A method for preparing air-stable AgBiS2 nanocrystals

Abstract

The application relates to a preparation method of air-stable AgBiS2 nanocrystals, and relates to a preparation method of stable AgBiS2 nanocrystals. The application aims to solve the problem that AgBiS2 colloidal nanocrystals prepared by an existing method are easily decomposed into bismuth oxide and silver sulfide under the combined action of oxygen and light, which is not conducive to the storage stability of the AgBiS2 colloidal nanocrystals in the environment, and reduces the photoelectric performance of the AgBiS2 colloidal nanocrystals. The method can be briefly described as follows: in the synthesis process of AgBiS2 colloidal nanocrystals, after the AgBiS2 colloidal nanocrystal solution is lowered to a certain temperature, a metal halide solution is injected into the nanocrystal solution, surface defects of the AgBiS2 colloidal nanocrystals are passivated through the metal halide, and AgBiS2 colloidal nanocrystals with high stability and uniform morphology under the environmental conditions are obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to a preparation method of stable AgBiS2 nanocrystals. BACKGROUND

[0002] AgBiS2 colloidal nanocrystals are a new generation of photoelectric materials which are non-toxic, rich in element reserves and can be prepared by solution method. The good band gap range (1-1.32 eV) of AgBiS2 colloidal nanocrystals makes it have good light response in the visible and infrared light regions. In addition, the excellent photovoltaic properties such as adjustable band gap, high dielectric constant, high absorption coefficient and high mobility promote the rapid development of AgBiS2 colloidal nanocrystals in photovoltaic applications. Benefiting from the wide absorption range and high absorption coefficient, the theoretical efficiency of AgBiS2 colloidal nanocrystal solar cells can reach 26%. AgBiS2 colloidal nanocrystals were initially used as counter electrode materials for solar cells. Until 2016, Konstantatos team

M. Bernechea, N. C. Miller, G. Xercavins, D. So, A. Stavrinadis and G. Konstantatos, Solution-processed solar cells based on environmentally friendly AgBiS2 nanocrystals, Nat. Photonics, 2016, 10 (8), 521-525.

[0003] However, the large specific surface area of ​​AgBiS2 colloidal nanocrystals results in a large number of dangling bonds on their surface, which provides recombination centers for photogenerated charge carriers, causing significant loss of photogenerated charge and ultimately severely affecting the performance of optoelectronic devices. Furthermore, Becker-Koch et al. [D. Becker-Koch, M. Albadejo-Siguan, J. Kress, R. Kumar, YJ Hofstetter, Q. An, AABakulin, F. Paulus and Y. Vaynzof, Oxygen-induced degradation in AgBiS2 nanocrystal solar cells, Nanoscale, 2022, 14(8), 3020-3030.] found that AgBiS2 colloidal nanocrystals easily decompose into bismuth oxide and silver sulfide under the combined effects of oxygen and light, which is highly detrimental to the storage stability of AgBiS2 colloidal nanocrystals in the environment. Therefore, exploring a suitable method for preparing air-stable AgBiS2 colloidal nanocrystals is of great significance for improving the photoelectric properties and stability of AgBiS2 colloidal nanocrystals. Summary of the Invention

[0004] The purpose of this invention is to address the problem that AgBiS2 colloidal nanocrystals prepared by existing methods are easily decomposed into bismuth oxide and silver sulfide under the combined effects of oxygen and light, which is detrimental to the storage stability of AgBiS2 colloidal nanocrystals in the environment and reduces their photoelectric properties. Therefore, this invention provides a method for preparing air-stable AgBiS2 nanocrystals.

[0005] A method for preparing air-stabilized AgBiS2 nanocrystals is specifically carried out according to the following steps:

[0006] 1. Mix the organic ligand with octadecene to obtain a mixed solution of organic ligand and octadecene; add silver source and bismuth source to the mixed solution of organic ligand and octadecene, first evacuate the vacuum for a period of time, then evacuate the vacuum and heat and stir for a period of time to obtain solution A, and continuously purge nitrogen gas into solution A.

