JP7006908B2 - Metal oxide nanoparticles and their manufacturing method - Google Patents

Description

The present invention relates to metal oxide nanoparticles and a method for producing the same.

Transparent plastic is an indispensable optical material in the field of electronics. However, transparent plastic is inferior to inorganic optical glass in terms of refractive index, thermal expansion rate, and heat resistance. Therefore, so-called organic-inorganic hybrid materials in which metal oxide nanoparticles such as zirconium oxide (ZrO ₂ ) or titanium oxide (TiO ₂ ), which are inorganic materials having a high refractive index, are dispersed in a transparent plastic are mainly used. It is expected in terms of improvement.

When two kinds of substances having different refractive indexes are combined with a size of about several hundred nm, which is a visible light wavelength, they become turbid due to optical scattering and cannot be used as a transparent material. In order to create a hybrid material that does not cause optical scattering, it is very important to synthesize metal oxide nanoparticles that are stably dispersed with a particle size of several nm to several tens of nm, which is sufficiently smaller than the visible light wavelength. become.

Metal oxide nanoparticles such as ZrO ₂ and TiO ₂ have a large surface free energy and tend to aggregate in water or an organic solvent. Therefore, a dispersant is used to improve the dispersibility of the metal oxide nanoparticles. For example, Non-Patent Document 1 discloses nanoparticles of TiO ₂ and ZrO ₂ surface-modified with zircesquioxane obtained by hydrolysis and condensation reaction of a silane coupling agent. The nanoparticles are highly dispersed in water. Further, as a dispersant for nanoparticles, organic phosphonic acid and a surfactant are used in Non-Patent Document 2 and Non-Patent Document 3, respectively.

Patent Document 1 discloses a metal oxide fine particle dispersion that is highly dispersed, has little aggregation, and is highly transparent. The metal oxide fine particle dispersion is obtained by dispersing the metal oxide fine particles and a strong acid in an aqueous solution containing alcohol.

Japanese Unexamined Patent Publication No. 2008-239461

Yoshiro Kaneko, "Preparation of Highlight Water-Dispersible Titanium-Silicon Binary Oxide Material Materials by Sol-Gel Method", 2011, JournalN. Shiori Takahashi, outside five, "Modification of TiO2 Nanoparticles with Oleyl Phosphate via Phase Transfer in the Toluene-Water System and Application of Modified Nanoparticles to Cyclo-Olefin-Polymer-Based Organic-Inorganic Hybrid Films Exhibiting High Refractive Indices", 2017 , ACS Applied Materials & Interfaces, 9, 1907 Pacifica M, 2 outsiders, "UV and visible light active acute dioxide colloids stabled by surfactants", 2014, Dalton Transacts80

However, it is unclear whether or not the metal oxide fine particle dispersion disclosed in Patent Document 1 is dispersed even in an organic solvent. Further, since the metal oxide fine particle dispersion contains "strong acid" in the dispersion liquid, it is considered that the pH of the aqueous solution is strongly acidic. In that case, it is difficult to hybridize with an acid-sensitive resin. Furthermore, it is unclear whether the metal oxide fine particle dispersion will be redispersed even after the solid product has been isolated. Therefore, the metal oxide fine particle dispersion disclosed in Patent Document 1 may be limited in its use as a raw material for hybrid materials.

Since the dispersants disclosed in Non-Patent Documents 1 to 3 contain organic components such as hydrocarbons, there is a problem in terms of heat resistance.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide metal oxide nanoparticles dispersed in both water and an organic solvent and having excellent heat resistance, and a method for producing the same.

The metal oxide nanoparticles according to the first aspect of the present invention are
Particles containing zirconium oxide or titanium oxide,
Conjugate base components of acids containing fluoroalkyl groups present on the surface of the particles,
including.

In this case, the particles are
Contains zirconium oxide,
The molar ratio of the zirconium atom to the conjugate base component is
1: 0.5-0.7,
It may be that.

In addition, the particles are
Contains titanium oxide,
The molar ratio of the titanium atom to the conjugate base component is
1: 0.2 to 0.5,
It may be that.

Further, the metal oxide nanoparticles according to the first aspect of the present invention are
The average particle size is 2-7 nm,
It may be that.

