JPH09329553A - Optical sensor for detection chemical substance dissolved or dispersed in water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical sensor which high sensitivity which detects a chemical substance dissolved or dispersed in water. SOLUTION: The optical sensor 1 for detecting a chemical substance in water is provided with a detection element 2 having a polymer thin film 22, a light source part 3 for radiating light for irradiating the polymer thin film 22, and a light detector 4 for detecting intensity of lights reflected from the polymer thin film 22. The detection element 2, light source part 3 and light detector 4 are fitted integrally with a housing 7. The polymer thin film 22 is formed on a high reflection substrate 21, and mutually acts on a chemical substance dissolved or scattered in water in a water passage 8.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a guided mode method (WG method), a surface plasma resonance method (SP) using a polymer thin film.
R method), interference amplification reflection method (IER method), and other optical detection methods, such as chemical substances dissolved or dispersed in water, particularly dissolved organic carbon in water (dissolvedorganic).
The present invention relates to an optical sensor for directly detecting carbon (hereinafter referred to as DOC). Polymer thin films interact with chemicals such as hydrocarbons by absorption or adsorption in water. As a result, the thickness and / or the refractive index of the polymer thin film changes depending on the concentration of the chemical substance. Therefore, by measuring such physical change by an optical method, a chemical substance dissolved or dispersed in water, In particular, it becomes possible to determine the concentration of DOC.

[0002]

The use of polymeric materials as optical sensors for the detection of chemical species in water has been well documented. Many reports are related to evanescent wave sensors using optical fibers or optical waveguides.

Carter et al. Described a method for identifying chemical species in a solution by an optical waveguide covered with a response film having a refractive index smaller than that of a waveguiding layer in US Pat. No. Re. 33,06
No. 4 specification. Light propagates in the optical waveguide by total internal reflection. Of the propagating light, only the evanescent wave generated by total reflection is involved in the interaction between the response film and the chemical species to be detected, and by the method such as Carter, light absorption, scattering, and fluorescence generation occur. Limited to interaction.

Hinrich et al. Describe the use of polymers on top of internal reflection elements for the detection of organic compounds in water "Determination of organic."
compounds by IR / ATR spec
troscopy withpolymer-coat
ed internal reflectionele
Ments "(Applied Spectrosco
py, Vol. 44, No. 10, 1990, p. 1641-16
46). However, the detection method of Hinrich et al. Is based on the absorption of infrared evanescent waves penetrating into the polymer film by the organic compound, and the polymer film excludes water and extracts the organic compound on the surface of the internal reflection element. Is used to increase the absorption signal.

Burk et al., "A fiber opt"
ic evanescent field absor
ption sensor for monitori
norganic contamination i
n water ”(Fresenius J. Ana
l. Chem. , (1994) 342, p. 394-
400) and "Fiber-optic evanes.
cent wavesenor for in si
tu termination of non-po
lar organic compounds in
water "(Sensors and Actuat
ors B 18-19 (1994) p. 291-29
In 5), we reported a similar method except using an optical fiber.

Further, Japanese Patent Laid-Open No. 7-85122 discloses that
A method for detecting organic solvents in water is disclosed by composing a cladding layer of an optical fiber with a chitosan composition. The intensity of the evanescent wave that penetrates the chitosan clad changes depending on the degree of swelling.
The concentration of the cladding varies with the ratio of water to solvent, so that the intensity of light propagating through the optical fiber is a function of the concentration of organic solvent in the water.

A major drawback of sensors utilizing evanescent waves is that the sensitivity of the sensor is limited because only a small portion of the input light is used for detection. Therefore, a long interaction distance is required to obtain a highly sensitive sensor. That is, there is a limit to making such a sensor compact.

Higher sensitivity can be obtained by using most of the detected input light. WO95 / 20
Japanese Patent Publication No. 151 (International Publication Date: July 27, 1995) discloses an optical fiber type chemical sensor having a multilayer structure. The response polymer layer is sandwiched between the core and the clad of the optical fiber, and the polymer layer serves as an optical waveguide layer because the refractive index of the polymer layer is larger than that of the core and the clad. Therefore, the light incident on the optical fiber is refracted into the polymer waveguide layer and propagates through the polymer waveguide layer toward the end of the sensor. However, in such a configuration,
Since the output photodetector must be installed near the output end, such a configuration is inconvenient when measuring a substance to be detected in water.

Many high-sensitivity polymers for detecting chemical substances in gas have been reported. Gurugliani and others are "Fabri
Cation of an integrated o
optical waveguide chemical
vapor microsensor by pt
opolymerization of a bifu
nctional oligomer "(Appl.
Phys. Lett. 48 (1986), p. Thirteen
11-1313) and "Integrated opti.
cal chemical vapor micros
ensor "(Sensors and Actuat
ors, 15 (1988), p. 25-31) reported a 1 μm-thick strip-type polymer waveguide that detects the presence of some organic vapors. Their method is to introduce unpolarized light into the waveguide channel by fiber coupling from one end and to take out the light propagating in the waveguide from the other end. As a result, the interaction between the polymer and the organic vapor is detected as a change in the transmitted (propagating) light intensity. The method of Grugliani et al. Is that (1) making a strip type waveguide requires a photopolymerizable polymer, and (2) it is very difficult to end-face bond to a thin film of a micrometer or less. Two points is not easy.

