Multifunctional semiconductor quantum dot and synthetic method and application thereof

Abstract

The invention relates to the technical field of semiconductor quantum dots, and discloses a multifunctional semiconductor quantum dot and a synthesis method and application thereof.The synthesis method comprises the steps that according to the proportion of a chemical formula Cs (AaBbCcDdEe) Cl6, chlorides of Cs, A, B, C, D and E are weighed to serve as raw materials; carrying out primary ball milling on the raw materials, adding oleylamine and oleic acid, and carrying out secondary ball milling; and dispersing the ball-milled powder in toluene, adding an inorganic ligand, stirring to obtain a solid-liquid, carrying out solid-liquid separation, and drying, crushing and grinding the separated solid material to obtain the multifunctional semiconductor quantum dot finished product. According to the invention, the high-entropy two-dimensional double-perovskite long-afterglow material integrating multiple functions of luminescence and photocatalysis is synthesized through a solid-liquid combined two-step method. Organic and inorganic ligand bonding is respectively carried out in solid and liquid synthesis environments, so that the luminescence property and the stability are improved, the exciton lifetime is prolonged, and light-source-free self-sufficient photocatalysis is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor quantum dots, and particularly to a multifunctional semiconductor quantum dot, a synthesis method thereof, and an application thereof. Background Art

[0002] In recent years, optoelectronic materials such as perovskite with photon / electron generation, separation, and transport properties have attracted wide attention. For luminescent materials, high fluorescence quantum yield is usually achieved by promoting radiative transitions and suppressing non-radiative transitions. However, at the same time, radiative transitions mean that photo-generated carriers are prone to recombination, which is very unfavorable for photocatalytic reactions (such as water splitting and degradation of organic pollutants, etc.). Therefore, limited by the two mutually exclusive physical and chemical processes of photo-generated carrier separation and recombination, it is a very challenging problem to simultaneously achieve photoluminescence and photocatalysis in the same system.

[0003] Perovskite shows great potential application prospects in many fields due to its unique photophysical properties (such as tunable emission wavelength, high quantum efficiency, ultra-long afterglow time, and environmental stability). However, there are still problems such as rare earth element shortage, band structure mismatch, and balance between carrier recombination and separation on the way to realizing multifunctional applications.

[0004] Currently, the above problems are generally solved by methods such as single doping substitution to slightly reduce the rare earth doping amount, regulating the band structure, or selecting a single organic ligand for surface passivation modification, etc. However, the doping amount of rare earth is still very high and the excited state and excited state energy levels cannot be completely matched with the redox potential to achieve the integrated application of luminescence and photocatalysis; moreover, the single organic ligand currently used can only modify the surface and cannot promote carrier migration, and the single preparation and synthesis process also limits the ligand modification process, making it impossible to achieve a long exciton lifetime, and the short afterglow effect cannot continuously provide a self-luminous source for photocatalytic reactions.

[0005] Therefore, there is an urgent need for a multifunctional semiconductor quantum dot, a synthesis method thereof, and an application thereof to solve the above technical problems. Summary of the Invention

[0006] The purpose of the present invention is to address the deficiencies in the prior art. Through a two-step solid-liquid synthesis process, organic and inorganic double ligand bonding is carried out to synthesize an all-inorganic high-entropy two-dimensional perovskite long afterglow material with good luminescence performance, certain catalytic performance, and low rare earth content as a multifunctional semiconductor quantum dot.

[0007] To achieve the above object, the present invention is implemented according to the following technical solution:

[0008] A synthesis method of a multifunctional semiconductor quantum dot, comprising the following steps:

[0009] S1, Weigh the chlorides of Cs, A, B, C, D, and E as raw materials according to the ratio of the chemical formula Cs(A a B b C c D d E e )Cl6;

[0010] In the chemical formula Cs(A a B b C c D d E e )Cl6, A is one of Mn 2+ , Zn 2+ , Sn 2+ ; B is Ni 2+ or Cu 2+ , C is Ag + or Na + ; D is one of Bi 3+ , In 3+ , Fe 3+ ; E is Yb 3+ ; a + b + c + d + e = 1;

[0011] S2, First, ball-mill the above raw materials. After the first ball-milling is completed, add oleylamine and oleic acid and then perform the second ball-milling; After the second ball-milling is completed, obtain the ball-milled powder;

[0012] S3, After dispersing the ball-milled powder in toluene, add an inorganic ligand and stir to obtain a solid-liquid mixture; Perform solid-liquid separation on the solid-liquid mixture, and dry the separated solid material to obtain the dried product;

[0013] S4, Crush and grind the dried product to obtain the finished product of the multifunctional semiconductor quantum dots, denoted as Z-Cs(A a B b C c D d E e )Cl6.

[0014] The finished product of the multifunctional semiconductor quantum dots Z-Cs(A a B b C c D d E e )Cl6 prepared by the present invention is an all-inorganic high-entropy two-dimensional perovskite long-afterglow material with integrated luminescence and photocatalysis.

[0015] Preferably, the finished product of the multifunctional semiconductor quantum dots Z-Cs(A a B b Cc D d E e ) Cl6 is bonded with organic ligands oleylamine and oleic acid, and inorganic ligand ZnCl2 on Cs(A a B b C c D d E e ) Cl6.

