A device and method for measuring the magnetization response and frequency spectrum of magnetic nanoparticles under the excitation of a multi-frequency magnetic field

Abstract

The application discloses a kind of magnetic nanoparticle magnetization response and frequency spectrum measuring device and method under multi-frequency magnetic field excitation, belong to nanometer test technical field, comprising: setting excitation magnetic field frequency and amplitude, generating alternating excitation magnetic field;The magnetization response of the measured magnetic nanoparticle sample under alternating magnetic field excitation is measured, and the magnetization response spectrum information thereof is obtained;The detection characteristics of the measured magnetic nanoparticle sample are calculated using the amplitude and phase of each harmonic of the magnetization response spectrum, and the dynamic magnetization curve of the measured magnetic nanoparticle sample is reconstructed.The application can realize the measurement of the magnetization response, spectrum and magnetization curve of the magnetic nanoparticle sample under multi-frequency magnetic field excitation, and can be applied to the calibration and measurement of the concentration of the magnetic nanoparticle under multi-frequency magnetic field excitation.

Description

Technical Field

[0001] This invention belongs to the field of nanotechnology, and more specifically, relates to a device and method for measuring the magnetization response and spectrum of magnetic nanoparticles under multi-frequency magnetic field excitation. Background Technology

[0002] In recent years, magnetic nanoparticles have been widely used in biomarker separation and detection, magnetic targeted drug delivery, magnetic nanoparticle imaging tracers, magnetic resonance imaging (MRI) contrast agents, tumor hyperthermia, and non-contact temperature measurement due to their unique properties such as superparamagnetism, high saturation magnetization, good biocompatibility, high temperature sensitivity, non-toxicity, and rapid metabolism. In these applications, the magnetic characterization of the magnetic nanoparticles used, especially their dynamic magnetization response and spectrum, is crucial prior information. Achieving real-time and accurate measurement of the magnetization response and spectrum of magnetic nanoparticles is of significant importance for assessing the feasibility of using magnetic nanoparticles in applications such as magnetic nanoparticle imaging and magnetic nanoparticle temperature measurement, calibrating the magnetization response of magnetic particles, and studying the physical mechanism of dynamic magnetization of magnetic nanoparticles.

[0003] The technology for measuring the magnetization response of magnetic nanoparticles has made some progress. Magnetization physics models and relaxation models based on magnetic nanoparticles can be used to study information such as particle type, size, and concentration. Furthermore, by coupling specific functional groups (such as polyethylene glycol, chitosan, lipids, and proteins) to magnetic nanoparticles in solution and then measuring their magnetization response, rapid detection of specific biomarkers can be achieved.

[0004] Existing methods for measuring the magnetization response and spectrum of magnetic nanoparticles have several aspects that urgently need optimization: Measurement systems often only allow for single-frequency measurements, lacking the ability to characterize the dynamic magnetization properties of magnetic nanoparticles under multiple excitation frequencies; in the excitation unit, factors such as excessive coil inductance cause the excitation module to output high power to maintain a large excitation magnetic field strength, resulting in excessively strong excitation magnetic field harmonic distortion and decreased measurement accuracy; in the measurement unit, the limited accuracy of magnetization response data acquisition and low sampling rate lead to limited accuracy of magnetization intensity harmonic data; and the overall integration of the measurement system is poor. Due to the large current in the excitation unit, unencapsulated systems pose significant safety risks and have poor portability during use. Summary of the Invention

[0005] To address the shortcomings and improvement needs of existing technologies, this invention provides a device and method for measuring the magnetization response and spectrum of magnetic nanoparticles under multi-frequency magnetic field excitation. The purpose is to study the magnetization response of magnetic nanoparticles under multi-frequency magnetic field excitation, and to comprehensively evaluate the magnetic properties of magnetic nanoparticles by taking into account the measurement results of magnetization intensity harmonics at different frequencies, thereby improving the measurement sensitivity of magnetic nanoparticles.

[0006] To achieve the above objectives, according to one aspect of the present invention, a device for measuring the magnetization response and spectrum of magnetic nanoparticles under multi-frequency magnetic field excitation is provided, characterized in that it includes: a multi-frequency magnetic field excitation unit, a sample placement unit, a signal measurement unit, and a central processing unit;

[0007] The multi-frequency magnetic field excitation unit includes a power amplifier subunit, an excitation coil subunit, and an impedance matching subunit. The power amplifier subunit is connected in series with the driving excitation coil subunit and the impedance matching subunit, and drives the latter two to generate a uniform alternating excitation magnetic field with multiple resonant frequencies.

