WO2022196486A1

WO2022196486A1 - Method for measuring optical spectrum and device for measuring same

Info

Publication number: WO2022196486A1
Application number: PCT/JP2022/010262
Authority: WO
Inventors: 肇川波; 哲也小平
Original assignee: 国立研究開発法人産業技術総合研究所
Priority date: 2021-03-18
Filing date: 2022-03-09
Publication date: 2022-09-22
Also published as: JP2022144260A

Abstract

The present invention provides a measurement method, as well as a device therefor, that makes it possible to measure an optical spectrum with high sensitivity, high accuracy, and stability even for a solution containing bubbles, without being affected by the generation or growth of the bubbles. The device is used to provide a cell with a solution having particles of a diffuse reflecting material added thereto and to measure the optical spectrum of the solution. The device includes: a rotary mechanism that performs rotational stirring about a rotation axis so as to form a dispersed flow of the particles of the diffuse reflecting material along an optical window of the cell; and an optical system that provides incident light through the optical window, that acquires diffuse reflection light scattered by the particles of the diffuse reflecting material, and that measures the optical spectrum thereof. With this device, particles of a diffuse reflecting material are added to a solution, and rotational stirring is performed about the rotation axis so as to form a dispersed flow of the particles of the diffuse reflecting material along the optical window of the cell. Incident light is provided through the optical window, diffuse reflection light scattering from the particles of the diffuse reflecting material is acquired, and the optical spectrum thereof is measured.

Description

Method and apparatus for measuring optical spectrum

The present invention relates to a method and device for measuring the optical spectrum of a solution, and more particularly to a method and device for measuring the optical spectrum of a solution containing air bubbles.

Hydrogen (H ₂ ) and carbon dioxide (CO ₂ ) can be selectively obtained by decomposing formic acid (HCOOH) in the presence of a suitable catalyst while generating little carbon monoxide (CO). For example, Patent Document 1 discloses a method of obtaining high-pressure hydrogen and carbon dioxide by performing a reaction in a pressure vessel using a liquid catalyst composed of a metal complex. Here, for in-situ observation of the deterioration state of the metal complex catalyst dissolved in the reaction solution, it is proposed to measure the optical spectrum of the solution. On the other hand, in a solution of such a reaction system, light is scattered and/or reflected by the generated bubbles (gas bubbles). Sufficient and stable light intensity cannot be obtained, resulting in a signal with a low signal-to-noise ratio (S/N ratio).

Here, many methods have been proposed to increase the S/N ratio in optical absorption spectrum measurement. For example, Patent Literature 2 discloses a method of collecting light using an integrating sphere to increase the light absorption intensity and measuring the light absorption spectrum. In addition, in Non-Patent Document 1, in general, in the diffuse reflection method for measuring powders and solid samples, the surface of the powder is impregnated with oil, which is a liquid, and dried, and the surface is mirror-finished. A method for measuring the light absorption spectrum by increasing the intensity of reflected light from fats and oils by the diffuse reflection method is described above.

JP 2016-124730 A JP-A-5-118911

As described above, in a reaction system that generates gas such as the decomposition reaction of formic acid, air bubbles contained in the solution make it difficult to accurately measure the light absorption spectrum of the solution. Also, bubbles (gas bubbles) are generated from the inner surface of the reaction vessel, adhere to the site, grow, and finally detach. That is, the volume, density, and distribution state of bubbles change temporally and spatially. Therefore, even if the photosensitivity of the light-receiving system is increased, in measurements that require a certain amount of time, such as wavelength sweep-type measurements and repeated (interval) measurements that track changes over time, temporal and spatial bubble is reflected in the measurement data, making stable and accurate measurement difficult.

The present invention has been made in view of the above circumstances, and its object is to propose a novel technique in a method and apparatus for measuring the optical spectrum of a solution. The object of the present invention is to provide a measuring method and an apparatus therefor, which can measure an optical spectrum with high sensitivity, high precision and stability without being affected by the generation and growth of bubbles even in a solution containing the same.

The inventors of the present application fundamentally reconsidered the concept and measurement method of the diffuse reflection method, which is generally a spectroscopic analysis method for powders and solid samples, and as a result of intensive research, liquid samples, in particular, gas It has been found that even in the case of a reaction system solution, it is possible to provide a measurement method and apparatus capable of temporally and spatially stabilizing the detection signal and increasing the signal intensity.

Specifically, in the conventional diffuse reflectance optical spectrum measurement, the object to be measured is generally a powder, which has a color that absorbs light and separates the individual particles. functions as a bearer of light scattering. At this time, a colorless and transparent gas (gas) such as air or a vacuum state due to degassing is interposed between the particles. Here, in the present invention, contrary to the concept of the conventional diffuse reflection method described above, the solution itself, which is the object to be measured, has a color, that is, has light absorption, and colorless and transparent powder particles are contained in the solution. I came up with the basic idea of diffusing or reflecting the light by dispersing the In other words, compared with the conventional diffuse reflection method, it can be said that there is a positive-negative relationship. Based on this idea, the present invention has been completed by combining the rotary stirring method described later.

