Modified carbon nanotube film terahertz metasurface specific biosensor and application thereof

Abstract

The invention discloses a high-selectivity terahertz metasurface biosensor based on a modified single-walled carbon nanotube film. The single-walled carbon nanotube metasurface layer is provided with a periodic opening resonance ring structure in an etched mode, is purified through strong acid, tip ultrasound, high-speed centrifugation, heat treatment and other schemes and is doped with gold nanoparticles from bottom to top in sequence. The invention also discloses an application of the high-selectivity terahertz metasurface biosensor based on the modified single-walled carbon nanotube film. The problems that in the prior art, a terahertz metasurface trace substance sensor is poor in modifiability, and high-selectivity sensing of trace substances cannot be achieved are solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of terahertz supersurface biosensor, and specifically relates to a highly selective terahertz supersurface biosensor based on a modified single-walled carbon nanotube film. The present invention also discloses the application of the highly selective terahertz supersurface biosensor based on the modified single-walled carbon nanotube film. Background Art

[0002] Terahertz waves have the characteristics of strong penetration, non-destructiveness and specific absorption of biological molecules, and have broad application potential in biomedicine, biochemistry and biophysics. Therefore, terahertz technology has become one of the research hotspots in the field of biosensors. In terahertz sensors, metasurface technology is widely used. This is because the metasurface is an artificial lattice composed of microstructures, which can not only effectively regulate the propagation characteristics of terahertz waves, but also the local resonance excited in the metasurface can show strong electromagnetic field enhancement near the periodic subwavelength structure, which can effectively convert the presence of trace analytes into observable changes in optical properties, including frequency shifts and amplitude shifts of resonance peaks in the spectrum. This promotes their application in the field of trace biochemical detection.

[0003] However, two key issues are common with current terahertz metasurface sensors. First, they are only sensitive to analytes that are close enough to the surface to interact with the resonantly enhanced near-field. Second, the mechanism of this matter-terahertz wave interaction is inherently non-specific, i.e., any analyte that changes the local environment will cause a response from the sensor. Therefore, metasurface-based terahertz sensors require a mechanism to capture analyte molecules close to the sensing surface with high selectivity.

[0004] Single-walled carbon nanotubes are nanotube-like structures formed by the curling of carbon atoms in a hexagonal arrangement. They have a unique one-dimensional morphology and excellent electrical, optical and mechanical properties. Usually, the diameter of single-walled carbon nanotubes is about 1 to 2 nm, and the length can reach several microns, so they have a high specific surface area and a large specific length. In addition, the large π bonds on the outer surface of carbon nanotubes are the chemical basis for the non-covalent bonding of carbon nanotubes with some macromolecules with conjugated properties, and specific recognition of biomolecules can be achieved through chemical modification. Therefore, using modified single-walled carbon nanotube films as the resonant layer of terahertz metasurface sensors, surface functionalization using antibodies can achieve selective and high-affinity analyte binding. Summary of the invention

[0005] The purpose of the present invention is to provide a highly selective terahertz metasurface biosensor based on modified single-walled carbon nanotube film to solve the problem that the terahertz metasurface trace substance sensor in the prior art has poor modifiability and cannot achieve highly selective sensing of trace substances.

[0006] Another object of the present invention is to provide an application of a highly selective terahertz supersurface biosensor based on a modified single-walled carbon nanotube film.

[0007] The first technical solution adopted by the present invention is a highly selective terahertz supersurface biosensor based on a modified single-walled carbon nanotube film, which is composed of a dielectric layer and a single-walled carbon nanotube supersurface layer etched with a periodic open resonant ring structure from bottom to top.

[0008] The first technical solution of the present invention is also characterized in that: The single-walled carbon nanotube super surface layer is an isotropic single-walled carbon nanotube film doped with gold nanoparticles purified by strong acid, tip ultrasound, high-speed centrifugation and heat treatment, or an anisotropic single-walled carbon nanotube film doped with gold nanoparticles purified by strong acid, tip ultrasound, high-speed centrifugation and heat treatment. The thickness of the single-walled carbon nanotube super surface layer ranges from 100 to 400 nm.

[0009] The dielectric layer is a polyethylene terephthalate dielectric layer with a thickness not exceeding 15 μm.

