Skip to main content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.


The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Preparation and Measurement Methods for Studying Nanoparticle Aggregate Surface Chemistry



Christopher W. Szakal, James McCarthy, Andrew R. Konicek, Kacie Louis, Benjamin Yezer, Andrew A. Herzing, Robert Hamers, Richard D. Holbrook


Despite best efforts at controlling nanoparticle (NP) surface chemistries, the environment surrounding nanomaterials is always changing and can impart a permanent chemical memory. We present a set of preparation and measurement methods to be used as the foundation for studying the surface chemical memory of engineered NP aggregates. We attempt to bridge the gap between controlled lab studies and real-world NP samples, specifically TiO2, by using well-characterized and consistently synthesized NPs,controllably producing NP aggregates with precision drop-on-demand inkjet printing for subsequent chemical measurements, monitoring the physical morphology of the NP aggregate depositions with scanning electron microscopy (SEM), acquiring ‘‘surface-to-bulk’’ mass spectra of the NP aggregate surfaces with time-of-flight secondary ion mass spectrometry (ToF-SIMS), and developing a data analysis scheme to interpret chemical signatures more accurately from thousands of data files. We present differences in mass spectral peak ratios for bare TiO2 NPs compared to NPs mixed separately with natural organic matter (NOM) or pond water. The results suggest that subtle changes in the local environment can alter the surface chemistry of TiO2 NPs, as monitored by Ti+/TiO+ and Ti+/C3H5+ peak ratios. The subtle changes in the absolute surface chemistry of NP aggregates vs. that of the subsurface are explored. It is envisioned that the methods developed herein can be adapted for monitoring the surface chemistries of a variety of engineered NPs obtained from diverse natural environments.
Journal of Environmental Monitoring


nanoparticles, TiO2: ToF-SIMS, surface chemistry, inkjet printing
Created June 8, 2012, Updated February 19, 2017