CN112251232A - Difunctional quantum dot microsphere composite nanomaterial, preparation method and application thereof - Google Patents
Difunctional quantum dot microsphere composite nanomaterial, preparation method and application thereof Download PDFInfo
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- G01N33/50—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing
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Abstract
The invention discloses a bifunctional quantum dot microsphere composite nano material, a preparation method and application thereof. The inner core layer of the composite nano material is SiO2Nanoparticles, middle layer of colloidal gold particles, and outer shell of negatively charged particlesQuantum dots; PEI self-assembly layers are arranged between the inner core layer and the middle layer and between the middle layer and the outer shell layer. The invention utilizes the layer-by-layer self-assembly characteristic of electropositive polymer Polyethyleneimine (PEI), firstly, SiO2A layer of colloidal gold is adsorbed on the surface of the nano-particles to form a silicon-core gold shell structure, and a layer of carboxylated quantum dots is adsorbed on the surface of the silicon-core gold shell to form the quantum dot microsphere composite nano-material with the colorimetric-fluorescent dual functions. The invention also discloses application of the composite nano material as a quantum dot label in fluorescence immunochromatography detection.
Description
Technical Field
The invention relates to the technical field of nano materials, in particular to a bifunctional quantum dot microsphere composite nano material, a preparation method and application thereof.
Background
Colloidal gold immunochromatography has been widely used in the field of biological detection as a rapid diagnostic technique. The colloidal gold is formed by that gold particles with a certain size are changed into a stable colloidal state due to electrostatic interaction to form a hydrophobic colloidal solution with negative electricity, and the gold particles are changed into the stable colloidal state due to the electrostatic interaction. The colloidal gold is used as a tracer marker for an antigen-antibody immune labeling technology (for example, a colloidal gold immunochromatographic test strip is used), but the colloidal gold diagnostic method has some inherent defects, including insufficient quantitative capability, only qualitative or semi-quantitative detection but not quantitative detection, poor detection sensitivity, false negative and the like.
The quantum dot microspheres are prepared by preparing luminescent material quantum dots and micron-sized or nano-sized microspheres into fluorescent quantum dot microspheres. Quantum dot microspheres have been widely used in the field of biological detection. However, quantum dot microspheres have some disadvantages, such as sensitive quantum dot properties, poor stability, easy agglomeration, etc., so that the use of the quantum dot microspheres is greatly limited. The quantum dot microspheres are compounded in carriers such as polymer materials, so that the stability, the fluorescence property and the better dispersibility of the quantum dot microspheres can be improved. Therefore, the fluorescent molecular label can be used as a fluorescent molecular label of an immunochromatography system and used for detection of biological antigens or antibodies.
In recent years, the core-shell structure composite nano-material has gained more and more attention and is widely applied in the fields of biology, medicine and chemistry. The silicon dioxide nano material has the advantages of good stability, reusability, strong dispersibility, controllable particle size, large specific area and the like, and is widely applied to the field of core-shell structure composite nano materials. However, at present, only the core-shell structure of the silicon sphere quantum dot exists, and the nanometer material of the bifunctional silicon core quantum dot combining the colloidal gold and the quantum dot is not available. The method for preparing the core-shell quantum dot has various methods, including a high-temperature injection method, a seed growth method, an ion exchange method and the like on the premise, but the preparation method of the silicon sphere nano composite material in the prior art is complex and has high operation difficulty.
The present invention is proposed to solve the above-mentioned technical problems.
Disclosure of Invention
The invention aims to provide a novel quantum dot microsphere composite nano material with double functions and monodispersity as well as a preparation method and application thereof. The preparation process of the bifunctional quantum dot microsphere composite nanomaterial utilizes the layer-layer self-assembly characteristic of electropositive polymer Polyethyleneimine (PEI), and structurally has a colloidal gold and quantum dot bifunctional shell. The material has the qualitative function of colloidal gold color comparison and excellent fluorescence property of quantum dots; can provide colorimetric signals readable by naked eyes and fluorescence signals excited by ultraviolet light, and can be used for preparing silicon sphere quantum dot microspheres with different particle sizes.
