A method for calculating the mass concentration of magnetic nanoparticles based on the half-height width of nuclear magnetic resonance spectrum

Abstract

The application discloses a kind of based on magnetic resonance spectrum half-width's magnetic nano particle mass concentration calculation method, belong to magnetic nano material testing technical field, the application with magnetic nano particle induces local magnetic field inhomogeneity and causes magnetic resonance spectrum to produce change as medium, the relationship between the mass concentration of magnetic nano particle and magnetic resonance spectrum half-width is established, since the saturation magnetization intensity of single magnetic nano particle is fixed, so the change of the mass concentration of magnetic nano particle is essentially the change of the number of magnetic nano particle, mass concentration and magnetic resonance spectrum half-width have linear relationship, the change of magnetic nano particle mass concentration can be reflected by measuring magnetic resonance spectrum half-width, realize the measurement of magnetic nano particle mass concentration.

Description

Technical Field

[0001] This invention belongs to the field of magnetic nanomaterial testing technology, and more specifically, relates to a method for measuring the mass concentration of magnetic nanoparticles based on nuclear magnetic resonance spectral parameters. Background Technology

[0002] Magnetic nanoparticles (MNPs) possess numerous excellent physical properties, such as their nanoscale size and superparamagnetic characteristics. Therefore, they have attracted considerable attention and application in biomedicine, nuclear magnetic resonance imaging, magnetohydrodynamics, and data storage. In practical applications, MNPs are encapsulated with surfactants and uniformly dispersed in a base liquid to form a stable colloidal suspension. This suspension is then subjected to an external magnetic field. The magnetization of magnetic nanoparticles (MNPs) in solution leads to the formation of cluster structures and alters the distribution of the surrounding magnetic field, resulting in localized magnetic field inhomogeneity, which manifests as broadening of the Full-width at half maximum (FWHM) in the nuclear magnetic resonance (NMR) spectrum. The concentration change of magnetic nanoparticles best reflects this FWHM broadening process, and the relationship between the two is well-defined in experimental data. However, traditional methods for measuring solution mass concentration, while maintaining high accuracy, suffer from high cost, large sample volume requirements, and limited applicability. Therefore, given a sufficient database established through magnetic resonance experiments, to fully utilize resources, it is possible to establish corresponding expressions for mass concentration and FWHM using the data obtained from magnetic resonance experiments, enabling the prediction of the sample's reagent mass concentration using the FWHM of the magnetic resonance spectrum. However, among existing methods for measuring solution mass concentration, high-precision NMR measurement offers high accuracy and strong structural resolution capabilities, but it is extremely costly, requires large sample volumes, and has limited applicability. Summary of the Invention

[0003] To address the technical problems existing in the prior art, this invention provides a method for calculating the mass concentration of magnetic nanoparticles based on the full width at half maximum (FWHM) of the nuclear magnetic resonance spectrum. Based on magnetic resonance, a mathematical model is established for the FWHM of the magnetic resonance spectrum, the particle size of the sample to be tested, and the mass concentration. Using this mathematical model, the mass concentration of the sample can be predicted by the particle size of the sample and its corresponding FWHM.

[0004] To achieve the above objectives, according to a first aspect of the present invention, a method for calculating the mass concentration of magnetic nanoparticles based on the full width at half maximum (FWHM) of nuclear magnetic resonance (NMR) spectra is provided. This method includes the following steps:

[0005] S1. At a set temperature T, the pure deuterium water reagent without the addition of magnetic nanoparticles was measured using nuclear magnetic resonance (NMR), and the full width at half maximum (FWHM) of the NMR spectrum was recorded. ;

[0006] S2. Selecting magnetic nanoparticle reagents with consistent nominal particle size, diluting them into reagents with different mass concentrations according to the proportion, and performing nuclear magnetic resonance experiments on the magnetic nanoparticle reagents with different concentrations to record the values of the half-height width in the corresponding nuclear magnetic resonance spectrum ;

[0007] S3. The sample points corresponding to the mass concentration and the half-height width recorded in S2 are discrete data points. After linear fitting of the discrete data points, the linear relationship between the half-height width of the nuclear magnetic resonance spectrum and the concentration of the magnetic nanoparticles under the condition of uniform particle size of the magnetic nanoparticles is obtained , wherein is the slope of the linear relationship between the half-height width of the nuclear magnetic resonance spectrum and the mass concentration of the magnetic nanoparticles, and C is the mass concentration of the magnetic nanoparticles in the test sample;

