WO2022141180A1 - Method for stripping graphene oxide nano membrane from substrate - Google Patents

Abstract

Provided is a method for stripping a graphene oxide nano membrane from a substrate. The method comprises: placing in a reduction chamber having HI steam for chemical reduction, reducing for 10 min or more in an environment that the concentration of HI is 0.3 g/L or more and the concentration of water steam is 0.07 g/L or less, and automatically stripping graphene oxide from the substrate. The beneficial effects are that: steps for preparing an independent film are reduced; the operation is simpler, cheaper, and faster; the problems that an AAO membrane cannot bear the weight of a transfer agent since the strength of the membrane is not enough after the size of the nano membrane is increased, and a transfer operation is difficult in a solid-phase transfer process are avoided; and the integrity and uniformity of a large-size film are ensured.

Description

A kind of method of peeling graphene oxide nanofilm from substrate technical field

The invention relates to the field of nanomaterials, in particular to a method for peeling graphene oxide nanofilm from a substrate.

Background technique

In recent years, graphene oxide-based high-performance graphene-based macroscopic assembled films have been widely used in electrical, thermal, magnetic, optical and other fields.

However, there are still the following problems: First, in the thickness direction, the sub-micron thick graphene film has a great interlayer separation structure, and its stability is poor in a high temperature operating environment, and at the same time it seriously reduces the material The limit performance; second, compared with single-layer graphene, the macroscopically assembled graphene thick film and the substrate do not have good adhesion, so they cannot be used in microelectronic components. To this end, an independent support for macro-assembled nano-thick graphene films is needed. On the one hand, as the primitive of graphene thick films, it provides basic research materials for the structural control of macro-assembled graphene thick films; on the other hand, it assists graphite oxide. The graphene-based graphene assembly film has penetrated into the field of microelectronic devices, greatly breaking through its application limitations, and has won a place in the application field of CVD-based single-layer graphene.

At present, there are two strategies for preparing graphene oxide-based self-supporting graphene films: one is the solution-assisted interfacial separation method, in which the substrate is etched away with chemical reagents or infiltrated and separated with the help of a sublimable solid phase transfer agent. interface; second, cold shrinkage method, which directly uses the thermal expansion and cold shrinkage effect of the solid phase transfer agent to grab the nano film from the substrate. Both strategies require the assistance of a solid phase transfer agent, which limits the lateral size of the prepared graphene nanofilm; at the same time, the application of a solid phase transfer agent is complicated to operate and easy to damage; the transfer agent has a certain toxicity, and the transfer agent volatilization consumption longer time.

To this end, a method for avoiding the transfer agent and the etchant is required, avoiding the disadvantages of the transfer agent and the etchant, and at the same time, a graphene nano-film with a large area can be obtained.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a method for peeling graphene oxide nanofilm from a substrate in view of the deficiencies of the prior art.

The object of the present invention is achieved through the following technical solutions: a method for peeling off a graphene oxide nanofilm from a substrate, wherein the substrate is a rigid substrate with a porosity greater than 60%, and the graphene oxide nanofilm has a thickness of 20% -100nm; the method is: place it in a reduction chamber with HI steam for chemical reduction, and reduce for more than 10 minutes in an environment where the concentration of HI is above 0.3g/L and the concentration of water vapor is below 0.07g/L, Graphene oxide is automatically exfoliated from the substrate.

In the present application, HI steam with low water vapor content can be directly input, or an evaporation chamber communicated with the reduction chamber can be used to vaporize the hydroiodic acid, so as to input the HI steam into the reduction chamber.