[0007] 2. Mix the sulfur source and octadecene evenly, first evacuate the vacuum for a period of time, then evacuate the vacuum and heat and stir for a period of time to obtain solution B, and continuously introduce nitrogen gas into solution B.

[0008] 3. Add the metal halide and thiodipropionic acid to oleylamine, heat and stir to obtain solution C;

[0009] 4. Heat solution A until the target reaction temperature is reached, then inject solution B into solution A under nitrogen protection to obtain solution D; stop heating and continue stirring. When solution D cools naturally to the target temperature, inject solution C into solution D to obtain solution E, and then continue stirring until it cools naturally to room temperature.

[0010] 5. Transfer solution E to a centrifuge tube, add washing solvent, centrifuge at high speed, discard the supernatant, add dispersing solvent and washing solvent, repeat washing and centrifugation, and finally obtain a black precipitate;

[0011] 6. The black precipitate was vacuum dried to obtain AgBiS2 nanocrystals with uniform particle size and air stability.

[0012] Advantages of this invention:

[0013] I. The present invention incorporates metal halides during the synthesis process, which improves the stability of AgBiS2 colloidal nanocrystals in air. At the same time, the present invention is simple to conduct, easy to operate, safe, reproducible, and easy to scale up.

[0014] II. The air-stable AgBiS2 nanocrystals prepared by this invention have excellent monodispersity and better stability under environmental conditions compared with AgBiS2 colloidal nanocrystals prepared by existing technologies.

[0015] Third, the air-stabilized AgBiS2 nanocrystals prepared by this invention can be used in thin-film optoelectronic devices and thermoelectric devices. Attached Figure Description

[0016] Figure 1 The images show X-ray diffraction patterns of AgBiS2 nanocrystals prepared in Examples 2, 3, 4, and 5. In the images, I represents AgBiS2 nanocrystals prepared in Example 2, II represents AgBiS2 nanocrystals prepared in Example 3, III represents AgBiS2 nanocrystals prepared in Example 4, and IV represents AgBiS2 nanocrystals prepared in Example 5.

[0017] Figure 2 X-ray diffraction patterns of AgBiS2 nanocrystals prepared in Examples 2, 3, 4, and 5 after one month under environmental conditions: I after one month is AgBiS2 colloidal nanocrystals prepared in Example 2; II after one month is AgBiS2 colloidal nanocrystals prepared in Example 3; III after one month is AgBiS2 colloidal nanocrystals prepared in Example 4; IV after one month is AgBiS2 colloidal nanocrystals prepared in Example 5.

[0018] Figure 3X-ray diffraction pattern of AgBiS2 nanocrystals prepared in Example 1, wherein V is AgBiS2 nanocrystals prepared in Example 1, and wherein V after one month is AgBiS2 colloidal nanocrystals prepared in Example 1 and stored under ambient conditions for one month;

[0019] Figure 4 Transmission electron microscopy image of AgBiS2 nanocrystals prepared in Example 1;

[0020] Figure 5 UV-Vis absorption spectrum of AgBiS2 nanocrystals prepared in Examples 4 and 5. DETAILED DESCRIPTION

[0021] Detailed implementation one: a method for preparing air-stable AgBiS2 nanocrystals, which is completed according to the following steps:

[0022] I. Mix the organic ligand and octadecene uniformly to obtain a mixed solution of the organic ligand and octadecene; add a silver source and a bismuth source to the mixed solution of the organic ligand and octadecene, first vacuumize for a period of time, then vacuumize and heat stir for a period of time to obtain solution A, and continuously introduce nitrogen into solution A;

[0023] II. Mix the sulfur source and octadecene uniformly, first vacuumize for a period of time, then vacuumize and heat stir for a period of time to obtain solution B, and continuously introduce nitrogen into solution B;

