CN109179421B - Method for preparing yellow or green silicon quantum dots - Google Patents
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Abstract
The invention discloses a method for preparing yellow or green silicon quantum dots, which comprises the following steps: (1) dispersing a silicon source, a first reducing agent and a second reducing agent in ultrapure water, and then stirring under the protection of protective gas to obtain a mixed solution; (2) heating the mixed solution obtained in the step (1) in a reaction container for reaction to obtain a silicon quantum dot solution; (3) and (3) mixing the silicon quantum dot solution obtained in the step (2) with an organic reagent, centrifuging and drying to obtain the solid silicon quantum dot. Based on the synergistic effect of the first reducing agent and the second reducing agent, the green or yellow silicon quantum dots with high quantum yield are synthesized in one step by a simple water phase method, and the silicon quantum dots with different emission wavelengths can be synthesized by adjusting the temperature of heating reaction, wherein the quantum yield of the green silicon quantum dots is 38.31%, and the quantum yield of the yellow silicon quantum dots is 29.36%.
Description
Technical Field
The invention belongs to the technical field of nano materials, and particularly relates to a method for preparing yellow or green silicon quantum dots.
Background
The silicon quantum dot is a novel silicon nano material, and has the advantages of small toxicity, good biocompatibility, adjustable light-emitting range, easy functionalization and the like compared with the traditional semiconductor quantum dot and organic dye, so that the silicon quantum dot has wide application prospect in the fields of biomedicine, photoelectron, catalysis, sensing and the like. The preparation method of the silicon quantum dots is various, but most of the methods synthesize the silicon quantum dots which show blue fluorescence. Because the short wavelength (blue) silicon quantum dots have poor penetrability to tissues, optical images of deep tissues in vivo are limited, almost all biological tissues can generate autofluorescence to short wavelength visible light so as to interfere the image effect, and the long wavelength (green to red) silicon quantum dots can easily penetrate through deep tissues of organisms, so that the application of the long wavelength (green to red) silicon quantum dots in vivo imaging, cancer treatment, light-emitting diodes and other aspects is wider.
Currently, few reports on the synthesis of long-wavelength (green to yellow) silicon quantum dots are reported, and the synthesis is generally realized by means of surface modification, electrochemical digestion or change of ultra-high temperature environmental digestion and the like. However, the methods have common defects of long reaction time, high reaction temperature, high requirements on instruments, complex preparation process and product purification process, too much raw material is input into the green silicon quantum dots synthesized by the current one-step hydrothermal method, the cost is high, and the yellow silicon quantum dots synthesized by the one-step hydrothermal method are not reported. Therefore, the preparation of the yellow and green silicon quantum dots with simple synthetic method, small material amount and high quantum yield becomes a research hotspot.
Disclosure of Invention
In view of the above defects or improvement needs of the prior art, the present invention aims to provide a method for preparing yellow or green silicon quantum dots, wherein the problems of difficult preparation of yellow or green silicon quantum dots can be effectively solved by improving the overall process flow of the preparation method and the conditions and parameters (including the types and proportions of the reaction raw materials) adopted by the key synthesis reaction, compared with the prior art, most methods of the prior art are blue silicon quantum dots, and only a small part of methods are used for preparing yellow or green silicon quantum dots, but since the prior art methods for preparing yellow or green silicon quantum dots still have the problems of low quantum yield, complex operation, high requirements on instruments and equipment, and the like, the present invention uses a silicon source raw material based on the synergistic effect of a reducing agent 1 (i.e. a first reducing agent) and a reducing agent 2 (i.e. a second reducing agent), the green or yellow silicon quantum dots with high quantum yield are synthesized in one step by a simple aqueous phase method, and preferably, the yellow or green silicon quantum dots can be independently prepared by integrally matching various parameters of the preparation method, especially by adjusting the temperature of the heating reaction (of course, the preparation method of the invention can also be used for obtaining the mixed product of the yellow and green silicon quantum dots). The quantum yield of the green silicon quantum dots is 38.31%, and the quantum yield of the yellow silicon quantum dots is 29.36%; the method has the advantages of cheap and easily-obtained raw materials, green and environment-friendly operation, good water solubility of the synthesized silicon quantum dots, stable photochemical performance, high quantum yield and wide application prospect in the fields of fluorescence labeling imaging, analysis and detection and the like.
