A double-layer nanocapsule Cu@C@Fe3O4 with Fe3O4 loaded on broken-shell C-coated Cu nanocapsule

Abstract

The application aims to provide a double-layer nanocapsule Cu@C@Fe3O4 of Fe3O4 loaded on broken shell C-coated Cu nanocapsule, which is a broken shell carbon-coated Cu nanocapsule loaded with Fe3O4, wherein single-phase Cu serves as an inner core, graphite C serves as an intermediate layer, and Fe3O4 nanoparticles are electrostatically adsorbed on the graphite C shell. The single-phase nanocapsule can be prepared in large quantities by using an off-body arc method and a sol-gel method, has good antibacterial performance, and also has good dielectric performance and magnetic performance, so it has good electromagnetic matching, has a wide effective absorption bandwidth in the whole 2-18 GHz frequency band, and thus the material can become a nanometer wave-absorbing material for electromagnetic wave absorption in the 2-18 GHz frequency band.

Description

Technical Field

[0001] This invention belongs to the field of materials and relates to a novel composite nanocapsule that simultaneously possesses electromagnetic wave absorption and antibacterial properties, as well as its preparation and application. Background Technology

[0002] The rapid development of electronic information technology, especially communication and detection technologies, has greatly promoted the widespread application of consumer electronics and industrial instruments, such as mobile phones and base stations, profoundly changing people's lifestyles and improving their quality of life. With the widespread application of high-frequency electromagnetic waves with higher electromagnetic energy in 5G technology, severe electromagnetic pollution, interference with the normal operation of precision electronic components, and threats to human physical and mental health will drive the urgent need to explore materials that resist electromagnetic interference. Unlike shielding materials, electromagnetic wave absorbing materials have a greater advantage in resisting electromagnetic interference effects because they can directly convert electromagnetic wave energy into heat dissipation instead of reflecting it back into the environment. Therefore, great efforts have been made to explore electromagnetic wave absorbers that are effective in absorbing wide bandwidths, lightweight, thin, and with strong absorption. However, in some cases, single absorbing materials still have limitations. In the field of medical devices and 5G devices in biological laboratories, electromagnetic radiation still threatens human health. Therefore, exploring materials that simultaneously possess electromagnetic wave absorption and antibacterial properties is of great significance. Metal-based antibacterial agents can attack a variety of bacterial components, making it more difficult for microorganisms to acquire drug-resistant mutations. They are among the most promising antibacterial material systems to date, inhibiting bacterial adhesion and biofilm formation. Meanwhile, with the continuous development of microwave absorbing materials, nanocomposite materials composed of A / B / C structures are approaching ideal absorption systems, providing a uniform absorbing matrix for gigahertz electromagnetic waves with wavelengths of millimeters or centimeters, achieving synergistic absorption of alternating electric and magnetic field energy. Correspondingly, how to utilize the structural characteristics of nanocomposite materials has become an unavoidable challenge in the innovative development of multifunctional microwave absorbing materials with simultaneous antibacterial properties.

[0003] Using a magnetic material as the core and a carbon material as the shell is a common model for coating magnetic materials with dielectric materials, which can synergistically absorb electric and magnetic field energy. However, coating magnetic materials on dielectric materials is not very common because carbon materials can suppress the skin effect caused by cross-linked magnetic microspheres and prevent the aggregation of magnetic particles. Therefore, early scientists used physical or chemical methods to prepare magnetic materials as the core and carbon materials as the shell in nanocomposite materials as microwave absorbing materials. A brief introduction to these dielectric-magnetic core-shell nanocomposite materials is as follows:

[0004] Patent CN10564733A discloses a FeCo@MXene core-shell composite microwave absorbing material and its preparation method. This material is a core-shell structure formed by coating layered MXene with magnetic FeCo nanoparticles, where the mass ratio of FeCo nanoparticles to MXene is 1:2 to 4. MXene has a layered microstructure with a surface rich in functional groups, allowing FeCo to coat the MXene surface and form a dielectric-magnetic two-phase heterojunction microstructure with significant dielectric polarization loss characteristics. Simultaneously, the FeCo coating on the MXene surface not only exhibits high-frequency natural resonance and a strong magnetic loss mechanism but also balances the difference between the complex dielectric spectrum and complex permeability spectrum of the composite material, facilitating matching with spatial impedance. Therefore, this material exhibits broadband strong electromagnetic wave absorption characteristics, with reflectivity results showing a bandwidth of 8.8 GHz exceeding -10 dB.

