KR100588987B1 - Machine of analyzing optically using surface plasmon resonance and method of analyzing the same - Google Patents

Abstract

The present invention relates to an optical analysis device for measuring the interaction of biochemicals and biomaterials using surface plasmon resonance, or measuring the thickness, refractive index and refractive index of a thin film.

The dynamic range and sensitivity of the angle resolution SPR system in the correlation between the measuring range of the SPR device and the prism structure are affected by various factors related to the SPR phenomenon, the refractive index of the prism and the shape of the prism.

Triangular prisms have superior sensitivity, although dynamic measurement range is limited for high refractive index solutions compared to hemispherical prisms. In order to improve the limitations of the triangular prism while maintaining the sensitivity, the method increases the base angle of the prism to increase the dynamic range and increase the inherent sensitivity without increasing the refractive index of the prism.

Hemispherical Prism, Surface Plasmon Resonance (SPR), Incident Angle, Metal Thin Film, Light Source, Refractive Index

Description

Machine of optically using surface plasmon resonance and method of analyzing the same

1 is a structural diagram of Kretschmann for generating surface plasmon

FIG. 2A is a total reflection graph of incident angle change in a prism on which a metal thin film is not deposited

Figure 2b is a reflection graph showing the surface plasmon resonance phenomenon in the metal prism deposited

3A is a block diagram of a point light source type incident angle resolution type surface plasmon resonance measuring device

3b is a block diagram of a wavelength-resolved surface plasmon resonance measuring device having a wedge shaped light

4 is a schematic diagram when detecting with an n-Channel PDA or CCD

5 is a path diagram of light with respect to an angle of incident light along an interface of each medium;

6 is a relationship between the measurement angle and the incident angle inside the actual prism

7 is an effect graph of the sensitivity and dynamic measurement range by the refractive index of the hemispherical prism

8 is a graph illustrating the relationship between the mechanical measurement angle and the incident angle inside the prism for the hemispherical prism and the five kinds of prisms having different base angles.

9 is a graph obtained by differentiating a result of angle conversion of prisms having different base angles.

FIG. 10 is a graph in which the x and y axes are interchanged in the graph of FIG. 8.

11 is a graph showing the relationship of the change of the resonance angle to the actual refractive index for the hemispherical prism and 90 ˚ prism

12A is a graph showing the change of the resonance angle for liquid samples having different refractive indices in a hemispherical prism

12b is a graph showing the change of the resonance angle for liquid samples having different refractive indices in a 90 ° prism

13A is a path diagram of incident light in an inverted trapezoid prism;

13B is a path diagram of incident light in a parallelogram prism;

FIG. 14 is a graph of reflectivity results in air for a prism without a metal thin film deposited on an inverted trapezoid prism;

FIG. 15 is a graph of reflectivity results in air for a prism without a metal thin film deposited on a parallelogram prism; FIG.

16 is an SPR curve graph of water having a refractive index of 1.33 for an inverted trapezoid prism and a parallelogram prism on which a metal thin film is deposited.

17A is a schematic diagram of an optical system of an angular resolution SPR measuring system using a prism according to the present invention;

Figure 17b is an optical system configuration of the wedge-shaped angle resolution type SPR measurement system using a prism according to the present invention

18 is an optical system diagram of a two-dimensional SPR image measuring system capable of detecting two or more measurement positions;

The present invention relates to an optical analysis device for measuring the interaction of biochemicals and biomaterials using surface plasmon resonance, or measuring the thickness, refractive index and refractive index of a thin film.

1 shows a Kretschmann structure for generating surface plasmons. The principle of surface plasmon resonance is known as quantization of charge density oscillation of electrons occurring on the surface of metal thin film, and it is known as surface electromagnetic waves propagating along the interface between metal and adjacent dielectric material. Various methods are known to excite the surface plasmon, but in order to generate the surface plasmon by the optical method, as shown in FIG. 1, the metal thin film 101 is formed on the interface between two media having different refractive indices so that total reflection can occur. ), So-called Crechmann (E. Kretschmann, Z. Phys. 241, 313, 1971.) structure can be constructed. Looking at the surface plasmon excitation process by the total reflection in the Kretschmann structure of Figure 1 as follows. First, when a monochromatic light 102 such as a laser enters a medium having a high refractive index such as the prism 103 toward a medium having a low refractive index such as air or a solution, part of the incident light passes through the bottom surface of the prism and partially reflects the light source. A photodetector 104 located opposite is reached. However, when the incident angle of the incident light based on the normal of the bottom surface of the prism exceeds a certain critical angle, the light passing through the bottom surface is no longer provided and all incident light is reflected. In this total reflection process, an evanescent wave is generated toward the medium having a lower refractive index at the interface of the medium.

