A microscopic imaging detection method of fe3o4 nanoparticles based on left and right-handed polarization modulation

Abstract

The application provides a Fe3O4 nanoparticle microscopic imaging detection method based on left and right polarization modulation, belongs to the technical field of photothermal science and detection and signal processing, and solves the problems that current nanometer single particles are difficult to observe and physical and chemical characteristics are difficult to obtain, and specifically comprises the following steps: determining a sample to be detected and preparing a slide sample; starting a computer, a data acquisition card, a lock-in amplifier, a galvanometer controller and a function generator; starting a power supply of an excitation light and a detection light laser and a refrigerator; setting detection parameters, setting laser power / current parameters, setting modulation parameters, and scanning and detecting the sample to be detected; loading a magnetic field; reading signals from the data acquisition card by the computer to obtain a photothermal detection result image; changing different laser parameters and the size of the magnetic field, repeating the above steps, obtaining a circular dichroism and magnetic circular dichroism detection result, measuring a magnetization curve, and monitoring a single nanoparticle magnetic moment flipping process.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of Fe3O4 Nanoparticle microscopic imaging detection method based on left and right polarized modulation, belong to photo-thermal science and detection and signal processing technical field. BACKGROUND

[0002] With the people's exploration scale of various materials gradually nanometer even atomization (10 -10 -10 -9 m), for observing object in nanometer scale and developed new technology, for building material structure-activity or structure-function relationship and proposed new method, and the new mechanism of reaction that has been reported or is exploring, constantly break through the cognitive boundary of physics, chemistry, biology, material science and other basic disciplines.Different from conventional average measurement, single particle and single molecule level detection pays more attention to the intrinsic property of individual nanomaterial, including its chemical composition, morphology and phase, crystal structure, spectrum and reaction activity etc.Information.From the perspective of a particle, single particle level characterization analysis compares the heterogeneity between particle and particle in horizontal, the heterophase of interaction between particle and environment;In longitudinal, according to the idea of individual-multimer-whole, the performance of a material is evaluated, and finally a bottom-up analysis framework is constructed for guiding the synthesis and characterization of materials, and correlating the structure and function of materials.

[0003] In existing research, Jiang Liwen et al. (Patent No: CN201711099225.7) discloses a detection method for single nanoparticles, which is based on the scattering of near-field evanescent wave encountering single nanoparticles, and the single nanoparticles are imaged by collecting the scattered signals with a CCD. The present invention has low cost, stable detection performance, fast detection speed, high sensitivity, and can be used for in-situ and portable detection, and can be extended to virus detection, nano-pollutants in the atmosphere and other applications. Wang Le et al. (Patent No: CN202311023958.8) discloses a single particle fluorescent powder screening system and method based on microscopic imaging spectrum, which relates to the technical field of LED fluorescent powder. The different emission spectra of different crystal phases under the microscopic imaging spectrometer are used to finely distinguish, and the position information is combined to realize fast and accurate positioning of suspected new fluorescent powder. The present invention avoids the tedious process of multiple synthesis and phase identification in traditional trial-and-error method and solid-state combinatorial chemistry. At the same time, the introduction of microscopic imaging spectrum technology can make up for the inaccuracy of naked eye recognition, and provide a more accurate judgment basis. Liu Jianguo et al. (Patent No: CN202410672383.0) discloses a nano single particle refractive index real part inversion method based on surface near-field microscopy technology, which relates to the field of nano-particle optical property measurement technology. The present invention can solve the shortcomings of existing refractive index real part measurement technology, and can accurately measure and invert the refractive index real part of different component nano single particle under different relative humidity in high humidity standard atmospheric pressure conditions. Li Wei et al. (Patent No: CN202311605386.4) discloses a nano-particle detection method and system based on hyperspectral imaging, which relates to the field of nano-particle detection. The composition of aerosol nanoparticles in the aerosol and the number of nanoparticles of different compositions are obtained by identifying the hyperspectral image of the aerosol through a neural network. The present invention uses a neural network to regard each hyperspectral sample (pixel) as a data sequence, analyzes the microscopic hyperspectral data from the sequence perspective, and improves the accuracy of the aerosol nanoparticle detection method. SUMMARY