In order to achieve the above purpose of the present invention, the technical solution adopted by the present invention is as follows:
a bifunctional quantum dot microsphere composite nanomaterial is disclosed, wherein the quantum dot microsphere composite nanomaterial has a core-shell structure; the inner core layer is SiO2Nano particles, wherein the middle layer is colloidal gold particles, and the outer shell layer is quantum dots with negative charges; and PEI self-assembly layers are arranged between the inner core layer and the middle layer and between the middle layer and the outer shell layer.
In a specific embodiment, the SiO2The particle size range of the nano particles is 100-350 nm; the thickness of the PEI self-assembly layer is 1-10 nm; the particle size of the quantum dot microsphere composite nano material is 150-400 nm; the colloidal gold particles with the fluorescence emission wavelength range of 400-800 nm are AuNP particles; the quantum dots with negative charges are carboxylated quantum dots; superior foodThe carboxylated quantum dots are selected from CdSe/ZnS-COOH particles.
The invention also provides a preparation method of the bifunctional quantum dot microsphere composite nano material, which comprises the following steps:
(1) mixing SiO2Adding the particles into water, and reacting with ultrasonic wave to obtain SiO2The particles are monodisperse to form SiO2An aqueous solution;
(2) SiO obtained in the step (1)2Adding the aqueous solution into a Polyethyleneimine (PEI) solution, and reacting PEI in SiO by ultrasonic reaction2The surface of the nano-particles is self-assembled to form PEI modified SiO with positive charge on the surface2@ PEI particles;
(3) SiO obtained in the step (2)2Adding the @ PEI particles into the colloidal gold particle solution, and enabling the colloidal gold particles to be tightly adsorbed on the SiO through ultrasonic reaction2The surface of the @ PEI particle is subjected to silicon-core gold-shell composite nano particle material (SiO)2@Au)；
(4) SiO obtained in the step (3)2Adding @ Au particles into a Polyethyleneimine (PEI) solution, and enabling PEI to react in SiO through ultrasonic reaction2Self-assembling the surface of the @ Au nano-particles again to form a second layer of PEI modified SiO with positive charge on the surface2@ Au @ PEI particles;
(5) SiO obtained in the step (4)2Adding the @ Au @ PEI particles into a negatively charged carboxylated quantum dot solution, and enabling electronegative carboxylated quantum dot particles to be tightly adsorbed on electropositive SiO through ultrasonic reaction2The material (SiO) of the difunctional quantum dot microsphere composite nano particle is obtained on the surface of the @ Au @ PEI particle2@Au@QDs)。
In one embodiment, in the step (1), the SiO2The particles are prepared using a silicon-containing precursor, a reducing agent, deionized water, and an organic solvent.
In the step (1), a precursor containing silicon and a reducing agent are added into an organic solvent, stirred uniformly and then put into a conical flask for carrying out
Synthesis ofReacting, centrifugally collecting a product after the reaction is finished to obtain SiO2And (3) granules.
Preferably, the silicon-containing precursor is tetraethyl orthosilicate (TEOS), the organic solvent is absolute ethyl alcohol, and the reducing agent is 27% -29% ammonia water, and the reaction is carried out at room temperature for 4-6 h.
In one embodiment, the volume ratio of the ethyl orthosilicate, 27% -29% ammonia water, deionized water and absolute ethyl alcohol is 3-5: 3-4: 5-8: 100, preferably 4: 3.5: 6: 100.
In the preparation method of the bifunctional quantum dot microsphere composite nanomaterial, in the step (2), the molecular weight of PEI is 5000-80000, and the concentration of PEI solution is 0.2-5 mg/mL, preferably 1 mg/mL; the time of the ultrasonic reaction is 20-60 min, preferably 40 min.
In one embodiment, after step (2), further comprising: mixing SiO2The @ PEI particles are centrifuged, washed with deionized water to remove excess PEI from the solution, and stored in deionized water for later use. The cleaning frequency after centrifugation is 1-2 times.
In one embodiment, in the step (3), the colloidal gold is AuNP particles prepared by a sodium citrate reduction method, the surface of the AuNP particles is negatively charged, and the particle size range is 3-50 nm; the ultrasonic reaction time is 20-50 min, preferably 30 min.
