CN103074058B - Low-toxicity heat-sensitive quantum dot material and preparation method thereof - Google Patents

Abstract

A low-toxicity heat-sensitive quantum dot material and a preparation method thereof of the present invention belong to the technical field of semiconductor nanometer material preparation. The present invention takes Cu-doped InP quantum dots as the core, first coats the semiconductor material ZnS isolation layer, isolates the inner and outer layers of materials, then coats the semiconductor material InP nanocrystalline shell layer, and the outermost layer coats the ZnS protective layer, and finally forms Quantum dots with a structure of CuInP/ZnS/CdSe/ZnS. The quantum dots of the present invention are highly sensitive to temperature. They emit green light at room temperature, red light at 200°C, and yellow light in different degrees at intermediate temperatures. The quantum dots are stable in nature, uniform in size, good in dispersibility, and The particles are perfectly spherical after layer coating; since the preparation of the present invention is a non-cadmium semiconductor material, it has the advantage of low toxicity, conforms to the synthesis concept of green chemistry, is environmentally friendly, and has strong applicability.

Description

A kind of low toxicity thermosensitive quantum dot material and preparation method thereof

technical field

The invention belongs to the technical field of semiconductor nanomaterial preparation, and relates to a low-toxicity heat-sensitive quantum dot material and a synthesis method thereof. The quantum dot material is highly sensitive to temperature, and the specific performance is that the material emits light of different colors under different temperature conditions. Moreover, the material itself and its preparation process are low-toxic and environmentally friendly.

Background technique

After the semiconductor material is gradually reduced from the bulk phase to a certain critical size (1-20 nanometers), the volatility of the carriers becomes significant, and the movement will be limited, resulting in an increase in kinetic energy. The corresponding electronic structure is continuous from the bulk phase to The energy level structure becomes a quasi-split discontinuity, a phenomenon known as the quantum size effect. The more common semiconductor nanoparticles, that is, quantum dots, mainly include II-VI, III-V and IV-VI groups. These types of quantum dots are well obeyed by the quantum size effect, and their properties change regularly with the size, for example, the absorption and emission wavelengths change with the size. Therefore, semiconductor quantum dots have very important applications in the fields of lighting, displays, lasers, and bioluminescent labels.

The earliest research on colloidal quantum dots can be traced back to 1982, when the Brus group first reported the preparation and optical properties of water-soluble semiconductor quantum dots. Since then, some groups have successively carried out the preparation and property research of different types of semiconductor quantum dots. Colloidal nanoparticles are generally known as point, rod or core-shell quantum dots, which are all single quantum dot systems grown on a particle basis.

In the field of colloidal semiconductor nanometers, some research teams have devoted themselves to preparing composite quantum dot systems. In the early research, the most meaningful attempt was the CdS-HgS-CdS (MewsA.; Eychmueller, A.; Weller, H.J.Phys.Chem. 1994, 98, 934-4) system proposed by Mews et al. in 1994. They Through the method of surface ion exchange, a single or multi-layer HgS was successfully inserted between two layers of CdS, and an obvious red shift was observed in the absorption spectrum. However, the absorption spectrum is not enough to determine whether each layer of quantum dot system can Independently exhibit the desired electronic or optical properties. In addition, the composite particle system exhibits a single broad and weak emission peak when excited. Due to the imperfect synthesis technology at that time, although the proposal of this model is very meaningful, the synthesis effect of particles and layer-by-layer coating in literature reports is relatively poor.

Later, in 2005, the Peng group used the method of ion adsorption to grow a certain thickness of ZnS between the two layers of CdSe, and adjusted the thickness of the ZnS isolation layer to realize whether the properties of the inner and outer two-layer quantum dot systems were related. Experiments have shown that this ion adsorption growth technology can precisely control the growth level of each monolayer particle, so as to better regulate the overall shell thickness. Nanoparticles. In the CdSe-ZnS-CdSe system (David, B.; Bridgette B.; Peng XJAm.Chem.Soc.2005, 127, 10889-10897), the thickness of the ZnS shell can grow from one layer to five layers, and ZnS is thinner For example, when there are one or two layers, the absorption and emission peaks of the outer layer CdSe cannot be observed. After the ZnS isolation layer reaches three to four layers, the stronger CdSe emission peak of the outer layer will gradually appear, and at the same time, the peak position of the inner CdSe will not be affected. In summary, Peng's group used ZnS with a wide band gap as the material for the isolation layer, and by changing the thickness of the ZnS shell, composite nanoparticles with dual emission peaks can be obtained. Later, people studied Mn-doped colloidal semiconductor nanoparticles, such as Zn _1-x Mn _x Se/ZnCdSe system (Chih-Hao, H.; Anna, W.; Haw, Y.Acs Nano.2011,5(12), 9511-9522), also have dual emission peaks, and these emissions have a strong temperature dependence. When changing the temperature, the two emission peaks can appear alternately. This kind of material, which can adjust the temperature range of bimodal emission only by changing the growth conditions, has great development potential in optical temperature control sensors.

