Polystyrene colloidal photonic crystal nanoparticles and preparation method and application thereof

Abstract

The present invention relates to the technical field of intersection of nanomaterial synthesis and microfluidic reactor engineering, and discloses a polystyrene colloidal photonic crystal nanoparticle, a preparation method and an application. The preparation method of polystyrene colloidal photonic crystal nanoparticles comprises the following steps: preparing an aqueous phase and an oil phase; 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 8ml / min-15ml / min; discharging the front-end waste liquid; conducting an emulsion polymerization reaction at 70°C-90°C, and cooling and centrifuging the reaction liquid to obtain polystyrene colloidal photonic crystal nanoparticles. While ensuring high monodispersity and precise size control, the structural regularity of the particles is improved, and high-throughput production is achieved 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.

Description

Technical Field

[0001] The present invention relates to the interdisciplinary field of nanomaterial synthesis and microfluidic reactor engineering, and in particular to a method for preparing polystyrene colloidal photonic crystal nanoparticles. Furthermore, the present invention relates to polystyrene colloidal photonic crystal nanoparticles prepared by the aforementioned method and their applications. Background Art

[0002] Colloidal photonic crystals (CPCs) are a class of materials with spatially periodic nanostructures. Their unique photonic band gap properties allow them to manipulate the propagation of light of specific wavelengths, holding significant potential for applications in structural color displays, biosensors, laser resonators, and flexible optoelectronic devices. The performance of these materials is highly dependent on the monodispersity, size controllability, and structural regularity of their constituent nanoparticles. However, conventional preparation methods struggle to simultaneously meet these requirements, limiting the practical applications of CPCs.

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

[0004] Emulsion polymerization involves dispersing styrene monomers with an emulsifier and then performing the polymerization reaction. However, this method suffers from issues such as a wide particle size distribution (PDI > 0.2) and poor batch reproducibility. This is primarily due to the dynamic adsorption of the emulsifier, which results in uneven particle growth rates. Furthermore, small fluctuations in reaction parameters (such as temperature and stirring speed) can significantly affect product consistency. Furthermore, subsequent purification processes (such as centrifugation to remove residual emulsifier) ​​can disrupt the ordered assembly of particles, further degrading material performance.

[0005] The dropwise polymerization method controls particle growth by gradually adding monomers or initiators. Although this method improves the controllability of particle size to a certain extent, the reaction kinetics are difficult to precisely control, and the throughput is extremely low (single batch output is usually <10mL / h), which cannot meet the needs of large-scale production.

[0006] The template-assisted assembly method uses a porous template to force the arrangement of nanoparticles, which can improve structural regularity. However, the template is expensive and difficult to be compatible with flexible substrates, which limits its application in the field of flexible electronics. Summary of the Invention

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

[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-to-oil flow rate ratio of 10:1, with a total flow rate of 8 ml / min-15 ml / min; S300, discharging the front-end waste liquid; S400, conducting an emulsion polymerization reaction at 70°C-90°C, cooling the reaction solution and then centrifuging it to obtain polystyrene colloidal photonic crystal nanoparticles.

[0009] Furthermore, the aqueous phase in step S100 is one of potassium persulfate aqueous solution, ammonium persulfate or azobisisobutylamidine hydrochloride.

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

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

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

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

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

[0015] Furthermore, after step S400 , a step is added: S500 , constructing the nanoparticles into a periodic photonic crystal structure by evaporation induction or template assistance.

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

[0017] According to another aspect of the present invention, an application of polystyrene colloidal photonic crystal nanoparticles is provided, wherein the polystyrene colloidal photonic crystal nanoparticles are used in structural color display devices, biosensor devices, laser feedback devices or flexible electronic devices.

[0018] The present invention has the following beneficial effects:

[0019] The method for preparing polystyrene colloidal photonic crystal nanoparticles of the present invention significantly narrows the particle size distribution (PDI≤0.1) and improves monodispersity through the coordinated control of the water-to-oil flow rate ratio (10:1) and the total flow rate (8ml / min-15ml / min). Compared with traditional emulsion polymerization, which results in uneven particle growth (PDI>0.2) due to dynamic adsorption of emulsifiers, the method for preparing polystyrene colloidal photonic crystal nanoparticles of the present invention ensures a constant monomer diffusion rate by fixing the water-to-oil ratio (10:1) and the total flow rate (8ml / min-15ml / min), thereby avoiding secondary nucleation caused by local concentration fluctuations. The constant monomer diffusion rate ensures synchronous growth of the particles, and precise fluid control eliminates local concentration gradients.

