CN114471750A - A method for the reliable synthesis of nano/submicron droplets by induced liquid-liquid phase separation and its application - Google Patents

Abstract

The invention relates to a method for reliably synthesizing nano/submicron droplets by controllably inducing liquid-liquid phase separation and application thereof, belonging to the field of nano materials. In an originally mutually soluble water-organic solvent homogeneous system, such as a water-ethanol system, a compound with a kosmotrope property is directly introduced or generated by reaction, so that the phase separation of the homogeneous system can be initiated, and the nano-scale liquid drops gradually nucleate and grow from the homogeneous system. The liquid drops generated by the method have the characteristics of small volume and good uniformity. By capturing these nano droplets, hollow nanostructures can be obtained. If certain functional compounds are introduced into the system, for example catalysts, drugs, etc. Then in the phase separation and liquid drop generation processes, the compounds can be synchronously loaded into the hollow nano structure, and a nano reactor and a drug carrier can be obtained. The method has the advantages of simple process, short production period and strong universality, and has good application prospect.

Description

A method for the reliable synthesis of nano/submicron droplets by induced liquid-liquid phase separation and its application

technical field

The present invention relates to a method for reliably synthesizing nanoscale/submicron droplets by controllably inducing phase separation. And a method for synthesizing hollow nanostructures, egg nanoreactors and drug carriers based thereon. It belongs to the field of nano-synthesis and manufacturing.

Background technique

Droplets are an important tool in micro- and nano-synthesis. But traditional methods are difficult to generate nano/submicron droplets reliably. Or it is impossible to generate small enough droplets and can only stop at the micrometer size, such as microfluidics (CN102008983B); or the generated droplets have uneven size and wide volume distribution, so only a small part can reach nanometers. / sub-micron scale, such as microemulsion systems (CN1077717A). Therefore, it is of great significance to realize the reliable synthesis of such droplets.

Traditional methods have attempted to use two immiscible liquids to form a two-phase system, and then break up one of the liquid phases into small droplets. In microfluidics, it is realized by a valve-like method; in an emulsion system, it is realized by the input of mechanical forces such as stirring and ultrasound. The method involved in the present invention does the opposite, so that a system with only a single liquid phase is spontaneously transformed into a two-phase system, so that tiny droplets are formed from the bottom up.

For nanoreactors and drug carriers, the synthesis of the hollow nanostructures themselves, which act as shells, is complex. Usually, sacrificial template nanoparticles need to be prepared first. With the template as the core, the outer layer is covered with a very thin nanoshell. Then, through chemical etching, the template is removed, leaving only the outer shell to obtain hollow nanostructures that act as carriers. This usually takes more than ten hours, and may need to be achieved through high temperature and high pressure reactions such as hydrothermal methods. On this basis, a separate step is also required to load catalysts or drugs into the above-mentioned hollow nanostructures. The loading is usually achieved by soaking the hollow nanostructured carrier in a catalyst or drug solution and allowing it to diffuse into the cavity of the carrier over ten or tens of hours. (CN105907743B, CN108478806A)

The traditional preparation method has the following problems:

1. The process is too complicated. Even if it is just a synthetic carrier, it requires three parts: template, shell, etching, and load. Each of these steps requires purification and cleaning of the product. The actual process is very complicated and the cost is high.

2. Sacrificial template nanoparticles lead to further increase in cost. The template itself, as a nanoparticle, is a high-cost raw material; but it is completely etched in the later stage, which is equivalent to being discarded at one time, which greatly increases the cost of the entire process.

3. Most of the reaction methods with high temperature and high pressure such as hydrothermal are required, which have high energy consumption and poor safety.

4. The efficiency of the load process is low. The loading process often takes tens of hours due to the dependence on diffusion phenomena, the immersion solution and the concentration gradient within it. In particular, some carrier shells use degradable materials such as silicone, which may be partially degraded in advance during long-term immersion, affecting their durability and the degradation process in practical applications.

