CN110420652B - NaYF4:Yb/Er@MoS2Core-shell structure micron crystal and preparation method thereof - Google Patents

Abstract

NaYF₄:Yb/Er@MoS₂The invention discloses a core-shell structure microcrystalline and a preparation method thereof, and relates to an up-conversion @ two-dimensional semiconductor material and a preparation method thereof. The NaYF of the invention₄:Yb/Er@MoS₂The core-shell structure of the microcrystalline is Yb³⁺、Er³⁺Double doped NaYF₄The micron crystal is taken as an inner core, and MoS is coated outside the inner core₂And (3) forming. Preparing a preparation method; mixing Na₂MoO₄·2H₂O、SC(NH₂)₂、H₂C₂O₄Adding into water to obtain a shell stock solution; then Yb is added³⁺、Er³⁺Double doped NaYF₄Adding the micron crystal into the shell layer stock solution for reaction, transferring the shell layer stock solution into a reaction kettle for hydrothermal reaction, cleaning and drying to obtain NaYF₄:Yb/Er@MoS₂Micron crystal with core-shell structure. The core-shell structure micron crystal structure is stable. Can be used in the field of photocatalysis.

Description

NaYF4:Yb/Er@MoS2Core-shell structure micron crystal and preparation method thereof

Technical Field

The invention relates to an up-conversion @ two-dimensional semiconductor material and a preparation method thereof.

Background

With the rapid development of economy, environmental pollution and energy crisis problems are receiving more and more attention. People strive to find clean renewable energy sources so as to achieve the purposes of protecting the environment and saving energy sources, solar energy, wind energy, biomass energy, hydrogen energy and the like are renewable energy sources, and the semiconductor photocatalysis technology capable of decomposing water into hydrogen provides a great potential direction for new energy sources of human beings. Factors influencing photocatalytic activity are: the band gap width and the energy band position of the semiconductor, the separation efficiency of photon-generated carriers, the spectral response range of the photocatalytic material and the like. The most commonly used photocatalytic material, TiO₂The band gap width is 3.2ev, the excitation wavelength is 387nm and is in an ultraviolet region, so that the hydrogen production by photocatalysis can be carried out only by absorbing ultraviolet light or ultraviolet rays in sunlight, and the photocatalysis efficiency is greatly limited. Upconverters have the property of converting near infrared light to ultraviolet and visible light, combining the low energy of two or more low energy near infrared photons, and "lifting" the excited electron to a desired levelThereby widening the spectral response range of the photocatalytic hydrogen generation catalyst to a near infrared region.

The combination of the current semiconductor material and the up-conversion luminescent material is generally simple physical mixing, the performance of a physically mixed sample depends on the uniformity degree of mixing, and in addition, the energy transmission efficiency between the two physically mixed substances is poor, so that the utilization rate of the product to sunlight is low.

Disclosure of Invention

The invention provides a NaYF to solve the technical problem of low sunlight utilization rate of a semiconductor and up-conversion composite material prepared by the existing physical mixing method₄:Yb/Er@MoS₂A core-shell structure micron crystal and a preparation method thereof.

The NaYF of the invention₄:Yb/Er@MoS₂The core-shell structure of the microcrystalline is Yb³⁺、Er³⁺Double doped NaYF₄The micron crystal is taken as an inner core, and MoS is coated outside the inner core₂Formed by NaYF₄:Yb³⁺/Er³⁺@MoS₂And (4) showing.

NaYF as described above₄:Yb/Er@MoS₂The preparation method of the core-shell structure micron crystal comprises the following steps:

firstly, mixing Na₂MoO₄·2H₂O、SC(NH₂)₂、H₂C₂O₄Adding the mixture into water, heating to 20-50 ℃, and stirring for 20-30 min to obtain a shell layer stock solution;

II, mixing Yb³⁺、Er³⁺Double doped NaYF₄Adding the micron crystals into the shell layer stock solution obtained in the step one, stirring and reacting for 0.6-0.8 h, transferring the reaction solution into a reaction kettle with a polytetrafluoroethylene lining, and sealing;

thirdly, placing the reaction kettle into a heating furnace, heating to 160-200 ℃, keeping for 24-48 h, cooling to room temperature, performing centrifugal separation, washing separated solid phase with ethanol, and drying to obtain NaYF₄:Yb/Er@MoS₂Micron crystal with core-shell structure.