[0008] The sample placement unit is used to place and move the sample to be tested, so that the sample is placed in the excitation magnetic field. The sample is a solid powder or solution containing magnetic nanoparticles.

[0009] The signal measurement unit includes an excitation magnetic field measurement subunit, a magnetic nanoparticle magnetization response measurement subunit, a preamplifier circuit subunit, and a data acquisition subunit. The excitation magnetic field measurement subunit is used to measure the excitation magnetic field. The magnetic nanoparticle magnetization response measurement subunit is used to measure the magnetization response signal of the sample under test in the excitation magnetic field. The preamplifier circuit subunit is used to amplify the magnetization response signal. The data acquisition subunit is used to acquire the magnetization response signal measured by the signal measurement unit and convert it into a digital signal that is easy to store and process, thereby measuring the magnetization response and spectrum of the sample.

[0010] The central processing unit receives the digital signal output by the signal measurement unit and obtains the magnetization response V of the magnetic nanoparticles by subtracting the signals measured before and after the sample is placed in the test. MNP (t), for V MNP (t) Perform spectral analysis to obtain the amplitude A(n) and phase of each harmonic response of the magnetization. Using A(n) and The detection characteristics of the magnetic nanoparticles to be tested are calculated, where n is the harmonic order and t is time;

[0011] The detection feature is one of the following: the amplitude and phase of each harmonic response; a weighted normalized combination of the amplitude and phase of each harmonic response.

[0012] According to the detection rules, different excitation magnetic field frequencies and amplitudes exist for different types of magnetic nanoparticle solutions, enabling high signal-to-noise ratio and high sensitivity detection of magnetic nanoparticle concentration information.

[0013] In summary, the above-described technical solutions conceived in this invention can achieve the following beneficial effects:

[0014] 1. This invention utilizes a multi-frequency magnetic field excitation unit composed of a power amplifier subunit, an impedance matching subunit, and an excitation coil subunit to measure the multi-frequency AC magnetization response information of the sample under test. It measures the signals before and after the sample is placed under test and calculates the difference. By calculating the amplitude and phase of each harmonic response of the magnetization signal, it completes the dynamic magnetization measurement of magnetic nanoparticles, which can obtain richer magnetization response information of magnetic nanoparticles and effectively improve the measurement sensitivity of magnetic nanoparticles.

[0015] 2. In the quantitative analysis of the magnetic nanoparticle content in the sample to be tested, the present invention has made various selections and comparisons of the detection features. It can select the amplitude and phase of each harmonic response or the weighted normalized combination of the amplitude and phase of each harmonic response, which can effectively ensure the detection accuracy of magnetic nanoparticle concentration information.

[0016] According to another aspect of the present invention, a method for measuring the magnetization response and spectrum of magnetic nanoparticles under multi-frequency magnetic field excitation is provided, comprising the following steps:

[0017] Step S10: Calibrate the multi-frequency magnetic field excitation unit, measure the excitation magnetic field, and measure the excitation current characterizing the excitation magnetic field to calculate the proportionality coefficient α between the excitation magnetic field and the excitation current.

[0018] Step S20: The signal measurement unit is calibrated to obtain the amplitude frequency characteristic Φ(ω) and phase frequency characteristic φ(ω) of the system transfer function;

[0019] Step S30: Set the preset excitation frequency and excitation magnetic field amplitude to generate a uniform alternating magnetic field as the excitation magnetic field H(t);

[0020] Step S40: Without placing the sample, measure the excitation coupling signal V0(t);

[0021] Step S50: After placing the sample to be tested, measure the AC magnetization response signal V1(t) of the magnetic nanoparticle sample in the alternating magnetic field.

[0022] Step S60: Subtract the signals from the two measurements; the result is the magnetization response V of the magnetic nanoparticles themselves. MNP (t), for V MNP (t) By performing spectral analysis, the amplitude A(n) and phase of each harmonic response of the magnetization can be obtained. Using the harmonic response amplitude A(n) and phase The AC magnetization intensity M(t) of the magnetic nanoparticles was reconstructed, and then the dynamic magnetization curve was plotted in combination with the excitation magnetic field H(t).

