Polystyrene colloid photonic crystal nano-particles as well as preparation method and application thereof

Abstract

The invention relates to the cross technical field of nano material synthesis and microfluidic reactor engineering, and discloses polystyrene colloidal photonic crystal nano particles as well as a preparation method and application thereof. The preparation method of the polystyrene colloidal photonic crystal nanoparticles comprises the following steps: preparing a water phase and an oil phase; injecting the water phase and the oil phase into the micro-fluidic chip according to a water-oil flow rate of 10: 1, wherein the total flow rate is 8-15ml / min; discharging front-section waste liquid; and carrying out emulsion polymerization reaction at 70-90 DEG C, cooling the reaction liquid, and carrying out centrifugal treatment to obtain the polystyrene colloid photonic crystal nanoparticles. The colloidal photonic crystal prepared by the preparation method disclosed by the invention has the advantages that the structural regularity of particles is improved while high monodispersity and precise size regulation are ensured, and high-throughput production is realized, so that the application requirements of the colloidal photonic crystal in the fields of display, sensing, flexible electronics and the like are met, and the technical problems of poor product consistency, poor material performance, low production efficiency and high cost are solved.

Description

Technical Field

[0001] The present invention relates to the cross - technical field of nanomaterial synthesis and microfluidic reactor engineering. In particular, it relates to a method for preparing polystyrene colloidal photonic crystal nanoparticles. In addition, the present invention also relates to polystyrene colloidal photonic crystal nanoparticles prepared by the above - mentioned method for preparing polystyrene colloidal photonic crystal nanoparticles and their applications. Background Art

[0002] Colloidal photonic crystals are a class of materials with spatially periodic nanostructures. Due to their unique photonic band - gap properties, they can regulate the propagation behavior of light with specific wavelengths and have important application values in the fields of structural color display, biosensing, laser resonators, and flexible optoelectronic devices. The performance of such materials highly depends on the monodispersity, size controllability, and structural regularity of the constituent nanoparticles. However, traditional preparation methods are difficult to meet these requirements simultaneously, resulting in limited practical applications of colloidal photonic crystals.

[0003] Currently, the preparation of polystyrene colloidal photonic crystals mainly relies on techniques such as emulsion polymerization, drop - wise polymerization, and template - assisted assembly.

[0004] In emulsion polymerization, styrene monomers are dispersed by emulsifiers and then polymerized. However, this method has problems such as a wide particle size distribution (PDI>0.2) and poor batch repeatability. This is mainly because the dynamic adsorption of emulsifiers leads to non - uniform particle growth rates, and small fluctuations in reaction parameters (such as temperature and stirring speed) will significantly affect the product consistency. In addition, the subsequent purification process (such as centrifugation to remove residual emulsifiers) may damage the ordered assembly structure of the particles, further reducing the material performance.

[0005] In drop - wise polymerization, the particle growth is controlled by gradually adding monomers or initiators. Although the size controllability is improved to a certain extent, the reaction kinetics are difficult to precisely regulate, and the throughput is extremely low (the single - batch production is usually <10 mL / h), which cannot meet the requirements of large - scale production.

[0006] In template - assisted assembly, porous templates are used to force the alignment of nanoparticles, which can improve the structural regularity. However, the template cost is high, and it is difficult to be compatible with flexible substrates, limiting its application in the field of flexible electronics. Summary of the Invention

[0007] The present invention provides a method for preparing and applying polystyrene colloidal photonic crystal nanoparticles, which can improve the structural regularity of the particles while ensuring high monodispersity and precise size control, and achieve high - throughput production to meet the application requirements of colloidal photonic crystals in the fields of display, sensing, and flexible electronics, so as to solve the technical problems of poor product consistency, poor material performance, low production efficiency, and high cost in the preparation of existing polystyrene colloidal photonic crystals.

[0008] According to one aspect of the present invention, a method for preparing polystyrene colloidal photonic crystal nanoparticles is provided, comprising the following steps: S100, preparing an aqueous phase and an oil phase; S200, injecting the aqueous phase and the oil phase into a microfluidic chip at a water-oil flow rate ratio of 10:1, with a total flow rate of 8 ml / min - 15 ml / min; S300, discharging the waste liquid in the front section; S400, performing an emulsion polymerization reaction at 70°C - 90°C, and centrifuging the reaction solution after cooling to obtain polystyrene colloidal photonic crystal nanoparticles.

[0009] Further, the aqueous phase in step S100 adopts one of potassium persulfate aqueous solution, ammonium persulfate, or azobisisobutyramidine hydrochloride.

[0010] Further, the oil phase in step S100 adopts at least one of styrene monomer, methacrylic acid, methyl methacrylate, α-methylstyrene, or divinylbenzene.

[0011] Further, the microfluidic chip in step S200 is made of glass or PDMS material.

[0012] Further, the channel width of the microfluidic chip is 50 μm - 200 μm.

[0013] Further, the aqueous phase in step S100 adopts potassium persulfate aqueous solution, and the concentration of potassium persulfate in the aqueous phase is 0.5 g / L - 2.0 g / L.

