A method for preparing Mn-doped CsPbBr3 nanowires

Abstract

This application relates to a method for preparing Mn-doped CsPbBr3 nanowires. The method comprises: 1) injecting a cesium oleate precursor solution into a mixed solution A, dispersing the resulting precipitate by centrifugation in an oil-phase solvent, and obtaining a CsPbBr3 nanowire seed solution; 2) injecting the CsPbBr3 nanowire seed solution into a mixed solution B to form Mn-doped CsPbBr3 nanowires, cooling the solution, and centrifuging the resulting precipitate. Mixed solution A is prepared by mixing octadecene, oleic acid, oleylamine, and lead bromide, heating the mixture until the lead bromide is fully dissolved, and then cooling the mixture; mixed solution B is prepared by mixing octadecene and manganese bromide and heating the mixture under an inert gas atmosphere. This method provides sufficient thermal energy for the dopant while minimizing Ostwald maturity, allowing the dopant to diffuse into the crystal without the use of highly corrosive acids. While maintaining the nanowire's shape anisotropy and overall dimensional uniformity, it can produce nanowires with ultra-small diameters, making it an effective method for synthesizing Mn-doped CsPbBr3 nanowires.

Description

Technical Field

[0001] The present application belongs to the technical field of luminescent materials, and specifically is a method for preparing Mn-doped CsPbBr3 nanowires. Background Art

[0002] All-inorganic CsPbX3 perovskite materials have excellent optoelectronic properties, with luminescence peaks covering the entire visible light range, making them suitable for applications in luminescent materials and lighting sources. Furthermore, all-inorganic CsPbX3 perovskite materials also possess high carrier mobility and low defect state density, leading to important applications in catalytic materials, photodetectors, and lasers.

[0003] The traditional method for synthesizing CsPbBr3 nanowires is the hot injection method. Patent document CN114479852A discloses a method for preparing CsPbBr3 nanowires. This method involves first hot-injecting a cesium oleate precursor into a mixed reaction system of octylamine, oleylamine, octadecene, and lead bromide. The reaction is continued in an ice-water bath until it reaches room temperature to synthesize a CsPbBr3 perovskite nanocrystal solution. The untreated nanocrystal sample is then directly injected into an autoclave to synthesize CsPbBr3 perovskite nanowires. The size of the CsPbBr3 perovskite nanowires is controlled solely by controlling the reaction time. The CsPbBr3 perovskite nanowires are then purified by centrifugation.

[0004] Mn-doped all-inorganic perovskite (CsPbX3, X = Cl, Br, I) nanocrystals are a promising material for optoelectronics due to their long luminescence lifetime, high quantum yield, and large Stokes shift. However, research on Mn-doped low-dimensional all-inorganic perovskites is currently scarce, and further research is urgently needed to promote the practical application of these materials in optoelectronic applications.

[0005] For Mn-doped CsPbX3 nanocrystals, wide-bandgap CsPbCl3 is an ideal host, while narrow-bandgap CsPbBr3 is difficult to obtain bright Mn luminescence due to energy level mismatch. 2+ When the source is present, the dissociation energy of the Mn-O bond formed in the reaction solution differs significantly from that of the Pb-Br bond, making Mn doping of CsPbBr3 difficult. Therefore, to prepare Mn-doped CsPbBr3 nanowires, it is necessary to adjust the chemical potentials of the host ions and impurity ions in the solution and lattice to suppress Ostwald ripening, thermodynamically favor impurity ion doping, and simultaneously provide sufficient thermal energy for the impurity ions to diffuse from the nanowire surface into the interior. Therefore, thermodynamically controlled diffusion doping is undoubtedly the optimal method for preparing Mn-doped CsPbBr3 nanowires.