However, since people's research in this field mainly focuses on the construction of model theory and the discovery of new materials, but does not pay attention to the sensitivity of the heat-sensitive material itself and whether the temperature-changing color is obvious, etc., there are still many problems before the actual application. problem needs to be resolved urgently. Among them, the most important thing is that the change of luminous color caused by temperature change is not clear enough, there is no clear correspondence between temperature and color, and the temperature range span is small, only from red to yellow.

In addition, as mentioned in the above-mentioned background material, most of the previous studies on this dual-wavelength luminescent composite nanoparticle contain the toxic element cadmium. It is well known that cadmium and its compounds have daunting toxicity. Stimulation of the respiratory tract can cause chemical pneumonia. Cadmium compounds are not easily absorbed by the intestines, but can be absorbed by the body through breathing and accumulate in the liver or kidneys, causing damage, especially the most obvious damage to the kidneys, manifested as renal tubular recycling dysfunction. It can also lead to osteoporosis and softening, and severe cases can cause death.

Contents of the invention

The technical problem to be solved by the present invention is to overcome the deficiencies in the background technology and provide a reusable low-toxicity and cadmium-free thermostat whose color changes clearly with temperature and whose discoloration interval can change from green to yellow to red. Sensitive quantum dot materials.

Technical problem of the present invention can be solved by following technical scheme:

A low-toxicity heat-sensitive quantum dot material, which has a structure of InP quantum dot core, ZnS isolation layer, InP nanocrystalline shell layer and ZnS protective layer. Doped InP quantum dots, the Cu doping amount is Cu:P=1:5-20 in molar ratio, and the InP nano crystal shell layer is 2-4 layers of InP.

The doping amount of Cu is preferably Cu:P=1:10 in molar ratio; the ZnS isolation layer is 3-6 layers of ZnS, preferably 4 layers, and the ZnS protective layer is 1-4 layers of ZnS, preferably 2 layer.

A method for preparing a low-toxicity heat-sensitive quantum dot material, including the preparation of a Cu-doped InP quantum dot core solution, the coating of a ZnS isolation layer, the coating of an InP nanocrystalline shell layer, and the coating of a ZnS protective layer ;

In the preparation process of the InP quantum dot nucleus solution, first, indium acetate and myristic acid are added to octadecene, and the temperature is raised to 80-120° C., wherein the molar ratio of indium acetate to myristic acid is 1:3.5, ten The consumption of octacene is that every mole of indium acetate uses 25 liters; Under the protection of nitrogen, the temperature is raised to 188°C, and the octadecene solution of 3-(trimethylsilyl)phosphorus is injected into octylamine and concentration of 0.2mol/L, wherein The molar ratio of injected octylamine to indium acetate is 12:1, and the molar ratio of injected phosphorus to indium acetate is 1:2; the temperature is lowered to 178°C, kept for 30 minutes and then lowered to 60-100°C, and the injected concentration is 0.005～0.02mol/L octadecene solution of copper myristate, the amount of copper myristate is Cu:P=1:5～20 in molar ratio, the temperature is raised to 150°C and kept for 20～40 minutes to obtain Cu-doped Mixed InP quantum dots (referred to as CuInP) core solution;

The coating process of the ZnS isolation layer is as follows: firstly, the Cu-doped InP quantum dot core solution is maintained at 120-160° C., and the materials are fed according to the shell layer components; React at 220-260°C for 30-45 minutes, then inject a layer of sulfur anion precursor solution, and react for 30-45 minutes; then maintain 220-260°C, alternately inject a layer of zinc cation precursor solution and Sulfur anion precursor solution and each reaction for 30-45 minutes, 3-6 times in total to form 3-6 layers of ZnS isolation layer; then the reaction system was lowered to room temperature, and chloroform and ethanol with a volume ratio of 1:10 were added The mixed solvent makes the quantum dots precipitate, and then centrifuges to obtain the purified ZnS-coated Cu-doped InP nanocrystalline quantum dots (referred to as CuInP/ZnS);

