Method for preparing cobaltosic oxide quantum dot aggregate through halide ion induction

Abstract

The invention discloses a method for preparing a cobaltosic oxide quantum dot aggregate through halide ion induction. The method comprises the following steps: fully mixing a cobalt source, halide salt, alcohol, polyvinylpyrrolidone, deionized water and hydrogen peroxide according to a set proportion to obtain a uniform mixture; transferring the mixture into a sealed container according to a preset volume ratio, heating to a preset temperature, and carrying out constant-temperature reaction for a set time; and after the reaction is completed, cooling a reaction product to room temperature, washing, and drying to obtain the cobaltosic oxide quantum dot aggregate. The cobaltosic oxide quantum dot aggregate with high particle size uniformity can be obtained under the optimal preparation condition, and the size is controllable from dozens of nanometers to micron; the method can be applied to the fields of catalysis, energy storage, sensing and the like, the preparation process is simple and feasible, the repeatability is good, the energy consumption is low, the cost is low, the process parameter proportion can be enlarged or reduced, and the method is suitable for industrial batch production.

Description

Technical Field

[0001] The invention relates to the technical field of nano material preparation, and in particular to a method for preparing cobalt tetroxide quantum dot aggregates by induction of halogen ions. Background Art

[0002] As an inorganic oxide material, cobalt tetroxide has a wide range of applications in many fields, including energy storage materials, magnetic materials, catalyst materials, and enamel pigments. Among them, quantum dot-sized cobalt tetroxide nanomaterials have attracted much attention due to their ultra-high specific surface area and other unique properties. However, there are two prominent problems with cobalt tetroxide quantum dots in a dispersed state: first, due to their extremely small size, it is difficult to use conventional means such as simple centrifugal operations to achieve washing, separation and purification; second, when they are used as energy storage materials and catalyst materials, the contact resistance between the dispersed particles of cobalt tetroxide quantum dots is large, which greatly limits the effective performance of their performance. In view of this, it is necessary to study the preparation method of size-controlled cobalt tetroxide quantum dot agglomerates, so as to solve the above two key problems in a targeted manner and provide an effective solution for the further application of cobalt tetroxide quantum dots in related fields. Summary of the invention

[0003] The purpose of the present invention is to provide a method for preparing cobalt tetroxide quantum dot agglomerates by halogen ion induction, aiming to solve the technical problems that cobalt tetroxide quantum dots are difficult to wash, separate and purify, and the contact resistance between dispersed particles of cobalt tetroxide quantum dots is large.

[0004] To achieve the above object, the present invention provides a method for preparing cobalt tetroxide quantum dot aggregates by halogen ion induction, comprising the following steps: The cobalt source, alcohol, polyvinyl pyrrolidone, deionized water and hydrogen peroxide are fully mixed according to a certain proportion to obtain a uniform mixture A; Adding a halide salt to mixture A to obtain mixture B; The mixture B is heated in a sealed container at a preset volume ratio and reacted at a constant temperature; After the reaction is finished, the reaction product is cooled to room temperature and washed with a centrifuge, and then freeze-dried at -40°C to obtain cobalt tetroxide quantum dot aggregates.

[0005] Wherein, the cobalt source is one or more of cobalt acetate, cobalt nitrate, cobalt sulfate and cobalt chloride.

[0006] The halide salt is an alkali metal halide salt, and the anion of the alkali metal halide salt is F - , Cl - Br - and I - One of them.

[0007] The alkali metal is one of Li, Na, K, Rb and Cs.

[0008] The volume ratio of the deionized water to the alcohol is (0-1):20, the volume ratio of the hydrogen peroxide to the alcohol is (0-1):20, and the mass ratio of the polyvinyl pyrrolidone to the cobalt source is (0.5-4):1; the mass volume ratio of the total mass of the polyvinyl pyrrolidone and the cobalt source to the total volume of the alcohol, water and hydrogen peroxide is (1-5): 160 g / mL; the concentration of the halide in the reaction raw materials is 1 μmol / L~20 mmol / L.

