A method for preparing nickel oxide nanoparticles based on centrifugal microfluidics technology

Abstract

The present invention relates to the field of inorganic synthesis and discloses a method for preparing nickel trioxide nanoparticles based on centrifugal microfluidic technology, comprising: (1) injecting a nickel salt aqueous solution and an alkaline aqueous solution containing an oxidant into a centrifugal microfluidic reactor respectively, and centrifuging them; adopting a clockwise and counterclockwise alternating rotation mode during the centrifugal reaction; (2) collecting the precipitate after the centrifugal reaction, and obtaining nickel trioxide nanoparticles through post-processing. The present invention adopts a new centrifugal microfluidic technology to synthesize nickel trioxide nanoparticles. The method of the present invention not only has high reaction efficiency and can significantly increase the yield; but also can achieve fine control of the particle size and morphology of the nickel trioxide nanoparticles during the preparation process by controlling variables such as rotation acceleration, speed, and time, providing a favorable basis for synthesizing nanoparticles with customized properties.

Description

Technical Field

[0001] The present invention relates to the field of inorganic synthesis, and in particular to a method for preparing nickel oxide nanoparticles based on centrifugal microfluidic technology. Background Art

[0002] Inorganic nanoparticles have unique properties and a wide range of applications. For example, nickel oxide (Ni2O3) nanoparticles have excellent electrical, optical, and magnetic properties and have become a promising material widely used in multiple fields. However, traditional methods for synthesizing nickel oxide nanoparticles cannot precisely control the particle size, microscopic shape, and purity of the nanoparticles, thus limiting their potential for application in more advanced fields. In recent years, microfluidic synthesis technology has become a new method for synthesizing nickel oxide nanoparticles, providing better control, reproducibility, and scalability.

[0003] Microfluidic synthesis technology has garnered increasing attention in recent years due to its ability to precisely control reaction conditions and exhibit unique fluid behaviors. Microfluidic platforms offer numerous advantages for nanoparticle synthesis, including excellent mixing efficiency, efficient heat transfer rates, and the ability to execute multiple steps in a controlled manner. These properties enable precise control over the nucleation, growth, and assembly processes of nanoparticles, enabling the synthesis of nickel oxide nanoparticles with customized properties tailored to individual needs.

[0004] Several reports have reported on the use of microfluidic synthesis techniques to prepare nanoparticles. For example, Lian et al. effectively connected the microfluidics used to produce TiO2 nanoparticles using a surfactant-coated sol-gel strategy, enabling uniform delivery of TiO2 nanoparticles to the surface of multi-walled carbon nanotubes and retaining rhodamine B for wastewater treatment. However, these synthetic methods suffer from low throughput, making them unsuitable for stable scale-up and industrialization. Furthermore, the degree of control over nanoparticle size and other aspects of these synthetic processes remains limited, making precise control of nanoparticles impossible. Summary of the Invention

[0005] To address the above technical issues, the present invention provides a method for preparing nickel trioxide nanoparticles based on centrifugal microfluidics. This method utilizes a novel centrifugal microfluidics technique to synthesize nickel trioxide nanoparticles. This method not only achieves high reaction efficiency, significantly increasing yield, but also allows for precise control of the particle size and morphology of the nickel trioxide nanoparticles during the preparation process by controlling variables such as rotational acceleration, speed, and time, providing a promising foundation for synthesizing nanoparticles with customized properties.

[0006] The specific technical solutions of the present invention are:

[0007] In a first aspect, the present invention provides a method for preparing nickel oxide nanoparticles based on centrifugal microfluidics technology, comprising the following steps:

[0008] (1) A nickel salt aqueous solution and an alkaline aqueous solution containing an oxidant are respectively injected into two storage bins of a centrifugal microfluidic reactor, and the centrifugal microfluidic reactor is placed in a centrifuge for centrifugal treatment; a clockwise and counterclockwise alternating rotation mode is adopted during the centrifugal treatment; during the centrifugal treatment, the nickel salt aqueous solution and the alkaline aqueous solution containing an oxidant are transported to a mixing chamber under the action of a centrifuge for a mixing reaction.

