Preparation method of quantum dot material with precisely regulated shell layer number
Patent Information
- Application Number
- CN202610913254.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-06-24
- Publication Date
- 2026-08-18
AI Technical Summary
[0005]（1）晶格失配问题加剧：CdS与CdSe的晶格失配度达到4%，在厚壳层生长过程中应力不断累积，最终导致大量缺陷产生
[0047] (1) Major breakthrough in shell thickness: For the first time, the growth of 20-layer CdSe shells of CdS/CdSe anti-type I quantum dots was achieved, with a total particle size of 16.5 nm and a shell thickness of about 6.29 nm.
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Figure CN122585956A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of semiconductor nanomaterial synthesis technology, and particularly relates to a method for preparing quantum dot materials with precisely controllable shell layer number. Background Technology
[0002] Quantum dots, due to their unique quantum confinement effect, have shown potential applications in photocatalysis, displays, and bioimaging. In the field of photocatalytic hydrogen production research, colloidal semiconductor quantum dots, with their precisely controllable band structure, high light absorption coefficient, and excellent charge transport performance, are considered an ideal model for studying the dynamics of photogenerated carrier transfer in photocatalytic systems.
[0003] Common type I core-shell quantum dots (such as CdSe / CdS) are characterized by the simultaneous confinement of photogenerated electrons and holes in the core region. While this improves the quantum yield of luminescence, the thick shell growth process is prone to lattice mismatch and the continuous accumulation of defects, limiting further shell thickness growth. In contrast, in anti-type I core-shell quantum dot structures (such as CdS / CdSe), the shell material CdSe has a narrower bandgap than the core material CdS. Excited photogenerated electrons and holes migrate to the CdSe shell. Due to the significant difference in electron and hole migration rates, the thicker shell in this band structure is more conducive to carrier separation, thus facilitating photocatalytic reactions.
[0004] However, the shell thickness of anti-type I CdS / CdSe quantum dots in existing technologies remains relatively thin. The largest reported shell thickness is approximately 2.61 nm (about 7-8 atomic layers), with a total particle size of approximately 9.14 nm. Further increases in shell thickness present the following key technical challenges:
[0005] (1) The problem of lattice mismatch is aggravated: the lattice mismatch between CdS and CdSe reaches 4%. During the growth of the thick shell, stress accumulates continuously, eventually leading to the generation of a large number of defects.
[0006] (2) Decreased optical performance: As the shell grows, the quantum yield usually decreases significantly and nonradiative recombination increases.
[0007] (3) Poor uniformity of layer number: It is difficult to grow uniformly layer by layer on the entire quantum dot surface, resulting in an excessively wide particle size distribution of the sample.
[0008] Therefore, developing a method for synthesizing high-quality CdS / CdSe anti-type I giant quantum dots with thick shells (more than 20 layers) in a precise and controllable manner is a technical problem that urgently needs to be solved in this field. Summary of the Invention
[0009] The purpose of this invention is to provide a method for preparing quantum dot materials with precisely controllable shell layer number, aiming to solve the problems mentioned in the background art.
[0010] The present invention is implemented as follows: a method for preparing quantum dot materials with precisely controllable shell layer number includes the following steps:
[0011] Step 1: Prepare CdS quantum dot cores;
[0012] A cadmium source, oleic acid (OA), and octadecene (ODE) were mixed and heated under inert gas protection until the cadmium source was completely dissolved. The mixture was then injected into a sulfur precursor solution, and after the reaction, it was purified to obtain CdS quantum dot cores.
[0013] Step 2: Prepare Cd-Se precursor solution;
[0014] Cadmium source was mixed with oleic acid and heated under inert gas protection until the cadmium source was completely dissolved. Octadecylene was added to adjust the concentration. Selenium powder, trioctylphosphine (TOP) and octadecylene were added and heated under inert gas protection until the selenium powder was completely dissolved to obtain a Cd-Se precursor solution.
[0015] Step 3: Layer-by-layer shell growth: The CdS quantum dot cores obtained in Step 1 are dispersed in a mixed solvent of octadecene and oleylamine (OAm), heated to 260-320℃ under inert gas protection, and injected dropwise into the Cd-Se precursor solution obtained in Step 2 using an injection pump to control the injection rate. Each injection volume is 0.03-0.04 mL. The number of CdSe shell atomic layers can be precisely controlled by controlling the number of injections.
