A Bi 4 O 5 I 2 / NaYF 4 :Yb,Tm composite material, preparation method and application

Abstract

The present invention provides a Bi4O5I2 / NaYF4:Yb,Tm composite material, a preparation method and an application thereof. The preparation method includes using Bi(NO3)·5H2O as the Bi source, KI as the I source, ethylene glycol as the solvent, adding a sodium hydroxide solution to adjust the pH value, and obtaining flaky Bi4O5I2 material through a solvothermal reaction; using NaOH as the Na source, NH4F as the F source, using absolute ethanol as the solvent, stirring and ultrasonicating to obtain solution A, using YCl3·6H2O as the Y source, YbCl3·6H2O as the Yb source, TmCl3·6H2O as the Tm source, using deionized water containing citric acid as the solvent, stirring and ultrasonicating to obtain solution B; dropping solution A into solution B, stirring, and obtaining rod-shaped NaYF4:Yb,Tm material through a solvothermal reaction; adding the obtained flaky Bi4O5I2 material and rod-shaped NaYF4:Yb,Tm material into absolute ethanol, ultrasonicating until completely dissolved, and finally obtaining the Bi4O5I2 / NaYF4:Yb,Tm composite material through a solvothermal reaction. The diameter of the Bi4O5I2 nanosheets prepared by the present invention is 30-70 nm, and the thickness is 8-15 nm. They have a large specific surface area and voids, and can absorb more light. By compounding with the rod-shaped NaYF4:Yb,Tm material to generate the Bi4O5I2 / NaYF4:Yb,Tm composite material, the utilization of the near-infrared spectrum is increased.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor nanomaterial photocatalysis, relates to composite materials, and particularly relates to a Bi 4 O 5 I 2 / NaYF 4 :Yb,Tm composite material, a preparation method thereof, and an application thereof. Background Art

[0002] In recent decades, with the increasing threat of energy shortage, the release of organic pollutants in wastewater has been increasing. These pollutants can indirectly damage human health through the food chain or directly harm the ecological environment. Therefore, finding environmentally friendly, economical, and simple technologies to solve these problems has attracted extensive attention from researchers. Existing sewage treatment methods include oxidation, filtration, adsorption, biological flocculation, etc. However, these traditional methods have problems such as high operating costs and secondary pollution when removing persistent pollutants. Therefore, the development of efficient and green sewage treatment technologies has become a research hotspot.

[0003] Semiconductor photocatalysis has become a promising research direction for alleviating the increasingly serious environmental and energy crises due to its ability to directly drive redox reactions using sunlight under mild reaction conditions. Based on the above advantages, semiconductor photocatalysis has been widely applied in hydrogen production, CO 2 reduction, nitrogen fixation, microbial disinfection, degradation of water and air pollutants, etc., solving the energy and environmental crises.

[0004] Previous studies have shown that there are various semiconductors with the ability to generate electrical and chemical energy under visible light. However, most semiconductor materials, such as Bi 4 O 5 I 2 , can only be excited by ultraviolet light and part of visible light, and ultraviolet light and visible light only account for about 50% of the entire solar spectrum, with a limited spectral utilization range. Summary of the Invention

[0005] Aiming at the defects and deficiencies existing in the prior art, the purpose of the present invention is to provide a Bi 4 O 5 I 2 / NaYF 4 :Yb,Tm composite material, a preparation method thereof, and an application thereof, so as to solve the problem of the limited spectral utilization range of Bi 4 O 5 I 2 monomer material in the degradation of organic matter.

[0006] To solve the above technical problems, the present invention is implemented by adopting the following technical solutions:

[0007] A Bi 4 O 5 I 2 / NaYF 4 :Yb,Tm composite material preparation method, comprising the following steps:

[0008] Step 1, prepare flaky Bi 4 O 5 I 2 precursor:

[0009] Using Bi(NO 3 )·5H 2 O as the Bi source, a soluble iodide as the I source, and ethylene glycol as the solvent to prepare a mixed solution, and then adding a sodium hydroxide solution to the mixed solution to adjust the pH value, and obtaining flaky Bi 4 O 5 I 2 precursor;

[0010] Step 2, prepare rod-shaped NaYF 4 :Yb,Tm precursor:

[0011] Step 2.1, using NaOH as the Na source, NH 4 F as the F source, and absolute ethanol as the solvent, stirring and ultrasonicating to obtain solution A;

[0012] Step 2.2, using YCl 3 ·6H 2 O as the Y source, YbCl 3 ·6H 2 O as the Yb source, TmCl 3 ·6H 2 O as the Tm source, and deionized water containing citric acid as the solvent, stirring and ultrasonicating to obtain solution B;