The method for producing metal oxide nanoparticles according to the second aspect of the present invention is as follows.
A reaction step in which a zirconium alkoxide or a titanium alkoxide is hydrolyzed and condensed using an acid containing a fluoroalkyl group contained in a solvent as a catalyst.
A drying step of removing the solvent to obtain a solid product,
A heating step that heats the solid product,
Including
In the reaction step, 1.0 equivalent of the zirconium alkoxide is reacted with 1.0 to 20.0 equivalents of the acid containing the fluoroalkyl group, and 1.0 equivalent of the titanium alkoxide is 1 .0 to 10.0 equivalents of the acid containing the fluoroalkyl group are reacted .

In this case, the acid containing the fluoroalkyl group is
Bis (trifluoromethanesulfonyl) imide,
It may be that.

Further, in the reaction step,
Hydrolyze and condense the zirconium alkoxide with trifluoromethanesulfonic acid or trifluoroacetic acid contained in the solvent as a catalyst.
It may be that.

The metal oxide nanoparticles according to the present invention are dispersed in both water and an organic solvent and have excellent heat resistance.

It is a figure which shows the infrared absorption (IR) spectrum of the ZrO2 nanoparticles synthesized in Example 1. _FIG . It is a figure which shows the energy dispersive X-ray (EDX) spectrum of the ZrO2 nanoparticles synthesized in Example 1. _FIG . It is a figure which shows the IR spectrum of the TiO ₂ nanoparticles synthesized in Example 1. FIG. It is a figure which shows the EDX spectrum of the TIO ₂ nanoparticles synthesized in Example 1. FIG. It is a figure which shows the photograph of the dispersion liquid of the ZrO2 nanoparticles synthesized in Example 1. _FIG . It is a figure which shows the visible-ultraviolet absorption (UV-Vis) spectrum of the dispersion liquid in various solvents of the ZrO2 nanoparticles synthesized in Example 1. _FIG . It is a figure which shows the photograph of the dispersion liquid of the TIO ₂ nanoparticles synthesized in Example 1. FIG. It is a figure which shows the UV-Vis spectrum of the dispersion liquid in the various solvents of the TIO ₂ nanoparticles synthesized in Example 1. FIG. It is a figure which shows the histogram obtained by the dynamic light scattering method (DLS) about the acetone dispersion liquid of the ZrO2 nanoparticles synthesized in Example 1. _FIG . (A) and (c) are diagrams showing the distribution of the scattering intensity of the dispersion liquid having the concentrations of 0.5 w / v% and 1.0 w / v%, respectively. (B) and (d) are diagrams showing the number distribution of dispersions having concentrations of 0.5 w / v% and 1.0 w / v%, respectively. It is a figure which shows the histogram obtained by the DLS about the acetone dispersion liquid of the TIO ₂ nanoparticles synthesized in Example 1. FIG. (A) and (c) are diagrams showing the distribution of the scattering intensity of the dispersion liquid having the concentrations of 0.5 w / v% and 1.0 w / v%, respectively. (B) and (d) are diagrams showing the number distribution of dispersions having concentrations of 0.5 w / v% and 1.0 w / v%, respectively. It is a figure which shows the EDX spectrum of the ZrO2 nanoparticles synthesized in Example ₁ and Example 5. In (a), (b), (c) and (d), zirconium tetra n-butoxide (ZTB) and bis (trifluoromethanesulfonyl) imide (HNTf ₂ ) are added to 1.0, 2.0 and 5.0, respectively. It is a figure which shows the EDX spectrum of the _ZrO2 nanoparticles synthesized by adding 10.0 equivalents. It is a figure which shows the EDX spectrum of the TIO ₂ nanoparticles synthesized in Example 1 and Example 6. (A), (b), (c) and (d) are synthesized by adding 2.0, 3.0, 4.0 and 5.0 equivalents of HNTf ₂ to titanium tetra n-butoxide (TTB), respectively. It is a figure which shows the EDX spectrum of the TIO ₂ nanoparticles.

An embodiment of the present invention will be described. The present invention is not limited to the following embodiments.

(Embodiment)
The metal oxide nanoparticles according to the present embodiment include particles containing ZrO ₂ or TiO ₂ and a conjugate base component of an acid containing a fluoroalkyl group present on the surface of the particles.

More specifically, the particles are nanoparticles containing ZrO ₂ or TiO ₂ . The particles may contain either TiO ₂ or ZrO ₂ or both.