Therefore, there is still a lack of a method for producing yolk-shell nanostructures, nanoreactors and drug carriers that can be facile, fast, safe, low-energy, and does not rely on diffusion loading.

SUMMARY OF THE INVENTION

The technical problem solved by the present invention is that it is difficult to reliably synthesize nano/submicron droplets. Therefore, a new way of thinking and method is proposed. At the same time, on this basis, the shortcomings of nanoreactor and drug carrier synthesis, including many steps, long cycle, high energy consumption, poor safety, and dependence on diffusion loading, are also solved.

In order to solve the above technical problems, the technical solution proposed by the present invention is: a method for reliably synthesizing nano/submicron droplets by inducing liquid-liquid phase separation, comprising the following steps:

S1: The original system is a homogeneous mixed solvent system of mutually soluble water and organic solvent, which specifically refers to two solvents that can be mutually soluble in any proportion. After mixing, only one liquid phase is obtained, and there is no phase-separated mixture;

S2: By introducing kosmotrope compounds, the above-mentioned mutual solution liquid mixture, which is originally one phase, is phase-separated;

Kosmotrope refers to substances that enhance the internal hydrogen bond network and/or intermolecular forces of water, and refers to water-soluble salts or sugars;

Kosmotrope can be directly added to the reaction system through its water and/or organic solvent solution; it can also be generated by reaction.

S3: This phase separation process produces nano-scale tiny droplets.

Preferably, the mixed solvent that is mutually miscible in any proportion in step S1 includes water-ethanol, water-n-propanol, water-isopropanol, water-tert-butanol, water-acetonitrile, water-dimethylformamide, Water-tetrahydrofuran, water-acetone or water-dimethyl sulfoxide.

Preferably, the kosmotrope compound in step S2 includes sodium citrate, sodium oxalate, ammonium citrate, ammonium oxalate, sodium phosphate, ammonium phosphate, sodium sulfate, ammonium sulfate, copper sulfate, sodium trimesate, glucose, sucrose or Sodium polyacrylate.

Preferably, in step S2, kosmotrope is generated by reaction, which can be neutralized by adding acid and alkali respectively to generate salt.

Preferably, a thickener can also be added in step S1 to suppress the fusion process of the tiny droplets and make them more uniform.

In order to solve the above technical problems, another technical solution proposed by the present invention is: a method based on the application of the method of claim 1, the method for reliably synthesizing nano/submicron droplets by inducing liquid-liquid phase separation is used for synthesizing hollow nanometers The hollow nanostructure is generated by in-situ micro-coating of the above-mentioned nano-scale tiny liquid; the in-situ micro-coating specifically refers to:

a. Introduce the raw materials required to react on the surface of the droplet to form a solid shell material;

b. The solid generated by the above-mentioned raw materials The solid shell generated by the shell of the material covers the droplets in situ to form a hollow nanostructure.

Preferably, the shell material and its corresponding raw materials in step a include silica-tetramethoxysilane, silica-tetraethoxysilane, silica-tetrabutoxysilane, polydopamine- Dopamine hydrochloride, polydopamine-dopamine oleate, calcium phosphate-calcium chloride, calcium phosphate-sodium phosphate, calcium phosphate-ammonium phosphate, organometallic framework HKUST-1- trimesic acid or organometallic framework HKUST-1 - Copper Oleate.

Preferably, the method for reliably synthesizing nano/submicron droplets by inducing liquid-liquid phase separation is used to synthesize nanoreactors or drug carriers: including

S1: Add the compound to be loaded into the liquid-liquid mixture; the so-called compound to be loaded is a compound with catalytic properties in the case of a nanoreactor; and a drug in the case of a drug carrier;

The addition of the compound to be loaded is divided into two situations:

a. Dissolve it in a homogeneous mixed solvent system before the reaction begins;

b. When the kosmotrope compound is introduced, it is dissolved together and added together;

S2: Generate tiny droplets containing the compound to be loaded inside;

S3: Micro-coating the above droplets to obtain hollow nanostructures, nanoreactors or drug carriers containing the compound to be loaded.

