CN1710154A - Method for Rapid Synthesis of CdTe Nanocrystals in Aqueous Phase under Mild Conditions - Google Patents

Abstract

The invention relates to preparation technique of a water dissolvable CdTe nano crystal in mild conditions. Inorganic substance Te powder and cadmium salt or their hydrate are adopted as reactor, and glutathione as stabilizer, the reaction takes place at 60 to 129 deg.C, while solution pH at 7.0 to 12.0, and lasts for 5 to 2 hours, producing CdTe nano crystal safely and quickly. The fluorescence color transmits from green, passing through yellow, orange and other intermediate colors, finally to red. The CdTe nanometer crystal produced with this technique is size easy controllable, well deconcentrated, of narrow and symmetric fluorescence emission peak, good bio-compatibility. The technique is of fine repeatability with quantum productivity 40 percent and very stable. The CdTe nanometer crystal produce with this technique can be applied to biology fluorescence marking research field.

Description

Method for Rapid Synthesis of CdTe Nanocrystals in Aqueous Phase under Mild Conditions

technical field

The invention relates to a method for preparing semiconductor cadmium telluride (CdTe) nanocrystals with high photoluminescence efficiency by using hydrothermal technology, in particular to a water-soluble CdTe nanocrystal precursor synthesized by using glutathione (GSH) as a stabilizer Aqueous solution, the CdTe nanocrystal precursor grows rapidly under mild conditions at a lower temperature, thereby synthesizing a method for CdTe nanocrystals with uniform scale and high luminous efficiency.

Background technique

CdTe nanocrystal is a semiconductor material with high luminescence quantum yield. , especially water-soluble semiconductor nanocrystals with high luminous intensity have been widely used in photonic devices, lasers, biotechnology, especially in bioluminescence labeling. Compared with traditional organic fluorescent dyes, luminescent nanocrystals have unique physical and chemical properties. Firstly, due to the quantum size effect of nanoscale particles, the emission color of nanocrystals changes from long wavelength to short wavelength (from red light to blue light) as the particle size decreases; secondly, using a single excitation light source can convert Simultaneous excitation of nanocrystals emitting various fluorescent colors makes it possible to conceive multiple fluorescent labels; in addition, inorganic nanocrystals have narrow emission peaks, are not easy to be photobleached, and have good chemical stability. CdTe nanocrystals are an important II-VI semiconductor material with high quantum yield. CdTe nanocrystals with high quantum yield can be obtained through organic reaction pathways, but the reagents required are very expensive, highly toxic, and the reaction conditions are very demanding. It is extremely unsafe to operate, insoluble in water, and has poor biocompatibility. It is difficult to apply to biomarkers, and further surface modification is required. The CdTe nanocrystals synthesized in aqueous phase have the advantages of good biocompatibility, simple synthesis conditions, low cost, good reproducibility, low toxicity, and mass production. However, it has the disadvantages of low quantum yield and broad emission peak. Therefore, in order to improve the quality of CdTe nanocrystals, post-treatments such as size-selective precipitation, selective photoetching, and surface modification are required to improve product quality.

In the traditional preparation method, when substances such as 3-mercaptopropionic acid or mercaptopropionic acid or 1-dihydroxypropanethiol are used as stabilizers, the reaction temperature needs to be around 200°C. CdTe nanocrystals can also be synthesized under low temperature conditions, but the growth of nanocrystals is very slow under this condition, and it generally takes at least 40 hours to obtain nanocrystals with larger emission wavelengths. Moreover, when the reflux time is longer, the reaction solution will change color and become black, the emission peak will become wider and asymmetrical, and the quantum yield will also decrease with the prolongation of reflux time. The emission wavelength of CdTe nanocrystals obtained by this method generally does not exceed 650nm.

In summary, CdTe nanocrystals prepared by organic reaction methods require high temperature and harsh reaction conditions; while aqueous phase synthesis of CdTe nanocrystals has low quantum yield and wide emission peaks, the stabilizers used in the background technology, nano Crystal growth is slow, and it takes a long time to obtain nanocrystals with larger emission wavelengths and so on. In order to overcome the shortcomings of preparing nanocrystals in the background technology, it is an important subject in this technical field to study a kind of water-phase CdTe nanocrystals that can be rapidly synthesized with high quantum yield under mild conditions at relatively low temperatures.

