A method for cryogenic xps characterization of liquid-solid interfaces

Abstract

The application discloses a kind of liquid-solid interface frozen XPS characterization method.The method comprises the following steps: (1) with thin layer two-dimensional material as solid phase, solid phase is transferred to liquid phase sample, and solid phase is salvaged with aluminium oxide substrate, at this time, a layer of liquid film of liquid phase sample is formed between aluminium oxide substrate and solid phase, and liquid-solid interface sample is constructed;(2) liquid-solid interface sample is fixed on sample holder, placed in liquid nitrogen and frozen, after liquid phase sample is frozen and solidified, it is placed into sample cavity and vacuumized, then it is transferred to test cavity for testing, solid phase is etched using ion beam etching technology, until the liquid-solid interface of solid phase and liquid phase sample is detected, so as to realize the XPS characterization of liquid-solid interface.The liquid sample is frozen and solidified by using liquid nitrogen cooling mode, which can meet the vacuum requirement of XPS characterization, and realize the characterization of liquid sample composition, valence state and other information in ultra-high vacuum environment.

Description

Technical Field

[0001] The present invention relates to the technical field of liquid-solid interface characterization, and in particular to a cryo-XPS characterization method for a liquid-solid interface. Background Art

[0002] Currently, the research and development of new materials is a hot topic in the field of materials science, encompassing fields such as materials science, life sciences, nanoscience, and catalysis. In addition to characterizing many solid substances, these studies also involve substances with certain volatility or instability in vacuum, such as liquid samples. X-ray photoelectron spectroscopy (XPS) can provide information on the elemental composition, chemical state, molecular structure, and chemical bonding of various compounds, providing an important basis for studying structure-activity relationships, controllable design, and functional development. XPS is generally used for surface analysis of solid samples. However, given the need for an ultra-high vacuum environment during testing, the sample to be tested must be thoroughly dry, non-volatile, free of volatile solvents, non-deliquescent, and free of water of crystallization. XPS analysis is generally difficult for unconventional samples and liquids with certain volatility or instability in vacuum, such as organic small molecules, metal-organic complexes, and organic electrolytes. Furthermore, characterization of liquid-solid interfaces (excluding ionic liquids) is even more challenging. Firstly, vacuum incompatibility is a major issue; conventional sample introduction methods can damage the instrument's vacuum chamber. Secondly, surface-sensitive XPS characterization techniques are difficult to directly detect the embedded liquid-solid interface. Summary of the Invention

[0003] Based on the above background technology, the purpose of the present invention is to provide a cryo-XPS characterization method for liquid-solid interfaces, which can overcome the vacuum incompatibility problem of liquid samples and, by combining the ion beam etching method, perform deep profiling of the liquid-solid interface to achieve XPS characterization of the embedded liquid-solid interface.

[0004] In order to achieve the above object, the technical solution of the present invention is as follows:

[0005] A cryo-XPS characterization method for a liquid-solid interface, comprising the following steps:

[0006] (1) Using a thin layer of two-dimensional material as the solid phase, the solid phase is transferred to a liquid sample and picked up with an aluminum oxide (Al2O3) substrate. At this time, a liquid film of the liquid sample is formed between the aluminum oxide substrate and the solid phase, thus constructing a liquid-solid interface sample;

[0007] (2) The liquid-solid interface sample is fixed on the sample holder and frozen in liquid nitrogen. After the liquid phase sample is frozen and solidified, it is placed in the sampling chamber and vacuumed. It is then transferred to the test chamber for testing. The solid phase is etched using ion beam etching technology until the liquid-solid interface of the solid and liquid phase samples is detected, thereby realizing the XPS characterization of the liquid-solid interface.

[0008] In the above technical solution, further, in step (1), the thickness of the solid phase is less than 100 nm.

[0009] In the above technical solution, further, in step (1), the solid phase material includes any one of graphene, boron nitride (BN), molybdenum disulfide (MoS2), tungsten disulfide (WS2), molybdenum diselenide (MoSe2), tungsten diselenide (WSe2), and MXene.

[0010] In the above technical solution, further, in step (2), the parameters of the ion beam etching are: ion source: Ar + , Energy: 3KV, Etching area: 2mm×2mm square.

[0011] In the above technical solution, further, in step (2), the injection chamber and the test chamber are both pre-cooled, and the pre-cooling time is 60 minutes.

[0012] The present invention first constructs a liquid-solid interface sample without surface contamination. Its ultra-thin covering layer can not only wrap the liquid to be characterized, but also be easily etched by ion beam, thereby exposing the liquid-solid interface underneath; secondly, the sample holder is cooled by adding liquid nitrogen, and the sample is etched by ion beam (Ar + The solid phase is etched by ion beam and gas cluster ion beam) etching technology to obtain a liquid-solid interface.

[0013] The beneficial effects of the present invention are:

[0014] (1) The present invention utilizes liquid nitrogen cooling to freeze and solidify the liquid sample, which can meet the vacuum requirements of XPS characterization and realize the characterization of the composition, valence state and other information of the liquid sample in an ultra-high vacuum environment.

[0015] (2) The liquid-solid interface sample without surface contamination constructed by the present invention is suitable for frozen surface characterization. Its ultra-thin covering layer can not only wrap the liquid to be characterized, but also be easily etched to expose the liquid-solid interface underneath.

