CN107413599B - The preparation method of concentration tension gradient self-assembled coating - Google Patents

Abstract

A method for preparing a concentration-tension gradient self-assembled coating, comprising: providing a substrate and a colloidal solution, the colloidal solution comprising a first liquid and colloidal particles dispersed in the first liquid; providing a second liquid, the first The two liquids are miscible with the first liquid, and the surface tension of the second liquid is smaller than the surface tension of the first liquid, and a liquid film is formed on the surface of the substrate with the second liquid; The membrane is in contact with the colloidal solution, thereby forming a concentration-tension gradient self-assembled coating on the surface of the substrate. The invention can simply and efficiently obtain uniform concentration tension gradient self-assembled coatings on different substrates.

Description

Preparation method of concentration-tension gradient self-assembled coating

technical field

The invention relates to the field of materials, in particular to a preparation method of a concentration tension gradient self-assembled coating.

Background technique

Colloidal particles are organic or inorganic particles that are monodisperse and have a size of nanometers or submicrometers. Nanoscale and submicron-scale materials have many unique properties in terms of light, electricity, magnetism, and force. Colloidal particles are also playing an increasingly important role in many aspects of people's lives. Forming colloidal particles on the surface of the substrate to form a single-layer or multi-layer colloidal particle film can not only protect the substrate but also enable the overall performance of properties that colloidal particles do not have. It can be used for anti-corrosion, catalysis, photoelectric devices, sensors and fields of biomedicine.

The preparation of the colloidal particle film is mainly through the self-assembly of the colloidal particle, that is, using the interaction force between the colloidal particle and the colloidal particle and between the colloidal particle and the substrate surface (Coulomb force, van der Waals force and hydrophobic force, etc.), so that Under these actions, colloidal particles move toward the direction of free energy reduction, and when the energy of the system reaches the minimum, a stable single-layer or multi-layer colloidal particle film is formed. Generally, self-assembly methods for preparing colloidal particle films include spin coating, convection, pulling and electrostatic force methods, among which spin coating, convection and pulling methods all use the colloidal solution on the surface of the substrate. The film effect formed when wet, the electrostatic force method is to make the colloidal particles assemble to the substrate surface under the action of electrostatic attraction.

However, the spin coating method cannot form a uniform single-layer or multi-layer colloidal particle film on the curved surface, and the operation method of the convection method is relatively complicated, and requires many control parameters. Although the electrostatic force method is suitable for curved surfaces, it usually needs to modify the substrate, and it is difficult to control the number of layers of colloidal particles. The pulling method is to use the liquid surface of the colloidal solution to form a meniscus at the place where it contacts the substrate. The evaporation of the solution in this area induces the convection of the solution. Under this action, the colloidal particles move to the top of the meniscus. The thinned particles on the surface are precipitated and adsorbed on the substrate, and at the same time, the liquid level of the colloidal solution is controlled to move slowly relative to the substrate, so that new menisci are continuously formed at different positions on the substrate surface and new colloidal particles are adsorbed. A film of colloidal particles forms on the surface of the substrate. This method takes a long time to form a colloidal particle film and is inefficient, and when it is applied on a curved surface substrate, during the relative movement process, the shape of the meniscus formed by the curved surface substrate and the liquid surface is constantly changing, resulting in Less than uniform film of colloidal particles.

SUMMARY OF THE INVENTION

Based on this, it is necessary to provide a preparation method that is simple and efficient, has wide applicability to different substrates, and can form a uniform concentration-tension gradient self-assembled coating.

A method for preparing a concentration tension gradient self-assembled coating, comprising:

providing a substrate and a colloidal solution comprising a first liquid and colloidal particles dispersed in the first liquid;

providing a second liquid, the second liquid is miscible with the first liquid, and the surface tension of the second liquid is smaller than the surface tension of the first liquid, forming a liquid film; and

The liquid film is contacted with the colloidal solution, thereby forming a concentration-tension gradient self-assembled coating on the surface of the substrate.

In one of the embodiments, the method of contacting the liquid film with the colloidal solution includes: putting the substrate formed with the liquid film into the colloidal solution, making the liquid film contact with the colloidal solution. Contacting the colloidal solution; the preparation method of the concentration-tension gradient self-assembled coating further includes: pulling the substrate formed with the concentration-tension gradient self-assembled coating out of the colloidal solution.

