Nanocrystal compositions, methods of making and using the same

Abstract

The application provides a nanocrystal composition and a preparation method and application thereof. The preparation method comprises the following steps: S1, preparing a hot melt adhesive containing a metal salt, the hot melt adhesive being the metal salt, or the hot melt adhesive comprising the metal salt and an organic dispersant; S2, mixing a plurality of nanocrystals with the hot melt adhesive at a temperature at which the hot melt adhesive is molten to form a metal salt-nanocrystal dispersion system; and S3, cooling the metal salt-nanocrystal dispersion system to obtain a solid nanocrystal composition. By the above preparation method, a large amount of metal salt is coated on the surface of the nanocrystal, and at least part of the metal salt can be combined with the surface of the nanocrystal in a chemical bond form, and the nanocrystal composition exists in a solid form at normal temperature due to the presence of the hot melt adhesive, so that the falling of the metal salt combined on the surface of the nanocrystal is effectively avoided, the water-oxygen resistance and photolysis resistance of the nanocrystal are greatly improved, and meanwhile, a high fluorescence quantum yield is maintained.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nanocrystal materials, in particular to a nanocrystal composition, a preparation method and application thereof. BACKGROUND

[0002] In the past two decades, nanocrystal synthesis chemistry mainly focuses on the size and shape monodisperse control and how to improve the fluorescence quantum yield, but it is not enough to only achieve size and shape monodisperse and improve the fluorescence quantum yield, more importantly, it is necessary to reduce the influence of environment, especially water and oxygen, on the optical, electrical and other properties of nanocrystals as much as possible, which has great value for the application research of nanocrystals.

[0003] The influence of oxygen and water on nanocrystals is often affected by light, which is respectively called photo-oxidation and photo-hydrolysis process of nanocrystals, resulting in the decrease of fluorescence quantum yield of nanocrystals, the broadening of fluorescence half-width and the like, which greatly hinders the application of nanocrystal materials. In order to avoid the occurrence of photo-hydrolysis and photo-oxidation, the obtained nanocrystals are usually stored in organic solvents to form a nanocrystal solution. Compared with single-component core nanocrystals, core-shell structure nanocrystals have higher optical and chemical stability, such as coating a thicker CdS shell layer on the CdSe nanocrystals to obtain nanocrystals with higher fluorescence quantum yield. In addition, other means for improving the stability of nanocrystals include preparing alloy structure nanocrystals and doping metal atoms (such as Al) in nanocrystals. The above-mentioned means improve the stability of nanocrystal solution to a certain extent, but the water and oxygen resistance of nanocrystal solution is still insufficient under light conditions. At present, the best means to achieve water and oxygen resistance of nanocrystals is to coat an oxide on the surface of nanocrystals. It is reported in the literature that the oxides coated on the surface of nanocrystals mainly include SiO2 and TiO2, but these oxides are difficult to eliminate the surface defects of nanocrystals, and also have many lattice defects, in addition, the crystal type mismatch between these oxides and nanocrystals also leads to the deterioration of the size distribution of nanocrystals and the decrease of optical and chemical stability.

[0004] In the application of nanocrystals (especially in display products), nanocrystals are often dispersed in a polymer adhesive, which to some extent hinders the direct contact of water and oxygen with nanocrystals. However, this means only slows down the rate of water and oxygen reaching the surface of nanocrystals, and once water and oxygen enter the polymer adhesive, the fluorescence quenching of nanocrystals under light conditions is still possible. SUMMARY

[0005] The main purpose of the present application is to provide a nanocrystal composition, a preparation method and application thereof, so as to solve the problem of weak water and oxygen resistance of nanocrystals in the prior art.

[0006] To achieve the above object, according to one aspect of the present application, there is provided a method for preparing a nanocrystal composition, the method comprising: step S1, preparing a hot melt adhesive comprising a metal salt, the hot melt adhesive being the metal salt, or the hot melt adhesive comprising the metal salt and an organic dispersant; step S2, mixing a plurality of nanocrystals with the hot melt adhesive at a temperature at which the hot melt adhesive is molten, to form a metal salt-nanocrystal dispersion system; and step S3, cooling the metal salt-nanocrystal dispersion system to obtain a solid nanocrystal composition.

[0007] Further, the weight ratio of the metal salt to the organic dispersant is 6:1 to 1:2, or the mass percentage of the metal salt in the hot melt adhesive is 40% to 90%.

[0008] Further, the metal salt is any one or more of a metal carboxylate and a metal phosphonate, preferably the metal carboxylate has a carboxylate group with a carbon atom number of 8 to 22, and preferably the metal phosphonate is selected from metal phosphonates having a hydrocarbon group with a carbon atom number of 4 to 22, and preferably the metal ion of the metal salt is selected from any one or more of sodium, magnesium, aluminum, potassium, calcium, cesium, zirconium, manganese, zinc, and cadmium.

[0009] Further, the organic dispersant is selected from any one or more of C8-C 22 alkanes, C8-C 22 alkenes, C8-C 22 alcohols, C8-C 22 esters, and squalane.

[0010] Further, the temperature at which the hot melt adhesive is molten is less than the decomposition temperature of the metal salt, or the temperature at which the hot melt adhesive is molten is 150 to 250°C.

[0011] Further, the solid nanocrystal composition has a viscosity of 300 to 3000 cps at 15 to 50°C.

[0012] Further, the hot melt adhesive further comprises a viscosity modifier, the viscosity modifier being selected from any one or more of trialkyl phosphines and C4-C 22 fatty amines, and preferably the weight ratio of the viscosity modifier to the metal salt is 1:3 to 5:1.

[0013] Further, the weight ratio of the metal salt to the nanocrystals is 1:1 to 1000:1, and preferably 10:1 to 1000:1.

[0014] Further, in step S2, the nanocrystals are added in the form of a nanocrystal solution, and preferably step S2 further comprises a process of removing a solvent from the nanocrystal solution.

