New Paper: Recovery of Nanoparticles from Solutions

[PGT]

For several years, we’ve been using a method we call “flash drying” to
recover nanoparticles from solutions. This paper gives a detailed
assessment of how well the method preserves the properties of the
particles. For many purposes, flash drying is more appropriate than
other commonly used methods like freeze drying.
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CITATION: Nurmi, J. T., V. Sarathy, P. G. Tratnyek, D. R. Baer, J. E.
Amonette, J. C. Linehan, and A. Karkamkar. 2010. Recovery of iron/iron
oxide nanoparticles from aqueous media: A comparison of methods and
their effects. J. Nanoparticle Res. Published online: May 15, 2010.
ABSTRACT: Most methods currently being used to recover Fe0-core/oxide-
shell nanoparticles from solutions (including the solvents they are
synthesized or stored in) are potentially problematic because they may
alter the particle composition (e.g., depositing salts formed from
solutes) or leave the particles prone to transformations during
subsequent storage and handling (e.g., due to residual moisture). In
this study, several methods for recovery of nanoparticles from aqueous
solution were studied to determine how they affect the structure and
reactivity of the recovered materials. Simple washing of the
nanoparticles during vacuum filtration (i.e., “flash drying”) can
leave up to ~17 weight percent residual moisture. Modeling
calculations suggest this moisture is mostly capillary or matric water
held between particles and particle aggregates, which can be removed
by drying for short periods at relative vapor pressures below 0.9.
Flash drying followed by vacuum drying, all under N2, leaves no
detectable residue from precipitation of solutes (detectable by X-ray
photoelectron spectroscopy, XPS), no significant changes in overall
particle composition or structure (determined by transmission electron
microscopy, TEM), and negligible residual moisture (by
thermogravimetric analysis, TGA). While this improved flash-drying
protocol may be the preferred method for recovering nanoparticles for
many purposes, we found that Fe0-core/oxide-shell nanoparticles still
exhibit gradual aging during storage when characterized
electrochemically with voltammetry.
LINK: http://dx.doi.org/10.1007/s11051-010-9946-x