Graphene liquid cell and preparation method and application thereof

Abstract

The application relates to the technical field of in-situ characterization and electron microscopy analysis of nanomaterials, in particular to a graphene liquid cell and a preparation method and application thereof. The graphene liquid cell comprises a first transmission electron microscope (TEM) carrier net, a second TEM carrier net and a liquid confined space formed between the first TEM carrier net and the second TEM carrier net; the second TEM carrier net is arranged above the first TEM carrier net, and a first double-layer graphene encapsulation window and a second double-layer graphene encapsulation window are oppositely arranged to jointly encapsulate the liquid confined space; the two double-layer graphene encapsulation windows each comprise two layers of graphene atomic layers arranged in a stack. The double-layer graphene encapsulation window has higher interlayer bonding stability and mechanical bearing capacity, can enhance the resistance of the double-layer graphene encapsulation window to external mechanical action, internal liquid pressure change and electron beam irradiation induced damage, and can improve the structural integrity of the liquid confined space and the liquid retention stability.

Description

Technical Field

[0001] This invention relates to the field of in-situ characterization and electron microscopy analysis of nanomaterials, specifically to a graphene liquid pool, its preparation method, and its application. Background Technology

[0002] Compared to traditional transmission electron microscopy, which can only observe solid samples, in-situ liquid phase transmission electron microscopy (LC-TEM) confines liquid samples in a closed space through a liquid cell, allowing the liquid to remain stable under electron beam irradiation, thereby enabling real-time characterization of nanoscale dynamic processes.

[0003] Currently, transmission electron microscopy (TEM) commonly employs encapsulation structures such as silicon nitride liquid cells, carbon film liquid cells, and graphene liquid cells. Among these, graphene, due to its atomic-level thickness, high electronic transparency, high mechanical strength, excellent flexibility, and chemical stability, can significantly reduce electron scattering and improve imaging resolution, making it an important window material for constructing ultrathin liquid cells. Graphene liquid cells (GLCs), formed by encapsulating two monolayer graphene films arranged opposite each other, have been widely used for in-situ observation of dynamic processes such as nanoparticle nucleation and growth, migration etching, and nanobubble generation. Under the combined action of high vacuum and electron beam irradiation, the liquid within the graphene liquid cell undergoes radiolysis, gas evolution, and local reconstruction, thereby forming confined liquid phase structures such as nanobubbles, ultrathin liquid films, nanodroplets, and liquid bridges. When solid nanomaterials are present in the system, a gas-liquid-solid three-phase interface can be further constructed. Such interfaces are widely found in systems such as electrocatalytic gas evolution, metal corrosion, liquid-phase nanomaterial growth, gas-liquid interface catalysis, and nano-confined reactions. Their structure and dynamic evolution directly affect material growth behavior, interfacial mass transfer efficiency, and reaction kinetics. Therefore, the in-situ construction and dynamic characterization of such interfaces have extremely high research value.

[0004] However, existing graphene liquid pools still have significant limitations: First, the graphene used is mostly derived from polycrystalline metal substrates such as copper foil, which have problems such as grain boundaries, differences in crystal orientation, steps, wrinkles, and large roughness on their surfaces. This leads to defects such as wrinkles, cracks, and local collapses after the graphene is transferred to the transmission electron microscope (TEM) grid, resulting in uneven thickness of the liquid confinement space and directly reducing the stability and reproducibility of the liquid pool. Second, existing technologies mostly use monolayer graphene as a single-sided encapsulation window. The suspended structure is prone to cracking and local leakage under liquid encapsulation, high vacuum environment, and electron beam irradiation, making it difficult to support long-term continuous in-situ observation. Third, existing research mostly focuses on single processes such as nanoparticle growth and nanobubble evolution, with insufficient research on the stable construction and continuous in-situ characterization of the gas-liquid-solid three-phase interface within the same confinement space, especially lacking a systematic design scheme for the relationship between the graphene encapsulation window structure, the substrate, and the stability of the liquid pool.

[0005] Therefore, there is an urgent need to provide a new graphene liquid pool to achieve the stable coexistence of gas-phase structures, liquid-phase structures and solid nanomaterials in the same confined space, and to realize continuous in-situ observation and dynamic characterization of the gas-liquid-solid three-phase interface. Summary of the Invention

[0006] The purpose of this invention is to provide a graphene liquid pool that improves the stability and repeatability of the liquid confinement space by optimizing the graphene encapsulation window structure and its preparation source, so as to achieve the stable coexistence of gas-phase structures, liquid-phase structures and solid nanomaterials in the same confinement space.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a graphene liquid pool, comprising a first transmission electron microscope (TEM) grid, a second TEM grid, and a liquid confinement space formed between the first TEM grid and the second TEM grid; The first transmission electron microscope (TEM) support includes a first support body and a first double-layer graphene encapsulation window covering the perforated area of ​​the first support body. The second transmission electron microscope (TEM) support includes a second support body and a second double-layer graphene encapsulation window covering the perforated area of ​​the second support body; The second transmission electron microscope (TEM) mesh is positioned above the first TEM mesh, and the first double-layer graphene encapsulation window and the second double-layer graphene encapsulation window are positioned opposite each other to jointly encapsulate and form the liquid confinement space. Both the first double-layer graphene encapsulation window and the second double-layer graphene encapsulation window include two stacked graphene atomic layers, and the two graphene atomic layers cover the hole areas corresponding to the first or second carrier body.

[0008] Furthermore, the two graphene atomic layers are formed by transferring a bilayer graphene film grown on the surface of a wafer-based single-crystal metal thin film substrate.

[0009] Furthermore, the wafer-based single-crystal metal thin film substrate is a Cu(111) copper single-crystal thin film substrate or a CuNi(111) copper-nickel single-crystal alloy thin film substrate formed on a wafer support substrate; The wafer support substrate is a sapphire wafer or a silicon oxide wafer.

