CN112852405A

CN112852405A - Synthetic method of circular polarization luminous chiral quantum dot film

Info

Publication number: CN112852405A
Application number: CN202110015390.XA
Authority: CN
Inventors: 陈苏; 王彩凤; 梁志宾
Original assignee: Suzhou Guonasi New Material Technology Co ltd
Current assignee: Suzhou Guonasi New Material Technology Co ltd
Priority date: 2021-01-07
Filing date: 2021-01-07
Publication date: 2021-05-28

Abstract

The invention discloses a method for synthesizing a chiral quantum dot film with circular polarization luminescence, which comprises the following steps: dispersing organic phase quantum dot powder in an organic solvent, introducing protective atmosphere to remove oxygen, adding chiral organic amine and carbon disulfide, stirring under an ice bath condition, centrifuging the obtained turbid solution, taking solid precipitate, performing vacuum drying to obtain chiral quantum dot powder, dispersing in a polymer solution, spin-coating a layer of film on a substrate, and performing vacuum drying to obtain the chiral quantum dot film with circular polarization luminescence. The method is simple to operate and has universality. The quantum dots after ligand exchange have potential application prospects in the fields of polarization control, negative refractive index, chiral sensing, novel display devices based on circular polarization fluorescence and the like.

Description

Synthetic method of circular polarization luminous chiral quantum dot film

Technical Field

The invention relates to a synthesis method of a chiral quantum dot film with circular polarization luminescence, belongs to the field of optics, and particularly relates to a method for preparing the chiral quantum dot film with the circular polarization luminescence, wherein a ligand exchange method is involved, and the induction of the chirality of quantum dots is realized.

Background

We refer to the phenomenon that an object cannot overlap its mirror image as chirality. Chirality plays a very important role in both nature and in life, and is the basis for the ordering and organization of life. The wide application prospect of chiral materials in the aspects of circular polarization luminescent materials (CPL), electrochemiluminescence materials (ECL), information storage, biological probes and the like makes researchers have great interest in the research of the chiral materials. In recent years, the research on chiral materials is vigorous, and a great number of chiral materials with excellent performance are prepared during the period, and meanwhile, a plurality of effective chemical methods for chiral construction are derived. Quantum dots have attracted attention as an excellent light-emitting material, and there are three general methods for synthesizing chiral quantum dots: firstly, directly adding a ligand to induce chirality when synthesizing quantum dots; secondly, ligand exchange is carried out on the basis of the synthesized quantum dots; and thirdly, grafting the achiral quantum dots on a chiral spiral structure to obtain a chiral signal.

Since the ligand can affect the chemical and electronic properties of the quantum dot, post-synthesis functionalization of achiral quantum dots by chiral ligands is an ideal method for inducing and controlling chirality of semiconductor nanomaterials.

Chirality is a description of the geometric properties that a mirror image of a structure cannot overlap with the original mirror image, i.e., the perfect symmetry element is not present. Applying this definition to nanoscale objects results in chiral nanostructures. Similar to chiral molecules, two non-superimposable nanostructures with mirror symmetry are called enantiomers. The important properties of chiral nanostructures are that they respond differently to polarized light, absorb differently to polarized light and thus possess circular bidirectionality (CD), different refractive indices lead to different optical rotation, and different emission rates lead to different circular polarization emissions. The chiral optical phenomenon not only has wide application prospect, but also becomes a powerful tool for researching chiral nano structures.

Disclosure of Invention

The invention aims to provide a synthetic method of a chiral quantum dot film capable of circularly polarizing and emitting light. The method has the advantages of simple experimental operation, mild reaction conditions and good universality. On one hand, the carbon disulfide and the chiral organic amine are reacted to generate the dithiocarbamic acid ligand, which has stronger coordination capacity, and the quantum dot can be induced to have chiral property through ligand exchange.

The technical scheme of the invention is as follows: a synthetic method of a chiral quantum dot film with circular polarization luminescence comprises the following specific steps: dispersing organic phase quantum dot powder in an organic solvent, introducing protective atmosphere to remove oxygen, adding chiral organic amine and carbon disulfide, stirring under an ice bath condition, centrifuging the obtained turbid solution, taking solid precipitate, performing vacuum drying to obtain chiral quantum dot powder, dispersing in a polymer solution, performing spin coating on a substrate by using a spin coating instrument to obtain a layer of film, and performing vacuum drying to obtain the chiral quantum dot film with circular polarization luminescence.