[0024] III. Add the metal halide and thiodipropionic acid to the oleylamine, heat stir to obtain solution C;

[0025] IV. Heat solution A, after reaching the target reaction temperature, inject solution B into solution A under the protection of nitrogen to obtain solution D; stop heating and continue stirring, and when solution D naturally cools to the target temperature, inject solution C into solution D to obtain solution E, and then continue stirring until it naturally cools to room temperature;

[0026] V. Transfer solution E to a centrifuge tube, add a washing solvent, and after high-speed centrifugation by a centrifuge, pour off the supernatant, add a dispersion solvent and a washing solvent, and repeat the washing and centrifugation to finally obtain black precipitate;

[0027] VI. Vacuum dry the black precipitate to obtain air-stable AgBiS2 nanocrystals with uniform particle size.

[0028] Specific embodiment two: the difference between this embodiment and specific embodiment one is that the organic ligand in step one is oleic acid; the volume ratio of the organic ligand to octadecene in step one is (5-15):(5-15); the temperature of vacuumizing and heating stirring in step one is 90-120℃, and the time of heating stirring is 1.5-5h. The other steps are the same as specific embodiment one.

[0029] Specific embodiment three: the difference between this embodiment and one of specific embodiment one or two is that the silver source in step one is silver acetate or silver nitrate; the concentration of the silver source in solution A in step one is 0.05-0.2mol / L; the bismuth source in solution A in step one is bismuth acetate or bismuth nitrate; the concentration of the bismuth source in solution A in step one is 0.07-0.5mol / L. The other steps are the same as specific embodiment one or two.

[0030] Specific embodiment four: the difference between this embodiment and one of specific embodiment one to three is that the sulfur source in step two is oleylamine sulfur or hexamethyldisilthiane. The other steps are the same as specific embodiment one to three.

[0031] The oleylamine sulfur in this embodiment is obtained by dissolving sulfur powder in oleylamine and stirring for 8-12h at room temperature; the molar amount of the sulfur powder to the volume of oleylamine is (0.5-2mol):1L.

[0032] Specific embodiment five: the difference between this embodiment and one of specific embodiment one to four is that the concentration of the sulfur source in solution B in step two is 0.1-1.1mol / L; the temperature of vacuumizing and heating stirring in step two is 80℃, and the time of heating stirring is 2h. The other steps are the same as specific embodiment one to four.

[0033] Specific embodiment six: the difference between this embodiment and one of specific embodiment one to five is:

[0034] The metal halide in step three is NaCl, KCl, CdCl2, PbCl2, BiCl3, NaBr, KBr, CdBr2, BiBr3, PbBr2, NaI, KI, BiI3, CdI2 or PbI2. The other steps are the same as specific embodiment one to five.

[0035] Specific embodiment seven: the difference between this embodiment and one of specific embodiment one to six is that the concentration of the metal halide in solution C in step three is 0.05-0.5mol / L, and the molar ratio of the metal halide to thiodipropionic acid in solution C is 1:(0.1-1). The other steps are the same as specific embodiment one to six.

[0036] Specific embodiment eight: the difference between this embodiment and one of the specific embodiments one to seven is that the volume ratio of solution A, solution B and solution C in step four is (5-20):(1-10):(0.5-5); solution A is heated in step four, after reaching 90-120℃, solution B is injected into solution A under nitrogen protection to obtain solution D; stop heating and continue stirring, when solution D is naturally cooled to 60-90℃, solution C is injected into solution D to obtain solution E, then continue stirring until naturally cooled to room temperature. The other steps are the same as specific embodiments one to seven.

[0037] Specific embodiment nine: the difference between this embodiment and one of the specific embodiments one to eight is that the dispersing solvent in step five is toluene; the washing solvent in step five is a mixture of one or more of acetone, methyl acetate, ethanol, methanol and isopropanol; the speed of high-speed centrifugation in step five is 4000-8000r / min, and the time of high-speed centrifugation is 3-10min. The other steps are the same as specific embodiments one to eight.

