JP3136104B2 - Optical sensor for detecting organic substances in water - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical sensor for detecting an organic substance dissolved in water, wherein the amount of light reflection is measured by using a sensitive polymer thin film. A polymer thin film that interacts with a dissolved organic substance by reaction, absorption, and adsorption to cause a physical change in film thickness and refractive index is used, and such a physical change in the polymer thin film is measured by an IER method (interference amplification reflection method, interfe).
rence enhanced reflection
an optical sensor that is optimal for determining the concentration of dissolved organic matter in water as measured by the method.

[0002]

2. Description of the Related Art Various reports have been made on the use of polymer thin films in optical sensors to detect gas phase species or chemicals dissolved in water. Many of these reports relate to optical fiber sensors or optical waveguide sensors using evanescent waves and guided waves.

As is well known, when light enters a boundary surface between a dielectric material having a refractive index of n _{1 and} a dielectric material having a refractive index of n ₂ (> n ₁ ), total internal reflection occurs.
The effect occurs when light is incident from the dielectric having the refractive index n _{2 to} the dielectric having the refractive index n ₁ , and the incident angle at that time is larger than the critical angle θc. In addition,
The critical angle θc of total reflection is given by the formula

## EQU1 ## It is represented by θc = sin ⁻¹ (n ₁ / n ₂ ). In this case, all the incident light is reflected into the dielectric of the refractive index n _2, the light will not enter into the dielectric of the refractive index n _1. However, there is a wave effect called an evanescent wave, and the evanescent wave has a refractive index of n ₁ and a refractive index of n _2.
Propagates parallel to the interface with the dielectric. The electric field E of the evanescent wave decays exponentially with the distance z from the boundary surface, and using the exponential function

## EQU2 ## It can be expressed by E = E ₀ exp (−z / d _p ). Here, E ₀ is the electric field at the boundary surface, and d _p is the electric field of the evanescent wave when the light is incident on the boundary surface at the incident angle θ decreases from the value at the boundary surface to 1 / e. The penetration thickness, defined as the distance when

Equation 3] _{d p = λ [2π (n} 2 2 sin 2 θ - n 1 2) 1/2] is represented by.

[0004] As is well known, optical waveguides operate on the principle of total internal reflection. Planar waveguide which is a kind, the third of the second medium and the refractive index n ₃ of the first medium of refractive index n ₂ the refractive index n ₁
Are sandwiched from above and below, and the refractive indices of those media are selected so that n ₂ > n ₃ ≧ n ₁ holds. When the light beam propagates in the first medium at an angle θ larger than the critical angle of total reflection at the interface between the first medium and another medium (in this case, sin θ> n ₃ / n ₂ ≧ n ₁ / n ₂ ), and are confined in the first medium by continuous total reflection. In this case, the waveguide phenomenon (waveguide)
ing), and the light beam present in the first medium is called guided wave. Optical fiber is a waveguide of another form, around the cylindrical core of refractive index n ₂ the refractive index n
₁ (<n ₂ ).