FIG. 2A illustrates the reflectivity of the incident light reflected from the bottom surface of the prism on which the metal thin film 101 is not deposited. In this case, the critical angle 201 in which total reflection of the light incident on the bottom surface of the prism may occur is also apparent. FIG. 2B shows a reflectance graph showing the surface plasmon resonance phenomenon in the prism in which the metal thin film is terminated, and the resonance angle 202 appears due to the deposition of the metal thin film. In the total reflection graph of the incident angle change of FIG. 2A, the dissipation wave has an effective distance of about a wavelength and plays an important role in transferring the energy of incident light to other media according to the optical conditions of the reflecting interface. In particular, when the wave-vector matching condition of the dissipation wave coincides with the optical condition of the surface plasmon which may exist in the metal thin film as shown in the following equation [1], the energy of the incident light is directed toward the thin metal thin film 101. As it passes, it causes surface plasmons in the metal film. However, the polarized light of the incident light must be p-polarized (TM polarized light) because the vibration mode of the surface plasmon is a longitudinal mode with respect to the surface. The surface plasmon excitation is called Surface Plasmon Resonance (SPR), and the light energy after reflection as a result of resonance is shown at a specific angle 202 as shown in FIG. 2B. It will decrease sharply.

nter Gauglitz, Sensors and Actuators B 54 3, 1999.)Where n _p , n _m , and n _s are the refractive indices of the prism, metal, and dielectric layer, respectively, and θ and λ represent the incident angle and wavelength of incident light (Jiri Homola, Sinclair S. Yee, G).

nter Gauglitz, Sensors and Actuators B 54 3, 1999.)

Referring to Equation [1], the resonance angle 202 of surface plasmon resonance, that is, the angle at which the reflected light is minimized, is greatly influenced by the refractive index of the lower dielectric layer. In other words, if the mass of the lower metal dielectric layer is increased or the structure is deformed due to some physicochemical action, the effective refractive index of the dielectric may change, resulting in a change in the resonance angle. Therefore, using the principle of SPR, which can measure the change of these materials by optical method, the biochemical reactions such as selective coupling or separation between various biochemicals can be changed into the resonance angle through proper chemical modification of the lower metal layer. SPR sensor can be used as a sensitive biochemical sensor. A reported paper (E. Stenberg, B. Persson, H. Roos, C. Urbaniczky, J. of Colloid and Interface Sci., 143, 2,513, 1991) shows that the refractive index of the dielectric layer is 0.001 for commercially available SPR sensors. As it changes, the change in the resonance angle changes by 0.1 °, which is known to correspond to a mass change of about 1 ng per mm area.

Various characteristics and usability of the SPR sensor discussed above have been verified in various fields such as biotechnology, environment, new drug development and food industry. In addition, about 10 years ago, the SPR sensor was commercialized in the form of a biosensor system, thanks to the excellent material sensing characteristics provided by the SPR phenomenon. In particular, with the advent of biochips, more attention has been gathered on the SPR sensor, which is a marker used in the process of studying the function of proteins, DNA, and RNA using the fluorescence method. It does not need to be used at all, and even without a marker, many biochemical phenomena can be measured with high sensitivity.

First of all, the fundamental reason why SPR can measure inherently high sensitivity without other auxiliary means such as markers is that the Sampling Depth of the evanescent wave formed within the range of several hundred nm from the surface is compared with other conventional optical methods. It's about being extremely small. In other words, the measurement area immobilized on the surface and the area of dissipation are much narrower than other optical methods, and using dissipation makes it possible to easily measure the interaction between materials with only a small amount of sample. The characteristics of the dissipation wave are not only for the application of SPR, but also for the use of optical waveguides.

In particular, the SPR method, which has excellent advantages in interface and surface measurement, is expected to be widely applied in the nanotechnology field recently. Typically, the formation process of the ultra thin film in the field of organic thin film application As a method of measuring the physical properties of the thin film itself at the same time, the value of its use is increasing.

