WO2021000892A1 - Iii-v族量子点的制备方法 - Google Patents

Iii-v族量子点的制备方法 Download PDF

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WO2021000892A1
WO2021000892A1 PCT/CN2020/099768 CN2020099768W WO2021000892A1 WO 2021000892 A1 WO2021000892 A1 WO 2021000892A1 CN 2020099768 W CN2020099768 W CN 2020099768W WO 2021000892 A1 WO2021000892 A1 WO 2021000892A1
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group iii
precursor
quantum dots
group
preparation
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PCT/CN2020/099768
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彭笑刚
徐哲恒
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浙江大学
纳晶科技股份有限公司
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    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y20/00—Nanooptics, e.g. quantum optics or photonic crystals
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y40/00—Manufacture or treatment of nanostructures
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    • C09K11/70—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing phosphorus

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  • This application relates to the field of quantum dot synthesis, specifically, to a method for preparing group III-V quantum dots.
  • Quantum dots QDs Colloidal semiconductor nanocrystals with a size within the quantum confinement range are widely used in the fields of display, biomedical marking, solid-state lighting, etc., as emission sources of common light-emitting devices in the industry.
  • the size of quantum dots is adjustable, the intrinsic luminescence purity is high, and it can be used as an ideal emitter emission source, CdSe-based quantum dots are generally regarded as the only quantum dots that can be directly produced and applied in the industry.
  • quantum dots still have stability problems, recently synthesized lead halide perovskite quantum dots have been found to have high optical properties.
  • the main purpose of this application is to provide a method for preparing III-V quantum dots to solve the problem that the size and particle size distribution of III-V quantum dots synthesized in the prior art are difficult to control.
  • a method for preparing III-V quantum dots includes: step S1, reacting a first trialkylphosphine ligand with a first III element precursor, The second group III element precursor is prepared; step S2, the second group III element precursor and the group V element precursor are reacted to obtain the first group III-V nanocluster; step S3, the first group III-V nanocluster The clusters, the precursor of the third group III element and the optional second trialkylphosphine ligand are mixed and reacted to prepare a first product system containing group III-V quantum dots.
  • the precursor of the third group III element is prepared by reacting the third trialkylphosphine ligand and the precursor of the fourth group III element or is prepared by using step S1.
  • first group III element precursor, the second group III element precursor, and the third group III element precursor are each independently selected from carboxylate precursors of group III elements.
  • first ligand trialkylphosphine, trialkylphosphine ligands second and third trialkylphosphine ligands are each independently selected from alkyl groups of C 1 ⁇ C 10 alkyl group is.
  • step S3 does not contain free fatty acids.
  • step S1 is performed at 20 to 150°C.
  • the molar ratio of the first trialkylphosphine ligand and the first group III element precursor is 1:10-3:1.
  • step S2 is performed at 10 to 150°C.
  • step S2 is performed at 20-50°C.
  • the molar ratio of the precursor of the above-mentioned group V element to the precursor of the second group III element is 1:10 to 1:2.
  • step S3 includes: injecting the first III-V group nanocluster into the third group III element precursor or injecting into the mixed system formed by the second trialkylphosphine ligand and the third group III element precursor
  • the first product system containing III-V quantum dots is prepared by the reaction in the process.
  • step S3 is performed at 220-260°C.
  • the concentration of the precursor of the third group III element in the raw material system formed in the step S3 is controlled to be 0.5-1 mmol/3 mL.
  • step S4 reacting the first product system with the second III-V family nanocluster, so that the III-V family quantum dots continue to grow, and the second III-V family nanocluster adopts step S1 And step S2.
  • the precursor of the third group III element in the above step S3 is excessive, so that the concentration of the precursor of the third group III element in the raw material system formed in the step S4 is 0.1-1 mmol/3mL.
  • step S3 it further includes separating and purifying the first product to obtain group III-V quantum dots; the preparation method further includes: making the group III-V quantum dots, the fifth group III element precursor and the third The III-V group nanocluster reacts, so that the III-V group quantum dots continue to grow.
  • the third group III-V nanocluster is prepared by step S1 and step S2, and the fifth group III element precursor is prepared by step S1 .
  • the reaction temperature in step S2 is 20-50°C.
  • the average size of the III-V quantum dots in the first product system is 2 to 4 nm.
  • the second group III element precursor formed by using the first trialkylphosphine ligand and the first group III element precursor is soluble at room temperature and has relatively small steric hindrance; using it and V
  • the group element precursor reaction can form the first group III-V nanoclusters with close consistency and extremely small size.
  • the reaction temperature of step S2 can be changed from the current commonly used The high temperature is extended to room temperature; the first III-V group nanocluster and the third group III element precursor and the optional second trialkylphosphine ligand are mixed for reaction to form an almost monodisperse III-V group quantum Dots, and thus realize the effective control of the size and particle size distribution of III-V quantum dots.
  • Figure 1a shows the liquid phase FTIR spectrum of Example 1
  • Figure 1b shows the 31 P NMR spectrum of Example 1
  • Figure 2a shows the ultraviolet absorption spectra of III-V nanoclusters obtained in Example 3 to Example 5;
  • Figure 2b shows the UV absorption spectra of the III-V family nanoclusters obtained in Comparative Example 1 and Comparative Example 3;
  • Figure 2c shows a comparison diagram of the in-situ reaction liquid phase FTIR spectra of Example 2 and Comparative Example 1 over time;
  • Figure 2d shows a comparison diagram of TMS-St concentration in the reaction of Example 2 and Comparative Example 1 over time
  • Fig. 3a shows the change diagram of the UV-Vis absorption peaks of InP quantum dots at various time points obtained during the heating process from room temperature to 260°C in Example 4;
  • Figure 3b shows the variation of UV-Vis absorption peaks of InP quantum dots at various time points during the reaction of Comparative Example 2 and Comparative Example 3 (corresponding to the upper right inset);
  • Fig. 3c shows the change diagram of the UV-Vis absorption peaks of InP quantum dots at various time points during the reaction process of Example 6;
  • FIG. 3d shows the change diagram of the UV-Vis absorption peaks of InP quantum dots at various time points during the reaction process of Example 7;
  • Fig. 3e shows the change graph of the UV-Vis absorption peaks of InP quantum dots at various time points during the reaction process of Example 8;
  • Fig. 4b shows the change diagram of the absorption peak position of the InP quantum dots obtained in Examples 9 to 11 and Comparative Example 4 with the change of the nanocluster concentration (calculated as P element);
  • Figure 5a shows the UV-Vis relative absorbance changes of InP quantum dots during the growth process of Examples 12 to 14 and Comparative Example 5;
  • Figure 5b shows a TEM image of the InP quantum dots obtained in Example 12.
  • Figure 5b' shows a TEM image (including a ruler) of the InP quantum dots obtained in Example 12;
  • Figure 5c shows a TEM image of InP quantum dots obtained in Comparative Example 5.
  • Figure 5d shows the particle size distribution diagrams of InP quantum dots obtained in Example 12 and Example 15;
  • Figure 5e shows the UV-Vis absorbance changes of InP quantum dots during the growth of Example 12 and Example 15
  • Figure 5f shows the peak positions of InP quantum dots during the growth of Example 12 and Example 15 The absorbance change graph of the peak position
  • Figure 6a shows the UV-Vis spectrum of InP quantum dots obtained in some embodiments
  • Figure 6b plots the half-width and valley/peak ratio of InP quantum dots at different absorption peak positions according to Figure 6a;
  • Figure 6c shows a TEM image of the InP quantum dots of Example 6
  • Figure 6d shows a TEM image of the InP quantum dots of Example 9
  • Figure 6e shows a high-resolution TEM image of the InP quantum dots of Example 9
  • 6f shows the X-ray diffraction (XRD) pattern of the InP quantum dots with an absorption peak of 618 nm in Example 9;
  • Figure 7 shows the UV-Vis spectra of Example 6 and Examples 16-17;
  • FIG. 8 shows the size distribution diagram of the quantum dots of Example 9 (the absorption peak position is 650 nm);
  • Figure 9 shows a schematic diagram of a quantum dot preparation route of some embodiments.
  • Fig. 10 shows a schematic diagram of a quantum dot preparation route of some embodiments.
  • the number of moles or the amount of a specific group element precursor is based on the number of moles of the specific group element.
  • the number of moles of the first group III element precursor calculate the number of moles of the first group III element precursor .
  • the ultraviolet-visible absorption peak refers to the first exciton absorption peak.
  • III-V quantum dots As analyzed in the background art of this application, although the synthesis method of III-V quantum dots has been improved in various aspects in the prior art, it is expected that the size and particle size distribution of III-V quantum dots can be controlled to improve Its size is monodisperse. However, the current results are not satisfactory. In order to control the size and particle size distribution of III-V quantum dots, this application provides a method for preparing III-V quantum dots.
  • a method for preparing III-V quantum dots includes: step S1, making the first trialkylphosphine ligand and the first III element precursor
  • the second group III element precursor is prepared by reaction; step S2, the second group III element precursor and the group V element precursor are reacted to obtain the first group III-V nanocluster; step S3, the first group III-V
  • the group nanocluster, the third group III element precursor and the optional second trialkylphosphine ligand are mixed and reacted to prepare a first product system containing group III-V quantum dots.
  • the second group III element precursor (can be regarded as a complex) formed by using the first trialkylphosphine ligand and the first group III element precursor is soluble at room temperature and has low steric hindrance;
  • the group V element precursor reaction can form the first group III-V nanoclusters with close consistency and extremely small size. Since the second group III element precursor is soluble at room temperature, the reaction temperature of step S2 can be changed from the current The commonly used high temperature is extended to room temperature to save energy; the first III-V group nanocluster and the third group III element precursor and the optional second trialkylphosphine ligand can be mixed to react to form an almost monodisperse Group III-V quantum dots, thereby realizing effective control of the size and particle size distribution of group III-V quantum dots.
  • the precursor of the third group III element is prepared by reacting the third trialkylphosphine ligand and the precursor of the fourth group III element or is prepared by step S1.
  • the trialkylphosphine ligand and the group III element precursor used in the preparation of the third group III element precursor may be different from the trialkylphosphine ligand and the group III element precursor used in the preparation of the first group III precursor. the same.
  • Group III element precursors also have the advantages that they are soluble in the reaction medium at room temperature, and have less steric hindrance to promote the reaction.
  • the above-mentioned III-V nanoclusters may not be separated and purified, and the entire reaction product can be used as a raw material for the III-V nanoclusters of step S3. There may be residual raw materials in the whole reaction product, such as precursors of the second group III elements.
  • the second trialkylphosphine ligand in step S3 may not be added, which has little effect on the quality of the synthesized quantum dots.
  • the foregoing first group III element precursor, second group III element precursor, and third group III element precursor are each independently selected from carboxylate precursors of group III elements.
  • the third group III element precursor when the third group III element precursor is not prepared by reacting the third trialkylphosphine ligand and the fourth group III element precursor, the third group III element precursor may also be a group III element ⁇ carboxylate precursor.
