Composite particles

Abstract

The present invention relates to composite particles comprising nanoparticles dispersed in a metal oxide matrix comprising alumina and zirconia.

Description

TECHNICAL FIELD

[0001] The present invention relates to composite particles comprising nanoparticles dispersed in a metal oxide matrix comprising zirconium oxide and optionally aluminum oxide. BACKGROUND

[0002] Semiconductor nanocrystals, commonly referred to as "quantum dots", are widely recognized as emissive materials. Their narrow fluorescence spectrum, full width at half maximum of about 30 nm, saturated color, and the possibility of tuning their fluorescence throughout the visible and infrared range make them an excellent candidate material for integration into displays as phosphors. Such semiconductors are also very efficient and selective high-pass filters. Indeed, the absorption is high for high-energy wavelengths, i.e. short wavelengths. Conversely, the absorption is low for low-energy wavelengths, i.e. long wavelengths. The transition between the two zones of high and low absorbance is generally steep, and the transition wavelength is determined by the electronic properties of the semiconductor nanocrystal.

[0003] However, quantum dots suffer from oxidative damage when exposed to air and humidity, which often leads to a sharp decrease in photoluminescence quantum yield (PLQY) or a degradation of the filtering performance. The use of quantum dots in light conversion layers tends to expose the quantum dots to high temperatures, high light intensities and high light fluxes, and / or to harmful substances in the environment, such as water or oxygen.

[0004] To ensure high long-term stability, further chemical reactions between the surface of the nanoparticles and harmful substances in the environment, such as water, oxygen or other harmful compounds, must be prevented during use. However, ligands commonly used to functionalize the surface of quantum dots do not effectively protect the surface from reactions with harmful substances or harmful compounds, and thus do not meet the required long-term performance.

[0005] In particular, the nanoparticles should exhibit high stability in terms of time and temperature under high photon flux. By stability, it is meant, for example, that the PLQY remains stable during use, or that the nanoparticles do not undergo photobleaching. This performance is particularly required for displays or lighting devices, such as diodes, light-emitting diodes (LEDs) or organic light-emitting diodes (OLEDs).

[0006] It is known to prevent harmful substances or harmful compounds from reaching the surface of inorganic nanoparticles by coating them with a protective shell. Silica is known to be an insulating protective material for inorganic nanoparticles. However, a shell consisting essentially of silica is not entirely satisfactory.

[0007] It is therefore an object of the present invention to provide composite particles having enhanced resistance to photobleaching, enhanced resistance to light flux, or enhanced stability under the action of temperature, environmental changes or harmful substances such as water and oxygen or other harmful compounds. Surprisingly, embedding the nanoparticles in a matrix comprising a mixture of aluminum oxide and zirconium oxide is particularly effective in preventing the degradation of the nanoparticles. SUMMARY

[0008] The present disclosure thus relates to composite particles comprising nanoparticles dispersed in a matrix, wherein:

[0009] - the nanoparticles (1) are semi-conductive nanoparticles; and

[0010] - the matrix is a metal oxide compound of the following formula

[0011] Al x Zr y M z O (I)

[0012] wherein M represents one or more than one metal element selected from Si, Ti, Hf, Ge, Sn or mixtures thereof;

[0013] wherein x, y and z represent the stoichiometric ratios of aluminum, zirconium and other metal elements, respectively;

[0014] x is from 0 to 3 / 5;

[0015] y is from 1 / 20 to 1 / 2; and

[0016] z is from 0 to 2 / 5, provided that when z is zero, (3 / 2x + 2y) = 1.

[0017] The present disclosure also relates to composite particles comprising nanoparticles dispersed in a matrix, wherein:

[0018] - the nanoparticles (1) are semi-conductive nanoparticles; and

[0019] - the matrix is a metal oxide compound of the following formula

[0020] Al x Zr y O (I)

[0021] wherein x and y represent the stoichiometric ratios of aluminum and zirconium, respectively;

[0022] x is from 0 to 3 / 5;

[0023] y is from 1 / 20 to 1 / 2; and (3 / 2x + 2y) = 1.

[0024] In an embodiment, x is from 1 / 20 to 8 / 15 and y is from 1 / 10 to 37 / 80. In a preferred embodiment, x is from 1 / 10 to 8 / 15 and y is from 1 / 10 to 17 / 40.

[0025] In an embodiment, the matrix further comprises a metal element selected from Si, Ti, Hf, Ge, Sn or mixtures thereof, in a concentration of 0.1 at.% to 15 at.%.

[0026] In an embodiment, the loading of nanoparticles in the composite particles is at least 1 %, preferably at least 2.5 %, more preferably at least 5 %, the loading being the mass ratio between the mass of nanoparticles comprised in the composite particles and the mass of the composite particles.

[0027] In an embodiment, more than 95 wt% of the nanoparticles in the composite particles are dispersed in the inner part of the composite particles, wherein the composite particles consist of an inner part surrounded by an outer layer, the outer layer covering the entire inner part; the outer layer represents less than 10 wt% of the weight of the composite particles and the thickness of the outer layer is greater than 5 nm or equal to 5 nm, preferably greater than 15 nm or equal to 15 nm.

[0028] In an embodiment, the nanoparticles are homogeneously dispersed in the matrix.

[0029] In an embodiment, alumina and zirconia represent more than 90 wt% of the matrix.

[0030] In an embodiment, the nanoparticles are III-V semiconducting nanoparticles, preferably phosphide quantum dots, preferably selected from InP quantum dots, Cd3P2quantum dots, Zn3P2quantum dots, AlP quantum dots, GaP quantum dots, TlP quantum dots. In another embodiment, the nanoparticles are I-III-VI2ternary semiconducting nanoparticles, preferably selected from CuInS2quantum dots, CuInSe2quantum dots, AgInS2quantum dots, AgInSe2quantum dots. In another embodiment, the nanoparticles are II-VI semiconducting nanoparticles, preferably selected from CdSe quantum dots, CdSeS quantum dots, ZnSe quantum dots, ZnSeS quantum dots. In another embodiment, the nanoparticles are selected from CuInZnS, CuInZnSe. Mixtures of various semiconducting nanoparticles can be embedded in the composite particles.

[0031] In embodiments, the nanoparticles are semiconducting heterostructure nanoparticles having a core selected from the group consisting of InP, Cd3P2, Zn3P2, AlP, GaP, TIP, CuInS2, CuInSe2, AgInS2, AgInSe2, CdSe, CdSeS, ZnSe, ZnSeS, CuInZnS, CuInZnSe. Mixtures of various semiconducting nanoparticles can be embedded in the composite particles.

[0032] In embodiments, the composite particles comprise nanoparticles selected from the group consisting of InP / ZnS quantum dots, InP / ZnSe quantum dots, InP / ZnSe x S( 1-x ) quantum dots, InP / CdS / ZnS quantum dots, InP / ZnSe / ZnS quantum dots, InP / ZnSe x S (1-x ) quantum dots, CuInS2quantum dots, CuInSe2quantum dots, AgInS2quantum dots, AgInSe2quantum dots, CdSe / CdS / ZnS quantum dots, CdSe x S( 1-x ) / CdS / ZnS quantum dots, CdSe / ZnSe / ZnS quantum dots, CdSe / ZnSe x S( 1-x ) / ZnS quantum dots, CdSe x S( 1-x ) / ZnSe / ZnS quantum dots, Cd x Zn( 1-x ) Se / ZnSe / ZnS quantum dots or mixtures thereof. Mixtures of various semiconducting nanoparticles can be embedded in the composite particles.

[0033] The present disclosure also relates to a method of preparing a composite particle as disclosed above, wherein the metal oxide matrix is obtained by hydrolysis of an aluminum alkoxide, a zirconium alkoxide and optionally other metal alkoxides.

[0034] The present disclosure also relates to a light conversion element comprising:

[0035] - a plurality of composite particles as disclosed above, the composite particles comprising fluorescent nanoparticles; and

[0036] - a polymeric matrix in which the plurality of composite particles is dispersed.

[0037] In embodiments, the amount of composite particles in the polymeric matrix is from 0.05 to 20% by weight, based on the weight of the light conversion element.

[0038] The present disclosure also relates to a display comprising a light conversion element as disclosed above.

[0039] This disclosure also relates to light-emitting diodes that include light-converting elements as disclosed above.

[0040] This disclosure also relates to the use of the light conversion element as disclosed above in a display, a light-emitting diode or an organic light-emitting diode.

[0041] definition

[0042] In this invention, the following terms have the following meanings:

[0043] "Atomic %" refers to the atomic percentage of an element in a compound. In this disclosure, the atomic percentage of the metal element in the metal oxide matrix is ​​given without considering oxygen. For example, Al₂O₃ contains 100 atomic % aluminum because no other metal elements are present in the metal oxide.

[0044] "Weight %" refers to the percentage by weight of a compound in a formulation or the percentage by weight of an element in a compound.