The NaYF of the invention₄:Yb/Er@MoS₂Core-shell structure microcrystalIs a stable NaYF₄:Yb³⁺/Er³⁺@MoS₂Heterogeneous core-shell structure, such stable structure being MoS₂The semiconductor and the up-conversion luminescent material are combined more tightly, so that the infrared photon energy can be utilized more efficiently. It is an off-white powder.

Coated in Yb³⁺、Er³⁺Double doped NaYF₄Nanocrystalline-outside nano MoS₂The S-Mo-S coordination in the edge lattice can lead to unsaturated Mo and S atoms, resulting in MoS₂The edges create better photocatalytically active sites. Upconversion of microcrystals and MoS₂The NaYF is formed by combining a stable core-shell structure and the application of up-conversion microcrystals₄:Yb/Er@MoS₂The core-shell structure microcrystalline can more efficiently utilize infrared light energy, the utilization of sunlight is expanded to a near-infrared region, so that the energy supply is more sufficient, and meanwhile, the stable structure of the core and shell ensures that the energy converted from the up-conversion microcrystalline can be continuously transmitted to MoS₂Thereby improving the photocatalytic efficiency.

The invention combines the nanometer size MoS₂Orderly assembled to Yb by chemical bonds or other micro-nano acting forces³⁺、Er³⁺Double doped NaYF₄The micron crystal surface can not only improve the transmission of fluorescence resonance energy, but also effectively prevent the up-conversion micron crystal nucleus from being polluted and inactivated.

The invention overcomes NaYF₄:Yb³⁺/Er³⁺@MoS₂The core-shell structure is not easy to grow and form, and the sunlight utilization rate is difficult to improve, so that the core-shell structure is prepared and has stable structure.

Drawings

FIG. 1 is the NaYF obtained in step one of example 1₄:20％Yb³⁺/2％Er³⁺Scanning electron microscope photo of 3000 times of microcrystal;

FIG. 2 shows the NaYF obtained in step one of example 1₄:20％Yb³⁺/2％Er³⁺Scanning electron microscope photo of 10000 times of micron crystal;

FIG. 3 shows NaYF obtained in example 1₄:20％Yb³⁺/2％Er³⁺@MoS₂Scanning electron microscope photos of core-shell structure microcrystals;

FIG. 4 shows NaYF obtained in example 1₄:20％Yb³⁺/2％Er³⁺@MoS₂Element mapping diagram of core-shell structure micron crystal;

FIG. 5 shows NaYF obtained in example 1₄:20％Yb³⁺/2％Er³⁺@MoS₂EDS energy spectrogram of core-shell structure micron crystal;

FIG. 6 shows NaYF obtained in example 1₄:20％Yb³⁺/2％Er³⁺@MoS₂XRD spectrogram of core-shell structure micron crystal;

FIG. 7 is the NaYF prepared in step one of example 1₄:20％Yb³⁺/2％Er³⁺、NaYF₄:20％Yb³⁺/2％Er^{3 +}And MoS₂Direct physical mixing of sample and NaYF₄:20％Yb³⁺/2％Er³⁺@MoS₂An up-conversion fluorescence spectrogram of the core-shell structure microcrystal;

FIG. 8 is a NaYF prepared in example 2₄:20％Yb³⁺/2％Er³⁺@MoS₂A transmission electron microscope photo of the core-shell structure microcrystal;

FIG. 9 is a NaYF prepared in example 2₄:20％Yb³⁺/2％Er³⁺@MoS₂An up-conversion emission spectrogram of the core-shell structure microcrystal;

FIG. 10 is a NaYF prepared in example 3₄:10％Yb³⁺/1％Er³⁺@MoS₂EDS energy spectrogram of core-shell structure micron crystal;

FIG. 11 is a NaYF prepared in example 3₄:10％Yb³⁺/1％Er³⁺@MoS₂An up-conversion emission spectrogram of the core-shell structure microcrystal.

