CN117946658B - Preparation method of uniform and stable nanoscale quantum dot fluorescent microspheres - Google Patents

Abstract

The invention relates to a preparation method of uniform and stable nanoscale quantum dot fluorescent microspheres. The preparation method comprises the following steps: preparing CdTe quantum dots by using shaddock peel extract as a reducing agent end capping agent; and coating porous polystyrene on the basis of synthesizing CdTe quantum dot silicon dioxide fluorescent microspheres to form nanoscale quantum dot fluorescent microspheres. The method provided by the invention is green, environment-friendly and low in toxicity, and can be used for synthesizing the nano-microspheres with uniform sizes of different particle diameters and strong fluorescence performance by changing the dosage of the reaction substances and the reaction conditions, and the method has the advantages of simplicity in operation, good monodispersity, good stability and the like.

Description

A method for preparing uniform and stable nanoscale quantum dot fluorescent microspheres

Technical Field

The invention belongs to the field of fluorescent material preparation, and in particular relates to a method for preparing uniform and stable nanometer-level quantum dot fluorescent microspheres.

Background Art

Quantum dots have excellent physical and chemical properties such as continuous absorption spectrum, narrow luminescence spectrum, high luminescence efficiency and resistance to photobleaching. They are a semiconductor material with broad application prospects. The synthesis process of cadmium telluride quantum dots is highly toxic and not environmentally friendly. In addition, its cadmium ions are easily released, which has potential cytotoxicity, and its particle size is too small and the surface energy is high, which limits its application. At present, the main preparation methods of quantum dot fluorescent microspheres include: (i) adsorption method, that is, dissolving water-soluble quantum dots in a water-soluble solvent, fully mixing with the microsphere aqueous solution system, and combining with the microspheres through hydrogen bonds, intermolecular forces, electrostatic forces, etc. to form fluorescent microspheres; (ii) encapsulation method, that is, highly dispersing quantum dots in the reaction system, and encapsulating quantum dots inside the microspheres through polymerization reaction; (iii) chemical coupling method, that is, connecting surface-modified microspheres or microspheres with functional groups to the quantum dots through chemical bonds to the surface or inside of the microspheres. Among them, the fluorescent microspheres obtained by method (i) are susceptible to the external environment on the surface of the quantum dots, which may cause the quantum dots to fall off or the fluorescence intensity to decrease; method (ii) effectively reduces the impact of the external environment on the quantum dots and has excellent photostability; the fluorescent microspheres obtained by method (iii) are chemically connected, and the quantum dots are more stable and less likely to fall off.

The present invention provides a rapid, simple and efficient green synthetic method for preparing cadmium telluride quantum dots. The toxicity of the quantum dots is further reduced by coating with silicon dioxide microspheres. The resistance of the quantum dot fluorescent microspheres is improved without affecting their fluorescence by further coating with porous polystyrene microspheres.

Summary of the invention

The purpose of the present invention is to provide a method for preparing uniform and stable nano-scale quantum dot fluorescent microspheres, and to further improve the fluorescence intensity and stability by encapsulating the quantum dots with nano-microspheres.

The objective of the present invention is achieved through the following technical solutions:

A method for preparing uniform and stable nanoscale quantum dot fluorescent microspheres comprises the following steps:

S1, after passing inert gas at room temperature, cadmium chloride is added to the grapefruit peel extract, and the mixture is continuously stirred for 5-10 minutes. Then, sodium borohydride and tellurium powder are added, and the mixture is reacted for 0.5-10 hours, and then centrifuged to harvest the precipitate, washed with ultrapure water for 2-3 times, and dried to obtain CdTe quantum dots.

S2, add anhydrous ethanol, CdTe quantum dots, and ammonia water into a sample bottle in sequence and perform magnetic stirring, slowly add tetraethyl orthosilicate dropwise, react under stirring for 2-3 hours, centrifuge to obtain a precipitate, wash the precipitate 2-3 times, and dry to obtain CdTe quantum dot silica microspheres.

S3, polyvinyl pyrrolidone and ethanol aqueous solution are mixed, heated to 60-80°C under inert gas, styrene and azobisisobutyronitrile are added and ultrasonically mixed, reacted for 1-3 minutes, CdTe quantum dot silica microspheres are added, stirred for 24-36 hours, centrifuged to obtain a precipitate, washed with anhydrous ethanol 2-3 times, and dried to obtain CdTe quantum dot silica@polystyrene microspheres.

S4, ultrasonically mix CdTe quantum dot silica@polystyrene microspheres, anhydrous ethanol, ultrapure water, and heptane, stir in a 60-80°C water bath for 5-10 hours, cool to room temperature, and centrifuge to obtain a precipitate, wash the precipitate 2-3 times with ethanol, and dry to obtain CdTe nanoscale quantum dot fluorescent microspheres.