[0016] Specifically, the step S1 includes the following steps:

[0017] S1. First, according to the capacity requirements of different ball mills, weigh the chlorides of Cs, A, B, C, D, and E as raw materials according to the ratio of the chemical formula Cs(A a B b C c D d E e ) Cl6; the chloride of A is one of MnCl2, ZnCl2, and SnCl2; the chloride of B is NiCl2 or CuCl2; the chloride of C is NaCl or AgCl; the chloride of D is one of BiCl3, InCl3, and FeCl3; the chloride of E is YbCl3.

[0018] Preferably, in the chemical formula Cs(A a B b C c D d E e ) Cl6, A is Mn 2+ , D is Bi 3+ or In 3+ .

[0019] Preferably, in the chemical formula Cs(A a B b C c D d E e ) Cl6, a∶b∶c∶d∶e = 3∶3∶1∶1∶2.

[0020] Preferably, in the step S2, the ball-to-material ratio of the first ball milling is (5 - 8)∶1, the time of the first ball milling is 5 - 10 min, and the rotation speed is 875 - 1125 rpm; the time of the second ball milling is 15 - 25 min, and the rotation speed is 875 - 1125 rpm.

[0021] Preferably, in the step S2, Cs(A a B b C c D d E e)The molar volume ratio of Cl6 to oleylamine is 2∶(20 - 40), and the comparison unit is mmol∶μL; Cs(A a B b C c D d E e )The molar volume ratio of Cl6 to oleic acid is 2∶(20 - 40), and the comparison unit is mmol∶μL.

[0022] Oleylamine and oleic acid can be added sequentially, or they can be mixed first and then added.

[0023] Specifically, step S2 includes the following steps:

[0024] S2. Put the above raw materials into the ball milling tank in sequence, and add zirconia balls with a ball-to-material ratio of (5 - 8)∶1. Pad a rubber ring at the seal of the ball milling tank, cover the ball milling cover and seal it well; Place the ball milling tank in a high-energy ball mill for the first ball milling. Through the combined action of mechanochemistry and the high-speed rotation and vibration of the ball mill, drive the grinding tank to perform periodic motion. The ball milling time for the first ball milling is 5 - 10 min, and the rotation speed is 875 - 1125 rpm; After the first ball milling is completed, transfer the ball milling tank to the glove box, open the ball milling tank, and use a pipette to add oleylamine (OAm) and oleic acid (OA) to the ball milling tank, Cs(A a B b C c D d E e )The molar volume ratio of Cl6 to oleylamine is 2∶(20 - 40), and the comparison unit is mmol∶μL; Cs(A a B b C c D d E e )The molar volume ratio of Cl6 to oleic acid is 2∶(20 - 40), and the comparison unit is mmol∶μL; Reseal the ball milling tank well, and use a high-energy ball mill for the second ball milling. The ball milling time for the second ball milling is 15 - 25 min, and the rotation speed is 875 - 1125 rpm; After the ball milling is completed, take out the ball milling tank and transfer it to the fume hood, open the ball milling tank, and obtain the ball-milled powder.

[0025] Preferably, in step S3, the inorganic ligand is ZnCl2, Cs(A a B b C c D d E e )The molar ratio of Cl6 to the inorganic ligand is 1∶(0.1 - 0.2).

[0026] In the present invention, the inorganic ligand ZnCl2 does not participate in the phase synthesis, but is bonded to the surface of the high-entropy perovskite single-phase Cs(A a B b C c D d E e )Cl6 to promote the carrier transport inside the multifunctional semiconductor quantum dot Z-Cs(A a B b C c D d E e )Cl6 to achieve a better photocatalytic effect.

[0027] Preferably, in the step S3, the process of solid-liquid separation is as follows: the solid-liquid mixture is centrifuged in a centrifuge tube, and the supernatant is discarded. Then, toluene is added to the centrifuge tube, and the precipitate is dispersed by ultrasonic dispersion and then centrifuged again, repeating several times.

[0028] Preferably, in the step S3, the drying temperature is 60-80 °C and the drying time is 4-6 h.

[0029] Specifically, the step S3 includes the following steps:

[0030] S3, the ball-milled powder is uniformly dispersed in toluene and ultrasonicated for 5 min. Then, the last weighed raw material ZnCl2 is added to the beaker and bonded as an inorganic ligand to the surface of the Cs(A a B b C c D d E e )Cl6 nanocrystals, and stirred at room temperature for 10 min; after the stirring is completed, the solid-liquid mixture in the beaker is transferred to a centrifuge tube, centrifuged for 10 min, and the supernatant is discarded. Then, a certain amount of toluene is added to the centrifuge tube again, and the precipitate is dispersed by ultrasonic dispersion and then centrifuged again, repeating three times; then the centrifuge tube is placed in an oven, the drying temperature is set at 60-80 °C, and the drying time is set at 4-6 h; the dried product is obtained.

[0031] The solid-liquid mixture in the above steps refers to the solid-liquid mixture. The ball-milled powder is prone to agglomeration and there will be some precipitation. The better-dispersed part of the powder will float in the upper liquid. Therefore, it is necessary to ultrasonicate to make it evenly dispersed before centrifugal separation.