In one embodiment, in step (3), the SiO2The volume ratio of the @ PEI particles to the colloidal gold particles is 1: 50.
in one embodiment, in the step (4), the molecular weight of the PEI is 5000-80000, and the concentration of the PEI solution is 0.2-5 mg/mL, preferably 1 mg/mL; the ultrasonic time is 30-70 min, preferably 60 min.
In one embodiment, after the step (4), SiO is further included2After the @ Au @ PEI particles are centrifuged, washing with deionized water to remove redundant PEI in the solution, and storing in the deionized water for use; and the washing frequency after centrifugation is 2-3 times.
In one embodiment, the carboxylated quantum dot particles in the step (5) are CdSe/ZnS-COOH particles, and the fluorescence emission wavelength range is 400-800 nm; the concentration of the quantum dots is 0.1 nmol-1 nmol; the time of the ultrasonic reaction is 20-50 min, preferably 30 min.
In one embodiment, in step (5), the SiO2The volume ratio of the @ Au @ PEI particles to the carboxylated quantum dot particles is 1: 50.
in one embodiment, after the step (5), the method further comprises preparing SiO2@ Au @ QDs are centrifuged by a centrifuge, washed by deionized water and resuspended in 10mL of deionized water; the number of cleaning times is 1-2 times, and preferably 2 times.
The invention also provides the application of the bifunctional quantum dot microsphere composite nano material as a quantum dot microsphere label in immunochromatography detection.
In a specific embodiment, the surface of the bifunctional quantum dot microsphere composite nanomaterial is modified with a recombinant antigen, and the recombinant antigen is coupled with an amino end of the recombinant antigen through a carboxyl group of a quantum dot shell to form a peptide chain.
In a specific embodiment, the specific steps of the application are as follows: the surface of the bifunctional quantum dot microsphere composite nano material is modified with a novel coronavirus recombinant antigen S1 serving as a multifunctional silicon sphere quantum dot microsphere immunity label (immuno-SiO)2@ Au @ QDs); mixing immuno-SiO2Coating @ Au @ QDs on a bonding pad (glass fiber) and preparing an immunochromatographic test strip for later use; 1 microliter of human clinical serum is added into 99 microliter of buffer solution and is uniformly mixed, then the mixture is added into a test strip sample inlet (anti-human IgG and IgM capture antibodies are respectively marked at a detection line), and a colorimetric or fluorescent signal at the detection line of the immunochromatography test strip is read after 15 minutes, so that not only can the fixed detection be realized by using a colloidal gold colorimetric method, but also the hypersensitivity detection can be realized by using quantum dot fluorescence.
Compared with the prior art, the invention has the advantages that:
(1) the bifunctional quantum dot microsphere composite nanomaterial provided by the invention structurally has a colloidal gold and quantum dot bifunctional shell; the material has the qualitative function of colloidal gold color comparison and excellent fluorescence property of quantum dots; can provide a colorimetric signal readable by naked eyes and a fluorescence signal excited by ultraviolet. The composite nano material has the advantages of adjustable size, strong stability, easy storage and realization of uniform particle size (good dispersibility); the method can be used for large-scale qualitative screening and small-scale hypersensitive quantitative screening. The bifunctional quantum dot microsphere composite nanomaterial prepared by the method has good dispersibility, colorimetric property and fluorescent property, controllable particle size, easy antibody modification of carboxyl on the surface, and wide application prospect in biological sample detection.
(2) The preparation method provided by the invention is simple and convenient to operate, low in cost, high in efficiency, good in quality stability and good in detection repeatability. The method provided by the invention utilizes the PEI layer-by-layer self-assembly, and SiO can be treated2The particle size of the particles is selected to regulate and control different particle sizes (150-400 nm) of the silicon sphere quantum dots.
(3) The bifunctional quantum dot microsphere composite nano material provided by the invention can be applied to a plurality of fields including biosensing, on-site rapid detection and the like. The antibody is detected on the surface modification of the bifunctional quantum dot microsphere composite nano material, and the fluorescent detector is combined, so that the rapid quantitative detection can be realized, and the method has good clinical application prospect and significance.