[0013] Step 2.3, dropping solution A into solution B and stirring, and obtaining rod-shaped NaYF 4 :Yb,Tm precursor;

[0014] Step 3, prepare Bi 4 O 5 I 2 / NaYF 4 :Yb,Tm composite material:

[0015] Mix the flaky Bi 4 O 5 I 2 precursor prepared in Step 1 and the rod-shaped NaYF 4: The Yb,Tm precursor is added to absolute ethanol and dissolved by ultrasonic treatment, and the reaction product is obtained through a solvothermal reaction; then, the reaction product is centrifuged, washed, and dried to obtain the Bi 4 O 5 I 2 / NaYF 4 :Yb,Tm composite material;

[0016] Among them, by mass percentage, the mass ratio of the Bi 4 O 5 I 2 precursor is 5% - 25%, and the mass ratio of the NaYF 4 :Yb,Tm precursor is 75% - 95%, and the sum of the mass percentages of each component is 100%

[0017] The present invention also has the following technical features:

[0018] Specifically, the soluble iodide described in step 1 includes KI and NaI.

[0019] Furthermore, the molar ratio of Bi(NO 3 )·5H 2 O to the soluble iodide in step 1 is: (1.8 - 2.2):1.

[0020] Furthermore, the molar ratio of NaOH to NH 4 F in step 2.1 is 2.5:(18 - 24); the molar ratio of YCl 3 ·6H 2 O, YbCl 3 ·6H 2 O, TmCl 3 ·6H 2 O to citric acid in step 2.2 is (0.75 - 0.8):(0.18 - 0.23):0.02:2.

[0021] Furthermore, the temperature of the solvothermal reaction described in step 1 is 140 - 160°C, and the reaction time is 10 - 14 h; the temperature of the solvothermal reaction described in step 2 is 190 - 210°C, and the reaction time is 8 - 9 h; the temperature of the solvothermal reaction described in step 3 is 140 - 160°C, and the reaction time is 1 - 2 h.

[0022] Furthermore, the method specifically includes the following steps:

[0023] Step 1. Prepare the flaky Bi 4 O 5 I 2 precursor:

[0024] Step 1.1: Dissolve 1.5 mol of Bi(NO 3 )·5H 2 O and 0.75 mol of KI in 35 ml of ethylene glycol, stir for 30 min to obtain a mixed material liquid;

[0025] Step 1.2: Add 40 ml of sodium hydroxide solution with a concentration of 0.1 mol / L to the mixed material liquid to adjust the pH value, then transfer the solution to a reaction kettle and seal it. Place the reaction kettle in an oven and carry out a solvothermal reaction at 150 °C for 12 h to obtain flaky Bi 4 O 5 I 2 precursor;

[0026] Step 2: Prepare rod-shaped NaYF 4 :Yb,Tm precursor:

[0027] Step 2.1: Add 2.5 mol of NaOH and 18 mol of NH 4 F to 15 ml of absolute ethanol, stir for 30 min and ultrasonicate for 60 min to obtain solution A;

[0028] Step 2.2: Add 0.8 mol of YCl 3 ·6H 2 O, 0.18 mol of YbCl 3 ·6H 2 O and 0.02 mol of TmCl 3 ·6H 2 O to 20 ml of deionized water containing 2 mol of citric acid, stir for 30 min and ultrasonicate for 60 min to obtain solution B;

[0029] Step 2.3: Drop solution A into solution B and stir for 30 min, then transfer the solution to a reaction kettle and seal it. Place the reaction kettle in an oven for solvothermal reaction, and carry out a solvothermal reaction at 200 °C for 8 h to obtain rod-shaped NaYF 4 :Yb,Tm precursor;

[0030] Step 3: Prepare Bi 4 O 5 I 2 / NaYF 4 :Yb,Tm composite material:

[0031] Dissolve 0.356 g of flaky Bi 4 O 5 I 2 precursor and 0.044 g of rod-shaped NaYF 4: The Yb,Tm precursor was added to 20 ml of absolute ethanol and dissolved by ultrasonic treatment. Then the solution was transferred into a reaction kettle and sealed. The reaction kettle was placed in an oven and subjected to solvothermal reaction at 140 °C for 1 h. After cooling, centrifugal washing, and drying, Bi 4 O 5 I 2 / NaYF 4 :Yb,Tm composite material was obtained.

[0032] The present invention also protects a Bi 4 O 5 I 2 / NaYF 4 :Yb,Tm composite material, which is prepared by the preparation method of the Bi 4 O 5 I 2 / NaYF 4 :Yb,Tm composite material as described above.

[0033] The present invention also protects the application of the Bi 4 O 5 I 2 / NaYF 4 :Yb,Tm composite material as described above as a photocatalytic material for degrading RhB.

