CN110655089B - Dispersion liquid with adjustable optical property and preparation method thereof - Google Patents
Dispersion liquid with adjustable optical property and preparation method thereof Download PDFInfo
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Abstract
The invention discloses a magnetic nano composite material and a preparation method thereof, and a dispersion liquid with adjustable optical properties and a preparation method thereof. The dispersion with adjustable optical properties comprises a magnetic nanocomposite material. The preparation method of the dispersion comprises the following steps: preparing a two-dimensional magnetic nanocomposite material; dispersing the two-dimensional magnetic nano composite material in a solution to prepare a colloidal dispersion liquid; and applying an external magnetic field to the colloidal dispersion liquid to obtain the composite material dispersion liquid with adjustable optical properties. The preparation method provided by the invention has the advantages of simple conditions, short preparation period, low cost and easiness in realization, and the prepared dispersion liquid with adjustable optical properties has high magnetic responsiveness and adjustable optical properties and has great application potential in the field of display devices.
Description
Technical Field
The invention belongs to the field of functional materials, and particularly relates to a dispersion with adjustable optical properties and a preparation method thereof.
Background
In recent years, the regulation and control of electromagnetic waves by assembling nanomaterials to construct artificial periodic structures have attracted great interest, such as plasma nanomaterials, magnetically responsive nanomaterials, anisotropic nanomaterials, and the like. Such bottom-up assembly methods have been reported, for example, electric field driving, magnetic field driving, thermal driving, noncovalent driving, and the like. Their ability to assemble ordered nanostructures determines the highly sophisticated applications of the materials in the field of nano-optoelectronics.
Michael has studied that gold and silver nanoparticle arrays exhibit local surface plasmon resonance in the visible and near infrared regions, and thus can cause strong light absorption and light scattering in a certain wavelength band. By utilizing the characteristic, the gold and silver nano array can be used as a liquid mirror surface, and reversible regulation and control of light transmission and reflection are realized through electric field regulation and control. The Yadong Yin realizes the ordered assembly of superparamagnetic ferroferric oxide through magnetic induction, and the scattering of visible light by the periodic array can be applied to the fields of structural color printing and field response display devices. However, the adjustability of the optical properties of the hybrid materials has not been reported. The hybrid material can provide an external field regulation source for the self-assembly of the ordered structure, and expand the range of raw materials which can be used as ordered nanostructure elements. If the external field controllability of the optical properties of the hybrid material is realized, the ordered and complex artificial nanostructure can be provided with stronger controllability, adjustability and stability, and the cost can be reduced.
Inorganic non-metallic mineral materials are a very important and young functional material. Anisotropic mineral nanoparticles such as montmorillonite, hectorite, gibbsite, etc. have been reported in large numbers in the past decade to spontaneously form ordered structures in aqueous dispersions, which in turn form liquid crystalline phases. However, the synthesis technology of inorganic liquid crystal is not mature, and the optical properties of liquid crystal phase are not controllable, so that it is difficult to apply inorganic mineral liquid crystal to actual life. Feng Lin recently reports that the diamagnetism of graphene is utilized to realize controllable magnetic control orientation and optical properties of graphene sheets, but the high cost of the graphene raw material determines that the material cannot be applied on a large scale.
Therefore, it is urgently needed to develop a dispersion liquid with adjustable optical properties to realize controllable alignment and optical properties of inorganic liquid crystals, which is of great practical significance to research and industrialization of inorganic liquid crystals.
Disclosure of Invention
In order to solve the above problems, the present inventors have conducted intensive studies and, as a result, have found that: and magnetically coating the non-magnetic anisotropic nano structure to obtain a two-dimensional magnetic nano composite material, then dispersing the two-dimensional magnetic nano composite material in a solution to prepare a colloidal dispersion liquid, and applying an external magnetic field to the colloidal dispersion liquid to obtain the dispersion liquid with adjustable optical properties. The preparation method has the advantages of simple conditions, short preparation period, low cost, strong stability of the obtained dispersion, high magnetic responsiveness, short relaxation time and adjustable optical property, and has great application potential in the field of display devices, thereby completing the invention.
A first aspect of the invention provides a magnetic nanocomposite material comprising magnetically-encapsulated anisotropic nanostructures, preferably magnetically-encapsulated anisotropic nanostructures.
The second aspect of the present invention provides a method for preparing a magnetic nanocomposite material according to the first aspect of the present invention, wherein the composite material is preferably a montmorillonite @ ferroferric oxide magnetic nanocomposite material, which is characterized by comprising the following steps:
1.1) preparing a suspension of montmorillonite;
1.2) adding Fe to the suspension obtained in step 1.1)2+And Fe3+Salt;
1.3) continuously adding an alkaline substance into the suspension, and setting the reaction time to obtain the montmorillonite @ ferroferric oxide magnetic nano composite material.
A third aspect of the invention provides a dispersion with tunable optical properties, wherein the dispersion comprises a magnetic nanocomposite material according to the first aspect of the invention.