A flat plate type polymer thin film optical waveguide as a sensor for detecting organic vapor is described in "Evaluation o
f polymer thin film waveg
guides as chemical sensor
s "(SPIE Proceedings, Vol. 1
368: Chemical, biochemica
l and and environmental II, 19
90) by Baumann and Burgess.
The absorption of chemical vapors by the polymer film results in a change in the waveguide properties of the polymer film. Baumann et al. Used two gratings (diffraction gratings) embedded in a substrate for light input / output coupling. However, such a grating coupler is difficult to manufacture and expensive. A simpler method using a prism coupler is described in “Optical gas detection us” by Osterfeld et al.
ing metal film enhanced l
eakymode spectroscopy "(Ap
pl. Phys. Lett. , 62 (19), (10
May 1993), p. 2310-2312). The metal reflection layer is sandwiched between the polymer film waveguide and the optical coupling prism, and the light incident on the interface between the metal and the prism is totally reflected at a certain optimum incident angle.
Guided modes are excited in the polymer film by the evanescent waves generated by total internal reflection.

It is not mentioned whether the polymer waveguides shown by Baumann et al. And Osterfeld et al. Can be used to detect organic carbon in water. Furthermore, the refractive index (= 1.3034) of the polymer film (Teflon AF) used by Osterfeld et al.
Since it is smaller than 1.33), the Teflon AF film does not function as a waveguide in water.

[0012]

DISCLOSURE OF THE INVENTION The present invention has been proposed to solve the above-mentioned problems of the known art, and has a simple structure and high sensitivity, and is easily dissolved or dispersed in water. It is an object of the present invention to provide an optical sensor for detecting a chemical substance, especially DOC.

[0013]

In order to achieve these objects, the present invention provides an optical sensor for directly detecting a chemical substance dissolved or dispersed in water, which polymer interacts with the chemical substance. A detection element having a thin film, a light source unit for emitting light for irradiating the polymer thin film, and a photodetector for detecting the intensity of light reflected from the polymer thin film. An optical sensor for

In the present invention, any chemical substance that can be absorbed or adsorbed by the polymer thin film can be detected.
Particularly, in the case of detecting organic carbon, it is preferable in terms of sensitivity and the like.

The detection element, the light source section and the photodetector are integrally held by the housing. The polymer thin film provided on the detection element is preferably formed on a flat substrate.
In one embodiment of the present invention, the polymer thin film is formed on a highly reflective substrate, and the interaction between the polymer thin film and the chemical substance in water is detected by the IER method. In another embodiment of the invention, the polymer thin film is formed on a highly reflective metal film deposited on a transparent substrate. The highly reflective metal film has a thickness equal to or less than the wavelength of light from the light source unit,
It is made of a material selected from the group consisting of silver, gold, chrome, silicon and germanium. In this embodiment, the interaction between the polymer thin film and the chemical substance in water is detected by one of the SPR method and the WG method.

The thickness of the polymer thin film is preferably 10 μm or less, more preferably 5 μm or less, still more preferably 3 μm or less. The light source unit is preferably a laser diode (LD) or a light emitting diode (LED) that emits visible light or infrared light, and the photodetector is preferably a photodiode or a phototransistor. The output of the photodetector is applied to an electrical circuit, which determines a signal representative of the concentration of chemicals in the water.

[0017]

In the present invention, the polymer film responds directly by absorbing or adsorbing chemicals in water, such interaction resulting in a change in the polymer film thickness and / or refractive index. Since such physical changes are related to the concentration of chemical substances in water, these physical changes are
The concentration of the chemical substance in the water can be determined by measuring with an optical method such as the method, the SPR method and the guided mode method.

In the above three optical methods, the concentration of chemicals in water may be measured as a function of the reflected light intensity at a fixed detection angle. In the case of the WG method, the chemical concentration is measured as a function of the reflectance in the polymer thin film or the angular position of the guided mode.

[0019]

DETAILED DESCRIPTION OF THE INVENTION Certain polymer thin films (described below) change their thickness and / or refractive index by absorbing or adsorbing chemicals such as organic carbon. The present invention detects chemicals in water by measuring these physical changes in polymer thin films. Hereinafter, some embodiments of the optical sensor according to the present invention will be described. In the following drawings, the same or similar components will be indicated by the same reference numerals,
Duplicate description is omitted.

FIG. 1 shows a first optical sensor according to the present invention.
FIG. 3 is a diagram schematically showing the configuration of the embodiment of FIG. 2. In this embodiment, the IER method is used. In FIG. 1A, the optical sensor 1 includes a detection element 2 and a detection element 2
A light source unit 3 that emits light so that light is incident on the light source 3 at an incident angle θ; and a first photodetector 4 for detecting the intensity of light emitted from the light source unit 3 and reflected by the polymer thin film 22. Is equipped with.

The detection element 2 is disposed on one surface of the substrate 5, and has a polymer thin film 22 formed on a flat reflective substrate 21 and in contact with water, as shown in FIG. 1B.
The reflective substrate 21 is preferably a highly reflective substrate,
For example, it may be a mirror, a semiconductor, a metal, or a thin film in which a metal material or a semiconductor material is deposited on a low reflective substrate.

