JPH0481662A - Light applied gas sensor - Google Patents

Abstract

PURPOSE:To identify gas without being interfered by electromagnetic noise by placing a plurality of kinds of organic films comprising an organic substance whose light absorption spectrum irreversibly varies due to adsorption/desorption of gas molecules respectively in a matrix on a substrate. CONSTITUTION:A filter transmitting light of 680nm, 580nm, 610nm and 540nm of filters corresponding to respective absorption wavelengths is placed to constitute an optical system. 1 refers to a light applies sensor of the invention, 11 refers to a glass substrate, and 12 refers to a coloring matter film arrayed in a matrix. In addition, 2 is a filter, 3 is a white light source, 4 is an optical fiber for radiation, 5 is an optical fiber for emission, 6 is a light receiver and 7 is a signal processor, respectively. Coloring light is incident from the light source 3, and the transmitted light is taken out by the optical fiber 5 from the right side of each coloring matter film. Intensity of the taken-out light is detected by the light receiver 6 comprising a photo diode. Since patterns of change in transmitted light intensity largely differ among respective kinds of gas, identification and qualitative analysis of target gas is possible by the pattern.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to an optical gas sensor that can detect and identify substances, particularly gases, using light.

(b) Problems to be Solved by Prior Art and Inventions In recent years, many types of gas sensors have been developed. L11 Komonoto using metal oxide semiconductor is very
It is common, but the selectivity is not high. Gas identification, ) possible -
There are infrared absorption type gas sensors, but they are limited to these small and simple molecules.

Therefore, recently, attempts have been made to identify various target gases by arranging multiple types of metal oxide semiconductor gas sensors and using the difference in output as a basis, and attempts to use quartz crystal oscillators coated with various gas detection substances have been made. .

However, when metal oxide semiconductors are used from the door, they are susceptible to electromagnetic noise, and there are problems with explosion-proofing due to the fact that they are heated to high temperatures. On the other hand, when using a crystal oscillator, there is a problem in that the device becomes complicated, such as requiring a device to measure the oscillation frequency.

The present invention was made under such circumstances, and in particular,
Gas identification is performed by using functional dyes that change the light absorption spectrum due to gas adsorption.
By doing so, the aim is to obtain a gas identification sensor that is not susceptible to electromagnetic noise, has excellent explosion-proof properties, and is therefore inexpensive.

(c) Means for Solving the Problems The present inventor has focused on the fact that certain functional dyes change color when adsorbing gas, and has conducted extensive research.

The molecular structure of functional dyes such as betaine-type dyes and cyanine-type dyes is a zwitterion structure, and the color of the dye changes due to the change in the polarization of the π-electron system that makes the functional dye color. or change. The degree of polarization varies depending on the polarity and other characteristics of the adsorbed molecules. Furthermore, acid-colorable functional dyes have a ring structure such as a lactone ring in their molecular structure, and when the ring is cleaved by an acid, color is developed using a π-electron system. When gas molecules are adsorbed, the interaction with the acid is weakened and the color development of the π-electron system is suppressed.

The present inventors have discovered that by utilizing the characteristics of such functional dyes, it is possible to construct a gas sensor in which the conventional problems have been resolved, and have thus arrived at the present invention.

Thus, according to the present invention, there is provided an optical application cassette in which a plurality of types of organic films made of organic substances whose light absorption spectra are reversibly changed by adsorption and desorption of gas molecules are arranged in matrix on a substrate. Ru.

In the present invention, a plurality of organic films having different optical properties are arranged in a matrix on the same substrate, and the color change of each organic film is measured so that the gas molecules can be identified from the pattern.

As the organic substance used in the present invention, a combination of a betaine type dye, a cyanine type dye, or an acid coloring type dye precursor and an acidic color developer is suitable. In the present invention, a plurality of types of organic dyes are used to construct a plurality of organic films each exhibiting different optical properties, that is, different changes in absorption spectra.

Here, as the betaine type dye, for example, betaine dyes known in the art such as 2.6 diphenyl-4-(2,4,6-)rifenyl-N=pyrinnio)-ferulate can be used, and cyanine type dyes can be used. For example, l-
Known melonoamine dyes and cyanine dyes such as methyl-4-(4-year-old xonoclohexa-2,5-noenylidene)-ethylidene 14-nohydrobiridine can be used. Second, acid coloring type dye precursors include triphenylmethane dyes, fluoran dyes, phthalide dyes,
Indolylphthalide dyes, lactam dyes, etc. are mentioned, and suitable acidic color developers to be used in combination with these include hisphenol A1 bisphenol S1 hisphenol F1p-hydroquine benzoic acid.

Organic films made of such organic substances can be formed in the form of thin films using each organic substance itself, but from the viewpoint of film stability and ease of film formation, polymers mixed with suitable film-forming polymers may be used. It is preferable to use it in the form of a molecular film. Examples of such film-forming polymers include polyvinyl acetate, polyvinyl butyral, polyvinyl chloride, polyacrylic acid or its ester, polymethacrylic acid or its ester, cellulose acetate, and the like.

