Preparation method of magnetic liquid metal nanoparticles

Abstract

The invention relates to a preparation method of magnetic liquid metal nanoparticles, and belongs to the technical field of magnetic nano materials. The preparation method comprises the following steps: ultrasonically dispersing liquid metal into a first solvent to obtain a liquid metal suspension, adding metal salt into the liquid metal suspension, and stirring and reacting for 10-30 minutes at the temperature of 40-50 DEG C to obtain a liquid metal salt solution; dissolving a reducing agent in a second solvent to obtain a reducing agent solution; under the stirring condition at the temperature of 40-60 DEG C, the reducing agent solution is dropwise added into the liquid metal salt solution, stirring reaction continues to be conducted for 5-10 min after titration is completed, washing and centrifugal separation are conducted through ethyl alcohol and deionized water in sequence, solid is subjected to vacuum drying, and the magnetic liquid metal nanoparticles are obtained. According to the method, the potential difference between liquid metal and metal salt ions and a heterogeneous interface provided by the liquid metal are utilized, in-situ reduction is conducted on the surfaces of the liquid metal nanoparticles through a wet chemical reduction method, magnetic particles grow on the surfaces of the liquid metal nanoparticles, and therefore the magnetic liquid metal nanoparticles anchored in situ through chemical bonding are obtained.

Description

Technical Field

[0001] The invention relates to a method for preparing magnetic liquid metal nanoparticles, belonging to the technical field of magnetic nanomaterials. Background Art

[0002] Liquid metal is a new multifunctional material with excellent fluidity, high thermal conductivity, high electrical conductivity, non-toxicity and overall stable chemical properties at room temperature. It is widely used in microfluidics, soft robotics, stretchable electronics, energy storage and other fields. Recently, composite materials modified by adding magnetic materials to liquid metal to give it magnetic properties have also been used in the field of magnetic fluids.

[0003] However, conventional pre-oxidation mechanical stirring (stirring and mixing liquid metal and magnetic particles under air for a long time) and alloy phase wetting (partial alloying of magnetic particles and liquid metal at a certain temperature) methods are all physical blending of the two to modify the liquid metal. There are problems such as uneven mixing of magnetic fluids and agglomeration, and poor suspension stability due to density difference between the two. In addition, the continuous alloying process of magnetic fluid magnetic particles in contact with liquid metal will also cause the magnetic fluid to demagnetize and fail. Summary of the invention

[0004] In view of the fact that existing liquid metal magnetic fluids are all prepared by physical blending, which inevitably leads to problems such as uneven mixing of the magnetic fluid, poor suspension stability, and easy demagnetization due to alloying, the present invention proposes a method for preparing magnetic liquid metal nanoparticles, namely, using a wet chemical reduction method to in-situ reduce and grow magnetic particles on the surface of liquid metal nanoparticles. Due to the heterogeneous interface and surface potential difference provided by the liquid metal, metal salt ions will preferentially nucleate and grow on the surface of the liquid metal nanoparticles, thereby obtaining chemically bonded in-situ anchored magnetic liquid metal nanoparticles.

[0005] A method for preparing magnetic liquid metal nanoparticles, the specific steps are as follows:

[0006] (1) adding liquid metal into a first solvent and performing ultrasonic dispersion treatment to obtain a liquid metal suspension;

[0007] (2) adding a metal salt to a liquid metal suspension, stirring and reacting at a temperature of 40 to 50° C. for 10 to 30 minutes to obtain a liquid metal salt solution; the metal salt is one or more of a cobalt salt, a nickel salt, and an iron salt;

[0008] (3) dissolving a reducing agent in a second solvent to obtain a reducing agent solution; the pH value of the second solvent is not less than 10;

[0009] (4) At a temperature of 40 to 60° C. and under stirring conditions, the reducing agent solution is dripped into the liquid metal salt solution drop by drop. After the titration is completed, the stirring reaction is continued for 5 to 10 minutes. The solution is washed with ethanol and deionized water in turn, centrifuged, and the solid is vacuum dried to obtain magnetic liquid metal nanoparticles. The core of the magnetic liquid metal nanoparticles is liquid metal, and the surface of the liquid metal is loaded with magnetic particles.

[0010] Preferably, the liquid metal in step (1) is Ga or Ga-A alloy, and A is one or more of In, Sn, Bi, Zn, and Al.

[0011] Preferably, the first solvent in step (1) is one or more of water, methanol, ethanol, isopropanol, and N,N-dimethylformamide.

[0012] Preferably, the concentration of the liquid metal in the liquid metal suspension in step (1) is 5 to 10 mg / mL.

