Dual-band sensor for terahertz molecular fingerprint detection of mixed substance

Abstract

The invention relates to a dual-band sensor for terahertz molecular fingerprint detection of a mixed substance, which is formed by arranging a plurality of molecular fingerprint sensing pixels with different structural parameters, each molecular fingerprint sensing pixel is formed by a plurality of double-cross aperture unit arrays, the sizes of the double-cross aperture units in different molecular fingerprint sensing pixels are different, and the sizes of the double-cross aperture units in different molecular fingerprint sensing pixels are different. And each double-cross aperture unit consists of two cross aperture unit structures with different arm lengths. According to the dual-band sensor, a wider detection range is covered and the number of sensing pixels is reduced through a dual-band simultaneous scanning method, meanwhile, the detection capability of the sensor on trace analytes is enhanced by using surface plasmon polaritons, and it is guaranteed that broadband signals of the detected objects are remarkably enhanced.

Description

Technical Field

[0001] The invention belongs to the technical field of terahertz molecular fingerprint sensing, and in particular relates to a dual-band sensor for terahertz molecular fingerprint detection of mixed substances. Background Art

[0002] Terahertz spectroscopy shows a wide range of application potential in the fields of biosensing and trace substance detection by analyzing the specific absorption peaks of biochemical molecules in the broadband terahertz region. However, the use of terahertz spectroscopy to measure analytes usually requires drying them into powdered samples and then pressing them into solid granular tablets, which often weigh hundreds of milligrams. This process significantly increases the detection cost and is not suitable for the detection of trace analytes, which in turn limits its practical application in the efficient detection of molecular fingerprints.

[0003] In recent years, terahertz molecular fingerprint sensing technology with multiplexing of geometric structure parameters has gained favor in the field of trace analyte detection. By introducing a multiplexing strategy in the metasurface structure, a continuous and wide terahertz spectral band can be obtained. This spectral band can cover the wide resonant absorption band of the analyte, thereby realizing the fingerprint detection of the analyte. Although this strategy of achieving multiplexing by changing the geometric structure shows innovative potential, it requires the preparation of a large number of independent meta-pixels, which may range from dozens to hundreds. This requirement inevitably leads to time-consuming preparation stages before detection and the actual detection process, limiting its practical application in the efficient detection of molecular fingerprints. Summary of the invention

[0004] The purpose of the present invention is to provide a dual-band sensor for terahertz molecular fingerprint detection of mixed substances. The dual-band sensor covers a wider detection range and reduces the number of sensing pixels through a dual-frequency simultaneous scanning method, and at the same time utilizes surface plasmon polaritons to enhance the sensor's detection ability for trace analytes, thereby ensuring that the broadband signal of the detected object is significantly enhanced.

[0005] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a dual-band sensor for terahertz molecular fingerprint detection of mixed substances, which is composed of a plurality of molecular fingerprint sensing pixels with different structural parameters, each molecular fingerprint sensing pixel is composed of a plurality of double cross aperture unit arrays, the double cross aperture units in different molecular fingerprint sensing pixels have different sizes, and each double cross aperture unit is composed of two cross aperture unit structures with different arm lengths.

[0006] Furthermore, in the two cross-aperture unit structures with different arm lengths, the low-frequency transmission spectrum is excited by the cross-aperture unit structure with the larger arm length, and the high-frequency transmission spectrum is excited by the cross-aperture unit structure with the smaller arm length.

[0007] Furthermore, the cross-aperture unit structure is used as a carrier to excite surface plasmon resonance; the cross-aperture unit structure is a femtosecond laser technology with a conductivity of 3.56×10 7 The femtosecond laser used has a pulse width of 45fs, a wavelength of 800nm ​​and a repetition frequency of 1kHz.

