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US-12624284-B2 - Method for preparing stable and bright luminescent quantum rod nanocomposites

US12624284B2US 12624284 B2US12624284 B2US 12624284B2US-12624284-B2

Abstract

Method of preparing a quantum rod nanocomposite, the method involving: combining a CdSe/CdS quantum rod, a metal ion catalyst, and a zinc precursor thereby forming a CdSe/Cd x Zn 1-x S/ZnS quantum rod, wherein 0≤X<1; optionally purifying the CdSe/Cd x Zn 1-x S/ZnS quantum rod; combining the CdSe/Cd x Zn 1-x S/ZnS quantum rod with an inorganic oxide precursor thereby forming an inorganic oxide encapsulated CdSe/Cd x Zn 1-x S/ZnS quantum rod, wherein the CdSe/Cd x Zn 1-x S/ZnS quantum rod is at least partially encapsulated by an inorganic oxide coating; and optionally combining the inorganic oxide encapsulated CdSe/Cd x Zn 1-x S/ZnS quantum rod with a binder thereby forming a binder coated inorganic oxide encapsulated CdSe/Cd x Zn 1-x S/ZnS quantum rod and curing the binder thereby forming the quantum rod nanocomposite.

Inventors

  • Maksym PRODANOV
  • Chengbin Kang
  • Valerii Vladimirovich Vashchenko
  • Abhishek Kumar Srivastava

Assignees

  • THE HONG KONG UNIVERSITY OF SCIENCE AND TECHNOLOGY

Dates

Publication Date
20260512
Application Date
20230915

Claims (20)