In an evanescent wave sensor or a guided wave sensor, light must propagate at an angle greater than the critical angle of total internal reflection. Typical examples of photochemical sensors based on evanescent waves or guided waves have been introduced in a number of known references, for example, US Pat. No. Re33,064, US Pat.
JP, WO95 / 20151 JP,
Hinrich et al., "I.
Determination of organic compounds by R / ATR spectroscopy (Deter
mination of organic compo
unds by IR / ATR spectrosco
py withpolymer-coatedinte
rnal reflectionelements) "
Applied Spectroscopy, 44 (1
990) 1641-1646, Bark et al., "Optical fiber evanescent monitoring for organic pollutants in water.
Field absorption sensor (A fiber optic
evanescentfield absorbatio
n sensor for monitoring o
rgnic containment in w
ater) "Fresenius J. et al. And Ch
em. , 342 (1922) 394-400, and
"Fiber-optic evanescent wave sensors (Fiber-opti for in situ determination of non-polar organic compounds in water).
c evsnescent wave sensor
for in situ determination
of non-polar organic comp
sounds in water) "Sensors
and Actuators B, 18-19 (199)
4) Fabrication of an integrated optical waveguide chemical vapor microsensor by photopolymerization of a bifunctional low polymer such as 291-295 and Grunini (Fabrication of an in
graded optical waveguid
e chemical vaporsensens
or by photopolymerization
of a bifunctional oligom
er) "Appl. Phys. Lett. , 48 (1
986) 1311-1313, and "Integrated photochemical vapor microsensor (Integrated optics)
al chemical vapor microse
nsor) "Sensors and Actuato
rs, 15 (1988) 25-31, Bauman and Burgess, "Evaluation of polymer thin film waveguides as chemical sensors."
n film waveguide as chemi
cal sensors) "SPIE Proceed
ins Vol. 1368: Chemical, b
iochemical, and environment
ntal fiber sensors II, 199
0, and Osterfeld et al., “Optical gas detection using metal film amplified leaky mode spectroscopy (Optical
gas detection using metal
film enhanced leaky mode
spectroscopy) "Appl. Phys.
Ltt. , 62 (1993) 2310-231.

[0006] Optical sensors that do not utilize evanescent waves or guided waves have also been reported. For example, Gorglitz et al. Report a method of reflection spectroscopy for the detection of organic vapors using swelling of polymer thin films (GTI Fachz. Lab., 889, 7/199).
0). In this method, a sensitive polymer thin film coated on a transparent substrate is irradiated vertically with white light from the substrate side, and the reflected light from the polymer thin film is converged and analyzed by a spectroscope. Here, the wavelength shift of the reflection spectrum caused by the interaction between the polymer and the organic vapor is measured as an index of the concentration of the organic vapor. As described below, the arrangement for vertically incident light has poor sensitivity and must rely on a spectral interferometer. In other words, the method of Goglitz et al. Is complicated, and the equipment for implementing it is expensive and large.

Japanese Patent Application No. 8-145581 filed on June 7, 1996 by the applicant of the present application discloses an invention relating to the use of a planar polymer thin film and the IER method for detecting dissolved organic substances in water. Has been disclosed. The invention uses a detection element in which a polymer thin film is coated on a highly reflective substrate such as opaque silicon or metal, and a light source and a photodetector are arranged above the polymer thin film, and a probe from the light source is used. A configuration is adopted in which water in which an organic substance is dissolved passes through light and reflected light from a polymer thin film. However, it has been found that this method is not always desirable. This is because bubbles or particles in the water scatter or block the light beam, causing large fluctuations and attenuation in the output signal.

[0008]

SUMMARY OF THE INVENTION The present invention has been proposed to overcome the above-mentioned problems, and provides an optical sensor for detecting dissolved organic substances dissolved in water which has a simple structure and high sensitivity. The purpose is to:

[0009]

According to the method adopted by the present invention, a detection element in which an optically transparent substrate is coated with a polymer thin film is used as in the report by Goglitz et al. The light source and the photodetector are arranged on the side where the polymer thin film is not formed. However, the inventors of the present invention have proposed that when light from a light source is incident on a polymer thin film at an angle smaller than the critical angle of total reflection but close to the critical angle, the light is perpendicularly incident as in the report of Goglitz et al. It has been found that the reflectance of the polymer thin film changes significantly as compared with the case. The present invention has been made based on such knowledge, and provides an optical sensor different from the conventional evanescent wave sensor and the covered waveguide sensor.

In order to achieve the above object, the present invention provides an optical sensor for directly detecting an organic substance dissolved in water, comprising: an optically transparent substrate; and an optical sensor formed on the substrate. At least one detecting element having a polymer thin film in contact with the water, at least one light source unit disposed on the substrate side of the detecting element, and a first light source unit disposed on the substrate side of the detecting element. Wherein the substrate couples the light from the light source unit to the polymer thin film at a predetermined incident angle, and detects the light reflected by the detection element by the first photodetector. The predetermined incident angle is smaller than the critical angle of total reflection at the interface between the polymer thin film and the water, and the thickness of the polymer thin film is 0. Sometimes
An optical sensor characterized in that the reflectance is set to a value of 0.1 or more .

