A bifunctional hybrid plasmonic sensor and application thereof

Abstract

The application discloses a kind of bifunctional hybrid type plasmonic sensor, including substrate, metal film, dielectric grating and metal nanoshell array;The metal film is evaporated on the substrate;The dielectric grating is located between the metal film and the metal nanoshell array;The metal nanoshell array is with the dielectric grating as template, and is inclined and evaporated on the surface of the dielectric grating;The metal film and the metal nanoshell array are coupled to form plasmon mode under the action of incident light wave.The bifunctional hybrid type plasmonic sensor is based on superstructure grating, RA and LSPR are fully coupled, and the intensity of coupling signal is fully played by controlling the angle of incident light.Thereby it can be used to detect the small change of external environment refractive index, and also can detect the small change of local refractive index generated by the combination of virus antibody and antigen adsorbed on the surface of structure.

Description

Technical Field

[0001] This invention relates to the field of micro-nano optical sensor technology, and in particular to a dual-function hybrid plasmon sensor and its applications. Background Technology

[0002] Localized surface plasmon resonance (LSPR) refers to the collective oscillation of free electrons within a metallic nanostructure in response to incident light waves. Benefiting from the strong local electromagnetic field enhancement capability of this physical process and its high sensitivity to changes in the refractive index of the local environment, LSPR has been widely applied in various biological and chemical sensing applications. In recent years, facing the threat of the novel coronavirus to public health, researchers have used different plasmonic nanostructures to conduct rapid and non-destructive detection of the virus, providing a fast and effective detection method for currently prevalent viruses. Studies have shown that plasmonic-based sensors have advantages such as simple testing methods, non-destructive / label-free operation, small size, and ease of integration, thus gaining popularity among researchers.

[0003] However, LSPRs typically have a wide resonant bandwidth, which to some extent reduces the resolution of this type of sensor, thus hindering its widespread application in sensors.

[0004] To address the aforementioned issues with LSPR sensors, researchers coupled broadband LSPRs with other modes possessing high quality factors (such as waveguide modes, microcavity resonant modes, higher-order plasmon modes, or Rayleigh anomalous diffraction modes). Utilizing the newly generated Fano resonant hybrid mode as the detection signal for the LSPR sensor can, to some extent, improve the sensor's performance.

[0005] Among the aforementioned Fano resonance hybrid mode LSPR sensors, those based on the coupling between plasmons and Rayleigh anomalous diffraction (RA) modes have attracted widespread attention from researchers. This is because the Rayleigh anomalous diffraction mode not only possesses a narrow-band, asymmetric resonance line shape, but it is also highly sensitive to changes in the refractive index of the external environment.

[0006] However, existing research lacks a suitable structural model, resulting in insufficient coupling and optimization between plasmon resonance (PRR) and refractive index (RA). This means that the high sensitivity of the RA mode in the hybrid system to the refractive index of the external environment is only utilized, without fully exploring the detection advantages of this hybrid sensor in detecting changes in the refractive index of the local environment. This technical deficiency will ultimately affect the application prospects of this hybrid LSPR sensor in biological sample detection. Summary of the Invention

[0007] The purpose of this invention is to address the technical deficiency in existing hybrid LSPR sensors, where the lack of sufficient coupling and optimization between the RA and LSPR limits their application in biological sample detection. This invention provides a bifunctional hybrid plasmonic sensor. This bifunctional hybrid plasmonic sensor is based on a metagrating, with sufficient coupling between the RA and LSPR, and the intensity of the coupling signal is fully utilized by controlling the angle of the incident light.

[0008] Another object of the present invention is to provide applications of the above-described dual-function hybrid plasmonic sensor. This dual-function hybrid plasmonic sensor can be used not only to detect minute changes in the refractive index of the external environment, but also to monitor minute changes in the refractive index of a local environment.

[0009] Another object of the present invention is to provide a dual-functional hybrid plasmonic sensing and detection system composed of the above-described dual-functional hybrid plasmonic sensor.

[0010] The technical solution adopted to achieve the purpose of this invention is:

[0011] A dual-function hybrid plasmon sensor includes a substrate, a metal thin film, a dielectric grating, and a metal nanoshell array;

[0012] The metal thin film is deposited on the substrate. On the one hand, it is used to eliminate transmitted light; on the other hand, as part of the meta-grating structure, it can couple with the metal nanoshell array under the action of incident light waves to form specific plasmon modes.

