CN114016139B

CN114016139B - Preparation method of nanocrystalline material

Info

Publication number: CN114016139B
Application number: CN202111319566.7A
Authority: CN
Inventors: 杜艳秋; 李海东; 程凤梅; 侯玥同; 祝慧
Original assignee: Jiaxing University
Current assignee: Jiaxing University
Priority date: 2021-11-09
Filing date: 2021-11-09
Publication date: 2022-07-29
Anticipated expiration: 2041-11-09
Also published as: CN114016139A

Abstract

The invention provides a preparation method of a nanocrystalline superlattice material with simple method and stable structure by combining an annular polymer brush and a water-n-butyl alcohol reverse emulsion technology. The nano-sized super-crystal material is obtained by adding a double-hydrophobic polyethylene glycol aqueous solution into a citrate modified gold nanosphere aqueous solution, mixing, and then carrying out a series of subsequent treatment steps. The invention obviously improves the structural stability of the super crystal by utilizing the physical entanglement of the annular polymer brush on the surface of the construction unit; by simply regulating and controlling the volume ratio of the gold nanosphere aqueous solution to the n-butyl alcohol, stable super-crystal materials with different morphological structures can be obtained.

Description

Preparation method of nanocrystalline superlattice material

Technical Field

The invention relates to the technical field of nano materials, in particular to a preparation method of a nanocrystalline superlattice material.

Background

The nanocrystalline super crystal is a superstructure which is spontaneously assembled by taking nanocrystals as building units and is arranged periodically. The unique periodic structure not only has the inherent quantum effect of the nano crystal, but also shows unique optical, electrical and magnetic properties, has wide application prospect in the fields of electronic devices, photoelectric materials, energy storage and the like, and becomes a new material which is concerned. Currently, the major methods for preparing three-dimensional nanocrystals include solvent evaporation and DNA-mediated crystallization, and by precisely controlling the size, shape and composition of individual nanocrystals, a wide variety of single-component or multi-component nanocrystal materials have been successfully prepared. For example, CN104404624A discloses a controllable preparation method of three-dimensional nanoplasmonic nanocrystals, i.e. a metal nanomaterial solution is dripped on the surface of a substrate, and the three-dimensional nanoplasmonic nanocrystal material is finally obtained by volatilizing the solvent for 15-30 hours. CN113417009A discloses a method for guiding nanoparticle supercrystals based on DNA origami and DNA tiling.

Although solvent evaporation and DNA-mediated methods have been successful in producing a variety of superlattice materials, these conventional methods have certain problems. For example, slow solvent evaporation of nanocrystal solutions is a key factor in the preparation of nanocrystals, and thus solvent evaporation methods often take hours or even days to obtain the desired nanocrystals. The DNA-mediated approach has greatly limited its practical application due to its high cost of DNA synthesis. In addition, the two assembling methods are driven by weak interaction between nanocrystalline building units to spontaneously form regular and ordered crystal structures. However, the weak interaction force of the building units often leads to poor structural stability of the superlattice, and the practical application of the superlattice is severely limited.

The annular polymer brush can greatly enrich the physicochemical properties of the surface/interface of the material and has developed into an effective means for regulating the micro-nano structure and properties of the surface of the material. However, there are no relevant literature and patent reports on the use of cyclic polymer brushes to produce structurally stable nanocrystals.

Therefore, how to develop a novel superlattice with simple process flow and stable structure to push the material to the key point of practical application has great scientific significance and application value.

Disclosure of Invention

In view of the above, the invention provides a method for preparing a nanocrystalline superlattice material with a simple method and a stable structure by combining a cyclic polymer brush and a water-n-butanol reverse emulsion technology.

In order to achieve the purpose, the invention adopts the following technical scheme:

a method for preparing a nanocrystalline superlattice material comprises the following steps:

(1) adding a double-hydrophobic polyethylene glycol (SH-PEG-SH) aqueous solution into a citrate modified gold nanosphere (AuNPs) aqueous solution, uniformly mixing, and reacting at 25 ℃ for 24 hours to obtain a mixed solution;

(2) washing the mixed solution to remove unreacted polyethylene glycol, then dispersing in water again to prepare a polyethylene glycol functionalized gold nanosphere (PEGylated AuNPs) aqueous solution with the concentration of 40-80nM for later use;

(3) placing the polyethylene glycol functionalized gold nanosphere aqueous solution into a container, adding an n-butyl alcohol solution, and performing ultrasonic treatment to obtain a black superlattice;

(4) and taking out the residual solution in the container, adding ether, and then airing at room temperature to obtain the nano-nanocrystal material.