[0045] "Core / shell" refers to a heterogeneous nanostructure comprising an inner portion (core) and a film or layer (shell) of at least one atom-thickness material different from the core covering all or part of the core's surface. A core / shell structure is represented as: core material / shell material. For example, a particle comprising a CdSe core and a ZnS shell is denoted as CdSe / ZnS. By extension, a core / shell / shell structure is defined as a core / a first shell structure comprising a film or layer of material different from the core covering all or part of the core's surface and / or a material different from the first shell (second shell). For example, a particle comprising a CdSe core, a CdS first shell, and a ZnS second shell is denoted as CdSe / CdS / ZnS. Core / shell nanostructures also include nanoparticles in which a material layer (shell)—embedded or encapsulated—is arranged on the core, and the shell has a compositional gradient from the core to the outside of the shell. In this case, the composition of the nanoparticle smoothly—e.g., continuously—changes from the core composition—e.g., CdSe—to the outer shell composition—e.g., ZnS. There is no precise boundary between the core and the shell, but the properties at the core center differ from those at the outer boundary of the shell. Furthermore, the core and shell can have different shapes; for example, dot-like structures—nanospheres, nanocubes, or any other nanoclusters—are provided as the core, while the shell grows laterally around the core, creating a heterogeneous structure with a nanoplate shape but containing dots within the nanoplate portion.

[0046] "Doping" refers to a material composition having a crystal structure—a core or a shell—in which a dopant element replaces the main element. Such a composition is hereinafter referred to as QD:dopant. For example, ZnSe quantum dots can be doped with manganese (Mn), such that some Zn is replaced by Mn, and is denoted as ZnSe:Mn.

[0047] "Encapsulation" refers to the state in which a material or matrix covers, surrounds, embeds, contains, includes, wraps, packages, or closes multiple particles, which can be nanoparticles (1) or composite particles (2).

[0048] "Fluorescence" refers to the property of a material to emit light after being excited by absorbing light. In fact, light absorption drives the material into an excited state, which eventually relaxes by emitting lower-energy (i.e., longer-wavelength—redshifted) light.

[0049] "Loading weight" refers to the mass ratio between the mass of the particles contained in the formulation and the mass of the formulation. For clarity, a loading weight of 10g particles mixed with 90g matrix is ​​defined as 10%.

[0050] "Average size" refers to the size of a swarm of particles, obtained by mathematically averaging the size of each individual particle in the swarm. In practice, the average size can be determined using electron microscopy: by fitting each visible particle in the microscope to a circle whose diameter defines the particle size, the average size is obtained by calculating the average of all individual sizes. Other methods, such as light scattering, can be used to indirectly determine the average size of a swarm of particles. Experimentally, particles are always obtained in the form of swarms. By extension in this disclosure, the average size of particles is the average size of a synthesized swarm of particles. For clarity, particles with an average size of 100 nm to 250 nm represent swarms of particles with an average size of 100 nm to 250 nm.

[0051] "Monodisperse" refers to a group of particles with a polydispersity index (PDI) of size distribution of less than 0.3, preferably less than 0.2.

[0052] "Nanoscale" refers to the size of a substance in which at least one physical property is directly determined by its size. For semiconductive nanoparticles, the nanoscale must be defined by the average Bohr radius of electron / hole pairs in the material, where quantum effects arise due to confinement. For the semiconductive materials disclosed herein, quantum effects occur when the size of the object in at least one dimension is less than 20 nm, preferably less than 10 nm, and more preferably less than 5 nm. For conductive particles, the nanoscale must be defined according to the resonance of the free electron gas density oscillation, which becomes relevant for optical measurements. In the range of 380 nm to 3 µm, for the conductive materials disclosed herein, the size of the object in at least one dimension is less than 20 nm.

[0053] "Nanoparticle" refers to a particle with at least one dimension of 0.1 nanometers to 100 nanometers. Nanoparticles can have any shape. Nanoparticles can be single particles or aggregates of multiple single particles, or composite particles containing single particles dispersed in a matrix. Single particles can be crystals. Single particles can have a core / shell or plate / crown structure.

[0054] "Nanoplate" refers to nanoparticles with a two-dimensional shape, that is, one dimension is smaller than the other two dimensions; the smaller dimension ranges from 0.1 nanometers to 100 nanometers. In the context of this invention, the smallest dimension (hereinafter referred to as thickness) is at least 1.5 times smaller (aspect ratio) than the other two dimensions (hereinafter referred to as length and width).

[0055] "PLQY" refers to photoluminescence quantum yield, which is the ratio of the number of fluorescent photons to the number of excited photons.

[0056] "Range" refers to the range of values. The lower and upper limits of the range are included within it.

[0057] "Semiconductive nanoparticles" refer to particles made of materials with an electronic structure corresponding to that of known semiconductive materials in the electronics industry, but at a nanoscale. Due to their specific electronic structure, semiconductive materials behave as high-pass absorbers. In fact, light with wavelengths higher than the band gap energy can be absorbed by semiconductive materials, generating electron / hole pairs, excitons, which subsequently recombine within the material and dissipate heat, or emit light, or both. Conversely, light with wavelengths lower than the band gap energy cannot be absorbed: semiconductive materials are transparent to these wavelengths. In macroscopic semiconductive materials, visible light is typically absorbed, while near / mid-infrared light is not. When semiconductive particles are nanoscale, the constraints—i.e., shape and nanoscale size—determine the electronic structure according to the rules of quantum mechanics, and light absorption may be limited to the ultraviolet range or both ultraviolet and high-energy visible light. Detailed Implementation

[0058] This disclosure relates to composite particles (2) comprising nanoparticles (1) dispersed in a matrix. The nanoparticles (1) are semi-conductive nanoparticles. The matrix is ​​a metal oxide compound comprising zirconium oxide and optionally aluminum oxide.

[0059] The composite particles (2) of the present invention can be used in a variety of applications, such as bioassays, filters, films, anti-counterfeiting marks, LEDs, or any application in which the composite particles are exposed to humidity.

[0060] Semiconductive nanoparticles

[0061] In this disclosure, the semiconductive nanoparticles can be any kind of semiconductive material prepared in the form of nanoparticles (1).

[0062] Suitable semiconductive nanoparticles can be selected from fluorescent semiconductive nanoparticles known as quantum dots, which can have different compositions, shapes and structures.

[0063] Quantum dot composition

[0064] In one embodiment, the quantum dot comprises a material of the following formula:

[0065] M x Q y E z A w (II)

[0066] Where M is selected from Zn, Cd, Hg, Cu, Ag, Au, Ni, Pd, Pt, Co, Fe, Ru, Os, Mn, Tc, Re, Cr, Mo, W, V, Nd, Ta, Ti, Zr, Hf, Be, Mg, Ca, Sr, Ba, Al, Ga, In, Tl, Si, Ge, Sn, Pb, As, Sb, Bi, Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Cs, or mixtures thereof; Q is selected from Zn, Cd, Hg, Cu, Ag, Au, Ni, Pd, Pt, Co, Fe, Ru. Os, Mn, Tc, Re, Cr, Mo, W, V, Nd, Ta, Ti, Zr, Hf, Be, Mg, Ca, Sr, Ba, Al, Ga, In, Tl, Si, Ge, Sn, Pb, As, Sb, Bi, Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Cs or mixtures thereof; E is selected from O, S, Se, Te, C, N, P, As, Sb, F, Cl, Br, I or mixtures thereof; A is selected from O, S, Se, Te, C, N, P, As, Sb, F, Cl, Br, I or mixtures thereof. x, y, z, and w are independently decimal numbers from 0 to 5; x, y, z, and w are not simultaneously equal to 0; x and y are not simultaneously equal to 0; z and w are not simultaneously equal to 0.

[0067] In particular, quantum dots can contain formula M x E y The material is M, where M is Zn, Cd, Hg, Cu, Ag, Al, Ga, In, Si, Ge, Pb, Sb or a mixture thereof; E is O, S, Se, Te, N, P, As or a mixture thereof. x and y are independently decimal numbers from 0 to 5, provided that x and y are not both 0.

[0068] In specific implementation schemes, quantum dots comprise materials selected from the group consisting of: CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, HgS, HgSe, HgTe, HgO, GeS, GeSe, GeTe, SnS, SnSe, SnTe, PbS, PbSe, PbTe, GeS2, GeSe2, SnS2, SnSe2, CuInS2, CuInSe2, CuInZnS, CuInZnSe, AgInS2, AgInSe2, CuS, Cu2S, Ag2S, Ag2Se, Ag2Te, FeS, FeS2, InP, Cd3P2, Zn3P2, CdO, Zn O, FeO, Fe2O3, Fe3O4, Al2O3, TiO2, MgO, MgS, MgSe, MgTe, AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, InN, InP, InAs, InSb, InAsP, TlN, TlP, TlAs, TlSb, MoS2, PdS, Pd4S, WS2, CsPbCl3, PbBr3, CsPbBr3, CH3NH3PbI3, CH3NH3PbCl3, CH3NH3PbBr3, CsPbI3, FAPbBr3, FAPbI3 (where FA represents formamidin), or mixtures thereof.

