Method of producing colloidal solutions of luminescent nanoplates of rare-earth oxides

FIELD: chemistry.

SUBSTANCE: solution of rare-earth salts is prepared, for example, nitrates of gadolinium, europium, terbium and ytterbium, in non-polar solvents - oleyl amine, oleic acid or compositions thereof with concentration of rare-earth elements of 0.05-0.1 mol/l. The solution is heated in an inert atmosphere of argon to 80-100°C and held at that temperature for 15-30 minutes. Diphenyl ether is then added in amount of 5-10 moles of ether per mole of rare-earth elements. The mixture is heated to 250-300°C and held for 1-2 hours. Excess polar solvent - acetone - is added to the obtained mixture. The coagulated nanoparticles are separated from the solution by centrifuging and the residue is redispersed in excess heptane. Colloidal solutions of luminescent nanoplates of rare-earth oxides with average diameter of 8-17 nm and thickness of 1-15 nm are obtained.

EFFECT: invention enables to obtain luminescent nanoplates of high morphological homogeneity, which ensures stability of their photo- and cathodoluminescent characteristics.

4 cl, 2 dwg, 4 ex

 

The invention relates to the technology of nanomaterials, specifically to the synthesis of colloidal solutions of luminescent oxide materials used for the deposition of ultra-thin fluorescent coatings, as well as the token.

The known method for the synthesis of nanocrystals of cerium dioxide, are capable of forming colloidal solutions [Taekyung Yu, Jin Joo, Yong Park II, Taeghwan Hyeon. Large-Scale Nonhydrolytic Sol-Gel Synthesis of Uniform-Sized Ceria Nanocrystals with Spherical, Wire, and Tadpole Shapes // Angew. Chem. Int. Ed. 2005, V. 44, p 7411-7414], which includes a heat treatment of a mixture of cerium nitrate, oleylamine, oleic acid, trioctylamine at a temperature of 320°C in an inert atmosphere, the isolation and purification of the obtained particles CeO2by replacing the solvent and redispersion obtained particles in nonpolar solvent.

A disadvantage of the known method is that it is used only to obtain the cerium dioxide, which is compared with oxides of rare earth elements is characterized by the absence of a number of functional properties, such as photoluminescence, cathodoluminescence.

The known method of synthesis of colloidal solutions of nanoparticles of oxides of gadolinium and yttrium, neodymium-doped [J.Thomas, .Jacqueline. Preparation of nanoparticles from metal salts or metal oxides // WO 2009107046], which includes heating the reaction mixture of the acetates of gadolinium (yttrium and neodymium by giammarino salt of ethylenediaminetetraacetic acid in aqueous solution to 50÷95°C, followed by adding to the reaction mixture of lauric acid with vigorous stirring of the solution, adding concentrated aqueous ammonia solution and aging the reaction mixture for 24 hours and then cooled to room temperature. After cooling, lauric acid solidifies and forms the second phase on the surface of the aqueous solution and is separated by decantation, and the obtained colloidal solution of oxide nanoparticles concentrated by evaporation. The formed oxide nanoparticles have a characteristic size of 1÷2 nm.

The disadvantage of this method is the long duration of the synthesis, which complicates the use of this method in industry, the inability to synthesize neoplastin oxides of gadolinium and yttrium, and too small a particle size, which affects their fluorescent characteristics.

A method of obtaining colloidal solutions of zinc oxide in non-polar solvents [Vmesnik, VST, Vchebanov, Juditial, Ashapuri. A method of obtaining a colloidal solution of zinc oxide in nonpolar solvents // EN 2403127], which is selected as a prototype. This method of obtaining includes heating the reaction mixture of oleylamine, oleic acid and inorganic zinc-containing precursor to 80÷400°C for 15÷30 minutes in an inert atmosphere, isothermal aging at a temperature of 200÷250°C for 1÷4 the aces, the addition of polar solvent, Department koagulirovat nanoparticles by centrifugation, redispersion precipitate in a non-polar solvent.

The disadvantage of the prototype is that it is only suitable for obtaining zinc oxide, which as a luminescent material in comparison with oxides of rare earth elements is limited due to the weak luminescence and low thermal and chemical stability. It should also be noted that with the use of this prototype, it is impossible to synthesize neoplastin luminescent materials.

The invention is aimed at finding ways to obtain fluorescent nanorods oxides of rare earth elements with a characteristic average particle diameter of 8÷1,7 nm and a thickness of 1÷17.5 nm in non-polar solvents, characterized by high morphological uniformity of the nanoparticles (in each specific embodiment, the coefficient of variation of diameter of nanorods <10%) and low cost of the resulting product due to the use of inorganic precursors, rare earth elements, namely nitrates of rare-earth elements.