The light source unit 3 includes a light source 31 and a beam splitter 3.
2 and a polarizing plate 33. The light source 31 is a laser diode (LD) or a light emitting diode (LED) and emits visible light or infrared light. The light emitted from the light source 31 is divided into two by a beam splitter 32, and one of the lights passes through a polarizing plate 33 to be polarized and then enters the polymer thin film 22 of the detection element 2. The light reflected from the polymer thin film 22 passes through the window 41 and enters the first photodetector 4, and its intensity is detected. The other light of the light divided into two by the beam splitter 32 is incident on the second photodetector 6 and converted into a signal indicating the light intensity for reference.

The first photodetector 4 and the second photodetector 6 are photodiodes or phototransistors, and the outputs of these photodetectors 4 and 6 are transmitted to an appropriate electronic circuit to generate the second photodetector. First photodetector 4 for output of detector 6
The ratio of the outputs of the two is determined, and this ratio is used to generate a signal representative of the concentration of the chemical.

The light source unit 3, the first photodetector 4 and the second photodetector 6 are attached to the housing 7 at appropriate positions so that the housing 7 forms a water channel 8 with the substrate 5. Further, the polymer thin film 22 of the detection element 2 is attached to the substrate 5 so as to come into contact with water. The light passing through the polarizing plate 33 is
It is preferable that the electric field vector of light is s-polarized light that is perpendicular to the plane of incidence on the polymer thin film 22.

The IER method is based on the fact that the intensity of light reflected from a thin dielectric film depends on the thickness of the dielectric film, and the thickness and / or refractive index of the polymer thin film 22 in contact with water. Is used to detect changes in the. Polymer thin film 2
2 absorbs or adsorbs a chemical substance in water to change its thickness and / or refractive index. Therefore,
When the polymer thin film 22 is irradiated by the light source unit 3, a change in the thickness and / or the refractive index of the polymer thin film 22 appears as a change in the intensity of the light reflected from the polymer thin film 22,
By measuring the intensity of this reflected light, the concentration of the chemical substance in the water can be measured.

FIG. 2 shows the thickness and s of the polymer thin film when the polymer thin film of the detection element in the optical sensor shown in FIG. 1 is formed on a silicon substrate and the polymer thin film is placed in water.
It is a relationship with the reflectance of polarized incident light (reflectance curve obtained by the IER method). The solid line shows the case where the incident angle θ is 80 °, the dotted line shows the case where the incident angle θ is 70 °, and the refractive index of the polymer thin film is 1.50.

The thickness of the polymer thin film 22 is several nm to 10 nm.
The thickness can be arbitrarily set within a range of up to μm, but in order to properly detect the thickness of the polymer thin film 22 by the IER method, the thickness is set to a value apart from the minimum value of the reflectance curve of FIG. It is desirable to do. Further, it can be seen from the reflectance curve of FIG. 2 that the greater the incident angle θ, the greater the modulation of the reflectance (the greater the change in reflectance with respect to the change in thickness), and the incident angle θ is 70 °, preferably 70 °. A larger angle is better.

FIG. 3 shows a second optical sensor according to the present invention.
2B is a diagram schematically showing the configuration of the embodiment of FIG. 3B, and FIG. 3B is an enlarged view showing a part of the structure of the detection element in FIG. The second embodiment differs from the first embodiment of FIG. 1 in that a polymer waveguide is used.

3A and 3B, a metal layer 23 is deposited on the bottom surface 91 of the prism 9, and a polymer thin film 22 serving as a polymer waveguide is formed on the metal layer 23 for detection. The element 2 is formed. The prism 9 is attached to a flow cell 10 having a water inlet 11 and a water outlet 12 such that the polymer thin film 22 faces the water flowing in the flow cell 10. The polarized light from the light source unit 3 is incident on the bottom surface 91 of the prism 9 at an angle larger than the total internal reflection angle of the prism 9, and the intensity of the light reflected by the bottom surface 91 is determined by the first photodetector 4. To be measured. The metal layer 23 has a thickness equal to or less than the wavelength of the light emitted from the light source 31, and is preferably composed of silver, gold, chrome, silicon or germanium.

When the light emitted from the light source 31 is totally reflected by the bottom surface 91 of the prism 9, an evanescent wave is generated,
This evanescent wave excites a guided mode light wave inside the polymer thin film 22. Excitation of the guided mode in such a polymer thin film, that is, optical coupling is performed by the bottom surface 91 of the prism 9.
The strongest is at the angle of incidence where the tangential component of the evanescent wave vector at is equal to the wave number vector of the light wave of the guided mode. Therefore, under such a condition, the energy of the incident light from the light source 31 shifts to the light wave of the guided mode inside the polymer thin film 22, and the intensity of the reflected light from the metal layer 23 sharply decreases.