[0008] Furthermore, the dual-band sensor is composed of 27 molecular fingerprint sensing pixels, the length P of the double cross aperture unit in the first molecular fingerprint sensing pixel is 217 μm, the length P of the double cross aperture unit in the second molecular fingerprint sensing pixel is 219 μm, and they increase successively in steps of 2 μm until the length P of the double cross aperture unit in the 27th molecular fingerprint sensing pixel is 269 μm.

[0009] Furthermore, the length of the double cross-aperture unit is P, and the width is P / 2, wherein the arm width of the aperture of a single cross-aperture unit structure is W=30μm, the thickness h=10μm, the arm length of the cross-aperture unit structure with a larger arm length is L1, and the spacing between it and the side of the double cross-aperture unit is d1=10μm, and the arm length of the cross-aperture unit structure with a smaller arm length is L2, and the spacing between it and the side of the double cross-aperture unit is d2=20μm, wherein L1=P / 2-2d1, L2=P / 2-2d2.

[0010] Furthermore, the dual-band sensor is used as a carrier for placing trace mixed substances; the mixed substances are lactose and glucose.

[0011] Furthermore, the dual-band sensor uses the localized surface plasmon mode generated by the double cross-aperture unit to localize the electric field at the tip of the cross-aperture to expand the interaction volume between the electric field and the analyte; the terahertz wave generates two wide transmission spectra by gradually scanning each molecular fingerprint sensing pixel, and the two transmission spectra are enveloped to form two wide envelope lines, the first broadband envelope curve covers the resonance absorption band of lactose, and the second broadband envelope curve covers the resonance absorption band of glucose, thereby realizing fingerprint detection of mixed substances.

[0012] Furthermore, the complex refractive index formula of lactose and glucose is:

[0013]

[0014] Among them, ε r is the dielectric constant, ε ∞ is the non-resonant background dielectric constant, ε p is the oscillation intensity factor, γ p is the decay rate of the absorption resonance, n is the refractive index, k is the extinction coefficient, and the angular frequency ω of lactose and glucose pThey are 1.37THz and 1.81THz respectively; therefore, lactose molecules and glucose molecules have an absorption peak at 1.37THz and 1.81THz respectively.

[0015] Furthermore, the absorbance enhancement factor of the lactose film analyte on the dual-band sensor in the wide frequency band of 1.28THz to 1.52THz is greater than 6.3dB; the absorbance enhancement factor of the glucose film analyte on the dual-band sensor in the wide frequency band of 1.53THz to 1.89THz is greater than 6.74dB.

[0016] Furthermore, the calculation formula of the absorbance enhancement factor is:

[0017]

[0018] Among them, A(f) and A Meta (f) shows the frequency-dependent absorbance of lactose on the fingerprint sensor and metal substrate, respectively, and f1 and f2 represent the starting and ending points of the frequency interval, respectively.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) The dual-band sensor for terahertz molecular fingerprint detection of mixed substances provided by the present invention benefits from the localized surface plasmon polaritons (LSPP) mode generated by the cross-aperture structure of the metal metamaterial, which localizes the electric field in the narrow space at the aperture tip, significantly expanding the interaction volume between the electric field and the analyte.

[0021] (2) Compared with the traditional geometric structure parameter multiplexing sensor, the dual-band sensor for terahertz molecular fingerprint detection of mixed substances provided by the present invention generates two envelope curves by means of a cross-aperture structure of different sizes, and has a wider molecular fingerprint detection range.

[0022] (3) The dual-band sensor for terahertz molecular fingerprint detection of mixed substances provided by the present invention has a wide detection range thanks to the geometric structure parameter multiplexing strategy. The detection signal intensity of the lactose film analyte at 1.37 THz is enhanced by about 25 times compared with the sensing method of direct detection on the metal substrate, and the absorbance enhancement factor in the wide frequency band of 1.28 THz to 1.52 THz is greater than 6.3 dB; the detection signal intensity of the glucose film analyte at 1.81 THz is enhanced by about 12.5 times, and the absorbance enhancement factor in the wide frequency band of 1.53 THz to 1.89 THz is greater than 6.74 dB, and the broadband signal is significantly enhanced. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a schematic diagram of a dual-band sensor in an embodiment of the present invention;

