A method for extending the fluorescence lifetime of CuInSe2 quantum dots
By modifying the surface of CuInSe2 quantum dots with ligand molecules with triplet energy of 1.0-1.5eV, energy transfer between the quantum dot exciton energy level and the ligand molecule triplet energy level is achieved, which solves the problem of short lifetime of CuInSe2 quantum dots and extends the lifetime by tens of microseconds to adapt to different luminescence applications.
Patent Information
- Application Number
- CN202211482643.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-11-24
- Publication Date
- 2025-09-16
- Estimated Expiration
- 2042-11-24
AI Technical Summary
The fluorescence lifetime of CuInSe2 quantum dots is short, which limits their application prospects in some slower physical and chemical processes. Existing technologies make it difficult to effectively control their excited state lifetime.
By modifying the surface of CuInSe2 quantum dots with ligand molecules with triplet energy of 1.0-1.5eV, such as 1-TCA, 2-TCA and 5-TCA, energy transfer between the quantum dot exciton energy level and the ligand molecule triplet energy level is achieved, thereby extending the exciton state lifetime.
The radiation lifetime of CuInSe2 quantum dots has been successfully extended from hundreds of nanoseconds to tens of microseconds to meet the needs of different luminescence applications.
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Figure CN118064152B_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a method for regulating the excited state lifetime of CuInSe2 quantum dots Background Art
[0002] In molecular systems, when the excited state energy is low, the non-radiative decay rate is very rapid due to the law of energy level differences. This results in a generally low molecular fluorescence yield in the near-infrared band. However, near-infrared light has important application prospects in fields such as bioimaging, so the development of near-infrared materials with high fluorescence quantum yield (PLQY) is crucial.
[0003] CuInSe2 quantum dots are a kind of heavy element-free near-infrared luminescent material, whose emission comes from the conduction band electrons and Cu + Due to the recombination of vacancies, the Stokes shift is typically large, and the full width at half maximum of the emission peak is wide. The electroacoustic coupling strength in quantum dots is weaker than the molecular vibrational modes, so the energy level difference law has little impact on the non-radiative decay of quantum dots. Non-radiative decay mainly originates from surface defect states, but the use of very strong ligands can greatly reduce this effect. Therefore, thiol-liganded CuInSe2 quantum dots generally have high PLQY. However, their fluorescence lifetime is typically only on the order of hundreds of nanoseconds, which limits their application prospects in some slower physical chemistry applications.
[0004] In quantum dots, the spin quantum number is not a good quantum number, and the exciton state is a mixture of triplets and singlets. Therefore, the emission lifetime cannot be controlled in a similar way to molecules. However, the surface of quantum dots usually has many molecular ligands. According to literature reports, if the triplet energy of the ligand molecule is lower than the exciton energy of the quantum dot, the exciton energy of the quantum dot can be transferred to the triplet energy level of the ligand molecule. On this basis, if the energy level difference between the ligand molecule and the quantum dot exciton energy level is designed to a certain value, so that the triplet state of the ligand molecule can return to the exciton energy level of the quantum dot, the radiation lifetime of the quantum dot can also be controlled.
[0005] We used 5-TCA as a ligand for CuInSe2 quantum dots and achieved the goal of regulating the lifetime of CuInSe2 quantum dots from 150ns to 69μs. Summary of the Invention
[0006] The present invention aims to regulate the excited state lifetime of CuInSe2 quantum dots to adapt to luminescence applications in different situations.
[0007] The method for regulating the excited state lifetime of CuInSe2 quantum dots is achieved by energy transfer between the exciton energy level of the CuInSe2 quantum dots and the triplet energy level of the ligand molecules.
[0008] In the method for regulating the excited state lifetime of CuInSe2 quantum dots, the surface ligand molecules of the CuInSe2 quantum dots are ligand molecules with triplet state energy of 1.0-1.5 eV, including 1-TCA, 2-TCA and 5-TCA.
[0009] In the method for regulating the excited state lifetime of CuInSe2 quantum dots, the number of surface ligand molecules of one CuInSe2 quantum dot is 1-100 (preferably 10-20).