Therefore, when the reflectance of the polymer thin film 22 is measured by changing the incident angle θ of the light from the light source 31, it is possible to recognize the excitation of the optical wave of the guided mode as a sharp attenuation of the reflectance curve at a certain resonance coupling angle. it can. FIG. 4 shows 2 μm thick poly (octadecyl methacrylate-co-glycidyl methacrylate) [hereinafter poly (ODMA-co-GLM
A), the experimental value showing the change of the reflectance of the polymer thin film 22 with respect to the incident angle θ of the light incident on the detection element 2 is shown, and the four guided modes TM ₁ , T
M ₂ , TM ₃ and TM ₄ can be confirmed. Poly (ODMA-c
o-GLMA) is made of SF11 glass (wavelength 632.
The refractive index at 8 nm is 1.7780) and is formed by spin coating on the surface of gold with a thickness of 50 nm deposited on the bottom surface of a rectangular prism. Poly (ODMA
-Co-GLMA) has a refractive index in water of about 1.46, which is higher than those of water and gold, and thus poly (ODM).
A-co-GLMA) functions as a waveguide.

When the polymer thin film 22 responds to a chemical substance in water, that is, when it absorbs or adsorbs a chemical substance, the thickness and / or the refractive index of the polymer thin film 22 change to cause resonance that excites a certain guided mode. The bond angle will shift. Such an angular shift is a function of chemical concentration. Thus, by measuring the shift of the resonant coupling angle of a certain guided mode, the concentration of the chemical substance in water can be detected. In FIG. 5, the polymer thin film 22 has a thickness of 2p.
₄ shows the resonant coupling angle shift δ of guided mode TM ₄ (FIG. 4) in response to pm of toluene. The solid line shows the relationship between the incident angle and the reflectance of the polymer thin film when toluene is 0 ppm, and the dotted line shows the relationship between the incident angle and the reflectance after the polymer thin film responds to 2 ppm of toluene.

Instead of measuring the shift of the resonance coupling angle, the incident angle θ of the light from the light source 31 is fixed to one side of the resonance of the guided mode, and the change in the intensity of the reflected light from the detecting element 2 is measured. By doing so, the concentration of the chemical substance in the water can be detected. Since the resonance is very sharp, even a very small shift of the resonant coupling angle will result in a large reflectance change.

The polymer thin film 22 shown in FIG. 3 must have a sufficient thickness to support at least one guided mode. For example, the cutoff thickness for the polymer thin film 22 having a refractive index in water of 1.45 to have the TE ₀ mode is about 284 nm. When the thickness of the polymer film 2 is below this cut-off thickness, no guided mode can exist in the polymer film 2. However, surface plasma resonance (surface plasma)
n resonance. Hereinafter, it is possible to observe another phenomenon called SPR).

Surface plasmons are plasma oscillations of free electrons existing at the metal boundary, and the plasma oscillations are affected by the index of refraction of the material on the near surface of the metal. For example, surface plasma vibration can be excited by causing p-polarized light to enter the bottom surface 91 of the prism 9 in the optical sensor having the configuration shown in FIG. 3 and causing an evanescent wave by total internal reflection. This plasma oscillation is at an incident angle θ at which the tangential component of the evanescent wave vector on the bottom surface 91 of the prism 9 matches the wave number vector of the plasma wave at the interface (that is, the substrate side) opposite to the polymer thin film 22 with respect to the metal layer 23. Be excited. At this time, the energy of the incident light is transferred to the plasma wave, and the reflected light intensity is sharply attenuated. This phenomenon is surface plasma resonance (SPR). Since the position of the resonance coupling angle of SPR strongly depends on the refractive index of the polymer thin film on the metal surface, the chemical substance in water can be detected even by using the SPR method.

When the reflectance of the totally internally reflected light is measured while changing the incident angle θ of the incident light, SPR can be experimentally observed as a sharp attenuation of the reflectance at a certain resonance coupling angle.
As an example of SPR observation, FIG. 6 shows a thickness of 50 nm deposited on the bottom surface of a rectangular prism made of SF11 glass (having a refractive index of 1.7780 at a wavelength of 632.8 nm).
Constructed using 107 nm thick poly (ODMA-co-GLMA) spin coated on the gold surface of FIG.
3 is a reflectance curve (SPR curve) showing how the reflectance of the optical sensor changes with respect to the incident angle θ.

Other optical sensors having the configuration shown in FIG. 3 and utilizing the SPR method are also feasible. The input light of this optical sensor is also p-polarized light, but the thinner the polymer thin film is, the better, and it is preferably in the range of several nm to several hundred nm. This is because the surface plasmon is a surface phenomenon and is sensitive to a change occurring at a position several nm to several hundred nm away from the surface of the metal. The polymer thin film absorbs or adsorbs a chemical substance in water, and the polymer thin film swells to change the thickness and / or the refractive index, thereby shifting the resonant coupling angle of the SPR. Therefore, by measuring the shift of the resonant coupling angle of SPR or by measuring the incident angle of light from the light source by SPR
It is possible to detect the concentration of the chemical substance in the water by fixing the resonance coupling angle of (3) and measuring the intensity change of the reflected light from the polymer thin film.

Since the change in the thickness and / or the refractive index of the polymer thin film is also influenced by the change in the temperature around the polymer thin film, the detection result of the optical sensor according to the present invention changes with temperature. Therefore, high-sensitivity measurement may require temperature control technology or temperature compensation technology. For this purpose, a temperature-controlled housing is used, a temperature sensor that generates a temperature-correction signal is used, and a temperature-sensitive polymer thin film is used to form a multi-channel device. It is possible to apply the method of outputting the signal of 1 or experimentally determining the temperature compensation factor.