[0006] In existing research, the traditional high-temperature hot injection method for synthesizing Mn-doped CsPbBr3 requires the addition of highly corrosive hydrobromic acid and a large amount of MnBr2 to achieve Mn 2+ The successful doping of ions, the crystallinity of the finished nanosheets is poor, as shown in the literature (Chem. Mater. 2018, 30, 2939-2944). Post-synthesis cation exchange at room temperature is currently the main method for synthesizing Mn-doped CsPbBr3, but for one-dimensional nanowires, due to its large specific surface area, the surface defect density is high and the stability is very poor. Currently, there is only one case report that successfully achieved Mn 2+ Ion doping, as documented in the literature (J. Phys. Chem. C. 2022, 126, 15829-15837), inevitably destroys the original crystal structure of the nanowires during post-processing, resulting in the formation of a nanocrystalline impurity phase in the finished product, with a peak appearing around 500nm in the luminescence spectrum. Therefore, how to prepare Mn-doped CsPbBr3 nanowires with uniform size and excellent luminescence performance has become an urgent challenge for researchers. Summary of the Invention

[0007] The technical problem to be solved by the present application is to provide a method for effectively preparing Mn-doped CsPbBr3 nanowires, which can be effectively prepared without adding highly corrosive hydrobromic acid to the reaction precursor and can be used to prepare Mn-doped CsPbBr3 nanowires under thermodynamic control. 2+ doped into the nanowire seed lattice, Mn 2+ internalized into the nanowire lattice, effectively achieving the Mn 2+ doping, while suppressing Ostwald ripening, retaining the original nanostructure, and realizing the preparation of Mn-doped ultra-fine nanowires.

[0008] To this end, this application adopts the following technical solutions:

[0009] A method for preparing Mn-doped CsPbBr3 nanowires comprises the following steps:

[0010] 1) injecting a cesium oleate precursor solution into a mixed solution A, centrifuging and removing the supernatant, and dispersing the resulting precipitate in an oil phase solvent to obtain a CsPbBr3 nanowire seed solution; 2) injecting the CsPbBr3 nanowire seed solution into a mixed solution B to form Mn-doped CsPbBr3 nanowires, cooling and centrifuging, and collecting the precipitate;

[0011] The cesium oleate precursor solution is prepared by mixing cesium carbonate, oleic acid and an oil phase solvent, and stirring and heating them under the protection of an inert gas; the mixed solution A is prepared by mixing octadecene, oleic acid, oleylamine and lead bromide, heating them until the lead bromide is fully dissolved, and then cooling them; the mixed solution B is prepared by mixing octadecene and manganese bromide, and heating them under an inert gas environment.

[0012] In at least one embodiment, during the preparation of the cesium oleate precursor solution:

[0013] The molar mass of the cesium carbonate is 0.68 mmol; the oil phase solvent is octadecene, and the volume ratio of the oleic acid to the oil phase solvent is 1:6-10.

[0014] The heating temperature is 130-170° C.; after obtaining the cesium oleate precursor solution, the temperature is lowered to 100° C. for standby use.

[0015] In at least one embodiment, during the preparation of the mixed solution A:

[0016] The volume ratio of octadecene, oleic acid and oleylamine is 6-8:0.6-1.4:1.

[0017] In at least one embodiment, during the preparation of the mixed solution B:

[0018] The molar mass of the manganese bromide is 0.05 to 0.7 mmol.

[0019] The heating temperature is 30-130°C.

[0020] In at least one embodiment, during the preparation of the cesium oleate precursor solution and the mixed solution B, the inert gas used is nitrogen or argon.

[0021] In at least one embodiment, in step 1):

[0022] The volume ratio of the cesium oleate precursor solution to the mixed solution A is 1:15-40; after the cesium oleate precursor solution is injected into the mixed solution A, it is kept at room temperature for 20-60 minutes.

[0023] The oil phase solvent may be octadecene.

[0024] In at least one embodiment, in step 2):

[0025] After the CsPbBr3 nanowire seed solution is injected into the mixed solution B, the heating temperature of the mixed solution B is maintained during its preparation, and the maintenance time is ≤30 minutes.

[0026] The cooling method may be an ice bath.