[0010] This application provides a method for preparing a graphene liquid pool, comprising the following steps: A wafer-based single-crystal metal thin film substrate is obtained, and a bilayer graphene film is grown on the surface of the wafer-based single-crystal metal thin film substrate to obtain a bilayer graphene / substrate composite structure. The bilayer graphene / substrate composite structure is cut to obtain multiple bilayer graphene transfer units with target size; Obtain a first and a second carrier body, attach the first and second carrier bodies to different bilayer graphene transfer units respectively, and make the bilayer graphene film face the corresponding first or second carrier body respectively to form a carrier body / bilayer graphene / substrate composite structure. The composite structure of the carrier / bilayer graphene / substrate is etched to remove the wafer-based single-crystal metal thin film substrate, so that the bilayer graphene film is transferred to the corresponding hole area of ​​the first carrier or the second carrier, forming the first transmission electron microscope carrier and the second transmission electron microscope carrier, respectively. The second transmission electron microscope (TEM) mesh and the first TEM mesh are assembled facing each other, so that the bilayer graphene films on the second TEM mesh and the first TEM mesh are brought close to each other to form a liquid confinement space, thus obtaining a graphene liquid pool.

[0011] Furthermore, the bilayer graphene / substrate composite structure is bonded to the first or second substrate using a polymer-free transfer method.

[0012] This application provides the application of the above-mentioned graphene liquid pool in in-situ characterization studies of gas-liquid-solid three-phase interfaces, including the following steps: S1. The sample to be tested, which contains liquid medium and solid nanomaterials, is loaded onto the first double-layer graphene encapsulation window, and the second transmission electron microscope (TEM) mesh is placed over the first TEM mesh so that the second double-layer graphene encapsulation window faces the first double-layer graphene encapsulation window, forming a sample liquid pool. S2. The graphene liquid pool is placed in the vacuum environment of a transmission electron microscope and subjected to continuous irradiation treatment. The electron beam irradiation effect induces the liquid medium to undergo gas-liquid phase transformation or interface reconstruction, so that a gas-liquid-solid three-phase interface in which gas phase structure, liquid phase structure and solid nanomaterial coexist is formed in the liquid confined space. S3. Continuously acquire transmission electron microscope image sequences to conduct in-situ observation of the dynamic evolution process of the gas-liquid-solid three-phase interface.

[0013] Furthermore, it also includes: performing image processing, structure recognition, and time series analysis on the acquired transmission electron microscope image sequence to obtain the dynamic parameters of the gas phase structure, liquid phase structure, and solid nanomaterials, respectively; Based on the dynamic parameters, the spatial and temporal evolution relationships of the gas-liquid-solid three-phase interface are established.

[0014] Furthermore, the dynamic parameters include one or more of the following: bubble size change, droplet size change, interface migration distance, interface fluctuation frequency, solid nanomaterial motion trajectory, diffusion rate, aggregation rate, and growth rate.

[0015] Furthermore, the gas phase structure includes any one or more of the following: nanobubbles induced by continuous irradiation treatment, nanobubbles retained during the encapsulation process, and nanobubbles formed by the precipitation of dissolved gases in a liquid system. The liquid phase structure includes any one or more of the following: confined liquid layer, ultrathin liquid film, nanodroplet, and liquid bridge; The solid nanomaterial is located at the boundary of the nanobubble, the edge of the nanodroplet, the ultrathin liquid film region, or the liquid bridge region.

[0016] Furthermore, the liquid medium is selected from one or more of deionized water, salt solution, metal ion solution or reaction precursor solution; The solid nanomaterial is selected from one or more of the following: metal nanoparticles, metal nanoclusters, two-dimensional materials, oxide nanomaterials, or nanoproducts formed under electron beam irradiation.

[0017] The beneficial effects of this invention are as follows: The graphene liquid pool provided in this application, by setting double-layer graphene encapsulation windows formed by stacking two layers of graphene atoms in the porous regions of the first and second carrier bodies, ensures that both the upper and lower encapsulation surfaces of the liquid confinement space are composed of continuous double-layer graphene structures. Compared with single-layer graphene encapsulation structures, double-layer graphene encapsulation windows have higher interlayer bonding stability and mechanical load-bearing capacity, enhancing the resistance of the encapsulation window to external mechanical forces, internal liquid pressure changes, and electron beam irradiation-induced damage, reducing the occurrence of window breakage, local collapse, and sealing failure. Simultaneously, the double-layer graphene encapsulation windows can improve the structural integrity and liquid retention stability of the liquid confinement space, enabling the gas phase region, liquid phase region, and the observed solid nanomaterial to coexist stably for a long time under transmission electron microscopy observation conditions, thereby improving the reliability and continuity of in-situ transmission electron microscopy observation of the dynamic processes at the gas-liquid-solid three-phase interface.

[0018] The graphene liquid pool provided in this application has a bilayer graphene encapsulation window obtained by transferring a bilayer graphene film grown on a wafer-based single-crystal metal thin-film substrate. Compared to traditional copper foil substrates, wafer-based single-crystal metal thin-film substrates have more uniform crystal orientation, lower surface roughness, and better in-plane structural consistency, providing a more stable growth interface for the formation of the bilayer graphene film and reducing grain boundary defects and structural discontinuities during graphene growth. Simultaneously, the higher surface flatness of the wafer-based single-crystal metal thin-film substrate helps reduce transfer-induced wrinkles, warping, and localized strain concentrations during graphene film transfer and encapsulation window formation. This results in a bilayer graphene encapsulation window with higher structural integrity, lower wrinkle density, and smaller surface undulations, enabling the formation of a liquid confinement space with more uniform thickness distribution and more stable morphology. This effectively reduces imaging interference caused by graphene window defects and uneven liquid layer thickness during in-situ observation using transmission electron microscopy, improves the stability of the liquid confinement space and the accuracy of sample interface positioning, thereby enhancing the observation quality and reliability of transmission electron microscopy for the gas-liquid-solid three-phase interface structure and dynamic evolution process.