[0011] In one embodiment of the present invention,
The optical sensor receives outputs of the second photodetector that directly receives the light from the light source unit, and outputs of the first photodetector and the second photodetector, and obtains a ratio of the outputs. An electronic circuit that outputs a signal indicating the concentration of the organic substance. The light source unit, the first photodetector, the second photodetector, and the optical coupling unit are connected to the detection element. It is attached to the housing in a predetermined positional relationship.

It is preferable that the polymer thin film is made of a material that enables the measurement of the organic substance by the IER method.
The thickness of the polymer thin film is preferably smaller than 10 μm. The substrate is, for example, a prism or a flat plate.
When the substrate is a flat plate, a diffraction grating is formed at a predetermined position on the substrate, or a grating layer on which a diffraction grating is formed is formed between the substrate and the polymer thin film or the polymer thin film of the substrate is formed. Or on the other side.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Some embodiments of the present invention will be described below in detail with reference to the drawings. The present invention relates to an optical sensor for detecting an organic substance in water by measuring changes in the refractive index and the thickness of a polymer thin film that reacts, absorbs, adsorbs, etc., with the organic substance to be detected. The optical sensor measures the concentration of the organic substance by detecting the change in the refractive index of the polymer thin film using the IER method. The IER method is a measurement method utilizing the fact that the intensity of light reflected from a dielectric thin film strongly depends on the thickness of the dielectric thin film.

FIG. 1 schematically shows a basic configuration of a detecting element used in an optical sensor according to the present invention.
In Figure 1, 1 is on one side of the refractive index n ₁ of the transparent substrate 2, the film thickness is detected elements polymer thin film 3 having a refractive index n ₂ and d is formed by spin coating. In addition to spin coating, general methods such as vapor deposition, dip coating, roller coating, sputtering, and CVD (chemical vapor deposition) can be used. It is assumed that the surface of the polymer thin film 3 opposite to the substrate 2 is in contact with water having a refractive index of n ₃ . A light source unit 4 that emits linearly polarized monochromatic light with a wavelength λ is disposed opposite the substrate 2. The monochromatic light 5 emitted from the light source unit 4 is incident on the substrate 2 at an angle θ, and is reflected on a boundary surface 6 between the polymer thin film 3 and water and a boundary surface 7 between the polymer thin film 3 and the substrate 2, respectively. Accordingly, the intensity of the reflected light from the detection element 1 is the superposition of the intensity of the light 8 reflected at the boundary surface 6 and the intensity of the light 9 reflected at the boundary surface 7, and
Therefore, depending on the optical path lengths of the individual lights 8, 9, the light 8,
9 is the sum or difference of the intensities.

The reflectance of the detecting element 1 shown in FIG.
It can be calculated from the well-known Fresnel equation. In addition,
For the Fresnel equation, see M.E. Born and E.L. Wolf, "Principles of Optical
s) ", Pergmon Press, 1959. Now, SF11 having a refractive index n ₁ of 1.7786
On one surface of a glass substrate, a film thickness d of 1.8 μm and a refractive index n
₂ is 1.493 poly (octadecyl methacrylate-c)
o-Glucidyl methacrylate) thin film (this is made of poly (O
DMA-GLMA) (which will be referred to as a thin film) is prepared by spin coating, and a poly (ODMA)
-GLMA) A thin film is disposed so as to be in contact with water having a refractive index n ₃ of 1.332.
When irradiated with 632.8 nm p-polarized light and s-polarized light, poly (ODMA-
GLMA) When the reflectance of the thin film was determined, a graph as shown in FIG. 2 was obtained. As shown in FIG.
A-GLMA) The critical angle θ _C23 of total reflection at the interface between the thin film and water is 48.495 °. Incidentally, the critical angle theta _{C1 2} of total reflection at the boundary surface between the SF11 glass substrate and a poly (ODMA-GLMA) thin film is 57.079 ° (not shown).