That is, the method according to the present invention is a method of measuring the optical spectrum of a solution provided in a cell, adding diffuse reflector particles to said solution and dispersing the flow of said diffuse reflector particles along the optical windows of said cell. While rotating and stirring around the rotation axis so as to form Characterized by

According to this feature, it is possible to measure the solution in the vicinity of the optical window and to measure the optical spectrum with high sensitivity, high accuracy and stability without being affected by the state of the other solution parts. It is possible to measure even high-concentration solutions and suspensions that could not be spectroscopically analyzed in the past, and it is possible to measure optical spectra in a wide wavelength range from ultraviolet to visible to near-infrared to infrared.

The above-described invention may be characterized by including a light collecting means for collecting the diffusely reflected light scattered by the diffusely reflecting material particles. According to this feature, the reflected light intensity can be increased, and the optical spectrum can be measured with high sensitivity and high accuracy.

In the above-described invention, the solution may contain air bubbles, and the air bubbles may be unevenly distributed around the rotating shaft by centrifugal force due to the rotational stirring. Further, the air bubbles may be characterized by being generated by the reaction of the solution. According to this feature, even if the solution contains air bubbles, the optical spectrum can be measured with high sensitivity and high accuracy without being affected by the generation or growth of the air bubbles.

An apparatus according to the present invention also provides a cell with a solution to which diffuse reflector particles have been added and measures the optical spectrum of the solution, wherein the dispersion of the diffuse reflector particles along the optical window of the cell. A rotating mechanism for rotating and agitating around a rotating shaft so as to form a flow, applying incident light through the optical window, obtaining diffusely reflected light scattered by the diffusely reflecting particles, and measuring its optical spectrum. and an optical system for

According to this feature, measurement can be performed in the solution in the vicinity of the optical window, and highly sensitive, highly accurate, and stable optical spectrum measurement can be performed without being affected by the state of other portions of the solution. It becomes like this. It is now possible to measure even high-concentration solutions and suspensions that could not be spectroscopically analyzed in the past, and it is possible to measure optical spectra in a wide wavelength range from ultraviolet to visible to near-infrared to infrared.

The above-described invention may be characterized by including light collecting means for collecting the diffusely reflected light scattered by the diffusely reflecting material particles. According to this feature, the intensity of reflected light can be increased, and high-sensitivity, high-precision, and stable optical spectrum measurement can be performed.

The above invention may be characterized in that the solution contains air bubbles, and a control unit that controls a rotation mechanism so that the air bubbles are unevenly distributed around the rotating shaft by the centrifugal force generated by the rotational stirring. According to this feature, even in a solution containing air bubbles, highly sensitive, highly accurate and stable optical spectrum measurement can be performed without being affected by the generation or growth of the air bubbles.

Fig. 3 shows the principle of measurement according to the invention; (b) is a schematic enlarged view of the portion P of (a). 1 is a schematic plan view of a device according to the invention; FIG. 1 is a plan view of essential parts of a device according to the invention; FIG. 1 is a side view of the main part of the device according to the invention; FIG. 1 is a graph of absorbance versus wavelength according to one embodiment of the present invention; 4 is a graph of absorbance versus solution concentration at each wavelength according to one embodiment of the present invention; 4 is a graph of absorbance versus wavelength according to a comparative example; It is a graph of absorbance versus solution concentration at each wavelength according to a comparative example. 1 is a graph of (a) absorbance vs. wavelength, (b) with its vertical axis enlarged at each concentration of a solution according to one embodiment of the present invention; 1 is a graph of (a) absorbance versus solution concentration at each wavelength according to one embodiment of the present invention, and (b) an enlarged vertical axis thereof. 1 is a graph showing (a) absorbance versus wavelength and (b) an enlarged vertical axis at each concentration of a diffuse reflector according to one embodiment of the present invention. 1 is a graph of (a) absorbance versus amount of diffuse reflector at each wavelength according to one embodiment of the present invention, and (b) an enlarged vertical axis thereof. 4 is a graph of light absorption spectra for various amounts of diffuse reflector according to one embodiment of the present invention; 1 is a structural formula of a catalyst used in one embodiment of the present invention; 1 is a graph of (a) absorbance versus wavelength and (b) an enlarged horizontal axis thereof at each measurement time according to one embodiment of the present invention; 2 is a graph of (a) absorbance versus wavelength at various concentrations of iridium complexes, and (b) absorbance versus concentration of iridium complexes at various wavelengths, according to one embodiment of the present invention. 1 is a graph of (a) absorbance versus wavelength and (b) absorbance versus measurement time according to one embodiment of the present invention. 4 is a graph of absorbance versus wavelength.

As shown in FIG. 1(a), in order to uniformly disperse the bubbles 110 in the solution S of a reaction system that generates gas such as the decomposition reaction of formic acid, the solution S is rotated in a rotary stirring vessel 100. Rotational stirring at high speed around the shaft is contemplated. Here, diffuse reflector particles 112 having a density higher than that of the solvent are put in the solution S and suspended. Then, due to centrifugal force, low-density bubbles 110 gather around the rotation axis (central axis) C of the rotary stirring tank 100, while high-density diffuse reflector particles 112 are unevenly distributed along the outer wall 100a of the rotary stirring tank 100. and forms a dispersed flow, and the air bubbles 110 are spatially separated. In this state, the incident light (probe light) _L0 is incident on the rotating stirring tank ₁₀₀ through the transparent outer wall 100a, and the reflected light (diffuse reflected light) L1 scattered by the diffuse reflector particles 112 is collected. By measuring the optical spectrum, the measurement can be made without being affected by the air bubble 110 . If the concentration of the diffuse reflector particles 112 is high, the distance between the particles for light reflection is shortened. As a result, the light absorption by the solution existing between the particles is apparently weakened and reflected in the diffuse reflectance spectrum. This will be described later in Examples.

