a comparative example of the spectrophotometric curves of the surface plasmon resonance sensor probes 1 and 3 shown in FIGS. 6 and 7, the same measurement was performed using the same aqueous solution in the conventional transmission type sensor 110b. The result is shown in FIG.

  As can be seen from the spectrophotometric curve of FIG. 8, the light intensity on the short wavelength side of each curve is the same curve and is not characterized. Therefore, for example, when a monochromatic light source is used, it is considered that it is quite difficult to determine the density with a conventional sensor.

  That is, in the case of the surface plasmon resonance sensor probe 3 shown in FIG. 7, when light with a monochromatic light source wavelength of 550 nm is incident, (f) with 40% glycerin, a transmitted light intensity of 0.85 is emitted from the emission end. Is done. (E) When glycerin is 30%, a transmitted light intensity with a light intensity of 0.80 is emitted from the exit end of the optical fiber. (D) When glycerin is 20%, a transmitted light intensity with a light intensity of 0.75 is emitted from the optical fiber. Since it is emitted from the end, the concentration of the aqueous solution can be specified by the emitted light intensity. On the other hand, in the conventional sensor 110b shown in FIG. 8, when a monochromatic light source wavelength of 550 nm is incident, the intensity of emitted light is about 0.8 regardless of the aqueous solution, and there is almost no difference. Therefore, it is almost impossible to specify the concentration. That is, it is quite difficult to specify the density with a monochromatic laser light source.

It is a figure showing the section composition of surface plasmon resonance sensor probe 1 concerning an embodiment of the invention. It is process drawing explaining the manufacturing method of the surface plasmon resonance sensor probe 1 which concerns on embodiment of this invention. It is a figure which shows the cross-sectional structure of the other surface plasmon resonance sensor probe 3 which concerns on embodiment of this invention. It is a block diagram of a refractive index measuring apparatus provided with the surface plasmon resonance sensor probe which concerns on embodiment of this invention. It is a graph which shows the result of having measured many kinds of measured samples using the surface plasmon resonance sensor probe concerning an embodiment of the invention. It is a graph which shows the spectral intensity curve which measured the to-be-measured sample from which density | concentration differs using the surface plasmon resonance sensor probe 1 which concerns on embodiment of this invention. It is a graph which shows the spectral intensity curve which measured the to-be-measured sample from which density | concentration differs using the surface plasmon resonance sensor probe 3 which concerns on embodiment of this invention. It is a graph which shows the spectral intensity curve which measured the to-be-measured sample from which density | concentration differs using the conventional surface plasmon resonance sensor probe 110b. It is a schematic diagram for demonstrating a surface plasmon resonance phenomenon. It is a figure which shows the cross-sectional structure of the conventional transmissive | pervious sensor 110a (a) and sensor 110b (b). It is a figure which shows the cross-sectional structure of the conventional transmission type sensor. It is a figure which shows the cross-sectional structure of the conventional reflection type sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Surface plasmon resonance sensor probe 2 ... Metal thin film layer 3 ... Surface plasmon resonance sensor probe 10 ... Optical fiber strand 11 ... Core 12 ... Cladding 13 ... Optical fiber 14 ... Curved part 15 ... Linear part 16 ... Fixing metal fitting 17 ... White Light source 18 ... Spectrometer 19 ... Photomal 20 ... PC for measurement

Claims (7)

  A surface plasmon resonance sensor characterized by having a detection portion in which a core of a curved portion formed by bending an optical fiber comprising a core and a clad into a U-shape is exposed, and a thin film of conductive metal is formed in the exposed portion. probe.   2. The surface plasmon resonance sensor probe according to claim 1, wherein the curved portion is formed by softening and melting an optical fiber.   The surface plasmon resonance sensor probe according to claim 1, wherein the detection unit includes the bending portion and a linear portion having a predetermined length provided continuously to the bending portion.   2. The surface plasmon resonance sensor probe according to claim 1, wherein the optical fiber has an outer diameter of the core of 10 [mu] m or less, and an outer diameter of the cladding is three times or less of the outer diameter of the core.   4. The bending portion according to claim 1, wherein the bending portion has a configuration in which the bending portion is folded back in a 180-degree direction, and the incident end surface and the emitting end surface of the optical fiber are located on the same plane. The surface plasmon resonance sensor probe according to Item. A bending process in which an optical fiber composed of a core and a clad is softened and melted and bent into a U-shape;
A cladding layer removing step of immersing an optical fiber including at least a curved portion bent into a U shape in an etching solution to remove the cladding layer;
A conductive metal coating step for forming a thin layer of conductive material on the surface of the core exposed by removing the cladding layer;
A method of manufacturing a surface plasmon resonance sensor probe, comprising: Heating the plastic clad silica fiber to decompose and disappear the clad layer;
A bending process in which the clad layer is decomposed and disappeared, and the exposed core is softened and melted and bent into a U-shape; and
A conductive metal coating step of forming a thin layer of conductive metal on the surface of the core including at least a curved portion bent into a U-shape;
The method of manufacturing a surface plasmon resonance sensor probe according to claim 6.

Images