The technical result is achieved by the method for obtaining colloidal solutions of luminescent rare earth oxide nanorods e the cops, characterized by a mean diameter of 8÷17 nm and a thickness of 1÷1.5 nm, namely, that prepare a solution of salts of rare earth elements in non-polar solvents, such as oleylamine, oleic acid or their composition, concentration of rare earth elements, 0.05÷0.1 moles per liter of solvent, heating the solution in an inert argon atmosphere up to 80÷100°C and maintained at this temperature for 15÷30 minutes, then add diphenyl ether at the rate of 5÷10 moles of ether per 1 mol of rare earth elements, heat the mixture to 250÷300°C and maintained at this temperature for 1÷2 hours, the obtained mixture is added an excess of polar solvent, coagulopathies nanoparticles is separated from the solution by centrifugation and conduct redispersion precipitate to obtain optically transparent colloidal solution, which is dissolved in an excess of heptane.

It is advisable that, as the inorganic salts of rare earth elements using nitrate gadolinium, europium, terbium and ytterbium.

It is possible that as the polar solvent used is acetone.

It is also advisable that the composition of oleylamine and oleic acid is prepared in the ratio 5÷7-to-1.

For the synthesis of colloidal solutions of oxides of rare earth elements use the following source reagents: gadolinium nitrate of hexage is at (Gd(NO 3)3·6H2O, reagent grade., Aldrich), europium nitrate pentahydrate (Eu(NO3)3·5H2O, reagent grade., Aldrich), terbium nitrate pentahydrate (Tb(NO3)3·5H2O, reagent grade., Aldrich), ytterbium nitrate, the uranyl (Yb(NO3)3·6H2O, reagent grade., Aldrich), oleylamine (C18H37N, technical, Fluka), oleic acid (CH3(CH2)7CH=CH(CH2)7COOH, reagent grade., Fluka), diphenyl ether (C12H10Oh, reagent grade., Fluka). During synthesis, purification and formation of colloidal solutions using the following solvents: acetone (C3H6O'clock, Hemmed), heptane (C7H16reference, Ecros). The synthesis is carried out in the three-neck flask in an inert atmosphere (argon, h) using the reverse water refrigerator to prevent evaporation boiling components of the reaction. For the synthesis of defined amounts of nitrates of rare-earth elements, oleylamine and oleic acid are placed in a flask and heated to 80÷100°C, followed by exposure at this temperature for 15÷30 minutes to dissolve the inorganic salts. The heating is carried out using mantle with temperature control of the reaction mixture using external thermocouple. Isothermal aging at this temperature leads to complete dissolution of nitrates of rare-earth elements in the reaction medium when formirovanie of oleates of rare earth elements. At lower temperatures below 80°C, there is no dissolution of inorganic salts, and at temperatures above 100°C begins their thermal decomposition. After complete dissolution of nitrates of rare-earth elements to the reaction mixture add diphenyl ether in a quantity sufficient for full coverage of the emerging particles, after which the flask is heated to a temperature of 250÷300°C, followed by exposure at this temperature for 60÷120 minutes.

The resulting solution is cooled, add to it an excess of acetone, after which there is a white precipitate coagulated colloidal particles of oxides of rare earth elements. The precipitate was separated by centrifugation, after which redispersing it in heptane.

Analysis of the obtained colloidal solutions produced using the methods of transmission electron microscopy (transmission electron microscope Leo IV with subsequent determination of the photos size 200-300 particles and determination of average particle size) and fluorescence spectroscopy (luminescence spectrometer Perkin-Elmer LS 55 with subsequent determination of the position of the absorption band, the identification of the main bands of emission and evaluation of the efficiency of luminescence). According to literature data, the mechanism of formation of oxides of rare earth elements (RE) of the RE ions in the above-described conditions is high temperature solvolysis of oleates of rare earth elements with education connection RE-OH; during the subsequent dehydration leads to the formation of oxides of rare earth elements.

The study of the influence of the concentration of inorganic salts in the original solution showed that at concentrations below 0.05 moles per liter of solvent, the yield of the final product is too small, and at concentrations above 0.1 mol per liter of the solvent is strong aggregation and coalescence of the emerging particles of oxides of rare earth elements.

It was found that the synthesis at temperatures below 250°C leads to the formation of colloidal particles of oxides of rare earth elements. It was also found that heat treatment at temperatures above 300°C leads to the formation of polydisperse product containing particles of oxides of rare earth elements by the size of 10-10000 nm. At the same time, in the range of 250-300°C is observed the formation of colloidal nanorods oxides of rare earth elements, including gadolinium, europium, terbium and ytterbium, soluble in nonpolar solvents.

