CN117191738A - Terahertz detection method for liquid sample - Google Patents
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Abstract
The application relates to the technical field of terahertz detection, in particular to a terahertz detection method for a liquid sample, which comprises the following steps: s1, performing transmission detection on a detection chip through a terahertz spectrometer to obtain a first absorption spectrum; s2, taking the terahertz detection chip as a carrier, dripping a trace amount of liquid sample on the detection chip, and performing transmission detection again to obtain a second absorption spectrum; s3, respectively performing curve optimization on the first absorption spectrum and the second absorption spectrum; s4, obtaining a representative peak of the curve from the processed image, and obtaining the resonant frequency according to the representative peak; s5, obtaining a resonance frequency offset through the difference of the vibration frequencies of the first absorption spectrum and the second absorption spectrum, and using the resonance frequency offset for characteristic comparison of the liquid sample. The peak value abnormality caused by various interferences can be effectively reduced, the fluctuation of detection is reduced, and the accuracy and the stability are improved. The method is particularly suitable for various interference which exists in the liquid sample and is difficult to eliminate, and the liquid sample is effectively analyzed.
Description
Technical Field
The application relates to the technical field of terahertz detection, in particular to a terahertz detection method for a liquid sample.
Background
Terahertz waves are an energy between microwaves and infrared. The special frequency of the terahertz wave enables the terahertz wave to obtain unique properties which are not possessed by microwaves and infrared rays. The energy generated by the terahertz wave band has good penetrability, and can meet the requirement of nondestructive detection because the energy does not generate ionizing radiation. In the existing terahertz detection, terahertz transmission detection is generally used for detecting the integral property of a substance. In the transmission detection process, terahertz waves penetrate through a detected substance sample, detection parameters are generated according to the absorption of the substance sample to the terahertz waves, and the existing common time domain spectrum and absorption spectrum are formed through different arrangement of the detection parameters. Different components and different structures in the substance sample can generate corresponding and interaction on different frequency bands in the terahertz wave, and as the frequency of the terahertz wave is wide, small differences in the component structures of the substance sample can be reflected, and the detection parameters or the display of the map are displayed. The characteristics in a common sample of a substance can be characterized by several peaks in the absorption spectrum.
However, with the development of terahertz detection technology, the variety of samples is becoming wider and wider. Among them, the liquid sample is one of the samples that is difficult to analyze effectively in the existing terahertz detection. The analysis difficulty is high, the accuracy is low because of poor uniformity of the liquid sample, and the result fluctuation is large and the reproducibility is poor; and also because of the large interference caused by the commonly used cavity-shaped fixtures for liquid samples. In the detection of a liquid sample, one of the factors that is difficult to avoid is water contained in the liquid sample as an impurity. In most liquid samples, the mass ratio of water to effective substances is usually quite different, and a large amount of water content causes the terahertz absorption spectrum of water to be close to and coincide with the terahertz absorption spectrum of a sample solution. Even if overlapping comparison of curves is made, it is still difficult to effectively separate the curve characteristics of water. An effective analysis method is lacking in the prior art to address the effective detection of liquid samples.
Disclosure of Invention
The application aims to overcome at least one defect of the prior art, and provides a terahertz detection method for a liquid sample, which is used for solving the problem that the liquid sample is difficult to effectively detect in the existing terahertz detection technology.
The technical scheme adopted by the application is that the terahertz detection method for the liquid sample comprises the following steps:
s1, performing transmission detection on a detection chip through a terahertz spectrometer to obtain a first absorption spectrum;
s2, taking the detection chip as a carrier, dripping a trace amount of liquid sample on the detection chip, and performing transmission detection again to obtain a second absorption spectrum;
s3, respectively performing curve optimization on the first absorption spectrum and the second absorption spectrum;
s4, obtaining a representative peak of the curve from the processed image, and obtaining the resonant frequency according to the representative peak;
s5, obtaining a resonance frequency offset through the difference of the vibration frequencies of the first absorption spectrum and the second absorption spectrum, and using the resonance frequency offset for characteristic comparison of the liquid sample.
In step S3, data fitting, data smoothing and data field point removing are performed on curves in the first absorption spectrum and the second absorption spectrum to form optimization processing on the curves.
