JP2001183321A - Method for evaluating photocatalytic film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for evaluating a photocatalyst capable of simply, quickly, accurately and effectively evaluating the photocatalyst. SOLUTION: An optical scanning type two-dimensional concentration distribution measuring device 1 has a sensor surface 8 on one surface of a semiconductor substrate 6 and emits a light 5 to the substrate 6. In this case, a shielding film 61 having liquid containability is provided to be contacted with the surface 8, and impregnated with a solution 81 for bringing about a catalytic reaction. Further, a transparent board 31 in which a photocatalytic film 32 is deposited by a combinatorial synthesis is provided above the film 61 so that the film 32 is contacted with the film 61. Thus, the film 32 is evaluated based on the change of a pH in the film 32 when irradiating the film 32 with an ultraviolet ray or a visible light 52 through the board 31.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for evaluating a photocatalytic film (high-throughput screening).

[0002]

BACKGROUND ART In recent years, utilization of hydrogen gas (H ₂ gas) as a next-generation energy source has been studied. The hydrogen gas, the electrolysis by addition of a catalyst, such as water, for example ^{_{NaOH, H 2 O → H +}} + OH - becomes as represented by chemical reaction formula, water is H ⁺ and (hydrogen ion) OH ^- (Hydroxyl ion) and H ⁺
, Hydrogen gas is obtained.

[0003] However, the above-described method for producing hydrogen gas requires electric energy and is costly. Therefore, recently, using a photocatalyst such as TiO ₂ ,
It has been considered that the above reaction is caused by ultraviolet light irradiation, preferably visible light irradiation, to produce hydrogen gas.

In recent years, materials with excellent photocatalytic activity in the visible light region have been energetically developed. However, due to differences in components of trace amounts of added elements, differences in formation conditions, and differences in catalyst structures, etc. The catalytic ability of photocatalysts varies greatly. A combinatorial synthesis method for synthesizing a large amount of catalysts having such a difference at once has been studied.

[0005]

Therefore, in the conventional photocatalytic activity evaluation, the amount of oxygen or hydrogen generated by dispersing a powder in water or installing a thin film in water and irradiating ultraviolet light or the like is measured. Although the method of evaluating has been performed,
With this method, it is difficult or impossible to evaluate the catalytic activity in each region of a sample prepared by a combinatorial synthesis method having a different composition and structure in a fine region in a substrate.

The present invention has been made in view of the above-mentioned matters, and an object of the present invention is to evaluate the catalytic ability of a large amount of a photocatalyst formed by a combinatorial synthesis method simply, quickly, and accurately. An object of the present invention is to provide a method for evaluating a photocatalytic film that can be performed.

[0007]

In order to achieve the above object, a method for evaluating a photocatalytic film according to the present invention has a sensor surface on one surface of a semiconductor substrate and irradiates the semiconductor substrate with light. A light-shielding film having a liquid content is provided in contact with the sensor surface of the optical scanning type two-dimensional concentration distribution measuring device configured as described above, and a solution that causes a catalytic reaction is impregnated in the light-shielding film. Above the film, a transparent substrate on which a photocatalytic film is deposited by a combinatorial synthesis method is provided so that the photocatalytic film is in contact with the light-shielding film, and the photocatalytic film when irradiated with ultraviolet light or visible light through the transparent substrate. The photocatalyst film is evaluated based on the change in pH at (1).

In the above method for evaluating a photocatalytic film, a light-shielding film having a liquid content is provided in contact with a sensor surface of an optical scanning type two-dimensional concentration distribution measuring device, and a solution causing a catalytic reaction on the light-shielding film is provided. And a transparent substrate on which a photocatalytic film is deposited by a combinatorial synthesis method is provided so that the photocatalytic film is in contact with the light-shielding film, and is irradiated with ultraviolet light or visible light in that state, and H is applied on the sensor surface.
A change in pH is observed while causing a decomposition reaction of ₂ O.

As the light-shielding film having the liquid content, a filter paper or a membrane filter dyed black or a black sponge or porous alumina having a thickness of 1 mm or less is suitable. .
A solution having a conductivity equivalent to 1 M KCl and having an oxidizing or reducing action is preferable. Examples of such a solution include a solution containing 0.1 M KCl and Fe ₂ (SO ₄ ) ₃ .