The composition of oleylamine and oleic acid is prepared in the ratio 5÷7 1 reasons ensure complete dissolution of the salts of rare earth elements in oleylamine.

The essence of the proposed and the finding is illustrated by the following accompanying illustrations:

Figure 1. Micrograph (left) and diagram of distribution of particle size (right) for a sample of gadolinium oxide doped with europium, synthesized at 280°C.

Figure 2. Micrograph (left) and diagram of distribution of particle size (right) for a sample of gadolinium oxide doped with europium, synthesized at 300°C.

Investigation of the influence of synthesis temperature on the micromorphology of the obtained particles showed that the increase of the synthesis temperature leads to an endogenous increase in the average diameter of the particles (Figure 1 and 2). At the same time increasing the duration of the synthesis contributes to a reduction in the average size of the particles, which may indicate the solubility of the particles of the oxides of rare earth elements in the reaction medium. Thus, the variation of the parameters during the formation of nanorods, such as temperature and duration, allows to obtain colloidal solutions of nanorods oxides of rare earth elements with a characteristic average particle diameter of 8÷17 nm and a thickness of 1÷1.5 nm in non-polar solvents.

Below are examples of implementations of the claimed invention. The examples illustrate but do not limit the proposed method.

Example 1

For the preparation of colloidal solutions of gadolinium oxide doped with europium based 0.08 mol of RE per liter of races is varicela, 0.625 g of gadolinium nitrate, 0.313 g of europium nitrate, 20 ml of oleylamine, 4 ml of oleic acid were placed in a reactor (three-neck flask with an inert atmosphere (argon), was heated to 100°C, kept at this temperature for 15 minutes, was added 1 ml of diphenyl ether, which corresponded to 5 moles of ether per 1 mol of RE, the mixture was heated up to 280°C, kept at this temperature for 2 hours. To the resulting solution was added 60 ml of acetone, precipitated precipitate was separated by centrifugation, centrifuged precipitate was dissolved in 10 ml of heptane to obtain optically transparent colloidal solution. The obtained colloidal neoplastin had an average diameter of 10.5 nm and a thickness of 1÷1.5 nm (see Figure 1).

For the obtained nanorods were determined luminescent characteristics. Set the position of the main bands of luminescence of ions of Eu3+(596 nm, 615 nm 624 nm). The luminescence efficiency was determined on the basis of the coefficient of assimetrichnost (the ratio of the intensity of the main band at 615 nm and the band at 596 nm), which for this sample amounted to 2.2.

Example 2

For the preparation of colloidal solutions of gadolinium oxide doped with europium based 0.08 mol of RE per liter of solvent, 0.625 g of gadolinium nitrate, 0.313 g of europium nitrate, 20 ml of oleylamine, 4 ml of oleic acid were placed in a reactor (three-neck flask with an inert atmosphere (argon), agrawala to 100°C, kept at this temperature for 15 minutes, was added 2 ml of diphenyl ether, which corresponded to 10 moles of ether per 1 mol of RE, the mixture was heated up to 300°C, kept at this temperature for 1 hour. To the resulting solution was added 60 ml of acetone, precipitated precipitate was separated by centrifugation, centrifuged precipitate was dissolved in 10 ml of heptane to obtain optically transparent colloidal solution. The obtained colloidal neoplastin had an average diameter of 15.5 nm and a thickness of 1÷1.5 nm (see Figure 2).

For the obtained nanorods were determined luminescent characteristics. Set the position of the main bands of luminescence of ions of Eu3+(596 nm, 615 nm 624 nm). The luminescence efficiency was determined on the basis of the coefficient of assimetrichnost (the ratio of the intensity of the main band at 615 nm and the band at 596 nm), which for this sample was 3.5.

Example 3

For the preparation of colloidal solutions of terbium oxide based 0.05 mole of RE per liter of solvent 0.533 g of terbium nitrate, 20 ml of oleylamine, 6 ml of oleic acid were placed in a reactor (three-neck flask with an inert atmosphere (argon), was heated up to 80°C, kept at this temperature for 15 minutes, was added 2 ml of diphenyl ether, which corresponded to 10 moles of ether per 1 mol of RE, the mixture was heated up to 250°C, kept at this temperature for 2 hours. To the resulting plants the oru was added 60 ml of acetone, the precipitation was separated by centrifugation, centrifuged precipitate was dissolved in 20 ml of heptane to obtain optically transparent colloidal solution. The obtained colloidal neoplastin had an average diameter of 8 nm and a thickness of 1÷1.5 nm.