The cladding process of described InP nanocrystal shell layer is, the Cu-doped InP nanocrystal quantum dot that will purify ZnS cladding is dispersed in octadecene; Use 1-2 liters of doped InP nanocrystalline quantum dots; heat up to 60-100°C, vacuumize and then heat up to 120-160°C under the protection of nitrogen, feed according to the shell composition, first add a layer of calculated amount of phosphorus Anion precursor solution, heat up to 180°C and react for 30-45 minutes, then inject a layer of calculated amount of indium cation precursor solution and react for 30-45 minutes; then maintain 180°C, alternately inject a layer of phosphorus anion precursor solution and indium cation precursor solution and each reaction for 30 to 45 minutes, a total of 2 to 3 times to form 2 to 3 layers of InP nanocrystalline shells, to obtain Cu-doped InP nanocrystals coated with ZnS and then coated with InP. Crystalline quantum dots (referred to as CuInP/ZnS/InP);

The coating process of the ZnS protective layer is as follows: firstly, the Cu-doped InP nanocrystalline quantum dot solution coated with ZnS and then coated with InP is maintained at 120-160 ° C, fed according to the shell layer components, and a layer of Calculate the amount of zinc cation precursor solution, heat up to 220-260°C for 30-45 minutes, then inject sulfur anion precursor solution for 30-45 minutes; after that keep 220-260°C, alternately inject a layer of zinc The cation precursor solution and the anion precursor solution of sulfur were reacted for 30 to 45 minutes each, and carried out 2 to 3 times in total to form 1 to 4 layers of ZnS protective layer; the final reaction system was cooled to room temperature, and the volume ratio of adding A 1:10 mixed solvent of chloroform and ethanol precipitated the quantum dots, and then centrifuged to obtain a purified low-toxicity heat-sensitive quantum dot material (referred to as CuInP/ZnS/InP/ZnS).

For all the coating processes in the present invention, when coating each layer, the calculation of the dosage of shell layer components can refer to the literature Chem.Mater.2010, 22, 1439.

In the preparation process of the Cu-doped InP quantum dot nucleus solution, the amount of copper myristate is preferably Cu:P=1:10 by molar ratio.

The coating process of the ZnS isolation layer is preferably carried out 4 times in total, and the coating process of the ZnS protective layer is preferably carried out 2 times in total.

The cation precursor solution of zinc is an octadecene solution of zinc stearate with a concentration of 0.5～1mol/L; the cation precursor solution of indium is that every mole of indium myristate is dissolved in 0.48 liters of three A solution obtained in a mixed solvent of butylphosphine and 0.52 liters of octadecene; the anion precursor solution of sulfur is an octadecene solution of elemental sulfur with a concentration of 0.5 to 1 mol/L; the anion precursor of phosphorus The solution is a solution obtained by dissolving 0.45 liter of octylamine and 0.55 liter of octadecene in a mixed solvent per mole of 3-(trimethylsilyl)phosphorus.

The present invention constructs core-shell quantum dots composed of different materials based on the energy band engineering theory. The ZnS material in the middle layer can effectively isolate the electron process of the inner and outer materials, so that they can emit light without mutual interference.

The thermosensitive material prepared by the invention belongs to the hydrophobic material, and the surface ligands are mainly long-chain alkyl carboxylic acids.

The heat-sensitive material prepared by the invention can be purified and dried to obtain a solid powder sample, and the luminescent color in the solid state will also change with temperature.

The heat-sensitive quantum dot material prepared by the invention has stable properties and can still change color with temperature after being placed for six months.

The heat-sensitive quantum dot material prepared by the invention can precisely control the thickness of each layer of material coating, and the particles after the shell layer coating are perfectly spherical, uniform in size and good in monodispersity.

The invention does not contain toxic heavy metals such as cadmium and mercury that are commonly present in semiconductor materials, is relatively environmentally friendly, and has strong potential applicability.