[0005] Patent CN103846065A discloses a method for preparing double-shell BaTiO3 / BN / Ni nanocapsules using a combination of DC arc method and sol-gel method. First, using a DC arc method with an amorphous Ni-B alloy as the anode (the Ni-B alloy anode target is formed by pressing amorphous Ni-B nano-alloy powder prepared by solid-state chemical reaction) and tungsten as the cathode, BN-coated Ni nanocapsules are prepared. Since the anode target is formed by pressing amorphous Ni-B nano-alloy powder prepared by solid-state chemical reaction, the problem of achieving one-step synthesis of BN-coated metal nanocapsules in conventional DC arc preparation methods is solved. Then, combining the sol-gel technique to prepare double-shell BaTiO3 / BN-coated Ni nanocapsules solves the problem of compositing ferroelectric and ferromagnetic materials at the nanoscale. This method is relatively simple, highly controllable, improves the transmission channel of electromagnetic waves within the nanocapsule, and allows for the regulation of the microwave absorption performance of the nanocapsule absorbing material in different wavebands.

[0006] Patent CN110272721A discloses a core-shell structured nitride / carbonyl iron thermally conductive and microwave-absorbing powder. Through pretreatment, surface aluminizing, high-temperature reaction, annealing, pulverization, separation, drying, and packaging, this powder is prepared using carbonyl iron powder, metallic aluminum, and nitrogen as raw materials. The preparation process is simple, the production cost is low, and it is easy for industrial production. The prepared thermally conductive and microwave-absorbing powder exhibits excellent electromagnetic wave absorption performance in the 2-18 GHz frequency band, achieving a simultaneous improvement in the material's electromagnetic wave absorption function and excellent thermal conductivity. This solves the problems of screening composite fillers and controlling component ratios in current production processes, providing high-performance functional powder raw materials for the preparation of novel thermally conductive and microwave-absorbing materials. Summary of the Invention

[0007] This invention provides a bilayer nanocapsule Cu@C@Fe3O4, in which Fe3O4 is supported on broken C-coated Cu nanocapsules. Using non-equilibrium plasma arc evaporation technology, graphite C-coated metallic Cu is spontaneously generated in situ by introducing the catalytic gas n-hexane. After heat treatment, Fe is adsorbed onto the surface of the Cu@C nanocapsules via a sol-gel method. 3+ After annealing, Cu@C@Fe3O4 bilayer nanocapsules are obtained. The Cu@C@Fe3O4 bilayer nanocapsules have both electromagnetic wave absorption and antibacterial properties, and have a wide range of applications.

[0008] One of the objectives of this invention is to provide a novel antibacterial material with good antibacterial properties and a bactericidal rate of up to 99.99%.

[0009] The second objective of this invention is to provide a novel microwave absorbing material that has high saturation magnetization and low coercivity at room temperature, and high dielectric constant and permeability throughout the 2-18 GHz frequency band. This enables the material to become a novel nano-absorbing material in the 2-18 GHz frequency band.

[0010] The technical solution of this invention is as follows:

[0011] A bilayer nanocapsule Cu@C@Fe3O4 consisting of Fe3O4 loaded on broken-shell C and coated with Cu, characterized in that: the structure of a single Cu@C@Fe3O4 nanocapsule has an A / B / C structure, wherein the broken-shell C is the middle layer, metallic Cu is the core, and Fe3O4 is the outermost layer coated on the broken-shell C.

[0012] The bilayer nanocapsules have a spherical morphology with nanoscale dimensions, preferably distributed in the range of 10-200 nm.

[0013] The above-mentioned double-layer nanocapsules are stable in air and can be used directly. They have natural antibacterial properties, as well as excellent dielectric and magnetic properties, thus exhibiting good electromagnetic matching. They have a wide effective absorption bandwidth across the entire 2-18 GHz frequency band, enabling this material to become a nano-absorbing material for electromagnetic wave absorption in the 2-18 GHz frequency band.

