A method for preparing doped nanocrystals using nanoemulsion

Abstract

The present invention relates to the fields of emulsion colloids, hydrothermal treatment, etc., and particularly relates to a method for preparing doped nanocrystals using nanoemulsion. First, latex particles containing organic salts are formed by dropping polymerizable monomers; then, the nanoemulsion particles are used as reactors to form doped nanocrystal precursors, and the precursors are uniformly distributed and have a size of 1-2 nanometers; finally, hydrothermal treatment is carried out to form nanoemulsion containing doped nanocrystals, whose particle size maintains the properties of being uniform, stable and not easily agglomerated. The average particle size of the doped nanocrystals is below 5 nanometers, and it can have advantages in aspects such as nano size and film formation.

Description

Technical Field

[0001] The present invention relates to the fields of emulsion colloids, hydrothermal treatment, etc., and particularly relates to a method for preparing doped nanocrystals using nanoemulsions. Background Art

[0002] Nanoemulsion particles are emulsion particles with a size in the range of 5 - 20 nanometers. Compared with traditional emulsion particles (particle size range of 80 - 500 nanometers), due to their unique structure, nanoemulsion particles have better surface properties, permeability, and transparency compared to traditional emulsion particles.

[0003] Certain alcohols are commonly used co - emulsifiers in emulsion polymerization. Since the addition of alcohols usually can greatly reduce the interfacial tension in the system, and even generate instantaneous negative interfacial tension. The introduction of a specific alcohol can enable the emulsifier in the system to better enter the water / oil interface, enhance the strength of the molecular interfacial film, and thus improve the emulsification effect. At the same time, the use of alcohols can increase the flexibility of the interface, making the interface easy to bend, and thus making the reaction easy to proceed. Generally, co - emulsifiers in the emulsion polymerization process have the following functions: 1. During the polymerization process, the co - emulsifier helps to stabilize monomers into sub - micron monomer droplets; 2. During the subsequent polymerization process, the presence of the co - emulsifier in monomer droplets without initiators reduces the equilibrium concentration of monomers in polymer colloids; 3. Since the nucleation process of colloids occurs in monomer droplets containing co - emulsifiers, its presence in polymer colloids helps the further swelling of the polymerization product after the polymerization ends.

[0004] Doping is the mixing of multiple substances together. Doping is usually used to change the chemical composition of materials. Doping can change the electronic structure of materials, modulate their bandgap size, conductivity, magnetism, photocatalytic performance, etc., enabling the performance of materials to be improved to meet new application requirements. The method of using nanoemulsions (below 20 nanometers) as nano - reactors to prepare doped nanocrystals may have potential advantages such as low film - forming thickness and good leveling property due to the small size of the emulsion. Summary of the Invention

[0005] The object of the present invention is to prepare nanoemulsions of doped nanocrystal precursors using an oil - soluble monomer and an organic salt mixture as the dispersed phase, and then form doped nanocrystal materials through hydrothermal treatment.

[0006] The above method is carried out according to the following steps:

[0007] (1) Preparation of nanoemulsion particles containing organic salts

[0008] At room temperature, an aqueous solution of a quantitative surfactant and a quantitative co-stabilizer are mixed and then transferred to a polymerization reactor from which air has been removed. The ultrasonic biological crusher maintains the ultrasonic state of the system. After heating to a certain temperature, a mixture of monomer 1 and an organic salt is added dropwise at a fixed rate. After reacting for a certain time, organic salt-containing nanoemulsion particles are obtained.

[0009] Among them, the surfactant is sodium dodecyl sulfate or a mixture of sodium dodecyl sulfate and alkylphenol polyoxyethylene ether (the mass ratio of the two emulsifiers before and after is 2 - 3:1); the co-stabilizer is isopropyl alcohol, n-propanol, n-butanol, isobutanol, etc.;

[0010] Monomer 1 is one or a mixture of several monomers such as methyl methacrylate, styrene, or 2-hydroxyethyl methacrylate;

[0011] The organic salt is an oleate, acetate, or isooctanoate of iron, cadmium, chromium, cobalt, nickel, or copper.