From the graph of FIG. 2, when the incident angle θ of light is larger than the critical angle θ _C23 (= 48.495 °), s-polarized light (TE wave) and p-polarized light of a poly (ODMA-GLMA) thin film (TM wave) has a reflectance of 1 and does not depend at all on the thickness of the poly (ODMA-GLMA) thin film.
On the other hand, when the incident angle θ is smaller than the critical angle θ _{C23, the} reflectance of the poly (ODMA-GLMA) thin film for s-polarized light and p-polarized light strongly depends on the thickness of the poly (ODMA-GLMA) thin film. .

FIG. 3 shows the thickness of the poly (ODMA-GLMA) thin film and the s-polarized light when the detection element used to obtain the graph of FIG. 2 is irradiated with light of the same wavelength (λ = 632.8 nm). Is a graph showing the relationship between the reflectance and the reflectance for a plurality of incident angles θ (<critical angle θ _C23 = 48.495 °). Comparing the graphs of FIG. 3 with each other, the incident angle θ
<When the critical angle theta _C23, the incident angle theta approaches the critical angle theta _C23, poly (ODMA-GLMA) reflectivity of the thin film strongly depends on the film thickness, when the incident angle theta is longitudinal 48 ° It can be seen that the dependence of the reflectance of the poly (ODMA-GLMA) thin film on its thickness is maximized. The degree of change in the reflectance rapidly decreases as the incident angle θ becomes smaller than the critical angle θ _C23 . When the incident angle θ is 10 °, the degree of change in reflectance is extremely small.

As described above, the arrangement of the goggles or the like for vertically incident light described in the prior art has a very small change in reflectance due to the thickness or refractive index of the polymer thin film, and therefore has poor sensitivity. An object of the present invention is to provide an optical sensor having high sensitivity and a simple configuration.

FIG. 4A is a sectional view schematically showing the configuration of the optical sensor according to the present invention. The optical sensor 10 includes a detection element 11, a light source unit 12, and a first photodetector 1.
3 and a second photodetector 14. As shown in FIG. 4B in an enlarged manner, the detection element 11 is formed by forming a polymer thin film 16 to a predetermined thickness on one surface of a prism 15 acting as the substrate 2 in FIG. On the flow cell 17 to be passed, the polymer thin film 16 is
7 is attached so as to come into contact with the water in 7. Flow cell 1
7 has an inlet 18 and an outlet 19 for water.

The light source section 12 includes a light source 20, a beam splitter 21, and a polarizing plate 22. The light source 20 is, for example, a laser diode (LD) or a light emitting diode (LE).
D) and emits visible light or infrared light. Light emitted from the light source 20 is split by the beam splitter 21 into probe light and reference light. The probe light passes through the polarizing plate 22 and becomes linearly polarized light. This linearly polarized light is preferably s-polarized light (ie, polarized light whose electric field is perpendicular to the plane of incidence). The probe light passes through the prism 15 and is incident on the polymer thin film 16 at an incident angle θ smaller than the critical angle θ _C of total reflection at the interface between the polymer thin film 16 and water, and is reflected by the polymer thin film 16. The reflected probe light is received by the first photodetector 13 and converted into a signal representing the intensity. On the other hand, the reference light which is the other light split into two by the beam splitter 21 is received by the second photodetector 14 and converted into a signal representing the light intensity for reference. The signals output from the first photodetector 13 and the second photodetector 14 are supplied to an appropriate electronic circuit having, for example, a sampling and holding circuit and a comparison circuit, and a ratio between the signals is obtained. By using this ratio, the concentration of the organic substance in the water can be determined.

In order to perform such light emission, reflection and detection, as shown in FIG. 4, a light source unit 12, a first light detector 13 and a second light detector 14 It is attached to the housing 23 in a predetermined relationship. Note that an optical fiber may be connected between the light source unit 12 and the prism 15 and between the prism 15 and the first photodetector 13. As the first photodetector 13 and the second photodetector 14, for example, a photodiode or a phototransistor can be used.