[0008] S4. Selecting multiple groups of magnetic nanoparticle reagents with inconsistent nominal particle sizes, diluting the reagents corresponding to each particle size into samples with different mass concentrations according to the steps in S2, and then performing magnetic resonance experiments on the magnetic nanoparticle reagents with different mass concentrations to record the values of the half-height width in the corresponding nuclear magnetic resonance spectrum;

[0009] S5. In each group of experiments in S4, the linear relationship between the half-height width (FWHM) and the mass concentration (mass concentration) under different particle sizes is obtained , the particle size corresponds to , and the discrete sample points are fitted to establish the linear relationship between the particle size d of the magnetic nanoparticles and the corresponding to the particle size of the particles, and the expression is: , wherein k is the slope of the linear relationship, d is the nominal particle size of the magnetic nanoparticles in the sample to be measured, and b is the intercept of the linear relationship ;

[0010] S6. The relationship between the mass concentration of the magnetic nanoparticles and the half-height width is obtained by the formulas in S3 and S5 , and according to the relationship, under the condition that the half-height width of the nuclear magnetic resonance spectrum corresponding to the magnetic nanoparticle reagent to be measured at a known concentration and the particle size d of the magnetic nanoparticles are known, the mass concentration of the magnetic nanoparticle reagent to be measured can be predicted.

[0011] Preferably, the fluctuation range of the set temperature T during measurement is limited to 280K-320K.

[0012] Preferably, the consistent parameters during the test are the temperature T, the particle size d of the magnetic nanoparticles, and the external magnetic field .

[0013] By the above scheme conceived by the present application, the following beneficial effects can be achieved:

[0014] The present application establishes a linear regression curve by using the correspondence between the parameters and concentration of magnetic nanoparticles in magnetic resonance spectrum, predicts the mass concentration of the magnetic nanoparticle sample according to the curve, reflects the mass concentration of the magnetic nanoparticles by the half-height width of the magnetic resonance spectrum, and provides higher measurement accuracy of the mass concentration. BRIEF DESCRIPTION OF DRAWINGS

[0015] Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings provided herein are for illustrative purposes only and are not considered a limitation of the present application. In order to more clearly illustrate the technical solutions of the present application, the drawings needed to be used in the embodiments will be briefly introduced as follows:

[0016] Figure 1 A flowchart of a magnetic nanoparticle mass concentration calculation method based on the half-height width of nuclear magnetic resonance spectrum is provided for the embodiments of the present application;

[0017] Figure 2 The relationship between the sample SHP-05 under different mass concentrations and the magnetic resonance half-height width is provided for the embodiments of the present application;

[0018] Figure 3 The relationship between the sample SHP-10 under different mass concentrations and the magnetic resonance half-height width is provided for the embodiments of the present application;

[0019] Figure 4 The relationship between the sample SHP-20 under different mass concentrations and the magnetic resonance half-height width is provided for the embodiments of the present application;

[0020] Figure 5 The relationship between the sample SHP-25 under different mass concentrations and the magnetic resonance half-height width is provided for the embodiments of the present application;

[0021] Figure 6 The relationship between the sample SHP-30 under different mass concentrations and the magnetic resonance half-height width is provided for the embodiments of the present application;

[0022] Figure 7 The relationship between the particle size of the magnetic nanoparticles and the linear curve slope of the half-height width-mass concentration is provided for the embodiments of the present application;

[0023] Figure 8 The error value between the predicted mass concentration and the actual concentration of SHP-05 is provided for the embodiments of the present application;

[0024] ​Figure 9 The error value of the SHP-10 predicted mass concentration and the actual concentration is provided for the embodiment of the present application;

[0025] Figure 10 The error value of the SHP-20 predicted mass concentration and the actual concentration is provided for the embodiment of the present application;

[0026] Figure 11 The error value of the SHP-25 predicted mass concentration and the actual concentration is provided for the embodiment of the present application;

[0027] Figure 12 The error value of the SHP-30 predicted mass concentration and the actual concentration is provided for the embodiment of the present application; DETAILED DESCRIPTION

[0028] In order to make the purpose, technical scheme of the present application clearer, the present application will be further described in detail below in combination with the drawings and embodiments. The specific embodiments described herein are only used to explain the content of the present application and do not limit the present application.