[0034] Advantageous technical effects of the present invention compared with the prior art:

[0035] (Ⅰ) The preparation method of the Bi 4 O 5 I 2 / NaYF 4 :Yb,Tm composite material provided by the present invention can prepare a Bi 4 O 5 I 2 / NaYF 4 :Yb,Tm composite material that can effectively improve the spectral utilization rate by controlling the molar ratio of the Bi 4 O 5 I 2 / NaYF 4 :Yb,Tm precursor and the reaction conditions of the solvothermal method; the flaky Bi 4 O 5 I 2 precursor prepared by the preparation method provided by the present invention has a large specific surface area and pores, can absorb more light, and can be in full contact with organic substances in the photocatalytic reaction.

[0036] (Ⅱ) The Bi 4 O 5 I 2 / NaYF4 Preparation method of Yb,Tm composite material, which has the advantages of simple process, short preparation period, low cost, etc.

[0037] (Ⅲ) The Bi 4 O 5 I 2 / NaYF 4 :Yb,Tm composite material has a more stable structure and is non-toxic.

[0038] (Ⅳ) The Bi 4 O 5 I 2 / NaYF 4 :Yb,Tm composite material has high photocatalytic performance for organic dyes. Under simulated sunlight, it can degrade 84.2% of RhB within 60 min; and Bi 4 O 5 I 2 / NaYF 4 :Yb,Tm composite material increases the utilization of the near-infrared spectrum. Under near-infrared light, it can degrade 43.0% of RhB within 240 min. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The drawings are used to provide a further understanding of the present disclosure and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present disclosure, but do not constitute a limitation to the present disclosure.

[0040] Figure 1 XRD pattern of the Bi 4 O 5 I 2 / NaYF 4 :Yb,Tm composite material prepared in Example 1;

[0041] Figure 2 SEM and Mapping patterns of the Bi 4 O 5 I 2 / NaYF 4 :Yb,Tm composite material prepared in Example 1, where (a) is the morphology diagram of the Bi 4 O 5 I 2 / NaYF 4 :Yb,Tm composite material, (b) is the Bi element Mapping diagram, (c) is the O element Mapping diagram, (d) is the I element Mapping diagram, (e) is the Na element Mapping diagram, (f) is the Y element Mapping diagram, (g) is the F element Mapping diagram, (h) is the Yb element Mapping diagram, (i) is the Tm element Mapping diagram;

[0042] Figure 3 The Bi 4 O 5 I 2 / NaYF 4 :Yb,Tm composite material prepared in Example 2; XRD pattern

[0043] Figure 4 The Bi 4 O 5 I 2 / NaYF 4 :Yb,Tm composite material prepared in Example 3; XRD pattern

[0044] Figure 5 The Bi 4 O 5 I 2 / NaYF 4 :Yb,Tm composite material prepared in Example 1; UV-Vis spectrum

[0045] Figure 6 The Bi 4 O 5 I 2 / NaYF 4 :Yb,Tm composite material prepared in Example 1; upconversion emission spectrum

[0046] Figure 7 The Bi 4 O 5 I 2 / NaYF 4 :Yb,Tm composite material prepared in Example 1; combined graph of absorption spectrum and upconversion emission spectrum

[0047] Figure 8 The Bi 4 O 5 I 2 / NaYF 4 :Yb,Tm composite material prepared in Examples 1 - 3; RhB degradation pattern

[0048] Figure 9 The Bi 4 O 5 I 2 / NaYF4:Yb,Tm composite material and its two monomer materials; RhB photocatalytic degradation pattern under near-infrared light

[0049] The technical solution of the present invention will be further described below in conjunction with the embodiments. Specific embodiments

[0050] The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments. However, the present invention is not limited to the following embodiments. For those of ordinary skill in the art in the technical field to which the present invention belongs, without departing from the concept of the present invention, several simple deductions or substitutions can be made, and all can prepare Bi 4 O 5 I 2 / NaYF 4 :Yb,Tm composite materials, which should all be regarded as falling within the protection scope of the present invention.

[0051] It should be noted that, unless otherwise specified, all raw materials in the present invention are all known raw materials in the prior art, and the inspection and testing equipment used are all commercially available.

[0052] Solvothermal reaction method: It refers to a new method for preparing materials in which the reaction precursors are dissolved in a non-aqueous solvent, loaded into a sealed reaction kettle, and reacted at a specific temperature and pressure. Solvothermal reaction is developed on the basis of hydrothermal reaction, replacing water in hydrothermal reaction with a non-aqueous solvent. Due to some substances that are insensitive to water, such as carbides and phosphides, the preparation process of these materials is restricted to a certain extent in hydrothermal reaction, while it is more mild and effective in solvothermal reaction, which promotes the development of solvothermal reaction. The solvothermal reaction method can dissolve and disperse the reactants, making them fully contact during the reaction process, and significantly enhancing the reaction activity. The system environment of solvothermal reaction is relatively special, and metastable phases that cannot be formed in hydrothermal reaction can be formed. In addition, the products generated by the solvothermal method have excellent dispersibility, and can prevent the oxidation of the products during the reaction process, improving the purity of the products.

