Method for preparing up-conversion fluorescent microcapsule with assistance of octadecyl phosphate modified nanoparticles

Abstract

The invention relates to a method for preparing up-conversion fluorescent microcapsules with assistance of octadecyl phosphate modified nanoparticles, and belongs to the technical field of self-healing microcapsules. The preparation method comprises the following steps: mixing and emulsifying a core material solution and a capsule wall material solution to form an o / w emulsion, and then carrying out polyurea formaldehyde capsule wall polymerization reaction on the o / w emulsion to obtain the microcapsule, wherein the core material solution is prepared from near-infrared excited rare earth up-conversion nanoparticles and linseed oil; the capsule wall material solution is prepared from polyurea formaldehyde and nano particles modified by octadecyl phosphate. According to the nano-particles modified by the octadecyl phosphate, the hydrophobicity of the nano-particles can be improved, the hydrophobicity of the nano-particles is improved, and the encapsulation efficiency of the UCNPs in the microcapsule core material is improved.

Description

Technical Field

[0001] The invention relates to the technical field of self-healing microcapsules, and in particular to a method for preparing up-conversion fluorescent microcapsules with the assistance of octadecyl phosphate modified nanoparticles. Background Art

[0002] Microcapsule self-healing protective material is a kind of intelligent bionic material. By simulating the healing mechanism of biological damage, it can accurately repair cracks and warn responses, extend the service life of the coating and reduce maintenance costs. At present, microcapsule technology has been widely used and tested in various fields, such as electronic engineering, medical bioengineering, civil engineering, etc. Microcapsule technology has received widespread attention due to its huge commercial and scientific research value. In 2001, Sottos first proposed the synthesis of self-healing epoxy resin, prepared polyurea formaldehyde microcapsules containing dicyclopentadiene (DCPD) by in-situ polymerization, and dispersed these microcapsules in epoxy resin together with Grubbs catalyst. When cracks occur in the coating, the microcapsules release DCPD to react with the catalyst, cross-link and cure, and thus repair the cracks. Tang prepared double-layer microcapsules containing AIEgens by a two-step method of interfacial polymerization and in-situ polymerization, in which AIEgens were dissolved in hexamethylene diisocyanate (HDI) as the core material, and the capsule wall was composed of polyurea or polyurea formaldehyde. After embedding microcapsules containing HDI into epoxy resin coating, when the coating is damaged, HDI reacts with water to polymerize and repair, while AIEgen can show the healing of scratches with high contrast due to fluorescence emission. This method is feasible in different polymer matrices by using two commercial AIEgens.

[0003] From the initial coating using metal catalysts and microcapsules loaded with healing agents (catalytic system) to the coating using single-component healing agent microcapsules (non-catalytic system), although the expensive and toxic metal catalysts have been abandoned, most studies still use single-component healing agents, such as isocyanates, epoxy resins, and tung oil, which still cause certain pollution to the environment. In addition, in recent years, most common fluorescent dyes in microcapsules are AIEgens, but the synthesis process of AIEgens is complicated, and due to the irregular solid-state molecular motion, its fluorescence emission effect is not ideal and its fatigue resistance is poor. AIEgens usually require ultraviolet light excitation, which may cause background color interference and may affect the stability of some ultraviolet light-cured healing agents. Finally, the durability of fluorescence is very important. In practical applications, the maintenance of the coating may take some time, so long-term visualization is necessary, and the stability of the visualization materials currently used is lacking. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a microcapsule loaded with octadecyl phosphate to modify the surface of nanoparticles and a preparation method thereof.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] In a first aspect, the present invention provides a method for preparing upconversion fluorescent microcapsules with the assistance of nanoparticles modified with n-octadecyl phosphate, comprising the following steps: mixing and emulsifying a core material solution and a capsule wall material solution to form an o / w emulsion, and then subjecting the o / w emulsion to a polyurea formaldehyde capsule wall polymerization reaction to obtain microcapsules; wherein the core material solution comprises near-infrared excited rare earth upconversion nanoparticles and linseed oil; and the capsule wall material solution comprises polyurea formaldehyde and nanoparticles modified with n-octadecyl phosphate.

