ZAIS-ZIF-8 core-shell structure light-emitting and photocatalytic material with ZAIS quantum dots wrapped by ZIF-8 in-situ growth, preparation of ZAIS-ZIF-8 core-shell structure light-emitting and photocatalytic material, light-emitting device and photocatalytic application of ZAIS-ZIF-8 core-shell structure light-emitting and photocatalytic material

Abstract

The invention discloses a preparation method and application of a solid light-emitting material and a photocatalyst with a core-shell structure (AIS ZIF-8 and ZAIS ZIF-8) of indium silver sulfide (AIS) and indium silver zinc sulfide (ZAIS) quantum dots and ZIF-8. The preparation method comprises the following steps: 1) preparing surface-modified AIS or ZAIS quantum dots and a 2-methylimidazole (2-mim) methanol precursor solution dispersed by the AIS or ZAIS quantum dots; and 2) injecting a Zn < 2 + > methanol solution and stirring to realize in-situ coating and growth of ZAIS by ZIF-8, thereby preparing the ZAIS-ZIF-8 core-shell structure. The ZAIS (at) ZIF-8 core-shell structure has obviously enhanced solid fluorescence light-emitting quantum efficiency and photocatalytic performance. According to the preparation method, a target product is prepared through inverse thermal injection and in-situ growth with a relatively simple process and relatively low cost, and the obtained ZAIS-coated ZIF-8 luminescent material and photocatalyst are of a dispersed ZAIS quantum dot structure wrapped by ZIF-8, have excellent photocatalytic activity and luminous efficiency and can be produced on a large scale. The ZAIS ZIF-8 catalyst disclosed by the invention can be widely applied to photocatalytic degradation of tetracycline, Cr (VI) and organic dyes, and is more excellent in performance in an actual wastewater system.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite nanomaterials, and relates to a ZAIS@ZIF-8 core-shell structure in which ZIF-8 crystals wrap and separate ZAIS quantum dots and its preparation. Its specific applications are in the fields of light-emitting LEDs, photocatalytic degradation of Cr(VI), and antibiotic wastewater treatment. Background Art

[0002] AgInS alloyed with ZnS 2 That is, zinc indium silver sulfide (ZAIS) quantum dots have broad application prospects in the fields of biological labeling, light-emitting devices, photocatalysis, etc. due to their band gaps and luminescence properties that can be synergistically adjusted by size and chemical composition, and the absence of highly toxic cadmium or lead elements.

[0003] As a catalyst in solution or a luminescent material in the solid state, aggregation is the main factor reducing its photocatalytic activity and luminescence quantum efficiency. Preventing aggregation in the liquid-phase catalytic environment or self-absorption of the quantum dot solid is the key to improving its photocatalytic efficiency or luminescence efficiency. Peng et al. synthesized ZAIS quantum dots using long alkyl-chain organic encapsulants such as dodecyl mercaptan. However, on the one hand, the obtained ZAIS quantum dots are not water-soluble, and on the other hand, these insulating alkyl chains hinder electron or hole transfer between the quantum dots and the aqueous solution or between the quantum dots and the dissolved gas, resulting in complex ligand exchange post-treatment and low photocatalytic activity. In addition, the aqueous solution stability and photo-stability of water-soluble AIS and ZAIS quantum dots are both low, and aggregation and photo-corrosion lead to a significant reduction in both photocatalytic activity and cycle stability. At the same time, due to the proximity of quantum dots to each other, obvious self-absorption occurs in the ZAIS quantum dot solid, resulting in limited luminescence efficiency of the quantum dot solid, or quantum dot films or patches composed of the quantum dot solid and PMMA, etc. By encapsulation with silicates, silicone ethers, or other polymers such as polyvinylpyrrolidone, etc., ZAIS with high luminescence performance can be obtained. However, due to the oil-soluble characteristics of these encapsulations, it is restricted to obtain a homogeneous film-forming precursor solution with water-soluble AIS or ZAIS quantum dots and prepare a high-efficiency solid luminescent film. Obtaining high-luminescence-efficiency or high-catalytic-activity AIS or ZAIS-based solid luminescent materials and heterogeneous photocatalytic materials with porous structure-restricted AIS or ZAIS quantum dots dispersed therein is still a challenge. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for directly synthesizing ZAIS@ZIF-8 by internally separating and encapsulating ZAIS quantum dots in ZIF-8 crystals. The ZAIS@ZIF-8 core-shell structure prepared by this method has significantly enhanced solid fluorescence quantum efficiency and photocatalytic activity.

[0005] In addition, the present invention also provides the application of the quantum dots obtained by the above aqueous-phase synthesis in the fields of light-emitting devices and photocatalysis, etc.

[0006] The present invention is specifically realized through the following technical solutions:

[0007] A preparation method of a ZAIS@ZIF-8 core-shell structure luminescent and photocatalytic material, comprising the following steps:

[0008] 1) Prepare water-soluble ZAIS quantum dots by aqueous-phase synthesis

[0009] First, dissolve a certain amount of salts of Ag + , In 3+ in a certain volume of deionized water, add one or several thiol ligands such as mercaptoacetic acid, mercaptoethylamine, glutathione, and amino ligands such as ethylenediamine, and adjust the pH value to 4-11 with an aqueous NaOH solution; secondly, under stirring conditions, reverse-inject an aqueous solution of Na 2 S etc. with a temperature of 40-100 °C into the above metal ion solution, continuously heat for a certain time to obtain an AgInS 2- quantum dot solution; finally, prepare an aqueous solution of Zn 2 with a certain concentration, add a certain amount of thiol ligands such as mercaptoacetic acid and mercaptopropionic acid thereto, and adjust the pH value to 4-11 with NaOH, and then add the thiol-coordinated Zn solution to the AgInS 2+ quantum dot solution. After continuously heating and keeping warm for a certain time, naturally cool to room temperature to obtain a ZAIS quantum dot solution. 2 quantum dot solution. After continuously heating and keeping warm for a certain time, naturally cool to room temperature to obtain a ZAIS quantum dot solution.