[0069] In one embodiment, the quantum dots are doped with at least one transition metal, such as Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Dd, Cr, Mo, W, Sg, Mn, Tc, Re, Bh, Fe, Ru, Os, Hs, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, or Au. Preferably, the quantum dots are doped with Mg, Mn, Al, Cu, Te, or Ag. In particular, ZnSe quantum dots doped with Mn:ZnSe:Mn, ZnSe quantum dots doped with Al:ZnSe:Al, or ZnSe quantum dots doped with Mg:ZnSe:Mg are suitable. The amount of dopant is preferably less than 10% by weight. A doping dose of 5% by weight or 2% by weight is suitable.

[0070] Quantum dot shape

[0071] In one implementation, quantum dots can have different shapes, provided that they exhibit nanoscale dimensions that lead to quantum confinement in nanoparticles.

[0072] Quantum dots can have nanoscale dimensions in three dimensions, allowing for quantum confinement in all three spatial dimensions. Such quantum dots are, for example, nanocubes or nanospheres.

[0073] Quantum dots can have nanoscale dimensions in two dimensions and even larger dimensions in the third: quantum confinement exists in two spatial dimensions. Such quantum dots are, for example, nanorods, nanowires, or nanorings.

[0074] Quantum dots can have a nanoscale size in one dimension and be larger in others: the quantum confinement exists only in one spatial dimension. Such quantum dots are, for example, nanoplates, nanosheets, nanoribbons, or nanodisks. Nanoplates are particularly interesting in this disclosure because their absorption cross-section—that is, the efficiency of capturing incident photons on a quantum dot—is ten times greater than that of nanospheres emitting the same wavelength with the same composition and structure. This higher cross-section significantly improves the sensitivity of measurements. Furthermore, compared to spherical quantum dots, nanoplates exhibit a narrower FWHM emission spectrum—typically below 40 nm—and a shorter photoluminescence decay time—approximately an order of magnitude.

[0075] The exact shape of a quantum dot determines its confinement properties, which in turn determine its electronic and optical properties.

[0076] Quantum dot structure

[0077] In the implementation scheme, the quantum dots are homogeneous. Homogeneous structure means that the quantum dots are uniform and have the same local composition throughout their entire volume. Homogeneous spherical quantum dots, such as... Figure 1 As shown in Figure A.

[0078] In an alternative implementation, the quantum dot is a heterogeneous structure. A heterogeneous structure means that the quantum dot consists of several sub-volumes, each with a composition different from its neighboring sub-volumes. In a specific implementation, all sub-volumes have a composition defined by equation (II) above, but with different parameters, namely elemental composition and stoichiometry.

[0079] An example of a heterostructure is a core / shell nanoparticle, where the core (11) has any of the shapes described above. The shell (12) is a layer that covers all or part of the core. A specific example of a core / shell heterostructure is a multilayer structure comprising a core (11) and several consecutive shells (12, 13). For convenience, these multilayer heterostructures are also referred to as core / shell below. The core (11) and shells (12, 13) can have the same shape—e.g., a sphere within a sphere—or different shapes—e.g., a sphere within a plate. Core / shell spherical nanoparticles such as Figure 1 As shown in B. Core / shell / shell spherical nanoparticles, such as Figure 1 As shown in C. The nanoparticles in the sphere's middle plate are as follows... Figure 1 As shown in D—also known as a point plate. Core / shell nanoplates, such as... Figure 1 As shown in E.

[0080] Another example of a heterostructure is the core / crown nanoparticle, where the core has any of the shapes described above. The crown is a band of material arranged around the core. This heterostructure is particularly useful when the core is a nanoplate and the crown is arranged at the edge of the nanoplate. Core / crown nanoplates, such as... Figure 1 As shown in F.

[0081] These heterostructures can have a compositional gradient from the core to the outer shell, resulting in no precise boundary between the core and the shell, but the properties at the core center differ from those at the outer shell boundary.

[0082] In the configuration, nanoparticle (1) is a group II-VI semiconducting nanoparticle containing a cadmium-, sulfur-, and selenium-based core, and selected from:

[0083] ·CdSe / CdS, CdSe / CdS / ZnS, CdSe / CdS / ZnSe, CdSe / CdS / ZnSe y S( 1-y CdSe / ZnSe / ZnS, CdSe / ZnSe x S( 1-x ) / ZnS、

[0084] ·CdSe x S( 1-x ) / ZnS、CdSe x S (1-x ) / ZnSe、CdSe x S( 1-x ) / ZnSe y S( 1-y ),CdSe x Te( 1-x ) / ZnS、CdSe x Te( 1-x ) / ZnSe、

[0085] ·CdSe / Cd y Zn( 1-y S、CdSe / Cd y Zn( 1-y S / ZnS, CdSe / Cd y Zn( 1-y S / ZnSe, CdSe / Cd y Zn( 1-y )S / ZnSe z S( 1-z )

[0086] ·CdSe / Cd y Zn( 1-y Se, CdSe / Cd y Zn(1-y )Se / ZnS、CdSe / Cd y Zn( 1-y )Se / ZnSe、CdSe / Cd y Zn( 1-y )Se / ZnSe z S( 1-z )、

[0087] ·CdSe x S( 1-x ) / CdS、CdSe x S( 1-x ) / CdS / ZnS、CdSe x S( 1-x ) / CdS / ZnSe、CdSe x S( 1-x ) / CdS / ZnSe y S( 1-y )、

[0088] ·CdSe x S( 1-x ) / Cd y Zn( 1-y )S、CdSe x S( 1-x ) / Cd y Zn( 1-y )S / ZnS、CdSe x S( 1-x ) / Cd y Zn( 1-y )S / ZnSe、CdSe x S( 1-x ) / Cd y Zn( 1-y )S / ZnSe z S( 1-z )、

[0089] ·CdSe x S( 1-x ) / Cd y Zn( 1-y )Se、CdSe x S( 1-x ) / Cd y Zn( 1-y )Se / ZnS、CdSe x S( 1-x ) / Cd y Zn( 1-y )Se / ZnSe、CdSe x S( 1-x ) / Cd y Zn(1-y )Se / ZnSe z S( 1-z );

[0090] Where x, y, and z are rational numbers from 0 (excluding) to 1 (excluding), and light is emitted through fluorescence. The emitted light is typically centered on a band within the visible light range of 380 nm to 780 nm. The emitted light typically has a full width at half maximum (FWHM) of less than 50 nm, preferably less than 30 nm, and more preferably less than 20 nm.

[0091] In the configuration, nanoparticle (1) is a group II-VI semiconducting nanoparticle containing a zinc, sulfur, and selenium-based core, and selected from:

[0092] ·ZnSe / ZnS, ZnSe / ZnSe y S( 1-y ZnTe / ZnSe y S( 1-y )

[0093] ·ZnSe x S( 1-x ) / ZnS、ZnSe x S( 1-x ) / ZnSe、ZnSe x S( 1-x ) / ZnSe y S( 1-y ), ZnSe x Te( 1-x ) / ZnS、ZnSe x Te( 1-x ) / ZnSe、ZnSe x Te( 1-x ) / ZnSe x S( 1-x ),

[0094] ·ZnSe / Cd y Zn( 1-y S、ZnSe / Cd y Zn( 1-y )S / ZnS、ZnSe / Cd y Zn( 1-y S / ZnSe, ZnSe / Cd y Zn( 1-y )S / ZnSe z S( 1-z )

[0095] ·ZnSe / Cd y Zn( 1-y Se, ZnSe / Cd y Zn(1-y )Se / ZnS、ZnSe / Cd y Zn( 1-y )Se / ZnSe、ZnSe / Cd y Zn( 1-y )Se / ZnSe z S( 1-z )、

[0096] ·ZnSe x S( 1-x ) / ZnS、ZnSe x S( 1-x ) / ZnS / ZnSe、ZnSe x S( 1-x ) / ZnS / ZnSe y S( 1-y )、

[0097] ·ZnSe x S( 1-x ) / Cd y Zn( 1-y )S、ZnSe x S( 1-x ) / Cd y Zn( 1-y )S / ZnS、ZnSe x S( 1-x ) / Cd y Zn( 1-y )S / ZnSe、ZnSe x S( 1-x ) / Cd y Zn( 1-y )S / ZnSe z S( 1-z )、

[0098] ·ZnSe x S( 1-x ) / Cd y Zn( 1-y )Se、ZnSe x S( 1-x ) / Cd y Zn( 1-y )Se / ZnS、ZnSe x S( 1-x ) / Cd y Zn( 1-y )Se / ZnSe、ZnSe x S( 1-x ) / Cd y Zn( 1-y )Se / ZnSe z S(1-z );

[0099] Where x, y, and z are rational numbers from 0 (excluding) to 1 (excluding), and light is emitted through fluorescence. The emitted light is typically centered on a band in the visible light range of 380 nm to 780 nm. The emitted light typically has a full width at half maximum (FWHM) of less than 50 nm, preferably less than 30 nm, and more preferably less than 20 nm.

