Spectrophotometer

Abstract

A spectrophotometer 1 is provided with: a light source 10 which emits light having a wavelength bandwidth including an excitation wavelength for causing a photoreaction in a target substance in a sample, and in which the number of photons in light having the excitation wavelength emitted from the light source is known; an integrating sphere 20 having a light-entering opening (21) through which light emitted from the light source enters, and a light-exiting opening (22) provided at a position deviated from the optical axis of light entering the light-entering opening; a sample placement part 23 provided to the light-entering opening; and a light intensity measurement unit 30 for measuring the intensity of light having the excitation wavelength emitted through the light-exiting opening.

Description

Technical Field

[0004] , ,

[0001] The present invention relates to a spectrophotometer.

Background Art

[0002] In order to evaluate the reaction efficiency of a photoreactive substance such as a photocatalyst, an index called the photoreaction quantum yield is used. The photoreaction quantum yield is calculated as the ratio of the number of molecules generated by the photoreaction of the photoreactive substance to the number of photons absorbed by the photoreactive substance. The number of photons absorbed by the photoreactive substance is measured by a spectrophotometer, and the number of molecules generated by the photoreaction of the photoreactive substance is measured by a gas chromatograph or a liquid chromatograph.

[0003] Patent Document 1 describes a spectrophotometer used for measuring the number of photons absorbed by a photoreactive substance. This device includes a sample cell, an excitation light source that irradiates the sample cell with excitation light, a measurement light source that irradiates the sample cell with measurement light, and a spectroscopic detection unit that wavelength-separates and detects the measurement light that has passed through the sample cell. Each part is arranged so that the optical path of the excitation light and the optical path of the measurement light are orthogonal. The excitation light source is a monochromatic light source such as an LED, and the measurement light source is a white light source such as a xenon lamp. In addition, for the excitation light source, one for which the number of photons (irradiation photon number) emitted from the light source and irradiated on the sample is known by preliminary measurement using an illuminometer or the like is used.

[0004] In the spectrophotometer of Patent Document 1, first, only the measurement light is irradiated on the sample cell in which the sample is enclosed, and the transmitted light is detected to obtain a first absorbance spectrum. Subsequently, with the sample cell irradiated with the excitation light, the measurement light is irradiated on the sample cell in the same manner as above, and the transmitted light is detected to obtain a second absorbance spectrum. The difference between the first absorbance spectrum and the second absorbance spectrum reflects the change in the light absorption rate due to the reaction of the photoreactive substance in the sample. The number of photons per unit time absorbed by the photoreactive substance in the sample is obtained by the product of the number of irradiation photons irradiated per unit time and the change in the light absorption rate of the photoreactive substance.

Prior Art Documents

[0005] [Patent Document 1] International Publication No. 2021 / 166310 [Non-patent literature]

[0006] [Non-Patent Document 1] Standard LED, [online], Nichia Corporation, [Retrieved November 9, 2021], Internet<URL:https: / / www.nichia.co.jp / jp / product / sled.html> [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] Photoreactive materials are used in a variety of products, such as cosmetics and semiconductor photocatalysts, and their forms vary, including sol, gel, and thin film. However, the spectrophotometer described in Patent Document 1 , non When measurement light is shone onto a homogeneous liquid sample or thin film sample, some of the light passing through the sample is scattered. Disorder Therefore, it is not possible to determine the correct light absorption rate. As a result, conventional spectrophotometers have the problem of being limited to measuring only homogeneous liquid samples in which such light scattering does not occur.