[0010] 1) Prepare a methanol precursor solution of a 2-mim precursor and an amino encapsulant such as triethylamine or CTAB in which ZAIS quantum dots are dispersed. The methanol precursor solution of Zn 2+

[0011] Dissolve a certain mass of 2-methylimidazole (2-mim) in methanol (MeOH) to form a clear solution; take a certain amount of ZAIS quantum dot solution, precipitate with an equal volume of ethanol, and centrifuge to obtain a ZAIS quantum dot solid. Disperse the quantum dot solid in the 2-mim methanol solution under ultrasonic conditions; measure a certain mass of zinc salts such as zinc nitrate or zinc acetate (Zn 2+ ), dissolve in a certain volume of methanol to obtain a Zn 2+ precursor solution

[0012] 2) Prepare a ZAIS@ZIF-8 core-shell structure catalyst

[0013] Under continuous stirring, Zn 2+The 2-mim solution was poured into the 2-mim methanol solution in which ZAIS was dispersed, stirred for 1-48 h, allowed to stand at room temperature for 1-48 h, and then centrifuged to collect the yellow solid, which was dispersed with deionized water, and then precipitated with an equal volume of methanol and centrifuged. The operation was repeated three times to remove the unreacted ions and ligands. The collected sample was dried under vacuum at 40 °C to obtain ZAIS@ZIF-8.

[0014] The silver salt described above is selected from Ag(OAc) or AgNO 3 One of them, and the indium salt described above is selected from In(OAc) 3 , InCl 3 , InBr 3 , InI 3 , In(NO 3 ) 3 Or In 2 (SO 4 ) 2 One of them, and the zinc salt is Zn(OAc) 2 , ZnCl 2 , ZnBr 2 , ZnI 2 , Zn(NO 3 ) 2 Or ZnSO 4 .

[0015] The molar ratio of the small molecule mercapto encapsulant to silver and indium is 1:1 to 1:40, and the molar ratio of silver to zinc salt is 1:10 - 10:1. The small molecule mercapto encapsulant is selected from one of mercaptoacetic acid, mercaptopropionic acid, mercaptoethylamine or cysteine.

[0016] The sulfur precursor described above is selected from one of sodium sulfide, potassium sulfide, ammonium sulfide or thiourea, and the S 2- Concentration is 1-50 mmol / L.

[0017] The molar ratio of the small molecule mercapto encapsulant to silver and indium is 1:1 to 1:40, and the molar ratio of silver to zinc salt is 1:10 - 10:1. The small molecule mercapto encapsulant is selected from one of mercaptoacetic acid, mercaptopropionic acid, mercaptoethylamine or cysteine.

[0018] The molar ratio of the zinc salt to 2-mim is 1:1 to 1:20.

[0019] The molar ratio of the 2-mim methanol solution of the ZAIS@ZIF-8 core-shell structure to the methanol solution of the zinc salt is 0.1:1 to 10:1.

[0020] The preparation method of the ZAIS@ZIF-8 described above is characterized in that the 2-mim solution of the ZAIS and Zn 2+The reaction temperature of the methanol solution is 20 - 70 °C, the stirring time is 1 - 24 h, and it is left standing at room temperature for 24 h.

[0021] The addition amount of the photocatalytic experimental ZAIS@ZIF-8 photocatalytic material is 10 mg of ZAIS@ZIF-8 photocatalytic material added to every 50 mL of potassium dichromate solution, where the concentration of the potassium dichromate solution is 28 mg / L. The ultrasonic time is 1 - 5 minutes, the light source is a 300 W xenon lamp with a visible light filter (wavelength greater than 420 nm), and the light irradiation treatment time is 10 - 120 minutes.

[0022] 3) Preparation of AIS@ZIF-8, ZAIS@ZIF-8 white light thin film

[0023] Take a certain mass of ZAIS@ZIF-8 and disperse it in DMF to obtain a DFM dispersion with a ZAIS@ZIF-8 concentration of 0.01 - 0.2 g / ml. Coat this dispersion on the surface of a flexible polymer film such as quartz glass or polyethylene film, place it in a vacuum drying oven, and vacuum it at 20 - 100 °C for 24 hours to prepare the AIS@ZIF-8, ZAIS@ZIF-8 thin film. Cut it to an appropriate size and paste it on the surface of a 395 or 455 nm LED to obtain red, green, and direct white light LEDs.

