CN115711895A - Method for in-situ characterization of nanobubbles in liquid environment - Google Patents
Method for in-situ characterization of nanobubbles in liquid environment Download PDFInfo
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- CN115711895A CN115711895A CN202211653330.1A CN202211653330A CN115711895A CN 115711895 A CN115711895 A CN 115711895A CN 202211653330 A CN202211653330 A CN 202211653330A CN 115711895 A CN115711895 A CN 115711895A
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Abstract
The invention discloses a method for in-situ characterization of nanobubbles in a liquid environment. The method comprises the following steps: (1) Depositing a graphene film on the metal carrying net to obtain a graphene carrying net; (2) plating a layer of metal film on the surface of the graphene net; (3) Heating to melt the metal film and then cooling to form metal nano particles on the surface of the graphene carrying net; (4) carrying out surface modification treatment on the obtained graphene net; (5) dropwise adding the aqueous solution on a graphene net; (6) Covering the other graphene film with the graphene carrying net dropwise added with the aqueous solution with the surface facing downwards to obtain a graphene liquid pool; (7) And (3) placing the graphene liquid cell into a transmission electron microscope after vacuum leak detection, and irradiating water by using an electron beam to generate nano bubbles and carrying out in-situ characterization on the nano bubbles. The method has the advantages of high time and space resolution, no introduction of other impurities and the like, and provides a new research means for exploring nano bubbles, gas/liquid/solid surface interface properties and the like.
Description
Technical Field
The invention relates to the field of nano processing and characterization, in particular to a method for generating and characterizing nano bubbles in liquid in situ.
Background
The bubbles are visible everywhere in our daily life, and the nano bubbles generally refer to bubbles with the diameter smaller than 1 μm, and have great application prospects in the aspects of mineral flotation, ultrasonic imaging, sewage treatment and the like. In addition, for reactions involving gases, such as fuel cells, hydrogen evolution from electrolyzed water, and photocatalysis, the gases often participate in the reactions in the form of nanobubbles at the nanoscale. Understanding the physical and chemical properties, the kinetic mechanism and the gas/liquid/solid interface properties of the nanobubbles has great significance for the application of the nanobubbles and the regulation and control of gas-containing multiphase reactions. However, due to the limitation of research means, most of the current research work on the dynamics of bubbles stagnates in the micrometer and millimeter scale, and the visual dynamic observation of bubbles in the nanometer or even atomic scale is lacked. There are many doubts about the bubble nucleation theory and the stability mechanism. For example, the critical radii of nanobubbles differ by at least one order of magnitude according to different computational models, and the theoretical nucleation rate and nucleation supersaturation are generally higher than experimentally observed. According to the young-laplace equation, for bubbles smaller than 1 μm, due to their high internal pressure, should collapse and disappear quickly, and the existence time thereof is theoretically predicted to be not more than 0.02 s. However, in 2000 Lou et al used atomic force microscopy imaging to image nanobubbles determined that nanobubbles could exist stably. In order to explain the situation that experimental phenomena are similar to classical theoretical prediction, various nanobubble stabilization mechanisms are proposed, including pollutant pinning, electrostatic theory, multi-body model and dynamic balance theory. However, these models either proved not to be universal or lacked experimental evidence support.