Preferably, it is characterized in that: the method for inducing liquid-liquid phase separation to reliably synthesize nano/submicron droplets is used for synthesizing nanoreactors and drug carriers, the loading process of the compound to be loaded, and the process of generating hollow nanostructures , is done synchronously in one reaction.

A method for the synthesis of nano/submicron droplets by controllably induced liquid-liquid phase separation. And based on it, a simple, fast, safe, low-energy-consumption method for the simultaneous synthesis of egg yolk-shell nanostructures, nanoreactors and drug carriers was developed. It includes the following steps:

S1: In a miscible homogeneous mixed solution, a compound with kosmotrope properties is introduced to induce phase separation.

The so-called homogeneous mixed solution that dissolves in each other refers to two solvents that are mutually soluble in any ratio. After mixing, only one liquid phase is obtained, and there is no phase-separated mixture. Including but not limited to water-ethanol, water-n-propanol, water-isopropanol, water-n-butanol, water-acetonitrile, water-dimethylformamide, water-tetrahydrofuran, water-acetone, water-dimethylformamide sulfoxide.

The so-called kosmotrope refers to substances that enhance the internal hydrogen bond network and/or intermolecular forces of water, mostly referring to salts, sugars, polyhydroxy polymers, etc. Including but not limited to sodium citrate, ammonium phosphate, glucose, sodium polyacrylate, etc.

The so-called introduction can be directly added to the reaction system through its water and/or organic solvent solution; it can also be realized by adding chemical raw materials that can generate kosmotrope, such as by adding citric acid and sodium hydroxide to neutralize the resulting Sodium citrate with kosmotrope properties.

S2: Generate nanoscale droplets.

S3: Introduce raw materials for reactions that generate solid shells on the droplet surface. The solid shell generated by the material encapsulates the droplets in situ, and hollow nanostructures can be obtained.

S4: If the compound to be loaded is added to the system, a nanoreactor or a drug carrier can be obtained.

The so-called compound to be loaded is a compound with catalytic properties in the case of a nanoreactor; and a drug in the case of a drug carrier.

The so-called addition can be dissolved in the homogeneous mixed solvent system before the reaction starts, or the kosmotrope compound can be dissolved and added together with it when the kosmotrope compound is introduced.

beneficial effect

Traditional methods have attempted to use two immiscible liquids to form a two-phase system, and then break up one of the liquid phases into small droplets. In microfluidics, it is realized by a valve-like method; in an emulsion system, it is realized by the input of mechanical forces such as stirring and ultrasound. The method involved in the present invention does the opposite, so that a system with only a single liquid phase is spontaneously transformed into a two-phase system, so that tiny droplets are formed from the bottom up.

The method can reliably synthesize nano/submicron-scale droplets through controllably induced liquid-liquid phase separation, and thereby efficiently synthesize hollow nanostructured nanoreactors and drug carriers.

In addition to salts, this method is a pioneering technique for inducing phase separation by sugars with excellent biocompatibility.

The synthesis of the above nanostructures by this method can realize the synthesis of the carrier and the loading of the catalytic substance/drug in one step, without the need to carry out separately. Compared with traditional methods, it is simpler, faster and faster.

The method can be realized at room temperature under normal pressure or at a lower temperature below 100 degrees Celsius, and is safer and energy-saving.

The loading process of this method no longer depends on the diffusion process. The load is larger and more uniform.

The method can be applied to a variety of different materials, such as silica, polydopamine, calcium phosphate, organometallic frameworks, and the like.

Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings.

Figure 1: Schematic illustration of controllable induced liquid-liquid phase separation to generate nano/submicron droplets

Figure 2: Dynamic Light Scattering Spectra of Nanoscale Droplets

Figure 3: Transmission electron microscopy images of the synthesis of hollow silica nanostructures by reaction to generate sodium citrate kosmotrope induced liquid-liquid phase separation.

