Near-critical CO2 medium enhanced photo-thermal microscopic imaging method based on circular polarization modulation

Abstract

The invention discloses a near-critical CO2 medium enhanced photo-thermal microscopic imaging method based on circular polarization modulation, and relates to a near-critical CO2 medium enhanced photo-thermal microscopic imaging method. The invention aims to solve the problem that a photo-thermal data signal of a detected object and a noise signal in a detection process cannot be separated due to weak signals in the existing photo-thermal microscopic imaging technology. The invention discloses a near-critical CO2 medium enhanced photo-thermal microscopic imaging method based on circular polarization modulation. The near-critical CO2 medium enhanced photo-thermal microscopic imaging method integrates the technical fields of a thermal lens characteristic mechanism, photo-thermal signal modulation, far-field microscopic imaging, multi-source signal unmixing and feature extraction, image deconvolution, deep learning and the like. Strong-signal high-contrast photo-thermal microscopic imaging for shallow surface defects of composite materials, nano materials, metal materials and high-molecular polymers can be realized. The invention belongs to the technical field of photo-thermal science and detection and signal processing.

Description

Technical Field

[0001] The invention relates to a near-critical CO2 medium enhanced photothermal microscopy imaging method, belonging to the technical field of photothermal science, detection and signal processing. Background Art

[0002] Far-field optical microscopy has the advantages of being non-invasive and having a long working distance, and is widely used in the fields of materials science, life science, medicine, and chemistry. Depending on whether fluorescent labels are used in the sample to be tested, it can be divided into labeled and label-free microscopy techniques. Labeled optical microscopy achieves information measurement of the sample to be tested by exciting and detecting the fluorescence generated by the optical probe in the sample. There are many fluorescent probes for labeled imaging, such as fluorescent protein markers, fluorescent organic molecules, quantum dots, etc., and the resolution can reach tens or even several nanometers. Although these imaging techniques occupy an important position in the application of biological sciences and medical sciences, they are subject to certain limitations in application due to the use of fluorescent probes. Imaging methods such as photoacoustic imaging, optical coherence tomography, stimulated Raman and photothermal imaging in label-free optical imaging techniques are not limited to fluorescent probes. Among them, photothermal imaging microscopy in label-free imaging not only has application potential in material detection, but also has great application prospects in life sciences and medical sciences. When performing photothermal microscopy of biological tissues, it is possible to add materials such as metal nanoparticles, or directly perform label-free imaging of some components within cells. If the resolution of pump-probe photothermal microscopy can be improved, the detection value of this imaging technology in biomedicine and materials science will be further improved.

[0003] The invention patent with patent number CN202211152302.1 discloses a method for detecting micro-nano plastics based on photothermal effect. The method relates to the field of micro-nano optics and utilizes the resonant absorption of 785nm laser by gold nanoparticles. A strong photothermal trap is formed in the solution through the photothermal effect. This allows micro-nano plastics to be efficiently enriched and captured. The enriched micro-nano plastics can be detected by surface enhanced Raman spectroscopy (SERS) technology, thereby realizing the detection of low-concentration micro-nano plastics. The invention solves the problem that existing means cannot effectively enrich and detect a large range of micro-nano plastics, and provides a new detection method for monitoring micro-nano plastics in water environments and detecting micro-nano plastics in the food industry, which has broad application prospects.

[0004] The utility model patent with the patent number CN201521120666.7 discloses a real-time imaging device for optical material defects based on photothermal detection and optical microscopy, including a sample stage for placing samples, a photothermal detection system and an optical microscopy system. The photothermal detection system includes a pump light source, a pump light focusing device, a detection light source, a detection light first focusing device and a detection device, and the optical microscopy system includes an optical illumination light source, an optical illumination light beam splitting device, an optical illumination light reflecting device, a pump light focusing device, an imaging lens and an imaging device. The utility model combines photothermal detection technology and optical microscopy technology together, effectively making up for the shortcomings of single-mode detection, realizing dual-mode, multi-parameter, and easy-to-position detection, which is conducive to broadening the application of photothermal detection technology and optical microscopy technology; at the same time, the photothermal detection system and the optical microscopy system in the present invention use the same focusing device, which reduces the number of components, reduces the size of the device, and reduces the cost.