[0009] (2) After the reaction is completed, the precipitate is collected, washed, filtered, dried, and ground to obtain nickel oxide nanoparticles.

[0010] Unlike existing conventional microfluidic processes, the present invention uses a new centrifugal microfluidic technology to synthesize nickel trioxide nanoparticles. The present invention can achieve fine control of the particle size and morphology of nickel trioxide nanoparticles during the preparation process by controlling variables such as rotational acceleration, speed, and time.

[0011] The present invention utilizes a centrifugal microfluidic reactor, leveraging centrifugal force to effectively increase the reaction rate within the microchannel reactor, thereby significantly increasing production. Furthermore, by controlling factors such as centrifugal acceleration / speed and reaction time, nickel oxide nanoparticles with a narrow particle size distribution can be obtained.

[0012] Preferably, in step (1), the nickel salt is Ni(NO3)2; the oxidant is NaClO; and the alkalinity of the alkaline aqueous solution is provided by sodium hydroxide.

[0013] When the above raw materials are used, the chemical reaction formula of the synthesis process is as follows:

[0014] 2(Ni(NO3)2·6H20)+NaclO+4NaOH→Nacl+Ni2O3↓+4Na(NO3)+14H2O

[0015] The nickel precursor Ni(NO3) dissolves in water to generate Ni 2+ and NO3 - . After that, the sodium hypochlorite containing active chlorine will decompose into Na + and ClO - , ClO - It will decompose into Cl - and O2. But under alkaline conditions, ClO - The self-decomposition of ClO is inhibited, and there is more active ClO in the solution. - Then ClO - with Ni 2+ Reaction, ClO - Cl in+ ions are reduced to Cl - , while 2Ni 2+ Loses two electrons to become 2Ni 3+ The product of the solution reaction is Ni2O3·xH2O, so it is necessary to heat and dry it to desorb the H2O in the black product.

[0016] Preferably, in step (1): the concentration of Ni(NO3)2 in the nickel salt aqueous solution is 3-3.5 g / mL; the concentration of active chlorine in the alkaline aqueous solution containing the oxidant is 3-7 wt%; and the volume ratio of the nickel salt aqueous solution to the alkaline aqueous solution containing the oxidant is 0.7-0.8:1.

[0017] Preferably, in step (1), the centrifugal treatment has a rotational acceleration of 4.2-30 rad / s2, a target rotation speed of 500-1000 rpm, and a time of 1-10 min. In the alternating rotation mode, the single clockwise and counterclockwise rotation times are equal.

[0018] Furthermore, the rotational acceleration of the centrifugal treatment is 4.2 rad / s2, the target rotation speed is 1000 rpm, and the time is 10 min.

[0019] Preferably, in step (2), the washing is performed by repeatedly washing with an aqueous solution containing the oxidant and deionized water.

[0020] Preferably, in step (2), the drying temperature is 85-95° C. and the drying time is 10-15 h.

[0021] In a second aspect, the present invention provides a centrifugal microfluidic reactor comprising a cover plate, a reaction chip, and a bottom plate stacked sequentially from top to bottom. In particular:

[0022] The cover plate is provided with at least one A material inlet and at least one B material inlet.

[0023] The reaction chip is provided with at least one A storage bin, at least one B storage bin, at least one A outlet channel, at least one B outlet channel, at least one mixing channel, and at least one mixing chamber; the A storage bin and the B storage bin are located in the center of the reaction chip and are distributed alternately; the mixing chamber is located at the edge of the reaction chip; the A material inlet / B material inlet, the A storage bin / B storage bin, the A outlet channel / B outlet channel, the mixing channel, and the mixing chamber are connected in sequence.

[0024] The working principle of the centrifugal microfluidic reactor of the present invention is as follows: the raw material liquid A and raw material liquid B for nanoparticle synthesis are respectively injected into the A storage bin and the B storage bin through the A material inlet and the B material inlet; the centrifugal microfluidic reactor is fixed on a centrifuge and centrifuged. Under the action of centrifugal force, the raw material liquid A and raw material liquid B are respectively transmitted through the A and B outlet channels and then converge at the mixing channel, and further fully mixed and reacted in the mixing chamber. In addition, the reactor rotates alternately clockwise and counterclockwise during centrifugation, making the liquid flow field in the mixing chamber more unstable, significantly increasing the phase exchange, and thus significantly improving the reaction efficiency. After the reaction is completed, the centrifugation is stopped, the product is collected in the mixing chamber, and the nanoparticles are obtained after post-processing.

