Dispersion comprising eu2+ doped inorganic luminescent nanoparticles for greenhouse applications and sheet structures, and coatings for greenhouses comprising such nanoparticles

Abstract

To provide improved luminescent inorganic particle-based coatings that exhibit broadband UV absorption and luminescent emission over the full PAR region, that are transparent (non-absorbing) in the PAR region, and that exhibit high luminescent quantum efficiency and absorbed photons.SOLUTION: A luminescent layer is described comprising an Eu2+ doped inorganic luminescent material comprising or consisting essentially of the elements Al and / or Si and the elements O and / or N, the doped inorganic luminescent material converting radiation of the UV region between 200 nm and 400 nm of the solar spectrum into the photosynthetically active radiation (PAR) region (400 nm to 700 nm) of the solar spectrum, wherein the Si concentration in the inorganic luminescent material is 0 to 45 atom%, the Al concentration is 0 to 50 atom%, the O concentration is 0 to 70 atom%, the N concentration is 0 to 60 atom%, and the Eu2+ concentration is 0.01 to 30 atom%.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention provides a method for producing Eu 2+ Luminescent inorganic nanoparticles, particularly, but not exclusively, Eu for greenhouse coatings. 2+ Luminescent inorganic nanoparticles, Eu 2+ Dispersions containing luminescent inorganic nanoparticles, transparent sheet structures containing such particles and glazing structures containing such nanoparticle coatings, as well as the Eu 2+ The present invention relates to a method for synthesizing luminescent inorganic nanoparticles. [Background technology]

[0002] Greenhouses provide a controlled climate environment for efficient plant and crop growth. To control and optimize sunlight entering a greenhouse, various types of coatings have been developed that can be used to coat the glazing structure or plastic transparent sheeting that is part of the greenhouse. Various pigment coatings with different optical properties, such as photoselective reflective coatings or diffuse coatings, are available to control light entering a greenhouse. Typically, these coatings are spray-coated and removable, allowing different coatings to be used depending on the season and / or type of plant being grown. Examples of such coatings are described in International Publication No. 2018 / 169404, which describes removable coatings for greenhouses containing pigments, such as chalk or titanium oxide. Based on such pigment dispersions, greenhouse glazing can be spray-coated with an infrared-reflective coating during the summer if plants are sensitive to high levels of IR radiation. Similarly, diffuse coatings can be used to eliminate the shading effect and uniformly expose plants in the greenhouse to sunlight.

[0003] The prior art has suggested further improving light transmission into greenhouses based on luminescent materials. Typically, these materials include transparent plastic sheets containing luminescent particles. Such materials can be optimized to convert a portion (or portions) of radiation in the electromagnetic spectrum to a different wavelength for more efficient use of that radiation. For example, an luminescent spectrum down-conversion layer applied as a luminescent coating on the greenhouse glazing structure can enhance crop growth by reducing the spectral mismatch between the solar spectrum and the photosynthetically active radiation (PAR) region (400 nm to 700 nm) of the crop by converting UV light (100 nm to 400 nm), which is often harmful to crops, into light in the PAR region that stimulates plant growth. For various vegetables grown in greenhouses, a 1% increase in light in the PAR region can increase plant production by approximately 1%. Therefore, such luminescent materials may have significant economic potential.

[0004] Examples of luminescent materials for greenhouses are described in U.S. Patent Application Publication No. 20170288080. This prior art document describes an example of a luminescent coating for greenhouses that includes a polymer layer with a fluorescent organic pigment, such as Lumogen 305, to absorb portions of the solar spectrum and use the energy of the absorbed photons to emit photons with wavelengths between 600 and 690 nm. The luminescent coating also absorbs a large portion of the solar spectrum (400 to approximately 640 nm) necessary for plant growth and flowering. Other examples of luminescent materials for greenhouses are described in NL1017077 and NL2002577, which describe plastic foils for greenhouses that include inorganic phosphors, particularly Y2O3-based phosphors, capable of converting part of the UV or IR light into visible light.

[0005] However, such luminescent materials for large-scale greenhouse applications are currently not commercially available. This is mainly because the luminescent materials have overlapping absorption and emission spectra in the PAR region. More generally, known luminescent phosphors for greenhouse applications, particularly dyes, also suffer from substantial photon losses due to overlapping excitation and emission spectra, making these materials unsuitable for large-scale commercial applications. For such applications, the coating should not only be able to efficiently convert multiple parts of the UV spectrum into visible light, but also satisfy other properties such as low toxicity, chemical stability, environmental friendliness, low cost, and suitability for large-scale production. Previously mentioned luminescent particles, such as Lumogen 305 or the Y2O3-based phosphor, do not meet these requirements. Finally, the material should also have advantageous optical properties in the PAR region, such as low backscattering / anti-reflection properties.

[0006] In view of the foregoing, therefore, there is a need in the art for improved luminescent inorganic particle-based coatings for greenhouses. In particular, there is a need for improved luminescent inorganic particle-based coatings that exhibit broadband UV absorption and luminescent emission throughout the PAR range (where the absorption and emission spectra do not overlap), are transparent (non-absorbing) in the PAR range, and exhibit high luminescent quantum efficiency (i.e., the ratio of emitted photons to absorbed photons). In addition, there is a need for improved inorganic particle-based coatings for greenhouses that have optical and structural properties suitable for greenhouse applications, including durability, hardness, color stability, and optical scattering properties. Summary of the Invention [Means for solving the problem]

[0007] It is an object of the present invention to reduce or eliminate at least one of the drawbacks known in the prior art. In a first aspect, the present invention provides a dispersion of luminescent nanoparticles for coating greenhouse glazing structures, the dispersion comprising an organic or aqueous medium and luminescent nanoparticles, the nanoparticles comprising Eu 2+ % doped SiAlON, wherein the Si concentration is selected from 0 to 33 atomic %, the Al concentration is selected from 0 to 40 atomic %, the O concentration is selected from 50 to 66 atomic %, the N concentration is selected from 0 to 10 atomic %, and Eu 2+ is selected from 0.0001 to 5 atomic %.

[0008] In one embodiment, the Si concentration is selected from 15 to 33 atomic %, the Al concentration is selected from 0.001 to 12 atomic %, the O concentration is selected from 50 to 66 atomic %, the N concentration is selected from 0.1 to 5 atomic %, and Eu 2+ The concentration can be selected from the range of 0.0001 to 3 atomic %.

[0009] In another embodiment, the Si concentration is selected from 30 to 33 atomic %, the Al concentration is selected from 0.01 to 2 atomic %, the O concentration is selected from 50 to 66 atomic %, the N concentration is selected from 0.1 to 1 atomic %, and Eu 2+ The concentration can be selected from the range of 0.0005 to 1 atomic %.

[0010] In one embodiment, the nanoparticles may have an average size of 1 to 1000 nm, preferably 10 to 800 nm, more preferably 20 to 600 nm.

[0011] In one embodiment, the dispersion may comprise from 1% to 80% by weight of nanoparticles, preferably from 5% to 50% by weight of nanoparticles, more preferably from 15% to 35% by weight of nanoparticles.