[0004] The present invention is to solve the problem that nano single particles are difficult to observe and the physical and chemical properties are difficult to obtain, and further proposes a Fe3O4 nanoparticle microscopic imaging detection method based on left and right polarization modulation, which specifically includes:

[0005] Step 1: drop the sample solution to be tested into the glass slide to prepare the glass slide sample and place it on the sample stage, and place the sample stage on the XYZ piezoelectric platform;

[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 and detection light laser power supply and the refrigerator, and control the laser power supply working temperature to maintain at 20℃;

[0008] Step 4: set the detection parameters, laser power / current parameters and modulation parameters, and perform scanning detection on the sample to be detected, and focus the sample detection signal on the detector;

[0009] Step 5: load the magnetic field, transmit the detection signal through the detector to the lock-in 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 the size of the magnetic field, repeat steps 4-6, and obtain the results of circular dichroism, photothermal linear dichroism and magnetic circular dichroism detection;

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

[0013] Step 9: turn off the laser power, function generator, lock-in amplifier, data acquisition card, galvanometer controller and computer and other devices after 5 minutes of test end interval.

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

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

[0016] Optionally, step 4 specifically includes:

[0017] Step 4.1: the excitation light with a wavelength of 532nm passes through a half-wave plate and a polarization cube 3 for continuous power adjustment, the power-adjusted laser passes through a spatial filter to realize beam shaping, and then enters a multi-modulation mode circuit after being modulated by an electro-optical modulator and an optical elastic modulator, wherein 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 mode circuit, expand the excitation light by using a beam expander, focus the light beam on the back focal plane of the objective lens by using a convex lens, and obtain the scattered detection light by reflecting the light beam through the thermal lens effect of the thermal lens. The scattered detection light is reflected by a dichroic mirror and reflected to the polarization cube 1 through a 1 / 4 wave plate;

[0019] Step 4.3: the excitation light with a wavelength of 780 nm is continuously power-adjusted by a half-wave plate and a polarization cube 2, the power-adjusted laser is reflected by a spatial filter and a mirror to the polarization cube 1, and then is transmitted by the polarization cube 1 after being mixed with the scattered probe light, and is focused on the detector through a long-pass filter and a convex lens.

[0020] Optionally, the circular polarization modulation circuit in step 4.1 is used to obtain a circular dichroism detection result, and includes a 1 / 4 wave plate and a beam expander system arranged in sequence from left to right.

[0021] The light intensity modulation circuit is used to obtain a photothermal detection result, and includes two parallel 1 / 4 wave plates, a beam expander system and a polarizer arranged in sequence from left to right.

[0022] The linear polarization modulation circuit is used to obtain a photothermal linear dichroism detection result, and includes two parallel 1 / 4 wave plates and a beam expander system arranged in sequence from left to right.

[0023] Optionally, the phase-locked amplifier in step 2 is connected through a frequency mixing function generator, and the function generator provides an electrical signal for an electro-optical modulator and an optical elastic modulator.

[0024] Optionally, step 5 specifically includes:

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

[0026] The present application has the following advantages:

[0027] Compared with the traditional fluorescence microscopic imaging, scanning electron microscope, projection electron microscope and other detection methods, the present application can fully utilize the characteristics that the magnetic circular dichroism of the magnetic nanoparticles produces absorption difference for left and right circularly polarized light under the action of the magnetic field, and the single Fe3O4 nanoparticle is detected by using the photothermal microscopic imaging technology to obtain the influence law of the shape and easy magnetization axis direction of the nanoparticle on the magnetization curve, and the measurement of the magnetic moment of the single nanoparticle is realized. For the imaging, magnetization curve measurement and magnetic moment flip process monitoring of the Fe3O4 nanoparticles, the present application is suitable for the quantitative analysis of the physical and chemical properties of microelectronic and micro-nano structure materials or the precise and non-destructive detection and evaluation of defects / damage. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 A schematic flowchart of a microscopic imaging detection method for Fe3O4 nanoparticles based on left and right cyclopolarization modulation provided by the present invention;

[0029] Figure 2 The diagram shows the magnetic field applied by the magnet and the magnitude of the magnetic field generated by the magnet at different distances, provided by the present invention. In Figure (2), (a) is a schematic diagram of the magnet placement position, and (b) is a schematic diagram of the relationship between the magnetic field and the distance.