[0053] The technical concept of the present invention is: taking advantage of the advantages of BiOX (X = Cl, Br, and I) such as a wide visible light utilization range, high separation rate of photo-generated carriers, excellent stability, and non-toxicity, by adjusting the ratio of X to O in BiOX, the positions of its VB and CB can be changed, thereby improving the photocatalytic activity. Bi 4 O 5 I 2 The crystal structure of is composed of [Bi 2 O 2 2+ layers and double layers of I - vertically staggered along the c-axis to form. There are weak van der Waals forces between the layers, and strong covalent bonds link within the layers. [Bi 2 O 2 2+ layers and double layers of I - will generate a static internal electric field (IEF) due to the polarization of non-uniform charge distribution between them, which can help separate electrons and holes. Bi 4 O 5 I 2 ​​It has a large dipole moment and layer spacing, which means a large polarization space and polarization force. The size of the polarization space and polarization force determines the size of the static internal electric field. Therefore, Bi 4 O 5 I 2 has a very high separation efficiency of internal electron-hole pairs, greatly enhancing its photocatalytic performance. By combining the Bi 4 O 5 I 2 material with the upconversion luminescent material NaYF 4 :Yb,Tm, the utilization of the near-infrared spectrum is increased, and the spectral response range of the photocatalyst is broadened.

[0054] The present invention provides a method for preparing a Bi 4 O 5 I 2 / NaYF 4 :Yb,Tm composite material, comprising the following steps:

[0055] Step 1, preparing a flaky Bi 4 O 5 I 2 precursor:

[0056] Using Bi(NO 3 )·5H 2 O as the Bi source, a soluble iodide as the I source, and ethylene glycol as the solvent to prepare a mixed solution. Then, a sodium hydroxide solution is added to the mixed solution to adjust the pH value, and a flaky Bi 4 O 5 I 2 precursor is obtained through a solvothermal reaction;

[0057] Step 2, preparing a rod-shaped NaYF 4 :Yb,Tm precursor:

[0058] Step 2.1, using NaOH as the Na source, NH 4 F as the F source, and absolute ethanol as the solvent, stirring and ultrasonicating to obtain solution A;

[0059] Step 2.2, using YCl 3 ·6H 2 O as the Y source, YbCl 3 ·6H 2 O as the Yb source, TmCl 3 ·6H 2 O as the Tm source, and deionized water containing citric acid as the solvent, stirring and ultrasonicating to obtain solution B;

[0060] Step 2.3, dropping solution A into solution B and stirring, and obtaining a rod-shaped NaYF 4: Yb, Tm precursor;

[0061] Step 3: Prepare Bi 4 O 5 I 2 / NaYF 4 : Yb, Tm composite material:

[0062] Add the flaky Bi 4 O 5 I 2 precursor prepared in Step 1 and the rod-shaped NaYF 4 : Yb, Tm precursor into absolute ethanol and dissolve them by ultrasonic treatment. Obtain the reaction product through solvothermal reaction; then centrifuge, wash, and dry the reaction product to obtain Bi 4 O 5 I 2 / NaYF 4 : Yb, Tm composite material;

[0063] Among them, by mass percentage, the mass ratio of the Bi 4 O 5 I 2 precursor is 5% - 25%, and the mass ratio of the NaYF 4 : Yb, Tm precursor is 75% - 95%. The mass percentages of each component add up to 100%.

[0064] Preferably, the soluble iodide in Step 1 includes KI and NaI.

[0065] Preferably, the molar ratio of Bi(NO 3 )·5H 2 O to the soluble iodide is (1.8 - 2.2):1.

[0066] Preferably, the molar ratio of NaOH to NH 4 F in Step 2.1 is 2.5:(18 - 24); the molar ratio of YCl 3 ·6H 2 O, YbCl 3 ·6H 2 O, TmCl 3 ·6H 2 O to citric acid in Step 2.2 is (0.75 - 0.8):(0.18 - 0.23):0.02:2.

[0067] Preferably, the temperature of the solvothermal reaction in Step 1 is 140 - 160 °C, and the reaction time is 10 - 14 h;

[0068] The temperature of the solvothermal reaction described in Step 2 is 190 - 210 °C, and the reaction time is 8 - 9 h; the temperature of the solvothermal reaction described in Step 3 is 140 - 160 °C, and the reaction time is 1 - 2 h.