[0024] Figure 2 Schematic diagram of the structure of a molecular fingerprint sensor pixel in an embodiment of the present invention;

[0025] Figure 3 Schematic diagram of the electric field of a double cross aperture unit in an embodiment of the present invention;

[0026] Figure 4 It is a detection principle diagram of an embodiment of the present invention;

[0027] Figure 5 1 is a comparison diagram of the absorbance spectra of lactose and glucose in an embodiment of the present invention;

[0028] Figure 6 is the absorbance enhancement factor of the lactose broadband in the embodiment of the present invention;

[0029] Figure 7 is the absorbance enhancement factor of the glucose broadband in the embodiment of the present invention.

[0030] In the figure: 1-dual-band sensor; 2-molecular fingerprint sensing pixel; 3-cross aperture unit structure with larger arm length; 4-cross aperture unit structure with smaller arm length; 5-lactose film; 6-glucose film. DETAILED DESCRIPTION

[0031] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0032] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0033] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0034] like Figure 1-2As shown, this embodiment provides a dual-band sensor for terahertz molecular fingerprint detection of mixed substances, wherein the dual-band sensor 1 is composed of a plurality of molecular fingerprint sensing pixels (Molecular fingerprint sensing pixels, MFSP) 2 with different structural parameters, each molecular fingerprint sensing pixel 2 is composed of a plurality of double cross aperture unit arrays, the double cross aperture unit sizes in different molecular fingerprint sensing pixels are different, but the double cross aperture unit sizes in the same molecular fingerprint sensing pixel are the same, and each double cross aperture unit is composed of two cross aperture unit structures with different arm lengths.

[0035] In the two cross-aperture unit structures with different arm lengths, the cross-aperture unit structure 3 with a larger arm length generates a low-frequency transmission spectrum, and the cross-aperture unit structure 4 with a smaller arm length generates a high-frequency transmission spectrum. The dual-band sensor is used as a carrier for placing trace mixed substances. The mixed substances are lactose and glucose. After covering the analyte, the low-frequency band detects the molecular fingerprint of lactose, and the high-frequency band detects the molecular fingerprint of glucose.

[0036] The cross-aperture unit structure is used as a carrier to excite surface plasmon resonance. The cross-aperture unit structure is a device that uses femtosecond laser technology to generate a 3.56×10 7 In this embodiment, the femtosecond laser pulse width is 45fs, the wavelength is 800nm, and the repetition frequency is 1kHz.

[0037] In this embodiment, the dual-band sensor is composed of 27 molecular fingerprint sensing pixels, the length P of the double cross aperture unit in the first molecular fingerprint sensing pixel is 217 μm, the length P of the double cross aperture unit in the second molecular fingerprint sensing pixel is 219 μm, and they increase in steps of 2 μm until the length P of the double cross aperture unit in the 27th molecular fingerprint sensing pixel is 269 μm.

[0038] The length of the double cross aperture unit is P, and the width is P / 2, wherein the arm width of the aperture of a single cross aperture unit structure is W=30μm, the thickness is h=10μm, the arm length of the cross aperture unit structure with a larger arm length is L1, and the spacing between it and the side of the double cross aperture unit is d1=10μm, and the arm length of the cross aperture unit structure with a smaller arm length is L2, and the spacing between it and the side of the double cross aperture unit is d2=20μm, wherein L1=P / 2–2d1, L2=P / 2–2d2.

[0039] The dual-band sensor uses the localized surface plasmon (LSPP) mode generated by the cross-aperture metal metamaterial (i.e., the dual cross-aperture unit) to localize the electric field at the cusp of the cross-aperture, significantly expanding the interaction volume between the electric field and the analyte, thereby achieving a significant enhancement of the molecular fingerprint broadband signal. The terahertz wave can generate two wide transmission spectra by gradually scanning 27 molecular fingerprint sensing pixels, and the two transmission spectra are enveloped to form two wide envelopes. The first broadband envelope curve covers the resonance absorption band of lactose, and the second broadband envelope curve covers the resonance absorption band of glucose, such as Figure 1 As shown, fingerprint detection of mixed substances is achieved. Therefore, a wide-band detection range of 0.6 THz is achieved, achieving the effect of significantly enhancing the molecular fingerprint broadband signal.