[0025] In order to make the microfluidic reactor more suitable for centrifugal treatment, the present invention optimizes the microfluidic reactor as follows:

[0026] (1) The storage bin is designed at the center of the reaction chip, and the mixing chamber, the main place for mixing and reaction, is designed at the edge of the reactor. This design facilitates the transfer of raw material liquid from the storage bin to the mixing chamber under the action of centrifugal force.

[0027] (2) Storage bins A and B are alternately distributed at the center of the reaction chip, allowing the same storage bin to feed multiple mixing chambers at the same time, reducing the volume and making the reactor structure more compact.

[0028] Preferably, the reaction chip is disc-shaped and is provided with multiple A storage bins, B storage bins, A outlet channels, B outlet channels, mixing channels and mixing chambers; and each A outlet channel, B outlet channel, mixing channel and mixing chamber constitutes a unit; and the multiple units are evenly and symmetrically distributed on the reaction chip.

[0029] In order to further make the microfluidic reactor suitable for centrifugal reaction, the present invention designs the reaction chip into a disc shape, and makes multiple units evenly and symmetrically distributed on the reaction chip, ensuring the consistency of feeding and reaction of each unit during the centrifugation process.

[0030] Preferably, the connecting end between the A outlet channel and the A storage bin, and the connecting end between the B outlet channel and the B storage bin are both curved flow channels; the connecting ends of the curved flow channel and the A storage bin and the B storage bin are respectively oriented toward the center of the reaction chip (that is, the arc at the connection with the storage bin is perpendicular); the A outlet channel and the B outlet channel form an angle of 85-95°.

[0031] The curved flow channel design allows for smooth material discharge during centrifugal processing, regardless of forward or reverse rotation. The 85-95° angle between outlet channels A and B is the optimal angle range determined by fluid dynamics simulation data. This facilitates rapid, uniform, and efficient mixing of the two materials without affecting flow rate.

[0032] Preferably, the mixing chamber is connected to the outlet of the mixing channel through an inlet convex cavity located at the top thereof. The mixing chamber is fan-shaped, and the inlet convex cavity is arc-shaped and located near the edge of the reaction chip.

[0033] The inlet convex cavity connects to the mixing channel. This design places the convex cavity at the top of the mixing chamber edge, on the same level as the mixing channel. Therefore, under the action of centrifugal force, the liquid initially converges at the inlet convex cavity for further mixing and reaction. The advantage of the arc-shaped design is that it facilitates the back-and-forth flow and collision of the liquid during alternating clockwise and counterclockwise centrifugal rotation, making the flow field here more unstable and significantly increasing phase exchange.

[0034] Preferably, at least one ventilation hole is provided on the top of each mixing chamber in the reaction chip and the cover plate.

[0035] During the research and development process, the inventor's team discovered that when the mixed raw liquid enters the mixing chamber, it repels the enclosed mixing chamber gas, adversely affecting the dynamics of the material under centrifugal action. To address this, the inventor designed a ventilation hole at the top of the mixing chamber to expel the gas. Furthermore, since atmospheric pressure remains balanced, only the internal and external air pressures need to be maintained consistent. Therefore, when the material enters the mixing chamber, only gas is expelled, without backflow.

[0036] Preferably, the ventilation hole is located in the mixing chamber close to the center of the reaction chip.

[0037] The ventilation holes are located near the center of the reaction chip because the mixing chamber is typically not fully loaded with liquid. Therefore, under centrifugal force, the liquid concentrates at the far edge of the mixing chamber, leaving a gap near the center. Placing the ventilation holes at this top position prevents liquid from being thrown out.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] (1) The present invention adopts a new centrifugal microfluidic technology to synthesize nickel trioxide nanoparticles. The method of the present invention not only has high reaction efficiency and can greatly improve the yield; but also can realize fine control of the particle size / morphology of nickel trioxide nanoparticles during the preparation process by controlling variables such as rotational acceleration, speed, and time, providing a favorable basis for synthesizing nanoparticles with customized properties.

