An apparatus and method for continuously preparing core-shell structure composite nanoparticles

Abstract

The application discloses a kind of continuous preparation nuclear shell structure composite nanoparticles device and method.The device described in the application includes injection pump, plasma microreactor, mass flow controller etc., and the plasma reactor includes internal electrode area, reaction zone, insulation area, contact area and water cooling area;Reaction zone is formed by winding polymer capillary outside insulation area;Contact area is used as anode;When preparing, use noble metal salt solution as load precursor, non-metallic material as substrate, under the push of argon, into the discharge area of plasma reactor, noble metal ions are reduced under the action of plasma, loaded on the surface of non-metallic material, and nuclear shell type composite nanoparticles are obtained.The device prepared in the application has simple structure, low price, good sealing property and is easy to disassemble and assemble.At the same time, different specifications of reactors can be assembled by selecting capillaries with different sizes and lengths, which can be used in the preparation of noble metal composite materials.

Description

Technical Field

[0001] This invention relates to the field of microreactors and nanomaterial preparation technology, and in particular to an apparatus and method for continuous preparation of core-shell structured composite nanoparticles. Background Technology

[0002] Noble metal nanomaterials are widely used in various fields due to their unique optical, electrical, biological, and catalytic properties. Composite materials formed by combining other non-metallic nanoparticles to create core-shell structures can not only produce synergistic effects with noble metal nanoparticles, enhancing their original properties, but also acquire additional functions, thereby expanding the application areas of the materials. However, the current preparation methods for such materials mainly involve chemical reduction, which uses chemical reducing agents to reduce noble metal ions to obtain noble metal nanoparticles, which are then loaded onto a support to form composite materials. Therefore, this method is demanding, complex, time-consuming, and inevitably introduces Cl-, NO3-, and SO42-. 2- Impurities such as hydrogen affect the purity and performance of the product, while also causing environmental pollution. Besides chemical reducing agents, some processes use wet impregnation combined with high-temperature calcination, introducing hydrogen to reduce noble metal ions to obtain the product. However, high-temperature calcination can cause nanoparticles to agglomerate, affecting catalytic performance. Furthermore, hydrogen is flammable and explosive, and leaks are difficult to detect, posing a significant safety hazard. With industrial development and increased emphasis on safe production, the simple, safe, continuous, and efficient preparation of core-shell composite nanoparticles with small particle size, high purity, and stable quality has attracted considerable attention.

[0003] Patent CN105419776A discloses a method for preparing metal-carbon core-shell structured nanoparticles. The metal-carbon core-shell structured nanoparticles obtained by this method have high purity and uniform morphology, but the reaction stage requires the use of sulfuric acid solution, which poses certain safety hazards.

[0004] Patent CN102019431B discloses a method for preparing metal nanoclusters / silica hollow core-shell structured nanoparticles. This method can obtain hollow silica core-shell materials with controllable size and morphology and uniform distribution, but it requires the addition of a wide variety of organic reagents and takes a long time.

[0005] Plasma and microreactor technologies are both highly efficient process intensification methods, representing the forefront and hot topics of current research, with broad development prospects. On the one hand, using microreactors for continuous synthesis instead of traditional batch operations not only ensures the accuracy, safety, controllability, and efficiency of the preparation process but also achieves product uniformity and stability. On the other hand, using electrons in plasma as a reducing agent instead of traditional chemical reducing agents and hydrogen can shorten reaction time, simplify the process flow, improve reaction safety, and avoid side reactions and separation / purification processes caused by chemical reducing agents.

[0006] Although there are many reports at home and abroad on the preparation of nanomaterials by plasma or microreactors, current plasma microreactors are generally made of materials such as quartz, glass, and metal, which are expensive, difficult to process (requiring mechanical equipment), and lack flexibility. Summary of the Invention

[0007] To address the aforementioned problems in existing technologies, this invention provides an apparatus and method for the continuous preparation of core-shell structured composite nanoparticles. This invention utilizes polymer capillaries as the material, combined with electrodes, to develop a coil-type plasma microreactor. The apparatus prepared by this invention has a simple structure, low cost, good sealing performance, and is easy to assemble and disassemble. Furthermore, microreactors of different sizes and lengths can be assembled into microreactors of various specifications for use in the preparation of noble metal composite materials. In addition, the preparation method of this invention utilizes a strong electric field to generate discharge within the channel, using electrons as a reducing agent instead of traditional chemical reducing agents or hydrogen gas, thus avoiding side reactions and impurities, simplifying the process, reducing production costs, and improving safety.

