Preparation method of non-lead perovskite nanowire with fluorescence emission peak adjustable along with excitation light wavelength

Abstract

The invention discloses a preparation method of a lead-free perovskite nanowire with a fluorescence emission peak adjustable along with the wavelength of excitation light. Comprising the following steps: S1, preparing a precursor solution A; s2, preparing a precursor solution B; s3, rapidly adding the precursor solution A into the precursor solution B at a certain temperature to obtain an original solution of the lead-free perovskite nanowire with the fluorescence emission peak adjustable along with the wavelength of the excitation light; s4, passivating surface defects of the nanowire; and S5, centrifugally purifying the lead-free perovskite nanowire. Compared with a traditional monodisperse perovskite nanowire, the non-lead perovskite nanowire has the advantages that the fluorescence peak of the non-lead perovskite nanowire can be subjected to red shift along with the increase of the wavelength of excitation light, and the fluorescence intensity is in the trend of increasing first and then decreasing.

Description

Technical Field

[0001] The invention relates to the fields of nano functional materials and display lighting, and in particular to a method for preparing a non-lead perovskite nanowire whose fluorescence emission peak is adjustable with the wavelength of excitation light. Background Art

[0002] In today's field of materials science, the research on luminescent materials has always attracted much attention. Perovskite materials have shown great application potential in many fields such as light-emitting diodes, solar cells, and lasers due to their excellent optical properties, including high luminescence efficiency and narrow emission bandwidth. However, although traditional lead-based perovskite materials have excellent optoelectronic properties, the lead element in them is toxic. During production, use and disposal, it may be released into the environment, causing pollution to soil, water sources and organisms, posing potential risks to human health. With the increasing attention paid to environmental protection and sustainable development, the development of non-toxic non-lead perovskite materials has become a hot topic in current research. In addition, nanowires, as a one-dimensional nanostructured material, have unique optical, electrical and mechanical properties. In the field of luminescent materials, nanowire structures can provide effective carrier transport channels, thereby enhancing luminescence efficiency. Moreover, by adjusting the size and shape of nanowires, their optical properties can be regulated.

[0003] In the field of materials science, especially luminescent materials, a large number of existing luminescent materials have inherent shortcomings in fluorescence performance. The position of the fluorescence peak is fixed and unchanged. In the face of various adjustments of the excitation light, there is no dynamic response capability. In the application scenarios such as multi-color display and fluorescence sensing that require strict flexible control of the emitted light, it is difficult to adapt on demand, which greatly limits the function expansion and product innovation. Furthermore, focusing on the preparation of non-lead perovskite nanowires, the current process is full of thorns. Many preparation methods require harsh reaction conditions such as high temperature and high pressure, which push up equipment costs and increase the difficulty of operation. They also rely on expensive instruments and cumbersome processes. From raw material processing to finished product purification, each stage is very expensive, which hinders large-scale production. In addition, some non-lead perovskite materials have weak stability and are sensitive to external environmental factors such as humidity, oxygen, and temperature. For example, if the humidity rises slightly, water molecules can invade the lattice to cause structural deformation and chemical bond breaking, and then the optical performance degrades, which seriously restricts practical applications. Therefore, it is urgent to develop a new preparation method for non-lead perovskite nanowires with adjustable fluorescence peaks with excitation light to meet the urgent needs of environmental protection and high-performance luminescent materials.

[0004] In addition, Chinese patent application CN2024111234783 records a method for preparing ultra-long perovskite nanowires in an air environment. This method uses a lead source, which will produce heavy metal pollution, damage the environment, and endanger human health. The nanowires synthesized by this method remain fixed as the wavelength of the excitation light changes.