Contents of the invention

The object of the present invention is to propose a method for rapidly synthesizing CdTe nanocrystals in water phase under mild conditions in view of the above problems.

The present invention uses inorganic tellurium (Te) powder and cadmium salts or their hydrates as reactants, uses glutathione (GSH) as a new stabilizer, and uses the water phase at 60-120°C under mild conditions. , the reaction time is up to 2 hours, and CdTe nanocrystals are prepared safely and rapidly in an open system. In the process of refluxing for 5 minutes to 2 hours, the particle size of nanocrystals increases with the prolongation of heating and refluxing time, and the obtained particle size range increases from 2nm to 4nm. At the same time, its emission wavelength increases from 500nm to 680nm, and the fluorescent color changes from green through various intermediate colors such as yellow and orange, and finally becomes red. The CdTe nanocrystal has good size controllability, good monodispersity, narrow and symmetrical fluorescence emission spectrum peak; good repeatability of synthesis method; quantum yield can reach 40%, and good stability.

The cadmium salt used in the present invention is cadmium chloride, or cadmium perchlorate, or cadmium nitrate (Cd(NO ₃ ) ₂ ), or cadmium acetate or their hydrates (such as: five-half hydrated cadmium chloride (CdCl ₂ ·5/2H ₂ O) etc.).

The stabilizer used in the present invention is GSH. Because there is an active sulfhydryl group on the GSH molecule, which has a strong ability to donate electrons, it is an important water-phase antioxidant. Using it as a stabilizer, the growth rate of nanocrystals is accelerated, the synthesis temperature is low, the conditions are mild, the quantum yield is greatly improved, and the fluorescence emission peak is narrow and symmetrical, and the particles have a narrow size distribution. According to reports, the surface of semiconductor nanocrystals is basically covered with carboxyl groups, and there are few amino groups. However, the surface of the nanocrystal synthesized by the method of the present invention has both carboxyl and amino groups, has good biocompatibility, and can be connected with various biomolecules without any post-treatment and modification work, which is a good method. fluorescent markers. It can be widely used in bioluminescence labeling research. It is even possible to think of the nanocrystal as a fluorescent protein molecule.

The synthetic method of CdTe nanocrystal of the present invention specifically comprises the steps:

1. Synthesis of potassium telluride hydride (KHTe) or sodium telluride hydride (NaHTe) aqueous solution by reacting Te powder with potassium borohydride (KBH ₄ ) or sodium borohydride (NaBH ₄ ):

Put 0.2-2mmol Te powder and 100-1000mg KBH ₄ or NaBH ₄ into a reaction bottle filled with 1-10ml deionized water, stir constantly, and plug the bottle mouth with a rubber stopper. Discharge the hydrogen generated in the system and react for 0.5-4 hours. During this process, the Te powder was continuously dissolved, and the solution first turned purple, then gradually became lighter in color, and finally became colorless. That is to synthesize colorless and transparent KHTe or NaHTe aqueous solution. spare.

2. Synthesis of CdTe nanocrystal precursor solution with cadmium salt, or its hydrate and stabilizer GSH:

Add 200-2000ml of deionized water into a three-neck reaction flask, then add 0.5mmol-20mmol of cadmium salt or its hydrate and GSH stabilizer to dissolve it, wherein the molar ratio of cadmium salt, KHTe or NaHTe, GSH is 1: 0.2-0.7: 2-3, then pass high-purity nitrogen gas for 15-40 minutes to remove oxygen in the system, adjust the pH value to 7.0-12.0 with NaOH and HCl, and then synthesize the CdTe nanocrystal precursor solution. spare.

3. Heating the CdTe nanocrystal precursor solution to synthesize CdTe nanocrystals:

Pour the KHTe or NaHTe solution into the three-neck reaction flask in the CdTe nanocrystal precursor solution, heat it to 60-120°C, connect the condenser tube to reflux the solvent, avoid a large amount of evaporation of the solvent, and keep stirring at the same time.

4. Collect CdTe nanocrystals of various sizes and fluorescence emission wavelengths:

In the reaction device at 60-120°C, within 5 minutes to 2 hours of the synthesis reaction, the synthesis reaction products are collected at different times, which are CdTe nanocrystals. As the reflow time prolongs, the size of the nanocrystals increases continuously. The CdTe nanocrystals collected at different times are CdTe nanocrystals with different sizes and fluorescence emission wavelengths. That is, CdTe nanocrystals of various luminescent colors from green through yellow and orange to red. Its fluorescence emission spectrum peaks from 500nm-680nm.