According to a fourth aspect of the present invention, there is provided a method for preparing the dispersion according to the third aspect of the present invention, preferably based on a two-dimensional magnetic nanocomposite material, comprising the steps of:
(1) preparing a two-dimensional magnetic nanocomposite material;
(2) dispersing the two-dimensional magnetic nano composite material in a solution to prepare a colloidal dispersion liquid;
(3) and applying an external magnetic field to the colloidal dispersion liquid to obtain the dispersion liquid with adjustable optical properties.
The invention also provides the application of the dispersion with adjustable optical properties in display devices.
The invention has the following beneficial effects:
(1) the invention takes the two-dimensional magnetic nano composite material as the element to prepare the dispersion liquid with adjustable optical property, and the method realizes the orientation controllability of the extrinsic magnetic two-dimensional nano material.
(2) The dispersion liquid with adjustable optical properties has strong stability, obvious agglomeration and sedimentation cannot be seen in the dispersion liquid within half a year, and good optical properties are kept; the magnetic responsiveness is high, and the relaxation time is short, can respond to the magnetic field change within 1 second. The transmittance of the liquid crystal phase can be controlled by applying an external magnetic field to the dispersion to obtain the liquid crystal phase, adjusting the concentration of the two-dimensional magnetic nanocomposite in the dispersion, the intensity of the magnetic field, the direction of the magnetic field and the pH value of the system (for example, when the acid concentration is 0.005mol/L and 0.001mol/L, the solution maintains relatively high transmittance), and the simple control of the optical properties of the liquid crystal phase of the dispersion is realized.
(3) According to the preparation method provided by the invention, the dispersion liquid with adjustable optical properties is obtained, an external magnetic field is applied to the dispersion liquid to obtain the photonic crystal, the reflectivity of the dispersion liquid to visible light can be controlled by adjusting the magnetic field intensity, the magnetic field direction and the incident light direction, the visible light reflection effects of the dispersion liquid are different due to different observation points, and thus the dispersion liquid with adjustable optical properties is obtained, and has great application potential in the field of display devices.
(4) The preparation method provided by the invention has the advantages of simple conditions, short preparation period, low cost and easy realization.
Drawings
FIG. 1 shows XRD patterns of montmorillonite as a raw material of examples 1 to 15 and comparative examples 1 to 13 of the present invention and montmorillonite @ ferroferric oxide prepared in example 1;
FIG. 2 shows TEM images of the raw material smectites of examples 1 to 15 of the present invention and comparative examples 1 to 13;
FIG. 3 shows a TEM image of montmorillonite @ ferroferric oxide prepared in example 1 of the present invention;
FIG. 4 is a schematic diagram showing the placement of an internal cross polarizer of an ultraviolet-visible spectrophotometer for testing the transmittance of liquid crystals in accordance with an embodiment of the present invention;
FIG. 5 shows a TEM image of montmorillonite @ ferroferric oxide prepared in example 3 of the present invention after magnetic field orientation;
FIG. 6 is a schematic diagram showing the relative positions of the external magnet, the montmorillonite @ ferroferric oxide based suspension sample and the observation point for examples 9-15 and comparative examples 5-13 of the present invention;
FIG. 7 shows the magnetic hysteresis loops of montmorillonite @ ferroferric oxide two-dimensional nanocomposite prepared in example 3 of the present invention and the raw material montmorillonite;
FIG. 8 shows polarization images under a polarization microscope of the dispersions obtained in examples 3, 6, 7 and 8 of the present invention;
FIG. 9 shows the light transmittance of the dispersions obtained in examples 1 to 5 of the present invention under crossed polarizers;
FIG. 10 shows the light transmittance of the dispersions of comparative examples 1 to 4 and example 3 of the present invention, wherein blank + P indicates that no sample is added and only an orthorhombic polarizing plate is added;
FIG. 11 shows the light transmittance of the dispersions obtained in example 3 and examples 12 to 15 of the present invention under crossed polarizers.
Detailed Description
The features and advantages of the present invention will become more apparent and appreciated from the following detailed description of the invention.
In one aspect, the present invention provides a magnetic nanocomposite material comprising magnetically-encapsulated anisotropic nanostructures, preferably magnetically-encapsulated anisotropic nanostructures.
According to the invention, the magnetic nanocomposite is obtained by magnetically coating anisotropic nanostructures.
According to the invention, the magnetic coating material forms a magnetic shell, wherein the magnetic shell comprises magnetic nanoparticles and a magnetic coating, the magnetic shell being coated on the surface of the anisotropic nanostructure, thereby forming a magnetic nanocomposite material.
According to the invention, the anisotropic nanostructures are non- (intrinsic) magnetic anisotropic nanostructures.
According to one embodiment of the invention, the anisotropic nanostructures are two-dimensional non- (intrinsic) magnetic anisotropic nanostructures.
In a further preferred embodiment, the anisotropic nanostructures are selected from one or both of non-magnetic nanoplatelets or nanodiscs.
In a still further preferred embodiment, the non-magnetic anisotropic nanostructures are selected from non-magnetic nanoplatelets.
According to the invention, the non-magnetic anisotropic nano structure is selected from one or more of inorganic materials, including mineral materials such as montmorillonite, gibbsite, hectorite and vermiculite, preferably includes montmorillonite, and more preferably montmorillonite, and crystal face diffraction peaks exist on the 2 theta of 7.10 degrees and 19.7 degrees on the XRD pattern of the montmorillonite.
