Fe3O4 nano-particle microscopic imaging detection method based on left-handed and right-handed polarization modulation

Abstract

The invention provides a Fe3O4 nano-particle microscopic imaging detection method based on left-handed and right-handed polarization modulation, belongs to the technical field of photo-thermal science and detection and signal processing, and solves the problems that at present, nano single particles are difficult to observe, and the physicochemical characteristics are difficult to obtain, the method specifically comprises the steps that a to-be-detected sample is determined, and a slide sample is prepared; starting a computer, a data acquisition card, a lock-in amplifier, a galvanometer controller and a function generator; starting an exciting light and probe light laser power supply and a refrigerator; detection parameters, laser power / current parameters and modulation parameters are set, and scanning detection is conducted on the detection sample piece; loading a magnetic field; the computer reads a signal from the data acquisition card to obtain a photo-thermal detection result image; different laser parameters and magnetic field sizes are changed, the steps are repeated, circular dichroism and magnetic circular dichroism detection results are obtained, magnetization curve measurement is carried out, and the single nanoparticle magnetic moment overturning process is monitored.

Description

Technical Field

[0001] The invention relates to a Fe3O4 nanoparticle microscopic imaging detection method based on left-handed and right-handed polarization modulation, and belongs to the technical field of photothermal science, detection and signal processing. Background Art

[0002] As people explore various materials, the scale is gradually becoming nanoscale or even atomic (10 -10 -10 -9 m), new technologies developed for observing objects at the nanoscale, new methods proposed for constructing material structure-activity or structure-function relationships, and new reaction mechanisms that have been reported or are being explored, constantly breaking through the cognitive boundaries of basic disciplines such as physics, chemistry, biology, and materials science. Unlike conventional averaged measurements, detection at the single particle and single molecule levels focuses more on the intrinsic properties of individual nanomaterials, including its chemical composition, morphology and phase, crystal structure, spectrum, and reactivity. From the perspective of a particle, the characterization analysis at the single particle level compares the heterogeneity between particles and the heterogeneity of the interaction between particles and the environment in the horizontal direction; in the vertical direction, it evaluates the performance of a material according to the idea of ​​individual-polymer-whole, and finally constructs a bottom-up analysis framework to guide the synthesis and characterization of materials and to relate the structure and function of materials.

[0003] In existing studies, Jiang Liwen et al. (patent number: CN201711099225.7) disclosed a detection method for a single nanoparticle, which is based on the scattering of a near-field evanescent wave upon encountering a single nanoparticle, and the CCD collects the scattered signal to image the single nanoparticle. The present invention has low cost, stable detection performance, fast detection speed, high sensitivity, can be used for in-situ and portable detection, and can be expanded to applications such as virus detection and nano-pollutants in the atmosphere. Wang Le et al. (patent number: CN202311023958.8) disclosed a single-particle phosphor screening system and method based on microscopic imaging spectroscopy, which relates to the field of LED phosphor technology, and uses the different emission spectra of different crystalline phases under a microscopic imaging spectrometer for fine distinction, and combines position information to achieve rapid and accurate positioning of suspected new phosphors. The present invention avoids the cumbersome process of multiple split synthesis and phase identification in traditional trial and error methods and solid-state combinatorial chemistry methods. At the same time, the introduction of microscopic imaging spectroscopy technology can make up for the shortcomings of inaccurate recognition by the naked eye and provide a faster and more accurate basis for judgment. Liu Jianguo et al. (patent number: CN202410672383.0) disclosed a method for inverting the real part of the refractive index of a single nanoparticle based on surface near-field microscopy technology, which relates to the technical field of measuring the optical properties of nanoparticles. The present invention can solve the deficiencies in the existing real part of refractive index measurement technology, and can accurately measure and invert the real part of the refractive index of single nanoparticles of different components at different relative humidity under high humidity standard atmospheric pressure conditions. Li Wei et al. (patent number: CN202311605386.4) disclosed a method and system for detecting nanoparticles based on hyperspectral imaging, which relates to the field of nanoparticle detection. The hyperspectral image of the aerosol is identified by a neural network, and the composition of the aerosol nanoparticles in the aerosol and the number of nanoparticles of different components are obtained. The present invention adopts a neural network, regards each hyperspectral sample (pixel) as a data sequence, analyzes the microscopic hyperspectral data from the perspective of the sequence, and improves the accuracy of the aerosol nanoparticle detection method. Summary of the invention

