Double-frequency single-walled carbon nanotube terahertz metasurface biosensor with high sensing performance

Abstract

The invention discloses a double-frequency single-walled carbon nanotube terahertz metasurface biosensor with high sensing performance, which is composed of two parts, the biosensor comprises an upper carbon nanotube resonator layer and a lower substrate, the resonator layer is composed of double-ring unit structures arranged in a periodic array, all the double-ring unit structures are the same, and the upper substrate and the lower substrate are arranged in parallel. Each unit structure is composed of two circular rings with the middle portions overlapped with each other, and the middles of the two circular rings are communicated. The terahertz metasurface sensor with high sensitivity is realized by combining the excellent photoelectric characteristics of the carbon nanotubes.

Description

Technical Field

[0001] The present invention belongs to the technical field of terahertz supersurfaces, and in particular relates to a single-walled carbon nanotube terahertz supersurface biosensor with dual-frequency high sensing performance. Background Art

[0002] Terahertz (THz) waves refer to electromagnetic waves with a frequency range of 0.1 to 10 THz. They have the characteristics of strong penetration, non-ionization, and non-destructiveness, and have wide application value in biomedicine, non-destructive testing and other fields. In addition, since the vibration frequencies of most important biomolecules fall within the THz range, THz spectroscopy has developed into a non-contact, label-free, and non-destructive method for studying chemical and biological substances. However, in THz trace substance sensing, the size of the sample is much smaller than the wavelength, which makes it difficult to detect trace samples below the microgram scale directly using THz time-domain spectroscopy. In recent years, researchers have effectively enhanced the interaction between THz waves and trace samples by using THz metasurfaces with strong local electromagnetic field enhancement effects as a sensor device. However, due to the inherent metal loss and corrosion of traditional THz metasurface biosensors designed based on metal materials, they usually generate large background noise during the detection of trace biochemical substances, which affects the sensitivity and repeatability of the detection. Carbon nanotubes are one-dimensional materials with unique structural properties, high electrical conductivity, thermal conductivity, and easy processing. Due to their excellent optoelectronic properties, carbon nanotubes have application prospects in various fields such as nanotechnology, environmental sensing, and biochemistry, making them a strong candidate for the next generation of optoelectronic materials. The emergence of carbon nanotubes provides a new option for the further development of new terahertz metasurfaces. Summary of the invention The purpose of the present invention is to provide a single-walled carbon nanotube terahertz supersurface biosensor with dual-frequency high sensing performance, combining the excellent optoelectronic properties of carbon nanotubes to realize a high-sensitivity terahertz supersurface sensor.

[0003] The technical solution adopted by the present invention is a single-walled carbon nanotube terahertz supersurface biosensor with dual-frequency and high sensing performance, which consists of two parts, including an upper carbon nanotube resonator layer and a lower substrate. The resonator layer is composed of a unit structure of double circular rings arranged in a periodic array. The unit structures of all double circular rings are the same. Each unit structure is composed of two circular rings whose middle parts overlap each other, and the two circular rings are connected in the middle.

[0004] The present invention is also characterized in that: One of the two circular rings of the unit structure is provided with an opening, and the opening and the overlapping parts between the two circular rings are on a straight line.

[0005] The opening directions of the circular rings of the unit structure are all consistent.

[0006] The value range of the opening length 2R of the overlapping part between the two rings is 15-25 um. The thickness H of the carbon nanotube resonator layer ranges from 1 to 5 um, and the thickness H0 of the substrate ranges from 25 to 35 um.

[0007] The periods of the unit structure of the carbon nanotube resonator layer along the X and Y directions are P and x =P y =100um, the outer diameter of the large ring is R2=26um, the inner diameter is R1=14um, the opening length of the overlapping part of the ring is 2R=20um, and the opening line width is B=10um.