[0029] The overall concept of the present application is: using the relationship between the half-height width in the magnetic resonance spectrum and the mass concentration of the magnetic nanoparticles, the mass concentration of the magnetic nanoparticles in the sample is calculated through the linear relationship between the half-height width and the mass concentration. In nuclear magnetic resonance, the magnetic nanoparticles will be magnetized to produce an induced magnetic field under the action of an external magnetic field, which will affect the local magnetic field around itself, resulting in non-uniform local magnetic field. The change of the mass concentration of the magnetic nanoparticles will cause the change of the induced magnetization intensity of the magnetic nanoparticles in the magnetic field, and the induced magnetic field will affect the magnetic field felt by the water protons around it, thereby changing the transverse relaxation time of the water protons In the theory of nuclear magnetic resonance, the half-height width and the transverse relaxation time have the following relationship: Therefore, the change of the induced magnetic field is reflected in the change of the half-height width in the nuclear magnetic resonance spectrum, and the half-height width has a linear relationship with the mass concentration during the change of the mass concentration. The regression curve of the half-height width and the mass concentration can realize the calculation of the mass concentration of the sample.

[0030] As shown in Figure 1 , the present application provides a magnetic nanoparticle mass concentration calculation method based on the half-height width of the nuclear magnetic resonance spectrum, which comprises the following steps:

[0031] Step S1. At a set temperature, the pure deuterium water reagent without adding magnetic nanoparticles is measured by the method of nuclear magnetic resonance, and the value of the half-height width FWHM in the nuclear magnetic resonance spectrum is recorded ;

[0032] In order to obtain the inherent half-height width of the reagent without adding magnetic nanoparticles, a magnetic resonance experiment is performed on the pure deuterium water reagent by the Spinsolve 60 nuclear magnetic resonance spectrometer to obtain the half-height width in the magnetic resonance spectrum , which is the fixed intercept of the regression curve of the mass concentration and the half-height width involved in the subsequent steps.

[0033] Step S2. Select magnetic nanoparticle reagents with consistent nominal particle size, dilute them in proportion to form reagents with different mass concentrations, and perform nuclear magnetic resonance experiments on the magnetic nanoparticle reagents with different concentrations to record the corresponding half-height width values in the nuclear magnetic resonance spectrum ;

[0034] For magnetic nanoparticles with consistent nominal particle size, after dilution, magnetic nanoparticle reagents with different mass concentrations are formed, i.e. the mass concentration of magnetic nanoparticles in the reagent is the independent variable. The purpose of recording the half-height width of the magnetic resonance spectrum is to establish the linear relationship between the mass concentration of magnetic nanoparticles and the half-height width in the subsequent steps.

[0035] S3. The sample points corresponding to the mass concentration and the half-height width recorded in S2 are in the form of discrete data points. After linear fitting of the discrete data points, the linear relationship between the half-height width of the nuclear magnetic resonance spectrum and the concentration of magnetic nanoparticles under the condition of uniform magnetic nanoparticle size is obtained , wherein is the slope of the linear relationship between the half-height width of the nuclear magnetic resonance spectrum and the mass concentration of magnetic nanoparticles, and C is the mass concentration of magnetic nanoparticles in the test sample;

[0036] A plurality of reagents with different mass concentrations are tested by the magnetic resonance method to obtain a plurality of discrete sample points of mass concentration and half-height width. The linear relationship between the mass concentration of magnetic nanoparticles and the half-height width can be obtained by fitting the sample points.

[0037] S4. Select a plurality of magnetic nanoparticle reagents with inconsistent nominal particle sizes, dilute the corresponding reagents at each particle size to different mass concentrations according to the steps in S2, and then perform magnetic resonance experiments on the magnetic nanoparticle reagents with different mass concentrations to record the corresponding half-height width values in the nuclear magnetic resonance spectrum.

[0038] Select a plurality of magnetic nanoparticle reagents with inconsistent nominal particle sizes, repeat the steps in S2, and establish the linear relationship between the mass concentration and the half-height width of the magnetic nanoparticles at different particle sizes. The purpose of recording the linear relationship between the mass concentration and the half-height width corresponding to the particle size d is to establish the linear relationship between the particle size d and the particle size corresponding to the .