According to the present invention, it is particularly preferred that the non-magnetic anisotropic nanostructure is selected from montmorillonite nanoplatelets.
According to the invention, the magnetic coating material is selected from ferromagnetic or superparamagnetic materials, preferably from one or more of ferrite, iron/cobalt/nickel (Fe/Co/Ni) and alloys thereof, iron nitride, preferably including ferroferric oxide (Fe/Co/Ni)3O4) More preferably Fe3O4The magnetic shell comprises Fe3O4Preferably from Fe3O4Form, for example, the Fe3O4Has diffraction peaks of crystal planes at the positions of 30.20 degrees, 35.42 degrees, 43.10 degrees, 53.60 degrees, 57.09 degrees and 62.70 degrees of 2 theta on an XRD pattern.
According to the invention, it is particularly preferred that the magnetic nanocomposite is a two-dimensional magnetic nanocomposite formed from ferriferrous oxide-coated montmorillonite, denoted as montmorillonite @ ferriferrous oxide two-dimensional magnetic nanocomposite.
According to the invention, crystal plane diffraction peaks exist at the positions of 7.10 degrees, 19.7 degrees, 30.20 degrees, 35.42 degrees, 43.10 degrees, 57.09 degrees and 62.70 degrees of 2 theta on an XRD (X-ray diffraction) pattern of the montmorillonite @ ferroferric oxide two-dimensional magnetic nano composite material.
The second aspect of the invention provides a preparation method of the magnetic nano composite material, wherein the composite material is montmorillonite @ ferroferric oxide two-dimensional magnetic nano composite material, and the preparation method comprises the following steps:
1.1) preparing a suspension of montmorillonite;
1.2) adding Fe to the suspension obtained in step 1.1)2+And Fe3+Salt;
1.3) continuously adding an alkaline substance into the suspension, and setting the reaction time to obtain the montmorillonite @ ferroferric oxide magnetic nano composite material.
According to the invention, in step 1.1), the smectite and water are mixed homogeneously to prepare a smectite suspension.
The inventor finds that the montmorillonite with high concentration and nanometer grain diameter is not easy to disperse into single pieces in water, is easy to agglomerate and is not beneficial to loading Fe3O4Therefore, the mass concentration of the montmorillonite in water is controlled within a certain range, the montmorillonite with the nano particle size can be uniformly dispersed in the water, the agglomeration degree is extremely low, and the montmorillonite dispersed into single sheet is convenient for loading Fe on the whole surface3O4。
According to the invention, the solid content of the montmorillonite suspension is 1-20 mg/mL, preferably 3-5 mg/mL.
According to the invention, step 1.1) is accompanied by stirring during the preparation and the dispersion of the smectite is carried out.
According to the invention, in step 1.2), Fe2+The salt is selected from one or more of ferrous sulfate, ferrous chloride and ferrous nitrate; fe3+The salt is selected from one or two of ferric chloride and ferric nitrate.
According to the invention, in step 1.2), Fe is added to the suspension obtained in step 1.1)2+And Fe3+Salt of in Fe2+And Fe3+Before adding salt, continuously introducing nitrogen into the suspension, discharging oxygen in the suspension, providing an oxygen-free reaction environment, and avoiding Fe2+Is oxidized.
According to the invention, the most sufficient Fe is obtained3O4，Fe2+And Fe3+The salt molar ratio is within a certain range, in Fe2+Salt and Fe3+In salt, Fe2+And Fe3+The molar ratio of (A) to (B) is 0.80:2.0 to 1.5: 2.0.
According to the invention, the weight of montmorillonite and Fe3+Fe in salt3+The ratio of the molar amount of (1) to (6) is 100 parts by weight, (3-6) parts by weight, wherein 1 part by weight is 1g, and 1mol is 1 part by mole.
According to the invention, Fe2+Salt and Fe3+The addition of the salt was accompanied by stirring.
According to the present invention, in step 1.3), the basic substance is selected from any one or more of sodium hydroxide, potassium hydroxide and ammonia water, preferably sodium hydroxide or ammonia water, more preferably ammonia water.
According to the invention, in the step 1.3), after the alkaline substance is added into the suspension obtained in the step 1.2), the pH value of the system is 8-12.
According to the invention, in step 1.3), an alkaline substance is added and the reaction is carried out to obtain Fe3O4A magnetic nano composite material coated with montmorillonite.
According to the invention, in step 1.3), Fe3O4The reaction temperature is 50-90 ℃, preferably 60-80 ℃; and/or the reaction time is 20min to 60min, preferably 30min to 40 min.
The present inventors have found that in the above reaction temperature range, Fe3O4Can form uniform coating layer on the surface of montmorillonite. At temperatures below 50 ℃, Fe3O4The formation amount of the montmorillonite surface is reduced and is not uniform mainly through self-nucleation in the liquid; fe in suspension when the temperature is higher than 90 DEG C3O4With increasing temperature, which results in Fe3O4The nanoparticles are beneficial to nucleation on the montmorillonite, but the nucleation rate is reduced due to high temperature; on the other hand, molecular motion at high temperature makes Fe3O4The nanoparticles grow on the montmorillonite, resulting in very thick Fe on the montmorillonite nanoplatelets3O4The surface of the shell and the montmorillonite is not uniform. In addition, when the alkaline substance is ammonia water, the ammonia water is easily decomposed due to high temperature, the operation difficulty is increased due to high-temperature reaction, and the production cost is increased.