Examples of the acid containing a fluoroalkyl group include bis (fluorosulfonyl) imide, bis (difluorophosphonyl) imide, HNTf ₂ , fluoromethanesulfonic acid, difluoromethanesulfonic acid, trifluoromethanesulfonic acid (TFSA), fluoroacetic acid, and the like. Examples thereof include difluoroacetic acid, trifluoroacetic acid (TFA), hexafluorophosphate and tetrafluoroboric acid.

More specifically, when the acid containing a fluoroalkyl group is HNTf ₂ (chemical formula (CF ₃ SO ₂ ) ₂ NH), the conjugate base component of the acid is represented by the chemical formula (CF ₃ SO ₂ ) ₂ N ⁻ . It is an ingredient.

The presence of a conjugate base component of an acid containing a fluoroalkyl group on the surface of a particle containing ZrO ₂ or TiO ₂ means that the conjugate base component covers at least a part of the particle, or at least one of the conjugate base components. Includes the part exposed from the particles. Preferably, in the metal oxide nanoparticles, at least a part of the conjugate base component is bonded to the molecule contained in the particle and exposed on the particle surface.

The molar ratio of the metal atom of the metal oxide contained in the particles to the conjugate base component is not particularly limited. When the particles contain ZrO ₂ , for example, the molar ratio of the zirconium atom to the conjugate base component is 1: 0.2 to 1, preferably 1: 0.5 to 0.7, and more preferably 1: 0. It is 6.

When the particles contain TiO ₂ , for example, the molar ratio of the titanium atom to the conjugate base component is 1: 0.2 to 1, preferably 1: 0.2 to 0.5, and more preferably 1: 0. It is 3.

The molar ratio of the metal atom of the metal oxide contained in the particles to the conjugate base component can be determined by a known method. Preferably, the molar ratio of metal atom to conjugate base component is determined using EDX.

The average particle size of the metal oxide nanoparticles according to the present embodiment is not particularly limited as long as it is several tens of nm or less, but is, for example, 0.1 to 80 nm, 0.5 to 50 nm, 1 to 30 nm, or 2 to 20 nm. Is. Preferably, the average particle size of the metal oxide nanoparticles is 2 to 7 nm. More specifically, when the particles contain ZrO ₂ , the average particle size of the metal oxide nanoparticles is 1 to 5 nm, preferably 2 to 4 nm. On the other hand, when the particles contain TiO ₂ , the average particle size of the metal oxide nanoparticles is 4 to 7 nm, preferably 5 to 6 nm.

The particle size of the metal oxide nanoparticles can be measured by a known method, for example, a sieving method, a precipitation method, a microscopic method, a light scattering method, a DLS, a laser diffraction / scattering method, an electrical resistance test, or the like. The particle size can be represented by a stalk-equivalent diameter, a circle-equivalent diameter, and a sphere-equivalent diameter, depending on the measurement method. Further, the particle size may be a number average particle size, a volume average particle size, an area average particle size, or the like expressed by averaging a plurality of particles as measurement targets. For example, the number average particle size is an average particle size calculated from a number distribution or the like based on measurements by a laser diffraction / scattering method or the like. Specifically, when the cumulative curve is obtained with the total volume of the powder population as 100%, the 50% diameter ( _D50 ), which is the particle size at the point where the cumulative curve becomes 50%, can be used as the average particle size. good.

Next, an example of a preferable production method for the metal oxide nanoparticles according to the present embodiment will be described. The method for producing metal oxide nanoparticles includes a reaction step, a drying step, and a heating step. In the reaction step, zirconium alkoxide or titanium alkoxide is hydrolyzed and condensed using an acid containing a fluoroalkyl group contained in the solvent as a catalyst.

The zirconium alkoxide is represented by the general formula Zr (OR) ₄ , and is not particularly limited as long as it produces ZrO ₂ by hydrolysis. A part of (OR) in the _formula may be substituted with acetylacetonate _{( C5H7O2} ) or _{ethylacetacetate ( C6H9O3} ). Preferably, the zirconium alkoxide is one in which the R moiety of the alkoxide is a lower (preferably C _1-6 ) alkyl group.