[0013] Preferably, the mass ratio of the metal salt in step (2) to the liquid metal in step (1) is 0.1 to 0.8:1.

[0014] Preferably, the reducing agent in step (3) is sodium borohydride, potassium borohydride or ascorbic acid, and the mass ratio of the reducing agent to the metal salt in step (2) is 0.25 to 0.4:1.

[0015] Preferably, the second solvent in step (3) is potassium hydroxide solution, sodium hydroxide solution, ammonia water or hydrazine hydrate solution, and the concentration of the reducing agent solution is 0.5 to 1.5 mol / L.

[0016] Preferably, the dropping speed of the reducing agent solution in step (4) is 0.5-1 ml / min.

[0017] The present invention utilizes ultrasound to uniformly disperse liquid metal in a first solvent, utilizes the potential difference between the liquid metal and the metal salt ions to accelerate the replacement reaction rate between the liquid metal and the metal salt ions at a specific temperature, and realizes the initial nucleation of magnetic metal particles on the surface of liquid metal nanoparticles; utilizes the strong reducing property of the reducing agent under alkaline conditions to enable the remaining metal salt ions to rapidly grow on the surface of the liquid metal nanoparticles and grow into magnetic nanoparticles; and by adjusting the elemental composition and proportion of the liquid metal, the type and content of the metal salt ions, magnetic liquid metal nanoparticles of different matrix types and magnetic strengths can be obtained.

[0018] The beneficial effects of the present invention are:

[0019] (1) The present invention utilizes a wet chemical reduction method to in-situ reduce and grow magnetic particles on the surface of liquid metal nanoparticles. Due to the heterogeneous interface and surface potential difference provided by the liquid metal, metal salt ions will preferentially nucleate and grow on the surface of the liquid metal nanoparticles, thereby obtaining chemically bonded in-situ anchored magnetic liquid metal nanoparticles.

[0020] (2) The wet chemical reduction method of the present invention grows magnetic nanoparticles in situ on the surface of liquid metal nanoparticles, solving the problems of poor overall suspension stability and uneven dispersion and easy agglomeration of magnetic particles caused by physical and mechanical mixing of conventional liquid metal magnetic fluids;

[0021] (3) The present invention can adjust the magnetic properties of magnetic liquid metal nanoparticles, including saturation magnetization intensity and coercive force, by changing the types and contents of liquid metal and magnetic particles, and can be used in different magnetic fluid fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a SEM image of the magnetic nickel particles loaded with liquid metal gallium nanoparticles in Example 1;

[0023] Figure 2 This is a SEM image of the magnetic cobalt particles loaded with liquid metal gallium indium nanoparticles in Example 2;

[0024] Figure 3 This is a SEM image of magnetic iron-cobalt-nickel particles loaded with liquid metal gallium nanoparticles in Example 3. DETAILED DESCRIPTION

[0025] The present invention is further described in detail below in conjunction with specific implementation modes, but the protection scope of the present invention is not limited to the described contents.

[0026] Example 1: A method for preparing magnetic liquid metal nanoparticles, the specific steps are as follows:

[0027] (1) adding liquid metal Ga into a first solvent (a mixed solvent of deionized water and ethanol in a volume ratio of 1:1), and subjecting the mixture to ultrasonic dispersion treatment for 120 min to obtain a liquid metal suspension with a concentration of 5 mg / mL;

[0028] (2) adding a metal salt (nickel chloride) to the liquid metal suspension, stirring and reacting at a temperature of 40° C. for 15 min to obtain a liquid metal salt solution; the mass ratio of the metal salt (nickel chloride) to the liquid metal Ga in step (1) is 0.7:1;

[0029] (3) dissolving a reducing agent (sodium borohydride) in a second solvent (a mixed solvent of ammonia water and hydrazine hydrate) to obtain a reducing agent solution; the pH value of the second solvent is 10, the concentration of ammonia water in the second solvent is 0.7 mol / L, the concentration of hydrazine hydrate is 0.5 mol / L, and the mass ratio of the reducing agent (sodium borohydride) to the metal salt (nickel chloride) in step (2) is 0.3:1;

[0030] (4) under the conditions of temperature of 50° C. and stirring speed of 300 r / min, the reducing agent solution was dripped into the liquid metal salt solution at a rate of 0.6 mL / min, and the stirring reaction was continued for 5 min after the titration was completed. The solution was washed with ethanol and deionized water in turn, separated by centrifugation (1000 r / min), and the solid was vacuum dried at a temperature of 45° C. to obtain magnetic liquid metal nanoparticles, wherein the core of the magnetic liquid metal nanoparticles is liquid metal Ga, and the surface of the liquid metal is loaded with magnetic particles Ni;

[0031] The SEM image of the magnetic nickel particles loaded with liquid metal gallium nanoparticles in this embodiment is as follows: Figure 1 As shown, the metal nickel particles are anchored on the surface of the liquid metal gallium nanoparticles; the EDS energy spectrum shows the distribution of Ni, Ga, and O elements. Obviously, the energy spectrum area of ​​Ga is smaller than that of Ni, which also indicates the growth of metal nickel on the surface of gallium nanoparticles. The existence of O is due to the slight oxidation of the surface of gallium nanoparticles.