(4) The difunctional quantum dot microsphere composite nano material provided by the invention is used as a silicon sphere quantum dot label for immunochromatography detection, and has a colorimetric signal readable by naked eyes and a fluorescence signal excited by ultraviolet. The fluorescent probe can be used as a large-scale rapid screening tool for basic units, and can also be used for carrying out fluorescent signal detection by virtue of a fluorescent reader, particularly for rapid quantitative detection of low-concentration samples. The quantum dot label has the advantages of good dispersibility, adjustable particle size, strong colorimetric and fluorescent properties, easiness for batch preparation, and capability of being used for qualitative and high-sensitivity detection of target substances in complex samples.
Drawings
FIG. 1 is a schematic diagram of a preparation method of a bifunctional quantum dot microsphere composite nanomaterial of the present invention;
FIG. 2 is a Transmission Electron Microscope (TEM) and element scanning image of each component in the preparation process of the bifunctional quantum dot microsphere composite nanomaterial, wherein a is SiO2TEM image of the particles, b image is SiO2TEM image of @ Au particles, c image is SiO2TEM image of @ Au @ QDs particle with d-f being SiO respectively2、SiO2@Au、SiO2High-definition transmission electron micrograph of @ Au @ QDs particle, g picture is SiO2The element scanning graph of @ Au @ QDs shows that colloidal gold particles and quantum dot particles are uniformly distributed on SiO2A surface;
FIG. 3 is a representation diagram of the preparation process of the bifunctional quantum dot microsphere composite nanomaterial, wherein a is SiO2、SiO2@Au、SiO2The particle size distribution diagram of the @ Au @ QDs particles shows that the particle size of the synthesized bifunctional quantum dot microsphere is 240nm, the b diagram is a Zeta potential diagram of each component, and the c diagram is a SiO2、SiO2@Au、SiO2The picture and the fluorescence spectrogram of the @ Au @ QDs particle under the excitation of sunlight and ultraviolet light show that only the synthesized bifunctional quantum dot microsphere has a colorimetric signal and a fluorescent signal;
FIG. 4 is SiO2Stability photograph of @ Au @ QDs, from which SiO was known2The @ Au @ QDs particle has stable fluorescence performance, can tolerate high-concentration salt ions, and has no decrease of fluorescence intensity along with the increase of time;
FIG. 5 is a process for preparing a surface-modified recombinant antigen of the bifunctional quantum dot microsphere composite nanomaterial of embodiment 2 of the present invention;
FIG. 6 is a flowchart of an experiment for detecting human IgG and IgM in serum using the bifunctional quantum dot microsphere tag of embodiment 3 of the present invention as a high performance fluorescent tag in combination with an immunochromatographic system;
FIG. 7 is a photograph and a bar chart of fluorescence intensity of a fluorescence and colorimetric result of detecting human IgG and IgM in serum by the immunochromatography system based on the bifunctional quantum dot microsphere tag of embodiment 3 of the present invention; as can be seen from the figure, the detection limit of the fluorescence result is 100 times higher than the colloidal gold colorimetric detection limit;
FIG. 8 is a repeated result of detecting clinical serum by the immunochromatography system based on the bifunctional quantum dot microsphere tag in example 3 of the present invention; as can be seen from the figure, the fluorescence intensity is basically unchanged when the same sample is detected, and the stable performance of the bifunctional quantum dot microsphere label is proved.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the following embodiments, and it should be understood that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.
Example 1
The prepared difunctional quantum dot microsphere composite nano material comprises SiO2The core, two PEI interlayers, one colloidal gold shell and one carboxylated quantum dot shell. Wherein SiO is2The particle size of the particle is 200nm, the thickness of the PEI interlayer is 5nm, the particle size of the colloidal gold particle is 4nm, the particle size of the carboxylated quantum dot is 10nm, the final particle size of the synthesized silicon sphere quantum dot is about 240nm, and the silicon sphere quantum dot has a color comparison signal and a fluorescence signal and is good in dispersibility.