[0010] The single-walled carbon nanotube ultra-surface layer was purified by strong acid, tip sonication, high-speed centrifugation and heat treatment and doped with gold nanoparticles according to the following steps: Step 1, purification of single-walled carbon nanotube powder: dissolving the single-walled carbon nanotube powder in a strong acid solution at a ratio of 1:100 and stirring at a stirring speed of not less than 2000 rpm, a stirring temperature of 80-100°C, and a stirring time of not less than 30 minutes; Step 2, after the single-walled carbon nanotube concentrated sulfuric acid mixed solution uniformly stirred in step 1 is allowed to stand for stratification, the excess concentrated sulfuric acid solution in the upper layer is poured out, and the mixture is dried in a vacuum environment at a temperature not lower than 200° C., to finally obtain acid-purified single-walled carbon nanotube powder; Step 3, dissolving the single-walled carbon nanotube powder treated in step 2 in a dispersion solution at a ratio of not less than 1 wt %, wherein the dispersion solution is an aqueous solution of any one of sodium dodecyl sulfate SDS, sodium dodecylbenzene sulfonate SDBS, polyvinylpyrrolidone PVP or sodium cholate; Step 4: subjecting the single-walled carbon nanotube solution obtained in step 3 to tip ultrasound, with a power of not less than 600 W and an ultrasound time of not less than 60 min. Step 5, subjecting the single-walled carbon nanotube dispersion treated in step 4 to high-speed centrifugation, with a centrifugal speed of not less than 15000 r / m and a centrifugal time of not less than 60 min, and taking out the supernatant after centrifugation; Step 6, mixing the gold nanoparticle solution with a particle size of 20-40 nm and the purified single-walled carbon nanotube supernatant obtained in step 5 at a ratio of 1:10; Step 7, placing the mixed solution obtained in step 6 in a mixer with a rotation speed of not less than 150 r / m and mixing for not less than 30 min; Step 8: Based on the acid-modified single-walled carbon nanotube powder obtained in step 4, a single-walled carbon nanotube film with a thickness ranging from 100 to 400 nm is obtained by vacuum filtration.

[0011] Step 9: annealing the single-walled carbon nanotube film obtained in step 8 in a vacuum environment at a temperature not lower than 200° C. to remove the residual dispersant.

[0012] A periodically arranged annular double-opening resonant ring structure is etched on the surface of a single-walled carbon nanotube supersurface layer, and the openings are arranged left and right and are asymmetric.

[0013] The outer radius of the annular double split ring resonator metasurface structure r 1 has a value range of 50-60µm, and the inner radius r 2 has a value range of 40µm, and the center angle θ The value range of 1 is 150-160°, corresponding to θ The value range of 2 is 130-140°. The period of the asymmetric open-ring resonant array is p x = p y , and its value range is 90-100µm.

[0014] The second technical solution adopted by the present invention is a highly selective terahertz supersurface biosensor based on a modified single-walled carbon nanotube film, which is used for terahertz supersurface trace biological material detection.

[0015] The second technical solution of the present invention is also characterized in that: The terahertz metasurface trace biological material detection is characterized by being implemented in the following steps: Step a, mixing a dispersion of colloidal gold nanoparticles modified with functional groups on the surface with the protein to be tested in a ratio of 2:1, fully stirring at room temperature to allow the functionalized gold nanoparticles to undergo adsorption reaction with the protein to be tested, the reaction time being 1-2 h to ensure that the colloidal gold and the protein are fully combined; Step b, high-speed centrifugation is performed at a speed of not less than 15000 r / min for a time of not less than 45 min, and finally a colloidal gold-protein complex precipitate is obtained; Step c, taking out the supernatant of the colloidal gold-protein complex precipitation, adding phosphate buffer in a ratio of 1:1 to the supernatant, repeating step b, repeating multiple times until a relatively pure colloidal gold-protein complex is obtained for testing; Step d, combining the super surface sensor with a polydimethylsiloxane (PDMS) microfluidic channel, wherein the combination comprises, from top to bottom, a PDMS layer with a liquid inlet and a liquid outlet, a sample area channel with a height of not less than 50 um and a 1:1 ratio with the surface area of ​​the super surface, a super surface sensor chip layer, and a fixed layer at the bottom; Step e, passing the colloidal gold nanoparticle dispersion that is not bound to the protein to be tested into the surface of the metasurface sensor in a ratio of 1:1 to the volume of the microfluidic channel, and using a transmission terahertz time-domain spectroscopy system to collect the transmission signal of the metasurface sensor loaded with the test object, and defining the transmission signal as 0 fM; Step f, cleaning the metasurface sensor with physiological saline after signal acquisition; Step g, respectively passing the functionalized colloidal gold nanoparticle-protein complex solution specifically bound by the cross-linking reaction to the transmission signal 0.3 fM, 0.6 fM, 1 fM, 1.5 fM, 2.2 fM, and 2.5 fM to the surface of the supersurface sensor combined with the microfluidic channel, and collecting the transmission signal of the single-walled carbon nanotube terahertz supersurface sensor coated with the functionalized colloidal gold nanoparticle-protein complex by using a transmission terahertz time-domain spectroscopy system; Step h: using the transmission signal of the metasurface loaded with functionalized colloidal gold nanoparticles collected in step e as a reference, data processing and analysis are performed on the detected terahertz signal of the colloidal gold-protein complex solution to extract characteristic information of the target substance and determine the presence and concentration of the protein to be tested.

