Preparation method of lead sulfide colloidal quantum dot / carbon nanotube composite material

Abstract

This invention belongs to the field of semiconductor nanomaterial preparation, specifically relating to the preparation of a lead sulfide colloidal quantum dot / carbon nanotube composite material. The synthesis method of this invention is as follows: First, a micron / submicron-sized lead source is synthesized using an aqueous solution precipitation method and reacted with functionalized carbon nanotubes in an organic reagent to form a suspension of carbon nanotubes and a lead precursor. Then, under a nitrogen atmosphere, elemental sulfur dissolved in oleylamine is rapidly injected into a mixed solution of carbon nanotubes and the lead precursor at a certain temperature. Finally, an in-situ growth method is used to obtain the lead sulfide colloidal quantum dot / carbon nanotube composite material stock solution. After centrifugation to remove impurities, the solution is purified to obtain the lead sulfide colloidal quantum dot / carbon nanotube composite material. This invention offers a short preparation cycle, controllable size of the lead sulfide colloidal quantum dots grown in situ on carbon nanotubes, high grafting rate, tunable optical properties, and good stability, making it suitable for the mass production of high-quality lead sulfide quantum dot / carbon nanotube composite materials.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor nanomaterial preparation, specifically relating to a method for preparing lead sulfide colloidal quantum dot / carbon nanotube composite material. Background Technology

[0002] Quantum dots are semiconductor nanocrystals characterized by tunability, broad excitation spectra, narrow emission spectra, and good photochemical stability. Among them, lead sulfide (PbS) quantum dots exhibit continuously tunable optical properties in the near-infrared wavelength range, demonstrating superior photoelectric properties in nonlinear optical devices, infrared electroluminescent devices, and solar cells.

[0003] Carbon nanotubes (CNTs), as one-dimensional nanostructures, have a huge surface area and a hollow tubular structure. This unique nanoscale structure gives them excellent electrical, mechanical and chemical properties, such as high electron mobility, chemical stability and high strength and hardness. They are one of the materials that are widely studied in the field of nanoscience.

[0004] In recent years, quantum dot-carbon nanotube composites have attracted widespread attention due to their unique optical properties and potential advantages in fields such as solar cells, light-emitting diodes, and photosensitive sensors. Sulfide quantum dots, as typical nanomaterials, exhibit unique optical properties different from ordinary semiconductor materials due to their quantum effects, and their low cost makes them a novel and practical photosensitive material. Carbon nanotubes, with their unique electrical properties, stable electrochemical properties, and extremely high specific surface area, can not only support the composite of quantum dots but also promote the separation and transport of charge carriers, allowing photogenerated charge carriers to flow towards the electrodes. Assembling lead sulfide quantum dots onto carbon nanotubes using specific methods can yield nanocomposite materials with excellent photoelectric properties. Wang et al. obtained an oil-phase PbS / CNT nanocomposite structure by ultrasonically grafting PbS quantum dots with oleamide as a ligand onto oleamide-treated acidified CNTs, and applied it to a solar cell with a conversion efficiency of 3.03%. However, most PbS quantum dots synthesized in aqueous phases are unstable and have uneven size distributions, while the stable and size-uniform oil phase exhibits a lower grafting rate onto CNTs. Therefore, we prepared lead sulfide colloidal quantum dot / carbon nanotube composite materials by in-situ growth. This method is simple to operate, has a short operation time, and the size of the quantum dots grafted onto the carbon nanotubes can be controlled with a high grafting rate. The resulting composite material is stable in air and can be prepared in large quantities. Summary of the Invention

[0005] To address the challenges of complex quantum dot synthesis processes and low grafting rates, this invention provides a method for preparing lead sulfide colloidal quantum dot / carbon nanotube composite materials. The method involves synthesizing micron / submicron-sized lead sources via aqueous solution precipitation, then reacting these sources with functionalized carbon nanotubes in an organic reagent to form a lead precursor modified on the carbon nanotube surface. Elemental sulfur is then introduced to grow colloidal lead sulfide quantum dots in situ on the functionalized carbon nanotubes, ultimately yielding the lead sulfide quantum dot / carbon nanotube composite material. This composite material exhibits uniform quantum dot size and morphology with a high grafting rate. The method includes the following steps:

[0006] (1) Weigh out sodium chloride and basic lead acetate separately to prepare aqueous solutions of a certain concentration; mix the two solutions and place them at a certain temperature for 10 min-60 min to obtain a white precipitate, rinse with distilled water, and finally dry to remove water to obtain basic lead chloride;

[0007] (2) In a nitrogen atmosphere, the basic lead chloride synthesized in step (1) and functionalized carbon nanotubes are added to a specific organic solvent and stirred. Then the mixed solution is heated to 90°C to 160°C and held for 25 min to 35 min (preferably 30 min). Finally, the vacuum is continuously evacuated for 25 min to 35 min (preferably 30 min) and the heating is turned off to obtain a mixed solution of functionalized carbon nanotubes and lead precursor while maintaining a nitrogen atmosphere.