[0032] Specifically, the step S4 includes the following steps:

[0033] S4, the dried product is placed in a crusher, and the crusher is used to grind it into coarser powdery particles. Then, the powder is put into a quartz mortar and further ground more finely into powder for 30-60 min; the finished product of the multifunctional semiconductor quantum dot is obtained.

[0034] The present invention also includes multifunctional semiconductor quantum dots synthesized by the above synthesis method.

[0035] The present invention also includes the applications of the multifunctional semiconductor quantum dots in multicolor fluorescence emission, detection, and outdoor lighting dust removal.

[0036] The finished product of the multifunctional semiconductor quantum dots prepared by the present invention, Z-Cs(A a B b C c D d E e )Cl6, as a long-afterglow luminescent high-entropy two-dimensional perovskite material, can emit and maintain monochromatic light of a fixed frequency band for a period of time (about 3600 s) after being briefly photoexcited. Subsequently, it can achieve light catalysis without an external light source by means of afterglow, and the carrier transport can be accelerated under the surface modification of inorganic ligands, improving the photocatalytic self-cleaning performance and addressing the problem that the luminescence performance of long-afterglow luminescent materials is easily damaged in a dusty environment.

[0037] The present invention synthesizes a high-entropy two-dimensional double perovskite long-afterglow material with integrated luminescence and photocatalysis functions through a two-step solid-liquid combination method. By separately bonding organic and inorganic ligands in the solid and liquid synthesis environments, not only is the luminescence performance and stability improved, but also the exciton lifetime is increased, achieving self-powered photocatalysis without a light source and expanding the application scope of two-dimensional perovskite materials in multicolor fluorescence emission, detection, outdoor lighting dust removal, etc.

[0038] Principle of action:

[0039] The present invention provides a synthesis route for preparing a luminescence-photocatalysis integrated all-inorganic high-entropy two-dimensional perovskite long-afterglow material through a two-step solid-liquid method, as well as an inorganic-organic double-ligand modification and bonding process technology.

[0040] The present invention selects Ag + , Na + , Mn 2+ , Ni 2+ , Zn 2+ , Cu 2+ , Fe 3+ , Sn 2+ , Bi 3+ , Yb 3+ , Eu 3+ and other combinations of elements with different valence states to synthesize a two-dimensional double perovskite Cs(A a B b C c D d E e )Cl, where A is Mn 2+ , B is Ni 2+ or Cu2+ , C is Ag + or Na + , D is Bi 3+ or In 3+ , E is Yb 3+ And the performance can reach the best when the doping ratio a∶b∶c∶d∶e = 3∶3∶1∶1∶2.

[0041] The present invention creatively uses a variety of multi-valent (+1, +2 and +3) non-toxic elemental ions to solid-solution synthesize an all-inorganic high-entropy two-dimensional perovskite long afterglow material in the material structure design, and optimizes the structure and performance by regulating the content of Bi 3+ in it. Compared with the traditional long afterglow single-doped and double-doped perovskite systems, the rare earth doping content is reduced by 80%. It can not only modify the energy band, make the excited state energy level match the redox potential, realize the integrated design and preparation of luminescent and photocatalytic materials, and synergistically make the lattice more stable with the high-entropy effect, realizing a higher fluorescence quantum yield and a wider visible light absorption, which has research and practical significance. In addition, in the synthesis and preparation path, the present invention adopts a solid-liquid phase synergistic preparation path. The high-energy ball milling method is used for solid-phase solvent-free green synthesis to pre-mill the material (the first ball milling), and then the organic ligands oleylamine and oleic acid are added for the second ball milling. Finally, the inorganic ligand ZnCl2 is subjected to organic liquid phase ligand bonding by the thermal injection method at room temperature, and finally the high-entropy perovskite powder is obtained through centrifugation and drying.

[0042] The organic ligand is added during ball milling and adheres to the surface of the powder during the ball milling process. In addition to playing a role in modifying surface defects, it can also play a role in assisting grinding. The combination of the organic ligand and the powder is physically adsorbed and wrapped on the surface of the powder. Ball milling plays a role in mixing and assisting grinding for the adhesion of the organic ligand.

[0043] The solid-liquid double ligands are beneficial to the surface modification of perovskite and the internal carrier conduction. Compared with the perovskite modified by ordinary doping and organic ligands, it shows enhanced fluorescence emission and has a certain photocatalytic degradation effect on organic pollutants.

