A method for controllable preparation of nanoparticles using a multi-channel microreactor

Abstract

This invention discloses a method for controllable preparation of nanoparticles using a multi-channel microreactor. The method utilizes a microchannel reactor to segment droplets and prepare quantitatively synthesized nanoparticles with controllable particle size. The invention employs capillary action to draw the reaction solution into the microchannel, segmenting one or more droplets (each droplet into 10-100 portions). By changing the width of the microchannel, controllable preparation of nanoparticles within a small range (±3 nm) can be achieved; by changing the length of the microchannel, controllable preparation of nanoparticles within a large range (±10-30 nm) can be achieved. Furthermore, the reactor structure of this invention is simple, enabling highly precise and quantitative synthesis of various nanoparticles. Compared to large-scale reactors, the miniaturization of the synthesis reaction in this invention effectively reduces energy waste and safety hazards, making it highly valuable for applications in safe chemical engineering, green chemical engineering, high-efficiency chemical engineering, microchemical engineering, and precise reaction monitoring.

Description

Technical Field

[0001] This invention relates to the field of controllable preparation methods for nanoparticles, and more specifically to a method for controllable preparation of nanoparticles using a multi-channel microreactor. Background Technology

[0002] Nanoparticles are defined as particles smaller than 100 nm in at least one dimension, and their morphology may include latex, polymer, ceramic particles, metal particles, and carbon particles. Due to their excellent properties such as surface and interface effects, small size effects, quantum size effects, and macroscopic quantum tunneling effects, nanoparticles have broad application prospects in electronics, sensing, catalysis, and biomedicine. However, the applications of nanoparticles are closely related to their microstructure. Generally, nanoparticles exhibit different thermal, optical, and electrical properties depending on their size.

[0003] With the increasing miniaturization, intelligence, and high integration of electronic products, the demand for conductive inks containing highly dispersed small-diameter silver nanoparticles is growing. Therefore, researching methods for controllable preparation of nanoparticles has significant practical importance and application value. Summary of the Invention

[0004] To address the aforementioned technical problems, the present invention aims to provide a method for controllably preparing nanoparticles using a multi-channel microreactor. This method achieves controllable preparation of nanoparticles across a wide range of particle sizes by altering the length, width, and / or height (reaction space) of the microchannel reactor. Specifically, changing the width of the microchannel enables controllable preparation of particles with a small size range (±3 nm), while changing the length of the microchannel enables controllable preparation of particles with a large size range (±10-30 nm).

[0005] A method for preparing nanoparticles includes preparing nanoparticles in a microchannel reactor.

[0006] According to an embodiment of the invention, the microchannel reactor comprises at least one microchannel. For example, it may contain one, two, three, or more microchannels, such as 1-10. 20 One microchannel, or 5-10 10 One microchannel.

[0007] This invention utilizes microchannels to cut reaction liquid droplets, thereby preparing nanoparticles with controllable particle size.

[0008] According to an embodiment of the present invention, the microchannel reactor refers to a reactor having reaction channels with a width in the micrometer range. For example, the width of the microchannel is less than 100 μm, such as 1-100 μm, 2-90 μm, or 5-80 μm, with exemplary values ​​of 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, and 80 μm. The controllable variable is 20 μm.

[0009] According to an embodiment of the present invention, the length of the microchannel is less than 30mm, for example 1-20mm, 2-15mm, with 3mm, 6mm, 9mm, and 12mm as exemplary, and 3mm as a controllable variable.

[0010] According to an embodiment of the present invention, the height of the microchannel reactor is less than 100 μm, for example 1-100 μm, 2-90 μm, or 5-80 μm, with exemplary values ​​of 10 μm, 20 μm, 30 μm, 50 μm, and 70 μm. The controllable variable is 20 μm.

[0011] According to an embodiment of the present invention, the cross-section of the microchannel can be, but is not limited to, a trapezoidal or square shape. For a microchannel with a trapezoidal cross-section, the width mentioned herein refers to the average width, i.e., the width of the median line.

[0012] In this invention, the amount of synthesized nanoparticles can be controlled by controlling the number of reaction microchannels.

[0013] For example, the reaction volume of 100 microchannels (each channel is 20 μm wide, 3 mm long, and 20 μm high) is 0.12 μL; 10 7 Each microchannel (20μm wide, 3mm long; total area 1.2m²) 2 The reaction volume was 0.012 L.