According to the above-described method, it is possible to measure even high-concentration solutions, suspensions, etc., for which optical spectra cannot be measured conventionally, regardless of whether gas is generated during the reaction and bubbles 110 are generated or not. The incident light L ₀ can also measure the optical spectrum using light in a wide range of wavelengths, such as ultraviolet to visible to near infrared to infrared, making it possible to measure the optical spectrum of reactions and solutions that could not be measured before. Become. Examples include water as the main solvent and hydrogen as the generated gas, but the combination is not limited to this combination. For example, it can be applied to optical spectrum measurement in a system in which a gas (bubbles) mixed with a solution exists. Moreover, the solvent is not limited to water, and inorganic, organic, and mixed solutions thereof can also be applied.

FIG. 1B is a partially enlarged view of FIG. According to this, the light L ₀ incident on the solution S, or the light reflected by or transmitted through a certain diffuse reflector particle 112, is reflected by or transmitted through another diffuse reflector particle 112. Repeat. Here, since the diffuse reflector particles 112 are made of a transparent material that does not absorb the incident light _L0 or the like, the light transmitted through the particles 112 is not attenuated. In other words, the attenuation of light is due to the solution S present between the diffuse reflector particles 112 .

Therefore, when the concentration of the diffuse reflector particles 112 increases, the average distance between the particles decreases, and the attenuation of light due to the light absorption of the solution S becomes difficult. be. On the other hand, when the concentration of the diffuse reflector particles 112 is low, the light absorption intensity is apparently stronger. For these reasons, if the concentration of the diffuse reflector particles 112 is too low, the frequency of diffuse reflection by the diffuse reflector particles 112 will decrease, and the effect of the air bubbles 110 will relatively increase. In addition, the incident light _L0 may pass through the solution S and reach the opposite side of the rotating stirring vessel (cell). For this reason, it should be considered that the measurement accuracy of the wavelength dependence of the light absorption intensity may be lowered. This will be discussed later.

FIG. 2 shows the concept of a measuring device that accommodates the above-described rotary stirring vessel 100 as a cell 30. As shown in FIG. The apparatus 1 comprises a light source section 10 including a light source 10a, reflecting

mirrors

11 and 12, a sample chamber 20 containing a cell 30, and a spectroscopic section 40. Incident light ( The probe light) L ₀ is directed to the cell 30 of the sample chamber 20 . Further, the reflected light L1 from the cell 30 is led to the spectroscopic section 40 via the reflecting mirror ₁₂ to perform spectroscopic analysis.

3 and 4 show a more detailed optical configuration around cell 30. FIG. Second reflecting mirrors 11 a and 12 a are inserted in the optical paths of the incident light L ₀ and the reflected light L ₁ , respectively, forming optical paths from the sample chamber 25 to the cell 30 and to the spectroscopic section 40 .

Here, the light source 10a of the light source unit 10 is selected according to the purpose of measurement, and is a light source that generates light of wavelengths in each region of ultraviolet, visible, near-infrared, and infrared light or in a region straddling these regions. is. As the light source, in addition to light sources such as halogen lamps, deuterium lamps, xenon lamps, and Globar lamps, monochromatic, high-luminance, and high-coherence light sources such as lasers can be selected according to the purpose.

Light from the light source 10 a is collected by the reflecting mirror 11 and can be applied to the cell 30 . If necessary, instead of the reflecting mirror 11, a lens, an optical fiber, or the like may be interposed therebetween. A sample made of a mixture of the solution S and the diffuse reflector particles 112 in the cell 30 emits _a reflected light L1 along with the irradiation of the incident light _L0 . The detection sensitivity can be enhanced by condensing the light with a condensing means such as the reflecting mirror 12 at a solid angle as large as possible. Note that the diffusely reflected light L1 may be condensed by _a lens, an optical fiber, or the like, as in the case of light irradiation. The condensed light is introduced into the spectroscopic section 40, and the light intensity corresponding to the wavelength is detected. The spectroscopic unit 40 can be selected according to its purpose, for example, a high-performance dual spectrometer with low stray light or a high-sensitivity two-dimensional detector in fluorescence/Raman scattering spectrum measurement.

The sample (solution) S in the cell 30 is irradiated with the incident light _L0 from the light source unit ₁₀ , and the reflected light L1 is spectroscopically detected to detect the light intensity. A known measurement method may be used in which the cell 30 is irradiated with monochromatic light that has been dispersed, instead of irradiating the cell 30 with light to be dispersed. Also, in fluorescence measurement, monochromatic light can be irradiated, and the spectroscopic unit 40 also has a spectroscopic function. Furthermore, for optical absorption spectra in the infrared region, modulated light that has passed through an interferometer (typically a Michelson interferometer) may be used as the incident light _L0 .