The current common methods for preparing the nano bubbles comprise a solution replacement method, an electrochemical method, an ultrasonic method, a pressure and pressure reduction method, a dipping self-generation method and the like. These methods do not allow for the high resolution in situ characterization of nanobubbles while they are being prepared. In recent years, various in situ characterization techniques have been used to study the dynamic behavior of nanobubbles in solution and have made some progress, but there are still limitations. For example, the in-situ spectroscopy method cannot acquire the morphology information of the nanobubbles; the spatial resolution of the in-situ optical imaging method is low; atomic force microscopes can achieve higher spatial resolution, but their temporal resolution is limited and can cause damage to bubbles. The transmission electron microscope can obtain ultrahigh time and spatial resolution, can obtain chemical composition information of the material, and has unique advantages in the aspect of nano material characterization. However, transmission electron microscopes need to work in high vacuum environments and cannot directly characterize liquids or gases. In-situ liquid environment transmission electron microscope technology, a liquid sample is sealed in a liquid pool formed by processing through a micro-nano manufacturing technology, and then the liquid sample is placed in a transmission electron microscope for observation, so that a plurality of breakthrough achievements are achieved in the fields of nanoparticle growth, etching, self-assembly and electrochemical properties in dynamic research solution. The liquid pools commonly used at present are a silicon nitride film liquid pool and an ultrathin carbon film liquid pool. The window thickness of the silicon nitride film liquid pool is generally larger than 10 nm, and the obtained liquid layer is thick and limited in resolution. The ultra-thin carbon film liquid pool can obtain higher resolution, but the carbon film has poor mechanical property and stability, is not resistant to long-time electron beam irradiation, and is easy to cause solution and gas leakage. And the ultra-thin carbon film liquid pool is difficult to directly seal pure water solution, so that nano particles are required to be mixed in the solution in order to improve the success rate, and a supporting coating water solution is formed between the upper carbon film and the lower carbon film. The nano-particle aqueous solution prepared by the chemical method inevitably introduces impurities such as surface ligands and the like, and influences the preparation and characterization of the subsequent nano-bubbles. Therefore, the method which has high stability, can generate in situ and represent the nano bubbles with high resolution is developed, and has important significance and wide application.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a method for preparing and characterizing nano bubbles in a high resolution mode in situ, and simultaneously solves the problem that the existing liquid pool preparation method is difficult to consider both mechanical stability and imaging resolution.
The technical scheme is as follows: in order to realize the purpose, the invention adopts the technical scheme that:
a method for in-situ characterization of nanobubbles in a liquid environment, the method comprising the following specific steps:
(1) Selecting a transmission electron microscope metal grid;
(2) Depositing a graphene film on the metal carrying net to obtain a graphene carrying net;
(3) Plating a layer of metal film on the surface of the graphene carrying net;
(4) Heating to melt the metal film and then cooling to form metal nano particles on the surface of the graphene carrying net;
(5) Placing the graphene carrying net containing the metal nano-particles into a plasma surface treatment instrument for surface modification treatment;
(6) Dripping 1-5 mu L of aqueous solution on the graphene net obtained in the step (5);
(7) Covering the other graphene net-carrying graphene film subjected to the treatment in the step (5) on the graphene net-carrying net dropwise added with the aqueous solution in a face-down manner, standing for more than 4 hours, covering a very small amount of aqueous solution in a gap between an upper layer graphene film and a lower layer graphene film supported by the metal nanoparticles, and volatilizing redundant liquid to prepare a graphene liquid pool;
(8) Putting the graphene liquid pool obtained in the step (7) into a vacuum leak detection system, if no leak exists, putting the graphene liquid pool into a transmission electron microscope, and turning on an electron gun switch to enable an electron beam to interact with the aqueous solution to generate nano bubbles;
(9) And (4) continuing irradiating the electron beam to perform in-situ characterization on the nanobubbles.
Wherein:
the metal mesh in the step (1) is one of a copper mesh, a gold mesh, a nickel mesh and a molybdenum mesh, and the mesh number of the metal mesh is 200-800 meshes.
And (3) preparing the graphene film in the step (2) by adopting a chemical vapor deposition method, wherein the number of graphene layers is 1-5.
And (4) the metal in the step (3) is gold or platinum.
And (3) preparing the metal film in the step (3) by adopting a magnetron sputtering or evaporation method, wherein the thickness of the metal film is 1-5 nm.
The heating in the step (4) is heating by using a heating table.
And (5) carrying out surface modification treatment on the graphene carrying net containing the metal nano particles by using oxygen or argon for 10 s.
Step (8) the electron beam dosage rate is more than 100 e - /Å 2 ∙s。
The invention provides a method for generating nano bubbles by using electron beam to hydrolyze water and carrying out in-situ observation.
Wherein;
the electron beam is generated by a transmission electron microscope, and the dose rate of the electron beam is more than 100 e - /Å 2 ∙s。
The invention also provides a graphene liquid pool for characterizing nano bubbles in liquid in a transmission electron microscope.