[0004] In order to solve the current problem that single nanoparticles are difficult to observe and the physical and chemical properties are difficult to obtain, the present invention proposes a Fe3O4 nanoparticle microscopic imaging detection method based on left-handed and right-handed polarization modulation, which specifically includes:

[0005] Step 1: drop the sample solution to be tested onto a glass slide to prepare a glass slide sample and place it on a sample stage, and then place the sample stage on an XYZ piezo stage;

[0006] Step 2: Turn on the computer, data acquisition card, lock-in amplifier, galvanometer controller and function generator;

[0007] Step 3: Turn on the excitation light, detection light laser power supply and refrigerator, and control the laser power supply operating temperature to maintain at 20°C;

[0008] Step 4: Set the detection parameters, laser power / current parameters and modulation parameters, scan and detect the sample to be tested, and focus the sample detection signal onto the detector;

[0009] Step 5: Load the magnetic field, transmit the detection signal through the detector to the phase-locked amplifier for signal demodulation, and transmit the demodulated signal to the data acquisition card;

[0010] Step 6: The computer reads the signal from the data acquisition card to obtain the photothermal detection result image;

[0011] Step 7: Change the input laser power and magnetic field size, repeat steps 4-6, and obtain circular dichroism, optical thermal linear dichroism, and magnetic circular dichroism detection results;

[0012] Step 8: Measure the magnetization curve of the Fe3O4 nanoparticles in the photothermal detection result image to obtain the magnetic moment size of the single nanoparticle and monitor the magnetic moment reversal process of the single nanoparticle;

[0013] Step 9: 5 minutes after the end of the test, turn off the laser power supply, function generator, phase-locked amplifier, data acquisition card, galvanometer controller, computer and other equipment.

[0014] Optionally, the preparation of the slide sample in step 1 specifically includes:

[0015] A 170 μm thick standard cover glass was used as the sample substrate, wherein the surface of the glass slide was coated with a 70-90Ω indium tin oxide conductive layer, hexadecane was used as the photothermal medium, and polyvinyl pyrrolidone-coated Fe3O4 nanoparticles with a diameter of 20.3±5 nm were used as samples for detection. The sample solution was dropped onto the surface of the glass slide, and the sample was evenly spread on the surface of the glass slide by spin coating to complete the preparation of the glass slide sample.

[0016] Optionally, step 4 specifically includes:

[0017] Step 4.1: The excitation light with an emission wavelength of 532nm is continuously power-adjusted through a half-wave plate and a polarization cube 3. The power-adjusted laser is then beam-shaped through a spatial filter, and then enters a multi-modulation mode circuit after dual polarization modulation through an electro-optic modulator and a photoelastic modulator. The multi-modulation mode circuit includes a circular polarization modulation circuit, an optical intensity modulation circuit, and a linear polarization modulation circuit.

[0018] Step 4.2: Output the corresponding modulated excitation light according to the modulation mode of the multi-modulation circuit, use the beam expansion system to expand the excitation light, use the convex lens to focus the light beam on the back focal plane of the objective lens, and use the thermal penetration effect of the thermal lens to generate reflection with sample information to obtain scattered detection light. The scattered detection light is reflected by the dichroic mirror and reflected by the 1 / 4 wave plate to the polarization cube 1;

[0019] Step 4.3: The excitation light with an emission wavelength of 780nm is continuously power-adjusted through a half-wave plate and polarization cube 2. The power-adjusted laser is reflected by polarization cube 1 through a spatial filter and a reflector, and is mixed with the scattered detection light and then transmitted through polarization cube 1. After passing through a long-pass filter and a convex lens, the sample detection signal is focused on the detector.