[0014] This invention also provides a method for preparing the aforementioned bilayer nanocapsules, characterized in that: Cu@C nanocapsules are prepared by a non-equilibrium ionic arc evaporation method, and Cu-coated C nanocapsules are obtained by heat treatment; then Fe is added using a sol-gel method. 3+ Electrostatic adsorption was performed on the outside of the broken C-coated Cu nanocapsules. After filtration, washing, and annealing under Ar / H2, Cu@C@Fe3O4 bilayer nanocapsules were obtained.

[0015] The process involves using a pure graphite electrode as the cathode and metallic Cu as the anode target, maintaining a distance of 1-10 mm between the cathode and the anode target; using an arc discharge current of 60-200 A and a voltage of 5-40 V; maintaining the arc for 5-30 minutes; using argon as the working gas and n-hexane as the catalyst gas; using argon with a partial pressure of 5-60 kPa and n-hexane with an amount of 10-40 ml (preferably 20 ml); and obtaining Cu@C nanocapsules by heat treatment at 150-200℃ for 1 h to obtain broken-shell C-coated Cu nanocapsules.

[0016] As a preferred technical solution:

[0017] The cathode is preferably a pure graphite electrode with a purity higher than 99.9%; the anode target is a bulk Cu metal with a purity higher than 99.9%.

[0018] The anode target is a cylindrical metal block with a diameter of 10-50 mm and a thickness of 10-30 mm.

[0019] The prepared broken-shell C-coated Cu nanocapsules were dissolved in anhydrous ethanol, and then FeCl3 aqueous solution was added, wherein the mass ratio of FeCl3 to Cu@C nanocapsules was 1:1; then the mixture was stirred at 80℃ for 5 h, centrifuged, and washed with water to obtain Fe 3+ Cu@C@Fe3O4 bilayer nanocapsules were prepared by annealing Cu@C at 450℃ for 4 hours under Ar / H2.

[0020] The cooling water temperature range for the water-cooled copper plate is 10-20℃.

[0021] This invention employs plasma arc evaporation technology, where the arc generates very high temperatures, causing a large amount of anode metal atoms and atomic clusters to evaporate. After leaving the high-temperature zone, these atoms and clusters collide with each other to form Cu nanoparticles. When the catalytic gas n-hexane (C2H6) is introduced, the arc decomposes it into C and H atoms, which dissolve into the molten Cu. During the evaporation process, C atoms, due to their small atomic size, dissolve in the formed Cu nanoparticle droplets. During the condensation of the Cu droplets, C atoms precipitate out due to supersaturation, forming a graphite C shell on the surface of the solidified Cu nanoparticles, ultimately resulting in C-encapsulated Cu nanoparticles.

[0022] This invention employs a sol-gel method after the plasma arc method, allowing the Cu nanocapsules encapsulated in the broken C shell to be uniformly dispersed in an FeCl3 aqueous solution for full reaction, followed by filtration, washing, and Ar / H2 annealing.

[0023] The bilayer nanocapsules of this invention possess both electromagnetic wave absorption and antibacterial properties, and can be used to prepare antibacterial materials, as well as as wave-absorbing materials in the frequency band between 2-18 GHz at room temperature or 400-500℃.

[0024] When the bilayer nanocapsule Cu@C@Fe3O4 described in this invention is used as an antibacterial material, its bactericidal rate against Gram-negative bacteria can reach 99.99%.

[0025] When the bilayer nanocapsule Cu@C@Fe3O4 described in this invention is used as a microwave absorbing material in the 2-18 GHz frequency band at room temperature or 400-500℃, 50 wt.% of the bilayer nanocapsule Cu@C@Fe3O4 is mixed with 50 wt.% of paraffin (a medium that does not absorb electromagnetic waves). The electromagnetic properties measured at room temperature show that the real part of its dielectric constant ε' is between 7-20 in the 2-18 GHz range, the imaginary part of its dielectric constant ε" is between 4-16 in the 2-18 GHz range, the real part of its complex permeability μ' is between 1.02-1.1 in the 2-18 GHz range, and the imaginary part of its complex permeability μ" is between 0-0.1 in the 2-18 GHz range. The effective absorption bandwidth of 50 wt.% of the bilayer nanocapsule Cu@C@Fe3O4 can reach 5.87 GHz (99% absorption). Attached Figure Description

[0026] Figure 1 After annealing with Ar / H2 at 400℃, 450℃, and 500℃, Cu@C@Fe2O3 was generated, respectively.

