Structural Evolutions of ZnS Nanoparticles in Hydrated
and Bare States
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Abstract
Suitable optoelectronic properties
and the nontoxic nature of ZnS
quantum dots capacitate exciting applications for these nanomaterials
especially in the field of biomedical imaging. However, the structural
stability of ZnS nanoparticles has been shown to be challenging since
they potentially are prone to autonomous structural evolutions in
ambient conditions. Thus, it is essential to build an understanding
about the structural evolution of ZnS nanoparticles, especially in
aqueous environment, before implementing them for in vivo applications.
In this study we compared the structure of ZnS nanoparticles relaxed
in a vacuum and in water using a classical molecular dynamics method.
Structural analyses showed that the previously observed three-phase
structure of bare nanoparticles is not formed in the hydrated state.
The bulk of hydrated nanoparticles has more crystalline structure;
however, the dynamic heterogeneity in their surface relaxation makes
them more polar compared to bare nanoparticles. This heterogeneity
is more severe in hydrated wurtzite nanoparticles, causing them to
show larger dipole moments. Analyzing the structure of water in the
first hydration shell of the surface atoms shows that water is mainly
adsorbed to the nanoparticles’ surface through Zn–O
interaction, which causes the structure of water in the first hydration
shell to be discontinuous