[0016] Step 4: Purification;
[0017] After the reaction was completed, CdS / CdSe anti-I type core-shell quantum dots were obtained by centrifugation, washing, and drying.
[0018] In a further technical solution, in step 1, the cadmium source is CdO, and the sulfur precursor solution is a solution of sulfur powder dissolved in octadecene.
[0019] A further technical solution, the specific steps of step 1 are as follows:
[0020] In a 100 mL three-necked flask, add 2.34 mmol CdO, 10 mL OA and 10 mL ODE in sequence, add a magnetic stir bar and stir at 300 r / min;
[0021] Deoxygenation was performed for 15 minutes using a vacuum circulation system, followed by dynamic vacuum dehydration at 120 °C for 20 minutes.
[0022] The atmosphere in the system was replaced with high-purity argon gas, and the temperature was raised to 260 °C until the CdO precursor was completely dissolved to form a colorless and transparent solution.
[0023] The pre-prepared sulfur precursor solution was injected and the reaction was carried out at 260 °C for 60 s.
[0024] After the reaction was completed, the mixture was immediately cooled to room temperature with an air gun to terminate the reaction. Then, an equal volume of n-hexane and ethanol mixed solvent was added, and the mixture was centrifuged at 10,000 r / min for 5 min. The precipitate was redispersed in n-hexane, and the washing was repeated 3 times.
[0025] The purified CdS cores were dispersed in n-hexane and stored at 4 °C.
[0026] In a further technical solution, the sulfur precursor solution is prepared by dissolving 1.17 mmol of sulfur powder in 5 mL of ODE, and is pre-dissolved at 60 °C.
[0027] A further technical solution, the specific steps of step 2 are as follows:
[0028] In a 100 mL three-necked flask, add 12 mmol CdO and 24.27 mL OA sequentially;
[0029] The device was subjected to vacuum degassing, stirred at room temperature for 1 hour, and then heated to 120 °C and held for 20 minutes.
[0030] Switch to an argon protective atmosphere and continue heating to 180 °C until CdO is completely dissolved, forming a clear and transparent pale yellow solution;
[0031] Slowly add 35.73 mL of ODE, adjust the system state, and then evacuate again at 100 °C for 15-20 min, before switching back to an argon atmosphere.
[0032] After the reaction is complete, stop heating, shut off the gas path and vacuum system according to the standard procedure, and purify and store the product after cooling to room temperature.
[0033] Take 3.86 mL of Cd-Se precursor solution and 0.8 mmol of selenium powder, add 1 mL of ODE and 1 mL of TOP, seal and remove; heat to 180 °C under argon protection atmosphere, stir for 30 min until completely dissolved, prepare Cd-Se precursor solution, cool to room temperature for later use.
[0034] In a further technical solution, in step 3, the prepared CdS / CdSe quantum dots have a CdS core and a CdSe shell, and the CdSe shell has 10 or 20 atomic layers.
[0035] Further technical solutions, specifically the preparation method of 10-layer CdS / CdSe quantum dots, are as follows:
[0036] Take 5 ml of washed CdS nuclei and transfer them to a 100 mL three-necked flask containing 2 mL ODE and 2 mL OAm;
[0037] Vacuum degassing for 15 min removes oxygen, then heating to 120 °C under vacuum and holding for 20 min evaporates n-hexane;
[0038] The solution was heated to 320 °C under argon protection.
[0039] When the temperature reaches 260 °C, the prepared Cd-Se precursor solution is injected using a syringe pump at a rate of 1.8 mL / hr, with each injection being 0.03 mL.
[0040] The experiment lasted 5 hours and 33 minutes and yielded CdS / CdSe quantum dots coated with 10 layers of CdSe shell.
[0041] A further technical solution, the specific method for preparing 20-layer CdS / CdSe quantum dots is as follows:
[0042] Take half of the 10-layer CdS / CdSe quantum dots and transfer them to a 100 mL three-necked flask (the flask does not contain ODE and OAm).