[0015] Further, the rate of change of the fluorescence peak position and the half-peak width of the nanocrystals in the nanocrystal composition obtained in step S3 is 0-2%.

[0016] Further, the metal salt-nanocrystal dispersion system is a homogeneous system.

[0017] According to another aspect of the present application, there is provided a nanocrystal composition, which is a solid, the nanocrystal composition comprising a plurality of nanocrystals and a metal salt, the plurality of nanocrystals being dispersed in the metal salt, at least a portion of the metal salt being a surface ligand of the nanocrystals.

[0018] Further, the weight ratio of the metal salt to the nanocrystals is 1:1-1000:1, and preferably the nanocrystal composition does not comprise a high molecular polymer or a polymerizable monomer.

[0019] Further, the viscosity of the nanocrystal composition at 15-50°C is 300-3000 cps.

[0020] Further, the metal salt is any one or more of a metal carboxylate and a metal phosphonate, preferably the metal carboxylate has a carboxylate group having a carbon number of 8-22, and preferably the metal phosphonate is selected from a metal phosphonate having a hydrocarbon group having a carbon number of 4-22, and preferably the metal ion of the metal salt is selected from any one or more of sodium, magnesium, aluminum, potassium, calcium, cesium, zirconium, manganese, zinc, and cadmium.

[0021] Further, the nanocrystal composition further comprises an organic dispersant, and preferably the weight ratio of the metal salt to the organic dispersant is 6:1-1:2, or preferably the mass percentage of the metal salt in the nanocrystal composition is 40-90%.

[0022] Further, the organic dispersant is selected from any one or more of a C8-C 22 alkane, a C8-C 22 alkene, a C8-C 22 alcohol, a C8-C 22 ester, and squalane.

[0023] Further, the nanocrystal composition further comprises a viscosity modifier, and the viscosity modifier is selected from any one or more of a trialkyl phosphine and a C4-C 22 aliphatic amine, and preferably the weight ratio of the viscosity modifier to the metal salt is 1:3-5:1.

[0024] According to another aspect of the present application, there is provided a light conversion device, the light conversion device comprising any one of the nanocrystal compositions described above.

[0025] Further, the above light conversion device has a decrease in fluorescence quantum yield of no more than 5% after undergoing Condition A, Condition A being: the initial light absorption rate of the light conversion device is 30%, 0.5 W / cm 2 The light conversion device is irradiated with blue light of the following light intensity for no less than 500 hours.

[0026] According to still another aspect of the present application, there is provided a light emitting device comprising the nanocrystal composition of any one of the above.

[0027] By the above preparation method, a large amount of metal salt is coated on the surface of the nanocrystal, and at least part of the metal salt can be combined with the surface of the nanocrystal in a chemical bond form. Moreover, the nanocrystal composition exists in a solid form at room temperature due to the presence of the hot melt adhesive, thereby effectively avoiding the falling off of the metal salt combined on the surface of the nanocrystal, greatly improving the water and oxygen resistance of the nanocrystal, and meanwhile maintaining a high fluorescence quantum yield. During storage and application, the nanocrystal is coated by the hot melt adhesive to isolate water and oxygen, thereby effectively avoiding photo-oxidation and photo-hydrolysis, and ensuring the performance stability during application. DETAILED DESCRIPTION

[0028] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the embodiments.

[0029] As analyzed in the background art of the present application, the existing water and oxygen isolation technology for nanocrystals cannot effectively maintain the water and oxygen resistance effect of the nanocrystals under light irradiation. At present, nanocrystals are preserved by disposing ligands on the surface of the nanocrystals and then preparing a nanocrystal solution. Since the ligands on the surface of the nanocrystals have solubility in the nanocrystal solution, defects will occur on the surface of the nanocrystals due to the falling off of the ligands in the nanocrystal solution, which will cause photo-oxidation and photo-hydrolysis of the nanocrystals. Secondly, under light irradiation, especially under strong light irradiation, the temperature in the nanocrystal solution or the optical film containing the nanocrystals will increase, further causing the ligands on the surface of the nanocrystals to fall off and form defects, thereby causing the nanocrystals to be more prone to photo-oxidation and photo-hydrolysis. Furthermore, even if the nanocrystals have been isolated from water and oxygen, the fluorescence quantum yield of the nanocrystals will be greatly reduced due to the movement of atoms on the surface of the nanocrystals and the falling off of the ligands under strong light irradiation. It can be seen that the water and oxygen resistance effect of the nanocrystals under light irradiation cannot be improved due to the easy falling off of the ligands. In order to solve this problem, the present application provides a nanocrystal composition, a preparation method and application thereof.

[0030] In a typical embodiment of the present application, a method for preparing a nanocrystal composition is provided, which comprises: step S1, preparing a hot-melt adhesive containing a metal salt, wherein the hot-melt adhesive is a metal salt, or the hot-melt adhesive comprises a metal salt and an organic dispersion; step S2, mixing a plurality of nanocrystals with the hot-melt adhesive at a temperature at which the hot-melt adhesive melts to form a metal salt-nanocrystal dispersion system; and step S3, cooling the metal salt-nanocrystal dispersion system to obtain a solid nanocrystal composition.

[0031] The present application uses the above-mentioned preparation method to coat a large amount of metal salt on the surface of the nanocrystal. At least part of the metal salt can be chemically bonded to the surface of the nanocrystal. Moreover, due to the presence of the hot-melt adhesive, the nanocrystal composition exists in a solid form at room temperature, thereby effectively preventing the metal salt bound to the surface of the nanocrystal from falling off, greatly improving the water and oxygen resistance of the nanocrystal, while maintaining a high fluorescence quantum yield. During the storage and application process of the above-mentioned nanocrystal composition, since the nanocrystals are coated with the hot-melt adhesive to isolate water and oxygen, photooxidation and photohydrolysis are effectively avoided, ensuring its performance stability during application.