[0008] The technical solution of the present invention is as follows:

[0009] The first objective of this invention is to provide an apparatus for preparing core-shell composite nanoparticles, comprising an argon gas cylinder 1, a mass flow meter 2, an injection pump, a plasma microreactor 6, an AC power supply 7, a ballast 8, an oscilloscope 9, and a collector 10; one end of the plasma microreactor 6 is connected to the argon gas cylinder 1 and the injection pump via a microchannel and a three-way valve, respectively; the mass flow meter 2 is provided between the argon gas cylinder 1 and the plasma microreactor 6; the injection pump is used to deliver a precursor solution and a substrate solution, specifically including one injection pump for delivering the substrate solution and multiple injection pumps for delivering the precursor solution, wherein "multiple" refers to ≥1; the other end of the plasma microreactor 6 is connected to the collector 10 for collecting the product;

[0010] The plasma microreactor 6 includes an inner electrode region 11, a reaction region 13, an insulating region 12, a grounding region 14, and a water cooling region 15. The inner electrode region 11 serves as the cathode, and the insulating region 12, the reaction region 13, the grounding region 14, and the water cooling region 15 are sequentially arranged on both sides. The reaction region 13 is a polymer capillary wound around the outside of the insulating region 12. The grounding region 14 serves as the anode. The water cooling region 15 is used to control the temperature of the liquid in the reaction.

[0011] The plasma microreactor 6, AC power supply 7, and ballast 8 form a closed loop; an oscilloscope 9 is connected to the AC power supply 7.

[0012] Furthermore, the internal electrode area 11 is a metal rod with a diameter of 10-60 mm and a length of 10-20 cm. The metal rod is made of a single metal, an alloy, or a composite metal. The single metal is one of iron, copper, zinc, or aluminum.

[0013] The insulating region 12 is made of glass, quartz, borax, plastic or polymer, and has a thickness of 1 to 4 mm. The thickness refers to the thickness of the insulating material located between the reaction region and the inner electrode region.

[0014] The polymer capillary is made of nylon, polyethylene, polytetrafluoroethylene, polyvinylpyrrolidone, or polyetheretherketone; the inner diameter of the polymer capillary is 0.5–6.0 mm, and the length is 1–10 m.

[0015] The grounding area 14 is made of conductive material, including tin foil, aluminum foil, copper mesh, or conductive glass; the water cooling zone 15 is formed by a jacket with a water circulation system. Specifically, the water cooling zone has a circulation pipeline inside the jacket of a certain thickness, which serves as a water coolant pipeline. The pipeline is made of rubber, polyetheretherketone, plastic, or glass.

[0016] Another object of the present invention is to provide a method for preparing core-shell composite nanoparticles using the above-described apparatus, comprising the following steps:

[0017] (1) Preparation of precursor solution and base solution: Using water as solvent, prepare noble metal salt solutions with a concentration of 0.1 to 2 mmol / L as precursor solutions; prepare non-metallic material solutions with a concentration of 1 to 5 mg / mL as base solutions;

[0018] (2) Add the precursor solution and base solution prepared in step (1) to the syringe, connect the device, set the extrusion rate of the injection pump, turn on the argon gas, clean the polymer capillary channel, regulate the argon gas flow rate through the mass flow controller 2, and remove impurities from the system.

