CN107936943A - A kind of quantum dot fluorescence intensity enhancing method based on dendrimer - Google Patents

Abstract

The invention discloses a method for enhancing the fluorescence intensity of quantum dots based on dendrimers. Using dendrimers as stabilizers to realize fluorescence enhancement between two quantum dots with different emission wavelengths belongs to the field of fluorescence analysis. The method comprises the following steps: synthesizing a quantum dot with dendrimers as a stabilizer; synthesizing another quantum dot with different emission wavelengths with other stabilizers; The ratio can achieve the effect of mutual enhancement of quantum dot fluorescence at different wavelengths, thereby improving the sensitivity of the quantum dot fluorescence detection method.

Description

A method for enhancing the fluorescence intensity of quantum dots based on dendrimers

technical field

The invention relates to the technical field of fluorescence analysis, in particular to a method for utilizing dendrimers to realize the mutual enhancement of fluorescence intensities of two quantum dots with different emission wavelengths.

Background technique

Quantum dots, also known as semiconductor nanocrystals, have the characteristics of wide excitation spectrum and controllable emission wavelength. By adjusting the size of quantum dots, the fluorescence wavelength can be changed, or multiple emission wavelengths can simultaneously detect different substances. At the same time, quantum dots have many advantages such as high luminous efficiency, good photostability, and resistance to photobleaching, and have broad application prospects in the fields of biomarkers, fluorescence analysis and detection.

However, the concentration of biological samples is low and the fluorescence is weak. When quantum dots are used in biological detection, in order to improve the detection sensitivity, their fluorescence intensity must be enhanced; due to the small size of quantum dots and high surface energy, agglomeration is easy to occur during the preparation process. Therefore, how to improve the preparation method of quantum dots, reduce the aggregation of quantum dots and improve their fluorescence intensity and stability is a key issue in the application and promotion of quantum dots.

Contents of the invention

In order to achieve the above object, the present invention provides a method for enhancing the fluorescence intensity of quantum dots based on dendrimers.

The method for enhancing the fluorescence intensity of quantum dots based on dendrimers is realized through the following technical scheme:

A method for enhancing the fluorescence intensity of quantum dots based on dendrimers, comprising the steps of:

(1) Using dendrimers as stabilizers to synthesize the first quantum dots;

(2) Synthesizing second quantum dots with different emission wavelengths with other stabilizers;

(3) Two kinds of quantum dots are mixed, and the fluorescence of quantum dots with different wavelengths is mutually enhanced by adjusting their molar ratio.

Preferably, the preparation of the first quantum dots comprises the following steps:

(1) Add 1.0×10 ^-3 mol/L metal ion solution such as Zn ²⁺ , Cd ²⁺ , Hg ^{2 +} or Cu ²⁺ to the dendrimer solution with a concentration of 1.0×10 ^-4 mol/L, Zn The molar ratio of ²⁺ , Cd ²⁺ , Hg ²⁺ or Cu ²⁺ ions to dendrimers is (1-20):1, and the pH of the solution is 6.8-7.2. After ultrasonic treatment for 1-3 hours, stir at room temperature to make Zn ^{2 +} , Cd ²⁺ , Hg ²⁺ or Cu ²⁺ ions coordinate with dendrimers to obtain a complex solution of metal ions and dendrimers;

(2) Add S ^2- , Se ^2- , or Te ^2- ion solution equal to the number of metal ions in moles to the solution in step (1), and react at 0-10°C for 1-3 hours to obtain dendrimer-wrapped Quantum dot solution, purified by dialysis, stored at low temperature.

Preferably, the inner core of the dendrimer in the step (1) is ethylenediamine, acrylonitrile, cystamine dihydrochloride or triethanolamine.

Preferably, the dendritic molecule in the step (1) is a spherical molecule with more than 4 generations, and its branch structure has amino groups; the terminal group of the dendritic molecule is amino, carboxyl, hydroxyl or ester group.

Preferably, the metal ion solution in the step (1) and step (2) adopts methanol, water or a mixed solution of the two.

Preferably, the preparation of the second quantum dots comprises the following steps:

(1) Zn ²⁺ , Cd ²⁺ or Hg ²⁺ as cation precursor solution, Se ^2- , Te ^2- or S ^2- as anion precursor solution;

(2) Add common stabilizers such as thioglycolic acid, mercaptopropionic acid, mercaptoethanol, mercaptoethylamine, glutathione, cysteine, thiourea or tiopronin, adjust the pH, and heat and reflux the precursor mixed solution to prepare quantum point.

