Method for calculating mass concentration of magnetic nanoparticles based on full width at half maximum of nuclear magnetic resonance spectrum

Abstract

The invention discloses a magnetic nanoparticle mass concentration calculation method based on the full width at half maximum of a nuclear magnetic resonance spectrum, and belongs to the technical field of magnetic nano material testing. The relationship between the mass concentration of the magnetic nanoparticles and the full width at half maximum of the magnetic resonance spectrum is established, the saturation magnetization intensity of a single magnetic nanoparticle is fixed, so that the change of the mass concentration of the magnetic nanoparticles is essentially the change of the number of the magnetic nanoparticles, and the mass concentration and the full width at half maximum of the magnetic resonance spectrum have a linear relationship; the change of the mass concentration of the magnetic nanoparticles can be reflected by measuring the full width at half maximum of the magnetic resonance spectrum, so that the measurement of the mass concentration of the magnetic nanoparticles is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of magnetic nanomaterial testing, and more specifically, relates to a method for measuring the mass concentration of magnetic nanoparticles based on nuclear magnetic resonance spectrum parameters. Background Art

[0002] Magnetic nanoparticles (MNPs) have many excellent physical properties, such as their nanoscale size and superparamagnetic characteristics. Therefore, they have received a lot of attention and applications in biomedicine, magnetic resonance imaging, magnetic fluids, data storage, etc. In practical applications, MNPs are wrapped by surfactants and evenly dispersed in the base liquid to form a stable colloidal suspension. Due to the effect of magnetization, the MNPs in the solution form a certain cluster structure after being magnetized and change the distribution of the magnetic field around themselves, making the "local" magnetic field uneven, which is reflected as the widening of FWHM in the nuclear magnetic resonance spectrum. Among them, the concentration change of magnetic nanoparticles can best reflect the process of FWHM widening. The relationship between the two is shown as a good linear relationship in the data obtained in the actual experiment. In addition, the traditional solution mass concentration measurement method has the problems of extremely high cost, large sample quantity and low applicability while maintaining high precision. Therefore, under the condition that a sufficient database has been established through magnetic resonance experiments, in order to achieve adequate utilization of resources, the data obtained in the magnetic resonance experiment can be used to establish the corresponding mass concentration and half-height width expression, so as to realize the function of predicting the mass concentration of the sample reagent to be tested by the half-height width of the magnetic resonance spectrum. However, among the existing methods for measuring the mass concentration of solutions, the high-precision measurement of the nuclear magnetic resonance method has high accuracy and strong structural analysis ability, but its cost is extremely high, requires a large sample quantity, and has low applicability. Summary of the invention

[0003] In order to solve the technical problems existing in the prior art, the present invention provides a method for calculating the mass concentration of magnetic nanoparticles based on the half-width of the nuclear magnetic resonance spectrum. On the basis of magnetic resonance, a mathematical model of the half-width of the magnetic resonance spectrum, the particle size of the sample to be tested and the mass concentration is established. With the help of this mathematical model, the mass concentration of the sample can be predicted through the particle size of the sample to be tested and its corresponding half-width of the spectrum.

[0004] To achieve the above object, according to a first aspect of the present invention, a method for calculating the mass concentration of magnetic nanoparticles based on the half-width of a nuclear magnetic resonance spectrum is provided, the method comprising the following steps:

[0005] S1. At a set temperature T, use the NMR method to measure the pure deuterium water reagent without adding magnetic nanoparticles, and record the half-height width FWHM value in the NMR spectrum ;

[0006] S2. Select magnetic nanoparticle reagents with consistent nominal particle sizes, dilute them into reagents of different mass concentrations according to the proportion, conduct nuclear magnetic resonance experiments on magnetic nanoparticle reagents at different concentrations, and record the corresponding half-height width values ​​in the nuclear magnetic resonance spectrum ;

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

[0008] S4. Select multiple groups of magnetic nanoparticle reagents with different nominal particle sizes, dilute the corresponding reagents at each particle size into samples of different mass concentrations according to the steps in S2, and then perform magnetic resonance experiments on the magnetic nanoparticle reagents of different mass concentrations, and record the half-height width values ​​of the corresponding nuclear magnetic resonance spectra;

[0009] S5. In each group of experiments in S4, the linear relationship between the half-width (FWHM) and mass concentration at different particle sizes was obtained. , particle size and Corresponding to different sample points, the discrete sample points are fitted to establish the relationship between the particle size d of the magnetic nanoparticles and the particle size. The linear relationship between them can be expressed as: , where k is the slope of the linear relationship, d is the nominal particle size of the magnetic nanoparticles in the sample to be tested, and b is the linear relationship The intercept of

[0010] S6. The relationship between the mass concentration of magnetic nanoparticles and the half-height width is obtained by using the formulas in S3 and S5. According to this relationship, the half-width of the nuclear magnetic resonance spectrum corresponding to the magnetic nanoparticle reagent with a known concentration is The mass concentration of the magnetic nanoparticle reagent to be tested can be predicted by the particle size d of the magnetic nanoparticles. .

