Ca3Sc2Si3O12: Ce < 3 + > / CQDs novel turquoise composite luminescent material and preparation method thereof

Abstract

The invention discloses a novel Ca3Sc2Si3O12: Ce < 3 + > / CQDs cyan green composite luminescent material, the composition of the luminescent material is Ca3Sc2Si3O12: Ce < 3 + > / CQDs, and Ca3Sc2Si3O12: Ce < 3 + > fluorescent powder and CQDs are subjected to chemical bonding to obtain the Ca3Sc2Si3O12: Ce < 3 + > cyan green composite luminescent material. The preparation technology of the composite luminescent material comprises the following steps: preparing Ca3Sc2Si3O12: Ce < 3 + > fluorescent powder by a sol-gel method, preparing green-light carbon dots CQDs by taking citric acid as a carbon source and urea as a nitrogen source through a one-step pyrolysis method, mixing the prepared Ca3Sc2Si3O12: Ce < 3 + > fluorescent powder with a CQDs solution, stirring for 1-4 hours in a beaker, putting into a reaction kettle, preserving heat for 8-16 hours in a drying oven at 120-180 DEG C, and centrifugally drying to obtain the Ca3Sc2Si3O12: Ce < 3 + > / CQDs cyan-green composite luminescent material. The composite luminescent material obviously improves the luminous intensity of the Ca3Sc2Si3O12: Ce < 3 + > fluorescent powder.

Description

Technical Field

[0001] The present invention relates to a Ca3Sc2Si3O 12 :Ce 3+ / CQDs (carbon quantum dots) composite luminescent material and its preparation technology. This composite material significantly improves the luminescence intensity of the Ca3Sc2Si3O 12 :Ce 3+ fluorescent material and belongs to the field of optoelectronic functional materials. Background Art

[0002] Rare earth luminescent materials have currently been widely used in different fields. Among them, Ca3Sc2Si3O 12 :Ce 3+ (CSS:Ce 3+ ) novel silicate garnet-phase phosphor combines the characteristics of a relatively large adjustable range of light color of silicate phosphors and the good matching of the garnet crystal field structure and the luminescence of Ce 3+ to become a luminescent material with excellent performance.

[0003] In the CSS:Ce 3+ cyan-green phosphor, Sc 3+ and Si 4+ partially replace Al 12 in Y3Al5O 3+ (YAG) to form a more flexible crystal field environment, enabling the luminescence peak of Ce 3+ to be adjusted to the green-yellow light range (500 - 580 nm). Its excitation spectrum covers the ultraviolet to blue light region (300 - 470 nm) and highly matches the emission wavelength of GaN-based LEDs (450–470 nm). In 2007, Yasuo Shimomura et al. discovered a novel silicate cyan-green phosphor CSS:Ce 3+ . This phosphor can emit high-brightness blue-green light under the excitation of 450 nm blue light, with a peak wavelength of 505 nm, and the fluorescence quenching amount of the phosphor at 150 °C is less than that of YAG:Ce 3+ . CSS-based fluorescent materials began to attract attention. In 2018, Swedish scientist Suchinder K compared the temperature dependence of the luminescence decay of three garnet-type fluorescent materials, CSS:Ce 3+ , Sr3Y2Ge3O 12 (SYG:Ce 3+ ) and YAG:Ce 3+ , and found that CSS:Ce 3+ has better thermal stability. Until 860 K, its decay time is almost constant, showing its excellent thermal stability.

[0004] Carbon quantum dots (CQDs) are a type of nanoparticles with a diameter less than 10 nm. In 2004, CQDs were first discovered by Xu et al. during the separation and purification of single-walled carbon nanotubes, which triggered subsequent research work. In 2006, Sun et al. prepared carbon nanoparticles with fluorescence properties by laser ablation of graphite powder and cement, and officially named them CQDs. Different from most semiconductor quantum dot materials, CQDs have low production costs, excellent optical stability, low toxicity, and chemical stability. Moreover, carbon dots have high fluorescence intensity and good stability after long-term storage. Therefore, carbon dots can be used to prepare multi-color LEDs, whether it is a single carbon dot matrix or a composite of carbon dots and other matrices can be used on LEDs.