  • the carboxylate in the carboxylate precursor is a carboxylate having a carbon chain length of 8-22.
  • the carboxylate precursor of the above group III element may be a product obtained by reacting a fatty acid salt and a fatty acid.
  • FTIR Fourier Fast Conversion Infrared Spectroscopy
  • the fourth group III element precursor may be a carboxylate precursor of a group III element.
  • the first trialkylphosphine ligand, the second trialkylphosphine ligand and the third trialkylphosphine ligand used in each step may be the same or different.
  • the alkyl group of each alkylphosphine ligand is independently It is selected from C 1 to C 10 alkyl groups. In other embodiments, the above-mentioned alkyl groups are further preferably n-butyl or n-octyl.
  • the reactant in step S3 does not contain free fatty acids, thereby reducing the etching of nanoclusters by free fatty acids.
  • the carboxylate precursor of the fourth group III element is a product obtained by the reaction of a fatty acid salt and a fatty acid
  • the amount of the fatty acid salt and fatty acid is controlled to control the third group III element precursor
  • Zero free fatty acids can be controlled to not include free fatty acids in the reactant in step S3.
  • step S1 when indium stearate (In(St) 3 ) is used as the carboxylate precursor of group III elements and TOP (trioctyl phosphine) is used as the first In the case of a trialkylphosphine ligand, the coordination reaction process in step S1 is as follows:
  • TOP+In(St) 3 In(TOP)(St) 3 .
  • the above step S1 is performed at 20-150°C. If it is performed at a higher temperature, the reaction time can be appropriately shortened.
  • the molar ratio of the first trialkylphosphine ligand and the first group III element precursor is preferably 1:10 to 3:1.
  • the molar ratio of the third trialkylphosphine ligand and the precursor of the fourth group III element is 1:10 to 3:1.
  • Group V elements can be selected from nitrogen, phosphorus, arsenic, antimony and bismuth.
  • the group V element precursors can be selected from the group V element precursors commonly used in the prior art.
  • the foregoing group V element precursors are tris(trimethylsilyl)phosphine and tris(dialkylsilyl) Phosphine, tris (dialkylamino) phosphine, tris (trimethylgermyl) phosphine, tris (dimethyl azolyl) phosphine, tris (trialkylsilyl) arsine, tris (two Alkylsilyl)arsine, tris(dialkylamino)arsine, phosphine, phosphorus trichloride, white phosphorus, calcium phosphide or sodium phosphide, but not limited thereto.
  • step S2 can be carried out in a wide range.
  • the above step S2 can be carried out at 10 to 150°C, preferably at 20°C. Performed at ⁇ 50°C.
  • step S2 is preferably performed in a non-polar solvent.
  • the addition amount of the precursor of the group V element and the precursor of the second group III element in step S2 may be based on the excess of the precursor of the second group III element, preferably the foregoing group V element precursor and the second group III element precursor.
  • the molar ratio of the element precursor is 1:10 to 1:2.
  • step S3 includes: adding the first III-V group Nanoclusters are injected into the precursor of the third group III element or into the mixed system formed by the second trialkylphosphine ligand and the precursor of the third group III element for reaction to prepare the first group containing III-V quantum dots Product system.
  • the above step S3 is performed in a non-polar solvent.
  • the initial concentration of the precursor of the third group III element in the raw material system formed in step S3 can be adjusted according to actual needs, thereby improving the raw material utilization rate or the optical performance of the quantum dots.
  • the raw material system formed in step S3 refers to a mixture of the first III-V group nanoclusters, the third group III element precursor and the optional second trialkylphosphine ligand.
  • the raw material system formed in step S3 further includes a non-polar solvent.
  • the concentration of the precursor of the third group III element in the raw material system in step S3 is controlled to be 0.5-1 mmol/3 mL. This concentration is the initial concentration before the reaction starts.
  • concentration of the precursor of the third group III element in the initial reactant of step S3 is higher, which can make the reaction proceed toward the positive reaction.
  • the volatilization of the precursor of the group V element generated by the reverse reaction is reduced to be taken away by the inert gas (the synthesis of quantum dots is usually carried out under an inert gas atmosphere), and the utilization of the precursor of the group V element is improved.
  • the III-V quantum dots Take the III-V quantum dots as InP quantum dots as an example, which reduces the occurrence of the following reactions:
  • the precursor of the second group III element is already in a liquid state at a higher temperature, and the above step S1 does not require additional solvent to dissolve the precursor of the second group III element.
  • the non-polar solvent in step S2 and step S3 may be independently selected from any one or more of octadecene, hexadecane, dodecane and squalane, but not Limited to this.
  • step S3 is performed at 220-320°C, preferably at 220-260°C, the formed III-V group
  • the size and particle size distribution of the quantum dots are more ideal, the peak shape of the UV-Vis first exciton absorption peak is sharper, and the high-order exciton absorption peak appears near the first exciton absorption peak, and the reaction efficiency is higher.
  • the reaction temperature in the above step S3 can be maintained at a specific temperature or fluctuate within the above temperature range.
  • the above preparation method further includes: step S4, reacting the first product system with the second III-V family nanocluster to make the III-V family quantum dots continue to grow, and the second III-V family nanocluster
  • the cluster can be prepared according to step S1 and step S2.
  • step S1 and step S2 can be re-synthesized III-V family nanoclusters as the second III-V family nanoclusters, wherein the raw materials used in the preparation can be the same as those used in the preparation of the first III-V family nanoclusters Different or the same, or take a part of the first III-V family nanoclusters from the product of step S2 as the second III-V family nanoclusters.
  • the raw material system formed in step S4 refers to a mixture of the first product system and the second III-V group nanoclusters.
  • the raw material system formed in step S4 further includes a non-polar solvent.
  • the precursor of the third group III element still exists in the first product system, which can be used for the growth of quantum dots in step S4.
  • the precursor of the third group III element does not exist in the first product system, and the precursor of the group III element may be additionally added in step S4 for the quantum dot growth in step S4.
  • the second III-V group nanoclusters are injected into the first product system. Injecting the second III-V family nanoclusters through step S4 can make the III-V family quantum dots continue to grow more uniformly, and can ensure that the grown III-V family quantum dots have a good size distribution.
  • the growth temperature of the quantum dots in step S4 can refer to the current temperature range commonly used for the growth of quantum dots.
  • step S4 is performed at 220-320°C. In order to better maintain monodispersity, it is more preferably 220-320°C. Performed at 260°C.
  • the reaction temperature in step S4 can be maintained at a specific temperature or fluctuate within the above range.
  • the concentration of the precursor of the third group III element has a significant effect on the sharpness of the UV-Vis absorption peak of the finally formed group III-V quantum dot. Generally, the sharper the absorption peak means the better the monodispersity of nanocrystal size.
  • the concentration of the precursor of the third group III element in the raw material system formed in step S4 is controlled to be 0.1-1 mmol/3 mL. This concentration is the initial concentration before the reaction starts.
  • step S3 further includes separating and purifying the first product system to obtain group III-V quantum dots.
  • the above preparation method further includes: reacting the III-V group quantum dots, the fifth group III element precursor, and the third group III-V nanocluster, so that the group III-V quantum dots continue to grow into more Large-size III-V family quantum dots, and the third III-V family nanoclusters are prepared by steps S1 and S2.
  • step S1 and step S2 can be re-synthesized III-V family nanoclusters as the third III-V family nanoclusters, wherein the raw materials used in the preparation can be the same as those used in the preparation of the first III-V family nanoclusters Different or the same, or take a part of the first group III-V nanoclusters from the product of step S2 as the third group III-V nanoclusters.
  • the fifth group III element precursor may be prepared in step S1, and the preparation materials thereof may be different or the same as the preparation materials of the second group III element precursor and the third group III element precursor.
  • the fifth group III element precursor may be a carboxylate precursor of a group III element.
  • the carboxylate precursor of the group III element may be aluminum carboxylate, indium carboxylate, or gallium carboxylate, but is not limited thereto.
  • the carboxylate precursor can be formate, acetate, propionate, butyrate, valerate, caproate, heptanoate, caprylate, dodecanoate, hexadecanoate , Stearate, oleate, benzoate, but not limited to these.
  • TMS-St can be removed by separation and purification, so the following reactions can be reduced and the utilization rate of the group V element precursor can be improved.
  • the presence of the foregoing fifth group III element precursor can promote the final size monodispersion of quantum dots.
  • the initial concentration of the fifth group III element precursor in the raw material system formed in step S4 can be adjusted according to actual needs, so as to improve the raw material utilization rate or the optical performance of the quantum dots.
  • the concentration of the precursor of the fifth group III element in the raw material system formed in step S4 is controlled to be 0.1-1mmol/3mL, which is the reaction
  • the initial concentration before the start makes each of the monodisperse III-V quantum dots grow in a layer-by-layer growth mode while maintaining monodispersity.
  • the reaction temperature in step S2 is 20-50°C. Mild temperature can get smaller size nanoclusters, and smaller size nanoclusters can improve the monodispersity of preparing large-size III-V quantum dots.
  • the reaction time of each step can be adjusted according to the reaction temperature.
  • the reaction can be stopped after the utilization of the raw materials is completed or the utilization of the raw materials is constant, and in some cases, it can also be terminated before the quantum dot size distribution deteriorates.
  • the average size of the III-V quantum dots in the first product system is 2 to 4 nm, and the ultraviolet-visible absorption peak is between 480 to 600 nm.
  • the average size of the III-V nanoclusters in step S2 is less than 2 nm, or less than 1 nm.
  • a III-V group quantum dot prepared by the above method the fluorescence emission peak wavelength of the III-V group quantum dot is between 520 and 700 nm, preferably the half-value width of the III-V group quantum dot At 40-50nm, the above-mentioned III-V quantum dots have the characteristics of uniform particle size and monodisperse size. In some embodiments, the III-V quantum dots prepared by the above method have a zinc blende structure.
  • the III-V quantum dots may be further coated or alloyed.
  • the processing method can refer to the existing technology.
  • the raw materials in each step are not limited to the above-mentioned types. In order to achieve different purposes, the raw materials in each step can be increased.
  • the raw materials in step S2 may also include one or more of group II element precursors and group VI element precursors, so as to form III-V-II group nanoclusters or III-V- II-VI group nanoclusters or III-V-VI group nanoclusters.
  • the raw material of the above step S3 further includes a doping element precursor, so as to achieve the doping of the III-V group quantum dots.
  • the doping element may be a doping element known in the prior art, such as a halogen and a transition metal element.
  • At least one non-alkylphosphine ligand may be added to the reaction system in any step.
  • carboxylate precursors of group III elements can also be used as a source of ligands.
  • a quantum dot composition and a light emitting device are provided, each of which includes quantum dots, which are III-V quantum dots or cores prepared by any of the above methods.
  • quantum dots which are III-V quantum dots or cores prepared by any of the above methods.
  • the above-mentioned light emitting device may be a photoluminescence device or an electroluminescence device.