[0100] In the configuration, nanoparticle (1) is a group II-VI semiconducting nanoparticle containing a core based on zinc, cadmium, sulfur, and selenium, and selected from:

[0101] ·Cd w Zn( 1-w Se / CdS, Cd w Zn( 1-w Se / CdS / ZnS, Cd w Zn( 1-w Se / ZnSe / ZnS, Cd w Zn( 1-w Se / CdS / ZnSe、Cd w Zn( 1-w )Se / CdS / ZnSeyS( 1-y ),

[0102] ·Cd w Zn( 1-w )Se x S( 1-x ) / ZnS、Cd w Zn( 1-w )Se x S( 1-x ) / ZnSe、Cd w Zn( 1-w )Se x S( 1-x ) / ZnSe y S( 1-y Cd w Zn( 1-w )Se x Te( 1-x ) / ZnS、Cd w Zn( 1-w )Se x Te( 1-x ) / ZnSe、

[0103] ·Cd w Zn( 1-w )Se / Cd y Zn( 1-y S、Cd w Zn(1-w )Se / Cd y Zn( 1-y )S / ZnS, Cd w Zn( 1-w )Se / Cd y Zn( 1-y )S / ZnSe, Cd w Zn( 1-w )Se / Cd y Zn( 1-y )S / ZnSe z S( 1-z )

[0104] ·Cd w Zn( 1-w )Se / Cd y Zn( 1-y )Se, Cd w Zn( 1-w )Se / Cd y Zn( 1-y )Se / ZnS, Cd w Zn( 1-w )Se / Cd y Zn( 1-y )Se / ZnSe, Cd w Zn( 1-w )Se / Cd y Zn( 1-y )Se / ZnSe z S( 1-z )、

[0105] ·Cd w Zn( 1-w )Tax x S( 1-x ) / CdS, Cd w Zn( 1-w )Tax x S( 1-x ) / CdS / ZnS, Cd w Zn( 1-w )Tax x S( 1-x ) / CdS / ZnSe, Cd w Zn( 1-w )Tax x S( 1-x ) / CdS / ZnSe y S( 1-y )、

[0106] ·Cd w Zn( 1-w )Tax x S(1-x ) / Cd y Zn( 1-y S、Cd w Zn( 1-w )Se x S( 1-x ) / Cd y Zn( 1-y )S / ZnS、Cd w Zn( 1-w )Se x S( 1-x ) / Cd y Zn( 1-y S / ZnSe, Cd w Zn( 1-w )Se x S( 1-x ) / Cd y Zn( 1-y )S / ZnSe z S( 1-z ),

[0107] ·Cd w Zn( 1-w )Se x S( 1-x ) / Cd y Zn( 1-y Se, Cd w Zn( 1-w )Se x S( 1-x ) / Cd y Zn( 1-y Se / ZnS, Cd w Zn( 1-w )Se x S( 1-x ) / Cd y Zn( 1-y Se / ZnSe, Cd w Zn( 1-w )Se x S( 1-x ) / Cd y Zn( 1-y )Se / ZnSe z S( 1-z );

[0108] Where w, x, y, and z are rational numbers between 0 (excluding) and 1 (excluding), and light is emitted through fluorescence. The emitted light is typically centered on a band in the visible light range of 380 nm to 780 nm. The emitted light typically has a full width at half maximum (FWHM) of less than 50 nm, preferably less than 30 nm, and more preferably less than 20 nm.

[0109] The most preferred group II-VI nanoparticles (1) are CdSe / CdS / ZnS, CdSe x S( 1-x ) / CdS / ZnS, CdSe / ZnSe / ZnS, CdSe / ZnSe x S( 1-x ) / ZnS、CdSe x S( 1-x ) / ZnSe / ZnS、Cd x Zn( 1-x )Se / ZnSe / ZnS.

[0110] Other particularly suitable nanoparticles (1) are group III-V semiconducting nanoparticles selected from InP / ZnS, InP / ZnSe, and InP / ZnSe. x S( 1-x ), InP / CdS / ZnS, InP / ZnSe / ZnS, InP / ZnSe x S( 1-x ) / ZnS, InP / GaP, Cu x In y Zn( 1-x-y )S / ZnS、In x As( 1-x )P / ZnSe x S( 1-x ), CsPbBr3, CsPbI3, FAPbI3, where FA represents formamidinium, and x and y are rational numbers between 0 (excluding) and 1 (excluding).

[0111] Other particularly suitable nanoparticles (1) are group I-III-VI2 semiconducting nanoparticles selected from AgInS2, AgInSe2, and Cu. x In( 1-x S2, Cu x In( 1-x Se2, especially CuInS2 and CuInSe2.

[0112] Other particularly suitable nanoparticles (1) are selected from doped quantum dots as the core, such as ZnSe:Mn / ZnS or ZnSe:Cu / ZnS.

[0113] Other particularly suitable nanoplatelets are selected from ZnTe / ZnSe. y S( 1-y ), ZnSe x Te( 1-x ) / ZnS、ZnSe x Te( 1-x ) / ZnSe、ZnSex Te( 1-x ) / ZnSe y S( 1-y ), where x and y are rational numbers between 0 (excluding) and 1 (excluding).

[0114] Matrix

[0115] In this disclosure, the matrix is ​​a metal oxide compound that contains at least aluminum and zirconium as metallic elements and has the following formula (I):

[0116] Al x Zr y M z O (I)

[0117] In formula (I), M represents one or more metallic elements selected from Si, Ti, Hf, Ge, Sn, or mixtures thereof. Doping the matrix with titanium can improve the matrix's conductivity—which is inherently insulating—and help prevent charge accumulation following quantum dot photoexcitation—which generates a pair of charges in the quantum dot. The titanium concentration used for doping is preferably less than 10 atomic%, where the atomic percentage is given only for metallic elements. Doping the matrix with hafnium can improve the matrix's density and / or adjust its refractive index. These properties are advantageous for reducing the refractive index difference between the matrix and the nanoparticles (1). Doping the matrix with silicon can reduce water permeability, thereby improving the matrix's efficiency in protecting the nanoparticles (1) from degradation under humid conditions. More generally, the dopant can be adjusted to regulate the matrix's refractive index or conductivity.

[0118] More specifically, without any theoretical proof, experiments appear to show that titanium doping enhances photocatalysis and stability at flux levels.

[0119] Similarly, in this disclosure, the composition of the matrix is ​​theoretical, and the atomic ratio should be understood as the target composition, provided that the final composition may contain up to 2% impurities. Impurities are additional elements that may be included in the composition, and these elements are not aluminum, zirconium, or selected dopants.

[0120] In equation (I), the stoichiometric coefficient of oxygen is fixed at 1. Therefore, the parameters x, y, and z are interrelated and depend on the coordination numbers of Al, Zr, and M elements in the metal oxide matrix.

[0121] Furthermore, x ranges from 0 to 3 / 5; y ranges from 1 / 20 to 1 / 2; and z ranges from 0 to 2 / 5. When z is zero, the relationship between x and y is (3 / 2x + 2y) = 1, in order to conform to the coordination number of alumina and zirconium oxide.

[0122] In a preferred embodiment, x is 1 / 40 to 8 / 15; y is 1 / 10 to 77 / 160. More preferably, x is 1 / 20 to 8 / 15; y is 1 / 10 to 37 / 80. Even more preferably, x is 1 / 10 to 8 / 15; y is 1 / 10 to 17 / 40. Table I below shows the equivalent relationship between x and y values ​​(z is zero) and the atomic percentages of aluminum and zirconium.

[0123]

[0124] Table I

[0125] For example, the metal oxide matrix corresponding to x=2 / 9, y=1 / 3, and z=0 is Al. 2 / 9 Zr 1 / 3 O, which contains 40 atomic percent aluminum and 60 atomic percent zirconium, where the atomic percentages are given only for metallic elements.

[0126] Similarly, the metal oxide matrix corresponding to x=8 / 15, y=1 / 10, and z=0 is Al. 1 / 15 Zr 1 / 10 O, which contains 84 atomic percent aluminum and 16 atomic percent zirconium, where the atomic percentages are given only for metallic elements.

[0127] Similarly, the metal oxide matrix corresponding to x=6 / 17, y=4 / 17, and z=0 is Al. 6 / 17 Zr 4 / 17 O, which contains 60 atomic percent aluminum and 40 atomic percent zirconium, where the atomic percentages are given only for the metal elements. The metal oxide matrix composition with x = 6 / 17 ± 0.03 and y = 4 / 17 ± 0.03 is particularly effective in protecting the nanoparticles (1).

