Preparation of a noble metal nanocluster luminescent material

Abstract

The present invention relates to the preparation of a noble metal nanocluster luminescent material, which includes: stirring silver salt and molecular sieve in the dark in a solution, followed by heat treatment to obtain a silver-loaded nanocluster luminescent molecular sieve, that is, a noble metal nanocluster luminescent material; wherein, the molecular sieve is a FAU molecular sieve with 1.5 ≤ Si / Al ≤ 4 and 0 < Ga / Al ≤ 5. Compared with the prior art, the present invention can achieve tunable luminescence of silver nanoclusters in the visible band by introducing heteroatom gallium and regulating the ratios of silicon, aluminum, and gallium.

Description

Technical Field

[0001] The present invention belongs to the technical field of photoluminescent materials, and relates to the preparation of a noble metal nanocluster luminescent material, and in particular to a method for preparing a noble metal nanocluster luminescent material with a molecular-like energy level structure. Background Art

[0002] Silver nanoclusters are oligomers composed of a few to dozens of silver atoms or ions, which can be electrically neutral or positively charged. They are only a few nanometers in size and lack a complete lattice structure. Because silver nanoclusters have a discrete energy level structure that is closely related to their composition and the crystal field environment in which they reside, their luminescence, caused by radiative transitions, is tunable across the entire visible wavelength range. They have broad application prospects in lighting displays, biomarkers, detection and sensing.

[0003] Because silver nanoclusters have high surface energy and easily aggregate into nonluminescent silver nanoparticles, a suitable matrix is ​​required to stabilize them and achieve optimal photoluminescence performance. Molecular sieves are microporous aluminosilicate crystals, typically composed of silicon-oxygen tetrahedra and aluminum-oxygen tetrahedra connected in various ways by bridging oxygen. They have over 200 topological structures. Molecular sieves, with their stable and rich pore structure, are ideal supports for stabilizing silver nanoclusters. In 2016, scientists from France and Belgium reported in Nature Materials that they could manipulate the size of Ag nanoclusters and, consequently, the fluorescence properties of Ag-zeolite materials by regulating the topology of the zeolite (Nat. Mater., 2016, 15, 1017–1022). Specifically, they used FAU molecular sieve as a support and obtained the Ag-zeolite material via ion exchange. However, the narrow spectral control range of this luminescent material and the need for improved luminescence intensity have hindered its further application. Summary of the Invention

[0004] The purpose of the present invention is to provide a preparation of a noble metal nanocluster luminescent material. The prepared material has efficient and adjustable luminescence performance in the visible band and is expected to be applied in lighting display, harmful gas detection and other fields.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] Molecular sieves are microporous aluminosilicate crystals usually formed by different connections of silicon-oxygen tetrahedra and aluminum-oxygen tetrahedra through bridging oxygen. There are more than two hundred kinds of their topological structures. Molecular sieves have stable and abundant pore structures and are ideal carriers for stabilizing silver nanoclusters. When the framework silicon and aluminum atoms of the molecular sieve are isomorphously replaced by other metal atoms, heteroatom-modified molecular sieves are obtained. Due to the differences in ionic radius, electronegativity, bonding energy, and bond length between the introduced framework heteroatoms and silicon-aluminum atoms, the lattice and pore structure of the molecular sieve are affected, thereby regulating the luminescence properties of the silver nanoclusters loaded therein.

[0007] The present invention proposes to carry out heteroatom modification of aluminosilicate molecular sieves with gallium atoms, prepare heteroatom molecular sieves with different silicon, aluminum, and gallium ratios by the direct hydrothermal synthesis method, and use them as carriers for the original growth of silver nanoclusters, obtaining a series of silver-loaded nanocluster luminescent molecular sieves with efficient and adjustable spectral properties.

