LSPR (Local Surface Plasmon Resonance) detection device and detection method based on wavelength phase co-modulation

Abstract

The invention discloses an LSPR (Localized Surface Plasmon Resonance) detection device and detection method based on wavelength phase co-modulation, and the device utilizes a liquid crystal variable delayer to carry out phase delay on polarized light so as to realize sinusoidal modulation of emergent light intensity. The difficulty of demodulating the LSPR phase signal is reduced, the acquisition speed of the LSPR phase signal is improved, and the detection sensitivity is greatly improved. A light intensity image is recorded through the area array detector, and each pixel of the area array detector corresponds to one sensing channel, so that the detection flux is effectively improved. The optical filter is used for carrying out tunable filtering on incident light, controllable wide-field excitation of the LSPR sensing chip with different wavelengths is realized, crosstalk among different spectrums caused by strong scattering of the LSPR nano-chip due to simultaneous excitation of a broadband light source is avoided, and the accuracy of the LSPR sensing technology is further improved. Moreover, a plurality of suitable wavelengths are spliced, and phase detection is performed on a specified site, so that the dynamic detection range of the LSPR phase signal is effectively expanded.

Description

Technical Field

[0001] The present invention relates to the field of optical sensing imaging, and more specifically, to an LSPR detection device and a detection method based on wavelength phase co-modulation. Background Art

[0002] Localized Surface Plasmon Resonance (LSPR) is a phenomenon of collective oscillation of electrons on the metal surface caused by light irradiating the surface of precious metal nanoparticles or metal microstructures. When the light wave frequency band coincides with the electron resonance frequency band, photons are effectively absorbed and scattered, resulting in a resonant absorption peak in the extinction spectrum.

[0003] The LSPR phenomenon depends on the shape, size and physical properties of the constituent materials of the nanostructure, as well as the dielectric properties of the environment. LSPR sensing technology is widely used in biomedical testing, environmental monitoring, materials science and other fields due to its real-time, label-free and high sensitivity. For example: detecting the interaction of biological molecules such as DNA and proteins. Compared with surface plasmon resonance (SPR) sensing technology, LSPR sensing technology has higher sensitivity and simpler optical path devices. Moreover, LSPR is easily combined with a variety of effects, such as photothermal effect, photoacoustic effect, magnetic effect, etc., to enhance its sensing performance or expand its application range.

[0004] LSPR sensing technology usually uses a broadband light source to induce the LSPR phenomenon, and then uses a spectrometer for spectral detection. The acquired spectral data is analyzed and the molecular interaction information is obtained by detecting the change in the position of the LSPR resonance spectrum. It mainly monitors the slight shift of the LSPR resonance spectrum, which directly reflects any change in the refractive index of the sample. However, the light intensity near the resonance peak is very weak, resulting in inaccurate positioning of the slight shift of the resonance spectrum. In addition, the simultaneous excitation of the broadband light source causes strong scattering of the LSPR nanochip, resulting in crosstalk between different spectra. This will lead to a decrease in the signal-to-noise ratio, severely limiting the sensitivity of the LSPR sensing technology and affecting its precise detection performance. Summary of the invention

[0005] In view of this, the present invention provides an LSPR detection device and a detection method based on wavelength phase co-modulation, which are used to solve the problems of poor accuracy and sensitivity of the existing LSPR sensing technology.

[0006] To achieve the above objectives, the proposed solution is as follows: A LSPR detection device based on wavelength phase co-modulation, the device comprising: a collimating lens, an optical filter, a polarizer, a liquid crystal adjustable delay device, a beam expansion lens group, a sensing unit, an analyzer, an imaging lens group, a planar array detector, and a broadband light source; The broadband light source emits broadband light to obtain initial incident light; The collimating lens collimates the initial incident light so that the initial incident light enters the optical filter vertically; The optical filter modulates the wavelength of the initial incident light to obtain narrow-band diffracted light; The polarizer polarizes the narrowband diffracted light to obtain polarized light; The liquid crystal variable retarder delays the phase of the polarized light, expands and collimates it through a beam expansion lens group, and then irradiates it onto the sensing unit, producing an LSPR effect. The polarizer filters the scattered light emitted by the sensor unit and records it on the area array detector through the imaging lens group to obtain a light intensity image.

[0007] Preferably, the device further comprises: an optical fiber coupling the initial incident light emitted by the broadband light source.

[0008] Preferably, the sensing unit comprises: Sensor chip interface, sensor chip substrate and sample flow cell.

[0009] Preferably, the device further comprises: a computing unit which reads the light intensity image of the area array detector and converts it into a two-dimensional intensity image.

[0010] Preferably, the polarization direction of the polarizer is 45° to the optical axis direction of the liquid crystal variable retarder, so that the intensities of the incident P-polarized light and S-polarized light are equal.