[0019] The preparation method provided in this application involves growing a continuous bilayer graphene film on a wafer-level single-crystal metal thin-film substrate and preparing a graphene liquid pool using a polymer-free transfer process. This results in graphene encapsulation windows with high mechanical strength, structural integrity, cleanliness, and electron transmission performance, while simultaneously improving the thickness uniformity and morphological stability of the liquid confinement space. By employing a polymer-free transfer method, the polymer residue problem associated with traditional methods using organic polymers such as PMMA as transfer media can be avoided. This reduces the impact of organic contaminants on the properties of the liquid medium, the surface state of the nanomaterials, and the gas-liquid-solid interface reaction process. Furthermore, it reduces electron beam scattering caused by contaminants, improving electron transmission efficiency and image quality during transmission electron microscopy observation, which is beneficial for achieving high-resolution in-situ observation of nanoscale structural evolution processes.

[0020] This application provides a graphene liquid cell for in-situ characterization of gas-liquid-solid three-phase interfaces. It enables the construction of such interfaces and utilizes electron beam irradiation to induce radiolysis, gas evolution, and interface structure reconstruction in the liquid medium. This allows gaseous, liquid, and solid nanomaterials to coexist stably within the same nanoscale confined space, achieving in-situ construction and dynamic, continuous, and quantitative characterization of the gas-liquid-solid three-phase interface. This application provides a new experimental platform for studying nanomaterial growth processes, catalytic reaction mechanisms, electrochemical interface evolution, and nanoscale interface dynamics.

[0021] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the preparation process of the graphene liquid pool shown in Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the preparation process of the graphene liquid pool shown in Embodiment 2 of the present invention; Figure 3 This is a schematic diagram of the preparation process of the graphene liquid pool shown in Embodiment 3 of the present invention; Figure 4 This is a scanning electron microscope image of the double-layer graphene encapsulation window shown in Embodiment 1 of the present invention; Figure 5 An atomic force microscope image of the double-layer graphene encapsulation window shown in Embodiment 1 of the present invention; Figure 6 An atomic force microscope image of the double-layer graphene encapsulation window shown in Embodiment 2 of the present invention; Figure 7This is a scanning electron microscope image of the double-layer graphene encapsulation window shown in Embodiment 3 of the present invention; Figure 8 The transmission electron microscope time-series image shows the formation and dynamic evolution of nanobubbles induced by electron beam irradiation in a graphene liquid pool as shown in Example 1 of this invention. Figure 9 The images are transmission electron microscope time-series images of the construction and evolution of the gas-liquid-solid three-phase interface in the graphene liquid pool and the migration behavior of solid nanoparticles under the action of nanobubbles, as shown in Example 1 of this invention.

[0023] Figure label: 1. Bilayer graphene / substrate composite structure; 11. Graphene transfer unit; 2. First transmission electron microscope (TEM) grid; 21. First grid body; 3. Second TEM grid; 31. Second grid body; 4. Monolayer graphene / substrate composite structure; 5. Grid body / graphene / substrate composite structure. Detailed Implementation

[0024] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0026] Please see Figure 1 This application discloses a preferred embodiment of a graphene liquid pool. The graphene liquid pool includes a first transmission electron microscope (TEM) mesh 2, a second TEM mesh 3, and a liquid confinement space formed between the first TEM mesh 2 and the second TEM mesh 3. The first TEM mesh 2 includes a first mesh body 21 and a first double-layer graphene encapsulation window covering the perforated area of ​​the first mesh body 21. The second TEM mesh 3 includes a second mesh body 31 and a second double-layer graphene encapsulation window covering the perforated area of ​​the second mesh body 31. The second TEM mesh 3 is disposed above the first TEM mesh 2, with the first and second double-layer graphene encapsulation windows facing each other to jointly encapsulate and form the liquid confinement space. Both the first and second double-layer graphene encapsulation windows each include two stacked graphene atomic layers, and these two graphene atomic layers cover the perforated area of ​​the corresponding first mesh body 21 or second mesh body 31. Ideally, each graphene atomic layer should have a continuous and dense morphology.

[0027] In this embodiment, a double-layer graphene encapsulation window, formed by stacking two atomic layers of graphene, is set in the perforated regions of the two carrier bodies. This suspended encapsulation window improves the sealing performance of the liquid confinement space, effectively suppressing liquid evaporation and contaminant intrusion, and enabling the nanoscale liquid environment to be stably maintained under the high vacuum environment of a transmission electron microscope. Compared to single-layer graphene, this double-layer graphene encapsulation window also has higher mechanical strength and resistance to electron beam irradiation, reducing the risk of graphene breakage, perforation, or failure during liquid encapsulation, and improving the structural stability and lifespan of the graphene liquid pool. Simultaneously, the near-atomic thickness of the double-layer graphene structure reduces the scattering effect during electron beam penetration, improving the electron imaging quality of the liquid phase region and the solid-liquid interface, supporting the precise observation of nanoscale dynamic processes. The liquid confinement space constructed through this double-layer graphene window allows for in-situ observation in a real liquid environment within the transmission electron microscope, overcoming the technical bottleneck of traditional TEM's inability to directly observe liquid samples.

[0028] In one embodiment, the two graphene atomic layers are formed by transferring a bilayer graphene film grown on the surface of a wafer-based single-crystal metal thin-film substrate. That is, the bilayer graphene film comprises two continuous graphene atomic layers covering the surface of the wafer-based single-crystal metal thin-film substrate. Using a wafer-level single-crystal metal thin film as the growth substrate enables large-area fabrication of bilayer graphene films, increasing the film coverage area and batch production capability. The resulting continuous bilayer graphene film has low defect density and high crystal quality, maintains the integrity of the bilayer structure during the transfer process, and can form a uniform and transparent liquid encapsulation window, improving the reliability of TEM observation.

