CN111253593A

CN111253593A - Method for assembling periodic nano structure on plane or curved surface by using soft matter interface

Info

Publication number: CN111253593A
Application number: CN202010175538.1A
Authority: CN
Inventors: 段忆翔; 吴孟璠
Original assignee: Sichuan University
Current assignee: Sichuan University
Priority date: 2020-03-13
Filing date: 2020-03-13
Publication date: 2020-06-09
Anticipated expiration: 2040-03-13
Also published as: CN111253593B

Abstract

The invention discloses a method for assembling periodic nano-structure on a plane or a curved surface by using a soft matter interface, which comprises the following steps: 1) preparing a gel aqueous solution with a proper concentration by using water or a water/PEG mixed solution as a solvent, and then carrying out ultrasonic treatment until a gel monomer is completely dissolved; 2) heating the obtained product in the step 1) to boiling, cooling to a semi-solid state, pouring the product on a target surface, removing bubbles and flattening the surface; 3) slowly cooling the system in the step 2) at room temperature until the hydrogel is completely solidified, and purging with clean air until no obvious water drop trace exists on the surface of the hydrogel; 4) then cutting off irregular hydrogel, and dropwise adding a proper amount of microsphere colloid suspension on the surface of the hydrogel; 5) drying the product obtained in the step 4) in an environment with the temperature of 30-90 ℃; the rapid and low-cost preparation of the large-area periodic nano-structure material with high reflectivity and absorption and reflection capacity is realized.

Description

Method for assembling periodic nano structure on plane or curved surface by using soft matter interface

Technical Field

The invention relates to the technical field of nano material preparation, in particular to a method for assembling a periodic nano structure on a plane or a curved surface by using a soft matter interface.

Background

Photonic Crystals (PCs) are a typical widely studied periodic nanostructured material with a variety of specific optical properties, including Photonic Band Gap (PBG), photon localization, low photon effects, and fluorescence enhancement effects. Based on the unique optical characteristics, PCs have great application potential in the fields of photonic devices, nanomaterials, solar cells, chemical and biological sensing and the like.

In recent years, various methods for preparing photonic crystal materials have been reported, and these methods can be classified into two types. The first approach is a top-down fabrication strategy, including photolithography, which requires cumbersome operations and expensive large-scale equipment, such as photolithography machines and vapor deposition instruments. The other preparation method is from bottom to top, adopts the self-assembly of the colloidal nano particles, and is widely applied due to low cost and no need of large-scale instruments. The existing self-assembly method of colloidal nanoparticles comprises a precipitation method, a vertical deposition method, a dipping deposition method, a spin coating method, a shear induction method and a Langmuir-Blodgett method, but the defects of time consumption, material waste, incapability of forming large-area photonic crystals with high optical performance and the like cannot be completely overcome. Although several methods of fabricating large scale photonic crystals have been explored, it should be recognized that rapid fabrication of large scale photonic crystals, high optical performance of three-dimensional PCs at planar or curved interfaces remains a challenge.

The hydrogel is an important soft substance and is widely applied to the fields of biochemical sensing, chemical separation, biomedical materials, drug delivery systems and the like. However, as a special interface with solid-liquid interface characteristics, the hydrogel interface has very few applications in the field of material science. The hydrogel interface provides an assembly environment similar to the surface of a liquid, which not only provides moderate surface tension for uniform diffusion of colloidal particle suspensions on a large scale, but also balances several non-covalent interactions and solvation effects during nanoparticle self-assembly. In addition, the semi-solid state of the hydrogel can maintain the crystalline state of the photonic crystal. On the basis, the hydrogel can be used as a novel nano colloid self-assembly platform and has excellent performance.

Disclosure of Invention

The invention aims to provide a method for assembling a periodic nano structure on a plane or a curved surface by using a soft matter interface, and the method realizes the quick and low-cost preparation of a large-area periodic nano structure material with high reflectivity and absorption and reflection capacity.