[0044] Beneficial effects:

[0045] (1) The present invention uses a two-step solid-liquid phase combination synthesis path to prepare a multifunctional semiconductor quantum dot with integrated luminescence and photocatalysis; compared with direct mixing and synthesis, the experimental results show better stability and higher luminescence efficiency;

[0046] (2) In the selection of elements, considering multiple factors such as the tolerance factor, electronic structure, entropy value, electronegativity, and lattice constant, multiple suitable non-toxic B-site multivalent doping elements (+1, +2, and +3) are selected. By choosing different raw materials, all-inorganic high-entropy two-dimensional perovskite long afterglow materials are finally synthesized; experiments prove that it has a longer exciton lifetime and can achieve long afterglow luminescence;

[0047] (3) The present invention uses organic and inorganic double ligand bonding. The former modifies and passivates surface defects to reduce non-radiative recombination, and the latter promotes internal carrier transport;

[0048] (4) The advantage of non-equimolar solid solution compared to equimolar solid solution is that trace elements are incorporated to ensure the stability of the original structure and mix the properties brought by other elements; this not only reduces the proportion of rare earth elements in traditional long afterglow materials but also expands the luminescence range of perovskite to the near-infrared region;

[0049] (5) Hybrid valence multi-ion solid solution can not only modify the energy band structure, improve the optical properties and stability of the material, but also synthesize higher-dimensional perovskite materials (the all-inorganic high-entropy two-dimensional perovskite long afterglow material Z-Cs(A a B b C c D d E e )Cl6) of the present invention, which is beneficial to carrier migration; the experimental results verify that the introduction of hybrid valence ions is beneficial to improving the luminescence intensity of the sample. Brief Description of the Drawings

[0050] Figure 1 is the preparation flow chart of Example 1 of the present invention;

[0051] Figure 2 is the XRD pattern of the multifunctional semiconductor quantum dots obtained in Example 1, Example 5, and Example 6 of the present invention and Cs2NaBiCl6 prepared in Comparative Example 3;

[0052] Figure 3 is the high-resolution transmission pattern of Z-Cs(Mn 0.3 Ni 0.3 Na 0.1 Bi 0.1 Yb 0.2 )Cl6 prepared in Example 1 of the present invention;

[0053] Figure 4 is the PL pattern of the multifunctional semiconductor quantum dots prepared in Example 1, Example 5, and Example 6 of the present invention and Cs2NaBiCl6 prepared in Comparative Example 3;

[0054] Figure 5Figure a in shows the photocatalytic degradation spectrum of the multifunctional semiconductor quantum dots prepared in Example 1 of the present invention for RhB under visible light; Figure 5 Figure b in shows the electrochemical impedance spectra of the samples obtained in Example 1, Comparative Example 1, and Comparative Example 2 under different preparation routes;

[0055] Figure 6 Figure a in shows the PL spectra of the samples obtained in Example 1, Comparative Example 1, and Comparative Example 2 of the present invention under different preparation routes; Figure 6 Figure b in shows the air stability PL spectrum of the sample prepared in Comparative Example 4; Figure 6 Figure c in shows the air stability PL spectrum of the sample of Example 1 of the present invention. Detailed implementation manners

[0056] The present invention will be further described below with specific examples. The illustrative examples and descriptions of the present invention are used to explain the present invention, but do not limit the present invention.

[0057] There are no particular restrictions on the sources of all raw materials of the present invention, and they can be purchased on the market or prepared by conventional methods well-known to those skilled in the art.

[0058] There are no particular restrictions on the purity of all raw materials of the present invention. The present invention preferably uses the conventional purity used in the art.

[0059] For the devices used in the present invention, those without particular restrictions are all commonly used devices in the art.

[0060] Example 1:

[0061] As Figure 1 shown, a synthesis method of multifunctional semiconductor quantum dots includes the following steps:

[0062] S1. First, according to the capacity requirements of different ball milling jars (the capacity of the ball milling jar used in this example is 2.5 g), aiming to prepare 2 mmol of Cs(Mn 0.3 Ni 0.3 Na 0.1 Bi 0.1 Yb 0.2 )Cl6 two-dimensional perovskite nanocrystals, weigh a certain amount of CsCl, MnCl2, NiCl2, NaCl, BiCl3, and YbCl3;

[0063] S2. Put the above raw materials into a ball milling jar in sequence, add zirconia balls (the diameter of the zirconia balls is 12.7 mm and the total weight is 11.2 g), pad a rubber ring at the sealing part of the ball milling jar, cover the ball milling lid and seal it well; place the ball milling jar in a high-energy ball mill for the first ball milling. Through the combined action of mechanochemistry and the high-speed rotation and vibration of the ball mill, drive the grinding jar to do periodic motion. The ball milling time for the first ball milling is 5 min and the rotation speed is 1000 rpm; after the first ball milling is completed, transfer the ball milling jar to a glove box, open the ball milling jar, use a pipette to add 20 μL of oleylamine (OAm) and 20 μL of oleic acid (OA) into the ball milling jar, reseal the ball milling jar well, and use a high-energy ball mill for the second ball milling. The ball milling time for the second ball milling is 15 min and the rotation speed is 1000 rpm; after the ball milling is completed, take out the ball milling jar and transfer it to a fume hood, open the ball milling jar to obtain the ball-milled powder.

[0064] S3. Uniformly disperse the ball-milled powder in toluene, sonicate for 5 min, then transfer it to a beaker and add 0.3 mmol of ZnCl2 weighed, which is bonded to the surface of the nanocrystals as an inorganic ligand, and stir at room temperature for 10 min; after the stirring is completed, transfer the solid and liquid in the beaker to a centrifuge tube, centrifuge for 10 min (rotation speed 10000 rpm), discard the upper clear liquid, add a certain amount of toluene to the centrifuge tube again, sonicate and disperse (for 10 min) to disperse the precipitate, then centrifuge again, and repeat three times; then place the centrifuge tube in an oven, set the drying temperature at 70 °C and the drying time at 5 h; obtain the dried product.