[0024] The beneficial effects of the present invention are as follows:

[0025] 1) The present invention uses the in-situ growth of ZIF-8 crystal method to wrap and separate ZAIS quantum dots, and prepares a large number of ZAIS@ZIF-8 core-shell structures through a simple room-temperature green synthesis process. By regulating the proportion of ZAIS, the self-excitation of internal quantum dots is regulated to control the luminescence wavelength and the separation and recombination efficiency of electron-hole pairs of the material, realizing the direct white light emission of the material;

[0026] 2) By controlling the ratio of the ZAIS encapsulant to the ZIF-8 precursor during the reaction process, the ratio of the composite ZIF-8 and ZAIS quantum dots can be controlled. The preparation method has strong controllability, easy control of process parameters, is safe, green, pollution-free, and has a high yield;

[0027] 3) The obtained ZAIS@ZIF-8 composite luminescent and photocatalytic material of the present invention has significantly improved photocatalytic performance for the reduction of uranyl and the degradation of pollutants such as tetracycline and improved luminescence efficiency compared with single materials, and can be used for photocatalytic wastewater treatment and white light emitting devices. Description of the Drawings Figure 1 a is the ultraviolet-visible absorption diagram of the products prepared in Example 1 and Comparative Example 1 of the present invention. The abscissa in the figure is the wavelength, and the ordinate is the relative intensity;

[0029] Figure 1b is the ultraviolet-visible absorption graph of the products prepared in Example 2 and Comparative Example 2 of the present invention;

[0030] Figure 2 are the transmission electron microscope and high-resolution transmission electron microscope pictures of Example 1 of the present invention and the emission spectrum graphs of the compositions of the products prepared in Example 1, Example 2, Comparative Example 1, and Comparative Example 2;

[0031] Figure 3 are the emission spectrum graphs of the compositions of the products prepared in Example 1, Example 2, Comparative Example 1, and Comparative Example 2 of the present invention;

[0032] Figure 4 are the emission spectrum graphs of Example 3, Example 4, and Comparative Example 3;

[0033] Figure 5 are the X-ray diffraction graphs of the products prepared in Example 1, Comparative Example 1, and Comparative Example 4, where the abscissa 2θ is twice the scanning angle and the ordinate is the diffraction intensity;

[0034] Figure 6 are the X-ray diffraction graphs of the products prepared in Comparative Example 1 and Comparative Example 3, where the abscissa 2θ is twice the scanning angle and the ordinate is the diffraction intensity;

[0035] Figure 7 a is the scanning electron microscope picture of Example 1, Figure 7 b and 7c are the transmission electron microscope and high-resolution transmission electron microscope pictures of Example 1, and 7d is the high-resolution electron microscope picture of Comparative Example 1, Figure 7 e is the high-resolution electron microscope picture of Comparative Example 3, Figure 7 f is the SEM picture of Comparative Example 4; Figure 8 is the comparative graph of the photocatalytic reduction U(VI) effect pictures of the products prepared in Example 1, Example 2, Comparative Example 1, Comparative Example 2, and Comparative Example 3. Detailed implementation manners

[0036] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0037] The present invention provides AIS@ZIF-8 and ZAIS@ZIF-8 core-shell structure luminescent materials and photocatalysts, and this method has simple process, low cost and excellent performance.

[0038] The preparation methods of the above-mentioned AIS@ZIF-8 and ZAIS@ZIF-8 photocatalytic materials are as follows:

[0039] 1) Prepare AIS and ZAIS quantum dot solids

[0040] Dissolve a certain amount of silver salt precursors such as silver nitrate or silver acetate in a certain volume of deionized water to form an Ag + solution; dissolve a certain amount of indium salts such as indium nitrate or indium acetate in a certain volume of deionized water to form an In 3+ solution; under stirring conditions, add a certain amount of molecules coexisting with amino and mercapto groups such as glutathione or cysteine to the above-mentioned Ag + and In 3+ solutions as ionic ligands and surface coating agents to form Ag-ligand and In-ligand solutions; add a certain amount of 1 mol / L NaOH or KOH solution to the Ag-ligand and In-ligand solutions respectively until a white precipitate is first formed and then the precipitate just dissolves again. Mix the transparent Ag-ligand and In-ligand solutions according to the molar ratio of Ag to In of 1:40 - 1:1, shake well and seal them in a glass reaction flask. Subsequently, dissolve a certain amount of sulfur source precursors such as sodium sulfide, thiourea or thioacetamide in deionized water, heat the sulfur source solution to 90°C - 100°C, and quickly inject it into the above-mentioned Ag-ligand and In-ligand mixed solution under heating and stirring conditions. After heating and stabilizing for a certain time, transfer it to a polytetrafluoroethylene hydrothermal kettle and seal it, heat it in a muffle furnace at 120 - 180°C for 0.5 - 30 hours, and naturally cool it to room temperature to obtain an AIS quantum dot solution. Add a certain volume of the AIS quantum dot solution to a certain volume of alcohols such as ethanol, methanol or isopropanol, naturally sediment and then centrifuge to obtain AIS quantum dot solids. Prepare an aqueous solution of Zn2+ with a certain concentration, add a certain amount of mercapto ligands such as mercaptoacetic acid and mercaptopropionic acid to it, and adjust the pH value to 4 - 11 with NaOH. Then inject the mercapto-coordinated Zn solution into the above-mentioned AIS quantum dot solution under the conditions of heating and stirring at 80 - 100°C, and keep it warm for 0.5 - 20 h to obtain a ZAIS quantum dot solution. Add a certain volume of the ZAIS quantum dot solution to a certain volume of alcohols such as ethanol, methanol or isopropanol, naturally sediment and then centrifuge to obtain ZAIS quantum dot solids.

[0041] 2) Prepare Zn 2+ and 2-mim methanol precursor solutions

[0042] Dissolve zinc salt and 2-methylimidazole (2-mim) in methanol (MeOH) respectively to form clear solutions. Add a certain amount of surfactants such as triethylamine, ethylenediamine, DTAB, CTAB, etc. to the methanol solution of dimethylimidazole to obtain a methanol solution of 2-mim and surfactants.

