3 research outputs found
Metallic-Nanostructure-Enhanced Optical Trapping of Flexible Polymer Chains in Aqueous Solution As Revealed by Confocal Fluorescence Microspectroscopy
Optical trapping of flexible polymer chains to a metallic
nanostructured
surface was explored by microscopic imaging and confocal fluorescence
spectroscopy. A fluorescence-labeled polyÂ(<i>N</i>-isopropylacrylamide)
was targeted, being a representative thermo-responsive polymer. Upon
resonant plasmonic excitation, it was clearly observed that polymers
were assembled into the excitation area to form molecular assemblies.
Simultaneously, fluorescence from the area was obviously intensified,
indicating an increase in the number of polymer chains at the area.
The excitation threshold of light intensity that was required for
obvious trapping was 1 kW/cm<sup>2</sup>, which was much lower by
a factor of 10<sup>4</sup> than that for conventional trapping using
a focused laser beam. The morphology of the assemblies was sensitive
to excitation intensity. We precisely evaluated temperature rise (Δ<i><i>T</i></i>) around the metallic nanostructure upon
plasmonic excitation: Δ<i><i>T</i></i> ≈
10 K at 1 kW/cm<sup>2</sup> excitation. This temperature rise was
an origin of a repulsive force that blocked stable trapping. On the
basis of experimental observations and theoretical calculations, we
quantitatively evaluated the plasmon-enhanced trapping force and the
thermal repulsive force (Soret effect). The overall mechanisms that
were involved in such plasmon-enhanced optical trapping are discussed
in detail. The smooth catch-and-release trapping (manipulation) of
polymer chains was successfully demonstrated
Metallic-Nanostructure-Enhanced Optical Trapping of Flexible Polymer Chains in Aqueous Solution As Revealed by Confocal Fluorescence Microspectroscopy
Optical trapping of flexible polymer chains to a metallic
nanostructured
surface was explored by microscopic imaging and confocal fluorescence
spectroscopy. A fluorescence-labeled polyÂ(<i>N</i>-isopropylacrylamide)
was targeted, being a representative thermo-responsive polymer. Upon
resonant plasmonic excitation, it was clearly observed that polymers
were assembled into the excitation area to form molecular assemblies.
Simultaneously, fluorescence from the area was obviously intensified,
indicating an increase in the number of polymer chains at the area.
The excitation threshold of light intensity that was required for
obvious trapping was 1 kW/cm<sup>2</sup>, which was much lower by
a factor of 10<sup>4</sup> than that for conventional trapping using
a focused laser beam. The morphology of the assemblies was sensitive
to excitation intensity. We precisely evaluated temperature rise (Δ<i><i>T</i></i>) around the metallic nanostructure upon
plasmonic excitation: Δ<i><i>T</i></i> ≈
10 K at 1 kW/cm<sup>2</sup> excitation. This temperature rise was
an origin of a repulsive force that blocked stable trapping. On the
basis of experimental observations and theoretical calculations, we
quantitatively evaluated the plasmon-enhanced trapping force and the
thermal repulsive force (Soret effect). The overall mechanisms that
were involved in such plasmon-enhanced optical trapping are discussed
in detail. The smooth catch-and-release trapping (manipulation) of
polymer chains was successfully demonstrated
Metallic-Nanostructure-Enhanced Optical Trapping of Flexible Polymer Chains in Aqueous Solution As Revealed by Confocal Fluorescence Microspectroscopy
Optical trapping of flexible polymer chains to a metallic
nanostructured
surface was explored by microscopic imaging and confocal fluorescence
spectroscopy. A fluorescence-labeled polyÂ(<i>N</i>-isopropylacrylamide)
was targeted, being a representative thermo-responsive polymer. Upon
resonant plasmonic excitation, it was clearly observed that polymers
were assembled into the excitation area to form molecular assemblies.
Simultaneously, fluorescence from the area was obviously intensified,
indicating an increase in the number of polymer chains at the area.
The excitation threshold of light intensity that was required for
obvious trapping was 1 kW/cm<sup>2</sup>, which was much lower by
a factor of 10<sup>4</sup> than that for conventional trapping using
a focused laser beam. The morphology of the assemblies was sensitive
to excitation intensity. We precisely evaluated temperature rise (Δ<i><i>T</i></i>) around the metallic nanostructure upon
plasmonic excitation: Δ<i><i>T</i></i> ≈
10 K at 1 kW/cm<sup>2</sup> excitation. This temperature rise was
an origin of a repulsive force that blocked stable trapping. On the
basis of experimental observations and theoretical calculations, we
quantitatively evaluated the plasmon-enhanced trapping force and the
thermal repulsive force (Soret effect). The overall mechanisms that
were involved in such plasmon-enhanced optical trapping are discussed
in detail. The smooth catch-and-release trapping (manipulation) of
polymer chains was successfully demonstrated