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

[0031] Figure 4 The images provided by this invention are photothermal, circular dichroism, and magnetic circular dichroism images of Fe3O4 particles. Figure 4 In the image, (a) is the photothermal microscopy amplitude map, (b) is the circular dichroism microscopy image, (c) is the circular dichroism microscopy image at B = 0.28T, and (d) is the magnetic circular dichroism microscopy image at B = -0.28T.

[0032] Figure 5 The magnetic circular dichroism curve of Fe3O4 particles provided by this invention. Figure 5 In the figure, (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 This invention provides a graph showing the magnetic moment reversal and probability distribution of nanoparticles under the influence of a magnetic field. Figure 6 In the diagram, (a) shows the magnetic moment reversal and probability distribution of P1 nanoparticles under the influence of a magnetic field, (b) shows the magnetic moment reversal and probability distribution of P9 nanoparticles under the influence of a magnetic field, and (c) shows the magnetic moment reversal and probability distribution of P10 nanoparticles under the influence of a magnetic field. Detailed Implementation

[0034] Combination Figures 1-6 This implementation method is described as follows: Figure 1 As shown, the steps of the Fe3O4 nanoparticle microscopic imaging detection method based on left- and right-hand polarization modulation described in this embodiment include:

[0035] S1: Identify the sample to be tested and prepare a glass slide sample;

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

[0037] S2: Turn on the Fe3O4 nanoparticle photothermal / magnetic circular dichroism microscopic imaging detection system based on left and right circular polarization modulation, wherein the microscopic imaging detection system includes a computer, a data acquisition card, a lock-in amplifier, a galvanometer controller and a function generator;

[0038] S3: Turn on the excitation light and probe light laser power supply and the refrigerator, and then maintain the laser power supply operating temperature to 20℃ to ensure the normal operation of the laser equipment;

[0039] S4: Set the detection parameters in the Fe3O4 nanoparticle photothermal / magnetic circular dichroism microscopic imaging detection system software based on left and right circular polarization modulation in the computer, set the laser power / current parameters, set the modulation parameters, and scan the detection sample;

[0040] S401: The excitation light with a wavelength of 532 nm passes through a half-wave plate and a polarization cube 3 for continuous power adjustment. The power-adjusted laser passes through a spatial filter to realize beam shaping, and then enters a multi-modulation circuit after passing through an electro-optical modulator and a photoelastic modulator, wherein the multi-modulation circuit includes a circular polarization modulation circuit, a light intensity modulation circuit and a linear polarization modulation circuit;

[0041] The multi-modulation 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, and includes a 1 / 4 wave plate and a beam expander system arranged in sequence from left to right. The light intensity modulation circuit is used to obtain photothermal detection results, and includes two parallel 1 / 4 wave plates, a beam expander 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, and includes two parallel 1 / 4 wave plates and a beam expander system arranged in sequence from left to right;

[0042] S402: According to the modulation mode output of the multi-modulation mode circuit, the corresponding modulated excitation light is output, the beam expander system is used to expand the excitation light, the convex lens is used to focus the light beam on the back focal plane of the objective lens, the thermal lens is used to generate the reflection with sample information to obtain the scattering detection light, the scattering detection light is reflected by the dichroic mirror and reflected to the polarization cube 1 through the 1 / 4 wave plate;

[0043] S403: The excitation light with a wavelength of 780nm passes through the half wave plate and the polarization cube 2 for continuous power adjustment, the power-adjusted laser is reflected by the spatial filter and the mirror to the polarization cube 1, and is mixed with the scattering detection light and transmitted by the polarization cube 1, and then passes through the long-pass filter and the convex lens to focus the sample detection signal on the detector.