In the optical sensor according to the present invention,
The incident angle θ when light emitted from the light source unit enters the polymer thin film is smaller than the critical angle θ _C of total reflection at the interface between the polymer thin film and water and is a value close to the critical angle θ _C It is desirable. By selecting an incident angle θ such that the reflectance when the film thickness is 0 is preferably 0.1 or more, particularly preferably 0.2 or more, and more preferably 0.3 or more, higher sensitivity can be obtained. A sensor is obtained. For example, as shown in the graph of FIG. 3, in the case of a poly (ODMA-GLMA) thin film spin-coated on an SF11 glass substrate, the incident angle θ of s-polarized light having a wavelength of 632.8 nm is 40 ° to 48 °.
It is preferred that On the other hand, the thickness of the polymer thin film is usually desirably in the range of several nanometers to 10 μm, but the thickness of the polymer thin film optimal for detection by the IER method is not particularly limited. However, as can be understood from the graph of FIG. 3, since the change in the reflectance is small near the maximum value or the minimum value of the reflectance, the film thickness of the polymer thin film is the film thickness at which the reflectance is maximized and the film thickness at which the reflectance is minimized. It is desirable to choose a value between the thickness.

The substrate of the detecting element of the optical sensor according to the present invention is preferably transparent, and its material is, for example, glass, plastic, polymer or semiconductor. Alternatively, a very thin (50 nm or less) metal layer, inorganic dielectric film, or semiconductor layer may be deposited on such a transparent substrate. However, the reflectivity of the polymer thin film varies depending on the refractive index of the material used for the substrate. FIG. 5 is a graph showing how the refractive index of the substrate affects the reflectance of the polymer thin film, where the refractive index n ₁ is 1.5143,
On one surface of the transparent substrates of 1.7786 and 2.3513, three poly (ODMA-GLMA) thin films having a thickness d of 1.8 μm and a refractive index n ₂ of 1.493 were formed by spin coating. Each detection element is prepared, and the refractive index n ₃
Is in contact with 1.332 water so that poly (ODMA-GL
MA) shows the relationship between the thickness of the polymer thin film and its reflectance when the substrate is irradiated with light having a wavelength λ of 632.8 nm with the thin film disposed. From this graph, it can be seen that the reflectance of the polymer thin film is more sensitive to the change in the film thickness when a substrate having a large refractive index is used, and therefore it is desirable.

The substrate will be further described. In the optical sensor shown in FIG.
Is a substrate 2 on which the polymer thin film 16 is formed. At the same time, the probe light from the light source unit 12 is coupled to the polymer thin film 16 and the reflected light therefrom is coupled to the first photodetector 13. It is also used as optical coupling means. However, such an optical coupling function is not limited to the prism, but can be realized by various means. Typical examples thereof include those using diffraction grating coupling and side coupling (side-light coupling). (coupling).

Hereinafter, a detection element using diffraction grating coupling will be described with reference to FIGS. 6A to 6D, and a detection element using side coupling will be described with reference to FIG. 6E. (A) shows a detection element in which a diffraction grating portion 25 is formed on a part of a surface of a transparent substrate 24 and a polymer thin film 26 is formed on the surface. The detection element shown in FIG. 2B has a grating layer 28 on which a diffraction grating portion 27 is formed between a substrate 24 and a polymer thin film 26. In the detection element shown in FIG. 3C, diffraction grating portions 25 are formed on a portion of the surface of the substrate 24 where light is incident and a portion where light reflected by the polymer thin film 26 is emitted. (D) shows a detection element in which a grating layer 28 having a diffraction grating portion 27 formed on a surface on which light is incident is used and provided on a surface of the substrate 24 which is not in contact with the polymer thin film 26. I have. On the other hand, in the detection element shown in FIG. 3E, light is incident on one side surface 29 of the substrate 24 perpendicular to the polymer thin film 26, and the reflected light from the polymer thin film 25 is extracted from the other side surface 30 so as to be connected to the side surface. Use

The material of the polymer thin film used in the optical sensor according to the present invention is as follows:

Embedded image Homopolymers or copolymers having the following are preferred.