  • the FTIR test shows that In 3+ in In(St) 3 forms a six-coordinate structure with carboxylate groups, and an octahedral structure with three carboxylate groups. After reacting with TOP, the FTIR test showed that each carboxylate group formed a monodentate chelate structure with In 3+ , and the resulting In(TOP)(St) 3 was a tetrahedral coordination structure. Wherein the ligand changes occur, In 3+ and exposing (TMS) 3 P site nucleophilic reactions taking place, and further accelerates the reaction of In 3+ and (TMS) 3 P's.
  • the 31 P NMR spectrum in Figure 1b also shows that TOP and In(St) 3 have a strong coordination effect.
  • concentration of TOP is less than In(St) 3
  • the 31 P NMR peak of TOP is from -30.819ppm
  • a significant shift to -6.7 ppm is similar to that observed for the complex formed by cadmium oleate and tributylphosphine (TBP).
  • TBP cadmium oleate and tributylphosphine
  • a single peak at -6.7 ppm indicates that when the TOP concentration is low, almost all TOP is tightly coordinated with indium ions.
  • the TOP in the solution exceeds 1 equivalent, two peaks are observed, one of which is a broad peak at -30.819 ppm.
  • broad peaks usually indicate that TOP molecules or TOP aggregates are in a complex chemical environment.
  • Figures 1a and 1b show that an In-TOP complex structure is formed between indium stearate and TOP.
  • the ratio of In to TOP in the structure is approximately 1:1.
  • the carboxylate group and The weakening of the bond between In ions may be due to the conversion from bidentate chelation to monodentate chelation.
  • its chemical formula is In(TOP )(St) 3 , the reaction formula is as follows:
  • Example 2 The difference from Example 2 is that the heating device is removed after five minutes, and the reaction mixture is cooled to 30°C.
  • Example 2 The difference from Example 2 is that the heating device is removed after five minutes, and the reaction mixture is cooled to 100°C.
  • Example 2 The difference from Example 2 is that the heating device is removed after five minutes, and the reaction mixture is cooled to 150°C.
  • the ultraviolet absorption spectra of the III-V nanoclusters obtained in Example 3 to Example 5 and Comparative Example 1 are shown in Figures 2a and 2b.
  • the values of (TMS) 3 P and In(TOP)(St) 3 of Example 2 The in-situ FTIR spectrogram that changes with time during the reaction is shown in Figure 2c.
  • Example 2 (the upper circle in the figure) and Comparative Example 1 (the bottom circle in the figure) form two clusters of the product trimethyl silicone stearyl during the reaction.
  • the concentration change of the acid ester (TMS-St) is shown in Figure 2d.
  • the concentration test method is to measure the absorbance at 1724 cm -1 by the FTIR method and perform conversion calculation.
  • TOP clusters can be obtained by reaction at a mild temperature (20-50°C), which appears as an almost colorless solution, as shown in Figure 2a at 320nm. Absorb shoulders. When the reaction temperature was increased to 150°C, the absorption shoulder gradually redshifted to 370nm, and band-edge absorption appeared at 430nm, which proved that the size of the TOP-cluster was growing rapidly. All TOP-clusters are stable when stored in low-temperature ODE solvents (below 10°C) and can grow at slightly higher temperatures.
  • Figure 2c shows the significant difference between the two reactions of Example 2 and Comparative Example 1. After mixing the reactants, both reactions proceeded rapidly, showing the rapid growth of trimethylsilicate stearate (TMS-St) .
  • TMS-St trimethylsilicate stearate
  • the reaction of In(TOP)(St) 3 and (TMS) 3 P in Example 2 is about 70% complete.
  • the 3 P reaction is about 50% complete.
  • the reaction showed a relatively slow process ( ⁇ 400s) to reach equilibrium, and (TMS) 3 P was mostly consumed in the first stage.
  • Embodiment 6 The difference from Embodiment 6 is that the TOP cluster 100 prepared in Embodiment 4 is quickly injected.
  • Embodiment 6 The difference from Embodiment 6 is that the TOP cluster 150 prepared in Embodiment 5 is quickly injected.
  • n-cluster 50 the n-cluster solution prepared in Comparative Example 1, referred to as n-cluster 50 , is quickly injected into the mixture in the three-necked flask.
  • Example 6 The difference from Example 6 is that the n-cluster 150 solution was quickly injected into the mixture in the three-necked flask.
  • the preparation process of the n-cluster 150 solution was the same as that of Comparative Example 1 except that the temperature was 150°C.
  • Figure 3a shows the variation of the UV-Vis spectra of InP quantum dots at various time points during the heating process of step S3 (from room temperature to 260°C) in Example 4;
  • Figure 3b shows when the comparative example 1 is used
  • Figures 3c to 3e show the results obtained when TOP-cluster solutions prepared at different temperatures are injected
  • Figure 3b shows that the size of the InP quantum dots finally obtained by using TOP-clusters (judged by the lowest energy absorption peak/shoulder) is significantly larger than the InP quantum dots obtained by directly heating n-clusters.
  • Figure 3b shows that there is only one absorption shoulder in the UV-Vis spectrum of InP quantum dots synthesized by n-cluster 50 thermal injection, indicating that the particle size distribution is poor. After a long period of growth, the absorption peak is only shifted to the position of ⁇ 510nm.
  • the absorption shoulder of InP quantum dots prepared by thermal injection of n-cluster 150 is even more limited to below 500 nm.
  • InP quantum dots prepared by thermal injection of TOP clusters synthesized at different temperatures can observe a well-defined absorption peak in a wide range of sizes, usually accompanied by high-energy absorption shoulder peaks, which indicates that the prepared InP quantum dots
  • the InP quantum dots have good size monodispersity.
  • Figure 2a shows that the size of the TOP cluster decreases with the decrease of the preparation temperature, but the final size of the nearly monodisperse InP quantum dots is significantly increased (in Figures 3c-3e, the vertical line marks the absorption peak).
  • step S3 When further studying the reaction temperature of step S3 to prepare monodisperse InP quantum dots, it is found that high-quality InP quantum dots can be synthesized above 220°C. See Fig. 7. As the injection temperature goes from 220°C to 260°C, the UV- Vis absorption spectrum characteristics are becoming more and more obvious. Continue to increase the injection temperature will only increase the reaction efficiency, but will not affect the optical properties of the InP quantum dots.
  • TOP-cluster 30 was added to the product system obtained in Example 6 with a syringe, and the dropping rate was 0.9 mL/h, which is equivalent to 0.135 mmol/h of P precursor.
  • the temperature is 240°C.
  • UV-Vis spectroscopy is performed through multiple samples to monitor the reaction in real time.
  • the heating device is removed and the reaction mixture is allowed to cool to room temperature.
  • chloroform/ethanol as a good solvent/poor solvent, the reaction product was separated and purified 3 times.
  • Example 4 The difference from Example 4 is that TOP-cluster 100 is added.
  • Example 4 The difference from Example 4 is that TOP-cluster 150 is added.
  • Example 4 The difference from Example 4 is that n-cluster 50 is added.
  • Examples 9 to 11 and Comparative Example 4 were used to study the effects of injecting TOP-clusters and n-clusters at different temperatures on the growth of InP quantum dots.
  • the ultraviolet absorption spectrum of the grown InP quantum dots is shown in Figure 4a, and the spectral curve is from From top to bottom are the curves of Example 9, Example 10, Example 11, Comparative Example 4, and Example 6;
  • Figure 4b shows the UV absorption of InP quantum dots during the reaction of different clusters as raw materials at different concentrations
  • the peak position changes, and the trend curve from top to bottom is Example 9, Example 10, Example 11, and Comparative Example 4;
  • Figure 4c shows half of InP quantum dots during the reaction process of different clusters as raw materials at different concentrations.
  • the peak width (HWHM) changes, the top trend curve is Comparative Example 4, and the rest are Example 11, Example 10, and Example 9 from top to bottom.
  • the scale and meaning of the abscissa in Figure 4b are the same as those in Figure 4c.
  • Figure 4a shows that the size and size distribution of the prepared InP quantum dots have an obvious relationship with the type of III-V nanocluster (TOP-cluster or n-cluster) added, and also have a greater relationship with the growth temperature during cluster preparation.
  • the n-cluster makes the growth of InP seeds (the InP quantum dots obtained in step S3 of Example 6 can be regarded as seeds, that is, seed crystals) limited, and the spectral characteristics of the corresponding InP quantum dots are not obvious.
  • the size of the corresponding InP quantum dots grows significantly after TOP-cluster injection growth.
  • the four curves from top to bottom in Figure 4b respectively show the changes in the absorption peak position of the InP quantum dots of Examples 9 to 11 and Comparative Example 4 in the step S4 reaction. It can be seen that the average size of the quantum dot changes with time. Generally, the absorption The larger the peak position, the larger the quantum dot size.
  • the results show that the final size of the InP quantum dots obtained by the reaction of the four different types of III-V nanoclusters is different from the size before the start of step S4. Only the reaction of TOP-cluster 30 reached the theoretically sufficient UV-Vis absorption peak position. Generally, the larger the size of the final InP quantum dots, the easier it is for the added nanoclusters to self-nucleate.
  • the TOP-clusters formed in advance at room temperature are almost not large enough to be used as new crystal nuclei.
  • the TOP-clusters formed at room temperature serve as the epitaxial growth monomer and are consumed for the reaction solution. InP seed growth.
  • the half-width at half maximum (HWHM) of the low-energy side of the absorption peak is used to semi-quantitatively illustrate the size distribution of InP quantum dots.
  • the final InP quantum dots obtained by the growth of large-sized III-V nanoclusters (either at high temperature or generated by In(St) 3 precursors) will not only reduce the size, but also deteriorate the size distribution. This may be because the bulky InP clusters are too large during the growth process to be fully utilized as monomers for epitaxial growth, and the severe self-nucleation phenomenon will reduce the size monodispersity of the final product. Therefore, it is preferable that the average size of the nanoclusters used in step S4 is smaller, which also means that the temperature for preparing the nanoclusters is better.
  • the quantum dots of Example 6 were purified and separated, and the purified quantum dots were added to the aforementioned In(TOP)(St) 3 solution to obtain a mixture, in which In(TOP)(St) 3 The content is 1 mmol.
  • the reaction is monitored in real time through multiple sampling UV-Vis spectroscopy tests. When the desired size of InP quantum dots is reached, the heating device is removed and the reaction mixture is cooled to room temperature. Using chloroform/ethanol as a good solvent/poor solvent, the reaction product was purified 3 times.
  • Example 12 The difference from Example 12 is that in a three-necked flask, 0.5 mmol indium acetate and 1.5 mmol stearic acid are mixed and heated to 150° C. for reaction for 20 minutes to form an indium stearate precursor. Continue to blow argon into the above system to remove the acetic acid produced by the metathesis reaction. Then keep 150°C, inject 0.7mL (approximately 1.5mmol) TOP into the three-necked flask, add 3mL ODE, obtain the solution of group III element (indium) precursor In(TOP)(St) 3 , use it as the raw material for the next step The reaction makes the content of In(TOP)(St) 3 0.2 mmol.