[0014] Further, the emulsion polymerization reaction time in step S400 is 10 minutes - 60 minutes.

[0015] Further, after step S400, the step S500 is added: S500, constructing the nanoparticles into a periodic photonic crystal structure by evaporation-induced or template-assisted means.

[0016] According to another aspect of the present invention, a polystyrene colloidal photonic crystal nanoparticle is further provided, which is prepared by the above method for preparing polystyrene colloidal photonic crystal nanoparticles. The particle size of the polystyrene colloidal photonic crystal nanoparticle is 100 nm - 400 nm, and the PDI is less than or equal to 0.1.

[0017] According to another aspect of the present invention, an application of the polystyrene colloidal photonic crystal nanoparticle is further provided, using the above polystyrene colloidal photonic crystal nanoparticle in a structural color display device, a biosensor device, a laser feedback device, or a flexible electronic device.

[0018] The present invention has the following beneficial effects: The preparation method of the polystyrene colloidal photonic crystal nanoparticles of the present invention, through the synergistic control of the water-oil flow rate ratio (10:1) and the total flow rate (8 ml / min - 15 ml / min), the particle size distribution is significantly narrowed (PDI ≤ 0.1), and the monodispersity is improved; compared with the traditional emulsion polymerization where the uneven growth of particles is caused by the dynamic adsorption of emulsifiers (PDI > 0.2), the preparation method of the polystyrene colloidal photonic crystal nanoparticles of the present invention ensures a constant monomer diffusion rate by fixing the water-oil ratio (10:1) and the total flow rate (8 ml / min - 15 ml / min), avoiding secondary nucleation caused by local concentration fluctuations; the constant monomer diffusion rate ensures the synchronous growth of particles, and the precise fluid control eliminates the local concentration gradient.

[0019] In the preparation method of the polystyrene colloidal photonic crystal nanoparticles of the present invention, the waste liquid in the front stage is discharged to remove the unstable products in the front stage, ensuring the size uniformity of the subsequent particles (deviation < ±2%).

[0020] In the preparation method of the polystyrene colloidal photonic crystal nanoparticles of the present invention, the high-temperature polymerization temperature is controlled at 70°C - 90°C. The high temperature accelerates the decomposition of the initiator, shortens the nucleation time, enables the synchronous growth of particles (the particle size is 100 nm - 400 nm, achieving precise regulation), and the crystallinity is increased, making the photonic bandgap more obvious.

[0021] In the preparation method of the polystyrene colloidal photonic crystal nanoparticles of the present invention, after the high-temperature emulsion polymerization reaction, the particles are collected by centrifugation after cooling. Cooling slows down the reaction rate to avoid over-polymerization, and high-purity polystyrene colloidal photonic crystal nanoparticles are obtained by centrifugal separation, further improving the monodispersity and stability.

[0022] The preparation method of the polystyrene colloidal photonic crystal nanoparticles of the present invention realizes the improvement of monodispersity, PDI ≤ 0.1, the adjustable range of particle size covers 100 nm - 400 nm, and impurities and unreacted monomers are removed by centrifugation to obtain high-purity polystyrene colloidal photonic crystal nanoparticles. By precisely controlling the mixing and reaction conditions of the aqueous phase and the oil phase through a microfluidic chip, the problems of poor monodispersity of particles, inflexible size regulation, and insufficient batch stability in the traditional method are solved.

[0023] In addition to the purposes, features, and advantages described above, the present invention has other purposes, features, and advantages. The present invention will be further described in detail below. Detailed implementation mode

[0024] The embodiments of the present invention are described in detail below. However, the present invention can be implemented in many different ways defined and covered by the following. Unless otherwise specified, the raw materials and reagents used in the following embodiments are all commercially available products or can be prepared by known methods.