[0032] The change rate of the fluorescence peak position and half-width of the nanocrystals used in step S2 and the nanocrystals in the solid nanocrystal composition obtained in step S3 is 0-2%. The quantum yield is improved by 0-10%. Taking the change rate of the fluorescence peak position as an example, the above-mentioned change rate refers to the ratio of the change value between the fluorescence peak position of the nanocrystal composition obtained by the preparation method of the present application and the fluorescence peak position of the nanocrystals before treatment, relative to the fluorescence peak position of the nanocrystals before treatment.

[0033] The above-mentioned “solid state” includes not only solids without any fluidity but also viscous colloids with a certain viscosity or fluidity. Based on the hot-melt adhesive used, the viscosity of the above-mentioned solid nanocrystalline composition at 15-50° C. is 300-3000 cps.

[0034] The above-mentioned "melting temperature of the hot-melt adhesive" refers to the temperature at which the hot-melt adhesive can remain in a liquid state. In addition, the hot-melt adhesive of the present application refers to an adhesive that can be melted at a certain temperature to form a colloid with a certain viscosity. There are many ways to form the above-mentioned hot-melt adhesive. In some embodiments, the above-mentioned step S1 includes: heating and melting the metal salt to form a hot-melt adhesive, wherein a metal salt that is solid at room temperature and melts after heating is selected, and the hot-melt adhesive formed by the molten metal salt can wrap the nanocrystals. Or the above-mentioned step S1 includes mixing and heating the metal salt with an organic dispersion to form a hot-melt adhesive. The hot-melt adhesive is formed by heating a mixture of a metal salt and an organic dispersion, and then further mixing the two to form a colloid, and the nanocrystals are wrapped with the colloid. After cooling, the above-mentioned two hot-melt adhesives return to a solid or viscous state.

[0035] In some embodiments, the above-mentioned solid nanocrystal composition is heated to the above-mentioned melting temperature to obtain the above-mentioned metal salt-nanocrystal dispersion system.

[0036] In addition, the viscosity of the nanocrystal composition formed can be adjusted by adjusting the ratio of the amount of the metal salt and the organic dispersant, preferably the weight ratio of the above-mentioned metal salt to the organic dispersant is 6:1 to 1:2, or the mass percentage of the metal salt in the hot melt adhesive is 40% to 90%. The higher the amount of the metal salt, the greater the viscosity of the nanocrystal composition, and even after cooling, a solid without flowability can be formed.

[0037] The metal salt used in the present application can be selected from metal salts that are structurally stable and can be melted at relatively low temperatures, such as any one or more of metal carboxylates, metal phosphonates; in some embodiments, the carboxylate of the metal carboxylate has a carbon atom number of 8 to 22, and the metal phosphonate is selected from metal phosphonates having a hydrocarbon group with a carbon atom number of 4 to 22; in some embodiments, the metal ion of the metal salt is selected from any one or more of sodium, magnesium, aluminum, potassium, calcium, cesium, zirconium, manganese, zinc, cadmium, and preferably a combination of multiple metal salts. For example, oleate, myristate, octanoate, butyrate, mixed acid salt (such as oleate-octanoate), and more specifically, waxy or blocky magnesium oleate, etc.

[0038] In some embodiments, the above-mentioned organic dispersant is selected from any one or more of C8-C 22 alkanes, C8-C 22 alkenes, C8-C 22 alcohols, C8-C 22 esters, and squalane, which form good dispersion performance with the metal salt.

[0039] In the formation of the hot melt adhesive, in some embodiments, the metal salt is heated and melted, and in order to avoid denaturation of the substance, the above-mentioned melting temperature is preferably greater than the melting temperature of the metal salt and less than the decomposition temperature of the metal salt. In other embodiments, the metal salt and the organic dispersant are mixed and heated, and in order to avoid the influence of high heating temperature on the nanocrystals, the above-mentioned melting temperature is preferably 150 to 250°C.

[0040] In addition, in order to further improve the stability of the hot melt adhesive and the uniformity of the nanocrystal coating, in some embodiments, the above-mentioned hot melt adhesive includes a viscosity modifier selected from any one or more of trialkyl phosphine, C4-C 22 fatty amines. In some embodiments, the alkyl group of the above-mentioned trialkyl phosphine has a carbon atom number of 4 to 22. In some embodiments, the weight ratio of the viscosity modifier to the metal salt is 1:3 to 5:1.

[0041] In some embodiments, the hot melt adhesive described above does not include a curable high molecular polymer or a polymerizable monomer.

[0042] Since the principle on which the method of the present application is based is mainly to utilize the physical coating of metal salt on nanocrystals, at least part of the metal salt can be combined with the surface of nanocrystals in the form of chemical bond, therefore, on the basis of meeting the requirement of the amount used for coating, in order to further improve the stability of coating, the more the amount of metal salt is used, the better; at the same time, in order to ensure the luminous efficiency of nanocrystals per unit mass, in some embodiments, the weight ratio of the metal salt to nanocrystals is 1:1-1000:1, preferably 10:1-1000:1.