[0007] The present invention provides a method for preparing upconversion fluorescent microcapsules assisted by nanoparticles modified with n-octadecyl phosphate, which effectively solves the defect that when near-infrared excited rare earth upconversion nanoparticles (UCNPs) are used as fluorescent substances, they will form a Pickering emulsion effect at the oil-water interface during the process of in-situ polymerization to form capsule walls, thereby causing UCNPs to aggregate in the capsule shell and significantly reducing the effective ingredients encapsulated in the core material. The present invention improves the hydrophobicity of hydrophilic nanoparticles by modifying the nanoparticles with n-octadecyl phosphate, promotes their adsorption at the oil-water interface, and improves the encapsulation rate of UCNPs in the core material in the microcapsule shell.

[0008] As a preferred embodiment of the first aspect, the near-infrared excited rare earth upconversion nanoparticles have a core-inner shell-outer shell structure; wherein the core layer is NaYF 4 The inner shell is NaYbF doped with rare earth ions. 4 :2% Er; the outer shell is NaYF 4 .

[0009] As a preferred embodiment of the first aspect, in the inner shell layer, Yb 3+ Ions as sensitizers, NaYbF 4 is the matrix; 3+ The doping molar concentration of the ions is 2%.

[0010] The present invention successfully increases the activator concentration to 98% through the core-inner shell-outer shell structure, thereby significantly improving the luminescence intensity of the upconversion nanoparticles.

[0011] As a preferred embodiment of the first aspect, the method for preparing near-infrared excited rare earth upconversion nanoparticles comprises: firstly, synthesizing the core layer NaYF by coprecipitation method 4 Then, the core layer NaYF 4Synthesis of inner shell NaYbF 4 :2%Er; Finally, the inner shell NaYbF 4 :2%Er on synthetic shell layer NaYF 4 , get NaYF 4 @NaYbF 4 :2%Er@NaYF 4 Upconversion nanoparticles.

[0012] As a preferred implementation manner of the first aspect, the mass ratio of the near-infrared excited rare earth up-conversion nanoparticles to the linseed oil is: near-infrared excited rare earth up-conversion nanoparticles: the linseed oil = 1:1600.

[0013] As a preferred implementation of the first aspect, the mass ratio of the linseed oil to the nanoparticles modified with n-octadecyl phosphate is: nanoparticles modified with n-octadecyl phosphate: linseed oil = 1:368.

[0014] The present invention has found that when the mass ratio of the linseed oil to the modified nanoparticles is 1:368, the encapsulation rate of UCNPs in the core material can be improved; especially when the mass ratio is 1:368, the effect is best.

[0015] As a preferred embodiment of the first aspect, the method for preparing the nanoparticles modified with octadecyl phosphate includes: adding an aqueous suspension of nanoparticles to a solution of octadecyl phosphate, heating and stirring, washing, collecting and drying to obtain nanoparticles modified with octadecyl phosphate.

[0016] As a preferred embodiment of the first aspect, the concentration of octadecyl phosphate in the solution of octadecyl phosphate is 0.5-5mM. Preferably, the concentration of octadecyl phosphate in the solution of octadecyl phosphate is 2mM. Studies have found that when the concentration of octadecyl phosphate in the solution of octadecyl phosphate is 0.5-5mM, the encapsulation rate of UCNPs in the core material can be improved, because the modification of octadecyl phosphate improves the hydrophobicity of the nanoparticles, especially when the concentration of octadecyl phosphate in the solution of octadecyl phosphate is 2mM, the effect is best.

[0017] As a preferred embodiment of the first aspect, the nanoparticles include TiO 2 、Al 2 O 3 、ZrO 2 、SiO 2 The present invention has been proved by experiments that the TiO 2 、Al 2 O 3 、ZrO 2 、SiO2 Both can improve the encapsulation rate of UCNPs in the core material.

[0018] As a preferred embodiment of the first aspect, the method for preparing the solution of octadecyl phosphate comprises: dissolving octadecyl phosphate in a mixture of ethanol and water, wherein the volume ratio of ethanol to water is 3:1.

[0019] As a preferred implementation of the first aspect, the capsule wall material solution further comprises water, ethylene-maleic anhydride, urea, resorcinol and ammonium chloride; and then the pH of the capsule wall material solution is adjusted to 3-4 with triethanolamine.