[0038] Specific embodiment ten: the difference between this embodiment and one of the specific embodiments one to nine is that the vacuum drying temperature in step six is 20-50℃, and the vacuum drying time is 0.5-1h. The other steps are the same as specific embodiments one to nine.

[0039] The beneficial effects of the present application are verified by the following examples:

[0040] Example one: a preparation method of air-stable AgBiS2 nanocrystals, characterized in that the preparation method is specifically completed according to the following steps:

[0041] I. Mix 12mL of oleic acid and 10mL of octadecene uniformly to obtain a mixed solution of oleic acid and octadecene; add 1.6mmol of silver acetate and 2mmol of bismuth acetate to the mixed solution of oleic acid and octadecene, first vacuum for 30min at room temperature, then heat and vacuum for 2h at 100℃, and continuously stir to obtain solution A, and continuously introduce nitrogen into solution A;

[0042] II. Mix 2mmol of hexamethyldisilthiane and 5mL of octadecene uniformly, first vacuum for 30min at room temperature, then heat and vacuum for 2h at 80℃ to obtain solution B, and continuously introduce nitrogen into solution B;

[0043] III. Add 0.2mmol of bismuth bromide and 0.04mmol of thiodipropionic acid to 2mL of oleylamine, heat and stir at 110℃ for 1h to obtain solution C;

[0044] Four, heating solution A to 100℃, then inject solution B into solution A under nitrogen protection, to obtain solution D; stop heating and continue stirring, when solution D is cooled to 75℃ naturally, inject solution C into solution D, to obtain solution E, then continue stirring until cooled to room temperature naturally;

[0045] Five, transfer solution E into centrifuge tube, add acetone, after high speed centrifugation by centrifuge, pour off supernatant, add toluene dispersion, after dispersion, use the mixture of acetone and methanol as centrifugal washing agent, high speed washing centrifugation once, finally obtain black precipitate;

[0046] The speed of high speed centrifugation in step five is 8000r / min, and the time of high speed centrifugation is 5min;

[0047] The volume ratio of acetone and methanol in the mixture of acetone and methanol in step five is 1:1;

[0048] Six, vacuum dry the black precipitate, to obtain AgBiS2 nanocrystal with uniform particle size and air stability;

[0049] The vacuum drying temperature in step six is 50℃, and the time of vacuum drying is 1h.

[0050] Example two: the difference between this example and example one is that in step three, 0.2mmol lead bromide and 0.04mmol thiodipropionic acid are added into 2mL oleylamine, heated and stirred at 110℃ for 1h, to obtain solution C. Other steps and parameters are the same as example one.

[0051] Example three: the difference between this example and example one is that in step three, 0.2mmol lead iodide and 0.04mmol thiodipropionic acid are added into 2mL oleylamine, heated and stirred at 110℃ for 1h, to obtain solution C. Other steps and parameters are the same as example one.

[0052] Example four: the difference between this example and example one is that in step three, 0.2mmol cadmium chloride and 0.04mmol thiodipropionic acid are added into 2mL oleylamine, heated and stirred at 110℃ for 1h, to obtain solution C. Other steps and parameters are the same as example one.

[0053] Example five: a preparation method of AgBiS2 nanocrystal, characterized in that the preparation method is completed according to the following steps:

[0054] 1. Mix 12 mL of oleic acid and 10 mL of octadecene evenly to obtain a mixed solution of oleic acid and octadecene; add 1.6 mmol of silver acetate and 2 mmol of bismuth acetate to the mixed solution of oleic acid and octadecene, first evacuate at room temperature for 30 min, then heat at 100 °C and evacuate at room temperature for 2 h, stirring throughout the process to obtain solution A, and continuously purging nitrogen gas into solution A.