[0005] Based on this, the present invention first prepared Ca3Sc2Si3O 12 :Ce 3+ fluorescent material by the sol-gel method, then prepared green carbon dots by a one-step pyrolysis method, and finally hydrothermally compounded Ca3Sc2Si3O 12 :Ce 3+ fluorescent material with CQDs to obtain a novel cyan-emitting material, and provided the preparation technology. Summary of the Invention

[0006] The present invention discovers a novel Ca3Sc2Si3O 12 :Ce 3+ / CQDs cyan composite luminescent material and preparation technology. The composition of the cyan composite luminescent material is Ca3Sc2Si3O 12 :Ce 3+ / CQDs, which is obtained by chemically bonding Ca3Sc2Si3O 12 :Ce 3+ phosphor and CQDs. The specific preparation process of the composite luminescent material is as follows: using calcium nitrate, scandium nitrate, cerium nitrate, citric acid, ethylene glycol, absolute ethanol, and TEOS (tetraethyl orthosilicate) as raw materials, the dosage of citric acid and ethylene glycol is 2-5 times that of metal ions. Mix and dissolve the raw materials, dry to obtain wet gel and dry gel. The dry gel is calcined in a muffle furnace at 500-800 °C for 2 h, ground evenly, and then kept in a high-temperature furnace C reducing atmosphere at 1200-1400 °C for 2-6 h to obtain cyan Ca3Sc2Si3O 12 :Ce 3+ fluorescent phosphor. Select citric acid as the carbon source and urea as the nitrogen source, and prepare green carbon dots by a one-step pyrolysis method. The prepared Ca3Sc2Si3O 12 :Ce 3+The fluorescent material is mixed with a 5 mg / ml CQDs solution and stirred in a beaker for 1 - 4 h. Then it is placed in a reaction kettle and kept in an oven at 120 - 180 °C for 8 - 16 h. After centrifugation and drying, Ca3Sc2Si3O 12 :Ce 3+ / CQDs composite luminescent materials are obtained. Carbon quantum dots have the characteristic of broad-spectrum absorption and can efficiently capture the energy of the excitation light. When the emission spectrum of CQDs matches the absorption spectrum of Ce 3+ (such as the 4f→5d transition), the energy can be transferred from CQDs to Ce 3+ through fluorescence resonance energy transfer (FRET), directly enhancing the excitation efficiency of Ce 3+ , thereby improving the luminescence performance of the Ca3Sc2Si3O 12 :Ce 3+ material. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 is the photoluminescence excitation spectrum diagram of the Ca3Sc2Si3O 12 :Ce 3+ fluorescent material sample synthesized in the present invention

[0008] Figure 2 is the photoluminescence emission spectrum diagram of the Ca3Sc2Si3O 12 :Ce 3+ fluorescent material sample synthesized in the present invention

[0009] Figure 3 is the photoluminescence excitation spectrum diagram of the CQDs material sample synthesized in the present invention

[0010] Figure 4 is the photoluminescence emission spectrum diagram of the CQDs material sample synthesized in the present invention

[0011] Figure 5 is the XRD diagram of the Ca3Sc2Si3O 12 :Ce 3+ / CQDs composite luminescent material sample synthesized in the present invention

[0012] Figure 6 is the photoluminescence excitation spectrum diagram of the Ca3Sc2Si3O 12 :Ce 3+ / CQDs composite luminescent material sample synthesized in the present invention

[0013] Figure 7 is the photoluminescence emission spectrum diagram of the Ca3Sc2Si3O 12 :Ce 3+ / CQDs composite luminescent material sample synthesized in the present invention DETAILED DESCRIPTION OF THE INVENTION

[0014] In the present invention, the Ca3Sc2Si3O 12 :Ce 3+ / CQDs composite luminescent material has the specific process described in detail as follows:

[0015] (1) Using citric acid and urea as raw materials, put them into an agate mortar according to the stoichiometric ratio, mix evenly, grind thoroughly, load the evenly ground powder into a crucible, and place it in a constant temperature drying oven at 180 - 240 °C for 2 - 6 h to obtain a black carbon dot precursor.