Preferably, said step (3) specifically includes the following steps:

Take a certain volume of the first quantum dots and the second quantum dots so that the molar ratio of the two quantum dots is (0.1-50):1, and dilute to the same volume with deionized water.

The invention is a method for enhancing the fluorescence intensity of quantum dots based on dendrimers, which mainly amplifies the fluorescent signals of quantum dots, and has the following characteristics: quantum dots are synthesized by using the inner cavity of dendrimers, and one dendrimer can accommodate multiple Quantum dots amplify the fluorescence signal of a single quantum dot; using the branch structure of dendrimers can reduce the self-collision energy loss of quantum dots and enhance the fluorescence intensity of quantum dots; quantum dots synthesized by using dendrimers as stabilizers have uniform size , Good dispersion, by adjusting the molar ratio of metal ions and dendrimers, the size of quantum dots can be effectively controlled, and the emission wavelength of quantum dots can be adjusted and controlled; the quantum dots synthesized by dendrimers have a large number of particles on the surface Functional groups, which can be connected to a variety of substances, and the dendrimers have good biocompatibility, and the quantum dots synthesized by them can be applied to the biological field; one kind of quantum dots synthesized by using dendrimers, and another kind of quantum dots synthesized with other stabilizers Dot mixing, by controlling the molar ratio of mixing, achieves the effect of mutual enhancement of the fluorescence of quantum dots with different wavelengths; the two quantum dots of the present invention can be designed as dual probes for simultaneous detection of two substances.

Description of drawings

Fig. 1 is a schematic diagram provided by the present invention.

Fig. 2 is a diagram of the fluorescence enhancement effect of CdS-PAMAM quantum dots with different concentrations of CdTe/CdS quantum dots in Example 1 provided by the present invention.

Fig. 3 is a graph showing the fluorescence enhancement effect of CdTe/CdS quantum dots with different concentrations of CdS-PAMAM quantum dots in Example 1 provided by the present invention.

Fig. 4 is an effect diagram of mixing CdS-PAMAM quantum dots and CdTe/CdS quantum dots in Example 1 provided by the present invention at a molar ratio of 4.7:1.

Fig. 5 is a graph showing the fluorescence enhancement effect of CdS-PAMAM quantum dots with different concentrations of CdSe/ZnS quantum dots according to Example 2 of the present invention.

Fig. 6 is a graph showing the fluorescence enhancement effect of CdSe/ZnS quantum dots with different concentrations of CdS-PAMAM quantum dots according to Example 2 of the present invention.

Fig. 7 is an effect diagram of mixing CdS-PAMAM quantum dots and CdSe/ZnS quantum dots at a molar ratio of 3.7:1 according to the second embodiment of the present invention.

Detailed ways

The technical solutions of the present invention will be described in detail below through specific examples, but the scope of the present invention is not limited by these examples.

Specific embodiment 1

This embodiment provides a method for enhancing the fluorescence intensity of quantum dots based on dendrimers, which specifically includes the following steps:

(1) Synthesize CdS quantum dots using PAMAM dendrimer with amino group at the end of G 4.0 as an internal template: add 1.0×10 ^-3 mol/L chlorine to the methanol solution of PAMAM dendrimer with a concentration of 1.0×10 ^-4 mol/L Cadmium chloride methanol solution, (n Cd ²⁺ :nPAMAM=10:1), adjust the pH of the solution to about 7.0, then sonicate for 1h, and then stir at room temperature for 24h to obtain the complexation of Cd ²⁺ ions and PAMAM dendrimers solution; then add S ^2- ion methanol solution to the complex solution, (n Cd ²⁺ :nS ^2- = 1:1), then react at 4°C for 1h to obtain a CdS quantum dot solution wrapped in dendrimers, and finally Quantum dots were purified by dialysis and stored in the refrigerator at 4°C;

(2) Synthesis of CdTe/CdS core-shell quantum dots:

Synthesis of NaHTe precursor: Dissolve 0.0638g Te powder and _0.0420g NaBH4 in 1mL deionized water, stir until the upper layer is a colorless and transparent solution, and the lower layer is a white powder.