[0065] S4. Place the dried product in a crusher, use the crusher to grind it into coarser powdery particles, then put the powder into a quartz mortar and further grind it more finely into powder for 30 min; obtain the finished product of the multifunctional semiconductor quantum dot Z-Cs(Mn 0.3 Ni 0.3 Na 0.1 Bi 0.1 Yb 0.2 )Cl6.

[0066] Analyze and characterize the obtained finished product of the multifunctional semiconductor quantum dot to determine its phase composition, luminescence and photocatalytic performance.

[0067] Example 2:

[0068] A method for synthesizing a multifunctional semiconductor quantum dot, comprising the following steps:

[0069] S1. First, according to the capacity requirements of different ball milling jars (the capacity of the ball milling jar used in this example is 2.5 g), to prepare 2 mmol of Cs(Mn 0.3 Ni 0.3 Ag 0.1In 0.1 Yb 0.2 aiming at Yb

[0070] S2, put the above raw materials into the ball milling jar in sequence, add zirconia balls (the diameter of the zirconia balls is 12.7 mm and the total weight is 11.2 g), pad a rubber ring at the sealing place of the ball milling jar, cover the ball milling cover and seal it well; place the ball milling jar in a high-energy ball mill for the first ball milling. Through the combined action of mechanochemistry and the high-speed rotation and vibration of the ball mill, drive the grinding jar to do periodic motion. The ball milling time for the first ball milling is 5 min and the rotation speed is 1000 rpm; after the first ball milling is completed, transfer the ball milling jar to the glove box, open the ball milling jar, use a pipette to add 20 μL of oleylamine (OAm) and 20 μL of oleic acid (OA) into the ball milling jar, reseal the ball milling jar well, and use a high-energy ball mill for the second ball milling. The ball milling time for the second ball milling is 15 min and the rotation speed is 1000 rpm; after the ball milling is completed, take out the ball milling jar and transfer it to the fume hood, open the ball milling jar to obtain the ball-milled powder;

[0071] S3, disperse the ball-milled powder evenly in toluene, ultrasonicate for 5 min, then transfer it to a beaker and add 0.3 mmol of ZnCl2 weighed, which is bonded to the surface of the nanocrystals as an inorganic ligand, and stir at room temperature for 10 min; after the stirring is completed, transfer the solid and liquid in the beaker to a centrifuge tube, centrifuge for 10 min (rotation speed 10000 rpm), discard the supernatant, add a certain amount of toluene to the centrifuge tube again, ultrasonically disperse (for 10 min) to disperse the precipitate, and then centrifuge again, repeat three times; then place the centrifuge tube in an oven, set the drying temperature at 70 °C and the drying time at 4 h; obtain the dried product;

[0072] S4, place the dried product in a crusher, use the crusher to grind it into coarser powdery particles, and then put the powder into a quartz mortar and grind it into powder more finely, grind for 30 min; obtain the finished product of multifunctional semiconductor quantum dots Z-Cs(Mn 0.3 Ni 0.3 Ag 0.1 In 0.1 Yb 0.2 )Cl6.

[0073] Example 3:

[0074] The difference between this example and Example 2 is that according to the chemical formula Cs(Mn 0.2 Ni 0.2 Ag 0.2 In 0.2 Yb 0.2) Using Cl6 to prepare two-dimensional perovskite nanocrystals, and the remaining steps are the same as those in Example 2. Finally, the finished product of multifunctional semiconductor quantum dots Z-Cs(Mn 0.2 Ni 0.2 Ag 0.2 In 0.2 Yb 0.2 )Cl6.

[0075] Example 4:

[0076] The difference between this example and Example 2 is that two-dimensional perovskite nanocrystals are prepared according to the chemical formula Cs(Mn 0.1 Ni 0.1 Ag 0.3 In 0.3 Yb 0.2 )Cl6, and the remaining steps are the same as those in Example 2. Finally, the finished product of multifunctional semiconductor quantum dots Z-Cs(Mn 0.1 Ni 0.1 Ag 0.3 In 0.3 Yb 0.2 )Cl6.

[0077] Example 5

[0078] The difference between this example and Example 1 is that two-dimensional perovskite nanocrystals are prepared according to the chemical formula Cs(Mn 0.1 Ni 0.1 Na 0.3 Bi 0.3 Yb 0.2 )Cl6, and the remaining steps are the same as those in Example 1. Finally, the finished product of multifunctional semiconductor quantum dots Z-Cs(Mn 0.1 Ni 0.1 Na 0.3 Bi 0.3 Yb 0.2 )Cl6.

[0079] Example 6

[0080] The difference between this example and Example 1 is that two-dimensional perovskite nanocrystals are prepared according to the chemical formula Cs(Mn 0.2 Ni 0.2 Na 0.2 Bi 0.2 Yb 0.2 )Cl6, and the remaining steps are the same as those in Example 1. Finally, the finished product of multifunctional semiconductor quantum dots Z-Cs(Mn 0.2 Ni 0.2 Na 0.2 Bi 0.2 Yb 0.2 )Cl6.

