A broadband white light cluster and its preparation method

Abstract

The present invention relates to the technical field of luminescent materials and preparation methods thereof, and discloses a broadband white light cluster and a preparation method thereof. The broadband white light cluster has the general chemical formula: x Cu y I z αH2O, where A comprises at least one alkylamine. The broadband white-light cluster luminescent material of the present invention has an excitation peak in the ultraviolet region, making it well compatible with commercial UV chips. Its emission peak width covers 400-800nm. Its large Stokes shift (150nm) effectively prevents reabsorption. By controlling the pressure within which the broadband white-light cluster luminescent material is exposed, the present invention achieves luminescence enhancement and spectral control. The broadband white-light cluster luminescent material of the present invention utilizes inexpensive raw materials, has a simple synthesis process, operates at a low temperature, and exhibits stable chemical properties and is pollution-free, making it suitable for large-scale production.

Description

Technical Field

[0001] The present invention relates to the technical field of luminescent materials and preparation methods thereof, and in particular to a broadband white light cluster and a preparation method thereof. Background Art

[0002] White light emitting diodes (W-LEDs) have been successfully applied in solid-state lighting, LCD backlight display, flat panel display and other fields due to their advantages such as high efficiency, color tunability, durability, long life, energy saving and environmental protection. At present, the most common way to achieve white light emission is to use a blue light emitting InGaN chip + a yellow light emitting Y3Al5O 12 :Ce 3+ Phosphor + red light emitting (such as CaAlSiN3:Eu 2+ , Sr2Si5N8:Eu 2+ , K2SiF6:Mn 4+ However, this method still has many problems: 1. The reabsorption phenomenon between multiple phosphors is serious; 2. The service life of different phosphors is different, and color drift is easy to occur during use. Therefore, the design and preparation of single-phase white light materials with large half-peak width is a hot research topic. As far as commonly used W-LED phosphors are concerned, the number of white light materials is quite limited. At present, a lot of research on white materials mainly focuses on rare earth ions (Eu 2+ 、Ce 3+ ) such as Sr2AlSi2O6N:Eu 2+ 、Sr3Ce(PO4)3:Eu 2+ 、Sr3Sc4O9:Ce 3+ 、Y3Si5N9O:Ce 3+ However, these materials have the following disadvantages: (1) the preparation conditions are relatively harsh (>1000℃), requiring high temperature and high pressure conditions; (2) the excitation and emission bands partially overlap, resulting in unbalanced white light emission; (3) the emission band is far from the photosensitive region of the human eye (400-700nm). In this context, the research on high-performance broadband white light emitting materials is of great significance to improving LED lighting, LCD backlight display and other fields. Summary of the Invention

[0003] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a broadband white light cluster and a preparation method thereof.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] A broadband white light cluster with the general chemical formula: A x Cu y I zαH2O, wherein A comprises at least one alkylamine, 0.001<x<10, 1≤y<10, 1≤z<10, and α≥1.

[0006] The above-mentioned method for preparing a broadband white light cluster comprises the following steps:

[0007] Step 1: cuprous iodide and an organic ammonium salt are used as main raw materials in a ratio of 1:3 to 3:1, hypophosphorous acid is added to inhibit oxidation of cuprous ions, a good solvent is added, mixed evenly, and then ultrasonicated for standby use;

[0008] Step 2: preparing a mixed solution of a good solvent and a poor solvent as a reaction solution;

[0009] Step 3: Filter the solution obtained in step 1 and inject the mixed solution in step 2;

[0010] Step 4: The solution obtained in step 3 was ultrasonically treated and allowed to stand, and the solvent was slowly evaporated. After two days, a broadband white light cluster single crystal was obtained.

[0011] Preferably, in step 1, the molar concentration of the reactant obtained is in the range of 0.1-0.5 mol / mL.

[0012] Preferably, in step 1, the amount of hypophosphorous acid used is 0.5-5% of the total solution volume.

[0013] Preferably, in step 1, the duration of ultrasonic treatment is 10 min.

[0014] Preferably, in step 2, the good solvent includes one or more of dichloromethane, N,N-dimethylformamide, dimethyl sulfoxide, and acetone; the poor solvent includes one or more of diethyl ether, n-hexane, ethanol, and acetonitrile.

[0015] Preferably, in step 2, the ratio of the poor solvent to the good solvent is 1:10-1:3.

[0016] The beneficial effects of the present invention are:

[0017] The broadband white light cluster luminescent material described in this invention has an excitation peak in the ultraviolet region, making it well compatible with commercial ultraviolet chips. Its emission peak width covers 400-800nm, and its large Stokes shift (150nm) effectively prevents reabsorption. By controlling the pressure within which the broadband white light cluster luminescent material is exposed, the invention achieves luminescence enhancement and spectral control. The broadband white light cluster luminescent material described in this invention utilizes inexpensive raw materials, a simple synthesis process, a low synthesis temperature, stable chemical properties, and is pollution-free, making it suitable for large-scale production.