[0013] The dielectric grating is located between the metal thin film and the metal nanoshell array. It serves two purposes: firstly, as a template for fabricating the metal nanoshell array, and secondly, as an isolation mechanism between the metal thin film and the metal nanoshell array. The structural parameters of the dielectric grating are optimized and determined through parameter scanning based on the operating wavelength of the sensor.

[0014] The metal nanoshell array is deposited on the surface of the dielectric grating using vacuum evaporation technology at a certain tilt angle, with the tilt angle adjusted according to the modulation depth of the dielectric grating.

[0015] The metal thin film and the metal nanoshell array are coupled together under the action of incident light waves to form a plasmonic mode.

[0016] In the above technical solution, the substrate material is silicon dioxide.

[0017] In the above technical solution, the material of the metal thin film includes, but is not limited to, metal materials such as gold, silver, aluminum, sodium and platinum; the thickness of the metal thin film is 50-150nm.

[0018] In the above technical solution, the dielectric grating is made of S1805 photoresist (PR) and is prepared by interference lithography. The structural parameters of the dielectric grating, such as the period P, modulation depth h, grating duty cycle D, and grating thickness d2 before it is fully developed, are optimized and determined by parameter scanning using FDTD Solution software based on the operating wavelength of the sensor.

[0019] In the above technical solution, the material of the metal nanoshell array includes, but is not limited to, metal materials with low absorption such as silver, aluminum and sodium; the thickness of the metal nanoshell array is 50-70 nm.

[0020] Another aspect of the present invention is the application of the above-described dual-function hybrid plasmon sensor in the detection of concentrations in environmental media.

[0021] Another aspect of the present invention is the application of the above-described dual-function hybrid plasmon sensor in biological sample detection.

[0022] In another aspect of the present invention, a dual-function hybrid plasmon sensing and detection system includes the aforementioned dual-function hybrid plasmon sensor, a sensor chamber, an incident light source, a semi-transparent mirror, and a fiber optic spectrometer; the dual-function hybrid plasmon sensor is fixed in the transparent sensor chamber; the incident light source uses a broadband plane wave, which, after passing through the semi-transparent mirror, illuminates the surface of the dual-function hybrid plasmon sensor, exciting plasmon modes and Rayleigh anomalous modes; subsequently, the light wave carrying the resonance signal is reflected by the dual-function hybrid plasmon sensor and the semi-transparent mirror to the fiber optic spectrometer for detection.

[0023] In the above technical solution, the sensor chamber is fixed on a rotating platform that can rotate around the y-axis to adjust the angle of the incident light source relative to the normal of the dual-function hybrid plasmon sensor structure.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] 1. The dual-function hybrid plasmonic sensor provided by the present invention is based on a metagrating, with full coupling between the RA and LSPR. The intensity of the coupling signal can be fully utilized by controlling the angle of the incident light, so that it can be used to detect small changes in the refractive index of the external environment, as well as to detect small changes in the local refractive index caused by the binding of viral antibodies and antigens adsorbed on the surface of the structure.

[0026] 2. The dual-functional hybrid plasmonic sensor provided by this invention has a simple structure, is easy to manufacture, and has low cost. It can be fabricated over a large area, laying the foundation for the realization of mass-producible plasmonic sensors. Attached Figure Description

[0027] Figure 1 The diagram shows the structure of a dual-function hybrid plasmon sensor.

[0028] Figure 2a The diagram shows a test setup for a dual-function hybrid plasmon sensor.

[0029] Figure 2b The diagram shows a schematic of the angle tuning method for a dual-function hybrid plasmon sensor.

[0030] Figure 3 The image shows the reflection spectrum response of the plasmonic sensor when the incident angle is 18° and the refractive index of the environment is 1.

[0031] Figure 4 The figure shows the simulated response characteristics of the sensor at different incident angles when the ambient refractive index is in the range of 1 to 1.02.

[0032] Figure 5 The figure shows the simulated response of the sensor at different angles when a dielectric film with a thickness of 0-8 nm is attached to the sensor surface.