To achieve the above object, according to the present invention, there is provided a method for preparing yellow or green silicon quantum dots, comprising the steps of:
(1) dispersing a silicon source, a first reducing agent and a second reducing agent in ultrapure water, and then stirring under the protection of protective gas to obtain a mixed solution;
(2) transferring the mixed solution obtained in the step (1) into a reaction container, introducing protective gas to remove oxygen, and then carrying out heating reaction to obtain a silicon quantum dot solution;
(3) and (3) mixing the silicon quantum dot solution obtained in the step (2) with an organic reagent, centrifuging and drying to obtain the solid silicon quantum dot.
As a further preferred aspect of the present invention, in the step (1), the silicon source is at least one selected from N-aminoethyl- γ -aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, and ureido silane, preferably N-aminoethyl- γ -aminopropyltrimethoxysilane;
the first reducing agent is at least one of catechol, resorcinol and protocatechuic acid; preferably, the first reducing agent is catechol;
the second reducing agent is at least one of sodium citrate, sodium sulfite, urea, thiourea, ascorbic acid and glucose; preferably, the second reducing agent is sodium citrate.
In the present invention, in the step (1), the mass ratio of the silicon source, the first reducing agent, and the second reducing agent dispersed in the mixed solution is preferably (0.206 to 1.03): (0.000275-0.0033): (0.0068-0.068);
preferably, the silicon source is dispersed in the mixed solution in an amount of 0.206 to 1.03g, the first reducing agent is dispersed in an amount of 0.000275 to 0.0033g, and the second reducing agent is dispersed in an amount of 0.0068 to 0.068g, per 10ml volume of the ultrapure water.
In a further preferred embodiment of the present invention, in the step (2), the heating reaction is performed at a reaction temperature of 100 to 160 ℃ for 2 to 6 hours.
In a further preferred embodiment of the present invention, the heating reaction in the step (2) is carried out at a temperature T
When the silicon source is N-aminoethyl-gamma-aminopropyltrimethoxysilane, the first reducing agent is catechol, the second reducing agent is sodium citrate, and T is higher than 130 ℃ and lower than or equal to 160 ℃, the obtained silicon quantum dots are green silicon quantum dots; when the silicon source is N-aminoethyl-gamma-aminopropyltrimethoxysilane, the first reducing agent is catechol, the second reducing agent is sodium citrate, and T is equal to or higher than 100 ℃ and equal to or lower than 130 ℃, the obtained silicon quantum dots are yellow silicon quantum dots.
As a further preferred aspect of the present invention, in the step (1), the protective gas is nitrogen or argon; the stirring time is 5-60 min.
In a further preferred aspect of the present invention, in the step (2), the heating reaction is performed by placing the mixed solution in a closed reaction vessel and heating the reaction vessel in a heating vessel;
the reaction vessel is a hydrothermal reaction kettle or a round-bottom flask; the heating container is a microwave hydrothermal reaction instrument, an oil bath pan, an electric heating constant temperature blast drying box or an electric heating sleeve;
preferably, the heating reaction is a high-pressure closed hydrothermal reaction.
As a further preferred aspect of the present invention, in the step (3), the organic reagent is acetonitrile, ethanol, methanol, acetone or dimethylsulfoxide; the silicon quantum dot solution and the organic reagent are mixed according to the volume ratio of 1: 2-10; preferably, the organic reagent is acetonitrile, and the silicon quantum dot solution and the acetonitrile are mixed according to the volume ratio of 1: 4;
the centrifugation is carried out for 5-30 min by using an ultrafiltration tube at the rotating speed of 5000-15000 rpm; the drying is drying by blowing with protective gas, freeze drying or vacuum drying.
Through the technical scheme of the invention, compared with the prior art, the synthetic reaction is carried out by utilizing the synergistic effect of the reducing agent 1 and the reducing agent 2, and the following beneficial effects can be obtained:
1. the method adopts a simple water phase method to synthesize the high-brightness yellow and green silicon quantum dots in one step, has cheap and easily-obtained raw materials, is green and environment-friendly to operate, and is easy for large-scale production in factories. The method adopts two types of reducing agents with different reducibility, wherein the first reducing agent (namely reducing agent 1) has weak reducibility, and the second reducing agent (namely reducing agent 2) has strong reducibility, and based on the synergistic effect of the reducing agent 1 and the reducing agent 2, the green or yellow silicon quantum dots with high quantum yield are synthesized in one step by a simple aqueous phase method.