[0025] The preparation method of the polystyrene colloidal photonic crystal nanoparticles in this embodiment includes the following steps: S100, prepare the aqueous phase and the oil phase; S200, inject the aqueous phase and the oil phase into the microfluidic chip at a water-oil flow rate ratio of 10:1, and the total flow rate is 8 ml / min - 15 ml / min; S300, discharge the waste liquid in the front section; S400, carry out emulsion polymerization reaction under the condition of 70°C - 90°C, and after the reaction solution is cooled, centrifugation treatment is carried out to obtain the polystyrene colloidal photonic crystal nanoparticles. In the preparation method of the polystyrene colloidal photonic crystal nanoparticles of the present invention, through the synergistic control of the water-oil flow rate ratio (10:1) and the total flow rate (8 ml / min - 15 ml / min), the particle size distribution is significantly narrowed (PDI ≤ 0.1), and the monodispersity is improved; compared with the traditional emulsion polymerization where the particle growth is uneven due to the dynamic adsorption of the emulsifier (PDI > 0.2), the preparation method of the polystyrene colloidal photonic crystal nanoparticles of the present invention ensures a constant monomer diffusion rate by fixing the water-oil ratio (10:1) and the total flow rate (8 ml / min - 15 ml / min), avoiding secondary nucleation caused by local concentration fluctuations; the constant monomer diffusion rate ensures the synchronous growth of the particles, and the precise fluid control eliminates the local concentration gradient. In the preparation method of the polystyrene colloidal photonic crystal nanoparticles of the present invention, the waste liquid in the front section is discharged to remove the unstable products in the front section, ensuring the size uniformity of the subsequent particles (deviation < ±2%). In the preparation method of the polystyrene colloidal photonic crystal nanoparticles of the present invention, the high-temperature polymerization temperature is controlled at 70°C - 90°C. The high temperature accelerates the decomposition of the initiator, shortens the nucleation time, enables the particles to grow synchronously (the particle size is 100 nm - 400 nm, achieving precise regulation), and the crystallinity is improved, and the photonic band gap is more obvious. In the preparation method of the polystyrene colloidal photonic crystal nanoparticles of the present invention, after the high-temperature emulsion polymerization reaction, centrifugation treatment is carried out to collect the particles after cooling. Cooling slows down the reaction rate to avoid over-polymerization, and high-purity polystyrene colloidal photonic crystal nanoparticles are obtained by centrifugal separation, further improving the monodispersity and stability. The preparation method of the polystyrene colloidal photonic crystal nanoparticles of the present invention realizes the improvement of monodispersity, PDI ≤ 0.1, the adjustable range of the particle size covers 100 nm - 400 nm, centrifuges to remove impurities and unreacted monomers, and obtains high-purity polystyrene colloidal photonic crystal nanoparticles. By precisely controlling the mixing and reaction conditions of the aqueous phase and the oil phase through the microfluidic chip, the problems of poor particle monodispersity, inflexible size regulation and insufficient batch stability in the traditional method are solved.

[0026] In this embodiment, to inject the aqueous phase and the oil phase into the microfluidic chip at a water-oil flow rate ratio of 10:1 and control the total flow rate within 8 - 15 mL / min, the design of the microfluidic chip needs to focus on the following aspects: 1. Selection of the channel configuration of the microfluidic chip structure: Adopt a flow-focusing or T / Y-shaped microchannel structure to ensure that the aqueous phase (continuous phase) symmetrically wraps the oil phase (dispersed phase) from both sides or all around, achieving precise control of the 10:1 flow rate ratio.

[0027] Flow-focusing type: Generate high shear force through the contraction section, which is more suitable for the generation of monodisperse droplets at a high total flow rate (15 mL / min).

[0028] T / Y type: Simple structure, suitable for preliminary optimization at a low total flow rate (8 - 10 mL / min).

[0029] Optimization of the channel size: Width of the main channel: The width of the aqueous phase channel is recommended to be 200 - 500 μm, and the width of the oil phase channel is 50 - 100 μm, matching the 10:1 flow rate ratio.

[0030] Design of the contraction section: If a flow-focusing structure is adopted, the width of the contraction section should be 50 - 100 μm to enhance the shear force and stabilize the droplet generation.

[0031] 2. Selection of the material of the microfluidic chip: Select a glass chip or a PDMS chip for the microfluidic chip.

[0032] Glass chip: Preferred for high-temperature (>70 °C) or strongly chemically corrosive systems (such as aqueous phases containing persulfate) to ensure long-term stability.

[0033] PDMS chip: Suitable for normal temperature or rapid prototyping development, but it needs to be made hydrophilic on its surface through plasma treatment to avoid channel blockage caused by the adhesion of the oil phase. Surface modification of the PDMS chip, hydrophilization treatment of the PDMS chip (such as oxygen plasma treatment or PEG coating), reduces the flow resistance of the aqueous phase and maintains the stability of the 10:1 flow rate ratio.

[0034] 3. Fluid control parameters: Flow rate matching: Set the flow rate of the aqueous phase to 7.27 - 13.64 mL / min, and the flow rate of the oil phase to 0.73 - 1.36 mL / min (distribute the total flow rate of 8 mL / min - 15 mL / min according to the 10:1 ratio). Use a high-precision syringe pump (error <1%) or a pneumatic drive system to ensure a constant flow rate ratio.

[0035] Pressure balance: By adjusting the outlet backpressure or channel resistance (such as adding a microcolumn array), balance the two-phase pressure to avoid flow rate ratio drift or droplet coalescence.

[0036] 4. Droplet generation and stability control: Capillary number (Ca) regulation: Keep the aqueous phase capillary number (Ca = μv / γ, where μ is viscosity, v is flow rate, and γ is interfacial tension) in the range of 10 - ² - 10 - ¹ to ensure droplet monodispersity (CV < 5%). The interfacial tension γ can be reduced by adding surfactants (such as SDS) to adapt to high flow rate conditions.

[0037] Temperature control: If the reaction requires high temperature (such as initiated by KPS), integrate a chip heating module (such as embedding heating wires in a glass chip) to avoid PDMS deformation due to high temperature.

[0038] 5. Verification and optimization methods: Real-time monitoring: Integrate an optical microscope or high-speed camera at the chip outlet to observe droplet size and generation frequency, and dynamically adjust the flow rate ratio.

[0039] Post-processing analysis: After collecting the droplets, detect the particle size distribution by a laser particle size analyzer (target CV < 3%) to infer the rationality of the chip design.