[0027] The precipitate obtained after the centrifugal separation is dispersed in an organic solvent for storage; the organic solvent can be selected from n-hexane.

[0028] Compared with the prior art, this application achieves at least the following beneficial effects:

[0029] 1. The synthesis conditions of the present invention are safe and simple, and the nanowires can be synthesized without using highly corrosive hydrobromic acid.

[0030] 2. The Mn-doped CsPbBr3 nanowires obtained by the method of the present application have uniform size distribution and a luminous efficiency of up to 50%.

[0031] 3. The Mn-doped CsPbBr3 nanowires obtained by the method of this application have an ultra-small diameter, with the smallest diameter reaching 2.38 nm.

[0032] 4. The synthesis method of this application is environmentally friendly and does not require the use of a large amount of MnBr2 in the reaction precursor. 2+ ions are doped into CsPbBr3 nanowires.

[0033] 5. The method of this application effectively solves the problem of the difficulty in realizing Mn-doped CsPbBr3. By regulating the reaction temperature and the amount of MnBr2 in the reaction precursor, the exciton emission wavelength and the Mn emission intensity can be easily adjusted, which is more conducive to promoting the practical application of such materials in the corresponding optoelectronic fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] One or more embodiments of the present application will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0035] Figure 1 The luminescence spectrum, absorption spectrum, and luminescence efficiency of the samples prepared in Examples 1 to 4 of the present application;

[0036] Figure 2 The luminescence spectrum and absorption spectrum of the sample prepared in Example 5 of the present application;

[0037] Figure 3 Transmission electron micrographs of the samples prepared in Examples 1 to 4 of the present application;

[0038] Figure 4 This is a transmission electron microscope photograph of the sample prepared in Example 5 of the present application. DETAILED DESCRIPTION

[0039] The present application will be described in detail below with reference to the exemplary embodiments shown in the accompanying drawings. However, it should be understood that the present application can be implemented in a variety of different forms and should not be construed as being limited to the embodiments described herein. These embodiments are provided herein to make the disclosure of the present application more complete and to fully convey the concepts of the present application to those skilled in the art.

[0040] The present application provides a method for preparing Mn-doped CsPbBr3 nanowires, the method comprising the following steps:

[0041] Step 1: Mix cesium carbonate, oleic acid, and an oil phase solvent, and stir and heat under inert gas protection until the solution becomes clear to obtain a cesium oleate precursor solution, which is then cooled to 100°C for use. The molar mass of cesium carbonate is 0.68 mmol, the oil phase solvent is preferably octadecene, the volume ratio of oleic acid to the oil phase solvent is preferably 1:6 to 10, more preferably 1:8, the inert gas is preferably nitrogen or argon (same as in step 5), more preferably nitrogen, and the heating temperature is 130 to 170°C, more preferably 150°C for 5 minutes.

[0042] Step 2: octadecene, oleic acid, oleylamine, and lead bromide are mixed, and the resulting mixed solution is heated to 150° C. and maintained at this temperature until the solution becomes clear and transparent. After the lead bromide is fully dissolved, the solution is cooled to room temperature to obtain a mixed solution A. The volume ratio of octadecene, oleic acid, and oleylamine is preferably 6 to 8:0.6 to 1.4:1, and more preferably 3.2:0.5:0.5.

[0043] Step 3: Injecting the cesium oleate precursor solution into mixed solution A to form CsPbBr3 nanowire seeds. The volume ratio of the injected cesium oleate precursor solution to mixed solution A is 1:15-40. After the cesium oleate precursor solution is injected into mixed solution A, it is maintained at room temperature for 20-60 minutes, preferably 40 minutes.

[0044] Step 4: Centrifuge the mixture obtained in step 3 at high speed, carefully remove the supernatant, and disperse the resulting precipitate in an oil phase solvent to obtain a CsPbBr3 nanowire seed solution. The oil phase solvent is preferably octadecene.

