JP2011001208A - METHOD OF PRODUCING MgIn2O4, AND MgIn2O4 MATERIAL - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of producing a MgInOmaterial capable of significantly decomposing organic materials in a visible light wavelength region of not less than 400 nm by a simpler method.SOLUTION: The method of producing MgInOcomprises the steps of: (1) obtaining a mixture by mixing MgCOand InCOso that the mole ratio of MgCOand InCOfalls into a region of between 1.05:1.0 to 1.2:1.0; (2) obtaining a first sintered compact by calcining the mixture at a temperature region of 800-1,000°C for 6 hours or more; and (3) obtaining MgInOby calcining the first sintered compact at a temperature region of 1,300-1,450°C for 12-24 hours.

Description

  The present invention relates to a photocatalytic material, and more particularly to a photocatalytic material that operates with visible light.

  Currently, environmental pollution due to various harmful chemical substances such as global warming due to the increase of greenhouse gases such as carbon dioxide and methane, acid rain due to nitrogen oxides, and the expansion of ozone holes due to chlorofluorocarbons such as halon on the earth. It is a big problem. In particular, organic substances occupy a large proportion of such harmful chemical substances, and purification of organic substances has become a major issue.

  Therefore, it has been studied to decompose such organic substances using a photocatalyst. When the photocatalyst absorbs light energy exceeding the band gap energy, it generates excited electrons (electrons excited from the valence band to the conduction band) and holes corresponding to the electrons. Therefore, the organic substance can be decomposed by reducing / oxidizing the organic substance with the excited electrons and / or holes.

A typical example of such a photocatalyst is titanium dioxide (TiO ₂ ), and this material is known to absorb light having a wavelength of about 380 nm to about 390 nm or less and exhibit photocatalytic properties ( For example, Non-Patent Document 1).

However, the wavelength of the light titanium dioxide (TiO ₂₎ is to exert a photocatalytic action, close to the ultraviolet region, light in the visible light region (about 360nm~ about 830 nm) can not be used very little. In other words, when titanium dioxide (TiO ₂ ) is used to decompose the organic substance, when visible light is used, the decomposition efficiency of the organic substance is extremely inefficient. Therefore, in practice, when titanium dioxide (TiO ₂ ) is used to decompose organic matter, it is necessary to irradiate the photocatalyst with light in the ultraviolet region. However, the method using light in the ultraviolet region requires a complicated operation compared to the method using visible light, and there is a problem that the apparatus becomes complicated and the cost of decomposing organic matter increases. Also, the use of ultraviolet rays has a problem in terms of safety.

On the other hand, recently, it has been reported that by using CaIn ₂ O ₄ , SrIn ₂ O ₄ , and BaIn ₂ O ₄ as photocatalyst materials, decomposition of organic substances can occur more effectively in the visible light region. (Non-patent document 2).

Moreover, until now, there is a document relating to the synthesis of MgIn ₂ O ₄ material as a transparent electron conductor that replaces indium tin oxide (ITO) (Non-patent Document 3).

“Frontier of Visible Light Responsive Photocatalyst Development”, Publisher NTS, 2002 J. et al. Tang, Z .; Zou, M .; Katagiri, T .; Kako, Y. et al. Ye, Catalysis Today, 93-95, 885-889, 2004 Naoyuki Ueda, Takahisa Omata, Naoko Hikuma, Kazushige Ueda, Hiroshi MIzoguchi, Takuya Hashimoto, Hiroshi Kawazoe, "New oxide phase with wide band gap and high electroconductivity, MgIn2O4", Appl. Phys. Lett. 61, (16), 19, Oct. 1992

However, in Non-Patent Document 3 described above, MgIn ₂ O ₄ cannot be synthesized unless the raw material powder is first heat-treated at 800 ° C. for 16 hours and then kept at 1400 ° C. for 72 hours or more. This document also focuses on the search for transparent electron conductor materials that can replace indium tin oxide (ITO). For this reason, it is unclear whether the MgIn ₂ O ₄ material obtained by this method exhibits photocatalytic properties in the visible light region (about 360 nm to about 830 nm), particularly in the visible light region having a wavelength of 400 nm or more.