[0020] The preparation method of polystyrene colloidal photonic crystal nanoparticles of the present invention discharges waste liquid and unstable products from the previous stage, thereby ensuring the size uniformity of subsequent particles (deviation <±2%).

[0021] The preparation method of polystyrene colloidal photonic crystal nanoparticles of the present invention controls the high-temperature polymerization temperature at 70°C-90°C. The high temperature accelerates the decomposition of the initiator, shortens the nucleation time, and enables synchronous growth of the particles (the particle size is 100nm-400nm, achieving precise control), while also improving the crystallinity and making the photonic band gap more obvious.

[0022] The preparation method of polystyrene colloidal photonic crystal nanoparticles of the present invention comprises the following steps: performing a high-temperature emulsion polymerization reaction, cooling, and centrifuging to collect particles; cooling to slow down the reaction rate to avoid overpolymerization; and centrifuging to obtain high-purity polystyrene colloidal photonic crystal nanoparticles, thereby further improving monodispersity and stability.

[0023] The present method for preparing polystyrene colloidal photonic crystal nanoparticles achieves improved monodispersity, a particle size index (PDI) of ≤ 0.1, and an adjustable particle size range of 100 nm to 400 nm through precise microfluidic flow rate control, high-temperature polymerization, and post-processing optimization. Centrifugation removes impurities and unreacted monomers to produce high-purity polystyrene colloidal photonic crystal nanoparticles. By precisely controlling the mixing and reaction conditions of the aqueous and oil phases using a microfluidic chip, the method overcomes the problems of poor particle monodispersity, inflexible size control, and insufficient batch stability associated with traditional methods.

[0024] In addition to the above-described objects, features and advantages, the present invention has other objects, features and advantages. The present invention is further described in detail below. DETAILED DESCRIPTION

[0025] The following examples of the present invention are described in detail, but the present invention can be implemented in a variety of different ways as defined and covered below. Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0026] The method for preparing polystyrene colloidal photonic crystal nanoparticles of this embodiment includes 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-to-oil flow rate ratio of 10:1, with a total flow rate of 8 ml / min-15 ml / min; S300, discharging the waste liquid from the front end; S400, conducting an emulsion polymerization reaction at 70°C-90°C, cooling the reaction solution and then centrifuging it to obtain polystyrene colloidal photonic crystal nanoparticles. The present method for preparing polystyrene colloidal photonic crystal nanoparticles significantly narrows the particle size distribution (PDI ≤ 0.1) and improves monodispersity through the coordinated control of the water-to-oil flow rate ratio (10:1) and the total flow rate (8 ml / min-15 ml / min). Compared to traditional emulsion polymerization, which results in uneven particle growth (PDI > 0.2) due to dynamic adsorption of the emulsifier, the present method for preparing polystyrene colloidal photonic crystal nanoparticles ensures a constant monomer diffusion rate by maintaining a fixed water-to-oil ratio (10:1) and a total flow rate (8 ml / min-15 ml / min), thus avoiding secondary nucleation caused by local concentration fluctuations. The constant monomer diffusion rate ensures synchronous particle growth, and precise fluid control eliminates local concentration gradients. The present method for preparing polystyrene colloidal photonic crystal nanoparticles also discharges waste liquid and unstable products from the previous stage, ensuring the size uniformity of subsequent particles (deviation < ±2%). The present invention's method for preparing polystyrene colloidal photonic crystal nanoparticles utilizes a high-temperature polymerization temperature controlled between 70°C and 90°C. High temperature accelerates initiator decomposition, shortens nucleation time, and enables synchronous particle growth (particle size ranges from 100nm to 400nm, enabling precise control). This method also enhances crystallinity and a more pronounced photonic band gap. Following high-temperature emulsion polymerization, the particles are cooled and then centrifuged to collect. Cooling slows the reaction rate to prevent overpolymerization, and centrifugation is performed to obtain high-purity polystyrene colloidal photonic crystal nanoparticles, further enhancing monodispersity and stability. The present method achieves improved monodispersity, with a PDI of ≤0.1, and an adjustable particle size range of 100nm to 400nm, through precise microfluidic flow rate control, high-temperature polymerization process, and post-processing optimization. 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 and oil phases through microfluidic chips, problems such as poor particle monodispersity, inflexible size control, and insufficient batch stability in traditional methods are solved.