Detailed Description

The first embodiment is as follows: NaYF of the present embodiment₄:Yb/Er@MoS₂The core-shell structure of the microcrystalline is Yb³⁺、Er³⁺Double doped NaYF₄The micron crystal is taken as an inner core, and MoS is coated outside the inner core₂Formed with NaYF₄:Yb³⁺/Er³⁺@MoS₂And (4) showing.

The second embodiment is as follows: the present embodiment is different from the present embodiment in Yb³⁺、Er³⁺Double doped NaYF₄Medium of micron crystal of Yb³⁺The doped atomic percentage is 10 to 30 percent; er³⁺The doped atomic percentage is 1 to 3 percent; the rest is the same as the first embodiment.

The third concrete implementation mode: the present embodiment is different from the first or second embodiment in Yb³⁺、Er³⁺Double doped NaYF₄Micron crystal of NaYF₄:Yb³⁺/Er³⁺The material is hexagonal phase, and the size of micron crystal is 2-3 mu m; the other is the same as in the first or second embodiment.

The fourth concrete implementation mode: detailed description of the preferred embodiment₄:Yb/Er@MoS₂The preparation method of the core-shell structure micron crystal comprises the following steps:

firstly, mixing Na₂MoO₄·2H₂O、SC(NH₂)₂、H₂C₂O₄Adding the mixture into water, heating to 20-50 ℃, and stirring for 20-30 min to obtain a shell layer stock solution;

II, mixing Yb³⁺、Er³⁺Double doped NaYF₄Adding the micron crystals into the shell layer stock solution obtained in the step one, stirring and reacting for 0.6-0.8 h, transferring the reaction solution into a reaction kettle with a polytetrafluoroethylene lining, and sealing;

thirdly, placing the reaction kettle into a heating furnace, heating to 160-200 ℃, keeping for 24-48 h, cooling to room temperature, performing centrifugal separation, washing separated solid phase with ethanol, and drying to obtain NaYF₄:Yb/Er@MoS₂Micron crystal with core-shell structure.

The fifth concrete implementation mode: the fourth difference between this embodiment and the embodiment is that Na is added in the first step₂MoO₄·2H₂O、 SC(NH₂)₂And H₂C₂O₄The molar ratio of (1), (3-5), (0.3-1.5); the rest is the same as the fourth embodiment.

The sixth specific implementation mode: the fourth or fifth difference between this embodiment and the embodiment is Na in the first step₂MoO₄·2H₂The ratio of the amount of O substance to the volume of water is 1mmol (10-15) mL; the other is the same as the fourth or fifth embodiment.

The seventh embodiment: the difference between the fourth embodiment and the sixth embodiment is that the temperature in the third step is 60-80 ℃ and the drying time is 2-6 h; the other is the same as one of the fourth to sixth embodiments.

The specific implementation mode is eight: this embodiment is different from the fourth to seventh embodiments in that Yb described in the second step³⁺、Er³⁺Double doped NaYF₄The micron crystal is synthesized by a hydrothermal method, and the synthesis steps are as follows:

(1) weighing 0.0459-0.1377 g of Er₂O₃、0.2364～0.7092g Yb₂O₃、0.9560～1.3839g Y₂O₃Respectively placing the three rare earth nitrate solutions into 50ml clean beakers, adding a proper amount of distilled water, heating the beakers in an electric furnace, dropwise adding a nitric acid solution, stirring the nitric acid solution by using a glass rod, stopping dropwise adding the nitric acid solution after the solution in the beakers is gradually clarified, continuing heating and stirring the nitric acid solution, cooling the nitric acid solution to room temperature after redundant acid is evaporated, and then fixing the volume of the nitric acid solution to a 100ml volumetric flask to obtain three rare earth nitrate solutions;

