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Theoretical Framework for Nanoparticle Reactivity as a Function of Aggregation State
Abstract
Theory is developed that relates the reactivity of nanoparticles to the structure
of aggregates they may form in suspensions. This theory is applied to consider the
case of reactive oxygen species (ROS) generation by photosensitization of C-60 fullerenes.
Variations in aggregate structure and size appear to account for an apparent paradox
in ROS generation as calculated using values for the photochemical kinetics of fullerene
(C-60) and its hydroxylated derivative, fullerol (C-60(OH)(22-24)) and assuming that
structure varies between compact and fractal objects. A region of aggregation-suppressed
ROS production is identified where interactions between the particles in compact aggregates
dominate the singlet oxygen production. Intrinsic kinetic properties dominate when
aggregates are small and/or are characterized by low fractal dimensions. Pseudoglobal
sensitivity analysis of model input variables verifies that fractal dimension, and
by extension aggregation state, is the most sensitive model parameter when kinetics
are well-known. This theoretical framework qualitatively predicts ROS production by
fullerol suspensions 2 orders of magnitude higher compared with aggregates of largely
undifferentiated C-60 despite nearly an order of magnitude higher quantum yield for
the undifferentiated C-60 based on measurements for single molecules. Similar to C-60,
other primary nanoparticles will exist as aggregates in many environmental and laboratory
suspensions. This work provides a theoretical basis for understanding how the structure
of nanoparticle aggregates may affect their reactivity.
Type
Other articleSubject
photophysical propertiesaqueous-solutions
c-60
fullerol
water
keratinocytes
c-60(oh)(18)
suspensions
mechanisms
radiation
chemistry, multidisciplinary
chemistry, physical
materials science, multidisciplinary
Permalink
https://hdl.handle.net/10161/3994Published Version (Please cite this version)
10.1021/1a9046963Citation
Hotze,Ernest M.;Bottero,Jean-Yves;Wiesner,Mark R.. 2010. Theoretical Framework for
Nanoparticle Reactivity as a Function of Aggregation State. Langmuir 26(13): 11170-11175.
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Show full item recordScholars@Duke
Mark Wiesner
James B. Duke Distinguished Professor of Civil and Environmental Engineering
Wiesner's research interests include membrane processes, nanostructured materials,
transport and fate of nanomaterials in the environment, nano plastics, colloidal and
interfacial processes, and environmental systems analysis.

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