Furthermore, the optical sensor according to the present invention can be provided with a plurality of detection elements and can measure the concentration of a mixture of a plurality of chemical substances in water. To achieve this, use polymer films that have low or low response to multiple chemicals in water, and use multiple polymer films that each selectively respond to different chemicals in water. To output a signal indicating the concentration of a mixture of multiple chemicals in water by combining the responses of the polymer thin films of, using multiple polymer thin films each showing different responses to the same or different chemicals in water. Outputting a signal indicating the concentration of a mixture of a plurality of chemical substances in water by combining the responses of these polymers, the one or more polymer thin films described above by the IER method, SPR
It is possible to output a signal indicating the concentration of a mixture of a plurality of chemical substances in water by using it in combination with an optical method such as the WT method or the WG method.

Further, in order to accurately determine the total amount of chemical substances or the concentrations of individual chemical substances or chemical substance groups, well-known pattern recognition techniques such as matrix analysis and neural network analysis together with a multi-channel optical sensor. Can be applied.

Materials for the polymer thin film 22 used in the optical sensor according to the present invention include the following repeating units:

Embedded image Homopolymers or copolymers having the following are preferred.

In the formula, X is --H, --F, --Cl, --B.
r, -CH _3, represents -CF _3, -CN or -CH ₂ -CH _3, R ¹ represents -R ² or -Z-R ^2, Z is, -O-,
-S -, - NH -, - NR 2 '-, - (C = Y) -, -
(C = Y) -Y -, - Y- (C = Y) -, - (SO 2)
-, - Y '- (SO 2) -, - (SO 2) -Y', - Y '
_{- (SO 2) -Y '-} , - NH- (C = O) -, - (C
= O) -NH -, - ( C = O) -NR 2 '-, - Y'-
(C = Y) -Y'- or -O- (C = O) - ( CH 2) n
Represents-(C = O) -O-, and Y is the same or different O.
Or S, Y ′ represents the same or different O or NH, n represents an integer of 0 to 20, R ² and R ² ′ represent the same or different hydrogen, linear alkyl group, branched It represents an alkyl group, a cycloalkyl group, an unsaturated hydrocarbon group, an aryl group, a saturated or unsaturated heterocycle, or a substitution product thereof. However, R ¹ is not hydrogen, a linear alkyl group, or a branched alkyl group.

In the formula, X is preferably H or CH ₃ , R ¹ is preferably a substituted or unsubstituted aryl group or --Z--R ² , and Z is preferably --O--,-(C =
O) -O- or -O- (C = O)-, and R ² is preferably a linear alkyl group, a branched alkyl group, a cycloalkyl group, an unsaturated hydrocarbon group, an aryl group, a saturated or It is an unsaturated heterocycle or a substitution product thereof.

The polymer used for the polymer thin film 22 may be a polymer consisting of only a single repeating unit (I), a copolymer consisting of another repeating unit (I) or the repeating unit (I), or the repeating unit (I) above. It may be a copolymer composed of two or more types of I). The arrangement of the repeating units in the copolymer can be any, for example, random copolymers, alternating copolymers, block copolymers or graft copolymers can be used. In particular, the polymer thin film 22
Is preferably prepared from polymethacrylic acid esters and polyacrylic acid esters. The side chain group of the ester is preferably a straight-chain or branched alkyl group or a cycloalkyl group, and preferably has 4 to 22 carbon atoms.