[0018] The present invention can achieve the regulation of broadband white light cluster luminescence by adjusting the ratio of the organic ligand and CuI at the A position (i.e., the ratio of x to y); when x:y is less than 0.8, the broadband white light cluster emits orange-red light; when 0.8≤x:y≤1.25, the broadband white light cluster emits white light; when x:y>1.25, the material emits blue light.

[0019] The present invention can achieve luminescence enhancement and spectral regulation by controlling the pressure of the clusters; as the pressure increases from 1atm to 0.9GPa, the emission intensity of the broadband white light clusters increases by at least 10 times, and the luminescence color gradually changes from white light to blue light; as the pressure continues to increase, the luminescence intensity begins to decrease, and the luminescence color gradually changes to green light; after the pressure is released, the luminescence color of the broadband white light clusters returns to white light, and the luminescence intensity is 2 times higher than that of the group not treated with pressure. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is the X-ray powder diffraction pattern of the sample (CTAB)2Cu2I4·2H2O prepared in Example 1 of the present invention. The inset is a photograph of the sample under sunlight and 365nm excitation;

[0021] Figure 2 This is a crystal structure diagram of the sample (CTAB) 2Cu2I4·2H2O prepared in Example 1 of the present invention;

[0022] Figure 3 This is the excitation spectrum of the sample (CTAB)2Cu2I4·2H2O prepared in Example 1 of the present invention;

[0023] Figure 4 This is the emission spectrum of the sample (CTAB)2Cu2I4·2H2O prepared in Example 1 of the present invention;

[0024] Figure 5 This is a lifetime diagram of different emission positions of the sample (CTAB)2Cu2I4·2H2O prepared in Example 1 of the present invention under 375nm excitation;

[0025] Figure 6 This is the temperature-dependent emission spectrum of the sample (CTAB) 2Cu 2 I 4 · 2H 2 O prepared in Example 1 of the present invention;

[0026] Figure 7 This is the high-pressure-dependent emission spectrum of the sample (CTAB) 2Cu 2 I 4 · 2H 2 O prepared in Example 1 of the present invention;

[0027] Figure 8 1 is the emission spectrum of the sample prepared in Example 2 of the present invention in different solvent systems. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0029] Example 1:

[0030] In this example, a cluster with the chemical formula (CTAB)2Cu2I4·2H2O was prepared according to the following method.

[0031] Preparation process of (CTAB)2Cu2I4·2H2O clusters: Hexadecyl ammonium bromide (99%), cuprous iodide (99%), potassium iodide (99.9%), hypophosphorous acid (50 wt.%), dichloromethane (analytical grade), and n-hexane (analytical grade) were used as raw materials. The raw materials were weighed according to the proportions shown in Table 1:

[0032] Table 1

[0033] Hexadecyl ammonium bromide Cuprous iodide Potassium iodide Hypophosphorous acid dichloromethane 1mmol 1mmol 0.2mmol 100 μL 10mL

[0034] After sonication for 10 minutes, filter and set aside. This is designated A1. Separately, mix 4 mL of dichloromethane and 1 mL of n-hexane. This is designated A2. Add 0.5 mL of A1 to A2 and sonicate for 2 minutes. Allow to stand and slowly evaporate the solvent at room temperature. After 2 days, a broadband white light cluster single crystal (CTAB)2Cu2I4·2H2O is obtained.

[0035] Figure 1 This is the XRD pattern of the (CTAB)2Cu2I4·2H2O cluster. The peak shape closely matches the calculated XRD Rietveld refinements, demonstrating successful synthesis. The cluster single crystals exhibit a rhombohedral shape, and their size can be tuned (from micrometers to centimeters) by manipulating the solvent ratio and type, as well as the reaction time. As shown in the inset, the single crystals emit bright white light when excited at 365nm.

[0036] Figure 2 The crystal structure of (CTAB)2Cu2I4·2H2O cluster is shown in Figure 2. The sample belongs to the monoclinic system, P-1 space group, and the unit cell parameters a, b, c, α, β, γ and V are 81.1060°, 87.2980°, 82.0630° and In the a, b directions, CTAB cations and Cu2I4 2- The anions form a two-dimensional structure with ionic bonds; in the c direction, the layers are stacked by the strong van der Waals force of CTAB to form a three-dimensional bulk crystal. 2- Basic structural unit. In terms of arrangement, the two Cu2I4 2-The units are perpendicular to each other and connected to each other through oxygen to form a copper-iodine chain; in structure, the two Cu2I4 2- The units have different Cu-Cu bond lengths, and Different structures and arrangements give the material different luminescence behaviors.