[0029] In one embodiment, the wafer-based single-crystal metal thin-film substrate includes at least one of a Cu(111) copper single-crystal thin-film substrate and a CuNi(111) copper-nickel single-crystal alloy thin-film substrate formed on a wafer support substrate. The high lattice matching between the Cu(111) and CuNi(111) crystal planes can induce ordered nucleation and continuous growth of graphene, thereby improving the crystal quality of the bilayer graphene film. Furthermore, the wafer-based single-crystal copper thin-film or single-crystal copper-nickel alloy thin-film substrate can provide a flatter and more uniform growth and transfer foundation for the bilayer graphene film, enabling the resulting bilayer graphene film to form a highly intact and flat suspended encapsulation window in the perforated region of the transmission electron microscope grid, thereby supporting the construction of a stable and precisely traceable graphene liquid pool and gas-liquid-solid three-phase interface. The wafer support substrate is a sapphire wafer, a silicon oxide wafer, or other insulating substrate with wafer-level support capabilities; and preferably a sapphire wafer. Sapphire wafers are characterized by high thermal stability, good dimensional stability, and strong high-temperature resistance, making them suitable for wafer-level graphene growth processes and significantly improving the consistency of batch production.

[0030] One embodiment provides a method for preparing the above-mentioned graphene liquid pool. The preparation method includes the following steps: A wafer-based single-crystal metal thin film substrate was obtained, and a bilayer graphene film was grown on the surface of the wafer-based single-crystal metal thin film substrate to obtain a bilayer graphene / substrate composite structure 1. The bilayer graphene / substrate composite structure 1 is cut to obtain multiple bilayer graphene transfer units 11 with target size; Obtain the first grid body 21 and the second grid body 31, attach the first grid body 21 and the second grid body 31 to different bilayer graphene transfer units 11 respectively, and make the bilayer graphene film face the corresponding first grid body 21 or second grid body 31 respectively to form a grid body / bilayer graphene / substrate composite structure 1. The composite structure 1 of the carrier body / bilayer graphene / substrate is etched to remove the wafer-based single crystal metal thin film substrate, so that the bilayer graphene is transferred to the hole area of ​​the corresponding first carrier body 21 or second carrier body 31, forming the first transmission electron microscope carrier body 2 and the second transmission electron microscope carrier body 3, respectively. The second transmission electron microscope (TEM) screen 3 and the first TEM screen 2 are assembled facing each other, so that the bilayer graphene films on the second TEM screen 3 and the first TEM screen 2 are brought close to each other to form a liquid confinement space, thus obtaining a graphene liquid pool.

[0031] This preparation method avoids the size limitations and equipment compatibility issues caused by directly growing graphene on the grid by first preparing a bilayer graphene film and then transferring it to a transmission electron microscope (TEM) support. The transfer of the bilayer graphene film is achieved using metal thin-film etching, resulting in a large-area continuous graphene window covering the grid's pores. This facilitates the formation of a stable and controllable liquid confinement space, improving the success rate of liquid sample encapsulation. The preparation method has a simple process flow, is compatible with existing TEM grid structures, and is suitable for large-scale fabrication.

[0032] In one embodiment, the bilayer graphene / substrate composite structure 1 is bonded to the first substrate 21 or the second substrate 31 using a polymer-free transfer method. In this embodiment or other embodiments, the polymer-free transfer method includes: dropping a volatile organic solvent onto the substrate, and using the capillary adhesion generated during the evaporation of the volatile organic solvent to bond and fix the bilayer graphene film to the substrate. In some embodiments, the volatile organic solvent is selected from isopropanol, ethanol, acetone, or combinations thereof. This polymer-free transfer method utilizes the capillary force generated by solvent evaporation to achieve bonding and fixation, which can reduce mechanical damage during the transfer process and improve the integrity retention rate of the bilayer graphene film; it can avoid the problem of polymer residue contamination on the graphene surface during traditional polymer-assisted transfer processes such as PMMA, improving the cleanliness of the encapsulation window. Simultaneously, it can also reduce the influence of organic contaminants on the chemical properties of liquid samples, improving the accuracy of in-situ TEM experimental results.

[0033] One embodiment provides the application of the above-mentioned graphene liquid pool in in-situ characterization studies of gas-liquid-solid three-phase interfaces. It includes the following steps: S1. The sample to be tested, which contains liquid medium and solid nanomaterials, is loaded onto the first double-layer graphene encapsulation window, and the second transmission electron microscope (TEM) mesh 3 is placed over the first TEM mesh 2, so that the second double-layer graphene encapsulation window faces the first double-layer graphene encapsulation window to form a sample liquid pool. S2. The graphene liquid cell is placed in the vacuum environment of a transmission electron microscope and subjected to continuous irradiation. The electron beam irradiation induces the liquid medium to undergo gas-liquid phase transformation or interface reconstruction, so that a gas-liquid-solid three-phase interface is formed in the liquid confinement space where gas phase structure, liquid phase structure and solid nanomaterial coexist. S3. Continuously acquire transmission electron microscope image sequences to conduct in-situ observation of the dynamic evolution process of the gas-liquid-solid three-phase interface.

[0034] When this graphene liquid cell is applied to in-situ characterization of gas-liquid-solid three-phase interfaces, stable interfaces can be directionally constructed by actively controlling the liquid environment through electron beam irradiation. This significantly improves the controllability of the interface formation process and enables the stable coexistence of liquid, gas, and solid nanomaterials under the high-vacuum environment of transmission electron microscopy, providing a dedicated experimental platform for in-situ research on real gas-liquid-solid interface processes. Combined with continuous TEM image acquisition, real-time tracking and observation of dynamic processes at the nanoscale interface can be achieved, overcoming the technical limitations of traditional static characterization methods. This method can be widely applied to the precise study of dynamic mechanisms such as nanoparticle migration, interfacial reactions, bubble nucleation, growth, and dissipation.