More specifically, as the zirconium alkoxide, zirconium tetraethoxydo, zirconium tetraisopropoxide, ZTB, zirconium tributoxymonoacetylacetate, zirconium dibutoxybis (ethylacetate acetate), zirconium monobutoxyacetylacetonate bis ( Ethylacetacetate) and mixtures thereof. Preferably, the zirconium alkoxide is ZTB.

The titanium alkoxide is represented by the general formula: Ti (OR) ₄ , and is not particularly limited as long as it produces TiO ₂ by hydrolysis. A part of (OR) in the _formula may be substituted with acetylacetonate _{( C5H7O2} ) or _{ethylacetacetate ( C6H9O3} ). Preferably, the titanium alkoxide is one in which the R moiety of the alkoxide is a lower (preferably C _1-6 ) alkyl group.

More specifically, as titanium alkoxide, titanium tetraethoxydo, titanium tetraisopropoxide, titanium tetra n-propoxide, TTB, titanium tetramethoxydo, titanium diisopropoxybis (acetylacetonate), titanium diiso Examples include propoxybis (ethylacetacetate) and mixtures thereof. Preferably, the titanium alkoxide is TTB.

The solvent used in the reaction step is not particularly limited as long as it does not interfere with the hydrolysis and condensation reaction of zirconium alkoxide or titanium alkoxide. For example, a mixed solvent of water and alcohol can be used. Examples of the alcohol of the mixed solvent include alcohols having a short alkyl group such as methanol, ethanol and propanol. When methanol is used as the alcohol, the ratio of water to methanol is 1:15 to 25, 1:18 to 22, preferably 1:19 by volume.

The concentration of the acid containing a fluoroalkyl group is not particularly limited and may be appropriately adjusted, for example, 0.1 to 1 mol / L, 0.2 to 0.8 mol / L, preferably 0.5 mol / L. When a zirconium alkoxide is used, an acid containing, for example, 1.0 to 20.0 equivalents of a fluoroalkyl group is mixed with the zirconium alkoxide. Preferably, the acid containing a fluoroalkyl group with respect to the zirconium alkoxide is 1.0 to 8.0 equivalents, 1.0 to 7.0 equivalents, more preferably 2.0 to 5.0 equivalents.

When zirconium alkoxide is used in the reaction step, HNTf ₂ , TFSA or TFA is particularly preferable as the acid containing a fluoroalkyl group contained in the solvent.

When titanium alkoxide is used, an acid containing, for example, 1.0 to 10.0 equivalents of a fluoroalkyl group is mixed with the titanium alkoxide. Preferably, the acid containing the fluoroalkyl group with respect to the titanium alkoxide is 2.0 to 10.0 equivalents, 3.0 to 8.0 equivalents, more preferably 5.0 to 7.0 equivalents.

When titanium alkoxide is used in the reaction step, HNTf ₂ is particularly preferable as the acid containing a fluoroalkyl group contained in the solvent.

The reaction step is carried out under the condition that the hydrolysis and condensation reaction (that is, the sol-gel reaction) proceeds. For example, an acid containing zirconium alkoxide or titanium alkoxide and a fluoroalkyl group may be stirred at room temperature for a predetermined time, for example, 1 to 6 hours, preferably 1 to 3 hours.

In the drying step, the solvent is removed to give a solid product. In the drying step, the solvent containing the product produced in the reaction step may be appropriately heated in order to promote the removal of the solvent. In this case, for example, the solvent may be heated to 50 to 60 ° C. In the heating step, the product may be further heated to about 150 ° C. after removing the solvent. By doing so, the reaction of the product can be further advanced.

Subsequently, the heating step heats the solid product. As a result, the metal oxide nanoparticles according to the present embodiment can be obtained. In the heating step, the solid product may be heated at 100-200 ° C, preferably 130-180 ° C, preferably 150 ° C. The heating time may be appropriately adjusted, but for example, when heating to 150 ° C., it is about 2 hours.

In addition, in order to remove an acid or the like containing a fluoroalkyl group, the crude product obtained by the drying step is washed with an organic solvent such as chloroform before the heating step, decanted and then dried under reduced pressure. May be good.

As described in detail above, the metal oxide nanoparticles according to the present embodiment are well dispersed in both water and an organic solvent as shown in Example 2 below, and have extremely high transparency. Moreover, since the metal oxide nanoparticles do not contain hydrocarbons, they are excellent in heat resistance.