[0040] Design key points of the microfluidic chip: In terms of structure, use flow focusing or T / Y-shaped channels, and scale the main channel width at a ratio of 10:1; in terms of materials, select glass or PDMS according to temperature / chemical requirements, and perform surface modification if necessary; in terms of control, use a high-precision pump + pressure balance to strictly maintain a flow rate ratio of 10:1; for verification and optimization, ensure stable droplet generation through capillary number and real-time monitoring. Through the design of the microfluidic chip, it is possible to efficiently generate monodisperse emulsions at a total flow rate of 8 mL / min - 15 mL / min, providing an ideal precursor for subsequent polymerization steps.

[0041] In this embodiment, the aqueous phase in step S100 uses one of potassium persulfate aqueous solution (KPS), ammonium persulfate (APS), and 2,2'-azobis(2-methylpropionamidine) dihydrochloride (AIBA). KPS / APS decomposes at 70 - 90 °C to generate sulfate radicals (SO4 - ·), which initiate the polymerization of styrene monomers; the sulfate ions (SO4 2- ) generated after the decomposition of KPS / APS or the hydrochloride residues (Cl -Adsorb on the particle surface to form a negatively charged layer, enhancing the colloidal stability, preventing particle aggregation (remaining stably dispersed even after centrifugation), and providing a uniform electrostatic repulsion basis for subsequent self-assembly of photonic crystals; The decomposition temperature of KPS / APS (above 70 °C) matches the reaction temperature, ensuring a uniform release of free radicals, avoiding explosive nucleation, improving the synchrony of particle growth, and the particle size deviation is < ±2%. AIBA decomposes to generate isobutyronitrile radicals (R·), which also efficiently initiate polymerization; The half-life of AIBA (about 10 hours at 60 °C, for example) provides a gentler reaction rate, improving the synchrony of particle growth, and the particle size deviation is < ±2%. The water-soluble initiator residues can be removed by centrifugation / dialysis, and the purity of the nanoparticles is > 99%, without yellowing or deterioration of optical properties caused by initiator residues; Suitable for high-precision photonic crystal devices (such as sensors, display materials); While oil-soluble initiators (such as BPO) are easily wrapped inside the particles and difficult to remove. Using KPS / APS / AIBA in the aqueous phase to achieve monodisperse nanoparticles (PDI ≤ 0.1); Enhance colloidal stability and self-assembly performance; Avoid side reactions and ensure the purity and optical properties of the product. Methyl methacrylate (MMA) has a copolymerization modification effect. For example, copolymerize with styrene (such as St-MMA copolymer) to adjust the polarity of the polymer chain and the glass transition temperature (Tg), lower Tg (to 80–90 °C), and enhance the melting bonding ability of the nanoparticles during self-assembly; Introduce an ester group (-COOCH3) to enhance surface wettability and improve the stability of the water-oil interface; When the copolymerization ratio is ≤ 20%, the optical properties of the photonic crystal can be maintained (the refractive index change is < 0.03). α-Methylstyrene (AMS) can achieve polymerization kinetics regulation. The steric effect of the methyl group at the α-position of styrene reduces the polymerization rate, inhibits explosive nucleation, prolongs the nucleation period, makes particle growth more synchronous (particle size deviation ±1%); Reduce side reactions caused by heat accumulation (such as the branching degree < 0.5%); Mix with styrene (the proportion of AMS is ≤ 10%) to avoid excessive inhibition of polymerization.

[0042] In this embodiment, the oil phase in step S100 uses at least one of styrene monomer (St), methacrylic acid (MAA), methyl methacrylate (MMA), α-methylstyrene (AMS) or divinylbenzene (DVB). Styrene monomer (St), as the main monomer of polystyrene (PS), forms a linear polymer chain through free radical polymerization, provides a high refractive index, and enhances the Bragg diffraction intensity of the photonic crystal; forms rigid spherical particles to ensure structural stability; when the monomer purity is >99%, polymerization defects caused by impurities (such as surface roughness <5nm) can be avoided. Divinylbenzene (DVB) has a cross-linking agent function, and the double bond structure participates in polymerization to form a three-dimensional cross-linked network, enhances mechanical strength, and prevents particle deformation during self-assembly; the degree of cross-linking is controllable (DVB accounts for 0.5-2%), and excessive amounts will lead to decreased swelling (solvent absorption rate <5%); the cross-linked structure inhibits the migration of polymer chains and improves the thermal stability of photonic crystals (temperature resistance >150°C). The choice of oil phase directly determines: the monodispersity of nanoparticles (AMS regulates polymerization kinetics); optical properties (St / MMA regulates refractive index); structural stability (DVB cross-linking enhancement). High water-oil ratio (10:1) and high total flow rate (8–15mL / min) generate strong shear forces in the microfluidic channel, cutting the oil phase monomers into uniform droplets (CV<3%); the initiator (such as KPS) in the water phase quickly diffuses to the surface of the oil droplets, initiating interfacial polymerization; generating monodisperse nanoparticles (particle size deviation ±2%), avoiding the multimodal distribution of particle size in traditional emulsion polymerization. High flow rate shortens the fluid residence time (<1 second), inhibits the premature decomposition of initiators (such as APS), and ensures that free radicals are released only at the oil droplet interface. The reactivity of monomers in the oil phase (such as the rapid polymerization of St, or the slow polymerization effect of AMS) and the flow rate synergistically regulate the polymerization kinetics; the polymerization rate is synchronized with the droplet generation rate to avoid fusion or branching caused by the accumulation of unreacted monomers. If the oil phase contains DVB, its double bonds react rapidly in the microfluidic channel at high flow rates to form a surface cross-linked layer, while the core is still a linear polymer (St or MMA). The surface hardness of the particles is improved, while the core swellability is maintained, which is suitable for stimulus-responsive photonic crystals. Styrene (St) works synergistically with high flow rates (12mL / min-15mL / min). St polymerizes rapidly at high flow rates to form solid high-refractive index particles, which are suitable for high-color saturation photonic crystals. MMA and AMS work synergistically with medium flow rates (10mL / min-12mL / min). MMA reduces Tg, AMS delays polymerization, and gradient polymerization is achieved with the flow rate to generate core-shell structure particles (the shell layer is MMA-AMS copolymer). St-DVB works synergistically with low flow rates (8mL / min-10mL / min). The lower flow rate prolongs the cross-linking time, forming a uniform cross-linked network, and improving the solvent resistance of the particles.

