Phosphate-containing multi-branched ligands and their modification methods and applications for metal oxide nanoparticles.

Abstract

This invention belongs to the field of optical thin film technology for optical devices, and relates to a ligand and a method for modifying metal oxide nanoparticles using this ligand, as well as its applications. This method of modifying metal oxide nanoparticles using a multi-branched ligand containing phosphate groups achieves precise control of reaction conditions and environment through a multi-ligand combination-step reaction modification approach. This results in a richer effect of the surface organic components of the metal oxide nanoparticles, exhibiting more transparent organic dispersion under high concentrations of the same inorganic particles. Furthermore, the multi-branched ligand containing phosphate groups shows higher reactivity with the surface of hydroxylated metal oxide nanoparticles, resulting in a more significant modification effect, with the surface organic ligand accounting for no less than 20% by thermogravimetric analysis.

Description

Technical Field

[0001] This invention belongs to the field of optical thin film technology for optical devices, and relates to a multi-branched ligand containing a phosphate group and a modification method and application of it to modify metal oxide nanoparticles. Background Technology

[0002] In recent years, with the continuous development of optoelectronic devices, new requirements have been placed on optical thin films in these devices. In particular, the refractive index (n) of the thin film must be tunably controlled in one or more directions, while the extinction coefficient (K) must remain essentially constant to reduce unnecessary light loss. Traditional optical thin film materials include inorganic glass and organic resins. Inorganic glass, due to its brittleness, fragility, and inflexibility, has limited its further application in flexible electronic devices. Therefore, organic resins, with their superior flexibility, are receiving increasing attention. However, the low refractive index of organic resins easily leads to significant total internal reflection light loss during application, further limiting their use in optical devices.

[0003] The emergence of organic-inorganic hybrid materials offers a solution to the aforementioned problems. Organic-inorganic hybrid materials modify organic resins by introducing high-refractive-index nanoparticles or atoms, resulting in flexible composite materials with high refractive indices. However, according to Rayleigh scattering, the imperfect homogeneity of the dispersion system often leads to an increase in the extinction coefficient K due to the influence of the inorganic dispersed particle size and doping concentration. Therefore, by effectively modifying the surface of the inorganic dispersed material, i.e., metal oxide nanoparticles, to achieve high-concentration, transparent, and stable dispersion in organic systems, inorganic-organic hybrid optical thin films with tunable refractive indices and low extinction coefficients can be prepared. These films can effectively perform constructive or destructive operations on visible light interference, reflection, and transmission, demonstrating significant application value in numerous optical devices.

[0004] Existing Chinese patent document 1 (publication number CN105931696A, publication date 2016.09.07) discloses the synthesis, capping and dispersion of nanocrystals. The proposed organic acid ligands, such as formic acid, acetic acid, propionic acid, butyric acid, hexanoic acid, heptanoic acid and oleic acid, and organic alcohol ligands, such as ethanol, propanol, butanol, oleyl alcohol and dodecyl alcohol, usually have flexible single-chain alkanes as their end groups. During the surface modification process of metal oxide nanocrystals, chain bending and chain folding inevitably occur, which leads to a decrease in the steric hindrance between particles, a reduction in the interparticle spacing, and agglomeration problems in a short period of time.

[0005] Existing Chinese Patent Document II (Publication No. CN106170872A, Publication Date 2016.11.30) discloses a high-refractive-index organosilicon nanocomposite material. The proposed silane ligands are typically used in experiments as single-ligand or multi-ligand mixtures to modify the surface of inorganic particles. However, the ligand exchange reaction under single-ligand modification exhibits a dynamic equilibrium; that is, even with excessive ligand modification, there is an upper limit to ligand modification, i.e., a saturation point for single-ligand modification. Multi-ligand mixtures also exhibit differences in reactivity between ligands. The competitive reactions between ligands and the interactions between different ligand monomers both limit the amount of organic ligands that substantially acts on the metal surface. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a multi-branched ligand containing a phosphate group and a modification method and application of the ligand to modify metal oxide nanoparticles, so as to solve the phenomenon that the transparency of existing hybrid materials decreases with the increase of inorganic nanoparticle doping concentration.

[0007] To achieve the above objectives, the present invention provides the following technical solution: On one hand, the present invention provides a multi-branched ligand containing a phosphate group, wherein the general structural formula of the multi-branched ligand is as follows (1):

[0008]

[0009] In formula (1), R1 and R2 are each independently any one of the following: a single bond, a substituted or unsubstituted C1 to C20 branched or straight-chain alkylene group, a substituted or unsubstituted C1 to C20 branched or straight-chain alkylene ether group, a substituted or unsubstituted C3 to C20 cycloalkylene group, a substituted or unsubstituted C6 to C30 aryl group, a substituted or unsubstituted C7 to C20 arylalkylene group, or a substituted or unsubstituted C1 to C20 monoalkylamino group.