The method for measuring the SPR phenomenon is classified based on the above equation [1] related to the resonance phenomenon, and the wavelength decomposition with the point light source type incident angle resolution type surface plasmon resonance measuring device of FIG. 3A and the wedge type light type of FIG. It can be divided into type surface plasmon resonance measuring device. First, the incident angle resolution type of FIG. 3A is a method of finding a resonance angle with minimum reflectivity for various incident angles as shown in FIG. 2B with respect to the optical structure of FIG. 1. As can be seen from Equation [1], since the angle of incident light is given as a function of the refractive index of the sample, this method can measure the change of the sample as the change of the resonance angle. Next, the wavelength resolution type finds a wavelength in which resonance occurs while changing the wavelength of light for a given angle of incidence by using the wavelength dependence of the refractive index of each medium. Both methods are already commercialized, but most measurement methods use incident angle resolution. In particular, the incident angle decomposition type is a method used to measure surface plasmon resonance, which is the most commonly used method. In detail, the incident angle decomposition method changes the incident angle of incident light within a certain range and measures the incident light with a wedge shape. By using the multi-channel optical sensor (CCD or Photodiode Array), the optical signal for incident angle within the wedge shape can be measured at once and divided into the method of tracking the change of resonance point.

Of course, diffraction gratings are used instead of prisms to create total reflection conditions, and various methods using flat waveguides or optical fibers have been developed for smaller and easier optical structures. However, in the case of commercially available SPR biosensors, many methods using multi-channel optical sensors and wedge-shaped light are being used to monitor biochemical reactions in real time. In order to quantify the physical properties of the thin film or to study the original surface plasmon resonance phenomenon, a method of measuring the photodiode by changing the angle of incidence is widely used.

을 나타낸다. 그리고 기기의 분해능은 SPR측정기기가 계측하여 결정할 수 있는 최소 물리량, 즉 측정 가능한 최소 굴절률을 나타낸다. 그런데 여기에서 액체시료의 굴절률이 SPR의 성능평가의 기준시료가 되는 것은 SPR이 많이 활용되고 있는 바이오센서분야의 주요 시료가 일반적으로 액체상이기 때문이다. 즉 금속박막위에 형성된 감지막이 액체상에 용해된 계측시료인 단백질이 나 이온과 같은 생화학물질과 반응한 결과 나타나는 공명각의 변화의 기준점은 대부분 액체시료자체의 공명각 근처에서 일어나기 때문이다. 그러므로 액체시료의 굴절률은 SPR측정에 있어서 기기설계의 기준점이며 성능평가의 주요 시료가 된다.This most commonly used incident angle resolution type SPR device has evolved over the last decades with various structures and applications since Kretschmann and Otto first announced the SPR excitation by optical methods. In particular, due to the excellent characteristics of SPR, as the SPR equipment has been commercialized, many studies have been conducted on the intrinsic performance and limitations of the SPR equipment. According to these studies, the performance of an SPR device is usually expressed by dynamic measurement range, sensitivity, and resolution, and the unit can be expressed based on the refractive index of the liquid sample. Here, the dynamic measurement range of the instrument means the range of measurable refractive index, and the sensitivity is the derivative of the measured physical quantity (angle) with respect to the change of the refractive index.

Indicates. The resolution of the device represents the minimum physical quantity that can be measured and determined by the SPR measuring device, that is, the minimum measurable refractive index. However, the refractive index of the liquid sample is the reference sample for the performance evaluation of the SPR because the main sample in the biosensor field in which SPR is widely used is generally liquid phase. In other words, the reference point of the change of the resonance angle resulting from the reaction of the sensing film formed on the metal thin film with a biochemical such as protein or ions, which is a measurement sample dissolved in the liquid phase, occurs mostly near the resonance angle of the liquid sample itself. Therefore, the refractive index of the liquid sample is the reference point of the instrument design in SPR measurement and is the main sample for performance evaluation.

These three indicators are performance indices that provide important performance criteria for determining and improving the performance of an SPR device. However, these three performance indicators are correlated with each other in terms of structural and principle aspects of the device, and thus have many limitations in maintaining all the performance indicators at the best. Among these, the resolution and dynamic measurement range of SPR devices are directly related to the parts performance and manufacturing technology used in the device, and the dynamic measurement range is limited to maximize the resolution. This problem mainly occurs in a method using a multichannel photodetector.