And coating liquid in a sandwich structure consisting of graphene, metal nanoparticles and graphene by utilizing Van der Waals force between the upper layer of graphene film and the lower layer of graphene film. Compared with the existing silicon nitride and ultrathin carbon film liquid pool, the graphene liquid pool has the advantages of good resolution and mechanical properties.
The metal nano-particles are used as gaskets to play a supporting role between two layers of graphene, and the success rate of sealing liquid can be improved. The metal nano-particles are prepared by a physical method, so that impurities introduced by a chemical method synthetic method are avoided, and side reactions caused by electron beam irradiation are reduced.
The method for in-situ characterization of the nano bubbles in the liquid environment can be used for simultaneously carrying out nano bubble generation and dynamic characterization, and has important value in the field of research on dynamic behaviors of nano bubble nucleation, growth, fusion, rupture and the like. The preparation method is simple, is suitable for various types of transmission electron microscopes, and has the advantages of high imaging resolution, good stability and the like.
Drawings
Fig. 1a is a transmission electron microscope image of a liquid cell of graphene prepared in example 1 of the present invention, and fig. 1b is a transmission electron microscope image of nanobubbles generated in example 1.
FIG. 2 is a transmission electron microscope sequence chart of the growth process of the nanobubbles in example 2 of the present invention.
FIG. 3 is a transmission electron microscope sequence chart of the nanobubble fusion process in example 3 of the present invention.
Detailed Description
The invention provides a method for generating and characterizing nano bubbles in situ, which comprises the steps of sealing an aqueous solution in a graphene liquid pool, placing the graphene liquid pool in a transmission electron microscope, using electron beams generated by the transmission electron microscope to radiolyze water to generate the nano bubbles, and dynamically characterizing the nano bubbles. The present invention will be further described with reference to the following examples and the accompanying drawings.
Example 1
Selecting a 400-mesh copper net;
depositing a single-layer graphene film on the copper carrying net by adopting chemical vapor deposition to form a graphene carrying net;
plating a layer of gold film with the thickness of 3 nm on the surface of the graphene net;
placing the gold film of the graphene carrying net on a heating platform upwards, heating until the gold film is molten, and then cooling to room temperature to form gold nanoparticles on the surface of the graphene carrying net;
placing the graphene carrying net containing the gold nanoparticles into an oxygen plasma surface treatment instrument for treatment for 10 s;
dropwise adding 5 mu L of water solution on the graphene carrying net treated by the plasma surface treatment instrument;
covering the other graphene net-carrying graphene film treated by the plasma surface treatment instrument with the surface facing downwards on the graphene net-carrying net dropwise added with the aqueous solution, standing for more than 4 hours, and volatilizing redundant liquid to obtain a graphene liquid pool;
and (3) carrying out vacuum leakage detection on the obtained graphene liquid pool, putting the graphene liquid pool into a transmission electron microscope, opening an electron gun switch to enable the electron beam to interact with the aqueous solution to generate nano bubbles, and characterizing the nano bubbles.
Example 2
Selecting a 400-mesh molybdenum carrying net;
depositing a double-layer graphene film on the copper carrying net by adopting chemical vapor deposition to form a graphene carrying net;
plating a layer of gold film with the thickness of 3 nm on the surface of the graphene net;
placing the gold film of the graphene carrying net on a heating platform upwards, heating until the gold film is molten, cooling to room temperature, and forming gold nanoparticles on the surface of the graphene carrying net;
placing the graphene carrying net containing the gold nanoparticles into an oxygen plasma surface treatment instrument for treatment for 10 s;
dripping 5 mu L of water solution on the graphene carrying net treated by the plasma surface treatment instrument;
covering the other graphene net-carrying graphene film treated by the plasma surface treatment instrument with the surface facing downwards on the graphene net-carrying net dropwise added with the aqueous solution, standing for more than 4 hours, and volatilizing redundant liquid to obtain a graphene liquid pool;
and (3) carrying out vacuum leakage detection on the obtained graphene liquid pool, putting the graphene liquid pool into a transmission electron microscope, opening an electron gun switch to enable an electron beam to interact with the aqueous solution to generate nano bubbles, and characterizing the nano bubbles. The correlation results are shown in FIG. 2.