[0043] In some embodiments, the weight ratio of the metal salt to nanocrystals is greater than or equal to 5:1, or greater than or equal to 10:1, or greater than or equal to 15:1, or greater than or equal to 20:1, or greater than or equal to 25:1, or greater than or equal to 30:1, or greater than or equal to 35:1, or greater than or equal to 40:1, or greater than or equal to 45:1, or greater than or equal to 50:1, or greater than or equal to 55:1, or greater than or equal to 60:1, or greater than or equal to 65:1, or greater than or equal to 70:1, or greater than or equal to 75:1, or greater than or equal to 80:1, or greater than or equal to 85:1, or greater than or equal to 90:1, or greater than or equal to 95:1, or greater than or equal to 100:1, or greater than or equal to 125:1, or greater than or equal to 150:1, or greater than or equal to 175:1, or greater than or equal to 200:1, or greater than or equal to 300:1, or greater than or equal to 400:1, or greater than or equal to 500:1, or greater than or equal to 600:1, or greater than or equal to 700:1, or greater than or equal to 800:1, or greater than or equal to 900:1, and less than or equal to 1000:1; or

[0044] less than or equal to 30:1, or less than or equal to 35:1, or less than or equal to 40:1, or less than or equal to 45:1, or less than or equal to 50:1, or less than or equal to 55:1, or less than or equal to 60:1, or less than or equal to 65:1, or less than or equal to 70:1, or less than or equal to 75:1, or less than or equal to 80:1, or less than or equal to 85:1, or less than or equal to 90:1, or less than or equal to 95:1, or less than or equal to 100:1, or less than or equal to 125:1, or less than or equal to 150:1, or less than or equal to 175:1, or less than or equal to 200:1, or less than or equal to 300:1, or less than or equal to 400:1, or less than or equal to 500:1, or less than or equal to 600:1, or less than or equal to 700:1, or less than or equal to 800:1, or less than or equal to 900:1, and greater than or equal to 5:1, or greater than or equal to 10:1, or greater than or equal to 15:1.

[0045] In the implementation of the above step S2, the nanocrystals can be pure nanocrystals synthesized by the user, or nanocrystals available on the market or stored in a solution. When the nanocrystals are added in the form of a nanocrystal solution in the above step S2, step S2 further includes a process of removing the solvent in the nanocrystal solution. The removal process can be heating or vacuuming to volatilize the solvent, or other means for removing the solvent in the nanocrystal solution in the prior art. The removal is not complete, and even if some solvent remains, it does not affect the implementation of the preparation method. The above solvent is a solvent with a boiling point lower than the melting temperature and capable of dissolving or dispersing the nanocrystals, for example, toluene, hexane, octane, etc.

[0046] In some embodiments, the metal salt-nanocrystal dispersion system formed in the above step S2 is a homogeneous system, which is conducive to the chemical bonding of the metal salt and the surface of the nanocrystals, and better improves the water-oxygen resistance of the nanocrystals.

[0047] In another typical embodiment of the present application, a nanocrystal composition is provided, which is a solid, and includes a plurality of nanocrystals and a metal salt. The plurality of nanocrystals are dispersed in the metal salt, and at least a portion of the metal salt is a surface ligand of the nanocrystals.

[0048] The metal salt in the nanocrystal composition of the present application has little effect on the fluorescence peak position and half-peak width of the nanocrystals. The change rate of the fluorescence peak position and half-peak width before and after the modification by the metal salt is within 0-2%. However, due to the protection of the metal salt, the water-oxygen resistance of the nanocrystals is effectively improved, so that the stability and service life of the nanocrystals during storage and use are improved. Moreover, compared with the initial nanocrystals, the fluorescence quantum yield of the nanocrystal composition does not decrease, but can be increased by 0-10%.

[0049] Since the main principle that the nanocrystal composition of the present application is based on is to utilize the physical coating of the nanocrystal by the metal salt, at least part of the metal salt can be combined with the surface of the nanocrystal in the form of chemical bond, therefore, on the basis of meeting the requirement of the amount used for realizing the coating, the more the amount of the metal salt is, the better it is for further improving the stability of the coating; meanwhile, in order to ensure the luminous efficiency of the nanocrystal per unit mass, in some embodiments, the weight ratio of the metal salt to the nanocrystal is 1:1-1000:1, preferably 10:1-1000:1.

[0050] In some embodiments, the weight ratio of the metal salt to the nanocrystal is greater than or equal to 5:1, or greater than or equal to 10:1, or greater than or equal to 15:1, or greater than or equal to 20:1, or greater than or equal to 25:1, or greater than or equal to 30:1, or greater than or equal to 35:1, or greater than or equal to 40:1, or greater than or equal to 45:1, or greater than or equal to 50:1, or greater than or equal to 55:1, or greater than or equal to 60:1, or greater than or equal to 65:1, or greater than or equal to 70:1, or greater than or equal to 75:1, or greater than or equal to 80:1, or greater than or equal to 85:1, or greater than or equal to 90:1, or greater than or equal to 95:1, or greater than or equal to 100:1, or greater than or equal to 125:1, or greater than or equal to 150:1, or greater than or equal to 175:1, or greater than or equal to 200:1, or greater than or equal to 300:1, or greater than or equal to 400:1, or greater than or equal to 500:1, or greater than or equal to 600:1, or greater than or equal to 700:1, or greater than or equal to 800:1, or greater than or equal to 900:1, and less than or equal to 1000:1; or

[0051] less than or equal to 30:1, or less than or equal to 35:1, or less than or equal to 40:1, or less than or equal to 45:1, or less than or equal to 50:1, or less than or equal to 55:1, or less than or equal to 60:1, or less than or equal to 65:1, or less than or equal to 70:1, or less than or equal to 75:1, or less than or equal to 80:1, or less than or equal to 85:1, or less than or equal to 90:1, or less than or equal to 95:1, or less than or equal to 100:1, or less than or equal to 125:1, or less than or equal to 150:1, or less than or equal to 175:1, or less than or equal to 200:1, or less than or equal to 300:1, or less than or equal to 400:1, or less than or equal to 500:1, or less than or equal to 600:1, or less than or equal to 700:1, or less than or equal to 800:1, or less than or equal to 900:1, and greater than or equal to 5:1, or greater than or equal to 10:1, or greater than or equal to 15:1.

[0052] and preferably the above nanocrystal composition does not include high molecular polymer or polymerizable monomer.

[0053] The above "solid" includes not only a solid without any fluidity, but also a viscous gel having a certain viscosity or fluidity, and the viscosity of the nanocrystal composition at 15-50°C is 300-3000 cps based on the performance of the metal salt used.