[0035] In one embodiment, when the graphene liquid pool is applied to in-situ characterization studies of the gas-liquid-solid three-phase interface, it further includes: image processing, structure recognition, and time series analysis of the acquired transmission electron microscope (TEM) image sequences to obtain dynamic parameters of the gas phase structure, liquid phase structure, and solid nanomaterials, respectively. The spatial and temporal evolution relationships of the gas-liquid-solid three-phase interface are then established based on these dynamic parameters. Through image processing, structure recognition, and time series analysis, information on the movement of bubbles, droplets, and nanoparticles can be extracted from continuous TEM images, improving data analysis efficiency. Simultaneously, by correlating structural changes with temporal information, the dynamic evolution law of the gas-liquid-solid interface can be obtained. In this embodiment or other embodiments, the dynamic parameters include one or more of the following: bubble size change, droplet size change, interface migration distance, interface fluctuation frequency, solid nanomaterial trajectory, diffusion rate, aggregation rate, and growth rate. By accurately extracting core kinetic parameters such as interface migration rate, particle trajectory, and growth rate, quantitative support can be provided for revealing the nanoscale interface reaction mechanism, promoting the upgrade from traditional "observation-based TEM" to "quantitative kinetic analysis-based TEM," significantly enhancing the application value of this technology.

[0036] In one embodiment, the gas phase structure includes one or more of the following: nanobubbles induced by continuous irradiation, nanobubbles retained during encapsulation, and nanobubbles formed by the precipitation of dissolved gases in a liquid system. The liquid phase structure includes one or more of the following: confined liquid layer, ultrathin liquid film, nanodroplet, and liquid bridge. The solid nanomaterial is located at the boundary of the nanobubble, the edge of the nanodroplet, the region of the ultrathin liquid film, or the region of the liquid bridge. In this embodiment or other embodiments, the liquid medium is selected from one or more of deionized water, salt solution, metal ion solution, or reaction precursor solution. The solid nanomaterial is selected from one or more of the following: metal nanoparticles, metal nanoclusters, two-dimensional materials, oxide nanomaterials, or nanoproducts formed under electron beam irradiation. This graphene liquid pool can be applied to aqueous systems, electrochemical systems, catalytic reaction systems, and material growth systems. When applied to in-situ characterization studies of gas-liquid-solid three-phase interfaces, this graphene liquid pool supports in-situ observation of various nanomaterial systems, has good versatility, and can be used to study the structural changes and interfacial behavior of nanomaterials under different liquid environments.

[0037] Example 1

[0038] A Cu(111) copper single-crystal thin film substrate with a sapphire wafer as the wafer support was obtained and used as the wafer-based single-crystal metal thin film substrate. Two layers of graphene atomic layers were grown in situ on the surface of the Cu(111) copper single-crystal thin film substrate using chemical vapor deposition to form a bilayer graphene film, resulting in a bilayer graphene / substrate composite structure 1. The results are as follows. Figure 1As shown in (a). Subsequently, a first grid carrier 21 and a second grid carrier 31 were obtained, and the first grid carrier 21 and the second grid carrier 31 were respectively bonded to the bilayer graphene / substrate composite structure 1, with the bilayer graphene film facing the corresponding first grid carrier 21 or second grid carrier 31. During the bonding process, 0.3 μL of isopropanol solution was dropped onto the surface of the first grid carrier 21 and the second grid carrier 31, and allowed to stand at room temperature to allow the isopropanol to gradually evaporate. With the capillary action and interfacial adsorption generated by the liquid evaporation, the bilayer graphene film and the grid carrier were fully bonded, improving the adhesion stability during the transfer of bilayer graphene, and forming a grid / bilayer graphene / wafer-based single-crystal metal film composite structure, as shown in (a). Figure 1 As shown in (b), the carrier / bilayer graphene / substrate composite structure 1 was placed in a 0.5 M sodium persulfate etching solution, as shown in Figure (b). Figure 1 As shown in (c), the Cu(111) copper single-crystal thin film substrate was selectively removed by wet etching while maintaining the integrity of the bilayer graphene film structure. After etching, the bilayer graphene film was transferred to the perforated areas of the first mesh body 21 and the second mesh body 31, forming the first transmission electron microscope (TEM) mesh 2 and the second TEM mesh 3 with suspended bilayer graphene encapsulation windows, respectively. The results are shown in Figure 3. Figure 1 As shown in (d). Then, the second transmission electron microscope (TEM) mesh 3 and the first TEM mesh 2 are assembled facing each other, so that the bilayer graphene encapsulation windows on the second TEM mesh 3 and the first TEM mesh 2 are close to each other, forming a liquid confinement space between the two bilayer graphene encapsulation windows, thereby obtaining a graphene liquid pool.

[0039] Example 2

[0040] The difference between this embodiment and Embodiment 1 is that: an amorphous wafer-based copper foil is used as the substrate, and a bilayer graphene film is grown on the surface of the copper foil using chemical vapor deposition to obtain a bilayer graphene / copper foil composite structure, such as... Figure 2 As shown in (a).

[0041] Subsequently, the bilayer graphene / substrate composite structure 1 was cut to obtain multiple bilayer graphene transfer units 11 with target dimensions. Then, a first grid body 21 and a second grid body 31 were obtained, and the first grid body 21 and the second grid body 31 were respectively attached to different bilayer graphene transfer units 11. Using the same method as in Example 1, the bilayer graphene film was transferred to a first transmission electron microscope (TEM) grid 2 and a second TEM grid 3. Afterwards, the first TEM grid 2 and the second TEM grid 3 were assembled facing each other to finally obtain a graphene liquid pool composed of the first TEM grid 2 and the second TEM grid 3, as shown below. Figure 2 As shown in (d).

[0042] Example 3

[0043] A Cu(111) copper single-crystal thin film substrate with a sapphire wafer as the wafer support was obtained as the wafer-based single-crystal metal thin film substrate. A monolayer of graphene atomic layer was grown on the surface of the Cu(111) copper single-crystal thin film substrate by chemical vapor deposition as the graphene film, resulting in a monolayer graphene / substrate composite structure. The results are as follows. Figure 3 As shown in (a).