[0008] A preparation method of a noble metal nanocluster luminescent material, comprising: stirring silver salt and molecular sieve in the dark in a solution, and then performing heat treatment to obtain a silver-loaded nanocluster luminescent molecular sieve, that is, a noble metal nanocluster luminescent material; wherein, the molecular sieve is a FAU molecular sieve with 1.5 ≤ Si / Al ≤ 4 and 0 < Ga / Al ≤ 5.

[0009] Further, the preparation method of the FAU molecular sieve includes: performing hydrothermal reaction on NaAlO2, SiO2, gallium salt, and alkali to obtain a molecular sieve product;

[0010] Further, the gallium salt is Ga(NO₃)₃.

[0011] Further, the alkali is NaOH.

[0012] Further, the mixing process of the silver salt and the molecular sieve includes: adding the molecular sieve into an AgNO₃ solution with a concentration not exceeding 50 mmol / L, and the solid-liquid ratio is 1 g:100 mL to 1 g:10 mL.

[0013] Further, the molar ratio of SiO₂ to NaAlO₂ is (1.5 - 4):1, and the molar ratio of Ga in the gallium salt to NaAlO₂ does not exceed 5.

[0014] Further, before the hydrothermal reaction, NaAlO₂, SiO₂, gallium salt, and alkali are fully stirred at 40 - 80 °C for 30 - 120 min.

[0015] Further, during the hydrothermal reaction, the reaction temperature is 80 - 160 °C, and the reaction time is 8 - 48 h.

[0016] Furthermore, during the light-shielded stirring process, the stirring temperature is 40 to 60° C., and the stirring time is 1 to 24 hours.

[0017] Furthermore, in the heat treatment process, the heat treatment temperature is 300-800° C. and the heat treatment time is 1-5 hours.

[0018] An application of a noble metal nanocluster luminescent material, including applications of the noble metal nanocluster luminescent material in lighting display and harmful gas detection.

[0019] Compared with the prior art, the present invention has the following characteristics:

[0020] By introducing the heteroatom gallium and regulating the ratios of silicon, aluminum, and gallium, this method achieves tunable luminescence of silver nanoclusters in the visible wavelength range. Compared with existing technologies, this method not only effectively improves the luminescence intensity of silver nanoclusters but also increases the half-width of their emission spectrum. Furthermore, the preparation method is simple and highly reproducible. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is the emission spectrum of the silver-loaded nanocluster luminescent molecular sieve prepared in Example 1;

[0022] Figure 2 : is the emission spectrum of the silver-loaded nanocluster luminescent molecular sieve prepared in Example 2;

[0023] Figure 3 The emission spectra of the silver nanocluster-loaded luminescent molecular sieve prepared in Example 3 are as follows: (1) the emission spectrum of silver nanoclusters in a FAU molecular sieve with Si / Al=2:1; (2) the emission spectrum of silver nanoclusters in a FAU molecular sieve with Si / Al / Ga=4:1:1;

[0024] Figure 4 is the emission spectrum of the silver-loaded nanocluster luminescent molecular sieve prepared in Example 4;

[0025] Figure 5 This is the XRD spectrum of the silver-loaded nanocluster luminescent molecular sieve prepared in Example 5. DETAILED DESCRIPTION

[0026] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0027] A method for preparing a noble metal nanocluster luminescent material comprises the following steps:

[0028] S1: Stir NaAlO₂, SiO₂, gallium salt, and alkali at 40 - 80 °C for 30 - 120 min, and then carry out hydrothermal reaction at 80 - 160 °C for 8 - 48 h to obtain FAU zeolite with 1.5 ≤ Si / Al ≤ 4 and 0 < Ga / Al ≤ 5;

[0029] Among them, the molar ratio of SiO₂ to NaAlO₂ is (1.5 - 4):1, the molar ratio of Ga in the gallium salt to NaAlO₂ does not exceed 5. The gallium salt is preferably Ga(NO₃)₃, the alkali is preferably NaOH, and SiO₂ is preferably gas-phase nano-SiO₂ particles;

