The intrinsic surface chemical characteristics of any material dictates how that material will interact with its surroundings, and how those intrinsic characteristics are modified by their surroundings can yield insight into transformed properties such as for solubility, adsorption, colloidal stability and surface reactivity. This research opportunity focuses on development of methodologies and tools for imaging these surface chemical characteristics by imaging X-ray photoelectron spectroscopy (i-XPS) in conjunction with conventional XPS and orthogonal techniques (e.g., vibrational spectroscopy and electron microscopy) using a wide range of materials. Specific areas of interest for method development using i-XPS includes (1) impact of sample preparation on acquired data (e.g., contamination, conductivity issues), (2) effect of ultra-high vacuum on the sample (e.g., outgassing, chemical modification by oxygen vacancies, cellular structural changes), (3) the effect of long term X-ray exposure on the samples of interest, and (4) extracting more quantitative information from stacks of parallel/hyperspectral imaging. The equipment available to perform these essential measurements is available at the National Institute of Standards and Technology and includes access to a state-of-the-art imaging X-ray photoelectron spectrometer (XPS). Supporting the XPS measurements are transmission electron microscopy, scanning electron microscopy, scanning probe microscopies, and infrared spectroscopy. Some examples of research topics include, but are not limited to (1) surface chemical characterization of microorganisms by i-XPS, (2) locating evidence for bioaccumulation of contaminants by chemical signature in microorganisms by i-XPS, (3) characterization of a cell wall/membrane and cross-sections by i-XPS, and (4) chemical characterization of micrometer scale, surface chemical transformations on materials relevant to consumer products by i-XPS.

 

Reference

Gorham JM, et al: “Detecting Carbon in Carbon: Exploiting Differential Charging to Obtain Information on the Chemical Identity and Spatial Location of Carbon Nanotube Aggregates in Composites by Imaging X-ray Photo-electron Spectroscopy” Carbon 2016

 

key words

Surface chemistry; X-ray photoelectron spectroscopy; Imaging; Metrology; XPS; Consumer products; Bioaccumulation; ESCA; Electron spectroscopy;

Citizenship:  Open to U.S. citizens

Level:  Open to Postdoctoral applicants