In some embodiments, the reduction chamber and the evaporation chamber are located in the same closed cavity, and the evaporation chamber is located below the reduction chamber, and the evaporation chamber is located in an oil bath or a water bath with a temperature of 80-120 degrees Celsius; The top of the reduction chamber is a condensation zone, and the temperature of the condensation zone is controlled at 0-40°C (usually at room temperature). The hydriodic acid solution evaporates into HI vapor and water vapor. On the one hand, the water vapor condenses at the top, which reduces the water vapor content in the cavity, while the condensation temperature of HI is lower, and it remains gaseous. As a more preferred solution, a water-absorbing material is arranged in the condensation area to absorb water vapor and condensed water, so as to prevent the condensed water from re-evaporating after falling back. As a common technical means used in the art, the water-absorbing materials are: porous and strongly water-absorbing materials such as water-absorbing filter paper and superabsorbent resin, and strong water-absorbing chemicals such as calcium chloride and phosphorus pentoxide.

For the convenience of preparation, an HI-resistant rack is provided in the reduction chamber for loading the substrate, such as a PTFE mesh rack, a hollow glass rack, and the like.

In some embodiments, the reduction chamber and the evaporation chamber are each located in a closed cavity. And the two closed cavities are communicated through a condenser pipe; the condenser pipe condenses the water vapor evaporated in the evaporation chamber, and returns to the evaporation chamber. The iodic acid solution is evaporated into HI vapor and water vapor, and the water vapor is condensed in the condenser tube and refluxed to the evaporation chamber, while the condensation temperature of HI is lower, and it remains gaseous. As a common knowledge in the art, by setting parameters such as the length, inclination, and condensation environment of the condensation pipe, the content of water vapor entering the reduction chamber can be effectively controlled.

Preferably, both the evaporation chamber and the reduction chamber are located in an oil bath or a water bath with a temperature of 80-120 degrees Celsius. In some preferred solutions, the temperature of the reduction chamber is lower than that of the evaporation chamber, which is beneficial to The hydrogen iodide gas diffuses rapidly toward the reduction chamber. At the same time, after the hydrogen iodide is completely evaporated, the existence of the temperature difference will cause a pressure difference on both sides, and then the hydrogen iodide with higher mass density will be distributed in the reduction chamber in the low temperature region.

In this application, the substrate is anodized aluminum, tetrafluoroethylene filter membrane, glass fiber filter membrane, and the like.

The beneficial effects of the present invention are:

First, the independent film preparation steps are reduced, and the operation is simpler, cheaper and shorter;

Second, this method does not require a transfer agent, which avoids the problems that the strength of the AAO film is insufficient to withstand the weight of the transfer agent after the size of the nanofilm increases and the transfer operation is difficult during the solid phase transfer process, ensuring the integrity of the large-sized film;

Third, the complete penetration of hydrogen iodide in the reduction process avoids the non-uniform reduction in the reduction process of the solid phase transfer method and the tearing effect of the shrinkage effect of the solid phase transfer agent on the film, which further ensures the uniformity of the nano-film.

Description of drawings

Fig. 1 is the stepwise separation process diagram of graphene film and substrate;

Figure 2 is a graphene oxide membrane (4 inches) obtained by suction filtration on a rigid anodized aluminum filter membrane.

Figure 3 is a graphene oxide membrane (4 inches) after separation. Among them, Figure A1 is the graphene nanofilm transferred by the solid phase transfer agent. B1-D1 are the non-damaged graphene nanofilms prepared by the transfer agent-free method in the present application (corresponding to Examples 1-3 in sequence); A2-D2 are corresponding enlarged views.

4 is a schematic plan view A and a schematic perspective view B of the separation device of Example 1;

Fig. 5 is the separation device diagram of embodiment 2;

FIG. 6 is a diagram of a separation device of Example 3. FIG.

Detailed ways

The applicant found in a large number of graphene exfoliation experiments that the concentration of hydriodic acid vapor during the reduction process was insufficient, the relative vapor pressure was small, and the HI vapor was insufficient to completely penetrate into the contact interface between the graphene film and the substrate;

In addition, the HI vapor is mixed with water vapor, which plays a role in wetting. On the one hand, it hinders the rapid penetration of HI, and on the other hand, it wets the interface and inhibits the interface separation. The asymmetric reduction and penetration of hydriodic acid greatly reduces the contact area and force of the interface agent, and the weak contact interface can be peeled off by solvents such as isopropanol; Cannot be separated from the base. In this application, we propose a graphene film exfoliation method for rigid substrates with pores. By regulating HI and controlling the vapor pressure of water, the asymmetric reduction of HI and the interfacial permeation are enhanced. Gradual separation (Figure 1).