In summary, a heat-sensitive quantum dot material with a core-shell structure and a preparation method thereof of the present invention have the following beneficial effects:

1. The prepared material is sensitive to temperature, and the color changes with temperature clearly.

2. The prepared material has a wide range of color change. As the temperature changes from room temperature to 200°C, the color of the material will gradually change from green to red, and experience different degrees of yellow in the middle.

3. The prepared material is stable and reusable.

4. The color of the prepared material also changes with the temperature in the solid state.

5. The preparation method can precisely control the coating thickness of each layer of material. After the shell layer is coated, the particles are perfectly spherical, uniform in size and good in monodispersity.

6. The prepared materials and preparation process are strictly cadmium-free and mercury-free, with the advantage of low toxicity, in line with the synthesis concept of green chemistry, friendly to the environment, and have strong potential applications.

Description of drawings

Fig. 1 is the spectrograms of thermosensitive quantum dot materials with core-shell structure obtained in the order of Examples 2, 5, 7, 9, 11, 13 and 14 of the present invention at different temperatures.

Fig. 2 is a transmission electron micrograph of InP quantum dot particles prepared in Example 2, and the diameter of the particles is about 2nm.

Fig. 3 is a transmission electron micrograph of quantum dots of CuInP/ZnS structure prepared in the order of Examples 2, 5, and 7, and the particle diameter is about 4.5nm.

Fig. 4 is a transmission electron microscope photograph of CuInP/ZnS/InP/ZnS structure quantum dots prepared in the order of Examples 2, 5, 7, 9, 11, and 13, and the particle diameter is about 8nm.

Fig. 5 is a schematic structural view of a low-toxicity heat-sensitive quantum dot material of the present invention.

Detailed ways

Prepare various anion and cation precursor injection solutions: prepare Zn, In, S, P precursor injection solutions, mix 10 millimoles of zinc stearate and 20 ml of octadecene, vacuumize and heat to 200 Dissolve at ℃ to obtain a 0.5mol/L precursor injection solution; mix 10mmol of zinc stearate and 10ml of octadecene, vacuumize and heat to 200℃ with nitrogen to dissolve, and obtain a 1mol/L precursor injection solution solution; take 10 mmol of indium myristate, 4.8 liters of tributylphosphine and 5.2 liters of octadecene and mix them, vacuumize nitrogen and heat to 250 ° C to dissolve, and obtain a 1mol/L In precursor injection solution; take 10 mmol Sulfur powder and 20 milliliters of octadecene were mixed, vacuumed and heated to 140° C. to dissolve, and a 0.5 mol/L S precursor injection solution was obtained; 10 millimoles of sulfur powder and 10 milliliters of octadecene were mixed, pumped Vacuum nitrogen and heat to 140 ° C to dissolve, and prepare a 1mol/L S precursor injection solution; take 10 mmol of 3-(trimethylsilyl)phosphorus, 4.5 liters of octylamine and 5.5 liters of octadecene Mixed, evacuated and nitrogen gas heated to 50 ° C to dissolve, to obtain a 1mol/L P precursor injection solution. To prepare a doping solution of 0.005mol/LCu, take 0.05 mmol of copper myristate and mix it with 10 milliliters of octadecene, vacuumize and heat at 70°C with nitrogen to dissolve; to prepare a doping solution of 0.01mol/LCu, take 0.1 milliliters Mix one mole of copper myristate with 10 ml of octadecene, vacuumize and heat at 70°C with nitrogen to dissolve; prepare a 0.02 mol/LCu doping solution, mix 0.2 mmol of copper myristate with 10 ml of octadecene, pump Vacuum nitrogen and heat at 70°C to dissolve; in addition, prepare a 0.2 mol/L octadecene solution of 3-(trimethylsilyl)phosphorus in a glove box.

The specific implementation of each step of preparing the non-cadmium heat-sensitive quantum dot material will be described in detail below in four parts.

Part 1: Preparation of InP quantum dot nucleus solution (Example 1-3)

Example 1:

First, prepare InP quantum dots: Take 0.2 millimoles of indium acetate and 0.7 millimoles of myristic acid and add them to 5 milliliters of octadecene, heat up to 80 ° C, after vacuuming, heat up to 188 ° C under the protection of nitrogen, inject 0.5 In a milliliter concentration of 0.2mol/L 3-(trimethylsilyl) phosphorus octadecene solution and 1.2 mmol octylamine, after injection, naturally cool down to 178°C, keep the temperature at 178°C for 30 minutes to obtain InP quantum dots , the obtained InP quantum dots have a diameter of about 2nm.