[0008] The beneficial effect of the present invention is that the dual-frequency high-sensing performance single-walled carbon nanotube terahertz metasurface biosensor is composed of a single-walled carbon nanotube film and polyimide, has a simple structure, is easy to process, is easy to prepare, and achieves high-performance sensing through a simple structure. Generally, sensitivity (S) and quality factor (FOM) are key parameters for evaluating the sensing performance of terahertz metamaterial sensors. The refractive index sensitivity (S) reflects the resonant frequency shift (∆ f ) and the refractive index change (∆ n ), FOM is defined as the ratio of sensing sensitivity to the full width at half maximum (FWHM) of the resonance peak. The terahertz metasurface designed by the present invention produces two strong resonance peaks within 0-2THz, with high sensing sensitivity and ultra-high quality factor (FOM). The resonance frequencies are 0.586THz and 1.68THz, respectively. The sensitivities of these two resonance peaks to the refractive index of the analyte are 184GHz / RIU and 508GHz / RIU, respectively, and the quality factors are 6.34 and 10.8, respectively. At the same time, the analyte thickness reaches the saturation thickness at 22um, which shows that the terahertz metasurface sensor designed by the present invention can have high sensing sensitivity and quality factor on the basis of realizing trace detection, effectively solving the challenges brought by the current ultra-high sensing sensitivity to practical applications. In addition, the metasurface effectively solves the difficulties of traditional metal-based metasurface sensors such as large metal loss and easy corrosion, and the detection accuracy and sensitivity of the device are further improved, so that it has the advantages of high sensitivity, high accuracy and specific detection in the practical application of trace biological material sensing detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 is a schematic diagram of an array of the present invention; Figure 2 It is a schematic diagram of the unit structure of the present invention; Figure 3The relationship between the resonance peak at 0.5 THz and the refractive index of a dual-frequency ultra-high-sensitivity single-walled carbon nanotube terahertz super-surface sensor of the present invention after covering analytes with different refractive indices; Figure 4 The relationship between the resonance peak at 1.3 THz and the refractive index of a dual-frequency ultra-high-sensitivity single-walled carbon nanotube terahertz super-surface sensor of the present invention after covering analytes with different refractive indices; Figure 5 A schematic diagram showing how the sensitivity of the present invention varies with the thickness of the analyte when detecting different analytes; Figure 6 The present invention discloses a dual-frequency ultra-high-sensitivity single-walled carbon nanotube terahertz ultra-sensitivity sensor, and shows a relationship between the quality factor under different analyte thicknesses.

[0010] In the figure, 1. resonator layer, 2. substrate. DETAILED DESCRIPTION

[0011] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0012] The single-walled carbon nanotube terahertz supersurface biosensor with dual-frequency high sensing performance of the present invention has a structure as follows Figure 1 As shown, it consists of two parts, including an upper carbon nanotube resonator layer 1 and a lower substrate 2. The resonator layer 1 is composed of a unit structure of double rings arranged in a periodic array. The unit structures of all double rings are the same. Each unit structure is composed of two rings whose middle parts overlap each other, and the two rings are connected in the middle.

[0013] One of the two circular rings of the unit structure is provided with an opening, and the opening and the overlapping parts between the two circular rings are on a straight line.

[0014] The opening directions of the circular rings of the unit structure are all consistent.

[0015] The value range of the opening length 2R of the overlapping part between the two rings is 15-25 um. The thickness H of the carbon nanotube resonator layer 1 is in the range of 1-5 um, and the thickness H0 of the substrate 2 is in the range of 25-35 um.

[0016] The periods of the unit structure of the carbon nanotube resonator layer 1 along the X direction and the Y direction are P and x =P y =100um, the outer diameter of the large ring is R2=26um, the inner diameter is R1=14um, the opening length of the overlapping part of the ring is 2R=20um, and the opening line width is B=10um.

[0017] The present invention introduces a combination of coupled resonators of various configurations through a simple manufacturing method, and can realize no less than 2 narrow-band strong resonance peaks with high sensing sensitivity in the range of 0-2 terahertz, and the two resonance peaks have a high quality factor. Since carbon nanotubes have excellent photoelectric properties and superior mechanical properties, carbon nanotube films can be bent any number of times without affecting their own performance. In addition, carbon nanotubes can also achieve the adjustment of the Fermi level. By doping carbon nanotubes, carbon nanotubes can be converted from P type to N type, thereby realizing a PN junction; then the Fermi level of the carbon nanotubes is adjusted by changing the concentration of the doping solution. These are all characteristics that metal materials do not have. The present invention proposes a new and feasible extension for the research in the field of terahertz metasurface sensing.

[0018] Example 1 The single-walled carbon nanotube terahertz supersurface biosensor with dual-frequency high sensing performance of the present invention has a structure as follows Figure 1 As shown, it is composed of two parts, including an upper carbon nanotube resonator layer 1 and a lower substrate 2. The resonator layer 1 is composed of a unit structure of double rings arranged in a periodic array. The unit structures of all double rings are the same. Each unit structure is composed of two rings with overlapping middle parts, and the two rings are connected in the middle. The choice of substrate layer 2 includes but is not limited to air, polyimide, polyethylene terephthalate, quartz, silicon, etc.

[0019] Example 2 The single-walled carbon nanotube terahertz supersurface biosensor with dual-frequency high sensing performance of the present invention has a structure as follows Figure 1 As shown, it consists of two parts, including an upper carbon nanotube resonator layer 1 and a lower substrate 2. The resonator layer 1 is composed of a unit structure of double rings arranged in a periodic array. The unit structures of all double rings are the same. Each unit structure is composed of two rings whose middle parts overlap each other, and the two rings are connected in the middle.

[0020] One of the two circular rings of the unit structure is provided with an opening, and the opening and the overlapping parts between the two circular rings are on a straight line.