In the present invention, step 1.3) further comprises: and after the reaction is finished, performing solid-liquid separation and drying. The solid-liquid separation mode can be any one or more of normal pressure filtration, vacuum filtration and centrifugal separation, and the centrifugal separation is preferred because the nano material has smaller particle size and larger filtration difficulty.
A third aspect of the invention provides a dispersion with tunable optical properties comprising a magnetic nanocomposite material according to the first aspect of the invention.
A fourth aspect of the present invention is to provide a method for preparing the dispersion with adjustable optical properties, preferably a dispersion with two-dimensional magnetic nanocomposite as a base element, the method comprising the steps of:
step 1: preparing the two-dimensional magnetic nano composite material.
According to the invention, in step 1, the two-dimensional magnetic nanocomposite material is, for example, montmorillonite @ ferroferric oxide two-dimensional magnetic nanocomposite material.
According to the invention, the preparation aspect of the montmorillonite @ ferroferric oxide two-dimensional magnetic nanocomposite is preferably the method provided by the second aspect of the invention.
Step 2: the two-dimensional magnetic nanocomposite is dispersed in a solution to prepare a colloidal dispersion.
In the present invention, the solution in step 2 is a dilute acid solution, preferably an aqueous solution of one or more of hydrochloric acid, sulfuric acid and phosphoric acid, more preferably an aqueous hydrochloric acid solution.
According to a preferred embodiment of the invention, the dilute acidic solution is a dilute aqueous hydrochloric acid solution.
According to one embodiment of the present invention, the pH of the dispersion system formed by dispersing the two-dimensional magnetic nanocomposite material in a solution is >1, and preferably the pH of the prepared colloidal dispersion is > 1.
In the invention, the magnetic nanocomposite material is added into a dilute acid solution, and a magnetic field is applied to generate a liquid crystal phase. Wherein the concentration of the dilute acid solution or the pH of the dispersion system can affect the transmittance of the liquid crystal phase. When the acid concentration is 0.005mol/L and 0.001mol/L, the solution keeps relatively high light transmittance; when the acid concentration is reduced to 0.0001mol/L, the light transmittance is rapidly reduced to 0; when the acid concentration was increased to 0.01mol/L, the light transmittance was reduced to half that of 0.05mol/L, and when the acid concentration was further increased, the light transmittance was reduced to 0. For example, when the wavelength is 700 nm, the light transmittance of the dispersion is 3.1% in the case of an acid concentration of 0.005 mol/L.
According to the invention, in step 2, the concentration of the dilute hydrochloric acid aqueous solution is 0.0001-0.05 mol/L, preferably 0.001-0.01 mol/L, and more preferably 0.005-0.01 mol/L.
In the present invention, the dispersion mode of the two-dimensional magnetic nanocomposite material in the dilute acid solution is not particularly limited, and the two-dimensional magnetic nanocomposite material can be dispersed by using the ultrasonic method, the stirring method, and the like commonly used in the art.
According to one embodiment of the invention, the montmorillonite @ ferroferric oxide two-dimensional magnetic nanocomposite prepared in the step 1 is dispersed in a dilute hydrochloric acid solution to form a stable colloidal dispersion liquid.
According to the invention, the colloidal dispersion prepared in step 2 shows good stability, and can maintain good suspension property after being placed for a long time, and simultaneously maintain good adjustability of optical properties, for example, the colloidal dispersion can be stored in the form of dispersion for more than six months.
In this application, a two-dimensional magnetic nanocomposite, such as montmorillonite @ ferroferric oxide magnetic nanocomposite, is dispersed in a dilute hydrochloric acid solution to obtain a pH>1, wherein the dilute hydrochloric acid solution provides H+Positive charge, so that the dispersion maintains high stability.
In the present invention, the solid content of the two-dimensional magnetic nanocomposite particles in the colloidal dispersion has an influence on the optical properties of the formed dispersion. After an external magnetic field is applied to the dispersion liquid, a liquid crystal phase is formed, the solid content of the dispersion liquid is increased, and the light transmittance of the liquid crystal phase is increased. When the concentration of the dispersion liquid is low, visible light can pass through the liquid crystal phase in a wide visible light wavelength range, but the light transmittance is low; the transmittance of the liquid crystal system is increased along with the increase of the solid content of the dispersion liquid, but the transmitted visible light wavelength is narrowed, and the red shift occurs because the ferroferric oxide black particles absorb light waves, and the absorption is more obvious along with the increase of the solid content of the dispersion liquid, so that the transmittance of the light waves in a low wavelength range is reduced. For example, at a wavelength of 720nm, the liquid crystal phase of a dispersion having a concentration of 2mg/mL can have a transmittance of 2.6% in the crossed polarizer.
According to the present invention, the solid content of the two-dimensional magnetic nanocomposite particles in the colloidal dispersion is 0.001mg/mL to 10mg/mL, preferably 0.125mg/mL to 2 mg/mL.