Therefore, there is still a need for a method for synthesizing MgIn ₂ O ₄ exhibiting good photocatalytic properties in a visible light region having a wavelength of 400 nm or more by a simpler method.

The present invention has been made in view of such problems. In the present invention, MgIn ₂ is capable of significantly decomposing organic substances in a visible light region having a wavelength of 400 nm or more by a simpler method. It is an object to provide a method for producing O ₄ material. It is another object of the present invention to provide an MgIn ₂ O ₄ material capable of significantly decomposing organic substances in a visible light region having a wavelength of 400 nm or more.

In the present invention, a method for producing MgIn ₂ O ₄ , comprising:
(1) Mixing MgCO ₃ and In ₂ CO _{3 so} that the molar ratio of MgCO ₃ and In ₂ CO ₃ is in the range between 1.05: 1.0 and 1.2: 1.0, Obtaining a mixture;
(2) firing the mixture in a temperature range of 800 ° C. to 1000 ° C. for 6 hours or more to obtain a first fired body;
(3) firing the first fired body in a temperature range of 1300 ° C. to 1450 ° C. for 12 to 24 hours to obtain MgIn ₂ O ₄ ;
A manufacturing method is provided.

  Here, in the method according to the present invention, the step (2) is a step of obtaining the first fired body by firing the mixture at a temperature range of 850 ° C. to 950 ° C. for 6 hours to 12 hours. good.

In the method according to the present invention, the step (3) is a step of obtaining the MgIn ₂ O ₄ by firing the first fired body in a temperature range of 1350 ° C. to 1450 ° C. for 12 hours to 24 hours. May be.

In the method according to the invention,
MgIn ₂ O ₄ has a quantum yield F (%).

で表したとき、
波長が４００ｎｍ〜４９０ｎｍの範囲の可視光の照射により、メチレンブルー試薬の分解に対して、０．０２％以上の量子収率が得られても良い：
ここで、Ｎｐ（個）は、前記可視光に含まれる光子の数であり、ｎ_ｄ（個）は、前記メチレンブルー試薬の分解された分子数である。

When expressed in
A quantum yield of 0.02% or more may be obtained for the decomposition of the methylene blue reagent by irradiation with visible light having a wavelength in the range of 400 nm to 490 nm:
Here, Np (number) is the number of photons contained in the visible light, and n _d (number) is the number of molecules decomposed by the methylene blue reagent.

  Furthermore, in the present invention, the quantum yield F (%) is

で表したとき、
波長が４００ｎｍ〜４９０ｎｍの範囲の可視光の照射により、メチレンブルー試薬の分解に対して、０．０２％以上の量子収率が得られることを特徴とするＭｇＩｎ_２Ｏ_４材料が提供される：
ここで、Ｎｐ（個）は、前記可視光に含まれる光子の数であり、ｎ_ｄ（個）は、前記メチレンブルー試薬の分解された分子数である。

When expressed in
An MgIn ₂ O ₄ material characterized in that a quantum yield of 0.02% or more is obtained for the decomposition of the methylene blue reagent upon irradiation with visible light in the wavelength range of 400 nm to 490 nm:
Here, Np (number) is the number of photons contained in the visible light, and n _d (number) is the number of molecules decomposed by the methylene blue reagent.

In the present invention, a method for producing an MgIn ₂ O ₄ material capable of significantly decomposing an organic substance in a visible light region having a wavelength of 400 nm or more can be provided by a simpler method. In addition, it is possible to provide an MgIn ₂ O ₄ material that can significantly decompose organic substances in the visible light region having a wavelength of 400 nm or more.