According to the invention, silicon quantum dots with different emission wavelengths (such as yellow luminescent silicon quantum dots with emission wavelengths of 530-540nm and green luminescent silicon quantum dots with emission wavelengths of 510-525nm) can be synthesized by adjusting the temperature of the heating reaction. The invention can use N-aminoethyl-gamma-aminopropyl trimethoxy silane, 3-aminopropyl triethoxy silane or urea silane and other raw materials containing silicon element which can be used for providing silicon element for a reaction system as a silicon source, uses a phenol weak reducing agent as a first reducing agent, uses a strong reducing agent as a second reducing agent, preferably uses catechol, resorcinol and protocatechuic acid as reducing agents 1, uses sodium citrate, sodium sulfite, urea, thiourea, ascorbic acid and glucose as reducing agents 2, and can synthesize silicon quantum dots with different colors by adjusting the temperature T of heating reaction of a mixed solution obtained by mixing the three materials with water in a reaction vessel. Preferably, when the silicon source is N-aminoethyl-gamma-aminopropyltrimethoxysilane, the reducing agent 1 is catechol, the reducing agent 2 is sodium citrate, and the temperature T of the mixed solution in the reaction vessel is more than 130 ℃ and less than or equal to 160 ℃, the obtained silicon quantum dots are green silicon quantum dots; when the silicon source is N-aminoethyl-gamma-aminopropyltrimethoxysilane, the reducing agent 1 is catechol, the reducing agent 2 is sodium citrate, and the temperature T of the mixed solution in a reaction vessel is more than or equal to 100 ℃ and less than or equal to 130 ℃ during heating reaction, the obtained silicon quantum dots are yellow silicon quantum dots; for example, green silicon quantum dots can be synthesized by controlling the temperature T of the mixed solution in the reaction vessel to be 150 ℃ and yellow silicon quantum dots can be synthesized by controlling the temperature T of the mixed solution in the reaction vessel to be 130 ℃, and the green or yellow silicon quantum dots have good stability.
2. The method synthesizes the green and yellow silicon quantum dots by using the synergistic effect of the reducing agent 1 and the reducing agent 2 for the first time (the emission wavelength of the yellow silicon quantum dot is 530-525 nm, and the emission wavelength of the green silicon quantum dot is 510-525nm), through the synergistic effect of the two, the quantum yield of the green silicon quantum dot can reach 38.31%, the quantum yield of the yellow silicon quantum dot can reach 29.36%, and the synthesized silicon quantum dots have good water solubility and stable photochemical performance.
Drawings
FIG. 1 is a fluorescence spectrum of three silicon quantum dots of example 1, comparative example 1 and comparative example 2.
Fig. 2 is a fluorescence spectrum and an ultraviolet-visible spectrum of the yellow silicon quantum dot prepared in example 1.
Fig. 3 is a fluorescence spectrum and an ultraviolet-visible spectrum of the green silicon quantum dot synthesized in example 2.
FIG. 4 is a fluorescence spectrum of the yellow silicon quantum dot synthesized in example 3.
FIG. 5 is a fluorescence spectrum of the green silicon quantum dots synthesized in example 4.
Fig. 6 is an infrared spectrum of two kinds of silicon quantum dots synthesized in example 1 and example 2.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
To illustrate the technical effects that can be achieved by the present invention, the following 2 comparative examples are given:
comparative example 1
(1) 0.0068g of sodium citrate and 0.206g N-aminoethyl-gamma-aminopropyltrimethoxysilane are dissolved in 10ml of ultrapure water and stirred for 30min under the protection of nitrogen.
(2) And (2) transferring the mixed solution in the step (1) into a hydrothermal reaction kettle, and putting the hydrothermal reaction kettle into an electric heating constant temperature air blast drying oven for hydrothermal reaction for 5 hours at 130 ℃ (before heating begins, the air in the hydrothermal reaction kettle can be discharged by protective gas such as nitrogen or argon) to obtain the blue silicon quantum dot solution. The quantum yield of the silicon quantum dots is 10.1% by calculation. The calculation method is as follows:
all samples were dissolved in water (η ═ 1.33) and their absorbance at 365nm was controlled to be less than 0.1, the relative quantum yields were calculated as follows:
ΦX＝ΦST(GradX/GradST)(ηX 2/ηST 2)
Φ is the quantum yield, Grad is the ratio of fluorescence area to absorbance, η is the refractive index of the solvent, ST represents the standard, X represents the sample.