Compared with the preparation method of solid phase transfer, the gas-phase separation method of the patented method is milder and hardly has any strong tearing effect on the film, while the law of solid phase transfer is opposite. The specific performance is as follows: First, AAO is a brittle material. During the operation of the solid phase transfer agent, it will have a weight burden on AAO, which will damage the AAO film or fail to have good coverage continuity, resulting in discontinuous peeling of the solid phase transfer agent. Complete graphene nanofilms cannot be obtained (Fig. 2); however, gas-phase reduction does not have these problems, so perfect large-sized graphene films can be obtained. In terms of microstructure, the solid-phase transfer method may cause strong adhesion between graphene oxide and AAO substrate due to insufficient reduction of graphene, and form hole-type tearing in local areas under the action of cold shrinkage (Figure 3A1-A2). ), while the mild gas-phase transfer method does not have this problem, and a perfect graphene film without any tearing can be obtained (Figure 3B-D).

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

Comparative Example 1

Graphene exfoliation using a solid phase transfer agent (CN201710953513.8), the graphene oxide film has a thickness of 100 nm and an area of 80±5 cm ² , and is deposited on a rigid tetrafluoroethylene filter membrane with a porosity of 60% by suction filtration .

When the solid phase transfer method is used for separation, the experimenter needs to operate carefully. If the operation is improper and the attention is not focused, it is very easy to damage the graphene nanomembrane, especially in the process of cold grasping of the transfer agent, there is a chance of local hole damage, see Figure 3A1~A2 . In addition, the graphene and the substrate are still partially adhered.

Further, macroscopically, due to the uneven deposition of temperature or transfer agent, the local stress distribution is uneven, and the solid phase transfer agent shrinks and grasps unevenly, so that a complete large-scale graphene film (3A1) cannot be obtained; Small adhesion or uneven reduction, the graphene cannot be effectively peeled off during the grasping process, and then tiny holes will be formed, resulting in uneven material and affecting its performance stability in application scenarios.

Example 1:

In this embodiment, the device as shown in FIGS. 4A-B is used to peel off the graphene oxide film. The graphene oxide film has a thickness of 100 nm and an area of 80±5 cm ² , and is deposited on a rigid material with a porosity of 60% by suction filtration. tetrafluoroethylene filter membrane (same as in Comparative Example 1).

The device includes a cylindrical cavity 3, and the cavity 3 contains a hydroiodic acid solution 2. Above the liquid level of the hydroiodic acid solution, a polytetrafluoroethylene mesh frame 2 is fixed to seal the top cover of the cylindrical cavity. 4 is provided with a water-absorbing filter paper 5 .

The lower part of the cylindrical cavity is located in a water bath 1 at 80 degrees Celsius, and the sample to be peeled off is placed on a PTFE mesh frame 2 .

Under heating, the hydroiodic acid solution evaporates into HI vapor and water vapor. On the one hand, the water vapor condenses on the top and is absorbed by the water-absorbing filter paper to reduce the water vapor content in the cavity. Keep gaseous.

In this embodiment, the volume of the cylindrical cavity 3 is 1 L and the bottom area is 120 cm ² . The mass concentration of the hydroiodic acid solution in the cavity 3 is 50%, the mass content of HI is 0.42g, and the rest is water (0.42g). Water absorption filter paper (2g) has a water absorption limit of 60% of its mass. The ambient temperature at the upper part of the cavity 3 is 0 degrees Celsius.

After 5 minutes of heating, the hydroiodic acid solution 2 was completely evaporated, and the hydrogen iodide solution contained was reduced to invisible to the naked eye. The condensation of some water droplets was seen on the top layer, and the absorbent paper was hygroscopic and swelled. After the sampling test, the water-absorbing filter paper gained 0.44g in weight. At this time, after gas sampling and acid-base test, the concentration of hydriodic acid remained at 0.33g/L. It is proved that the water vapor content in cavity 3 is below 0.07g/L. After 1 hour, the acid-base test was carried out through gas sampling, and the concentration of hydriodic acid remained at 0.32g/L.