[0010] X1 and X2 are each independently any one of hydrogen, epoxy, (meth)acrylate, aromatic, amino, or olefinic groups.

[0011] The multi-branched ligand structure provided by this invention has a hydroxyl group (-OH) at one end anchored to the surface of a hydroxylated oxide via a covalent bond formed through a dehydration-etherification reaction. The -OR group (R being a long-chain alkyl, alkenyl, aryl, etc.) at the other end achieves effective dispersibility in different organic systems through the principle of like compatibility (polarity, structure, etc.). Furthermore, the presence of the phosphate group provides a weakly acidic reaction environment, which is more conducive to the hydrolysis and etherification of the hydroxyl group.

[0012] Furthermore, the general structural formula of the above-mentioned multi-branched ligands is one of formulas (2) to (12):

[0013]

[0014]

[0015]

[0016] On the other hand, the present invention provides a modification method for metal oxide nanoparticles by modifying the surface of hydroxylated metal oxide nanoparticles with multi-branched ligands containing phosphate groups as described above. The modification method involves using multiple ligands to modify the surface of hydroxylated metal oxide nanoparticles in steps to complete the surface modification of the metal oxide nanoparticles; at least one of the multiple ligands is a multi-branched ligand containing phosphate groups.

[0017] Furthermore, the metal oxide nanoparticles are prepared by a high-temperature, high-pressure solvothermal synthesis method, the specific preparation method of which is as follows:

[0018] Step 1.1: Dissolve or mix the metal oxide precursor solution in at least one solvent to produce a solution;

[0019] Step 1.2: Transfer the solution to a high-pressure reactor and heat it to 200℃~450℃. Stir at a speed of 300rpm~800rpm and react at a constant temperature for 3h~12h.

[0020] Step 1.3: Cool naturally to a lower temperature and collect the synthesized metal oxide nanoparticles.

[0021] Furthermore, the surface of the metal oxide nanoparticles is first purified, and then the surface of the purified metal oxide nanoparticles is subjected to hydroxylation treatment. The specific method of hydroxylation treatment is as follows:

[0022] Step 2.1: Add at least one metal oxide nanoparticle to an inorganic or organic acid to form a first mixed solution; or, first add at least one metal oxide nanoparticle to an inorganic acid for acid washing, and then treat the precipitate collected by centrifugation with an organic acid to form the first mixed solution.

[0023] Step 2.2: Heat the first mixed solution to 30℃~100℃ and stir for 0.5h~72h;

[0024] Step 2.3: Allow the supernatant to settle naturally, remove the supernatant, collect the lower layer of acid-washed metal oxide nanoparticles, and add a weakly alkaline organic solvent until the pH is 4-6;

[0025] Step 2.4: Clean, let stand for 12h to 72h, and collect the hydroxylated metal oxide nanoparticles.

[0026] Specifically, the reaction mechanism of hydroxylation mainly involves the adsorption of hydrogen ions generated by ionization or hydrolysis in solution by oxygen vacancies on the surface of metal oxide nanoparticles in an acidic environment, thereby completing the hydroxylation of the metal oxide nanoparticle surface through chemical bonding. Furthermore, due to the large specific surface area and high surface activity of metal nanoparticles, defects on the crystal surface readily adsorb hydroxyl ions generated in solution, further achieving hydroxylation of the metal oxide nanoparticle surface through electrostatic interactions.

[0027] Furthermore, since the hydroxylated metal oxide nanoparticles provide sufficient reaction sites for subsequent ligand exchange, the surface of the metal oxide nanoparticles can be fully modified and their high concentration (>70%) can be stably dispersed in non-water-soluble media by using multi-branched ligand stepwise reactions.

[0028] Specifically, the steps for the above-mentioned step-by-step modification are as follows:

[0029] S3.1 Disperse or dissolve the hydroxylated metal oxide nanoparticles in at least one solvent to form a second mixed solution;

[0030] S3.2 Add ligand A in appropriate proportion according to the content of metal oxide nanoparticles, stir, and react at room temperature or by heating for 0.5h to 18h; the mass ratio of ligand A to metal oxide nanoparticles is 1:5 to 2:3.

[0031] S3.3. Natural cooling and temperature reduction, followed by centrifugation or antisolvent precipitation of metal oxide nanoparticles; then dispersing the metal oxide nanoparticles in another solvent, adding a corresponding proportion of ligand B, stirring, and reacting at room temperature or by heating for 2h to 24h; the mass ratio of ligand B to metal oxide nanoparticles is 1:5 to 2:3.