Although the concave reflecting mirror 12 is used here, barium sulfate or alumina is used instead of the reflecting mirror ₁₂ for the purpose of condensing the diffusely reflected light L1 from the sample in the cell 30 and guiding it to the spectroscopic section 40 . The diffusely reflected light L1 may be condensed at _a larger solid angle by using an integrating sphere coated with a white powder such as, for example, or coated with a metal such as aluminum or gold. However, when the light absorption of the solution (sample) is strong, the reflected light L ₁ from the solution (sample) in the cell 30 may be mixed with the reflected light L ₂ from the surface of the cell 30 (see FIG. 4 in particular). It is also required to prevent this and improve measurement accuracy.

In general, when a flat solid powder is irradiated with light, the diffusely reflected light is emitted at a solid angle of 2π. Therefore, as long as the solution in the cell 30 can be irradiated with light, there is no condition on the angle of incidence. _The same applies to the direction of the detected reflected light L1. However, since the angular dependence of the intensity distribution of the reflected light L1 is maximized when the incident angle and the reflection angle _match , as in the case of light reflection in a normal smooth-plane continuum material, It is preferable to collect the _diffusely reflected light L1. At this time, since the reflection angle is close to the reflection angle of specularly reflected light from the surface of the cell 30, it is necessary to pay attention to mixing of the specularly reflected light, as described above.

The sample chamber 20 is a chamber (space) in which the temperature and pressure of the cell 30 can be kept constant, and the sample chamber 20 and the cell 30 may be integrated. It can be appropriately selected according to the temperature and pressure conditions required for the process, the medium to be introduced into the cell 30, and the like.

For example, to cool the temperature of the cell 30, a cryostat or the like is used to control the temperature with liquid helium, liquid nitrogen, liquid oxygen, liquid carbon dioxide, etc., and each temperature of -269 ° C., -196 ° C., -183 ° C. or higher can be controlled in At this time, it is necessary that the solution to be measured does not solidify (freeze). As a heat medium, for example, Dowtherm A, silicone oil, water, or the like is used for temperature control, and the temperature can be controlled at each temperature of 257° C., 150° C., and 100° C. or less.

Also, the pressure can be controlled to a negative pressure of 10 ⁻⁵ Pa, 0.1 Pa, 10 Pa, 1.01325×10 ⁵ Pa (normal pressure) or higher by a vacuum pump. Furthermore, the positive pressure of 1 MPa, 10 MPa, 100 MPa, 1 GPa, and 1 PPa (petapascal) can be controlled by a pressure pump.

The inner wall of the sample chamber 20 can be selected to be a metal such as an aluminum material or a highly reflective material with a metallic luster. For example, when the density of the diffuse reflector particles 112 is low, the incident light L ₀ introduced into the cell 30 is less likely to be scattered by the diffuse reflector particles 112 and may reach the inner surface of the sample chamber 20 containing the cell 30. There is In the near infrared-visible-ultraviolet light region, aluminum can reflect this light back to the surface of the cell 30 that is irradiated with light to increase the intensity of the reflected light. In other words, the inner wall of the sample chamber 20 can also function as an integrating sphere. However, when the amount of bubbles 110 generated is large, or when the size of the bubbles 110 is large, there is a possibility that the reflected light intensity fluctuates over time.

As for the shape of the cell 30 in the sample chamber 20, at least the surface on which the incident light _L0 is incident is preferably spherical, planar, or cylindrical. It can be selected according to the conditions required for measurement, such as a cylindrical shape. Furthermore, as described above, in the diffuse reflectance measurement, the reflected light L2 from the surface of the cell 30 does not _travel _on the same optical path as the target diffuse reflected light L1 from the solution S, and is not guided to the spectroscopic section 40. It is necessary to A cylindrical (columnar) cell having an axis of rotational symmetry is more suitable if this condition is satisfied and high-speed stirring is possible without sedimentation of the diffuse reflector particles 112 . _In addition, since the spherical surface tends to spread the reflected light L2 and become the same optical path as the _diffusely reflected light L1, it is necessary to sufficiently consider the optical path design such as the relative angle between the incident light _L0 and the cell 30.

The material of the cell 30 in the sample chamber 20 or the material of the optical window portion of the cell 30 irradiated with the incident light _L0 is not particularly limited as long as it is transparent to the wavelength to be used. Any material that is used as a window member for the application and that is chemically stable against the solvent may be used. For example, borosilicate glass, quartz glass, synthetic quartz glass, non-fluorescent quartz glass, black quartz glass, infrared synthetic quartz glass, chalcogenite glass, plastic (main components are polystyrene (PS), polymethyl methacrylate (PMMA) , polyacrylic acid (PAA), etc.), zinc sulfide (ZnS), zinc selenide (ZnSe), thallium bromoiodide (KRS-5), calcium fluoride (CaF ₂ ), barium fluoride (BaF ₂ ), bromine Potassium chloride (KBr), sapphire (Al ₂ O ₃ ), diamond (C), germanium (Ge), silicon (Si), or the like can be used as appropriate.