  • Example 12 The difference from Example 12 is that in a three-necked flask, 0.2 mmol of indium acetate and 0.6 mmol of stearic acid are mixed and heated to 150° C. for reaction for 20 minutes to form an indium stearate precursor. Continue to blow argon into the above system to remove the acetic acid produced by the metathesis reaction. Then keep 150°C, inject 0.3mL (approximately 0.6mmol) TOP into the three-necked flask, and add 3mL ODE to obtain a solution of group III element precursor In(TOP)(St) 3 , which is used as the raw material for the next reaction to make The content of In(TOP)(St) 3 is 0.5 mmol.
  • Example 12 The difference from Example 12 is that there is no preparation process for the precursor of group III elements.
  • the quantum dots (ultraviolet absorption peak at 500 nm) of Example 6 were purified and separated and dissolved in 3 mL ODE to form a quantum dot system without In(TOP)(St) 3 (that is, its concentration was 0 mmol). Heat to 240°C, and use a syringe to add TOP-cluster 30 to the aforementioned quantum dot system, with a dropping rate of 0.9 mL/h, which is equivalent to 0.135 mmol/h of P precursor. The reaction is monitored in real time through multiple sampling UV-Vis spectroscopy tests. When the desired size of InP quantum dots is reached, the heating device is removed and the reaction mixture is cooled to room temperature. Using chloroform/ethanol as a good solvent/poor solvent, the reaction product was purified 3 times.
  • Example 12 The difference from Example 12 is that in a three-necked flask, 1 mmol indium acetate and 3.5 mmol stearic acid are mixed and heated to 150° C. for reaction for 20 minutes to form an indium stearate precursor.
  • Example 12 the absorption peak position of the quantum dots increased steadily during the growth process, but after the presence of a higher concentration of stearic acid (Hst) in Example 15, the absorption peak position of the quantum dots did not increase steadily, and the growth process 5e, the UV-Vis absorbance of the quantum dots is always inferior to that of Example 12, indicating that free fatty acids can reduce the concentration of quantum dot seeds, and etching occurs instead of dissolving newly formed crystal nuclei. Therefore, it is preferred that free fatty acids are not present during the reaction.
  • Hst stearic acid
  • Example 6 The difference from Example 6 is that the mixture is heated to 220°C, that is, the temperature of the nanoclusters is 220°C when the nanoclusters are injected.
  • Example 6 The difference from Example 6 is that the mixture is obtained by heating to 240°C, that is, the temperature when the nanoclusters are injected is 240°C.
  • Example 6 The UV-Vis spectra of Example 6, Examples 16-17 are shown in Fig. 7.
  • the Abs-650 in the figure represents a quantum dot with the first exciton absorption peak at 650 nm, and so on.
  • Figure 6a shows the UV-Vis spectra of InP quantum dots during the process of Example 6 (corresponding to the three spectral curves below) and Example 9 (corresponding to the five spectral curves above), and the UV-Vis absorption peak position of InP quantum dots ⁇ 480-660nm) is the same as typical CdSe quantum dots, and the absorption spectrum characteristics are very similar to those of CdSe quantum dots.
  • the UV-Vis spectrum in Figure 6a has obvious absorption characteristics, including absorption peaks and high-energy absorption shoulders.
  • the HWHM on the long wavelength side of the absorption peak can characterize the homogeneity of each quantum dot in the quantum dot assembly. With the red shift of the absorption peak, it steadily decreases from 122 meV to 81 meV ( Figure 6b) . It can be seen that increasing the size of quantum dots without changing the size distribution can narrow the peak width steadily.
  • the HWHM defined above mainly measures low-energy absorption peaks (or large-size nanoparticles on one side), so we use the valley/peak absorption ratio as a parameter to define the sharpness of the absorption spectrum.
  • the valley here is the lowest point between the absorption peak and the high-energy shoulder in the UV-Vis spectrum.
  • the size dependence (or peak position dependence) of HWHM and valley/peak absorption ratio of Fig. 6b does not follow the same trend, but Fig. 6a illustrates that a series of InP samples obtained in the embodiment have clear absorption peaks.
  • Fig. 6e is a representative high-resolution TEM image of the InP quantum dots in the embodiment, and its cross-lattice fringes clearly define the single crystal properties of facets.
  • Figure 6f is an X-ray diffraction (XRD) pattern of InP quantum dots with an absorption peak of 618 nm, further confirming that it is a zinc blende structure.
  • XRD X-ray diffraction

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Abstract