[0045] Step 5: mixing octadecene and manganese bromide, and heating under an inert gas environment to obtain a mixed solution B. The heating temperature is 30-130° C., preferably 90° C.

[0046] Step 6: Inject the CsPbBr3 nanowire seed solution into mixed solution B to form Mn-doped CsPbBr3 nanowires. After the CsPbBr3 nanowire seed solution is injected into mixed solution B, the heating temperature during the preparation of mixed solution B is maintained for ≤30 minutes, preferably 5 minutes.

[0047] Step 7: Cool the reaction mixture to room temperature using an ice bath, centrifuge in an oily solvent, and disperse the resulting precipitate in an organic solvent to obtain a Mn-doped CsPbBr3 nanowire solution. The organic solvent is preferably n-hexane.

[0048] The principle of preparing Mn-doped CsPbBr3 nanowires in this application is:

[0049] Under thermodynamic control, Mn 2+Under quasi-equilibrium conditions, it enters the nanowire seed crystal lattice and is internalized by entropy-driven crystal ion diffusion. During the doping process, only the trace ligands carried by the nanowire seed itself are present, which avoids the formation of Mn-O bonds in the precursor solution that are not conducive to doping. 2+ Through the introduction of MnBr2, Mn in the solution 2+ and Pb 2+ The chemical potential of Mn increases, which inhibits Ostwald ripening and makes the nanowires stay at high temperature for a long time without phase change. 2+ Ions diffuse from the nanowire surface to the interior of the nanowire to provide sufficient thermal energy; Br - The increase of Mn in the lattice leads to 2+ The chemical potential drops to a level that is thermodynamically favorable for solid solution formation, thereby facilitating the formation of doped nanowires.

[0050] The present application will be described in detail below with reference to specific embodiments, and the raw materials involved in the embodiments are all commercially available. In the absence of conflict, the following embodiments and features in the embodiments may be combined with each other.

[0051] Example 1

[0052] Mn-doped CsPbBr3 nanowires were prepared under thermodynamic control according to the following reaction conditions and steps:

[0053] Step 1: Add 0.68 mmol of cesium carbonate, 1.3 mL of oleic acid, and 10 mL of octadecene to a 50 mL three-necked flask at room temperature, evacuate, and introduce inert gas (nitrogen) to remove residual water molecules and low-boiling organic matter. Under the protection of nitrogen, stir and heat the mixed solution to 150° C. and maintain this temperature until the solution becomes clear and transparent to obtain a cesium oleate precursor solution, which is then cooled to 100° C. for use.

[0054] Step 2: 3.2 mL of octadecene, 0.5 mL of oleic acid, 0.5 mL of oleylamine, and 0.2 mmol of lead bromide were added to a 50 mL three-necked flask, evacuated, and introduced with inert gas (nitrogen) to remove residual water molecules and low-boiling organic matter. Under the protection of nitrogen, the mixed solution was stirred and heated to 150° C. After the lead bromide was fully dissolved, the temperature was cooled to room temperature to obtain a mixed solution A;

[0055] Step 3: inject 0.2 mL of the cesium oleate precursor solution obtained in step 1 into the mixed solution A obtained in step 2, and place it at room temperature for 30 minutes to form CsPbBr3 nanowire seeds;

[0056] Step 4: Transfer the mixed solution obtained in step 3 to a centrifuge tube, carefully remove the supernatant after high-speed centrifugation, and then disperse the obtained precipitate in octadecene to obtain a CsPbBr3 nanowire seed solution.

[0057] Step 5: 4 mL of octadecene and 0.05 mmol of manganese bromide were added to a 50 mL three-necked flask, vacuumed, and introduced with inert gas (nitrogen) to remove residual water molecules and low-boiling organic matter. Under the protection of nitrogen, the mixed solution was stirred and heated to 90° C. to prepare mixed solution B;

[0058] Step 6: injecting the CsPbBr3 nanowire seed solution obtained in step 4 into the mixed solution B obtained in step 5, and maintaining the mixture at 90° C. for 5 minutes to form Mn-doped CsPbBr3 nanowires;

[0059] Step 7: Use an ice bath to cool the reaction temperature to room temperature and transfer the mixture to a centrifuge tube. Centrifuge at 3500 rpm for 3 min to obtain a precipitate, which is then dispersed in n-hexane to obtain a Mn-doped CsPbBr3 nanowire solution.