Comparative example 2
(1) 0.0011g of catechol and 0.206g N-aminoethyl-gamma-aminopropyltrimethoxysilane are dissolved in 10ml of ultrapure water and stirred for 30min under the protection of nitrogen.
(2) And (2) transferring the mixed solution in the step (1) into a hydrothermal reaction kettle, and placing the hydrothermal reaction kettle in an electric heating constant-temperature air-blowing drying oven to react for 5 hours at the temperature of 130 ℃, wherein the obtained product almost has no fluorescence.
The following are specific embodiments of the present invention:
example 1
(1) 0.0068g of sodium citrate, 0.0011g of catechol and 0.206g N-aminoethyl-gamma-aminopropyltrimethoxysilane are dissolved in 20ml of ultrapure water and stirred for 30min under the protection of nitrogen.
(2) And (2) transferring the mixed solution in the step (1) into a hydrothermal reaction kettle, and putting the hydrothermal reaction kettle into an electric heating constant temperature air blast drying oven for hydrothermal reaction for 4 hours at 130 ℃ (before heating begins, the air in the hydrothermal reaction kettle can be discharged by protective gas such as nitrogen or argon) to obtain the yellow silicon quantum dot solution.
(3) And (3) mixing the solution in the step (2) with acetonitrile in a volume ratio of 1:4, centrifuging at 8000rpm for 10min, removing supernatant, and freeze-drying to obtain the solid silicon quantum dots.
The quantum yield of silicon quantum dots was calculated by comparing the ratio of the fluorescence area (excitation wavelength 420nm) to the absorbance using rhodamine 6G dissolved in ethanol as a reference (quantum yield 95%), all samples were dissolved in water (η 1.33) and their absorbance at 420nm was controlled to be less than 0.1, the relative quantum yield calculation formula was as follows:
ΦX＝ΦST(GradX/GradST)(ηX 2/ηST 2)
Φ is the quantum yield, Grad is the ratio of fluorescence area to absorbance, η is the refractive index of the solvent, ST represents the standard, X represents the sample.
Comparative example 1 only contains silicon source N-aminoethyl-gamma-aminopropyltrimethoxysilane and reducing agent 2 (namely, a second reducing agent) sodium citrate as raw materials, and can only synthesize blue silicon quantum dots; comparative example 2 only the silicon source N-aminoethyl- γ -aminopropyltrimethoxysilane and the reducing agent 1 (i.e., the first reducing agent) catechol, the synthesized silicon quantum dots showed almost no fluorescence. The raw materials of the embodiment 1 comprise silicon source N-aminoethyl-gamma-aminopropyltrimethoxysilane, reducing agent 1 catechol and reducing agent 2 sodium citrate, the quantum yield of the synthesized yellow silicon quantum dots is 29.36%, and the synergistic effect of the reducing agent 1 and the reducing agent 2 is very obvious and the high-brightness yellow silicon quantum dots can be effectively synthesized. FIG. 1 shows fluorescence spectra of three silicon quantum dots of example 1, comparative example 1 and comparative example 2. Fig. 2 is a fluorescence spectrum and an ultraviolet-visible spectrum of the yellow quantum dot synthesized in example 1. As can be seen from the figure, the emission wavelength of the synthesized silicon quantum dot in example 1 is 538nm at the optimal excitation wavelength of 420 nm. The silicon quantum dots show yellow fluorescence under the irradiation of a 365nm ultraviolet lamp. The quantum yield was calculated to be 29.4%.
Example 2
(1) 0.0068g of sodium citrate, 0.0011g of catechol and 0.206g N-aminoethyl-gamma-aminopropyltrimethoxysilane are dissolved in 20ml of ultrapure water and stirred for 30min under the protection of nitrogen.
(2) And (2) transferring the mixed solution in the step (1) into a hydrothermal reaction kettle, and putting the hydrothermal reaction kettle into an electric heating constant temperature air blast drying oven for hydrothermal reaction for 5 hours at the temperature of 150 ℃ (before heating begins, the air in the hydrothermal reaction kettle can be discharged by protective gas such as nitrogen or argon) to obtain the green silicon quantum dot solution.
