A method for preparing lead sulfide quantum dots, lead sulfide quantum dots and applications

Abstract

The application relates to a lead sulfide quantum dot preparation method, which specifically comprises the following steps: rapidly injecting an amine solution of activated zinc dithiocarbamate into a mixed solution of lead chloride and oleylamine to make it nucleate and grow, and adjusting the size of the synthesized PbS quantum dots by adjusting temperature and growth time, etc. A single precursor zinc dithiocarbamate completely replaces ZnS quantum dots as a nucleation and growth sulfur source, does not need to be added dropwise, saves time, omits the complex steps of synthesizing ZnS quantum dots, and can be stably kept at a certain size for a long time without ripening.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor nanomaterials, and particularly relates to a lead sulfide quantum dot preparation method, lead sulfide quantum dots and application. BACKGROUND

[0002] At present, the main methods for preparing PbS quantum dots include hydrothermal / solvothermal method, heat injection method, heat up method, coprecipitation method, sol-gel method, microemulsion method and pyrolysis method. Among these methods, the cation exchange method is a specific heat injection method, and the process thereof is relatively complex. However, the quantum dots prepared by the cation exchange method have precise peak control, uniform size distribution, excellent light-emitting efficiency and stability. Therefore, the cation exchange method is particularly suitable for the production of optoelectronic devices.

[0003] In the implementation process of the cation exchange method, different sizes of zinc sulfide (ZnS) quantum dots are usually synthesized first, and these quantum dots are used for the nucleation and subsequent dropwise growth of lead sulfide (PbS) quantum dots. However, the synthesis process of ZnS quantum dots is complicated, consumes a large amount of anti-solvent, requires a large investment of manpower and time, and it is difficult to ensure the reproducibility of the concentration of ZnS quantum dots.

[0004] In order to further improve the efficiency of the cation exchange method, it is expected to find a new type of sulfur precursor which can replace the original ZnS quantum dots for nucleation and dropwise growth, so as to optimize the size distribution of PbS quantum dots, reduce production cost, and save time and manpower. SUMMARY

[0005] In the prior art, the synthesis and cleaning steps of the ZnS quantum dots used for growth are very complicated, the concentration is difficult to control, and the dropwise injection method takes a long time. The present application provides a single precursor zinc dithiocarbamate which completely replaces ZnS quantum dots as a sulfur source for nucleation and growth, which not only saves time without dropwise injection, but also saves the complex steps of synthesizing ZnS quantum dots.

[0006] Based on the problems existing in the prior art, the present application aims to provide a lead sulfide quantum dot preparation method, which comprises:

[0007] S1, dissolving lead chloride in oleylamine to form a first solution in which the lead chloride reaches a first concentration;

[0008] S2, dissolving zinc dithiocarbamate in amine to form a second solution in which the zinc dithiocarbamate reaches a second concentration, and centrifuging the second solution after heating for a first time to obtain supernatant;

[0009] S3, injecting the supernatant of the second solution into the first solution rapidly to form a first mixed solution, and nucleating and growing quantum dots of the first mixed solution, and obtaining the lead sulfide quantum dots of a predetermined size after maintaining for a second time.

[0010] According to an embodiment of the present application, the second concentration is less than the first concentration.

[0011] According to an embodiment of the present application, after the step S3, the method further comprises:

[0012] S4, cooling the first mixed solution in a water bath, injecting n-hexane and oleic acid during the cooling process, and performing centrifugal treatment; extracting the supernatant of the first mixed solution, adding a polar solvent for cleaning, and separating the lead sulfide quantum dots.

[0013] According to an embodiment of the present application, the centrifugal treatment in the step S4 is performed at a speed of 4000-7000 r / min.

[0014] According to an embodiment of the present application, the step S1 further comprises:

[0015] After forming the first solution, vacuumizing and then filling a protective gas, and then increasing the temperature and standing, and then decreasing the temperature to 110-130℃.

[0016] According to an embodiment of the present application, the protective gas comprises an inert gas, nitrogen or argon.

[0017] 8. According to an embodiment of the present application, the first time and / or the second time is 20-60 minutes.

[0018] The present application further provides a lead sulfide quantum dot, which is prepared by the method according to any one of the above embodiments.

[0019] The present application further provides an application of the lead sulfide quantum dot prepared by the method according to any one of the above embodiments, characterized in that the lead sulfide quantum dot is applied to a colloidal quantum dot infrared detector, a solar cell or a light emitting device.