The data fitting uses the following formula in particular to form a peak characterization of the curve:
the spectral response function H (ω), specifically:
wherein E is ref (ω) is the reference signal before placement of the liquid sample; e (E) sam (ω) is the reference signal after placement of the liquid sample; />Refractive index (complex number); alpha is the absorption coefficient; omega is the angular frequency; d is the thickness of the sample; c is the light velocity; a (ω) is an amplitude function; />Is a phase function; i is an imaginary unit.
Refractive index functionThe method comprises the following steps: />Where α (ω) is an absorption coefficient function.
The absorption coefficient function α (ω), specifically:
dielectric constant function ε * (ω), specifically:where n is the refractive index (real number).
In step S5, the resonant frequency offset is obtained by the difference between the two resonant frequencies, and is calculated by the following formula:
the frequency offset Δf (GHz) is specifically: Δf (GHz) =f sample -f Blank chip The method comprises the steps of carrying out a first treatment on the surface of the Wherein f sample Representing peak frequencies in the second absorption spectrum; f (f) Blank chip Which is representative of the peak frequency in the first absorption spectrum.
In steps S1 and S2, the detection parameters of the dynamic transmission detection are: the laser is 700nm to 900nm, the terahertz spectrum width is 0.05THz to 4.5THz, the maximum time domain scanning range is 1000ps to 2000ps, the dynamic range is 70dB to 90dB, and the scanning speed is 12Hz to 22Hz.
The detection chip comprises: a chip substrate; the resonant structure is arranged on the chip substrate in an array manner;
the resonant structure includes: the substrate is arranged between the three-dimensional layer and the chip substrate;
the stereoscopic layer includes: a plurality of circumferentially disposed arrow structures, and a ring structure connected to the arrow structures;
the thickness of the three-dimensional layer is 0.8 μm to 1.1 μm, and a three-dimensional micro-space with the exposed surface of the base layer as the bottom surface is formed between the arrow structure and the ring structure.
The ring structure is hollow square, the arrow structures are arranged in the ring structure, and the four arrow structures are arranged in the ring structure in a central symmetry manner;
the arrow structure includes a head end and a tail end; the tail ends are connected with the ring structure, and the head ends point to the center of the ring structure.
The head end is isosceles right triangle, the tail end is the rectangle, and the hypotenuse of head end and the minor face coincidence of tail end and center link to each other, and the right angle of head end is directional ring structure's center.
The length of the bevel edge is 7 mu m plus or minus 0.35 mu m, and the distance between two adjacent head ends is 1 mu m plus or minus 0.05 mu m;
the distance between the outer frame and the inner frame of the ring structure is equal to the length of the short side and is 3.5 mu m plus or minus 0.3 mu m;
the length of one side of the outer frame is 24 mu m plus or minus 0.5 mu m.
The dimensions of the chip substrate are: length 8+ -0.5 mm, width 8+ -0.5 mm, height 0.5+ -0.05 mm;
the three-dimensional layer is made of gold, the base layer is made of titanium, and the thickness of the three-dimensional layer is 450-550 times of that of the base layer;
the distance between two adjacent resonant structures is 6 μm + -0.3 μm.
Compared with the prior art, the application has the beneficial effects that: the method is different from the prior method for analyzing the absorption spectrum, the highest peak frequency or average peak frequency or the like is used as a comparison characteristic to identify the structural composition of the sample, and the intervention of the detection chip and the deviation of the resonance frequency of the relative detection chip are used as the comparison characteristic, so that peak value abnormality caused by various interferences can be effectively reduced, the fluctuation of detection is reduced, and the accuracy and the stability are improved. The method is particularly suitable for various interference which exists in the liquid sample and is difficult to eliminate, and the liquid sample is effectively analyzed. Through the utilization of the detection chip, the local field can be effectively enhanced in the terahertz detection process. Resonance can be enhanced by detecting molecular interactions of the chip with the liquid sample. Resonance can be used as a distinguishing characteristic for detecting substances, and the change of the refractive index and the surrounding medium constant in the terahertz parameter can be identified through the change of the resonance peak, so that the detection method of the liquid sample with high sensitivity and convenience and rapidness in detection is formed.
Drawings
FIG. 1 is a schematic structural view and a partial enlarged view of a detection chip according to the present application.
FIG. 2 is a schematic diagram of a resonance structure of a detection chip according to the present application.
FIG. 3 is a perspective view of a resonance structure of a detection chip according to the present application.
FIG. 4 is a schematic diagram and a partial enlarged view of a detection chip according to the present application.
FIG. 5 is a simulation diagram of the resonance peak of the detection chip of the present application.