[0069] Preferably, the diameter of the flaky Bi 4 O 5 I 2 is 30 - 70 nm, and the thickness is 8 - 15 nm.

[0070] Following the above technical solution, specific embodiments of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent transformations made on the basis of the technical solution of this application fall within the protection scope of the present invention.

[0071] Example 1:

[0072] Following the above technical solution, in this example, first, 1.5 mol of Bi(NO 3 )·5H 2 O and 0.75 mol of KI are dissolved in 35 ml of ethylene glycol and stirred for 30 min until the solution becomes clear to obtain a mixed material solution. 40 ml of a sodium hydroxide solution with a concentration of 0.1 mol / L is added to the mixed material solution to adjust the pH value, and then the solution is transferred into a reaction kettle and sealed. The reaction kettle is placed in an oven and subjected to a solvothermal reaction at 150 °C for 12 h. After the reaction is completed and naturally cooled, it is centrifuged, washed, and dried in a drying oven to obtain a flaky Bi 4 O 5 I 2 precursor;

[0073] Weigh 2.5 mol of NaOH and 18 mol of NH 4 F, add 15 ml of absolute ethanol, stir for 30 min until the solution becomes clear, and ultrasonicate for 60 min to prepare Solution A; take 0.8 mol of YCl 3 ·6H 2 O, 0.18 mol of YbCl 3 ·6H 2 O and 0.02 mol of TmCl 3 ·6H 2 O, add them to 20 ml of deionized water containing 2 mol of citric acid, stir for 30 min until the solution becomes clear and ultrasonicate for 60 min to prepare Solution B. Drop Solution A into Solution B and stir until the solution becomes clear. After stirring, transfer the solution into a reaction kettle and seal it. Place the reaction kettle in an oven and carry out a solvothermal reaction at 200 °C for 8 h. After the reaction is completed and naturally cooled, it is centrifuged, washed, and dried in a drying oven to obtain a rod-shaped NaYF 4 :Yb,Tm precursor;

[0074] Dissolve 0.356 g of flaky Bi 4 O 5 I 2 precursor and 0.044 g of rod-shaped NaYF 4 :Yb,Tm precursor in 20 ml of absolute ethanol by ultrasonic dissolution. Transfer the solution into a reaction kettle and seal it. Place the reaction kettle in an oven for solvothermal reaction. Carry out solvothermal reaction at 140 °C for 1 h. After the reaction is completed and naturally cooled, wash by centrifugation and dry in a drying oven to obtain a pale yellow powder.

[0075] In this example, the obtained product was analyzed by XRD and SEM, and the results are as follows:

[0076] First, compare the XRD pattern of the product prepared in this example with the standard cards JCPDS 41-2590 of Bi 4 O 5 I 2 and the XRD pattern of JCPDS 16-0334 of NaYF 4 . The results are as Figure 1 shown: Diffraction peaks belonging to Bi 4 O 5 I 2 exist at 28.8°, 31.4°, 37.1°, 42.3°, 44.9°, 49.2°, 54.3°, 59.7° and 65.4°, which respectively belong to the (-411), (020), (-404), (-323), (422), (006), (811), (-822) and (804) crystal planes of Bi 4 O 5 I 2 ; Diffraction peaks belonging to NaYF 4 exist at 17.2°, 39.7°, 43.5°, 62.4°, 71.0° and 77.5°, which respectively correspond to the (100), (111), (201), (220), (311) and (302) crystal planes of NaYF 4 . This fully demonstrates that the Bi 4 O 5 I 2 precursor and NaYF 4 :Yb,Tm precursor composed of Bi 4 O 5 I 2 / NaYF 4 :Yb,Tm composite material is prepared in this example, without other impurities.

[0077] As Figure 2 (a) shows, the finally obtained product consists of nano-flaky Bi 4 O 5 I2 Precursors and micro - rod - shaped NaYF 4 :Yb,Tm precursors, and its structure is: nano - sheet - shaped Bi with a diameter of 30 - 70 nm and a thickness of 8 - 15 nm 4 O 5 I 2 Precursors grow on the micro - rod - shaped NaYF 4 :Yb,Tm precursors. For Figure 2 (a), elemental composition analysis gives Figure (b)-(i). It can be seen that Bi, O, I, Na, Y, F, Yb, and Tm elements are evenly distributed in the selected area, and are generally similar to the structure in the SEM image, and there are no other impurity elements. Combining the analysis of SEM and Mapping indicates that the prepared material is Bi 4 O 5 I 2 / NaYF 4 :Yb,Tm composite material.