[0020] The present application has the following beneficial effects: by injecting the amine solution of the activated zinc dithiocarbamate into the mixed solution of lead chloride and oleylamine rapidly to make it nucleate and grow, the size of the synthesized PbS quantum dots is controlled by controlling the temperature and the growth time. The present application provides a single precursor zinc dithiocarbamate to completely replace ZnS quantum dots as a nucleation and growth sulfur source, without dropwise injection, saving time, and eliminating the complex steps of synthesizing ZnS quantum dots, and the size can be stable for a long time without ripening. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments or the prior art, the following will briefly introduce the drawings needed to be used in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without any creative effort.

[0022] Figure 1 is the growth absorption curve of PbS quantum dots of the embodiment 1 of the present application;

[0023] Figure 2 is the growth absorption curve of PbS quantum dots of the embodiment 2 of the present application;

[0024] Figure 3 is the growth absorption curve of PbS quantum dots of the embodiment 3 of the present application;

[0025] Figure 4 is the X-ray diffraction pattern of PbS quantum dots of the embodiment of the present application;

[0026] Figure 5 is the TEM pattern of PbS quantum dots of the embodiment of the present application. DETAILED DESCRIPTION

[0027] The following description of the embodiments is made with reference to the accompanying drawings, which illustrate specific embodiments in which the present application can be practiced.

[0028] Embodiment one

[0029] Based on the deficiencies in the prior art, an embodiment of the present application provides a lead sulfide quantum dot preparation method, and the specific steps include:

[0030] A lead sulfide quantum dot preparation method, the preparation method includes:

[0031] S1, lead chloride is dissolved in oleylamine to form a first solution in which the lead chloride reaches a first concentration; wherein, after forming the first solution, vacuum is extracted and then protective gas is filled, and then the temperature is raised to 140℃ and maintained for 30min, and then the temperature is lowered to 110℃.

[0032] S2, zinc dithiocarbamate is dissolved in oleylamine to form a second solution in which the zinc dithiocarbamate reaches a second concentration, and the supernatant is taken by centrifugation after the second solution is heated for a first time. Preferably, the heating temperature of the second solution is 110℃-130℃, and the first time of closed heating is 20-60 minutes (min).

[0033] According to an embodiment of the present application, the second concentration is less than the first concentration, preferably, the first concentration is 0.3 mol / L, the second concentration is preferably 0.15 mol / L, and the ratio of the first concentration to the second concentration is preferably 2:1, in which case quantum dots having an absorption peak in the range of 1200 nm-1450 nm can be obtained, and the size distribution of the quantum dots is better.

[0034] S3, rapidly injecting the supernatant of the second solution into the first solution to make the quantum dots in the mixture nucleate and grow, and obtaining the lead sulfide quantum dots of a predetermined size after maintaining for a second time. Preferably, the second time is 20-60 minutes (min).

[0035] wherein the length of the second time required for growth is determined according to the predetermined size of the lead sulfide quantum dots required; generally, the longer the growth time, the larger the size of the lead sulfide quantum dots obtained, and after 40 min, the size of the lead sulfide quantum dots basically no longer grows, and the size of the lead sulfide quantum dots hardly changes and does not mature within 40 min of continued heating.

[0036] According to an embodiment of the present application, after the step S3, the method further comprises:

[0037] S4, water-bath cooling the first mixture, injecting n-hexane and oleic acid during the cooling process, and performing centrifugal treatment; extracting the supernatant of the first mixture and adding a polar solvent for cleaning, and separating the lead sulfide quantum dots.

[0038] wherein after growing to the required size of the lead sulfide quantum dots, the first mixture is rapidly water-bath cooled, 90 ml of n-hexane is injected when the temperature is reduced to about 70°C, 40 ml of oleic acid is injected when the temperature is reduced to about 40°C, and after the injection is completed, the temperature is maintained at room temperature for more than 10 min. Then, the first mixture is subjected to centrifugal treatment, the centrifugal speed is preferably 4000-7000 r / min, the centrifugal time is more than 3 min, the supernatant of the first mixture is extracted and cleaned by adding acetone, and the supernatant is subjected to the above-mentioned centrifugal process twice to separate the lead sulfide quantum dots.

[0039] Embodiment Two

[0040] This embodiment is basically similar to the technical solution of Embodiment One, and the difference lies in that the zinc dithiocarbamate is dissolved in different types of amines.

[0041] The synthesis steps of the lead sulfide quantum dots further comprise:

[0042] S2, dissolving zinc dithiocarbamate in octylamine to form a second solution in which the zinc dithiocarbamate reaches a second concentration, and after being heated at 110°C-130°C for 20-60 min, the supernatant is obtained by centrifugation.

[0043] According to an embodiment of the present application, the second concentration is less than the first concentration, preferably, the first concentration is 0.3 mol / L, and the second concentration is preferably 0.15 mol / L, and the ratio of the first concentration to the second concentration is preferably 2:1, in which ratio, quantum dots with an absorption peak within 1200-1600 nm can be obtained, and the size distribution is good.