Preferably, the organic phase quantum dot is CdSe, CdSe @ ZnS or CuInS taking oleic acid or oleylamine as a ligand₂One of (a) and (b); the emission peak of the organic phase quantum dot is 450nm-650 nm.

Preferably, the organic solvent is chloroform or n-hexane; after the organic phase quantum dot powder is dispersed in the organic solvent, the concentration of the organic phase quantum dots is 1 multiplied by 10^-6mol/mL-1×10^-5mol/mL。

Preferably, the chiral amine is chiral cyclohexanediamine; the molar ratio of the organic quantum dots, the chiral organic amine and the carbon disulfide is 1: (200-1000): (400-2500).

Preferably, the nitrogen or argon is used in the protective atmosphere, and the oxygen removal time is 12-16 h; the ice bath temperature is-5 ℃ to 0 ℃; stirring at 600-1200 r/min under ice bath condition for 12-18 h; the centrifugal speed is 8000r/min-12000r/min, and the centrifugal time is 8min-10 min.

Preferably, the polymer in the polymer solution is polymethyl methacrylate (PMMA) or polyurethane (TPU); the solvent in the polymer solution is N, N-Dimethylformamide (DMF) or dimethyl sulfoxide (DMSO); the mass fraction of the polymer in the polymer solution is 10-20%.

Preferably, the mass ratio of the chiral quantum dot powder to the polymer is 1: (1000-1500).

Preferably, the substrate is a glass or silicon wafer.

The spin coating speed is preferably 1800rpm-2400rpm for 60s-90 s.

The preferable temperature of the vacuum drying is 30-45 ℃, and the drying time is 12-24 h.

Has the advantages that:

1. the synthetic method of the chiral quantum dot film with circular polarization luminescence is simple, and the chiral quantum dot film with circular polarization luminescence has a large-scale preparation prospect.

2. The synthesis method has wide applicability, and can be used for semiconductors of organic phases with oleic acid or oleylamine as ligands.

3. The synthesis method of the invention has no limit on the emission peak positions of the organic semiconductor quantum dots with different emissions, and has wide applicability.

4. The reduction degree of the quantum yield of the quantum dots before and after ligand exchange is not large, and the quantum dots can have higher quantum yield.

Drawings

FIG. 1 is a CdSe fluorescence plot of oleic acid as ligand before ligand exchange as described in example 6;

FIG. 2 is a graph of fluorescence data for chiral quantum dots after ligand exchange of example 6;

FIG. 3 is a circular dichroism plot (CD) of chiral quantum dots after ligand exchange of example 6;

figure 4 is a photograph of the spin-coated film of example 6 under sunlight and uv excitation.

Detailed Description

In order to enhance understanding of the present invention, the present invention will be described in further detail with reference to examples, which are provided for illustrating the present invention and are not limited to the examples.

Example 1

30mL of CdSe @ ZnS solution (1X 10) dispersed in chloroform was taken^-6mol/mL) is added into a four-mouth flask (emission wavelength is 501nm), oxygen is removed for 12h by introducing nitrogen atmosphere while magnetic stirring, then 0.006mol of ligand chiral cyclohexanediamine and 0.012mol of carbon disulfide are added, and stirring is continued for 18h at-5 ℃ at 800 r/min. The solution became cloudy, centrifuged at 12000r/min for 8 minutes and then filtered through neutral filter paper. After drying, 0.0010g of chiral quantum dot powder was dispersed in 10g of PMMA-DMF solution, wherein the solution wasThe mass fraction of PMMA in the composition is 15 percent. The prepared spin coating solution was spin-coated on a spin coater at 2000r/min for 60 seconds using glass as a substrate. Then dried in a vacuum drying oven for 12h at 40 ℃. The emission peak positions of the quantum dots before and after ligand exchange are not changed, the emission peak positions are 501nm, and the quantum yield is reduced from initial 78% to 56%. And the presence of chirality was confirmed by circular dichroism measurement of CD.

