研究目的
Investigating the surface chemistry of black phosphorus during ambient degradation to understand the oxidation mechanisms and stability issues.
研究成果
The degradation of liquid exfoliated few-layer black phosphorus involves initial formation of non-bridging oxide species that convert to unstable bridging oxide species (P-O-P), which hydrolyze to form volatile phosphorus oxides like phosphoric acid that evaporate, leading to surface decomposition. Multilayered bulk BP shows higher stability with less bridging oxide formation. These insights can aid in developing protection methods for BP in applications.
研究不足
The study is limited to liquid exfoliated BP and may not fully represent other forms like mechanically exfoliated BP. The high-vacuum conditions in XPS could cause evaporation of volatile oxidation products, potentially underestimating oxide presence. The analysis focuses on surface chemistry and may not capture bulk degradation effects. Sample preparation under inert conditions might not mimic real-world ambient exposures perfectly.
1：Experimental Design and Method Selection:
The study uses liquid exfoliation to produce few-layer black phosphorus, followed by exposure to ambient conditions. X-ray photoelectron spectroscopy (XPS) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) are employed to analyze chemical changes. Additional techniques include Raman spectroscopy, atomic force microscopy (AFM), scanning transmission electron microscopy (STEM), and transmission electron microscopy (TEM) for structural and morphological characterization.
2：Sample Selection and Data Sources:
Black phosphorus was purchased from Smart Elements (purity 99.998%) and exfoliated in N-methyl-2-pyrrolidone (NMP) under inert conditions. Samples were dropcast on Si wafers or Ti substrates for analysis. Data were collected over time periods of ambient exposure (e.g., 0 days, 2 days, 7 days, 2 weeks).
3：998%) and exfoliated in N-methyl-2-pyrrolidone (NMP) under inert conditions. Samples were dropcast on Si wafers or Ti substrates for analysis. Data were collected over time periods of ambient exposure (e.g., 0 days, 2 days, 7 days, 2 weeks). List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: Equipment includes a bath sonicator (Branson 1800), Oxford Applied Research Escabase XPS system, Nicolet 6700 Infrared Spectrometer, QE65PRO OceanOptics spectrometer, Park XE-100 AFM system, FEI Helios NanoLab 600i SEM, and Jeol 2100 TEM. Materials include BP, NMP, acetonitrile (ACN), Si wafers, and Ti substrates.
4：Experimental Procedures and Operational Workflow:
BP was exfoliated in degassed NMP using sonication, centrifuged, and purified with ACN washes. Samples were exposed to ambient conditions (~60% humidity, 19°C, light). XPS and ATR-FTIR spectra were acquired at various time points, with data processing using CasaXPS software. AFM, STEM, and TEM were used for imaging.
5：Data Analysis Methods:
XPS data were corrected to a Shirley background and fitted to Voigt profiles, with charge correction applied. ATR-FTIR spectra were collected at 2 cm?1 resolution and averaged over 300 scans. Raman spectra were analyzed for phonon modes, and imaging data were interpreted for morphological changes.
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ACN
acetonitrile
Sigma-Aldrich
Used for purification washes of exfoliated black phosphorus samples.
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Spectrometer
QE65PRO
OceanOptics
Used for Raman scattering spectroscopy to characterize the phonon modes and crystallinity of black phosphorus.
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SEM
Helios NanoLab 600i
FEI
Used for scanning transmission electron microscopy to obtain high-resolution images of black phosphorus structure and degradation.
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TEM
Jeol 2100
Jeol
Used for transmission electron microscopy to confirm crystallinity and measure d-spacings of black phosphorus flakes.
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NMP
anhydrous N-metyl-2-pyrrolidone
Sigma-Aldrich
Solvent used for liquid exfoliation of black phosphorus under inert conditions.
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Bath sonicator
Branson 1800
Branson
Used for sonication during the exfoliation of black phosphorus to produce few-layer flakes.
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XPS system
Escabase
Oxford Applied Research
Used for x-ray photoelectron spectroscopy to analyze the surface chemistry and oxidation states of black phosphorus.
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Infrared spectrometer
Nicolet 6700
Nicolet
Used for attenuated total reflectance Fourier transform infrared spectroscopy to identify chemical bonds and oxidation products on the black phosphorus surface.
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AFM system
Park XE-100
Park
Used for atomic force microscopy in non-contact mode to image the morphology and degradation of black phosphorus flakes.
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Black phosphorus
Smart Elements
The primary material studied, used as the source for exfoliation and degradation experiments.
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