[0019] (3) The precursor solution and argon gas are introduced into the plasma microreactor 6 in a gas-liquid two-phase flow. After the flow rate stabilizes, the AC power supply 7 is turned on and a voltage of 200-800V is applied to the internal electrode to break down the argon gas and generate plasma discharge. At the same time, the oscilloscope is adjusted until the plasma discharge stabilizes. At this time, the noble metal ions in the precursor solution are reduced to noble metal nanoparticles under the action of plasma and loaded on the surface of non-metallic materials to obtain the reaction solution.

[0020] (4) The reaction liquid is collected by collector 10, and after centrifugation and drying, core-shell composite nanoparticles are obtained.

[0021] Further, in step (1), the noble metal salt is one or more of silver nitrate, palladium nitrate, sodium chloropalladiumate, palladium chloride, chloroauric acid, chloroplatinic acid, potassium chloroplatinate, sodium chloroplatinate, and platinum chloride; the non-metallic material is one of carbon black, graphene, graphene oxide, carbon nanotubes, spherical silicon dioxide, and spherical nano-silicon.

[0022] Further, in step (2), the mass ratio of noble metal ions in the precursor solution to non-metallic materials in the base solution is 1:1000 to 1:10; the noble metal ions are one or more of silver ions, palladium ions, gold ions, and platinum ions; the extrusion rate of the injection pump is 0.01 to 2 mL / min; and the flow rate of argon gas is 5 to 100 sccm.

[0023] Furthermore, in step (3), the power applied to the inner electrode region electrode after stabilization is 1 to 10 W, and the reduction time is 5 to 60 s.

[0024] Furthermore, the size and distribution of core-shell composite nanoparticles can be controlled by adjusting the concentration of the precursor solution and the injection rate.

[0025] This invention uses a noble metal salt solution as a loading precursor and a non-metallic material as a substrate. The solution is injected into the discharge region of a plasma microreactor by an injection pump and argon gas. The noble metal ions are reduced under the action of electrons and formed into a shell on the surface of the non-metallic material, resulting in core-shell composite nanoparticles. Under plasma conditions, the nanoparticles formed all carry the same charge. According to the principle of like charges repelling each other, the nanoparticles will repel each other, thus hindering further aggregation between the nanoparticles, resulting in composite nanoparticles that are smaller in size and more uniformly distributed.

[0026] This invention can increase the yield of core-shell composite nanoparticles by increasing the inner diameter of the hollow tube and increasing the area of ​​the plasma reaction region. It can also shorten the reaction time by increasing the extrusion speed of the injection pump. Furthermore, it can control the loading and size of noble metals in the product by adjusting the concentration and flow rate of the precursor solution, thereby regulating the product's properties. The loading and size of noble metals increase with increasing concentration of the noble metal precursor solution and decrease with increasing flow rate.

[0027] This invention can also form different types of core-shell composite nanoparticles by changing the types of noble metal and non-metal precursors.

[0028] The noble metal nanoparticles and composite nanoparticles formed by this invention have smaller sizes in plasma media due to electrostatic repulsion.

[0029] The beneficial technical effects of this invention are as follows:

[0030] 1) This invention utilizes polymer capillaries, combined with electrodes, to assemble a coil-type plasma microreactor. Compared to traditional quartz, glass, and metal reactors, it is inexpensive, easy to assemble and disassemble, highly flexible, has good sealing properties, and does not require special machining equipment. Furthermore, the plasma microreactor described in this invention allows for flexible adjustment of the microreactor's specifications and output by replacing capillaries of different diameters and lengths, making it very easy to scale up production. The prepared device and method have broad application prospects in the fields of fine chemical synthesis, nanomaterial preparation, and organic matter degradation.

[0031] 2) This invention employs a continuous production method, utilizing an injection pump and mass flow controller to precisely control the flow rates of liquids and gases. This results in products with good uniformity and stable quality. Furthermore, plasma can charge noble metal particles, reducing aggregation and ensuring the preparation of products with small particle size and narrow size distribution. In addition, reactant concentration, flow rate, and residence time can be changed online, allowing for real-time adjustment of product composition, size, and properties, providing a wide range of operational flexibility.

