CN112981483B - Method for preparing oriented NaGdF by adopting electrodeposition 4 :Eu 3+ Method for down-converting film materials - Google Patents

Abstract

The invention discloses a method for preparing oriented NaGdF ₄ :Eu ³⁺ down-conversion thin film material by electrodeposition. Using N-(2-hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid as a chelating agent to complex with gadolinium and europium ions, in the process of electrodeposition, the oxidation of sodium ascorbate in the solution produces Hydrogen ions release gadolinium and europium ions to form NaGdF ₄ :Eu ³⁺ films with sodium ions and fluoride ions. By adjusting the deposition voltage, NaGdF ₄ :Eu ³⁺ thin films with (110) crystal plane orientation can be prepared, which exhibit stronger down-conversion luminescence properties and higher quantum yields. The invention has the characteristics of simple operation, mild and controllable conditions, short deposition time and low cost.

Description

A method for preparing oriented NaGdF4:Eu3+ down-conversion thin film material by electrodeposition

technical field

The invention relates to the preparation of down-conversion fluorescent materials, in particular to a method for preparing oriented NaGdF ₄ :Eu ³⁺ down-conversion thin film materials by electrodeposition.

Background technique

Down-conversion luminescent materials, which can convert a high-energy photon into two or more low-energy photons that can be utilized, are widely used in photovoltaic power generation, high-efficiency mercury-free fluorescent lamps, and color plasma flat-panel displays. The hexagonal NaGdF ₄ is a good down-conversion host material. Compared with NaYF ₄ , NaGdF ₄ not only has a comparable intensity of down-conversion luminescence, but also is an ideal UV sensitizer, which can also activate the down-conversion of rare earth ions. Luminescence (such as Eu ³⁺ and Tb ³⁺ ) makes it have strong red and green light emission in the visible light region. Europium ions are widely used and are good red fluorescent materials. The luminescence of europium ions is affected by the crystal structure. The position in the lattice and the surface state are different, and the luminescence properties are also different. Therefore, NaGdF ₄ :Eu ³⁺ down-conversion materials have attracted much attention.

So far, many preparation methods for _NaGdF down-conversion thin film materials have been developed, such as metal organic chemical vapor deposition, sol-gel method, polymer intercalation method, pulsed laser deposition, etc. In comparison, the electrodeposition method is a simpler and milder method, and at the same time, the orientation of the crystal phase and even the crystal plane can be adjusted by adjusting the deposition temperature and deposition potential. In this invention, a europium ion-doped NaGdF ₄ down-conversion fluorescent thin film material is prepared by electrochemical deposition. The equipment is simple, the operation is convenient, the conditions are mild, and the film is (110) oriented, showing higher quantum yield. It is expected to expand the application of NaGdF ₄ in photovoltaics, fluorescent lamps and plasma displays.

SUMMARY OF THE INVENTION

The purpose of the present invention is to simply and efficiently prepare the oriented NaGdF ₄ down-conversion fluorescent thin film material doped with europium ions by the method of electrodeposition.

The invention firstly discloses a method for preparing oriented NaGdF ₄ :Eu ³⁺ down-conversion thin film material by electrodeposition, which comprises the following steps:

1) Weigh Gd ³⁺ and Eu ³⁺ in deionized water and mix in a molar ratio of 15:1-23:1, add N-(2-hydroxyethyl) ethylenediamine with an equimolar amount of cation in the mixed solution -N,N',N'-triacetic acid, then add sodium fluoride; moles of the N-(2-hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid and sodium fluoride The ratio is 1:15-50,

2) After the solution of step 1) is fully mixed, sodium ascorbate is added, and the mol ratio of N-(2-hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid and sodium ascorbate is 1:5-20; Adjust the pH of the solution to 7-9 to obtain an electrolyte;

3) at 40～100 ℃, the electrolytic solution obtained in step 2) is used as the electrolytic solution of the three-electrode system to carry out electrodeposition, and the deposition potential relative to the reference electrode is controlled to be 0.4V～2.0V, and the deposition time is ≥500s; After the end, the NaGdF ₄ :Eu ³⁺ film is obtained on the working electrode;

4) The NaGdF ₄ :Eu ³⁺ thin film prepared by electrodeposition is rinsed with deionized water and air-dried, annealed at 200-300° C. for 4-8 hours, then lowered to room temperature and taken out.