[0044] S3, rapidly injecting the supernatant into the first solution to make the quantum dots of the mixture nucleate and grow, and maintaining for 20-60 min to obtain lead sulfide quantum dots of a predetermined size.

[0045] In the formula, the second time length is determined according to the predetermined size of the lead sulfide quantum dots required; generally, the longer the growth time, the larger the size of the lead sulfide quantum dots obtained, and after 40 min, the size of the lead sulfide quantum dots basically no longer grows, and the growth size almost does not change and no ripening occurs within 20 min of continued heating.

[0046] According to an embodiment of the present application, after the step S3, the method further comprises:

[0047] S4, water-bath cooling the first mixture, injecting n-hexane and oleic acid during the cooling process, and performing centrifugal treatment; extracting the supernatant of the first mixture and adding a polar solvent for cleaning, and separating the lead sulfide quantum dots.

[0048] In the formula, after growing to the required size of the lead sulfide quantum dots, the first mixture is rapidly water-bath cooled, 90 ml of n-hexane is injected when the temperature is reduced to about 70°C, 40 ml of oleic acid is injected when the temperature is reduced to about 40°C, and after the injection is completed, the temperature is maintained at room temperature for more than 10 min. Then, the first mixture is subjected to centrifugal treatment, the centrifugal speed is preferably 4000-7000 r / min, the centrifugal time is more than 3 min, the supernatant of the first mixture is extracted and acetone is added for cleaning, and the supernatant is subjected to the above centrifugal process twice to separate the lead sulfide quantum dots.

[0049] Example Three

[0050] The technical solution of this embodiment is basically similar to that of Example Two, and the difference lies in the temperature of injecting the sulfur source.

[0051] The synthesis steps of the lead sulfide quantum dots further comprise:

[0052] S1, dissolving lead chloride in oleylamine to form a first solution of the lead chloride reaching a first concentration;

[0053] After the first solution is formed, vacuum is extracted and protective gas is filled, the temperature is raised to 140℃ and maintained for 30 minutes, and then the temperature is lowered to 120℃.

[0054] S2, zinc dithiocarbamate is dissolved in octylamine to form a second solution of zinc dithiocarbamate with a second concentration, and after being heated at 110-130℃ for 20-60 minutes, the supernatant is obtained by centrifugation.

[0055] According to an embodiment of the present application, the second concentration is less than the first concentration, preferably, the first concentration is 0.3 mol / L, and the second concentration is preferably 0.15 mol / L, and the ratio of the first concentration to the second concentration is preferably 2:1, and in this ratio, quantum dots with an absorption peak in the range of 1200-1700 nm can be obtained, and the size distribution is good.

[0056] S3, the supernatant is quickly injected into the first solution to make the quantum dots of the mixed solution nucleate and grow, and maintained for 20-60 minutes to obtain lead sulfide quantum dots with a predetermined size.

[0057] According to the desired size of the lead sulfide quantum dots, the second time required for growth is determined; generally, the longer the growth time, the larger the size of the obtained lead sulfide quantum dots, and after 40 minutes, the size of the lead sulfide quantum dots basically does not grow, and the growth size is almost unchanged and does not mature within 20 minutes of continued heating.

[0058] According to an embodiment of the present application, after the step S3, it further comprises:

[0059] S4, the first mixed solution is cooled in a water bath, and n-hexane and oleic acid are injected during the cooling process, and centrifugal treatment is performed; the supernatant of the first mixed solution is extracted and washed with a polar solvent, and the lead sulfide quantum dots are separated.

[0060] After the desired size of the lead sulfide quantum dots is obtained, the first mixed solution is quickly cooled in a water bath, 90ml of n-hexane is injected when the temperature is reduced to about 70℃, 40ml of oleic acid is injected when the temperature is reduced to about 40℃, and the injection is completed in a room temperature environment for more than 10 minutes. Then, the first mixed solution is subjected to centrifugal treatment, the centrifugal speed is preferably 4000-7000r / min, the centrifugal time is more than 3 minutes, the supernatant of the first mixed solution is extracted and washed with acetone, and the supernatant is subjected to the above centrifugal process twice to separate the lead sulfide quantum dots.

[0061] One embodiment of the present invention also provides a lead sulfide quantum dot, comprising the lead sulfide quantum dot prepared by the method described in any of the above embodiments.

[0062] like Figures 1-5 As shown, the growth absorption curves of lead sulfide quantum dots directly obtained by the preparation methods described in Examples 1 to 3 of the present invention, as well as the X-ray diffraction pattern and TEM image of the lead sulfide quantum dots with an absorption peak at 1700 nm, demonstrate that the lead sulfide quantum dots synthesized by the preparation method of the present invention have high stability and good size distribution.