[0005] In summary, in order to solve the various problems existing in the prior art, there is an urgent need for a new method for preparing non-lead perovskite nanowires with adjustable fluorescence peaks depending on the excitation light to meet the needs of environmentally friendly and high-performance luminescent materials. Summary of the invention

[0006] The present invention provides a method for preparing non-lead perovskite nanowires whose fluorescence emission peak can be adjusted with the wavelength of excitation light, and the specific steps are as follows: S1: Prepare precursor solution A in an inert environment; S2: Prepare precursor solution B in an inert environment; S3: synthesizing a non-lead perovskite nanowire stock solution whose fluorescence emission peak can be adjusted with the wavelength of the excitation light; S4: passivation of nanowire surface defects; S5: Purify the perovskite nanowires by centrifugation to obtain a non-lead perovskite nanowire whose fluorescence emission peak is adjustable with the wavelength of the excitation light.

[0007] Furthermore, step S1 is specifically as follows: In an inert atmosphere glove box, a certain amount of cesium salt is weighed using an electronic balance accurate to milligrams and placed in a clean three-necked flask equipped with a precision magnetic stirrer. Then, a certain amount of non-coordinating solvent and organic cationic ligand are added. The mixture is stirred at a certain speed B1 for a certain time T1 at a temperature A1 until the solution is clear and transparent with no signs of agglomeration or precipitation as observed by the naked eye. This successfully obtains a precursor solution A with excellent uniformity and full reaction activity.

[0008] Furthermore, step S2 is specifically as follows: In an inert atmosphere glove box, use an electronic balance accurate to milligrams to weigh divalent non-lead metal halide salts and place them in a clean three-necked flask equipped with a precision magnetic stirrer. Then slowly inject a certain amount of octadecene, and then stir at a certain temperature A2 and a certain speed B2 for a certain time T2. Subsequently, add a certain amount of organic anion ligands and organic cationic ligands, and then use a gradient temperature increase method until the solution is clear and transparent with no signs of agglomeration or precipitation as observed by the naked eye, and successfully obtain a precursor solution B with excellent uniformity and full reaction activity.

[0009] Furthermore, step S3 is specifically as follows: The precursor solution B prepared in the three-necked flask S2 is heated to temperature A3 and stirred at a stirring speed B3. At the same time, an appropriate amount of the precursor solution A prepared in advance is quickly injected into the three-necked flask with the help of a precision injection pump. With strong shearing and mixing effects, the nucleation "switch" is activated. After that, the temperature A3 is maintained for a certain period of time T3. During this period, the in-situ spectral characterization instrument is used to closely "track" the growth progress, size dynamics, and fluorescence characteristics of the nanowires. The reaction parameters are fine-tuned in time according to the monitoring data feedback to achieve "intelligent" fine control of the growth process. When the nanowire growth is completed, the three-necked flask is quickly placed in pre-cooled anhydrous ethanol to stop the further growth of the nanowires and obtain the original nanowire solution C.

[0010] Furthermore, step S4 is specifically as follows: A certain amount of short-chain halogenated ligands is added to the original nanowire solution C, and stirred at a certain temperature A4 and a stirring speed B4 for a certain time T4 to obtain a non-lead perovskite nanowire solution D with excellent luminescence performance.

[0011] Furthermore, step S5 is specifically as follows: A predetermined amount of anti-solvent is added to the D solution prepared in S4 and centrifuged. Subsequently, the obtained precipitate is added to the solvent for dispersion treatment again, and then a predetermined amount of anti-solvent is added to the dispersed solution, centrifuged, and the obtained precipitate is added to the solvent for dispersion treatment again. The purpose of this centrifugation process is to remove the reaction waste generated during the synthesis of the nanowires, and finally successfully obtain non-lead perovskite nanowires whose fluorescence emission peak is adjustable with the wavelength of the excitation light.

[0012] Further, in step S1, the cesium salt is one or more of cesium carbonate, cesium vanadate, cesium nitrate, cesium oxalate, cesium chromate, cesium permanganate, cesium borate, cesium silicate, cesium tungstate, cesium molybdate, cesium dihydrogen phosphate, cesium propionate, cesium butyrate, cesium citrate, and cesium tartrate; the organic cationic ligand is one or more of octanoic acid, oleic acid, stearic acid, trioctylphosphine oxide, and capric acid; the non-coordinating solvent is octadecene. The temperature A1 is 60-155°C; the stirring time T1 is 15-240min; the stirring speed B1 is 200-800rpm. The concentration of the precursor solution A is 0.0018-0.4235g / mL.