FIG. 6 is an absorption spectrum of a liquid sample before use of the detection chip.
FIG. 7 is an absorption spectrum of a liquid sample after use of the detection chip.
FIG. 8 is a schematic diagram showing the shift of resonance peaks formed when the detection chip is used for detecting a liquid sample.
Fig. 9 is a flowchart of a terahertz detection method in the present application.
Reference numerals illustrate: chip substrate 100, resonance structure 200, base layer 210, stereo layer 220, arrow structure 221, head end 2211, tail end 2212, ring structure 222, outer frame 2221, inner frame 2222, and stereo micro-space 230.
Detailed Description
The drawings are for illustrative purposes only and are not to be construed as limiting the application. For better illustration of the following embodiments, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the actual product dimensions; it will be appreciated by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.
Example 1
As shown in fig. 9, the present embodiment is a terahertz detection method for a liquid sample, including the following steps:
s1, performing transmission detection on a detection chip through a terahertz spectrometer to obtain a first absorption spectrum; the first absorption spectrum is used for calculating as a frequency offset to determine the actual frequency of the detection chip; the detection chip is used for enhancing the local field and resonance.
S2, taking the detection chip as a carrier, dripping a trace amount of liquid sample on the detection chip, and performing transmission detection again to obtain a second absorption spectrum; and adding a liquid sample on the same detection chip, wherein the liquid sample and the detection chip fully act. Under the action of the detection chip, the curve of the liquid sample can be optimized, the peak characteristics are highlighted, and the fluctuation is reduced;
s3, respectively performing curve optimization on the first absorption spectrum and the second absorption spectrum; through curve optimization, redundant interference peaks can be eliminated, and a representative peak with a well-characterized curve and a highlighted whole curve is formed.
S4, obtaining a representative peak of the curve from the processed image, and obtaining the resonant frequency according to the representative peak; the frequency representing the peak contains the characteristics of the overall curve.
S5, obtaining a resonance frequency offset through the difference of the vibration frequencies of the first absorption spectrum and the second absorption spectrum, and using the resonance frequency offset for characteristic comparison of the liquid sample.
The method is different from the prior method for analyzing the absorption spectrum, the highest peak frequency or average peak frequency or the like is used as a comparison characteristic to identify the structural composition of the sample, and the intervention of the detection chip and the deviation of the resonance frequency of the relative detection chip are used as the comparison characteristic, so that peak value abnormality caused by various interferences can be effectively reduced, the fluctuation of detection is reduced, and the accuracy and the stability are improved. The method is particularly suitable for various interference which exists in the liquid sample and is difficult to eliminate, and the liquid sample is effectively analyzed. Through the utilization of the detection chip, the local field can be effectively enhanced in the terahertz detection process. Resonance can be enhanced by detecting molecular interactions of the chip with the liquid sample. Resonance can be used as a distinguishing characteristic for detecting substances, and the change of the refractive index and the surrounding medium constant in the terahertz parameter can be identified through the change of the resonance peak, so that the detection method of the liquid sample with high sensitivity and convenience and rapidness in detection is formed.
In step S3, data fitting, data smoothing and data field point removing are performed on curves in the first absorption spectrum and the second absorption spectrum to form optimization processing on the curves. The data fitting is to display a curve with obvious characteristics through a mode of formula adjustment on the terahertz parameters obtained through detection, the data smoothing is to remove redundant curve bending, the continuous and regular change is highlighted by utilizing the change trend of the curve, and the data field removing points are used for reducing interference and eliminating abrupt peak values which do not accord with the regular change.
The data fitting uses the following formula in particular to form a peak characterization of the curve:
wherein E is ref (ω) is the reference signal before placement of the liquid sample; e (E) sam (ω) is the reference signal after placement of the liquid sample; />Refractive index (complex number); alpha is the absorption coefficient; omega is the angular frequency; d is the thickness of the sample; c is the light velocity; a (ω) is an amplitude function; />Is a phase function; i is an imaginary unit.
Refractive index functionThe method comprises the following steps: />Where α (ω) is an absorption coefficient function.
The absorption coefficient function α (ω), specifically:
dielectric constant function ε * (ω), specifically:where n is the refractive index (real number).
In step S5, the resonant frequency offset is obtained by the difference between the two resonant frequencies, and is calculated by the following formula:
the frequency offset Δf (GHz) is specifically: Δf (GHz) =f sample -f Blank chip The method comprises the steps of carrying out a first treatment on the surface of the Wherein f sample Representing peak frequencies in the second absorption spectrum; f (f) Blank chip Which is representative of the peak frequency in the first absorption spectrum.