Figure 4: Transmission electron microscope image of gold-loaded nanoreactor and energy dispersive X-ray spectrum of gold element

Figure 5: UV-Vis spectrum of the drug carrier loaded with doxorubicin, and a photo of the product accumulating in the bottom supernatant colorless after centrifugation

Figure 6: Transmission electron microscope image (A) and powder X-ray color image (B) of the copper-based organometallic framework material HKUST-1 hollow nanostructures

Figure 7: Transmission electron microscopy image of calcium phosphate hollow nanostructures

Figure 8: Transmission electron microscopy image of polydopamine hollow nanostructures

Figure 9: Transmission electron microscopy images of silica hollow nanostructures synthesized by water-acetonitrile (A), water-dimethyl amide (B) and water-tetrahydrofuran systems (C), scale bar 200 nm

Figure 10: Transmission electron microscopy images of glucose-induced water-ethanol phase separation to form nanodroplets and synthesis of hollow nanostructures

Figure 11: TEM image of hollow nanostructures formed by sodium citrate-induced water-ethanol phase separation without thickener

Detailed ways

Example 1

Controllable induced liquid-liquid phase separation to generate nano/submicron micro droplets:

In 95 mL of ethanol solution dissolved with 5 mM citric acid and 1% by mass of hydroxypropyl cellulose (HPC) thickener, add 5 mL of deionized water, then under vigorous stirring, add 5 mL of 0.36 M sodium hydroxide ( NaOH) in ethanol. The dynamic light scattering pattern of the product shows that the droplets are in nano/submicron size with a narrow size distribution. as shown in picture 2.

Example 2

The reaction generates sodium citrate kosmotrope to induce liquid-liquid phase separation to synthesize hollow silica nanostructures:

In 95mL of ethanol solution dissolved with 5mM citric acid and 1% by mass of hydroxypropylcellulose (HPC), 5mL of deionized water was added, and then under vigorous stirring, 5mL of 0.36M sodium hydroxide (NaOH) was added weak. Then 0.6 mL of tetramethoxysilane (TEOS) was added. Then let stand for 6 hours. The product was washed several times with absolute ethanol and deionized water to obtain hollow silica nanostructures. As shown in Figure 3, the hollow silica nanoarchitecture has good uniformity.

Example 3

Synthesis of gold-loaded nanoreactors:

This example belongs to the case where the compound to be loaded is dissolved in a homogeneous mixed solvent. In 100 mL of ethanol solution dissolved in 10 mM citric acid, 10 mg/mL chloroauric acid, and 75 mg/mL polyvinylpyrrolidone (PVP) thickener, add 5 mL of deionized water, and then, under vigorous stirring, add 5 mL of approximately 5 M ammonia water . Then, 0.3 mL of TEOS was added, and the reaction was allowed to stand for 10 h. The product was washed several times with absolute ethanol and deionized water to obtain a gold-loaded nanoreactor. As shown in Figure 4, the loading of the gold nanoreactor is very large, and a large amount of gold element signal can be clearly seen.

Example 4

Synthesis of Drug Carrier Loaded with Doxorubicin

This example belongs to the case where the compound to be loaded is added together with the kosmotrope dissolved together. In 100 mL of ethanol solution with 5 mM citric acid and 1% by mass HPC thickener dissolved, under vigorous stirring, 50 μL of about 5 M ammonia water dissolved with 0.8 mM doxorubicin was added. Then 0.15 mL of tetramethoxysilane (TEOS) was added. The reaction was allowed to stand for 10h. The product is washed several times with absolute ethanol to obtain nanometer hollow mesoporous silica loaded with doxorubicin. As shown in Figure 5, the UV-Vis spectrum showed the characteristic absorption of doxorubicin; after centrifugation, the product was aggregated in the bottom supernatant and the colorless photo showed that doxorubicin has been loaded on the drug carrier, rather than free in solution middle.