[0032] S3.4 Repeat the precipitation step in S3.3. When the thermogravimetric ratio of the organic ligand in the stepwise modified metal oxide nanoparticles is not less than 20%, the modification is completed, and the modified metal oxide nanoparticles are used to conduct an organic system dispersion experiment.

[0033] It should be noted that the stepwise modification is typically performed two or three times: When the stepwise modification is performed twice, i.e., after modification with ligands A and B, if the thermogravimetric ratio of the organic ligand is not less than 20% after repeating the precipitation step, the modification is complete, and the modified metal oxide nanoparticles are used for organic system dispersion experiments. When the stepwise modification is performed three times, i.e., after modification with ligands A and B, if the thermogravimetric ratio of the organic ligand is still less than 20% after repeating the precipitation step, ligand C is added for a third modification, until the thermogravimetric ratio of the organic ligand is not less than 20%, the modification is complete, and the modified metal oxide nanoparticles are used for organic system dispersion experiments. At least one of ligands A, B, and C must be a multi-branched ligand containing a phosphate group.

[0034] Specifically, the aforementioned metal oxide nanoparticles include at least one of zirconium oxide, titanium oxide, zinc oxide, aluminum oxide, nickel oxide, and hafnium oxide, and the average particle size of the metal oxide nanoparticles ranges from 1 nm to 20 nm.

[0035] Furthermore, the precipitated metal oxide nanoparticles can achieve transparent and stable dispersion at high concentrations, and can be well dispersed in organic systems including methanol, ethanol, propanol, butanol, toluene, benzyl alcohol, phenol, n-hexane, n-heptane, dichloromethane, ethyl acetate, acetonitrile, oleic acid, oleylamine, hexanoic acid, octanoic acid, tetrahydrofuran, pyridine, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, acetone, and mixtures thereof.

[0036] Furthermore, the organic dispersion of the surface-modified metal oxide particles can be dispersed in polymerizable monomers by removing the solvent through rotary evaporation, filtration, or other methods; the polymerizable monomers include, but are not limited to, acrylic polymerizable monomers, oligomers, and their combinations.

[0037] On another front, the present invention also provides surface-modified inorganic metal oxide nanoparticles obtained by the above-mentioned modification method, which are transparently and stably dispersed in an organic solvent to form an organic dispersion. The solvent can be removed by rotary evaporation, vacuum filtration, etc., and the dispersion is then carried out in polymerizable monomers. Preferably, the composite is carried out in acrylate monomers, which have high permeability and high reactivity, i.e., a fast UV curing rate, enabling simple and rapid film formation applications.

[0038] Furthermore, the thickness and patterning of the aforementioned inorganic-organic composite resin material precursor liquid can be controlled by methods such as scraping, spin coating, embossing, dip coating, drop coating, plasma spraying, electrostatic spraying, ultrasonic spray deposition, inkjet printing, screen printing, and mold casting. With the aid of ultraviolet curing, flexible optical films with characteristics such as high refractive index tunability and low extinction coefficient can be quickly fabricated. This demonstrates high flexibility and applicability in applications of various optoelectronic devices (such as light-emitting diodes, solar cells, patterned optical lenses, distributed Bragg mirrors, projectors, televisions, digital cameras, smartphones, eyeglasses, anti-reflective glass, etc.).

[0039] Specifically, the optical thin film made using the inorganic-organic composite resin material has a refractive index of 1.515 to 1.800 and a light transmittance of over 95%.

[0040] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0041] (1) The ligand has a hydroxyl group (-OH) at one end that is anchored to the surface of the hydroxylated oxide through a covalent bond formed by a dehydration-etherification reaction; the -OR group at the other end achieves effective dispersibility in different organic systems through the principle of like compatibility. Moreover, the presence of the phosphate group provides a weakly acidic reaction environment for the system, which is more conducive to the hydrolysis and etherification of hydroxyl groups.

[0042] (2) A modification method using phosphate-containing multi-branched ligands to modify metal oxide nanoparticles achieves precise control over reaction conditions (reaction temperature, stirring rate, and reaction time) and reaction environment (acidity / alkalinity and gas atmosphere) through a multi-ligand combination-step reaction modification approach. This results in richer surface organic components on the metal oxide nanoparticles, exhibiting more transparent organic dispersion at high concentrations (>70%) of the same inorganic particles. Furthermore, the phosphate-containing multi-branched ligands exhibit higher reactivity with the hydroxylated metal oxide nanoparticle surface, resulting in a more significant modification effect, with the surface organic ligands accounting for >20% by thermogravimetric analysis.