[0023] Step S70: Calculate the detection characteristics of the magnetic nanoparticles using the amplitude and phase of each harmonic response of the magnetic nanoparticles.

[0024] Step S80: Change the preset frequency and excitation magnetic field amplitude, and perform multiple measurements of multiple frequencies and multiple excitation magnetic field amplitudes to obtain richer magnetization response information of the magnetic nanoparticles to be tested.

[0025] The detection feature is one of the following: the amplitude and phase of each harmonic response; a weighted normalized combination of the amplitude and phase of each harmonic response.

[0026] This invention provides a method for measuring the magnetization response and spectrum of magnetic nanoparticles under multi-frequency magnetic field excitation. It measures the harmonic response and dynamic magnetization curve of the magnetization intensity of magnetic nanoparticles. Utilizing a multi-frequency, multi-excitation magnetic field amplitude measurement method, the frequency and amplitude of the excitation magnetic field can be adjusted independently to measure the magnetization response information of magnetic nanoparticles under different magnetic fields, effectively improving the sensitivity of magnetic nanoparticle detection and deepening the understanding of their dynamic magnetization characteristics. In summary, this invention achieves multi-frequency measurement of the magnetization response of magnetic nanoparticles by changing the frequency of a preset alternating magnetic field. It measures the excitation coupling of the background environment and the magnetization response of the magnetic nanoparticle sample under multiple frequencies, and then calculates the difference to obtain the magnetization response of the magnetic nanoparticles themselves. By calculating the harmonics of the magnetization response, richer magnetization response information of the magnetic nanoparticles can be obtained, while effectively improving the measurement sensitivity of magnetic nanoparticle concentration information.

[0027] In some optional embodiments, the detection feature is the amplitude of each odd-order harmonic of the third order and above.

[0028] Experiments show that after regressing the concentration information of magnetic nanoparticles using the amplitudes of the third and higher odd harmonics, the regression effect of the lower harmonics is more linear than that of the higher harmonics and is closer to the theoretical value of the concentration information of the sample. Therefore, the third harmonic has the best effect when performing regression of odd harmonics alone.

[0029] In some optional embodiments, the detection feature is a combination feature of the amplitudes of the third and above odd harmonics; the combination feature is a weighted normalized matrix of the harmonic amplitudes.

[0030] Experiments show that using a weighted normalized multiple harmonic matrix to regress the concentration information of magnetic nanoparticles yields better results than using only the third harmonic matrix. This method can accurately detect magnetic nanoparticles in the solution, and the regression results are close to the theoretical values. Attached Figure Description

[0031] Figure 1 This is a flowchart of the measurement process in Example 1.

[0032] Figure 2 This is a flowchart of the measurement and calibration process for the excitation magnetic field generated by the multi-frequency magnetic field excitation unit in Example 1.

[0033] Figure 3 This is a flowchart of the signal measurement unit calibration process in Example 1.

[0034] Figure 4 This is a graph showing the relationship between the magnetization response spectrum and the dynamic magnetization curve of the magnetic nanoparticles in Example 1.

[0035] Figure 5 This is a flowchart of the measurement process in Example 2.

[0036] Figure 6 This is a block diagram of the magnetization response and spectrum measurement device for magnetic nanoparticles under multi-frequency magnetic field excitation in Example 3.

[0037] Figure 7 This is a schematic diagram of the magnetization response and spectrum measurement device of magnetic nanoparticles under multi-frequency magnetic field excitation in Example 3.

[0038] Figure 8 This is a schematic diagram of a single-stage differential measurement coil.

[0039] Figure 9 This is a schematic diagram of a two-stage differential measurement coil.

[0040] Figure 10 This is a schematic diagram of a magnetic sensor.

[0041] Figure 11 This is a schematic diagram of the spectrum and dynamic magnetization curve of magnetic nanoparticles under multi-frequency magnetic field excitation. Detailed Implementation

[0042] To further illustrate the objectives, technical solutions, and advantages of this invention, the following description, in conjunction with the accompanying drawings and embodiments, provides a more concrete explanation of the invention. Note that the specific embodiments described herein are merely illustrative and not intended to limit the scope of the invention; furthermore, the technical features involved in the various embodiments described below can be combined with each other provided they do not conflict with each other.