[0060] Example 2

[0061] The reaction conditions and steps of this embodiment are basically the same as those of Example 1, except that the heating temperature in step 5 is 30°C.

[0062] Example 3

[0063] The reaction conditions and steps of this embodiment are basically the same as those of Example 1, except that the heating temperature in step 5 is 60°C.

[0064] Example 4

[0065] The reaction conditions and steps of this embodiment are basically the same as those of Example 1, except that the heating temperature in step 5 is 100°C.

[0066] The reaction temperature of Examples 1 to 4 was increased from 30°C to 100°C. The luminescence and absorption spectra of the obtained Mn-doped CsPbBr3 nanowires were as follows: Figure 1 As shown in the figure, the sharp and narrow exciton absorption peak at approximately 440 nm indicates that these Mn-doped CsPbBr3 nanowires have a strong quantum confinement effect. Under the same MnBr2 feed ratio, the luminescence intensity of the Mn-excitons gradually increases with increasing reaction temperature, while the Mn emission wavelength remains essentially unchanged at approximately 600 nm. The luminescence efficiency can reach nearly 50%.

[0067] Example 5

[0068] The reaction conditions and steps of this embodiment are basically the same as those of Example 1, except that in step 5, the amount of manganese bromide is 0.7 mmol and the heating temperature is 120°C. The luminescence and absorption spectra of the Mn-doped CsPbBr3 nanowires prepared under these conditions are shown in Figure 2. Figure 2As shown in the figure, the high temperature of 120℃ intensifies the Ostwald ripening, the exciton emission wavelength red-shifts to around 460nm, the Mn emission intensity is greater than the exciton emission intensity, and the absorption spectrum maintains the strong quantum confinement effect characteristics of perovskite nanowires.

[0069] Experimental Example 1

[0070] The Mn-doped CsPbBr3 nanowires prepared in Examples 1 to 4 were subjected to transmission electron microscopy experiments. Figure 3 The morphology and size distribution of the Mn-doped CsPbBr3 nanowires prepared in Examples 1 to 4 were analyzed as the reaction temperature increased from 30°C to 100°C. Transmission electron microscopy images show that the samples are nanowires with ultra-small diameters and uniform orientation. The samples are uniform in size and lack impurities such as nanosheets and nanocrystals. Furthermore, as the injection temperature increases, the nanowire diameters gradually increase, ranging from 2.38 to 3.02 nm. These are the smallest diameter Mn-doped CsPbBr3 nanowires synthesized to date.

[0071] Experimental Example 2

[0072] The Mn-doped CsPbBr3 nanowires prepared in Example 5 were subjected to transmission electron microscopy experiments. Figure 4 The morphology and size distribution of the Mn-doped CsPbBr3 nanowires prepared in Example 5 are shown. Transmission electron microscopy images show that the sample consists of ultra-small diameter nanowires with consistent orientation. Even at 120°C, these nanowires maintain a uniform size distribution, lacking impurities such as nanosheets and nanocrystals. Exposure to 120°C exacerbates Ostwald ripening, increasing the nanowire diameter to 3.27 nm.