Terahertz waves pass through the detection chip, more echoes and interference are generated by the spectrum, and a smoother curve is obtained by acquiring the frequency shift spectrum and the absorption coefficient of a liquid sample and combining the mathematical principles of weighting multiple data fitting and spectrum analysis simulation decomposition. The terahertz absorption spectrum before fitting has more signal interference peaks in the original data; after the algorithm treatment, the resonance peak of the curve almost forms a smooth curve.
In steps S1 and S2, the detection parameters of the dynamic transmission detection are: the laser is 700nm to 900nm, the terahertz spectrum width is 0.05THz to 4.5THz, the maximum time domain scanning range is 1000ps to 2000ps, the dynamic range is 70dB to 90dB, and the scanning speed is 12Hz to 22Hz.
The detection chip comprises: a chip substrate 100; the resonant structures 200 are arranged on the chip substrate 100 in an array manner.
The resonant structure 200 includes: a base layer 210 and a three-dimensional layer 220 made of metal, wherein the base layer 210 is disposed between the three-dimensional layer 220 and the chip substrate 100.
The base layer 210 is used to buffer and connect the stereo layer 220 with the chip substrate 100.
The stereoscopic layer 220 includes: a plurality of circumferentially arranged arrow structures 221, and a ring structure 222 connected to said arrow structures 221.
The cooperation of the arrow structures 221 and the ring structures 222 helps to enhance the effect of the local field.
The thickness of the stereoscopic layer 220 is 0.8 μm to 1.1 μm, and a stereoscopic micro space 230 is formed between the arrow structure 221 and the ring structure 222 with the exposed surface of the base layer 210 as a bottom surface.
In the terahertz detection process, the shift of the resonance frequency is influenced by the dielectric effect generated by the three-dimensional micro-space 230, so that the interaction between the sample and the terahertz wave is enhanced in a three-dimensional design mode, and the sensitivity of the terahertz sensor can be improved.
The ring structure 222 is hollow square, the arrow structures 221 are arranged in the ring structure 222, and the number of the arrow structures 221 is four and the arrow structures 221 are arranged in the ring structure 222 in a central symmetry manner.
Arrow structures 221 act as equivalent capacitances to gap structures and ring structures 222 act as equivalent inductances.
The arrow structure 221 includes a head end 2211 and a tail end 2212; the trailing ends 2212 are each connected to the ring structure 222, and the leading ends 2211 are each directed toward the center of the ring structure 222.
The thickness of the three-dimensional layer 220 reaches 0.8 μm to 1.1 μm, which breaks through the plain design of the traditional chip below 200nm, and forms a three-dimensional structure, so that the three-dimensional layer 220 can form three-dimensional contact with a sample, the interaction with sample molecules is greatly increased, obvious resonance occurs, the formation of obvious resonance characteristics is helpful to change the identification refractive index and the change of surrounding media, and high sensitivity and resolution are provided.
The head end 2211 is in the shape of an isosceles right triangle, the tail end 2212 is in the shape of a rectangle, the hypotenuse of the head end 2211 coincides with the short side of the tail end 2212 and is connected with the center, and the right angle of the head end 2211 points to the center of the ring structure 222.
As shown in fig. 5, when the three-dimensional micro-space 230 generated after the structure is generated is polarized along a certain direction in the terahertz electric field direction, the terahertz transmission spectrum can obtain obvious characteristic resonance peaks more easily, and can obtain a higher signal-to-noise ratio.
The length of the oblique side is 7 μm + -0.35 μm, and the distance between the adjacent two ends 2211 is 1 μm + -0.05 μm.
The distance between the outer frame 2221 and the inner frame 2222 of the ring structure 222 is equal to the length of the short sides and is 3.5 μm±0.3 μm.
One side of the outer frame 2221 is 24 μm.+ -. 0.5. Mu.m.
The dimensions of the chip substrate 100 are: 8+ -0.5 mm long, 8+ -0.5 mm wide and 0.5+ -0.05 mm high.
The three-dimensional layer 220 is made of gold, the base layer 210 is made of titanium, and the thickness of the three-dimensional layer 220 is 450 to 550 times the thickness of the base layer 210.
The distance between two adjacent resonant structures 200 is 6 μm±0.3 μm.