[0043] 3) Preparation of AIS@ZIF-8 and ZAIS@ZIF-8 materials

[0044] Disperse a certain amount of AIS or ZAIS solid in a methanol solution containing 2-mim and triethylamine by ultrasonic dispersion method. Then, under continuous stirring, pour this solution into the Zn 2+ methanol solution, heat and stir at 20 - 70 °C for 1 - 48 h, let it stand at room temperature for natural sedimentation, then centrifuge to collect the yellow solid, redisperse it with methanol to remove unreacted ions and ligands. After repeating the above dispersion - centrifugation procedure 3 times, the collected sample is dried under vacuum at 40 °C to obtain AIS@ZIF-8 or ZAIS@ZIF-8.

[0045] Furthermore, the above synthesis of AIS and ZAIS, AIS@ZIF-8 and ZAIS@ZIF-8 is carried out in a sealed sample bottle.

[0046] Furthermore, the temperature for synthesizing ZAIS from AIS is 80 - 100 °C, and the synthesis temperature of AIS@ZIF-8 and ZAIS@ZIF-8 is 20 - 70 °C. The stirring time of the 2-mim solution and the Zn dispersion containing ZAIS is 1 - 24 h, and it stands at room temperature for 24 h. 2+ Furthermore, the silver salt is selected from one of Ag(OAc) or AgNO3, the indium salt is selected from one of In(OAc)3, InCl3, InBr3, InI3, In(NO3)3 or In2(SO4)2, and the zinc salt is Zn(OAc)2, ZnCl2, ZnBr2, ZnI2, Zn(NO3)2 or ZnSO4.

[0047] Furthermore, the molar ratio of the small molecule mercapto encapsulant to silver and indium is 1:1 - 1:40, the molar ratio of silver to zinc salt is 1:10 - 10:1, and the small molecule mercapto encapsulant is selected from one of mercaptoacetic acid, mercaptopropionic acid, mercaptoethylamine or cysteine.

[0048] Furthermore, the sulfur precursor is selected from one of sodium sulfide, potassium sulfide, ammonium sulfide or thiourea, and the S

[0049] concentration is 1 - 50 mmol / L. 2- Furthermore, the molar ratio of the small molecule mercapto encapsulant for obtaining ZAIS from AIS to silver and indium is 1:1 - 1:40, the molar ratio of silver to zinc salt is 1:10 - 10:1, and the small molecule mercapto encapsulant is selected from one or several of mercaptoacetic acid, mercaptopropionic acid, mercaptoethylamine or cysteine.

[0050] Furthermore, the molar ratio of the small molecule mercapto encapsulant for obtaining ZAIS from AIS to silver and indium is 1:1 - 1:40, the molar ratio of silver to zinc salt is 1:10 - 10:1, and the small molecule mercapto encapsulant is selected from one or several of mercaptoacetic acid, mercaptopropionic acid, mercaptoethylamine or cysteine.

[0051] Further, the molar ratio of the AIS@ZIF-8 or ZAIS@ZIF-8 core-shell structured AIS or ZAIS quantum dots to 2-mim is 1:10 - 1:100, and the molar ratio of the zinc salt to 2-mim is 1:1 - 1:20. The zinc salt is selected from ZnI 2 , ZnCl 2 , ZnBr 2 , ZnAc 2 , Zn(SO 4 ) 2 or Zn(NO 3 ) 2 and is one of them.

[0052] Further, the amino surface coating agent of the AIS@ZIF-8 or ZAIS@ZIF-8 core-shell structure is triethylamine, CTAB, cetyltrimethylammonium bromide, and the molar ratio of the amino coating agent to 2-mim is 1:1000 - 1:10.

[0053] Example 1

[0054] The preparation method of the red-emitting AIS@ZIF-8 (Ag:In = 1:5) photocatalytic material is as follows:

[0055] 1) Preparation of water-soluble ZAIS quantum dots by aqueous-phase synthesis

[0056] First, dissolve a certain amount of 0.0234 g of Ag(Ac) and 0.1168 g of In(Ac) 3 salts in a certain volume of deionized water, add 0.56 g of glutathione aqueous solution, and adjust the pH value to 4 - 11 with NaOH aqueous solution; secondly, inject the aqueous solution of sulfur source such as 100 ml of 20 mM 90 °C Na 2 S, thioacetamide or thiourea into the above metal ion solution under stirring conditions, and heat for 30 min to obtain the AgInS 2 quantum dot solution.

[0057] 4) Prepare a 2-mim methanol precursor solution in which AIS quantum dots are dispersed and a Zn 2+ methanol precursor solution

[0058] Dissolve 131.2 mg of 2-methylimidazole (2-mim) in 5 ml of methanol (MeOH) to form a clear solution, and add 10 mg of CTAB; take 10 ml of ZAIS quantum dot solution, precipitate with an equal volume of ethanol, and centrifuge to obtain the ZAIS quantum dot solid. Disperse the quantum dot solid in the 2-mim methanol solution under ultrasonic conditions; measure 58.4 mg of zinc salt such as zinc acetate dihydrate, dissolve it in 5 ml of methanol to obtain the Zn 2+ precursor solution

[0059] 5) Preparation of AIS@ZIF-8 core-shell structure catalyst

[0060] Under continuous stirring, Zn 2+ The 2-mim solution was poured into the 2-mim methanol solution in which AIS was dispersed, and stirred for 24 h. After standing at room temperature for 24 h, the yellow solid was collected by centrifugation, dispersed with deionized water, and then precipitated with an equal volume of methanol and centrifuged. The operation was repeated three times to remove unreacted ions and ligands. The collected sample was dried under vacuum at 40 °C to obtain ZAIS@ZIF-8.