As shown in Example ₄ , when the metal oxide nanoparticles contain ZrO2, the metal oxide nanoparticles can be redispersed even if precipitation and dispersion are repeated a plurality of times using water, methanol and acetone as solvents. Further, when TiO ₂ is contained, redispersion is possible even if precipitation and dispersion are repeated a plurality of times using acetone as a solvent. Therefore, since the metal oxide nanoparticles according to the present embodiment can be easily redispersed, they can be reused and are advantageous in practical use.

The metal oxide nanoparticles contain ZrO ₂ or TiO ₂ . Since ZrO ₂ and TiO ₂ are materials having a high refractive index, they can be used as materials for light emitting diode (LED) encapsulants, thin lenses, optical fibers, etc. by hybridizing the metal oxide nanoparticles with a transparent resin. .. Further, the metal oxide nanoparticles containing TiO ₂ can also be used as a photocatalyst.

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the examples.

(Example 1: Synthesis of ZrO ₂ nanoparticles and TiO ₂ nanoparticles)
ZrO2 nanoparticles _were synthesized as follows. A solution of HNTf ₂ diluted to 0.5 mol / L with a mixed solvent of water / methanol (1:19, v / v) was added to an 85% ZTB1-butanol solution (0.9028 g, 2.0 mmol) in a 50 mL sample bottle. 5.0 equivalent (20 mL, 10 mmol) was added to ZTB (mol), and the mixture was stirred at room temperature for 1 hour.

Next, the obtained solution was transferred to a disposal tray (manufactured by AS ONE, made of polypropylene containing a filler, 100 mm × 70 mm × 13 mm), heated in an open system (about 50 to 60 ° C.), and the solvent was distilled off. Further, it was heated in an oven at 150 ° C. for 2 hours. Then, the obtained crude product was washed with chloroform, decanted, dried under reduced pressure, and heated again in an oven at 150 ° C. for ₂ hours to obtain ZrO2 nanoparticles (ZrO2 _- NTf2 _- NP) as a product. (0.6237g).

In addition, TiO ₂ nanoparticles were synthesized as follows. TTB (0.6090 g, 2.0 mmol) and 1-butanol (0.1075 g) were mixed with TTB / 1-butanol (85:15, w / w) in a 50 mL sample bottle, and HNTf ₂ water / A solution diluted to 0.5 mol / L with a mixed solvent of methanol (1:19, v / v) was added in an amount of 5.0 equivalents (20 mL, 10 mmol) to TTB (mol), and the mixture was stirred at room temperature for 1 hour.

Subsequently, the obtained solution was transferred to a disposal tray (manufactured by ASONE, made of polypropylene containing a filler, 100 mm × 70 mm × 13 mm), heated in an open system (about 50 to 60 ° C.), and the solvent was distilled off. Further, it was heated in an oven at 150 ° C. for 2 hours. Then, the obtained crude product was washed with chloroform, decanted, dried under reduced pressure, and heated again in an oven at 150 ° C. for 2 hours to obtain TIM ₂ nanoparticles (TIO ₂ -NTf _2- ) as a product. NP) was obtained (0.3050 g).

The structures of ZrO ₂ -NTf ₂ -NP and TiO ₂ -NTf ₂ -NP were confirmed by Fourier transform infrared spectroscopy (FT-IR) and EDX. For the sample for FT-IR measurement, KBr for infrared absorption measurement and a small amount of ZrO2 _- NTf2 _- NP or _TiO2 -NTf2 _- NP are sufficiently ground in an agate mortar, and pressure is applied using a tablet molder. Pellets were used. An FT / IR-4200 type A (manufactured by JASCO Corporation) was used as an FT-IR analytical instrument.

As a sample for EDX measurement, a carbon tape was attached to an aluminum plate, and ZrO2 _- NTf2 _- NP or TIO2 _- NTf2 _- NP was attached thereto. Quanta400 (manufactured by FEI Japan) was used as an EDX analytical instrument.

(result)
FIG. 1 shows the IR spectrum of ZrO2 _- NTf2 _- NP. Absorption peaks derived from the sulfonyl group and trifluoromethyl group of NTf ₂ were observed in the IR spectrum. FIG. 2 shows the EDX spectrum of ZrO2 _- NTf2 _- NP. According to the EDX spectrum, the atomic number ratio of Zr and S was 1.00 to 1.17, and the molar ratio of the Zr atom and the _NTf2 component was about 1: 0.59. From the above results, it was shown that ZrO2 _{- NTf2 -} NP contained an _NTf2 component in addition to ZrO2, even though it was washed with chloroform, which is a good solvent for _HNTf2 .