The preparation method of the bifunctional quantum dot microsphere composite nanomaterial of the embodiment, as shown in fig. 1, includes the following steps:
(1) preparing 200nm SiO with good dispersibility2The core is as follows:
100mL of absolute ethanol, 6mL of deionized water, and 3.5mL of 28% ammonia water were added to a 200mL jar in this order, a clean stir bar was added, and magnetic stirring was performed for 20 min. 4mL of ethyl orthosilicate solution is rapidly added at a time and stirred at room temperature for 5 h. After the reaction is finished, centrifuging at 6000rpm for 6min to obtain SiO2Washing the precipitate with anhydrous ethanol for 3 times, vacuum drying the product in a vacuum oven at 60 deg.C for 6 hr to obtain 200nm SiO2The dry powder of the particles is ready for use.
(2) Preparation of SiO2@ PEI particle:
weighing about 10mg of 200nm SiO2The particles were dissolved in 50mL of freshly prepared PEI solution (1mg/mL) and sonicated for 40 minutes. Centrifuged at 6000rpm for 6min, washed 2 times with deionized water and resuspended in 5mL of deionized water for use.
(3) Preparation ofSilicon-core gold-shell SiO2@ Au particles:
SiO to be prepared2@ PEI solution (5mL) was added to 100mL of 4nm AuNP solution, and vigorous sonication was performed for 30 minutes to strongly positively charge the surface of SiO2@ PEI adsorbs heavily negatively charged AuNP to form SiO2@ Au particles. Centrifuge at 5500rpm for 6min, wash with deionized water and resuspend in 5mL deionized water for use.
(4) Preparation of SiO2@ Au @ PEI particle:
SiO to be prepared2@ Au solution (5mL) was added to 50mL of freshly prepared PEI solution (1mg/mL) and sonicated for 60 minutes. Centrifuge at 5500rpm for 6min, wash with deionized water for 2 times, and resuspend in 5mL of deionized water for use.
(5) Preparation of bifunctional quantum dot microsphere SiO2@ Au @ QDs particle:
SiO to be prepared2Adding the @ Au @ PEI solution (5mL) into 100mL CdSe/ZnS-COOH solution, and carrying out intense ultrasonic treatment for 30 minutes to obtain SiO with strong positive charges on the surface2@ QDs @ PEI adsorbs a large amount of negatively charged CdSe/ZnS-COOH to form SiO2@ Au @ QDs quantum dot particles. Centrifuged at 5000rpm for 6min, washed once with deionized water and resuspended in 10mL of deionized water for use.
FIG. 2, a shows SiO obtained in step (1) of this example2Core particles, wherein b is SiO prepared in the step (3)2@ Au particles, c diagram is SiO produced in step (5)2Transmitted Electron Microscopy (TEM) of @ Au @ QDs particles. According to the TEM result, the difunctional quantum dot microsphere composite nano material has uniform particle size, and the colloidal gold shell and the quantum dot shell are sequentially wrapped on the SiO2The surface of the particles, so that the product has both a colorimetric and a fluorescent signal.
The characterization result of the bifunctional quantum dot microsphere composite nanomaterial prepared in this example is shown in fig. 3. In FIG. 3, a is SiO2The particle size distribution diagram of @ Au @ QDs particles; the bifunctional quantum dot microsphere composite nano material provided by the invention is prepared by adopting a PEI (polyetherimide) mediated layer-by-layer self-assembly method, and the change of Zeta potential of each component in a b diagram in figure 3 shows that the strong positive electricity adsorption effect of PEI is utilized to adsorb electronegative colloidal gold and quantum dots on the surface of a silicon core(ii) a In FIG. 3, c is SiO2、SiO2@Au、 SiO2The picture and the fluorescence spectrogram of @ Au @ QDs excited by sunlight and ultraviolet light show that only the synthesized bifunctional quantum dot microspheres have colorimetric signals and fluorescent signals.
The stability result of the bifunctional quantum dot microsphere composite nanomaterial prepared in this example is shown in fig. 4. As can be seen from the figure, the double-function quantum dot microsphere SiO2The @ Au @ QDs particle is able to tolerate high concentrations of salt ions without the change in fluorescence intensity over time. The fluorescent property of the bifunctional quantum dot microsphere is stable.