[0078] The pale - yellow solid product obtained in this example was tested by ultraviolet - visible diffuse reflectance spectroscopy (UV - Vis DRS), and the results are as Figure 5 shown. It can be seen from the figure that: in the absorption spectrum of the product, an obvious absorption peak appears at 900 - 1000 nm. This is because the 3+ transition of Yb 2 F 5 / 2 → 2 F 7 / 2 results in a large absorption interface at 980 nm for it. Therefore, it is judged that this absorption peak is the characteristic absorption peak of Yb 3+ ions. In addition, a strong absorption peak appears near 500 nm in the absorption spectrum of the product, and this should be the characteristic absorption peak of Bi 4 O 5 I 2 . The absorption spectrum analysis confirms the presence of Bi 4 O 5 I 2 / NaYF 4 :Yb,Tm composite material. 4 O 5 I 2 .

[0079] Figure 6 This is the up - conversion luminescence spectrum diagram of the product obtained in this example under the excitation of a 980 nm semiconductor diode. It can be seen from the figure that: its emission peaks are all characteristic emission peaks of Tm 3+ ions. The ultraviolet emission peaks at wavelengths of 291 nm, 346 nm, and 364 nm respectively come from the 3+ transition of Tm 1 I6 → 3 H 6 , 1 I 6 → 3 F 4 and 1 D 2 → 3 H 6 Radiative transition, the two blue light emission peaks at wavelengths of 450nm and 475nm come from Tm 3+ Ionic 1 D 2 → 3 F 4 and 1 G 4 → 3 H 6 Radiative transition.

[0080] Embodiment 2:

[0081] This embodiment provides a Bi 4 O 5 I 2 / NaYF 4 :Yb, Tm composite material preparation method, the method is basically the same as the preparation method of Example 1, the difference is that in this embodiment, 0.380g of flaky Bi 4 O 5 I 2 Precursor and 0.020 g rod-shaped NaYF 4 :Yb, Tm precursor is used for preparation, and finally a light yellow powder is obtained.

[0082] In this embodiment, Bi 4 O 5 I 2 / NaYF 4 : The preparation method of Yb, Tm composite material, such as Figure 3 As shown in the XRD spectrum, it can be proved that the Bi prepared in this embodiment 4 O 5 I 2 / NaYF 4 :Yb,Tm composite materials are made of Bi 4 O 5 I 2 and NaYF 4 :Composed of Yb,Tm.

[0083] Embodiment 3:

[0084] This embodiment provides a method of improving the spectrum utilization rate of Bi 4 O 5 I 2 / NaYF 4 Preparation method of Yb,Tm composite material, which is basically the same as the preparation method in Example 1, except that in this example, 0.300 g of flaky Bi 4 O 5 I 2 precursor and 0.100 g of rod-shaped NaYF 4 :Yb,Tm precursor were used for preparation, and finally a pale yellow powder was obtained.

[0085] Using Bi in this example 4 O 5 I 2 / NaYF 4 :Yb,Tm composite material preparation method, as Figure 4 shown, it can be proved in the XRD pattern that the Bi 4 O 5 I 2 / NaYF 4 :Yb,Tm composite material is composed of Bi 4 O 5 I 2 and NaYF 4 :Yb,Tm.

[0086] Application test:

[0087] For the Bi 4 O 5 I 2 / NaYF 4 :Yb,Tm composite materials prepared in Example 1, Example 2 and Example 3, a photocatalytic degradation experiment of RhB was carried out under simulated sunlight. The time interval was selected as 15 min, and 5 mL of the pollutant solution was taken. The taken pollutant solution was centrifuged, and the supernatant was taken for absorbance test.

[0088] The calculation formula of the pollutant degradation rate is as follows:

[0089]

[0090] Among them, η is the photocatalytic degradation rate, C 0 is the initial concentration of the pollutant solution, and C t is the concentration of the solution at time t.

[0091] The test results are as Figure 8 shown. Among them, taking the 0 moment as the node, the left side corresponds to the dark reaction stage in the photocatalytic experiment, and the right side corresponds to the degradation process after the visible light source is turned on. From Figure 8 it can be seen that: in the dark reaction stage, the Bi prepared in Example 1 4 O 5I 2 / NaYF 4 :Yb,Tm composite material has an adsorption degree of less than 5%, with the fastest photocatalytic rate in the photoreaction, and the degradation rate reaches 84.2% in 60 minutes.