[0054] In some embodiments, the viscosity of the nanocrystal composition at 15-50°C is greater than or equal to 300 cps, or greater than or equal to 350 cps, or greater than or equal to 400 cps, or greater than or equal to 450 cps, or greater than or equal to 500 cps, or greater than or equal to 550 cps, or greater than or equal to 600 cps, or greater than or equal to 650 cps, or greater than or equal to 700 cps, or greater than or equal to 750 cps, or greater than or equal to 800 cps, or greater than or equal to 850 cps, or greater than or equal to 900 cps, or greater than or equal to 950 cps, or greater than or equal to 1000 cps, or greater than or equal to 1500 cps, or greater than or equal to 2000 cps, or greater than or equal to 2500 cps, and less than or equal to 3000 cps; or

[0055] The viscosity at 15-50°C is less than or equal to 600 cps, or less than or equal to 650 cps, or less than or equal to 700 cps, or less than or equal to 750 cps, or less than or equal to 800 cps, or less than or equal to 850 cps, or less than or equal to 900 cps, or less than or equal to 950 cps, or less than or equal to 1000 cps, or less than or equal to 1500 cps, or less than or equal to 2000 cps, or less than or equal to 2500 cps, or less than or equal to 3000 cps, and greater than or equal to 300 cps, or greater than or equal to 400 cps, or greater than or equal to 500 cps.

[0056] The metal salt used in the present application can be selected from a metal salt that is structurally stable and can be molten at a relatively low temperature, such as any one or more of metal carboxylate, metal phosphonate, preferably a combination of multiple; in some embodiments, the carboxylate of the metal carboxylate has a carbon atom number of 8-22, and the metal phosphonate is selected from a metal phosphonate having a hydrocarbon group with a carbon atom number of 4-22; in some embodiments, the metal ion of the metal salt is selected from any one or more of sodium, magnesium, aluminum, potassium, calcium, cesium, zirconium, manganese, zinc, and cadmium.

[0057] In some embodiments of the present application, to improve the uniformity of the nanocrystals coated by the metal salt, the nanocrystal composition further comprises an organic dispersant. One skilled in the art can adjust the viscosity of the nanocrystal composition formed by adjusting the ratio of the amount of the metal salt and the organic dispersant, preferably the weight ratio of the metal salt to the organic dispersant is 1:5 to 1:1, or the mass percentage of the metal salt in the nanocrystal composition is 40% to 90%.

[0058] In some embodiments, the organic dispersant is selected from any one or more of C8to C 22 alkanes, C8to C 22 alkenes, C8to C 22 alcohols, C8to C 22 esters, squalane. In some embodiments, the weight ratio of the metal salt to the organic dispersant is 6:1 to 1:2. The higher the amount of the metal salt, the higher the viscosity of the nanocrystal composition, and even after cooling, a solid without flowability can be formed.

[0059] Further, to further improve the stability of the hot melt adhesive and the uniformity of the nanocrystals coated, in some embodiments, the nanocrystal composition further comprises a viscosity modifier selected from any one or more of trialkyl phosphine, C4to C 22 fatty amines. In some embodiments, the number of carbon atoms of the alkyl group of the trialkyl phosphine is 4 to 22. In some embodiments, the weight ratio of the viscosity modifier to the metal salt is 1:3 to 5:1.

[0060] Since the metal salt in the nanocrystal composition of the present application is mainly used to improve the water and oxygen resistance of the nanocrystals by coating the nanocrystals, the type of the nanocrystals is not particularly selected, such as the above-mentioned nanocrystals are Group II-VI compounds, Group IV-VI compounds, Group I-III-VI compounds, Group I-II-IV-VI compounds, Group III-V compounds, or combinations thereof, especially the above-mentioned nanocrystals without cadmium.

[0061] The above-mentioned Group II-VI compounds can further comprise Group III metals. The above-mentioned Group III-V compounds can further comprise Group II metals (e.g., InZnP). The above-mentioned Group II-VI compounds can be binary compounds such as ZnS, ZnSe, ZnTe, ZnO, HgS, HgSe, HgTe, MgSe, MgS, or combinations thereof; ternary compounds such as ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, HgZnS, HgZnSe, HgZnTe, MgZnSe, MgZnS, or combinations thereof; or quaternary compounds such as HgZnTeS, ZnTeSeS, HgZnSeS, HgZnSeTe, HgZnSTe, or combinations thereof.

[0062] The above Group IV-VI compound can be: a binary compound such as SnS, SnSe, SnTe, PbS, PbSe, PbTe, or a combination thereof; a ternary compound such as SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, SnPbTe, or a combination thereof; or a quaternary compound such as SnPbSSe, SnPbSeTe, SnPbSTe, or a combination thereof.

[0063] Examples of the above Group I-III-VI compound can include CuInSe2, CuInS2, CuInGaSe, and CuInGaS, but are not limited thereto.

[0064] Examples of the above Group I-II-IV-VI compound can include CuZnSnSe and CuZnSnS, but are not limited thereto.

[0065] The above Group III-V compound can be: a binary compound such as GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb, or a combination thereof; a ternary compound such as GaNP, GaNAs, GaNSb, GaPAs, GaPSb, AlNP, AlNAs, AlNSb, AlPAs, AlPSb, InNP, InNAs, InNSb, InPAs, InPSb, or a combination thereof; or a quaternary compound such as GaAlNP, GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs, GaInNSb, GaInPAs, GaInPSb, InAlNP, InAlNAs, InAlNSb, InAlPAs, InAlPSb, or a combination thereof.

[0066] In some embodiments, the above nanocrystal is a core-shell nanocrystal or an alloy nanocrystal or a nanocrystal with a doping element.

[0067] In some embodiments, the above nanocrystal does not include a perovskite, carbon dot, or silicon dot type nanocrystal.

