JPH06331639A - Measuring method for flow velocity of solid-liquid interface liquid layer - Google Patents

Abstract

PURPOSE:To accurately measure the flow velocities of a solid-liquid interface liquid layer in micrometer and submicrometer and the distribution of the flow velocities. CONSTITUTION:A measuring method for the flow velocities of a liquid layer at the interface between a solid and a liquid comprises generating a transient diffraction grating by exciting of a photosensitive material such as a photochromic compound in the liquid by means of exciting light, then stopping irradiation of the exciting light, and, with transient diffraction which is the requirement for transmission, measuring the relationship between the relaxation time of diffracted light intensity and diffraction intensity by a probing beam, using the known average flow velocity of the solid-liquid interface liquid layer as a parameter. As a result, the relationship between the decay time of the diffracted light intensity and the average flow velocity is measured and, with transient diffraction which is the requirement for total reflection, the decay time of the diffracted light intensity is measured from the relationship between the relaxation time of the diffracted light intensity which is obtained using the penetration depth of evanescent light as a parameter and the diffraction intensity by the probing beam, and the flow velocities of the solid-liquid interface liquid layer and the distribution of the flow velocities are measured from the relationship between the average flow velocity and the relaxation time of the diffracted light intensity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring the flow velocity of a solid-liquid interface liquid layer. More specifically, the present invention is directed to the development of new materials, pharmaceuticals, photoresponsive materials, etc., research and development of new physical and chemical processes, and further development of industrial technology. The present invention relates to a method for measuring the flow velocity of a solid-liquid interface liquid layer that enables accurate measurement of the flow velocity and the flow velocity distribution.

[0002]

2. Description of the Related Art Conventionally, in the research and development of various fields and the development and application of industrial technology, it has been possible to evaluate the physical properties and changes of materials and their physical chemical processes by utilizing photochemical reactions. It is often done. Further, detailed analysis of this photochemical reaction at the solid-liquid interface has also been performed. In this case, in general,
The sample solution is often flowed at a flow rate in order to prevent successive reactions and collect the reactants efficiently.

In such a flow of the sample solution, the flow velocity at the interface is a very important factor. Therefore, accurately grasping the flow velocity at the solid-liquid interface causes the photochemical reaction appropriately and efficiently. Will be needed to evaluate.
Furthermore, even in the case of micromachines, which have been greatly developed in recent years, the flow velocity at the solid-liquid interface can be accurately determined at the interface, for example, when analyzing the relationship between the fluid flow and the surface characteristics of the micromachine. It is indispensable to measure.

Conventionally, as a method for measuring the flow velocity in a solid-liquid interface liquid layer, mass transfer as an average value, that is, a method for obtaining the average flow velocity in the liquid layer is easy in principle, and therefore widely used. Is used for. However, when the reaction field of micrometer and sub-micrometer and the photochemical reaction in the solid-liquid interface liquid layer are handled strictly, the average flow velocity of such liquid layer becomes completely meaningless. For example, it has been pointed out that the polymer association state and composition are different from the bulk properties in the range of 0.2 μm at the interface with the polymer material on the solid substrate (Chem. Materials, 3 , 413
(1991)) Furthermore, not only in such a polymer material, but also in various liquids in general, due to a special intermolecular force such as hydrogen bond, the liquid in the liquid layer has a non-uniform structure. It is expected that a unique situation will occur at the solid-liquid interface.

That is, for the reasons described above, it is considered that the flow velocity becomes slower than the average value in the vicinity of the solid surface of the solid-liquid interface, and it becomes remarkable particularly in the micrometer and sub-micrometer order regions. Therefore, measuring the flow velocity of the solid-liquid interface layer in the micrometer or sub-micrometer region is an important and indispensable basis for conducting chemical reaction analysis in the microscopic region. In fact, the method of measuring the flow velocity of the liquid in the solid-liquid interface liquid layer of the sub-micrometer order has not been known so far.

The present invention has been made in view of the above circumstances, overcomes the limitation of the conventional method for measuring the flow velocity of the solid-liquid interface liquid layer, and has a thickness of micrometer and sub-micrometer. It is an object of the present invention to provide a method for measuring the flow velocity of a solid-liquid interface liquid layer that accurately measures the flow velocity of the interface liquid layer nondestructively.

[0007]

The present invention is to solve the above-mentioned problems by providing a flow velocity measuring method for measuring the flow velocity of a liquid layer at the interface between a solid and a liquid, which comprises irradiating the liquid layer with excitation light to obtain a transient state. After generating the diffraction grating, stop the irradiation of excitation light and measure the flow velocity of the solid-liquid interface liquid layer and its velocity distribution from the disappearance time of the diffracted light intensity by transient diffraction under the transmission and total reflection conditions. A method for measuring the flow velocity of a solid-liquid interface liquid layer is provided.