[0081] Comparative Example 1

[0082] S-p route:

[0083] S1. First, according to the capacity requirements of different ball milling jars (2.5 g), aiming to prepare 2 mmol of Cs(Mn 0.3 Ni 0.3 Na 0.1 Bi 0.1 Yb 0.2 )Cl6 two-dimensional perovskite nanocrystals, weigh a certain amount of CsCl, MnCl2, NiCl2, NaCl, BiCl3 and YbCl3;

[0084] S2. Put the above raw materials into the ball milling jar in sequence, and add zirconia balls (the diameter of the zirconia balls is 12.7 mm and the total weight is 11.2 g). Pad a rubber ring at the seal of the ball milling jar, cover the ball milling lid and seal it well; Place the ball milling jar in a high-energy ball mill for the first ball milling. Through the combined action of mechanochemistry and the high-speed rotation and vibration of the ball mill, drive the grinding jar to do periodic motion. The ball milling time for the first ball milling is 5 min and the rotation speed is 1000 rpm; After the first ball milling is completed, transfer the ball milling jar to the glove box, open the ball milling jar, use a pipette to add 20 μL of oleylamine (OAm) and 20 μL of oleic acid (OA) to the ball milling jar, then add 0.3 mmol of ZnCl2, reseal the ball milling jar well, and use a high-energy ball mill for the second ball milling. The ball milling time for the second ball milling is 15 min and the rotation speed is 1000 rpm; After the ball milling is completed, take out the ball milling jar and transfer it to the fume hood, open the ball milling jar to obtain the sample of this comparative example.

[0085] Comparative Example 2

[0086] L-p route:

[0087] S1. Aiming to prepare 2 mmol of Cs(Mn 0.3 Ni 0.3 Na 0.1 Bi 0.1 Yb 0.2 )Cl6 two-dimensional perovskite nanocrystals, weigh a certain amount of CsCl, MnCl2, NiCl2, NaCl, BiCl3 and YbCl3;

[0088] S2. Uniformly disperse the powder obtained in step S1 in toluene, and ultrasonicate for 5 min. Then transfer it to a beaker and add 0.3 mmol of ZnCl2, 20 μL of oleylamine (OAm), and 20 μL of oleic acid (OA) that have been weighed. Stir at room temperature for 10 min. After the stirring ends, transfer the solid-liquid mixture in the beaker to a centrifuge tube, centrifuge for 10 min (rotation speed: 10000 rpm), discard the supernatant. Add a certain amount of toluene to the centrifuge tube again, ultrasonically disperse (for 10 min) to disperse the precipitate, and then centrifuge again. Repeat this three times. Then place the centrifuge tube in an oven, set the drying temperature at 70 °C, and set the drying time to 5 h to obtain the dried product.

[0089] S3. Place the dried product in a crusher and use the crusher to grind it into coarser powdery particles. Then put the powder into a quartz mortar and further grind it more finely into powder for 30 min to obtain the sample of this comparative example.

[0090] Comparative Example 3

[0091] Preparation of Cs2NaBiCl6:

[0092] S1. First, according to the capacity requirements of different ball milling jars (2.5 g), aiming to prepare 2 mmol of Cs2NaBiCl6 two-dimensional perovskite nanocrystals, weigh a certain amount of CsCl, NaCl, and BiCl3.

[0093] S2. Put the above raw materials into the ball milling jar in sequence, and add zirconia balls (the diameter of the zirconia balls is 12.7 mm, and the total weight is 11.2 g). Pad a rubber ring at the sealing part of the ball milling jar, cover the ball milling lid and seal it well. Place the ball milling jar in a high-energy ball mill for the first ball milling. Through the combined action of mechanochemistry and the high-speed rotation and vibration of the ball mill, drive the grinding jar to perform periodic motion. The ball milling time for the first ball milling is 5 min, and the rotation speed is 1000 rpm. After the first ball milling ends, transfer the ball milling jar to a glove box, open the ball milling jar, use a pipette to add 20 μL of oleylamine (OAm) and 20 μL of oleic acid (OA) to the ball milling jar, reseal the ball milling jar well, and use a high-energy ball mill for the second ball milling. The ball milling time for the second ball milling is 15 min, and the rotation speed is 1000 rpm. After the ball milling ends, take out the ball milling jar and transfer it to a fume hood, open the ball milling jar to obtain the sample of this comparative example.