[0008] The problem that this invention aims to solve is the number of photons of light absorbed by heterogeneous liquid samples or thin film samples. correct The objective is to provide a spectrophotometer capable of taking measurements. [Means for solving the problem]

[0009] The spectrophotometer according to the present invention, which was developed to solve the above problems, A light source that emits light in a wavelength band including an excitation wavelength that causes a photoreaction in a target substance in a sample, wherein the number of photons in the excitation wavelength light emitted from the light source is known, An integrating sphere having a light inlet into which light emitted from the light source is incident, and a light outlet located off-center from the optical axis of the light incident into the light inlet, A sample placement section provided at the light inlet, A light intensity measuring unit that measures the intensity of the light of the excitation wavelength emitted from the light output port. It is equipped with. [Effects of the Invention]

[0010] The spectrophotometer according to the present invention uses a single light source that combines the functions of both a conventional excitation light source and a measurement light source. In this spectrophotometer, first, light is irradiated from the light source without placing a sample in the sample placement area, and the intensity of the light at the excitation wavelength is measured by the light intensity measurement unit. Subsequently, the sample is placed in the sample placement area provided at the light entrance of the integrating sphere, and light is irradiated from the light source. In the spectrophotometer according to the present invention, the absorption rate of the light at the excitation wavelength of the target substance contained in the sample is determined based on the intensity of the light at the excitation wavelength when no sample is placed and the intensity of the light at the excitation wavelength when the sample is placed. Furthermore, the number of photons per unit time of the light at the excitation wavelength absorbed by the target substance is calculated by the product of the number of photons per unit time of the light at the excitation wavelength emitted from the light source and the absorption rate of the light. In the spectrophotometer according to the present invention, the intensity of the light at the excitation wavelength contained in the transmitted light, including forward scattered light from the sample, is measured by the light intensity measurement unit, and the absorbance is determined based on that intensity, so the number of photons of light absorbed by heterogeneous liquid samples and thin film samples can be measured. [Brief explanation of the drawing]

[0011] [Figure 1] A schematic diagram of one embodiment of the spectrophotometer according to the present invention. [Figure 2] A diagram illustrating the configuration used to measure the total energy of light emitted from a light source. [Figure 3] A flowchart illustrating an example of the measurement procedure using the spectrophotometer in this embodiment. [Modes for carrying out the invention]

[0012] An embodiment of the spectrophotometer according to the present invention will be described below with reference to the drawings. The spectrophotometer 1 according to the present invention is used to calculate the photon number of light absorbed by a photoreactive substance, which is necessary for calculating the photoreaction quantum yield of the photoreactive substance such as a photocatalyst.

[0013] FIG. 1 shows a schematic configuration of the spectrophotometer 1 of this embodiment. The spectrophotometer 1 is composed of a light source 10, an integrating sphere 20, a spectroscopic detection unit 30, and a control and processing unit 40.

[0014] The light source 10 emits light in a wavelength band including an excitation wavelength that causes a photoreaction in a target substance (photoreactive substance) contained in a sample to be measured. In this embodiment, a light source called a white LED (for example, a spectral total radiant flux standard LED described in Non-Patent Document 1) is used as the light source 10.

[0015] The integrating sphere 20 has a light incident port 21 for incident light emitted from the light source 10 and a light emission port 22 for emitting light from the inside of the integrating sphere 20. In the integrating sphere 20 of this embodiment, the light incident port 21 and the light emission port 22 are provided such that the central axis C1 of the light emitted from the light source 10 and incident on the light incident port 21 is orthogonal to the central axis C2 of the light emitted from the light emission port 22 to the spectroscopic detection unit 30. A sample placement unit 23 is provided at the light incident port 21. This sample placement unit 23 includes a sample cell for accommodating a liquid sample and a mechanism for fixing a film-like sample. Further, the light emission port 22 and the entrance of the spectroscopic detection unit 30 are connected by an optical fiber 24.

[0016] The spectroscopic detection unit 30 has a spectroscope 31 that separates the light emitted from the light emission port 22 by wavelength, and a photodetector 32 that detects the light after being wavelength-separated by the spectroscope. For example, a diffraction grating is used for the spectroscope 31. For example, a linear sensor having a plurality of detection elements arranged in the direction in which the wavelength-separated light spreads is used for the photodetector 32. vessel 31 For example, a diffraction grating is used for the spectroscope 31. For example, a linear sensor having a plurality of detection elements arranged in the direction in which the wavelength-separated light spreads is used for the photodetector 32.

