Polycarbosiloxane-coated fluorescent material and emulsion method for preparing the same

Abstract

This invention discloses a polycarbosiloxane-coated fluorescent material and its emulsion preparation method, belonging to the field of fluorescent material technology. The preparation method includes: mixing a phosphor (the object to be coated), a polysiloxane precursor containing silane-hydrogen bonds, a vinyl-containing cyclic siloxane, and a catalyst to form a homogeneous oil-phase mixture; dispersing a surfactant in deionized water to form a homogeneous aqueous phase; dropwise adding the oil-phase mixture into the aqueous phase to form an oil-in-water emulsion; and performing a crosslinking polycondensation curing reaction at elevated temperature to form a polycarbosiloxane coating layer on the phosphor surface. This preparation method is simple, mild, and highly versatile. The fluorescent material obtained by this method has a continuous, superhydrophobic SiOC coating layer on its surface, exhibiting excellent stability under high temperature and high temperature and high humidity environments.

Description

Technical Field

[0001] This invention relates to the field of fluorescent materials technology, specifically to a polycarbosiloxane-coated fluorescent material and its emulsion preparation method. Background Technology

[0002] Fluorescent materials, such as carbon nitride, perovskite, silicates, aluminates, fluorides, and various halides, have wide applications in solid-state lighting, flat panel displays, environmental sensing, bioimaging, and radiation detection due to their excellent optical properties. However, these materials generally face severe environmental stability challenges in practical applications. In humid environments, hydrolysis easily occurs, leading to fluorescence quenching; under high-temperature conditions, performance degrades due to thermal decomposition or lattice distortion; and in acidic or alkaline corrosive atmospheres, the surface chemical structure is easily damaged. These stability defects severely limit their application in harsh or high-reliability scenarios such as outdoor, automotive, deep-sea, deep-space, and industrial online monitoring.

[0003] To improve the stability of fluorescent materials, existing technologies mainly employ surface coating or encapsulation strategies. Common methods include sol-gel methods, atomic layer deposition (ALD), chemical vapor deposition (CVD), and organic polymer coating. Sol-gel methods typically require high-temperature post-processing, making them unsuitable for heat-sensitive materials, and the coating layer is prone to cracking. While ALD and CVD can prepare dense and uniform inorganic layers, their processes are complex, equipment is expensive, and they are difficult to scale up for powder materials. Organic polymer coating, although simple in process, suffers from insufficient heat and weather resistance, resulting in limited long-term protective effects. Therefore, existing technologies either have demanding process conditions and high costs, or insufficient protective performance and poor versatility, failing to meet the industrial demand for providing durable and stable protection for various fluorescent materials under mild conditions.

[0004] Polycarbosiloxane (SiOC), as an organic-inorganic hybrid material, combines the flexibility and hydrophobicity of organic materials with the thermal stability and chemical resistance of inorganic materials. Furthermore, it exhibits low dielectric constant and good light transmittance, theoretically making it an ideal protective coating for fluorescent materials. However, achieving uniform, dense, and robust SiOC coating on diverse phosphor surfaces under mild conditions far below the decomposition temperature of fluorescent materials, using a simple, universal, and scalable process, remains a pressing challenge in the current technological field. This invention addresses this technological gap by proposing an innovative emulsion-based preparation strategy. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the first objective of this invention is to provide a simple, mild, and versatile emulsion method for preparing polycarbosiloxane (SiOC) coatings. The second objective of this invention is to provide a polycarbosiloxane (SiOC) coated fluorescent material prepared by this method that exhibits excellent resistance to hydrolysis, high temperatures, and corrosion.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a method for preparing polycarbosiloxane-coated fluorescent materials via an emulsion method, comprising the following steps: Phosphor, polysiloxane precursor containing silane-hydrogen bonds, vinyl-containing cyclic siloxane and catalyst are mixed to form a homogeneous oil phase mixture; The surfactant is dispersed in deionized water to form a homogeneous aqueous phase; The oil phase mixture is added dropwise to the aqueous phase to form an oil-in-water emulsion; The water-in-oil emulsion is heated to cause the components in the oil phase mixture to undergo cross-linking and polycondensation reactions and solidify, forming a polycarbosiloxane coating layer on the surface of the phosphor.

[0007] Furthermore, the phosphor is a fluorescent material to be coated.