[0033] In the figure: 1-substrate, 2-metal thin film, 3-dielectric grating, 4-metal nanoshell array, 5-bifunctional hybrid plasmon sensor, 6-sensor chamber, 6-1-sensor chamber inlet, 6-2-sensor chamber outlet, 7-semi-transparent mirror, 8-fiber optic spectrometer, 9-incident light source. Detailed Implementation

[0034] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0035] Example 1

[0036] A dual-function hybrid plasmonic sensor, such as Figure 1 As shown: It includes a substrate 1, a metal thin film 2, a dielectric grating 3, and a metal nanoshell array 4;

[0037] The substrate is made of silicon dioxide (SiO2), with a refractive index of 1.46. The metal thin film 2 is deposited on the substrate 1 using vacuum evaporation technology. It serves two purposes: firstly, to eliminate transmitted light; and secondly, as part of a metagrating structure, it can couple with the metal nanoshell array 4 under the influence of incident light waves to form specific plasmon modes. The metal thin film 2 is made of the noble metal gold (Au), with a thickness of d1 = 70 nm.

[0038] The dielectric grating 3 is located between the metal thin film 2 and the metal nanoshell array 4. It serves two purposes: firstly, as a template for fabricating the metal nanoshell array 4, and secondly, as an isolation between the metal thin film 2 and the metal nanoshell array 4. The dielectric grating template is made of S1805 photoresist (PR). The dielectric grating is fabricated using interference lithography. The structural parameters of the dielectric grating are optimized and determined using FDTD Solution software for parameter scanning. In this embodiment, the operating wavelength of the dual-function hybrid plasmon sensor is selected in the range of 450-750 nm. Based on this operating wavelength, the optimized structural parameters of the dielectric grating are: period P = 465 nm, modulation depth h = 260 nm, grating duty cycle D = 0.35, and grating undeveloped thickness d2 = 50 nm.

[0039] The metal nanoshell array 4 is made of silver (Ag). Using the dielectric grating 3 as a template, it is deposited on both sides of the dielectric grating 3 at a certain tilt angle using vacuum evaporation technology. The tilt angle is adjusted according to the modulation depth of the dielectric grating 3. The thickness of the metal nanoshell array 4 is about 50 nm, and the modulation depth H of the metal nanoshell array 4 is 310 nm.

[0040] The metal thin film 2 and the metal nanoshell array 4 are coupled together under the action of incident light waves to form a plasmonic mode.

[0041] Example 2

[0042] This embodiment is based on the dual-function hybrid plasmon sensor introduced in Embodiment 1, and describes the dual-function hybrid plasmon sensing and detection system composed of it.

[0043] like Figure 2a As shown, the dual-function hybrid plasmon sensor 5 is fixed in a transparent sensor chamber 6. The liquid (gas) to be measured is drawn into the sensor chamber 6 through the inlet 6-1. After the liquid (gas) fills the entire sensor chamber 6, it flows out from the outlet 6-2, forming a stable circulation system with the external liquid (gas). It should be noted that the transparent sensor chamber 6 is fixed on a rotating platform that can rotate around the y-axis. Tuning the angle of the rotating platform can be equivalent to changing the angle θ between the incident light and the normal to the structure, such as... Figure 2b As shown.

[0044] A broadband plane wave, TM polarized, is used as the incident light source 9 to illuminate the dual-function hybrid plasmon sensor 5. The broadband incident light wave passes through a semi-transparent mirror 7 and then illuminates the surface of the structure, exciting plasmon modes in the structure and Rayleigh anomalous modes in the grating structure. Figure 3The reflectance spectrum of the sensor at an incident angle of θ = 18° and an ambient refractive index n = 1 is shown. The broadband reflection valleys correspond to the plasmonic modes generated by the coupling of the metal nanoshell array 4 and the metal thin film 2, while the narrow-band reflection peaks correspond to the Rayleigh reflection modes coupled with the plasmonic modes. Subsequently, light waves carrying the resonance signal are reflected by the bifunctional hybrid plasmonic sensor 5 and the semi-transparent mirror 7 into the fiber optic spectrometer 8. By monitoring the spectral shift of the resonance mode in the fiber optic spectrometer 8, minute changes in the concentration of the ambient medium (liquid or gas) are detected (see Example 3), or minute changes in the local refractive index caused by the binding of viral antibodies and antigens adsorbed on the surface of the bifunctional hybrid plasmonic sensor 5 (see Example 4).