本申请提供了一种III-V族量子点的制备方法。该制备方法包括：步骤S1，使第一三烷基膦配体和第一III族元素前体反应，制备得到第二III族元素前体；步骤S2，使第二III族元素前体、V族元素前体反应，得到第一III-V族纳米簇；步骤S3，将第一III-V族纳米簇、第三III族元素前体和可选的第二三烷基膦配体混合进行反应，制备得到含III-V族量子点的第一产物体系。使用第一三烷基膦配体和第一III族元素前体形成的第二III族元素前体在室温下可溶且空间位阻较小，可以形成具有接近一致性状和尺寸极小的第一III-V族纳米簇，进而可以形成几乎单分散的III-V族量子点，实现了尺寸和粒径分布的有效控制。

Description

III-V族量子点的制备方法 技术领域
本申请涉及量子点合成领域，具体而言，涉及一种III-V族量子点的制备方法。
背景技术
尺寸在量子限域范围内的胶体半导体纳米晶(量子点QDs)作为工业常见的发光器件发射源，如在显示、生物医药标记、固态照明等领域得到了广泛应用。虽然量子点的尺寸可调、本征发光纯度高、可以作为理想的发射器发射源，但是以CdSe为基础的量子点通常被认为是工业上唯一可直接生产应用的量子点。尽管量子点还存在稳定性问题，但是最近合成的含铅卤化物钙钛矿量子点被发现具有很高的光学性能。然而上述两种材料中含有的Cd元素和Pb元素引起了社会广泛的关注，因此InP成为了无Cd/Pb的量子点的理想替代品。合成InP和其他III-V族量子点在过去的25年里获得很大的关注。尺寸单分散的CdSe量子点很容易合成，且尺寸可调，其第一激子吸收峰能够覆盖大部分可见光区域(450～650nm)。但是现阶段InP量子点的尺寸和粒径分布在合成化学上都较难控制。
在过去的25年里，所有II-VI族量子点的合成方法都或多或少地被用在III-V族量子点的合成中，但基本上都失败了。CdSe和InP之间有如此大差异，第一种猜测是因为III-V族化合物有更多的共价性质，这是材料本质问题，因此没有简单的解决方案。第二种猜测是In和P前体反应活性有差异，这些前体通常是三(三甲基甲硅烷基)膦((TMS) 3P)和羧酸铟盐。相关研究人员沿着这个猜测投入了大量的研究来降低P前体的反应性，这些研究都得到一定的成果。
最近，发明人发现由脂肪酸铟配体(InP量子点最常见的配体)带来的拥挤的表面钝化能阻碍InP QDs的生长。通过选取具有大体积和较短链长的配体，可以获得更大尺寸的InP量子点，尽管它们的尺寸单分散性仍然显著差于CdSe量子点。在文献中，已经有几个课题组通过研究采用脂肪酸锌辅助InP量子点的合成，或者用脂肪酸锌盐替代脂肪酸酸铟来消除拥挤的表面钝化。尽管通过这种方法合成出的InP量子点会因为掺杂进锌离子而降低其光学性质，但需要指出的是，这种方法已经能合成出迄今为止具有最尖锐吸收光谱的InP量子点。
发明内容
本申请的主要目的在于提供一种III-V族量子点的制备方法，以解决现有技术中所合成的III-V族量子点的尺寸和粒径分布难以控制的问题。
为了实现上述目的，根据本申请的一个方面，提供了一种III-V族量子点的制备方法，包括：步骤S1，使第一三烷基膦配体和第一III族元素前体反应，制备得到第二III族元素前体；步骤S2，使第二III族元素前体、V族元素前体反应，得到第一III-V族纳米簇；步骤S3，将第一III-V族纳米簇、第三III族元素前体和可选的第二三烷基膦配体混合进行反应，制备得到含III-V族量子点的第一产物体系。
进一步地，上述第三III族元素前体为第三三烷基膦配体和第四III族元素前体反应制备得到或者采用步骤S1制备而成。
进一步地，上述第一III族元素前体、第二III族元素前体、第三III族元素前体各自独立地选自III族元素的羧酸盐前体。
进一步地，上述第一三烷基膦配体、第二三烷基膦配体和第三三烷基膦配体中的烷基各自独立地选自C 1～C 10的烷基。
进一步地，上述步骤S3的反应物中不包含自由脂肪酸。
进一步地，上述步骤S1在20～150℃下进行。
进一步地，上述第一三烷基膦配体和第一III族元素前体的摩尔比为1:10～3:1。
进一步地，上述步骤S2在10～150℃下进行。
进一步地，上述步骤S2在20～50℃下进行。
进一步地，上述V族元素前体与第二III族元素前体的摩尔比为1:10～1:2。
进一步地，上述步骤S3包括：将第一III-V族纳米簇注入到第三III族元素前体中或者注入到第二三烷基膦配体和第三III族元素前体形成的混合体系中进行反应，制备得到含III-V族量子点的第一产物体系。
进一步地，上述步骤S3在220～260℃下进行。
进一步地，上述步骤S3中，控制第三III族元素前体在步骤S3所形成的原料体系中的浓度为0.5～1mmol/3mL。
进一步地，上述制备方法还包括：步骤S4，使第一产物体系和第二III-V族纳米簇反应，从而使III-V族量子点继续生长，第二III-V族纳米簇采用步骤S1和步骤S2制备而成。
进一步地，上述步骤S3中的第三III族元素前体过量，使第三III族元素前体在步骤S4所形成的原料体系中的浓度为0.1～1mmol/3mL。
进一步地，在上述步骤S3中，还包括将第一产物进行分离纯化，得到III-V族量子点；制备方法还包括：使III-V族量子点、第五III族元素前体和第三III-V族纳米簇反应，从而使III-V族量子点继续生长，第三III-V族纳米簇采用步骤S1和步骤S2制备而成，第五III族元素前体采用步骤S1制备而成。
进一步地，上述第二III-V族纳米簇或第三III-V族纳米簇的制备过程中，步骤S2的反应温度为20～50℃。
进一步地，上述第一产物体系中的III-V族量子点的平均尺寸为2～4nm。
应用本申请的技术方案，使用第一三烷基膦配体和第一III族元素前体形成的第二III族元素前体在室温下可溶且空间位阻相对较小；利用其与V族元素前体反应可以形成具有接近一致性状和尺寸极小的第一III-V族纳米簇，由于第二III族元素前体在室温下可溶，因此使得步骤S2的反应温度可以从目前常用的高温扩展至室温；以第一III-V族纳米簇和第三III族元素前体和可选的第二三烷基膦配体混合进行反应，可以形成几乎单分散的III-V族量子点，进而实现了对III-V族量子点的尺寸和粒径分布的有效控制。
附图说明
构成本申请的一部分的说明书附图用来提供对本申请的进一步理解，本申请的示意性实施例及其说明用于解释本申请，并不构成对本申请的不当限定。在附图中：
图1a示出了实施例1的液相FTIR光谱图；
图1b示出了实施例1的 31P NMR谱图；
图2a示出了实施例3至实施例5所得到的III-V族纳米簇的紫外吸收光谱图；
图2b示出了对比例1和对比例3所得到的III-V族纳米簇的紫外吸收光谱图；
图2c示出了实施例2和对比例1的随时间变化的原位反应液相FTIR光谱对比图；
图2d示出了实施例2和对比例1的随时间变化的反应中TMS-St浓度对比图；
图3a示出了实施例4在室温到260℃的升温过程中所得到的各个时间点的InP量子点的UV-Vis吸收峰的变化图；
图3b示出了对比例2和对比例3(对应右上插图)反应过程中各个时间点的InP量子点的UV-Vis吸收峰的变化图；
图3c示出了实施例6反应过程中各个时间点的InP量子点的UV-Vis吸收峰的变化图；
图3d示出了实施例7反应过程中各个时间点的InP量子点的UV-Vis吸收峰的变化图；
图3e示出了实施例8反应过程中各个时间点的InP量子点的UV-Vis吸收峰的变化图；
图4a示出了实施例9至11及对比例4得到的InP量子点的UV-Vis光谱图；
图4b示出了实施例9至11及对比例4得到的InP量子点的吸收峰位随着纳米簇浓度(以P元素计)变化的变化图；
图4c示出了实施例9至11及对比例4得到的InP量子点的半半峰宽随着纳米簇浓度(以P元素计)变化的变化图；
图5a示出了实施例12至14及对比例5的生长过程中的InP量子点的UV-Vis相对吸光度变化图；
图5b示出了实施例12得到的InP量子点的TEM图；
图5b’示出了实施例12得到的InP量子点的TEM图(含标尺)；
图5c示出了对比例5得到的InP量子点的TEM图；
图5d示出了实施例12和实施例15得到的InP量子点的粒径分布图；
图5e示出了实施例12和实施例15的生长过程中的InP量子点的UV-Vis吸光度变化图；图5f示出了实施例12和实施例15的生长过程中InP量子点峰位和该峰位的吸光度变化图；
图6a示出了某些实施例得到的InP量子点的UV-Vis光谱图；
图6b根据图6a绘制了InP量子点不同吸收峰位下的半半峰宽和谷/峰比；
图6c示出了实施例6的InP量子点的TEM图；
图6d示出了实施例9的InP量子点的TEM图；
图6e示出了实施例9的InP量子点的高分辨率TEM图；
图6f示出了实施例9吸收峰为618nm的InP量子点的X射线衍射(XRD)图；
图7示出了实施例6、实施例16～17的UV-Vis光谱图；
图8示出了实施例9(吸收峰位为650nm)的量子点尺寸分布图；
图9示出了某些实施例的量子点制备路线示意图；
图10示出了某些实施例的量子点制备路线示意图。
具体实施方式
需要说明的是，在不冲突的情况下，本申请中的实施例及实施例中的特征可以相互组合。下面将参考附图并结合实施例来详细说明本申请。
需要说明的是，本申请的说明书和权利要求书中的术语“第一”、“第二”等是用于区别类似的对象，而不必用于描述特定的顺序或先后次序。应该理解这样使用的数据在适当情况下可以互换，以便这里描述的本申请的实施例。此外，术语“包括”和“具有”以及他们的 任何变形，意图在于覆盖不排他的包含，例如，包含了一系列步骤或单元的过程、方法、产品或器件不必限于清楚地列出的那些步骤或单元，而是可包括没有清楚地列出的或对于这些过程、方法、产品或器件固有的其它步骤或单元。
某特定族元素前体的摩尔数或者量以该特定族元素的摩尔数为准，比如第一III族元素前体的摩尔数，则计算第一III族元素前体中III族元素的摩尔数。如无特殊说明，紫外可见吸收峰指的是第一激子吸收峰。
如本申请背景技术所分析的，现有技术中虽然对III-V族量子点的合成方法进行了各方面改进，以期望对III-V族量子点的尺寸和粒径分布进行控制，进而改善其尺寸单分散性。但是，目前的效果并不如意。本申请为了控制III-V族量子点的尺寸和粒径分布，提供了一种III-V族量子点制备方法。
在本申请一种典型的实施方式中，提供了一种III-V族量子点的制备方法，该制备方法包括：步骤S1，使第一三烷基膦配体和第一III族元素前体反应，制备得到第二III族元素前体；步骤S2，使第二III族元素前体、V族元素前体反应，得到第一III-V族纳米簇；步骤S3，将第一III-V族纳米簇、第三III族元素前体和可选的第二三烷基膦配体混合进行反应，制备得到含III-V族量子点的第一产物体系。
使用第一三烷基膦配体和第一III族元素前体形成的第二III族元素前体(可以认为是一种配合物)在室温下可溶且空间位阻较小；利用其与V族元素前体反应可以形成具有接近一致性状和尺寸极小的第一III-V族纳米簇，由于第二III族元素前体在室温下可溶，因此使得步骤S2的反应温度可以从目前常用的高温扩展至室温，节省能耗；以第一III-V族纳米簇和第三III族元素前体和可选的第二三烷基膦配体混合进行反应，可以形成几乎单分散的III-V族量子点，进而实现了对III-V族量子点的尺寸和粒径分布的有效控制。
在一些实施例中，第三III族元素前体为第三三烷基膦配体和第四III族元素前体反应制备得到或者采用步骤S1制备而成。量子点制备路线示意图参见图9。其中第三III族元素前体制备所采用的三烷基膦配体和III族元素前体可以和制备第一III族前体所采用的三烷基膦配体和III族元素前体不同或相同。第III族元素前体同样具有室温可溶于反应媒介，且空间位阻较小可促进反应进行的优势。
在一些实施例中，步骤S2反应完毕后，上述III-V纳米簇可以不进行分离纯化，反应产物整体可作为步骤S3的III-V纳米簇的原料。该反应产物整体中可能存在残留的原料，如第二III族元素前体。