Example 2
The embodiment is a terahertz detection method for a liquid sample, which comprises the following steps: and (3) introducing high-purity nitrogen into the sample bin, wherein the flow rate of the nitrogen is about 15L/min, and introducing the nitrogen to remove the interference of water vapor.
S1, performing transmission detection on a detection chip through a terahertz spectrometer to obtain a first absorption spectrum; the first absorption spectrum is used for calculating as a frequency offset to determine the actual frequency of the detection chip; the detection chip is used for enhancing the local field and resonance.
S2, taking the detection chip as a carrier, dripping a trace amount of liquid sample on the detection chip, and performing transmission detection again to obtain a second absorption spectrum; and adding a liquid sample on the same detection chip, wherein the liquid sample and the detection chip fully act.
The initial spectra of the first absorption spectrum and the second absorption spectrum were plotted as described in fig. 6 before the detection chip was used. It can be seen that the liquid sample is greatly disturbed by water, and the peak value coincidence ratio of the two is high, even if individual peak values are different, if the analysis result difference of the maximum peak value or the average peak value is small, the effective distinction is difficult. After the detection chip is utilized, the actually obtained curve is shown in fig. 7 under the enhancement effect of the local field, and the ripple curve in fig. 7 is the second absorption spectrum.
S3, respectively performing curve optimization on the first absorption spectrum and the second absorption spectrum.
The optimized first and second absorption spectra are shown in fig. 8.
S4, obtaining a representative peak of the curve from the processed image, and obtaining the resonant frequency according to the representative peak; the frequency representing the peak contains the characteristics of the overall curve.
S5, obtaining a resonance frequency offset through the difference of the vibration frequencies of the first absorption spectrum and the second absorption spectrum, and using the resonance frequency offset for characteristic comparison of the liquid sample.
The terahertz parameters include at least: absorption coefficient, refractive index, dielectric constant.
In step S3, data fitting, data smoothing and data field point removing are performed on curves in the first absorption spectrum and the second absorption spectrum to form optimization processing on the curves.
The data fitting uses the following formula in particular to form a peak representation of the curve:
wherein E is ref (ω) is the reference signal before placement of the liquid sample; e (E) sam (ω) is the reference signal after placement of the liquid sample; />Refractive index (complex number); alpha is the absorption coefficient; omega is the angular frequency; d is the thickness of the sample; c is the light velocity; a (ω) is an amplitude function; />Is a phase function; i is an imaginary unit.
Refractive index functionThe method comprises the following steps: />Where α (ω) is an absorption coefficient function. The absorption coefficient function α (ω), specifically: />
Dielectric constant function ε * (ω), specifically:wherein n is a foldEmissivity (real number).
In step S5, the resonant frequency offset is obtained by the difference between the two resonant frequencies, and is calculated by the following formula:
the frequency offset Δf (GHz) is specifically: Δf (GHz) =f sample -f Blank chip The method comprises the steps of carrying out a first treatment on the surface of the Wherein f sample Representing peak frequencies in the second absorption spectrum; f (f) Blank chip Which is representative of the peak frequency in the first absorption spectrum.
Terahertz waves pass through the detection chip, more echoes and interference are generated by the spectrum, and a smoother curve is obtained by acquiring the frequency shift spectrum and the absorption coefficient of a liquid sample and combining the mathematical principles of weighting multiple data fitting and spectrum analysis simulation decomposition. The terahertz absorption spectrum before fitting has more signal interference peaks in the original data; after the algorithm treatment, the resonance peak of the curve almost forms a smooth curve.
In addition to the frequency offset Δf, the absorption peak intensity offset Δi can be detected in combination, where Δi=i sample -I Blank chip . According to the difference of different liquid samples on terahertz spectrum information, a spectrum database can be further constructed for automatic identification function algorithm, the liquid samples are prepared again, the labels are removed for blind measurement, and corresponding terahertz spectrum information is obtained. According to the established terahertz spectrum information database and the automatic identification function algorithm of the liquid sample, the automatic identification and authentication of different liquid samples are realized, the effectiveness and reliability of the database and the automatic identification algorithm for testing the liquid sample are tested, and further modification and perfection are carried out according to the feedback result, so that an accurate, efficient and sensitive detection means is provided for the detection and authentication of the liquid sample. In this embodiment, the liquid sample mentioned in the present application can be a liquid sample prepared by using water as a solvent and using Chinese medicine powder as a solute.