An example of a flow of a manufacturing method of MgIn ₂ O ₄ according to the present invention seen schematically. The X-ray diffraction measurement results of the samples the samples according to Example 1, illustrates in conjunction with standard peak of MgIn ₂ O _4. It is the figure which showed an example of the absorption spectrum of a methylene blue reagent. It is the figure which showed roughly the testing apparatus for evaluating the photocatalytic characteristic of a sample. It is the figure which showed the spectrum of the light radiated | emitted from a Hg-Xe light source. It is the figure which showed schematically the another test apparatus for evaluating the photocatalytic characteristic of a sample. It is the figure which showed the measurement result in the continuous light irradiation test of the sample sample which concerns on Example 1. FIG. It is the figure which showed the test result at the time of interrupting light irradiation in the middle of the light irradiation test of the sample sample which concerns on Example 1, and starting light irradiation again after that. 5 is a graph showing the relationship between the concentration M of methylene blue reagent and absorbance A. The X-ray diffraction measurement results of the samples the samples according to Comparative Example 1, illustrates in conjunction with standard peak of In ₂ O _3.

  Hereinafter, the present invention will be described in detail.

As described above, titanium dioxide (TiO ₂ ), which is a typical material for photocatalysts, does not exhibit photocatalytic properties unless it has light with a wavelength close to the ultraviolet region (about 380 nm or less). Therefore, in the normal case, ultraviolet rays are used as excitation light irradiated to titanium dioxide (TiO ₂ ). However, such a method using light in the ultraviolet region requires a complicated operation as compared with a method using visible light, and there is a problem that the apparatus becomes complicated and the cost of decomposing organic matter increases. Also, the use of ultraviolet rays has a problem in terms of safety.

On the other hand, recently, it has been reported that the use of CaIn ₂ O ₄ , SrIn ₂ O ₄ , and BaIn ₂ O ₄ as photocatalyst materials can cause decomposition of organic substances in the visible light region (non-patent document). Reference 2). However, this document does not describe the MgIn ₂ O ₄ material.

On the other hand, another document shows that a MgIn ₂ O ₄ material was obtained by firing a mixture of MgCO ₃ and In ₂ O ₃ at a high temperature (Non-patent Document 3). However, in this method, MgIn ₂ O ₄ cannot be synthesized unless the raw material is first heat-treated at 800 ° C. for 16 hours and then kept at 1400 ° C. for 72 hours or more. That is, this method requires high temperature firing of raw materials at a high temperature of 1400 ° C. for 72 hours, that is, 3 days or more, and is not a very efficient method for synthesizing materials. In addition, it is unclear whether the MgIn ₂ O ₄ material obtained by this method exhibits good photocatalytic properties in the visible light region (about 360 nm to about 830 nm), particularly in the visible light region having a wavelength of 400 nm or more. .

Under such a background, the inventors of the present application have been diligently researching and developing a material exhibiting favorable photocatalytic characteristics in a visible light region having a wavelength of 400 nm or more. Then, as the photocatalyst material, when using MgIn ₂ O ₄ fabricated in a characteristic and novel way, in the visible light region having a wavelength of above 400 nm, found that the decomposition of organic matter may occur, leading to the present invention .

That is, in the present invention,
A method for producing MgIn ₂ O ₄ , comprising:
(1) Mixing MgCO ₃ and In ₂ CO _{3 so} that the molar ratio of MgCO ₃ and In ₂ CO ₃ is in the range between 1.05: 1.0 and 1.2: 1.0, Obtaining a mixture;
(2) firing the mixture in a temperature range of 800 ° C. to 1000 ° C. for 6 hours or more to obtain a first fired body;
(3) firing the first fired body in a temperature range of 1300 ° C. to 1450 ° C. for 12 to 24 hours to obtain MgIn ₂ O ₄ ;
A manufacturing method is provided.