[0043] Vacuum degassing for 15 minutes, followed by heating under vacuum to 120 °C and holding for 20 minutes to remove n-hexane;
[0044] Argon gas was introduced, and the temperature was raised to 320 °C. When the temperature reached 260 °C, the Cd-Se precursor solution was injected using a syringe pump at a rate of 1.8 mL / hr, with each injection being 0.03 mL.
[0045] The reaction time was 5 hours and 33 minutes, and CdS / CdSe quantum dots with 20 CdSe shells were obtained.
[0046] The present invention provides a method for preparing quantum dot materials with precisely controllable shell layer number, which has the following beneficial effects:
[0047] (1) Major breakthrough in shell thickness: For the first time, the growth of 20-layer CdSe shells of CdS / CdSe anti-type I quantum dots was achieved, with a total particle size of 16.5 nm and a shell thickness of about 6.29 nm.
[0048] (2) Precise and controllable number of layers: Through the layer-by-layer injection method, the atomic-level precise control of the number of layers was achieved, and samples with two different shell thicknesses of 10 layers and 20 layers were successfully prepared, with narrow particle size distribution and good sample uniformity.
[0049] (3) The tunable range of the absorption spectrum is significantly broadened: As the shell layer increases from 10 layers to 20 layers, the first exciton absorption peak redshifts from 675 nm to 702 nm, achieving continuous tunability of 27 nm, which effectively expands the application range of the material in optoelectronic devices.
[0050] (4) Excellent crystal quality: XRD analysis shows that the prepared quantum dots have a high-quality wurtzite crystal structure, indicating that the method of the present invention effectively suppresses the generation of defects in the thick shell growth process.
[0051] (5) High process repeatability: The synthesis process conditions are controllable, the process window is wide, and it is suitable for large-scale production.
[0052] (6) Wide range of applications: The 10-layer and 20-layer CdS / CdSe quantum dots prepared have high application potential in photocatalytic hydrogen production, bioimaging, photodetectors, solar cells and other fields. Attached Figure Description
[0053] Figure 1 TEM image of 10 layers of CdS / CdSe quantum dots;
[0054] Figure 2 TEM image of 20 layers of CdS / CdSe quantum dots;
[0055] Figure 3 Histograms of particle size distribution for 10-layer and 20-layer CdS / CdSe quantum dots;
[0056] Figure 4 Comparison of UV-Vis absorption spectra of 10-layer and 20-layer CdS / CdSe quantum dots;
[0057] Figure 5 Comparison of XRD spectra of 10-layer and 20-layer CdS / CdSe quantum dots. Detailed Implementation
[0058] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.
[0059] The specific implementation of the present invention will be described in detail below with reference to specific embodiments.
[0060] An embodiment of the present invention provides a method for preparing quantum dot materials with precisely controllable shell layer number, comprising the following steps:
[0061] Includes the following steps:
[0062] Step 1: Prepare CdS quantum dot cores;
[0063] Cadmium source, oleic acid and octadecene were mixed and heated under inert gas protection until the cadmium source was completely dissolved. The mixture was then injected with a sulfur precursor solution and purified after reaction to obtain CdS quantum dot cores.
[0064] Step 2: Prepare Cd-Se precursor solution;
[0065] Cadmium source was mixed with oleic acid and heated under inert gas protection until the cadmium source was completely dissolved. Octadecylene was added to adjust the concentration. Selenium powder, trioctylphosphine and octadecylene were added and heated under inert gas protection until the selenium powder was completely dissolved to obtain a Cd-Se precursor solution.
[0066] Step 3: Layer-by-layer shell growth: The CdS quantum dot cores obtained in Step 1 are dispersed in a mixed solvent of octadecene and oleylamine, heated to 260-320℃ under inert gas protection, and injected dropwise into the Cd-Se precursor solution obtained in Step 2 using an injection pump to control the injection rate. Each injection volume is 0.03-0.04 mL. The number of atomic layers of the CdSe shell is precisely controlled by controlling the number of injections.
[0067] Step 4: Purification;
[0068] After the reaction was completed, CdS / CdSe anti-I type core-shell quantum dots were obtained by centrifugation, washing, and drying.