And step 3: and applying an external magnetic field to the colloidal dispersion liquid to obtain the dispersion liquid with the optical property regulated and controlled along with the magnetic field.
According to the present invention, the magnet is placed at a certain position of the colloidal dispersion liquid to apply an external magnetic field to the colloidal dispersion liquid, and the distance between the magnet and the colloidal dispersion liquid and the magnetic field intensity have a correlation, so that the magnitude of the magnetic field intensity can be controlled by adjusting the distance between the magnet and the colloidal dispersion liquid or increasing the number of the magnets.
In this way, according to the invention, the magnitude of the magnetic field strength can be controlled in the range of 0-300mT, preferably 10-300mT, more preferably 20-300 mT.
In the invention, by applying an external magnetic field, the stress of the particles and the electrostatic repulsion among the particles are kept balanced, so that an ordered structure is formed and a liquid crystal phase is formed.
In the invention, an external magnetic field and visible light are applied to the dispersion liquid, in the presence of the visible light, when the distance between the ordered structures is similar to the wavelength of the visible light by adjusting the intensity of the magnetic field, photonic crystals can be formed, the dispersion liquid generates Bragg diffraction on the visible light, and the macroscopic expression shows that the dispersion liquid converts the visible light from a transmission state to a reflection state along with the change of the intensity of the magnetic field.
In the present invention, the direction of the applied magnetic field is arbitrary, and is, for example, 0 to 180 ℃. By changing the direction of the magnetic field, liquid crystal phases with different directions of orientation are obtained, and the polarization condition of the liquid crystal phases can be observed by a polarization microscope. The transmittance in the case of polarized light can be measured by an ultraviolet-visible spectrophotometer by adding orthogonal polarizers in front of and behind the sample cell, and the schematic diagram is shown in fig. 4.
In the invention, the light transmittance of the liquid crystal phase of the dispersion liquid is controlled by adjusting the magnetic field intensity and the magnetic field direction of the external magnetic field and controlling the pH value of the dispersion liquid system.
In the invention, the reflectivity of the dispersion liquid to visible light is controlled by adjusting the intensity of an external magnetic field, the direction of the magnetic field and the direction of incident light, wherein the direction of the incident light is adjusted according to the angle of the magnetic field and the incident light, the direction of the magnetic field is determined according to the angle of the magnetic field and a normal line, the angle of the magnetic field and the incident light is 0-180 degrees, the reflection effect is observed at an observation point, and the schematic position diagram is shown in fig. 6.
Thus, according to the present invention there is also provided the use of liquid crystals and photonic crystals of the above-described tunable optical property dispersions, primarily for use in display devices.
Examples
The present invention is further described below by way of specific examples. However, these examples are only illustrative and do not set any limit to the scope of the present invention.
In the following examples and comparative examples, various materials or reagents are mentioned, which are not particularly limited, and commercially available raw materials may be used, or they may be prepared by a conventional method on a laboratory scale or a production scale.
Example 1
The montmorillonite @ ferroferric oxide two-dimensional magnetic nano composite material is prepared by the following steps: preparing 100mL of 1mg/mL montmorillonite aqueous suspension; introducing nitrogen into the suspension for protection, continuously stirring, adding 1.0mmol of ferric chloride and 0.5mmol of ferrous sulfate, and reacting at 60 ℃ for 5 minutes; continuously adding 5mL of ammonia water, reacting for 30 minutes at 60 ℃, centrifuging, washing and drying the suspension to obtain the montmorillonite @ ferroferric oxide two-dimensional magnetic nano composite material;
adding the prepared montmorillonite @ ferroferric oxide two-dimensional magnetic nano composite material into 0.001mol/L hydrochloric acid to prepare 0.125mg/mL dispersion liquid, and uniformly stirring to obtain stable colloid dispersion liquid;
1 magnet was placed 2 cm from the colloidal dispersion.
Example 2
The experimental procedure of example 1 was repeated except that the obtained montmorillonite @ ferroferric oxide two-dimensional magnetic nanocomposite was added to 0.001mol/L hydrochloric acid to prepare a 0.25mg/mL dispersion.
Example 3
The experimental procedure of example 1 was repeated except that the obtained montmorillonite @ ferroferric oxide two-dimensional magnetic nanocomposite was added to 0.001mol/L hydrochloric acid to prepare a 0.5mg/mL dispersion.
Example 4
The experimental procedure of example 1 was repeated except that the obtained montmorillonite @ ferroferric oxide two-dimensional magnetic nanocomposite was added to 0.001mol/L hydrochloric acid to prepare a 1.0mg/mL dispersion.
Example 5
The experimental procedure of example 1 was repeated except that the obtained montmorillonite @ ferroferric oxide two-dimensional magnetic nanocomposite was added to 0.001mol/L hydrochloric acid to prepare a 2.0mg/mL dispersion.
Example 6
The experimental procedure of example 3 was repeated except that the magnetic field direction was rotated by 45 °, and the other steps were the same as in example 3.
Example 7
The experimental procedure of example 3 was repeated except that the magnetic field direction was rotated by 90 °, and the other steps were the same as in example 3.
Example 8
The experimental procedure of example 3 was repeated except that the magnetic field direction was rotated by 135 °, and the other steps were the same as in example 3.