[0012] In one embodiment, the organic medium can include an organic solvent (eg, hexane, ethanol, heptane, toluene, chloroform, dichloromethane) containing 0.5% to 10% by weight of a polymer additive.

[0013] In one embodiment, the aqueous medium may comprise an alkaline aqueous solution, such as an ammonium solution or a sodium hydroxide solution, the alkaline aqueous solution comprising 1% to 10% by weight of a water-based polymeric additive.

[0014] In one embodiment, the surface of the nanoparticles may be modified with one or more types of ligands, such as stearic acid, oleic acid, octanoic acid, oleylamine, octylamine, octanethiol, trioctylphosphine, preferably the modification includes sonication of the nanoparticles.

[0015] In one embodiment, the surface of the nanoparticles can be modified by chemical bond formation, such as silanization or esterification, to attach the nanoparticles to one or more long organic side chains having a chain length of 8 to 18 carbons.

[0016] In one embodiment, the dispersion may further comprise inorganic porous nanoparticles, preferably porous silicon oxide nanoparticles.

[0017] In a further aspect, the present invention provides a transparent plastic sheet for a greenhouse, comprising a transparent polymeric material and, dispersed in the polymeric material, Eu. 2+ and inorganic luminescent nanoparticles doped with Eu. 2+ % doped SiAlON, wherein the Si concentration is selected from 0 to 33 atomic %, the Al concentration is selected from 0 to 40 atomic %, the O concentration is selected from 50 to 66 atomic %, the N concentration is selected from 0 to 10 atomic %, and Eu 2+ The present invention may relate to the transparent plastic sheet, wherein the content of the metal oxide is selected from 0.0001 to 5 atomic %.

[0018] In one embodiment, the Si concentration is selected from 15 to 33 atomic %, the Al concentration is selected from 0.001 to 12 atomic %, the O concentration is selected from 50 to 66 atomic %, the N concentration is selected from 0.1 to 5 atomic %, and Eu 2+The concentration can be selected from the range of 0.0001 to 3 atomic %.

[0019] In one embodiment, the Si concentration is selected from 30 to 33 atomic %, the Al concentration is selected from 0.01 to 2 atomic %, the O concentration is selected from 50 to 66 atomic %, the N concentration is selected from 0.1 to 1 atomic %, and Eu 2+ The concentration is selected from the range of 0.0005 to 1 atomic %.

[0020] In a further aspect, the thickness of the sheet may be selected from 1 to 1000 micrometers, preferably from 10 to 500 mm, more preferably from 40 to 120 micrometers.

[0021] In a further aspect, the present invention provides a luminescent glazing structure for a greenhouse, comprising a glazing structure and a coating disposed on at least a portion of a surface of the glazing structure, the coating comprising a transparent polymeric material and, dispersed in the polymeric material, Eu. 2+ and inorganic luminescent nanoparticles doped with Eu. 2+ % doped SiAlON, wherein the Si concentration is selected from 0 to 33 atomic %, the Al concentration is selected from 0 to 40 atomic %, the O concentration is selected from 50 to 66 atomic %, the N concentration is selected from 0 to 10 atomic %, and Eu 2+ is selected from 0.0001 to 5 atomic %, or preferably, the Si concentration is selected from 15 to 33 atomic %, the Al concentration is selected from 0.001 to 12 atomic %, the O concentration is selected from 50 to 66 atomic %, the N concentration is selected from 0.1 to 5 atomic %, and Eu 2+ The concentrations are selected from 0.0001 to 3 atomic %, or more preferably, the Si concentration is selected from 30 to 33 atomic %, the Al concentration is selected from 0.01 to 2 atomic %, the O concentration is selected from 50 to 66 atomic %, the N concentration is selected from 0.1 to 1 atomic %, and Eu 2+ The concentration of the luminescent glazing structure is selected from the range of 0.0005 to 1 atomic %.

[0022] In one embodiment, the thickness of the coating may be selected from 10 to 200 micrometers, preferably 20 to 180 micrometers, more preferably 50 to 150 micrometers.

[0023] In a first aspect, the present invention provides a Eu 2+ Inorganic luminescent materials doped with Eu 2+ The present invention relates to luminescent nanoparticle and microparticle coatings, and to glazing and transparent sheeting structures for greenhouses comprising such nanoparticle coatings. The luminescent particles can comprise or consist essentially of the elements Al and / or Si and the elements O and / or N. These luminescent particles are optimized for converting solar radiation in the UV region of the spectrum, from 200 nm to 400 nm, into radiation in the photosynthetically active radiation (PAR) region, from 400 nm to 700 nm. In one embodiment, the nanoparticles are selected from Eu 2+ % doped SiAlON, wherein the Si concentration is selected from 0 to 33 atomic %, the Al concentration is selected from 0 to 40 atomic %, the O concentration is selected from 50 to 66 atomic %, the N concentration is selected from 0 to 10 atomic %, and Eu 2+ is selected from the range of 0.0001 to 5 atomic percent.

[0024] For the sake of brevity, in this disclosure, Eu 2+ doped SiAlON (SiAlON:Eu 2+ ) References to nanoparticle and microparticle materials are 2+ SiAlON doped with Eu 2+ SiAlO, doped with Eu 2+ SiAlN, doped with Eu 2+ SiON, doped with Eu 2+ AlON, Eu doped 2+ Thus, the SiAlON material is a linear combination of the neutral units SiO, AlO, AlN, and SiN, i.e. *SiO2+b * Al2O3+c * AlN+d * It may include any SiAlON stoichiometry that can be described as Si3N4 (where a, b, c, and d can take all values independent of one another, including 0 and non-integer values).

[0025] The Eu 2+ The Eu doped SiAlON particles can be used in luminescent down-conversion coatings for greenhouse glazing structures and plastic sheets. 2+ The Eu doped SiAlON particles can be dispersed in a plastic transparent sheet structure to form a particle dispersed sheet material. 2+ The SiAlON particles doped with ZnO have advantageous luminescent properties, including broadband UV absorption, luminescence emission in the PAR region, transparency (non-absorption) to photons in the PAR region, non-overlapping absorption and emission spectra, and high luminescent quantum efficiency (LQE), i.e., the ratio of emitted photons to absorbed photons. Additionally, the particles have optical, structural, and mechanical properties that make them compatible with greenhouse glazing structures. For example, in one embodiment, the luminescent nanoparticle coating can be non-scattering or at least have low-scattering properties. In another embodiment, the micron-sized luminescent particle coating has light-diffusing properties.

[0026] The luminescence conversion material is in particular a compound containing Eu for optical structures, such as glazing structures and sheet structures for greenhouses. 2+ Suitable for SiAlON nanoparticles doped with .

[0027] EU 2+ The optical properties of SiAlON:Eu doped nanoparticles have a set of characteristics that make them ideal for luminescent coatings for greenhouses, glazing structures, and plastic sheeting structures. 2+The nanoparticles have strong absorption in the UV region and emission in the PAR region, with no or at least little overlap in the absorption regions, and a luminescence quantum efficiency (LQE) near 1. In addition, the nanoparticles have excellent properties with respect to durability, including, for example, chemical stability, thermal stability, hardness, and color stability.