[0027] In this example, to achieve a water-to-oil flow rate ratio of 10:1 for the aqueous phase and the oil phase to be injected into the microfluidic chip, and to control the total flow rate at 8-15 mL / min, the design of the microfluidic chip should focus on the following:

[0028] 1. Channel configuration selection of microfluidic chip structure:

[0029] Flow-focusing or T-type / Y-type microchannel structures are used to ensure that the water phase (continuous phase) symmetrically wraps the oil phase (dispersed phase) from both sides or all around, achieving precise 10:1 flow rate ratio control.

[0030] Flow focusing type: high shear force is generated by the contraction section, which is more suitable for the generation of monodisperse droplets at high total flow rates (15mL / min).

[0031] T / Y type: simple structure, suitable for initial optimization of low total flow rate (8-10mL / min).

[0032] Channel size optimization:

[0033] Main channel width: The recommended width of the water phase channel is 200-500μm, and the oil phase channel width is 50-100μm, matching a flow ratio of 10:1.

[0034] Contraction section design: If a flow focusing structure is used, the width of the contraction section should be 50-100 μm to enhance the shear force and stabilize droplet generation.

[0035] 2. Material selection for microfluidic chips:

[0036] Microfluidic chips can be glass chips or PDMS chips.

[0037] Glass chips: preferably used in high temperature (>70°C) or highly chemically corrosive systems (such as aqueous phases containing persulfate) to ensure long-term stability.

[0038] PDMS chips: Suitable for room temperature or rapid prototyping, but require plasma treatment to render the surface hydrophilic to prevent oil adhesion and channel clogging. Surface modification of the PDMS chip involves hydrophilizing the chip (e.g., oxygen plasma treatment or PEG coating) to reduce water flow resistance and maintain a stable 10:1 flow ratio.

[0039] 3. Fluid control parameters:

[0040] Flow rate matching: The aqueous phase flow rate was set at 7.27-13.64 mL / min, and the oil phase flow rate was set at 0.73-1.36 mL / min (a 10:1 ratio for a total flow rate of 8 mL / min-15 mL / min). A high-precision syringe pump (error <1%) or pneumatic drive system was used to ensure a constant flow rate ratio.

[0041] Pressure balance: By adjusting the outlet back pressure or channel resistance (such as adding a micropillar array), the two-phase pressure is balanced to avoid flow rate ratio drift or droplet fusion.

[0042] 4. Droplet generation and stability control:

[0043] Capillary number (Ca) control: Keep the water phase capillary number (Ca = μv / γ, μ is viscosity, v is flow rate, γ is interfacial tension) at 10 - ²-10 - ¹ range to ensure droplet monodispersity (CV < 5%). The interfacial tension γ can be reduced by adding a surfactant (such as SDS) to adapt to high flow rate conditions.

[0044] Temperature control: If the reaction requires high temperature (such as KPS initiation), an integrated chip heating module (such as a glass chip embedded with a heating wire) can be used to prevent PDMS from deforming due to high temperature.

[0045] 5. Verification and optimization methods:

[0046] Real-time monitoring: Integrate an optical microscope or high-speed camera at the chip outlet to observe the droplet size and generation frequency, and dynamically adjust the flow rate ratio.

[0047] Post-processing analysis: After collecting the droplets, the particle size distribution is measured using a laser particle size analyzer (target CV < 3%) to infer the rationality of the chip design.

[0048] Key design elements of the microfluidic chip include: structure, flow focusing or T / Y-shaped channels, with the main channel width scaled at a 10:1 ratio; material selection, glass or PDMS depending on temperature and chemical requirements, with surface modification if necessary; control, a high-precision pump with pressure balancing to maintain a strict 10:1 flow rate ratio; validation and optimization, stable droplet generation through capillary number and real-time monitoring. The microfluidic chip design ensures efficient generation of monodisperse emulsions at a total flow rate of 8mL / min-15mL / min, providing ideal precursors for subsequent polymerization steps.