4 is a schematic view of detecting a detector portion using an n-Channel PDA or CCD 401 in the configuration of the SPR measuring apparatus. When detecting wedge-shaped light at a constant angle 403 through the n-channel photodetector 401, the resolution is determined by L 402, which is the distance between the number of channels and the SPR sensing unit in the prism and the detector. Therefore, the first step to increase resolution is to increase the number of channels. This method limits the number of channels per unit area due to the limitations of current photodetector fabrication technology. Next, for the given optimal number of channels, the resolution L can be increased by increasing the length L of the wedge-shaped light in Fig. 4 or by using the lens system as an optical method, but this method can also increase the structural aspect or optical Due to the inherent limitations of the device, there are limitations to the technical improvement. Of course, the research on the structure of the device with optimized performance using these methods has been published and commercialized previously, and other researches that have improved the performance by adding various signal processing techniques have been published. However, as suggested earlier, this set of measures to improve the resolution results in maintaining or decreasing the figure of merit rather than in terms of improving the dynamic range. In the case of wedge fluorescence, the dynamic measurement range is determined by the spreading angle of the light. When the angle is widened to increase the dynamic measurement range, the size and distance of the photodetector are limited. This is a problem that must be compromised.

In addition, the sensitivity of the SPR device is greatly influenced by various physical quantities related to the SPR phenomenon, which is influenced by the wavelength of light used or the characteristics of the metal, that is, the type of metal thin film, the refractive index, and the refractive index of the prism used. Moreover, the refractive index of the prism affects the dynamic measurement range as well as the sensitivity of the device. As the refractive index of the prism increases, the dynamic measurement range increases under a given condition. However, the sensitivity decreases as the refractive index of the prism increases, as shown in the following table. In addition, the sensitivity of the SPR device is closely related to the resolution of the SPR device. Referring to the definition of the sensitivity of the SPR device, it is easy to see that the higher the sensitivity under the same conditions, such as the range of refractive index, the better the resolution. In other words, the resolution of measured values such as angle and light intensity is fundamentally limited in precision, such as the noise of the device itself or the problem of the accuracy of manufacturing the device, but it is necessary to measure when the sensitivity of the device is improved by appropriate methods. The measurement limit of the physical quantity is much lower, resulting in better resolution.

Taken together, technical efforts to improve the performance of SPR equipment are important to approach fundamental problems, such as improving the performance of parts and optimized design of structures, but inherent limitations due to the level of manufacturing technology are difficult to overcome. to be. Therefore, in principle, it is necessary to find a way to further improve the performance of the device, and the important performance indicators can be summarized by the dynamic range and sensitivity of the device. However, there are many limitations as described above in order to satisfy these two performance indices simultaneously in the conventional technical level or method. Therefore, the conventional angular resolution SPR system, which is commercially available or reported in the literature, has been mostly researched and developed in the direction of improving only one of two performance indicators. For example, most commercially available SPR systems are designed to measure the low-refractive index solution, such as buffer, so that the dynamic range is relatively large, with a refractive index of 1.33 to 1.40, but resolution is measured in units of refractive index. It is designed to have a precision of about 10 ^-6 . In addition, high refractive index prisms, such as various organic solvents, have been used to improve the dynamic measurement range even if performance is reduced in terms of sensitivity in terms of sensitivity.

[Purpose of invention]                         

In the present invention, it was conceived that there are many limitations in improving both performances at the same time with the conventional technical level or method in the dynamic measurement range and sensitivity which critically affect the performance improvement of the angular resolution SPR device. Accordingly, an object of the present invention is to improve the two performance indicators simultaneously by reconsidering the correlation between the measuring method and the structure of the prism in the principle aspect of SPR to overcome the above limitations.

In the correlation between the measuring range of a SPR device and the prism structure, the dynamic measuring range and sensitivity of the angular resolution SPR system depend on various factors related to the SPR phenomenon, but are generally most affected by the refractive index of the prism. This is because the SPR phenomenon is generated by the dissipation wave related to the total reflection, so that the total reflection condition can be maintained when the refractive index of the liquid sample is smaller than the refractive index of the prism. However, the refractive index of the liquid sample that can be actually measured in the SPR device has a range of values much lower than that of the prism corresponding to the total reflection condition. This is because, firstly, the resonance angle associated with SPR has a relatively larger value than the critical angle associated with total reflection, and next, except for the hemispherical prism, the measurement range of the angle where resonance occurs is limited by the structure of the prism. This is because the optical structure that determines the angle of incidence of light in the process of measuring SPR depends on the geometry of the prism, so that the incident angle θ _G (508) of the mechanically determined light is different from the incident angle θ _R (505) within the prism associated with total reflection. Because. Therefore, the relationship between θ _G (508) and θ _R (505) should be closely examined by examining the dynamic range of the refractive index of the measurable liquid sample. Must be quantified.