Polymers particularly suitable for the polymer thin film 22 are poly (dodecyl methacrylate) poly (isodecyl methacrylate) poly (2-ethylhexyl methacrylate) poly (2-ethylhexyl methacrylate-co-methyl methacrylate) poly (methacryl) Acid 2-ethylhexyl-co-styrene) poly (methyl methacrylate-co-2-ethylhexyl acrylate) poly (methyl methacrylate-co-2-ethylhexyl methacrylate) poly (isobutyl methacrylate-co-glycidyl methacrylate) poly (Cyclohexyl methacrylate) Poly (octadecyl methacrylate) Poly (octadecyl methacrylate-co-styrene) Poly (vinyl propionate) Poly (dodecyl methacrylate-co-styrene) Poly (dodecyl methacrylate) -Co-glycidyl methacrylate) poly (butyl methacrylate) poly (butyl methacrylate-co-methyl methacrylate) poly (butyl methacrylate-co-glycidyl methacrylate) poly (2-ethylhexyl methacrylate-co-glycidyl methacrylate ) Poly (cyclohexyl methacrylate-co-glycidyl methacrylate) Poly (cyclohexyl methacrylate-co-methyl methacrylate) Poly (benzyl methacrylate-co-methacrylic acid 2-
Ethylhexyl Poly (2-ethylhexyl methacrylate-co-diacetone acrylamide) Poly (2-ethylhexyl methacrylate-co-benzyl-methacrylate-co-glycidyl methacrylate) Poly (2-ethylhexyl methacrylate-co-methyl methacrylate) co-glycidyl methacrylate) poly (vinyl cinnamate) poly (butyl methacrylate-co
-Methacrylic acid) poly (vinyl cinnamate-co-dodecyl methacrylate) poly (tetrahydrofurfuryl methacrylate) poly (hexadecyl methacrylate) poly (2-ethylbutyl methacrylate) poly (2-hydroxyethyl methacrylate) poly (methacrylic) Acid cyclohexyl-co-isobutyl methacrylate) poly (cyclohexyl methacrylate-co-2-ethylhexyl methacrylate) poly (butyl methacrylate-co-2-ethylhexyl methacrylate) poly (butyl methacrylate-co-isobutyl methacrylate) poly (Cyclohexyl methacrylate-co-butyl methacrylate) Poly (cyclohexyl methacrylate-co-dodecyl methacrylate) Poly (butyl methacrylate-co-ethyl methacrylate) Poly (meth Butyl methacrylate-co-octadecyl methacrylate) Poly (butyl methacrylate-co-styrene) Poly (4-methylstyrene) Poly (cyclohexyl methacrylate-co-benzyl methacrylate) Poly (dodecyl methacrylate-co-benzyl methacrylate) ) Poly (octadecyl methacrylate-co-benzyl methacrylate) Poly (benzyl methacrylate-co-tetrahydrofurfuryl methacrylate) Poly (benzyl methacrylate-co-hexadecyl methacrylate) Poly (dodecyl methacrylate-co-methyl methacrylate) ) Poly (dodecyl methacrylate-co-ethyl methacrylate) Poly (2-ethylhexyl methacrylate-co-dodecyl methacrylate) Poly (2-ethylhexyl methacrylate-co-octademethacrylate) Poly) (2-ethylbutyl methacrylate-co-benzyl methacrylate)) poly (tetrahydrofurfuryl methacrylate-co-glycidyl methacrylate) poly (styrene-co-octadecyl acrylate) poly (octadecyl methacrylate-co-methacryl) Glycidyl acidate) Poly (4-methoxystyrene) Poly (2-ethylbutyl methacrylate-co-glycidyl methacrylate) Poly (styrene-co-tetrahydrofurfuryl methacrylate) Poly (2-ethylhexyl methacrylate-co-propyl methacrylate) Poly (octadecyl methacrylate-co-isopropyl methacrylate) Poly (3-methyl-4-hydroxystyrene-co-4-
Hydroxystyrene) Poly (styrene-co-2-ethylhexyl methacrylate-co-glycidyl methacrylate).

In the above methacrylic acid ester polymer or copolymer, acrylic acid may be used instead of methacrylic acid. The above polymer can be cross-linked by itself, but can be cross-linked by introducing a compound having a cross-linking reactive group into the polymer. Examples of such a reactive group for crosslinking include an amino group, a hydroxyl group, a carboxyl group, an epoxy group, a carbonyl group and a urethane group and derivatives thereof, and maleic acid, fumaric acid, sorbic acid, itaconic acid and cinnamic acid. And their derivatives. Substances having a chemical structure capable of forming carbene or nitrene upon irradiation with visible light, ultraviolet light or high-energy radiation can also be used as a crosslinking agent. Since the thin film formed by the cross-linked polymer is insoluble, the stability of the polymer thin film 22 can be increased by cross-linking the polymer. The crosslinking method is not particularly limited, and conventionally known crosslinking methods such as heating and irradiation with light or radiation can be used.

[0047]

EXAMPLES Some examples of the optical sensor according to the present invention will be described below.

Example 1 FIG. 7 is a curve showing how the response of the optical sensor having the structure shown in FIG. 3 changed with time when the concentration of toluene in water was 4 ppm. is there. The detection element was a poly (ODMA-co-GLM) having a thickness of 2 μm spin-coated on gold having a thickness of 50 nm deposited on the bottom surface of a right-angle prism made of SF11 glass.
It consists of A). The light source is a laser diode having a wavelength of 670 nm, and the light from the laser diode is divided into two to form a reference beam and a measurement beam, and the reference beam is sent to a silicon photodiode for reference, while the measurement beam passes through a polarizing plate to p The light was made incident on the bottom surface of the rectangular prism as polarized light. The incident angle of the measurement beam was set to the lower angle of resonance of the TM ₄ guided mode shown in FIG. When the intensity of the measurement beam reflected by the bottom surface of the prism was measured with a silicon photodiode for measurement, four guided modes as shown in FIG. 4 were observed.

The outputs of the two photodiodes, one for the reference and one for the measurement, are supplied to an electronic divider, and the ratio of the output of the photodiode for the measurement to the output of the photodiode for the reference is obtained, and this ratio is sent to an electric circuit. An output signal was obtained which was representative of the response of the optical sensor. As a result of this measurement, it was found that in the case of toluene in water, the detection limit was smaller than the concentration of 1 ppm, and the 90% response time (time required to reach a complete response) was within 3 minutes.

Example 2 : FIG. 8 shows how the response of the same optical sensor used in Example 1 varied with the concentration of toluene in water. However, the response from the optical sensor is measured as the change in reflectance with respect to the change in concentration of toluene. From this measurement, it was found that the optical sensor has a linear response to toluene having a concentration of 0 to 20 ppm in water.

Example 3 : FIG. 9 shows how the output signal of the same optical sensor used in Example 1 changed with time when the concentration of toluene in water was 20 ppm. There is. However, the polymer thin film of the optical sensor used in this measurement was made of poly (ODMA-c) with a thickness of 107 nm.
o-GLMA) and the light source has a wavelength of 632.8n.
It is a m-helium-neon laser. This 107n
By using a polymer thin film with a thickness of m, the surface plasma resonance as shown in FIG. 6 was observed.