[0016] The beneficial effect of the present invention is that a highly selective terahertz supersurface biosensor based on a modified single-walled carbon nanotube film has excellent electrical and optical properties, high modifiability, good biocompatibility and other properties after modification. By further using laser etching technology to etch a periodically arranged open resonant ring structure on the surface of the single-walled carbon nanotube film on the basis of preparing the modified single-walled carbon nanotube film by the classical multi-stage vacuum filtration method, a strong resonant coupling characteristic can be achieved in the terahertz range, which effectively solves the difficulties of traditional metal-based supersurface sensors such as large metal loss and easy corrosion and the inability to achieve highly selective detection. The detection specificity and sensitivity of the device are further improved, thereby having great potential in the sensing of trace biological substances. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The schematic diagram of the array structure of the highly selective terahertz supersurface biosensor based on the modified single-walled carbon nanotube film of the present invention; Figure 2This is a schematic diagram of the structure of a highly selective terahertz supersurface biosensor unit based on a modified single-walled carbon nanotube film according to the present invention; Figure 3 The terahertz transmission spectra of the highly selective terahertz supersurface biosensor based on the modified single-walled carbon nanotube film of the present invention before and after the single-walled carbon nanotube film is doped with gold nanoparticles; Figure 4 (a) is a schematic diagram of the structure of a metasurface unit combined with a microfluidic channel; Figure 4 (b) is a schematic diagram of the supersurface unit structure combined with microfluidic channels Figure 4 (c) is a schematic diagram of a supersurface sensor loaded with functionalized gold nanoparticles combined with a microfluidic channel; FIG4( d ) is a schematic diagram of a supersurface sensor combined with a microfluidic channel into which a colloidal gold-protein complex solution is introduced; Figure 5 The present invention discloses a terahertz transmission spectrum of a highly selective terahertz supersurface biosensor based on a modified single-walled carbon nanotube film after the sensor is loaded with proteins of different molar masses.

[0018] In the figure, 1. single-walled carbon nanotube super surface layer, 2. dielectric layer, 3. upper opening, 4. microfluidic channel, 5. liquid inlet hole, 6. liquid outlet hole, 7. functionalized gold nanoparticles not bound to the protein to be tested, 8. colloidal gold-protein complex bound to the protein to be tested. DETAILED DESCRIPTION

[0019] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0020] The invention is based on a highly selective terahertz supersurface biosensor based on a purified single-walled carbon nanotube film doped with gold nanoparticles, combined with Figure 1 , from bottom to top, it is composed of a dielectric layer 2 and a single-walled carbon nanotube supersurface layer 1 etched with a periodic open resonant ring structure and purified and doped with gold nanoparticles through strong acid, tip ultrasound, high-speed centrifugation and heat treatment.

[0021] The single-walled carbon nanotube super surface layer 1 is an isotropic single-walled carbon nanotube film doped with gold nanoparticles purified by strong acid, tip ultrasound, high-speed centrifugation and heat treatment, or an anisotropic single-walled carbon nanotube film doped with gold nanoparticles purified by strong acid, tip ultrasound, high-speed centrifugation and heat treatment. The thickness of the single-walled carbon nanotube super surface layer 1 ranges from 100 to 400 nm.

[0022] The dielectric layer 2 is a polyethylene terephthalate dielectric layer with a thickness not exceeding 15 μm.

[0023] The purification and doping of the single-walled carbon nanotube super surface layer 1 are carried out according to the following steps: Step 1, purification of single-walled carbon nanotube powder: dissolving the single-walled carbon nanotube powder in a strong acid (concentrated sulfuric acid / concentrated nitric acid, etc.) solution at a ratio of 1:100 and stirring at a stirring speed of not less than 2000 rpm, a stirring temperature of 80-100°C, and a stirring time of not less than 30 minutes; Step 2, after the single-walled carbon nanotube concentrated sulfuric acid mixed solution uniformly stirred in step 1 is allowed to stand for stratification, the excess concentrated sulfuric acid solution in the upper layer is poured out, and the mixture is dried in a vacuum environment at a temperature not lower than 200° C., to finally obtain acid-purified single-walled carbon nanotube powder; Step 3, dissolving the single-walled carbon nanotube powder treated in step 2 in a dispersion at a ratio of not less than 1wt%, wherein the dispersion may be an aqueous solution of a polymer such as sodium dodecyl sulfate (SDS), sodium dodecylbenzene sulfonate (SDBS), polyvinylpyrrolidone (PVP) or sodium cholate; Step 4: subjecting the single-walled carbon nanotube solution obtained in step 3 to tip ultrasound, with a power of not less than 600 W and an ultrasound time of not less than 60 min. Step 5, subjecting the single-walled carbon nanotube dispersion treated in step 4 to high-speed centrifugation, with a centrifugal speed of not less than 15000 r / m and a centrifugal time of not less than 60 min, and taking out the supernatant after centrifugation; Step 6, mixing the gold nanoparticle solution with a particle size of 20-40 nm and the purified single-walled carbon nanotube supernatant obtained in step 5 at a ratio of 1:10; Step 7, placing the mixed solution obtained in step 6 in a mixer with a rotation speed of not less than 150 r / m and mixing for not less than 30 min; Step 8: Based on the acid-modified single-walled carbon nanotube powder obtained in step 4, a single-walled carbon nanotube film with a thickness ranging from 100 to 400 nm is obtained by vacuum filtration.

[0024] Step 9: annealing the single-walled carbon nanotube film obtained in step 8 in a vacuum environment at a temperature not lower than 200° C. to remove the residual dispersant.

[0025] The surface of the single-walled carbon nanotube super surface layer 1 is etched with a periodically arranged double-open resonant ring structure, and the openings are arranged left and right and are asymmetric. Here, the structural shape of the resonator includes but is not limited to circular, square and other structures. This asymmetric resonant structure can produce a strong coupling effect with the terahertz wave, which is specifically manifested in the generation of Fano resonance with anti-parallel surface current characteristics at low frequency positions and dipole resonance with parallel surface current characteristics at high frequency positions.