在一些实施例中，步骤S3中的第二三烷基膦配体可以不添加，对合成量子点的质量几乎没有影响。
在一些实施例中，上述第一III族元素前体、第二III族元素前体和第三III族元素前体各自独立地选自III族元素的羧酸盐前体。在一些实施例中，当第三III族元素前体不是第三三烷基膦配体和第四III族元素前体反应制备得到的时，第三III族元素前体也可以为III族元素的羧酸盐前体。优选羧酸盐前体中的羧酸根为碳链长度为8～22的羧酸根。上述III族元素的羧酸盐前体可以为脂肪酸盐和脂肪酸反应得到的产物。傅里叶快速转换红外线光谱分析仪(FTIR)测试表明在III族元素的羧酸盐前体中的III族元素与羧酸根基团成双齿螯合结构，与三个羧酸根基团成六配位八面体结构。III族元素的羧酸盐前体与三烷基膦配体反应后，FTIR测试显示每个羧酸根基团与III族元素呈单齿结构，形成的第二III族元素前体也可以成为羧酸盐前体，其呈四面体结构，配位结构的改变会有利于III族元素前体与V族元素前体的反应效率，进而能够进一步控制接近一致性状和尺寸极小的具有第一三烷基膦配体的III-V族纳米簇的形成效率。
在一些实施例中，第四III族元素前体可以为III族元素的羧酸盐前体。
用于各步骤中第一三烷基膦配体、第二三烷基膦配体和第三三烷基膦配体可以相同也可以不同，优选各个烷基膦配体的烷基各自独立地选自C 1～C 10的烷基，在另一些实施例中，上述烷基进一步优选为正丁基、正辛基。
在一些实施例中，步骤S3的反应物中不包含自由脂肪酸，从而减少自由脂肪酸对纳米簇的刻蚀。在一些实施例中，当第四III族元素的羧酸盐前体为脂肪酸盐和脂肪酸反应得到的产物时，通过控制脂肪酸盐和脂肪酸的量，从而控制第三III族元素前体中零自由脂肪酸，进而可以控制步骤S3的反应物中不包含自由脂肪酸。
在一个InP量子点制备的具体实施例中，步骤S1中，当以硬脂酸铟(In(St) 3)为III族元素的羧酸盐前体和以TOP(三辛基膦)作为第一三烷基膦配体时，步骤S1中的配位反应过程如下：
TOP+In(St) 3＝In(TOP)(St) 3。
在一种实施例中，上述步骤S1在20～150℃下进行，如果在较高的温度下进行，可以适当缩短反应时间。
基于上述反应原理，优选第一三烷基膦配体和第一III族元素前体的摩尔比为1:10～3:1。
类似地，优选第三三烷基膦配体和第四III族元素前体的摩尔比为1:10～3:1。
V族元素可选自氮、磷、砷、锑和铋。V族元素前体可以从现有技术中常用的V族元素前体中进行选择，比如上述V族元素前体为三(三甲基甲硅烷基)膦、三(二烷基甲硅烷基)膦、三(二烷基胺基)膦、三(三甲基甲锗烷基)膦、三(二甲基甲氮烷基)膦、三(三烷基甲硅烷基)胂、三(二烷基甲硅烷基)胂、三(二烷基胺基)胂、磷化氢、三氯化磷、白磷、磷化钙或磷化钠，但不限于此。
在一些实施例中，如前所述，由于第二III族元素前体在室温下可溶，步骤S2的可实施温度范围较广，上述步骤S2可以在10～150℃下进行，优选在20～50℃下进行。在一些实施例中，为了加快反应进程，优选步骤S2在非极性溶剂中进行。
在一些实施例中，步骤S2中V族元素前体与第二III族元素前体的添加量可以以第二III族元素前体过量为准，优选上述V族元素前体与第二III族元素前体的摩尔比为1:10～1:2。以III-V族量子点为InP量子点为例，发明人在反应过程中利用液相FTIR对反应进行原位监控，根据监控结果推测该步骤中发生的主要反应如下：
In(TOP)(St) 3+(TMS) 3P→InP(TOP-Cluster)+TMS-St+TOP
而传统利用In(St) 3作为III族元素前体时，与(TMS) 3P反应的反应如下：
In(St) 3+(TMS) 3P→InP(n-Cluster)+TMS-St。
另外在监控过程中可以发现InP(n-Cluster)的紫外可见吸收峰比InP(TOP-Cluster)的紫外可见吸收峰红移很多，说明所形成的InP(TOP-Cluster)的粒径相对于InP(n-Cluster)显著减小，有利于形成尺寸单分散性的III-V族量子点。
经过试验证明，实施步骤S3时，在一些实施例中，可以进一步采用如下方式对所形成的量子点的尺寸和粒径分布进行更有效地控制，上述步骤S3包括：将第一III-V族纳米簇注入第三III族元素前体中或者注入到第二三烷基膦配体和第三III族元素前体形成的混合体系中进行反应，制备得到含III-V族量子点的第一产物体系。在一些实施例中，上述步骤S3在非极性溶剂中进行。
在另一些实施例中，步骤S3中，第三III族元素前体在步骤S3所形成的原料体系中的初始浓度可以根据实际需要进行调整，从而提高原材料利用率或者量子点的光学性能。步骤S3 所形成的原料体系指的是，第一III-V族纳米簇、第三III族元素前体和可选的第二三烷基膦配体的混合物。在一些实施例中，步骤S3所形成的原料体系还包括非极性溶剂。
在一些实施例中，步骤S3中，控制第三III族元素前体在步骤S3中的原料体系中的浓度为0.5～1mmol/3mL。该浓度为反应开始前的初始浓度，通过控制第三III族元素前体的浓度，第三III族元素前体在步骤S3的初始反应物中的浓度较高，可以使得反应朝正反应进行从而减少逆反应生成的V族元素前体的挥发被惰性气体(量子点的合成通常在惰性气体氛围下进行)带走，提高V族元素前体的利用率。以III-V族量子点为InP量子点为例，即减少以下反应的发生：
(InP) cluster+TMS-St+TOP→In(TOP)(St) 3+(TMS) 3P↑
在一些实施例中，第二III族元素前体在较高温度下已经为液体状态，上述步骤S1不需要额外使用溶剂去溶解第二III族元素前体。
在一些实施例中，上述步骤S2和步骤S3中的非极性溶剂可以各自独立地选自十八烯、十六烷、十二烷和角鲨烷中的任意一种或多种，但不限于此。
为了进一步提高所合成的量子点的质量，本申请进一步对加热反应温度进行了研究，发现步骤S3在220～320℃下进行，优选在220～260℃下进行时，所形成的III-V族量子点的尺寸和粒径分布更为理想，UV-Vis第一激子吸收峰的峰形更加尖锐，且在第一激子吸收峰附近出现高阶激子吸收峰，且反应效率更高。上述步骤S3反应温度可以保持在特定温度，也可以在上述温度范围内进行波动。
为了进一步合成大尺寸量子点，优选上述制备方法还包括：步骤S4，使第一产物体系和第二III-V族纳米簇反应使III-V族量子点继续生长，第二III-V族纳米簇可以按照步骤S1和步骤S2制备。具体地，可以重新按步骤S1和步骤S2合成III-V族纳米簇作为第二III-V族纳米簇，其中制备所采用的原料可以和第一III-V族纳米簇的制备所采用的原料不同或者相同，或者从步骤S2产物中取一部分第一III-V族纳米簇作为第二III-V族纳米簇。步骤S4所形成的原料体系指的是，第一产物体系和第二III-V族纳米簇的混合物。在一些实施例中，步骤S4所形成的原料体系还包括非极性溶剂。
在一些实施例中，第一产物体系中仍然存在第三III族元素前体，可用于步骤S4的量子点生长。在一些实施例中，第一产物体系中不存在第三III族元素前体，则可以在步骤S4中额外添加III族元素前体用于步骤S4的量子点生长。
在一些实施例中，步骤S4中，将第二III-V族纳米簇注入至第一产物体系中。通过步骤S4注入第二III-V族纳米簇可以使III-V族量子点继续生长更为均匀，能够保证生长后的III-V族量子点具有良好的尺寸分布。在一些实施例中，步骤S4中量子点的生长温度可以参考目前量子点生长常用的温度范围，优选步骤S4在220～320℃下进行，为了更好地保持单分散性，更优选在220～260℃下进行。步骤S4反应温度可以保持在特定温度，也可以在上述范围内进行波动。
在一些实施例中，其中第三III族元素前体的浓度对最终形成的III-V族量子点的UV-Vis吸收峰的尖锐度具有明显影响。通常，吸收峰越尖锐意味着纳米晶尺寸单分散性越好。通过步骤S3中的第三III元素前体过量，控制第三III族元素前体在步骤S4所形成的原料体系中的浓度为0.1～1mmol/3mL。该浓度为反应开始前的初始浓度，通过控制第三III族元素前体的浓度，使得单分散的III-V族量子点中各个量子点以逐层生长的模式保持单分散性进行生长。
在一些实施例中，在步骤S3中，还包括将第一产物体系进行分离纯化，得到III-V族量子点。
在一些实施例中，上述制备方法还包括：使III-V族量子点、第五III族元素前体和第三III-V族纳米簇反应，从而使III-V族量子点继续生长成更大尺寸的III-V族量子点，第三III-V族纳米簇采用步骤S1和步骤S2制备而成。具体地，可以重新按步骤S1和步骤S2合成III-V族纳米簇作为第三III-V族纳米簇，其中制备所采用的原料可以和第一III-V族纳米簇的制备所采用的原料不同或者相同，或者从步骤S2产物中取一部分第一III-V族纳米簇作为第三III-V族纳米簇。
在一些实施例中，第五III族元素前体可以采用步骤S1制备而成，其制备原料可以和第二III族元素前体和第三III族元素前体的制备原料不同或相同。量子点制备路线示意图参见图10。在一些实施例中，第五III族元素前体可以为III族元素的羧酸盐前体。
在一些实施例中，III族元素的羧酸盐前体可以为羧酸铝、羧酸铟或者羧酸镓，但不限于此。羧酸盐前体可以为甲酸盐、乙酸盐、丙酸盐、丁酸盐、戊酸盐、己酸盐、庚酸盐、辛酸盐、十二烷酸盐、十六烷酸盐、硬脂酸盐、油酸盐、苯甲酸盐，但不限于此。
以III-V族量子点为InP量子点为例，通过分离纯化可以去除TMS-St，因此可以减少下述的反应，提高V族元素前体的利用率。
(InP) cluster+TMS-St+TOP→In(TOP)(St) 3+(TMS) 3P↑
上述第五III族元素前体的存在可以促进最终量子点的尺寸单分散。
在另一些实施例中，步骤S4中，第五III族元素前体在步骤S4所形成的原料体系中的初始浓度可以根据实际需要进行调整，从而提高原材料利用率或者量子点的光学性能。在上述实施例中，通过步骤S4中补加第五III族元素前体，控制第五III族元素前体在步骤S4所形成的原料体系中的浓度为0.1～1mmol/3mL，该浓度为反应开始前的初始浓度，使得单分散的III-V族量子点中各个量子点以逐层生长的模式保持单分散性进行生长。
在一些实施例中，在新的III-V族纳米簇的制备过程中，所述步骤S2的反应温度为20～50℃。温和的温度可以得到较小尺寸的纳米簇，而较小尺寸的纳米簇可以提高制备大尺寸III-V族量子点的单分散性。
在一些实施例中，各个步骤的反应时间可以根据反应温度进行调整，一般根据原料利用完毕或者原料利用率恒定后可以停止反应，某些时候也可以在量子点尺寸分布恶化前终止。
在一些实施例中，上述第一产物体系中的III-V族量子点的平均尺寸为2～4nm，其紫外可见吸收峰在480～600nm之间。
在另一些实施例中，步骤S2中的III-V族纳米簇的平均尺寸小于2nm，或者小于1nm。
在一些实施例中，上述方法制得的一种III-V族量子点，该III-V族量子点的荧光发射峰波长在520～700nm之间，优选III-V族量子点的半峰宽在40～50nm，上述III-V族量子点具有粒度均匀、尺寸单分散的特点。在一些实施例中，上述方法制得的III-V族量子点具有闪锌矿结构。
在一些实施例中，在制备得到III-V族量子点后，还可以对III-V族量子点进一步进行包覆或者合金化处理。处理方法可以参考现有技术。