[0009] The concentration of the halide salt in the reaction raw material is 1 μmol / L~20 mmol / L.

[0010] Specifically, when the alkali metal halide is NaF and the concentration of NaF in the reaction raw material is 1.2 μmol / L, the size of the cobalt tetroxide quantum dot agglomerates is 210 nm.

[0011] Specifically, when the alkali metal halide salt is NaCl and the concentration of NaCl in the reaction raw material is 1.2 μmol / L, the size of the cobalt tetroxide quantum dot agglomerates is 50 nm.

[0012] Specifically, when the alkali metal halide salt is NaBr and the concentration of NaBr in the reaction raw material is 1.2 μmol / L, the size of the cobalt tetroxide quantum dot agglomerates is 140 nm.

[0013] Specifically, when the alkali metal halide is NaI and the concentration of NaI in the reaction raw material is 1.2 μmol / L, the size of the cobalt tetroxide quantum dot aggregates is 220 nm.

[0014] Wherein, the alcohol is one or more of methanol, ethanol, propanol, ethylene glycol and glycerol.

[0015] Wherein, the volume ratio of the volume of the mixture to the volume of the reaction container is (1-4):5.

[0016] The isothermal reaction temperature is 100°C to 160°C, and the reaction time is 6 to 24 h.

[0017] 1. A method for preparing cobalt tetroxide quantum dot aggregates by halogen ion induction of the present invention comprises mixing a cobalt source, a halogen salt, an alcohol, polyvinyl pyrrolidone, deionized water and hydrogen peroxide in a certain proportion, heating the mixture to a preset temperature in a sealed reaction container at a certain volume ratio and reacting the mixture at a constant temperature for more than 6 to 24 hours. After the reaction is completed, the reaction product is cooled to room temperature and washed, and dried to obtain cobalt tetroxide quantum dot aggregates. Under the optimal preparation conditions, cobalt tetroxide quantum dot aggregates with high particle size uniformity can be obtained, and the size can be controlled from tens of nanometers to micrometers.

[0018] 2. The cobalt oxide quantum dot aggregates prepared by the method of the present invention can be used in the fields of catalysis, energy storage and sensing. The preparation process is simple and easy, has good repeatability, low energy consumption and low cost, can scale up or down the process parameter ratio, and is suitable for industrial mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 TEM images of cobalt oxide quantum dot aggregates at different magnifications provided in Example 1 of the present invention Figure 2 This is the EDS image of the cobalt oxide quantum dot agglomerate provided in Example 1 of the present invention. Figure 3 This is a low magnification TEM image of the cobalt oxide quantum dot agglomerates provided in Example 2 of the present invention. Figure 4 This is a high magnification TEM image of the cobalt oxide quantum dot agglomerates provided in Example 2 of the present invention. Figure 5 This is a low magnification TEM image of the cobalt oxide quantum dot agglomerates provided in Example 3 of the present invention. Figure 6 This is a high magnification TEM image of the cobalt oxide quantum dot agglomerates provided in Example 3 of the present invention. Figure 7 This is a low magnification TEM image of the cobalt oxide quantum dot agglomerates provided in Example 4 of the present invention. Figure 8 This is a high magnification TEM image of the cobalt tetroxide quantum dot agglomerates provided in Example 4 of the present invention. Fig. 9 This is a TEM image of the cobalt oxide quantum dot agglomerate provided in Example 5 of the present invention. Fig.10 This is the EDS element distribution diagram of the cobalt oxide quantum dot agglomerate provided in Example 5 of the present invention. Fig.11 This is a low magnification TEM image of the cobalt tetroxide quantum dot agglomerates provided in Example 6 of the present invention. Fig.12 This is a high magnification TEM image of the cobalt oxide quantum dot agglomerates provided in Example 6 of the present invention. Fig.13 This is the EDS image of the cobalt oxide quantum dot agglomerate provided in Example 7 of the present invention. Fig.14 This is the EDS image of the cobalt oxide quantum dot agglomerates provided in Example 8 of the present invention. DETAILED DESCRIPTION