Among them, the preparation method of grapefruit peel extract is as follows: cut the grapefruit peel into small pieces, dry and grind into powder to obtain grapefruit peel powder; mix the grapefruit peel powder and ultrapure water in a mass ratio of 1:9, ultrasonicate in a 50-60°C water bath for 15-30 minutes, then microwave irradiate for 1-2 hours, filter to obtain the filtrate, and adjust the pH to 9-10 to obtain the grapefruit peel extract.

Preferably, the mass ratio of cadmium chloride, sodium borohydride, tellurium powder and grapefruit peel powder described in S1 is 3:2:(0.5-1):(10-20); the mass ratio of anhydrous ethanol, CdTe quantum dots, ammonia water and tetraethyl orthosilicate described in S2 is 80:(0.1-1):(0.5-1):(1-2); the mass ratio of CdTe quantum dot silica microspheres and styrene in S3 is 0.001-0.005, the mass ratio of styrene, AIBN and PVP is 30:(0.9-1.5):(4-30), the mass ratio of styrene to ethanol aqueous solution is 1:(4-9), and the volume of ethanol to water in ethanol aqueous solution is (2-4):1; The volume ratio of anhydrous ethanol and ultrapure water in S4 is (1-4):1, the volume ratio of heptane to anhydrous ethanol is 1:(5-10), and the volume mass ratio of heptane to CdTe quantum dot silica@polystyrene microspheres is 1 ml:(0.01-0.1) g.

Preferably, the tetraethyl orthosilicate alcohol solution in S2 is prepared in a volume ratio of tetraethyl orthosilicate to anhydrous ethanol of 1:32.

Preferably, in the method for preparing the grapefruit peel extract, the microwave power is 100-300w.

Preferably, the stirring speed in S2 is 1000-2000 rpm/min, and the stirring speed in S3 is 200-600 rpm/min.

The above technical solution of the present invention has the following advantages compared with the prior art:

The present invention provides a method for preparing uniform and stable nano-scale quantum dot fluorescent microspheres, wherein the preparation of CdTe quantum dots uses grapefruit peel extract as a reducing agent and a capping agent, and the grapefruit peel extract contains rich polyphenols, flavonoids, alkaloids, saponins and other excellent reducing agents, and as the concentration of the extract increases, smaller particles with wider band gap energy can be formed, and the method is simple, cost-effective, and the synthesis process is green, environmentally friendly and non-toxic. A series of nano-scale quantum dot silica microspheres with uniform particle size, good monodispersity, high stability and strong fluorescence performance can be prepared by the Stöber method. Compared with the reverse microemulsion method, the raw materials of this method are easy to obtain, environmentally friendly, and easy to operate. It does not require harsh reaction conditions and expensive equipment, and has a very broad application prospect and is suitable for industrial production. On this basis, porous polystyrene is coated, and multi-scattering does not affect the fluorescence performance of quantum dots. It also has the advantages of silica and polystyrene, good dispersibility, uniformity and stability.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific embodiments of the present invention in conjunction with the accompanying drawings, wherein:

FIG. 1 is a real picture of the uniform and stable nano-scale quantum dot fluorescent microspheres prepared in Example 1 of the present invention under natural light and 365 nm ultraviolet light.

FIG. 2 is a transmission electron microscope image of the CdTe quantum dot silica microspheres prepared in Example 1 of the present invention.

FIG3 is a scanning electron microscope image of uniform and stable nanoscale quantum dot fluorescent microspheres having a particle size of approximately (a) 300 nm and (b) 700 nm prepared in Examples 1 and 2 of the present invention, respectively.

FIG. 4 is a fluorescence emission spectrum of uniform and stable nanoscale quantum dot fluorescent microspheres with orange emission and near-infrared emission prepared in Examples 1 and 2 of the present invention.

DETAILED DESCRIPTION

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

Embodiment 1

Cut the grapefruit peel of Guangxi Shatian pomelo into small pieces, dry and grind into powder to obtain grapefruit peel powder; mix the grapefruit peel powder and ultrapure water in a mass ratio of 1:9 to prepare a 10% grapefruit peel aqueous solution, ultrasonicate in a 60°C water bath for 30 minutes, then irradiate with 270W microwave for 2 hours, filter to obtain the filtrate, and adjust the pH to 10 to obtain the grapefruit peel extract.