[0063] This invention also protects the specific applications of the lead sulfide quantum dots prepared in the above embodiments.

[0064] Semiconductor quantum dots are quasi-zero-dimensional nanomaterials. When the particle size enters the nanoscale, size confinement induces size effects, quantum confinement effects, macroscopic quantum tunneling effects, and surface effects. This results in low-dimensional properties in nanoscale systems that differ from macroscopic and microscopic systems, exhibiting many physicochemical properties unlike those of bulk materials. All properties of quantum dots change with their size; for example, the emission and absorption wavelengths of quantum dots can be tuned by adjusting their size. Furthermore, colloidal quantum dots prepared through solution processing offer advantages such as low cost and large-scale production capabilities, making them widely used in optoelectronic devices such as solar cells, light-emitting diodes, field-effect transistors, and photodetectors.

[0065] One embodiment of this invention, a colloidal quantum dot infrared detector, as a new generation of near-infrared detectors, possesses characteristics such as simple material preparation, tunable bandgap, low cost, and ease of integration with various readout circuits, and is expected to occupy a place in the field of near-infrared detectors. Since the IV-VI binary compound PbS is a narrow bandgap semiconductor material with advantages such as a large dielectric constant, a narrow bandgap (0.41 eV), and a high absorption coefficient, PbS quantum dots have broad market prospects in optoelectronic devices and communications.

[0066] A colloidal quantum dot infrared detector is also provided, comprising lead sulfide quantum dots prepared by the method described in any of the above embodiments. The lead sulfide quantum dots exhibit high stability and good size distribution, making them suitable for use in colloidal quantum dot infrared detectors. Furthermore, as a next-generation near-infrared detector, the colloidal quantum dot infrared detector possesses advantages such as simple material preparation, adjustable material bandgap, low cost, and ease of integration with various readout circuits, and is expected to gain a foothold in the near-infrared detector field.

[0067] In summary, the embodiment of the present application provides a lead sulfide quantum dot preparation method, lead sulfide quantum dot and detector. Wherein the amine solution of activated zinc dithiocarbamate is quickly injected into the mixed solution of lead chloride and oleylamine to make it nucleate and grow, and the size of the synthesized PbS quantum dot is regulated by regulating the temperature and growth time. The single precursor zinc dithiocarbamate provided by the present application is used to replace the ZnS quantum dot as the nucleation and growth sulfur source, which not only does not need to be added dropwise, saves time, and eliminates the complex steps of synthesizing ZnS quantum dots, and can be stable at a certain size for a long time without ripening.

[0068] It should be noted that although the present application is disclosed as above with specific embodiments, the above embodiments are not intended to limit the present application, and those of ordinary skill in the art can make various modifications and decorations without departing from the spirit and scope of the present application, therefore the protection scope of the present application is defined by the scope of the claims.

Claims

1. A method for preparing lead sulfide quantum dots, characterized in that, The preparation method comprises: S1, dissolving lead chloride in oleylamine to form a first solution of the lead chloride reaching a first concentration; After forming the first solution, vacuumizing and then filling with a protective gas, and then standing after warming, and then cooling to 110-130 DEG C; S2, dissolving zinc dithiocarbamate in amine to form a second solution of the zinc dithiocarbamate reaching a second concentration, centrifuging and taking supernatant after sealing and heating the second solution for a first time, wherein the sealing and heating temperature of the second solution is 110-130 DEG C, and the first time is 20-60 minutes; The ratio of the first concentration to the second concentration is 2:1; S3, rapidly injecting the supernatant into the first solution to form a first mixed solution, and quantum dot nucleation and growth of the first mixed solution, and then obtaining lead sulfide quantum dots of a predetermined size after maintaining for a second time, wherein the second time is 20-60 minutes.

2. The method of claim 1, wherein the lead sulfide quantum dots are prepared by the method comprising: After the step S3, further comprising: ​ S4, water bath cooling the first mixed solution, injecting n-hexane and oleic acid during the cooling process, centrifuging, extracting supernatant, adding a polar solvent for cleaning, and then separating the lead sulfide quantum dots.

3. The method for preparing lead sulfide quantum dots according to claim 2, characterized in that, The centrifuging in the step S4 is at a speed of 4000-7000 r / min.

4. The method for preparing lead sulfide quantum dots according to claim 1, characterized in that, The protective gas comprises an inert gas.

5. The method for preparing lead sulfide quantum dots according to claim 1, characterized in that, The protective gas comprises nitrogen.

6. The method for preparing lead sulfide quantum dots according to claim 4, characterized in that, The inert gas is argon.

Images