[0032] 3) Unlike traditional chemical preparation techniques, this invention does not require the introduction of chemical reagents and hydrogen. It uses electrons as a reducing agent to achieve efficient reduction of noble metal ions, avoiding side reactions and separation and purification processes caused by chemical reagents. This greatly simplifies the reaction process, shortens the reaction time, reduces environmental pollution, and improves reaction safety.

[0033] 4) Compared with traditional plasma reactors, the coil-type plasma microreactor of this invention does not require vacuum equipment, can generate stable discharge under atmospheric pressure, and has good sealing performance, avoiding the influence of air. In addition, due to the large specific surface area of ​​the polymer capillary, the reactor dissipates heat quickly, and the heat can be quickly carried away by the cooling layer, avoiding reactor damage and particle agglomeration caused by heat accumulation. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the structure of the core-shell composite nanoparticle device prepared according to the present invention.

[0035] Figure 2 This is a cross-sectional view of the plasma microreactor of the present invention.

[0036] Figure 1-2 In the middle: 1. Argon gas cylinder; 2. Mass flow meter; 3. Injection pump I; 4. Injection pump II; 5. Injection pump III; 6. Plasma microreactor; 7. AC power supply; 8. Ballast; 9. Oscilloscope; 10. Collector; 11. Internal electrode area; 12. Insulation area; 13. Reaction area; 14. Grounding area; 15. Water cooling area.

[0037] Figure 3 This is a current-voltage graph collected by an oscilloscope in Embodiment 1 of the present invention.

[0038] Figure 4 The image shows the TEM spectrum of the platinum-carbon composite nanomaterial prepared in Example 1 of this invention.

[0039] Figure 5 The image shows the EDX spectrum of the platinum-carbon composite nanomaterial prepared in Example 1 of this invention.

[0040] Figure 6 The image shows the TEM spectrum of the gold-silica composite nanomaterial prepared in Example 2 of this invention.

[0041] Figure 7 This is a SEM image of the gold-silica composite nanomaterial prepared in Example 2 of the present invention.

[0042] Figure 8 The image shows the EDX spectrum of the gold-silver alloy-graphene composite nanomaterial prepared in Example 3 of this invention. Detailed Implementation

[0043] The present invention will now be described in detail with reference to the accompanying drawings.

[0044] This invention provides an apparatus for preparing core-shell composite nanoparticles, comprising an argon gas cylinder 1, a mass flow meter 2, an injection pump, a plasma microreactor 6, an AC power supply 7, a ballast 8, an oscilloscope 9, and a collector 10; the argon gas cylinder 1 can supply argon gas to the apparatus; the mass flow meter 2 can control the amount of argon gas supplied.

[0045] The syringe pump is used to deliver the precursor solution and the base solution. In one embodiment, the syringe pump includes one syringe pump for delivering the base solution and two syringe pumps for delivering the precursor solution. In one embodiment, the syringe pump may include one syringe pump for delivering the base solution and one syringe pump for delivering the precursor solution. In another embodiment, the syringe pump may include one syringe pump for delivering the base solution and three syringe pumps for delivering the precursor solution. The number of syringe pumps for delivering the precursor solution may also be four, five, six, etc.

[0046] One end of the plasma microreactor 6 is connected to the argon cylinder 1 and the injection pump via a microchannel and a three-way valve, respectively; a mass flow meter 2 is provided between the argon cylinder 1 and the plasma microreactor 6; and the other end of the plasma microreactor 6 is connected to a collector 10 for collecting the product.

[0047] The plasma microreactor 6 includes an inner electrode region 11, a reaction region 13, an insulation region 12, a grounding region 14, and a water cooling region 15. The inner electrode region 11 serves as the cathode, and the insulation region 12, the reaction region 13, the grounding region 14, and the water cooling region 15 are arranged sequentially on both sides. The reaction region 13 is a polymer capillary wound around the insulation region 12. The grounding region 14 serves as the anode. The water cooling region 15 is used to control the temperature of the liquid in the reaction. The plasma microreactor 6, the AC power supply 7, and the ballast 8 form a closed loop. An oscilloscope 9 is connected to the AC power supply 7.