The synthesis method of the invention has the advantages of fast synthesis reaction, simple and safe operation, low synthesis temperature, mild conditions and the like. The obtained CdTe nano crystal quantum yield is high, which can reach 40%. The synthesized nano crystal has uniform size, narrow fluorescent emission spectrum peak, symmetrical peak shape and good biocompatibility. Various characterizations show that there are amino and carboxyl functional groups on its surface, which can be used to connect various biological substances, and can be widely used in the field of bioluminescence labeling research without any post-treatment and modification.

Mouse toxicity test in vivo: Take 20 mice and divide them into two groups, half male and half female, inject 1-2ml of normal saline into the tail vein of the mice in the control group; inject 1-2ml of pure CdTe nanocrystal solution into the tail vein of the mice in the treatment group , Observed for 30 days, the two groups of mice had no adverse reaction, no significant difference. Experiments prove that the nano crystal solution is non-toxic.

Description of drawings

Figure 1 is the UV-Vis absorption spectrum of CdTe nanocrystals. It mainly reflects the good particle size and monodispersity of CdTe nanocrystals.

Figure 2 is the fluorescence emission spectrum of CdTe nanocrystals. It reflects the emission wavelength and color of the particles. The narrower the half-peak width and the more symmetrical the peak shape, the better the monodispersity.

Fig. 3 is an X-ray diffraction spectrum. Reflecting the crystal properties of CdTe nanocrystals, it is proved to be the crystal structure of sphalerite cubic facets.

Figure 4 is a transmission electron microscope imaging photo. It reflects the uniformity of particle size and size of CdTe nanocrystals.

Fig. 5 is an infrared absorption spectrum diagram. It shows that the surface of the nanocrystal synthesized by this method has not only carboxyl group but also amino functional group, which can be used to connect various biological reagents.

Detailed ways

The synthesis method of the present invention is further illustrated by the following examples, but it is not meant to limit the synthesis method of the present invention.

Embodiment one

1. Reaction of Te powder and KBH ₄ to synthesize KHTe aqueous solution:

Put 0.48mmol Te powder and 290mg KBH ₄ into a reaction bottle filled with 1ml of water, keep stirring and stopper the bottle mouth with a rubber stopper, and use a hollow needle to discharge the hydrogen gas generated by the system through the pinhole, and react for 1 hour , during this process, the Te powder is continuously dissolved, the solution first turns purple, the color becomes lighter, and finally becomes colorless and transparent, that is, the KHTe aqueous solution is synthesized. spare.

2. Using CdCl ₂ , KHTe and stabilizer GSH to synthesize the aqueous solution of nanocrystal precursor:

In a three-necked reaction flask, add 400 ml of deionized water, add 0.96 mmol of CdCl ₂ and 2.4 mmol of GSH stabilizer, and dissolve them. The molar ratio of CdCl ₂ , KHTe, and GSH is 1:0.5:2.5. Then pass high-purity nitrogen gas for 20 minutes to remove the oxygen in the system, adjust the pH value to 11.0 with NaOH, and synthesize the CdTe nanocrystal precursor aqueous solution. spare.

3. Heating the aqueous solution of CdTe nanocrystal precursor to synthesize CdTe nanocrystal:

Pour the KHTe aqueous solution into a three-necked reaction flask filled with a CdTe nanocrystal precursor aqueous solution, heat to 100°C, connect a condenser to reflux the solvent, avoid a large amount of solvent evaporation, and keep stirring at the same time;

4. Collect CdTe nanocrystals:

In a reaction bottle heated at 100°C, the synthesis reaction was carried out for 30 minutes, and part of the CdTe nanocrystal solution was collected to obtain CdTe nanocrystals with a uniform particle size of about 2.2nm and an orange fluorescence emission wavelength of 570nm.