[0030] S2: Add the FAU zeolite into an AgNO₃ solution with a concentration not exceeding 50 mmol / L, with a solid-liquid ratio of 1 g:100 mL - 1 g:10 mL, stir in the dark at 40 - 60 °C for 1 - 24 h, then centrifuge, wash with water, and dry to obtain a solid product; <000(0071>S3: Heat-treat the solid product at 300 - 800 °C for 1 - 5 h, and after cooling to room temperature, obtain silver-loaded nanocluster luminescent zeolite, that is, a noble metal nanocluster luminescent material.

[0032] The zeolite used in the present invention has a FAU-type topological structure, and the T atoms in the primary structure unit TO₄ tetrahedron of the zeolite are silicon, aluminum, and gallium in different proportions; the preparation process includes the preparation of heteroatom FAU-type zeolite with different framework silicon, aluminum, and gallium proportions, and the ion exchange of the obtained heteroatom FAU-type zeolite with silver nitrate solutions of different concentrations, and the heat treatment at different temperatures and times in the later stage to promote the formation of silver nanoclusters; the obtained silver-loaded nanocluster luminescent zeolite emits visible light with an adjustable emission band under ultraviolet light excitation.

[0033] Compared with the prior art, the silver nanoclusters formed in the gallium atom zeolite in the present invention have a significantly increased luminescence intensity compared to those in the silicon-aluminum zeolite, and the full width at half maximum of the emission spectrum is effectively broadened; at the same time, by adjusting the proportion of silicon, aluminum, and gallium in the zeolite, the luminescence band of the silver nanoclusters can be regulated in the visible band.

[0034] An application of a noble metal nanocluster luminescent material, including the application of the noble metal nanocluster luminescent material in lighting display and harmful gas detection.

[0035] The following examples are implemented on the premise of the above technical solutions of the present invention, and detailed implementation methods and specific operation processes are given, but the protection scope of the present invention is not limited to the following examples.

[0036] In the following examples, the average particle size of the gas-phase nano-SiO₂ particles is 7 - 40 nm.

[0037] Example 1:

[0038] A noble metal nanocluster luminescent material having a molecular-like energy level structure, wherein the preparation method comprises the following steps:

[0039] (1) Weigh 3.65 g of NaOH and dissolve it in 50 mL of deionized water. After it is fully dissolved, add 0.98 g of NaAlO2 and 5.88 g of Ga(NO3)3. Stir until the solution is clear and then slowly add 5.40 g of SiO2.

[0040] (2) The mixture was placed in an oil bath and stirred thoroughly at 40°C for 40 min, then poured into a polytetrafluoroethylene reactor and reacted at 100°C for 24 h. After cooling, the supernatant was removed, centrifuged and washed with water three times, and dried in an oven at 60°C for 24 h.

[0041] (3) Prepare 100 mL of 20 mmol / L AgNO3 solution, then add 2.0 g of the above molecular sieve product, and then place in an oil bath at 50°C in the dark and stir for 3 h;

[0042] (4) The product was then centrifuged and washed with water three times, and then dried in an oven at 60°C for 24 h to obtain a solid product;

[0043] (5) The solid was transferred into a corundum crucible and heated to 600 °C and kept warm for 2 h, ensuring a heating rate of 3 °C / min, and finally a silver-loaded nanocluster luminescent molecular sieve was obtained.

[0044] Figure 1 This is the emission spectrum of the silver nanocluster-loaded luminescent molecular sieve, with an emission peak at 535 nm.

[0045] Example 2:

[0046] A noble metal nanocluster luminescent material having a molecular-like energy level structure, wherein the preparation method comprises the following steps:

[0047] (1) Weigh 4.38 g of NaOH and dissolve it in 50 mL of deionized water. After it is fully dissolved, add 2.30 g of NaAlO2 and 1.79 g of Ga(NO3)3. Stir until the solution is clear and then slowly add 5.94 g of SiO2.