Example 5

Synthesis of Copper-Based Organometallic Framework Material HKUST-1 Hollow Nanostructures

In 100 mL of ethanol solution dissolved with 1% HPC by mass, 15 mL of 120 mM copper sulfate aqueous solution was added under vigorous stirring, and then 1 mL of 80 mM trimesic acid ethanol solution was added. The reaction system was sealed and heated to 65 degrees Celsius for 20 minutes. The product was washed several times with absolute ethanol and deionized water to obtain hollow nanoparticles of organometallic framework HKUST-1 material. As shown in Figure 6, the X-ray diffraction pattern proved that it was indeed HKUST-1.

Example 6

Synthesis of Calcium Phosphate Hollow Nanostructures

To 100 mL of an ethanol solution in which 10 mM phosphoric acid and 75 mg/mL polyvinylpyrrolidone (PVP) thickener were dissolved, 5 mL of approximately 5 M ammonia was added with vigorous stirring. Then, 5 mL of 1M calcium chloride solution in ethanol was added, and the reaction was allowed to stand for 30 minutes. The product is washed several times with absolute ethanol and deionized water to obtain calcium phosphate hollow nanoparticles. As shown in Figure 7.

Example 7

Synthesis of Polydopamine Hollow Nanostructures

In 95 mL of ethanol solution dissolved with 10 mM citric acid, 2 mg/mL dopamine hydrochloride and 1% by mass HPC, 5 mL of deionized water was added, and then under vigorous stirring, 5 mL of about 5 M ammonia water was added. Then let stand for 12h. The product was washed several times with absolute ethanol and deionized water to obtain polydopamine hollow nanoparticles. As shown in Figure 8.

Example 8

Silica hollow nanostructures synthesized by water-acetonitrile, water-dimethyl amide and water-tetrahydrofuran systems:

This example demonstrates that controllable induced liquid-liquid phase separation can be applied in a wider range of homogeneous mixed solvent systems. In 95mL of acetonitrile, dimethylformamide and tetrahydrofuran solution dissolved with 5mM citric acid and 1% by mass of hydroxypropyl cellulose (HPC), 10mL of deionized water were added, and then 5mL were added under vigorous stirring. 2M ammonia in ethanol. Then 0.15 mL of tetramethoxysilane (TEOS) was added separately. The reaction was allowed to stand for 10h. The products were washed several times with absolute ethanol and deionized water, respectively, to obtain the respective silica hollow nanostructures. As shown in Figure 9.

Example 9

Glucose-induced water-ethanol phase separation to generate nanodroplets and synthesis of hollow nanostructures

In an ice-water bath, 100 mL of an ethanol solution containing 3 mM sodium hydroxide and 1% mass percent hydroxypropyl cellulose (HPC) was dissolved. 7.4 mL of an aqueous solution of 2M glucose dissolved was added with vigorous stirring. Then 0.6 mL of tetramethoxysilane (TEOS) was added. Then, the reaction was allowed to stand for 6 h in an ice-water bath. The product was washed several times with absolute ethanol and deionized water to obtain hollow silica nanostructures. As shown in Figure 10.

Example 10

Sodium citrate induced water-ethanol phase separation without thickener to generate hollow nanostructures

In 95 mL of 5 mM citric acid and 1% ethanol solution, 5 mL of deionized water was added, followed by 5 mL of 0.36 M sodium hydroxide (NaOH) solution in ethanol with vigorous stirring. Then 0.6 mL of tetramethoxysilane (TEOS) was added. Then let stand for 6 hours. The product was washed several times with absolute ethanol and deionized water to obtain hollow silica nanostructures. As shown in Figure 11, it can be seen that the hollow nanostructures have irregular shapes, demonstrating the process of droplet fusion. It can be seen that tiny droplets can be generated in the absence of thickeners and used to synthesize hollow nanostructures, but thickeners do improve product homogeneity.

The present invention is not limited to the specific technical solutions described in the above embodiments, and all technical solutions formed by using equivalent replacements are within the protection scope of the present invention.