In the method according to the invention, the firing time in step (3) is within 24 hours (ie up to 1 day). Therefore, with the method according to the present invention, MgIn ₂ O ₄ can be produced more easily than in the prior art.

Further, MgIn ₂ O ₄ produced according to the present invention exhibits sufficient photocatalytic properties even in the visible light region having a wavelength of 400 nm or more, as will be described in detail later. Therefore, MgIn ₂ O ₄ produced according to the present invention can be used as a photocatalyst for decomposing organic substances using light in the visible light region.

Incidentally, when employing the method according to the invention, compared with the conventional, more simply, the specific reasons that can produce MgIn ₂ O ₄ is now unknown.

However, according to the results of analysis, it is considered that MgIn ₂ O ₄ has not yet been generated at the stage immediately after step (2). Therefore, the following is considered as an effect of the method according to the present invention. The

In the method according to the present invention, MgCO ₃ and In ₂ CO ₃ are used as raw materials. In this case, the method according to the invention, the MgCO ₃ and _{an In} 2 CO _3, the molar ratio of MgCO ₃ and _{an In} 2 CO ₃ 1.05: 1.0 to 1.2: in the range between 1.0 To obtain a mixture. The method according to the invention also comprises a step (2) of heat treating MgCO ₃ and In ₂ CO ₃ at a lower temperature before the step of reacting this mixture at an elevated temperature, ie step (3).

Therefore, in the present invention, by interposing this step (2) with respect to a mixture containing MgCO ₃ and In ₂ CO ₃ that are contained in a larger molar ratio, in the subsequent step (3), The reaction between them may be promoted.

For example, in step (2), it is conceivable that MgCO ₃ (at least a part thereof) changes to an oxide. In this case, in a mixture of MgCO ₃ and _{an In} 2 CO _3, as the ratio of MgCO ₃ is large, the more MgCO ₃ is decomposed and changed into oxides. Accordingly, in the reaction in the subsequent step (3), energy required for decomposition of MgCO ₃ into an oxide is reduced, so that the input energy is more preferentially sintered between oxides. It may be possible to use the reaction effectively.

Or in heat treatment of step (2), the MgCO ₃ and _{an In} 2 CO ₃ mixture decomposed MgCO ₃ contained more, CO ₂ becomes prone state, thereby easily forming reaction subsequent composite oxide It is also possible that

Incidentally, the above description is based on the consideration that uses the measurement results and the like that currently exist, when carrying out the method according to the invention, by other mechanisms, MgIn ₂ O ₄ may be generated. That is, it should be noted that the actual formation mechanism of MgIn ₂ O ₄ has no influence on the scope of the present invention.

FIG. 1, an example of a flow of a manufacturing method of MgIn ₂ O ₄ according to the invention is shown schematically. As shown in FIG. 1, the manufacturing method of MgIn ₂ O ₄ according to the present invention includes at least
(1) Mixing MgCO ₃ and In ₂ CO _{3 so} that the molar ratio of MgCO ₃ and In ₂ CO ₃ is in the range between 1.05: 1.0 and 1.2: 1.0, Obtaining a mixture;
(2) firing the mixture in a temperature range of 800 ° C. to 1000 ° C. for 6 hours or more to obtain a first fired body (S120);
(3) firing the first fired body in a temperature range of 1300 ° C. to 1450 ° C. for 12 to 24 hours to obtain MgIn ₂ O ₄ (S130);
Have Hereinafter, each step will be described.

(Step S110)
First, MgCO _{3 as} a raw material and In ₂ CO ₃ are mixed. These raw materials may be in a powder state or in other states.

Here, the mixing ratio of MgCO ₃ and In ₂ CO ₃ is prepared such that MgCO ₃ is somewhat increased in terms of molar ratio. That is, the molar ratio of MgCO ₃ and In ₂ CO ₃ is in the range of 1.05: 1.0 to 1.2: 1.0, and the molar ratio of both is, for example, 1.1: 1. It may be zero.