[0048] (2) The mixture was placed in an oil bath and stirred at 50°C for 60 min, then poured into a polytetrafluoroethylene reactor and reacted at 120°C for 24 h. After cooling, the supernatant was removed, washed with water by centrifugation three times, and dried in an oven at 60°C for 24 h.

[0049] (3) Prepare 100 mL of 10 mmol / L AgNO3 solution, then add 5.0 g of the above molecular sieve product, and then place in an oil bath at 50°C in the dark and stir for 3 h;

[0050] (4) The product was then centrifuged and washed with water three times, and then dried in an oven at 60°C for 24 h to obtain a solid product;

[0051] (5) The solid was transferred into a corundum crucible and heated to 700 °C and kept warm for 2 h, ensuring a heating rate of 3 °C / min, and finally a silver-loaded nanocluster luminescent molecular sieve was obtained.

[0052] Figure 2 This is the emission spectrum of the silver nanocluster-loaded luminescent molecular sieve, with an emission peak at 550nm.

[0053] Example 3:

[0054] A noble metal nanocluster luminescent material having a molecular-like energy level structure, wherein the preparation method comprises the following steps:

[0055] (1) Weigh 3.65 g of NaOH and dissolve it in 50 mL of deionized water. After it is fully dissolved, add 1.64 g of NaAlO2 and 5.11 g of Ga(NO3)3. Stir until the solution is clear and then slowly add 5.40 g of SiO2.

[0056] (2) The mixture was placed in an oil bath and stirred thoroughly at 40°C for 40 minutes, then poured into a polytetrafluoroethylene reactor and reacted at 110°C for 24 hours. After cooling, the supernatant was removed, washed with water by centrifugation three times, and dried in an oven at 60°C for 24 hours.

[0057] (3) Prepare 100 mL of 20 mmol / L AgNO3 solution, then add 2.0 g of the above molecular sieve product, and then place in an oil bath at 50°C in the dark and stir for 3 h;

[0058] (4) The product was then centrifuged and washed with water three times, and then dried in an oven at 60°C for 24 h to obtain a solid product;

[0059] (5) The solid was transferred into a corundum crucible and heated to 600 °C and kept warm for 2 h, ensuring a heating rate of 3 °C / min, and finally a silver-loaded nanocluster luminescent molecular sieve was obtained.

[0060] Figure 3 This is the emission spectrum of the silver nanocluster-loaded luminescent molecular sieve. Compared with the emission spectrum of the molecular sieve without gallium heteroatoms prepared under the same conditions (NaAlO2 with an additional molar amount equal to gallium is added in step (1)), the emission spectrum of the silver nanocluster is significantly broadened and the luminescence is significantly enhanced.

[0061] Example 4:

[0062] A noble metal nanocluster luminescent material having a molecular-like energy level structure, wherein the preparation method comprises the following steps:

[0063] (1) Weigh 3.65 g of NaOH and dissolve it in 50 mL of deionized water. After it is fully dissolved, add 0.82 g of NaAlO2 and 6.39 g of Ga(NO3)3. Stir until the solution is clear and then slowly add 4.86 g of SiO2.

[0064] (2) The mixture was placed in an oil bath and stirred thoroughly at 40°C for 40 minutes, then poured into a polytetrafluoroethylene reactor and reacted at 140°C for 24 hours. After cooling, the supernatant was removed, centrifuged and washed with water three times, and dried in an oven at 60°C for 24 hours.

[0065] (3) Prepare 80 mL of 30 mmol / L AgNO3 solution, then add 1.0 g of the above molecular sieve product, and then place in an oil bath at 60 ° C in the dark and stir for 3 h;

[0066] (4) The product was then centrifuged and washed with water three times, and then dried in an oven at 60°C for 24 h to obtain a solid product;

[0067] (5) The solid was transferred into a corundum crucible and heated to 650 °C and kept warm for 3 h, ensuring a heating rate of 3 °C / min, and finally a silver-loaded nanocluster luminescent molecular sieve was obtained.