[0043] To address the lack of functionality and means in existing magnetic nanoparticle measurement devices and methods for characterizing the dynamic magnetization characteristics of magnetic nanoparticles under multi-excitation frequency conditions, this invention proposes a device and method for measuring the magnetization response and spectrum of magnetic nanoparticles under multi-frequency magnetic field excitation. The overall approach involves measuring the AC magnetization response of the background environment without the sample being tested, and measuring the third and higher odd-order harmonics of the AC magnetization response of the magnetic nanoparticle sample in an alternating magnetic field after the sample is placed. This allows for the measurement of the magnetic nanoparticle magnetization response spectrum and dynamic magnetization curve. Since the diamagnetic properties of water in the solution of the magnetic nanoparticles only interfere with the fundamental frequency component of the harmonic information, this measurement process does not depend on the fundamental frequency information in the AC magnetization response, and the third and higher odd-order harmonic information remains unaffected. Therefore, by separately adjusting the amplitude and frequency of the AC excitation magnetic field, richer magnetization response information of the magnetic nanoparticles can be obtained, while effectively improving the measurement sensitivity of magnetic nanoparticle concentration information.

[0044] The following is an example.

[0045] Example 1:

[0046] A method for measuring the magnetization response and spectrum of magnetic nanoparticles under multi-frequency magnetic field excitation, such as Figure 1 As shown, it includes the following steps:

[0047] Step S10: Measure and calibrate the excitation magnetic field generated by the multi-frequency magnetic field excitation unit;

[0048] Step S20: The signal measurement unit is calibrated to obtain the amplitude frequency characteristic Φ(ω) and phase frequency characteristic φ(ω) of the system transfer function;

[0049] Step S30: Set the preset excitation frequency and excitation magnetic field amplitude to generate a uniform alternating magnetic field as the excitation magnetic field H(t);

[0050] Step S40: Without placing the sample, measure the excitation coupling signal V0(t);

[0051] Step S50: After placing the sample to be tested, measure the AC magnetization response signal V1(t) of the magnetic nanoparticle sample in the alternating magnetic field.

[0052] Step S60: Subtract the signals from the two measurements; the result is the magnetization response V of the magnetic nanoparticles themselves. MNP (t), for V MNP (t) By performing spectral analysis, the amplitude A(n) and phase of each harmonic response of the magnetization can be obtained. Using the harmonic response amplitude A(n) and phase The AC magnetization intensity M(t) of the magnetic nanoparticles was reconstructed, and then the dynamic magnetization curve was plotted in combination with the excitation magnetic field H(t).

[0053] Step S70: Calculate the detection characteristics of the magnetic nanoparticles using the amplitude and phase of each harmonic response of the magnetic nanoparticles.

[0054] Step S80: Change the preset frequency and excitation magnetic field amplitude, and perform multiple measurements of multiple frequencies and multiple excitation magnetic field amplitudes to obtain richer magnetization response information of the magnetic nanoparticles to be tested.

[0055] In this embodiment, the detection feature is the amplitude of each odd-order harmonic of the third order and above.

[0056] To more clearly explain the magnetization response and spectrum measurement method of magnetic nanoparticles under multi-frequency magnetic field excitation of the present invention, the following is in conjunction with... Figure 1 The steps in the embodiments of the present invention will be described in detail below.

[0057] The method for magnetization response and spectrum measurement of magnetic nanoparticles under multi-frequency magnetic field excitation according to the first embodiment of the present invention includes steps S10-S80, each step of which is described in detail below:

[0058] Step S10: Measure and calibrate the excitation magnetic field generated by the multi-frequency magnetic field excitation unit.

[0059] like Figure 2 The diagram shows a flowchart of a method for measuring and calibrating the excitation magnetic field generated by a multi-frequency magnetic field excitation unit, according to an embodiment of a method for measuring the magnetization response and spectrum of magnetic nanoparticles under multi-frequency magnetic field excitation. The calibration process using current and magnetic field measurement tools specifically includes:

[0060] Step S11: Measure the amplitude of the excitation current using current measuring tools such as ammeters or current sensors;

[0061] Step S12: Measure the magnetic field amplitude of the excitation magnetic field using a magnetic field measuring tool such as a gaussmeter;

[0062] Step S13: Calculate the ratio of the measured magnetic field amplitude to the current amplitude, and determine the proportionality coefficient α between the excitation magnetic field and the excitation current by taking multiple measurements.

[0063] Step S14: The excitation magnetic field is measured by monitoring the current.