Example 9
The montmorillonite @ ferroferric oxide two-dimensional magnetic nano composite material is prepared by the following steps: preparing 100mL of 1mg/mL montmorillonite aqueous suspension; introducing nitrogen into the suspension for protection, and continuously stirring; adding 1.0mmol of ferric chloride and 0.5mmol of ferrous sulfate, and reacting at 60 ℃ for 5 minutes; continuously adding 5mL of ammonia water, and reacting for 30 minutes at 60 ℃; and centrifuging, washing and drying the suspension to obtain the montmorillonite @ ferroferric oxide two-dimensional magnetic nano composite material.
Adding the prepared montmorillonite @ ferroferric oxide two-dimensional magnetic nano composite material into 0.001mol/L hydrochloric acid to prepare 0.5mg/mL dispersion liquid, and uniformly stirring to obtain stable colloid dispersion liquid;
3 magnets were placed 0 cm from the colloidal dispersion, visible light was applied according to FIG. 6, and the sample was observed at the position shown in FIG. 6. Wherein the angle between the magnetic field and the incident light is 135 degrees.
Example 10
The experimental procedure of example 9 was repeated except that 3 pieces of magnets were placed 1 cm from the colloidal dispersion, and the other steps were the same as in example 9.
Example 11
The experimental procedure of example 9 was repeated except that no magnet was placed beside the colloidal dispersion, and the other steps were the same as in example 9.
Example 12
This embodiment is different from example 3 in that no magnet is placed beside the colloidal dispersion liquid, and the other steps are the same as example 3.
Example 13
This embodiment is different from example 3 in that 1 magnet was placed 3 cm beside the colloidal dispersion liquid, and the other steps are the same as example 3.
Example 14
This embodiment is different from example 3 in that 1 magnet was placed 1 cm beside the colloidal dispersion liquid, and the other steps are the same as example 3.
Example 15
This embodiment is different from example 3 in that 3 pieces of magnets are placed 1 cm beside the colloidal dispersion liquid, and the other steps are the same as example 3.
Comparative example
Comparative example 1
The experimental procedure of example 3 was repeated except that the hydrochloric acid concentration was 0.0001mol/L, and the other steps were the same as in example 3.
Comparative example 2
The experimental procedure of example 3 was repeated except that the hydrochloric acid concentration was 0.005mol/L and the other steps were the same as in example 3.
Comparative example 3
The experimental procedure of example 3 was repeated except that the hydrochloric acid concentration was 0.01mol/L, and the other steps were the same as in example 3.
Comparative example 4
The experimental procedure of example 3 was repeated except that the hydrochloric acid concentration was 0.05mol/L, and the other steps were the same as in example 3.
Comparative example 5
The experimental procedure of example 9 was repeated except that the angle of the magnetic field to the incident light was 0 deg., and the other steps were the same as in example 9.
Comparative example 6
The experimental procedure of example 9 was repeated except that the angle of the magnetic field to the incident light was 15 deg., and the other steps were the same as in example 9.
Comparative example 7
The experimental procedure of example 9 was repeated except that the angle of the magnetic field to the incident light was 30 °, and the other steps were the same as in example 9.
Comparative example 8
The experimental procedure of example 9 was repeated except that the angle of the magnetic field to the incident light was 65 °, and the other steps were the same as in example 9.
Comparative example 9
The experimental procedure of example 9 was repeated except that the angle of the magnetic field to the incident light was 90 deg., and the other steps were the same as in example 9.
Comparative example 10
The experimental procedure of example 9 was repeated except that the angle of the magnetic field to the incident light was 110 deg., and the other steps were the same as in example 9.
Comparative example 11
The experimental procedure of example 9 was repeated except that the angle of the observation point and the magnetic field was 75 °, and the other steps were the same as in example 9.
Comparative example 12
The experimental procedure of example 9 was repeated except that the angle of the observation point and the magnetic field was 60 °, and the other steps were the same as in example 9.
Comparative example 13
The experimental procedure of example 9 was repeated except that the angle of the observation point and the magnetic field was 45 °, and the other steps were the same as in example 9.
Examples of the experiments
X-ray diffraction analysis (XRD): the samples were analyzed using an X-ray powder diffractometer model Bruker D8Advance, germany (Cu target ka radiation) at λ 0.15406nm, step width 0.02, operating voltage 40kV and operating current 40 mA.
Vibration magnetometer: LAKESHORE, model 730T, measured at ambient temperature.
Transmission electron microscope: the Hitachi H-8100 type transmission electron microscope is adopted, and the accelerating voltage is as follows: 200 kV.
Means for generating a magnetic field: the specification of the neodymium iron boron magnet 3 block is 60 × 20 × 5 mm.
A polarizing microscope: model OLYMPUS BX-51, shot OLYMPUS DP-73.
Ultraviolet-visible spectrophotometer: UV 6100.
Experimental example 1: characterization of montmorillonite @ ferroferric oxide two-dimensional magnetic nanocomposite
The raw material montmorillonite used in examples 1 to 15 and comparative examples 1 to 14 of the present invention and the montmorillonite @ Fe obtained in example 13O4XRD detection is carried out on the two-dimensional magnetic nano composite material, and the two-dimensional magnetic nano composite material is matched with montmorillonite and Fe in JCPDS database3O4And comparing the XRD spectrums of the quartz and the quartz, and the result is shown in figure 1.