When this optical sensor is actually used, it is placed in an optical system between a light source and a light receiving section, and various optical systems can be applied. As a light source, two methods are considered: a combination of a white light source and a filter, and an LED lamp. It is also possible to use a LEI lamp, but the wavelength is limited, but it is cheaper and more compact, and the method using a filter allows the wavelength to be changed, but the price of the filter is added. The light receiving section uses a photodiode, a phototransistor, and a photoelectric cell t. Optical systems can be of a transmissive type or a reflective type. In the case of a transmission type, a film is produced on a transparent substrate made of glass or polymer, and in the case of a reflection type, a film is produced on a reflective substrate such as silver or aluminum. An optical fiber may be used for the optical system, and in this case, the optical fiber is
Select the appropriate one depending on the format.

It is preferable that signal processing is performed by an external microcomputer and identification is thereby performed.

(d) The absorption spectrum of each organic film changes reversibly due to the adsorption of working gas molecules, but the pattern of this change differs depending on the target gas. Therefore, it is possible to identify the target gas type based on the pattern of change in the absorption spectrum of each organic film.

(e) Examples The present invention will be explained in detail below.

Example 1 (a) 2,6-nophenyl 4, a type of betaine dye
- (2,4,5-1-rifuniruN-pyridinio)
Dye film made of ferulate and cellulose acetate prepared by spin coding method, (b) Melonoamine dye 1-
Methyl-4-r (4-oxychlorohexa-2,5-
(c) A dye film made of crystal violet lactone and hisphenol A1 polyvinyl chloride prepared by a spin code method, (4) ) Four types of dye films (a) to (d) made of indolylphthalide-based coloring dye (i) and bisphenol A1 polyvinyl chloride and prepared by a spin coding method were placed on a glass substrate in a matrix form (2 x 2 ). Here, the thickness of each pigment film is about 0.4 μm, and the size is 8×8 r.

A filter 61 corresponding to each absorption wavelength is placed on the top of each film! Onm, 580nm, 61
Install a filter that transmits 0nm and 540nm light,
An optical system as shown in FIG. 1(A) was constructed. In the figure, J
is an optical gas sensor of the present invention, +1 is a glass substrate, and I
2 shows a matrix-arranged r-dime membrane. 2 is a filter, 3 is a white light source, 4 is an irradiation optical fiber, 5 is an output fiber, 6 is a light receiver, and 7 is a signal processing section.

The matrix-like pigment film similar to the above is shown in Figure 1 (
As shown in B), it can be arranged on an aluminum plate 13 to form a reflective optical gas sensor. FIG. 1(B) further shows an optical system consisting of a light emitting diode 8, two branched optical fibers, and a photodiode IO, where II is a signal processing section.

In FIG. 1(A), colored light is incident from a light source 3, and the transmitted light is extracted from the right side of each pigmented film through a tip fiber 5. The intensity of the extracted light is detected by a photoreceiver consisting of a photodetector.

The optical system was installed in various gas atmospheres (ethanol, acetone, methanol, ethyl acetate), and the transmitted light intensity (output voltage difference) was evaluated for the transmitted light under gas-free conditions (blank). is shown in Fig. 2 (expressed relatively with the output voltage difference relative to ethanol as 1).

As shown in the figure, the pattern of changes in transmitted light intensity differs greatly depending on each gas, and it can be seen that the target gas can be identified and qualitatively determined based on this pattern.

Example 2 In place of the pigment film (e) in Example 1, a pigment film (eo) made of crystal violet lactone, hisphenol A1 cellulose acetate and produced by a spin coding method was used, and this pigment film (eo ) at the top of 61
An optical system including the gas sensor of the present invention was constructed in the same manner as in Example 1 except for arranging a 0 nm filter.f2.

Using this optical system, the increase/decrease pattern of each absorbance (vs. blank) was adjusted under humid air, methanol, and ethanol gas atmospheres. The results are shown in Table 1.

Table 1 Color Element Film vinegar Humidity 1-11-m= Methanol - -1 Ethanol 1 =------= (Note) Absorbance decrease is indicated by -.

indicates an increase in absorbance.

In this way, from the increase/decrease pattern of absorbance, i! ii! , it can be seen that methanol and ethanol can be clearly distinguished.

(f) Effects of the Invention According to the optical processor of the present invention, gas components can be optically identified and detected based on the pattern of change in the absorption spectrum of each organic film for various gases. Therefore,
It is susceptible to interference from electromagnetic noise; tin scum can be easily identified, and it has excellent explosion-proof properties. However, compared to conventional gas sensors, there are some disadvantages, such as point 11j, which can be manufactured at a lower cost.

[Brief explanation of drawings]

FIGS. 1(A) and 1(B) are schematic diagrams showing an optical system for gas detection using the optical gas sensor of the present invention, and FIGS. 2(A) to (D) are schematic diagrams showing this optical system. It is a graph figure which shows the result when various gases were judged using. 1... Optical gas sensor, 11... Glass substrate, 12... Dye film, 1
3... Aluminum plate. ? Figure 52 (A) (B) (C) (D)

Claims (1)

[Scope of Claims] 1. An optical gas sensor comprising a matrix of a plurality of organic films each made of an organic material whose light absorption spectrum changes reversibly by adsorption and desorption of gas molecules on a substrate. 2. The gas sensor according to claim 1, wherein the organic film is a polymer film containing an organic substance. 3. The gas sensor according to claim 1, wherein the organic substance is a combination of a betaine type dye, a cyanine type dye, or an acid coloring type dye precursor and an acidic color developer.