The method for evaluating a photocatalyst film according to the present invention may be performed as follows. That is, after dropping a solution that causes a catalytic reaction on the photocatalytic film deposited by the combinatorial synthesis method on the surface of the transparent substrate, the photocatalytic film is irradiated with ultraviolet light or visible light to cause a catalytic reaction, and then, A transparent substrate, having a sensor surface on one surface of a semiconductor substrate, and the photocatalyst above the sensor surface of an optical scanning type two-dimensional concentration distribution measuring device configured to irradiate light to the semiconductor substrate. The photocatalytic film is evaluated based on a change in pH of the photocatalytic film when the film is provided so as to be in contact with the liquid layer provided on the upper surface of the sensor surface (claim 2).

In this case, a photocatalytic film formed on the transparent substrate by a combinatorial synthesis method is irradiated with ultraviolet light or visible light to cause a catalytic reaction. Thereafter, the transparent substrate is placed on the liquid layer provided on the sensor surface. Then, a change in pH is observed with the photocatalyst film in contact with the photocatalyst film.

As the liquid layer, it is preferable to use, for example, agar gel or polyacrylamide gel.

In any of the methods for evaluating a photocatalytic film, the change in pH depends on the time until a region having a different pH is detected, the size of the pH change region formed after a certain period of time after the reaction, and the region. By analyzing the pH value (proton amount) of p
The size of the H region and the p that is further generated in the pH change region
It can be grasped by analyzing the H value and the like.

In the method for evaluating a photocatalyst film according to the present invention, the reaction in the catalyst film is visualized by an image image, and qualitative catalytic activity can be grasped instantaneously. The ability can be grasped numerically.

In the method for evaluating a photocatalyst film according to the present invention, even if a plurality of (many) photocatalyst films are provided on a transparent substrate, the catalytic ability of each photocatalyst film can be quickly and simultaneously grasped, and the combinatorial The photocatalytic film formed by the synthesis method can be evaluated efficiently and accurately.

The method for evaluating a photocatalyst film according to claim 2 is characterized in that:
Compared with the first aspect, there is an advantage that the measurement can be performed without considering the influence of light on the sensor surface at all.

[0017]

1 to 3 show a first embodiment of the present invention. First, an optical scanning type two-dimensional concentration distribution measuring apparatus 1 used in the photocatalytic film evaluation method of the present invention will be described with reference to FIG.

In FIG. 1, reference numeral 2 denotes a measuring device main body, which comprises a sensor section 3 and a light irradiating section 5 for irradiating the sensor section 3 with light 4.

The sensor section 3 is formed by sequentially applying a SiO ₂ layer 7 and a Si ₃ N ₄ layer 8 on one surface (upper surface in the illustrated example) of a substrate 6 made of a semiconductor such as silicon by a method such as thermal oxidation or CVD. Formed so as to respond to H ⁺ . Reference numeral 9 denotes a sensor holder which includes the sensor surface of the sensor unit 3 (in this case, the Si ₃ N ₄ layer 8) and has a cell function provided so as to face the sensor surface. And the like can be accommodated in a state of being in contact with the sensor surface 8. The sensor surface 8 is, for example, 30 mm square.

Reference numerals 10 and 11 are counter electrodes and reference electrodes provided to face the sensor surface 8, and are connected to a potentiostat 16 described later. Reference numeral 12 denotes an ohmic electrode for extracting a current signal provided on the semiconductor substrate 6, and is connected to a potentiostat 16 via a current-voltage converter 17 and an operational amplifier circuit 18, which will be described later.

Reference numeral 13 denotes a sensor unit scanning device that scans the sensor unit 3 in a two-dimensional direction, that is, an X direction (horizontal direction in the illustrated example) and a Y direction (a direction perpendicular to the paper surface in the illustrated example). It is configured so as not to hinder the irradiation of the light 4 from the irradiation unit 5 to the sensor unit 3, and is controlled by a signal from the optical scanning control device 14.

The light irradiating section 5 is composed of, for example, a laser light source, and is provided on the lower surface side of the semiconductor substrate 6 (opposite to the sensor surface 8). In accordance with the control signal, the semiconductor substrate 6 of the sensor unit 3 which is scanned in the two-dimensional direction by the sensor unit scanning device 13 is intermittently irradiated with the laser beam 4 adjusted to have the optimum beam diameter. It is configured.

Reference numeral 15 denotes a control box for controlling the measuring apparatus main body 2, a potentiostat 16 for applying an appropriate bias voltage to the semiconductor substrate 6, and a control box 15 taken out from the ohmic electrode 12 formed on the semiconductor substrate 6. A current-voltage converter 17, which converts a current signal into a voltage signal,
It comprises an operational amplifier circuit 18 to which a signal from the current-voltage converter 17 is input, an interface board 19 for transmitting and receiving signals to and from the operational amplifier circuit 18 and outputting a control signal to the sensor unit scanning control device 14.

