Patent RU-2692929-C1 (RU)
Title: Method for colloidal synthesis of quantum dots of a core structure / multilayer shell
Inventor: Samokhvalov Pavel Sergeevich
IPC: B82B3/00
Filed: 2018-10-10
Granted: 2019-06-28
Abstract: FIELD: physics. 
     SUBSTANCE: use of colloidal synthesis of photoluminescent semiconductor nanoparticles (quantum dots) of nucleus / multilayer shell structure for colloidal synthesis. Essence of the invention lies in the fact that the method of colloidal synthesis of quantum dots of the nucleus / multilayer shell structure includes the following stages: the first stage of preparation of precursors, including preparation of precursors of chalcogens and metals of II and VI groups for synthesis of nuclei of quantum points and escalating the shell; second stage of synthesis of quantum dot nuclei, involving heating precursor of metal to 240–280 °C, chalcogen precursor injection, reduced temperature to 210–230 °C, incubation for 3–5 minutes, as well as subsequent reduction of temperature to 55–65 °C; at the third stage, purification of the synthesized quantum dot nuclei involves adding to the reaction mixture with the synthesized nuclei the precipitation quantum points in an amount equal to the initial volume of the reaction mixture, centrifuging and dissolving quantum dot nuclei in a nonpolar solvent, followed by gel filtration of the obtained quantum dot nuclei in a nonpolar solvent, as well as counting the number of synthesized quantum dot kernels; fourth stage of modification of surface ligands of quantum dot nuclei, including addition to obtained solution of 1000-fold excess, relative to number of quantum dot nuclei, oleylamine and sodium borohydride, further deposition of quantum dots by adding precipitator in volume equal to volume of solution with nuclei of quantum dots, centrifugation of obtained mixture, and adding to obtained residue with nuclei quantum dots of 1000-fold excess, relative to number of nuclei of quantum dots, oleylamine and sodium borohydride, as well as a non-polar solvent for complete dissolution of the quantum dot quantum deposit, then the obtained solution is filtered and a precipitant is added to the filtrate until complete quantum dot coagulation, subsequent centrifugation of the obtained mixture, dissolving a residue of quantum dot nuclei in a nonpolar solvent, and filtering the obtained solution of quantum dot nuclei into a flask with an organic solvent and then stripping the nonpolar solvent at 50–70 °C; at the fifth stage, a multilayer shell is built up, for which the cleaned quantum dot kernels are transferred into a three-necked flask, through which the reaction mixture is evacuated, the inert gas is fed and precursors are added, after which oleylamine quantum dots are added to the solution of the purified nuclei in an amount of at least 1000-fold excess relative to the number of quantum dot nuclei, evacuation of said mixture and its heating to 90–100 °C for 18–22 minutes, with blowing of inert gas and subsequent cooling to 50–60 °C, first layer of shell, including addition of stabilizing agent, heating to 100–120 °C for 8–12 minutes, adding a given number of metal precursor atoms, heating to 165–175 °C, holding the reaction mixture at this temperature for 8–12 minutes, cooling mixture to 100–120 °C, adding a predetermined number of chalcogen precursor atoms, followed by heating to 165–175 °C, holding the reaction mixture at this temperature for 8–12 minutes, cooling the reaction mixture to 100–120 °C, and building second, third and subsequent layers according to a procedure similar to buildup of first layer of shell, wherein after completion of last layer of shell layer additionally held for 8–12 minutes at 165–175 °C and cooled to 55–65 °C in inert gas current; sixth stage of modification of surface ligands of quantum dot shell, including addition to synthesized quantum points of precipitant, until complete coagulation of quantum dots, centrifugation and complete dissolution of quantum point precipitate in organic solvent mixture, salts of primary amine and alkylcarbonic acid, preheated until complete dissolution of components, subsequent incubation of quantum dots in said solution for 10–14 hours, filtration, and addition of stabilizing agent, followed by removal of organic solvent. 
     EFFECT: possibility of obtaining highly stable quantum dots with high fluorescence efficiency, and preparation of their surface for binding of biological recognition molecules, for their subsequent use in creation of highly sensitive biomedical diagnostic test systems. 
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