[0094] Comparative Example 4

[0095] S1. First, according to the capacity requirements of different ball milling jars (the capacity of the ball milling jar used in this example is 2.5 g), aiming to prepare 2 mmol of Cs(Mn 0.3 Ni 0.3 Na 0.1 Bi 0.1Yb 0.2 )Taking Cl6 two-dimensional perovskite nanocrystals as the target, a certain amount of CsCl, MnCl2, NiCl2, NaCl, BiCl3 and YbCl3 were weighed;

[0096] S2, the above raw materials were successively put into the ball milling tank for ball milling, and zirconia balls (the diameter of the zirconia balls was 12.7 mm and the total weight was 11.2 g) were added. A rubber ring was placed on the sealing part of the ball milling tank, and the ball milling cover was covered and sealed well; the ball milling tank was placed in a high-energy ball mill for the first ball milling. Through the combined action of mechanochemistry and the high-speed rotation and vibration of the ball mill, the grinding tank was driven to perform periodic motion. The ball milling time for the first ball milling was 5 min and the rotation speed was 1000 rpm; after the first ball milling was completed, the ball milling tank was transferred to the glove box, the ball milling tank was opened, 20 μL of oleylamine (OAm) and 20 μL of oleic acid (OA) were added to the ball milling tank using a pipette, the ball milling tank was resealed well, and the high-energy ball mill was used for the second ball milling. The ball milling time for the second ball milling was 15 min and the rotation speed was 1000 rpm; after the ball milling was completed, the ball milling tank was taken out and transferred to the fume hood, the ball milling tank was opened, and the sample of this comparative example was obtained.

[0097] As Figure 2 shown, the XRD patterns of the multifunctional semiconductor quantum dots obtained in Example 1, Example 5, and Example 6 of the present invention and Cs2NaBiCl6 prepared in Comparative Example 3 are shown; in the figure, "3∶3∶1∶1∶2" corresponds to the multifunctional semiconductor quantum dots prepared in Example 1; in the figure, "1∶1∶3∶3∶2" corresponds to the multifunctional semiconductor quantum dots prepared in Example 5; in the figure, "2∶2∶2∶2∶2" corresponds to the multifunctional semiconductor quantum dots prepared in Example 6.

[0098] It can be Figure 2 learned that a tiny ratio hardly causes a change in the structure and will cause partial lattice distortion. When a∶b∶c∶d∶e = 3∶3∶1∶1∶2, compared with the equal solid solution ratio, the diffraction peaks are sharper and smoother, which indicates that the crystallinity of the phase is better and the structure is more complete.

[0099] As Figure 3 shown, the high-resolution transmission pattern of Z-Cs(Mn 0.3 Ni 0.3 Na 0.1 Bi 0.1 Yb 0.2 )Cl6 prepared in Example 1 of the present invention is shown.

[0100] Figure 3Fully illustrate the successful preparation of quantum dots. It can be seen from the figure that the average size of the particle diameter is about 10 - 20 nm, and the successful introduction of multiple small - radius ions is also successfully verified by the shortening of the lattice spacing. This is consistent with the results of the above - mentioned XRD( Figure 2 ).

[0101] As Figure 4 shown, the PL spectra of the multifunctional semiconductor quantum dots prepared in Example 1, Example 5, and Example 6 of the present invention and Cs2NaBiCl6 prepared in Comparative Example 3 are shown.

[0102] From Figure 4 , it can be understood that when a∶b∶c∶d∶e = 3∶3∶1∶1∶2, the luminescence efficiency is higher compared to the equal - amount solid - solution ratio. This is because the introduction of Mn and Ni will become activators. The Bi 3+ ions in the host lattice of the main lattice Cs2NaBiCl6 absorb near - ultraviolet light and transfer the energy to the Mn 4 T1→ 6 A1 transition to the Mn 2+ activator. Therefore, the higher the introduction amount, the higher the PL.

[0103] As Figure 5 shown, Figure a is the photocatalytic degradation spectrum of the multifunctional semiconductor quantum dots prepared in Example 1 of the present invention for RhB (rhodamine B) under visible light; Figure b is the electrochemical impedance spectrum of the samples obtained by Example 1, Comparative Example 1, and Comparative Example 2 under different preparation paths.

[0104] From Figure 5 Figure a, it can be understood that under the dual action of organic ligands and inorganic ligands, the Z - Cs(Mn 0.3 Ni 0.3 Na 0.1 Bi 0.1 Yb 0.2 )Cl6 prepared in Example 1 has certain catalytic performance.

[0105] The process of photocatalytic degradation of RhB under visible light is as follows: 40 mg of the sample (Z - Cs(Mn 0.3 Ni 0.3 Na 0.1 Bi 0.1 Yb 0.2 )Cl6) prepared in Example 1 is added to a 10 mg / L RhB solution. First, dark adsorption is carried out for 30 min under dark conditions, and then a 300 W xenon lamp (with a 420 nm filter to simulate visible light) is turned on. 3 mL of the sample is taken every 10 min for absorbance testing. The attenuation of the absorbance represents the decrease in concentration, which also indicates the photocatalytic effect.

[0106] Figure 5 In Figure b, the S-p route curve corresponds to the sample prepared in Comparative Example 1; the L-p route curve corresponds to the sample prepared in Comparative Example 2; the S / L-p route curve corresponds to the sample prepared in Example 1.

[0107] From Figure 5 Figure b, it can be understood the influence on carrier transport under different preparation routes. It can be seen that the impedance loop of the multifunctional semiconductor quantum dots synthesized by the solid-liquid phase (inorganic-organic ligand combination) preparation route adopted in Example 1 is the smallest, indicating that the current transmission efficiency is the highest. Compared with the other two synthesis routes, it is more conducive to carrier transport, which demonstrates the advantages of the preparation method of the present invention.