Preferably, the concentration of the amphiphobic polyethylene glycol aqueous solution in the step (1) is 1 mM; the concentration of the citrate modified gold nanosphere aqueous solution is 1.2 nM.

The beneficial effects brought by the optimization are as follows: the gold nanosphere solution has low concentration and reacts with the dimercapto polyethylene glycol solution, thereby ensuring that an annular polymer brush is formed on the surface of the gold nanosphere

Preferably, the molecular weight of the amphiphobic polyethylene glycol in the step (1) is 1000-10000; the diameter of the gold nanosphere is 5-30 nm.

Preferably, the molar ratio of the amphiphobic polyethylene glycol to the citrate modified gold nanospheres in the step (1) is 5000: 1.

The above molar ratio is adopted to ensure that the surface of the nanogold forms the annular polymer brush with high grafting density.

Preferably, the washing in step (2) is 3 times by using deionized water.

Preferably, the volume ratio of the polyethylene glycol functionalized gold nanosphere aqueous solution to the n-butanol solution in the step (3) is 1 (4-8).

In the technical scheme, the super-crystals with different morphological structures can be obtained by regulating the volume ratio of the two.

Preferably, the ultrasonic treatment time in the step (3) is 10s, and the ultrasonic frequency is 25 kHz.

Preferably, the amount of diethyl ether added in step (4) is 50. mu.L.

Through the technical scheme, compared with the prior art, the invention has the following beneficial effects:

(1) The existing method for preparing the super crystal has complex process and long sample preparation period, and usually needs several hours or even several days; the cyclic polymer brush and the water-n-butyl alcohol reverse emulsion technology are used for preparing the super-crystal material, the experimental preparation process is simple, the sample preparation period is short, and the whole process only needs a few minutes;

(2) in the prior art, the superlattice material is mostly prepared by self-assembly of weak interaction force of a building unit, but the structural stability of the superlattice is poor. The invention obviously improves the structural stability of the super crystal by utilizing the physical entanglement of the annular polymer brush on the surface of the construction unit; by simply regulating and controlling the volume ratio of the gold nanosphere aqueous solution to the n-butyl alcohol, stable super-crystal materials with different morphological structures can be obtained.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.

FIG. 1 is a flow chart of the preparation method of the present invention;

FIG. 2 is a topological structure representation of a gold nanosphere surface cyclic polymer. Wherein, (a) is the dynamic light scattering result of the AuNPs and PEGylated AuNPs samples; (b) the S2p element core spectrum of the PEGylated AuNPs sample;

FIG. 3 is a representation of the stability of the superlattice structure. Wherein (a) is an SEM image of the structure of the assembly without freezing with diethyl ether; (b) shows SAXS diagram of the assembly structure without ether freezing; (c) is SEM image of the super crystal after ether freezing; (d) a super crystalline SAXS pattern after ether freezing;

fig. 4 shows a superlattice with different morphologies. Wherein, (a) is a scanning electron microscope image of a 40nM PEGylated AuNPs concentration super crystal; (b) scanning electron microscope images of 60nM PEGylated AuNPs; (c) scanning electron microscope images of the PEGylated AuNPs with the concentration of 80 nM; (d) scanning electron microscope images of the 80nM PEGylated AuNPs concentration.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

First, dimercapto-modified polyethylene glycol (molecular weight: 10000) powder was dissolved in deionized water to prepare an aqueous solution having a concentration of 1 mM. Then adding the mixture into an AuNPs aqueous solution modified by citrate with the diameter of 20nm according to the molar ratio of 5000:1 (SH-PEG-SH/AuNPs), carrying out vortex oscillation mixing, and reacting for 24 hours at the temperature of 25 ℃. To remove unreacted polyethylene glycol molecules, deionized water was centrifuged three times and redispersed in water for further use.