The invention also discloses another method for preparing the oriented NaGdF ₄ :Eu ³⁺ down-conversion thin film material by electrodeposition, which comprises the following steps:

1) Weigh Gd ³⁺ and Eu ³⁺ in deionized water and mix in a molar ratio of 15:1-23:1, add N-(2-hydroxyethyl) ethylenediamine with an equimolar amount of cation in the mixed solution -N,N',N'-trisodium triacetate, then add sodium fluoride or ammonium fluoride; the N-(2-hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid The molar ratio of trisodium to sodium fluoride or ammonium fluoride is 1:15-50,

2) After the solution of step 1) is fully mixed, add sodium ascorbate, and the molar ratio of N-(2-hydroxyethyl)ethylenediamine-N,N',N'-sodium triacetate and sodium ascorbate is 1:5-20 ; Adjust the pH of the solution to 7-9 to obtain an electrolyte;

3) at 40～100 ℃, the electrolytic solution obtained in step 2) is used as the electrolytic solution of the three-electrode system to carry out electrodeposition, and the deposition potential relative to the reference electrode is controlled to be 0.4V～2.0V, and the deposition time is ≥500s; After the end, the NaGdF ₄ :Eu ³⁺ film is obtained on the working electrode;

4) The NaGdF ₄ :Eu ³⁺ thin film prepared by electrodeposition is rinsed with deionized water and air-dried, annealed at 200-300° C. for 4-8 hours, then lowered to room temperature and taken out.

As a preferred solution of the present invention, the Gd ³⁺ and Eu ³⁺ are added in the form of oxides or salts. When they are added in the form of oxides, the oxides are first dissolved with acid and then configured into a mixed solution.

As a preferred solution of the present invention, in the step 2), sodium hydroxide solution and dilute nitric acid are used to adjust the pH of the solution.

As a preferred solution of the present invention, the three-electrode system uses ITO or FTO conductive glass as the working electrode, platinum electrode as the counter electrode, and silver/silver chloride electrode as the reference electrode.

Preferably, in the step 3), the deposition potential relative to the reference electrode is controlled to be 0.8-1.2V, and the deposition time is 1000-2000s.

The invention also proposes the oriented NaGdF ₄ :Eu ³⁺ down-conversion thin film material prepared by the method.

The present invention utilizes the electrodeposition method to prepare the NaGdF ₄ :Eu ³⁺ down-conversion fluorescent thin film material doped with europium ions. It is mild and is expected to be mass-produced and applied in photovoltaics, fluorescent lamps and plasma display fields.

Description of drawings

Fig. 1 is the X-ray diffractogram of the NaGdF ₄ :Eu ³⁺ film prepared by comparative example disodium EDTA;

Figure 2 shows the X-ray diffraction patterns of NaGdF ₄ :Eu ³⁺ obtained after different deposition times at 50°C and 0.4V and 1.0V deposition voltage;

Figure 3 shows the X-ray diffraction patterns of NaGdF ₄ :Eu ³⁺ obtained by depositing at different temperatures for 1000s under deposition voltages of 0.4V and 1.0V;

Figure 4 shows the field emission scanning electron microscope images of NaGdF ₄ :Eu ³⁺ obtained by depositing NaGdF 4 :Eu 3+ at different temperatures for 1000s under deposition voltages of 0.4V and 1.0V;

Figure 5 is the down-conversion fluorescence emission diagram of NaGdF ₄ :Eu ³⁺ obtained under deposition voltages of 0.4V and 1.0V;

Table 1 shows the down-conversion fluorescence quantum yield and fluorescence lifetime of NaGdF ₄ :Eu ³⁺ under different deposition voltages.

Detailed ways

Example 1

1) Add 1 mmol N-(2-hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid to the aqueous solution prepared by mixing 0.95mmol Gd(NO ₃ ) ₃ and 0.05mmol Eu(NO ₃ ) ₃ , then add 40mmol sodium fluoride, add 10mmol sodium ascorbate after fully mixing, use 1M sodium hydroxide solution and dilute nitric acid to adjust the pH of the solution to 7-9 to obtain electrolyte;

2) At 70°C, with FTO conductive glass as the working electrode, platinum electrode as the counter electrode, and silver/silver chloride electrode as the reference electrode, a three-electrode system was formed, which was placed in the electrolyte for electrodeposition. The deposition potential of the silver chloride electrode is 1.0V, and the deposition time is 1000s;

3) The NaGdF ₄ :Eu ³⁺ thin film prepared by electrodeposition was rinsed with water and air-dried, placed in a muffle furnace, set to temperature program, annealed at 230° C. for 6 hours, then lowered to room temperature, and taken out.