Embodiment two

1. Reaction of Te powder and NaBH ₄ to synthesize NaHTe aqueous solution:

Put 0.48mmol Te powder and 250mg NaBH ₄ into a reaction bottle filled with 2ml deionized water, stir constantly, stop the bottle mouth with a rubber stopper, and at the same time, use a hollow needle to discharge the hydrogen generated in the system through a pinhole , reacted for 1.5 hours. During this process, the Te powder was continuously dissolved, and the solution first turned purple, then gradually became lighter in color, and finally became colorless. That is, a colorless and transparent NaHTe aqueous solution is synthesized. spare.

2. Using CdCl ₂ , NaHTe and stabilizer GSH to synthesize the aqueous solution of nanocrystal precursor:

In a three-neck flask, add 600 ml of deionized water, add 2.4 mmol of CdCl ₂ and 4.8 mmol of GSH stabilizer, and dissolve them. The molar ratio of CdCl ₂ , NaHTe, and GSH is 1:0.2:2. Then pass high-purity nitrogen for 20 minutes to remove the oxygen in the system, adjust the pH value to 10.0 with NaOH, and synthesize the CdTe nanocrystal precursor aqueous solution. spare.

3. Synthesis of CdTe nanocrystals by heating:

Pour the NaHTe aqueous solution into the three-neck reaction flask of the CdTe nanocrystal precursor aqueous solution, heat it to 90°C, connect the condenser to reflux the solvent, avoid a large amount of solvent evaporation, and keep stirring at the same time;

4. Collect CdTe nanocrystals:

In a reaction bottle heated at 90°C, the synthesis reaction was carried out for 1 hour, and part of the CdTe nanocrystal solution was collected to obtain a red fluorescent CdTe nanocrystal with a particle size of about 2.5nm and a fluorescence emission wavelength of 610nm.

Embodiment Three

1. Reaction of Te powder and KBH ₄ to synthesize KHTe aqueous solution:

Put 0.96mmol Te powder and 500mg KBH ₄ into a reaction bottle filled with 5ml deionized water, stir constantly, and stopper the bottle mouth with a rubber stopper. At the same time, use a hollow needle to discharge the hydrogen generated in the system through a pinhole , reacted for 2 hours. During this process, the Te powder was continuously dissolved, and the solution first turned purple, then gradually became lighter in color, and finally became colorless. That is to synthesize colorless and transparent KHTe aqueous solution. spare.

2. Using CdCl ₂ ·5/2H ₂ O, KHTe and stabilizer GSH to synthesize the aqueous solution of nanocrystal precursor:

Add 1000ml of deionized water into a three-necked flask, add 1.92mmol of CdCl ₂ ·5/2H ₂ O and 6mmol of GSH stabilizer, and dissolve them. The molar ratio of CdCl ₂ , NaHTe, and GSH is 1:0.5:3. Then pass high-purity nitrogen gas for 20 minutes to remove the oxygen in the system, adjust the pH value to 9.0 with NaOH, and synthesize the CdTe nanocrystal precursor aqueous solution. spare.

3. Synthesis of CdTe nanocrystals by heating:

Pour the KHTe aqueous solution into the three-necked reaction flask of the CdTe nanocrystal precursor aqueous solution, heat to 100°C, connect the condenser to reflux the solvent, avoid a large amount of solvent evaporation, and keep stirring at the same time;

4. Collect CdTe nanocrystals:

In a reaction bottle heated at 100°C, the synthesis reaction was carried out for 1.5 hours, and part of the CdTe nanocrystal solution was collected to obtain a red fluorescent CdTe nanocrystal with a particle size of about 3nm and a fluorescence emission wavelength of 650nm.

Embodiment four

1. Reaction of Te powder and KBH ₄ to synthesize KHTe aqueous solution:

Put 0.48mmol Te powder and 280mg KBH ₄ into a reaction bottle filled with 1ml of water, stir constantly, plug the bottle mouth with a rubber stopper, and use a hollow needle to discharge the hydrogen generated by the system through the pinhole, and react 1 Hours, during this process, the Te powder was continuously dissolved, the solution first turned purple, the color continued to fade, and finally became colorless and transparent, that is, the KHTe aqueous solution was synthesized. spare.