And (4) analyzing results:

firstly, the hydrodynamic radius before and after grafting gold nanoparticles to polyethylene glycol is characterized by using a dynamic light scattering method, as shown in fig. 2 a. The hydrodynamic radius of the unmodified gold nanoparticles is 25.0 nm. After the annular polyethylene glycol molecular brush is successfully grafted through an Au-S bond, the hydrodynamic radius is increased to about 65 nm. In addition, the core spectrum analysis of the S2p element was performed on the sample surface using X-ray photoelectron spectroscopy (XPS), and the result is shown in FIG. 2 b. An Au-S (161.5 eV) characteristic peak appears in an S2p core spectrogram, and a free sulfydryl-SH signal is not detected, so that the polyethylene glycol molecular chain is successfully grafted to the surface of the gold nano particle, and a cyclic polymer brush is formed.

Example 2:

first, dimercapto-modified polyethylene glycol (molecular weight: 10000) powder was dissolved in deionized water to prepare an aqueous solution having a concentration of 1 mM. Then adding the mixture into an AuNPs aqueous solution modified by citrate with the diameter of 20nm according to the molar ratio of 5000:1 (SH-PEG-SH/AuNPs), carrying out vortex oscillation mixing, and reacting for 24 hours at the temperature of 25 ℃. To remove unreacted polyethylene glycol molecules, deionized water was centrifuged three times to prepare an aqueous solution of 80 nM PEGylated AuNPs. The method adopts water-n-butyl alcohol reverse emulsion technology to self-assemble the super crystal, namely a liquid transfer gun is used for taking 20 mu L of PEGylated AuNPs solution into a 1ml glass bottle, then 120 mu L of n-butyl alcohol solution is added into the glass bottle, ultrasonic treatment is carried out for 10s, and a large amount of super crystal materials can be collected at the bottom of the glass bottle after natural standing. And finally, completely removing the n-butanol solution, carefully adding 50 mu L of ether solution to freeze the structure, and naturally airing to obtain the super-crystal material with stable structure.

And (4) analyzing results:

the water-n-butyl alcohol reverse emulsion template technology is adopted to prepare the super-crystal material. For a water-n-butanol system, before the water phase is ultrasonically emulsified, a clear phase interface exists between the PEGylated AuNPs aqueous solution and the n-butanol, and the water phase cannot spontaneously diffuse into the n-butanol phase; after the ultrasonic emulsification, the aqueous phase containing the PEGylated AuNPs forms micro-droplets in the n-butanol phase, and then the water in the aqueous phase rapidly and spontaneously diffuses into the n-butanol phase, so that the self-assembly of the nano-particles in the water can be carried out to form the super-crystals. The superlattice morphology structure and the internal ordered structure were characterized using scanning electron microscopy and SAXS, respectively, as shown in fig. 3a and 3 b. As a result, the structural stability of the super crystal is poor, and the morphology structure and the internal ordered structure of the super crystal are destroyed in the drying process. This is because n-butanol is a good solvent for polyethylene glycol, and the annular polymer brush on the surface of the adjacent nanoparticles is in a stretched state, and cannot lock the ordered structure of the nanocrystals by mutual entanglement. To prepare structurally stable nanocrystals, we further frozen the nanocrystals obtained by the water-n-butanol reverse emulsion method using the poor solvent of polyethylene glycol, diethyl ether. Then, the morphology structure of the frozen super crystal is characterized by using a scanning electron microscope, as shown in fig. 3 c. It was found that after freezing treatment, a structurally stable micrometer-sized three-dimensional superlattice was obtained, and the SAXS result indicated that the superlattice was able to maintain its internal ordered structure during drying (fig. 3 d), mainly because the cyclic polymer brush on the nanoparticle surface would collapse molecular chains in ethanol solution, and further lock the internal structure of the superlattice through mutual entanglement between the cyclic molecular chains. The above results demonstrate that structurally stable nanocrystalline materials can be rapidly prepared within minutes in combination with a water-n-butanol reverse emulsion template and freezing techniques.