[0027] XRD patterns of Cu@C@Fe3O4 and Cu@C@Fe.

[0028] Figure 2 Transmission electron microscopy image of Cu@C@Fe3O4 bilayer nanocapsules.

[0029] Figure 3 Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images of Cu@C@Fe3O4 bilayer nanocapsules, (a) SEM image.

[0030] (a) 2 μm, (b) 200 nm, (c) 20 nm, (d) 5 μm, (e) 200 nm, (f) 20 nm, (g) 20 nm.

[0031] nm.

[0032] Figure 4 X-ray photoelectron characteristic energy spectra, (a) Cu@C@Fe2O3, Cu@C@Fe3O4, Cu@C@Fe

[0033] (b) X-ray photoelectron characteristic energy spectrum of Fe 2p; Cu@C@Fe2O3,

[0034] X-ray photoelectron signature spectrum of Cu2p in Cu@C@Fe3O4 and Cu@C@Fe.

[0035] Figure 5Raman spectra of Cu@C@Fe2O3, Cu@C@Fe3O4, and Cu@C@Fe.

[0036] Figure 6 Hysteresis loop of Cu@C@Fe3O4 bilayer nanocapsules at 300K.

[0037] Figure 7 Comparison of TG values ​​for Cu@C@Fe2O3, Cu@C@Fe3O4, and Cu@C@Fe nanocapsules.

[0038] Figure 8 The complex permittivity of Cu@C@Fe2O3, Cu@C@Fe3O4, and Cu@C@Fe nanocapsules varies with...

[0039] The relationship between frequency and (a) the real part of the dielectric constant and frequency, and (b) the imaginary part of the dielectric constant and frequency.

[0040] Figure 9 Dielectric loss of Cu@C@Fe2O3, Cu@C@Fe3O4, and Cu@C@Fe nanocapsules varies with frequency.

[0041] The relationship between the rate of change.

[0042] Figure 10 Complex magnetic permeability of Cu@C@Fe2O3, Cu@C@Fe3O4, and Cu@C@Fe nanocapsules as a function of frequency

[0043] The relationship between the permeability and frequency, (a) the real part of permeability and frequency, (b) the imaginary part of permeability and frequency.

[0044] Figure 11 The magnetic loss of Cu@C@Fe2O3, Cu@C@Fe3O4, and Cu@C@Fe nanocapsules varies with frequency.

[0045] The changing relationship.

[0046] Figure 12 3D plots of reflection loss (RL)-frequency-thickness of Cu@C@Fe2O3, Cu@C@Fe3O4, and Cu@C@Fe nanocapsules, (a) Cu@C@Fe2O3,

[0047] (b)Cu@C@Fe3O4, (c)Cu@C@Fe.

[0048] Figure 13 Photograph of bacterial colonies formed by E. coli in a Cu@C@Fe3O4 sample after 24 hours of incubation.

[0049] Figure 14 Bar chart showing the antibacterial rates of Cu@C@Fe3O4 and C@Fe3O4 samples against Escherichia coli.

[0050] Figure 15 Around 24 hours later, E. coli was observed in Cu@C@Fe3O4 samples and C@Fe3O4 samples, as well as uncoated samples.

[0051] SEM images of Cu@C@Fe3O4 samples cultured together with blank samples: (a) Cu@C@Fe3O4 sample with a concentration of 20 g / ml, (b) Cu@C@Fe3O4 sample with a concentration of 100 g / ml.

[0052] (c) C@Fe3O4 sample, (d) uncoated blank sample.

[0053] Figure 16 Cu@C@Fe3O4 sample, C@Fe3O4 sample and uncoated blank sample with E. coli

[0054] Staining images of live / dead bacteria before and after 24 hours of interaction: (a) Cu@C@Fe3O4 sample with a concentration of 20 g / ml, (b) Cu@C@Fe3O4 sample with a concentration of 100 g / ml, (c) C@Fe3O4 sample, (d) uncoated blank sample.