The solution (medium) S in the cell 30 varies depending on the reaction system, and the material of the diffuse reflector particles 112 is selected according to each solution. It is necessary that the reflector particles 112 themselves be made of a transparent powder material that does not absorb light. In addition, it is preferable that the material has a refractive index greatly different from the refractive index of the solution S because the diffusely reflected light from the diffuse reflector particles 112 is observed. Furthermore, a material that is chemically stable with respect to the solvent used and does not affect the reaction should be appropriately selected. For example, various ceramics (alumina, zirconia, silica, ceria, calcia, titania, hafnium oxide, magnesia, barium oxide, tungsten oxide, barium titanate, boron nitride, aluminum nitride, hydroxyapatite), various salts (lithium chloride, sodium chloride) , potassium chloride, calcium chloride, magnesium chloride, barium chloride, lithium fluoride, sodium fluoride, potassium fluoride, calcium fluoride, magnesium fluoride, barium fluoride, magnesium sulfate, calcium sulfate, barium sulfate, magnesium carbonate, carbonate calcium, barium carbonate), diatomaceous earth, carbon, various glasses (quartz, soda lime glass, crystal glass, etc.), various plastics (polytetrafluoroethylene (PTFE), polystyrene (PS), polymethyl methacrylate (PMMA), polyacrylic Acid (PAA, etc.), polymer fine particles, or a composite material thereof can be used. Furthermore, the diffuse reflector particles 112 made of these materials and other functional particles may be appropriately combined and dispersed in the solution S for use.

The particle size of the diffuse reflector particles 112 is required to be a size that effectively diffuses reflection in the wavelength range to be measured. When the particle size is smaller than the wavelength, Mie scattering and Rayleigh scattering, not scattering due to specular reflection on the particle surface of the diffuse reflector particles 112, occur. Therefore, although it is appropriately selected according to the wavelength, it is preferable that the particle diameter size of the diffuse reflector particles 112 is approximately the same as or larger than the wavelength to be measured. On the other hand, if it is too large, it will be difficult to disperse it in the solution S by stirring, and it will settle. Also, multiple reflections and transmissions resulting in diffuse reflection may not be obtained within the finite size cell 30 . In this case, the intensity of the diffusely reflected light may become weak and may not be approximated as diffusely reflected light. Therefore, when the diffuse reflector particles 112 having a large particle size are used, the size of the depth direction of the cell 30 with respect to the incident light _L0 and the spot size of the incident light _L0 irradiated to the cell 30 are detected. _Ingenuity is required, such as adjusting the range on the surface of the cell 30 of the diffusely reflected light L1. Typically, for example, when a wavelength of ultraviolet to visible light of 190 to 700 nm is used for measurement, the particle size of the diffuse reflector particles 112 may be about 1 μm. Further, when using a wavelength of near infrared to infrared, it is sufficient if it is about 700 nm to about 1000 μm (1 mm). Therefore, particles having a size or size range of 1 μm to 1000 μm, which is the size of powders of various ceramics, may be used.

Regarding the concentration of the diffuse reflector particles 112 put into the cell 30, the higher the concentration of the diffuse reflector particles ₁₁₂ , the stronger the intensity of the diffusely reflected light L1, which improves the measurement sensitivity and reduces the influence of the air bubbles 110. can be reduced, but on the other hand, the amount of solution S is reduced, making it difficult to obtain the optical spectrum itself. Therefore, it is preferable to adjust the concentration appropriately according to the reaction conditions. Typically, the optimum concentration conditions can be selected and used in the reaction solution in the range of 0.001% by weight or more and 100% by weight or less.

The solution S inside the cell 30 is rotationally stirred to generate centrifugal force, and the separation of the air bubbles 110 can be promoted, but the required number of rotations depends on the viscosity of the reaction solution and the amount of gas generated. Typically, it can be appropriately adjusted within the range of 1 to 10000 revolutions/minute.

Rotational stirring of the solution S inside the cell 30 is provided by a rotating mechanism controlled by the controller, and the method is not particularly limited, but includes, for example, a stirrer 32 consisting of a magnetic stirrer and a stirring unit 33 . Alternatively, various methods such as a method using a mechanical stirrer and a method of rotating the cell 30 can be used.

By rotating and stirring the solution S inside the cell 30 , it is possible to suppress adhesion of the air bubbles 110 to the inner wall of the cell 30 . In addition, since the solution S is mechanically stimulated by stirring, bubbles 110 are generated not only on the inner wall of the cell 30 where bubbles 110 are likely to be generated in the stationary state but also in the entire solution S. This suppresses the bubble 110 from growing and suppresses the influence of the large bubble 110 that has grown on the measurement. In other words, although many small bubbles 110 are generated, they are gathered at the center of rotation inside the cell 30 by rotational stirring. It can also be mixed in and give the same function as this.

The diffuse reflector particles 112 in the cell 30 and the generated air bubbles 110 microscopically undergo dynamic changes as the solution S is stirred. This can give temporal intensity fluctuations to the diffusely reflected light L _1. Here, the reflected light L ₁ detected by the spectroscopic unit 40 is subjected to time smoothing processing, and the time constant is set to 0.1 to 1 second. If so, it was confirmed that there is no particular problem with the observation sensitivity of the examples described later. This is because the area on the surface of the cell 30 illuminated by the incident light _L0 and the depth at which the incident light _L0 penetrates into the cell 30 are sufficient, and the dynamic changes described above are spatially and temporally It is a situation that is generally averaged. Note that, as described above, when a finite number of large bubbles 110 exist within the spatial region that is the optical path of the incident light _L0 , it may not be possible to regard dynamic changes that can be averaged.

