A dual-band sensor for terahertz molecular fingerprint detection of mixed substances

Abstract

The present application relates to a kind of dual-band sensor for mixed substance terahertz molecular fingerprint detection, 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 dual-cross aperture unit arrays, the size of dual-cross aperture unit in different molecular fingerprint sensing pixels is different, and each dual-cross aperture unit is composed of two cross aperture unit structures with different arm lengths.The dual-band sensor covers a wider detection range and reduces the number of sensing pixels by using the method of dual-frequency simultaneous scanning, and at the same time, the detection ability of the sensor to trace analysis is enhanced by using surface plasmon polariton, which ensures the significant enhancement of broadband signal of the detected substance.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of terahertz molecular fingerprint sensing, and particularly relates to a dual-band sensor for terahertz molecular fingerprint detection of mixed substances. BACKGROUND

[0002] Terahertz spectroscopy has shown great potential in the field of biosensing and trace substance detection by analyzing the specific absorption peaks of biochemical molecules in the wide frequency terahertz region. However, the use of terahertz spectroscopy for analyte measurement usually requires the analyte to be first dried into a powder sample and then pressed into a solid granular tablet, which often weighs up to several hundred milligrams. This process significantly increases the cost of detection and is not suitable for the detection of trace analytes, thereby limiting its practical application in efficient molecular fingerprint detection.

[0003] In recent years, terahertz molecular fingerprint sensing technology with geometric structure parameter multiplexing has received attention in the field of trace analyte detection. By introducing a multiplexing strategy in the super surface structure, a continuous and relatively wide terahertz spectral band can be obtained. This spectral band can cover the wide resonance absorption band of the analyte, thereby achieving fingerprint detection of the analyte. Although this strategy of changing the geometry to achieve multiplexing shows innovative potential, it requires the preparation of a large number of independent meta-pixels, which can range from tens to hundreds. This requirement inevitably leads to a time-consuming preparation stage before detection and actual detection process, limiting its practical application in efficient molecular fingerprint detection. SUMMARY

[0004] The present application aims to provide a dual-band sensor for terahertz molecular fingerprint detection of mixed substances, which covers a wider detection range and reduces the number of sensing pixels by using a dual-frequency simultaneous scanning method, and simultaneously enhances the detection ability of the sensor for trace analytes using surface plasmon polaritons, thereby significantly enhancing the broadband signal of the detected substance.

[0005] To achieve the above-mentioned purpose, the technical solution adopted by the present application is as follows: 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 structure parameters, each molecular fingerprint sensing pixel is composed of a plurality of dual-cross aperture unit arrays, the dual-cross aperture unit size in different molecular fingerprint sensing pixels is different, and each dual-cross aperture unit is composed of two cross aperture unit structures with different arm lengths.

[0006] Further, 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 a larger arm length, and the high-frequency transmission spectrum is excited by the cross aperture unit structure with a 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 device that uses femtosecond laser technology to generate a 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 the length increases 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 = 30 μm, the thickness h = 10 μm, 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 = 10 μm, 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 = 20 μm, 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 dual cross-aperture unit to localize the electric field at the cusp 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 enveloping 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 thin 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 thin 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) represents 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 enhancement is significant. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of a dual-band sensor according to an embodiment of the present invention;

[0024] Figure 2 Structure diagram of molecular fingerprint sensing pixel in the embodiment of the present application;

[0025] Figure 3 Electric field diagram of double cross aperture unit in the embodiment of the present application;

[0026] Figure 4 Detection principle diagram of the embodiment of the present application;

[0027] Figure 5 Absorption rate spectrum comparison diagram of lactose and glucose in the embodiment of the present application;

[0028] Figure 6 Absorbance enhancement factor of lactose wideband in the embodiment of the present application;

[0029] Figure 7 Absorbance enhancement factor of glucose wideband in the embodiment of the present application.

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

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

[0032] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs.

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

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

[0035] Among 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 for exciting surface plasmon resonance. The cross aperture unit structure is formed on an aluminum foil with a conductivity of 3.56×10 7 S / m by using femtosecond laser technology. In this embodiment, the femtosecond laser pulse width used is 45 fs, the wavelength is 800 nm, and the repetition frequency is 1 kHz.

[0037] In this embodiment, the dual-band sensor is composed of 27 molecular fingerprint sensing pixels, the length P of the dual-cross aperture unit in the 1st molecular fingerprint sensing pixel is 217 μm, the length P of the dual-cross aperture unit in the 2nd molecular fingerprint sensing pixel is 219 μm, and the length P of the dual-cross aperture unit in the 27th molecular fingerprint sensing pixel is 269 μm, which is increased by a step of 2 μm.