[0021] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and are not to be construed as limitations of the present invention. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined. Example 1

[0022] A method for preparing cobalt tetroxide quantum dot aggregates by halogen ion induction, the specific steps are as follows: 0.249 g of cobalt acetate, 40 mL of ethanol, 0.4 g of polyvinyl pyrrolidone, 1 mL of hydrogen peroxide and 10 μL of 5 mmol / L NaF aqueous solution were added to make the final concentration of NaF in the reaction raw material 1.2 μmol / L; the reaction raw materials were mixed evenly and sealed in a stainless steel reactor lined with 100 mL of polytetrafluoroethylene liner, and the volume ratio of the mixture to the volume of the stainless steel reactor was about 42:100. The reactor was placed in a heating device and heated to 140 °C and kept at a constant temperature for 12 h. After the reaction was completed, the reaction product was cooled to room temperature, washed with anhydrous ethanol and deionized water, and then freeze-dried to obtain cobalt tetraoxide quantum dot aggregates.

[0023] TEM images of the cobalt oxide quantum dot aggregates prepared in this example at different magnifications are shown in Figure 1 . Figure 1 a is a low-magnification TEM image, which shows that the size and morphology of the cobalt oxide quantum dot agglomerates are relatively uniform, and the agglomerate size is about 210 nm. Figure 1 b and c are high magnification TEM images, which show that the agglomerates are composed of quantum dots with a particle size of less than 5 nm. The EDS spectrum of the quantum dot agglomerates prepared in this example is shown in FIG. Figure 2 , from which we can know that the elements contained in the agglomerates are Co and O. Figure 2 The C and Cu shown in the figure come from the grid support film used for transmission electron microscopy characterization. Example 2

[0024] A method for preparing cobalt tetroxide quantum dot aggregates by halogen ion induction, the specific steps are as follows: 0.249 g of cobalt acetate, 39.9 mL of ethanol, 0.4 g of polyvinyl pyrrolidone, 1 mL of hydrogen peroxide and 10 μL of 0.5 mol / L NaF aqueous solution were mixed evenly and sealed in a stainless steel reactor lined with 100 mL of polytetrafluoroethylene liner. The volume ratio of the mixture to the volume of the stainless steel reactor was about 42:100. The reactor was placed in a heating device and heated to 140 °C and reacted at a constant temperature for 12 h. After the reaction was completed, the reaction product was cooled to room temperature, washed with anhydrous ethanol and deionized water, and then freeze-dried to obtain cobalt tetraoxide quantum dot aggregates.

[0025] The low magnification TEM image of the cobalt oxide quantum dot agglomerates prepared in this example is shown in Figure 3 It can be seen that the size and morphology of the cobalt oxide quantum dot agglomerates are relatively uniform, and the agglomerate size is about 460 nm. Figure 4 This is a high-magnification TEM image, which shows that the agglomerates are composed of quantum dots with a particle size of less than 5 nm. Example 3

[0026] A method for preparing cobalt tetroxide quantum dot aggregates by halogen ion induction, the specific steps are as follows: 0.249 g of cobalt acetate, 40 mL of ethanol, 0.4 g of polyvinyl pyrrolidone, 0.02 1 g of NaF and 1 mL of hydrogen peroxide were mixed evenly and sealed in a stainless steel reactor lined with 100 mL of polytetrafluoroethylene liner, so that the final concentration of NaF in the reaction raw materials was 12 mmol / L, and the volume ratio of the mixture to the volume of the stainless steel reactor was about 42:100. The reactor was placed in a heating device and heated to 140 °C and reacted at a constant temperature for 12 h. After the reaction was completed, the reaction product was cooled to room temperature, washed with anhydrous ethanol and deionized water, and then freeze-dried to obtain cobalt tetraoxide quantum dot aggregates.