[0011] Preferably, the polarization direction of the analyzer is perpendicular to the polarization direction of the polarizer.

[0012] A LSPR detection method based on wavelength phase co-modulation is applied to the above-mentioned LSPR detection device based on wavelength phase co-modulation, and the method comprises: The optical filter and the liquid crystal adjustable retarder modulate the wavelength and phase of the initial incident light respectively, and perform wavelength matching on each designated sensing site of the sensing unit to obtain a candidate wavelength; The optical filter is scanned sequentially based on the candidate wavelengths, and the LSPR phase at each candidate wavelength is recorded through a liquid crystal tunable retarder; The LSPR phase of each sensing site at the same wavelength is integrated according to the wavelength to obtain the LSPR phase signal change curve at each wavelength.

[0013] Preferably, the optical filter and the liquid crystal adjustable retarder modulate the wavelength and phase of the initial incident light respectively, and the process of performing wavelength matching on each designated sensing site of the sensing unit includes: The optical filter steps the wavelength of the initial incident light within a preset range; At each wavelength, the liquid crystal tunable retarder sinusoidally modulates the initial incident light; The area array detector records the intensity image obtained by scanning at each wavelength; According to each group of intensity values ​​of the sensing sites, the light intensity curve of each sensing site is obtained; The LSPR phase of the corresponding sensing site is calculated based on each light intensity curve, and the phase-wavelength relationship curve of each sensing site is obtained; The optimal resonance wavelength corresponding to each sensing site is determined based on the phase-wavelength relationship curve, and the optimal resonance wavelength of each sensing site is used as a candidate wavelength.

[0014] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects: (1) The present invention uses a liquid crystal variable retarder to phase-delay polarized light, thereby achieving sinusoidal modulation of the intensity of the outgoing light. This allows the specific binding information of the target molecule to be obtained by recording and demodulating the changes in the LSPR phase signal on the surface of the sensor chip. This reduces the difficulty of demodulating the LSPR phase signal and increases the speed of acquiring the LSPR phase signal. Compared with the traditional method of monitoring the offset of the LSPR resonance spectrum, the present invention greatly improves the detection sensitivity.

[0015] (2) The present invention records a series of light intensity images through an array detector. Each pixel of the array detector corresponds to a sensing channel, which effectively improves the detection flux.

[0016] (3) Using optical filters to tunably filter the incident light, we can achieve wide-field controllable excitation of the LSPR sensor chip with different wavelengths, avoid strong scattering of the LSPR nanochip caused by simultaneous excitation of broadband light sources, and cause crosstalk between different spectra, further improving the accuracy of LSPR sensing technology. In addition, multiple suitable wavelengths are spliced ​​to perform phase detection on designated sites, effectively expanding the detection dynamic range of the LSPR phase signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0018] Figure 1 A schematic diagram of the structure of an LSPR detection device based on wavelength phase co-modulation provided in an embodiment of the present invention; Figure 2 A flow chart of a LSPR detection method based on wavelength phase co-modulation provided by an embodiment of the present invention; Figure 3 A schematic diagram of wavelength sequential scanning results provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] First, combine Figure 1 An LSPR detection device based on wavelength phase co-modulation provided by an embodiment of the present invention is as follows: Figure 1 As shown, the device comprises: Collimating lens 1, optical filter 2, polarizer 3, liquid crystal adjustable delay device 4, beam expansion lens group, sensor unit, analyzer 10, imaging lens group, planar array detector 13, broadband light source 14.

[0021] The broadband light source 14 may be a white light source that emits broadband light to obtain initial incident light.

[0022] The collimating lens 1 collimates the initial incident light so that the initial incident light enters the optical filter vertically. After the initial incident light is collimated by the collimating lens 1, it enters the optical filter 2 vertically. The optical filter 2 modulates the wavelength of the initial incident light to obtain narrow-band diffracted light. The optical filter 2 modulates the incident light into narrow-band diffracted light of each target wavelength (candidate wavelength), and the narrow-band diffracted light of each target wavelength is polarized by the polarizer 3 to obtain polarized light. The polarization direction of the polarizer 3 is 45° to the optical axis direction of the liquid crystal adjustable retarder 4, so that the intensity of the incident P polarized light and S polarized light is equal, ensuring a good sinusoidal interference spectrum signal.

[0023] The polarized light emitted by the liquid crystal variable delay device 4 is then expanded and collimated by the beam expansion lens group so that the light beam can fully illuminate the entire sensing area. Figure 1 As shown, the beam expanding lens group includes a first beam expanding lens 5 and a second beam expanding lens 6. After the liquid crystal adjustable retarder 4 phase-retards the polarized light, the first beam expanding lens 5 and the second beam expanding lens 6 are used for beam expansion and collimation. The parallel light emitted from the second beam expanding lens 7 is irradiated to the sensing unit to generate the LSPR effect. Figure 1As shown, the sensor unit includes a sensor chip substrate 7, a sensor chip interface 8 and a sample flow cell 9. The sample to be detected is passed into the sample flow cell 9 for detection. The sensor chip substrate 7 can be made of any optically transparent material such as BK7 glass, SF11 glass, etc. The sensor chip interface 8 can be distributed with precious metal particles of different nanostructures and different nano sizes, such as gold nano islands, silver nano islands, etc. according to the measurement requirements.