In one of the embodiments, the surface tension of the second liquid is less than or equal to 1/2 of the surface tension of the first liquid.

In one of the embodiments, the surface of the substrate used to form the liquid film is a plane or a curved surface.

In one of the embodiments, the surface of the substrate used to form the liquid film is a continuous surface or a discontinuous surface.

In one embodiment, the first liquid is water, and the second liquid is at least one of ethanol, acetone, acetic acid and methanol.

In one of the embodiments, during the process of pulling the substrate out of the colloidal solution, the sandwich between the surface of the substrate formed with the concentration-tension gradient self-assembled coating and the liquid level of the colloidal solution The angle is greater than 45° and less than 135°.

In one embodiment, the speed at which the substrate is pulled out of the colloid solution is less than 5 mm/s.

In one embodiment, the speed at which the substrate is pulled out of the colloid solution is greater than 2 mm/s.

In one embodiment, after the substrate is pulled out of the colloid solution, the step of drying the substrate is further included.

In the preparation method of the concentration tension gradient self-assembled coating provided by the present invention, when the liquid film is in contact with the colloidal solution, the second liquid diffuses to the first liquid, and forms a layer separated from the substrate The closer the surface distance, the higher the concentration gradient of the second liquid. Since the surface tension of the second liquid is smaller than that of the first liquid, an interfacial tension gradient can be formed in which the closer the distance to the surface of the substrate is, the smaller the interfacial tension is. Under the action of the interfacial tension gradient, the colloidal particles move toward the direction in which the interfacial tension decreases until they contact the surface of the substrate, and are adsorbed on the surface of the substrate under the action of van der Waals gravity to form a self-assembled coating .

The present invention utilizes the interfacial tension gradient formed by the first liquid and the second liquid to quickly realize the self-assembly of the colloidal particles and the preparation of the self-assembled coating, and can form a uniform coating on different substrates. The self-assembled coating has high preparation efficiency, simple operation, easy control and low cost, and is conducive to large-scale industrial preparation.

Description of drawings

Fig. 1 is the flow chart of the preparation method of concentration tension gradient self-assembled coating provided by the present invention;

2 is a scanning electron micrograph of the concentration tension gradient self-assembled coating provided in Example 1 of the present invention;

3 is a scanning electron micrograph of the concentration tension gradient self-assembled coating provided by Example 2 of the present invention;

Fig. 4 is a scanning electron micrograph of the concentration tension gradient self-assembled coating provided in Example 3 of the present invention.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail through the following embodiments and in conjunction with the accompanying drawings. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

Please refer to Figure 1, the first embodiment of the present invention provides a method for preparing a concentration-tension gradient self-assembled coating, including:

S1, providing a substrate and a colloidal solution, the colloidal solution comprising a first liquid and colloidal particles dispersed in the first liquid;

S2, providing a second liquid, the second liquid is miscible with the first liquid, and the surface tension of the second liquid is smaller than the surface tension of the first liquid, and using the second liquid on the surface of the substrate forming a liquid film; and

S3, bringing the liquid film into contact with the colloidal solution, so as to assemble the colloidal particles on the surface of the substrate to form a self-assembled coating.

In step S1, the material and type of the substrate are not limited, and can be selected according to actual needs. The surface of the substrate used to form the liquid film may be a plane or a curved surface. The surface of the substrate used to form the liquid film may be a continuous surface or a discontinuous surface, such as a mesh surface. The substrate can be prepared from at least one of organic materials, inorganic materials and metal materials. The substrate may also be a fibrous substrate.

The types of the colloidal particles and the first liquid are not limited, as long as the colloidal solution can be formed. The first liquid may be at least one of an organic solvent and an inorganic solvent, for example, the first liquid may be water. The colloidal particles may be inorganic particles (such as nano-silver particles) or organic particles (such as polytetrafluoroethylene capsule particles, PTFE). The shape of the colloidal particles can be spherical or capsule.

In step S2, the type of the second liquid is not limited, as long as it can wet the substrate to form the liquid film. Preferably, the second liquid itself has relatively low surface tension so as to form the liquid film on the substrate. The second liquid may be at least one of ethanol, acetone, acetic acid and methanol.

The method of forming the liquid film on the substrate with the second liquid is not limited. In one embodiment, the method for forming the liquid film on the substrate with the second liquid includes: fully immersing the substrate in the second liquid, and then removing the substrate from the second liquid to form the liquid film on the substrate. The relatively uniform liquid film can be obtained simply and quickly by adopting the pulling method. Preferably, said substrate is vertically liftable from said second liquid.