[0048] Furthermore, the internal electrode area 11 is a metal rod with a diameter of 10-60 mm and a length of 10-20 cm. The metal rod is made of a single metal, alloy, or composite metal; the single metal is one of iron, copper, zinc, or aluminum. The insulating area 12 is made of glass, quartz, borax, plastic, or polymer, with a thickness of 1-4 mm.

[0049] The polymer capillary is made of nylon, polyethylene, polytetrafluoroethylene, polyvinylpyrrolidone, or polyetheretherketone; the inner diameter of the polymer capillary is 0.5–6.0 mm, and the length is 1–10 m.

[0050] The inner diameter of the polymer capillary is 0.5mm, 1.0mm, 2.0mm, 3.0mm, 4.0mm, 5.0mm or 6.0mm; the length is 1m, 2m, 3m, 4m, 5m, 6m, 7m, 8m, 9m or 10m.

[0051] The grounding area 14 is made of a flexible conductive material, including tin foil, aluminum foil, copper mesh, or conductive glass;

[0052] The water cooling zone 15 is formed by a jacket with a water circulation system. Specifically, the water cooling zone has a circulation pipeline inside the jacket of a certain thickness, which serves as a water coolant pipeline. The pipeline is made of rubber, polyetheretherketone, plastic, or glass.

[0053] Example 1

[0054] An apparatus for preparing core-shell composite nanoparticles, reference Figure 1The device includes: an argon cylinder 1, a mass flow meter 2, an injection pump, a plasma microreactor 6, an AC power supply 7, a ballast 8, an oscilloscope 9, and a collector 10. One end of the plasma microreactor 6 is connected to the argon cylinder 1 and the injection pump via a microchannel and a three-way valve, respectively. The mass flow meter 2 is installed between the argon cylinder 1 and the plasma microreactor 6. The injection pump is used to deliver the precursor solution and the base solution, specifically including one injection pump for delivering the base solution and one injection pump for delivering the precursor solution. The other end of the plasma microreactor 6 is connected to the collector 10 for collecting the product.

[0055] The plasma microreactor 6 includes an inner electrode region 11, a reaction region 13, an insulation region 12, a grounding region 14, and a water cooling region 15. The inner electrode region 11 serves as the cathode, and the insulation region 12, the reaction region 13, the grounding region 14, and the water cooling region 15 are arranged sequentially on both sides. The reaction region 13 is a polymer capillary wound around the insulation region 12. The grounding region 14 serves as the anode. The water cooling region 15 is used to control the temperature of the liquid in the reaction. The plasma microreactor 6, the AC power supply 7, and the ballast 8 form a closed loop. An oscilloscope 9 is connected to the AC power supply 7.

[0056] The internal electrode area 11 is a metal rod with a diameter of 30mm and a length of 15cm, and the metal rod is made of copper.

[0057] The insulating area 12 is made of quartz and has a thickness of 2mm.

[0058] The polymer capillary is made of polytetrafluoroethylene; the inner diameter of the polymer capillary is 2.0 mm and the length is 5 m.

[0059] The grounding area 14 is made of a flexible conductive material, specifically tin foil; the water cooling zone 15 is formed by a jacket with a water circulation system. Specifically, the water cooling zone has a circulation pipeline inside the jacket of a certain thickness, which serves as a water coolant pipeline, and the pipeline is made of rubber.

[0060] A method for preparing core-shell composite nanoparticles using the above-mentioned apparatus includes the following steps:

[0061] (1) Using water as a solvent, prepare 10 mL of chloroplatinic acid solution with a concentration of 0.5 mmol / L as the precursor solution; and prepare 10 mL of carbon black solution with a concentration of 1 mg / mL as the base solution.

[0062] (2) Connect the device, set the mass flow meter opening to 15 sccm, and maintain it for 1 min to ensure that the air in the tube is completely discharged. Accurately add 10 mL of 0.5 mmol / L chloroplatinic acid solution to injection pump 3, and add 10 mL of 1 mg / mL carbon black dispersion to injection pump 5. Set the extrusion speed of the two injection pumps to 1 mL / min.