In the formula, X is -H, -F, -C1, -B
_{r, -CH 3, -CF 3,} -CN or _-CH 2 _{-CH 3}
Wherein R ¹ represents -R ² or -ZR ² , and Z represents-
O -, - S -, - NH-, one ^{NR 2 '-, - (C} = Y)
-,-(C = Y) -Y-, -Y- (C = Y)-,-(S
O ₂ )-, -Y '-(SO ₂ )-,-(SO ₂ )-
_{Y ', - Y' - (} SO 2) -Y '-, - NH- (C =
O)-,-(C = O) -NH-,-(C = O) -N
^{R 2 '-, - Y'} - (C = Y) -Y'- or -O- (C
_{= O) - (CH 2)} n - (C = O) represents -O-, 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, R ² and R ² ′ represent the same or different hydrogen, It represents a linear alkyl group, a branched alkyl group, a cycloalkyl group, an unsaturated hydrocarbon group, an aryl group, a saturated or unsaturated hetero ring, or a substituted product thereof. However, R ¹ is not hydrogen, a side chain 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 -ZR 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 hetero ring or a substituted product thereof.

The polymer used for the polymer thin film may be a polymer consisting of only a single repeating unit (I) or a copolymer consisting of another repeating unit and the above-mentioned repeating unit (I). ) May be used. The sequence of the repeating units in the copolymer may be any, for example, random copolymer,
Alternating, block or graft copolymers can be used. In particular, the polymer thin film is preferably prepared from polymethacrylates and polyacrylates. 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.

Particularly preferred polymers for the polymer film are poly (dodecyl methacrylate) poly (isodecyl methacrylate) poly (2-ethylhexyl methacrylate) poly (2-ethylhexyl methacrylate-co-methyl methacrylate) poly (methacrylic 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-) o-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-meth-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 ( Poly (cyclohexyl methacrylate-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 (methacrylic Butyl acrylate-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-methacrylic acid) Methyl) poly (dodecyl methacrylate-co-ethyl methacrylate) poly (2-ethylhexyl methacrylate-co-dodecyl methacrylate) poly (2-ethylhexyl methacrylate-co-octa methacrylate) Poly (2-ethylbutyl methacrylate-co-benzyl methacrylate)) poly (tetrahydrofurfuryl methacrylate-co-glycidyl methacrylate) poly (styrene-co-octadecyl acrylate) poly (octadecyl methacrylate-co-methacryl) Glycidyl acid) 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 methacrylic 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 can be increased by cross-linking the polymer. The crosslinking method is not particularly limited, and a conventionally known crosslinking method, for example, a method by heating or a method by irradiation with light or radiation can be used.

In the optical sensor according to the present invention,
Since the refractive index of the polymer thin film and the swelling of the polymer thin film fluctuate with temperature, the characteristics of the optical sensor must be affected to some extent by the temperature. Therefore, temperature control or temperature compensation is required to perform accurate measurement.
Such temperature control or temperature compensation includes (1) housing the optical sensor in a temperature-controlled case, or controlling the temperature of water flowing in the flow cell, and (2) attaching a temperature sensing element to the optical sensor. To make a temperature correction signal, (3)
It can be realized by using an appropriate method such as generating a temperature correction reference signal using a polymer that is more sensitive to temperature than a polymer thin film.

Further, the configuration of the optical sensor according to the present invention can be changed so that the concentration of a mixture of organic substances (for example, hydrocarbons) dissolved in water can be measured. Such modifications include (1) using one type of polymer thin film with low or low sensitivity to multiple organic substances, (2) using multiple polymer thin films, each responding to another type of organic substance, A method of generating a signal representing the concentration of a mixture of organic substances by combining the responses of each polymer thin film (3) using a plurality of polymer thin films each showing a different response to the same or another organic substance in water A method of generating a signal representing the concentration of the mixture of organic substances by combining the responses of the respective polymer thin films; (4) using one or more of the above-described polymer thin films by different optical methods (for example, IER method, surface Plasmon resonance or combined guided mode spectroscopy) to generate a signal representing the concentration of a mixture of organic substances, alone or in combination It can be implemented by use. In this case, depending on the mode of using the methods (1) to (4) alone or in combination, it may be necessary to provide a plurality of detection elements, light source units, and photodetectors.