[0008] (3) At room temperature, elemental sulfur is added to oleylamine to prepare a sulfur precursor solution of a certain concentration. Then, a certain volume of sulfur precursor solution is rapidly injected into the functionalized carbon nanotube and lead precursor mixed solution obtained in step (2). The solution is heated to a certain temperature and held for 0.5 min to 20 min. Finally, the solution is cooled to 10℃ to 30℃ to obtain a mixed stock solution of lead sulfide colloidal quantum dots / carbon nanotubes.

[0009] (4) After centrifuging to remove free quantum dots and impurities, the mixed stock solution prepared in step (3) is diluted with quantum dot solvent. Then, the lead sulfide colloidal quantum dot / carbon nanotube solution is purified with a polar organic solvent and dried by centrifugation to obtain the lead sulfide colloidal quantum dot / carbon nanotube composite material. Finally, the obtained composite material is redispersed and stored in a specific solvent.

[0010] More preferably, in step (1), the concentrations of sodium chloride and basic lead acetate are 0.2M to 2M; the reaction temperature is 25℃ to 100℃; and the basic lead chloride has any morphology of micron or submicron size.

[0011] More preferably, the organic reagent in step (2) is at least two of octylamine, oleylamine, oleic acid, and octadecene; the functionalized carbon nanotube in step (2) is at least one of multi-walled carbon nanotube and single-walled carbon nanotube; and the mass ratio of carbon nanotube to basic lead chloride in step (2) is 1:50 to 1:5.

[0012] More preferably, in step (2), the functionalized carbon nanotubes include, but are not limited to, carboxylation and amination, with carboxylated carbon nanotubes being preferred; wherein the carboxylation method is to react carbon nanotubes with a strong oxidizing agent at a certain temperature, and the strong oxidizing agent is at least one of concentrated sulfuric acid, concentrated nitric acid and hydrogen peroxide, with concentrated sulfuric acid and concentrated nitric acid being preferred; wherein the amination method is to co-pyrolyze carbon nanotubes with an organic solvent such as acetamide at an appropriate temperature;

[0013] More preferably, the concentration of the sulfur precursor solution in step (3) is 0.1M to 0.5M; and the temperature of the lead precursor during sulfur injection in step (3) is 60℃ to 160℃.

[0014] More preferably, the quantum dot solvent in step (4) is one of toluene, chloroform, and hexane; the polar organic solvent is at least one of methanol, ethanol, butanol, and acetone, preferably ethanol and acetone; the specific solvent is at least one of toluene, chloroform, hexane, decane, and decene; and the first exciton absorption peak range of the lead sulfide colloidal quantum dot / carbon nanotube composite material is 900 nm to 2000 nm.

[0015] Compared with the prior art, the beneficial effects of the present invention are:

[0016] (1) The size or absorption peak of lead sulfide colloidal quantum dots grown in situ on carbon nanotubes is easy to control, and the reaction results are reproducible.

[0017] (2) Quantum dots have a high grafting rate on carbon nanotubes;

[0018] (3) The raw materials used are chemically stable and easy to store;

[0019] (4) The prepared composite material is stable in air. Attached Figure Description

[0020] Figure 1 This is a TEM image of the lead sulfide colloidal quantum dot / carbon nanotube composite material prepared in Example 1 of the present invention. Detailed Implementation

[0021] The preparation method of the present invention will be further described in detail below with reference to specific examples. It should be understood that the following examples are only used to explain the present invention, and any changes or improvements made to the implementation method based on the technical concept of the present invention are within the protection scope of the appended claims.

[0022] Example 1

[0023] A: Weigh 1.2g of sodium chloride and 6g of basic lead acetate (Pb(CH3COO)2·Pb(OH)2) and dissolve them in 15ml of distilled water to prepare 1.37M and 0.7M solutions respectively; then mix the two solutions and react at 80℃ for 15min. Wash the resulting white precipitate with distilled water and dry to obtain basic lead chloride; prepare an acid solution by uniformly stirring 75ml of concentrated nitric acid and 25ml of concentrated sulfuric acid (volume ratio 3:1), and weigh 0.5g of multi-walled carbon nanotubes and add them to the solution. After stirring in a good acid solution for 2 hours, the mixture was washed alternately with deionized water and anhydrous ethanol, and finally centrifuged and dried to obtain carboxylated carbon nanotube material. 0.278 g (0.001 mol) of the synthesized basic lead chloride and 40 mg of carboxylated CNTs were added to 15 ml of octylamine / oleic acid / octadecene mixed reagent, heated to 130 °C for 30 min under nitrogen protection, and then heated under vacuum for 30 min before stopping the heating and cooling the solution to 70 °C to obtain a mixed solution of carboxylated carbon nanotubes and lead precursor.