(3) And (3) mixing the solution in the step (2) with acetonitrile in a volume ratio of 1:4, centrifuging at 8000rpm for 10min, removing supernatant, and freeze-drying to obtain the solid silicon quantum dots. Fig. 3 is a fluorescence spectrum and uv-vis spectrum of the green quantum dot synthesized in example 2. As can be seen, the emission peak of the silicon quantum dot is 522nm at an optimal excitation wavelength of 420 nm. The silicon quantum dots show green fluorescence under the irradiation of a 365nm ultraviolet lamp. The quantum yield was calculated to be 38.3%.
Example 3
(1) 0.0068g of thiourea, 0.000275g of resorcinol and 1.03g of 3-aminopropyltrimethoxysilane were dissolved in 10ml of ultrapure water and stirred for 5min under the protection of nitrogen.
(2) And (2) transferring the mixed solution obtained in the step (1) into a hydrothermal reaction kettle, and placing the hydrothermal reaction kettle in a microblog hydrothermal reaction instrument for hydrothermal reaction for 2h at 130 ℃ (before heating begins, air in the hydrothermal reaction kettle can be exhausted by protective gas such as nitrogen or argon), so as to obtain the yellow silicon quantum dot solution.
(3) And (3) mixing the solution in the step (2) with dimethyl sulfoxide according to the volume ratio of 1:2, centrifuging at 10000rpm for 10min, removing supernatant, and freeze-drying to obtain the solid silicon quantum dots. Fig. 4 is a fluorescence spectrum of the yellow quantum dot synthesized in example 3. As can be seen, the emission peak of the silicon quantum dot is located at 535nm at an optimal excitation wavelength of 420 nm. Under an ultraviolet lamp of 365nm, the silicon quantum dots show yellow fluorescence. The quantum yield was calculated to be 25.4%.
Example 4
(1) 0.068g of urea, 0.0033g of protocatechuic acid and 0.206g of 3-aminopropyltriethoxysilane were dissolved in 10ml of ultrapure water and stirred for 10min under the protection of argon.
(2) And (2) transferring the mixed solution in the step (1) into a round-bottom flask, introducing nitrogen to discharge air in the kettle, sealing the round-bottom flask (the loading volume of the round-bottom flask can be 5 times of the volume of the added precursor), and placing the round-bottom flask into an oil bath kettle to react for 6 hours at 100 ℃ to obtain the green silicon quantum dot solution.
(3) And (3) mixing the solution in the step (2) with ethanol according to the volume ratio of 1:10, centrifuging at 10000rpm for 8min, removing supernatant, and drying in vacuum to obtain the solid silicon quantum dots. The quantum yield of the silicon quantum dots is calculated to be 22.6%.
FIG. 5 is a fluorescence spectrum of the synthetic silicon quantum dot of example 4. As can be seen, the emission wavelength of the silicon quantum dots is 518nm under the optimal excitation wavelength of 420 nm. Under an ultraviolet lamp of 365nm, the silicon quantum dots show green fluorescence.
Example 5
(1) 0.0068g of ascorbic acid, 0.275g of catechol and 0.206g N-aminoethyl-gamma-aminopropyltrimethoxysilane are dissolved in 10ml of ultrapure water and stirred for 20min under the protection of argon.
(2) And (2) transferring the mixed solution in the step (1) into a round-bottom flask, sealing the round-bottom flask by using a rubber plug, introducing nitrogen into the round-bottom flask at a constant speed, simultaneously inserting a needle on the rubber plug to form an air vent, discharging gas in the round-bottom flask, starting heating reaction, and placing the round-bottom flask into an oil bath kettle to react for 3 hours at the temperature of 140 ℃ to obtain the green silicon quantum dot solution. In the heating reaction process, the needle head is always inserted into the rubber plug to form a vent hole, and nitrogen is continuously introduced at a constant speed.
(3) And (3) mixing the solution in the step (2) with methanol in a volume ratio of 1:6, centrifuging at 15000rpm for 5min, removing supernatant, and freeze-drying to obtain the solid silicon quantum dots. The quantum yield of the silicon quantum dots is calculated to be 35.0%. Under an ultraviolet lamp of 365nm, the quantum dots show green fluorescence.
Example 6
(1) 1.03g of ureido silane, 0.0033g of resorcinol and 0.068g of sodium sulfite were dissolved in 10ml of ultrapure water and stirred for 40min under the protection of nitrogen.
