Biligand construction long-term high luminescence water-soluble quantum dot fluorescent probe

Abstract

The application discloses a long-term high-luminous water-soluble quantum dot fluorescent probe with a double-ligand structure, and comprises the following steps: step S2, preparation of CdSe precursors; step S3, synthesis of CdSe quantum dots; step S4, preparation of water-soluble quantum dots; step S5, preparation of simple water-soluble quantum dot test paper; and step S6, detection of CdSe quantum dots and metal ions or detection of the antibiotic tetracycline. The application transfers oil-phase quantum dots to water-phase by simply adding double amphiphilic substances on the surface, and the fluorescence efficiency of the quantum dots is improved compared with that of original quantum dots, and the high luminance can be maintained for more than one month; the overall operation steps are simple, and the problem that the fluorescence gradually decreases and disappears in a short period of time in the prior art is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of quantum dot synthesis, in particular to a long-term high-luminous water-soluble quantum dot fluorescent probe constructed by double ligands. BACKGROUND

[0002] Quantum dots, also known as nanocrystals or artificial atoms, are quasi-zero-dimensional nanoparticles composed of II-VI or III-V elements. Generally, the size of quantum dots in three dimensions is below 100 nanometers (nm). Due to quantum confinement effect, electrons and holes in quantum dots have discrete energy level structure and can emit fluorescence after excitation.

[0003] A fluorescent probe refers to a kind of fluorescent molecule with characteristic fluorescence in the ultraviolet-visible-near infrared region, and its fluorescence properties (excitation and emission wavelength, intensity, lifetime, polarization, etc.) can be sensitively changed with the properties of the environment, such as polarity, refractive index, viscosity, etc.

[0004] There are three common ways for water-soluble modification of quantum dots in the prior art:

[0005] (1) Ligand exchange: replacing the surface ligand with a hydrophilic ligand;

[0006] (2) Silica coating: the water-solubility of quantum dots is endowed by the hydrophilic groups on the surface of silica, which shows good optical stability and thermal stability, and can be combined with biological bodies;

[0007] (3) Coating with amphiphilic organic polymer: the hydrophobic end of the polymer is combined with the surface of the oil quantum dots, and the hydrophilic end of the polymer enables the quantum dots to disperse in water.

[0008] The above prior art has the following problems in actual application:

[0009] (1) In the process of ligand exchange, the physical and chemical states of the surface atoms of quantum dots are inevitably changed, which significantly reduces the fluorescence quantum efficiency of quantum dots, and further reduces the detection effect as a probe;

[0010] (2) In the process of coating with silica, the fluorescence quantum efficiency is reduced and the quantum dots are aggregated and settled, which affects the actual application of the probe, and the method has the problem of high cost due to complex steps;

[0011] In combination with the above content, in the process of coating with amphiphilic organic polymer, the stability of quantum dots is not improved, and in the process of phase transfer, energy transfer occurs in quantum dots, resulting in a decrease in fluorescence intensity, which affects the detection effect as a probe.

[0012] To solve the above problems, we provide a dual-ligand constructed long-term high luminescence water-soluble quantum dot fluorescent probe. SUMMARY

[0013] The purpose of the present application is to provide a dual-ligand constructed long-term high luminescence water-soluble quantum dot fluorescent probe in order to solve the problems raised in the above.

[0014] To achieve the above purpose, the present application provides the following technical solutions:

[0015] The dual-ligand constructed long-term high luminescence water-soluble quantum dot fluorescent probe comprises the following steps:

[0016] Step S1, synthesis of Cd(AC)2-OAm precursor: mix 571 mg (2.5 mmol) of cadmium acetate Cd(AC)2 powder with 3 ml of oleylamine (OAm) in a 5 ml vial, shake vigorously for 5 minutes and then slightly heat, continue to shake until the solid is dissolved, thereby obtaining CdOAm in the form of a clear solution, wherein CdOAm is the first ligand;

[0017] Step S2, preparation of CdSe precursor: under the protection of an argon atmosphere, inject trioctylphosphine acid (TOP) into selenium powder to prepare a TOP-Se solution, then dilute with 1-octadecene (ODE) to a concentration of 1.5 M, continue to stir for more than 12 hours to ensure complete dissolution, and finally store in a sealed flask;

[0018] Step S3, synthesis of CdSe quantum dots: mix 46 mg (0.4 mmol) of Cd(AC)2 powder with 317 μl of oleic acid in a 10 ml vial, shake vigorously for 5 minutes and then slightly heat until the solid is dissolved, obtaining cadmium oleate in the form of a clear solution, then add 500 μl (4 mmol) of (Z)-9-octadecenamide (OLAm) at room temperature, add 2 ml of ODE as a solvent, and heat the mixture at 260°C for 3 minutes, quickly inject 0.8 ml of TOPSe solution while hot, continue to react at 260°C for a given period of time, remove and cool to room temperature, and the prepared quantum dot solution contains 0D / 1D NCs, mix with a solution containing n-hexane and ethanol (1:4, v / v), centrifuge at a speed of 4000 rpm for 5 min, and after purification for three times, disperse the precipitate in dichloromethane for further characterization;

