Preparation method of perovskite quantum dot / noble metal nanoparticle composite material

Abstract

The present invention belongs to the field of perovskite quantum dots, and relates to a method for preparing a composite material of perovskite quantum dots / precious metal nanoparticles. The composite material has good photocatalytic activity and can degrade about 69% of Sudan III within 5 hours. It can be used as a new photocatalyst for degrading Sudan III. The synthesis method proposed by the present invention is to first reduce AuX on the surface of CsX nanoparticles, the precursor of perovskite quantum dots, so as to deposit Au, and then react CsX with Pb(OA)2 to generate a perovskite quantum dot / Au composite material. The traditional method is to first synthesize perovskite quantum dots and then deposit Au. The method proposed by the present invention can avoid the perovskite quantum dots and Au caused by the traditional method. + ions and avoid the production of by-products (such as Cs2Au2Br6), which is of great significance for the synthesis and photocatalytic applications of quantum dots.

Description

Technical Field

[0001] The invention belongs to the field of perovskite quantum dots and relates to a method for preparing a perovskite quantum dot / noble metal nanoparticle composite material. Background Art

[0002] In 1958, Moller et al. first reported the crystal structure of all-inorganic perovskite CsPbX3 (IPQDs, X = Cl, Br, I). In 2014, Kovalenko synthesized CsPbX3 (X = Cl, Br, I) nanocrystals for the first time using hot injection method.

[0003] As a new type of optoelectronic material, CsPbX3 quantum dots have excellent photoluminescence performance, ultra-high quantum yield, tunable band gap and narrow luminescence peak. Due to the rapid movement of halides in the perovskite lattice, a fast and active anion exchange reaction can be carried out in solution or solid state, which is a unique property of perovskite quantum dots. The quantum confinement effect of CsPbX3 quantum dots is more significant, and they can show a strong fluorescence effect at room temperature. The width of their photoluminescence spectrum is narrow, usually between 12nm and 42nm, and the quantum yield can reach 50% to 90%. Compared with traditional CdSe / CdS-ZnS quantum dots, in terms of quantum yield, CsPbBr3 quantum dots can reach about 90%, which is much higher than 65% of CdSe / CdS-ZnS quantum dots. The efficient luminescence of all-inorganic perovskite quantum dots mainly comes from the synergistic effect of their high exciton binding energy, surface halogen self-passivation, and CsPbX3 / X-type quantum well band structure. At present, there are two main ways to control the emission wavelength of IPQDs: one is to change the halogen composition, and its emission spectrum gradually red-shifts and broadens with Cl→Br→I. The second is to use the quantum confinement effect to control the emission wavelength by adjusting the size of quantum dots. In the high-temperature method, within the appropriate temperature range, the size of quantum dots increases with the increase of reaction temperature, and the emission wavelength of quantum dots will red-shift with the increase of size. This spectrum regulation mechanism is the unique advantage of IPQDs. At present, there are many methods to prepare CsPbX3 quantum dots, among which the representative methods include: 1) hot injection, the preheated Cs precursor is injected into the PbX2 solution at a specific temperature to form nanocrystals; 2) room temperature method, CsX and PbX2 dissolved in a good solvent are added to a poor solvent, and the huge decrease in solubility immediately produces a highly supersaturated state, resulting in rapid recrystallization.

[0004] Sudan III is a lipophilic azo dye containing a naphthalene compound. In addition to being used for dyeing paints, motor oils, and cloth polishes, it is also illegally used as a food additive. Since 1995, Sudan has been banned as a food additive due to the nature of its chemical structure, which has significant toxic effects on the liver and kidney organs of the human body and is carcinogenic. More importantly, Sudan dyes are generally insoluble in water and are difficult to remove once they enter the digestive system. Therefore, it is of great significance to develop a feasible and effective method for degrading Sudan pollutants.

[0005] CsPbX3 (X = Cl, Br, I) / Au nanoparticle composites have good conversion luminescence and semiconductor properties. As the main body of the conversion mechanism and the photogenerated electron transfer body, its built-in electric field, small size of gold nanoparticles and high specific surface area can promote higher light absorption and carrier separation under visible light, thereby obtaining better photocatalytic performance. This study has opened up a new way for the application of halide perovskite materials in the photocatalytic degradation of pollutants. At present, since the optoelectronic applications of IPQDs are mainly concentrated in solar cells, light-emitting devices, lasers, photodetectors, etc., other applications such as photocatalysis are rarely reported, which greatly limits the potential application of perovskite quantum dots in the photodegradation of pollutants such as Sudan III under visible light. Summary of the invention

[0006] The purpose of the present invention is to overcome the defects and shortcomings of the above-mentioned prior art. In view of the above problems, the present invention uses organic ligands to reduce AuX on the surface of CsX, and then reacts with Pb(OA)2 solution to obtain CsPbX3 / Au nanoparticle composite materials. This method has not been reported in patents or non-patent literature.