Then, Cu doping is carried out: the prepared InP quantum dots are directly cooled to 60°C, and a total amount of 1 ml of octadecene solution of copper myristate with a concentration of 0.005mmol/L is dropped into the system, and then the temperature is raised to 150°C, keep the temperature for 20 minutes to get a Cu-doped InP quantum dot nucleus solution, the amount of Cu doped is Cu:P=1:20 by molar ratio.

Example 2:

First, prepare InP quantum dots: Take 0.2 millimoles of indium acetate and 0.7 millimoles of myristic acid and add them to 5 milliliters of octadecene, heat up to 100 ° C, after vacuuming, heat up to 188 ° C under the protection of nitrogen, inject 0.5 0.2 mol/L 3-(trimethylsilyl) phosphine octadecene solution and 1.2 mmol octylamine, after injection, naturally cool down to 178°C, keep the temperature at 178°C for 30 minutes to obtain InP quantum dots , the obtained InP quantum dots have a diameter of about 2nm.

Then, Cu doping is carried out: the prepared InP quantum dots are directly cooled to 80 ° C, and a total amount of 1 milliliter of octadecene solution of copper myristate with a concentration of 0.01 mmol/L is dropped into the system, and then the temperature is raised to 150°C, keep the temperature for 30 minutes to get a Cu-doped InP quantum dot nucleus solution, the amount of Cu doped is the molar ratio Cu:P=1:10.

Example 3:

First, prepare InP quantum dots: take 0.2 millimoles of indium acetate and 0.7 millimoles of myristic acid and add them to 5 milliliters of octadecene, heat up to 120 ° C, after vacuuming, heat up to 188 ° C under the protection of nitrogen, inject 0.5 0.2 mol/L 3-(trimethylsilyl) phosphine octadecene solution and 1.2 mmol octylamine, after injection, naturally cool down to 178°C, keep the temperature at 178°C for 30 minutes to obtain InP quantum dots , the obtained InP quantum dots have a diameter of about 2nm.

Then, Cu doping is carried out: the prepared InP quantum dots are directly cooled to 100° C., and a total amount of 1 milliliter of octadecene solution of copper myristate with a concentration of 0.02 mmol/L is dropped into the system, and then the temperature is raised to 150°C, keep the temperature for 40 minutes to get a Cu-doped InP quantum dot nucleus solution, the amount of Cu doped is Cu:P=1:5 by molar ratio.

The second part: coating ZnS isolation layer and purification (embodiments 4-7)

Example 4:

Maintain the Cu-doped InP quantum dot nuclear solution prepared in any one of Examples 1 to 3 to 120°C, calculate the required coating amount of the nuclear solution according to the feeding amount, and inject a layer with a concentration of 0.5mol/L Zn cation precursor solution, the reaction temperature was raised to 220° C. to grow the quantum dot shell for 45 minutes, and then a layer of S anion precursor solution with a concentration of 0.5 mol/L was injected, and the same reaction was performed for 45 minutes. Thereafter, the two precursor solutions were alternately injected at 220° C. and reacted for 45 minutes each to coat 3 layers in total. The dosages of the Zn and S precursor injection solutions are as follows: 0.24 milliliters, 0.4 milliliters, and 0.58 milliliters from the first to the third layer.

Example 5:

Maintain the Cu-doped InP quantum dot nuclear solution prepared in any one of Examples 1 to 3 to 140°C, calculate the required coating amount of the nuclear solution according to the feeding amount, and inject a layer with a concentration of 0.5mol/L Zn cation precursor solution, the reaction temperature was raised to 240° C. to grow the quantum dot shell for 40 minutes, and then a layer of S anion precursor solution with a concentration of 0.5 mol/L was injected, and the same reaction was performed for 40 minutes. Thereafter, the two precursor solutions were alternately injected at 240° C. and reacted for 40 minutes each to coat 4 layers in total. The dosages of Zn and S precursor injection solutions are as follows: 0.24 ml, 0.4 ml, 0.58 ml, 0.8 ml from the first to the fourth layer.