[0092] For the Bi 4 O 5 I 2 / NaYF 4 :Yb,Tm composite material, single material Bi 4 O 5 I 2 and single material NaYF 4 :Yb,Tm, a photocatalytic degradation experiment of RhB was carried out under near-infrared light. A time interval of 60 minutes was selected, and 5 mL of the pollutant solution was taken. The taken pollutant solution was centrifuged, and the supernatant was taken for absorbance testing. The test results are as Figure 9 shown. Among them, taking the 0 moment as the node, the left side corresponds to the dark reaction stage in the photocatalytic experiment, and the right side corresponds to the degradation process after the near-infrared light source is turned on. It can be seen from the figure that in the dark reaction, the adsorption degree of the Bi 4 O 5 I 2 / NaYF 4 :Yb,Tm composite material is less than 5%, and it has the fastest photocatalytic rate in the photoreaction. The degradation rate reaches 43.0% in 240 minutes. When only NaYF 4 :Yb,Tm material is dispersed in the RhB solution, only less than 5.5% of RhB is degraded or adsorbed after half an hour of dark reaction and four hours of photoreaction, indicating that NaYF 4 :Yb,Tm has very little degradation efficiency for RhB. When only Bi 4 O 5 I 2 material is dispersed in the RhB solution, the RhB concentration drops by about 15.2%. Since Figure 5 it is known that the light with a wavelength of 980 nm is not within the absorbable spectrum range of the single Bi 4 O 5 I 2 material, so the decrease in the RhB concentration in this part comes from the adsorption performance of the Bi 4 O 5 I 2 material.

[0093] Figure 7 The absorption spectrum of the Bi 4 O 5 I 2 / NaYF 4 :Yb,Tm composite material (Figure 5 ) and the upconversion emission spectrum ( Figure 6 ) are combined. It can be observed that the upconversion luminescence emitted by the radiative transition of Tm 3+ ions is within the absorption wavelength range of Bi 4 O 5 I 2 , indicating that Bi 4 O 5 I 2 can effectively absorb the upconversion luminescence of NaYF 4 :Yb,Tm. In summary: under near-infrared light, Figure 6 the emission light of Tm 4 O 5 I 2 / NaYF 4 :Yb,Tm composite material at the positions of 291nm, 346nm, 364nm, 450nm and 475nm is observed. In the composite system, the photon energy emitted by the radiative transition of Tm 3+ ions at 291nm (~4.26eV), 346nm (~3.573eV), 364nm (~3.425eV), 450nm (~2.756eV), 475nm (~2.611eV) is greater than the band gap of Bi 3+ O 4 O 5 I 2 , that is, these upconversion luminescences are within the absorption wavelength range of Bi 4 O 5 I 2 . Through the radiative reabsorption process of upconversion luminescence, Bi 4 O 5 I 2 absorbs the energy of these radiative photons, and the electrons in the valence band are excited to jump to the conduction band to become photogenerated electrons after absorbing the energy. These energy transfer processes can directly and effectively transfer the energy to the surrounding Bi 4 O 5 I 2 for photocatalytic reactions. Bi 4 O 5 I 2 can absorb more ultraviolet light and visible light during the photoreaction, thereby enhancing the photocatalytic performance

[0094] The preferred embodiments of the present disclosure have been described in detail above in conjunction with the accompanying drawings. However, the present disclosure is not limited to the specific details in the above embodiments. Within the technical concept of the present disclosure, various simple modifications can be made to the technical solutions of the present disclosure, and these simple modifications all belong to the protection scope of the present disclosure.

[0095] In addition, it should be noted that, among the various specific technical features described in the above specific embodiments, without conflict, they can be combined in any suitable way. To avoid unnecessary repetition, the present disclosure will not separately describe various possible combination methods.

[0096] Furthermore, any combinations can be made among the various different embodiments of the present disclosure, as long as they do not violate the idea of the present disclosure, and they should also be regarded as the content disclosed by the present disclosure.