5 shows a path of light with respect to the angle of incident light along the interface of each medium. The first incident light 510 forms an angle of θ _G 508 with the normal 501 of the prism underside 511. This forms an angle of θ _i 507 with the normal 502 with respect to the incidence plane 509 of the prism having the prism bottom and an internal angle of α 503. The incident light enters the prism 504 and proceeds at an angle of θ _ii 506 with the normal of the incident surface due to the refractive index of the prism. The propagated light again forms an angle between N ₂ 501 and θ _R (505), which is the base normal.

As shown in FIG. 5, the path of light incident from the right side is determined by the angle of incidence and the angle of refraction at each interface where the prism and another medium meet. When Snell's law is applied to find the incidence angles and refraction angles for the normals N ₁ and N ₂ at each interface, the refraction angles of the light refracted in the prism with respect to the incident angle θ _i of the light incident on the prism oblique plane are as follows.

In Equation 2, n _P represents the refractive index of the prism for a given wavelength of light.

Next, if the incident angle in the prism of the light incident on the lower surface of the prism is θ _R and the angle of the prism is α

Can be expressed as At this time, since the path of the reflected light is opposite to that of the incident, the path of the reflected light can be expressed by the above method.

It should be noted here that if light enters the center of a semicircle into a semi-spherical prism rather than a triangular prism, the normal N ₁ will always be a line passing through the center of the circle and the light will travel along the normal, so the incident angle θ _R is Without the help of [2] and [3], θ _R = θ _G where θ _G represents the mechanical angle of measurement given by the rotating device. However, in the case of a prism having an arbitrary angle, such as a triangle, the above-described transformation relationship is necessary because of reflection and refraction in the prism plane. The following equation [2] is used to determine θ _i of the equation [2] as the measurement angle θ _G when expressed as the incident angle θ _R in the case of a triangular prismatic prism it is represented by the formula [5] as follows.

Unlike the hemispherical prism of Equation [6] above, the triangular prism of Equation [5] shows that the incident angle θ _R is nonlinear for a given measurement angle θ _G. The results applied to the prism and the hemispherical prism are shown in FIG.

6 shows the relationship between the mechanical measurement angle and the incident angle inside the actual prism. The x axis is the mechanical angle of measurement and the y axis is the angle of incidence inside the prism. 5 and 6, the x-axis of FIG. 6 represents θ _G 508 of FIG. 5, and the y-axis of FIG. 6 represents θ _R of FIG. 5.

In the graph of FIG. 6, the hemispherical prism 601 corresponds to a mechanical measurement angle and an actual angle of incidence in the prism at 1: 1, but the BK7 (602), BaK4 (603), and SF10 (604) materials having different refractive indices of the prism are different. In the case of the triangle 45˚ prism, it can be seen that the measurement range of the actual incident angle is limited compared to the given mechanical measurement angle range. However, it can be seen that the difference in the refractive index of the prism does not significantly affect the distortion of the angle compared to the tendency.

On the other hand, the sensitivity of the SPR device, which is defined as the change of the resonance angle with respect to the change of the refractive index of the sample, is largely changed by the refractive index of the prism as described above. In particular, the sensitivity and dynamic measurement range are greatly changed according to the refractive index of the prism as shown in FIG. 7 when the measurement angle and the incidence angle in the prism correspond to a one-to-one correspondence like a hemispherical prism. As discussed earlier, the dynamic range increases, but the sensitivity corresponding to the slope of the curve decreases.

FIG. 7 shows the effect of sensitivity and dynamic measurement range on the refractive index of hemispherical prisms made of BK7 (701), BaK4 (702), and SF10 (703) materials having different refractive indices at a wavelength of 633 nm, using the Fresnel equation. The results are calculated for the three-layer SPR structure for gold thin films with optical constants n = 0.2134, k = 3.5, and d = 50 nm. In FIG. 7, the x axis represents the refractive index of the liquid sample and the y axis represents the resonance angle.

FIG. 8 shows 45 ° (805), 60 ° (804), 75 ° (803), 90 ° (802), and 100 ° (801) different from the hemispherical prism 806 among the BK7 prisms at a wavelength of 633 nm. The relationship between the mechanical measurement angle for the five kinds of prisms having the base angle 503 and the angle of incidence inside the actual prism is shown. In the case of a triangular prism that is not hemispherical as shown in FIG. 8, the sensitivity of the SPR device is affected by the effect of the prism's structure in addition to the refractive index of the prism due to the distortion phenomenon between the actual incident angle and the measurement angle discussed above. Referring to the previous results, it can be seen that in the case of the triangular prism, the sensitivity of the device increases with the effect of the distortion of the measurement angle and the incident angle as well as the sensitivity change due to the prism refractive index effect. Of course, since the angle of incidence of the hemispherical prism or the triangular prism is the same for the same prism refractive index, the sensitivity is not the same when the angle of incidence is expressed by the angle of incidence in the prism. However, in terms of the actual measurement angle, the triangular prism is more sensitive than the hemispherical prism due to the distortion of the angle. However, in the case of the triangular prism, the sensitivity is improved but the dynamic range is severely limited compared with the hemispherical prism.