[0068] In another typical embodiment of the present application, a nanocrystal composition is provided, including any of the above nanocrystal compositions. Since the nanocrystal composition of the present application has good water and oxygen resistance, the structure and performance are relatively stable during storage and use, and thus can be applied to various nanocrystal compositions and provide good light emitting efficiency.

[0069] In another exemplary embodiment of the present application, a light conversion device comprising any of the nanocrystal compositions described above is also provided. The light conversion device of the present application has high luminous efficiency and can maintain relative stability during storage and use. The light conversion device described above can be a nanocrystal diffusion plate, a nanocrystal lens, or the like.

[0070] In another exemplary embodiment of the present application, a light emitting device comprising any of the nanocrystal compositions described above is also provided. In some embodiments, the light emitting device comprises a cathode, an anode, and an emissive layer disposed between the cathode and the anode, the emissive layer comprising any of the nanocrystal compositions described above.

[0071] The light emitting device described above has the nanocrystal composition of the present application, and thus can have high luminous efficiency and stability, thereby ensuring the light emitting performance of the light emitting device.

[0072] Through experimental research, the decrease in fluorescence quantum yield of the light emitting device described above after undergoing Condition A is not more than 5%, Condition A being: the initial light absorption rate of the light emitting device is 30%, the light emitting device is irradiated with blue light having a wavelength of 450 nm at an intensity of 0.5 W / cm2for 500 hours. 2 The light emitting device is irradiated with blue light having the following intensity for no less than 500 hours. The wavelength of the blue light can be 430-480 nm.

[0073] The beneficial effects of the present application will be further illustrated below in conjunction with examples and comparative examples.

[0074] Example 1

[0075] 5 mmol of magnesium acetate, 10 mmol of oleic acid, and 2 mL of ODE (1.58 g) were placed in a 100 mL three-necked flask, the temperature was raised to 200°C, and nitrogen was blown for 30 min to form a hot-melt adhesive containing magnesium oleate (2.94 g); while maintaining the temperature at 200°C, the hot-melt adhesive was injected with a toluene solution of CdSe / CdZnS core-shell nanocrystals (450 nm absorbance OD = 400, wherein the mass of the CdSe / CdZnS core-shell nanocrystals was 0.086 g), and nitrogen was blown to remove the toluene, thereby forming a metal salt-nanocrystal dispersion system; the temperature was lowered to below 150°C, and a nanocrystal composition was obtained.

[0076] Example 2

[0077] Take 5 mmol of magnesium acetate, 10 mmol of oleic acid, 2 mL of ODE and place them in a 100 mL three-necked flask, raise the temperature to 200°C, exhaust for 30 min with nitrogen to form a hot melt adhesive containing magnesium oleate; keep the temperature at 200°C, inject CdSe / CdZnS core-shell nanocrystal toluene solution (450 nm absorbance OD = 400) into the hot melt adhesive, after exhausting the toluene with nitrogen, inject 1 mL of TOP solution to adjust the viscosity, and form a metal salt-nanocrystal dispersion system; cool to below 150°C to obtain a nanocrystal composition.

[0078] Example 3

[0079] Take 5 mmol of magnesium acetate, 10 mmol of oleic acid, 2 mL of ODE and place them in a 100 mL three-necked flask, raise the temperature to 200°C, exhaust for 30 min with nitrogen to form a hot melt adhesive containing magnesium oleate; keep the temperature at 200°C, inject CdSe / CdZnS core-shell nanocrystal toluene solution (450 nm absorbance OD = 400) into the hot melt adhesive, after exhausting the toluene with nitrogen, inject 1 mL of TOP solution to adjust the viscosity, and form a metal salt-nanocrystal dispersion system; cool to below 150°C to obtain a nanocrystal composition.

[0080] Example 4

[0081] Take 5 mmol of magnesium acetate, 10 mmol of oleic acid, 2 mL of ODE and place them in a 100 mL three-necked flask, raise the temperature to 200°C, exhaust for 30 min with nitrogen to form a hot melt adhesive containing magnesium oleate; keep the temperature at 200°C, inject CdSe / CdZnS core-shell nanocrystal toluene solution (450 nm absorbance OD = 400) into the hot melt adhesive, after exhausting the toluene with nitrogen, inject 1 mL of TOP solution to adjust the viscosity, and form a metal salt-nanocrystal dispersion system; cool to below 150°C to obtain a nanocrystal composition.

[0082] Example 5

[0083] Take 5 mmol of magnesium acetate, 5 mmol of oleic acid, 5 mmol of octanoic acid, 2 mL of ODE and place them in a 100 mL three-necked flask, raise the temperature to 200°C, exhaust for 30 min with nitrogen to form a hot melt adhesive containing magnesium octanoate-oleate (2.24 g); keep the temperature at 200°C, inject CdSe / CdZnS core-shell nanocrystal toluene solution (450 nm absorbance OD = 400) into the hot melt adhesive, exhaust the toluene with nitrogen, inject 1 mL of TOP solution to form a metal salt-nanocrystal dispersion system; cool to below 150°C to obtain a nanocrystal composition.

[0084] Example 6

[0085] Take 10 mmol of magnesium acetate, 20 mmol of oleic acid, 2 mL of ODE and place them in a 100 mL three-necked flask, raise the temperature to 200°C, exhaust for 30 min with nitrogen to form a hot melt adhesive containing magnesium oleate; keep the temperature at 200°C, inject CdSe / CdZnS core-shell nanocrystal toluene solution (450 nm absorbance OD = 400) into the hot melt adhesive, exhaust the toluene with nitrogen, form a metal salt-nanocrystal dispersion system; cool to below 150°C to obtain a nanocrystal composition.