[0063] (3) After a period of time, the chloroplatinic acid solution and carbon black dispersion are mixed evenly. After the mixture and gas flow into the plasma device 6 in a continuous two-phase flow, room temperature aqueous solution is introduced into the water-cooled area in reverse to protect the reaction pipeline and reduce the evaporation loss of the reaction liquid. Then, the AC power supply 7 is turned on, and an 800V voltage is applied to the internal electrode to break down the argon gas and generate plasma discharge. The power output is adjusted to maintain 2W. The oscilloscope is adjusted until the plasma discharge is stable, and the reaction liquid within 5 to 60 seconds after the discharge is stable is collected.

[0064] (4) After the solution in the injection pump is completely squeezed out, the plasma device is turned off. The collected product is centrifuged and dried at 60°C to obtain core-shell composite nanoparticles. In addition, after the plasma is ignited, the voltage-current graph is collected using an oscilloscope to calculate the plasma reaction power.

[0065] The characterization data of the platinum-carbon composite nanomaterials prepared in this example are as follows: Figure 3-5 As shown, from the current-voltage diagram ( Figure 3 As can be seen from the data, when the AC power is turned on, the current and voltage data collected by the oscilloscope, calculated using the formula, show that the AC power supply's response power is 2W. From... Figure 4 It can be seen that the ultra-small platinum nanoparticles are uniformly dispersed on the surface of carbon black, encapsulating the carbon black and forming a platinum nanoshell. From Figure 5 The EDX spectrum shows obvious carbon and platinum peaks, proving that the product has high purity and no residual chlorine in the raw materials. Table 1 shows the relevant yields of the products prepared under different conditions.

[0066] Example 2

[0067] An apparatus for preparing core-shell composite nanoparticles is disclosed, with the same structure as in Example 1. The method for preparing core-shell composite nanoparticles using the apparatus is the same as in Example 1, except that: 10 mL of 0.5 mmol / L chloroauric acid solution is added to injection pump 3, and 10 mL of 3 mg / mL spherical silica dispersion is added to injection pump 5. The extrusion speed of injection pumps 3 and 5 is controlled at 0.5 mL / min. The mass flow meter connected to argon cylinder 1 is set to an opening of 20 sccm.

[0068] Figure 6-7 The image shows the characterization of the gold-silica composite nanomaterial prepared in Example 2: from TEM (… Figure 6As shown in the image, gold nanoparticles are clearly adhered to the surface of silica; from Figure 7 The SEM images show that the gold nanoparticles clearly encapsulate the silica, forming a corresponding core-shell structure.

[0069] Example 3

[0070] An apparatus for preparing core-shell composite nanoparticles is disclosed, with the same structure as in Example 1, except that the injection pumps include one injection pump 5 for delivering the base solution and two injection pumps 3 and 4 for delivering the precursor solution. The method for preparing core-shell composite nanoparticles using this apparatus is the same as in Example 1, except that: 5 mL of 0.2 mmol / L chloroauric acid solution is accurately added to injection pump 3, and 5 mL of 0.3 mmol / L silver nitrate solution is accurately added to injection pump 4; the extrusion speed of injection pumps 3 and 4 is controlled at 0.5 mL / min. 10 mL of 2 mg / mL graphene dispersion is accurately added to injection pump 5, and the extrusion speed of injection pump 5 is controlled at 1 mL / min. The AC power supply is controlled at 4 W.

[0071] Figure 8 Characterization of the gold-silver alloy-graphene composite nanomaterials prepared in Example 3: From Figure 8 The EDX spectrum shows a distinct carbon peak, and characteristic peaks belonging to gold and silver elements are also observed.