[0020] Optionally, the circular polarization modulation circuit in step 4.1 is used to obtain the circular dichroism detection result, including a quarter wave plate and a beam expansion system arranged from left to right;

[0021] The light intensity modulation circuit is used to obtain the photothermal detection results, including two parallel 1 / 4 wave plates, a beam expansion system and a polarizer arranged from left to right;

[0022] The linear polarization modulation circuit is used to obtain the optical thermal linear dichroism detection results, including two parallel 1 / 4 wave plates and a beam expansion system arranged from left to right.

[0023] Optionally, the phase-locked amplifier in step 2 is connected to a function generator via a frequency mixer, and the function generator provides electrical signals to the electro-optic modulator and the photoelastic modulator.

[0024] Optionally, step 5 specifically includes:

[0025] A plurality of NdFeB permanent magnets are stacked into a thin magnet rod, which is connected to the sample stage. A uniform and stable magnetic field is applied to the sample to be tested through the thin magnet rod, and the direction of the magnetic field is parallel to the optical axis. The distance from the thin magnet rod to the XYZ piezoelectric stage is changed by computer-controlled XYZ piezoelectric moving stage to change the magnetic field size, and magnetic circular dichroism detection is performed in combination with the circular polarization modulation circuit in the multi-modulation circuit.

[0026] The beneficial effects of the present invention are:

[0027] The present invention is based on multiple technical fields such as the mechanism of fusion thermal lens characteristics, photothermal signal modulation, far-field microscopy, multi-source signal unmixing and feature extraction. Compared with traditional detection methods such as fluorescence microscopy, scanning electron microscopy, and projection electron microscopy, the present invention can fully utilize the characteristic that the magnetic circular dichroism of magnetic nanoparticles produces absorption differences for left-handed and right-handed circularly polarized light under the action of a magnetic field. The photothermal microscopy technology is used to detect a single Fe3O4 nanoparticle to obtain the influence of the shape of the nanoparticle and the direction of the easy magnetization axis on the magnetization curve, thereby realizing the measurement of the magnetic moment of a single nanoparticle. The present invention is suitable for the quantitative analysis of the physicochemical properties of materials such as microelectronics and micro-nano structures, or the precise non-destructive detection and evaluation of defects / damages for imaging, magnetization curve measurement, and magnetic moment reversal process monitoring of Fe3O4 nanoparticles. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A schematic diagram of a process flow of a Fe3O4 nanoparticle microscopic imaging detection method based on left-handed and right-handed polarization modulation provided by the present invention;

[0029] Figure 2 A schematic diagram of the magnetic field application method provided by the present invention and the magnitude of the magnetic field generated by the magnet at different distances. In Figure (2), (a) is a schematic diagram of the magnet setting position, and (b) is a schematic diagram of the corresponding relationship between the magnetic field and the distance;

[0030] Figure 3 The photothermal microscopic image of Fe3O4 nanoparticles provided by the present invention is Figure 3 In the figure, (a) is a photothermal micrograph, (b) is a P-CG network processing diagram, (c) is a photothermal micrograph after labeling, and (d) is a single nanoparticle photothermal signal distribution diagram;

[0031] Figure 4 The photothermal, circular dichroism and magnetic circular dichroism images of Fe3O4 particles provided by the present invention are as follows: Figure 4 In the figure, (a) is the photothermal microscopy amplitude image, (b) is the circular dichroism microscopy image, (c) is the circular dichroism microscopy image when B = 0.28T, and (d) is the magnetic circular dichroism microscopy image when B = -0.28T;

[0032] Figure 5 The magnetic circular dichroism curve of Fe3O4 particles provided by the present invention is as follows: Figure 5 , (a) is the magnetic circular dichroism curve of p1 nanoparticles, (b) is the magnetic circular dichroism curve of p2 nanoparticles, (c) is the magnetic circular dichroism curve of p3 nanoparticles, (d) is the magnetic circular dichroism curve of p4 nanoparticles, (e) is the magnetic circular dichroism curve of p5 nanoparticles, and (f) is the magnetic circular dichroism curve of p6 nanoparticles;