[0040] (2) The present invention optimizes part of the structure of the centrifugal microfluidic reactor in a targeted manner based on the characteristics of the centrifugal microfluidic technology, making the reactor more suitable for centrifugal reactions. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is the SEM image of the Ni2O3 nanoparticles synthesized in Example 2;

[0042] Figure 2 The X-ray diffraction (XRD) pattern of Ni2O3 nanoparticles synthesized in Example 2 of the present invention;

[0043] Figure 3 This is the particle size distribution diagram of each group of nanoparticles in Example 2 of the present invention;

[0044] Figure 4 Figure 2 shows the particle size distribution of each group of nanoparticles in Example 2 of the present invention under different conditions: (a) at 1000 rpm for different times and accelerations; (b) at 500 rpm for different times and accelerations; (c) at different speeds and accelerations for 5 minutes; (d) at different speeds and accelerations for 10 minutes.

[0045] Figure 5 This is a schematic diagram of the overall appearance of a centrifugal microfluidic reactor of the present invention;

[0046] Figure 6 A side perspective view of a centrifugal microfluidic reactor of the present invention;

[0047] Figure 7 A top view of the cover plate of the centrifugal microfluidic reactor of the present invention;

[0048] Figure 8 A bottom view of the cover plate of the centrifugal microfluidic reactor of the present invention;

[0049] Figure 9 A top view of the reaction chip of the centrifugal microfluidic reactor of the present invention;

[0050] Figure 10 A perspective view of a reaction chip of a centrifugal microfluidic reactor of the present invention;

[0051] Figure 11 A bottom view of the reaction chip of the centrifugal microfluidic reactor of the present invention;

[0052] Figure 12 The figure is a structural schematic diagram of the bottom sealing plate of the centrifugal microfluidic reactor of the present invention.

[0053] The figures are marked as: cover plate 1, reaction chip 2, bottom plate 3, material inlet A 11, material inlet B 12, fluid expansion groove 20, material storage bin A 21, material storage bin B 22, outlet channel A 23, outlet channel B 24, mixing channel 25, mixing chamber 26, inlet convex chamber 27, ventilation hole 28, bottom sealing plate 29. DETAILED DESCRIPTION

[0054] The present invention will be further described below with reference to the embodiments.

[0055] Overall embodiment

[0056] A method for preparing nickel oxide nanoparticles based on centrifugal microfluidics technology comprises the following steps:

[0057] (1) A nickel salt (preferably Ni(NO3)2) aqueous solution with a concentration of 3-3.5 g / mL and an alkaline (preferably sodium hydroxide) aqueous solution containing an oxidant (preferably NaClO, with an active chlorine concentration of 3-7 wt%) are respectively injected into two storage bins of a centrifugal microfluidic reactor, and the volume ratio of the nickel salt aqueous solution to the alkaline aqueous solution containing the oxidant is 0.7-0.8:1. The centrifugal microfluidic reactor is placed in a centrifuge for centrifugal treatment. During the centrifugation process, a clockwise and counterclockwise rotation mode of equal time is adopted; the rotation acceleration is 4.2-30 rad / s2, the target speed is 500-1000 rpm, and the time is 1-10 min; further, the rotation acceleration of the centrifugal treatment is 4.2 rad / s2, the target speed is 1000 rpm, and the time is 10 min. During the centrifugal treatment process, the nickel salt aqueous solution and the alkaline aqueous solution containing the oxidant are transported to the mixing chamber under the action of centrifugation for mixing reaction.

[0058] (2) After the centrifugal reaction is completed, the precipitate is collected, and repeatedly washed with an aqueous solution containing an oxidant (preferably NaClO) and deionized water, filtered, dried (85-95° C., 10-15 h), and ground to obtain nickel oxide nanoparticles.

[0059] The centrifugal microfluidic reactor comprises a cover plate 1, a reaction chip 2 and a bottom plate 3 stacked in sequence from top to bottom.