  In this step S110, a dispersant may be used to facilitate mixing. The dispersant is not particularly limited, and for example, alcohol such as ethanol or water is used.

(Step S120)
Next, the mixture is fired in the air at a temperature range of 800 ° C. to 1000 ° C. for 6 hours or longer (first firing). The temperature of the first baking is particularly preferably in the range of 850 ° C to 950 ° C. Moreover, it is preferable that the time of 1st baking is the range of 6 hours-12 hours.

Thereby, a part or all of MgCO ₃ is changed to an oxide, or in these compounds, CO ₂ is generated and MgCO ₃ is easily decomposed. However, according to the result of analysis, it is considered that a sufficient amount of MgIn ₂ O ₄ has not yet been generated in this step.

  After the first firing, the fired body is cooled by furnace cooling or the like.

  Thereafter, the obtained sample may be pulverized. This further increases the uniformity of the finally obtained material.

(Step S130)
Next, the obtained fired body is fired in a temperature range of 1300 ° C. to 1450 ° C. for 6 hours or longer (second firing).

  The temperature of the second baking is particularly preferably in the range of 1350 ° C to 1450 ° C. Moreover, it is preferable that the time of 2nd baking is the range of 12 hours-24 hours.

  Thereafter, the fired body is cooled by furnace cooling or the like.

Through the above steps, the MgIn ₂ O ₄ compound according to the present invention can be obtained.

  Examples according to the present invention will be described below.

Example 1
(Sample synthesis)
First, MgCO ₃ powder (purity 99%, manufactured by Wako Pure Chemical Industries, Ltd.) and In ₂ CO ₃ powder (purity 99.99%, manufactured by Nilaco Corporation) were mixed in ethanol. The molar ratio of MgCO ₃ to In ₂ CO ₃ was 1.1: 1.0.

  Next, the mixed sample was put in a dryer (ISUZU DRYING OVEN MODEL 2-2045) at about 80 ° C. and held for 5 hours to dry the mixed sample. Further, the dry mixed sample was pulverized to prepare pellets.

  Next, this pellet was put in an electric furnace (YAMATO FO510) and fired at about 900 ° C. for 12 hours in the atmosphere (first firing).

  The obtained fired body was cooled to room temperature and pulverized again, and then this powder was put in an electric furnace (TSR-430, Yamada Denki Co., Ltd.) and fired at about 1400 ° C. for 24 hours in the atmosphere (No. 1). 2 firing). The obtained sample sample was a reddish gray color. This sample is referred to as a sample sample according to Example 1.

(result of analysis)
X-ray diffraction measurement was performed using the sample sample according to Example 1. The obtained diffraction peak is shown in FIG. In FIG. 2, the upper row shows the measurement results, and the lower row shows the standard diffraction peak of MgIn ₂ O ₄ . It can be seen that the diffraction peak of the sample sample matches the standard diffraction peak of MgIn ₂ O ₄ .

(Evaluation of photocatalytic properties)
Using the sample sample according to Example 1, an organic matter decomposition test was performed, and the photocatalytic characteristics of the sample sample according to Example 1 were evaluated.

As the organic substance, a methylene blue (C ₁₆ H ₁₈ N ₃ S · Cl) reagent (MERCK Corporation) represented by the following molecular structure was used.

図３には、メチレンブルー試薬の吸収スペクトルの一例を示す。メチレンブルーの最大吸収強度が得られる波長は、約６６０ｎｍ〜６６５ｎｍの範囲である。

FIG. 3 shows an example of the absorption spectrum of the methylene blue reagent. The wavelength at which the maximum absorption intensity of methylene blue is obtained is in the range of about 660 nm to 665 nm.

  The test apparatus 100 shown in FIG. 4 was used for the organic substance decomposition test.

  The test apparatus 100 includes a light source 120, an infrared light blocking filter 130, an ultraviolet light blocking filter 140, and a plastic cell 160.