(2) 30ml of Y (NO) was measured out separately₃)₃Solution, 16ml Yb (NO)₃)₃Solution, 8ml Er (NO)₃)₃Adding 42ml of distilled water into the solution in a 100ml volumetric flask for dilution to obtain a mixed rare earth nitrate solution;

(3) weighing 0.6299g NaF in a 50ml clean centrifuge tube, adding 30ml distilled water, and performing ultrasonic dissolution for later use;

(4) 8.8230g of trisodium citrate is weighed and put into a 100ml beaker, and the beaker is transferred into a 100ml volumetric flask for dissolving and fixing the volume for standby;

(5) adding 4ml of sodium citrate solution and 6ml of mixed rare earth nitrate solution into a clean beaker containing magnetons, stirring for 20min on a magnetic stirrer, adding 28.8ml of prepared sodium fluoride solution, and continuing stirringStirring for 30min, placing the reaction solution into polytetrafluoroethylene lining, placing into a reaction kettle, performing hydrothermal reaction at 180 deg.C for 24 hr, centrifuging, and washing with ethanol for 3 times to obtain NaYF₄:(10～30)Yb³⁺/(1～3)Er³⁺；

The other is the same as one of the fourth to sixth embodiments.

The following examples are used to demonstrate the beneficial effects of the present invention:

example 1: NaYF of the embodiment₄:Yb/Er@MoS₂The preparation method of the core-shell structure micron crystal comprises the following steps:

one, hydrothermal synthesis of Yb³⁺、Er³⁺Double doped NaYF₄Micron crystal NaYF₄:20％Yb³⁺/2％Er³⁺: the method comprises the following specific steps:

(1) weighing 0.0918g Er₂O₃、0.4728g Yb₂O₃、1.1291g Y₂O₃Respectively placing the three rare earth nitrate solutions into 50ml clean beakers, adding a proper amount of distilled water, heating the beakers in an electric furnace, dropwise adding a nitric acid solution, stirring the nitric acid solution by using a glass rod, stopping dropwise adding the nitric acid solution after the solution in the beakers is gradually clarified, continuing heating and stirring the nitric acid solution, cooling the nitric acid solution to room temperature after redundant acid is evaporated, and then fixing the volume of the nitric acid solution to a 100ml volumetric flask to obtain three rare earth nitrate solutions;

(2) 30ml of Y (NO) was measured out separately₃)₃Solution, 16ml Yb (NO)₃)₃Solution, 8ml Er (NO)₃)₃Adding the solution into a 100ml volumetric flask, and adding 42ml of distilled water for dilution to obtain a mixed rare earth nitrate solution;

(3) weighing 0.6299g NaF, adding into a 50ml clean centrifuge tube, adding 30ml distilled water, and performing ultrasonic dissolution for later use;

(4) 8.8230g of trisodium citrate is weighed and put into a 100ml beaker, and the beaker is transferred into a 100ml volumetric flask for dissolving and fixing the volume for standby;

(5) adding 4ml of sodium citrate solution and 6ml of mixed rare earth nitrate solution into a clean beaker with magnetons, stirring for 20min on a magnetic stirrer, adding 28.8ml of prepared sodium fluoride solution, continuing stirring for 30min, and adding the mixture into the clean beakerThe reaction solution is put into a polytetrafluoroethylene inner liner and is put into a reaction kettle for hydrothermal reaction for 24 hours at the temperature of 180 ℃, centrifugal separation is carried out, and 3 times of washing is carried out by ethanol to obtain Yb³⁺、Er³⁺Double doped NaYF₄Microcrystalline, noted NaYF₄:20％Yb³⁺/2％Er³⁺；

