阅读说明：本技术 一种波导耦合长程表面等离子共振传感器及其测量方法 (Waveguide coupling long-range surface plasma resonance sensor and measuring method thereof ) 是由 汪之又 刘莉 吴了 周远 代竞 于 2019-12-16 设计创作，主要内容包括：本发明公开了传感器及传感技术领域的一种波导耦合长程表面等离子共振传感器及其测量方法,传感器结构包括基底、上包被层、折射率可调介质层、折射率匹配介质层、金属下包被层、表面修饰层和样品池,波导介质层、折射率匹配介质层和上包被层、金属下包被层形成波导结构,用于产生波导模式激发LRSPR现象,折射率匹配介质层、表面修饰层和样品池中的检测介质层和金属下包被层组成LRSPR结构,用于实现WCLRSPR,通过在波导介质层上施加交流电压采集WCLRSPR反射光强度的微分信号,同时采用直流电压扫描读取微分信号的零点,最后以零点对应的直流电压幅度作为折射率变化的检测结果。(The invention discloses a waveguide coupling long-range surface plasma resonance sensor and a measuring method thereof in the technical field of sensors and sensing, wherein the sensor structure comprises a substrate, an upper coating layer, a refractive index adjustable dielectric layer, a refractive index matching dielectric layer, a metal lower coating layer, a surface modification layer and a sample cell, wherein the waveguide dielectric layer, the refractive index matching dielectric layer, the upper coating layer and the metal lower coating layer form a waveguide structure, used for generating the waveguide mode excitation LRSPR phenomenon, the refractive index matching dielectric layer, the surface modification layer, the detection dielectric layer in the sample cell and the metal lower coating layer form an LRSPR structure, for realizing WCLRSPR, differential signals of the intensity of the WCLRSPR reflected light are collected by applying alternating voltage on the waveguide medium layer, and simultaneously, scanning and reading a zero point of the differential signal by adopting direct-current voltage, and finally, taking the amplitude of the direct-current voltage corresponding to the zero point as a detection result of the refractive index change.)

1. A waveguide coupling long-range surface plasmon resonance sensor is characterized in that: the method comprises the following steps:

a prism (1);

a glass substrate (2), the glass substrate (2) being mounted at the bottom of the prism (1);

an upper metal coating layer (3), the upper metal coating layer (3) being mounted on the bottom of the glass substrate (2);

the refractive index adjustable dielectric layer (4), the refractive index adjustable dielectric layer (4) is installed at the bottom of the upper metal coating layer (3);

the refractive index matching medium layer (5), the refractive index matching medium layer (5) is arranged at the bottom of the refractive index adjustable medium layer (4);

a lower metal coating layer (6), wherein the lower metal coating layer (6) is arranged at the bottom of the refractive index matching medium layer (5);

the surface modification layer (7), the surface modification layer (7) is arranged at the bottom of the lower metal coating layer (6);

the sample cell (8), the sample cell (8) is installed at the bottom of the surface modification layer (7).

2. A waveguide-coupled long-range surface plasmon resonance sensor according to claim 1, wherein: the upper metal coating layer (3) is silver and has a thickness of 30 nm.

3. A waveguide-coupled long-range surface plasmon resonance sensor according to claim 1, wherein: the lower metal coating layer (6) is silver and has a thickness of 30 nm.

4. A waveguide-coupled long-range surface plasmon resonance sensor according to claim 1, wherein: the refractive index adjustable dielectric layer (4) is made of a high polymer material with an electro-optic effect, the refractive index is 1.6, and the thickness is 1000 nm.

5. A waveguide-coupled long-range surface plasmon resonance sensor according to claim 1, wherein: the refractive index matching medium layer (5) is made of Teflon, the refractive index is 1.35, and the thickness is 2000 nm.

6. A waveguide-coupled long-range surface plasmon resonance sensor according to claim 1, wherein: a certain gap is reserved between the lower surface of the surface modification layer (7) and the sample cell (8).

7. The waveguide-coupled long-range surface plasmon resonance sensor and the measuring method thereof according to claim 1, characterized in that: the surface modification layer (7) is a monomolecular self-assembly layer of 11-mercapto undecanoic acid, the thickness is 10nm, and the refraction is 1.35.