[0043] (3) The present invention employs a high-temperature and high-pressure synthesis method to achieve the preparation of metal oxides with small particle size (3nm~5nm), high phase purity, and high dispersibility, thereby reducing the loss caused by light scattering from the inorganic particles themselves. The surface hydroxylation treatment of the metal oxides using inorganic / organic acids provides abundant reaction sites for ligand modification on the surface of the aforementioned inorganic particles, ensuring the successful progress of the reaction. Attached Figure Description

[0044] Figure 1 This is a TEM image (scale bar is 10 nm) of the zirconium oxide nanocrystals synthesized by hydrothermal method in Example 1 of the present invention.

[0045] Figure 2 This is a TEM image (scale bar is 5 nm) of the zirconium oxide nanocrystals synthesized by hydrothermal method in Example 1 of the present invention.

[0046] Figure 3 The XRD curve of the zirconium oxide nanocrystals synthesized by hydrothermal method in Example 1 of this invention;

[0047] Figure 4 This is a graph showing the thermogravimetric ratio of the high-concentration dispersion system of zirconium nanoparticles in Example 3 of the present invention.

[0048] Figure 5 The curve showing the change in refractive index of the inorganic-organic composite resin material prepared in this invention as a function of zirconium oxide mass fraction;

[0049] Figure 6 This is a TEM image (scale bar is 10 nm) of titanium dioxide nanocrystals synthesized by hydrothermal method in Example 5 of the present invention. Detailed Implementation

[0050] Exemplary embodiments will be described in detail below. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of compositions and methods consistent with some aspects of the present invention as detailed in the appended claims.

[0051] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to embodiments.

[0052] Example 1

[0053] This embodiment provides a method for modifying the surface of metal oxide nanoparticles using multi-branched ligands containing phosphate groups. The method involves stepwise modification of the hydroxylated metal oxide nanoparticle surface using multiple ligands to achieve surface modification. At least one of the multiple ligands is a multi-branched ligand containing a phosphate group. The specific steps of the above modification method are as follows:

[0054] Step 1: Prepare 3nm-5nm zirconium oxide nanocrystals:

[0055] First, thoroughly mix 14.39g of 80% (by weight) zirconium-butanol solution with 200ml of benzyl alcohol and transfer the mixture to a high-temperature and high-pressure reactor (Shanghai Yanzheng Instruments YZPR-500). Open the inlet and outlet valves of the reactor and slowly introduce nitrogen gas from the inlet to replace the air in the reactor and prevent water and oxygen contamination from affecting the reaction.

[0056] Then, close the inlet and outlet valves of the above-mentioned reactor to ensure the airtightness of the reaction environment; then heat the reactor to 325°C and mechanically stir at 600 rpm for 5 hours at a constant temperature.

[0057] Finally, turn off the heating, continue mechanical stirring at 600 rpm, and allow to cool naturally to room temperature (approximately 7 hours). Collect the synthesized milky white solution containing zirconia nanocrystals; the TEM image of the zirconia nanocrystals is shown below. Figure 1-2 As shown, see the XRD curve. Figure 3 As shown.

[0058] Step 2: Purify the surface of the zirconia nanocrystals:

[0059] First, the collected milky white solution containing zirconium oxide nanocrystals was centrifuged at 7800 rpm for 15 minutes to collect the lower white precipitate.

[0060] The white precipitate was then redispersed in a fresh ethanol solution and sonicated for 20 min. The lower layer of zirconia nanoparticles was then collected by centrifugation at 6500 rpm for 10 min. The zirconia nanoparticles were then redispersed in a fresh ethanol solution, and the sonication and centrifugation were repeated 2 to 3 times to ensure that the surface of the zirconia nanoparticles was thoroughly cleaned and purified.

[0061] Step 3: Perform hydroxylation treatment on the surface of the purified zirconium oxide nanoparticles:

[0062] 2.0 g of cleaned and purified zirconium oxide nanoparticles were dispersed in 55 ml of 1 M hydrochloric acid solution and stirred at 600 rpm for 24 h at room temperature.

[0063] The above solution was allowed to settle naturally (approximately 0.5 hours) to remove the supernatant hydrochloric acid. The lower layer of acid-washed white zirconium oxide particles was collected, and tetrahydrofuran solution was added to adjust the pH of the system to within the range of 4–6. After sonicating for 20 minutes to remove free or unstable groups on the zirconium oxide surface, the solution was allowed to settle and the white precipitate of hydroxylated zirconium oxide nanoparticles was collected.

