CN110054205B - Cesium iodide nanocrystal and preparation method and application thereof - Google Patents
Cesium iodide nanocrystal and preparation method and application thereof Download PDFInfo
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Abstract
The invention relates to the technical field of quantum dots, and particularly provides cesium iodide nanocrystals and a preparation method thereof. The preparation method of the cesium iodide nanocrystal at least comprises the following steps: reacting the cesium source precursor solution with the iodine source precursor solution at 165-195 ℃ for 5-12 min, and immediately quenching after the reaction is finished to obtain cesium iodide nanocrystals; the cesium source precursor solution and the iodine source precursor solution are not dissolved with oxygen molecules and water molecules. The preparation method synthesizes ionic cesium iodide nanocrystals with different morphologies, the obtained cesium iodide nanocrystals have no other phases or impurities or byproducts, the purity is as high as 99.9% or more, the optical conversion capacity and efficiency are better than those of a block material, and the defect that the block scintillator material is slow in reaction time can be overcome to a certain extent.
Description
Technical Field
The invention belongs to the technical field of quantum dots, and particularly relates to cesium iodide nanocrystals and a preparation method and application thereof.
Background
In the society of modern technological development, nanomaterials play an increasingly important role in various fields. In the past decades, in the research on nano-scale materials, metal nano-materials, semiconductor nano-materials, and magnetic nano-materials are the most studied nano-materials. Semiconductor nanocrystals, also referred to as quantum dots, have a radius less than or approximately equal to the radius of a bohr exciton, among others. In quantum dot materials, cadmium selenide (CdSe), cadmium telluride (CdTe), cadmium sulfide (CdS) and the like are the most classical, and the exploration of the cadmium selenide (CdSe), the cadmium telluride (CdTe), the cadmium sulfide (CdS) and the like not only promotes the development of basic research, but also has important significance in the aspect of technical application. Until now, the fluorescence emission of several quantum dots depends on the size of the size and the distribution characteristics of the size, and still attracts many researchers. This is mainly due to the quantum confinement effect of the nanocrystals. The optical properties of these conventional binary or multinary metal chalcogenides are greatly enhanced in their bulk materials due to quantum size effects. Besides, the multifunctional surface chemical property and the free colloidal state are provided, so that the multifunctional surface chemical property and the free colloidal state can be well dispersed in various solvents and matrixes, and finally the multifunctional surface chemical property and the free colloidal state can be compatibly applied to different equipment. For a metal nanocrystal, many physical parameters of the metal nanocrystal have influence on the properties of the metal nanocrystal, such as size, shape, element composition, crystal structure and the like, the properties of the metal nanocrystal can be changed by changing any one parameter, and the flexibility and range of the nanocrystal change are very sensitive to specific parameters, such as in the applications of Local Surface Plasmon Resonance (LSPR) and Surface Enhanced Raman Scattering (SERS), researches show that for gold (Au) and silver (Ag) nanocrystals; in other words, the morphology and structure of the LSPR plays an important role in the number, location and strength of the LSPR. In the aspect of catalytic application, there is a research surface to improve the active form of metal nanocrystals by reducing the size. In recent years, magnetic nanoparticles have been studied in applications including chemistry, biomedicine, electronics and material engineering, and have special paramagnetic properties, and because the surface has too many atoms, but only a small coordination number causes unsaturation in the distribution of magnetic moments, the orbital and spin moments of the particles are greatly improved. The magnetic nano-particles can regulate and control the physical and chemical properties of the tobacco tar through the adjustment of the size. These properties different from bulk materials make magnetic nanomaterials widely used in cancer diagnosis, giant magnetoresistance, magnetic liquids, magnetic recording, soft magnetic refrigeration, and magneto-optical devices.