Example 2
The surface of the bifunctional quantum dot microsphere composite nanomaterial provided by the invention is provided with carboxylated quantum dots, and carboxyl on the surface can be used for coupling antibodies, so that the surface functionalization of the nanomaterial can be realized. The step of modifying the antibody on the surface of the bifunctional quantum dot microsphere composite nanomaterial provided by the invention is shown in FIG. 5, and comprises the following steps:
1mg of SiO2@ Au @ QDs powder was dissolved in 1mL of 2- (N-morpholine) ethanesulfonic acid solution (0.1M, pH 5.5), then 100. mu.L of carbodiimide solution (0.01M) and 20. mu. L N-hydroxysuccinimide solution (0.1M) were added, and ultrasonic reaction was carried out for 15min to activate SiO2The carboxyl group on the surface of @ Au @ QDs; then the SiO is recovered by centrifugation2@ Au @ QDs, resuspended in 200. mu.L of PBST solution (0.01M, pH 7.4); adding 15 mu g of new crown recombinant antigen S1, carrying out shake reaction at room temperature for 2h, then adding 150 mu L of BSA (10%), continuing to carry out blocking reaction for 1h, centrifugally recovering the product, washing the product for 1 time by PBST, suspending the product in 100 mu L of PBST, adding 100 mu L of gold-labeled diluent, uniformly mixing, then spreading the mixture on a nitrocellulose membrane to prepare a binding pad, and assembling the binding pad into a test strip for later use.
Example 3
The surface of the bifunctional quantum dot microsphere composite nanomaterial provided by the invention can be used as a high-performance colorimetric and fluorescent nano label for an immunochromatography system after being modified with a recombinant antigen. In the embodiment, the novel coronavirus recombinant antigen S1 modified bifunctional quantum dot microsphere label is combined with an immunochromatography system to detect IgG and IgM with different concentrations in human serum. Fig. 6 is a flowchart of an experiment for rapidly detecting IgG and IgM in human serum by using the bifunctional quantum dot microsphere label shown in this embodiment as a silica sphere fluorescent label in combination with an immunochromatographic system. FIG. 7 is a test analysis result for detecting IgG and IgM in human neocoronal positive serum based on the bifunctional quantum dot microsphere immunochromatographic system. In FIG. 7, panel a shows the fluorescence results (365nm wavelength UV excitation) of test strips for detecting IgG and IgM in human serum with different dilution times. It can be seen from the figure that the colorimetric and fluorescence intensities on the test strip detection line (T line) are gradually reduced with the increase of the dilution factor of the new corona positive serum, the colorimetric signal observed by naked eyes is diluted by 1 ten thousand times, and the detection limit of the reading value of the fluorescence analyzer is diluted by 100 ten thousand times. From the figure, the detection limit of the fluorescence result is 100 times higher than the colorimetric detection limit of colloidal gold (in the figure, in (i) is the colorimetric result of the colloidal gold of the bifunctional quantum dot microsphere label, and in (ii) is the fluorescence result of the bifunctional quantum dot microsphere label). In FIG. 7, b is a bar graph of fluorescence signals based on the bifunctional quantum dot microsphere labels, which is established according to different dilution times of human serum positive for new coronary and T-line fluorescence signal intensity. Error bars are obtained for five measurements. FIG. 8 is a repeated result of detecting clinical serum by the immunochromatography system based on the bifunctional quantum dot microsphere label in embodiment 3 of the present invention. The result shows that the immunochromatography system based on the bifunctional quantum dot microsphere label has good stability.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and such modifications and substitutions do not depart from the spirit and scope of the present invention as defined by the appended claims.
Claims (10)
1. A bifunctional quantum dot microsphere composite nanomaterial is characterized in that the quantum dot microsphere composite nanomaterial has a core-shell structure;
the inner core layer isSiO2Nano particles, wherein the middle layer is colloidal gold particles, and the outer shell layer is negatively charged quantum dots; and PEI self-assembly layers are arranged between the inner core layer and the middle layer and between the middle layer and the outer shell layer.