[0012] The mass concentration of the surfactant aqueous solution is 1 - 2%.

[0013] The mass ratio of the surfactant aqueous solution, co-stabilizer, monomer 1, and organic salt is 100:1 - 3:2:0.1; the dropping rate of the mixture of monomer 1 and organic salt is 1% of the mixture mass per minute.

[0014] The power of the ultrasonic biological crusher is 200 W, the polymerization temperature is controlled at 60 °C, and the polymerization reaction time is 2 hours.

[0015] (2) Preparation of nanoemulsion particles containing nanocrystal precursors:

[0016] At room temperature, a solution of a quantitative organic amine and a quantitative monomer 2 is added dropwise to a quantitative bottom liquid of organic salt-containing nanoemulsion particles prepared in step (1). After maintaining the crushing and polymerization temperature in the ultrasonic biological crusher for a certain time, the preparation of nanoemulsion particles containing nanocrystal precursors is completed.

[0017] Among them, the organic amine is n-butylamine, n-pentylamine, isobutylamine, etc.; monomer 2 is a hydroxyl-containing vinyl monomer such as 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, or 2-hydroxypropyl methacrylate, etc.; the solvent used to dissolve monomer 2 is benzene, toluene, or xylene, and the mass ratio of organic amine, monomer, and solvent is 1:2:7.

[0018] The mass ratio of the solution mass to the bottom liquid mass of the organic salt-containing nanoemulsion particles used in step (1) is 1 - 2:100. The solution dropping rate is 5% of the solution mass per minute.

[0019] The power of the ultrasonic biological crusher is 200 W, the polymerization temperature is controlled at 60 °C, and the polymerization time is 1 hour.

[0020] (3) Preparation of doped nanocrystals:

[0021] At room temperature, a certain concentration of water-soluble doped metal salt is added at once to the nanocrystal precursor-containing latex particles prepared in the quantitative step (2), and then transferred to a high-pressure reactor; then placed in an oven at a set temperature and kept warm for a predetermined time, and the reaction liquid is taken out after hydrothermal treatment to obtain an emulsion containing doped nanocrystals.

[0022] The water-soluble doped metal salt is a functional nitro salt, such as strontium nitrate, samarium nitrate or europium nitrate, and the mass concentration of the water-soluble doped metal salt in the aqueous solution is 0.1-0.5%.

[0023] The mass ratio of the amount of the water-soluble doped metal salt added to the reverse phase miniemulsion prepared in step (2) is 0.1-0.5:50.

[0024] The hydrothermal treatment sets the insulation temperature to 80-120°C and the predetermined insulation time to 8-24 hours.

[0025] The present invention adopts the "post-drip" emulsion polymerization method, and the monomer is continuously dripped into the polymerization system in a single component or pre-emulsified state. Compared with the traditional polymerization process, the semi-continuous emulsion polymerization process can effectively control the reaction rate of the polymerization process. Compared with the traditional emulsion polymerization process, the semi-continuous emulsion polymerization process can effectively control the size and morphology of the latex particles.

[0026] The nano-latex precursor is formed by oil-soluble doping materials, and then the nano-latex containing doped nanocrystals is formed by hydrothermal treatment, which has advantages in nano-size and film formation. This method of preparing doped nanocrystals has potential application prospects in the fields of photoelectric conversion, battery materials and catalysis.

[0027] The present invention has the following advantages:

[0028] 1. By adding polymerizable monomers, latex particles containing organic salts of about 10 nanometers can be formed;

[0029] 2. Using nano latex particles as a reactor can form doped nanocrystal precursors, which are evenly distributed and have a size of 1-2 nanometers;

[0030] 3. After hydrothermal treatment under mild conditions, the nano latex particles containing doped nano crystals maintain uniform, stable and non-agglomerated properties, and the average particle size of the doped nano crystals is less than 5 nanometers. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is an electron microscope image of the latex particles after polymerization in step (1) of Example 1.