[0028] In one embodiment, the Eu 2+ The luminescent nanoparticles consist essentially of the elements Al and / or Si and the elements O and / or N, where the term consist essentially of means that the material may contain trace amounts of other elements in amounts of 0.1% or less. 2+ The luminescent material is composed of the elements Al and / or Si and the elements O and / or N, or is composed of the elements Al, Si, O, N.

[0029] The luminescent SiAlON:Eu 2+ The nanoparticles provide a wide tunable range of emission in the visible spectrum by varying the ratio of Si to Al and / or the ratio of O to N. In further embodiments, the emission can also be tuned by varying the ratio of Eu 2+ As a result, the luminescent SiAlON:Eu 2+ A wide range of material compositions exists, which correspond to emissions in the blue to red range (400 nm to 700 nm), making these luminescent materials ideal for adapting the emission wavelength to the needs of the greenhouse farmer.

[0030] This range of Si-rich compositions produces luminescent SiAlON:Eu with high IQE, absorbing photons in the UV range of 200-400 nm and emitting photons in the PAR region. 2+ This results in nanoparticles.

[0031] The aforementioned luminescent SiAlON:Eu 2+ The materials may be used in optical structures, such as glazing structures for greenhouses, including glass panes coated with these materials.

[0032] In one embodiment, the glass plate can be a highly transparent diffusive glass sheet having a high haze factor. In one embodiment, the diffusive glass plate can have a light transmittance of greater than 90% and a haze factor of greater than 70%. For example, the glass material can include one or more surfaces with optical scattering centers and / or textures to scatter light passing through the glass plate. Thus, the Eu 2+ Luminescent radiation produced by the dopants and incoming solar radiation passing through the optical structure is scattered in multiple directions, thereby producing diffused light for photo-grown crops.

[0033] Light scattering can be achieved by patterning or texturing one or both sides of the glass plate. Thus, in one embodiment, at least one surface of the glass plate can include a pattern and / or texture to scatter light in multiple directions.

[0034] In one embodiment, the SiAlON:Eu 2+ The luminescent layer may be configured as a diffuse coating to scatter luminescent radiation and incident solar radiation in multiple directions, where the particles in the luminescent particle-based coating are micron-sized SiAlON:Eu 2+ It is a particle.

[0035] In one embodiment, the SiAlON:Eu 2+ The luminescent material may be integrated within and / or part of the diffusive coating.

[0036] In one embodiment, the anti-reflective (AR) structure is SiAlON:Eu for optimal coupling of UV and solar light to the luminescent material. 2+ It can be provided with a luminescent material.

[0037] In one embodiment, the AR structure can include two or more dielectric layers, and the thickness and refractive index of the dielectric layers can be selected to form an AR structure for coupling UV and PAR to the luminescent layer. In one embodiment, the AR structure can be provided in a luminescent coating on a transparent substrate and optimized for coupling UV and PAR to the luminescent layer.

[0038] In one embodiment, the light-emitting layer may be provided on a glass platelet having a refractive index of about 1.5. In another embodiment, a transparent polymer-based platelet may be used instead of the glass platelet.

[0039] In one embodiment, the SiAlON:Eu 2+ The luminescent material can be synthesized as particles, e.g., nanoparticles. These particles can be (mono)dispersed in a binder material (organic or inorganic binder, e.g., SiO2, etc.) and applied as a coating on a transparent substrate. In one embodiment, the nano-sized particles can have an average particle size of 1 nm to 700 nm. The use of nano-sized particles can eliminate or at least minimize light scattering, which can reduce LCL efficiency.

[0040] In a further aspect, the present invention provides an optical structure comprising a transparent substrate having a first surface, a second surface and both surfaces, and at least one light-emitting layer provided on at least one of the first surface and / or the second surface of the transparent substrate, the light-emitting layer comprising or consisting essentially of the elements Al and / or Si and the elements O and / or N, and wherein Eu 2+ The doped inorganic luminescent material converts radiation in the UV region of the solar spectrum (200 nm to 400 nm) into the photosynthetically active radiation (PAR) region of the solar spectrum (400 nm to 700 nm), and the nanoparticles are 2+% doped SiAlON, wherein the Si concentration is selected from 0 to 33 atomic %, the Al concentration is selected from 0 to 40 atomic %, the O concentration is selected from 50 to 66 atomic %, the N concentration is selected from 0 to 10 atomic %, and Eu 2+ The present invention may relate to the optical structure described above, wherein the content of the element is selected from the range of 0.0001 to 5 atomic %.

[0041] In one embodiment, the at least one transparent substrate can be an inorganic transparent substrate, such as a glass substrate, or the transparent substrate is a polymer-based transparent substrate.

[0042] In one embodiment, the at least one transparent substrate has a high haze, preferably the transparent substrate is a diffuse-type transparent substrate having a high haze, the high haze being greater than 70%, preferably greater than 80%, more preferably greater than 90%, and / or the light-emitting layer has a low haze, the low haze being less than 20%, preferably less than 10%, more preferably less than 2%.

[0043] In one embodiment, the at least one light-emitting layer comprises the Eu 2+ The nanoparticles may comprise nanoparticles of an inorganic luminescent material doped with , preferably the nanoparticles have an average size of 1 nm to 700 nm, preferably 2 nm to 500 nm, more preferably 5 nm to 400 nm, and even more preferably 10 nm to 300 nm.

[0044] In one embodiment, the at least one light-emitting layer is an amorphous layer or a nanocrystalline layer.

[0045] In one embodiment, the transparent substrate can have a low haze, the low haze being less than 20%, preferably less than 10%, more preferably less than 2%, and / or the at least one light-emitting layer can have a high haze, the high haze being greater than 70%, preferably greater than 80%, or more preferably greater than 90%.

[0046] In one embodiment, the light emitting layer comprises SiAlON:Eu 2+ It may comprise microparticles, preferably the microparticles have an average size of 0.7 to 200 microns, preferably 0.8 to 100 microns, more preferably 1 to 30 microns.

[0047] In one embodiment, the optical structure may further comprise an anti-reflective AR coating, preferably a multi-layer AR coating, to couple light into the optical structure, and preferably the AR coating is provided on the light-emitting layer, or the light-emitting layer is part of or embedded in the AR coating.

[0048] In one embodiment, the optical structure may be optically connected to at least one photovoltaic cell, preferably optically connected to one of the two surfaces of the optical structure.

[0049] In a further aspect, the present invention may relate to a window assembly for a greenhouse comprising an optical structure according to any of the embodiments of the present application.

[0050] In one embodiment, high refractive index SiAlON:Eu 2+ Luminescent materials, such as SiAlN:Eu 2+ The luminescent material can be synthesized as particles, e.g., nanoparticles with an average size of 100-300 nm. These particles can be sparsely distributed on the surface of a transparent substrate of a low refractive index material, e.g., glass. Sparsely distributed here means that the average distance between particles is 200-700 nm. Such sparsely distributed luminescent nanoparticles can form a broadband anti-reflection coating for light in the PAR range.