[0019] Step S4, preparation of water-soluble quantum dots: 500ul of quantum dot solution dispersed in dichloromethane is taken, 5ul of CdOAm precursor solution is added, after a period of reaction, dichloromethane is completely evaporated, and a water solution of suitable surfactant is added, wherein the surfactant is the second ligand, in the ultrasonic machine, ultrasonic is performed for 5min, and then centrifugation is performed at a speed of 4000rpm for 1min, and the supernatant is the water-soluble quantum dots;

[0020] Step S5, preparation of simple water-soluble quantum dot test paper: filter paper is cut into two rectangular pieces, similar to pH test paper, the filter paper is placed into the prepared stable luminescent water-soluble CdSe quantum dot solution, soaked for a period of time, taken out and dried in an oven, and a glass rod is used to dip the above-mentioned solution on the test paper, and dried, and then observed under a UV lamp.

[0021] Step S6, detection of CdSe quantum dot metal ions and / or antibiotic tetracycline: after 500ul of metal ions is taken, titration is performed on the quantum dot test paper, and the quantum dot quenching can be observed on the test paper in real time.

[0022] Preferably, in the step S1, the ratio of selenium to trioctylphosphonic acid (TOP) is 1:1.2 during the synthesis of Cd(AC)2-OAm precursor.

[0023] Preferably, in the step S2, Cd(AC)2-OAm can also be Cd(AC)2-OLAm.

[0024] Preferably, in the step S4, the water solution can be cetyltrimethylammonium bromide (CTAB) during the preparation of water-soluble quantum dots.

[0025] Preferably, in the step S4, the water solution can also be double-decyl dimethyl ammonium bromide (DDAB) during the preparation of water-soluble quantum dots.

[0026] Preferably, in the step S4, the water solution can also be sodium dodecyl sulfate (SDS) during the preparation of water-soluble quantum dots.

[0027] Preferably, in the step S4, the water solution can also be gelatin during the preparation of water-soluble quantum dots.

[0028] Compared with the prior art, the present application has the following beneficial effects:

[0029] The present application can transfer oil-phase quantum dots to water-phase by simply adding a double amphiphilic substance on the surface, and the fluorescence efficiency is improved compared with the original quantum dots, and the high luminescence can be maintained for more than one month, the overall operation steps are simple, and the problem of gradual decrease of fluorescence in a short period of time and disappearance in the prior art is solved. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 Flowchart of the present application; DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0032] Embodiment 1:

[0033] The long-term high-emission water-soluble quantum dot fluorescent probe is constructed by using a double-ligand structure. The production and application thereof will be described in detail as follows:

[0034] Step S1, synthesis of Cd(AC)2-OAm precursor: 571 mg (2.5 mmol) of cadmium acetate Cd(AC)2 powder is mixed with 3 ml of oleylamine (OAm) in a 5 ml vial, and then vibrated vigorously for 5 minutes and slightly heated, and the vibration is continued until the solid is dissolved, so as to obtain CdOAm in the form of a clear solution, wherein CdOAm is the first ligand;

[0035] Step S2, preparation of CdSe precursor: under the protection of argon atmosphere, tri-octylphosphonic acid (TOP) is injected into selenium powder to prepare a TOP-Se solution, and then diluted with 1-octadecene (ODE) to a concentration of 1.5 M, and stirred for more than 12 hours to ensure complete dissolution, and finally stored in a sealed flask;

[0036] Step S3, synthesis of CdSe quantum dots: 46 mg (0.4 mmol) of Cd(AC)2 powder is mixed with 317 μl of oleic acid in a 10 ml vial, and then vibrated vigorously for 5 minutes and slightly heated until the solid is dissolved, to obtain cadmium oleate in the form of a clear solution, then 500 μl (4 mmol) of (Z)-9-octadecenamide (OLAm) is added at room temperature, 2 ml of ODE is further added as a solvent, and the mixture is heated at 260°C for 3 minutes, 0.8 ml of TOPSe solution is quickly injected while hot, and the reaction is continued at 260°C for a given time, and then removed and cooled to room temperature, to prepare a quantum dot solution containing 0D / 1D NCs, which is mixed with a solution containing n-hexane and ethanol (1:4, v / v), and centrifuged at a speed of 4000 rpm for 5 min, and after purification for three times, the precipitate is dispersed in dichloromethane for further characterization;

[0037] Step S4, preparation of water-soluble quantum dots: 500 μl of quantum dot solution dispersed in dichloromethane is taken, 5 μl of CdOAm precursor solution is added, after reaction for a period of time, dichloromethane is completely evaporated, and a water solution of a suitable surfactant is added, wherein the surfactant is a second ligand, ultrasonic treatment is performed in an ultrasonic machine for 5 min, and centrifugation is performed at a speed of 4000 rpm for 1 min, and the supernatant is the water-soluble quantum dots;

[0038] Step S5, preparation of simple water-soluble quantum dot test paper: filter paper is cut into two rectangular pieces, similar to pH test paper, the filter paper is placed in the prepared water-soluble CdSe quantum dot solution with stable luminescence, soaked for a period of time, taken out and dried in an oven, and a glass rod is used to dip the above-mentioned solution on the test paper, and dried and observed under a UV lamp.