[0024] The analyzer 10 filters the scattered light emitted by the sensor unit and records the light intensity image on the array detector 13 through the imaging lens group. The imaging lens group includes a first imaging lens 11 and a second imaging lens 12. The forward scattered light of each sensing site on the sensor chip interface 8 passes through the analyzer 10 and is directly imaged on the array detector 13 by the first imaging lens 11 and the second imaging lens 12. The polarization direction of the analyzer 10 is perpendicular to the polarization direction of the polarizer 3.

[0025] The embodiment of the present invention uses a liquid crystal variable retarder to phase-delay polarized light, thereby achieving sinusoidal modulation of the intensity of the outgoing light. This allows the specific binding information of the target molecule to be obtained by recording and demodulating the changes in the LSPR phase signal on the surface of the sensor chip. This reduces the difficulty of demodulating the LSPR phase signal and increases the speed of acquiring the LSPR phase signal. Compared with the traditional method of monitoring the offset of the LSPR resonance spectrum, the present invention greatly improves the detection sensitivity.

[0026] The embodiment of the present invention records a series of light intensity images through an area array detector, and each pixel of the area array detector corresponds to a sensing channel, thereby effectively improving the detection flux.

[0027] The embodiment of the present invention uses an optical filter to perform tunable filtering on the incident light, realizes controllable wide-field excitation of LSPR sensor chips with different wavelengths, avoids strong scattering of LSPR nanochips caused by simultaneous excitation of broadband light sources, and causes crosstalk between different spectra, further improving the accuracy of LSPR sensing technology. The embodiment of the present invention realizes controllable wide-field excitation of LSPR sensor chips with different wavelengths, splices multiple suitable wavelengths, performs phase detection on designated sites, and effectively expands the detection dynamic range of LSPR phase signals.

[0028] Furthermore, the LSPR detection device based on wavelength phase co-modulation provided in the embodiment of the present invention may further include: an optical fiber 15 and a calculation unit 16 on the basis of the above-mentioned embodiment.

[0029] The optical fiber 15 couples the initial incident light emitted by the broadband light source 14. The broadband light emitted by the broadband light source 14 is coupled out through the optical fiber 15 and then collimated by the collimating lens 1.

[0030] The calculation unit 16 reads the light intensity image of the area array detector 13 and converts it into a two-dimensional intensity image.

[0031] This embodiment also provides a LSPR detection method, which is applied to the above-mentioned LSPR detection device. Figure 2 The LSPR detection method based on wavelength phase co-modulation provided by an embodiment of the present invention is introduced, and the method includes: The sample to be detected is passed into the sample circulation pool 9, the original image of the sensor chip interface 8 is collected, and the designated sensing site on the sensor chip interface 8 is confirmed.

[0032] First, for each designated sensing site (S i ) to perform wavelength matching operation to obtain the optimal resonance wavelength λ of each sensing site i The optical filter and the liquid crystal tunable retarder modulate the wavelength and phase of the initial incident light respectively, and perform wavelength matching on each designated sensing site of the sensing unit to obtain a candidate wavelength.

[0033] Specifically, the optical filter 2 steps the wavelength of the initial incident light within a preset range. The optical filter 2 step-scans the wavelength within a preset wider spectral range, and at each wavelength, the liquid crystal adjustable delay device 4 is used to perform sinusoidal modulation of the light intensity of the initial incident light. The array detector 13 records the intensity image obtained by scanning at each wavelength. Subsequently, based on each group of intensity values ​​of the sensing site, the light intensity curve of each sensing site is obtained, and a group of intensity values ​​of each sensing site is formed into a light intensity curve. Based on each light intensity curve, the LSPR phase of the corresponding sensing site is calculated, and the phase-wavelength relationship curve of each sensing site is obtained. Based on the phase-wavelength relationship curve, the optimal resonance wavelength corresponding to each sensing site is determined, and the optimal resonance wavelength of each sensing site is used as a candidate wavelength.

[0034] The LSPR phase corresponding to each light intensity curve is calculated using a correlation algorithm, and then a phase-wavelength relationship curve of each sensing site within a spectral scanning cycle is established. The phase-wavelength relationship curve is differentiated, and the abscissa corresponding to the extreme point of the derivative, i.e., the wavelength, is the optimal resonant wavelength λ of each sensing site. i The optimal sensing wavelength corresponding to each sensing site is determined by wavelength matching operation as candidate wavelengths λ0, λ1, λ2, ..., λ n .