[0005] In order to make full use of the thermal lens effect characteristics of materials to achieve three-dimensional precise detection of defect size / morphology, the present invention relates to a near-critical CO2 medium enhanced photothermal microscopy method based on circular polarization modulation. The invention is based on vector diffraction theory, heat transfer and electromagnetic field theory, and can achieve strong signal and high contrast photothermal microscopy imaging of shallow surface defects in composite materials, nanomaterials, metal materials and polymers (the photothermal signal is improved by more than 3 orders of magnitude). Summary of the invention

[0006] The present invention aims to solve the problem that the current photothermal microscopy technology has weak signals and cannot separate the photothermal data signal of the object being measured from the noise signal in the detection process, and further proposes a near-critical CO2 medium enhanced photothermal microscopy imaging method based on circular polarization modulation.

[0007] The technical solution adopted by the present invention to solve the above problems is: the steps of the present invention include:

[0008] Step 1, identify the sample to be tested and prepare the capillary sample;

[0009] Step 2, placing the prepared capillary sample in the sample block and connecting the air inlet and the air outlet;

[0010] Step 3, introducing high-pressure carbon dioxide gas medium;

[0011] Step 4: Connect components such as Peltier and temperature sensor, wait for the temperature to stabilize before testing, and the computer reads the photothermal signal from the data acquisition card and processes it to obtain a single-point photothermal signal;

[0012] Step 5: Perform multiple imaging tests, and the computer reads the signals of each point from the data acquisition card and processes them to obtain the test result image, and summarize the test results;

[0013] Step 6: Change different detection parameters, repeat steps 4 to 5, and obtain a signal enhancement graph;

[0014] Step 7: After the test, turn off the Peltier, temperature controller, carbon dioxide pressure regulating gas system and computer after a 5-minute interval.

[0015] Furthermore, step 1 specifically includes the following steps:

[0016] Step 101: Use a tube wall thickness of 0.15 mm and an inner hole side length of 0.3 mm 0.6×0.6×50 mm 3 The square quartz capillary is used as the cavity and carries the sample;

[0017] Step 102, immersing the capillary in an aqueous solution of aminopropyltriethoxysilane for 15 minutes;

[0018] Step 103, rinse the inner and outer walls of the capillary with ultrapure water, and blow dry with nitrogen N2;

[0019] Step 104, immersing one end of the capillary into the prepared sample solution, and the sample solution overcomes gravity and fills the capillary along the tube wall under the action of capillary force;

[0020] Step 105, after the capillary is left to stand for 15 minutes, the capillary is rinsed again with ultrapure water and blown dry with N2;

[0021] Step 106: When it is necessary to prepare a nanoparticle sample, immerse one end of the capillary into the prepared nanoparticle solution so that the solution fills the capillary;

[0022] Step 107, perform pure water flushing and N2 drying operations to facilitate subsequent connection to the gas system.

[0023] Furthermore, in step 3, industrial-grade liquid carbon dioxide cylinders, nitrogen cylinders and gas cylinders are used to achieve pressure regulation of carbon dioxide.

[0024] Furthermore, the concentration of carbon dioxide in the carbon dioxide cylinder is greater than 99.9%.

[0025] The beneficial effects of the present invention are as follows: compared with traditional detection methods such as fluorescence microscopy and photoacoustic microscopy, the present invention can fully utilize the characteristics of near-critical CO2 with an ultra-high refractive index temperature coefficient. The use of near-critical CO2 as a medium for photothermal microscopy can amplify the photothermal signal obtained by detection, thereby improving the signal contrast. Specifically, for strong signal and high-contrast photothermal microscopy of shallow surface defects of composite materials, nanomaterials, metal materials and high-molecular polymers, the photothermal signal is improved by more than 3 orders of magnitude. The present invention is suitable for non-destructive detection of conductive materials such as aerospace, microelectronics and micro-nano structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic diagram of the principle of the near-critical CO2 medium-enhanced photothermal microscopy imaging method based on circular polarization modulation;