[0027] The low magnification TEM image of the cobalt oxide quantum dot agglomerates prepared in this example is shown in Figure 5 It can be seen that the size and morphology of the cobalt oxide quantum dot agglomerates have become less uniform, and the agglomerate size is about 230 nm. Figure 6This is a high-magnification TEM image, which shows that the agglomerates are composed of quantum dots with a particle size of about 8 nm. Example 4

[0028] A method for preparing cobalt tetroxide quantum dot aggregates by halogen ion induction, the specific steps are as follows: 0.249 g of cobalt acetate, 39.9 mL of ethanol, 0.4 g of polyvinyl pyrrolidone, 1 mL of hydrogen peroxide and 10 μL of 5 mmol / L NaCl aqueous solution were mixed evenly and sealed in a stainless steel reactor lined with 100 mL of polytetrafluoroethylene liner. The volume ratio of the mixture to the volume of the stainless steel reactor was about 42:100. The reactor was placed in a heating device and heated to 140 °C and reacted at a constant temperature for 12 h. After the reaction was completed, the reaction product was cooled to room temperature, washed with anhydrous ethanol and deionized water, and then freeze-dried to obtain cobalt tetraoxide quantum dot aggregates.

[0029] The low magnification TEM image of the cobalt oxide quantum dot agglomerates prepared in this example is shown in Figure 7 It can be seen that the size and morphology of the cobalt oxide quantum dot agglomerates are relatively uniform, and the agglomerate size is about 50 nm. Figure 8 This is a high-magnification TEM image, which shows that the agglomerates are composed of quantum dots with a particle size of less than 5 nm. Example 5

[0030] A method for preparing cobalt tetroxide quantum dot aggregates by halogen ion induction, the specific steps are as follows: 0.249 g of cobalt acetate, 39.9 mL of ethanol, 0.4 g of polyvinyl pyrrolidone, 1 mL of hydrogen peroxide and 10 μL of 5 mmol / L NaBr aqueous solution were mixed evenly and sealed in a stainless steel reactor lined with 100 mL of polytetrafluoroethylene liner. The volume ratio of the mixture to the volume of the stainless steel reactor was about 42:100. The reactor was placed in a heating device and heated to 140 °C and reacted at a constant temperature for 12 h. After the reaction was completed, the reaction product was cooled to room temperature, washed with anhydrous ethanol and deionized water, and then freeze-dried to obtain cobalt tetraoxide quantum dot aggregates.

[0031] The low magnification TEM image of the cobalt oxide quantum dot agglomerates prepared in this example is shown in Fig. 9 It can be seen that the size and morphology of the cobalt oxide quantum dot agglomerates are relatively uniform, and the agglomerate size is about 140 nm. Fig.10 yes Fig. 9 From the EDS element surface distribution map of the area, it can be seen that the agglomerates are composed of O and Co, and are evenly distributed. Example 6

[0032] A method for preparing cobalt tetroxide quantum dot aggregates by halogen ion induction, the specific steps are as follows: 0.249 g of cobalt acetate, 39.9 mL of ethanol, 0.4 g of polyvinyl pyrrolidone, 1 mL of hydrogen peroxide and 10 μL of 5 mmol / L NaI aqueous solution were mixed evenly and sealed in a stainless steel reactor lined with 100 mL of polytetrafluoroethylene liner. The volume ratio of the mixture to the volume of the stainless steel reactor was about 42:100. The reactor was placed in a heating device and heated to 140 °C and kept at a constant temperature for 12 h. After the reaction was completed, the reaction product was cooled to room temperature, washed with anhydrous ethanol and deionized water, and then freeze-dried to obtain cobalt tetraoxide quantum dot aggregates.

[0033] The low magnification TEM image of the cobalt oxide quantum dot agglomerates prepared in this example is shown in Fig.11 It can be seen that the size and morphology of the cobalt oxide quantum dot agglomerates are relatively uniform, and the agglomerate size is about 220 nm. Fig.12 This is a high-magnification TEM image, which shows that the agglomerates are composed of quantum dots with a particle size of less than 5 nm.