[0033] Figure 6 The magnetic moment reversal and probability distribution diagram of nanoparticles under the magnetic field provided by the present invention, Figure 6 In the figure, (a) is the magnetic moment reversal and probability distribution diagram of P1 nanoparticles under the action of a magnetic field, (b) is the magnetic moment reversal and probability distribution diagram of P9 nanoparticles under the action of a magnetic field, and (c) is the magnetic moment reversal and probability distribution diagram of P10 nanoparticles under the action of a magnetic field. DETAILED DESCRIPTION

[0034] Combination Figure 1-6 To illustrate this embodiment, Figure 1 As shown, the steps of a Fe3O4 nanoparticle microscopic imaging detection method based on left-handed and right-handed polarization modulation described in this embodiment include:

[0035] S1: Identify the samples to be tested and prepare slide samples;

[0036] A 170 μm thick standard cover glass was used as the sample substrate. The surface of the glass was coated with a 70-90Ω indium tin oxide (ITO) conductive layer. Hexadecane was used as the photothermal medium. Fe3O4 nanoparticles (nanoComposix, MGPN20, diameter 20.3±5 nm) coated with polyvinyl pyrrolidone (PVP) were used as the sample for detection. The sample solution was dropped onto the surface of the glass slide, and the sample was evenly spread on the surface of the glass slide by spin coating. The glass slide was placed on a sample stage, and the sample stage was placed on an XYZ piezoelectric stage.

[0037] S2: Turn on the Fe3O4 nanoparticle photothermal / magnetic circular dichroism microscopy detection system based on left-handed and right-handed polarization modulation, where the microscopy detection system includes a computer, a data acquisition card, a phase-locked amplifier, a galvanometer controller and a function generator;

[0038] S3: Turn on the excitation light, detection light laser power supply and refrigerator, so that the operating temperature of the laser power supply is maintained at 20°C to ensure the normal operation of the laser equipment;

[0039] S4: setting detection parameters, laser power / current parameters, modulation parameters in the software of the Fe3O4 nanoparticle photothermal / magnetic circular dichroism microscopy detection system based on left-handed and right-handed polarization modulation in the computer, and performing scanning detection on the detection sample;

[0040] S401: The excitation light with an emission wavelength of 532nm is continuously power-adjusted through a half-wave plate and a polarization cube 3, and the power-adjusted laser is then beam-shaped through a spatial filter, and then enters a multi-modulation mode circuit after dual polarization modulation through an electro-optic modulator and a photoelastic modulator, wherein the multi-modulation mode circuit includes a circular polarization modulation circuit, an optical intensity modulation circuit, and a linear polarization modulation circuit;

[0041] The multi-modulation mode circuit includes a circular polarization modulation circuit, a light intensity modulation circuit and a linear polarization modulation circuit. The circular polarization modulation circuit is used to obtain circular dichroism detection results, including a 1 / 4 wave plate and a beam expansion system arranged in sequence from left to right; the light intensity modulation circuit is used to obtain photothermal detection results, including two parallel 1 / 4 wave plates, a beam expansion system and a polarizer arranged in sequence from left to right; the linear polarization modulation circuit is used to obtain photothermal linear dichroism detection results, including two parallel 1 / 4 wave plates and a beam expansion system arranged in sequence from left to right;

[0042] S402: Outputting corresponding modulated excitation light according to the modulation mode of the multi-modulation mode circuit, using a beam expansion system to expand the excitation light, using a convex lens to focus the light beam on the back focal plane of the objective lens, generating a reflection with sample information through the thermal penetration effect of the thermal lens to obtain scattered detection light, and the scattered detection light is reflected by a dichroic mirror and reflected by a 1 / 4 wave plate to a polarization cube 1;

[0043] S403: The excitation light with an emission wavelength of 780nm is continuously power-adjusted through a half-wave plate and polarization cube 2. The power-adjusted laser is reflected by polarization cube 1 through a spatial filter and a reflector, and is mixed with the scattered detection light and then transmitted through polarization cube 1. After passing through a long-pass filter and a convex lens, the sample detection signal is focused on the detector.