Example 1: (dye: measurement of alizarin solution)
Diffuse reflector particles made of alumina powder were added to an aqueous solution of alizarin, which is known as a dye. Here, alumina is insoluble in water and chemically stable in solutions (solvents). The aqueous solution in which the alumina particles are dispersed becomes cloudy. That is, it satisfies the requirements suitable for the diffuse reflector particles described above. Although a representative example using alumina is shown here, similar results are obtained with diffuse reflector particles made of an equivalent material.

Specifically, after dissolving 2.56 mg of alizarin in 25 mL of sodium hydrogen carbonate aqueous solution (manufactured by Wako Pure Chemical Industries, Ltd.), 0.249, 0.189, 0.122, 0.0387 and 0.0104 mmol, respectively /L each solution. To each solution, 200 mg of α-alumina powder (particle size: average particle diameter of about 1 μm, manufactured by Kojundo Chemical Laboratory Co., Ltd.) was added as a diffuse reflector. This was sequentially placed in a quartz cylindrical cell with an outer diameter of φ25 mm, an inner diameter of φ23.5 mm, and a length of 200 mm. The suspension was stirred and suspended at a speed of 800 rpm at a height of 20 mm), and the reflected light spectrum was measured. The diffuse reflectance of 100% was obtained by placing only the α-alumina powder in the cylindrical cell described above. The diffuse reflectance of 0% was obtained by placing a shielding plate in the middle of the scattered light path to prevent scattered light from entering the detector of the spectrophotometer. The measured diffuse reflectance spectrum is divided by the diffuse reflectance spectrum of only the sodium bicarbonate aqueous solution without alizarin, and the value is calculated according to the Kubelka-Munk formula (KM = (1-r) ² /2r) to obtain the diffuse reflectance r. It was converted into an absorbance (KM: Kubelka-Munk), which is a dimensionless quantity proportional to the absorption coefficient.

For spectroscopy, a Cary 5000 UV-Vis spectrophotometer manufactured by Agilent Technologies, Inc. was used. The irradiation area of the irradiation light was adjusted to about φ5 mm on the cell surface, and the size of the mirror was a concave mirror with a diameter of 100 mm. The measurement range was a wavelength range from 900 nm to 200 nm, and the scan speed was 100 nm/min.

On the other hand, as a comparative example, a transmissive measurement was performed by putting an aqueous solution of alizarin without adding a diffuse reflector into a square quartz cell. In the same manner as described above, 2.27 mg of alizarin was dissolved in 25 mL of an aqueous sodium hydrogen carbonate solution (manufactured by Wako Pure Chemical Industries, Ltd.) and diluted to give 0.0378, 0.0189, 0.00378, 0.00189, and 0.000378 mmol/ Each solution of L was prepared. Each solution was stored in a quartz prismatic cell with a side length of 10 mm, the temperature was set to 18 ° C., and the transmitted light absorption spectrum was measured using a Cary 60 UV-Vis spectrophotometer manufactured by Agilent Technologies. I made a measurement.

FIG. 5 shows the light absorption spectrum obtained by converting the measured diffuse reflectance spectrum using the Kubelka-Munk formula described above. Further, FIG. 6 shows a graph showing the concentration dependency by setting the absorbance at each wavelength of 520 nm, 330 nm and 261 nm from these light absorption spectra on the vertical axis and the solution concentration on the horizontal axis. Further, as comparative examples, FIGS. 7 and 8 show graphs showing the light absorption spectrum and the concentration dependency measured in a general transmission cell. As can be seen from these results, in the example, a result corresponding to the transmitted light absorption spectrum measured using a general transmissive cell in the comparative example was obtained. Similarly, the signal intensity increased linearly with concentration, reflecting the measurement of the transmitted light absorption spectrum using a general transmission cell. That is, it can be seen that the method of the present invention can measure the light absorption spectrum in the same manner as in the conventional method.

Example 2: (Substrate Concentration Dependence)
In the same manner as in Example 1, a diffuse reflector made of α-alumina powder was added to an aqueous solution of cobalt (II) nitrate, which was placed in a quartz cylindrical cell and stirred and suspended to obtain a reflected light spectrum. I made a measurement.

200 mg of α-alumina powder (manufactured by Kojundo Chemical Laboratory Co., Ltd.) was dispersed as a diffuse reflector in 20.039 g of water. Then, solutions were prepared by adding 37.77, 56.43, 83.47 and 165.16 mg of cobalt (II) nitrate hexahydrate (manufactured by Wako Pure Chemical Industries, Ltd.). In the same manner as in Example 1, each solution was sequentially placed in a quartz cylindrical cell, the temperature was set to 18° C., and the mixture was stirred and suspended with a Teflon stirrer at a speed of 800 rpm.・Diffuse reflectance spectra were measured with a Cary 5000 UV-Vis spectrophotometer manufactured by Technology Co., Ltd. The measured diffuse reflectance spectrum is divided by the diffuse reflectance spectrum of alumina only, and the value is converted into absorbance (KM), which is a dimensionless quantity proportional to the absorption coefficient, according to the Kubelka-Munk equation described above. converted.