[0049] In this embodiment, the aqueous phase in step S100 is one of potassium persulfate aqueous solution (KPS), ammonium persulfate (APS), and azobisisobutylamidine hydrochloride (AIBA). KPS / APS decomposes at a high temperature of 70–90°C to produce sulfate radicals (SO4 - ·), initiating polymerization of styrene monomer; sulfate ions (SO4 2- ) or the hydrochloride residue of AIBA (Cl -) adsorbs onto the particle surface, forming a negatively charged layer that enhances colloidal stability and prevents particle aggregation (remaining stably dispersed even after centrifugation), providing a uniform electrostatic repulsion foundation for subsequent photonic crystal self-assembly. The decomposition temperature of KPS / APS (above 70°C) matches the reaction temperature, ensuring uniform free radical release and avoiding explosive nucleation. This improves particle growth synchrony and results in a particle size deviation of <±2%. AIBA decomposes to form isobutyronitrile radicals (R·), which also efficiently initiate polymerization. The short half-life of AIBA (e.g., approximately 10 hours at 60°C) provides a more gradual reaction rate, improving particle growth synchrony and resulting in a particle size deviation of <±2%. Water-soluble initiator residues can be removed by centrifugation / dialysis, resulting in nanoparticles with a purity >99% and no yellowing or optical degradation caused by initiator residues. These nanoparticles are suitable for high-precision photonic crystal devices (such as sensors and display materials). Oil-soluble initiators (such as BPO) tend to become encapsulated within the particles and are difficult to remove. The aqueous phase uses KPS / APS / AIBA to achieve monodisperse nanoparticles (PDI ≤ 0.1), enhance colloidal stability and self-assembly performance, and avoid side reactions, ensuring product purity and optical properties. Methyl methacrylate (MMA) has copolymerization modification properties. For example, copolymerization with styrene (e.g., St-MMA copolymer) modulates the polarity and glass transition temperature (Tg) of the polymer chain, lowering the Tg to 80–90°C and improving the melt bonding ability of the nanoparticles during self-assembly. The introduction of ester groups (-COOCH3) enhances surface wettability and improves water-oil interfacial stability. When the copolymerization ratio is ≤20%, the optical properties of the photonic crystal (refractive index change <0.03) can be maintained. α-Methylstyrene (AMS) can achieve polymerization kinetics regulation. The steric effect of the α-methyl group in styrene reduces the polymerization rate, inhibits explosive nucleation, prolongs the nucleation period, and makes particle growth more synchronous (particle size deviation ±1%); it also reduces side reactions caused by heat accumulation (such as branching degree <0.5%); and it can be mixed with styrene (AMS proportion ≤10%) to avoid excessive inhibition of polymerization.

[0050] In this embodiment, the oil phase in step S100 utilizes at least one of styrene monomer (St), methacrylic acid (MAA), methyl methacrylate (MMA), α-methylstyrene (AMS), or divinylbenzene (DVB). Styrene monomer (St), as the primary monomer of polystyrene (PS), forms linear polymer chains through free radical polymerization, providing a high refractive index and enhancing the Bragg diffraction intensity of the photonic crystal. Rigid spherical particles are formed, ensuring structural stability. A monomer purity of >99% can avoid polymerization defects caused by impurities (e.g., surface roughness <5nm). Divinylbenzene (DVB) acts as a crosslinker, with its double bonds participating in polymerization to form a three-dimensional crosslinked network, enhancing mechanical strength and preventing particle deformation during self-assembly. The degree of crosslinking is controllable (DVB content 0.5–2%); excessive amounts can result in decreased swelling properties (solvent absorption <5%). The crosslinked structure inhibits polymer chain migration, improving the thermal stability of the photonic crystal (temperature resistance >150°C). The choice of oil phase directly determines: nanoparticle monodispersity (AMS modulates polymerization kinetics); optical properties (St / MMA modulates refractive index); and structural stability (DVB cross-linking enhances). A high water-to-oil ratio (10:1) and high total flow rate (8–15 mL / min) generate strong shear forces within the microfluidic channel, fragmenting the oil-phase monomers into uniform droplets (CV <3%). Initiators (such as KPS) in the aqueous phase rapidly diffuse to the oil droplet surface, initiating interfacial polymerization and producing monodisperse nanoparticles (size deviation ±2%), avoiding the multimodal size distribution observed in traditional emulsion polymerization. High flow rates shorten fluid residence time (<1 second), inhibiting premature decomposition of initiators (such as APS), ensuring 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 retarded polymerization of AMS) synergistically controls polymerization kinetics, synchronizing the polymerization rate with the droplet generation rate to avoid fusion or branching caused by accumulation of unreacted monomers. If the oil phase contains DVB, its double bonds react rapidly within the microfluidic channel at high flow rates, forming a surface crosslinked layer. The core remains a linear polymer (St or MMA), increasing the particle surface hardness while maintaining the core's swellability, making it suitable for stimuli-responsive photonic crystals. Styrene (St) synergizes with high flow rates (12-15 mL / min), allowing St to rapidly polymerize at high flow rates, forming solid, high-refractive-index particles suitable for high-color saturation photonic crystals. MMA and AMS synergize with moderate flow rates (10-12 mL / min), with MMA lowering the Tg and AMS delaying polymerization. Adjusting the flow rate allows for gradient polymerization, resulting in core-shell particles (with an MMA-AMS copolymer shell). St-DVB synergizes with low flow rates (8-10 mL / min), prolonging the crosslinking time and forming a uniform crosslinked network, improving the particles' solvent resistance.

