Method for regulating and controlling particle size and doping of Ag2Se colloidal quantum dots

Abstract

A particle size and doping regulation and control method of high-quality Ag2Se colloidal quantum dots (CQDs) relates to a quantum dot control technology, and comprises the following steps: injecting AgNO3 containing an Ag source and a TOP-Se precursor solution containing an Se source into a three-necked round-bottom flask filled with an oleylamine solution, and carrying out reaction, nucleation and growth in vacuum and inert gas atmosphere to finally form Ag2Se CQDs. And the particle size, the morphology and the absorption are changed by changing the precursor proportion and the reaction time. The method is low in cost, simple to operate and easy to implement.

Description

Technical Field

[0001] The present invention relates to a colloidal quantum dot control technology, in particular to a particle size and doping control technology of Ag2Se colloidal quantum dots (CQDs). Background Art

[0002] Quantum dots are degenerately doped semiconductor nanomaterials that exhibit unique optical properties in the mid-wave to long-wave infrared. Thermal infrared sensing and imaging technologies are based on single-crystal or epitaxial semiconductors, and colloidal quantum dots (QDs) are emerging as alternative materials due to their cost-effectiveness and multifunctionality.

[0003] Pb-based and Hg-based colloidal quantum dot materials are currently a research hotspot in the field of infrared detection. Infrared photoelectric detectors are continuously expanding in the application fields of military, medical, and civilian use. However, Pb-based and Hg-based colloidal quantum dots have the problem of high toxicity and serious environmental pollution. Summary of the invention

[0004] The present invention provides a method for regulating the particle size and doping of Ag2Se colloidal quantum dots (CQDs), which solves the problem that Pb-based and Hg-based colloidal quantum dots are highly toxic and cause serious environmental pollution, and the preparation method is simple and efficient.

[0005] The particle size and doping control method of Ag2Se colloidal quantum dots is characterized in that the preparation steps of the method are as follows: S1, adding Se powder to trioctylphosphine and dissolving it after ultrasonication to prepare TOP-Se solution; S2, adding silver nitrate to oleylamine solution, heating to 80 °C and evacuating to prepare a precursor solution; S3, heating the solution obtained in step S2 to 140°C, quickly adding the TOP-Se solution prepared in step S1 to the precursor solution to obtain a black solution, reacting for 5-60 min, and then cooling in a water bath to room temperature; S4, adding a solution of n-butanol and anhydrous ethanol mixed in a ratio of 2:1 to the black solution obtained in step S3, washing and centrifuging to remove the solution, and obtaining Ag2Se CQDs powder; S5, adding non-polar solvent n-octane to Ag2Se CQDs powder to prepare a quantum dot ink solution of a certain concentration; In the precursor, the ratio of Ag:Se is 2:1-6:1.

[0006] In the step S4, the centrifugation is performed 3 times, the first centrifugation speed is 7000 rpm / min, the centrifugation time is 5 min, the second and third centrifugation speeds are 5000 rpm / min, and the centrifugation time is 3 min.

[0007] The quantum dot ink solution of a certain concentration is prepared according to usage requirements.

[0008] Ag2Se quantum dots (silver selenium quantum dots) are nanomaterials composed of silver and selenium. As a semiconductor material, it has a narrow band gap advantage of 0.15 eV, which enables it to be well extended to medium and long-wave infrared absorption. On the one hand, it makes up for the problem that quantum dots containing heavy metal elements such as lead or mercury are highly toxic to the environment and biological systems, and can effectively reduce the pollution of quantum dots to the environment. On the other hand, Ag2Se CQDs have good conductivity and photoelectric properties and can be used as an excellent semiconductor material.

[0009] The technical effects and advantages of the present invention are that the preparation method is simple, effective and repeatable; the size of quantum dots can be controlled within a range of 6.5-8.0 nm, the absorption can be controlled within a range of 4.5-6.0 μm, and the synthesized quantum dots have good monodispersity in morphology. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 Transmission electron microscopy images of Ag2Se CQDs with different reaction times; It can be seen from the figure that when synthesizing Ag2Se quantum dots, the reaction time has a great influence on its morphology and size. Figures (a), (b), (c), and (d) are transmission electron micrographs of Ag2SeCQDs when the Ag:Se ratio is 2:1 and the reaction time is 5 min, 15 min, 30 min, and 60 min. The quantum dots in the figures have good monodispersity and no agglomeration. The average particle sizes of the obtained quantum dots are 6.5 nm, 7.1 nm, 7.4 nm, and 8.2 nm, respectively. The quantum dots synthesized in Figures (a)-(d) are all spherical and have relatively good dispersion, except that agglomeration occurs at some reaction times. When the reaction time is 30 min, the monodispersity and size uniformity of the quantum dots are the best.

[0011] Figure 2 Fourier infrared spectra of Ag2Se CQDs at different reaction times; It can be seen from the figure that the sharp peak is the CH vibration at 3.5 μm and the CO2 peaks at 4.24 μm and 4.28 μm; the reaction time is 5 min, 15 min, 30 min, 60 min corresponding to the absorption of 4.8 μm, 5.1 μm, 5.4 μm, 5.8 μm respectively; the infrared absorption of Ag2Se CQDs at 4.5-6.0 μm indicates that the prepared Ag2Se CQDs have the characteristics that can be used for infrared detection, and it can be seen that with the increase of time, the size increases accordingly, and the absorption peak also red-shifts accordingly.