[0060] in:

[0061] The cover plate is disc-shaped and is provided with at least one A material inlet 11 and at least one B material inlet 12 .

[0062] The reaction chip is disc-shaped and is provided with at least one A storage bin 21, at least one B storage bin 22, at least one A outlet channel 23, at least one B outlet channel 24, at least one mixing channel 25, and at least one mixing chamber 26. Specifically:

[0063] Storage bin A and storage bin B are located in the center of the reaction chip and are distributed alternately; the mixing chamber is fan-shaped and located at the edge of the reaction chip; the mixing chamber is connected to the outlet end of the mixing channel through an arc-shaped inlet convex cavity 27 located at the top of the reaction chip near the edge of the reaction chip. At least one ventilation hole 28 is provided at the top of each mixing chamber near the center of the reaction chip in the reaction chip and the cover plate. A removable bottom sealing plate 29 is provided at the bottom of each mixing chamber. A material inlet / B material inlet, storage bin A / storage bin B, outlet channel A / outlet channel B, mixing channel and mixing chamber are connected in sequence. In the case where there are multiple storage bins A, storage bins B, outlet channels A, outlet channels B, mixing channels and mixing chambers, the same storage bins A and B are connected to multiple outlet channels A and B, and each outlet channel A, outlet channel B, mixing channel and mixing chamber constitutes a unit, and multiple units are evenly and symmetrically distributed on the reaction chip. In each unit, outlet channel A and outlet channel B are symmetrically arranged, and the channel formed by outlet channel A, outlet channel B and mixing channel is Y-shaped (outlet channel A and outlet channel B are at an angle of 85-95°). Further preferably, the connection between the A storage bin and outlet channel A, and the connection between the B storage bin and outlet channel B are both provided with a fluid expansion groove 20 with a trumpet-shaped decreasing flow path. At the same time, the connection end between outlet channel A and storage bin A, and the connection end between outlet channel B and storage bin B are both curved flow channels; the connection ends of the curved flow channels and storage bin A and storage bin B are respectively facing the center of the reaction chip; the connection point between the mixing channel and the mixing chamber is located on the center line of the mixing chamber. The width of outlet channel A and outlet channel B is 0.5-3mm; the width of the mixing channel is 1-6mm, and the width of outlet channel A and outlet channel B is less than the width of the mixing channel. The bottom plate is disc-shaped and is detachably connected to the reaction chip.

[0064] Optionally, the cover plate, the reaction chip and the base plate are made of plastic such as acrylic, PEEK, PTFE, PFA, or metal such as 316L.

[0065] The centrifugal microfluidic reactor is used for nanoparticle synthesis: raw material liquids A and B for nanoparticle synthesis are injected into storage bins A and B through material inlet A and material inlet B, respectively; the centrifugal microfluidic reactor is mounted on a centrifuge and subjected to centrifugal reaction, with alternating clockwise and counterclockwise rotations during centrifugation; after the reaction is completed, the centrifugation is stopped, and the product is collected in a mixing chamber, washed, filtered, dried, and ground to obtain nanoparticles. Preferably, the nanoparticles do not include nickel oxide nanoparticles.

[0066] Example 1

[0067] (1) Centrifugal microfluidic reactor, such as Figure 5 and Figure 6As shown, it includes a cover plate 1, a reaction chip 2 and a bottom plate 3 stacked in sequence from top to bottom.

[0068] like Figure 7 and Figure 8 As shown, the cover plate is disc-shaped and is provided with two A material inlets 11 , two B material inlets 12 , eight screw fixing holes (through which the cover plate is fixed to the reaction chip) and eight ventilation holes 28 .