The invention is realized by the following technical scheme: a method for assembling periodic nanostructures on a plane or a curved surface by using a soft matter interface comprises the following steps:

1) preparing a 0.2-2% gel aqueous solution (preferably 1% gel aqueous solution) by using water or a water/PEG mixed solution as a solvent, and then carrying out ultrasonic treatment until a gel monomer is completely dissolved; wherein, water is used as a solvent in order to match the polarity, ionic strength and the like of the solvent in the microsphere colloid suspension; the solid gel monomer can be quickly dissolved into water by adopting ultrasonic treatment;

2) heating the obtained product in the step 1) to boiling, slowly cooling to a semi-solid state, pouring the product on a target surface (a flat or curved surface), and removing bubbles and a flat surface (namely, moderately shaking the product until the surface is flat and removing bubbles in the liquid); the shaking mode is adopted until the surface is smooth and bubbles in the liquid are removed so as to provide a regular area for the self-assembly of the microspheres on the soft matter interface;

3) slowly cooling the system in the step 2) at room temperature until the hydrogel is completely solidified, and slightly purging by using clean air until no obvious water drop trace exists on the surface of the hydrogel; the water drops on the surface of the hydrogel are removed by using clean air so as to avoid the influence of the water drops on a microsphere colloidal suspension system (microsphere colloidal suspension);

4) then cutting off irregular hydrogel, and dropwise adding a proper amount of microsphere colloidal suspension (only enough for completely covering the size of a target area) on the surface of the hydrogel (taking special care not to damage the surface of the gel during dropwise adding); the purpose of cutting off irregular hydrogel is to provide a relatively regular plane and use the surface tension of the microsphere colloidal suspension to control the dispersion area of the microsphere colloidal suspension so as to achieve the purpose of controlling the assembly thickness of the microspheres;

5) drying the product obtained in the step 4) in an environment with the temperature of 30-90 ℃ under the condition of avoiding external force influences such as air disturbance, vibration and the like; wherein, the air disturbance, vibration and other operations are avoided to avoid the influence of external force in the drying self-assembly process of the microsphere colloid suspension.

In order to further realize the invention, the following arrangement mode is adopted: the water/PEG mixed solution is obtained by mixing water and PEG and fully stirring.

In order to further realize the invention, the following arrangement mode is adopted: the molecular weight range of the PEG is 100-1000.

In order to further realize the invention, the following arrangement mode is adopted: the molecular weight selected for the PEG is 200.

In order to further realize the invention, the following arrangement mode is adopted: the gel is agarose gel, chitosan gel or hyaluronic acid gel.

In order to further realize the invention, the following arrangement mode is adopted: the concentration range of the gel aqueous solution finally obtained in the step 1) is 0.2-2%.

In order to further realize the invention, the following arrangement mode is adopted: the concentration of the gel aqueous solution finally obtained in the step 1) is 1%.

In order to further realize the invention, the following arrangement mode is adopted: in the step 2), surface leveling is performed in a shaking mode.

In order to further realize the invention, the following arrangement mode is adopted: the material of the microsphere is Polystyrene (PS), silicon dioxide, titanium dioxide, polymethyl methacrylate, poly (N-isopropyl acrylamide), metal or the like.

In order to further realize the invention, the following arrangement mode is adopted: in the step 5), the temperature environment for drying is 70 ℃.

The invention provides a surface assembly environment between solid and liquid by using a hydrogel interface, on one hand, the semi-liquid interface property of the interface firstly provides medium surface tension for uniform diffusion of microsphere colloid suspension on a large scale, and also balances several non-covalent interactions and solvation effects in the self-assembly process of the nano microspheres. On the other hand, the semi-solid interface property of the hydrogel interface can maintain the crystal state of the photonic crystal. Therefore, the microspheres in the microsphere colloid suspension can be orderly arranged in a large scale in multiple layers, and a large-area periodic nano-structure material with high reflectivity and absorption and reflection capacity is obtained.

Compared with the prior art, the invention has the following advantages and beneficial effects:

the soft matter interface assembly method is very quick, and experiments show that only 20 minutes are needed from interface preparation to microsphere assembly completion.

The soft matter interface assembling method is suitable for flat and curved interfaces and has wide application range.

The soft matter interface assembling method is suitable for preparing large-area periodic nano structures in the square decimeter level. And does not depend on large-scale equipment, and is simple and convenient to operate.

The periodic nano structure prepared by the invention has extremely high reflection and absorption capacity to light in a specific wavelength region.

The PEG-agarose gel preparation method and the soft matter interface assembly method can keep the gel state of the periodic nanostructure for a long time after being combined, and two stable periodic nanostructures with different PBGs can be obtained by only using microspheres with one particle size.