[0014] In this invention, the reaction amount of each channel = the width of the microchannel * the height of the microchannel reactor * the length of the microchannel.

[0015] According to an embodiment of the present invention, the microchannel reactor is formed by combining a substrate with a microwall array.

[0016] According to an embodiment of the present invention, the substrate material can be a heat-resistant material with a flat surface (which does not deform when heated) and will not react with the reaction solution. For example, the substrate material can be, but is not limited to, one of silicon wafers, quartz wafers, glass wafers, iron wafers, copper wafers, aluminum wafers, and alumina wafers.

[0017] According to an embodiment of the present invention, the substrate is planar, and the microwall array has a bottom and a plurality of parallel "microwalls" protruding from the bottom thereon, with a microchannel in the microchannel reactor formed between every two microwalls.

[0018] According to an embodiment of the present invention, the thickness of the microwall is 1-50 μm; exemplary values ​​are 5 μm, 10 μm, 20 μm, and 30 μm. The center-to-center distance between two adjacent microwalls is in the micrometer range, for example, less than 200 μm.

[0019] According to an embodiment of the present invention, the microwall array is prepared by first fabricating a microgroove array using a dicing method, and then obtaining the microwall array through a replication method. The dicing method, for example, uses a dicing machine to scribe grooves with a certain spacing and depth on a silicon wafer. The replication method, for example, is a conventional template method, which involves adding a solution containing polymer monomers into the microgrooves to carry out a polymerization reaction, and then removing the solution from the microgrooves.

[0020] According to an embodiment of the present invention, the microwall array is prepared from at least one of polydimethylsiloxane (PDMS), copolyester, polyvinyl alcohol, polycarbonate, polyvinyl chloride, cellulose acetate, ethyl cellulose, ethylene alcohol-vinyl acetate, ethylene-propylene polymer and sodium alginate.

[0021] The microwall array of the present invention does not deform when heated and does not react with the reaction solution, and can be selected according to experimental conditions.

[0022] According to an embodiment of the present invention, the reaction solution may be dropped onto one side (outer side) of the microchannel opening and spontaneously drawn into the microchannel by capillary action; or it may be dropped onto the substrate surface and then the microchannels of the microwall array are tightly attached to the substrate with the microchannels facing downwards, so as to uniformly distribute the reaction solution in each microchannel.

[0023] In this invention, the reaction solution is prepared in advance and then placed in the microchannel for reaction to ensure that the initial concentration of the reaction solution in the channel is uniform.

[0024] According to an embodiment of the present invention, the reaction solution includes a reaction precursor and a solvent.

[0025] According to an embodiment of the present invention, the reaction precursor may be a metal salt. For example, the metal element in the metal salt may be at least one selected from silver, gold, titanium, iron, etc.

[0026] According to one embodiment of the present invention, the metal salt may be at least one of silver acetate, silver nitrate, chloroplatinic acid, chloroauric acid, tetraisopropanol titanate, iron acetylacetonate, etc.

[0027] According to embodiments of the present invention, the solvent includes, but is not limited to, water or an organic solvent (e.g., one of methanol, ethanol, ethylene glycol, n-hexane, cyclohexane, ethyl acetate, and toluene).

[0028] According to an embodiment of the present invention, the reaction solution further includes a reducing agent and other auxiliary substances, such as surfactants, morphology control agents, dispersants, etc.

[0029] According to one embodiment of the present invention, the dispersant is, for example, at least one of polyvinylpyrrolidone, cetyltrimethylammonium bromide (CTAB), sodium citrate, etc.

[0030] According to one embodiment of the present invention, the reducing agent is, for example, at least one selected from ethylene glycol, sodium borohydride, sodium citrate, etc.

[0031] According to one embodiment of the present invention, the morphology control agent is, for example, at least one of FeCl3, CuCl2, HCl, NaCl, NaBr, sodium citrate, polyacrylic acid, etc.

[0032] In this invention, the slight difference in the reaction solution refers to ±(0.01-0.2μL).

[0033] According to an embodiment of the present invention, the particle size of the nanoparticles is 5-120nm, with examples being 5nm, 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 80nm, 100nm, and 120nm.

[0034] According to an embodiment of the present invention, the quantitative controllable particle size of the nanoparticles includes both small-range and large-range regulation.