Example 2

1) Add 1 mmol N-(2-hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid to the aqueous solution prepared by mixing 0.95mmol Gd(NO ₃ ) ₃ and 0.05mmol Eu(NO ₃ ) ₃ , then add 40mmol sodium fluoride, add 10mmol sodium ascorbate after fully mixing, use 1M sodium hydroxide solution and dilute nitric acid to adjust solution pH to 7-9, obtain electrolyte;

2) At 70°C, with FTO conductive glass as the working electrode, platinum electrode as the counter electrode, and silver/silver chloride electrode as the reference electrode, a three-electrode system was formed, which was placed in the electrolyte for electrodeposition. The deposition potential of the silver chloride electrode is 0.4V, and the deposition time is 1000s;

3) The NaGdF ₄ :Eu ³⁺ thin film prepared by electrodeposition was rinsed with water and air-dried, placed in a muffle furnace, set to temperature program, annealed at 230° C. for 6 hours, then lowered to room temperature, and taken out.

Example 3

1) Add 1 mmol N-(2-hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid to the aqueous solution prepared by mixing 0.95mmol Gd(NO ₃ ) ₃ and 0.05mmol Eu(NO ₃ ) ₃ , then add 40mmol sodium fluoride, add 10mmol sodium ascorbate after fully mixing, use 1M sodium hydroxide solution and dilute nitric acid to adjust the pH of the solution to 7-9 to obtain electrolyte;

2) At 50°C, with FTO conductive glass as the working electrode, platinum electrode as the counter electrode, and silver/silver chloride electrode as the reference electrode, a three-electrode system is formed, which is placed in the electrolyte for electrodeposition. The deposition potential of the silver chloride electrode is 1.0V, and the deposition time is 1000s;

3) The NaGdF ₄ :Eu ³⁺ thin film prepared by electrodeposition was rinsed with water and air-dried, placed in a muffle furnace, set to temperature program, annealed at 230° C. for 6 hours, then lowered to room temperature, and taken out.

Example 4

1) Add 1 mmol N-(2-hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid to the aqueous solution prepared by mixing 0.95mmol Gd(NO ₃ ) ₃ and 0.05mmol Eu(NO ₃ ) ₃ , then add 40mmol sodium fluoride, add 10mmol sodium ascorbate after fully mixing, use 1M sodium hydroxide solution and dilute nitric acid to adjust the pH of the solution to 7-9 to obtain electrolyte;

2) At 50°C, with FTO conductive glass as the working electrode, platinum electrode as the counter electrode, and silver/silver chloride electrode as the reference electrode, a three-electrode system is formed, which is placed in the electrolyte for electrodeposition. The deposition potential of the silver chloride electrode is 0.4V, and the deposition time is 1000s;

3) The NaGdF ₄ :Eu ³⁺ thin film prepared by electrodeposition was rinsed with water and air-dried, placed in a muffle furnace, set to temperature program, annealed at 230° C. for 6 hours, then lowered to room temperature, and taken out.

Example 5

1) Add 1 mmol N-(2-hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid to the aqueous solution prepared by mixing 0.95mmol Gd(NO ₃ ) ₃ and 0.05mmol Eu(NO ₃ ) ₃ , then add 40mmol sodium fluoride, add 10mmol sodium ascorbate after fully mixing, use 1M sodium hydroxide solution and dilute nitric acid to adjust the pH of the solution to 7-9 to obtain electrolyte;

2) At 50°C, with FTO conductive glass as the working electrode, platinum electrode as the counter electrode, and silver/silver chloride electrode as the reference electrode, a three-electrode system is formed, which is placed in the electrolyte for electrodeposition. The deposition potential of the silver chloride electrode is 1.0V, and the deposition time is 3000s;

3) The NaGdF ₄ :Eu ³⁺ thin film prepared by electrodeposition was rinsed with water and air-dried, placed in a muffle furnace, set to temperature program, annealed at 230° C. for 6 hours, then lowered to room temperature, and taken out.

