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Probing Liquid Surfaces under Vacuum Using SEM and TOF-SIMS

Journal Article · · Lab on a Chip, 11(15):2481-2484
DOI:https://doi.org/10.1039/C0LC00676A· OSTI ID:1019201
Applying vacuum-based molecular probes of liquid surfaces would aid many environmental, biological, and industrial studies. However the high vapor pressure of water and most organic solvents largely prohibit this use. We report a newly developed versatile and self-contained vacuum interface for high-vapor pressure liquid surfaces, and its application in a time of flight secondary ion mass spectrometer (TOFSIMS) and scanning electron microscope (SEM). The self-contained module requires no wires or tubing connections to the outside of the instrument. It uses a microfluidic channel with a 3 micrometer diameter window into the flowing fluid beneath it. This window supports the liquid against the vacuum by the liquid’s surface tension, while limiting the high-density vapor region traversed by the probe beams to only a few microns. This aperture size also limits temperature and concentration changes due to evaporation of the solvent. The beam damage caused by the probe beams is largely negligible, as the flowing liquid surface self-renews. We demonstrate the performance of this microfluidic interface for in situ liquid surface TOFSIMS (ISLS-TOFSIMS) and SEM (ISLS-SEM) for chemical analysis of liquid surfaces. This device enables in situ liquid (ISL) studies in a wide range of vacuum analytical methods beyond SEM and TOFSIMS.
Research Organization:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Organization:
USDOE
DOE Contract Number:
AC05-76RL01830
OSTI ID:
1019201
Report Number(s):
PNNL-SA-76770; 36601; 42330; 36603; KC0301020
Journal Information:
Lab on a Chip, 11(15):2481-2484, Journal Name: Lab on a Chip, 11(15):2481-2484 Journal Issue: 15 Vol. 11
Country of Publication:
United States
Language:
English

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