[0064] Step 4: Thorough surface modification of zirconia nanoparticles using a multi-ligand combination-step reaction:

[0065] 2.0 g of zirconia particles after surface hydroxylation were dispersed in 35 ml of ethanol solution, and 0.8 g of 2-methyl-2-acrylate-2-(phosphonooxy)ethyl ester was added. The mixture was ultrasonically treated for 10 min, heated to 75 °C, and stirred at 600 rpm for 5 h.

[0066] The above solution was centrifuged at 4500 rpm for 6 min, and the lower white precipitate was collected. The zirconia nanocrystal precipitate was redispersed in 5 ml of hexanoic acid solution, stirred at 600 rpm, and 0.5 g of di(methacryloyloxyethyl) hydrogen phosphate was added dropwise under heating at 55 °C. The mixture was heated and stirred for 3 h. After naturally cooling to room temperature, the zirconia nanoparticles modified with the dual ligands were collected by centrifugation at 5500 rpm for 10 min.

[0067] The organic ligands in the zirconia nanoparticles (I) modified with the above dual ligands account for 21.5% of the thermogravimetric ratio, and can form a stable THF dispersion with a concentration of 72%.

[0068] Example 2

[0069] This embodiment provides a method for modifying the surface of metal oxide nanoparticles using multi-branched ligands containing phosphate groups. Multiple ligands are used to modify the surface of hydroxylated metal oxide nanoparticles in a stepwise manner, thus completing the surface modification. At least one of the multiple ligands is a multi-branched ligand containing a phosphate group. The specific steps of this modification method are basically the same as in Example 1, except that step 4 involves using a combination of multiple ligands in a stepwise reaction to fully modify the surface of the zirconium oxide nanoparticles, as detailed below:

[0070] 2.0 g of zirconia particles after surface hydroxylation were dispersed in 35 ml of ethanol solution, 1.0 g of 2-methacryloyloxyethylphenylphosphoric acid was added, and the mixture was sonicated for 10 min. Then, the mixture was stirred at 600 rpm at room temperature for 30 min.

[0071] The above solution was centrifuged at 8500 rpm for 10 min to collect the lower precipitate. The precipitate was redispersed in 20 ml of ethanol, and 5 μl of 1 M hydrochloric acid was added. The mixture was stirred at 300 rpm for 5 min, then stirred at 600 rpm. Under heating conditions of 75 °C, 0.5 g of methoxytris(ethoxy)propyltrimethoxysilane was added dropwise, and the mixture was heated and stirred for 1 h. After naturally cooling to room temperature, the zirconia nanoparticles modified with the dual ligands were collected by centrifugation at 7800 rpm for 15 min.

[0072] The organic ligands in the zirconia nanoparticles (II) modified with the above dual ligands account for 23.7% of the thermogravimetric ratio, and can form a stable THF dispersion with a concentration of 73.5%.

[0073] Example 3

[0074] This embodiment provides a method for modifying the surface of metal oxide nanoparticles using multi-branched ligands containing phosphate groups. Multiple ligands are used to modify the surface of hydroxylated metal oxide nanoparticles in a stepwise manner, thus completing the surface modification. At least one of the multiple ligands is a multi-branched ligand containing a phosphate group. The specific steps of this modification method are basically the same as in Example 1, except that step 4, the method of using a combination of multiple ligands in a stepwise reaction to fully modify the surface of zirconia nanoparticles, differs from that in Example 1, as detailed below:

[0075] First, 2.0 g of zirconia particles after surface hydroxylation treatment were dispersed in 35 ml of phosphoric acid solution (where phosphoric acid is used as both a solvent and a reaction ligand) and stirred at room temperature for 0.5 h. Then, a petroleum ether / tetrahydrofuran mixed solution (volume ratio of 1:1) was added to precipitate zirconia nanoparticles.

[0076] Then, the above-mentioned zirconia nanoparticles were redispersed in 55 ml of ethanol solution, stirred at 600 rpm, and 1.0 g of polyethylene glycol methacrylate phosphate was added dropwise under heating conditions of 65 °C. Finally, the mixture was heated and stirred for 5 h, and after naturally cooling to room temperature, the zirconia nanoparticles modified with the dual ligands were collected by centrifugation at 7800 rpm for 15 min (III).

[0077] The organic ligand thermogravimetric composition of the zirconia nanoparticles (III) modified with the above dual ligands was 29.5% (see [link to product description]). Figure 4 It can form a stable THF dispersion with a concentration of 74%.