8. A method of measuring a waveguide-coupled long-range surface plasmon resonance sensor according to claim 1, characterized by: the method specifically comprises the following steps:

s1: materials: the device comprises a laser (9), a polarizing plate (10), a lens (11), a unit photoelectric detector (12), a direct-current voltage output device (13), an alternating-current voltage output device (14) and a data processing system (15);

s2: calibration: introducing a standard substance with known refractive index into a sample cell (8), connecting a voltage output end of a direct-current voltage output device (13) and an alternating-current voltage output device (14) which are connected in series with an upper metal coating layer (3) and a lower metal coating layer (6), collimating output light beams of a laser (9) sequentially through a polarizing plate (10) and a lens (11), then entering an interface of a prism (1) and the upper metal coating layer (3), reflecting the collimated output light beams into a unit photoelectric detector (12) on the interface, inputting signals of the unit photoelectric detector (12) into a data processing system (15), and recording zero values of the signals;

s3: measurement: a detection object medium is introduced into the sample cell (8), the positions of other components are kept unchanged, the refractive index of the detected object is changed relative to a standard object, the resonance angle is shifted, the unit photoelectric detector (12) receives a reflected light beam at the interface of the prism (1) and the upper metal coating layer (3), the data processing system (15) searches a signal zero point according to the output of the unit photoelectric detector (12), the external voltage of the refractive index adjustable dielectric layer (4) is adjusted by step length 10mV, the voltage amplitude and the frequency of the alternating voltage output device (14) are kept unchanged, the unit photoelectric detector (12) receives the reflected light beam at the interface of the prism (1) and the upper metal coating layer (3) when the direct voltage value is changed every time, and the data processing system (15) finds a zero point searching signal according to the output of the unit photoelectric detector (12), and recording the direct current voltage at the moment as a measurement result of the refractive index of the detected object, and calculating and simulating the corresponding relation between the external voltage applied to the refractive index adjustable dielectric layer (4) and the refractive indexes of different detected objects.

Technical Field

The invention relates to the technical field of sensors and sensing, in particular to a waveguide coupling long-range surface plasmon resonance sensor and a measuring method thereof.

Background

The p-polarized light beam with certain wavelength and incident angle couples energy into a Surface plasma wave which exists on an interface and is exponentially attenuated along the direction vertical to the interface in a mode of exciting evanescent waves on a metal and medium interface through a prism coupler, wherein the phenomenon that the coupling ratio is the largest is called Surface plasma Resonance (SPR for short), and the generated corresponding incident angle is called a Resonance angle. By angular scanning, SPR absorption peaks can appear on the reflection spectrum. When the refractive index of the medium in contact with the metal surface is different, the resonance angle is different. By measuring the change in reflected light intensity near the resonance angle, certain characteristic parameters of the medium near the metal surface (such as refractive index) and their amount of change can be detected. Wherein, the larger the Depth-Width Ratio (DWR) of the absorption peak is, the higher the signal-to-noise Ratio and resolution of the detection result are.

Based on the SPR technique described above, various studies have been made on different media, metal structures, detection sensitivity thereof, and the like, in order to further improve DWR of an absorption peak of an SPR sensor, in which Waveguide Coupling Surface Plasmon Resonance (WCSPR) is mainly generated in a structure composed of a metal layer, a Waveguide layer, and a metal layer. WCSPR uses waveguide mode to excite SPR to monitor the change of environment and obtain the parameters of analyte. In the resonance angle measurement method based on the WCSPR structure, different methods for voltage modulation auxiliary measurement are researched. The voltage modulation auxiliary measuring methods all adopt a medium with the refractive index capable of being regulated by voltage as a waveguide layer material. In the method for measuring the resonance angle assisted by alternating voltage modulation (Optics Express, 2009, vol17, p4468-4478), a differential signal of an absorption peak of a WCSPR to an incident angle is obtained through alternating voltage modulation, and the resonance angle is measured by searching a zero point of the differential signal. In the direct-current voltage modulation auxiliary resonance angle measurement method (international patent: WO2011/066667a1), the zero-crossing point of the differential signal of the double-unit photodetector is searched through amplitude scanning of the direct-current voltage to realize measurement of the resonance angle, and the method has the defects that the DWR of the WCSPR is not high enough, detection accuracy needs to be guaranteed through zero point adjustment before measurement, operation is complex, and the response speed of the method is reduced through differential operation.

The Long-range surface Plasmon Resonance (LRSPR) of the buffer medium-metal-detection medium multilayer structure can increase the proportion of incident light coupled into evanescent waves through surface Plasmon wave coupling of the upper surface and the lower surface of a metal film, so that the DWR of an absorption peak is improved, the material with the refractive index capable of being adjusted through voltage can be used as the LRSPR structure of the buffer medium, the Resonance angle can be measured in an angle scanning mode through direct-current voltage assistance, but the angle scanning speed is low, and the response speed of the method is reduced.