For the obtained nanorods were determined luminescent characteristics. Set the position of the main bands of luminescence of ions Tb3+(414 nm and 487 nm, 544 nm and 584 nm).

Example 4

For the preparation of colloidal solutions of ytterbium oxide based 0.1 mole of RE per liter of solvent 0.900 g of ytterbium nitrate, 15 ml of oleylamine, 5 ml of oleic acid were placed in a reactor (three-neck flask with an inert atmosphere (argon), was heated up to 80°C, kept at this temperature for 15 minutes, was added 2 ml of diphenyl ether, which corresponded to 7 moles of ether per 1 mol of RE, the mixture was heated up to 300°C, kept at this temperature for 1 hour. To the resulting solution was added 60 ml of acetone, precipitated precipitate was separated by centrifugation, centrifuged precipitate was dissolved in 20 ml of heptane to obtain optically transparent colloidal solution. The obtained colloidal neoplastin had an average diameter of 17 nm and a thickness of 1÷1.5 nm.

For the obtained nanorods were determined luminescent characteristics. Set the position of the main band of the infrared luminescence of ions Yb3+(975 nm).

Thus, the proposed method of synthesis allows to obtain colloidal solutions of nanorods oxides of rare earth elements in non-polar solvents. The advantages of the present invention are: high morphological uniformity of particles, ensuring the stability of the functional (photo and cathodoluminescence) characteristics; use as starting substances inorganic salts of rare earth elements, which allows to significantly reduce the cost of synthesis at the expense of abandoning the use of expensive ORGANOMETALLIC reagents; the possibility of obtaining new materials suitable for making ultra-thin fluorescent coatings.

1. The method of obtaining colloidal solutions of fluorescent nanorods oxides of rare earth elements, characterized by a mean diameter of 8÷17 nm and a thickness of 1÷1.5 nm, namely, that prepare a solution of salts of rare earth elements in non-polar solvents, such as oleylamine, oleic acid or their composition, concentration of rare earth elements is 0.05÷0.1 moles per liter of solvent, heating the solution in an inert argon atmosphere up to 80÷100°C and maintained at this temperature for 15÷30 min, then add diphenyl ether at the rate of 5÷10 moles of ether per 1 mol of rare earth elements heat mixture is up to 250÷300°C and maintained at this temperature for 1÷2 h, to the obtained mixture is added an excess of polar solvent, coagulopathies nanoparticles is separated from the solution by centrifugation and conduct redispersion precipitate to obtain optically transparent colloidal solution, which is dissolved in an excess of heptane.

2. The method according to claim 1, wherein as the inorganic salts of rare earth elements using nitrate gadolinium, europium, terbium and ytterbium.

3. The method according to claim 1, characterized in that the polar solvent used is acetone.

4. The method according to claim 1, characterized in that the composition of oleylamine and oleic acid is prepared in the ratio 5÷7 to 1.



 

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EFFECT: efficient production of trifluorides of rare-earth elements with minimum content of impurities of oxygen-containing phases.

1 ex

FIELD: chemistry.

SUBSTANCE: invention relates to a composition consisting of cerium oxide and an oxide of another rare-earth element with high specific surface area of 20 m2/g after calcination at temperature 1000°C for 5 hours. The method of obtaining the composition involves a step for preparing a medium containing a cerium compound, heating said medium, separating the precipitate from the liquid medium, adding a compound of another rare-earth element and obtaining another liquid phase, heating the obtained medium, changing pH of the reaction mixture obtained after heating to a basic pH, separating and calcining the precipitate.

EFFECT: composition is effective when used as a catalyst or catalyst support at high temperatures.

12 cl, 2 tbl, 7 ex

FIELD: chemistry.

SUBSTANCE: invention can be used when obtaining filler for structural and functional materials. A reaction mixture containing carbon and catalyst precursors in the current of a carrier gas is fed into the reaction zone of a reactor. The carbon precursor used is carbon-containing compounds selected from: methane, ethane, propane, benzene, toluene, xylenes, methanol, ethanol, propanol, isopropanol, ethylene, propylene, acetylene or mixture thereof. The catalyst precursor used is transition metal compounds selected from: dicyclopentadienyl compounds of transition metals of general formula (h-C5H5)2M, carbonyls of transition metals, or mixtures thereof. Synthesis of single-wall carbon nanotubes is carried out in the presence of growth activators in form of water vapour and/or thiophene, or homologues thereof at temperature 1050-1200 °C. Temperature of the reaction mixture at the input of the reaction zone is kept higher than the evaporation temperature of the catalyst precursor but lower than decomposition temperature thereof.

EFFECT: high output and quality of single-wall carbon nanotubes.

3 cl, 1 tbl, 2 ex

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