[0027] Figure 2 This is a schematic diagram of the principle of the near-critical CO2 pressure regulating gas circuit system;

[0028] Figure 3 It is a schematic diagram of photothermal microscopy imaging and signal distribution of gold nanoparticles in hexadecane or critical point CO2;

[0029] Figure 3 (a) is a schematic diagram of photothermal microscopy imaging of hexadecane medium;

[0030] Figure 3 (b) is a schematic diagram of the photothermal signal distribution of hexadecane medium;

[0031] Figure 3 (c) is a schematic diagram of photothermal microscopy imaging of near-critical CO2 medium;

[0032] Figure 3 (d) is a schematic diagram of the distribution of photothermal signals in the near-critical CO2 medium;

[0033] Figure 4 This is a diagram of the photothermal signal enhancement measured in CO2 medium at different temperatures and pressures. DETAILED DESCRIPTION

[0034] Specific implementation method 1: Figure 1 As shown, a near-critical CO2 medium enhanced photothermal microscopy imaging method based on circular polarization modulation includes the following specific steps:

[0035] Step 1: Identify the sample to be tested and prepare the capillary sample; the specific process includes:

[0036] Step 101: Use a tube wall thickness of 0.15 mm and an inner hole side length of 0.3 mm 0.6×0.6×50 mm 3 The square quartz capillary is used as the cavity and carries the sample;

[0037] Step 102, immersing the capillary in an aqueous solution of aminopropyltriethoxysilane for 15 minutes;

[0038] Step 103, rinse the inner and outer walls of the capillary with ultrapure water, and blow dry with nitrogen N2;

[0039] Step 104, immersing one end of the capillary into the prepared sample solution, and the sample solution overcomes gravity and fills the capillary along the tube wall under the action of capillary force;

[0040] Step 105, after the capillary is left to stand for 15 minutes, the capillary is rinsed again with ultrapure water and blown dry with N2;

[0041] Step 106: When it is necessary to prepare a nanoparticle sample, immerse one end of the capillary into the prepared nanoparticle solution so that the solution fills the capillary;

[0042] Step 107, perform pure water flushing and N2 drying operations to facilitate subsequent access to the gas system;

[0043] Step 2, placing the prepared capillary sample in the sample block and connecting the air inlet and the air outlet;

[0044] Step 3, introducing high-pressure carbon dioxide gas medium; using industrial-grade liquid carbon dioxide cylinders, nitrogen cylinders and cylinders to achieve pressure regulation of carbon dioxide; the concentration of carbon dioxide in the carbon dioxide cylinder is greater than 99.9%.

[0045] Step 4: Connect components such as Peltier and temperature sensor, wait for the temperature to stabilize before testing, and the computer reads the photothermal signal from the data acquisition card and processes it to obtain a single-point photothermal signal;

[0046] Step 5: Perform multiple imaging tests, and the computer reads the signals of each point from the data acquisition card and processes them to obtain the test result image, and summarize the test results;

[0047] Step 6: Change different detection parameters, repeat steps 4 to 5, and obtain a signal enhancement graph;

[0048] Step 7: After the test, turn off the Peltier, temperature controller, carbon dioxide pressure regulating gas system and computer after a 5-minute interval.

[0049] Wherein, the ratio of aminopropyltriethoxysilane to the aqueous solution is 1:10.

[0050] How it works

[0051] The near-critical CO2 medium-enhanced photothermal microscopy method based on circular polarization modulation in the present invention integrates multiple technical fields such as thermal lens characteristic mechanism, photothermal signal modulation, far-field microscopy, multi-source signal unmixing and feature extraction, image deconvolution, and deep learning, and can achieve strong signal and high contrast photothermal microscopy of shallow surface defects of composite materials, nanomaterials, metal materials, and polymers (the photothermal signal is improved by more than 3 orders of magnitude).