[0055] Figure 17 Graph showing the relationship between the increase in sample concentration and the amount of copper ions released.

[0056] Figure 18 Cu@C@Fe3O4 sample, C@Fe3O4 sample, PBS solution and blank sample were incubated for 24 h.

[0057] The results of ROS quantification produced by bacterial cells were then obtained.

[0058] Figure 19 Cu@C@Fe3O4 sample, C@Fe3O4 sample, PBS solution and blank sample were incubated for 24 h.

[0059] The following is a graph showing the fluorescence intensity of ROS produced by bacterial cells. Detailed Implementation

[0060] In the following embodiments, unless otherwise specified, a graphite electrode with a purity of 99.9% was used as the cathode, and the consumable anode target was a cylindrical Cu metal block. The catalytic reaction gas used was n-hexane. The mass ratio of FeCl3 to Cu@C nanocapsules was 1:1. The cooling water temperature of the water-cooled copper disc ranged from 10-20°C.

[0061] Example 1

[0062] Preparation of Cu@C nanocapsules encapsulated with C using plasma arc co-evaporation technique:

[0063] In the plasma arc discharge evaporation process, the consumable anode target used is a cylindrical Cu metal block with a diameter of 20 mm and a thickness of 10 mm, and the distance between the graphite cathode and the anode target is 1.5 mm. The cavity is evacuated to a vacuum level of 5 × 10⁻⁶. -3 After Pa, argon gas (20 kPa) and 10 ml of n-hexane were introduced into the vacuum chamber. A DC power supply was connected, and the voltage was adjusted to 18-20 V. Arc discharge occurred between the anode target and the cathode, generating an arc discharge current of 80 A. During the arc discharge, the working current and voltage were adjusted to maintain relative stability, and the arc duration was 30 minutes. Cu metal bulk was evaporated. In the above reaction atmosphere, Cu@C nanocapsules encapsulating Cu with graphite C were prepared. After the reaction gas was extracted, powdered Cu@C nanocapsules were collected on the inner wall of the vacuum chamber. The collected nanocapsules were heat-treated at 200 °C for 1 h, dissolved in a small amount of anhydrous ethanol, and then FeCl3 aqueous solution was added. The mixture was then stirred at 80 °C for 5 h, filtered and washed, and annealed at 450 °C for 4 h under Ar / H2 to obtain Cu@C@Fe3O4 bilayer nanocapsules.

[0064] Figure 1 The X-ray diffraction (XRD) patterns of the obtained Cu@C@Fe2O3, Cu@C@Fe3O4, and Cu@C@Fe are given. It can be seen from the patterns that the core consists of single-phase Fe2O3, Fe3O4, and Fe in sequence, while the outer shell of C is not shown in the XRD pattern due to its small mass.

[0065] Figure 2 A high-resolution transmission electron microscope (TEM) image of Cu@C@Fe3O4 is given. The TEM image confirms that the core is Cu and the interplanar spacing of its (111) characteristic crystal plane is 0.208 nm.

[0066] Figure 3 Scanning electron microscope (SEM) and transmission electron microscope (TEM) images of Cu@C@Fe3O4 bilayer nanocapsules are presented. The images show that the particles are all spherical.

[0067] Figure 4 The Fe in the core of Cu@C@Fe3O4 bilayer nanocapsules is given. 2p With Cu 2p The X-ray photoelectron characteristic energy spectrum shows that Cu exists in elemental form, while Fe exists in Fe2O3, Fe3O4, and Fe forms, respectively.

[0068] Figure 5 Raman spectra of Cu@C@Fe2O3, Cu@C@Fe3O4, and Cu@C@Fe nanocapsules are presented. The figure indicates two characteristic scattering peaks of the C shell, located at 1335.54 cm⁻¹.-1 With 1582.05cm -1 This represents the disordered and ordered C structures of the C-shell, respectively, and the I-structure of the Cu@C@Fe3O4 bilayer nanocapsule. D / I G The value is the highest, and the defects are the most numerous.

[0069] Figure 6 The magnetic properties of Cu@C@Fe3O4 bilayer nanocapsules at 300K are indicated. The magnetism is ferromagnetic, with a saturation magnetization of 20 emu / g and a coercivity of 82 Oe at room temperature.