[0051] In this embodiment, the microfluidic chip in step S200 is made of glass or PDMS. Glass microfluidic chips offer excellent chemical inertness and are resistant to strong acids, strong bases, and organic solvents (such as styrene monomer), ensuring long-term stability of the reaction system. Its hydrophilic surface facilitates uniform flow of the aqueous phase, reduces particle adsorption, and improves product purity. Glass's high thermal stability makes it suitable for high-temperature polymerization conditions (such as the 70–90°C required for persulfate initiators), and its optical transparency supports real-time monitoring of the reaction process. Furthermore, the rigid structure of glass maintains precise microchannel dimensions and avoids flow rate fluctuations. PDMS microfluidic chips offer flexibility and ease of processing, enabling complex microchannel designs and close integration with other components, reducing the risk of leakage. PDMS's hydrophobic surface can be temporarily rendered hydrophilic through plasma treatment, making it suitable for water-oil two-phase systems. However, long-term use may affect performance due to swelling or loss of hydrophilicity. PDMS has low temperature resistance and is prone to deformation at high temperatures, making it more suitable for mild reaction conditions or rapid prototyping. The choice of microfluidic chip materials will affect the chemical compatibility, thermal stability, surface properties and processing accuracy of the microfluidic chip, thereby regulating the efficiency and controllability of the emulsion formation and polymerization process.

[0052] In this embodiment, the channel width of the microfluidic chip ranges from 50μm to 200μm. Narrow channels (50μm-100μm) generate high shear forces, generating tiny droplets with a diameter of 1-10μm, suitable for preparing submicron nanoparticles. Within channels with a diameter of 50-100μm, the laminar flow effect is significant, ensuring turbulent mixing of the two-phase fluids. Wide channels (150μm-200μm) can form larger droplets of 20-50μm, suitable for preparing micron-sized particles. A 200μm channel can modestly increase flow rate (up to 15mL / min) without compromising flow stability. Microscale channels enable surface tension to far outweigh bulk forces, resulting in droplet formation dominated by interfacial tension rather than gravity. Enhanced channel wall effects facilitate the formation of monodisperse emulsions. Narrow channels with widths ranging from 50μm to 200μm significantly increase the specific surface area, accelerating the diffusion of initiators from the aqueous phase to the oil phase and shortening polymerization times by 30-50%. The 50μm-200μm width is compatible with conventional photolithography / soft lithography processes, ensuring a machining accuracy of ±2μm. This size range balances throughput and precision requirements, avoiding the risk of clogging in overly narrow channels. The channel size design achieves monodisperse droplets (PDI <0.05), high reaction efficiency (conversion >99%), and increased hourly production throughput while maintaining a 10:1 water-to-oil ratio. The channel is too narrow, <50μm, and nano-scale particles or undissolved initiators are easily deposited in the narrow channel (especially <30μm), leading to irreversible blockage and frequent shutdown for cleaning; maintaining a total flow rate of 8mL / min–15mL / min requires extremely high driving pressure, which conventional syringe pumps cannot stably control, causing flow rate fluctuations (deviation >10%) and destroying the 10:1 water-oil ratio; the shear force in the ultra-narrow channel is too strong, and the droplet size generated is <500nm. Subsequent polymerization is prone to cause particle agglomeration due to the large specific surface area (PDI>0.3); the defect rate of the photolithography / etching process in channels <50μm increases (such as glass chip breakage and PDMS channel collapse), resulting in increased processing costs. When the channel is too wide (>200 μm, or even >300 μm), the intermediate Reynolds number (Re) approaches the transitional flow region, with Re >10. Eddies appear at the water-oil interface, leading to droplet polydispersity and a CV >15%. Macroscale effects become apparent, with gravity and inertial forces interfering with droplet formation, requiring the addition of high-concentration surfactants and contaminating product purity. Wide channels reduce specific surface area, slowing initiator diffusion and monomer conversion, requiring complex post-processing of residual monomers. Furthermore, the size uniformity of the photonic crystal particles deteriorates (increasing the half-width of the Bragg diffraction peak), resulting in substandard optical performance. Therefore, strictly controlling the channel width within the 50–200 μm range is a critical parameter threshold for balancing throughput, precision, and stability.