Drawings

FIG. 1 is a picture of periodic nanostructures fabricated on flat and curved surfaces using soft material interface assembly;

the reference numbers in fig. 1 are: 1-36cm²Large area periodic nanostructure, 2-periodic nanostructure prepared on the curved surface of glass, 3-periodic nano junctionAnd (5) forming a scanning electron microscope picture.

Fig. 2 is a flow chart of the method of the present invention.

Fig. 3 is a reflectance spectrum (100% with a high reflectance aluminum mirror) of a periodic nanostructure prepared using this method.

Fig. 4 is a transmission spectrum of a periodic nanostructure prepared using this method in a hydrogel state (the inset is a partial magnified view).

Fig. 5 is a transmission spectrum of a periodic nanostructure prepared using this method in a dry state (the inset is a partial magnified view).

FIG. 6 is photographs taken at different angles in the sun of periodic nanostructures (agarose gel state) prepared using microsphere colloidal suspensions of different particle sizes.

FIG. 7 is a graph of the change in reflectance spectra of periodic nanostructures (agarose gel state) prepared using a 253nm particle size colloidal suspension of microspheres at different angles of incident light.

FIG. 8 is a graph of the change in the position of the reflection peak with time at room temperature for periodic nanostructures (agarose gel state) prepared using a colloidal suspension of microspheres of 212nm particle size.

FIG. 9 is a graph of the reflection peak position over time at room temperature for periodic nanostructures (PEG-Sepharose phase) prepared using a colloidal suspension of microspheres of 212nm particle size.

FIG. 10 is a reflectance spectroscopy system (100% with a high reflectance aluminum mirror); FIG. 10 is a graph labeled 1-normal incidence and 2-measurement of reflection spectra of incident light at different angles.

Detailed Description

The following examples are given to illustrate the present invention and it is necessary to point out here that the following examples are given only for the purpose of further illustration and are not to be construed as limiting the scope of the invention, which is susceptible to numerous insubstantial modifications and adaptations by those skilled in the art in light of the present disclosure.

Example 1:

a method for assembling periodic nanostructures on a plane or a curved surface by using a soft matter interface realizes the rapid and low-cost preparation of large-area periodic nanostructure materials with high reflectivity and absorption and reflection capacity, and comprises the following steps:

1) preparing a gel aqueous solution with a proper concentration (0.2-2% concentration, preferably 1% concentration) by using water or a water/PEG mixed solution as a solvent, and then carrying out ultrasonic treatment until a gel monomer (such as agarose) is completely dissolved; wherein, water is used as a solvent in order to match the polarity, ionic strength and the like of the solvent in the assembled microsphere colloid suspension; the solid gel monomer (such as agarose) can be completely dissolved into water by ultrasonic treatment;

4) then cutting off irregular hydrogel, and dropwise adding a proper amount of microsphere colloidal suspension (only enough for completely covering the size of a target area) on the surface of the hydrogel (taking special care not to damage the surface of the gel during dropwise adding); the purpose of cutting off irregular hydrogel is to provide a relatively regular plane and use the surface tension of the microsphere colloidal suspension to control the dispersion area of the microsphere colloidal suspension, so as to achieve the purpose of controlling the assembly thickness of the microspheres;

5) drying the product obtained in the step 4) in an environment with the temperature of 30-90 ℃ under the condition of avoiding external force influences such as air disturbance, vibration and the like, wherein the preferable temperature is 70 ℃; wherein, the air disturbance, vibration and other operations are avoided to avoid the influence of external force in the drying self-assembly process of the microsphere colloid suspension.

Example 2:

the present embodiment is further optimized based on the above embodiment, and the same parts as those in the foregoing technical solution will not be described herein again, and further to better implement the present invention, the following setting manner is particularly adopted: the water/PEG mixed solution is obtained by mixing water and PEG and fully stirring.

Example 3:

the present embodiment is further optimized based on any of the above embodiments, and the same parts as those in the foregoing technical solutions will not be described herein again, and in order to further better implement the present invention, the following setting modes are particularly adopted: the molecular weight range of the PEG is 100-1000; preferably, the PEG is selected to have a molecular weight of 200.

Example 4:

the present embodiment is further optimized based on any of the above embodiments, and the same parts as those in the foregoing technical solutions will not be described herein again, and in order to further better implement the present invention, the following setting modes are particularly adopted: the gel is agarose gel, chitosan gel or hyaluronic acid gel.