Disclosure of Invention

The invention aims to provide a waveguide coupling long-range surface plasmon resonance sensor and a measuring method thereof, which solve the defects of slow angle scanning speed and reduced response speed of the method in the prior art, when a detection medium changes, differential signals of WCLRSPR reflected light intensity are acquired by applying alternating voltage on a waveguide medium layer, meanwhile, zero points of the differential signals are scanned and read by adopting direct current voltage, and finally, the amplitude of the direct current voltage corresponding to the zero points is used as a detection result of refractive index change.

In order to achieve the purpose, the invention provides the following technical scheme: a waveguide-coupled long-range surface plasmon resonance sensor, comprising:

a prism;

a glass substrate mounted at the bottom of the prism;

an upper metal coating layer mounted on the bottom of the glass substrate;

a refractive index adjustable dielectric layer mounted at the bottom of the upper metal cladding layer;

the refractive index matching medium layer is arranged at the bottom of the refractive index adjustable medium layer;

a lower metal cladding layer mounted at the bottom of the index matching dielectric layer;

the surface modification layer is arranged at the bottom of the lower metal coating layer;

and the sample cell is arranged at the bottom of the surface modification layer.

Preferably, the upper metal coating layer is silver and has a thickness of 30 nm.

Preferably, the lower metal coating layer is silver and has a thickness of 30 nm.

Preferably, the refractive index adjustable medium layer is made of a high polymer material with an electro-optic effect, the refractive index is 1.6, and the thickness is 1000 nm.

Preferably, the refractive index matching medium layer is made of Teflon, the refractive index is 1.35, and the thickness is 2000 nm.

Preferably, a certain gap is left between the lower surface of the surface modification layer and the sample cell.

Preferably, the surface modification layer is a monomolecular self-assembly layer of 11-mercaptoundecanoic acid, the thickness of the monomolecular self-assembly layer is 10nm, and the refraction of the monomolecular self-assembly layer is 1.35.

A measuring method of a waveguide coupling long-range surface plasmon resonance sensor specifically comprises the following steps:

s1: materials: the device comprises a laser, a polaroid, a lens, a unit photoelectric detector, a direct current voltage output device, an alternating current voltage output device and a data processing system;

s2: calibration: introducing a standard substance with known refractive index into the sample cell, connecting a voltage output end of the direct-current voltage output device and a voltage output end of the alternating-current voltage output device which are connected in series with the upper metal coating layer and the lower metal coating layer, collimating a laser output light beam by a polaroid and a lens in sequence, then entering an interface of a prism and the upper metal coating layer, reflecting the light beam on the interface and entering a unit photoelectric detector, inputting a signal of the unit photoelectric detector into a data processing system, and recording a zero value of the signal;

s3: measurement: the sample cell is filled with a detection object medium, the positions of other components are kept unchanged, the resonance angle shifts because the refractive index of the detected object changes relative to the standard object, the unit photoelectric detector receives the reflected light beam of the prism and the upper metal coating interface, the data processing system searches a signal zero point according to the output of the unit photoelectric detector, the external voltage of the refractive index adjustable dielectric layer is adjusted by the step length mV, and the voltage amplitude and the frequency of the alternating voltage output device are kept unchanged, when the DC voltage value is changed each time, the unit photoelectric detector receives the reflected light beam of the prism and the upper metal coating interface, the data processing system searches for a zero point signal according to the output of the unit photoelectric detector, records the DC voltage at the moment as the measurement result of the refractive index of the detected object, and calculating the corresponding relation between the simulated applied voltage applied to the refractive index adjustable medium layer and the refractive indexes of different detected objects.

Compared with the prior art, the invention has the beneficial effects that: the invention provides a novel waveguide coupling long-range surface plasmon resonance (WCLRSPR) sensor structure, which comprises a substrate, an upper coating layer, a refractive index adjustable dielectric layer, a refractive index matching dielectric layer and a metal lower coating layer, wherein the refractive index adjustable dielectric layer and the refractive index matching dielectric layer are combined into a waveguide dielectric layer, the upper coating layer and the metal lower coating layer form a waveguide structure for generating a waveguide mode to excite the LRSPR phenomenon, the refractive indexes of the refractive index matching dielectric layer and a detection dielectric layer are close to each other, and the refractive indexes of the refractive index matching dielectric layer and the detection dielectric layer and the metal lower coating layer form an LRSPR structure for realizing the WCLRSPR. Differential signal collection of WCLRSPR reflected light intensity is realized by applying alternating voltage on the waveguide medium layer, meanwhile, direct voltage scanning is adopted to read the zero point of the differential signal, and finally, the direct voltage signal corresponding to the zero point is used as the detection result of the refractive index change.