That is, the present invention is a method for nondestructively measuring the flow velocity and flow velocity distribution of a liquid in a solid-liquid interface liquid layer in the micrometer and sub-micrometer regions of the liquid layer at the solid-liquid interface, and it is a transient due to a permeation condition. Based on the measurement by diffraction, the measurement is performed by the transient diffraction method under the condition of total reflection. As a more specific embodiment, for example, a photoresponsive substance such as a photochromic compound is allowed to exist in a liquid in advance, these are excited by excitation light to generate a transient diffraction grating, and then the irradiation of the excitation light is stopped. The relaxation time of the intensity of the diffracted light observed by the probe light is defined by the average flow velocity of the liquid layer calculated from the flow rate per unit time of the liquid and the cross-sectional area of the flow cell used by the transient diffraction method under the transmission conditions. The relationship is measured, and the extinction time of the diffracted light intensity is obtained from the result, and then the relationship between the extinction time of the diffracted light intensity and the average flow velocity of the liquid layer is obtained.

Next, the transient diffraction grating spectroscopy under the condition of total reflection is used to obtain the relaxation time of the diffracted light intensity with the penetration depth of the evanescent wave as a parameter. From this result, the extinction time of the diffracted light intensity is obtained. . At this time, the liquid is flowing at the average flow velocity in the bulk state, but it is smaller than this value in the vicinity of the interface. That is, it is possible to estimate the flow velocity corresponding to the relaxation time of the diffracted light intensity measured under the total reflection condition from the relationship between the relaxation time of the diffracted light intensity obtained under the transmission condition and the average flow velocity of the liquid layer. The flow velocity and flow velocity distribution of the liquid layers of the micrometer and sub-micrometer solid-liquid interface liquid layers will be obtained.

In the present invention, a He-Ne laser is preferable for the probe light and 300 n for the excitation light.
An ultraviolet picosecond or nanosecond pulsed laser in the vicinity of m to 380 nm is desirable.

[0011]

The principle of the method for measuring the flow velocity at the solid-liquid interface according to the present invention will be described below. Generally, when a pulsed laser is applied to a sample solution in which a photoresponsive substance such as a photochromic compound is present in advance, a photoresponsive reaction occurs, whereby
Since a change in the concentration of the reaction system occurs, a corresponding change in the refractive index is induced.

Therefore, in the present invention, as illustrated in FIG. 1, for example, by irradiating the same region of the sample with two excitation lights at a certain angle θ at the same time, the interference of the laser light is generated. Since the molecules are excited along the stripes, a transient diffraction grating with a change in the refractive index due to the change in concentration is generated, and the generation and disappearance processes are detected with probe light such as sub-picosecond white light or He-Ne laser light. be able to.

It is known that the generated transient diffraction grating relaxes due to various causes, but the slow diffusion component that decays on the time scale of millisecond order is governed by the mass diffusion equation. The attenuation process of the transient diffraction grating due to the diffusion of this material is

[0014]

[Equation 1]

It is represented by Here, N (x, t) is the concentration of the product generated by the photochromic reaction or the like with the position x and the time t as a function, A is the pitch of the diffraction grating, and τ is the life of the product. τ _D represents the relaxation time due to diffusion of the product, and τ _D is the mass diffusion coefficient D _mass ,

[0016]

[Equation 2]

Is given by From equation (1), the attenuation τ ′ _g of the diffraction grating amplitude is

[0018]

[Equation 3]

Is given by Since the observed diffraction efficiency (η) is proportional to N (x, t) ² , if the disappearance time of the observed diffracted light intensity is τ _g ,

[0020]

[Equation 4]

Is obtained. For example, when spirooxazine is used as a photochromic compound, the product lifetime τ is on the order of seconds, and when the grating pitch A is micrometer or submicrometer, τ
_D is generally well as tau _D / tau = 0 because several milliseconds order of several 100 microseconds, tau _D to both sides of the equation (3)
As a result, τ _D = τ ′ _g , and therefore equation (4) becomes

[0022]

[Equation 5]

Can be approximated by On the other hand, when the sample is caused to flow, the generated transient diffraction grating is forcibly extinguished, so equation (2) is substituted into equation (5) and the relaxation term due to flow is set to f (v). Considering τ _g

[0024]

[Equation 6]

It can be approximated as follows. Next, f in equation (6)
When the relationship between (v) and v is obtained, τ _g (v) and v
The relationship of

[0026]

[Equation 7]

It becomes as follows. Here, a and b are constants obtained from the experimental results, and τ _g (0) is τ _g when v = 0. Transforming equation (6),

[0028]

[Equation 8]

This equation (8) takes into consideration the equation (7),

[0030]

[Equation 9]

Then, after all,

[0032]

[Equation 10]

It becomes Therefore, the relation between the relaxation term f (v) due to the flow and the flow velocity v can be obtained from the equation (10), and as a result, the relaxation time τ _g (v) and v of the diffracted light intensity can be obtained from the equation (6). You can ask for a relationship. Next, the transient diffraction grating is generated under the condition of total reflection. Under the condition of total internal reflection, the region generated by the transient diffraction grating is several hundreds from the interface.
By measuring the extinction time τ _g of the diffraction intensity of the transient diffracted light in this region to be equal to or less than nm, the flow velocity v in the solid-liquid interface liquid layer can be obtained by performing back calculation from the equation (6).