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

[0012] Preferably, during the test, the parameters that remain consistent are temperature T, magnetic nanoparticle size d, external magnetic field .

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

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

[0015] Various other advantages and benefits will become apparent to those skilled in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only used to illustrate the preferred embodiments and are not to be considered as limiting the present invention. In order to more clearly illustrate the technical solution of the present invention, the following is a brief introduction to the drawings required for use in the embodiments, wherein:

[0016] Figure 1 A flow chart of a method for calculating the mass concentration of magnetic nanoparticles based on the half-width of a nuclear magnetic resonance spectrum provided by an embodiment of the present invention;

[0017] Figure 2 The relationship between the sample SHP-05 provided in the embodiment of the present invention and the half-width of magnetic resonance at different mass concentrations;

[0018] Figure 3 The relationship between the sample SHP-10 provided in the embodiment of the present invention and the half-height width of the magnetic resonance under different mass concentration conditions;

[0019] Figure 4 The relationship between the sample SHP-20 provided in the embodiment of the present invention and the half-width of magnetic resonance at different mass concentrations;

[0020] Figure 5 The relationship between the sample SHP-25 provided in the embodiment of the present invention and the half-width of magnetic resonance at different mass concentrations;

[0021] Figure 6 The relationship between the sample SHP-30 provided in the embodiment of the present invention and the half-width of magnetic resonance at different mass concentrations;

[0022] Figure 7 The slope of the linear curve of the particle size and half-height width-mass concentration of the magnetic nanoparticles provided in the embodiment of the present invention is relationship;

[0023] Figure 8 The error value between the predicted mass concentration and the actual concentration of SHP-05 provided in the embodiment of the present invention;

[0024] Fig. 9 The error value between the SHP-10 predicted mass concentration and the actual concentration provided in the embodiment of the present invention;

[0025] Fig.10 The error value between the SHP-20 predicted mass concentration and the actual concentration provided in the embodiment of the present invention;

[0026] Fig.11 The error value between the predicted mass concentration and the actual concentration of SHP-25 provided in the embodiment of the present invention;

[0027] Fig.12 The error value between the predicted mass concentration and the actual concentration of SHP-30 provided in the embodiment of the present invention; DETAILED DESCRIPTION

[0028] In order to make the purpose and technical solution of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. The specific embodiments described here are only used to explain the content of the present invention and are not used to limit the present invention.

[0029] The overall concept of the present invention is to use the relationship between the half-width of the magnetic nanoparticles in the magnetic resonance spectrum and the mass concentration of the magnetic nanoparticles, and calculate the mass concentration of the magnetic nanoparticles in the sample through the linear relationship between the half-width and the mass concentration. In nuclear magnetic resonance, the magnetic nanoparticles will be magnetized under the action of an external magnetic field to generate an induced magnetic field, which will affect the local magnetic field around itself, resulting in uneven local magnetic field. Changes in the mass concentration of magnetic nanoparticles will cause changes in 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 NMR theory, the half-width and transverse relaxation time Existence relationship: Therefore, the change of induced magnetic field is reflected in the NMR spectrum as the change of half-width. It has a linear relationship with mass concentration, as shown by the half-width The regression curve with mass concentration can be used to calculate the mass concentration of the sample.

[0030] like Figure 1 As shown, the present invention provides a method for calculating the mass concentration of magnetic nanoparticles based on the half-width of the nuclear magnetic resonance spectrum, the method comprising the following steps:

[0031] Step S1. At a set temperature, use the nuclear magnetic resonance method to measure the pure deuterium water reagent without adding magnetic nanoparticles, and record the half-height width FWHM value in the nuclear magnetic resonance spectrum. ;

[0032] In order to obtain the intrinsic half-width of the reagent when no magnetic nanoparticles were added, a magnetic resonance experiment was performed on the pure deuterated water reagent using a Spinsolve 60 nuclear magnetic resonance spectrometer to obtain the half-width in the magnetic resonance spectrum. , is the fixed intercept of the regression curve of mass concentration and half-width involved in the subsequent steps.