[0032] Figure 2 This is an electron microscope image of the latex particles after polymerization in step (2) of Example 1. Detailed implementation mode

[0033] The present invention will be further described in detail below with reference to examples.

[0034] Example 1

[0035] (1) Preparation of organic salt nanoemulsion particles:

[0036] At room temperature, a surfactant solution formed by 100 g of a 1% mass concentration mixed emulsifier (sodium dodecyl sulfate and octylphenol polyoxyethylene ether, with the mass ratio of the former and latter two emulsifiers being 2:1) and 1 g of isopropanol co-stabilizer were mixed and transferred to a polymerization reactor purged of air, and the system was maintained in an ultrasonic state by a 200 W ultrasonic biological pulverizer; after heating to 60 °C, a mixture of 2 g of methyl methacrylate monomer and 0.1 g of iron isooctanoate was added dropwise at a rate of 0.021 g / minute. After reacting for 2 hours, organic salt nanoemulsion particles were obtained. The average particle size of the emulsion particles was 4 nm, as Figure 1 shown.

[0037] (2) Preparation of nanoemulsion particles containing nanocrystal precursors:

[0038] At room temperature, a solution formed by 0.1 g of n-butylamine, 0.2 g of 2-hydroxyethyl methacrylate, and 0.7 g of benzene was added dropwise to 100 g of the bottom liquid of the organic salt nanoemulsion particles prepared in step (1) at a rate of 0.05 g / minute, and pulverization was maintained in a 200 W ultrasonic biological pulverizer. The polymerization temperature was controlled at 60 °C and the polymerization time was 1 hour. The preparation of nanoemulsion particles containing nanocrystal precursors was completed. The average particle size of the emulsion particles was 6 nm, as Figure 2 shown.

[0039] (3) Preparation of doped nanocrystals:

[0040] At room temperature, 0.1 g of a 0.1% mass concentration samarium nitrate solution was added once to 50 g of the nanoemulsion particles containing nanocrystal precursors prepared in step (2), and transferred to a high-pressure reaction kettle; the hydrothermal treatment was set with a holding temperature of 80 °C and a predetermined holding time of 24 hours. After the hydrothermal treatment, the reaction solution was taken out to obtain a nanoemulsion containing samarium-doped ferrite nanocrystals. X-ray diffraction detection showed that the doped nanomaterial conformed to the characteristic diffraction peaks of the iron oxide PDF standard card, and the secondary diffraction peak of the samarium-doped ferrite nanocrystals shifted to the right in the spectrum; the average particle size of the nanocrystals was calculated to be 3 nm according to the half-peak width of the diffraction peak.

[0041] Example 2

[0042] (1) Preparation of organic salt nanoemulsion particles:

[0043] At room temperature, 100 grams of a surfactant solution formed by 2% mass concentration of sodium dodecyl sulfate and 3 grams of n-butanol co-stabilizer were mixed and then transferred to a polymerization reactor with air removed. The system was maintained in an ultrasonic state by a 200W ultrasonic biological crusher. After heating to 60 °C, 1.8 grams of methyl methacrylate, 0.2 grams of styrene monomer, and 0.1 gram of cobalt isooctoate mixture were added dropwise at a rate of 0.021 grams per minute. After reacting for 2 hours, organic salt nano latex particles were obtained, and the average particle size of the latex particles was 3 nanometers.

[0044] (2) Preparation of nano latex particles containing nanocrystal precursors:

[0045] At room temperature, a solution formed by 0.2 grams of isobutylamine, 0.4 grams of hydroxypropyl methacrylate, and 1.4 grams of toluene was added dropwise to 100 grams of the bottom liquid of organic salt nano latex particles prepared in step (1) at a rate of 0.10 grams per minute. The crushing in a 200W ultrasonic biological crusher was maintained, the polymerization temperature was controlled at 60 °C, and the polymerization time was 1 hour. The preparation of nano latex particles containing nanocrystal precursors was completed, and the average particle size of the latex particles was 5 nanometers.