Example 3
Selecting a 400-mesh golden net;
depositing 5 layers of graphene films on the gold-loaded net by adopting chemical vapor deposition to form a graphene-loaded net;
plating a platinum film with the thickness of 3 nm on the surface of the graphene net;
placing the platinum film of the graphene carrying net on a heating platform upwards, heating until the platinum film is molten, cooling to room temperature, and forming platinum nanoparticles on the surface of the graphene carrying net;
placing the graphene carrying net containing the platinum nano-particles into an oxygen plasma surface treatment instrument for treatment for 10 s;
dropwise adding 5 mu L of water solution on the graphene carrying net treated by the plasma surface treatment instrument;
covering the other graphene net-carrying graphene film treated by the plasma surface treatment instrument with the surface facing downwards on the graphene net-carrying net dropwise added with the aqueous solution, standing for more than 4 hours, and volatilizing redundant liquid to obtain a graphene liquid pool;
and (3) carrying out vacuum leakage detection on the obtained graphene liquid pool, putting the graphene liquid pool into a transmission electron microscope, opening an electron gun switch to enable an electron beam to interact with the aqueous solution to generate nano bubbles, and characterizing the nano bubbles. The correlation results are shown in FIG. 3.
Claims (8)
1. A method for in-situ characterization of nanobubbles in a liquid environment comprises the following specific steps:
(1) Selecting a transmission electron microscope metal grid;
(2) Depositing a graphene film on the metal carrying net to obtain a graphene carrying net;
(3) Plating a layer of metal film on the surface of the graphene net;
(4) Heating to melt the metal film and then cooling to form metal nano particles on the surface of the graphene carrying net;
(5) Placing the graphene carrying net containing the metal nano particles into a plasma surface treatment instrument for surface modification treatment;
(6) Dripping 1-5 mu L of aqueous solution on the graphene net obtained in the step (5);
(7) Covering the other graphene film of the graphene carrying net subjected to the treatment in the step (5) on the graphene carrying net dropwise added with the aqueous solution in a face-down manner, standing for more than 4 hours, covering a very small amount of aqueous solution in a gap between an upper layer of graphene film and a lower layer of graphene film supported by the metal nanoparticles, and volatilizing redundant liquid to prepare a graphene liquid pool;
(8) Putting the graphene liquid pool obtained in the step (7) into a vacuum leakage detection system, putting the graphene liquid pool into a transmission electron microscope after no leakage occurs, and opening an electron gun switch to enable electron beams to interact with an aqueous solution to generate nano bubbles;
(9) And (4) continuing irradiating the electron beam to perform in-situ characterization on the nanobubbles.
2. The method for in-situ characterization of the nanobubbles in the liquid environment according to claim 1, wherein the metal mesh in step (1) is one of copper mesh, gold mesh, nickel mesh or molybdenum mesh, and the mesh number of the metal mesh is 200 to 800 meshes.
3. The method for in-situ characterization of the nanobubbles in the liquid environment according to claim 1, wherein the graphene film in the step (2) is prepared by chemical vapor deposition, and the number of layers of the graphene film is 1 to 5.
4. The method for in-situ characterization of nanobubbles in liquid environment of claim 1 wherein the metal film of step (3) is gold or platinum.
5. The method for in-situ characterization of nanobubbles in liquid environment according to any of claims 1 and 4, wherein the metal film of step (3) is prepared by magnetron sputtering or evaporation, and the thickness of the metal film is 1nm-5 nm.
6. The method for in-situ characterization of nanobubbles in liquid environment of claim 1 wherein the heating of step (4) is heating with a heating stage.
7. The method for in-situ characterization of nanobubbles in liquid environment of claim 1, wherein in step (5), oxygen or argon is selected for surface modification treatment of graphene mesh containing metal nanoparticles for 10 s.
8. The method according to claim 1, wherein the electron beam dose rate in step (8) is greater than 100 e - /Å 2 ∙s。
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| CN118443700A (en) * | 2024-07-03 | 2024-08-06 | 北京大学 | Method for preparing porous carbon film transmission electron microscope carrier net by using soft template with porous array structure |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN118443700A (en) * | 2024-07-03 | 2024-08-06 | 北京大学 | Method for preparing porous carbon film transmission electron microscope carrier net by using soft template with porous array structure |
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