[0013] Further, in step S2, the divalent non-lead metal halide salt is one or more of calcium chloride, magnesium chloride, strontium chloride, barium chloride, calcium bromide, magnesium bromide, strontium bromide, barium bromide, calcium iodide, magnesium iodide, strontium iodide, and barium iodide; the organic anion ligand is one or more of oleylamine, octylamine, and trioctylphosphine oxide; the organic cationic ligand is one or more of oleic acid, octyl acid, and trioctylphosphine; the temperature A2 is 80-120°C, the rotation speed B2 is 300-900 rpm, and the stirring time T2 is 30-180 min.

[0014] The specific method of gradient heating is as follows: in the initial stage, the temperature is steadily increased from room temperature to 80-150℃ at 5-10℃ / min, and the temperature is kept constant for 1-2 hours to help the precursor to mature initially and fully activate the molecules; then the temperature is increased to 150-220℃ at a rate of 2-8℃ / min, and stirred at this temperature for 30-60min. The concentration of precursor solution B is 0.0023~0.2472g / mL.

[0015] Further, in step S3, The injection volume of the precursor solution A is 0.2~2.4mL, the temperature A3 is 150~220℃; the stirring speed B3 is 300~1200 rpm, and the time T3 is 5s~48h.

[0016] Further, in step S4, The short-chain halogenated ligand is one or more of cesium chloride, rubidium chloride, potassium chloride, sodium chloride, cesium bromide, rubidium bromide, potassium bromide, sodium bromide, cesium iodide, rubidium iodide, potassium iodide, sodium iodide, ammonium iodide, iron iodide, and copper iodide; the temperature A4 is room temperature to 180°C; the stirring time T4 is 20 to 240 min; the stirring speed B4 is 400 to 1000 rpm, and the molar ratio of the short-chain halogenated ligand to the divalent non-lead metal halide salt is 0.002 to 0.231: 1.

[0017] Further, in step S5, The volume ratio of the anti-solvent to the solvent is 0.2-2.5:1, the solvent is one of toluene, n-hexane, cyclohexane, benzene, and octane, the anti-solvent is one or more of methyl acetate and ethyl acetate, the concentration of the non-lead perovskite nanowire solution is 5.5-150 mg / mL; the rotation speed during each centrifugation is 1500-7000 rpm, and the centrifugation time for each time is 1-15 min.

[0018] Furthermore, the inert atmosphere is a nitrogen or argon atmosphere.

[0019] Compared with traditional monodisperse perovskite quantum dots, lead-free perovskite nanowires show many remarkable advantages.

[0020] 1. In the application of perovskite light-emitting diodes (LEDs), the fluorescence peak position of traditional perovskite luminescent materials is fixed, which limits the adjustment range of the LED's emission wavelength. However, the fluorescence peak of this titanium ore nanowire has the characteristics of a large range of red shift, so that the emission color of the LED can be changed by adjusting the wavelength of the excitation light. For example, in a full-color LED screen, by precisely controlling the wavelength of the excitation light, the nanowires can emit light of different colors, achieve more accurate color display, and improve the color gamut and color accuracy of the display device. For LEDs used for lighting, the adjustable fluorescence peak can adjust the color temperature of the light according to different environments and user needs. For example, when reading at night, the light can be adjusted to a warmer tone to reduce the stimulation of blue light to the eyes; in a working environment, it can be adjusted to a cooler tone to improve work efficiency.