[0043] In this embodiment, the microfluidic chip in step S200 is made of glass or PDMS material. When the microfluidic chip is a glass chip, it has excellent chemical inertness, can withstand strong acids, strong bases and organic solvents (such as styrene monomer), ensuring the long-term stability of the reaction system; its surface hydrophilicity helps the uniform flow of the aqueous phase, reduces particle adsorption, and improves the product purity; the high thermal stability of glass makes it suitable for high-temperature polymerization conditions (such as 70–90 °C required by persulfate initiators), and its optical transparency supports real-time monitoring of the reaction process; in addition, the rigid structure of glass can maintain the precise size of the microchannels, avoiding fluctuations in the flow rate. When the microfluidic chip is a PDMS chip, it has flexibility and easy processability, can achieve complex microchannel designs, and can fit tightly with other components, reducing the risk of leakage; the hydrophobic surface of PDMS can be temporarily converted to hydrophilic by plasma treatment to adapt to the water-oil two-phase system, but its performance may be affected by swelling or attenuation of hydrophilicity during long-term use; PDMS has low heat resistance and is prone to deformation at high temperatures, so it is more suitable for mild reaction conditions or rapid prototyping. The choice of the microfluidic chip material affects the chemical compatibility, thermal stability, surface properties and processing accuracy of the microfluidic chip, thereby regulating the efficiency and controllability of the emulsion generation and polymerization processes.

[0044] In this embodiment, the channel width of the microfluidic chip is 50 μm - 200 μm. Narrow channels (50 μm - 100 μm) generate high shear forces and can produce micro-droplets with a particle size of 1 - 10 μm, which are suitable for preparing sub-micron-sized nanoparticles; within the 50 - 100 μm channels, the laminar flow effect is significant, ensuring that the two-phase fluids are mixed without turbulence. Wide channels (150 μm - 200 μm) can form larger droplets of 20 - 50 μm, which are suitable for preparing micron-sized particles; the 200 μm channel can appropriately increase the flow rate (up to 15 mL / min) without destroying the flow stability. The micro-scale channels make the surface tension much greater than the body force, and the droplet generation is dominated by the interfacial tension rather than gravity; the wall effect of the channels is enhanced, which is beneficial to the formation of monodisperse emulsions; the narrow channels with a channel width of 50 μm - 200 μm can significantly increase the specific surface area and accelerate the diffusion of the initiator from the aqueous phase to the oil phase; the polymerization reaction time can be shortened by 30 - 50%; the width of 50 μm - 200 μm is compatible with conventional photolithography / soft lithography processes, ensuring a processing accuracy of ±2 μm; this size range can balance the requirements of flux and precision and avoid the risk of blockage in overly narrow channels. The channel size design can achieve monodisperse droplets (PDI < 0.05), high reaction efficiency (conversion rate > 99%), and a production flux of liters per hour while maintaining a water-oil ratio of 10:1. If the channel is too narrow, < 50 μm, nano-sized particles or undissolved initiators are likely to deposit in the narrow channels (especially < 30 μm), resulting in irreversible blockage and frequent shutdowns for cleaning; maintaining a total flow rate of 8 mL / min - 15 mL / min requires an extremely high driving pressure, and conventional syringe pumps cannot stably control it, leading to flow rate fluctuations (deviation > 10%), which disrupts the 10:1 water-oil ratio; the shear force in ultra-narrow channels is too strong, generating droplets with a particle size < 500 nm, and subsequent polymerization is likely to cause particle agglomeration (PDI > 0.3) due to the excessive specific surface area; the defect rate of photolithography / etching processes increases in channels < 50 μm (such as glass chip fracture, PDMS channel collapse), resulting in increased processing costs. If the channel is too wide, > 200 μm, and even when the wide channel > 300 μm, the medium Reynolds number Re is close to the transition flow region, Re > 10, and vortices appear at the water-oil interface, resulting in droplet polydispersity, CV > 15%; the macroscopic scale effect appears, and gravity / inertial forces interfere with droplet generation, requiring the addition of a high concentration of surfactant, which contaminates the product purity; the specific surface area of the wide channel decreases, the diffusion rate of the initiator decreases, the monomer conversion rate decreases, and the residual monomers require complex post-treatment; the size uniformity of the photonic crystal particles deteriorates (the half-width of the Bragg diffraction peak increases), and the optical performance does not meet the standards. Therefore, strictly controlling the channel width within the range of 50 μm - 200 μm is the key parameter threshold for balancing flux, precision, and stability.