Reference numeral 20 performs various controls and calculations,
A computer as a control / arithmetic unit having an image processing function; 21 is an input device such as a keyboard and a mouse;
22, a display device such as a color display; and 23, a memory device.

Before describing the method for evaluating a photocatalyst film of the present invention using the optical scanning type two-dimensional concentration distribution measuring apparatus 1 having the above-described configuration, the method for forming a photocatalyst film will be briefly described with reference to FIG. Will be described.

As shown in FIG.
A transparent substrate 31 to be prepared is prepared. This transparent substrate 31
For example, SrTiO_Three(Strontium titanate) or Al
_TwoO _Three(Alumina), for example, 15 mm x 15 m
m (thickness is about 0.25 to 0.5mm)
is there.

[0027] Then, by using the appropriate method, on one surface of the transparent substrate 31, a TiO ₂ is epitaxially grown to form a plurality of photocatalytic film 32 (see FIG. 3 (B)). One size of the photocatalytic film 32 is, for example, 2 m
The size is about mx 2 mm (the thickness is about 10 ^-4 mm). For example, as shown in FIG. 3C, nine pieces are formed, and the forming conditions are slightly different depending on the combinatorial synthesis method. For example, the temperature and pressure at the time of formation, other substances to be added, and the amounts thereof are made different. Each of these photocatalytic films 32 is, for example,
Is registered in the computer 20 on the basis of the mark 33 formed in the computer 20.

Next, a method for evaluating the catalytic ability of the photocatalytic film 32 formed on the transparent substrate 31 will be described with reference to FIGS.

In FIG. 1, reference numeral 41 denotes a sample holding member for holding a transparent substrate 31 having a plurality of photocatalyst films 32 formed on one surface (hereinafter referred to as a sample 34). A first holding portion 43, which is freely provided and is mounted on one upper surface 9 a of the sensor holder 9 and is pivotally mounted, and a base 44 mounted on the other upper surface 9 b of the sensor holder 9 are screwed. The second holding member 46 moves in the horizontal direction by the attached screw member 45, and is configured to detachably hold a pair of opposite sides of the transparent substrate 31 of the sample 34.

In FIG. 1, reference numeral 51 denotes a UV light source that emits strong ultraviolet rays (UV) 52, and is configured to irradiate at least the entire surface of the sample 34.

In order to evaluate the photocatalyst film 32 in the sample 34, first, as shown in FIG. 2A, moisture can be contained on the upper surface of the sensor surface 8;
A light-shielding film 61 having a liquid-containing property that does not allow light to pass therethrough is adhered. As the light shielding film 61, a filter paper or a membrane filter dyed black or a black sponge or porous alumina having a thickness of 1 mm or less can be used. The light-shielding film 61 has a conductivity equivalent to 0.1 M KCl and a solution having an oxidizing or reducing action, for example, 0.1 M KCl.
An appropriate amount of a solution containing KI and Fe ₂ (SO ₄ ) ₃ is impregnated.

The light-shielding film 61 in which the solution has been impregnated may be arranged so as to be in close contact with the sensor surface 8.

Then, the sample 34 manufactured as shown in FIG. 3 is held by the sample holding member 41 such that the photocatalytic film 32 is in close contact with the light shielding film 61. In this case, all the photocatalyst films 32 in the sample 34 are completely adhered to the light shielding film 61.

In the above state, the UV light source 51 sends the UV light 52
Is irradiated on the sample 34, the UV light 52 passes through the transparent substrate 31 and reaches the nine photocatalyst films 32. This U
In the photocatalytic film 32 irradiated with the V light 52, H ₂
O is decomposed to generate H ⁺ , and the pH of the portion of the photocatalytic film 32 that is in contact with the sensor surface 8 changes. This pH change can be measured only in a minute area, and is a change that can be detected by the optical scanning type two-dimensional concentration distribution measuring device 1.

Therefore, as shown in FIGS. 1 and 2B, the counter electrode 10 and the reference electrode 11 are mounted so as to reach the light-shielding film 61, and the potential is set so that a depletion layer is generated in the semiconductor substrate 6. A DC voltage from the stat 16 is applied between the comparison electrode 11 and the ohmic electrode 12 to apply a predetermined bias voltage to the semiconductor substrate 6. In this state, the laser light 4 is applied to the semiconductor substrate 6 at a constant cycle (for example, 10
kHz), the semiconductor substrate 6 is illuminated intermittently.
To generate an AC photocurrent. The intermittent irradiation of the laser light 4 is performed by inputting a control signal of the computer 20 through the interface board 19. The photocurrent is a value reflecting the pH of the light-shielding film 61 in contact with the sensor surface 8 at a point facing the irradiation point of the semiconductor substrate 6, and by measuring the value, the pH value at this portion You can know.