[0069] The method is verified in conjunction with a specific embodiment, which includes the following steps:
[0070] Step 1: Synthesis of CdS cores;
[0071] In a 100 mL three-necked flask, add 2.34 mmol CdO, 10 mL oleic acid (OA), and 10 mL octadecene (ODE) in sequence, add a magnetic stir bar, and stir at 300 r / min.
[0072] Deoxygenation was performed for 15 minutes using a vacuum circulation system, followed by dynamic vacuum dehydration at 120 °C for 20 minutes.
[0073] The atmosphere in the system was replaced with high-purity argon gas, and the temperature was raised to 260 °C until the CdO precursor was completely dissolved to form a colorless and transparent solution.
[0074] The pre-prepared sulfur precursor solution (1.17 mmol sulfur powder dissolved in 5 mL ODE, pre-dissolved at 60 °C) was rapidly injected and the reaction was carried out at 260 °C for 60 s.
[0075] After the reaction was complete, immediately cool to room temperature with an air gun to terminate the reaction. Then, add an equal volume of a mixed solvent of n-hexane and ethanol, centrifuge at 10000 r / min for 5 min, and redisperse the precipitate in n-hexane. Repeat the washing process 3 times.
[0076] The purified CdS cores were dispersed in n-hexane and stored at 4 °C. The concentration of CdS cores in the solution was determined by the position of the first exciton absorption peak in the UV-Vis absorption spectrum.
[0077] Step 2: Preparation of Cd-Se precursor solution;
[0078] A Cd-Se precursor solution was prepared using cadmium oxide (CdO) and oleic acid (OA) as raw materials and octadecene (ODE) as solvent. The specific steps are as follows:
[0079] In a 100 mL three-necked flask, add 12 mmol CdO and 24.27 mL OA sequentially.
[0080] The device was subjected to vacuum degassing, and after stirring at room temperature for 1 hour, the temperature was raised to 120 °C and held for 20 minutes to remove water and oxygen from the system.
[0081] Switch to an argon protective atmosphere and continue heating to 180 °C until the CdO is completely dissolved, forming a clear and transparent pale yellow solution.
[0082] Slowly add 35.73 mL of ODE, adjust the system state, and then evacuate again at 100 °C for 15-20 min, before switching back to an argon atmosphere.
[0083] After the reaction is complete, stop heating, shut off the gas path and vacuum system according to the standard procedure, cool to room temperature, purify and preserve the product, which can then be used for shell growth experiments.
[0084] Take 3.86 mL of Cd-Se precursor solution and 0.8 mmol of selenium powder, add 1 mL of ODE and 1 mL of trioctylphosphine (TOP), seal and remove. Heat to 180 °C under an argon atmosphere and stir for 30 min until completely dissolved to prepare a Cd-Se precursor solution. Cool to room temperature for later use.
[0085] Step 3: Synthesis of 10 layers of CdS / CdSe quantum dots;
[0086] Take 5 ml of washed CdS nuclei and transfer them to a 100 mL three-necked flask containing 2 mL ODE and 2 mL oleylamine (OAm);
[0087] Vacuum degassing for 15 min removes oxygen, then heating to 120 °C under vacuum and holding for 20 min evaporates n-hexane;
[0088] The solution was heated to 320 °C under argon protection.
[0089] When the temperature reaches 260 °C, the prepared Cd-Se precursor solution is injected using a syringe pump at a rate of 1.8 mL / hr, with each injection being 0.03 mL.
[0090] The experiment lasted 5 hours and 33 minutes and yielded CdS / CdSe quantum dots coated with 10 layers of CdSe shell.
[0091] Step 4: Synthesis of 20 layers of CdS / CdSe quantum dots;
[0092] Referring to the 10-layer CdS / CdSe quantum dot sample from step 3, the operation in step 3 is repeated to obtain CdS / CdSe quantum dots coated with a 20-layer CdSe shell. The specific steps are as follows:
[0093] Take half of the 10-layer CdS / CdSe quantum dots and transfer it to a 100 mL three-necked flask (the flask should not contain 2 mL ODE and 2 mL OAm). Degas under vacuum for 15 minutes, then heat to 120 °C under vacuum and hold for 20 minutes to remove n-hexane. Purge with argon and heat to 320 °C. When the temperature reaches 260 °C, start injecting the Cd-Se precursor solution using a syringe pump at a rate of 1.8 mL / hr, injecting 0.03 mL (containing CdSe) each time, for a reaction time of 5 hours and 33 minutes.