FIG. 3 shows the IR spectrum of TiO ₂ -NTf ₂ -NP. Absorption peaks derived from the sulfonyl group and trifluoromethyl group of NTf ₂ were observed in the IR spectrum. FIG. 4 shows the EDX spectrum of TiO ₂ -NTf ₂ -NP. According to the EDX spectrum, the atomic number ratio of Ti and S was 1.00 to 0.57, and the molar ratio of the Ti atom and the NTf ₂ component was about 1: 0.29. From the above results, it was shown that TiO _{2-NTf 2-NP contains an NTf 2 component in addition to TiO 2 , even though} it was washed with chloroform, which is a good solvent for HNTf ₂ .

(Example 2: Dispersity evaluation of ZrO2 _- NTf2 _- NP and _TiO2 -NTf2 _- NP)
The dispersibility of ZrO2 _- NTf2 _- NP and _TiO2 -NTf2 _- NP was visually and UV-Vis. ZrO ₂ -NTf ₂ -NP or TiO ₂ -NTf ₂ -NP was added to various solvents at 1.0 w / v%, and the dispersibility was visually evaluated.

In the measurement of UV-Vis, a dispersion liquid (1.0 w / v%) of ZrO2 _- NTf2 _- NP or _TiO2 -NTf2 _- NP as a measurement sample is dropped into a 10 mm square quartz cell in an amount of about 2.5 mL. And measured in the transmittance mode. A V-630 spectrophotometer (manufactured by JASCO Corporation) was used for the measurement of UV-Vis.

(result)
ZrO2 _- NTf2 _- NP showed good dispersibility in water, dimethyl sulfoxide (DMSO), N, N-dimethylformamide (DMF), methanol, ethanol and acetone (see FIG. 5). These dispersions were transparent and slightly orange in color. On the other hand, ZrO2 _- NTf2 _- NP did not show dispersibility in ethyl acetate, chloroform, toluene and hexane.

FIG. 6 shows UV-Vis spectra of ZrO2 _- NTf2 _- NP water, DMSO, DMF, methanol, ethanol and acetone dispersions. Both dispersions showed high transmittance, supporting the high transparency of the dispersions. Furthermore, from the UV-Vis spectra of these dispersions, it was confirmed that light was absorbed in the blue wavelength region, which is the complementary color of orange, which is the color of the dispersions.

TiO ₂ -NTf ₂ -NP showed good dispersibility in water, DMSO, DMF and acetone (see FIG. 7). These dispersions were transparent and slightly orange in color. On the other hand, TIM _{2-NTf 2 -} NP did not show dispersibility in methanol, ethanol, ethyl acetate, chloroform, toluene and hexane.

FIG. 8 shows the UV-Vis spectra of TiO ₂ -NTf ₂ -NP water, DMSO, DMF and acetone dispersions. Both dispersions showed high transmittance, supporting the high transparency of the dispersions. Furthermore, from the UV-Vis spectra of these dispersions, it was confirmed that light was absorbed in the blue wavelength region, which is the complementary color of orange, which is the color of the dispersions. Furthermore, since the light transmittance is almost 0% in the ultraviolet light wavelength region, it was confirmed that TIM ₂ -NTf ₂ -NP has the ultraviolet absorption characteristic characteristic of TiO ₂ .

(Example 3: Evaluation of particle size of ZrO2 _- NTf2 _- NP and _TiO2 -NTf2 _- NP)
The particle sizes of ZrO2 _- NTf2 _- NP and _TiO2 -NTf2 _- NP were evaluated by DLS.

As a sample for DLS measurement, 1 to 1 of ZrO2 _- NTf2 _- NP or _TiO2 -NTf2 _- NP acetone dispersion (0.5 w / v% and 1.0 w / v%) in a 10 mm square quartz cell. The one dropped by about 5 mL was used. As a DLS measuring device, Nano-ZS90 (manufactured by Malvern) was used.