[0026] The outer radius of the annular double open ring resonator structure r 1 has a value range of 50-60µm, and the inner radiusr 2 has a value range of 40µm, and the center angle θ The value range of 1 is 150-160°, corresponding to θ The value range of 2 is 130-140°. The period of the asymmetric open-ring resonant array is p x = p y , and its value range is 90-100µm.

[0027] The highly selective terahertz supersurface biosensor based on a modified single-walled carbon nanotube film of the present invention is used for detecting trace biological substances on the terahertz supersurface.

[0028] The terahertz metasurface trace biological material detection is implemented in the following steps: Step a, mixing a dispersion of colloidal gold nanoparticles modified with functional groups on the surface with the protein to be tested in a ratio of 2:1, fully stirring at room temperature to allow the functionalized gold nanoparticles to undergo adsorption reaction with the protein to be tested, the reaction time being 1-2 h to ensure that the colloidal gold and the protein are fully combined; Step b, high-speed centrifugation is performed at a speed of not less than 15000 r / min for a time of not less than 45 min, and finally a colloidal gold-protein complex precipitate is obtained; Step c, taking out the supernatant of the colloidal gold-protein complex precipitation, adding phosphate buffer in a ratio of 1:1 to the supernatant, repeating step b, repeating multiple times until a relatively pure colloidal gold-protein complex is obtained for testing; Step d, combining the super surface sensor with a polydimethylsiloxane (PDMS) microfluidic channel, wherein the combination comprises, from top to bottom, a PDMS layer with a liquid inlet and a liquid outlet, a sample area channel with a height of not less than 50 um and a 1:1 ratio with the surface area of ​​the super surface, a super surface sensor chip layer, and a fixed layer at the bottom; Step e, passing the colloidal gold nanoparticle dispersion that is not bound to the protein to be tested into the surface of the metasurface sensor in a ratio of 1:1 to the volume of the microfluidic channel, and using a transmission terahertz time-domain spectroscopy system to collect the transmission signal of the metasurface sensor loaded with the test object, and defining the transmission signal as 0 fM; Step f, cleaning the metasurface sensor with physiological saline after signal acquisition; Step g, using a syringe to respectively pass the functionalized colloidal gold nanoparticle-protein complex solution specifically bound by a cross-linking reaction to the transmission signal 0.3 fM, 0.6 fM, 1 fM, 1.5 fM, 2.2 fM, and 2.5 fM to the surface of the supersurface sensor combined with the microfluidic channel, and using a transmission terahertz time-domain spectroscopy system to collect the transmission signal of the single-walled carbon nanotube terahertz supersurface sensor coated with the functionalized colloidal gold nanoparticle-protein complex; Step h: using the transmission signal of the metasurface loaded with functionalized colloidal gold nanoparticles collected in step e as a reference, data processing and analysis are performed on the detected terahertz signal of the colloidal gold-protein complex solution to extract characteristic information of the target substance and determine the presence and concentration of the protein to be tested.

[0029] Example 1 The invention is based on a highly selective terahertz supersurface biosensor based on a modified single-walled carbon nanotube film, combined with Figure 1 , from bottom to top, it is composed of a dielectric layer 2 and a single-walled carbon nanotube film supersurface layer 1 that is purified and doped with gold nanoparticles and etched with a periodic annular open resonant ring structure.

[0030] The single-walled carbon nanotube super surface layer 1 is an isotropic single-walled carbon nanotube film doped with gold nanoparticles purified by strong acid, tip ultrasound, high-speed centrifugation and heat treatment, or an anisotropic single-walled carbon nanotube film doped with gold nanoparticles purified by strong acid, tip ultrasound, high-speed centrifugation and heat treatment. The thickness of the single-walled carbon nanotube super surface layer 1 ranges from 100 to 400 nm.

[0031] The dielectric layer 2 is a polyethylene terephthalate dielectric layer with a thickness not exceeding 15 μm.

[0032] Example 2 The highly selective terahertz supersurface biosensor based on a modified single-walled carbon nanotube film of the present invention is used for detecting trace biological substances on the terahertz supersurface.