  As the light source 120, a mercury xenon (Hg-Xe) lamp (manufactured by Hamamatsu Photonics) was used. The rated voltage / current of the light source is about 20-30 kV / 7.5A. FIG. 5 shows the spectrum of light emitted by the light source 120. The light emitted from the light source 120 has a wide wavelength from the ultraviolet region to the infrared region. In particular, it has large peaks in four regions having wavelengths of about 405 nm, about 450 nm, about 550 nm, and about 580 nm.

  As the infrared light blocking filter 130, a COMMERICAL IR cut filter manufactured by Edmund was used. The infrared light blocking filter 130 can block wavelengths in the infrared region (wavelength of about 830 nm or more) among the wavelengths of light emitted from the light source 120.

  As the ultraviolet light blocking filter 140, an acrylic plate having a length of 10 cm, a width of 10 cm, and a thickness of 5 mm was used. The ultraviolet light blocking filter 140 can block the wavelength in the ultraviolet region (wavelength of about 380 nm or less) of the light that has passed through the infrared light blocking filter 130. Therefore, the light irradiated to the plastic cell 160 has only a wavelength in the range of 400 nm to 830 nm.

A plastic cell 160 having an outer dimension of 10 mm in length, 10 mm in width, and 45 mm in height and having a wall thickness of 1 mm was used. On the bottom of the plastic cell 160, 0.1 g of a sample sample 170 of MgIn ₂ O _{4 according} to Example 1 manufactured by the above-described method was spread. The plastic cell 160 was filled with about 3.6 ml of methylene blue reagent 180 having a concentration of 1.0 × 10 ⁻⁵ mol / l. The light irradiation area of the sample sample 170 is 81 mm ² .

  The distance from the light source 120 to the plastic cell 160 was 11 cm. The power of the light source 120 was 7.0 mW.

  As another configuration, a test apparatus 200 as shown in FIG. 6 was used. The test apparatus 200 has the same configuration as the test apparatus 100 described above. However, the test apparatus 200 further includes a band pass filter 150 between the ultraviolet light blocking filter 140 and the plastic cell 160.

  As the bandpass filter 150, a COM narrowband interference filter (product numbers 43104 and 43116) manufactured by Edmund was used. The band-pass filter 150 can pass only light having a specific selected wavelength out of the light that has passed through the ultraviolet light blocking filter 140 toward the plastic cell 160. For example, in the case of the bandpass filter having the product number 43104, only light having a wavelength of 405 nm can be passed. Further, in the case of the band-pass filter having the product number 43116, only light having a wavelength of 488 nm can be passed.

In addition, when the test apparatus 200 was used, the power P of the light irradiated to the plastic cell 160, ie, the sample sample 170, was 0.414 mW / cm ² when the wavelength was 405 nm. On the other hand, when the wavelength was 488 nm, the power P of the light applied to the sample sample 170 was 0.796 mW / cm ² .

  Using such a test apparatus 100 or 200, the sample sample 170 was irradiated with light from the upper part of the plastic cell 160. The sample sample 170 was arranged so that the longitudinal direction substantially faces the light source 220 (see FIGS. 4 and 6). The experiment was conducted in a dark room.

  7 and 8 show the results of a light irradiation test obtained using the test apparatus 100. FIG. That is, this test result is a result when the sample sample is irradiated with light having a wavelength in the range of 400 nm to 830 nm. 7 and 8, the horizontal axis represents the irradiation time (Hour), and the vertical axis represents the absorbance A of the methylene blue reagent. FIG. 7 shows the result in the continuous light irradiation test, and FIG. 8 shows the test result when the light irradiation is interrupted in the middle of the test and then the light irradiation is started again.

  FIG. 7 shows that the absorbance of the methylene blue reagent decreases with increasing light irradiation time. In addition, it can be seen from FIG. 8 that the absorbance of the methylene blue reagent does not change in the time region where no light is irradiated. These results suggest that the sample sample according to Example 1 exhibits photocatalytic properties when irradiated with light in the wavelength range of 400 nm to 830 nm.