In summary, the two types of prisms having the same refractive index, that is, the hemispherical prism and the triangular prism, have good sensitivity but relatively limited dynamic range, and especially for the refractive index of the solution. In the case of, the dynamic measuring range is improved, but the sensitivity is slightly lower than the triangular prism. In other words, the dynamic range and sensitivity are not affected only by the prism refractive index, but it can be changed by the geometric structure of the prism.

In the present invention, the structure of the prism with improved sensitivity and dynamic measurement range is as follows. As described above, the reason that the dynamic measurement range and sensitivity of the SPR device may vary depending on the structure or shape of the prism is that distortion occurs between the actual measurement angle and the incident angle in the prism. This phenomenon occurs because the angle of measurement corresponds to the angle of incidence in the prism nonlinearly by the conversion equation of Equation [5]. The most direct variable affecting the dynamic range and sensitivity in the equation is the base angle of the prism. ) Is obvious when looking at the formula. Therefore, in order to examine the effect of the prism structure on the dynamic measurement range and sensitivity of the device, the result of calculating the conversion relationship between the measurement angle and the incident angle when the value of the base angle of the prism is changed is shown in FIG. 8.

FIG. 9 is a graph obtained by differentiating a result of angle conversion of prisms having different base angles shown in FIG. 8. In FIG. 9, as the base angle of the prism increases to 45 ° (901), 60 ° (902), 75 ° (903), 90 ° (904), and 100 ° (905), the range of the incident angle in the prism for a given measurement angle You can see that the slope changes as you move upwards. In particular, if you look at the graph of the change in the slope with respect to the change of the angle, the change in the slope is formed in the inflection point around the angle corresponding to the base angle of the prism appears symmetrically. The trend of the graph shown in FIG. 9 means that the larger the base angle of the prism, the sharper the change in the slope than the other prism having the smaller base angle in a certain measurement range.

FIG. 10 is a graph showing the graph of FIG. 8 simply to have a comparative advantage compared to FIG. 8 by swapping the x-axis and the y-axis, and the angle of measurement for the incident angle in the prism given a prism having a larger base angle of the prism than the hemispherical prism. You can see that the change is huge. In particular, considering that the change in the resonance angle with respect to the refractive index change of the liquid sample is determined by Equation [1], it can be seen that as the base angle of the prism increases, the sensitivity of the SPR device is improved.

In addition, it can be seen that the prism of the prism in the case where the prism is small is limited to the actual angle of incidence in the prism compared to the mechanical angle of incidence. Considering that the range of the angle of incidence is directly related to the dynamic measurement range, the prism of the prism is It can be seen that the area of the dynamic measurement range increases in the direction of high refractive index as it increases. This is achieved by changing the base angle of the prism, not simply by increasing the refractive index, by improving the performance of the triangular prism, which has a fundamental limitation of dynamic range, despite its superior sensitivity compared to the hemispherical prism. It is. Of course, the dynamic measurement range is not improved compared to the hemispherical prism, but it can be measured even though the measurement near the refractive index of the solution, which is actually the effective dynamic measurement range required for the application, is not a hemispherical prism.

11 is a graph showing the relationship between the change in the resonance angle with respect to the actual refractive index for the hemispherical prism 1101 and 90 ° prism 1102 of BaK4 having a refractive index of 1.5667 and the x-axis is the refractive index of the liquid sample and the y-axis is Resonance angle. FIG. 11 shows that the 90 [deg.] Prism can be used to have a superior sensitivity while having an effective dynamic measurement range similar to that of the hemispherical prism.

12A illustrates liquid samples having different refractive indices of 1.32 (1201), 1.34 (1202), 1.36 (1203), 1.38 (1204), 1.40 (1205), and 1.42 (1206) in the hemispherical prism 1101 of FIG. Figure 12b shows the change in the resonant angle with respect to Fig. 12b is 1.32 (1201), 1.34 (1202), 1.36 (1203), 1.38 (1204), 1.40 (1205) different for the 90 ° prism 1102 of Figure 11 , 1.42 (1206) shows the change in resonance angle for a liquid sample.