[0072] Examples 4-10

[0073] The structures of the apparatuses for preparing core-shell composite nanoparticles described in Examples 4-10 are the same as in Example 1. The methods for preparing core-shell composite nanoparticles using these apparatuses are the same as in Example 1, except that: the precursor solution extrusion rate, polymer capillary diameter, argon flow rate, precursor solution concentration, volume, and reaction time in Examples 4-6 are shown in Table 1, and the remaining conditions are the same as in Example 1; the precursor solution extrusion rate, polymer capillary diameter, argon flow rate, precursor solution concentration, volume, and reaction time in Examples 7-10 are shown in Table 1, the carbon black solution concentration is 3 mg / mL, and the volume is 10 mL, and the remaining conditions are the same as in Example 1.

[0074] Example 11

[0075] An apparatus for preparing core-shell composite nanoparticles has the same structure as in Example 1, except that the inner electrode region 11 is a metal rod with a diameter of 10 mm and a length of 10 cm, and the metal rod is made of iron.

[0076] The insulating area 12 is made of glass with a thickness of 1 mm.

[0077] The polymer capillary is made of nylon; its inner diameter is 0.5 mm and its length is 1 m.

[0078] The grounding area 14 is made of a flexible conductive material, specifically tin foil; the water cooling zone 15 is formed by a jacket with a water circulation system. Specifically, the water cooling zone has a circulation pipeline inside the jacket of a certain thickness, which serves as a water coolant pipeline, and the pipeline is made of rubber.

[0079] The method for preparing core-shell composite nanoparticles using the above apparatus is the same as in Example 1. The difference is that the extrusion speed is 0.01 mL / min; the plasma power is 1 W; and the reduction time is 60 s.

[0080] Example 12

[0081] An apparatus for preparing core-shell composite nanoparticles has the same structure as in Example 1, except that the inner electrode region 11 is a metal rod with a diameter of 60 mm and a length of 20 cm, and the metal rod is made of aluminum.

[0082] The insulating area 12 is made of plastic with a thickness of 4mm.

[0083] The polymer capillary is made of polyetheretherketone; the inner diameter of the polymer capillary is 6.0 mm and the length is 10 m.

[0084] The grounding area 14 is made of a flexible conductive material, specifically aluminum foil; the water cooling zone 15 is formed by a jacket with a water circulation system. Specifically, the water cooling zone has a circulation pipeline inside the jacket of a certain thickness, which serves as a water coolant pipeline, and the pipeline is made of glass.

[0085] The method for preparing core-shell composite nanoparticles using the above apparatus is the same as in Example 1. The difference is that the extrusion speed is 2 mL / min; the argon gas flow rate is 100 sccm; the plasma power is 10 W; and the reduction time is 5 s.

[0086] Test example:

[0087] The product collected by the post-reaction collector in this embodiment of the invention was placed in a BETA2-8LDPLUS freeze dryer for 72 hours to remove the solution from the collected product. Then, the mass of the freeze-dried sample was measured using a high-precision electronic balance. The reading obtained by the electronic balance is the yield of the composite material after the reaction. Then, ICP-OES was used to quantitatively analyze the platinum element in the freeze-dried sample to determine the mass fraction of platinum nanoparticles in the product. Finally, the molar yield of platinum nanoparticles was calculated, and the results are shown in Table 1.

[0088] Table 1. Yields of platinum-carbon composite nanomaterials prepared in Examples 1, 4-10 under different conditions.

[0089]

[0090] As shown in Table 1, reducing the extrusion rate of the precursor solution and increasing the reaction time will increase the final yield of platinum nanoparticles. In addition, under the same volume, the yield of platinum nanoparticles is directly proportional to the precursor concentration. At the same time, increasing the diameter of the polymer capillary can also increase the yield of platinum nanoparticles.