[0033] The terahertz metasurface trace biological material detection is implemented in the following steps: Step a, mixing a dispersion of colloidal gold nanoparticles modified with functional groups on the surface with the protein to be tested in a ratio of 2:1, fully stirring at room temperature to allow the functionalized gold nanoparticles to undergo adsorption reaction with the protein to be tested, the reaction time being 1-2 h to ensure that the colloidal gold and the protein are fully combined; Step b, high-speed centrifugation is performed at a speed of not less than 15000 r / min for a time of not less than 45 min, and finally a colloidal gold-protein complex precipitate is obtained; Step c, taking out the supernatant of the colloidal gold-protein complex precipitation, adding phosphate buffer in a ratio of 1:1 to the supernatant, repeating step b, repeating multiple times until a relatively pure colloidal gold-protein complex is obtained for testing; Step d, combining the super surface sensor with a polydimethylsiloxane (PDMS) microfluidic channel, wherein the combination comprises, from top to bottom, a PDMS layer with a liquid inlet and a liquid outlet, a sample area channel with a height of not less than 50 um and a 1:1 ratio with the surface area of ​​the super surface, a super surface sensor chip layer, and a fixed layer at the bottom; Step e, passing the colloidal gold nanoparticle dispersion that is not bound to the protein to be tested into the surface of the metasurface sensor in a ratio of 1:1 to the volume of the microfluidic channel, and using a transmission terahertz time-domain spectroscopy system to collect the transmission signal of the metasurface sensor loaded with the test object, and defining the transmission signal as 0 fM; Step f, cleaning the metasurface sensor with physiological saline after signal acquisition; Step g, respectively passing the functionalized colloidal gold nanoparticle-protein complex solution specifically bound by the cross-linking reaction to the transmission signal 0.3 fM, 0.6 fM, 1 fM, 1.5 fM, 2.2 fM, and 2.5 fM to the surface of the supersurface sensor combined with the microfluidic channel, and collecting the transmission signal of the single-walled carbon nanotube terahertz supersurface sensor coated with the functionalized colloidal gold nanoparticle-protein complex by using a transmission terahertz time-domain spectroscopy system; Step h: using the transmission signal of the metasurface loaded with functionalized colloidal gold nanoparticles collected in step e as a reference, data processing and analysis are performed on the detected terahertz signal of the colloidal gold-protein complex solution to extract characteristic information of the target substance and determine the presence and concentration of the protein to be tested.

[0034] Example 3 The invention is based on a highly selective terahertz supersurface biosensor based on a purified single-walled carbon nanotube film doped with gold nanoparticles, combined with Figure 1 , from bottom to top, it is composed of a dielectric layer 2 and a single-walled carbon nanotube supersurface layer 1 etched with a periodic open resonant ring structure and purified and doped with gold nanoparticles through strong acid, tip ultrasound, high-speed centrifugation and heat treatment.

[0035] The single-walled carbon nanotube super surface layer 1 is an isotropic single-walled carbon nanotube film doped with gold nanoparticles purified by strong acid, tip ultrasound, high-speed centrifugation and heat treatment, or an anisotropic single-walled carbon nanotube film doped with gold nanoparticles purified by strong acid, tip ultrasound, high-speed centrifugation and heat treatment. The thickness of the single-walled carbon nanotube super surface layer 1 ranges from 100 to 400 nm.

[0036] The dielectric layer 2 is a polyethylene terephthalate dielectric layer with a thickness not exceeding 15 μm.

[0037] The purification and doping of the single-walled carbon nanotube super surface layer 1 are carried out according to the following steps: Step 1, purification of single-walled carbon nanotube powder: dissolving the single-walled carbon nanotube powder in a strong acid (concentrated sulfuric acid / concentrated nitric acid, etc.) solution at a ratio of 1:100 and stirring at a stirring speed of not less than 2000 rpm, a stirring temperature of 80-100°C, and a stirring time of not less than 30 minutes; Step 2, after the single-walled carbon nanotube concentrated sulfuric acid mixed solution uniformly stirred in step 1 is allowed to stand for stratification, the excess concentrated sulfuric acid solution in the upper layer is poured out, and the mixture is dried in a vacuum environment at a temperature not lower than 200° C., to finally obtain acid-purified single-walled carbon nanotube powder; Step 3, dissolving the single-walled carbon nanotube powder treated in step 2 in a dispersion at a ratio of not less than 1wt%, wherein the dispersion may be an aqueous solution of a polymer such as sodium dodecyl sulfate (SDS), sodium dodecylbenzene sulfonate (SDBS), polyvinylpyrrolidone (PVP) or sodium cholate; Step 4: subjecting the single-walled carbon nanotube solution obtained in step 3 to tip ultrasound, with a power of not less than 600 W and an ultrasound time of not less than 60 min. Step 5, subjecting the single-walled carbon nanotube dispersion treated in step 4 to high-speed centrifugation, with a centrifugal speed of not less than 15000 r / m and a centrifugal time of not less than 60 min, and taking out the supernatant after centrifugation; Step 6, mixing the gold nanoparticle solution with a particle size of 20-40 nm and the purified single-walled carbon nanotube supernatant obtained in step 5 at a ratio of 1:10; Step 7, placing the mixed solution obtained in step 6 in a mixer with a rotation speed of not less than 150 r / m and mixing for not less than 30 min; Step 8: Based on the acid-modified single-walled carbon nanotube powder obtained in step 4, a single-walled carbon nanotube film with a thickness ranging from 100 to 400 nm is obtained by vacuum filtration.

[0038] Step 9: annealing the single-walled carbon nanotube film obtained in step 8 in a vacuum environment at a temperature not lower than 200° C. to remove the residual dispersant.

[0039] The surface of the single-walled carbon nanotube super surface layer 1 is etched with a periodically arranged double-open resonant ring structure, and the openings are arranged left and right and are asymmetric. Here, the structural shape of the resonator includes but is not limited to circular, square and other structures. This asymmetric resonant structure can produce a strong coupling effect with the terahertz wave, which is specifically manifested in the generation of Fano resonance with anti-parallel surface current characteristics at low frequency positions and dipole resonance with parallel surface current characteristics at high frequency positions.