Embodiment 6:

Maintain the Cu-doped InP quantum dot nuclear solution prepared in any one of Examples 1 to 3 to 160°C, calculate the required coating amount of the nuclear solution according to the feeding amount, and inject a layer with a concentration of 0.5mol/L Zn cation precursor solution, the reaction temperature was raised to 260 ° C for 30 minutes to grow the quantum dot shell, and then injected a layer of S anion precursor solution with a concentration of 0.5 mol/L, and reacted for 30 minutes. Thereafter, the two precursor solutions were alternately injected at 260° C. and reacted for 30 minutes each to coat 6 layers in total. The dosages of Zn and S precursor injection solutions are: from the first layer to the sixth layer: 0.24 ml, 0.4 ml, 0.58 ml, 0.8 ml, 1 ml, 1.3 ml.

Embodiment 7:

The temperature of the quantum dot solution whose structure is CuInP/ZnS prepared in Examples 4-6 is lowered to room temperature, and a mixed solvent of 1 ml of chloroform and 10 ml of ethanol is added to precipitate the quantum dots, and then centrifuged at a speed of 4000 rpm for 20 Minutes, the purified CuInP/ZnS quantum dots were obtained.

The third part: coated InP nanocrystalline shell layer (Examples 8-9)

Embodiment 8:

Purify the quantum dots with core-shell structure prepared in any one of Examples 4 to 6 by the method of Example 7, and then disperse them into 5 ml of octadecene and put them into a three-necked flask, raise the temperature to 60° C., and pump Vacuum nitrogen was repeated three times, the temperature was raised to 120°C, a layer of P anion precursor solution with a calculated concentration of 1mol/L was added, the temperature was raised to 180°C to grow the shell for 45 minutes, and then In was injected with a concentration of 1mol/L. The cation precursor solution was also grown for 45 minutes, and then the anion and cation precursor solutions were alternately injected at 180°C and kept for 45 minutes each, and a total of 2 layers of InP materials were coated to obtain quantum dots with a structure of CuInP/ZnS/InP. The dosages of cation and anion precursor solutions are: from the first layer to the second layer: 0.53 milliliters, 0.68 milliliters.

Embodiment 9:

Purify the quantum dots with a core-shell structure prepared in any one of Examples 4 to 6 by the method of Example 7, and then disperse them in 5 ml of octadecene and put them into a three-necked flask, raise the temperature to 100° C., and pump Vacuum nitrogen was repeated three times, the temperature was raised to 160°C, the concentration of In and P precursor injection solution was 1mol/L, and a layer of calculated amount of P anion precursor solution was added, and the temperature was raised to 200°C to grow the shell for 30 minutes. Then inject a cation precursor solution of In with a concentration of 1mol/L, and grow for 30 minutes, and then keep 200°C to alternately inject anion and cation precursor solutions and keep for 30 minutes each, and a total of 3 layers of InP materials are coated, and the structure is obtained. Quantum dots of CuInP/ZnS/InP. The dosages of cation and anion precursor solutions are: from the first layer to the third layer: 0.53 milliliters, 0.68 milliliters, 0.85 milliliters.

Part 4: Coating ZnS protective layer and purification (Examples 10-13)

Example 10:

On the basis of the quantum dots with a core-shell structure prepared in Example 8 or 9, a layer of ZnS material is coated again to play a stabilizing effect, and the quantum dot solution with a core-shell structure prepared in Example 8 or 9 is maintained at 120 ° C. Add a layer of calculated amount of Zn cation precursor solution with a concentration of 1mol/L, heat up to 220°C to grow the shell for 45 minutes, and then inject a layer of calculated amount of S anion precursor solution with a concentration of 1mol/L, the same After growing for 45 minutes, a heat-sensitive quantum dot solution with a structure of CuInP/ZnS/InP/ZnS was obtained. The dosages of the cation and anion precursor solutions are both: 1 ml.

Example 11:

On the basis of the quantum dots with core-shell structure prepared in Example 8 or 9, coat 2 layers of ZnS materials to play a stabilizing effect, and use the precursor injection solution of Zn and S with a concentration of 1mol/L to convert Example 8 or 9. Maintain the quantum dot solution with core-shell structure at 140°C, add a layer of calculated amount of Zn cation precursor solution, raise the temperature to 260°C to grow the shell layer for 30 minutes, and inject a layer of calculated amount of S anion before body solution, also grow for 30 minutes, then maintain 260 ℃ and alternately inject cation and anion precursor solutions and keep each for 30 minutes, a total of 2 layers of InP materials are coated, and a heat-sensitive quantum dot solution with a structure of CuInP/ZnS/InP/ZnS is obtained . The dosages of the cation and anion precursor solutions are: from the first layer to the second layer: 1 milliliter, 1.2 milliliters.