[0070] Figure 7 A comparison of TG values ​​for Cu@C@Fe2O3, Cu@C@Fe3O4, and Cu@C@Fe nanocapsules is presented, showing that Cu@C@Fe3O4 has the least mass loss.

[0071] Figure 8 The relationships between the complex dielectric constants of Cu@C@Fe2O3, Cu@C@Fe3O4, and Cu@C@Fe nanocapsules and frequency are presented: (a) the real part of the dielectric constant versus frequency, and (b) the imaginary part of the dielectric constant versus frequency. The real and imaginary parts of the dielectric constant of the Cu@C@Fe3O4 sample are both greater than those of the Cu@C@Fe2O3 and Cu@C@Fe samples.

[0072] Figure 9 The dielectric loss of Cu@C@Fe2O3, Cu@C@Fe3O4, and Cu@C@Fe nanocapsules as a function of frequency is presented. The dielectric loss of the Cu@C@Fe3O4 sample is significantly higher than that of the other two samples.

[0073] Figure 10 The relationship between the complex permeability and frequency for Cu@C@Fe2O3, Cu@C@Fe3O4, and Cu@C@Fe nanocapsules is presented. Notably, the real and imaginary parts of the permeability of the Cu@C@Fe3O4 sample are smaller than those of the other two samples.

[0074] Figure 11 The magnetic loss of Cu@C@Fe2O3, Cu@C@Fe3O4, and Cu@C@Fe nanocapsules as a function of frequency is presented. Notably, the real and imaginary parts of the magnetic permeability of the Cu@C@Fe3O4 sample are smaller than those of the other two samples.

[0075] Figure 12Three-dimensional plots of reflection loss (RL)-frequency-thickness are presented for Cu@C@Fe2O3, Cu@C@Fe3O4, and Cu@C@Fe nanocapsules. The Cu@C@Fe3O4 sample has an effective absorption bandwidth of 5.87 GHz and an absorber thickness of 1.8 mm.

[0076] Figure 13 Photographs of E. coli colonies formed on Cu@C@Fe3O4 samples after 24 hours of incubation are shown. A rapid decrease in the number of colonies formed on agar plates coated with Cu@C@Fe3O4 samples was observed.

[0077] Figure 14 The bar chart shows the bactericidal rates of Cu@C@Fe3O4 and C@Fe3O4 samples against *E. coli*. When the sample concentrations were 20 g / ml and 50 g / ml, the bactericidal rates against *E. coli* increased slightly, to 32% and 62%, respectively. At a sample concentration of 100 g / ml, the efficiency of inhibiting bacterial growth was roughly estimated to exceed 90%. Subsequently, at a sample concentration of 150 g / ml, the bactericidal rate against *E. coli* reached 99%. This demonstrates that Cu@C@Fe3O4 samples can effectively inhibit bacterial proliferation.

[0078] Figure 15 SEM images of *E. coli* cultured with Cu@C@Fe3O4 samples, C@Fe3O4 samples, and an uncoated blank sample are presented before and after 24 hours. Very few bacteria were found on the medium coated with Cu@C@Fe3O4 samples, and these bacterial cells appeared to be severely damaged. Cu@C@Fe3O4 effectively inactivated the bacteria, causing cell membrane rupture and leakage of contents. This indicates that the composite Cu@C@Fe3O4 sample has a good ability to inhibit bacterial proliferation.

[0079] Figure 16 Images of live / dead bacteria stained with Cu@C@Fe3O4, C@Fe3O4, and uncoated blank samples before and after 24 hours of interaction with E. coli are presented. When the concentration of Cu@C@Fe3O4 sample is 20 g / ml, the majority of live cells with intact cell membranes (SYTO 9) are present, while the minority of dead cells with ruptured cell membranes (PI) are present. When the concentration of Cu@C@Fe3O4 sample is 100 g / ml, the majority of live cells with intact cell membranes (SYTO 9) are present, while the majority of dead cells with ruptured cell membranes (PI) are present.