Claims

1. A Bi 4 O 5 I 2 / NaYF 4 :Yb,Tm composite material preparation method, It is characterized in that It includes the following steps: Step 1. Prepare flaky Bi 4 O 5 I 2 Precursor: Using Bi(NO 3 )·5H 2 O as the Bi source, a soluble iodide as the I source, and ethylene glycol as the solvent to prepare a mixed solution, and then adding a sodium hydroxide solution to the mixed solution to adjust the pH value, and obtaining flaky Bi 4 O 5 I 2 precursor through solvothermal reaction; Step 2: Prepare rod-shaped NaYF 4 :Yb,Tm precursor: Step 2.1: Using NaOH as the Na source, NH 4 F as the F source, and absolute ethanol as the solvent, a solution A is prepared after stirring and ultrasonic treatment; Step 2.2: Using YCl 3 ·6H 2 O as the Y source, YbCl 3 ·6H 2 O as the Yb source, TmCl 3 ·6H 2 O as the Tm source, using deionized water containing citric acid as the solvent, stirring and ultrasonicating to obtain solution B; Step 2.3: Drop solution A into solution B and stir to obtain rod-shaped NaYF 4 :Yb,Tm precursor through solvothermal reaction; Step 3: Prepare Bi 4 O 5 I 2 / NaYF 4 :Yb,Tm composite material: Add the flaky Bi prepared in Step 1 4 O 5 I 2 precursor and the rod-shaped NaYF 4 :Yb,Tm precursor prepared in Step 2 into absolute ethanol and dissolve them by ultrasonic treatment, and obtain the reaction product through a solvothermal reaction; then centrifugally wash and dry the reaction product to obtain the Bi 4 O 5 I 2 / NaYF 4 :Yb,Tm composite material; Among them, in terms of mass percentage, Bi 4 O 5 I 2 precursor accounts for 5% to 25% of the mass, and NaYF 4 :Yb,Tm precursor accounts for 75% to 95% of the mass, and the sum of the mass percentages of each component is 100%; In step 1, the molar ratio of Bi(NO 3 )·5H 2 O to the soluble iodide is (1.8 - 2.2):1; The molar ratio of NaOH to NH 4 F in step 2.1 is 2.5:(18 - 24); the molar ratio of YCl 3 ·6H 2 O, YbCl 3 ·6H 2 O, TmCl 3 ·6H 2 O to citric acid in step 2.2 is (0.75 - 0.8):(0.18 - 0.23):0.02:2; The flaky Bi 4 O 5 I 2 has a diameter of 30 to 70 nm and a thickness of 8 to 15 nm.

2. The Bi 4 O 5 I 2 / NaYF 4 : Preparation method of Yb,Tm composite material It is characterized in that The soluble iodides described in step 1 include KI and NaI.

3. The preparation method of the Bi 4 O 5 I 2 / NaYF 4 :Yb,Tm composite material as claimed in claim 1 It is characterized in that The temperature of the solvothermal reaction described in step 1 is 140-160 °C, and the reaction time is 10-14 h; The temperature of the solvothermal reaction described in step 2 is 190-210 °C, and the reaction time is 8-9 h; the temperature of the solvothermal reaction described in step 3 is 140-160 °C, and the reaction time is 1-2 h.

4. The preparation method of the Bi 4 O 5 I 2 / NaYF 4 :Yb,Tm composite material It is characterized in that The method specifically includes the following steps: Step 1, Prepare flaky Bi 4 O 5 I 2 Precursor: Step 1.1, Dissolve 1.5 mol of Bi(NO 3 )·5H 2 O and 0.75 mol of KI in 35 ml of ethylene glycol Stir for 30 min to obtain a mixed material liquid; Step 1.2: Add 40 ml of sodium hydroxide solution with a concentration of 0.1 mol / L to the mixed solution to adjust the pH value, then transfer the solution into a reaction kettle and seal it. Place the reaction kettle in an oven and carry out a solvothermal reaction at 150 °C for 12 h to obtain flaky Bi 4 O 5 I 2 precursor; Step 2. Prepare rod-shaped NaYF 4 :Yb,Tm: Step 2.1: Add 2.5 mol of NaOH and 18 mol of NH 4 F to 15 ml of absolute ethanol, stir for 30 min and ultrasonicate for 60 min to obtain Solution A; Step 2.2: Add 0.8 mol of YCl 3 ·6H 2 O, 0.18 mol of YbCl 3 ·6H 2 O, and 0.02 mol of TmCl 3 ·6H 2 O into 20 ml of deionized water containing 2 mol of citric acid, stir for 30 min and ultrasonicate for 60 min to obtain Solution B; Step 2.3: Add solution A dropwise to solution B and stir for 30 min, then transfer the solution into a reaction kettle and seal it. Place the reaction kettle in an oven for solvothermal reaction at 200 °C for 8 h to obtain rod-shaped NaYF 4 :Yb,Tm precursor; Step 3: Prepare Bi 4 O 5 I 2 / NaYF 4 :Yb,Tm composite material: Add 0.356 g of flaky Bi 4 O 5 I 2 precursor and 0.044 g of rod-shaped NaYF 4 :Yb,Tm precursor to 20 ml of anhydrous ethanol, dissolve by ultrasonic treatment, then transfer the solution into a reaction kettle and seal it. Place the reaction kettle in an oven and carry out solvothermal reaction at 140 °C for 1 h, then cool, centrifuge, wash, and dry to obtain Bi 4 O 5 I 2 / NaYF 4 :Yb,Tm composite material.

5. A Bi 4 O 5 I 2 / NaYF 4 :Yb,Tm composite material It is characterized in that Prepared by using the preparation method of the Bi 4 O 5 I 2 / NaYF 4 :Yb,Tm composite material according to any one of claims 1 to 4.

6. The application of Bi 4 O 5 I 2 / NaYF 4 :Yb,Tm composite material as a photocatalytic material for the degradation of RhB.

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