[0045] In this embodiment, the aqueous phase in step S100 uses an aqueous solution of potassium persulfate, and the concentration of potassium persulfate in the aqueous phase is 0.5 g / L - 2.0 g / L. 0.5 g / L is the minimum effective concentration to ensure that there are enough free radicals (SO4- ·) Initiate the reaction; 2.0 g / L is the safety upper limit to avoid explosive initiation leading to local overheating (temperature rise < 5 °C) and maintain the reaction stability; the concentration range is 0.5 g / L - 2.0 g / L, and the number of generated free radicals matches the diffusion rate of the oil-phase monomer (such as styrene), forming particles with a particle size of 200 nm - 500 nm and a PDI < 0.1; the decomposition product K2SO4 of KPS can be removed by dialysis without affecting the optical properties of the product. When the concentration of potassium persulfate in the aqueous phase is lower than 0.5 g / L, it will lead to insufficient free radicals, resulting in polymerization lag, reduced conversion rate, and the need to extend the reaction time; the unreacted monomers accumulate in the microfluidic channel, easily causing blockage; there are too few nucleation sites, with a small amount of large particles coexisting with a large amount of unreacted monomers, resulting in an increase in PDI; in addition, it will lead to deterioration of optical properties, a decrease in the color saturation of the photonic crystal structural color, and an increase in the full width at half maximum of the Bragg diffraction peak. When the concentration of potassium persulfate in the aqueous phase is higher than 2.0 g / L, it will lead to explosive polymerization, and the excessive free radicals will cause the chain reaction to get out of control, resulting in local temperature rise, leading to branching / crosslinking inside the particles; the microfluidic chip (such as a PDMS chip) will deform at high temperature, and the channel width will change; it will lead to the destruction of the particle morphology, multinucleation to form irregular aggregates, and a decrease in the yield after centrifugation; it will cause initiator residue pollution, and the excessive decomposition of KPS produces a high concentration of K + and SO4 2- , and it requires several times the dialysis volume to be cleared, increasing the production cost.

[0046] In this embodiment, the emulsion polymerization reaction time in step S400 is 10 minutes - 60 minutes. Controlling the emulsion polymerization reaction time within the range of 10 - 60 minutes enables rapid initiation and preliminary polymerization, improves the conversion rate, ensures complete conversion of the monomer, and reduces the residue amount; when the emulsion polymerization reaction time is controlled within a short time (10 - 20 minutes), primary particles with a smooth surface are formed; when the emulsion polymerization reaction time is controlled within a long time (30 - 60 minutes), it promotes the densification of the internal structure and increases the density; when the emulsion polymerization reaction time is controlled within 40 - 50 minutes, the molecular weight distribution is the narrowest, avoiding branching caused by over-polymerization. When the emulsion polymerization reaction time < 10 minutes, incomplete polymerization occurs, the conversion rate drops sharply, there are a large number of unreacted monomers, resulting in difficulties in subsequent centrifugation; performance defects occur, the mechanical strength of the particles decreases, and the photonic crystal structural color is unstable; process problems occur, the risk of emulsion stratification at the microfluidic outlet increases, and additional terminator needs to be added, increasing the cost. When the emulsion polymerization reaction time > 60 minutes, over-reaction will occur, leading to an excessive cross-linking degree and the loss of particle swelling properties; it will lead to an increase in energy consumption, and the by-products at high temperature will increase exponentially; the equipment loss increases, the fouling rate of the reaction kettle increases, and the service life of the centrifuge bearing shortens.