[0035] Specifically, the optical filter 2 is scanned sequentially based on the candidate wavelengths, and the LSPR phase at each candidate wavelength is recorded through the liquid crystal tunable retarder 4 .

[0036] At the initial time t0, the wavelength λ0 is fixed by the optical filter 2, and the liquid crystal variable retarder 4 is modulated to obtain and record the phase information at this wavelength; then at time t1, the optical filter 2 is switched to the wavelength λ1, and the LSPR phase information is obtained and recorded through the liquid crystal variable retarder 4. n The last candidate wavelength λ is recorded at time n After the LSPR phase information is obtained, at t n+1 At this moment, switch back to the first candidate wavelength λ0 and repeat the above process until the end of the experiment. Figure 3 Schematic diagram of sequential wavelength scanning.

[0037] The LSPR phase of each sensing site at the same wavelength is integrated according to the wavelength to obtain the LSPR phase signal change curve at each wavelength.

[0038] Specifically, the LSPR phase signal is integrated. All LSPR phase signals at the same wavelength are re-integrated according to the wavelength and output as LSPR phase signal change curves at each wavelength to obtain the refractive index change of each sensing site of the sensor chip interface 8 at multiple wavelengths.

[0039] Finally, it should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0040] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0041] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A LSPR detection device based on wavelength phase co-modulation, characterized in that: The device includes: Collimating lens, optical filter, polarizer, liquid crystal adjustable retarder, beam expander lens group, sensor unit, analyzer, imaging lens group, area array detector, broadband light source; The broadband light source emits broadband light to obtain initial incident light; The collimating lens collimates the initial incident light so that the initial incident light enters the optical filter vertically; The optical filter modulates the wavelength of the initial incident light to obtain narrow-band diffracted light; The polarizer polarizes the narrowband diffracted light to obtain polarized light; The liquid crystal variable retarder delays the phase of the polarized light, expands and collimates it through a beam expansion lens group, and then irradiates it onto the sensing unit, producing an LSPR effect. The polarizer filters the scattered light emitted by the sensor unit and records it on the area array detector through the imaging lens group to obtain a light intensity image.

2. The LSPR detection device based on wavelength phase co-modulation according to claim 1, characterized in that: The device also includes: the optical fiber couples the initial incident light emitted by the wide-spectrum light source.

3. The LSPR detection device based on wavelength phase co-modulation according to claim 1, characterized in that: The sensing unit comprises: Sensor chip interface, sensor chip substrate and sample flow cell.

4. The LSPR detection device based on wavelength phase co-modulation according to claim 3, characterized in that: The device also includes: a calculation unit that reads the light intensity image of the area array detector and converts it into a two-dimensional intensity image.

5. The LSPR detection device based on wavelength phase co-modulation according to claim 1, characterized in that: The polarization direction of the polarizer is 45° to the optical axis direction of the liquid crystal variable retarder, so that the intensities of the incident P polarized light and S polarized light are equal.

6. The LSPR detection device based on wavelength phase co-modulation according to claim 1, characterized in that: The polarization direction of the analyzer is perpendicular to the polarization direction of the polarizer.

7. A LSPR detection method based on wavelength phase co-modulation, characterized in that: The LSPR detection device based on wavelength phase co-modulation according to any one of claims 1 to 6, the method comprising: The optical filter and the liquid crystal adjustable retarder modulate the wavelength and phase of the initial incident light respectively, and perform wavelength matching on each designated sensing site of the sensing unit to obtain a candidate wavelength; The optical filter is scanned sequentially based on the candidate wavelengths, and the LSPR phase at each candidate wavelength is recorded through a liquid crystal tunable retarder; The LSPR phase of each sensing site at the same wavelength is integrated according to the wavelength to obtain the LSPR phase signal change curve at each wavelength.

8. The LSPR detection method based on wavelength phase co-modulation according to claim 7, characterized in that: The optical filter and the liquid crystal adjustable retarder respectively modulate the wavelength and phase of the initial incident light, and perform wavelength matching on each designated sensing site of the sensing unit, including: The optical filter steps the wavelength of the initial incident light within a preset range; At each wavelength, the liquid crystal tunable retarder sinusoidally modulates the initial incident light; The area array detector records the intensity image obtained by scanning at each wavelength; According to each group of intensity values ​​of the sensing sites, the light intensity curve of each sensing site is obtained; The LSPR phase of the corresponding sensing site is calculated based on each light intensity curve, and the phase-wavelength relationship curve of each sensing site is obtained; The optimal resonance wavelength corresponding to each sensing site is determined based on the phase-wavelength relationship curve, and the optimal resonance wavelength of each sensing site is used as a candidate wavelength.

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