[0020] In a second aspect, the present invention provides a microcapsule prepared by the method for preparing microcapsules loaded with octadecyl phosphate to modify the surface of nanoparticles according to the first aspect.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention uses UCNPs as a microcapsule fluorescent substance, and introduces a place-occupying mechanism of nanoparticles modified with octadecyl phosphate in the polymer capsule wall during the preparation of the microcapsules, so that the fluorescence intensity of the oil phase flowing out of the microcapsules is increased. The nanoparticles modified with octadecyl phosphate can improve the hydrophobicity of the nanoparticles and improve the encapsulation rate of UCNPs in the core material.

[0023] In addition, the present application uses non-toxic, non-volatile, green and environmentally friendly linseed oil as a healing agent, and uses UCNPs with excellent photostability and chemical stability, no background light source and high selectivity as fluorescent substances to synthesize dual-functional microcapsules with autonomous damage area reporting and damage healing.

[0024] The present application adopts near-infrared excited rare earth upconversion nanoparticles (UCNPs) with large anti-Stokes shift, high conversion efficiency, no background fluorescence interference, excellent photostability and chemical stability as fluorescent substances. UCNPs and linseed oil are mixed as core materials, and fluorescent microcapsules with polyurea formaldehyde (PUF) as capsule walls are synthesized by in-situ polymerization and Pickering effect. The present invention adopts nanoparticles modified with octadecyl phosphate to occupy oil-water interface sites. During the shell polymerization process, place-occupying nanoparticles are introduced to occupy the shell wall position of the microcapsule, so that more UCNPs remain in the oil phase. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The kernel NaYF provided in Example 1 4 and core-shell-shell NaYF 4 @NaYbF 4 :2%Er@NaYF 4Schematic diagram of the structural components, fluorescence mechanism and hexagonal phase of upconversion nanoparticles (where a: is the core NaYF 4 TEM image; b: NaYF with core-shell-shell structure 4 @NaYbF 4 :2%Er@NaYF 4 TEM image of upconversion nanoparticles; c: NaYF with core-shell-shell structure 4 @NaYbF 4 :2%Er@NaYF 4 Emission spectrum of upconversion nanoparticles under 980nm excitation; d: XRD spectrum);

[0026] Figure 2 Schematic diagram of the synthesis mechanism of rare earth-doped UCNPs linseed oil / polyurea formaldehyde microcapsules provided in Example 1 of the present application (wherein, optical microscope image of the microcapsule (i); scanning electron microscope (SEM) showing the outer surface of the microcapsule (ii) and the inside of the capsule wall (iii); proposed synthesis mechanism (iv); core material solutions of microcapsules synthesized under 980nm excitation were collected: (a) linseed oil, (b) linseed oil containing UCNPs, (c) linseed oil containing UCNPs, ODPA-modified or modified TiO 2 Occupies the oil-water interface sites; (d) linseed oil contains UCNPs, ODPA modified or modified Al 2 O 3 Occupies the oil-water interface sites; (e) Linseed oil contains UCNPs, ODPA-modified or modified ZrO 2 Occupies the oil-water interface sites; (f) linseed oil contains UCNPs, ODPA-modified or modified SiO 2 Occupies oil-water interface sites);

[0027] Figure 3 The effects of different ODPA concentrations on the loading amount of upconverting nanoparticles in microcapsules, luminescence intensity and TiO 2 Schematic diagram of the effect of hydrophobicity (where a: the effect of the loading amount of upconverting nanoparticles and luminescence intensity in microcapsules with different ODPA concentrations; b: the effect of TiO 2 Effect of water contact angle of nanoparticles);

[0028] Figure 4 The ODPA-modified TiO 2 Schematic diagram of the effect of different amounts of nanoparticles added on the loading amount and luminescence intensity of upconverted nanoparticles in microcapsules;

[0029] Figure 5Schematic diagram of the effect of different types of ODPA-modified nanoparticles on the loading amount and luminescence intensity of upconversion nanoparticles in microcapsules provided in the examples of the present application (wherein, a: scanning electron microscope (SEM) image of the outer surface of the microcapsule and the inside of the capsule wall; b: effect of different types of ODPA-modified nanoparticles on the loading amount and luminescence intensity of upconversion nanoparticles in microcapsules). DETAILED DESCRIPTION