After nitrogen was introduced at room temperature, 3 g of cadmium chloride was added to 100 g of 10% grapefruit peel extract, and the mixture was stirred continuously at 500 rpm/min for 5 min. Then, 2 g of sodium borohydride and 1 g of tellurium powder were added. After reacting for 1 h, the mixture was centrifuged at 5000 rpm/min, the precipitate was harvested, washed with ultrapure water 3 times, and dried to obtain CdTe quantum dots.

The volume ratio of tetraethyl orthosilicate to anhydrous ethanol is 1:32 to prepare a tetraethyl orthosilicate solution. 80 g of anhydrous ethanol, 0.5 g of CdTe quantum dots, and 0.5 g of ammonia water are sequentially added into a sample bottle and magnetically stirred at a speed of 2000 rpm/min. 66 g of tetraethyl orthosilicate solution is slowly added dropwise. After reacting for 3 hours under stirring conditions of 2000 rpm/min, the precipitate is obtained by centrifugation at a speed of 5000 rpm/min. The precipitate is washed 2-3 times and dried to obtain CdTe quantum dot silica microspheres.

Ethanol aqueous solution was prepared according to the volume ratio of ethanol to water being 3:1. 20 g of polyvinyl pyrrolidone and 270 g of ethanol aqueous solution were mixed, nitrogen was passed through, and the mixture was heated to 60°C. 30 g of styrene and 1.5 g of azobisisobutyronitrile were added and ultrasonically mixed. After reacting for 3 minutes, 0.08 g of CdTe quantum dot silica microspheres were added, and the mixture was stirred at 600 rpm/min for 24 hours. The precipitate was obtained by centrifugation, washed twice with anhydrous ethanol, and dried to obtain CdTe quantum dot silica@polystyrene microspheres.

0.05 g CdTe quantum dot silica@polystyrene microspheres, 6 g anhydrous ethanol, 2 g ultrapure water, and 1 ml heptane were ultrasonically mixed, stirred at 600 rpm/min in a 60°C water bath for 10 h, cooled to room temperature, and centrifuged at 5000 rpm/min to obtain a precipitate. The precipitate was washed three times with ethanol and dried to obtain CdTe nanoscale quantum dot fluorescent microspheres.

Embodiment 2

Cut the grapefruit peel of Guangxi Shatian pomelo into small pieces, dry and grind into powder to obtain grapefruit peel powder; mix the grapefruit peel powder and ultrapure water in a mass ratio of 1:9 to prepare a 10% grapefruit peel aqueous solution, ultrasonicate in a 50°C water bath for 15 minutes, then irradiate with 270W microwaves for 1 hour, filter the filtrate, and adjust the pH to 9 to obtain the grapefruit peel extract.

After nitrogen was introduced at room temperature, 3 g of cadmium chloride was added to 200 g of 10% grapefruit peel extract, and the mixture was stirred continuously at 1000 rpm/min for 5 min. Then, 2 g of sodium borohydride and 1 g of tellurium powder were added. After reacting for 10 h, the mixture was centrifuged at 5000 rpm/min, the precipitate was harvested, washed three times with ultrapure water, and dried to obtain CdTe quantum dots.

The volume ratio of tetraethyl orthosilicate to anhydrous ethanol was 1:32 to prepare a tetraethyl orthosilicate solution. 80 g of anhydrous ethanol, 1 g of CdTe quantum dots, and 0.75 g of ammonia water were sequentially added into a sample bottle and magnetically stirred at a speed of 1000 rpm/min. 66 g of tetraethyl orthosilicate solution was slowly added dropwise. After reacting for 2 h under stirring conditions of 1000 rpm/min, the solution was centrifuged at a speed of 5000 rpm/min to obtain a precipitate. The precipitate was washed 3 times and dried to obtain CdTe quantum dot silica microspheres.

Ethanol-water solution was prepared according to the volume ratio of ethanol to water of 3:1. 5 g polyvinyl pyrrolidone and 120 g ethanol-water solution were mixed, nitrogen was passed through, and the mixture was heated to 80°C. 30 g styrene and 1 g azobisisobutyronitrile were added and ultrasonically mixed. After reacting for 2 min, 0.08 g CdTe quantum dot silica microspheres were added and stirred at 200 rpm/min for 36 h. The precipitate was obtained by centrifugation and washed twice with anhydrous ethanol and dried to obtain CdTe quantum dot silica@polystyrene microspheres.

0.05 g CdTe quantum dot silica@polystyrene microspheres, 6 g anhydrous ethanol, 2 g ultrapure water, and 1 ml heptane were ultrasonically mixed, stirred at 200 rpm/min in an 80°C water bath for 10 h, cooled to room temperature, and centrifuged at 5000 rpm/min to obtain a precipitate. The precipitate was washed three times with ethanol and dried to obtain CdTe nanoscale quantum dot fluorescent microspheres.