Weighing 0.72g of Na₂MoO₄·2H₂O、0.96g SC(NH₂)₂、0.22g H₂C₂O₄Adding into 30mL deionized water, placing on a magnetic stirrer, heating to 30 deg.C, and stirring for 20min to obtain shell stock solution;

thirdly, 0.205g of NaYF prepared in the first step₄:20％Yb³⁺/2％Er³⁺Adding the micron crystals into the shell stock solution obtained in the second step, stirring and reacting at room temperature for 0.8h, transferring the reaction solution into a reaction kettle with a volume of 50mL and a polytetrafluoroethylene lining, and sealing;

fourthly, placing the reaction kettle into a blast drying oven, heating to 180 ℃ and keeping for 30 hours, after the reaction is finished, naturally cooling the reaction kettle to room temperature, removing supernatant, adding 10ml of ethanol into bottom-layer solid for centrifugal separation, washing separated solid-phase substances for 3 times by using ethanol, adding washed samples into 5ml of ethanol, and placing the samples into a 60 ℃ drying oven for drying for 2 hours to obtain NaYF₄:20％Yb^{3 +}/2％Er³⁺@MoS₂Micron crystal with core-shell structure.

The NaYF obtained in step one of this embodiment₄:20％Yb³⁺/2％Er³⁺The SEM image of 3000 times of micron crystal is shown in FIG. 1, NaYF₄:20％Yb³⁺/2％Er³⁺The scanning electron micrograph of the microcrystal is 10000 times as shown in figure 2. As can be seen from FIGS. 1 and 2, the NaYF prepared₄:20％Yb³⁺/2％Er³⁺The micron crystal is hexagonal and flaky, has clean surface, no impurity and high crystallization degree.

NaYF obtained in this example₄:20％Yb³⁺/2％Er³⁺@MoS₂The core-shell structure microcrystal is off-white powder, and its scanning electron microscope image is shown in FIG. 3As shown in FIG. 3, the NaYF core-shell structure₄:20％Yb³⁺/2％Er³⁺@MoS₂Surface roughness of the microcrystals, indicating MoS₂Hexagonal phase NaYF deposited on the surface of crystal nucleus₄:20％Yb³⁺/2％Er³⁺@MoS₂The crystallite size was about 2.4 μm.

NaYF obtained in this example₄:20％Yb³⁺/2％Er³⁺@MoS₂The mapping diagram of the elements of the core-shell structure microcrystal is shown in FIG. 4, the mapping diagram comprises Mo, S, F, Y, Na, Yb and Er elements, as can be seen from FIG. 4, Mo and S signals appear on the hexagonal flaky surface, and MoS is also confirmed₂Deposited on NaYF₄:20％Yb³⁺/2％Er³⁺A microcrystalline surface. The Na, Y and F elements have very strong signals and are hexagonal and completely consistent with the result of a scanning electron microscope. The same uniform dispersion of the Yb and Er signals also appears in the figure, indicating that Yb and Er have been uniformly doped into NaYF₄In the crystal lattice.

NaYF obtained in this example₄:20％Yb³⁺/2％Er³⁺@MoS₂The EDS energy spectrum of the core-shell structure microcrystalline element is shown in FIG. 5, and as can be seen from FIG. 5, Na, Y, F, Yb, Er, Mo and S signal peaks exist in the core-shell structure particles, and the correlation with the element mapping result proves that a stable NaYF is successfully grown₄:20％Yb³⁺/2％Er³⁺@MoS₂A core-shell structure.

NaYF obtained in this example₄:20％Yb³⁺/2％Er³⁺@MoS₂The XRD spectrum of the core-shell structure micro-crystal is shown in FIG. 6, and it can be seen from FIG. 6 that very strong diffraction peaks appear at 16 °, 31 °, 34 °, 39 °, 43 °, 53 °, 71 °, 78 °, and NaYF₄The standard spectrogram (JCPDS:16-0344) has very high goodness of fit, which indicates that NaYF₄:20％Yb³⁺/2％Er³⁺The crystal nuclei have a very high degree of crystallization. Diffraction peaks at 15 DEG and 33 DEG are standard MoS₂Correspondingly, the formation of stable NaYF was confirmed₄:20％Yb³⁺/2％Er³⁺@MoS₂A core-shell structure.