Example 6

1) Add 1 mmol N-(2-hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid to the aqueous solution prepared by mixing 0.95mmol Gd(NO ₃ ) ₃ and 0.05mmol Eu(NO ₃ ) ₃ , then add 40mmol sodium fluoride, add 10mmol sodium ascorbate after fully mixing, use 1M sodium hydroxide solution and dilute nitric acid to adjust the pH of the solution to 7-9 to obtain electrolyte;

2) At 50°C, with FTO conductive glass as the working electrode, platinum electrode as the counter electrode, and silver/silver chloride electrode as the reference electrode, a three-electrode system is formed, which is placed in the electrolyte for electrodeposition. The deposition potential of the silver chloride electrode is 1.0V, and the deposition time is 500s;

3) The NaGdF ₄ :Eu ³⁺ thin film prepared by electrodeposition was rinsed with water and air-dried, placed in a muffle furnace, set to temperature program, annealed at 230° C. for 6 hours, then lowered to room temperature, and taken out.

Example 7

1) Add 1 mmol N-(2-hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid to the aqueous solution prepared by mixing 0.95mmol Gd(NO ₃ ) ₃ and 0.05mmol Eu(NO ₃ ) ₃ , then add 40mmol sodium fluoride, add 10mmol sodium ascorbate after fully mixing, use 1M sodium hydroxide solution and dilute nitric acid to adjust the pH of the solution to 7-9 to obtain electrolyte;

2) At 50°C, with FTO conductive glass as the working electrode, platinum electrode as the counter electrode, and silver/silver chloride electrode as the reference electrode, a three-electrode system is formed, which is placed in the electrolyte for electrodeposition. The deposition potential of the silver chloride electrode is 0.4V, and the deposition time is 500s;

3) The NaGdF ₄ :Eu ³⁺ thin film prepared by electrodeposition was rinsed with water and air-dried, placed in a muffle furnace, set to temperature program, annealed at 230° C. for 6 hours, then lowered to room temperature, and taken out.

Example 8

1) Add 1 mmol N-(2-hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid to the aqueous solution prepared by mixing 0.95mmol Gd(NO ₃ ) ₃ and 0.05mmol Eu(NO ₃ ) ₃ , then add 40mmol sodium fluoride, add 10mmol sodium ascorbate after fully mixing, use 1M sodium hydroxide solution and dilute nitric acid to adjust the pH of the solution to 7-9 to obtain electrolyte;

2) At 50°C, with FTO conductive glass as the working electrode, platinum electrode as the counter electrode, and silver/silver chloride electrode as the reference electrode, a three-electrode system is formed, which is placed in the electrolyte for electrodeposition. The deposition potential of the silver chloride electrode is 0.4V, and the deposition time is 3000s;

3) The NaGdF ₄ :Eu ³⁺ thin film prepared by electrodeposition was rinsed with water and air-dried, placed in a muffle furnace, set to temperature program, annealed at 230° C. for 6 hours, then lowered to room temperature, and taken out.

Comparative Example (Disodium EDTA)

1) Add 1 mmol disodium EDTA to the aqueous solution configured with 0.95 mmol Gd(NO ₃ ) ₃ and 0.05 mmol Eu(NO ₃ ) ₃ , then add 40 mmol sodium fluoride, add 10 mmol sodium ascorbate after thorough mixing, Use 1M sodium hydroxide solution and dilute nitric acid to adjust the pH of the solution to 7-9 to obtain an electrolyte;

2) At 50°C, with FTO conductive glass as the working electrode, platinum electrode as the counter electrode, and silver/silver chloride electrode as the reference electrode, a three-electrode system is formed, which is placed in the electrolyte for electrodeposition. The deposition potential of the silver chloride electrode is 1.0V, and the deposition time is 1000s;

3) The NaGdF ₄ :Eu ³⁺ thin film prepared by electrodeposition was rinsed with water and air-dried, placed in a muffle furnace, set to temperature program, annealed at 230° C. for 6 hours, then lowered to room temperature, and taken out.

Table 1 shows the NaGdF ₄ :Eu ³⁺ down-converted fluorescence quantum yield and fluorescence lifetime of Examples 1 and 2 at different deposition voltages. Films deposited at 1.0 V have longer fluorescence lifetimes and quantum yields, mainly due to their (110) orientation.