Example 2

40mL of CdSe @ ZnS solution (1X 10) dispersed in chloroform was taken^-6mol/mL) is added into a four-mouth flask (emission wavelength is 501nm), oxygen is removed for 16h by introducing nitrogen atmosphere while magnetic stirring, then 0.04mol of ligand chiral cyclohexanediamine and 0.1mol of carbon disulfide are added, and stirring is continued for 12h at 0 ℃ and 1200 r/min. The solution became turbid, centrifuged at 8000r/min for 10 minutes and then filtered through neutral filter paper. After drying, 0.0010g of chiral quantum dot powder is dispersed in 10g of PMMA-DMF solution, wherein the mass fraction of PMMA in the solution is 10%. The prepared spin-coating liquid is spin-coated for 90s on a spin-coating instrument at 1800r/min by taking glass as a base material. Then dried in a vacuum drying oven for 24h at 30 ℃. The emission peak positions of the quantum dots before and after ligand exchange are not changed, the emission peak positions are 501nm, and the quantum yield is reduced from initial 78% to 54%. And the presence of chirality was confirmed by circular dichroism measurement of CD.

Example 3

30mL of CdSe @ ZnS solution (3X 10) dispersed in chloroform was taken^-6mol/mL) is added into a four-mouth flask (emission wavelength is 501nm), oxygen is removed for 14h by introducing nitrogen atmosphere while magnetic stirring, then 0.09mol of ligand chiral cyclohexanediamine and 0.18mol of carbon disulfide are added, and stirring is continued for 16h at 1200r/min at-2 ℃. The solution became turbid, centrifuged at 8000r/min for 10 minutes and then filtered through neutral filter paper. After drying, 0.0013g of chiral quantum dot powder is dispersed in 10g of PMMA-DMF solution, wherein the mass fraction of PMMA in the solution is 15%. The prepared spin-coating liquid is spin-coated for 60s on a 2400r/min spin-coating instrument by taking a silicon wafer as a base material. Then dried in a vacuum drying oven for 18h at 40 ℃. The emission peak positions of the quantum dots before and after ligand exchange are not changed, the emission peak positions are 501nm, and the quantum yield is reduced from initial 78% to 58%. And measuring CD by circular dichroismConfirming the existence of chirality.

Example 4

30mL of CdSe @ ZnS solution (3X 10) dispersed in chloroform was taken^-6mol/mL) is added into a four-mouth flask (the emission wavelength is 590nm), oxygen is removed for 12h by introducing nitrogen atmosphere while magnetic stirring, then 0.03mol of ligand chiral cyclohexanediamine and 0.06mol of carbon disulfide are added, and stirring is continued for 12h at the temperature of 0 ℃ and the speed of 1200 r/min. The solution became turbid, centrifuged at 8000r/min for 8 minutes and then filtered through neutral filter paper. After drying, 0.002g of chiral quantum dot powder was dispersed in 10g of TPU-DMF solution, the mass fraction of TPU in the solution was 20%. The prepared spin coating solution was spin-coated on a spin coater at 2000r/min for 60 seconds using glass as a substrate. Then dried in a vacuum drying oven for 12h at 40 ℃. The emission peak positions of the quantum dots before and after ligand exchange are unchanged, and are 590nm, and the quantum yield is reduced from initial 72% to 62%. And the presence of chirality was confirmed by circular dichroism measurement of CD.

Example 5

60mL of CdSe @ ZnS solution (1X 10) dispersed in chloroform was taken^-5mol/mL) is added into a four-mouth flask (the emission wavelength is 590nm), oxygen is removed for 12h by introducing nitrogen atmosphere while magnetic stirring, then 0.3mol of ligand chiral cyclohexanediamine and 0.45mol of carbon disulfide are added, and stirring is continued for 12h at 0 ℃ for 1000 r/min. The solution became turbid, centrifuged at 8000r/min for 8 minutes and then filtered through neutral filter paper. After drying, 0.001g of chiral quantum dot powder was dispersed in 10g of TPU-DMSO solution, the mass fraction of TPU in the solution being 15%. The prepared spin coating solution was spin-coated on a spin coater at 2000r/min for 70s using glass as a substrate. Then dried in a vacuum drying oven at 45 ℃ for 18 h. The emission peak positions of the quantum dots before and after ligand exchange are unchanged, and are 590nm, and the quantum yield is reduced from initial 72% to 58%. And the presence of chirality was confirmed by circular dichroism measurement of CD.