[0061] Example 2

[0062] The preparation method of the orange-emitting AIS@ZIF-8 (Ag:In = 1:10) photocatalytic material is as follows:

[0063] 1) Preparation of water-soluble ZAIS quantum dots by aqueous-phase synthesis

[0064] First, a certain amount of 0.0117 g of Ag(Ac) and 0.1168 g of In(Ac) 3 salts were dissolved in a certain volume of deionized water, 0.56 g of glutathione aqueous solution was added, and the pH value was adjusted to 4 - 11 with NaOH aqueous solution; secondly, under stirring conditions, a sulfur source aqueous solution such as 100 ml of 20 mM 90 °C Na 2 S, thioacetamide or thiourea was inversely injected into the above metal ion solution, and heated for 30 min to obtain an AgInS 2 quantum dot solution.

[0065] 6) Preparation of a 2-mim methanol precursor solution in which AIS quantum dots are dispersed and a Zn 2+ methanol precursor solution

[0066] 131.2 mg of 2-methylimidazole (2-mim) was dissolved in 5 ml of methanol (MeOH) to form a clear solution, and 10 mg of CTAB was added; 10 ml of AIS quantum dot solution was taken, precipitated with an equal volume of ethanol, and centrifuged to obtain AIS quantum dot solid. The quantum dot solid was dispersed in a 2-mim methanol solution under ultrasonic conditions; 58.4 mg of zinc salts such as zinc acetate dihydrate was weighed and dissolved in 5 ml of methanol to obtain a Zn 2+ precursor solution

[0067] 7) Preparation of AIS@ZIF-8 core-shell structure catalyst

[0068] Under continuous stirring, Zn 2+The 2-mim solution was poured into the 2-mim methanol solution in which AIS was dispersed, and stirred for 24 h. After standing at room temperature for 24 h, the yellow solid was collected by centrifugation, dispersed with deionized water, and then precipitated with an equal volume of methanol and centrifuged. The operation was repeated three times to remove the unreacted ions and ligands. The collected sample was dried under vacuum at 40 °C to obtain orange fluorescent AIS@ZIF-8.

[0069] Example 3

[0070] The preparation method of the yellow-light-emitting ZAIS@ZIF-8 (Ag:In = 1:10) photocatalytic material is as follows:

[0071] 1) Preparation of water-soluble ZAIS quantum dots by aqueous-phase synthesis

[0072] First, a certain amount of 0.0234 g of Ag(Ac) and 0.1168 g of In(Ac) 3 salts were dissolved in a certain volume of deionized water, 0.56 g of glutathione aqueous solution was added, and the pH value was adjusted to 4 - 11 with NaOH aqueous solution; secondly, under stirring conditions, an aqueous solution of a sulfur source such as 100 ml of 20 mM Na 2 S, thioacetamide or thiourea at 90 °C was reversely injected into the above metal ion solution, and heated for 30 min to obtain an AgInS 2 quantum dot solution; finally, 0.176 g of Zn(Ac) 2 .2H 2 O and 0.146 g of mercaptoacetic acid were dissolved in 2 ml of water, and the pH value was adjusted to 8 with NaOH, and then the Zn solution coordinated with thiol was added to 30 ml of the above AgInS 2 quantum dot solution. After continuous heating at 90 °C for 30 minutes, it was naturally cooled to room temperature to obtain a ZAIS quantum dot solution.

[0073] 8) Preparation of a 2-mim methanol precursor solution in which ZAIS quantum dots are dispersed and a Zn 2+ methanol precursor solution

[0074] 131.2 mg of 2-methylimidazole (2-mim) was dissolved in 5 ml of methanol (MeOH) to form a clear solution, and 10 mg of CTAB was added; 10 ml of ZAIS quantum dot solution was taken, precipitated with an equal volume of ethanol, and centrifuged to obtain a ZAIS quantum dot solid. The quantum dot solid was dispersed in a 2-mim methanol solution under ultrasonic conditions; 58.4 mg of zinc salts such as zinc acetate dihydrate was weighed and dissolved in 5 ml of methanol to obtain a Zn 2+ precursor solution

[0075] 9) Preparation of ZAIS@ZIF-8 core-shell structure catalyst

[0076] Under continuous stirring, Zn2+ The 2 - mim solution was poured into the 2 - mim methanol solution in which ZAIS was dispersed, and stirred for 24 h. After standing at room temperature for 24 h, the yellow solid was collected by centrifugation, dispersed with deionized water, and then precipitated with an equal volume of methanol and centrifuged. The operation was repeated three times to remove unreacted ions and ligands. The collected sample was dried under vacuum at 40 °C to obtain yellow - light ZAIS@ZIF - 8.

[0077] Example 4

[0078] The preparation method of the green - emitting ZAIS@ZIF - 8 (Ag:In = 1:10) photocatalytic material is as follows:

[0079] 1) Preparation of water - soluble ZAIS quantum dots by aqueous - phase synthesis

[0080] First, a certain amount of 0.0117 g of Ag(Ac) and 0.1168 g of In(Ac) 3 salts were dissolved in a certain volume of deionized water, 0.56 g of glutathione aqueous solution was added, and the pH value was adjusted to 4 - 11 by NaOH aqueous solution; secondly, under stirring conditions, an aqueous solution of a sulfur source such as 100 ml of 20 mM Na 2 S, thioacetamide or thiourea at 90 °C was reverse - injected into the above - mentioned metal ion solution, and heated for 30 min to obtain an AgInS 2 quantum dot solution; finally, 0.088 g of Zn(Ac) 2 .2H 2 O and 0.073 g of mercaptoacetic acid were dissolved in 1 ml of water, and the pH value was adjusted to 8 with NaOH. Then the Zn solution coordinated with thiol was added to 30 ml of the above - mentioned AgInS 2 quantum dot solution. After continuously heating at 90 °C for 30 minutes, it was naturally cooled to room temperature to obtain a ZAIS quantum dot solution.