Hereinafter, the method of measuring the flow velocity of the solid-liquid interface liquid layer according to the present invention will be described in more detail with reference to examples.

[0035]

EXAMPLE A solution prepared by dissolving about 10 ⁻³ M of spirooxazine, which is a photochromic compound, in 1-butanol was prepared.
The diffracted light intensity in the photochromic reaction was measured by the transient diffraction method under the transmission condition by using a total reflection cell including a sapphire prism. The dependence of the intensity of the diffracted light on the average flow velocity of the liquid layer is as shown in FIG.

It can be seen from FIG. 2 that the disappearance time τ _g of the diffracted light intensity observed increases as the average flow velocity of the liquid layer increases. The method of the present invention aims to obtain the flow velocity v in the solid-liquid interface liquid layer by measuring the extinction time τ _g of the diffracted light intensity. Therefore, referring to FIG. The average flow velocity v of the liquid layer is plotted against the extinction time τ _{g of the} intensity. This is shown in FIG.

As illustrated in FIG. 3, a good linear relationship is obtained between the average flow velocity of the liquid layer and the logarithm of 1 / τ _g as described above, and the average flow velocity v of the liquid layer is experimentally determined as described above. The result is as shown in Expression (7). Here, v is the average flow velocity of the liquid layer, and in this embodiment, a = 9 × 10 ⁻² m / s, τ
_{It was g} (0) = 690 μs.

Further, by the transient diffraction method under the condition of total reflection,
The diffracted light intensity was measured, and the time dependence of the diffracted light intensity was as shown in FIG. From this figure, it is apparent that the disappearance time of the diffracted light intensity is delayed in the solid-liquid interface liquid layers of micrometer and sub-micrometer. This indicates that the flow velocity is slow in the solid-liquid interface liquid layer.

The penetration depth dp of the evanescent light as the excitation light is the critical angle θc from the incident angle dependence of the fluorescence intensity.
After experimentally obtaining

[0040]

[Equation 11]

Was calculated using In this equation (11), λ ₀ is the wavelength of the excitation light, n ₁ is the refractive index of sapphire,
θi is the incident angle of the excitation light on the sample. Total reflection critical θ
In the case of the sapphire / 1-butanol interface, c was experimentally determined to be 52.1 °. That is, the extinction time τ _g of the diffracted light intensity at that position can be measured by using the penetration depth dp of the evanescent light as the excitation light as a parameter, and this τ _g can be measured by the transient diffraction method under the above transmission conditions. By substituting into the known formula (6), the flow velocity at the depth dp can be obtained. Of course, d
It is also possible to measure the flow velocity distribution by changing p.

Table 1 shows the relationship between the thickness dp of the solid-liquid interface liquid layer and the flow velocity obtained from the above calculation.

[0043]

[Table 1]

As shown in Table 1, the average flow velocity of the liquid layer is 0.12 m / sec, but 200 nm from the vicinity of the interface.
It is calculated that there is almost no flow in the following areas.

[0045]

As described in detail above, according to the present invention, it is possible to accurately measure the flow velocity and the flow velocity distribution of the solid-liquid interface liquid layer of micrometer and sub-micrometer.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the principle of a flow velocity measuring method for a solid-liquid interface liquid layer of the present invention.

FIG. 2 is a correlation diagram showing the relationship between the relaxation time of diffracted light intensity and the diffraction intensity using the transmission diffraction method.

3 is a relationship diagram showing the relationship between the relaxation time of the diffracted light intensity of FIG. 2 and the average flow velocity of the liquid layer.

FIG. 4 is a relationship diagram showing a relationship between relaxation time of diffracted light intensity and diffraction intensity using a total reflection diffraction method.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Takayuki Ito, 32, Saizo Sanzocho, Ukyo-ku, Kyoto City, Kyoto Prefecture No. 604 Joytel Saiin (72) Inventor, Hiroshi Masuhara 2-4-16, Minamikonoike-cho, Higashi-Osaka, Osaka

Claims (1)

[Claims] 1. A flow velocity measuring method for measuring the flow velocity of a liquid layer at an interface between a solid and a liquid, wherein the liquid layer is irradiated with excitation light to generate a transient diffraction grating, and then the irradiation of excitation light is stopped.
A method for measuring the flow velocity of a solid-liquid interface liquid layer, which comprises measuring the flow velocity of the solid-liquid interface liquid layer and its velocity distribution from the disappearance time of the diffracted light intensity by transient diffraction under transmission conditions and total reflection conditions.