[0008] Furthermore, the phosphor is selected from at least one of carbon nitride, perovskite, halide, silicate, aluminate and fluoride.

[0009] Furthermore, the phosphor is carbon nitride or perovskite.

[0010] Furthermore, the polysiloxane precursor containing silane-hydrogen bonds is polymethylhydrosiloxane; the vinyl-containing cyclic siloxane is tetramethyltetravinylcyclotetrasiloxane; and the catalyst is a platinum catalyst.

[0011] Furthermore, the mass ratio of the phosphor to the polysiloxane precursor containing silane-hydrogen bonds and the vinyl-containing cyclic siloxane is (0.001-1):1:1, and the mass ratio of the vinyl-containing cyclic siloxane to the catalyst is 1:(0.0001-0.01).

[0012] Furthermore, the surfactant is Tween 80, and the mass ratio of it to deionized water is (0.001-0.15):1.

[0013] Furthermore, the crosslinking polycondensation reaction and curing temperature is 30-500℃, and the time is 10-120 minutes.

[0014] In this invention, the Si-H bonds in the polysiloxane precursor undergo addition with the vinyl C=C double bonds in the cyclic siloxane to form Si-C bonds, resulting in chemical cross-linking between molecules. This transforms the linear structure into a three-dimensional network structure with Si-O-Si bonds as the main chain, thus exhibiting better temperature and humidity resistance.

[0015] Secondly, the present invention provides a polycarbosiloxane-coated fluorescent material prepared by the above method.

[0016] Furthermore, the material surface has a continuous polycarbosiloxane coating layer, which has superhydrophobic properties.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1. The oil-in-water emulsion method provided by this invention, by mixing the reaction precursor with phosphor in the oil phase and then cross-linking and curing it in a mild aqueous environment, is applicable to phosphors with unstable characteristics such as carbon nitride, perovskite, and halides, which are susceptible to temperature differences, deliquescence, and poor corrosion resistance, thus achieving the universality of the coating technology. The entire process requires no complex equipment, and the reaction temperature can be as low as 30°C, far below the decomposition temperature of most fluorescent materials, avoiding the damage to the structure of the fluorescent material itself caused by high temperatures.

[0018] 2. The polycarbosiloxane coating layer (SiOC coating layer) formed by this invention is dense, uniform, and firmly bonded to the phosphor substrate. It possesses intrinsic superhydrophobicity, effectively blocking the penetration of water vapor, oxygen, and corrosive ions. Experiments show that the morphology of the coated fluorescent material remains unchanged after high-temperature treatment (e.g., 350℃), and its fluorescence performance decays very little under harsh high-temperature and high-humidity environments (e.g., 120℃ hydrothermal), significantly improving the stability of the phosphor in terms of hydrolysis resistance, high-temperature resistance, and chemical corrosion resistance.

[0019] 3. The polycarbosiloxane coating layer (SiOC coating layer) formed by the method of this invention has good light transmittance and low dielectric constant. Furthermore, the coating process is mild and does not significantly damage the luminescent centers of the phosphor, thus well preserving the original luminescent properties of the material. This coating material can be directly used in fields with stringent environmental stability requirements, such as LED packaging, outdoor displays, deep-sea sensing, in vivo imaging, and radiation detection, significantly extending device lifespan and broadening its application scenarios. Attached Figure Description

[0020] Figure 1 Comparison of scanning electron microscope (SEM) images of SiOC-coated graphitic carbon nitride prepared in Example 1 after treatment at room temperature (RT) and high temperature (HT, 350°C).

[0021] Figure 2 , Figure 3 , Figure 4, Figure 5 The image shows the elemental distribution (mapping) of SiOC-coated graphitic carbon nitride prepared in Example 1.

[0022] Figure 6 The fluorescence spectra of SiOC-coated graphitic carbon nitride prepared in Example 1 after treatment at room temperature (RT) and high temperature (HT, 350℃) are compared.

[0023] Figure 7 The graph shows the change in fluorescence intensity retention of SiOC-coated graphitic carbon nitride prepared in Example 1 over time (or before and after treatment) under hydrothermal treatment at 120°C. (Note: The uncoated raw graphitic carbon nitride phosphor underwent complete hydrolysis under the same conditions, making effective fluorescence performance testing and comparison impossible.) Figure 8 The images show a comparison of SEM images of the SiOC-coated CsPbBr3 prepared in Example 2 after treatment at room temperature (RT) and high temperature (HT, 400℃).