[0016] (2) Grind the black carbon dot precursor into powder in an agate mortar, add it to a centrifuge tube containing 100 ml of deionized water, centrifuge for 3 - 15 min, take the supernatant, filter it through a 0.22 - um microporous filter membrane to obtain a transparent CQDs solution. Put the CQDs solution into a pre - treated dialysis bag, place the loaded dialysis bag into a beaker containing deionized water, stir for 24 - 48 h, collect the liquid inside the dialysis bag, put this liquid into the refrigerator, freeze it into ice cubes, and freeze - dry it to obtain purified carbon dots.

[0017] (3) Prepare a 5 mg / ml CQDs solution, mix the prepared Ca3Sc2Si3O 12 :Ce 3+ fluorescent material with the CQDs solution, stir in a beaker for 1 - 4 h, and put the evenly mixed solution into a reaction kettle and keep it warm in an oven at 120 - 180 °C for 8 - 16 h. Take out the composite material, and obtain the Ca3Sc2Si3O 12 :Ce 3+ / CQDs composite luminescent material through centrifugation and drying.

[0018] Figure 1 is the photoluminescence excitation spectrum of the Ca3Sc2Si3O 12 :Ce 3+ fluorescent material sample synthesized in the present invention, which has the highest excitation peak at 450 nm.

[0019] Figure 2 is the photoluminescence emission spectrum of the Ca3Sc2Si3O 12 :Ce 3+ fluorescent material sample synthesized in the present invention, which has the highest emission peak at 505 nm under blue light excitation.

[0020] Figure 3 is the photoluminescence excitation spectrum of the CQDs material sample synthesized in the present invention, which has an excitation peak at 450 nm.

[0021] Figure 4It is the photoluminescence emission spectrum of the synthesized CQDs material sample of the present invention, which has the highest emission peak at 520 nm under blue light excitation.

[0022] Figure 5 is Ca3Sc2Si3O 12 :Ce 3+ / CQDs composite fluorescence material sample's XRD pattern, which is consistent with the diffraction peaks of the standard card PDF#74-1578, indicating that the CQDs composite will not affect the crystal structure of the Ca3Sc2Si3O 12 :Ce 3+ fluorescent material.

[0023] Figure 6 is the prepared Ca3Sc2Si3O 12 :Ce 3+ / CQDs composite fluorescence material's photoluminescence excitation spectrum, which has the highest excitation peak at 450 nm, also indicating that CQDs will not change the excitation peak of the Ca3Sc2Si3O 12 :Ce 3+ fluorescent material and significantly improve the luminescence of this material.

[0024] Figure 7 is the prepared Ca3Sc2Si3O 12 :Ce 3+ / CQDs composite fluorescence material's photoluminescence emission spectrum, which has the highest emission peak at 505 nm under blue light excitation, also indicating that CQDs will not change the emission peak of the Ca3Sc2Si3O 12 :Ce 3+ fluorescent material and significantly improve the luminescence of this material.

Claims

1. A novel Ca3Sc2Si3O 12 :Ce 3+ / CQDs turquoise composite luminescent material, and the composition of the luminescent material is Ca3Sc2Si3O 12 :Ce 3+ / CQDs, which is obtained by chemically bonding Ca3Sc2Si3O 12 :Ce 3+ phosphor and CQDs.

2. Based on Claim 1, the preparation technique of the composite luminescent material is to prepare Ca3Sc2Si3O 12 :Ce 3+ phosphor, using citric acid as the carbon source and urea as the nitrogen source, and preparing green carbon dots CQDs by one-step pyrolysis method. Mix the prepared Ca3Sc2Si3O 12 :Ce 3+ phosphor with the CQDs solution, stir in a beaker for 1 - 4 h, put it into a reaction kettle, keep it warm in an oven at 120 - 180 °C for 8 - 16 h, and obtain the Ca3Sc2Si3O 12 :Ce 3+ / CQDs cyan - green composite luminescent material through centrifugation and drying.

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