[0033] Step S2. Select a magnetic nanoparticle reagent with a consistent nominal particle size, dilute it into reagents of different mass concentrations according to the ratio, perform nuclear magnetic resonance experiments on the magnetic nanoparticle reagents at different concentrations, and record the corresponding half-height width in the nuclear magnetic resonance spectrum. ;

[0034] For magnetic nanoparticles with consistent nominal particle size, magnetic nanoparticle reagents of different mass concentrations are formed after dilution, that is, the mass concentration of the magnetic nanoparticles in the reagent is used as the independent variable, and magnetic resonance testing is performed. The purpose of recording the half-width of its magnetic resonance spectrum is to subsequently establish a linear relationship between the mass concentration of the magnetic nanoparticles and the half-width.

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

[0036] By using the magnetic resonance method to test multiple groups of reagents with different mass concentrations, a number of discrete sample points of mass concentration and half-width were obtained. By fitting the sample points, the linear relationship between the mass concentration of magnetic nanoparticles and the half-width was obtained.

[0037] S4. Select multiple groups of magnetic nanoparticle reagents with different nominal particle sizes, dilute the corresponding reagents at each particle size into samples of different mass concentrations according to the steps in S2, and then perform magnetic resonance experiments on the magnetic nanoparticle reagents of different mass concentrations, and record the half-height width values ​​of the corresponding nuclear magnetic resonance spectra;

[0038] Select multiple groups of magnetic nanoparticle reagents with different nominal particle sizes, repeat the steps of 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 different particle sizes is to establish the subsequent particle size d and the corresponding particle size. The linear relationship between them.

[0039] S5. In each group of experiments in S4, the linear relationship between the half-width (FWHM) and mass concentration at different particle sizes was obtained. , particle size and Corresponding to different sample points, the discrete sample points are fitted to establish the relationship between the particle size d of the magnetic nanoparticles and the particle size. The linear relationship between them can be expressed as: , where k is the slope of the linear relationship, d is the nominal particle size of the magnetic nanoparticles in the sample to be tested, and b is the linear relationship The intercept of

[0040] Different particle sizes correspond to different linear relationships between half-width (FWHM) and mass concentration. In the linear relationship obtained by fitting, the linear relationship between the corresponding half-width and the mass concentration of magnetic nanoparticles can be determined by the particle size. , so as to achieve the subsequent measurement of sample mass concentration.

[0041] S6. The relationship between the mass concentration of magnetic nanoparticles and the half-height width is obtained by using the formulas in S3 and S5. According to this relationship, the half-width of the nuclear magnetic resonance spectrum corresponding to the magnetic nanoparticle reagent with a known concentration is The mass concentration of the magnetic nanoparticle reagent to be tested can be predicted by the particle size d of the magnetic nanoparticles. ;

[0042] For the sample to be tested, after the nominal particle size of the magnetic nanoparticles in the reagent and the corresponding half-height width of the magnetic resonance spectrum are known, The mass concentration can be calculated By comparing with the mass concentration of known samples, the temperature measurement deviation value is obtained to measure the measurement accuracy.

[0043] Example

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

[0045] A magnetic resonance experiment was conducted on pure deuterium water reagent, and the half-width of its nuclear magnetic resonance spectrum was recorded as .

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

[0047] SHP series magnetic nanoparticle reagents SHP-05, SHP-10, SHP-20, SHP-25 and SHP-30 (Ocean NanoTech) with nominal core particle sizes of 5 nm, 10 nm, 20 nm, 25 nm and 30 nm were selected. All of them have Fe3O4 as the magnetic core, and the surface of the magnetic core is coated with a monolayer of oleic acid and a monolayer of amphiphilic polymer, so they have good water solubility and monodispersity.

[0048] The alternative 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 were selected respectively, and magnetic resonance experiments were carried out on a Spinsolve 60 nuclear magnetic resonance spectrometer. The half-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 the following figure. Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 shown.