[0064] like Figure 3 The diagram shown is a flowchart of the signal measurement unit calibration process of one embodiment of a method for measuring the magnetization response and spectrum of magnetic nanoparticles under multi-frequency magnetic field excitation according to the present invention.

[0065] Step S20 involves calibrating the signal measurement unit to obtain the amplitude-frequency characteristic Φ(ω) and phase-frequency characteristic φ(ω) of the system transfer function, specifically including:

[0066] Step S21: Input a reference sweep frequency signal to the multi-frequency magnetic field excitation unit;

[0067] Step S22: Assemble calibration tools, such as calibration coils and calibration samples, into the signal measurement unit;

[0068] Step S23: Based on spectrum analysis techniques such as digital phase-locked loop (PLL) technology, and using methods such as lock-in amplifiers, data acquisition cards, and host computer programs, during the frequency sweep process, the current signal in the multi-frequency magnetic field excitation unit and the reference sweep signal, as well as the voltage signal output by the measurement unit and the reference sweep signal, are respectively phase-locked and amplified to obtain two pairs of amplitude phase combinations.

[0069] Step S24: Perform multiple measurements and data processing on the two pairs of amplitude and phase combinations to obtain the amplitude-frequency characteristic Φ(ω) and phase-frequency characteristic φ(ω) of the system transfer function.

[0070] Step S30: Set the preset excitation frequency and excitation magnetic field amplitude to generate a uniform alternating magnetic field as the excitation magnetic field H(t).

[0071] Step S40: Without placing the sample, measure the excitation coupling signal V0(t).

[0072] Step S50: After placing the sample to be tested, measure the AC magnetization response signal V1(t) of the magnetic nanoparticle sample in the alternating magnetic field.

[0073] Step S60: Subtract the signals from the two measurements; the result is the magnetization response V of the magnetic nanoparticles themselves. MNP (t), for V MNP (t) By performing spectral analysis, the amplitude A(n) and phase of each harmonic response of the magnetization can be obtained. Using the harmonic response amplitude A(n) and phase The AC magnetization M(t) of the magnetic nanoparticles was reconstructed, and then the dynamic magnetization curve was plotted in conjunction with the excitation magnetic field H(t), specifically including:

[0074] Step S61: The magnetization response V(t) of the magnetic nanoparticles themselves is proportional to the time derivative of the AC magnetization M(t) of the magnetic nanoparticles, i.e.

[0075]

[0076] Step S62, based on the dynamic magnetization physical model, taking the Langevin magnetization model and the Debye relaxation model as examples, the AC magnetization intensity M(t) satisfies nonlinear characteristics and can be expanded into a Fourier series:

[0077]

[0078] Where f is the frequency of the excitation magnetic field, the calculated amplitude of the nth harmonic of the theoretical magnetic nanoparticle magnetization response is M. n Phase is

[0079] Step S63: Combine the proportionality coefficient α between the excitation magnetic field and the excitation current described in step S13 to solve for the excitation magnetic field H(t);

[0080] Step S64: Perform spectral analysis on the magnetization response V(t), such as Fourier transform, to obtain its spectrum and extract the harmonic response amplitude V(n) and phase.

[0081] In step S65, combining the amplitude frequency characteristic Φ(ω) and phase frequency characteristic φ(ω) of the system transfer function described in step S24, the harmonic response V(n) is inversely transformed using mathematical methods such as inverse Fourier transform, in conjunction with steps S61 and S62, to reconstruct the AC magnetization intensity M(t) of the magnetic particles.

[0082] Step S66: Plot the dynamic magnetization curve using M(t) and H(t).

[0083] Step S70: Calculate the detection characteristics of the magnetic nanoparticles using the amplitude and phase of each harmonic response of the magnetic nanoparticles.

[0084] Step S80: Change the preset frequency and excitation magnetic field amplitude, and perform multiple measurements of multiple frequencies and multiple excitation magnetic field amplitudes to obtain richer magnetization response information of the magnetic nanoparticles to be tested.

[0085] The relationship between the magnetization response spectrum and the measured physical quantity of the dynamic magnetization curve of the magnetic nanoparticles in Example 1 is shown in the figure. The experiment shows that after regressing the concentration information of the magnetic nanoparticles using the amplitude of each odd-order harmonic of the third order and above, the regression effect of the lower harmonics is better than that of the higher harmonics, and is closer to the theoretical value of the concentration information of the sample to be tested. Therefore, the third harmonic has the best effect when performing regression of odd-order harmonics alone.