  Next, Table 1 summarizes the results of the light irradiation test obtained using the test apparatus 200.

  Table 1 collectively shows the amount of decrease ΔA in the absorbance of the methylene blue reagent after continuous irradiation (4.5 hours) with light of wavelengths 405 nm and 488 nm.

なお、この表１には、各波長における分解試験で得られた、メチレンブルー試薬の分解された分子数ｎｄ、光子数Ｎｐ、および量子収率Ｆの値についても示されている。

Table 1 also shows values of the number of molecules nd, the number of photons Np, and the quantum yield F of the methylene blue reagent obtained in the decomposition test at each wavelength.

  Here, the quantum yield F (%) means the number of organic molecules that can be decomposed by one photon contained in the light irradiated on the photocatalyst. The quantum yield can be used as an index for evaluating the photocatalytic properties of the sample.

  The quantum yield F (%) can be calculated from the following procedure 1 to procedure 2.

(Procedure I) Calculation of the number of photons Np used for the decomposition of the methylene blue reagent The energy E ₁ (J) per photon is c as the speed of light (3.0 × 10 ⁸ m / s), and h is plank When the constant is (6.626 × 10 ⁻³⁴ Js) and λ is the wavelength of light,

で表される。

It is represented by

Further, the total energy irradiated to the sample from the light source during the experiment is E _ALL (J) where P is the power of the light source and t is the irradiation time.

で表される。

It is represented by

  Therefore, from the equations (3) and (4), the number Np (number) of photons irradiated to the sample during the experiment is

となる。

It becomes.

(Procedure 2) Calculation of the number n _d of decomposition molecules of the methylene blue reagent On the other hand, the number of molecules n _d (number) of the methylene blue reagent decomposed during the experiment can be calculated by the following procedure.

  First, the relationship between the number of molecules (m) of the methylene blue reagent and the absorbance A is calculated.

  The molar concentration M (mol / L) of the methylene blue reagent is proportional to the absorbance A of the methylene blue reagent,

で表される。ここで、ａ（（ｍｏｌ／Ｌ）^−１）は、メチレンブルー試薬の濃度Ｍと吸光度Ａの関係を表す検量線の傾きであり、ｂは、同じ検量線の切片である。

It is represented by Here, a ((mol / L) ⁻¹ ) is the slope of the calibration curve representing the relationship between the concentration M of the methylene blue reagent and the absorbance A, and b is the intercept of the same calibration curve.

  When the volume of the methylene blue reagent is v (mL), the number of moles m (mol) of the methylene blue reagent is

で求められる。また、メチレンブルー試薬の分子は、１ｍｏｌ当たり、６．０２×１０^２３個存在するので、メチレンブルー試薬の分子数ｎ（個）は、

Is required. In addition, since there are 6.02 × 10 ²³ molecules of methylene blue reagent per mol, the number of molecules (number) of the methylene blue reagent is

で表される。

It is represented by

  From the formulas (6) to (8), the number of molecules (m) of the methylene blue reagent is calculated using the absorbance A of the methylene blue reagent.

で表される。

It is represented by

Accordingly, the number of molecules n _d (number) of the methylene blue reagent decomposed during the experiment is the change in absorbance of the methylene blue reagent by ΔA (that is, the difference between the absorbance A0 before the light irradiation and the absorbance A after the light irradiation, ΔA = A0-A)

で表される。

It is represented by

  Therefore, from the formulas (5) and (10), the quantum yield F (%) is

として算出することができる。

Can be calculated as

In addition, in calculating the quantum yield F (%) shown in Table 1, the following values were used as the values of each parameter:
The wavelength of light λ was either 405 nm or 488 nm. The irradiation time t was 16200 seconds (4.5 hours). The value of power P, if the wavelength λ is 405 nm, and 0.414mW / cm ^2, wavelength λ is the case of 488 nm, was 0.796mW / cm ^2. The concentration M and volume v of the methylene blue reagent were 1.0 × 10 ⁻⁵ mol / L and 3.6 mL, respectively.