[0128] Similarly, the metal oxide matrix corresponding to x=2 / 5, y=1 / 5, and z=0 is Al. 2 / 5 Zr 1 / 5 O, which contains 66.7 atomic percent aluminum and 33.3 atomic percent zirconium, where the atomic percentages are given only for the metal elements. The metal oxide matrix composition with x = 2 / 5 ± 0.03 and y = 1 / 5 ± 0.03 is particularly effective in protecting the nanoparticles (1).

[0129] Similarly, the metal oxide matrix corresponding to x=3 / 7; y=5 / 28 and z=0 is Al. 3 / 7 Zr 5 / 28 O, which contains 70 atomic percent aluminum and 30 atomic percent zirconium, where the atomic percentages are given only for metallic elements.

[0130] Similarly, for metal oxide matrices corresponding to x=1 / 10 and y=1 / 10, the value of z can vary from z=13 / 40 if all elements represented by M have a coordination number of 2–MO2–, and if z=0, all elements represented by M have a coordination number of 1.5–M2O3.

[0131] In a preferred embodiment, x is 2 / 9 to 6 / 17.

[0132] In a preferred embodiment, y is 4 / 17 to 1 / 3.

[0133] In the embodiments, alumina and zirconium oxide account for more than 90% by weight of the matrix, preferably more than 95% by weight of the matrix.

[0134] Figure 5 This indicates that composite particles encapsulating quantum dots with different matrices are at 450 nm and 100 W / cm². 2 The change in photoluminescence intensity over time under excitation. The percentages of aluminum and zirconium are atomic percentages. Quantum dots are aged at 50°C and 90% humidity. It was observed that the more zirconium oxide in the matrix, the less the photoluminescence decreased over time.

[0135] Figure 6 This study compared the PLQY (particulate energy gain) of composite particles encapsulating quantum dots with different matrices immediately after preparation with that after immersion in water for one week. The percentages of aluminum and zirconium are atomic percentages. It was observed that the higher the zirconium oxide content in the matrix, the less the PLQY decreased after immersion in water for one week.

[0136] Figure 7 SEM images of quantum dots encapsulated with different matrices after 96 hours of storage in water are shown. The percentages of aluminum and zirconium are atomic percentages. Deterioration of the quantum dots with the aluminum-rich matrix was observed during storage in water. Specifically, the alumina dissolved and redeposited in water in a triangular shape, altering the original spherical structure of the encapsulated quantum dots. Conversely, the zirconium-rich matrix tolerated storage in water without structural degradation.

[0137] Furthermore, infrared spectroscopy analysis has been performed on the encapsulated quantum dots aged in water, and the encapsulated quantum dots contain corresponding to Figure 7 Various matrices were observed. The infrared spectrum of the aluminum-rich matrix showed additional peaks, which is due to the recrystallization of the matrix in water in a triangular shape.

[0138] In summary, when quantum dot-encapsulated composite particles are exposed to water, the zirconium-rich matrix is ​​more durable than the aluminum-rich matrix.

[0139] In the implementation scheme, the matrix further comprises a metallic element selected from silicon (Si), titanium (Ti), hafnium (Hf), germanium (Ge) or tin (Sn) at a concentration of 0.1 atomic% to 15 atomic% wherein the atomic percentage is given only for the metallic element.

[0140] Composite particles

[0141] In this disclosure, the composite particles (2) are encapsulated in a metal oxide matrix to form the composite particles (2).

[0142] In the embodiment, the loading of nanoparticles (1) in the composite particle (2) is at least 1%, preferably at least 2.5%, and more preferably at least 5%, wherein the loading is the mass ratio between the mass of the nanoparticles (1) contained in the composite particle (2) and the mass of the composite particle (2). In fact, the performance of the composite particle (2) is directly proportional to the concentration of the nanoparticles (1) it contains. Therefore, a high concentration of nanoparticles (1) is advantageous. However, it should be noted that increasing the concentration of nanoparticles (1) without reducing its performance (e.g., due to aggregation or manufacturing processes) is not easy.

[0143] More precisely, for nanoparticles (1) that emit green fluorescence (wavelength from 510 nm to 580 nm) under blue light irradiation at a wavelength of 450 nm, the loading is preferably at least 2.5%, more preferably at least 5%, and optionally at least 10%. For nanoparticles (1) that emit red fluorescence (wavelength from 600 nm to 680 nm) under blue light irradiation at a wavelength of 450 nm, the loading is preferably at least 1%, more preferably at least 2%, and optionally at least 5%.

[0144] In some embodiments, the loading of nanoparticles (1) in the composite particle (2) is even less than 1%. This is particularly ideal for nanoparticles (1) with strong absorption and high PLQY: a low concentration of nanoparticles (1) is sufficient to achieve the desired light conversion. A loading of nanoparticles (1) in the composite particle (2) in the range of 0.1% to 1% may be preferred. This is particularly relevant for red fluorescent nanoparticles (1).

[0145] Furthermore, the geometric distribution of nanoparticles (1) in composite particles (2) can be controlled in several ways.

[0146] In the embodiment, more than 95% by weight of the nanoparticles (1) in the composite particle (2) are dispersed in the internal portion of the composite particle (2). The internal portion means that the composite particle (2) consists of an internal portion surrounded by an outer layer. The outer layer covers the entire internal portion. The outer layer accounts for less than 10% by weight of the composite particle (2) and has a thickness greater than or equal to 5 nm. In a preferred embodiment, the outer layer has a thickness greater than or equal to 15 nm. The distribution of these nanoparticles (1) in the composite particle (2) is as follows: Figure 4 As shown in the photograph, it can be clearly seen that there are no nanoparticles in the outer layer (1). Therefore, the nanoparticles are protected from the external environment by at least the outer layer, the properties of which are determined by the composition of the matrix of alumina and zirconium oxide.

[0147] In the implementation scheme, the nanoparticles (1) are uniformly dispersed in the matrix. "Uniform" means that the nanoparticles (1) do not aggregate, do not contact each other, and are separated by the metal oxide matrix. Each nanoparticle (1) is separated from its adjacent nanoparticles (1) by an average minimum distance.

[0148] In the embodiment, more than 95% by weight of nanoparticles (1) in the composite particle (2) are uniformly dispersed in the internal portion of the composite particle (2).

[0149] In the embodiment, at least two different types of nanoparticles (1) are dispersed in the matrix. For example, a first type of nanoparticle (1) that emits green light by fluorescence and a second type of nanoparticle (1) that emits red light by fluorescence are mixed in the same composite particle. Such a composite particle (2) containing at least two different types of nanoparticles (1) is particularly suitable for a light conversion element (3): when irradiated with a single excitation light (typically blue light with a wavelength of about 450 nm), green and red light can be emitted simultaneously with unabsorbed blue light, thereby producing uniform white light. In a preferred embodiment, the weight concentration of green fluorescent nanoparticles (1) divided by the weight concentration of red fluorescent nanoparticles (1) is 25 to 4, preferably 20 to 5. For clarity, the weight concentration of green fluorescent nanoparticles (1) divided by the weight concentration of red fluorescent nanoparticles (1) is equal to ten, corresponding to a weight of green fluorescent nanoparticles (1) in the composite particle (2) being ten times that of red fluorescent nanoparticles (1).

[0150] In the implementation scheme, the composite particles (2) exhibit a low specific surface area—contributed by both surface roughness and internal partial porosity—which can be characterized by nitrogen adsorption-desorption in the Brunauer–Emmett–Teller (BET) theory. The low specific surface area is associated with difficulty for oxygen or water to permeate through the matrix. In fact, the matrix has high barrier properties to protect the nanoparticles from degradation. A low BET value is preferred, below 15 m at a nitrogen pressure of 650 mmHg. 2 / g, preferably below 5m under a nitrogen pressure of 650mmHg. 2 / g. However, the composite particles (2) may exhibit higher BET values, up to 50 m² / g, and still provide high protection against degradation by oxygen or water. Without being bound by theory, it seems the matrix may have a large macroscopic porosity, but a very dense matrix surrounding the nanoparticles (1) results in a larger BET value. Furthermore, the outer layer without the nanoparticles (1) may be porous, but this does not affect the overall barrier properties of the matrix.

[0151] The composite particles (2) can be in the form of a monodisperse population. Monodisperse composite particles (2) are advantageous for various reasons, depending on the application. When composite particles (2) are used in fluid processes, such as lateral tomography in medical diagnostics, a uniform size distribution leads to more reproducible results. When composite particles (2) are used in optical elements (filters or light sources, including conversion light sources), a uniform size distribution avoids uncontrolled light diffusion and ensures the spatial uniformity of the optical element. It also prevents the transfer of charge generated after photon absorption from one nanoparticle (1) to another nanoparticle (1), which could lead to charge quenching without fluorescence, a phenomenon known as inter-nanoparticle quenching.