The time point of adding CdTe quantum dot silica microspheres in step S3 will affect the formation rate and coverage rate of polystyrene microspheres. If the initiation time is too short, it will affect the form of polystyrene, and if the initiation time is too long, it will reduce the coverage rate of CdTe quantum dot silica microspheres.

In step S1, by controlling the reaction time, quantum dots emitting wavelengths ranging from visible light to near-infrared wavelengths can be prepared, and a stable fluorescence quantum yield of more than 50% can be prepared.

By controlling the addition of quantum dots with different emission wavelengths, quantum dot fluorescent microspheres with different colors can be obtained; by controlling the content of the reaction substances and reaction conditions such as rotation speed, temperature, reaction time, etc., nanoscale quantum dot fluorescent microspheres with different particle sizes can be obtained.

Claims (5)

1. A method for preparing uniform and stable nanoscale quantum dot fluorescent microspheres, comprising the following steps: S1, adding cadmium chloride to the grapefruit peel extract after passing an inert gas at room temperature, stirring continuously for 5-10 minutes, then adding sodium borohydride and tellurium powder, reacting for 0.5-10 hours, centrifuging, harvesting the precipitate, washing with ultrapure water 2-3 times, and drying to obtain CdTe quantum dots; S2, adding anhydrous ethanol, CdTe quantum dots, and ammonia water into a sample bottle in sequence and performing magnetic stirring, slowly adding tetraethyl orthosilicate solution dropwise, reacting for 2-3 hours under stirring conditions, centrifuging to obtain a precipitate, washing the precipitate 2-3 times, and drying to obtain CdTe quantum dot silica microspheres; S3, polyvinyl pyrrolidone and ethanol aqueous solution are mixed, heated to 60-80°C under inert gas, styrene and azobisisobutyronitrile are added and ultrasonically mixed, reacted for 1-3 minutes, CdTe quantum dot silica microspheres are added, stirred for 24-36 hours, centrifuged to obtain a precipitate, washed with anhydrous ethanol 2-3 times, and dried to obtain CdTe quantum dot silica@polystyrene microspheres; S4, ultrasonically mixing CdTe quantum dot silica@polystyrene microspheres, anhydrous ethanol, ultrapure water, and heptane, stirring in a water bath at 60-80° C. for 5-10 hours, cooling to room temperature and centrifuging to obtain a precipitate, washing the precipitate 2-3 times with ethanol, and drying to obtain CdTe nanoscale quantum dot fluorescent microspheres; Among them, the preparation method of grapefruit peel extract is as follows: cut the grapefruit peel into small pieces, dry and grind into powder to obtain grapefruit peel powder; mix the grapefruit peel powder and ultrapure water in a mass ratio of 1:9, ultrasonicate in a 50-60°C water bath for 15-30 minutes, then microwave irradiate for 1-2 hours, filter to obtain the filtrate, and adjust the pH to 9-10 to obtain the grapefruit peel extract. 2. The method for preparing uniform and stable nano-scale quantum dot fluorescent microspheres according to claim 1, characterized in that the mass ratio of cadmium chloride, sodium borohydride, tellurium powder, and grapefruit peel powder described in S1 is 3:2:(0.5-1):(10-20); the mass ratio of anhydrous ethanol, CdTe quantum dots, ammonia water, and tetraethyl orthosilicate described in S2 is 80:(0.1-1):(0.5-1):(1-2); the mass ratio of CdTe quantum dot silica microspheres and styrene in S3 is 0.001-0.005, the mass ratio of styrene, AIBN, and PVP is 30:(0.9-1.5):(4-30), the mass ratio of styrene to ethanol aqueous solution is 1:(4-9), and the volume of ethanol to water in ethanol aqueous solution is (2-4):1; The volume ratio of anhydrous ethanol and ultrapure water in S4 is (1-4):1, the volume ratio of heptane to anhydrous ethanol is 1:(5-10), and the volume mass ratio of heptane to CdTe quantum dot silica@polystyrene microspheres is 1 ml:(0.01-0.1) g. 3. according to the preparation method of the described homogeneous stable nanometer quantum dot fluorescent microsphere of claim 1, it is characterized in that, in S2, tetraethyl orthosilicate solution is prepared by tetraethyl orthosilicate and anhydrous ethanol volume ratio of 1:32. 4. The method for preparing uniform and stable nano-scale quantum dot fluorescent microspheres according to claim 1, characterized in that the microwave power in the preparation method of the grapefruit peel extract is 100-300W. 5. The method for preparing uniform and stable nanoscale quantum dot fluorescent microspheres according to claim 1, characterized in that the stirring speed in S2 is 1000-2000 rpm/min, and the stirring speed in S3 is 200-600 rpm/min.