In steps S1 and S2, the detection parameters of the dynamic transmission detection are: the laser is 700nm to 900nm, the terahertz spectrum width is 0.05THz to 4.5THz, the maximum time domain scanning range is 1000ps to 2000ps, the dynamic range is 70dB to 90dB, and the scanning speed is 12Hz to 22Hz.
The detection chip comprises: a chip substrate 100; the resonant structures 200, the resonant structures 200 are arranged on the chip substrate 100 in an array. The resistivity of the chip substrate 100 is equal to or greater than 20kΩ·cm. The resonant structure 200 includes: the substrate 210 is disposed between the three-dimensional layer 220 and the chip substrate 100. The stereoscopic layer 220 includes: a plurality of circumferentially disposed arrow structures 221, and a ring structure 222 connected to the arrow structures 221. As shown in fig. 3, the thickness of the stereoscopic layer 220 is 0.8 μm to 1.1 μm, and a stereoscopic micro space 230 is formed between the arrow structure 221 and the ring structure 222 with the exposed surface of the base layer 210 as a bottom surface. The sharp points in the three-dimensional micro-space 230 are rounded. The thickness of the stereoscopic layer 220 is specifically 1 μm. The ring structure 222 is hollow square, the arrow structures 221 are arranged in the ring structure 222, and the arrow structures 221 are four and are arranged in the ring structure 222 in a central symmetry manner. The chip base 100 can be specifically made of high-resistance silicon material, quartz material, flexible material PI material, or polytetrafluoroethylene PTFE material.
Arrow structure 221 includes a head end 2211 and a tail end 2212. The trailing ends 2212 are each connected to the ring structure 222, and the leading ends 2211 are each directed toward the center of the ring structure 222. Head end 2211 is in the shape of an isosceles right triangle, tail end 2212 is in the shape of a rectangle, the hypotenuse of head end 2211 coincides with the short side of tail end 2212 and is connected with the center, and the right angle of head end 2211 points to the center of ring structure 222. The center line of the tail 2212 passing through the center of the short side is perpendicular to one side of the inner frame 2222 connected with the tail 2212. In the present embodiment, the resonance structure 200 includes an outer frame 2221 having a square shape and an inner frame 2222 having a square shape, and a ring structure 222 is formed between the outer frame 2221 and the inner frame 2222, and the outer frame 2221 overlaps with the center of the inner frame 2222. The inner frame 2222 is provided with an arrow structure 221 arranged in a central symmetry manner, and the arrow structure 221 comprises: a first arrow, a second arrow, a third arrow, and a fourth arrow; the first, second, third, and fourth arrows each include a head end 2211 and a tail end 2212.
The tail ends 2212 of the first, second, third and fourth arrows are respectively connected to the inner frame 2222 and perpendicular to each other, and the head ends 2211 of the first, second, third and fourth arrows are all oriented toward the center of the inner frame 2222. Because the inner frame 2222 is square, and the first arrow, the second arrow, the third arrow and the fourth arrow are centrosymmetric, that is, a rotation angle of 90 degrees exists between the first arrow and the second arrow, a rotation angle of 90 degrees exists between the second arrow and the third arrow, a rotation angle of 90 degrees exists between the third arrow and the fourth arrow, and a rotation angle of 90 degrees exists between the fourth arrow and the first arrow, the whole resonance structure 200 is in a symmetrical three-dimensional structure, and the biological sample solution is convenient to be uniformly distributed in the resonance structure 200 in the subsequent detection process.
The head end 2211 of the first arrow, the second arrow, the third arrow and the fourth arrow are isosceles right triangles, the tail end 2212 is rectangular, the hypotenuse of the isosceles triangle is connected with the short side of the rectangle, and the central line of the head end 2211 is coincident with the central line of the tail end 2212. Dividing the ring structure 222 into a first area, a second area, a third area and a fourth area which are sequentially connected end to end and are in a long strip shape; the tail 2212 of the first arrow is connected to the first region, the tail 2212 of the second arrow is connected to the second region, the tail 2212 of the third arrow is connected to the third region, and the tail 2212 of the fourth arrow is connected to the fourth region. In this manner, each edge of the ring structure 222 is connected to an arrow such that there is better electrical communication between the ring structure 222, the first arrow, the second arrow, the third arrow, and the fourth arrow.