[0152] The average size of the composite particle (2) is preferably 50 nm to 50 µm, more preferably 100 nm to 10 µm. Composite particles (2) with an average size of 50 nm to 250 nm are particularly suitable for micro-LED and Q-LED applications, where the light source is pixelated, and the side length of the square pixel can be as small as 3 µm (e.g., virtual reality displays) or 5 µm to 20 µm (e.g., head-up displays, automotive displays, or wearable displays). The size of the composite particle (2) is an order of magnitude smaller than the pixel, which ensures that the composite particle (2) is adequately distributed in the pixel, thereby achieving uniform light emission across all pixels. Composite particles (2) with an average size of 250 nm to 500 nm are particularly suitable for mini-LED and QD enhancement film applications. Composite particles (2) with an average size of 500 nm to 2000 nm are particularly suitable for detection, where the size of one of the composite particles (2) determines the light intensity that can be used to identify a positive association between the target analyte and the composite particle (2) (by fluorescence when fluorescent nanoparticles (1) are used). Composite particles with an average size greater than 500 nm (2) are particularly suitable for use in polymer films.

[0153] The composite particles (2) can be chemically modified on their surface. Chemical modification can be achieved through grafting, molecular adsorption, or physical processes (thermal, vacuum, or gas-phase treatment). Chemical modification can use biomolecules designed to specifically interact with a target. Chemical modification can use compatibilizers, allowing the composite particles (2) to be incorporated into complex formulations (e.g., resins, varnishes, coatings, colloidal dispersions, etc.) without causing aggregation or phase separation of the composite particles (2).

[0154] All of the following technically acceptable structural combinations A i B j —Whether as nanoparticles (1) themselves, or as heterostructured nanoparticles (1) containing the structure described above as a core—combined with a matrix, suitable composite particles (2) can be produced:

[0155] • Nanoparticles (1):

[0156] A1. Phosphide group III-V quantum dots selected from InP, Cd3P2, Zn3P2, AlP, GaP, and TlP;

[0157] A2. Group II-VI quantum dots selected from CdSe, CdSeS, ZnSe, and ZnSeS;

[0158] A3. I-III-VI2 ternary quantum dots selected from CuInS2, CuInSe2, AgInS2, and AgInSe2;

[0159] A4. Quantum dots selected from CuInZnS and CuInZnSe.

[0160] • Matrix:

[0161] B1. The formula is Al x Zr y The matrix is ​​composed of O, where x is 2 / 9 to 6 / 17 and y is 4 / 17 to 1 / 3. The matrix, consisting only of alumina and zirconium oxide, is particularly dense, thus limiting the diffusion of gases or harmful chemicals into the composite particles (2).

[0162] B2. The formula is Al x Zr y M z The matrix is ​​O, where M represents silicon; x ranges from 1 / 20 to 8 / 15; y ranges from 1 / 10 to 37 / 80; and z ranges from 1 / 100 to 1 / 20. Adding silicon to the matrix results in reduced water permeability.

[0163] B3. The formula is Al x Zr y M z The matrix is ​​O, where M represents titanium; x ranges from 1 / 20 to 8 / 15; y ranges from 1 / 10 to 37 / 80; and z ranges from 1 / 100 to 1 / 20. The addition of titanium prevents charge accumulation after quantum dot photoexcitation.

[0164] B4. The formula is Al x Zr y M z The matrix is ​​O, where M represents hafnium; x is 1 / 20 to 8 / 15; y is 1 / 10 to 37 / 80; and z is 1 / 100 to 1 / 20. Adding hafnium can increase the density of the matrix and / or adjust its refractive index.

[0165] Therefore, the following is a list of possible composite particles: CdSe / ZnSe / ZnS in a Zr-100% matrix; CdSe / ZnSe / ZnS in an Al / Zr-(67 / 33) matrix; CdSe / CdS / ZnS in a Zr-100% matrix; CdSe / CdS / ZnS in an Al / Zr-(67 / 33) matrix; InP / ZnSe / ZnS in a Zr-100% matrix; InP / ZnSe / ZnS in a Zr-100% matrix; nS in Al / Zr-(67 / 33) matrix; CuIn(Zn)S / ZnS in Zr-100% matrix; CuIn(Zn)S / ZnS in Al / Zr-(67 / 33) matrix; CuIn(Zn)Se / ZnSe / ZnS in Zr-100% matrix; CuIn(Zn)Se / ZnSe / ZnS in Al / Zr-(67 / 33) matrix—all percentages of aluminum and zirconium are atomic percentages.

[0166] Preparation method

[0167] The present invention also relates to a method for preparing composite particles (2) as disclosed above, wherein the metal oxide matrix is ​​obtained by hydrolysis of aluminum alkoxide, zirconium alkoxide and optionally other metal alkoxides.

[0168] The composite particles (2) can be obtained by the method disclosed in WO2018 / 220165, the entire contents of which are incorporated herein by reference, wherein the precursor of the metal oxide matrix is ​​an aluminum alkoxide, a zirconium alkoxide, and optionally other metal alkoxides.

[0169] Metal alkoxides are widely available compounds with good compatibility, allowing for the preparation of alkoxide mixtures by condensation under acidic or basic conditions—resulting in metal oxides with mixed compositions, as disclosed above. The molar ratio of the metal alkoxides defines the atomic percentage of the metal in the resulting metal oxide after condensation.

[0170] The preferred aluminum alkoxide is aluminum tert-butoxy.

[0171] Preferred zirconium alkoxides are zirconium n-propoxide Zr(OC3H7)4, for example, a solution dissolved in 1-propanol.

[0172] Preferred silanolates are tetramethoxysilane Si(OCH3)4 (commonly known as methyl silicate) and tetraethoxysilane Si(OC2H)4. s )4 (commonly known as ethyl silicate) or methyltriethoxysilane.

[0173] Preferred titanium alkoxides are tetraisopropyl titanate Ti(OisoC3H7)4, tetraethoxytitanium, or tetrabutoxytitanium.

[0174] Preferred hafnium alkoxides are methoxy hafnium, n-propoxy hafnium, isopropoxy hafnium, and / or ethoxy hafnium.

[0175] Optical element

[0176] This disclosure also relates to a light conversion element (3) comprising a plurality of composite particles (2) as disclosed in any of the embodiments above, provided that the composite particles (2) comprise fluorescent nanoparticles (1); and a polymer matrix (31) wherein the plurality of composite particles (2) are dispersed.

[0177] The light conversion element (3) is used in conjunction with a light source, typically a blue light source. The nanoparticles (1) absorb light from the light source and emit lower-energy (i.e., redshifted) light through fluorescence. Ultimately, the light emitted by the light source is converted into light of another wavelength (longer).

[0178] The polymer matrix can be any material known to those skilled in the art, particularly including polystyrene-based matrices, polymethyl methacrylate-based matrices, silicone-based matrices, or sol-gel-based matrices.

[0179] Based on the weight of the light conversion element (3), the amount of composite particles (2) in the polymer matrix (31) is preferably from 0.05% to 20% by weight. An amount of less than 0.05% by weight of composite particles (2) in the polymer matrix (31) results in low light conversion efficiency, which is unacceptable for the light conversion element (3). Therefore, a higher weight concentration is preferred. However, the presence of more than 20% by weight of composite particles (2) in the polymer matrix (31) typically leads to aggregation or phase separation of the composite particles (2), ultimately resulting in a decrease in light conversion efficiency and light emission uniformity. A more preferred amount of composite particles (2) in the polymer matrix (31) is from 0.1% to 10% by weight. If the light conversion element (3) is intended to partially absorb blue light from a light source, the amount of composite particles (2) in the polymer matrix (31) is preferably from 0.05% to 3% by weight: a lower concentration of composite particles reduces the overall absorption rate of the light conversion element (3).

[0180] Based on the weight of the light conversion element (3), the amount of nanoparticles (1) in the polymer matrix (31) is preferably from 100 ppm to 5000 ppm.

[0181] In this embodiment, at least two different types of composite particles (2) are dispersed in the matrix. For example, a first type of composite particle (2) comprising nanoparticles (1) that emit green light by fluorescence and a second type of composite particle (2) comprising nanoparticles (1) that emit red light by fluorescence are mixed in the matrix. This embodiment is particularly suitable for light conversion elements (3): when irradiated with a single excitation light (typically blue light with a wavelength of about 450 nm), green and red light can be emitted simultaneously with unabsorbed blue light, thereby producing uniform white light. In a preferred embodiment, the weight concentration of green fluorescent nanoparticles (1) divided by the weight concentration of red fluorescent nanoparticles (1) is 25 to 4, preferably 20 to 5. For clarity, the weight concentration of green fluorescent nanoparticles (1) divided by the weight concentration of red fluorescent nanoparticles (1) is equal to ten, corresponding to a weight of green fluorescent nanoparticles (1) in the composite particle (2) being ten times that of red fluorescent nanoparticles (1).