[0055] 2. Mix 2 mmol of hexamethyldisiloxane and 5 mL of octadecene evenly, evacuate at room temperature for 30 min, and then heat at 80 °C and evacuate for 2 h to obtain solution B.

[0056] 3. After heating solution A to 100°C, solution B is injected into solution A under nitrogen protection to obtain solution D;

[0057] 4. Transfer solution D to a centrifuge tube, add acetone, centrifuge at high speed, discard the supernatant, add toluene to disperse, and after dispersion, add a mixture of acetone and methanol to wash, wash and centrifuge once at high speed to finally obtain a black precipitate.

[0058] The high-speed centrifugation in step four is performed at a speed of 8000 r / min for 5 min.

[0059] In step four, the volume ratio of acetone to methanol in the mixture is 1:1.

[0060] 5. The black precipitate was dried under vacuum to obtain AgBiS2 nanocrystals;

[0061] The vacuum drying temperature in step six is ​​50°C, and the vacuum drying time is 1 hour.

[0062] Figure 1 The images show X-ray diffraction patterns of AgBiS2 nanocrystals prepared in Examples 2, 3, 4, and 5. In the images, I represents AgBiS2 nanocrystals prepared in Example 2, II represents AgBiS2 nanocrystals prepared in Example 3, III represents AgBiS2 nanocrystals prepared in Example 4, and IV represents AgBiS2 nanocrystals prepared in Example 5.

[0063] from Figure 1 It can be seen that the air-stabilized AgBiS2 colloidal nanocrystals prepared by adding different metal halides exhibit sharper diffraction peaks and better crystallinity. No other impurity peaks were observed in the figure, confirming the high purity of the prepared AgBiS2 colloidal nanocrystals.

[0064] Figure 2X-ray diffraction patterns of AgBiS2 nanocrystals prepared in Example 2, 3, 4, 5 after one month under ambient conditions, I after one month is AgBiS2 colloidal nanocrystals prepared in Example 2, II after one month is AgBiS2 colloidal nanocrystals prepared in Example 3, III after one month is AgBiS2 colloidal nanocrystals prepared in Example 4, IV after one month is AgBiS2 colloidal nanocrystals prepared in Example 5;

[0065] It can be seen from Figure 2 that I after one month, II after one month, III after one month are AgBiS2 nanocrystals stabilized by lead bromide, lead iodide, cadmium chloride respectively, and no extra peaks appear, while IV after one month is AgBiS2 nanocrystals without stabilization, and extra peaks appear. By comparison with standard card (PDF #6-294), the extra peaks are attributed to bismuth oxide. This result shows that the use of metal halide can improve the stability of AgBiS2 colloidal nanocrystals under ambient conditions.

[0066] Figure 3 X-ray diffraction pattern of AgBiS2 nanocrystals prepared in Example 1, V is AgBiS2 nanocrystals prepared in Example 1, V after one month is AgBiS2 colloidal nanocrystals prepared in Example 1 and placed under ambient conditions for one month;

[0067] It can be seen from Figure 3 that AgBiS2 nanocrystals prepared in Example 1 have no extra peaks and the diffraction peaks are sharp, indicating good crystallinity. Compared with AgBiS2 colloidal nanocrystals prepared in Example 2 using lead bromide, the cation of metal halide is changed, and the obtained AgBiS2 colloidal nanocrystals also have good stability, indicating that the cation can be replaced for further study of the effect of different cations on AgBiS2 colloidal nanocrystals.

[0068] Figure 4 Transmission electron microscopy image of AgBiS2 nanocrystals prepared in Example 1;

[0069] It can be seen from Figure 4 that AgBiS2 nanocrystals prepared using bismuth bromide have good monodispersity.

[0070] Figure 5 UV-visible absorption spectra of AgBiS2 nanocrystals prepared in Example 4, 5.

[0071] It can be seen from Figure 5It can be seen that the AgBiS2 nanocrystals prepared with cadmium chloride have the light absorption ability in the range of 400-1100 nm, and the light absorption ability in the visible light band is the best.