[0053] In this embodiment, the aqueous phase in step S100 is a potassium persulfate aqueous solution, and the concentration of potassium persulfate in the aqueous phase is 0.5g / L-2.0g / L. 0.5g / L is the minimum effective concentration to ensure that there are sufficient free radicals (SO4- ) to initiate the reaction; 2.0 g / L is a safe upper limit to avoid explosive initiation and local overheating (temperature rise <5°C) and maintain reaction stability; within the concentration range of 0.5 g / L-2.0 g / L, the number of free radicals generated matches the diffusion rate of oil-phase monomers (such as styrene), forming particles with a diameter of 200 nm-500 nm and a PDI <0.1; the KPS decomposition product, K2SO4, can be removed by dialysis without affecting the product's optical properties. When the potassium persulfate concentration in the aqueous phase is lower than 0.5 g / L, insufficient free radicals will result, leading to delayed polymerization, reduced conversion, and the need for extended reaction times; unreacted monomers will accumulate in the microfluidic channel, easily causing clogging; too few nucleation sites will result in the coexistence of a small number of large particles with a large amount of unreacted monomers, resulting in an increased PDI; and this can also lead to degraded optical properties, decreased color saturation of the photonic crystal structure, and an increase in the half-width of the Bragg diffraction peak. When the concentration of potassium persulfate in the aqueous phase is higher than 2.0 g / L, explosive polymerization will occur, and excessive free radicals will trigger a runaway chain reaction, resulting in local temperature rise, leading to internal branching / cross-linking of particles; microfluidic chips (such as PDMS chips) will deform at high temperatures, and the channel width will change; it will lead to the destruction of particle morphology, multi-nuclear nucleation to form irregular agglomerates, and the yield will decrease after centrifugation; it will cause initiator residual contamination, and excessive KPS will decompose to produce high concentrations of K + and SO4 2- , requiring double the dialysis volume to remove, increasing production costs.

[0054] In this embodiment, the emulsion polymerization reaction time in step S400 is 10 minutes to 60 minutes. Controlling the emulsion polymerization reaction time within the range of 10-60 minutes allows for rapid initiation and preliminary polymerization, improves conversion, ensures complete monomer conversion, and reduces residual amounts. When the emulsion polymerization reaction time is controlled to a short time (10-20 minutes), primary particles with smooth surfaces are formed. When the emulsion polymerization reaction time is controlled to a long time (30-60 minutes), internal structure densification is promoted, resulting in increased density. When the emulsion polymerization reaction time is controlled to 40-50 minutes, the molecular weight distribution is narrowest, avoiding branching caused by excessive polymerization. When the emulsion polymerization reaction time is less than 10 minutes, incomplete polymerization occurs, the conversion rate plummets, and a large amount of unreacted monomers makes subsequent centrifugation difficult. Performance defects occur, the mechanical strength of the particles decreases, and the photonic crystal structural color becomes unstable. Process problems arise, the risk of emulsion stratification at the microfluidic outlet increases, and additional terminators need to be added, increasing costs. When the emulsion polymerization reaction time is greater than 60 minutes, an overreaction will occur, resulting in excessive crosslinking and loss of particle swelling. This will increase energy consumption and the exponential increase in side reaction products at high temperatures. Equipment losses will increase, the scaling rate of the reactor will increase, and the life of the centrifuge bearings will be shortened.