[0044] The monolayer graphene / substrate composite structure 4 was cut to obtain multiple graphene transfer units 11 with target dimensions.

[0045] A first graphene substrate 21 and a second graphene substrate 31 are obtained. The first graphene substrate 21 and the second graphene substrate 31 are then bonded to different graphene transfer units 11, with the graphene film facing the corresponding first graphene substrate 21 or second graphene substrate 31. During the bonding process, 0.3 μL of isopropanol solution is dropped onto the surfaces of the first graphene substrate 21 and the second graphene substrate 31, respectively, and allowed to stand at room temperature to allow the isopropanol to gradually evaporate. This increases the interaction force between the monolayer graphene film and the first graphene substrate 21 or the second graphene substrate 31, ensuring complete bonding and forming a graphene substrate / graphene / substrate composite structure 5. The result is as follows: Figure 3 As shown in (b).

[0046] like Figure 3 As shown in (c), the composite structure 5 of the carrier / graphene / substrate was placed in a 0.5 M sodium persulfate etching solution and etched to remove the Cu(111) copper single crystal thin film substrate, so that the graphene film was transferred to the corresponding hole region of the first carrier 21 or the second carrier 31, forming the first transmission electron microscope carrier 2 and the second transmission electron microscope carrier 3, respectively. The results are as follows. Figure 3 As shown in (d).

[0047] The second transmission electron microscope (TEM) screen 3 and the first TEM screen 2 are assembled facing each other, so that the graphene films on the second TEM screen 3 and the first TEM screen 2 are brought close to each other to form a liquid confinement space, thus obtaining a graphene liquid pool.

[0048] The morphology of the suspended graphene encapsulation windows on the first transmission electron microscope (TEM) support 2 and the second TEM support 3 prepared in Examples 1, 2, and 3 were characterized. Specifically, atomic force microscopy (AFM) or scanning electron microscopy (SEM) were used for characterization, and the results are as follows: Figures 4-7 As shown.

[0049] Depend on Figure 4 and Figure 5As can be seen, on the first transmission electron microscope (TEM) mesh 2 and the second TEM mesh 3 prepared in Example 1, the bilayer graphene film can continuously cover the mesh hole area, forming a complete suspended bilayer graphene encapsulation window. Furthermore, this bilayer graphene encapsulation window has fewer damaged areas, a lower number of surface wrinkles, and smaller changes in the height of the suspended area, exhibiting high integrity and flatness. The main reason for achieving this effect is that this example uses a wafer-based Cu(111) single-crystal thin film as the graphene growth substrate. Compared to traditional copper foil substrates, single-crystal thin film substrates have more uniform crystal orientation and lower surface roughness, which can reduce defect formation during graphene growth and wrinkle-induced deformation during transfer. Therefore, the bilayer graphene encapsulation window formed by the transfer of the bilayer graphene film grown on a wafer-based single-crystal metal thin film substrate has a more uniform suspended area and lower wrinkle-induced undulations, which is beneficial for forming a liquid confinement space with uniform thickness and stable morphology, thereby ensuring higher repeatability of the position and morphology of the gas-liquid-solid three-phase interface. Meanwhile, Example 1 uses a continuous bilayer graphene structure on both packaging surfaces, rather than a combination of two independent single-layer graphene windows. This results in better mechanical stability and lower leakage risk during liquid loading, vacuum environment and electron beam irradiation, and can support longer-term continuous in-situ observations.

[0050] In Example 2, copper foil was used as the graphene growth substrate. Because copper foil typically has significant grain size variations, grain boundary defects, and high surface roughness, it can easily lead to wrinkles, localized stress concentrations, and damage to the graphene film during the graphene transfer process. Figure 6 As shown, compared with Example 1, the bilayer graphene encapsulation window obtained in Example 2 has more wrinkles, irregular undulations and local defect areas. The liquid confinement space formed is prone to problems such as uneven size, local height changes and unstable liquid distribution.

[0051] Example 3 employs single-layer graphene fabrication windows on two independent encapsulation surfaces; that is, single-layer graphene encapsulation windows are transferred and formed on both the first and second substrates. Although the graphene liquid pool formed by combining the upper and lower single-layer graphene encapsulation windows contains two graphene atomic layers, these two graphene atomic layers are located on two independent encapsulation surfaces, and are not equivalent to a single encapsulation surface employing a continuous bilayer graphene structure. Figure 7As shown, in Example 3, the first transmission electron microscope (TEM) support 2 and the second TEM support 3 exhibit significantly more damaged and discontinuous areas in the suspended graphene encapsulation window compared to the structure in Example 1 where each encapsulation surface is a double-layer graphene film. Furthermore, due to the lower thickness of the single-layer graphene window, its resistance to mechanical loads and local defect propagation is weaker, making it more prone to damage, collapse, or local leakage during liquid loading, encapsulation, and the vacuum environment of TEM. Therefore, the stability of the structure obtained in Example 3 is lower than that of the liquid pool structure in Example 1 where each encapsulation surface uses a double-layer graphene encapsulation window.

[0052] The above results show that the graphene liquid pool of this application can stably complete the in-situ TEM preparation and dynamic characterization of the gas-liquid-solid three-phase interface by using a wafer-based single-crystal metal substrate to achieve low-wrinkle and high-integrity graphene film construction, and by configuring a double-layer graphene window on each encapsulation surface.

[0053] The graphene liquid pool prepared in Example 1 was applied to the in-situ construction study of the gas-liquid interface under transmission electron microscopy. The specific method is as follows: First, 0.3 μL of liquid medium was dropped onto the first transmission electron microscope (TEM) screen 2 obtained in Example 1, so that the liquid medium covered or contacted the first bilayer graphene encapsulation window. Then, the second TEM screen 3 was placed above the first TEM screen 2, with the second bilayer graphene encapsulation window facing the first bilayer graphene encapsulation window and covering the droplet. After standing for several minutes, excess liquid medium evaporated, and some liquid medium was confined between the two bilayer graphene encapsulation windows, forming a sample liquid pool with both upper and lower encapsulation surfaces being bilayer graphene. Then, the resulting sample liquid pool was placed in a transmission electron microscope for observation under a high vacuum environment.