[0045] Example 3

[0046] This embodiment is based on Examples 1 and 2 to introduce its application in the detection of concentration in environmental media.

[0047] Concentration of environmental media, that is, the concentration of liquids or gases in the environment.

[0048] As described in Example 2, when the incident light wave enters the dual-function hybrid plasmon sensing system at a suitable angle, the fiber optic spectrometer 8 displays a narrow-band reflection peak. The wavelength corresponding to this reflection peak is the resonant wavelength of the coupled Rayleigh anomalous mode. When the refractive index of the external environment increases, the resonant wavelength will undergo a certain degree of redshift. The formula for Rayleigh anomalous diffraction of the metagrating is nP(sin(θ)+1)=λ, where n represents the refractive index of the sensor's environment, P represents the period of the metagrating, θ represents the angle of incident light, and λ represents the resonant wavelength of Rayleigh anomalous diffraction. It can be seen that when the grating period and incident angle remain unchanged, the sensor's resonant wavelength and its redshift are linearly related to the environmental refractive index. Therefore, the environmental refractive index can be calculated by detecting the resonant wavelength. Since the higher the concentration of the environmental medium, the higher the environmental refractive index, i.e., the two are positively correlated, small changes in the concentration of the environmental medium can be detected by changes in the environmental refractive index. To verify the above application and analyze its detection sensitivity, this embodiment used FDTD Solution software to simulate the sensing response characteristics under different refractive indices. In this simulation, we set the refractive index variation range to 1-1.02, with a variation step size of 0.02. The test results are as follows. Figure 4 As shown.

[0049] from Figure 4It can be seen that (1) thanks to the high response sensitivity of the Rayleigh anomalous diffraction mode to changes in the refractive index of the external environment, when the incident light angles are 0°, 10° and 20°, the resonance wavelength of the coupled Rayleigh anomalous mode redshifts to different magnitudes as the refractive index of the external environment increases. That is, the sensor can detect such small changes in the refractive index of the environment, verifying the feasibility of the above application. (2) With the increase of the incident angle, the redshift amplitude of the sensor resonance peak with the change in the refractive index of the environment increases (the slope of the curve increases), and the sensitivity of the device is effectively improved. When the incident light angle is 20°, the sensitivity of the sensor reaches S=dλ / dn≈600nm / RIU, where dλ represents the redshift of the resonance peak and dn represents the small range of refractive index change. Further increasing the incident light angle can further improve the sensitivity of the sensor.

[0050] Example 4 This example is based on Examples 1 and 2 and introduces its application in biological sample detection.

[0051] The paper "The Optimal Aspect Ratio of Gold Nanorods for Plasmonic Bio-sensing" (Plasmonics (2010) 5:161–167; DOI 10.1007 / s11468-010-9130-2) introduces a method for simulating the detection of biological sample quantities by using a thin film of a certain refractive index and thickness to replace biomolecules. In this method, the amount of biological sample is simulated by adjusting the thickness of the film; the greater the film thickness, the higher the corresponding biological sample content.

[0052] In this application, drawing on the aforementioned method, a dielectric thin film is used to simulate biological samples formed by antibody-antigen binding. When a certain amount of biological sample adheres to the sensor surface, it is equivalent to setting a dielectric thin film on the sensor surface, thereby changing the refractive index of the local environment on the sensor surface. Correspondingly, the resonant wavelength of the coupled Rayleigh anomalous mode will undergo a certain degree of redshift. The larger the amount of biological sample, the greater the redshift of the resonant wavelength. Therefore, by detecting the resonant wavelength and calculating the redshift, the amount of biological sample adhered to the sensor surface can be inferred.

[0053] To verify the above application and analyze its detection sensitivity, this embodiment used FDTD Solution software to simulate the sensing response characteristics under different dielectric film thicknesses. In this simulation, the tuning range of the dielectric film thickness was set to 0-8 nm, the thickness variation step was 2 nm, and the refractive index of the film was 1.5. The test results are as follows: Figure 5 As shown.