Drawings

FIG. 1 is a schematic structural view of the present invention;

FIG. 2 is a schematic structural diagram of a structural measurement method according to the present invention;

FIG. 3 is a flow chart of a method for measuring a structure according to the present invention;

FIG. 4 is a graph showing the response of the intensity of reflected light as a function of the refractive index of the detection medium according to the present invention;

FIG. 5 is a graph showing the response of the resonance angle of the present invention to the refractive index of the detection medium layer;

FIG. 6 is a graph showing the response of the intensity of reflected light with the variation of the refractive index tunable dielectric layer according to the present invention;

FIG. 7 is a graph showing the response of the resonance angle of the present invention to the refractive index of a refractive index tunable dielectric layer;

FIG. 8 is a diagram showing the relationship between the applied voltage of the refractive index adjustable dielectric layer and the refractive indexes of different objects to be detected.

In the figure: 1 prism, 2 glass substrate, 3 upper metal coating layer, 4 refractive index adjustable dielectric layer, 5 refractive index matching dielectric layer, 6 lower metal coating layer, 7 surface modification layer, 8 sample cell, 9 laser, 10 polaroid, 11 lens, 12 unit photoelectric detector, 13 DC voltage output device, 14 AC voltage output device, 15 data processing system.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The invention provides a waveguide coupling long-range surface plasmon resonance sensor, which can measure and detect the change of the refractive index of a medium layer by adjusting the refractive index of a refractive index adjustable medium layer through mixing alternating current and direct current compared with the traditional SPR sensor, and please refer to FIG. 1, which comprises the following steps: the device comprises a prism 1, a glass substrate 2, an upper metal coating layer 3, a refractive index adjustable dielectric layer 4, a refractive index matching dielectric layer 5, a lower metal coating layer 6, a surface modification layer 7 and a sample cell 8;

referring again to fig. 1, prism 1;

referring to fig. 1 again, a glass substrate 2 is mounted at the bottom of the prism 1;

referring again to fig. 1, an upper metal coating 3 is mounted on the bottom of the glass substrate 2, the upper metal coating 3 is silver, has a thickness of 30nm and a refractive index of 0.04+6.9624 i;

referring to fig. 1 again, the refractive index adjustable dielectric layer 4 is installed at the bottom of the upper metal coating layer 3, the refractive index adjustable dielectric layer 4 is made of a high polymer material with an electro-optic effect, the refractive index is 1.6, and the thickness is 1000 nm;

referring to fig. 1 again, the refractive index matching medium layer 5 is installed at the bottom of the refractive index adjustable medium layer 4, the refractive index matching medium layer 5 is made of teflon, the refractive index is 1.35, and the thickness is 2000 nm;

referring to fig. 1 again, the lower metal coating layer 6 is installed at the bottom of the refractive index matching dielectric layer 5, and the lower metal coating layer 6 is silver, has a thickness of 30nm and a refractive index of 0.04+6.9624 i;

referring to fig. 1 again, the surface modification layer 7 is installed at the bottom of the lower metal coating layer 6;

referring to fig. 1 again, the sample cell 8 is installed at the bottom of the surface modification layer 7, a gap is left between the lower surface of the surface modification layer 7 and the sample cell 8, the sample cell 8 is used for holding a detection medium layer, and the material is usually polydimethylsiloxane.

The working principle is as follows: one of the core components of the sensor is a WCLRSPR sensing chip, refer to part a of fig. 1, the WCLRSPR sensing chip includes an upper metal coating layer 3, a refractive index adjustable medium layer 4, a refractive index matching medium layer 5, a lower metal coating layer 6, a surface modification layer 7 and a sample cell 8, the chip can be prepared on a glass substrate 2 or a prism 1, the sample cell 8 is arranged at the lower surface of the surface modification layer 7, a certain gap is left between the lower surface of the surface modification layer 7 and the sample cell 8, the sample cell 8 is used for containing a detection medium, the liquid level of the detection medium is in contact with the lower surface of the surface modification layer 7, and the sensing chip based on external field modulationTwo sensitivity parameters exist in the device, and the resonance angle theta of the zero point signal is adjusted corresponding to the alternating voltage₀Refractive index n to the refractive index-adjustable medium layer 4₆And the refractive index n of the detection medium₁₀Their expression is as in formula 1-1,