[0039] S5. In each group of experiments in S4, according to the linear relationship between the full width at half maximum (FWHM) and the mass concentration at different particle sizes, the corresponding particle size of different particle sizes is obtained , the particle size is corresponding to different sample points, the discrete sample points are fitted, and the linear relationship between the particle size d of the magnetic nanoparticle and the particle size corresponding to the is established, and the expression is: , wherein k is the slope of the linear relationship, d is the nominal particle size of the magnetic nanoparticle in the sample to be measured, and b is the intercept of the linear relationship ;

[0040] Different particle sizes correspond to different linear relationships between the full width at half maximum (FWHM) and the mass concentration (mass concentration). In the linear relationship fitted by the particle size corresponding to the , the linear relationship between the full width at half maximum and the mass concentration of the magnetic nanoparticle can be determined by the particle size , so as to realize subsequent measurement of the mass concentration of the sample.

[0041] S6. The relationship between the mass concentration of the magnetic nanoparticle and the full width at half maximum is obtained by the formula in S3 and S5 , according to the relationship, in the case that the full width at half maximum corresponding to the magnetic resonance spectrum of the magnetic nanoparticle reagent to be measured is known, and the particle size d of the magnetic nanoparticle is known, the mass concentration of the magnetic nanoparticle reagent to be measured can be predicted.

[0042] For the sample to be measured, after the nominal particle size of the magnetic nanoparticle in the reagent and the corresponding magnetic resonance spectrum full width at half maximum are known, the mass concentration can be calculated by , by comparing with the mass concentration of the known sample, the deviation value of the measurement is obtained, so as to measure the measurement accuracy.

[0043] Embodiment

[0044] 1. The acquisition of the magnetic resonance full width at half maximum without adding the magnetic nanoparticle reagent is described as follows:

[0045] The pure deuterium water reagent is subjected to magnetic resonance experiment, and the full width at half maximum of the nuclear magnetic resonance spectrum is recorded as .

[0046] 2. The acquisition of the magnetic nanoparticle reagent with uniform particle size and different mass concentrations is described as follows:

[0047] SHP series of magnetic nanoparticles reagents SHP-05, SHP-10, SHP-20, SHP-25 and SHP-30 (Ocean NanoTech company) with nominal core particle sizes of 5 nm, 10 nm, 20 nm, 25 nm and 30 nm respectively, all of which have Fe3O4 as the magnetic core and are coated with a single layer of oleic acid and a single layer of amphiphilic polymer on the surface of the magnetic core, thus having good water solubility and monodispersity;

[0048] The selected magnetic nanoparticle reagents with mass concentrations of 0.01 mg / mL, 0.025 mg / mL, 0.05 mg / mL, 0.1 mg / mL and 0.25 mg / mL respectively were subjected to magnetic resonance experiments on a Spinsolve 60 nuclear magnetic resonance spectrometer, and the half-height width values of the nuclear magnetic resonance spectra were recorded. The linear relationships of the magnetic nanoparticle reagents SHP-05, SHP-10, SHP-20, SHP-25 and SHP-30 at different mass concentrations are shown in Figure 2 、 Figure 3 、 Figure 4 、 Figure 5 、 Figure 6 .

[0049] 3. The half-height width corresponding to different particle sizes and the mass concentration corresponding curve were obtained, and the description is as follows:

[0050] The half-height width values of the samples of different mass concentrations and different particle sizes were fitted to obtain the linear curve of the half-height width of different particle sizes and the mass concentration in the form of , which are as follows:

[0051]

[0052]

[0053]

[0054]

[0055]

[0056] wherein, in the expression of is the slope of the linear relationship between the half-height width of the nuclear magnetic resonance spectrum and the mass concentration of the magnetic nanoparticles, C is the mass concentration of the magnetic nanoparticles in the test sample, is the value of the half-height width FWHM in the nuclear magnetic resonance spectrum of the pure deuterium water reagent without adding magnetic nanoparticles, is the correlation coefficient of the linear regression formula, is the experimental condition for obtaining the data of each fitting formula, such as , is expressed as a linear relationship, value is 95.2037, corresponding linear relationship under the condition of 1.56Hz, corresponding linear regression formula in formula (1) is 0.99598, indicates that the fitting formula of the magnetic resonance half-height width of the SHP-05 aqueous solution sample is obtained by measuring the sample under different mass concentrations using a nuclear magnetic resonance instrument with a main magnetic field of 1.41T.

[0057] 4. The linear relationship between the particle size d and the corresponding to the particle size of the particle size is described as follows:

[0058] By fitting the slope of the half-height width corresponding to the different particle sizes and the mass concentration corresponding curve, the linear relationship between the particle size d and the corresponding to the particle size of the particle size is obtained, as shown in Figure 7 , which is expressed as:

[0059] ;

[0060] 5. The obtaining of the mass concentration measurement function is described as follows:

[0061] The expression of the half-height width and the mass concentration can be derived from the relationship obtained in steps 3 and 4. For a sample to be measured with a known particle size and a half-height width of the magnetic resonance spectrum, the particle size d and the half-height width are brought into the above formula, and the mass concentration of the sample can be calculated.