(result)
FIG. 9 shows a DLS histogram for an acetone dispersion of ZrO2 _- NTf2 _- NP. When the number average particle size of ZrO2 _- NTf2 _- NP was determined, it was about 3 nm without depending on the concentration of the dispersion liquid (see FIGS. 9 (b) and 9 (d)). From the distribution of the scattering intensity shown in FIGS. 9 (a) and 9 (c), aggregates of less than 100 nm were formed, but in the number distribution shown in FIGS. 9 (b) and 9 (d), the number of the aggregates was large. It was shown to be very few. From this, it is considered that the acetone dispersion of ZrO2 _- NTf2 _- NP has high transparency.

FIG. 10 shows a DLS histogram for an acetone dispersion of TiO ₂ -NTf ₂ -NP. When the number average particle size of TiO ₂ -NTf ₂ -NP was determined, it was about 6 nm without depending on the concentration of the dispersion liquid (see FIGS. 10 (b) and 10 (d)). From the distribution of the scattering intensity shown in FIGS. 10 (a) and 10 (c), agglomerates of about 130 nm were formed, but in the number distribution shown in FIGS. 10 (b) and 10 (d), the number of the agglomerates was large. It was shown to be very few. From this, it is considered that the acetone dispersion of TiO ₂ -NTf ₂ -NP has high transparency.

(Example 4: Examination of redispersibility of ZrO2 _- NTf2 _- NP and _TiO2 -NTf2 _- NP)
Precipitation and dispersion were repeated 3 times with ZrO2 _- NTf2 _- NP aqueous dispersion, methanol dispersion and acetone dispersion (all 1.0 w / v%) to examine whether redispersion was possible. did. Further, the redispersion of the aqueous dispersion of _TiO2 -NTf2 _- NP and the acetone dispersion (1.0 w / v%) was also examined in the same manner.

(result)
ZrO2 _- NTf2 _- NP showed good dispersibility in all dispersions even after the third dispersion. On the other hand, regarding TiO ₂ -NTf ₂ -NP, the aqueous dispersion became cloudy when precipitation and dispersion were repeated once, but the acetone dispersion had good dispersibility even when precipitation and dispersion were repeated three times. Indicated.

(Example 5: Examination of the effect of equivalent variation on the dispersibility of ZrO2 _- NTf2 _- NP and the coverage of _NTf2 components)
1.0 equivalent (4 mL, 2 mmol) and 2.0 equivalent (8 mL) of the HNTf ₂ solution (0.5 mol / L) added to ZTB (2.0 mmol) in the synthesis of ZrO ₂ -NTf ₂ -NP of Example 1 above. 4 mmol) and 10.0 equivalents (40 mL, 20 mmol) were used to synthesize ZrO ₂ -NTf ₂ -NP in the same manner as in Example 1. The dispersibility of the obtained ZrO2 _- NTf2 _- NP was evaluated. In addition, the structure of ZrO2 _- NTf2 _- NP was confirmed by EDX.

(result)
In addition to the ZrO ₂ -NTf ₂ -NP synthesized in Example 1 (5.0 equivalents of HNTf ₂ to ZTB), the dispersibility of ZrO ₂ -NTf ₂ -NP synthesized at each equivalent examined in this example was obtained. It is shown in Table 1. From this result, it was shown that a certain degree of dispersibility was maintained even if the equivalent was reduced.

11 (a) to 11 (d) show EDX spectra of ZrO2 _- NTf2 _- NP synthesized at 1.0, 2.0, 5.0 and 10.0 equivalents, respectively. Even if the equivalent amount was changed, the coverage with the NTf ₂ component hardly changed, and it was shown that the molar ratio of the Zr atom and the NTf ₂ component was about 1: 0.52 to 0.56.

(Example 6: Examination of the effect of equivalent variation on the dispersibility of TiO ₂ -NTf ₂ -NP and the coverage of NTf ₂ components)
2.0 equivalents (8 mL, 4 mmol) and 3.0 equivalents (12 mL) of the HNTf ₂ solution (0.5 mol / L) added to TTB (2.0 mmol) in the synthesis of TiO ₂ -NTf ₂ -NP of Example 1 above. , 6 mmol) and 4.0 equivalents (16 mL, ₈ mmol) were synthesized in the same manner as in Example ₁ . The dispersibility of the obtained TiO ₂ -NTf ₂ -NP was evaluated. In addition, the structure of TiO ₂ -NTf ₂ -NP was confirmed by EDX.