[0038] The length of the dual-cross aperture unit is P, and the width is P / 2, wherein the arm width W of the aperture of a single cross aperture unit structure is 30 μm, the thickness h is 10 μm, the arm length of the cross aperture unit structure with a larger arm length is L1, and the spacing d1 of the side of the dual-cross aperture unit is 10 μm, the arm length of the cross aperture unit structure with a smaller arm length is L2, and the spacing d2 of the side of the dual-cross aperture unit is 20 μm, 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., a double cross-aperture unit) to localize the electric field at the sharp point of the cross-aperture, significantly expanding the interaction volume between the electric field and the analyte, thereby achieving the effect of significantly enhanced molecular fingerprint broadband signal. By gradually scanning the 27 molecular fingerprint sensing pixels, the terahertz wave can generate two wide transmission spectra, and the envelopes of the two transmission spectra form two wide envelope lines, the first wide frequency envelope curve covers the resonance absorption band of lactose, and the second wide frequency envelope curve covers the resonance absorption band of glucose, as shown in Figure 1 , thereby achieving fingerprint detection of the mixed substance. Therefore, a wide frequency detection range of 0.6 THz is achieved, achieving the effect of significantly enhanced molecular fingerprint broadband signal.

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

[0041]

[0042] wherein 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 absorption resonance, n is the refractive index, k is the extinction coefficient, and the angular frequency ω p of lactose and glucose is 1.37 THz and 1.81 THz, respectively; therefore, the lactose molecule and the glucose molecule have a distinct absorption peak at 1.37 THz and 1.81 THz, respectively.

[0043] The electric field diagram as shown in Figure 3 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. As shown in Figure 4 , the lactose analyte layer 5 and the glucose analyte layer 6 are applied to the surface of the sensor, and the absorption peak of the mixture is detected by scanning the sensing pixels. By comparing the difference before and after the transmission spectrum covers 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 about 25 times and about 12.5 times higher than the reference absorption spectrum of the sample detected directly on the metal substrate, as shown in Figure 5 .

[0044] In order to better quantify the broadband sensing enhancement performance, we define the absorbance enhancement factor, and the calculation formula is:

[0045]

[0046] wherein A(f) and A Meta(f) represents 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 factors obtained from the simulation calculation that the absorbance enhancement factors of the lactose film in the wide frequency band of 1.28THz to 1.52THz are all greater than 6.3dB, and the enhancement factor at 1.37THz reaches a maximum of 13.8dB; the absorbance enhancement factors of the glucose film in the frequency band of 1.53THz to 1.89THz are all 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 mixtures.

[0048] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other manner. Any person skilled in the art may utilize the above-disclosed technical content to modify or modify the present invention into equivalent embodiments. However, any simple modifications, equivalent variations, and modifications to the above embodiments that do not depart from the technical content of the present invention and are based on the technical essence of the present invention remain within the scope of protection 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 multiple molecular fingerprint sensing pixels with different structural parameters. Each molecular fingerprint sensing pixel is composed of multiple double cross aperture unit arrays. The double cross aperture units in different molecular fingerprint sensing pixels have different sizes. Each double cross aperture unit is composed of two cross aperture unit structures with different arm lengths. 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; 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 The femtosecond laser pulse width was 45fs, the wavelength was 800nm, and the repetition rate was 1kHz. The dual-band sensor is composed of 27 molecular fingerprint sensing pixels. The length of the double cross aperture unit in the first molecular fingerprint sensing pixel is P = 217 μm, the length of the double cross aperture unit in the second molecular fingerprint sensing pixel is P = 219 μm, and the length increases in steps of 2 μm until the length of the double cross aperture unit in the 27th molecular fingerprint sensing pixel is P = 269 μm. The length of the double cross aperture unit is P, and the width is P / 2, wherein the arm width W of the aperture of a single cross aperture unit structure is 30 μm, and the thickness h is 10 μm. 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=10 μm. 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=20 μm, wherein L1=P / 2–2d1, L2=P / 2–2d2.

2. 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.

3. The dual-band sensor for terahertz molecular fingerprint detection of mixed substances according to claim 2, 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 cusp of the cross-aperture, thereby expanding 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, which are then encapsulated 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.

4. The dual-band sensor for terahertz molecular fingerprint detection of mixed substances according to claim 3, 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, 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 absorption peak at 1.37THz and 1.81THz respectively.

5. The dual-band sensor for terahertz molecular fingerprint detection of mixed substances according to claim 3, characterized in that: The absorbance enhancement factor of the lactose thin 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 thin film analyte on the dual-band sensor in the wide frequency band of 1.53THz to 1.89THz is greater than 6.74dB.

6. The dual-band sensor for terahertz molecular fingerprint detection of mixed substances according to claim 5, characterized in that: The calculation formula of the absorbance enhancement factor is: Among them, A(f) and A Meta (f) represents 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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