[0182] The polymer matrix may also contain scattering objects, such as oxide nanoparticles. These scattering objects tend to increase the optical path length of photons passing through the light conversion element (3), thereby increasing the probability of photon absorption by the semiconductive nanoparticles (1) and resulting in improved light conversion. Based on the weight of the light conversion element (3), the amount of scattering objects in the polymer matrix (31) is preferably from 0.1% to 5% by weight, more preferably from 0.5% to 2.5% by weight. Furthermore, the increased diffusion of the polymer matrix leads to an increase in the haze of the light conversion element (3), which is desirable for the light source.

[0183] The light conversion element (3) may be in the form of a thin film (suitable for being laid on a light source) or a solid component, optionally having additional optical properties, for example, if the solid component is shaped as an optical lens—thus providing a focusing effect on the fluorescent light—or designed as a pattern of spatially distributed fluorescent light—for example in a pixelated structure.

[0184] The light conversion element (3) may be included in a display, LED (light-emitting diode), mini-LED, micro-LED or OLED.

[0185] Therefore, this disclosure also relates to displays that include the light conversion element (3) as disclosed in any of the embodiments above. A display is a device or apparatus that displays image signals. Display devices or apparatuses include all devices that display images, continuous frames, or video, such as, but not limited to, LCD displays, televisions, projectors, computer monitors, personal digital assistants, mobile phones, laptops, tablets, MP3 players, CD players, DVD players, Blu-ray players, head-mounted displays, glasses, helmets, headwear, head-mounted devices, smartwatches, watch phones, or smart devices.

[0186] Therefore, this disclosure also relates to light-emitting diodes (LEDs), mini-LEDs, or micro-LEDs that include the light conversion element (3) disclosed in any of the embodiments above.

[0187] Finally, this disclosure relates to the use of the light conversion element (3) in a display (particularly in thin film form) or a light-emitting diode (particularly in thin film or solid component form). Attached Figure Description

[0188] Figure 1 A to Figure 1 F shows various nanoparticles (1) with homogeneous (A) or heterogeneous structures: spherical core / shell (B), spherical core / shell / shell (C), plate midpoint (D), nanoplate core / shell (E) and nanoplate core / crown (F).

[0189] Figure 2A composite particle (2) is shown, comprising multiple spherical nanoparticles (1) encapsulated in a metal oxide matrix.

[0190] Figure 3 An optical element (3) comprising composite particles (2) in a polymer matrix is ​​shown.

[0191] Figure 4 Electron micrographs of a composite particle (2) containing zinc-based nanoparticles (1) within a zirconium-rich matrix are shown. Zinc and zirconium elements within the composite particle were identified by energy-dispersive X-ray (EDX) analysis. The left image is the original image: the center of the composite particle (2) appears slightly different from the periphery due to the zinc-related EDX signal. The right image highlights some sites of zinc signaling within the nanoparticles (1) (indicated by shaded areas). A zinc-deficient outer layer can be observed, with an estimated thickness of approximately 50 nm.

[0192] Figure 5 The relationship between the photoluminescence intensity of quantum dots encapsulated with different matrices under 450 nm, 100 W / cm² excitation and the aging time of the encapsulated quantum dots is shown.

[0193] Figure 6 The histograms compare the PLQY of quantum dots encapsulated with different matrices immediately after preparation and after one week in water.

[0194] Figure 7 SEM images of quantum dots encapsulated with different matrices stored in water for 96 hours are shown.

[0195] Example

[0196] The present invention is further illustrated by the following embodiments.

[0197] Scheme 1 : Optical performance evaluation.

[0198] The optical property protection of nanoparticles dispersed in the matrix was evaluated using the following method:

[0199] First, the nanoparticles were evaluated to determine their photoluminescence quantum yield (PLQY). 50 µg of nanoparticles dispersed in 3 mL of heptane were irradiated with a light source at a wavelength of 450 nm and a power of 10 µW / cm². Fluorescence was measured to determine the PLQY.

[0200] The nanoparticles were then processed into a metal oxide matrix, and the PLQY of the composite particles was measured. It was observed that embedding the nanoparticles did not reduce the PLQY. Furthermore, the absorption of the composite particles was measured: the sample was irradiated with controlled-power blue light at a wavelength of 450 nm, and the following light values ​​were measured: the power of blue light transmitted through the sample (unabsorbed light) and the fluorescence power (optionally measured for different wavelength ranges, typically for the corresponding green and red wavelength ranges). This measurement is not an absolute determination of PLQY, but it provides a quantitative estimate of the fluorescence efficiency. For ease of operation, the composite particles can be embedded in a polymethyl methacrylate polymer for optical measurements.

[0201] The composite particles were then stored in an accelerated aging chamber at 50°C and 90% relative humidity under constant irradiation with 450nm wavelength blue light at 6mW / cm² (hereinafter referred to as AccTEST1). Other aging tests could also be run: controlled at 22°C and 50% relative humidity under constant irradiation with 1500mW / cm² blue light at 450nm wavelength (hereinafter referred to as AccTEST2); controlled at 85°C and 50% relative humidity without light (hereinafter referred to as AccTEST-dark1); and controlled at 60°C and 90% relative humidity without light (hereinafter referred to as AccTEST-dark2). Aging tests could also be performed under natural light: constant irradiation corresponding to a D65 light source, with a total power of 500W / m², for 8, 16, 24, or 48 hours (hereinafter referred to as AccTEST-white8 / 16 / 24 / 48 respectively). This light source can be obtained by combining various light sources (xenon lamps, artificial daylight fluorescent lamps combining visible and ultraviolet output, metal halide lamps) with filters (e.g., P / N56077769 from Atlas Material Testing Technology GmbH). During accelerated aging tests, fluorescence power is measured (continuously or periodically), and the aging time (denoted as T90) required to observe a 10% decrease in fluorescence power is determined. In other words, at the start of the accelerated aging test, fluorescence is set to 100%, and time T90 is measured when the fluorescence power reaches 90%. Similarly, time T85 corresponding to a 15% decrease in fluorescence power can be measured.

[0202] For the composite particles according to the present invention, under AccTEST1 conditions, T90 is typically greater than 2500 hours.

[0203] Scheme 2: TEM observation.

[0204] The distribution of nanoparticles within the composite particles was measured using the following method.

[0205] The composite particles were placed on a transmission electron microscope (STEM Jeol JSM-7800F) grid. The same sample was then further observed using energy-dispersive X-ray diffraction (EDX) analysis to locate the presence of some metallic elements within the composite particles. EDX images show the distribution of the nanoparticles within a matrix primarily composed of aluminum and zirconium.

[0206] Example 1 : CdSe quantum dots in a metal oxide matrix comprising only the metal elements aluminum and zirconium.

[0207] CdSe nanoparticles were prepared according to existing techniques (Lhuillier E. et al., Acc. Chem. Res., 2015, 48 (1), pp 22–30; Pedetti S. et al., J. Am. Chem. Soc., 2014, 136 (46), pp16430–16438; Ithurria S. et al., J. Am. Chem. Soc., 2008, 130, 16504–16505; Nasilowski M. et al., Chem. Rev. 2016, 116, 10934−10982).

[0208] Using the method disclosed in WO2018 / 220165, CdSe nanoparticles were treated with aluminum tert-butoxy and zirconium propoxide precursor to obtain Al 6 / 17 Zr 4 / 17 The composite particles consist of an O matrix containing 60 atomic percent aluminum and 40 atomic percent zirconium, with CdSe nanoparticles embedded within it. The loading of CdSe nanoparticles in the composite particles is set to 0.5%.

[0209] Then CdSe@Al 6 / 17 Zr 4 / 17 The O composite particles were placed under AccTEST1 conditions, and their fluorescence power was measured during aging under 450 nm blue light irradiation. Finally, T90 was determined.

[0210] Examples 2-20.

[0211] Example 1 was repeated according to the composite particles defined in Table II below:

[0212]

[0213] Table II

[0214] Core / shell / shell nanoplate A: CdSe 0.45 S 0.55 / Cd 0.30 Zn 0.70S / ZnS has a core with a thickness of 1.2 nm, a lateral dimension (i.e., length or width) greater than 8 nm, and shells with thicknesses of 2.5 nm and 2 nm, respectively, and emits red fluorescence.

[0215] Core / shell / shell nanoplates B: CdSe 0.72 S 0.28 / CdS / ZnS has a core with a thickness of 1.2 nm, a lateral dimension (i.e., length or width) greater than 8 nm, and shells with thicknesses of 3.5 nm and 0.5 nm, respectively, and emits red fluorescence.

[0216] The core / shell / shell nanospheres (C:CdSe / CdS / ZnS) have a core with a diameter of 4.5 nm and shells with thicknesses of 1.5 nm and 1 nm, respectively, and emit red fluorescence.