Table 1

Fig. 1 is the X-ray diffraction pattern of the NaGdF ₄ :Eu ³⁺ thin film prepared by disodium EDTA in the comparative example; Fig. 2a is the deposition of 3000s, 1000s, 500s under the condition of 1.0V from top to bottom at 50°C The XRD pattern of the prepared NaGdF ₄ :Eu ³⁺ , Figure 2b is the XRD pattern of the NaGdF ₄ :Eu ³⁺ prepared by depositing 3000s, 1000s, 500s under the condition of 0.4V from top to bottom, the film as a whole has (110 ) orientation, and the films deposited under the condition of 1.0V have better orientation. Figure 3a shows the XRD patterns of NaGdF ₄ :Eu ^{3 +} deposited at 90°C, 70°C and 50°C for 1000 s when the deposition voltage is 1.0V from top to bottom, and Figure 3a shows the deposition voltage from top to bottom At 0.4V, the XRD patterns of NaGdF ₄ :Eu ³⁺ deposited at 90 ℃, 70 ℃ and 50 ℃ for 1000 s, and the films deposited at 1.0 V have better orientation. Figures 4a, c, and e are the field emission scanning electron microscope images of NaGdF ₄ :Eu ³⁺ deposited at 50°C, 70°C, and 90°C when the deposition voltage is 0.4 V, respectively; Figures 4b, d, and f are respectively The field emission scanning electron microscope images of NaGdF ₄ :Eu ³⁺ deposited at 50 ℃, 70 ℃ and 90 ℃ when the deposition voltage is 1.0V. The samples deposited at 0.4V were mainly fusiform or spherical particles, while the samples deposited at 1.0V were mainly prismatic, which consisted of smaller prisms. Figure 5 is the down-conversion fluorescence emission spectrum of the prepared NaGdF ₄ :Eu ³⁺ thin films when the deposition voltage is 0.4V and 1.0V. The emissions at 590 nm and 615 nm correspond to ⁵ D ₀ → ⁷ F ₁ and ⁵ D ₀ → ⁷ F ₂ transitions, respectively. Overall, the films deposited at 1.0 V exhibited stronger fluorescence emission.

It can be seen from the figure that the films prepared by the method of the comparative example have no good orientation, and the (100), (110), (101), (201), (211) and (111) orientations are all distributed, while Under the same conditions, the film prepared by the method of the present invention basically has only the (110) orientation peak, mainly because of the unique complex of N-(2-hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid and gadolinium ion. Due to the combined characteristics, a large amount of gadolinium ions can be rapidly released during the electrodeposition process. It can be seen that the present invention is a good method for electrodeposition preparation of (110) oriented NaGdF ₄ :Eu ³⁺ down-conversion thin film materials.

The above-mentioned embodiments only represent several embodiments of the present invention, and the descriptions thereof are specific and detailed, but should not be construed as a limitation on the scope of the patent of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can also be made, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention should be subject to the appended claims.

Claims (2)

1. Method for preparing oriented NaGdF by adopting electrodeposition ₄ :Eu ³⁺ A method of down-converting a film material, comprising the steps of:

1) weighing Gd according to the molar ratio of 15:1-23:1 ³⁺ With Eu ³⁺ Adding the mixture into deionized water for mixing, adding N- (2-hydroxyethyl) ethylenediamine-N, N ', N' -triacetic acid with the molar quantity equal to that of cations into the mixed solution, and then adding sodium fluoride; the molar ratio of the N- (2-hydroxyethyl) ethylenediamine-N, N ', N' -triacetic acid to the sodium fluoride is 1:15-50, and the Gd is ³⁺ With Eu ³⁺ Adding the mixed solution in the form of oxide or salt, and when the mixed solution is added in the form of oxide, dissolving the oxide with acid to prepare a mixed solution;

2) fully mixing the solution obtained in the step 1), and adding sodium ascorbate, wherein the molar ratio of N- (2-hydroxyethyl) ethylenediamine-N, N ', N' -triacetic acid to the sodium ascorbate is 1: 5-20; adjusting the pH value of the solution to 7-9 by adopting a sodium hydroxide solution and dilute nitric acid to obtain an electrolyte;

3) performing electrodeposition by taking the electrolyte obtained in the step 2) as the electrolyte of a three-electrode system at the temperature of 40-100 ℃, controlling the deposition potential of 0.8-1.2V relative to a reference electrode, and performing deposition for 1000-2000 s; after the electrodeposition is finished, NaGdF is obtained on the working electrode ₄ :Eu ³⁺ A film; the three-electrode system takes ITO or FTO conductive glass as a working electrode, a platinum electrode as a counter electrode and a silver/silver chloride electrode as a reference electrode;

4) preparing the obtained NaGdF by electrodeposition ₄ :Eu ³⁺ The film is washed by deionized water and dried, annealed at the temperature of 200-300 ℃ for 4-8 hours, cooled to room temperature and taken out.

2. An oriented NaGdF prepared according to the method of claim 1 ₄ :Eu ³⁺ Down-converting the film material.

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