[0030] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0031] TiO 2 : purchased from AEROXIDE (Degussa), item number or product name: P25 fumed titanium dioxide;

[0032] Octadecyl phosphate (ODPA): purchased from J&K Scientific (J&K Scientific), product name: n-octadecyl phosphoric acid;

[0033] Al 2 O 3 : purchased from Alfa Aesar, product name alumina;

[0034] ZrO 2 : Purchased from Alfa Aesar, product name zirconium dioxide;

[0035] SiO 2 : Purchased from Alfa Aesar, product name silicon dioxide;

[0036] Example 1 Preparation method of microcapsules loaded with ODPA modified nanoparticle surface

[0037] 1. TiO2 modified by octadecyl phosphate (ODPA) 2 Preparation of Nanoparticles:

[0038] 1) Preparation of ODPA solution: 0.0697 g of ODPA was dissolved in 100 mL of a mixture of ethanol and water, wherein the volume ratio of ethanol to water was 3:1; the concentration of the ODPA solution was 2 mM.

[0039] 2) 5wt% AEROXIDE TiO 2 Preparation of P25 aqueous suspension: 5 g of AEROXIDE TiO 2 P25 was dissolved in 95 mL of aqueous solution.

[0040] 3) 5 wt% AEROXIDE TiO 2The P25 aqueous suspension was added dropwise to the above ODPA solution under continuous stirring and heated at 80°C for 24 hours; the mixture was collected after washing with ethanol three times and dried at 50°C to obtain ODPA-modified TiO 2 .

[0041] 2. NaYF with core-inner shell-outer shell structure 4 @NaYbF 4 :2%Er@NaYF 4 Synthesis and Characterization of Upconversion Nanoparticles:

[0042] 1) NaYF 4 @NaYbF 4 :2%Er@NaYF 4 Synthesis of upconversion nanoparticles with core-inner-shell-outer shell structure

[0043] Nuclear solution preparation (Synthesis of nuclear):

[0044] 4 mL of rare earth acetate (Y(CH 3 CO 2 ) 3 ) (0.2 M) aqueous solution was added to a 50 mL flask containing 6 mL oleic acid (OA) and 14 mL octadecene (ODE). The mixture was heated at 150 °C for 50 min to form a lanthanide-oleate precursor solution and then cooled to 45 °C. Subsequently, 7.9 mL NH 4 F (0.4 M) and 2 mL of NaOH (1 M) methanol solution were added, and the resulting solution was stirred for 90 minutes. After the methanol evaporated, the solution was heated to 290 ° C under an argon atmosphere for 1 hour and then cooled to room temperature. The matrix nanoparticles were precipitated by adding ethanol, collected by centrifugation at 6000 rpm for 3 minutes, washed several times with ethanol, and redispersed in 4 mL of toluene to obtain the core particle solution, i.e., the first layer of core NaYF 4 Nanoparticles.

[0045] Preparation of core-shell solution (Synthesis of core-shell):

[0046] 3.92 mL of rare earth (Yb(CH 3 CO 2 ) 3 )(0.2M) aqueous solution and 0.08mL(Er(CH 3 CO 2 ) 3) (0.2 M) aqueous acetate solution was added to a 50 mL flask containing 6 mL oleic acid (OA) and 14 mL octadecene (ODE). The mixture was heated at 150 °C for 50 min to form a lanthanide-oleate precursor solution and then cooled to 45 °C. Subsequently, the pre-synthesized core solution was added and 7.9 mL of NH 4 F (0.4 M) and 2 mL of NaOH (1 M) methanol solution were added, and the resulting solution was stirred for 90 minutes. After the methanol evaporated, the solution was heated to 290 °C under an argon atmosphere for 1 hour and then cooled to room temperature. The nanoparticles were precipitated by adding ethanol, collected by centrifugation at 6000 rpm for 3 minutes, washed several times with ethanol, and redispersed in 4 mL of toluene to obtain a core-shell solution, namely NaYF 4 @NaYbF 4 :2% Er nanoparticles.