[0051] Therefore, the luminescent SiAlON:Eu 2+The material can form or be part of an anti-reflection structure or coating in a variety of ways, for example, luminescent SiAlON:Eu containing relatively high amounts of Si (>32 atomic %) and O (>64 atomic %) (corresponding to a luminescent material with a high LQE). 2+ The material composition can have a refractive index lower than 1.51 (glass), which makes the composition suitable as an anti-reflective coating.

[0052] Alternatively, the luminescent SiAlON:Eu 2+ The material is alternating high and low refractive index SiAlON:Eu 2+ The composition can be incorporated into a multilayer dielectric AR stack. Additionally, the material can be used by depositing relatively high refractive index 200-700 nm nanoparticles as a nanoparticle coating on a low refractive index substrate (e.g., a glass substrate), whereby the nanoparticle coating forms a plasmon resonant structure with broadband antireflection properties.

[0053] In one embodiment, a refractive index-matching organic binder (e.g., PET, PE, PVB, PVA, PC, PP, PVP, epoxy resin, silicone, PS, PMA derivatives, etc.) can be used as a transparent binder material for the nano-sized particles. The (mono)dispersed precursor of the coating can be applied onto a transparent (clear diffusing) substrate using a wet coating technique, such as spray coating, roll-to-roll coating, dip coating, doctor blade coating, brush coating, spin coating, etc.

[0054] In one embodiment, the SiAlON:Eu 2+The luminescent material can be synthesized as micron-sized particles. These particles can be (mono)dispersed in a binder material and applied as a coating on a transparent substrate. The micron-sized particles can have an average particle size of 0.7-16 μm in diameter. The particles can promote the diffusion of solar irradiation and luminescent emission, which is beneficial for plant growth. The light diffusion can distribute the incident light evenly, which has several advantages, such as improved crop yield, more leaves, lower harvest temperature, and shorter harvest time. Thus, the micron-sized luminescent SiAlON:Eu 2+ The particles can act as both a light conversion layer and a light diffusion layer (light scattering layer).

[0055] In one embodiment, the nanosized and micron sized SiAlON:Eu 2+ The particles can be dispersed as a colloidal solution in a solvent (nanoparticle dispersion), such as water, hexane, toluene, ethanol, isopropanol, etc., and mixed proportionally with existing agro-industrial coating precursors that already have anti-reflection, light-diffusing, and / or light-selective purposes. The combined effect of light conversion and / or light-diffusing can thus be achieved.

[0056] In one embodiment, the nanosized and micron sized SiAlON:Eu 2+ The particles can be dispersed in a transparent plastic film or sheet (eg, PE, ETFE, PVC, PMMA, polycarbonate, etc.).

[0057] In one embodiment, the SiAlON:Eu 2+ Luminescent nanoparticles can be synthesized based on a sol-gel synthesis process. The nanoparticles are prepared from precursors of the elements Si, Al, O and / or N, and Eu. 2+Nanoparticles synthesized based on such sol-gel processes can be dispersed in solvents containing polymer additives. Nanoparticle dispersions synthesized based on such sol-gel processes can be applied directly onto substrates by conventional wet coating techniques. Various post-deposition treatments (varying temperature, ramp rate, reactant gas pressure, reactant gas composition, reactant gas flow, etc.) can be applied to the coating for desired optical, chemical, and mechanical performance. Also, trace amounts of binder material precursors can be included in the liquid precursor for various purposes, such as controlling solution viscosity, increasing coating adhesion, minimizing coating porosity, modifying coating surface morphology, etc.

[0058] The present invention will be further illustrated by reference to the accompanying drawings, which show, in schematic form, embodiments according to the invention, it being understood that the invention is in no way limited to these specific embodiments. [Brief explanation of the drawings]

[0059] [Figure 1A] FIG. 1A shows a photograph of a luminescent nanoparticle coating according to one embodiment of the present invention. [Figure 1B] FIG. 1B shows an IQE graph of a luminescent nanoparticle coating according to one embodiment of the present invention. [Figure 2] FIG. 2 shows the excitation and emission spectra of a luminescent nanoparticle coating according to one embodiment of the present invention. [Figure 3] FIG. 3 shows the transmission of a luminescent coating sample according to one embodiment of the present invention illuminated by solar radiation. [Figure 4] FIG. 4 shows a luminescent nanoparticle coating according to one embodiment of the present invention. [Figure 5] FIG. 5 shows a transparent sheet structure including a luminescent nanoparticle coating according to various embodiments of the present invention. [Figure 6] FIG. 6 shows a transparent sheet structure including a luminescent nanoparticle coating according to various embodiments of the present invention. [Figure 7A]FIG. 7A shows a transparent sheet structure including a luminescent particle-based anti-reflective coating according to one embodiment of the present invention. [Figure 7B] FIG. 7B shows a transparent sheet structure including a luminescent particle-based anti-reflective coating according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0060] Detailed Description of the Invention In the present disclosure, divalent europium (Eu) compounds with excellent and improved properties for greenhouse and crop growth applications are disclosed. 2+ ) doped SiAlON luminescent nanoparticle materials are described. The improved properties include improved luminescent, optical and / or material properties compared to luminescent materials for greenhouse applications known from the prior art.

[0061] Surprisingly, certain SiAlON:Eu 2+ The composition contains Eu, which absorbs UV and emits PAR. 2+ It has been found that the absorption and emission spectra of SiAlON materials doped with Eu exhibit little or no overlap. 2+ It has been found that SiAlON materials doped with Eu absorb a substantial portion of the UV band of the solar spectrum and convert radiation in this band to radiation of longer wavelengths, particularly in the photosynthetically active radiation (PAR) region. SiAlON host materials exhibit excellent properties in terms of mechanical strength, chemical inertness and heat resistance, which is why they are used in protective and anti-reflective coatings in the glass industry. 2+ The SiAlON material doped with Cr forms a highly stable conversion material with optical properties that are compatible with glazing structures for greenhouses.

[0062] The nanoparticle materials, their advantages, and their use in luminescent coatings for greenhouses and luminescent sheeting structures for greenhouses are described in more detail below with reference to the accompanying drawings.

[0063] Figure 1A shows the nanoparticles SiAlON:Eu irradiated by UV light. 2+ 1 shows a photograph of a structured glass platelet coated with the nanoparticle SiAlON:Eu coating. 2+ The coating was photographed under broadband UV light emitting radiation in the PAR region, i.e., 400-700 nm. 2+ A dispersion of SiAlON nanoparticles doped with BaSO4 was prepared by dispersing 3.5 wt. % nanoparticles in an uncured acrylic polymer matrix with a pH of 11. Prior to the coating process, the glass plate was washed with 36 wt. % hydrochloric acid, ethanol, and deionized water using ultrasonication. The coating was thermally treated at 150°C for 30 minutes. Figure 1B shows the internal quantum efficiency (IQE) graph of the nanoparticle coating, which exhibits very high quantum efficiency. BaSO4 was used as a reference, since it is assumed to uniformly reflect UV-VIS light. This reference is then used to indicate how much light is absorbed (including the sample holder). The absorbance and IQE can then be determined, where the IQE is measured based on the so-called "DeMello method."