[0040] The complex refractive index formula of lactose and glucose is:

[0041]

[0042] Among them, ε r is the dielectric constant, ε ∞ is the non-resonant background dielectric constant, ε p is the oscillation intensity factor, γ p is the decay rate of the absorption resonance, n is the refractive index, k is the extinction coefficient, and the angular frequency ω of lactose and glucose p They are 1.37THz and 1.81THz respectively; therefore, lactose molecules and glucose molecules have an obvious absorption peak at 1.37THz and 1.81THz respectively.

[0043] like Figure 3 The electric field diagram shown in FIG. 1 illustrates that the low-frequency resonance is excited by the cross-aperture unit structure 3 with a larger arm length, and the high-frequency resonance is excited by the cross-aperture unit structure 4 with a smaller arm length. Figure 4 As shown, the lactose analyte layer 5 and the glucose analyte layer 6 are coated on the sensor surface, and the absorption peak of the mixture is detected by scanning the sensing pixels. Comparing the difference between the transmission spectrum before and after covering the analyte film, the maximum absorption rate of the lactose film analyte at 1.37 THz is 21%, and the maximum absorption rate of the glucose film analyte at 1.81 THz is 13%, which is enhanced by about 25 times and about 12.5 times respectively compared with the reference absorption spectrum of the sample directly detected on the metal substrate. Figure 5 shown.

[0044] In order to better quantify the broadband sensing enhancement performance, we defined the absorbance enhancement factor, which is calculated as:

[0045]

[0046] Among them, A(f) and A Meta(f) shows the frequency-dependent absorbance of lactose on the fingerprint sensor and metal substrate, respectively, and f1 and f2 represent the starting and ending points of the frequency interval, respectively.

[0047] The performance test results of this embodiment are as follows Figure 6 , 7 As shown, it can be seen from the wide-band absorbance enhancement factor obtained by simulation calculation that the absorbance enhancement factor of the lactose film in the wide frequency band of 1.28THz to 1.52THz is greater than 6.3dB, and the enhancement factor at 1.37THz reaches a maximum of 13.8dB; the absorbance enhancement factor of the glucose film in the range of 1.53THz to 1.89THz is greater than 6.74dB, and the enhancement factor at 1.81THz reaches a maximum of 10.9dB. These all confirm that the sensor can clearly observe the molecular fingerprint of the analyte. In addition, with the help of the dual-band detection strategy, the number of scans is reduced and the efficiency of molecular fingerprint detection is improved. Therefore, the dual-band sensor for terahertz molecular fingerprint detection of mixed substances provided by the present invention shows extraordinary application potential in the field of non-destructive sensing of trace mixing.

[0048] The above is only a preferred embodiment of the present invention, and does not limit the present invention in other forms. Any technician familiar with the profession may use the above disclosed technical content to change or modify it into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention still belongs to the protection scope of the technical solution of the present invention.

Claims

1. A dual-band sensor for terahertz molecular fingerprint detection of mixed substances, characterized in that: It is composed of a plurality of molecular fingerprint sensing pixels with different structural parameters. Each molecular fingerprint sensing pixel is composed of a plurality of double cross aperture unit arrays. The sizes of the double cross aperture units in different molecular fingerprint sensing pixels are different. Each double cross aperture unit is composed of two cross aperture unit structures with different arm lengths.

2. A dual-band sensor for terahertz molecular fingerprint detection of mixed substances according to claim 1, characterized in that: In the two cross-aperture unit structures with different arm lengths, the low-frequency transmission spectrum is excited by the cross-aperture unit structure with the larger arm length, and the high-frequency transmission spectrum is excited by the cross-aperture unit structure with the smaller arm length.