[0047] Preparation of core-inner-shell-outer shell solution (Synthesis of core-inner-shell-outer shell):

[0048] 4 mL of rare earth acetate (Y(CH 3 CO 2 ) 3 ) (0.2M) aqueous solution was added to a 50 mL flask containing 6 mL oleic acid (OA) and 14 mL octadecene (ODE). The mixture was heated at 150 °C for 50 min to form a lanthanide-oleate precursor solution and then cooled to 45 °C. Subsequently, the pre-synthesized core-shell solution was added and 7.9 mL of NH 4 F (0.4 M) and 2 mL of NaOH (1 M) methanol solution were added, and the resulting solution was stirred for 90 minutes. After the methanol evaporated, the solution was heated to 290 °C under an argon atmosphere for 1 hour and then cooled to room temperature. The nanoparticles were precipitated by adding ethanol, collected by centrifugation at 6000 rpm for 3 minutes, washed several times with ethanol, and redispersed in 4 mL of toluene. The core-inner shell-outer shell solution, i.e., NaYF 4 @NaYbF 4 :2%Er@NaYF 4 Core-inner-shell-outer shell structured upconverted nanoparticles.

[0049] 2) NaYF 4 @NaYbF 4 :2%Er@NaYF 4 Characterization of upconverted nanoparticles with core-inner-shell-outer shell structure ( Figure 1 ):

[0050] (1) TEM morphology analysis of upconversion nanoparticles:

[0051] We constructed NaYF that emits orange fluorescence4 @NaYbF 4 :2%Er@NaYF 4 Core-shell-shell structured upconverted nanoparticles, Yb 3+ / Er 3+ The upconversion process is confined to the inner shell of the nanoparticle ( Figure 1 (b)). Shell NaYF 4 Designed to protect nanoparticles from surface quenching, the fluorescence intensity is enhanced under 980nm excitation ( Figure 1 (bc)). The upconversion nanoparticles of the present invention are synthesized by epitaxial growth from the core layer to the shell layer, including NaYbF 4 :2% Er inner shell epitaxial growth of NaYF 4 shell.

[0052] (2) XRD phase analysis of upconversion nanoparticles:

[0053] NaYF 4 and core-inner-shell-outer shell NaYF 4 @NaYbF 4 :2%Er@NaYF 4 The powder was measured by XRD, which confirmed that the NaYF prepared by the present invention 4 @NaYbF 4 :2%Er@NaYF 4 The upconversion nanoparticles have a hexagonal phase with high crystallinity of the nanoparticles ( Figure 1 (d)).

[0054] 3. Based on modified TiO 2 Preparation of nanoparticle microcapsules ( Figure 2 )

[0055] 1) Preparation of core material solution: 30 mL of linseed oil was used as the core mixture, and after ultrasonic treatment for 4 hours, 150 uL of UCNPs (upconversion nanoparticles) was added, and the mixture was mixed evenly by vortex oscillation to prepare the core material solution for later use;

[0056] 2) Preparation of capsule wall material solution: ODPA modified TiO 2 (75 mg), ethylene-maleic anhydride EMA (0.31 g), urea (1.25 g), resorcinol (0.125 g) and ammonium chloride (0.125 g) were added to a 250 mL beaker containing 62.5 mL of deionized water and mixed while stirring; then the pH value was adjusted to 3.5 using TEA (ethanolamine);

[0057] 3) Preparation of microcapsules: The core material solution was slowly added to the capsule wall material solution at room temperature at a stirring rate of 600 rpm, and mechanical stirring was used for emulsification for 20 minutes to form a stable o / w emulsion. 2.93 mL of formaldehyde was added to the emulsion, stirred for 5 minutes, and the reaction temperature was raised to 55 ° C and the reaction was continued for 4 hours to polymerize the capsule wall. After the reaction, the microcapsules were washed with deionized water, ethanol and acetone respectively and vacuum filtered, and then the product was dried to obtain microcapsules (labeled as UCNPs / TiO 2 / ODPA).

[0058] In this example, poly(urea-formaldehyde) (PUF) microcapsules loaded with linseed oil were successfully prepared by a mature in-situ polymerization method as a polymer repair agent.

[0059] With the help of ethylene-maleic anhydride (EMA) as a stabilizer, linseed oil can be evenly suspended in the water phase and form a stable oil-water emulsion. Since urea and formaldehyde are soluble in water, they form a layer of aqueous solution around the linseed oil droplets. When the polyurea reaction begins, the aqueous solution begins to polymerize and form a shell ( Figure 2 a).