[0010] As a preferred solution, the present invention uses CuInSe2 as the surface ligand of CuInSe2 quantum dots. One CuInSe2 quantum dot is surface-modified with 10-20 ligand molecules, which can successfully control the original radiation lifetime of the CuInSe2 quantum dot of 150ns to 69μs.
[0011] The present invention modifies the quantum dot surface with a ligand whose triplet energy is close to the exciton state of the CuInSe2 quantum dot by regulating the ligand on the quantum dot surface. The exciton energy of the CuInSe2 quantum dot can be quickly transferred to the triplet state of the ligand molecule. At the same time, since the energy of the molecular triplet state is close to the exciton energy of the CuInSe2 quantum dot, energy transfer from the molecular triplet state back to the exciton state of the CuInSe2 quantum dot can also occur, thereby extending the lifetime of the exciton state of the CuInSe2 quantum dot. This method can extend the lifetime of the quantum dot exciton state with a radiation lifetime of hundreds of nanoseconds to tens of microseconds. BRIEF DESCRIPTION OF THE DRAWINGS
[0012] Figure 1 Schematic diagram of the method for regulating CuInSe2 quantum dots.
[0013] Figure 2 To regulate the fluorescence lifetime of CuInSe2 quantum dots before and after. DETAILED DESCRIPTION
[0014] The present invention is further illustrated by examples and drawings.
[0015] Example 1
[0016] 0.56 g of Se particles, 2 mL of diphenylphosphine, and 2 mL of oleylamine were mixed and heated to 90°C under a nitrogen atmosphere to form a Se precursor solution. 0.55 g of zinc acetate, 5 mL of octadecene, 4 mL of oleylamine, and 1 mL of dodecanethiol were mixed and heated to 120°C under a nitrogen atmosphere to form a zinc sulfide shell precursor solution.
[0017] 87 mg of indium acetate, 28 mg of zinc acetate, 3 mL of oleylamine, and 3 mL of octadecene were added to a three-necked flask and maintained at 80°C under a nitrogen atmosphere for 30 minutes. Then, 58 mg of cuprous iodide was quickly added. The temperature was raised to 190°C, and 0.43 g of a Se precursor solution was quickly added. The temperature was then maintained at 190°C for 10 minutes. The temperature was then lowered to 80°C, and 10 mL of hexane and 10 mL of acetone were added. The mixture was centrifuged at 7200 rpm for 10 minutes, and the precipitate was dissolved in n-hexane to obtain CuInSe2 cores with a particle size of 2.5 nm.
[0018] The resulting CuInSe2 core was added to 3 mL of octadecene and 1 mL of zinc sulfide shell precursor. The temperature was raised to 180°C and maintained for one hour under an anhydrous nitrogen atmosphere. The temperature was then lowered to 80°C, and 10 mL of n-hexane and 10 mL of acetone were added. The mixture was centrifuged at 7200 rpm, and the resulting precipitate was dissolved in hexane. The resulting quantum dots had a particle size of 3 nm and a quantum fluorescence yield of approximately 50%.
[0019] Take 5 ml of the above quantum dots with a concentration of 10 μmol / L, add 0.002 g of 5-TCA powder, ultrasonicate for 10 minutes, and filter to obtain a clear solution. Place the solution in a glove box for 1 hour to remove oxygen, and then place it in a sealed container to test its fluorescence lifetime.
[0020] 1 μmol / L of the above-mentioned CuInSe2 quantum dot solution with dodecanethiol ligand and 1 μmol / L of a mixed solution of CuInSe2 / 5-TCA (1:12, ratio of the number of CuInSe2 quantum dots to the number of ligand molecules) were placed in a 1 cm cuvette to test their fluorescence lifetimes respectively, using a fluorescence spectrometer (Edinburgh Instruments; FLS1000-stm).