A scintillator is a device that converts high-energy photons from X-rays, gamma rays, etc. into a beam of light in the ultraviolet-visible diffuse scattering (UV-vis) range. In addition, accelerated charged particles such as electrons, protons, or heavier ions, even neutrons, can be reconverted to a flash of light by their detection energy deposition upon interaction with the scintillator matrix. Due to this property, scintillator materials are used in spectral or energy converters, etc. Scintillation is a common phenomenon that can occur in gases, liquids, and solids. There are two more important scintillator materials in a solid, a solid inorganic scintillator material and a solid organic scintillator material, respectively. Among them, inorganic scintillator materials account for a large proportion in practical applications and developments, such as cesium iodide scintillators and nano scintillators. As mentioned previously, one property that measures scintillator materials is decay time, the shorter the decay time, the better the radiation detection capability. However, the scintillators of this type have certain disadvantages, such as barium fluoride, copper iodide, etc., and although they are scintillating materials which decay rapidly, the limitations of the wavelength and growth size of the ultraviolet region cause much inconvenience for detection. The cesium iodide scintillator material has a highly symmetric cubic crystal system, is easy to grow large-size single crystals, has a relatively short decay time (less than 10ns), and therefore, has a great deal of research on cesium iodide scintillators doped with other elements and pure cesium iodide. For a pure cesium iodide scintillator material, it is generally considered that there are two luminescence components, one dominant luminescence wavelength, i.e., the fast component, and one slow component. The smaller the ratio of fast and slow components, the better the performance of the material. Because the raw materials and the preparation process are different, the performances of the pure cesium iodide obtained from different researches are different. In the research of pure cesium iodide crystals, the following problems still remain to be solved: (1) although large bulk cesium iodide materials have good optical properties, larger single crystal cesium iodide materials are very fragile and easily damaged; (2) the growth of larger single crystals is expensive, the consumed time is longer, and the growth of high quality is also limited; (3) for inorganic cesium iodide materials in particle form, their size and scalability are good, but their solubility in organic solvents and polymer matrices is low; (4) the cesium iodide material obtained by the gel method is in a gel state, and therefore, the light transmittance is not so good, and the light emission performance is seriously affected. In addition, the transparent cesium iodide nanocrystals prepared by the sol-gel method have a surface that is not very flat after being made into a thin film and have poor particle uniformity, and in practical applications, very high requirements are placed on the thickness, flatness, particle size, and uniformity of the thin film.
Disclosure of Invention
Aiming at the problems of low solubility, poor luminescence performance, poor particle uniformity, over-fragility and the like in an organic solvent and a polymer matrix in the existing gel method for preparing cesium iodide, the invention provides a preparation method of cesium iodide nanocrystals.
And cesium iodide nanocrystals obtained by the above preparation method and use thereof.
In order to achieve the purpose, the technical scheme of the invention is as follows:
a preparation method of cesium iodide nanocrystals at least comprises the following steps: reacting the cesium source precursor solution with the iodine source precursor solution at 165-195 ℃ for 5-12 min, and immediately quenching after the reaction is finished to obtain cesium iodide nanocrystals;
the cesium source precursor solution and the iodine source precursor solution are not dissolved with oxygen molecules and water molecules.
Correspondingly, the cesium iodide nanocrystal is prepared by the preparation method of the cesium iodide nanocrystal, and is any one of spherical nanocrystals, hexagonal flaky nanocrystals and cubic bulk nanocrystals.
And the application of the cesium iodide nanocrystal in the fields of medical imaging and electron emitter imaging.
The preparation method of the cesium iodide nanocrystal has the beneficial effects that:
compared with the prior art, the preparation method of the cesium iodide nanocrystal synthesizes ionic cesium iodide nanocrystals with different shapes, and the obtained cesium iodide nanocrystal has no other phases or impurities, has no by-products, and has the purity as high as 99.9% or more. The preparation method has the advantages of simple process, controllable nano crystal morphology and the like in the preparation process.
The cesium iodide nanocrystal provided by the invention is used as a nano scintillator, the three-dimensional confinement effect and the electron and hole wave functions are better overlapped, the cesium iodide nanocrystal has better optical conversion capability and efficiency than a block material, and the cesium iodide nanocrystal can make up for the defect that the block scintillator material is slow in reaction time to a certain extent. Therefore, the method can be widely applied to the fields of medical imaging, electron emitter imaging and the like.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is an XRD pattern of cesium iodide nanocrystals prepared in examples 1, 2, and 3 of the present invention;
FIG. 2 is a Transmission Electron Microscope (TEM) image of spherical cesium iodide nanocrystals prepared in example 1 of the present invention;
FIG. 3 is a High Resolution Transmission Electron Microscopy (HRTEM) image of spherical cesium iodide nanocrystals prepared in example 1 of the present invention;
FIG. 4 is a TEM and HRTEM image of hexagonal plate-shaped cesium iodide nanocrystals prepared in example 2 of the present invention;
FIG. 5 is a TEM and HRTEM image of cubic cesium iodide nanocrystals prepared in example 3 of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The embodiment of the invention provides a preparation method of cesium iodide nanocrystals. The preparation method at least comprises the following steps:
reacting the cesium source precursor solution with the iodine source precursor solution at 165-195 ℃ for 5-12 min, and immediately quenching after the reaction is finished to obtain cesium iodide nanocrystals;
the cesium source precursor solution and the iodine source precursor solution are not dissolved with oxygen molecules and water molecules.