[0049] 3. The half-width and mass concentration curves corresponding to different particle sizes are obtained as follows:

[0050] The half-height width values ​​obtained from the samples with different mass concentrations and different particle sizes are fitted to obtain the form: The half-width and mass concentration linear curves corresponding to particles of different particle sizes are:

[0051]

[0052]

[0053]

[0054]

[0055]

[0056] in, In the expression of is the slope of the linear relationship between the half-width of the NMR spectrum and the mass concentration of magnetic nanoparticles, C is the mass concentration of magnetic nanoparticles in the test sample, is the value of the half-maximum 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 equation, is the experimental condition for obtaining the data of each fitting formula, such as in formula (1) , expressed as In the linear relationship of The value is 95.2037, The corresponding linear relationship under the condition of 1.56Hz is: The correlation coefficient of the linear regression equation in expression (1) is 0.99598. It shows that it is a fitting formula of the magnetic resonance half-width obtained by measuring SHP-05 aqueous solution samples at different mass concentrations using a nuclear magnetic resonance instrument with a main magnetic field of 1.41T.

[0057] 4. Particle size d corresponds to particle size The linear relationship between is obtained as follows:

[0058] By fitting the half-height width corresponding to the above different particle sizes and the slope of the mass concentration corresponding curve, the particle size d and the particle size corresponding to the particle size are obtained. The linear relationship, such as Figure 7 As shown, it is expressed as:

[0059] ;

[0060] 5. The mass concentration measurement function is obtained as follows:

[0061] Through the relationship obtained in step 3 and step 4, the expression of half-width and mass concentration can be derived For a sample with known particle size and half-height width of magnetic resonance spectrum, the particle size d and half-height width are Substitute into the above formula to calculate the mass concentration of the sample .

[0062] 6. Calculated mass concentration The deviation of is obtained as follows:

[0063] Using the fitting obtained above , calculate the mass concentration of the sample , and the measured Compare with the mass concentration of known samples to obtain the mass concentration measurement deviation ,like Figure 8 , Fig. 9 , Fig.10 , Fig.11 , Fig.12 shown.

[0064] It can be seen from the actual experimental data that the half-width of the magnetic nanoreagent is linearly related to the mass concentration, and the slope of the linear relationship between the half-width and the mass concentration increases with the increase of the particle size, and forms a linear relationship.

[0065] It will be easily understood by those skilled in the art that the above description is only 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 in the protection scope of the present invention.

Claims

1. A method for calculating the mass concentration of magnetic nanoparticles based on the half-width of nuclear magnetic resonance spectrum, characterized in that: The method comprises the following steps: S1. At a set temperature T, use the NMR method to measure the pure deuterium water reagent without adding magnetic nanoparticles, and record the half-height width FWHM value in the NMR spectrum ; S2. Select magnetic nanoparticle reagents with consistent nominal particle sizes, dilute them into reagents of different mass concentrations according to the proportion, conduct nuclear magnetic resonance experiments on magnetic nanoparticle reagents at different concentrations, and record the corresponding half-height width values ​​in the nuclear magnetic resonance spectrum ; S3. The sample points corresponding to the mass concentration and half-width recorded in S2 are expressed as discrete data points. After linear fitting of the discrete data points, the linear relationship between the half-width of the nuclear magnetic resonance spectrum and the concentration of the magnetic nanoparticles under the condition of uniform magnetic nanoparticle size is obtained. ,in, is the slope of the linear relationship between the half-width of the NMR spectrum and the mass concentration of magnetic nanoparticles, and 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, dilute the corresponding reagents at each particle size into samples of different mass concentrations according to the steps in S2, and then perform magnetic resonance experiments on the magnetic nanoparticle reagents of different mass concentrations, and record the half-height width values ​​of the corresponding nuclear magnetic resonance spectra; S5. In each group of experiments in S4, the linear relationship between the half-width (FWHM) and mass concentration at different particle sizes was obtained. , particle size and Corresponding to different sample points, the discrete sample points are fitted to establish the relationship between the particle size d of the magnetic nanoparticles and the particle size. The linear relationship between them can be expressed as: , where k is the slope of the linear relationship, d is the nominal particle size of the magnetic nanoparticles in the sample to be tested, and b is the linear relationship The intercept of S6. The relationship between the mass concentration of magnetic nanoparticles and the half-height width is obtained by using the formulas in S3 and S5. According to this relationship, the half-width of the nuclear magnetic resonance spectrum corresponding to the magnetic nanoparticle reagent with a known concentration is The mass concentration of the magnetic nanoparticle reagent to be tested can be predicted by the particle size d of the magnetic nanoparticles. .

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

3. The method for calculating the mass concentration of magnetic nanoparticles based on the half-width of nuclear magnetic resonance spectrum according to claim 1, characterized in that: During the test, the parameters that remained consistent were temperature T, magnetic nanoparticle size d, and external magnetic field. .

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

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