[0044] S5: loading magnetic field;

[0045] In this embodiment, the magnet is arranged as follows Figure 2 As shown in (a), this embodiment uses multiple NdFeB permanent magnets stacked into a thin magnet rod, connects the thin magnet rod to the sample stage, applies a uniform and stable magnetic field to the sample to be tested through the thin magnet rod, and the direction of the magnetic field is parallel to the optical axis. The XYZ piezoelectric moving stage is controlled by a computer to change the distance from the thin magnet rod to the XYZ piezoelectric stage to change the magnetic field size. The corresponding relationship between the magnetic field and the distance is shown in FIG. Figure 2 (b) and combined with the circular polarization modulation circuit in the multi-modulation circuit to perform magnetic circular dichroism detection

[0046] S6: The computer reads the signal from the data acquisition card to obtain the photothermal detection result image. Figure 2 (a) Figure 2 (b) Figure 2 (c) and Figure 2 (d)

[0047] S7: Change different laser parameters and magnetic field sizes, repeat S4-S6, and obtain circular dichroism and magnetic circular dichroism detection results. The detection results are as follows: Figure 4 (a) Figure 4 (b) Figure 4 (c) and Figure 4 (d)

[0048] S8: Yes Figure 4 The magnetization curves of the P1 to P6 nanoparticles in (a) were measured. The measurement results of the P1 to P6 nanoparticles are shown in Figure 5 (a) Figure 5 (b) Figure 5 (c) Figure 5 (d) Figure 5 (e) and Figure 5 (f)

[0049] S9: Image matching Figure 4 The P1 nanoparticles in (a), the P9 nanoparticles in the circular dichroism detection, and the P10 nanoparticles in the magnetic circular dichroism detection results monitor the magnetic circular dichroism gMCD signals at different external magnetic induction intensities. The results are as follows Figure 6 (a). Figure 6 (b) and Figure 6 (c)

[0050] In summary, the present invention is based on multiple technical fields such as the mechanism of fusion thermal lens characteristics, photothermal signal modulation, far-field microscopy, multi-source signal unmixing and feature extraction. Compared with traditional detection methods such as fluorescence microscopy, scanning electron microscopy, and projection electron microscopy, the present invention can make full use of the characteristic that the magnetic circular dichroism of magnetic nanoparticles produces different absorption of light in left-handed and right-handed circularly polarized states under the action of a magnetic field. The photothermal microscopy technology is used to detect a single Fe3O4 nanoparticle to obtain the influence of the shape of the nanoparticle and the direction of the easy magnetization axis on the magnetization curve, thereby realizing the measurement of the magnetic moment of a single nanoparticle. For the imaging of Fe3O4 nanoparticles, the magnetization curve measurement, and the monitoring of the magnetic moment reversal process, the present invention is suitable for the quantitative analysis of the physicochemical properties of materials such as microelectronics and micro-nano structures, or the precise non-destructive detection and evaluation of defects / damages.

[0051] S10: 5 minutes after the end of the test, turn off the laser power supply, function generator, phase-locked amplifier, data acquisition card, galvanometer controller, computer and other equipment.

[0052] 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 Fe3O4 nanoparticle microscopic imaging detection method based on left-handed and right-handed polarization modulation, characterized in that: The steps of the Fe3O4 nanoparticle microscopic imaging detection method based on left-handed and right-handed polarization modulation include: Step 1: drop the sample solution to be tested onto a glass slide to prepare a glass slide sample and place it on a sample stage, and then place the sample stage on an XYZ piezo stage; Step 2: Turn on the computer, data acquisition card, lock-in amplifier, galvanometer controller and function generator; Step 3: Turn on the excitation light, detection light laser power supply and refrigerator, and control the laser power supply operating temperature to maintain at 20°C; Step 4: Set the detection parameters, laser power / current parameters and modulation parameters, scan and detect the sample to be tested, and focus the sample detection signal onto the detector; Step 5: Load the magnetic field, transmit the detection signal through the detector to the phase-locked amplifier for signal demodulation, and transmit the demodulated signal to the data acquisition card; Step 6: The computer reads the signal from the data acquisition card to obtain the photothermal detection result image; Step 7: Change the input laser power and magnetic field size, repeat steps 4-6, and obtain circular dichroism, optical thermal linear dichroism, and magnetic circular dichroism detection results; Step 8: Measure the magnetization curve of the Fe3O4 nanoparticles in the photothermal detection result image to obtain the magnetic moment size of the single nanoparticle and monitor the magnetic moment reversal process of the single nanoparticle; Step 9: 5 minutes after the end of the test, turn off the laser power supply, function generator, phase-locked amplifier, data acquisition card, galvanometer controller, computer and other equipment.