The technical scheme of the preparation method of the invention is further explained in detail below.
The cesium source precursor solution is a cesium source precursor solution of octadecene and oleic acid, that is, the solvent is a mixture of octadecene and oleic acid, and the solute is a cesium-containing substance.
Preferably, in the cesium-source precursor solution, the volume ratio of the mixture of octadecene and oleic acid is (28-35): 1. when the cesium source is dissolved in the mixed solvent obtained by octadecene and oleic acid in the ratio, the dissolution speed of the cesium source is high, and a good oil phase solution can be obtained.
Preferably, the cesium source is cesium carbonate.
In order to avoid other side reactions caused by the dissolution of cesium carbonate in octadecene and oleic acid and side reactions in the preparation of cesium iodide nanocrystals, drying and oxygen removal treatment are required before the dissolution of the cesium iodide in the octadecene and oleic acid, so that the purity of the octadecene and oleic acid is improved, and the possibility of side reactions is reduced.
Preferably, the solute of the iodine source precursor solution is any one of germanium diiodide, sodium iodide, potassium iodide, calcium iodide and tin tetraiodide, and the iodine sources are easy to dissolve and do not introduce other side reaction product impurities; the solvent of the iodine source precursor solution is a mixture of oleic acid, oleylamine and octadecene, and the oleic acid, the oleylamine and the octadecene are used as the solvent of the iodine source precursor solution, so that an iodine source is dissolved in the solvent to obtain an oil phase solution, and introduction of other components such as water is avoided.
Preferably, in the solvent of the iodine source precursor solution, the ratio of the oleic acid: oleylamine: octadecene ═ 1: 1: (18-22).
If cubic cesium iodide nanocrystals need to be obtained, the solvent of the iodine source precursor solution comprises trioctylphosphine in addition to oleic acid, oleylamine and octadecene, and the volume ratio of the trioctylphosphine to the octadecene is (1.8-2.5): 1. after trioctylphosphine is added into the iodine source precursor solution, the hexagonal flaky cesium iodide nanocrystalline is favorable for further generating cubic cesium iodide nanocrystalline.
According to the components of the cesium source precursor solution and the iodine source precursor solution, the ratio of cesium element in the cesium source precursor solution to iodine element in the iodine source precursor solution is (4.0-5.0) according to a molar ratio: (3.0-9.5). Under the conditions, the generated cesium iodide nanocrystals can be gradually changed into hexagonal sheets and cubic blocks from spheres with the increase of the input amount of the iodine source and the extension of the reaction time. For example, when the molar weight ratio of the cesium element to the iodine element is 4.6:3.06, reacting for 5min to obtain spherical cesium iodide nanocrystals; if the molar ratio of the two is about 4.6:6.13 and the reaction time is prolonged to about 10min, hexagonal flaky cesium iodide nanocrystals are generated; the molar ratio of the two is about 4.6:9.19, the reaction time is prolonged to about 10min, and when trioctylphosphine is contained in the iodine source precursor solution, cubic bulk cesium iodide nanocrystals can be obtained.
In the invention, the quenching treatment can effectively solve the problems of nonuniform grain size, uneven surface and the like of the generated cesium iodide nano-crystal.
Preferably, the quenching process is a water bath or an oil bath.
The preparation method of the cesium iodide nanocrystal provided by the invention can be used for preparing ionic cesium iodide nanocrystals with different morphologies, the obtained cesium iodide nanocrystal has no other phases or impurities, no by-products and high purity of 99.9% or more. The preparation method has the advantages of safe and reliable production process, simple and easily-controlled process conditions, low production cost, controllable nanocrystalline morphology and the like in the preparation process, and is suitable for industrial large-scale production.
The cesium iodide nanocrystal obtained by the preparation method has high purity and controllable morphology, can be used as a nano scintillator, has a three-dimensional confinement effect and better superposition of electron and hole wave functions, has better optical conversion capability and efficiency than a block material, and can make up for the defect that the block scintillator material is slow in reaction time to a certain extent. Therefore, the method can be widely applied to the fields of medical imaging, electron emitter imaging, particle physics and the like.
In order to more effectively explain the technical solution of the present invention, the technical solution of the present invention is explained below by specific examples.