[0021] 2. In terms of biological fluorescence labeling. The environment inside a living organism is complex and changeable, and the requirements for fluorescent markers are also very high. The red-shift characteristics of the fluorescence peak of titanium ore nanowires can be used for multi-color labeling. Different cell structures or biological molecules can be labeled with red-shifted nanowire fluorescence under different excitation lights. By selecting the appropriate excitation light wavelength, mutual interference between fluorescence signals can be avoided. For example, when simultaneously labeling nucleic acids and proteins in cells, the red-shifted fluorescence peak of nanowires is used to use an excitation light to make the nanowire labeled nucleic acid produce a color of fluorescence, and then by changing the excitation light wavelength, the nanowire labeled protein produces another color of fluorescence, thereby achieving high-resolution, multi-color imaging of biological samples, which is helpful for more in-depth research on physiological and pathological processes in cells.

[0022] 3. In the field of optical sensing. For optical sensing applications such as environmental monitoring and chemical substance detection, this red shift characteristic can be used to build highly sensitive sensors. Different chemicals or environmental factors may affect the red shift characteristics of the fluorescence peak of the nanowires. For example, when detecting a certain type of gas molecules, the interaction between the gas molecules and the surface of the titanite nanowires may cause the degree of red shift of the fluorescence peak of the nanowires to change. By monitoring this red shift change, high-precision detection of the concentration of gas molecules can be achieved. Similarly, when detecting ion concentrations or biomarkers in solutions, the red shift change of the fluorescence peak can also be used as an important detection signal, providing a new and highly sensitive detection method for environmental and biomedical detection.

[0023] 4. This application does not use a lead source, which can effectively avoid environmental pollution. In addition, the precursor solution in this application is prepared in an inert atmosphere environment, which can prevent the oxygen in the air from oxidizing the precursor and prevent water molecules in the air from entering the precursor solution and affecting the synthesis quality of the nanowires. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A low-magnification transmission electron microscope morphology image of a non-lead perovskite nanowire obtained in a method for preparing a non-lead perovskite nanowire with a fluorescence emission peak adjustable with the wavelength of excitation light according to the present invention; Figure 2 It is a fluorescence spectrum diagram of the non-lead perovskite nanowire under different excitation lights obtained in the preparation method of the non-lead perovskite nanowire with a fluorescence emission peak adjustable with the wavelength of the excitation light according to the present invention; Figure 3 A curve diagram showing the variation of the fluorescence emission peak of the non-lead perovskite nanowire obtained in the method for preparing the non-lead perovskite nanowire with a fluorescence emission peak adjustable with the wavelength of the excitation light according to the present invention; Figure 4 A graph showing the change of the fluorescence intensity of the non-lead perovskite nanowires obtained in the method for preparing the non-lead perovskite nanowires with a fluorescence emission peak adjustable with the wavelength of the excitation light according to the present invention as a function of the wavelength of the excitation light; Figure 5 The fluorescence spectra of ordinary lead-based perovskite nanocrystals under different excitation lights in a method for preparing non-lead perovskite nanowires with a fluorescence emission peak adjustable with the wavelength of the excitation light according to the present invention. DETAILED DESCRIPTION

[0025] The present invention will be further described below through specific embodiments in conjunction with the accompanying drawings.

[0026] Example 1 A method for preparing non-lead perovskite nanowires with a fluorescence emission peak adjustable with the wavelength of excitation light, comprising the following steps: S1: Prepare precursor solution A in an inert environment; In a glove box with a nitrogen atmosphere, 0.4 g of cesium carbonate was weighed using an electronic balance accurate to milligrams and placed in a clean three-necked flask equipped with a precision magnetic stirrer. Then 12 mL of octadecene, 1.2 mL of oleic acid, and 0.8 mL of octanoic acid were added. The flask was heated to 150°C and stirred at 800 rpm for 90 min until the solution was clear and transparent with no signs of agglomeration or precipitation as observed by the naked eye. A cesium precursor solution with excellent uniformity and full reaction activity was successfully obtained. The concentration of the cesium precursor solution was 0.0285 g / mL.