The NaYF prepared by the step one₄:20％Yb³⁺/2％Er³⁺，NaYF₄:20％Yb³⁺/2％Er³⁺And MoS₂Direct physical mixing of samples and NaYF obtained in this example₄:20％Yb³⁺/2％Er³⁺@MoS₂Performing upconversion fluorescence spectrum test on core-shell structure microcrystal, wherein a test light source is 1W/cm²The obtained spectrum of 980nm laser is shown in FIG. 7, NaYF₄:20％Yb³⁺/2％Er³⁺The spectral curve of (A) is shown in curve a, from which it can be seen that NaYF₄:20％Yb³⁺/2％Er³⁺The up-conversion fluorescence of (1) comprises 3 strong emission spectrum peaks respectively positioned at 525nm, 540nm and 660nm and respectively corresponding to Er³⁺Of ions²H_11/2→⁴I_15/2、⁴S_3/2→⁴I_15/2And⁴F_9/2→⁴I_15/2is detected.

NaYF₄:20％Yb³⁺/2％Er³⁺And MoS₂The spectral curve of the sample with direct physical mixing is shown as b, from which it can be seen that only 20% of the green emission is MoS₂And (4) absorbing.

Coating MoS₂After the shell is formed, the NaYF is obtained₄:20％Yb³⁺/2％Er³⁺@MoS₂The spectrum curve of the core-shell structure microcrystal is shown as c, and NaYF can be seen from the curve c₄:Yb/Er@MoS₂The position of an emission peak of the core-shell structure microcrystal is not changed, and the fluorescence emission intensity is obviously changed. NaYF₄:Yb³⁺,Er³⁺@MoS₂The core-shell structure particles have stronger absorption and conversion effects on 525nm and 540nm green emitted light, and the intensity of the green emitted light is about 60 percent of the photon energy of MoS₂The absorption of the shell layer leads to the great reduction of the spectral intensity, thereby knowing the NaYF of the core-shell structure₄:Yb/Er@MoS₂The core-shell structure microcrystal has more excellent light conversion performance.

Example 2: NaYF of the embodiment₄:20％Yb³⁺/2％Er³⁺@MoS₂The preparation method of the core-shell structure micron crystal comprises the following steps:

synthesis of Yb by hydrothermal method in the same manner as in example 1³⁺、Er³⁺Double doped NaYF₄Micron crystal NaYF₄:20％Yb³⁺/2％Er³⁺；

Weighing 0.48g of Na₂MoO₄·2H₂O、0.68g SC(NH₂)₂、0.14g H₂C₂O₄Adding into 30mL deionized water, placing on a magnetic stirrer, heating to 30 deg.C, and stirring for 30min to obtain shell stock solution;

thirdly, 0.205g of NaYF prepared in the first step₄:20％Yb³⁺/2％Er³⁺Adding the micron crystals into the shell stock solution obtained in the second step, stirring and reacting at room temperature for 0.6h, transferring the reaction solution into a reaction kettle with a volume of 50mL and a polytetrafluoroethylene lining, and sealing;

fourthly, placing the reaction kettle into a blast drying oven, heating to 200 ℃ and keeping for 24 hours, after the reaction is finished, naturally cooling the reaction kettle to room temperature, removing supernatant, adding 10ml of ethanol into bottom-layer solid for centrifugal separation, washing separated solid-phase substances for 3 times by using ethanol, adding washed samples into 10ml of ethanol, and placing the samples into an oven at 80 ℃ for drying for 2 hours to obtain NaYF₄:20％Yb^{3 +}/2％Er³⁺@MoS₂Micron crystal with core-shell structure.

NaYF prepared in this example₄:20％Yb³⁺/2％Er³⁺@MoS₂The transmission electron micrograph of the core-shell structure microcrystal is shown in FIG. 8, and it can be seen from FIG. 8 that the microcrystal is hexagonal and is hexagonal NaYF₄:20％Yb³⁺/2％Er³⁺Surface deposition of MoS₂The surface of the microcrystal is rough.