[0021] When testing a pure quantum dot solution (concentration of 1 μM), the cuvette was placed on the sample holder and excited using the instrument's built-in picosecond laser at an excitation wavelength of 600 nm. The fluorescence decay curve at 900 nm was measured over time, and the fluorescence decay curve obtained was fitted with a single exponential decay curve to obtain a fluorescence lifetime of 150 ns. When testing a CuInSe2 / 5-TCA (1:20) mixed solution, the cuvette was placed on the sample holder and excited using the instrument's built-in microsecond pulsed xenon lamp. In conjunction with the instrument's spectrometer, an excitation wavelength of 600 nm was selected, and the fluorescence decay curve at 900 nm was measured. The fluorescence decay curve obtained was fitted with a single exponential decay curve to obtain a fluorescence lifetime of 60 μs.
[0022] Example 2
[0023] 0.56 g of Se particles, 2 mL of diphenylphosphine, and 2 mL of oleylamine were mixed and heated to 90°C under a nitrogen atmosphere to form a Se precursor solution. 0.55 g of zinc acetate, 5 mL of octadecene, 4 mL of oleylamine, and 1 mL of octanethiol were mixed and heated to 120°C under a nitrogen atmosphere to form a precursor solution for the zinc sulfide shell layer.
[0024] 87 mg of indium acetate, 28 mg of zinc acetate, 3 mL of oleylamine, and 3 mL of octadecene were added to a three-necked flask and maintained at 80°C under a nitrogen atmosphere for 30 minutes. Then, 58 mg of cuprous iodide was quickly added. The temperature was raised to 195°C, and 0.43 g of a Se precursor solution was quickly added. The temperature was then maintained at 195°C for 10 minutes. The temperature was then lowered to 80°C, and 10 mL of hexane and 10 mL of acetone were added. The mixture was centrifuged at 7200 rpm for 10 minutes, and the precipitate was dissolved in n-hexane to obtain CuInSe2 cores with a particle size of 3.0 nm.
[0025] The resulting CuInSe2 core was added to 3 mL of octadecene and 1 mL of zinc sulfide shell precursor. The temperature was raised to 180°C under a nitrogen atmosphere and held for one hour. The temperature was then lowered to 80°C, and 10 mL of n-hexane and 10 mL of acetone were added. The mixture was then centrifuged at 7200 rpm, and the resulting precipitate was dissolved in hexane. The resulting quantum dots had a particle size of 3.5 nm and a quantum fluorescence yield of approximately 40%.
[0026] Take 5 ml of the above quantum dots with a concentration of 10 μmol / L, add 0.002 g of 5-TCA powder, and ultrasonicate for 10 minutes. Place the filtered solution in a glove box for 1 hour to remove oxygen, and then place it in a sealed container to test its fluorescence lifetime.
[0027] 1 μmol / L of the above-mentioned CuInSe2 quantum dot solution with octanethiol ligand and 1 μmol / L of CuInSe2 / 5-TCA (1:20) mixed solution were placed in 1 cm cuvettes to test their fluorescence lifetimes respectively, using a fluorescence spectrometer (Edinburgh Instruments; FLS1000-stm).
[0028] When testing a pure quantum dot solution (concentration of 1 μM), the cuvette was placed on the sample holder and excited using the instrument's built-in picosecond laser at an excitation wavelength of 600 nm. The fluorescence decay curve at 900 nm was measured over time, and the fluorescence decay curve obtained was fitted with a single exponential decay curve to obtain a fluorescence lifetime of 130 ns. When testing a CuInSe2 / 5-TCA (1:12) mixed solution, the cuvette was placed on the sample holder and excited using the instrument's built-in microsecond pulsed xenon lamp. In conjunction with the instrument's spectrometer, an excitation wavelength of 600 nm was selected, and the fluorescence decay curve at 900 nm was measured. The fluorescence decay curve obtained was fitted with a single exponential decay curve to obtain a fluorescence lifetime of 63 μs.
[0029] Example 3
[0030] A mixture of 0.56 g of Se particles, 2 mL of diphenylphosphine, and 2 mL of oleylamine was heated to 90°C under a nitrogen atmosphere to form a Se precursor solution. A mixture of 0.55 g of zinc acetate, 5 mL of octadecene, 4 mL of oleylamine, and 1 mL of hexanethiol was heated to 120°C under a nitrogen atmosphere to form a precursor solution for the zinc sulfide shell layer.