As can be seen from FIG. 1, Fe was not supported3O4Has a XRD pattern of montmorillonite having crystal plane diffraction peaks at 2 theta of 7.10 DEG and 19.7 DEG, Fe3O4The XRD pattern of the composite material has crystal plane diffraction peaks at the positions of 30.20 degrees, 35.42 degrees, 43.10 degrees, 53.60 degrees, 57.09 degrees and 62.70 degrees of 2 theta, and the crystal plane diffraction peaks at the positions of 7.10 degrees, 19.7 degrees, 30.20 degrees, 35.42 degrees, 43.10 degrees, 57.09 degrees and 62.70 degrees of 2 theta on the XRD pattern of the composite material show that Fe is successfully loaded on the montmorillonite3O4。
The transmission electron microscope test was performed on the montmorillonite samples used in examples 1 to 15 and comparative examples 1 to 14, and the results are shown in FIG. 2. As can be seen from the figure, the surface of the uncoated montmorillonite is relatively smooth and is a two-dimensional nano material in a sheet shape.
The transmission electron microscope test was performed on the montmorillonite @ ferroferric oxide obtained in example 1, and the result is shown in fig. 3. As can be seen from the figure, the surface of montmorillonite is rough, withThe existence of the nano-particle coating, the uniform distribution of the nano-particles on the surface, no obvious agglomeration phenomenon, and the indication of Fe3O4The nano particles are uniformly coated on the surface of the montmorillonite.
The montmorillonite @ ferroferric oxide two-dimensional magnetic nanocomposite prepared in example 1 and the raw material montmorillonite were subjected to saturation magnetization test, and the obtained magnetic curve is shown in fig. 7.
As can be seen from FIG. 7, the magnetization intensity of the montmorillonite used as the raw material is zero, and the montmorillonite and the ferroferric oxide two-dimensional magnetic nanocomposite material shows non-magnetism, while the hysteresis loops of the montmorillonite and the ferroferric oxide two-dimensional magnetic nanocomposite material are two coincident magnetization curves, and the saturation magnetization intensity of the montmorillonite and the ferroferric oxide two-dimensional magnetic nanocomposite material reaches 60.3emu/g, which indicates that the nanocomposite material has superparamagnetism.
Therefore, the ferroferric oxide nanoparticles are successfully coated on the surface of the montmorillonite, and the fact that the magnetic shell formed by coating the ferroferric oxide nanoparticles endows the montmorillonite, namely the high-dispersity nanosheet, with superparamagnetism is shown. The superparamagnetism can enable the montmorillonite @ ferroferric oxide two-dimensional magnetic nano composite material to be oriented along a magnetic field under the action of the magnetic field to form an ordered anisotropic structure, and the response to the magnetic field is immediate and not delayed.
Experimental example 2: formation of liquid crystal phases and photonic crystals
The montmorillonite @ ferroferric oxide composite dispersions prepared in examples 3 and 6-8 were subjected to polarization condition testing by a polarization microscope, and the results are shown in FIG. 8. Wherein the content of the first and second substances,
corresponding to examples 3, 6, 7 and 8, respectively. It was observed that the montmorillonite @ ferroferric oxide colloidal dispersion appeared as a birefringent phase in the polarizing microscope and it can be seen from fig. 8 that the change in the field of view in the polarizing microscope immediately occurred from brightest to darkest or from darkest to brightest as the direction of the magnetic field changed, i.e. every 45 degrees rotation of the direction of the magnetic field. This phenomenon indicates that a liquid crystal phase is prepared by this method, and that the optical properties of the liquid crystal can be controlled by controlling the direction of the magnetic field to control the transmittance of the liquid crystal.
The light transmission of the montmorillonite @ ferroferric oxide dispersions prepared in examples 9-11 was observed under light conditions. It was found that the montmorillonite @ ferroferric oxide dispersion achieved a transition from the transmitted to the reflected state of visible light with increasing magnetic field strength. It is known that the distance between the ordered structures is close to the wavelength of visible light, and bragg diffraction occurs in visible light. This phenomenon indicates that a photonic crystal is prepared by this method, and the reflectivity of the photonic crystal to visible light can be controlled by controlling the intensity of magnetic field.
Experimental example 3: factors influencing the optical properties of the liquid-crystalline phase
The colloidal dispersions of examples 1-5 with different concentrations of montmorillonite @ ferroferric oxide were tested for light transmittance under crossed polarizers. The results are shown in FIG. 9. As can be seen from fig. 9, as the concentration of the composite dispersion increases, the transmittance of the liquid crystal increases, but the transmission wavelength becomes narrower. This may be caused by absorption of light waves by ferroferric oxide.
The transmittance of the montmorillonite @ ferroferric oxide dispersions prepared in comparative examples 1-4 and example 3 was measured under crossed polarizers and the results are shown in fig. 10. As can be seen from fig. 10, the transmittance of the liquid crystal changes depending on the concentration of hydrochloric acid, and the effect of the pH on the transmittance of the liquid crystal phase is shown.