(2) Transferring the mixed solution in the step (1) into a round-bottom flask, sealing the round-bottom flask by using a rubber plug, introducing nitrogen into the round-bottom flask at a constant speed, inserting a needle into the rubber plug to form an air vent, discharging gas in the round-bottom flask, starting heating reaction, placing the round-bottom flask into an electric heating jacket, and reacting at 140 ℃ for 3 hours to obtain the green silicon quantum dot solution. In the heating reaction process, the needle head is always inserted into the rubber plug to form a vent hole, and nitrogen is continuously introduced at a constant speed.
(3) And (3) mixing the solution in the step (2) with methanol in a volume ratio of 1:6, centrifuging at 12000rpm for 20min, removing supernatant, and drying by using nitrogen to obtain the solid silicon quantum dot. The quantum yield of the silicon quantum dots is calculated to be 22.4%. Under an ultraviolet lamp of 365nm, the quantum dots show green fluorescence.
Example 7
(1) 0.068g of glucose, 0.0022g of amino acid and 0.406g of 3-aminopropyltrimethoxysilane are dissolved in 40ml of ultrapure water and stirred for 60min under the protection of argon.
(2) And (2) transferring the mixed solution obtained in the step (1) into a hydrothermal reaction kettle, and placing the hydrothermal reaction kettle in an electric heating constant-temperature air-blast drying oven to react for 4 hours at 160 ℃ to obtain a green silicon quantum dot solution.
(3) And (3) mixing the solution in the step (2) with acetone according to the volume ratio of 1:3, centrifuging at 8000rpm for 20min, removing supernatant, and blow-drying with argon to obtain the solid silicon quantum dots. Under an ultraviolet lamp of 365nm, the quantum dots show green fluorescence.
Fig. 1 is a fluorescent spectrum of three silicon quantum dots synthesized in example 1, comparative example 1 and comparative example 2, respectively. As can be seen from the figure, the silicon quantum dots synthesized in example 1 are not only superior to those synthesized in comparative examples 1 and 2 in fluorescence intensity, but also have longer emission wavelength.
Fig. 2 is a fluorescence spectrum and an ultraviolet-visible spectrum of the silicon quantum dot synthesized in example 1. As can be seen, the emission wavelength of the silicon quantum dots is 538nm under the optimal excitation of 420 nm. Under an ultraviolet lamp of 365nm, the silicon quantum dots show yellow fluorescence. In addition, the silicon quantum dot can observe two obvious ultraviolet absorption peaks at 233nm and 254nm besides the main ultraviolet absorption peak at 420 nm.
Fig. 3 is a fluorescence spectrum and an ultraviolet-visible spectrum of the silicon quantum dot synthesized in example 2. As can be seen, the emission wavelength of the silicon quantum dots is 520nm under the optimal excitation of 420 nm. Under an ultraviolet lamp of 365nm, the silicon quantum dots show green fluorescence. In addition, the silicon quantum dots have no residual ultraviolet absorption except the main ultraviolet absorption peak at 420 nm.
Fig. 4 is a fluorescence spectrum of the silicon quantum dot synthesized in example 3. As can be seen, the emission wavelength of the silicon quantum dots is 535nm under the optimal excitation of 420 nm. Under an ultraviolet lamp of 365nm, the silicon quantum dots show yellow fluorescence.
Fig. 5 is a fluorescence spectrum of the silicon quantum dot synthesized in example 4. As can be seen, the emission wavelength of the silicon quantum dots is 518nm under the optimal excitation of 420 nm. Under an ultraviolet lamp of 365nm, the silicon quantum dots show green fluorescence.
Fig. 6 is an infrared spectrum of the silicon quantum dots synthesized in examples 1 and 2. As can be seen, 3367cm-1The peak is an O-H stretching vibration peak, and the carboxyl absorption peak is positioned at 1663cm-1The absorption peak at 2395 is due to C-H unsaturated stretching vibration, 1131-1010cm-1The absorption band of (b) indicates the presence of Si-O-Si.