2. The Fe3O4 nanoparticle microscopic imaging detection method based on left-handed and right-handed polarization modulation according to claim 1 is characterized in that: The preparation of the slide sample in step 1 specifically includes: A 170 μm thick standard cover glass was used as the sample substrate, wherein the surface of the glass slide was coated with a 70-90Ω indium tin oxide conductive layer, hexadecane was used as the photothermal medium, and polyvinyl pyrrolidone-coated Fe3O4 nanoparticles with a diameter of 20.3±5 nm were used as samples for detection. The sample solution was dropped onto the surface of the glass slide, and the sample was evenly spread on the surface of the glass slide by spin coating to complete the preparation of the glass slide sample.

3. The Fe3O4 nanoparticle microscopic imaging detection method based on left-handed and right-handed polarization modulation according to claim 1 is characterized in that: Step 4 specifically includes: Step 4.1: The excitation light with an emission wavelength of 532nm is continuously power-adjusted through a half-wave plate and a polarization cube 3. The power-adjusted laser is then beam-shaped through a spatial filter, and then enters a multi-modulation mode circuit after dual polarization modulation through an electro-optic modulator and a photoelastic modulator. The multi-modulation mode circuit includes a circular polarization modulation circuit, an optical intensity modulation circuit, and a linear polarization modulation circuit. Step 4.2: Output the corresponding modulated excitation light according to the modulation mode of the multi-modulation circuit, use the beam expansion system to expand the excitation light, use the convex lens to focus the light beam on the back focal plane of the objective lens, and use the thermal penetration effect of the thermal lens to generate reflection with sample information to obtain scattered detection light. The scattered detection light is reflected by the dichroic mirror and reflected by the 1 / 4 wave plate to the polarization cube 1; Step 4.3: The excitation light with an emission wavelength of 780nm is continuously power-adjusted through a half-wave plate and polarization cube 2. The power-adjusted laser is reflected by polarization cube 1 through a spatial filter and a reflector, and is mixed with the scattered detection light and then transmitted through polarization cube 1. After passing through a long-pass filter and a convex lens, the sample detection signal is focused on the detector.

4. The Fe3O4 nanoparticle microscopic imaging detection method based on left-handed and right-handed polarization modulation according to claim 3 is characterized in that: The circular polarization modulation circuit in step 4.1 is used to obtain the circular dichroism detection result, including a quarter wave plate and a beam expansion system arranged from left to right; The light intensity modulation circuit is used to obtain the photothermal detection results, including two parallel 1 / 4 wave plates, a beam expansion system and a polarizer arranged from left to right; The linear polarization modulation circuit is used to obtain the optical thermal linear dichroism detection results, including two parallel 1 / 4 wave plates and a beam expansion system arranged from left to right.

5. The Fe3O4 nanoparticle microscopic imaging detection method based on left-handed and right-handed polarization modulation according to claim 1 is characterized in that: The phase-locked amplifier in step 2 is connected to a function generator via a mixing frequency, and the function generator provides electrical signals for the electro-optic modulator and the photoelastic modulator.

6. The Fe3O4 nanoparticle microscopic imaging detection method based on left-handed and right-handed polarization modulation according to claim 1 is characterized in that: Step 5 specifically includes: A plurality of NdFeB permanent magnets are stacked into a thin magnet rod, which is connected to the sample stage. A uniform and stable magnetic field is applied to the sample to be tested through the thin magnet rod, and the direction of the magnetic field is parallel to the optical axis. The distance from the thin magnet rod to the XYZ piezoelectric stage is changed by computer-controlled XYZ piezoelectric moving stage to change the magnetic field size, and magnetic circular dichroism detection is performed in combination with the circular polarization modulation circuit in the multi-modulation circuit.

Images