[0027] S2: Prepare precursor solution B in an inert environment; In a glove box with a nitrogen atmosphere, 0.1 g of strontium chloride was weighed using an electronic balance accurate to milligrams and placed in a clean three-necked flask equipped with a precision magnetic stirrer. 10 mL of octadecene was then slowly injected, and then stirred at 80°C at a stirring speed of 300 rpm for 50 min. 1.0 mL of oleic acid, 1.0 mL of oleylamine and 2.0 mL of trioctylphosphine were then added to the solution. The temperature was then steadily raised from room temperature to 120°C at a rate of 6°C / min, and kept at a constant temperature for 1 hour. The temperature was then raised to 200°C at a rate of 5°C / min, and stirred at this temperature for 30 min. A strontium chloride precursor solution with excellent uniformity and full reaction activity was successfully obtained, and the concentration of the strontium chloride precursor solution was 0.0071 g / mL.

[0028] S3: synthesizing a non-lead perovskite nanowire stock solution whose fluorescence emission peak can be adjusted with the wavelength of the excitation light; The strontium chloride precursor solution prepared in the S2 three-necked flask was heated to 170°C and stirred at a stirring speed of 300rpm. At the same time, 2.4ml of cesium precursor solution was quickly injected into the three-necked flask with the help of a precision syringe pump. With strong shearing and mixing, the nucleation "switch" was activated. After that, the temperature was maintained at 170°C for 20 minutes. During this period, the in-situ spectral characterization instrument was used to closely "track" the growth progress, size dynamics, and fluorescence characteristics of the nanowires. The reaction parameters were fine-tuned in time according to the monitoring data feedback to achieve "intelligent" fine control of the growth process. When the nanowire growth is completed, the three-necked flask is quickly placed in pre-cooled anhydrous ethanol to stop the further growth of the nanowires and obtain the original nanowire solution C.

[0029] S4: passivation of nanowire surface defects; 0.050 g of cesium chloride was added to 10 mL of the original nanowire solution C, and the mixture was stirred at 100° C. and 500 rpm for 240 min to obtain a lead-free perovskite nanowire solution D with excellent luminescence performance.

[0030] S5: Purify the perovskite nanowires by centrifugation to obtain a non-lead perovskite nanowire whose fluorescence emission peak is adjustable with the wavelength of the excitation light.

[0031] Take 2 mL of the solution prepared by S4, add 4 mL of ethyl acetate thereto, centrifuge, and then add the obtained precipitate to n-hexane for dispersion again; add 4 mL of ethyl acetate to the solution again, then centrifuge, and then add the obtained precipitate to n-hexane for dispersion again, and finally successfully obtain a clean nanowire solution, wherein the rotation speed during each centrifugation is 5000 rpm and the centrifugation time is 5 min.

[0032] First, the morphology of the nanowires was characterized, and it was found that the length of the synthesized nanowires was 500-1300 nm, and the diameter was only about 5-10 nm ( Figure 1 ). Then, through the characterization of the fluorescence spectrum of the nanowires, it was found that as the wavelength of the excitation light increases, the peak of the fluorescence peak also red-shifts. When the wavelength of the excitation light increases continuously from 300nm to 500nm, the emission wavelength of the nanowire increases from 380nm to 500nm ( Figure 2-3 ), and the luminescence intensity increases first and then decreases. When the wavelength of the excitation light is 380nm, the fluorescence intensity of the nanowire is the largest ( Figure 4 ). For comparison, we also characterized lead-based perovskite nanocrystals and found that as the wavelength of the excitation light increases, the position of the fluorescence peak remains unchanged, and the intensity of the fluorescence peak remains basically unchanged ( Figure 5 ).