Example 5:

the present embodiment is further optimized based on any of the above embodiments, and the same parts as those in the foregoing technical solutions will not be described herein again, and in order to further better implement the present invention, the following setting modes are particularly adopted: the concentration range of the gel aqueous solution finally obtained in the step 1) is 0.2-2%; preferably, the concentration of the gel aqueous solution finally obtained in the step 1) is 1%.

Example 6:

the present embodiment is further optimized based on any of the above embodiments, and the same parts as those in the foregoing technical solutions will not be described herein again, and in order to further better implement the present invention, the following setting modes are particularly adopted: in the step 2), surface leveling is performed in a shaking mode.

Example 7:

the present embodiment is further optimized based on any of the above embodiments, and the same parts as those in the foregoing technical solutions will not be described herein again, and in order to further better implement the present invention, the following setting modes are particularly adopted: the material of the microsphere is polystyrene, silicon dioxide, titanium dioxide, polymethyl methacrylate, poly (N-isopropyl acrylamide), metal or the like.

Example 8:

the implementation steps are shown in FIG. 2

1) Preparing a 1% agarose aqueous solution by using water, and then carrying out ultrasonic treatment until agarose is completely dissolved;

2) heating the solution obtained in the step 1) to boil, and then slowly cooling to be in a semi-solid state. Pouring on a target surface (a flat or curved surface is shown in figure 1), and then moderately shaking until the surface is flat and removing air bubbles in the liquid;

3) slowly cooling the system in the step 2) at room temperature, and slightly flushing the surface of the gel with clean air until no obvious water drop trace exists after the gel is completely solidified;

4) then cutting off irregular hydrogel, and dropwise adding a proper amount of microsphere colloid suspension on the surface of the gel (taking care to avoid damaging the surface of the gel);

5) and finally, avoiding the influence of external force such as air disturbance, vibration and the like, and drying in an environment at the temperature of 70 ℃.

During verification, all the reflected spectra are collected from a set of optical fiber spectrum collection system as shown in fig. 10, and the system comprises a tungsten lamp light source, optical fibers, a mobile station, a spectrometer and a computer. The light source is turned on, the high-reflection aluminum mirror is used as a comparison group and is set to have the reflectivity of 100%, the light source is turned off and is set to have the reflectivity of 0%, and the prepared periodic nano structure is placed as a sample to adjust the distance between the sample and incident light. Incident light emitted by the light source is projected on the surface of the periodic nanostructure and then reflected into a spectrometer and displayed on a computer in a spectrum form. Due to the Photonic Band Gap (PBG), light at band gap wavelengths is reflected or absorbed because it cannot pass through to the medium, so the position of the reflection peak reflects to some extent the position of the PBG. FIG. 3 shows that the reflectivity of the nano-periodic structure to light in the PBG range reaches 86%. FIGS. 6 and 7 show that the PBG position changes under different angles of incident light, which is a characteristic property of microsphere arrangement. That is, the microspheres are to a large extent regularly arranged.

The transmission spectrum of the periodic nanostructures was obtained using an ultraviolet-visible spectrophotometer. The periodic nano results were attached to the glass surface and placed in the sample cell of a spectrophotometer and measured using transmission mode. Wherein fig. 4 and 5 are nano-periodic structures assembled from 212nm microspheres, the transmission efficiency of the periodic nanostructures in the hydrogel state and in the dry state to light in the PBG range is below 0.1% and 0.6%.

Example 9:

the PBG position of periodic nanostructures depends mainly on three factors: 1) the refractive index contrast between the two periodic media (spheres and surrounding phase), 2) the lattice constant (spacing between spheres), and 3) the fill factor (volume of spheres compared to volume of surrounding phase) after drying the gel-state periodic nanostructures, the water in the microsphere array is displaced by air (refractive index decreases) and the photonic band gap will blue-shift as shown in fig. 8-9. That is, the PBG sites differ between the gel and xerogel states. Based on this, we can obtain two photonic crystals with different photonic band gaps by keeping the periodic nanostructure in a gel state for a long time. We have designed a polyethylene glycol (PEG) hydrogel that is capable of significantly longer retention times (over 14000 minutes) than agarose gels. The preparation steps are as follows:

6) preparing a water/PEG-200 mixed solution by using water and fully stirring;

7) dissolving agarose by using the mixed solution in the step 6) as a solvent, and carrying out ultrasonic treatment;

8) and (3) replacing the solution in the step 2) in the step 8 with the solution in the step 7) to carry out the step 5), thus obtaining the periodic nanostructure which is prepared by the PEG-agarose hydrogel interface in an auxiliary way and can keep the gel state for a long time.