[0024] B: Mix 0.032 g (0.001 mol) of elemental sulfur with 3.5 ml of oleylamine at room temperature and rapidly dissolve it by sonication to obtain a 0.286 M sulfur precursor solution; then, under a nitrogen atmosphere, rapidly inject the sulfur precursor solution into the mixed solution obtained in step A; after a constant temperature reaction at 70 °C for 30 s, cool to 26 °C to obtain the stock solution containing lead sulfide quantum dot-carbon nanotube composite material;

[0025] C: Centrifuge the stock solution prepared in step B to separate the free PbS quantum dots and the PbS / CNTs composite material. Disperse the resulting composite material in chloroform, purify it with ethanol, and centrifuge again. Redissolve the purified composite material in chloroform to obtain a PbS / CNTs nanocomposite material with a first exciton absorption peak at 1310 nm. Its TEM image is shown below. Figure 1 As shown.

[0026] Example 2

[0027] A: Weigh 1.2g of sodium chloride and 6g of basic lead acetate (Pb(CH3COO)2·Pb(OH)2) and dissolve them in 15ml of distilled water to prepare 1.37M and 0.7M solutions respectively; then mix the two solutions and react at 80℃ for 15min. Wash the resulting white precipitate with distilled water and dry to obtain basic lead chloride; prepare an acid solution by uniformly stirring 75ml of concentrated nitric acid and 25ml of concentrated sulfuric acid (volume ratio 3:1), and weigh 0.5g of multi-walled carbon nanotubes and add them to the solution. After stirring in a good acid solution for 2 hours, the mixture was washed alternately with deionized water and anhydrous ethanol, and finally centrifuged and dried to obtain carboxylated carbon nanotube material. 0.278 g (0.001 mol) of the synthesized basic lead chloride and 40 mg of carboxylated CNTs were added to 15 ml of a mixed reagent of octylamine / oleylamine / octadecene. The mixture was heated to 130 °C for 30 min under nitrogen protection, and then the reaction was carried out under vacuum for 30 min. After heating was stopped, the solution was cooled to 90 °C to obtain a mixed solution of carboxylated carbon nanotubes and lead precursor.

[0028] B: Mix 0.032 g (0.001 mol) of elemental sulfur with 3.5 ml of oleylamine at room temperature and rapidly dissolve it by ultrasonication to obtain a 0.286 M sulfur precursor solution; then, under a nitrogen atmosphere, rapidly inject the sulfur precursor solution into the mixed solution obtained in step A; after a constant temperature reaction at 90 °C for 30 s, cool to 26 °C to obtain the stock solution containing lead sulfide quantum dot-carbon nanotube composite material;

[0029] C: Centrifuge the stock solution prepared in step B to separate the free PbS quantum dots and PbS / CNTs composite material. Disperse the obtained composite material in chloroform, add ethanol for purification, centrifuge again, and redissolve the purified composite material in chloroform to obtain a PbS / CNTs nanocomposite material with a first exciton absorption peak position of 1420 nm.

[0030] Example 3

[0031] A: Weigh 1.2g of sodium chloride and 6g of basic lead acetate (Pb(CH3COO)2·Pb(OH)2) and dissolve them in 15ml of distilled water to prepare 1.37M and 0.7M solutions respectively; then mix the two solutions and react at 80℃ for 15min. Wash the resulting white precipitate with distilled water and dry to obtain basic lead chloride; prepare an acid solution by uniformly stirring 75ml of concentrated nitric acid and 25ml of concentrated sulfuric acid (volume ratio 3:1), and weigh 0.5g of multi-walled carbon nanotubes and add them to the prepared solution. In an acidic solution, after stirring for 2 hours, the mixture was washed alternately with deionized water and anhydrous ethanol, and finally centrifuged and dried to obtain carboxylated carbon nanotube material. 0.278 g (0.001 mol) of the synthesized basic lead chloride and 40 mg of carboxylated CNTs were added to 15 ml of a mixed reagent of octylamine / oleic acid / octadecene. The mixture was heated to 130 °C for 30 min under nitrogen protection, and then the reaction was carried out under vacuum for 30 min. After heating was stopped, the solution was cooled to 120 °C to obtain a mixed solution of carboxylated carbon nanotubes and lead precursor.