Further, by the sensor section scanning device 13,
By moving the sensor unit 3 in the two-dimensional direction (X, Y directions), the semiconductor substrate 6 is irradiated with the laser beam 4 so as to be scanned in the two-dimensional direction, and the position signal (X, Y), and a two-dimensional image showing the state of the pH distribution formed on the light-shielding film 61 on the screen of the display device 22 as shown in FIG. 71 is displayed.

The image display is performed, for example, as follows. Assuming now that the image size is 2 cm × 2 cm and the pixel size is 100 μm, the pH values at each measurement point (200 × 200) are arranged corresponding to the position coordinates of the measurement points. The arranged values are displayed as a chemical image 71 similar to, for example, an STM (scanning tunneling microscope) image corresponding to a gray scale or a color scale.

Then, in the computer 20, after a catalytic reaction occurs in the photocatalytic film 32,
the time until the pH value is detected by the sensor surface 8,
The size of the pH change region formed after a certain time, pH
It is possible to analyze the pH distribution and the like that further occur in the change region.

As will be understood from the above description, the optical scanning type two-dimensional concentration distribution measuring apparatus 1 used in the method for evaluating a photocatalytic film of the present invention can accurately and quickly detect even a small pH change in a very small area. This can be grasped, image-processed, and displayed on the screen of the display device 22 as a two-dimensional image 71. Therefore, according to the method for evaluating a photocatalyst film of the present invention, the evaluation of the photocatalyst film 32 can be performed more easily and quickly than in the past.

That is, by observing the pH distribution in the light-shielding film 61, it is possible to observe the movement of protons in the photocatalytic film 32, and to quantitatively evaluate the catalytic ability of the photocatalytic film 32 based on this. And an index for evaluating them can be obtained. In other words,
The photocatalytic film 32 can be directly evaluated in accordance with its substance, and therefore, the catalytic ability of the photocatalytic film 32 can be accurately and reliably evaluated.

In the above-described method for evaluating a photocatalytic film, even a minute pH change in a minute region can be accurately and promptly grasped. Since it is indicated as 71, the catalytic ability of the plurality of photocatalyst films 32 can be measured individually, and more detailed evaluation can be performed.

FIG. 4 shows a second embodiment of the present invention. The method for evaluating a photocatalytic film in this embodiment differs from the first embodiment in that the catalytic reaction is performed by an optical scanning type. Rather than being performed on the sensor surface 8 of the two-dimensional concentration distribution measuring device 1, it is performed on another site, and the sample 34 in which the catalytic reaction has progressed is applied to the liquid layer provided on the sensor surface 8.
The photocatalyst film was placed in contact with the photocatalyst film,
Observe the change in

The members used in this embodiment are the same as the members used in the first embodiment. That is, as shown in FIG.
To the UV light source 51 so that the photocatalyst film 32 faces upward.
Provided below. Then, a solution causing a catalytic reaction, that is, a solution having a conductivity equivalent to 0.1 M KCl and having an oxidizing or reducing action, for example, 0.1 M KCl and Fe
A solution 81 containing ₂ (SO ₄ ) ₃ is dropped on each photocatalyst film 32 by, for example, 0.1 μl using an appropriate member 82.
Then, the entire surface of each photocatalytic film 32 is irradiated by the UV light source 51. As a result, a catalytic reaction is performed in the photocatalytic film 32, and a decomposition reaction of H ₂ O is performed.
⁺ Occurs.

Next, the upper surface of the sensor surface 8
A gel film 91 having a conductivity equivalent to MKCl is provided in close contact. The gel film 91 can be formed, for example, by heating a solution containing 0.1 M KCl and 1.5% agar at an appropriate temperature and then cooling.

Then, on the upper surface of the gel film 91,
Sample 3 in which a catalytic reaction has occurred in the photocatalytic film 32
4 is provided such that the photocatalyst film 32 is in close contact with the gel film 91. Then, as shown in FIG.
When the counter electrode 10 and the comparative electrode 11 are mounted so as to reach the gel film 91 and a predetermined bias voltage is applied,
As in the first embodiment, a two-dimensional image 71 is displayed on the display device 22 (see FIG. 4C).

In the optical scanning type two-dimensional concentration distribution measuring apparatus 1 described above, the comparison electrode 11 may be omitted and a bias voltage may be applied via the counter electrode 10. However, reference electrode 1
1 can more stably apply a bias voltage to the semiconductor substrate 6.