[0086] Example 7

[0087] Take 5 mmol of aluminum oleate, 1 ml of ODE and place them in a 100 mL three-necked flask, raise the temperature to 200°C to form a hot melt adhesive; keep the temperature at 200°C, inject CdSe / CdZnS core-shell nanocrystal toluene solution (450 nm absorbance OD = 400) into the hot melt adhesive, exhaust the toluene with nitrogen, form a metal salt-nanocrystal dispersion system; cool to below 150°C to obtain a nanocrystal composition.

[0088] Example 8

[0089] Take 5 mmol of magnesium acetate, 10 mmol of dodecyl phosphonic acid, 2 mL of ODE and place them in a 100 mL three-necked flask, raise the temperature to 200°C, exhaust for 30 min with nitrogen to form a hot melt adhesive containing magnesium dodecyl phosphonate (2.61 g); keep the temperature at 200°C, inject CdSe / CdZnS core-shell nanocrystal toluene solution (450 nm absorbance OD = 400) into the hot melt adhesive, exhaust the toluene with nitrogen, form a metal salt-nanocrystal dispersion system; cool to below 150°C to obtain a nanocrystal composition.

[0090] Example 9

[0091] Take 5 mmol of zirconium acetate, 10 mmol of oleic acid, 2 mL of ODE and place them in a 100 mL three-necked flask, raise the temperature to 200°C, exhaust for 30 min with nitrogen to form a hot melt adhesive containing zirconium oleate (3.27 g); keep the temperature at 200°C, inject CdSe / CdZnS core-shell nanocrystal toluene solution (450 nm absorbance OD = 400) into the hot melt adhesive, exhaust the toluene with nitrogen, form a metal salt-nanocrystal dispersion system; cool to below 150°C to obtain a nanocrystal composition.

[0092] Example 10

[0093] Take 5 mmol of magnesium acetate, 10 mmol of oleic acid, 2 mL of ODE and place them in a 100 mL three-necked flask, raise the temperature to 200°C, exhaust with nitrogen for 30 min to form a hot melt adhesive containing magnesium oleate; keep the temperature at 200°C, inject CdSe / CdZnS core-shell nanocrystal toluene solution (450 nm absorbance OD = 40) into the hot melt adhesive, exhaust the toluene with nitrogen, form a metal salt-nanocrystal dispersion system; cool to below 150°C to obtain a nanocrystal composition.

[0094] Example 11

[0095] Take 5 mmol of magnesium acetate, 10 mmol of oleic acid, 2 mL of ODE and place them in a 100 mL three-necked flask, raise the temperature to 200°C, exhaust with nitrogen for 30 min to form a hot melt adhesive containing magnesium oleate; keep the temperature at 200°C, inject CdSe / CdZnS core-shell nanocrystal toluene solution (450 nm absorbance OD = 40) into the hot melt adhesive, exhaust the toluene with nitrogen, form a metal salt-nanocrystal dispersion system; cool to below 150°C to obtain a nanocrystal composition.

[0096] Comparative Example 1: Prepare a CdSe / CdZnS core-shell nanocrystal-ODE solution.

[0097] Comparative Example 2: Prepare an InP / ZnSe / ZnS core-shell nanocrystal-ODE solution.

[0098] Method for preparing a nanocrystal optical film:

[0099] Prepare a PET film with a water vapor transmission rate of about 2 g / m 2 ·24h, oxygen transmission rate of about 20 cm 3 / m 2 ·24h·0.1MPa. On the above PET film, a nanocrystal glue is arranged, and then a PET film is arranged on the nanocrystal glue, and then the nanocrystal glue is cured to obtain a nanocrystal optical film. The above nanocrystal glue is a UV glue based on an acrylic polymer, wherein the mass fraction of the nanocrystals is 2% (the nanocrystal composition prepared by using the above examples or the core-shell nanocrystal solution of each comparative example), the mass fraction of the acrylic monomer is 20%, the mass fraction of the acrylic polymer is 70%, and the mass fraction of other additives is 8%.

[0100] The above nanocrystal optical film is subjected to light stability test respectively, and the test conditions are: the equipment used is a forced air drying oven, the relative humidity is <5%, the blue light with a wavelength of 460 nm and a light intensity of 0.5 W / cm 2 is irradiated for 500 hours at 70°C. The fluorescence peak position and half-width are recorded in Table 1 by using an integrating sphere tester to measure the fluorescence spectrum.

[0101] The detection method of quantum yield is as follows: a 450nm blue LED is used as a backlight source, an integrating sphere is used to test the blue backlight spectrum and the spectrum of light transmitted through the nanocrystal optical film, and the integral area of the spectrum is used to calculate the quantum yield. Quantum yield = area of nanocrystal emission peak in nanocrystal optical film / (area of blue backlight peak - area of blue peak not absorbed by the nanocrystal optical film) * 100%.

[0102] The test method of initial light absorption rate is as follows: the nanocrystal optical film is used as a test object, a 450nm blue LED is used as a backlight source, an integrating sphere is used to test the blue backlight spectrum and the spectrum of light transmitted through the nanocrystal optical film, and the integral area of the spectrum is used to calculate the light absorption rate. Initial light absorption rate = (area of blue backlight peak - area of blue peak not absorbed by the nanocrystal optical film) / area of blue backlight peak * 100%.

[0103] The viscosity detection method is as follows: a Brookfield viscometer (model DV-II + Pro) is used to measure the viscosity, and the temperature is controlled at 25 DEG C. The viscosity of the nanocrystal composition of examples 1, 3, 5 and 7 is recorded in table 2.

