Suspended particle
devices (SPDs) adapted for controlling the transmission of electromagnetic
radiation have become an area of considerable focus for smart window
technology due to their desirable properties, such as instant and
precise light control and cost-effectiveness. Here, we demonstrate
a SPD with tunable transparency in the visible regime using colloidal
assemblies of nanoparticles. The observed transparency using ZnS/SiO<sub>2</sub> core/shell colloidal nanoparticles is dynamically tunable
in response to an external electric field with increased transparency
when applied voltage increases. The observed transparency change is
attributed to structural ordering of nanoparticle assemblies and thereby
modifies the photonic band structures, as confirmed by the finite-difference
time-domain simulations of Maxwell’s equations. The transparency
of the device can also be manipulated by changing the particle size
and the device thickness. In addition to transparency, structural
colorations and their dynamic tunability are demonstrated using α-Fe<sub>2</sub>O<sub>3</sub>/SiO<sub>2</sub> core/shell nanomaterials, resulting
from the combination of inherent optical properties of α-Fe<sub>2</sub>O<sub>3</sub>/SiO<sub>2</sub> nanomaterials and coloration
due to their tunable structural particle assemblies in response to
electric stimuli