[0073] The above embodiments and experimental examples illustrate:

[0074] The method of the present application can not only be used to incorporate Mn into CsPbBr3, but also to prepare Mn-doped CsPbBr3 nanowires with ultra-small diameters. These nanowire diameters are within the range of 2.38-3.27nm, with uniform size distribution, easy adjustment of exciton emission wavelength and Mn luminous intensity, and luminous efficiency of up to 50%. Relative to literature (Chem.Mater.2018,30,2939-2944), under the conditions of traditional hot injection synthesis, Mn is difficult to incorporate into the CsPbBr3 system. It is necessary to add highly corrosive hydrobromic acid and increase the amount of MnBr2 in the reaction precursor. The amount of MnBr2 in the literature reaction precursor is 5 times that of PbBr2. The Mn-doped CsPbBr3 nanowires synthesized in this application do not need to use hydrobromic acid. When the amount of MnBr2 in the reaction precursor is only 0.25 times that of PbBr2, Mn-doped CsPbBr3 nanowires with adjustable Mn luminous intensity can be obtained. The only literature report that Mn doped CsPbBr3 nanowires (J.Phys.Chem.C.2022,126,15829-15837) was achieved by post-synthesis method. Hydrobromic acid is still needed to synthesize CsPbBr3 nanowires. 2+ The ions destroyed the structure of the CsPbBr3 nanowires, and the finished product had an impurity phase, resulting in an impurity peak at 500nm in the luminescence spectrum. The luminescence spectrum of the Mn-doped CsPbBr3 nanowires synthesized in this application showed no impurity phase luminescence other than exciton and Mn luminescence, indicating that this application not only effectively inhibited the Ostwald ripening of the nanowires, but also ensured that the luminescence performance of the nanowires was not damaged during the doping process. By adopting this application to synthesize Mn-doped CsPbBr3 nanowires, the exciton luminescence wavelength and the Mn luminescence intensity can be easily adjusted by regulating the reaction temperature and the amount of MnBr2 in the reaction precursor. The synthesis method is simple and environmentally friendly, and has beneficial technical effects. The method of this application is expected to be used to prepare other nanomaterials, and provide a valuable reference for various doped semiconductor nanostructures that could not be synthesized through kinetic pathways or cation exchange before.

[0075] It should be understood that all the above embodiments are illustrative rather than restrictive, and various modifications or variations made by those skilled in the art to the specific embodiments described above based on the concept of this application should be within the scope of protection of this application.

Claims

1. A method for preparing Mn-doped CsPbBr3 nanowires, characterized in that: The following steps are involved: 1) injecting a cesium oleate precursor solution into a mixed solution A, centrifuging and removing the supernatant, and dispersing the resulting precipitate in an oil phase solvent to obtain a CsPbBr3 nanowire seed solution; the volume ratio of the cesium oleate precursor solution to the mixed solution A is 1:15-40; after the cesium oleate precursor solution is injected into the mixed solution A, it is maintained at room temperature for 20-60 minutes; the oil phase solvent is octadecene; 2) injecting the CsPbBr3 nanowire seed solution into mixed solution B to form Mn-doped CsPbBr3 nanowires, cooling and centrifuging to obtain a precipitate; after injecting the CsPbBr3 nanowire seed solution into mixed solution B, maintaining the heating temperature used in preparing mixed solution B for a period of ≤30 min; The cesium oleate precursor solution is prepared by mixing cesium carbonate, oleic acid and an oil phase solvent, stirring and heating under inert gas protection; the heating temperature is 130-170° C. After obtaining the cesium oleate precursor solution, the temperature is cooled to 100° C. for standby use; the molar mass of the cesium carbonate is 0.68 mmol; the oil phase solvent is octadecene, and the volume ratio of the oleic acid to the oil phase solvent is 1:6-10; The mixed solution A is prepared by mixing octadecene, oleic acid, oleylamine and lead bromide, heating the mixture until the lead bromide is fully dissolved, and then cooling the mixture; the volume ratio of octadecene, oleic acid and oleylamine is 6-8:0.6-1.4:1; The mixed solution B is prepared by mixing octadecene and manganese bromide and heating them under an inert gas environment; the molar mass of the manganese bromide is 0.05 to 0.7 mmol; and the heating temperature is 30 to 130°C.

2. The method according to claim 1, wherein: During the preparation of the cesium oleate precursor solution and the mixed solution B, the inert gas used is nitrogen or argon.

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