[0024] Figure 9 The image shows a comparison of the fluorescence emission spectra of SiOC-coated CsPbBr3 prepared in Example 2 after treatment at room temperature (RT) and high temperature (HT, 400℃).

[0025] Figure 10 The graph shows the change in fluorescence intensity retention of SiOC-coated CsPbBr3 prepared in Example 2 under hydrothermal treatment at 120℃ over time (or before and after treatment). (Note: Uncoated raw CsPbBr3 powder undergoes complete hydrolysis under the same conditions, making effective fluorescence performance testing and comparison impossible.) Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments and accompanying drawings. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0027] In the description of this invention, it should be noted that the numerical ranges of components such as mass ratios in the claims and specification of this invention include the recorded endpoint values ​​and cover reasonable errors or deviations caused by conventional experimental or measurement methods that can be understood by those skilled in the art.

[0028] This invention provides an emulsion method for preparing polycarbosiloxane-coated fluorescent materials. The core of this method lies in utilizing an oil-in-water emulsion system to synthesize and solidify a SiOC protective layer in situ on the surface of the phosphor. The polysiloxane precursor containing silane-hydrogen bonds (such as PHMS) and a vinyl-containing cyclic siloxane (such as D4Vi) undergo cross-linking via hydrosilylation under the action of a platinum catalyst, forming a Si-OC network structure.

[0029] In this invention, the phosphor is not particularly limited and can be any fluorescent material requiring improved environmental stability, especially recommended for materials sensitive to water and heat such as carbon nitride, perovskites (e.g., CsPbBr3), and halides. The preferred temperature for the crosslinking polycondensation reaction and curing is 50-200°C, and the preferred time is 20-60 minutes. These optimized parameters help to obtain a product with uniform coating and optimal performance while ensuring the reaction proceeds fully.

[0030] Example 1, as a preferred embodiment of the present invention, provides a method for preparing polycarbosiloxane-coated fluorescent materials using an emulsion method, comprising the following steps: Weigh 20 mg of graphitic carbon nitride phosphor, 10 g of polymethylhydrosiloxane (PHMS) and 10 g of tetramethyltetravinylcyclotetrasiloxane (D4Vi) solution, mix them evenly, and then add dropwise a solution of isopropanol chloroplatinate with a platinum (Pt) content of 8 mg as a catalyst. The mixture is then sonicated to obtain a homogeneous oil phase. 100 mg of Tween 80 is dispersed in 50 g of deionized water to form a homogeneous aqueous phase. The oil phase is then added dropwise to the aqueous phase, and the mixture is heated to 80 °C for crosslinking and polycondensation to solidify, forming a SiOC coating layer on the surface of the graphitic carbon nitride phosphor material, thus obtaining SiOC-coated graphitic carbon nitride.

[0031] Example 2, as a preferred embodiment of the present invention, provides a method for preparing polycarbosiloxane-coated fluorescent materials using an emulsion method, comprising the following steps: Weigh 15 mg of CsPbBr3 phosphor, 10 g of polymethylhydrosiloxane (PHMS), and 10 g of tetramethyltetravinylcyclotetrasiloxane (D4Vi) solution, mix them thoroughly, and then add a solution of isopropanol chloroplatinate with a platinum (Pt) content of 6 mg as a catalyst. The mixture is then sonicated to obtain a homogeneous oil phase. 150 mg of Tween 80 is dispersed in 80 g of deionized water to form a homogeneous aqueous phase. The oil phase is then added dropwise to the aqueous phase, and the mixture is heated to 120 °C for crosslinking and polycondensation to solidify, forming a SiOC coating layer on the surface of the CsPbBr3 phosphor material, thus obtaining SiOC-coated CsPbBr3.

[0032] The structure, composition and optical properties of the SiOC-coated fluorescent materials obtained in Examples 1 and 2 were characterized.

[0033] Depend on Figure 1 It can be seen that the graphitic carbon nitride fluorescent microspheres coated with SiOC did not undergo morphological changes such as cracking or deformation after high temperature (HT, 350℃) treatment, exhibiting certain high temperature resistance.

[0034] Depend on Figure 2 , Figure 3 , Figure 4 and Figure 5 It can be seen that the coating material is composed of Si, O and C elements, which is consistent with the product of polymethylhydrosiloxane and tetramethyltetravinylcyclotetrasiloxane condensation reaction.