[0091] The above embodiments are merely illustrative of the process flow of the present invention. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, or improvements made by those skilled in the art without departing from the principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An apparatus for preparing core-shell composite nanoparticles, characterized in that, The device includes an argon cylinder (1), a mass flow meter (2), an injection pump, a plasma microreactor (6), an AC power supply (7), a ballast (8), an oscilloscope (9), and a collector (10). One end of the plasma microreactor (6) is connected to the argon cylinder (1) and the injection pump via a microchannel and a three-way valve, respectively. A mass flow meter (2) is provided between the argon cylinder (1) and the plasma microreactor (6). The injection pump is used to deliver the precursor solution and the base solution, specifically including one injection pump for delivering the base solution and at least one injection pump for delivering the precursor solution. The other end of the plasma microreactor (6) is connected to the collector (10) for collecting the product. The plasma microreactor (6) includes an inner electrode region (11), a reaction region (13), an insulation region (12), a grounding region (14), and a water cooling region (15). The inner electrode region (11) serves as the cathode, and the insulation region (12), reaction region (13), grounding region (14), and water cooling region (15) are arranged sequentially on both sides. The reaction region (13) is a polymer capillary wrapped around the outside of the insulation region (12). The grounding region (14) serves as the anode. The water cooling region (15) is used to control the temperature of the liquid in the reaction. The plasma microreactor (6) forms a closed loop with the AC power supply (7) and the ballast (8); an oscilloscope (9) is connected to the AC power supply (7). The polymer capillary is made of nylon, polyethylene, polytetrafluoroethylene, polyvinylpyrrolidone, or polyetheretherketone; the inner diameter of the polymer capillary is 0.5~6.0 mm, and the length is 1~10 m.

2. The apparatus according to claim 1, characterized in that, The inner electrode area (11) is a metal rod with a diameter of 10~60mm and a length of 10~20cm. The metal rod is made of a single metal, an alloy or a composite metal. The single metal is one of iron, copper, zinc or aluminum.

3. The apparatus according to claim 1, characterized in that, The insulating area (12) is made of glass, quartz, borax, or plastic, and has a thickness of 1-4 mm.

4. The apparatus according to claim 1, characterized in that, The grounding area (14) is made of conductive material, including tin foil, aluminum foil, copper mesh or conductive glass; the water cooling area (15) is composed of a jacket with a water circulation system.

5. A method for preparing core-shell composite nanoparticles using the apparatus according to any one of claims 1-4, characterized in that, The method includes the following steps: (1) Preparation of precursor solution and base solution: Using water as solvent, prepare noble metal salt solutions with a concentration of 0.1~2 mmol / L as precursor solutions; prepare non-metallic material solutions with a concentration of 1~5 mg / mL as base solutions; (2) Add the precursor solution and base solution prepared in step (1) to the syringe, connect the device, set the extrusion rate of the injection pump, turn on the argon gas, clean the polymer capillary channel, regulate the argon gas flow rate through the mass flow controller (2), and remove impurities from the system. (3) The precursor solution, the base solution and argon gas are introduced into the plasma microreactor (6) in a gas-liquid two-phase flow. After the flow rate stabilizes, the AC power supply (7) is turned on and a voltage of 200~800V is applied to the internal electrode to break down the argon gas and generate plasma discharge. At the same time, the oscilloscope is adjusted until the plasma discharge stabilizes. At this time, the noble metal ions in the precursor solution are reduced to noble metal nanoparticles under the action of plasma and loaded on the surface of non-metallic materials to obtain the reaction solution. (4) The reaction liquid is collected by collector (10), and after centrifugation and drying, core-shell composite nanoparticles are obtained.

6. The method according to claim 5, characterized in that, In step (1), the precious metal salt is one or more of silver nitrate, palladium nitrate, sodium chloropalladiumate, palladium chloride, chloroauric acid, chloroplatinic acid, potassium chloroplatinate, sodium chloroplatinate, and platinum chloride; the non-metallic material is one of carbon black, graphene, graphene oxide, carbon nanotubes, spherical silicon dioxide, and spherical nano-silicon.

7. The method according to claim 5, characterized in that, In step (2), the mass ratio of noble metal ions in the precursor solution to non-metallic materials in the base solution is 1:1000 to 1:10; the extrusion rate of the injection pump is 0.01 to 2 mL / min; and the flow rate of argon gas is 5 to 100 sccm.

8. The method according to claim 5, characterized in that, In step (3), the restoration time is 5~60 s.

9. The method according to claim 5, characterized in that, The size and distribution of core-shell composite nanoparticles can be controlled by adjusting the concentration of the precursor solution and the injection rate.

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