[0034] Example 7 A method for preparing cobalt tetroxide quantum dot aggregates by halogen ion induction, the specific steps are as follows: 0.21 g of cobalt acetate, 0.01 g of cobalt acetate, 0.01 g of cobalt nitrate, 0.01 g of cobalt sulfate and 0.01 g of cobalt chloride, 78 mL of ethanol, 0.4 g of polyvinyl pyrrolidone, 1 mL of hydrogen peroxide, 1 mL of water and 10 μL of 5 mmol / L NaI aqueous solution were mixed evenly and sealed in a stainless steel reactor lined with 100 mL of polytetrafluoroethylene liner. The volume ratio of the mixture to the volume of the stainless steel reactor was about 80:100. The reactor was placed in a heating device and heated to 140 °C and kept at a constant temperature for 12 h. After the reaction was completed, the reaction product was cooled to room temperature, washed with anhydrous ethanol and deionized water, and then freeze-dried to obtain cobalt tetraoxide quantum dot aggregates.

[0035] The EDS image of the cobalt oxide quantum dot agglomerates prepared in this example is shown in Fig.13 , from which we can know that the elements contained in the agglomerates are Co and O. Example 8

[0036] A method for preparing cobalt tetroxide quantum dot aggregates by halogen ion induction, the specific steps are as follows: 0.249 g of cobalt acetate, 17 mL of ethanol, 0.25 mL of methanol, 0.25 mL of propanol, 0.25 mL of ethylene glycol, 0.25 mL of glycerol, 0.4 g of polyvinyl pyrrolidone, 1 mL of hydrogen peroxide, 1 mL of water, and 10 μL of 5 mmol / L NaI aqueous solution were mixed evenly and sealed in a stainless steel reactor lined with 100 mL of polytetrafluoroethylene liner. The volume ratio of the mixture to the volume of the stainless steel reactor was about 20:100. The reactor was placed in a heating device and heated to 140 °C and reacted at a constant temperature for 12 h. After the reaction was completed, the reaction product was cooled to room temperature, washed with anhydrous ethanol and deionized water, and then freeze-dried to obtain cobalt tetraoxide quantum dot aggregates.

[0037] The EDS image of the cobalt oxide quantum dot agglomerates prepared in this example is shown in Fig.14 , from which we can know that the elements contained in the agglomerates are Co and O. Example 9

[0038] A method for preparing cobalt tetroxide quantum dot aggregates by halogen ion induction, the specific steps are as follows: 0.183 g of cobalt nitrate, 40 mL of ethanol, 0.2 g of polyvinyl pyrrolidone, 1 mL of hydrogen peroxide and 10 μL of 5 mmol / L LiBr aqueous solution were mixed evenly and sealed in a stainless steel reactor lined with 100 mL of polytetrafluoroethylene liner. The volume ratio of the mixture to the volume of the stainless steel reactor was about 42:100. The reactor was placed in a heating device and heated to 180 °C and kept at a constant temperature for 6 h. After the reaction was completed, the reaction product was cooled to room temperature, washed with anhydrous ethanol and deionized water, and then freeze-dried to obtain cobalt tetraoxide quantum dot aggregates. Example 10

[0039] A method for preparing cobalt tetroxide quantum dot aggregates by halogen ion induction, the specific steps are as follows: 0.249 g of cobalt acetate, 57 mL of ethanol, 0.9 g of polyvinyl pyrrolidone, 2 mL of water and 14.4 μL of 5 mmol / L KCl aqueous solution were mixed to make the final concentration of KCl in the reaction raw material 1.2 μmol / L; mixed evenly and sealed in a stainless steel reactor lined with 100 mL polytetrafluoroethylene liner, and the volume ratio of the mixture to the volume of the stainless steel reactor was about 60:100. The reactor was placed in a heating device and heated to 100 ° C and reacted at a constant temperature for 24 hours. After the reaction was completed, the reaction product was cooled to room temperature, washed with anhydrous ethanol and deionized water, and then freeze-dried to obtain cobalt tetraoxide quantum dot aggregates. Embodiment 11