In fact, the sensitivity and response time of the optical sensor according to the present invention vary depending on the type of the organic substance to be measured. Therefore, in order to accurately measure the total amount of organic substances and the concentration of individual organic substances or groups of organic substances in various applications, the optical sensor is multi-channeled by the above-described methods (1) to (4). It is also possible to use in combination with a known pattern recognition technique (for example, matrix analysis, neural network analysis).

Hereinafter, an actual example of a result of measurement of an organic substance in water using the optical sensor according to the present invention will be described with reference to FIGS. The optical sensor used to obtain these measurement results has the same configuration as the optical sensor shown in FIG. 4, and the detection element is a 1 μm thick poly (ODMA-GLMA) thin film formed on a SF11 glass substrate by spin coating. And the glass substrate is made of poly (ODMA-GLM
A) A 90 ° glass prism is mounted on a surface on which no thin film is formed by using a refractive index matching oil.
A He-Ne laser having a wavelength of 632.8 nm was used as a light source, and a photodiode was used as a first photodetector and a second photodetector. As described above, the laser light emitted from the light source is split into the probe light and the reference light by the beam splitter. The probe light is converted into s-polarized light by a polarizing plate, is incident on the prism at an incident angle of 45 °, and supplies the probe light reflected by the poly (ODMA-GLMA) thin film to the first photodetector. On the other hand, the reference light is supplied to a second photodetector. Signals representing the intensities of the probe light and the reference light were generated by the first photodetector and the second photodetector, respectively, and supplied to the electronic circuit to obtain measurement results.

Example 1: FIG. 7 shows that the concentration in water was 10-20.
5 is a graph depicting the reflectance of an optical sensor as a function of time when 0 ppm of toluene is dissolved. This graph shows that the optical sensor of the present invention has high sensitivity and quick response. The detection limit is around 1-2 ppm, and the 90% response time is less than 2 minutes.

The relationship between the response of the detection element and the concentration of toluene in water is as shown in FIG.
It was found that the reflectance of the detection element changed linearly in proportion to the concentration of toluene in water.

In Example 2, in order to examine the relationship between the response of the detection element and the concentration of other organic substances in water, the reflectance of the detection element was determined for benzene and p-xylene in addition to toluene. Was measured while changing the concentrations of the organic substances, and the graph of FIG. 9 was obtained. from here,
Assuming that the response of the detection element changes linearly in proportion to the concentrations of the three organic substances of toluene, benzene and p-xylene, and that the sensitivity of the detection element to benzene is 1, assuming that the sensitivity of the detection element to benzene is 1, The sensitivities to xylene were found to be 3.5 and 9.25, respectively.

[0039]

As will be understood from the above description of the present invention in detail with reference to some embodiments, the present invention has a higher sensitivity and accuracy than a conventional optical sensor proposed by Googlitz or the like. This provides a special effect that an optical sensor that is expensive and has a simple configuration can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a basic configuration of a detection element used for an optical sensor according to the present invention.

FIG. 2 is a graph showing a relationship between an incident angle of light and a reflectance of a polymer thin film in the detection element of FIG.

FIG. 3 is a graph showing the relationship between the thickness of a polymer thin film and its reflectance in the detection element of FIG. 1 for a plurality of incident angles.

FIG. 4A is a cross-sectional view schematically showing one embodiment of an optical sensor according to the present invention, and FIG. 4B is an enlarged view of a part thereof.

5 is a graph showing the relationship between the thickness of a polymer thin film and its reflectance in the optical sensor of FIG. 4 for a plurality of substrates having different refractive indices.