wherein C1 and C2 are constants, based on the detection principle of the intensity detection sensor of AC/DC mixed modulation, when the detected object is the reference detected object, the external fields of the refractive index adjustable medium layer 4 and the refractive index matching medium layer 5 are 0, and the resonance angle of WCLRSPR is theta₁When the substance to be detected is another substance n₁₀Change and resonance angle delta theta₀₁The refractive index adjustable dielectric layer is adjusted by adopting direct current voltage, and the resonance angle generates minus delta theta₀₁Is changed to return the resonance angle to theta₁To obtain a compound of the formula 1-2,

C₂Δn₆+C₁Δn₁₀＝0(1-2)，

formula 1-2 illustrates that n can be measured₆Can be implemented with n₁₀In particular, the refractive index n of the detection medium is measured₁₀Firstly, a standard substance with known refractive index can be selected to obtain the resonance angle when the WCLRSPR sensing chip uses the standard substance, then the standard substance of the sensing chip is replaced by the detection medium, at this time, the formula 1-2 can be used to know that only the refractive index n of the external field refractive index adjustable medium layer 4 is changed₆So that the change of the refractive index caused by the replacement of the standard substance by the detection medium layer in the WCLRSPR sensing chip can be compensated by reaching a proper value, thereby keeping the resonance angle of the whole WCLRSPR sensor unchanged, and on the other hand, the formula 1-2 can also show that no matter n is adopted₁₀The change of (2) is small, and the measurement result measured by using the compensation principle is not influenced by the shape of the resonance absorption peak of the WCLRSPR sensor, so that the intensity detection LRSPR sensor based on external field modulation can improve the dynamic range of the measurement result compared with the existing intensity detection LRSPR sensor.

The invention also provides a measuring method of the waveguide coupling long-range surface plasmon resonance sensor, which specifically comprises the following steps:

s1: materials: a laser 9, a polarizing plate 10, a lens 11, a unit photodetector 12, a direct-current voltage output device 13, an alternating-current voltage output device 14, and a data processing system 15;

s2: calibration: introducing a standard substance with a known refractive index into the sample cell 8, connecting a voltage output end of a direct current voltage output device 13 and an alternating current voltage output device 14 which are connected in series with the upper metal coating layer 3 and the lower metal coating layer 6, wherein the output voltage of the direct current voltage output device 13 is 0V, the output amplitude of the alternating current voltage output device 14 is 50V, the frequency is 10kHz, the refractive index of the voltage-modulated refractive index adjustable dielectric layer 4 is adjusted, a light beam output by the laser 9 is collimated by a polaroid 10 and a lens 11 in sequence, then enters an interface of the prism 1 and the upper metal coating layer 3, and is reflected at the interface to enter the unit photoelectric detector 12, a signal of the unit photoelectric detector 12 is input into a data processing system 15, and a zero value of the signal;

s3: measurement: the sample cell 8 is filled with a detection object medium, the positions of other components are kept unchanged, the refractive index of the detected object is changed relative to a standard object, the resonance angle is shifted, the unit photoelectric detector 12 receives a reflected light beam at the interface of the prism 1 and the upper metal coating layer 3, the data processing system 15 searches a signal zero point according to the output of the unit photoelectric detector 12, as the refractive index n of the external field modulation refractive index adjustable medium layer 4, the thickness d of the medium layer, the electro-optical coefficient gamma 33 of the medium layer and C1 and C2 in 1-1 are LRSPR structural parameters according to a formula 2-2 and a formula 2-2, the direct current voltage value S required by the output of the minimum signal can be preliminarily calculated according to the formulas 1-2 and 2-2, and then the external voltage of the refractive index adjustable medium layer 4 is adjusted by the step length of 10mV within the range from S-5V to S +, and meanwhile, the voltage amplitude and the frequency of the alternating voltage output device 14 are kept unchanged, when the direct voltage value is changed each time, the unit photoelectric detector 12 receives a reflected light beam at the interface of the prism 1 and the upper metal coating layer 3, the data processing system 15 searches for a zero point signal according to the output of the unit photoelectric detector 12 until the zero point signal is found, the direct voltage at the moment is recorded as a measurement result of the refractive index of the detected object, and the corresponding relation between the simulated external voltage applied to the refractive index adjustable medium layer 4 and the refractive indexes of different detected objects is calculated.