[0040] A method for preparing cobalt tetroxide quantum dot aggregates by halogen ion induction, the specific steps are as follows: 0.498 g of cobalt acetate, 75 mL of ethanol, 0.4 g of polyvinyl pyrrolidone, 3 mL of hydrogen peroxide, 1 mL of water, and 19.2 μL of 5 mmol / L CsCl aqueous solution were mixed evenly and sealed in a stainless steel reactor lined with 100 mL of polytetrafluoroethylene liner. The volume ratio of the mixture to the volume of the stainless steel reactor was about 80:100. The reactor was placed in a heating device and heated to 150 °C and reacted at a constant temperature for 15 h. After the reaction was completed, the reaction product was cooled to room temperature, washed with anhydrous ethanol and deionized water, and then freeze-dried to obtain cobalt tetraoxide quantum dot aggregates.

[0041] The above disclosure is only part of the embodiments of the present invention, which cannot be used to limit the scope of the present invention. Ordinary technicians in this field can understand that all or part of the processes of the above embodiments and equivalent changes made according to the claims of the present invention are still within the scope of the invention.

Claims

1. A method for preparing cobalt tetroxide quantum dot aggregates induced by halogen ions, characterized in that: The following steps are involved: The cobalt source, alcohol, polyvinyl pyrrolidone, deionized water and hydrogen peroxide are fully mixed according to a certain proportion to obtain a uniform mixture A; Adding a halide salt to mixture A to obtain mixture B; The mixture B is heated in a sealed container at a preset volume ratio and reacted at a constant temperature; After the reaction is completed, the reaction product is cooled to room temperature and washed, and then dried to obtain cobalt tetroxide quantum dot aggregates.

2. The method for preparing cobalt tetroxide quantum dot aggregates by halogen ion induction according to claim 1, characterized in that: The cobalt source is one or more of cobalt acetate, cobalt nitrate, cobalt sulfate and cobalt chloride.

3. The method for preparing cobalt tetroxide quantum dot aggregates by halogen ion induction according to claim 1, characterized in that: The halide salt is an alkali metal halide salt, and the anion of the alkali metal halide salt is F - , Cl - Br - and I - One of them.

4. The method for preparing cobalt tetroxide quantum dot aggregates by halogen ion induction according to claim 3, characterized in that: The alkali metal is one of Li, Na, K, Rb and Cs.

5. The method for preparing cobalt tetroxide quantum dot aggregates by halogen ion induction according to claim 4, characterized in that: The volume ratio of the deionized water to the alcohol is (0-1):20, the volume ratio of the hydrogen peroxide to the alcohol is (0-1):20, and the mass ratio of the polyvinyl pyrrolidone to the cobalt source is (0.5-4):1; the mass volume ratio of the total mass of the polyvinyl pyrrolidone and the cobalt source to the total volume of the alcohol, water and hydrogen peroxide is (1-5): 160 g / mL; the concentration of the halide in the reaction raw materials is 1 μmol / L~20 mmol / L.

6. The method for preparing cobalt tetroxide quantum dot aggregates by halogen ion induction according to claim 1, characterized in that: The alcohol is one or more of methanol, ethanol, propanol, ethylene glycol and glycerol.

7. The method for preparing cobalt tetroxide quantum dot aggregates by halogen ion induction according to claim 1, characterized in that: The volume ratio of the volume of the mixture to the volume of the reaction container is (1-4):

5.

8. The method for preparing cobalt tetroxide quantum dot aggregates by halogen ion induction according to claim 1, characterized in that: The temperature of the isothermal reaction is 100°C to 180°C, and the reaction time is 6 to 24 hours.

Images