[0037] Figure 3 Figure 2 shows the excitation spectra of (CTAB)2Cu2I4·2H2O clusters monitored at different emission peak positions. The peaks of the excitation spectra are all located at 345nm, showing similar peak shapes and spectral characteristics, indicating that these emission bands originate from the same excited state.

[0038] Figure 4 The emission spectra of (CTAB)2Cu2I4·2H2O clusters under different excitation wavelengths have a Stokes shift of 130nm. The emission spectrum covers the entire visible light range, showing dual-band luminescence characteristics. The luminescence peaks are located at 497nm and 620nm, respectively, and the FWHM is 225nm.

[0039] Figure 5 Figure 2 is the fluorescence decay curve of (CTAB)2Cu2I4·2H2O clusters at different luminescence peaks. It can be seen that under 375nm pulse diode excitation, the fluorescence decay lifetime of the clusters at different peaks is between 1.49-1.75μs. The same fluorescence lifetime of the order of microseconds indicates that these luminescence bands may originate from different luminescence centers in the same excited state.

[0040] Figure 6 The temperature-dependent emission spectrum of the (CTAB)2Cu2I4·2H2O cluster shows that the material exhibits bimodal emission at different temperatures. Huang-Kun factors fitting the two luminescence centers revealed a Huang-Kun factor of 9.9 for the high-energy peak and 63.1 for the low-energy peak. These Huang-Kun factors are larger than those of many conventional luminescent materials, indicating strong electron-phonon coupling and the formation of STEs. As the temperature increases from 10K to 250K, the luminescence intensity of the luminescence band gradually increases; as the temperature continues to rise from 250K, the intensity of the luminescence band gradually decreases. Thermally induced enhancement of electron-phonon coupling increases the STE concentration, leading to enhanced luminescence. Simultaneously, thermally induced increases in non-radiative losses lead to reduced luminescence. These two factors compete with each other. The former is more advantageous in the temperature range of 10-250K, while the latter is more advantageous in the temperature range above 250K.

[0041] Figure 7This is the pressure-dependent emission spectrum of the (CTAB)2Cu2I4·2H2O cluster. Under normal pressure, the cluster sample exhibits white light emission. As the pressure gradually increases, the fluorescence continues to increase, and the luminescence changes from white light to blue light. After 0.9 GPa, the fluorescence intensity begins to weaken continuously as the pressure continues to increase, and the luminescence gradually changes from blue light to green light. The phenomenon of pressure-induced fluorescence enhancement is very obvious, from the white light state at normal pressure (PLQY of about 10%) to the strongest fluorescence intensity at 0.9 GPa, with an intensity increase of about 10 times. The enhanced electron-phonon coupling caused by high-pressure induced structural distortion is the main reason for the enhanced luminescence.

[0042] Example 2:

[0043] In this example, the cluster precursor was prepared according to the recipe of Example 1, except that a DMF-water mixed solution was used as the reaction solvent.

[0044] Figure 8 The following are emission spectra of samples prepared in a DMF-water system at different ratios: fe = V(H₂O) / V(DMF+H₂O). When fe = 0, the solution is clear and transparent, non-luminescent. As the fe content gradually increases to 20%, the solution becomes turbid and emits orange-red light under near-ultraviolet excitation. As the fe content gradually increases to 28%, the material's luminescence shifts to white light. Further increasing the fe content to 33%, the material exhibits blue light emission.

[0045] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A broadband white light cluster, characterized in that: Its chemical formula is: (CTAB)2Cu2I4·2H2O.

2. The method for preparing a broadband white light cluster according to claim 1, wherein: The following steps are involved: Step 1: Use 1 mmol (mass fraction) of 99% cetyltrimethylammonium bromide, 1 mmol (mass fraction) of 99% cuprous iodide, 0.2 mmol (mass fraction) of 99.9% potassium iodide, 100 μL (mass fraction) of 50 wt.% hypophosphorous acid solution, and 10 mL of dichloromethane, sonicate for 10 minutes, then filter and set aside; Step 2: Take 4 mL of dichloromethane and 1 mL of n-hexane and mix them evenly; Step 3: Take 0.5 mL of the solution obtained in step 1 and inject it into the solution obtained in step 2, and sonicate for 2 minutes; Step 4: The solution obtained in step 3 was allowed to stand, and the solvent was slowly evaporated at room temperature. After 2 days, a broadband white light cluster single crystal (CTAB)2Cu2I4·2H2O was obtained.

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