[0064] Figure 2 shows the excitation and emission spectra of the particle-based coating shown in Figure 1A. As shown in the figure, the spectra show little or no overlap and exhibit excellent UV absorption centered at 320 nm and PAR emission centered at 450 nm. The nanoparticles were synthesized using an exemplary synthesis process of sol-gel technology as follows: The composition of the particles was Eu with a doping concentration of 1 mol %. 2+ Including Si 1.92 Al 0.08 O 1.08 N 1.92In this embodiment, the nanoparticles may have an average particle size (average diameter) of 100 to 300 nm. The size distribution of the nanoparticles may be determined based on scanning electron microscopy (SEM) images or dynamic light scattering (DLS) measurements, which are well known in the art.

[0065] The SiAlON:Eu described with reference to the embodiments of this application 2+ The nanoparticle coating exhibits excellent conversion characteristics. Figure 3 shows the coated SiAlO:Eu SiO 2 ... 2+ 1 shows a transmission graph of the sample.

[0066] The SiAlON:Eu 2+ Luminescent particles can be synthesized based on wet chemical processes, such as sol-gel synthesis using different precursors for the elements Si, Al, O, N, and Eu. Various post-deposition treatments, such as thermal annealing, can be applied to the materials for desired optical, chemical, and mechanical performance.

[0067] The SiAlON:Eu 2+ Particles can be synthesized using a sol-gel method involving compounds such as tetraethyl orthosilicate (TEOS) and europium salts with the formula Si(OC2H5)4, Al(NO3)3. Optionally, ethanol and / or citric acid can be added to aid in nanoparticle formation. Nitride formation can be facilitated by a nitrogen-filled sintering environment. Polymer coatings and / or laminations can be created by dispersing the nanoparticles in a matrix material. The selection and optimization of such matrix polymers can be based on the application and requirements. Epoxy resins, polymethyl methacrylate (PMMA), and polysiloxanes are some common materials into which these nanoparticles can be incorporated.

[0068] In one embodiment, SiAlON:Eu 2+ A sol-gel synthesis method that can be used to produce nanopowder materials can include the following steps: Stoichiometric weighing of TEOS and Al, N, O and Eu precursors: 7.7447 g Si(OC2H5)4, 0.3299 g Al(NO3)3, 0.0681 g Eu2O3; Dissolving europium oxide Eu2O3 in a minimum amount of dilute nitric acid, Dissolving aluminum nitrate (Al(NO3)3) in ethanol and placing it on a heating plate; Dissolve TEOS (Si(OC2H5)4) in ethanol and place it on a heating plate; mixing the TEOS solution with an Al(NO3)3 solution and an Eu2O3 solution to form a colloidal solution (sol) mixture; evaporating the mixture on the heating plate to form about 20 ml of sol; aging the sol in a dryer at 60°C for 72 hours to form a gel structure; calcining the gel in air at 500°C to remove any residual organic content; Sintering at 1100°C in a reducing atmosphere. Grinding the product in an agate mortar to form particles, such as nano-sized particles or micron-sized particles.

[0069] In another embodiment, SiAlO(N):Eu 2+ A sol-gel synthesis method for producing particles may include the following steps: TEOS and Al, N, O and Eu precursors: stoichiometric weighing of 7.7447 g Si(OC2H5)4; (TEOS), 0.3299 g Al(NO3)3·9H2O, and 0.1274 g Eu(C2H3O2)3 (Eu(Ace)); dissolving Eu(Ace) in deionized water to form a first colloidal solution (Sol 1); dissolving Al(NO3)3·9H2O in 6 g of ethanol to form a second colloidal solution (Sol 2) and preheating the solution at 60°C for 15 minutes; dissolving TEOS in 3.4253 g of ethanol to form a third colloidal solution (Sol 3) (EtOH:TEOS ≈ 2:1 molar ratio) and preheating the mixture at 60° C. for 15 minutes; mixing Sol 1 and Sol 2 to form a fourth colloidal solution (Sol 4); adding Sol 3 dropwise to Sol 4; evaporating the mixture on a heating plate to form about 20 ml of sol; aging the sol in an oven at 60°C for 24 hours to form a gel structure; The product was ground using a mortar and pestle to give white SiAlO(N):Eu 2+ forming a powder; calcining in air at 500°C for 5 hours at a heating rate of 3°C / min to remove any residual organic content and allowing the product to cool naturally; grinding the product after calcination; sintering at 1100°C for 3 hours under a reducing atmosphere (7%H2 / 93%N2) with a heating rate of 3°C / min and allowing the product to cool naturally; grinding the product to form nanophosphors.

[0070] The above process yielded 2 grams of nanoparticles, the composition of which was Si 1.92 Al 0.08 O 3.96 :1 mol% Eu, the Si / Al ratio is 24, and the Eu doping concentration is 1%, resulting in a composition of Si:32.0 at.%, Al:1 at.%, O2 66 at.%, and Eu:1 at.%. Based on the above synthesis method, various SiAlON:Eu 2 Nanoparticle materials can be produced. 2+ The nanoparticle material has a Si concentration selected from 0 to 33 atomic %, an Al concentration selected from 0 to 40 atomic %, an O concentration selected from 50 to 66 atomic %, an N concentration selected from 0 to 10 atomic %, and Eu 2+This can be achieved by selecting from 0.0001 to 5 atomic %.

[0071] In one embodiment, the SiAlON:Eu 2+ Nanoparticles of a substance can be synthesized. In another embodiment, the average particle size can be selected from 2 to 400 nm in diameter. In a further embodiment, the average particle size can be selected from 5 to 100 nm in diameter. The nano-sized particles can provide advantageous optical properties to nanoparticle coatings, for example, eliminating or at least minimizing light scattering that can reduce the efficiency of such luminescent coatings.

[0072] The SiAlON:Eu 2+ Nanoparticles can be (mono)dispersed in a transparent polymer binder medium to form a nanoparticle dispersion. A nanoparticle dispersion can be achieved by dispersing nanoparticles in a carrier medium (which can be briefly referred to as a binder or medium), applying the nanoparticle dispersion as a coating onto a transparent substrate, such as a glazing structure or a polymer sheet, and drying the nanoparticle coating to form a polymer nanoparticle coating on the substrate. The coating can be formed using known coating techniques, such as spray coating. To form a nanoparticle dispersion, the surface of the nanoparticles can be modified using a surface modification process.