Example 12:

On the basis of the quantum dots with core-shell structure prepared in Example 8 or 9, 4 layers of ZnS materials are coated to stabilize, and the concentration is 1mol/L. or 9. Maintain the quantum dot solution with core-shell structure at 140°C, add a layer of calculated amount of Zn cation precursor solution, raise the temperature to 260°C to grow the shell layer for 30 minutes, and inject a layer of calculated amount of S anion before body solution, also grown for 30 minutes, then kept at 260 °C and alternately injected cation and anion precursor solutions and kept for 30 minutes each, covering a total of 4 layers of InP materials to obtain a heat-sensitive quantum dot solution with a structure of CuInP/ZnS/InP/ZnS . The dosages of cation and anion precursor solutions are: from the first layer to the fourth layer: 1 milliliter, 1.2 milliliter, 1.4 milliliter, 1.7 milliliter.

Example 13:

The heat-sensitive quantum dot solution prepared by any one of Examples 10 to 12 with the structure CuInP/ZnS/InP/ZnS is cooled to room temperature, and a mixed solvent of 1 milliliter of chloroform and 10 milliliters of ethanol is added to precipitate the quantum dots, and then each Minute 4000 rotation speed centrifugation for 20 minutes, the purified low toxicity heat-sensitive quantum dot material with the structure of CuInP/ZnS/InP/ZnS can be obtained.

Example 14:

Dry the heat-sensitive quantum dot material solid sample with the structure of CuInP/ZnS/InP/ZnS precipitated in Example 13 in a vacuum oven to finally obtain a solid powder sample, and perform a temperature-variable fluorescence test to obtain a spectrum as shown in Figure 1. At 20°C, because the fluorescence quantum efficiency of the green-emitting InP nanocrystalline shell is much higher than that of the red-emitting core material CuInP, the overall material is green; since the InP nanocrystalline shell is thermally unstable Yes, as the temperature rises, the green light is gradually quenched. At 200 ° C, the green light is completely quenched, and the core material CuInP is thermally stable. As the temperature rises, the red light almost maintains the original efficiency, so when When the temperature reaches about 200°C, the overall material will completely display red light. At the intermediate temperature, the green light efficiency will decrease but not be completely quenched, and the overall material will show different degrees of yellow light.

Claims (7)