[0047] In this embodiment, after step S400, the following step is added: S500. The nanoparticles are constructed into a periodic photonic crystal structure by an evaporation-induced or template-assisted method. In the evaporation-induced method, during the solvent evaporation process, the capillary force drives the self-assembly of the nanoparticles to form a face-centered cubic (FCC) or hexagonal close-packed (HCP) structure. The lattice constant is controllable, and the particle size is controlled within 100 nm - 500 nm, which directly determines the position of the photonic bandgap. The regulation accuracy in the visible light band is ±5 nm. In the evaporation-induced method, the coffee ring effect is reduced by slow drying, so that the grain boundary defect density < 0.1%. The FCC structure induced by evaporation has solvent responsiveness: when exposed to solvents such as acetone, the lattice expands and the structural color redshifts (sensitivity 2 nm / vol%). In the template-assisted method, the assembly is guided by a micron-scale colloidal template or a lithography pattern to achieve a non-close-packed structure, and the adjustable range of the bandgap is extended to the near-infrared. The template-assisted method can pre-design defect sites (such as point defects / line defects) for signal enhancement in photonic crystal sensors. The pore structure prepared by the template-assisted method can be loaded with responsive polymers to achieve temperature / pH-controlled color change, with a short response time and a fast response speed. Step S500 converts the nanoparticles into functionalized photonic crystals through two complementary technologies. Evaporation-induced method can prepare responsive structural color materials at low cost and on a large scale; template-assisted method can customize the complex structures required for optical devices with high precision. The two work together to solve the key conversion problem from laboratory to industrialization, while meeting the optical performance and large-scale requirements.

[0048] The polystyrene colloidal photonic crystal nanoparticles of this embodiment are prepared by using the preparation method of the above-mentioned polystyrene colloidal photonic crystal nanoparticles. The particle size of the polystyrene colloidal photonic crystal nanoparticles is 100 nm - 400 nm, and the PDI is less than or equal to 0.1.

[0049] The application of the polystyrene colloidal photonic crystal nanoparticles of this embodiment is to use the above-mentioned polystyrene colloidal photonic crystal nanoparticles in structural color display devices, biosensor devices, laser feedback devices or flexible electronic devices.

[0050] During implementation, a method for preparing polystyrene colloidal photonic crystal nanoparticles based on a microfluidic system is provided. Styrene monomer is used as the oil phase, and an aqueous solution of potassium persulfate is used as the water phase. By constructing a microfluidic chip with an intersection structure, the water-oil flow rate ratio of 10:1 is injected into the channel, and a stable emulsion system is formed under the condition of a total flow rate of 10 mL / min. Set the waste liquid discharge volume of 0.6 mL to remove the unstable front-end fluid, and set a heating module at the end of the channel to maintain the system temperature at 80 °C to achieve emulsion polymerization reaction. Finally, polystyrene nanoparticles with a particle size between 200 nm and 400 nm, uniform distribution and good monodispersity are prepared. This method has mild reaction conditions, and the product has excellent particle size consistency. It can form a periodically arranged photonic crystal structure through subsequent drying or template-induced self-assembly, and is widely used in the fields of structural color materials, biosensing and optoelectronic devices, etc.

[0051] As an integrated, continuous and parameter-programmable chemical synthesis platform, microfluidic chip technology provides a microscale regulation environment for polymerization reactions, and has advantages such as high interfacial stability, fast mixing efficiency and uniform reaction rate. It is especially suitable for the precise control of droplet size and distribution in emulsion polymerization. However, at present, the related research on using microfluidic technology for styrene-based emulsion polymerization reaction to prepare photonic crystal precursor particles is still in its infancy, lacking a systematic control process and integrated solution. Therefore, the present invention develops a method for synthesizing polystyrene nanoparticles based on a microfluidic reaction system, which is of great significance for promoting the high-quality preparation and industrialization of colloidal photonic crystal materials.

[0052] A method for preparing colloidal photonic crystal nanoparticles based on a microfluidic system includes the following steps: (1) Raw material preparation: The oil phase is pure styrene monomer; the water phase is potassium persulfate (KPS) dissolved in deionized water, with a concentration of 0.5 g / L - 2.0 g / L.

[0053] (2) Microfluidic system setup: Use a Y-shaped or staggered structure microfluidic chip. The main channel injects the oil phase, and the side channel injects the water phase. The width of the chip channel is 50 μm - 200 μm, and the chip material is glass.

[0054] (3) Flow rate control: Inject the water and oil phases into the system at a flow rate ratio of 10:1, and control the total flow rate to 10 mL / min.

[0055] (4) Discharge of front-end waste liquid: Discharge 0.6 mL of mixed waste liquid at the initial stage of the reaction to ensure the stability of the flow field in the main reaction section.

[0056] (5) Reaction heating: Set a constant temperature heating module at the end of the channel, control the temperature at 80 °C, and the reaction time is 10 minutes - 60 minutes.

[0057] (6) Particle collection: The reaction solution was centrifuged after cooling to obtain polystyrene colloidal particles with a particle size in the range of 100–400 nm and a PDI less than or equal to 0.1.

[0058] (7) Photonic crystal construction: The obtained particles can form a periodic arrangement on a solid substrate by evaporation-induced or template-assisted methods to construct a three-dimensional colloidal photonic crystal structure.

[0059] Example 1: (1) Styrene monomer was used as the oil phase, and potassium persulfate solution (1 g / L) was used as the water phase; (2) They were injected into a Y-shaped glass microfluidic chip at 0.91 mL / min (oil phase) and 9.09 mL / min (water phase) respectively to form a stable emulsion; (3) 0.6 mL of the front-stage waste liquid was discharged at the initial stage; (4) The temperature at the end of the channel was set at 80 °C and reacted for 10 minutes; (5) The reaction solution was collected and centrifuged at 8000 rpm for 10 min to obtain milky white colloidal particles; (6) The particle size analysis results showed that the particle distribution was concentrated at 240 ± 15 nm, the PDI was 0.08, and the SEM image showed that the particles were spherical and regular; (7) A laser particle size analyzer and a scanning electron microscope (SEM) were used to analyze its structure, and it was confirmed that it had good monodispersity and particle size consistency.