需要说明的是，各个步骤中的原料不仅限于上述几种，为了实现不同的目的，各个步骤中的原料可以增加。例如，在一些实施例中，步骤S2中的原料还可以包括II族元素前体、VI族元素前体中的一种或多种，从而形成III-V-II族纳米簇或者III-V-II-VI族纳米簇或者III-V-VI族纳米簇。又例如，在一些实施例中，上述步骤S3的原料还包括掺杂元素前体，从而实现对III-V族量子点的掺杂。掺杂元素可以是现有技术已知的掺杂元素，比如卤素、过渡金属元素。 又例如，在一些实施例中，至少一种非烷基膦配体可以加入到任一步骤的反应体系中。需要说明的是，在一些实施例中，III族元素的羧酸盐前体也可以作为配体的来源。
在本申请又一种典型的实施方式中，提供了一种量子点组合物和发光器件，各自均包括量子点，该量子点为上述任一种方法制备得到的III-V族量子点或者核壳结构的III-V族量子点。上述发光器件可以是光致发光器件或者电致发光器件。
以下将结合实施例和对比例，进一步说明本申请的有益效果。
实施例1
第二III族元素前体In(TOP)(St) 3的制备
将TOP(三辛基膦)加入到In(St) 3(硬脂酸铟)的十二烷溶液中，不断增加TOP的加入量(0、0.3、0.6、1、3个当量，当量是指TOP与In(St) 3的摩尔比)，采用液相FTIR监测液相中物质的反应，监测结果见图1a(0当量时为虚线，强度峰值由大到小的曲线分别对应3、1、0.6、0.3个当量)，同时采用核磁共振(NMR)分析不同TOP和In(St) 3摩尔比所得到的配合物In(TOP)(St) 3的 31P NMR，结果见图1b。
图1a中，随着TOP用量的增多，COO-(羧酸根)基团的不对称伸缩振动模式不断发生变化，直到加入与其等量的TOP。In(St) 3的不对称伸缩振动在红外谱图中表现为位于1585cm -1和1544cm -1处的多重峰。当TOP的浓度和In(St) 3浓度相同时，不对称伸缩振动变成高频，表现为1604cm -1的峰。这种频移被认为是羧酸盐基团和金属离子之间的键合显著弱化的特征，即从双齿鳌合转变为单齿鳌合。FTIR测试表明在In(St) 3中的In 3+与羧酸根基团成六配位结构，与三个羧酸根基团成八面体结构。与TOP反应后，FTIR测试显示每个羧酸根基团与In 3+呈单齿鳌合结构，从而形成的In(TOP)(St) 3为四面体配位结构。上述配位改变的发生，暴露出In 3+与(TMS) 3P发生亲核反应的位点，进而加快了In 3+与(TMS) 3P的反应。
图1b的 31P NMR图谱同样表明TOP和In(St) 3之间具有强烈的配位(coordination)作用，当TOP的浓度小于In(St) 3时，TOP的 31P NMR峰从-30.819ppm显著偏移到-6.7ppm，类似于油酸镉和三丁基膦(TBP)形成的配合物所观察到的。在-6.7ppm处的单个尖峰表明TOP浓度较低时，几乎所有TOP都与铟离子牢固配位。当溶液中的TOP超过1当量时，观察到两个峰，其中一个为-30.819ppm处的宽峰。在核磁共振谱中，宽峰通常表明TOP分子或TOP聚集物(aggregation)处于复杂的化学环境中。
总体看来，图1a和1b总体表明硬脂酸铟盐和TOP之间形成了In-TOP配合物结构，结构中In和TOP的比例近似1:1，形成配合物后，羧酸根基团和In离子之间的键变弱，可能是因为从双齿鳌合转换为单齿鳌合结构，考虑电荷平衡及反应过程中没有产生单独的酸或其他羰基化合物，可以推论其化学式为In(TOP)(St) 3，反应式如下：
In(St) 3+TOP→InP+In(TOP)(St) 3
实施例2
III-V族纳米簇的制备
在三口烧瓶中，将0.3mmol醋酸铟和0.9mmol硬脂酸混合并加热至150℃反应20min，形成硬脂酸铟前体。向反应体系中持续吹氩气以除去复分解反应产生的乙酸。然后向三口烧瓶中注入0.4mL(约0.9mmol)TOP，五分钟后移除加热装置，使反应混合物冷却至室温，得到第二III族元素前体In(TOP)(St) 3。此时向其中快速注入0.48mL(TMS) 3P的ODE溶液(约0.15mmol(TMS) 3P)，反应进行约1分钟，所形成的产物命名为TOP-Cluster或TOP-簇。整个反应过程都在氩气保护下剧烈地搅拌。
实施例3
与实施例2的区别在于，五分钟后移除加热装置，使反应混合物冷却至30℃。
实施例4
与实施例2的区别在于，五分钟后移除加热装置，使反应混合物冷却至100℃。
实施例5
与实施例2的区别在于，五分钟后移除加热装置，使反应混合物冷却至150℃。
对比例1
在三口烧瓶中，将0.3mmol醋酸铟和0.9mmol硬脂酸混合并加热至150℃反应20min，形成硬脂酸铟前体。向反应体系中持续吹氩气以除去复分解反应产生的乙酸。待温度冷却至50℃后，向三口烧瓶中注入0.48mL(TMS) 3P的ODE溶液(约0.15mmol(TMS) 3P)，反应进行约1分钟，所形成的产物命名为n-Cluster或n-簇或nTOP-簇。整个反应过程都在氩气保护下剧烈地搅拌。
实施例3至实施例5和对比例1所得到的III-V族纳米簇的紫外吸收光谱图见图2a和2b，实施例2的(TMS) 3P和In(TOP)(St) 3的反应过程中随时间变化的原位FTIR光谱图见图2c，实施例2(图中上方圈)和对比例1(图中下方圈)形成两种簇的反应过程中产物三甲基硅硬脂酸酯(TMS-St)的浓度变化参见图2d，浓度测试方法为以FTIR法测1724cm -1处的吸光度并进行转换计算。
鉴于In(TOP)(St) 3前体在ODE中良好的溶解性，TOP簇可以在温和的温度(20-50℃)下反应得到，表现为几乎无色的溶液，图2a在320nm处有吸收肩。当反应温度提高到150℃时，吸收肩逐渐红移到370nm，并在430nm出现带边吸收，证明TOP-簇的尺寸在快速增长。所有TOP-簇储存在低温ODE溶剂中(低于10℃)都很稳定，能够在稍高的温度下生长。
图2b所显示的对比例1中，在反应溶液中使用In(St) 3作为III族元素前体，不加入TOP，在相同温度下的n-簇的吸收峰比TOP-簇的吸收峰红移很多，说明n-簇的尺寸较小。特别是In(St) 3在ODE中室温溶解度低，50℃是其反应的最低温度，这样所制备的InP的n-簇尺寸较小。
图2c展示了实施例2和对比例1两种反应的显著区别点，在混合反应物后，两种反应都迅速进行，表现出三甲基硅硬脂酸酯(TMS-St)的快速增长。在第一阶段(0-15s)，实施例2中的In(TOP)(St) 3和(TMS) 3P的反应完成了约70％，对比例1中的In(St)3和(TMS) 3P的反应完成了约50％。过了第一阶段后，反应都呈现出相对比较慢的过程(～400s)才达到平衡，(TMS) 3P在第一阶段被消耗了大部分。反应达到平衡时，实施例2的In(TOP)(St) 3与(TMS) 3P完全反应并转化为TOP-Cluster与TMS-St。但对比例1的TMS-St生成量只有88％这意味着约～12％的(TMS) 3P没有和In(St) 3反应。另外，在通常的反应温度下，(TMS) 3P在高温下也因被挥发而造成更多浪费。这说明用In(TOP)(St) 3替换In(St) 3后，能够提高(TMS) 3P的利用率。
图2a至2d的结果共同说明两种前体In(TOP)(St) 3和In(St) 3具有很关键的差别，图2d表明In(TOP)(St) 3的反应活性高于In(St) 3，会促使(TMS) 3P更完全地转换为TOP-簇。
实施例6
III-V族量子点的制备
将In(Ac) 3(1mmol)和3mmol硬脂酸在三口烧瓶中加热至150℃，得到第三III族元素前体，在氩气流下保温20分钟除去上述体系中的乙酸。接下来，将3mL ODE和1.4mL(约3mmol)TOP加入到三口烧瓶中，150℃保持5min后，加热至260℃得到混合物。向三口烧瓶中的混合物中快速注入实施例3准备的TOP-簇 30溶液。在第一次注入后，反应温度降至 240℃持续进行。通过多次取样的UV-Vis光谱测试来监控反应。30℃下制备的TOP簇标记为TOP-簇 30，以此类推。
实施例7：
与实施例6的区别在于，快速注入实施例4准备的TOP簇 100。
实施例8：
与实施例6的区别在于，快速注入实施例5准备的TOP簇 150。
对比例2：
与实施例6的区别在于，向三口烧瓶中的混合物中快速注入对比例1准备的n-簇溶液，简称n-簇 50。
对比例3：
与实施例6的区别在于，向三口烧瓶中的混合物中快速注入n-簇 150溶液，n-簇 150溶液的制备过程除了温度为150℃之外其他同对比例1。
其中，图3a示出了实施例4在步骤S3升温过程中(从室温到260℃)各个时间点的InP量子点的UV-Vis光谱的变化图；图3b示出了当采用对比例1的n-簇代替TOP-簇时所得到的各个时间点的InP量子点的UV-Vis吸收峰的变化图；图3c至3e示出了注入不同温度下制备的TOP-簇溶液时所得到的各个时间点的InP量子点的UV-Vis吸收峰的变化图。
图3a和3b的对比可以看出，采用TOP-簇最终得到的InP量子点大小(通过最低能吸收峰/肩来判断)明显大于直接加热n-簇得到的InP量子点。图3b表明利用n-簇 50热注射合成InP量子点的UV-Vis光谱中只有一个吸收肩，说明粒径分布差，经过长时间的生长，吸收峰也只是位移到了～510nm的位置。而n-簇 150热注射制备的InP量子点的吸收肩更是限制在500nm以下。相反，不同温度合成的TOP簇通过热注射的方法制备的InP量子点在较宽的尺寸范围内都可以观察到一个界限清晰的吸收峰，通常伴随着高能量的吸收肩峰，这表明所制备的InP量子点具有较好的尺寸单分散性。图2a中表明TOP簇的尺寸随着制备温度的降低而降低，但近似单分散的InP量子点的最终尺寸是显著增大的(图3c-3e中，垂直线标记吸收峰值)。
进一步地研究步骤S3制备单分散InP量子点的反应温度时发现，在220℃以上可以合成高质量的InP量子点，参见图7，随着注射温度从220℃到260℃，最终产品的UV-Vis吸收图谱特征越来越明显。继续提高注射温度只会提高反应效率，但不会影响InP量子点的光学性能。
实施例9
III-V族量子点的生长
为了合成更大尺寸的III-V族量子点，利用注射器向实施例6所得到的产物体系中加入TOP-簇 30，其滴加速度0.9mL/h，相当于P前体0.135mmol/h，反应温度为240℃。通过多次取样进行UV-Vis光谱测试从而实时监测反应。当达到所需尺寸的InP量子点时，移走加热装置，使反应混合物冷却至室温。使用氯仿/乙醇作为良溶剂/不良溶剂，对反应产物分离提纯3次。
实施例10
与实施例4的区别在于加入的是TOP-簇 100。
实施例11
与实施例4的区别在于加入的是TOP-簇 150。
对比例4
与实施例4的区别在于加入的是n-簇 50。
通过实施例9至11及对比例4研究注入不同温度下得到的TOP-簇和n-簇对InP量子点生长的影响，长大后的InP量子点的紫外吸收光谱见图4a，光谱曲线从上至下分别是实施例9、实施例10、实施例11、对比例4、实施例6的曲线；图4b示出了不同簇在不同浓度下作为原料的反应过程中InP量子点的紫外吸收峰位变化，趋势曲线从上至下分别是实施例9、实施例10、实施例11、对比例4；图4c示出了不同簇在不同浓度下作为原料的反应过程中InP量子点的半半峰宽(HWHM)变化，最上面的趋势曲线为对比例4，其余从上至下依次为实施例11、实施例10和实施例9。图4b的横坐标的刻度及含义同图4c。
图4a显示，制备的InP量子点尺寸和尺寸分布与添加的III-V族纳米簇类型(TOP-簇或n-簇)有明显的关系，且与簇制备时的生长温度也有较大关系。n-簇使得InP种子(实施例6的步骤S3中得到的InP量子点可视为种子，即晶种)的生长有限，对应的InP量子点的光谱特征不明显。相反，相比于n-簇，从UV-Vis吸收光谱特征来看，对应的InP量子点的尺寸在TOP-簇注射生长后有显著地生长。此外，也可以看出通过降低制备TOP-簇的合成温度，最终获得的InP量子点在尺寸和尺寸分布方面变得更好。