2. Using Cd(NO ₃ ) ₂ , KHTe and stabilizer GSH to synthesize the aqueous solution of nanocrystal precursor:

Add 400ml of deionized water, 0.96mmol of Cd(NO ₃ ) ₂ and 2.4mmol of GSH stabilizer into a three-neck reaction flask, and dissolve them. The molar ratio of CdCl ₂ , KHTe, and GSH is 1:0.5:2.5. Then pass high-purity nitrogen gas for 20 minutes to remove the oxygen in the system, adjust the pH value to 8.0 with NaOH, and synthesize the CdTe nanocrystal precursor aqueous solution. spare.

3. Heating the aqueous solution of CdTe nanocrystal precursor to synthesize CdTe nanocrystal:

Pour the KHTe aqueous solution into a three-necked reaction flask filled with a CdTe nanocrystal precursor aqueous solution, heat to 100°C, connect a condenser to reflux the solvent, avoid a large amount of solvent evaporation, and keep stirring at the same time;

4. Collect CdTe nanocrystals:

In a reaction bottle heated at 100°C, the synthesis reaction was carried out for 10 minutes, and part of the CdTe nanocrystal solution was collected to obtain a green fluorescent CdTe nanocrystal with a particle size of about 2nm and a fluorescence emission wavelength of 530nm.

Embodiment five

The CdTe nanocrystals synthesized by this method are proved by methods such as ultraviolet-visible absorption spectrum, fluorescence emission spectrum, X-ray diffraction spectrum, and transmission electron microscope imaging images (see Fig. 1-Fig. 4), and the synthetic product is uniform and has Very good monodispersity; good fluorescence properties, narrow half-width, symmetrical peak shape; good stability. According to the results of infrared absorption spectrum ( FIG. 5 ), the surface of the nanocrystal has both amino and carboxyl groups.

Claims (5)

1, the method that water synthesizes the cadmium telluride nanocrystal fast under a kind of mild conditions, its feature comprises the steps:

(1) by Te powder and KHTe or NaHTe reaction, the synthetic tellurium hydrogen-change potassium or sodium hydrogen telluride aqueous solution: with 0.2-2mmol Te powder and 100-1000mg KBH ₄Or NaBH ₄Put into the reaction flask of 1-10ml deionized water, stir,, reacted 0.5-4 hour, when solution becomes water white transparency, be the aqueous solution of synthetic KHTe or NaHTe with the hydrogen that produces in the hollow needle discharging system, standby;

(2) with cadmium salt or its hydrate and the synthetic nanocrystalline precursor solution of CdTe of gsh stablizer:

In three neck reaction flasks, add the 200-2000ml deionized water, the cadmium salt or its hydrate and the gsh stablizer that add 0.5-20mmol then, make its dissolving, wherein the mol ratio of cadmium salt, KHTe or NaHTe, gsh is 1: 0.2-0.7: 2-3, logical high pure nitrogen 15-40 minute, adjust pH 7.0-12.0, the promptly synthetic nanocrystalline precursor solution of CdTe, standby;

(3) it is nanocrystalline to add thermal synthesis CdTe:

The aqueous solution of KHTe or NaHTe is poured in the three neck reaction flasks of the nanocrystalline precursor solution of CdTe, made it to be heated to 60-100 ℃, synthetic CdTe is nanocrystalline, connects prolong and makes solvent refluxing, constantly stirs;

(4) it is nanocrystalline to collect CdTe:

In reaction flask, within the building-up reactions 5 minutes-2 hours, collect the building-up reactions product, it is nanocrystalline to be CdTe.Nanocrystalline at the CdTe that different time is collected, the CdTe of various glow colors that is different size and fluorescent emission wavelength is nanocrystalline, and its size is 2nm-4nm, and its fluorescence emission spectrum peak is 500nm-680nm.

2, according to the described synthetic method of claim 1, it is characterized in that: the synthetic nanocrystalline precursor of CdTe, synthesis temperature is 60～120 ℃; The pH value of solution value is 7.0-12.0; Generated time is 5 minutes-2 hours.

3, according to claim 1,2 described synthetic methods, it is characterized in that: said cadmium salt is Cadmium chloride fine powder or cadmium perchlorate or cadmium nitrate or cadmium acetate or their hydrate.

4, according to claim 1,2,3 described synthetic methods, it is characterized in that: the said stablizer that uses is gsh.

5, according to claim 1,2,3,4 described synthetic methods, it is characterized in that: the mol ratio of cadmium salt, KHTe or NaHTe, gsh is 1: 0.2～0.7: 2～3.

Images