[0073] In one embodiment, the surface of nanoparticles can be modified with various types of ligands by sonication (i.e., applying ultrasonic energy having a frequency of >20 KHz to the particles). Examples of such ligands can include stearic acid, oleic acid, octanoic acid, oleylamine, octylamine, octanethiol, and trioctylphosphine. Alternatively, in one embodiment, the surface of nanoparticles can be modified by chemical bond formation, such as silanization, esterification, or similar processes. Such chemical bond formation processes can be used to attach one or more long organic side chains having a chain length of 8 to 18 carbons to the surface of the nanoparticles. Surface modification of the nanoparticles based on ligands and / or chemical bond formation can allow the nanoparticles to be easily dispersed in the carrier medium, thereby preventing nucleation of the particles.

[0074] A nanoparticle dispersion can be formed based on the above particle treatment, and the weight percentage (wt%) of the nanoparticles in the nanoparticle dispersion can be selected from 1% to 80% by weight, preferably 5 to 50% by weight, and more preferably 15 to 35% by weight.

[0075] In one embodiment, the (modified) nanoparticles can be dispersed in an organic solvent at a concentration of 1% to 80%, more preferably 5% to 50%, and more preferably 15% to 35%. In some embodiments, the (modified) nanoparticles can be dispersed in an organic solvent at a concentration of 25±10%. The organic solvent can include hexane, ethanol, heptane, toluene, chloroform, and dichloromethane. The solvent can further include 0.5% to 10% of a polymeric dispersant. Examples of such polymeric dispersants can include PP, PE, PVP, PMA derivatives, PS, PU, etc.

[0076] In another embodiment, the (modified) nanoparticles can be dispersed in an aqueous solvent, such as an alkaline aqueous solution including ammonium and sodium hydroxide solutions, which can further contain 1% to 10% of a water-based polymeric dispersant, including polyacrylates, polyurethanes, copolymers, etc. (PP, PE, PVP, PMA derivatives, PS, PU, etc.).

[0077] In one embodiment, the polymeric dispersant and binder are acrylic, urethane, acylate, or epoxy based polymeric dispersants or binders, respectively.

[0078] In further embodiments, the dispersions may be formed based on polymer binders, as described in WO 2018 / 169404, which is incorporated herein by reference.

[0079] The polymeric dispersant acts as a dispersant to disperse the nanoparticles and crosslinks during drying to form a polymeric nanoparticle coating. The polymeric dispersant enhances the long-term stabilization of the nanoparticles in the medium by combining the steric hindrance of the solubilizing side chains and the electrostatic repulsion of the charges on the anchoring groups. In addition, the polymeric dispersant enables a controlled polymerization process to provide a high-quality nanoparticle coating layer.

[0080] In one embodiment, a refractive index-matching organic binder (e.g., PET, PE, PVB, PVA, PC, PP, PVP, epoxy resins, silicones, PS, PMA derivatives, etc.) can be used to form the nanoparticle dispersion.

[0081] (Mono)dispersed nanoparticle coatings can be formed by applying nanoparticle dispersions onto transparent (clear, diffusing) substrates, such as glass platelets or transparent polymer sheets, using wet coating techniques, such as spray coating, roll-to-roll coating, dip coating, doctor blade coating, brush coating, etc. Thus, high-quality, substantially non-scattering or low-scattering SiAlON:Eu 2+ Luminescent nanoparticle coatings can be achieved in an efficient and inexpensive manner. Based on the aforementioned wet coating techniques, nanoparticle coatings with thicknesses of 10-200 micrometers, preferably 20-180 micrometers, and more preferably 50-150 microns can be achieved.

[0082] In one embodiment, the SiAlON:Eu 2+ The luminescent material can be synthesized as micron-sized particles. The micron-sized particles can be (mono)dispersed in a binder material and applied as a coating on a transparent substrate in the same manner as described above with reference to the nano-sized particles. In one embodiment, the micron-sized particles can have an average particle size selected from a diameter of 0.5 μm to 15 μm. The particles can promote the diffusion of solar irradiation and luminescent emission, which is beneficial for plant growth. The light diffusion can distribute the incident light evenly, which has several advantages, such as improved crop yield, more leaf count, lower harvest temperature, and shorter harvest time. Thus, the micron-sized luminescent SiAlON:Eu 2+ The particles can act as both a light conversion layer and a light diffusion layer.

[0083] The luminescent particle-based materials described with reference to the embodiments herein can be used in glazing and transparent sheeting structures for greenhouses and buildings for indoor agriculture. Exemplary advantageous optical structures are described below with reference to Figures 4-7.

[0084] FIG. 4 illustrates a glazing structure including a luminescent particle-based coating according to one embodiment of the present invention. As shown in the figure, the optical structure may include a transparent glass plate or transparent polymer sheet 402 having a first surface 404 and a second surface 406, where the first surface is configured to receive external sunlight 410 and the second surface is configured to couple light 414 exiting the glazing structure to a greenhouse. The glazing structure or polymer sheet may be part of or used in a greenhouse. For glazing structures, the length of the glazing may be selected from 300 to 100 cm, preferably 250 to 140 cm, and more preferably 220 to 160 cm, and the width of the glazing may be selected from 200 to 40 cm, preferably 180 to 50 cm, and more preferably 160 to 60 cm. Typical dimensions (length x width) may include 2.140 x 1.122 mm, 1.650 x 1.22 mm, 1.650 x 997 mm, and 1.650 x 730 mm. Additionally, the glazing may have a thickness of 6 to 3 mm, preferably 5.5 to 3.5 mm, and more preferably 5.0 to 3.5 mm.

[0085] The SiAlON:Eu 2 The nanoparticle coating can be applied by spray coating the aforementioned nanoparticle dispersion onto a first surface of a substrate, such as glazing. A further coating 412 containing no nanoparticles can be applied to the luminescent nanoparticle coating for protection using a wet coating process. Typically, the composition of the protective coating can be the same as or similar to the polymer binder material of the nanoparticle coating.

[0086] In one embodiment, the surface of the glazing may be subjected to a surface treatment to introduce a light-scattering top surface. The surface-scattering interface may be introduced to maximize light coupling out of the second (bottom) surface of the glazing. The surface treatment may include an etching process to create a textured surface.

[0087] The etching process can be a wet etching process or a dry etching process. Wet etching processes work by dissolving surface portions by immersing the surface in a chemical solution. In one embodiment, a mask can be used to selectively etch material. Dry etching processes can be based on sputtering or dissolving material. This can be achieved by a reactive ion etching process or an ion beam. The resulting surface features (and therefore scattering properties) can be tailored by adjusting various etching parameters (e.g., plasma feed gas, reactive gas type and flow, gas pressure, etching time, etc.) and measuring the scattering properties of the textured surface. The textured surface can have a regular (periodic) pattern or a random pattern.

[0088] The texture pattern can have features (diameter and height) in the nanometer to micrometer range. Texture features produced based on a mask-based etching process can include cones, pyramids, microlenses in the nanometer range (approximately 10 nm to 1000 nm), or features in the micrometer range, e.g., 1 micrometer to 500 micrometers. Alternatively, texture features produced based on a mask-less etching process can result in substantially random texture features with dimensions in the nanometer or micrometer range.