[0094] Step 5: Purification and Preservation;
[0095] After the reaction is complete, allow it to cool naturally to room temperature.
[0096] Add an equal volume of a mixed solvent of ethanol and acetone, and centrifuge at 10000 r / min for 5 min.
[0097] The precipitate was redissolved in hexane and then washed with ethanol / acetone. This process was repeated three times.
[0098] The final product was dispersed in n-hexane for storage.
[0099] If solid powder is required, place it in a vacuum drying oven and dry it at 40 °C for 12 hours.
[0100] The structural characteristics of the 10-layer and 20-layer CdS / CdSe anti-type I giant quantum dots are shown in Table 1 below:
[0101] Table 1
[0102]
[0103] The sample characterization and performance analysis are as follows:
[0104] (1) Morphology and particle size distribution (TEM):
[0105] like Figures 1-3 As shown, transmission electron microscopy (TEM) results reveal that both samples exhibit near-monodispersive spherical morphology with a narrow particle size distribution. This demonstrates that the proposed method can achieve precise control over the number of shell layers, resulting in samples with excellent uniformity. Specifically, the 20-layer CdS / CdSe quantum dots achieved a total particle size of 16.5 nm and a shell thickness of approximately 6.29 nm, significantly exceeding the shell thickness reported in existing technologies (the maximum value in the literature is approximately 2.61 nm, with a total particle size of approximately 9.14 nm).
[0106] (2) Optical absorption characteristics (UV-Vis):
[0107] UV-Vis absorption spectroscopy was performed on samples coated with 10 and 20 CdSe shells. Figure 4 As shown, as the number of shell layers increased from 10 to 20, the first exciton absorption peak of the sample redshifted from 675 nm to 702 nm, a redshift of 27 nm. This phenomenon can be attributed to the weakening of the quantum confinement effect and the enhancement of electronic coupling at the core / shell interface during shell thickening, directly proving the successful growth and thickness control of the shell.
[0108] (3) Crystal structure analysis (XRD):
[0109] like Figure 5 As shown, the X-ray diffraction patterns of the 10-layer and 20-layer samples both show clear characteristic diffraction peaks, which are consistent with the standard diffraction peak positions of the wurtzite CdS / CdSe structure, and the diffraction peak intensities are high, indicating that the prepared quantum dots have excellent crystal quality.
[0110] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A method for preparing quantum dot materials with precisely controllable shell layer number, characterized in that, Includes the following steps: Step 1: Prepare CdS quantum dot cores; The cadmium source, OA and ODE were mixed and heated under inert gas protection until the cadmium source was completely dissolved. The mixture was then injected with a sulfur precursor solution and purified after reaction to obtain CdS quantum dot cores. Step 2: Prepare Cd-Se precursor solution; The cadmium source was mixed with oleic acid and heated under inert gas protection until the cadmium source was completely dissolved. ODE was added to adjust the concentration. Selenium powder, TOP and ODE were added and heated under inert gas protection until the selenium powder was completely dissolved to obtain a Cd-Se precursor solution. Step 3: Layer-by-layer shell growth: The CdS quantum dot cores obtained in Step 1 are dispersed in a mixed solvent of ODE and OAm, heated to 260-320℃ under inert gas protection, and the Cd-Se precursor solution obtained in Step 2 is injected dropwise with the injection rate controlled by an injection pump. Each injection volume is 0.03-0.04 mL. The number of atomic layers of the CdSe shell is precisely controlled by controlling the number of injections. Step 4: Purification; After the reaction was completed, CdS / CdSe anti-I type core-shell quantum dots were obtained by centrifugation, washing, and drying.
2. The method for preparing quantum dot materials with precisely controllable shell layer number according to claim 1, characterized in that, In step 1, the cadmium source used is CdO.