Example 1
A preparation method of spherical cesium iodide nanocrystals comprises the following steps:
(1) impurity removal treatment of a solvent: putting 50mL octadecene into a single-neck round-bottom flask, sealing the flask by using a rubber plug, then putting the flask into an oil bath at 140 ℃, inserting a syringe needle on the rubber plug, connecting the syringe needle with a double-row pipe, vacuumizing the flask for 30min under the condition of the oil bath at 140 ℃, introducing argon after the flask is completely pumped out, and simultaneously inserting a protective balloon filled with argon on the rubber plug to prevent air, water or other impurities from entering the flask. Oleic acid and oleylamine were treated in the same way for later use.
(2) Preparation of a cesium-source precursor solution: putting 0.015g of cesium carbonate into a three-neck round-bottom flask with a closed side opening, connecting the cesium carbonate to a condenser pipe, connecting the condenser pipe with a double-row pipe, lubricating the joint with vacuum grease to ensure the tightness, vacuumizing the round-bottom flask containing the cesium carbonate to remove air, water and other components in the flask, repeatedly filling argon, and vacuumizing to ensure that air and moisture are completely removed. After the extraction, 3mL of octadecene and 0.1mL of oleic acid which had been subjected to drying treatment were added to the side port of a three-necked flask, and the solution in the flask was heated to 150 ℃ until cesium carbonate was completely dissolved, until finally becoming a colorless transparent solution which was used as a cesium-source precursor solution in synthesis, and was ready for use.
(3) Preparation of iodine source precursor solution: and (2) weighing 0.01g of germanium diiodide in a glass vial by using a balance in a glove box, sealing the glass vial by using a rubber plug, taking out the glass vial, protecting the glass vial by using an argon ball, adding 0.2mL of dried oleic acid and 0.2mL of dried oleylamine respectively and 2mL of octadecene, placing the glass vial on an oil bath, heating the glass vial to 100 ℃ until the glass vial is dissolved to form a colorless and transparent solution, and using the solution as an iodine source precursor solution in synthesis for later use.
(4) Heating the cesium source precursor solution obtained in the step (2) to 180 ℃, quickly injecting the iodine source precursor solution prepared in the subsequent step (3) into the cesium source precursor solution heated to 180 ℃, reacting at a constant temperature for 5min, and immediately quenching the three-neck flask by using a water bath.
(5) Collecting reaction liquid obtained by cold water bath quenching in a 50mL centrifuge tube, centrifuging at 8000r/min for 8min to obtain cesium iodide nanocrystals at the bottom and on the wall of the centrifuge tube, taking the cesium iodide nanocrystals, adding 5mL n-hexane into the obtained cesium iodide nanocrystals, performing ultrasonic treatment by using an ultrasonic machine to uniformly disperse the cesium iodide nanocrystals in the cesium iodide nanocrystals, performing centrifugal separation, performing ultrasonic treatment, dispersion and centrifugation by using the n-hexane again, and dispersing the finally obtained cesium iodide nanocrystals in the n-hexane.
Example 2
A preparation method of hexagonal flaky cesium iodide nanocrystals comprises the following steps:
(1) impurity removal treatment of a solvent: putting 50mL octadecene into a single-neck round-bottom flask, sealing the flask by using a rubber plug, then putting the flask into an oil bath at 140 ℃, inserting a syringe needle on the rubber plug, connecting the syringe needle with a double-row pipe, vacuumizing the flask for 30min under the condition of the oil bath at 140 ℃, introducing argon after the flask is completely pumped out, and simultaneously inserting a protective balloon filled with argon on the rubber plug to prevent air, water or other impurities from entering the flask. Oleic acid and oleylamine were treated in the same way for later use.
(2) Preparation of a cesium-source precursor solution: putting 0.015g of cesium carbonate into a three-neck round-bottom flask with a closed side opening, connecting the cesium carbonate to a condenser pipe, connecting the condenser pipe with a double-row pipe, lubricating the joint with vacuum grease to ensure the tightness, vacuumizing the round-bottom flask containing the cesium carbonate to remove air, water and other components in the flask, repeatedly filling argon, and vacuumizing to ensure that air and moisture are completely removed. After the extraction, 3mL of octadecene and 0.1mL of oleic acid which had been subjected to drying treatment were added to the side port of a three-necked flask, and the solution in the flask was heated to 150 ℃ until cesium carbonate was completely dissolved, until finally becoming a colorless transparent solution which was used as a cesium-source precursor solution in synthesis, and was ready for use.