[0089] A measure of the surface roughness of the surface interface is the standard deviation of the Gaussian scattering distribution of light scattered at the surface interface. Such measurements are well known in the art, for example, Kurita et al., Optical surface roughness measurement from scattered light approximated by two-dimensional Gaussian function, Transactions on Engineering Sciences, vol. 2, 1993. This paper is incorporated by reference into this disclosure.

[0090] In another embodiment, the backscattering effect that may be caused by the nanoparticles can be reduced using porous SiO2 nanoparticles. In one embodiment, the porous nanoparticles can be added to the luminescent nanoparticles. In one embodiment, 0.1 to 5 wt. % of the porous nanoparticles can be added to the luminescent nanoparticles. In a further embodiment, 0.5 to 2.0 wt. % of the porous nanoparticles can be added to the luminescent nanoparticles. In another embodiment, the porous nanoparticles typically have the same or similar size or size distribution as the luminescent nanoparticles. The porous nanoparticles provide anti-reflective properties to the coating. The porous SiO2 nanoparticles reduce the refractive index of the coating layer relative to the substrate, thereby substantially reducing backscattering of light exiting the substrate through the second surface and increasing light coupling.

[0091] The light-emitting layer can be deposited (e.g., coated or sputtered) directly onto the surface of the substrate. Alternatively, one or more layers, such as an adhesion layer, a buffer layer, and / or a passivation layer, can be deposited on the substrate before the light-emitting layer is deposited on the substrate.

[0092] In a further embodiment, instead of a coating over the substrate, the nano-sized and micron-sized SiAlON:Eu 2+ The particles can be dispersed in a transparent polymer (e.g., PE, ETFE, PVC, PMMA, polycarbonate, etc.), which is then molded into a transparent plastic film or sheet that can be used in greenhouses. Typically, the thickness of such a sheet can be 1 to 1000 micrometers, preferably 10 to 500 mm, and more preferably 40 to 120 micrometers. Furthermore, 1 to 80% by weight, preferably 5 to 50% by weight, and more preferably 15 to 35% by weight of luminescent nanoparticles can be dispersed in the film.

[0093] In the embodiment of FIG. 5, the optical structure is a substantially non-scattering or low-scattering SiAlON:Eu 2+It may include a nanoparticle coating 508 and a highly scattering transparent substrate 502 (also called a diffusive transparent substrate). Such a layer may be a SiAlON:Eu in an inorganic or organic matrix material. 2+ The matrix material may comprise nanoparticles. In one embodiment, the matrix material may be an amorphous dielectric material, such as SiAlON, Si3N4, Al2O3, Ti2O3, etc. In another embodiment, the matrix material may be a transparent organic dielectric material, such as PMMA, polyacrylic acid, polycarbonate, polyethylene, or fiberglass. Such nanoparticle coatings may be achieved based on suitable particle synthesis methods and coating techniques, as described herein.

[0094] The substrate 502 may include a diffusing transparent substrate. For example, in one embodiment, the substrate may be a diffusing glass substrate. Diffusing glass materials may be optimized for light transmission (particularly in the PAR region) while simultaneously scattering light in random directions as it leaves the substrate. In one embodiment, the diffusing glass substrate may include scattering structures to diffusely scatter the light. Instead of a glass substrate, a (diffusing) transparent polymer-based substrate may be used, which is provided with light-scattering structures that cause diffuse light to leave the optical structure on a second surface.

[0095] The optical structure shown in Figure 5 receives radiation in the solar spectrum ranging from UV to IR radiation. The UV light is converted to PAR radiation by the divalent Eu dopants 512 in the SiAlON nanoparticles. 2+ The PAR light 514 produced by the doped sites and the PAR light 518 from sunlight will exit the optical structure as diffused light, which is beneficial to plant growth.

[0096] 6, the optical structure can include a highly scattering luminescent thin film layer 608 and a low scattering transparent substrate 602. In one embodiment, the luminescent thin film layer is a thin film polycrystalline SiAlON:Eu 608 disposed on a low scattering transparent substrate, such as a glass substrate or a transparent polymer-based substrate. 2+ In another embodiment, thin film polycrystalline SiAlON:Eu 2+ Instead, a highly scattering microparticle-based coating layer can be used. Such a layer can be made of micron-sized SiAlON:Eu in an inorganic or organic matrix material. 2+ The matrix material may comprise particles. In one embodiment, the matrix material may be an amorphous dielectric material, such as SiAlON, Si3N4, Al2O3, Ti2O3, etc. In another embodiment, the matrix material may be a transparent organic dielectric material, such as PMMA, polyacrylic acid, polycarbonate, polyethylene, or fiberglass. Such micron particle coatings may be achieved based on suitable particle synthesis methods and coating techniques, as described herein.

[0097] 6 receives radiation in the solar spectrum ranging from UV to IR radiation, where UV light is converted to PAR radiation by the divalent Eu dopants 612 in the SiAlON layer. 2+ The PAR light emitted by the Eu doped material is scattered into the low scattering transparent substrate. Furthermore, the doped SiAlON layer acts as a scattering layer for the visible portion, including the PAR region. Therefore, this portion of the sunlight is scattered into the diffusing substrate. 2+ The PAR light 614 produced by the doped sites and the PAR light 618 from sunlight will exit the optical structure as diffused light, which is beneficial to plant growth.

[0098] It is anticipated that the present invention is not limited to the optical structures described with reference to Figures 4-6. For example, in further embodiments, the optical structure may include a highly scattering luminescent thin film layer and a highly scattering transparent substrate. Thus, the luminescent layer and the substrate are configured together to produce diffused light leaving the optical structure. In such embodiments, the optical structure may be optimized to transmit and produce highly diffused light in the PAR range when exposed to solar radiation.

[0099] Furthermore, in one embodiment, instead of (or in addition to) providing one or more luminescent layers on the first surface, a low-scattering or low-scattering luminescent layer can be provided on a second surface of the transparent substrate, which can be either a high-scattering (diffuse) substrate or a low-scattering substrate depending on the application.

[0100] 7A and 7B show an optical structure according to yet another embodiment. In this embodiment, luminescent nanoparticles 708 having an average size of 100-300 nm are distributed sparsely on a first (top) surface 704 of a transparent substrate 702. Sparsely distributed here means that the average distance between particles is 200-700 nm. The luminescent particles are formed from a luminescent SiAlON:Eu SiO 2 film, which has a relatively high refractive index. 2+ For example, in one embodiment, the particulate material may be a silicon-based nanoparticle. 4+ , O 2+ and Eu 2+ The luminescent material may include AlN doped with ions, which results in a refractive index of the luminescent material of approximately 2.14, forming a luminescent anti-reflective coating according to one embodiment of the present invention.