The transmittance of the montmorillonite @ ferroferric oxide dispersions prepared in examples 12 to 15 and 3 was measured under different magnetic field strength conditions, and the results are shown in fig. 11, and it can be seen from fig. 11 that the ordered structure can be normalized by increasing the magnetic field strength in a certain magnetic field range (0-300mT), thereby improving the transmittance of the liquid crystal.
In summary, the transmittance of the liquid crystal phase of the dispersion can be controlled by controlling the magnetic field, the concentration of the dispersion and the pH of the dispersion, so that the optical properties of the liquid crystal can be controlled.
Experimental example 4: factors affecting the optical properties of photonic crystals
The dispersions obtained in comparative examples 5 to 10 and example 9 were observed for their photoresponse. The observation shows that the visible light reflection of the dispersion changes in brightness with the change in the direction of the magnetic field, indicating that the effect of the dispersion on the visible light reflection changes.
The optical response of the photonic crystal dispersions prepared in comparative examples 11, 12 and 13 and example 9 was observed. As a result, it was found that the dispersion of comparative example 11 was darker, the dispersions of comparative examples 12 and 13 were brighter, and the brightness of the dispersion obtained in example 9 was between those of comparative examples 11 and 12, indicating that the effect of the dispersion on the reflection of visible light was changed.
In summary, the reflectance of visible light by the dispersion can be controlled by controlling the direction of the magnetic field, the direction of the incident light, and the intensity of the magnetic field.
The invention has been described in detail with reference to specific embodiments and illustrative examples, but the description is not intended to be construed in a limiting sense. Those skilled in the art will appreciate that various equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its embodiments without departing from the spirit and scope of the present invention, which fall within the scope of the present invention. The scope of the invention is indicated in the appended claims.
Claims (5)
1. An optically tunable dispersion comprising a magnetic nanocomposite material, said magnetic nanocomposite material being a magnetically clad anisotropic nanostructure,
the anisotropic nanostructure is a non-magnetic anisotropic nanostructure selected from one or two of non-magnetic nanosheets or nanodiscs,
the non-magnetic anisotropic nanostructure comprises montmorillonite, the magnetic coating forms a magnetic shell, the magnetic shell comprises one or both of magnetic nanoparticles and a magnetic coating,
the magnetic coating material is ferroferric oxide, and a two-dimensional magnetic nano composite material formed by montmorillonite coated with ferroferric oxide is marked as montmorillonite @ ferroferric oxide magnetic nano composite material;
the dispersion is based on a two-dimensional magnetic nanocomposite and is prepared according to a method comprising the following steps:
(1) preparing a two-dimensional magnetic nanocomposite material;
(2) dispersing a two-dimensional magnetic nano composite material in a solution to prepare a colloid dispersion liquid, wherein the solution is one or more of hydrochloric acid, sulfuric acid, phosphoric acid and nitric acid, and the solid content of the two-dimensional magnetic nano composite material of the colloid dispersion liquid is 0.001-10 mg/ml;
(3) applying an external magnetic field to the colloidal dispersion liquid to obtain a composite material dispersion liquid with adjustable optical properties;
the montmorillonite @ ferroferric oxide magnetic nanocomposite is prepared by the method comprising the following steps of:
1.1) preparing a suspension of montmorillonite;
the solid content of the montmorillonite suspension is 3-5 mg/mL;
1.2) adding Fe to the suspension obtained in step 1.1)2+And Fe3+Salt;
in Fe2+And Fe3+Before adding salt, continuously introducing nitrogen into the suspension, discharging oxygen in the suspension, and providing an oxygen-free reaction environment;
Fe2+salt and Fe3+Stirring is carried out during the addition of the salt;
1.3) continuously adding an alkaline substance into the suspension, and setting the reaction time to obtain the montmorillonite @ ferroferric oxide magnetic nano composite material;
the alkaline substance is sodium hydroxide or ammonia water;
production of Fe in step 1.3)3O4The reaction temperature is 60-80 ℃; the reaction time is 30-40 min.
2. The dispersion according to claim 1,
an XRD pattern of the montmorillonite has crystal face diffraction peaks at 7.10 degrees and 19.7 degrees of 2 theta.
3. A process for preparing a dispersion according to claim 1 or 2, based on a two-dimensional magnetic nanocomposite material, characterized in that it comprises the following steps:
(1) preparing a two-dimensional magnetic nanocomposite material;
(2) dispersing a two-dimensional magnetic nano composite material in a solution to prepare a colloid dispersion liquid, wherein the solution is one or more of hydrochloric acid, sulfuric acid, phosphoric acid and nitric acid, and the solid content of the two-dimensional magnetic nano composite material of the colloid dispersion liquid is 0.001-10 mg/ml;
(3) and applying an external magnetic field to the colloidal dispersion liquid to obtain the composite material dispersion liquid with adjustable optical properties.
4. The production method according to claim 3, wherein in the step (2), the solution is an aqueous hydrochloric acid solution,
the pH of the system is > 1.
5. The preparation method according to claim 3, wherein in the step (2), the two-dimensional magnetic nanocomposite of the colloidal dispersion has a solid content of 0.125mg/ml to 2.0mg/ml, so as to form a stable colloidal dispersion.
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