The silicon quantum dot solution containing the silicon quantum dots generated by the reaction in the invention can be mixed with an organic reagent firstly, and then the solid silicon quantum dots are obtained by centrifugal drying. In the invention, the heating reaction generates silicon quantum dot solution, preferably, the precursor solution is transferred into a closed reaction container and placed in a heating container for reaction for a period of time; heating to react to generate the silicon quantum dot solution, preferably adopting a hydrothermal reaction kettle as a reaction container, and preferably adopting an electric heating constant temperature air blast drying oven as a heating container.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (8)
1. A method for preparing yellow or green silicon quantum dots is characterized by comprising the following steps:
(1) dispersing a silicon source, a first reducing agent and a second reducing agent in ultrapure water, and then stirring under the protection of protective gas to obtain a mixed solution;
(2) transferring the mixed solution obtained in the step (1) into a reaction container, introducing protective gas to remove oxygen, and then carrying out heating reaction to obtain a silicon quantum dot solution; wherein the heating reaction is carried out at a reaction temperature of 100-160 ℃ for 2-6 h;
(3) mixing the silicon quantum dot solution obtained in the step (2) with an organic reagent, centrifuging and drying to obtain solid silicon quantum dots;
in the step (1), the silicon source is N-aminoethyl-gamma-aminopropyltrimethoxysilane;
the first reducing agent is catechol;
the second reducing agent is sodium citrate;
in the step (1), the mass ratio of the silicon source, the first reducing agent and the second reducing agent dispersed in the mixed solution is (0.206 to 1.03): (0.000275-0.0033): (0.0068-0.068).
2. The method for preparing yellow or green silicon quantum dots according to claim 1, wherein in the step (1), the amount of the silicon source dispersed in the mixed solution is 0.206 to 1.03g, the amount of the first reducing agent dispersed in the mixed solution is 0.000275 to 0.0033g, and the amount of the second reducing agent dispersed in the mixed solution is 0.0068 to 0.068g per 10ml volume of the ultrapure water.
3. The method for preparing yellow or green silicon quantum dots according to claim 1, wherein it is noted that if the heating reaction in the step (2) is heating to a temperature T, then
When the silicon source is N-aminoethyl-gamma-aminopropyltrimethoxysilane, the first reducing agent is catechol, the second reducing agent is sodium citrate, and T is higher than 130 ℃ and lower than or equal to 160 ℃, the obtained silicon quantum dots are green silicon quantum dots; when the silicon source is N-aminoethyl-gamma-aminopropyltrimethoxysilane, the first reducing agent is catechol, the second reducing agent is sodium citrate, and T is equal to or higher than 100 ℃ and equal to or lower than 130 ℃, the obtained silicon quantum dots are yellow silicon quantum dots.
4. The method for preparing yellow or green silicon quantum dots according to claim 1, wherein in the step (1), the protective gas is nitrogen or argon; the stirring time is 5-60 min.
5. The method for preparing the yellow or green silicon quantum dots according to claim 1, wherein in the step (2), the heating reaction is carried out by placing the mixed solution in a closed reaction vessel and placing the reaction vessel in a heating vessel for heating;
the reaction vessel is a hydrothermal reaction kettle or a round-bottom flask; the heating container is a microwave hydrothermal reaction instrument, an oil bath pan, an electric heating constant temperature blast drying box or an electric heating jacket.
6. The method for preparing yellow or green silicon quantum dots according to claim 5, wherein in the step (2), the heating reaction is a high-pressure closed hydrothermal reaction.
7. The method for preparing yellow or green silicon quantum dots according to claim 1, wherein in the step (3), the organic reagent is acetonitrile, ethanol, methanol, acetone or dimethylsulfoxide; the silicon quantum dot solution and the organic reagent are mixed according to the volume ratio of 1: 2-10;
the centrifugation is carried out for 5-30 min by using an ultrafiltration tube at the rotating speed of 5000-15000 rpm; the drying is drying by blowing with protective gas, freeze drying or vacuum drying.
8. The method for preparing yellow or green silicon quantum dots according to claim 7, wherein in the step (3), the organic reagent is acetonitrile, and the silicon quantum dot solution and the acetonitrile are mixed according to a volume ratio of 1: 4.
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Application publication date: 20190111 Assignee: Kunming Neutrino New Materials Co.,Ltd. Assignor: SOUTH CENTRAL University FOR NATIONALITIES Contract record no.: X2023420000223 Denomination of invention: A Method for Preparing Yellow or Green Silicon Quantum Dots Granted publication date: 20200714 License type: Common License Record date: 20230706 |