Claims

1. A method for preparing air-stable AgBiS2 nanocrystals, characterized in that The preparation method is specifically completed according to the following steps: I. The organic ligand is mixed with octadecene uniformly to obtain a mixed solution of the organic ligand and octadecene; the silver source and the bismuth source are added into the mixed solution of the organic ligand and octadecene, vacuum is drawn for a period of time, vacuum is drawn and heated and stirred for a period of time, solution A is obtained, and nitrogen is continuously introduced into solution A; The organic ligand in step one is oleic acid; II. The sulfur source and octadecene are mixed uniformly, vacuum is drawn for a period of time, vacuum is drawn and heated and stirred for a period of time, solution B is obtained, and nitrogen is continuously introduced into solution B; The sulfur source in step two is oleylamine sulfur or hexamethyldisilthiane; III. The metal halide and thiodipropionic acid are added into oleylamine, heated and stirred to obtain solution C; The metal halide in step three is NaCl, KCl, CdCl2, PbCl2, BiCl3, NaBr, KBr, CdBr2, BiBr3, PbBr2, NaI, KI, BiI3, CdI2 or PbI2; IV. Solution A is heated, solution B is injected into solution A under the protection of nitrogen after reaching 90-120 DEG C, and solution D is obtained; The heating is stopped and the stirring is continued, solution C is injected into solution D when solution D is naturally cooled to 60-90 DEG C, solution E is obtained, and then the stirring is continued until it is naturally cooled to room temperature; V. Solution E is transferred into a centrifuge tube, a washing solvent is added, the supernatant is poured out after high-speed centrifugation by a centrifuge, a dispersing solvent and a washing solvent are added, and the washing and centrifugation are repeated to finally obtain black precipitate; VI. The black precipitate is vacuum dried to obtain AgBiS2 nanocrystals with uniform particle size and air stability.

2. The method according to claim 1, wherein The volume ratio of the organic ligand to octadecene in step one is (5-15):(5-15); the temperature of vacuum drawing and heating and stirring in step one is 90-120 DEG C, and the time of heating and stirring is 1.5-5 h.

3. The method for preparing air-stabilized AgBiS2 nanocrystals according to claim 1, characterized in that... The silver source in step one is silver acetate or silver nitrate; the concentration of the silver source in solution A in step one is 0.05-0.2 mol / L; the bismuth source in solution A in step one is bismuth acetate or bismuth nitrate; and the concentration of the bismuth source in solution A in step one is 0.07-0.5 mol / L.

4. The method for preparing air-stabilized AgBiS2 nanocrystals according to claim 1, characterized in that... The concentration of the sulfur source in solution B in step two is 0.1-1.1 mol / L; the temperature of vacuum drawing and heating and stirring in step two is 80 DEG C, and the time of heating and stirring is 2 h.

5. The method for preparing air-stabilized AgBiS2 nanocrystals according to claim 1, characterized in that... The concentration of the metal halide in solution C in step three is 0.05-0.5 mol / L, and the molar ratio of the metal halide to thiodipropionic acid in solution C is 1:(0.1-1).

6. The method for preparing air-stabilized AgBiS2 nanocrystals according to claim 1, characterized in that... The volume ratio of solution A, solution B and solution C in step four is (5-20):(1-10):(0.5-5).

7. The method for preparing air-stabilized AgBiS2 nanocrystals according to claim 1, characterized in that... The dispersing solvent in step five is toluene; the washing solvent in step five is a mixture of one or more of acetone, methyl acetate, ethanol, methanol and isopropanol; the speed of high speed centrifugation in step five is 4000r / min-8000r / min, and the time of high speed centrifugation is 3min-10min.

8. The method for preparing air-stabilized AgBiS2 nanocrystals according to claim 1, characterized in that... The temperature of vacuum drying in step six is 20℃-50℃, and the time of vacuum drying is 0.5h-1h.

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