[0081] 2) Preparation of a 2 - mim methanol precursor solution in which ZAIS quantum dots are dispersed and a Zn 2+ methanol precursor solution

[0082] 131.2 mg of 2 - methylimidazole (2 - mim) was dissolved in 5 ml of methanol (MeOH) to form a clear solution, and 10 mg of CTAB was added; 10 ml of ZAIS quantum dot solution was taken, precipitated with an equal volume of ethanol, and centrifuged to obtain a ZAIS quantum dot solid. The quantum dot solid was dispersed in a 2 - mim methanol solution under ultrasonic conditions; 58.4 mg of zinc salts such as zinc acetate dihydrate was weighed and dissolved in 5 ml of methanol to obtain a Zn 2+ precursor solution

[0083] 3) Preparation of the ZAIS@ZIF - 8 core - shell structure catalyst

[0084] Under continuous stirring, Zn 2+ The 2 - mim solution was poured into the 2 - mim methanol solution in which ZAIS was dispersed, and the mixture was stirred for 24 h. After standing at room temperature for 24 h, the yellow solid was collected by centrifugation, dispersed with deionized water, and then precipitated with an equal volume of methanol and centrifuged. This operation was repeated three times to remove unreacted ions and ligands. The collected sample was dried under vacuum at 40 °C to obtain ZAIS@ZIF - 8.

[0085] Comparative Example 1

[0086] The preparation method of the solid of red - emitting AIS quantum dots without encapsulation is as follows:

[0087] First, a certain amount of 0.0234 g of Ag(Ac) and 0.1168 g of In(Ac) 3 salts were dissolved in a certain volume of deionized water, 0.56 g of glutathione aqueous solution was added, and the pH value was adjusted to 4 - 11 by NaOH aqueous solution; secondly, under stirring conditions, an aqueous solution of a sulfur source such as 100 ml of 20 mM Na 2 S, thioacetamide or thiourea at 90 °C was inversely injected into the above - mentioned metal ion solution, and heated for 30 min to obtain an AgInS 2 quantum dot solution. After ethanol precipitation, centrifugation, and drying, the AIS quantum dot solid was obtained.

[0088] Figure 1 Figure a shows the UV - Vis spectra of the products prepared in Example 1 and Comparative Example 1 of the present invention. It can be seen that for the AIS@ZIF - 8 composite structure sample, compared with AIS, the absorption has a red - shift and the visible light absorption is enhanced; Figure 2 Figure is the fluorescence emission spectrum comparison diagram of the products prepared in Example 1, Example 2, Comparative Example 1, and Comparative Example 2 of the present invention. The fluorescence quantum efficiency of Example 1 is 18%, much higher than 4% of Comparative Example 1. The fluorescence emission peak position of Example 1 is 590 nm, red - shifted by 15 nm compared with the corresponding Comparative Example 1 and Comparative Example 2, and the full width at half maximum of the fluorescence peak is significantly broadened by 35 nm, indicating that the formation of the core - shell structure is beneficial to enhancing the white light emission; Figure 4 Figure is the X - ray diffraction pattern of the products prepared in Example 1, Comparative Example 1, and Comparative Example 4, where the abscissa 2θ is twice the scanning angle and the ordinate is the diffraction intensity. It can be seen that Example 1 contains the X - ray diffraction characteristic peaks of Comparative Example 1 and Comparative Example 4; Figure 6 Figure a is the scanning electron microscope image of Example 1, and it can be seen that it has the morphology of ZIF - 8, Figure 6 Figures b and 6c are the transmission electron microscope and high - resolution transmission electron microscope images of Example 1, and it can be seen that the quantum dots are uniformly distributed inside the material, Figure 6 Figure d is the high - resolution electron microscope image of Comparative Example 1, and it can be seen that the core - shell structure realizes the uniform dispersion of AIS in the crystal; Figure 7It is a comparative diagram of the photocatalytic reduction of U(VI) effect diagrams of the products prepared in Example 1, Example 2, Comparative Example 1, Comparative Example 2, and Comparative Example 3. It is easy to find that the ZAIS@ZIF-8 photocatalyst in Example 3 has excellent degradation performance, while the pure AIS in Comparative Example 1 basically has no photocatalytic effect, which proves the effectiveness of the present invention.

[0089] Comparative Example 2

[0090] The preparation method of the orange-emitting AIS quantum dot solid without encapsulation is as follows:

[0091] First, dissolve a certain amount of 0.0117 g of Ag(Ac) and 0.1168 g of In(Ac) 3 salts in a certain volume of deionized water, add 0.56 g of glutathione aqueous solution, and adjust the pH value to 4 - 11 with NaOH aqueous solution; secondly, inject the aqueous solution of sulfur source such as 100 ml of 20 mM Na 2 S, thioacetamide or thiourea at 90 °C into the above metal ion solution under stirring conditions, and heat for 30 min to obtain the AgInS 2 quantum dot solution. After ethanol precipitation, centrifugation, and drying, the AIS quantum dot solid is obtained.