[0086] Example 2:

[0087] A method for measuring the magnetization response and spectrum of magnetic nanoparticles under multi-frequency magnetic field excitation, such as Figure 3 As shown. This embodiment is similar to Embodiment 1 above, except that in this embodiment, the detection feature is the combination feature of the amplitude values ​​of each odd-order harmonic of the third order and above; the combination feature is the weighted normalization matrix of the harmonic amplitude values.

[0088] Experiments show that using a weighted normalized multiple harmonic matrix to regress the concentration information of magnetic nanoparticles yields better results than using only the third harmonic matrix. This method can accurately detect magnetic nanoparticles in the solution, and the regression results are close to the theoretical values.

[0089] Example 3:

[0090] A device for measuring the magnetization response and spectrum of magnetic nanoparticles under multi-frequency magnetic field excitation is shown in the block diagram below. Figure 6 As shown in the diagram. Figure 7 As shown, it includes a multi-frequency magnetic field excitation unit, a sample placement unit, a signal measurement unit, and a central processing unit.

[0091] The multi-frequency magnetic field excitation unit includes a power amplifier subunit, an excitation coil subunit, and an impedance matching subunit. The power amplifier subunit is connected in series with the drive excitation coil subunit and the impedance matching subunit, and drives the latter two to generate a uniform alternating excitation magnetic field with multiple resonant frequencies.

[0092] The sample placement unit is used to place and move the sample to be tested, so that the sample is placed in the excitation magnetic field. The sample is a solid powder or solution containing magnetic nanoparticles.

[0093] The signal measurement unit includes an excitation magnetic field measurement subunit, a magnetic nanoparticle magnetization response measurement subunit, a preamplifier circuit subunit, and a data acquisition subunit. The excitation magnetic field measurement subunit is used to measure the excitation magnetic field. The magnetic nanoparticle magnetization response measurement subunit is used to measure the magnetization response signal of the sample under test in the excitation magnetic field. The preamplifier circuit subunit is used to amplify the magnetization response signal. The data acquisition subunit is used to acquire the magnetization response signal measured by the signal measurement unit and convert it into a digital signal that is easy to store and process, thereby measuring the magnetization response and spectrum of the sample.

[0094] The central processing unit receives the digital signal output by the signal measurement unit and obtains the magnetization response V of the magnetic nanoparticles by subtracting the signals measured before and after the sample is placed in the test. MNP (t), for V MNP (t) Perform spectral analysis to obtain the amplitude A(n) and phase of each harmonic response of the magnetization. Using A(n) and The detection characteristics of the magnetic nanoparticles to be tested are calculated, where n is the harmonic order and t is time;

[0095] The detection feature is one of the following: the amplitude and phase of each harmonic response; a weighted normalized combination of the amplitude and phase of each harmonic response.

[0096] According to the detection rules, different excitation magnetic field frequencies and amplitudes exist for different types of magnetic nanoparticle solutions, enabling high signal-to-noise ratio and high sensitivity detection of magnetic nanoparticle concentration information.

[0097] To provide different measurement methods under varying requirements for measurement sensitivity, signal-to-noise ratio, etc., different differential measurement subunits can be used in the experiment, such as... Figure 8 Single-stage differential coil, Figure 9 Two-stage differential coils, Figure 10 Magnetic sensor.

[0098] The schematic diagram of the spectrum and dynamic magnetization curve of magnetic nanoparticles under multi-frequency magnetic field excitation measured in this invention is shown below. Figure 11 As shown.