In order to avoid the influence of the above-mentioned sampling measurement on the graphene film, the same device is set up in this embodiment, and the sampling of the water-absorbing filter paper (2g) and the gas in the cavity are not carried out, and the same graphene oxide film is directly peeled off, and the processing time is 4h, after 4h, the graphene is detached, as shown in Figures 3B1-B2. It can be seen from the figure that under the reduction of hydriodic acid, the graphene film is completely detached from the substrate under the action of stress, and there is no macroscopic damage or microscopic pores during the detachment process.

Example 2:

In this embodiment, the device as shown in FIG. 5 is used to peel off the graphene oxide film. The graphene oxide film has a thickness of 60 nm and an area of 80±5 cm ² . on an aluminum filter.

The device includes two left and right cavities 11 and 12 . The cavities 11 and 12 are communicated through an inclined condenser pipe 13 . Both chambers 11 and 12 are placed in a water bath 14 at 80 degrees Celsius.

The cavity 11 is filled with a hydroiodic acid solution, and the cavity 12 is used for placing the graphene oxide film to be peeled off. The hydriodic acid solution in the cavity 11 is volatilized, and the water vapor in it is condensed and returned to the cavity 11 in the condenser tube, while the condensation temperature of HI is higher, which is input to the cavity 12 through the condenser tube 13 to construct the cavity 12 Environment with high HI concentration and low water vapor concentration.

In this embodiment, the volume of the cavities 11 and 12 is 400 mL, and the bottom area is 50 cm ² . The content of the hydriodic acid solution in the cavity 11 is 0.5g (the mass concentration of HI is 55%), the ambient temperature of the condenser tube 13 is 40 degrees Celsius, the length of the condenser tube is 20cm, and the inclination angle is 30 degrees, which can effectively ensure the cavity Construction of an environment with high HI concentration and low water vapor concentration in body 12.

It has been proved by experiments that after heating for 5 minutes, the hydroiodic acid solution completely evaporates, the water vapor condenses and returns to the cavity 11 at the front of the condenser tube, and no condensed water is produced at the rear of the condenser tube, indicating that almost no water vapor enters the right side. side recovery chamber. After the acid-base test of the gas sampling in the reduction chamber, the concentration of hydriodic acid remained at 0.43g/L.

After 30 minutes, the evaporation chamber on the right kept the evaporation-condensation reflux, and there was still no condensed water at the rear of the condenser tube. After sampling the gas in the reduction chamber for acid-base test, the concentration of hydriodic acid remained at 0.41g. /L.

In order to avoid the influence of the above sampling measurement on the graphene film, the same device is set up in this embodiment, and the gas in the cavity is not sampled, and the same graphene oxide film is directly peeled off. After 1h of reduction, the graphene is separated. See Figures 3C1-C2. It can be seen from the figure that under the reduction of hydriodic acid, the graphene film is completely detached from the substrate under the action of stress, and there is no macroscopic damage or microscopic pores during the detachment process.

Example 3:

In this embodiment, the device as shown in FIG. 6 is used to peel off the graphene oxide film. The graphene oxide film has a thickness of 60 nm and an area of 80±5 cm ² . on an aluminum filter.

The device includes two left and right cavities 11 and 12 . The cavities 11 and 12 are communicated through an inclined condenser pipe 13 . The cavity 11 is placed in an oil bath 14 of 120 degrees Celsius, and the cavity 12 is placed in a water bath 14 of 80 degrees Celsius.

The cavity 11 is filled with a hydroiodic acid solution, and the cavity 12 is used for placing the graphene oxide film to be peeled off. The hydriodic acid solution in the cavity 11 is volatilized, and the water vapor in it is condensed and returned to the cavity 11 in the condenser tube, while the condensation temperature of HI is higher, which is input to the cavity 12 through the condenser tube 13 to construct the cavity 12 Environment with high HI concentration and low water vapor concentration.