  1. 1 . A method of preparing a quantum rod nanocomposite, the method comprising: combining a CdSe/CdS quantum rod, a metal ion catalyst, and a zinc precursor thereby forming a CdSe/Cd x Zn 1-x S/ZnS quantum rod, wherein 0≤X<1; optionally purifying the CdSe/Cd x Zn 1-x S/ZnS quantum rod; combining the CdSe/Cd x Zn 1-x S/ZnS quantum rod with an inorganic oxide precursor thereby forming an inorganic oxide encapsulated CdSe/Cd x Zn 1-x S/ZnS quantum rod, wherein the CdSe/Cd x Zn 1-x S/ZnS quantum rod is at least partially encapsulated by an inorganic oxide coating; and optionally combining the inorganic oxide encapsulated CdSe/Cd x Zn 1-x S/ZnS quantum rod with a binder thereby forming a binder coated inorganic oxide encapsulated CdSe/Cd x Zn 1-x S/ZnS quantum rod and curing the binder thereby forming the quantum rod nanocomposite.
  2. 2 . The method of claim 1 , wherein the zinc precursor is a zinc salt.
  3. 3 . The method of claim 1 , wherein the zinc precursor is Zn(O(C═O)R 1 ) 2 , ZnO 2 (P═O)R 1 , Zn(S(C═S)N(R 1 ) 2 ) 2 , or a mixture thereof, wherein R 1 is C 1 -C 30 alkyl or C 3 -C 30 cycloalkyl.
  4. 4 . The method of claim 1 , wherein the metal ion catalyst comprises a metal ion selected from the group consisting of Ti 2+ , Fe 2+ , Ni 2+ , Hg 2+ , Pb 2+ , Pd 2+ , Cu + , Cu 2+ , Ag + , and Au + .
  5. 5 . The method of claim 1 , wherein the metal ion catalyst comprises a metal ion selected from the group consisting of Cu + , Cu 2+ , Ag + , and Au + .
  6. 6 . The method of claim 1 , wherein the metal ion catalyst is combined with the CdSe/CdS quantum rod before the zinc precursor is combined; or the metal ion catalyst is combined with the CdSe/CdS quantum rod after the zinc precursor is combined.
  7. 7 . The method of claim 1 , wherein the metal ion catalyst is present at 0.01-10 mol % relative to Cd in the CdSe/CdS quantum rod.
  8. 8 . The method of claim 1 , wherein the inorganic oxide coating comprises aluminium oxide, titanium oxide, zinc oxide, zirconium oxide, magnesium oxide, silica, or a mixture thereof.
  9. 9 . The method of claim 1 , wherein the inorganic oxide precursor is selected from the group consisting of Ti(OR 2 ) 4 , Al(OR 2 ) 3 , Si(OR 2 ) 4 , perhydropolysilazane, and mixtures thereof, wherein R 2 for each instance is independently C 1 -C 10 alkyl.
  10. 10 . The method of claim 1 , wherein the inorganic oxide precursor is selected from the group consisting of aluminum isopropoxide, tetraethoxysilane, and mixtures thereof.
  11. 11 . The method of claim 1 , wherein the step of combining the CdSe/Cd x Zn 1-x S/ZnS quantum rod with the inorganic oxide precursor further comprises combining an auxiliary agent having the chemical structure: (R 2 O) 3 Si—(CH 2 ) n A 1 , wherein n is a whole number selected from 1-20; and A 1 is —CO 2 H, —NH 2 , —PO(OH) 2 , or —SH; or the step of combining the CdSe/Cd x Zn 1-x S/ZnS quantum rod with the inorganic oxide precursor further comprises combining a modifying agent selected from the group consisting of an alkali hydroxide, an inorganic salt, a reducing agent, and a water absorber.
  12. 12 . The method of claim 1 , wherein the binder is a UV curable binder or a thermal curable binder.
  13. 13 . The method of claim 1 , wherein the binder comprises one or more monomers selected from the group consisting of acrylate, methacrylate, styrene, vinyl chloride, acrylonitrile, cyanoacrylate; and an epoxy-based binder; or the binder is a polymer selected from the group consisting of polyvinylidene chloride, nylon, ethylene-vinyl alcohol, polyvinyl fluoride, and polytetrafluoroethylene.
  14. 14 . The method of claim 1 , wherein the binder coated inorganic oxide encapsulated CdSe/Cd x Zn 1-x S/ZnS quantum rod is exposed to a partial vacuum one or more times prior to curing the binder.
  15. 15 . The method of claim 1 , wherein the quantum rod nanocomposite has a photoluminescence quantum yield of 77-88% and a luminescence wavelength between 460-660 nm.
  16. 16 . The method of claim 1 , wherein the metal ion catalyst is copper (I) acetate, silver (I) acetate, silver (I) nitrate, or a mixture thereof; the zinc precursor is a zinc (II) carboxylate, a zinc (II) phosphonate, a zinc (II) dithiocarbamate, or a mixture thereof; the inorganic oxide precursor is selected from the group consisting of Ti(OR 2 ) 4 , Al(OR 2 ) 3 , Si(OR 2 ) 4 , perhydropolysilazane, and mixtures thereof, wherein R 2 for each instance is independently C 1 -C 10 alkyl; and the inorganic oxide encapsulated CdSe/Cd x Zn 1-x S/ZnS quantum rod is combined with the binder, wherein the binder the binder is a UV curable binder or a thermal curable binder; or the binder is a polymer selected from the group consisting of polyvinylidene chloride, nylon, ethylene-vinyl alcohol, polyvinyl fluoride, and polytetrafluoroethylene.
  17. 17 . The method of claim 16 , wherein the metal ion catalyst is copper (I) acetate; the zinc precursor is Zn(O(C═O)R 1 ), wherein R 1 is C 1 -C 30 alkyl; and the inorganic oxide precursor is selected from the group consisting of Ti(OR 2 ) 4 , Si(OR 2 ) 4 , and mixtures thereof.
  18. 18 . The method of claim 16 , wherein the metal ion catalyst is copper (I) acetate; the zinc precursor is zinc oleate; and the inorganic oxide precursor is Ti(OiPr) 4 , Si(OEt) 4 , or a mixture thereof.