[0054] Two phenomena were observed during the observation process. First, after the electron beam was turned on, the continuous action of the electron beam on the liquid medium caused radiolysis or local gas evolution, thereby gradually forming nanobubbles in the confined liquid. With the extension of electron beam irradiation time, the nucleation, growth, and influence on the surrounding liquid phase structure of the nanobubble structure could be observed. Second, such as... Figure 8As shown, pre-existing nanobubbles can be observed after the electron beam is turned on. Analysis suggests that these nanobubble structures originate from: trace amounts of gas remaining during liquid encapsulation, the release of dissolved gases from the liquid medium in a high-vacuum environment, and localized gas-phase cavities formed by liquid evaporation and contraction during encapsulation. All of these nanobubbles can serve as gas-phase structural regions, forming a stable gas-liquid interface together with the surrounding confined liquid. Nanobubbles formed or observed in either of these two phenomena can function as gas-phase structures, while the surrounding residual liquid can form confined liquids, ultrathin liquid films, nanodroplets, liquid bridges, and other liquid-phase structures, thus constructing a gas-liquid interface within the liquid confinement space. By continuously acquiring transmission electron microscopy (TEM) image sequences, the generation, morphological evolution, interface migration, and induced liquid-phase structure reconstruction processes of the nanobubble structures can be recorded.

[0055] This also demonstrates that gas-phase structures can be generated in situ during electron beam irradiation under a transmission electron microscope (TEM), or they may already exist in the sample's liquid cell when the electron beam is turned on. Regardless of whether the gas-phase structure originates from electron beam-induced generation, gas retained during encapsulation, or gas precipitated under high vacuum, it can co-form with the confined liquid structure to form a gas-liquid interface that can be observed in situ under a TEM. This gas-liquid interface, further coupled with solid nanomaterials, can be used to construct and characterize gas-liquid-solid three-phase interfaces.

[0056] The graphene liquid pool prepared in Example 1 was applied to the construction and characterization of the gas-liquid-solid three-phase interface. The specific method is as follows: S1. Prepare a sample containing a liquid medium and solid nanomaterials. The liquid medium is deionized water, and the solid nanomaterials are metal nanoparticles. Load 0.3 μL of the sample onto the first transmission electron microscope (TEM) screen 2, ensuring the sample covers the first bilayer graphene encapsulation window. Then, place the second TEM screen 3 over the first TEM screen 2, aligning the second bilayer graphene encapsulation window with the first bilayer graphene encapsulation window, together forming a liquid confinement space. Allow it to stand for several minutes, confining part of the sample between the two bilayer graphene encapsulation windows, forming a sample liquid pool.

[0057] S2. Place the sample liquid cell in the vacuum environment of a transmission electron microscope and irradiate it with an electron beam. The electron beam induces a gas-liquid phase transition or interfacial structure reconstruction in the liquid medium, resulting in a gas-liquid-solid three-phase interface in the confined space where gas phase structure, liquid phase structure, and solid nanomaterials coexist.

[0058] S3. Continuously acquire transmission electron microscope image sequences to conduct in-situ observation of the dynamic evolution process of the gas-liquid-solid three-phase interface.

[0059] Two phenomena were observed during the observation process. First, after the electron beam was turned on, it continuously acted on the sample in the liquid cell, causing radiolysis or local gas evolution, thus gradually forming nanobubbles in the confined liquid. As the electron beam irradiation time increased, the nanobubble structure gradually grew, altering the spatial distribution of the surrounding liquid medium and causing the liquid medium to form ultrathin liquid films, nanodroplets, liquid bridges, and other liquid-phase structures. Second, nanobubble structures were observed in the sample liquid cell immediately after the electron beam was turned on, as shown in the following results. Figure 9 As shown, the solid-phase structure includes metallic nanoparticles. Solid nanomaterials can be located at bubble boundaries, droplet edges, ultrathin liquid film regions, or near liquid bridges, and are situated within the same transmission electron microscope observation area as the gas and liquid phase structures. Therefore, in-situ construction and dynamic observation of the gas-liquid-solid three-phase interface can be achieved.

[0060] like Figure 9 As shown, the dynamic morphological evolution of nanobubbles can be observed in the transmission electron microscope (TEM) image sequence: the gas-liquid interface undergoes directional migration over time, and during the gradual advancement of the interface, it exerts forces on neighboring nanoparticles, driving them to produce controllable displacements. This demonstrates that the graphene liquid pool provided in Example 1 can construct a gas-liquid-solid three-phase interface in a TEM and achieve in-situ observation of the dynamic behavior of solid nanomaterials at the three-phase interface. Furthermore, this example not only allows observation of the formation and evolution of nanobubbles but also enables simultaneous observation of liquid phase structure reconstruction and the movement and structural changes of solid nanomaterials near the gas-liquid-solid three-phase interface, thereby achieving in-situ TEM characterization of the coupled evolution process of the gas-liquid-solid three-phase interface.

[0061] Based on the transmission electron microscope image sequence acquired from the graphene liquid pool obtained in Example 1, a quantitative analysis of the dynamic process of the three-phase interface was performed. Specifically, the image sequence was first preprocessed, including one or more of the following: image alignment, drift correction, contrast adjustment, noise reduction, or inter-frame smoothing. Then, the preprocessed images were subjected to structure identification to obtain gas-phase structure parameters, liquid-phase structure parameters, and solid nanomaterial parameters. The gas-phase structure parameters included bubble area, perimeter, contour coordinates, and area change rate; the liquid-phase structure parameters included nanodroplet area, perimeter, contour coordinates, and area change rate; and the solid nanomaterial parameters included centroid position, trajectory, migration distance, instantaneous velocity, and average velocity. Based on the dynamic parameters of the gas-phase structure, liquid-phase structure, and solid nanomaterial, the temporal and spatial correspondences of the gas-liquid-solid three-phase interface were established, and the coupled dynamic behavior in the three-phase interface was analyzed.