[0099] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A device for measuring the magnetization response and frequency spectrum of magnetic nanoparticles under the excitation of a multi-frequency magnetic field, characterized in that The application relates to a multi-frequency magnetic field excitation unit, a sample placing unit, a signal measuring unit, a data collecting unit and a central processing unit. The multi-frequency magnetic field excitation unit comprises a power amplification subunit, an excitation coil subunit and an impedance matching subunit; the power amplification subunit is connected in series with the excitation coil subunit and the impedance matching subunit, and drives the latter two to make the multi-frequency magnetic field excitation unit generate uniform alternating excitation magnetic fields of multiple resonance frequencies. The power amplification subunit is used for receiving digital signals and performing power amplification to generate alternating voltage signals with power output. The excitation coil subunit is connected to the power amplification subunit, and alternating currents of specific frequencies make the excitation coil subunit generate uniform alternating excitation magnetic fields through solenoid, Helmholtz coil or saddle coil. The impedance matching subunit is connected in series with the power amplification subunit and the excitation coil subunit, and a resonance circuit is constructed by using an impedance matching method to match multiple resonance frequencies, so that the excitation coil has low impedance at the resonance point and helps to suppress harmonic distortion, thereby making the multi-frequency magnetic field excitation unit generate uniform alternating excitation magnetic fields of multiple frequencies. The sample placing unit is used for placing and moving a sample containing magnetic nanoparticles in a solid powder or solution to place the sample in the excitation magnetic field. The signal measuring unit comprises an excitation magnetic field measuring subunit, a magnetic nanoparticle magnetization response measuring subunit, a preamplifier circuit subunit and a data collecting subunit; the excitation magnetic field measuring subunit is used for measuring the excitation magnetic field; the magnetic nanoparticle magnetization response measuring subunit is used for measuring the magnetization response signal of the sample in the excitation magnetic field; the preamplifier circuit subunit is used for amplifying the magnetization response signal; and the data collecting subunit is used for collecting the magnetization response signal measured by the signal measuring unit and converting the magnetization response signal into a digital signal convenient for storage and processing, and then measuring the magnetization response and spectrum of the sample. The detection characteristic is a weighted and normalized combination of the harmonic response amplitude and phase. The central processing unit receives the digital signal outputted by the signal measuring unit, and subtracts the signal measured before the sample is put into from the signal measured after the sample is put into to obtain the magnetization response V of the magnetic nanoparticle itself MNP The central processing unit receives the digital signal outputted by the signal measuring unit, and subtracts the signal measured before the sample is put into from the signal measured after the sample is put into to obtain the magnetization response V of the magnetic nanoparticle itself MNP The central processing unit receives the digital signal outputted by the signal measuring unit, and subtracts the signal measured before the sample is put into from the signal measured after the sample is put into to obtain the magnetization response V of the magnetic nanoparticle itself The central processing unit receives the digital signal outputted by the signal measuring unit, and subtracts the signal measured before the sample is put into from the signal measured after the sample is put into to obtain the magnetization response V of the magnetic nanoparticle itself The central processing unit receives the digital signal outputted by the signal measuring unit, and subtracts the signal measured before the sample is put into from the signal measured after the sample is put into to obtain the magnetization response V of the magnetic nanoparticle itself The method comprises the following steps:

2. A method for measuring the magnetization response and frequency spectrum of magnetic nanoparticles under the excitation of a multi-frequency magnetic field, wherein the method uses the device for measuring the magnetization response and frequency spectrum of magnetic nanoparticles under the excitation of a multi-frequency magnetic field according to claim 1, characterized in that, Step S10: measuring and calibrating the excitation magnetic field generated by the multi-frequency magnetic field excitation unit; Step S20: calibrating the signal measuring unit to obtain the amplitude-frequency characteristic Phi (omega) and the phase-frequency characteristic phi (omega) of the system transfer function, wherein omega is the angular frequency; Step S30: setting a preset excitation frequency and an excitation magnetic field amplitude to generate a uniform alternating magnetic field as the excitation magnetic field H (t); Step S40: without placing the sample, measuring the excitation coupling signal V0 (t); Step S50: after placing the sample, measuring the alternating magnetization response signal V1 (t) of the magnetic nanoparticle sample in the alternating magnetic field; Step S70: calculating the detection characteristic of the magnetic nanoparticle by using the harmonic response amplitude and phase of the magnetic nanoparticle; Step S60, subtracting the twice measured signals, the result is the magnetic response V of the magnetic nanoparticle itself MNP (t), and performing frequency spectrum analysis on V MNP (t) can obtain the harmonic response amplitude A(n) and phase Using the harmonic response amplitude A(n) and phase Reconstructing the AC magnetization M(t) of the magnetic nanoparticle, and further combining the excitation magnetic field H(t) to draw the dynamic magnetization curve; Step S80: changing the preset frequency and the excitation magnetic field amplitude to perform multiple measurements of multiple frequencies and multiple excitation magnetic field amplitudes, thereby obtaining more abundant magnetization response information of the magnetic nanoparticle; The detection characteristic is a weighted and normalized combination of the harmonic response amplitude and phase. ​

Images