[0044] S5: Load magnetic field;

[0045] The setting mode of the magnet in the embodiment is as shown in Figure 2 (a), and the embodiment adopts a plurality of NdFeB permanent magnets stacked into a thin magnet rod, the thin magnet rod is connected with the sample stage, a uniform and stable magnetic field is applied to the sample to be measured through the thin magnet rod, the direction of the magnetic field is parallel to the optical axis, the distance between the thin magnet rod and the XYZ piezoelectric moving stage is changed by the computer control XYZ piezoelectric moving stage to change the magnetic field size, and the corresponding relationship between the magnetic field and the distance is as shown in Figure 2 (b), and the magnetic circular dichroism detection is performed in combination with the circular polarization modulation circuit in the multi-modulation mode circuit

[0046] S6: The computer reads the signal from the data acquisition card to obtain the photothermal detection result image, and the detection is as shown in Figure 2 (a), Figure 2 (b), Figure 2 (c), and Figure 4 (d);

[0047] S7: Change different laser parameters and magnetic field size, repeat S4-S6, obtain circular dichroism and magnetic circular dichroism detection results, and the detection results are as shown in Figure 4 (a), Figure 4 (b), Figure 4 (c), and Figure 4 (d);

[0048] S8: The magnetization curve measurement is performed on the P1-P6 nanoparticles in Figure 5 (a), and the measurement results of the P1-P6 nanoparticles are as shown in Figure 5 (a), Figure 5 (b), Figure 5 (c), Figure 5 (d), Figure 5 (e), and Figure 4 (f);

[0049] S9: The magnetic circular dichroism detection results of the P1-P6 nanoparticles are as shown in the figureFigure 6 The P1 nanoparticles in (a) and the P9 nanoparticles in the circular dichroism detection, as well as the P10 nanoparticles in the magnetic circular dichroism detection results, were used to monitor the magnetic circular dichroism gMCD signals under different external magnetic induction intensities. The results are as follows: Figure 6 (a). Figure 6 (b) and ​ As shown in (c);

[0050] In summary, this invention integrates multiple technical fields, including thermal lens characteristics, photothermal signal modulation, far-field microscopic imaging, multi-source signal demixing, and feature extraction. Compared to traditional detection methods such as fluorescence microscopy, scanning electron microscopy, and transmission electron microscopy, this invention fully utilizes the characteristic that the magnetic circular dichroism of magnetic nanoparticles absorbs light in left- and right-hand circularly polarized states under the influence of a magnetic field. By using photothermal microscopy to detect individual Fe3O4 nanoparticles, the influence of the shape of the nanoparticle and the direction of its easy magnetization axis on the magnetization curve can be obtained, realizing the measurement of the magnetic moment of a single nanoparticle. For the imaging, magnetization curve measurement, and monitoring of the magnetic moment reversal process of Fe3O4 nanoparticles, this invention is applicable to the quantitative analysis of the physicochemical properties of microelectronic and micro / nanostructure materials, or the precise non-destructive testing and evaluation of defects / damage.

[0051] S10: Five minutes after the end of the test, turn off the laser power supply, function generator, lock-in amplifier, data acquisition card, galvanometer controller, and computer.

[0052] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent substitutions, and improvements made to the above embodiments without departing from the scope of the present invention, based on the technical essence of the present invention and within the spirit and principles of the present invention, shall still fall within the protection scope of the present invention.