[0016] (3) The present invention uses cryo-XPS combined with ion beam etching to characterize the embedded liquid-solid interface, which is suitable for the characterization of liquid-solid interfaces in various systems. The combination of surface-sensitive XPS characterization and ion beam etching can perform in-depth analysis of the frozen liquid-solid interface and obtain information such as the structure and chemical composition of the interface. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The schematic diagram and physical picture of the liquid-solid interface sample constructed in Example 1, a is a schematic diagram of the constructed liquid-solid interface sample, b is a photo of the sample in a frozen state, c is a photo of the Ar + Photo of the sample after ion beam etching test;

[0018] Figure 2 The liquid-solid interface sample obtained in Example 1 was prepared under Ar + XPS spectra during ion beam etching. DETAILED DESCRIPTION

[0019] The present invention will be described in detail below by way of examples, but the scope of the claims of the present invention is not limited by these examples. Meanwhile, the examples are only partial conditions for achieving this purpose, and do not mean that these conditions must be met to achieve this purpose.

[0020] Example 1

[0021] The CVD-grown ~10nm graphene / copper foil sample was etched in a 0.1M ammonium persulfate solution to remove the copper substrate and obtain a self-supporting graphene. The graphene was transferred to water for cleaning and then transferred to a 0.1M KCl aqueous solution. It was then picked up with an aluminum oxide (Al2O3) substrate. At this time, a layer of KCl aqueous solution liquid film formed between the aluminum oxide substrate and the graphene, thereby constructing a graphene-covered 0.1M KCl aqueous solution liquid-solid interface sample, as shown in FIG. Figure 1 shown.

[0022] The liquid-solid interface sample was placed directly in liquid nitrogen for 3 minutes for rapid freezing. The sample was then quickly placed in a pre-cooled 60-minute injection chamber with a sample stage temperature of -120°C and vacuumed. Finally, the sample was transferred to a pre-cooled 60-minute main chamber with a sample stage temperature of -120°C for testing. 3kV energy was used and the etching area was 2×2mm. 2 Ar + Graphene was etched under ion beam etching conditions, and the cryo-XPS test results were as follows: Figure 2As shown, each spectral line represents the XPS spectrum after 2 minutes of etching. In the initial spectrum (0 minutes), the presence of the O 1s peak indicates that there may be oxidation on the graphene surface. After 2 minutes of etching, the O 1s peak disappears, indicating that the oxide layer on the graphene surface is cleaned. The C1s peak at this time comes from graphene. After about 8 minutes of etching (i.e., the 5th spectral line), O1s, K 2p and Cl 2p signals begin to appear, indicating that XPS can detect the KCl aqueous solution at the liquid-solid interface. After 14 minutes of etching (the 8th spectral line), the C 1s peak completely disappears, indicating that the graphene has been completely etched at this time. After 24 minutes of etching, the Al2p peak still does not appear, indicating that the aluminum oxide substrate has not been etched. This also shows that the O1s peak is completely derived from H2O without interference from the aluminum oxide substrate, thereby achieving the characterization of the liquid-solid interface.

[0023] The above examples demonstrate that freezing can solidify aqueous solutions and stably store them in an ultra-high vacuum environment. Furthermore, combining surface-sensitive XPS characterization with ion beam etching allows for in-depth profiling of the frozen liquid-solid interface, revealing information such as its structure and chemical composition.

[0024] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. The scope of protection of the present invention shall be determined by the scope defined in the claims. Other variations or modifications may be made based on the above description. Obvious variations or modifications derived therefrom shall remain within the scope of protection of the present invention.

Claims

1. A cryo-XPS characterization method for liquid-solid interface, characterized in that: The method comprises the following steps: (1) Using a thin layer of two-dimensional material as the solid phase, the solid phase is transferred to the liquid phase sample, and the solid phase is picked up with an alumina substrate. At this time, a liquid film of the liquid phase sample is formed between the alumina substrate and the solid phase, thus constructing a liquid-solid interface sample; (2) The liquid-solid interface sample is fixed on the sample holder and frozen in liquid nitrogen. After the liquid phase sample is frozen and solidified, it is placed in the sampling chamber and vacuumed. It is then transferred to the test chamber for testing. The solid phase is etched using ion beam etching technology, and the XPS spectrum is collected simultaneously. The exposure of the solid-liquid interface is judged by monitoring the appearance of characteristic element signals originating from the liquid phase sample in the XPS spectrum until the liquid-solid interface of the solid and liquid phase samples is detected, thereby realizing the XPS characterization of the liquid-solid interface.

2. The cryo-XPS characterization method according to claim 1, wherein In step (1), the thickness of the solid phase is less than 100 nm.

3. The cryo-XPS characterization method according to claim 1, wherein In step (1), the solid phase material includes any one of graphene, boron nitride, molybdenum disulfide, tungsten disulfide, molybdenum diselenide, tungsten diselenide, and MXene.

4. The cryo-XPS characterization method according to claim 1, wherein In step (2), the parameters of the ion beam etching are: ion source: Ar + , Energy: 3KV, Etching area: 2 mm × 2 mm square.

5. The cryo-XPS characterization method according to claim 1, wherein In step (2), the injection chamber and the test chamber are both precooled, and the precooling time is 60 minutes.

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