[0104] Table 1

[0105]

[0106]

[0107]

[0108] Table 2

[0109]

[0110] From the above description, it can be seen that the above-mentioned embodiments of the present application achieve the following technical effects:

[0111] The present application wraps a large amount of metal salt on the surface of the nanocrystal by the above preparation method, at least part of the metal salt can be combined with the surface of the nanocrystal in the form of chemical bond, and the nanocrystal composition exists in the form of solid at room temperature due to the presence of the hot melt adhesive, thereby effectively avoiding the falling off of the metal salt combined on the surface of the nanocrystal, greatly improving the water and oxygen resistance of the nanocrystal, and maintaining high fluorescence quantum yield. The above-mentioned nanocrystal composition is effectively prevented from photooxidation and photolysis during storage and application because the nanocrystal is wrapped by the hot melt adhesive to isolate water and oxygen, thereby ensuring the performance stability during application.

[0112] The above merely provides the preferred embodiments of the present application, and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the principles and technical scope of the present application shall fall into the scope of the present application.

Claims

1. A method for preparing a nanocrystalline composition, characterized in that: The preparation method comprises: Step S1, preparing a hot melt adhesive, wherein the hot melt adhesive comprises a metal salt and an organic dispersion, wherein the metal salt is any one or more of a metal carboxylate and a metal phosphonate, wherein the carboxylate radical of the metal carboxylate has a carbon number between 8 and 22, and the metal phosphonate is selected from a metal phosphonate having a hydrocarbon group with a carbon number between 4 and 22; Step S2, at a melting temperature of the hot melt adhesive, which is 150-250° C., mixing a plurality of nanocrystals with the hot melt adhesive to form a metal salt-nanocrystal dispersion system, wherein the nanocrystals are added in the form of a nanocrystal solution, and step S2 further includes removing the solvent from the nanocrystal solution; and Step S3, cooling the metal salt-nanocrystal dispersion system to obtain a solid nanocrystal composition; The viscosity of the solid nanocrystalline composition at 15-50° C. is 300-3000 cps; the weight ratio of the metal salt to the organic dispersion is 6:1-1:2, or the mass percentage of the metal salt in the hot melt adhesive is 40%-90%.

2. The preparation method according to claim 1, characterized in that The metal ions of the metal salt are selected from any one or more of sodium, magnesium, aluminum, potassium, calcium, cesium, zirconium, manganese, zinc, and cadmium.

3. The preparation method according to claim 1, characterized in that The organic dispersant is selected from C8~C 22 Alkanes, C8~C 22 Olefins, C8~C 22 Alcohol, C8~C 22 Any one or more of esters, squalane.

4. The preparation method according to claim 1, characterized in that The melting temperature is lower than the decomposition temperature of the metal salt.

5. The preparation method according to claim 1, characterized in that The hot melt adhesive further comprises a viscosity modifier, wherein the viscosity modifier is selected from trialkylphosphine, C4-C 22 Any one or more of the fatty amines.

6. The preparation method according to claim 5, characterized in that The weight ratio of the viscosity modifier to the metal salt is 1:3 to 5:

1.

7. The preparation method according to claim 1, characterized in that The weight ratio of the metal salt to the nanocrystal is 1:1 to 1000:

1.

8. The preparation method according to claim 1, characterized in that The weight ratio of the metal salt to the nanocrystal is 10:1 to 1000:

1.

9. The preparation method according to claim 1, characterized in that The change rate of the fluorescence peak position and half-peak width of the nanocrystals used in the step S2 and the nanocrystals in the solid nanocrystal composition obtained in the step S3 is 0-2%.

10. The preparation method according to claim 1, characterized in that The metal salt-nanocrystalline dispersion system is a homogeneous system.

11. A nanocrystalline composition, characterized in that The nanocrystal composition is solid, comprising a plurality of nanocrystals and a metal salt, wherein the plurality of nanocrystals are dispersed in the metal salt, and at least a portion of the metal salt is a surface ligand of the nanocrystal; The viscosity of the nanocrystalline composition is 300 to 3000 cps at 15 to 50° C.; the nanocrystalline composition does not include or also includes an organic dispersion; the weight ratio of the metal salt to the organic dispersion is 6:1 to 1:2, or the mass percentage of the metal salt in the nanocrystalline composition is 40% to 90%, the metal salt is any one or more of a metal carboxylate and a metal phosphonate, the number of carbon atoms of the carboxylate radical of the metal carboxylate is between 8 and 22, and the metal phosphonate is selected from a metal phosphonate having a hydrocarbon group with 4 to 22 carbon atoms.

12. The nanocrystalline composition according to claim 11, characterized in that The weight ratio of the metal salt to the nanocrystal is 1:1 to 1000:

1.

13. The nanocrystalline composition according to claim 12, characterized in that The nanocrystalline composition does not include a high molecular weight polymer or a polymerizable monomer.

14. The nanocrystalline composition according to claim 11, characterized in that The metal ions of the metal salt are selected from any one or more of sodium, magnesium, aluminum, potassium, calcium, cesium, zirconium, manganese, zinc, and cadmium.

15. The nanocrystalline composition according to claim 11, characterized in that The organic dispersant is selected from C8~C 22 Alkanes, C8~C 22 Olefins, C8~C 22 Alcohol, C8~C 22 Any one or more of esters, squalane.

16. The nanocrystalline composition according to claim 11, characterized in that The nanocrystalline composition further comprises a viscosity modifier, wherein the viscosity modifier is selected from trialkylphosphine, C4-C 22 Any one or more of the fatty amines.

17. The nanocrystalline composition according to claim 16, characterized in that The weight ratio of the viscosity modifier to the metal salt is 1:3 to 5:

1.

18. A light conversion device, characterized in that: The nanocrystalline composition comprises the nanocrystalline composition according to any one of claims 11 to 17.

19. The light conversion device according to claim 18, wherein The fluorescence quantum yield of the photoconversion device decreases by no more than 5% after undergoing condition A, wherein the condition A is: the initial light absorption rate of the photoconversion device is 30%, 0.5 W / cm 2 The light conversion device is irradiated with blue light of the following intensity for no less than 500 hours.

20. A light emitting device, characterized in that: The nanocrystalline composition comprises the nanocrystalline composition according to any one of claims 11 to 17.

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