[0032] Example 2: A method for preparing magnetic liquid metal nanoparticles, the specific steps are as follows:

[0033] (1) adding liquid metal GaIn into the first solvent (isopropanol) and subjecting the mixture to ultrasonic dispersion for 150 min to obtain a liquid metal suspension with a concentration of 7.5 mg / mL;

[0034] (2) adding a metal salt (cobalt chloride) to the liquid metal suspension, stirring and reacting at a temperature of 50° C. for 25 min to obtain a liquid metal salt solution; the mass ratio of the metal salt (cobalt chloride) to the liquid metal GaIn in step (1) is 0.3:1;

[0035] (3) dissolving a reducing agent (potassium borohydride) in a second solvent (a mixed solvent of potassium hydroxide and hydrazine hydrate) to obtain a reducing agent solution; the pH value of the second solvent is 14, the concentration of potassium hydroxide in the second solvent is 1.5 mol / L, the concentration of hydrazine hydrate is 1.0 mol / L, and the mass ratio of the reducing agent (sodium borohydride) to the metal salt (cobalt chloride) in step (2) is 0.3:1;

[0036] (4) at a temperature of 40° C. and a stirring rate of 350 r / min, the reducing agent solution was dripped into the liquid metal salt solution at a rate of 0.8 mL / min, and the stirring reaction was continued for 8 min after the titration was completed. The solution was washed with ethanol and deionized water in turn, separated by centrifugation (2000 r / min), and the solid was vacuum dried at a temperature of 40° C. to obtain magnetic liquid metal nanoparticles, wherein the core of the magnetic liquid metal nanoparticles is liquid metal GaIn, and the surface of the liquid metal is loaded with magnetic particles Co;

[0037] The SEM image of the magnetic cobalt particles loaded with liquid metal gallium indium nanoparticles in this embodiment is as follows: Figure 2 As shown, the metal cobalt particles are anchored on the surface of the liquid metal gallium indium nanoparticles; the EDS energy spectrum shows the distribution of Co, Ga, In, and O elements. Obviously, the energy spectrum area of ​​Ga and In is smaller than that of Co, which also indicates the growth of metal cobalt on the surface of gallium indium nanoparticles. The existence of O is due to the slight oxidation of the surface of gallium indium nanoparticles.

[0038] Embodiment 3: A method for preparing magnetic liquid metal nanoparticles, the specific steps are as follows:

[0039] (1) adding liquid metal Ga into a first solvent (N,N-dimethylformamide) and subjecting the mixture to ultrasonic dispersion for 180 min to obtain a liquid metal suspension having a concentration of 10 mg / mL;

[0040] (2) adding a metal salt (iron chloride, cobalt chloride and nickel chloride in a mass ratio of 1:1:1) to the liquid metal suspension, stirring and reacting at a temperature of 50° C. for 30 min to obtain a liquid metal salt solution; the mass ratio of the metal salt to the liquid metal Ga in step (1) is 0.5:1;

[0041] (3) dissolving a reducing agent (ascorbic acid) in a second solvent (a mixed solvent of aqueous ammonia and sodium hydroxide) to obtain a reducing agent solution; the pH value of the second solvent is 12, the concentration of aqueous ammonia in the second solvent is 1.1 mol / L, the concentration of sodium hydroxide is 1.1 mol / L, and the mass ratio of the reducing agent (ascorbic acid) to the metal salt in step (2) is 0.4:1;

[0042] (4) under the conditions of temperature of 60° C. and stirring speed of 400 r / min, the reducing agent solution was dripped into the liquid metal salt solution at a rate of 1 mL / min, and the stirring reaction was continued for 8 min after the titration was completed, and the solution was washed with ethanol and deionized water in turn, separated by centrifugation (1500 r / min), and the solid was vacuum dried at a temperature of 60° C. to obtain magnetic liquid metal nanoparticles, wherein the core of the magnetic liquid metal nanoparticles is liquid metal Ga, and the surface of the liquid metal is loaded with magnetic particles Fe, Ni and Co;

[0043] The SEM image of the magnetic iron-cobalt-nickel particles loaded with liquid metal gallium nanoparticles in this embodiment is as follows: Figure 3 As shown, the metal iron, cobalt and nickel particles are anchored on the surface of the liquid metal gallium nanoparticles; the EDS energy spectrum shows the distribution of Fe, Co, Ni, Ga and O elements. Obviously, the energy spectrum area of ​​Ga is smaller than that of Fe, Co and Ni, which also shows that the metal iron, cobalt and nickel grow on the surface of gallium nanoparticles. The existence of O is due to the slight oxidation of the surface of gallium nanoparticles.