[0007] Develop a method for preparing perovskite quantum dot / Au nanoparticle composite materials.

[0008] The method for preparing the perovskite quantum dot / noble metal nanoparticle composite material provided by the present invention comprises the following steps:

[0009] 1) Preparation of Cs-oleic acid precursor: First, Cs2CO3 and oleic acid were added to a three-necked flask, followed by heating, stirring and vacuuming to remove water from the system. After vacuuming, argon was introduced and heating was continued until Cs2CO3 was completely dissolved.

[0010] 2) Preparation of ZnX2 solution: First, add ZnX2 (X = Cl, Br, I), oleic acid, octadecene and oleylamine into a three-necked flask, then heat, stir and vacuum to remove water and air in the system. After vacuuming, introduce argon and continue heating until ZnX2 is completely dissolved.

[0011] 3) Preparation of Pb(OA)2 solution: First, add PbO and oleic acid into a three-necked flask until PbO is completely dissolved.

[0012] 4) Preparation of CsX nanoparticles: The precursor obtained in step 1) is quickly injected into step 2) (70-80°C), and then the solution injected with the precursor is placed in an ice water bath and cooled to room temperature. The cooled solution is then centrifuged and the obtained precipitate is dispersed in toluene (or n-hexane, chlorobenzene) to obtain a CsX nanoparticle dispersion.

[0013] 5) Preparation of CsX / Au nanoparticles: Take the product obtained in step 4), add AuX particles to dissolve under vigorous stirring, centrifuge after the reaction, and disperse the obtained precipitate in toluene.

[0014] 6) Preparation of CsPbX3 nanoparticles: Take the product obtained in step 4), add the product obtained in step 3) under vigorous stirring, centrifuge after the reaction is completed, and disperse the obtained precipitate in toluene (or n-hexane, chlorobenzene) to obtain a CsPbX3 nanoparticle dispersion.

[0015] 7) Preparation of CsPbX3 / Au nanoparticles: Take the product obtained in step 5), add the product obtained in step 3) under vigorous stirring, centrifuge after the reaction is completed, and disperse the obtained precipitate in toluene (or n-hexane, chlorobenzene) to obtain CsPbX3 / Au nanoparticles.

[0016] The flask can be heated in an oil bath in the above step.

[0017] Preferably, the relationship between the amount of Cs2CO3 and the amount of oleic acid is 0.1mmol-0.6mmol:5mL-50mL.

[0018] Preferably, in the preparation of the ZnX2 solution, the amount of ZnX2: the amount of octadecene: the amount of oleic acid: the amount of oleylamine = 0.1mmol-0.6mmol: 8mL-40mL: 0.2mL-10mL: 0.2mL-10mL, and the heating temperature is 50°C to 160°C.

[0019] Preferably, in the preparation of Pb(OA)2 solution, the amount of PbO: the amount of oleic acid = 0.1 mmol-0.6 mmol: 5 mL: 30 mL, and the heating temperature is 80°C to 160°C.

[0020] Preferably, in the preparation of the CsX / Au nanoparticle dispersion, the mass of AuX is 0.04 times the mass of CsX.

[0021] More specific:

[0022] In step 1), the amount of Cs2CO3 used is preferably 0.1 mmol to 0.6 mmol, and the amount of oleic acid used is preferably 5 mL to 50 mL.

[0023] In the step 2), the amount of octadecene used is preferably 8 mL to 40 mL, and the heating temperature is preferably 50° C. to 160° C.

[0024] The amount of ZnX2 is preferably 0.1 mmol to 0.6 mmol.

[0025] The amount of oleic acid used is preferably 0.2 mL to 10 mL.

[0026] The amount of oleylamine used is preferably 0.2 mL to 10 mL.

[0027] The amount of PbO used in step 3) is preferably 0.1 mmol to 0.6 mmol.

[0028] The amount of oleic acid is preferably 5 mL to 30 mL.

[0029] The heating temperature is preferably 80°C to 160°C.