[0080] Figure 17A graph showing the relationship between increasing sample concentration and the amount of copper ions released is presented. As the concentration of the sample containing Cu@C@Fe3O4 increases, the amount of Cu ions also increases from 2% to 3% and then to 11%. When the sample concentration is 150 g / ml, the concentration of Cu ions is 10%.

[0081] Figure 18 The quantitative results of ROS produced by bacterial cells after culturing Cu@C@Fe3O4 sample, C@Fe3O4 sample, PBS solution and blank sample for 24 h are presented.

[0082] Figure 19 The following graphs show the ROS fluorescence intensity of bacterial cells after culturing Cu@C@Fe3O4 sample, C@Fe3O4 sample, PBS solution and blank sample for 24 h.

[0083] Example 2

[0084] In the plasma arc discharge evaporation process, the consumable anode target used is a Cu metal cylinder with a diameter of 20 mm and a thickness of 10 mm, and the distance between the graphite cathode and the anode target is 1.5 mm. The cavity is evacuated to a vacuum level of 5 × 10⁻⁶. -3 After Pa, argon gas at 20 kPa and 10 ml of n-hexane were introduced into the plasma arc discharge chamber. A DC power supply was connected, and the voltage was adjusted to 18-20 V. Arc discharge occurred between the anode target and the cathode, generating an arc discharge current of 80 A. During the arc discharge, the working current and voltage were adjusted to maintain relative stability, and the arc duration was 30 minutes. Cu at the anode evaporated, and Cu@C nanocapsules were prepared in the above reaction atmosphere. After the reaction gas was extracted, powdered Cu@C nanocapsules were collected on the inner wall of the vacuum chamber. The collected nanocapsules were heat-treated at 200 °C for 1 h, dissolved in a small amount of anhydrous ethanol, and then FeCl3 aqueous solution was added. After stirring at 80 °C for 5 h, the mixture was filtered, washed, and annealed at 400 °C for 4 h under Ar / H2 to obtain Cu@C@Fe2O3 bilayer nanocapsules.

[0085] Example 3

[0086] In the plasma arc discharge evaporation process, the consumable anode target used is a Cu metal cylinder with a diameter of 20 mm and a thickness of 10 mm, and the distance between the graphite cathode and the anode target is 1.5 mm. The cavity is evacuated to a vacuum level of 5 × 10⁻⁶. -3After Pa, argon gas at 20 kPa and 10 ml of n-hexane were introduced into the plasma arc discharge chamber. A DC power supply was connected, and the voltage was adjusted to 18-20 V. Arc discharge occurred between the anode target and the cathode, generating an arc discharge current of 80 A. During the arc discharge, the working current and voltage were adjusted to maintain relative stability, and the arc duration was 30 minutes. Cu at the anode evaporated, and Cu@C nanocapsules were prepared in the above reaction atmosphere. After the reaction gas was extracted, powdered Cu@C nanocapsules were collected on the inner wall of the vacuum chamber. The collected nanocapsules were heat-treated at 200 °C for 1 h, dissolved in a small amount of anhydrous ethanol, and then FeCl3 aqueous solution was added. After stirring at 80 °C for 5 h, the mixture was filtered, washed, and annealed at 500 °C for 4 h under Ar / H2 to obtain Cu@C@Fe bilayer nanocapsules.

[0087] Comparative Example 1

[0088] In the plasma arc discharge chamber, the consumable anode target used is a Cu metal cylinder with a diameter of 20 mm and a height of 10 mm. The distance between the ink cathode and the anode target is 1.5 mm. The chamber is evacuated to a vacuum level of 5 × 10⁻⁶ mm. -3 Argon gas at 20 kPa and 10 ml of n-hexane were introduced into the plasma arc discharge chamber. A DC power supply was connected, and the voltage was adjusted to 18-20 V. Arc discharge occurred between the anode target and the cathode, generating an arc discharge current of 80 A. During the arc discharge, the working current and voltage were kept relatively stable, and the arc duration was 30 minutes. Cu at the anode evaporated, and Cu@C nanocapsules were prepared in the above reaction atmosphere. After the reaction gas was extracted, powdered Cu@C nanocapsules were collected on the inner wall of the vacuum chamber. The collected nanocapsules were dissolved in a small amount of anhydrous ethanol, and then FeCl3 aqueous solution was added. After stirring at 80 °C for 5 h, the mixture was filtered, washed, and annealed at 450 °C for 4 h under Ar / H2 to obtain multilayered nanocapsules. Because the final product did not undergo heat treatment at 200 °C for 1 h, its antibacterial properties were very poor, mainly because copper ions could not be released.