图4b从上至下四条曲线分别显示了实施例9至11及对比例4的InP量子点在步骤S4反应中吸收峰位变化，可以看出量子点平均尺寸随时间的变化，一般地，吸收峰位越大，量子点尺寸越大。结果显示，四个不同类型III-V族纳米簇反应分别得到的InP量子点最终的尺寸与步骤S4开始前的尺寸都各不相同。只有TOP-簇 30的反应达到了理论上充分生长的UV-Vis吸收峰位置。一般地，最终的InP量子点尺寸越大，加入的纳米簇越容易发生自成核。在室温下预先形成的TOP-簇几乎都不够大，从而难以作为新晶核，在步骤S4InP量子点进一步生长期间，室温下形成的TOP-簇作为外延生长单体，并被消耗用于反应液中InP种子的生长。
根据图4c使用吸收峰的低能量侧的半半峰宽(HWHM)半定量地说明InP量子点的尺寸分布。借助大尺寸的III-V纳米簇生长(无论是高温下或是In(St) 3前体生成的)获得的最终InP量子点不仅会使得尺寸降低，同时尺寸分布也变差。这可能是因为大体积的InP簇在生长过程中太大，无法被充分利用为外延生长的单体，而且严重的自成核现象会降低最终产物的尺寸单分散性。因此，优选步骤S4中使用的纳米簇平均尺寸较小，也意味着制备纳米簇的温度低一些较好。
实施例12
III-V族量子点的生长
在三口烧瓶中，将1mmol醋酸铟和3mmol硬脂酸混合并加热至150℃反应20min，形成硬脂酸铟前体。向上述体系中持续吹氩气以除去复分解反应产生的乙酸。然后保持150℃，向三口烧瓶中注入1.4mL(约0.9mmol)TOP，加入3mL ODE，得到III族元素前体In(TOP)(St) 3的溶液。
将实施例6的量子点(紫外吸收峰为500nm)进行纯化分离，将纯化的量子点加至前述In(TOP)(St) 3的溶液中得到混合物，其中In(TOP)(St) 3的含量为1mmol。加热至240℃，利用注射器向混合物中加入TOP-簇 30，其滴加速度0.9mL/h，相当于P前体0.135mmol/h。通过多次取样UV-Vis光谱测试从而实时监测反应。当达到所需尺寸InP量子点时，移走加热装置使反应混合物冷却至室温。使用氯仿/乙醇作为良溶剂/不良溶剂，对反应产物提纯3次。
实施例13
与实施例12的区别在于，在三口烧瓶中，将0.5mmol醋酸铟和1.5mmol硬脂酸混合并加热至150℃反应20min，形成硬脂酸铟前体。向上述体系中持续吹氩气以除去复分解反应产生的乙酸。然后保持150℃，向三口烧瓶中注入0.7mL(约1.5mmol)TOP，加入3mL ODE， 得到III族元素(铟)前体In(TOP)(St) 3的溶液，将其作为原料进行下一步反应，使得In(TOP)(St) 3的含量为0.2mmol。
实施例14
与实施例12的区别在于，在三口烧瓶中，将0.2mmol醋酸铟和0.6mmol硬脂酸混合并加热至150℃反应20min，形成硬脂酸铟前体。向上述体系中持续吹氩气以除去复分解反应产生的乙酸。然后保持150℃，向三口烧瓶中注入0.3mL(约0.6mmol)TOP，加入3mL ODE，得到III族元素前体In(TOP)(St) 3的溶液，将其作为原料进行下一步反应，使得In(TOP)(St) 3的含量为0.5mmol。
对比例5
与实施例12的区别在于，没有III族元素前体制备过程。
将实施例6的量子点(紫外吸收峰为500nm)进行纯化分离并溶解于3mL ODE中形成量子点体系，不加In(TOP)(St) 3(即其浓度为0mmol)。加热至240℃，利用注射器向前述量子点体系中加入TOP-簇 30，其滴加速度0.9mL/h，相当于P前体0.135mmol/h。通过多次取样UV-Vis光谱测试从而实时监测反应。当达到所需尺寸InP量子点时，移走加热装置使反应混合物冷却至室温。使用氯仿/乙醇作为良溶剂/不良溶剂，对反应产物提纯3次。
图5a中可以看出，In(TOP)(St) 3越高，相对吸光度的峰越尖锐，从图5b、图5b’和图5c的TEM图中可以看出，高浓度的In(TOP)(St) 3可以得到更好的尺寸单分散，图5d至5f也印证了这一点，从而说明In(TOP)(St) 3过量添加使得量子点在生长时期尺寸单分散性会更好。
实施例15
与实施例12的区别在于，在三口烧瓶中，将1mmol醋酸铟和3.5mmol硬脂酸混合并加热至150℃反应20min，形成硬脂酸铟前体。
参见图5f，实施例12中，量子点生长的过程的吸收峰位稳定增加，但是实施例15存在较高浓度硬脂酸(Hst)后，量子点的吸收峰位没有稳定增加，而且生长过程中，参见图5e，量子点的紫外可见吸光度始终不如实施例12，说明自由脂肪酸可以降低量子点种子的浓度，发生了刻蚀，而非溶解新形成的晶核。因此，优选反应过程中不存在自由脂肪酸。
实施例16
与实施例6的区别在于，加热至220℃得到混合物，即注入纳米簇时的温度220℃。
实施例17
与实施例6的区别在于，加热至240℃得到混合物，即注入纳米簇时的温度240℃。
实施例6、实施例16～17的UV-Vis光谱图见图7。
需要说明的是，附图中Abs-650代表的是第一激子吸收峰位为650nm的量子点，以此类推。图6a为实施例6(对应下面三条光谱曲线)过程中和实施例9(对应上面五条光谱曲线)过程中的InP量子点的UV-Vis光谱图，InP量子点的UV-Vis吸收峰位(～480-660nm)与典型的CdSe量子点相同，而且吸收光谱特征与CdSe量子点的吸收光谱非常相似。特别是图6a中UV-Vis光谱具有明显的吸收特征，包括吸收峰和高能吸收肩。正如上文所说，在吸收峰的长波长侧的HWHM可以表征量子点集合体中各个量子点的同质性，随着吸收峰的红移，其从122meV稳定地降低到81meV(图6b)。由此可知，增大量子点尺寸，且尺寸分布不变，其峰宽可稳定地变窄。
如上所述，在InP生长过程中通常会不断形成小的纳米粒子。这意味着在InP量子点的UV-Vis吸收峰往小尺寸一侧有明显拖尾。上面定义的HWHM主要测量低能吸收峰(或者说 是大尺寸一侧纳米粒子)，因此我们将谷/峰吸收比作为参数来定义吸收光谱的尖锐度。这里的谷是UV-Vis光谱中吸收峰和高能肩之间的最低点。图6b的HWHM和谷/峰吸收比的尺寸依赖性(或峰位依赖性)不遵循相同的趋势，但图6a说明实施例得到的一系列InP样品都有清晰的吸收峰。用TEM测试小尺寸的InP量子点(UV-Vis吸收峰在～550nm以下)是比较困难的，因此其大小采用文献(Xie,R.；Li,Z.；Peng,X.,Nucleation K inetics vs Chemical Kinetics in the Initial Formation of Semiconductor Nanocrystals.J.Am.Chem.Soc.2009,131(42),15457-15466)报道的尺寸曲线间接确定。其他样品的尺寸和形状则使用TEM测定(图5b，6c，6d)。在650nm处有吸收峰的InP量子点(图6d)的平均尺寸被确定为5.7nm，具有相对偏差7％(图8)。对比类似尺寸的CdSe纳米晶体，这个尺寸分布水准是比较高的。
图6e是实施例中InP量子点具有代表性的高分辨率TEM图像，其交叉晶格条纹明确定义的小平面的单晶性质。图6e中晶格常数，
Figure PCTCN2020099768-appb-000001
(200)、
Figure PCTCN2020099768-appb-000002
(220)、
Figure PCTCN2020099768-appb-000003
(111)与闪锌矿InP结构一致。图6f是吸收峰为618nm的InP量子点的X射线衍射(XRD)图，进一步证实其为闪锌矿结构。
以上所述仅为本申请的优选实施例而已，并不用于限制本申请，对于本领域的技术人员来说，本申请可以有各种更改和变化。凡在本申请的精神和原则之内，所作的任何修改、等同替换、改进等，均应包含在本申请的保护范围之内。

Claims (18)

  1. 一种III-V族量子点的制备方法，其特征在于，包括：
    步骤S1，使第一三烷基膦配体和第一III族元素前体反应，制备得到第二III族元素前体；
    步骤S2，使所述第二III族元素前体、V族元素前体反应，得到第一III-V族纳米簇；
    步骤S3，将所述第一III-V族纳米簇、第三III族元素前体和可选的第二三烷基膦配体混合进行反应，制备得到含III-V族量子点的第一产物体系。
  2. 根据权利要求1所述的制备方法，其特征在于，所述第三III族元素前体为第三三烷基膦配体和第四III族元素前体反应制备得到或者采用所述步骤S1制备而成。
  3. 根据权利要求2所述的制备方法，其特征在于，所述第一III族元素前体、所述第二III族元素前体、所述第三III族元素前体各自独立地选自III族元素的羧酸盐前体。
  4. 根据权利要求2所述的制备方法，其特征在于，所述第一三烷基膦配体、所述第二三烷基膦配体和所述第三三烷基膦配体中的烷基各自独立地选自C 1～C 10的烷基。
  5. 根据权利要求1所述的制备方法，其特征在于，所述步骤S3的反应物中不包含自由脂肪酸。
  6. 根据权利要求1所述的制备方法，其特征在于，所述步骤S1在20～150℃下进行。
  7. 根据权利要求1所述的制备方法，其特征在于，所述第一三烷基膦配体和所述第一III族元素前体的摩尔比为1:10～3:1。
  8. 根据权利要求1所述的制备方法，其特征在于，所述步骤S2在10～150℃下进行。
  9. 根据权利要求1所述的制备方法，其特征在于，所述步骤S2在20～50℃下进行。
  10. 根据权利要求1所述的制备方法，其特征在于，所述V族元素前体与所述第二III族元素前体的摩尔比为1:10～1:2。
  11. 根据权利要求1所述的制备方法，其特征在于，所述步骤S3包括：将所述第一III-V族纳米簇注入到所述第三III族元素前体中或者注入到所述第二三烷基膦配体和所述第三III族元素前体形成的混合体系中进行反应，制备得到含III-V族量子点的第一产物体系。
  12. 根据权利要求1所述的制备方法，其特征在于，所述步骤S3在220～260℃下进行。
  13. 根据权利要求1所述的制备方法，其特征在于，所述步骤S3中，控制所述第三III族元素前体在步骤S3所形成的原料体系中的浓度为0.5～1mmol/3mL。
  14. 根据权利要求1或2所述的制备方法，其特征在于，所述制备方法还包括：
    步骤S4，使所述第一产物体系和第二III-V族纳米簇反应，从而使所述III-V族量子 点继续生长，所述第二III-V族纳米簇采用所述步骤S1和所述步骤S2制备而成。
  15. 根据权利要求14所述的制备方法，其特征在于，所述步骤S3中的所述第三III族元素前体过量，使所述第三III族元素前体在步骤S4所形成的原料体系中的浓度为0.1～1mmol/3mL。
  16. 根据权利要求1或2所述的制备方法，其特征在于，在所述步骤S3中，还包括将所述第一产物进行分离纯化，得到所述III-V族量子点；所述制备方法还包括：使所述III-V族量子点、第五III族元素前体和第三III-V族纳米簇反应，从而使所述III-V族量子点继续生长，所述第三III-V族纳米簇采用所述步骤S1和所述步骤S2制备而成，所述第五III族元素前体采用所述步骤S1制备而成。
  17. 根据权利要求14或16所述的制备方法，所述第二III-V族纳米簇或所述第三III-V族纳米簇的制备过程中，所述步骤S2的反应温度为20～50℃。
  18. 根据权利要求1所述的制备方法，其特征在于，所述第一产物体系中的III-V族量子点的平均尺寸为2～4nm。
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