[0032] B: Mix 0.032 g (0.001 mol) of elemental sulfur with 3.5 ml of oleylamine at room temperature and rapidly dissolve it by sonication to obtain a 0.286 M sulfur precursor solution; then, under a nitrogen atmosphere, rapidly inject the sulfur precursor solution into the mixed solution obtained in step A; after a constant temperature reaction at 120 °C for 30 s, cool to 26 °C to obtain the stock solution containing lead sulfide quantum dot-carbon nanotube composite material;

[0033] C: Centrifuge the stock solution prepared in step B to separate the free PbS quantum dots and PbS / CNTs composite material. Disperse the obtained composite material in chloroform, add ethanol for purification, centrifuge again, and redissolve the purified composite material in chloroform to obtain a PbS / CNTs nanocomposite material with a first exciton absorption peak position of 1545 nm.

[0034] Example 4

[0035] A: Weigh 1.2g of sodium chloride and 6g of basic lead acetate (Pb(CH3COO)2·Pb(OH)2) and dissolve them in 15ml of distilled water to prepare 1.37M and 0.7M solutions respectively; then mix the two solutions and react at 80℃ for 15min. Wash the resulting white precipitate with distilled water and dry to obtain basic lead chloride; prepare an acid solution by uniformly stirring 75ml of concentrated nitric acid and 25ml of concentrated sulfuric acid (volume ratio 3:1), and weigh 0.5g of multi-walled carbon nanotubes and add them to the prepared solution. In an acidic solution, after stirring for 2 hours, the mixture was washed alternately with deionized water and anhydrous ethanol, and finally centrifuged and dried to obtain carboxylated carbon nanotube material. 0.278 g (0.001 mol) of the synthesized basic lead chloride and 40 mg of carboxylated CNTs were added to 15 ml of a mixed reagent of octylamine / oleic acid / octadecene. The mixture was heated to 130 °C for 30 min under nitrogen protection, and then the reaction was carried out under vacuum for 30 min. After heating was stopped, the solution was cooled to 140 °C to obtain a mixed solution of carboxylated carbon nanotubes and lead precursor.

[0036] B: Mix 0.032 g (0.001 mol) of elemental sulfur with 3.5 ml of oleylamine at room temperature and rapidly dissolve it by sonication to obtain a 0.286 M sulfur precursor solution; then, under a nitrogen atmosphere, rapidly inject the sulfur precursor solution into the mixed solution obtained in step A; after a constant temperature reaction at 140 °C for 30 s, cool to 26 °C to obtain the stock solution containing lead sulfide quantum dot-carbon nanotube composite material;

[0037] C: Centrifuge the stock solution prepared in step B to separate the free PbS quantum dots and PbS / CNTs composite material. Disperse the obtained composite material in chloroform, add ethanol for purification, centrifuge again, and redissolve the purified composite material in chloroform to obtain a PbS / CNTs nanocomposite material with a first exciton absorption peak position of 1650 nm.

[0038] Example 5

[0039] A: Weigh 1.2g of sodium chloride and 6g of basic lead acetate (Pb(CH3COO)2·Pb(OH)2) and dissolve them in 15ml of distilled water to prepare 1.37M and 0.7M solutions respectively; then mix the two solutions and react at 80℃ for 15min. Wash the resulting white precipitate with distilled water and dry to obtain basic lead chloride; prepare an acid solution by uniformly stirring 75ml of concentrated nitric acid and 25ml of concentrated sulfuric acid (volume ratio 3:1), and weigh 0.5g of multi-walled carbon nanotubes and add them to the prepared solution. In an acidic solution, after stirring for 2 hours, the mixture was washed alternately with deionized water and anhydrous ethanol, and finally centrifuged and dried to obtain carboxylated carbon nanotube material. 0.278 g (0.001 mol) of the synthesized basic lead chloride and 40 mg of carboxylated CNTs were added to 15 ml of a mixed reagent of octylamine / oleylamine / octadecene. The mixture was heated to 130 °C for 30 min under nitrogen protection, and then the reaction was carried out under vacuum for 30 min. After heating was stopped, the solution was cooled to 160 °C to obtain a mixed solution of carboxylated carbon nanotubes and lead precursor.