[0012] Figure 3 Transmission electron microscopy images of Ag2Se CQDs with different precursor ratios; Figures (a), (b), (c), and (d) are transmission electron micrographs of Ag2Se CQDs at Ag:Se ratios of 3:1, 4:1, 5:1, and 6:1 with a reaction time of 30 min. It can be seen from the figures that Figure (b) shows the case where the Ag:Se ratio is 4:1, at which time the quantum dot size is 7.5 nm, and at this time the quantum dot particle size, monodispersity, and crystallinity are the best.

[0013] Figure 4 Fourier infrared spectra of Ag2Se CQDs with different precursor ratios; It can be seen from the figure that when the proportion of precursor Ag is increased, the second exciton peak appears. If the proportion of precursor Ag continues to increase, when the precursor ratio is 5:1, the absorption peak will disappear.

[0014] Figure 5 is a transmission electron microscope image of Example 9; It can be seen from the figure that the morphology of the quantum dots is poor and the monodispersity is not good. DETAILED DESCRIPTION

[0015] The present invention is further described in detail below through examples and specific characterization tests, but it should not be understood that the scope of the present invention is limited to the following examples.

[0016] Example 1: Particle size and doping control method of Ag2Se colloidal quantum dots. The preparation steps of the method are as follows: S1, 0.079 g of Se powder was added into 0.5 mL of trioctylphosphine (TOP) and dissolved by ultrasonication for 2 h to prepare TOP-Se solution.

[0017] S2, take 0.68g of silver nitrate (AgNO3), add it into a three-necked flask containing 30mL of oleylamine solution, heat it to 80℃ and evacuate it for 1 hour to prepare a precursor solution; S3, heating the solution obtained in step S2 to 140° C., quickly adding the TOP-Se solution prepared in step S1 into the three-necked flask to obtain a black solution, reacting for 30 min, and then cooling to room temperature in a water bath.

[0018] S4, adding a solution of n-butanol and anhydrous ethanol mixed in a ratio of 2:1 to the black solution obtained in step 3, washing the solution three times and then centrifuging to remove the solution to obtain Ag2Se CQDs powder; The three centrifugations were performed at a speed of 7000 rpm / min for the first centrifugation and a centrifugation time of 5 min; the second and third centrifugations were performed at a speed of 5000 rpm / min and a centrifugation time of 3 min; S5, add non-polar solvent n-octane to Ag2Se CQDs powder to prepare quantum dot ink solution of a certain concentration, then filter it with a 0.22 µm filter and mix it according to needs.

[0019] Example 2: Particle size and doping control method of Ag2Se colloidal quantum dots. In step S2, 0.34 g of silver nitrate (AgNO3) is taken. In step S3, the reaction time is 5 min. The other steps and contents are the same as in Example 1.

[0020] Example 3: Particle size and doping control method of Ag2Se colloidal quantum dots. In step S2, 0.34 g of silver nitrate (AgNO3) is taken. In step S3, the reaction time is 15 min. The other steps and contents are the same as in Example 1.

[0021] Example 4: Particle size and doping control method of Ag2Se colloidal quantum dots. In step S2, 0.34 g of silver nitrate (AgNO3) is taken. In step S3, the reaction time is 30 min. The other steps and contents are the same as in Example 1.

[0022] Example 5: Particle size and doping control method of Ag2Se colloidal quantum dots. In step S2, 0.34 g of silver nitrate (AgNO3) is taken. The reaction time in step S3 is 60 min. The other steps and contents are the same as in Example 1.

[0023] Example 6: Particle size and doping control method of Ag2Se colloidal quantum dots. In step S2, 0.51 g of silver oxide (AgNO3) is taken. In step S3, the reaction time is 30 min. The other steps and contents are the same as in Example 1.

[0024] Example 7: Particle size and doping control method of Ag2Se colloidal quantum dots. In step S2, 0.85 g of silver oxide (AgNO3) is taken. In step S3, the reaction time is 30 min. The other steps and contents are the same as in Example 1.

[0025] Example 8: Particle size and doping control method of Ag2Se colloidal quantum dots. In step S2, 1.02 g of silver oxide (AgNO3) is taken. In step S3, the reaction time is 30 min. The other steps and contents are the same as in Example 1.

[0026] Example 9: Particle size and doping control method of Ag2Se colloidal quantum dots. In step S2, 0.34 g of silver oxide (AgNO3) is taken. In step S3, the reaction time is 2 min. The other steps and contents are the same as in Example 1.

Claims

1. The particle size and doping control method of Ag2Se colloidal quantum dots, characterized in that The preparation steps of this method are as follows: S1, adding Se powder to trioctylphosphine and dissolving it after ultrasonication to prepare TOP-Se solution; S2, adding silver nitrate to oleylamine solution, heating to 80°C and evacuating to prepare a precursor solution; S3, heating the solution obtained in step S2 to 140°C, quickly adding the TOP-Se solution prepared in step S1 to the precursor solution to obtain a black solution, reacting for 5-60 min, and then cooling in a water bath to room temperature; S4, adding a solution of n-butanol and anhydrous ethanol mixed in a ratio of 2:1 to the black solution obtained in step S3, washing and centrifuging to remove the solution, and obtaining Ag2Se CQDs powder; S5, adding non-polar solvent n-octane to Ag2Se CQDs powder to prepare a quantum dot ink solution of a certain concentration; In the precursor, the ratio of Ag:Se is 2:1-6:

1.

2. The particle size and doping control method of Ag2Se colloidal quantum dots according to claim 1, characterized in that In the step S4, the centrifugation is performed 3 times, the first centrifugation speed is 7000 rpm / min, the centrifugation time is 5 min, the second and third centrifugation speeds are 5000 rpm / min, and the centrifugation time is 3 min.

Images