[0069] like Figure 9 and Figure 10 As shown, the reaction chip is disc-shaped and is provided with two fan-shaped columnar A storage bins 21, two fan-shaped columnar B storage bins 22, four A outlet channels 23, four B outlet channels 24, four mixing channels 25 and four mixing chambers 26. Specifically:

[0070] Two A storage bins and two B storage bins are located in the center of the reaction chip and are spaced apart to form a cylindrical shape. Four mixing chambers are fan-shaped and evenly distributed at the edge of the reaction chip. The mixing chambers are connected to the outlet of a mixing channel through a circular arc-shaped inlet convex cavity 27 located near the top of the reaction chip. Two ventilation holes 28 are provided at the top of each mixing chamber near the center of the reaction chip, penetrating the cover plate. Figure 11 and Figure 12 As shown, the bottom of each mixing chamber is provided with a removable bottom sealing plate 29. The same A and B storage bins are connected to two adjacent A and B outlet channels, and each A outlet channel, B outlet channel, mixing channel and mixing chamber constitute a unit, and the four units are evenly and symmetrically distributed on the reaction chip. In each unit, the A outlet channel and the B outlet channel are symmetrically arranged, and the channel formed by the A outlet channel, the B outlet channel and the mixing channel is Y-shaped (the A outlet channel and the B outlet channel are at a 90° angle), and the connection between the A storage bin and the A outlet channel, and the connection between the B storage bin and the B outlet channel are both provided with a fluid expansion groove 20 with a trumpet-shaped flow path decreasing, and at the same time, the connection end of the A outlet channel and the A storage bin, and the connection end of the B outlet channel and the B storage bin are both curved flow channels; the connection ends of the curved flow channel and the A storage bin and the B storage bin are respectively facing the center of the reaction chip; the connection point between the mixing channel and the mixing chamber is located on the center line of the mixing chamber. The width of the A outlet channel and the B outlet channel is 2mm; the width of the mixing channel is 4mm. The top and bottom of the reaction chip are also provided with screw fixing holes.

[0071] like Figure 5 As shown, the bottom plate is disc-shaped, and four screw fixing holes are provided on its upper surface, which are detachably connected to the reaction chip through screws.

[0072] The cover, reaction chip and base are made of transparent acrylic.

[0073] (2) Synthesis of nickel trioxide nanoparticles: Dissolve 0.8g Ni(NO3)2·6H2O in 15ml deionized water, labeled as solution A. Take another beaker and dissolve 1.6g NaOH in 20ml NaClO solution containing 5wt% active chlorine, labeled as solution B. Use a centrifugal microfluidic reactor to inject solution A into two opposite A storage bins and inject solution B into two opposite B storage bins. Fix the centrifugal microfluidic reactor on a centrifuge. Start the centrifuge and centrifuge at different speeds (using a forward and reverse alternating mode: forward for 1min, reverse for 1min). It can be seen that the two solutions quickly form black particles and gather in the mixing chamber. After 5 minutes, turn off the machine, open the bottom plate and the bottom seal of the reaction chip to collect the product. The generated black precipitate (Ni2O3*xH2O) is further washed repeatedly with NaClO solution and deionized water. After filtration, the final dark black precipitate was placed in a dryer at 90°C for 12 hours, and finally the product was ground to obtain Ni2O3 nanoparticles.

[0074] The chemical reaction formula of the above synthesis process is as follows:

[0075] 2(Ni(NO3)2·6H2O)+NaclO+4NaOH→Nacl+Ni2O3↓+4Na(NO3)+14H2O

[0076] The nickel precursor Ni(NO3)2·6H2O dissolves in water to generate Ni 2+ and NO3. Thereafter, sodium hypochlorite containing 5wt% active chlorine will decompose into Na + and ClO - , ClO - It will decompose into Cl - and O2. But under alkaline conditions, ClO - The self-decomposition of ClO is inhibited, and there is more active ClO in the solution. - Then ClO - with Ni 2+ Reaction, ClO - Cl in + ions are reduced to Cl - , while 2Ni 2+ Loses two electrons to become 2Ni 3+ The product of the solution reaction is Ni2O3·xH2O, so it is necessary to heat and dry it to desorb the H2O in the black product.

[0077] Performance Testing

[0078] (1) The morphology and microstructure of Ni2O3 nanoparticles synthesized by microfluidics were characterized using scanning electron microscopy (SEM). Figure 1The following is a SEM image of NiO nanoparticles obtained under centrifugal conditions of 30 rad / s², 500 rpm, and 5 minutes. The SEM results reveal that the NiO nanoparticles have a complete shape and are bound together to form loose aggregates. Unlike traditional synthesis methods, which typically require several hours, this method shortens the reaction time to just 5 minutes, demonstrating the superior performance of the centrifugal microfluidic process.