[0040] Example 4 The highly selective terahertz supersurface biosensor based on a modified single-walled carbon nanotube film of the present invention is used for detecting trace biological substances on the terahertz supersurface.

[0041] The terahertz metasurface trace biological material detection is implemented in the following steps: Step a, mixing a dispersion of colloidal gold nanoparticles modified with functional groups on the surface with the protein to be tested in a ratio of 2:1, fully stirring at room temperature to allow the functionalized gold nanoparticles to undergo adsorption reaction with the protein to be tested, the reaction time being 1-2 h to ensure that the colloidal gold and the protein are fully combined; Step b, high-speed centrifugation is performed at a speed of not less than 15000 r / min for a time of not less than 45 min, and finally a colloidal gold-protein complex precipitate is obtained; Step c, taking out the supernatant of the colloidal gold-protein complex precipitation, adding phosphate buffer in a ratio of 1:1 to the supernatant, repeating step b, repeating multiple times until a relatively pure colloidal gold-protein complex is obtained for testing; Step d, combining the super surface sensor with a polydimethylsiloxane (PDMS) microfluidic channel, wherein the combination comprises, from top to bottom, a PDMS layer with a liquid inlet and a liquid outlet, a sample area channel with a height of not less than 50 um and a 1:1 ratio with the surface area of ​​the super surface, a super surface sensor chip layer, and a fixed layer at the bottom; Step e, passing the colloidal gold nanoparticle dispersion that is not bound to the protein to be tested into the surface of the metasurface sensor in a ratio of 1:1 to the volume of the microfluidic channel, and using a transmission terahertz time-domain spectroscopy system to collect the transmission signal of the metasurface sensor loaded with the test object, and defining the transmission signal as 0 fM; Step f, cleaning the metasurface sensor with physiological saline after signal acquisition; Step g, using a syringe to respectively pass the functionalized colloidal gold nanoparticle-protein complex solution specifically bound by a cross-linking reaction to the transmission signal 0.3 fM, 0.6 fM, 1 fM, 1.5 fM, 2.2 fM, and 2.5 fM to the surface of the supersurface sensor combined with the microfluidic channel, and using a transmission terahertz time-domain spectroscopy system to collect the transmission signal of the single-walled carbon nanotube terahertz supersurface sensor coated with the functionalized colloidal gold nanoparticle-protein complex; Step h: using the transmission signal of the metasurface loaded with functionalized colloidal gold nanoparticles collected in step e as a reference, data processing and analysis are performed on the detected terahertz signal of the colloidal gold-protein complex solution to extract characteristic information of the target substance and determine the presence and concentration of the protein to be tested.

[0042] Example 5 Terahertz metasurface biosensors based on modified single-walled carbon nanotube films can capture specific analytes by appropriately modifying the surface of single-walled carbon nanotubes, enrich the concentration of analytes on the sensing surface, and provide enhanced specificity and effective amplification of the substance-terahertz wave mechanism, ultimately achieving high selectivity and high sensitivity detection of biomolecules to overcome the two limitations of traditional terahertz metasurface sensors. This sensor has the advantages of rapid response, high selectivity and good stability, providing a new and efficient detection method for biomedical diagnosis, biochemical analysis and drug screening.

[0043] like Figure 1 Schematic diagram of the array structure of the highly selective terahertz supersurface biosensor based on modified single-walled carbon nanotube film of the present invention. Figure 1 As shown, this metasurface sensor is composed of a single-walled carbon nanotube open resonant ring 1 with a thickness not exceeding 400nm and a polyethylene terephthalate dielectric layer 2 with a thickness of 15μm from top to bottom. Here, the single-walled carbon nanotube layer is purified and doped with gold nanoparticles through strong acid, tip ultrasound, high-speed centrifugation and heat treatment, so that the metasurface has excellent dielectric properties in the terahertz range. Compared with the unpurified and undoped single-walled carbon nanotube film, the resonance intensity of the metasurface sensor of the single-walled carbon nanotube film after acid purification and doping in the terahertz range can be increased by at least 50%.

[0044] like Figure 2 The present invention discloses a schematic diagram of a periodic unit structure in a single-walled carbon nanotube terahertz supersurface biosensor with multi-frequency narrow-band absorption, such as Figure 2 As shown, the outer radius of the annular double split ring resonator metasurface structure r 1 has a value range of 50-60µm, and the inner radius r 2 has a value range of 40µm, and the center angle θThe value range of 1 is 150-160°, corresponding to θ The value range of 2 is 130-140°. The period of the asymmetric open-ring resonant array is p x = p y , and its value range is 90-100µm.

[0045] like Figure 3 : The terahertz transmission spectra (polarization direction is along the horizontal direction) of the terahertz supersurface sensor based on the acid-modified single-walled carbon nanotube film in this embodiment before purification and doping and after modification. Figure 3 As shown by the black solid line and dotted line, this terahertz metasurface has an obvious coupling resonance peak at the resonance frequency of 0.95 THz. In order to further improve the resonance characteristics of the metasurface and thus improve the detection sensitivity of the sensor, the present invention purifies and dopes the single-walled carbon nanotube powder by purification through strong acid, tip ultrasound, high-speed centrifugation and heat treatment and doping with gold nanoparticles. The results show that after purifying and doping the single-walled carbon nanotube film, the coupling resonance peak intensity of the device is significantly increased.