[0092] Figure 1 Figure b shows the UV-visible spectra of the products prepared in Example 2 and Comparative Example 2 of the present invention. The abscissa in the figure is the wavelength, and the ordinate is the relative intensity. It can be seen that the absorption of the AIS@ZIF-8 composite structure sample is redshifted and the visible light absorption is enhanced compared with AIS; Figure 2 It is a comparative diagram of the fluorescence emission spectra of the products prepared in Example 1, Example 2, Comparative Example 1, and Comparative Example 2 of the present invention. The fluorescence quantum efficiency of Example 2 is 45%, which is much higher than 20% of Comparative Example 2. The fluorescence emission peak positions of Example 2 are 585 nm, which are redshifted by 20 nm compared with the corresponding Comparative Example 1 and Comparative Example 2, and the full width at half maximum of the fluorescence peak is significantly broadened by 45 nm, indicating that the formation of the core-shell structure is beneficial to enhancing the white light emission. This result further proves that constructing the ZIF-8 shell structure is beneficial to realizing fluorescence enhancement and emission band broadening, thereby facilitating the enhancement of white light emission.

[0093] Comparative Example 3

[0094] The preparation method of AIS-ZnS luminescence is as follows:

[0095] First, dissolve a certain amount of 0.0117 g of Ag(Ac) and 0.1168 g of In(Ac) 3The salt is dissolved in a certain volume of deionized water, 0.56 g of glutathione aqueous solution is added, and the pH value is adjusted to 4 - 11 with NaOH aqueous solution; secondly, 100 ml of 20 mM Na 2 aqueous solution of sulfur source such as S, thioacetamide or thiourea is reversely injected into the above metal ion solution under stirring conditions, and heated for 30 min to obtain AgInS 2 quantum dot solution; finally, 0.088 g of Zn(Ac) 2 .2H 2 O in 1 ml of water, and then this Zn solution is added to 30 ml of the above AgInS 2 quantum dot solution. After continuously heating at 90 °C for 30 minutes, it is naturally cooled to room temperature to obtain an AIS-ZnS solution.

[0096] Figure 3 Figs. 3, 4 and 10 are the emission spectra of Example 3, Example 4 and Comparative Example 3. The fluorescence peak positions of Example 3 and Example 4 are 565 and 515 nm respectively, while the emission peak position of Comparative Example 3 redshifts from 570 nm of pure AIS (Comparative Example 1) to 620 nm. It can be seen that yellow-green light ZAIS@ZIF-8 cannot be obtained without using mercapto to coordinate with zinc, which confirms the unique role of using mercapto small molecules to coordinate with zinc ions in the present invention for obtaining yellow-green light ZAIS@ZIF-8; Figure 5 Fig. 11 is the X-ray diffraction pattern of the products prepared in Comparative Example 1 and Comparative Example 3, where the abscissa 2θ is twice the scanning angle and the ordinate is the diffraction intensity. It can be seen that in the process of doping zinc in AIS in Comparative Example 3, the formation of ZnS phase and the aggregation of quantum dots are caused by the failure to use mercapto to coordinate with zinc, which is also the reason why the fluorescence not only does not increase and blue-shift but instead shows aggregation quenching and a large range of red-shift after adding zinc; Figure 6 Fig. 12e is the high-resolution electron microscope image of Comparative Example 3, and it can be seen that a large number of quantum dots without ZIF-8 shell material agglomerate; Figure 7 Fig. 13 is a comparative diagram of the photocatalytic reduction U(VI) effect diagrams of the products prepared in Example 1, Example 2, Comparative Example 1, Comparative Example 2 and Comparative Example 3. It is easy to find that Comparative Example 3 only shows certain photocatalytic performance, and the uranyl removal rate is about 45%, which is much lower than 98% of ZAIS@ZIF-8 in Example 3.

[0097] Comparative Example 4:

[0098] 131.2 mg of 2-methylimidazole (2-mim) is dissolved in 5 ml of methanol (MeOH) to form a clear solution, and 10 mg of CTAB is added; 58.4 mg of zinc salt such as zinc acetate dihydrate is weighed and dissolved in 5 ml of methanol to obtain Zn 2+ precursor solution. Under continuous stirring, Zn 2+The 2-mim solution was poured into the 2-mim methanol solution in which CTAB was dispersed, and stirred for 24 h. After standing at room temperature for 24 h, the white solid was collected by centrifugation, dispersed with deionized water, and then precipitated and centrifuged with an equal volume of methanol. The operation was repeated three times to remove unreacted ions and ligands. The collected sample was dried under vacuum at 40 °C to obtain ZIF-8.

[0099] Figure 4 The X-ray diffraction pattern of Comparative Example 4 was shown, which was consistent with the results of ZIF-8 reported in the literature. The diffraction intensity at the corresponding peak positions in Example 1 was significantly reduced, indicating that the crystallinity and crystal size of the ZIF structure in AIS@ZIF-8 were greatly reduced due to the internal encapsulation of a large number of AIS quantum dots. Figure 6 f shows the SEM image of Comparative Example 4, and it can be seen that it has a more regular geometric shape and larger size than the core-shell structure of Example 1; however, as Figure 7 shown, Comparative Example 4 only showed an adsorption removal rate of about 45%, and there was no obvious photocatalytic effect under light illumination, indicating that the combination of the two could achieve the synergistic removal of uranyl by adsorption and photocatalytic reduction.