Same as Embodiment 2, in this embodiment, the volume of the cavities 11 and 12 is 400 mL, and the bottom area is 50 cm ² . The content of the hydroiodic acid solution in the cavity 11 is 0.3g (the mass concentration of HI is 55%), the ambient temperature where the condenser tube 13 is located is 20 degrees Celsius, the length of the condenser tube is 20cm, and the inclination is 30 degrees, which can effectively ensure the cavity Construction of an environment with high HI concentration and low water vapor concentration in body 12.

It has been proved by experiments that after heating for 5 minutes, the hydroiodic acid solution completely evaporates, the water vapor condenses and returns to the cavity 11 at the front of the condenser tube, and no condensed water is produced at the rear of the condenser tube, indicating that almost no water vapor enters the right side. side recovery chamber. After the acid-base test of the gas sampling in the reduction chamber, the concentration of hydriodic acid remained at 0.33g/L.

After 10 minutes, the evaporation chamber on the right kept the evaporation-condensation reflux, and there was still no condensed water at the rear of the condenser tube. After sampling the gas in the reduction chamber for acid-base test, the concentration of hydriodic acid remained at 0.30g. /L.

In order to avoid the influence of the above-mentioned sampling measurement on the graphene film, the same device is set up in this embodiment, and the gas in the cavity is not sampled, and the same graphene oxide film is directly peeled off. After reduction for 2h, the graphene is separated. See Figures 3D1-D2. It can be seen from the figure that under the reduction of hydriodic acid, the graphene film is completely detached from the substrate under the action of stress, and there is no macroscopic damage or microscopic pores in the detachment process.

Claims (9)

1. A method for peeling off a graphene oxide nano-film from a substrate, wherein the substrate is a rigid substrate with a porosity greater than 60%, and the graphene oxide nano-film has a thickness of 20-100 nm; it is characterized in that the method is: placing Carry out chemical reduction in a reduction chamber with HI vapor until graphene oxide is automatically peeled off from the substrate; during the reduction process, at least in an environment where the concentration of HI is above 0.3g/L, and the concentration of water vapor is below 0.07g/L Reduction for more than 10min.
2. The method according to claim 1, characterized in that, the method further adopts an evaporation chamber communicated with the reduction chamber to vaporize the hydroiodic acid, so as to input the HI vapor into the reduction chamber.
3. The method according to claim 2, wherein the reduction chamber and the evaporation chamber are located in the same closed cavity, the evaporation chamber is located below the reduction chamber, and the evaporation chamber is located in oil with a temperature of 80-120 degrees Celsius bath or water bath; the top of the reduction chamber has a condensation zone, and the temperature of the condensation zone is 0-40°C.
4. The method according to claim 3, wherein the condensation zone is provided with a water-absorbing material, and the water-absorbing material is a porous strong water-absorbing material such as water-absorbing filter paper, superabsorbent resin, calcium chloride, phosphorus pentoxide, etc. Isostrong absorbent chemicals.
5. The method of claim 3, wherein the reduction chamber is provided with an HI-resistant rack for loading the substrate.
6. The method according to claim 5, wherein the carrier is a polytetrafluoroethylene mesh frame, a hollow glass frame, or the like.
7. The method according to claim 2, wherein the reduction chamber and the evaporation chamber are respectively located in a closed cavity. And the two closed cavities are communicated through a condenser pipe; the temperature of the condenser pipe is 0-40°C. The condensation pipe condenses the water vapor evaporated in the evaporation chamber and returns to the evaporation chamber.
8. The method according to claim 7, wherein the evaporation chamber and the reduction chamber are located in an oil bath or a water bath with a temperature of 80-120 degrees Celsius, and the temperature of the reduction chamber is lower than that of the evaporation chamber.
9. The method according to claim 1, wherein the substrate is anodized aluminum, a tetrafluoroethylene filter membrane, or a glass fiber filter membrane.

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