[0040] B: Mix 0.032 g (0.001 mol) of elemental sulfur with 3.5 ml of oleylamine at room temperature and rapidly dissolve it by sonication to obtain a 0.286 M sulfur precursor solution; then, under a nitrogen atmosphere, rapidly inject the sulfur precursor solution into the mixed solution obtained in step A; after a constant temperature reaction at 160 °C for 30 s, cool to 26 °C to obtain the stock solution containing lead sulfide quantum dot-carbon nanotube composite material;

[0041] C: Centrifuge the stock solution prepared in step B to separate the free PbS quantum dots and PbS / CNTs composite material. Disperse the obtained composite material in chloroform, add ethanol for purification, centrifuge again, and redissolve the purified composite material in chloroform to obtain a PbS / CNTs nanocomposite material with a first exciton absorption peak position of 1725 nm.

[0042] The above description merely illustrates preferred embodiments of the present invention, and while the description is relatively specific and detailed, it should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications, improvements, and substitutions without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A method for preparing a lead sulfide colloidal quantum dot / carbon nanotube composite material, characterized in that, Specifically, the steps include the following: (1) Weigh out sodium chloride and basic lead acetate separately to prepare aqueous solutions of a certain concentration; mix the two solutions and place them at a certain temperature to react and obtain a white precipitate, which is then washed with distilled water and finally dried to remove water to obtain basic lead chloride; (2) In a nitrogen atmosphere, the basic lead chloride synthesized in step (1) and the functionalized carbon nanotubes are added to an organic solvent and stirred. The organic solvent is at least two of octylamine, oleylamine, oleic acid and octadecene. The functionalized carbon nanotubes are carboxylated carbon nanotubes. The mass ratio of the carboxylated carbon nanotubes to the basic lead chloride is 1:50-1:

5. Then the mixed solution is heated to 90°C-160°C and held for 25min-35min. Finally, the vacuum is continuously evacuated for 25min-35min and then the heating is turned off to obtain a mixed solution of functionalized carbon nanotubes and lead precursor while maintaining a nitrogen atmosphere. (3) At room temperature, elemental sulfur is added to oleylamine to prepare a sulfur precursor solution with a concentration of 0.1M-0.5M. Then, the sulfur precursor solution is rapidly injected into the mixed solution of carboxylated carbon nanotubes and lead precursor obtained in step (2). Then, it is kept at 60°C-160°C for 0.5min-20min. Finally, the solution is cooled to 10°C-30°C to obtain a mixed stock solution of lead sulfide colloidal quantum dots / carbon nanotubes. (4) After centrifuging to remove free quantum dots and impurities, the mixed stock solution prepared in step (3) is diluted with quantum dot solvent. Then, the lead sulfide colloidal quantum dot / carbon nanotube solution is purified with polar organic solvent and dried by centrifugation to obtain lead sulfide colloidal quantum dot / carbon nanotube composite material. Finally, the obtained composite material is redispersed and stored in a specific solvent. The first exciton absorption peak of the prepared lead sulfide colloidal quantum dot / carbon nanotube composite material is in the range of 900nm-2000nm.

2. The method for preparing a lead sulfide colloidal quantum dot / carbon nanotube composite material according to claim 1, characterized in that: In step (1), the concentrations of sodium chloride and basic lead acetate are 0.2M-2M; the reaction temperature is 25℃-100℃; the reaction time is 10min-60min; and the basic lead chloride has any morphology with micron or submicron dimensions.

3. The method for preparing a lead sulfide colloidal quantum dot / carbon nanotube composite material according to claim 1, characterized in that: In step (2), the carboxylated carbon nanotubes are at least one of carboxylated multi-walled carbon nanotubes and carboxylated single-walled carbon nanotubes.

4. The method for preparing a lead sulfide colloidal quantum dot / carbon nanotube composite material according to claim 1, characterized in that: The method for preparing carboxylated carbon nanotubes in step (2) is as follows: a strong oxidizing agent is stirred and reacted with carbon nanotubes, wherein the strong oxidizing agent is at least one of concentrated sulfuric acid, concentrated nitric acid and hydrogen peroxide.

5. The method for preparing a lead sulfide colloidal quantum dot / carbon nanotube composite material according to claim 1, characterized in that: The quantum dot solvent in step (4) is at least one of toluene, chloroform, and hexane.

6. The method for preparing a lead sulfide colloidal quantum dot / carbon nanotube composite material according to claim 1, characterized in that: The polar organic solvent in step (4) is at least one of methanol, ethanol, butanol, and acetone.

7. The method for preparing a lead sulfide colloidal quantum dot / carbon nanotube composite material according to claim 1, characterized in that: The specific solvent in step (4) is at least one of toluene, chloroform, hexane, decane and decene.

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