The position of the periodic nanostructure reflection peaks prepared at the interface of the two gels (PEG-agarose and agarose) was monitored over time under room temperature conditions using the reflectance spectroscopy system of fig. 10, and the results are shown in fig. 8 and 9.

Analysis based on the above example:

after the hydrogel dried, the water in the periodic nanostructures was replaced by air (refractive index decreased), resulting in a blue-shift of the PBG. That is, the PBG sites of the periodic nanostructures are different in the gel and xerogel states. On the basis, by keeping the gel state of the nano periodic structure for a long time, the periodic nano structures of two different PBGs can be obtained by only using Polystyrene (PS) microsphere colloidal suspension with one particle size. In order to keep the water content of the hydrogel for a long time, polyethylene glycol-agarose (PEG-200) is used as an additive of the hydrogel, and a novel PEG agarose gel with good moisture retention is designed. In addition, PEG sepharose does not undergo a blue shift in PBG at room temperature for longer than 250 hours compared to 1% sepharose. However, in the first 2500 minutes, the PBG sites of PEG agarose showed a red shift of about 15nm, probably due to the gradual replacement of the original water as the interstitial medium of the periodic nanostructures by the aqueous PEG-200 solution during the evaporation of the colloidal suspension of PS microspheres. In conclusion, the method has potential application prospect in the field of material preparation.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way, and all simple modifications and equivalent variations of the above embodiments according to the technical spirit of the present invention are included in the scope of the present invention.

Claims

1. A method for assembling a periodic nano structure on a plane or a curved surface by using a soft matter interface is characterized by comprising the following steps: the method comprises the following steps:

1) preparing a 0.2-2% gel aqueous solution by using water or a water/PEG mixed solution as a solvent, and then carrying out ultrasonic treatment until a gel monomer is completely dissolved;

2) heating the obtained product in the step 1) to boiling, cooling to a semi-solid state, pouring the product on a target surface, removing bubbles and flattening the surface;

3) slowly cooling the system in the step 2) at room temperature until the hydrogel is completely solidified, and purging with clean air until no obvious water drop trace exists on the surface of the hydrogel;

4) then cutting off irregular hydrogel, and dropwise adding a proper amount of microsphere colloid suspension on the surface of the hydrogel;

5) drying the product obtained in the step 4) in an environment with the temperature of 30-90 ℃.

2. The method for assembling periodic nanostructures on a plane or a curved surface by using soft material interface as claimed in claim 1, wherein: the water/PEG mixed solution is obtained by mixing water and PEG and fully stirring.

3. The method for assembling periodic nanostructures on a plane or a curved surface by using soft material interface as claimed in claim 2, wherein: the molecular weight range of the PEG is 100-1000.

4. A method for assembling periodic nanostructures on a plane or curved surface using soft material interface as claimed in claim 3, wherein: the molecular weight selected for the PEG is 200.

5. The method for assembling periodic nanostructures on a plane or a curved surface by using soft material interface as claimed in claim 1, 2, 3 or 4, wherein: the gel is agarose gel, chitosan gel or hyaluronic acid gel.

6. The method for assembling periodic nanostructures on a plane or a curved surface by using soft material interface as claimed in claim 1, 2, 3 or 4, wherein: the concentration range of the gel aqueous solution finally obtained in the step 1) is 0.1-3%.

7. The method for assembling periodic nanostructures on a plane or a curved surface by using soft material interface as claimed in claim 6, wherein: the concentration of the gel aqueous solution finally obtained in the step 1) is 1%.

8. The method for assembling periodic nanostructures on a plane or a curved surface by using soft material interface as claimed in claim 1, 2, 3, 4 or 7, wherein: in the step 2), surface leveling is performed in a shaking mode.

9. The method for assembling periodic nanostructures on a plane or a curved surface by using soft material interface as claimed in claim 1, 2, 3, 4 or 7, wherein: the material of the microsphere is Polystyrene (PS), silicon dioxide, titanium dioxide, polymethyl methacrylate, poly (N-isopropyl acrylamide) or metal.

10. The method for assembling periodic nanostructures on a plane or a curved surface by using soft material interface as claimed in claim 1, 2, 3, 4 or 7, wherein: in the step 5), the temperature environment for drying is 70 ℃.