[0035] Depend on Figure 6 It can be seen that the fluorescence performance of graphitic carbon nitride fluorescent microspheres coated with SiOC is enhanced after high-temperature treatment.

[0036] Depend on Figure 7 It can be seen that, after treatment, SiOC-coated graphitic carbon nitride still maintained a high fluorescence intensity (>90%). It is important to note that the uncoated pristine graphitic carbon nitride phosphor rapidly hydrolyzed under the same 120℃ hydrothermal treatment conditions, resulting in complete structural destruction and the inability to detect a valid fluorescence signal. Therefore, it failed to achieve the desired fluorescence intensity. Figure 7 Comparable curves were formed. This result demonstrates that the SiOC coating layer of this invention has excellent water-blocking properties and can effectively protect sensitive fluorescent materials from hydrolytic damage.

[0037] Depend on Figure 8 It can be seen that the SiOC-coated CsPbBr3 fluorescent microspheres did not undergo morphological changes such as cracking or deformation after high temperature (HT) treatment, exhibiting certain high temperature resistance.

[0038] Depend on Figure 9 It can be seen that the fluorescence performance of CsPbBr3 fluorescent microspheres coated with SiOC did not decay after high-temperature treatment, showing good high-temperature resistance.

[0039] Depend on Figure 10 It can be seen that, after treatment, SiOC-coated CsPbBr3 still maintained a high fluorescence intensity (>90%). It is important to note that the uncoated pristine CsPbBr3 phosphor rapidly hydrolyzed under the same 120℃ hydrothermal treatment conditions, resulting in complete structural destruction and the inability to detect a valid fluorescence signal. Similarly, it failed to... Figure 10 A comparable curve is formed in the middle.

[0040] Finally, it should be noted that the above embodiments are merely preferred embodiments of the present invention used to illustrate the technical solutions of the present invention, and are not intended to limit the invention, nor are they intended to limit the patent scope of the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention. That is to say, any changes or refinements made to the main design concept and spirit of the present invention that are not of substantial significance, but whose technical problems are still consistent with the present invention, should be included within the protection scope of the present invention. In addition, the direct or indirect application of the technical solutions of the present invention to other related technical fields are similarly included within the patent protection scope of the present invention.

Claims

1. A method for preparing a polysiloxane-coated fluorescent material emulsion, characterized by, Includes the following steps: Phosphor, polysiloxane precursor containing silane-hydrogen bonds, vinyl-containing cyclic siloxane and catalyst are mixed to form a homogeneous oil phase mixture; The surfactant is dispersed in deionized water to form a homogeneous aqueous phase; The oil phase mixture is added dropwise to the aqueous phase to form an oil-in-water emulsion; The water-in-oil emulsion is heated to cause the components in the oil phase mixture to undergo cross-linking and polycondensation reactions and solidify, forming a polycarbosiloxane coating layer on the surface of the phosphor.

2. The production method according to claim 1, characterized by, The phosphor is a fluorescent material to be coated.

3. The production method according to claim 2, characterized by, The phosphor is selected from at least one of carbon nitride, perovskite, halide, silicate, aluminate and fluoride.

4. The production method according to claim 3, characterized by, The phosphor is carbon nitride or perovskite.

5. The preparation method according to claim 1, characterized in that, The polysiloxane precursor containing silane-hydrogen bonds is polymethylhydrosiloxane; the vinyl-containing cyclic siloxane is tetramethyltetravinylcyclotetrasiloxane; and the catalyst is a platinum catalyst.

6. The method of claim 1, wherein, The mass ratio of the phosphor to the polysiloxane precursor containing silane-hydrogen bonds and the vinyl-containing cyclic siloxane is (0.001-1):1:1, and the mass ratio of the vinyl-containing cyclic siloxane to the catalyst is 1:(0.0001-0.01).

7. The preparation method according to claim 1, characterized in that, The surfactant is Tween 80, and its mass ratio with deionized water is (0.001-0.15):

1.

8. The method of claim 1, wherein, The cross-linking polycondensation reaction and curing are carried out at a temperature of 30-500℃ for 10-120 minutes.

9. A polycarbosilane-coated phosphor, characterized by, Prepared by the method according to any one of claims 1 to 9.

10. The polysiloxane-coated phosphor material of claim 10, wherein The material surface has a continuous polycarbosiloxane coating layer, which has superhydrophobic properties.

Images