[0055] In this embodiment, step S500 is added after step S400 to construct the nanoparticles into a periodic photonic crystal structure through evaporation-induced or template-assisted methods. In the evaporation-induced method, capillary forces drive the nanoparticles to self-assemble during solvent evaporation, forming a face-centered cubic (FCC) or hexagonal close-packed (HCP) structure. The lattice constant is controllable, and the particle size is controlled within 100nm–500nm, directly determining the photonic band gap position, with a controllable accuracy of ±5nm in the visible light band. During evaporation-induced evaporation, slow drying is used to reduce the coffee ring effect, keeping the grain boundary defect density below 0.1%. The evaporation-induced FCC structure is solvent-responsive: when exposed to solvents such as acetone, the lattice expands, causing the structural color to redshift (sensitivity 2nm / vol%). Template-assisted methods utilize micron-scale colloidal templates or photolithographic patterns to guide assembly, achieving non-close-packed structures and extending the bandgap tunability range into the near-infrared. Template-assisted methods can pre-design defect sites (such as point and line defects) for signal enhancement in photonic crystal sensors. Template-assisted pore structures can be loaded with responsive polymers, achieving temperature- and pH-controlled color changes with short and rapid response times. Step S500 transforms nanoparticles into functionalized photonic crystals using two complementary techniques. Evaporation-induced methods enable low-cost, large-scale fabrication of responsive structural color materials, while template-assisted methods enable high-precision customization of complex structures required for optical devices. These two approaches synergistically address the critical transition from laboratory to industrial scale, while simultaneously meeting the demands for both optical performance and scalability.

[0056] The polystyrene colloidal photonic crystal nanoparticles of this embodiment are prepared by the above-mentioned preparation method of 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.

[0057] The polystyrene colloidal photonic crystal nanoparticles of this embodiment are used in structural color display devices, biosensor devices, laser feedback devices or flexible electronic devices.

[0058] During implementation, a method for preparing polystyrene colloidal photonic crystal nanoparticles based on a microfluidic system is provided, using styrene monomer as the oil phase and potassium persulfate aqueous solution as the water phase. By constructing a microfluidic chip with an intersection structure, a water-oil flow rate ratio of 10:1 is injected into the channel to form a stable emulsion system at a total flow rate of 10 mL / min. A waste liquid discharge volume of 0.6 mL is set to remove unstable front-end fluid, and a heating module is set at the end of the channel to maintain the system temperature at 80°C to achieve emulsion polymerization. Finally, polystyrene nanoparticles with a particle size between 200 nm and 400 nm, uniform distribution, and good monodispersity are prepared. The reaction conditions of this method are mild, 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, biosensors, and optoelectronic devices.

[0059] As an integrated, continuous, and parameter-programmable chemical synthesis platform, microfluidic chip technology provides a microscale control environment for polymerization reactions, with advantages such as high interface stability, fast mixing efficiency, and uniform reaction rate. It is particularly suitable for precise control of droplet size and distribution in emulsion polymerization. However, the current research on the use of microfluidic technology for styrene emulsion polymerization to prepare photonic crystal precursor particles is still in its infancy and lacks systematic control processes and integrated solutions. 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.

[0060] The method for preparing colloidal photonic crystal nanoparticles based on a microfluidic system comprises the following steps:

[0061] (1) Raw material configuration: The oil phase is pure styrene monomer; the aqueous phase is potassium persulfate (KPS) dissolved in deionized water with a concentration of 0.5 g / L–2.0 g / L.

[0062] (2) Construction of microfluidic system: A Y-shaped or staggered structure microfluidic chip is used, the main channel is injected with oil phase, and the side channel is injected with water phase. The chip channel width is 50μm–200μm, and the chip material is glass.

[0063] (3) Flow rate control: The water-oil phase was injected into the system at a flow rate ratio of 10:1, and the total flow rate was controlled at 10 mL / min.

[0064] (4) Discharge of waste liquid from the front section: 0.6 mL of mixed waste liquid is discharged at the initial stage of the reaction to ensure the stability of the flow field in the main reaction section.

[0065] (5) Reaction heating: A constant temperature heating module is set at the end of the channel, the temperature is controlled at 80 °C, and the reaction time is 10 minutes to 60 minutes.

[0066] (6) Particle collection: The reaction solution is cooled and then centrifuged 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.

[0067] (7) Photonic crystal construction: The obtained particles can be arranged periodically on a solid substrate through evaporation induction or template assistance to construct a three-dimensional colloidal photonic crystal structure.

[0068] Example 1:

[0069] (1) Styrene monomer was used as the oil phase and potassium persulfate solution (1 g / L) was used as the aqueous phase;

[0070] (2) The oil phase and the water phase were injected into the Y-shaped glass microfluidic chip at a flow rate of 0.91 mL / min and 9.09 mL / min, respectively, to form a stable emulsion.