2. The quantum dot microsphere composite nanomaterial of claim 1, wherein the SiO is2The particle size range of the nano particles is 100-350 nm; the thickness of the PEI self-assembly layer is 1-10 nm; the particle size of the quantum dot microsphere composite nano material is 150-400 nm; the fluorescence emission wavelength range is 400-800 nm;
the colloidal gold particles are AuNP particles;
the negatively charged quantum dots are carboxylated quantum dots, and preferably, the carboxylated quantum dots are CdSe/ZnS-COOH particles.
3. The preparation method of the bifunctional quantum dot microsphere composite nanomaterial according to claim 1, characterized by comprising the following steps:
(1) mixing SiO2Adding the particles into water, and reacting with ultrasonic wave to obtain SiO2The particles are monodisperse to form SiO2An aqueous solution;
(2) SiO obtained in the step (1)2Adding the aqueous solution into a PEI solution, and enabling PEI to be in SiO through ultrasonic reaction2Self-assembling the particle surface to form PEI modified SiO with positive charge on the surface2@ PEI particles;
(3) SiO obtained in the step (2)2Adding the @ PEI particles into the colloidal gold particle solution, and enabling the colloidal gold particles to be tightly adsorbed on the SiO through ultrasonic reaction2The SiO of the silicon-core gold shell is obtained on the surface of the @ PEI particle2@ Au composite nanoparticles;
(4) SiO obtained in the step (3)2Adding the @ Au composite nano particles into a PEI solution, and enabling PEI to be in the SiO through ultrasonic reaction2Self-assembling the surface of the @ Au composite nano-particles again to form a second layer of PEI modified SiO with positive charge on the surface2@ Au @ PEI particles;
(5) subjecting the product obtained in step (4)SiO2Adding the @ Au @ PEI particles into a negatively charged carboxylated quantum dot solution, and adsorbing the negatively charged carboxylated quantum dot particles on positively charged SiO by virtue of ultrasonic reaction2The material SiO of the difunctional quantum dot microsphere composite nano particle is obtained on the surface of the @ Au @ PEI particle2@Au@QDs。
4. The production method according to claim 3, wherein, in the step (1), the SiO is2The particles are prepared by reacting a silicon-containing precursor, a reducing agent, deionized water and a solvent at room temperature for 4-6 hours;
preferably, the silicon-containing precursor is tetraethoxysilane, the reducing agent is ammonia water with the concentration of 27% -29%, and the solvent is absolute ethyl alcohol;
more preferably, the volume ratio of the ethyl orthosilicate, 27% -29% ammonia water, deionized water and absolute ethyl alcohol is 3-5: 3-4: 5-8: 10, preferably 4: 3.5: 6: 100.
5. The preparation method according to claim 3, wherein in the step (2), the molecular weight of the PEI is 5000-80000, and the concentration of the PEI solution is 0.2-5 mg/mL, preferably 1 mg/mL; the time of the ultrasonic reaction is 20-60 min, preferably 40 min.
6. The preparation method according to claim 3, wherein in the step (3), the colloidal gold particles are AuNP particles prepared by a sodium citrate reduction method, the surface of the AuNP particles is negatively charged, and the particle size range is 3-50 nm; the time of the ultrasonic reaction is 20-50 min, preferably 30 min.
7. The preparation method according to claim 3, wherein in the step (4), the molecular weight of the PEI is 5000-80000, and the concentration of the PEI solution is 0.2-5 mg/mL, preferably 1 mg/mL; the time of the ultrasonic reaction is 30-70 min, preferably 60 min.
8. The preparation method according to claim 3, wherein in the step (5), the carboxylated quantum dot particles are CdSe/ZnS-COOH particles; the concentration of the carboxylated quantum dots is 0.1 nmol-1 nmol; the time of the ultrasonic reaction is 20-50 min, preferably 30 min.
9. The bifunctional quantum dot microsphere composite nanomaterial of claim 1 or 2, being used as a quantum dot label in immunochromatography detection.
10. The application of claim 9, wherein the surface of the bifunctional quantum dot microsphere composite nanomaterial is modified with a recombinant antigen, and the recombinant antigen forms peptide chain coupling with an amino terminal of the recombinant antigen through a carboxyl group of a quantum dot shell.
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