Claims (9)

1. A method for reliably synthesizing nano/submicron droplets by inducing liquid-liquid phase separation, characterized by comprising the steps of:

s1: the original system is a homogeneous mixed solvent system of mutually soluble water and an organic solvent, in particular to a mixture which only has one liquid phase and does not have split phase and is obtained by mixing two solvents which can be mutually soluble in any proportion;

s2: introducing a kosmotrope compound to enable the miscible liquid mixture which is originally one phase to be subjected to phase separation;

the kosmotrope refers to a substance which can enhance hydrogen bond network and/or intermolecular force in water, and refers to water-soluble salts or saccharides;

the kosmotrope can be directly added into a reaction system through a solution of water and/or an organic solvent; or may be produced by reaction;

s3: the phase separation process generates nano-sized fine droplets.

2. The method for reliably synthesizing nano/submicron droplets by inducing liquid-liquid phase separation according to claim 1, wherein the mixed solvent miscible at any ratio in step S1 comprises water-ethanol, water-n-propanol, water-isopropanol, water-tert-butanol, water-acetonitrile, water-dimethylformamide, water-tetrahydrofuran, water-acetone, or water-dimethylsulfoxide.

3. The method for reliably synthesizing nano/submicron liquid droplets by inducing liquid-liquid phase separation according to claim 1, wherein said kosmotrope compound in step S2 comprises sodium citrate, sodium oxalate, ammonium citrate, ammonium oxalate, sodium phosphate, ammonium phosphate, sodium sulfate, ammonium sulfate, copper sulfate, sodium trimesate, glucose, sucrose, or sodium polyacrylate.

4. The method for reliably synthesizing nano/submicron droplets by inducing liquid-liquid phase separation according to claim 1, wherein the kosmotrope is generated by reaction in step S2, and the salt is generated by neutralization by adding acid and alkali, respectively.

5. The method for the reliable synthesis of nano/submicron droplets by inducing liquid-liquid phase separation according to claim 1, characterized in that: the merging process of the fine droplets may also be suppressed to be more uniform by adding a thickener in step S1.

6. An application based on the method of claim 1, characterized in that: the method for reliably synthesizing nano/submicron droplets by inducing liquid-liquid phase separation is used for synthesizing hollow nanostructures, and the hollow nanostructures are generated by realizing in-situ micro-coating on the nanoscale micro liquid; the in situ micro-coating specifically refers to:

a. introducing raw materials which can react on the surface of the liquid drop to generate a solid shell material;

b. the liquid drops are coated in situ by the solid material shell generated by the raw materials to form the hollow nano structure.

7. Use of the method according to claim 6, characterized in that: the shell material in the step a and the raw materials corresponding to the shell material comprise silicon dioxide-tetramethoxysilane, silicon dioxide-tetraethoxysilane, silicon dioxide-tetrabutoxysilane, polydopamine-dopamine hydrochloride, polydopamine-dopamine oleate, calcium phosphate-calcium chloride, calcium phosphate-sodium phosphate, calcium phosphate-ammonium phosphate, organic metal framework HKUST-1-trimesic acid or organic metal framework HKUST-1-copper oleate.

8. Use of the method according to claim 6, characterized in that: the method for reliably synthesizing nano/submicron droplets by inducing liquid-liquid phase separation for synthesizing a nano reactor or a drug carrier comprises the following steps:

s1: adding the compound to be supported to the liquid-liquid mixture; the compound to be supported is a compound having catalytic properties in the case of a nanoreactor; and in the case of a drug carrier, a drug;

the addition of the compound to be loaded is divided into two cases:

a. dissolving the mixture in a homogeneous mixed solvent system before the reaction;

b. when the kosmotrope compound is introduced, the kosmotrope compound is added together with the kosmotrope compound dissolved in the kosmotrope compound;

s2: generating micro liquid drops containing the compound to be loaded inside;

s3: and micro-coating the liquid drops to obtain a hollow nano structure containing a compound to be loaded, a nano reactor or a drug carrier.

9. Use of the method according to any of claims 6-8, characterized in that: the method for reliably synthesizing nano/submicron droplets by inducing liquid-liquid phase separation is used for synthesizing a nano reactor and a drug carrier, and the process of loading a compound to be loaded and the process of generating a hollow nano structure are synchronously completed in one reaction.

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