1. A low toxicity thermosensitive quantum dot material, its structure has InP quantum dot core, ZnS isolation layer, InP nanocrystalline shell and ZnS protective layer, and described InP quantum dot core is that the fluorescent peak position is 650nm～800nm For Cu-doped InP quantum dots, the Cu doping amount is Cu:P=1:5-20 in molar ratio, the InP nanocrystalline shell layer is 2-4 layers of InP; the ZnS isolation layer is 3-4 layers. 6 layers of ZnS, the ZnS protection layer is 1-4 layers of ZnS. 2. A kind of low-toxicity thermosensitive quantum dot material according to claim 1, is characterized in that, described Cu doping amount is by molar ratio Cu:P=1:10. 3. A low-toxicity thermosensitive quantum dot material according to claim 1, characterized in that, the thickness of the ZnS isolation layer is 4 layers of ZnS, and the thickness of the ZnS protective layer is 2 layers of ZnS. 4. a preparation method of the low-toxic heat-sensitive quantum dot material of claim 1, has the preparation of Cu-doped InP quantum dot nucleus solution, the cladding of ZnS isolation layer, the cladding of InP nano crystal shell layer and ZnS protective layer The coating process; In the preparation process of the InP quantum dot nucleus solution, first, indium acetate and myristic acid are added to octadecene, and the temperature is raised to 80-120° C., wherein the molar ratio of indium acetate to myristic acid is 1:3.5, ten The consumption of octacene is that every mole of indium acetate uses 25 liters; Under the protection of nitrogen, the temperature is raised to 188°C, and the octadecene solution of 3-(trimethylsilyl)phosphorus is injected into octylamine and concentration of 0.2mol/L, wherein The molar ratio of injected octylamine to indium acetate is 12:1, and the molar ratio of injected phosphorus to indium acetate is 1:2; the temperature is lowered to 178°C, kept for 30 minutes and then lowered to 60-100°C, and the injected concentration is 0.005～0.02mol/L octadecene solution of copper myristate, the amount of copper myristate is Cu:P=1:5～20 in molar ratio, the temperature is raised to 150°C and kept for 20～40 minutes to obtain Cu-doped Mixed InP quantum dot core solution; The coating process of the ZnS isolation layer is as follows: firstly, the Cu-doped InP quantum dot core solution is maintained at 120-160° C., and the materials are fed according to the shell layer components; React at 220-260°C for 30-45 minutes, then inject a layer of sulfur anion precursor solution, and react for 30-45 minutes ; then maintain 220-260°C, alternately inject a layer of zinc cation precursor solution and Sulfur anion precursor solution and each reaction for 30-45 minutes, 3-6 times in total to form 3-6 layers of ZnS isolation layer; then the reaction system was lowered to room temperature, and chloroform and ethanol with a volume ratio of 1:10 were added The mixed solvent makes the quantum dots precipitate, and then centrifuges to obtain the purified ZnS-coated Cu-doped InP nanocrystalline quantum dots; The cladding process of described InP nanocrystal shell layer is, the Cu-doped InP nanocrystal quantum dot that will purify ZnS cladding is dispersed in octadecene; Use 1-2 liters of doped InP nanocrystalline quantum dots; heat up to 60-100°C, vacuumize and then heat up to 120-160°C under the protection of nitrogen, feed according to the shell composition, first add a layer of calculated amount of phosphorus Anion precursor solution, heat up to 180°C and react for 30-45 minutes, then inject a layer of calculated amount of indium cation precursor solution and react for 30-45 minutes ; then maintain 180°C, alternately inject a layer of phosphorus anion precursor solution and indium cation precursor solution and each reaction for 30 to 45 minutes, a total of 2 to 3 times to form 2 to 3 layers of InP nanocrystalline shells, to obtain Cu-doped InP nanocrystals coated with ZnS and then coated with InP. Crystal quantum dots; The coating process of the ZnS protective layer is as follows: firstly, the Cu-doped InP nanocrystalline quantum dot solution coated with ZnS and then coated with InP is maintained at 120-160 ° C, fed according to the shell layer components, and a layer of Calculate the amount of zinc cation precursor solution, heat up to 220-260°C for 30-45 minutes, then inject sulfur anion precursor solution for 30-45 minutes; after that keep 220-260°C, alternately inject a layer of zinc The cation precursor solution and the anion precursor solution of sulfur were reacted for 30 to 45 minutes each, and carried out 2 to 3 times in total to form 1 to 4 layers of ZnS protective layer; the final reaction system was cooled to room temperature, and the volume ratio of adding A 1:10 mixed solvent of chloroform and ethanol precipitates the quantum dots, and then centrifuges to obtain a purified low-toxicity thermosensitive quantum dot material. 5. the preparation method of a kind of low toxicity thermosensitive quantum dot material according to claim 4 is characterized in that, the consumption of copper myristate in the preparation process of described Cu-doped InP quantum dot nuclear solution is molar Ratio Cu:P=1:10. 6. according to the preparation method of claim 4 or 5 described a kind of low toxicity heat-sensitive quantum dot material, it is characterized in that, the coating process of described ZnS barrier layer carries out altogether 4 times, and the coating process of described ZnS protective layer The coating process was carried out 2 times in total. 7. The preparation method of a kind of low-toxicity thermosensitive quantum dot material according to claim 4, is characterized in that, the cation precursor solution of described zinc is that concentration is 0.5～1mol/L zinc stearate ten Octacene solution; the cation precursor solution of indium is a solution obtained by dissolving every mole of indium myristate in 0.48 liters of tributylphosphine and 0.52 liters of octadecene mixed solvent; the anion precursor of the sulfur The solution is an octadecene solution of elemental sulfur with a concentration of 0.5 to 1mol/L; the anion precursor solution of phosphorus is dissolved in 0.45 liters of octylamine and 0.55 liters of phosphorus per mole of 3-(trimethylsilyl) phosphorus A solution obtained in a mixed solvent of octadecene.