[0054] from Figure 5It can be seen that (1) thanks to the strong local field enhancement effect of plasmons and their high response sensitivity to changes in the local environment, the Rayleigh anomalous mode coupled with plasmons can clearly detect the change in the thickness of the dielectric film adhered to the surface of the structure when the incident light angles are 0°, 9° and 14°, respectively, verifying the feasibility of the above application. (2) When the incident angle is 9°, the sensor sensitivity shows the best effect when using the optimized coupling mode between LSPR and RA. At this time, the overall quality factor (FOM) of the sensor is high. layer * =dλ / (dl*Δλ) RA ) = 0.139, where dl and Δλ RA (3) Compared with RA sensors at the same incident angle (θ=9°), the FOM (Full width at half maximum) is the largest. layer * =0.024), the hybrid plasmonic sensor based on LSPR and RA coupling shows significant advantages, with the overall quality factor improved by more than 5 times.

[0055] As can be seen from Examples 3 and 4: (1) Sensors with different characteristics should be used to detect minute changes in the refractive index of the external environment and to monitor minute changes in the refractive index of the local environment caused by low concentrations of molecules attached to the sensor surface. (2) The plasmon polariton sensor with meta-grating proposed in the examples can detect the above two application scenarios with high sensitivity by adjusting the angle of the incident light, and is therefore an optimized sensor with dual functions.

[0056] The above description is only a preferred embodiment of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A dual-functional hybrid plasmon sensor, characterized in that: The FANO hybrid plasmonic sensor based on LSPR and RA coupling includes a substrate, a metal thin film, a dielectric grating, and a metal nanoshell array. The metal thin film is deposited on the substrate, which serves to eliminate transmitted light on one hand, and on the other hand, as part of the meta-grating structure, it couples with the metal nanoshell array under the action of incident light waves to form a specific plasmon mode. The dielectric grating is located between the metal thin film and the metal nanoshell array; the structural parameters of the dielectric grating are optimized and determined by parameter scanning based on the operating wavelength of the sensor; the structural parameters of the dielectric grating are: period... P =465nm, modulation depth h =260 nm, grating duty cycle D =0.35, the thickness of the grating not fully developed. d 2 =50 nm; The metal nanoshell array is deposited at an angle on the surface of the dielectric grating, using the dielectric grating as a template, and the angle of tilt is adjusted according to the modulation depth of the dielectric grating. The metal thin film and the metal nanoshell array are coupled together under the action of incident light waves to form a plasmonic mode; The substrate material is silicon dioxide; The metal thin film is made of one of the following materials: gold, silver, aluminum, sodium, and platinum. The thickness of the metal film is 50-150 nm.

2. The dual-functional hybrid plasmon sensor as described in claim 1, characterized in that: The dielectric grating is made of photoresist.

3. The dual-functional hybrid plasmon sensor as described in claim 1, characterized in that: The dielectric grating is fabricated using interference lithography.

4. The dual-functional hybrid plasmon sensor as described in claim 1, characterized in that: The metal nanoshell array is made of one of silver, aluminum, and sodium. The thickness of the metal nanoshell array is 50-70 nm.

5. The application of the dual-function hybrid plasmon sensor as described in any one of claims 1-4 in the detection of concentration in environmental media.

6. The application of the bifunctional hybrid plasmon sensor as described in any one of claims 1-4 in biological sample detection.

7. A dual-function hybrid plasmon sensing and detection system, characterized in that, Includes the bifunctional hybrid plasmonic sensor, sensor chamber, incident light source, semi-transparent and semi-reflective mirror, and fiber optic spectrometer as described in any one of claims 1-4; The dual-function hybrid plasmon sensor is fixed in the transparent sensor chamber; The incident light source is a broadband plane wave, which illuminates the surface of the dual-function hybrid plasmon sensor after passing through a semi-transparent mirror, exciting plasmon modes and Rayleigh anomalous modes; subsequently, the light wave carrying the resonance signal is reflected by the dual-function hybrid plasmon sensor and the semi-transparent mirror to the fiber optic spectrometer for detection.

8. The dual-function hybrid plasmon sensing and detection system as described in claim 7, characterized in that: The sensor chamber is fixed on a rotating platform that rotates about the y-axis to adjust the angle of the incident light source relative to the normal of the dual-function hybrid plasmon sensor structure.

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