Further, before forming the liquid film on the substrate, the step of cleaning the substrate may also be included to remove residual stains on the surface of the substrate. The substrate may be cleaned with at least one of acetone, ethanol and deionized water. After cleaning, the surface of the substrate is dried to form the liquid film.

In step S3, when the liquid film is in contact with the colloidal solution, the second liquid diffuses toward the first liquid and forms a layer that is closer to the surface of the substrate, the second liquid The higher the concentration of the concentration gradient. Since the surface tension of the second liquid is smaller than that of the first liquid, an interfacial tension gradient can be formed in which the closer the distance to the surface of the substrate is, the smaller the interfacial tension is. Under the action of the interfacial tension gradient, the colloidal particles move toward the direction in which the interfacial tension decreases until they contact the surface of the substrate, and are adsorbed on the surface of the substrate under the action of van der Waals gravity to form the self-assembly coating.

The preparation method of the concentration tension gradient self-assembly coating provided by the present invention can quickly realize the self-assembly of the colloidal particles by using the interfacial tension gradient formed by the first liquid and the second liquid, and the operation is simple and efficient, easy to realize, and control parameters Less, and has universal applicability to different substrates. In addition, no matter what kind of substrate is used, the self-assembly conditions of the colloidal particles are the same, so a uniform self-assembled coating can be obtained.

When the second liquid is a volatile solvent (such as ethanol), the liquid film can be quickly contacted with the colloid solution to prevent the second liquid from volatilizing before the liquid film contacts the colloid solution.

The greater the difference between the surface tension of the second liquid and the surface tension of the first liquid, the smoother and faster the colloidal particles can be adsorbed on the substrate and the smoother and faster the formation of the self-assembled coating. Preferably, the surface tension of the second liquid is less than or equal to 1/2 of the surface tension of the first liquid.

After the self-assembled coating is formed, even if the first liquid and the second liquid are uniformly mixed by diffusion, the interfacial tension gradient disappears, and the self-assembled coating is due to the van der Waals force, etc., can still be firmly adsorbed on the surface of the substrate.

In one embodiment, the substrate formed with the liquid film may be put into the colloid solution, so that the liquid film is in contact with the colloid solution. Since the colloidal particles in the colloidal solution may be a large number, in addition to self-assembling on the surface of the substrate to form a self-assembled coating, some colloidal particles may exist freely in the second liquid, the preparation of the concentration tension gradient self-assembled coating After forming the concentration tension gradient self-assembled coating, the method may further include:

S4, pulling out the substrate formed with the concentration-tension gradient self-assembled coating from the colloidal solution.

In step S4, pulling the substrate out of the colloid solution specifically refers to making the surface of the substrate formed with the self-assembled coating and the The liquid surface angle of the colloidal solution is greater than 0° and less than 180°, so that the colloidal solution containing free colloidal particles that are not assembled into a self-assembled coating remains in the process of preventing the substrate from being detached from the colloidal solution The self-assembled coating affects the uniformity of the self-assembled coating. Preferably, in the process of pulling the substrate out of the colloidal solution, the angle between the surface of the substrate on which the concentration-tension gradient self-assembled coating is formed and the liquid level of the colloidal solution is greater than 45° and less than 135°, to ensure that no excess colloidal solution remains on the substrate.

The substrate can be slowly pulled out of the colloid solution, so that the colloid solution will not be carried out by the substrate, thereby ensuring the uniformity of the finally obtained self-assembled coating. Preferably, the speed at which the substrate is pulled out of the colloid solution is less than 5 mm/s, so as to ensure that the colloid solution will not be carried out by the substrate. More preferably, the speed at which the substrate is pulled out of the colloid solution is greater than 2 mm/s, so that the substrate can be quickly detached from the colloid solution.

After the step S4, a step of drying the substrate may also be included to remove the first liquid and/or the second liquid on the surface of the substrate. The method of drying the substrate can be selected according to actual needs, for example, the substrate can be dried by natural air drying.