[0062] 6. The obtaining of the deviation of the calculated mass concentration is described as follows:

[0063] The mass concentration of the sample is calculated using the fitted , and the measured is compared with the known mass concentration of the sample to obtain the mass concentration measurement deviation , as shown in Figure 8 , Figure 9 , Figure 10 , Figure 11 , Figure 12 .

[0064] From the actual experimental data, it can be seen that the half-height width of the magnetic nanometer reagent is linearly related to the mass concentration, and the slope of the linear relationship between the half-height width and the mass concentration increases with the increase of the particle size, and the linear relationship is formed.

[0065] Those skilled in the art can easily understand that the above description is only the preferred embodiment of the present application, and is not intended to limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for calculating the mass concentration of magnetic nanoparticles based on the full width at half maximum (FWHM) of nuclear magnetic resonance (NMR) spectra, characterized in that, The method includes the following steps: S1. At a set temperature T, the pure deuterium water reagent without the addition of magnetic nanoparticles was measured using nuclear magnetic resonance (NMR), and the full width at half maximum (FWHM) of the NMR spectrum was recorded. ; S2. Select magnetic nanoparticle reagents with consistent nominal particle size, dilute them to different mass concentrations according to the specified ratio, and perform nuclear magnetic resonance experiments on the magnetic nanoparticle reagents at different concentrations, recording the corresponding full width at half maximum (FWHM) values ​​in the NMR spectra. ; The sample points corresponding to the mass concentration and full width at half maximum (FWHM) recorded in S3 and S2 are represented as discrete data points. After linear fitting of the discrete data points, the linear relationship between the FWHM of the nuclear magnetic resonance spectrum and the concentration of magnetic nanoparticles is obtained under the condition of uniform magnetic nanoparticle size. ,in, denoted as the slope of the linear relationship between the full width at half maximum (FWHM) of the nuclear magnetic resonance spectrum and the mass concentration of magnetic nanoparticles, where C is the mass concentration of magnetic nanoparticles in the test sample. S4. Select multiple groups of magnetic nanoparticle reagents with different nominal particle sizes. Following the steps in S2, dilute the corresponding reagents for each particle size into samples of different mass concentrations. Then, perform magnetic resonance experiments on magnetic nanoparticle reagents of different mass concentrations and record the full width at half maximum (FWHM) values ​​in the corresponding nuclear magnetic resonance spectra. S5. In the experiments of S4, based on the linear relationship between the lower half-width (FWHM) and mass concentration for different particle sizes, the corresponding values ​​for different particle sizes were obtained. Particle size and For different sample points, the discrete sample points are fitted to establish the relationship between the magnetic nanoparticle size d and the particle size. The linear relationship between them is expressed as follows: Where k is the slope of the linear relationship, d is the nominal particle size of the magnetic nanoparticles in the sample, and b is the linear relationship. The intercept; S6. Using the formulas in S3 and S5, we obtain the relationship between the mass concentration of magnetic nanoparticles and the full width at half maximum (FWHM). According to this relationship, the full width at half maximum (FWHM) of the nuclear magnetic resonance spectrum corresponding to a known concentration of magnetic nanoparticle reagent is... Given the particle size d of the magnetic nanoparticles, the mass concentration of the magnetic nanoparticle reagent to be tested can be predicted. .

2. The method for calculating the mass concentration of magnetic nanoparticles based on the full width at half maximum (FWHM) of nuclear magnetic resonance (NMR) spectrum according to claim 1, characterized in that, In S1, the temperature T set during measurement is limited to a fluctuation range of 280 K to 320 K.

3. The method for calculating the mass concentration of magnetic nanoparticles based on the full width at half maximum (FWHM) of nuclear magnetic resonance (NMR) spectrum according to claim 1, characterized in that, During the testing process, the following parameters were kept constant: temperature T, magnetic nanoparticle size d, and external magnetic field. .

4. The method for calculating the mass concentration of magnetic nanoparticles based on the full width at half maximum (FWHM) of nuclear magnetic resonance (NMR) spectrum according to claim 1, characterized in that, In actual experimental data, under the above conditions, the relationship between the full width at half maximum (FWHM) and the mass concentration of magnetic nanoparticles is linear.

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