(3) Preparation of iodine source precursor solution: and (2) weighing 0.03g of germanium diiodide in a glass vial by using a balance in a glove box, sealing the glass vial by using a rubber plug, taking out the glass vial, protecting the glass vial by using an argon ball, adding 0.2mL of dried oleic acid and 0.2mL of dried oleylamine respectively and 2mL of octadecene, placing the glass vial on an oil bath, heating the glass vial to 100 ℃ until the glass vial is dissolved to form a colorless and transparent solution, and using the solution as an iodine source precursor solution in synthesis for later use.
(4) Heating the cesium source precursor solution obtained in the step (2) to 180 ℃, quickly injecting the iodine source precursor solution prepared in the subsequent step (3) into the cesium source precursor solution heated to 180 ℃, reacting at a constant temperature for 10min, and immediately quenching the three-neck flask by using a water bath to obtain hexagonal flaky cesium iodide nanocrystals.
(5) Collecting reaction liquid obtained by cold water bath quenching in a 50mL centrifuge tube, centrifuging at 8000r/min for 8min to obtain cesium iodide nanocrystals at the bottom and on the wall of the centrifuge tube, taking the cesium iodide nanocrystals, adding 5mL n-hexane into the obtained cesium iodide nanocrystals, performing ultrasonic treatment by using an ultrasonic machine to uniformly disperse the cesium iodide nanocrystals in the cesium iodide nanocrystals, performing centrifugal separation, performing ultrasonic treatment, dispersion and centrifugation by using the n-hexane again, and dispersing the finally obtained cesium iodide nanocrystals in the n-hexane.
Example 3
A preparation method of cubic bulk cesium iodide nanocrystals comprises the following steps:
(1) impurity removal treatment of a solvent: putting 50mL octadecene into a single-neck round-bottom flask, sealing the flask by using a rubber plug, then putting the flask into an oil bath at 140 ℃, inserting a syringe needle on the rubber plug, connecting the syringe needle with a double-row pipe, vacuumizing the flask for 30min under the condition of the oil bath at 140 ℃, introducing argon after the flask is completely pumped out, and simultaneously inserting a protective balloon filled with argon on the rubber plug to prevent air, water or other impurities from entering the flask. Oleic acid and oleylamine were treated in the same way for later use.
(2) Preparation of a cesium-source precursor solution: putting 0.015g of cesium carbonate into a three-neck round-bottom flask with a closed side opening, connecting the cesium carbonate to a condenser pipe, connecting the condenser pipe with a double-row pipe, lubricating the joint with vacuum grease to ensure the tightness, vacuumizing the round-bottom flask containing the cesium carbonate to remove air, water and other components in the flask, repeatedly filling argon, and vacuumizing to ensure that air and moisture are completely removed. After the extraction, 3mL of octadecene and 0.1mL of oleic acid which had been subjected to drying treatment were added to the side port of a three-necked flask, and the solution in the flask was heated to 150 ℃ until cesium carbonate was completely dissolved, until finally becoming a colorless transparent solution which was used as a cesium-source precursor solution in synthesis, and was ready for use.
(3) Preparation of iodine source precursor solution: and (2) weighing 0.03g of germanium diiodide in a glove box by using a balance, placing the germanium diiodide in a glass vial containing 1mL of trioctylphosphine, sealing the germanium diiodide with a rubber plug, taking out the germanium diiodide in a sealed manner, protecting the germanium diiodide with an argon ball, adding 0.2mL of dried oleic acid and oleylamine and 2mL of octadecene, placing the germanium diiodide on an oil bath, heating the mixture to 100 ℃ until the mixture is dissolved to be a colorless and transparent solution, and using the solution as an iodine source precursor solution in synthesis for later use.
(4) Heating the cesium source precursor solution obtained in the step (2) to 180 ℃, quickly injecting the iodine source precursor solution prepared in the subsequent step (3) into the cesium source precursor solution heated to 180 ℃, reacting at a constant temperature for 10min, and immediately quenching a three-neck flask by using a water bath to obtain cubic cesium iodide nanocrystals.
(5) Collecting reaction liquid obtained by cold water bath quenching in a 50mL centrifuge tube, centrifuging at 8000r/min for 8min to obtain cesium iodide nanocrystals at the bottom and on the wall of the centrifuge tube, taking the cesium iodide nanocrystals, adding 5mL n-hexane into the obtained cesium iodide nanocrystals, performing ultrasonic treatment by using an ultrasonic machine to uniformly disperse the cesium iodide nanocrystals in the cesium iodide nanocrystals, performing centrifugal separation, performing ultrasonic treatment, dispersion and centrifugation by using the n-hexane again, and dispersing the finally obtained cesium iodide nanocrystals in the n-hexane.