Synthesis of CdTe core: Dissolve 0.0285g CdCl ₂ ·2.5H ₂ O in 25mL deionized water; add 20.5μL mercaptoacetic acid (MPA), adjust the pH to 9.0-11.0, add 15μL NaHTe precursor under the protection of nitrogen, and then pass N ₂ 15min, put it in the refrigerator at 4°C and keep it away from light overnight.

Synthesis of the shell: Add 2.4mL, 25mmol/L Cd ²⁺ /MPA mixture (n Cd ²⁺ :nMPA=1:2) and 17.6mL CdTe core to the three-necked flask, adjust the pH to 9.0-11.0, at 90 The reaction was carried out at ℃ for 8 hours, and then stored in the refrigerator at 4℃ and protected from light.

(3) Explore the optimal molar ratio of fluorescence enhancement of CdS-PAMAM quantum dots

Add 100μLCdS-PAMAM quantum dots to a 1.5mL centrifuge tube (add 4 parts in parallel), then add different volumes of CdTe/CdS core-shell quantum dots, and finally dilute to 200μL with deionized water to make the CdTe/CdS quantum dots The molar ratios mixed with CdS-PAMAM quantum dots were 0.06:1, 0.1:1, 0.17:1, and 0.2:1, respectively, and then the fluorescence of the mixed solution was measured. With the increase of the amount of CdTe/CdS core-shell quantum dots, The fluorescence of CdS-PAMAM gradually increases, and reaches the extreme value when the molar ratio is 0.2:1, and the amount of CdTe/CdS core-shell quantum dots continues to increase when the molar ratio is 0.2:1 (the results are shown in Figure 2);

(4) Explore the optimal molar ratio of fluorescence enhancement of CdTe/CdS quantum dots

Add 100μLCdTe/CdS core-shell quantum dots to a 1.5mL centrifuge tube (add 4 parts in parallel), then add different volumes of CdS-PAMAM quantum dots, and finally dilute to 200μL with deionized water to make the CdS-PAMAM quantum dots The molar ratios mixed with CdTe/CdS core-shell quantum dots were: 0.5:1, 1:1, 3:1, 4:1, and then the fluorescence of the mixed solution was measured. With the increase of the amount of CdS-PAMAM quantum dots , the fluorescence of CdTe/CdS gradually increases, and reaches the extreme value when the molar ratio is 4:1, and the amount of CdS-PAMAM quantum dots continues to increase when the molar ratio is 4:1 (the results are shown in Figure 3);

(5) Figure 4 is the fluorescence effect diagram of CdS-PAMAM quantum dots and CdTe/CdS quantum dots mixed at a molar ratio of 4.7:1, and the blank fluorescence diagram of CdS-PAMAM quantum dots and CdTe/CdS quantum dots diluted to the same concentration .

Specific embodiment 2

This embodiment provides a method for enhancing the fluorescence intensity of quantum dots based on dendrimers, which specifically includes the following steps:

(1) Synthesize CdS quantum dots (referring to Example 1) with the PAMAM dendrimer of the amino group at the end of G4.0 as an internal template;

(2) Synthesis of CdSe/ZnS quantum dots (reference ^[1] ):

Synthesis of NaHSe precursor: Dissolve 0.0316 g of Se powder and 0.0632 g of NaBH in ₁ mL of deionized water, and stir until the black powder disappears.

Synthesis of CdSe/ZnS quantum dots: Add 40mL, 0.02mol/L cadmium chlorate and 0.21mL MPA to a three-necked flask, adjust the pH of the solution to (9.0-11.0), add 1mL NaHSe precursor under nitrogen protection, and place the solution at 96 ℃ heating 3h. Then, 2 mL of 0.01 mol/L zinc acetate and 2 mL of 0.01 mol/L sodium sulfide were alternately added to the above solution. The final solution was further refluxed at 96°C for 48h, and then stored in a refrigerator at 4°C and protected from light.

(3) Explore the optimal molar ratio of fluorescence enhancement of CdS-PAMAM quantum dots

Add 100 μL of CdS-PAMAM quantum dots to a 1.5mL centrifuge tube (add 4 parts in parallel), then add different volumes of CdSe/ZnS quantum dots, and finally dilute to 200 μL with deionized water to make the CdSe/ZnS quantum dots and The molar ratios of CdS-PAMAM quantum dots mixed are: 1:0.13, 1:0.19, 1:0.25, 1:0.38, and then measure the fluorescence of the mixed solution, with the increase of the amount of CdSe/ZnS core-shell quantum dots, The fluorescence of CdS-PAMAM gradually increases, and reaches the extreme value when the molar ratio is 1:0.38, and the amount of CdSe/ZnS core-shell quantum dots continues to increase when the molar ratio is 1:0.38 (the results are shown in Figure 5);