[0089] Comparative Example 2

[0090] In the plasma arc discharge chamber, the consumable anode target used is a Cu elemental metal cylinder with a diameter of 20 mm and a height of 10 mm. The distance between the ink cathode and the anode target is 1.5 mm. The chamber is evacuated to a vacuum level of 5 × 10⁻⁶ mm. -3Argon gas at 20 kPa and 10 ml of n-hexane were introduced into the plasma arc discharge chamber. A DC power supply was connected and the voltage was adjusted to 18-20 V. Arc discharge occurred between the anode target and the cathode, generating an arc discharge current of 80 A. During the arc discharge, the working current and voltage were adjusted to maintain relative stability, and the arc duration was 30 minutes. Cu at the anode evaporated, and Cu@C nanocapsules were prepared in the above reaction atmosphere. After the reaction gas was extracted, powdered Cu@C nanocapsules were collected on the inner wall of the vacuum chamber. The collected nanocapsules were heat-treated at 200 °C for 1 h, dissolved in a small amount of anhydrous ethanol, and then FeCl3 aqueous solution was added. After stirring at 80 °C for 5 h, the mixture was filtered and washed, and annealed at 450 °C for 2 h under Ar / H2 to obtain multilayer nanocapsules. Due to the annealing at 450 °C for 2 h, the final product had poor microwave absorption properties, mainly because the crystallinity was affected and Fe3O4 was not completely formed.

[0091] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing bilayer nanocapsules Cu@C@Fe3O4, in which Fe3O4 is loaded onto broken-shell C-coated Cu nanocapsules, characterized in that: Cu@C nanocapsules were prepared by non-equilibrium plasma arc evaporation method, and broken shell C coated Cu nanocapsules were obtained after heat treatment; then Fe 3+ Cu@C@Fe3O4 double-layer nanocapsules were obtained after electrostatic adsorption on the outside of the broken shell C coated Cu nanocapsules, filtration, washing, and annealing treatment under Ar / H2. The non-equilibrium plasma arc evaporation method uses high-purity graphite as a cathode, a metal block Cu as an anode target material, and a distance of 1-10 mm between the cathode and the anode target material; the arc discharge current is 60-200 A, and the voltage is 5-40 V; the arc holding time is 5-30 minutes, the working gas used is argon, the catalytic gas used is n-hexane, the argon partial pressure is 5-60 kPa, and the n-hexane amount is 10-40 ml; the obtained Cu@C nanocapsules are subjected to heat treatment at 150-200 ℃ for 1 h to obtain the nanocapsules of C-coated Cu with broken shells. The prepared broken shell C-coated Cu nanocapsules were dissolved in anhydrous ethanol, and an aqueous solution of FeCl3 was added, wherein the mass ratio of FeCl3 to Cu@C nanocapsules was 1:1; then stirring was carried out at 80 ℃ for 5 h, centrifugation and water washing were carried out to obtain Fe 3+ @Cu@C, and then Cu@C@Fe3O4 double-layer nanocapsules were prepared by annealing treatment at 450 ℃ for 4 h under Ar / H2.

2. The preparation method of the double-layer nanocapsule Cu@C@Fe3O4 with Fe3O4 loaded on the broken shell of C-coated Cu nanocapsule according to claim 1, characterized in that: The anode target material is a cylindrical metal block with a diameter of 10-50 mm and a thickness of 10-30 mm.

3. Double-layer nanocapsules prepared by the process according to any one of claims 1 or 2, characterized in that: The double-layer nanocapsules have both electromagnetic wave absorption characteristics and antibacterial properties.

4. Use of the double-layer nanocapsules according to claim 3, characterized in that: The double-layer nanocapsules are used for preparing antibacterial materials.

5. Application of the double-layer nanocapsules of claim 3 as a wave-absorbing material in a frequency range of 2-18 GHz at room temperature or 400-500 ℃.

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