3. The dual-band sensor for terahertz molecular fingerprint detection of mixed substances according to claim 1, characterized in that: The cross aperture unit structure is used as a carrier to excite surface plasmon resonance; the cross aperture unit structure is a femtosecond laser technology in which the conductivity is 3.56×10 7 The femtosecond laser used has a pulse width of 45fs, a wavelength of 800nm ​​and a repetition frequency of 1kHz.

4. The dual-band sensor for terahertz molecular fingerprint detection of mixed substances according to claim 1, characterized in that: The dual-band sensor is composed of 27 molecular fingerprint sensing pixels, the length P of the double cross aperture unit in the first molecular fingerprint sensing pixel is 217 μm, the length P of the double cross aperture unit in the second molecular fingerprint sensing pixel is 219 μm, and they increase in sequence with a step size of 2 μm until the length P of the double cross aperture unit in the 27th molecular fingerprint sensing pixel is 269 μm.

5. The dual-band sensor for terahertz molecular fingerprint detection of mixed substances according to claim 4, characterized in that: The length of the double cross aperture unit is P, and the width is P / 2, wherein the arm width of the aperture of a single cross aperture unit structure is W=30μm, the thickness is h=10μm, the arm length of the cross aperture unit structure with a larger arm length is L1, and the spacing between it and the side of the double cross aperture unit is d1=10μm, and the arm length of the cross aperture unit structure with a smaller arm length is L2, and the spacing between it and the side of the double cross aperture unit is d2=20μm, wherein L1=P / 2–2d1, L2=P / 2–2d2.

6. The dual-band sensor for terahertz molecular fingerprint detection of mixed substances according to claim 1, characterized in that: The dual-band sensor is used as a carrier for placing trace mixed substances; the mixed substances are lactose and glucose.

7. A dual-band sensor for terahertz molecular fingerprint detection of mixed substances according to claim 6, characterized in that: The dual-band sensor uses the localized surface plasmon mode generated by the dual cross-aperture unit to localize the electric field at the sharp point of the cross-aperture to expand the interaction volume between the electric field and the analyte; the terahertz wave gradually scans each molecular fingerprint sensing pixel to generate two wide transmission spectra, and the two transmission spectra are enveloped to form two wide envelope lines. The first broadband envelope curve covers the resonance absorption band of lactose, and the second broadband envelope curve covers the resonance absorption band of glucose, thereby realizing fingerprint detection of mixed substances.

8. The dual-band sensor for terahertz molecular fingerprint detection of mixed substances according to claim 7, characterized in that: The complex refractive index formula of lactose and glucose is: Among them, ε r is the dielectric constant, ε ∞ is the non-resonant background dielectric constant, ∈ p is the oscillation intensity factor, γ p is the decay rate of the absorption resonance, n is the refractive index, k is the extinction coefficient, and the angular frequency ω of lactose and glucose p They are 1.37THz and 1.81THz respectively; therefore, lactose molecules and glucose molecules have an absorption peak at 1.37THz and 1.81THz respectively.

9. The dual-band sensor for terahertz molecular fingerprint detection of mixed substances according to claim 7, characterized in that: The absorbance enhancement factor of the lactose film analyte on the dual-band sensor in the wide frequency band of 1.28THz to 1.52THz is greater than 6.3dB; the absorbance enhancement factor of the glucose film analyte on the dual-band sensor in the wide frequency band of 1.53THz to 1.89THz is greater than 6.74dB.

10. The dual-band sensor for terahertz molecular fingerprint detection of mixed substances according to claim 9, characterized in that: The calculation formula of the absorbance enhancement factor is: Among them, A(f) and A Meta (f) shows the frequency-dependent absorbance of lactose on the fingerprint sensor and metal substrate, respectively, and f1 and f2 represent the starting and ending points of the frequency interval, respectively.

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