  19. 19 . The method of claim 18 , wherein the binder is a UV curable binder.
  20. 20 . The method of claim 19 , wherein the binder coated inorganic oxide encapsulated CdSe/Cd x Zn 1-x S/ZnS quantum rod is exposed to a partial vacuum one or more times prior to curing the binder.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS The present application claims priority from U.S. Provisional Patent Application No. 63/425,283, filed on Nov. 14, 2022, which is hereby incorporated by reference in its entirety. TECHNICAL FIELD The present disclosure relates to a method of preparing a quantum rod nanocomposite. BACKGROUND The discovery of quantum dots (QDs) with superior optical properties, compared to conventional phosphors, resulted in a revolution in the display industry, which applies not only for LCD, but also for OLED display technology. The quantum dot backlight possesses very sharp, separately located, blue, green and red peaks boosting up the display color gamut by ˜30%, which substantially improves color diversity and making it suitable for new gen ultra-HD (4K and 8K) television. Quantum dot LED (QLED) display technology's rapid commercialization resulted in a new premium product with improved performance. However, QLED technology is disadvantaged by its high price and power consumption, which result from a separate continuous film comprising the QDs within the backlight unit resulting in higher material consumption, production cost and light losses when embedded into the display. In this sense, an on-chip coating would be the most efficient configuration. In addition, it would be cheaper as a smaller amount of material is needed. Moreover, in this case, no additional film is used in the display structure. Simple replacement of backlight LEDs with QDs embedded LED would serve the purpose. Implementation of this technology is restricted by thermal quenching of quantum dots, which reduces their efficiency dramatically because of high temperature on top of LED chip. Quantum rods are much more stable than QDs and do not show thermal quenching effect up to 160-200° C. However, two problems still hamper their extensive use as an LED down-converter. First is the long-term stability of quantum rods, which still must be improved for practical application as a down-converter in an on-chip configuration. Despite the absence of serious thermal quenching, long-term photostability of quantum rods is currently limited in the range of hours to tens of hours, depending on the testing conditions. This is far from the industry requirements and must be improved. Another problem facing the adoption of quantum rods is complicated and irreproducible synthesis of the quantum rod material emitting in the green, cyan and blue region. Current methods involving a Cd2+ to Zn2+ exchange approach are very sensitive to quantum rod size, CdS shell thickness and presence of surface defects. As a result, a highly labor-intensive process is required to finally synthesize CdSe/CdS dot-in-rod material capable of undergoing the cation exchange reaction. Moreover, following the Cd2+ to Zn2+ exchange reaction, depending on the surface defects configuration can also proceed with a serious increase of the emission FWHM (full width at half maximum of the luminescence peak) and takes many hours at temperature˜350° C. to achieve green (λmax˜520 nm) emitting product. Thus, overall reproducibility is rather low. There thus exists a need to develop improved methods for preparing quantum rod nanocomposites with enhanced properties that address at least some of the shortcomings described above. SUMMARY Provided herein is a quantum rod down-converting nanocomposite and methods for preparation thereof, which address existing synthetic challenges and improve the quantum material photostability. First, CdSe/CdS quantum rods of the desired length and width are prepared and use it as a framework for the further controlled synthesis of quantum rods with a luminescence at any desired wavelength. This can be accomplished by controlled cation exchange reaction of Cd2+ to Zn2+ using a catalytic amount of a metal ion catalyst having a softness parameter less than that of one or both of Cd2+ and Zn2+ ions and high ion mobility. Further, to improve photoluminescence efficiency and chemical stability of the material, an additional ZnS shell is grown by adding a zinc precursor as needed. The as-prepared quantum rods are then mixed with an inorganic oxide precursor, following by formation of the said inorganic oxide material in presence of the quantum rods, thereby, encapsulating the quantum rods within inorganic oxide matrix. As the formed inorganic oxide material can porous, once obtained it can be mixed with liquid filler and the pores can be filled by multiple vacuumizing of the mixture. Finally, the liquid filler is solidified by the proper method. The as-prepared quantum rod nanocomposite has a required luminescent property and improved photostability. In a first aspect provided herein is a method of preparing a quantum rod nanocomposite, the method comprising: combining a CdSe/CdS quantum rod, a metal ion catalyst, and a zinc precursor thereby forming a CdSe/CdxZn1-xS/ZnS quantum rod, wherein 0≤X<1; optionally purifying the CdSe/CdxZn1-xS/ZnS quant