As shown in FIGS. 11, 12A, and 12B, when the refractive index of the solution is increased by 1.32 to 0.02, the 90 ° prism can be measured in a much wider area than the hemispherical prism. However, the results of FIGS. 11, 12A, and 12B are calculated using the Fresnel equation for the three-layer SPR structure for the gold thin film having optical constants of n = 0.2134, k = 3.5, and d = 50nm.

FIG. 13A is a schematic diagram of transmission and reflection generated when incident light from an inverted trapezoid prism 1304 passes through an initial entrance surface 1301 and a bottom surface 1302 and a final exit surface 1303 of the prism. Is a schematic diagram of the transmission and reflection that occurs when the incident light at the parallelogram prism 1308 passes through the initial incident surface 1305 and the bottom surface 1306 and the final exit surface 1307 of the prism.

Based on the tendency shown in FIGS. 11 and 12A and 12B, the design of the prism base at an angle of more than 90 ° without limit in order to maximize the increase of the dynamic measurement range and the increase of the sensitivity is shown in FIG. 13A. It is shown that it is impossible by the schematic diagram. The reason for this is that, as shown in FIG. 13A, which is an inverted trapezoidal prism, the light incident from the right side of the prism far below 90 ° is partially reflected and partially transmitted to each incident surface except the bottom surface of the metal film. This is because the transmittance rapidly decreases toward the lower angle as shown in FIG. 13A during the process. As a result, the total reflectivity across the three boundaries is expressed by:

Therefore, since the base angle of the prism is limited to improve the performance of the SPR measurement, in order to improve the limitation of the permeability, a parallelogram-shaped prism in which only one side has a large base angle and the other side has a small base angle as shown in FIG. It can be seen that the transmittance at each side in the case of using is improved than in the case of FIG. 14 using the inverted trapezoidal prism as shown in FIG. This is due to the fact that the SPR phenomenon is fundamentally related to the angle of incidence in the prism, and that angle is affected by the first plane of incidence, so that the angle from the plane after reflection from the bottom plane is not important.

14 and 15 show reflectivity in air for a prism not depositing a thin metal film. FIG. 14 shows an inverse trapezoid and FIG. 15 shows a parallelogram.

In FIG. 14, the upper curve 1401 shows the transmittance with respect to the first incident surface 1301 or the last transmissive surface 1303 of FIG. 13A, and the lower curve 1402 shows each surface (see FIG. 13A). This is the result of the light intensity passing through the entire inverted trapezoid prism considering both transmittance and reflectivity of 1301, 1302, and 1303.

In FIG. 15, the first curve 1501 is the transmittance past the last transmissive surface 1307 of FIG. 13B, and the second curve 1502 is the first incident surface 1305 of FIG. 13B. Transmittance is shown, and the third curve 1503 is the result of the light intensity passing through the entire equilateral quadrangle prism in consideration of both the transmissivity and the reflectivity of each side 1305, 1306, 1307 in FIG. 13B.

FIG. 16 shows an SPR curve of water having a refractive index of 1.33 for an inverted trapezoid prism and a parallelogram prism on which a metal thin film is deposited. The SPR curve 1601 for the parallelogram prism is more clearly shown in the inverted point of inflection near the 27 ° which represents the critical angle compared to the SPR curve 1602 for the prism.

FIG. 17A is an optical system configuration diagram of an angle resolution type SPR measuring system using a scanning method using the prism described with reference to FIGS. 5, 9, and 11. In FIG. 17A, incident light 1706 starting from a monochromatic light source 1702 such as a laser passes through a beam splitter 1704, and some incident light reaches a photodiode 1703 for measuring a reference signal, and the other incident light is a prism having a metal thin film deposited thereon. After reflecting from the bottom surface of 1705, the actual signal measuring diode 1701 is reached.

FIG. 17B is an optical system configuration diagram of a wedge-type angle resolution type SPR measuring system using the prism described with reference to FIGS. 5, 9, and 11. FIG. 17B shows a multichannel photodetector 1707 after a wedge shaped light 1709 is made from an optical system 1708 consisting of a light source and several lenses, reflected from the bottom surface of a deposited prism 1705. A series of optical system configurations are shown.