[0108] For the S-p route of Comparative Example 1, the method of adding organic and inorganic ligands by ball milling is adopted, and this method will cause the problem of uneven bonding of inorganic ligands. The L-p route of Comparative Example 2 is synthesized in a liquid at room temperature, and the samples prepared by this method have poor stability. In Example 1, due to the synthesis by high-energy ball milling first to obtain a higher energy input, the structure will be more stable. Using the S / L-p route can better bond the inorganic ligands evenly on the powder, so higher carrier transport efficiency can be achieved. The structural incompleteness of the samples in Comparative Example 2 will directly affect the performance.

[0109] As Figure 6 described, Figure 6 Figure a in Figure 5 is the PL spectrum of the samples obtained in Example 1, Comparative Example 1, and Comparative Example 2 of the present invention under different preparation routes; Figure 6 Figure b in

[0110] From Figure 6 Figure a, it can be understood that Example 1 of the present invention adopting the S / L-p route (solid-liquid phase synthesis route) can achieve higher PL intensity, which benefits from a more stable crystal structure and the uniform wrapping of organic ligands. The passivation of surface defects can achieve higher radiative recombination.

[0111] Figure 6 Figures b and c indicate that the multi-ligand combination of organic and inorganic ligands in Example 1 can achieve higher stability compared with the traditional organic ligands in Comparative Example 4, and can still maintain a relatively high PL intensity after 14 hours.

[0112] The technical solution of the present invention is not limited to the limitations of the above specific embodiments. Any technical deformation made according to the technical solution of the present invention falls within the protection scope of the present invention.

Claims

1. A synthesis method of a multifunctional semiconductor quantum dot, characterized in that, It includes the following steps: S1, according to the ratio of the chemical formula Cs(A a B b C c D d E e )Cl6, weigh the chlorides of Cs, A, B, C, D, and E as raw materials; In the chemical formula Cs(A a B b C c D d E e )Cl6, A is one of Mn 2+ , Zn 2+ , Sn 2+ ; B is Ni 2+ or Cu 2+ , C is Ag + or Na + ; D is one of Bi 3+ , In 3+ , Fe 3+ ; E is Yb 3+ ; a + b + c + d + e = 1; S2, conduct the first ball milling on the above raw materials. After the first ball milling is completed, add oleylamine and oleic acid and then conduct the second ball milling; after the second ball milling is completed, obtain the ball-milled powder. S3, disperse the ball-milled powder in toluene, add an inorganic ligand and stir to obtain a solid-liquid mixture; conduct solid-liquid separation on the solid-liquid mixture, and dry the separated solid material to obtain the dried product. S4. The dried product is crushed and ground to obtain the finished product of the multifunctional semiconductor quantum dots, denoted as Z-Cs(A a B b C c D d E e )Cl6.

2. The synthesis method of a multifunctional semiconductor quantum dot according to claim 1, wherein: In the chemical formula Cs(A a B b C c D d E e )Cl6, A is Mn 2+ ; D is Bi 3+ or In 3+ .

3. The synthesis method of a multifunctional semiconductor quantum dot according to claim 1, characterized in that: In the chemical formula Cs(A a B b C c D d E e )Cl6, a∶b∶c∶d∶e = 3∶3∶1∶1∶2.

4. The synthesis method of a multifunctional semiconductor quantum dot according to claim 1, wherein: In the step S2, the ball-to-material ratio of the first ball milling is (5-8):1, the time of the first ball milling is 5-10 min, and the rotation speed is 875-1125 rpm; the time of the second ball milling is 15-25 min, and the rotation speed is 875-1125 rpm.

5. A method for synthesizing a multifunctional semiconductor quantum dot according to claim 1, characterized in that: In the step S2, the molar volume ratio of Cs(A a B b C c D d E e )Cl6 to oleylamine is 2:(20 - 40), and the comparison unit is mmol:μL; Cs(A a B b C c D d E e )Cl6 to oleic acid is 2:(20 - 40), and the comparison unit is mmol:μL.

6. A method for synthesizing a multifunctional semiconductor quantum dot according to claim 1, characterized in that: In step S3, the inorganic ligand is ZnCl2, and the molar ratio of Cs(A a B b C c D d E e )Cl6 to the inorganic ligand is 1:(0.1 - 0.2).

7. A method for synthesizing a multifunctional semiconductor quantum dot according to claim 1, characterized in that: In the step S3, the process of solid-liquid separation of the solid-liquid mixture is as follows: centrifuge the solid-liquid mixture in a centrifuge tube and discard the upper clear liquid, then add toluene to the centrifuge tube, ultrasonically disperse to disperse the precipitate, and then centrifuge again, repeating several times.

8. A method for synthesizing a multifunctional semiconductor quantum dot according to claim 1, characterized in that: In the step S3, the drying temperature is 60-80 °C, and the drying time is 4-6 h.

9. A multifunctional semiconductor quantum dot synthesized by the synthesis method of a multifunctional semiconductor quantum dot according to any one of claims 1-8.

10. The application of the multifunctional semiconductor quantum dot according to claim 9 in multicolor fluorescence emission, detection, and outdoor lighting dust removal.

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