In order to verify that the final products obtained in examples 1 to 3 are spherical cesium iodide nanocrystals, hexagonal flaky cesium iodide nanocrystals and cubic bulk cesium iodide nanocrystals, respectively, the respective performance tests are performed on the spherical cesium iodide nanocrystals, the hexagonal flaky cesium iodide nanocrystals and the cubic bulk cesium iodide nanocrystals, and the tests specifically include X-ray powder diffraction (XRD), Transmission Electron Microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) tests.
(I) XRD test
The final product obtained was tested according to the standard of conventional XRD test, and the test results are shown in fig. 1.
From the XRD patterns, the three diffraction spots can all correspond well to the standard card, which is PDF #06-0311, and corresponds to the simple cubic phase (Pm3m), and no other miscellaneous peaks appear, which proves that the phase of the cesium iodide nanocrystals obtained in examples 1, 2, and 3 is relatively pure, and no by-products or other phases are generated, wherein the peaks corresponding to 2 θ ═ 27.59, 39.42, 48.79, 56.97, 64.43, 71.46, and 78.23 ° are {110}, {200}, {211}, {220}, {310}, {222}, and {321} crystal planes, respectively.
(II) TEM and HRTEM test
Specific test results are shown in fig. 2-5 according to the operation modes of conventional TEM and HRTEM scanning.
Wherein, fig. 2 and 3 show the spherical cesium iodide nanocrystals obtained in example 1, fig. 2 shows cesium iodide nanospheres observed under a low-power transmission electron microscope, and it can be seen from the figure that the synthesized cesium iodide nanocrystals have good monodispersity, uniform size, and average particle size of 15 nm. FIG. 3 shows the finer morphology of the nanospheres observed under high-magnification TEM, which clearly shows the surface lattices measured by Digital Micrograph software with the lattice spacing of
Corresponding to the crystal lattice of the (110) crystal plane.
Fig. 4 is the hexagonal plate-shaped cesium iodide nanocrystal obtained in example 2, and fig. 4 is the hexagonal plate-shaped cesium iodide nanocrystal under a low-power transmission electron microscope. Similarly, through measurement, the average side length is 40nm, the insets are high-power transmission electron microscope pictures, and through measurement, the lattice spacing is matched with the (110) crystal face in a standard card, and meanwhile, clear lattice stripes also show that the obtained nanocrystals have good crystallinity;
FIG. 5 is a plot of the cubic cesium iodide nanocrystals obtained in example 3, as shown in FIG. 5, with the cubic blocks having an average edge length of about 40nm, and the inset also illustrates that the lattice matches the (110) crystal plane of the cesium iodide crystals.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.
Claims (2)
1. A preparation method of cesium iodide nanocrystals is characterized by at least comprising the following steps:
reacting the cesium source precursor solution with the iodine source precursor solution at 165-195 ℃ for 5-12 min, and immediately quenching after the reaction is finished to obtain cesium iodide nanocrystals; wherein the quenching treatment is water bath or oil bath;
the cesium source precursor solution and the iodine source precursor solution are not dissolved with oxygen molecules and water molecules;
according to the molar ratio, the ratio of cesium element in the cesium source precursor solution to iodine element in the iodine source precursor is (4.0-5.0): (3.0-9.5);
the cesium source precursor solution is a cesium carbonate solution, and a solvent of the cesium carbonate solution is a mixture of octadecene and oleic acid; the volume ratio of the octadecene to the oleic acid is (28-35): 1;
the iodine source precursor solution is any one of a germanium diiodide solution, a sodium iodide solution, a potassium iodide solution, a calcium iodide solution or a tin tetraiodide solution, and the solvent of the iodine source precursor solution is a mixture of oleic acid, oleylamine and octadecene;
the volume ratio of the oleic acid: oleylamine: octadecene = 1: 1: (18-22);
the solvent of the iodine source precursor solution further comprises trioctylphosphine, and the volume ratio of the trioctylphosphine to the octadecene is (1.8-2.5): 1.
2. the method for preparing cesium iodide nanocrystals according to claim 1, wherein said cesium source precursor solution and said iodine source precursor solution are prepared in an inert atmosphere in the absence of oxygen.
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