NaYF prepared in this example₄:20％Yb³⁺/2％Er³⁺@MoS₂The up-conversion emission spectrogram of the core-shell structure microcrystal is shown in FIG. 9, and as can be seen from FIG. 9, the prepared NaYF₄:20％Yb³⁺/2％Er³⁺@MoS₂Sample laser at 980nmUnder the excitation of a light source, 3 up-conversion fluorescence emission spectrum peaks are generated, namely green light of 525nm and 540nm and red light of 660nm, the intensity of the green light generation peak is 107, and the result is matched with the result of example 1, which shows that the patented method can prepare MoS (MoS) which converts infrared light into visible light region₂The shell layer absorbs and utilizes high-performance materials, and can be applied to the field of photocatalysis.

Example 3: NaYF of the embodiment₄:10％Yb³⁺/1％Er³⁺@MoS₂The preparation method of the core-shell structure micron crystal comprises the following steps:

one, hydrothermal synthesis of Yb³⁺、Er³⁺Double doped NaYF₄Micron crystal NaYF₄:10Yb³⁺/1Er³⁺The preparation method comprises the following steps:

(1) 0.0459g Er is weighed₂O₃、0.2364g Yb₂O₃、1.2884g Y₂O₃Respectively placing the mixture into 50ml clean beakers, adding a proper amount of distilled water, heating the mixture on an electric furnace until the mixture is heated, dropwise adding a nitric acid solution, stirring the mixture by using a glass rod, stopping dropwise adding the nitric acid solution after the solution in the beakers is gradually clarified, continuing heating and stirring the mixture, cooling the mixture to room temperature after redundant acid is evaporated, and then fixing the volume to a 100ml volumetric flask to obtain three rare earth nitrate solutions;

(2) 30ml of Y (NO) was measured out separately₃)₃Solution, 16ml Yb (NO)₃)₃Solution, 8ml Er (NO)₃)₃Adding 42ml of distilled water into the solution in a 100ml volumetric flask for dilution to obtain a mixed rare earth nitrate solution;

(3) weighing 0.6299g NaF in a 50ml clean centrifuge tube, adding 30ml distilled water, and performing ultrasonic dissolution for later use;

(4) 8.8230g of trisodium citrate is weighed and put into a 100ml beaker, and the beaker is transferred into a 100ml volumetric flask for dissolving and fixing the volume for standby;

(5) adding 4ml of sodium citrate solution and 6ml of mixed rare earth nitrate solution into a clean beaker with magnetons, stirring for 20min on a magnetic stirrer, adding 28.8ml of prepared sodium fluoride solution, continuing stirring for 30min, and filling the reaction solution into a polytetrafluoroethylene liningAdding into a reaction kettle, performing hydrothermal reaction at 180 deg.C for 24 hr, centrifuging, washing with ethanol for 3 times to obtain Yb³⁺、Er³⁺Double doped NaYF₄Microcrystalline, noted NaYF₄:10Yb³⁺/1Er³⁺；

Weighing 1.21g of Na₂MoO₄·2H₂O，1.14g SC(NH₂)₂，0.27g H₂C₂O₄Adding into 30mL deionized water, placing on a magnetic stirrer, heating to 30 deg.C, and stirring for 30min to obtain shell stock solution;

thirdly, 0.205g of NaYF prepared in the first step₄:10％Yb³⁺/1％Er³⁺Adding the micron crystals into the shell stock solution obtained in the second step, stirring and reacting at room temperature for 0.7h, transferring the reaction solution into a reaction kettle with a volume of 50mL and a polytetrafluoroethylene lining, and sealing;

fourthly, placing the reaction kettle into a blast drying oven, heating to 190 ℃ and keeping for 24 hours, after the reaction is finished, naturally cooling the reaction kettle to room temperature, removing supernatant, adding 10ml of ethanol into bottom-layer solid for centrifugal separation, washing separated solid-phase substances for 3 times by using ethanol, adding washed samples into 10ml of ethanol, and placing the samples into a 70 ℃ drying oven for drying for 2 hours to obtain NaYF₄:10％Yb^{3 +}/1％Er³⁺@MoS₂Micron crystal with core-shell structure.

