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In contrast to a conventional nanoparticle dimer plasmon ruler, this new one shows an approximately linear relationship between the resonance wavelength shifts and nanosphere dimer interparticle separation for a linear plasmon ruler.
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With
the advent of nanometer-sized machines, there is considerable demand
for stable, precise tools to measure absolute distances and distance
changes. One way to do this is with a plasmon ruler. In physics jargon, a
"plasmon" is the quasiparticle resulting from the quantization of
plasma oscillation; it's essentially the collective oscillations of the
free electron gas at a metallic surface, often at optical frequencies.
A
noble metallic dimer (a molecule that results from combining two
entities of the same species) has been used as a plasmon ruler to make
absolute distance and distance change measurements.
Physicists
at China's Wuhan University discovered that nanospheres combined with a
nanorod dimer could be used to solve the problem of measurement
sensitivity. They provide details about their findings in the American
Institute of Physics' Journal of Applied Physics.
Shao-Ding
Liu and Mu-Tian Cheng used a nanostructure as a linear plasmon ruler.
Nanospheres were used to modify surface plasmon coupling of a nanorod
dimer. They found that the resonance wavelength shift increases
approximately linearly with the increasing of a nanosphere's
interparticle separations -- resulting in a structure that's useful as a
plasmon ruler with homogenous measurement sensitivity.
"A
nanoparticle dimer plasmon ruler possesses many advantages because its
measurement sensitivity is homogeneous, it can operate in the
near-infrared region, and the structure's size and nanorod aspect ratio
can be modified freely to get the desired measurement range and
sensitivity," notes Liu.
Applications
for the linear plasmon ruler extend beyond studies of optical
properties of metallic nanostructures to single-molecule microscopy,
surface-enhanced Raman spectroscopy, waveguiding and biosensing.
The
article, "Linear plasmon ruler with tunable measurement range and
sensitivity" by Shao-Ding Liu and Mu-Tian Cheng will appear in the
Journal of Applied Physics.
Study abstract
SOURCE: American Institute of Physics