[0039] Step S6, detection of CdSe quantum dot metal ions and / or antibiotic tetracycline: after 500 ul of metal ions are taken, titration is performed on the quantum dot test paper, and the quantum dots can be observed on the test paper in real time.

[0040] Further, in step S2, the ratio of selenium to trioctylphosphoric acid (TOP) is 1:1.2.

[0041] Example 2:

[0042] On the basis of example 1, the further scheme provided by the application is that in step S1, the synthesis process of Cd(AC)2-OAm precursor, Cd(AC)2-OAm can also be Cd(AC)2-OLAm.

[0043] On the basis of example 1, the further scheme provided by the application is that in step S4, the preparation process of water-soluble quantum dots, the water solution can be hexadecyl trimethyl ammonium bromide (CTAB).

[0044] On the basis of example 1, the further scheme provided by the application is that in step S4, the preparation process of water-soluble quantum dots, the water solution can also be double-decyl dimethyl ammonium bromide (DDAB).

[0045] On the basis of example 1, the further scheme provided by the application is that in step S4, the preparation process of water-soluble quantum dots, the water solution can also be sodium dodecyl sulfate (SDS).

[0046] On the basis of example 1, the further scheme provided by the application is that in step S4, the preparation process of water-soluble quantum dots, the water solution can also be gelatin.

[0047] To sum up: through the operation of steps S1 and S3, long-term high-efficiency light emission of quantum dots is promoted, the quantum dots have higher fluorescence efficiency, application in actual detection is promoted, that is, the brighter the more sensitive, the lower the lower limit of the substance that can be detected, and the problem of low fluorescence intensity and light emission in a short time in the prior art is solved.

[0048] Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art can make modifications to the technical solutions recorded in the foregoing embodiments or make equivalent replacements to part of the technical features, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A long-lasting, high-luminescence, water-soluble quantum dot fluorescent probe constructed with dual ligands, characterized in that, Includes the following steps: Step (1) Synthesis of Cd(AC)2-OAm precursor: 571 mg (2.5 mmol) of cadmium acetate (Cd(AC)2) powder and 3 mL of oleylamine (OAm) were mixed in a 5 mL vial, shaken vigorously for 5 minutes and then heated gently. The shaking was continued until the solid dissolved, thus obtaining a clear solution of CdOAm. Under the protection of an argon atmosphere, trioctyl phosphate (TOP) was injected into the selenium powder to prepare a TOP-Se solution. Then, it was diluted with 1-octadecene (ODE) to a concentration of 1.5 M. The solution was stirred continuously for more than 12 hours to ensure complete dissolution. Finally, it was stored in a sealed flask. Step (II) Synthesis of CdSe quantum dots: 46 mg (0.4 mmol) of Cd(AC)2 powder was mixed with 317 μL of oleic acid in a 10 mL vial, shaken vigorously for 5 minutes and then heated gently until the solid dissolved to obtain a clear solution of cadmium oleate. Then, 500 μL (4 mmol) (Z)-9-octadecenoic acid amide (OLAm) was added at room temperature, and 2 mL of LODE was added as a solvent. The mixture was heated at 260 °C for 3 minutes, and 0.8 mL of TOP-Se solution was quickly injected while hot. The reaction was continued at 260 °C for a given period of time. The mixture was then removed and cooled to room temperature. The prepared quantum dot solution contained OD / 1DNCs. It was mixed with a solution containing n-hexane and ethanol in a 1:4 v / v ratio and centrifuged at 4000 rpm for 5 min. After purification three times, the precipitate was dispersed in dichloromethane for further characterization. Step (3) Preparation of water-soluble quantum dots: Take 500 μL of quantum dot solution dispersed in dichloromethane, add 5 μL of CdOAm precursor solution, react for a period of time, evaporate the dichloromethane completely, add an aqueous solution of a suitable surfactant, sonicate in an ultrasonic machine for 5 min, and then centrifuge at 4000 rpm for 1 min. The supernatant is the water-soluble quantum dots. In step (iii) of the preparation of water-soluble quantum dots, the aqueous solution is hexadecyltrimethylammonium bromide (CTAB).

2. The dual-ligand constructed long-term high-luminescence water-soluble quantum dot fluorescent probe according to claim 1, characterized in that: In the synthesis of the Cd(AC)2-OAm precursor in step (I), the ratio of selenium to trioctyl phosphate (TOP) is 1:1.

2.

3. The dual-ligand constructed long-term high-luminescence water-soluble quantum dot fluorescent probe according to claim 1, characterized in that: In the process of synthesizing the Cd(AC)2-OAm precursor in step (I), Cd(AC)2-OAm can also be Cd(AC)2-OLAm.

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