[0030] The centrifugal speed in step 4) is preferably 3000 rpm to 13000 rpm, and the centrifugal time is preferably 3 min to 30 min;

[0031] The amount of the precursor is preferably 0.5 mL-3 mL;

[0032] In the step 5), the amount of CsX used is preferably 0.01 mmol-0.5 mmol;

[0033] The amount of AuX is preferably 0.04 times the amount of CsX;

[0034] The centrifugal speed is preferably 6000 rpm-12000 rpm, and the centrifugal time is preferably 3 min to 30 min;

[0035] The amount of CsX or CsX / Au in step 6) and step 7) is preferably 0.5 mL-20 mL;

[0036] The amount of Pb(OA)2 is preferably 0.2mL-8mL;

[0037] The solvent is a solvent that can disperse but not dissolve CsX, CsX / Au and perovskite nanocrystal / Au nanoparticle composite materials.

[0038] The solvent is but not limited to n-hexane, toluene, and chlorobenzene, and the amount used is preferably 4 mL to 40 mL.

[0039] The centrifugal speed is preferably 3000 rpm to 10000 rpm, and the centrifugal time is preferably 3 min to 30 min.

[0040] The difference between the perovskite quantum dots composited with precious metals proposed in the present invention and the existing similar perovskite quantum dots is that:

[0041] 1. CsPbX3 / Au nanoparticles have a larger specific surface area and more active sites, which increases their photoactivity;

[0042] 2. By utilizing Au deposition to form CsPbX3 / Au heterostructure nanoparticles, a balanced Fermi level is generated. At the interface between perovskite and gold, there is a "built-in" electric field from perovskite to gold form. The electric field quickly removes free carriers, thereby establishing a depletion region, which can enhance the separation of photoinduced holes and electrons, inhibit their recombination, and further improve their photocatalytic performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 Schematic diagram of the principle of forming CsPbBr3 NCs and Au-CsPbBr3 NCs from CsBr NCs.

[0044] Figure 2 This is the XRD pattern of Au-CsPbBr3.

[0045] Figure 3 XRD patterns of CsBr NCs, CsPbBr3 NCs, and Au-CsPbBr3 NCs.

[0046] Figure 4 TEM morphologies of CsBr NCs (left) and Au-CsBr NCs (right).

[0047] Figure 5 TEM morphology of Au-CsPbBr3 NCs.

[0048] Figure 6 This is the Sudan III concentration-time curve with different catalysts added under visible light. DETAILED DESCRIPTION

[0049] The present invention is not limited to the following specific embodiments. A person skilled in the art can implement the present invention in various other specific embodiments according to the contents disclosed in the present invention, or any simple changes or modifications made to the design structure and ideas of the present invention fall within the protection scope of the present invention. It should be noted that the embodiments and features in the embodiments of the present invention can be combined with each other without conflict.

[0050] The present invention is further described in detail below in conjunction with embodiments:

[0051] Comparative Example 1

[0052] Step 1) Weigh 0.65 g of Cs2CO3 (Aladdin, purity 99.99%, commercially available product), dissolve it in a three-necked flask containing 10 mL of oleic acid (OA), then heat and stir, and evacuate at 120°C for 1 h to remove water in the system. After evacuation, introduce argon gas until Cs2CO3 is completely dissolved to obtain a Cs-oleic acid precursor solution;

[0053] Step 2) Weigh 0.1801 g of ZnBr2 (Aladdin, purity 99.99%, commercially available product), dissolve it in a three-necked flask containing 2 mL of OA, 2 mL of oleylamine (OAm) and 4 mL of octadecene (ODE), then heat and stir, and evacuate the system at 80°C for 1 h to remove water. After the evacuation, introduce argon until the ZnBr2 is completely dissolved to obtain a ZnBr2 solution.

[0054] Step 3) Weigh 0.22 g of PbO and dissolve it in a three-necked flask containing 10 mL of oleic acid, then heat to 80° C. until PbO is completely dissolved to obtain a Pb(OA)2 solution.

[0055] Step 4) 1 mL of the Cs-oleic acid precursor solution prepared in step 1) was rapidly injected into the ZnBr2 solution (70-80°C) prepared in step 2), and placed in an ice water bath 5 minutes after the injection was completed, cooled to room temperature, and then post-processed: the solution cooled to room temperature was centrifuged at a centrifugal speed of 3800 rpm for 10 minutes, and the precipitate was dispersed in 12 mL of toluene solvent to obtain a CsBr nanoparticle dispersion, and its concentration was adjusted to 25 mg / mL (such as Figure 4 (shown on the left).