Example 6

30mL of CdSe solution (6X 10) dispersed in chloroform was taken^-6mol/mL) was added to a four-necked flask (emission wavelength of 631nm, fluorescence spectrum shown in FIG. 1), oxygen was removed by introducing nitrogen atmosphere while magnetically stirring for 12 hours, and then 0.09mol of oxygen was addedAnd (3) continuously stirring the ligand chiral cyclohexanediamine and 0.18mol of carbon disulfide at 0 ℃ for 12 hours at 1000 r/min. The solution became turbid, centrifuged at 8000r/min for 8 minutes and then filtered through neutral filter paper. After drying, 0.0018g of chiral quantum dot powder (the fluorescence spectrum of the chiral quantum dot is shown in fig. 2, and the circular dichroism spectrum of the chiral quantum dot powder is shown in fig. 3, which confirms the existence of chirality) is dispersed in 10g of PMMA-DMF solution, wherein the mass fraction of PMMA in the solution is 20%. The prepared spin coating solution was spin-coated on a spin coater at 2000r/min for 60 seconds using glass as a substrate. Then dried in a vacuum drying oven for 12h at 40 ℃. A physical representation of the chiral polarizing film is shown in FIG. 4. The emission peak positions of the quantum dots before and after ligand exchange are unchanged, namely 631nm, and the quantum yield is reduced from 83% initially to 64%.

Claims

1. A synthetic method of a chiral quantum dot film with circular polarization luminescence comprises the following specific steps: dispersing organic phase quantum dot powder in an organic solvent, introducing protective atmosphere to remove oxygen, adding chiral organic amine and carbon disulfide, stirring under an ice bath condition, centrifuging the obtained turbid solution, taking solid precipitate, performing vacuum drying to obtain chiral quantum dot powder, dispersing in a polymer solution, spin-coating a layer of film on a substrate, and performing vacuum drying to obtain the chiral quantum dot film with circular polarization luminescence.

2. The synthesis method according to claim 1, wherein the organic phase quantum dot is CdSe, CdSe @ ZnS or CuInS₂One of (a) and (b); the emission peak of the organic phase quantum dot is 450nm-650 nm.

3. The synthesis method according to claim 2, wherein the organic solvent is chloroform or n-hexane; the concentration of the organic phase quantum dots after the organic phase quantum dot powder is dispersed in the organic solvent is 1 multiplied by 10^-6mol/mL-1×10^- ⁵mol/mL。

4. The synthesis method according to claim 1, wherein the chiral organic amine is chiral cyclohexanediamine; the molar ratio of the organic quantum dots, the chiral organic amine and the carbon disulfide is 1: (200-1000): (400-2500).

5. The synthesis method according to claim 1, wherein the protective atmosphere is nitrogen or argon, and the oxygen removal time is 12-16 h; the ice bath temperature is-5 ℃ to 0 ℃; stirring at 600-1200 r/min under ice bath condition for 12-18 h; the centrifugal speed is 8000r/min-12000r/min, and the centrifugal time is 8min-10 min.

6. The method of claim 1, wherein the polymer in the polymer solution is polymethyl methacrylate or polyurethane; the solvent in the polymer solution is N, N-dimethylformamide or dimethyl sulfoxide; the mass fraction of the polymer in the polymer solution is 10-20%.

7. The synthesis method according to claim 1, wherein the mass ratio of the chiral quantum dot powder to the polymer is 1: (1000-1500).

8. The synthesis process according to claim 1, characterized in that the substrate is a glass or silicon wafer.

9. The method of claim 1, wherein the spin coating speed is 1800rpm-2400rpm for 60s-90 s.

10. The synthesis method according to claim 1, characterized in that the temperature of vacuum drying is 30-45 ℃ and the drying time is 12-24 h.