[0052] The present invention proposes a near-critical CO2 medium enhanced photothermal microscopy imaging method based on circular polarization modulation. The basic principle of this method is as follows: Figure 1As shown. The function of the sample block is to accommodate the near-critical CO2 medium and the nanoparticles to be tested. It consists of an air inlet, an air outlet, an O-ring, a connecting block and a capillary. When imaging, the capillary sample needs to be inserted into the reserved hole of the connecting block, and the gap is filled with resin glue to achieve sealing. The air inlet and outlet are connected to the connecting block with bolts, and the O-ring is placed at the pipe connection to prevent gas leakage from the connection gap. In order to prevent the surface reflection of the sample block from interfering with the experiment when it is irradiated by the laser, a through hole is left in the center of the connecting block. The function of the sample stage is to fix the sample block for detecting and heating the CO2 medium to make it reach a near-critical state. It consists of a sample block, a Peltier and a temperature sensor. Four semiconductor Peltiers are used as heat sources, PT1000 is used as a temperature sensor for real-time temperature measurement, and a PID temperature controller (MeerstetterEngineering GmbH, TEC-1089-SV) is used to control the temperature. Due to the small aperture of the capillary, the temperature of the CO2 gas in the capillary cannot be directly measured by the temperature detector. Therefore, the detector is placed in the sample stage, 30 mm away from the sample block, and the temperature of CO2 is measured by heat conduction between the sample stage and the sample block.

[0053] The above is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent replacement and improvement made to the above embodiments without departing from the content of the technical solution of the present invention, based on the technical essence of the present invention, within the spirit and principles of the present invention, still fall within the protection scope of the technical solution of the present invention.

Claims

1. A near-critical CO2 medium enhanced photothermal microscopy imaging method based on circular polarization modulation, characterized in that: The specific steps include: Step 1, identify the sample to be tested and prepare the capillary sample; Step 2, placing the prepared capillary sample in the sample block and connecting the air inlet and the air outlet; Step 3, introducing high-pressure carbon dioxide gas medium; Step 4: Connect components such as Peltier and temperature sensor, wait for the temperature to stabilize before testing, and the computer reads the photothermal signal from the data acquisition card and processes it to obtain a single-point photothermal signal; Step 5: Perform multiple imaging tests, and the computer reads the signals of each point from the data acquisition card and processes them to obtain the test result image, and summarize the test results; Step 6: Change different detection parameters, repeat steps 4 to 5, and obtain a signal enhancement graph; Step 7: After the test, turn off the Peltier, temperature controller, carbon dioxide pressure regulating gas system and computer after a 5-minute interval.

2. The method for near-critical CO2 medium enhanced photothermal microscopy based on circular polarization modulation according to claim 1, characterized in that: Step 1 specifically includes the following steps: Step 101: Use a tube wall thickness of 0.15 mm and an inner hole side length of 0.3 mm 0.6×0.6×50 mm 3 The square quartz capillary is used as the cavity and carries the sample; Step 102, immersing the capillary in an aqueous solution of aminopropyltriethoxysilane for 15 minutes; Step 103, rinse the inner and outer walls of the capillary with ultrapure water, and blow dry with nitrogen N2; Step 104, immersing one end of the capillary into the prepared sample solution, and the sample solution overcomes gravity and fills the capillary along the tube wall under the action of capillary force; Step 105, after the capillary is left to stand for 15 minutes, the capillary is rinsed again with ultrapure water and blown dry with N2; Step 106: When it is necessary to prepare a nanoparticle sample, immerse one end of the capillary into the prepared nanoparticle solution so that the solution fills the capillary; Step 107, perform pure water flushing and N2 drying operations to facilitate subsequent connection to the gas system.

3. The method for near-critical CO2 medium enhanced photothermal microscopy based on circular polarization modulation according to claim 1, characterized in that: In step 3, industrial-grade liquid carbon dioxide cylinders, nitrogen cylinders and gas cylinders are used to achieve pressure regulation of carbon dioxide.

4. The method for near-critical CO2 medium enhanced photothermal microscopy based on circular polarization modulation according to claim 3, characterized in that: The concentration of carbon dioxide in the carbon dioxide cylinder is greater than 99.9%.

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