The center lines of the first arrow and the third arrow coincide with the midpoint connecting lines of the first area and the third area, and the center lines of the second arrow and the fourth arrow coincide with the midpoint connecting lines of the second area and the fourth area. That is, the first, second, third, and fourth arrows are symmetrically distributed along the lateral and longitudinal symmetry axes of the outer frame 2221. The length of the bevel edge is 7 mu m +/-0.35 mu m, and the distance between two adjacent head ends 2211 is 1 mu m +/-0.05 mu m; the distance between the outer frame 2221 and the inner frame 2222 of the ring structure 222 is equal to the length of the short side and is 3.5 μm±0.3 μm; the outer frame 2221 and the inner frame 2222 are square. One side of the square outer frame 2221 is 24 μm±0.5 μm long. The dimensions of the chip substrate 100 are: 8+ -0.5 mm long, 8+ -0.5 mm wide and 0.5+ -0.05 mm high. The three-dimensional layer 220 is gold and the base layer 210 is titanium. In addition, the three-dimensional layer 220 can be made of copper or aluminum. The thickness of the stereoscopic layer 220 is 450 to 550 times the thickness of the base layer 210. The base layer 210 is specifically 2nm. The distance between two adjacent resonant structures 200 is 6 μm±0.3 μm.
As shown in fig. 1, the upper left side is a detection chip with a size of 8mm x 8mm and a thickness (not shown) of 0.5mm. The distance j between two adjacent resonant structures 200 is 6 μm, see the partial enlargement of fig. 1. As shown in fig. 2, the outer frame 2221 has a side length f of 24 μm. The distance w between the outer frame 2221 and the inner frame 2222 of the ring structure 222 is 3.5 μm. The short side length h of the tail 2212 is 3.5 μm. The length e of the hypotenuse of head 2211 is 7 μm; the distance g between the adjacent head ends 2211 is 0.5 μm. As shown in fig. 4, the resonant structures 200 are arranged in an array on the surface of the detection chip, specifically, are arranged in an array with equal intervals and multiple rows and multiple columns. In this embodiment, the liquid sample is a liquid sample prepared from powder of Chinese medicine (bear gall) and high-purity water. In fig. 6, the terahertz detection is based on the terahertz detection commonly used in the prior art and using high purity water as a reference sample, and the peaks of the liquid sample are disordered and dense as seen by a spectrum, so that effective information is difficult to directly extract from the liquid sample for optimization, and the method is based on the fact that other impurities in the water serving as a solvent are discharged as much as possible. During the actual liquid sample detection process, more impurities are generated, and various fluctuation of the curve is larger and more chaotic.
Fig. 7 shows that after the detection is completed by the detection chip, the terahertz detection is performed again by dropping the liquid sample onto the detection chip with the detection chip as a carrier without moving the detection chip and maintaining the state of the previous detection. From the absorption spectrum, the peak value curve is orderly and clear after the detection chip is adopted, the peak value confusion degree is greatly reduced, and the regular change can be extracted more easily. And particularly, after data fitting, smoothing, field point removing and other curve optimization are adopted, a single-peak smooth characterization curve is obtained from the absorption spectrum.
As shown in fig. 8, after the detection by the detection chip, the characteristic of the liquid sample can be identified by using the resonance frequency shift generated by the detection chip before and after the liquid sample is dropped. Fig. 8 shows absorption curves before and after the liquid sample is dropped on the test chip. The curve is subjected to data and image optimization processing, and the resonance offset can be calculated from the frequency of the front-back offset of the resonance peak of the curve so as to be used for quality detection. The difference between the two curves is small from the curve observation, if the two curves are analyzed from the resonance peak frequency, the frequency corresponding to the two peaks can be accurately read, the frequency corresponding to the two peaks before dripping is 1.530THz, and the frequency corresponding to the liquid sample after dripping is 1.552THz, so that the frequency deviation is accurately calculated and used as the comparison characteristic of the liquid sample. In this embodiment, the detection chip is a metamaterial chip.
It should be understood that the foregoing examples of the present application are merely illustrative of the present application and are not intended to limit the present application to the specific embodiments thereof. Any modification, equivalent replacement, improvement, etc. that comes within the spirit and principle of the claims of the present application should be included in the protection scope of the claims of the present application.