[0046] Example 6 Figures 4 (a) to 4 (d) show highly selective terahertz metasurface biosensors based on modified single-walled carbon nanotube films for trace protein detection, which mainly include the following four steps: First, a single-walled carbon nanotube terahertz metasurface device with strong coupling resonance characteristics is designed and prepared based on the modified single-walled carbon nanotube film, as shown in Figure 4 (a). Further, the above-mentioned metasurface sensor is combined with a PDMS microfluidic channel, as shown in Figure 4 (b). A certain amount of functionalized colloidal gold nanoparticles is introduced into the surface of the above-mentioned metasurface sensor according to a certain proportion, and a transmission terahertz time-domain spectroscopy system is used to collect the transmission signal. After the signal is collected, the metasurface sensor is cleaned, as shown in Figure 4 (c). Finally, the functionalized colloidal gold nanoparticle-protein complex solution specifically bound by a cross-linking reaction is introduced into the metasurface sensor, as shown in Figure 4 (d). Among them, the upper opening 3 can be seen in Figure 4 (b), and the microfluidic channel 4, the liquid inlet 5, the liquid outlet 6, the functionalized gold nanoparticles 7 not bound to the protein to be tested, and the colloidal gold-protein complex 8 bound to the protein to be tested can be seen in Figure 4 (c) and Figure 4 (d). Taking the transmission signal of the metasurface loaded with functionalized colloidal gold nanoparticles collected in the step of Figure 4 (c) as a reference, the single-walled carbon nanotube terahertz metasurface into which the functionalized colloidal gold nanoparticle-protein complex solution is passed is tested using a transmission terahertz time-domain spectroscopy system to achieve high-selective terahertz metasurface sensing of trace proteins, as shown in Figure 4 (d).

[0047] Figure 5According to the above embodiment, the highly selective terahertz supersurface biosensor based on modified single-walled carbon nanotube film is used for terahertz transmission spectroscopy of trace serum amyloid protein (SAA) specific detection. Figure 5 As shown, when the SAA protein gradually increases from 0.1fM to 1fM, the metasurface sensor can comprehensively reflect its concentration change through the frequency shift and amplitude shift of the coupled resonance peak resonant frequency point. As an example, since the acid-modified single-walled carbon nanotube film shows strong dielectric properties in the terahertz range, the metasurface sensor can be used for trace SAA protein detection with a detection sensitivity of up to 40 GHz / fM.

[0048] The present invention gives full play to the strong modifiability, biocompatibility and good photoelectric properties of single-walled carbon nanotubes, and discloses as an embodiment a single-walled carbon nanotube terahertz supersurface biosensor that can realize high-sensitivity and high-selectivity sensing detection of trace substances, especially trace biological substances, providing a new option to solve the problem that traditional terahertz supersurface sensors cannot realize specific detection. It provides a new approach.

[0049] The present invention further improves the dielectric properties of single-walled carbon nanotube films in the terahertz range by purifying and doping them, designs and processes a periodic array structure on the surface, and can achieve a strong local electromagnetic field enhancement effect in the terahertz band. A highly selective complex solution of colloidal gold nanoparticles and proteins is further introduced onto the super surface, and its trace concentration changes are further characterized by terahertz time-domain spectroscopy technology, so as to solve the related technical problems existing in traditional terahertz super surface trace biological substance detection technology.

Claims

1. A highly selective terahertz metasurface biosensor based on modified single-walled carbon nanotube film, characterized in that: From bottom to top, it is composed of a dielectric layer (2) and a single-walled carbon nanotube supersurface layer (1) etched with a periodic open resonant ring structure.

2. The highly selective terahertz supersurface biosensor based on modified single-walled carbon nanotube film according to claim 1, characterized in that: The single-walled carbon nanotube super surface layer (1) is an isotropic single-walled carbon nanotube film doped with gold nanoparticles purified by strong acid, tip ultrasound, high-speed centrifugation and heat treatment, or an anisotropic single-walled carbon nanotube film doped with gold nanoparticles purified by strong acid, tip ultrasound, high-speed centrifugation and heat treatment, and the thickness of the single-walled carbon nanotube super surface layer (1) ranges from 100 to 400 nm.

3. The highly selective terahertz supersurface biosensor based on modified single-walled carbon nanotube film according to claim 1, characterized in that: The dielectric layer (2) is a polyethylene terephthalate dielectric layer with a thickness not exceeding 15 μm.