[0079] (2) X-ray diffraction (XRD) analysis was used to investigate the crystal structure and purity of the products obtained at different rotation speeds (500 rpm, 1000 rpm, 1500 rpm) (the test samples were directly collected in the mixing chamber without subsequent post-processing). Figure 2 As shown, the synthesis process was 5 minutes without any purification or washing procedures. Therefore, due to the presence of impurities, mainly sodium chloride (NaCl), which is a by-product of the reaction, the XRD results showed impurity peaks. Comparing the three rotation speeds, the 500 rpm group had additional peaks around the main peak of Ni2O3 (31.66°), indicating that the purity of the particles was relatively low. As the rotation speed increased (1000 rpm), the appearance of impurity peaks decreased, and the curve near 31.66° became smoother. In the 1500 rpm group, the curve looked very smooth with little interference, confirming the high purity of the crystal surface.

[0080] (3) The effects of different rotation speeds, accelerations, and times on particle diameter were further analyzed. The statistical method for the diameter of the synthesized Ni2O3 nanoparticles was to use ImageJ to identify spherical particles in the SEM results, randomly select 40 particles from the SEM images, count the particle diameters, and analyze their distribution and curves.

[0081] In order to study the effects of different factors on microfluidic synthesis, the data were divided into 8 groups: 500rpm-5min-4ac, 500rpm-10min-4ac, 1000rpm-5min-4ac, 1000rpm-10min-4ac, 500rpm-5min-8ac, 500rpm-10min-8ac, 1000rpm-5min-8ac, and 1000rpm-10min-8ac, and their effects were analyzed separately. Among them, acceleration 4 and 8 represent the acceleration level, and the actual acceleration is 4.2rad / s2 and 30rad / s2 respectively. Figure 3 and 4 As shown: Figure 4As shown in (a), at 1000 rpm, the minimum diameter range observed was 100-200 nm. Within this range, the 1000 rpm-10 min-4 ac group exhibited the highest particle counts. Comparing the 1000 rpm-5 min-4 ac group with the 1000 rpm-10 min-4 ac group, it can be seen that with increasing reaction time, the particle size range shifts from larger to smaller. In the 1000 rpm-10 min-4 ac group, approximately 80% of the particles were below 300 nm, while in the 1000 rpm-5 min-4 ac group, only approximately 60% were below 300 nm. Similar results were obtained for the 1000 rpm-5 min-8 ac and 1000 rpm-10 min-8 ac groups, where the diameter range was more concentrated below 400 nm. Notably, in the 1000 rpm-10 min-8 ac group, nearly 90% of the particles were below 400 nm, and the number of particles in this range was the highest, indicating a narrower particle diameter distribution.

[0082] like Figure 4 As shown in (b), at 500 rpm, the highest number of particles in the 500 rpm-10 min-4 ac group was between 200 and 300 nm. Compared to the 500 rpm-5 min-4 ac group, a significant shift in the peak from 300-400 nm to 200-300 nm was observed. This effect became more pronounced when comparing the 500 rpm-5 min-8 ac group with the 500 rpm-10 min-8 ac group. The particle size distribution was broad at 500 rpm-5 min-8 ac, with an average particle size above 580 nm. However, with increasing reaction time, the diameter distribution became more concentrated and shifted to a lower range. With increasing stirring time, the average particle size decreased significantly in the 500 rpm-8 ac and 1000 rpm-8 ac conditions, while the effect was relatively small in the 500 rpm-4 ac and 1000 rpm-4 ac conditions.

[0083] like Figure 4As shown in (c) and (d), under the same reaction time and acceleration, increasing the rotational speed leads to a decrease in particle diameter and a narrower diameter distribution. Under the 5 min 4 ac condition, the 1000 rpm-5 min 4 ac outperforms the 500 rpm-5 min 4 ac. In the 1000 rpm-5 min 4 ac group, over 90% of the particles are smaller than 400 nm, with the majority concentrated around 200 nm. In contrast, for the 500 rpm-5 min 4 ac group, the diameter range is more concentrated between 300 nm and 500 nm. Similar results are obtained for the 500 rpm-5 min 8 ac and 1000 rpm-5 min 8 ac groups, as well as the 500 rpm-10 min 4 ac and 1000 rpm-10 min 4 ac groups.