[0071] (3) At the initial stage, 0.6 mL of front-end waste liquid is discharged;

[0072] (4) The temperature at the end of the channel was set to 80°C and the reaction was continued for 10 minutes;

[0073] (5) The reaction solution was collected and centrifuged at 8000 rpm for 10 min to obtain milky white colloidal particles;

[0074] (6) Particle size analysis results show that the particle distribution is concentrated at 240 ± 15 nm, the PDI is 0.08, and the SEM image shows that the particles are spherical and regular;

[0075] (7) Its structure was analyzed using a laser particle size analyzer and scanning electron microscope (SEM), confirming that it has good monodispersity and particle size consistency.

[0076] (8) Regular photonic crystal structures are formed on silicon wafers by natural evaporation of solvents.

[0077] Example 2:

[0078] (1) Increase the KPS concentration to 1.5 g / L, and the other conditions are the same as in Example 1;

[0079] (2) The polymerization time is extended to 20 minutes;

[0080] (3) The particle size of the obtained particles is 180±10nm, the PDI is reduced to 0.05, the particle size is smaller and the distribution is more concentrated;

[0081] (4) The self-assembled sample shows an obvious structural color band gap under UV-Vis reflectance spectrum.

[0082] Example 3:

[0083] A mixture of 10 ml of styrene monomer (St) and 75 μl of methacrylic acid (MAA) was used as the oil phase, and 0.11 g of potassium persulfate was dissolved in 10 ml of ultrapure water as the aqueous phase. The aqueous and oil phases were injected into the microfluidic chip at a water-to-oil flow rate ratio of 10:1, with a total flow rate of 10 ml / min. All other conditions were the same as in Example 1.

[0084] The obtained particle size was 122.7±17 nm and the PDI was 0.1.

[0085] Comparative Example 1:

[0086] The water phase and the oil phase were injected into the microfluidic chip at a water-to-oil flow rate ratio of 10:1, with a total flow rate of 20 ml / min. The remaining conditions were the same as those in Example 3.

[0087] The obtained particles have a particle size of about 71.4 nm and a PDI of 1.

[0088] Comparative Example 2:

[0089] The water phase and the oil phase were injected into the microfluidic chip at a water-to-oil flow rate ratio of 3:1, with a total flow rate of 20 ml / min. The remaining conditions were the same as those in Example 3.

[0090] The obtained particle size is about 83.3 nm and the PDI is 0.877.

[0091] Matters not covered by the present invention are known technologies.

[0092] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, 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, they should be considered to be within the scope of this specification.

[0093] The above-described embodiments merely illustrate several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that a person skilled in the art would be able to make numerous modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

[0094] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing polystyrene colloidal photonic crystal nanoparticles, characterized in that: The following steps are involved: S100, preparing water phase and oil phase; The aqueous phase in step S100 uses a potassium persulfate aqueous solution, and the concentration of potassium persulfate in the aqueous phase is 0.5 g / L-2.0 g / L; S200, the water phase and the oil phase were injected into the microfluidic chip at a water-to-oil flow rate ratio of 10:1, with a total flow rate of 8 ml / min-15 ml / min; The channel width of the microfluidic chip is 50μm-200μm; S300, discharge the waste liquid from the front section; S400, performing emulsion polymerization at 70° C.-90° C., cooling the reaction solution and then centrifuging it to obtain polystyrene colloidal photonic crystal nanoparticles.

2. The method for preparing polystyrene colloidal photonic crystal nanoparticles according to claim 1, characterized in that: The oil phase in step S100 uses at least one of styrene monomer, methacrylic acid, methyl methacrylate, α-methylstyrene or divinylbenzene.

3. The method for preparing 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.

4. The method for preparing polystyrene colloidal photonic crystal nanoparticles according to any one of claims 1 to 3, characterized in that: The emulsion polymerization reaction time in step S400 is 10 minutes to 60 minutes.

5. The method for preparing polystyrene colloidal photonic crystal nanoparticles according to any one of claims 1 to 3, characterized in that: Add the following steps after step S400: S500, constructing the nanoparticles into a periodic photonic crystal structure through evaporation induction or template assistance.

6. A polystyrene colloidal photonic crystal nanoparticle, characterized in that: The polystyrene colloidal photonic crystal nanoparticles are prepared by the preparation method of any one of claims 1 to 5, wherein the particle size of the polystyrene colloidal photonic crystal nanoparticles is 100nm-400nm, and the PDI is less than or equal to 0.

1.

7. An application of polystyrene colloidal photonic crystal nanoparticles, characterized in that: The polystyrene colloidal photonic crystal nanoparticles according to claim 6 are used for structural color display devices, preparation of biosensor devices, laser feedback devices or flexible electronic devices.