[0062] The above method can convert in-situ transmission electron microscopy image sequences into quantifiable three-phase interface dynamic data. This not only records the evolution of nanobubbles and liquid phase structures, but also analyzes the migration, adsorption, desorption, coalescence, and splitting behavior of solid nanomaterials near the gas-liquid-solid three-phase interface, thus providing a data foundation for studying the dynamics of the gas-liquid-solid three-phase interface in a nano-confined environment.

[0063] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0064] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A graphene liquid pool, characterized in that, It includes a first transmission electron microscope (TEM) mesh, a second TEM mesh, and a liquid confinement space formed between the first TEM mesh and the second TEM mesh; The first transmission electron microscope (TEM) support includes a first support body and a first double-layer graphene encapsulation window covering the perforated area of ​​the first support body. The second transmission electron microscope (TEM) support includes a second support body and a second double-layer graphene encapsulation window covering the perforated area of ​​the second support body; The second transmission electron microscope (TEM) mesh is positioned above the first TEM mesh, and the first double-layer graphene encapsulation window and the second double-layer graphene encapsulation window are positioned opposite each other to jointly encapsulate and form the liquid confinement space. Both the first double-layer graphene encapsulation window and the second double-layer graphene encapsulation window include two stacked graphene atomic layers, and the two graphene atomic layers cover the hole areas corresponding to the first or second carrier body.

2. The graphene liquid pool as described in claim 1, characterized in that, The two graphene atomic layers are formed by transferring a bilayer graphene film grown on the surface of a wafer-based single-crystal metal thin film substrate.

3. The graphene liquid pool as described in claim 2, characterized in that, The wafer-based single-crystal metal thin film substrate is a Cu(111) copper single-crystal thin film substrate or a CuNi(111) copper-nickel single-crystal alloy thin film substrate formed on a wafer support substrate. The wafer support substrate is a sapphire wafer or a silicon oxide wafer.

4. The method for preparing the graphene liquid pool according to any one of claims 1-3, characterized in that, Includes the following steps: A wafer-based single-crystal metal thin film substrate is obtained, and a bilayer graphene film is grown on the surface of the wafer-based single-crystal metal thin film substrate to obtain a bilayer graphene / substrate composite structure. The bilayer graphene / substrate composite structure is cut to obtain multiple bilayer graphene transfer units with target size; Obtain a first and a second carrier body, attach the first and second carrier bodies to different bilayer graphene transfer units respectively, and make the bilayer graphene film face the corresponding first or second carrier body respectively to form a carrier body / bilayer graphene / substrate composite structure. The composite structure of the carrier / bilayer graphene / substrate is etched to remove the wafer-based single-crystal metal thin film substrate, so that the bilayer graphene film is transferred to the corresponding hole area of ​​the first carrier or the second carrier, forming the first transmission electron microscope carrier and the second transmission electron microscope carrier, respectively. The second transmission electron microscope (TEM) mesh and the first TEM mesh are assembled facing each other, so that the bilayer graphene films on the second TEM mesh and the first TEM mesh are brought close to each other to form a liquid confinement space, thus obtaining a graphene liquid pool.

5. The preparation method according to claim 4, characterized in that, The bilayer graphene / substrate composite structure is bonded to the first or second substrate using a polymer-free transfer method.

6. The application of the graphene liquid pool according to any one of claims 1-3 in in-situ characterization studies of the gas-liquid-solid three-phase interface, characterized in that, Includes the following steps: S1. The sample to be tested, which contains liquid medium and solid nanomaterials, is loaded onto the first double-layer graphene encapsulation window, and the second transmission electron microscope (TEM) mesh is placed over the first TEM mesh so that the second double-layer graphene encapsulation window faces the first double-layer graphene encapsulation window, forming a sample liquid pool. S2. The graphene liquid pool is placed in the vacuum environment of a transmission electron microscope and subjected to continuous irradiation treatment. The electron beam irradiation effect induces the liquid medium to undergo gas-liquid phase transformation or interface reconstruction, so that a gas-liquid-solid three-phase interface in which gas phase structure, liquid phase structure and solid nanomaterial coexist is formed in the liquid confined space. S3. Continuously acquire transmission electron microscope image sequences to conduct in-situ observation of the dynamic evolution process of the gas-liquid-solid three-phase interface.

7. The application as described in claim 6, characterized in that, It also includes: performing image processing, structure recognition, and time series analysis on the acquired transmission electron microscope image sequence to obtain the dynamic parameters of the gas phase structure, liquid phase structure, and solid nanomaterials, respectively; Based on the dynamic parameters, the spatial and temporal evolution relationships of the gas-liquid-solid three-phase interface are established.

8. The application as described in claim 7, characterized in that, The dynamic parameters include one or more of the following: bubble size change, droplet size change, interface migration distance, interface fluctuation frequency, solid nanomaterial motion trajectory, diffusion rate, aggregation rate, and growth rate.

9. The application as described in claim 6, characterized in that, The gas phase structure includes any one or more of the following: nanobubbles induced by continuous irradiation treatment, nanobubbles retained during the encapsulation process, and nanobubbles formed by the precipitation of dissolved gases in a liquid system. The liquid phase structure includes any one or more of the following: confined liquid layer, ultrathin liquid film, nanodroplet, and liquid bridge; The solid nanomaterial is located at the boundary of the nanobubble, the edge of the nanodroplet, the ultrathin liquid film region, or the liquid bridge region.

10. The application as described in claim 6, characterized in that, The liquid medium is selected from one or more of deionized water, salt solution, metal ion solution or reaction precursor solution; The solid nanomaterial is selected from one or more of the following: metal nanoparticles, metal nanoclusters, two-dimensional materials, oxide nanomaterials, or nanoproducts formed under electron beam irradiation.

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