The ability to produce
a diverse spectrum of hollow nanostructures
is central to the advances in many current and emerging areas of technology.
Herein, we report a general method to craft hollow nanostructures
with highly tunable physical and chemical parameters. The key strategy
is to regenerate the nanoscale sacrificial templates in a galvanic
replacement reaction through site-selective overgrowth. As examples,
we demonstrate the syntheses of nanocages and nanotubes made of silver,
gold, palladium, and/or platinum with well-controlled wall thicknesses
and elemental distributions. Using the nanocages of silver and gold
as models, we demonstrate they possess intriguing plasmonic properties
and offer superior performance in biosensing applications. This study
provides a powerful platform to customize hollow nanostructures with
desired properties and therefore is expected to enable a variety of
fundamental studies and technologically important applications.
Current
methods for tuning the plasmonic properties of metallic
nanoparticles typically rely on alternating the morphology (i.e.,
size and/or shape) of nanoparticles. The variation of morphology of
plasmonic nanoparticles oftentimes impairs their performance in certain
applications. In this study, we report an effective approach based
on the control of internal structure to engineer morphology-invariant
nanoparticles with tunable plasmonic properties. Specifically, these
nanoparticles were prepared through selective growth of Ag on the
inner surfaces of preformed Ag–Au alloyed nanocages as the
seeds to form Ag@(Ag–Au) shell@shell nanocages. Plasmonic properties
of the Ag@(Ag–Au) nanocages can be conveniently and effectively
tuned by varying the amount of Ag deposited on the inner surfaces,
during which the overall morphology of the nanocages remains unchanged.
To demonstrate the potential applications of the Ag@(Ag–Au)
nanocages, they were applied to colorimetric sensing of human carcinoembryonic
antigen (CEA) that achieved low detection limits. This work provides
a meaningful concept to design and craft plasmonic nanoparticles.
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