[0035] Preferably, the small-range control refers to the particle size difference of the nanoparticles being ±3nm, for example -3nm, -2nm, -1nm, 1nm, 2nm, and 3nm.

[0036] Preferably, the wide range of control refers to the particle size difference of the nanoparticles being ±(10-30nm), for example -30nm, -20nm, -10nm, 5nm, 10nm, 20nm, and 30nm.

[0037] In this invention, the micron-level spatial range is 0.01-0.2 μL.

[0038] According to embodiments of the present invention, the nanoparticles may be, but are not limited to, one, two or more of the following: metal nanoparticles, alloy nanoparticles, metal oxide nanoparticles and composite metal oxide nanoparticles.

[0039] For example, the metal nanoparticles can be at least one of gold nanoparticles, silver nanoparticles, and platinum nanoparticles.

[0040] For example, the alloy nanoparticles can be gold-silver core-shell particles, etc.

[0041] For example, the metal oxide nanoparticles can be at least one of silicon dioxide, iron tetroxide, titanium dioxide, etc.

[0042] For example, the composite metal oxide nanoparticles can be titanium dioxide-silver composite particles, etc.

[0043] The beneficial effects of this invention:

[0044] (1) This invention utilizes a microchannel reactor to segment droplets and prepare quantitatively synthesized nanoparticles with controllable particle size. The reaction solution is drawn into the microchannel using capillary action, and one or more droplets are segmented (e.g., each droplet is segmented into 10-100 parts). By changing the width of the microchannel, a small-range (±3nm) particle size can be controlled; by changing the length of the microchannel, a large-range (±10-30nm) particle size can be controlled. This reactor has a simple structure and can achieve high-precision, controllable, and quantitative synthesis of various nanoparticle sizes. Compared to large-scale reactors, the miniaturization of the synthesis reaction effectively reduces energy waste and safety hazards, making it highly valuable for applications in safe chemical engineering, green chemical engineering, high-efficiency chemical engineering, microchemical engineering, and precise reaction monitoring.

[0045] (2) This invention uses a micrometer-wide channel as a synthesis reactor. The droplets are cut through the microchannel to precisely control the reaction amount (micro-scale), thereby achieving high-precision controllable micro-scale synthesis of various nanoparticle sizes. Furthermore, the micrometer-scale space of the microchannel reactor limits the amount of reactants, thus limiting the growth of nanoparticles. By changing the width of the microchannel, controllable preparation of nanoparticles with small-range (±3nm) particle size variations can be achieved; by changing the length of the microchannel, controllable preparation of nanoparticles with large-range (±10-30nm) particle size variations can be achieved. Simultaneously, due to its micrometer-scale spatial distribution, the microchannel ensures a uniform distribution of the reaction solution concentration during the reaction process, resulting in better monodispersity of the prepared nanoparticles. Moreover, because the reactor is micro-sized, it has strong application value in safe chemical engineering, green chemical engineering, high-efficiency chemical engineering, microchemical engineering, and precise reaction monitoring.

[0046] (3) This invention utilizes microchannels as reactors, which can replace traditional macroscopic reaction vessels. It is simple, fast, flexible, and easy to use, and is safer, more energy-efficient, and more efficient. The silver nanoparticles prepared by this invention exist within microchannels. Since microchannels are commonly used as templates for template printing (such as printed electronics, template transfer, self-assembly, etc.), it is expected to further realize the precise and controllable preparation and assembly of nanoparticles, which has potential application value in microelectronic circuits, optical components, and magnetic devices. Attached Figure Description

[0047] Figure 1This is a schematic diagram of the microchannel reactor of the present invention.

[0048] Figure 2 This is a process diagram illustrating the preparation of the microchannel reactor of the present invention.

[0049] Figure 3 The image shows the PDMS microwall and the assembled microchannel reactor fabricated in Example 1 of this invention.

[0050] Figure 4 This is a process diagram of the controllable preparation of nanoparticles using the multi-channel microreactor of the present invention.

[0051] Figure 5 The images shown are transmission electron microscope (TEM) images of silver nanoparticles prepared by microchannel reactors of 16 different sizes in Example 2 of this invention.

[0052] Figure 6 This is a particle size distribution chart of silver nanoparticles prepared using microchannels with a width of 20 μm and lengths of (3 mm, 6 mm, 9 mm, and 12 mm) in Example 3 of the present invention.