[0068] Figure 4 This is the emission spectrum of the prepared silver nanocluster luminescent molecular sieve. It can be observed that the emission wavelength of the sample is 522nm.

[0069] Example 5:

[0070] A noble metal nanocluster luminescent material having a molecular-like energy level structure, wherein the preparation method comprises the following steps:

[0071] (1) Weigh 3.65 g of NaOH and dissolve it in 50 mL of deionized water. After it is fully dissolved, add 1.64 g of NaAlO2 and 7.67 g of Ga(NO3)3. Stir until the solution is clear and then slowly add 5.10 g of SiO2.

[0072] (2) The mixture was placed in an oil bath and stirred thoroughly at 60°C for 40 minutes, then poured into a polytetrafluoroethylene reactor and reacted at 150°C for 12 hours. After cooling, the supernatant was removed, centrifuged and washed with water three times, and dried in an oven at 60°C for 24 hours.

[0073] (3) Prepare 100 mL of 50 mmol / L AgNO3 solution, then add 5.0 g of the above molecular sieve product, and then place in an oil bath at 50°C in the dark and stir for 3 h;

[0074] (4) The product was then centrifuged and washed with water three times, and then dried in an oven at 70°C for 24 h to obtain a solid product;

[0075] (5) The solid was transferred into a corundum crucible and heated to 700 °C and kept warm for 2 h, ensuring a heating rate of 3 °C / min, and finally a silver-loaded nanocluster luminescent molecular sieve was obtained.

[0076] Figure 5 This is the XRD diagram of the silver nanocluster-loaded luminescent molecular sieve. It can be observed that the sample has a good FAU molecular sieve structure.

[0077] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. A method for preparing a noble metal nanocluster luminescent material, characterized in that: The method includes: stirring silver salt and molecular sieve in the dark in a solution, followed by heat treatment to obtain silver-loaded nanocluster luminescent molecular sieve, that is, noble metal nanocluster luminescent material; Among them, the molecular sieve is FAU molecular sieve with 1.5 ≤ Si / Al ≤ 4 and 0 < Ga / Al ≤ 5; The preparation method of the FAU molecular sieve includes: performing hydrothermal reaction on NaAlO2, SiO2, gallium salt, and alkali to obtain a molecular sieve product; During the stirring in the dark, the stirring temperature is 40 - 60 °C, and the stirring time is 1 - 24 h; During the heat treatment, the heat treatment temperature is 300 - 800 °C, and the heat treatment time is 1 - 5 h.

2. The method for preparing a noble metal nanocluster luminescent material according to claim 1, characterized in that: The gallium salt is Ga(NO3)3, and the alkali is NaOH.

3. The method for preparing a noble metal nanocluster luminescent material according to claim 1, wherein: The stirring in the dark of the silver salt and the molecular sieve includes: adding the molecular sieve into an AgNO3 solution with a concentration not exceeding 50 mmol / L, and the solid-liquid ratio is 1 g:100 mL - 1 g:10 mL.

4. The method for preparing a noble metal nanocluster luminescent material according to claim 1, characterized in that: The molar ratio of SiO2 to NaAlO2 is (1.5 - 4):1, and the molar ratio of Ga in the gallium salt to NaAlO2 does not exceed 5.

5. The method for preparing a noble metal nanocluster luminescent material according to claim 1, characterized in that: Before the hydrothermal reaction, first stir NaAlO2, SiO2, gallium salt, and alkali at 40 - 80 °C for 30 - 120 min.

6. The method for preparing a noble metal nanocluster luminescent material according to claim 1, characterized in that: During the hydrothermal reaction, the reaction temperature is 80 - 160 °C, and the reaction time is 8 - 48 h.

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