[0078] Example 4

[0079] Based on Example 1, this example provides a method for modifying the surface of zirconia nanoparticles using multi-branched ligands containing phosphate groups. The specific steps are basically the same as in Example 1, except that: step 4, using a combination of multiple ligands in a stepwise reaction to fully modify the surface of the zirconia nanoparticles, is as follows:

[0080] First, 2.0 g of zirconia particles after surface hydroxylation treatment were dispersed in 55 ml of phosphoric acid solution and stirred at room temperature for 0.5 h. Then, a petroleum ether / tetrahydrofuran mixed solution (volume ratio of 1:1) was added to precipitate zirconia nanoparticles.

[0081] Then, the above-mentioned zirconia nanoparticles were redispersed in 35 ml of ethanol solution, stirred at 800 rpm, and 1.0 g of ethanolamine phosphate was added dropwise under heating at 75 °C. Finally, the reaction was heated and stirred for 3 h, and after naturally cooling to room temperature, the zirconia nanoparticles modified with the dual ligands were collected by centrifugation at 7500 rpm for 15 min (IV).

[0082] The organic ligands in the zirconia nanoparticles (IV) modified with the above dual ligands account for 22.7% of the thermogravimetric ratio, and can form a stable THF dispersion with a concentration of 72.8%.

[0083] Example 5

[0084] Based on the technical solutions described in Examples 1-3, this embodiment provides a method for modifying the surface of titanium oxide nanoparticles using multi-branched ligands containing phosphate groups. This method includes the synthesis and surface treatment of 7nm-10nm titanium oxide nanocrystals, and the principle is largely the same as described in Examples 1-3. The method of dual-ligand combination-step modification of the titanium oxide particle surface after surface hydroxylation treatment will be described in detail below:

[0085] Add 1.0 g of 2-methacryloyloxyethylphenylphosphonic acid to 50 ml of benzyl alcohol solution, followed by 5 μl of hexanoic acid solution. Sonicate for 5 min, then stir at 300 rpm for 10 min. Add dropwise a benzyl alcohol dispersion of 2.0 g of surface-hydroxylated titanium dioxide particles to the above solution. Heat to 65 °C and stir at 600 rpm for 5 h. After cooling to room temperature, centrifuge at 7800 rpm for 15 min, and collect the lower white precipitate. TEM image of the precipitate is shown below. Figure 6 As shown.

[0086] The collected white precipitate was redispersed in an ethanol solution, and 0.8 g of 2-methyl-2-acrylate-2-(phosphonooxy)ethyl ester was added. The mixture was sonicated for 5 min, heated to 70 °C, and stirred at 600 rpm for 3 h. Then, a petroleum ether / tetrahydrofuran mixed solution (volume ratio 1:1) was added as an antisolvent to precipitate the particles. The dual-ligand modified titanium dioxide nanoparticles (I) were collected by centrifugation.

[0087] The organic ligands in the titanium dioxide nanoparticles (I) modified with the above dual ligands account for 23.0% of the thermogravimetric ratio, and can form a stable dispersion of benzyl alcohol with a concentration of 70.5%.

[0088] Example 6

[0089] Based on the technical solutions described in Examples 1-3, this embodiment provides a method for modifying the surface of titanium dioxide nanoparticles using multi-branched ligands containing phosphate groups. The method of dual-ligand combination-step modification of the titanium dioxide particle surface after surface hydroxylation treatment will be described in detail below:

[0090] First, add 1.5g of di(2-ethylhexyl) phosphate to 50ml of benzyl alcohol solution, then add 10μl of butyric acid solution, sonicate for 10min, and stir at 500rpm for 20min.

[0091] Then, the benzyl alcohol dispersion of 2.0 g of surface-hydroxylated titanium dioxide particles was added dropwise to the above solution, heated to 75 °C, and stirred at 600 rpm for 3 h. After cooling to room temperature, the mixture was centrifuged at 8000 rpm for 15 min and the lower white precipitate was collected.

[0092] The collected white precipitate was then redispersed in an ethanol solution, and 2 g of oxocyclic-2-ylmethyl phosphate dihydrogen salt was added. The mixture was sonicated for 5 min, heated to 70 °C, and stirred at 600 rpm for 5 h. Finally, a petroleum ether / tetrahydrofuran mixed solution (volume ratio 1:1) was added as an antisolvent to precipitate the particles, and the dual-ligand modified titanium dioxide nanoparticles (II) were collected by centrifugation.

[0093] The organic ligands in the titanium dioxide nanoparticles (II) modified with the above dual ligands account for 23.5% of the thermogravimetric ratio, and can form a stable dispersion of benzyl alcohol with a concentration of 70.2%.