Claims

1. A Fe3O4 nanoparticle microscopic imaging detection method based on left and right-handed polarization modulation, characterized in that, The steps of the Fe3O4 nanoparticle microscopic imaging detection method based on left and right circular polarization modulation include: Step 1: Drop the sample solution to be tested into a glass slide to prepare a glass slide sample and place it on a sample stage, and place the sample stage on a XYZ piezoelectric 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 and probe light laser power supply and the refrigerator, and control the laser power supply to maintain the working temperature to 20℃; Step 4: Set the detection parameters, laser power / current parameters and modulation parameters, and scan and detect the sample to be tested, and focus the sample detection signal on the detector; Step 4 specifically includes: Step 4.1: The excitation light with a wavelength of 532nm is continuously power-adjusted through a half-wave plate and a polarization cube 3, the power-adjusted laser passes through a spatial filter to realize beam shaping, and then enters a multi-modulation mode circuit after being double-polarization-modulated by an electro-optical modulator and an optical elastic modulator, wherein the multi-modulation mode circuit includes a circular polarization modulation circuit, an optical intensity modulation circuit and a linear polarization modulation circuit; The circular polarization modulation circuit in step 4.1 is used to obtain circular dichroism detection results, including a 1 / 4 wave plate and a beam expander system arranged in sequence from left to right; The optical intensity modulation circuit is used to obtain optical thermal detection results, including two parallel 1 / 4 wave plates, a beam expander system and a polarizer arranged in sequence from left to right; The linear polarization modulation circuit is used to obtain optical thermal linear dichroism detection results, including two parallel 1 / 4 wave plates and a beam expander system arranged in sequence from left to right; Step 4.2: According to the modulation mode output of the multi-modulation mode circuit, the corresponding modulated excitation light is output, the beam expander system is used to expand the excitation light, the convex lens is used to focus the light beam on the back focal plane of the objective lens, the thermal lens is used to generate reflected light with sample information through the thermal lens effect, the scattered probe light is reflected by the dichroic mirror and reflected to the polarization cube 1 through the 1 / 4 wave plate; Step 4.3: The excitation light with a wavelength of 780nm is continuously power-adjusted through a half-wave plate and a polarization cube 2, the power-adjusted laser passes through a spatial filter and a reflecting mirror to reflect the polarization cube 1, and then mixes with the scattered probe light and transmits with the polarization cube 1, and then passes through a long-pass filter and a convex lens to focus the sample detection signal on the detector; Step 5: Load the magnetic field, transmit the detection signal through the detector to the lock-in 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 optical thermal 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 optical thermal detection result image, obtain the single nanoparticle magnetic moment size, and monitor the single nanoparticle magnetic moment flipping process; Step 9: Turn off the laser power supply, function generator, lock-in amplifier, data acquisition card, galvanometer controller and computer after 5 minutes of interval after the test is completed.

2. The Fe304 nanoparticle microscopic imaging detection method based on left and right-handed polarization modulation according to claim 1, characterized in that, The preparation of the glass 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 was plated with an indium tin oxide conductive layer of 70-90 Ω, hexadecane was used as the photothermal medium, and polyvinylpyrrolidone-coated Fe3O4 nanoparticles with a diameter of 20.3 ± 5 nm were used as the sample for detection. The sample solution was dropped onto the surface of the glass, and the sample was uniformly spread on the surface of the glass by spin coating to complete the preparation of the glass sample.

3. The Fe304 nanoparticle microscopic imaging detection method based on left and right-handed polarization modulation according to claim 1, characterized in that, The phase-locked amplifier in step 2 is connected through a frequency mixer and a function generator, and the function generator provides an electrical signal for the electro-optical modulator and the photoelastic modulator.

4. The Fe304 nanoparticle microscopic imaging detection method based on left and right-handed polarization modulation according to claim 1, characterized in that, Step 5 specifically includes: A plurality of NdFeB permanent magnets are stacked into a thin magnet rod, the thin magnet rod is connected to the sample stage, a uniform and stable magnetic field is applied to the sample to be measured through the thin magnet rod, the direction of the magnetic field is parallel to the optical axis, the distance between the thin magnet rod and the XYZ piezoelectric moving stage is changed to change the size of the magnetic field through computer control, and the magnetic circular dichroism detection is performed in combination with the circular polarization modulation circuit in the multi-modulation mode circuit.

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