[0084] In contrast, the acceleration factor exhibited different behavior from the other two factors. Under the 5-min condition, increasing the acceleration from 4 to 8 (representing an increase from 4.2 rad / s² to 30 rad / s²) resulted in an increase in particle diameter. Comparing the 500 rpm-5 min-4 ac and 500 rpm-5 min-8 ac groups, as well as the 1000 rpm-5 min-4 ac and 1000 rpm-5 min-8 ac groups, the diameter distribution range gradually widened with increasing acceleration. Similar results were observed under the 10-min condition, with larger diameters and a wider diameter distribution under the 8 ac condition compared to the 4 ac condition.

[0085] Unless otherwise specified, the raw materials and equipment used in the present invention are commonly used in the art; the methods used in the present invention are conventional methods in the art unless otherwise specified.

[0086] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent transformation made to the above embodiment based on the technical essence of the present invention still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for preparing nickel oxide nanoparticles, characterized in that include: (1) A nickel salt aqueous solution and an alkaline aqueous solution containing an oxidant are respectively injected into two storage bins of a centrifugal microfluidic reactor, and the reactor is placed in a centrifuge and centrifuged in a clockwise and counterclockwise alternating rotation mode; the nickel salt aqueous solution and the alkaline aqueous solution containing an oxidant are transported to a mixing chamber under the action of centrifugation for mixing and reaction; (2) After the reaction, the precipitate is collected, washed, filtered, dried, and ground; The reactor includes the following stacked up from top to bottom: Cover plate: equipped with at least one inlet for material A and at least one inlet for material B; The reaction chip is equipped with at least one A storage bin, at least one B storage bin, at least one A outlet channel, at least one B outlet channel, at least one mixing channel, and at least one mixing chamber. The A and B storage bins are located in the center of the reaction chip and are spaced apart. The mixing chamber is located at the edge of the reaction chip. The A material inlet / B material inlet, the A storage bin / B storage bin, the A outlet channel / B outlet channel, the mixing channel, and the mixing chamber are connected in sequence. The mixing chamber is connected to the outlet end of the mixing channel via a convex inlet cavity at its top. The mixing chamber is fan-shaped, and the convex inlet cavity is arc-shaped and located near the edge of the reaction chip. Base plate.

2. The method according to claim 1, wherein: In step (1): The nickel salt is Ni(NO3)2; The oxidant is NaClO; The alkalinity of the alkaline aqueous solution is provided by sodium hydroxide.

3. The method according to claim 2, wherein: In step (1): The concentration of Ni(NO3)2 in the nickel salt aqueous solution is 3-3.5 g / mL; The concentration of active chlorine in the alkaline aqueous solution containing the oxidant is 3-7wt%; The volume ratio of the nickel salt aqueous solution to the alkaline aqueous solution containing the oxidant is 0.7-0.8:

1.

4. The method according to any one of claims 1 to 3, characterized in that: In step (1): the centrifugal rotational acceleration is 4.2-30 rad / s2, the target rotation speed is 500-1000 rpm, and the time is 1-10 min.

5. The method according to claim 4, wherein: In step (1): the centrifugal rotational acceleration is 4.2 rad / s2, the target speed is 1000 rpm, and the time is 10 min.

6. The method according to claim 4, wherein: In step (1): the time of a single clockwise rotation and a single counterclockwise rotation in the alternating rotation mode are equal.

7. The method according to any one of claims 1 to 3, characterized in that: In step (2): the washing is performed by repeatedly washing with an aqueous solution containing the oxidant and deionized water.

8. The method according to any one of claims 1 to 3, characterized in that: In step (2): the drying temperature is 85-95°C and the drying time is 10-15 hours.

9. The method according to claim 1, wherein: At least one ventilation hole is provided on the top of each mixing chamber in the reaction chip and the cover plate; the ventilation hole is located at a position of the mixing chamber close to the center of the reaction chip.

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