FIG. 9 shows the relationship between the concentration M and the absorbance A of the methylene blue reagent. In the calibration curve obtained from this figure, the slope a was 0.938 × 10 ⁴ (mol / L) ⁻¹ and the intercept b was −0.0075.

  When the quantum yield F (%) was calculated using the above values, in the case of light irradiation with a wavelength of 405 nm, the quantum yield F (%) was 0.0452%, and in the case of light irradiation with a wavelength of 488 nm, The quantum yield F (%) was 0.0219%.

(Comparative Example 1)
Synthesis of MgIn ₂ O ₄ was attempted by the same method as in Example 1. However, in Comparative Example 1, pellets obtained by drying and pulverizing the mixed sample were placed in an electric furnace (YAMATO FO510) and fired at about 900 ° C. for 12 hours in air (first firing). The obtained fired body was cooled to room temperature and pulverized again, and then this powder was placed in an electric furnace (TSR-430, Yamada Denki Co., Ltd.) and fired at about 1160 ° C. for 60 hours in the atmosphere. (Second firing).

  The obtained sample sample was yellow. This sample is referred to as a sample sample according to Comparative Example 1.

In FIG. 10, the X-ray-diffraction measurement result of the sample sample which concerns on the comparative example 1 is shown. In FIG. 10, the upper row is the measurement result, and the lower row is the standard diffraction peak of In ₂ O ₃ . The diffraction peak of the sample sample coincided with the standard diffraction peak of In ₂ O ₃ , and it was found that MgIn ₂ O ₄ was not generated in Comparative Example 1.

  The present invention can be applied to a photocatalyst production method and the like.

100, 200 Test apparatus 120 Light source 130 Infrared light blocking filter 140 Ultraviolet light blocking filter 150 Band pass filter 160 Plastic cell 170 Sample 180 Methylene blue reagent.

Claims (5)

A method for producing MgIn ₂ O ₄ , comprising:
(1) Mixing MgCO ₃ and In ₂ CO _{3 so} that the molar ratio of MgCO ₃ and In ₂ CO ₃ is in the range between 1.05: 1.0 and 1.2: 1.0, Obtaining a mixture;
(2) firing the mixture in a temperature range of 800 ° C. to 1000 ° C. for 6 hours or more to obtain a first fired body;
(3) firing the first fired body in a temperature range of 1300 ° C. to 1450 ° C. for 12 to 24 hours to obtain MgIn ₂ O ₄ ;
A manufacturing method comprising:   The step (2) is a step of obtaining a first fired body by firing the mixture in a temperature range of 850 ° C to 950 ° C for 6 hours to 12 hours. Production method. The step (3) is a step of firing the first fired body in a temperature range of 1350 ° C to 1450 ° C for 12 hours to 24 hours to obtain MgIn ₂ O _4. 3. The production method according to 1 or 2. MgIn ₂ O ₄ has a quantum yield F (%).

When expressed in
The quantum yield of 0.02% or more is obtained for the decomposition of the methylene blue reagent by irradiation with visible light having a wavelength in the range of 400 nm to 490 nm. Production method described:
Here, Np (number) is the number of photons contained in the visible light, and n _d (number) is the number of molecules decomposed by the methylene blue reagent. Quantum yield F (%)

When expressed in
MgIn ₂ O ₄ material characterized in that a quantum yield of 0.02% or more is obtained for the decomposition of the methylene blue reagent by irradiation with visible light having a wavelength in the range of 400 nm to 490 nm:
Here, Np (number) is the number of photons contained in the visible light, and n _d (number) is the number of molecules decomposed by the methylene blue reagent.

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