[0060] (8) A regular photonic crystal structure was formed on the silicon wafer by natural evaporation of the solvent.

[0061] Example 2: (1) The concentration of KPS was increased to 1.5 g / L, and the other conditions were the same as in Example 1; (2) The polymerization time was extended to 20 minutes; (3) The obtained particle size was 180 ± 10 nm, and the PDI decreased to 0.05, with smaller particle size and more concentrated distribution; (4) The self-assembled sample showed an obvious structural color band gap under the UV-Vis reflection spectrum.

[0062] Example 3: 10 ml of styrene monomer (St) was mixed with 75 μl of methacrylic acid (MAA) as the oil phase, and 0.11 g of potassium persulfate was dissolved in 10 ml of ultrapure water as the water phase; the water phase and the oil phase were injected into the microfluidic chip at a water-oil flow rate ratio of 10:1, and the total flow rate was 10 ml / min. The other conditions were the same as in Example 1.

[0063] The obtained particle size was 122.7 ± 17 nm, and the PDI was 0.1.

[0064] Comparative Example 1: The aqueous phase and the oil phase were injected into the microfluidic chip at a water-oil flow rate ratio of 10:1, and the total flow rate was 20 ml / min. Other conditions were the same as those in Example 3.

[0065] The obtained particle size was about 71.4 nm, and the PDI was 1.

[0066] Comparative Example 2: The aqueous phase and the oil phase were injected into the microfluidic chip at a water-oil flow rate ratio of 3:1, and the total flow rate was 20 ml / min. Other conditions were the same as those in Example 3.

[0067] The obtained particle size was about 83.3 nm, and the PDI was 0.877.

[0068] Matters not covered by the present invention are well-known techniques.

[0069] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0070] The above-described embodiments merely represent several implementation manners of the present invention, and the description thereof is relatively specific and detailed. However, it should not be construed as a limitation on the scope of the invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the appended claims.

[0071] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of polystyrene colloidal photonic crystal nanoparticles, characterized in that It includes the following steps: S100. Prepare an aqueous phase and an oil phase; S200. Inject the aqueous phase and the oil phase into a microfluidic chip at a water-oil flow rate ratio of 10:1, and the total flow rate is 8 ml / min - 15 ml / min; S300. Drain the waste liquid in the front section; S400. Conduct an emulsion polymerization reaction under the condition of 70 °C - 90 °C. After the reaction solution is cooled, centrifugation treatment is carried out to obtain polystyrene colloidal photonic crystal nanoparticles.

2. The preparation method of the polystyrene colloidal photonic crystal nanoparticles according to claim 1, characterized in that, The aqueous phase in step S100 uses one of potassium persulfate aqueous solution, ammonium persulfate or azobisisobutyramidine hydrochloride.

3. The preparation method of the polystyrene colloidal photonic crystal nanoparticles according to claim 2, characterized in that, The oil phase in step S100 uses at least one of styrene monomer, methacrylic acid, methyl methacrylate, α-methylstyrene or divinylbenzene.

4. The preparation method of the polystyrene colloidal photonic crystal nanoparticles according to claim 1, characterized in that, The microfluidic chip in step S200 is made of glass or PDMS material.

5. The preparation method of the polystyrene colloidal photonic crystal nanoparticles according to claim 4, wherein, The channel width of the microfluidic chip is 50 μm - 200 μm.

6. The preparation method of the polystyrene colloidal photonic crystal nanoparticles according to any one of claims 2 to 5, characterized in that, The aqueous phase in step S100 uses potassium persulfate aqueous solution, and the concentration of potassium persulfate in the aqueous phase is 0.5 g / L - 2.0 g / L.

7. The preparation method of the polystyrene colloidal photonic crystal nanoparticles according to any one of claims 1 to 5, characterized in that, The emulsion polymerization reaction time in step S400 is 10 minutes - 60 minutes.

8. The preparation method of the polystyrene colloidal photonic crystal nanoparticles according to any one of claims 1 to 5, characterized in that, After step S400, add the step: S500. Construct the nanoparticles into a periodic photonic crystal structure by evaporation-induced or template-assisted means.

9. A polystyrene colloidal photonic crystal nanoparticle, characterized in that, Prepared by the preparation method of the polystyrene colloidal photonic crystal nanoparticles described in any one of claims 1 to 8, the particle size of the polystyrene colloidal photonic crystal nanoparticles is 100 nm - 400 nm, and the PDI is less than or equal to 0.

1.

10. Application of polystyrene colloidal photonic crystal nanoparticles, characterized in that, Use the polystyrene colloidal photonic crystal nanoparticles described in claim 9 for structural color display devices, biosensor devices, laser feedback devices or flexible electronic devices.