[0060] However, when used together with upconversion nanoparticles dispersed in linseed oil as the core agent, very weak luminescence was observed in the final oil phase collected from the ruptured microcapsules, indicating that the encapsulation efficiency of the upconversion nanoparticles in the microcapsule oil phase was low ( Figure 2 b).

[0061] The main factor limiting the loading efficiency is the self-assembly of upconversion nanoparticles at the oil-water interface in the Pickering emulsion. The polymerization reaction occurs on the surface of the stabilized linseed oil droplets, and the microcapsules with the PUF-UCNPs shell are subsequently synthesized. Figure 2 b(iv)).

[0062] To solve the problem of limiting loading efficiency, we adopted a “placeholder” encapsulation strategy. 2 Nanoparticles act as "placeholders" to occupy the oil-water interface and stabilize the emulsion together with EMA ( Figure 2 c) TiO 2 Nanoparticles are inherently hydrophilic, which makes it difficult for them to be effectively adsorbed on the oil-water interface. Therefore, their hydrophobicity must be appropriately increased to promote their adsorption on the oil-water interface. 2 The hydrophilicity of TiO2 can be improved, thereby promoting its adsorption on the oil-water interface. 2Nanoparticles, which occupy the sites of the microcapsule shell wall during the shell polymerization process, allow more upconversion nanoparticles to remain in the oil phase ( Figure 2 c(iv)). Elemental analysis from the inside of the microcapsules confirmed the presence of TiO 2 Trapped in the shell wall Figure 2 c(iii)).

[0063] Examples 2-5, Comparative Example 1

[0064] Examples 2-5 and Comparative Example 1 The microcapsules were prepared by the method of Example 1, except that different amounts of ODPA were added. The specific amounts are shown in the following table:

[0065] Table 1:

[0066] Group ODPA addition amount (unit: g) ODPA concentration (mM) Water contact angle Example 1 0.0697 2 91±2° Example 2 0.0174 0.5 53±2° Example 3 0.0349 1 72±2° Example 4 0.1046 3 105±1° Example 5 0.17425 5 119±4° Comparative Example 1 0 0 19±2°

[0067] The microcapsules prepared in Examples 1-5 and Comparative Example 1 were tested and it was found that with the increase of ODPA concentration, TiO 2 The water contact angle of the nanoparticles also increases ( Figure 3 b), indicating that its hydrophobicity is enhanced. The optimal ODPA concentration was determined to be 2 mM (Example 1), at which time ODPA modified TiO 2 The water contact angle of the nanoparticles is about 91±2°, and the luminescence intensity of the core material is the strongest ( Figure 3 a). However, it can be seen from Examples 4-5 that the higher the ODPA concentration, the stronger the luminescence intensity of the core material. The ODPA concentration in Examples 4-5 is greater than that in Example 1, but its luminescence intensity is not as high as that in Example 1 ( Figure 3 a).

[0068] Examples 6-9, Comparative Example 2

[0069] Examples 6-9 and Comparative Example 2: Microcapsules were prepared by the method of Example 1, except that different modified TiO 2 Addition amount, specific addition amount is as follows:

[0070] Table 2:

[0071] Group <![CDATA[ODPA-modified TiO 2 Addition amount (unit: mg)]]> Example 1 75 Example 6 25 Example 7 50 Example 8 100 Example 9 200 Comparative Example 2 0

[0072] To further illustrate the ODPA-modified TiO 2 Effect of nanoparticles. Different amounts of ODPA-modified TiO were added to the microcapsules. 2 The microcapsules prepared in Examples 6-10 and Comparative Example 2 were tested, and the results were as follows. Figure 4As shown, optical microscope images of microcapsules of Examples 6-10 and Comparative Example 2 and the luminescence intensity of the core material collected from the ruptured capsules are shown. 2 When the dosage increased, the core contents were observed to emit brighter light, further verifying that TiO 2 As “placeholder particles”, they occupy the shell wall sites, thus promoting the encapsulation of upconversion nanoparticles in the oil phase. 2 When (Example 1), the upconversion luminescence intensity of the collected core material is 20.9 times higher than that of the capsule without the placeholder. 2 The loading amount of upconversion nanoparticles in the microcapsules can be increased, thereby improving the visualization ability of the microcapsules after crushing. However, it can be seen from Examples 8-9 that it is not the ODPA-modified TiO 2 The higher the addition amount, the higher the loading amount of upconversion nanoparticles in the microcapsule. 2 The added amount is greater than that of Example 1, but the loading amount and luminescence intensity of the upconversion nanoparticles in the microcapsules are less than those of Example 1 ( Figure 4 ).