FIG. 9 shows the light absorption spectrum obtained by converting the measured diffuse reflectance spectrum. In addition, FIG.9(b) expands the vertical axis|shaft which shows the light absorbency in (a). The absorption peak appearing at 300 nm in the figure is due to nitrate ions (NO ₃ ⁻ ), and the absorption at 500 nm is due to cobalt ions (Co ²⁺ ). Also, FIG. 10 shows a graph plotting the concentration and absorbance of the cobalt nitrate solution at wavelengths of 221, 305 and 527 nm. From these, it can be seen that the signal intensity is proportional to the concentration. In FIG. 10(a), it seems that there is a tendency to saturate at a certain light intensity (approximately 20 KM) or more, but this is due to the dynamic range of the spectroscope.

Example 3: (Diffuse reflector concentration)
An aqueous solution of cobalt (II) nitrate with varying amounts of a diffuse reflector consisting of α-alumina powder was placed in a quartz cylindrical cell, and the reflection spectrum was measured while stirring and suspending.

After dissolving 164.59 mg of cobalt (II) nitrate hexahydrate (manufactured by Wako Pure Chemical Industries, Ltd.) in 20.029 g of water, α-alumina powder (Kojundo Chemical Co., Ltd.) was used as a diffuse reflector. 51, 102, 153, 203, 303, and 403 mg of α-alumina (the amount ratio of α-alumina is 0.25, 0.50, 0.75, 1.00, and 2.00, respectively). 00 wt%) was created. In addition, a solution containing only cobalt (II) nitrate was also prepared without adding α-alumina powder. Each solution was placed in a quartz cylindrical cell and measured in the same manner as described above. Divide the measured diffuse reflectance spectrum of the solution containing cobalt (II) nitrate by the diffuse reflectance spectrum measured only with the solution containing only alumina without adding cobalt (II) nitrate, and calculate the value according to the Kubelka-Munk equation. , the diffuse reflectance r was converted into absorbance (KM), which is a dimensionless quantity proportional to the absorption coefficient.

FIG. 11 shows the light absorption spectrum after conversion. FIG. 11(b) is an enlarged view of the vertical axis indicating the light intensity in (a). Almost no diffusely reflected light was obtained with a solution containing no alumina as a diffusely reflecting material. Therefore, a spectrum with a low S/N ratio was obtained over the entire measurement area. In particular, a spectrum corresponding to nitrate ions could not be obtained in the wavelength region of 320 nm or less. On the other hand, when 0.25 wt % (50 mg of alumina/20 g of water) or more of the diffuse reflection material was applied, a diffuse reflection spectrum caused by cobalt (II) nitrate was obtained.

FIG. 12 shows a graph plotting the concentration and absorbance of the cobalt nitrate solution at wavelengths of 221, 305, and 527 nm. As shown in FIG. 12(a) and FIG. 12(b) in which the vertical axis is enlarged, it can be seen that a solution containing 0.5 wt % or more of alumina as a diffuse reflector exhibits concentration dependence.

Here, although the concentration of the cobalt nitrate solution remains unchanged, it is observed that the apparent absorbance (light absorption intensity) tends to gradually decrease as the concentration of α-alumina increases. As noted above, this is due to variations in the average distance between diffuse reflector particles. The light absorption by cobalt ions in the aqueous solution is not so strong in the first place, and when the concentration of alumina is 0.5 wt% or less, the contribution of the diffuse reflector particles is small, so the incident light does not reach the back surface of the solution cell. , the diffuse reflectance spectrum cannot be measured accurately, and the light absorption is considered to be rather weak. That is, there is a suitable concentration of diffuse reflector particles for accurate diffuse reflectance spectral measurements.

FIG. 13 shows the intensity of the light absorption spectrum (diffuse reflectance) for each concentration of alumina as the diffuse reflection material. Baseline correction is required.

Example 4: (Decomposition reaction of formic acid)
Using a catalyst composed of an iridium complex shown in FIG. 14, a diffuse reflector composed of α-alumina powder was added to an aqueous solution of formic acid. A diffuse reflectance spectrum was measured while decomposing to obtain carbon dioxide and hydrogen.

As a diffuse reflector, 200 mg of α-alumina powder (manufactured by Kojundo Chemical Laboratory Co., Ltd.) is dispersed in 20 g of a 3.7 mol/L formic acid aqueous solution, and 5.68 mg of an iridium complex (see FIG. 14) is dissolved. Housed in a quartz cylindrical cell. The temperature of this cell was adjusted to 50° C., and the inside was stirred with a Teflon stirrer at a speed of 1000 rpm. After confirming the generation of air bubbles and after a predetermined time (0, 14, 50, 88 minutes), a diffuse reflectance spectrum was measured. The spectrum obtained was transformed by the Kubelka-Munk equation to obtain a light absorption spectrum.

FIG. 15 shows the converted light absorption spectrum. In addition, FIG.15(b) is the graph which expanded the horizontal axis of (a).