[0033] Example 2 A method for preparing non-lead perovskite nanowires with a fluorescence emission peak adjustable with the wavelength of excitation light, comprising the following steps: S1: Prepare precursor solution A in an inert environment; In a glove box with a nitrogen atmosphere, 0.24 g of cesium nitrate was weighed using an electronic balance accurate to milligrams and placed in a clean three-necked flask equipped with a precision magnetic stirrer. Then 12 mL of octadecene, 1.2 mL of oleic acid, and 0.8 mL of octanoic acid were added. The flask was heated to 120°C and stirred at 500 rpm for 150 min until the solution was clear and transparent with no signs of agglomeration or precipitation as observed by the naked eye. A cesium precursor solution with excellent uniformity and full reaction activity was successfully obtained. The concentration of the cesium precursor solution was 0.0170 g / mL.

[0034] S2: Prepare precursor solution B in an inert environment; In a glove box with a nitrogen atmosphere, 0.08g of calcium chloride was weighed using an electronic balance accurate to milligrams and placed in a clean three-necked flask equipped with a precision magnetic stirrer. Then 10mL of octadecene was slowly injected, and then stirred at 100°C at a stirring speed of 600rpm for 100min. Subsequently, 1.0mL of oleic acid, 1.0mL of oleylamine and 2.0mL of trioctylphosphine were added, and then the temperature was steadily increased from room temperature to 150°C at a rate of 5°C / min, and kept at a constant temperature for 1.5 hours. Then, the temperature was increased to 200°C at 6°C / min and stirred at this temperature for 60 min. A strontium chloride precursor solution with excellent uniformity and full reaction activity was successfully obtained. The concentration of the calcium chloride precursor solution was 0.0058g / mL.

[0035] S3: synthesizing a non-lead perovskite nanowire stock solution whose fluorescence emission peak can be adjusted with the wavelength of the excitation light; The strontium chloride precursor solution prepared in the S2 three-necked flask was heated to 200°C and stirred at a stirring speed of 800rpm. At the same time, 0.8ml of cesium precursor solution was quickly injected into the three-necked flask with the help of a precision syringe pump. With strong shearing and mixing effects, the nucleation "switch" was activated. After that, the temperature was maintained at 200°C for 6s. During this period, the in-situ spectral characterization instrument was used to closely "track" the growth progress, size dynamics, and fluorescence characteristics of the nanowires. The reaction parameters were fine-tuned in time according to the monitoring data feedback to achieve "intelligent" fine control of the growth process. When the nanowire growth is completed, the three-necked flask is quickly placed in pre-cooled anhydrous ethanol to stop the further growth of the nanowires and obtain the original nanowire solution C.

[0036] S4: passivation of nanowire surface defects; 0.038 g of rubidium chloride was added to 10 mL of the original nanowire solution C, and the mixture was stirred at 150° C. and 800 rpm for 120 min to obtain a lead-free perovskite nanowire solution D with excellent luminescence performance.

[0037] S5: Purify the perovskite nanowires by centrifugation to obtain a non-lead perovskite nanowire whose fluorescence emission peak is adjustable with the wavelength of the excitation light.

[0038] Take 2 mL of the solution prepared by S4, add 4 mL of ethyl acetate thereto, centrifuge, and then add the obtained precipitate to n-hexane for dispersion again; add 4 mL of ethyl acetate to the solution again, then centrifuge, and then add the obtained precipitate to n-hexane for dispersion again, and finally successfully obtain a clean nanowire solution, wherein the rotation speed during each centrifugation is 2000 rpm and the centrifugation time is 10 min.

Claims

1. A method for preparing non-lead perovskite nanowires with tunable fluorescence emission peaks depending on the wavelength of excitation light, characterized in that: The specific steps are as follows: S1: Prepare precursor solution A in an inert environment; S2 prepares precursor solution B in an inert environment; S3: synthesizing a non-lead perovskite nanowire stock solution whose fluorescence emission peak can be adjusted with the wavelength of the excitation light; S4: passivation of nanowire surface defects; S5: Centrifugal purification of a non-lead perovskite nanowire whose fluorescence emission peak can be adjusted with the wavelength of the excitation light.

Images