[0056] Step 5) Take 5 mL of the CsBr nanoparticle dispersion prepared in step 4), add 2 mL of the Pb(OA)2 solution prepared in step 3), stir for 30 seconds, centrifuge the solution after the reaction, and centrifuge at a speed of 12000 rpm for 5 minutes. Finally, take the precipitate and disperse it in toluene to obtain the final product CsPbBr3 quantum dot dispersion, and then adjust its concentration to 10 mg / mL.

[0057] Step 6) Take 5 mL of the CsPbBr3 quantum dot dispersion prepared in step 5) and add 2 mg of AuBr particles under stirring conditions, react for 10 min, centrifuge the solution after the reaction, the centrifugal speed is 12000 rpm, 5 min, take the precipitate and disperse it in 5 mL of toluene to obtain the final product Au-CsPbBr3 quantum dot dispersion, and adjust its concentration to 10 mg / mL. This method will change the structure of perovskite quantum dots, and Cs2Au2Br6 byproducts (such as Figure 2 shown).

[0058] The final product was used for photocatalytic reaction: 80 mL of Sudan III solution (10 mg / L, solvent: toluene) was prepared, 36 mL was taken and injected into a transparent glass bottle, and 4 mL of Au-CsPbBr3 dispersion (10 mg / mL) prepared in step (6) of comparative example 1 was added; the mixed solution was stirred in the dark for 12 h to reach adsorption-desorption equilibrium; then visible light irradiation (30 mW / cm2) was applied, and samples were taken every 30 min to characterize the concentration of Sudan III in the solution. The results showed that under the photocatalytic action of Au-CsPbBr3, after 6 hours of illumination, the concentration of Sudan III solution was reduced to 81% of the initial concentration.

[0059] Comparative Example 2

[0060] Referring to Comparative Example 1, a CsPbBr3 quantum dot dispersion was prepared and its concentration was adjusted to 10 mg / mL. Similar to Comparative Example 1, the product was used for photocatalytic reaction. Under the photocatalytic action of CsPbBr3, after 6 hours of illumination, the concentration of Sudan III solution decreased to 88% of the initial concentration ( Figure 6 ).

[0061] Example 1

[0062] First, 10 mL of the CsBr nanoparticle dispersion prepared in step 4) of Comparative Example 1 was taken, 10 mg of AuBr was added (the mass ratio of CsBr nanoparticles to AuBr was calculated to be 25:1), and after reacting for 1 h, the dispersion was centrifuged at a centrifugal speed of 7500 rpm for 5 min, and the precipitate was dispersed in toluene to obtain an Au-CsBr nanoparticle composite material dispersion (such as Figure 4 (right) and 3 (right)).

[0063] Then, 5 mL of Au-CsBr nanoparticle composite material dispersion was added to 2 mL of Pb(OA)2 solution prepared according to step 3) of Comparative Example 1, and stirred for 30 s. After the reaction, the solution was centrifuged at a speed of 12000 rpm for 5 min. Finally, the precipitate was dispersed in toluene to obtain the final product, Au-CsPbBr3 quantum dot dispersion, and its concentration was adjusted to 10 mg / mL (such as Figure 5 (left)). The Au-CsPbBr3 quantum dot product does not contain Cs2Au2Br6 byproduct ( Figure 3 (Left)).

[0064] Similar to Comparative Example 1, the final product was used for photocatalytic reaction. Under the photocatalytic action of Au-CsPbBr3, after 6 hours of illumination, the concentration of Sudan III solution decreased to 28% of the initial concentration ( Figure 6 ).

[0065] Example 2

[0066] First, weigh 0.65g of Cs2CO3 (Aladdin, purity 99.99%, commercially available product), dissolve it in a three-necked flask containing 10mL of oleic acid (OA), then heat and stir, and evacuate at 120°C for 1h to remove water in the system. After the evacuation, introduce argon until Cs2CO3 is completely dissolved to obtain a Cs-oleic acid precursor solution; weigh 54.52mg of ZnCl2 (Aladdin, purity 99.99%, commercially available product), dissolve it in a three-necked flask containing 2mL of OA, 2mL of OAm and 4mL of ODE, then heat and stir, and evacuate at 80°C for 1h to remove water in the system. After the evacuation, introduce argon until ZnCl2 is completely dissolved to obtain a ZnCl2 solution.

[0067] Next, 1 mL of the Cs-oleic acid precursor solution prepared in this example was rapidly injected into the ZnCl2 solution (80-100°C), and placed in an ice water bath 5 minutes after the injection was completed, cooled to room temperature, and then the CsCl nanoparticle dispersion was obtained according to the post-treatment method in step 4) of comparative example 1, and its concentration was adjusted to 25 mg / mL.