4. The highly selective terahertz supersurface biosensor based on modified single-walled carbon nanotube film according to claim 1, characterized in that: The single-walled carbon nanotube ultra-surface layer (1) is purified by strong acid, tip ultrasound, high-speed centrifugation and heat treatment and doped with gold nanoparticles according to the following steps: Step 1, purification of single-walled carbon nanotube powder: dissolving the single-walled carbon nanotube powder in a strong acid solution at a ratio of 1:100 and stirring at a stirring speed of not less than 2000 rpm, a stirring temperature of 80-100°C, and a stirring time of not less than 30 minutes; Step 2, after the single-walled carbon nanotube concentrated sulfuric acid mixed solution uniformly stirred in step 1 is allowed to stand for stratification, the excess concentrated sulfuric acid solution in the upper layer is poured out, and the mixture is dried in a vacuum environment at a temperature not lower than 200° C., to finally obtain acid-purified single-walled carbon nanotube powder; Step 3, dissolving the single-walled carbon nanotube powder treated in step 2 in a dispersion solution at a ratio of not less than 1 wt %, wherein the dispersion solution is an aqueous solution of any one of sodium dodecyl sulfate SDS, sodium dodecylbenzene sulfonate SDBS, polyvinylpyrrolidone PVP or sodium cholate; Step 4: subjecting the single-walled carbon nanotube solution obtained in step 3 to tip ultrasound, with a power of not less than 600 W and an ultrasound time of not less than 60 min. Step 5, subjecting the single-walled carbon nanotube dispersion treated in step 4 to high-speed centrifugation, with a centrifugal speed of not less than 15000 r / m and a centrifugal time of not less than 60 min, and taking out the supernatant after centrifugation; Step 6, mixing the gold nanoparticle solution with a particle size of 20-40 nm and the purified single-walled carbon nanotube supernatant obtained in step 5 at a ratio of 1:10; Step 7, placing the mixed solution obtained in step 6 in a mixer with a rotation speed of not less than 150 r / m and mixing for not less than 30 min; Step 8: Based on the acid-modified single-walled carbon nanotube powder obtained in step 4, a single-walled carbon nanotube film with a thickness ranging from 100 to 400 nm is obtained by vacuum filtration; Step 9: annealing the single-walled carbon nanotube film obtained in step 8 in a vacuum environment at a temperature not lower than 200° C. to remove the residual dispersant.

5. The highly selective terahertz supersurface biosensor based on modified single-walled carbon nanotube film according to claim 1, characterized in that: The single-walled carbon nanotube super surface layer (1) is etched on the surface of a periodically arranged annular double-opening resonant ring structure, wherein the openings are arranged left and right and are asymmetric.

6. The highly selective terahertz supersurface biosensor based on modified single-walled carbon nanotube film according to claim 1, characterized in that: The outer radius of the annular double split resonant ring metasurface structure r 1 has a value range of 50-60µm, and the inner radius r 2 has a value range of 40µm, and the center angle θ The value range of 1 is 150-160°, corresponding to θ The value range of 2 is 130-140°, and the period of the asymmetric open-loop resonant array is p x = p y , and its value range is 90-100µm.

7. Highly selective terahertz metasurface biosensor based on modified single-walled carbon nanotube film for detection of trace biological substances on terahertz metasurface.

8. The terahertz metasurface trace biological material detection according to claim 7, characterized in that: Follow the steps below to implement it: Step a, mixing a dispersion of colloidal gold nanoparticles modified with functional groups on the surface with the protein to be tested in a ratio of 2:1, fully stirring at room temperature to allow the functionalized gold nanoparticles to undergo adsorption reaction with the protein to be tested, the reaction time being 1-2 h to ensure that the colloidal gold and the protein are fully combined; Step b, high-speed centrifugation is performed at a speed of not less than 15000 r / min for a time of not less than 45 min, and finally a colloidal gold-protein complex precipitate is obtained; Step c, taking out the supernatant of the colloidal gold-protein complex precipitation, adding phosphate buffer in a ratio of 1:1 to the supernatant, repeating step b, repeating multiple times until a relatively pure colloidal gold-protein complex is obtained for testing; Step d, combining the super surface sensor with the polydimethylsiloxane PDMS microfluidic channel, the combination from top to bottom includes a PDMS layer with a liquid inlet and a liquid outlet, a sample area channel with a height of not less than 50um and a 1:1 ratio with the surface area of ​​the super surface, a super surface sensor chip layer, and a fixed layer at the bottom; Step e, passing the colloidal gold nanoparticle dispersion that is not bound to the protein to be tested into the surface of the metasurface sensor in a ratio of 1:1 to the volume of the microfluidic channel, and using a transmission terahertz time-domain spectroscopy system to collect the transmission signal of the metasurface sensor loaded with the test object, and defining the transmission signal as 0 fM; Step f, cleaning the metasurface sensor with physiological saline after signal acquisition; Step g, respectively passing the functionalized colloidal gold nanoparticle-protein complex solution specifically bound by the cross-linking reaction to the transmission signal 0.3 fM, 0.6 fM, 1 fM, 1.5 fM, 2.2 fM, and 2.5 fM to the surface of the supersurface sensor combined with the microfluidic channel, and collecting the transmission signal of the single-walled carbon nanotube terahertz supersurface sensor coated with the functionalized colloidal gold nanoparticle-protein complex by using a transmission terahertz time-domain spectroscopy system; Step f: using the transmission signal of the metasurface loaded with functionalized colloidal gold nanoparticles collected in step e as a reference, data processing and analysis are performed on the detected terahertz signal of the colloidal gold-protein complex solution to extract characteristic information of the target substance and determine the presence and concentration of the protein to be tested.

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