[0046] (3) Preparation of doped nanocrystals:

[0047] At room temperature, 0.5 grams of a 0.5% mass concentration samarium nitrate solution was added once to 50 grams of the nano latex particles containing nanocrystal precursors prepared in step (2), and then transferred to a high-pressure reaction kettle; the hydrothermal treatment was set with a holding temperature of 120 °C and a predetermined holding time of 8 hours. After the hydrothermal treatment, the reaction solution was taken out to obtain an emulsion containing samarium-doped cobalt oxide salt nanocrystals. X-ray diffraction detected that the doped nanomaterial conformed to the characteristic diffraction peaks of the cobalt oxide PDF standard card, and the secondary diffraction peak of the samarium-doped cobalt oxide salt nanocrystals shifted to the right in the pattern; the average particle size of the nanocrystals was calculated to be 2 nanometers according to the full width at half maximum of the diffraction peak.

[0048] Example 3

[0049] (1) Preparation of organic salt nano latex particles:

[0050] At room temperature, 100 grams of a surfactant solution formed by 1.5% mass concentration of a mixed emulsifier (sodium dodecyl sulfate and nonylphenol polyoxyethylene ether, the mass ratio of the former and latter two emulsifiers is 3:1) and 2 grams of isobutanol co-stabilizer were mixed and then transferred to a polymerization reactor with air removed. The system was maintained in an ultrasonic state by a 200W ultrasonic biological crusher. After heating to 60 °C, 1.8 grams of methyl methacrylate, 0.2 grams of styrene monomer, and 0.1 gram of cadmium oleate mixture were added dropwise at a rate of 0.021 grams per minute. After reacting for 2 hours, organic salt nano latex particles were obtained, and the average particle size of the latex particles was 5 nanometers.

[0051] (2) Preparation of nano latex particles containing nanocrystal precursors:

[0052] At room temperature, a solution formed by 0.15 g of isobutylamine, 0.3 g of hydroxypropyl methacrylate and 1.05 g of toluene was added dropwise to 100 g of the bottom liquid containing organic salt nanoemulsion particles prepared in step (1) at a rate of 0.075 g / minute, and pulverized in a 200W ultrasonic biological pulverizer. The polymerization temperature was controlled at 60 °C and the polymerization time was 1 hour. The preparation of nanoemulsion particles containing nanocrystal precursors was completed, and the average particle size of the emulsion particles was 8 nm.

[0053] (3) Preparation of doped nanocrystals:

[0054] At room temperature, 0.25 g of a 0.25% mass concentration europium nitrate solution was added once to 50 g of the nanoemulsion particles containing nanocrystal precursors prepared in step (2), and then transferred to a high-pressure reaction kettle; the hydrothermal treatment was set with a holding temperature of 100 °C and a predetermined holding time of 16 hours. After the hydrothermal treatment, the reaction solution was taken out to obtain an emulsion containing samarium-doped cadmium oxide salt nanocrystals. X-ray diffraction detection showed that the doped nanomaterial conformed to the characteristic diffraction peaks of the cadmium oxide PDF standard card, and the secondary diffraction peak of the samarium-doped cadmium oxide salt nanocrystals shifted to the right in the pattern; the average particle size of the nanocrystals was calculated to be 5 nm based on the full width at half maximum of the diffraction peak.

[0055] The above description of the embodiments is to enable those of ordinary skill in the art to understand and apply the present invention. It is obvious that those familiar with the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative labor. Therefore, the present invention is not limited to the embodiments herein, and all modifications made by those skilled in the art according to the disclosure of the present invention should be within the protection scope of the present invention.