[0217] The core / shell / shell nanospheres D: CdSe / ZnSe / ZnS have a core with a diameter of 4.5 nm and shells with thicknesses of 1.5 nm and 1 nm, respectively, and emit green fluorescence.

[0218] Core / shell / shell nanoplates E: CdSe 0.72 S 0.28 / ZnSe / ZnS has a core with a thickness of 1.2 nm, a lateral dimension (i.e., length or width) greater than 8 nm, and shells with thicknesses of 3.5 nm and 0.5 nm, respectively, and emits red fluorescence.

[0219] The core / shell / shell nanoparticles F:InP / ZnSe / ZnS have a core with a diameter of 4.0 nm and shells with thicknesses of 2 nm and 1 nm, respectively, and emit red fluorescence.

[0220] Core / shell / shell nanoparticles G:InP / ZnSe / ZnS, have a core with a diameter of 3.0 nm and shells with thicknesses of 2 nm and 1 nm, respectively, and emit red fluorescence.

[0221] The core / shell / shell nanoparticles H:InP / ZnSe / ZnS have a core with a diameter of 2.5 nm and shells with thicknesses of 1.5 nm and 1.25 nm, respectively, and emit green fluorescence.

[0222] Core / shell / shell nanoparticle I: InP / ZnSe / ZnS, with a core of 2.5 nm in diameter and shells of 2.75 nm and 2.50 nm in thickness, respectively, emits green fluorescence.

[0223] Core / shell / shell nanoplate J: CdSe 0.10 S 0.90 / ZnS / Cd 0.20 Zn 0.80S has a core with a thickness of 1.5 nm, a lateral dimension (i.e., length or width) greater than 10 nm, and shells with thicknesses of 1 nm and 2.5 nm, respectively, and emits green fluorescence.

[0224] Core / shell nanospheres K:CdSe 0.10 S 0.90 / ZnS has a core with a diameter of 4 nm and a shell with a thickness of 1 nm, and emits green fluorescence.

[0225] The core / shell nanoparticles, L:InP / ZnS, have a diameter of 3.5 nm and emit green fluorescence.

[0226] The core / shell nanoparticles M: InP / ZnSe, with a diameter of 4.4 nm, emit green fluorescence.

[0227] The core / shell / shell nanoparticles (N:InP / GaP / ZnS) have a diameter of 7.2 nm and emit green fluorescence.

[0228] The core / shell / shell nanoparticles, O:InP / ZnSe / ZnS, have a diameter of 7.4 nm and emit green fluorescence.

[0229] Comparative Example C1

[0230] Example 1 was repeated, except for the nature of the matrix: the nanoparticles were encapsulated in pure silica (SiO2), using a comparable method—using silanolates instead of other metal alkoxides. Under AccTEST1 conditions, the measured T90 was below 500 hours.

[0231] Example 21 : Light conversion element

[0232] The following composition was extruded and molded into a 1.5 mm thick film: 0.165 g of core / shell / shell nanospheres C (emitting red fluorescence) encapsulated in an aluminum / zirconium matrix—equivalent to 35 ppm of nanoparticles in the film—and 0.165 g of core / shell / shell nanospheres D (emitting green fluorescence) encapsulated in an aluminum / zirconium matrix—equivalent to 250 ppm of nanoparticles in the film—were mixed with 100 g of polystyrene. 1 g of scattering particles (nano-TiO2) was added to achieve a final film haze of approximately 70%. When irradiated with blue light at a wavelength of 450 nm, the film allowed some blue light to pass through (without absorption), and some blue light was absorbed; the fluorescence then converted to green and red light, resulting in a uniform white light source overall.

[0233] Under accelerated aging conditions (AccTEST1), the quality (hue, chromaticity, color gamut, intensity) of the white light source remained stable for more than 2500 hours, meaning that the parameter changes of the white light source were less than 10% of their initial values.

Claims

1. A composite particle (2) comprising nanoparticles (1) dispersed in a matrix, wherein: • Nanoparticles (1) are semiconductive nanoparticles; and • The matrix is ​​a metal oxide compound of the following formula Hand x Zr y O (I) Where x and y represent the stoichiometric ratios of aluminum and zirconium, respectively; x ranges from 0 to 3 / 5; y is between 1 / 20 and 1 / 2; and (3 / 2x+2y)=1.

2. The composite particles (2) according to claim 1, wherein x is 1 / 20 to 8 / 15 and y is 1 / 10 to 37 / 80, preferably x is 1 / 10 to 8 / 15 and y is 1 / 10 to 17 / 40.

3. The composite particles (2) according to claim 1 or 2, wherein the matrix further comprises a metal element at a concentration of 0.1 atomic% to 15 atomic% selected from Si, Ti, Hf, Ge, Sn or mixtures thereof.

4. The composite particle (2) according to any one of claims 1 to 3, wherein the loading of nanoparticles (1) in the composite particle (2) is at least 1%, preferably at least 2.5%, more preferably at least 5%, and the loading is the mass ratio of the mass of nanoparticles (1) contained in the composite particle (2) to the mass of the composite particle (2).

5. The composite particle (2) according to any one of claims 1 to 4, wherein more than 95% by weight of the nanoparticles (1) in the composite particle (2) are dispersed in the inner portion of the composite particle (2), wherein the composite particle (2) consists of an inner portion surrounded by an outer layer that covers the entire inner portion; the outer layer accounts for less than 10% by weight of the composite particle (2), and the outer layer has a thickness greater than or equal to 5 nm, preferably greater than or equal to 15 nm.

6. The composite particles (2) according to any one of claims 1 to 5, wherein the nanoparticles (1) are uniformly dispersed in the matrix.

7. The composite particles (2) according to any one of claims 1 to 6, wherein alumina and zirconium oxide constitute more than 90% by weight of the matrix.

8. The composite particle (2) according to any one of claims 1 to 7, wherein the nanoparticle (1) is selected from the group consisting of, or comprises a core selected from the group consisting of: • Group III-V semiconducting nanoparticles, preferably phosphide quantum dots, and more preferably selected from InP quantum dots, Cd3P2 quantum dots, Zn3P2 quantum dots, AlP quantum dots, GaP quantum dots, and TlP quantum dots; or • Group I-III-VI2 semiconducting nanoparticles, preferably selected from CuInS2 quantum dots, CuInSe2 quantum dots, AgInS2 quantum dots, and AgInSe2 quantum dots; • Group II-VI semiconducting nanoparticles, preferably selected from CdSe quantum dots, CdSeS quantum dots, ZnSe quantum dots, and ZnSeS quantum dots; Quantum dots selected from CuInZnS and CuInZnSe; or Its mixture.

9. The composite particles (2) according to any one of claims 1 to 7, wherein the nanoparticles (1) are selected from: • InP / ZnS quantum dots, InP / ZnSc quantum dots, InP / ZnSc x S( 1-x Quantum dots, InP / CdS / ZnS quantum dots, InP / ZnSc / ZnS quantum dots, InP / ZnSe x S( 1-x ) / ZnS quantum dots; or CuInS2 quantum dots, CuInSe2 quantum dots, AgInS2 quantum dots, AgInSe2 quantum dots; • CdSe / CdS / ZnS quantum dots, CdSe x S (1-x CdS / ZnS quantum dots, CdSe / ZnSe / ZnS quantum dots, CdSe / ZnSe x S( 1-x ZnS quantum dots, CdSe x S( 1-x ) / ZnSe / ZnS quantum dots, Cd x Zn( 1-x Se / ZnSe / ZnS quantum dots; or Its mixture.

10. The composite particles (2) according to any one of claims 1 to 9, wherein the matrix is ​​of formula Al x Zr y M z Metal oxide compounds of O, • Wherein M represents one or more metallic elements, said metallic elements being selected from Si, Ti, Hf, Ge, Sn, or mixtures thereof, and • z ranges from 0 to 2 / 5, provided that when z is zero, (3 / 2x + 2y) = 1.

11. A method for preparing composite particles (2) according to any one of claims 1 to 10, wherein the metal oxide matrix is ​​obtained by hydrolysis of aluminum alkoxides, zirconium alkoxides and optionally other metal alkoxides.

12. A light conversion element (3), comprising: - A plurality of composite particles (2) according to any one of claims 1 to 10, said composite particles (2) comprising fluorescent nanoparticles (1); and - A polymer matrix (31) in which multiple composite particles (2) are dispersed.

13. The light conversion element (3) according to claim 12, wherein the amount of composite particles (2) in the polymer matrix (31) is from 0.05% by weight to 20% by weight, based on the weight of the light conversion element (3).

14. A display comprising a light conversion element (3) according to claim 12 or claim 13.

15. A light-emitting diode comprising the light conversion element (3) according to claim 12 or claim 13.

16. Use of the light conversion element (3) according to claim 12 or claim 13 in a display or in a light-emitting diode.

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