In the light scanning type two-dimensional density distribution measuring apparatus 1, instead of moving the sensor unit 3 in the X and Y directions, a light irradiation unit scanning device is provided in the light irradiation unit 5, 5 may be moved in the X and Y directions,
Further, a laser beam scanning device may be provided between the light irradiation unit 5 and the sensor unit 3 to move the laser beam 4 in the X and Y directions.

Further, in the optical scanning type two-dimensional density distribution measuring apparatus 1, the laser beam 4 from the light irradiating section 5 is irradiated from the side opposite to the sensor surface 8 of the semiconductor substrate 6. Alternatively, irradiation may be performed from the sensor surface 8 side. As the light irradiating section 5, a light irradiating section incorporated in the semiconductor substrate 6 may be employed as shown in, for example, Japanese Patent Application Laid-Open No. 8-213580.

In the method for evaluating the photocatalyst film, the photocatalyst film 32 is irradiated with the UV light 5 from the UV light source 51.
In this case, visible light such as sunlight may be irradiated instead. In addition, the wavelength of the light applied to the photocatalyst film 32 may be changed stepwise or continuously. In this case, the wavelength at which the pH changes is observed, and this is used to evaluate the catalytic ability. Index.

Further, the number of photocatalyst films 32 exceeding nine may be formed on the transparent substrate 31.
Only two may be provided.

In each of the above embodiments, the photocatalytic film 32 formed by the combinatorial synthesis method is used.
However, the present invention is not limited to this, and can be similarly applied to the evaluation of other materials (metals and functional films) synthesized by a combinatorial synthesis method.

[0052]

According to the method for evaluating a photocatalyst film of the present invention, the catalytic function of a material such as a photocatalyst film synthesized by a combinatorial synthesis method can be evaluated very simply, quickly and accurately. Can greatly contribute to the research and development of new and useful photocatalytic films.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing an entire configuration of an apparatus used for a method for evaluating a photocatalytic film according to a first embodiment.

FIG. 2 is a diagram for explaining the evaluation method.

FIG. 3 is a diagram schematically showing a method of manufacturing a sample used in the evaluation method.

FIG. 4 is a diagram illustrating a method for evaluating a photocatalytic film according to a second embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Optical scanning type two-dimensional density distribution measuring apparatus, 4 ... Light, 6 ... Semiconductor substrate, 8 ... Sensor surface, 31 ... Transparent substrate, 32 ... Photocatalytic film, 52 ... Ultraviolet light, 61 ... Light shielding film, 81 ... Catalytic reaction , A liquid layer that causes the

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takashi Omori 9-2 Kizugawadai, Kizu-cho, Kizu-cho, Soraku-gun, Kyoto Prefecture Within the Institute for Research on Global Environmental Technology (72) Eiji Suzuki Kizugawadai, Kizu-cho, Satsura-gun, Kyoto 9-chome No.2 Within the Research Institute for Innovative Technology for the Earth (72) Inventor Satoshi Nomura 2 Higashi-cho, Kichijoin-gu, Minami-ku, Kyoto, Kyoto Prefecture Within Horiba, Ltd. (72) Inventor Yuji Matsumoto Aoba-ku, Yokohama-shi, Kanagawa 1-6-1 Aobadai Urban Resort Aobadai Room 101 (72) Inventor Hideomi Koinuma 3-47-8 Ogikubo, Suginami-ku, Tokyo F-term (reference) 2G060 AA08 AA20 AE18 AE40 AF03 AG11 HC10 4G069 AA20 BA48A CC33 EA08

Claims (2)

[Claims] 1. A semiconductor substrate having a sensor surface on one surface and a liquid-containing two-dimensional concentration distribution measuring device configured to irradiate the semiconductor substrate with light. A light-shielding film having a photocatalytic film is provided in contact with the light-shielding film, and a solution causing a catalytic reaction is impregnated into the light-shielding film. The film is provided so as to be in contact with the light-shielding film, and the photocatalytic film is evaluated based on a change in pH in the photocatalytic film when ultraviolet light or visible light is irradiated through the transparent substrate. Evaluation method of photocatalytic film. 2. A solution causing a catalytic reaction is dropped on a photocatalytic film deposited on a surface of a transparent substrate by a combinatorial synthesis method, and then the photocatalytic film is irradiated with ultraviolet light or visible light to cause a catalytic reaction, Then, the transparent substrate,
Having a sensor surface on one surface of the semiconductor substrate, above the sensor surface of the optical scanning type two-dimensional concentration distribution measuring device configured to irradiate the semiconductor substrate with light,
P in the photocatalytic film when the photocatalytic film is provided so as to contact a liquid layer provided on the upper surface of the sensor surface.
A method for evaluating a photocatalytic film, wherein the photocatalytic film is evaluated based on a change in H.