[0053] Figure 7 This is a particle size distribution chart of silver nanoparticles prepared using microchannels with a width of 40 μm and lengths of (3 mm, 6 mm, 9 mm, and 12 mm) in Example 3 of the present invention.

[0054] Figure 8 This is a particle size distribution chart of silver nanoparticles prepared using microchannels with a width of 60 μm and lengths of (3 mm, 6 mm, 9 mm, and 12 mm) in Example 3 of the present invention.

[0055] Figure 9 This is a particle size distribution chart of silver nanoparticles prepared using microchannels with a width of 80 μm and lengths of (3 mm, 6 mm, 9 mm, and 12 mm) in Example 3 of the present invention. Detailed Implementation

[0056] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0057] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0058] Example 1

[0059] Using a dicing machine (Shenyang Heyan Technology), the polished surface of a 2-inch diameter silicon wafer was diced into a trench structure with a depth of 20μm, a width of 23μm, and center-to-center spacing between adjacent trenches of 40μm, 60μm, 80μm, and 100μm, respectively. After plasma surface treatment (air conditions, 200W, 300s), the silicon wafer was placed in a vacuum desiccator containing 20μL of trifluoromethyltrimethylsilane, evacuated, and kept at 90℃ for 30 minutes for hydrophobic treatment. After removing the silicon wafer, a mixture of 7g dimethylsiloxane and initiator (Dow Corning 184) at a mass ratio of 1:10 is poured onto the surface of the silicon wafer. After leveling, it is placed in a vacuum dryer and kept under vacuum for 10 minutes. Then, it is placed in an oven at 70°C for 60 minutes. Finally, the polydimethylsiloxane (PDMS) is peeled off from the silicon wafer to obtain a microwall array template (e.g., with a wall height of 20μm, a wall width of 20μm (median line width), and center-to-center spacing between adjacent walls of 40μm, 60μm, 80μm, and 100μm respectively). Figure 1 As shown, the microwall array was cut into small pieces of 4mm × (3mm, 6mm, 9mm, 12mm). Each of the 16 different sizes of microwalls was then combined with a smooth glass substrate, specifically, the protruding parts of the microwalls were bonded to the substrate to form a tiny space, thus assembling a microchannel reactor, as shown. Figure 3 As shown.

[0060] Example 2

[0061] At room temperature, 40g of polyvinylpyrrolidone (PVP) was added to a single-necked flask containing 150mL of ethylene glycol and stirred until completely dissolved (pale yellow color). 6.4g of silver nitrate solid (AgNO3) was added to the mixture and stirred until completely dissolved (dark brown color). The mixture was then stored away from light for later use. The 16 microchannel reactors of different sizes obtained in Example 1 were placed on a heating plate and kept at 120℃. A drop of AgNO3 reaction solution was dropped from one side of the microchannel. The reaction solution was rapidly drawn into the channel by capillary action (within 10 seconds). After the channel was filled with the reaction solution, excess reaction solution at the channel inlet was absorbed with filter paper. The mixture was kept at this temperature for 30 minutes. The Ag element content in the channels of different sizes varied, as shown in Table 1 (the horizontal column in Table 1 represents the length of the microchannel, and the vertical column represents the width of the microchannel). After reacting for 30 minutes, the mixture was allowed to cool naturally to room temperature. Then, the PDMS microwall and glass substrate were separated. A drop of ultrapure water was placed on the PDMS microwall (ensuring coverage of all microchannels). After ultrasonic dispersion for 60-120 seconds, 10 μL of the dispersion was dropped onto a copper grid for transmission electron microscopy. After the water evaporated, the morphology of silver nanoparticles prepared in 16 different sized microchannel reactors was characterized using transmission electron microscopy (TEM). Figure 5 The image shows TEM images of silver nanoparticles prepared by microchannels of 16 different sizes. As can be seen from the image, the particle size of the synthesized silver nanoparticles increases with the increase of the length and width of the microchannels.