[0021] The opening directions of the circular rings of the unit structure are all consistent.

[0022] The value range of the opening length 2R of the overlapping part between the two rings is 15-25 um. Example 3 like Figure 1 The schematic diagram of the array structure of the present invention is shown in the figure. As shown in the figure, the super surface sensor is 30 um It is composed of polyimide and 5um single-walled carbon nanotube film.

[0023] like Figure 2 The schematic diagram of the unit structure of the present invention is shown, which is composed of two circular rings, the middle parts overlap each other, and the annular hollow area and the rectangle subtracted from the right circular ring are obtained by Boolean operation. This design can achieve two resonance enhancements at different frequencies. The period of the metasurface along the X direction and the Y direction are P respectively. x =P y =100um, the outer diameter of the large ring is R2=26um, the inner diameter is R1=14um, and the opening length of the overlapping part of the ring is 2R=20um. The crack line width on the right side of the structure is B=10um.

[0024] like Figure 3 , 4 The figure shows the degree of shift of the resonance frequency when the present invention detects different analytes. It can be seen from the figure that as the refractive index of the analyte increases, the resonance frequency of the resonance peak red shifts, and the degree of shift can reflect the sensitivity. The sensitivity calculation formula is: ,in S represents the sensitivity to the refractive index of the analyte, represents the formant frequency shift, Represents the change in the refractive index of the analyte. Through the calculation formula, it can be obtained that the metasurface sensor proposed in the present invention has a high sensing sensitivity to the refractive index of the analyte, and the sensing sensitivities are 184 GHz / RIU and 508 GHz / RIU at the resonant frequencies of 0.586 THz and 1.68 THz, respectively.

[0025] like Figure 5 The figure shows the relationship between the sensing sensitivity of the present invention to the analyte and the thickness of the analyte. Increasing the thickness of the analyte can improve the sensing sensitivity of the metasurface device. When the analyte thickness is 22um, the sensitivity region is saturated. At this time, it is the saturation thickness, and the metasurface has the highest sensing sensitivity. This shows that the present invention can achieve trace detection.

[0026] like Figure 6 The figure shows the study of the resonance peak quality factor of the present invention, where the analyte thickness increases from 2um to 26um with a step length of 4um; the quality factor of the first resonance peak is 6.34, and the quality factor of the second resonance peak is 10.8.

[0027] The single-walled carbon nanotube terahertz metasurface biosensor with dual-frequency high sensing performance can achieve a strong local electromagnetic field enhancement effect in the terahertz band by designing and processing a periodic array structure on the surface of the single-walled carbon nanotube film, and then can highly sensitively identify the tiny disturbance introduced into the trace sample through the terahertz spectrum signal. On the other hand, due to the strong modifiability and biocompatibility of the carbon nanotube film itself, the proposed high-sensitivity terahertz metasurface sensor device based on the single-walled carbon nanotube film can be specifically modified and modified by antigens and antibodies, thereby achieving highly sensitive and specific detection of trace biological samples.

Claims

1. Single-walled carbon nanotube terahertz supersurface biosensor with dual-frequency high sensing performance, characterized in that: The invention is composed of two parts, including an upper carbon nanotube resonator layer (1) and a lower substrate (2). The resonator layer (1) is composed of a unit structure of double circular rings arranged in a periodic array. The unit structures of all double circular rings are the same. Each unit structure is composed of two circular rings whose middle parts overlap each other, and the two circular rings are connected in the middle.

2. The dual-frequency high-sensing performance single-walled carbon nanotube terahertz supersurface biosensor according to claim 1 is characterized in that: One of the two circular rings of the unit structure is provided with an opening, and the opening and the overlapping parts between the two circular rings are on a straight line.

3. The dual-frequency high-sensing performance single-walled carbon nanotube terahertz supersurface biosensor according to claim 2 is characterized in that: The opening directions of the circular rings of the unit structure are all consistent.

4. The dual-frequency high-sensing performance single-walled carbon nanotube terahertz supersurface biosensor according to claim 2 is characterized in that: The value range of the opening length 2R of the overlapping part between the two rings is 15-25 um.

5. The dual-frequency high-sensing performance single-walled carbon nanotube terahertz supersurface biosensor according to claim 1, characterized in that: The thickness H of the carbon nanotube resonator layer (1) is in the range of 1-5 um, and the thickness H0 of the substrate 2 is in the range of 25-35 um.

6. The dual-frequency high-sensing performance single-walled carbon nanotube terahertz supersurface biosensor according to claim 1, characterized in that: The periods of the unit structure of the carbon nanotube resonator layer (1) along the X direction and the Y direction are P and x =P y =100um, the outer diameter of the large ring is R2=26um, the inner diameter is R1=14um, the opening length of the overlapping part of the ring is 2R=20um, and the opening line width is B=10um.

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