The incident angle of the p-polarized measurement beam with respect to the bottom surface of the prism is 60.82 °, and this angle is SP.
In FIG. 6 showing the resonance coupling angle in the R method, it is on the side of a small incident angle. When the output signal of the optical sensor was recorded as a function of time, the output signal increased in response to toluene having a concentration of 20 ppm, and the 90% response time was around 3 minutes.

Example 4 Using an optical sensor according to the IER method having the structure shown in FIG. 1, the concentration in water is 0 to 300 ppm.
Of toluene was measured. The detection element is poly (ODMA) with a thickness of 1.95 μm spin-coated on a silicon substrate.
-Co-GLMA) and was attached to the housing as shown in Figure 1 and water was introduced into the housing by suction. The light source was a laser diode emitting light of wavelength 670 nm. The light from this laser diode was divided into two beams, a reference beam and a measurement beam. The measurement beam was s-polarized light that was linearly polarized by a polarizing plate and was made incident on the polymer thin film at an incident angle of 80 ° through a glass window.

The intensity of the measurement beam reflected by the polymer thin film was measured by a silicon photodiode for measurement, and the intensity of the reference beam was measured by a silicon photodiode for reference. The outputs of these two silicon photodiodes are fed to an electronic divider, the ratio of the output of the reference silicon photodiode to the output of the measuring silicon photodiode is determined, and is used by the electrical circuit to output Got the signal. FIG. 10 shows the fourth embodiment.
Is a plot of the reflectance measured by the optical sensor at, as a function of the concentration of toluene in water,
It can be seen that the response of the optical sensor is not linear in the concentration range of 0-300 ppm.

Example 5 : In order to detect DOC in water, it is desirable that the polymer thin film responds to many DOCs to be detected. Therefore, a large number of DOCs in water were measured using the optical sensor in Example 1 having a poly (ODMA-co-GLMA) layer having a thickness of 2 μm, and the measurement results are as shown in the following table. It was In this table, "sensitivity" is a value representing the change in reflectance as a percentage, and "time" is a 90% response time.

[0056]

[Table 1] Organic compound concentration (ppm) Sensitivity time (min) Toluene C ₇ H ₈ 2 41.72 6 Benzene C ₆ H ₆ 2 10.34 4 Chlorobenzene C ₆ H ₅ Cl 2 87.07 9 Nitrobenzene C ₆ H ₅ NO ₂ 2 23.28 1.5 P-xylene C ₈ H ₁₀ 2 126.86 15 Chloroform CHCl ₃ 2 8.71 3 Carbon tetrachloride CCl ₄ 2 21.55 11.5 1,2-dichloroethane CH ₂ CH ₂ Cl 2 6.03 1.5 Dichloromethane CH ₂ Cl ₂ 2 1.38 1 Diethyl ether C ₄ H ₁₀ O 100 11.21 1.5 Tetrahydrofuran O (CH ₂ ) ₄ 100 9.48 1 Acetone C ₃ H ₆ 500 8.62 1 Propanol C ₃ H ₈ O 500 6.03 1 Methanol CH ₄ O 500 0.00 Acetic acid C ₂ H ₄ O ₂ 500 3.45 <1 Hydrochloric acid HCl 2000 25 <1 Sulfuric acid H ₂ SO ₄ 2000 6.67 <1

From this table, it can be seen that the sensitivity and response time of the optical sensor vary depending on the type of DOC to be detected. Therefore, in order to detect many DOCs in various industrial and environmental applications, a multi-channel system with an array of detector elements, an array of polymer films or an array of sensors is needed. Further, in order to accurately determine the total amount of DOC or the concentration of each DOC or DOC group, known pattern recognition techniques such as matrix analysis and neural network analysis can be used together with such a multi-channel system. .

Regarding such a pattern recognition technique, "Anal. Chem." 1088, 60, 28.
01-2811, Susan L. et al. Ros
e-Pehrsson et al., "Detection of
Hazardous Vapors Includi
ng Mixtures Using Pattern
Recognition Analysis of
Responses from Surface Aco
"Sensors and Materials," a paper titled "Ustic Wave Device."
Vol. 1 (1995) 013-022 S
ang-Mok Chang et al., “Development”
nt of Odorant Sensor Usin
g SAW Response Oscillator
IncorporatingOdorant-Sen
sitive LB Films and Neura
l-Network Pattern Recogni
"Sion Scheme", "Senso"
rs and Actuators B "26-27
(1995) 126-134.
s Hierlemann et al., "Polymer-ba"
sed sensor arrays and mul
ticomponent analysis for
the detection of hazardou
s organic vapors in the e
nvironment ”.

[0059]

As is apparent from the above description of the present invention in detail with reference to some embodiments and examples,
Compared with the optical fiber sensor described in the prior art,
In the optical sensor according to the present invention, the change in the thickness and / or the refractive index of the polymer thin film interacting with the chemical substance is
Since the direct detection is performed by an optical method such as the ER method, the WG method, or the SPR method, it is possible to detect such a slight change in the thickness and / or the refractive index with high sensitivity. Since the polymer thin film can be easily formed by a general method such as spin coating, it is possible to obtain a special effect that the manufacturing of the optical sensor itself is facilitated.