Example 3:

first, a dimercapto-modified polyethylene glycol (molecular weight 10000) powder was dissolved in deionized water to prepare an aqueous solution having a concentration of 1 mM. Then adding the mixture into an AuNPs aqueous solution modified by citrate with the diameter of 20nm according to the molar ratio of 5000:1 (SH-PEG-SH/AuNPs), carrying out vortex oscillation mixing, and reacting for 24 hours at the temperature of 25 ℃. To remove unreacted polyethylene glycol molecules, deionized water was centrifuged three times to prepare aqueous solutions of PEGylated AuNPs at concentrations of 40, 60, 80, and 100nM, respectively. The method comprises the steps of adopting a water-n-butyl alcohol reverse emulsion technology to self-assemble the super-crystal, namely taking 20 mu L of PEGylated AuNPs solution with different concentrations in a 1ml glass bottle by using a liquid transfer gun, then adding 120 mu L of n-butyl alcohol solution into the glass bottle, carrying out ultrasonic treatment for 10s, and collecting a large amount of super-crystal materials at the bottom of the glass bottle after naturally standing. And finally, completely removing the n-butyl alcohol solution, carefully adding 50 mu L of ether solution to freeze the structure, and naturally airing to obtain the super-crystal materials with different morphological structures.

And (4) analyzing results:

the concentration of the PEGylated AuNPs solution is adjusted to prepare the super-crystal materials with different shapes. Scanning electron microscope results show that when the concentration of the PEGylated AuNPs solution is 40 nM, the lamellar super crystal with stable structure can be prepared by using the water-n-butanol reverse emulsion method, as shown in FIG. 4 a. Through an aqueous solution. When the concentration of PEGylated AuNPs solution is 60 nM, a disk-shaped superlattice with a certain thickness can be obtained, as shown in FIG. 4 b. The concentration of PEGylated AuNPs is continuously increased to 100nM, and finally the spherical three-dimensional super-crystal material is obtained. According to the experimental results, the nanocrystalline materials with different morphological structures can be prepared according to the actual application requirements by simply regulating and controlling the concentration of the nanoparticles.

In the present specification, the embodiments are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. The device disclosed in the embodiment corresponds to the method disclosed in the embodiment, so that the description is simple, and the relevant points can be referred to the description of the method part.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a nanocrystalline superlattice material is characterized by comprising the following steps:

(1) adding a double-mercapto polyethylene glycol aqueous solution into a citrate modified gold nanosphere aqueous solution, uniformly mixing, and reacting at 25 ℃ for 24 hours to obtain a mixed solution;

(2) Washing the mixed solution to remove unreacted polyethylene glycol, and then dispersing in water again to prepare a polyethylene glycol functionalized gold nanosphere water solution with the concentration of 40-80nM for later use;

(3) placing the polyethylene glycol functionalized gold nanosphere aqueous solution into a container, then adding a 99% pure n-butyl alcohol solution, and performing ultrasonic treatment to obtain a black superlattice;

(4) and taking out the residual solution in the container, adding ether, and then airing at room temperature to obtain the nanocrystalline superlattice material.

2. The method for preparing a nanocrystal super crystal material as claimed in claim 1, wherein the concentration of the amphiphobic polyethylene glycol aqueous solution in the step (1) is 1 mM; the concentration of the citrate modified gold nanosphere aqueous solution is 1.2 nM.

3. The method as claimed in claim 1, wherein the molecular weight of the amphiphobic polyethylene glycol in step (1) is 1000-10000; the diameter of the gold nanosphere is 5-30 nm.

4. The method for preparing a nanocrystalline material according to claim 1, wherein the molar ratio of the amphiphobic polyethylene glycol to the citrate-modified gold nanospheres in step (1) is 5000: 1.

5. The method for preparing a nanocrystal super crystal material as claimed in claim 1, wherein the washing in step (2) is 3 times of washing with deionized water.

6. The method for preparing a nanocrystalline superlattice material according to claim 1, wherein the volume ratio of the polyethylene glycol functionalized gold nanosphere aqueous solution to the n-butanol solution in the step (3) is 1 (4-8).

7. The method for preparing a nanocrystalline material according to claim 1, wherein in step (3), the ultrasonic treatment time is 10s, and the ultrasonic frequency is 25 kHz.

8. The method according to claim 1, wherein the amount of diethyl ether added in step (4) is 50 μ L.