Claims

1. A method for preparing a ZAIS@ZIF-8 core-shell structure catalyst, characterized in that: The following steps are involved: 1) Preparation of ZAIS quantum dot solution First, Ag + 、In 3+ The salt is dissolved in a certain volume of deionized water, and one or more thiol ligands such as thioglycolic acid, mercaptoethylamine, glutathione, and amino ligands such as ethylenediamine are added, and the pH value is adjusted to 4-11 by using an aqueous solution of NaOH; secondly, 2-20 mmol / LS of Na2S or the like with a temperature of 40-100°C is injected into the solution in reverse phase. 2- The aqueous solution is stirred and heated to obtain an AgInS2 quantum dot solution; a certain concentration of Zn 2+ The mixed solution of the AgInS2 quantum dot solution and the small molecule thiol ligand is added dropwise to the mixed solution under heating and stirring at a certain temperature, and after continuous heating and heat preservation for a certain period of time, the mixed solution is naturally cooled to room temperature to obtain the ZAIS quantum dot solution. 2) Prepare a methanol solution of ZAIS quantum dots and 2-mim precursor dispersed with amino surface encapsulating agent, and Zn 2+ Precursor methanol solution A certain amount of 2-methylimidazole (2-mim) was dissolved in methanol (MeOH) to form a clear solution; a certain amount of ZAIS quantum dot solution was taken, precipitated with an equal volume of ethanol, and centrifuged to obtain ZAIS quantum dot solid, which was then dispersed in triethylamine (TEA), dodecyltrimethylammonium bromide (DTAB) or hexadecyltrimethylammonium bromide (CTAB) and 2-mim precursor methanol solution under ultrasonic conditions; a certain amount of zinc salt (Zn nitrate or zinc acetate) was taken 2+ ), dissolved in a certain volume of methanol to obtain Zn 2+ Precursor solution. 3) Preparation of ZAIS@ZIF-8 core-shell structure catalyst Under continuous stirring, a certain concentration of Zn 2+ The solution was poured into the methanol solution of 2-mim and TEA or CTAB in which ZAIS was dispersed, stirred for 1-48 hours, and allowed to stand at room temperature for 1-48 hours. The yellow solid was collected by centrifugation and redispersed with methanol to remove unreacted ions and ligands. After the above dispersion-centrifugation procedure was repeated 3 times, the collected samples were dried under vacuum at 40°C to obtain ZAIS@ZIF-8. A similar and consistent method can be used to prepare the AIS@ZIF-8 core-shell structure.

2. The method for dispersing the ZAIS quantum dot solution according to claim 1, characterized in that The Zn precursor used was Zn 2+ The complex formed with one of the thiol ligands such as thioglycolic acid, cysteine, glutathione, etc., the molar ratio of the zinc salt to the thiol ligand is 1:10-10:1, and the temperature is 20-150°C.

3. The molar ratio of the silver or copper salt to the indium salt is 1:1 to 1:10, the silver salt is selected from one of Ag(OAc) or AgNO3, the indium salt is selected from one of In(OAc)3, InCl3, InBr3, InI3, In(NO3)3 or In2(SO4)2, and the zinc salt is Zn(OAc)2, ZnCl2, ZnBr2, ZnI2, Zn(NO3)2 or ZnSO4.

4. The preparation method according to claim 1, characterized in that: The sulfur precursor is selected from one of sodium sulfide, potassium sulfide, ammonium sulfide or thiourea. 2- The concentration is 1-50mmol / L.

5. The preparation method according to claim 1, characterized in that: The molar ratio of the small molecule thiol encapsulating agent to silver and indium is 1:1-1:40, the molar ratio of silver to zinc salt is 1:10-10:1, and the small molecule thiol encapsulating agent is selected from one of thioglycolic acid, mercaptopropionic acid, thioethylamine or cysteine.

6. The triethylamine, DTAB or CTAB or other fatty amine or fatty ammonium salt-based surface encapsulating agent and 2-mim precursor methanol precursor solution for AIS or ZAIS quantum dots dispersion according to claim 1, characterized in that: The molar ratio of the AIS or ZAIS quantum dots to 2-mim is 1:10-1:100, and the molar ratio of the amino surface encapsulating agent to 2-mim is 1:1000-1:

10.

7. The temperature of the synthetic ZAIS quantum dot solution according to claim 1, 2 or 3 is 20-150°C, and the constant temperature hydrothermal time is 0.5-60h.

8. The preparation method according to claim 1, characterized in that: The molar ratio of the zinc salt to 2-mim is 1:1 to 1:20, and the zinc salt is selected from one of ZnI2, ZnCl2, ZnBr2, ZnAc2, Zn(SO4)2 or Zn(NO3)2.

9. The preparation method according to claim 1, characterized in that: The molar ratio of the 2-mim methanol solution of the ZAIS@ZIF-8 core-shell structure to the methanol solution of the zinc salt is 0.1:1 to 10:

1.

10. The method for preparing ZAIS@ZIF-8 according to claim 1, characterized in that: The 2-mim solution of ZAIS and Zn 2+ The reaction temperature of the methanol solution is 20-70°C, the stirring time is 1-24h, and it is allowed to stand at room temperature for 24h.

11. The ZAIS@ZIF-8 core-shell structure prepared by the preparation method according to claim 1.

12. The ZAIS@ZIF-8 core-shell structure according to claim 11, characterized in that The quantum dots are water-soluble dispersed ZAIS alloy quantum dots, quasi-zero-dimensional multinary semiconductor nanocrystals with a size of 0.5-5nm, and the composite material structure is a core-shell structure of the quantum dots uniformly dispersed in ZIF-8 crystals.

13. Application of the ZAIS@ZIF-8 core-shell structure according to claim 11 in white light emitting devices and photocatalytic uranyl reduction and degradation of tetracycline antibiotics.

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