Claims (10)
1. The terahertz detection method for the liquid sample is characterized by comprising the following steps of:
s1, performing transmission detection on a detection chip through a terahertz spectrometer to obtain a first absorption spectrum;
s2, taking the detection chip as a carrier, dripping a trace amount of liquid sample on the detection chip, and performing transmission detection again to obtain a second absorption spectrum;
s3, respectively performing curve optimization on the first absorption spectrum and the second absorption spectrum;
s4, obtaining a representative peak of the curve from the processed image, and obtaining the resonant frequency according to the representative peak;
s5, obtaining a resonance frequency offset through the difference of the vibration frequencies of the first absorption spectrum and the second absorption spectrum, and using the resonance frequency offset for characteristic comparison of the liquid sample.
2. The method for terahertz detection of a liquid sample according to claim 1, wherein step S3 is specifically,
and performing data fitting, data smoothing and data field point removing on the curves in the first absorption spectrum and the second absorption spectrum to form optimization processing on the curves.
3. The method of claim 2, wherein the data fitting uses the following formula to form a peak representation of the curve:
the spectral response function H (ω), specifically:
wherein E is ref (ω) is the reference signal before placement of the liquid sample; e (E) sam (ω) is the reference signal after placement of the liquid sample;refractive index (complex number); alpha is the absorption coefficient; omega is the angular frequency; d is the thickness of the sample; c is the light velocity; a (ω) is an amplitude function; />Is a phase function; i is an imaginary unit.
Refractive index functionThe method comprises the following steps:
where α (ω) is an absorption coefficient function.
The absorption coefficient function α (ω), specifically:
dielectric constant function ε * (ω), specifically:
where n is the refractive index (real number).
4. The terahertz detection method of claim 1, wherein in step S5, the resonance frequency offset is obtained by the difference between two resonance frequencies, and is calculated by the following formula:
the frequency offset Δf (GHz) is specifically:
ΔF(GHz)＝f sample -f blank chip
Wherein f sample Representing peak frequencies in the second absorption spectrum; f (f) Blank chip Which is representative of the peak frequency in the first absorption spectrum.
5. The method for terahertz detection of a liquid sample according to claim 1, wherein in steps S1 and S2, detection parameters of dynamic transmission detection are:
the laser is 700nm to 900nm, the terahertz spectrum width is 0.05THz to 4.5THz, the maximum time domain scanning range is 1000ps to 2000ps, the dynamic range is 70dB to 90dB, and the scanning speed is 12Hz to 22Hz.
6. The method for terahertz detection of a liquid sample according to any one of claims 1 to 5, wherein the detection chip includes: a chip substrate; the resonant structure is arranged on the chip substrate in an array manner;
the resonant structure includes: the substrate is arranged between the three-dimensional layer and the chip substrate;
the stereoscopic layer includes: a plurality of circumferentially disposed arrow structures, and a ring structure connected to the arrow structures;
the thickness of the three-dimensional layer is 0.8 μm to 1.1 μm, and a three-dimensional micro-space with the exposed surface of the base layer as the bottom surface is formed between the arrow structure and the ring structure.
7. The method for terahertz detection of a liquid sample according to claim 6, wherein,
the ring structure is hollow square, the arrow structures are arranged in the ring structure, and the four arrow structures are arranged in the ring structure in a central symmetry manner;
the arrow structure includes a head end and a tail end; the tail ends are connected with the ring structure, and the head ends point to the center of the ring structure.
8. The method for terahertz detection of a liquid sample according to claim 7, wherein the head end is in the shape of an isosceles right triangle, the tail end is in the shape of a rectangle, the hypotenuse of the head end coincides with the short side of the tail end and is connected with the center, and the right angle of the head end is directed to the center of the ring structure.
9. The method for terahertz detection of a liquid sample according to claim 8, wherein,
the length of the bevel edge is 7 mu m plus or minus 0.35 mu m, and the distance between two adjacent head ends is 1 mu m plus or minus 0.05 mu m;
the distance between the outer frame and the inner frame of the ring structure is equal to the length of the short side and is 3.5 mu m plus or minus 0.3 mu m;
the length of one side of the outer frame is 24 mu m plus or minus 0.5 mu m.
10. The method for terahertz detection of a liquid sample according to claim 1, wherein,
the dimensions of the chip substrate are: length 8+ -0.5 mm, width 8+ -0.5 mm, height 0.5+ -0.05 mm;
the three-dimensional layer is made of gold, the base layer is made of titanium, and the thickness of the three-dimensional layer is 450-550 times of that of the base layer;
the distance between two adjacent resonant structures is 6 μm + -0.3 μm.
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