[0017] The control and processing unit 40 has a storage unit 41. In the storage unit 41, data such as the total energy of the light emitted from the light source 10, the emission spectrum, and the number of photons for each wavelength are stored. Further, the control and processing unit 40 includes a measurement control unit 42 and an absorbed photon number calculation unit 43 as functional blocks. The entity of the control and processing unit 40 is a general personal computer, and the above functional blocks are realized by executing a spectrophotometry program installed in advance. Furthermore, an input unit 48 such as a keyboard and a mouse, and a display unit 49 such as a liquid crystal display are connected to the control and processing unit 40.

[0018] Next, a procedure for measuring the number of photons of the light absorbed by the photochemical reaction of the target substance in the sample using the spectrophotometer 1 of this embodiment will be described with reference to the flowchart of FIG. 3.

[0019] Before measuring the sample to be analyzed, the number of photons of the light at the excitation wavelength emitted from the light source 10 is determined. Here, first, the total energy of the light emitted from the light source 10 is measured (step 1). This measurement is performed by making the light emitted from the light source 10 enter an illuminance meter (also called a power sensor) 50 as shown in FIG. 2.

[0020] Subsequently, the light source 10 is returned to the position shown in FIG. 1 (however, no sample is placed), the light emitted from the light source 10 is made to enter the integrating sphere 20 from the light incident port 21, and the light emitted from the light emission port 22 of the integrating sphere 20 is introduced into the spectroscopic detection unit 30. In the spectroscopic detection unit 30, the introduced light is wavelength-separated by the spectroscope 31, and the intensity of each wavelength is measured by the photodetector 32. Thereby, the emission spectrum of the light source 10 (the intensity of the light for each wavelength per unit time) is obtained (step 2).

[0021] Subsequently, based on the total energy of the light emitted from the light source 10 acquired in step 1, the emission spectrum of the light source 10 acquired in step 2, and the energy of a single photon at each wavelength (hc / λ, where h is Planck's constant, c is the speed of light, and λ is the wavelength), the number of photons for each wavelength emitted from the light source 10 is calculated (step 3) and stored in the memory unit 41. Note that unless there is a change in the emission spectrum due to deterioration of the light source 10, it is sufficient to perform steps 1 to 3 once when the light source 10 is installed and store the data on the number of photons for each wavelength in the memory unit 41; it is not necessary to perform this each time a sample is measured.

[0022] Next, when the user places the sample on the sample placement unit 23 (step 4) and instructs the start of measurement, the measurement control unit 42 irradiates the sample with light from the light source 10. The light that passes through the sample enters the integrating sphere 20 from the light entrance 21, is reflected one or more times, and is then introduced into the optical fiber 24 from the light exit 22 and enters the spectral detection unit 30. The light that enters the spectral detection unit 30 is wavelength-separated by the spectrometer 31 and detected by the photodetector 32. The photodetector 32 outputs a signal representing the intensity of light of each wavelength that has entered each detection element of the photodetector 32.

[0023] The measurement control unit 42 reads the output signal from the photodetector 32 (data on the intensity of light detected by each detection element) and stores it in the storage unit 41. When new data is stored in the storage unit 41, the absorbed photon number calculation unit 43 creates transmitted light spectrum data from that data (step 5).

[0024] Once the transmitted light spectrum data is created, the absorbance photon number calculation unit 43 further creates absorbance spectrum data from the emission spectrum data acquired in step 2 and the transmitted light spectrum data acquired in step 5 (step 6), and displays the absorbance spectrum on the screen of the display unit 49.

[0025] Once absorbance spectral data is obtained, the absorbance photon number calculation unit 43 calculates the absorbance photon number using the following formula (step 7).

number

[0026] Once the number of absorbed photons is calculated using the above equation (1), the value is displayed on the screen of the display unit 49 along with the absorbance spectrum data.