(result)
In addition to the TiO ₂ -NTf ₂ -NP synthesized in Example 1 (5.0 equivalents of HNTf ₂ with respect to TTB), the dispersibility of the TiO ₂ -NTf ₂ -NP synthesized at each equivalent examined in this example was obtained. It is shown in Table 2. From this result, it was found that the dispersibility decreased when the equivalent was reduced.

12 (a) to 12 (d) show EDX spectra of TiO ₂ -NTf ₂ -NP synthesized at 2.0, 3.0, 4.0 and 5.0 equivalents, respectively. When the amount of HNTf ₂ with respect to TTB was reduced, the coverage with the NTf ₂ component decreased. From the above results, in order to maintain excellent dispersibility, the molar ratio of the Ti atom to the NTf ₂ component must be at least about 1: 0.29, and if the NTf ₂ component is less than this, the dispersion is excellent. It was shown that sex was not obtained.

(Example 7: Examination of the effect of trifluoromethyl group on dispersibility)
It was examined whether the presence or absence of the trifluoromethyl group affects the dispersibility of the nanoparticles synthesized in Example 1. Similar to Example 1, ZTB (0.9028 g, 2 mmol) or TTB (0.6090 g, 2 mmol) in a 50 mL sample bottle with TFSA, TFA or hydrochloric acid (HCl) water / methanol (1:19, v /). v) Add 5.0 equivalents (20 mL, 10 mmol) to ZTB or TTB (mol) of a solution diluted to 0.5 mol / L with a mixed solvent, and carry out a sol-gel reaction to carry out ZrO2 _- NP and TIO. ₂ -NP was obtained.

(result)
The dispersibility of ZrO ₂ -NP and TiO ₂ -NP in each solvent was evaluated by visual observation. Table 3 shows the dispersibility of ZrO ₂ -NP and TiO ₂ -NP. From this result, in ZrO ₂ , not only HNTf ₂ but also TFSA and TFA showed dispersibility, while HCl did not show dispersibility, so the presence of trifluoromethyl group was a product. It turned out to be important for the dispersion of. In TiO ₂ , HNTf ₂ showed dispersibility, but when TFSA, TFA and HCl were used, it did not show dispersibility, so that HNTf ₂ specifically affects the dispersibility of the product. all right.

The embodiments described above are for the purpose of explaining the present invention and do not limit the scope of the present invention. That is, the scope of the present invention is shown not by the embodiment but by the scope of claims. And various modifications made within the scope of the claims and within the equivalent meaning of the invention are considered to be within the scope of the present invention.

The present invention is suitable for producing metal oxide nanoparticles that are stably dispersed in various solvents.

Claims (7)

Particles containing zirconium oxide or titanium oxide,
Conjugate base components of acids containing fluoroalkyl groups present on the surface of the particles,
Including metal oxide nanoparticles. The particles are
Contains zirconium oxide,
The molar ratio of the zirconium atom to the conjugate base component is
1: 0.5-0.7,
The metal oxide nanoparticles according to claim 1. The particles are
Contains titanium oxide,
The molar ratio of the titanium atom to the conjugate base component is
1: 0.2 to 0.5,
The metal oxide nanoparticles according to claim 1. The average particle size is 2-7 nm,
The metal oxide nanoparticles according to any one of claims 1 to 3. A reaction step in which a zirconium alkoxide or a titanium alkoxide is hydrolyzed and condensed using an acid containing a fluoroalkyl group contained in a solvent as a catalyst.
A drying step of removing the solvent to obtain a solid product,
A heating step that heats the solid product,
Including
In the reaction step, 1.0 equivalent of the zirconium alkoxide is reacted with 1.0 to 20.0 equivalents of the acid containing the fluoroalkyl group, and 1.0 equivalent of the titanium alkoxide is 1 Reacting an acid containing 0.0 to 10.0 equivalents of the fluoroalkyl group,
Method for producing metal oxide nanoparticles. The acid containing a fluoroalkyl group is
Bis (trifluoromethanesulfonyl) imide,
The method for producing metal oxide nanoparticles according to claim 5. In the reaction step,
Hydrolyze and condense the zirconium alkoxide with trifluoromethanesulfonic acid or trifluoroacetic acid contained in the solvent as a catalyst.
The method for producing metal oxide nanoparticles according to claim 5.

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