[0062] Table 1. Ag content in 16 different sized channels

[0063]

[0064] Note: The width of the microchannel = the center-to-center distance between adjacent walls - the wall width

[0065] Example 3

[0066] TEM images of silver nanoparticles prepared by 16 different-sized microchannel reactors obtained in Example 2 were analyzed using ImageJ software (indiscriminate, multiple, 200 particles). The results were then statistically analyzed using Origin software to obtain the particle size distribution of silver nanoparticles obtained under different conditions. The results are as follows: Figure 6-9 As shown in the figure, it can be seen that the particle size of the synthesized silver nanoparticles increases with the increase of the microchannel length and width; the average results are shown in Table 2. The results in Table 2 show that by changing the width of the microchannel, controllable preparation of nanoparticles within a small range (±3nm) can be achieved; by changing the length of the microchannel, controllable preparation of nanoparticles within a large range (±10-30nm) can be achieved.

[0067] Table 2

[0068]

[0069]

[0070] Note: The width of the microchannel = the center-to-center distance between adjacent walls - the wall width

[0071] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method of preparing nanoparticles, characterized by, This includes preparing nanoparticles by cutting and reacting reaction liquid droplets through microchannels in a microchannel reactor; The microchannel reactor comprises 1-10 20 microchannels; the width of the microchannel is 10-100 μm; the length of the microchannel is 1-20 mm; the height of the microchannel is 1-100 μm; The cross-section of the microchannel is either trapezoidal or square; The microchannel reactor is formed by combining a substrate with a microwall array; The microwall array has a bottom and multiple parallel "microwalls" protruding from the bottom thereon, with a microchannel formed between every two microwalls in the microchannel reactor; The microwall array is prepared from at least one of polydimethylsiloxane (PDMS), copolyester, polyvinyl alcohol, polycarbonate, polyvinyl chloride, cellulose acetate, ethyl cellulose, ethylene alcohol-vinyl acetate, ethylene-propylene polymer and sodium alginate.

2. The method of claim 1, wherein the nanoparticles are prepared by a method comprising: The substrate material is one of silicon wafers, quartz wafers, glass wafers, iron wafers, copper wafers, aluminum wafers, and alumina wafers.

3. The method of claim 1, wherein the nanoparticles are prepared by a method comprising: The thickness of the microwall is 1-50 μm.

4. The method for preparing nanoparticles as described in claim 1, characterized in that, The microwall array is prepared by first fabricating a microgroove array using a dicing method, and then obtaining the microwall array through a complex method.

5. The method for preparing nanoparticles according to any one of claims 1-4, characterized in that, The reaction solution includes a reaction precursor and a solvent; The reaction precursor is a metal salt.

6. The method for preparing nanoparticles as described in claim 5, characterized in that, The metal element in the metal salt is at least one of silver, gold, titanium, and iron; The solvent is water or an organic solvent.

7. The method for preparing nanoparticles as described in claim 6, characterized in that, The metal salt is at least one of silver acetate, silver nitrate, chloroplatinic acid, chloroauric acid, tetraisopropanol titanate, and iron acetylacetonate. The organic solvent is one of methanol, ethanol, ethylene glycol, n-hexane, cyclohexane, ethyl acetate, and toluene.

8. The method for preparing nanoparticles as described in claim 6, characterized in that, The reaction solution also includes reducing agents and other auxiliary substances.

9. The method for preparing nanoparticles as described in claim 8, characterized in that, The other auxiliary substances are surfactants, morphology control agents, and dispersants; The dispersant is at least one of polyvinylpyrrolidone, cetyltrimethylammonium bromide (CTAB), and sodium citrate; The reducing agent is at least one of ethylene glycol, sodium borohydride, and sodium citrate; The morphology control agent is at least one of FeCl3, CuCl2, HCl, NaCl, NaBr, sodium citrate, and polyacrylic acid.

10. The method for preparing nanoparticles according to any one of claims 1-4, characterized in that, The nanoparticles have a particle size of 5-120 nm.

11. The method for preparing nanoparticles according to any one of claims 1-4, characterized in that, The nanoparticles are one, two or more of the following: metal nanoparticles, alloy nanoparticles, metal oxide nanoparticles or composite metal oxide nanoparticles.

12. The method for preparing nanoparticles as described in claim 11, characterized in that, The metal nanoparticles are at least one of gold nanoparticles, silver nanoparticles and platinum nanoparticles. The alloy nanoparticles are gold-silver core-shell particles; The metal oxide nanoparticles are at least one of silicon dioxide, iron tetroxide, and titanium dioxide. The composite metal oxide nanoparticles are titanium dioxide-silver composite particles.

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