[0027] The measurement control unit 42 determines whether the elapsed time since the start of measurement has reached the time set in advance by the user. If the elapsed time since the start of measurement has not yet reached the set time (NO in step 8), the process returns to step 5 and the same process as above is performed. If the elapsed time since the start of measurement has reached the set time (YES in step 8), the measurement is terminated.

[0028] Conventional spectrophotometers employ a configuration in which a sample sealed in a sample cell is irradiated with light from a measurement light source, and the intensity of the light that passes through the sample cell is measured by a spectroscopic detector. As a result, it was not possible to measure samples that scatter the measurement light passing through the sample (sample cell) (for example, heterogeneous liquid samples or film-like samples).

[0029] In contrast, the spectrophotometer 1 of this embodiment uses a single light source 10 that combines the functions of both the measurement light source and the excitation light source in a conventional spectrophotometer. Furthermore, an integrating sphere 20 is used, with a sample placement section 23 provided at its light entrance 21, where the sample is placed. By adopting this arrangement, even if forward scattering occurs in the light passing through the sample placed in the sample placement section 23, the light is incident on the integrating sphere 20, reflected one or more times within it, and then incident on the spectroscopic detection unit 30. Therefore, even heterogeneous liquid samples and film-like samples, which could not be measured with conventional spectrophotometers, can be measured, including the number of absorbed photons during the photoreaction of the target substance contained in those samples. correct It can be calculated.

[0030] The above embodiments are merely examples and can be modified as appropriate in accordance with the spirit of the present invention.

[0031] In the above embodiment, a white LED was used as the light source 10, but other types of white light sources may be used. A monochromatic light source can also be used as the light source 10. When a monochromatic light source is used as the light source 10, the light emitted from the integrating sphere 20 is also monochromatic, so there is no need to use a spectroscopic element, and a photodetector having only a single detection element can be used instead of the spectroscopic detection unit 30. Note that when a monochromatic light source is used as the light source 10, the light source 10 can be measured both when the sample is not placed on the sample placement unit 23 and when the sample is placed on it. Light The device is irradiated with light, and the intensity of single-wavelength light emitted from the integrating sphere 20 is measured to determine the absorption rate of light at that wavelength.

[0032] In the above embodiment, an integrating sphere 20 was used in which the central axis of the light incident from the light source 10 to the light inlet 21 and the central axis of the light taken into the optical fiber 24 from the light outlet 22 were orthogonal to each other. However, the light inlet 21 and the light outlet 22 can be placed at appropriate positions as long as the light outlet 22 is not located on the central axis of the light incident from the light source 10 to the light inlet 21.

[0033] [Pattern] Those skilled in the art will understand that the above-described exemplary embodiments are specific examples of the following embodiments.

[0034] (Section 1) A spectrophotometer according to one aspect of the present invention is A light source that emits light in a wavelength band including an excitation wavelength that causes a photoreaction in a target substance in a sample, wherein the number of photons in the excitation wavelength light emitted from the light source is known, An integrating sphere having a light inlet into which light emitted from the light source is incident, and a light outlet located off-center from the optical axis of the light incident into the light inlet, A sample placement section provided at the light inlet, A light intensity measuring unit that measures the intensity of the light of the excitation wavelength emitted from the light output port. It is equipped with.