Claims

1. A doped nanocrystal prepared using nanoemulsion, characterized in that, The steps of the preparation method of the doped nanocrystal are as follows: (1) Preparation of nano latex particles containing organic salts: At room temperature, the aqueous solution of the surfactant and the stabilizer are mixed and transferred to a polymerization reactor from which air is removed, and an ultrasonic bio-crusher is used to maintain the system in an ultrasonic state; after heating, a mixture of monomer 1 and an organic salt is added dropwise at a fixed rate to carry out a polymerization reaction, thereby obtaining nano latex particles containing organic salts; Monomer 1 is one or a mixture of methyl methacrylate, styrene or hydroxyethyl methacrylate; the organic salt is oleic acid, acetic acid or isooctanoic acid salt of iron, cadmium, chromium, cobalt, nickel or copper; (2) Preparation of nano latex particles containing nanocrystal precursors: Add the solution of organic amine and monomer 2 dropwise to the base solution of nano latex particles containing organic salt prepared in step (1) at room temperature, maintain the pulverization and polymerization temperature in the ultrasonic bio-pulverizer, and complete the preparation of nano latex particles containing nano crystal precursors; The organic amine is n-butylamine, n-pentylamine or isobutylamine; the monomer 2 is hydroxyethyl methacrylate, hydroxyethyl ethyl acrylate or hydroxypropyl methacrylate; (3) Preparation of doped nanocrystals: At room temperature, a water-soluble doped metal salt solution is added to the nano-latex particles containing the nano-crystal precursor prepared in step (2) at one time, and the particles are transferred to a high-pressure reactor; the particles are then placed in an oven at a set temperature and kept warm for a predetermined time, and the reaction liquid is taken out after hydrothermal treatment to obtain an emulsion containing doped nano-crystals; The water-soluble doping metal salt is strontium nitrate, samarium nitrate or europium nitrate.

2. The doped nanocrystal prepared using nanoemulsion as described in claim 1, wherein, In step (1), the surfactant is sodium dodecyl sulfate or a mixture of sodium dodecyl sulfate and alkylphenol polyoxyethylene ether, and the co-stabilizer is isopropanol, n-propanol, n-butanol or isobutanol.

3. The doped nanocrystal prepared by using nanoemulsion as claimed in claim 2, wherein, In step (1), the mass ratio of sodium dodecyl sulfate and alkylphenol polyoxyethylene ether in the surfactant is 2-3:1, the mass concentration of the surfactant aqueous solution is 1-2%; the mass ratio of the surfactant aqueous solution, the stabilizer, the monomer 1 and the organic salt is 100:1-3:2:0.1; and the dripping speed of the mixture of the monomer 1 and the organic salt is 1% of the mixture mass / minute.

4. The doped nanocrystal prepared by using nanoemulsion as described in claim 1, wherein, Step (1) The power of the ultrasonic bio-crusher is 200 W, the polymerization temperature is controlled at 60° C., and the polymerization reaction time is 2 hours.

5. The doped nanocrystal prepared by using nanoemulsion as described in claim 1, wherein The solvent for dissolving monomer 2 in step (2) is benzene, toluene or xylene.

6. The doped nanocrystal prepared by using nanoemulsion as described in claim 5, characterized in that, The mass ratio of the organic amine, monomer 2 and solvent in step (2) is 1:2:7; the mass ratio of the solution mass to the base solution containing organic salt nano latex particles used in step (1) is 1-2:100; and the solution dropping speed is 5% solution mass / minute.

7. The doped nanocrystal prepared by using nanoemulsion as described in claim 1, wherein, Step (2) The power of the ultrasonic bio-crusher is 200 W, the polymerization temperature is controlled at 60° C., and the polymerization time is 1 hour.

8. The doped nanocrystal prepared by using nanoemulsion as claimed in claim 1, wherein The mass concentration of the water-soluble doped metal salt solution in step (3) is 0.1-0.5%; the mass ratio of the water-soluble doped metal salt to the nano-latex particles containing nano-crystal precursor prepared in step (2) is 0.1-0.5:

50.

9. The doped nanocrystal prepared by using nanoemulsion according to claim 1, wherein In step (3), the hydrothermal treatment is performed at a temperature of 80-120° C. and a predetermined holding time of 8-24 hours.

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