[Brief description of drawings]

FIG. 1A is a diagram schematically showing a configuration of a first embodiment of an optical sensor according to the present invention, and FIG. 1B is a diagram showing a configuration of a detection element.

FIG. 2 is a diagram showing a reflectance curve showing the relationship between the thickness of a polymer thin film and the reflectance in the optical sensor of FIG.

3A is a diagram schematically showing a configuration of a second embodiment of an optical sensor according to the present invention, and FIG. 3B is a diagram showing a configuration of a detection element.

FIG. 4 is a diagram showing a reflectance curve showing the relationship between the incident angle and the reflectance of light incident on the polymer thin film in the optical sensor of FIG.

FIG. 5 shows a polymer thin film in the optical sensor of FIG.
It is a figure which shows the relationship between the incident angle and the reflectance when making it respond to pm toluene, and the shift of the resonant coupling angle of the waveguide mode TM ₄ .

6 is a diagram showing the relationship between the incident angle and the reflectance obtained for one specific example of the optical sensor of FIG.

FIG. 7 is a diagram showing how the response of an optical sensor having the same configuration as the optical sensor of FIG. 3 changes with time for 4 ppm of toluene in water.

FIG. 8 is a diagram showing how the reflectance of an optical sensor having the same configuration as the optical sensor of FIG. 3 changes with respect to the concentration of toluene in water.

9 is a diagram showing how the response of an optical sensor of the same configuration as the optical sensor of FIG. 3 varies with time for 20 ppm toluene in water.

10 is a diagram showing how the reflectance of an optical sensor having the same configuration as the optical sensor of FIG. 1 changes with respect to the concentration of toluene in water.

[Explanation of symbols]

1: Optical sensor, 2: Detection element, 21: High reflection substrate, 22: Polymer thin film, 23: Metal layer, 3: Light source part, 31: Light source, 32: Beam splitter, 33:
Polarizing plate, 4: first photodetector, 41: window, 5: substrate, 6: second photodetector, 7: housing, 8: water channel,
9: Prism, 10: Flow cell, 11: Inlet, 12: Outlet

Claims (8)

[Claims] 1. An optical sensor for directly detecting a chemical substance dissolved or dispersed in water, comprising a detection element having a polymer thin film that interacts with the chemical substance, and emitting light for irradiating the polymer thin film. An optical sensor comprising: a light source unit for controlling the light intensity; and a photodetector for detecting the intensity of light reflected from the polymer thin film. 2. The optical sensor according to claim 1, wherein the chemical substance is organic carbon. 3. The polymer thin film is formed on a highly reflective substrate, and the interaction between the polymer thin film and the organic carbon in water is detected by an IER method.
Alternatively, the optical sensor described in 2. 4. The polymer thin film is formed on a highly reflective metal film deposited on a transparent substrate, and the highly reflective metal film has a thickness equal to or less than a wavelength of light from the light source unit, and Made of a material selected from the group consisting of silver, gold, chrome, silicon and germanium, and the interaction of the polymer thin film with organic carbon in water is determined by one of the SPR method and the WG method. The optical sensor according to claim 1, wherein the optical sensor is detected. 5. The optical sensor according to claim 1, wherein the polymer thin film has a thickness of 10 μm or less. 6. The material of the polymer thin film comprises the following repeating units: (In the formula, X is -H, -F, -Cl, -Br, -C.
H _3, represents -CF _3, -CN or -CH ₂ -CH _3, R ¹
It represents the -R ² or -Z-R ^2, Z is, -O -, - S -, - NH -, - NR 2 '-, -
(C = Y)-,-(C = Y) -Y-, -Y- (C = Y)
_{-, - (SO 2) -} , - Y '- (SO 2) -, - (S
_{O 2) -Y ', - Y} ' - (SO 2) -Y '-, - NH-
(C = O)-,-(C = O) -NH-,-(C = O)-
^{NR 2 '-, - Y'} - (C = Y) -Y'- or -O-
(C = O) - (CH 2) n - (C = O) -O- represents, Y represents the same or different O or S, Y 'represents the same or different O or NH, n Represents an integer of 0 to 20, and R ² and R ² ′ represent the same or different hydrogen, linear alkyl group, branched alkyl group, cycloalkyl group, unsaturated hydrocarbon group, aryl group, saturated or unsaturated. Represents a heterocycle or a substitution product thereof. However, R ¹ is not hydrogen, a linear alkyl group, or a branched alkyl group. In the formula, X is preferably H
Or CH ₃ , R ¹ is preferably a substituted or unsubstituted aryl group or —Z—R ² , and Z is preferably —
O-,-(C = O) -O-, or -O- (C = O)-
And R ² is preferably a linear alkyl group, a branched alkyl group, a cycloalkyl group, an unsaturated hydrocarbon group, an aryl group, a saturated or unsaturated heterocycle, or a substitution product thereof. 6. The optical sensor according to claim 1, wherein the optical sensor is a homopolymer or a copolymer. 7. The optical sensor according to claim 6, wherein the material of the polymer thin film is a polymer or copolymer of methacrylic acid or acrylate. 8. The electric circuit according to claim 1, further comprising an electric circuit for receiving the output of the photodetector, wherein the electric circuit obtains a signal representing the concentration of the organic carbon. The optical sensor described.