[0101] It is known from U.S. Patent Application Publication No. 2013 / 0194669 that a layer of high-refractive-index nanoparticles sparsely distributed on the surface of a low-refractive-index material, such as a glass substrate, can function as a broadband antireflection coating. Here, the nanoparticles can be arranged in an ordered array, or alternatively, the nanoparticles can be randomly distributed on the surface of the transparent substrate. The antireflection properties of such a nanoparticle layer can contribute to the formation of plasmon modes when sunlight 710 interacts with nanoparticles having dimensions in the 200-700 nm range. These plasmon modes effectively scatter the light into the substrate, as shown in the figure. The AR layer of luminescent nanoparticles converts UV light in the solar spectrum to PAR light and acts as an efficient broadband antireflection layer for the remainder of the solar spectrum, particularly the visible portion of the solar spectrum.

[0102] The phraseology used herein is merely for the purpose of describing particular embodiments and is not intended to limit the present invention. As used herein, the singular forms "a," "an," and "the" are intended to encompass the plural forms as well, unless the context clearly indicates otherwise. Furthermore, it will be understood that the words "comprise" and / or "comprising," as used herein, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0103] Functional elements in the following claims are intended to encompass any structure, material, or act that performs that function in combination with the elements of other claims as specifically claimed, in addition to corresponding structure, material, acts, and equivalents of all means or steps. The description of the present invention has been presented for illustrative purposes, but it is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the invention as set forth in the appended claims. The embodiments have been chosen and described in order to best explain the principles and practical application of the invention, and to enable those skilled in the art to understand the invention in its various forms, with various modifications as suited to the particular uses contemplated.

Claims

1. 1. A dispersion of luminescent nanoparticles for coating a greenhouse glazing structure, comprising: comprising an organic or aqueous medium and luminescent nanoparticles, The nanoparticles are Eu ２＋ %, wherein the Si concentration is selected from 0 to 33 atomic %, the Al concentration is selected from 0 to 40 atomic %, the O concentration is selected from 50 to 66 atomic %, the N concentration is selected from 0 to 10 atomic %, and Eu ２＋ is selected from 0.0001 to 5 atomic %.

2. The Si concentration is selected from 15 to 33 atomic %, the Al concentration is selected from 0.001 to 12 atomic %, the O concentration is selected from 50 to 66 atomic %, the N concentration is selected from 0.1 to 5 atomic %, and Eu ２＋ The concentration is selected from 0.0001 to 3 atomic percent, or preferably The Si concentration is selected from 30 to 33 atomic %, the Al concentration is selected from 0.01 to 2 atomic %, the O concentration is selected from 50 to 66 atomic %, the N concentration is selected from 0.1 to 1 atomic %, and Eu ２＋ The concentration is selected from 0.0005 to 1 atomic %. The dispersion of claim 1.

3. 3. The dispersion according to claim 1 or 2, wherein the nanoparticles have an average size of 1 to 1000 nm, preferably 10 to 800 nm, more preferably 20 to 600 nm.

4. 4. The dispersion according to any one of claims 1 to 3, wherein the dispersion comprises from 1% to 80% by weight of nanoparticles, preferably from 5% to 50% by weight of nanoparticles, more preferably from 15% to 35% by weight of nanoparticles.

5. 5. The dispersion of any one of claims 1 to 4, wherein the organic medium comprises an organic solvent (e.g., hexane, ethanol, heptane, toluene, chloroform, dichloromethane) containing 0.5% to 10% by weight of the polymer additive.

6. 5. The dispersion of claim 1, wherein the aqueous medium comprises an alkaline aqueous solution, such as an ammonium solution or a sodium hydroxide solution, and the alkaline aqueous solution comprises 1% to 10% by weight of a water-based polymeric additive.

7. 7. The dispersion of any one of claims 1 to 6, wherein the surface of the nanoparticles is modified with one or more types of ligands, such as stearic acid, oleic acid, octanoic acid, oleylamine, octylamine, octanethiol, trioctylphosphine, preferably the modification comprises ultrasonic treatment of the nanoparticles.

8. 7. The dispersion of any one of claims 1 to 6, wherein the surface of the nanoparticles is modified by chemical bond formation, such as silanization or esterification, to attach the nanoparticles to one or more long organic side chains having a chain length of 8 to 18 carbons.

9. The dispersion of any one of claims 1 to 8, wherein the dispersion further comprises inorganic porous nanoparticles, preferably porous silicon oxide nanoparticles.

10. A transparent plastic sheet for a greenhouse, A transparent polymeric material, and Eu dispersed in the polymeric material. ２＋ the inorganic luminescent nanoparticles doped with The nanoparticles are Eu ２＋ %, wherein the Si concentration is selected from 0 to 33 atomic %, the Al concentration is selected from 0 to 40 atomic %, the O concentration is selected from 50 to 66 atomic %, the N concentration is selected from 0 to 10 atomic %, and Eu ２＋ is selected from 0.0001 to 5 atomic %, or preferably, The Si concentration is selected from 15 to 33 atomic %, the Al concentration is selected from 0.001 to 12 atomic %, the O concentration is selected from 50 to 66 atomic %, the N concentration is selected from 0.1 to 5 atomic %, and Eu ２＋ The concentration is selected from 0.0001 to 3 atomic percent, or more preferably, The Si concentration is selected from 30 to 33 atomic %, the Al concentration is selected from 0.01 to 2 atomic %, the O concentration is selected from 50 to 66 atomic %, the N concentration is selected from 0.1 to 1 atomic %, and Eu ２＋ The concentration is selected from 0.0005 to 1 atomic %. the transparent plastic sheet;

11. 11. The transparent plastic sheet according to claim 10, wherein the thickness of the sheet is selected from 1 to 1000 micrometers, preferably from 10 to 500 mm, more preferably from 40 to 120 micrometers.

12. 1. A luminescent glazing structure for a greenhouse, comprising: glazing structures, a coating provided on at least a portion of the surface of the glazing structure; Including, The coating comprises a transparent polymeric material and, dispersed in the polymeric material, Eu ２＋ the inorganic luminescent nanoparticles doped with The nanoparticles are Eu ２＋ %, wherein the Si concentration is selected from 0 to 33 atomic %, the Al concentration is selected from 0 to 40 atomic %, the O concentration is selected from 50 to 66 atomic %, the N concentration is selected from 0 to 10 atomic %, and Eu ２＋ is selected from 0.0001 to 5 atomic %, or preferably, The Si concentration is selected from 15 to 33 atomic %, the Al concentration is selected from 0.001 to 12 atomic %, the O concentration is selected from 50 to 66 atomic %, the N concentration is selected from 0.1 to 5 atomic %, and Eu ２＋ The concentration is selected from 0.0001 to 3 atomic percent, or more preferably, The Si concentration is selected from 30 to 33 atomic %, the Al concentration is selected from 0.01 to 2 atomic %, the O concentration is selected from 50 to 66 atomic %, the N concentration is selected from 0.1 to 1 atomic %, and Eu ２＋ The concentration is selected from 0.0005 to 1 atomic %. The luminescent glazing structure.

13. 12. A luminescent glazing structure according to claim 11, wherein the coating has a thickness selected from 10 to 200 micrometers, preferably from 20 to 180 micrometers, more preferably from 50 to 150 micrometers.

14. A greenhouse comprising the luminescent glazing structure or luminescent sheet according to any one of claims 10 to 13.

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