FIGS. 6A to 6D are diagrams illustrating a modified example of the detection element in the optical sensor according to the present invention, wherein FIGS.
FIG. 3A is a diagram illustrating a detection element using diffraction grating coupling, and FIG. 3E is a diagram illustrating a detection element using side coupling.

FIG. 7 is a graph showing the time change of the response of the optical sensor according to the present invention when the organic substance in water is toluene having a concentration of 10 to 200 ppm.

FIG. 8 is a graph showing that the response of the optical sensor according to the present invention changes linearly with changes in the concentration of toluene in water.

FIG. 9 is a graph showing that the response of the optical sensor according to the present invention changes linearly with changes in the concentration of toluene, benzene and p-xylene in water.

[Explanation of symbols]

1: detection element, 2: substrate, 3: polymer thin film, 4:
Light source, 6, 7: boundary surface, 10: optical sensor, 1
1: detection element, 12: light source unit, 13: first light detector, 14: second light detector, 15: prism, 1
6: polymer thin film, 17: flow cell, 20: light source,
21: beam splitter, 22: polarizing plate, 23: housing, 24: substrate, 26: polymer thin film, 2
5, 27: diffraction grating portion, 28: grating layer.

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Hironobu Yamamoto 1-3-2 Minamidai, Kawagoe-shi, Saitama Hoechst Industry Co., Ltd. Advanced Materials Technology Laboratory (72) Inventor Akihiro Takaya 1-3-Minamidai, Kawagoe-shi, Saitama 2 Hoechst Industry Co., Ltd. Advanced Materials Technology Laboratory (56) References JP-A-7-260773 (JP, A) JP-A-8-184560 (JP, A) JP-A-6-222006 (JP, A) (58) ) Field surveyed (Int. Cl. ⁷ , DB name) G01N 21/00-21/83 JICST file (JOIS)

Claims (9)

(57) [Claims] 1. An optical sensor for directly detecting an organic substance dissolved in water, comprising: an optically transparent substrate; and a polymer thin film formed on the substrate and in contact with the water. One detection element and at least one detection element disposed on the substrate side of the detection element
And a first photodetector disposed on the substrate side of the detection element, wherein the substrate couples light from the light source unit to the polymer thin film at a predetermined incident angle. And functioning as an optical coupling means for coupling the light reflected by the detection element to the first photodetector, wherein the predetermined incident angle is set to the interface between the polymer thin film and the water. Is smaller than the critical angle of total reflection at 0 and the thickness of the polymer thin film is 0
An optical sensor characterized in that the reflectance is set to a value that is 0.1 or more . 2. The optical sensor according to claim 1, wherein the second light detector directly receives light from the light source unit, the first light detector, and the second light detector. An electronic circuit that receives the outputs of the above and outputs a signal representing the concentration of the organic substance by calculating the ratio of the outputs. 3. The optical sensor according to claim 2, wherein the light source unit, the first photodetector, the second photodetector, and the optical coupling unit are provided with respect to the detection element. An optical sensor, comprising: a housing for maintaining the positional relationship of the optical sensor. 4. The optical sensor according to claim 1, wherein the polymer thin film is made of a material that enables measurement of the organic substance by an IER method. Sensor. 5. The optical sensor according to claim 1, wherein the thickness of the polymer thin film is 10 μm.
An optical sensor characterized in that it is selected smaller than. 6. The optical sensor according to claim 1, wherein the substrate is a prism. 7. The optical sensor according to claim 1, wherein the substrate is a flat plate, and a diffraction grating is formed at a predetermined position on the substrate. Sensor. 8. The optical sensor according to claim 1, wherein the substrate is a flat plate, and a grating layer having a diffraction grating is provided between the substrate and the polymer thin film. Alternatively, the optical sensor is provided on a surface of the substrate on which the polymer thin film is not formed. 9. The optical sensor according to claim 1, wherein the substrate is a flat plate, and a side coupling is used as the coupling unit. Sensor.