We also performed measurements at different catalyst concentrations. Specifically, as a diffuse reflector, 200 mg of α-alumina powder (manufactured by Kojundo Chemical Laboratory Co., Ltd.) was dispersed in 20 g of a 0.1 mol/L formic acid aqueous solution, and 5.12 mg of an iridium complex (see FIG. 14) was dispersed. Furthermore, 4.80 mg was added (total 9.92 mg) and dissolved, stored in a quartz cylindrical cell in the same manner as above, temperature adjusted to 50 ° C., and stirred at a speed of 1000 rpm with a Teflon stirrer. and measured 10 minutes later. The spectrum obtained was transformed by the Kubelka-Munk equation to obtain a light absorption spectrum.

FIG. 16(a) shows the light absorption spectrum at each concentration of the iridium complex as a catalyst, and FIG. 16(b) shows a graph plotting the absorbance at each wavelength of 240, 330, 299, and 259 nm. rice field. As can be seen, there is a proportional relationship between catalyst concentration and absorbance.

FIG. 17(a) shows the light absorption spectrum of only the solution of the iridium complex, which is the catalyst, superimposed on the light absorption spectrum of the solution in which the formic acid is completely decomposed and no bubbles are generated. Furthermore, FIG. 17(b) shows the change in absorbance with time at a wavelength of 222 nm, which corresponds to the absorption of formic acid. From this, it can be seen that the state of decrease due to the decomposition of formic acid has a proportional relationship with the absorbance. In other words, it can be seen that the progress of formic acid decomposition by the catalyst can be observed by this method.

Furthermore, FIG. 18 shows a comparison with measurement by the transmission method. Since the catalyst concentration is different (this method: 5.00 × 10 ^-4 mol / L, transmission method: 1.00 × 10 ^-4 mol / L and 2.50 × 10 ^-4 mol / L), the optical spectrum Although the absorption intensities are different, the shapes of the spectrum diagrams are almost the same, indicating that this method can be measured in the same way as the transmission method.

Although exemplary embodiments according to the present invention and modifications based thereon have been described so far, the present invention is not necessarily limited to these, and a person skilled in the art may depart from the scope of the appended claims. Without further ado, one could find various alternative embodiments.

1 device 10 light source unit 10a

light source

11, 12 reflecting mirror 20 sample chamber 30 cell 40 spectroscopic unit 100 rotating stirring tank 110 bubble 112 diffuse reflector particles

Claims

A method for measuring the optical spectrum of a solution applied to a cell, comprising:
Diffuse reflector particles are added to the solution and are rotationally agitated about an axis of rotation so as to form a dispersed stream of the diffuse reflector particles along the optical windows of the cells, while directing incident light through the optical windows. A method for measuring the optical spectrum of a solution, characterized in that the diffusely reflected light scattered by the diffuse reflector particles is obtained and the optical spectrum thereof is measured.
The method for measuring an optical spectrum according to claim 1, further comprising light collecting means for collecting the diffusely reflected light scattered by the diffuse reflector particles.
The optical spectrum measuring method according to claim 1 or 2, characterized in that the solution contains air bubbles, and the air bubbles are unevenly distributed around the rotating shaft by centrifugal force generated by the rotational stirring.
The optical spectrum measuring method according to claim 3, wherein the bubbles are generated by a reaction of the solution.
5. The optical spectrum measuring method according to claim 1, wherein the cell has a cylindrical shape having an axis of rotational symmetry, and the axis of rotational symmetry coincides with the axis of rotation. .
6. The diffuse reflector particles according to any one of claims 1 to 5, characterized in that said diffuse reflector particles are made of a transparent powder material having no optical absorption for said incident light and having a different refractive index than said solution. method for measuring the optical spectrum of
The optical spectrum measuring method according to any one of claims 1 to 6, wherein the optical spectrum is a light absorption spectrum.
The optical spectrum measuring method according to any one of claims 1 to 6, wherein the optical spectrum is a fluorescence/Raman scattering spectrum.
1. An apparatus for applying a solution to which diffuse reflector particles are added to a cell and measuring the optical spectrum of the solution, comprising:
a rotating mechanism for rotating and agitating around a rotating shaft so as to form a dispersed flow of the diffuse reflector particles along the optical window of the cell;
and an optical system for applying incident light through the optical window, obtaining diffusely reflected light scattered by the diffuse reflector particles, and measuring the optical spectrum of the light. Device.
The optical spectrum measuring device according to claim 9, characterized by comprising light collecting means for collecting the diffusely reflected light scattered by the diffuse reflector particles.
11. The optical system according to claim 9, wherein the solution contains air bubbles, and a control unit is provided for controlling a rotating mechanism so that the air bubbles are unevenly distributed around the rotating shaft by centrifugal force generated by the rotational stirring. Spectral measuring device.
12. The optical spectrum measuring apparatus according to claim 9, wherein the cell is cylindrical having an axis of rotational symmetry, and the axis of rotational symmetry is aligned with the axis of rotation. .
The optical spectrum measuring device according to any one of claims 9 to 12, wherein the optical spectrum is a light absorption spectrum.
13. The optical spectrum measuring apparatus according to claim 9, wherein the optical spectrum is a fluorescence/Raman scattering spectrum.