[0035] The spectrophotometer described in paragraph 1 uses a single light source that combines the functions of both a conventional excitation light source and a measurement light source. In this spectrophotometer, first, light is irradiated from the light source without placing a sample in the sample placement area, and the intensity of the light at the excitation wavelength is measured by the light intensity measurement unit. Subsequently, the sample is placed in the sample placement area provided at the light entrance of the integrating sphere, and light is irradiated from the light source. In the spectrophotometer described in paragraph 1, the absorption rate of the light at the excitation wavelength of the target substance contained in the sample is determined based on the intensity of the light at the excitation wavelength when no sample is placed and when the sample is placed. Furthermore, the number of photons of the light at the excitation wavelength absorbed by the target substance is calculated by the product of the number of photons of the light at the excitation wavelength emitted from the light source and the absorption rate of the light. In the spectrophotometer described in paragraph 1, the intensity of the light at the excitation wavelength contained in the transmitted light, including forward scattered light from the sample, is measured by the light intensity measurement unit, and the absorbance is determined based on that intensity, so the number of photons of light absorbed by heterogeneous liquid samples or thin film samples correct It can be measured.

[0036] (Section 2) In the spectrophotometer described in paragraph 1, further, When no sample is placed in the sample placement area Light intensity measurement unit The intensity of the light of the excitation wavelength detected by the above, and the state in which the sample is placed in the sample placement area. Light intensity measurement unit A calculation processing unit calculates the absorption rate of the light of the excitation wavelength by the target substance based on the intensity of the light of the excitation wavelength detected by the calculation processing unit. It is equipped with.

[0037] (Section 3) In the spectrophotometer described in paragraph 2, The processing unit further calculates the number of photons of light absorbed by the target material based on the number of photons of the excitation wavelength and the absorption rate.

[0038] The spectrophotometer described in paragraph 2 allows for the easy acquisition of the absorption rate of light at the excitation wavelength by the target substance, while the spectrophotometer described in paragraph 3 allows for the easy acquisition of the number of photons of light at the excitation wavelength absorbed by the target substance.

[0039] (Section 4) In a spectrophotometer described in any of paragraphs 1 to 3, The aforementioned light source is a white LED light source, The light intensity measuring unit includes a spectrometer that separates the light emitted from the light output port by wavelength, and a photodetector that detects the light separated by wavelength by the spectrometer.

[0040] The spectrophotometer described in paragraph 4 can acquire an absorbance spectrum in a wavelength band including the excitation wavelength, and calculate the number of photons of light absorbed by the target substance based on the absorbance peak centered in that wavelength band. [Explanation of Symbols]

[0041] 1...Spectrophotometer 10…Light source 20...integrating sphere 21...Light entrance 22…Light emission port 23...Sample placement section 24… Fiber optic 30…Spectroscopic detection unit (light intensity measurement unit) 31...Spectrometer 32…Photodetector 40…Control and Processing Unit 41...Storage section 42...Measurement Control Unit 43... Absorbed Photon Calculation Unit 48...Input section 49…Display section 50…Luminance meter

Claims

1. A light source that emits light in a wavelength band including an excitation wavelength that causes a photoreaction in a target substance in a sample, wherein the number of photons in the excitation wavelength light emitted from the light source is known, An integrating sphere having a light inlet into which light emitted from the light source is incident, and a light outlet located off-center from the optical axis of the light incident into the light inlet, A sample placement section provided at the light inlet, A light intensity measuring unit that measures the intensity of the light of the excitation wavelength emitted from the light output port. Equipped with, The aforementioned sample is a sol, gel, or thin film. The aforementioned light source is a white light source, and the spectrophotometer is also used.

2. moreover, A calculation processing unit calculates the absorption rate of light of the excitation wavelength by the target substance based on the intensity of the light of the excitation wavelength detected by the light intensity measurement unit when no sample is placed in the sample placement unit, and the intensity of the light of the excitation wavelength detected by the light intensity measurement unit when a sample is placed in the sample placement unit. A spectrophotometer according to claim 1, comprising:

3. The spectrophotometer according to claim 2, wherein the calculation processing unit further calculates the number of photons of light absorbed by the target material based on the number of photons of the excitation wavelength light and the absorption rate.

4. The aforementioned light source is a white LED light source, The spectrophotometer according to claim 1, wherein the light intensity measuring unit comprises a spectrometer that separates the light emitted from the light output port by wavelength, and a detector that detects the light separated by wavelength by the spectrometer.

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