Example 1:

The silicon wafer was washed successively with acetone, ethanol, and deionized water for 5 minutes each, and dried with argon gas after cleaning. Put the silicon wafer into absolute ethanol, pull it out of the liquid surface vertically, and the ethanol spreads into a thin film on the surface of the silicon wafer. Dilute the PTFE colloid solution with a mass fraction of 60% with deionized water into a 6% PTFE colloid solution, ultrasonically stir for 10 minutes, and put the substrate vertically into the 6% PTFE colloid solution before the ethanol volatilizes Then, pull out the liquid surface vertically at a speed of 3 mm/s, and place the silicon wafer in the air to dry naturally. After the water evaporates, it is characterized by a scanning electron microscope. As shown in Figure 2, it can be seen that the silicon wafer is covered with PTFE. Covered by the self-assembled coating, the PTFE self-assembled coating is single-layer and has good uniformity.

Example 2:

This embodiment is basically the same as the embodiment 1, except that the mass fraction of the PTFE colloid solution is diluted to 12% by deionized water. Characterized by a scanning electron microscope, as shown in Figure 3, the silicon wafer is covered by a PTFE self-assembled coating, and the PTFE self-assembled coating is double-layered and has good uniformity.

Example 3:

This embodiment is basically the same as the embodiment 1, except that the base is a stainless steel mesh. Characterized by a scanning electron microscope, as shown in Figure 4, the stainless steel mesh is covered by a PTFE self-assembled coating, and the PTFE self-assembled coating has good uniformity.

As can be seen from the above examples, the self-assembly method of colloidal particles provided by the present invention is not only simple, efficient, and easy to implement, but also can be applied to substrate surfaces such as plane and curved surfaces, and has strong applicability, and the self-assembly coating The number of layers of colloidal particles in the medium can be accurately controlled according to the concentration of the colloidal solution. The greater the concentration of the colloidal solution, the more layers of the self-assembled coating, so that a single-layer or multi-layer self-assembled coating can be obtained. coating.

The technical features of the above-mentioned embodiments can be combined arbitrarily. To make the description concise, all possible combinations of the technical features in the above-mentioned embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, should be considered as within the scope of this specification.

The above-mentioned embodiments only express several implementation modes of the present invention, and the descriptions thereof are relatively specific and detailed, but should not be construed as limiting the patent scope of the invention. It should be pointed out that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the appended claims.

Claims (9)

1. A preparation method of concentration tension gradient self-assembled coating, comprising: providing a substrate and a colloidal solution comprising a first liquid and colloidal particles dispersed in the first liquid; providing a second liquid, the second liquid is miscible with the first liquid, and the surface tension of the second liquid is smaller than the surface tension of the first liquid, forming a liquid film; and The liquid film is contacted with the colloidal solution, so that the colloidal particles are assembled on the surface of the substrate to form a concentration tension gradient self-assembled coating. 2. the preparation method of concentration tension gradient self-assembled coating according to claim 1, is characterized in that, described method that described liquid film is contacted with described colloidal solution comprises: will be formed with the described liquid film Putting the substrate into the colloidal solution, making the liquid film contact with the colloidal solution; The preparation method of the concentration-tension gradient self-assembled coating further includes: pulling the substrate formed with the concentration-tension gradient self-assembled coating out of the colloidal solution. 3. The method for preparing a concentration-tension gradient self-assembled coating according to claim 1, wherein the surface tension of the second liquid is less than or equal to 1/2 of the surface tension of the first liquid. 4. The method for preparing a concentration-tension gradient self-assembled coating according to claim 1, wherein the surface of the substrate used to form the liquid film is a plane or a curved surface. 5. the preparation method of concentration tension gradient self-assembled coating according to claim 1 is characterized in that, described first liquid is water, and described second liquid is at least one in ethanol, acetone, acetic acid and methyl alcohol . 6. the preparation method of concentration tension gradient self-assembly coating according to claim 2, is characterized in that, in the process that described substrate is pulled out from described colloidal solution, make to form the described concentration tension gradient self-assembly The included angle between the substrate surface of the coating and the liquid surface of the colloid solution is greater than 45° and less than 135°. 7. The method for preparing the concentration-tension gradient self-assembled coating according to claim 2, characterized in that the speed at which the substrate is pulled out of the colloid solution is less than 5 mm/s. 8 . The method for preparing a concentration-tension gradient self-assembled coating according to claim 2 , wherein the speed at which the substrate is pulled out of the colloidal solution is greater than 2 mm/s. 9 . The method for preparing a concentration-tension gradient self-assembled coating according to claim 2 , further comprising a step of drying the substrate after the substrate is pulled out from the colloid solution.