A method for preparing magnetic liquid metal nanoparticles

Abstract

The present invention relates to a method for preparing magnetic liquid metal nanoparticles, belonging to the technical field of magnetic nanomaterials. The method comprises ultrasonically dispersing liquid metal into a first solvent to obtain a liquid metal suspension, adding a metal salt to the liquid metal suspension, and stirring and reacting at a temperature of 40-50°C for 10-30 minutes to obtain a liquid metal salt solution; dissolving a reducing agent in a second solvent to obtain a reducing agent solution; and dripping the reducing agent solution dropwise into the liquid metal salt solution at a temperature of 40-60°C under stirring conditions. After the titration is completed, the stirring reaction is continued for 5-10 minutes, and the solution is washed sequentially with ethanol and deionized water, centrifuged, and the solid is vacuum dried to obtain magnetic liquid metal nanoparticles. The method utilizes the potential difference between the liquid metal and the metal salt ions and the heterogeneous interface provided by the liquid metal to in situ reduce and grow magnetic particles on the surface of the liquid metal nanoparticles via a wet chemical reduction method, thereby obtaining chemically bonded and in situ anchored magnetic liquid metal nanoparticles.

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 that exhibits excellent fluidity, high thermal and electrical conductivity, non-toxicity, and overall chemical stability at room temperature. It is widely used in microfluidics, soft robotics, stretchable electronics, and energy storage. Recently, composite materials modified with magnetic materials to impart magnetic properties to liquid metal have also been used in magnetic fluids.

[0003] However, conventional methods such as pre-oxidation mechanical stirring (stirring the liquid metal and magnetic particles under air for a long time) and alloy phase wetting (partially alloying the magnetic particles with the liquid metal at a certain temperature) modify the liquid metal through physical blending. This can lead to problems such as uneven mixing of the magnetic fluid, resulting in agglomeration, and poor suspension stability due to the density difference between the two. Furthermore, the continuous alloying process between the magnetic fluid particles and the liquid metal can also lead to demagnetization and failure of the magnetic fluid. 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 and 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 to 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 added dropwise into the liquid metal salt solution. 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 the liquid metal nanoparticles; utilizes the strong reducing property of the reducing agent under alkaline conditions to make the remaining metal salt ions grow rapidly on the surface of the liquid metal nanoparticles and grow into magnetic nanoparticles; by adjusting the elemental composition and proportion of the liquid metal, the type and content of the metal salt ions, magnetic liquid metal nanoparticles with 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 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 mechanical mixing in 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 type and content 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 an SEM image of liquid metal gallium nanoparticles loaded with magnetic nickel particles in Example 1;

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

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

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

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

[0027] (1) Liquid metal Ga was added to a first solvent (a mixed solvent of deionized water and ethanol with a volume ratio of 1:1) and subjected 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) At a temperature of 50°C and a stirring rate of 300 r / min, the reducing agent solution was dripped into the liquid metal salt solution at a rate of 0.6 mL / min. After the titration was completed, the stirring reaction was continued for 5 min, and the solution was washed with ethanol and deionized water in sequence, separated by centrifugation (1000 r / min), and the solid was vacuum-dried at a temperature of 45°C to obtain magnetic liquid metal nanoparticles. 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 presence 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 ultrasonically dispersing the solution 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 added dropwise to the liquid metal salt solution at a rate of 0.8 mL / min. After the titration was completed, the stirring reaction was continued for 8 min, and the solution was washed with ethanol and deionized water in sequence, separated by centrifugation (2000 r / min), and the solid was vacuum-dried at a temperature of 40°C to obtain magnetic liquid metal nanoparticles. The core of the magnetic liquid metal nanoparticles was liquid metal GaIn, and the surface of the liquid metal was 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 the energy spectrum area of ​​Co, which also indicates the growth of metal cobalt on the surface of gallium indium nanoparticles. The presence of O is due to the slight oxidation of the surface of gallium indium nanoparticles.

[0038] Example 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 with a concentration of 10 mg / mL;

[0040] (2) adding a metal salt (ferric 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 ammonia water and sodium hydroxide) to obtain a reducing agent solution; the pH value of the second solvent is 12, the concentration of ammonia water 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) At a temperature of 60°C and a stirring rate of 400 r / min, the reducing agent solution was dripped into the liquid metal salt solution at a rate of 1 mL / min. After the titration was completed, the stirring reaction was continued for 8 minutes, and the solution was washed with ethanol and deionized water in sequence, separated by centrifugation (1500 r / min), and the solid was vacuum-dried at a temperature of 60°C to obtain magnetic liquid metal nanoparticles. The core of the magnetic liquid metal nanoparticles was liquid metal Ga, and the surface of the liquid metal was 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 shown in FIG. Figure 3 As shown, metallic iron, cobalt, and nickel particles are anchored on the surface of liquid metal gallium nanoparticles; the EDS spectrum shows the distribution of Fe, Co, Ni, Ga, and O elements. Obviously, the energy spectrum area of ​​Ga is smaller than the energy spectrum area of ​​Fe, Co, and Ni, which also indicates the growth of metallic iron, cobalt, and nickel on the surface of gallium nanoparticles. The presence 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 through hysteresis loops of Examples 1 to 3

[0046] Example Saturation magnetization coercive force 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 liquid metal surface, thereby affecting the magnetic differences of the material system of the embodiment.

[0048] The above describes the specific embodiments of the present invention in detail, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in this field without departing from the scope 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 to 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 added dropwise into the liquid metal salt solution. 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 in 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.

Images