[0031] 87 mg of indium acetate, 28 mg of zinc acetate, 3 mL of oleylamine, and 3 mL of octadecene were added to a three-necked flask and maintained at 80°C under a nitrogen atmosphere for 30 minutes. Then, 58 mg of cuprous iodide was quickly added. The temperature was raised to 185°C, and 0.43 g of a Se precursor solution was quickly added. The temperature was then maintained at 185°C for 10 minutes. The temperature was then lowered to 80°C, and 10 mL of hexane and 10 mL of acetone were added. The mixture was centrifuged at 7200 rpm for 10 minutes, and the precipitate was dissolved in n-hexane to obtain CuInSe2 cores with a particle size of 2.0 nm.
[0032] The resulting CuInSe2 core was added to 3 mL of octadecene and 1 mL of zinc sulfide shell precursor. The temperature was raised to 180°C under a nitrogen atmosphere and maintained for one hour. The temperature was then lowered to 80°C, and 10 mL of n-hexane and 10 mL of acetone were added. The mixture was centrifuged at 7200 rpm, and the resulting precipitate was dissolved in hexane. The resulting quantum dots had a particle size of 3.0 nm and a quantum fluorescence yield of approximately 40%.
[0033] Take 5 ml of the above quantum dots with a concentration of 10 μmol / L, add 0.002 g of 5-TCA powder, and ultrasonicate for 10 minutes. Place the filtered solution in a glove box for 1 hour to remove oxygen, and then place it in a sealed container to test its fluorescence lifetime.
[0034] 1 μmol / L of the above-mentioned CuInSe2 quantum dot solution with hexanethiol ligand and 1 μmol / L of CuInSe2 / 5-TCA (1:10) mixed solution were placed in 1 cm cuvettes to test their fluorescence lifetimes respectively, using a fluorescence spectrometer (Edinburgh Instruments; FLS1000-stm).
[0035] When testing a pure quantum dot solution (concentration of 1 μM), the cuvette was placed on the sample holder and excited using the instrument's built-in picosecond laser at an excitation wavelength of 600 nm. The fluorescence decay curve at 900 nm was measured over time, and the fluorescence decay curve obtained was fitted with a single exponential decay curve to obtain a fluorescence lifetime of 110 ns. When testing a CuInSe2 / 5-TCA (1:10) mixed solution, the cuvette was placed on the sample holder and excited using the instrument's built-in microsecond pulsed xenon lamp. The instrument's spectrometer was used to select an excitation wavelength of 600 nm, and the fluorescence decay curve at 900 nm was measured. The fluorescence decay curve obtained was fitted with a single exponential decay curve to obtain a fluorescence lifetime of 60 μs.
Claims
1. A method for regulating the excited state lifetime of CuInSe2 quantum dots, characterized by: The surface of CuInSe2 quantum dots with an emission center wavelength of 800-950nm is modified with ligand molecules with a triplet energy level of 1.0-1.5 eV; the CuInSe2 quantum dots are CuInSe2 quantum dots with a zinc sulfide shell and ligands on the surface; the ligand molecules are one or more of 1-tetrabenzoic acid, 2-tetrabenzoic acid and 5-tetrabenzoic acid; The number of ligand molecules modified on the surface of a CuInSe2 quantum dot is 10-20; the ligands on the surface of the CuInSe2 quantum dot are one or two of octanethiol (OT) and hexanethiol (HT).
2. The method for regulating the excited state lifetime of CuInSe2 quantum dots according to claim 1, characterized in that: The ligand molecule is 5-tetrabenzoic acid (5-TCA).
3. The method for regulating the excited state lifetime of CuInSe2 quantum dots according to claim 1, characterized in that: The size of the CuInSe2 core is 2-4 nm, and the shell thickness is 0.1-1 nm.
4. The method for regulating the excited state lifetime of CuInSe2 quantum dots according to claim 1, characterized in that: The ligand on the surface of CuInSe2 quantum dots is HT.