3. The method for preparing quantum dot materials with precisely controllable shell layer number according to claim 2, characterized in that, The specific steps of step 1 are as follows: In a 100 mL three-necked flask, add 2.34 mmol CdO, 10 mL OA and 10 mL ODE in sequence, add a magnetic stir bar and stir at 300 r / min; Deoxygenation was performed for 15 minutes using a vacuum circulation system, followed by dynamic vacuum dehydration at 120 °C for 20 minutes. The atmosphere in the system was replaced with high-purity argon gas, and the temperature was raised to 260 °C until the CdO precursor was completely dissolved to form a colorless and transparent solution. The pre-prepared sulfur precursor solution was injected and the reaction was carried out at 260 °C for 60 s. After the reaction was completed, the mixture was immediately cooled to room temperature with an air gun to terminate the reaction. Then, an equal volume of n-hexane and ethanol mixed solvent was added, and the mixture was centrifuged at 10,000 r / min for 5 min. The precipitate was redispersed in n-hexane, and the washing was repeated 3 times. The purified CdS cores were dispersed in n-hexane and stored at 4 °C.
4. The method for preparing quantum dot materials with precisely controllable shell layer number according to claim 3, characterized in that, The sulfur precursor solution was prepared by dissolving 1.17 mmol of sulfur powder in 5 mL of ODE, and was pre-dissolved at 60 °C.
5. The method for preparing quantum dot materials with precisely controllable shell layer number according to claim 3, characterized in that, The specific steps of step 2 are as follows: In a 100 mL three-necked flask, add 12 mmol CdO and 24.27 mL OA sequentially; The device was subjected to vacuum degassing, stirred at room temperature for 1 hour, and then heated to 120 °C and held for 20 minutes. Switch to an argon protective atmosphere and continue heating to 180 °C until CdO is completely dissolved, forming a clear and transparent pale yellow solution; Slowly add 35.73 mL of ODE, adjust the system state, and then evacuate again at 100 °C for 15-20 min, before switching back to an argon atmosphere. After the reaction is complete, stop heating, shut off the gas path and vacuum system according to the standard procedure, and purify and store the product after cooling to room temperature. Take 3.86 mL of Cd-Se precursor solution and 0.8 mmol of selenium powder, add 1 mL of ODE and 1 mL of TOP, seal and remove; heat to 180 °C under argon protection atmosphere, stir for 30 min until completely dissolved, prepare Cd-Se precursor solution, cool to room temperature for later use.
6. The method for preparing quantum dot materials with precisely controllable shell layer number according to claim 5, characterized in that, In step 3, the prepared CdS / CdSe quantum dots have a CdS core and a CdSe shell, with the CdSe shell having 10 or 20 atomic layers.
7. The method for preparing quantum dot materials with precisely controllable shell layer number according to claim 6, characterized in that, The specific method for preparing 10-layer CdS / CdSe quantum dots is as follows: Take 5 ml of washed CdS nuclei and transfer them to a 100 mL three-necked flask containing 2 mL ODE and 2 mL OAm; Vacuum degassing for 15 min removes oxygen, then heating to 120 °C under vacuum and holding for 20 min evaporates n-hexane; The solution was heated to 320 °C under argon protection. When the temperature reaches 260 °C, the prepared Cd-Se precursor solution is injected using a syringe pump at a rate of 1.8 mL / hr, with each injection being 0.03 mL. The experiment lasted 5 hours and 33 minutes and yielded CdS / CdSe quantum dots coated with 10 layers of CdSe shell.
8. The method for preparing quantum dot materials with precisely controllable shell layer number according to claim 7, characterized in that, The specific method for preparing 20-layer CdS / CdSe quantum dots is as follows: Take half of the 10-layer CdS / CdSe quantum dots and transfer them to a 100 mL three-necked flask; Vacuum degassing for 15 minutes, followed by heating under vacuum to 120 °C and holding for 20 minutes to remove n-hexane; Argon gas was introduced and the temperature was raised to 320 °C. When the temperature reached 260 °C, the Cd-Se precursor solution was injected using a syringe pump at a rate of 1.8 mL / hr, with each injection being 0.03 mL. The reaction time was 5 hours and 33 minutes, and CdS / CdSe quantum dots with 20 CdSe shells were obtained.