[0073] Examples 10-12, Comparative Example 3

[0074] Examples 10-12 and Comparative Example 3 The microcapsules were prepared by the method of Example 1, except that Al 2 O 3 、ZrO 2 and SiO 2 Replace the TiO in Example 1 2 The details are as follows:

[0075] Table 3:

[0076]

[0077]

[0078] The microcapsules prepared in Examples 10-12 and Comparative Example 3 were tested. Other ODPA-modified nanoparticles (ODPA-modified Al 2 O 3 ODPA modified ZrO 2 and ODPA-modified SiO 2 ) can also effectively act as placeholder particles and enhance the luminescence intensity of the core material by 8.9 times, 7.7 times, and 5.8 times, respectively ( Figure 2 df, Figure 5), thereby improving the loading efficiency of upconversion nanoparticles, while nanoparticles without ODPA modification cannot improve the loading efficiency of upconversion nanoparticles ( Figure 5 ).

[0079] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for preparing upconversion fluorescent microcapsules assisted by octadecyl phosphate modified nanoparticles, characterized in that: The steps include: The core material solution and the capsule wall material solution are mixed and emulsified to form an o / w emulsion, and then the o / w emulsion is subjected to a polyurea formaldehyde capsule wall polymerization reaction to obtain microcapsules; wherein, The core material solution includes near-infrared excited rare earth up-conversion nanoparticles and linseed oil; The capsule wall material solution comprises polyurea formaldehyde and nanoparticles modified with n-octadecyl phosphate.

2. The preparation method according to claim 1, characterized in that: The near-infrared excited rare earth up-conversion nanoparticles have a core-inner shell-outer shell structure; wherein, The core layer is NaYF4; The inner shell layer is NaYbF4:2%Er doped with rare earth ions; The outer shell layer is NaYF4.

3. The preparation method according to claim 2, characterized in that: In the inner shell, Yb 3+ ions as sensitizers, NaYbF4 as matrix; the Er 3+ The doping molar concentration of the ions is 2%.

4. The preparation method according to claim 3, characterized in that: The preparation method of the near-infrared excited rare earth upconversion nanoparticles comprises: first, synthesizing a core layer NaYF4 by a coprecipitation method; then, synthesizing an inner shell layer NaYbF4:2% Er on the core layer NaYF4 by a layer-by-layer epitaxial growth method; finally, synthesizing an outer shell layer NaYF4 on the inner shell layer NaYbF4:2% Er by a layer-by-layer epitaxial growth method to obtain NaYF4@NaYbF4:2%Er@NaYF4 upconversion nanoparticles.

5. The preparation method according to claim 1, characterized in that: The mass ratio of the near-infrared excited rare earth up-conversion nanoparticles to the linseed oil is: near-infrared excited rare earth up-conversion nanoparticles: the linseed oil = 1:1600.

6. The preparation method according to claim 1, characterized in that: The mass ratio of the linseed oil to the nanoparticles is: nanoparticles modified with n-octadecyl phosphate: linseed oil = 1:

368.

7. The preparation method according to claim 1, characterized in that: The preparation method of the nanoparticles modified with octadecyl phosphate comprises: adding an aqueous suspension of the nanoparticles into a solution of octadecyl phosphate, heating and stirring, washing, collecting and drying to obtain the nanoparticles modified with octadecyl phosphate.

8. The preparation method according to claim 7, characterized in that: The mass ratio of octadecyl phosphate to the nanoparticles is: octadecyl phosphate modification: nanoparticles = 1:71.

7.

9. The preparation method according to claim 1, characterized in that: The capsule wall material solution also includes water, ethylene-maleic anhydride, urea, resorcinol and ammonium chloride; and then triethanolamine is used to adjust the pH of the capsule wall material solution to 3-4.

10. A microcapsule with nanoparticles modified with octadecyl phosphate on its surface, characterized in that: Microcapsules prepared by the preparation method according to any one of claims 1 to 9.

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