[0094] Example 7

[0095] Based on the technical solutions described in Examples 1-3, this embodiment provides a method for modifying the surface of mixed titanium oxide and alumina nanoparticles using multi-branched ligands containing phosphate groups. The method of dual-ligand combination-step modification of the surface of titanium oxide and alumina particles after surface hydroxylation treatment will be described in detail below:

[0096] First, add 1.5g of di(2-ethylhexyl) phosphate to 35ml of benzyl alcohol solution, then add 10μl of acetic acid solution, sonicate for 10min, and stir at 600rpm for 15min.

[0097] Then, the benzyl alcohol dispersion of 2.0 g of surface-hydroxylated titanium dioxide particles was added dropwise to the above solution, heated to 55 °C, and stirred at 600 rpm for 3 h. After cooling to room temperature, the mixture was centrifuged at 8000 rpm for 15 min and the lower white precipitate was collected.

[0098] The collected white precipitate was then redispersed in an ethanol solution, and 2g of ethanolamine phosphate was added. The mixture was sonicated for 5 minutes, heated to 65℃, and stirred at 600rpm for 5 hours to form a mixed solution M.

[0099] 2.0 g of alumina particles after surface hydroxylation were dispersed in 35 ml of ethanol solution, 5 ml of phosphoric acid solution was added, the temperature was heated to 50 °C, and the mixture was stirred at 500 rpm for 3 h. After centrifugation at 7600 rpm for 5 min, the precipitate at the bottom layer was collected and redispersed in ethanol solution to form mixed solution N.

[0100] Finally, the mixed solution M and mixed solution N were sonicated for 20 min, and then a petroleum ether / tetrahydrofuran mixed solution (volume ratio of 1:1) was added as an antisolvent to precipitate the particles. The ligand-modified titanium oxide and alumina nanoparticles were collected by centrifugation.

[0101] The organic ligand thermogravimetric ratio of the above-mentioned ligand-modified titanium oxide and aluminum oxide mixed nanoparticles is 24.5%, which can form a stable dispersion of benzyl alcohol with a concentration of 71.2%.

[0102] Example 8

[0103] Based on the zirconia nanoparticles containing dual ligands prepared in any of the above Examples 1-4, the dispersion containing 2.0 g of zirconia nanoparticles was naturally cooled to room temperature, centrifuged at 5500 rpm for 10 min, the supernatant solvent and residual unreacted ligand monomers were discarded, and the lower white precipitate was collected and the following operations were performed:

[0104] First, add 35 ml of tetrahydrofuran solvent to the white precipitate, sonicate the solution containing zirconium oxide nanoparticles for 5 min, centrifuge at 2500 rpm for 3 min, discard the small amount of incompletely dispersed precipitate in the lower layer, and collect the supernatant to form a transparent nanocrystalline tetrahydrofuran dispersion.

[0105] Then, the tetrahydrofuran dispersion containing well-dispersed zirconium oxide nanoparticles was ultrasonically pretreated for 5 min. 1.0 g of the optimized acrylic resin composition (OPPEA:DCPA:TEGDMA weight ratio of 5:3:2) was added to the above transparent nanocrystalline tetrahydrofuran dispersion, and the mixture was ultrasonically treated for 30 min, heated to 50°C, and stirred at 600 rpm for 3 h.

[0106] Finally, after naturally cooling to room temperature, the above mixed solution was slowly evaporated at 40°C and 15 rpm using a rotary evaporator to remove most of the tetrahydrofuran solvent. To ensure complete removal of residual solvent, the solution was then transferred to a round-bottom flask, stirred at 50 rpm, and evacuated under vacuum for 12 hours using an oil pump. The acrylic composite resin doped with zirconia nanocrystals was then collected.

[0107] Example 9

[0108] Based on Example 7, this example also provides an optical film made using an inorganic-organic composite resin material, as follows: The acrylic composite resin doped with zirconium oxide nanocrystals obtained in Example 8 is collected into a brown serum bottle, and 3% (by weight) of TPO photoinitiator is added. The mixture is stirred at 800 rpm for 1 hour at room temperature in the dark until the TPO is completely dissolved.

[0109] Then, the above solution was drop-coated onto a glass substrate and imprinted into a film, which was then transferred to a nitrogen glove box. A pressure of 60 mW / cm² was used. 2 It was cured by irradiation with a UV lamp for 40 seconds. After curing, the refractive index was 1.75, the thickness was 10μm, the curing rate was 95.2%, and the light transmittance was ≥98.0%.