FIG. 18 is an optical system configuration diagram of a two-dimensional SPR image measuring system capable of detecting two or more measurement positions using the prism described with reference to FIGS. 5, 9, and 11. FIG. 18 shows parallel light 1806 in an optical system 1801 composed of a light source and several lenses to reflect a two-dimensional multi-channel photodetector 1803 after a metal thin film is reflected from the bottom surface of the deposited prism 1802. A series of optical system configurations reached is shown. In FIG. 18, the optical system 1801 composed of a light source and several lenses and a two-dimensional multichannel photodetector 1803 may change or fix an angle with respect to a bottom surface of the prism. At this time, if the angle between the optical system 1801 and the two-dimensional multi-channel photodetector 1803 composed of a light source and several lenses is fixed, the angle of incidence 1805 may be different depending on the type of sample to be measured. By changing the base angle, the angle of incidence 1805 of light with respect to the bottom of the prism can be changed as desired. In addition, if the angle of the optical system 1801 composed of a light source and several lenses and the two-dimensional multi-channel photodetector 1803 can be changed, the angle of the prism can be fixed.

As described above, the conventional triangular prism has a superior dynamic range compared to the hemispherical prism due to the optical structure, although the dynamic measurement range is limited to a solution having a high refractive index. In order to improve the fundamental limitation of the triangular prism, by increasing the base angle of the prism, the dynamic measuring range is increased without increasing the refractive index of the prism, and the inherent sensitivity is further increased to have a dynamic measuring range similar to that of the hemispherical prism. Sensitivity to the solution resulted in an almost double increase compared to the hemispherical prism. The prism can be used as a disposable SPR sensor chip by directly depositing a metal thin film under the prism without using a material for refractive index matching because of its advantages of being easier to process than a hemispherical prism. In particular, its useful value may be high in the field where measurement is required for high refractive index solutions such as organic solvents. Moreover, almost all conventional systems have a method of attaching and exchanging sensor chips under fixed prism, which limits the range of refractive index measurement.However, if a prism is replaced by a disposable one, it is easy to replace prism sensor chips with different refractive indices. By doing so, there is an advantage of controlling the refractive index measurement range of the sample.

Claims (8)

Light source; A prism through which light incident from the light source is transmitted and having a base angle satisfying the following equations (1), (2), (3) and (4); θ _ii = sin ^-1 (sinθ _i / n _p ) ..................... One), θ _R = α + θ _ii ......... 2), θ _i = θ _G -α ........................................... (3), θ _R = α + sin ^-1 [{sin (θ _G -α)} / n _p ] ... (4), Here, θ _i , θ _ii , θ _R , θ _G , n _p and α are each the angle of incidence of light incident on the prism, the angle of refraction of light passing through the prism, between the normal of the underside of the prism and the light passing through the prism, respectively. Means the angle between the normal of the underside of the prism and the light beam incident on the prism, the refractive index of the prism relative to the wavelength of the light, and the base angle of the prism, A metal thin film positioned below the prism and having light incident therethrough; And And an optical detector for detecting light reflected from the metal thin film. The method of claim 1, The prism is an optical analysis device comprising a triangular prism made of BK7, BaK4, SF10 material. The method of claim 1, An optical analysis device, characterized in that the base angle of the prism comprises less than 90 °. The method of claim 1, The prism is a parallelogram prism, the optical analysis device, characterized in that one base angle is smaller than the other base angle. The method of claim 1, And an optical diode for reference signal measurement to which light irradiated from the light source is incident. Irradiates light from the light source, The light is incident on a prism having a base angle satisfying the following equations (1), (2), (3) and (4), θ _ii = sin ^-1 (sinθ _i / n _p ) ..................... One), θ _R = α + θ _ii ......... 2), θ _i = θ _G -α ........................................... (3), θ _R = α + sin ^-1 [{sin (θ _G -α)} / n _p ] ... (4), Here, θ _i , θ _ii , θ _R , θ _G , n _p and α are each the angle of incidence of light incident on the prism, the angle of refraction of light passing through the prism, between the normal of the underside of the prism and the light passing through the prism, respectively. Means the angle between the normal of the underside of the prism and the light beam incident on the prism, the refractive index of the prism relative to the wavelength of the light, and the base angle of the prism, Light passing through the prism is incident on a metal thin film located below the prism, and Detecting the light reflected from the metal thin film. The method of claim 6, A part of the light irradiated from the light source is incident to the photodiode for reference signal measurement to measure the reference signal, and the remaining part of the light comprises the incident to the metal thin film. The method of claim 6, The light source is an optical analysis method comprising a monochromatic light source.

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