[0068] Then, according to the preparation method of Example 1, the CsBr nanoparticles were replaced by the CsCl nanoparticles prepared above, and AuBr was replaced by AuCl. The remaining steps were the same as in Example 1 to prepare the Au-CsPbCl3 quantum dot dispersion.

[0069] Finally, the protein was purified by centrifugation and its concentration was adjusted to 10 mg / mL.

[0070] Similar to Comparative Example 1, the final product was used for photocatalytic reaction. Under the photocatalytic action of Au-CsPbCl3, after 6 hours of illumination, the concentration of Sudan Red III solution decreased to 73% of the initial concentration.

[0071] Example 3

[0072] Weigh 0.128 g of ZnI2 (Aladdin, purity 99.99%, commercially available product) to replace ZnCl2, and the remaining steps are the same as in Example 2 to prepare an Au-CsPbI3 quantum dot dispersion, and then adjust its concentration to 10 mg / mL.

[0073] Similar to Comparative Example 1, the final product was used for photocatalytic reaction. Under the photocatalytic action of Au-CsPbI3, the concentration of Sudan Red III solution decreased to 40% of the initial concentration after 6 hours of illumination.

[0074] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solutions and concepts of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for preparing a perovskite quantum dot / noble metal nanoparticle composite material, characterized in that: The following steps are involved: 1) Preparation of Cs-oleic acid precursor: First, Cs2CO3 and oleic acid were added to a three-necked flask, followed by heating, stirring and vacuuming to remove water from the system. After vacuuming, argon was introduced and heating was continued until Cs2CO3 was completely dissolved; 2) Preparation of ZnX2 solution: First, ZnX2, oleic acid, octadecene and oleylamine were added to a three-necked flask, followed by heating, stirring and vacuuming to remove water and air in the system. After vacuuming, argon was introduced and heating was continued until ZnX2 was completely dissolved; X = Cl or Br or I; 3) Preparation of Pb(OA)2 solution: First, add PbO and oleic acid into a three-necked flask until PbO is completely dissolved; 4) Preparation of CsX nanoparticle dispersion: Cs-oleic acid precursor is quickly injected into ZnX2 solution, and the temperature is maintained at 70-80°C. Then, the solution injected with the precursor is placed in an ice water bath and cooled to room temperature. The cooled solution is then centrifuged and the obtained precipitate is dispersed in toluene, hexane or chlorobenzene to obtain a CsX nanoparticle dispersion; 5) Preparation of CsX / Au nanoparticle dispersion: AuX particles are added to the CsX nanoparticle dispersion under vigorous stirring to dissolve, centrifuged after the reaction is completed, and the obtained Au-CsX nanoparticles are dispersed in toluene to obtain an Au-CsX nanoparticle composite material dispersion; 6) Preparation of CsPbX3 / Au nanoparticles: Pb(OA)2 solution was added to the Au-CsX nanoparticle composite dispersion under vigorous stirring. After the reaction was completed, the mixture was centrifuged and the obtained precipitate was dispersed in toluene, n-hexane or chlorobenzene to obtain CsPbX3 / Au nanoparticles.

2. The method for preparing a perovskite quantum dot / noble metal nanoparticle composite material according to claim 1, characterized in that: The relationship between the amount of Cs2CO3 and the amount of oleic acid is 0.1mmol-0.6mmol:5mL-50mL.

3. The method for preparing the perovskite quantum dot / noble metal nanoparticle composite material according to claim 1, characterized in that: In the preparation of ZnX2 solution, the amount of ZnX2: the amount of octadecene: the amount of oleic acid: the amount of oleylamine = 0.1mmol-0.6mmol: 8mL-40mL: 0.2mL-10mL: 0.2mL-10mL, and the heating temperature is 50℃ to 160℃.

4. The method for preparing a perovskite quantum dot / noble metal nanoparticle composite material according to claim 1, characterized in that: In the preparation of Pb(OA)2 solution, the amount of PbO: the amount of oleic acid = 0.1mmol-0.6mmol: 5mL: 30mL, and the heating temperature is 80℃ to 160℃.

5. The method for preparing the perovskite quantum dot / noble metal nanoparticle composite material according to claim 1, characterized in that: In the preparation of CsX / Au nanoparticle dispersion, the mass of AuX is 0.04 times the mass of CsX.

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