NaYF prepared in this example₄:10％Yb³⁺/1％Er³⁺@MoS₂An EDS energy spectrum of the core-shell structure microcrystal is shown in FIG. 10, and it can be seen from FIG. 10 that Na, Y, F, Yb, Er, Mo and S signal peaks exist in the core-shell structure particles.

NaYF prepared in this example₄:10％Yb³⁺/1％Er³⁺@MoS₂The up-conversion emission spectrogram of the core-shell structure microcrystal is shown in FIG. 11, and as can be seen from FIG. 11, the prepared NaYF₄:10％Yb³⁺/1％Er³⁺@MoS₂The sample generates 3 up-conversion fluorescence emission spectrum peaks under the excitation of 980nm laser light source, which are respectively green light of 525nm and 540nm and red light of 660nm, and the green light generates peaksThe strength was about 100, which is slightly weaker than the sample prepared in example 1, since only 10% Yb was doped in the core³⁺And 1% Er³⁺Ions, causing the nucleus to luminesce itself less than the NaYF₄:20％Yb³⁺/2％Er³⁺Crystal nuclei, but from the viewpoint of emission peak position and intensity of up-conversion fluorescence, it was also confirmed that the material prepared by this method is capable of converting infrared light into visible green light and is MoS₂The shell layer is absorbed and utilized, and has great potential in the application field of photocatalysis.

Claims (6)

1. NaYF₄:Yb/Er@MoS₂The core-shell structure micron crystal is characterized in that the micron crystal is Yb³⁺、Er³⁺Double doped NaYF₄The micron crystal is taken as an inner core, and MoS is coated outside the inner core₂The structure is as follows; in which Yb is expressed³⁺、Er³⁺Double doped NaYF₄Micron crystal of NaYF₄:Yb³⁺/Er³⁺The hexagonal phase and the micron crystal size of the hexagonal phase are 2-3 mu m.

2. The NaYF of claim 1₄:Yb/Er@MoS₂A core-shell structure of a microcrystalline characterized by being Yb³⁺、Er³⁺Double doped NaYF₄Medium of micron crystal of Yb³⁺The doped atomic percentage is 10 to 30 percent; er³⁺The doped atomic percentage is 1 to 3 percent.

3. Preparing a NaYF according to claim 1₄:Yb/Er@MoS₂The method for preparing the core-shell structure microcrystal is characterized by comprising the following steps of:

firstly, mixing Na₂MoO₄·2H₂O、SC(NH₂)₂、H₂C₂O₄Adding the mixture into water, heating to 20-50 ℃, and stirring for 20-30 min to obtain a shell layer stock solution;

II, mixing Yb³⁺、Er³⁺Double doped NaYF₄Adding the micron crystals into the shell layer stock solution obtained in the step one, stirring and reacting for 0.6-0.8 h, and transferring the reaction solution to a beltSealing the reaction kettle with the polytetrafluoroethylene lining;

thirdly, placing the reaction kettle into a heating furnace, heating to 160-200 ℃, keeping for 24-48 h, cooling to room temperature, performing centrifugal separation, washing separated solid phase with ethanol, and drying to obtain NaYF₄:Yb/Er@MoS₂Micron crystal with core-shell structure.

4. The NaYF of claim 3₄:Yb/Er@MoS₂The preparation method of the core-shell structure microcrystal is characterized in that Na in the step one₂MoO₄·2H₂O、SC(NH₂)₂And H₂C₂O₄The molar ratio of (1), (3-5), (0.3-1.5).

5. The NaYF of claim 3 or 4₄:Yb/Er@MoS₂The preparation method of the core-shell structure microcrystal is characterized in that Na in the step one₂MoO₄·2H₂The ratio of the amount of O to the volume of water is 1mmol (10-15) mL.

6. The NaYF of claim 3 or 4₄:Yb/Er@MoS₂The preparation method of the core-shell structure microcrystalline is characterized in that the drying temperature in the third step is 60-80 ℃, and the drying time is 2-6 h.

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