[0044] The hysteresis loop results of Examples 1 to 3 are shown in Table 1;

[0045] Table 1 Saturation magnetization and coercive force obtained by hysteresis loops in Examples 1 to 3

[0046] Example Saturation magnetization Coercivity 1 13.432emu / g 3.304Oe 2 6.131emu / g 2.615Oe 3 9.789emu / g 2.974Oe

[0047] The magnetic liquid metal nanoparticles of Example 1 have a saturation magnetization of 13.432emu / g and a coercive force of 3.304Oe; the magnetic liquid metal nanoparticles of Example 2 have a saturation magnetization of 6.131emu / g and a coercive force of 2.615Oe; the magnetic liquid metal nanoparticles of Example 3 have a saturation magnetization of 9.789emu / g and a coercive force of 2.974Oe. The magnetic differences of the samples of Examples 1-3 are attributed to the differences in the mass ratio of the metal salt to the liquid metal in each system, the pH difference of the second solution, and the mass ratio of the reducing agent (sodium borohydride) to the liquid metal. This will lead to differences in the magnetism and content of the magnetic nanoparticles that are in-situ reduced and loaded on the surface of the liquid metal, thereby affecting the magnetic differences of the material system of the embodiment.

[0048] The specific implementation modes of the present invention are described in detail above, but the present invention is not limited to the above implementation modes, and various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present invention.

Claims

1. A method for preparing magnetic liquid metal nanoparticles, characterized in that: The specific steps are as follows: (1) adding liquid metal into a first solvent and performing ultrasonic dispersion treatment to obtain a liquid metal suspension; (2) adding a metal salt to a liquid metal suspension, stirring and reacting at a temperature of 40 to 50° C. for 10 to 30 minutes to obtain a liquid metal salt solution; the metal salt is one or more of a cobalt salt, a nickel salt, and an iron salt; (3) dissolving a reducing agent in a second solvent to obtain a reducing agent solution; the pH value of the second solvent is not less than 10; (4) At a temperature of 40 to 60° C. and under stirring conditions, the reducing agent solution is dripped into the liquid metal salt solution drop by drop. After the titration is completed, the stirring reaction is continued for 5 to 10 minutes. The solution is washed with ethanol and deionized water in turn, centrifuged, and the solid is vacuum dried to obtain magnetic liquid metal nanoparticles. The core of the magnetic liquid metal nanoparticles is liquid metal, and the surface of the liquid metal is loaded with magnetic particles.

2. The method for preparing magnetic liquid metal nanoparticles according to claim 1, characterized in that: In step (1), the liquid metal is Ga or Ga-A alloy, and A is one or more of In, Sn, Bi, Zn, and Al.

3. The method for preparing magnetic liquid metal nanoparticles according to claim 1, characterized in that: The first solvent in step (1) is one or more of water, methanol, ethanol, isopropanol, and N,N-dimethylformamide.

4. The method for preparing magnetic liquid metal nanoparticles according to claim 1, characterized in that: The concentration of the liquid metal in the liquid metal suspension of step (1) is 5 to 10 mg / mL.

5. The method for preparing magnetic liquid metal nanoparticles according to claim 1, characterized in that: The mass ratio of the metal salt in step (2) to the liquid metal in step (1) is 0.1 to 0.8:

1.

6. The method for preparing magnetic liquid metal nanoparticles according to claim 1, characterized in that: The reducing agent in step (3) is sodium borohydride, potassium borohydride or ascorbic acid, and the mass ratio of the reducing agent to the metal salt in step (2) is 0.25 to 0.4:

1.

7. The method for preparing magnetic liquid metal nanoparticles according to claim 1 or 6, characterized in that: The second solvent in step (3) is potassium hydroxide solution, sodium hydroxide solution, ammonia water or hydrazine hydrate solution, and the concentration of the reducing agent solution is 0.5-1.5 mol / L.

8. The method for preparing magnetic liquid metal nanoparticles according to claim 7, characterized in that: The dropping speed of the reducing agent solution in step (4) is 0.5-1 ml / min.

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