(4) Explore the optimal molar ratio of fluorescence enhancement of CdSe/ZnS quantum dots

Add 100μLCdSe/ZnS quantum dots to a 1.5mL centrifuge tube (add 4 parts in parallel), then add different volumes of CdS-PAMAM quantum dots, and finally dilute to 200μL with deionized water to make CdS-PAMAM quantum dots and CdSe /ZnS quantum dots mixed molar ratios are: 0.53:1, 1.1:1, 1.6:1, 3.7:1, and then measure the fluorescence of the mixed solution, with the increase of the amount of CdS-PAMAM quantum dots, CdSe/ZnS The fluorescence gradually increases, reaching the extreme value when the molar ratio is 3.7:1, and continuing to increase the amount of CdSe/ZnS quantum dots is consistent with the molar ratio of 3.7:1 (the results are shown in Figure 6);

(5) Figure 7 is the fluorescence effect diagram of CdS-PAMAM quantum dots and CdSe/ZnS quantum dots mixed at a molar ratio of 3.7:1, and the blank fluorescence diagram of CdS-PAMAM quantum dots and CdSe/ZnS quantum dots diluted to the same concentration .

The above examples are only preferred implementations of the present invention. It should be pointed out that for those of ordinary skill in the art, some improvements made without departing from the present invention are still within the protection scope of the present invention.

Claims (7)

1. a kind of quantum dot fluorescence intensity enhancing method based on dendrimer, it is characterised in that including the steps：

(1) using dendrimer the first quantum dot is synthesized for stabilizer；

(2) with the second different quantum dot of other stabilizers synthesis launch wavelength；

(3) two amounts point is mixed with different mol ratio, by regulating and controlling molar ratio, realizes different wave length quantum dot fluorescence intensity Mutual enhancing effect.

2. the quantum dot fluorescence intensity enhancing method according to claim 1 based on dendrimer, it is characterised in that：It is described Step (1) specifically includes the steps：

Zn is added into dendrimer solution²⁺、Cd²⁺、Hg²⁺Or Cu²⁺Deng metal ion, Zn²⁺、Cd²⁺、Hg²⁺Or Cu²⁺Ion and tree Shape molecule molar ratio is (1-20):1；Adjust solution pH be 7 or so, be ultrasonically treated 1-3h after, obtain metal ion with it is tree-like The complex solution of molecule.The S equal with metal ion is added into above-mentioned complex solution^2-、Se^2-Or Te^2-Ion is molten Liquid, reacts 1-3h at 0-10 DEG C, the quantum dot solution of dendrimer parcel, dialysis purification, Cord blood is made.

3. the quantum dot fluorescence intensity enhancing method according to claim 2 based on dendrimer, it is characterised in that：It is described The kernel of dendrimer is ethylenediamine, acrylonitrile, 2-aminoethyl disulfide dihydrochloride or triethanolamine.

4. the quantum dot fluorescence intensity enhancing method according to claim 3 based on dendrimer, it is characterised in that：It is described Dendrimer is 4 global molecular more than generation, has amino in its crotch structure；The end group of the dendrimer is ammonia Base, carboxyl, hydroxyl or ester group.

5. the quantum dot fluorescence intensity enhancing method according to claim 4 based on dendrimer, it is characterised in that：It is described Metal ion solution uses the mixed solution of methanol, water or both.

6. according to any quantum dot fluorescence intensity enhancing methods based on dendrimer of claim 1-5, its feature exists In：The synthesis step of second quantum dot is as follows：

(1)Zn²⁺、Cd²⁺Or Hg²⁺As cation precursor solution, Se^2-、Te^2-Or S^2-As anion precursor solution；

(2) thioacetic acid, mercaptopropionic acid, mercaptoethanol, mercaptoethylmaine, glutathione, cysteine, thiocarbamide or general sieve of sulphur are added The common stabilizer such as peaceful, adjusts pH, is heated to reflux precursor mixed solution and prepares quantum dot.

7. the quantum dot fluorescence intensity enhancing method according to claim 6 based on dendrimer, it is characterised in that：It is described In step (3), the molar ratio of the first quantum dot and the second quantum dot is (0.1-50):1, with deionized water constant volume.