[0110] In summary, this invention provides a multi-branched ligand containing a phosphate group and its application in the surface modification of metal oxide nanoparticles synthesized by a high-temperature, high-pressure method. It also proposes a stepwise solvent-multiple ligand modification method for surface modification. The surface-modified inorganic metal oxide nanoparticles obtained using this method can be stably and transparently dispersed at high concentrations in various organic solvents. (See [link to relevant documentation]). Figure 4 As shown. Furthermore, combined with Figure 5 As shown, by changing the doping concentration of the metal oxide, the refractive index of the composite material can be precisely controlled in the range of 1.515 to 1.800 while maintaining a transmittance of over 95%, demonstrating high flexibility and applicability in the application of many optoelectronic devices.

[0111] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention.

[0112] It should be understood that the present invention is not limited to the content already described above, and various modifications and changes can be made without departing from its scope. The scope of the present invention is limited only by the appended claims.

Claims

1. A method for modifying metal oxide nanoparticles, characterized in that, The surface of hydroxylated metal oxide nanoparticles was modified stepwise using multiple ligands to achieve surface modification. At least one of the multiple ligands was a multi-branched ligand containing a phosphate group, and the structural formula of the multi-branched ligand containing the phosphate group was one of formulas (2) to (12). Equation (2) Equation (3) Equation (4) Equation (5) Equation (6) Equation (7) Equation (8) Equation (9) Equation (10) Equation (11) Equation (12); The metal oxide nanoparticles were prepared by a high-temperature, high-pressure solvothermal synthesis method, the specific preparation method of which is as follows: Step 1.1: Dissolve or mix the metal oxide precursor solution in at least one solvent to produce a solution; Step 1.2: Transfer the solution to a high-pressure reactor and heat it to 200℃~450℃. Stir at 300rpm~800rpm and react at a constant temperature for 3h~12h. Step 1.3: Allow the material to cool naturally and collect the synthesized metal oxide nanoparticles; First, the surface of the metal oxide nanoparticles is purified, and then the surface of the purified metal oxide nanoparticles is hydroxylated. The specific method of the hydroxylation treatment is as follows: Step 2.1: Add at least one metal oxide nanoparticle to an inorganic or organic acid to form a first mixed solution; Step 2.2: Heat the first mixed solution to 30℃~100℃ and stir for 0.5h~72h; Step 2.3: Allow the supernatant to settle naturally, remove the supernatant, collect the lower layer of acid-washed metal oxide nanoparticles, and add a weakly alkaline organic solvent until the pH reaches 4-6. Step 2.4: Clean, let stand for 12h~72h, and collect the hydroxylated metal oxide nanoparticles; The step-by-step modification is as follows: S3.1 Disperse or dissolve the hydroxylated metal oxide nanoparticles in at least one solvent to form a second mixed solution; S3.2 Add ligand A in the appropriate proportion according to the content of metal oxide nanoparticles, stir, and react at room temperature or by heating for 0.5h to 18h; the mass ratio of ligand A to metal oxide nanoparticles is 1:5 to 2:

3. S3.

3. Natural cooling and temperature reduction, followed by centrifugation or anti-solvent method to precipitate metal oxide nanoparticles; the metal oxide nanoparticles are then dispersed in another solvent, and a corresponding proportion of ligand B is added. The mixture is stirred and reacted at room temperature or by heating for 2 to 24 hours. The mass ratio of ligand B to metal oxide nanoparticles is 1:5 to 2:

3. S3.4 Repeat the precipitation step in S3.

3. When the thermogravimetric ratio of organic ligands in the stepwise modified metal oxide nanoparticles is not less than 20%, the modification is completed, and the modified metal oxide nanoparticles are used to conduct an organic system dispersion experiment. Among them, at least one of ligand A in S3.2 and ligand B in S3.3 is a multi-branched ligand containing a phosphate group; The metal oxide nanoparticles are selected from at least one of zirconium oxide, titanium oxide, zinc oxide, aluminum oxide, nickel oxide, and hafnium oxide, and the average particle size of the metal oxide nanoparticles ranges from 1 nm to 20 nm.

2. The modification method according to claim 1, characterized in that, After the surface of the metal oxide nanoparticles is modified, the organic ligands account for no less than 20% of the thermogravimetric content.

3. An application of surface-modified inorganic metal oxide nanoparticles obtained by the modification method of claim 1, characterized in that, It is transparently and stably dispersed in an organic resin to prepare an inorganic-organic composite resin material.

4. The application of the surface-modified inorganic metal oxide nanoparticles obtained by the modification method according to claim 3, characterized in that, An optical thin film can be prepared using the inorganic-organic composite resin material, with a refractive index of 1.515~1.800 and a light transmittance of over 95%.

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